SZL series double barrel vertical chain grate biomass steam boiler combustion mode is chain grate. The boiler is divided into two major parts, the boiler body part uses a light furnace wall, the installation period is short, after the boiler arrives at the installation site, it can be run by closing the two major parts, laying the lower furnace wall, installing the auxiliary machine system such as slag extraction machine, fan and smoke duct, and connecting the water and electricity. The boiler burns the biomass forming solid fuel, the fuel hopper falls on the grate, and burns with the grate into the furnace, the flue gas enters the convection tube bundle area after the smoke barrier wall, the flue gas flows to the S-shaped bend, the use of inertia to separate the dust in the flue gas and fall into the ash hopper set below, with the grate running and the slag falling into the slag hopper, the slag machine discharged the furnace body. The flue gas of the boiler passes through the multi-tube cyclone dust collector and the cloth bag dust collector dust removal device to ensure that the atmospheric pollutant discharge requirements of the boiler system meet the standards. SZL series double barrel vertical chain grate biomass boiler has high automation level, safe and stable operation, suitable fuel and low smoke emission concentration. At the back of the furnace is a burning-out chamber and a convection tube bundle. The flue gas enters the tail flue through the furnace, burn-off chamber, convection tube bundle and nosing device, and is discharged into the atmosphere through the dust collector, induced draft fan and chimney. The front wall is equipped with a secondary air device, which is controlled by a valve and opened when the boiler is running to improve the combustion efficiency.