Effect of blending ratio and catalyst loading on co-gasification of wood chips and coconut waste

Catalytic co-gasification is an important tar reforming technique, which may appreciably improve the quality of syngas through tar reforming reaction. In this study, wood chips (WC) were co-gasified with two coconut wastes, namely coconut shells (CS) and coconut fronds (CF), in a downdraft gasifier. The dolomite and limestone were used as tar reforming mediums. The effect of the blending ratio, catalyst type, biomass type and catalyst to biomass loading on gas composition and heating value of the syngas was investigated for different WC/CS and WC/CF blends. The results revealed that the WC/CS blending ratio of 70:30 produces the highest H₂ amount (11.70 vol.%), which was 31% higher than the H₂ amount of the other blends. The HHV_syngas of 70:30 blend was measured about 4.96 MJ/Nm³, which was also higher among all the tested blends. The co-gasification of 70:30 blend of WC/CS, when compared with same blending ratio WC/CF, produced two times higher CO, 60% higher H₂ and 75% higher HHV_syngas. During catalytic co-gasification of WC/CS blends with dolomite and limestone, the dolomite yielded 24%, 13.8% and 25.6% increment in CO, H₂, and CH₄, respectively. It is concluded that the coconut wastes can be substituted or co-gasified with wood after carrying out some major changes in a gasifier geometry.     

松木屑与褐煤催化共气化特性实验研究

为了更加深入地了解松木屑及褐煤催化气化特性,对松木屑进行酸洗脱灰预处理,采用同步热分析仪研究松木屑灰成分中碱金属及碱土金属元素在气化过程中的作用,同时尝试将不同浓度催化剂(K2 CO3及CaO)添加到酸洗脱灰/褐煤样品中,研究松木屑灰成分、不同催化剂浓度以及催化剂种类对松木屑与褐煤催化共气化特性影响规律。实验结果表明,脱灰预处理对于生物质的单独气化影响不大,通过木屑/煤样与脱灰木屑/煤样对比可以断定生物质灰成分中碱金属及碱土金属对生物质与煤共气化有催化作用,其中添加 K2 CO3催化剂样品在650℃以后催化作用明显,且最大焦炭气化速率随 K2 CO3比例增加呈先增大后减小的规律,其中7％ K2 CO3脱灰木屑/煤气化速率最大,表现出更好的催化作用。同浓度下CaO样品的催化作用要弱于K2 CO3样品,但其在挥发分析出阶段的最大析出速率始终高于 K2 CO3样品,与浓度无关。     

在流化床气化炉中生物质与煤共气化的研究（I）以空气-水蒸汽为气化剂生产低热值燃气

在600kW流化床气化炉工业示范装置上以空气-水蒸汽为气化剂,将生物质／煤按不同比例进行了共气化的实验研究。在实验研究的运行条件下,得到了生物质／煤混合比例对气化炉工作温度、燃气热值、气体产率和气化效率等重要技术参数的影响。对玉米芯／煤的比例为81／19时的典型实验结果表明：气化炉工作温度869℃,空气当量比ER=0．21,S／B=0．20时,气体产率1．96m^3／kg,燃气热值6．4MJ／m^3,气化效率71．3％,燃气中焦油含量小于l0mg／m^3,该炉经过连续运行考核,运行平稳,工况稳定。     

褐煤负载有机钠盐水蒸气气化实验与动力学分析

基于模拟双马来酰亚胺工业废液,通过对负载乙酸钠和碳酸钠的褐煤水蒸气气化的实验,分别研究了反应温度、催化剂负载浓度对气化特性的影响。结果表明:碳酸钠和乙酸钠作为催化剂对褐煤水蒸气气化都具有明显的催化效果,但当碳酸钠的负载量超过10%之后会出现抑制现象,而乙酸钠作为催化剂并没有出现抑制现象;在相同温度或负载浓度的条件下,负载乙酸钠的催化效果要优于负载碳酸钠时的催化效果。对实验数据进行动力学分析发现,均相模型和缩核模型都能够有效描述本研究的实验结果。     

煤与重质油共气化热态模拟实验

以固定床为反应器,焦炭和胜利常压渣油为原料,进行煤与重质油共气化热态模拟实验,考察了不同操作参数对出口气体成分及结焦生成物的影响。结果表明:当m(氧气)∶m(水蒸气)∶m(渣油)为0.3∶1.0∶1.0、裂解温度为800℃、停留时间小于0.5 s时,烯烃(C2H4 C3H6)、烷烃(CH4 C2H6)和合成气(H2 CO)的体积分数分别为24%、28%和37%。应用扫描电镜观察了焦炭介质表面上结焦生成物的形貌,发现通氧气后结焦生成物残留量较少。热态模拟实验结果进一步表明,煤与重质油共气化可以制备低碳烯烃,同时联产合成气,且能有效地解决重质油裂解造成的结焦问题。     

