Mercury Transformation and Distribution Across a Polyvinyl Chloride (PVC) Production Line in China

The production of polyvinyl chloride (PVC) via the calcium carbide process utilizes a catalyst containing large amounts of mercury (Hg) and is therefore one of the most important sources of anthropogenic Hg in China. To measure the emission of Hg from PVC production, we established a flowchart for the calcium carbide process, for which we quantified the Hg content of the material/product at each step. Results indicated that 71.5% of the total Hg (HgT) was lost from the catalyst, most of which was recovered by the Hg remover, accounting for 46.0% of the total Hg (HgT). We determined that 3.7% of the HgT was released into the environment, mostly in solid wastes and byproducts such as hydrochloric acid. Furthermore, no Hg has been detected in the PVC end product. However, we were only able to account for 78.1% of the Hg across the whole system, leaving 21.7% unaccounted for in the mass balance. A rough estimation indicates that most of the “missing” Hg had accumulated in deposits on the inner surface of conv...