US3769197A - Pollution free fuels - Google Patents

Abstract

THE PRODUCTION OF LIQUID AND GASEOUS FUELS FROM COAL INCLUDING THE USE OF A METAL OXIDE FOR DESULFURIZATION.

Description

Oct. 30, 1973 L.. E, LEAs Er AL POLLUTION FREE FUELS Filed qgl'y 9, 1971 Eqwhm United States Patent O l, 3,769,197 PoLLUTroNQFREE FUELS Lawrence E. Leas, Simi, Calif., and Robert L. Leas and Cecil J. Johnson, Columbia City, Ind., assignors to Leas i 'Brothers Developmentl Corporation, Columbia City,

1- Filed July 9, 1971, ser. No. 161,249 `nmol. c1og1/00 U.s. `cl. 20ss 9 claims .y ABSTRACT-oranti DISCLOSURE The', production of 4liquid and gaseous fuels from coal Vincluding thel use of a: metal oxide fordesulfurization.

This vinvention jiielates--to the production of fuels from ,coal'`and-more` particularly, to the production of desul- Yfurizjed yand pollutiorirfree fuels..

It isdesirble from an economical standpoint to use icoalfoiF producingv both liquidand gaseous fuels since 1co'alfis .relatively inexpensive compared to petroleum crude oiLard is 'quite .abundant in contrast to our rapidly .dwingling domesticl supply of the petroleum natural resource.`;One.of .the biggest drawbacks in using coal as a source for gasoline, or. the like, or for gaseous fuels, is its yhiglr'sulfur content. This problem is of even greater vtalcen from .the liquidsv as hydrogen sulfide.

Y Itl is. a further objective of this invention to coke and then .gasifyV the residualcoal liquids from the extraction and fractionation operation in a Lcombined coker and gasifienyvhereinthe coal liquids yare gasied with hot carbon dioxide tolforni a carbonmonoxide-rich gas, which is thenintroduced to a metal oxide bed, whereby any sulfur contaminants in the carbon monoxide reacts with the metal toform a metal sulfide, yandis thereby removed from the gases resulting ina substantially sulfur-free carbon monoxide-rich gaseous productln alternate cycles air is introduced .to the gasier to burn the materials therein to a higher temperature and air is also introduced to the desulfurizer metal oxide 4.bed to oxidize it back to its higher oxide formand liberate the sulfur therein as sulfur dioxide which.,is. sent'toasulfur recovery system.

, Itis another' objective vof, this invention to perform the coking and the gasifying operation in the same reactor thereby eliminating excessive handling of the residual liquids andv solids. l i

It is another objective of thisinvention to combust the carbon monoxide product of the gasification step in a combustor in the presence of heated air at a temperature not td exceed-2500` whereby' the production of nitrogen 'oxidesfinithe combustionY gases is minimized.

` These'andf other objects' ofthe invention will become more apparent to--those skilled-finV the art-by reference to the.- following detailed description when viewed'in light of the-.accompanying drawings. wherein:

The single tigureis :ay diagrammatic illustration of the process of this invention. 1

As Vshown Ain the drawing, .,coal from line 2 and make-up slag and recycle y,slag fromlines l4 and `6 respectively, are mixed .together-and .introduced into an extraction unit 8 YviaV line 10.A The extraction. unit isv shown diagrammatically audit is'to be understood that it is of Vconven- ICC tional construction and operation and may include a plurality of extractors. Hydro-treated solvent is introduced to the extraction unit via line 12 and valve 13. A portion or all of therhydro-treated solvent may ebe bypassed through valve 14 and line 16 to a heat exchanger 18 and absorber unit 20 and then sent to the extractor via line 22, as will be explained more'fully hereinafter. Ash is taken from the extractor via line 24 and slag is recycled, as mentioned earlier, via line 4. By recycling the slag, only a fraction thereof needs replacing during each cycle. Extracted coal liquids and solvent leaves the extraction unit 8 vita line 26 and enter fractionation unit 28 wherein the lighter distillates in gases are taken off via lines 30 and 32, respectively, and sent to hydro-treating unit 34. The heavy residues from the fractionation unit leave from the lower end thereof via line 36 vand are subjected to vacuum distillation in distillation unit 38, with the distillates being ta'ken therefrom Via line 40 and introduced to the hydro-treating unit 34 along with the lighter distillates and gases from the fractionation unit 28.

