US3565766A - Copyrolysis of coal and heavy carbonaceous residue - Google Patents

Abstract

HEAVY HYDROCARBONACCEOUS RESIDUES ARE UPGRADED TO LIGHTER FRACTIONS BY COPYROLYZING THEM WITH COAL PARTICLES-PREVIOUSLY HEATED TO REMOVE FROM ABOUT 1% TO ABOUT 10% VOLATILES THEREFROM-IN THE FLUIDIZED STATE, AT A TEMPERATURE BETWEEN ABOUT 850*F., AND ABOUT 1100*F. AND RECOVERING THE RESULTANT OILY DISTILLATES AND CARBONACEOUS RESIDUES.

Description

COPYROLYSIS OF COAL AND HEAVY CARBONACEOUS RESIDUE BY MJONES Feb.23, 1971 `R.T.EDD|NGER ErAL 3,565,766 l COPYROLYSIS OF COAL AND HEAVY CARBONACEOUS RESIDUE Filed Jan. 24, 1969 2 Sheets-Sheetl Unted States Patent O 3,565,766 COPYROLYSIS OF COAL AND HEAVY CARBONACEOUS RESIDUE Ralph Tracy Eddinger, Princeton Junction, and .lohn F.

Jones, Princeton, NJ., assignors, by mesne assignments,

to the United States of America as represented by the Secretary of the Interior Filed Jan. 24, 1969, Ser. No. 793,735 Int. Cl. C101) 49/22, 55/10 U.S. Cl. 201-23 5 Claims ABSTRACT F THE DISCLOSURE Heavy hydrocarbonaceous residues are upgraded to lighter fractions by copyrolyzing them with coal particles-previously heated to remove from about 1% to about volatiles therefrom-in the fluidized state, at a temperature between about 850 F., and about 1100" F. and recovering the resultant oily distillates and carbonaceous residues.

BACKGROUND OF THE INVENTION (A) Field of the invention This invention relates to the processing of hydrocarbonaceous materials. More particularly, the invention pertains to the upgrading, to lower boiling products, of heavy hydrocarbon oils of the type recovered from petroleum, oil shale, tar sands, and coal refining.

(B) Description of the prior art The treatment of heavy hydrocarbonaceous residues for the purposes of converting them to more valuable lighter fractions is well known in the renery art. Commonly, the conversion is eifected by the so-called delayed coking process wherein the residues are heated in a coking vessel, thereby forrning lower boiling hydrocarbon fractions and a residue of bulk coke. More recently the coking has been performed in a uidized bed. This is more efficient than delayed coking and moreover produces coke in powder rather than massive form.

It is also known to upgrade coal by heating it to form valuable oils, The basic procedure is to pyrolyze coal in a coking vessel and recover the oil distillate and carbonized residue or coke. Considerable improvements in the technology have been made and in this connection reference is made to U.S.P. 3,375,175 to Eddinger et al. In this process coal is pyrolyzed in a series of fluidized beds, in which the temperature of each succeeding stage is increased until essentially all volatiles have been evolved. The devolatilized, tinely divided char residue is a valuable and useful carbonaceous byproduct.

SUMMARY OF THE INVENTION It has now been discovered that a heavy hydrocarbonaceous residue can be upgraded to yield lower boiling fractions by the uidized copyrolysis of the residue with coal particles-previously heated until about 1-l0% volatiles have been removed therefrom-for a time sufcient to remove all of the volatiles from the coal and residue condensible to oily liquids and recovering said oily liquids, product char and gas.

DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS According to the present invention, generally satisfactory results are realized by introducing the heavy hydrocarbonaceous residue into the appropriate stage of a multistage coal pyrolysis system of the type disclosed in the aforecited patent. The Eddinger et al. process provides for the carbonization to be performed in the absence of 'ice added oxygen, thereby favoring maximum production of tar. In the Eddinger et al. process of coal pyrolysis, -tinely divided coal is heated at low pressures in a plurality of fluidized beds at successively higher temperatures, the result of which is to bring about an increase in yield of oily liquids recoverable from the coal, In general, the process comprises the steps of:

(1) In a first stage, heating the nely divided coal below its fusion temperature under oxygen-free conditions in a iirst tluidized bed formed by passing an inert gasiform stream upwardly through the stage to maintain the coal in the uidized state until about 1% to about 10% of the coal volatiles have been removed as overheads and recovering oily liquids from said overheads,

(2) In at least a second stage, passing the so-treated coal into at least one other uidized bed which is iuidized by the gaseous overheads from the subsequent stages at a temperature above that of the rst bed and below the fusion point of the solids fed to that stage, under oxygenfree conditions, for a time suicient to remove nearly all of the volatiles form the coal condensible to oily liquids.

