Cost effective greenhouse gas reductions in the steel industry from an Organic Rankine Cycle

Abstract

Large quantities of low grade heat (LGH) are generated within many process industries, and the recovery of LGH is a potentially significant means of improving process efficiency, but it is often difficult to find an appropriate internal heat load. One alternative is to use appropriate technologies to convert the low grade heat to electricity for use on site. This paper describes the environmental and techno-economic evaluation of a case study examining the potential application of an Organic Rankine Cycle (ORC) to generate electricity from LGH from the stacks of a coke oven used in steel production. 21 MW of LGH was available for recovery at the plant and resource accounting and lifecycle analysis methods were used to evaluate the environmental and economic benefits of the operation of an ORC. The results showed that between 1 and 3% of the CO(2) emitted directly through the production of coke would be offset by installation of an ORC, with lifecycle environmental impacts of coke production reduced by less than 1 %, although this was sufficient to offset over 10,000 t CO(2) annually. However, the amount of electricity generated was sufficient to replace all currently imported electricity and economic analysis indicated a relatively attractive discounted payback period of between 3 and 6 years, suggesting this may be a commercially viable option, which could present a relatively cost effective method of achieving greenhouse gas savings in the process industries.