US2243052A - Manufacture of gas and coke - Google Patents

Description

May 20, 1941. G. H. NILES ETAL MANUFACTURE 01? GAS AND COKE Original Filed Dec. 14, 1936 2 Sheets-Sheet 1 l NVENTORS ALFRED JOHNJO/V gILE'NN Ii Nil-6'6 ATTQRNEY H. NILES ETAL MANUFACTURE 6F GAS AND COKE May 20, 1941.

iginal Filed Dec. 14, 1936 2 Sheets-Sheet 2 ATTORNEY Patented May 20, 1941 MANUFACTURE OF GAS AND COKE Glenn H. Niles, Ridgewood, and Alfred Johnson,

Summit, N.

J., assignors to Combustion Utilities Corporation, New York, N. Y., a corporation oi Maine Original application December 14, 1936, Serial No. 115,668. Divided and this application March 16, 1938, Serial No. 196,110

Claims.

The present invention relates to the manufacture of gas and coke, and more particularly concerns improved apparatus for simultaneously carbonizing coal and supplementing the volume of coal gas produced with a mixture of oil gas and water gas having similar combustion characteristics to coal gas. The apparatus of the present invention was originally described in our co-pending application, Serial No. 115,668, filed December 14, 1936, of which the present case is a division. Attention is also directed to the copending application, Serial No. 293,552, filed Sept. 6, 1939, in which the process is claimed.

Coal gas as normally produced in high temperature coke ovens and gas retorts, has a calorific value in the neighborhood or 500-600 B. t. u. per cubic footand a specific gravity oi. Ail- .60. Coke ovens and gas retorts are frequently used as the main source of supply of town gas for distribution to domestic and industrial consumers. Many as distribution systems which employ coke ovens or gas retorts as the principal source of gas are subject at times to peak loads and/or to a gradual increase in average load which taxes the gas making capacity of the coke ovens or gas retorts supplying the system. so

It has been the practice for many years to temporarily increase the gas making capacity of a gas retort or coke oven by introducing oil into the oven or retort charge during part of the carbonizing cycle. Likewise it has been the practice for many years to pass steam through a charge of hot coke in a retort or oven during the latter part of the carbonizing cycle or at the end of carbonization, for the purpose of generating water gas to add to the coal gas produced during a normal cycle.

When oil is cracked in intimate contact with incandescent carbon in a charge of coal undergoing carbonization in a high temperature coke oven or gas retort, the cracking is so severe owing to the high temperatures of the coke surfaces on which the cracking takes place, that any resulting cracked oil gas has a calorific value considerably lower and a specific gravity lower than that of coal gas (owing to the large proportion of hydrogen in the oil gas) and a substantial amount of the finely divided carbon black residue of cracking is deposited on the coke and retort walls, or is carried out of the in a high temperature coke oven or retort, the steam is dissociated and reacts with the carbon of the coke producing a mixture of hydrogen and carbon monoxide'which is commonly designated water gas. Water gas has a specific gravity which is considerably higher than that of coal gas and a calorific value which is considerably lower than that 01' coal gas, so that water gas has combustion characteristics widely differing from those of coal gas. A mixture of water gas and coal gas containing any substantial amount of water gas cannot be safely burned without readjusting the burners of domestic and industrial heating appliances which have been previously adJusted for burning coal gas alone. Another result of passing steam through a charge of coal undergoing carbonization in a coke oven or gas retort is that such procedure markedly increases the porosity and fragility of the coke, making it unsuitable for many purposes such as for use as metallurgical coke.

It has been proposed to increase the gas making capacity of a coal carbonizing retort by passing both steam and hydrocarbon through the charge of incandescent coke in intimate contact therewith during the latter part of the carbonizing period or after its termination. However, this operation adversely afiects the structure oi. the coke and in practice does not produce a gas having substantially the same com- H bustion characteristic as coal gas, because whenretort in the gas stream, building up obstructive carbon deposits in the gas ofitake pipes and purifying system.

