US3703052A

US3703052A - Process for production of pipeline quality gas from oil shale

Info

Publication number: US3703052A
Application number: US88652A
Authority: US
Inventors: Henry R Linden
Original assignee: Institute of Gas Technology
Current assignee: GTI Energy
Priority date: 1970-11-12
Filing date: 1970-11-12
Publication date: 1972-11-21
Anticipated expiration: 1989-11-21

Abstract

A process for producing a high methane content, synthetic pipeline gas from oil shale. Oil shale is processed so as to provide a shale oil fraction, and solids including shale fines and spent shale. The shale oil and a hydrogen rich gas are introduced into a hydrogasifier chamber which is maintained at a temperature of about 1,100*-1,600* F., and at a pressure of about 500-2,000 psig, so as to convert the shale oil by hydrogasification into a high methane content, synthetic pipeline gas, normally liquid aromatic hydrocarbons, and a carbonaceous solid residue. Pulverized solids are passed through the hydrogasifier and into a gasifier chamber, maintained at a pressure of about 500-2,000 psig. and at a temperature of about 1,500*-2,100* F., to remove the carbonaceous residue or coke formed in the hydrogasifier. Shale fines and spent shale are also introduced into the gasifier wherein a gaseous mixture is formed by reaction with steam and oxygen or with steam and air. The gaseous mixture is then converted to a hydrogen rich gas either directly, by a carbon monoxide shift reaction (when steam and oxygen are used in the gasifier) or indirectly, by the steam-iron process (when steam and air are used in the gasifier). In the steam-iron process, the gaseous mixture is the reducing agent for iron oxides formed when added steam is converted to hydrogen over the reduced iron oxides. The hydrogen rich gas is purified and primarily includes hydrogen alone, in the case of the steam-iron process, or a combination of hydrogen and methane, in the case of the carbon monoxide shift process. This hydrogen rich gas is thereafter introduced to the hydrogasifier chamber to form the high methane content gas. All or a portion of the solids leaving the gasifier are recirculated back to the hydrogasifier.

Description

United States Patent Linden [4 1 Nov. 21, 1972 [54] PROCESS FOR PRODUCTION OF processed so as to provide a shale oil fraction, and PIPELINE QUALITY GAS FROM ()IL solids including shale fines and spent shale. The shale SHALE oil and a hydrogen rich gas are introduced into a hydrogasifier chamber which is maintained at a tem- [72] lnvemor: Henry Lmde! La Grange Park perature of about l,l00l,600 F., and at a pressure 1]]. of about 500-2,000 psig, so as to convert the shale oil 7 Assignee; Institute f Gas Technology by hydrogasification into a high methane content, synthetic pipeline gas, normally liquid aromatic [22] Flled: 1970 hydrocarbons, and a carbonaceous solid residue. Pul- [211 App} 38,652 verized solids are passed through the hydrogasifier and into a gasifier chamber, maintained at a pressure of about SOD-2,000 psig. and at a temperature of about [52] US. Cl ..48/2l5, 48/197 R, 48/210 1 50 L2 100 F to remove the carbonaceous residue [51] Int. Cl. ..C0lb 2/14, COlb 2/22 or k f d in the hydrogasifier. Shale fines and Fleld of Search spent hale are also introduced into the gasifier 48/211 wherein a gaseous mixture is formed by reaction with steam and oxygen or with steam and air. The gaseous References Cited mixture is then converted to a hydrogen rich gas either directly, by a carbon monoxide shift reaction UNlTED STATES PATENTS (when steam and oxygen are used in the gasifier) or 2,634,286 4/1953 Elliott et al. ..48/ 197 R indirectly, by the steam-iron process (when steam and 2,654,663 l0/l953 Gorin ..48/l97 R air are used in the gasifier). In the steam-iron process, 2,687,950 8/1954 Kalbach ..48/210 X the gaseous mixture is the reducing agent for iron ox- 2,82l,465 1/1958 Garbo ..48/2l5 ides fonned when added steam is converted to 3,347,647 10/1967 Feldkirchner et al....48/ 197 R hydrogen over the reduced iron oxides. j123 i233? E3223?11:13::3133115323/5i35E The hydhhhhh hhh as h hhhhhd hhh hhhhhhh Primary ExaminerMorris O. Wolk Assistant ExaminerR. E. Serwin AttorneyMolinare, Allegretti, Newitt & Witcoff ABSTRACT A process for producing a high methane content, synthetic pipeline gas from oil shale. Oil shaleis cludes hydrogen alone, in the case of the steam-iron process, or a combination of hydrogen and methane, in the case of the carbon monoxide shift process. This hydrogen rich gas is thereafter introduced to the hydrogasifier chamber to form the high methane content gas. All or a portion of the solids leaving the gasit' arerc' ltedb ktoth h to "f. er 6 1 7 %Ilaim 3 Draw lng igi s [er GAS PRODUCT ans 1 7 10 HYDIFOG/VJ/F/El? f OIL SHALL GA 5 PROCESSOR C0 VERTE 5/0125 04x00: 14 MIXTURE sPzwr s/mu' (719C014 TING C 0 [(5 GA 5/! IE I? Cl/PCl/L A TING so 1. D8

a /v l/Yfl/FO E I? cw FUR/FICA 770 lira/Pod! IP/ CA! 645 PATENTEDuum m2 SHEET '1 OF 3 .Zin/nfor; @Yenr- Ii. linden 0% Num:

P'A'TENTEDNMZI I972 SHEET 2 BF 3 Inv/entor: 9 1?. lin

PROCESS FOR PRODUCTION OF PIPELINE QUALITY GAS FROM OIL SHALE BACKGROUND OF THE INVENTION FIELD OF THE INVENTION AND DESCRIPTION OF THE PRIOR ART This invention relates to a process for the manufacture of a high methane content, synthetic pipeline gas suitable as a substitute for or as a supplement to natural gas and it particularly relates to such a process wherein oil shale is used in the production of the synthetic pipeline gas.

