CA1303820C - Four catalytic reactor extended claus process - Google Patents
Four catalytic reactor extended claus processInfo
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- CA1303820C CA1303820C CA000489547A CA489547A CA1303820C CA 1303820 C CA1303820 C CA 1303820C CA 000489547 A CA000489547 A CA 000489547A CA 489547 A CA489547 A CA 489547A CA 1303820 C CA1303820 C CA 1303820C
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- sulfur
- claus
- reactor
- reaction zone
- preconditioning
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Abstract
ABSTRACT
A Claus process sulfur recovery plant comprising a Claus thermal reaction zone and four Claus catalytic reaction zones is operated for the recovery of sulfur, at least three of the Claus catalytic reaction zones being capable of opera-tion either under sulfur adsorption-type conditions or under regeneration or preconditioning type conditions, with nor-mally two of the three Claus catalytic reaction zones being operated under adsorption-type conditions while the other is operating under regeneration or preconditioning type condi-tions. Periodically, sulfur laden catalyst from the adsorption-type reaction zones can be regenerated using a process gas stream derived from the sulfur recovery process followed by preconditioning the freshly regenerated reactor, and placing the freshly regenerated, preconditioned reactor into the final adsorption position for the recovery of sulfur.
A Claus process sulfur recovery plant comprising a Claus thermal reaction zone and four Claus catalytic reaction zones is operated for the recovery of sulfur, at least three of the Claus catalytic reaction zones being capable of opera-tion either under sulfur adsorption-type conditions or under regeneration or preconditioning type conditions, with nor-mally two of the three Claus catalytic reaction zones being operated under adsorption-type conditions while the other is operating under regeneration or preconditioning type condi-tions. Periodically, sulfur laden catalyst from the adsorption-type reaction zones can be regenerated using a process gas stream derived from the sulfur recovery process followed by preconditioning the freshly regenerated reactor, and placing the freshly regenerated, preconditioned reactor into the final adsorption position for the recovery of sulfur.
Description
3~
IMPROVED FOUR CATALYTIC REACTOR EXTENDED
CLAUS PROCESS
The invention relates to gas processingO In a particular aspect, the invention relates to processing gases containing hydrogen sulfide for the recovery of ele-mental sulfur. In a further aspect, the invention relates 15 to such a process utilizing the Claus reaction in a Claus process sulfur recovery plant comprising a Claus thermal reaction zone and two or more Claus catalytic reaction zones, at least one of the two or more Claus catalytic reaction zones being operated periodically under condi-20 tions effective for forming and depositing elemental ~i sulfur on the catalyst.
FIELD OF THE INVENTION
.
The conventional Claus process for sulfurrecovery from hydrogen sulfide containing gas is widely 25 practiced and accounts for a major portion of total world-wide sulfur production. Such Claus processes utilize the Claus reaction for the recovery of sulfur:
H2S + l/2 SO2 ~ 3/2 S + ~ o Typical Claus process sulfur recovery plants can include a Claus thermal reaction zone or furnace in which the hydrogen sulfide containing gas can be combusted in the pres-ence of an oxidant such as oxygen or air to form an effluent stream comprising unreacted hydrogen sulfide, sulfur dioxide, and formed elemental sulfur, as well as other compounds~
This effluent stream can then be in-troduced into a series of \
~3~,P3 one, two, or more Claus catalytic reaction zones typically operated so that the resulting formed sulfur is continuously removed in the vapor phase, that is, the reaction zones are operated above the temperature at which significant sulfur deposition on the catalyst can occur. The elemental sulfur can then be removed from the Claus catalytic reaction zone effluent streams by condensation at appropriate points in the process. Recovery of sulfur from a hydrogen sulfide con-taining stream can be as high as about 96% for two Claus catalytic reaction zone plants or about 97~ for three Claus catalytic reaction zone plants.
In many instances, however, this level of recovery will be inadequate either because of economic or because of environmental considerations. To meet the higher levels which can be required, a number of treatment processes have been developed to increase the level of overall sulfur recovery. Certain of these processes involve extensions of the Claus reaction under conditions whlch favor additional removal of hydrogen sulfide from the gas stream being pro-cessed. Thus, the residual level of sulfur compounds can be significantly reduced by operating one or more of the Claus catalytic reaction zones under conditions of temperature, pressure, and composition such that the preponderance of formed elemental sulfur is deposited on the catalyst. Simi-larly, the Claus reaction in one or more Claus reactors can likewise be driven ln the direction of removal of hydrogen sulfide and sulfur dioxide from the process stream by removing water from the stream prior to carrying out the Claus reaction in said one or more Claus reactors.
It will be appreciated by those familiar with this art area that other processes not involving an extension of the Claus reaction are also available and have been utilized for the further removal of hydrogen sulfide and other sulfur compounds from process gas streams. These other processes include such as the SCOT (Shell Claus Off-gas Treating)l, BSRP
(Beavon Sulfur Re~overy Process), the Beavon-Stretford Pro-cess, and the like. However r to the extent that it is eco-nomically and technically feasible, use of the Claus reaction ~3~33~
either directly or of the extended Claus reaction is preferred for reasons of simplicity~ ease oE operation and maintenance, and other similar reasons.
SWMMARY OF THE INVENTION
According to the invention, there is provided a process for the recovery of sulfur from an acid gas stream comprising hydrogen sulfide in a Claus process sulfur recovery plant. ~he Claus process sulfur recovery plant can comprise a Claus thermal reaction zone and four Claus cata-lytic reaction zones Rl, R2, R3, and R4 and at least four sulfur condensers Cl~ C2, C3, and C~. The process comprises passing the acid gas stream successively through the Claus thermal reaction zone and then successively through a first position Claus catalytic reaction zone, a second position Claus catalytic reaction zone, a third position Claus cata-lytic reaction zone, and a fourth position Claus catalytic reaction zone, at least the third and fourth position Claus catalytic reaction zones being operated under conditions of temperaturer pressure, and composition for depositing a pre-ponderance of the sulfur on the catalyst therein. The pro-cess further comprises rotating at least three of the reac-tors Rl, R2, R3, and R4 through the third and fourth positions operated under conditions effective for depositing the preponderance of the sulfur on the catalyst and periodi-cally regenerating such reactors with a process gas stream derived from the sulfur recovery process upstream of the second position Claus catalytic reaction zone. Following regeneration, the freshly regenerated reactors can be precon-ditioned by introducing thereinto a cold stream having an inlet temperature effective for condensing sulfur on at least a portion of the catalyst and passing the resulting stream through at least a remaining substantial portion of the cata-lyst prior to placing the freshly regenerated reactor in the fourth position operated under conditions effective for depo-siting a preponderance of the formed sulfur on the catalyst therein. In another aspect of the invention, the freshly regenerated second position Claus catalytic reaction zone can be preconditioned by passing a stream lean in sulfur and ~3~3~
sulfur compounds in contact with at least a substantial portion of the catalyst in the freshly regenerated second position Claus catalytic reaction zone for a period of time effective for reducing an increase in sulfur emissions occur-ring where a hot, freshly regenerated reactor is switched into a final position of a series of Claus catalytic reaction zones without preconditioning prior to switching the thus-preconditioned Claus catalytic reaction zone into the fourth (final) position.
In accordance with one aspect of the invention there is provided such a process for the recovery of sulfur from a feed stream comprising hydrogen sulfide by passing the feed stream successively through a Claus thermal reaction zone, a Claus catalytic reaction zone in a first position, a Claus catalytic reaction zone in a second pOsitiOIl~ a Claus catalytic reaction zone in a third position, and a Claus catalytic reaction zone in a fourth position, the Claus cata-lytic reaction zones in the third and fourth positions being operated under conditions effective for depositing the pre-ponderance of the formed elemental sulfur on the catalyst therein. In accordance with this aspect of the invention, the Claus catalytic reaction zone in the first position can be a dedicated reaction zone which is operated at all times as a high temperature Claus catalytic converter under condi-tions of temperature and pressure and composition such that the formed elemental sulfur is continuously removed from the first position Claus catalytic reaction zone in the vapor phase~ According to this aspect of the invention, the Claus catalytic reaction zones in the second, third, and fourth positions are rotated successively and sequentially for the recovery of sulfur through the second positionJ the fourth position, the third position, and back to the second posi-tion, subject to in accordance with one method of the inven-tion a temporary departure from this sequence for purposes of preconditioning the freshly regenerated second position Claus catalytic reaction zone by introducing a cold stream ther-einto having a temperature effective for condensing sulfur on at least a portion of the catalyst and passing the resulting ~3~3~
stream in contact with a remaining substantial portion of the catalyst or b~ passing a stream lean in sulfur and sulfur compounds, at least in comparison with the stream used for regeneration, in contact with a substantial portion of the catalyst in the hot, freshly regenerated catalytic reaction zone and reducing an increase in sulfur emissions occurring where a ~ot, freshly regenerated reactor is switched without preconditioning into a final position of a series of Claus catalytic reaction zones prior to switching the thus-preconditioned freshly regenerated catalytic reaction zone into the fourth position. As will be appreciated from the above, the freshly regenerated Claus catalytic reaction zone after preconditioning will be rotated into the fourth posi-tion operated as described under adsorption conditions thereby placing the freshly regenerated Claus catalytic reac-tion ~one which will have a substantial portion of the cata-lyst therein having a very low residual sulfur loading in the final adsorption position thus favoring the removal of hydrogen sulfide and sulfur dioxide remaining in the process gas stream to a very low level.
Further in accordance with this aspect of the invention, it will be appreciated that a Claus catalytic reaction zone previously loaded with sulfur by successive operation in the fourth and then in the third position, can be rotated into the second position for regeneration by the effluent gas stream from the first position Claus catalytic reaction zone. In this position, the laden sulfur can be removed from the catalyst by heating with the effluent from the first position Claus catalytic reaction zone and concur-rently a high temperature, Claus catalytic reaction is facil-itated in the second position catalytic reaction zone, the reactor in the second position thus performing concurrently regeneration and Claus sulfur recovery functions.
