Sulfite, calcium, decomposition

Scale formation in the scrubber can lead to sodium carbonate as an additional dry sorbent in the scrubber. Alternatively, limestone is also introduced into combustion chambers to treat sulfur dioxide emissions. Decomposition of CaC03 into CaO and CO2 occurs in the combustion chamber, and the resulting CaO combines with S02 to produce calcium sulfite. Notice that this process produced another potentially environmentally harmful pollutant (CO2) as it gets rid of a definite environmentally harmful pollutant (SO2). 

Solid Calcium Sulfite. Recent thermodynamic studies of calcium sulfite by mass spectroscopy indicated that calcium sulfite dissociates into calcium oxide and sulfur dioxide (12). Under atmospheric pressure, this dissociation reaction is slow in the range below 250°C. We find under these conditions substantial decomposition of sulfite, yielding sulfate, elemental sulfur as well as thiosulfate. These observations are consistent with experiments by Brewer (13), and confirm old observatons made by wet-analysis of these complex solids (14). Our work confirms seventy year old literature reports which suggested evidence for thiosulfate, trithionate and dithionate in old pulping sulfite liquor which yellows when kept in air-free, sealed ampules (15-18). 

A convenient laboratory method for the preparation of SO2 in a Kipp generator has used the decomposition with dilute H2SO4 of cubes made of three parts calcium sulfite and one part calcium sulfate. 

High temperature thermodynamic data are available only for three sulfites calcium, potassium, and sodium. Most sulfites are fairly unstable, decomposing at relatively low temperatures. The decomposition reactions are not always exactly known, with diverse decomposition products, including sulfur, being reported. There are two major decomposition reactions (1) decomposition to the oxide and S02, and (2) oxidation-reduction (disproportionation) to the sulfate and oxide and S02, i.e.,... 

For the preparation of paper, the incrustations must be removed. To accomphsh this, there are two main processes decomposition with sodium hydroxide ( soda pulp ) or with calcium hydrogen sulfite ( sulfite pulp ). The soda pulp process generates water-soluble phenolates of lignin. In a remarkable manner, the hydrogen sulfite process yields benzylsidfonic acids (Holmberg decomposition). 

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