Effect of operating and design variables on stripped sour water quality
As technology evolves, 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 in order to provide high quality of stripped water with insignificant traces of NH3 and H2S. This must be achieved within the minimum operating costs.
This work analyses the effect of operating/design variables (such as feed temperature, feed location, number of stages, and steam flow rate) on the stripped water quality in two cases (A refluxed absorber without a reboiler and an absorber with a side compressor). HYSYS V.8 simulation tool was used to accurately simulate the two cases. The feed data was acquired from the factory of POSCO (Pohang Iron and Steel Corporation) in South Korea.
It was found that the best stripping efficiency in the refluxed absorber was when the feed was fed at the first stage, with maximum feed temperature, number of stages and steam flow rate. For the absorber with compressor, the feed was fed in the first stage and the reflux split and the pressure ratio were changed to monitor their effect on the tower efficiency. Results showed that increasing the reflux split increases the flow rate of NH3 and acid gases in the off gas, while increasing their concentration in treated water (200 ppm) restricting the use of reflux split. It also proved that increasing the pressure ratio carries more energy to the sour water feed heat exchanger. The effect of
changing the pressure ratio on the compressed gas temperature and the compressor duty was also studied. Results of the treated wastewater streams guarantee that the effluent sour water obeys standard environmental regulations