US3917468A

US3917468A - Synthetic natural gas production

Info

Publication number: US3917468A
Application number: US422051A
Authority: US
Inventors: Den Berg Godfried J Van; Frank K G Ouwerschuur
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1972-12-15
Filing date: 1973-12-05
Publication date: 1975-11-04
Anticipated expiration: 1992-11-04
Also published as: FR2327306A1; ES421419A1; NL7217059A; NL171597C; JPS4989701A; CA1014741A; DE2362032A1; ZA739450B; JPS5748597B2; GB1451937A; BE808277A; IT1000835B; NL171597B; FR2327306B1; IN138705B; DD108720A5; DE2362032C2

Abstract

A process for the production of synthetic natural gas or town gas is described wherein the hot gaseous product of the partial combustion of a carbonaceous fuel, containing hydrogen and carbon monoxide, is passed into a carburetting zone at a temperature of from 700 to 1100*C and therein enriched with a volatile hydrocarbon carburant which on evaporation into the hot gaseous product of partial combustion is thermally cracked into methane and lighter unsaturated hydrocarbons. The carburetted gas product is then passed into a hydrogenation zone maintained at a temperature sufficient to further decompose any remaining hydrocarbon carburant and to hydrogenate the unsaturated hydrocarbons. In this process coke formation in the carburetting zone is substantially minimized by introducing the volatile hydrocarbon carburant into the carburetting zone in the form of a thin layer of liquid which is maintained at a temperature below that at which thermal cracking occurs during the time the carburant is not adsorbed by the hot gas stream.

Description

United States Patent [191 Van den Berg et al.

[451 Nov. 4, 1975 SYNTHETIC NATURAL GAS PRODUCTION [75] Inventors: Godfried J. Van den Berg; Frank K. G. Ouwerschuur, The Hague, both of Netherlands [73] Assignee: Shell Oil Company, Houston, Tex.

[22] Filed: Dec. 5, 1973 [21] Appl. No.: 422,051

[30] Foreign Application Priority Data Dec. 15, 1972 Netherlands 7217059 [52] US. Cl 48/199 R; 48/116; 48/205; 48/219; 239/434.5; 261/157; 261/DIG. 54

[51] Int. Cl. C10J H20 [58] Field of Search 48/219, 205, 215, 202, 48/199 R, 199 FM, 197 FM, 197 R, 144, 116,118,109, 96,196 R; 261/118, 78 A,

DIG. 54, 157; 259/4; 239/434, 434.5, 132.3

[56] References Cited UNITED STATES PATENTS 2,716,597 8/1955 Linder 48/197 R 2,971,829 2/1961 Van Rossum 48/215 Primary ExaminerS. Leon Bashore Assistant ExaminerGeorge C. Yeung [57] ABSTRACT A process for the production of synthetic natural gas or town gas is described wherein the hot gaseous product of the partial combustion of a carbonaceous fuel, containing hydrogen and carbon monoxide, is passed into a carburetting zone at a temperature of from 700 to ll00C and therein enriched with a volatile hydrocarbon carburant which on evaporation into the hot gaseous product of partial combustion is thermally cracked into methane and lighter unsaturated hydrocarbons. The carburetted gas product is then passed into a hydrogenation zone maintained at a temperature sufficient to further decompose any remaining hydrocarbon carburant and to lhydrogenate the unsaturated hydrocarbons. In this process coke formation in the carburetting zone is substantially minimized by introducing the volatile hydrocarbon carburant into the carburetting zone .in the form. of a thin layer of liquid which is maintained at a temperature below that at which thermalcracking occurs during the time the carburant is not adsorbed by the hot gas stream.

2 Claims, 3 Drawing Figures US. Patent Nov. 4, 1975 Sheet 10f2 3,917,468

FIG. 2

US. Patent Nov. 4, 1975 Sheet 2 of2 3,917,468

SYNTHETIC NATURAL GAS PRODUCTION BACKGROUND OF THE INVENTION This invention relates to an improved process for production of a synthetic natural gas of sufficient calorific value to be of use as town gas. More particularly, this invention is directed to a process wherein the gaseous product of partial combustion, being composed mainly of hydrogen and carbon monoxide which have relatively low calorific value, is upgraded in fuel value by mixing (carburetting) said gaseous product with the vapors of a volatile hydrocarbon at a temperature sufficient to thermally crack the hydrocarbon into methane and light unsaturated hydrocarbons, which are subsequently hydrogenated to afford a high-fuel value town gas, while at the same time avoiding problems tocoke formation which are inherent in such a carburetting procedure.

