A novel approach of accurately rationing adsorbent for capturing pollutants via chemistry calculation: Rationing the mass of CaCO_3 to capture Br-containing substances in the pyrolysis of nonmetallic particles of waste printed circuit boards

摘要

Pyrolysis technology is advised to dispose nonmetallic particles of waste printed circuit boards to produce oils and gases. During pyrolysis, brominated flame retardants in nonmetallic particles are converted into small-molecular Br-containing substances. They disperse into oil and gas so as to cause secondary pollution. Then, CaCO3 is suggested to be employed to capture the small-molecular Br-containing substances. However, too much CaCO3 will produce over solid wastes. Less CaCO3 might not capture the total Br-containing substances. How to ration the mass of adsorbent for capturing pollutant has not been detailed investigated. This paper found HBr was the main Br-containing substances during high temperature pyrolysis of nonmetallic particles. The capture process of HBr was detailed investigated by the method of computational chemistry. At the condition of 973 K and 100 Pa, HBr was captured by chemical reaction and physical absorption of CaCO3. Unit cell of CaCO3 reacted with two HBr to form CaBr2, and the generated unit cell of CaBr2 can adsorb 0.011 HBr. 0.0106 g CaCO3 can absorb all HBr produced by high temperature vacuum pyrolysis of 1 g nonmetallic particles. This paper contributes a novel approach to accurately ration the mass of adsorbents employed for capturing pollutants.