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EP0061111B1 - Method for the underground gasification of solid combustible materials - Google Patents

Method for the underground gasification of solid combustible materials Download PDF

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Publication number
EP0061111B1
EP0061111B1 EP82102053A EP82102053A EP0061111B1 EP 0061111 B1 EP0061111 B1 EP 0061111B1 EP 82102053 A EP82102053 A EP 82102053A EP 82102053 A EP82102053 A EP 82102053A EP 0061111 B1 EP0061111 B1 EP 0061111B1
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European Patent Office
Prior art keywords
fuel
temperature
supercritical
gas
process according
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Expired
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EP82102053A
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German (de)
French (fr)
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EP0061111A3 (en
EP0061111A2 (en
Inventor
Hubert Dr. Coenen
Ernst Dr. Kriegel
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Fried Krupp AG
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Fried Krupp AG
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    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/24Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/164Injecting CO2 or carbonated water
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/166Injecting a gaseous medium; Injecting a gaseous medium and a liquid medium
    • E21B43/168Injecting a gaseous medium
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/18Repressuring or vacuum methods
    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/24Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
    • E21B43/243Combustion in situ

Definitions

  • the invention relates to a method for underground gasification of solid fuels, in which the fuel stored below the surface of the earth is first digested and then converted into a gaseous fuel by a chemical reaction with a gasifying agent.
  • the gas generated during underground gasification has a calorific value of approx. 1350 kcal / Nm 3 when 60% oxygen and 40% water vapor are used as the gasifying agent.
  • This gas is extracted from the fuel store via the boreholes and can be used as heating gas or - after appropriate pretreatment - as synthesis gas.
  • the known digestion processes have the disadvantage that in particular the volatile organic components present in the solid fuels are not removed. This leads to the fact that during the actual underground gasification, the volatile constituents are expelled from the gasified storage section and the gas-permeable pores and cracks present in the adjacent storage section stick together. In addition, the water present in the solid fuel is not removed by the known digestion processes, which means that the calorific value of the gas generated by underground gasification is reduced accordingly.
  • the invention has for its object to provide a method for underground gasification of solid fuels, in which the volatile constituents contained in the solid fuel can be obtained and which provides a gas with a high calorific value.
  • the steerability and economy of underground gasification should be improved with the invention.
  • the object underlying the invention is achieved in that the fuel is digested by treatment with a gas in the supercritical state during the day, the volatile organic compounds contained in the fuel and water dissolving in the supercritical gas, and that from the loaded supercritical gas phase the organic compounds dissolved in it and the dissolved water are separated in at least two fractions by reducing the pressure and / or changing the temperature during the day.
  • DE-B-1 493 190 discloses a process for separating organic substance mixtures by treating the mixtures with a supercritical gas and then separating the substances dissolved in the supercritical gas phase by lowering the pressure and / or increasing the temperature;
  • supercritical gases in the underground gasification of solid fuels as disintegrants, since it could not be expected that the volatile organic compounds in particular could advantageously be extracted from the solid fuel during the day and recovered during the day.
  • extracting the volatile components is prevented that they stick the gas-permeable pores of the fuel in the gasification process and thus adversely affect the gas permeability of the fuel.
  • the water present in the fuel is largely absorbed by the supercritical gas, as a result of which the calorific value of the gas generated during underground gasification increases accordingly.
  • the fractional separation of the gaseous and liquid organic compounds extracted from the fuel and of the water provided by the invention advantageously enables raw materials, in particular aromatic hydrocarbons, to be obtained.
  • the separation of the dissolved substances can be carried out according to the invention solely by lowering the pressure or solely by changing the temperature (increasing or decreasing the temperature) or by simultaneously reducing the pressure and changing the temperature (increasing or decreasing the temperature).
  • the gas in the supercritical state has a temperature of 10 to 100 ° C. above its critical temperature and a pressure of 2 to 300 bar above its critical pressure when it enters the fuel store.
