Process for the recovery of hydrocarbon fractions from hydrocarbonaceous solids
Process and apparatus for extraction of oil and hydrocarbons from crushed hydrocarbonaceous solids (101), such as oil shale, involving the pyrolyzing of the crushed solids (101) with liquid hydrocarbon (104) and hot gas such as syn gas (103) rich in hydrogen, carbon dioxide and carbon monoxide or a solid hydrocarbon such as gilsonite. Crushed hydrocarbonaceous solids are treated with a hydrocarbon and hot gas in a rotary kiln (105) where the crushed solids are cascaded into the hot gas for sufficient time to strip the volatile liquids and gases found in the solids, removing the vaporized liquids, enriched hot gas and spent crushed solids from the kiln, fractionating the vaporized liquids (106) and enriched syn gas into the desired fractions. Use of hot syn gas is particularly suited for use in conjunction with combined-cycle electricity generation (110) and in the preparation of various by-products. The process efficiently recycles heat and energy to reduce harmful atmospheric emissions and reliance on external energy sources.
This application is a continuation-in-part of U.S. application Ser. No. 11/035,383, filed Jan. 12, 2005, which is a continuation-in-part of PCT Application No. PCT/US2003/021926, filed Jul. 14, 2003, which designated the United States and claims priority to U.S. application Ser. No. 10/194,993, filed Jul. 12, 2002, now issued as U.S. Pat. No. 6,709,573, each of which are incorporated herein by reference in their entireties.
FIELD OF THE INVENTIONThis invention is related to the recovery of hydrocarbons from solid carbonaceous materials, and more specifically to an improved process using hot gas and liquid hydrocarbon in a generally horizontal rotary kiln.
BACKGROUND OF THE INVENTIONWorldwide demand for hydrocarbons and related petrochemicals and fertilizers is increasing at a rapid annual rate. Crude petroleum and natural gas are basic in satisfying these demands while at the same time many industries have experienced shortages despite the discovery of new oil and gas sources. Therefore, alternate solid hydrocarbon sources and feed stocks, such as coal, tar sands, oil shale and solid crudes present an ever increasingly attractive source for meeting demand for hydrocarbon products.
Oil shale and tar sands, also known as oil sands and bituminous sands, are particularly promising sources of these needed products as large deposits are found in Canada and the United States. The largest known deposit of oil shale is the Green River formation in Utah, Colorado and Wyoming with about a third of such deposits in the state of Utah. The hydrocarbon resource locked in the Green River formation has been estimated to be in excess of 1.5 trillion barrels. This is a considerable resource considering known world oil shale reserves amount to just over 2.5 trillion barrels, by conservative estimates.
The demand for hydrocarbon resources makes development of the Green River formation virtually certain. During the 1970s and 1980s several oil shale operations were developed in Colorado and Utah, however due primarily to economic considerations most of these operations have since ceased. An average recovery of about 29 to 34 gallons of oil per ton of oil shale was typical of these previous recovery efforts.
Green River oil shale is a petroliferous material (heavy viscous oil material) which is as high as 25% by weight with an average of 12% by weight hydrocarbon. The recovered oil is about 17°-25° API gravity, frequently averaging about 21°, and contains a low amount of sulfur and low aromaticity. The Green River shale has relatively high moisture content of between about 0.4% to 6%. Ranges for analysis of several samples of Green River oil shale are shown in Table 1. The balance of the components, not shown in the table, are made up primarily of various minerals and trace metals.
The largest known deposits of tar sands are the Athabasca sands found in northern Alberta, Canada which underlay more than 13,000 square miles at a depth up to 2,000 ft. Of the 24 states in the United States that contain tar sands, about 90% of such deposits are in the state of Utah. The hydrocarbon resource locked in the Utah tar sands has been estimated to be in excess of 25 billion barrels.
However, the Utah tar sands, being of non-marine origin, have somewhat different chemical and physical characteristics than the Athabascan sands which are of marine origin, and do not respond as well to the traditional process used to extract oil from tar sands. Utah tar sands are generally hard consolidated sand stone closely associated with petroliferous material (heavy viscous oil material) which is as high as 13% by weight with an average of 10.5% by weight hydrocarbon. The oil is about 13°-18° API gravity and contains a low amount of sulfur, e.g. less than about 0.9% by weight, low aromaticity and a very low water content. The Athabascan sand has an encapsulating water film surrounding each sand grain, which makes it amenable to a water-wetting process. The absence of this water film on the Utah sand grain necessitates using other technology for extracting the oils.
