80-85 per cent of the energy used is heat energy (the balance being electrical power). The chemical reaction to convert limestone into clinker requires heat as ...
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Waste not, want not By Mr. Devi Prasa d
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Generating power from process waste heat is a concept that is rarely seen in the cement industry. Andhra Pradesh Cement Works is the first company in India to run a highly efficient power plant by recovering waste heat using the novel Organic Rankine Cycle principle. Their breakthrough project has earned the admiration of the industry as well as plenty of carbon credits
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ndhra Pradesh Cement Works (APCW) has created history by using heat from waste gases to run a power plant.
It has put up a `33 crore, 4.2MW plant for generating power by recovering heat from clinker cooler waste gases.
APCW team: (Sitting from left) Mr. K. R. Reddy, Mr. K. N. R. K. Sharma, Mr. V. Devi Prasad, Mr. M. A. Rahim and Mr. K. Ankanna (Standing from left) Mr. S. V. Purushottam Reddy, Mr. P. Laxmi Narayana Reddy, Mr. P. Tirupal Reddy, Mr. D. Nagasayana Rao, Mr. B. Rajasekhara Reddy and Mr. L. Ramalingeswara Reddy
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The pioneering project has already become the talk of the cement industry. What is truly remarkable is that the technology can be replicated in any plant anywhere. In fact, the Ministry of Environment and Forests and Andhra Pradesh Pollution Control Board have recommended this technology to various industries and the plant has been the focus of visits from companies such as Gas Authority of India, other cement companies, Steel Authority of India, and consultants like Avant-Garde and Fichtner.
The flow of power
In a cement plant, as much as 80-85 per cent of the energy used is heat energy (the balance being
electrical power). The chemical reaction to convert limestone into clinker requires heat as high as 1,350oC. This vast heat energy calls for huge requirement of fossil fuels. For several years now, UltraTech has been working to reduce fossil fuel consumption through process optimisation and re-using waste heat energy. Mr. Devi Prasad, Vice President, Captive Power Plant, APCW said, “The waste gases from the manufacturing process are recovered and re-diverted inside the mill for use in pre-heating raw material. By the time they are finally released, there is minimal heat loss and minimal impact on the atmosphere.”
The waste gases from the manufacturing process are recovered and re-diverted inside the mill to be used in pre-heating raw material. By the time they are released, there is minimal heat loss and minimal impact on the atmosphere. mr. devi prasad, vice president, captive power plant, andhra pradesh cement works
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the automated cement plant along river penna in tadipatri
With such eco-efficient measures already in place, APCW was using only 685 to 690 kilo calorie per kilogramme of clinker. Although it is rare for any company in the world to achieve this level of heat recovery, APCW realised that theoretically there was the potential to save even more heat energy. It was a tough technical challenge because temperatures of waste gases are already very low at this stage of the production process, 46
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and a different technology and process was needed to recover the residual heat. And although, this heat, when recovered, could not be used in the manufacturing process, it could be used in a power plant.
Out of the box thinking Since temperature at the waste recovery stage was low, a chemical process was needed to recover the heat. In order to do this, the team thought of sourcing the technology based on the Organic Rankine
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Cycle principle (where n-pentane, an colourless and water-insoluble hydrocarbon liquid, is used as motive fluid in place of steam). This is a truly unique project, apart from one example of the Organic Rankine Cycle application in Germany (in another industry), there
was no one the team could tap for inputs. Also the original quotations for the technology turned out to be too high. To make the project viable, the team decided to bring project costs down by partly indigenising the technology. The engineering for this project was done in-house (see figure below).
Cycle diagram of power generation from clinker cooler waste gas
Clinker Cooler Heat Source
Waste Heat Oil Heater
ORMAT Energy Converter
Waste gas
Clinker Cooler Waste Gas
Thermal Oil Circuit
Pentane-Circuit
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The project, Non-conventional With the success of this commissioned in Energy Development project, all major players of Andhra Pradesh March 2007, has clocked 23,650 (NEDCAP) in 2009. are putting up heat hours of operation The power plant is a recovery units in their with 98 per cent clean development existing plants and new availability. It has mechanism (CDM) cement plants are being given a competitive designed with waste heat project; to date 22,695 edge to the APCW CERs have been recovery in mind. unit in terms of issued and other low power cost. 10,823 are expected. It is the cheapest power source with the average cost of power generation This innovation has huge potential being `0.20 only. The project generates outside the cement industry as it 2.1 million units per annum which can be replicated in any sector. With means a saving of `8 crore every year. the success of this project, all major players are putting up heat recovery National impact units in their existing plants and new With this project, a new process was cement plants are being designed with born at APCW. And the rest as they say, waste heat recovery in mind. is history, or shall we say chemistry? Not only is this another example of the UltraTech Cement has become a role Group’s commitment to sustainability, model for technology implementation. but, as fossil fuels become scarcer It won the CII-National Award for and power costs edge further Excellence in Energy Management northwards, waste heat recovery is in 2007 for innovation and the Best going to be a strategic option to gain Energy Conservation Award by cost leadership in manufacturing. n 48
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(With inputs from Mr. Bimal Kumar Modi) issue 1
