US2798032A - Method of destructively distilling oil shale in a producer-type of retort - Google Patents

Description

METHOD F DESTRUCTHVELY DISTliLLING OIL SHALE IN A PRDUCER-TYPE 0F RETORT James W. Martin, Tnckahoe, N. Y., assigner to Carhonic Products, luc., New York, N. Y., a corporation of New York Application February 26, 1953, Serial No. 339,079

12 Claims. (Cl. 202-6) The present invention relates to an improved method of recovering oil, gases, and other by-products from oil shale and similar kerogen-containing materials, and, more particularly, to an improved method of destructively distilling such materials by using a combustion-supporting gas containing carbon dioxide and oxygen in a critical ratio.

It is well known that heretofore the conventional method of obtaining oil from oil shale involved the initial mining of the shale from the ground, the intermediate preparation thereof for thermal treatment in retorts, the subsequent destructive distillation of the thus-prepared shale in retorts `by heat and the recovery of oils and byproducts from the vapors and gases distilled from such retorts, and the final removal of the residual spent shale from the distillation Zone of such `retorts and its subse-V quent combustion under the retorts to supply some of the heat. Although attempts were made to overcome difficulties and disadvantages of prior processes, none, as far as I am aware, was entirely successful when carried into practice commercially on an industrial scale.

I have discovered an improved method of destructively distilling oil shale which overcomes the difficulties and disadvantages of prior processes and attempts and which provides the art with new results. V

It has likewise been found that in the presence of an excess of carbon dioxide (above 40%) in the gases entering the distillation zone the following desirable effects take place:

(a) The carbon dioxide forms loose temporary compounds with the hydrocarbons and tends to make these compounds more volatile and thus more quickly and completely removed from the shale, and

(b) The carbon dioxide under the foregoing conditions tends to preserve carbon to hydrogen linkagesin the newly formed hydrocarbons thereby preventing the further cracking of these unsaturated and aromatic hydrocarbons and simultaneously decreasing the formation of saturated hydrocarbons of the aliphatic and naphthenic types.

It is an object of the present invention to provide an improved process for the destructive distillation of oil shale in which gaseous products of combustion with high heat content and with high carbon dioxide content are effectively utilized. Y

It is a further object of the invention to provide an improved process for the destructive distillation of oil shale wherein means will be used to limit the formation of hydrogen and light gases of the methane series while at the same time increasing the production of the members of the olefenic and aromatic series.

It is likewise within the contemplation of the invention to provide an improved process for the destructive distillation of oil shale which will effect a fixation and recovery of ammonia and similar basic nitrogen compounds.

Among the further objects of the present invention is the provision of an improved process for the destructive distillation of oil shale which will provide combustion- ICC supporting gas containing carbon dioxide and oxygen in a critical ratio, which will prevent relatively high temperatures in the zone of destructive distillation of oil shale, which will maintain relatively low temperatures in the combustion zone, and which will bathe the zone of destructive distillation with hot carbon dioxide and thus mix carbon dioxide with resultant gaseous hydrocarbons.

Other objects and advantages will become apparent from the following description taken in conjunction with the4 accompanying drawing which illustrates diagrammatically and partly in section the operating portion of a producer-type of retort used on Colorado oil shale.

In my new improved process, oil shale or similar kerogen-containing raw materials, such as torbanites, lignites, cannel, and certain other coals, and carbonaceous ma terials are heated in a retort in an atmosphere supplied with combustion-supporting gas containing carbon dioxide and oxygen in a critical ratio whereby the evolved gas and vapor distillates produced are substantially free from aliphatic and naphthenic hydrocarbons and are rich in the commercially many times more valuable unsaturated and aromatic hydrocarbons and the compounds similar to aromatic hydrocarbons, but having sulfur, oxygen or nitrogen in their composition, such as derivatives of pyridine, quinoline, thiophen, cresols, etc. For the purpose of the present specification, the latter ring-type products will be considered as included within the expression aromatic compounds.