A comparison of the Athabascan tar sands with a sample of Utah tar sands obtained from Asphalt Ridge is shown in Table 2.
The high viscosity, low sulfur content, low water content and other significant differences keep the Utah tar sands from responding well to commonly used extraction processes.
A number of oil recovery methods related to oil shale and tar sands have been tested in the laboratory or in small operations in the field. These processes involve various techniques such as hot water processes, cold water processes, solvent processes, thermal processes and the like, but in most cases, they possess certain limitations which make them unsuitable for use on a commercial basis. Further, many of these processes leave over 20% of the organic carbon behind in the spent shale. A process which would be effective with these particular oil shales and tar sands would be a significant advance in the art.
It is desirable, therefore, to provide a new and efficient process for the extraction of hydrocarbonaceous material from solids containing such material and particularly from Green River oil shale. Another desirable goal is to provide unique synergies to facilitate the economical production of various products from hydrocarbonaceous solids. It is a further desire to provide such an extraction process which could utilize equipment now in commercial use, meet present day EPA standards and could be rapidly put into commercial production to meet the urgent demand for various hydrocarbon products.
SUMMARY OF THE INVENTIONIt has now been discovered that these and other desires can be accomplished by the process of the present invention which relates to a new and improved process for extracting oil and other valuable hydrocarbons from crushed hydrocarbonaceous solids, such as oil shale, by means of a thermal technique using a special source of heat. The process of the present invention represents an improvement upon U.S. Pat. No. 4,725,350, hereby incorporated by reference in its entirety, and which is also the work of the present inventor.
Specifically, the present invention provides a new and efficient process for extracting valuable oils and other hydrocarbons from crushed hydrocarbonaceous solids which comprises optional blending of the crushed solids to provide a substantially uniform feed composition and preheating the crushed hydrocarbonaceous solids to remove residual water. The crushed solids are treated in a generally horizontal rotary kiln having a slight slope downward with hot gas at an elevated temperature and sprayed liquid hydrocarbon. Preferably, the process within the rotary kiln occurs in the absence of water, or at least being substantially free of water. The pressure inside the kiln can be maintained below 500 psi and the crushed solids can be heated using the hot gas for sufficient time to strip volatile hydrocarbon containing liquids and gases found in the crushed solids. The hydrocarbon rich vaporized materials and spent solids are removed from the kiln and the gaseous products are fractionated into desired fractions.
In a more detailed aspect of the present invention the hot gas can be introduced into the rotary kiln at a temperature between 700° F. and 2500° F. and the crushed solids are preheated to a temperature between 100° F. and 350° F. to reduce the heating load on the kiln.
In yet a more detailed aspect of the invention the hot gas is a hot syn gas which is a product of coal gasification. In one alternative embodiment, the hot syn gas can be injected inside the rotary kiln such that an enriched syn gas is produced upon contact with the crushed solids. The enriched syn gas may be used as a starting material for the manufacture of other products such as methanol, ammonia, urea and natural gas or combusted and utilized in a combined-cycle electricity generation step to supplement the heating and power needs of the process.
The new process presents distinct advantages over the known processes for extraction of hydrocarbons from oil shale, and is particularly adapted for use in the treatment of oil shale and tar sands obtained from most worldwide deposits. Particular advantage is found in the fact that Utah oil shale is located near large deposits of coal and facilitating a unique combination of the two techniques of coal gasification and the utilization of the syn gas therefrom directly in the oil shale extraction process. In addition, the use of the special hydrogen and carbon dioxide-containing hot gas effects an upgrading of the products as to yield and quality, e.g. 5 to 25% increase in yield of light ends, e.g. gasoline and lighter fractions, and thus presents a desirable economic advantage. As used herein, all percents are by weight unless specifically identified otherwise. The enriched syn gas has a variety of potential uses, all of which increase the economic and practical utility of the process of the present invention. Among these uses are the production of methanol, ammonia, urea, natural gas and recoverable heat value. Further, gas produced in the process may be used for the production of electricity in a combined-cycle power generation step. This reduces the need for off-site electrical power and minimizes burning so as to reduce atmospheric emissions of harmful gases to well below EPA standards.
Preferably, substantially no water is present in the reaction zone as any residual water is removed during the preheat stage. This has many advantages, such as lower heat requirement during the reaction in the rotary kiln, as well as improved yield. Furthermore, there would be no need for building expensive dams and other water collection projects prior to the operation of the process. In addition, the process utilizes equipment now in commercial production and does not require specially produced equipment which may require long periods of time for construction.