When steam is passed through a charge of incandescent carbon undergoing carbonization ever steam and "hydrocarbon in reactive proportions are heated in intimate contact with incandescent carbon in a coking oven operating at normal temperatures, a major portion 01' the oiwgen liberated by dissociation of the steam reacts with the carbon of the coke, and the hydrocarbon is highly cracked to a gas consisting chiefly of hydrogen by surface reactions in contact with the incandescent coke.

The primary object of the present invention is to provide means adapted for increasing the gas making capacity of a coking oven or gas retort by producing in the retort or oven a supplemental mixture of oil gas and water gas having a calorific value and gravity and burning characteristics about the same as coal gas.

With the above object in mind one important feature of the invention resides in generating a mixture of oil gas and water gas having substantially the same burning characteristics as coal gas within a coking oven simultaneously with the production of coke and coal gas, by reactions which are carried out above the incandescent coke and with intimate contact between controlled volumes of the atomized oil, coal gas and steam during vapor phase cracking, whereby reactions between the steam and carbon residue of cracking occur substantially without adverse eii'ect on the retort temperature or on the gaseous and solid products of the coking operation.

Another object of the invention is to provide attachments for an externally heated coke oven or gas retort whereby the upper portion of said oven above the normal top level of a charge of coal undergoing coking therein may be adapted for the simultaneous generation of a mixture of cracked oil gas and water gas having substantially the same burning characteristics as the coal gas simultaneously produced. 1

with the above and other objects and features in view the inventionconsists in the improved apparatus which is hereinafter described and more particularly defined in the accompanying claims.

In the following particular description of the invention reference will be had to the accompanying drawings, in which:

Fig. 1 is a view in vertical side elevation, with parts broken away and parts in longitudinal section, showing a horizontal gas retort bench having associated therewith steam-oil atomizing nozzles opening into the retorts above the normal top level of. charages of coal undergoing carbonization therein; Fig. 2 is a vertical transverse section of a portion of the retort bench showing ducted to the restricted throat of mixer 26 from a pipe 32 and passage 33 into an annular chamber 34 surrounding the mixer throat, and thence into the restricted portion of the throat through a plurality of radial orifices 36. Steam is supplied to the inlet end of the mixer 26 from a pipe 33 through a smal1 adjustably positioned Venturi member 40 spaced behind and axially aligned with the inlet end of the Venturi 26. Provision is made for supplying air to the mixer through a pipe 42 leading to a chamber 44 which surrounds and communicates with the inlet of the mixer and with the discharge nozzle of Venturi 46. The Venturi 46 is externally threadedat 46 to engage threads in the centrally apertured rear end of block 26 in order to permit adjustment of the spacing of member 40 from the inlet end portion of the retort, the atomizer nozzle 36 is the disposition of a pair of retorts and surrounding gas heating flues, taken on the section 2-2 of Fig. 1; Fig. 3 is an enlarged sectional view of steam-oil atomizing nozzles of a preferred type employed with the retorts shown in Fig. 1; Fig. 4

is a view in longitudinal section showing a coke retort for carbonization, and also through which the completed coke may be discharged. Heat for carbonizing the retort charge is developed by combustion of fuel gas in the flues l4 surrounding the retort and is transmitted to the charge by conduction through the walls 12 (see Fig. 2) Gas produced in each retort during the carbonization of the charge is removed through an oiftake pipe l8 ported out in the top of the retort adjacent the door IS. The ofltake pipe conducts the gas into a hydraulic main 20 through which the gas is carried to purifying equipment and thence to a holder (not shown). A steam-oil atomizer 22 is mounted horizontally in the rear wall of retort ID in position to project an atomized oilsteam mixture" into the retort immediately below the roof of the retort and above the normal top level of a charge of coal therein. The atomizer 22 is shown as mounted centrally at the cool end of a high temperature resistant refractory tube 24 having its hot end ported out in the retort and extending rearwardly through the back wall of the retort. As shown in Fig. 3, the principal elements of the atomizer 22 include a Venturi oil and steam mixer and atomizer 26 forming part of an apertured cap 28 adapted to fit overthe outer end of tube 24, and having a Venturi discharge nozzle .30. which projects into and is axially aligned within the tube 24. Oil is conmounted axially within a horizontally disposed open ended mixer tube 43 which is designed to function as a baflle between the discharge nozzle of the mixer and the gas discharge outlet from the retort, as well as for an injector sleeve to draw gases into the path of the oil-steam jet issuing from the atomizer and thereby eii'ect 'recirculation of the gases by injector efiect, prolong ingthe time of sojourn of the oil and steam and gases produced by reaction thereof, within the retort. Another method of introducing the steam-oil mixture through the front of the retort is by a high temperature alloy pipe 36a lying on the floor of the retort I01) and opening into the space 10 above the retort charge adjacent the back wall of the retort.