In accordance with another aspect of the invention, regeneration of a reactor in the second position can be effected at a temperature in the ranye of about 425 to about 550F and during a second period at a temperature in the range of about 550 to about 650F prior to preconditioning.
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In accordance with further aspects of the invention, after regeneration, the freshly regenerated reac-tors can be preconditioned prior to being rotated into the fourth position either by reducing the temperature o~ the feed gas to the freshly regenerated reactor, or by going tem-porarily to a previous configuration of reactors as will be discussed below in more detail, to effect preconditioning of the freshly regenerated reactor prior to rotation into the fourth position.
BR~EF D~SCRIPTION OF THE DRAWINGS
The invention will be further understood and appre-ciated from the following detailed description and the draw-ings in which:
Figure 1 illustrates schematically a first mode (Mode A) of the process according to the instant invention;
E'igure 2 illustrates schematically a second mode (Mode ~) of the process according to the instant invention; and Figure 3 illustrates schematically a third mode (Mode C) of the process according to the instant invention.
The invention will be further understood and appre-ciated from the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, there is provided a process for the recovery of sulfur from a feed stream com-prising hydrogen sulfide which utilizes a Claus process sulfur recovery plant comprising a thermal reaction zone and four Claus catalytic reaction zones, Rl, R2, R3, and R4.
According to a pre~erred embodiment, the Claus process sulfur recovery plant can have one reactor, Rl, which always func-tions in the first position as a high temperature, Claus catalytic reaction zone from which elemental sulfur is con-tinuously being removed in the vapor phase, and three other reactors, R2, R3, and R4, which can be rotated between second position, third position, and fourth position operation, the reactors in the third and fourth positions being operated ~ ~q ~
under conditions effective for forming and depositing the preponderance of elemental sulfur on the surface of the cata-lyst.
As used in the instant specification and claims, the symbols Rl, R2, etc., Cl, C2, etc.~ shall refer to spe-cific pieces of equipment whereas the notation first position reactor, second position reactor, etc~, and first position condenser, second position condenser, shall refer to equip-ment position or location relative to the acid gas stream being processed. Thus, a first position reactor is upstream of a second position reactor, etc., and a first position con-denser is upstream of a second position condenser, etc. Fur-ther, a first position condenser will for purposes of this specification refer to a condenser upstream of a first posi-tion reactor, a second position condenser shall refer to a condenser upstream of a second reactor, and so forth.
Salient features of the process according to the invention are the following. (1) When a reactor previously laden with sulfur by being rotated successively through the fourth and third positions is being regenerated, it is simul-taneously operating as a second stage Claus catalytic reac-tion zone, preferably with the temperature being higher than normal for a second stage Claus catalytic reaction zone, but in accordance with one aspect of the invention, lower during at least part of regeneration than is conventional during regeneration of sulfur-laden catalyst. (2) The regeneration period can preferably consist of two high temperature per-iods, the first period being conducted at an effluent temper-ature in the range of about 425 to about 550F, most prefer-ably at a temperature in the range of about 500 to about 525F, and the second period being conducted at an effluent temperature in the range of about 550 to about 650F, prefer-ably 5~5 to 600F. (3) The reheat exchanger according to one aspect of the invention can be eliminated upstream of the second position reactor since hot effluent gas from the first position Claus catalytic reaction zone can be bypassed around the second condenser to reheat the feed to the second posi-tion ~laus catalytic reaction zoneO (~) There can be two ~L3~-J~
catalytic reaction zones operated in series at all times under conditions effective for depositing a preponderance of the formed sulfur on the catalyst, so overall recovery can remain high throughout the process. (5) Only nine switching valves are required, with only six of those being required to give positive shut-off.
The Claus thermal reaction zone which is utilized in accordance with the invented method can be any suitable Claus thermal reaction zone such as, for example, a muffle-tube furnace, a fire-tube furnace, and the like, which can be selected and designed in accordance with principles familiar to those skilled in this art area. Similarly, the Claus catalytic reaction zones can comprise any suitable vessel for containing catalyst facilitating the Claus reaction, whether in fixed-bed or fluid/moving bed format, and can be selected, sized, and designed in accordance with principles well estab-lished in this art area.
In accordance with a preferred embodiment of the invention, reactor Rl can be operated as a conventional first stage Claus reactor in the first position. Broadly, the tem-perature of reactor Rl can thus be in the range of from about above the sulfur condensation point to about 700F, prefer-ably in the range of ahout 550F to about 650F, most prefer-ably in the range of about 575F to about 625F~ ~f neces-sary, or appropriate, the temperature in the first Claus catalytic reaction zone can be maintained at a higher temper-ature, for example, at about 695F for maximum conversion of organic sulfur compounds to H2S while minimizing sulfidiza-tion of carbon steel. The efluent from the first position Claus catalytic reactor can be removed and provided to a second position condenser and can then be reheated, in accor-dance with a preferred embodiment of the invention, by a por-tion of the first position Claus catalytic reactor effluent gas, or by other means familiar to those skilled in this art area. The reheated effluent gas from the first position Claus catalytic reactor can then be provided to the second position Claus catalyti~ reactor which can be operated con-currently for high temperature Claus conversion and simulta-~3~33~
g neously be undergoing catalyst regeneration, the secondposition Claus catalytic reactor previously having been rotated successively for the recovery of sulfur through the fourth and third positions. The effluent stream from the second position Claus catalytic reactor can then be cooled in a third position condenser and the gas can flow without reheating to a third position Claus catalytic reactor which can be operated as a Claus adsorption-type reactor with, preferably, a slightly elevated temperature, for example, 320F inlet and 355F outlet, as compared with conventional adsorption-type operation. Conventional operating tempera-tures can, of course, also be employed. The effluent from the third position Claus catalytic reactor can then be cooled and sulfur condensed and removed in a fourth position sulfur condenser and the cooled effluent gas therefrom can then be provided to a fourth position Claus catalytic reaction zone which can have an inlet temperature in the range from about 160 to about 330F preferably in the range of about 250 to about 330F and most preferably having an inlet temperature of about 260F but an effluent temperature of, for example, only about 266F due to the low residual sulfur content of the process gas stream entering the fourth position reactor.
It will be appreciated from the exemplary temperature rises set forth above that most of the low temperature Claus cata-lytic reaction in accordance with a preferred embodiment of the invention occurs in the third position Claus catalytic reactor and that the rate of sulfur deposition can therefore be very low in the fourth position Claus catalytic reactor.
According to a preferred embodiment of the inven-tion, the second position Claus catalytic reactor can be regenerated during two high temperature periods, the first period being conducted at a lower than usual regeneration effluent temperature, for example, in the range of about 425 to about 550F, most preferably at about 500-525F, and a second period having an effluent temperature preferably in the range of about 550 to about 650F, p~eferably from about 575 to 600F. It will be appreciated by those skilled in the art that the usual phases of regeneration will occur during ~3~3~
these two periods. These phases are outlined briefly as follows. First occurs initial hea~ing of the catalyst to the plateau temperature. Then the temperature remains essen tially constant for a period of time as most of the sulfur deposited on the catalyst is vaporized from the catalyst.
The third phase of regeneration is the final temperature rise. ~hus, heat-up and plateau phases will typically occur during the lower temperature period, and the final tempera ture rise will occur during the high temperature period. As indicated, after the low temperature regeneration period, the inlet temperature to the second position Claus catalytic reactor can be increased and held there until the reactor configuration is changed. The higher temperature can prefer-ably be achieved by bypassing more of the first position Claus catalytic reactor effluent around the second position condenser and directly to the second position Claus catalytic reactor. The purpose of this higher temperature period of regeneration is to desorb additional sulfur from the catalyst to prepare the reactor for adsorption. Thus, with a given sulfur concentration in the vapor, increasing the temperature causes the residual sulfur loading to decrease. Thus, by regenerating during a second period at a high temperature, a lower residual sulfur loading can be accomplished; then by preconditioning in a nonfinal position as hereinafter described, residual sulfur loading on the catalyst can be further lowered and a temporary increase in emissions during final cooling of a freshly regenerated reactor in the final position can be reduced or eliminated; and then by operating the freshly regenerated and preconditioned reactor in the fourth position at a low temperature, the equilibrium concen-tration of sulfur in the vapor after it traverses the cata-lyst bed of the fourth position Claus catalytic reactor will be very low thus increasing the overall sulfur recovery effi-ciency to about 99.5~ overall.
In accordance with a preferred aspect of the inven-tion, after completion of the high temperature regeneration of the reactor in the second position, it is desirable to precondition the catalyst befGre switching the freshly regen-~3~
erated second position Claus catalytic reactor into the fourth position for adsorption-type operation. If the reac-tors were to be switched without preconditioning the catalyst in the second position Claus catalytic reactor, then immedi-ately after switching the catalyst in the freshly regenerated reactor would still have a high temperature/ for example, about 625F and, for example, the water content of the feed gas could react with the sulfur still adsorbed on the cata-lyst and could form hydrogen sulfide and sulfur dioxide by the reverse Claus reaction which would flow clirectly into the tail gas line. The resulting increase in sulfur emissions, although temporary, can be significant in their effect on the overall sulfur recovery efficiency, and can be substantially reduced or prevented by preconditioning the freshly regener-ated second position Claus catalytic reactor as hereinafter described in detail prior to moving it into the fourth posi-tion. Two procedures for preconditioning the freshly regen-erated second position Claus catalytic reactor prior to switching into the fourth position will be discussed. Others methods of preconditioning will, of course, be apparent to persons skilled in this art area in accordance with the ins-tant invention.
