Laboratory evaluation of calcium-, iron-, and potassium-based carbon composite sorbents for capture of hydrogen chloride gas

The pyrolysis of PVC containing waste plastics produce hydrogen chloride (HCl) in addition to valuable chemical feedstock. The removal of HCl from the process is essential, as it is corrosive and produces halogenated hydrocarbons in liquid products, which cannot be used as fuel. A laboratory scale experimental study on sorption of hydrogen chloride was carried out using fixed bed microreactor at atmospheric pressure. Calcium (Ca-C), iron (Fe-C), and potassium (K₂CO₃-C) based carbon composite sorbents were developed and used in the present investigation; optimum sorption reaction conditions for the maximum utilization of sorbent capacity were determined. The results suggest that the calcium carbonate carbon composite sorbent (Ca-C) reacted with hydrogen chloride gas leaving no residual HCl gas for 12 h (breakthrough point). Approximately 63% of theoretical sorbent capacity was observed under the following optimized reaction conditions: linear gas velocity, 0.18 m/s; inlet HCl concentration, 1820 ppm; weight of sorbent, 2 g; particle size, 0.25 mm; and total gas flow: 535 mL/min. A sorption temperature of 350°C was found to be optimum for the effective reaction of hydrogen chloride with sorbent. The effect of particle size, total gas flow, inlet hydrogen chloride concentration, and effect of temperature on the adsorption capacity of Ca-C sorbent was studied.