US20080314726A1

US20080314726A1 - Hybrid Energy System

Info

Publication number: US20080314726A1
Application number: US12/066,185
Authority: US
Inventors: Edek Choros
Original assignee: Individual
Current assignee: Millennium Synfuels LLC
Priority date: 2005-09-08
Filing date: 2006-09-08
Publication date: 2008-12-25
Also published as: EP1966346A1; WO2007028208A1; CA2621185A1; CN101313051A

Abstract

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.

Description

FIELD OF THE INVENTION

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 INVENTION

The 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 INVENTION

In 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.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be described with reference to the accompanying drawings, of which:

FIG. 1: Represents an overview of the general business method;

FIG. 2: Illustrates an overview of the hybrid energy system process;

FIG. 3: Shows a schematic of the removal of ammonias;

FIG. 4: Illustrates a schematic of the processing of the hydrocarbon distillate fraction otherwise known as “Syncrude”;

FIG. 5: Represents a schematic of the generation of electrical power from char residue;

FIG. 6: Represents a schematic of the production and purification of manufactured gas;

FIG. 7: Illustrates an overview of the upgrading of coal distillate;

FIG. 8: Shows a schematic of the integrated energy system; and

FIG. 9: Shows an alternative schematic of the integrated energy system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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, FIG. 1 shows a schematic of process steps for producing coal derived fuels, whereby coal from a coal mine 1.0, is transferred to a distillation plant having a distillation means, for example, a retort, 2.0 where the coal is pyrolysed. The products of the pyrolysis of coal may be variously processed. Generally, the destructive distillation of coal generates distillate vapours, which upon reduction in temperature to a more or less ambient temperature (298 K), such as through heat transfer condensation processes, provides a gaseous fraction, a liquid fraction. There is also the remaining char residue. The liquid fraction may further be separated into a liquid hydrocarbon fraction and an aqueous liquid fraction. For example, the distillate, including useful by-products 9.0, and gaseous and condensable synfuels 5.0 can be further processed into manufactured gas 6.0—usually a mixture of hydrogen gas and hydrocarbons syncrude 7.0—a condensable synthetic liquid hydrocarbon fraction (at ambient temperature) and an aqueous liquid fraction containing sulphurous and nitrogenous products. The relative amount of the aqueous fraction generated may depend on, for example, the water content of the coal pyrolysed, or, whether or not the distillation is assisted by steam. Other processes such as aqueous scrubbing also generate aqueous fractions. Manufactured gas produced by destructive distillation has been variously known, for example, as illuminating gas or coal gas. Manufactured gas produced by destructive distillation of, for example, coal or peat, is usually a mixture of hydrogen gas and hydrocarbons. Manufactured gas produced from destructive distillation processes should not be confused with other synthetic gases such as “water gas” (a mixture of carbon dioxide and H₂formed by the reaction of water with carbon monoxide) or syngas (a mixture of carbon monoxide and H₂produced from the reaction of methane with steam). Hydrogen gas may be prepared from manufactured gas. The method of producing H₂from hydrocarbons is referred to as “steam reforming” (7.3) or “catalytic oxidation” and on an industrial scale is the dominant method for producing H₂.
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: C_nH_2n+2and 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 H₂in 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 H₂gas 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 H₂over 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 FIG. 2 schematic, a schematic shows that coal 1.3 is mined 1.2 from a coal mine 1.0, and then transported 1.4 to the distillation plant. Coals with a liptinite content are generally regarded as providing greater quantities of syncrude on destructive distillation. However other coals, such as the brown coal lignite, are also suitable. In general, lower rank coals, or coals with a Mean Maximum Vitrinite Reflectance of less than 1% are preferable for the processes described herein. Coals with a high ash content are also tolerated. Generally, carbonaceous materials such as coal washing rejects, lignite, oil shale or combinations thereof, are suitable for use in the present invention. Preferably, the distillation plant and power station are near a source of feed material. The coal 1.3 is transferred 1.4 to the pyrolysis chamber of the retort 2.1 of the distillation plant. The feed coal 1.3 may be used in the pyrolysis chamber substantially as it arrives from the mine 1.0, that is, as raw, unwashed coal. Using raw coal may result in significant savings in constructional, operational and capital costs. It is not necessary to pulverise the feed coal to the dust fraction size, for example, as used in Pulverised Fuel Power stations. Coal crushing to a top size of 6 mm may only be required, thus providing an additional capital and operating cost savings. The coal may