Design and construction of test apparatus for SO₂ adsorption research

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Virginia Polytechnic Institute and State University


A detailed literature review investigated the major factors affecting the reduction of sulfur dioxide (SO₂) emissions to the atmosphere. As determined from this review, there is a great need for a regenerable, negligible waste, flue gas desulfurization system that can economically compete with existing, non-regenerable, considerable waste systems.

Experimental apparatus was designed and constructed for use in future investigations of the adsorption of SO₂ from a simulated flue gas, which will be used for an ultimate prototype system design. The apparatus consists of an air-drying plenum, centrifugal fan, heat exchanger, mixing/adsorbing column, exhaust unit, and devices for pressure, temperature, SO₂-concentration, and flow measurement. A detailed description of the apparatus is included.

The initial system start-up consisted of calibrating flow nozzles, and testing the performance of the drying plenum and gas chromatographic system. Flow nozzles were calibrated for air using a rotameter, and then the calibrated flow rates were compared to theoretical flow rates obtained assuming inviscid flow. Excellent agreement between the calibrated and theoretical values was observed, except at very low rotameter scale positions where the possible percentage of reading error is large. A performance test was conducted that revealed the drying plenum's ability to provide extremely dry air (less than 1 per cent H₂O by volume) for flow rates ranging from 8.8 to 35.5 std m³/hr (5.2 to 20.9 scfm). The gas chromatographic system used for measuring SO₂ concentration levels was found unsatisfactory due to its irregular and irratic response, and as a result of functional problems involving the SO₂ injection technique and the required analysis time.

An equilibrium combustion analysis for a high sulfur-content coal was accomplished using a computer program developed by NASA at the Lewis Research Center. Unlike procedures commonly used for coal combustion analyses, which assume complete combustion, this program uses the minimization of Gibbs' free energy to predict the extent of reaction (combustion). Combustion products calculated by this program for Christian County, Illinois coal are presented.