GB1590706A

GB1590706A - Partial oxidation process

Info

Publication number: GB1590706A
Application number: GB2080678A
Authority: GB
Original assignee: Texaco Development Corp
Current assignee: Texaco Development Corp
Priority date: 1978-05-19
Filing date: 1978-05-19
Publication date: 1981-06-10

Description

(54) PARTIAL OXIDATION PROCESS (71) We, TEXACO DEVELOPMENT COR PORATION, a Corporation organized and existing under the laws of the State of Delaware, United States of America, of 135 East 42nd Street, New York, New York 10017, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a partial oxidation process for making synthesis gas, fuel gas, or reducing gas along with mechanical work, electrical energy, or both.

In the partial oxidation process, the effluent gas stream leaving the gas generator at a temperature in the range of 815 to 19300C must be cooled below the equilibrium temperature for the desired gas composition. This is done at present by quenching the effluent gas stream in water, or by cooling the gas stream in a waste heat boiler, thereby producing saturated steam. Both of these methods of gas cooling result in large increases in entropy and reduced thermal efficiencies. This problem is substantially overcome according to the present invention by using the sensible heat in the hot effluent gas stream leaving the partial oxidation gas generator at a higher level of heat exchange.

U.S. Patent No. 3 868 817 discloses the production of a purified fuel gas which is burned in the combusition chamber of a gas turbine. The clean flue gas is then expanded in a turbine.

At its maximum exit temperature, i.e. 815 to 19300C, an effluent gas stream comprising raw synthesis gas, reducing gas, or fuel gas from a free flow noncatalytic partial oxidation gas generator is passed, according to the present invention through a first heat exchange zone in heat exchange with a continuous stream of heat transfer fluid, preferably comprising a portion of the product gas which circulates in a substantially closed power loop. The heat transfer fluid absorbs heat from the effluent gas stream and is then passed through a turbine to produce mechanical work and electrical energy. The fuel feed stream, and optionally the free-oxygen containing gas feed stream, may be separately preheated in a separate heat exchange zone by heat exchange with the heat transfer fluid leaving said turbine.Optionally, by-product steam and/ or superheated steam may be produced subsequently by the absorption of sensible heat remaining in the effluent gas stream. The high steam superheat temperature gives a high conversion efficiency in a steam turbine.

In accordance with one embodiment of the invention, a shell and tube heat exchanger in which cleaned and optionally purified generator gas is continuously bled from inside the tubes to the outside, or the reverse, is employed. The bleedstream mixes with the effluent gas stream passing through the heat exchanger. By this means a continuously flowing protective sheath or curtain of the comparatively cooler bleedstream is placed between the surfaces of the tubes and headers, if any, in the heat exchanger and the surrounding hot effluent gas stream from the gas generator, which enters the heat exchanger at maximum temperature. The surfaces of the tubes and headers, if any, are thereby protected against corrosive gas attack and deposits of ash, slag, and soot.

A portion of the mixture of effluent gas and gaseous bleed stream from said heat exchanger is cleaned, optionally purified, and discharged from the system as the product gas. A portion of the product gas, e.g. 1 to 50 volume as as makeup for the bleedstream, is com- pressed along with the cooled turbine exhaust to a pressure greater than that in the gas generator and recycled to said heat exchanger for reheating.

The invention will be further understood by reference to Figures 1 and 2 of the accompanying drawings which are schematic representations of two preferred embodiments of the process.

The present invention provides a process for producing gaseous mixtures comprising H2 and CO by the partial oxidation of a fuel containing carbon and hydrogen with a free-oxygen containing gas at a temperature in the range of 815 to 1930 C and a pressure in the range of 1 to 250 atmospheres absolute in the reaction zone of a free-flow noncatalytic gas generator, which comprises (1) continously passing raw effluent gas leaving the gas generator through a first heat exchange zone in heat exchange with a heat transfer fluid; (2) introducing the resulting stream of hot heat transfer fluid into a power developing means as the working fluid and thereby producing power; (3) cooling the heat transfer fluid leaving (2) by noncontact heat exchange with at least one other material in a separate heat exchange zone; and (4) recycling the heat transfer fluid from (3) to the first heat exchange zone of step (1).

In accordance with one preferred embodiment, the heat transfer fluid from step (4) is recycled to the first heat exchange zone in step (1) at a temperature of 260 to 7050C and a pressure of 10 to 105 atmospheres absolute and leaves said first heat exchange zone at a temperature of 705 to 15400C and at substantially the same pressure; the power developing means in step (2) is a turbine, and heat transfer fluid is removed therefrom at a temperature of 260 to 9850C and a pressure of 1 to 10 atmospheres absolute and is then cooled in step (3) to a temperature of 15 to 6500C without solidification; and the recycling means in step (4) is a gas compressor or pump.

The present invention pertains to an improved continous partial oxidation gasification process for producing synthesis gas, reducing gas, or fuel gas along with valuable by-product saturated and superheated stream. Mechanical work, i.e. gas compression, and electrical energy, are also produced by the process. The gas streams produced by the partial oxidation comprise H2 and CO, and generally one or more of the group H2 O, CO2, H2 S, COS, CH4, N2, Ar, and particulate carbon.

A continuous effluent gas stream of raw synthesis gas, reducing gas or fuel gas is produced in the refractory lined reaction zone of a free-flow unpacked noncatalytic partial oxidation fuel gas generator. The gas generator is preferably a vertical steel pressure vessel, such as shown in the drawing and described in U.S.

Patent No. 2 992906.

A wide range of combustible carbon- and hydrogen-containing organic materials may be reacted in the gas generator with a free oxygen containing gas optionally in the presence of a temperature moderating gas to produce said effluent gas stream.

Any fuel containing carbon and hydrogen that can generally be employed in a partial oxidation gas generator, including gaseous, liquid, and solid hydrocarbons, carbonaceous materials, and mixtures thereof, can be used in accordance with the present invention. In fact, substantially any combustible carbon containing organic material, fossil fusel, or slurries thereof, may be emp]oyed. For example, there are (1) pumpable slurries of solid carbonaceous fuels, such as coal, lignite, particulate carbon petroleum coke, concentrated sewer sludge, and mixtures thereof in water or a liquid hydrocarbon; (2) gas-solid suspension such as finely ground solid carbonaceous fuels dispersed in either a temperature moderating gas or in a gaseous hydrocarbon; and (3) gas-liquid-solid disprsions, such as atomized liquid hydrocarbon fuel or water and particulate carbon dispersed in a temperature-moderating gas.

The hydrocarbonaceous fuel may have a sulfur content in the range of 0 to 10% by weight and an ash content in the range of 0 to 15% by weight.

The term liquid hydrocarbon, as used herein to describe suitable liquid feedstocks, is intended to include various materials, such as liquefied petroleum gas, petroleum distillates and residues, gasoline, naphtha, kerosine, crude petroleum, asphalt, gas oil, residual oil, tar-sand oil and shale oil, coal derived oil, aromatic hydrocarbon (such as benzene, toluene, xylene fractions), coal tar, cycle gas oil from fluidcatalytic-cracking operation, furfural extract of coker gas oil, and mixtures thereof. Gaseous hydrocarbon fuels, as used herein to describe suitable gaseous feedstocks include methane, ethane, propane, butane, pentane, natural gas, water-gas, coke-oven gas, refinery gas, acetylene tail gas, ethylene off-gas, synthesis gas, and mixtures thereof.Both gaseous and liquid feeds may be mixed and used simultaneously, and may include paraffinic, olefinic, naphthenic, and aromatic compounds in any proportion.

Also usable as fuels containing carbon and hydrogen are oxygenated hydrocarbonaceous organic materials including carbohydrates, cellulosic materials, aldehydes, organic acids, alcohols, ketones, oxygenated fuel oil, waste liquids and by products from chemical processes containing oxygenated hydrocarbonaceous organic materials and mixtures thereof.

The fuel feed may be at room temperature or it is preferably preheated to a temperature from 315 to 650 C, e.g. 430 C, but preferably below its cracking temperature. Preheating of the fuel may be accomplished by noncontact heat exchange with heat transfer fluid that was previously heated by heat exchange with the effluent gas stream directly leaving the gas generator. The fuel may be introduced into the burner in liquid phase or in a vaporized mixture with a temperature moderator. Suitable temperature moderators include superheated steam, saturated steam, unsaturated steam, water, CO2 -rich gas, a portion of the cooled exhaust from a turbine employed downstream in the process, nitrogen in air by-product nitrogen from a conventional air separation unit, and mixtures of the aforesaid temperature moderators.

The use of a temperature moderator to moderate the temperature in the reaction zone depends in general on the carbon to hydrogen ratio of the feed stock and the oxygen content of the oxidant stream. A temperature moderator may not be required with some gaseous hydrocarbon fuels, but one is generally used with liquid hydrocarbon fuels and with substantially pure oxygen. The temperature moderator may be introduced in admixture with either or both reactant streams. Alternatively, the temperature moderator may be introduced into the reaction zone of the gas generator by way of a separate conduit in the fuel burner.