Finally the process presents an additional economic advantage in that the oil vaporized off the oil shale will be in vapor form and can be sent directly to a fractionating tower for refining, thereby eliminating the expense of reheating the hydrocarbons for fractionation.
Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
While the process of the invention is described hereinafter with particular reference to the processing of oil shale using specific language to describe the same, it will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention. For example, it will be apparent that the process can also be used to treat a great variety of hydrocarbon-containing solids, such as tar sands, solid crude oil, gilsonite, peat, and mixtures of two or more of these materials, or any other hydrocarbon-containing solids with inert materials.
Process Overview
The following overview is designed to provide a brief synopsis of the process of the present invention, while the particulars of each step will be discussed in greater detail below. Hydrocarbonaceous solids are treated to recover valuable hydrocarbon fractions. The process of the present invention provides several additional advantages which increase the economic value of the process. Several of these advantages include the production of an enriched synthetic gas which can be used to produce a variety of industrial chemicals and may be used in the production of electricity to supplement various energy requirements of the process.
Referring now to
Hydrocarbonaceous Solids Preparation
Referring now to
The above-described solid materials are crushed into small particles before further processing. The target particle size is less than about 1 inch and ranges from about 0.1 to about 1 inch. Particle sizes below about 0.1 inches are undesirable as the particles become entrained in the exit gases. Although, some entrainment of solid particles is acceptable, down-stream processes may be adversely affected. Particle sizes between about 0.25 and 0.75 inches give good results under a variety of conditions.
Due to the nature of many mined materials, the composition of incoming feed may vary considerably over time. Such variations often cause undesirable shifts in the required thermal load, rate of recovery, and fractionation parameters. The composition of the hydrocarbonaceous material may vary over a wide range and depends upon the type and geographic origin of the material. Further, hydrocarbonaceous solid deposits vary in composition from the same source. In order to reduce this variation, it is often desirable to blend the hydrocarbonaceous materials either before or after crushing to provide a substantially uniform feed composition prior to preheating. This is most often accomplished by stockpiling the materials horizontally and then taking vertical cuts as feed to the process.
Preheat
According to
The preheating can be accomplished before being introduced into the hopper or while being maintained in the hopper. Conventional heating equipment may be used for this purpose. BTUs obtained from other portions of the process may also be a suitable source of heat for the preheating step. Spent solids recovered at the end of the process, heat from coal gasification, or heat produced from combustion of various products are several non-limiting examples of heat sources which could be used to reduce the requirement of extra-process energy. As shown in
Hot Gas Preparation
An important feature of the present invention is providing a hot gas at an elevated temperature to the rotary kiln. Non-limiting examples of suitable hot gases can include syn gas, nitrogen gas, hydrogen gas, carbon dioxide gas, combustion gases, combinations thereof, and any other gas having a high heat content which does not also adversely react with the liquid hydrocarbon, liberated hydrocarbons, and/or solids. For example, natural gas, waste gas, or other fuel gases can be combusted to produce heat which can be in thermal communication with the rotary kiln.
In one currently preferred aspect, the hot gas can be a hot gas containing hydrogen and carbon dioxide as shown in step 103 of
Coming under special consideration is hot gas containing from 25 vol % to 40 vol % hydrogen and from 10 vol % to 20 vol % carbon dioxide at a temperature of 1500° F. to 2500° F. Such hot synthesis gas, i.e. syn gas, may be economically provided from the gasification of coal. One coal gasification process which would suffice for purposes of the present invention is described in Oil and Gas Journal, Jun. 19, 1972, page 26 as the Koppers-Totzek process. Although a variety of improvements have been made to the process the basic gasification process remains the same. According to that process, a mixture of steam and oxygen entrains the pulverized coal and gasifies it in the gasifier or combustion chamber 13, shown in
In general, the gasification process is carried out by partially combusting the pulverized coal with a limited volume of oxygen at a temperature between about 1500° F. and 3600° F. If a temperature of between about 1900° F. and 3600° F. is employed, the syn gas produced will contain minimal by-products such as tars, phenols, condensable hydrocarbons, molten slag particles and salts. The gasification process is usually carried out in the presence of oxygen and steam, wherein the purity of the oxygen is at least 90% by volume, with nitrogen, carbon dioxide and argon being permissible impurities. Some coals contain significant amounts of water which may require drying before gasification. The reaction conditions within the gasifier are maintained by the regulation of the weight ratio of the oxygen to moisture and ash free coal in the range of 0.6 to 1.0, or the range 0.8 to 0.9. Specific details of the equipment and procedures employed are known to those skilled in the art and are described in various sources such as U.S. Pat. No. 4,350,103 and U.S. Pat. No. 4,963,162. Additionally, in one embodiment, Chevron gasifiers can be used to provide the hot syn gas. These types of gasifiers reduce or eliminate the need for cooling the gas prior to injection into the rotary kiln. The ratio between oxygen and steam may be selected so that from 0.0 to 1.0 parts by volume of steam is present per part by volume of oxygen. The oxygen used may also be heated before contact with the pulverized coal. Although not necessary the oxygen may be provided at temperatures from about 380° F. to 950° F. The conditions within the gasifier may also vary widely. The gasifier pressure may vary from about 1 to 500 atm (absolute), with relatively low pressures of up to 40 atm usually being sufficient, and residence times may vary from about 0.1 to 15 seconds.
