US2946670A - Manufacture of synthesis gas - Google Patents

Description

July 26, 1960 T. H. WHAL'EY MANUFACTURE OF SYNTHESIS GAS l Filed March 11, 1957 all N llll 2,946,670k .Patented July 26, 1960- MANUFACTURE F SYNTHESIS GAS Filed Mar. 11, 1957,7'Se'r. o; 645,044 Claims. (Cl. iS-206) This invention relatesfto a method for the 'gasification of solid carbonaceous fuels.V In one of its more speciic aspects it relates to the manufacture of synthesis gas from solid carbonaceous fuels. K Y

The invention comprises a process for effecting gasi- Itication of solid carbonaceous fuels by reactiony with oxygen under turbulent ow conditions in an elongated reaction zone of restricted cross-sectional area. According to the process of this invention, a dispersion of solid carbonaceous fuel in a gasiform carrier is mixed with uncombined oxygen and passed as a conned stream at a velocity in excess of `about 50 feet per second, preferablyvin excess of 100 feet per second,`through an elongated reactor of restricted,cross-sectional area to effect reactionl between said solid carbonaceous fuel and said oxygen and produce and hydrogen. ,l

The process of the present invention is especially use-v4 ful in connection with the generationof carbon-monoxide and hydrogen from solid carbonaceous fuels'` by partial oxidation. Coke, coal ofvarious grades,vfor example,r lignite, bituminous, and anthracite coals, oilr4 sand,tarV sand,and oil shale are suitable as fuels for the'process. The mixture of carbon monoxide andV hydrogen produced by this process may `beusedlasa source offeedl o gasy for the synthesis of alcohol. orf hYdI0carbons,-as a source of fuel gas,V or for the manufacture ofrhydrogen useful for ammonia synthesis. v

' lz lThefgasiiication of solid fuels by reaction with oxygen and steam at temperatures above about 2000 F. is well known. Y Processes are wellY known for the gasication of! a solid fuel maintained in a bed within thereactiongzone wherein the fuel bed may be in the Yform of a' stationary bed, a moving bed, or ya bed of uidi'zed solids. More recently, means have been developed for the partial oxidation of solid carbonaceous fuels by reaction of said fuels with an oxygen containing gas in a closed unobstructed reaction zone at a temperature within the range of about 2000 to Iabout 3500 F. such as is described in the copending application of Du Bois Eastman 'and Leon Gaucher Serial No. 490,214,`i1ed February 24, 1955, now Patent No. 2,864,677. I have now found that coal may be gasifed in a reaction zonehaving an exceptionally high ratio of length to diameter under conditions of highly turbulent ow at temperatures considerably below those heretofore employed. v

For the sake of simplicity, in the'following'v detailed description of theinvention, the process will be described as applied to treatment of coal. The application of thev present invention to solid carbonaceous fuels other than coal will be evident to one skilled in the art from the detailed description of this invention and the example of its application to coal. A

In accordance with this invention, solid carbonaceous material is admixed with acarrier uid andL passedv through a heating zone. Relatively coarse particles of solidA material may be used. The suspension is passedas a confined'stream in highly turbulent low through a heata gas comprising carbon monoxide f about onepart water per partgofcoal by ,Weightfis` ing zone maintained at an elevated temperature. Gases,-l vapors, or liquids may be used `as the suspending medium; vaporizable liquids, particularly Waterand hydrocarbons and mixturesthereof, are preferred. Suitable gases-infcludehydrocarbon gases-for example, methane, natural gas, refinery gases, synthesis tail gas, coal gas,'hydrogen, carbon monoxide, carbon dioxide, nitrogen, steam, and mixtures composed of or `comprising the above-mentioned gases. After preheating the dispersion of'fuel particles in gasifiorm carrier uid with little, or no reaction taking place, uncombined oxygen, for examplefair or oxygen in concentrated form, is mixed with the dispersion and thergasiiication reactionicarried out as described in more` detail` hereinafter.