From 0 to 100% of any superheated steam produced subsequently in the subject process may be used to preheat and disperse the liquid fuel, or to preheat and entrain the solid fuels and then be introduced into the gas generator.

The weight ratio of total amount of H2 O to fuel introduced into the reaction zone of the gas generator is generally in the range of 0 to 5.

When comparatively small amounts of H2 are charged to the reaction zone, for example through the burner to cool the burner tip, the H2 0 may be mixed with either the fuel, the free-oxygen-containing gas, the temperature moderator, or a combination thereof. In such case, the weight ratio of water to fuel may conveniently be in the range of 0.0 to 1.0, and more preferably 0.0 to 0.2.

The term "free-oxygen containing gas", as used herein means air, oxygen-enriched air, i.e.

greater than 21 mole % oxygen, and substantially pure oxygen, i.e. greater than 95 mole % oxygen, (the remainder comprising N2 and rare gases). Free-oxygen containing gas may be introduced into the burner at a temperature in the range of ambient to 9850 C. The ratio of free oxygen in the oxidant to carbon in the feedstock (O/C, atom/atom) is preferably in the range of 0.7 to 1.5. Preheating the freeoxygen containing gas may be accomplished by noncontact heat exchange with a heat transfer fluid that was previously heated by heat exchange with the effluent gas stream directly leaving the gas generator. In such case, the heat transfer fluid is preferably inert.

The feedstreams are introduced into the reaction zone of the fuel gas generator by means of fuel burner. Suitably, an annulus-type burner, such as described in U.S. Patent No.

2 928 460, may be employed.

The feedstreams are reacted by partial oxidation without a catalyst in the reaction zone of a free-flow gas generator at an autogenous temperature in the range of 815 to 1930 C and at a pressure in the range of 1 to 250 atmospheres absolute (ato. abs.). The reaction time in the fuel gas generator is generally 1 to 10 seconds. The effluent stream of gas leaving the gas generator may comprise CO, H2, CO2, CH4, H2 O, N2, Ar, H2 S, and COS. Unreacted particulate carbon (on the basis of carbon in the feed by weight) is generally 0.2 to 20% by weight from liquid feeds, but is usually negligible from gaseous hydrocarbon feeds. The specific composition of the effluent gas is dependent on actual operating conditions and feed streams.Synthesis gas substantially comprises H2 +CO; all or most of the H2 0 and CO2 are removed for reducing gas; and the CH4 content is maximized for fuel gas.

A continuous stream of hot effluent gas, at substantially the same temperature and pressure as in the reaction zone leaves from the axial exit port of the gas generator and is then introduced directly into a first heat exchange zone.

Optionally, a solids separation zone (not shown in the drawing) may be inserted between the exit port of the gas generator and the first heat exchange zone. The solids separation zone may comprise a free-flow catch-pot, i.e. slag chamber, which may be inserted in the line before the first heat exchanger. By this means at least a portion of any solid matter, i.e. particulate carbon, ash, slag, refractory, and mixtures thereof that may be entrained in the hot effluent gas stream, or which may flow from the gas generator, i.e. slag, ash, or bits of refractory may be separated from the effluent gas stream and be recovered with very little, if any, pressure drop in the line. A typical freeflow slag chamber that may be employed is shown in Figure 1 of the drawing for U.S.

Patent No. 3 528 930.

At least a portion of the sensible heat in the effluent gas stream directly leaving the gas generator or the solids separation zone is recovered in a first heat exchange zone. Thus, noncontact heat exchange takes place in a heat exchange zone between a continuous stream of heat transfer fluid entering from a closed power loop and the continuous stream of effluent gas directly leaving the gas generator, at an exit temperature of 815 to 19300C. The heat transfer fluid may, for example, enter the first heat exchange zone at a temperature of 260 to 705 C and leave at a temperature of 705 to 1540 C. The hot raw gas stream may be corres pondlagly reduced in temperature by 400 to 1500 C, by giving up at least a portion of its sensible heat to the heat transfer fluid.Optionally, the raw gas stream may be then further cooled, cleaned to remove particulate carbon, purified to remove unwanted gas constituents, and used as product gas. Cooling to a temperature in the range of 175 to 400 C and some cleaning may be effected by contacting the gas stream with a scrubbing fluid. For example, the raw gas stream may be immersed in water or a liquid hydrocarbon contained in a quench tank, such as shown in U.S. Patent No. 2 896, 927. Other suitable gas cleaning and purifying methods will be described later.

Optionally in a third heat exchange zone downstream of the first and second zones, a portion of the remaining sensible heat in the process gas stream may be passed in noncontact heat exchange with boiler-feed-water and thereby produce steam having a temperature in the range of 145 to 3750C and a pressure in the range of 4 to 240 atmospheres absolute. In such case the temperature of the process gas may drop 165 to 5600 C.

In another embodiment of the process, the process gas stream, directly after being passed in noncontact heat exchange with heat transfer fluid in the first heat exchange zone, is passed into a second heat exchange zone in noncontact heat exchange with a continuous stream of steam, in the manner as previously produced in said third heat exchange zone. Thus, super heated steam may be produced at a temperature in the range of 395 to 5951C and a pressure in the range of 4 to 240 atmospheres absolute.

At least a portion of the by-product superheated steam produced by the subject process may be introduced into the partial oxidation gas generator, where it may react and thereby contribute to the amount of hydrogen in the effluent gas stream. Further, the thermal efficiency of the process is improved. Condensation problems that may result when steam and fuels are mixed together, may be avoided by using superheated steam. Advantageously, a portion of the superheated steam may be used as the working fluid in a turbocompressor to compress air feed to an air separation unit for producing substantially pure oxygen (95 mole or more). At least a portion of this oxygen may be introduced into the gas generator as at least a portion of the free-oxygen containing gas. The superheated steam may also be used as the working fluid in a turboelectric generator.

Starting with superheated steam at a very high temperature, and converting the heat into electricity, favourably affects the conversion efficiency.

As used herein by definition, the word "noncontact" means that there is no mixing between the two gas streams. Preferably, these two streams run in opposite directions, i.e.

countercurrent flow. However, they may run in the same direction, i.e. concurrent flow. Any suitable heat exchanger that is capable of withstanding the temperatures and pressures of the fluids may be used. Heat resistance metals and ceramics may be employed as construction materials. Shell and tube and fire-tube construction may be employed.

The three heat exchange zones may be contained in separate vessels connected in series.

Alternatively, the first and second, the second and third, or all three heat exchange zones may be contained within the same shell. For example, the first and second heat exchange zones may be conrained within the first shell and the third heat exchanger may be contained in a separate shell connected in series with the first shell, as shown in the drawing.

The effluent gas stream from the gas generator may flow through the tubes of a shell and tube-type heat exchanger or pass through in the shell side of any of the three heat exchangers.

Simultaneously, the other fluid passes in heat exchange through the remaining path in noncontact, preferably countercurrent, flow. The preferred procedure, however, to prevent solids build-up and fouling of the heat exchanger, is to split the effluent gas stream into a plurality of high velocity streams, which are passed through a plurality of small diameter coils or tubes in the heat exchanger.

fhe heat transfer fluid heated in the first heat exchange zone is preferably a portion of the synthesis gas, reducing gas, or fuel gas produced in the process and generally comprising inmole%: H2 70 to 10, CO 15 to 57, CO2 O to 5, N2 0 to 75, Ar 0 to 1.0, CH4 0 to 25, H2 S0to2.0,COSOtoO.1,andH200to20.

Other heat transfer fluids which may be used in the closed power loop may be H2 0, helium, nitrogen, argon, hydrogen, or mixtures comprising H2+CO. Hydrogen transfers more heat with less material and at a lower metal temperature. Further, hydrogen may be produced in the process of the invention by purifying the effluent gas stream, to be further described.

Because hydrogen is readily available as a low cost by-product of the present process, and because of its favourable thermal properties, hydrogen is particularly advantageous for use as a heat transfer fluid. Alternatively, the heat transfer fluid may be sodium, potassium, mercury, or sulfur, in gaseous or liquid state.

The hot heat transfer fluid leaves the first heat exchange zone at a temperature in the range of 705 to 15400C and a pressure in the range of 10 to 105 atmospheres absolute and is passed through at least one power-developing turbine as the working fluid. Coupled, through a variable-speed drive if desired, to the axis of the turbine and driven thereby, may be at least one electric generator and at least one turbocompressor or pump. Thus, free-oxygen containing gas may be compressed to the desired loop pressure by means of another compressor.

Alternatively, a single multi-stage turbocompressor may be employed with the different fluids being compressed in the different stages of the compressor.

The heat transfer fluid may leave the turbine at a temperature in the range of 260 to 9850C.

Preferably, the pressure is in the range of 1 to 10 atmospheres absolute. It may then be passed through a fourth heat exchange zone in noncontact heat exchange with a feed stream of fuel. Optionally, the free-oxygen containing gas feedstream may be similarly preheated. In such a case, the heat transfer fluid in the power loop should preferably be one which would not react with the oxygen in the event of leakage. Two separate conventional shell and tube-type heat exchangers connected in tandem may be employed in the fourth heat exchange zone. Alternatively, two heat exchangers contained in the same shell may be employed to preheat these two separate feed streams. The heat transfer fluid may be passed through the tubes or through the shell side in one or both heat exchangers.