Broadly stated, the present invention contemplates a Vsolution to the vexatious problem confronting the art in effecting combustion of fixed carbon of oil shale by a gaseous mixture of oxygen and carbon dioxide in critical proportions or ratios. By utilizing special mixtures containing oxygen or air and carbon dioxide in critical proportions or ratios, a relatively low and regulated temperature can be obtained. The temperature in the combustion zone within the oil shale structure is preferably kept well below about l000 C. to limit the formation of carbon monoxide. Furthermore, the temperatures in the zones of destructive distillation are controlled to a temperature range above about 400 C. and below about 600 C., and preferably within a range of about 425 C. to about 550 C. Such critical regulation can be effected by controlling the ratio of carbon dioxide to oxygen (or air) in the oxidizing gas fed into the combustion zone as will be explained in detail hereinafter.

Generally speaking, my improved process for the destructive distillation of oil shale contemplates the following features and operations:

1. The maintenance of predetermined, controlled and critical temperatures, such as from about 400 C. to about 600 C., in the distillation zone of a system for the distillation of hydrocarbons from kerogen-containing natural substances. v

2. The use of a uid chemical, such as carbon dioxide, having the property of preserving the carbon-hydrogen linkages of the hydrocarbons formed or evolved during the process of distillation.

3. The use of a gas which will promote the formation of unsaturated hydrocarbon gaseous and liquid cornpounds.

4. The use of a gas which will promote the formation of aromatic gaseous and liquid compounds.

5. The use of a fluid which is of acid nature so as to tix and render non-volatile at condenser temperatures, the ammoniacal compounds distilled.

6. The use of a gaseous catalyst, carbon dioxide.

In carrying the invention into practice, it is preferred to control the combustion temperature by the use of a predetermined and critical oxygenzcarbon dioxide ratio in the oxidizing gas. The critical ratios can be varied from about 30% to about 80% carbon dioxide. InV

order to control combustion in an oxidizing air mixture, carbon dioxide in the optimum proportion possible (say about 40%) is preferred, or up to 80% of carbon dioxide when oxygen gas is used. Such mixtures will convey the needed heat from a combustion zone to a zone in which the heat is required (reaction or distillation zone).

Carbon dioxide can be separated from the resulting iixed gases by partial liquefaction by compression, by dissolving the former in water under pressure in a carbon dioxide separator or by means of chemicals; and the remaining gases, mostly combustible, may be either further separated or used as such for fuel.- In some cases, where the combustible gases mixed with the carbon dioxide are in -relatively large amounts, this separation process may be omitted and the whole gas mixture used as fuel,

The atmosphere in which thedistillation of the kerogencontaining material is heated is found to be inetective in the present process when the percentage of carbon dioxide reaching the distillation zone is below 30% but is increasingly elec'tive as the percentage of carbon dioxide rises to and above 40% and until at 80 to 100% carbon dioxide, with external heating of the retort, there are essentially only unsaturated and aromatic (including heterocyclic ring compounds) oil and gaseous compounds formed. Dilution of the heating atmosphere with steam in moderate percentages does not seem to affect adversely the process and aids in the control of the temperatures of the combustion and distillation zones.

It will be noted that the carbon dioxide is not destroyed in the process and that carbon dioxide ine-the percentages used acts as a catalyst. This is one of the few cases r perhaps the only known case where carbon dioxide acts as a catalyst to changeY the course'of a chemical reaction.'

about 375 C. is required, somewhat higher temperatures such as 450 C. serve to speed up this production of oil, ctc., but use of much higher temperatures, of say 550 C. to 600 C. are objectionable in that-oil cracking occurs with destruction of the earlier formed more valuable products. In my present process where a high carbon dioxide atmosphere is present, these reaction temperatures are not substantially changed.

In my improved process, the exit hydrocarbon gases will consist essentially of ethylene, propylene and butylenes, together with the heating gases (now cooled) of hydrogen, carbon dioxide and nitrogen, small amounts of carbon monoxide, ammonia, water vapor, and but traces of hydrogen sulfide, oxygen and methane.

The liquid condensate consists essentially of unsaturated hydrocarbons, aromatic hydrocarbons and the heterocyclic products closely related to the aromatic hydrocarbons and often spoken of as aromatic because many of their chemical properties are closely similar to those of the aromatic hydrocarbons. Of course, there will be traces of the gases mentioned hereinbefore dissolved in this oily mixture as first condensed but the amounts are insignificant. Saturated compounds, such as aliphatic hydrocarbons and naphthenes are absent and thereby distinguish this oily product from well petroleum or normal shale oil or similar products.

