Electric Power Generation from Kiln Off-Gases
By Narayana (‘Jay’) Jayaraman
Table 1. Comparison between SRC and ORC systems.
|1||More suitable for high temperature applications.||Can be used for low temperature gases. Typically, not suitable for gas temperature > 4000C|
|2||Lower efficiency||Conversion efficiency is higher – higher power potential for the same waste heat|
|3||Use of water makes it cheaper, though a water treatment plant will be necessary||Both thermal oil and the organic fluid are very expensive|
|4||Relatively safer||Organic fluid is flammable. The thermal oil has a flash point of around 3000C|
|5||Spillage risks are not an environmental threat||Though both loops are sealed, there is some risk of spillage of hydrocarbon fluids|
|6||Higher maintenance due to potential corrosion of turbine||Less maintenance. The organic fluid does not corrode the turbine.|
|7||Lower initial investment||Higher investment costs|
Most plants expect a payback period of 5 years, which can happen only with high power tariffs (>0.10 $/kWh) and very favorable configurations (large kiln with high temperature gases) and much lower CapEx (~3-4 M $/MWe power). WHR projects are many times financially feasible if the Government provides a good incentive for waste heat utilization and for reducing the carbon footprint. It is to be emphasized that the Owner requires an experienced consulting company having expertise in cement/lime process as well as WHR systems to truly evaluate opportunities and integrate designs with the existing plant operations.
This article was contributed by Narayana (Jay) Jayaraman, Director – Technical Services at PEC Consulting Group LLC.
Narayana (Jay) Jayaraman
Mr. Jayaraman has over 48 years of experience in the cement industry with expertise in plant conceptualization, layout, various operating systems, process calculations, production optimization, and Waste Heat Recovery (WHR) based power projects for cement and lime plants. He has led several studies to estimate realistic waste heat for power generation. He has had in-depth exposure to the technical, economic, and commercial aspects of large cement projects, and extensive experience in the upgrade and optimization of existing plants. He earned a BS in Mechanical Engineering from Osmania University, Hyderabad, India, and an MS in Mechanical Engineering from the Indian Institute of Technology, Kharagpur, India.
PEC Consulting provides the crucial role of due diligence, choice of appropriate capacity and system, and engineering for integrating with the plant.