US2071286A - Oil gasification process - Google Patents

Description

Feb. 16, 1937. A. JOHNSON ET AL OIL GASIFICATI-ON PROCESS Filed April 25, 1953 v: [N VENTORS ALFRED c/Ofl/Vzf 01V CHARL :5 Elf/tMM/NGER A TTORNE Y 1 Patented Feb. 16, 1937 UNITED STATES PATENT 'OFFICE OIL GASIFICATION PROCESS Application April 25, 1933, Serial No. 667,818

2 Claims.

This invention relates to the gasiflcation of hydrocarbons for the production of a combustible gas having a uniform preselected heating value and specific gravity adapting it for the usual industrial and domestic purposes. More particularly the invention involves a novel'process and apparatus-for the production, from hydrocarbon oils,or from other fluid hydrocarbons such as butane and propane,-of a rich combustible gas having a uniform preselected heating value within the range of from 500 to 1200 or more B. t. u. per cu. it.

According to a preferred form of the invention a combustible gas having a heating value within the range from 800 to 1100 B. t. u. per cu. ft. is produced directly in a single generator shell,- thus rendering the invention of great utility in connection with stand-by equipment used to handle peak loads in systems transporting and distributing natural gas or similar combustible gases of high heating value.

In many respects this invention is similar to and embodies principles of the oil gasiflcation process described in the copending patent application of Alfred Johnson, Serial No. 561,354 filed September 5, 1931 for Oil gasification process and apparatus. It essentially involves the utilization of a heat-insulated generator shell having therein a refractory filtering screen; and it provides during the heating cycle for the alternate successive blasting of the generator screen upwardly and downwardly for the purpose of consuming the carbon deposited therein during a prior gas-making cycle.

Among the more important objects of the present invention are: to provide in novel manner in a process for manufacturing a rich combustible gas from hydrocarbons for supplying the heat requirements of the process in part by the controlled combustion of the carbon formed by the cracking of hydrocarbons in an earlier gas-making cycle, and in substantial'part by the regulated burning of a fuel mixture in connection with the respective blasting of air upwardly and downwardly through a refractory generator screen; and to provide in novel manner for the uniform continuous production in a single shell unit of a combustible gas of high uniform heating value.

In its broadest scope, the invention involves the employment of alternate up-and-down blast stages of a heating cycle through a highly heated filter bed or screen of selectively sized refractory bodies within a gas generator, under conditions adapted to consume the carbon previously deposited within the screen during a previous gasmaking cycle.

The up-blast stage of the heating cycle preferably is divided into two unequal sub-stages, in the first of which blast air alone is used for con- 5 suming the larger part of the carbon within the screen, and particularly that lying in the lower portion of the screen. In the second sub-stage,

a regulated quantity of oil or other fluid hydrocarbon is burned in the presence of air sufllcient not only to completely'consume the said hydrocarbon but also preferably to burn a small additional quantity of the carbon present in the screen. The resultant combustion gases passing upwardly through the screen flow directly to the stack from the generator top.

During the down-blast stage, which preferably also is divided into two sub-stages, the first substage is carried out with an air blast alone, for burning substantially all of the remainder of the carbon present in the screen. Thereafter in the second sub-stage a small amount of oil or other hydrocarbon is completely consumed with air introduced therewith in the generator above the screen,the hot combustion gases passing downwardly through the refractory screen and thence directly to a stack. Preferably the heating operation is so carried out that the amount of heat developed in the generator and the screen is approximately that required to limit the extent of the cracking of hydrocarbons during the gasmaking cycle, to yield a generator gas having the heating value indicated.

This invention is based in substantial part upon the discovery that by blasting a refractory generator screen successively or concurrently with air and with the highly heated combustion gases from the regulated burning of a combustible fluid adjacent and within a refractory filter or generator screen, the blasting being divided into two separate stages in one of which the screen is blasted upwardly,--and in the other of which the screen is blasted downwardly,-it is possible to effect a. very uniform heat distribution within the screen and adapt it for the productionon a 5 commercial scale of a high B. t. u. gas-which in certain instances may have a heating value, close to that of natural gas.

The general tendency for a rising hot zone to exist in any up-blast system is readily counteracted by the additional down-blast stage which helps to carry beat down into the refractory screen. Thus the top of the screen may readily be maintained at a suitable temperature.

In the accompanying drawing, which illustrates a gas generator illustrating one form of the invention; and

Fig. 2 is a vertical sectional-view taken through a gas generator illustrating a second modification of the invention.

