As a renewable energy source with zero carbon dioxide emissions, biomass energy is regarded by countries around the world as one of the important ways to achieve sustainable energy transformation. In this context, boilers, as indispensable thermal energy conversion equipment in the development of the national economy, are playing an increasingly prominent role and can provide hot water or steam for process production. Especially in an environment where coal combustion is restricted, biomass-fueled boilers have huge development potential in the market. However, in actual operation, the thermal efficiency of many biomass boilers is generally low. The reasons need to be analyzed in depth and practical improvement suggestions put forward to improve the overall thermal efficiency level.

1. Reasons for low thermal efficiency:

1.1 Unreasonable boiler structure: 

In the boiler structural design, the air chamber sealing is not high, which may lead to air cross-flow and air leakage problems, thereby increasing the boiler heat loss and reducing the boiler thermal efficiency. The traditional "eight"-shaped furnace structure design is unreasonable and cannot meet the requirements for segmented combustion of biomass boilers, resulting in low fuel combustion efficiency.

1.2 Long-term low-load operation: 

Long-term low-load operation of the boiler will increase heat loss and reduce thermal efficiency. The main reasons include the purchase of boilers with too large capacity and the operator's failure to monitor and adjust the boiler's operating conditions in a timely manner, resulting in the operating load deviating from the economic load range.

1.3 Exhaust smoke heat loss is relatively large: 

Exhaust smoke heat loss is one of the main heat losses and is affected by the exhaust smoke temperature and excess air coefficient. A high excess air coefficient and high exhaust gas temperature will lead to a decrease in thermal efficiency. Reasons include unreasonable air distribution, system air leakage, lagging air adjustment methods, etc.

1.4 Unqualified boiler water quality: 

Unsatisfactory boiler water quality will lead to the generation of scale, increase heat transfer resistance, and reduce boiler thermal efficiency. The main reasons include poor water quality management, mismatched water treatment equipment, and insufficient water treatment personnel.

2. Suggestions for improving boiler thermal efficiency:

2.1 Improve the level of boiler design and manufacturing:

- Optimize the boiler structure, consider effectively utilizing the waste heat of the flue gas, increase the heating surface at the rear or use multiple heat exchange methods to reduce the exhaust gas temperature.

- Improve the thermal insulation performance of the boiler, ensure good sealing and thermal insulation performance of each component of the boiler, and reduce heat loss.

2.2 Improve the energy-saving management system during use:

- Clarify the responsibilities of energy conservation and environmental protection managers, include boiler operating parameters into the scope of daily inspections, and handle abnormal situations in a timely manner.

- Establish a fuel entry inspection analysis and management system to ensure that the biomass pellet fuel used matches the boiler design.

2.3 Improve the technical ability level of boiler operators:

- Strengthen energy-saving training for boiler operators and conduct regular combustion test and adjustment test training to improve operators' ability to monitor and adjust boiler operating conditions.

- Adopt a thin biomass fuel layer, low-wind operation mode, and adjust the grate speed according to load changes to optimize boiler operating conditions.

3. Conclusion:

Industrial boilers play an important role as thermal power equipment in the national economy. However, the particularity of biomass boilers makes their thermal efficiency relatively low. By in-depth analysis of the causes of low thermal efficiency and taking corresponding improvement suggestions, the overall thermal efficiency of biomass boilers can be effectively improved, thereby promoting efficient use of energy and achieving sustainable development. This series of improvement measures will help promote the wider application of biomass energy in the industrial field and make a substantial contribution to the energy transition.