In my copending application, Ser. No. 88,651 filed on even date herewith, entitled Fossil Fuel Hydrogasification Process for Production of Synthetic Pipeline Gas," I describe and claim a process for producing a high methane content, synthetic pipeline gas from various liquid fossil fuels and solid fossil fuels. The process herein described is particularly directed to the production of synthetic pipeline gas from oil shale. Oil shale is a sedimentary rock containing typically about -30 percent by weight of a solid, organic, petroleum like substance known as kerogen. Interest in a suitable, economical process for producing a synthetic pipeline gas from oil shale is high because of the increasing shortage of natural gas supplies in the United States, as compared to the abundant reserves of commercial grades of oil shale, particularly in the northwestern areas of Colorado and adjoining areas of Utah and Wyoming.

Natural gas suitable for distribution to residential, commercial and industrial consumers is characterized by heating values of about 900-1,100 BTU/SCF, and by a high methane content, normally 80 percent by volume or greater. Such natural gas often contains ethane and sometimes nitrogen. When the nitrogen content is high, propane and butane, in addition to ethane, may be left in the gas to compensate for the diluting effect of the nitrogen. Sulfur compounds, carbon dioxide, and higher hydrocarbons are normally removed from natural gas before distribution because they have an undesirable effect on transmission, distribution and use of the natural gas. Therefore, in order to provide a suitable substitute for or supplement to natural gas, such a supplement or substitute should consist primarily of ethane and methane and have only a minimal amount of other constituents. The elementary composition of suitable natural gas supplements or substitutes is therefore about percent by weight of hydrogen, and 75 percent by weight of carbon, corresponding to a carbon to hydrogen weight ratio of 3:1.

Substantial difficulties are encountered in producing natural gas substitutes or supplements from oil shale because kerogen contains more carbon and less hydrogen than that of the elementary composition of natural gas constituents. Typically, kerogen has a carbon to hydrogen weight ratio of about 7 8:1, dispersed intimately among a large excess of undesired mineral constituents. Because of this shortage of hydrogen, in order to make a suitable high methane content, synthetic pipeline gas from oil shale, hydrogen must either be added to the oil shale or carbon must be rejected from the oil shale. As to removal of carbon from oil shale, this is generally considered to be uneconomical. As to the prior art, the gasification of the oil shale is generally accomplished in one of two ways. First, the gasification may be based on conventional processing, such as retorting of the oil shale into a crude shale oil, which is then gasified by one of several known techniques which involve either direct hydrogenation with an external source of hydrogen and/or indirect hydrogenation by reaction of the shale oil with steam to form hydrogen and carbon monoxide which are then recombined to form methane by a catalytic process. Secondly, in newer processing techniques, the crushed oil shale is contacted with a hot hydrogen rich gas to accomplish destructive hydrogenation or hydrogasification of the kerogen directly.

When retorting is used as the first step of an oil shale gasification process, much of the valuable organic carbon content of the shale remains in the residual material. Typically, when oil shale from the northwestern area of Colorado is heated to temperatures on the order of 1,000 E, about 66 percent of the organic matter is converted to shale oil, 12 percent is converted to a low heating value gas, and 22 percent remains in the spent shale as a carbonaceous residue. This residual carbonaceous material has a low value as a solid fuel, since it is greatly diluted by the mineral, matter contained in the sedimentary rock host material, which generally constitutes about 70-90 percent by weight of the raw oil shale. However, in commercial retorts, some of the carbonaceous material and a portion of the gas produced are used as the fuel for heating the shale.

Another problem encountered in using a retorting step for making a pipeline quality gas from crude oil shale is that the crushing of the oil shale to sizes useful in the various designs of vertical shaft retorts also forms a large quantity of fines which cannot be processed without additional special equipment.

When oil shale is used as the solid fuel in the primary gasification step and when even pure hydrogen is the hydrogasification medium, it is not possible to produce pipeline quality gas directly. Oil shales, such as in the deposits in the northwestern area of Colorado, and the adjoining areas of Utah and Wyoming, commonly contain dolomite and calcite, both of which are calcined under hydrogasification conditions giving off copious quantities of carbon dioxide by the following endothermic reactions:

Mg CO MgO CO:

and

CaCO Ca0 CO2 Much of the carbon dioxide formed in these reactions reacts with the valuable hydrogen in the feed gas to form carbon monoxide and steam by the reaction:

Thus, much of the prior art on direct oil shale gasification, such as that taught in U.S. Pat. No. 3,118,746, employs or uses raw, hot synthesis gas, which contains all of the above gaseous materials to avoid costly, and wasteful dual purification. A catalytic methanation step is also required to achieve a suitably high methane content gas with a high heating value, but it is difficult to exceed about 900 BTU/SCF because of thermodynamic limitations on the reaction:

C 3H2 2 CH4 [4,0

Still another problem inthe direct use of oil shale for gasification is that the oil shale retorts before it gasifies. Colorado oil shale typically begins to retort, that is, destructively distill, to form oil, at about 500 F. and retorts quite completely at l,000 F. Hydrogasification, that is, the reaction of kerogen and hydrogen in forming methane, ethane, propane, etc. begins at about l,050 F. Thus, in counter current contacting of fresh shale and hydrogen rich gas, desirably used from a thermal efficiency standpoint as this permits the recovery of large amounts of sensible heat in the spent shale and the hot product gas, relatively little gas and a large quantity of liquid products are produced. This is the type of procedure disclosed in U.S. Pat. No. 3,1 18,746.

Although thermally less efficient, co-current moving bed or a highly backmixed fluidized bed operation is used to produce high gas yields. To achieve the hydrogasification threshold temperature of about l,050 F., very high hydrogen rich feed gas temperatures are required because the heat requirements for raising a large proportion of mineral diluents to reaction temperatures are so high.