In accordance with a specific aspect of the inven-tion, preconditioning of the second position Claus catalytic reactor can be efEected by introducing a cold stream ther-einto, the cold stream preferably having an inlet temperature effective for condensing sulfur on at least a portion of the catalyst and passing the resulting stream in contact with a remaining substantial portion of the catalyst for a period of time effective to remove additional residual sulfur deposited on the catalyst therefrom and, preferably, to achieve some cooling of the catalyst. Alternatively, the preconditioning can be effected by passing a stream lean in sulfur and sulfur compounds in contact with at least a substantial portion of the catalyst and further reducing the residual sulfur loading level before switching into the final position~ The addi-tional sulfur removed from the regenerated catalyst can then react in the fourth position reactor and will not appear as ~3~
an increase in sulfur emissions. Thus, preferably the cold stream will have a temperature below about 330~, preferably in the range of about 160 to about 330F and most preferably in the range of about 250 to about 330F, since a stream having this temperature range is readily available in the proce~s and avoids problems due to sulfur solidification and water condensation which can occur at lower temperatures if a process stream is utilized. The preconditioning period can be continued for a period effective to eliminate or signifi-cantly reduce the temporary rise in sulfur emissions which otherwise would occur after switching the freshly regenerated Claus catalytic reaction zone into the final position. The minimum period of time can be readily determined by the person skilled in the art by observing the operation of the plant. Thus, the operator can observe emissions from the plant in accordance with the invention, for example, with a Continuous Stack Emissions Monitor (CSEM), determine the occurrence and time frame of the temporary increase in emis-sions occurring when a hot, freshly regenerated reactor is switched into a final position, and can increase the precon-ditioning time until the temporary increase has been signifi-cantly ameliorated, for example, reduced by a factor of about 10~ or more, preferably by a factor of about 50% or more, and most preferably by a factor of about ~0% or more. Based upon our investigations, it appears that generally a relatively short period of time will be effective, for example, on the order of a few hours, preferably on the order of one or two hours or less. Broadly, the period can range from a few minutes to a few hours; preferably the preconditioning period will not exceed about 25~ of the period of time ordinarily required for adsorption~type operation of a reactor. It will be appreciated by the person skilled in the art that most cooling of a reactor will occur after switching into the fourth ~final) position concurrently with adsorption-type operation.
In accordance with one aspect of the invention, preconditioning of the second position freshly regenerated Claus catalytic reactor can be accomplished by leaving all ~3~33~
switching valves in the regenerating position as hereinafter described in more detail, and reducing the temperature of the feed gas to the second position Claus catalytic reactor. In accordance with a second aspect of the invention, precondi-tioning of the second position freshly regenerated Claus catalytic reactor can be achieved by temporarily rotating the reactors so that the freshly regenerated Claus catalytic reactor assumes the position it occupied prior to regenera-tion, that is, rotating the reactor to the third position, for a brief period of preconditioning in accordance with the invention, the time period being effective for reducing the residual sulfur loading of at least a substantial portion of the catalyst, and then rotating the preconditioned reactor forward into the fourth position where adsorption continues first in the Eourth position and then after switching modes in the third position prior to regeneration in the second position in accordance with the invention. During the brief preconditioning period the reactor in the third position can receive low temperature effluenk gas from the reactor which previously was in the fourth position but now is temporarily in the second position.
Thus, in accordance with a first preconditioning method, the reheat gas flow from the first position Claus catalytic reactor to the second position Claus catalytic reactor can be eliminated and the temperature of the feed gas to the second position Claus catalytic reactor can be reduced by cooling in the second position condenser to less than ~bout, for example, 300F which can precondition the second position reactor from, for example, about 625F to a lower temperature, for example, about 400F in a few hours. How-ever, because the regenerating gas is relatively rich in sulfur species, the catalyst bed of the freshly regenerated reactor can have a slightly higher residual sulfur loading than will occur with a second preconditioning method herein-after described.
In accordance with a second preconditioning methodl following regeneration of the second position Claus catalytic reactor, the reactor can be switched into the position it ?3~2~
~ 14-occupied prior to regeneration~ that is, into the third position. ~uring the preconditioning stepl regeneration gas is no longer needed for the second position reactor, conse-quently reheat gas to the second position Claus catalytic reactor can be discontinued. During preconditioning, the effluent from the second position Claus catalytic reactor and the third position condenser can be provided to the third position Claus catalytic reactor at a low temperature, for example, as low as about 252F and can precondition the third position reactor at the maximum possible rateO During pre~
conditioning, the effluent from the second position reactor can then flow on to the third position, fourth position, and the tail gas line. Thus, the temporary increase in sulfur emissions which can occur during cooling of a freshly regen-erated reactor can be remo~ed by a downstream reactor prior to the freshly regenerated reactor belng switched into the final position. This preconditioning method can result in slightly faster preconditioning of the freshly regenerated reactor temporarily in the third position than the first pre-conditioning method and can moreover decrease the residual loading level because the preconditioning is being effected by a relatively low sulur content gas. However, the hourly emissions rate can increase slightly because the fourth posi-tion reactor during the coolin~ phase can be at a somewhat higher temperature, for example, at about 355F, instead of at about 266F as is preferred during normal operation for sulfur recovery.
When a four Claus catalytic reaction zone plant is operated in accordance with the invention, the overall recovery of sulfur can be about 99.5%. The cycle time can be varied depending upon the sulfur loading on the catalyst beds in the third and fourth position reactors. The minimum time between reactor rotation will be set by the required time to regenerate the bed which, can be, for example, about 9 hours.
The maximum time can be determined by the maximum loading allowed for the third position (first adsorption) reactor.
For an 18-hour period between rotation, or 54-hour full cycle, the maximum loading on the catalyst in the third posi-~L3~;?3~ '"~
tion can be, for example, about 0.66 lbs sulfur/lb catalyst and about 0.15 lb/lb for the fourth position Claus catalytic reactor. Calculation and determination of loading rates, cycle times, and the like can be readily determined by per-sons skilled in this art area in view of the instant specifi-cation and claims~
The invention will be further understood and appre-ciated by the following detailed description of the drawings.
DETAILED DESCRIPTION OF THE DRAW~NGS
Figures 1, 2, and 3, respectively, illustrate sche matically three modes of operation in accordance with the invention as follows: a first mode (Mode A) in which the reactor flow sequence is Rl, R2, R3, and R4 wherein R2 is on regeneration and R3 and R4 are on adsorption; a second mode (Mode B) in which the reactor flow sequence is Rl, R3, R~, R2 wherein reactor R3 is on regeneration and reactors R4 and R2 are on adsorption; and a third mode (Mode C) in which the reactor flow sequence is Rl, ~4, R2, and R3 and wherein reactor R4 i5 on regeneration and reactors R2 and R3 are on adsorption.
Referring now in particular to Figure 1, Figure 1 represents schematically a first mode (Mode A) of the process according to the invention utilizing a Claus thermal reaction zone, five condensers, Cl, C2, C3, C4, and C5, and fou~ reac-tors, Rl, R2, R3 and R4, operated in series for the recovery of sulfur from an acid gas feed stream, the reactors R2, R3, and R4 being rotatable successively through the second, fourth, and third positions. Thus, in Figure 1, valves 52V
in line 52, 92V in line 92, 90V in line 90 and 98V in line 9B
are shown open; and valves 64V in line 64, 78V in line 78, 94V in line 94, 88V in line 88 and 96V in line 96 are shown closed.
Referring now to Figure 1 in detail, an acid gas stream comprising hydrogen sulfide can be introduced by line 10 into a Claus furnace (Claus thermal reaction zone) 14, as illustrated a muffle-tube furnace having an integrally associated waste heat boiler 16. An oxidant, for example, oxygen contained in air can be introduced by line 12 into the ~3~3~2~
furnace. In -the furnace, the hydrogen sulfide can be combusted in the presence of the oxygen to produce a hot effluent gas stream comprising hydrogen sulfide, sulfur dioxide, and elemental sulfur, as well as other compounds.
The furnace (thermal reaction zone) effluent stream can be provided to the waste heat boiler 16 for cooling and recovery of heat. A portion of the effluent can be cooled by multiple passes, for example, by a two pass sequence, in the waste heat boiler 16 to a temperature in the range of about 550 to about 650F and can be removed by line 18 to first position condenser 20 (Cl) where the stream can be further cooled to below, for example, about 260F and liquid sulfur can be removed via line 22. A second portion of the effluent from the Claus thermal reaction zone 14 can be removed from the waste heat boiler 16 after, for example, a single pass ther-ethrough at a temperature in the range of about 800 to about 1200F and can be passed through ]ine 2~ and associated valve 24V and combined with the effluent from the first position condenser 20 to form a stream in lines 30 and 32 having an inlet temperature in the range of about 400 to about 500F
for introduction into the first position Claus catalytic reaction zone 36 (Rl) having an effluent temperature most preferably in the range of about 575-625F. The amount of bypass reheat provided by line 24 can be controlled by uti~
lizin~ a temperature controlled valve 24V, the valve being controllable by a temperature dependent signal from line 30 as shown schematically by reference numeral 34, the valve being illustrated as partly open.
In the first position Claus catalytic reaction zone 36, hydrogen sulfide and sulfur dioxide remaining in the effiuent stream from the first position condenser Cl can be further reacted in the presence of a Claus catalyst for facilitating the Claus reaction preferably at a temperature in the range of from about 550 to about 650F and elemental sulfur can be produced which can be removed continuously from the first position reactor Rl in the vapor phase, for example, by line 42 and can be provided to a second position sulfur condenser 44 (C2) where the effluent stream can be cooled and sulfur removed by line 46.
~3~33~
The cooled sulfur-denuded stream can then be removed from the second position condenser C2 by line 48 and can be reheated by utilizing a portion of first position Claus catalytic reaction zone effluent via line 38 and asso-ciated valve 38V shown partly open, to produce in line 50 a feed to the second position Claus catalytic reaction zone having a temperature as in the ranges set forth above for regeneration during the second position operation. It will be appreciated that during the regeneration period, concur-rently the forward Claus reaction is being catalyzed and ele-mental sulfur is formed and removed in the vapor phase from the second position reactor. In the illustrated embodiment of FIGURE 1, valve 52V is shown as open and therefore the reactor 54 (R2) occupies the second position, the reactor 68 ~R3) occupies the third position, and the reactor 80 (R4) occupies the fourth position. Thus r in accordance with this configuration of the equipment, the effluent from the first position Claus catalytic reactor can be introduced via line 52 and associated valve 52V into the second position Claus catalytic reactor which in this configuration comprises reactor 54 (R2). The reactor in the second position has in accordance with the invention previously been rotated for the recovery of sulfur successively through the fourth position and the third position prior to being rotated into the second position. The inlet gas in line 52 can be adjusted to tem-perature ranges in accordance with certain aspects of the invention by which regeneration is accomplished at different temperatures. Thus, during a first period of regeneration, the temperature in line 52 to reactor 54 can be in the range of about 425 to about 550F whereas in the second period of regeneration, the temperature can be in the range of from about 550 to about 650F. The effluent from the reactor in the second position, in the illustrated configuration of Figure 1, from reactor 54 (R2) can then be removed by line 56 to third position condenser 58 (C3) where sulfur can be con-densed and removed by line 60.
