【作者】 吉恒松；

【导师】 王谦；

【作者基本信息】 江苏大学 ， 工程热物理， 2014， 博士

【摘要】 生物质气化制取燃气或富氢合成气,是生物质能转换利用的有效途径,对于能源的可持续利用和环境保护具有重要意义,目前还处于探索阶段。很多学者对生物质制氢技术进行了较为深入的研究,但由于气化反应器和气化剂的差异,以及操作条件的影响所取得的效果也各不相同。针对这个问题,提出基于感应加热技术的流化床生物质气化技术路线,设计并建立了小型感应加热式生物质气化试验系统,从反应器内部为流态化的生物质颗粒热解和气化过程提供热量,实现气化过程的全程准确控温,并进行了气化反应器的升温特性试验、进料速率标定试验。以稻壳为生物质原料,水蒸汽和空气为气化剂,进行了生物质气化制取高热值燃气实验、生物质气化制氢试验,对生物质气化工艺过程进行模拟计算,最后进行了生物质气化过程的(?)分析。主要研究内容和结论如下：进行生物质气化制氢试验研究,考察了气化温度、蒸汽生物质质量比(S/B)、当量比(ER)对产物气成分和产氢率的影响。试验结果表明：气化温度在800℃时,H2浓度随着S/B增大或ER减小而升高,H2产率分别在S/B为1.5和ER为0.22存在最大值。在温度为950℃、S/B为1.5、ER为0.22时,H2浓度和产率同时达到最大值35.47%和78.22g/kg。产物气有通过促进变换反应,进一步提高H2浓度和产率的潜力。采用交互正交试验设计方法,进行生物质气化制取热值燃气试验,研究了气化过程的操作条件对产物气低位热值的影响。各因素及其交互作用对低位热值影响的主次顺序为：当量比>气化温度>蒸汽生物质质量比>气化温度与当量比的交互作用>蒸汽生物质质量比与当量比的交互作用>气化温度与蒸汽生物质质量比的交互作用,其中当量比、气化温度、蒸汽生物质质量比对燃气低位热值的影响特别显著。交互作用分析获得生物质气化制取燃气的较优方案：气化温度750℃,蒸汽生物质质量比0.75,当量比0.25,在该条件下燃气的低位热值最高(6.530MJ/m3)。采用交互正交试验设计方法,进行生物质气化制取富氢合成气试验,研究了气化过程的操作条件对氢气浓度的影响。极差分析和方差分析的结果一致表明：在试验条件范围内,各因素及其交互作用对H2浓度的影响主次顺序为：当量比>气化温度>蒸汽生物质质量比>气化温度与蒸汽生物质质量比的交互作用>蒸汽生物质质量比与当量比的交互作用>气化温度与当量比的交互作用,其中当量比、气化温度、蒸汽生物质质量比对氢气浓度的影响特别显著。交互作用分析获得生物质气化制氢最佳的工作条件：气化温度800℃,蒸汽生物质质量比2.5,当量比0.22,在该条件下氢气浓度最高(38.27%)。建立基于ASPEN PLUS软件的生物质空气-蒸汽气化模型,通过对气化工艺过程进行模拟计算以及灵敏度分析,研究了蒸汽生物质质量比、气化温度、当量比等因素对生物质气化指标的影响。研究结果表明：在750-950℃范围内,随着气化温度的提高,H2浓度不断增加,CO浓度降低,产物气的产率逐步提高,产物气的热值降低,产氢率提高,蒸汽分解率提高；随着S/B在1.6～2.4范围内增大,H2浓度提高,CO、CH4和CO2浓度降低,产物气的产率提高,产物气热值降低,蒸汽分解率提高；随着ER在0.20～0.28范围内增大,CO、H2、CH4浓度降低,C02浓度提高,产物气产率增大,产物气中可燃组分浓度降低和不可燃组分浓度提高造成产物气热值降低,蒸汽分解率的模拟值先增加后降低,存在峰值。本文所建模型比较全面的反映了生物质气化的规律,能够为试验系统设计、调试和运行提供理论指导。建立感应加热式气化反应器的气化进程(?)流图,计算气化过程中的各项物流的(?),研究了操作条件对产物气(?)值分布的影响、(?)效率和气化效率的影响。(?)分析表明：当气化温度由750℃升高到950℃时,产物气的(?)值呈现增加的趋势,气化进程的气化效率和(?)效率均升高；当S/B从1.6增加到2.4时,产物气的(?)值呈现增加的趋势,气化效率随着S/B的增加而升高,但是(?)效率先增加再降低,表明S/B存在一个最佳值；当ER从0.2增加到0.28时,产物气总(?)值先增加后降低。随着ER的增大,气化效率和(?)效率都是先增加后降低的趋势,这就表明从能量的合理利用角度考虑,ER存在一个最佳值,本章研究中ER为0.26时气化效率和(?)效率同时达到最高。在产物气(?)圳值中,H2和CO的圳值占有较大比例,对产物气总(?)值的贡献较大；气化过程中伴随着许多不可逆过程会导致能量品质的下降,导致(?)效率低于气化热效率。更多还原

