METHOD FOR THE ENERGY-EFFICIENT AND ENVIRONMENTALLY FRIENDLY OBTENTION OF LIGHT OIL AND/OR FUELS ON THE BASIS OF CRUDE BITUMEN FROM OIL SHALES AND/OR OIL SANDS

Abstract

The present invention relates to a method for the energy-efficient and environmentally friendly obtention of light oil and/or fuels on the basis of crude bitumen from oil shales and/or oil sands (1) by thermal use of carbonaceous residues which are obtained during this process, whereby the carbonaceous residues are converted at temperatures below 1800° C. into sulfur-poor, gaseous cleavage products (31) by sub-stoichiometric oxidation with oxygen-containing gas in an updraft gasifier (19) which is operated with a bulk material moving bed while alkaline substances are added. The cleavage products are then converted into sensible heat by hyperstoichiometric oxidation and are used for the production of heated aqueous process media (2) for physically comminuting the oil sands and/or oil shales (1) and/or for separating of the crude bitumen (7) from the rock material and/or as process heat for the thermal fractioning (12) of the crude bitumen (7).

Description

The present invention relates to a method for energy-efficient, environmentally friendly extraction of light oil and/or fuels from crude bitumen from oil shale and/or oil sands (A) by thermal exploitation of carbon-containing compounds (E) occurring in this extraction.

Because of the strong worldwide demand for fossil fuels and petroleum-based raw materials, as well as the expected long-term scarcity of conventional petroleum, the recovery of energy carriers and raw materials from oil shale and/or oil sand resources is becoming increasingly important.

Naturally occurring oil sands or oil shale comprise natural rock and contain up to 20% of a bitumen mixture. This bitumen mixture essentially contains organic carbon compounds with different molecular weights and boiling points.

BACKGROUND OF THE INVENTION

To make these carbon compounds accessible to purposeful extraction, the bitumen mixture must first be separated from the natural rock component.

The separation of the bitumen from these natural rock masses can be done essentially via two technologies.

Quarrying by open pit mining:

In this method, the rock mass containing bitumen is carried away using overburden dredgers or wheel loaders and transported to the processing plants with heavy road vehicles. The processing is done as a rule in the following process steps:

1. Breaking up/comminuting the rock, as a rule while supplying water vapor or hot water

2. Sending the resultant suspension to the first extraction step, where sediment and water form as the lower separation layer, and bitumen with foam forms as the upper separation layer.

3. Carrying away the lower sediment and water layer to usually artificial lakes or water lagoons.

4. Carrying away the upper bitumen layer to the second extraction step, where residues of water and fine particles are separated out. The bitumen is usually dissolved in an organic solvent (as a rule, “naphtha”, which is a product of the light-oil recovery process). What is obtained is so-called crude bitumen.

5. The crude bitumen is sent to ensuing bitumen processing (“upgrading”).

Recovery by the so-called “in-situ method”:

In this technology, the crude bitumen is already recovered in the soil, below the surface and without breaking up the rock masses. This is accomplished as follows:

6. High-pressure water vapor is injected into deep bitumen-containing rock strata. As a result, a thermal liquefaction of the crude bitumen is achieved.

7. This liquefied crude bitumen is carried purposefully into underground collection points and pumped from there to the surface, by means of suitable pumping technology.

8. The crude bitumen thus recovered then, as a rule, follows the same further procedure as in step 5 above.

Extraction of light oil and liquid fuels from crude bitumen:

The crude bitumen (possibly from both recovery methods) is combined in the next processing plant (“upgrading”). There, the following process steps are usually performed:

9. From the mixture comprising crude bitumen and naphtha, the volatile hydrocarbons are distilled off. At the end, what remains is an insoluble residue, called pet coke. Depending on the material used, it can contain up to 10% sulfur components.

10. The gaseous hydrocarbons from the distillation are separated by fractionated condensation into naphtha, kerosene, and gas oil; naphtha is as a rule at least partially returned to the process

11. Depending on the quality required of the individual fractions, desulfurization can be done in the further step. This is usually done by means of hydrogenation and separating out of the elemental sulfur.

12. At the end of the process come the storage and shipping out of the liquid fractions.

However, the method described above for recovering light oil and fuels from oil shale and/or oil sands has considerable disadvantages.