In a preferred embodiment, the solidfuel in particle form is admixed with a liquid which may be converted to vapor form Von heating. .Sufficient liquid is employed to form a `slurry or suspension of the solid.'l The suspension isV passed through a tubular heating zone, for example, a heating coil, whereinl it is heated and substantially all of the liquid converted to vapor. A; dispersion,y of powdered solid in vapor is formed in the heating step, and at the same time, some disintegration of the` solid takes place. The extent'of disintegration depends upon the characteristics of the solid, the length' of the heatingl coil, and the velocity of the dispersion in the coil. Some volatile constituents may be distilled from' the coal in, the heating step. A gasiform dispersion of powdered, solid in vapors is produced as the result of the heating step.L The pulverization of solid materials by this'method is covered by U.S. Patent 2,735,787 to DuBois Eastman'` Iand Leon Gaucher. In the preparation ofthe dispersion,

more readily handled. Since disintegration of thec'oal;

maybe Vaccomplished in the kpreheate'r as taughtiin thef patent to Eastmanand Gaucher, this,4 may be us-edto:V

eliminate costly conventionalmechanical pulverizati'on.

Thesolid fuel may VVbelcrushed mechanically to about;` 'l

one-*fourth inch in average diameter withfa relatively small expenditure of power.` Furtherreduction in size becomesv progressively more expensive, pulverization requiring large expenditures of power. v

Y Numerous vaporizableliquids are suitable for V the prepav aration of the suspension;4 Waterv and oils are preferredA Water, petroleum and coal oils,`petroleum and-coalldis-r tillates, and related organic compounds are preferredoils for uselin the process. Specific examples of vaporiiable v' liquids suitable'for use in the present process include water; gasoline, kerosene, naphtha, and gas oil fractions ofpetroleum distillates; a light oil, middle oil or tar fraction of a coal'ldistillate; aromatics, for example, lbenzene, toluene; parans, for example, hexane, heptane, and so forth; naphthenes, for example, cyclohexane and the like; hydroaromatics, for example, tetralin, decalin; and vmixtures of these various liquids.

Water and oilmixtures, suitably in the form of emulsions, maybe used in preparing the suspension. `Vari# ousoils or tars `may Vbe `used in conjunctiony with water: in making up the suspension. An oil or tarfraction der-H rived from the `coal is especially useful in nialingupfthe,y suspension. v l.

vThe quantity, of liquid duiixd with fheeali the slurry may varyconsiderably depending upon proc sA requirements-and thefeed material. A ,minimum f quired to forma Y The liquid content,'off a .co

water slurry, iforfexample, maybe controlledby ii1St`m1x-,. l, *A ving the coal with a quantity of water in :excess of there-Q, quiredV quantity and adjusting the Water content by,A removal of `excess water in -a conventional thickener. The.,

3 with a diaphragm type pump or similar equipment commonly used'for handling similar suspensions of solids.

Substantial amounts of steam may be used in the prodlfctian f hydrvsen and, Gerben @mideby werden. with oxygenn 'atftempe'raturles within the of' this process Some, lignite'.`S already cqtaiawetsr. in Sumner! quantity to meet th theoreticalsteana requirements of the p rocess.

The suspension is fedinto the-,heated tube at a rate sufiicle'nt. to maintain dispersion ofI the solid particles in the uid.- The linear velocity of' slurry att-he inlet to the heating coilI shouldA be withinthe range of from about onehalfs to about ten feet per second; suitablyy above aboutione foot persecond,` The velocity of gaseous dispersion of powdered; coal andvapor, for example, at theoutleto fJthe` coil is within the range of from about 50 toabout 500l feet per second, suitably above `about 100 feetper second.VK e i The temperature at ythe outlet ofthe heating coil may range fromabout 250L to L1400 F.V The temperature should-,be at leastsufiicientto insure substantially complete vaporizationof liquid-present in the dispersion -at the-pressure existing in the heating zone, Preferably a temperature within the-range of 60G-to l2tl0,"t F; is attainedI at the outletofJ the coil; a temperature in the neighborhood oflOOOF. is generally suitable.