be preheated before the distillation chamber is charged. Preferably, the coal is transferred to the retort 2.1 by gravity feed 1.4. Gases and other volatile hydrocarbons are then distilled from the coal by the process of low temperature carbonisation, otherwise known as destructive distillation 2.2. The distillation may be conducted under reduced pressure and is preferably conducted within a temperature range of about 400-700° C. The raw manufactured or “synthetic” gas 6.1, and the condensable hydrocarbon fraction-syncrude 7.0, are separated by a heat exchange condensation process 5.1. The syncrude can be further processed to provide, for example, oils, fuels and bitumen. The syncrude can be, for example, further fractionally distilled into many fractions to yield a number of useful organic products, including benzene, toluene, xylene, naphthalene, anthracene, and phenanthrene. Raw distillates, may form the starting point for the synthesis of numerous further products. The residual pitch left from the fractional distillation may used for paving, roofing, waterproofing, and insulation. The specific gravity of the liquid distillate may vary depending on factors such as: the temperature at which the carbonisation is conducted, and how the fractions are condensed or collected. Residuum formed from the further distillation of coal distillation liquids may have an even higher specific gravity.
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 FIG. 3 schematic, after pyrolysis of the coal, the gas leaving 2.2 the pyrolysis chamber 2.1 may be quenched with a spray of aqueous liquor (flushing liquor) 5.1.0 which results in a liquid condensate stream 5.2.1 and a gas stream 6.1. As the raw retort gas is cooled, hydrocarbon vapour can condense forming aerosols, which are carried along with the gas flow. Electrostastic precipitators can be used to charge the particles which may then collected from the gas by means of electrostatic attraction. The raw gas 6.1 and the flushing liquor are then separated and flow to by-product plants for treatment. Ammonia can be separated from the gas stream for example in the form of ammonium sulphate 6.2.1. The generation of ammonium sulphate can take various forms, for example, by contacting the gas stream with sulphuric acid. Alternatively the ammonia can be removed from the gas stream by scrubbing with water. Scrubbing with water further removes some hydrogen sulphide and hydrogen cyanide from the gas stream. The water-wash ammonia process is improved at lower gas temperatures. The ammonia solution can be processed in a still to provide a concentrated ammonia solution or to form ammonium sulphate. Another related process is the removal of ammonia from the gas stream using a solution of mono-ammonium phosphate. This process produces saleable anhydrous ammonia. Light oils and naphthalene can also be scrubbed from the gas stream, for example, by using a wash oil. The light oils and naphthalene can be stripped together or as separate fractions. The light oil may also be left in the gas to increase its calorific value. The flushing liquor is transferred to a liquor plant. The hydrocarbon fraction can be separated from the aqueous fraction by decantation 5.2.2. The aqueous flushing liquor can then be processed to provide ammonia which can be fed back into the gas stream upstream of the ammonia strip, or can be otherwise integrated into the ammonia processing system. The liquor can be further processed to remove components such as basic nitrogeneous hydrocarbons (e.g. pyridines), phenols and cyanides, or treated on-site, for example, in a biological effluent plant.
In the FIG. 4 schematic, the liquid condensable fractions of hydrocarbons are collected 5.1 and the aqueous phase separated from the organic phase 5.2.1. The aqueous phase is likely to contain some water-soluble hydrocarbons such as phenols and nitrogenous bases which can be recovered. Phenols, for example, can be recovered by conversion to their sodium salts by reaction with NaOH. Nitrogenous bases can be similarly recovered as salts by reaction with an appropriate counterion. Due, for example, to their different densities, the phases may be separated, by using a separation funnel or drain, or by centrifugation. The generally hydrophilic and hydrophobic nature of the respective liquid aqueous and liquid hydrocarbon fractions may also assist their separation from each other. After separation from the aqueous phase, the liquid hydrocarbon “syncrude” fraction 7.0 component can be transferred to an oil refinery 7.1 where it is further processed into, for example, oils, fuels such as petroleum fuels, and bituminous components. As mentioned, the aqueous fraction 5.2.2 is a source of ammonia and water soluble hydrocarbons such as phenols and nitrogenous bases 6.7.
