Hybrid Energy System
A hybrid method for producing energy from a carbonaceous material including the steps of: heating the carbonaceous material under a reduced oxygen atmosphere in a distillation plant to generate distillate vapours; processing the resulting distillate vapours; transferring the char residue from the distillation plant to a power station boiler; and combusting the char residue in the power station boiler for the generation of electrical power. The char residue is transferred to a power station boiler while the char residue retains heat from the heating in the distillation plant. An integrated energy conversion system including: a distillation plant for the destructive distillation of carbonaceous material to afford distillate vapours and a char residue; a power station boiler; a means of transferring the char residue at a temperature between 300 to 700° C. from the distillation plant to the bed power station; and collection means for the distillate vapours.
This invention relates generally to processes and systems for the efficient utilisation of fuel. For example, the invention relates to processes and systems for the pyrolysis of carbonaceous material for the generation of fuels and electrical energy.
BACKGROUND OF THE INVENTIONThe efficient and effective utilisation of natural resources, particularly fossil fuel resources, is of increasing importance given their finite nature. From an economic standpoint, losses from the current methods of utilisation of fuel are largely due to the failure to recover valuable by-products, and the failure to sufficiently achieve energy maximisation. The lack of proper recovery methods for fossil fuel by-products has also exacerbated pollution problems associated with the combustion of such fuels. In addition to the ineffective use of current resources and the associated pollution problems mentioned, the world's crude oil reserves are depleting (for the last thirty years only one barrel of oil was discovered for every 2 barrels of oil produced). These factors indicate that methods for the efficient usage of alternative fuel sources to crude oil are desirable.
It has been known for over 100 years that coal can be used to produce hydrocarbon fuels. The process of distilling oil from coal, substantially in the absence of oxygen, is called variously “destructive distillation” or “low temperature carbonisation”. Generally, it can be said that destructive distillation has for its purpose the abatement of excessive pollution on the one hand, and the increase in overall efficiency of fuel utilisation and by-product recovery on the other hand.
Particularly useful by-products formed from the pyrolysis of coal are nitrogenous and sulphurous materials. These by-products are useful for the production of materials such as sulphuric acid, elemental sulphur, ammonia and ammonia salts, and fertilisers. As such, the recovery of these chemical compounds is highly desirable. Their recovery is further desirable as these compounds are also significant pollutants resulting from the inefficient processing of coal.
Coal is not a uniform fuel source. Depending on the type of coal used, it is envisaged that destructive distillation can produce between 50 L to 250 L of oil per tonne of coal (corresponding to 0.3 to 1.5 barrels of oil per tonne of coal). At a price of AU $85/barrel this, for example, would correspond to AU $25 to AU $127 additional value per tonne of processed coal. Through the destructive distillation process, only 25% to 30% of total energy of the feed coal is converted to hydrocarbon fuel. The remaining energy source, in the form of a char residue, is recovered and employed as a fuel source for a conventional power station. An operation consuming 2 million tonne of low grade coal per year could produce 2 million barrels of oil per year (based on an expected oil yield of 1.0 barrels per tonne of coal), corresponding to a current value of approximately AU $170 million per annum. The coal char residue and gas from 2 million tonnes of coal per annum would provide sufficient fuel for a 200 MW power station.
SUMMARY OF THE INVENTIONIn one aspect the invention provides a hybrid method for producing energy from a carbonaceous material including the steps of:
-
- (i) heating the carbonaceous material under a reduced oxygen atmosphere in a distillation plant to generate distillate vapours;
- (ii) processing the resulting distillate vapours;
- (iii) transferring the char residue from the distillation plant to a power station boiler; and
- (iv) combusting the char residue in the power station boiler for the generation of electrical power.
In one embodiment, the char residue is transferred to a power station boiler while the char residue retains heat from the heating in the distillation plant.
Suitably, the char residue is transferred from the distillation plant to the power station boiler by one or more of double dump valve, pipe and conveyor.