In the last two decades, there has developed a huge petrochemical industry, essentially an aliphatic chemical industry based on addition productsmade `from -unsatu` rated hydrocarbons, e. g., automobile anti-freeze glycols made from mixtures of ethylene and propylene hydrocarbons, Petroleum gases and liquids normally carry no unsaturated hydrocarbons such as ethylene and propylene and to obtain these petroleum has to undergo a severe and expensive cracking and purification process. By my invention, the cheap raw gases obtained in the retorting can at Y once, even though mixed with other gases, be used as starting materials for such aliphatic petrochemicals production. For other products used as raw materials for petrochemicals the liquid unsaturated hydrocarbons are also Well adapted.

In World War II, there began the production of aromatics such as benzol and toluol by a succession of expensive chemical and physical steps from saturated petroleum hydrocarbons, particularly the six and seven carbon atom aliphatic hydrocarbons, and this production has and will increase for many years as these products form the basis of our more important thermo-setting and thermo-plastic resins, plastics, synthetic rubber, explosives and some of the newer textiles, etc. In the production of these products, one of the catalysts used is platinum and the process is spoken of as the platforming process.

The liquid product formed by my improved process is largely aromatic and, as such, it will be cheaper and a much more advantageous material for the production of aromatic chemicals than the crude well petroleum now used.

Heat is the primary agent for obtainingvolatile hydrocarbons, etc., from natural material containing kerogen. Such pyrolysis leaves in the ash a non-distillable carbon residue ordinarily called coke, e. g. oil shale coke or more simply shalecoke Such coke can be burned and the resulting heat used to destructively distill the kerogen to produce the oils and vapors wished.

Formerly the oil shale or other kerogen-containing material was placed in stationary or rotating retorts and heat applied externally through the wall of the retort. Later years have developed processes where the heat is applied internally, mostly by the use of retorts built on the principle of a gas producer.

For my new process many types of equipment can be used but I prefer a retort based on the design of the modern water-jacketed stationary gas producer with a moving ash grate, such as the common Wellman- Galusha gas producer. However, in operation of such an internally heated retort much lessfair is fed than when producer gas is the desired product, in order that the pyrolysis can be carried out at the much lower temperature required to avoid burning or over-cracking the oil produced.

The volumes of air andV of carbon dioxide and of steam, if steam is used, will vary with the percentage of kerogenl present in the material being fed the retort, the sizeof the lumps offeed material, the character of the oil and gas products desired and for other reasons, and also with the low operating temperatures desired in the kerogen pyrolysis zone (distilling or reaction zone). Low temperatures favor unsaturates, higher temperatures, the aromatics.

g The accompanying drawing illustrates a vertical section through the operating portion of al producer type retort used on a Colorado oil shale capable of yielding 25 gallons oil per ton of oil shale for the production primarily of unsaturated and aromatic hydrocarbons as raw materials for petrochemical operations. Entering the distillation zone, the heating gases have 40% or higher carbon dioxide content, but the oxidizing gas mixture fed at the bottom of the retort to produce this ratio needs to contain only 30% carbon dioxide. The-ratio of carbon dioxide to oxygen in the feed gasto shale coke zone as given is approximately two volumes to one, i. e., 30% carbon dioxide to 14% oxygen, or 30% carbon dioxide, 70% air (3% air is oxygen). Two to one isa low ratio. For high ratios commercial oxygen would be added to the fel' aisil'pply.

For the purpose of giving those skilled in the art al better understanding of the invention, the following illustrative examples are given:

Example I Example Il When 40% carbon dioxide is used in the distillation zone, the composition of the crude shale oil and gas was 5% saturates, 60% unsaturates and 16% true aromatics.

Example III Using an externally heated retort operating at 400 to 500 C. and continually running in a slow stream of 100% carbon dioxide at about atmospheric pressure so that the oil shale was continually in contact with only carbon dioxide and its own vapors as the pyrolysis proceeded, the oil and gas resulting contained no saturates (parafiins and naphthenes), but did contain 68% unsaturates, and 20% true aromatics.

