根据反应机理确定转化炉水碳比及其控制方案

对于以天然气为原料,采用ICI工艺的甲醇装置,选择合理的转化炉进料水碳比对整个工艺非常重要,而确定水碳比必须要综合考虑转化炉内的各种反应。本文简述根据转化炉内的反应机理来确定进料水碳比及其控制方案。1根据转化炉内化学反应的机理确定水碳比1.1转化反应机理脱硫后的天然气进气(甲烷含量大于97%)与2 940 kPa的蒸汽混合后,进入一段转化炉进     

合成甲醇原料气成分对产量的影响

通过对义马气化厂甲醇装置近期产量变化的原因分析,认为原料气中二氧化碳应大于1.2％,才能使催化剂呈现出高活性;原料气中甲烷含量越低,甲醇产量越高;原料气的氢碳比应满足合成塔入口气的氢碳比大于3,才能得到较高的甲醇产量。     

甲烷水蒸气重整制氢反应及其影响因素的数值分析

本文通过建立包含动量、能量、质量以及化学反应的多物理场耦合数值模型, 以多孔介质模型表征催化剂层, 对工业转化炉管中的甲烷水蒸气重整制氢过程进行了详细分析。计算得到了转化炉管内甲烷重整过程反应物及产物气体的速度、温度及浓度场分布, 以此分析了甲烷重整制氢过程的反应特性, 并阐明了转化炉管的壁面温度、原料气入口水碳比以及入口速度对甲烷转化率的影响。结果表明:水蒸气重整在转化炉管的入口区域反应迅速, 沿着气体流动方向, 反应速率由于反应物浓度的不断降低而减小, 导致混合气体流动速度和温度也逐渐趋于稳定;水碳比和转化管壁面温度的增加以及原料气体入口流速的降低, 都会提高甲烷的转化率。本文所得到的结论对于优化实际生产中甲烷水蒸气重整制氢反应的工况条件具有一定的参考和借鉴意义。     

水气比测定装置的改进

我公司合成氨生产以天然气为原料，水碳比（加入水蒸气的物质的量与原料气中碳的物质的量之比）是一段转化炉的重要控制指标之一。水碳比过低，造成催化剂上结炭而导致催化剂损坏；水碳比过高则使催化剂承受过大的压力而导致催化剂损坏，且不经济。水碳比是由水气比（加入水蒸气的物质的量与原料气物质的量之比）计算得到的，因此水气比的准确测定非常关键。     

基于ASPEN模拟计算的甲烷二氧化碳重整反应研究

使用ASPEN对甲烷二氧化碳重整反应进行模拟计算,研究反应温度、压力以及原料气中二氧化碳浓度对重整反应影响。结果表明,提高反应温度,增加原料气中二氧化碳浓度可以提高甲烷转化率,降低合成气中氢碳比。同时,对现有工业化项目的转化合成气的氢碳比进行了模拟计算,结果与实际运行值吻合,模型有良好的预测性。     

制氢装置的水碳比控制方案优化

以某炼油厂制氢装置的水碳比控制方案为基础,提出两个比值控制优化概念:预转换水碳比和总水碳比。描述这两种水碳比的计算方法,并介绍以全流量和水碳比值为联锁条件的两个主要联锁方案,为制氢装置水碳反应控制提供了灵活和有效的解决方案。     

褐煤鲁奇炉气化制甲醇合成圈方案的比较

以褐煤为原料采用鲁奇加压气化生产甲醇的主要特点是原料气中甲烷含量高,须将甲烷转化成有效合成气。本文主要围绕不同的转化方案,从投资、运行费用等几方面分析了不同的合成圈方案,并进行比较,为同类装置的设计提供参考。     

合成氨预转化系统的改造

采用预转化工艺,解决原料气中高碳烃含量高的问题。初次尝试后,达到了提高热反应效率、降低水碳比、降低能耗、解决超温问题、延长盘管使用寿命的目的。     

水碳比对转化反应的影响分析

基于天然气转化工艺的技术原理，介绍了水碳比对转化反应的影响。主要从甲烷蒸汽转化反应热力学分析和低水碳比对转化反应的影响两个方向分析水碳比对转化反应的影响。经过分析过程获取最佳水碳比，进而将其应用于某公司天然气转化工艺生产实践，确认最佳水碳比具有较高可行性。     

天然气蒸汽转化制氢装置水碳比控制及联锁设计优化探讨

在天然气蒸汽转化制氢单元中,水碳比控制和联锁设计是非常重要的环节.结合以往天然气转化制氢装置工程设计经验,提出水碳比控制及联锁的优化方案,以满足改进后控制方案的安全性和可操作性,进而实现水碳比的平稳控制,确保装置的正常连续生产.     