It is therefore an important object of this invention to provide a process for producing a synthetic pipeline quality gas from oil shale wherein many of the disadvantages of prior art procedures used in producing synthetic pipeline gas from oil shale are substantially avoided.

it is also an object of this invention to produce a high heating value, high methane content syntheticpipeline quality gas from oil shale by use of a conventional retorting process combined with hydrogasification of crude shale oil, while efficiently utilizing the native carbonaceous matter in the spent shale and in the fresh oil shale fines, as well as the carbonaceous matter in the coke or carbonaceous residue deposited during the hydrogasification step, for producing the required hydrogen.

it is a further object of this invention to substantially avoid contamination of the hydrogasification zone with carbon dioxide commonly formed by decomposition of the mineral carbonates contained in oil shale to thereby allow direct production of a high heating value, high methane content, synthetic pipeline gas without use of a catalytic methanation step, which imposes a thermodynamic limitation on the heating value of the product gas.

It is another object of this invention to produce a high methane content synthetic pipeline quality gas from oil shale wherein the consumption of oxygen in the production of hydrogen rich gas, used in the hydrogasification step, is minimized or substantially avoided.

[t is yet another object of this invention to provide a process for producing a synthetic pipeline quality gas from oil shale wherein a highly efficient use of the wellknown steam-iron process is employed in producing the hydrogen rich gas used during the hydrogasification of shale oil in the production of the synthetic pipeline quality gas.

It is still a further object of this invention to provide a process for producing a synthetic pipeline quality gas from oil shale wherein the hydrogasitication zone and gasitication zone are completely separated, with steam and oxygen or steam and air and spent shale and shale fines being introduced only to the gasification zone, in order to minimize the presence of oxygen-containing compounds, such as carbon dioxide, carbon monoxide, and steam in the raw product gas.

Still another object of this invention is to provide a process for producing a synthetic pipeline quality gas from oil shale without the use of a catalyst in the gasification zone, so as to avoid detrimental effects to the catalyst by sulfur and nitrogen compounds, coke deposits, and mineral contaminants.

It is still another object of this invention to produce a high heating value pipeline quality gas composed primarily of methane, ethane, and relatively small amounts of unreacted hydrogen, hydrocarbons, and inert diluents from oil shale by providing a continuous process operating over a range of pressures equivalent to those used in long distance gas transmission and under conditions of temperature, reaction time, and feed ratios of crude shale oil, spent oil shale, fresh oil shale fines, steam and oxygen or steam and air which minimize the formation of by-products and the loss of carbonaceous materials.

Further purposes and objects of this invention will appear as the specification proceeds.

The foregoing objects are accomplished by providing a process for producing a high methane content, synthetic pipeline gas from oil shale. Oil shale is processed so as to provide a shale oil fraction, and solids include shale fines and spent shale. The shale oil and a hydrogen rich gas are introduced into a hydrogasifier chamber which is maintained at a temperature of about l,l00-l ,600 F., and at a pressure of about SOD-2,000 psig, so as to convert the shale oil by hydrogasification into a high methane content, synthetic pipeline gas, normally liquid aromatic hydrocarbons, and a carbonaceous solid residue. Pulverized solids are passed through the hydrogasifier and into a gasifier chamber, maintained at a pressure of about SOD-2,000 psig. and at a temperature of about l,5002,l00 F., to remove the carbonaceous residue or coke formed in the hydrogasifier. Shale tines and spent shale are also introduced into the gasifier wherein a gaseous mixture is formed by reaction with steam and oxygen or steam and air. The gaseous mixture is then converted to a hydrogen rich gas either directly, by a carbon monoxide shift reaction (when steam and oxygen are used in the gasifier) or indirectly, by the steam-iron process (when steam and air are used in the gasifier). In the steam-iron process, the gaseous mixture is the reducing agent for iron oxides formed when added steam is converted to hydrogen over the reduced iron oxides.

The hydrogen rich gas is purified and primarily includes hydrogen alone, in the case of the steam-iron process, or a combination of hydrogen and methane, in the case of the carbon monoxide shift process. This hydrogen rich gas is thereafter introduced to the hydrogasifier chamber to form the high methane content gas. All or a portion of the solids leaving the gasifier are recirculated back to the hydrogasifier.

BRIEF DESCRIPTION OF THE DRAWINGS Particular embodiments of the present invention are illustrated in the accompanying drawings wherein:

FIG. 1 is a simplified block diagram illustrating my process in a particularly simplified form;

FIG. 2 is a detailed diagrammatic view illustrating one particular embodiment of the invention shown in FIG. 1; and

FIG. 3 is a detailed diagrammatic view illustrating an alternate embodiment of the invention illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, my process is generally illustrated in block diagram form. Oil shale is first introduced to a shale processing section which subjects the oil shale to crushing and retorting for recovering crude shale oil and also spent shale and shale fines.

The crude shale oil is thereafter passed to the hydrogasifier 12. In the hydrogasifier 12, the normally liquid shale oil is converted into the desired synthetic pipeline gas, plus a carbonaceous residue, and normally liquid aromatic hydrocarbons. The vessel 12 is maintained preferably at a pressure of about 500 psig or above, but need not be maintained over about 2,000 psig. The temperature in the hydrogasifier vessel is maintained at about l,l00-1,600 F. and preferably at about l,200-1,500 F. Hydrogen rich gas is also introduced into the hydrogasifier l2. Circulating solids comprising processed or spent oil shale solids are also introduced to the hydrogasifier 12 in a manner to be described hereinafter in greater detail. A suitable motivating force is provided for the circulating solids. Preferably, a portion of the hydrogen rich gas used in the hydrogasifier 12 functions as the motivating force for the solids. Desirably, the bed of solids is maintained in the hydrogasifier 12 in the fluidized state by one or more streams of hydrogen rich gas, preferably entering the hydrogasifier 12 from its lower portion. The hydrogen rich gas is one of the reactants in the hydrogasifier 12 for forming the high methane content, synthetic pipeline gas.

