Magnetic desulfurization of airborne pulverized coal
AssigneeMobil Oil Corporation
InventorTsoung-Yuan Yan
Life of this patent
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Abstract
A process for removing pyrite particles from coal by pulverizing and fluidizing a coal in the presence of (a) heated air, followed by removing pyrite particles with a high-gradient magnetic separator; or (b) a hot, inert gas from which condensables are separated, followed by countercurrently further heating the coal in a succession of fluidized stages with hot oxygen-containing gas to a temperature at which the pyrite particles are sufficiently converted to pyrrhotite, magnetite, and gamma-hematite to raise the average magnetic susceptibility to at least 2 .times. 10.sup.6, and removing the pyrite minerals by magnetic separation means. The beneficiated coal or semicoke particles are fed with heated air and evolve volatile matter to the combustion zone of a furnace.
Claims19
A method for producing a rapidly burning fuel for large-scale electrical and steam generation by:
- A. preheating a coal, having a high content of inorganic sulfur and 35-50 percent by weight of volatile matter on a moisture-free basic, to a temperature high enough to enhance the magnetic susceptibility of said inorganic sulfur, while preventing agglomeration of said coal and while selectively retaining said volatile matter as a portion of said rapidly burning fuel, by:
- 1. disintegrating said coal to about 200 mesh to form pulverized coal while passing a stream of heated gas therethrough at sufficient velocity to entrain and fluidize said pulverized coal,
- 2. drying said pulverized coal and separating the dried coal from said heated gas within a fluidized stage to form dried pulverized coal, and
- 3. successively entraining said dried pulverized coal with a stream of hot oxygen-containing gas in sequential fluidized stages having successively higher temperatures, while passing said oxygen-containing gas countercurrently thereto, so that said dried pulverized coal is subjected to a final temperature of about 480.degree.-600.degree. C. and said inorganic sulfur has enhanced magnetic susceptibility;
- B. magnetically removing at least a portion of said inorganic sulfur having enhanced magnetic susceptibility by passing said dried pulverized coal through a magnetic separator means to produce a beneficiated coal;
- and
- C. entraining said beneficiated coal with a mixed oxygen-containing gas, which selectively contains all evolved volatile matter from said sequential fluidized stages, and controllably feeding said beneficiated coal, said evolved volatile matter, and said mixed oxygen-containing gas, as said rapidly burning fuel, to the combustion zone of a furnace used for said large-scale electrical and steam generation.
A method for (a) preheating bituminous, high bituminous, and sub-bituminous coals having a high content of pyritic sulfur to a temperature high enough for enhancing the magnetic susceptibilities of said pyritic sulfur while preventing agglomeration of said coals, (b) magnetically removing at least a portion of said pyritic sulfur from said coals to form beneficiated coals, and (c) controllably admitting said beneficiated coals, with at least a remaining fraction of evolved volatile matter and sufficient combustion air, to the combustion zone of a furnace as a rapidly burning fuel that is easily metered and has a reasonably low content of sulfur, comprising:
- A. forming a dried pulverized coal and an oily distillate within a closed cycle for a heated inert gas by the following steps:
- 1. disintegrating a coal containing pyritic sulfur to about 200 mesh to form a pulverized coal while passing heated inert gas therethrough at sufficient velocity to entrain and fluidize said pulverized coal,
- 2. drying said pulverized coal, partially distilling volatile matter therefrom, and separating said pulverized coal from said inert gas within a fluidized stage, and
- 3. condensing said partially distilled volatile matter from said inert gas to form said oily distillate and recirculating said inert gas, after heating thereof to form said heated inert gas, to the coal being disintegrated;
- and
- B. forming said rapidly burning fuel within a counter-current cycle for a heated oxygen-containing gas by the following steps:
- 1. successively entraining said pulverized coal with a stream of heated oxygen-containing gas in sequential fluidized steps having successively high temperatures while passing said oxygen-containing gas countercurrently thereto, so that said pulverized coal is subjected to a final temperature of about 480.degree.-600.degree. C that enhances said magnetic susceptibilities of said pyritic sulfur,
- 2. passing said pulverized coal through a magnetic means and magnetically removing said at least a portion of said pyritic sulfur therefrom to produce a beneficiated coal, and
- 3. entraining said beneficiated coal with cooled oxygen containing gas, which contains said at least a remaining fraction of evolved volatile matter from said sequential fluidized stages, and controllably feeding said beneficiated pulverized coal, said evolved volatile matter, and said oxygen-containing gas to the combustion zone of a furnace.
Dependencies are inferred from the claim text.