Waste Heat Recovery for Power Generation

Waste heat from cement kilns is usually used for drying of raw materials and fuel. Depending on the humidity of the raw materials and the cooler technology, additional waste heat is available from the kiln gases (preheater exit gas) and cooler exhaust air. This heat can be used for electricity production. Power can be produced by using a steam cycle, an organic rankine cycle, or the KALINA process. The low temperature level of the waste heat in cement plants (200 – 400 °C) limits the efficiency to a maximum of 20 – 25%. However, 25 to 30% of plant's power demand can be met through generating power from waste heat.  

Heat recovery for power is most economical for long dry kilns but long dry kilns with preheaters in China and Europe have power production installations. Heat recovery for power production may not be feasible in plants where the waste heat is used in raw mills to extensively dry the raw material - which offers a more efficient and economic option (US EPA, 2010. p22). 

It has been reported that there are at least 33 cogeneration units in various cement plants with total capacity about 200 MW in Japan. In China about 24 kilns having capacity of 2000 ton per day and above have cogeneration units with supplementary fired boilers to meet about 22 –– 36 kWh/t clinker.

Development Status Products
Commercial
clinker

Waste Heat Recovery for Power GenerationCosts & Benefits

Parent Process: Clinker Making
Energy Savings Potential

Typically, 8–22 kWh/t-clinker can be produced without changes to kiln operation. Generation up 45 kWh/t clinker is possible by modifying kiln operations (e.g. less cyclone stages or by-passing upper stage(s) (CSI/ECRA, 2009. p. 31)

Chinese flag In China, production potential is reported to be around 24-32 kWh/t-clinker using domestic technology and 28-36 kWh/t-clinker using foreign technogly.  39 kWh/t-clinker is achieved in a Chinese plant using Japanese technology

Japanese flag Japanese technologies are reported to be able to produce 45 kWh/t clinker. 

Indian flag The potential for Indian plants are reported to be 20-24 kWh/t clinker.  

Chinese Flag 48.5 GWh/y of net electricity production was projected for a 8 MW WHR unit installed at a 4500 tpd plant in China (UNFCC, 2008).

CO2 Emission Reduction Potential

Indian flag The 8 MW power plant installed by the Indian Cements Ltd. (for their 4500 tpd plant) has been reported to reduce the CO2 emissions by 45 000 tons per year (PCA, 2008). 

Chinese Flag With the installation of a 9 MW WHR plant to a plant with 5000 tpd capacity, annual CO2 emission reductions in excess of 52 000 ton year is planned (UNFCC, 2007)

Chinese Flag 41 000 t CO2/y reduction is expected with the installation of an 8 MW waste heat recovery unit in a 4500 tpd plant in China. 

Costs

For a plant with 2 millon t-clinker/y capacity, installation costs are estimated to be between € 15-25 million. Operational costs are estimated to decrease by €0.3–1.2/t-clinker (CSI/ECRA, 2009. p.32).

Chinese flag Investment per kW are estimated to be about 6000-10000 RMB (US $ 940 - 1570) for Chinese technology and 16,000 - 22 000 RMB (US $2500 to 3400) for foreign technology for China.  Estimated payback periods are usually less than 3 years.  

Chinese flag For China it was estimated that  for a 2000 ton per day (730,000 annual ton) kiln capacity, about 20 kWh/t clinker of electricity could be generated for an investment of 20 to 30 million RMB (US $ 3.1 to 4.7 million).

Indian flag For India, investment costs are given to be around $2.25 million per MW capacity. Indian Cements Ltd. has put up an up to 8 MW power plant using Japanese technology for its 4500 tpd plant for a total investment of US $ 18.7 million (PCA, 2008).  

Chinese Flag The installation cost of the 8 MW WHR unit in a 4500 tpd plant in China is reported to be RMB 58.8 million. The project is reported to have an IRR of 6.65% (the IRR value is stated to be 17.08% with carbon credits) [2008 values]. (UNFCC, 2008)

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Waste Heat Recovery for Power GenerationSchematic

Waste Heat Recovery for Power Generation Publications

Energy Efficiency Improvement Opportunities for the Cement Industry

The U.S. Environmental Protection Agency’s (EPA) energy guide, Energy Efficiency Improvement and Cost Saving Opportunities for Cement Making, discusses energy efficiency practices and technologies that can be implemented in cement manufacturing plants. This ENERGY STAR guide provides current real world examples of cement plants saving energy and reducing cost and carbon dioxide emissions.

Page Number: 

14-16

Development of State of the Art Techniques in Cement Manufacturing: Trying to Look Ahead

The report represents the independent research efforts of the European Cement Research Academy (ECRA) to identify, describe and evaluate technologies which may contribute to increase energy efficiency and to reduce greenhouse gas emissions from global cement production today as well as in the medium and long-term future. 

Page Number: 

31-32

Page Number: 

10

Waste Heat Recovery for Power Generation Reference Documents

Hebei Quzhai Cement 9000kW Waste Heat Recovery Project - CDM Project Design Document

This design document provides technical details of a Clean Development Mechanism Project, which involves the installation of 9000 kW waste heat recovery system for a 5000 tpd capacity cement plant in China.  The project is expected to reduce CO2 emissions by 52 000 tons year. 

Page Number: 

2

8MW pure low temperature waste heat recovery (WHR) for power generation in SDIC Hainan Cement Co., Ltd. - CDM Project Design Document

This UNFCC CDM project design document provides the details of an 8 MW waste heat recovery unit to be installed in a 4500 tpd cement plant in China.  The project is expected to generate 48.5 GWh/y of net electricity and reduce CO2 emissions by 41 000 t/year

Available and Emerging Technologies for Reducing Greenhouse Gas Emissions from the Portland Cement Industry

 

This document provides information on control techniques and measures that are available to mitigate greenhouse gas (GHG) emissions from the cement manufacturing sector. It includes a useful table where mitigation measures are summarized, along with their energy and economic saving potentials and implementation costs.  

Page Number: 

22

Page Number: 

35-36