Method of operating a spent pulping liquor combustion apparatus

Claim 1

An integrated process for the recovery of energy and chemical values from spent pulping liquor which comprises an initial stage of subjecting spent pulping liquor concentrated to at least about 50% by weight solids content to combustion with air at temperatures from about 1100 deg. F. to about 1300 deg. F. in a fluidized-bed reaction chamber, said chamber providing: (a) an entrained fluidized-bed in a first space region containing a first relatively fine solid bed particle consisting substantially of combustion residue salts of spent pulping liquor combustion in air; (b) in a second more limited space region within the first space region, a second relatively dense fluidized bed containing a relatively coarse solid bed particle component consisting substantially of combustion residue salts of spent pulping liquor combustion in air; (c) a recirculation path for the first particle component from the first space region through the dense fluidized-bed in the more limited space region, wherein a portion of the fine particle solid is separated and removed from the upper portion of the reaction chamber, conveyed to and passed through a fluidized-bed containing heat-exchanger means for removing heat values from said separated and removed fine particle size solid, and said separated and removed fine particle size solid is subsequently reintroduced into the fluidized-bed reaction chamber below the surface of the relatively dense fluidized-bed; (d) said first and second fluidized-beds containing a minimal quantity of particle sizes intermediate between the average particle size of said first fluidized-bed and the average particle size of said second fluidized-bed; and (e) fluidizing air provided to fluidize said first and second fluidized-beds at a superficial velocity of from about 15 to about 30 feet per second.