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In China, Xinjiang province has vast reserves of high alkali coal resources. However, in coal-fired boilers, fouling and slagging on heating surface caused by alkali metals significantly limit the efficient utilization of the coals. Based on gas-phase alkali metal detection, combined with flue gas temperature monitoring, heat transfer calculation and other methods, slagging monitoring was carried out on the heating surface of a tangentially-fired boiler burning high alkali coal. The influence of air distribution on flame temperature, gas-phase alkali metal mass concentration and heating surface heat transfer in the furnace was analyzed, and a quantitative relationship between the gas-phase alkali metal mass concentration and the heating surface heat transfer was established. Preliminary monitoring of fouling and slagging on the heating surface was also conducted. The results indicate that, slag sample on the water wall side was quite different from that on the flue gas side. The covered water wall surface was loose and porous, while the flue gas side was dense and hard black coke. Significant macroscopic differences were observed, with sodium crystalline phases mainly in the form of feldspar. The highest alkali metal concentration were observed in the main combustion zone of the boiler. The higher the ratio of upper to lower secondary air, the higher the temperature and gaseous alkali metal concentration in the furnace. An increase in the average gaseous alkali metal concentration by 1 mg/m3 resulted in a decrease in the heat transfer of the water wall by 0.82×108 kJ at 300 MW on a tangentially-fired boiler burning high alkali coal.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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