Experiment and Kinetic Study of Elemental Mercury Adsorption over a Novel Chlorinated Sorbent Derived from Coal and Waste Polyvinyl Chloride

摘要

This paper describes the synthesis of a novel chlorinated sorbent through one-step pyrolysis of waste polyvinyl chloride (PVC)/coal blends and its application for elemental mercury removal. The effects of pyrolysis temperature (600, 700, 800 degrees C) and mixing ratio (9:1, 3:1) on Hg0 adsorption efficiency was tested in a laboratory-scale fixed bed reactor. For sorbents T8C9P1 and T83P1, a complete removal of mercury was maintained for 30 min at 140 degrees C. Ion chromatography (IC) analysis, Brunauer-Emmett-Teller (BET) surface area, and X-ray photoelectron spectroscopy (XPS) analysis were used to characterize the sorbents. The results suggested that co-pyrolysis of PVC and coal could fix the pernicious element to a certain extent, leading to a few percent reduction of Cl emission (2.6-13.3%). The XPS and temperature-programmed-desorption (TPD) data showed that parts of the C-Cl functional group were converted into ionic Cl during the Hg0 adsorption process, which indicated that the C-Cl bond is the major active component for mercury removal via chemisorption. The adsorption kinetics analysis demonstrated that the elemental mercury adsorption on chlorine-modified sorbent was mainly controlled by chemisorption, and the effect of intraparticle diffusion became apparent after an elapsed time of 25 min. Most C-Cl bonds were assumed to be formed when high molecular weight carbon free radicals and HCl (or Cl free radical) appeared synchronously during co-pyrolysis. Based on the results, the co-pyrolysis of PVC and coal is a multifunctional process for Cl fixation and satisfies the requirements for the synthesis of candidate mercury sorbent.