Thomas B. Gibbons takes a look at the Conventional Rankine Cycle’s application in the cement sector
Duane Tilden‘s insight:
>The first major waste heat recovery (WHR) system in a cement plant was the 15 MW unit installed by Kawasaki Heavy Industries for Taiheiyo Cement in 1982. This was a conventional Rankine Cycle using heat from both the kiln and the clinker cooler. As the benefits became generally recognised within the industry, WHR units, the vast majority of which involved the conventional Rankine Cycle, were installed to provide up to about 30% of the power requirements of the plant. The main sources of waste heat were the exhaust from both the preheater and the clinker cooler and, in some of the developing countries where power outages are not unusual, the WHR system may be the only source of reliable power available to the plant operator.
Improvement in the overall efficiency of cement manufacture has resulted in lower exhaust gas temperatures and this development has provided opportunities for alternative technologies, notably the Organic Rankine Cycle (ORC) and the Kalina Cycle, which are more effective in recovering waste heat from lower temperature gases.<
We have all seen the Rankine Cycle engine, most typically as the inefficient steam locomotive. The modern efficient designs use turbines to convert heat energy from two reservoirs of different temperatures to mechanical energy.
The Organic Rankine Cycle engine uses a fluid – vapor phase change other than water/steam and a wide range of compounds are available including proprietory mixtures. These mixtures allow for the conversion to mechanical energy in a wide range of applications and temperatures. Two such applications would be waste heat to energy and geothermal energy systems.
September 2011 Report by the Geological Survey of Canada suggests 100 projects could provide much of the country’s power needs…
Duane Tilden‘s insight:
“Canada’s in-place geothermal power exceeds one million times Canada’s current electrical consumption,” the report notes, though also stating most of that available power could not actually be produced. “Environmental impacts of geothermal development are relatively minor compared to other energy developments, however there are still key issues to be addressed….Geothermal installations have the potential to displace other more costly and environmentally damaging technologies.”
There is at least 5000 megawatts of available geothermal power in various parts of British Columbia, Alberta, and the Yukon. What’s more, the report’s authors write, the cost of delivering geothermal power is expected to rival the costs of coal within 15 years or so. The limitations of developing the huge geothermal resource have a lot to do with location: Some of the most promising areas are far away from load centers, and the costs of developing huge transmission corridors to bring the power to where it is needed would make such projects unfeasible. Still, there is enough located in accessible areas to make a big difference.