Bharat Heavy Electricals Limited (BHEL), Tiruchi, successfully demonstrated a full-load operation of its first 250 MW Circulating Fluidised Bed (CFB) boiler supplied to Neyveli Lignite Corporation (NLC) at Neyveli on February 4. The second unit is in advanced stages of erection. It is stated to be the highest capacity CFB Boiler in the whole of South East Asia.
The successful demonstration of the unit's performance signals the use of a new technology for utilising India's vast lignite resource in an environmentally friendly and efficient manner.
The plant has a list of new technical advances such as natural circulation technology for highest possible steam pressures (180 bar) for higher turbine efficiency and avoiding circulating pump for boilers; Pantleg Configuration, split furnace at the bottom, a feature useful for further scaling up the unit capacity up to 500 MW ranges; low SOx (Sulphur Oxide) and NOx (Nitrogen Oxide) emissions; and rotary quad sector air heaters.
The CFB technology also helped in overcoming one of the perennial problems faced in Neyveli due to presence of Marcasite (a form of Iron Sulphide- FeS2) which causes slagging at operating temperatures and forms ash deposits on waterwall tubes.
The CFB technology employs much lower temperatures (<900ºC) and thus avoids slagging issues caused by Marcasite, giving smooth boiler operation. CFB boilers are also able to handle high moisture, up to 55 per cent, a key feature required by most Lignite Mines as they have high levels of stored thermal energy in their circulating ashes.
This vast reserve of stored thermal inventory makes possible maintaining lower load operation without oil support.
BHEL, with its strong technology sourcing from Lentjes, Germany, and active collaborative projects with leading Indian and International Institutes, utilises one the largest CFB Test Rig facilities in the world, and is uniquely positioned to customise design to meet the varying fuel properties while meeting International standards.
Two CFB Boilers of 125 MW capacity supplied by BHEL to NLC, Barsingsar, Rajasthan, have also achieved sustainable full-load operation.