In processes for the partial combustion of fuels such as, inter alia, heavy fuel oil, petroleum distillates or residues, liquid fuel containing process soot or slurries of coal grit in water, a gas principally containing hydrogen and carbon monoxide is obtained at temperatures above approximately lOC. In such processes some soot is inevitably formed and this gives rise to a suspension of fine soot particles in the hot gas produced.-

The gas thus produced has a relatively low calorific value, this being usually in the range of 1000 to 3000 kcal./Nm In order to be used as town gas, however, a calorific value of more than 5000 kcal./Nm is generally required. The required increase in calorific value can be effected by combining the gas product of partial combustion, maintained at a temperature between 700 and 1 100C, with a stream of lighter weight volatile hydrocarbons which evaporate into the gas stream and are subsequently pyrolyzed. This procedure which for clarity and convenience will be designated herein as carburetting the hot gas product of partial combustion with a volatile hydrocarbon carburanti.e., the gas product of partial combustion is enriched by mixing with volatile carbon compounds-results in the formation of methane and lighter unsaturated hydrocarbon compounds in the gas stream. This carburetted gas stream is then suitably passed into a hydrogenation zone maintained at a high temperature to further crack any remaining hydrocarbon carburant and to hydrogenate the unsaturated compounds thereby affording a high fuel value synthetic natural gas or town gas. If desired steam may be injected into the gas before, during or after carburetting in order to reduce soot formation. For efficient carburetting the presence of an excess amount of hydrogen is required. Gas obtained by partial combustion usually meets this requirement; there is a sufficient amount of hydrogenation to either prevent or essentially repress the formation of additional soot.

In a typical down stream processing scheme the hot carburetted gas leaving the hydrogenator is cooled, for example to a temperature at which the soot and any hydrogen sulfide may be removed from it or at which a catalytic conversion of the carbon monoxide or a catalytic methane treatment can be carried out, and then desirably is further cooled in a waste heat boiler, since the amount of available heat is considerable and may be applied for the production of high pressure steam. Since the gas usually contains soot, it is desirable to employ a waste heat boiler in which the hot gas is passed through helically-wound tubes which are externally 2 cooled by means of boiling water. The soot deposits less readily on the walls of the helical tubes than it does on the walls of straight tubes. The tubes therefore do not become choked with soot.

While the processing scheme, described above in general terms, would seem to be a rather attractive way of increasing the calorific value of the gas product of partial combustion, there is a problem relating to the use of conventional procedures and apparatus in the carburetting step which substantially detract from the viability of the overall process. In conventional carburetting techniques the liquid hydrocarbon carburant is injected directly into the hot carburetting zone (heated via contact with the hot gas stream from partial combustion) by means of an injection nozzle at rather high velocity relative to the velocity of the hot gas stream. Typically, the hot gas velocity ranges from 1-3 m/sec while the velocity for the carburant on injection into the carburetting zone ranges from 10-40 m/sec. When these conventional injection techniques are employed it has been found that a small part of the liquid carburant flows over the rim of the injection nozzle and into an area where little hydrogen and much carburant is present. This gives rise to pyrollytic cracking and to the accumulation of solid substances. It is not quite certain whether this is coked oil, i.e., carbon or tarry and gummy substances having a very high molecular weight and a high carbon content. One of the possibilities is polymerization of unsaturated compounds being formed. The accumulations are found in the carburetting zone in the immediate vicinity of and on the injection nozzle for the carburant. For most efficient operation these accumulations should be removed periodically and this requires the whole process to be stopped. This is an expensive and difficult operation which, moreover, causes inconvenience for the consumer of the gas produced. It is even possible that considerable reductions in the diameter of the carburetting zone will occur as a consequence of the accumulation of the said solid substances. In this case the pressure in the partial combustion of gasification reactor upstream of the carburetting zone may rise to unacceptably high levels.

The present invention provides a solution for these and similar problems.

