IL100798A

IL100798A - Method for the exploitation of oil shales

Info

Publication number: IL100798A
Application number: IL10079892A
Authority: IL
Original assignee: Gewertz Moshe; Yam Kiryat; Kz Cemeon; Feldman Issa
Priority date: 1992-01-29
Filing date: 1992-01-29
Publication date: 1994-08-26
Also published as: RU2049804C1; BR9300270A; DE4302040A1; IL100798A0

Description

METHOD FOR THE EXPLOITATION OIL SHALES THE APPLICANT: 1. Mashe GEWERT2 (507.) (50%) γ~ΐ .ΐλ num .1 10/1, Jacob Nimri St. Kiryat- jv~ip ,10/1 npi 'inj . Cemeon AZANS Y (85%) (E5*/.) 'poup IT wo .a 11, Kadimah St. Haifa. .Π3 ■* π ,11 nn 1 nrp aim 3. Issa FELDMAN (25'/.) (25*/.) 1»T75- n ^ .3 3a', Itzhac St. Haifa. . Π31 π , ' N3 n^ ' n 1 rn THE INVENTOR : Moshe GEWERTZ lO/t, Jacob Nimri St. Kiryat-Yam. .α'-Π'Π , lO/l 3 .V 'IMJ The present invention relates to a new process for the exploitation of oil shales. More particularly, the invention relates to a new process for the recovery of valuable components from oil shales which are low in organic matter and rich in mineral constituents.

BACKGROUND OF THE INVENTION The term oil shales covers a wide variety of laminated sedimentary rocks containing two main constituents: (1) Organic matter, that can be released by destructive distillation, and (2) mineral constituents which consist mainly of clay, calcite, dolomite and iron compounds.

Oil shale deposits occur in many countries of the world and in sedimentary rocks of virtually all ages. These deposits vary widely as to size,constitution and strength of the shale. Broadly, two main categories of oil shales can be distinguished:oil shales which are rich in organic matter and contain relatively low mineral constituents, and those which are low in organic matter and rich in mineral constituents. Thus for instance, oil shales from Green River (U.S.A.) contain 22.1 CaO and 70% conversion of organic matter to oil, whereas these from Israel contain 64.8% CaO and said conversion is only 48%. On the other hand, oil shales from Iraty (Brazil) contain only 2.6% CaO. These figures clearly indicate the big diffe- rences which exist in the constituents of oil shales from various sources.

Application of heat is the only means that has been found for producing shale oil and numerous mechanical devices known as retorts, have been developed for this purpose. Retorting involves the crushing and heating at high temperatures of about 500°C raw shales followed by cooling and discharging of almost equally large quantities of spent shales. While this method is feasile and even economically applicable for oil shales which are relatively low in organic matter, such as in Autumn (Prance), it was not considered economically to be utilized for oil shales which are low in organic matter but contain high amounts of minerals, such as in Israel.

The first recorded reference on processing of oil shales is a U.K. Patent dated 1694, in which oil was distilled out from "the stone". Later on, many processes were developed based on retorting, inserting improvements for the recovery of as much as possible of the energy present in the oil shales. The main disadvantages of retorting are high-energy requirements, low conversion of the organic matter to liquid and the presence of olefins and heteroato s in the product.Attempts were tried to obviate the energy requirements, by utilizing solvent extraction of the oil shales at ambient temperature. Using common solvents for petroleum, such as benzene, acetone, carbon disulfide, etc. only a very small amount of the organic matter could be extracted.

As known, the organic matter in oil shales is mainly an insoluble, solid material called kerogen, which has a high molecular weight being of a polymeric nature.Oil per-se is not present in oil shales,but upon its pyrolysls at about 500°C, a liquid hydrocarbon with some gaseous products and a solid residue is generated. There are some prior patents claiming the extraction of oil shales kerogen in common organic solvents at temperatures in the range of 200°C to 400°C. Significant amounts of oils were indeed extracted at these temperatures, reaching up to 85% at 350°C but excessive vaporization and cracking of the solvent rendered the process to be inoperable.

In a recent U.S. Patent (4,737,267) a method is described for extracting samples of U.S. oil shales with a supercritical toluene at about 400°c and a pressure of about 1200 psi. Under these conditions it is claimed that an increase in the oil yield extracted was achieved.

An interesting thermal solution process was recently published (1988 Eastern Oil Shale Symposium Proceedings, p. 301-313) by Cha.,C.Y. et al. The process involves three main steps: (1) pyrolysls of the oil shales in the presence of recycled product oil at a temperature below 400 C; (2) pyrolysis of the residue at a temperature above 400°C and (3) combustion of the solid residue and pyrolysis gas to generate process heat. The process seems that has some beneficial aspects particularly for those oil shales which are rich in organic matter.