The circulating solids in the hydrogasifier l2 serve a two-fold function. First, the shale solids act as a heat transfer medium. Secondly, these solids provide a carrying medium for moving the deposited carbonaceous residue or coke formed in the hydrogasifier l2 therefrom to the gasifier vessel 14.

When oxygen is utilized in the gasifier 14, the hydrogen rich gas introduced into the hydrogasifier 12, after conventional purification, should contain less than about 10 percent by volume of undesirable diluents, including nitrogen, carbon dioxide and carbon monoxide. Preferably, the content of each undesirable diluents is less than about 5 percent by volume. The nitrogen content of the hydrogen rich gas depends primarily on the nitrogen content of the oxygen which is introduced to the gasifier 14, although some nitrogen will be produced from the oil shale introduced to the gasifier 14. The hydrogen rich gas introduced to the hydrogasifier 12, however, may contain relatively large proportions of methane without detrimental effects. Substantial quantities of steam in the hydrogen rich gas, however are to be avoided.

By maintaining the hydrogasifier 12 at the stated condition, the crude shale oil is converted into a gaseous mixture of high methane content, normally liquid aromatic hydrocarbons, ranging from benzene to high boiling polycyclics, and a carbonaceous residue or coke. The ratio between the amount of hydrogen in the hydrogen rich gas entering the hydrogasifier 12 and the crude shale oil determines the product distribution. The higher the hydrogen to oil feed ratio, more gas and less coke is formed, while as the hydrogen-feed oil ratio decreases, less gas and more coke is formed. The formation of liquid aromatics is less sensitive to operating conditions and properties of the shale oil, and generally falls in the range of about 5-20 percent by weight of the crude shale oil feed stock. Higher pressures, higher temperatures and higher hydrogen to shale oil feed ratio in the hydrogasifier 12 all tend to reduce the amount of liquid products formed in the hydrogasifier 12.

Advantageously, the ratio of hydrogen rich gas to crude shale oil is adjusted within a range of about 40-80 percent of the stoichiometric requirements for converting the crude shale oil to methane. The lower level of the range corresponds to conditions wherein a substantial portion of hydrogen is produced from the deposited coke in the hydrogasifier 12 while the higher level corresponds to conditions where most of the hydrogen is produced from oil shale fines and from the carbonaceous material remaining in the spent shale resulting from the retorting step in the shale processor section 10. As percent of the stoichiometric hydrogen requirement is approached, more and more unreacted hydrogen leaves the hydrogasifier 12 with the product gas so that it is not practically possible to produce a gas of the desired 900l,l00 BTU/SCF of heating value.

As indicated previously, the circulating solids in the hydrogasifier 12 are passed, preferably by gravity feed, from the hydrogasification vessel 12 to the gasifier vessel 14. The circulating solids and the deposited residue or coke formed in the hydrogasifier 12 are introduced to the gasifier 14 in order to form a gaseous mixture which is ultimately used in the production of the hydrogen rich gas which is used in the hydrogasifier 12 for producing the high methane content, synthetic pipeline gas.

In addition to the circulating solids with deposited coke passing from the hydrogasifier 12 to the gasifier l4, spent shale and shale fines from the oil shale processor 10 are introduced to the gasifier 14. This is an important feature of my invention because the oil shale processor waste materials are used as a source of carbonaceous material for ultimate hydrogen production, supplementing the carbonaceous residue or coke formed in the hydrogasifier 12. This is in contrast to the prior art, where an external source of hydrogen is used in the shale oil hydrogasification, such as by means of a Texaco or Shell gasifier which converts additional shale oil to hydrogen by gasification with steam and oxygen. Furthermore, the total process, beginning with the crushed shale and finishing with pipeline quality gas, is self balancing over a wide range of efficiencies in the crushing and retorting operations using different oil shales, thereby providing a valuable and unexpected result. The reason for this is that when higher propor tions of the spent shale and shale fines are formed in relation to the crude shale oil, more hydrogen is generated and transmitted to the hydrogasifier 12. This then results in a higher conversion of crude shale oil to pipeline quality gas, and a reduced amount of coke formation.

The gaseous mixture formed in the gasifier 14 is transferred to the gas converter 16 wherein suitable reactions take place in order to form the hydrogen rich gas which is passed to the hydrogasifier 12. As will be described hereinafter in greater detail, in the embodiment of FIG. 2, the gaseous mixture comprises hydrogen, carbon monoxide, carbon dioxide and methane. Such mixture is subjected to the carbon monoxide shift reaction in the converter 16, wherein steam converts the carbon monoxide to carbon dioxide and hydrogen over suitable catalysts. In the alternate process, the gaseous mixture comprises carbon dioxide, carbon monoxide, nitrogen, and gaseous water. Because of the high proportion of nitrogen in the gaseous mixture, it cannot be converted directly to hydrogen rich gas in the converter 16.-Instead, this gaseous mixture is used as the reducing agent for iron oxides, with the reduced iron oxides used, in turn, to convert added steam to hydrogen.

After passing from the gas converter 16, the hydrogen rich gas passes through a purification processing system 18 to remove undesirable diluents such as carbon dioxide, water vapor and sulfur compounds. The purification processing is substantially conventional in providing the hydrogen rich gas used in the hydrogasifier vessel 12.

Referring to FIG. 2, there is provided a more detailed diagram illustrating one preferred embodiment useful in the practice of the process shown in FIG. 1. In this embodiment, the oil shale is first introduced to a primary crusher 20, where it is crushed into a lump shale fraction or component and a shale fines fraction or component. The lump shale is then introduced to a retorting unit 22, operating at a temperature of about l,0O F. and essentially atmospheric pressure.

The retort 22 processes the lump shale generally, into three components. First, a low BTU gas is produced which may be useful for certain purposes, a spent shale component, and the crude shale oil component. The spent shale is passed through a secondary crusher 24, and the crushed spent shale is combined with the shale fines from the primary crusher 20 for ultimate introduction to the gasifying phase of my process. The crude shale oil component is passed through a heat exchanger 26 for preheating prior to introduction to the hydrogasifier 12.