(3) In a nal stage passing, the thus-treated coal into a nal luidized bed which is uidized by an oxygen-containing gas at a still higher temperature, to substantially devolatilize the coal, and

(4) Recovering the oily liquids from all stages subsequent to the first stage from the overheads of the second stage.

In practicing the invention, the hydrocarbonaceous residue in particulate form is introduced into a carbonization stage which follows the first stage of the Eddinger et al. process. Where the coal is carbonized in a series of stages, the hydrocarbonaceous material can be introduced at any one of the stages or combination of them. Both the hydrocarbonaceous material and coal undergo mutual carbonization in the presence of one another, resulting in the production of oily liquids and product char, in essentially the manner as when the coal alone is subjected to the same treatment. That is to say, the presence of the hydrocarbonaceous material in no way interferes with normal operation of the multistage coal pyrolysis. This is surprising since the presence of hydrocarbonaceous materials would be expected to cause severe coalescence of the coal particles during carbonization with concomitant loss of uidization. Apparantly the prepyrolysis of the coal particles in the rst stage greatly diminishes their agglomeration tendencies to such an unexpected extent that they can tolerate the presence of the oily particles of the hydrocarbonaceous material.

A further advantage which is realized from the invention is a marked reduction in the loss of coal fines from the uidized beds.

The hydrocarbonaceous material is conveniently introduced into the coal pyrolysis stages in the form of an atomized spray. This can readily be effected by heating the material to increase its uidity, whereby it can be pumped and sprayed into the reaction vessel where the coal is being carbonized Such hydrocarbonaceous materials represent the heavy residues left over from petroleum, oil shale, tar sands, and coal refining operations; they are available in a number of grades and types. A familiar class of these materials is the heavy residue remaining from atmospheric or vacuum crude distillation in the relining of petroleum. It is readily upgraded to valuable light fractions by the process of the invention. Other types of hydrocarbonaceous residues give comparable results.

The ratio of hydrocarbonaceous materials to coal will of course vary with a particular type of coal being subjected to pyrolysis. The ratio will also vary with the type of hydrocarbonaceous material being processed. Gener- 3 ally speaking however, we have ascertained that ratios in the neighborhood of 1:1 up to about 4:1 of coal by hydrocarbonaceous residue are readily processed in the manner of the present invention. By using high volatile C bituminous or subbituminous coals wherein the secondstage coal carbonization reactor temperature is above 900 F., operation with variable feed concentrations is feasible. Where the residue is premixed with char from the first stage before injection into the second stage, the char is more readily transported into the second-stage reactor at the lower ratio 2 parts coal, 1 part of residue. On the other hand, when operating with high volatile B bituminous coal, preferable ratios of coal to oil are 3 or 4. This is a consequence of the second-stage reactor being operated below 900 F. At this temperature the more refractory-type of residue does not undergo sucient thermal cracking and vaporization to permit operability of the fluidized bed. The oil tends to ball up the char particles in the bed whereby fluidization cannot be maintained. When injecting the more refractory residue into the third Stage at the lower coal to oil ratios, there appears to be a partial condensation of the residue vapors in the preceding second stage causing operating problems. Under these conditions, 4 to 1 ratio is preferred over 3 to 1 ratio. Accordingly, it has been our nding that the preferred ratio of coal to residuum is about 3 or 4 to 1, the type of coal tending to be the deciding factor. Preferably, the residue is introduced into a stage at a temperature above 900 F. with 950 F. being preferred. Temperatures below 900 F. generally produce poor results. Operating at temperatures above 1000 F. tends to form more gas and coke, at the expense of liquid yield. Here again, the particular type of coal being processed is the deciding factor on these temperature ranges. A small quality control run with a particular coal and residue will readily determine the optimum set of temperatures and conditions. In general, the pressure and residence times fall within the ranges set forth in the previously cited U.S. patent to Eddinger et al.

The process herein can best be understood by reference to the accompanying drawings in which FIG. 1 is the flow sheet of our process as applied to high volatile B bituminous coal with char recycle using petroleum residuum as the hydrocarbonaceous residue. FIG. 2 is a flow sheet of our process as applied to high volatile C bituminous coal and petroleum residuum.