Synthesis gas production using steam hydrogasification and steam reforming

Experimental work has been carried out on the mixed reforming reaction, i.e., simultaneous steam and CO₂ reforming of methane under a wide range of feed compositions and four different reaction temperatures from 700 °C to 850 °C using a commercial steam reforming catalyst. The experiments were conducted for a CO₂/CH₄ ratio from 0 to 2 and a steam to methane ratio from 3 to 5. The effect of CO₂/CH₄ ratio on the exit H₂/CO ratio and the conversions of the reactants indicate that the dry reforming reaction is dominant under increased carbon dioxide in the feed. Steam reforming of typical steam hydrogasification product gas consisting of CO, H₂ and CO₂ in addition to steam and methane has also been investigated. The H₂/CO ratio of the product synthesis gas varies from 4.3 to 3.7 and from 4.8 to 4.1 depending on the feed composition and reaction temperature. The CO/CO₂ ratios of the synthesis gas varied from 1.9 to 2.9 and 2.0 to 3.3. The results are compared with simulation results obtained through the Aspen Plus process simulation tool. The results demonstrate that a coupled steam hydrogasification and reforming process can generate a synthesis gas with a flexible H₂/CO ratio from carbon-containing feedstocks.     

Hydrogen production by the catalytic steam reforming of methanol part 1: The thermodynamics

The thermodynamic equilibria involved in the catalytic steam reformation of methanol to produce hydrogen have been examined over the ranges of pressure 101–3040 kPa, temperature 400–700K and water to methanol feed ratio 1.5–0.67. Four models have been considered based upon possible reaction products and the equilibrium composition of each model calculated. The presence of methane and carbon reduce the quantity and quality of hydrogen produced. The best condition for hydrogen production occurs at 500K in the model in which carbon (soot) and methane gas are excluded and where pressures are low, and water is in excess in the feed. To achieve these conditions in practice the reactions for methane formation, which is thermodynamically favoured, and the appearance of carbon (soot) must be inhibited.     

Steam reforming of biogas over a Rh/Al2O3 catalyst in an annular microreactor

The article deals with the catalytic steam reforming of biogas of model composition into hydrogen and carbon monoxide over a Rh/γ-Al₂O₃ catalyst in an annular microchannel reactor. The reforming of biogas consisting of 60% methane and 40% carbon dioxide in a steam medium has been experimentally investigated under isothermal conditions while activating the reactions on the inner convex wall of the annular microchannel with a thin catalyst layer. The experiments have been performed at a residence time of 0.12 s, reactor temperatures of 750 and 860°C, and a water: biogas molar ratio of 0.8 to 3.1 in the feed. The range of water: biogas molar ratios maximizing the hydrogen yield has been determined for the model biogas. By changing the reactor temperature and water: biogas molar ratio, it is possible to widely vary the hydrogen: carbon monoxide molar ratio in the resulting synthesis gas.     

Combination of Sorption-Enhanced Steam Methane Reforming and Electricity Generation by MCFC: Concept and Numerical Simulation Analysis

Abstract

Reformed gas made by the steam methane reforming(SMR) process is used as fuel feed to MCFC, but it is not as good as pure hydrogen due to the presence of CO₂ and CO. The sorption-enhanced steam methane reforming(SE-SMR) process can reduce CO₂ and CO to a low level and produce high purity hydrogen. Considering the merits of similar operating temperatures (about 500°C) and carbon dioxide recycle, a novel concept of a six-step sorption-enhanced steam methane reforming (SE-SMR) combined with electricity generation by molten carbonate fuel cell (MCFC) is proposed. In the present paper, a cycle of the SE-SMR process, which include the steps of reaction/adsorption, depressurization, gas purges (nitrogen and reformed gas, respectively), and pressurization with reformed gas, is modeled and analyzed. The process stream in the SE-SMR process is used as anode feed in MCFC. According to the result of numerical simulation, a fuel cell grade hydrogen product (above 80% purity) at the SE-SMR temperature of 450°C can be obtained. A carbon dioxide recycle mechanism is developed for cathode feed of MCFC from flue gas by burning with excess air to achieve a proper CO₂/air ratio (about 30:70). The novel electricity generation system, which can operate at lower energy consumption and high purity hydrogen feed is helpful for the MCFC'S performance and life time.     

