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Waste not, Want notBy Mr. Devi prasaD

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Andhra 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.

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

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.”

mr. devi prasad, vice president, captive power plant, andhra pradesh cement works

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.

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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,

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 thinkingSince 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

the autoMateD ceMent plant along river penna in taDipatri

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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

waste gas

thermal oil circuit

clinker cooler waste gas

pentane-circuit

clinker cooler heat source

waste heat oil heater orMat energy converter

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The project, commissioned in March 2007, has clocked 23,650 hours of operation with 98 per cent availability. it has given a competitive edge to the APCW unit in terms of low power cost. it is the cheapest power source with the average cost of power generation being `0.20 only. The project generates 2.1 million units per annum which means a saving of `8 crore every year.

National impact With this project, a new process was born at APCW. And the rest as they say, is history, or shall we say chemistry?

UltraTech Cement has become a role model for technology implementation. it won the Cii-National Award for Excellence in Energy Management in 2007 for innovation and the Best Energy Conservation Award by

Non-conventional Energy Development of Andhra Pradesh (NEDCAP) in 2009. The power plant is a clean development mechanism (CDM) project; to date 22,695 CERs have been issued and other 10,823 are expected.

This innovation has huge potential outside the cement industry as it can be replicated in any sector. With the success of this project, all major players are putting up heat recovery units in their existing plants and new cement plants are being designed with waste heat recovery in mind.

Not only is this another example of the Group’s commitment to sustainability, but, as fossil fuels become scarcer and power costs edge further northwards, waste heat recovery is going to be a strategic option to gain cost leadership in manufacturing. n

with the success of this project, all major players

are putting up heat recovery units in their

existing plants and new cement plants are being

designed with waste heat recovery in mind.

(With inputs from Mr. Bimal Kumar Modi)