US2207985A - Manufacture of gas - Google Patents

Description

INVENTORS N O S N H O J w.. R AM 5 M. BRAN DEGE BY l July 16, 1940. A. JOHNSON Erm. V MANUFACTURE OF GAS Filed May 24, 1957 Patented Juy lo, 1940 l 2,207,985 i t UNITED STATES PATENT OFFICE,

MANUFACTURE OF GAS Alfred Johnson, Summit, and Morris M. Brandegee, Plainfield, N. J., assig'nors to Combustion Utiliti'es Corporation,-New York, N. X., a corporation of Maine Application May 24, 1931, serial No. 144,432

3 claims. (o1. 2oz-23) 'This invention relates to the manufacture of After stripping this tar from the gas the combustible gas, and more 'particularly congas has a heating value of 900-1600 B. t. u. per cerns an improved method of converting petrolecu. ft., and must be reformed to produce a gas um oils into combustible gas of combustion charhaving combustion characteristics more nearly 5 acteristics generally adapted for use in industrial resembling coal gas or water gas or whatever type and domestic heating. of gas is finally desired. For producing a final Methods heretofore suggested for converting gas of relatively high B. t. u. (for example 1000 the gas oil and fuel oil fractions of petroleum B. t. u.) only part 0f the i'ioh gas produced in oil into a fuel gas have not generally been very the lst stage need be reformed-after which the efilcient. One reason for this is that, Such probalance of the rich gas is admixed with the reo posed methods have usually involvedv a single formed gasstage oil cracking operation which yields a gas Another feature of the invention resides in an of relatively low caloric value and gravity, along improved continuous process for Simultaneously with considerable production of free carbon, and carbonizing coal and generating both oil gas some heavy petroleum tar and pitch of. little and Coal gas having Similar combustion charu value. acteristics in a multiple retort coal gas generat- 'Ihe primary object of the present invention is ing unit by an Operating Cycle which insures to provide an improved and economically efli- Segregation of Coal-tar and 0i1tarbypr0duots. cient process by which heavy petroleum oil disand recovery 0f an oil tar having a large content tlllates and residual oils may be converted to a of benZol and toluolfuel gas with a minimum economie 105s through With the above and other objects and features conversion to .free carbon and unsaleable heavy in View, the invention Consists of the improved tar. y method of generating combustible gas which is Another object of the present invention is to hereinafter described and more particularly deprovide improved operating cycles, either conned by the accompanying Claims- 25 tinuous or intermittent, whereby existing gas In the drawing forlning a Dart hereof there retort benches may be operated efficiently and have been illustrated Preferred apparatus aieconomically for converting petroleum oils into rangementst adapted for Practicing the Process saleable domestic fuel gas and light oil by-prodof the Present invention.

ucts. The drawing is a view in vertical side eleva- 3 Another object of 'the present invention is to tion. With Darts broken away and parts in longiprovide improved operating cycles for existing tudinal section, showing a horizontal gas retort coal gas retort benches whereby the production bench having associated therewith oil and gas capacity of such apparatus may be considerably injection nOZZleS and an Oil gas Purifying and increased at a minimum cost by simultaneous reforming circuit of the type contemplated bythe 35 production of oil gas, coal gas and/or 'Water present processgas therein without adverse effect on quality of in the drawing the retort bench therein shown the resulting gaseous, liquid and solid prodembodies a plurality of horizontal gas retorts ucts. Y H0, Illia, having refractory walls H2 surround- 40 A feature of the invention resides in an imed by heating flues H4- Each retort has at its 40 proved two-stage method whereby petroleum gas forward end a removable door i i6 through which oil and fuel oil fractions can be efliciently and a Charge of Coal may be introduced to the retort economically converted into high yields of marfor carbonization, and also through which the ketable light oil and fuel gas products. completed coke may be discharged. Heat for Petroleum oils, l. e., gas oil and heavy fuel oil carbonizing the retort charge is developed by 45 fractions, can be cracked by. the first 10W temvcombustion of fuel gas in the fiues lll, and is perature vapor-phase cracking stage of the prestransmitted to the charge by conduction through ent process (operating in the temperature range the walls H2. Gas which is produced in the up- 11001700 F. at atmospheric pressure) to proper retort H0 during ,the carbonization of the duce a rich gas carrying 87%18% by weight of charge is removed throughv an off-take pipe H8 50 the oil used of polymer tar vapors. The tar which is ported out in the top of the retort adwhich is recovered by condensation and scrubjacent the door IIB. This oE-take conducts the bing is a valuable low gravity tar sometimes congas into a hydraulic main |20 through which the taining as much as 10%-60% of light oilsbegas is carried to purifying equipment and thence 56 longing to the benzene toluene and xylene series. t0 a holder (not shown). u

