US2166094A - Manufacture of high calorific value gas - Google Patents

Description

July 11, 1939- .A. JOHNSON ET AL 4 MANUFACTURE OF HIGH CALORIFIC VALUE GAS Filed 'June 24, 19s?- z .m 50m 7 RSD Y M 0 CNN E J 6 m N E B w VJ MI T mo T M A um Amm STEAM OIL f I /I /I/ Patented July 11, 1939 UNITED STATES;

MANUFACTURE 01- HIGH CALORIFIC VALUE. GAS

Alfred Johnson, Summit, an'dg Morris M. Brandegee, Plainfield, N. J.

' Application June 24, 1937, Serial No. l50,058 t '7 Claims. (Ol 18-196) This invention relates tothe manufacture of combustible gas, and more particularly concerns an improved method of generatinggas having a chemical composition and combustion characteristics adapting it as a substitute for natural gas. The primary object of the present invention is to meet the demand for a plan whereby existing .three-shell water gas generating sets may be economically employed for generating a standby or peak load gaseous fuel having calorific value and combustion characteristics adapting it for use as a substitute for natural gas in appliances adjusted for burning natural gas.

Natural gas as now distributed as a fuel to many industrial and domestic throughout the country, possesses certain characteristics which are diflicult to duplicate economically in gas generating units such as the standard three-shell water gas generating set. Most of the natural gas thus distributed has a calorific value in the rangs 900-1100 B. t. u.'/cu. ft., a specific gravity of approximately .62,,and a methane content of approximately 70-90%, together with a small content of ethane and illuminants, and nitrogen and other inerts.

Most natural gas distribution systems are subject at times to temporary failures of the gas supply, or to the imposition of peak loads and/or I v to a gradual increase in average load which taxes the natural gas supply capacity of the system. To take care of such emergencies and to insure continuous service, most such systems are pro-' vided with standby gas generating units which are frequently of the standard three-shell water gas generating type. Water gas, however; is not a suitable substitute fuel-for use in appliances adjusted for burning natural gas, the reason being that water gas has a lower specific gravity, a much lower calorific value, and combustion characteristics differing so widely from those of natural gas that it can not be safely burned in appliances adjusted for burning natural gas, without first readjusting the appliances.

Any manufactured gas which is employed as a substitute for natural gas in gas burning appliances adjusted for natural gas must have com bustion characteristics adapting it for use as fuel in such appliances without faulty utilization results of the type evidenced by flash-backs in the burners or combustion with smoky flame. Chemical and physical properties of carbureted water gas and other manufactured-gases evidencing their unsuitability as substitutes for natural gas, are a low methane content, high illuminant content, high rate of flame propagation, high hydroconsumers gen and CO content, and large content of inerts such as CO2 and nitrogen. The production of oil gas in a water gasset operating on the usual carbu'reted water gas cycle makes very inefficient use of the gas making capacity of the set, for the 5 reason that the gas making capacity of the generator unit is used almost entirely in the manufacture of low B..t.'u. blast gases and of water gas'which can not be tolerated in 'more than small amounts in any natural gas substitute, on '10 account of its poor utilization characteristics and low heating value. I I

Another object of the present invention is to provide simple operating cycles on which water; gas generating sets may be operated for produc tion of natural gas substitutes in aneconomically efficient manner. I

With the above object in mind an importantfeature of the invention resides in improved operating cycles for a standard water gas set whereby the temperatures of the coke bed and the space velocities of oil, steam and hydrocarbon gases through the bed are held within narrow ranges, within which experience has shown-that a satisfactory natural gas substitute can be made in a practically efiicient and commercially economical manner. The process of the present invention contemplates production of a natural gas substitute by a two-stage or three-stage gasmake cycle. In other words, the final make gas consists of amixture of two or three distinct components each manufactured in a.distinct operating phase 'of the process. The basic componentof the final make gas is produced by a gas reforming opera: tion in which natural gas,'oil refinery tail gas or other oil gas high in gaseous hydrocarbon --con-, tent, isreformed to a gas of lower calorific value I .(about 600 B. t. u./cu. ft.) andrelatively high methane content (30%50%) bypassing the gas 40 to be reformed, with or without a small amount of steam, at high velocity through a bed of coke or other solid fuel held at a temperature in the narrow range 1800 F.-2000 F. With proper temperature and space velocity control this basic component of the make gas can be held to a high methane and low CO content and to a low content (not to exceed 10%-20%) .of inert diluent gases such as nitrogen and CO2.

