In many industrial processes water is used for cooling of machines, ovens and intermediate products. The common practice is to direct this water into a cooling tower where it partly evaporates, transferring the excess heat into the environment. The cooled water is then recycled into the same industrial process.
In order to prevent buildup of salts causing corrosion and scaling, part of the cooling water is discharged as wastewater. This leads to increased use of freshwater to make up for the evaporation losses and the wastewater discharge. In the future Green Steel manufacturing, cooling water temperatures can reach 85°C, offering high potential for waste heat recovery and reuse. However, suspended solids in the cooling water limit the effectiveness and reliability of heat exchanger systems.
The CORNERSTONE project addresses this challenge by developing heat exchangers tailored for industrial wastewaters with high suspended solids and salt content. The goal is to prevent clogging by adjusting the heat exchanger's design, flow speed and introduction of ultrasonic waves. The project also includes monitoring and maintenance measures for reliable operation. The recovered heat will be used for water preheating and blowdown water recovery by membrane distillation, aiming to create more energy-efficient water treatment systems and reduce fresh water demand as well as the carbon footprint.
@BFI, Scheme of proposed waste heat recovery from the gas scrubbing
circuit of a direct reduction plant in the future Green Steel manufacturing