生物质粗燃气自热重整调变的热力学分析

运用吉布斯自由能最小化方法对生物质粗燃气自热重整过程进行了热力学分析,研究了重整反应过程中的温度,O2/CH4摩尔比及焦油摩尔分数等因素对平衡产物组成的影响规律。研究结果表明:低温有利于CO歧化与加氢反应,而高温促进了CH4和CO2的转化,提高合成气H2+CO摩尔分数,降低H2/CO摩尔比。O2/CH4摩尔比的增加有利于生物质燃气从部分氧化反应向完全氧化反应转变,促进了CH4的重整反应而抑制了CO2的转化;O2/CH4摩尔比的增加降低了合成气H2+CO摩尔分数,降低了H2/CO摩尔比,在重整后的生物质粗燃气中,n(H2)/n(CO)≈1。积碳量随温度升高和O2/CH4摩尔比的增加逐渐减少,随着焦油(C10H8)物质的量的增加而增加。焦油物质的量增加提高了合成气中H2与CO摩尔分数,是重整反应的重要原料。优化的生物质燃气自热重整反应条件为温度1 023 K,O2/CH4摩尔比0.7,焦油摩尔分数<1%。     

甲烷自热重整制合成气热力学平衡分析

使用1stOpt2.5计算软件编程计算甲烷自热重整制合成气反应平衡组成,考察温度、原料比对体系组分平衡的影响。通过计算结果指出最适宜的反应条件,为甲烷自热重整制合成气催化剂的研究与开发提供热力学依据。     

碳还原重晶石制备硫化钡的热力学研究

运用热力学计算软件HSC对碳还原重晶石制备硫化钡的热力学进行了研究,计算了不同温度下反应体系可能发生的反应的标准摩尔焓变、吉布斯自由能和平衡常数,分析了各热力学参数与温度之间的关系,考察了反应温度、反应气氛、原料组成、原料杂质对硫酸钡转化率的影响。结果表明:迅速提高反应温度,避免反应物在低温停留时间,有利于提高硫化钡生成率;进入体系的O2含量、C含量应适量;原料中Si O2、Fe2O3和Al2O3等杂质会降低产物Ba S含量。     

柴油自热重整制氢反应及反应器

设计了带预热段的绝热管式反应器(A型)和带喷嘴及预热段的绝热管式反应器(B型),设计了相应流程并组建了柴油自热重整制氢装置,以直馏柴油为原料,研究了2种反应器内的柴油自热重整制氢反应行为。研究结果表明:2种结构的反应器均能用于柴油自热重整制氢,采用带喷嘴的绝热管式反应器可以确保雾化及气化效果良好,柴油热裂解生成甲烷的反应有助于柴油制氢过程。     

流化床在甲烷临氧CO2重整反应中的作用研究

在流化床反应器中进行甲烷临氧CO₂重整制合成气反应。通过计算分析了催化剂颗粒在床层内的流化特性。对比实验表明,流化床反应器在催化剂活性、稳定性、自热过程以及催化剂积炭等方面均体现出比固定床反应器的优越性。在流化床反应器中进行的甲烷自热重整反应,甲烷的转化率接近热力学平衡值,床层温度梯度小于10 ℃, 反应20 h后,催化剂表面无积炭。     

二氧化碳和水蒸气重整制甲醇的热力学分析

二氧化碳和水蒸气重整制甲醇是有效利用二氧化碳资源的重要途径,具有重要的经济和环保意义。从热力学角度进行分析,找出合理的反应条件,以提高甲醇的选择性和收率,对指导CO2和H2O反应具有重要意义。文中基于Gibbs最小自由能原理对该体系的热力学平衡进行了相关计算,分析了温度、压力、原料配比H2O/CO2等条件对该反应体系平衡组成的影响。结果表明:改变温度对体系的平衡组成影响不大,而体系的平衡组成随着压力和原料配比H2O/CO2的增大而增大。得到优化反应条件为初始原料摩尔比n(H2O)/n(CO2)为7∶3,温度约为500 K,压力为8 MPa。这对二氧化碳水蒸气重整制甲醇反应条件的优化具有一定的指导价值。     

固体超强酸催化合成乙酸异戊酯

用固体超强酸SO42-/Fe2O3-Al2O3作催化剂,以冰乙酸和异戊醇为原料合成乙酸异戊酯,考察了醇酸摩尔配比、反应时间、反应温度对反应收率的影响,得出反应的最佳条件为：反应时间30 min,原料异戊醇与冰乙酸的摩尔配比为2.0∶1.0,催化剂用量为乙酸用量的3%,固体超强酸SO24-/Fe2 O3-Al2 O3作催...     

