part 1: overview of cogeneration and its status in asia - Fire

Summary of country study – Bangladesh 136
3.2 Technical Potential for Cogeneration
3.2.1 Identification of sub-sectors with cogeneration potential
Industrial cogeneration is a vital part of any strategy designed to reduce emissions of carbon
dioxide. The advantage of cogeneration is that it is available now, a true “no-regrets”
technology justified in many applications on economic grounds alone. Cogeneration is a
well-tried technology in Bangladesh, already meeting around 10 per cent of the total
electricity requirements of Bangladesh. These include mainly industrial plants like fertilizer
factories, sugar mills, paper mills, textile spinning mills, etc.
Cogeneration of process steam and electricity is widely recognized to be one of the most
important single measures for achieving energy savings in the industrial/commercial sector.
After extensive site visits and surveys the following industrial and commercial sectors of the
country were identified with cogeneration potential.
Industrial Sectors: pharmaceutical industry, edible oil refinery, paper recycling mill, textile
processing mill, textile spinning mill, jute mill, tobacco curing, food processing, tea estate,
tannery plant, knitting and hosiery plant, soap and chemical industry, cement plant, food
industry, ceramic industry, distillery plant, and industrial estate.
Commercial Sectors: hotel, hospital, cinema hall, housing complex, shopping complex, and
office complex.
3.2.2 Existing cogeneration facilities in the country
Cogeneration in textile spinning mill
The company analyzed here is one of the largest spinning mills in Bangladesh, with a
capacity to produce 70,230 spindles. It went into production in July 1992. At present the
turnover is nearly 1,480 million Taka. The mill operates 24 hours a day, for 360 days a year.
The mill requires both electrical energy and thermal energy for production. There are seven
Waukesha Gas Generators in the mill, with a total generation capacity of 6.4 MW. Each
generator has an electricity generation capacity of 920 kW. Electrical energy is mainly used
to run different 3-phase motors. Besides, there are a few single-phase motors, fans, lights,
heaters, etc.
There is only one fire-tube boiler operating with natural gas as fuel, with a rated capacity to
produce 1.5 ton/hour of steam at around 5 bar for the process.
The mill opted for cogeneration due to the following reason. The ambient temperature in the
processing section was very high, at around 40-45°C, making it difficult for people to work
continuously at high temperatures. Moreover the quality of the product was affected as the
machines were not running properly at high temperatures. On the other hand, the
temperature of the exhaust gases from gas engine generator was around 500°C. The
management of the mill incorporated two waste heat boiler so that about 5 ton/hour of steam
generated at 6 bar is used to drive vapour absorption chillers. The chilled water produced
with no energy cost decreases the air temperature in the production section from 42°C to
20°C. As a result, total energy cost is reduced while ensuring reliability of power supply,
reducing environment pollution and increasing overall efficiency.
The power output from the generators and the cooling capacity of the two chillers as
functions of time are presented in Figure 3.2 and 3.3.