Design of Fixed Grate Biomass Boiler

Fixed Grate Biomass Boiler is double-drum natural circulation medium-temperature and medium-pressure boiler. The furnace is surrounded by water wall tubes, and furnace outlet has wing wall. A convection superheater is in the convection flue duct. Staggered convection tube bundle is between upper and lower drums, and flue gas enters tail flue duct through tube bundle. Steel tube economizer are in the tail flue duct, and cyclone dust collector is at the lower part of economizer.

The fuel enters the furnace through the fuel feeder. Adjust the feeding speed and feeding air volume to adapt to fixed grate biomass boiler load and fuel changes. It adopts fixed water-cooled grate.

Table 1 Biomass Fuel Characteristic

Normally we use inclined reciprocating grate to burn biomass in China; it includes grate bar, transmission mechanism and reciprocating mechanism. The structure is complex, grate bar is easy to burn out and coke, and boiler overhaul is difficult. Aiming at such situation, we design water-cooled inclined fixed grate. Grate is inclined, and heat-resistant cast iron grate bar are above water-cooled supporting pipe. Biomass fuel can be burned completely, and at the same time, grate bar can be cooled. Biomass ash will drop to the slag outlet with secondary air in the rear wall. Primary air enters the furnace through bottom ventilation holes to cool the grate, prolonging service life and distribute air evenly.

Table 2 Fixed Grate Biomass Boiler Design Parameter