  • These condition conditions ensure that the gas on the one hand maintains its supercritical state in the fuel store and on the other hand is introduced into the fuel store with an economically justifiable expenditure of energy.
  • the temperature of the supercritical gas on its extraction path decreases during the day so that it has a temperature which is 5 to 15 ° C. above its critical temperature when it exits the fuel store.
  • the temperature gradient of the supercritical gas provided according to the invention during the day thus prevents extracted substances from precipitating out of the fuel store before the supercritical gas phase emerges and the gas-permeable pores of the fuel sticking together.
  • the invention also proposes that the entry temperature of the supercritical gas into the fuel store be reduced by 2 to 50 ° C during the digestion.
  • the extraction capacity of the supercritical gas is continuously increased during the digestion of the fuel store, and the reduction in the extraction speed, which is caused by the decrease in the amount of substance to be extracted during the digestion, can be compensated for by increasing the dissolving capacity of the supercritical gas. Because the entry temperature of the supercritical gas into the fuel store is reduced during the digestion and the exit temperature of the supercritical gas from the fuel store is only slightly above the critical temperature of the gas, the zone within which the supercritical gas has a maximum extraction effect migrates into advantageously opposite to the flow direction of the supercritical gas.
  • the process according to the invention can be carried out with particularly good success if C0 2 is used for the digestion of the fuel, since supercritical C0 2 has a sufficiently good solvent capacity both for water and for the organic compounds contained in the solid fuel and can be used without expensive safety precautions .
  • ethane, ethene, propane or mixtures of these gases are used for the digestion of the fuel. When using this procedural measure according to the invention, however, care must be taken to avoid security risks.
  • Coal deposits are particularly suitable for underground gasification, for which mining does not seem worthwhile and which in particular contain no water-bearing layers.
  • the method can also be used for oil shale and oil sands deposits if the geological conditions allow it.
  • a prerequisite for the applicability of the method according to the invention is a dense deposit from which the loaded supercritical gas phase can be almost completely recovered.
  • Two vertical boreholes 2a, 2b are drilled in such a coal deposit 1. about the borehole 2a that used in the exclusion of supercritical C0 2 is conveyed into the coal deposits.
  • the supercritical C0 2 can also supercritical propane, ethane. Ethene or mixtures of these gaseous hydrocarbons are used, but it must be ensured that the use of these gases does not pose any safety risks.
  • the supercritical C0 2 has a temperature of approx. 60 ° and a pressure of approx. 300 bar when it enters the fuel store.
  • the supercritical C0 2 diffuses through the coal store and is loaded with volatile organic compounds and water.
  • the water content of the coal is on average around 1% by weight, and this water is usually absorbed by the supercritical gas phase, since it is loaded with water until it is saturated.
  • the water from highly water-containing or water-bearing fuel layers is only partially extracted from the supercritical gas phase. The further the digestion of the coal pre-standard progresses, the more diffusion channels are created, so that a high permeability of the coal deposit for gases is achieved.
  • Supercritical gas phase 4 emerges at borehole 2b and is separated into its components. The ratio of supercritical gas quantity to digested coal quantity is between 1: 3 and 1:10.
  • the dissolved organic compounds are converted from the supercritical C0 2 according to their. Molecular weight and the dissolved water deposited in a known manner by lowering the pressure and / or changing the temperature.
  • the regenerated digestion means 6 is compressed in the pump 7 to the supercritical pressure required for the digestion of the fuel and heated in the heat exchanger 8 to the required supercritical temperature. It then arrives in borehole 2a in the supercritical state. Since a certain amount of disintegrant is lost during the digestion, new gas - in the present case C0 2 - is continuously fed into the circuit from the storage tank 9.

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  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • Physics & Mathematics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Processing Of Solid Wastes (AREA)
  • Solid Fuels And Fuel-Associated Substances (AREA)
  • Extraction Or Liquid Replacement (AREA)
  • Industrial Gases (AREA)

Description

Die Erfindung betrifft ein Verfahren zur Untertagevergasung fester Brennstoffe, bei dem der unter der Erdoberfläche lagernde Brennstoff zunächst aufgeschlossen und dann durch eine chemische Reaktion mit einem Vergasungsmittel in einen gasförmigen Brennstoff umgewandelt wird.The invention relates to a method for underground gasification of solid fuels, in which the fuel stored below the surface of the earth is first digested and then converted into a gaseous fuel by a chemical reaction with a gasifying agent.

