Recovery of Waste Heat Jan02

Recovery of Waste Heat...

Recovery of Waste Heat  Waste heat is the heat which is generated in a process due to the combustion of fuel or due to a chemical reaction and then discharged into the environment without being put to practical use. Sources of waste heat include hot combustion gases discharged into the atmosphere, process off  gases, conductive, convective and radiative losses from equipment and the heated products leaving various  industrial processes (hot coke, hot metal, liquid steel, and hot rolled product etc.), and heat transfer from hot equipment surfaces (heat transferred to cooling water). Waste heat recovery consists of the capture and reuse of the waste heat of the industrial processes for heating or for generating mechanical or electrical work. Typical uses include combustion air preheating, preheating of fuel gas, boiler feed water preheating, raw material preheating, generation of process steam, and production of steam for power generation etc. The basic idea behind the recovery of the waste heat is to try to recover maximum amounts of heat in the plant and to reuse it as much as possible, instead of just releasing it into the environment (air or a nearby river). Waste heat is intrinsic to all manufacturing processes. During the industrial manufacturing processes, around 20 % to 50 % of the energy consumed is ultimately lost via waste heat contained in streams of hot exhaust gases and liquids, as well as through heat conduction, convection, and radiation from the surface of the hot equipments as well as from the heated products. Waste heat recovery is a valuable alternative approach for improving overall energy efficiency improvements of the industrial furnaces. Energy efficiency  which can be achieved through waste heat recovery is normally in the range of 10 % to 50 %. The essential fact is...