污泥化学链气化特性试验研究

为改善污泥气化效果,采用化学链气化技术处置污泥.在小型流化床上进行试验,基于赤铁矿载氧体,研究了O/C物质的量比、气化温度和水蒸气体积分数对污泥气化特性的影响以及赤铁矿多次连续循环过程中的物化性能.结果表明:赤铁矿会显著提高污泥的气化程度和碳转化率;当O/C物质的量比增大时,合成气中CO和CH_4的体积分数下降,H_2的体积分数呈现先下降后上升的趋势;随着气化温度的升高,合成气中CO和H_2的体积分数逐渐提高,CO_2和CH_4的体积分数降低,碳转化率不断提高;当水蒸气体积分数增大时,CO_2和H_2的体积分数逐渐提高,CO和CH_4的体积分数不断下降,碳转化率提高;赤铁矿在长时间运行中表现出良好的反应性.     

固体燃料在O_2气氛下气化特性研究

基于Gibbs自由能最小化原理和Van Krevelen坐标系研究了不同固体燃料在O2气氛下完全气化时的气化特性。结果表明:当固体燃料完全气化时,CO、CO2、H2和H2O摩尔分数变化范围分别为0.4-1.0,0-0.15,0-0.45,0-0.08。当固体燃料H/C比固定时,在低O/C比下,H2和CO含量保持恒定;在高O/C比下,O/C比增加会减少当量氧气比,降低气化温度。气化炉有效能效率随O/C比增加而减小。当固体燃料O/C比固定时,气化温度随H/C比增加而减少,CO含量减少,而H2、CO2和H2O含量增加。     

高温加压气流床内生物质气化特性的实验研究

在15～20 kg/h规模的沉降式加压气化实验装置上,实验研究了高温条件下,不同O/C摩尔比对生物质气化特性的影响,并根据实验气化炉的边界条件,建立了相应的气化模型.模型计算结果与实验结果吻合较好,模型能够很好的预测气化参数对生物质气流床气化特性的影响.研究结果袁明:在气化还原反应区,高温有利于气化反应向吸热方向进行;O/C比在1.0～2.0范围内,随O/C比的增加,CO、H2均呈现先增加后减小的趋势,可燃气体成分(CH4 H2 CO)占总合成气的50%左右;部分燃烧反应区温度在1600 K以上时,碳转化率大于90%,冷煤气效率达到50%左右.     

生物质气流床气化制取合成气的试验研究

利用一套小型生物质层流气流床气化系统,研究了稻壳、红松、水曲柳和樟木松4种生物质在不同反应温度、氧气/生物质比率(O/B)、水蒸汽/生物质比率(S/B)以及停留时间下对合成气成分、碳转化率、H2/CO以及CO/CO2比率的影响.研究表明4种生物质在常压气流床气化生成合成气最佳O/B范围为0.2～0.3(气化温度.1300℃),高温气化时合成气中CH4含量很低,停留时间为1.6s时其气化反应基本完毕.加大水蒸汽含量可增加H2/CO比率,在S/B为0.8时H2/CO比率都在1以上,但水蒸汽的过多引入会影响煤气产率.气化温度是生物质气流床气化最重要的影响因素之一.     

CO2气氛下生物质气化制氢的数值分析

生物质气化制氢有重要的工业应用价值,本文采用ASPEN PLUS软件数值模拟了稻壳在流化床中的气化过程。本次模拟运用吉布斯自由能最小化原理,选择RGibbs和RYield模块,采用CO2作为气化剂,计算获得了气化温度、CO2质量流量、CO2和稻壳质量比和碳转化率对产氢率的影响规律。结果表明：在CO2质量流量为200kg/h时,H2的生成率高达43%。随着CO2/B增加,CO和CO2体积分数逐渐升高,CH4体积分数下降,H2体积分数在不同的气化温度下趋于平稳（600~700℃）或下降（800~1000℃）。随着气化温度升高,碳转化率增加;随着CO2和稻壳质量比的升高,碳转化率下降。     

基于活性炭的微波辐射CO_2重整CH_4的研究

以木质活性炭为催化剂,在微波加热实验台上进行了CO2重整CH4的实验研究,考察了活性炭的升温特性,比较了CH4裂解、CH4/CO2重整和CO2气化反应中反应气转化率,分析了反应温度、CH4与CO2物质的量比值和空气流速对重整反应的影响,测试了活性炭的催化活性.结果表明,微波辐射下活性炭床层温度迅速升高;重整反应中CH4转化率高于裂解反应,而CO2转化率低于气化反应;提高反应温度、减小CH4与CO2物质的量比值和降低空气流速均利于提高CH4和CO2转化率,同时降低合成气中H2与CO物质的量比值;初始阶段活性炭表现出较好的催化活性,40 min后活性炭迅速失活.     