The coke oven 50 which is shown in Fig. 4 has removable doors 52 at each end to allow for discharging the coke from the oven, and is also provided with a pair of charging spouts or tubes 54 opening at spaced points into the top of the oven through which a charge of coal may be introduced preliminary to the carbonization thereof within the oven. The oven is heated by combustion of fuel gases in fines 56 (similar to flues I 4, Fig. 2) surrounding the side walls and overlying the roof of the oven. Gas produced in the retort as a result of carbonization of the charge is removed through an ofitake pipe 58. Caps 60 are provided for each fuel charging spout to seal the oven against admission of air or loss of gas through the charging spout during the period of carbonization. The special design of coal chargng spout cap which is numbered 62 in the drawmgs, is placed on one of the fuel charging spouts during a part of the canbonization period for the purpose of projecting an atomized mixture of oil and steaminto the top of the retort 50 above the charge undergoing carbonization therein, after chamber 34 in the cap 62, the chamber 34 communicably connecting with the throat of mixer 26 through orifices corresponding with orifices 36 of Fig. 3. Air enters a chamber communicably connecting with the inlet end of mixer 26 and steam is introduced to the inlet end of the mixer through a Venturi nozzle 40 which is adjustably spaced from the inlet end of mixer 26.

The operation of the gas retorts l shown in Fig. 1 and of the coke oven 50 of Fig. 4 is substantially the same. Coal, preferably bituminous coking coal, is first charged to the retort or oven to approximately the depth indicated in the drawings, leaving a free gas removal space" above the charge, after which the charging doors are closed and heat is applied to the retorts by circulation of burning gaseous fuels through the heating flues (including I4 and 56) which surround the walls of the retorts l0 and ovens 50. After heating the charges of coal in the retorts and ovens for a period which may vary from 2 to 6 hours, (depending on the temperatures maintained in the heating flues and on the thickness of the retort walls), the top and peripheral portions of the retort charge will have had their temperatures raised to above 1700 F. with theformation of a thin layer of coke. Carbonization of a charge of coal proceeds from the periphery inwardly at a rate which is substantially inversely proportional to the square of the thickness of the fuel charge. Consequently a retort or oven charge which may require from 12 to 18 hours for complete coking will develop a layer of coke two to three inches in depth in its outer periphery within a period of two to six hours.

The coal gas which is evolved from the charge undergoing carbonization normally has an average calorific value of 550 B. t. u. per cubic foot and a mean specific gravity of about .50 based on a specific gravity of 1 for air. According to the present invention a pre-formed mixture of atomized oil and steam is only introduced into the upper portion of the retort above the fuel charge after the upper part of the charge has been converted to coke, and after the temperatures in the upper part of the retort or oven have been raised above 1700 F. While continuing the carbonization of the charge and while continuing the circulation of heating gases through the heating flues I 4 and 56 surrounding the ovens and retorts, the atomized mixture of oil and steam is introduced by the Venturi mixers 26 in the open reaction zone which lies between the top of the charge and the gas offtakes (l8 of Fig.1 and 58 of Fig. 4). It is essential that the oil and steam mixture which is introduced by the mixer and atomizer 26 shall be very finely atomized and intimately mixed at the time it enters the reaction space or chamber Ill overlying the retort or oven charge. Likewise it is desirable that the introduction of oil-steam mixture into this reaction space 10 shall only continue so long as the temperature within such space lies in the range 1700 F.-2100 F. The invention does not normally contemplate the introduction of air along with the oil and steam through the atomizer 26, but provision is made for the introduction of air in limited amounts in order that the apparatus and process may be rendered sufficiently flexible to take care of brief periods of peak demand when the gas making capacity 01. the retorts and ovens is insufficient to meet the demand without introduction of controlled small amounts of air along with the oil and steam.