The hydrogasifier vessel 12 comprises a closed upright cylindrical vessel having internal baffles 28, which generally define an upwardly moving central bed 30 and a downwardly moving annular bed 32. Circulating solids, which are passed upwardly in the hydrogasifier vessel 12, are introduced thereto through the central feed tube 34 connected to the bottom of the hydrogasifier vessel 12. A lift pot 36 provides the motivating force for the solids by use of one stream of the hydrogen rich gas introduced to the hydrogasifier.

Hydrogen rich gas is also passed through the heat exchanger 26, through which the feed oil is also passed. Hydrogen rich gas passes from the heat exchanger 26, into the central feed tube 34, while the feed oil, after passing through the heat exchanger 26, also passes to the tube 34, but at a position above the feed point of the hydrogen rich gas. Other streams of hydrogen rich gas are also injected directly into the lower end of the hydrogasification vessel 12, as shown. Thus, the hydrogen rich gas is passed into the circulating stream of solids at several different locations, including in the lift pot 36, in the central feed tube 34, below the hydrogasification vessel 12, and directly into the bottom of the hydrogasifier 12.

The annular downwardly moving bed 32 is intercepted by a downwardly angled channel 38 from where the circulating solids, including carbonaceous residue are passed to the steam-oxygen gasifier 40.

The design of hydrogasification vessel 12 is patterned after prior art, notably the (British) Gas Councils Fluidized Bed Hydrogenator. Other designs are, of course, feasible. However, the spatial relationships between

vessels

12, 40 and 36 of FIG. 2 are an important part of this invention. Movement of the solids, through the hydrogasifier vessel 12 and the gasifier vessel 40 and to the lift pot 36, and contacting of the various gaseous, liquid and solid feed streams and the solids, is advantageously accomplished by fluidizing the solids in the hydrogasifier vessel 12 and gasifier vessel 40 and by gravity flow of the solids from the hydrogasifier vessel 12 to the gasifier vessel 40 and to the lift pot 36.

Combined spent shale and fresh shale fines passing from the primary crusher 20 and from the secondary crusher 24 are transported to a pair of upright, interconnected fossil fuel charging lock hoppers 42 which are mounted directly over the gasifier vessel 40. The spent shale and shale fines charging of the gasifier 40 is preferably accomplished through alternate paths. One path of feed for the spent shale and shale fines is directly into the top of the vessel 40 by suitable valve controls. Alternatively, a branch line 44 passing from the hoppers 42 is provided to direct spent shale and shale fines directly into the downwardly angled channel 38 for gravity feed of the spent shale and shale fines to the steam-oxygen gasifier 40. Suitable valves are provided so that the desired introductory path of travel of the solids to the gasification vessel 40 is selected and so that solids can be charged against pressures of about 500-2,000 psig. The steam-oxygen gasifier 40 is maintained at a temperature of about 1,500-2,l00 F. and preferably at 1,600-] ,900 F., while the pressure in the gasifier vessel 40 is maintained at a level which is equivalent to that of the hydrogasifier 12.

It is important that the fresh shale fines and the spent shale are introduced into the gasifier 40 in a manner which allows for the direct formation of methane and ethane from the fresh and carbonized kerogen by destructive hydrogenation (hydrogasification) through contact with the hot, hydrogen rich gas present in the gasifier 40. However, it is also desirable to minimize the formation of high-boiling liquid products in this vessel so as not to complicate the purification process for production of the relatively high-purity hydrogenmethane gas to be recycled to the hydrogasifier 12. Thus, if large amounts of kerogen-rich oil shale fines are available, the mixture of these fines and spent shale from retorting must be introduced in the gasifier 40 either in a manner which provides for concurrent downward flow of gas and solids during the solids heatup period, or in extreme cases, directly into the solids leaving the hydrogasifier 12 through channel 38. However, care must be taken in the design of the gasifier 40 to minimize the destruction of reactive constituents in the shale feed materials by premature exposure to steam and oxygen in the high-temperature zone of the gasifier 40, so as not to unnecessarily reduce the highly desirable direct formation of methane in this vessel.

in the gasifier vessel 40, steam and oxygen are introduced for converting the carbon therein into a synthesis gas including hydrogen, carbon monoxide, carbon dioxide, and gaseous water. The reactions in the gasifier 40 include the following:

C+O C0, (3)

C+ 1/20 CO (4) Since reaction (1) is highly endothermic, oxygen is introduced to the steam-oxygen gasifier 12 so as to convert a portion of carbon in the vessel 40 by the exothermic reactions (3) and (4) to form carbon dioxide and carbon monoxide. Reaction (3) is a gas phase reaction which maintains a close approach to chemical equilibrium. I

By maintaining the steam-oxygen gasifier vessel 40 at the stated conditions, and by providing for vigorous fluidization and backmixing of the circulating solid material passing into the gasifier unit 40 with the in coming steam and oxygen streams, substantial amounts of methane are formed in the gasification vessel 40. Although the specific reaction mechanism is not fully understood, the amount of methane formed under these conditions is considered to be significantly greater than predictable from the thermodynamic equilibrium of the classic methanation reaction:

It is believed that the high level of methane formation is the result of continuous activation of the carbonaceous material by partial conversion thereof with steam and oxygen. The high methane formation is helpful in this embodiment as it reduces the consumption of costly oxygen in at least two ways: first, less heat needs to be generated by the oxidation reaction as methane formation is an exothermic reaction; and secondly, any carbon which is gasified in the form of methane does not have to be gasified by the endothermic steam decomposition reaction (I). The higher methane formation in the steam-oxygen gasifier 40 also adds to the total production of pipeline quality gas per unit of fresh oil shale fed to the process.

The spent shale solids pass from the lower end of the gasifier vessel 40, by gravity feed, to the lift pot 36, where the hydrogen rich gas recirculates these shale solids to the hydrogasifier 12. A continuous stream of high ash residue is withdrawn at the bottom of the base of the gasifier 40 through the hopper 46, so as to prevent a build up of excess spent solids in the gasifier 40.

