METHOD AND INSTALLATION FOR PROCESSING WASTE

Abstract: Installation for generating power, comprising: a main combustion chamber (16), being provided with means for generating steam, at least one supplementary combustion chamber (3) for burning carbonaceous materials, like wood, etcetera; a guiding duct (17) for guiding the flue gases (14) of said at least one secondary combustion chamber to the main combustion chamber, whereby the main combustion chamber is fit for burning fossil fuels. Preferably, the installation forms part of a power station.

Description: METHOD AND INSTALLATION FOR PROCESSING WASTE The present invention relates to an installation for generating power, comprising: a main combustion chamber, being provided with means for generating steam,- at least one supplementary combustion chamber for burning carbona- ceous materials, like wood, etcetera; a guiding duct for guiding the flue gases of said at least one secondary combustion chamber to the main combustion chamber. Such an installation is known from WO-A-81/01713. This prior art installation is fit for processing waste materials only. In this respect it is noted that, keeping the low energy content of waste in mind, the electrical power generated by such an installation is limited. Of course it is possible to scale up the installati- ons, but this leads to problems with the supply of waste materials and to large and voluminuous installations, which are difficult to operate economically. The aim of the invention is to provide an installa¬ tion and a method which is adapted for generating a substantial amount of electrical power and whereof the capital costs are limited. Therefore the present invention provides such an installation wherein the main combustion chamber is fit for burning fossil fuels. This offers the possibility to use conventional power stations, to which an additional installation may be added for the burning of waste materials. Also the waste materials are burned to a high extent leading to less ashes, whereas the installation already present for burning off fossil fuels provides in highly efficient use of the heat provided by the burning of the waste materials. Put it otherwise, the waste materials are burned, saving an amount of fossil fuels in keeping the power of the power station equally. In this respect it is noted that trials have been made to burn waste materials in the main combustion chamber of a power station. Bearing in mind that those combustion chambers are arranged for firing of substanti- ally powder sized particles, the waste materials have to be pre-processed by cutting or sawing them to the requi¬ red size. This involves substantial problems, so that this is not a very attractive option. According to a preferred embodiment particle removal means have been provided in the guiding duct. In view of the fact that waste materials often lead to flue gases with a high proportion of unburned ash-like materials, this feature leads to the advantage that the ashes reach the main combustion chamber which would lead to contamination of the main combustion chamber and to affecting the combustion process therein. According to another preferred embodiment the parti¬ cle removal means are arranged to remove particles with sizes down to a size which does not stop the process as in the main combustion chamber. These particle removal means may include at least one cyclone, or at least one electrostatic filter. Of course other implementations may be used. According to another preferred embodiment the main combustion chamber is fit for burning pulverized coal. According to another preferred embodiment preheaters are incorporated in the duct for the flue gases of the main combustion chambers for heating the combustion air for the main and secondary combustion chambers. In a preferred embodiment of the invention the waste material is burned in a so-called TORBED * reactor. The TORBED * reactor is a device which holds particles more or less in fluidisation, whilst the particles make a toroi¬ dal motion. For a more thorough description of the TORBED * reactor reference is made to EP-B-0 068 853, EP-A-0 293 103, EP-A-0 288 141 and EP-A-0 286 273. According to the invention the pre-burning of the waste material may take place in a normal oxygen environ- ment, for example when air is used as combustion air. This will result in flue gas that mainly comprises N 2 , 0., CO. and H.O. This type of flue gas may be used in a con¬ ventional boiler and by doing this, the amount of conven- tional fuel required may be reduced. When pure oxygen is used for burning the waste a flue gas comprising only 0., C0 2 and H.O is formed. Thus no nitrogen is present. If this type of flue gas is passed to a boiler then heat is absorbed and oxygen is used for combustion. In case the waste is burned in a low oxygen environ¬ ment, for example if flue gas from the power station or the combustion chamber itself is used as combustion gas, the flue gas of the TORBED * will still comprise amounts of CO. and H 2 0 but mostly CO, Ν. and H.. The thus obtained flue gas has reducing properties and may be used for various purposes. If fed to the boiler it will burn out and thereby reduce the amount of conventional fuel used. Because of its reducing properties it may be used as a re-burning agent for reducing ΝO χ . This process also takes place in the boiler. As an alternative the thus obtained flue gas may be sold as a reducing agent or for the production of H 2 . For the latter purpose a refinery should preferably be pre- sent in the vicinity of the power station because trans¬ port costs would make the process otherwise too expensi¬ ve. According to the invention the waste material and fuels are thus processed by burning it. The resulting products ashes, heat and flue gas may be either re-used, sold or stored. Ashes take in a much smaller amount of space than the initial wastes. Storage thereof is there¬ fore substantially simplified and less costly. The process of the invention is so-called "CO neu- tral". Carbonaceous waste material that is dumped will automatically produces carbon dioxide (CO ) and methane (CHJ eventually. Fossil fuels like coal are under the surface of the earth inert till exploitation and will not produce CO. by themselves, like wastes do. If the waste material is used according to the invention, still CO. is produced, even quicker than when dumped. However, the process of the invention will indirectly result in a replacement of part of the fossil fuel conventionally needed. The fuel that is saved by this will not produce CO.. In this situation one may speak of a "CO. neutral" process. The ashes resulting from a conventional boiler fed with fossil fuel, like coal, are of a well-defined compo¬ sition. Therefore, they may be used as such in construc¬ tion works, like road building and the like. If these ashes would cqntain contaminants resulting from material that is co-combusted with the conventional fuel, this would no longer be possible. Not only would the ashes be mistrusted by the user, but the risk of leaching of pollutants into the environment would be high. The invention is suited for a multitude of waste types. Preferably, carbonaceous wastes are used, such as wood, timber, chemical waste, municipal waste, vegetable, fruit and garden waste and the like. Even polymeric materials, like PVC, may be burned. Furthermore, the invention may be used for fuel types that are difficult to process in a conventional boiler like cokes etcetera. The method of the invention may result in a more flexible management of the power station. In case the boiler is not used to the full 100 % the pre-combustion chamber may be switched off. As an alternative the com¬ bustion chamber may still be in operation, but the flue gas may either be stored or carried away to be sold or for the production of pure H.. If stored it may be used again during peak hours. If waste material such as clean wood is used for co- combustion in the boiler, it must be reduced in size prior to introduction in the boiler. However, according to the invention the waste material need not necessarily be reduced before being burned in the TORBED * . This is a very important advantage of the method of the invention since the pre-processing costs thereof are therefore lower. The principles of the present invention may find application in various practical embodiments that fall within the scope of this invention, but are not extensi¬ vely described here since the skilled person will be capable of designing installations suited for a parti¬ cular purpose based on the information given in this application. The invention will therefore be illustrated with reference to one embodiment only, schematically shown in the Figure. In this embodiment waste material 1 is fed via a conduit 2 to a TORBED * 3. The TORBED * 3 comprises means 4 for supplying the waste to the toridal bed 5. The bed 5 is produced by means of an air flow 6 that is supplied through a supply pipe 7. The air flow is channeled through a series of blades 8 thus causing the toridal motion of the bed 5. The TORBED 9 also comprises a burner 9 fed by means of a fuel pipe 10. The ashes 11 are dis- carded through an opening 12 along the periphery of the bed and collected in a container 13. As an alternative the ashes may be fed to the boiler together with flue gas. The flue gas produced (symbolized by arrows 14) is discharged through a pipe 15 in the top of the TORBED * 3. The flue gas 14 is transported to the boiler 16 via a conduit 17 or optionally via a cyclone. Depending on the type of gas used for the pre-burning process the flue gas is discharged through one or more of the outlets 18, 19, 20, 21 and 22. The use of a surplus of air will result in flue gas type A, comprising N 2 , CO., H.O, 0., dust and other com¬ pounds. Use of a low amount of oxygen results in flue gas type B, having reducing properties and comprising CO, H., H.O, 0_, CO. and dust. Outlet 18 may be used for flue gas types A and B. Type A may also be injected via outlet 19 or together with the powder coal 25 introduced via inlet 20. Gases of type B may be introduced together with so-called secon¬ dary air at outlet 20. Outlet 21 may be used for discharging flue gas type A together with so-called tertiary air. Reburn fuel (type B) may be introduced via outlet 22. The boiler further comprises a series of burners 25, and an outlet for slag or bottom ash 26. The heat produced in the boiler may for example be used for the generation of steam for driving a turbine (not shown) . The water from which the steam is produced may already be pre-heated by the heat generated in the TORBED * 3. For this purpose the TORBED * is provided with a spiral pipe 23. Water 24 is transported through the spiral, pre-heated there and transported to a steam generating device (not shown) .

