Effect of industrial ashes with high carbon and calcium-rich on slagging characteristics of blending Zhundong coals
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摘要: 结合灰熔融测定、固定床和一维沉降炉实验,详细研究两种工业高碳富钙型灰(除尘灰和烘干灰)分别作为添加剂对高、低钠混煤结渣特性的影响。结果表明,原混煤在取样温度1000 ℃时已存在大量无定型硅,升高温度这些组分极易诱发低温共融反应。添入5%除尘灰后混煤煤灰的软化温度提高幅度高达100 ℃,能使混煤煤灰中CaO/SiO2质量比达到2.5,促使新相硅酸二钙和钙铝榴石生成,能够有效改善混煤的高温结渣倾向。沉降炉实验工况下探针收集灰样中主要物相均为钙铝黄长石,掺入两种添加剂后均可促使含硅物相演变为结晶矿物相,抑制非晶相含硅组分诱发的低温熔融,但添入5%烘干灰后探针表面结渣倾向改善的效果不显著。Abstract: Influence of two kinds of industrial ashes with high carbon and calcium-rich as additives (drying ash and fly ash) on slagging characteristics for blends of high and low sodium coals was studied in detail. Experiments were performed including ash fusion temperature tests, ashing for blending coals with/without additives in a fixed bed furnace and slagging on un-cooled probe in a drop tube furnace. The results show that there is a large amount of amorphous silicon at 1000 ℃ during combustion of raw blending coals, which easily leads to low-temperature eutectic reaction at higher temperature. Adding 5% fly ash can raise soften temperature of the blended coal ashes by 100 ℃, and mass ratio of CaO to SiO2 in ashes reaches up to 2.5. Dicalcium silicate and grossular are newly generated, which effectively reduce the slagging propensities. The main phase in slag samples collected on the probe is identified as gehlenite after adding two industrial ashes into raw blending coals. The addition of two typical ashes can transform amorphous silicon into its crystalline mineral phase, inhibit formation of low-temperature eutectics. In contrast to the case of adding 5% fly ash, impact of adding 5% drying ash into raw blending coals on slagging tendency of the ash particles on un-cooled probe is insignificant.
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Key words:
- additives /
- ash fusion temperature /
- high-sodium coal /
- blending coal /
- slagging characteristics
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表 1 煤样元素分析及工业分析
Table 1 Ultimate and proximate analyses of raw coals
Low sodium coal High sodium coal C/% 65.11 73.43 H/% 4.19 3.52 O/% 16.48 18.00 N/% 1.07 0.68 S/% 0.82 0.57 Ad/% 12.33 3.80 Vd/% 40.59 38.03 FCd/% 47.08 58.17 Mar/% 5.06 6.64 表 2 混煤煤灰与添加剂的元素分析
Table 2 Elemental contents of raw coals ashes, blending coals ash and additives ashes
Composition
w/%High
sodium
coal ashLow
sodium
coal ashBlending
coals ashFly
ashDrying
ashSiO2 6.51 30.05 21.15 5.4 4.09 Al2O3 6.09 18.93 13.56 0.97 1.65 Fe2O3 4.95 9.91 8.46 0.48 1.48 CaO 31.99 24.16 24.9 58.83 14.86 MgO 12.49 7.07 8.06 2.71 4.87 Na2O 7.74 0.61 3.45 0.14 0.78 K2O 0.18 1.41 1.03 0.15 1.14 SO3 28.11 4.65 18.79 0.79 3.19 P2O5 0.10 0.32 0.22 0.06 0.04 CO2 1.84 2.88 0.38 30.47 67.89 表 3 各工况主要元素配比
Table 3 Main elemental ratios at different experimental conditions
w/% Blending
coalsBlending coals +2.5%
fly ashBlending coals +5%
fly ashBlending coals +2.5%
drying ashBlending coals +5%
drying ashCaO 24.9 35.44 42.82 26.8 28.39 SiO2 21.15 18.79 17.13 20.38 19.74 Al2O3 13.56 11.42 9.91 12.8 12.16 MgO 8.06 7.33 6.81 8.69 9.22 Na2O 3.45 2.87 2.47 3.35 3.27 Fe2O3 8.46 7.09 6.13 8.11 7.82 Ca/Si 1.18 1.89 2.5 1.32 1.44 Ca/(Si+Al) 0.72 1.17 1.58 0.81 0.89 Ca∶Si∶Al 1.8∶1.6∶1 3.1∶1.6∶1 4.3∶1.7∶1 2.1∶1.6∶1 2.3∶1.6∶1 -
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