ABSTRACT
About 63.36% of the electricity consumed in India is generated by thermal power plants. Out of which more than 50% (77458.88 MW and 52.55%) of India’s commercial energy demand is met through the country’s vast coal reserves. Coal based thermal power stations are presently the mainstay of power development and this is likely to be so in the immediate future also, considering the present status of the projects and various constraints in development of hydro and nuclear power. Presently, about 200 Million Tonnes of coal is consumed yearly in the power sector and this requirement would continue to increase in the coming years.
The average price of coal (Coal spot prices at Newcastle Index) exceeded $136.2/ metric ton in year 2008 compared to $70.4/metric ton just one year ago (2007)! However, due to economic slow down, thermal or steam coal is expected to fall between $75/MT-$105/MT (average $90/MT), as predicted by price outlook analysis by early 2009, which is still higher than average coal price below $50/metric ton before 2005. To put this into perspective, a 600 HP boiler operating at a 50% average load for 8760 hours per year would have consumed $178,800 in coal in year 2005 but will consume $315,540 in coal per year at today’s cost! Fuel cost per year is given in figure 1. The increased cost of fuel has affected operational costs for all boilers regardless of size, age, or manufacturer.
The India dependence on coal, as well as the escalating energy demands of China, India and other countries will likely drive energy prices (fuel price) higher in the future. This increase in the cost of fuel has driven responsible boiler manufacturers to develop new products or modify existing ones in order to reduce thermal energy losses and save fuel. In this paper, area of heat losses in industrial boilers has been identified first. For this purpose, case study of heat balance sheet of four different industrial boilers, Tata Power Plant, Trombay (using coal and liquid fuel), Dhanu Thermal Power Station, DTPS ( using coal) and National Rayon Chemicals Limited, NRC ( using coal) has been taken.
Case study results indicate that despite of many common energy measures added (like, economizer, air pre heater, soot blowers, blow down recovery and water treatment etc) high heat losses are observed due to dry flue gas and moisture and hydrogen in the fuel (wet flue gas loss). Heat loss due to dry flue gas is 3% for oil fuel (Tata Power), 4.39% and 4.844% for pulverized fuel (Tata power & DTPS) and 15% for stoker fired boiler (NRC). Wet flue gas loss (Heat in the form of superheated steam, originating from the hydrogen and water in the fuel) is in the range of 5-6%, which pays a significant amount of heat loss.
Heat loss due to unburnt carbon and combustible in ash is also significant heat loss, which is in the range of 0.5% – 0.7% for pulverized fuel and upto 6% for stoker fired boiler. The heat loss due to moisture in air and radiation heat loss is upto 0.21%. Blow down loss is minimized and other losses are insignificant ( <0.1%).
By first identifying the areas of energy losses and roughly quantifying it, overall savings potential has been estimated by taking operational changes, improved design and better maintainenece action in that area. Lastly, cost of all energy saving options has been estimated with their payback period.