The cooled sulfur-denuded effluent stream from the third position condenser 58 (C3) can then be introduced via ~3`1~3~
line 62 and line 92 having associated valve 92V into the third position Claus catalytic reactor, in the illustrated configuration, reactor 68 (R3) at a temperature ir. the range of from about 160 to about 330F, preferably at about 320F.
In the third position Claus catalytic reactor, the Claus con-version can be accomplished under conditions of temperaturel pressure, and composition such that the preponderance of the formed sulfur is deposited on the catalyst. The effluent stream from the third position Claus catalytic reaction zone can then be removed, for example, by line 70 to fourth con-denser 72 (C4) from which sulfur can be removed by line 74.
The resulting sulfur-denuded effluent stream from the fourth position condenser 72 (C4) can then be provided to the fourth position Claus catalytic reactor, in the illus-trated configuration, reactor 80 (R4) via line 76, line 90, and associated valve 90V for further conversion and removal of elemental sulfur by depositing on the catalyst in the fourth position Claus catalytic reactor. The effluent stream from the fourth position Claus catalytic reactor can then be removed by line 82 and provided to fifth position condenser 84 (C5) where elemental sulfur can be removed (if present, for example, when the reactor R4 is in the second or the third position - Cf. Figures 2 and 3, respectively), for example, by line 86. The tail gas exiting the fifth position condenser can then be provided to an incinerator by being passed through line 98 having associated valve 98V to line 100 and then to an incinerator (not shown).
Referring now in particular to Figure 2, Figure 2 represents schematically a second mode ~Mode B) of the pro-cess according to the invention wherein valves 64V, 9~V, 88V
and 94V are shown open; and valves 52V, 92V, 78V, 96V and 98V
are shown closed. The other reference numerals of Figure 2 are as set forth in the discussion of Figure 1 and will not be here repeated. It will be appreciated by observing the flow sequence of the configuration of Figure 2 that the reactor sequence will be Rl, R3~ R4, R2. It will be further appreciated that the first, second, third, fourth, and fifth position condensers will be Cl, C2, C4, C5 and C3, respec-tively.
~3~3E32~
Referring now to Figure 3 in particular, Figure 3 represents a third mod~ ~Mode C) according to the invention wherein the valving is such that the reactor flow sequence is Rl, R4, R2, and R3. Thus, valves 7~V, 88V, 92V, and 96V are shown open; and valves 52V, 6~V, 90V, 94V, and 98V are shown closed. The other reference numerals of Figure 3 are as set forth in Figure 1 and will not be here repeated. Similarly, it will be appreciated that the first position, second posi-tion, third position, fourth position, and fifth position condensers are respectively Cl, C2, C5, C3~ and C4.
By referring to the drawings of Figures 1, 2, and 3, it will be noted that the normal rotation sequence for the recovery of sulfur in accordance with the invention will be from Mode A (Figure 1) to Mode B (Figure 2) to Mode C
~Figure 3). In accordance with one method of preconditioning according to the invention, this rotation sequence can be departed from temporarily to permit preconditioning of the freshly regenerated reactor which has been regenerated in the second position. In accordance with this aspect of the invention, the rotational sequence would be as follows:
Mode A (regenerate R2), Mode C transition (precondition R2), Mode B (regenerate R3), Mode A transition (precondition R3), Mode C (regenerate R4), and Mode B transition (precondition R4) r then return to Mode A (regenerate R2) and so forth.
Typically, the time required for a preconditioning mode will be on the order of a few hours or less, for example, on the order of about 1 or ~ hours or less. It will be appreciated that this period of time will not be long enough to reduce the temperature of the preconditloned reactor to an ultimate value desired for fourth position adsorption-type operation;
calculations can, however, be made by one skilled in the art which will show that the regeneration mode just completed can reduce the residual sulfur loading of the catalyst to a low level so that a relatively short preconditioning time period can result in removing substantially all o~ the remaining deposited residual sulfur as well as providing adequate ini-tial preconditioning of the catalyst.
~L3~ 2~3 It will be evident from the above that regeneration of a reactor in the second position (R2 of Mode A) can reduce the residual sulfur loading on the catalyst to a low level, and that then the loading will further be reduced during the preconditioning step in which the same reactor (R2) can operate in the third position. During successive modes, B
and C, when the same reactor R2 operates in the fourth posi-tion and then in the third position, the sulfur loading grad-ually increases~ slowly during Mode B, then rnore rapidly during Mode C. Prior to the time when the sulfur loading on the catalyst while operating in the third position Claus catalytic reactor exceeds a predetermined maximum allowable level, preferably less than that at which the instantaneous recovery of sulfur starts to drop, the reactor in the second position can be cooled in accordance with either of the two methods described above. Thus, referring to the Figures 1, 2, and 3, the valve 38V can be closed to eliminate or reduce reheat gas flow from the effluent from the first position Claus catalytic reactor to the inlet to the second position Claus catalytic reactor and, simultaneously, if desired, steam generation in the second position condenser can be reduced, for example, from about 60 psig to about 15 psig.
This can reduce the temperature of the feed gas to the second position reactor to less than about, for example, 300F and can cool the second position reactor from about 625F to a lower temperature, for example, about 400F. Alternatively, the other preconditloning method described above can be used.
It will be appreciated that there has been provided an improved four Claus catalytic reaction zone process for the recovery of sulfur which is capable of recoveries on the order of about 99.5%. It will be further appreciated that the invention is not limited by the preferred embodiment described herein but will also be applicable to other four Claus catalytic reactor plants for the recovery of sulfur in which a reactor can be regenerated in the second position and can be rotated for adsorption-type operation successively into the fourth (final) position and then into the third position prior to regeneration. The invention therefore ~3i~
should not be considered limited by the detailed description of the preferred embodiment set forth herein as required, but by the claims appended hereto.
IMPROVED FOUR CATALYTIC REACTOR EXTENDED
CLAUS PROCESS
The invention relates to gas processingO In a particular aspect, the invention relates to processing gases containing hydrogen sulfide for the recovery of ele-mental sulfur. In a further aspect, the invention relates 15 to such a process utilizing the Claus reaction in a Claus process sulfur recovery plant comprising a Claus thermal reaction zone and two or more Claus catalytic reaction zones, at least one of the two or more Claus catalytic reaction zones being operated periodically under condi-20 tions effective for forming and depositing elemental ~i sulfur on the catalyst.
FIELD OF THE INVENTION
.
The conventional Claus process for sulfurrecovery from hydrogen sulfide containing gas is widely 25 practiced and accounts for a major portion of total world-wide sulfur production. Such Claus processes utilize the Claus reaction for the recovery of sulfur:
H2S + l/2 SO2 ~ 3/2 S + ~ o Typical Claus process sulfur recovery plants can include a Claus thermal reaction zone or furnace in which the hydrogen sulfide containing gas can be combusted in the pres-ence of an oxidant such as oxygen or air to form an effluent stream comprising unreacted hydrogen sulfide, sulfur dioxide, and formed elemental sulfur, as well as other compounds~
This effluent stream can then be in-troduced into a series of \
~3~,P3 one, two, or more Claus catalytic reaction zones typically operated so that the resulting formed sulfur is continuously removed in the vapor phase, that is, the reaction zones are operated above the temperature at which significant sulfur deposition on the catalyst can occur. The elemental sulfur can then be removed from the Claus catalytic reaction zone effluent streams by condensation at appropriate points in the process. Recovery of sulfur from a hydrogen sulfide con-taining stream can be as high as about 96% for two Claus catalytic reaction zone plants or about 97~ for three Claus catalytic reaction zone plants.
In many instances, however, this level of recovery will be inadequate either because of economic or because of environmental considerations. To meet the higher levels which can be required, a number of treatment processes have been developed to increase the level of overall sulfur recovery. Certain of these processes involve extensions of the Claus reaction under conditions whlch favor additional removal of hydrogen sulfide from the gas stream being pro-cessed. Thus, the residual level of sulfur compounds can be significantly reduced by operating one or more of the Claus catalytic reaction zones under conditions of temperature, pressure, and composition such that the preponderance of formed elemental sulfur is deposited on the catalyst. Simi-larly, the Claus reaction in one or more Claus reactors can likewise be driven ln the direction of removal of hydrogen sulfide and sulfur dioxide from the process stream by removing water from the stream prior to carrying out the Claus reaction in said one or more Claus reactors.
It will be appreciated by those familiar with this art area that other processes not involving an extension of the Claus reaction are also available and have been utilized for the further removal of hydrogen sulfide and other sulfur compounds from process gas streams. These other processes include such as the SCOT (Shell Claus Off-gas Treating)l, BSRP
(Beavon Sulfur Re~overy Process), the Beavon-Stretford Pro-cess, and the like. However r to the extent that it is eco-nomically and technically feasible, use of the Claus reaction ~3~33~
either directly or of the extended Claus reaction is preferred for reasons of simplicity~ ease oE operation and maintenance, and other similar reasons.