The temperature` and pressure relationships affecting vaporiz'ation are well-known. The heatingA zone is ata pressure somewhat-higher than the pressure of the associatedreaction zonet- In the generation ofl fuel or synthesis gas, itis desirable to operatethe gasification step atan elevatedpressure,A rforlexample, 100 to 600 poundspverl square inch-gauge; The heatingstepisoperatedat-a prssureL suiiicienttoV effect flow through the tubular reaction zone;

Oxygen-ofj relatively high purity, atleast 80 molpercentiand `preferably at-least 95 mol percent is used; thereby Alargely eliminati-ng nitrogen from the reactant feed to thegas-generator. v

Oxygends-reacted with the powdered-fuel in-a tubular reaction zone. Turbulent ow. conditions.aremaint'ained in--theitubular reaction zone/by imparting-awelocityiin excess ofA about- 50`-feet per-second; preferably in excess` of=100xfeetpeiyisecond tothe reactants.- The reactionpressureimay rangefromlabout` atmospherietoabout 600 pounds per squareineh' gaugeonhighen Thereaction temperature is maintained in-thelrange of abcmt--l500to about` 2060i- The-temperature-of` thereaction zone may` lbe-corxtrollerl-by cooling theexternal surface ofthereaction zone `or` byintroducingone of the,` reactants, pref-r erabIyoXygen, at aplurality Iofpointsin the reactionl zone: or both means-ofcooling-may be employeds Ad-l vantageously, the exothermic heat of` reaction may be employed for the generationvofsteamby disposing the tubular reaction zone within a steamV generator.V `Alternatively, the heatof-reaction may be employedfor preheating gas or steam,y for example, for superheatingsteam.` A tubular reactor within a steam generator or superheater has several advantagesY in; additionwto the generation of ,usefulsteam.v Advantageously, thegsteam generation pressurecan be selectedandontrolled at alevel such that the pressure ofthe steam generatonbalancesA the pressure Within the tubular reaction zone and thereby substantially reduces thestress appliedjto the tubular ref actor. The use of balanced pressures is particularly signiiicantin view of the high temperatures employedication wellistawiddr; The

' adyaiitageofthe process o fthis invention is that' reactor surfaces is effectively avoided and the solid ash is readily separated from the gaseous products.

A further advantage of the process of this invention is that the reactor inherently provides a large contact surface for the reactants which facilitates the control of reaction temperature.

Another advantage of'lthef use of a tubular reaction zone isthat it` may readily be disposed. within` a shell maintained' at high pressure in order to balance the interuel; and.; external pressure.. Y

Another advantage of theJprocess of thisfinvention is that exothermic reaction eiectsrinternal heating and the reaction zonemay hayeaconsidrably higher temperature than the temperature of the tube wall which confines the reaction zone. v t

The accompanying drawing diagrammatically illustrates one `form of the process of this invention. Although thedrawingillustrates one arrangement ofapparatus in whichF the'process o f'` this invention may be practiced, itjisnotrintendedrto limit the invention to the particular apparatus or material described;

Coal feed' 10,from an external source not shown;` is introduced into mixer 11 wherein it is mixed with a vaporizable liquid such as water introduced'through line 1 2' to form a slurry of coal andfwater. The resulting slurryis passed to thickener -13- wherein rthe concentra-` tions of c oal andwater in the slurry are'adjusted. Exc ess water is returnedto `the mixer through line 14: The resulting kslurry is.withdrawn fromthe thickener through line 151 andis forcedby pump 16 through-line17 to heat exchanger 18 wherein the slurry is preheated-by heat exchange with euent products. Preheatedslurry isrthen passed through line Ztl'to heating coil 21- disposed in heater 22";

In the heating coil the slurry is heated toa temperature sufficient-to vaporize substantially allof'the water.

The resulting'mixture oflcoaldispersed iny steam is disi charged from coil 21' through line 22 to separator 23:

deposition 4 of la sl'aglofashL onthe- 75 Separator Zmay be operated `at substantially the same pressure as that existingatgthe outletof the heatingvycoil or ata-somewhat-lower pressure: A- pressure` drop-at` the outlet-ofthe hea"ngcoil is helpful in disintegrating the coal. A portion ofrlthe steam is separated fromlthe coal1 steamwdispersionin-separator 231andis withdrawn through-line 24forexternal use.- A dispersionofther coal in the remaining steamiswithdrawnffromseparm ton-23; throughline 25 andl passed totubular reaction c oil26 Which-"is disposed in-steam-generator-ZT Oxyy gen from ane externalsourcenot shown-n linei-stliiiisi introduced to the inlet ofithelreaction coil througlrline 30a. Additional'oxygentomaintain and control reactiontemperature'to effect-substantially complete conversionof the coal tol synthesis gas is introduced as necessary throughlines 30bfand Stlcatintermediate points within` the reaction coil. Water`is-introduced 'to thestream generator throughline 31^and is convertedto steamwhich is discharged through line 32for external Vuse-not shown. Efiuent product `from reaction coil 26A is. discharged` through; line 33'and passes to ash separator MrWhGhmayr suitably be of the cyclone type. Ash is separated fromthe product gasin the separator and discharged from thesystemthrough line w35:V The resulting productgas` passes through line 36"to heatexchanger 18 where-itsupplies" ar'part of Ithe heat. requiredfot heating the slurry, feed. Cool lproduct gas from he at vexchanger 18 isdi`schar'ge"dthroughlinep37 `for further purification or* use.`