Robust modeling,analysis and optimization of entrained flow co-gasification of petcoke with coal using combined array design

This study is focused on robust modeling, analysis and optimization of entrained flow co-gasification of petcoke with coal, which is very important to the stable operation of this process as well as downstream processes. Unlike general robust modeling method that traditional Taguchi's crossed array design is applied, combined array design was used in this study. Then based on the exiting general experiments and the constructed robust models, a systematic investigation was conducted into the effects exerted by oxygen and steam concentrations (OC and SC) not only on the mean but also on the variance of H₂, CO and (H₂ + CO) production. Finally, the co-gasification process was robustly optimized. The result reveals that the average production of H₂, as well as that of (H₂ + CO), rises with OC increasing but declines with SC increasing. Moreover, higher OC inhibits the fluctuations in H₂ and (H₂ + CO) production, while higher SC makes their fluctuations more notable. The robust optimization solutions of OC and SC are observed to be 1.56% and 50%, respectively.     

Gasification of wastes: The impact of the feedstock type and co-gasification on the formation of volatiles and char

A gasification pilot plant was built up in order to investigate the influence of both feedstock type and co-gasification on the distribution and composition of the products. The results showed that at the same process condition, different feedstocks could result in different product yields. For instance, the highest gas yield was obtained from tire gasification, while the lowest one belonged to weed gasification. The characterization of the products showed the presence of different components and functionalities in the samples produced. In addition, the co-gasification of the feedstocks resulted in the products with different specifications than single feeding, proving the existence of different reaction pathways. This means that feedstocks and their derivatives could interact with each other and resulted in nonproportional yields and composition for the char, tar, and gaseous products in comparison with the products from the gasification of the single feedstocks. As an example, the tar from co-gasification had a lower content of acids but a higher content of amines and amides. This confirmed that co-gasification influenced the reaction network significantly, impacting the formation of gases, tar, and char, originated from the cross-interaction among the reaction intermediates derived from the pyrolysis/gasification of the various feedstocks.     

生物质焦与煤共气化特性研究

本文利用非等温热重分析法研究了生物质焦与煤的共气化特性,探讨了生物质焦与煤共气化反应特征温度的变化情况,并分别运用Doyle和Coats-Redfern近似函数计算了反应动力学参数.采用Doyle法计算时,相关系数R2值比Coats-Redfern法更大,因此Doyle法计算结果更合理.采用Doyle法计算出：生物质焦的气化反应活化能为134.97 kJ/mol,烟煤和无烟煤分别是197.85 kJ/mol和171.36 kJ/mol.随着无烟煤、烟煤中生物质焦掺混的比例增加,反应活化能不断下降.研究结果表明：生物质焦可以促进两种煤的气化反应,降低煤的最终反应温度和气化反应活化能.     

一种新型共气化工艺的开发

As one of promising clean coal technologies used to reduce pollutant emission and CO2 discharge, cogasification has been extensively investigated. In this paper, a new co-gasification technology using coal and natural gas was developed. The distinct advantages of this technology are the excellent fuel flexibility and the availability to establish the gasifler by reconstructing the blast furnace or similar shaft furnace. Based on the concept of the new co-gasification technology, lab-scale experiments and modeling study were carried out. The obtained results indicate that gasification is undertaken at ideal thermodynamic environment where quasi-equilibrium could be reached without catalysts. The modeling results are in agreement with experimental data, demonstrating the validity of the model and that Aspen Plus is a useful tool for the analysis of the co-gasification process. Furthermore,the effect of major operation parameters, including oxygen flow rate and steam flow rate, on co-gasification process was investigated using the developed model.     

水蒸气/CO2/O2与无烟煤共气化过程研究

为综合利用固体氧化物燃料电池（SOFCs）产生的高温水蒸气及CO2尾气,采用流化床气化装置对水蒸气、O2、CO2气化晋城无烟煤过程进行了研究。结果表明：当气化温度为900 ℃时,增加水蒸气/CO2摩尔比,促进了煤的水蒸气气化反应和水汽变换反应的发生,使气化制得的合成气中H2含量增加,CO含量先增加然后基本保持不变;随着气化剂中O2流量的增加,合成气中CO体积分数先增加后减小,当气化剂中水蒸气、CO2与O2的摩尔比为14∶56∶30时,合成气中有效成分（CO+H2）体积分数达到最大（44.9%）;此外,优化得出赤泥的最佳添加量为8%,其含有的氧化铁等催化成分可以显著提高合成气中有效成分。