SWMMARY OF THE INVENTION
According to the invention, there is provided a process for the recovery of sulfur from an acid gas stream comprising hydrogen sulfide in a Claus process sulfur recovery plant. ~he Claus process sulfur recovery plant can comprise a Claus thermal reaction zone and four Claus cata-lytic reaction zones Rl, R2, R3, and R4 and at least four sulfur condensers Cl~ C2, C3, and C~. The process comprises passing the acid gas stream successively through the Claus thermal reaction zone and then successively through a first position Claus catalytic reaction zone, a second position Claus catalytic reaction zone, a third position Claus cata-lytic reaction zone, and a fourth position Claus catalytic reaction zone, at least the third and fourth position Claus catalytic reaction zones being operated under conditions of temperaturer pressure, and composition for depositing a pre-ponderance of the sulfur on the catalyst therein. The pro-cess further comprises rotating at least three of the reac-tors Rl, R2, R3, and R4 through the third and fourth positions operated under conditions effective for depositing the preponderance of the sulfur on the catalyst and periodi-cally regenerating such reactors with a process gas stream derived from the sulfur recovery process upstream of the second position Claus catalytic reaction zone. Following regeneration, the freshly regenerated reactors can be precon-ditioned by introducing thereinto a cold stream having an inlet temperature effective for condensing sulfur on at least a portion of the catalyst and passing the resulting stream through at least a remaining substantial portion of the cata-lyst prior to placing the freshly regenerated reactor in the fourth position operated under conditions effective for depo-siting a preponderance of the formed sulfur on the catalyst therein. In another aspect of the invention, the freshly regenerated second position Claus catalytic reaction zone can be preconditioned by passing a stream lean in sulfur and ~3~3~
sulfur compounds in contact with at least a substantial portion of the catalyst in the freshly regenerated second position Claus catalytic reaction zone for a period of time effective for reducing an increase in sulfur emissions occur-ring where a hot, freshly regenerated reactor is switched into a final position of a series of Claus catalytic reaction zones without preconditioning prior to switching the thus-preconditioned Claus catalytic reaction zone into the fourth (final) position.
In accordance with one aspect of the invention there is provided such a process for the recovery of sulfur from a feed stream comprising hydrogen sulfide by passing the feed stream successively through a Claus thermal reaction zone, a Claus catalytic reaction zone in a first position, a Claus catalytic reaction zone in a second pOsitiOIl~ a Claus catalytic reaction zone in a third position, and a Claus catalytic reaction zone in a fourth position, the Claus cata-lytic reaction zones in the third and fourth positions being operated under conditions effective for depositing the pre-ponderance of the formed elemental sulfur on the catalyst therein. In accordance with this aspect of the invention, the Claus catalytic reaction zone in the first position can be a dedicated reaction zone which is operated at all times as a high temperature Claus catalytic converter under condi-tions of temperature and pressure and composition such that the formed elemental sulfur is continuously removed from the first position Claus catalytic reaction zone in the vapor phase~ According to this aspect of the invention, the Claus catalytic reaction zones in the second, third, and fourth positions are rotated successively and sequentially for the recovery of sulfur through the second positionJ the fourth position, the third position, and back to the second posi-tion, subject to in accordance with one method of the inven-tion a temporary departure from this sequence for purposes of preconditioning the freshly regenerated second position Claus catalytic reaction zone by introducing a cold stream ther-einto having a temperature effective for condensing sulfur on at least a portion of the catalyst and passing the resulting ~3~3~
stream in contact with a remaining substantial portion of the catalyst or b~ passing a stream lean in sulfur and sulfur compounds, at least in comparison with the stream used for regeneration, in contact with a substantial portion of the catalyst in the hot, freshly regenerated catalytic reaction zone and reducing an increase in sulfur emissions occurring where a ~ot, freshly regenerated reactor is switched without preconditioning into a final position of a series of Claus catalytic reaction zones prior to switching the thus-preconditioned freshly regenerated catalytic reaction zone into the fourth position. As will be appreciated from the above, the freshly regenerated Claus catalytic reaction zone after preconditioning will be rotated into the fourth posi-tion operated as described under adsorption conditions thereby placing the freshly regenerated Claus catalytic reac-tion ~one which will have a substantial portion of the cata-lyst therein having a very low residual sulfur loading in the final adsorption position thus favoring the removal of hydrogen sulfide and sulfur dioxide remaining in the process gas stream to a very low level.
Further in accordance with this aspect of the invention, it will be appreciated that a Claus catalytic reaction zone previously loaded with sulfur by successive operation in the fourth and then in the third position, can be rotated into the second position for regeneration by the effluent gas stream from the first position Claus catalytic reaction zone. In this position, the laden sulfur can be removed from the catalyst by heating with the effluent from the first position Claus catalytic reaction zone and concur-rently a high temperature, Claus catalytic reaction is facil-itated in the second position catalytic reaction zone, the reactor in the second position thus performing concurrently regeneration and Claus sulfur recovery functions.
In accordance with another aspect of the invention, regeneration of a reactor in the second position can be effected at a temperature in the ranye of about 425 to about 550F and during a second period at a temperature in the range of about 550 to about 650F prior to preconditioning.
~3~
In accordance with further aspects of the invention, after regeneration, the freshly regenerated reac-tors can be preconditioned prior to being rotated into the fourth position either by reducing the temperature o~ the feed gas to the freshly regenerated reactor, or by going tem-porarily to a previous configuration of reactors as will be discussed below in more detail, to effect preconditioning of the freshly regenerated reactor prior to rotation into the fourth position.
BR~EF D~SCRIPTION OF THE DRAWINGS
The invention will be further understood and appre-ciated from the following detailed description and the draw-ings in which:
Figure 1 illustrates schematically a first mode (Mode A) of the process according to the instant invention;
E'igure 2 illustrates schematically a second mode (Mode ~) of the process according to the instant invention; and Figure 3 illustrates schematically a third mode (Mode C) of the process according to the instant invention.
The invention will be further understood and appre-ciated from the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, there is provided a process for the recovery of sulfur from a feed stream com-prising hydrogen sulfide which utilizes a Claus process sulfur recovery plant comprising a thermal reaction zone and four Claus catalytic reaction zones, Rl, R2, R3, and R4.
According to a pre~erred embodiment, the Claus process sulfur recovery plant can have one reactor, Rl, which always func-tions in the first position as a high temperature, Claus catalytic reaction zone from which elemental sulfur is con-tinuously being removed in the vapor phase, and three other reactors, R2, R3, and R4, which can be rotated between second position, third position, and fourth position operation, the reactors in the third and fourth positions being operated ~ ~q ~
under conditions effective for forming and depositing the preponderance of elemental sulfur on the surface of the cata-lyst.
As used in the instant specification and claims, the symbols Rl, R2, etc., Cl, C2, etc.~ shall refer to spe-cific pieces of equipment whereas the notation first position reactor, second position reactor, etc~, and first position condenser, second position condenser, shall refer to equip-ment position or location relative to the acid gas stream being processed. Thus, a first position reactor is upstream of a second position reactor, etc., and a first position con-denser is upstream of a second position condenser, etc. Fur-ther, a first position condenser will for purposes of this specification refer to a condenser upstream of a first posi-tion reactor, a second position condenser shall refer to a condenser upstream of a second reactor, and so forth.
Salient features of the process according to the invention are the following. (1) When a reactor previously laden with sulfur by being rotated successively through the fourth and third positions is being regenerated, it is simul-taneously operating as a second stage Claus catalytic reac-tion zone, preferably with the temperature being higher than normal for a second stage Claus catalytic reaction zone, but in accordance with one aspect of the invention, lower during at least part of regeneration than is conventional during regeneration of sulfur-laden catalyst. (2) The regeneration period can preferably consist of two high temperature per-iods, the first period being conducted at an effluent temper-ature in the range of about 425 to about 550F, most prefer-ably at a temperature in the range of about 500 to about 525F, and the second period being conducted at an effluent temperature in the range of about 550 to about 650F, prefer-ably 5~5 to 600F. (3) The reheat exchanger according to one aspect of the invention can be eliminated upstream of the second position reactor since hot effluent gas from the first position Claus catalytic reaction zone can be bypassed around the second condenser to reheat the feed to the second posi-tion ~laus catalytic reaction zoneO (~) There can be two ~L3~-J~
catalytic reaction zones operated in series at all times under conditions effective for depositing a preponderance of the formed sulfur on the catalyst, so overall recovery can remain high throughout the process. (5) Only nine switching valves are required, with only six of those being required to give positive shut-off.
The Claus thermal reaction zone which is utilized in accordance with the invented method can be any suitable Claus thermal reaction zone such as, for example, a muffle-tube furnace, a fire-tube furnace, and the like, which can be selected and designed in accordance with principles familiar to those skilled in this art area. Similarly, the Claus catalytic reaction zones can comprise any suitable vessel for containing catalyst facilitating the Claus reaction, whether in fixed-bed or fluid/moving bed format, and can be selected, sized, and designed in accordance with principles well estab-lished in this art area.
In accordance with a preferred embodiment of the invention, reactor Rl can be operated as a conventional first stage Claus reactor in the first position. Broadly, the tem-perature of reactor Rl can thus be in the range of from about above the sulfur condensation point to about 700F, prefer-ably in the range of ahout 550F to about 650F, most prefer-ably in the range of about 575F to about 625F~ ~f neces-sary, or appropriate, the temperature in the first Claus catalytic reaction zone can be maintained at a higher temper-ature, for example, at about 695F for maximum conversion of organic sulfur compounds to H2S while minimizing sulfidiza-tion of carbon steel. The efluent from the first position Claus catalytic reactor can be removed and provided to a second position condenser and can then be reheated, in accor-dance with a preferred embodiment of the invention, by a por-tion of the first position Claus catalytic reactor effluent gas, or by other means familiar to those skilled in this art area. The reheated effluent gas from the first position Claus catalytic reactor can then be provided to the second position Claus catalyti~ reactor which can be operated con-currently for high temperature Claus conversion and simulta-~3~33~
g neously be undergoing catalyst regeneration, the secondposition Claus catalytic reactor previously having been rotated successively for the recovery of sulfur through the fourth and third positions. The effluent stream from the second position Claus catalytic reactor can then be cooled in a third position condenser and the gas can flow without reheating to a third position Claus catalytic reactor which can be operated as a Claus adsorption-type reactor with, preferably, a slightly elevated temperature, for example, 320F inlet and 355F outlet, as compared with conventional adsorption-type operation. Conventional operating tempera-tures can, of course, also be employed. The effluent from the third position Claus catalytic reactor can then be cooled and sulfur condensed and removed in a fourth position sulfur condenser and the cooled effluent gas therefrom can then be provided to a fourth position Claus catalytic reaction zone which can have an inlet temperature in the range from about 160 to about 330F preferably in the range of about 250 to about 330F and most preferably having an inlet temperature of about 260F but an effluent temperature of, for example, only about 266F due to the low residual sulfur content of the process gas stream entering the fourth position reactor.
