Energy Recovery From Furnace Off-Gas: Analysis of an Integrated Energy Recovery System by Means of Dynamic Simulation

Abstract

Surplus heat recovery and electricity generation from furnace off-gas has been implemented at several silicon and ferro-alloy plants in Norway. There is likely significant potential for improvement of both technology elements, system concept, and operation methodology. The main reported issues in current systems include challenging heat recovery due to heat exchanger wear, operation instabilities due to intermittent changes in furnace off-gas conditions, as well as required downtime due to system maintenance. In this study, an integrated system for energy recovery from furnace off-gas has been analyzed by means of dynamic simulations with Dymola/Modelica. Electricity generation using a steam Rankine cycle and heat export to district heating were included. Efficient operation of the system is challenged by frequently occurring temperature spikes in the off-gas and fluctuating district heating demand. Focus of this study was the comparison of different operation modes to efficiently handle the transient effects and their impact on overall energy system performance.