Referring now to the drawing, numeral ll designates a generator shell provided with a suitable refractory lining l2. Mounted in the lower part of the generator is a. refractory arch 14 supporting thereon a gas-permeable filter bed or screen I6 of considerable depth formed of refractory bodies,the latter of which may, if desired, be impregnated or coated with, or may otherwise contain high-melting metals such as nickel, cobalt, vanadium, chromium or platinum, or alloys thereof, functioning as catalysts or reaction promoters for the water gas reaction between steam and carbon or hydrocarbons,--as well as being highly efllcient heat transfer agencies. The depth of the screen varies from around 2 ft. upwardly, depending upon the nature and size of the refractory material, and upon such conditions of operation as the temperatures to be maintained in the screen, and the rate of flow of gas therethrough. While the size and shape of the refractory bodies may vary considerably,-it has been found that where employing a screen depth of from 2 to 6 ft.,refractory bodies ranging in size from 1 x 1 x 1 to approximately 3 x 1 x 1 /4 inches in size are eminently satisfactory. It is preferred in the present invention that the uppermost layers of refractory bodies forming the screen be of somewhat larger size than those in the lower portion of the screen. These bodies may be oblong or round in form. The latter shape is particularly desirable in the upper layers of the screen.

While the material composing the refractory screen preferably-is highly heat-refractory, such as high alumina fire brick, carborundum, pure alundum, and high silica refractories, adapted to withstand temperatures above 3000 F.,-other refractories adapted for use at lower temperatures may also be utilized in the screen.

The generator is provided with the' usual upper stack outlet l8 having a stack valve 20. The base of the generator below the arch l4 also is directly connected with a gas outlet 22 having at its outlet end a stack valve 24. The outlet 22 is connected to a wash box 26 by means of gas-duct 26 having therein the valve 30. The wash box is provided with the usual gas outlet 32.

For introducing steam into the base of the generator below the arch l4 there is provided a valve-controlled steam line 34. For introducing a mixture of fluid fuel and air 'to be combusted within the space 36 below the generator arch I4, there are provided respectively a valve-controlled fluid fuel line 38 and a valve-controlled air line 40. A valve-controlled steam line 42 provides for the introduction of steam into the upper part of the generator above the refractory screen. Likewise the valve-controlled fluid fuel lines 44 and the valve-controlled air lines 46 provide for the introduction into the upper part of the generator at a plurality of points above the refractory screen of combustible mixtures of fluid fuel and air for heating purposes during the heating cycle, and for the introduction to the generator of make oil during each gas-making cycle.

A gas off-take bustle pipe 48 is directly connected by branch conduits 50 with the generator interior at points about vertically midway of the refractory screen. The bustle pipe 46 is directly connected with the wash box through a conduit 62 havin therein a valve 53.

In the modification of the invention illustrated in Fig. 2, the construction in general is similar to that of Fig. 1,-the difference being that in the modification of Fig. 2, the generator space above the refractory screen has been provided with a refractory arch 60 having supported thereon refractory checkerwork 62. The steam, fluid fuel, and air connections 42, 44, and 46, lead into the interior of the generator at points above the said checkerwork construction 62. There is thus deflned between the top of the refractory screen and the lower part of the refractory arch 60, a combustion chamber 64 to which the oil or other fluid hydrocarbon is directly introduced through a valve-controlled line 66, and to which air or other combustion-supporting gas may be introduced through valve-controlled conduit 68.

Provisions are made for observing at all times the temperature existing within the refractory screen, particularly in the lower part thereof, for ascertaining whether the down-flowing fluids in the gas-making cycle have cooled the screen to a point where practical operation ceases. For this purpose a thermocouple 10 may be disposed in the refractory screen approximately 4 inches from the'lower part thereof. A second thermocouple I2 advantageously is located in the gas offtake line 22 closely adjacent the generator.

In the preferred practice of the invention according to the modification illustrated in Fig. 1,assuming that the generator is cold, and that the refractory screen is free from carbon deposits-the bottom burner is operated by the proper adjustment of the fuel and air lines 38 and 4ll,--the stack valve 20 being open and the valves 24, 30 and 53 being closed. The highlyheated combustion gases flow upwardly through the refractory screen, thereby heating the same more or less uniformly to a high gas-making temperature, after which they flow out through the stack iii. In certain instances in which substantial amounts of carbon are present in the screen, additional air is required to be introduced through line 40. However, in such instances there is a distinct tendency towards uneven heating of the bed due to the non-uniform distribution of carbon therein. Therefore it is preferred to shorten the time of the first of the heating stages, in which the combustion gases and air flow upwardly, and to follow this up-stage with a down-stage wherein highly-heated combustion gases are produced above the refractory screen by fuel and air introduced through lines 44-46, in amounts sufllcient for complete combustion of the said fuel, with or Without additional air when substantial amounts of carbon are present in the screen. During the down-blast stage, the stack valve 20 is closed and the stack valve 24 is open.