Es ist bekannt, daß feste Brennstoffe, insbesondere Kohle, am Ort ihres Vorkonmmens vergast werden können, wodurch die mechanische Brennstofförderung üerflüssig wird und auch weniger abbauwürdige Brennstoffvorkommen genutzt werden können. Bei den bekannten Untertagevergasungsverfahren werden von der Erdoberfläche Sohrlöcher bis in die Lagerstätte des Brennstoffs niedergebracht. Über diese Bohrlöcher wird das Brennstofflager durch einen geeigneten Prozeß aufgeschlossen, wobei eine Erhöhung der bereits mehr oder weniger vorhandenen Gasdurchlässigkeit des Brennstoffs eintritt. Anschließend wird in das aufgeschlossene Brennstofflacer über eines oder mehrere Bohrlöcher das Vergasungsmittel eingeführt und die Vergasungsreaktion durch Zündung gestartet. Als Vergasungsmittel werden Luft, mit Sauerstoff angereicherte Luft oder mit Wasserdampf vermischte Luft vervendet. Bei der Untertagevergasung laufen die nachfolgend aufgeführten bekannten Vergasungsreaktionen
ab:

Figure imgb0001
Figure imgb0002
Figure imgb0003
Figure imgb0004
Figure imgb0005
Figure imgb0006
It is known that solid fuels, in particular coal, can be gasified at the point of their pre-existence, which makes mechanical fuel delivery superfluous and also makes it possible to use less deposits of fuel that are not degradable. In the known underground gasification processes, sooth holes are drilled from the surface of the earth into the fuel deposit. The fuel store is opened up via these boreholes by a suitable process, with an increase in the gas permeability of the fuel which is already more or less present. The gasification agent is then introduced into the digested fuel lacer via one or more boreholes and the gasification reaction is started by ignition. Air, air enriched with oxygen or air mixed with water vapor are used as gasifying agents. The known gasification reactions listed below are used for underground gasification
from:
Figure imgb0001
Figure imgb0002
Figure imgb0003
Figure imgb0004
Figure imgb0005
Figure imgb0006

Das bei der Untertagevergasung entstehende Gas hat bei Verwendung von 60% Sauerstoff und 40% Wasserdampf als Vergasungsmittel einen Heizwert von ca. 1350 kcal/Nm3. Dieses Gas wird über die Bohrlöcher aus dem Brennstofflager geförert und kann als Heizgas oder - nach entsprechender Vorbehandlung - als Synthesegas verwendet werden.The gas generated during underground gasification has a calorific value of approx. 1350 kcal / Nm 3 when 60% oxygen and 40% water vapor are used as the gasifying agent. This gas is extracted from the fuel store via the boreholes and can be used as heating gas or - after appropriate pretreatment - as synthesis gas.

Der Aufschluß des Brennstofflagers vor der eigentlichen Untertagevergasung ist erforderlich, um das Brennstofflager für das Vergasungsmittel und das entstehende Gas genügend durchlässig zu machen. Für den Aufschluß des Brennstofflagers können folgende bekannte Aufschlußprozesseverwendet werden:

  • 1. Widerstandsverfahren: Hierbei werden in die Bohrlöcher Elektroden eingebracht, und an die Elektroden wird ein Strom angelegt, der das Brennstofflager erhitzt und im Brennstoff verkokte Zonen schafft, die für Gase durchlässig sind.
  • 2. Kanalbrennverfahren: Bei diesem Verfahren werden in das Brennstofflager Kanäle eingebrannt.
  • 3. Hydraulische Bohrlochbehandlung: Hierbei werden im Brennstofflager durch eingepreßte Flüssigkeiten Risse erzeugt.
  • 4. Direktes Bohren: Bei diesem Verfahren werden von den senkrechten Bohrlöchern abgelenkte Bohrlöcher in das Brennstofflager bis zum nächsten senkrechten Bohrloch vorgetrieben. Im Anschluß daran kann das abgelenkte Bohrloch noch durch ausbrennen erweitert werden.
The digestion of the fuel storage before the actual underground gasification is necessary in order to make the fuel storage sufficiently permeable for the gasification agent and the resulting gas. The following known digestion processes can be used for the digestion of the fuel store:
  • 1. Resistance method: Electrodes are inserted into the boreholes and a current is applied to the electrodes, which heats the fuel store and creates coked zones in the fuel that are permeable to gases.
  • 2. Channel combustion process: This process burns channels into the fuel store.
  • 3. Hydraulic borehole treatment: Cracks are created in the fuel store by injected liquids.
  • 4. Direct drilling: This method drills boreholes deflected from the vertical boreholes into the fuel store to the next vertical borehole. The deflected borehole can then be expanded by burning out.