工艺条件对Ni/A12 O3和Ni/CeO2-A12O3催化剂在甲烷自热重整制氢反应中催化性能的影响

采用共沉淀法制备γ-A12O3载体和不同Ce添加量的CeO2-A12O3载体,然后用浸渍法制备Ni负载质量分数10%的Ni/γ-A12O3和Ni/CeO2-A12O3催化剂.在固定床微反装置中考察了反应温度、原料气配比和CH4空速等工艺条件对Ni/γ-A12O3和Ni/Ce30A170Oδ催化剂在甲烷自热重整制氢反应中催化性能的影响.结果表明,添加Ce的催化剂催化性能有较大提高,在Ni/Ce30A170O3催化剂上,反应温度750 ℃时,CH4转化率94.3%,与Ni/A12O3催化剂相比,提高20%.Ni/γ-A12O3和Ni/CeO2-A12O3催化剂的CH4转化率均随反应温度的升高而增大.原料气中n(O2):n(CH4)和n(H2O):n(CH4)的增加均能提高各催化剂的CH4转化率.但n(O2):n(CH4)和n(H2O):n(CH4)的变化对各催化剂的催化性能的影响不同.随着n(O2):n(CH4)的增大,产物中n(H2):n(CO)降低,n(CO2):n(CO CO2)升高;而n(H2O):n(CH4)增大时,产物n(H2):n(CO)和n(CO2):n(CO CO2)均升高.随着CH4空速的增加,Ni/A12O3催化剂上CH4转化率、n(H2):n(CO)和n(CO2):n(CO CO2)均较大程度下降;而在Ni/Ce30A170Oδ催化剂上,随着CH4空速的增加,CH4转化率、n(H2):n(CO)和n(CO2):n(CO CO2)变化不大.     

镍盐的焙烧温度对Ni-Cu/ZrO_2-CeO_2-Al_2O_3催化剂在甲烷自热重整制氢中的影响

以Na2CO3为沉淀剂,在pH为9的沉淀条件下,采用并流沉淀法制备催化剂载体,考察了催化剂的活性组分前驱体Ni(NO3)2的焙烧温度(550、650和750℃)对Ni-Cu/ZrO2-CeO2-Al2O3在甲烷自热重整制氢反应的影响,并采用SEM方法表征了催化剂的表面结构。结果表明,Ni(NO3)2的焙烧温度对Ni-Cu/ZrO2-CeO2-Al2O3催化剂上的NiO颗粒分散性及催化剂的低温活性有很大的影响,650℃焙烧生成的催化剂上的NiO颗粒较小,分布均匀,分散性好,在反应温度650～850℃内,该催化剂的活性明显高于焙烧温度为550℃和750℃制备的催化剂。     

Al_4O_4C的碳热还原合成及其反应动力学

以氧化铝(Al2O3)和石墨(C)为原料,采用碳热还原工艺合成铝氧碳(Al4O4C),借助于X射线衍射仪和场发射扫描电子显微镜研究了加热温度和保温时间对合成铝氧碳(Al4O4C)的影响。结果表明:提高加热温度,可加快Al2O3和C反应生成Al4O4C的反应速率;延长保温时间可增大Al2O3和C反应生成Al4O4C的反应程度。在反应初期主要为固-固反应,Al2O3和C直接接触反应生成Al4O4C和一氧化碳(CO);后期主要为气-固反应,Al2O3和CO气体反应生成Al4O4C和二氧化碳(CO2)。计算得到气-固反应的频率因子和活化能分别为338.66和264.19kJ/mol。     

固定式质子交换膜燃料电池的天然气重整制氢

介绍了固定式质子交换膜燃料电池用氢气的各种天然气重整方法,其中包括水蒸气重整法、自热重整法和化学闭合燃烧法。同时简述了氢气进一步纯化的水煤气变换反应、选择氧化、变压吸附和气体膜分离脱一氧化碳的方法。通过上述重整和提纯的处理,最终能制备出满足固定式质子交换膜燃料电池要求的氢气。     

The Evaluation of Oxide Catalysts’ Properties in Test Reactions

Oxidative dehydrogenation of cyclohexane could be very promising and complementary test reaction to evaluation of redox properties of the catalyst surface, which are very important in the selection of materials for neutralisation of NO_x. The process is autothermic and it runs in significantly lower temperatures than conventional dehydrogenation.     

基于提升支持向量机的多组分气体分析

针对大规模高维气体分析样本难以计算的问题,提出一种提升的支持向量机学习方法.该方法将支持向量机等效为一定的KKT条件的同时,能通过检测样本在训练空间的转移始终保持KKT条件成立,起始训练样本的规模最少可以是2个.在对多组分气体分析的实验中,传统的支持向量机学习方法需要时间34 h左右,而提升支持向量机学习的时间为2.7 h,计算速度提高12.6倍.     

