The Indian cement industry needs to explore more avenues for tapping alternate fuels, say RA Krishnakumar, Executive Director and R Rajamohan, Senior General Manager (IE, Environment and PH), Dalmia Cement (Bharat) Ltd.
The Indian cement industry is the second largest in the world with a total installed capacity of 390 million tonnes per annum (MTPA) with a forecast to reach 600 MTPA by 2025, in tandem with increases in the country's aggregate energy demand. Though the Indian cement industry has achieved excellence in energy efficiency, Alternative Fuel and Raw Material (AFR) usage still remains a concern. The current Thermal Substitution Rate (TSR) in the Indian cement industry is less than 3 per cent, as compared to some European countries that have a TSR as high as 80 per cent. Every 10 per cent TSR is estimated to reduce emissions by 22 kg CO2/MT of cement. Increased use of AFR is identified as one of the key levers to reduce CO2 emission in the Indian cement industry.
Co-processing and Municipal Solid Waste
Co-processing ranks higher in the waste hierarchy, in comparison to disposal through landfills or incineration, and cement kilns have an important role to play in processing waste in an environmentally sustainable way. Based on the existing quantity of waste gen-eration and future forecasting of different waste-derived fuels, Municipal Solid Waste (MSW) accounts for about 57 per cent, equivalent to 14 per cent TSR (refer to Table 1 and Chart 1).
MSW and Refuse Derived Fuel
MSW is a heterogeneous mixture, and includes biodegradable, inert, recyclable, electrical & electronic, pesticides and hazardous wastes. Currently, of the estimated 62 million tonnes (MT) of MSW generated annually in urban areas, more than 80 per cent is disposed of at dump yards in an unhygienic manner leading to problems of health and environmental degradation. Refused Derived Fuel (RDF) which is generated from MSW can be utilised as an effective alternate fuel in cement plants, which can result in reduction of waste going to landfills, and can ensure a sustainable way of waste management in the country. These processes have become even more important in light of the Centre's Smart Cities and Swatch Bharat missions. (Refer to Table 2). Segregation of MSW and pre-processing before it is sent to cement plants is essential to ensure increase in availability of waste to cement plants for co-processing.
Share of Alternate Fuels on TSR (%)
Waste processing at Dalmia Cement's Dalmiapuram Unit
In line with the company's corporate vision where sustainability plays a critical role, AFR is a focus area with TSR of around 11 per cent at Dalmia's Dalmiapuram unit in Tamil Nadu. Among the various alternate fuels being used, the cement major has also explored RDF from Tiruchirapalli City MSW, in collaboration with the City Corporation and the city MSW processing agency. At Tiruchirappalli City Corporation, the MSW generated per day is 436 MT and MSW composition is as given in Table 3. The City MSW processing agency receives the MSW at its allotted site from the Corporation everyday and processes the same for output of compost (50 tonnes per day) and RDF (80 tonnes per day) and the balance is rejected. After reaching the MSW processing site, raw segregation is carried out by removing plastics and non-biodegradable wastes, followed by screening for segregation of +120 mm size wastes. Subsequently, the process allows <120 mm size wastes for microbial reaction by creating a heap for 30-40 days. After degradation, it is allowed for screening to segregate <4 mm, 4-35 mm and 35-120 mm sizes. Waste with size of 4 mm is used for compost preparation, 4-35 mm is used as RDF and 35-120 mm particles are sent to landfills as reject. In this process, about 80 tonnes per day of RDF is generated. The expected CV is 2,000 to 2500 Kcal/kg, and the moisture content is around 15-20 per cent, but actual CV is around 1,800 Kcal/kg and moisture is over 25 per cent. Dalmia Cement Bharat has tried this RDF in its Dalmiapuram plant along with other AFR materials in its existing AFR feeding system. This AFR feeding system - with a capacity of 50 TPD - was developed by the company's in-house team with an innovative idea. An abandoned passenger lifts up the fuel feed to the pre-calciner floor at 48 m height, followed by a hopper and feeding arrangement with belt/screw conveyors, supported by a triple feed gate.
The cement industry can be a useful conduit for processing of waste. Co-processing of waste in cement kilns is a scientific and proven option, more so with the recent proposed statutory changes in environmental laws.
With this, the cement industry, which had been branded as a high polluter, has actually become a solution provider, with its consumption of waste from other industries. For MSW RDF co-processing in cement kilns, source-segregated collection is critical, and pre-processing to maintain consistency in fuel quality, calorific value, size and moisture is a must.
These measures can help in the meeting the following objectives:
- 25 per cent Thermal Substitution Rate in Indian Cement Industry (target: Year 2025)
- India's COP21 commitment on carbon emission reduction
- Meeting the increased energy demands in a sustainable way, as Indian cement annual production capacity is estimated to reach 600 MT by 2025 (it is currently 390 MT). The 'polluter pays' principle must be practiced in our country, as it is done in developed countries. Our Indian cement plants can be an effective option for disposal of municipal, industrial and hazardous waste. This will create a win-win situation for both local administrations and cement plants.
The challenges encountered while trying this RDF usage were:
- Inconsistency in specifications and quantity availability;
- Less Calorific Value;
- Higher moisture content, requiring additional fuel to dry the feed;
- Odour emitted during the process. However, Dalmia Bharat has overcome the above problems in coordination with the city MSW processing agency and ensuring potential quantity availability with consistency.
The article has been authored by RA Krishnakumar, Executive Director and R Rajamohan, Senior General Manager (IE, Environment and PH), Dalmia Cement (Bharat) Ltd, Dalmiapuram.