In the hydro-treating unit 34, hydrogen is introduced via line 42 from hydrogen generator 44. Gasoline exits from the hydro-treater via line 46 and high density diesel fuel is taken olf via line 48. The heavier fuel oil leaves the hydro-treating unit via line 50 with a portion thereof being recycled back as solvent to the extraction unit 3 via line 12 and the rest being taken olf for storage. Additionally, any sulfur in the coal liquids is reacted with the hydrogen in the hydro-treating unit to form hydrogen sulde which is taken off via line 52 and sent to a Claus reactor `54 for the production of elemental sulfur.

It is to be understood that the extraction, fractionation and hydro-treating units, and the vacuum distillation unit, are conventional items in the art. l

The heavy residues from the vacuum distillation unit 38 leaves distillation unit and are introduced to a combination coker-gaser 56 via line 58. The unit 56 is illustrated diagrammatically. However, it is to -be understood that it is to be of the type disclosed in applicants copending application Ser. No. 162,180, led July 13, 1971, entitled Reactor. The reactor unit disclosed therein comprises concentric cham-bers with the central chamber 60 containing materials to be gasied, and the outer concentric chamber 62 receiving a metal oxide preferably cobalt oxide. The inner and outer chambers are separated by an annular divider Wall 64 having passageways 66 in the bottom thereof permitting gases to llow from the outer chamber to the inner chamber. The combination cokergasier operates on alternate cycles of (a) air feed to preheat the bed and, (b) carbon dioxide feed to gasify the carbonaceous materials therein to a carbon monoxide-rich gas.

Carbon monoxide is introduced to chamber 62 via line 68 and reacts with the cobalt oxidetherein in an endothermic action to produce superheated carbon dioxide. The carbon dioxide enters thev centralv chamber 54v by means of the passageways 66 and gasies the coke therein to additional carbon monoxide-rich gases in the ratio of approximately 2:1 with regard to the initial carbon monoxide infeed. The gas leaves via line 70 entraining some vaportherein due to the incomplete removal of the liquidsfrom the feed residue. The gaseous stream with the vapors enters an absorber 20 wherein these vapors are removed by the incoming solvent stream from line 16. The carbon monoxide-.rich gas then leaves theabsorber l via line 74 and issent to a desulfurizing unit 76.

v The desulfurizing unit 76 comprisesa bed of metal oxide., .preferably cobalt oxide in its higheroxide form. The ratio of cobalt oxide to the amount of carbon monoxide introduced tothe desulfurizing unit 76 is such that only a'portionof thecarbon monoxide reacts to form carbon dioxide, yet substantially allofthe sulfur contaminants in the carbon monoxide-rich gas reacts with the cobalt to form cobalt sulfide thereby removing the sulfur from the gas. The amount of carbon monoxide that goes to carbon dioxide can also be controlled by regulating the velocity of the gases flowing therethrough.

The desulfurized carbon monoxide gases including some carbon dioxide leave the desulfurizer 76 via line 78 wherein a portion thereof is taken olf via lines 79 and 80 and recycled via compressor 52 and line 68 to the cokergasifier for the carbon monoxide production stage. Additional carbon monoxide can be provided prior to the desulfurization step via shunt line 84. Still another portion of the carbon monoxide is introduced from line 80 to hydrogen generator 88 wherein it is reacted with steam for the production of hydrogen which is then introduced to the hydro-treating unit via line 42 in the manner heretofore described. The remainder of the carbon monoxiderich gases are introduced to a combustor 90 and are combusted with heated air under compression introduced via line 92. The exhaust gases are passed through heat exchanger 94 giving up process heat, and are then expanded through power wheel 96. The exhaust gases therefrom are taken off via line 98 and may be used for drying or stripping operations.

The materials in the combined coker-gasilier are preheated in an alternate cycle by an introduction of excess air to the cobalt oxide chamber 62 by means of line 100. The metal therein, having been reduced to a metal or a lower oxide during the previous cycle by the introduction of carbon monoxide, is then oxidized back to its higher oxide form by the introduction of excess air with the remaining air being introduced to the chamber 64 via passageways 66 for burning the materials therein to a higher temperature. 'Ihe nitrogen-rich gases from the air-burn stage are taken off via line 102 and introduced to a second desulfurizing unit 104 also containing a metal oxide, preferably cobalt oxide in its higher oxide form. The sulfur in the nitrogen-rich gases reacts with the cobalt to form cobalt sulfide thereby removing the sulfur from the stream. The desulfurized nitrogen is then expanded through a power wheel 106 and combined with the exhaust from the combustor 90 in line 98 for use in drying and stripping operations.

