Safe and effective operation and energy saving and emission reduction of the boiler life cycle

Power station boilers continue to develop in the direction of high parameters, large capacity and high grade, boiler manufacturing technology and manufacturing materials have not made breakthrough progress, energy conservation and emission reduction requirements are becoming more and more stringent, and boiler manufacturing and operation are required to develop in a safer and more effective direction.

1 Improvement measures for effective and safe operation of boilers

The boiler needs to consume a lot of energy during operation, and effectively improving the boiler operating efficiency can reduce the boiler energy consumption and improve the efficiency of the entire power plant. Due to the large amount of high temperature and high pressure steam generated during operation, the boiler as a pressure-bearing vessel must maintain a high degree of attention to safety and improve the stability of boiler operation.

1. 1. Strengthen material research and development

With the vigorous development of domestic power generation in recent years, China has been in an advanced position in the field of boiler manufacturing, and continues to carry out the research and development and manufacturing of higher-grade boilers, the main steam parameters of the new type of boiler under development can reach 700 °C, 29Mpa, and the important condition restricting the continued improvement of parameters is the material, the research and development of higher parameters high temperature heating surface materials has not been effectively solved, and if all imported materials are used, it will lead to a rapid rise in costs. It cannot be really applied to industrial production. Therefore, we should organize experts to carry out more in-depth research on material research and development, on the one hand, to develop high-quality materials that can withstand high temperature and high pressure, on the other hand, we must also minimize the cost of material manufacturing, so that it can be better applied in the field of boiler manufacturing.

1. 2 Optimize boiler design

The design parameters of the boiler directly determine the efficiency of the boiler, and more and more high-parameter, million-level, ultra-supercritical and other types of boilers are put into the R&D and operation stage, which effectively improves the operating efficiency of the boiler, and the efficiency test of the million-level ultra-supercritical secondary reheating boiler put into operation in China has reached 95.2%. In order to improve the boiler operation efficiency more effectively and maintain safe operation, the designer should continue to optimize the boiler design, and the key research directions should include burner optimization, boiler heating surface layout adjustment, and adding multi-stage heating surface at the tail, in order to reduce the number of combustion pollutants generated and reduce smoke temperature loss. For example, through burner performance optimization, we can effectively improve the combustion effect of pulverized coal while reducing pollutant emissions such as NOx, thereby reducing the carbon content loss in boiler slag and fly ash, and further improving boiler efficiency.

1. 3 Strengthen combustion adjustment

The combustion state of the boiler in the combustion process will directly affect the combustion efficiency of the boiler, maintain the low coking rate and good stability of the furnace, which is the basis for ensuring the safe and effective operation of the boiler. Whether it is a new unit or an old unit, the professional commissioning team should be invited to cooperate with the operation personnel to jointly carry out the boiler systematic combustion adjustment, through the milling system adjustment, primary and secondary air ratio adjustment, steam parameter adjustment, etc. to comprehensively improve the combustion state of the boiler, relevant studies show that after the combustion adjustment of the system, the carbon content of the boiler fly ash can be controlled within 1%, the exhaust gas temperature can be controlled within the design range, and the boiler combustion operation mode can be optimized. At the same time, in the process of combustion adjustment, we should pay attention to the ratio of wind powder of the boiler, which is conducive to the boiler combustion in a stable state and can effectively reduce the ineffective phenomenon of boiler combustion.

2 Boiler energy saving and emission reduction improvement measures

Power station boiler energy supply is basically coal, oil and gas, natural gas and other fossil energy, the mineral characteristics of this energy itself caused in the furnace combustion, the production of a large number of sulfide and nitride and other polluting gases, accompanied by CO2 and other greenhouse gases, and the combustion of flue gas will also take away a large amount of waste heat, the future should focus on the development of furnace to reduce pollutant emission combustion technology, and waste heat utilization technology.

2. 1 Flue gas deep cooling and utilization technology

At present, the domestic boiler tail heat exchanger is often arranged with low-temperature economizer and flue gas cooler, etc., and the low-temperature economizer transformation is a flue gas deep cooling and utilization method that many power plants are using. In order to better realize the deep utilization of flue gas, the design concept of waste heat boiler can be learned from the manufacturing process of low-temperature economizer, replacing the finned tube as the heat exchange element, and effectively increasing the heat exchange area. In this regard, the transformation of low-temperature economizer will become the most effective measure for the deep cooling area and utilization of flue gas, and a unit of Yuhuan Power Plant has effectively improved the boiler efficiency after the implementation of low-temperature economizer transformation, and played a better reference and reference role for the transformation of other large-parameter boilers in China.

2. 2 Actively carry out burner transformation

In recent years, China’s power plants have completed the desulfurization and denitrification transformation, and the tail flue gas treatment has been able to meet the needs. In order to adapt to higher emission reduction goals in the future, the in-depth research and development of the burner structure should be carried out under the premise that the boiler efficiency is not affected, and effective combustion and low nitrogen combustion should be realized from the structure, such as the stratified combustion technology concept studied in recent years, which is to physically realize the step-by-step combustion of fuel, solve the situation of insufficient fuel combustion, and reduce the problem of generating a large number of polluting gases during combustion. In the long run, the transformation of the burner and the transformation of the heating surface are the most effective measures for the future energy-saving and emission-reduction transformation.

2. 3 SCR denitrification and cleaning and regeneration technology

SCR can use catalyst nitrogen oxides for reduction treatment to further reduce boiler NOx emissions, so that nitrogen oxides from more than 100ppm at the boiler outlet to less than 10ppm. The core equipment of SCR is the catalyst, how to maintain the catalyst activity is the work of reducing NOx emissions during the production process, from this aspect should strengthen the material structure research and development and equipment research and development of catalyst cleaning, strengthen the material research and development of catalyst regeneration technology, to avoid the unexpected situation of catalyst failure during production. At the same time, from the perspective of power plant operation, the development of more efficient and durable catalyst structures and technologies can help improve SCR efficiency and catalyst service life, and fundamentally reduce the cost of denitration from the equipment.

3 Concluding remarks

In summary, while the power station boiler continues to develop on the road with high parameters and large capacity, it should also continue to carry out the in-depth development and transformation of the existing equipment structure, no matter which direction of improvement will have a positive impact on the operation safety and energy saving and emission reduction of the boiler, and achieve the improvement of boiler operation efficiency. Subject to the limitations of materials and processes, we should focus on boiler design optimization, burner modification, heating surface transformation, through these transformations to protect the long-term effective and stable operation of the boiler, while achieving the goal of energy conservation and emission reduction.