Effect of operating and design variables on stripped sour water quality

    Machines. Technologies. Materials., Vol. 13 (2019), Issue 8, pg(s) 345-348

    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


    Desalination by flue gas humidification-dehumidification using two different flue gas compositions

    Machines. Technologies. Materials., Vol. 13 (2019), Issue 7, pg(s) 302-305

    The objective of the work is to utilize waste heat from power stations’ flue gases in desalination of seawater by humidificationdehumidification. Two power station fuels namely fuel oil and natural gas are considered. The two fuels differ in composition, calorific value, and usage of percent excess air requirements. In order to achieve the same electric power production, the composition (moisture content and specific heat) and amount of flue gases ensuing from combustion of the above two fuels will be different. One humidificationdehumidification desalination scheme is generated and results are compared with respect to the anticipated cost of produced water versus
    the source of flue gases. Cost is calculated on the basis of energy balance and design equations. The scheme includes: preheating of seawater using hot flue gas, humidification of an air stream by direct contact with seawater, and dehumidification of the same stream by indirect cooling in a condenser. In case of fuel oil combustion, desulphurization of the flue gas by seawater is also included. The cost of produced fresh water includes the fixed cost of heat exchangers, condensers, humidifiers, packing, pumps and fans based on the cost index of 2018, and the operating cost is based on the current electricity cost. The results show that the total cost of the produced water is much less in the case of using flue gases ensuing from natural gas fueled power stations. This happens because the flue gases in this case have a very high humidity ratio which will result in the condensation of a significant amount of water on cooling. As a result, the total amount of fresh water produced is greater than in the case of fuel oil flue gases.



    Science. Business. Society., Vol. 2 (2017), Issue 1, pg(s) 3-6

    A quick and accurate determination of the physical properties of seawater represents an important aspect of research dealing with processes that involve wide variations in temperature, pressure, and concentration. The physical data should be cast in a form readily compatible with the development of mathematical models associated with the synthesis and optimization of industrial processes involving heat and mass transfer operations on seawater. In this work, previously reported experimental data pertaining to the variation of seawater physical properties are correlated into simple empirical mathematical forms enabling their straight forward inclusion into mathematical models associated with seawater and brackish water desalination.