By far the larger proportion by volumeof the final make gas consists of enriching oil gas which is produced by cracking petroleum gas oil or fuel oil fractions under carefully controlled conditions of temperature and space velocity.

The present process in its preferred form con- 'ocity of between..6=1 gal. of oilper sq.,-ft.; of cross sectional grate area per minute, in the presence. of about 2-4 lbs.' of steam per lb. of mm pro! ducean' oil gas of approximately 1000 B. t. \L/Gua -'level of, conduits II and N with a grate 36 upon templates carrying out such oil cracking operations partly in the generator and partly in the carbureter and superheater sections, of a standard water gas set. High gravity fuel oils (8-24 B.) are preferably cracked in contact with the coke bed in the generator at temperatures in the range 1700 l t-1900? F. and ate. space velftbaloritle value containing approximately has optimum utilization characteristics as a H 50% methane and 20%-30% hydrogemthf'e balance consisting chiefly oi illuminant 34 .3 g

B. gas oil is preferably cracked-within the carbureter and, superheaterunits of the set-'at-tcm:

peratures. in the range 15 00-,-17 0' at space velocities of 14% gals. of oilper-"sd, ft.

of cracking zone cross section per minuta'g'to produce an enrichingoil gas of 1100-1300 B. t. 11'./ cu. ft. containingin the neighborhood of 35%- 50% methane; 20%.-30% hydrogen; and, 20%- '30% illuminanta' The temperatures indicated above are those which experience has I shown as necessary in i order .toj produce a gas of suitable natural gas utilisation characteristics and calorific value. Y Bycarrying out'theoperati min more than one stagewith careful-control of temperature and s'pace velocitiswithin the ranges 'indicated above, there'suiting mixture of reform gas and oil gas natural gassubstitute, and is produced in maximum'yield with a minimum loss in eificiency resulting from the formation of lamp black and heavy viscoustars during the oil cracking stage. The process-as practised resultsintrapping any lamp black which is produced,'and in utilizing the potential heat thereof in heating up the ap' paratus, thereby reducing the cost of more ex pensive fuels such as-coke and oil. 1 I With-the above and'other'objects and features in view, the invention consists in the improved method of manufacturing a natural gas substitute which 'is hereinafter described and more particularly defined by the accompanying claims. In the 'following description reference will be made to the accompanying drawing, illustrating modified designs-oi standard three-shell water gas generating sets adapted for'practisin'gthe process which forms the subject of the present invention. Referring to the drawing- 1 Fig. lis a viewin vertical section, with parts shown in elevation, of a three-shell water gas set the'design of which has been modified to include a generator oil spray, a combination forced draft oil burner and .oil spray at the top of the carbureter, and hot valve and backrun connectionswhereby the set may be operated in accordance with several different operating cycles; and Fig. 2 is also a view in vertical section of a three-shell water gas set which differs from the set shownin Fig. 1 in substituting a shallow screen of broken ceramic bricks for the checkerbrick carburetor filling and in providing connections whereby the set may be operated with a reverse airblast.

Referring to Fig. 1 of the drawing, numeral 10 designates a gas generator which is connected at its top through conduit l2 with a carbureter H.

The carbureter is connected at its base through conduit I'B with a superheater I8. A conduit 20- duit 26 equipped with a three-way valve 28 leads off from the upper part of superheater II to a wash box 30, and a gas oiftake pipe 32 is ported out from the wash box. Another conduit connects the base of the generator directly to the conduit 28 and wash box 3| through the threeway valve 28.

' Generator II is provided at a point above the which is supported a layer of coke or other solid gas-making fuel several feet in depth. The bed of coke within the generator I. is replenished from time to time through a charging door" at the top of the generator. The carbureter H is also provided near its base with a refractory ,checkerbrick arch ll upon which is supported check'erbrick 42 filling the carbureter to a depth of several feet. The superheater II is also filled vwith checkerbrick fl throughout a substantial portion of its height, and is equipped with a stack v The base of the generator II is provided with a and a specially designed combination forced draft oil burner and oil spray unit 5!. is mounted at the top and in the vertical axis of the carbureter l4.