The flow and progression of the char during transfer is optionally controlled via, double dump valves, screws, vibration, compressed air, gravity, heat resistant belt conveyor, chain conveyer, vibrating conveyer such as a vibrating tube conveyer, high temperature rotary valves, or any combination thereof.
The carbonaceous material may be selected from coal, coal washing rejects, low quality coal such as lignite, oil shale, and any combination thereof.
Preferably, the carbonaceous material, when subjected to destructive distillation, provides a high level of volatile hydrocarbon components. In some embodiments, up to 30% of the total energy of the carbonaceous material is converted to liquid and gaseous hydrocarbon fractions.
In one embodiment the carbonaceous material is coal.
In another embodiment the carbonaceous material has less than 1.0% Mean Maximum Vitrinite Reflectance.
In a preferred embodiment the carbonaceous material is a high Liptinite coal.
In yet another embodiment the carbonaceous material is heated to between about 400 to about 700° C.
In a further embodiment, the distillate vapour is reduced in temperature by heat exchange to a temperature of below about 150° C.
In another embodiment, the distillate vapour is reduced in temperature by heat exchange to a temperature of below about 30° C.
In still further embodiments the distillate is reduced in temperature to below about 25° C. and yet further embodiments to about 0° C.
In another embodiment the carbonaceous material is heated under reduced pressure.
Generally, the distillation plant has a retorting means in which the carbonaceous material is pyrolysed. The atmosphere of the retort chamber has a reduced level of oxygen gas compared to air. Preferably the atmosphere of the retort is substantially without oxygen gas.
Preferably the char residue is transferred from the distillation plant to the power plant boiler at a temperature of between 300 to 700° C.
In a second aspect the invention provides an integrated energy conversion system including:
-
- (i) a distillation plant for the destructive distillation of carbonaceous material to afford distillate vapours and a char residue;
- (ii) a power station boiler;
- (iii) a means of transferring the char residue at a temperature between 300 to 700° C. from the distillation plant to the bed power station; and
- (iv) collection means for the distillate vapours.
In one embodiment the means for collection of the vapours is by condensation of a condensable portion of the vapours. The vapours may be condensed through heat exchange. The distillate vapours may be condensed to provide a liquid hydrocarbon distillate fraction.
The power station may be a conventional power station or a fluidised bed power station.
Preferred embodiments of the invention will be described with reference to the accompanying drawings, of which:
Referring to the drawings it will be appreciated that the invention may be implemented in various forms, and that this description is given by way of example only.
Turning to the drawings,
As mentioned, the gaseous fraction, produced by the destructive distillation process, is usually a mixture of low molecular weight hydrocarbons and hydrogen gas, and other gases such as carbon monoxide and carbon dioxide. The relative percentage of hydrogen gas (H2) and gaseous hydrocarbons (represented, for example by the chemical formulae: CnH2n+2 and C2H2′ wherein n is an integer) may vary depending upon the temperature of distillation, and upon the pressure (typically reduced pressure) at which the distillation is conducted. Generally, illuminating gas consists mainly of methane, ethylene and hydrogen. The relative amounts of hydrocarbon components to H2 in gas produced by destructive distillation may vary with an increase in temperature. It is usually observed that an increase in temperature will bring an increase in the amount H2 gas produced, with a decrease in hydrocarbon gas. The gaseous hydrocarbon component has been shown (for example for bituminous coal) to decrease from about 50% at about 400° C. to about 35% at about 900° C. Whereas the percentage of H2 over the same range increases from about 20% to about 55%. Typically, as temperatures of greater than 600° C. are reached, the hydrocarbon components are more prone to decomposition. However, this may depend upon the pressure (reduced or otherwise) under which the distillation is conducted.
The remaining char residue 3.0—a high calorific fuel, is transferred to a power station where it is combusted in a boiler for the production of electricity 8.0. The power station may be a conventional power station or a fluidised bed power station. Before transfer to the power station, some of the char residue may also be partially reacted with superheated steam for the generation of hydrogen gas. In such a case, the remaining char residue is transferred to the power station after this process step has been completed.
