高灰熔点煤的加压催化气化:K_2CO_3催化活性及钾回收特性

以高灰熔点煤和含钾催化剂的灰渣为研究对象,分别考察了加压固定床反应器中K_2CO_3催化半焦水蒸气气化的反应性和灰渣中钾催化剂的回收特性。实验结果表明煤中添加K_2CO_3能够促进碳的转化,随着K_2CO_3负载量和气化温度的增加,碳转化率增大,CH4收率增加。在3.5 MPa和800℃下,K_2CO_3负载量为15%时,碳转化率达到96.1%,CH4收率达到0.24 m3·(kg C)-1。灰渣中钾催化剂的回收率随碳转化率的增加先升高后减小,这与催化剂在灰渣中的存在方式有关。通过优化水洗和消解条件,高碳转化率下灰渣中的钾催化剂的总回收率高达96.5%。     

煤催化气化过程中钾催化剂回收的实验研究

对内蒙平庄煤-蒸汽催化气化过程残渣中KOH催化剂的回收进行了实验研究,考察了时间、温度、水渣比和洗涤次数等条件对钾催化剂回收率的影响。实验结果表明,水蒸气催化气化过程中,催化剂的流失可忽略不计。水洗法回收可溶钾占总钾量的80%,回收所得催化剂的有效成分为K2CO3和KOH,占总回收钾量的90%以上。钾收率随时间的增长而快速提高,一般洗涤4 h即可达到预期的收率;升高温度和增大水渣比能明显提高催化剂的收率;水洗洗涤3次,能回收90%左右的可溶钾。     

府谷煤CO2催化气化反应性的研究

加入适宜的催化剂可以提高气化反应速率,降低起始气化温度。为了研究不同阴离子（SO₄^2-、CO₃^2-、Cl^-）盐对府谷煤热失重过程的影响,利用热重分析仪对负载了8种催化剂（K₂CO₃、K₂SO₄、KCl;Na₂CO₃、Na₂SO₄、NaCl;FeSO₄、FeCl₂）的煤样进行了CO₂气化实验,其中每克府谷煤的K⁺、Na⁺、Fe²⁺负载量分别为0.001mol。同时采用升温动力学模型进行了数据拟合。实验结果表明：催化剂对煤与CO₂的低温热解并无明显的催化作用,而在高温气化阶段催化效果显著。对于钾盐和钠盐催化剂,当阳离子相同时,其催化活性顺序为：CO₃^2->SO₄^2->Cl^-。对于铁盐催化剂,FeSO₄的催化活性优于FeCl₂。动力学结果发现：负载催化剂煤样的活化能大小符合上述实验规律,分布在169～232.6kJ/mol之间,相比原煤（267.9kJ/mol）都有一定程度的降低。     

煤加氢催化气化影响因素的实验研究

<正>近年来,天然气市场的强烈需求以及"富煤、贫油、少气"的能源分布特点刺激了国内学者对于煤制代用天然气的兴趣[1-2]。煤加氢气化能使产生的粗煤气中含有高浓度的甲烷,有利于生产代用天然气[3]。目前,人们在高温条件下对加氢气化反应进行了广泛的研究。为了降低气化反应温度,减少对反应设备材料的要求,同时又保持较快的气化反应     

低灰熔点无烟煤煤焦与CO_2催化气化特性研究

利用碱金属碳酸盐作催化剂,对低灰熔点无烟煤煤焦与CO2的催化气化反应活性进行研究.结果表明,反应活性主要受温度、催化剂种类及担载量的影响,催化活性顺序为:K2CO3Na2CO3Li2CO3,煤焦的反应活性随着催化剂担载量的增加而提高;在反应过程中,催化剂与煤焦中的物质会发生一定程度的反应,生成不溶性盐;煤焦的比表面积会随着催化剂担载量的增大而减小,但催化活性反而增强,其主要受到催化剂提供的反应活性中心的影响.     

