Waste Heat Recovery
Waste heat recovery is any method that recaptures waste heat that was discharged as a byproduct of one process and puts it to use in another process. Waste heat is excess heat that was generated during processes such as fuel combustion or a chemical reaction and then released into the ambient environment without utilizing its full energy. Processes that waste heat recovery units recover excess energy from include cement kilns, nitric acid process gases, thermal oxidizer gases, fume incinerator gases, coking and petrochemical incinerator gases. Depending upon the process, waste heat does not necessarily have to be hot; it can be any temperature from that of chilled cooling water to very high temperature waste gases. However, higher temperatures typically equate to a higher quality of heat recovery and greater cost-efficiency. Industries that typically utilize waste heat recovery equipment include oil and gas, bio-diesel, textile, cement, food processing, glass, steel and pharmaceutical. By reducing overall plant energy consumption as well as greenhouse gas emissions, waste heat recovery systems are becoming increasingly popular amid growing environmental concerns and increasingly stringent carbon dioxide emission regulations.
There are several different types of waste heat recovery equipment. Waste heat recovery heat exchangers utilize the same basic idea, transferring heat from one gaseous or liquid substance to another, replacing typical coolants with gases or liquids which need to be heated anyway. This alteration allows facilities to recycle their own energy. This can be achieved in several ways. First, a recuperative heat exchange system would capture the hot gas and steam through an overhead duct and carry it to one of two types of heat exchangers: shell and tube heat exchangers or flat plate heat exchangers. Typical shell and tube heat exchangers use a "bundle" of tubes encased in a shell, in which heat energy is transferred from hot liquids or gases flowing through in through the tubes to liquid or coolant which flows over and around the tubes within the shell, capturing heat energy and flowing back out. Plate and flat plate heat exchangers work similarly with hot and cold liquid chambers separated by metal plates. Refrigerators use flat plate heat exchangers to create cool air. Additional waste heat recovery equipment includes waste heat recovery boilers, which require waste gases to contain sufficient usable heat to produce steam or hot water. Waste heat recovery boilers may be designed to work with either radiant or convective heat sources.