Moisture in pyrolysis gas under pressure
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Is it true that pressure helps to remove moisture from the pyrolysis gas? Thank you; does anyone know the reason?
Pressure must be applied to raise the water content above the saturated vapor pressure of water at the temperature of the medium, so that water can condense and dehydration can occur. If cooling is applied to lower the temperature of the medium, thereby reducing the saturated vapor pressure of water, the dehydration effect improves, but the operating costs increase.
Assuming that the water vapor component, along with the other gas components in the pyrolysis gas, behaves as an ideal gas system and obeys Dalton’s law of partial pressures, at normal pressure and when cooled to 40°C, the saturated water vapor pressure is 7.4 kPa; thus, the proportion of water in the gas is 7.4/101 = 7.3 v%. If it is compressed to 1.0 MPaG, and then cooled by condensation to 40°C with the condensate water separated out, the saturated water vapor pressure still remains 7.4 kPa since it depends only on temperature; as a result, the water content in the gas is 7.4/1100 = 0.67 v%, meaning that the amount of water in the gas is significantly reduced.