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...     

煤和石油焦气化过程中汞的挥发特性

针对胜利褐煤、府谷烟煤、高平无烟煤、金山石油焦和燕山石油焦等5种样品,研究了煤和石油焦的气化率及汞的挥发特性.结果表明,H2O气氛下的气化率和汞的挥发率大于CO2气氛下的气化率和汞的挥发率;煤和石油焦中水分含量的增加促进了原料的气化;随着气化率的增加,汞的挥发率增大;煤中汞的释放主要发生在气化前期,石油焦则在气化后期释放汞;随着煤和石油焦中S质量分数的增加,汞的挥发率增大;煤和石油焦共气化时的气化率和汞的挥发率均介于煤和石油焦单独气化时的气化率和汞的挥发率之间.     

准东煤碱金属赋存形态及对燃烧特性的影响

实验研究了准东煤碱金属赋存形态以及不同萃取处理方式对其燃烧特性的影响.结果表明,准东煤的碱金属钠含量明显高于其他煤种,而钾的含量低于其他煤种.准东煤碱金属赋存形态与其他煤种差异很大,准东煤中的碱金属钠主要以水溶性钠形式存在.经过不同萃取方式处理后的准东煤样燃烧的DTG曲线均明显向高温区偏移,燃烧特性变差.萃取方式对准东煤样燃烧行为的影响存在显著差异,水溶性和有机形式的碱金属会对煤燃烧起到催化作用.     

石油焦的气化反应特性

针对3种不同的石油焦，在热天平上考察了不同的化学反应条件，包括温度、压力和气氛等因素对气化反应的影响．研究结果发现，在水蒸气气氛下石油焦具有良好的气化反应活性，而在二氧化碳气氛下石油焦气化反应进行得相当缓慢，相同条件下的C-H2O反应速率是C-CO2反应速率的十几倍，在60％水蒸气的实验温度条件下，每升高50℃，平均气化反应速率提高1倍；1000℃时，水蒸气分压对平均气化反应速率的影响不均匀，分压增加，影响减小．随着反应的不断进行，气化反应速率存在最大值，而出现最大值时的转化率不受反应温度和压力的影响，而与气化介质有关．根据实验结果，分析得到了3种石油焦在水蒸气条件下反应速率与温度、水蒸气分压和转化率的关系式，并得到了3种石油焦气化反应的活化能。     

准东煤中钠元素赋存形态及洗煤对气化特性影响

为探究准东煤中钠元素赋存形态及洗煤对准东煤气化特性的影响,采用逐级洗煤法对准东煤进行洗煤处理。利用电感耦合等离子体质谱仪、离子色谱仪和X 射线衍射仪研究了准东煤中钠元素赋存形态及含量。利用热重分析仪研究了煤样的气化特性,并采用等转化率法计算气化反应动力学参数。结果表明：准东煤中钠元素主要以水溶钠为主,但并非以钠盐化合物晶体的形式存在于煤中。洗煤对煤样孔结构特性和矿物质含量均产生影响,矿物质含量较低时,气化特性主要由煤样的孔结构特性决定。随着洗煤程度加深,煤焦碳转化率达到90 %时所需的时间由5.35 min延长至12.02 min,气化反应活性指数逐渐降低,气化反应活化能由177.7～214.8 增大至203.5～252.4 kJ.mol-1。     

湿式循环富氧燃烧碱性元素对煤炭反应性的影响

利用等温热重方法,在湿式循环富氧燃烧气氛下研究了典型碱性元素Na和Ca对煤炭反应性的影响.结果表明:在800℃和900℃下,φ(O2)分别为21%、27%和32%的湿式循环富氧燃烧过程中,水蒸气的存在均会加速煤粉燃烧,而且煤炭的燃烧反应性随水蒸气体积分数的升高而提高;在燃烧过程中,Na和Ca同时对气化反应和氧化反应具有催化作用,增大了煤炭的燃烧平均反应速率,Ca的催化效果要优于Na;在较低含量条件下Na的催化作用随其含量的增加而增强,而在较高含量条件下Na的催化作用无明显差异.     

