Double alkali process for removal of sulfur dioxide from gas streams
An improved double alkali process is disclosed which is useful for the removal of sulfur dioxide from gas streams, especially waste gas streams derived from coal-fired plants which also contain entrained fine particles of ash which contain alkali, which process comprises leaching soluble alkali from said entrained fine particles to establish an aqueous alkali scrubbing solution, scrubbing the resulting gas stream with said scrubbing solution, which circulates between said leaching and scrubbing steps, followed by bleeding off a portion of the resulting scrubber effluent to a regeneration system wherein the alkali scrubbing solution is regenerated. The scrubber effluent contains a relatively higher amount of alkali bisulfite and regeneration is in two main stages: a first stage wherein the alkali bisulfite is oxidized to alkali sulfate with formation of sulfuric acid followed by reaction of the acid with a calcium carbonate slurry to produce insoluble calcium carbonate and carbon dioxide gas; and a second stage wherein lime is added and reacts with the alkali sulfate to form insoluble calcium sulfate and alkali hydroxide. After thickening and filterhing the reaction product of the second stage regeneration step, alkali carbonate is added thereto in a clarifier in a softening step (i.e., to remove dissolved calcium as a solid) which forms an overflow containing alkali hydroxide which is recycled to the scrubbing step and an (insoluble) calcium carbonate slurry which in turn is recycled to the first stage regeneration reaction. The primary advantage of the present invention is the total elimination for any alkali make-up to the system. This is accomplished by forming in situ the alkali scrubbing solution using the alkali contained in the entrained fine particles carried to the scrubber.
- Assignee:
- AirPol, Inc.
- Patent Number(s):
- US 4452766
- OSTI ID:
- 6435335
- Resource Relation:
- Patent File Date: Filed date 30 Aug 1982; Other Information: PAT-APPL-412941
- Country of Publication:
- United States
- Language:
- English
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20 FOSSIL-FUELED POWER PLANTS
42 ENGINEERING
COAL
COMBUSTION PRODUCTS
SCRUBBING
FLUE GAS
DESULFURIZATION
SULFUR DIOXIDE
REMOVAL
AQUEOUS SOLUTIONS
ASHES
CARBONATES
FOSSIL-FUEL POWER PLANTS
GASEOUS WASTES
HYDROXIDES
LEACHING
PROCESS SOLUTIONS
REGENERATION
SULFATES
SULFITES
WASTE PRODUCT UTILIZATION
CARBON COMPOUNDS
CARBONACEOUS MATERIALS
CHALCOGENIDES
CHEMICAL REACTIONS
DISPERSIONS
DISSOLUTION
ENERGY SOURCES
FOSSIL FUELS
FUELS
HYDROGEN COMPOUNDS
MATERIALS
MIXTURES
OXIDES
OXYGEN COMPOUNDS
POWER PLANTS
RESIDUES
SEPARATION PROCESSES
SOLUTIONS
SULFUR COMPOUNDS
SULFUR OXIDES
THERMAL POWER PLANTS
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200202 - Fossil-Fueled Power Plants- Waste Management- Noxious Gas & Particulate Emissions
424000 - Engineering- Pollution Control Equipment- (1980-1989)