After bringing the refractory screen to proper gas-making temperatures within the range of from 1450 to 1850 F., depending upon the desired heating value of the gas to be produced, the stack valve 24 is closed, and oil or other fluid hydrocarbon is distributed upon the generator screen at suitable rates through lines 44, preferably together with a small amount of steam around .2 pound per pound of oil introduced through line 42 for controlling the velocities of the gases through the generator. Immediately following the oil gasiflcation stage, steam alone is introduced to the generator through line 42 a o'nmao iication stage. By its use carboncarried within gas-making cycle, if desired. In either instance the screen is consumed, and screen temperatures and gas velocities are controlled.

The hydrocarbon and steam may be introduced to the generator concurrently throughout the theresultant gases and vapors-produced in the upper part of the generator by the high temperatures therein are drawn downwardly through the refractory screen and flow through the outlet conduit 22 and valve-controlled line 28 to the wash box, and thence to suitable purification apparatus and to storage. In the event substantial quantities of carbon remain in the fuel bed from a previous gas-making cycle,-n'ot havmg been removed in the immediately preceding heating cyclef-the steam flowing downwardly through therefractory screen alone or with the oil gas not only reacts with the oil but also assists in cleaning up the carbon in the screen and 30 facilitates temperature control therein.

Byseparating the gas-making cycle intotwo stages as described above, the ordinary tendency for the hydrogen produced in the oilcracking stage to inhibit by mass action the wa- 3; ter gas reaction of the steam and carbon of the refractory screen is reduced or'eliminated.

'Where a low gravity gas in the neighborhood of .6 gravity is desired, very small amounts of steam would ordinarily be usedwith the oil in the make cycle; although for a more efficient type of operation where a somewhat, higher gravity gas in the neighborhood of .7 is desired, it is preferred to employ from about .3 1b. to 1 poundof steam per pound of oil. While the 5 usual gas-making rates utilizing small amounts higher gas-making rates.

of oil in the neighborhood of from .1 to .3 gallon per square foot of cross-sectional area per minute may be employed, it is preferred according to the present invention, to utilize much A rate processing in excess of .5 gallon and upwardly of 2.0 gallons of oil per square foot of cross-sectional area of the screen per minute is more suitable.

When the generator and screen temperature has been reduced to a point unsuitable for continued gasiflcation, the oil flow through lines 44 is cut off. The generator is then purged of oil vapors and gases by steam flowing downwardly through the same from the line 42, the gas going to the wash box through line 28. The stack valve 20 is then opened, and a short up-steam purge is used, the steam being introduced into the base of the generator through line 34.

The generator is now ready for the succeeding c5 heating operation. Valve 30 is now closed; and

an up-blast of air is introduced into the cham-- ber 36 through the conduit 40, and flows through the carbon-carrying screen, the air being generally employed in sufficient amount to burn the 70 major portion of the carbon present in the screen.

The heat thus developed raises the temperatures, particularly in the upper part of the screen and of the upper generator walls. Following this first part of the up-blast stage, a small, regu- 75 lated amount of oil or other fluid fuel is introduced with the air through line lllthe air being present in amount at least sufilcient to completelyfcombust the said fuel and preferably to burn-an additional portion'of the carbon present in the screen. The up-blast heating stage is then discontinued, and air is introduced into the upper part of the generator through line 46; the airflow through line 40 is then cut off, and the stack valve 24 is opened. The stack valve 20 is then closed. By this method of operation it is possible to avoid the down steam purge following the up-blast stage of the heating cycle.

.' -.The air introduced through line is highly heated in the'generator top and thence flows downwardly through the refractory screen, combusting a substantial amount of the remaining carbon present in the upper portion of the screen;-the resultant combustion gases flowing through gas outlet 22 and out the stack past valve 24.

Fuel is then introduced through lines upper part of the generator, together with air 44 to the flowing thereto through lines l6,-the air being out the screen temperatures. After this has been accomplished, the fiows of air and gas through conduits 44 and 15 are discontinued, and the down-stream purge is carried out with steam introduced through line l2,the purged gases flowing out through stack valve 24. This down steam purge'may be avoided by continuing the flow of fuel through. lines 44 after the air flow through lines 46 is cut oil. The stack valve 24 is then closed, and the succeeding gas-making cycle is begun in the manner described.