SUMMARY OF THE INVENTION It has now been found that the carbon or coke accumulation which occurs in the carburetting zone of the process described above, wherein the hot gas product of partial combustion is carburetted with a volatile hydrocarbon, can be substantially avoided if the liquid hydrocarbon carburant is passed. into the carburetting zone in a thin layer on carburetting zone surfaces which are cooled by external means "to such an extent that during the time that the carburant is not adsorbed by the hot gas it is maintained and remains at a temperature below which thermal cracking occurs. Accordingly, the instant invention provides a process for the production of synthetic natural gas or town gas which comprises a. partially combusting a carbonaceous fuel in a par tial combustion zone to produce a hot gaseous product containing hydrogen and carbon monoxide;

b. carburetting the hot gas product of the partial combustion zone maintained at a temperature of between 700 and 1 C with a volatile liquid hydrocarbon carburant in a carburetting zone thereby effecting volatilization of the carburant into the hot gas and the accompanying thermal cracking of the carburant into methane and lighter unsaturated hydrocarbons, said liquid carburant being introduced into the carburetting zone in the form of a thin layer maintained at a temperature below that at which thermal cracking occurs during the time the carburant is not absorbed by the hot c. passing the carburetted product of the carburetting zone into a hydrogenation zone maintained at elevated temperatures wherein any remaining volatilized hydrocarbon carburant is further decomposed by thermal cracking and the unsaturated hydrocarbon compounds are hydrogenated and;

d. cooling the hot gaseous product of the hydrogenation zone.

In the operating according to the process of this invention, it has been surprisingly found that carburetting is not adversly affected when the injection of the carburant into the gas to be carburetted is not carried out under high pressure or at a great speed and as directly as possible as is dictated by conventional procedures. That is, with the instant process it is essential that the carburant be introduced into the carburetting zone at a velocity which is considerably lower than when the carburant is injected by means of an injection nozzle char= acteristic of conventional processes. Thus, the process of the instant invention not only avoids the accumulation of coke or carbon deposits in the carburetting zone; but additionally does not require that the pressure of the carburant be raised in advance of injection to a value well above the pressure of the gas in the carburetting zone in order to achieve high carburant injection velocities.

In carrying out the carburetting step according to this invention it is critical that the hydrocarbon carburant be introduced into the carburetting zone in the form of a thin layer of liquid which is maintained below the cracking temperature of the carburant before it is absorbed by (volatilized into) the gas to be carburetted. Accordingly, another aspect of this invention is concerned with an apparatus for carburetting the hot gas product of the partial combustion of a carbonaceous fuel with a volatile hydrocarbon carburant wherein the liquid carburant is supplied to the carburetting zone as a thin layer or film which is maintained below cracking temperatures by externally supplied cooling on all those surfaces of the carburetting zone in which the carburant is in contact before it is absorbed in the gas to be carburated.

THE DRAWINGS The invention will be described in greater detail with reference to the accompanying drawings. These drawings which illustrate the process and apparatus of the present invention are intended to be illustrative rather than limiting on its scope.

FIG. 1 is a lateral view of an apparatus set up suitable for carrying out the process of the invention.

FIG. 2 is a partial cross-section of the carburetting apparatus according to the invention taken along line 2-2 of FIG. 1.

FIG. 3 is a diagrammatic drawing of an alternative embodiment of the carburetting apparatus according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In basic terms the invention relates to a process and apparatus for the production of a synthetic natural gas or town gas having a calorific value of more than 1,000 kcal. per Nm by partially combusting a carbonaceous fuel in a partial combustion zone comprising a refractory gasification reactor, carburetting the hot gas from the gasification reactor with a carburant at a temperature between 700C and 1 C in a carburetting zone which connects the gasification reactor to a hydrogenation zone, conducting the desired reactions in the carburetted gas in the hydrogenation zone (reactor) and cooling the gas obtained from the hydrogenation zone.

The first step of the process according to the invention involves a typical partial combustion procedure wherein a conventional carbonaceous fuel source, such as those detailed above (heavy fuel oil, coal grit, etc), is combined with less than the theoretical amount of oxygen present in an oxygen-containing gas at temperatures in excess of 1000C to yield a gaseous product containing as principal components, hydrogen and carbon monoxide. Since this step of the process is wholly conventional and quite well known by those skilled in the art it need not be detailed further herein.