Example IV For comparison with Example III another run was made using an inert gas atmosphere instead of the chemically active carbon dioxide gas but otherwise the same conditions. The inert gas used was nitrogen continually run in as a slow stream of 100% nitrogen at the same rate, same pressure, same operating temperature and using the same equipment and other conditions except that the oil shale was continually in -contact only with nitrogen and its own vapors as the pyrolysis proceeded, the oil and gas resulting contained 15% of saturates and 50% unsaturates and 33% of aromatics.

Those skilled in the art will appreciate the surprising result brought about by the presence of carbon dioxide in accordance with the present invention. The foregoing were all run at about 500 C. in the distillation zone. Other research work and tests show that when operation is at a somewhat higher temperature, the percentage of aromatics can be doubled but at a sacrifice of the percentage of unsaturated hydrocarbons.

It is to be noted that the present invention is not to be confused with the process of oil shale distillation commercially used in Estonia wherein a mixture of air and steam, but no carbon dioxide, is used to burn the shale coke at a temperature above 1000 C. in brick-lined rotating producer-type retorts. Nor should the present invention be confused with the gas-combustion process developed in 1951 by the U. S. Bureau of Mines using the small (1 8" diameter) experimental retort at Rie, Colorado. In this shale retort, a combustion temperature of 770 C. is produced by burning a mixture of air and wet recycled gas previously produced in this process. This recycled gas has a heating value of but 85 B. t. u. per cubic foot and a typical analysis of the dry gas exit shows 24% carbon dioxide, 60% nitrogen, 12% combustibles, besides the moisture. It requires a fourth its volume of air to burn its combustibles. Accordingly, the feed mixture to the combustion zone will carry only about 17% carbon dioxide and the distillate obtained by the pyrolysis of the kerogen will be largely saturated hydrocarbon with lesser quantities of olefenic and aromatic hydrocarbons-just the reverse of that given by the present invention.

It will be noted that while both of these processes use equipment somewhat similar to that used in the process of present invention, the processes themselves are quite different. Both use much` higher temperatures (1000 C. and 770 C.) and much lower percentages (0% and 17%) of carbon dioxide than does the present process of at least 30% in the feed gas and 40% at the top of the combustion zone. Moreover, the result of the process shows up in the change in the character of the oil and gas produced, being essentially of the olefenic and aromatic instead of primarily aliphatic hydrocarbons.

The present application is a continuation-in-part of my co-pending patent application, Serial No. 64,401.

Although the present invention has been described in conjunction with preferred embodiments, itis to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

l claim:

l. An improved method of destructively distilling oil shale and similar kerogen-containing natural materials in a retort to produce oil and gases which comprises heating saidmaterial to a temperature of about 300 to 500 degrees C. in an atmosphere containing oxygen and more than 40% carbon dioxide, said carbon dioxide and oxygen in said atmosphere being in the ratio of at least two to one.

2. An improved method of destructively distilling oil shale and similar kerogen-containing natural materials in a producer-type of retort to produce oils, gases and ash which comprises establishing a column having a cold zone on the top and a hot ash zone on the bottom with a preheating zone, a distillation zone, a hot zone, and a re zone in between; feeding kerogenous material to the top of said column, withdrawing hot ash from the bottom of said column, blowing a combustion-supporting gas containing carbon dioxide and oxygen in a ratio of at least 2 to 1 upwardly and through the aforesaid zones to burn hot shale coke in said lire zone and to produce hot gas at a temperature of about 350 to 450 degrees C., passing said hot gas containing upwards of 40% carbon dioxide into the shale Zone to cause distillation of oil vapors and gas to continue to flow upwardly to preheat the kerogenous material in said preheating zone coming from said cold zone; removing oil mist, vapors and gas coming off said cold zone; conveying said oil mist, vapors and gas to a separator to condense oil and by-products while permitting gas to go to a holder.