In the
The condensation process also allows for extraction of ammonia 5.2 in an aqueous fraction. The raw manufactured gas 6.1 can be subjected to further purification processes 6.2 such as extraction of nitrogenous and sulphurous gases and filtration of particulate matter to provide a clean manufactured gas 6.3. The manufactured gas can be used as fuel in the boiler of the fluidised bed power station (FBPS) 6.5, can be used to heat the retort 6.4, can be sold as a high energy fuel, and can further processed. For example, manufactured gas can be catalytically reformed for the synthesis of fertilisers and methanol. The nitrogen and sulphur components of the coal can be recovered 6.6 as useful by-products 6.7. After the volatile materials have been distilled from the coal, the char residue is transferred 3.1 from the pyrolysis chamber 2.1 to a power station boiler, such as a fluidised bed power station boiler 4.1, where it is combusted to generate steam 4.2 to drive a turbine 4.3 for the generation 4.5 of electricity 8.0.
In the
In the
Alternatively, the pyrolysis of coal may be aided by steam injection 2.3. The steam is led in, optionally at the top, along the sides, or the bottom of the retort, through a valve or valves to take care of the thermal expansion. The steam and gas are led through a hot heat exchange unit or condenser 5.1 (n=1) where the heavy oils are taken out providing a first liquid distillate fraction. The remaining gases, or distillate vapours, then go to a cold condenser where the steam and oils are condensed 5.1 (n=2) to provide a second liquid distillate fraction comprised of an aqueous and organic phase. The remaining gas is then led off. The hot condenser reduces the temperature of the gases to about 150° C. The cold condenser is designed to reduce the temperature of the gases to from about 25° C. to about 50° C. The temperature of the coolant, typically water, is up to 25° C. but may be as low as about 0° C. The finishing point of the distillation may be at various stages and with regard to various objectives. The condensed liquid goes to the separator where the liquid hydrocarbon distillate fraction or “syncrude” 7.0 and the aqueous distillate fraction 5.2.2 are separated 5.2.1. The syncrude is taken to the crude storage tanks before being, for example, cracked and refined 7.1. Hydrogen gas formed from, for example, the destructive distillation of coal, or by the reaction of superheated steam with char residue, may be used in catalytic hydrogenation processes to upgrade syncrude products resulting from destructive distillation.
In the
In the
Turning to
The liquid distillate fraction or “syncrude” can be further refined through one or more upgrading processes. One such upgrading process is fractional distillation 7.2. Other upgrading processes include cracking processes and hydrotreating processes 7.4. Prior to the commencement of the refining, the stored syncrude can cleaned of contaminants such as sand and water and if required can be preheated through heat exchange processes such as passing the syncrude via a pipe through or by a heat generating body.
The heated syncrude can be upgraded by using heat to produce chemical splitting of the syncrude into combustion gas (furnace fuel gas), liquid products, and residuum (solid, complex hydrocarbons that often end up as asphalt). The syncrude can be upgraded (7.4) by catalytic hydrogenation in the presence of a partial pressure of hydrogen gas. The hydrogen required for catalytic hydrogenation can be generated by steam reformation 7.3 of manufactured gases or can be generated, for example, from the reaction of superheated steam with hot char residue.
In general, in the refining process, the longer the hydrocarbon molecule, the higher the boiling point. The temperature needed to boil out gasoline might be only 40 Celsius while a temperature of over 400 Celsius might be needed for heavy gas oil. The different boiling points of substances can be used to fractionally separate them by fractional distillation 7.2 in a fractionating unit such as a fractionating tower. For example, the following substances (lightest to heaviest or from the top of the tower to the bottom) are produced: off gas, straight run gasoline (composed of molecules with about 5 to about 10 carbons in length), kerosene distillate (with molecules of about 11 to about 15 carbons in length), light gas oil (about 13 to about 17 carbons), and heavy gas oil (about 18 to about 25 carbons), used for lubricating oils.
Collecting trays located at intervals up the tower collect products according to their density, with the least dense products such as off gas and straight run gasoline being trapped and siphoned off closer to the top of the fractionating tower, with the heavier materials such as the gas oils being taken off closer to the tower's bottom.
