US 3904387 A
A process for gasifying char or coke with heated sulfur dioxide to produce a combustible fuel gas.
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Description (OCR text may contain errors)
United States Patent [1 1 Kertamus et al.
[4 1 Sept. 9, 1975 FUEL GAS MANUFACTURE  Inventors: Norbert ,I. Kertamus, Alliance;
Warnie L. Sage, Louisville; Mark A. Paisley, Alliance, all of Ohio The Babcock & Wilcox Company, New York, N.Y.
Filed: Aug. 26, 1974 Appl. No.: 500,817
US. Cl. 48/210; 48/197 R Int. Cl. C10J 3/06; CIOJ 3/54 Field of Search 48/197,210, 209, 215,
 References Cited UNITED STATES PATENTS 3,745,109 7/1973 Heredy et al. 48/210 X 3,840,354 10/1974 Donath 3,870,480 3/l975 Moss 48/l97 X Primary ExaminerR. E. Serwin Attorney, Agent, or Firm-Joseph M. Maguire; Robert J. Edwards v [5 7 ABSTRACT A process for gasifying char or coke with heated sulfur dioxide to produce a combustible fuel gas.
10 Claims, 2 Drawing Figures GASIFIER GAS-SOLI 0s suLFJ R SEPARATOR CONDENSER :52 CONCENTRATOR i 02 k, sou Rci-: 54
PATENTED 9%975 3,904,387
/ V GAS-SOLIDS SULFUR SEPARATOR CONDENSER i 52 502 CONCENTRATOR 1 F i W I -54 LJSQUBCEJ H62 22 2s 30 1 1 g 18 Q 2 4 g GAS-SOLIDS 2 SULFUR SEPARATOR CONDENSER 16 /32 j 1 28A P 22 64 Q 34 CATALYTIC s0 OXIDIZER CONCENTRATOR FUEL GAS MANUFACTURE BACKGROUND OF THE INVENTION The present invention relates to gasification and more particularly to a continuous process for yielding a combustible gas from the gasification of char or coke.
There is a present day growing concern with the rapid depletion of natural gas and oil resources resulting from the rise in the industrial civilization level throughout the world. With this concern comes an acute awareness that immediate steps must-be taken to conserve our gas and oil resources and to develop processes whereby greater use can be made of our ample coal reserves.
The use of coal as a fuel in electric generating power plants has been on a decline in recent years due to enviwith heated gaseous sulfur dioxide to produce a gaseous mixture of carbon monoxide and elemental sulfur. Entrained solids are removed from the gaseous mixture and the latter is cooled through indirect heat exchange so as to condense the sulfurthereby leaving a gas comprised primarily of carbon monoxide and having the prerequisite heat value to qualify as a fuel.
The condensed sulfur is burned in the presence of heated air to produce a gaseous mixture of sulfur dioxide and nitrogen which is then passed through a conventional sulfur dioxide recovery system to effect separation of the nitrogen and sulfur dioxide, the latter is then heated preparatory to use as the gasifying agent. Oxygen, from a separate source, may be added during the sulfur dioxide heating stage in the event that the gasification temperature drops below the level required ronmental constraints which rendered the conversion of coal to electricity uneconomieal. Since coal is by far the most abundant of all fossil fuel reserves, the development of a process for producing clean fuel gas from coal or its by-products would reduce our dependence on natural gas and oil while providing an economical fuel capable of meeting the new environmental standards.
The basic process for converting solid coal to fuel gas in the form of carbon monoxide is well known. In fact, the town gas," used before the availability of natural gas, was produced by burning coal under a reducing atmosphere.
Present day coal gasification processes involve the combustion of char or coke with oxygen to yield a combustible gas through the following reaction:
C /2 CO Another process for the use of air in lieu of oxygen and its reaction is expressed below:
c+ /2o +1.88 1 1 co+ 1.88 N
Depending on the type of process, the upper temperature level during gasification is of prime concern due to reaction rates or kinetics.
In air-blown entrainment gasification, the short residence time in the high-temperature zone determines gas quality and the fraction of coal gasified. Any variable that reduces temperature, such as a heat loss or presence of steam, detracts from gas quality. The disadvantage of this process stems from the fact that air tends to dilute the coal gas produced to an unsatisfactory low heat content and introduces nitrogen which cannot be economically removed from the produced coal gas.
Where the process uses oxygen instead of air, there are generated such extreme temperatures that some steam addition is necessary to moderate the gasification temperature. With steam addition. a second consuming reaction occurs to reduce heat liberation and produce hydrogen and carbon monoxide. The disadvantage of oxygen-blown gasification is the high cost of the associated oxygen plant.