Air for operating the oil burner element of the unit 50 enters the unit tangentially from a valved secondary air connection 52. Valved steam supply connections 54 and 56 open respectively into the top 01' the generator and into the top of the superheater. Also a valved hydrocarbon gas supply line 51 conducts hydrocarbon gas from a source (not shown) into a vertical manifold 58 from which the gas may enter the generator ll either below the grate 3 or above the bed of fuel in the -generator. Manifold 58, together with a valved by-pass connection 6', also serves for conducting steam from the steam supply pipe 54 into the base of thegenerator.

The combination oil burner and oil spray unit 50 which is mounted vertically at the'top of the carbureter consists essentially of an outer cylindrical shell or T having a tangential side inlet for air from the air supply pipe 52. The bottom outlet of the T 50 is bolted to the top carbureter nozzle. Oil is supplied to an axially mounted oil burner 64 by a valved oil pipe 6, and steam for atomizing the oil is supplied by a valved steam connection 68. A multi-nozzle water cooled rosette type 011 spray it is suspended concentrically r around the oil burner 64 within the'T Blfcarbureting oil being conducted to the spray froman oil supply pipe 12, while any steam desired for purging .the spray is conducted thereto from a steam connection I4. The combined burner and oil spray unit is further cooled by secondary air which enters the T tangentially from the pipe 52' on its way through the T 50 into the top of the carbureter ll.

Referring to Fig. 2', corresponding parts are numbered the same as in Fig. 1. The, principal difference between the apparatus of Fig. 2 and that of Fig. 1 consists of replacing the'carburete'r checkerbrick 42 of Fig. 1 with a carbon filtering and cracking screen 15 consisting of a bed of small substantially uniformly sized ceramic bricks or balls. The depth of the screen 16 is preferably in the neighborhood of only two to three feet. Since temperatures as high as 2000 F. may be developed within the screen ",it is preferably composed of 'mulllte forming type of refractory the air" blast passed throughthe generator fuel or'other high aluminaceramic brick adapted to withstand spelling due to the alternate heating and cooling. The individual ceramic bricks or balls which make up the screen 16 are preferably sized so that their maximum linear dimensions or diameter lies in the range 2 to 3 inches.

A valved air supply pipe 18 is ported out in the top of the superheater element I! ofthe water gas set illustrated in Fig. 2,'and anadditional waste gas stack valve 80 is ported out of the gas of!- take I at a point between the three-way valve ill and the wash'box'".

For control purposes, thermocouples 82 are mounted in the lower portion of the carbureterand in the lower portion of the superheater.

For convenience of illustration, the water gas sets which have been illustrated in Figs. 1 and 2 have been shown asfltted with hot valves and connections, not all of which are necessary for practising any one of the preferred operating of coke is employed in the generator", and the first step consists in raising the temperature of the coke bed in the generator and the tempera- "tures of the refractory fillings of the carbureter and superheater to gas making temperatures.- During this heating period, primary blast. air may. be introduced from connection 46 into the base-- burner 4. By employing the oil burner at the top of the carbureter the temperatures of the refractory fillings of. the carbureter and superheater can be raised to the desired operating range regardless of the condition of the coke bed in the generator, and due to the high flame temperature of the burning oil the products of com- I bustion thereby produced have a higher temperature and transfer heat to the refractory at a high.

rate, thereby shortening the heating period and correspondingly increasing the gas make capacity of the set.

At the end of the heating period stack valve 45 at the top of the superheater I8 is closed, the

air supply is cut off at the valves in pipes 46 and 52, and the oil burner 64 is also cut off. After a short upsteam purge natural gas oil gas or other hydrocarbon gas is then introduced into the base of the generator through gas connection 51 and manifold 58, and the oil sprays 48 and 10 at the top of the generator and carbureter are turned on, make gas passing in series through the bed of coke in the generator and thence through the carbureter and superheater to the wash box 30 and out to storage through ofitake 32.

In order to accomplish the stated object df the invention, which is the production of a natural gas substitute, the heating operation is controlled either by employing a small amount of steam in bed, or by using a short steam purge following operation which takes place during the first p'art of the make cycle is'continued until the temperature of the coke bed in the generator has been reduced within the range 1700 F.-1900 F. The supply of hydrocarbon gas and steam is then cut oif by closing the valves in the pipes 51 and '58, at the same time closing hot valve 24 and opening hot valve 22. During the latter part of the gas make period oil gas is produced by continuing the introduction of oil into the top of the generator through oil spray 48, and passing the resulting oil vapors and gas downwardly through the bed of coke in the generator and thence through the connection into the top of steam purge, after which the cycle is repeated.