The mixture of oil band steam which is introdu'ced-into the chamber Ill overlying the charge enters an atmosphere of coal gas which continuously exists in chamber I0, by reason of the evolution of gas from the coal undergoing carbonization. The point of introduction of the atomized oil and steam is either in an end of the oven or retort which is remote from the end in which gas is removed from the retort, or is baffled from the gas oiftake and directed away therefrom in order to insure the necessary time for cracking and water gas reactions to occur within the reaction chamber III.

The oil-steam mixture is introduced into the retort above the retort charge in a direction and at a velocity which insures against substantial penetration of the coke by the injected oil and steam, because, as previously pointed out, any oil cracking which takes place in intimate contact with incandescent coke, i. e. within an incandescent coke bed, is so severe as to yield considerable amounts of carbon and a gas which is of two low a calorific value for practical blending with coal gas.

The rate of introduction of steam and oil into the retort is preferably controlled within proportions of about 7 to 12 pounds of steam per gallon of oil. The rate of introduction of the oil-steam mixture is also preferably regulated to develop about 15% to 40% of the total volume of gas produced in the retort or oven, and to hold the temperatures in the reaction space 10 at the top of the oven or retort in the range 1700-2100 F. If the temperatures developed are below about 1700 F. in the retort or oven during the period of introduction of oil and steam, the volume ratio of oil gas to water gas produced becomes too large,

and'the calorific value and gravity of the gas produced becomes too high for suitable-blending with coal gas. The volume ratio of cracked oil gas to water gas in a mixture which blends satisfactorily with coal gas averages about 45/55. The presence of steam in intimate contact with the oil undergoing cracking is necessary in order to prevent excessive cracking and in order to furnish the oxygen (produced by dissociation of steam) which is necessary to react with any carbon residue of cracking to produce CO.

Some variation is permissible in the character of the hydrocarbon oil which is employed as the source of the oil gas. Certain light coal tars and fuel oil fractions of petroleum can be used, but the preferred oil is the ordinary gas oil fraction of petroleum. The necessary intimate contact between the oil and steam for successful practice of the process can apparently only be secured by thoroughly atomizing the oil with the steam prior to its introduction into the reaction space which lies between the top of the coke charge and the roof of the retort. In this finely atomized condition the oil is quickly vaporized preliminary to cracking, and the cracking of the oil takes place coincidentally with some cracking of the heavier components of the coal gas, (1. e. tar vapors) and in such intimate contact with the steam as to insure that any oil carbon formed is immediately taken up by the oxygen of dissociated steam to produce CO. It is not practicable to introduce hydrocarbon oil alone into the reaction zone at the top of the retort, because with the temperatures obtaining in the retort, such oil would be I excessively cracked, producing a cracked gas having combustion characteristics which would be unsuitable for blending with the coal gas, and simultaneously producing carbon black in. amounts which would rapidly clog the ofl'take pipes and build up heat transfer resistant deposits on the retort walls. It is only when steam and its dissociation products are present in intimate association with the oil undergoing cracking that the cracked oil gas-water gas mixture which is produced has combustion characteristics corresponding with those of coal gas.