The reduced cobalt oxide in the desulfurizing units 104 and 76 are oxidized to their higher oxide form during alternate cycles by the introduction of air from compressor 108 via lines 110 and 112. The sulfide reacts with the oxygen in the air to form sulfur dioxide which is taken off from the desulfurizing units with the nitrogen via line 114 and introduced into the Claus reactor S4 along with the hydrogen sulfide from the hydro-treating unit for the formation of elemental sulfur.

It is to be understood that in this process multiple units in parallel may be used to render the process continuous. For example, two combination coker-gasifers may be used with one being in the air-burn stage while the other is in the carbon monoxide production stage. The same is true for each of the cobalt desulfurizing units 76 and 104, with one being in the desulfurizing stage while the other one is in the regeneration stage. Further, a Rankine cycle uid system may be used for cooling the various liquid and gaseous streams with the heat taken from the system being used for additional power generation.

The combined Coker-gasifier is operated cyclically to produce primarily threev separate products, (a) a high purity carbon monoxide gas, (b) a nitrogen-rich gas, and (c) volatile hydrocarbons that are recycled with the fresh solvent to the extractor section. In this three-cycle operation: (a) the coal liquidsuor tar coking takes v-place by injecting the liquid tar on the hot packing within the gasifer at the end of the cobalt reduction stepto facilitate the then recycledl carbon monoxide tok strip the volatiles out through the transfer lin'e. to be recovered as a liquid in the solvent absorber. while the solid coke is retained Within the gasifier as a thin deposit on the packing for the heating and gasification cycles-to follow; v(b) the dcposited coke is then superheated by the hot compressed air that burns the residual carbon from the extractor operation and also burns a small portion of the coke within the gasifier, with the exhaust air from thercarbon burning containing primarily superheated nitrogen, carbon dioxide, and some oxygen; and, I'(c) carboni-monoxide gas is recycled to the then oxidized cobalt in the annular space thereby reducing the cobalt, generating superheated carbon dioxide which with its entrained oxygen ows directly through ports intro the bottom of the gasier, which in turn generates carbon monoxide. Therefore, the cornbined Coker-gasifier virtually eliminates the otherwise need fora separate coking unit with its associated solids handling problem.

The following are examples illustrative of the process of this invention:

EXAMPLE 1 Wt. percent basis: Percent Moisture 6.4 l Volatile matter v30.9 Fixed carbon 51.2 Ash 1 1.5

The coal and slag were'dried with 350 F. nitrogen to remove most of the moisture. Solvent was pumped into the reactor and the extractorpressure was maintained at 300 p.s.i.a. for the run. 'I 'hesolvent used was tetralin. After introduction of the solvent to fill the extractor, heat was applied and heated to 850 F. The solvent was circulated until the 850 F. wasfbtained in the extractor and then this solvent was accumulated and solvent entered the top of the extractor at 800 F. and `exited the bottom'fof the extractor. The feed rate wasmaintained at30 #/hr. and all the solvent was accumulated. A total of 50 pounds of solvent was used during the extraction run. 80.4 pounds of solvent plus extracted coalliquids wereobtained after the product output wascooledvto .F. 3;.1. pounds of gases were obtained from the vapor-liquid separator after cooling. The analysis of the gases on a volume Abasis was as follows:

APercent Carbon dioxide 30.2 Carbon monoxide 5.5 Hydrogen 19.8 Methane 40.1 Hydrogen sulfide 2.4 Ethylene 0.6 C3s and C4s 1.4

V4.2 pounds of material were burned to carbonv dioxide and water.,Afte1 cooling, the ash was separated Vfrom the slag. 6.2 pounds of ash remained after the"extraction andcke combustion.

'Ihe solvent and extracted coal liquids Were fractionated at 850 F. and at low pressure to remove any remaining gases and liquids from the residue or heavy fraction. 0.5 pounds of gases (90% methane by volume) was obtained and 0.6 pounds of Water was condensed from the gas stream. 70.2 pounds of solvent and extracted liquids were obtained as well as 8.7 pounds of heavy material after 4the fractionation was completed. This material (residue from the fractionation unit) was subjected to a vacuum .distillation at 5 p.s.i.a. and 800 F. and an additional 0.7 pounds of liquids were obtained which were mixed with the 70.2 pounds of liquids for a total of 70.9 pounds of liquids for hydrotreating. 7.6- pounds of residue were obtained from the vacuum fractionation unit for use in the coker-gasier.