Die bekannten Aufschlußprozesse haben den Nachteil, daß insbesondere die in den festen Brennstoffen vorhandenen flüchtigen organischen Bestandteile nicht entfernt werden. Dies führt dazu, daß bei der eigentlichen Untertagevergasung die flüchtigen Bestandteile aus dem vergasten Lagerabschnitt ausgetrieben werden und die im benachbarten Lagerabschnitt vorhandenen gasdurchlässigen Poren und Risse verkleben. Außerdem wird das im festen Brennstoff vorhandene Wasser durch die bekannten Aufschlußprozesse nicht entfernt, was dazu führt, daß der Heizwert des durch Untertagevergasung erzeugten Gases entsprechend herabgesetzt wird.The known digestion processes have the disadvantage that in particular the volatile organic components present in the solid fuels are not removed. This leads to the fact that during the actual underground gasification, the volatile constituents are expelled from the gasified storage section and the gas-permeable pores and cracks present in the adjacent storage section stick together. In addition, the water present in the solid fuel is not removed by the known digestion processes, which means that the calorific value of the gas generated by underground gasification is reduced accordingly.

Der Erfindung liegt die Aufgabe zugrunde, ein Verfahren zur Untertagevergasung fester Brennstoffe zu schaffen, bei dem die im festen Brennstoff enthaltenen flüchtigen Bestandteile gewonnen werden können und das ein Gas mit hohem Heizwert liefert. Auerdem soll die Lenkbarkeit und Wirtschaftlichkeit der Untertagevergasung mit der Erfindung verbessert werden.The invention has for its object to provide a method for underground gasification of solid fuels, in which the volatile constituents contained in the solid fuel can be obtained and which provides a gas with a high calorific value. In addition, the steerability and economy of underground gasification should be improved with the invention.

Die der Erfindung zugrunde liegende Aufgabe wird dadurch gelöst, daß der Brennstoff durch Behandlung mit einem im überkritischen Zustand befindlichen Gas unter Tag aufgeschlossen wird, wobei sich die im Brennstoff enthaltenen flüchtigen organischen Verbindungen sowie Wasser im überkritischen Gas lösen, und daß aus der beladenen überkritischen Gasphase die in ihr gelösten organischen Verbindungen sowie das gelöste Wasser durch Druckerniedrigung und/oder Temperaturänderung über Tag in wenigstens zwei Fraktionen abgeschieden werden. Aus der DE-B- 1 493 190 ist zwar ein Verfahren zur Trennung organischer Stoffgemische durch Behandlung der Gemische mit einem überkritischen Gas und anschließender Abscheidung der in der überkritischen Gasphase gelösten Stoffe durch Druckerniedrigung und/oder Temperaturerhöhung bekannt; für den Fachmann ist es aber nicht naheliegend, überkritische Gase bei der Untertagevergasung fester Brennstoffe als Aufschlußmittel einzusetzen, da nicht erwartet werden konnte, daß insbesondere die flüchtigen organischen Verbindungen aus dem festen Brennstoff in vorteilhafter weise unter Tag extrahiert und über Tag zurückgewonnen werden können. Durch die Extraktion der flüchtigen Bestandteile wird verhindert, daß sie die gasdurchlässigen Poren des Brennstoffs beim Vergasungsprozeß verkleben und so die Gasdurchlässigkeit des Brennstoffs nachteilig beeinflussen. Außerdem ist es vorteilhaft, daß das im Brennstoff vorhandene Wasser durch das überkritische Gas weitgehend aufgenommen wird, wodurch sich der Heizwert des bei der Untertagevergasung erzeugten Gases entsprechend erhöht. Durch die nach der Erfindung vorgesehene fraktionsweise Abscheidung der aus dem Brennstoff extrahierten gasförmigen und flüssigen organischen Verbindungen sowie des Wassers können in vorteilhafter Weise Rohstoffe, insbesondere aromatische Kohlenwasserstoffe, gewonnen werden. Die Abscheidung der gelösten Stoffe kann nach der Erfindung allein durch Druckerniedrigung oder allein durch Temperaturänderung (Temperaturerhöhung oder Temperatursenkung) oder durch gleichzeitige Druckerniedrigung und Temperaturänderung (Temperaturerhöhung oder Temperatursenkung) erfolgen.The object underlying the invention is achieved in that the fuel is digested by treatment with a gas in the supercritical state during the day, the volatile organic compounds contained in the fuel and water dissolving in the supercritical gas, and that from the loaded supercritical gas phase the organic compounds dissolved in it and the dissolved water are separated in at least two fractions by reducing the pressure and / or changing the temperature during the day. DE-B-1 493 190 discloses a process for separating organic substance mixtures by treating the mixtures with a supercritical gas and then separating the substances dissolved in the supercritical gas phase by lowering the pressure and / or increasing the temperature; However, it is not obvious to a person skilled in the art to use supercritical gases in the underground gasification of solid fuels as disintegrants, since it could not be expected that the volatile organic compounds in particular could advantageously be extracted from the solid fuel during the day and recovered during the day. By extracting the volatile components is prevented that they stick the gas-permeable pores of the fuel in the gasification process and thus adversely affect the gas permeability of the fuel. It is also advantageous that the water present in the fuel is largely absorbed by the supercritical gas, as a result of which the calorific value of the gas generated during underground gasification increases accordingly. The fractional separation of the gaseous and liquid organic compounds extracted from the fuel and of the water provided by the invention advantageously enables raw materials, in particular aromatic hydrocarbons, to be obtained. The separation of the dissolved substances can be carried out according to the invention solely by lowering the pressure or solely by changing the temperature (increasing or decreasing the temperature) or by simultaneously reducing the pressure and changing the temperature (increasing or decreasing the temperature).