Thermodynamics of Hydrogen Generation from Methane for Domestic Polymer Electrolyte Fuel Cell Systems

Low temperature fuel cells such as the Polymer Electrolyte Fuel Cell (PEFC) are preferably used for domestic applications because of their moderate operating conditions. Using the existing distribution system, natural gas is used as a source for a hydrogen rich gas to power this fuel cell type. The high requirements on the fuel gas quality as well as high conversion efficiencies for the small local gas processing units are critical aspects in the evaluation of decentralized fuel cell systems. In the present paper, three typical gas processing methods are evaluated for the supply of a hydrogen rich gas for PEFCs: steam reforming, partial oxidation, and autothermic conversion. All three processes are studied in detail by varying the relevant process parameters: temperature, pressure, steam to fuel ratio, and oxygen to fuel ratio. The results are graphically displayed in numerous nomograms. With the help of these graphs, regions of stable operation and the sensitivity to the operational parameters are discussed. For all three gas processing methods, the graphs generated display methane conversion, the hydrogen yield, and the yields of unwanted components, i.e., carbon monoxide and solid carbon. Although only steady‐state operating conditions were simulated, critical modes of operation, which might occur during start‐up or transient operation can easily be identified. For instance, operating conditions where soot is generated have to be avoided under all circumstances. All simulations were done with the Gibb's reactor model of a commercial simulation program. The Gibb's reactor model was found to be a suitable tool, since the simulated results compared well with reported literature data. According to the simulation results, the methane‐steam‐reforming process appears to be favorable for application to PEFCs. Methane conversion and hydrogen yields are highest for this process while the yield of CO is relatively low.     

STUDY AND IMPROVEMENT OF RIHANI-DORAISWAMY ESTIMATION METHOD FOR Cp° WITH COMPUTER PROGRAM

Based on the group contribution method of Rihani and Doraiswamy, a program system has been set up for automatically analyzing structures and computing ideal gas heat capacities. The method was verifled by using evaluated literature data of 479 organic compounds. The assessment of its computing precision and applicability has been made and some new group parameters recommended.     

A novel biomass air gasification process for producing tar-free higher heating value fuel gas

Biomass is a promising sustainable energy source. A tar-free fuel gas can be obtained in a properly designed biomass gasification process. In the current study, a tar-free biomass gasification process by air was proposed. This concept was demonstrated on a lab-scale fluidized bed using sawdust under autothermic conditions. This lab-scale model gasifier combined two individual regions of pyrolysis, gasification, and combustion of biomass in one reactor, in which the primary air stream and the biomass feedstock were introduced into the gasifier from the bottom and the top of the gasifier respectively to prevent the biomass pyrolysis product from burning out. The biomass was initially pyrolyzed and the produced char was partially gasified in the upper reduction region of the reactor, and further, char residue was combusted at the bottom region of the reactor in an oxidization atmosphere. An assisting fuel gas and second air were injected into the upper region of the reactor to maintain elevated temperature. The tar in the flue gas entered the upper region of the reactor and was decomposed under the elevated temperature and certain residence time. This study indicated that under the optimum operating conditions, a fuel gas could be produced with a production rate of about 3.0 Nm³/kg biomass and heating value of about 5000 kJ/Nm³. The concentration of hydrogen, carbon monoxide and methane in the fuel gas produced were 9.27%, 9.25% and 4.21%, respectively. The tar formation could be efficiently controlled below 10 mg/Nm³. The system carbon conversion and cold gasification efficiency reached above 87.1% and 56.9%, respectively. In addition, the investigation of energy balance for the scale-up of the proposed biomass gasification process showed that the heat loss could be recovered by approximately 23% of total energy input. Thus, partial fuel gas that was produced could be re-circulated and used to meet need of energy input to maintain the elevated temperature at the upper region of reactor for tar decomposition. It was predicted the heating value of product fuel gas would be 8000 kJ/Nm³ if the system was scaled up.     

基于控制室爆炸载荷的可燃气云等价尺寸阈值

火气系统是防控气体泄漏灾害的重要安全屏障。可燃气体泄漏后与空气混合形成可燃气云,其爆炸属于体积爆炸,具有复杂性和多变性,因此将其折算为等价气云并提出阈值尺寸计算方法,是实现火气系统探测器网络量化布设的关键输入指标。选取控制室为受体,以载荷作为爆炸冲击波超压的临界值,运用多能法倒序计算,逆推得到对应的等价气云尺寸作为探测阈值,进而利用等价气云方法与高斯扩散模型得到火气系统探测临界时间。通过某LNG罐区案例分析,定量确定了该罐区可承载的气云尺寸最大值及扩散临界时间。数值计算表明,等价气云尺寸阈值不仅可以作为火气系统探测设计的量化输入指标依据,并可对探测时间设置以及气体泄漏及爆炸的防控措施提供理论支持。     

Comparison of modified newton's methods

A comparative evaluation was made of the performance of the Broyden-Schubert method, the finite-difference Newton's method and a hybrid method. Four problems deried from the simulation of a natural gas liquefaction process were used as bench-marks. The results show the hybrid method to be an effective combination of the advantages of the two methods with modest but worthwhile savings in computing time.     

伴有复杂反应气液吸收过程的模拟计算

建立了板式塔和填料塔中伴有复杂反应气液吸收过程模拟计算的严格数学模型，并给出模拟计算的程序框图。探讨了模型的解法，并用二乙醇胺和甲醇溶液吸收Ｈ＿２Ｓ和ＣＯ＿２的工厂操作实测数据对模型进行了验证。