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|Title:||Use of evaporative coolers for close circuiting of the electroplating process||Authors:||Munsamy, Megashnee||Issue Date:||2011||Abstract:||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
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
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.
|Description:||Submitted in fulfilment of the requirements of the egree of Master of Technology: Chemical Engineering, Durban University of Technology, 2011.||URI:||http://hdl.handle.net/10321/685|
|Appears in Collections:||Theses and dissertations (Engineering and Built Environment)|
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