Example densate. The coal on a dry basis has the following ultimate analysis:

Weight percent This slurry of coal vand Water is passed through a heat exchanger and externally fired tubular heater, at a heater inlet pressure of 1200 p.s.i.g., Where it is heated to an exit temperature of 750 F. The resulting dispersion of coal in steam is passed through a cyclone separator where 4,500 pounds per hour of steam are separated and the remaining 3,300 pounds per hour of steam Acontaining the original 7,680 pounds of coal are charged to a reaction coil. Oxygen of 95 percent purity at a temperature of 300 F. is ladded at a rate of 78,000 `standard cubic feet per hour to the coal-in-steam dispersion.

This mixture of reactants is passed through the reaction coil at an average linear Velocity of 450 feet per second. Reaction takes place between the oxygen, steam and coal to produce gaseous products comprising principally carbon monoxide and hydrogen. The exothermic heat of reaction is Iabsorbed -by the generation of steam in a steam generator which surrounds the reaction coil and maintains the temperature of the reactants in the coil at about 1625 F. The effluent from the reactor coil is directed to a cyclone where Iash and unconverted coal is separated in the amount of 966 pounds per hour from the gaseous products. After suitable heat exchange and cooling for the condensation of unreacted steam, a dry synthesis gas is produced in the amount of 280,000 standard cubic feet per hour having the following analysis:

Constituent: Mol percent Carbon monoxide 56.0 Hydrogen 33.3 Carbon dioxide 7.1 Methane 0.5 Nitrogen vand argon 2.3 Hydrogen and carbonyl sulfides .0.8

Total 100.00

Obviously many modifications and variations of the invention as hereinbefore set forth may -be made without departing from the spirit and scope thereof and only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A process for the gasication of a solid carbonaceous fuel which comprises forming ya slurry of particles of said carbonaceous fuel in water, passing said slurry as a coniined stream through an externally heated elongated heating zone to vaporize substantially all of the water in said slurry' and to vform a dispersion of particles of said carbonaceous fuel in steam, withdrawing said dispersion from the heating zone `at a velocity of at least 50 feet per second, introducing the particles of solid carbonaceous fuel dispersed in steam into an elongated reaction zone, introducing gas comprising uncombined oxygen into the reaction zone with the dispersion, imparting a velocity in excess of about 50 Ifeet per second and at least as great as the velocity at which the dispersion is removed from the heating zone to the resulting stream of particles dispersed in steam and said gas in the elongated reaction zone to efect highly turbulent flow in the reaction zone, passing the stream of solid particles dispersed in steam and said gas through said elongated reaction zone at a pressure within the range of about atmospheric to about 600 p.s.i.g. and at an autogenous temperature within the range of from about 1500 F. to about 2000 F. thereby effecting a reaction between said uncombined oxygen and substantially all of said solid particles of said dispersion to yield a product gas comprising hydrogen and carbon monoxide, said Velocity in excess of about 50 feet per second being maintained in the reaction zone until said reaction is substantially complete and `discthanging product gas comprising carbon monoxide and hydrogen from said reaction zone.

2. The process of claim l in which said product gas is passed in indirect heat exchange with said slurry to preheat the latter before it is introduced into the heating zone.

3. The process of claim l in which the slurry is formed at substantially atmospheric pressure and is passed to the heating zone at superatmospheric pressure.