The hot gas product of the partial combustion zone is then passed into the carburetting zone where it mixed with a volatile liquid hydrocarbon carburant, the mixing occuring substantially in the vapor state. The temperature of the hot gas throughout the carburetting zoneranges substantially between 700 and 1l0OC. This temperature is sufficient to cause the hydrocarbon carburant to thermally crack into methane and lower unsaturated hydrocarbon compounds on vaporization into the hot gas stream. As indicated above, it is critical that the liquid carburant be supplied to the carburetting zone as a thin layer or film which is maintained at a temperature below that at which it begins to undergo thermal cracking during the time that the carburant is not absorbed by the hot gas stream. To maintain the liquid carburant as a thin film on the carburetting zone surface it is generally necessary to supply the carburant at injection velocities below those encountered with conventional injection nozzle systems. The rate at which the carburant is introduced unto the carburetting zone for purposes of this invention can be conveniently expressed in terms of residence time in the car buretting zone, thus eliminating any dependence on specific carburetting zone size and shape. Although for the process of the invention it is in principle permissible to have residence times of up to 10 seconds for the usual types of carburant, the residence time of the liquid carburant in the carburetting zone is preferably not less than 0.1 second or more than 1.0 second. Within this range the risk of the temperature exceeding in places the lower limit at which cracking is possible, will be lowest. This lower limit is of course largely dependent on the residence time of the liquid carburant.

Carburetting is preferably carried out by passing liquid carburant into the carburetting zone in a thin layer around a cooled rim along which flows the hot gas from the gasification reactor. As the hot gas flows along the rim the carburant is absorbed by the gas and only becomes cooled at the very last moment. Since the carburant passes around the rim it does not make earlier contact with the flowing gas, so that the temperature of the carburant can easily be kept low.

In order to achieve a gradual absorption of the carburant by the hot gas, which, according to the invention, substantially prevents the formation of coke or carbon accumulations, it is preferred to pass the carburant in the carburetting zone in a thin layer for some distance along a cooled wall alongwhich the said hot gas is flowing. In this case the said cooled wall suitably ends in a sharp transition, the liquid carburant being partly absorbed by the said hot gas on its way along the cooled wall and the rest being absorbed at the sharp transition. Since care is taken that during the contact with the hot gas the velocity of the carburant is not too high, no accumulation occurs. The velocity of the flow of hot gas in the carburetting zone is preferably between and 1200 m/sec., the supply of carburant being such that the thickness of the layer of carburant film on the cooled wall is less than 1 mm. The flow of the carburant along the said cooled wall is preferably in the direction of flow of the hot gas.

In order to keep the temperature of the liquid carburant as low as possible, it is preferably supplied to the carburetting zone in a thin layer along a cooled wall along which the hot gas does not flow. The liquid carburant is then suitably supplied along this cooled wall in a direction opposed to the direction of flow of the hot gas.

The invention is particularly suitable for a liquid carburant consisting of a petroleum fraction, such as gas oil, naphtha and kerosine. It is especially these and similar carburants which tend to crack or polymerize on the injection nozzle in the conventional process.

If in the way already described, the liquid carburant is supplied along a cooled wall along which there is no flow of hot gas, and then passed further along a cooled wall along which there is a flow of hot gas up to a sharp transition where the liquid carburant is absorbed by the gas, it may be advantageous to pass the liquid carburant around a free wall arranged in the carburetting zone which wall is internally cooled, the carburant being introduced into the carburetting zone against the side facing the outside of the carburetting zone, then creeping round the end of the free wall and proceeding on the side of the free wall facing a center line of the carburetting zone, before being absorbed in the gas flowing along the latter side. It is preferred to use a carburetting zone having a rotationally symmetrical or substantially rotationally symmetrical construction, thus minimizing the risk of accumulations in the carburetting zone.

As mentioned above, the carburetted gas is passed into a hydrogenator in order to complete the desired reactions, i.e., to allow, inter alia, the evaporated carburant to further decompose and unsaturated compounds to become hydrated. The carburetted gas is very suitably passed into a hydrogenator where the gases are internally recirculated via an internal division of the hydrogenator.

