What the Heck is Wanton Waste?
Every sportsman worth his salt knows what wanton waste is. No, it is not week old wontons from your favorite Chinese restaurant. The exact definition can be blurred by overly obscure laws, but essentially, it means to intentionally waste something that is usable. Many industrial plants have large quantities of wanton waste in the form of heat escaping through stacks, process cooling loops, waste water loops, flash steam, refrigeration condenser water, hydraulic cooling systems…the list can go on and on. The vast majority of the operators know they are losing this heat, but don’t know how, or where to use it.
Is it Wanton Waste or a Process Requirement?
The key to cost effective heat recovery is having a constant heating requirement; anything from preheating process water, boiler make-up water, combustion air, or even preheating reverse osmosis water. Process heat recovery can be used for conditioning the space if a combination of make-up air heating and dehumidification reheating is required. If the only heating requirement in place is seasonal, then the rejected process heat is not considered wanton waste because it is a process requirement and does not have a suitable year-round use, although there may be some instances where using it for seasonal heating may be viable.
So, it is Wanton Waste. Now what?
Now that there is a place to put the waste heat, what is the process? In many cases, nothing needs to be done to the waste stream. Using more of the heat from the gas already being burned is one of the largest savings opportunities available. For instance, use the stack gases directly out of the boiler to preheat the incoming make-up or process water. Vented steam can also be captured and used to preheat the incoming water, which then could be used to heat whatever the process requires. Stack gas economizers and vent condensers are cost effective ways to achieve this type of heat recovery.
If the waste stream is a dust collector or cyclone exhausting hot air, the air can also be used to heat process water or even combustion air. This can be done with a heat exchanger or a wet scrubber under the right conditions.
What about low grade process heat? Heat recovery chillers can be used to boost the waste heat temperature to a higher, more usable temperature, while also providing chilled water. This equipment can take a waste stream at 70-80 degrees and produce a heat stream at temperatures exceeding 150 degrees. Water at this temperature is very common with process cooling loops and on the condenser side of refrigeration systems. This can be used to heat whatever the facility requires, but the key to cost effective process heat recovery is a continuous need for heat.
Cost Effective = Everybody’s Happy
The bottom line is that as gas prices rise heading into the heating / hunting season, some facilities can look at using the heat they are already producing more effectively. Process heat recovery can be accomplished in many different ways depending on the specifics of the facility. Heat recovery uses less resources and SAVES MONEY. Therefore, everyone is happy, from the accountants to the other critters we share the world and its resources with.