For instance, extracting the crude bitumen from the rock masses requires considerable amounts of hot water and water vapor. Per volumetric unit of light oil, up to 6 volumetric units of water have to be used. The preparation of steam and hot water is usually done in boilers fired by natural gas. The demand for natural gas is extremely high and leads to an extraordinarily unfavorable energy balance of the entire process. Moreover, as a result the specific CO₂ emissions per barrel of light oil obtained is fundamentally unacceptable ecologically and in view of the need to use valuable resources sparingly.

The pet coke remaining behind in the distillation of the crude bitumen (step 9) contains sulfur in concentrations of up to 10%. This is fundamentally a valuable energy carrier. However, because of its high sulfur content, it cannot readily be used in combustion processes, such as for generating water vapor or hot water. Ensuring environmentally sound thermal exploitation is therefore questionable and is possible, if at all, only at disproportionate expense for flue gas desulfurization.

For the present invention, the object has therefore arisen of furnishing a method which does not have the disadvantages of the prior art but permits energy-efficient exploitation of carbon carriers contained in oil sands and/or oil shale, which handles fossil fuels (such as natural gas) sparingly, and which on its own can generate sufficient energy carriers to supply the requisite energy demand for the exploitation process, at least in part.

This is attained according to the invention in that the carbon-containing compounds contain sulfur and by substoichiometric oxidation with oxygen-containing gas in a countercurrent gasifier operated with a moving bed of bulk material are converted, with the addition of alkaline substances, at temperatures <1800° C. into low-sulfur gaseous cleavage products, and these cleavage products are then converted by superstoichiometric oxidation into perceptible heat, and are used for generating heated aqueous process media for a physical comminution of the oil sands and/or oil shale and/or for separating the crude bitumen out of the rock mass and/or as process heat for a thermal fractionation of the crude bitumen.

It has been demonstrated that the residues that were not heretofore exploited because of the problems with sulfur are capable of improving the energy balance in the recovery of light oil and/or fuels from oil shale and/or oil sands considerably. By the appropriate exploitation of the carbon ingredients, the threat to the environment from carbon compounds that until now remained in the residues is overcome as well.

For example, as carbon-containing compounds, solid residues from the aqueous separation of crude bitumen from the rock mass and/or solid residues from the thermal fractional distillation of the crude bitumen can be used.

A refinement of the method is especially advantageous in which the countercurrent gasifier is embodied as a vertical process chamber with a calcination zone and an oxidation zone, in which the calcined carbon- and sulfur-containing residues oxidize with oxygen-containing gas, and the gaseous reaction products are drawn off at the top of the vertical reaction chamber, in the form of a vertical shaft furnace, through which a bulk material that itself is not oxidized flows continuously from top to bottom, and the oxygen-containing gas is introduced at least partially below the oxidation zone, thereby further advancing the rising gas stream. The advantage of an inert bulk material is that the mechanical properties of the pile can be more easily varied and adapted to the essential aspects of the method.

Examples of as alkaline substances that can be used are metal oxides, metal carbonates, metal hydroxides or mixtures thereof, which are metered into the gas phase above the calcination zone and/or are admixed with the carbon-containing compounds before entering the vertical process chamber. Elements of the alkali metals or elements of the alkaline earth metals, especially calcium, are preferred for forming the metal oxides, carbonates of hydroxides, since particularly in the form of calcium oxide, catalytic effects have a favorable effect on the courses of the method.

Adding the alkaline substances at least partially in fine-granular form, with a particle size of <2 mm, has proved advantageous, as has a substoichiometric oxidation at a λ of <0.5, especially preferably <0.3.

The sulfur-binding mechanisms proceed especially advantageously by addition of alkaline substances under reductive conditions, in which the gaseous sulfur compounds occurring in the countercurrent gasifier at temperatures of above 400° C. from the ingredients of the carbon-and sulfur-containing residues are converted by chemical reaction with the alkaline substances into solid sulfur compounds, and these solid sulfur compounds are at least partially carried out with the gaseous reaction products, and are removed from the gas phase by fine-material separation at temperatures above 300° C. In this way, the sulfur can be removed from the process especially economically.