The 70.9 pounds of liquids (solvent and extracted coal liquids) were hydro-treated at 950 F. and 2000 p.s.i.a. using a cobalt molybdate catalyst on an alumina carrier. Hydrogen consumption was 0.72fpounds. The amount of gases obtained duringI hydro-treatment was 1.8 pounds. The material wasy `f'ra'ctionatevdand the following yields `were obtained on a solvent free basis.

Enough gases are available to produce the necessary hydrogen. u

Assuming that the net process heat or heat recovery (net) 'can be used in a Rankine cycle power generator, that thecokelifs burned with air at 300 p.s.i.a. and expanded in a gas turbine, that the material sent to the gasier iswburned and gasied with carbon dioxide, the ldesulfurizers are operated at 1000 F., the gasier is operated at 2000 F., the carbon monoxide not required for recycle carbon dioxide is burned with air in a combustor .at 300 p.s.i.a. and expanded through a gas turbine, and the ,gases are used for hydrogenproduction-this calculation gives a calculated electrical generation product output of 20.5 k.w. hr. using the above example feed and products.

EXAMPLE 2 60 pounds of the same coal as in Example 1 were mixed with 40 pounds of Vslag andV placed inside the extractor as described in Example 1. The coal was crushed before mixing withlthe slag and the particles of coal used varied from V32" diameter to l diameter. The slag was approximately diameter. The coal had the same proximate analysis as the coal used in Example 1. Drying of the coal and slag was accomplished by nitrogen at 360 F. to, remove most of the moisture. Solvent was pumped into the, reactor` and 200 p.s.i.a..pressure was maintained on ,the extractor for theduration of the run. The temperature of the extractor and solvent was maintained at 800 F. The feed rate of the'sol'ventwas.v maintained at 25 #/hr. andthe liquids and gases were cooled to 90 F. and the lg'asesh'were'vented through a wet testgasmeter and analysisfw'vere taken o .ffthev gases. Theliquids were accumulated. Inail, -65 pfouudqsofsolventwas fed into the extrac- '6 tor. 3.2 pounds of gases were obtained during extraction with the following volumetric analysis:

98.2 pounds of solvent and extracted coal liquids were obtained from the extractor.

After the extraction was completed, 600 nitrogen was injected into the extractor to remove any liquids which may be present. The stream was cooled and 0.5 pounds of liquids were obtained and added to the other liquids for a total of 98.7 pounds of solvent and extracted liquids from the extractor. The coke deposits were burned with 660 F. air and by analysis of the combustion stream for carbon dioxide and Water vapor. 6.1 pounds of this material Was calculated to have been burned. After cooling, the ash was separated from the slag. 7.05 pounds of ash were removed.

The solvent and extracted coal liquids were fractionated at 800 F. and at low pressure to remove any remaining gases and also to remove the liquids from the heavy fraction. 0.4 pounds of gases (91% methane) was obtained as well as 0.7 pounds of water. 86.8 pounds of liquids and 10.6 pounds of heavy material were obtained. The 10.6 pounds of heavy material was vacuum fractionated at 750 F. and 5 p.s.i.a. and an additional 0.4 pounds of liquids were obtained which were added to the 86.6 pounds for a total of 87.2 pounds of liquids for hydrotreating. 9.9' pounds of heavy material suitable for the Coker-gasifier were obtained from the vacuum fractionator.

The 87.2 pounds of liquids were hydro-treated at 900 F. and 2000 p.s.i.a. pressure over a cobalt molybdate catalyst on an alumina carrier. Hydrogen consumption was 0.91 pounds. The amount of gases obtained (not including the hydrogen recycle) was 1.87 pounds. The liquid material was fractionated for solvent recovery and the following materials were obtained on a solvent free basis:

Pounds Gasoline 4.7 Fuel oil 20.1

Enough gases were available to produce the required hydrogen.

Yield obtained on MAF Basis Making the same assumptions as in Example 1 except the coke is burned at 200 p.s.i.a. and not 300 p.s.i.a. and the combustor is operated at 200 p.s.i.a. instead of 300 p.s.i.a., a calculated electrical generation output of 27.6 k.w. hr. was obtained.

EXAMPLE 3 pounds of Venezuela crude oil `with the following analysis were charged into the fractionator and fractionated at 800 F. and at low pressure.

Crude oil analysis: I

Gravity-16.5 API, Specific gravity-09561, Sulfur content-32%, wt.

