New Efficient Configurations for Sour Wastewater Treatment-

Abstract

Due to the technological development, the environmental legislations on pollutant concentrations in aqueous effluents tend to tighten and increase. As a result, sour water must be handled and processed properly to provide a high quality of stripped water with insignificant traces of NH3 and H2S in it. This must be achieved within the minimum operating costs. This research investigates the stripping configurations of sour water effluents from various industries. The research also offers an insight on different scenarios and configurations to accomplish set targets satisfying the environmental law criteria. This research introduces a range of heat integration schemes for better energy savings, further vapor recompression VRC technique is opted for its ability to maximize energy savings. This research analyses the effect of operating and design variables on the stripped water quality such as feed temperature, feed location, reflux split, and steam flow rate. The option of adding new equipment is also addressed to maximize heat integration and enhance the efficiency of the process. Thus, several schemes and process configurations are explored to treat industrial sour water waste streams seeking better efficiency. These configurations differ from one another in heat integration layout and whether VRC is utilized or not. Energy efficiency and economics of the proposed configurations are considered as decisive factors in this research study. The case study adopted are based on published data taken from some iron and steel factories in South Korea named POSCO (Pohang Iron and Steel Corporation). Results of the treated wastewater streams guarantee that the effluent sour water obeys standard environmental regulations, i.e., NH3 contents range from 30 to 80 ppm and H2S concentration falls below 0.1 ppm. The obtained results of the seven different scenarios are compared to the original case study. It is found that scenario 7 is the most economical solution saving 51.54 % in total annual cost when compared to the original case study, while satisfying the treated water environmental regulations with a concentration of 3.19 ppm NH3 and 0.05 ppm H2S. Scenario 7 creates its own steam unlike the original case study where steam utility is needed extensively. However, scenario 7 consumes 15 % more electricity than the original case study but still shows 56.34 % less utility cost in overall. The optimum process configuration can be employed for other sour water purification systems such as those from petroleum refiners. An ongoing research work is focusing on the use of internal heat integration for more energy savings and economics improvement.