Transformation and deposition characteristics of sodium in Zhundong high sodium coal under different reaction atmospheres
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摘要: 为了获得循环流化床工艺下不同反应气氛对准东高钠煤中钠的迁移转化与积灰特性的影响,在0.4 t/d循环流化床实验装置上开展了相同床温(950℃)下的新疆沙尔湖高钠煤的气化(还原性气氛)与燃烧(氧化性气氛)实验研究。结果表明,气化和燃烧气氛下飞灰与积灰中Na主要以NaCl的形式存在;气化比燃烧更容易将Na、Cl固留在底渣和飞灰中,相应的进入气相中的Na、Cl更少;燃烧气氛下,部分NaCl会被烟气中的SO2硫化,生成稳定性更高的Na2SO4并冷凝在飞灰和积灰棒表面,燃烧过程中产生的飞灰粒径更细,积灰更严重;沙尔湖煤燃烧与气化过程中存在HCl对金属壁面的腐蚀。Abstract: In order to obtain the influences of different reaction atmospheres on transformation and deposition characteristics of sodium in Zhundong high sodium coal for circulating fluidized bed technology, gasification (reducing atmosphere) and combustion (oxidizing atmosphere) experiments were carried out, respectively, at 950℃ for Xinjiang SEH high sodium coal in a 0.4 t/d circulating fluidized bed experimental apparatus. The results show that Na in fly ash and deposition ash exists mainly as NaCl. Na and Cl are easier to be reserved in bottom ash and fly ash during gasification comparing with combustion, and correspondingly less Na and Cl enter into gas phase. Part of NaCl is sulfurized by SO2 and more stable Na2SO4 is produced under combustion atmosphere and condenses on the surface of ash deposition probes. More fine particulates are produced during combustion and perform worse deposition problems. The corrosion of HCl to the metal wall exists in the process of SEH coals' combustion and gasification.
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Key words:
- Zhundong high sodium coal /
- circulating fluidized bed /
- combustion /
- gasification /
- migration of Na /
- deposition
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图 2 0.4 t/d循环流化床实验装置示意图(测点位置)
1: primary air; 2: coal hopper; 3: screw feeder; 4: coal spreading air; 5: riser; 6: cyclone separator; 7: loop seal; 8: recirculation air; 9: flue gas; T1-T11: temperature measuring point; a: slag sampling; b: cyclone fly ash sampling; c: tail fly ash sampling; d: deposition probe
Figure 2 CFB system of 0.4 t/d for high alkali coal thermochemical conversion experiments (measuring point location)
图 4 底渣与旋风飞灰样品的XRD谱图
a: SiO2; b: NaAlSiO4; c: Ca2Al2SiO7; d: NaCl; e: Ca2MgSi2O7; f: Ca12Al14O33; g: KNa3(AlSiO4)4; h: Ca3Fe2(SiO4)3; i: Fe2O3; j: Al2O3; k: MgO; m: CaSO4; n: Na2SO4; o: Na8(SO4)(Al6Si6O24); r: K2SO4
Figure 4 XRD patterns analysis of bottom ash and fly ash samples (a): bottom slag; (b): cyclone fly ash
表 1 沙尔湖煤的煤质分析
Table 1 Analysis of SEHc
Proximate analysis w/% Ultimate analysis w/% Lower heating value
Qar, net/(MJ·kg-1)Chemical components in ash w/% Ash fusion temperature t/℃ Mar Ad Vdaf FCd C N H O S Cl SiO2 Al2O3 Fe2O3 CaO MgO TiO2 SO3 P2O5 K2O Na2O DT ST HT FT 11.02 14.66 30.46 43.86 51.54 0.58 2.36 19.73 0.11 1.138 17.93 41.98 17.59 6.87 19.39 2.49 1.08 1.82 0.18 0.66 4.38 1 120 1 130 1 140 1 150 表 2 沙尔湖煤中不同赋存形态Na的分布
Table 2 Different occurrence modes of alkali metals in SEHc
Alkali metal Content w/% water soluble ammonium acetate soluble hydrochloric acid soluble insoluble Na 88.51 7.88 1.81 1.8 表 3 高岭土的化学成分分析
Table 3 Chemical analysis of kaolin
Component SiO2 Al2O3 K2O TiO2 Fe2O3 MgO Na2O CaO Cr2O3 Others Content w/% 83.91 12.01 1.45 0.94 0.59 0.14 0.12 0.09 0.03 0.72 表 4 工况下沿程温度分布
Table 4 Temperature distribution along the path under working condition
Atmosphere Temperature t/℃ T2 T6 T8 T9 T10 Tc Td Combustion 950 944 904 811 730 701 580 Gasification 952 941 917 816 726 697 572 -
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