Method of and apparatus for producing combustible gases from...

Gas: heating and illuminating – Generators – Cupola

Reexamination Certificate

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Details

C048S1970FM, C048S203000, C048S206000, C201S021000

Reexamination Certificate

active

06312483

ABSTRACT:

TECHNICAL FIELD
This invention relates to a method of and apparatus for producing combustible gases from pulverized solid fuel such as pulverized coal, and more particularly, coal having a high ash content. It is particularly suitable for use in power plants that generate heat or electricity.
BACKGROUND OF THE INVENTION
The Winkler Process is a well-known method of solid fuel gasification using a fluidized bed. In this process, crushed or pulverized fuel is gasified in a fluidized bed using blast steam-oxygen, or steam-air, forced draft. This one-step process works well for the gasification of lignites; but problems are encountered in the case of bituminous coals. Such problems arise because of the high content of volatile substances in bituminous coals which produce considerable amounts of tars in the gasification process. The gasification process carbonizes the tar into particles that tend to agglomerate; and this adversely affects the reliability of gas producers of this kind.
Another well-known process of gasification of coal involves a counter-flow, multiple-stage, fluidized bed. In this process, the coal is initially outgassed by uncleaned gas, and semi-coked by hot uncleaned low-calorie producer gas, which is fed to the using equipment (a boiler plant or gas turbine) following dust removal and proper cleaning. This method is sometimes referred to as the Westinghouse process prototype.
It is an object of the present invention to provide a new and improved method of and apparatus for generating combustible gases from pulverized coal, and more particularly, coal having a high ash content, which overcome or substantially ameliorates the problems of the prior art described above.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides a method of and apparatus for generating combustible gases from pulverized solid fuel such as pulverized coal by semi-coking and predrying the pulverized coal in a reactor in the absence of oxygen to produce a solids stream that includes carbonaceous material and a gas stream that includes hydrocarbon gases and tar fumes. The carbonaceous material in the solids stream is gasified in a fluidized bed using steam and hot air to produce an output stream that includes combustible gases and coke particles. The output stream is combined with the gas stream to form a combined stream which is separated into a combustible gas stream and a hot particulate stream. At least a part of the hot particulate stream is applied to the reactor.
The fluidized bed used in this invention should have a larger mass of inert material than fresh fuel than is used in conventional processes, e.g., the Westinghouse process, in order to prevent agglomeration of particles in the reactor due to the application to the reactor of the hot particulate stream as the heat transfer agent for semi-cocking. Preferably, the mass ratio of inert material to fresh fuel in the fluidized bed is not less than about 2:1, and preferably lying between 2:1 to 12:1, although the ratio may be even higher.
The present invention also includes dividing the hot particulate stream into a first portion that is applied to the reactor and a second portion that is burned to produce flue gases, and transferring heat from the flue gases to air for producing the hot air used for the fluidized bed. Preferably, the burning of the second portion is carried out using air above the stoichiometric value, and effectively flame neutralizes toxic substances, e.g., phenols, CaSO
4
carbon disulfide, etc.


REFERENCES:
patent: 2579397 (1951-12-01), Roetheli
patent: 2579398 (1951-12-01), Roetheli
patent: 2582712 (1952-01-01), Howard
patent: 2588075 (1952-03-01), Barr et al.
patent: 2609283 (1952-09-01), Kalbach
patent: 2622973 (1952-12-01), Barr
patent: 2662816 (1953-12-01), Kalbach
patent: 3966633 (1976-06-01), Friedman
patent: 4347064 (1982-08-01), Reh et al.
patent: 4696679 (1987-09-01), Albulescu et al.
patent: 4999030 (1991-03-01), Skinner et al.
patent: 87102473 (1988-06-01), None
patent: 2068014 (1981-08-01), None

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