The conclusion which can be found in the prior art on this subject is that the solvent extraction based on a supercritical fluid, seems that has some advantages which appear to outweigh their disadvantages and should be considered as the most promising route for the exploitation of oil shales.

There are some references which deal particularly with the processing of oil shales which contain high amounts of mineral constituents. In a report by A.B. Vol'Epshteln et al (Khimiya Tvendogo Tapliva, Vol.14, 2, 67-70, 1980), there are summarized some experiments on the thermal dissolution of Baltic combustible shales, carried out in a flow-through apparatus. The oil shales were heated for 6 to 10 hours at a temperature in the range of 400°-430° at a pressure of 30 to 50 atmospheres, in the presence of a solvent which has a boiling point in the range of 210° -340°C. The ratio between the solvent to oil shales was 1.3 to 1. Under these conditions, occurs a degradation of the organic matter present in the oil shales which are transformed into a soluble state, due to a cracking reaction obtaining a heavy oil-extract as the main product. This extract is mentioned to be useful as a power fuel, as a raw material for the production of electrode coke, as bitumen for road building and as a crude oil for obtaining hydrocarbons. The separation of the liquid products is carried out by distillation.

In the Israeli Patent No. 51676, there is claimed a process for the production of fuel gas and hydrocarbons from carbonate-containing oil shales. According to this process the following steps are involved; (a) oil shales are retorted at a temperature of about 500°C by hot gases which comprise mainly hydrogen, c°2» CO and steam; (b) the residual coke-containi g gravel is further heated at a temperature of up to 1100°C in the presence of steam and air; and (c) the calcined lime residue of the oil shales is quenched in water producing steam and a slurry of slaked lime which is disposed of.

The above brief review clearly indicates the interest which is attributed to the subject of exploitation of oil shales by many scientists, particularly in these days, looking for an alternative source to fuel to be produced in a most economical way.

It is an object of the present invention to provide a process for the exploitation of low grade oil shales. It is anobher object of the present invention to provide a process in which the two main constituents of said low grade oil shales - organic matter and mineral moiety -are efficiently recovered as valuable products. It is! yet another object of the present invention, to provide a process for the exploitation of low grade oil shales and even possible without producing any reject which has to be disposed of.

BRIEF DESCRIPTION OF THE INVENTION The invention consists in a process for the thermal dissolution of oil shales which are rich in mineral constituents (hereinafter referred to also as low-grade oil shales) and possess a low content of organic matter which comprises the steps of: (a) cracking a mixture of said oil shales with a heavy fraction of heavy fuel having a boiling point of above 350°C at a temperature in the range of 350-600°C and a pressure of 5 to 80 atmospheres the ratio between said fuel fraction and oil shales being in the range of 0.5:1 and 5:1; (b) recovering from the gases going out from the cracking reactor a hydrocarbon fuel having a boiling point of up to 350°C and (c) the residue produced, which comprises the mineral constituents, being recovered and used as a raw material for various purposes. It was unexpectedly been found that the above particular type of oil shales, possess a surprising catalytic effect on the cracking of a heavy fraction of fuel by producing valuable fractions of hydrocarbon fuel. The process according to the present invention has the beneficial effect that imparts a substantially complete exploitation of the oil shales constituents: - valuable fuel products from the organic matter, and . useful by-products from the mineral part, which is a major fraction of this type of oil shales, as a raw raw material for many purposes.

DESCRIPTION OF THE DRAWINGS Figure 1, illustrates the behaviour of cracking reaction of a heavy fraction of fuel alone (graph A), and the behaviour of the same heavy fraction of fuel in the presence of the low grade shales (graph B).

Figure 2, is a schematic flowsheet of the process according to the invention.

From Figure 1, it can be noticed the beneficial effect imparted to the cracking of a heavy fraction of fuel in the presence of the low grade shales.The physical properties of the heavy fraction of fuel used in the cracking reactions illustrated in these graphs were as follows: - Specific gravity: 0.99 g/ccy - Viscosity: above 150cps at 80°C, and - Boiling point (beginning) 370-400°C.

Thus, whereas in the cracking reaction of the heavy fraction of fuel alone, resulted only a small amount of products having a boiling point of up to 300°C which raises a pressure below 10 atmospheres, compared with a significant greater amount of products which raises a pressure of about 70 atmospheres, resulted with the same fraction of heavy fuel in the presence of said oil shales.