' by'cutti-ng off the purge steam supplyto the gen- ;elrator, opening the stack, and starting the reintroduction of blast air to the base of the generator, supplemented if desired by the operation of the oil burner 64 at the top of the carbureter.

When operating 'on a cycle such as that just I described the calorific value and. combustion characteristics of the make gas produced are regulated largely by the temperatures which are maintained in the generator fuel bed and in the refractory fillings of the carbureter and superheater, andby the rates of introduction and rates of passage of the hydrocarbon gas, oil vapors and steam employed through the generator fuel bed -and through the refractory fillings of the car' bureter and superheater. These temperatures are controlled by regulating the supplies of air, oil, gas and steam to the generator and the supplies of air, oil and steam to the carbureter oil sprayburner unit.

A second cycle which may be practised in the apparatus of Fig. l isa modification of the first cycle described, according to which oil gas is produced in the generator l0 simultaneously with a gas reformingcperation. In practising this cycle the apparatus is heated up with a forward blast, and between heating periods hydrocarbon gas for reforming is conducted into the top of the generator through gas inlet- 51 and manifold 58, with or without admixture therewith of a small amount of steam supplied from pipe 54. Simultaneously with the gas, fuel oil or gas oil is introduced to the top of the generator through oil spray 48. The oil is rapidly vaporized and the'oil vapors cracked in an atmosphere of hydrocarbon gas undergoing reforming, during the passage of oil produce an enriching gas of approximately 1100-1300 B. t. u./cu. ft. during the passage of the vaporized carbureter oil in an atmosphere of reform gas and oil gas through the checkerbrick bottom of the generator through connection into the top of the carbureter. The blow gases are burned with secondary air while passing downwardly through the carbureter and upwardly through the superheater. Following the down blast in the generator, the valve in air supply connection ,84 is closed, the hot valves 22 and 24 are reversed, and air is blasted upwardly through the generator from the air connection 46. This air is preferably saturated with steam introduced through the connections 54, 60, and 58 into the bottom of the generator. The hot producer gas product of the upblast is burned with secondary air in the carbureter and superheater, and the blast gases are exhausted through the stack valve 45.

Following the down and up blasts there is a short steam purge, during which steam is introduced in the bottom of the generator for a few seconds, resulting water gas being either burned and the product exhausted to atmosphere, or conducted through the carbureter and superheater in an unburned condition for blending with the make gas. closed and hydrocarbon gas to be reformed is introduced from connection 51 into the base of .the generator beneath the grates, with simultaneous introduction of oil into the top of the generator and into the top of the carbureter through oil sprays 48 and 10. The oil thus introduced is vaporized and cracked in the upper portion of the generator fuel bed and in the carbureter in an atmosphere of reform gas as the reform gas and vaporized oil pass through the top of the generator and through the carbureter and carbureter screen 16.

This gas reform part of the cycle may be followed by a second stage of the make cycle in which oil gas is produced within the generator fuel bed by spraying oil onto the top of the bed and conducting the vaporized oil downwardly through the bed and thence through connection 20 into the top of the carbureter, where additional oil gas may be generated by introduction of spray oil through the element 10. This downrun of oil is suspended whenever the temperature of the generator fuel bed drops below 1700 F., and the make cycle is closed with a short down steam purge during which steam is introduced through the steam inlet 54 and carried succes sively through the generator fuel bed and through the carbureter screen 16 and superheater checkerbrick. i A fourth cycle will now be described in which use is made of the backrun connection 34. The set is first heated to a suitable operating temperature by an up blast, as in the previous cycles described. The up blast is followed with short upsteam purge, the purge gases normally being exhausted through the stacks Following the steam purge natural gas or other hydrocarbon gas to be reformed enters the base of the generrator from connection 51, and the reform gas which is produced within the generator is carbureted by oil sprayed into the top of the car- The stack valve'is then bureter and/or into the top of the generator. The mixture of reform gas and oil gas thus produced is conducted through the carbureter and superheater and thence through the wash box to a holder (not shown). Part of this gas may be returned to the gas connection 57 for reforming during the same or a subsequent make cycle.