After the pulverized coal, oxygen, and steam have been reacted, the reaction products, which comprise hydrogen, carbon monoxide, carbon dioxide, water and various impurities, are removed from the gasifier. This product stream, which normally has a temperature between 1500° F. and 3200° F., contains the impurities mentioned and entrained slag, including various carbon-containing solids. In order to facilitate removal of these solids and impurities from the gas, the reaction product stream should be first quenched and cooled.
The gas that is produced from coal gasification is essentially carbon monoxide, hydrogen and carbon dioxide with a relatively small percentage of nitrogen, hydrogen sulfide, carbonyl sulfide, and traces of other compounds. This hot syn gas generally contains from about 10 vol % to about 70 vol %, and preferably from about 25 vol % to 60 vol % hydrogen, from about 10 vol % to about 70 vol %, and preferably 40 vol % to 60 vol % carbon monoxide, and from about 5 vol % to about 30 vol %, and preferably 10 vol % to 20 vol % carbon dioxide. In addition, more than 50% of the ash solids drop down through a quench and is eliminated in gas stream. A coal gasifier for example, using 3,400 tons of coal a day will produce over 364 million cu. ft. of 800 BTU/SCF gas daily. This would be sufficient to produce approximately 50,000 barrels of oil a day according to the method of the present invention.
An advantage of using syn gas from coal gasification is the presence of significant amounts of both hydrogen and carbon dioxide. As mentioned before, the hydrogen atmosphere aids in cracking and pyrolysis of the hydrocarbons while the presence of carbon dioxide further enhances the yield of hydrocarbons. Thus, by carrying out the process of the present invention in an atmosphere containing substantial amounts of both hydrogen and carbon dioxide improved results are obtained.
Another advantage of using hot syn gas from the gasification of coal by the Koppers-Totzek process is found in the fact that this technique produces large amounts of nitrogen in the oxygen step and this can be further reacted with enriched syn gas from the present process to produce valuable anhydrous ammonia as a by-product, described in more detail below. Production of ammonia in this manner appears more reliable than producing ammonia from natural gas.
Referring to
Injected Hydrocarbon
A hydrocarbon material can be injected along with the crushed hydrocarbonaceous solids to achieve improved recovery and results. For example, a liquid hydrocarbon can be injected or sprayed into the rotary kiln. Alternatively, a solid hydrocarbon such as gilsonite, peat, residuums, or the like can be provided as fines and then injected into the rotary kiln, injected along with the hot gas, or provided in a organic slurry. Preferably the solid hydrocarbons can be injected in a dry, non-slurry form. These solid hydrocarbons can preferably be provided as fines having an average diameter of less than about 0.75 inches, and preferably less than about 0.5 inches. A finer solid particle will vaporize and participate in hydrocarbon recovery in a shorter time than larger particles. In one currently preferred aspect, the solid hydrocarbon can be gilsonite. This type of additive can be beneficial as it can be a very cheap feed stock and can improve recovery rates and efficiencies with minimal additional cost and load on the process.
