Heat Recovery From Process Streams
Water, sea water, or air-cooled process condensers and process coolers reject waste heat to the atmosphere from many process streams. In the search for energy efficiency, they continue to be candidates for waste heat recovery.
Process waste heat recovery from the effluent of exothermic reforming fired heaters and from FCC regenerators, are two major waste heat recovery areas. On the water side, these units are similar. They transfer heat from a hot stream to incoming boiler feedwater and/or generate steam at pressures and temperatures required in the plant. This type of waste heat recovery is done in all of Company’s Hydrogen Plants, Ammonia Plants, and Type IV FCC Units.
Steam is generated in some process units because of process considerations. These would include Isocracker reactor effluent exchangers (to remove exothermic heat of reaction), hydrogen reformer effluent (high temperature of process stream and the need for steam within the unit), crude unit pump-around circuits (for ease of control), and the vacuum residuum product exchanger (simplicity of operation). The following calculation evaluates the alternatives of air cooling a process stream versus heating makeup boiler feedwater with it.