When the free-oxygen feed stream is preheated in the fourth heat exchange zone, the temperature of the stream of heat transfer fluid after heat exchange with the free-oxygen containing gas may be in the range of 35 to 820"C. The free-oxygen containing gas may enter the system at a temperature in the range of ambient to 540 C and a pressure in the range of atmospheric to 250 atmospheres absolute.

After being compressed to a pressure above that of the gas generator by means of said compressor, the free-oxygen containing gas may be preheated to a temperature in the range of 95 to 9850C by noncontact heat exchange with said heat transfer fluid as previously described, or in a separate heater, and then passed into said gas generator by way of a burner.

The temperature of the stream of heat transfer fluid after heat exchange with the hydrocarbonaceous feed may be in the range of 15 to 6500C, but above the solidification temperature. The fuel, enters the system at a temperature in the range of ambient to 2600 C.

The fuel may be preheated by being pumped through the heat exchanger in noncontact heat exchange with the heat transfer fluid where its temperature is increased to a value in the range of95 to 6500C.

Alternatively, the heat transfer fluid in the fourth heat exchange zone may be cooled to a temperature in the range of 15 to 150 OC by noncontact heat exchange with boiler feed water. The boiler feed water may enter the fourth heat exchange zone at a temperature of ambient to 375 C, and may leave as hot water or steam at a temperature in the range of 35 to 595"C. Optionally, the steam produced may be used as the working fluid in a steam turbine.

By way of a burner, the aforesaid preheated stream of free-oxygen containing gas and the stream of fuel, optionally in admixture with a temperature moderator, are then introduced into the partial oxidation gas generator. The impinging streams produce in the reaction zone a gaseous dispersion of fuel in free-oxygen containing gas and optionally temperature moderator.

After heat exchange, with said feedstream of fuel, the heat transfer fluid may be optionally, passed through another heat exchanger. For example, boiler-feed-water at ambient temperature may be preheated to a temperature in the range of 35 to 2600C by noncontact heat exchange with said heat transfer fluid, which may be reduced to a temperature in the range of 15 to 1500C, but above its solidification temperature.

The temperature, and preferably the pressure, of said heat transfer fluid is then increased, and the cycle is repeated as previously discussed. In the case of a gaseous heat transfer fluid, pressure is increased to 10 to 105 atmospheres absolute by means of a compressor driven by an expansion turbine. Similarly, a turbine-driven or magnetic pump may be used for circulating heat transfer fluids in the liquid state.

The heat transfer fluid may remain in the gaseous phase throughout the power loop.

Alternatively, the heat transfer fluid may remain in the liquid phase throughout the power loop. In still another embodiment, the heat transfer fluid may change from one phase, i.e.

liquid or gaseous to the other phase in the power loop, depending on the conditions of temperature and pressure. For example, the heat transfer fluid may be pumped into the first heat exchange zone as a liquid and vaporized therein by absorbing heat from the effluent gas stream from the gas generator. The gaseous heat transfer fluid is then expanded in a power producing turbine. Then by heat exchange with one or more feedstreams to the gas generator or with H2 0, the heat transfer fluid may be cooled and condensed into the liquid phase.

A pump may be used to circulate the liquid heat transfer fluid back to the first heat exchange zone, and the cycle is then repeated.

Magnetic pumps may be used which may be energized by an electric generator that is driven by said turbine.

The raw product gas stream leaves the third heat exchanger, where boiler feed water is converted into steam, and optionally it may be passed through another heat exchanger where the temperature may be reduced by 25 to 300"C.

The cooled stream of raw product gas is passed into a gas cleaning zone where particulate carbon and any other entrained solids may be removed therefrom. Slurries of particulate carbon in a liquid hydrocarbon fuel may be produced in the cleaning zone, and may be recycled to the fuel gas generator as at least a portion of the feedstock. Any conventional procedure suitable for removing suspended solids from a gas srream may be used. In one embodiment of the invention, the stream of raw product gas is introduced into a gas-liquid scrubbing zone, where it is scrubbed with a scrubbing fluid, such as liquid hydrocarbon or water. A suitable liquid-gas tray-type column is more fully described in U.S. Patent No.

3 816 332.

Thus, by passing the stream of raw synthesis gas up a scrubbing column, in direct contact and countercurrent flow with a suitable srubbing fluid, or with dilute mixtures of particulate carbon and scrubbing fluid, flowing down the column, the particulate carbon may be removed from the synthesis gas. A slurry of particulate carbon and scrubbing fluid is removed from the bottom of the column and sent to a carbon separation of concentration zone. This may be done by any conventional means that may be suitable, e.g. filtration, centrifuge, or gravity settling, or by liquid hydrocarbon extraction such as the process described in U.S. Patent No. 2 992 906. Clean scrubbing fluid, or dilute mixtures of scrubbing fluid and particulate carbon, is recycled to the top of the column for scrubbing more synthesis gas.

Other suitable conventional gas cooling and cleaning procedures may be used in combination with, or in place of, the aforesaid scrubbing column. For example, the stream of synthesis gas may be introduced below the surface of a pool of quenching and scrubbing fluid by means of a dip-tube unit, or the stream of syn thesis gas may be passed through a plurality of scrubbing steps, including an orifice-type scrubber or venturi nozzle scrubber such as shown in U.S. Patent No. 3 618 296.

Substantially no particulate carbon is produced with gaseous hydrocarbonaceous fuels, such as natural gas or methane. In such a case, the above-mentioned gas scrubbing step may not be necessary.

H2S, COS and NH3 may be present in the process gas stream, depending upon the sulfur and nitrogen content of the fuel. Any gaseous impurities such as CO2, H2 S, COS or H2 0 may be removed in a gas purification zone, from the cooled and cleaned stream of gas leaving the gas cleaning zone. Suitable conventional processes may be used, involving refrigeration and physical or chemical absorption with solvents, such as methanol, N.methylpyrrolidone, triethanolamine, or propylene carbonate, or alternatively with hot potassium carbonate.

In solvent absorption processes, most of the CO2 absorbed in the solvent may be released by simple flashing. The rest may be removed by stripping. This may be done most economically with nitrogen. Nitrogen may be available as a low cost by-product when a conventional air separation unit is used for producing substantially pure oxygen (95 mole percent 2 or more) for use as the free-oxygen containing gas in the gas generator. The regenerated solvent is then recycled to the absorption column for reuse. When necessary, final clean up may be accomplished by passing the process gas through iron oxide, zinc oxide, or activated carbon to remove residual traces of H2 S or organic sulfide.

Similarly, the H2 S and COS containing solvent may be regenerated by flashing and stripping with nitrogen, or alternatively by heating and refluxing at reduced pressure without using an inert gas. The H2 S and COS are then converted into sulfur by a suitable process.

For example, the Claus process may be used for producing elemental sulfur from H2 S, as described in Kirk-Othmer Encyclopedia of Chemical Technology, Second Edition, Volume 19, John Wiley, 1969, page 353. Excess SO2 may be removed and discarded in chemical combination with limestone, or by means of a suitable commercial extraction process.

A stream of clean synthesis gas leaves the gas purification zone at a temperature of 35 to 430"C and at a pressure in the range of 10 to 180 atm. abs., and preferably 15 to 60 atm.

abs., and most preferably at a pressure substantially the same as that produced in the gas generator less ordinary line drop.

Clean synthesis gas having the following composition in mole % may be made by the aforesaid process : H2 10 to 48, CO 15 to 48, and the remainder comprising N2+Ar. At a great economic benefit, a portion of the synthesis gas may be used as heat transfer fluid.

Some of the synthesis gas may be introduced into the aforesaid loop of heat transfer fluid as make-up and to replace leakage from for example seals and flanges. The remainder of the synthesis gas may be reacted over a catalyst to produce chemicals. For example, a stream of synthesis gas having a mole ratio (H2 /CO) of 2 to 12, and at a temperature of 200 to 400 C, may be passed through a chamber containing methanol catalyst to synthesize methanol. The methanol catalyst may be zinc oxide, copper oxide or a mixture thereof, plus chromium, magnesium, aluminum or a mixture thereof, as a promoter.