煤催化加氢气化研究进展

煤加氢气化制天然气技术具有工艺路径短、热效率高等优点,其应用基础研究备受关注。但煤中存在部分致密的芳香碳结构,加氢反应性较差,即使在苛刻的反应条件下(~1 000℃、~7 MPa H_2),仍难以转化。通过引入催化剂,进行煤催化加氢气化可在温和的反应条件下实现煤的碳转化率和CH_4收率的同步提高。论述了碱金属(K、Na等)、碱土金属(Ca)和过渡金属(Fe、Co、Ni等)催化剂对模型碳加氢气化的催化作用原理。探讨了反应温度、氢气压力、和碳结构对C-H_2催化反应的影响规律,分析了适用于原煤催化加氢气化的最佳催化剂及工艺条件,并从CH_4和轻质液体焦油等产物生成规律、煤中碳结构随着反应进行的衍变过程等角度,讨论了催化剂分别对煤加氢热解和热解半焦加氢气化的催化作用行为。提出了煤催化加氢气化联产CH_4和轻质液体焦油技术从基础走向应用的进一步研究建议。现有研究结果表明,过渡金属与碱土金属组成的二元催化剂(Fe/Co/Ni-Ca)对煤加氢气化的活性较高。过渡金属元素在反应过程中主要提供C-H_2反应所需的活性氢,并削弱C—C键的键能;碱土金属元素Ca主要促进Fe/Co/Ni的分散,防止其发生硫中毒失活,并增强Fe/Co/Ni与碳之间的相互作用。温度升高一方面为化学键断裂过程提供了更高能量,加速C-H_2反应,另一方面促进催化剂在煤结构中扩散,提升催化剂的供氢和断键效率。升高压力促进了活性氢的供应,同时CH_4浓度得到稀释,反应向生成CH_4的方向移动。以5%Co-1%Ca为催化剂,在850℃、3 MPa H_2反应条件下,30 min内可同时达到90.0%的碳转化率和77.3%的CH_4收率。Co-Ca催化剂在煤加氢热解过程中具有催化解聚和催化加氢的作用,提高焦油和CH_4收率,同时催化剂在煤加氢热解过程中对煤结构产生催化活化作用,使得生成的半焦具有较高的气化活性。煤催化加氢气化的机理研究目前仍处于推测阶段,另外,该技术气化剂、煤种的适应性,催化剂循环利用性能有待进一步阐明。     

多级逆流水洗法回收催化气化灰渣中的钾催化剂

采用逆流水洗法将1 t/d煤催化气化工艺过程开发装置(PDU)稳态排放灰渣中的水溶性钾进行回收.研究了六级逆流水洗操作对灰渣中钾催化剂的回收效果,并考察了水洗液中钾含量对灰渣中钾析出效果的影响.结果表明:灰渣中可溶性钾与总钾质量比为62％,采用不同水洗工艺可将可溶性钾全部回收,单级逆流水洗工艺和六级逆流水洗工艺的耗水量...     

CO2 gasification kinetics of two alberta coal chars

CO₂ gasification kinetics of chars from two Alberta coals (Obed Mountain, high volatile bituminous and Highvale, subbituminous) have been studied using a thermogravimetric analyzer (TGA) and a fixed bed reactor. Charification and gasification reactions were performed sequentially in both the TGA instrument and in the fixed bed reactor to simulate real gasifier operating conditions. TGA and fixed bed data were processed numerically to evaluate the kinetic rate of CO₂ gasification of the chars. Calculated gasification kinetics could be correlated using both the volume reaction and the grain models. Activation energies of the kinetic rate constants were near 200 kJ/mol for both Highvale and Obed Mountain coal chars using the TGA data. The activation energies calculated for the Obed Mountain coal char using the fixed bed reactor were about 250 kJ/mol. For all the cases studied the calculated activation energies were nearly the same for both the volume and grain reaction models.     

添加剂对催化气化工艺中煤灰结渣性及气化性能影响研究

煤催化气化工艺中碱金属催化剂的引入加剧了气化炉的结渣，直接影响了流化床气化炉的正常操作。煤灰的烧结特性是流化床气化炉结渣的主要影响因素之一。通过自制的压差法烧结温度测定实验装置，并结合XRD 等分析表征及Factsage热力学软件模拟计算，考察了不同添加剂对煤灰烧结特性及气化性能的影响，并从矿物学角度探讨了添加剂对煤灰结渣特性及气化工艺的影响。结果表明，添加硅铝系添加剂可提高煤灰的烧结温度；相比硅系添加剂，添加高铝系添加剂对改善煤灰的烧结温度效果更明显；高铝系添加剂可作为一种高效的阻熔剂，但因在气化过程中容易同催化剂反应，导致催化剂催化性能降低，对煤的气化活性及催化剂回收率产生不利影响；添加氧化钙添加剂，煤的灰熔温度及烧结温度均增加，随氧化钙含量增加，灰熔点及烧结温度均升高，且对气化活性及催化剂回收率有良性作用；氧化钙可作为改善煤种结渣性的添加剂用于催化气化工艺中，需根据煤种性质及工艺特点确定适宜的添加量。     

Potassium‐catalyzed steam gasification of ash‐free lignite coal with CO2 capture

The purpose of this research was to study steam gasification of ash‐free coal integrated with CO₂ capture in the presence of a K₂O catalyst for enhancement of the key water‐gas shift reaction and promotion of hydrogen production. To achieve this goal, gasification experiments on ash‐free coal (AFC) were carried out at varying temperatures (600, 650, 675, 700, and 750 °C) with a sorbent‐to‐carbon (CaO/C) ratio of 2 and a catalyst (K₂O) loading of 0.2 g/g (20 weight percent (wt%)) in a fixed‐bed reactor equipped with a gas chromatography analyzer. The sorbent‐to‐carbon (CaO/C) ratio of 2 is based on dry and ash‐free basis. The CaO/C ratio and K₂O wt% were chosen to maximize hydrogen production based on our previously determined optimal values. The AFC was originally extracted from raw lignite coal using organic solvents, which allowed the sorption‐enhanced gasification to be conducted with minimal ash‐catalyst interactions. The effect of temperature on the yield and the initial reaction rate were investigated. The optimal reaction temperature of 675 °C was determined. Carbon balance and final carbon conversions were calculated based on the residue analysis. Activation energy was also calculated using intrinsic kinetics of the reaction. In this study, using AFC offered the potential advantage of operating the gasification process with catalyst recycle.     