It will be appreciated from the exemplary temperature rises set forth above that most of the low temperature Claus cata-lytic reaction in accordance with a preferred embodiment of the invention occurs in the third position Claus catalytic reactor and that the rate of sulfur deposition can therefore be very low in the fourth position Claus catalytic reactor.
According to a preferred embodiment of the inven-tion, the second position Claus catalytic reactor can be regenerated during two high temperature periods, the first period being conducted at a lower than usual regeneration effluent temperature, for example, in the range of about 425 to about 550F, most preferably at about 500-525F, and a second period having an effluent temperature preferably in the range of about 550 to about 650F, p~eferably from about 575 to 600F. It will be appreciated by those skilled in the art that the usual phases of regeneration will occur during ~3~3~
these two periods. These phases are outlined briefly as follows. First occurs initial hea~ing of the catalyst to the plateau temperature. Then the temperature remains essen tially constant for a period of time as most of the sulfur deposited on the catalyst is vaporized from the catalyst.
The third phase of regeneration is the final temperature rise. ~hus, heat-up and plateau phases will typically occur during the lower temperature period, and the final tempera ture rise will occur during the high temperature period. As indicated, after the low temperature regeneration period, the inlet temperature to the second position Claus catalytic reactor can be increased and held there until the reactor configuration is changed. The higher temperature can prefer-ably be achieved by bypassing more of the first position Claus catalytic reactor effluent around the second position condenser and directly to the second position Claus catalytic reactor. The purpose of this higher temperature period of regeneration is to desorb additional sulfur from the catalyst to prepare the reactor for adsorption. Thus, with a given sulfur concentration in the vapor, increasing the temperature causes the residual sulfur loading to decrease. Thus, by regenerating during a second period at a high temperature, a lower residual sulfur loading can be accomplished; then by preconditioning in a nonfinal position as hereinafter described, residual sulfur loading on the catalyst can be further lowered and a temporary increase in emissions during final cooling of a freshly regenerated reactor in the final position can be reduced or eliminated; and then by operating the freshly regenerated and preconditioned reactor in the fourth position at a low temperature, the equilibrium concen-tration of sulfur in the vapor after it traverses the cata-lyst bed of the fourth position Claus catalytic reactor will be very low thus increasing the overall sulfur recovery effi-ciency to about 99.5~ overall.
In accordance with a preferred aspect of the inven-tion, after completion of the high temperature regeneration of the reactor in the second position, it is desirable to precondition the catalyst befGre switching the freshly regen-~3~
erated second position Claus catalytic reactor into the fourth position for adsorption-type operation. If the reac-tors were to be switched without preconditioning the catalyst in the second position Claus catalytic reactor, then immedi-ately after switching the catalyst in the freshly regenerated reactor would still have a high temperature/ for example, about 625F and, for example, the water content of the feed gas could react with the sulfur still adsorbed on the cata-lyst and could form hydrogen sulfide and sulfur dioxide by the reverse Claus reaction which would flow clirectly into the tail gas line. The resulting increase in sulfur emissions, although temporary, can be significant in their effect on the overall sulfur recovery efficiency, and can be substantially reduced or prevented by preconditioning the freshly regener-ated second position Claus catalytic reactor as hereinafter described in detail prior to moving it into the fourth posi-tion. Two procedures for preconditioning the freshly regen-erated second position Claus catalytic reactor prior to switching into the fourth position will be discussed. Others methods of preconditioning will, of course, be apparent to persons skilled in this art area in accordance with the ins-tant invention.
In accordance with a specific aspect of the inven-tion, preconditioning of the second position Claus catalytic reactor can be efEected by introducing a cold stream ther-einto, the cold stream preferably having an inlet temperature effective for condensing sulfur on at least a portion of the catalyst and passing the resulting stream in contact with a remaining substantial portion of the catalyst for a period of time effective to remove additional residual sulfur deposited on the catalyst therefrom and, preferably, to achieve some cooling of the catalyst. Alternatively, the preconditioning can be effected by passing a stream lean in sulfur and sulfur compounds in contact with at least a substantial portion of the catalyst and further reducing the residual sulfur loading level before switching into the final position~ The addi-tional sulfur removed from the regenerated catalyst can then react in the fourth position reactor and will not appear as ~3~
an increase in sulfur emissions. Thus, preferably the cold stream will have a temperature below about 330~, preferably in the range of about 160 to about 330F and most preferably in the range of about 250 to about 330F, since a stream having this temperature range is readily available in the proce~s and avoids problems due to sulfur solidification and water condensation which can occur at lower temperatures if a process stream is utilized. The preconditioning period can be continued for a period effective to eliminate or signifi-cantly reduce the temporary rise in sulfur emissions which otherwise would occur after switching the freshly regenerated Claus catalytic reaction zone into the final position. The minimum period of time can be readily determined by the person skilled in the art by observing the operation of the plant. Thus, the operator can observe emissions from the plant in accordance with the invention, for example, with a Continuous Stack Emissions Monitor (CSEM), determine the occurrence and time frame of the temporary increase in emis-sions occurring when a hot, freshly regenerated reactor is switched into a final position, and can increase the precon-ditioning time until the temporary increase has been signifi-cantly ameliorated, for example, reduced by a factor of about 10~ or more, preferably by a factor of about 50% or more, and most preferably by a factor of about ~0% or more. Based upon our investigations, it appears that generally a relatively short period of time will be effective, for example, on the order of a few hours, preferably on the order of one or two hours or less. Broadly, the period can range from a few minutes to a few hours; preferably the preconditioning period will not exceed about 25~ of the period of time ordinarily required for adsorption~type operation of a reactor. It will be appreciated by the person skilled in the art that most cooling of a reactor will occur after switching into the fourth ~final) position concurrently with adsorption-type operation.
In accordance with one aspect of the invention, preconditioning of the second position freshly regenerated Claus catalytic reactor can be accomplished by leaving all ~3~33~
switching valves in the regenerating position as hereinafter described in more detail, and reducing the temperature of the feed gas to the second position Claus catalytic reactor. In accordance with a second aspect of the invention, precondi-tioning of the second position freshly regenerated Claus catalytic reactor can be achieved by temporarily rotating the reactors so that the freshly regenerated Claus catalytic reactor assumes the position it occupied prior to regenera-tion, that is, rotating the reactor to the third position, for a brief period of preconditioning in accordance with the invention, the time period being effective for reducing the residual sulfur loading of at least a substantial portion of the catalyst, and then rotating the preconditioned reactor forward into the fourth position where adsorption continues first in the Eourth position and then after switching modes in the third position prior to regeneration in the second position in accordance with the invention. During the brief preconditioning period the reactor in the third position can receive low temperature effluenk gas from the reactor which previously was in the fourth position but now is temporarily in the second position.
Thus, in accordance with a first preconditioning method, the reheat gas flow from the first position Claus catalytic reactor to the second position Claus catalytic reactor can be eliminated and the temperature of the feed gas to the second position Claus catalytic reactor can be reduced by cooling in the second position condenser to less than ~bout, for example, 300F which can precondition the second position reactor from, for example, about 625F to a lower temperature, for example, about 400F in a few hours. How-ever, because the regenerating gas is relatively rich in sulfur species, the catalyst bed of the freshly regenerated reactor can have a slightly higher residual sulfur loading than will occur with a second preconditioning method herein-after described.
In accordance with a second preconditioning methodl following regeneration of the second position Claus catalytic reactor, the reactor can be switched into the position it ?3~2~
~ 14-occupied prior to regeneration~ that is, into the third position. ~uring the preconditioning stepl regeneration gas is no longer needed for the second position reactor, conse-quently reheat gas to the second position Claus catalytic reactor can be discontinued. During preconditioning, the effluent from the second position Claus catalytic reactor and the third position condenser can be provided to the third position Claus catalytic reactor at a low temperature, for example, as low as about 252F and can precondition the third position reactor at the maximum possible rateO During pre~
conditioning, the effluent from the second position reactor can then flow on to the third position, fourth position, and the tail gas line. Thus, the temporary increase in sulfur emissions which can occur during cooling of a freshly regen-erated reactor can be remo~ed by a downstream reactor prior to the freshly regenerated reactor belng switched into the final position. This preconditioning method can result in slightly faster preconditioning of the freshly regenerated reactor temporarily in the third position than the first pre-conditioning method and can moreover decrease the residual loading level because the preconditioning is being effected by a relatively low sulur content gas. However, the hourly emissions rate can increase slightly because the fourth posi-tion reactor during the coolin~ phase can be at a somewhat higher temperature, for example, at about 355F, instead of at about 266F as is preferred during normal operation for sulfur recovery.
When a four Claus catalytic reaction zone plant is operated in accordance with the invention, the overall recovery of sulfur can be about 99.5%. The cycle time can be varied depending upon the sulfur loading on the catalyst beds in the third and fourth position reactors. The minimum time between reactor rotation will be set by the required time to regenerate the bed which, can be, for example, about 9 hours.
The maximum time can be determined by the maximum loading allowed for the third position (first adsorption) reactor.
For an 18-hour period between rotation, or 54-hour full cycle, the maximum loading on the catalyst in the third posi-~L3~;?3~ '"~
tion can be, for example, about 0.66 lbs sulfur/lb catalyst and about 0.15 lb/lb for the fourth position Claus catalytic reactor. Calculation and determination of loading rates, cycle times, and the like can be readily determined by per-sons skilled in this art area in view of the instant specifi-cation and claims~
The invention will be further understood and appre-ciated by the following detailed description of the drawings.
