Battelle Development Corporation

Ke-Tien Liu

Herman Nack

Satya P Chauhan

Edgel P Stambaugh

Herman F Feldmann

Nitrogen oxide pollutants are substantially reduced and sulfur dioxide minimized in multisolid fluidized beds by staged combustion of the fuel. The lower combustion region is operated at substoichiometric conditions such that NO.sub.x is reduced by carbon and carbon monoxide to nitrogen gas. The upper combustion region is operated at excess oxygen conditions to complete the combustion of char and carbon monoxide. Elevated temperature excursions in the upper region which deter sulfur capture are prevented by recycling cool entrained bed particles therethrough.

NO.sub.X reduction in multisolid fluidized bed combustors

A process for treating solid particles (66) of a raw carbonaceous fuel (62) such as coal having an original sulfur content comprises producing (at 68) a slurry (74) of a quantity of the raw fuel particles and a liquid medium (70) comprising water, at least one alkali metal compound including a substantial amount of sodium or potassium sulfide or polysulfide or a combination thereof, and a catalytic agent (72) comprising calcium or magnesium oxide or carbonate, or dolomite. The slurry is subjected (in 78) for an effective period of time to elevated temperature and pressure effective with the alkali metal compounds and water to cause the medium to penetrate the microscopic structure of the particles and to chemically and physically incorporate a substantial amount of the catalytic agent into the structure. The readily separable medium is separated (at 84) from the fuel particles and the particles are washed (at 84,106) to produce a particulate fuel product (88,110) containing the incorporated catalytic agent. A substantial portion (90,94) of the separated medium is added (at 70) to the slurry produced as above. A sufficient quantity of the catalytic agent is added (at 72) to the medium or the slurry to replace the catalytic agent removed from the slurry with the particulate fuel product. More raw fuel particles (66) are added to the medium or the slurry. The foregoing steps are carried out continually with a multiplicity of new additions of the raw fuel particles and with a multiplicity of reuses of the separated medium to produce fuel product particles (88,110) containing a quantity of sulfur that is not less than the original sulfur content, in addition to the catalytic agent.

Solid fuel preparation method

A method of operating a fluidized bed system in a single vessel, typically as a combustor system for power or steam generation burning high-sulfur coal or as a gasifier for high-sulfur coal, which comprises forming an entrained fluidized bed in a first space region containing a first solid bed particle component, such as sand or hematite ore containing over 90% Fe.sub.2 O.sub.3, forming in a limited space region partially within the first region a dense fluidized bed containing a second solid bed particle component, such as larger particles of the hematite, both first and second component particles essentially comprising a material having long-term physical and chemical stability in the fluidized bed system so as to be substantially nonagglomerating and not subject to substantial attrition therein, effecting division of the dense fluidized bed into upper and lower zones, providing a recirculation path such as through a cyclone separator and particle reservoir for the first particle component from the first space region through the upper zone of the dense fluidized bed in the more limited space region, operating the fluidized bed system at a velocity such that the second component particles are effectively retained in the dense fluidized bed in the more limited space region, whereas the first component particles recirculate and interpenetrate through the upper zone thereof commingling with the second component particles, and maintaining different temperatures in the upper and lower zones of the dense fluidized bed. Typically, the temperature of the upper zone of the dense fluidized bed is conducive to capture of sulfur gases by a sorbent while a high temperature in the lower zone of the dense fluidized bed is maintained to be conducive to combustion of fuel and calcination of sorbent (for combustors) or gasification of fuel (for gasifiers).

Two-zone fluid bed combustion or gasification process

A method of operating a fluidized bed system, typically as a combustor system for power or steam generation by burning high-sulfur coal, which comprises forming an entrained fluidized bed in a first space region containg a first solid bed particle component, such as a hematite ore containing over 90% Fe.sub.2 O.sub.3, or limestone, forming in a more limited space region within the first region a dense fluidized bed containing a second solid bed particle component, such as larger particles of the hematite, essentially comprising a material having long-term physical and chemical stability in the fluidized bed system so as to be substantially non-agglomerating and not subject to substantial attrition therein, providing a recirculation path such as through a cyclone separator and particle reservoir for the first particle component from the first space region through the dense fluidized bed in the more limited space region, and operating the fluidized bed system at a velocity such that the second component particles are effectively retained in the dense fluidized bed in the more limited space region, whereas the first component particles recirculate and interpenetrate therethrough, commingling with the second component particles.

Growing community of inventors

Columbus, OH, United States of America

Ke-Tien Liu