The present invention relates to a process and an apparatus for the production of energy and a process and an apparatus for the production of methanol.
Numerous processes and apparatus are already known for the production of energy and/or methanol from organic raw materials.
Some of these processes and apparatus are based on the principle that an organic material is subjected to controlled oxidation wherein the energy carrier hydrogen is produced. The obtained hydrogen is supplied to a fuel cell and converted into current, according to the actual current requirements. Since storage of excess gaseous hydrogen is labourious and must especially satisfy stringent safety requirements when used in private households, hydrogen is normally catalytically converted together with carbon monoxide or carbon dioxide into the fluid energy carrier methanol in order to store its energy content, wherein the hydrogen can be re-extracted from the methanol and converted into current according to requirements by means of a reforming reaction.
A process for the storage of energy present in the form of hydrogen is disclosed in DE 196 44 684 A1, wherein carbon dioxide, especially resulting from exhaust emissions, is converted after mixing with the hydrogen in a reactor into the energy carriers methane, methanol or ethanol.
A process and an apparatus for the production of electrical energy from bio-raw materials is disclosed in DE 44 30 750 C2, wherein a hydrogen and carbon monoxide-containing crude fuel gas is produced from the bio-raw materials by means of partial oxidation with an oxygen-containing gasification medium in an oxidation reactor. From the fuel gas, the hydrogen proportion is placed into intermediate storage by reaction with a storage material, especially a so-called hydride store or with metal oxides, so that rapid removal of the hydrogen from the storage can be carried out according to requirements, and the hydrogen can be transported into a fuel cell module for conversion into current.
A process and an apparatus for the production of hydrogen by means of the gasification of bio-raw materials is disclosed in DE 197 34 259 A1, wherein the bio-raw material is gasified into a hydrogen-containing crude gas in the presence of supplied water vapour in a vaporization reactor. The hydrogen proportion of the crude gas is separated from the residual gas at especially-high purity and can either be converted into current in a fuel cell, stored as methanol by synthesis with carbon dioxide or used for other purposes. In order to increase the degree of effectiveness in this process, the energy content of the low-hydrogen residual gas is also used in that it is combusted either in a closed cycle for the production of heat energy for the creation of water vapour or outside the cycle.
A process is known from EP 0 257 018 A2 for thermal utilisation of waste and/or waste fuels, wherein the waste and/or waste fuels are supplied to a gasifying reactor which is directly heated with gas and/or oil and the gases extracted from the gasifying reactor are supplied to a combustion chamber for the production of energy, especially for the production of steam. A portion of the flue gases from the combustion chamber is fed back to the gasifying reactor under pressure.
A process is known from DE 32 28 532 A1 for the carbonisation and gasification of solids which contain carbon wherein hot gases, amongst others, are used to heat the reactors, these gases being produced in a combustion chamber by combustion of a portion of the carbonisation gas produced in the carbonisation zone.
In xe2x80x9cEnergy Recovery From Waste: The Application of Gasification Technologiesxe2x80x9d, La Chimica e l""Industria, 1996, No. 5, pp. 603-607, P. Pollesel gives an overview of the use of gasification processes to extract energy from waste, especially from bio-mass. Amongst other things, Pollesel mentions that the gases produced during gasification can be combusted in a gas turbine or a diesel engine to produce mechanical energy which can then be converted into electrical energy.
Consequently, the object of the present invention is to provide a process and an apparatus for the production of energy and methanol respectively wherein optimised exploitation of the energy content of the organic starting material occurs in order to attain especially economical operation, and simultaneously allowing control of the proportions of released and stored energy respectively, according to requirements.
A process according to claim 1 and an apparatus according to claim 9 or 11 is suggested as a solution for this object. The process for the production of energy, according to the invention, comprises the following steps:
1. Combustion of fuel in an internal combustion engine to create mechanical energy and hot exhaust gas which contains carbon dioxide and water vapour,
2. Reduction of the hot exhaust gas components carbon dioxide and water into a synthesis gas which contains carbon monoxide and hydrogen in an environment containing a supplied organic material,
3. Supply of the synthesis gas produced in step 2 to the internal combustion engine.
According to claim 7, methanol synthesis is inserted between steps 2 and 3 of the process according to the invention in order to produce methanol.
The steps of the process, according to the invention are set out for a recirculating operation, from which at different points energy in the form of electrical energy (current), heat energy and stored chemical energy (methanol) can be removed and/or added at various points, wherein the removal and supply can be regulated according to requirements, allowing optimised utilisation of the energy content of the organic starting material.
Therefore in accordance with the invention, a fuel which is preferably fluid or gaseous and contains hydrocarbon is combusted on supply of air or oxygen in an internal combustion engine, creating mechanical energy, exhaust gas and heat energy. The exhaust gas released by the internal combustion engine, which contains carbon dioxide and water vapour, is supplied to a thermochemical reactor in which organic material such as biomass, coal, organic waste and such like is present. In the thermo-chemical reactor, carbon dioxide and water are reduced into carbon monoxide and hydrogen from the exhaust gas stream from the internal combustion engine, whilst the organic material is oxidised. The temperature required for the reaction is produced by the heat energy of the exhaust gas stream. Insofar as the temperature attainable by the inflowing exhaust gas is not sufficient to start or to maintain the reaction, a part of the hot exhaust gas stream from the internal combustion engine can be separated from the rest of the stream and used as an external heat supply for heating the thermochemical reactor and/or the temperature level required for the reaction can be increased by the supply of oxygen or air. Advantageously, the temperature of the hot exhaust gas is between approximately 900xc2x0 C. and approximately 1000xc2x0 C. In this way, the hot exhaust gas from the internal combustion engine is directly used as a valuable energy carrier whilst the mechanical energy produced by the internal combustion engine is available for other purposes.
