A Mini-Review of Industrial Waste Sources, Efficiency Enhancement Techniques, and Heat Upgrade Solutions with an Emphasis on Thermochemical Processes

Industries consume huge amounts of energy to cover their needs and produce significant amounts of waste heat at various temperature levels and in different forms. The proper exploitation of these waste heat streams to produce useful outputs (e.g., higher temperature heat, electricity, etc.) would increase the overall efficiency and sustainability of industries. The objective of the present mini-review article is to briefly discuss the main available waste heat sources in industries (e.g., flue gases, hot radiative surfaces, etc.) and the possible ways for exploiting them. Different industries, including Aluminum, Cement, Ceramic, Chemical, Food & Beverages, Glass, Iron & Steel, Paper/Pulp, and Wood, are covered. Energy efficiency improvement techniques such as heat recovery, air preheating, thermal storage, condensing economizers, organic Rankine cycles, heat pipes, etc. are investigated. An emphasis is also given to heat upgrade techniques for producing heat at higher temperatures than the waste heat to be re-used again in the industry. Thermochemical heat upgrading is studied in more detail because of its promising attributes. The conclusions of this work highlight the most efficient methods for waste heat recovery and upgrading in the industry as well as the future directions in this area.