S Awasthi1, A Tewari2, V Takroo2 and R Srivastava2
1Isgec, A-4,Sector -24, Noida 201301, India, sanjayawasthi@isgec.co.in
2Isgec, A-7, Sector -63, Noida 201301, India
Biomass (including bagasse) is acknowledged as a renewable and eco-friendly energy source, gaining traction on a global scale. Combustion of some biomass has always been a challenge in traveling-grate technology because of the highly fouling and corrosive nature of ash. This has resulted in reduced operating days of boilers and affected the life of pressure and non-pressure parts. This paper presents a comprehensive review of the latest developments in biomass-utilizing traveling grates in boilers, particularly those operating with high steam parameters (pressure and temperature). Burning biomass in high pressure and temperature boilers always yields savings in fossil fuel use, and results in more power generation. The essential elements of the firing system are highlighted, with a focus on the traveling-grate technology, which stands out as a key characteristic of these boilers. It explores recent advancements made in design of furnace, superheater, metallurgy of grate bars and pressure parts, and air split in the combustion of various challenging biomass types, including mustard husk, soya husk, paddy straw, pith, and vinasse. The traveling grate has proved its advantages of exceptional fuel flexibility; low unburnt fuel rates, high operational efficiency, and reduced emissions. It also highlights the issues related to superheater fouling and corrosion caused by biomass ash, as well as low-temperature corrosion and its mitigation. Two case studies are presented: a high-pressure dual-fuel boiler (biomass + vinasse) at a sugar factory in north India, having parameters of 100 t/h/85 kg/cm2 (a)/510 °C, and a 45 t/h/67 kg/cm2 (a) /460 °C traveling grate boiler that burns mustard stalk, soya stalk, and high gross calorific value (GCV) coal in a chemical plant in eastern India that has an operating cycle of 253 days.