The gas reform portion of the make cycle is followed by production of oil gas within the generator on a downrun cycle wherein oil is introduced at the top of the generator through the oil and steam, is terminated by a steam purge which proceeds for a few seconds after the oil sprays 48 have been cut off, the steam being introduced through the connection 56 at the top of the superheater, and the purge gases removed by the backrun connection 34 through the wash box to the holder, or exhausted to atmosphere through stack valve 80 on the wash box side of the three-way valve 28. This down purge may be followed by a short up purge with steam introduced into the.base of the generator before the reintroduction of air.

A fifth cycle which may be practised in the apparatus shown in Fig. 2 involves a reverse air blast operation in which are is introduced into the top' of the superheater through air connection '18. In passing through the refractory filling of the superheater and carbureter the air burns out any carbon deposited thereon during a preceding make cycle. The reverse blow gases after passing downwardly through the generator fuel bed are removed from the foot of the generator through backrun connection 34 and normally exhausted to atmosphere through the stack connection 80. This reverse air blast is followed in the cycle by a short upsteam purge, which may in turn be followed by an upblast and by another steam purge. During the first part of the make cycle rich hydrocarbon gas is reformed by passing upwardly through the generator fuel bed and thence in series through the carbureter and superheater, with simultaneous enrichment of the reform gas by carbureter oil gas produced in the carbureter and superheater elements. This first portion of the make cycle is followed by a second stage during which oil gas is produced in the generator during a downrun, the oil being introduced through the oil sprays 48 to the top of the generator with simultaneous introduction of a small amount of steam on a backrun into the top of the superheater through connection 56.

The process is essentially a cyclic process for manufacturing chiefly from oil a gas having combustion characteristics and calorific value sufficiently near to the corresponding properties of natural gas that it may be safely used as a peak load or standby fuel in natural gas distribution systems. three phase system. In the first phase a basic gaseous component is produced by reforming natural gas, oil gas, or other gas rich in gaseous The process is essentially a two or' hydrocarbons, within the coke bed of a water gas generator, while regulating the temperature of the coke bed and the space velocity at which the gas is passed therethrough to yield a. reform gas having a calorific value not substantially lower than 600 B. t. u./cu. ftfwith a methaneethane content not substantially less than 30%- '35% by volume, and an inert content of C02 and nitrogen not substantially in excess of 15% by volume. The second phase of the proces: consists of an oil cracking operation carried out in an atmosphere of reform gas, wherein fuel oil or gas oil is cracked at a controlled rate and within controlled temperature limits to yield an enriching gas of 1100-1300 B. t. u./cu. ft. having a methane content of at least 35% and an ethane and illuminant content in the range 25-30%.

gas within the generator coke bed at a temperature in the range 1800-2000 F. with a gas velocity through the coke bed of 50-125 cu. ft. per;

min. per sq. ft. of generator grate area, in the presence of 1 1b. of steam for every 25-70 cu. ft. of gas.

The other make gaswhich is illustrated in the table is a standby gas produced by recycling part of the make oil gas, with the same operating conditions in the generator as set forth above except that the amount of steam is decreased to approximately 1 lb. of steam for every 45-125 cu. ft. of oil gas reformed. During the reforming operation the volume of the gas is increased so that every cu. ft. of natural gas yields approximately 1.91 cu. ft. of reformed gas, and every cu. ft. of oil gas yields approximately 1.68 cu. ft. of reformed gas.

Percent component 00,, n1, 0., oo, 11,, on. 0.11., :5 gas Volume ratio perperperperperperper- N I B. t. u./cu'. it. gram reformed gas cent cent cant cent cent cent cent my Reform Combined to raw gas gas oil gases Raw 90 Naturalga! 0 1 3.8 0.1 82.2 6.1 7.7 1040 0.65 Oil gm 1 2 21. 0 0.2 6.7 25. 8 38. 2 3.4 2. 6 1000 0. 66 Reformed gas:

Prom natural m" 2 0 2. 4 0.3 10. 8 34. 2 36. 7 13.0 556 0. 53 1, 91 From oil gas 2 4 2. 4 0.4 16. 8 41.9 30, 5 1.8 3. 8 580 .49. 52 1, 68 Generator oil gas and carburetor oil 0. 8 27. 5 0. 1 3. 8 21. 4 40. 4 3. 8 2. 2 1121 0. 71 M oil gm with orm gar: I From natural gas. 1. 1 22. 1 0. 2 5. 2 24. 2 39. 7 3. 0 4. 5 1000 0. 67 21. 4 Irom oil gas..- 1. 2 21. 9 0. 2 6.7 25. 8 38. 2 3. 4 2. 8 1000 0. 66 22. 4

According to a third phase of the process which is more or less optional, additional oil gas of relatively high methane content (above 35%) may be produced within the bed of coke in the generator simultaneously with or immediately following the gas reforming operation. In general, the oil cracking operations are conducted at a temperature range below that at which the gas reforming phase is carried out, and on the other hand the gas reforming phase is practised within a temperature range considerably below that which normally obtains within the coke bed of a water gas generator during the usual water gas generating cycle.