DETAILED DESCRIPTION OF THE DRAW~NGS
Figures 1, 2, and 3, respectively, illustrate sche matically three modes of operation in accordance with the invention as follows: a first mode (Mode A) in which the reactor flow sequence is Rl, R2, R3, and R4 wherein R2 is on regeneration and R3 and R4 are on adsorption; a second mode (Mode B) in which the reactor flow sequence is Rl, R3, R~, R2 wherein reactor R3 is on regeneration and reactors R4 and R2 are on adsorption; and a third mode (Mode C) in which the reactor flow sequence is Rl, ~4, R2, and R3 and wherein reactor R4 i5 on regeneration and reactors R2 and R3 are on adsorption.
Referring now in particular to Figure 1, Figure 1 represents schematically a first mode (Mode A) of the process according to the invention utilizing a Claus thermal reaction zone, five condensers, Cl, C2, C3, C4, and C5, and fou~ reac-tors, Rl, R2, R3 and R4, operated in series for the recovery of sulfur from an acid gas feed stream, the reactors R2, R3, and R4 being rotatable successively through the second, fourth, and third positions. Thus, in Figure 1, valves 52V
in line 52, 92V in line 92, 90V in line 90 and 98V in line 9B
are shown open; and valves 64V in line 64, 78V in line 78, 94V in line 94, 88V in line 88 and 96V in line 96 are shown closed.
Referring now to Figure 1 in detail, an acid gas stream comprising hydrogen sulfide can be introduced by line 10 into a Claus furnace (Claus thermal reaction zone) 14, as illustrated a muffle-tube furnace having an integrally associated waste heat boiler 16. An oxidant, for example, oxygen contained in air can be introduced by line 12 into the ~3~3~2~
furnace. In -the furnace, the hydrogen sulfide can be combusted in the presence of the oxygen to produce a hot effluent gas stream comprising hydrogen sulfide, sulfur dioxide, and elemental sulfur, as well as other compounds.
The furnace (thermal reaction zone) effluent stream can be provided to the waste heat boiler 16 for cooling and recovery of heat. A portion of the effluent can be cooled by multiple passes, for example, by a two pass sequence, in the waste heat boiler 16 to a temperature in the range of about 550 to about 650F and can be removed by line 18 to first position condenser 20 (Cl) where the stream can be further cooled to below, for example, about 260F and liquid sulfur can be removed via line 22. A second portion of the effluent from the Claus thermal reaction zone 14 can be removed from the waste heat boiler 16 after, for example, a single pass ther-ethrough at a temperature in the range of about 800 to about 1200F and can be passed through ]ine 2~ and associated valve 24V and combined with the effluent from the first position condenser 20 to form a stream in lines 30 and 32 having an inlet temperature in the range of about 400 to about 500F
for introduction into the first position Claus catalytic reaction zone 36 (Rl) having an effluent temperature most preferably in the range of about 575-625F. The amount of bypass reheat provided by line 24 can be controlled by uti~
lizin~ a temperature controlled valve 24V, the valve being controllable by a temperature dependent signal from line 30 as shown schematically by reference numeral 34, the valve being illustrated as partly open.
In the first position Claus catalytic reaction zone 36, hydrogen sulfide and sulfur dioxide remaining in the effiuent stream from the first position condenser Cl can be further reacted in the presence of a Claus catalyst for facilitating the Claus reaction preferably at a temperature in the range of from about 550 to about 650F and elemental sulfur can be produced which can be removed continuously from the first position reactor Rl in the vapor phase, for example, by line 42 and can be provided to a second position sulfur condenser 44 (C2) where the effluent stream can be cooled and sulfur removed by line 46.
~3~33~
The cooled sulfur-denuded stream can then be removed from the second position condenser C2 by line 48 and can be reheated by utilizing a portion of first position Claus catalytic reaction zone effluent via line 38 and asso-ciated valve 38V shown partly open, to produce in line 50 a feed to the second position Claus catalytic reaction zone having a temperature as in the ranges set forth above for regeneration during the second position operation. It will be appreciated that during the regeneration period, concur-rently the forward Claus reaction is being catalyzed and ele-mental sulfur is formed and removed in the vapor phase from the second position reactor. In the illustrated embodiment of FIGURE 1, valve 52V is shown as open and therefore the reactor 54 (R2) occupies the second position, the reactor 68 ~R3) occupies the third position, and the reactor 80 (R4) occupies the fourth position. Thus r in accordance with this configuration of the equipment, the effluent from the first position Claus catalytic reactor can be introduced via line 52 and associated valve 52V into the second position Claus catalytic reactor which in this configuration comprises reactor 54 (R2). The reactor in the second position has in accordance with the invention previously been rotated for the recovery of sulfur successively through the fourth position and the third position prior to being rotated into the second position. The inlet gas in line 52 can be adjusted to tem-perature ranges in accordance with certain aspects of the invention by which regeneration is accomplished at different temperatures. Thus, during a first period of regeneration, the temperature in line 52 to reactor 54 can be in the range of about 425 to about 550F whereas in the second period of regeneration, the temperature can be in the range of from about 550 to about 650F. The effluent from the reactor in the second position, in the illustrated configuration of Figure 1, from reactor 54 (R2) can then be removed by line 56 to third position condenser 58 (C3) where sulfur can be con-densed and removed by line 60.
The cooled sulfur-denuded effluent stream from the third position condenser 58 (C3) can then be introduced via ~3`1~3~
line 62 and line 92 having associated valve 92V into the third position Claus catalytic reactor, in the illustrated configuration, reactor 68 (R3) at a temperature ir. the range of from about 160 to about 330F, preferably at about 320F.
In the third position Claus catalytic reactor, the Claus con-version can be accomplished under conditions of temperaturel pressure, and composition such that the preponderance of the formed sulfur is deposited on the catalyst. The effluent stream from the third position Claus catalytic reaction zone can then be removed, for example, by line 70 to fourth con-denser 72 (C4) from which sulfur can be removed by line 74.
The resulting sulfur-denuded effluent stream from the fourth position condenser 72 (C4) can then be provided to the fourth position Claus catalytic reactor, in the illus-trated configuration, reactor 80 (R4) via line 76, line 90, and associated valve 90V for further conversion and removal of elemental sulfur by depositing on the catalyst in the fourth position Claus catalytic reactor. The effluent stream from the fourth position Claus catalytic reactor can then be removed by line 82 and provided to fifth position condenser 84 (C5) where elemental sulfur can be removed (if present, for example, when the reactor R4 is in the second or the third position - Cf. Figures 2 and 3, respectively), for example, by line 86. The tail gas exiting the fifth position condenser can then be provided to an incinerator by being passed through line 98 having associated valve 98V to line 100 and then to an incinerator (not shown).
Referring now in particular to Figure 2, Figure 2 represents schematically a second mode ~Mode B) of the pro-cess according to the invention wherein valves 64V, 9~V, 88V
and 94V are shown open; and valves 52V, 92V, 78V, 96V and 98V
are shown closed. The other reference numerals of Figure 2 are as set forth in the discussion of Figure 1 and will not be here repeated. It will be appreciated by observing the flow sequence of the configuration of Figure 2 that the reactor sequence will be Rl, R3~ R4, R2. It will be further appreciated that the first, second, third, fourth, and fifth position condensers will be Cl, C2, C4, C5 and C3, respec-tively.
~3~3E32~
Referring now to Figure 3 in particular, Figure 3 represents a third mod~ ~Mode C) according to the invention wherein the valving is such that the reactor flow sequence is Rl, R4, R2, and R3. Thus, valves 7~V, 88V, 92V, and 96V are shown open; and valves 52V, 6~V, 90V, 94V, and 98V are shown closed. The other reference numerals of Figure 3 are as set forth in Figure 1 and will not be here repeated. Similarly, it will be appreciated that the first position, second posi-tion, third position, fourth position, and fifth position condensers are respectively Cl, C2, C5, C3~ and C4.
By referring to the drawings of Figures 1, 2, and 3, it will be noted that the normal rotation sequence for the recovery of sulfur in accordance with the invention will be from Mode A (Figure 1) to Mode B (Figure 2) to Mode C
~Figure 3). In accordance with one method of preconditioning according to the invention, this rotation sequence can be departed from temporarily to permit preconditioning of the freshly regenerated reactor which has been regenerated in the second position. In accordance with this aspect of the invention, the rotational sequence would be as follows:
Mode A (regenerate R2), Mode C transition (precondition R2), Mode B (regenerate R3), Mode A transition (precondition R3), Mode C (regenerate R4), and Mode B transition (precondition R4) r then return to Mode A (regenerate R2) and so forth.
Typically, the time required for a preconditioning mode will be on the order of a few hours or less, for example, on the order of about 1 or ~ hours or less. It will be appreciated that this period of time will not be long enough to reduce the temperature of the preconditloned reactor to an ultimate value desired for fourth position adsorption-type operation;
calculations can, however, be made by one skilled in the art which will show that the regeneration mode just completed can reduce the residual sulfur loading of the catalyst to a low level so that a relatively short preconditioning time period can result in removing substantially all o~ the remaining deposited residual sulfur as well as providing adequate ini-tial preconditioning of the catalyst.
~L3~ 2~3 It will be evident from the above that regeneration of a reactor in the second position (R2 of Mode A) can reduce the residual sulfur loading on the catalyst to a low level, and that then the loading will further be reduced during the preconditioning step in which the same reactor (R2) can operate in the third position. During successive modes, B
and C, when the same reactor R2 operates in the fourth posi-tion and then in the third position, the sulfur loading grad-ually increases~ slowly during Mode B, then rnore rapidly during Mode C. Prior to the time when the sulfur loading on the catalyst while operating in the third position Claus catalytic reactor exceeds a predetermined maximum allowable level, preferably less than that at which the instantaneous recovery of sulfur starts to drop, the reactor in the second position can be cooled in accordance with either of the two methods described above. Thus, referring to the Figures 1, 2, and 3, the valve 38V can be closed to eliminate or reduce reheat gas flow from the effluent from the first position Claus catalytic reactor to the inlet to the second position Claus catalytic reactor and, simultaneously, if desired, steam generation in the second position condenser can be reduced, for example, from about 60 psig to about 15 psig.
