Coal char gasification for co-production of fuel gas and methane decomposition catalysts

Partial gasification of coal char was conducted with addition of metal oxides for co-production of fuel gas and methane decomposition catalysts. Effect of the metal composition (Ni, Co and Fe based mono- or bi-metals) was investigated on the fuel gas production and the resultant catalyst surface and textural properties, morphology and performance in catalytic methane decomposition (CMD). Besides H₂-rich fuel gas production (the combustion energy up to 11.03–23.42 MJ/kg_char) from the gasification, the gasification residue can directly serve as the effective and efficient catalyst for CMD. The Fe and Fe–Co composite oxides were found to be better among the mono- and bi-metallic oxides for the fuel gas production during the gasification, respectively. The Ni-based mono-/bi-metallic catalysts could display high and stable methane conversion (up to 80%) during the 600-min CMD test at 850 °C. Promotional role of the second metal in CMD was discussed on the carbon diffusion, metal mobility and reducibility, formation and growth of the deposited carbons. The formed carbon morphology after CMD was analyzed based on the Kirkendall effect and Tammann temperature and further correlated to the potential catalyst deactivation.     

五彩湾煤半焦水热脱钠提质及其燃烧特性的演变

利用电感耦合等离子体原子发射光谱仪(ICP-AES)分析新疆五彩湾原煤及其热解提质半焦中钠的赋存形式，考察了水热脱钠前后半焦的钠含量，采用热重分析仪和Flynn-Wall-Ozawa(FWO)方法建立五彩湾煤焦燃烧反应动力学模型，获得半焦燃烧动力学参数并分析脱钠对半焦燃烧特性的影响。结果表明:五彩湾原煤及其半焦中钠的赋存形式以水溶性钠为主，半焦总脱钠率高于原煤，水溶性钠的存在不利于半焦燃烧。600 ℃热解半焦的水热脱钠率高达82.59%，在所有实验焦样中，经水热脱钠后的半焦燃烧特性指数最高，燃烧活性最好。     

停留时间对低阶煤快速热解产物分布、组成及结构的影响

利用自由落下床反应器，研究了快速热解过程中颗粒停留时间对神木烟煤和内蒙古褐煤热解过程的影响,并进一步延长快速热解新生半焦停留时间考察了半焦的二次热解过程。结果表明，快速热解过程中颗粒停留时间的增加促进了挥发分的析出，神木烟煤热解焦油产率持续增加，内蒙古褐煤热解焦油产率先增加后降低。停留时间对焦油品质有明显影响，随时间的增加，两种煤快速热解轻质油中苯类和苯酚类单环化合物含量均先增加后降低，进一步延长停留时间，多环芳烃化合物含量显著增加。快速热解半焦的二次热解主要促进了气体的生成，焦油产率和组成无明显变化，挥发分的进一步析出促进了半焦微孔的发展，神木烟煤和内蒙古褐煤半焦比表面积均显著增加。这表明，在以高品质焦油为目标产品时，采用较低的反应温度、较适宜的煤粒停留时间的快速热解工艺条件是可取的。     

生活垃圾热解半焦-热解油重整过程中水分的消耗与转移

热解炭原位重整城市固体废物的挥发分是改善热解产物的良好方法。在这个过程中，水蒸气在产品转化中起着重要作用。为了了解水分在重整过程中的作用，本研究中将热解液中的油相和水相分离，然后用D₂O代替重整过程中的水相，以跟踪液体、气体和固体之间的氢转移。热解油/焦炭重整过程在600、700和800℃下进行。用GC-MS（气相色谱质谱法）分析重整后液体中的油相；IR-MS（同位素比质谱法）分析重整后液体和固体中的氘浓度。研究发现，在实验温度范围内，水蒸气对焦炭的气化作用非常弱，当D₂O/焦炭的比例为2/1时，D₂O中2％（质量）的氘在反应后残留在炭中;但水蒸气与热解油的气化反应很强烈，在800℃时，78.68％（质量）的热解液（水油混合物）被气化,且热解油中脂肪烃被大量分解，重整液的油相组分中芳香烃占到96.17%；同时，当D₂O/油的比例为2/3时，D₂O中59％的氘转移到合成气中。研究结果将为生活垃圾热解处理控制最终产物提供理论指导。     

低阶煤固定流化床热解及半焦气化实验研究

采用固定流化床研究了三种低阶煤的常压热解及其热解半焦的气化特性，探究了样品粒度、反应温度、反应时间及流化气中O2含量对上述过程的影响，确定了循环流化床热解-气化耦合工艺适宜的反应条件。结果表明，在实验选择范围内，样品的粒度基本不会影响热解过程，在水蒸气气氛下，温度越高，热解气体产率越高，半焦产率越低；600 ℃和20 min时能获得最高的焦油产率。循环流化床热解-气化耦合工艺碳的有效利用率率高于原煤固定流化床气化工艺，同时副产煤焦油；温度越高，有效气产率和有效碳转化率越高；实验范围内，O2含量对合成气产率的影响较小，但可以调节H2和CO的相对含量；900 ℃、半焦气化15 min即可获得较理想的合成气产率及有效碳转化率。     

