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

Summary of country study – Bangladesh 139
heaters, evaporators and pans, etc. Turbine exhaust steam is used in processing juice, i.e.
mainly heating purposes. Another automatic steam reduction valve reduces 3 kg/cm 2 steam
to 1 kg/cm 2 to supply make up steam. Totally 80 per cent of the condensate is recovered
and about 20 per cent make up water is needed for the boiler. During plant visit, it was
observed that steam used in heating air of 6 forced air supply units of sugar dryer was being
operated with an open bypass valve of traps causing live steam discharge to drains.
Though all sugar mills have cogeneration facilities, they operate only during the season, i.e.
150 days per year. If they can be operated during off-season by applying Balancing,
Modernization, Rehabilitation & Expansion (BMRE) Programme, more power generated can
alleviate the power shortage in the country.
Most sugar factories have low-pressure (15 bar) boilers. By installing high-pressure boilers,
these can produce more power efficiently. The choice of boiler pressure of 64 kg/cm 2 and
above appears inevitable for mills intending to sell power to the national grid. Typically, a
well-designed 2,500 tons crushed/day plant can sell 10 MW of power to national grid.
There are several technical financial and institutional impediments to the use of energy
efficient sugar mills, the most important ones being the policy initiatives and shortage of
financial resources. In most sugar factories, there is a lack of sound technical management
to maintain high-pressure boilers. The existing low-pressure boiler is itself not being
maintained satisfactorily in most cases with the result that there are interruptions in crushing
sugar cane. In any event, sugar being still a highly regulated industry, the management is
occupied with sugar cane farmers, and the financial and administrative problems of
producing and selling, and very few have the time to take up the additional responsibility of
electricity cogeneration.
Cogeneration with improved technology should be seriously considered in sugar factories of
Bangladesh as it offers the following advantages:
• It causes no pollution as the bagasse does not produce flash, or sulphur compared to coal
used in a thermal plant;
• It needs no foreign exchange as the machinery needed for cogeneration boilers, turbines,
etc., is indigenously available;
• It has a low gestation period of two years compared with four to six years of construction
period for a coal-based thermal plant;
• It has a much lower installation and recurring cost compared with a conventional fossil fired
power plant;
• It is small in size and is invariably in the rural area, so the transmission and distribution
losses are minimal compared with any centralized plant requiring long lines of distribution;
• It places no financial and administrative burden on the utility as it is executed and managed
by the sugar factory;
It improves the financial position of the sugar factory.
Cogeneration in paper mill
A newsprint paper mill having a steam turbine cogeneration facility is covered here. The mill
presently generates 13.1 MW and purchases 2.5 MW from the utility grid to meet all the
electrical energy needs of the site, including the residential zones. Furnace oil is used in
boilers for steam generation.
Steam generated at 42 bar and 400°C in three boilers with a total installed capacity of 161
ton/hour, is mainly used in three backpressure turbines to generate electricity. After partial