Provision is also made for removal of fines, preferably, with a gas-solids separator 48, which is located at the upper portion of the steam-oxygen gasifier vessel 40. The separator 48 recirculates the shale solids or fines which are entrained in the synthesis gas passing from the gasifier 40, back thereto. Steam is desirably introduced at the lower end of the gasifier 40 while multiple streams of a steam-oxygen'mixture are introduced to the gasifier 40 intermediate the bottom and top of the moving bed located therein. Passing from separate sources, steam and oxygen are intermixed, prior to passage through a heat exchanger 50, for preheating of the steam-oxygen mixture before introduction to the gasifier 40.

The raw hydrogen rich gas passing from the separator 48 also passes through the heat exchanger 50 for cooling prior to introduction to a carbon monoxide shift reactor 52. The carbon monoxide shift reactor is preferably maintained at about 550750 F. Prior to introduction to the shift reactor 52, the raw hydrogen rich gas comprises a gaseous mixture of hydrogen, carbon monoxide, carbon dioxide, methane, hydrogen sul fide, carbon oxysulfide, gaseous water and benzol. After passing through the carbon monoxide shift reactor 52, the carbon monoxide in the gaseous mixture is substantially removed and the mixture is then passed through a waste heat boiler 54. In the shift reactor 52, the gas is subjected to the well known carbon monoxide shift reaction or the water gas reaction, wherein steam converts carbon monoxide in the gaseous mixture to carbon dioxide and hydrogen over a suitable catalyst, typically iron-chromia.

The gaseous mixture is then passed through the hot carbonate scrubbing unit 56, which substantially removes carbon dioxide, hydrogen sulfide and carbon oxysulfide. The remaining gaseous mixture is then passed to a cooler-condenser unit 58 where water and crude benzol are removed.

Upon passing from the cooler-condenser unit 58, the treated gaseous mixture, now a high hydrogen content gas, primarily hydrogen and methane, is passed through a compresser 60 and finally through a heat exchanger 62. The hydrogen rich gas is then circulated to the hydrogasifier 12 through the previously described and multiple paths of travel.

The product gas, primarily methane, formed in the hydrogasifier 12, passing from the hydrogasifier l2 and through a solids separator 64 at the upper end of the hydrogasifier 12, passes through the heat exchanger 62 for cooling or, alternatively may by-pass the heat exchanger 62 through the line 66. The product gas passes through a waste heat boiler 68 and then to a water scrubbing condenser where crude benzol and aromatic oils are removed. Following passage through the water scrubbing condenser 75, wherein ammonia is also removed, the product gas is passed to the monoethanolamine scrubbing unit 72, where hydrogen sulfide and organic sulfur compounds are removed. The gas is finally passed through an activated carbon unit 73 for removal of more organic sulfur and benzol. The product gas leaving the activated carbon unit 73 is a high heating value synthetic pipeline gas having a heating value in the desired range of 900-l,l00 BTU/SCF.

The product gas and hydrogen rich gas purification systems described are conventional, as are the heat exchange and recovery systems described. However,

the difficult and inefficient catalytic methanation step, used in the prior art for producing pipeline quality gas from oil shale in much prior oil gasification, is not required in the product gas purification system because the hydrogasification vessel 12 is isolated from the oxygen containing streams. Temperature control in the hydrogasification vessel 12, in which exothermic reactions take place, is accomplished by control of the hydrogen rich gas temperature through partial or total bypass of the heat exchanger 62. Additional control is obtained by raw product gas recycle after heat recovery in the product gas waste boiler 68.

In FIG. 3, there is shown an alternate embodiment of my invention, wherein the gasifier vessel forms a different gaseous mixture than in the embodiment shown in FIG. 2.

Generally, the hydrogasifier of the embodiment of FIG. 3 operates at the same conditions with substantially the same reactions as that in the embodiment of FIG. 2. However, the reaction conditions in the gasifier of FIG. 3 are different and a producer gas comprising nitrogen, carbon dioxide, carbon monoxide and gaseous water is formed therein. The producer gas is subsequently passed to a vessel wherein the producer gas is used as the reducing agent for iron oxides formed in the production of hydrogen rich gas by reaction of added steam and the reduced iron oxides. The hydrogen thus formed is then passed to the hydrogasifier for formation of the desired synthetic pipeline gas.

As in the embodiment of FIG. 2, the hydrogasifier vessel 74 is maintained at a pressure of 500 psig or above, but need not be over 2,000 psig. The temperature is maintained at about 1,ll,600 F. and preferably at about l,200-l,500 F. The feed oil is the same, that is, shale oil, which is processed in the same manner as that discussed relative to the embodiment of FIG. 2. The hydrogasifier 74 is constructed like that of the embodiment of FIG. 2, and the circulating solids are passed into the vessel 74 through the upright central feed tube 76. A lift pct 78 is used to effect the upward lifting force for the circulating solids through introduction of a stream of pressurized hydrogen rich gas.

Hydrogen rich gas is also introduced to the hydrogasifier 74 through its bottom portion, and, after passage through the heat exchanger 80 through which the shale oil is also passed, to the feed tube 76 at a position intermediate the vessel 74 and the lift pot 78. The circulating solids pass out from the hydrogasifier vessel 74 through the downwardly angled channel 82 by gravity feed, the circulating solids also carrying the carbonaceous residue or coke remaining after the reaction of shale oil and the hydrogen rich gas in the hydrogasifier 74.