旋转滑动弧促进甲烷干重整制取合成气

实验考察了常温常压下,利用旋转滑动弧等离子体促进CH4-CO2重整制取合成气的效果,分析了放电电压、CH4体积分数和供气流量等参数对反应物转化率、产物选择性和经济效益等的影响.实验发现,CH4体积分数增加,会使CH4转化率升高,CO2转化率先增后减.流量增加,会使CH4、CO2转化率整体呈下降趋势.流量为12,L/min时,CH4、CO2最高转化率分别为43.78%、42.66%,H2、CO最高选择性分别为44.20%、32.48%,H2/CO体积比范围为0~1.56.单位摩尔量合成气所需电耗最低为195.06,kJ/mol,能量转化效率最高为46.535%.     

城市生活垃圾气化产气特性实验研究

在氮气、空气和富氧三种气氛条件下对城市生活垃圾气化过程进行实验研究,考察了温度、升温速率及反应气氛对城市生活垃圾气化的影响。总结出了城市生活垃圾气化过程中产生的CO,H2,CH4,CO2四种主要气体产物的体积分数在250～950℃的变化规律。氮气气氛下,在250～500℃的低温区段,CO气体的体积分数随升温速率的升高而降低;在500～950℃的高温区段,CO气体的体积分数随升温速率的升高而增加。H2在500℃之后才开始产生,其体积分数在500～950℃随升温速率的升高而增加。CO,H2,CH4三种气体在各个温度点处的体积分数都随气氛中氧气体积分数的增加而降低,而CO2气体在各个温度点处的体积分数则随气氛中氧气体积分数的增加而升高。     

气流床气化炉内气体浓度的分布规律

常压条件下,在两喷嘴对置热模试验平台上,对含碳化合物(柴油)的气化过程进行了试验研究.在不同的氧油比条件下,用水冷不锈钢取样探头在炉内3个轴向位置和合成气出口位置取样,气体经预处理系统后,用质谱仪分析主要气体(O2、CO2、CO、H2和CH4)的体积分数.研究了不同试验条件下的气化炉升温过程,以及稳定工况下气化炉内不同径向位置气体分布规律.结果表明,喷嘴平面附近,升温速率以1 000℃为界限,明显地分为两个线性区,CH4体积分数可作为指示气化炉温度的指标.最佳氧油比为0.90～1.20 m3/kg左右.     

污泥与准东煤在CO2气氛下的共气化特性研究

为探究污泥与准东煤在CO2气氛下的共气化特性,利用电加热式固定床和热重分析仪研究了共气化产气特性规律及共气化动力学特性规律,并采用Model-free Method计算了共气化反应活化能.结果表明:等温气化过程中CO、H2和CH4的体积分数随着反应的进行先升高后降低;随着准东煤质量分数的增加,可燃气中CO体积分数逐步升...     

煤灰对石油焦水蒸气气化的影响

通过热天平实验，研究了煤灰存在时石油焦的水蒸气气化反应行为．实验研究发现，煤灰对石油焦水蒸气气化反应活性具有较好的催化作用，而且催化作用的好坏受煤灰添加均匀性的影响．煤灰含量增加，石油焦气化反应速率增加；在煤灰含量较小时，煤灰含量的变化对反应速率的影响较大．但随着煤灰含量增加，煤灰含量的变化对反应速率的影响逐渐不明显．煤灰的存在降低了石油焦气化反应的反应活化能．     

准东煤灰熔融特性试验研究

将神华准东煤（神华煤）和天池能源准东煤（天池煤）与碱沟煤按照不同质量掺混比进行混合并制得灰样,将NaCl、CaO、Al2O3和SiO2按不同添加比例加入神华煤和天池煤并制成灰样,对上述混合灰样的熔融特性进行研究.结果表明：碱沟煤掺混2种准东煤后,随着准东煤质量掺混比的增大,混合灰各个灰熔点特征温度先降低后升高;随着灰样中Na含量增加,准东煤灰样的变形温度显著降低,软化温度、半球温度和流动温度先降低后趋于不变;当灰样中Na含量达到一定比例后,NaCl对准东煤灰熔融特性的影响明显减弱;CaO对准东煤灰熔点的影响较复杂,可以降低也可以提高灰熔点;随着Al2O3添加比例的增加,准东煤灰熔点先升高后急剧降低;随着SiO2添加比例的增加,神华煤灰样的变形温度先升高后降低,而天池煤灰样的变形温度逐步升高,其他3个特征温度均逐渐降低.     