4. A process for the gasification of a solid carbonaceous fuel which comprises forming a `slurry of particles of said carbonaceous fuel in Water, passing said slurry as a confined stream through an externally heated elongated heating zone to vaporize substantially all of the water in said slurry and to form a dispersion of particles of isaid carbonaceous fuel in steam, withdrawing said dispersion from the heating zone at a velocity of at least 50 feet per second, introducing the particles of solid carbonaceous fuel dispersed in steam into an elongated reaction zone, introducing gas comprising uncombined oxygen Ainto the reaction zone with the dispersion, imparting a velocity in excess of about feet per second and atleast as great as the velocity at which the dispersion is lremoved from the heating zone to the resulting stream of particles dispersed in steam and said gas in the reaction zone to effect highly turbulent flow in the reaction zone, passing the stream of solid particles dispersed in steam and said gas through said elongated reaction zone at a pressure within the range of about atmospheric to about 600 p.s.i.g. and at an autogenous temperature within the range of from about 1500 F. to about 2000 F. thereby effecting reaction between said uncombined oxygen and substantially all of said solid particles of said dispersion to yield a product gas comprising hydrogen and carbon monoxide, said vvelocity in excess of about 100 feet per second being maintained in the reaction zone until said reaction is substantially complete and discharging product gas comprising carbon monoxide and hydrogen from said reaction zone.

5. The process of claim 4 in which the internal and external pressure of the reaction zone are substantially equal.

References Cited in the file of this patent UNITED STATES PATENTS 1,286,135 Somermeier Nov. 26, 1918 1,901,170 Karrick Mar. 14, 1933'- 2,047,499y Towne July 14, 1936 2,552,866 Ramseyer May 15, 1951 2,621,117 Garrison Dec. 9, 1952 FOREIGN PATENTS 152,285 Australia July 13, 1953 459,044 Italy Aug. 23, 1950

Claims (1)

1. A PROCESS FOR THE GASIFICATION OF A SOLID CARBONACEOUS FUEL WHICH COMPRISES FORMING A SLURRY OF PARTICLES OF SAID CARBONACEOUS FUEL IN WATER, PASSING SAID SLURRY AS A CONFINED STREAM THROUGH AN EXTERNALLY HEATED ELONGATED HEATING ZONE OF VAPORIZE SUBSTANTIALLY OF ALL OF THE WATER IN SAID SLURRY AND TO FORM A DISPERSION OF PARTICLES OF SAID CARBONACEOUS FUEL IN STEAM, WITHDRAWING SAID DISPERSION FROM THE HEATING ZONE AT A VELOCITY OF AT LEAST 50 FEET PER SECOND, INTRODUCING THE PARTICLES OF SOLID CARBONACEOUS FUEL DISPERSED IN STEAM INTO AN ELONGATED REACTION ZONE, INTRODUCING GAS COMPRISING UNCOMBINED OXYGEN INTO THE REACTION ZONE WITH THE DISPERSION, IMPARTING A VELOCITY IN EXCESS OF ABOUT 50 FEET PER SECOND AND AT LEAST AS GREAT AS THE VELOCITY AT WHICH THE DISPERSION IS REMOVED FROM THE HEATING ZONE OF THE RESULTING STREAM OF PARTICLES DISPERSED IN STEAM AND SAID GAS IN THE ELONGATED REACTION ZONE OF EFFECT HIGHLY TURBULENT FLOW IN THE REACTION ZONE, PASSING THE STREAM OF SAID PARTICLES DISPERSED IN STREAM AND SAID GAS THROUGH SAID ELONGATED REACTION ZONE AT A PRESSURE WITHIN THE RANGE OF ABOUT ATMOSPHERIC TO ABOUT 600 P.S.I.G. AND AT AN AUTOGENOUS TEMPERATURE WITHIN THE RANGE OF FROM ABOUT 1500*F. TO ABOUT 2000*F. THEREBY EFFECTING A REACTION BETWEEN SAID UNCOMBINED OXYGEN AND SUBSTANTIALLY ALL OF SAID SOLID PARTICLES OF SAID DISPERSION TO YIELD A PRODUCT GAS COMPRISING HYDROGEN AND CARBON MONOXIDE, SAID VELOCITY IN EXCESS OF ABOUT 50 FEET PER SECOND BEING MAINTAINED IN THE REACTION ZONE SAID REACTION IS SUBSTANTIALLY COMPLETE AND DISCHARGING PRODUCT GAS COMPRISING CARBON MONOXIDE AND HYDROGEN FROM SAID REACTION ZONE.

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