Assessing the catalytic effect of coal ash constituents on the CO2 gasification rate of high ash, South African coal

The catalytic effect of inorganic species, within the ash, on the CO₂ gasification of three South African coals containing similar carbon-structural properties (elemental, structural and petrographical properties) was assessed. The reactivity of the coals with a particle size between 150 and 250 μm was determined in a thermo gravimetric analyser. The reactivity was measured at temperatures between 900 and 1000 °C, pressures between 1 and 10 bar, and fractions of CO₂ between 10 and 30%. For the selected coals, the reactivity decreased with ash content, and was found to be dependent on the composition of the ash. Specifically, the reactivity increased with calcium and magnesium content and alkali index.     

德士古煤气化工艺CO2排放分析

煤化工是高耗能高CO₂排放的工业,利用热力学分析方法对其工艺过程中能量利用情况进行分析,可以有效地发现工艺的能量利用缺陷和节能潜力,为过程的节能优化改造提供依据.目前热力学分析方法主要包括能量衡算法和(火用)分析法,本文在对传统热力学方法进行分析和评价的基础上,指出了已有方法的不足,提出了新的熵(火用)分析相结合的分析方法,并以德士古煤气化工艺为例,分别使用传统的能量衡算法、(火用)分析法和本文提出的熵(火用)结合分析法对工艺过程的能量利用情况进行了分析,获得了工艺过程中内各模块的能量、熵增和(火用)损分布.在此基础上,将(火用)损与工艺过程中CO₂排放量建立联系,经过计算得到了工艺过程中各个设备对应的CO₂排放分布和(火用)损系数,得出气化炉是工艺过程中主要的节能位置.这种能量与CO₂排放的关联能为工艺过程的节能减排提供理论依据.     

典型高灰熔融性煤焦水蒸气气化特性研究

为解决我国高灰熔融性煤的利用难题,采用等温热重法,研究了典型贵州高灰熔融性煤焦在不同气化温度及不同水蒸气含量下的气化特性,并采用混合反应模型对试验数据进行处理,求取动力学参数。结果表明,在不同水蒸气含量下,随着气化反应温度的升高,典型贵州煤焦的反应性提高,气化反应速率的峰值增大,气化反应时间缩短;气化剂中水蒸气含量越多,煤焦反应性越好,气化反应速率的峰值越大,但当水蒸气含量大于30%后差别不明显;典型贵州煤焦与水蒸气反应的反应级数为0.912 9~1.620 9,活化能为149.34~165.12 k J/mol。     

配煤对煤灰熔点的影响及灰熔点预测模型研究

针对皖北刘桥二矿煤（A）属于高灰熔点煤,无法满足Shell气化炉液态排渣的需要。考察了采用配煤技术降低煤A的灰熔点的效果,结果表明,配煤可以显著的降低煤A的高灰熔融性。使其能够满足Shell气化炉液态排渣工艺的要求。并采用最小二乘法对灰熔点与煤灰灰成分之间建立并回归了预测模型,预测模型方程表明,若能增加配煤煤灰中MgO的含量可显著降低煤灰熔点,增加配煤煤灰中CaO的含量可使煤灰熔点降低,在煤灰中SiO2和Al2O3总含量一定的条件下,高硅低铝的配煤煤灰可进一步降低煤灰熔点。同时该模型能较好地预测三种原煤配煤的灰熔点。     

Application of K2CO3 catalysts in the coal gasification process using nuclear heat

Conventional gasification processes use coal not only as feedstock to be gasified but also for supply of energy for reaction heat, steam production, and other purposes. With a nuclear high temperature reactor (HTR) as a source for process heat, it is possible to transform the whole of the coal feed into gas. This concept offers advantages over existing gasification processes: saving of coal, as more gas can be produced from coal; less emission of pollutants, as the HTR is used for the production of steam and electricity instead of a coal-fired boiler; and a lower production cost for the gas. However, the process has the disadvantage that the temperature is limited to the outlet temperature (950 °C max) of the helium cooling gas of the HTR. Therefore the possibility of catalytic steam gasification was examined. Model calculations based on experimental results show that use of 3–4 wt% relative to coal of K²CO³ catalyst increases the throughput of a large scale nuclear gasification plant by ≈65%, while gas production costs decrease by ≈15%. Corrosion by catalysts is not significant at low concentration (< 5 wt%) and low temperature (< 900 °C).