Effect of potassium carbonate on coal ash sintering and mineral transformation in H2O-H2-CO-CO2 atmosphere
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摘要: 在水蒸气气化气氛（水蒸气-氢气-一氧化碳-二氧化碳混合气氛）下考察了反应压力对负载碳酸钾煤灰烧结温度的影响，建立了包含煤的灰分、煤灰化学组成、催化剂负载量及反应压力因素的煤灰烧结温度预测关系式，预测结果与实测烧结温度的误差在±15℃（2%）范围内。利用X射线衍射仪和FactSage热力学计算软件对不同气氛和压力下煤灰中的矿物组成及含量的变化规律进行了分析。结果表明，碳酸钾与煤灰中的硬石膏、方解石反应生成硫酸钾和碳酸钾钙；水蒸气气化气氛下硫酸钾和赤铁矿被还原，碳酸钾钙的分解温度随反应压力的增大而升高；负载催化剂煤灰中氢氧化钾的量随温度和压力的提高而增加，不同压力下煤灰的最低烧结温度与氢氧化钾的含量有关，当氢氧化钾的含量达到一定值时，不同压力下对应的温度与实验测得的煤灰烧结温度接近。Abstract: The influence of reaction pressure on the sintering temperature of potassium carbonate loaded coal ash was investigated in H2O-H2-CO-CO2 atmosphere. An empirical equation for sintering temperature calculation was derived based on the content of ash, the ash composition, the catalyst loading and the reaction pressure. The deviation between the calculated value and the experimental value was within ±15 ℃ (2%). The transformation of two coal ashes was investigated by X-ray diffractometer and thermodynamic calculation. It was found that potassium carbonate could react with anhydrite and calcite in coal to produce potassium sulfate and butschliite. The potassium sulfate and hematite could be reduced in the H2O-H2-CO-CO2 atmosphere, and the decomposition temperature of butschliite increased with the increase of pressure. Moreover, the content of potassium hydroxide in the potassium loaded coal ash increased with the increase of temperature and pressure. The minimum sintering temperatures of coal ash under different pressures were related to the content of potassium hydroxide; when the contents of potassium hydroxide in ashes reached to a certain value, the calculated minimum sintering temperature was very close to the experimental one under different pressures.
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图 1 加压压差法煤灰烧结温度测定装置示意图
Figure 1 Schematic diagram of pressurized sintering temperature determination apparatus
1-constant pressure valve; 2-mass flowmeter; 3-high-pressure water pump; 4-preheater-heater; 5-cylinder ash column; 6-gas distributor; 7-electric furnace; 8-differential manometer; 9-thermocouple; 10-gas liquid separator; 11-back pressure regulator; 12-volumetric flow meter
图 4 烧结温度预测值和测试值的比较
Figure 4 Comparison of calculated sintering temperature with experimental one
图 5 鄂尔多斯原煤灰及负载碳酸钾煤灰不同条件下反应后的XRD谱图
Figure 5 XRD patterns of EEDS raw coal ash and potassium carbonate loaded coal ash under different conditions
(a): EEDS raw coal ash; (b): EEDS-K coal ash a: EEDS raw coal ash; b: EEDS-N2-3.5 MPa; c: EEDS-mixture-3.5 MPa; d: EEDS-K ash; e: EEDS-K-N2-3.5 MPa; f: EEDS-K-mixture-0.1 MPa; g: EEDS-K-mixture-3.5 MPa; Q: quartz-SiO2; A: anhydrite-CaSO4; C: calcite-CaCO3; H: hematite-Fe2O3; Mu: muscovite-K0.77Al1.93(Al0.5Si3.5)O10(OH)2; An: anathite-CaAl2SiO8; Ma:magnetite-Fe3O4; Ar: arcanite-K2SO4; CaO: calcium oxide-CaO; B: butschliite-K2Ca(CO3)2; PC: potassium carbonate-K2CO3; PH: potassium carbonate hydrate-K2CO3 ·1.5H2O; PA: potassium aluminate silicate-K0.85Al0.85Si0.15O2; PS: potassium silicate-K2Si4O9; KA: kaliophilite-KAlSiO4
图 6 文山原煤灰及负载碳酸钾煤灰不同条件下反应后的XRD谱图
Figure 6 XRD patterns of WS raw coal ash and potassium carbonate loaded coal ash under different conditions
(a): WS raw coal ash; (b): WS-K coal ash a: WS raw coal ash; b: WS-N2-3.5 MPa; c: WS-mixture-3.5 MPa; d: WS-K ash; e: WS-K-N2-3.5 MPa; f: WS-K-mixture-0.1 MPa; g: WS-K-mixture-3.5 MPa; Q: quartz-SiO2; A: anhydrite-CaSO4; C: calcite-CaCO3; H: hematite-Fe2O3; I: illite-K(Al4Si2O9(OH)3); An: anathite-CaAl2SiO8; Mu: muscovite-K0.77Al1.93(Al0.5Si3.5)O10(OH)2; Ma: magnetite-Fe3O4; Ar: arcanite-K2SO4; CaO: calcium oxide-CaO; B: butschliite-K2Ca(CO3)2; PH: potassium carbonate hydrate-K2CO3 ·1.5H2O; PC: potassium carbonate-K2CO3; PA: potassium aluminate silicate-K0.85Al0.85Si0.15O2; PS: potassium silicate-K2Si4O9; KA: kaliophilite-KAlSiO4
图 7 负载催化剂文山煤灰中碳酸钾钙含量的计算
Figure 7 Calculated results of the content of butschliite in WS-K coal ash versus temperature
图 8 负载催化剂煤灰中氢氧化钾含量随温度的变化
Figure 8 Calculated results of the content of KOH versus temperature (a): WS-K ash; (b): EEDS-K ash
表 1 煤样的工业分析和元素分析
Table 1 Proximate and ultimate analyses of coal samples
Sample Proximate analysis wd/% Ultimate analysis wd/% A V FC C H N St O* WS 18.29 39.73 41.98 53.78 3.91 1.61 1.24 21.17 EEDS 4.79 35.43 59.78 73.83 4.37 0.66 0.90 15.45 A: ash; V: volatile matter; FC: fixed carbon; d: dry base; St: total sulfur; *: by difference 
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表 2 煤灰的化学组成
Table 2 Chemical composition of coal ashes
Sample Content w/% SiO2 Al2O3 TiO2 CaO Fe2O3 MgO K2O Na2O SO3 WS 33.52 15.58 0.57 20.96 10.75 1.34 1.73 0.21 13.62 EEDS 29.09 11.34 0.72 21.28 17.48 0.76 0.48 0.70 15.24
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表 3 模拟计算负载碳酸钾煤灰的化学组成
Table 3 Calculated composition of potassium carbonate loaded coal ashes
Sample Content w/% K2Ca(CO3)2 K2CO3 KAlSiO4 K2SO4 K2Si2O5 Fe2O3 Mg2SiO4 Na2Ca2Si3O9 Ca3Fe2Si3O12 CaOMgOSiO2 WS K-ash 34.09 18.73 18.54 13.93 9.64 4.12 0.90 0.05 - - EEDS K-ash 9.87 30.44 11.27 32.81 - 2.05 - 1.30 11.31 0.95
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