Comparison of air and steam stripping: removal of organic halogen compounds from process wastewaters

In the engineering practice there are two basic alternatives of physicochemical treatment for the removal of volatile compounds from process wastewaters: stripping with air or stripping with steam. In this work these alternatives are investigated and compared in the case of a real industrial problem that is typical for the fine chemical industry and general conclusion is drawn. The removal of the organically bound halogens, called adsorbable organically bound halogens, is investigated. The two alternatives, air and steam stripping, are first modeled in the professional software environment of ASPEN Plus®. The model is validated on the data of an existing air stripper for the removal of organic halogens. Same organic halogens removal is applied for the design of a steam stripper. It is proved that the steam stripping shows better operability and economic performance than the air stripping moreover the volatile and/or adsorbable organically bound halogen compounds can be recovered in the distillate and they can be reused improving the sustainability

Terephthalic acid from renewable sources: early-stage sustainability analysis of a bio-PET precursor

The present work was performed because of the paramount importance of terephthalic acid (PTA) in the current chemical industry. It represents the missing element for the production of 100% bio-PET (polyethylene terephthalate) and has a market with continuous growth. The other monomer, monoethylene glycol (MEG), is already widely available from renewable sources. Considering the wide relevance, not only scientific but also social, covered by the possibility of producing one of the most frequently used polymers from renewable sources, this analysis is aimed at the environmental assessment of alternative routes for the production of PTA. In order to do this, the life cycle assessment (LCA) methodology was adopted as a scientific tool which is able to estimate the environmental performance of three pathways from different renewable sources, comparing the results with the traditional technology. An early stage approach was used by comparing different scenarios with two independent methods: CED (cumulative energy demand) and ReCiPe. The results prove that the bio-routes to PTA could be very competitive, in particular, if organic waste streams are converted into raw materials for the production of building blocks. On the other hand, the adoption of dedicated crops has some limitations and it seems not to be the right solution to mitigate climate change by reducing fossil sources