In a desired course of the method, in the vertical process chamber and/or in the gas phase of the drawn-off gaseous reaction products in the presence of water vapor and calcium oxide and/or calcium carbonate and/or calcium hydroxide, a calcium-catalyzed reformation of substantial proportions is performed, at temperatures of above 400° C., of the resultant cleavage products, containing oil and/or tar, that have a chain length of greater than C4, into carbon monoxide, carbon dioxide, and hydrogen.

The moving bed of bulk material is preferably formed by additional metering of coarse material, in order to increase the flowability of the bulk material and/or its gas permeability, and the coarse material is admixed with the carbon-containing compounds before entering the vertical process chamber. As the coarse material, mineral substances and/or other inorganic substances, such as mixtures of substances, having a particle size in the range of from 2 mm to 300 mm, and especially preferably oil sand and/or oil shale, can be used. The latter case is especially preferred, since as a result, a method course in which resources occurring on site can be used and exploited directly is made possible.

Using wood and/or other biogenic materials as coarse material, with a suitable particle size, can also be advantageous. Often, these materials are available in the vicinity of the site where the method is performed, so given the short transportation distances, their use is favorable for the sake of overall energy efficiency.

Inert bulk material can be separated off at the lower end of the vertical process chamber from the fine material and ashes produced and can be returned at least partially to the process as coarse material, so that the distances the masses have to be moved can be kept short. It can also be advantageous to convert the carbon-containing compounds before their use in the countercurrent gasifier by agglomeration into particles with a particle size in the range between 2 mm and 300 mm, in order to improve the flowability of the bulk material and/or its gas permeability, as is done with the additional metering in of coarse material.

For the gas countercurrent, the development of a differential pressure in a range of from 50 to 100 mbar (ü) in the vertical process chamber, between the top and the bottom, has proved advantageous.

FIG. 1 shows one example of an integrated method for producing light oil and fuels by breaking down the oil sands and oil shale in open pit mining.

The oil sands and oil shale (A) quarried by open pit mining are mechanically comminuted via breaker systems (1). This is usually done by mixing in hot water or also water vapor (2). Hot water/water vapor is produced in boiler systems (3).

The suspension resulting from the mechanical comminution is delivered to a first extraction stage (4). Here, as a rule, hot water/water vapor is added again. After intensive mixing, in the extraction stage (4) a separation of the phases is performed by settling. A water/sediment phase (B) forms as the lower phase. It is separated off and usually deposited in artificial lagoons or lakes (6).

The upper phase (7) essentially contains crude bitumen. It is separated off and delivered to the next process step (C).

In the first extraction stage, a middle phase (8) forms as a rule; besides water/sediment, it can also contain significant amounts of crude bitumen. This middle phase can be delivered to a second extraction stage (9). Here, a second separation is performed, in which the lower water/sediment phase (D) is separated off and likewise deposited in artificial lagoons or lakes (6). The upper phase (10) essentially contains crude bitumen and is likewise delivered to the next process stage (C).

In process step (C), the crude bitumen can be mixed with organic solvents, such as naphtha (11), which is obtained as a product in the later bitumen refining process. Depending on the quality of the bitumen, undissolved residues (E), also called pet coke, can occur here.

The dissolved crude bitumen is delivered to a distillation stage (12), where the volatile ingredients are evaporated off by adding heat by means of hot steam (13) from the boiler systems and using suitable distillation equipment; additional pet coke (E) remains behind, as a nonvolatile ingredient. This pet coke comprises carbon-rich residues, which have a high thermal value but can contain up to 10% sulfur.

The volatile ingredients (14) are separated, for instance via fractionated condensation (15), into various boiling fractions, which can comprise light oil (16), naphtha (11), and various fuels (17), among other things.

The method described is very energy-intensive, since very large quantities of hot water/water vapor have to be produced in boiler systems (3). Until now, considerable quantities of fossil fuels, especially natural gas (18), have been used for the purpose.

The method of the invention provides for replacing this natural gas entirely or in part with synthesis gas (20) generated in the countercurrent gasifier (19), and using this synthesis gas as fuel in the boiler systems.

