定向调控生物质CO_(2)/H_(2)O气化制取H_(2)/CO合成气的热力学分析北大核心CSCD

文章对以CO_(2)/H_(2)O为气化剂的生物质气化,生产H_(2)/CO为3∶1的合成气的反应过程进行了热力学分析。研究发现,提高气化温度可以增大H_(2)和CO的总产率,且超过700℃基本没有CH_(4)和C的生成;通过控制气化剂CO_(2)/H_(2)O的通入比例,可以实现H_(2)/CO合成气的定向调控;CO_(2)通入量的增大可以提高CO产率,降低H_(2)/CO为3∶1的合成气的气化温度(临界温度)和所对应的(H_(2)+CO)总产量;H_(2)O通入量的增加可以增大H_(2)产率,提高临界温度和所对应的(H_(2)+CO)总产量。文章拟合出临界温度和所对应的(H_(2)+CO)总产量与CO_(2)和H_(2)O通入量的关系式,为工业生产H_(2)/CO为3∶1的合成气以及后续甲烷化提供理论支持。     

H2SO4／H2O体系增温型吸收式热泵的热力学分析

本文以硫酸和水为工质，在较宽的范围内用放增温型吸收热泵进行了第一类热力学分析和第二类热力学分析，并指出应用前景。     

Cu/La2O3/Al2O3催化剂上甲醇水蒸气重整制氢反应

研究以并流共沉淀法制备Cu/La2 O3 /Al2 O3 系列催化剂催化甲醇水蒸气重整制氢反应过程 ,考察了La2 O3含量、反应温度、水醇比、液体空速 (WHSV)等因素对催化剂活性的影响。结果表明 :催化剂表现出较好的低温活性、高氢气选择性和稳定性。La2 O3 质量分数为 15 % ,在 2 5 0℃反应时 ,催化剂活性表现最佳 ,甲醇摩尔转化率为94 .5 % ,氢气选择性为 10 0 % ,CO摩尔分数为 1.0 5× 10 -7。     

运行参数对甲醇重整制氢的热力学特性影响研究

针对以氢气为燃料的动力系统运行条件需求,构建了甲醇重整反应热力学和化学平衡反应体系,以某功率型号燃料电池/燃气轮机(Solid Oxide Fuel Cell/Gas Turbine,SOFC/GT)混合动力系统为研究对象,分析其额定工况、变工况运行时,温度、水碳比和压力对各重整产物分布及产氢率的影响.结果 表明:额定...     

薄水铝石转化为γ-Al2O3的热力学及结构分析

近年来,不同相态的氢氧化铝或氧化铝热力学参数的研究日趋完善,为分析氧化铝相态转变过程的热力学提供了基础.利用相关物质的可靠热力学数据,采用一水软铝石(结构与拟薄水铝石相近)的热力学参数作为薄水铝石的热力学参数进行计算,分析了薄水铝石转化为γ-Al2O3的热力学.这种转化在较宽的温度范围内,既是熵增反应,也是放热反应和吉...     

碳热还原SO2反应选择性的热力学分析及实验探究

针对燃煤烟气SO_2脱除技术面临的可持续发展困境,以固体碳材料为还原剂的碳热SO_2还原制硫磺技术具有重要发展前景,其中抑制非目标副产物的伴生是实现SO_2定向还原的关键。基于吉布斯自由能最小原理对碳热还原SO_2反应进行平衡产物量的计算,并通过固定床-FTIR实验分析反应的气相产物,探究了硫产率、副产物CO、COS和CS_2的生成规律。基于温度对反应热力学平衡的影响,结合副反应,来推断出合理的反应机理。在摩尔比n(C)∶n(SO_2)≤1.0时体系中主要发生反应C+SO_2→S+CO_2,副产物CS_2生成量级仅为10~(-4),理论硫产率可维持在0.9以上。过量的碳会促进COS由主反应物一步生成,高温、碳过量会促进COS向CS_2的转化反应。相关研究结果对实际应用时最佳工况的选取以及单质硫选择性的提高具有重要指导意义。     

载氧体与氯化氢反应的热力学分析和实验研究

针对生活垃圾化学链式燃烧过程中可能出现的污染和腐蚀问题,研究了金属载氧体和HCI之间的相互作用.采用热力学平衡方法,分析了NiO、Fe2O3、CuO和CaSO4四种载氧体在不同温度下,水分和碳参与反应时氯气的生成情况;并进行了HC1和Fe2O3的高温反应实验.结果表明:温度对氯气的生成影响显著;水分的加入会减少氯气的生成;在有水分参与的反应中,碳的加入会使氯气生成量降低.从氯气生成量角度考虑,温度在700～900K时,Fe2O3可用作生活垃圾化学链式燃烧过程的载氧体.     

