A review of waste heat recovery technologies towards molten slag in steel industry

Molten slag exhausted with critically high temperature of about 1450–1550°C is a potential resource of energy and raw materials. Water quenching is a traditional heat recovery technology, which uses cold water to cool down slag so as to achieve the desired glassy by-products. However, this technology consumes a huge amount of water and fails to recover the sensible heat of slag. To save energy and reduce water consumption, some other heat recovery technologies have thus been proposed. Generally, current heat recovery technologies can be classified into physical and chemical methods. Regarding the physical methods, mechanical crushing, air blast and centrifugal granulating process, etc. are widely investigated. With respect to chemical methods, methane reforming reaction and coal gasification process, etc. are proposed. Unfortunately, all these methods cannot fulfill the sustainable requirement. This paper aims to review the proposed granulation and heat recovery technologies. Their working principle, current research status, challenges and future prospects are presented. The waste heat recovery and utilization technologies, which give consideration to both heat recovery rate and cooled slag particles with high quality and high additional value, will be a key to achieve sustainable development for the iron and steel industry.