3. The improved method set forth in claim 2 in which the temperature of the vapors and gas flowing upwardly from about C. through the hot ash zone, to above 500 C. in the lire zone, and passing through the hot shale coke zone decreasing to about 450 C. in the distillation zone and to about 400 C. in the preheating zone and to about 350 C. in the gaseous zone while the temperature of the shale moving downwardly in the column iA creases from about 30 C. in the gaseous zone to about C. in the cold zone, to about 250-350 C. in the preheating zone, to about 400-450 C. in the distillation zone, to about 500 C. in the hot shale coke zone and to about 600 C. in the lire Zone and then to decrease the temperature to about 300 C. in the hot ash zone.

4. The improved method set forth in claim 2 in which the combustion-supporting gas contains about 30% carbon dioxide and 70% air.

5. The improved method set forth in claim 1 in which the carbon dioxide is varied from about 40% to about 80% and the resulting oil and gas contains less than 15% of saturates, from 35% to 68% unsaturates and from 5% to 20% aromatics.

6. In the method of destructively distilling oil shale and similar kerogen-containing natural materials in a producer-type of retort to produce oil, gases, and other products that improvement which comprises heating said materials to a temperature of about 350 C. to about 450 C. in an atmosphere of about 30% to about 80% ofk carbon dioxide and containing carboni dioxideA andv oxygen in a ratio Vof-at least2 to 1-.

7. In they method ofi destructively distilling2 oil shale andsimilarir kerogen-containingv natural materials in a retort to produce oil, gases andother products that im* provernent Whichcomprises using` at least 30% of carbonV dioxide at atemperature of about350to'450 degrees C. as argaseouszcatalystinthef presence of oxygen for increasing thev'productiorr of unsaturated 'and aromatic hydrocarbons in the thermal decomposition of said materials, said carbon dioxide and oxygen being present in a ratio of vatleastZto l.

8. In, the method of destructively` distilling oil shale and similarv kerogen-containing n-atural'materialsfin a retort to produce oil, gases and'other products that irnprovement-which'comprisesutilizing gaseous products of combustionat'a temperature of about 350 to 450 degrees C. with high heat content and with high carbon dioxide content of at least 30% in the presence of oxygen to eiectively distill said=kerogen`ous` materials, said carbon dioxide and oxygen being present in a ratio of at least 2 to -1.

9. In the method of destructively distilling oil shale and similar kerogen-containing natural materials in a retort toproduce oil, gases and other products that irnprovementwhich comprises' usinga combustion-supporting Ygas containingcarbondioxide and oxygen ina critical ratio of atleast 2 to l tolmaintain a temperature in the zone of destructive distillationvin the range` of 350 to 450 degrees C. while bathing the zone of destructive distillation with hot carbon-dioxide present to an extent of at least 30% 'and mixing carbon dioxide -wtih evolved hydrocarbons. v

l0.V Themethod set forth lin' claim 9 in which the temperature lin combustion Zone is keptA below 600 C. to limit the formation of carbon-monoxide and the ternperatrsre 'in the distillationfzone is controlled within a range of about 350 to 450 degrees C.

l1. The method set forth in claim 9 in which the critical ratio can be varied by varying the carbon dioxide from about 30% to about-80%.

12, The method set'forth in claim 9 -in which carbon dioxide is separated from the-evolved hydrocarbons andV gas and reused in the combustion-supporting gas.

References Ctedin the le of this patent UNITED STATES PATENTS` 1,509,667 .Carlin se'pfgzs, 1924 f FOREIGN PATENTS 346/26 Australia D66. 14, 1926

Claims (1)

1.AN IMPROVED METHOD OF DESTRUCTIVELY DISTILLING OIL SHALE AND SIMILAR KEROGAN-CONTAINING NATURAL MATERIALS IN A RETORT TO PRODUCE OIL AND GASES WHICH COMPRISES HEATING SAID MATERIAL TO A TEMPERATURE OF ABOUT 300 TO 500 DEGREES C, IN AN ATMOSPHERE CONTAINING OXYGEN AND MORE THAN 40% CARBON DIOXIDE, SAID CARBON DIOXIDE AND OXYGEN IN SAID ATMOSPHERE BEING IN THE RATIO OF AT LEAST TWO TO ONE.

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