Characteristics of gaseous nitrogen release in coal fluidized bed combustion under different atmospheres

doi:10.11949/0438-1157.20211020

Abstract

Abstract:

The release of four main gaseous nitrogen products (HCN, NH₃, NO and NO₂) from bituminous coal and anthracite with different particle sizes during pyrolysis, gasification and combustion were studied by using a micro fluidized bed reactor combined with a rapid process mass spectrometer at 850—940℃. The results show that the micro fluidized bed can detect the dynamic release sequence and type of volatile-N and char-N in real time. The change of pyrolysis, gasification and combustion reaction atmosphere mainly affects the release of HCN and NH₃. The gaseous nitrogen of pyrolysis is mainly produced from volatiles. The released amount of HCN and NH₃ in combustion is affected by temperature, while the released amount of gaseous nitrogen products in gasification changes little with temperature. The changes in coal particle size and temperature have complex effects on various gaseous releases in bituminous coal and anthracite. Among them, the release characteristics of NH₃ are important characteristics that distinguish the release of volatile N and semi-coke.

Key words: fluidized bed, coal combustion, size distribution, gaseous nitrogen

摘要：

利用微型流化床反应装置，结合快速过程质谱仪，在850~940℃操作温度下，研究了三种不同粒度分布烟煤和无烟煤在热解、气化和燃烧反应条件下四种主要气态氮产物HCN、NH₃、NO和NO₂的释放规律。结果表明，微型流化床可以实时检测挥发分氮和焦炭氮的动态释放序和类型，热解、气化和燃烧反应气氛的改变主要影响HCN和NH₃的释放量。热解产物的气态氮主要是来自于挥发分，燃烧反应的HCN和NH₃的释放量与温度有明显关系，而气化反应的各类气态氮释放量随温度变化波动不大。煤颗粒尺寸和温度变化对烟煤和无烟煤中各类气态氮释放量产生影响比较复杂，其中NH₃的释放特性是区分挥发分N释放和半焦N释放的重要特征。

关键词: 流化床, 煤燃烧, 粒度分布, 气态氮

CLC Number:

TQ 038

Haolong BAI, Liangliang FU, Guangwen XU, Dingrong BAI. Characteristics of gaseous nitrogen release in coal fluidized bed combustion under different atmospheres[J]. CIESC Journal, 2022, 73(2): 876-886.

白浩隆, 付亮亮, 许光文, 白丁荣. 流化床煤燃烧过程不同气氛下的气态氮释放特征[J]. 化工学报, 2022, 73(2): 876-886.

Figures/Tables 13

Table 1 Proximate and ultimate analysis of the coal samples

Sample	Proximate analysis/%(mass,air dry basis)				Ultimate analysis/%( mass,ash-free dry basis)
Sample	M	V	A	FC	C	H	N	S
BC500~1000	4.23	26.32	3.60	65.85	75.79	4.418	1.005	0.61
BC230~500	4.38	26.03	4.97	64.63	73.84	4.706	1.004	0.63
BC20~230	4.71	26.78	6.47	62.05	74.06	4.599	0.919	0.59
AC500~1000	1.36	9.77	22.15	66.71	63.35	3.103	1.218	0.45
AC230~500	1.23	8.09	19.61	71.07	74.43	3.42	1.229	0.44
AC20~230	1.27	8.26	18.26	72.21	72.24	3.422	1.21	0.42

Fig.1 Schematic diagram of the micro fluidized bed reaction analyzer(MFBRA)

Fig.2 Illustration of the normalized N/C estimation method

Fig.3 Gaseous nitrogen release characteristics during pyrolysis

Fig.4 Gaseous nitrogen release characteristics during gasification of bituminous coal samples at 910℃

Fig.5 Effect of coal quality on gaseous nitrogen release characteristics in gasification at 910℃

Fig.6 Variation of gaseous nitrogen release amount with temperature in bituminous coal gasification

Fig.7 Variation of gaseous nitrogen release amount with temperature in anthracite coal gasification

Fig.8 Gaseous nitrogen release characteristics during combustion of bituminous coal samples at 910℃

Fig.9 Gaseous nitrogen release amount of different coal samples during combustion at 910℃

Fig.10 Variation of gaseous nitrogen release amount with temperature in bituminous coal combustion

Fig.11 Variation of gaseous nitrogen release amount with temperature in anthracite coal combustion

Fig.12 Routes of primary gaseous nitrogen release during fluidized bed combustion

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