用于PEMFC的天然气水蒸气制氢系统

针对质子交换膜燃料电池（PEMFC）的应用要求,开发了一个包括天然气水蒸气重整、CO变换和变压吸附净化的制氢工艺过程,并着重对重整反应和变压吸附的操作条件进行了实验研究。考察了温度、空速和水碳比对重整反应的影响,得到适宜的工艺操作条件,实验结果表明：温度650℃、水碳比6、空速42h^-1时,氢气含量为70.21%,甲烷转化率为77.41%;分析了温度、流速对变压吸附脱除CO效果的影响,结果表明：在0.2MPa、40℃和吸附、脱附时间120s的条件下,产品气中CO浓度接近于1×10^-6,经过多次循环后产品气质量稳定,可以连续获得满足80W质子交换膜燃料电池要求的高纯度氢气。     

催化部分氧化甲烷制合成气的平衡热力学研究

The catalytic partial oxidation of methane to syngas (CO H2) has been simulated thermodynamically with the advanced process simulator PRO/Ⅱ. The influences of temperature,pressure,CH4/O2 ratio and steam addition in feed gas on the conversion of CH4 selectively to syngas and heat duty required were investigated, and their effects on carbon formation were also discussed. The simulation results were in good agreement with the literature data taken from a spouted bed reactor.     

基于Aspen Plus的焦炉气制甲烷工艺模拟与分析

利用Aspen Plus模拟软件对焦炉煤气制甲烷工艺进行了流程模拟。分析了甲烷化反应压力、过热蒸汽与反应进料气质量比对反应器出口温度和甲烷产量的影响。结果显示,当反应压力在10×103kPa³0×103kPa时,可调控两个反应器出口温度范围均为0℃30×103kPa时,可调控两个反应器出口温度范围均为0℃⁵0℃,甲烷产量变化很大;当过热蒸汽与反应进料气质量比在0.0550℃,甲烷产量变化很大;当过热蒸汽与反应进料气质量比在0.05⁰.40时,可调控第一、二级反应器出口温度范围分别为0℃0.40时,可调控第一、二级反应器出口温度范围分别为0℃⁵0℃和0℃50℃和0℃²5℃,甲烷产量变化不大。     

天然气二氧化碳空气和水蒸汽制合成气的热力学研究

采用化学热力学的方法对天然气、二氧化碳、空气和水蒸汽制合成气反应体系进行计算，分别计算了反应温度、原料气组成以及反应压力的影响。计算结果表明：升高反应温度，有利于该反应的进行；原料气各物质的比例不同，可以制备不同C／H比的合成气；升高压力对该反应不利。     

快速变压吸附制氢工艺的模拟与分析

目前工业上主要通过变压吸附技术从蒸汽甲烷重整气中制取氢产品气。然而,能源需求量的快速增加使得传统变压吸附技术在产量方面的不足越发明显。为此,进行了快速变压吸附从蒸汽甲烷重整气中制取氢气的模拟研究。采用活性炭和5A分子筛作为吸附剂,并以测得的原料气中各组分在两种吸附剂上的吸附数据为基础,进行了六塔快速变压吸附工艺的数值模拟与分析。在分析了塔内温度、压力和固相的浓度分布后,探究了进料流量、双层吸附剂高度比以及冲洗进料比三个操作参数对于快速变压吸附工艺性能的影响,结果表明：原料气组成为H₂/CH₄/CO/CO₂=76%/3.5%/0.5%/20%,吸附压力为22 bar（1 bar=10⁵ Pa）,解吸吹扫压力为1.0 bar,处理量为0.8875 mol·s^-1,吸附剂床层高度比为0.5∶0.5,冲洗进料比为22.37%时,可获得H₂纯度99.90%,回收率69.88%,此时H₂产量为0.4713 mol·s^-1。相比之下,氢气纯度为99.90%时,尽管PSA工艺回收率为83.40%,但处理量只有0.39 mol·s^-1,因此H₂产量仅为0.2472 mol·s^-1。     

Characteristics of the product from steam activation of sewage sludge

Steam activation of a dried sewage sludge was studied to produce hydrogen rich gas and sludge char for converting to energy and resources. A batch-type wire mesh reactor was used to study the characteristics of the steam activation. The characteristics of activation product (i.e., producer gas, gravimetric tar, light tar, and sludge char) were identified.With the increase in the steam feed rate, the sludge char decreased but the producer gas increased, having higher gas heating value. And tar generation slightly increased when a small amount of steam was fed, but when the steam feed rate significantly increased, tar decreased because part of the tar was converted into light gas.Hydrogen and carbon monoxide increased with the increase in the steam feed rate. And carbon dioxide, methane, ethylene, and ethane reached their maximum according to different production mechanisms up to decreasing the species.The gradually increase in the steam feed rate resulted in the creation of micropores, which developed to the maximum when the steam flow rate was 14 mL/g min. When excessive steam was supplied, however, micropores sank due to the resulting sintering phenomenon, and the adsorption capacity deteriorated. The sludge char had a mean pore size of 6.229 nm, which is the size of mesopores from which condensible tar (the cause of damage on the device) is properly adsorbed and removed.