In accordance with one embodiment of the invention, at least a portion of heat transfer fluid is bled into the effluent gas in the first heat exchange zone which is a shell and tube heat exchanger comprising a plurality of tubes or coils. Optionally, the ends of the tubes and coils terminate in upstream and downstream headers. The headers may be placed inside or outside of the shell. The tubes, and optionally the headers, if any, are provided with openings in the walls through which at least a portion, e.g. 1 to 50 volume %, more preferably 3 to 25 volume %, of the gaseous heat transfer fluid bleeds into the hot effluent gas stream which is simultaneously passing through the heat exchanger at a lower pressure.Before complete mixing takes place, the comparatively cooler bleedstream of gaseous heat transfer fluid forms a continuously flowing protective sheath or curtain between the hot effluent gas stream and the surface of the tubes and headers, if any, that would ordinarily be contracted by the effluent gas stream. By this means the surfaces of the tubes and headers, if any, such as the upstream header, may be cooled and protected against corrosive gas attack, as well as from deposits of ash, slag, and soot that may be contained in the effluent gas stream. Figure 2 of the accompanying drawings shows the gaseous heat transfer fluid flowing up through the shell side df the first heat exchanger and the hot effluent gas stream from the gas generator or from a solids separation zone following said gas generator, simultaneously flowing down through the tubes and headers of said heat exchanger. Alternatively, the gaseous heat transfer fluid may flow up through the tubes and headers of said first heat exchanger with the effluent gas stream simultaneously flowing down through the shell side of the heat exchanger. Heat exchange takes place in the first heat exchanger by radiation, convection, and by direct contact between the bleedstream of gaseous heat transfer fluid and the hot effluent gas stream from the gas generator.

In this embodiment of the invention, the gaseous heat transfer fluids enters the first heat exchange zone at a temperature of 35 to 7050C e.g. 35 to 2600C and leaves at a temperature in the range of 425 to 1540 C, say 700 to 15400C.

The pressure of the heat transfer fluid exceeds the pressure of the hot effluent gas stream, generally by up to 7 atmospheres, e.g. 0.3 to 3.5 atmospheres, but may be greater still. This provides a suitable pressure differential for bleeding the gaseous heat transfer fluid through openings, such as narrow slots or small diameter holes, e.g. 0.025 to 1.6 mm., in the walls of the tubes and headers, if any. The hot raw effluent gas stream leaves the first heat exchange zone at a temperature in the range of 150 to 16500C, say 315 to 13150C. At least a portion of the sensible heat of the hot effluent gas stream is given up to the heat transfer fluid. Porous metals and ceramics may be used in the first heat exchanger. The effluent gas stream from the gas generator may flow through the tubes of a shell and tube-type heat exchanger or pass through in the shell side.Simultaneously, the gaseous heat exchange fluid passes in heat exchange through the remaining path in preferably indirect flow.

The gaseous heat transfer fluid heated in the first heat exchange zone is preferably a portion of the synthesis gas, reducing gas, or fuel gas produced in the process and comprising in mole %: H2 70 to 10, CO 15 to 57, CO2 0 to 5, N2 0to75,Ar0to 1.0, CH4 0 to 25. H2S 0 to 2.0, COS 0 to 0.l,andH2O0to 20. In one embodiment, hydrogen, i.e. 98 mole % or more is produced from the effluent gas stream from the gas generator and used as the gaseous heat transfer fluid.

The raw effluent gas stream can then optionally be further cooled, cleaned to remove particulate carbon, and optionally purified to remove unwanted gas constituents. Cooling the raw gas stream to a temperature of 35 to 430"C, more preferably 150 to 3500C, and some cleaning may be effected by contacting the gas stream with a scrubbing fluid. For example, the raw gas stream may be immersed in water or a liquid hydrocarbon contained in a quench tank such as shown in U.S. Patent No.

2 896 927.

Particulate carbon and any other entrained solids, if present, may be removed from the raw product gas in the gas cleaning zone, and optionally recycled as fuel, as described above.

At least a portion, e.g. 5 to 100 volume %, of the gas stream may by-pass the gas purification zone, depending on the composition of the gas stream.

A portion of the product gas may be burned in the combustor of a gas turbine as fuel. The gaseous products of combustion are then passed through an expansion turbine as the working fluid for the production of power, for example to power gas compressors or electric generators.

When it is desired to produce hydrogen from synthesis gas, the CO is converted into H2+CO2 by the water-gas shift reaction. The CO2 is removed by chemical absorption to produce substantially pure hydrogen, i.e. at least 98 mole % H2. Hydrogen transfers more heat with less material and at a lower metal temperature.

Because hydrogen is readily available as a low cost by-product of the invention, and because of its favourable thermal properties, hydrogen is particularly advantageous for use as the gaseous heat transfer fluid. Thus, at a great economic benefit, at least a portion of the product gas is used as said gaseous heat transfer fluid in the power loop as make-up to replace said bleed stream and any leakage from for example seals and flanges. This make-up stream may be 1 to 50 volume %, say 3 to 25 volume % of the total amount of gaseous heat transfer fluid. The temperature of the make-up gas stream is generally 35 to 430"C, more preferably 175 to 4000C and the pressure may be 1 to 1 80 atmospheres, more preferably 15 to 60 atmospheres.

In this embodiment, the hot gaseous heat transfer fluid may leave the first heat exchange zone at a temperature of 425 to 1 5400C, say 425 to 980"C, and a suitable pressure in the range of 150 to 3800 psia, and may then, as previously described, be passed through at least one power-developing turbine as the working fluid. It may then be passed, as previously described, through a fourth heat exchange zone where it is cooled by noncontact heat exchange with at least one of the following materials: a feed stream of fuel, the free-oxygen containing gas feedstream, steam, and water. The general configuration of this fourth heat exchange zone has been described above.

After passing through the fourth heat exchange zone the pressures of the gaseous heat transfer fluid and the make-up gaseous heat transfer fluid are then increased and the cycle is repeated as previously discussed. These pressures are increased above that of the raw effluent gas stream passing through the first heat exchange zone in order to permit bleeding of the gaseous heat transfer fluid through the holes in the tubes and headers, if any, and into the raw effluent gas stream. The pressure differential between said stream is generally 0.3 to 7 atmospheres, e.g. 1 to 5 atmospheres. For example, the gaseous heat transfer fluid and make-up gas may be compressed to a pressure of 10 to 260 atmospheres absolute, e.g. 10 to 100 atmospheres absolute, but above that of the raw effluent gas stream in the first heat exchanger.Advantageously, the compressor may be driven by the expansion turbine. The heat transfer fluid remains in the gaseous phase throughout the power loop.

A more complete understanding of the invention may be had by reference to the accompanying Drawings which show the two previously described embodiments in detail. All of the lines and equipment are preferably insulated to minimize heat loss. In the Drawings, like numbers are used for like portion of the apparatus.

Referring to Figure 1, free-flow noncatalytic partial oxidation gas generator 1 lined with refractory material 2 has an upstream axiallyaligned flanged inlet port 3, a downstream axially-aligned flanged outlet port 4, and an unpacked reaction zone 5. Annulus type burner 6, with centre passage 7 in alignment with the axis of gas generator 1 is mounted in inlet port 3. Centre passage 7 has an inlet 8 and a converging conically shaped nozzle 9 at the tip of the burner. Burner 6 is also provided with concentric coaxial annulus passage 10 that has an inlet 11 and a conically shaped discharge passage 12.

Burners of other design may also be used.

Connected to outlet port 4 is the flanged inlet port 15 of shell and tube high temperature heat exchanger 16. Optionally, a solids or slag separator (not shown in the drawing) may be inserted between outlet 4 of gas generator 1 and inlet 15 of heat exchanger 16. Heat exchanger 16 is formed as a single unit with an upper chamber 18 and a lower chamber 20, although separate units can be employed if desired. The flanged inlet 22 of heat exchanger 23 is connected to flanged outlet port 21 of lower chamber 20.The effluent gas stream from gas generator 1 passes through outlet port 4, inlet port 15 of heat exchanger 16, internal tubes or multiple coils 17 in upper chamber 18, internal tubes or multiple coils 19 in lower chamber 20 which are in series with internal tubes or multiple coils 17, and downstream flanged outlet port 21.The partially cooled effluent gas stream passes through inlet port 22 of heat exchanger 23, tubes or multiple coils 24, and then leaves through flanged outlet port 25.

A continuous stream of fuel previously described, may be pumped into the system by way of line 30.

The fuel is preheated in heat exchanger 31 by being passed through an internal conduit, for example coils 32, in noncontact countercurrent heat exchange with a stream of heat transfer fluid which flows through heat exchanger 31, for example on the shell side. The preheated fuel feedstream in line 33 is optionally mixed with a continuous stream of superheated steam from line 34, or a stream of other temperature-modelating gas from line 35, valve 36, and line 37, for example steam from line 80 in a "T" fitting or mixer (not shown).

The feed mixutre is then passed through line 39, inlet 11, annulus passage 10, and discharge passage 12 of bumer 6 into reaction zone 5 of partial oxidation gas generator 1.

Simultaneously, a continuous stream of preheated free-oxygen containing gas from line 40 is passed through centre passage 7 and nozzle 9 of burner 6 into reaction zone 5 of gas generator 1 in admixture with the fuel and steam.

The free-oxygen containing gas enters the system through line 41 and is compressed above the pressure in the gas generator by means of turbocompressor 42. Optionally, the compressed free-oxygen containing gas may be pre hedted by being passed through line 43, 44, valve 45, line 46 and into heat exchanger 31 where it passes through an internal conduit i.e. coil 47, line 48, and into line 40. The freeoxygen containing gas may be preheated by noncontact countercurrent heat exchange with heat transfer fluid which enters heat exchanger 31 through line 49 and which then passes through on the shell side. Alternatively, the free-oxygen containing gas in line 43 may be passed through line 50, valve 51, line 52, heater 53 (optional), line 54, line 40 and into burner 6.

