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Journal of ZheJiang University (Engineering Science)  2021, Vol. 55 Issue (7): 1361-1367    DOI: 10.3785/j.issn.1008-973X.2021.07.015
    
Experimental study on characteristics of alkaline hydroxide to eliminate NH4Cl ash deposition
Yu-guo NI(),Hao ZHOU*(),Shi-hao HU
State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
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Abstract  

By simulating the atmosphere of NH4Cl in coal-fired power plants, the rules that how NH4Cl caused ash deposition to affect the heat flux density of the heat-transfer surfaces were studied. A drop tube furnace system was used to simulate the boiler tail flue, an oil circulation system for temperature control, a probe system for ash deposition, the temperature inside and outside of the probe was monitored in real time to obtain the heat flux density on the probe surface. NaOH, Mg(OH)2, and Ca(OH)2 were used as additives to study the removing effect of three alkaline hydroxides on NH4Cl in the flue gas. Results showed that NH4Cl had a weak adhesion ability to ash, and the decrease in heat flux density on the heat-transfer surface was mainly caused by the deposition of NH4Cl. Among the three additives, Ca(OH)2 could narrow the decrease of heat flux density on the top of the probe, reducing the ratio of the decrease to 3.61%, while NaOH could narrow the decrease of the heat flux density at the bottom of the probe, reducing the ratio of the decrease to 6.46%. Although Mg(OH)2 could reduce the decrease of the heat flux density at the top of the probe, it would enlarge the decrease of the heat flux density at the bottom of the probe.



Key wordsheat flux?density      ash deposition      NH4Cl      additive      alkaline hydroxide     
Received: 21 May 2020      Published: 05 July 2021
CLC:  TK 11  
Fund:  国家重点研发计划资助项目(2018YFB0604104)
Corresponding Authors: Hao ZHOU     E-mail: yg-ni@163.com;zhouhao@zju.edu.cn
Cite this article:

Yu-guo NI,Hao ZHOU,Shi-hao HU. Experimental study on characteristics of alkaline hydroxide to eliminate NH4Cl ash deposition. Journal of ZheJiang University (Engineering Science), 2021, 55(7): 1361-1367.

URL:

https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2021.07.015     OR     https://www.zjujournals.com/eng/Y2021/V55/I7/1361


碱性氢氧化物消除NH4Cl积灰特性实验研究

通过模拟燃煤电厂中NH4Cl氛围,研究NH4Cl如何影响飞灰沉积引起受热面热流密度变化. 实验采用竖式炉系统模拟锅炉尾部烟道,油循环系统控制温度,探针收集积灰,实时监测探针内外表面温度,获得探针受热面热流密度,将NaOH,Mg(OH)2,Ca(OH)2作为脱除剂,研究3种碱性氢氧化物对烟气中NH4Cl的脱除效果. 研究发现,NH4Cl对灰分的黏附能力较弱,受热面热流密度降低主要由NH4Cl析出形成的沉积层引起. 在3种脱除剂中,Ca(OH)2能够改善探针顶部热流密度降低,将热流密度降低率缩小到3.61%;NaOH能够改善探针底部热流密度降低,将降低率缩小到6.46%;Mg(OH)2虽然能够减少探针顶部热流密度降低,但会引起探针底部热流密度降低加剧.


关键词: 热流密度,  灰沉积,  NH4Cl,  脱除剂,  碱性氢氧化物 
Fig.1 Schematic diagram of experimental system
参数 数值 单位 参数 数值 单位
烟气温度 310±5 NH4质量浓度 0.15 g·mL?1
烟气流速 10.0 m·s?1 工况1:无脱除剂
给灰量 2.66 kg·h?1 工况2:NaOH 67.29 g·h?1
蠕动泵流量 10 mL·min?1 工况3:Mg(OH)2 48.78 g·h?1
探针顶部
外孔温度
100±2 工况4:Ca(OH)2 62.24 g·h?1
探针底部
外孔温度
90±2
Tab.1 Ash deposition characteristics experiment parameters
化合物 wB/% 化合物 wB/%
SiO2 52.640 MgO 1.390
Al2O3 25.570 SO3 1.228
CaO 7.330 TiO2 1.070
Fe2O3 6.690 P2O5 0.468
Na2O 1.640 SrO 0.198
K2O 1.610 BaO 0.166
Tab.2 XRF results of original fly ash
Fig.2 Schematic diagram of probe
Fig.3 Figure of ash deposition on top, side and bottom of probe
Fig.4 Relative heat flux density curves at top and bottom of probe
Fig.5 Decrease rate of heat flux density at top and bottom of probe
Fig.6 XRD photos of ash deposition under different conditions
工况 顶部 底部
原灰 SiO2、莫来石(Al6Si2O13) SiO2、莫来石(Al6Si2O13)
1 SiO2、NH4Cl SiO2、NH4Cl
2 SiO2、NH4Cl、NaCl SiO2、NH4Cl、NaCl
3 SiO2、NH4Cl、Mg(OH)2 SiO2、NH4Cl、Mg(OH)2
4 SiO2、NH4Cl SiO2、NH4Cl
Tab.3 Main substances in ash deposition
Fig.7 SEM photos of ash deposition under different conditions
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