An apparatus suitable for the production of gas having a calorific value of more than 1000 kcal. lNm according to the process of the invention, as mentioned above, comprises a refractory gasification reactor for the partial combustion of a fuel, a carburetting zone for carburetting the hot gas from the gasification reactor with a hydrocarbon carburant, a hydrogenation reactor to conduct the desired reactions in the carburetted gas and optionally a waste heat boiler to cool the gas from the hydrogenator and produce steam. According to the invention this apparatus is characterized by means for 6 passing liquid carburant in a thin layer into the carburetting zone and at the same time cooling the carburant.

The carburetting zone of the apparatus according to the invention in general terms comprises a closed chamber, preferably cylindrical in shape, having (a) an inlet for introduction of the hot gas stream from the partial combustion zone whereby the flow of hot gas is directed along the axis of the closed chamber parallel to the walls of the closed chamber; (b) an inlet for introduction of the hydrocarbon curburant by which the carburant enters the closed chamber at a direction perpendicular or opposed to the direction of the flow of hot gas and forms a thin film or layer on the surface of the closed chamber when .in contact with the hot gas; (c) a means for supplying external cooling, preferably by cooling devices in the chamber walls, to the surfaces of the closed chamber which are contacted by the thin layer of carburant which is also in contact with the hot gas flow; and (d) an outlet for withdrawingthe carburetted hot gas mixture.

The carburetting zone of the above-mentioned apparatus, preferably contains a rim with cooling devices wherein external cooling is supplied to the surface of the rim and means for passing the carburant in liquid form around this rim, the rim being situated such that during operation the hot gas from the gasification reactor flows along it.

The carburetting zone suitalbly contains a wall with cooling devices to supply external cooling to the carburetting zone surface of the wall as well as means for passing the liquid carburant along this wall, the wall being situated such that during operation the hot gas from the gasification reactor flows along it. This wall with cooling devices preferably ends in a sharp transition. The liquid carburant is thereby gradually absorbed by the hot gas. The carburetting zone preferably contains a wall with cooling devices and means for introducing the liquid carburant into the carburetting zone along this wall, the wall [being situated such that during operation the hot gas does not flow along it. With such a carburetting zone there is no risk of accumulations occurring and the carburant can be supplied gradually.

The carburetting zone is preferably provided with a free wall with internal cooling devices which supply externally generated cooling to the wall surface, one side directed outwardly perpendicular to the axis of the closed chamber and one side facing the axis of the closed chamber. Along the former side the liquid carburant is suitably introduced into the carburetting zone, while along the latter side the liquid carburant continues into the carburetting zone and makes contact with the hot gas.

A functional apparatus is obtained when the carburetting zone has a rotationally symmetrical or substantially rotationally symmetrical construction.

It is preferred to employ a carburetting zone provided with a cooled .venturi-shaped contraction. In the middle of this contractionin longitudinal view the carburant supply is mounted, so that an outer shell of the hot gas is pre-cooled in the first part of the venturi, before coming into contact with the cooled carburant film in the second part.

Referring to FIG. 1 the apparatus suitable for use in the process of the invention comprises an empty refractory gasification reactor 1, provided with a pipe 2 for the supply of fuel to the combustion chamber 3 of the 7 reactor and with a supply pipe 4 for the oxygen.

The apparatus also comprises a reactor discharge 5 arranged as a carburetting zone, this also being empty and being partly provided with refractory lining. The carburetting zone comprises a hydrocarbon supply 6, through which liquid carburant can be supplied to the jacket 7.

By means of a flange 8 the discharge tube 5 is connected to a

hydrogenator

9,10,11, consisting of two parallel columns 9 and 11, and a bent intermediate pipe 10. This hydrogenator is empty and is entirely lined with refractory bricks. The columns 9 and 11 are connected to the intermediate pipe by means of flanges l2 and 13, respectively. The end of the upturned U- shaped hydrogenator is coupled to a waste heat boiler by means of a connection 14 and a flange 15.

This waste heat boiler consists of an empty-refractory brick-lined-bottom vessel 16 and a steam boiler 17 mounted vertically on the bottom vessel, which boiler is connected to the vessel 16 by means of a flange 18. The steam boiler is equipped with a water supply 19 near its base and a discharge 20 for high-pressure steam at its top. Through the stem boiler 17 runs a helically wound gas pipe 21, which communicates with the bottom vessel 16 via the straight bottom end 22 and which passes through the boiler wall at the top via the gas discharge 23.

In carrying out the process according to the invention the apparatus shown in FIG. 1 operates as follows.