中温条件下铝镁锂合金与水反应的动态过程

铝水反应是铝作为新能源的一种主要利用方式。为了探究熔融态下铝水反应的动态传递规律,利用自制的反应器,研究了中温条件下铝镁锂合金与水蒸气反应的动态过程,并对反应器内部的温度、压力、氢产率进行了实时监测。实验结果表明:启动温度为500℃时,通入水蒸气后,反应器内部温度迅速升高,最高温度为791℃;金属反应区的截面温度分布差异较大,存在局部的核心高温区;随着反应的进行,核心高温区自进水口处向外向下传递,传递速率约为0.33 mm/s,该速率主要是由水蒸气扩散速率和热传递速率共同决定的。     

添加CO_2/H_2O对正丁醇火焰中碳烟反应的影响

耦合简化的正丁醇动力学机理和固定分区碳烟模型,研究了在空气中添加CO_2或H_2O蒸气对正丁醇同轴扩散火焰中碳烟质量分数和数密度的影响,计算结果表明:添加CO_2或H_2O蒸气后,整体上二者均降低;此外,添加CO_2后各反应与组分生成往火焰下游移动.碳烟数密度的降低是由于温度和苾(A4)浓度降低引起的成核速率的下降,而碳烟质量分数的降低主要是由于H摩尔分数、颗粒总表面积及温度降低引起的脱氢加乙炔(HACA)速率的下降.碳烟最终在火焰下游被完全氧化,主要氧化组分为OH.     

Synergistic effect of the fresh Co,Ni, and anion ions on aluminum or magnesium with water reactions

To analyze the effect of Co and Ni on hydrogen generation in water, the reactions of Mg and Al with water in CoCl₂ and NiCl₂ solutions are studied in terms of amount of H₂ produced and rate of reaction. Mg rapidly reacts with water in CoCl₂ and NiCl₂, producing high amount of H₂ without induction time. While there is a short induction time is detected for Al─H₂O reaction in CoCl₂ and NiCl₂. In addition to the galvanic cell behavior of the Mg (Al)/Co (Ni) compounds formed, Co and Ni catalyze the hydrogen production reaction; however, the agglomeration of Co or Ni leads to a noticeable decrease in H₂ production. The open‐circuit potential in CoCl₂ and NiCl₂ solutions after the addition of Mg or Al at ambient temperature shows an obvious change, coinciding with the initiation of the hydrogen generation process. Mg rapidly reacts with water in Co (Ac)₂, CoSO₄, Ni (Ac)₂ and NiSO₄ solutions as a consequence of its intrinsic metallic properties and of the formation of Co or Ni. The hydrogen production amount is lower (<200 ml g^?1) in Co (NO₃)₂ and Ni (NO₃)₂, even after adding NaCl. No reaction occurs when adding Al in CoSO₄, Co (Ac)₂, Co (NO₃)₂, NiSO₄, Ni (Ac)₂, and Ni (NO₃)₂. The synergistic effect of Co, Ni, and anion ions in water affects the rate of Al or Mg corrosion and hydrogen generation.     

Hydrolysis H2 generation behavior of AM50 alloy waste coactivated by Mg-based master alloys

Mg-25 wt%Ni (Mg25Ni) or Mg-30 wt%Ce (Mg30Ce) master alloys were firstly introduced by high-energy ball milling (HEBM) to surface activate AM50 alloy waste and activated AM50-Mg25Ni, AM50-Mg30Ce and AM50-Mg25Ni–Mg30Ce are obtained. The hydrolysis H₂ generation behavior are comparatively investigated. The results show that AM50-Mg25Ni with 10 wt% Mg25Ni can rapidly generate 500.1 mL/g H₂ within 5 min at 298 K, which is higher than that of AM50 alloy waste (213.9 mL/g H₂). Mg30Ce master alloy is unsuitable for activation of AM50 alloy waste due to the deterioration initial hydrolysis kinetics (only 90.3 mL/g H₂ in 5 min) originated from the severe agglomeration of AM50-Mg30Ce particles. As high as 427.2 mL/g and 776.5 mL/g H₂ can be generated by coactivated AM50-Mg25Ni–Mg30Ce within initial 5 and 30 min, which are higher than those of AM50 alloy waste (213.9 and 715.7 mL/g H₂) at 298 K. The thermodynamic behaviors of AM50 alloy waste is accelerated by Mg25Ni and Mg30Ce. The E_a of coactivated AM50-Mg25Ni–Mg30Ce sample is 37.1 kJ/mol, which is lower than that of AM50 alloy waste (52.0 kJ/mol) The coactivation effect and mechanism of Mg25Ni and Mg30Ce is investigated. This work provides an effective activation strategy for modification of Mg alloy waste to generate H₂.     