A synthesis gas which contains carbon monoxide and hydrogen is produced in the thermo-chemical reactor under suitable pressure and temperature conditions. The synthesis gas may contain other non-troublesome components such as, for example, carbon dioxide or methane, and undesired or troublesome solid, fluid and/or gaseous components such as, for example, suspended particles or sulphurous gases. The troublesome or undesired components can have a disadvantageous effect on further steps of the process, according to the invention, e.g. they can cause deactivation of a catalyst. Hence a filtration step is provided downstream for removal of the undesired or troublesome components.
The synthesis gas from the thermo-chemical reactor which contains carbon monoxide and hydrogen and which has been purified in the filtration step is mixed in a gas mixing unit with air oxygen or oxygen from an oxygen tank and is supplied to the internal combustion engine as a fuel. In this way, the supply of the thermo-chemical redox process with hot exhaust gas is ensured.
Insofar as more synthesis gas is produced than is required for the operation of the internal combustion engine, as an alternative the synthesis gas, which contains carbon monoxide and hydrogen and which has been purified in the filtration process can be synthesised into the energy carrier methanol from carbon monoxide and hydrogen or carbon dioxide and hydrogen in an exothermic reaction according to a conventional process in a reactor which contains a suitable catalyst. Apart from heat energy, resultant reaction products are methanol and optionally water as well as non-converted synthesis gas. The reaction products are cooled in a downstream cooling unit. The precipitating methanol can be fed into a tank and stored. According to requirements, the stored methanol can be supplied to the internal combustion engine as a fuel, or used for other purposes e.g. as a fuel for motor vehicles.
Excess, non-converted residual synthesis gas from the methanol synthesis is supplied to the internal combustion engine as described above.
In an embodiment of the Invention, the mechanical energy produced by the internal combustion engine is transformed into current by means of a generator. The current can either be available for the supply of a private household, stored in batteries or fed into the supply mains.
In a further embodiment of the invention, a fuel cell in a fuel cell unit is supplied via a gas mixer with oxygen and hydrogen in order to produce current, wherein the oxygen can be supplied from an oxygen tank or can be air oxygen and the hydrogen either originates from the synthesis gas purified by the filtration process or by reformation from the stored methanol. An especially-high degree of effectiveness for conversion of stored chemical energy into electrical energy can be attained with this type of current production. Furthermore, it is possible to adapt the production of current to an existing load by using the chemical energy of the stored methanol.
In an especially advantageous embodiment of the invention, heat resulting from the individual process steps, especially the radiated heat of the internal combustion engine, the generator, the methanol reactor and the cooling unit, can be supplied to a heat store where it is available, for example, for heating the thermo-chemical reactor or for heating rooms.
In a further especially advantageous embodiment of the invention, the material and energy streams can be controlled by means of a controller, e.g. a microprocessor control. This especially relates to the control of exhaust gas supply from the internal combustion engine into the thermo-chemical reactor, the control of the gas streams in the gas mixing unit, the monitoring and control of the parameters of the methanol synthesis, temperature regulation in various process steps, regulation of the energy streams of the heat storage and monitoring the level or regulation of the supply of organic material into the thermo-chemical reactor. In this way, optimum supply of the elements of the individual process steps with substrates and energy is attained at all times. Simultaneously, the energy content of the fuel is optimally used and adaptation of energy extraction and energy storage to the respective requirements is made possible.
In order to further solve the object which forms the basis of the invention, an apparatus is suggested for the production of energy and/or methanol, especially for implementation of the hereinbefore-described process. The apparatus, according to the invention, comprises an internal combustion engine, a thermo-chemical reactor disposed downstream of the internal combustion engine for reduction of the exhaust gas, which is produced in the internal combustion engine and which contains carbon dioxide and water steam, into a synthesis gas which contains carbon monoxide and hydrogen. An inlet is provided for the synthesis gas into the internal combustion engine so that energy may be produced. For the production of methanol, a methanol reactor is disposed downstream of the thermo-chemical reactor for Synthesis of methanol from the synthesis gas of the thermo-chemical reactor, wherein the synthesised residual gas and/or methanol from the methanol synthesis are fed into the internal combustion engine.
In an advantageous embodiment of the invention, a generator which can be driven by the internal combustion engine is provided for the production of current. Furthermore, a fuel cell apparatus disposed downstream of the thermo-chemical reactor can be provided for the production of current from methanol and/or at least part of the hydrogen produced in the thermo-chemical reactor.
In a further embodiment of the apparatus according to the invention, in order to store energy a heat storage is provided for storage of the heat generated with the apparatus. The heat storage serves especially for storage of the radiated heat from the exothermic process steps, for example from the internal combustion engine, the generator, the methanol synthesis and/or the cooling unit. The stored radiated heat is used in the exothermic process steps in the thermo-chemical reactor or for other purposes. Furthermore, a methanol tank is provided for storage of the synthesised methanol, wherein the stored methanol can be supplied to the internal combustion engine and/or the fuel cell apparatus if required.
Other advantages and embodiments of the invention can be seen in the description and the accompanying drawing.