Referring to the drawings, FIG. l discloses the preferred mode of operation with high volatile B bituminous coal. The coal is rst crushed to a size desirable for fluidization, generally -14 mesh, and is fed into a first fluidized bed where it is maintained at a temperature sufficiently below the fusion temperature of the coal to prevent the mass from fusing, but sufficiently high to remove substantial quantities of volatiles in addition to unbound water. In high volatile B bituminous coals, this range is from about 600 F. to about 650 F. Fluidization is by means of an inert gas, preferably hot, oxygen-free ue gas, which both heats and fluidizes, although external heating may be used. About 1% to 10% of the weight of the dry coal is removed as overhead during a residence time of from about 1 to 30 minutes; of this overhead, about half represents material condensible to oily hydrocarbon liquids.

The dried preheated coal and hot residuum can then be separately fed into the second stage, although preferably to the third stage, where the mixture is immediately heated to a higher temperature, but below the fusion point of the coal, to start driving out the bulk of volatiles from the coal and residuum. The fluidizing medium is for the sake of heat economy the overhead from the third stage and consists of gas plus condensibles from that stage. Residence time is from l to 30 minutes-tempera ture from 800 F. to 900 F. The second stage overhead includes all the gas and condensibles formed from the combined pyrolysis of coal and residuum excluding that which comes out of the preheating stage. In general there is enough condensible hydrocarbon to yield a total of about 35% to 60% oily liquid based on the combined Weight of the original dry coal and residuum. The amount of gas produced is a function of the manner in which the fourth stage is operated and can be varied from about 10% to about 30% by weight of the original coal and residuum. Char from the fourth stage will vary from about 35% to 60% by weight of the original coal and residuum reflecting both the treatment in the last stage and the ash level in the original coal. Alternatively the fluidizing medium may be any inert gas and external heating may be used. However, it is preferable to avoid oxygen-fed at this second stage if high oil yields are to be realized.

The partially devolatized char from stage 2 goes into a third stage in which further fluidized bed pyrolysis of the coal-residuum mixture is effected at temperatures of the order of 950 F. to 1050 F. The uidizing medium is preferably the overhead of stage 4. After 1 to 30 minutes in this stage, the char contains little more than a percent or so of volatiles 4which are recoverable as liquid condensates. The char from stage 3 is fed into a fluidized calcination bed maintained at a temperature between 1500 F. and 1800 F. by internal combustion of the char by the gas fed into the reactor as a fluidizing medium which may be air or oxygen. The overhead goes into stage three to act as a iluidizing medium. It may contain a very small amount of condensibles; otherwise its constituents are dependent on the amount of oxygen in the fluidizing gas, and total residence time in the bed, these factors together controlling the temperature and the composition of the gas discharged. Preferably residence times are from 1 to 30 minutes, and with high oxygen concentrations, to achieve a temperature of 1600 F. in the bed, and an exit gas with high concentrations of hydrogen and carbon monoxide.

Referring to FIG. 2, this discloses a preferred mode of operation with high volatile 'bituminous coal and petroleum residuum. Generally, the process of FIG. 2 is conducted identically to that of FIG. 1, except the residuum can be admixed with char prior to injection into carbonization stages 2 or 3. Moreover, stage 2 of FIG. 2 1s operated at a temperature of 950 F. to 1000 F. which is higher than that of FIG. 1.

In the following examples, the fluidized bed reactors consist of a series of hollow steel cylindrical vessels. The rst stage serves to effect prepyrolysis of the particles wherein 1 to 10% volatiles are removed. Stages 2 and 3 where the main pyrolysis of residuum and coal takes place while stage 4 is the combustion and gas forming stage. The lnside diameters of the stages are 18, 12, l0 and 8 Inches, respectively. Approximately 100 pounds of material can be processed per hour. s The residuum previously heated to increase its fluidity, 1s' pumped into a feed nozzle for injection into the requlsite carbonization stage. The coal particle are produced 1n any convenient comminuting equipment such as a hammer mill.

Oxygen diluted with nitrogen, steam, or recycle gas for temperature control is used to uidize the last stage and provides the heat required for all but the first stage, which is externally heated. The second and third stages are fluidized and receive heat from the olf-gas of the next heater stage. A portion of the second stage heat requirements is supplied by hot re-cycled char from the third stage, and, similarly, the third stage by char lfrom the fourth stage as needed. Alternatively, oxygen can be added to the third stage at some loss of oil yield. Using multi-stage fluidized beds rather than a single fluidized bed for the copyrolysis of bituminous coal and petroleum residuum has the advantage that caking coals can be continuously processed without agglomeration.