The heavy residuum (26 to over 60 carbons), however, may be subjected to even more refining. The residuum can receive more heating in a vacuum tower, where light vacuum gas oil and heavy vacuum gas oil can be extracted from it. Tarry solids can be sent through another heat exchange and then subjected to hydrocracking processes 7.4. For example, the residuum can be subjected to pressure, heat, catalysts, and hydrogen gas (which assists in breaking down the extremely complex hydrocarbon bonds in the residuum). Further gases and liquids are produced. The gases include: hydrogen sulfide from which sulfur can be extracted and gas that can be collected for use as furnace fuel. The collected liquids are re-directed back to the fractionating unit. The products of fractional distillation can be subjected to further upgrade such as hydrotreating and hydrocracking, and the products of hydrotreating and hydrocracking can also be further subjected to fractional distillation.
A hydrotreater is one “upgrading” process unit in a refinery that is used to treat products such as gasoline, kerosene and diesel and intermediates such as gas oil. A hydrotreater uses hydrogen to saturate aromatics and olefins as well as to remove undesirable compounds of elements such as sulphur and nitrogen.
Typical major elements of a hydrotreater unit are a heater, a fixed-bed catalytic reactor and a hydrogen compressor. The catalyst promotes the reaction of the hydrogen with the sulfur compounds such as mercaptans to produce hydrogen sulphide or H2S, which is then usually bled off and treated with amine in an amine treater. The hydrogen also saturates hydrocarbon double bonds, which helps raise the stability of the fuel.
A hydrocracker is a somewhat similar upgrading refinery unit that uses a higher severity such as a stronger catalyst and higher pressure to crack hydrocarbon molecules into smaller ones, for example to convert gas oil and diesel to lighter hydrocarbons such as gasoline blending stocks and butanes. A hydrocracker usually has a hydrotreater as the first step to remove the sulfur and nitrogen compounds that could act as a poison to the hydrocracking catalyst.
Hydrocracking is assisted by the presence of an elevated partial pressure of hydrogen. The products of this process are saturated hydrocarbons. The products of this reaction process depend on the reaction conditions (temperature, pressure, catalyst activity) used. Products may range from range ethane and LPG, to heavier hydrocarbons such as isoparaffins. Hydrocracking may be facilitated by a bifunctional catalyst that is capable of rearranging and breaking hydrocarbon chains as well as adding hydrogen to aromatic and olefins to produce naphthenes and alkanes.
Major products from hydrocracking are jet fuel, diesel, relatively high octane rating gasoline fractions and LPG. These products may have a very low content of sulphur and other contaminants. Fuel hydrocarbons derived from syncrude may include a variety of refined petroleum products. For example, gasoline contains hundreds of hydrocarbon compounds, some heterocyclic compounds. The hydrocarbon compounds are mainly C5 to C12 chains of carbon and hydrogen atoms that have boiling points in the range of 23° to 200° C. Petroleum engineers usually classify hydrocarbons in three groups, paraffins (straight chain and cyclic saturated hydrocarbons, i.e., no double bonds present), olefins (unsaturated hydrocarbons, i.e., compounds that contain double bonds), and aromatics (compounds that consist of benzene rings). The exact composition of gasoline varies greatly and depends on its crude source and the method of manufacture. Benzene, toluene, ethylebenzene and xylenes (BTEX) can occur in gasoline through the distillation process and also are added for their antiknock characteristics and octane enhancement. BTEX compounds may make up about 16% of gasoline by weight.
Diesel is composed of hydrocarbons that have boiling points between about 200° and about 300° C. Diesel contains larger hydrocarbons than gasoline with carbon numbers that may range from about 10 to about 19. Fuel oil is a term used for a variety of petroleum products. Fuel oils include kerosene, stove oil, furnace fuel oil, diesel, and bunker oil. Bunker oil is a heavy fuel oil used to power ships. Fuel oils may be distillate oils like diesel, kerosene, furnace fuel oil, and stove oil, or residual oils like bunker oil. Distillate oils are vaporised and condensed during the distillation process from crudes, and therefore have a definite boiling point range. Residual oils contains residue from the distillation of crude. As a result, residual oils contain high boiling and asphaltic components. Jet fuel, for example, is typically made by blending naphtha, gasoline, and kerosene according to specifications set by the military and commercial aviation. The composition of jet fuels will vary greatly depending on the source and method of manufacture.
