Integrated Control Technology for High Temperature Corrosion in Boiler
High temperature corrosion has become a common problem of boilers in many large coal fired power plants. It causes boiler water wall becoming thinner leading to pipe leakage or break accidents. According to survey, the repair downtime of domestic units of capacity 300MW and above caused by pipe break accounts for about 40% of total. Therefore, high temperature corrosion not only affects the safe operation of the boiler, but also causes huge economic loss. The integrated high temperature corrosion control technology developed LY Power can solve this problem effectively. The technology can be implemented from three parts as follows.
Near-wall air technology
Combustion of pulverized coal under oxygen deficient conditions produces CO, which is the main reason for the formation of reducing atmosphere. When the H2S concentration in flue gas is more than 0.01%, it will have strong corrosion effect to the boiler water wall tube, so the H2S and CO content in the near-wall area will directly affect the degree of high-temperature corrosion. Therefore, it will help to introduce a flow of air to the high temperature corrosion region to increase the oxygen concentration, and to consume the H2S and CO in the near-wall region to improve the reducing atmosphere in the water wall region. By adding a near-wall air nozzle, the air enters the furnace through the nozzle and forms a layer of oxide "protective film" in the near-wall area which will destroy the reducing atmosphere and consume H2S. Meanwhile, the "protective film" can also lower the water wall temperature in this area.
Combustion equipment retrofit
The unburnt pulverized coal with sharp edges and corners may have considerable wearing effect on the water wall. It can destroy the less robust protective layer on the wall formed by the corrosion products, resulting in the rapid reaction between the flue gas medium and the pure metal. This combination of corrosion and wear can greatly aggravate the process of wall tube damage. To fundamentally improve this phenomenon of flame flushing water wall, it is needed to optimize the combustion equipment of the boiler and to change the primary and secondary air jet flow rigidity, angle, swirl intensity and other parameters. Meanwhile, the evenness of pulverized coal & air flow should be enhanced and make the coal flow to each burner be as equal as possible, so as to ensure the equal momentum of coal & air jet flow, proper fineness of the pulverized coal, and to realize quick and stable combustion.
High temperature corrosion protective coating technology
The new inorganic material for heat insulation coating, which LY Power developed with National Academy of Sciences, applies nanoparticle technology, compound emitting agent technology, system binding agent technology, and it has the characteristics of high emissivity, high thermal conductivity, resistance to fouling and slagging, resistance to high temperature corrosion, and improvement of wear resistance. Spray the new material for heat insulation coating on the heating surface of the substrate to protect it from oxidation, corrosion and coking, and improve the heat exchange efficiency of the equipment. After the application of this technology, the coating surface emissivity will be stably above 0.9 when the heating surface is in high temperature environment. At the same time, the coating enables the surface to have a stable and durable high emissivity within the wide infrared spectrum. Its property of anti-slagging (self-cleaning) can greatly improve the heat transfer performance (enhance radiation heat transfer and heat conduction).
To middle of 2020, this technology has been applied to unit #1 & #2 of Guodian Feixian Power Plant and unit #6 of Guodian Jingmen Power Plant.
The design of near-wall air nozzle is suitable for various boilers and various water wall tube.
Optimization and reconstruction design of burners and secondary air nozzles.
Ensure low NOx emission of coal fired boiler without high-temperature corrosion occurring in the boiler water wall.