The gas which is produced in retort Illia is removed through an off-take pipe |2| into a gas cooler and interchanger |22, and thence to a tar scrubber |23. From the scrubber |23 puried gas is returned by an exhauster pump |24 through interchanger |22 and pipe |25 to a gas injector |26 which is mounted in the rear wall of retort in position to project an atomized gas-steam mixture into the retort. This rich gas may be forced through a light oil recovery plant by exhauster 24 and circuit |29 prior to its return through cooler |22 to retort H0.

A steam-oil atomizer |21 is mounted horizontally in the rear wall of retort Illa in position to project an atomized oil-steam mixture into the retort. The atomizer |21 is shown as mounted centrally at the cool end of a high temperature refractory tube |28 having its hot end.

ported out in the retort and extending rearwardly thro'ugh the back wall of the retort. Oil is conducted to the mixing throat of burner |21 from an oil preheating coil |28, by a valved feed pipe |30. Steam is supplied to the inlet end of the burner |21 from a pipe |32. Provision is made for supplying air and steam to the gas burner |26 through valved pipes |34 and |36, respectively.

'I'he gas retorts can be operated on a continuous or substantially continuous cycle, because heat for their operation is derived by continuous combustion of gas in the ues surrounding the retort walls. While only two retorts have been illustrated, the cycle is designed for application to a bench of several retorts operating on alternate charging and discharging periods.

Coal, preferably bituminous coking coal, is rst charged to oneor more retorts` indicated by the numericall designation |||).to approximately thefull depth of the retort, after which vthe charging doors are closed and heat is applied to--the retort byv circulation of burning gaseous fuel through theV heating ues ||4 which surround the Walls of the retort. After heating the charges of coal in the retorts H0 for a period of from one to six hours, the top and peripheral portions of the charge in one retort ||0 will have been raised in temperature to above 1700 F., with formation of a thin layer of Ycoke. Carbonization of a. charge of coal in a retort proceeds from the periphery inwardly at a rate which is substantially inversely proportional to the square of the thickness of Athe charge. Consequently a retort charge which may require from 12 to 18 hours for complete colnng, will develop a layer of coke 2 to 3 inches in depth in its outer periphery within a period of from one to six hours.

After heating the charge of coal in retort ||0 for a period of say one to three hours, a second retort Illia is charged with a full charge .of previously formed coke, and heat is applied to the charge in retort la'by circulation of burning gases through the heating ue surrounding this retort, the charging cycles and heating of retorts l0 and lilla being timed so that when a charge undergoing carbonization in retort il@ has been stabilized in the temperature range i700 F.-2200 F., the temperature of the charge of coke in retort lllia should be substantially simultaneously stabilized at a temperature in the range 1100V F.1700 F.

At the time the coal and coke charges in retorts lill and H011, respectively, have been brought to the above indicated stabilized temperatures, atomized petroleum oil (atomized fuel oil or gas oil) is introduced into the hot coke charge in retort Illia through the oil atomizer |21. Steam is usually employed for atomizing the oil. The oil is preferably preheated before introduction into the retort, ||0a by passing itthrough preheating' coil |28 in the waste gas flue which serves for conducting hot flue gases away fromthe retort setting.