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 FIG. 5 schematic, the char residue is transferred 3.1 from the retort to a FBPS boiler. The char residue is a high energy source fuel, similar to coke and has a higher calorific value than coal itself. The char residue also provides a high energy fuel with negligible water content. Preferably the char residue is transferred to the boiler heated, that is, at or about the temperature at which destructive distillation was conducted, which is usually up to about 700° C. By transferring the char residue from the distillation plant pyrolysis chamber to the fluidised bed power plant boiler at or about the distillation temperature, significant energy savings are achieved, as the heat energy of the char residue is not lost. Preferably the fluidised bed power station is in close proximity to the distillation plant, more preferably it is within 100 metres of the distillation plant, even more preferably it is next to the distillation plant. The retort of the distillation plant may be located above the boiler of the power station such that a minimum transfer distance is required to move the hot char from the retort to the boiler. The retort and boiler may be connected, for example, by a double dump valve. More than one retort may be located within the vicinity of the boiler in order to provide, as required, sufficient char residue to fire the boiler. A positive pressure of an inert gas, such as nitrogen, in the direction of the char flow, helps to avoid unwanted gases from the boiler entering the retort chamber. The char residue may be piped or transported by heat resistant conveyor from the distillation plant to the fluidised bed power station boiler. The char flow may be controlled via screws, double dump valve, vibration, compressed air, gravity, high temperature rotary valves, heat resistant belt conveyor, chain conveyer, vibrating conveyer such as vibrating tube conveyer, or any combination of the above means. The char residue is then combusted in the fluidised bed boiler in order to produce energy 4.2.1 in the form of steam in order to drive a turbine 4.3 in order to generate 4.5 electricity 8.0. Often, the hot char residue 3.1 is combined with a sorbent 4.1.1, for example limestone, in the fluidised bed boiler 4.1. The sorbent further minimises sulphur emissions by reacting with sulphurs to produce a coal combustion by-product 4.1.2. Coal combustion products (CCPs) are the inorganic residues that remain after coal is combusted, and include sorbent materials used in fluidised bed boilers. Examples of CCPs are (bottom ash, boiler lag, fly ash). CCPs can be successfully used in cements and concrete. Components of CCPs have different physical and chemical properties that make them suitable for different applications. Examples of applications are as synthetic gypsum in wall board manufacture, mine reclamation, road bases, and structural fill. Flue gas emission from the boiler can be further controlled by pre-emission purification of the gas stream to remove particulate matter and noxious gases 4.2.2 before being sent to the stack 4.2.3. One flu-gas desulphurisation method uses ammonia as the sorbent. The product is ammonium sulphate. Sulphate is the preferred form of sulphur readily assimilated by crops and ammonium sulphate is the ideal sulphate compound for soil supplements because it also provides nitrogen from the ammonia. Copper oxide is another regenerable sorbent to capture sulphur dioxide from flue gases in order to collect sulphur as a saleable by-product such as for example, elemental sulphur, ammonium sulphate fertiliser or sulphuric acid. Copper oxide can also catalytically reduce nitrogen oxides. Alternatively, sulphur can be removed from flue gas through the use of sorbents, such as metal oxide or calcium-based sorbents, or through the use of sulphur dioxide reduction catalysts. Other metal salts such as zinc titanate or zinc ferrite may be used to create metal sulphides which can be processed to regenerate the metal salts for reuse and concentrated SO₂. Harmful gaseous nitrogenous components such as NO_xcan be removed by processes such as Selective Catalytic Reduction (SCR) with ammonia, or by selective non-catalytic reduction (SNCR) or equivalent. Selective non-catalytic reduction (SNCR) is a post combustion method of controlling NO_xemissions in which ammonia or urea is mixed with air or steam and injected into a combustion chamber at high temperatures where it reacts at high temperatures with NO_xto produce nitrogen and water. By the SCR process, ammonia is injected into the flue gas where it reacts with NO_xin the presence of a catalyst, such as titanium or vanadium to produce nitrogen and water.
In the FIG. 6 schematic, after condensation of the condensable hydrocarbon fraction 5.1, the raw manufactured gas 6.1 can be filtered to remove particulate matter 6.2.1. Particulate emissions can be controlled by electrostatic precipitators (ESPs) and fabric filters (e.g. bag-house filters). ESPs are common devices for particulate control and have been commercially applied to collect dusts, fumes and mist particles. Fabric filters can achieve a high collection efficiency. A number of different filter media available for different filtering applications. Advanced gas flow distribution systems for fabric filters can eliminate abrasion and thus reduce bag wear. Hybrid systems combine electrostatic precipitation with fabric filtration to achieve high particulate removal efficiencies at low costs. Other methods include, and ceramic filters, cyclone filters and wet scrubbers including venturi, jet and EDV scrubbers. Before or after particulate filtration, sulphurous components can be extracted from the gas stream. HCN and COS can be removed via a hydrolysis reactor 6.2.2, acidic gas (e.g. H₂S) can then be absorbed from the gas stream 6.2.3 and through, for example, the Claus process 6.7.2, can be converted to elemental sulphur and then to sulphuric acid. Typically, the Claus process produces elemental sulfur by burning H₂S in