Impacts of char structure evolution and inherent alkali and alkaline earth metallic species catalysis on reactivity during the coal char gasification with CO2/H2O

In this work, we studied the effects of char structural evolution and alkali and alkaline earth metallic species (AAEMs) catalysis on the reactivity during the char gasification with CO₂, H₂O, and their mixture. The gasified chars with different carbon conversion levels were prepared, and their physicochemical structures were characterized via nitrogen adsorption and FT‐Raman techniques. The concentrations of AAEMs in different modes were obtained by the sequential chemical extraction method. The reactivities of the raw and gasified chars were analyzed by the thermogravimetric analysis. The gasification atmospheres had varied effects on the physicochemical structure of coal char. The gasified char obtained in the CO₂ atmosphere had a lower aromatic condensation degree compared with that obtained in the H₂O atmosphere, irrespective of the temperature. The impact of the atmospheres on the specific surface area of the char varied with the temperature because H₂O and CO₂ have different routes of development of pore structure with coal char. A large specific surface area facilitates the exposure and dispersion of more AAEMs on the surface of the channel, which is conducive to their contact with the gasification agent to play the catalytic role. Thus, the reactivity of the gasified char is well correlated with its specific surface area at different gasification temperatures. In the absence of AAEMs, the chemical structure of coal char becomes the dominant factor affecting the reactivity.     

松木颗粒热解与高温蒸汽气化半焦产率及形貌特征分析

以成型松木颗粒为原料，进行低温热解，研究了热解温度和升温速率对生成的松木半焦产率及官能团的影响。以试验得到的松木半焦进行蒸汽气化试验，对比分析了温度对半焦重整气化形貌特征、比表面积和平均孔径的影响。研究表明：随着热解温度升高，松木半焦脂肪族结构峰消失转化为烃等小分子物质及气化气，进而降低半焦产率。升温速率升高，半焦产率呈先下降后升高的趋势，在800℃升温速率为30K/min时半焦产率最低。不同温度热解和蒸汽气化对比试验表明，温度相对较低时（500℃）热解和蒸汽气化半焦孔隙结构相近，随着温度的升高，蒸汽气化半焦结构发生明显变化，900°C时出现了更小的孔道结构且比表面积增加明显。蒸汽引入使松木半焦和水蒸气发生热解反应的同时发生了脱氢反应，气化半焦形貌出现熔融和烧结现象。     

油页岩矿物质催化半焦燃烧特性及机理

利用微型流化床反应分析仪（MFBRA）研究了油页岩矿物质催化半焦燃烧特性，重点考察了半焦内部矿物质和外部页岩灰床料对半焦燃烧的催化作用，揭示了流化床反应器中半焦燃烧过程和机理。结果表明：内部矿物质和外部床料对半焦燃烧均具有明显催化作用，而两者共同催化效果最为显著。矿物质中CaO和Fe₂O₃对半焦燃烧具有催化活性，CaO催化作用强于Fe₂O₃。油页岩半焦燃烧反应活化能在60.41~78.97 kJ/mol之间，矿物质的催化作用会明显降低反应活化能。流化床反应器中，矿物质对半焦燃烧的催化作用主要表现在四个反应，即：挥发分裂解和燃烧、半焦表面炭燃烧、半焦内部炭燃烧以及一氧化碳燃烧。     

Modeling the influence of changes in aliphatic structure on char surface area during coal pyrolysis

The influence of changes in aliphatic structure on char surface area during coal pyrolysis was modeled, and the effect was introduced to a previous char surface area model for lignite pyrolysis established based on the chemical percolation devolatilization (CPD) model. The modified model can predict not only the N₂ and CO₂ char surface area during rapid pyrolysis of three lignites but also the CO₂ char surface area of two high-volatile bituminous coals; the agreement of the modified model with experiments is improved at high temperatures. The decrease in aliphatic chain length can reduce adsorption positions around aromatic core, and decrease char surface area. When mass release is more than 55% at about 1,100 K, the predicted N₂ char surface area starts to decrease with further generation of volatiles, and the increase of predicted CO₂ char surface area with increasing generation of volatiles also become slow at the end of mass release.     

高温烟气中煤焦气化行为

针对高温烟气中煤焦的气化行为，本文采用FactSage 6.1计算了煤焦在高温烟气下的高温反应特性，并利用热重分析仪分析了煤焦气化行为。通过沉降炉实验进一步研究了不同温度、气体配比、粒径条件下气体产物的动态析出特性，同时计算了评价指标α、β、LHV值。结果表明：随着温度的升高，气体产物H₂和CO的含量增加，β、α、LHV值增大，CH₄和CO₂的含量下降。在温度为1200℃时，β、α值分别由CO₂/CO比为10∶70时的10.80%、5.21%增加到CO₂/CO比为50∶30时的24.71%、41.06%。同时，随着CO₂/CO比值的增大，高温烟气对煤焦气化反应抑制减弱。通过对比反应温度和粒径对煤焦气化反应的影响，得出反应温度远大于粒径对煤焦气化反应的影响。通过实验验证了向高温烟气中喷吹煤焦制备高品质可燃气体方法的可行性。