【Abstract】 Biomass gasification process is one of the effective ways of producing gas or hydrogen-rich synga, and have marked meaning in pollution reduction and sustainable development. It is still in the primary stage. Due to differences of the types of gasifier, the gasifying agent and the operating conditions, many researchers had performed experimental studies in biomass gasification but obtained different results. In order to deal with the problem, a technical way for fluidized bed biomass gasification based on induction heating was presented and a small-scale experiment system of biomass gasification based on induction heating was designed and constructed, performing tests of reactor temperature rise properties and feed rate of biomass. The reactor in the system provided heat for pyrolysis and gasification processes of the fluidized biomass pellets, realizing accurate temperature control in the whole gasification process.In the experiments of producing high calorific value fuel gas, rice husk was applied as fuel and steam was used as gasifying agent. What’s more, the simulation and exergy analysis of the biomass gasification process were also carried out. The main experimental results and conclusions are as follows in this dissertation:Steam and air gasification studies were carried out. The effects of reactor temperature, steam-to-biomass ratio (S/B), and equivalence ratio (ER) on gas composition and hydrogen yield were investigated. According to the experimental results, we could find that when the reactor temperature was800℃, the hydrogen content increased with the increase of S/B or the decrease of ER, hydrogen yield reached its maximum at the S/B of1.5or at the ER of2.2. The highest hydrogen content (35.47%) and the highest hydrogen yield (78.22g hydrogen/kg biomass), was achieved simultaneously at a reactor temperature of950℃, ER of0.22, and S/B of1.5. The product gas had great potential for further enhancing the hydrogen content and yield by promoting the shift reaction.The orthogonal test design was used in the sensitivity analysis of the three principal factors and their interactive influences for the lower heating value of gas. The range analysis and variance analysis were applied to analyze the results, and the best resultant of factor lever and the significance relation of key factor influencing the lower heating value was obtained. The results showed that in the range of experimental parameters, the order from master to minor was equivalence ratio> gasification temperature> steam/biomass mass ratio> interactive influences of steam/biomass mass ratio and equivalence ratio> interactive influences of gasification temperature and steam/biomass mass ratio> interactive influences of gasification temperature and equivalence ratio. Equivalence ratio, gasification temperature and steam/biomass mass ratio had a notable effect on the lower heating value of gas. The best application conditions were obtained by interactive analysis, when the gasification temperature was750℃, the steam/biomass mass ratio was0.75, and the equivalence ratio was0.25, the lower heating value of gas reaches its maximum of6.530MJ/m3.In view of the multiple factors and their interactive influences affecting the hydrogen concentration of biomass gasification, biomass gasification for hydrogen-rich gas tests were performed, the effects of gasification temperature, steam/biomass mass ratio, and equivalence ratio on the hydrogen concentration were investigated with the methods of interactive orthoplan, range analysis and variance analysis were applied to analyze the sensitivity of these factors and their interactive influences. The results achieved by both analysis were same. The study indicated that gasification temperature, steam/biomass mass ratio, and equivalence ratio had a notable effect on the hydrogen concentration, and so did the interactive influences of gasification temperature and steam/biomass mass ratio. The best application conditions were obtained by interactive analysis, when the gasification temperature was800℃, the steam/biomass mass ratio was2.5and the equivalence ratio was0.22, hydrogen concentration reached its maximum of38.27%.The simulation of hydrogen generation from biomass gasification was carried out, using ASPEN PLUS software to establish gasification model. The gasification parameters included reactor temperature, steam-to-biomass ratio and equivalence ratio, and their effects on the indexes of gasification were discussed. The results showed that in the range of750to950℃, with the increase of gasification temperature, there appeared increase in the concentration of H2and the product gas yield, as well as the hydrogen yield and steam decomposition rate. Meanwhile, it also enabled the reduction of CO and the heating value of the product gas. Besides, with the increase of S/B in the range of1.6to2.4, there increased the concentration of H2, the product gas rate and steam decomposition rate, which also reduced the concentration of CO, CH4and CO2and the heating value of the product gas. Furthermore, with the increase of S/B in the range of0.2to0.28, there appeared decrease in the concentration of CO, H2and CH4and combustible components of product gas, and increase in the concentration of CO2, the product gas yield and non-combustible components of product gas. Besides, the simulation of the steam decomposition rate increased first and then decreased, indicating that there was a peak. In this paper, simulation results indicated that the established model could reveal the rule of hydrogen production deeply. The establishment of such a model provided theoretical instruction for designing, debugging and operation of experiment system.In this section, lots of studies were carried out, including establishment of the exergy gasification process flow diagram of the induction heating gasification reactor, calculation of the exergy of various reactant among the gasification process and analysis of the effects of the operating conditions on the product gas, which containing the effects on exergy distribution, exergetic efficiency and gasification efficiency. And the studies above showed that, when the gasification temperature increased from750℃to950℃, the exergy value of gas would tend to increase and there would also have promotions to the gasification efficiency of the gasification process and exergetic efficiency. The exergy value of product gas tended to increase with increase in S/B from1.6to2.4and so did the gasification efficiency. However, exergetic efficiency increased first and then decreased, indicating the presence of an optimum value among S/B. When the ER varied from0.2to0.28, the total exergy value of product gas increased first and then decreased. With the increase of ER, the exergy value of gas would reach the peak at0.26. Meanwhile, gasification efficiency and exergy efficiency tended to first increase and then decrease, which also both reached the peak when ER was0.26at the same time. This indicated that there was an optimum value of S/B, from the perspective of the rational use of energy considerations. Among the exergy values of product gas, H2and CO accounted for a large proportion and also made a greater contribution to the total exergy values of product gas. A lot of irreversible processes accompany with the gasification process would result in a decrease in the quality of energy and lead to exergy efficiency being less efficient than gasification thermal efficiency.更多还原