Heat recovery applications can be found in electroplating processes, where simultaneous heating and cooling requirements
exist throughout the year. Chemical cleaning, scouring, scale and rust
removing, neutralization, temperature control of plating baths, recondensation for
recovery of chemicals, and ventilation are all phases in the process that requires
heating and/or cooling.
The following typical installation is an example of simple, yet efficient, energy conservation. A medium-sized company in the electroplating industry was heating plating baths and pickling and scouring solutions by electric immersion heaters. Cooling of various other baths is simultaneously required and was done by city and well water. With 6,000 operating hours per year and an average price of $0.059 per kWh-for electricity and a water cost of $1.72 per 1,000 gallons, it became essential to find a more economical solution.
A heat pump was installed for 12 plating baths, which simultaneously delivers cool water at 60°F and hot water at 150°F to two sets of buffer tanks. Cold or warm water is circulated from these tanks to titanium plate heat exchangers to control bath temperatures. The cooling duty is 117,000 BTUH; the heating duty is 177,000 BTUH; and the total output of the unit is thus 294,000 BTUH, while the electric power input is 16.7 kW. The resulting COP (power input to circulating pumps not included) is thus 5.2.
The total investment cost for a completely new installation includes the heat pump equipment; 12 titanium heat exchangers; two PVC buffer tanks; three pumps and all control equipment, piping, insulation, electric wiring plus installation; and startup labor cost. Using the above prices for energy and water, an economic evaluation showed that the energy and water savings gave a simple payback of the investment over a period of 2.2 years.
