Waste water heat recovery is attractive from a BTU content stand point, but if the stream is anything but clean, there are many obstacles to overcome. Corrosion and fouling (plugging) of heat exchangers is a common problem that leads to early failure of many poorly designed systems. A common term for these systems is ‘gray water heat recovery’ systems.
Facilities that are hooked to city sewers may be adding cold water to their waste stream to cool it down in order to meet local codes. This wastes both heat and water, making the application even more attractive.
Consider waste heat recovery when there is a simultaneous need for heating water and dumping water. The higher the flow rate and dump temperature the higher the potential savings.
Wastewater is pumped to the tube side of the heat exchanger. Fresh water enters the heat exchanger shell and flows around the tubes in a direction counterflow to the wastewater within the tubes. As the fluids pass one another in opposing directions, heat is transferred through the walls of the stainless steel tubing preheating process water typically to over 100ºF.
The cooled wastewater can be reused, recycled, treated or discharged.
Heat Recovery General
Economizers and Flue Gas Condensers see www.CleanBoiler.org
11500 47th Street, North
Clearwater, Florida 33762
Go to their web site at www.kemcosystems.com
Source: Text by Bob Fegan based on content from web sites linked above; image of waste recovery system schematic from Kemco web site 2-2005; Revised 10/2005;