To illustrate results obtainable by practising the process, a table is appended hereto which shows the character of gas which is treated in the reforming stage of the process, the composition of the oil gas which is produced during the oil cracking phase of the process, and the composition of the resulting high B. t. u. make gas. In producing the gas indicated in the table, the oil used in the generator was a 3% Conradson carbon fuel oil having a gravity in the range 20- 24 B. The oil used in the carbureter was a. gas oil of 34-36 B. gravity. Oil was cracked in the generator within a temperature range 1700- 1900 F. at the rate of 0.6-1.0 gal. of oil per sq. ft. of generator grate area per minute, in the I By reference to the table, it will be noted that the final make gas has approximately the samecomposition, irrespective of the type of hydrocarbon gas which is reformed and irrespective of the type of oil which is used for enriching the reformed gas. The final make gas which is produced has considerably lower illuminant and carbon monoxide content, and a considerably higher methane content, than any corresponding gas which has been heretofore produced within a water gas generating'set operating with a bed of 'coke. The make gas of the present invention also has a considerably lower content of inerts, with possibly a slightly higher content of hydrogen, than gases which have heretofore been proposed as natural gas substitutes. The result is that the gas produced by the process of the present invention has a much higher utilization value as a natural gas substitute than gases produced by any other known process. Furthermore the cost of producing a natural gas substitute gas by the present process is lower than the cost of producing other similar gases because of lower oil consumption and coke and steam requirements. Furthermore the present process can be carried out with high capacity in a three-shell water gas generating set, with consequent reduction in 1a- I bor and investment costs chargeable to each 1000 cu. ft. of gas produced.

The final make gas usually consists of approximately 48% by volume of the carbureter oil gas, approximately 30% by volume of the generator oil gas, and approximately 22% by volume of the reform gas. The carbureting oil gas is produced in the carburetor within an atmosphere of reform gas passed therethrough from the generator. This insures maximum efficiency in the conversion of the oil introduced into the carburetor to a gas of suitably high calorific value and methane content. r

The invention having been thus described, what is claimed as new is:

1. In manufacturing combustible gas of calorific value and combustion characteristicsv substantially corresponding to those of natural gas, the cyclic process which comprises periodically raising the temperature of a bed of coke in a gas generator within the range 1800-2000 F. by blasting a mixture of air and steam therethrough, burning the blow gases thereby produced and regenerating heat thereby developed, and between air blasting periods reforming hydrocarbon gas to a gas of lower calorific value by passing the gas through the heated coke bed at a rate of about 100-125 cu. ft. per sq. ft. of generator grate area per minute, and enriching the reform gas by vaporizing and cracking oil, the oil being exposed at substantially atmospheric pressure to cracking temperatures in the range 1500" F.- 1900 F. at'the rate of approximately 0.64.5 gal. of oil per sq. ft. of crackingzone area per minute in an atmosphere of hot reform gas.

2. An improved cyclic process of making combustible gas of calorific value and combustion characteristics substantially corresponding to those of natural gas in apparatus comprising a single gas generator, a single carbureter, and a single superheater connected in series, with a bed of incandescent coke in the generator and refractory brick in the carburetor and superheater, which process comprises periodically heating up the apparatus by blasting a mixture of air and steam in series upwardly through the bed of coke in the generator and thence through the checkerbrick filling of the carburetor and superheater while burning the blow gases with secondary air which is introduced into the top of the carbureter, and between periods of heating reforming hydrocarbon gas by passing it through the high temperature bed of coke at a rate of about 100125 cu. ft. per sq. ft. of generator grate area per minute while holding the coke bed in the range 1800 F.-2000 F. and simultaneously gencrating oil gas within the carburetor and superheater in an atmosphere of the hot reform gas from the generator, the oil being exposed to maximum cracking temperatures in the range l500 F.l800 F. at the rate of approximately 0.6-1.5 gal. of oil per sq. ft. of carburetor cracking area per minute.