EXAMPLE 1 FIG. 2.

The conditions of operatiton, together with the res obtained, are summarized in the following table:

ults

TABLE I.-RUNS WITH MCKINLEY HIGH VOLATILE C BITUMINOUS COAL AND SHORT RESIDUUM Run Dry coal weight;1 100 100 100 Short residuurn weightl. 50 3S 58 Product yield distribution:

55.2 2.9 60.0 65.0 18.5 34.8 45.1 62.2 ig 15.8 12.3 21.6 25.7 Aqueous liquor Weightl 10.5 10.4 5.1

Total 100.0 50 0 138.0 158.0

1 All weights are in pounds.

Average staging temperature F.:

Stage `I-600-650 Stage II-950-1,000 Stage III-l,000-1,200 Stage IV-1,600

As can be seen from an inspection of the data in the table, the yields of char and volatiles obtained from Copyrolysis of residuum and coal are not completely additive from individual pyrolysis; whereas the oil yields are nearly additive, the char and gas yields vary. This is evident iby comparing the amount of pyrolysis products obtained individually from the pyrolysis of coal and residuum and when a like amount of coal and residuum is copyrolyzed. Moreover, the data contained in this ample also shows that decreasing the coal-residuum ratio The procedure of Example 1 was essentially repeated 4 and the results thereof, along with the conditions are set forth in the table below:

TABLE II.-RUNS WITH CROWN HIGH VOLATILE B BI- TUMINOUS COAL AND RESIDUUM Run Dry coal weightl. 100 100 100 100 Residuum type Long Medium Short Residuum weight.. 39 23 29 Residuum to stage II II III Product yield distribution:

Char weightl 56. 6 57. 0 61. 0 62. S Oil Weight1 19. 5 54. 5 4l. 1 32. 8 Gas weightl 13. 8 14. 2 1l. 9 19. 7 Liquor Weight1 10. 1 13. 3 9. 0 13. 7

Total 100. 0 139. 0 123. 0 129. 0

1 All weights are in pounds.

Average staging temperature F.:

Stage I-60 Stage II-835 Stage `III-1,200 Stage IV-'1,600

As will be noted from an inspection of the data aforesaid, the process of the invention can be run with high volatile bituminous B coal and moreover various types of residua can be used.

The identification and analysis of the coal and residua used in the examples are summarized in the following tables:

TABLE IIL-ANALYSES OF COALS Coal McKinley l Crown 2 Proximate analysis, Weight percent:

Moisture 11.6 10.0 Volatile mattei' 35. 5 34. 0 Fixed carbon 44. 7 45. 5 8. 2 10. 5

68. 5 67. 7 5. 1 5. 1 1. 2 1. 7 U. 7 4. 0 15. 2 9. 9 9. 3 11. 6 Sieve analysis, Tyler mesh, cumulative weight percent:

16 0 0 28" 30.5 31.1 48 58.7 59.2 77. 8 76. 9 200. 89.0 87.4 325 93.4 91.9 Bulk denslty, lb./cn. it 46 47 Higher heating value, dry basis, B.t.u./lb 12,000 12. 400

1 A high-volatile C bituminous coal from New Mexico. 2 A high-volatile B bituminous coal from the Illinois number 6 seam.

TABLE IV.-ANALYSES OF RESID UA Residuum type Short Medium Long Residuuin description (l) 2 3 Gravity, API 13.)?, 3 Carbon residue, weight percent 25.0 9. 1 5. l Ultimate analysis, weight percent:

1Vacuum-dashed, visbroken and vacuum-dashed again; boiling point above 1,00()o F.

2 Vacuum-flashed only.

3 Initial boiling point around 750 F.

What is claimed is:

1. A multistage, fluid bed process of upgrading a heavy hydrocarbonaceous residue. to lower boiling fractions, while simultaneously pyrolyzing finely divided coal which comprises (l) in a rst stage heating the finely divided coal below its fusion temperature in a first uidized bed formed by passing an inert gasiform stream upwardly through the stage to maintain the coal in the uidized state until about 1% to about 10% of the coal volatiles have been removed as overheads and recovering oily liquids from said overheads;

(2) in at least a second stage passing the so-treated coal and the heavy hydrocarbonaceous residue or a vapor into at least one other fluidized bed which is liuidized by the gaseous overhead from the subsequent stages at a temperature above that of the first bed and below the fusion point of the solids fed to that stage for a time suiiicient to remove nearly all of the volatiles condensible to other liquids;

(3) in a inal stage passing the thus treated coal and residue into a iinal uidized bed which is uidized by an oxygen containing gas at a still higher temperature to substantially devolatilize the coal and residue; and

(4) recovering the oily liquid from all stages subsequent to the irst stage, from the overhead of the second stage.

