Chain Grate Steam Boiler is a single drum water and fire tube biomass boiler, and the combustion equipment is chain grate. The chain grate steam boiler body is divided into upper and lower parts, which is convenient for transportation and installation. The upper part includes drum and internal thread pipe, water wall pipe, header and so on; lower part includes water wall pipe, rear furnace arch. The outside is furnace wall with insulation material.

The lower part is combustion equipment, i.e. scale chain grate. The grate is suitable for the combustion of biomass briquette fuel, since the fire grate segment is compact. The horizontal arrangement can reduce the overall height of chain grate steam boiler compared to inclined reciprocating grate. The bottom of grate is equipped with separate air supply, and primary air enters from both sides of the air chamber. The ash after combustion falls at the ash well, and is discharged by the screw slag remover.

The biomass briquette fuel is fed from star feeder to chain grate surface. The moisture in biomass fuel is evaporated through the heating of flame and high temperature flue gas. When the temperature rises to 250~350℃, the volatiles precipitates and catches fire, and the fuel becomes high temperature coke. In order to ensure complete and stable combustion of volatile matter and coke, the lower part of front wall has secondary air. The secondary air distribution accounts for over 30% of the total amount and the wind speed is 26m/s.

Big heating area can increase chain grate boiler efficiency, and reduce flue gas temperature at furnace outlet. In order to improve the thermal efficiency, the biomass pellet boiler has economizer and air preheater to utilize waste heat. After the flue gas comes out of threaded pipe, it first passes through economizer to increase feed water temperature. The secondary air is heated to 50～60℃ by the flue gas and enters the furnace through the air duct. Design flue gas exhaust temperature is 162.99℃.