3. A'process as defined in claim 2 in which the make cycle is split into two parts, the first part constituting the gas reform operation as defined in claim 1, and the second part comprising a generator oil gas producing stage during which fuel oil is vaporized and cracked by passing it in series through the coke in the generator and through the carburetor and superheater, after the coke bed temperature has been stabilized in the range 1700-1900 F., oil being passed through the-coke bed at a rate of approximately .8 gal. of oil per sq. ft.. of generator grate area per minute in admixture with approximately fi ths ths lbs, of steam per lb. of oil.

4. An improved cyclic process of making combustible gas'having a calorific value in the range 900-1100 B. t. u./cu. ft. and combustion characteristics substantially corresponding with those of natural gas in apparatus comprising a single areaoaa which comprises periodically heating up the ap-: paratus by air blasting the coke in the generator and burning the blast gases thereby produced in contact with the carbureter screen and the superheater checkerbrick, and between periods of heating introducing hydrocarbon gas into the top of the generator and simultaneously spraying oil into the top of the carburetor, reforming the gas in the generator fuel bed and cracking the oil in the carbureter in an atmosphere'of the reform gas, passing the mixed oil gas-reform gas there by produced through the superheater, and returning a part of the reform gas-oil gas mixture into the generator in admixture with a small amount of steam, the temperature and rate of injection of gas, oil and steam into the apparatus being controlled and adjusted to produce a final reform gas-oil gas make having a calorific value and combustion characteristics within the range specified.

5. In manufacturing combustible gas having a calorific value in the neighborhood of 1000 B. t.u./ cu. ft. and a methane content of at least 35%, the cyclic process which comprises periodically raising the temperature of a bed of coke in a gas generator to l800 F.-2000 F. by blasting a mix-=- ture of air and steam therethrough, burning the blow gases thereby produced and regenerating heat thereby developed, and between air blasting periods reforming hydrocarbon gas to a gas of lower calorific value by passing it through the heated coke bed at the rate of 100-125 cubic feet per sq. ft. of generator grate area per minute, generating oil gas by introducing fuel oil into the top of the generator and passing the iuei oil vapors downwardly through the generator fuel bed at a rate of about .6-1 gal. per sq. ft. of genera tor grate area per minute, and enriching the reform gas and the generator oil gas by vaporizing and cracking oil utilizing heat regenerated from the blow gases, such oil being exposed at sub stantially atmospheric pressure to cracking temperatures in the range 1500-l800 F. at the rate of approximately .75-1 gals. of oil per sq. ft. of cracking zone area per minute, in an atmosphere of the hot reform gas.

6. An improved cyclic process of making combustible gas in apparatus comprising a single gas generator having therein a bed of coke, a single carbureter having therein a carbon filtering screen of small uniformly sized ceramic pieces supported transversely thereof, and a single super-heater filled with checkerbrick, which process comprises periodically heating up the apparatus by blasting the bed of coke in the generator with air, burning the blow gas at the top of the carbureter, and passing the products of combustion in admixture with sufficient excess air to burn off deposited carbon in series through the carbureter screen and superheater checkerbrick, and between periods of heating spraying high gravity oil into the top of the generator while simultaneously passing hydrocarbon gas containing upwards of 85% gaseous hydrocarbons longitudinally through the generator fuel bed, passing the mixture of vaporized oil and reform gas through the carburetor screen, thereby further cracking the oil and depositing oil carbon within the screen, passing the mixed oil gas and reform gas through the superheater, and before beginning the next heating operation purging the appara tus with a backsteam purge in series through the superheater, carbureter and generator, followed by a short reverse air purge through the same path followed by the steam purge.

10 bed, and'between heating periods passing hydrocarbon gas of high methane content through the coke bed and conducting the reform gas thus produced through the refractory bed while simultaneously spraying petroleum oil onto the refractory bed, removing the resulting reform gascracked oil gas mixture from beneath-the refractory bed, and recycling 9. portion of the reform gas-oil gas mixture in admixture with a controlled amount of steam through the bed of .coke to thereby produce a reform gas adapted for enrichment with oil gas to produce a final gasmixture of the calorific value and methane content indicated;

ALFRED JOHNS-ON. uoaais M. Bamnmqna.

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