A pair of uprightly spaced, fossil fuel charging lock hoppers 84 are mounted above the gas producer vessel 86. In this embodiment, only one fossil fuel charging passage is provided for direct feed of the solid fuel to the channel 82 for gravity feed of the shale solids to the gasifier vessel 86, together with the circulating solids which carry the carbonaceous residue or coke from the hydrogasifier 74. As contrasted to the embodiment of FIG. 2, in the embodiment of FIG. 3, steam and air are used as reactants in the vessel 86 rather than steam and oxygen. Thus, the present embodiment is a desirable altemate method in the event that oxygen is considered too costly. When air is used, however, the producer gas contains a relatively high portion of nitrogen (about 40 percent by volume on a dry basis) and thus such gas is not a direct source of hydrogen rich gas. However, the producer gas is used as an integral part of the process which directly produces the hydrogen rich gas. Thus, the processing of the producer gas varies from the processing of the gaseous mixture formed in the gasifier of the embodiment of FIG. 2. Furthermore, the present embodiment does not intend to produce methane in the vessel 86, which production is normally favored by the relatively low temperature operation of the steam-oxygen gasifier 40 used in the embodiment of FIG. 2. In this embodiment, the gaseous mixture produced in the vessel 86, as will be described hereinafter, is used as a reducing gas for the steam-iron process. Thus, any methane which is formed in the gasifier 86 does not add to the yield of pipeline quality, high methane content gas.

Circulating solids pass downwardly by gravity feed from the gasifier vessel 86 to the lift pot 78 and the hydrogen rich gas transports these solids back to the hydrogasifier 74. Since these circulating solids comprise spent oil shale, a continuous stream of high ash residue is withdrawn at the base of the vessel 86 through the solids discharge hopper 88. Provision is also made for removal of fines, preferably at the gassolids separator 90, located at the upper portion of the gasifier vessel 86.

Air is introduced in multiple locations to the lower portion of the vessel 86 after passage through the compressor half of an expander-compressor unit 92, and also after preheating in a heat exchanger 94. Steam is also introduced into the lower portion of the vessel 86. The producer gas passing from the separator 90 is cooled in the heat exchanger 94 prior to introduction to the steam-iron processor unit 96. The producer gas, at this point of the process, generally comprises carbon dioxide, carbon monoxide, nitrogen, and gaseous water.

In the steam-iron processor 96, iron ore or other iron oxide materials are subjected to cyclic oxidation and reduction at elevated temperatures. The steam-iron process is well known and is described, for example, in US. Pat. Nos. 3,222,147 and 3,442,620. An upper oxidizer section 98 and a lower reducer section 100 are provided, a restricted channel 102 interconnecting the bottom of the oxidizer 98 and the top of the reducer 100.

Iron oxide, oxidized in the oxidizer section 98, is reduced by the producer gas, which is introduced into the reducer section 100, by the following reactions, for example:

The spent producer gas after use in the reducer section 98 is advantageously passed through a gas-solids separator 104 and the spent producer gas may be used to drive the expander-compressor unit 92. The spent producer gas may thereafter be used as a low BTU fuel gas. The reducer section 100 is desirably maintained at a pressure of about ZOO-2,000 psig and at a temperature of about 1 ,400l ,600 F.

The reduced iron oxide is discharged at the bottom of the reducer section 100 by gravity feed through the discharge channel 106 and is passed to a liftpot 108. Steam is injected into the lift pot 108 and is not only the oxidizing agent for the reduced iron oxide, but it is the motivating force for lifting the reduced iron oxide to the oxidizing section 98. Entrained iron and iron oxide are passed through a separator 110 from which the iron and iron oxide are discharged by gravity to the oxidizer section 98. DEsirably, the oxidizeris maintained at a temperature of about l,300l,500 F. and at a pressure of about ZOO-2,000 psig. Steam from the separator is injected to the oxidizer 98, as shown. In the course of reaction of the steam, which is the direct source of hydrogen, with iron or lower iron oxides, hydrogen is formed by reactions such as:

The hydrogen thus formed in the oxidizer section 98 is passed through a gas-solids separator 112. Any entrained iron or iron oxide is recovered and returned to the steam-iron processer 96. The hydrogen produced is then passed through a waste heat boiler 114 and through a water condenser 116 for removal of gaseous water or steam. At this point, the hydrogen content of the gas is at least about 90 percent by volume.

Since the steam-iron processer 96 operates generally at a lower pressure than the hydrogasifier vessel 74 and the gasifier vessel 86, the hydrogen is passed through a compressor unit 118. The hydrogen is then passed through a heat exchanger 120 for preheating prior to introduction at multiple locations to the hydrogasifier 74.

The gas formed in and passing from the hydrogasifier 74 is thereafter processed in a manner similar to the embodiment of FIG. 2. Thus, the gas is passed through a gas-solids separator 122, and if desired, may be cooled by passage through the heat exchanger 120. The gas is cooled again in a waste heat boiler 124. Thereafter, the product gas passes through a water scrubbing condenser 126 for removal of crude benzol, aromatic oils, and ammonia, through a monoethanolamine scrubbing unit 128, for removal of hydrogen sulfide and organic sulfur compounds, and through an activated carbon unit 130 for separation of more organic sulfur and benzol from the product gas. The product gas resulting is a high methane content, synthetic pipeline gas having a heating value of 900-1 ,100 BTU/SCF.

While in the foregoing, there has been provided a detailed description of particular embodiments of the present invention, it is to be understood that all equivalents obvious to those having skill in the art are to be included within the scope of the invention as claimed.

What I claim and desire to secure by Letters Patent l. A process for producing a high methane content, synthetic pipeline gas from oil shale, said process comprising the steps of recovering shale oil and carbon containing shale solids from said oil shale, promoting a hydrogenation reaction in a first chamber between said shale oil and hydrogen rich gas in the presence of circu-- lating solids to produce said high methane content,

synthetic pipeline gas and a carbonaceous residue, introducing said circulating solids, said carbonaceous residue and said carbon containing shale solids into a second chamber, gasifying in said second chamber said carbonaceous residue and said carbon containing shale solids with a free oxygen containing gas and steam to provide a gaseous mixture and at least a portion of said circulating solids, using said circulating solids as a heat transfer medium during the production of said gaseous mixture, promoting a reaction using said gaseous mixture for production of said hydrogen rich gas used in said hydrogenation of said shale oil, transporting at least a portion of said circulating solids directly from said second chamber to said first chamber, and carrying said carbonaceous residue formed upon hydrogenation directly from said first chamber to said second chamber with said circulating solids.