Claims: CLAIMS 1. Installation for generating power, comprising: - a main combustion chamber, being provided with means for generating steam,- - at least one supplementary combustion chamber for burning carbonaceous materials, like wood, etcetera; - a guiding duct for guiding the flue gases of said at least one secondary combustion chamber to the main combustion chamber, characterized in that the main com¬ bustion chamber is fit for burning fossil fuels. 2. Installation for generating power according to claim 1, characterized in that the installation forms part of a power station. 3. Installation according to claim 1 or 2, characte¬ rized in that the in the guiding duct particle removal means have been provided. 4. Installation according to claim 3, characterized in that the particle removal means are arranged to remove particles with sizes down to a size which does not dis¬ turb the processes in the main combustion chamber. 5. Installation according to claim 3 or 4, characte¬ rized in that the paticle removal means include at least one cyclone. 6. Installation according to claim 3, 4 or 5, cha¬ racterized in that the particle removal means include at least an electrostatic filter. 7. Installation according to one of the preceding claims, characterized in that the main combustion chamber is fit for burning pulverized coal. 8. Installation according to one of the preceding claims, characterized in that in the duct for the flue gases of main combustion chamber air preheaters are incorporated for heating the combustion air for the main and secondairy combustion chambers. 9. Installation according to one of the preceding claims, wherein the main combustion chamber extends substantially vertical, and injection means are provided for injecting the flue gases of the secondary combustion chamber into the main combustion chamber, characterized in that the injection means are substantially located in that part of the main combustion chamber wherein the combustion takes place. 10. Installation according to one of the claims 1-8, wherein the main combustion chamber extends substantially vertical, and injection means are provided for injecting the flue gases of the secondary combustion chamber into the main combustion chamber, characterized in that the injection means are substantially located in the upper part of the main combustion chamber. 11. Installation according to one of the preceding claims, characterized in that the secondary combustion chamber is a combustion chamber according to the TORBED principle. 12. Method for burning carbonaceous materials and fossil fuels, characterized in that the installation according to one of the preceding claims is used.

Inventors: JANSSEN FRANSISCUS JOHANNES JO, KONINGS ANTONIUS JOCABUS ADRIA, JANSSEN, FRANSISCUS, JOHANNES, JOSEPHUS, GERARDUS, KONINGS, ANTONIUS, JOCABUS, ADRIANUS
Applicants: JANSSEN FRANSISCUS JOHANNES JO, KEMA NV, KONINGS ANTONIUS JOCABUS ADRIA, JANSSEN, FRANSISCUS, JOHANNES, JOSEPHUS, GERARDUS, KONINGS, ANTONIUS, JOCABUS, ADRIANUS, N.V. KEMA
Application year: 1996
Main classification: F23G5
IPC codes: F22B31, F23G5