With the advent of the era of "carbon peak and carbon neutrality", environmental protection policies have become stricter, coal burning is strictly prohibited in many places, and enterprises are looking for alternative fuels for survival and development. As the most potential renewable energy, biomass energy can not only realize the harmlessness, reduction and resource utilization of various organic wastes, thereby improving the ecological environment, but also help optimize the energy structure and realize the synergy of carbon peak, carbon neutrality and environmental pollution control, so it has become the first choice of many factories. In 2021, Guangzhou Kechao Thermo Technology Co., Ltd. renovated two "antique" boilers for a large sugar group:

•The original boiler was manufactured by Guangzhou Boiler Factory, which was manufactured in 1983 and has been in operation for 40 years.

• Boiler model SHS20-25/400-GAII, designed fuel for bagasse and pulverized coal, burn bagasse in the pressing season, and burn pulverized coal in normal times.

•The boiler is a cogeneration unit equipped with a 1.5MW back-pressure turbine generator, and the exhaust steam is used for sugar extraction and sugar refining production.

Biomass fuel has the characteristics of a wide range of sources, a variety of categories, etc., the combustion characteristics of various fuels are different, especially the biomass bulk materials such as agricultural and forestry waste, building template waste are more challenging in combustion, from the combustion characteristics of the above-mentioned biomass bulk materials, the main factors affecting its combustion are moisture and shape, and different shapes will directly lead to differences in unit volume weight, the moving characteristics of wood chip combustion, and the permeability of the material layer to air. Guangzhou Kechao has accumulated rich experience in the design and operation of special boilers, for biomass bulk materials, we have carefully designed and laid out in terms of combustion mode, air supply, combustion chamber shape and volume, in the furnace structure, due to the volatilization analysis of the combustion flame is longer, the furnace should have enough height, the flue gas rising speed is 3~4m/s, the residence time is not less than 2.5s, and the reasonable distribution of a wind and two, Three airs to improve the temperature field in the furnace, promote the flue gas mixing disturbance, let the volatiles be fully combusted, reduce the chemical incomplete combustion loss, and achieve the combustion effect of full combustion and low nitrogen emission. The modified boiler has the following characteristics:

▶ The new boiler model SHL20-2.45/400-S is designed to burn bulk biomass materials (agricultural and forestry waste, construction waste).

▶ The chain grate layer combustion technology and the specially designed furnace structure are more suitable for the combustion characteristics of biomass bulk materials, and the low-temperature and high-efficiency low-oxygen combustion is truly realized.

▶ The more penetrating secondary and tertiary air arrangements can effectively reduce nitrogen oxide emissions and reduce alkali metal solidification ash at the tail.

▶ The two-stage feeding system ensures quantitative, continuous and balanced feeding, with a large amount of redundancy, and overcomes the problems of easy bridging, arching and blockage of bulk material transportation.

After two years of actual operation, the boiler fully reached the design index after the transformation, and the output was sufficient when burning the crushed material of eucalyptus roots with high moisture and sediment impurities, and the temperature and pressure parameters met the requirements of the steam turbine intake.