While continuing application' of heat to the-7 coke charge in retort ||0a by circulation of heating gases through the heating iiues III, the atomized oil or atomized mixture of oil and steam is injected longitudinally into the retort and through the retort charge. It is desirable that introduction of oil, or oil and steam, into the charge in retort |||la shall only take place when the temperature of the retort charge lies in the range 1100 F.1700 F., and preferably in the.

range 1300* F.1500 F. Likewise vit is desirable that the introduction of rich gas to the retort charge ||0 shall not begin until the temperature of the retort charge in ||0 shall have been stabilized in the temperature rang 1700 F.-2200 F.

During the short time that the atomized oil or oil-steam mixture remains in contact with the charge of coke in retort Illia. the oil is cracked forming a richoil gas of 2100-950 B. t. u./cu, ft.

The gas thus produced exits from the retort through olf-take pipe |2| and is cooled -by passing .it through the heat interchanger |22. .The rich scrubbed out of thegas, and the gas is then carred by a return pipe |25 back. through an exhauster |24 to the heat interchanger |22 wherein it absorbs preheat by'heat interchange with the hot gas entering the interchanger from retort Hlla. From the interchanger |22 the cleaned and puried rich gas is forced through the gassteam mixer |26 into and through retort H0, in which a chargeA of coal is being carbonized. The mixture of devaporized rich oil gas and steam which is introduced into retort ||0 enters an atmosphere of coal gas4 which is continuously Y being liberated from the charge in the retort as the coal therein undergoes carbonizatiom u The coal gas which is evolved` in retort ||0 normally has an average caloric value of 550 B. t. u. per cu. ft. and a mean specic gravity of about .50 based on a specic gravity of one for air. By varying the rates of introduction of oil gas .and steam through the mixer |26 into the -retort ||0, and by varying the temperatures obtaining in the retorts ||||a and llll'within the temperature range` specified, the resulting mix-4 ture of reformed oil gas and coal gas can be adjusted as to heating value and speciiic gravity Within the ranges 45th-800 B. t. u. per cu. ft. and

.40 and .65 gravity. The resulting mixture of coal gas and oil gas may have substantially'the same combustion characteristics as coal gas, so that'by the present method a retort setting can have its gas producing capacity increasedA as much as 50% Without any substantialv increase in plant investment. Furthermore this increase in capacity can be accomplished without any substantial increase vin operating cost, because the tar and light oil luy-products which are asoman recovered form a by-product tar have a saleable value which substantially pays -for the fuel oil is operated at a temperature in the range 1100- out having therein a charge of coke.

1700 F. and preferably in the range 1300 F.- 1500 F. When operating the retort within the above specified temperature range the oil-steam mixture which is introduced to the retort charge, and the oil gas-water gas product thereof, is passed through the retort charge from end to end at a rate such that the atomized oil and resulting crackd oil gas is exposed to the temperatures obtained within the retort for a period of only about 0.25-1.5 seconds.

It will be understood that the retort Hoa can be operated as an oil cracking zone with- However, more efficient heat transfer and better cracking is obtained when employing a charge of coke or of small sized ceramic brick in the retort Illia. Retort temperatures below 1700 F. vin retort Illia are necessary particularly when employing a coke charge therein, in order to reduce to a minimum the production of unsaleable heavy tar and free carbon. Likewise oil gas may be reformed in retort l I when the retort is empty or filled with fully carbonized coke or refractory, on a straight two-stage reform oil gas cycle. The carbon resulting from the cracking of oil may be reacted with steam.

When steam is introduced with the oil into retort Ila the proportion of steam to oil is preferably maintained within the limits 1/10 to 5/10 lb. of steam per 1b. of oil. The rate of introduction of oil,- or oil-steam mixture, to the retort charge, is also preferably regulated to produce a rich oil gas having a calorific value in the range 950- 2100 B. t. u. per cu. ft., while holding the temperature in the retort Illla in the range 1100- 1700" F. In the same way the rate of introduction of oil gas for reforming into the retort l I0 is also preferably regulated, as is also the rate of introduction of any steam or air along with the oil gas, so as to produce a reformed gas normally having substantially the combustion characteristics of coal gas, while holding the temperature within v the retort IIO within the range 1700* F.-2200 F.