In Figure 2, it is presented the flowsheet of the process which comprises the following parts: A vessel (1) which contains the heavy fraction of fuel, boiling point above 350°C, being one of the constituents of the mixture to undergo the cracking reaction. In case that said fraction of fuel appears as a solid or as a viscous material, a heating element (la) is provided in the vessel. The oil shales to be used, enter from the container (2) and are mixed with said fraction of fuel in the vessel (3).The homogenized slurry is conveyed through a pump (4) into a cracking reactor (5) provided with a chimney (6). The products resulted from the reactor are conveyed into a separator (7).

The by-product from the cracking unit comprises the solid generated from the mineral constituent of the oil shales. A major part which contains calcium oxide, is passed through a conveyor (8) situated in the cracking unit. Due to the particular active state of the calcium oxide, it will be useful to adsorb the hydrogen sulfide^ from the gaseous stream going out from the cracking reactor. In this manner the fuel product will be substantially-free, fact which has a particular advantage from an environmental point of view. This is an additional advantage of the process, since this desulfurization is obtained without any additional reagent.

The main gaseous stream is condensed and entered into a separator (11) provided with cooling water (12) and exit water (1.3), the final by-products being accumulated into two vessels (14 and 15). The hot gases (17,18) which accompany these products are recycled to the container (1) and will assist the heating of the heavy fraction of fuel which enters in the cracking reactor (5).

Another solid material obtained as a by-product from the separator (7), contains coke coated on the mineral constituent and is accumulated (22). This material can be used as a substitute to the natural coal. This solid material may also be recycled in the process according to this invention by its burning in the reactor (5) and the resulted hot gases will heat the mixture of oil shales and heavy fraction of fuel. In this manner a better heat recovery for the entire process is achieved.

Another use for the solid residue is as a raw material for the manufacture of asphalt.

Still another use for this solid residue, which is very rich in minerals is in the manufacture of cement as known from some prior references.

The cracking per-se of hydrocarbons is indeed known,being carried out in the presence of costl catalysts, which has to be regenerated after one or two stages. This is due to the fact that some coke, which is generated during the cracking, covers the surface of the catalyst until it will be deactivated. This is actually considered as one of the main reasons why in the usual cracking, only light fractions of fuel, which produce less coke, are suggested to be used. Contrary to this usual cracking, according to the present invention any heavy fraction of fuel, including even a solid residue from any refinery plant, which is liquefied by heating in the vessel (1) can be utilized. The main role of the heavy fuel fraction, and if required after heating, is to dissolve the organic matter from the oil shales.

The weight ratio between the heavy fuel fraction to the oil shales in the cracking reaction is generally in the range of between 0.5:1 to 5:1, depending on the particular products and by-products which are desired to be obtained. Thus, when more hydrocarbons and less coke are desired, this ratio should be in the range of 0.5 1 to 2:1. Whereas when more coke, to be used instead of coal - Il ¬ ls desired, this ratio will be preferably in the range of 2:1 to 5:1.

The particles size of the oil shales which enter in the cracking reactor, depends on the desired product. In case that the main purpose is to produce fuels as a source for energy, particles size in the range of 0.05mm to 5 mm. On the other hand, in case that asphaltene are desired, to be used as a raw material for asphalt production, and fuel are the main desired products to be obtained, smaller particles size of oil shales of below 0.3 mm and even of 0.05 mm are to be preferred.

The pressure which will prevail in the cracking reactor is in the range of 5 to 80 atmospheres and depends on the particular fraction of fuel used in the process as well as on the desired products to be obtained.

The most preferred temperature for carrying out the cracking reaction, will be in the range of between 330°C to 570°C.

The beneficial effect imparted to the cracking of a heavy fraction of fuel by the low grade oil shales, appears clearly from the following Table 1 which summarizes some cracking experiments. The heavy fraction of fuel utilized was a residue from a viscosity breaker plant (specific gravity 0.99 g/cc) from the Refinery (Haifa, Israel). The weight ratio between said fuel fraction and oil shales was 2:1. A comparative experiment of cracking was carried out with the same fuel fraction but in the absence of said oils shales.

Table 1 : Fuel fractions obtained by the cracking of heavy fraction of fuel alone (A) and of the same fuel fraction in the presence of low grade oil shales (B).

Up to 175°C Up to 200°C Up to 235°C Up to 350°C A: 0 0 456 17% Bs 20% 25% 30% 57% The above results clearly show, that the most useful fractions of fuel, i.e. with a boiling point of up to 235°C, which result by cracking of a heavy fraction of fuel, can be obtained only in the presence of low grade oil shales. In the absence of said oil shales, only a small fraction with a a very high boiling point was obtained.

