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Title: Crystal growth and agglomeration of calcium sulfite hemihydrate crystals

Flue gas desulfurization (FGD) processes are most commonly utilized to remove sulfur dioxide from stack gases of coal- or oil-fired plants. In the simple slurry technology, SO{sub 2} is absorbed by a slurry of lime/limestone to form calcium sulfite crystals of acicular habit and its strong agglomeration, requiring large clarifiers and filters to dewater the sludge to make an acceptable landfill. Crystal growth and agglomeration of calcium sulfite hemihydrate crystals from solution were studied by reacting Ca(OH){sub 2} with NaHSO{sub 3} in a pH-stat semibatch crystallizer. Single platelet crystals and agglomerates of platelet crystals were produced in the pH range from 5.80 to 6.80. The crystallization mechanism changed from primary nucleation to crystal growth in the progressive precipitation. Using the titration curves, the growth rate was calculated from the titration rate at the final stage of operation. The crystal growth rates of calcium sulfate hemihydrate crystals were found to obey the parabolic rate law in the low supersaturation range. Another point to be noted is that the precipitates of calcium sulfite hemihydrate in agitated suspensions have a tendency to form agglomerates. It was found that the degree of agglomeration is a weak function of relative supersaturation and magma density, whilemore » the pH value is a key factor that affects the degree of agglomeration. Addition of EDTA also has an effect on the agglomeration of calcium sulfite hemihydrates.« less
Authors:
 [1] ;  [2]
  1. National Taiwan Univ., Taipei (Taiwan, Province of China). Dept. of Chemical Engineering
  2. Long-Hau Junior College, Tao-Yuan (Taiwan, Province of China). Dept. of Chemical Engineering
Publication Date:
OSTI Identifier:
63159
Resource Type:
Journal Article
Resource Relation:
Journal Name: Industrial and Engineering Chemistry Research; Journal Volume: 34; Journal Issue: 4; Other Information: PBD: Apr 1995
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
20 FOSSIL-FUELED POWER PLANTS; 01 COAL, LIGNITE, AND PEAT; 02 PETROLEUM; CALCIUM COMPOUNDS; CRYSTAL GROWTH; AGGLOMERATION; SULFITES; LIMESTONE; SULFIDATION; CALCIUM OXIDES; HYDRATES; FOSSIL-FUEL POWER PLANTS; WASTE MANAGEMENT; SULFUR DIOXIDE; AIR POLLUTION CONTROL; RESIDUES; WATER REMOVAL