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 coalfired 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 filtering 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:
- 6201303
- 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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Related Subjects
GASEOUS WASTES
DESULFURIZATION
LEACHING
SCRUBBING
HYDROXIDES
REMOVAL
SULFUR DIOXIDE
ASH CONTENT
FOSSIL-FUEL POWER PLANTS
REGENERATION
SCRUBBERS
SOLUBILITY
SULFURIC ACID
CHALCOGENIDES
CHEMICAL REACTIONS
DISSOLUTION
EQUIPMENT
HYDROGEN COMPOUNDS
INORGANIC ACIDS
OXIDES
OXYGEN COMPOUNDS
POLLUTION CONTROL EQUIPMENT
POWER PLANTS
SEPARATION PROCESSES
SULFUR COMPOUNDS
SULFUR OXIDES
THERMAL POWER PLANTS
WASTES
320305* - Energy Conservation
Consumption
& Utilization- Industrial & Agricultural Processes- Industrial Waste Management