Furnaces – Process – Treating fuel constituent or combustion product
Reexamination Certificate
2002-08-09
2003-12-16
Bennett, Henry (Department: 3749)
Furnaces
Process
Treating fuel constituent or combustion product
C110S346000, C110S345000, C110S229000, C110S224000, C110S225000, C110S230000, C110S250000
Reexamination Certificate
active
06662735
ABSTRACT:
The invention concerns a reactor and a process for gasifying and/or melting materials. In particular, the invention concerns the material and/or energetic utilization of any type of refuse, e.g., with principally organic constituents, but also such utilization of special waste. However, the reactor and process of the invention are also well suited for the gasification and melting of feed materials of any composition as well as for the production of energy by the use of organic substances.
Solutions to the problem of thermal disposal of various types of waste and other materials have long been sought. In addition to combustion processes, various gasification processes are known, which are aimed chiefly at achieving results with the least possible impact of hazardous substances on the environment and at reducing both the expense associated with the treatment of the feed materials and the gases that arise in the process. However, the previously known processes are characterized by an expensive technology that is difficult to manage and by the associated high disposal costs for the feed material or refuse to be treated.
DE 43 17 145 C1 describes a process based on the principle of degasification for the disposal of variously composed waste materials. In the cited process, dust-containing gases that arise are completely drawn off as circulating gas and then burned with oxygen in the melting and superheating zone. However, as tests have shown, this circulation of the gas and the likewise described exhausting of the excess gas between the circulating gas exhaust port and the likewise described exhausting of the excess gas between the circulating gas exhaust port and the melting and superheating zone do not lead to the stated goal of obtaining an excess gas that contains only very few pollutants. If the circulating gas cupola also described in the cited document is used to carry out the process, then, among other problems, the pollutant load of the excess gas is so great that the gas management this necessitates for cleaning the excess gas becomes so expensive that economical disposal of the given waste materials is no longer possible.
DE 196 40 497 C2 describes a coke-fired circulating-gas cupola for the ultilization of waste materials. This circulating-gas cupola is characterized by the fact that an additional gas vent is located below the charging hopper. The pyrolysis gases drawn off at this point are returned by a circulating-gas line to the lower section of the furnace, in which combustion of the gases occurs. Since the discharge zone for the excess gases is located above the hot zone, not only excess gases, but also a large fraction of pyrolysis gases are exhausted, so that the gas mixture also contains hydrocarbons that are difficult to remove. The subsequent gas management thus becomes extremely expensive, and the environmental load increases.
DE 198 16 864 A1, on the other hand, describes a coke-fired circulating-gas cupola, in which the excess gas exhaust system is located below the melting and superheating zone. Although the quality of the excess gases can be increased in this way, since the discharged gases are greatly reduced as they flow through the superheating zone, the spatial proximity of the superheating zone results in very hot excess gases, which must then be cooled at considerable expense. Another problem is that this configuration causes slags and dusts to start to sinter in downstream parts of the discharge-side gas line. On the other hand, the temperatures in the hearth region below the gas discharge are no longer sufficiently high to maintain the molten metals and molten slags present in this region in a molten state under various charging conditions. This interferes with or entirely prevents the tapping which must be performed.
The prior-art solutions cited above are all based on the basic principle of recirculation of a partial stream of the gases that are formed, such that the gases are drawn off in the upper region of the furnace and returned to the lower region of the furnace. The engineering world has been proceeding on the assumption that this gas circulation is also necessary for heating the feed column through use of the countercurrent principle. However, the circulating-gas principle brings the following disadvantages with it: The gases rising in the shaft furnace cool off in the feed column, so that condensation phenomena of pyrolysis products in the gas withdrawal zones, in the circulating gas lines, and in the gas jet compressors needed for returning the circulating gas lead to problems that interfere with the function of the circulating-gas furnace. During the withdrawal of the circulating gas in the prior-art processes, dust particles and small particles of refuse material are necessarily withdrawn at the same time, which, together with the condensed pyrolysis products, lead to deposits that are difficult to remove inside the entire circulating gas distribution system. Furthermore, the feed column can be heated at only a relatively slow rate by the ascending circulating gas, so that, especially in the gasification of waste materials that contain large amounts of plastics, pieces of waste material adhere to the wall of the shaft and can ultimately lead to total obstruction of the furnace.
One of the goals of the present invention is thus to develop an improved reactor and a process for gasifying and melting feed materials, which avoid the disadvantages of prior-art reactors and processes. One specific goal is to achieve simple, inexpensive, and environmentally friendly material utilization and/or energetic utilization of refuse. We would especially like to enhance the functional reliability of this type of reactor by largely avoiding the operational problems associated with the circulating-gas system. Another goal of the invention is the significant reduction of the pollutant load of the excess gas to be discharged, so that the amount of work that needs to be done in a subsequent gas purification stage can be minimized.
Pursuant to these goals, and others which will become apparent hereafter, one aspect of the present invention resides in a reactor having a charge section with a feed opening through which the feed materials are charged to the reactor from above. A pyrolysis section which has an expanded cross section is located below the charging section so that a discharge cone of the feed material can form. Gas supply devices open into the pyrolysis section substantially at a level of the expanded cross section so that hot gases can be fed to the discharge cone. A melting and superheating section is located below the pyrolysis section and has a narrowing cross section. Upper injection devices are arranged immediately below a level of the narrowing of the cross section for supplying energy-rich medium to the melting and superheating section. A reduction section is located below the melting and superheating section and has gas exhaust devices through which excess gases are exhausted. A hearth is provided with a tap below the reduction section for accumulating and draining molten metal and molten slag. Lower injection devices are provided so that energy-rich medium is supplyable directly above the molten metal and slag and below the gas exhaust devices so as to prevent solidification of the molten metal and slag. In accordance with the invention, the principle of the circulating-gas process, which has long been applied in prior-art solutions, is abandoned, and instead a shaft furnace, which operates on the countercurrent principle, is used as the reactor. By completely abandoning the conventional circulating-gas system, all of the associated problems of condensation of pyrolysis products and the formation of undesirable deposits are completely avoided. In addition, partial conglomeration of the feed materials already starts to occur in the upper part of the reactor due to the shock-like heating of the feed column, so that adherence to the inside wall of the reactor is largely eliminated. The double injection of oxygen and fuel gas (gas mixtures
Tischer Eckhardt
Wuchert Frank
Bennett Henry
Maschinen- und Stahlbau GmbH
Rinehart K. B.
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