Industrial processes produce energy in form of heat that is disposed of or simply released into the atmosphere. Waste heat recovery is the process of recovering this heat energy and reusing it in the production process. By recovering waste heat, plants can reduce energy costs and CO2 emissions, while simultaneously increasing energy efficiency. Examples of waste heat recovery systems are: Economizers: Boiler stack economizers use heat energy from the gas expelled in the heating process into the stack to heat boiler feed water and reduce the amount of energy required to make steam. Waste Heat Boilers: They recover heat generated in furnaces or exothermic chemical reactions at industrial plants. The heat generated at these locations is used to generate pressured steam in a waste heat boiler. Heat Recovery Steam Generator: Many highly efficient industrial plants with cogeneration or combined cycle systems use a gas-turbine to generate electricity whose exhaust contains extremely hot vapor. The hot gas is recovered and passed through a heat recovery steam generator which creates superheated steam that drives a downstream steam-turbine. The turbine can either drive a generator (combined cycle system) or just use the steam in process applications (cogeneration or combined heat and power (CHP)). Absorption chillers: Some energy efficient CHP systems may add refrigeration by incorporating absorption chillers that use waste heat or steam from other systems. The chilling processes involve condensation and evaporation of a refrigerant within the chiller. The waste heat/steam drives the evaporation of the refrigerant, which - when cooling down - will absorb heat for outside temperature. Steam Thermocompression: The steam compressor recovers low-pressure steam leftover from various processes and pressurizes it by mixing it with high-pressure motive steam. The result is low/mid-pressure steam that can be reused in another process.