The process, whether conducted on an intermittent or continuous cycle, has two phases, which may be characterized as a rich gas make and a lean gas make. During the rich gas making phase, the principal operation is one of vaporphase oil cracking and polymerization at relatively moderate temperatures (1100 F.-l700 F.) and usually in the presence of some steam vor water gas, to yield a rich gas product of high heating value along with light oils and tar under conditions producing a minimum of free carbon residue. During this first phase steam is not employed during the `make in excess of 0.1-0.5 lb. per pound of oil. By stripping the tar and valuable light oil vapors from the rich gas product produced in the rst phase of the processbefore practicing the second phase during which the stripped high B. t. u. gas product is reformed to a lean make gas-a valuable liquid by-product is recovered andat the same time the gas that is to be reformed in the second phase is stripped of the constituents which are the principal source of the large free carbon waste which vis encountered whenever an attempt is made to crack such oils in one stage operation into a iinal lean gas product. After the removal of this tar the rich make gas from the irst phase can be reformed in the second phase at a higher temperature (1700 F.2200 F.) by gas phase cracking reactions carried out in an atmosphere of steam, water gas and/or coal gas, substantially without the formation of any free carbon.

To further illustrate the advantages of the process the following table is given which shows the effect of cracking temperature during the first phase of cracking on products recovered from two typical oils:

Cracking results of rst stage of cracking when using gas oil, are shown below- Temperature crack' o ing.-. 11oo F. 19.00 F. 1500 F. 170 F- Recoverable light oil pound per pound oil 085 120 100 068 Free carbon produced pound per pound oil.l Trace .105 .355 Liquid dtar produeeg poun per poun oil 780 400 255 110 Total light oil, carbon and tar; Round per poundo .865 .520 .460 .533 Percent free carbon k in tar (no screen).. .10 29.2 Above 50% with free deposit.

Percent free carbon intar (withscteen). .10 5.9 32.5 Cu. it. scrubbed gas per gallon oil 12. 7 49. 2 71. 9 91.0 B. t. u. per cu. ft.

scrubbed gw 1637 1525 1220 905 Sp. gravity scrubbed gas. .965 .888 .68 .465 B. t. u. in scrubbed gas per gallon of oli cracked 21,800 74,900 87,700 82,300 Time of contact .5 sec. to 1.5 sec. Steam pounds per pound oil 0.06 0.10 0.25 0.50

Vperature cracking range with good results. 'Ihe distinguishing difference over use of gas/oil being the production or more tar and free carbon and slightly lowergas yields. The calo-ric value and gravity of the 'gas over this range of cracking is essentially the same as that secured from gas oil. The following table shows results secured from a 16.5 A. P. I. Bunker rC oil containing 10% Conradson carbon.

.f ll Tentge "f uoo F. 1ao0 F. 15o0 F. 1700 F.

Recoverable light oil pound per pound f. oil .064 090 075 051 Free carbon produced pound per pound oil....k .100 100 179 .366 Liquid gar produceg poun per poun Oil 735 450 341 232 Total light oil, carbon and tar; pound per pound oil 899 640 595 649 Percent free carbon in tar (no screen). 12. 0 18. 7 34. 5 Above 50% with free carbon deposit. Percent iree carbon Blxtar (vith scrbeg- 2. 0' 3. 2 7. 4 19. 2

u. n scm gas per gallon oil.-- 17, 900 64, 700 75, 600 71, 000 Time in contact. .5 sec. to 1.5 sec. Steam-lbs. per lb. of

oil 0. 10 0. 15 0. 30 0. 60

The above cracking results for the first stage of oil cracking for gas and fuel oils over the low cracking temperature range 1100*? F.1700 F. are