The continous stream of hot effluent has leaving the partial oxidation gas generator by way of outlet 4 is cooled by being passed through heat exchanger 16 first in noncontact countercurrent heat exchange with a stream of heat transfer fluid in upper chamber 18, optionally followed by noncontact heat exchange with a counterflowing stream of steam in lower chamber 20. For example, heat transer fluid in line 56 is passed through flanged inlet 57 and passes up through upper chamber 18 on the shell side 58. The heat transfer fluid is heated by the down flowing effluent gas stream, which flows through tubes or multi-coils 17. The hot heat transfer fluid leaves heat exchanger 16 by way of flanged outlet 59 and line 60.The continuous stream of partially cooled effluent gas flowing down heat exchanger 16 through multicoils or tubes 17 then optionally passes in noncontact heat exchange with a continous up flowing stream of steam flowing up through the shell side 61 of lower chamber 20. The steam picks up heat thereby and is converted into superheated steam which leaves lower chamber 20 through outlet nozzle 62 and line 63.

Optionally, but preferably, at least a portion of the superheated steam is introduced into gas generator 1 as the temperature moderator. For example, a stream of superheated steam may be passed through lines 63, 64 valve 65, line 34 and mixed in line 39 as previously discussed with fuel feed. The remainder of the stream of superheated seam from line 63 may be withdrawn by way of line 66, valve 67, and line 68, and may be for example introduced into a power producing steam turbine 55 as the working fluid. In the embodiment using a third heat exchange zone, the partially cooled effluent gas stream leaves bottom chamber 20 through outlet 21 and enters heat exchanger 23 by way of inlet 22. In passing down through heat exchanger 23, by way of tubes of multi-coils 24, the effluent gas stream passes in noncontact heat exchange with a counterflowing stream of boiler feed water passing on the shell side 69.

The boiler feed water is thereby heated to produce steam by absorbing at least a portion of the remaining sensible heat in the effluent gas stream. For example, the boiler-feed water enters heat exchanger 23 through line 70 and flanged inlet 71. As the water passes up through heat exchanger 23, on the shell side 69 for example, it absorbs heat from the stream of effluent gas flowing down through heat exchanger 23 through multi-coils 24, and leaves through flanged outlet 72 and line 73 as steam.

Optionally, the steam may be passed through valve 74, line 75, and flanged inlet 76 to bottom chamber 20, where it may be converted into superheated steam, as previously described. An alternative arrangement, not shown in the drawing, would have the heat transfer fluid flowing up through tubes in heat exchanger 16 in noncontact heat exchange with the raw synthesis gas flowing down through upper compartment 18 on the shell side 58. In such an embodiment no superheated steam would be produced. Similarly, in another embodiment the raw synthesis gas may flow down through heat exchanger 23 on the shell side 69 in noncontact heat exchange with water flowing up through coils 24. Compartments 18 and 20 may be contained in the same shell or in separate shells. Optionally, a portion of the steam may be removed from heat exchanger 23 by way of flanged outlet 77, line 78, valve 79 and line 80.This steam may be used elsewhere in the system for example as the working fluid in a steam turbine or to provide heat.

The cooled effluent gas stream leaves heat exchanger 23 by way of outlet 25, line 85 and optionally may be cooled further in heat exchanger 86, for example by preheating hydrocarbonaceous fuel before it is introduced into carbon removal zone 87 by way of line 88.

Then by conventional methods as previously described, particulate carbon may be removed from the effluent gas stream which enters the carbon removal zone 87 by way of line 89. For example, particulate carbon may be removed by a solvent extraction process in which pumpable slurries of particulate carbon in heavy fuel oil are produced. In such case, the hydrocarbonaceous fuel enters the carbon removal zone through line 88 and the carbon slurry is removed by way of line 90. The carbon slurry may comprise at least a portion of the hydrocarbonaceous feed introduced into the system through line 30.

The clean effluent gas stream in line 91 is purified of unwanted gas impurities i.e. CO2, COS, H2S, CH4, and NH3, in gas purification zone 92 by conventional procedures, as previously described. The cleaned and purified product as stream leaves through lines 93 and 94. Optionally a portion of the produce gas stream is compressed and introduced into the loop of heat transfer fluid as make-up for example by way of line 95, valve 96, line 97, turbo-compressor 98, and line 56.

The heat transfer fluid circulating in the substantially closed loop may perform two functions. Firstly, it serves as a heat transfer fluid by absorbing in heat exchanger 16 at the highest possible temperature, sensible heat from the effluent gas stream produced in the partial oxidation gas generator, and then releasing this heat in heat exchanger 31 for example to preheat hydrocarbonaceous feed stream 30, and optionally free-oxygen containing gas stream 43. Secondly, the heat transfer fluid may serve as the working fluid in turbine 100 which produces mechanical power by driving, for example, compressors 98 and 42, and electrical energy by driving, for example, electrical generator 101. Compressors 98 and 42 are shown in the drawing to be on the same axial shaft 102-105 as turbine 100.Electric generator 101 is shown with shaft 105 connected to shaft 104 by means of flexible coupling 106. Other suitable mechanical linkages may be used for transferring the rotational power produced by expansion turbine 100.

After passing through the shell side of heat exchanger 31, the heat transfer fluid is passed through line 110, optionally through heat exchanger 111 which may be used for preheating boiler feed water, and lines 112 and 113 into compressor 98 or alternatively into a pump. The loop is closed by circulating heat transfer fluid through line 56 into heat exchanger 16 for reheating. Optionally a portion of the heat transfer fluid may be discharged from the loop by way of line 114, valve 115 and line 116.

An alternative scheme, not shown in the drawing, would be to preheat boiler feed water by heat exchange with heat transfer fluid in heat exchanger 31 before this boiler feed water is introduced into heat exchange 23.

In the embodiment of the invention shown in Figure 2, the same reference numerals are used as in Figure 1. The construction and operation of the gas generator 1 are the same as in Figure 1.

Connected to outlet port 4 is the flanged inlet port 15 of shell and tube high temperature heat exchanger 16 which comprises a plurality of tubes 17, whose upper ends terminate in upstream header 14 and whose lower ends terminate in downstream header 26. Small diameter holes 27 in tubes 17 and in both headers 14 and 26 permit a portion of the gaseous heat transfer fluid flowing outside the tubes and headers to bleed in and mix with the hot effluent gas stream flowing within the tubes and headers. Before mixing is complete, however, a continuously flowing sheath or curtain of gaseous heat transfer fluid, bleeding through the openings, forms between the inside surfaces of the tubes and headers and the surrounding hot effluent gas stream. Optionally, a solids or slag separator (not shown in the drawing) may be inserted between outlet 4 of gas generator 1 and inlet 15 of heat exchanger 16.Heat exchanger or superheater 58 and heat exchanger 23 are optionally inserted in the line downstream from heat exchanger 16 to make respectively superheated steam and saturated or unsaturated steam by utilizing the sensible heat in the effluent gas stream from the gas generator.

In a first heat exchange zone, gaseous heat transfer fluid circulating in a power loop is reheated. Thus, the effluent gas stream from gas generator 1 may pass through outlet port 4, inlet port 15, and upper chamber 18 containing heat exchanger 16. Heat exchanger 16 comprises upstream header 14, tubes or multiple coils 17, downstream header 26, and shell side 13. Small diameter holes in tube 17 and headers 14 and 26 permit the passage of gaseous heat transfer fluid, as previously mentioned.

The partially cooled effluent gas stream leaving heat exchanger 16 in upper chamber 18 may be optionally passed through heat exchanger or superheater 58 in lower chamber 20 to provide heat for superheating steam. Thus, the effluent gas stream passes from upper chamber 18 through tubes or multiple coils 19 of heat exchanger 58 in lower chamber 20 and leaves by outlet port 21. Steam passes up through the shell side 61 of heat exchanger 58 and is superheated.

Optionally, in heat exchanger 23, steam may be produced from boiler feed water. Thus the partially cooled effluent gas stream leaves heat exchanger 58 through port 21, enters heat exchanger 23 through inlet 22, passes through tubes or multiple coils 24, and leaves by outlet 25. Boiler feed water passes up through the shell side 69 of heat exchanger 23.

A continuous stream of fuel may be pumped into the system by way of line 30.

The fuel is preheated in heat exchanger 31 by being passed through internal conduit means, for example coils 32, in noncontact countercurrent heat exchange with a stream of heat transfer fluid which flows through heat exchanger 31, for example on the shell side.

The preheated fuel in line 33 is optionally mixed with a continuous stream of superheated steam from line 34, or a stream of other temperature-moderating gas from line 35, valve 36, and line 37, for example steam from line 80, in a "T" fitting or mixer (not shown). The feed mixture is then passed through line 39, inlet 11, annulus passage 10, and discharge passage 12 of burner 6 into reaction zone 5 of partial oxidation gas generator 2.

