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Author: search.filters.author.Munsamy, Megashnee

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    Cleaner technology systems for surface finishing : evaporative coolers for close circuiting low temperature plating process
    (Elsevier, 2013-12-10) Munsamy, Megashnee; Telukdarie, Arnesh; Zhang, W.
    In the electroplating process, the rinse system generates large quantities of wastewater requiring treatment prior to disposal to municipal systems. The use of conventional water treatment systems is a challenge due to the presence of hazardous components. In addition, this does not solve the problem of the generation of rinse wastewater, but only treats it. Thus the focus was on point-source reduction technologies, specifically the application of a three-stage low flow counter current rinse for recovery of the rinse water in the plating bath, enabling close circuiting of the plating bath rinse system. However, recovery of the rinse water into the plating bath is impeded by the low rates of evaporation, especially in the low temperature plating baths. Alternative methodologies to heating were investigated to facilitate evaporation, with evaporative cooling being identified as the most feasible option. Evaporative cooling facilitates evaporation, whilst maintaining the plating bath temperature within the operational limits. For the recovery of the rinse water in the plating bath, the rate of evaporation in the plating bath must be equivalent to the fresh make-up water requirements of the rinse tanks. The Closed Circuit Plating System (CCPS) model was developed to enable the proper design and/or implementation of an evapo-rative cooler; whereby the user specified inputs are evaluated in achieving the required evaporation rates for the recovery of the rinse water in the plating bath. The key characteristic of the CCPS model is the minimum requirement of proprietary plating solution specific information. The inputs for the model are chemical composition of the plating solution, flowrates, temperature and height of the cooling tower. The outputs from the model are evaporation rates and equilibrium temperatures of the plating bath and cooling tower. The primary limitation of the CCPS model is that it is based on an airewater system. Single and multiple variable sensitivity analyses were performed on the plating plant operational pa-rameters to determine their influence on close circuiting of the rinse plating system: plating solution composition and operational temperature; ambient air temperature; air flow rate and the surface area of the packing in the cooling tower. The results from the model indicated the upper limit plating solution opera-tional temperature, high air flow rates, low ambient air temperature and large surface area of packing facilitated water evaporation rates and lower equilibrium temperatures in the plating bath and cooling tower. The sensitivity analyses will allow the electroplater to optimise the operating conditions to achieve the required evaporation rates for recovery of the rinse water into the plating bath, while simultaneously maintaining the outputs of the electroplating plant and reducing the rinse wastewater generation to almost zero.
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    Use of evaporative coolers for close circuiting of the electroplating process
    (2011) Munsamy, Megashnee; Ndinisa, V. N.; Telukdarie, Arnesh
    The South African electroplating industry generates large volumes of hazardous waste water that has to be treated prior to disposal. The main source of this waste water has been the rinse system. Conventional end-ofpipe waste water treatment technologies do not meet municipality standards. The use of technologies such as membranes, reverse osmosis and ion exchange are impractical, mainly due to their cost and technical requirements. This study identified source point reduction technologies, close circuiting of the electroplating process, specific to the rinse system as a key development. Specifically the application of a low flow counter current rinse system for the recovery of the rinse water in the plating bath was selected. However, the recovery of the rinse tank water was impeded by the low rates of evaporation from the plating bath, which was especially prevalent in the low temperature operating plating baths. This master’s study proposes the use of an induced draft evaporative cooling tower for facilitation of evaporation in the plating bath. For total recovery of the rinse tank water, the rate of evaporation from the plating bath has to be equivalent to the rinse tanks make up water requirements. A closed circuit plating system mathematical model was developed for the determination of the mass evaporated from the plating bath and the cooling tower for a specified time and the equilibrium temperature of the plating bath and the cooling tower. The key criteria in the development of the closed circuit plating system model was the requirement of minimum solution specific data as this information is not readily available. The closed circuit plating system model was categorised into the unsteady state and steady state temperature regions and was developed for the condition of water evaporation only. The closed circuit plating system model was programmed into Matlab and verified. The key factors affecting the performance of the closed circuit plating system were identified as the plating solution composition and operational temperature, ambient air temperature, air flow rate and cooling tower iv packing surface area. Each of these factors was individually and simultaneously varied to determine their sensitivity on the rate of water evaporation and the equilibrium temperature of the plating bath and cooling tower. The results indicated that the upper limit plating solution operational temperature, high air flow rates, low ambient air temperature and large packing surface area provided the greatest water evaporation rates and the largest temperature drop across the height of the cooling tower in the unsteady state temperature region. The final equilibrium temperature of the plating bath and the cooling tower is dependent on the ambient air temperature. The only exception is that at low ambient air temperatures the rate of water evaporation from the steady state temperature region is lower than that at higher ambient air temperatures. Thus the model will enable the electroplater to identify the optimum operating conditions for close circuiting of the electroplating process. It is recommended that the model be validated against practical data either by the construction of a laboratory scale induced draft evaporative cooling tower or by the application of the induced draft evaporative cooling tower in an electroplating facility.