Understanding the effect of calcium containing compounds on ash deposition during boiler operation: experiment study and dynamics calculation

During the operation of the boiler, the ash deposition phenomenon in the furnace will cause abnormal operation of the boiler system. This will lead to an increase the pollutant emission. To relieve the pollutant emission during the abnormal operation of the boiler, the mechanism of ash deposition was investigated from the perspective of reducing the phenomenon for ash deposition in this paper. Calcium-containing compounds play an important role in ash deposition burning coal. Therefore, the influence of calcium-containing compounds on ash deposition was investigated with Zhundong coal in a horizontal tube furnace in this paper. Furthermore, the binding and diffusion properties of calcium-containing compounds on the oxide film's surface were characterized under different temperatures by molecular dynamics simulations. The growth process of surface crystals was also researched by kinetic Monte Carlo method. The results indicated the precipitation rate of calcium gradually increases with the increase of combustion temperature. CaO, CaSO4, and CaSiO3 can play an important role in ash deposition burning Zhundong coal. CaSO4 is more easily to react with alpha-Fe2O3 (110) than CaO or CaSiO3. The diffusion coefficient of CaSO4, CaO, or CaSiO3 increases gradually with the increase of temperature. Furthermore, the system composed of CaSO4 and oxide film is more affected by temperature than that of CaO or CaSiO3 and oxide film. Moreover, under the whole temperature, the content of CaSO4 on the surface of the oxide film is the most. Finally, three calcium-containing minerals can promote each other during the deposition process and accelerate the formation of ash deposits.

Automated summary

This paper investigates the mechanism of ash deposition during abnormal operation of the boiler and finds that calcium-containing compounds play a crucial role. The precipitation rate of calcium and the diffusion coefficient of compounds are influenced by temperature. CaSO4 has the most significant impact on the oxide film, promoting the formation of ash deposits.