obtained when the oil feed and steam rate is that substantially as shown. With higher rates the cracking temperature required to give the same results is slightly greater, although within praclthe formation of free carbon starts at a temperature slightly below 1300 F., witha rather rapid increase in quantity at temperature in excess of 1500 F. The free carbon yield in the temperature range of 1500 F. to 1700 F. is within practical operating limits for fair operating results, but gives some deposit difficulties with free carbon and stiff heavy tar in the'cooling system. It will further be noted that an optimum light oil and thermal hydrocarbon gas recovery occurs in the temperature range of 13001500 F., and that while the tar yield within this range is less than that below 1300" F. the quality is unimpaired with excessive free carbon, as the quantity of the latter, even though not screened out as with coke or refractories in a retort, is not excessive.

We have also noted that an optimum produc-` tion of toluene, benzol, and xylene occurs over the cracking temperature range of 13001500 F. Below this range the light oil, While aromatic, contains a large per cent of low boiling point parailin oils, while above this temperature range `at 1500 to 1700" F. an optimum yield of benzene occurs, with a rather rapid decline in the toluene yield.

Above 1700 F. the quantity of the light oil lfractions falls rapidly. Thevliquid tar yield is low, free carbon in large quantities appears, and thle hydrocarbon thermal yield of gas produced fa ls. Y

Having described our invention, what we claim as new is 1. The process of converting a petroleum fuel oil into fuel gas of predetermined caloriiic value and specific gravity together with a valuable liquid by-product which comprises, vaporizing and cracking a flowing stream of the oil while admixed with .0S-0.3 lb. of steam per lb. of oil at a temperature in the range 13001500 F., and at substantially atmospheric pressure, controlling the rate of passage of the oil steam mixture through the reaction zone to limit the time of exposure of the reaction mixture to the temperatures indicated Within a period of 1/2-11/,2`

seconds,lcooling the gaseous reaction`products and separating tar and condensable hydrocarbon liquids therefrom, and reheating the resultant xed gas and owing it in contact with incandescent solid carbonaceous fuel at a temperature of 1700" F.2200 F. in the presence of sufficient steam to adjust the calorific value and gravity.

2. The process of converting a petroleum fuel oil into a valuable liquid by-product and fuel gas, whichl comprises atomizing a continuously owing stream of said fuel oil with 10%-50% by weight of steam and projecting the atomized oil and steam into and rapidly through a bed of hot coke while applying heat thereto in amounts suicient to maintain the coke bed at oil cracking temperatures in the range 1100 F.-1700 F.,

simultaneously carbonizing coal in a. zone separate from the oil cracking zone, cooling theA gaseous products of the cracking reaction and separatingtherefrom condensable liquid hydrocarbon F.-2200 F., to produce a mixture of coal gas,

water and oil gas having substantially the combustion characteristics of coal gas.

3. A process of coking coal and manufacturing gas which comprises transmitting heat to a stationary charge of coking coal in a'retort and thereby raising the temperature of a portion of the charge above that at which coke is formed v and coal gas is liberated, after the body of co'a'1\ in the retort has been partly converted to coke and the temperature has been stabilized in the range 1700 F.-2200 .F., passing an atomized` stream of oilthrough a separate oil vaporizing A and cracking zone maintained yat a temperature of 1100 F.-1700 F., cooling the cracked oil gas and separating condensable liquid hydrocarbon products therefrom, reheating the tar free gas thereby produced, flowing the gas through the incandescent coke in the retort in admixture with steam While continuing application of heat to the coke in the retort in amounts sufcient to maintain the temperature therein in the range 1700 F.2200 F., and completing the coking operation while adjusting the time of contact of the oil gas andsteam with the coke, and the proportions of oil gas and steam, 'to produce a reformed oll gas having substantially the combustion characteristics of coal gas, and discharging coke and gas separately from the retort.

ALFRED JOHNSON.

MORRIS M. BRANDEGEE.

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