The fuel supplied via 2 together with less than the theoretical amount of oxygen is incompletely burned in reactor 1. An amount of steam may optionally be supplied via the bumer or by other means. A crude gas stream leaves the reactor via 5 at a temperature of approximately l200l400C. This gas usually contains some soot and mainly comprises hydrogen and carbon monoxide. However, inter alia, water vapor, carbon dioxide, hydrogen sulfide are also usually present.

This hot crude gas is then carburetted in the discharge tube 5. The gas should usually first be cooled below 1100C. It is also advantageous for an excess amount of water vapor to be present in the gas. To this end an amount of water is suitably injected into the tube 5 via 24 or into the bottom of the reactor via 25. A liquid carburant in the form of a hydrocarbon fraction is then injected into the gas in one or more steps. If carburetting is carried out in several steps it is possible to inject additional water between two steps in order to cool the gas and to increaese the amount of water vapor present.

After the gas has been carburetted the desired reactions take place in the

hydrogenator

9, 10, 11. Here any drops of liquid carburant still present evaporate, unsaturated hydrocarbons are hydrogenated, a certain methanization takes place, and hydrocarbons react with steam while forming hydrogenand carbon monoxide.

The crude carburetted gas which now contains a not inconsiderable percentage of methane, is passed into the bottom vessel of the waste heat boiler at a temperature between about 800C and 1100C, eventually leaving this waste heat boiler at a temperature of usually less than 400C. The waste heat boiler produced steam under a considerable pressure.

It will be understood that within the scope of the invention many alterations can be made of the apparatus shown. For example, the hydrogenator may be of an entirely different shape, and, for example, be arranged in a horizontal plane instead of vertically. The waste heat boiler may also be different and, for example, have a number of helical gas pipes instead of one, have a differently shaped bottom vessel, or employ another coolant. It may also be of a completely different type.

An embodiment of the carburetting apparatus according to the invention is shown in detail in FIG. 2. FIG. 2 represents a horizontal partial cross-section of the carburetting apparatus taken along line 22 in FIG. 1. For clarity and convenience the carburetting zone jacket 7 in FIG. 1 is not shown in FIG. 2. However, it will be understood that this jacket surrounds the apparatus shown in partial cross-section including the discharge tube 5 which is shown. A cylindrical inner wall 26 of the discharge tube 5 is provided with a refractory lining 33 of the carburetting zone in order to allow flow of the hot gas to be carburetted in flre direction indicated by the arrow. In the refractory lining 33 there is a ring groove 27 for the supply of liquid carburant. For the further flow of the carburant and to insure the desired supply of carburant in the form of a thin film a cooled wall 28 with a cylindrically inverted inner part 29 projecting freely in the route of the flowing gas is arranged in the groove 27. Further, a Z-shaped profiled and cooled ring 30 is arranged under the ring (28,29) so as to form a Z-shaped slit 31. The carburant is introduced into the carburetting zone via this slit. The side of the cooled wall (28,29) facing the ring 30 and the slit 31, faces the outside of the carburetting zone and the hot gas does not flow along it. The side 32 of the cooled wall 29 freely mounted in the carburetting zone on the other hand is facing the center line of the carburetting zone; and the hot gases flow along it. A suitable coolant is circulated through the

passageways

50 and 51 to cool the

walls

28,29 and 30 by conduit means coupled to the openings between the walls (not shown in FIG. 2).

When the apparatus is in operation the liquid carburant is passed into the carburetting zone in a thin layer via the cooled slit 31, that is to say, via the rim 34 to the side 32 along which the hot gas is flowing. At 35 there is a sharp transition where the remaining liquid carburant can be absorbed by the hot gas. Part of the liquid carburant is already absorbed by the hot gas between the

rims

34 and 35.

The carburetting zone may be constructed differently and possess, for example, differently shaped walls for the introduction of liquid carburant.

