Process integration of sodium hypophosphite production

The case study of flexible integrated flowsheet development for sodium hypophosphite production is presented. It is based on phosphoric sludge utilization process. The weight concentration of phosphorous in raw materials is equal to 30–50%. The reaction and separation parts of the system were designed based on detailed analysis of production stages. After that the process equipment was selected. Process modelling is made for annual production of hypophosphite equal to 2500 t. It permitted to extract process streams for heat energy integration and to define their parameters. The operating pinch procedure was used to estimate the consumption of hot and cold utilities for non-integrated process. The influence of utilities cost on minimal temperature difference is investigated. Analysis of heat system topology modification depending on energy prices is conducted. Optimal structure of heat recovery system and minimal temperature difference are determined. It is shown that optimal integrated process consumes 45% of hot and 30% of cold utilities required by non-integrated process.