2. A multistage, uid bed process of upgrading a heavy hydrocarbonaceous residue to lower boiling fractions, while simultaneously pyrolyzing particles of high volatile C bituminous coal which comprises (l) in a rst stage heating the coal to a temperature of about 600 F. to about 650 F. in a first fluidized bed formed by passing an inert gasiform stream upwardly through the stage to maintain the coal in the fluidized state until about 1% to about 10% of the coal volatiles have been removed as overheads and recovering oily liquids from said overheads;

(2) passing the thus treated coal and vaporized hydrocarbonaceous residue into a second bed which is fluidized by the gaseous overheads from the subse.- quent stages at a temperature of 950 F. to 1000 F. for a time sulicient to remove substantial amounts of volatiles from the products;

(3) passing the thus partially pyrolyzed products along with a further quantity of hydrocarbonaceous residue into a third lluidized bed which is fluidized by the gaseous overheads from the subsequent stages, at a temperature of 1000 F. to 1200 'R for a time sufficient to reduce the remaining volatiles in the coal and hydrocarbonaceous residue condensible to oily liquid to no more than about 1%;

(4) passing this product of pyrolyzed coal and hydrocarbonaceous residue into a fourth iluidized bed which is uidized by an oxygen containing gas maintained at a temperature of 1500 F. to 1600 EF. to substantially devolatilize the char; and

(5) recovering the condensibles from the overheads of all stages subsequent to the second stage from the overhead of the second stage.

3. The method of claim 1 in which oxygen containing gas is fed into the fourth fluidized bed to react the char to provide heat and the overheads are fed countercurrently to the third and second stages to heat them.

4. A multistage, fluid bed process of upgrading a heavy hydrocarbonaceous residue to lower boiling fractions while simultaneously pyrolyzing particles of high volatile B bituminous coal which comprises (l) in a first stage heating the coal to a temperature of about 650 F. in a rst fluidized bed formed by passing an inert gasiform stream upwardly through the stage to maintain the coal in the fluidized state until about 1% to about 10% of the coal volatiles have been removed as overheads and recovering oily liquid from said overheads;

(2')- passing the thus treated coal into a second stage which is fiuidized by the. gaseous overheads from the subsequent stages at a temperature of `800 F. to 900 F. for a time sufficient to remove substantial amounts of volatiles;

(3) passing the thus partially pyrolyzed coal particles along with the hydrocarbonaceous residue into a third fluidized bed which is fluidized by the gaseous overheads from the subsequent stages at a temperature of 1000 F. to 1200 F. for a time su'icient to reduce the remaining volatiles in the coal and hydrocarbonaceous residue condensible to oily liquid to no more than about 1%;

(4) passing this product of pyrolyzed coal and hydrocarbonaceous residue into a fourth uidized bed which is uidized by an oxygen containing gas maintained at a temperature of 1500 F. to 1600 F. to substantially devolatilize the char; and

(5) recovering the condensibles from the overheads of all stages subsequent to the second stage from the overhead of the second stage.

5. The method of claim 3, wherein char is recycled from the nal stage to a preceding stage.

References Cited UNITED STATES PATENTS Re. 24,574 l2/l958 Welinsky 201--31 2,955,077 10/1960 Welinsky 201-3 l 2,982,701 5/l96l Scott 208-11 3,011,953 12/1961 Foch 201-44 FOREIGN PATENTS 413,927 7/ 1934 Great Britain 201-23 785,994 1/1957 Great Britain 201-23 WILBUR L. BASCOMB, JR., Primary Examiner D. EDWARDS, Assistant Examiner U.S. Cl. XR.

UNITED STATES PATENT oFFICE CERTIFICATE OF CORRECTION Parent No. V3,565,766 Dated February 23, 1971 Inventor(s) Ralph Tracy Eddinger and John F. Jones It is certified that error appears in the. above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 2, "by" Should read --to.

Column l line l5, "fed" should read --eed.

Column 4, line SO, "are" Should be inserted at end of line Column 5, line 67, "60" should read -600.

Siszned and sealed this 28th day of March l 972 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents ORM PID-1050 (1069)

Images