FIG. 3 is a diagrammatic illustration of such an alternative carburetting zone.

the connecting tube 36, which connects the gasification reactor (not shown) with the hydrogenator 37, contains a carburetting zone. This tube 36 has a cooled rotationally

symmetrical restriction

38, 39, which is situated on either side of a ring slit 40 for the supply of liquid carburant. The hot gas to be carburetted flows into the carburetting zone via the jacket 7 and through the tube 36in the direction indicated by the arrow, and the carburant is supplied to the ring slit 40 in the direction likewise indicated. The liquid carburant then enters the carburetting zone in a thin layer along the inner side 41 of the cooled wall 38along which the hot gas is also flowing. The cooling of the walls of the

striction

38 and 39 is diagrammatically illustrated by the

water shells

42 and 43. w

A particular advantage of this embodiment of the carburetting zone is that the part of the hot gas that comes into contact with the carburant film on the wall 38 is cooled in advance on wall 39.

9 After having been carburetted the gas enters the hydrogenator 37 via connecting tube 36, and is hydrogenated. The gas subsequently passes from the hydrogenator to a waste heat boiler (not shown) to be cooled.

We claim as our invention:

l. A process for the production of town gas which comprises a. partially combusting a carbonaceous fuel selected from the class consisting of heavy fuel oil, petroleum distillates or residues, liquid fuel containing process soot and slurries of coal grit in water in a partial combustion zone to produce a hot gaseous product containing hydrogen and carbon monoxide;

b. carburetting the hot gas product of the partial combustion zone maintained at a temperature of between 700 and 1 100C with a volatile liquid hydrocarbon carburant in a carburetting zone thereby effecting volatilization of the carburant into the hot gas and the accompanying thermal cracking of the carburant into methane and lighter unsaturated hydrocarbons, said liquid carburant having a residence time in the carburetting zone 10 between about 0.1 and 10 seconds and being introduced into the carburetting zone in the form of a thin layer maintained at a. temperature below that at which thermal cracking occurs during the time the carburant is not absorbed by the hot gas;

c. passing the carburetted product of the carburetting zone into a hydrogenation. zone maintained at ele vated temperatures wherein any remaining volatilized hydrocarbon carburant is further decomposed by thermal cracking and the unsaturated hydrocarbon compounds are hydrogenated and;

d. cooling the hot gaseous product of the hydrogena tion zone.

2. The process of claim 1 wherein the liquid hydrocarbon carburant is maintained as a thin layer below the cracking temperature of the carburant while in contact with the hot gas by means of external cooling supplied to' all of the carburetting zone surfaces with which the thin layer of carburant comes into contact with during the time that said carburant is also in contact with the hot gas.

Claims

1. A PROCESS FOR THE PRODUCTION OF TOWN GAS WHICH COMPRISES A. PARTIALLY COMBUSTING A CARBONACEOUS FUEL SELECTED FROM THE CLASS CONSISTING OF HEAVY FUEL OIL, PETROLEUM DISTILLATES OR RESIDUES, LIQUIDS FUEL CONTAINING PROCESS SOOT AND SLURRISES OF COAL GRIT IN WATER IN A PARTIAL COMBUSTION ZONE TO PRODUCE A HOT GASEOUS PRODUCT CONTAINING HYDROGEN AND CARBON MONOXIDE, B. CARBURETING THE HOT GAS PRODUCT OF THE PARTIAL COMBUSTION ZONE MAINTAINED AT A TEMPERATURE OF BETWEEN 700* AND 1100*C WITH A VOLATILE LIQUID HYDROCARBON CARBUTANT IN A CARBURETTING ZONE THEREBY EFFECTING VOLATILIZATION OF THE CARBUTANT INTO THE HOT GAS AND THE ACCOMPANYING THERMAL CRACKING OF THE CARRBUTANT INTO METHANE AND LIGHTER UNSATURATED HYDROCARBONS, SAID LIQUID CARBURANT HAVING A RESIDENCE TIME IN THE CARBUTTING ZONE BETWEEN ABOUT 0.1 AND 10 SECONDS AND BEING INTRODUCEED ONTO THE CARBURETTING ZONE IN THE FORM OF A THIN LAYER MAINTAINED AT A TEMPERATURE BELOW THAT AT WHICH THERMAL CRACKING OCCURS DURIN THE TIME THE CARBURANT IS NOT ABSORBED BY THE HOT GAS,

2. The process of claim 1 wherein the liquid hydrocarbon carburant is maintained as a thin layer below the cracking temperature of the carburant while in contact with the hot gas by means of external cooling supplied to all of the carburetting zone surfaces with which the thin layer of carburant comes into contact with during the time that said carburant is also in contact with the hot gas.