Ash Deposition and Slagging Behavior of Xinjiang High-Alkali Coal in a 20MWth Cyclone Combustion Test Facility

The circulating fluidized bed (CFB) boiler is a mainstream technology of biomass combustion generation in China. The high flue gas flow rate and relatively low combustion temperature of CFB make the deposition process different from that of a grate furnace. The dynamic deposition process of biomass ash needs further research, especially in industrial CFB boilers. In this study, a temperature-controlled ash deposit probe was used to sample the deposits in a 12 MW CFB boiler. Through the analysis of multiple deposit samples with different deposition times, the changes in micromorphology and chemical composition of the deposits in each deposition stage can be observed more distinctively. The initial deposits mainly consist of particles smaller than 2 μm, caused by thermophoretic deposition. The second stage is the condensation of alkali metal. Different from the condensation of KCl reported by most previous literatures, KOH is found in deposits in place of KCl. Then, it reacts with SO2, O2 and H2O to form K2SO4. In the third stage, the higher outer layer temperature of deposits reduces the condensation rate of KOH significantly. Meanwhile, the rougher surface of deposits allowed more calcium salts in fly ash to deposit through inertial impact. Thus, the elemental composition of deposits surface shows an overall trend of K decreasing and Ca increasing.

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Prediction of Fouling and Slagging in Pulverized-Coal Fired Furnaces

Volume 1: Fuels and Combustion, Material Handling, Emissions; Steam Generators; Heat Exchangers and Cooling Systems; Turbines, Generators and Auxiliaries; Plant Operations and Maintenance ◽

10.1115/power2013-98045 ◽

2013 ◽

Author(s):

Ezra Bar-Ziv ◽

Efim Korytnyi ◽

Miron Perelman ◽

Roman Saveliev ◽

Boris Chudnovsky

Keyword(s):

Fly Ash ◽

South African ◽

Fluid Dynamic ◽

Test Facility ◽

Mineral Matter ◽

Ash Deposition ◽

Dynamic Simulations ◽

Good Comparison ◽

Combustion Experiment

The objective of this paper is to develop a method for predicting the fouling dynamics and thermal resistance of a certain coal and its fly ash in a coal-fired utility boiler as well as determine the emissivity of the fly ash in order to optimize soomblowing procedures for fouling clean-up. The methodology comprises combustion experiment in a 50kW test facility, characterization of the coal and its mineral matter and the consequent fly ash as well a series of computational fluid dynamic simulations. Ash deposition from Cerrejon D Colombian and Billiton-Prime South African coals were studied and their behavior predicted in 575MW tangentially-fired and 550MW opposite-wall boilers. Good comparison was obtained between predicted results and actual data from the boilers.

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Effects of temperature and additives on ash transformation and melting of high-alkali-chlorine coal

Thermal Science ◽

10.2298/tsci200313271z ◽

2020 ◽

Vol 24 (6 Part A) ◽

pp. 3501-3510

Author(s):

Jingbin Zi ◽

Daoyang Ma ◽

Zia Rahman ◽

Xuebin Wang ◽

Hao Li ◽

...

Keyword(s):

Coal Ash ◽

Ash Deposition ◽

High Sodium ◽

Melting Characteristics ◽

Ash Melting ◽

Calcium Magnesium ◽

Effects Of Temperature ◽

High Alkali ◽

Main Component ◽

High Aluminum

The high contents of sodium and chlorine in Shaerhu coal aggravate severe slag-ging ash deposition and corrosion in boilers. Adding proper additives is an effec-tive way to reduce slagging ash deposition and corrosion. Based on the experi-mental study, this paper investigated the effect of combustion temperature, types of additives, and its amount on the ash transformation and melting of high sodium chloride Shaerhu coal. The ash melting characteristics, elemental compositions and mineral compositions of the ash produced under different conditions were characterized. Results showed that the contents of calcium, magnesium, and sul-phur in the coal ash varied slightly with the temperature increasing. Chlorine and sodium released rapidly from coal at 550-815?C and 550-700?C, respectively. At 1050?C, calcium silicate was observed as the main component of the ash. The addition of different additives had no significant effect on chlorine and sodium capture. The addition of silicon species lowered the ash fusion temperatures, while the aluminum had an opposite effect. To prevent the furnace from slagging, a high aluminum additive is proposed to be adopted.

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