In many circumstances, liquid hydrocarbons can be preferred over solid hydrocarbons as a material which is injected into the rotary kiln. A liquid hydrocarbon, such as crude oil or hydrocarbon product condensates, is also delivered to the rotary kiln 14. The liquid hydrocarbon may be delivered from a container 12 via line 19 at any point in the kiln 14 or added to the crushed solids prior to entry into the kiln. For example, in
In yet an additional aspect, the injected hydrocarbon can be introduced in a co-current flow configuration such as that shown in
Horizontal Rotary Kiln
Referring now to
Although direct heating of the crushed solids can be preferable in some circumstances, indirect heating using the hot gas can also provide sufficient recovery of hydrocarbons from the crushed solids. In one alternative embodiment, the hot gas can be directed to an indirect heating device outside the rotary kiln. In this way the crushed solids are treated by the hot gas via heating. The indirect heating device can be any suitable device for directing heat from the hot gas toward the interior of the rotary kiln and the crushed solids contained therein. In one specific embodiment, the indirect heating device can be a concentric shell oriented around at least a portion of the rotary kiln. The concentric shell can have an inlet and an outlet operatively connected thereto such that hot gas can enter and leave the interior shell space. The concentric shell can form an enclosed jacket around at least a portion of the rotary kiln in a manner similar to a heat exchanger. The hot gas can be syn gas, natural gas, nitrogen, combustion gases, or any other gas having a sufficient heat value to vaporize volatile components from the crushed solids.
The rate of rotation of the kiln can be adjusted as needed to bring about the desired separation and volatilization of the hydrocarbonaceous material. The use of the rotary kiln as described above permits the use of particles having a moderately fine particle size such as those that might be present in the solid materials of the type found in oil shale deposits, although extremely fine particles may become entrained in the gas and necessitate additional scrubbing to remove before fractionation. One also employs a very low pressure in the rotary kiln which will vary over a narrow range, e.g. 5 psi to 30 psi. Pressures from 5 psi to about 15 psi and from about 5 psi to about 10 psi have generally provided satisfactory results. However, it has also been found that increased pressures within the kiln can increase cracking to produce lighter hydrocarbon fractions, increase hydrocracking and separation rates to allow for increased throughput, and improve recovery efficiencies. It is thought that the increased pressure increases the rate at which gases penetrate the solids, thus allowing for improved reaction kinetics and transport kinetics. Further, an increased pressure can prevent oxygen from being drawn into the rotary kiln which may cause dangerous explosive conditions. Unfortunately, higher pressures also create additional practical problems such as leaks and physical limitations of available equipment. As a general matter, pressures inside the rotary kiln can be from about 1 psi to about 500 psi. Current equipment makes pressures above about 100 psi difficult, expensive, and impractical to maintain; however, it is expected that the principles of the present invention can be readily applied to higher pressures should appropriate equipment become available. As a practical matter, pressures from about 1 psi to about 100 psi may be achieved, and preferably from about 10 psi to about 50 psi. It should be noted that these pressures are obviously gauge pressures (psig), i.e. a baseline of 0 psi is atmospheric. Thus, it can be often desirable to operate the rotary kiln at the highest practical pressure that can be achieved for a particular system, depending on the available equipment.
Although catalysts need not be employed in the process of the present invention to obtain the desired results, in some cases it may be desirable to accelerate the production of certain products or improve pyrolysis to employ catalytic materials in the rotary kiln. Such catalysts are commercially available and some common examples include nickel, vanadium, and various heterogeneous catalysts.
As the temperature employed in the kiln is important, it is necessary to maintain proper preheat temperature, syn gas temperature and liquid hydrocarbon temperature to produce the needed temperature in the kiln. Shown below in Table 3, is an illustration of the relationship of preheat temperature and syn gas temperature to bring about the desired kiln temperature.
The parameters are adjusted so that the temperature in the kiln is between 600° F. and 1,000° F. with temperatures between 700° F. and 900° F. giving particularly good results.
As shown in
According to the method of the present invention, between about 88% and 99% of the hydrocarbonaceous material in the original crushed solids is recovered. In most cases, the solids leaving the kiln should have no more than 1 or 2% of hydrocarbonaceous material remaining on the solid particles. At a syn gas temperature of about 1000° F. to 2500° F., a crude oil temperature of about 50° F. to 150° F., a crushed solids entry temperature of 350° F., and particle size of about 0.75 inch of oil shale, a residence time of about 10 to 20 minutes should be sufficient to effect the necessary separation. At 10% load and a residence time of about 12 minutes, the rate of rotation of the rotary kiln is between 2 and 5 rpm. Fifteen minute retention times are current typical operating conditions. However, residence times from about 5 to 90 minutes can be used to achieve a desired yield and separation, and most often from about 10 to about 60 minutes.
