Waste heat utilisation during moulding sand reclamation process

Abstract

The paper presents research to develop a complete system for recovering, storing and utilising the thermal energy of the knocked-out moulding sand. The cooling of the moulding sand is slow and, therefore, moulding sand cannot be used in a regeneration station and returned to the foundry process quickly. The moulding sand cooling process can be accelerated, and the recovered heat can be used in other energy-intensive processes in the foundry. As for now, the heat recovery methods or the ways of the heat further use are unknown. This paper presents the concept of a heat recovery system that allows to utilise the heat contained in moulding sand knocked out of large moulds at temperatures between 350 and 400 °C. The permissible moulding sand temperature at the inlet to the regeneration station should not exceed 90 °C. It is assumed that the moulding sand will be cooled with water in two vertical cylindrical tanks where heat exchangers with finned tubes will be placed. Using numerical modelling, the design of a heat exchanger for moulding sand cooling was selected. The capacity of the developed heat exchanger is 600 kW. Numerical analyses and experimental tests confirmed that the heat exchanger can absorb all the heat from the moulding compound and cool it down to 90 °C within 6 h. Implementing the developed system will reduce the foundry's CO2 emissions by 329 tonnes annually.