This can reduce the temperature of the feed gas to the second position reactor to less than about, for example, 300F and can cool the second position reactor from about 625F to a lower temperature, for example, about 400F. Alternatively, the other preconditloning method described above can be used.
It will be appreciated that there has been provided an improved four Claus catalytic reaction zone process for the recovery of sulfur which is capable of recoveries on the order of about 99.5%. It will be further appreciated that the invention is not limited by the preferred embodiment described herein but will also be applicable to other four Claus catalytic reactor plants for the recovery of sulfur in which a reactor can be regenerated in the second position and can be rotated for adsorption-type operation successively into the fourth (final) position and then into the third position prior to regeneration. The invention therefore ~3i~
should not be considered limited by the detailed description of the preferred embodiment set forth herein as required, but by the claims appended hereto.
Claims (11)
1. Process for the recovery of sulfur from an acid gas stream comprising hydrogen sulfide in a Claus proc-ess sulfur recovery plant wherein the Claus process sulfur recovery plant comprises a Claus thermal reaction zone and four Claus catalytic reaction zones R1, R2, R3 and R4, the process comprising passing the acid gas stream successively in series for the recovery of sulfur through the Claus thermal reaction zone and then through a first position Claus catalytic reaction zone, a second position Claus catalytic reaction zone, a third position Claus catalytic reaction zone, and a fourth position Claus catalytic reaction zone, both of the third and fourth position Claus catalytic reaction zones being operated at all times under conditions effective for depositing a preponderance of the formed sulfur on the catalyst, the process further comprising rotating at least three of the reactors R1, R2, R3, and R4 through the third and fourth positions operated under condi-tions for depositing a preponderance of the formed sulfur on the catalyst, periodically rotating reactors having cata-lysts laden with sulfur from the third position to the second position and from the fourth position to the third position and continuing depositing a preponder-ance of formed sulfur on the thus rotated reactors in the third position regenerating the thus rotated reactors while operating in the second position with a process gas stream derived from the sulfur recovery process upstream of the second position Claus catalytic reaction zone, preconditioning the freshly regenerated reac-tors after regeneration by introducing thereinto a cold stream and cooling a portion, but not all, of the cata-lyst therein, to a temperature effective for forming and depositing sulfur thereon, and passing the result-ing stream lean in sulfur and sulfur compounds in con-tact with the remaining portion of catalyst, and after preconditioning placing the freshly regenerated reactor in the fourth position for the recovery of sulfur and cooling the remaining portion of the thus-preconditioned freshly regenerated catalyst to a temperature effective for forming and depositing sulfur thereon and continuing operation in the fourth position under such conditions.
2. The Process of Claim 1 wherein:
preconditioning is effected by temporarily decreasing the temperature of the inlet gas stream to the freshly regenerated reactor to a temperature effec-tive for preconditioning.
preconditioning is effected by temporarily decreasing the temperature of the inlet gas stream to the freshly regenerated reactor to a temperature effec-tive for preconditioning.
3. The Process of Claim 1 wherein:
preconditioning is effected by utilizing con-denser effluent from a condenser positioned upstream of the freshly regenerated second position reactor and temporarily reducing the temperature of the inlet feed to the second position reactor.
preconditioning is effected by utilizing con-denser effluent from a condenser positioned upstream of the freshly regenerated second position reactor and temporarily reducing the temperature of the inlet feed to the second position reactor.
4. The Process of Claim 1 wherein:
preconditioning is effected by temporarily rotating the freshly regenerated reactor into the third position operated under conditions effective for depos-iting a preponderance of the formed sulfur on the cata-lyst temporarily for cooling prior to rotating the thus cooled reactor into the fourth position.
preconditioning is effected by temporarily rotating the freshly regenerated reactor into the third position operated under conditions effective for depos-iting a preponderance of the formed sulfur on the cata-lyst temporarily for cooling prior to rotating the thus cooled reactor into the fourth position.
5. The Process of Claim 1 wherein:
the plant comprises a Claus thermal reaction zone and four Claus catalytic reaction zones, R1, R2, R3, and R4, and the process comprises passing the acid gas stream successively in series for the recovery of sulfur through the Claus thermal reaction zone and a first position Claus catalytic reaction zone, a second position Claus catalytic reaction zone, a third posi-tion Claus catalytic reaction zone, and a fourth posi-tion Claus catalytic reaction zone, both of the third and fourth position Claus catalytic reaction zones being operated at all times under conditions effective for depositing a preponderance of the formed sulfur on the catalyst therein;
the process further comprising rotating reac-tors R2, R3, and R4 through the third and fourth posi-tions operated under conditions effective for depositing a preponderance of the formed sulfur on the catalyst, periodically rotating reactors having cata-lysts laden with sulfur from the third position to the second position and from the fourth position to the third position and continuing depositing a preponder-ance of formed sulfur on the -thus rotated reactors in the third position, regenerating the thus rotated reactors while operating in the second position with a gas stream derived from the sulfur recovery process upstream of the second position Claus catalytic reaction zone and downstream of the first position Claus catalytic reaction zone, preconditioning the freshly regenerated reac-tor after regeneration in the second position by intro-ducing thereinto a cold stream having a temperature effective for condensing sulfur on at least a portion of the catalyst and passing the resulting stream in contact with a remaining substantial portion of the catalyst, and after preconditioning placing the freshly regenerated reactor in the fourth position for the recovery of sulfur and continuing cooling of the thus-preconditioned freshly regenerated reactor in the fourth position concurrent with operation under condi-tions effective for depositing a preponderance of formed sulfur on the catalyst.
the plant comprises a Claus thermal reaction zone and four Claus catalytic reaction zones, R1, R2, R3, and R4, and the process comprises passing the acid gas stream successively in series for the recovery of sulfur through the Claus thermal reaction zone and a first position Claus catalytic reaction zone, a second position Claus catalytic reaction zone, a third posi-tion Claus catalytic reaction zone, and a fourth posi-tion Claus catalytic reaction zone, both of the third and fourth position Claus catalytic reaction zones being operated at all times under conditions effective for depositing a preponderance of the formed sulfur on the catalyst therein;
the process further comprising rotating reac-tors R2, R3, and R4 through the third and fourth posi-tions operated under conditions effective for depositing a preponderance of the formed sulfur on the catalyst, periodically rotating reactors having cata-lysts laden with sulfur from the third position to the second position and from the fourth position to the third position and continuing depositing a preponder-ance of formed sulfur on the -thus rotated reactors in the third position, regenerating the thus rotated reactors while operating in the second position with a gas stream derived from the sulfur recovery process upstream of the second position Claus catalytic reaction zone and downstream of the first position Claus catalytic reaction zone, preconditioning the freshly regenerated reac-tor after regeneration in the second position by intro-ducing thereinto a cold stream having a temperature effective for condensing sulfur on at least a portion of the catalyst and passing the resulting stream in contact with a remaining substantial portion of the catalyst, and after preconditioning placing the freshly regenerated reactor in the fourth position for the recovery of sulfur and continuing cooling of the thus-preconditioned freshly regenerated reactor in the fourth position concurrent with operation under condi-tions effective for depositing a preponderance of formed sulfur on the catalyst.
6. The Process of Claim 5 wherein:
preconditioning is effected by temporarily decreasing the temperature of the inlet gas stream to the freshly regenerated reactor to a temperature effec-tive for preconditioning.
preconditioning is effected by temporarily decreasing the temperature of the inlet gas stream to the freshly regenerated reactor to a temperature effec-tive for preconditioning.
7. The Process of Claim 5 wherein:
preconditioning is effected by utilizing con-denser effluent from a condenser positioned upstream of the freshly regenerated reactor and temporarily reduc-ing the temperature of the inlet feed to the second position reactor.
preconditioning is effected by utilizing con-denser effluent from a condenser positioned upstream of the freshly regenerated reactor and temporarily reduc-ing the temperature of the inlet feed to the second position reactor.
8. The Process of Claim 5 wherein:
the preconditioning is effected by introduc-ing a cold stream into the reactor freshly regenerated in the second position, the cold stream having an inlet temperature effective for condensing sulfur on at least a portion of the catalyst and passing the resulting stream in contact with a remaining substantial portion of the catalyst.
the preconditioning is effected by introduc-ing a cold stream into the reactor freshly regenerated in the second position, the cold stream having an inlet temperature effective for condensing sulfur on at least a portion of the catalyst and passing the resulting stream in contact with a remaining substantial portion of the catalyst.
9. The Process of Claim 8 wherein:
the cold stream has a temperature in the range of from about 160 to about 330°F.
the cold stream has a temperature in the range of from about 160 to about 330°F.
10. The Process of Claim 8 wherein:
the cold stream has a temperature in the range of about 250 to about 330°F.
the cold stream has a temperature in the range of about 250 to about 330°F.
11. The Process of Claim 8 wherein:
the preconditioning is effected for a period of less than about 2 hours.
the preconditioning is effected for a period of less than about 2 hours.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US64890484A | 1984-09-07 | 1984-09-07 | |
| US648,904 | 1984-09-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1303820C true CA1303820C (en) | 1992-06-23 |
Family
ID=24602695
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000489547A Expired - Lifetime CA1303820C (en) | 1984-09-07 | 1985-08-28 | Four catalytic reactor extended claus process |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1303820C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2023081181A1 (en) * | 2021-11-02 | 2023-05-11 | Saudi Arabian Oil Company | Sulfur recovery by solidifying sulfur on reactor catalyst |
-
1985
- 1985-08-28 CA CA000489547A patent/CA1303820C/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2023081181A1 (en) * | 2021-11-02 | 2023-05-11 | Saudi Arabian Oil Company | Sulfur recovery by solidifying sulfur on reactor catalyst |
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