The production of the synthesis gas is done by gasification of carbon-containing materials in a countercurrent gasifier (19), which is embodied as a vertical process chamber. A bulk material (21) flows through this process chamber from top to bottom. The bulk material can preferably comprise material of a coarse particle size, and as the bulk material, it is also suitable to use sediment (B) and/or (D). Especially advantageously, the bulk material can also be formed partially by the oil sand/oil shale (A); in this case, it can also be advantageous for the material, before being used as bulk material, to be comminuted mechanically to a particle size of less than 20 cm. Further residues from the method described above can be added to this bulk material before it enters the countercurrent gasifier. For that purpose, the pet coke (E), which because of its high carbon content has a high thermal value, is particularly well suited. The mixture of bulk material and residues flows through the vertical process chamber (19) by gravity from top to bottom. The countercurrent gasifier has burner lances (22) in its middle region, which ensure constant- load firing in the vertical process chamber and the stationary development of a burning zone (23). These burner lances can be fueled by fossil fuels (24) and oxygen-containing gas (25). Alternatively to the fossil fuels, synthesis gas from the countercurrent gasifier (20), or the crude bitumen (C) dissolved in naphtha, can also be used.

At the lower end of the vertical process chamber, oxygen-containing gas (26) is introduced. This gas serves first to cool down the bulk material before in a cooling zone (27) before it leaves the vertical process chamber. The oxygen-containing gas is thus preheated as it continues to flow upward in the vertical process chamber. On the countercurrent gasification principle, the oxygen from the oxygen-containing gas reacts with the carbon-containing materials in the bulk material by oxidation, and the quantity of oxygen-containing gas is adjusted such that a total lambda of less that 0.5 is established in the vertical process chamber. As a result, first a burning zone (23) is formed, in which residues of the carbon-containing material react with oxygen to form CO₂. Farther upward, the oxygen decreases further, so that finally, only low-temperature carbonization can occur, until still farther upward, all the oxygen is finally consumed, and a pyrolysis zone (28) forms,

Conversely, if one looks at the flow of the bulk material and the carbon-containing materials from top to bottom, what happens first in the pyrolysis zone (28) is drying of the typically moist materials used, until an intrinsic temperature of 100° C. is reached. After that, the intrinsic temperature of the materials rises further, causing the gasification process to begin, and at an intrinsic temperature of up to 500° C., the formation of methane, hydrogen and CO begins. After extensive degassing, the intrinsic temperature of the materials that are moving downward increases further because of the hot gases rising from the burning zone (23), so that finally, the carbon-containing materials are entirely degassed and now comprise nothing but residual coke, so-called pyrolysis coke, and ash components. The pyrolysis coke is transported with the bulk material farther downward in the vertical process chamber, where it is converted partly into CO at temperatures above 800° C. with the CO₂ components from the burning zone by Boudouard conversion and likewise gasified. Some of the pyrolysis coke also reacts in this zone by the water-gas reaction with water vapor, which is likewise present in the hot gases, forming CO and hydrogen. Finally, at temperatures below 1800° C., residues of the pyrolysis coke are practically completely combusted and thermally utilized in the burning zone (23) along with the oxygen-containing gas flowing in from below. As a result, it is possible for the countercurrent gasifier to be supplied with virtually all the energy needed for the gasification. This is also known as an autothermal gasification process.

Water (29), as an additional cooling and gasification medium, can also be metered into the cooling zone via water lances (30).

The synthesis gas formed in the vertical process chamber is extracted at the upper end by suction (31), so that in the upper gas chamber (32), a slight underpressure of from 0 to 200 mbar is established.

Depending on the quality of the substances used, considerably amounts of gaseous sulfur compounds can occur during the gasification process. It is therefore advantageous if alkaline substances (33) are admixed with the bulk material before it enters the vertical process chamber. For this purpose, metal oxides, metal hydroxides, or metal carbonates are especially suitable, and the use of fine-granular calcium oxide is especially preferred, since because of its reactivity and large surface area it reacts spontaneously with the gaseous sulfur compounds formed and thereby forms solid sulfur compounds, which are quite predominantly removed from the vertical process chamber together with the synthesis gas that is extracted by suction. Still other contaminants, such as chlorine, hydrogen chloride, or even heavy metals, can be bound highly effectively to the CaO and removed from the process in the same way.