These parameters are also controlled so as to minimize the secondary decomposition of the valuable hydrocarbon material to form coke and other undesirable by-products. This can be accomplished in most cases by the use of lower temperatures and shorter reaction periods. It should be noted here that the hydrogen atmosphere has several advantages. As the hydrocarbon material is vaporized and continues to heat, a portion of the material will pyrolyze and crack to form smaller hydrocarbon chains. As long as temperatures are controlled to avoid excessive coke formation this improves the quality and value of the hydrocarbon fractions ultimately recovered. Hydrogen will react with vapors deficient in hydrogen to form more light ends for removal at the fractionation step. The presence of the hydrogen atmosphere brings about a 5% to 25% increase in yield of light end products as compared to the conventional thermal process using hot gas free of hydrogen. Further, the hydrogen atmosphere prevents excessive undesirable secondary decomposition and production of aromatics, toxic off-gases and coke. Under hydrogen-deficient conditions pyrolysis is inefficient and a greater amount of char or coke is produced decreasing the yield of useful hydrocarbons. The hydrogen not only facilitates removal of the hydrocarbons imbedded in the particles, but much of the sulfur present in the crushed solids will be picked up by the hydrogen and may be carried to a sulfur removal unit. Additionally, the presence of a substantial amount of carbon dioxide has proven to positively affect the yields of hydrocarbons from Green River oil shale and Utah tar sands. Typically, a carbon dioxide content of between about 10% and 20% of the incoming hot syn gas provides the cited results.
Any substantially horizontal rotary kiln should suffice for the present invention. Various internal configurations are also possible. Referring to
Product Removal
After the crushed solids travel the length of the rotary kiln, the resulting enriched syn gas, hydrocarbon containing vapors and spent solids are removed from the kiln. The enriched syn gas contains a portion of the original syn gas components, methane, particulates and other light components. As shown in
The products taken from the kiln generally comprise 10-30% enriched syn gases, 5-25% volatilized condensates, 1-10% coke, and 60-85% spent solids. Product yield, excluding the spent solids, from various types of tar sands is illustrated in Table 4.
Key:
ATH—Athabasca Sands,
TST—Tar Sand Triangle,
AR—Asphalt Ridge,
PRS—P.R. Spring,
WIL—Wilmington.
Enriched syn gas analyzed by gas chromatography and mass spectrometry gave the results shown in Table 5 as to the Tar Sand Triangle run.
Typical analysis of the vaporized hydrocarbon is shown in Table 6 giving the carbon and ring analysis of condensates obtained from the Tar Sand Triangle run.
Separation of Gaseous Fractions
The gaseous products removed from the rotary kiln are separated in step 106 of
The quantity of these components, and particularly those in the lighter oil range, are significantly improved by the presence of hydrogen and carbon dioxide in the treating gas as shown in the example below. Typical recovery of oil from oil shale is between about 30 and 36 gallons per ton of crushed oil shale, while average recovery of oil from tar sands is slightly lower at about 20 to 30 gallons per ton of crushed tar sands.
Additional Products
In the embodiment shown in
Referring now to
CO+H2O→CO2+H2
The excess water and carbon dioxide, along with any other impurities are then removed from gas-shift reactor 40 via line 42 to tank 43 and purified hydrogen is produced which is drawn from reactor 40 via line 41 and passed to reactor 44. At this point nitrogen is provided to reactor 44 via line 46 from source 45 (i.e. from the coal gasification step or an air separation process) to form liquid ammonia. The reactants are combined and react according to the equation:
3H2+N2→2NH3
This process is endothermic and may require some additional heating to drive the reaction toward the ammonia product which is taken to tank 49 via line 47 for further use or sale. Actual parameter determinations are easily made by those skilled in process design and reaction kinetics depending on the specific ammonia synthesis process chosen.
Another step in the process shown in
2H2+CO→CH3OH
Moderate temperatures and pressures are generally required. For example, Cu/ZnO and Cu/ZnO/Al2O3, catalysts are used at temperatures between 200° and 300° C. and 50 to 350 atm. Further, the stoichiometric ratio of hydrogen to carbon monoxide in common syn gas is well suited for this reaction with carbon monoxide acting as the limiting reagent. The resulting methanol is then taken from catalytic reactor 36 to tank 38 via line 37 from which it may be sold or used as a precursor for other commercial chemicals. Although yields and selectivity for methanol production vary widely, several processes have improved yields and selectivity to over 50%, and even over 90%.