the presence of a catalyst and recovering the sulfur from the resulting vapour as a condensate. Hydrogen sulfide (H₂S) is a smelly, corrosive, highly toxic gas. H₂S is commonly found in natural gas and is also made at coal power stations, especially if the coal contains a lot of sulfur compounds. Because H₂S is such an obnoxious substance, it is converted to non-toxic and useful elemental sulfur at most locations where it is produced. Claus sulphur recovery units can be combined with various tail gas units, for example: Beavon Tail Gas Unit and Selective Amine Tail Gas Unit. For boilers operating with heavy residue and coke containing large amounts of sulphur, recovery of the sulphur in the form of sulphuric acid becomes an attractive alternative. As mentioned, process economy is improved by increasing sulphur content due to the recovery of the heat of reaction and due to the sales value of the sulphur, in this case sulphuric acid product. Sulphur in the form of sulphuric acid can also be extracted from coal gases by the wet sulphuric acid (WSA) process (Topsøe). In short, the WSA Process is a catalytic process which converts H₂S and CS₂into SO₂as a first stage. SO₂is then converted into SO₃, and the SO₃reacts with the water vapour and is condensed as concentrated sulphuric acid of commercial quality (94-97% wt depending on actual design conditions). A large variety of sulphur containing effluents for example: hydrogen sulphide rich gases, Claus process tail gases, and boiler flue gases may be treated by this method. The process is also suitable for the treatment of sulphur containing gases with a high hydrocarbon content. The WSA process may be used in conjunction with the Claus process. In the Smoven process, coal gas is fed into an entrained-flow reactor containing a Zn-based sorbent, where sulphur components are absorbed leaving clean manufactured gas which passes through. When saturated with sulphur, or when reactivity is insufficient for practical sulphur removal, the sulphided sorbent passes to a separate reactor where it is regenerated in an oxygen rich atmosphere. The regenerated sorbent is then transferred back to the entrained-flow reactor to take part in another sorbent cycle. The regeneration reaction produces a tail gas rich in SO₂which may be used in the production of elemental sulphur, liquid SO₂or sulphuric acid. Other processes for the removal of hydrogen sulphide include absorption with potassium carbonate solution, absorption with an ammonia solution, or absorption with monoethanolamine solution.
Turning to FIG. 7, generally, the range of products of destructive distillation includes the following: fuel gases; light gasoline; naphtha; kerosene; diesel; and residuum 7.5.
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 C₅to C₁₂chains 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 FIG. 8, a schematic of the integrated energy conversion system is shown including a distillation plant with a retort 2.0, a power station including a boiler 4.1, a means for transferring char residue 3.1, and a collection means for the distillate vapours 5.1. In general, the hot char exits from the bottom of the retort and is transferred to the boiler of a power station. As shown in the alternative schematic of FIG. 9, the hot char may be transferred via a dual valve system whereby an opening at 2.01 opens to allow the egress of the char residue into an intermediate transfer section denoted by 3.1. The size of the intermediate transfer section will depend on the amount of coal being pyrolysed during the retorting process. The valve at 2.02 opens to allow the char residue to enter the power station boiler. Such a valve system is known as a double dump valve system. The char residue may be transferred via a conveyer section as shown at 3.1 of FIG. 8. The char exits the retort at 2.01 and is transferred onto a conveyer 3.1 at 2.02. The conveyer at 3.1 may be a pipe angled to provide gravity assistance to the transfer of the hot char. The transfer of the char from the retort to the conveyer may also be a dual valve process such as with a double dump valve. The distillate vapours exit the retort and condense via heat exchange. As previously discussed, depending on the reduction in temperature accomplished by the heat exchange process, there may be further liquid hydrocarbon fractions isolable, is addition to gaseous fractions. Gases can continue through the chamber 5.1 for further processing. The liquid distillate residue is collected (5.1) and the hydrocarbon fraction is further processed for upgrading. The hydrocarbon distillate can be transferred (5.10) for upgrading by fractional distillation (20.2) in a distillation tower (20.0) to provide hydrocarbon fractions as final products or materials may be further upgraded, or, the liquid hydrocarbon distillate fraction can be transferred such as by piping (5.12), directly from 5.1 to a hydrocracking plant to be cracked, optionally preceded by hydrotreating. The hydrocracked distillate can then be transferred (5.14) to a distillation tower (20.0) and further fractionally distilled to provide synthetic fuels 7.5. The direction of the arrow at 20.1 is representative of the range of different boiling points of different hydrocarbon fractions. The perpendicular arrows at 20.2 are representative of the different boiling fractions being bled off (separated).

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.