气流床撞击流水煤浆气化火焰光谱辐射特性实验研究

doi:10.3964/j.issn.1000-0593(2020)02-0465-07

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摘要：火焰光谱检测技术应用于气化炉有效监控，能实时反映气化炉工况，保障气化炉稳定运行。采用实验室规模的气流床撞击水煤浆气化装置，利用光纤光谱仪通过对气化炉不同部位进行探测，研究了水煤浆气化火焰在距离撞击平面不同轴向位置L处的光谱辐射特性，并利用不同自由基强度及分布对气化炉内各反应区进行表征，为气化炉运行工况提供依据。结果表明：在300～800 nm范围内可检测到明显的OH^*(306.7和309.8 nm)，H^*₂(382 nm)，CH^*(314.5和387 nm)，Na^*(589 nm)，Ar(671 nm)和K^*(404，768和770 nm)特征峰，而各种粒子激发方式及分布方式不同，可用于实现火焰宏观特征的表征。从紫外至可见光区域。水煤浆气化火焰中存在强烈的背景辐射，主要包括颗粒在高温下产生的黑体辐射及CO^*₂受热激发产生的350～600 nm的连续旋转辐射，强烈的背景辐射对自由基强度辐射测定形成干扰，需通过计算扣除背景辐射。利用检测到的各自由基强度分布可对气化火焰进行表征，OH^*分布可表征火焰反应区域，而CH^*存在范围相对较窄，仅存在于-10 cm<L<10 cm反应剧烈区域。在0.9≤O/C≤1.1时，OH^*与CH^*峰值强度最大值出现在撞击平面附近，随O/C增加，CH^*峰值强度最大值分布范围向向上流股中偏移。不同平面处OH^*/CH^*强度比值随O/C的变化不同，OH^*/CH^*强度反映了自由基激发路径的变化，OH^*/CH^*强度在撞击平面处最低，化学激发占主导。化学激发主要发生区域在-10 cm≤L≤10 cm范围内。撞击平面附近Na^*强度较大，而随着|L|增大，Na^*强度有所减小，其中向上流股中Na^*强度高于向下流股中强度，而K^*在-20 cm≤L≤20 cm范围内强度变化比较无序。由于碱金属粒子激发方式为热激发，因此可利用其分布判断火焰高温区域。由于煤中Na和K粒子含量较少，且存在形式多样，利用Na^*和K^*表征O/C会出现较大误差。由于碱金属强度受到背景辐射影响较小，可用于表征火焰频率，并可反映气化效果。Na^*自发辐射强度随火焰撞击过程中可产生脉动而呈现峰谷分布。随着O/C增加 Na^*峰谷频率越高，说明随着氧气气速逐渐增加，火焰脉动剧烈。且Na^*强度逐渐增加，说明剧烈的撞击有助于反应的进行。煤中挥发分在撞击区内析出，而挥发分中大部分的H反应并产生H^*₂辐射，H^*₂强度可表征煤中挥发分的反应程度。

关键词：光谱辐射；气流床气化炉；化学激发；热激发；燃烧诊断

Abstract：The flame spectrum detection technology applied to the effective monitoring of gasifier can reflect the working condition of gasifier in real time and guarantee the stable operation of gasifier. Based on the bench-scale entrained flow gasifier, the different chemiluminescence characteristics at different axial positions of the impinging plane (L) of coal-water slurry (CWS) flame are studied by the spectrometer, and the reaction zones in gasifier are characterized by different radical intensity and distributions. The results show that: OH^*(306.7 nm, 309.8 nm), H^*₂ (382 nm), CH^*(314.5 nm，387 nm), Na^*(589 nm), Ar(671 nm)and K^*(404 nm, 768 nm, 770 nm) characteristic peaks can be detected in the range of 300～800 nm. Different particle distributions can be used to characterize the macroscopic characteristics of flame. There is also a strong background radiation in CWS gasification flame. The background radiation mainly comes from the blackbody radiation generated by coal particles at high temperature and continuous rotational radiation of 350～600 nm generated by CO^*₂. The strong background radiation will interfere with the determination of free radical intensity radiation, which will be deducted by the calculation. The distribution of OH^* can be used to characterize the flame reaction region, while CH^* only exists in a relatively narrow reaction region of -10 cm<L<10 cm. When 0.9≤O/C≤1.1，OH^* and CH^* peak intensity exist at the impinging plane. With the increase of O/C, the existence position of CH^* peak intensity turns to upstream. The intensity ratio of OH^*/CH^* varies with the change of O/C at different positions. OH^*/CH^* reflects the change of free radical excitation path. OH^*/CH^* is the lowest at the impinging plane, because of chemical excitation dominates. Chemical excitation mainly occurs in the range of -10 cm＜L＜10 cm. The intensity of Na^* near the impinging plane is relatively high, but with the increase of |L|, the Na^* intensity will decrease. The Na^* intensity in the upstream is higher than that in the downstream. Different from Na^*，the change of K^* intensity is disordered in the region of -20 cm<L<20 cm. Since the excitation mode of alkali particles (Na^* and K^*) is thermal excitation, the distribution of alkali particles can be used to judge the high temperature region of the flame. However, due to the low content of Na and K particles in coal, the use of Na^* and K^* to characterize O/C will cause a large error. Because Na^* and K^* is less affected by background radiation, it can be used to characterize the flame frequency and reflect the gasification effect. Na^* intensity fluctuates with the impact of flames. With the increase of O/C, the frequency of Na^* intensity can indicate the change of flame fluctuation with the increase of oxygen gas velocity. And the Na^* strength gradually increase, indicating that the violent impact is conducive to the reactions. There is a high intensity of H^*₂ in the impinging zone, and the H^*₂ intensity can represent the reactions of volatile matter.

Key words：Spectral radiation; Entrained-flow gasifier; Chemical excitation; Thermal excitation; Combustion diagnosis

收稿日期: 2018-12-19 修订日期: 2019-04-06

中图分类号:

O433.5

基金资助: 国家重点研发计划(2017YFB0602601)，国家自然科学基金项目(21676091)资助

通讯作者: 龚岩，于广锁 E-mail: gsyu@ecust.edu.cn; yangong@ecust.edu.cn

作者简介: 宋旭东，1988年生，宁夏大学省部共建煤炭高效利用与绿色化工国家重点实验室讲师 e-mail: xdsong@nxu.edu.cn

引用本文:

宋旭东，郭庆华，龚岩，苏暐光，白永辉，于广锁. 气流床撞击流水煤浆气化火焰光谱辐射特性实验研究[J]. 光谱学与光谱分析, 2020, 40(02): 465-471.
SONG Xu-dong, GUO Qing-hua, GONG Yan, SU Wei-guang, BAI Yong-hui, YU Guang-suo. Chemiluminescence Characteristics of Coal-Water Slurry Impinging Flames in Bench-Scale Entrained Flow Gasifier. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2020, 40(02): 465-471.

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