Owing to the fact that the oil cracking reaction takes place above the coke bed in an atmosphere of steam, less heat is consumed in generating a unit volume of the oil gas-water gas mixture than would be the case if the oil cracking and water gas reactions were carried out within the bedof coal and coke in the retort. Apparently this is explainable in part by the 'iact thatthe reactions which take place are The invention having been thus described, what is claimed as new is:

1. Apparatus for producing coke and gas comprising a coal carbonizing retort having heat conductant'walls suitable for transfer of heat from outside the retort to a stationary charge of coal therein, a mixer and atomizer ported out chiefly vapor phase reactions between nascent absorbed in completing and stabilizing the endothermic reactions which occur.

As previously indicated, the oil steam mixture which is introduced to the reaction zone at the top of the retort is preferably proportioned in the range of seven to twelve pounds of steam per gallon of gas'oil, and the cracked oil gas and water gas should be removed from the retort at such a rate that they do not sojourn in the reaction zone for a period greater than about six'seconds. Assuming a reaction temperature in the range of 1700 F.-2100 F. in the zone overlying the charge of coal in the retort, the period of the oil cracking and water gas reactions should be limited within four to six seconds at 1700 F., and one to two seconds at 2100 F. It has been observed that when carbonizing a charge of coking coal in a coking oven one foot in width and twelve feet long with a reaction space I0 one foot in depth overlying the charge, the optimum period of the oil cracking and water gas reactions in space 10 lies within the range of two to two and one half seconds, with the gas outlet spaced several feet away from the oil and steam inlet, while operating the retort in a. preferred mean temperature range of 1800-l900 F. with an oil-steam mixture proportioned in the preferred ratio previously indicated.

Inview of the fact that the oil cracking and water gas generating portion of a cycle only occupies about half of the period between the time of charging the retort and the time of discharging, the process of the present invention is best practiced with a plurality of retorts operating on alternate cycles. The reason for this should be clear from the fact that the oil cracking and water gas generating steps can only be practiced with optimum results after the top of the charge has been coked, and after the retort temperature has reached equilibrium in the preferred range of 1800 F.-1900 F., or at least in the allowable range of l'l00-2100 F.

horizontally in the top adjacent one end of the retort and having valved supply pipe attachments whereby as many as three different gas generating fluids may be introduced simultaneously into the retort in intimate mixture above the normal top level of a charge of coal therein, a gas oiftake ported out in the retort above the charge, and means permitting introduction of coal into the retort and discharge of coke there- 2. Apparatus for producing coke and gas comprising a coal carbonizing retort, having heat conductant walls, disposed with its major axis in a horizontal position within ,a heating furnace, a removable door at one end of said retort for the introduction of coal thereinto and for the discharge of coke therefrom, a mixer and atomizer having a discharge nozzle ported out in the top of the retort adjacent one end thereof in a substantially horizontal plane, valved supply pipes for conducting oil and steam to the Venturi mixer, and a gas oiftake ported out of the top of the retort.

3. Apparatus for producing coke and gas comprising a coal carbonizing retort, having heat conductant walls, disposed with its major axis in a horizontal position within a heating furnace, a removable door at one end of said retort for the introduction of coal thereinto and for the discharge of coke therefrom, a gas oiftake ported out in the retort at the top and adjacent one end, and a steam injection pipe ported out horizontally in the retort immediately in front of the gas ofitake and having a discharge nozzle I and injector sleeve disposed in bailling relation to outflow of gas through the ofitake.

4. An apparatus for producing gas comprising an externally heated retort, injector means to atomize liquid fuel into said retort, a tubular member having open ends disposed within said retort adjacent said injector whereby the atomized fuel stream passes through said tubular member and whereby a portion of the gases within said retort are drawn into said tubular member by the entraining action of said atomized fuel stream.

5. An apparatus for producing gas comprising an externally heated retort, means within said retort dividing the same into two chambers, said chambers being in continuously open communication at two spaced points, means for in jecting a stream of liquid fuel into one of said chambers to entrain a portion of the gaseous contents of the other of said chambers and thereby create a continuous flow of a portion of the gaseous contents of one chamber into the other.

GLENN H. NILES. ALFRED JOHNSON.

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