Nach der Erfindung ist es besonders vorteilhaft, wenn das im überkritischen Zustand befindliche Gas bei seinem Eintritt in das Brennstofflager eine Temperatur von 10 bis 100° C über seiner kritischen Temperatur und einen Druck von 2 bis 300 bar über seinem kritischen Druck hat. Durch diese Zustandsbedingungen wird sichergestellt, daß das Gas einerseits auch im Brennstofflager seinen überkritischen Zustand beibehält und andererseits mit einem wirtschaftlich vertretbaren Energieaufwand in das Brennstofflager eingebracht wird. Ferner ist nach der Erfindung vorgesehen, daß die Temperatur des überkritischen Gases auf seinem Extraktionsweg unter Tag so abnimmt, daß es bei seinem Austritt aus den Brennstofflager eine Temperatur aufweist, die 5 bis 15° C über seiner kritischen Temperatur liegt. Durch diese Maßnahme wird erreicht, daß sich das überkritische Gas auf seinem Extraktionsweg laufend mit einer größeren Menge an extrahierten Verbindungen belädt, da das Lösungsvermögen überkritischer Gase in einem Temperaturbereich, der wenig oberhalb der kritischen Temperatur liegt, in der Regel ein Optimum aufweist und mit steigender Temperatur abnimmt. Durch den nach der Erfindung unter Tag vorgesehenen Temperaturgradienten des überkritischen Gases wird also vermieden, daß extrahierte Stoffe vor dem Austritt der überkritischen Gasphase aus dem Brennstofflager ausfallen und die gasdurchlässigen Poren des Brennstoffs verkleben. Die Erfindung schlägt auch vor, daß die Eintrittstemperatur des überkritischen Gases in das Brennstofflager während des Aufschlusses um 2 bis 50°C gesenkt wird. Dadurch wird das Extraktionsvermögen des überkritischen Gases während des Aufschlusses des Brennstofflagers laufend gesteigert, und die Verringerung der Extraktionsgeschwindigkeit, die von der Abnahme der zu extrahierenden Stoffmenge während des Aufschlusses verursacht wird, kann durch die Steigerung des Lösungsvermögens des überkritischen Gases ausgeglichen werden. Dadurch, daß die Eintrittstemperatur des überkritischen Gases in das Brennstofflager während des Aufschlusses gesenkt wird und die Austrittstemperatur des überkritischen Gases aus dem Brennstofflager nur wenig oberhalb der kritischen Temperatur des Gases liegt, wandert die Zone, innerhalb der das überkritische Gas eine maximale Extraktionswirkung hat, in vorteilhafter Weise entgegengesetzt zur Strömungsrichtung des überkritischen Gases. Das erfindungsgemäße Verfahren kann mit besonders gutem Erfolg durchgeführt werden, wenn zum Aufschluß des Brennstoffs C02 verwendet wird, da überkritisches C02 sowohl für Wasser als auch für die im festen Brennstoff enthaltenen organischen Verbindungen ein hinreichend gutes Lösungsvermögen besitzt und ohne aufwendige Sicherheitsvorkehrungen eingesetzt werden kann. Außerdem hat C02 einen kritischen Druck von pkrit = 73,9 bar und eine kritische Temperatur von Tkrit = 31°C, die seinen Einsatz zum Aufschluß unterirdischer Kohlevorkommen für die Untertagevergasung wirtschaftlich sinnvoll erscheinen lassen, zumal in vielen Brennstofflagern eine Temperatur herrscht, die oberhalb der kritischen Temperatur des CO liegt. Nach der Erfindung ist ferner vorgesehen, daß zum Aufschluß des Brennstoffs Äthan, Äthen, Propan oder Mischungen dieser Gase verwendet werden. Bei der Anwendung