准东煤中钠元素赋存形态及洗煤对气化特性的影响

为探究准东煤中钠元素赋存形态及洗煤对准东煤气化特性的影响,采用逐级洗煤法对准东煤进行洗煤处理。利用电感耦合等离子体质谱仪、离子色谱仪和X射线衍射仪研究了准东煤中钠元素赋存形态及含量。利用热重分析仪研究了煤样的气化特性,并采用等转化率法计算气化反应动力学参数。结果表明:准东煤中钠元素主要以水溶钠为主,但并非以钠盐化合物晶体的形式存在于煤中。洗煤对煤样孔结构特性和矿物质含量均产生影响,矿物质含量较低时,气化特性主要由煤样的孔结构特性决定。随着洗煤程度加深,煤焦碳转化率达到90%时所需的时间由5.35延长至12.02 min,气化反应活性指数逐渐降低,气化反应活化能由177.7～214.8增大至203.5～252.4 kJ/mol。     

高碱煤中钠基化合物对灰熔融特性的影响

选取新疆准东煤田高钠煤(五彩湾煤和天池煤)为研究对象,研究了准东煤中碱金属钠的赋存形态和钠基化合物对煤灰熔融特性影响机制.向低温灰中添加不同比例的Na_2O然后制取其高温混灰,利用X射线衍射仪分析矿物质组分在不同成灰温度下演化规律,探究碱金属钠对准东煤灰熔融特性的影响机制.结果表明:准东煤中钠以水溶钠形式为主;天池煤随着钠含量的增加,灰熔融温度先降低后趋于稳定;五彩湾煤随着钠含量的增加,灰熔融温度先降低后升高.天池煤掺混10%,Na_2O导致灰熔融温度降低,是由于煤灰中白云石、氢氧化钙分解产生大量CaO,碱金属钠促进CaO与煤灰中Si、Al等反应生成含钙钠的低温共熔体,且有低熔点矿物无水芒硝生成;五彩湾煤掺混10%,Na_2O导致灰熔融温度降低,是由于煤灰中新生成低熔点的钙铁辉石和无水芒硝,且碱金属钠促进钙铝黄长石和镁黄长石等含钙矿物质的低温共熔反应,掺混过量Na_2O导致灰熔融温度升高,这是由于煤灰中生成了大量高熔点矿物质.     

准东五彩湾煤中碱/碱土金属含量及迁移特性试验研究

了解新疆准东煤中碱金属不同赋存形态的含量及其在燃烧过程的迁移特性对于了解准东煤燃烧过程中的沾污结渣特性具有重要意义。采用以去离子水、醋酸铵溶液、盐酸为萃取剂的有序萃取法测量准东五彩湾煤中不同赋存形态的K、Na、Ca、Mg,研究了不同萃取时间、粒径下煤燃烧过程中碱/碱土金属的迁移特性。结果表明,采用有序萃取法测量煤中Na、Ca和Mg含量的推荐测量时间为12 h,而K的则应大于24 h;从大粒径准东五彩湾煤中萃取得到的水溶性Na、Ca、Mg含量相对较少,醋酸铵溶性、盐酸溶性和不溶性含量受粒径影响不大;煤中Ca含量较高,Na、Mg含量次之,K含量较低;可溶性Na占煤中Na的质量分数为90%。Ca和Mg主要以醋酸铵溶性成分存在,可溶性成分占比高达90%;准东五彩湾煤在900℃温度下,约有一半可溶性Na迁移到了气相中,可溶性K同样有较明显的迁移量,但Ca、Mg的迁移量较少。     

流化床部分煤气化影响因素研究

在流化床部分气化炉上系统研究了流化风量、给煤量、水蒸气量、床层温度、静止床层高度、煤种、催化剂等因素对煤气成分和热值的影响,研究结果表明:流化风量、给煤量、水蒸气量、静止床层高度对煤气成分的影响较为复杂,4者都存在最佳范围;床层温度是影响煤气成分的主要因素,煤气热值与温度成正比;增加床层高度,有利于H2、CO生成和CH4分解;烟煤的煤气中含有的可燃成分(H2、CO、CH4)含量比无烟煤高,优质烟煤比劣质烟煤更适合于气化;Ca、Na、K等碱土金属化合物对煤气化具有催化作用,且Na2CO3和K2CO3的催化能力比CaO强。     

Co-gasification reactivity of petroleum coke with coal and coal liquefaction residue

In this work, experimental study on co-gasification of petroleum coke with coal and coal liquefaction residue (CLR) under CO₂ atmosphere was investigated in a temperature-programmed reactor. The effect of ashes from coal/CLR and metallic oxide on gasification reactivity of petroleum coke was also investigated. The calculated and experimental gasification conversion was compared to analysis the synergetic effect during co-gasification. The results indicated that the petroleum coke has a much lower reactivity than that of coal/CLR chars, while it can be greatly improved by co-gasifying with coal/CLR. The synergetic effect on co-gasification of petroleum coke with coal/CLR was presented as the progress of co-gasification reaction. It was found that the synergetic effect can be enhanced with increasing coal proportion. However, as the increase of coal rank, the synergetic effect gradually weakened during the co-gasification process. In the selected coal/CLR samples, the low rank coal and CLR exhibited a better effect when co-gasifying with petroleum coke. The difference of synergetic effect was probably attributed to the catalytic effect of mineral matters in different coal/CLR. According to composition analyses of various ashes and the co-gasification reactivity of samples, it can be concluded that high content of active components such as Ca- and Fe-in coal/CLR was beneficial to co-gasifying with petroleum coke, while high content of inert Si- and Al- components in coal tended to resist the reaction.     