Simultaneously, a continuous stream of preheated free-oxygen containing gas from line 40 is passed through centre passage 7 and nozzle 9 of burner 6 into reaction zone 5 of gas generator 1 in admixture with fuel and steam. The free-oxygen containing gas enters the system through line 41 and is compressed above the pressure in the gas generator by means of turbocompressor 42. Optionally, the compressed free-oxygen containing gas may be preheated by being passed through line 43, 44, valve 45, line 46 and into heat exchanger 31 where it passes through an internal conduit i.e. coil 47, line 48, and into line 40. The free-oxygen containing gas may be preheated by noncontact countercurrent heat exchange with heat transfer fluid which enters heat exchanger 31 through line 49 and which then passes through on .he shell side.Alternatively, the free-oxygen containing gas in line 43 may be passed through line 50, valve 51. line 52, heater 53 (optional), line 54, line 40, and into burner 6.

The continuous stream of hot effluent gas leaving the partial oxidation gas generator by way of outlet 4 is partially cooled by being passed through heat exchanger 16 in noncontact countercurrent heat exchange with stream of gaseous heat transfer fluid. For example, the gaseous heat transfer fluid in line 56 is passed through flanged inlet 57 and passes up through top compartment 18 of heat exchanger 16 on the shell side. The hot gaseous heat transfer fluid leaves heat exchanger 16 by way of flanged outlet 59 and line 60. In one embodiment, (not shown) the continuous stream of partially cooled effluent gas flowing down heat exchanger 16, by-passes heat exchangers 58 and 23 and is then introduced into line 85, optional cooler 86, carbon removal zone 87, and optional gas purification zone 92.Then, at least a portion of the produce gas is passed through line 97 into compressor 98, to be further described.

An alternative embodiment, shown in Figure 2 of the Drawings, depicts the production of by-product saturated steam, superheated steam, or both, as previously described. The partially cooled effluent gas stream leaving heat exchanger 16 passed down through tubes or coils 19 in noncontact countercurrent heat exchange with a continuous stream of steam flowing up through the shell side 61 of a second heat exchange zone comprising heat exchanger 58.

The steam picks up heat thereby, and is converted into superheated steam, which leaves heat exchanger 58 through outlet nozzle 62 and line 63. Optionally, but preferably, at least a portion of said superheated steam is introduced into gas generator 1 as the temperature moderator. For example, a stream of superheated steam may be passed through lines 63, 64, valve 65, and line 34, and mixed in line 39 as previously discussed with fuel feed from line 33. The remainder of the stream of superheated steam from line 63 may be withdrawn by way ofline 66, valve 67, line 68, and may be for example introduced into a power producing steam turbine 55 as the working fluid. The turbine exhaust leaves by line 18. Compressor 82 is driven by turbine 55 and compresses air from line 83. The compressed air from line 84 is separated in air separation unit 195 into a stream of oxygen in line 196 and nitrogen in line 199. The oxygen in line 196 may be introduced into gas generator 1 as free-oxygen containing gas. In the embodiment using a third heat exchange zone comprising heat exchanger 23, the partially cooled effluent gas stream leaves the bottom compartment 20 of heat exchanger 58 through outlet 21 and enters heat exchanger 23 by way of inlet 22. In passing down through heat exchanger 23 by way of tubes or multi-coils 24, the effluent gas stream passes in noncontact heat exchange with a counterflowing stream of boiler feed water passing on the shell side 69. The boiler feed water is thereby heated to produce steam by absorbing at least a portion of the remaining sensible heat in the effluent gas stream.For example, the boiler-feed water enters heat exchanger 23 through line 70 and flanged inlet 71. As the water passes up through heat exchanger 23, on the shell side 69 for example, it absorbs heat from the stream of effluent gas flowing down through heat exchanger 23 through multi-coils 24, and leaves through flanged outlet 72 and line 73 as steam. Optionally, the steam may be passed through valve 74, line 75, and flanged inlet 76 to bottom compartment 20 where it may be -converted into superheated steam, as previously described. An alternative arrangement, not shown in Figure 2 of the Drawings, would have the gaseous heat transfer fluid flowing up through tubes in heat exchanger 16 in heat exchange with the raw synthesis gas flowing down through upper compartment 18 on the shell side 58.Similarly, in other embodiments, the raw synthesis gas may flow down through heat exchangers 58 or 23, or both, on the shell side 61 or 69, or both, in noncontact heat exchange with steam or water in the remaining passages.

Compartments 18 and 20 may be contained in the same shell or in separate shells.

Optionally, a portion of the steam may be removed from heat exchanger 23 by way of flanged outlet 77, line 78, valve 79 and line 80.

This steam may be used elsewhere in the system for example as the working fluid in a steam turbine or to provide heat. Similarly, a portion of the superheated steam from outlet 62 of heat exchanger 58 may be optionally exported through lines 63, 107, valve 108, and line 109.

The cooled effluent gas stream leaves heat exchanger 23 by way of outlet 25, and line 85 and optionally may be cooled further inheat exchanger 86, for example by preheating hydrocarbonaceous fuel before it is introduced into carbon removal zone 87 by way of line 88. Then by conventional methods as previously described, particulate carbon may be removed from the cffluent gas stream which enters the carbon removal zone 87 by way of line 89.

The clean effluent gas stream in line 91 may be optionally passed through line 130, valve 131, and line 132 into gas purification zone 92 and purified of any unwanted gas impurities e.g. CO2, COS, H2 S, CH4 or NH3, by conventional procedures, as previously described. The cleaned and purified produce gas stream leaves through lines 93, 133,94 valve 120 and 121.

Optionally, at least a portion of the cleaned gas stream in line 91 may by-pass gas purification zone 92 by way of line 134, valve 135, and line 136.

A portion of the product gas stream in line 97 is compressed in compressed in compressor 98 nd introduced into the loop of gaseous heat transfer fluid by way of line 56 as make-up to replace the gaseous heat transfer fluid that bleeds into the effluent gas srream in heat exchanger 16.

The gaseous heat transfer fluid circulating in the substantially closed loop may perform two functions, as described above. Firstly it serves as a heat transfer fluid in heat exchanger 16; and secondly, it may serve as the working fluid in turbine 100. These further uses of the heat transfer fluid are described in connection with Figure 1 above.

EXAMPLES The following examples illustrate preferred embodiments of the process of this invention.

The processes are continuous and the quantities specified are on an hourly basis for all streams of materials. Volumes are expressed at OOC and 1 atmosphere pressure. Pressures are absolute pressures.

EXAMPLE 1 The embodiment of the invention represented by Example 1 is depicted in Figure 1 of the Drawings. 89842.5 cubic metres of raw synthesis gas are continuously produced in a free-flow noncatalytic gas generator by partial oxidation of an hydrocarbonaceous fuel to be further described with oxygen (about 99.7 volume percent purity). The hydrocarbonaceous fuel is a pumpable slurry comprising 470.3 Kg. of particulate carbon, recovered later by cleaning the raw synthesis gas product and 26014 Kg. of reduced crude oil having the following ultimate analysis in Wt. %: C 85.87, H2 11.10, S 2.06, N2 0.78, 2 0.16 and ash 0.04. Further the reduced crude oil has an API gravity of 12.5 (specific gravity 0.983), a heat of combusition of 10185 cal/g. and a viscosity of 479 Saybolt Seconds Furol at 500C (1170 centistrokes).The hydrocarbonaceous fuel was previously preheated to a temperature of 260"C by noncontact indirect heat exchange with heat transfer fluid, to be further described.

13007 Kg. of superheated steam, produced subsequently in the process at a temperature of 3990C and a pressure of about 40.8 atmospheres are mixed with the fuel to produce a feed mixture having a temperature of about 295"C, which is continously introduced into the annulus passage of an annulus-type burner and which discharges into the reaction zone of said gas generator. About 19937 cubin metres of oxygen at a temperature of about 260"C are continously passed through the centre passage of the burner and mixed with the dispersion of superheated steam, fuel oil, and particulate carbon. The oxygen stream was previously preheated by noncontact indirect heat exchange with heat transfer fluid, to be further described.

Partial oxidation and related reactions take place in the free-flow reaction zone of the gas generator to produce a continuous effluent stream of raw synthesis gas at a temperature of 1305"C and a pressure of 28.2 atmospheres.

The effluent stream of hot raw synthesis gas from the gas generator passes down through the tubes of a separate first shell and tube heat exchanger comprising two zones. In the first zone, the effluent stream of synthesis gas is cooled to a temperature of 473"C by noncontact indirect heat exchange with a continuous stream of heat transfer fluid, comprising clean and purified synthesis gas passing up on the shell side. Then in the second zone, the stream of raw synthesis gas passing down through the tubes is cooled to a temperature of 435 C by noncontact indirect heat exchange with 13007 Kg. of saturated steam which passes up through the shell side of the second zone of said first heat exchanger at a temperature of 2420C and a pressure of 42.2 atmospheres.The saturated steam is converted into about 13007 Kg. of superheated steam which leaves the first heat exchanger at a temperature of 399"C and a pressure of 40.8 atmospheres. As previously described, at least a portion of this continuous stream of superheated steam is introduced into the gas generator, preferably in admixture with the fuel. Optionally, a portion of the superheated steam is used as the working fluid in a turbocompressor, for example in an air separation plant for producing the free-oxygen feed to the gas generator.