煤质对水煤浆气化性能的影响研究

煤质与气流床气化炉的匹配性至关重要,其不但影响气化炉的运行条件,也影响气化性能。本文选择了10种来自新疆和陕西北部的煤样进行了工业分析、元素分析、灰组成分析、灰熔点分析以及成浆性测试,并筛选出适合水煤浆气化的煤样。同时借助Aspen Plus软件对适合水煤浆气化的煤样在相同的煤浆浓度、碳转化率及操作压力条件下开展煤质对水煤浆气化性能影响的模拟分析。结果表明煤中灰含量越高,冷煤气效率和有效气含量越低,比氧耗和比煤耗越高;煤中O/C质量比和H/C质量比的增加也会导致冷煤气效率和有效气含量降低,比氧耗和比煤耗增加。因此从水煤浆气化经济性考虑,建议水煤浆气化煤质灰含量小于9.0wt%,煤中O/C质量比小于0.173,H/C质量比小于0.065。     

煤灰熔融行为及其矿物质作用机制的量化研究

选取典型高灰熔点和低灰熔点煤种,利用X射线衍射仪(XRD)和扫描电镜能谱仪(SEMEDX)对高温气化条件下煤灰熔融行为及其矿物质演变规律进行了实验研究与量子化学计算.结果表明:高温下大量莫来石的生成是导致煤灰试样A具有高灰熔融温度的主要原因;煤灰试样B中由于存在较多的硬石膏、钠长石等低熔融矿物质,且CaO与莫来石反应生成钙长石与钙黄长石的化学反应在煤灰试样B熔融过程中起到了关键作用,从而使其具有低的熔融温度.经量子化学计算分析表明,由于莫来石易与电子接受体结合而难与电子给予体结合,在煤灰熔融过程中,莫来石易与煤灰中常见的碱性阳离子(Ca2+、Mg2+、Fe2+、Na+、K+)电子接受体反应生成其他物质,通过添加不同的阳离子可促使莫来石向不同矿物质转变,可以进一步控制煤灰的熔融变化过程及其熔融温度.     

Circulating Fluidized Bed Gasification of Low Rank Coal:Influence of O_2/C Molar Ratio on Gasification Performance and Sulphur Transformation

To promote the utilization efficiency of coal resources,and to assist with the control of sulphur during gasification and/or downstream processes,it is essential to gain basic knowledge of sulphur transformation associated with gasification performance.In this research we investigated the influence of O_2/C molar ratio both on gasification performance and sulphur transformation of a low rank coal,and the sulphur transformation mechanism was also discussed.Experiments were performed in a circulating fluidized bed gasifier with O_2/C molar ratio ranging from 0.39 to 0.78 mol/mol.The results showed that increasing the O_2/C molar ratio from 0.39 to 0.78 mol/mol can increase carbon conversion from 57.65%to 91.92%,and increase sulphur release ratio from 29.66%to63.11%.The increase of O_2/C molar ratio favors the formation of H_2S,and also favors the retained sulphur transforming to more stable forms.Due to the reducing conditions of coal gasification,H_2S is the main form of the released sulphur,which could be formed by decomposition of pyrite and by secondary reactions.Bottom char shows lower sulphur content than fly ash,and mainly exist as sulphates.X-ray photoelectron spectroscopy(XPS)measurements also show that the intensity of pyrite declines and the intensity of sulphates increases for fly ash and bottom char,and the change is more obvious for bottom char.During CFB gasification process,bigger char particles circulate in the system and have longer residence time for further reaction,which favors the release of sulphur species and can enhance the retained sulphur transforming to more stable forms.     

Hydrogen production from lignite via supercritical water in flow-type reactor

A supercritical water reactor with throughput of 10  kg/h was set up, which was operated with continuous feeding of coal water slurry. The effects of reaction temperature (500–650 °C), pressure (20.0–30.0 MPa), Ca/C molar ratio (0–0.45) and O/C molar ratio (0–0.35) on the hydrogen generation characteristics were investigated. It is found that there is a notable increase in the hydrogen content and yield with the increase of reaction temperature. The hydrogen yield increases from 24.67 ml/g to 135.73 ml/g when the temperature increases from 500 °C to 650 °C. The contents of CO₂ in gas product decrease, while that of hydrogen increases with the increase of Ca/C molar ratio. At Ca/C molar ratio of 0.45, nearly all CO₂ is fixed. Correspondingly, the content of hydrogen in gas is 73.29%, and the yield of hydrogen is 348.30 ml/g compared to 135.42 ml/g in the absent of CaO. Moreover, both of CaO and KOH catalyze gasification and water-shift reaction. The formation of hydrogen and the carbon gasification efficiency are improved by the added H₂O₂ when O/C ratio is less than 0.3.     