In the above operations the heating value of the resultant gas is generally controlled by regulating the time of contact of the 011 within the high temperature refractory screen, and the temperature of the refractory bodies forming the screen. The latter may be determined by noting the temperature of the gases leaving the screen, by means of a thermocouple or the like which may be located in the gas ofitake 22,but preferably within the refractory screen at a point from 4 to i 10 inches above the bottom of the screen.

The average gas temperatures within the screen when introducing the gas-making oil at a rate of .5 gallon per square foot of screen cross-sectional area per minute as determined in actual operation are given below. These temperatures increase as the oil rate is increased:

Heating value Temp. of gases of gas leaving screen B. t. u. F.

While the quality of the oil, both as to its chemical constitution and its gravity, affect the above temperatures somewhat, the differences involved are not critical. With lower molecularweight hydrocarbons higher temperatures are required than with hydrocarbons of higher molecular weight, where the same fuel velocities through the generator screen are employed. Typical analyses of combustible gases made in accordance with the present invention are given for an 800 and for a 1000 B. t. 11. gas, in connection with the manufacture of which a small amount of steam was supplied with the oil merely for oil-atomization purposes,i. e. about .1 pound of steam per pound of oil.

800-850 LOGO-1,050 Gas 13. t. u. range B.t.u. per B. t.u.per

cu. it on. it.

An important advantage of the above-described operation involving the controlled combustion of fuel above the refractory screen during the downblast phase of the heating cycle resides in the fact that a very large quantity of the heat thus produced is absorbed and reradiated by the upper side walls of the generator which greatly improves the heating efliciency of the cycle and, during the subsequent gas-making cycle, facilitates the vaporization of the oil before it reaches the screen and converts Conradson carbon (that is, low temperature cracking and vaporization carbon) into a finely divided form which is then carried into the screen rather than, as in prior practices, largely deposited upon the top. The particular type of screen or filter composed of small refractory bodies permits high oil rates within the generator many times those employed in the usual single shell oil generators now in use. Normally, fluid tar is produced within the refractory screen with little or no lamp black.

In accordance with one form of the invention, the process is so operated that a complete set of heating and gas-making cycles occupies between and minutes. This period, however, may be lengthened to 10 to minutes, or even longer. The rich combustible gas issuing from the refractory screen during the various portions of each gas-making cycle will then have a greater range of heating values than where smaller periods are employed, because in the former instance the refractory screen and generator will be carried to a higher temperature prior to beginning the gasmaking cycle; and during the latter part thereof the screen will be quenched to a lower temperature where the shorter periods are employed. The longer the cycle,-the greater the quantity of carbon deposited upon the screen during the first part of the gas-making step; and this is available for reheating the screen upon the succeeding heating cycle.

In many cases, such as that mentioned immediately above, the temperature of the refractory screen at the beginning of the make cycle may be so high as to produce a cracked gas of too low a B. t. u. value in the event that all of the oil vapors and other fluids are passed completely through the refractory screen. In such instances, it is within the scope of the invention to ing cycle continues and the refractory screen I becomes progressively cooler, the heating value of the offcoming gases may be controlled by reducing the percentage of the gases flowing to the wash box past valve 53, or by closing this valve completely.

In view of the fact that a large portion of the energy required for the practice of the process is of the nature of heat utilized in the vaporization of the oil before-and as it enters the screen, a form of series'heating of the generator and screen can be undertaken preferably utilizing the modification 'of apparatus illustrated in Fig. 2.

In this form of the invention, the gas-making cycle is similar to that previously described. The up-blast stage of the heating cycle is performed in manner similar to that already described in connection with the other modification of the invention; and the highly heated combustion gases serve to heat not only the refractory screen but also in the case of the apparatus of Fig. 2, the checker-work construction 62 in the upper part of the generator. In this up-blast stage, the additional regulated burning within the chamber 84 of a combustible mixture of fluid fuel and air introduced through the lines 66 and 68 of Fig.2, preferably is carried out for the purpose of highly heating the checkerwork 62. This mixture may be replaced in certain instances by secondary air introduced into chamber 64 through lin! 68 or through line 46 (Fig. 1).

In the preferred form of the down-blast stage of the heating cycle, combustion air is introduced above the checker-work construction 62 and, in passing downwardly is preheated by the latter,after which it mixes in chamber 64 with a combustible mixture introduced through lines 66, 68. The resultant combustion products pass downwardly through the screen, and thence to the stack.