Additionally, it can be appropriate to use coarse-granular metal oxides, metal hydroxides or metal carbonates as bulk material, in order on the one hand to increase the proportion of bulk material to the carbon-containing materials and on the other also to make alkaline reaction partners available in the lower part of the vertical process chamber for binding the gaseous sulfur compounds.

The synthesis gas extracted by suction contains dust, which essentially comprises the solid sulfur compounds, fine-granular alkaline substances, other contaminants, and inert particles. This synthesis gas containing dust can be treated in the gas chamber of the vertical process chamber, or after leaving the vertical process chamber, in the presence of water vapor and fine-granular calcium oxide at temperatures of over 400° C. This temperature can be established by suitable adjustment of the quantity of oxygen-containing gas (26) at the lower end of the vertical process chamber or by means of the calorific output of the burner lances (22) in the burning zone. However, it is especially advantageous to use direct fining in the synthesis gas via burner lances (34), which are operated stoichiometrically with fuel and oxygen-containing gas or even with an excess of oxygen-containing gas. This thermal posttreatment in the presence of water vapor and calcium oxide ensures that the oils and tars still present in the synthesis gas will be split off by the catalytic action of the calcium oxide.

The dust-containing synthesis gas is then freed of dust at temperatures above 300° C. by way of hot-gas filtration (35). The filter dust (36) containing sulfur is spun out of the process and either disposed of or put to an alternative use.

The resultant synthesis gas is practically sulfur-fee and can be used as fuel in the boiler systems (3). Depending on conditions on site or on the requirements of the boiler systems, it may be necessary to cool down the synthesis gas using gas coolers (38) and to free it of condensates, before it can be used in the boiler systems.

The condensate (39) that occurs can be used again at least partially as a cooling and gasification medium via the water lances (30) in the vertical process chamber.

The combustion of the cleaned synthesis gas (20) permits the boiler systems to be operated without requiring that the flue gas (40) be treated by means of complicated flue gas desulfurization.

The bulk material mixture (41) emerging from the lower end of the vertical process chamber essentially contains coarse-particle bulk material, ash residues, and fine-granular bulk material. The fine-granular bulk material may still contain slight amounts of sulfur products and other contaminants.

The entire bulk material stream can be stored (42) in its entirety. However, it is especially preferable to screen the bulk material mixture (43), with the coarse fraction (44) preferably put at least partially into circulation and used again as bulk material in the vertical process chamber.

The fine screened fraction (45), together with the filter dust (36) that contains sulfur, is spun out of the process and disposed of or put to an alternative use.

FIG. 2 shows an example of an integrated method for extracting light oils and fuels, in which the crude bitumen is quarried by the subsurface in-situ method.

In the in-situ method, the crude bitumen is not obtained by breaking down the soil and extracting it; instead, it is liquefied by melting in the earth's crust and brought to the surface via pumping systems.

In this process, high-pressure steam from the boiler system (3) is injected into bituminous soil (1) by means of special lance systems (2). As a result, the bitumen is liquefied (4) and diverted to underground collection points (5). From there, the liquid crude bitumen is brought to the surface via ascending pipelines (6) and special conveyor systems (7). This liquid crude bitumen is then used in the next process stage C.

A further technology contemplates the use of special burner lances (8), by way of which partial combustion of the crude bitumen in the earth's crust is initiated. This can be done for instance by superstoichiometric combustion of fossil fuels (9) with oxygen-containing gas (10), as a result of which the excess oxygen-containing gas (10) effects a partial combustion of the crude bitumen in the soil and thereby furnishes energy for the liquefaction of the crude bitumen.

According to the invention, it is also possible in this example to produce the required high-pressure steam in the boiler systems (3) using synthesis gas (20) as fuel. Synthesis gas can also be used as fuel for the partial combustion via the special burner systems (8).

Often, the in-situ method is also combined with the open-pit mining of FIG. 1. In both cases, crude bitumen is extracted, which is then combined in process stage (3) and further refined.

The further course of the process after process stage (C) is analogous to the description of FIG. 1.