The process according to the present invention is characterized by its versatility, whereby the products which could be obtained from the separator and the resulted by-products, can be obtained by adjusting the reaction conditions and the ratio between the components. High pressure of above 20 atmospheres or ratio of 2:1 fuel to oil shales, will produce more asphaltenes to be used for the manufacture of asphalt. On the other hand, when more calcium oxide is desired to be used as a filler or as a desulfurizing agent, a low pressure of about 5 atmospheres will be used. In case that the object of the process is to utilize a maximum amount of oil shales and to . recover the organic matter as fuel, or as raw material for producing chemicals, the heavy fractions (boiling point above 350°C) will be recovered, while the lighter fractions (boiling point below 350°C) can be recycled to the cracking reactor as a solvent of the organic matter present in the oil shales.

While the invention will be hereinafter illustrated by some specific Examples, it should be understood that these Examples are presented only for a better understanding of the invention, without limiting the scope of the invention, A person skilled in the art, after reading the present specification will be in a position to insert some modifications, without being outside the invention as covered by the appended Examples.

The concentrations mentioned in the Examples are by weight percentage.

Claims

- 16 - 100,798/2 C L A I M S :

1. A process for the utilization of the organic and mineral constituents present in oil shales by a thermal dissolution of organic matter, which comprises the steps of: (a) cracking a mixture of oil shales low in organic constituents, with a fraction of heavy fuel having a boiling point of above 350°C, at a temperature in the range of 350° to 600°C and a pressure in the range of 5 to 80 atmospheres, the weight ratio between said fuel fraction and oil shales being in the range of between 1 :0.5 and 1 :5; (b) recovering from the gases emanating from the cracking step (a) a hydrocarbon fuel having a boiling point of up to 300°C, and (c) utilizing the resulting residue containing the mineral constituents as a raw material in the chemical industry.

2. The process according to Claim 1, wherein said cracking is improved by the presence of said oil shales.

3. The process according to Claims 1 or 2, wherein the temperature during the cracking reaction is in the range of 500°C to 570°C.

4. The process according to Claims 1 to 3, wherein the particle size of the oil shales is in the range of between 0.05 to 5 mm.

5. The process according to Claim 1,wherein th.e lighter fractions of fuel resulting from the process,are recycled to the cracking reaction to dissolve the organic matter present in the oil shales.

7. \ The process according to Claim 6, wherein said calcium oxide is utilized for the desulf urization of the resulting gases going out from the cracking reactor.

8. The process according to Claim 1, wherein the gases going out from the cracking reactor are used to heat the mixture of oil shales and heavy fuel fraction.

9. The process according to Claim 1, wherein the ratio between the heavy fraction of fuel to the oil shales is in the range of 0.5:1 to 2:1, producing a significant amount of hydrocarbons.

10. The process according to Claim 1, wherein the weight ratio between the heavy fraction of fuel to the oil shales is in the range of 2:1 to 5:1.producing a significant amount of coke.

11. A process for the utilization of the organic and mineral constituents present in oil shales, substantially as described in the specification and claimed in any one of the previous Claims. For the Applicants, Patent Attorney EXAMPLE 1. The following reagents were introduced into a retort: 50.8 g of oil shales, containing 64.8% calcium oxide and about 10% organic matter, and 81 g of a heavy fuel residue, 75% thereof having a boiling point of above 375°C. The retort was heated for about 60 minutes at a temperature of 420°C. The pressure in the autoclave was about 55 atmospheres. The following fuel fractions were obtained: Up to 200°C: 25%. Up to 350°C: 60%. Up to 375°C: 70% and Above 375°C: 30%. EXAMPLE 2. An amount of 40 g of the oil shales, as in Example 1, was mixed with 82 g of a fuel residue, 50% thereof having a boiling point of above 350°C. The mixture was introduced into a retort and heated at 385°C for about 70 min. The pressure was about 63 atmospheres. The following fuel fractions were obtained: Up to 150°C: 8%. Up to 230°C: 18%. Up to 310°C: 40% and Above 310°C: 60%. EXAMPLE 3. An amount of 101.7 g of the oil shales as in the previous Examples, was mixed with 190 g of the same fuel residue as in Example 2. The mixture was introduced into a retort - 15 - and heated at 400°C for about 75 tnin. The pressure was about 40 atmospheres. The resulted product consisted of 9.2% of fuel which could replace the commo diesel oil, 50.8 of gas oil and 11.9% of petrol coke.