In a slightly different form of operation, during the down-blast stage of the heating cycle, combustion air, followed by a combustible mixture of fluid fuel and air are successively introduced above the checker-work construction 62 thereby producing heat, a substantial amount of which is absorbed within the checker-work construction and the remainder of which then flows downwardly through the refractory screen in the usual manner, and thence to the stack.

Under certain conditions, a regulated amount of a combustible mixture of fluid fuel and air concurrently is introduced above the screen through the respective lines 66 and 68, and to the central combustion chamber 64 to further facilitate the heating of the chamber 64 and the refractory screen I6.

In the immediately following gas-making cycle, steam introduced through the line 42 is superheated in its passage through the checker-work 62; and later, in its passage through the chamber 64, this superheat facilitates the vaporization and cracking of the hydrocarbon introduced at that time upon the refractory screen through the lines 66.

It is within the scope of the present invention to employ in either of the stages of the heating cycle any suitable combustible mixture of combustible fluid and a. combustion-supporting fluid.

These combustible mixtures preferably are overventilated (that is, containing an excess of combustion supporting fluid) so as to be effective for substantially reducing the amount of carbon in the refractory screen by reaction therewith.

In the gas-making cycle, while it is preferred to employ hydrocarbon oils,-particularly those around the gravity of fuel oil or slightly heavier, and having A. P. 'I. gravities of 12 to 18 the invention is in no wise limited to the use of these oils. On the contrary it is within the scope of the invention to employ a wide variety of liquid and gaseous hydrocarbons, including natural gas, refinery gases, butane, propane, and the like.

In instances of the use of each hydrocarbon or mixture-containing hydrocarbons it is only essential to supply, by the controlled combustion of fuel in the manner indicated, that portion of the heat required for the cracking of hydrocarbons during the gas-making cycle which is not supplied by the controlled combustion of the carbon and tar formed in the screen during an earlier gas-making cycle; and to so regulate the direction of flow of the resultant hot combustion gases in the generator as to maintain the refractory screen throughout at an approximately uniform selected temperature which,- at the high gas-making rates generally employed with the corresponding short times of contact of the gases with the high-temperature refractory screen,--insures an amount of cracking providing commercial yields of the desired high B. t. u. value gas.

Because of the simplicity of the apparatus construction, the invention has great commercial value for use both as standby and base load equipment in industrial gas-making plants, and particularly those required to supply rather widely variable seasonal or other deniands where the maximum gas-making demand upon the plant is felt only occasionally; but where the equipment cost is high.

The invention is not limited to the treatment of the fluid hydrocarbons named: but on the other hand is equally applicable to the production of a rich combustible gas from other hydrocarbons such as natural gas and refinery gases.

The invention is susceptible of modification within the scope of the appended claims.

We claim:

1. In a cyclic process for making combustible gas wherein during a gas make period hydrocarbons are cracked by passing the same through a deep carbon filtering bed of highly heated refractory pieces with resultant deposition ofcarbon on the surfaces of the refractory which carbon is burned during a subsequent air blast period, the steps comprising successively blasting air vertically in both directions through the bed between make periods, burning fluid fuel within the bed during the blast period, controlling the amount of air employed during the blast period to an amount approximately sufficient to burn the said fluid fuel and to consume the carbon deposited within the bed during the preceding make period, withdrawing combustion gases produced during the upblast stage from the upper part of the generator above the screen, concurrently burning additional fluid fuel above the said screen, -regenerating heat from the combustion gases at points in their path above the screen, and utilizing heat thus regenerated for preheating air for use in a subsequent down blast stage of the heating cycle and for preheating steam for use in a subsequent gas making period.

2. In a cyclic process for making combustible gas wherein during a gas make period liquid hydrocarbons are cracked by passing the same downwardly through a deep carbon filtering screen of small highly heated refractory pieces, with resultant formation of gas and deposition of carbon on the surfaces of the refractory which carbon is burned during a subsequent air blast period, the steps comprising successively blasting air vertically in both directions through the screen between make periods, burning fluid fuel within the screen during the blast period, controlling the amount of air employed during the blast period to an amount approximately suffi cient to burn the said fluid fuel and to consume the carbon deposited within the screen during the preceding make period, and regulating the calorific value of the gas produced during the make period by withdrawing a regulated amount of the make gas peripherally from the vertical midportion of the screen, while withdrawing the remaining portion of the make gas from below the screen.

CHARLES E. HEMMINGER.

ALFRED JOHNSON.

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