A portion of the enriched syn gas may also be used to produce urea at step 113, as shown in
2NH3+CO2→H2NCONH2+H2O
The reaction is carried out at moderate temperatures of about 250° F. and 400° F. and a pressure of between about 100 and 350 atm. The final urea product is removed from reactor 50 via line 53 to tank 54. The urea product is then used or sold and is most commonly used as a fertilizer.
In another aspect of the present invention the enriched syn gas may be further separated to produce natural gas in step 114, as shown in
In another more detailed aspect of the present invention a portion of the enriched syn gas is removed for use as a fuel mixture which is burned and used to generate electricity in a combined cycle electricity generation step 110 of
A simplified view of such a combined-cycle process is shown in
Further, the spent solids recovered in step 107 of
The description herein is designed to enable those skilled in the art to practice the method of the present invention and as such details well within the capacity of those skilled in the art will require some design and experimentation to determine exact operating parameters. Further, not all possible interconnections have been explained and diagrammed. For example, the water source 60 may be supplemented by water condensed from the gas-shift reactor off-gas tank 43 shown in
The operation of the process of the invention is illustrated by the following example showing the use of hot syn gas obtained from the gasification of eastern coal and crude oil for the pyrolysis of Green River oil shale.
For the hot syn gas production step, 5,000 lbs. of eastern coal was dried to between 2% and 8% moisture and crushed to particle size of about 0.75 inch. The crushed coal was conveyed into a feed bin where it was continuously discharged into a mixed nozzle where it was entrained in oxygen and low-pressure steam. Moderate temperature and high burner velocity prevented the reaction of coal and oxygen before entry into the gasification zone. The oxygen, steam and coal reacted in the gasifier at a temperature of 3330° F. The carbon and volatile matter of the coal was gasified to produce a hot syn gas, and the coal ash converted into a molten slag. About 50-70% of this slag was dropped into a water quench tank and was carried from the tank to the disposal system as a granular solid, and the remainder is entrained in the gas exiting the gasifier. Gas leaving the gasifier was quenched to remove any entrained slag droplets and then passed through a heat exchanger to reduce the temperature to about 2100° F.
Green River Oil Shale was crushed to particle size of less than about 0.75 inch at 70° F. and passed into a preheater where it was preheated to a temperature of 350° F. and then taken by screw conveyor to a rotary kiln. The particles were cascaded over the hot syn gas at 2100° F. obtained from the coal gasification process described above. Further, crude oil at 80° F. was sprayed into the kiln at the entry point of the hot syn gas. The crushed solids outlet temperature was about 1000° F. and the outlet gas and vaporized materials temperature was about 1100° F. The kiln at a 5° slope was rotated at 5 rpm and a residence time of about 20 minutes. The vaporized hydrocarbons, enriched syn gas and spent solids were then passed to a separator hopper. The spent solids were removed at the bottom by screw conveyor and the vapors and gas taken to a cyclone where fine particles were removed and thence to the fractionation column. The data from this run is shown in Tables 8 and 9 below. The yields are calculated excluding the spent solids.
The vaporized hydrocarbon was then subjected to fractionation resulting in the hydrocarbon fraction yields as shown in Table 9.
The above process was repeated without the use of a gas containing hydrogen and carbon dioxide and resulted in much lower yield of light end products. As noted above, the presence of the hydrogen and carbon dioxide gives from 5% to 25% increase in the yield of the light end products.
CONCLUSIONThe process of the invention can be operated on a batch, semi-continuous or continuous manner and is ideally suited for large-scale continuous operation. A plant designed to handle 75,000 tons of shale a day would yield 50,000 barrels a day of oil, 1,440 tons of liquid ammonia by-products or the equivalent of 26,300 barrels of methanol, 63,000 tons of cement feed, and minimal off-gases.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. The present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore to be embraced therein.
Claims
1. A thermal method for treating crushed hydrocarbonaceous solids to extract hydrocarbons therefrom, comprising the steps of:
- (a) preheating a crushed hydrocarbonaceous solids;
- (b) treating the preheated crushed hydrocarbonaceous solids in a substantially horizontal rotary kiln having an upper end and a slight slope downward with (i) a hot gas at an elevated temperature, and (ii) an injected hydrocarbon which vaporizes, wherein pressure inside the rotary kiln is greater than atmospheric pressure and the crushed solids are introduced at the upper end of the rotary kiln and are heated by the hot gas for a sufficient time to vaporize volatile components from the crushed solids to produce vaporized hydrocarbon materials and spent solids; and
- (c) removing the vaporized hydrocarbon materials and spent solids from the horizontal rotary kiln.
