Gas: heating and illuminating – Processes – Coal and water
Patent
1989-05-19
1991-11-12
Kratz, Peter
Gas: heating and illuminating
Processes
Coal and water
48 73, 48210, C10J 354
Patent
active
050644440
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process for the allothermic gasification of coal under pressure with steam, in a gas generator containing heat-exchange tubes for the heat-transfer medium, as well as to a fluidized bed gas generator for carrying out the process.
THE RELATED ART
Basically, the gasification of solid fuels takes place at elevated temperatures. The heat required for the heating and conversion, is either provided through partial combustion (autothermic process) or through supply of external heat (allothermic process). Compared to the autothermic gasification, the allothermic gasification has the advantage that the fuel does not have to be partially burned in the gasification zone, in order to provide the necessary heat. In the allothermic gasification, the heat can be provided from any external sources, such as for instance high-temperature core reactors, but also from combustion chambers, wherein a fraction of the gas product is burned. This advantage is afforded in the case of coal gasification up to high conversion degrees, as well as in the case of partial gasification, whereby next to a gas a fine coke is to be produced, e.g. for a process for the production of pig iron, with coupled gas production.
Allothermic fluidized bed gas generators of horizontal and vertical construction are known per se, for instance from German Patent 24 23 951.8, German Patent 25 49 784.1, German Patent 31 12 708.8 and German Patent 30 42 142. In these inventions, a common departure point was that in all zones of the gas generator the heat carrier is supplied parallelly with the high lead temperature, also for instance in the coal dosage zone. In this zone, the heating of the coal takes place, whereby also the volatile components contained in the coal are eliminated. Thereby, the individual coal particles, in their structure and chemical composition, make the transition to the state of coke particles. While the eliminated volatile substances, particularly the resulted tars, are further converted in secondary reactions, the resultant coke starts to gasify. The process of release of the volatile substances and of coke formation, which precedes the actual gasification process, is called pyrolysis. Subsequently, the corresponding zone of the gas generator, wherein the pyrolysis basically takes place, is called the pyrolysis zone.
It is the object of the invention to develop the process of the aforementioned kind so that the supplied heat is optimally used, as well as to provide a suitable gas generator.
SUMMARY OF THE INVENTION
This object is attained in a process for allothermic gasification of coal under pressure of steam in a gas generator containing heat-exchange tubes for a heat-transfer medium wherein the hot heat-transfer medium coming through the heat-exchange tubes in the gas generator is first introduced into a gasification zone and subsequently into a pyrolysis zone, while the coal to be gasified is passed in counterflow through the gas generator, so that for coal heating and pyrolysis the already cooled down heat-transfer medium is used, while heat required for gasification is extracted from a still hot stream of heat-transfer medium.
Due to the successive arrangement of gasification- and pyrolysis zones, considered from the heat-transfer side, the entire energy at high temperature is made available to the gasification zone, a fact which is very favorable to the kinetics, i.e. the speed of the gasification process. Subsequently, the entire heat-transfer medium reaches the pyrolysis zone with a lower entering temperature, and remains there to cover the heat needs for the heating and the pyrolysis process. Since the heat carrier and gasification medium are traveling in counterflow, there results a clearly improved heat utilization of the heat-transfer medium. From the point of view of kinetics, the lowered temperature has no negative effect on the pyrolysis reaction, because there it is less a matter of high temperatures, than of sufficiently large amounts of available heat. This is
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Gappa Gunther
Kalwitzki Heinrich
Knop Klaus
Kubiak Helmut
Schroter Hans J.
Bergwerksverband GmbH
Dubno Herbert
Kratz Peter
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