SUMMARY OF THE INVENTION The present invention relates to processes for obtaining carbon monoxide fuel gas from the reaction of gaseous sulfur dioxide with char or coke.
Accordingly, there is provided a main embodiment whereby hot char or coke is brought into direct contact for sustained reaction. 5 An alternate embodiment of the invention dispenses with the need for a separate source of oxygen by pro-' trioxide, the latter is then heated to a temperature level causing the dissociation of sulfur trioxide into oxygen enriched sulfur dioxide to be used as the gasifying agent.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic representation of a system embodying the invention as related to a process for yielding a combustible gas from the gasification of char or coke..
FIG. 2 is a schematic representation of an alternate system embodying the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION FIGS. 1 and 2 are schematic illustrations of systems which are related to processes whereby sulfur dioxide is used to gasify carbonaceous matter to yield a combustible'fuel gas.
In accordance with the present invention, hot carbonaceous matter 12 is supplied to a gasifier 14 to be contacted therein by a heated continuous stream 16 of concentrated sulfur dioxide. The carbonaceous matter 12 must contain less than 1%, by weight, of hydrogen C and is either char derived from a conventional gasification process or coke such as that used for various met allurgical processes.
The sulfur dioxide reacts with the char or coke to produce a gaseous mixture 18 of carbon monoxide and elemental sulfur.
The reaction in the system depicted in FIG. 1 is as follows:
2C (Char or Coke) S0 2CO /2 8 The reaction in the system depicted in FIG. 2 includes enrichment with up to 33% oxygen and is as follows:
The ehar'or coke contained within the gasifi er '14 may be either in a fixed or fluidized state the latter condition being maintained by theflowing stream of heated sulfur dioxide. 7 1 I I The gaseous mixture 18 is conveyed from the gasifier 14 to a gas-solids separator for the removal of ungasifled particulates 22. Th e gas-solids separator, 20 is one of many presently known in the art, for example. a mechani cal or bed-filjteritype separator. g,
The Substantially solids-free gaseous mixture 24 of carbon monoxide and elemental sulfurexiting from the separator 2i) is conveyed to a sulfur condenser which is a known indirect type heat exchanger. for example, a shell and tube heat exchanger. preferably one having the gaseous mixture 24 flowing through th'ef tubes and the enteringcoolant 28 passing ov er th'e tubes. and exiting as shownby 28A. The heat ex changer paramcf c'rs are such that the'gaseous mixture" 24; Within the condenser 26, maintained afacontrolled temperature in the ran ge' of 280F to 3 l'5F to dissociate the carbon monoxide and elemental sulfur as follows: i l
Thejco n ibustible fuel gas 30 produced in a 'c'cordanc'e with the present invention, has a carbon monoxide content in the range of 95to l()%and a heatvalu ein ex cess' 'c'wf-3 00'Btu/scf. The'fuel gas 30 leaving thc coh: denser 26 is a'high quality clean gas which m; beuscd as fuelin a second-stage combustioii' device oras a feed gas for petrochemical applications.
The elemental sulfur contained within the gaseous mixture 24 is liquified in the condenscrZQand is thereafter conveyed as liquid sulfur 32 to a sulfur burner 34 and associated combustion chamber 36 of a type known inthe'artffor example. the burner and combustion chamber disclosed -in'U.S. Pat. No. -3,723.068 is-" sued on Mar. 27. 1973, in the name of R. A. Mcllroy' et al. The liquidsulfur 32*is entrained by a regulated quantity of heated air 38 and burned to producea'gaseous mixture of sulfur dioxide a nd nitrogen as follolvs: V 1.. A,
chambers 44-and- -l6. respectively. and includes anelevator 48 which receives cooled refractory particles from the lo we r chamber-46 and returns themto theparticles flow into the lower chamber 46 where they, in
turn. give up heat to the gases passing therethrough.
Referring specifically to FIG. 1, thecooled gaseous mixture 40A, exiting from the fluid heater 42, is conveyed to a sulfur dioxide concentrator 50 wherein the nitrogen 52 is removed thereby leaving a concentrated gaseous stream 16A containing in excess of 99% of sulfur dioxide.- The concentrator 50 is of a typeknown in the art. for example. the recovery. system disclosed in US. Pat. No. 3.758.668 issued on Sept. 1 l, l973'.- in the name of Lapple et al, and which employs a slurry, containing magnesium oxide, to absorb the sulfur dioxidefrom the gaseous mixture 40A. and to form magnesium sulfide crystals which are thereafter separated from the slurry and heatcdto reduce the water of crystallization, and arepelletized with carbon and a binder to form pellets which are thermally treated for dissociation into reactive -magnesium oxide particles and gaseous sulfur dioxide, the former being returned to the absorption zone of the recovery system.