Turning to
Claims
1. A method for producing energy from a carbonaceous material including:
- (i) heating the carbonaceous material in a distillation plant under a reduced oxygen atmosphere to generate distillate vapours and a char residue;
- (ii) processing the resulting distillate vapours by condensing and separating one or more liquid fractions from non-condensing gaseous fractions;
- (iii) transferring the char residue at a temperature in the range of 200° C. to 700° C. from the distillation plant to a power station boiler; and
- (iv) combusting the char residue in the power station boiler for the generation of electrical power.
2. The method of claim 1 wherein the char residue is transferred from the distillation plant to the fluidised bed power station boiler by one or more of a double dump valve, pipe or conveyor.
3. The method of either of claim 1 or claim 2 wherein the transfer of char is controlled via, double dump valves, screws, vibration, compressed air, gravity, heat resistant belt conveyor, chain conveyer, vibrating conveyer such as a vibrating tube conveyer, high temperature rotary valves, or any combination thereof.
4. The method of claim 1 wherein the carbonaceous material is heated to between 400 to 700° C.
5. The method of claim 1 wherein the distillation plant comprises a retort in which the heating of the carbonaceous material is conducted.
6. The method of claim 5 wherein the char residue is transferred from the retort to the power plant boiler at a temperature of between about 300 to about 600° C.
7. The method of any of claims 1 to 6 wherein the carbonaceous material is selected from coal, coal washing rejects, low quality coal such as lignite, oil shale, and any combination thereof.
8. The method of claim 7 wherein the carbonaceous material is coal.
9. The method of claim 8 wherein the coal has less than 1.0% Mean Maximum Vitrinite Reflectance.
10. The method of either of claim 8 or claim 9 wherein the coal is a high liptinite coal.
11. The method of claim 1 wherein the carbonaceous material is heated under reduced pressure.
12. The method of claim 1 wherein step (i) further includes the addition of water vapour.
13. The method of claim 12 wherein the water vapour is selected from steam or super-heated steam.
14. The method of claim 1 wherein the temperature of the distillate vapours is reduced to below about 250° C.
15. The method of claim 1 wherein the temperature of the distillate vapours is reduced to below about 150° C.
16. The method of claim 1 wherein the temperature of the distillate vapours is reduced to below about 30° C.
17. The method of any of claims 14 to 16 wherein a portion of the distillate vapours condense to provide a liquid distillate fraction.
18. The method of claim 17 wherein the liquid distillate fraction includes an aqueous fraction and a hydrocarbon fraction.
19. The method of claim 18 wherein the aqueous fraction and the hydrocarbon fraction are separated.
20. The method of claim 19 wherein the hydrocarbon fraction is separated from the aqueous fraction through one or more of gravity, suction or centrifugation.
21. The method of any of claims 17 to 20 further comprising the step of upgrading the hydrocarbon component of the distillate fraction.
22. The method of claim 21 wherein the upgrading is performed by one or more of extraction with aqueous acid, extraction with aqueous base, solvent extraction, fractional distillation, hydrotreating or hydrocracking.
23. An integrated energy conversion system including:
- (v) a distillation plant for the destructive distillation of carbonaceous material to afford a distillate and a char residue;
- (vi) a power station;
- (vii) a means of transferring the char residue from the distillation plant to the power station while still retaining heat of the destructive distillation in the char residue; and
- (viii) a collection means for the distillate.
24. The system of claim 23 wherein the power station is a fluidised bed power station.
Type: Application
Filed: Sep 8, 2006
Publication Date: Dec 25, 2008
Inventor: Edek Choros (Queensland)
Application Number: 12/066,185
International Classification: C10B 49/02 (20060101); C10B 47/06 (20060101); C10B 53/00 (20060101); C10G 1/02 (20060101);