dieser erfindungsgemäßen Verfahrensmaßnahme ist allerdings darauf zu achten, daß Sicherheitsrisiken vermieden werden.According to the invention, it is particularly advantageous if the gas in the supercritical state has a temperature of 10 to 100 ° C. above its critical temperature and a pressure of 2 to 300 bar above its critical pressure when it enters the fuel store. These condition conditions ensure that the gas on the one hand maintains its supercritical state in the fuel store and on the other hand is introduced into the fuel store with an economically justifiable expenditure of energy. It is further provided according to the invention that the temperature of the supercritical gas on its extraction path decreases during the day so that it has a temperature which is 5 to 15 ° C. above its critical temperature when it exits the fuel store. This measure ensures that the supercritical gas is continuously loaded with a larger amount of extracted compounds on its extraction path, since the solubility of supercritical gases in a temperature range that is slightly above the critical temperature is usually optimal and increases with increasing Temperature decreases. The temperature gradient of the supercritical gas provided according to the invention during the day thus prevents extracted substances from precipitating out of the fuel store before the supercritical gas phase emerges and the gas-permeable pores of the fuel sticking together. The invention also proposes that the entry temperature of the supercritical gas into the fuel store be reduced by 2 to 50 ° C during the digestion. As a result, the extraction capacity of the supercritical gas is continuously increased during the digestion of the fuel store, and the reduction in the extraction speed, which is caused by the decrease in the amount of substance to be extracted during the digestion, can be compensated for by increasing the dissolving capacity of the supercritical gas. Because the entry temperature of the supercritical gas into the fuel store is reduced during the digestion and the exit temperature of the supercritical gas from the fuel store is only slightly above the critical temperature of the gas, the zone within which the supercritical gas has a maximum extraction effect migrates into advantageously opposite to the flow direction of the supercritical gas. The process according to the invention can be carried out with particularly good success if C0 2 is used for the digestion of the fuel, since supercritical C0 2 has a sufficiently good solvent capacity both for water and for the organic compounds contained in the solid fuel and can be used without expensive safety precautions . In addition, C0 2 has a critical pressure of p crit = 73.9 bar and a critical temperature of T kr i t = 31 ° C, which make it economically sensible to use it to dig out underground coal deposits for underground gasification, especially as a temperature in many fuel stores prevails, which is above the critical temperature of the CO. According to the invention it is further provided that ethane, ethene, propane or mixtures of these gases are used for the digestion of the fuel. When using this procedural measure according to the invention, however, care must be taken to avoid security risks.