Effect of fuel blend composition on hydrogen yield in co-gasification of coal and non-woody biomass

In this study, torrefaction of sunflower seed cake and hydrogen production from torrefied sunflower seed cake via steam gasification were investigated. Torrefaction experiments were performed at 250, 300 and 350 °C for different times (10–30 min). Torrefaction at 300 °C for 30 min was selected to be optimum condition, considering the mass yield and energy densification ratio. Steam gasification of lignite, raw- and torrefied biomass, and their blends at different ratios were conducted at downdraft fixed bed reactor. For comparison, gasification experiments with pyrochar obtained at 500 °C were also performed. The maximum hydrogen yield of 100 mol/kg fuel was obtained steam gasification of pyrochar. The hydrogen yields of 84 and 75 mol/kg fuel were obtained from lignite and torrefied biomass, respectively. Remarkable synergic effect exhibited in co-gasification of lignite with raw biomass or torrefied biomass at a blending ratio of 1:1. In co-gasification, the highest hydrogen yield of 110 mol/kg fuel was obtained from torrefied biomass-lignite (1:1) blend, while a hydrogen yield from pyrochar-lignite (1:1) blend was 98 mol/kg. The overall results showed that in co-gasification of lignite with biomass, the yields of hydrogen depend on the volatiles content of raw biomass/torrefied biomass, besides alkaline earth metals (AAEMs) content.     

Catalytic steam co-gasification of biomass and coal in a dual loop gasification system with olivine catalysts

A dual loop gasification system (DLG) has been previously proposed to facilitate tar destruction and H₂-rich gas production in steam gasification of biomass. To sustain the process auto-thermal, however, additional fuel with higher carbon content has to be supplied. Co-gasification of biomass in conjunction with coal is a preferred option. Herein, the heat balance of the steam co-gasification of pine sawdust and Shenmu bituminous coal in the DLG has been analyzed to verify the feasibility of the process with the help of Aspen Plus. Upon which, the co-gasification experiments in the DLG have been investigated with olivine as both solid heat carriers and in-situ tar destruction catalysts. The simulation results show that the self-heating of the DLG in the co-gasification is achieved at the coal blending ratio of 28%, gasification circulation ratio of 19 and reforming circulation ratio of 20 when the gasifier temperature 800 °C, reforming temperature 850 °C, combustor temperature 920 °C and S/C 1.1. The co-gasification experiments indicate that the tar is efficiently destructed in the DLG at the optimized reformer temperature and with olivine catalysts.     

Steam co-gasification of Japanese cedarwood and its commercial biochar for hydrogen-rich gas production

In this study, steam gasification and co-gasification of Japanese cedarwood and its commercial biochar were performed in a lab-scale fixed-bed reactor to investigate the feasibility for producing H₂-rich syngas. Ultimate analysis, proximate analysis, Brunauer-Emmett-Teller (BET) surface area analysis, and scanning electron microscopy (SEM) were conducted to understand the changes caused by the carbonization process. The effects of gasification temperature and steam flow rate on gas production yield from the steam gasification of the individual samples were investigated at first, which showed larger gas production yield and less tar yield for the steam gasification of the commercial biochar than that of raw cedarwood, indicating that the commercial biochar obtained from the carbonization process was more beneficial for the gasification. The co-gasification of raw Japanese cedarwood and its commercial biochar with different mixing ratios was conducted at different reaction temperatures. The synergistic effect was obviously observed. Especially, the commercial biochar with the highly porous structure and high content of alkali and alkaline earth metal (AAEM) species might provide the catalytic effect on cracking and reforming of tar derived from the raw cedarwood, resulting in a larger H₂ yield. However, the catalytic effect and gasification reactivity of biochar would decrease by increasing the amount of raw-cedarwood in the blends due to the coke deposition on the surface of biochar.     

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．     

Co-gasification of coal gangue and pine sawdust on a self-made two-stage fixed bed: Effect of mixing ratio

In this paper, the synergistic effect of co-gasification for coal gangue and pine sawdust was studied on a self-made two-stage gasification fixed bed experimental device. The results indicated that there was synergistic effect between coal gangue and pine sawdust. With the gasification temperature was 850 °C, the catalytic reforming temperature was 900 °C, the steam flow was 2 ml/min and the mixing ratio of coal gangue and pine sawdust was 1:1. The co-gasification synergistic effect yields the best results, the H₂ volume fraction reached its highest value of 37.2%, with a synergistic coefficient of 0.22. Under this condition, the number of mesopores in co-gasification char was the largest and the absorbance of the hydroxyl (-OH) functional group was the smallest. The alkali metal (K, Ca) content reached a maximum of 22.18%, which was conducive to the formation of hydrogen.     