2. The method of claim 1, wherein the hot gas is injected inside the rotary kiln and the injected hydrocarbon mixes with the hot gas.
3. The method of claim 1, wherein the hot gas is directed to an indirect heating device outside the rotary kiln.
4. The method of claim 3, wherein the indirect heating device is a concentric shell oriented around at least a portion of the rotary kiln.
5. The method of claim 1, wherein the hot gas is syn gas, nitrogen gas, hydrogen gas, carbon dioxide gas, carbon monoxide, or combinations thereof.
6. The method of claim 5, wherein the hot syn gas containing hydrogen is introduced into the kiln at a temperature between 700° F. and 2500° F.
7. The method of claim 3, wherein the hot syn gas containing hydrogen is obtained from coal gasification.
8. The method of claim 1, wherein the pressure inside the rotary kiln is from about 1 psi to about 100 psi.
9. The method of claim 1, wherein the crushed hydrocarbonaceous solids are preheated to a temperature between about 100° F. and 350° F. before being introduced into the kiln.
10. The method of claim 1, wherein the crushed solids have a residence time in the kiln of from about 5 to 90 minutes.
11. The method of claim 1, wherein the injected hydrocarbon is a solid gilsonite hydrocarbon.
12. The method of claim 1, wherein the injected hydrocarbon is a liquid hydrocarbon which is introduced into the kiln at a rate of between about 5 and 50 gallons of liquid hydrocarbon per ton of crushed hydrocarbonaceous solids.
13. The method of claim 1, wherein the injected hydrocarbon is liquid crude oil.
14. The method of claim 13, wherein the crushed hydrocarbonaceous solids is oil shale.
15. The method of claim 13, wherein the crude oil is introduced into the kiln at a rate from about 30 and 50 gallons of crude oil per ton of crushed oil shale.
16. The method of claim 13, wherein the crushed hydrocarbonaceous solids are tar sands.
17. The method of claim 16, wherein the crude oil is introduced into the kiln at a rate from about 20 and 25 gallons of crude oil per ton of tar sands.
18. The method of claim 1, further comprising the step of fractionating the vaporized hydrocarbon materials into desired fractions.
19. The method of claim 18, wherein the hot gas is a syn gas which is injected inside the rotary kiln and forms an enriched gas during contact with the crushed solids, and wherein the enriched gas from the step of fractionating is passed through a catalytic converter to form methanol.
20. The method of claim 18, wherein the hot gas is a syn gas which is injected inside the rotary kiln and forms an enriched gas during contact with the crushed solids, and wherein the enriched gas from the step of fractionating is combined with nitrogen from a coal gasification process to produce liquid ammonia.
21. The method of claim 1, further comprising the step of producing electricity in a combined cycle comprising:
- (a) recovering an enriched gas from the rotary kiln for use as a fuel gas;
- (b) combusting the fuel gas to produce a first heated gas which is directed to a gas turbine which is operatively connected to a first generator wherein the first heated gas is reduced in pressure through the gas turbine to produce a second heated gas; and
- (c) using the second heated gas to produce steam which is directed to a steam turbine which is operatively connected to a second generator.
22. A system for extracting hydrocarbons from hydrocarbonaceous solids comprising:
- (a) a substantially horizontal rotary kiln having an upper end and a slight slope downward to a lower end and having a crushed hydrocarbonaceous solids source operatively connected to the upper end;
- (b) a hot gas source in thermal communication with the rotary kiln;
- (c) a liquid hydrocarbon source operatively connected to either the upper end or the lower end; and
- (d) a separation chamber operatively connected to a lower end of the horizontal rotary kiln.
23. The system of claim 22, further comprising a fractionation column operatively connected to the separation chamber.
24. The system of claim 22, wherein the hot gas source is a coal gasifier configured to produce a hot syn gas.
25. The system of claim 22, further comprising a combined-cycle electricity generator operatively connected to the separation chamber.
26. The system of claim 22, further comprising an indirect heating device oriented around at least a portion of the rotary kiln.
Type: Application
Filed: Oct 11, 2005
Publication Date: Apr 13, 2006
Inventor: Anthon Smith (Lindon, UT)
Application Number: 11/249,037
International Classification: C10G 1/00 (20060101);