煤及生物质燃烧多波长耦合光解PLIF气相碱金属多组份测量研究

This proposal mainly focus on the measurement problem of gas phase alkali species during coal and biomass combustion process. Multi-wave coupling photo-fragmentation PLIF technology will be used for the selective detection of KOH/NaOH、KCl/NaCl、K2SO4/Na2SO4 species. An integrated OPO laser will be used for the laser wavelength tunable according to the different energy threshold for photo-fragmentation of the abovementioned species. Two dimensional K/Na atomic PLIF imaging technology will be utilized for the measurement of K/Na atoms after species photo-fragmentation. Based on the variation of laser energy before and after the flame, quantative calibration of the PLIF signal can be realized based on Beer-Lambert law of absorption theory. At the same time, multi points breakdown Multi-Points LIBS technology will be used for total K/Na element emission measurement. After integration data of the multi points, K/Na emission flux can be obtained. After time integration, total alkali metal emission information can be obtained. This information can be used for validation with the photo-fragmentation species data as well as the offline analysis data. Together with particle temperature, measured by two line thermometry, and particle diameter, measured by imaging technology, an overall kinetic model will be developed for the gas phase alkali metal releasing during coal and biomass particle combustion process. This model can be used for coupling modeling of the coal and biomass combustion process as well as developing new combustion technology in the future.

本项目针对煤及生物质颗粒燃烧过程中的气相碱金属释放检测问题，采用多波长耦合光解PLIF技术对KOH/NaOH、KCl/NaCl、K2SO4/Na2SO4等气相碱金属组份进行分别测量，采用OPO一体化激光器进行光解波长调制，根据各组分光解能量阀值的不同，选择性实现各碱金属组份的分别光解，然后采用K/Na原子的PLIF技术进行2D成像检测。结合火焰前后的激光能量信息，采用Beer-Lambert定量结合吸收法原理进行PLIF信号的定量化处理。并结合多点击穿的Multi-Points LIBS技术对煤及生物质颗粒燃烧过程中释放的K、Na元素总量进行测量，通过积分获得燃烧颗粒下游断面碱金属释放通量，时间积分后获得总量释放信息，用于对前述各碱金属组份的组份平衡计算和离线化学分析数据的对比验证。结合双色法颗粒测温、图像法粒径测量建立全面的煤及生物质颗粒燃烧过程过程中的碱金属释放动力学模型。

煤及生物质中富含的碱金属（K、Na）会在热转化过程中释放，造成严重的积灰、结渣和腐蚀问题，威胁设备的安全运行。发展新型碱金属在线测量方法，实现包括多种碱金属化合物在内的碱金属主要成分动态监测，对我国能源安全高效利用十分重要。本项目基于平面激光诱导荧光PLIF技术，多波长耦合光解技术MLIPF和多点激光诱导击穿光谱LIBS技术，建立了碱金属多组分（K/Na原子、KOH/NaOH、KCl/NaCl）高时间、空间分辨的在线定量测量方法，实现了多种碱金属组分的同时在线监测。为了验证测量方法的可行性，本项目测量了多种生物质燃烧全过程的碱金属多组分动态释放特性，结果发现，秸秆类生物质碱金属释放强度要高于木质类生物质。对于木质类生物质，碱金属主要以KOH的形式释放，而对于秸秆类生物质，由于其Cl含量较高，烟气中的碱金属主要以KCl的形式存在。两种生物质的K原子释放都主要存在于燃烧初期，但略有不同，木质类生物质K原子的最大释放强度出现在挥发分阶段，而秸秆类生物质的最大K原子释放强度出现在焦炭燃烧阶段的初期。随后，为了建立煤及生物质碱金属释放的动力学模型，本项目发展了基于多点LIBS的碱金属释放总量在线测量方法，并研究了准东煤和生物质燃烧过程中碱金属释放特性。研究发现，准东煤的碱金属释放分为脱挥发分、焦炭燃烧和灰反应三个明显的阶段，而生物质仅存在脱挥发分和碳反应两个主要阶段。进而，结合颗粒表面温度信息，本项目获取了碱金属释放动力学参数，从而建立了关于煤及生物质燃烧过程中碱金属释放的动力学方程。