Steam co-gasification of coal and biomass – Synergy in reactivity of fuel blends chars

Development of clean coal technologies is the answer to increasing energy demand and environmental concerns related to conventional coal processing technologies. The technologies of fossil fuel gasification are technically proven and commercially available. Attempts of utilization of waste materials and renewable energy resources in gasification-based energy generation systems has been made, but wide application of such systems is still hindered by issues inherently combined with the characteristics of the materials. These include discontinuous supplies of a fuel of limited resources and varying composition resulting in poor economy of small-scale systems and operating problems related to tars formation and corrosion, especially when biomass utilization is considered. In the light of the above co-gasification seems to offer several advantages through mitigation of undesired effects of both carbon-intensive utilization of coal and low efficient and troublesome operation of biomass/waste-fed gasification systems. The experimental results presented in the paper address the issues of determination of potential synergy effects resulting from the utilization of fuel blends composed of materials of various physical and chemical characteristics, which are still insufficiently discussed in the literature, especially when hydrogen-rich gas production in co-gasification is concerned. The results of reactivity tests of fuel blends of coal and energy crops biomass in the process of steam co-gasification in a laboratory scale fixed bed reactor at 700, 800 and 900 °C are given proving the synergy effect in co-gasification reflected in increased reactivity of fuel blends when compared to coal and biomass chars reactivity under similar process conditions.     

Steam and supercritical water gasification of densified canola meal fuel pellets

In this research, canola meal was densified using bio-additives including alkali lignin, glycerol, and l-proline. The fuel pellet's formulation was optimized. The best fuel pellet demonstrated relaxed density and mechanical durability of 1015 kg/m³ and 99.0%, respectively. Synchrotron-based computer tomography technique indicated that lack of water in pellet formulation resulted in a twofold increase in pellet porosity. Thermogravimetric analysis showed that ignition temperature (240 °C) and burn-out temperature (640 °C) for fuel pellet were smaller than those for coal. Impacts of process parameters were evaluated on the quality of the gas product obtained from pellet's steam gasification and hydrothermal gasification. The gasification experiments showed production of untreated syngas with a suitable range of H₂/CO molar ratio (1.3–1.6) using steam gasification. Hydro-thermal gasification produced a larger molar ratio of H₂/CO (1.8–51.2) for the gas product. Modeling of pellet's steam gasification showed an excellent agreement with experimental results of steam gasification.     

Hydrogen and syngas production from catalytic steam gasification of char derived from ion-exchangeable Na- and Ca-loaded coal

Catalytic steam gasification of char derived from low-rank coal possesses substantial potential as a source of hydrogen energy and syngas feedstocks, and its performances are largely associated with the employed catalysts. Therein, ion-exchangeable Na or Ca species are always regarded as excellent in-situ catalysts in low-rank coal. In this paper, gasification of Na-Char, Ca-Char and a Na/Ca-Char mixture with different partial pressures of steam was performed within a temperature range of 700–900 °C using a micro fluidized bed reaction analyzer. The results indicate that Na and Ca species could accelerate the gas release rate during gasification and even significantly increase H₂ production, in sharp contrast to non-catalytic gasification. Variations in the product gases during Na-Char and Ca-Char gasification were completely different, which associated with the different deactivation pathways and catalytic reaction mechanisms of Na and Ca catalysts. With an increasing gasification temperature, the decreasing trend of H₂ production for Na-Char gasification was mainly due to the loss of Na during gasification. Conversely, the enhancement of Ca activity promoted the H₂ production. The H₂/CO ratio of Ca-Char gasification at 700 °C approximately ranged from 1.0 to 2.0 as a function of the partial pressure of steam, which suggested catalytic gasification can be suitable for hydrogen-rich production and subsequent synthesis reactions. In addition, gasification of Na/Ca-Char mixture produced a higher hydrogen content in the product gases than that of Na-Char or Ca-Char gasification alone, particularly for the 30%Na/70%Ca-Char mixture. It implies that the high H₂ production of 70%Ca30%Na-Char mixture was attributed to the cooperative effects of the Na and Ca species on the catalytic activity. This study provides comprehensive information regarding the effects of ion-exchangeable Na, Ca and a Na/Ca mixture on the hydrogen production and syngas composition during steam gasification, which provides new insight into the utilization of low-rank coal.