Der Gegenstand der Erfindung wird nachfolgend anhand der Zeichnung näher erläutert. Für die Untertagevergasung sind insbesondere Kohlevorkommen geeignet, für die ein bergmännischer Abbau nicht lohnend erscheint und die insbesondere keine wasserführenden Schichten enthalten. Das Verfahren kann aber auch bei Ölschiefer- und Ölsand-Lagerstätten angewendet werden, wenn die geologischen Verhältnisse dies zulassen. Voraussetzung für die Anwendbarkeit des erfindungsgemäßen Verfahrens ist nämlich eine dichte Lagerstätte, aus der die beladene überkritische Gasphase nahezu vollständig zurückgewonnen werden kann.The object of the invention is explained in more detail with reference to the drawing. Coal deposits are particularly suitable for underground gasification, for which mining does not seem worthwhile and which in particular contain no water-bearing layers. The method can also be used for oil shale and oil sands deposits if the geological conditions allow it. A prerequisite for the applicability of the method according to the invention is a dense deposit from which the loaded supercritical gas phase can be almost completely recovered.

In ein derartiges Kohlevorkommen 1 werden zwei senkrechte Bohrlöcher 2a, 2b niedergebracht. über das Bohrloch 2a wird das zum Auschluß verwendete überkritische C02 in das Kohlevorkommen 1 gefördert. Anstelle des überkritischen C02 können auch überkritische Propan, Äthan. Äthen oder Mischungen dieser gasförmigen Kohlenwasserstoffe verwendet werden, wobei allerdings gewährleistet sein muß, daß durch die Verwendung dieser Gase keine Sicherheitsrisiken entstehen. Das überkritische C02 hat bei seinem Eintritt in das Brennstofflager eine Temperatur von ca. 60° und einen Druck von ca. 300 bar. Das überkritische C02 diffundiert durch das Kohlelager und belädt sich dabei mit flüchtigen organischen Verbindungen sowie mit Wasser. Der Wassergehalt der Kohle liegt im Durchschnitt bei ca. 1 Gew.-%, und dieses Wasser wird in der Regel von der überkritischen Gasphase aufgenommen, da sie sich bis zur Sättigung mit Wasser belädt. Das Wasser aus stark wasserhaltigen oder wasserführenden Brennstoffschichten wird nur zum Teil von der überkritischen Gasphase extrahiert. Je weiter der Aufschluß des Kohlevorkormens fortschreitet, desto mehr Diffusionskanäle werden-geschaffen, so daß eine hohe Permeabilität des Kohlevorkommens für Gase erreicht wird. Die beladene. überkritische Gasphase 4 tritt am Bohrloch 2b aus und wird in ihre Bestandteile aufgetrennt. Das Verhältnis von überkritischer Gasmenge zu aufgeschlossener Kohlemenge liegt zwischen 1 : 3 und 1 : 10.Two vertical boreholes 2a, 2b are drilled in such a coal deposit 1. about the borehole 2a that used in the exclusion of supercritical C0 2 is conveyed into the coal deposits. 1 Instead of the supercritical C0 2 can also supercritical propane, ethane. Ethene or mixtures of these gaseous hydrocarbons are used, but it must be ensured that the use of these gases does not pose any safety risks. The supercritical C0 2 has a temperature of approx. 60 ° and a pressure of approx. 300 bar when it enters the fuel store. The supercritical C0 2 diffuses through the coal store and is loaded with volatile organic compounds and water. The water content of the coal is on average around 1% by weight, and this water is usually absorbed by the supercritical gas phase, since it is loaded with water until it is saturated. The water from highly water-containing or water-bearing fuel layers is only partially extracted from the supercritical gas phase. The further the digestion of the coal pre-standard progresses, the more diffusion channels are created, so that a high permeability of the coal deposit for gases is achieved. The loaded one. Supercritical gas phase 4 emerges at borehole 2b and is separated into its components. The ratio of supercritical gas quantity to digested coal quantity is between 1: 3 and 1:10.