2. The process of claim 1 wherein said recovering step includes passing said oil shale through a first crusher to separate said oil shale into shale fines and lump shale, retorting said lump shale to form said shale oil and spent shale, crushing said spent shale, and combining said shale fines with said spent shale for introduction to said second chamber.

3. The process of claim 1 wherein said first chamber is maintained at a pressure of about 500-2000 psig and at a temperature of about l,100-l ,600 F., said second chamber is maintained at a pressure of about SOD-2,000 psig and at a temperature of about l,500-2 ,100 F., and said oxygen containing gas includes both steam and oxygen for forming a gaseous mixture which includes hydrogen, methane, carbon dioxide and carbon monoxide.

4. The process of claim 1 wherein said second chamber is maintained at a pressure of about 500-2,000 psig and at a temperature of about l,500-2 ,100 F., and said oxygen containing gas includes both steam and oxygen for forming a gaseous mixture which includes hydrogen, methane, carbon monoxide and carbon dioxide.

5. The process of claim 1 wherein said hydrogen rich gas contains less than about 10 percent by volume of diluents including carbon dioxide, carbon monoxide and nitrogen.

6. The process of claim 1 wherein the ratio of hydrogen rich gas to shale oil introduced into said first chamber is maintained at less than percent of the stoichiometric requirements for converting said shale oil into methane.

7. The process of claim 1 wherein the ratio of hydrogen rich gas to shale oil introduced into said first chamber is maintained within a range of about 40-80 percent of the stoichiometric requirements for converting said shale oil into methane.

8. The process of claim 1 wherein said circulating solids with said carbonaceous residue deposited thereon are carried from said first chamber to said second chamber by gravity feed.

9. The process of claim 1 including the step of discharging a portion of said circulating solids from said second chamber.

10. The process of claim 1 wherein said circulating solids in said first chamber are maintained in the fluidized state therein with said hydrogen rich gas.

11. The process of claim 1 including the step of adding said carbon-containing shale solids to said circulating solids and said carbonaceous residue during movement thereof from said first chamber to said second chamber.

12. The process of claim 1 wherein said product gas has a heating value of about 900-1 ,100 BTU/SCF.

, 13. The process of claim 4 wherein said reaction using said gaseous mixture is a carbon monoxide shift reaction for producing said hydrogen rich gas directly from said gaseous mixture.

14. The process of claim 1 including the steps of maintaining said second chamber at a pressure of about SOD-2,000 psig and at a temperature of about 2,000-2 ,500 F., and said oxygen containing gas comprises air and steam which are introduced into said second chamber for producing a gaseous mixture which includes nitrogen, carbon dioxide, carbon monoxide and gaseous water.

15. The process of claim 14 wherein said reaction comprises using said gaseous mixture as the reducing agent for iron oxides, said iron oxides being formed when added steam is converted to hydrogen over reduced iron oxides, said steam being the direct source of hydrogen rich gas.

16. The process of claim 1 wherein said transporting step includes providing means for moving said solids to said first chamber.

17. The process of claim 16 including the step of spatially arranging said first chamber, said second chamber and said moving means to provide for gravity flow between said first chamber and said second chamber and between said second chamber and said moving means for lifting said circulating solids from said moving means to said first chamber.

Claims

1. A process for producing a high methane content, synthetic pipeline gas from oil shale, said process comprising the steps of recovering shale oil and carbon containing shale solids from said oil shale, promoting a hydrogenation reaction in a first chamber between said shale oil and hydrogen rich gas in the presence of circulating solids to produce said high methane content, synthetic pipeline gas and a carbonaceous residue, introducing said circulating solids, said carbonaceous residue and said carbon containing shale solids into a second chamber, gasifying in said second chamber said carbonaceous residue and said carbon containing shale solids with a free oxygen containing gas and steam to provide a gaseous mixture and at least a portion of said circulating solids, using said circulating solids as a heat transfer medium during the production of said gaseous mixture, promoting a reaction using said gaseous mixture for production of said hydrogen rich gas used in said hydrogenation of said shale oil, transporting at least a portion of said circulating solids directly from said second chamber to said first chamber, and carrying said carbonaceous residue formed upon hydrogenation directly from said first chamber to said second chamber with said circulating solids.

3. The process of claim 1 wherein said first chamber is maintained at a pressure of about 500-2000 psig and at a temperature of about 1,100*-1,600* F., said second chamber is maintained at a pressure of about 500-2,000 psig and at a temperature of about 1,500*-2,100* F., and said oxygen containing gas includes both steam and oxygen for forming a gaseous mixture which includes hydrogen, methane, carbon dioxide and carbon monoxide.

4. The process of claim 1 wherein said second chamber is maintained at a pressure of about 500-2,000 psig and at a temperature of about 1,500*-2,100* F., and said oxygen containing gas includes both steam and oxygen for forming a gaseous mixture which includes hydrogen, methane, carbon monoxide and carbon dioxide.

6. The process of claim 1 wherein the ratio of hydrogen rich gas to shale oil introduced into said first chamber is maintained at less than 100 percent of the stoichiometric requirements for converting said shale oil into methane.

12. The process of claim 1 wherein said product gas has a heating value of about 900-1,100 BTU/SCF.

13. The process of claim 4 wherein said reaction using said gaseous mixture is a carbon monoxide shift reaction for producing said hydrogen rich gas directly from said gaseous mixture.

14. The process of claim 1 including the steps of maintaining said second chamber at a pressure of about 500-2,000 psig and at a temperature of about 2,000*-2,500* F., and said oxygen containing gas comprises air and steam which are introduced into said second chamber for producing a gaseous mixture which includes nitrogen, carbon dioxide, carbon monoxide and gaseous water.