Design and thermodynamic analysis of a flash power system driven by process heat of continuous casting grade steel billet

Abstract

Hot charging of continuous cast steel billets is usually considered an effective method for recovering heat. However, for certain grades of steel, the hot charging process may affect the steel surface quality. To overcome this issue, the billet is commonly cooled down before rolling, resulting in substantial heat loss. Thus, the recovery of useful waste heat without affecting steel quality is an important research topic. In this study, the design of a flash power system driven by the process heat of continuous casting grade steel billet is proposed. The influences of shunted water temperature and flash pressure on exergy recovery rate are studied via the thermodynamic methods. Moreover, a case study based on actual data is analyzed to verify the thermodynamic results and the energy recovery of the proposed system. The results indicate that the system exergy recovery rate increases with increasing shunted water temperature. Keeping the shunted temperature unchanged the exergy recovery rate firstly increases and later decreases with increasing flash pressure. At a fixed shunt temperature, an optimum flash pressure exists. At the maximum exergy recovery rate the net output power of the studied plant is 6361 kW, a value that greatly reduces the need for purchased electricity.