Zur Trennung der beladenen überkritischen Gasphase gelangt diese nacheinander in 5 Fraktioniereinrichtungen 5a, 5b, 5c, 5d, 5e. In diesen Fraktioniereinrichtungen werden aus dem überkritischen C02 die gelösten organischen Verbindungen entsprechend ihrem. Molekulargewicht sowie das gelöste Wasser durch Druckerniedrigung und/oder Temperaturänderung in bekannter Weise abgeschieden. Das regenerierte Aufschlußmittel 6 wird in der Pumpe 7 auf den zum Aufschluß des Brennstoffs erforderlichen überkritischen Druck komprimiert und im Wärmetauscher 8 auf die erforderliche, überkritische Temperatur erwärmt. Es gelangt anschließend im überkritischen Zustand in das Bohrloch 2a. Da während des Aufschlusses eine bestimmte Aufschlußmittelmenge verloren geht, wird aus dem Vorratstank 9 ständig neues Gas - im vorliegenden Fall C02 - in den Kreislauf gefördert.In order to separate the loaded supercritical gas phase, it passes into 5 fractionation devices 5a, 5b, 5c, 5d, 5e. In these fractionation units, the dissolved organic compounds are converted from the supercritical C0 2 according to their. Molecular weight and the dissolved water deposited in a known manner by lowering the pressure and / or changing the temperature. The regenerated digestion means 6 is compressed in the pump 7 to the supercritical pressure required for the digestion of the fuel and heated in the heat exchanger 8 to the required supercritical temperature. It then arrives in borehole 2a in the supercritical state. Since a certain amount of disintegrant is lost during the digestion, new gas - in the present case C0 2 - is continuously fed into the circuit from the storage tank 9.

Bei Laboruntersuchungen wurde festgestellt, daß eine überkritische Gasphase, die aus Kohlenwasserstoffen besteht, bis zu 50 Gew.-% der extrahierten Kohle aufnimmt. Der aus der überkritischen Gasphase zurückgewonnene Extrakt besteht aus leicht-, mittel- und schwerflüchtigen organischen Verbindungen und aus geringen Wassermengen. Eine Hydrierung des Extraktes liefert folgende Produkte:

Figure imgb0007
Laboratory tests have shown that a supercritical gas phase consisting of hydrocarbons absorbs up to 50% by weight of the extracted coal. The extract recovered from the supercritical gas phase consists of volatile, medium and low volatile organic compounds and small amounts of water. Hydrogenation of the extract provides the following products:
Figure imgb0007

Claims (6)

1. A process for the underground gasification of solid fuels, wherein the fuel deposited below the earth's surface is first broken down and then transformed into a gaseous fuel by a chemical reaction with gasification agent, characterized in that the fuel broken down under ground with a gas in the supercritical condition, and the volatile organic compounds contained in the fuel and also water are dissolved in the supercritical gas, whereafter the organic compounds dissolved in the charged supercritical gas phase and also the dissolved water are separated above ground into at least two fractions by lowering the pressure and/or changing the temperature.
2. A process according to Claim 1, characterized in that the gas in the supercritical condition has a temperature of 10 to 100°C above its critical temperature and a pressure of 2 to 300 bar above its critical pressure when it enters the fuel deposit.
3. A process according to Claims 1 and 2, characterized in that the temperature of the supercritical gas so decreases over its path of extraction under ground that on emergence from the fuel deposit is has a temperature lying 5 to 15° C above its critical temperature.
4. A process according to Claims 1 to 3, characterized in that during the breaking down of the fuel the temperature at which the supercritical gas enters the fuel deposit is lowered by 2 to 50° C.
5. A process according to Claims 1 to 4, characterized in that C02 is used to break down the fuel.
6. A process according to Claims 1 to 4, characterized in that ethane, ethene, propane or mixtures of these gases are used to break down the fuel.
EP82102053A 1981-03-21 1982-03-13 Method for the underground gasification of solid combustible materials Expired EP0061111B1 (en)

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DE3111137A DE3111137C2 (en) 1981-03-21 1981-03-21 Process for underground gasification of solid fuels with prior unlocking of the deposit

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CS247065B2 (en) 1986-11-13
EP0061111A3 (en) 1984-07-18
DE3111137C2 (en) 1985-06-13
CA1170977A (en) 1984-07-17
DE3111137A1 (en) 1982-10-28
AU552221B2 (en) 1986-05-22
PL133246B1 (en) 1985-05-31
US4446921A (en) 1984-05-08
ZA821848B (en) 1983-03-30
EP0061111A2 (en) 1982-09-29
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AU8075282A (en) 1982-09-30
JPS57168991A (en) 1982-10-18

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