Waste heat recovery from quenching towers

Abstract

Steel plants are one of the largest sources of waste heat. Waste heat recovery throughout the steelmaking process is not a new phenomenon. One of the sources of waste heat is found in the coke plant. Cokes are an essential part of steel production. During the coking process hot cokes are cooled down. Most coke plants in the world traditionally use water, so called wet quenching. In this process, all the heat put into the cokes is dispersed to the environment as steam. This waste heat source has huge potential. The goal of this study is to find a method to utilise this waste heat and to evaluate this method’s technical and economic feasibilities.
The chief issue that must be tackled in a design is the fact that the steam generated during a quench is close to atmospheric pressure. Another issue to be solved is that of the solid particles suspended in the steam. Several potential designs were produced to use the steam from a quench to recover the waste heat. Based on several criteria, the design using the Synext engine was found to be the superior one and was developed further.
This design is divided into three sections, capture, cleaning and storage. A water wall and capture valve are used to capture the steam. An impaction and a cyclone separator are used to rid the steam of the solid particles to the extent that their detrimental effect to the Synext engine is minimised. The sepa-rators’ dimensions are derived based on the steam input and Synext engine requirements. The steam is then stored in a storage vessel.
A Simulink model of the design is composed to simulate the process and evaluate its efficiency and technical feasibility. The model’s findings show that the outputs for certain cases require unreasonable dimensions for the design. The economic analysis showed the designs costs make it an unlucrative investment.