Gas: heating and illuminating – Generators – Cupola
Patent
1986-03-13
1988-04-26
Lacey, David L.
Gas: heating and illuminating
Generators
Cupola
48 63, 48 64, 48 89, 122 4D, 110245, 422141, 422142, 422143, 201 31, C10J 368
Patent
active
047402164
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for the gasification of waste, especially light waste such as wood chips, paper and plant waste, which consists of a fluidized bed reactor in which a pyrolysis takes place, followed by combustion of the waste.
Although various types of fluidized bed reactors for the gasification of waste are already known, the present invention is aimed at providing a new type of reactor which is essentially suitable for the gasification of light products such as paper and plastic residues, wood chips and plant waste, and the like.
According to the present invention, the device for the gasification of waste consists of two concentric chambers, each chamber having a bottom portion with the two concentric chambers communicating through their respective bottom portions, wherein a first chamber, called a pyrolysis chamber, is intended to implement the pyrolysis of the waste supplied, and wherein the other chamber, called a combustion chamber, is intended to implement the combustion of the matter subjected to pyrolysis in the first chamber, the combustion being maintained by a stream of air with or without steam under pressure, which entrains the pyrolyzed matter from the pyrolysis chamber into the combustion chamber by induction through the bottom, the fluidized bed of the pyrolysis chamber being supplied by a part of the pyrolysis and/or combustion gases which is recycled and heated beforehand in the combustion chamber, and the fluidized bed in the combustion chamber being supplied by said stream of air with or without steam under pressure.
According to a preferred embodiment of the present invention, the device for the gasification of waste consists of two concentric chambers communicating at the bottom, wherein the outer chamber forms the pyrolysis chamber and wherein the inner chamber forms the combustion chamber.
According to a preferred embodiment of the present invention, a part of the mixture of the recycled pyrolysis and combustion gases passes through a heat exchanger which forms the dividing wall between the inner and outer chambers, before being conveyed to the fluidization device of the pyrolysis chamber.
Advantageously, the fluidized bed of the pyrolysis chamber contains a refractory, noncombustible substance with a weight similar to that of the waste, for example expanded clay beads or chamotte beads, which act as a heat carrier.
It is thus found that, according to the invention, a circulation is established between the pyrolysis chamber and the combustion chamber, by virtue of the induction of the matter from the pyrolysis chamber via the bottom, due to the relative velocity of the air and/or of the steam injected into the combustion chamber in relation to the velocity of the fluidizing gases in the pyrolysis chamber; this giving rise to differences in the apparent density between the two beds.
The combustion is advantageously controlled by adjustment of the relative flow rates of each of the gases and, in particular, by the speed of rotation of a fan which may be provided for injecting the air or the rate of flow of steam into the combustion chamber, for example the lower chamber.
By virtue of the advantageous arrangement of the gasification device of the invention, the temperature of the fluidized bed in the pyrolysis chamber is easily kept constant. In fact, the expanded clay beads, which accumulate heat, are also entrained in the circulation described above and are thus reheated in the combustion chamber before moving into the pyrolysis chamber, where they are again drawn via the bottom into the combustion chamber with the other waste. Furthermore, the fluidizing gases in the pyrolysis chamber are hot gases which are recovered and preheated once again by a heat exchanger arranged in the combustion chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
Other details and advantages will become more clearly apparent from the reading of the following examples, described with the aid of the figures, in which:
FIG. 1 is an embodiment of the gasification device of the present inven
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patent: 4436057 (1984-03-01), Cross et al.
patent: 4464247 (1984-08-01), Thacker
patent: 4505230 (1985-03-01), Caplin
Cokerill Mechanical Industries, Inc.
Lacey David L.
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