The gaseous stream 16A, of sulfur dioxide,, exiting from the concentrator 50is routed to-.:the lower chamber 46of fluid heater'42. to be heatedby the refractory particles circulating therethrpugh The heated gaseous stream 16 of sulfur dioxide leaving the lower chamber 46 isconveyed to the gasifierlfifor the manufacture of combustible fuel gas. Aaseparate source 54 of nitro-; gen-freeoxygen is available to supply a regulated quan-. tity of oxygen 56.to the lower chamber 4 6 for oxygen enrichment of the gaseous strcamvlfi of sulfur dioxide; whenever-required, to maintainthe temperature necessary for sustained reaction withinv the gasifier 14.
1 -Referring specifically'to IG. 2, there isshown a systern which provides for-the :additionpf up to. 33% ,oxygen to the heated gaseous stream 16 of sulfur dioxide, used for gasification, without resort to a cryogenieoxygen plant. The system usesthe reversible sulfur dioxide to sulfurtrioxide .reaction in the manner set forth below:
of a catalyst. for example, vanadium pentoxide .or p.lati-- num. which .speeds;,up;the v reaction without affecting the .equilibrium.. Themcatalytie oxidation stage takes place at .areaction temperature of less than 1800F. usuallyjin the range of 70091 10 850F and is expressed as follows:-' t
. The gaseous mixture 6 4, .exitingfrom..the catalytic oxidizer 62, may contain up to 85% diluent nitrogen with sulfur trioxide. Thc gaseousmixture 654is fed-to a sulfur trioxide concentrator 66 for theseparation of ni trog en 8 and concentrated sulfur trioxide 70.'The, separation stage is" effected by, using highly concentrated sulfurieacid to scrub outthe sulfur trioxide thereby obtaining sulfur trij'oxidc, enriched sulfuric acid, the latter is then conveyed fto an evaporator.which gasifics the sulfur trioxide. v
The gaseous stream 70 of sulfur trioxide. exiting from the concentrator (viris routed to thelowc'r chamber 46 of fluid heater 42 to be heated by the refractory particles circulating there'through. The heat, supplied in chamber 46 is at a jt'emperaturelin..excessof 18003 thereby decomposing the gaseous sulfur trioxide to 0xygen enriched sulfur dioxide.as expressed belowp so-i so. v. 0.
The heated gaseous stream 16 of sulfur dioxide cnrichcd with up to 33% oxygen is conveyed to the gasifier 14 for the manufacture of combustible fuel gas.
While in accordance with provisions of the statutes there is illustrated and described herein a specific embodiment of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.
The embodiments of the invention in which an exclusive property of privilege is claimed are defined as follows:
l. A process for converting hot carbonaceous matter to gaseous fuel comprised primarily of carbon monoxide. and including the steps of:
gasifying the carbonaceous matter through direct contact with heated gaseous sulfur oxides to produee a gaseous mixture of carbon monoxide and sulfur, removing entrained solids from said gaseous mixture, obtaining said gaseous fuel from the substantially solids-free gaseous mixture by condensing the sulfur through indirect heat exchange with a coolant,
thermally reacting the condensed sulfur in the presence of air to produce a gaseous mixture of sulfur oxides and nitrogen,
separating th sulfur oxides and the nitrogen of said last named gaseous mixture, and
heating the sulfur oxides prior to gasifying said carbonaceous matter.
2. The process according to claim 1 wherein the step of gasifying the carbonaceous matter comprises gasifying char.
3. The process according to claim 1 wherein the step of gasifying the carbonaceous matter comprises gasifying coke.
4. The process according to claim 1 including the step of fluidizing said carbonaceous matter.
5. The process according to claim 4 wherein the step of fluidizing said carbonaceous matter comprises fluidizing with heated gaseous sulfur oxides.
6. The process according to claim 1 wherein the step of thermally reacting the condensed sulfur in the presence of air includes burning the sulfur to produce a gaseous mixture of sulfur dioxide and nitrogen.
7. The process according to claim 6 wherein said gaseous mixture of sulfur dioxide is oxidized in the presence of air and a catalyst to produce a gaseous mixture of sulfur trioxide and nitrogen.
8. The process according to claim 7 wherein the step of heating the gaseous sulfur oxides includes decomposing sulfur trioxide to sulfur dioxide and oxygen.
9. The process according to claim 1 wherein the step of gasifying the carbonaceous matter comprises gasifying carbonaceous matter having less than one percent by weight of hydrogen.
10. The process according to claim 1 wherein the step of heating the sulfur oxides comprises heating said sulfur oxides to a temperature in excess of 1800F.