The partially cooled stream of raw synthesis gas leaving the second zone of said first heat exchanger is then passed through the tubes of a separate second heat exchanger and cooled to a temperature of about 2710C by heat exchange with 13007 Kg. of boiler feed water supplied in a continous stream. A stream of about 13007 Kg. of said by-product saturated steam is thereby produced at a temperature of about 2530C and a pressure of about 41.5 atmospheres. As previously described, at least a portion of this saturated steam is passed into the second zone of the first heat exchanger for conversion into superheated steam.

The continuous effluent stream of raw synthesis gas leaving the second heat exchanger after heat exchange with the boiler feed water is at a pressure which is substantially the same as that in the reaction zone of the gas generator, less ordinary pressure drop in the lines and heat exchangers. This pressure drop may be less than about 2 atmospheres. The composition of the stream of raw synthesis gas leaving the second heat exchanger is as follows: H2 41.55, CO 41.59, CO2 4.61,he 0 11.46,H2S 0.40, COS 0.02, CH4 0.13, N2 0.21. and Ar 0.03. About 474.5 Kg. of unconverted particulate carbon are entrained in the effluent stream of raw synthesis gas. Particulate carbon and other gaseous impurities may be removed from the raw synthesis gas in conventional downstream gas cleaning and purifiying zones.

A stream of synthesis gas product is produced having the following composition in mole %: H2 47.5, CO 47.5, CO2 4.5, and the remainder con.prising a mixture of CH4, Ar, N2, and COS. A portion of said product gas is used in a substantially closed loop as the heat transfer fluid; and it also serves as the working fluid in the expansion turbine.

Thus 70617 Kg. of said heat transfer fluid enters the first zone of said first heat exchanger at a temperature of 424"C and a pressure of 29.25 atmospheres.

The stream ofheat transfer fluid leaves said heat exchanger at a temperature of 1205"C and at substantially the same pressure, and is then passed through a power developing expansion turbine. The temperature and pressure of the heat transfer fluid leaving the expansion turbine is 664"C and 3.2 atmospheres respectively.

After passing in noncontact indirect heat exchange with the oxygen feedstream and the stream of hydrocarbonaceous feed respectively, the temperature of the heat transfer fluid is 529"C. The heat transfer fluid is then cooled to a temperature of 490C by heat exchange with boiler feed water. Then by means of a compressor driven by said expansion turbine, the pressure of the heat transfer fluid is raised to 29.25 atmospheres. Make-up H2+CO may be also introduced into said compressor to account for seal leakage, etc. The aforesaid expansion turbine also provides the driving force for an oxygen feed compressor, and for an electric generator. The compressed heat transfer fluid is then recycled to said first zone of said first heat exchanger.

EXAMPLE 2 The embodiment of the invention represented by Example 2 is depicted in Figure 2 of the Drawings. 89842.5 cubic metres of raw synthesis gas are continously produced as described in Example 1.

The effluent stream of hot raw synthesis gas from the gas generator passes down through the tubes of a separate first shell and tube feet exchanger comprising two zones. In the first zone, the effluent stream of synthesis gas is cooled to a temperature of 466"C by noncontact countercurrent heat exchange with a continuous stream of gaseous heat transfer fluid comprising clean and purified synthesis gas passing up on the shell side. About 5 vol. % of the gaseous heat transfer fluid entering the first heat exchanger bleeds through small diameter holes in the tubes and headers, forms a continuous moving protective sheath between the inside surfaces of the tubes and headers and the stream of hot effluent gas passing through the tubes and headers, and then mixes with the effluent gas stream. Then, in the second zone, in a separate second shell and tube heat exchanger, the stream of raw synthesis gas passing down through the tubes is cooled to a temperature of about 435"C by noncontact countercurrent heat exchange with 13007 Kg. of saturated steam, which passes up through the shell side of the second zone of said second heat exchanger at a temperature of 253 C and a pressure of 41.5 atmospheres. The saturated steam is converted into about 13007 Kg. of superheated steam which leaves the first heat exchanger at a temperature of about 399"C and a pressure of 40.8 atmospheres. As des- cribed, in Example 1, at least a portion of this continuous stream of superheated steam is introduced into the gas generator, preferably in admixture with the fuel.Optionally, a portion of the superheated steam can be used as the working fluid in a turbocompressor, for example in an air separation plant for producing the free-oxygen feed to the gas generator.

The partially cooled stream of raw synthesis gas leaving the second heat exchanger is then passed through the tubes of a separate third heat exchanger, and cooled to a temperature of about 271 C by heat exchange with about 13007 Kg. of boiler feed water, supplied in a continuous stream. A stream of by-product saturated steam is thereby produced at a temperature of about 253 C. As previously described, at least a portion of this saturated steam is passed into the second heat exchanger for conversion into superheated steam.

The continuous effluent stream of raw synthesis gas leaving the third heat exchanger after heat exchange with said boiler feed water is at a pressure which is substantially the same as that in the reaction zone of the gas generator, less ordinary pressure drop in the lines and heat exchanger. This pressure drop may be less than about 2 atmospheres. The composition of the stream of raw synthesis gas leaving the gas generator is as follows in mole %: H2 41.55, CO 41.59, CO2 4.61,H2O 11.46,H2S0.40,COS 0.02, CH4 0.13, N2 0.21, and Ar 0.03. About 474.5 Kg. of unconverted particulate carbon are entrained in the effluent stream of raw synthesis gas. Particulate carbon and other gaseous impurities may be removed from the raw synthesis gas in conventional downstream gas cleaning and purifying zones.A stream of synthesis gas product is produced having the following composition in mole %: H2 47.5, CO 47.5, CO2 4.5, and the remainder comprising a mixture of CH4, Ar, N2 and COS. A portion of this product gas is used in a substantially closed loop as make-up gaseous heat transfer fluid.

Thus 70617 Kg. of the gaseous heat transfer fluid enters the first heat exchanger at a temperature of 424"C and a pressure of 29.25 atmospheres.

About 5 vol. % of the gaseous heat transfer fluid bleeds through the openings in the tubes.

The remainder of the stream of heat transfer fluid leaves the first heat exchanger at a temperature of 1 2430C and at substantially the same pressure, and is then passed through a power developing expansion turbine. The pressure of the heat transfer fluid leaving the expansion turbine is about 3.2 atmospheres, and the temperature falls about 555 C. After passing in nonnontact countercurrent heat exchange with the oxygen feed-stream, the stream of hydrocarbonaceous feed, and boiler feed water, the temperature of the gaseous heat transfer fluid is reduced to about 49 C. Then, by means of a compressor driven by the expansion turbine, the pressure of the heat transfer fluid is raised to 29.25 atmospheres.Make-up gaseous heat transfer fluid is introduced into the compressor, as previously mentioned, to account for bleeding through the tube and header walls in heat exchanger 16, and such losses as seal leakage.

The aforesaid expansion turbine also provides the driving force for an oxygen feed compressor and for an electric generator. The compressed heat transfer fluid is then recycled to said first zone of said first heat exchanger.

Advantageously, by this embodiment of the process, the severity of the operating conditions on heat exchanger tubes and headers may be minimized and controlled. Since fouling of the heat transfer surfaces is prevented, the surface area required for a given amount of heat will be decreased from about 25 to 25%. Further, the size of the heat exchangers may be decreased about 50 to 75%. Bleeding will not necessarily be required over the full length of the tubes, since the gas temperatures are reduced near the downstream end due to heat transfer; and the strength of attack by hydrogen sulfide is correspondingly reduced.Accordingly, the tubes and headers may be made from heat- and corrosionresistant materials at the upstream (hot) end, and less expensive materials at the downstream (cooler) end. Dissimilar materials may be joined by close fitting slip joints.This would eliminate thermal stresses due to the growth of the tubes and permit firm tie-down of the headers. The leakage that would occur can be controlled by the fit and would be incorporated as part of the bleed system described previously.

WHAT WE CLAIM IS:- 1. A process for producing gaseous mixtures comprising H2 and CO by the partial oxidation of a fuel containing carbon and hydrogen with a free-oxygen containing gas at a temperature in the range of 815 to 1930 C and a pressure in the range of 1 to 250 atmospheres absolute in the reaction zone of a free-flow noncatalytic gas generator, which comprises (1) continuously passing raw effluent gas leaving the gas generator through a first heat exchange zone in heat exchange with a heat transfer fluid; (2) introducing the resulting stream of hot heat transfer fluid into a power developing means as the working fluid and thereby producing power; (3) cooling the heat transfer fluid leaving (2) by non-contact heat exchange with at least one other material in a separate heat exchange zone; and (4) recycling the heat transfer fluid from (3) to the first heat exchange zone of step (1).