Circulating fluidized bed gasification of low rank coal: Influence of O<Subscript>2</Subscript>/C molar ratio on gasification performance and sulphur transformation

To promote the utilization efficiency of coal resources, and to assist with the control of sulphur during gasification and/or downstream processes, it is essential to gain basic knowledge of sulphur transformation associated with gasification performance. In this research we investigated the influence of O₂/C molar ratio both on gasification performance and sulphur transformation of a low rank coal, and the sulphur transformation mechanism was also discussed. Experiments were performed in a circulating fluidized bed gasifier with O₂/C molar ratio ranging from 0.39 to 0.78 mol/mol. The results showed that increasing the O₂/C molar ratio from 0.39 to 0.78 mol/mol can increase carbon conversion from 57.65% to 91.92%, and increase sulphur release ratio from 29.66% to 63.11%. The increase of O₂/C molar ratio favors the formation of H₂S, and also favors the retained sulphur transforming to more stable forms. Due to the reducing conditions of coal gasification, H₂S is the main form of the released sulphur, which could be formed by decomposition of pyrite and by secondary reactions. Bottom char shows lower sulphur content than fly ash, and mainly exist as sulphates. X-ray photoelectron spectroscopy (XPS) measurements also show that the intensity of pyrite declines and the intensity of sulphates increases for fly ash and bottom char, and the change is more obvious for bottom char. During CFB gasification process, bigger char particles circulate in the system and have longer residence time for further reaction, which favors the release of sulphur species and can enhance the retained sulphur transforming to more stable forms.     

煤灰对流化床氮氧化物排放影响的试验研究

在流化床试验台上分别燃烧典型烟煤和褐煤,测量加入煤灰和煤灰中无机矿物质（CaO、MgO、Fe2O3、Al2O3、CaSO4、MgSO4）前后N2O和NO排放质量浓度的变化,研究煤灰对流化床氮氧化物排放的影响及其主要活性成分.结果表明：煤灰能降低N2O排放质量浓度,提高NO排放质量浓度;燃料氮向NOx的总转化率随着灰分质量分数的增加而提高;煤灰中影响氮氧化物排放的主要活性成分为CaO、Fe2O3和MgO.     

Comparative studies on steam gasification of ash-free coals and their original raw coals

Catalytic gasification of raw coals at mild condition is not realized yet mainly due to deactivation of catalysts via their irreversible interaction with mineral matters in coal. As a means to achieve repeated use of catalysts, four different ash-free coals (AFCs) containing less than 0.2 wt% ash are produced in this work. Steam gasification of ash-free coals (AFCs) and their parent raw coals of various ranks ranging from lignite (Eco) to coking coal (Posco) is performed in a fixed bed reactor at 700–900 °C. Regardless of the rank of the parent raw coals, all the AFCs behave like a highly carbonized coal such that their gasification rate are similarly slow and they exhibit relatively low H₂/CO ratio. The steam gasification and associated CO to CO₂ conversion of the AFCs are, however, significantly enhanced by K₂CO₃, resulting in the higher H₂/CO and CO₂/CO molar ratio.     

The impact of additives upon the slagging and fouling during Zhundong coal gasification

Ash-related problems may induce serious slagging problems in gasification boilers, especially in the presence of alkali and alkaline earth metals at high concentrations. Suitable additives have shown to be promising in suppressing the slagging characteristics of high-alkali coal. In this study, the results of lab-scale experiments for Zhundong coal were demonstrated, especially in Yihua coal (YHc) here, with six common additives, which are kaolin (A), boehmite (B), corundum (C), quartz (D), raw vermiculite (E) and ripe vermiculite (F), at fractions of 3%, 6%, and 9%. The priority of reactions involving AAEM-based species was investigated by characterizing ash samples and thermodynamic equilibrium calculation by Factsage 7.2. The gasification residue of YHc alone (O) was adopted as the reference sample. All six additives could affect the release and transformation of Na, the capture order from high to low was A, F, E, O, B, D, and C, and the slagging risks of different samples were F, E, D, O, A, B, and C in sequence. Given both the ability of additives to capture alkali/alkaline earth metal-based species and the ATFs of the coal ashes, kaolin was proved as a suitable additive for YHc gasification. Furthermore, 6% (mass ratio) was considered the most reasonable addition ratio.