Claims

1. A method for energy-efficient, environmentally friendly extraction of light oil and/or fuels from crude bitumen from oil shale and/or oil sands by thermal exploitation of carbon-containing compounds occurring in this extraction, characterized in that the carbon-containing compounds contain sulfur and by substoichiometric oxidation with oxygen-containing gas in a countercurrent gasifier operated with a moving bed of bulk material are converted, with the addition of alkaline substances, at temperatures <1800° C. into low-sulfur gaseous cleavage products, and these cleavage products are then converted by superstoichiometric oxidation into perceptible heat, and are used for generating heated aqueous process media for a physical comminution of the oil sands and/or oil shale and/or for separating the crude bitumen out of the rock mass and/or as process heat for a thermal fractionation of the crude bitumen.

2. The method of claim 1, characterized in that as carbon-containing compounds, solid residues from the aqueous separation of crude bitumen from the rock mass and/or solid residues from the thermal fractionation of the crude bitumen are used.

3. The method of claim 1, characterized in that the countercurrent gasifier is embodied as a vertical process chamber with a calcination zone and an oxidation zone, in which the calcined carbon- and sulfur-containing residues oxidize with oxygen-containing gas, and the gaseous reaction products are drawn off at the top of the vertical reaction chamber, the vertical process chamber being in the form of a vertical shaft furnace, through which a bulk material that itself is not oxidized flows continuously from top to bottom, and the oxygen-containing gas is introduced at least partially below the oxidation zone, thereby further advancing the rising gas stream.

4. The method of claim 1, characterized in that as alkaline substances, metal oxides, metal carbonates, metal hydroxides or mixtures of two or three of these substances are used, and are metered purposefully into the vertical process chamber and/or into the gas phase above the calcination zone, and/or are admixed with the carbon-containing compounds before entering the vertical process chamber.

5. The method of claim 4, characterized in that the metal oxides, metal carbonates, and metal hydroxides contain elements of the alkali metals or elements of the alkaline earth metals and especially preferably contain calcium as a cation.

6. The method of claim 1, characterized in that the alkaline substances are used at least partially in fine-granular form with a particle size of less than 2 mm.

7. The method of claim 1, characterized in that the substoichiometric oxidation is performed at a lambda of less than 0.5 and especially preferably of less than 0.3.

8. The method of claim 1, characterized in that by addition of alkaline substances under reductive conditions, the gaseous sulfur compounds occurring in the countercurrent gasifier are converted at temperatures of above 400° C. from the ingredients of the carbon- and sulfur-containing residues by chemical reaction with the alkaline substances into solid sulfur compounds, and these solid sulfur compounds are at least partially carried out with the gaseous reaction products, and are removed from the gas phase by fine-material separation at temperatures above 300° C.

9. The method of claim 1, characterized in that in the vertical process chamber and/or in the gas phase of the drawn-off gaseous reaction products in the presence of water vapor and calcium oxide and/or calcium carbonate and/or calcium hydroxide, a calcium-catalyzed reformation of substantial proportions is performed, at temperatures of above 400° C., of the resultant cleavage products, containing oil and/or tar, that have a chain length of greater than C4, into carbon monoxide, carbon dioxide, and hydrogen.

10. The method of claim 1, characterized in that the moving bed of bulk material is formed partially by additional metering of coarse material, in order to increase the flowability of the bulk material and/or its gas permeability, and the coarse material is admixed with the carbon-containing compounds before entering the vertical process chamber.

11. The method of claim 10, characterized in that as the coarse material, mineral substances and/or other inorganic substances or mixtures of substances, having a particle size in the range of from 2 mm to 300 mm, and especially preferably oil sands and/or oil shale, are used.

12. The method of claim 10, characterized in that as the coarse material, wood and/or other biogenic materials having a particle size in the range of from 2 mm to 300 mm are used.

13. The method of claim 10, characterized in that the coarse material at the lower end of the vertical process chamber is separated from the fine material and ashes obtained and is at least partially returned to the process again as oversized material.

14. The method of claim 1, characterized in that the carbon-containing compounds, before being used in the countercurrent gasifier, are converted by agglomeration into particles having a particle size in the range between 2 mm and 300 mm.

15. The method of claim 1, characterized in that in the vertical process chamber, between the top and the bottom, a differential pressure in a range of from 50 to 100 mbar is developed.