2. A process as claimed in Claim 1, wherein the heat transfer fluid from step (4) is recycled to the first heat exchange zone in step (1) at a temperature of 260 to 7050C and a pressure of 10 to 105 atmospheres absolute and leaves said

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. exchanger at a temperature of about 399"C and a pressure of 40.8 atmospheres. As des- cribed, in Example 1, at least a portion of this continuous stream of superheated steam is introduced into the gas generator, preferably in admixture with the fuel. Optionally, a portion of the superheated steam can be used as the working fluid in a turbocompressor, for example in an air separation plant for producing the free-oxygen feed to the gas generator. The partially cooled stream of raw synthesis gas leaving the second heat exchanger is then passed through the tubes of a separate third heat exchanger, and cooled to a temperature of about 271 C by heat exchange with about 13007 Kg. of boiler feed water, supplied in a continuous stream. A stream of by-product saturated steam is thereby produced at a temperature of about 253 C. As previously described, at least a portion of this saturated steam is passed into the second heat exchanger for conversion into superheated steam. The continuous effluent stream of raw synthesis gas leaving the third heat exchanger after heat exchange with said boiler feed water is at a pressure which is substantially the same as that in the reaction zone of the gas generator, less ordinary pressure drop in the lines and heat exchanger. This pressure drop may be less than about 2 atmospheres. The composition of the stream of raw synthesis gas leaving the gas generator is as follows in mole %: H2 41.55, CO 41.59, CO2 4.61,H2O 11.46,H2S0.40,COS 0.02, CH4 0.13, N2 0.21, and Ar 0.03. About 474.5 Kg. of unconverted particulate carbon are entrained in the effluent stream of raw synthesis gas. Particulate carbon and other gaseous impurities may be removed from the raw synthesis gas in conventional downstream gas cleaning and purifying zones.A stream of synthesis gas product is produced having the following composition in mole %: H2 47.5, CO 47.5, CO2 4.5, and the remainder comprising a mixture of CH4, Ar, N2 and COS. A portion of this product gas is used in a substantially closed loop as make-up gaseous heat transfer fluid. Thus 70617 Kg. of the gaseous heat transfer fluid enters the first heat exchanger at a temperature of 424"C and a pressure of 29.25 atmospheres. About 5 vol. % of the gaseous heat transfer fluid bleeds through the openings in the tubes. The remainder of the stream of heat transfer fluid leaves the first heat exchanger at a temperature of 1 2430C and at substantially the same pressure, and is then passed through a power developing expansion turbine. The pressure of the heat transfer fluid leaving the expansion turbine is about 3.2 atmospheres, and the temperature falls about 555 C. After passing in nonnontact countercurrent heat exchange with the oxygen feed-stream, the stream of hydrocarbonaceous feed, and boiler feed water, the temperature of the gaseous heat transfer fluid is reduced to about 49 C. Then, by means of a compressor driven by the expansion turbine, the pressure of the heat transfer fluid is raised to 29.25 atmospheres.Make-up gaseous heat transfer fluid is introduced into the compressor, as previously mentioned, to account for bleeding through the tube and header walls in heat exchanger 16, and such losses as seal leakage. The aforesaid expansion turbine also provides the driving force for an oxygen feed compressor and for an electric generator. The compressed heat transfer fluid is then recycled to said first zone of said first heat exchanger. Advantageously, by this embodiment of the process, the severity of the operating conditions on heat exchanger tubes and headers may be minimized and controlled. Since fouling of the heat transfer surfaces is prevented, the surface area required for a given amount of heat will be decreased from about 25 to 25%. Further, the size of the heat exchangers may be decreased about 50 to 75%. Bleeding will not necessarily be required over the full length of the tubes, since the gas temperatures are reduced near the downstream end due to heat transfer; and the strength of attack by hydrogen sulfide is correspondingly reduced.Accordingly, the tubes and headers may be made from heat- and corrosionresistant materials at the upstream (hot) end, and less expensive materials at the downstream (cooler) end. Dissimilar materials may be joined by close fitting slip joints.This would eliminate thermal stresses due to the growth of the tubes and permit firm tie-down of the headers. The leakage that would occur can be controlled by the fit and would be incorporated as part of the bleed system described previously. WHAT WE CLAIM IS:-

1. A process for producing gaseous mixtures comprising H2 and CO by the partial oxidation of a fuel containing carbon and hydrogen with a free-oxygen containing gas at a temperature in the range of 815 to 1930 C and a pressure in the range of 1 to 250 atmospheres absolute in the reaction zone of a free-flow noncatalytic gas generator, which comprises (1) continuously passing raw effluent gas leaving the gas generator through a first heat exchange zone in heat exchange with a heat transfer fluid; (2) introducing the resulting stream of hot heat transfer fluid into a power developing means as the working fluid and thereby producing power; (3) cooling the heat transfer fluid leaving (2) by non-contact heat exchange with at least one other material in a separate heat exchange zone; and (4) recycling the heat transfer fluid from (3) to the first heat exchange zone of step (1).

first heat exchange zone at a temperature of 705 to 1 5400C and at substantially the same pressure; the power developing means in step (2) is a turbine, and heat transfer fluid is removed therefrom at a temperature of 260 to 985"C and a pressure of 1 to 10 atmospheres absolute and is then cooled in step (3) to a temperature of 15 to 6500C without solidification; and the recycling means in step (4) is a gas compressor or pump.

3. A process as claimed in Claim 1 or 2, wherein raw effluent gas is cooled, cleaned by removing entrained solids, and purified to remove unwanted gaseous constituents, thereby producing a stream of product gas.

4. A process as claimed in Claim 3, wherein a portion of product gas is mixed as make-up with at least a portion of the cooled heat transfer fluid from (3), the resulting gas mixture is compressed by means of a gas compressor driven by said power developing means, and the resulting compressed gaseous heat transfer fluid is recycled into the first heat exchange zone in (1).

5. A process as claimed in Claim 4, wherein said gas mixture is compressed to a pressure greater than that in the gas generator.

6. A process as claimed in any of Claims 3 to 5, wherein the raw effluent gas is cooled by noncontact heat exchange with water thereby producing saturated steam.

7. A process as claimed in any of Claims 3 to 6, wherein the raw effluent gas is cooled by direct contact with water.

8. A process as claimed in any preceding claim, wherein the heat transfer fluid is H2 O, helium, nitrogen, argon, hydrogen, or a mixture of H2+CO.

9. A process as claimed in any of Claims 1 to 7, wherein the heat transfer fluid is sodium potassium, mercury, or sulphur.

10. A process as claimed in any of Claims 1 to 7, wherein a portion of the product gas is used as the heat transfer fluid.

11. A process as claimed in Claim 10, wherein the product gas is substantially pure hydrogen obtained by purifying the effluent.

12. A process as claimed in Claims 10 or 11, wherein the first heat exchange zone comprises a shell and tube heat exchanger, and a portion of cleaned and compressed product gas constituting the heat transfer fluid is continuously bled into the raw effluent gas in step (1) by way of openings in the walls of said tubes, thereby placing a sheath or curtain of gaseous heat transfer fluid between the surface of the tubes and the effluent gas.

13. A process as claimed in Claim 12, wherein about 1 to 50 volume % of the product gas is used as heat transfer fluid.

14. A process as claimed in any preceding claim, wherein the heat transfer fluid is cooled in step (3) by being passed in non-contact heat exchange firstly with a feed stream of freeoxygen containing has whose temperature is thereby increased to 90 to 9850C and secondly with a feed stream of fuel whose temperature is thereby increased to 90 to 6500C.

15. A process as claimed in any preceding claim, wherein a portion of the power developed from said power developing means in step (2) is used to drive an electric generator.

16. A process as claimed in any preceding claim, wherein the effluent gas stream leaving the first heat exchange zone is cooled by indirect heat exchange with steam in a second heat exchange zone, thereby producing superheated steam.

17. A process as claimed in Claim 16, wherein the effluent gas stream leaving the second heat exchange zone is cooled by indirect heat exchange with water in a third heat exchange zone, thereby producing steam; and the steam is introduced into the second heat exchange zone to produce superheated steam.

18. A process as claimed in any preceding claim, wherein at least a portion of the byproduct superheated steam is used as working fluid in a steam turbine used to compress air feed to an air separation unit, thereby producing oxygen for reacting in the gas generator.

19. A process as claimed in any preceding claim, wherein at least a portion of the superheated steam is introduced as the working fluid into a steam turbine for producing mechanical work or electrical energy.

20. A process as claimed in any preceding claim, wherein a portion of the product gas stream is burnt in the combustor of a gas turbine as fuel, and the resulting gaseous combustion products are passed through an expansion turbine for the production of mechanical power.

21. A process as claimed in any preceding claim, wherein at least a portion of unwanted solid particulate carbon, ash, slag, scale, refractory, and/or mixtures thereof is removed from the raw effluent gas stream before it is introduced into the first heat exchange zone.

22. A process as claimed in Claim 1 and substantially as hereinbefore described with reference to Figure 1 of the drawings.

23. A process as claimed in Claim 2 and substantially as hereinbefore described with reference to Figure 2 of the drawings.