Distillation analysis using Bureau of nMines routine Crude oil analysis, vol. percent:

4.8 pounds were taken E overhead into a flash chamber wherein 0.7 pounds of light gasoline were vented and 4.1 pounds of liquids remained. An additional 17.3 pounds of liquids were taken olf for a total liquid output of 21.4 pounds. 77.8 pounds of this material remained at this condition and this was fractionated in a vacuum fraction ator at 750 F. and 5 p.s.i.a. A total of 22.2 pounds of liquids were obtained and added to the other liquids for a total of 43.6 pounds of liquids for hydro-treating. 54.6 pounds of material from the vacuum distillation were suitable for feed to the coker-gasier unit.

The 43.6 pounds of liquids were hydro-treated at 900 F. and 2000 p.s.i.a. pressure over a cobalt molybdate catalyst on an alumina carrier. Hydrogen consumption was 1.32 pounds. The product was sent to a vapor-liquid separator whereinn 3.4 pounds of gases were recovered with the following analysis: (not including the hydrogen recycle).

Analysis, wt. percent: Percent Hydrogen sulfide 50.2 Nitrogen 9.4 Water vapor 0.1 Methane 27.2 Ethylene 0.3 Ethane 12.1 C3S & C4S 0.7

After separating the liquid fraction, the following were obtained:

The hydrogen could be made from the gases after desulfurization and the light gasoline, additional hydrogen, if required, could be obtained from part of the gasoline fraction.

Assumingthe gasier-coker and the `carbon monoxide operate at 300 p.s.i.a. and making the other assumptions as made in Example 1, with the exception of the extractor burning of the coke and this power wheel, a calculated electrical generation product output of 104 k.w. hr. was

obtained, using the material to 'the Coker-gasitied. Part of the coke willbe burned with air to heat up the bed and to furnish the endothermic heat of reaction andV this will be expanded through a gas power wheel.

In a general manner, while there has been discolsed an effective and eicient embodiment of the invention, it should be well understood that the invention is not limited v8 to such embodiment as there might be changes made in the arrangement, disposition, andform of the parts without departing from theprinciple ofthe present invention as comprehended within the scope ofthe accompanying claims.

1. A method of producing desulfurized fuels vcomprising the steps of:

feeding coal to an extractor wherein coal liquids are extracted therefrom' with a hydro-treating'solven" distilling oif the lighter hydrocarbon distillates from the coal liquids and leaving a coal liquid residue=l1av ing a sulfur content; 1 i passing the liquid residue through a .coker-gasifer wherein the liquid is cokedand `thecokeformed is then gasied to a carbon monoxide-rich gas; and contacting the carbonfmonoxide-rich gaseswith a metal oxide wherein any ,sulfur in said carbon monoxide reacts with the metal to vform a metal sulfide thereby removing the sulfur from ,they gases.

2. The method of claim 1 wherein said metal oxide is cobalt oxide. f 7' 3. The method of claim 1 wherein a portion of said desulfurized carbon monoxide is mixed with heated air in a combustor and combusted, and the product gasesfrom said combustion are expanded through a power generating wheel.

4. A method as in claim 1 and wherein the`carbon monoxide is burned at a temperature less than 2500" F. to avoid the production of nitrogen oxides.

S. The method of claim 1 wherein-a portion of said desulfurized carbon monoxide is treated-with steam to produce hydrogen, and reacting said' hyrdrogen with said distillates in a hydro-treating.stepwherein any;sulfur in said distillates is reacted withthe hydrogen to form hydro- ,gen sulfide.

6. The method of claim 1 whereinsaid coke is gasied with carbon dioxide. i

7. The method of claim 5 including forming asecond metal oxide bed, recycling a portion of said carbon monoxide through said second metal oxide bed instead of said first metal oxide bed wherein the carbon monoxidereduces said metal oxide and is oxidized to superheated carbon dioxide which is introduced to said Coker-gasilier -for gasifying said coked coal liquids. v

8. The method of claim .6 wherein` excess air is introvduced to said second metaloxide bedinan alternate cycle to oxidize said reduced metal oxide lback to its higher oxide form, and then passingsaid excess air including a high nitrogen content` to saidr gasiiier 'for coking'A said liquids, and burning saidcoked 'coal liquidsto a higher temperature, and desulfurizing'the 'nitrogenich product gases in a third metal oxide bed. e i l I i 9. The method of claim 7 wherein said first and third metal oxide desulfurizing beds are on alternate cycles purged with air to oxidize the'bed `'back to its higher oxide form and to react with the sulfide theerin to form sulfur dioxide which is taken olf to a puresulfur recovery system. f ReferencesV Cited v UNITED STATES PATENTS DELBER'T E. GANTzgfpiimry Examiner 1. w.V HELLWEGE, Asststanfnxmiaerf

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