横掠不同型式光滑管束流动的热力学分析和比较

对横掠不同型式光滑管束的流动进行了热力学分析，在熵产分析的基础上对不同型式的光滑管比较了它们热力学性能的优劣，总结发现了一些规律性的结论，对于横掠光滑管束的优化设计具有重要的指导意义。     

Theoretical analysis of LiBr/H2O absorption refrigeration systems

A computational model is developed for the parametric investigation of single‐effect and series flow double‐effect LiBr/H₂O absorption refrigeration systems. The effects of generator, absorber, condenser, evaporator and dead state temperatures are examined on the performance of these systems. The parameters computed are coefficient of performance (COP), exergy destruction rates, thermal exergy loss rates, irreversibility and exergetic efficiency. The results indicate that COP and exergetic efficiency of both the systems increase with increase in the generator temperature. There exist different optimum values of generator temperature for maximum COP and maximum exergetic efficiency. The optimum generator temperature is lower corresponding to maximum exergetic efficiency as compared to optimum generator temperature corresponding to maximum COP. The effect of increase in absorber, condenser and evaporator temperatures is to decrease the exergetic efficiency of both the systems. The irreversibility is highest in absorber in both systems. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermodynamic analysis of a lithium bromide/water absorption system for cooling and heating applications

Absorption systems have the potential of employing thermal energy such as waste heat to produce both chilled water and hot water for building cooling and heating applications. In the present study, a lithium bromide/water (LiBr/H₂O) absorption system for cooling and heating applications was analysed on the basis of the first and second laws of thermodynamics. Simulation was employed to determine the coefficient of performance (COP) and the exergetic efficiency of the absorption system under different operating conditions such as the heat source, cooling water, chilled water, and supply hot water temperatures. Copyright © 2001 John Wiley & Sons, Ltd.     

PdAgAu alloy with high resistance to corrosion by H2S

PdAgAu alloy films were prepared on porous stainless steel supports by sequential electroless deposition. Two specific compositions, Pd₈₃Ag₂Au₁₅ and Pd₇₄Ag₁₄Au₁₂, were studied for their sulfur tolerance. The alloys and a reference Pd foil were exposed to 1000H₂S/H₂ at 623 K for periods of 3 and 30 h. The microstructure, morphology and bulk composition of both non-exposed and H₂S-exposed samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). XRD and SEM analysis revealed time-dependent growth of a bulk Pd₄S phase on the Pd foil during H₂S exposure. In contrast, the PdAgAu ternary alloys displayed the same FCC structure before and after H₂S exposure. In agreement with the XRD and SEM results, sulfur was not detected in the bulk of either ternary alloy samples by EDS, even after 30 h of H₂S exposure. X-ray photoelectron spectroscopy (XPS) depth profiles were acquired for both PdAgAu alloys after 3 and 30 h of exposure to characterize sulfur contamination near their surfaces. Very low S 2p and S 2s XPS signals were observed at the top-surfaces of the PdAgAu alloys, and those signals disappeared before the etch depth reached ∼10 nm, even for samples exposed to H₂S for 30 h. The depth profile analyses also revealed silver and gold segregation to the surface of the alloys; preferential location of Au on the alloys surface may be related to their resistance to bulk sulfide formation. In preliminary tests, a PdAgAu alloy membrane displayed higher initial H₂ permeability than a similarly prepared pure Pd sample and, consistent with resistance to bulk sulfide formation, lower permeability loss in H₂S than pure Pd.     

Effect of Si content on H2 production using Al-Si alloy powders

The effect of Si content in Al-Si alloy powder with NaOH on H₂ production was investigated. The total amount of H₂ produced decreased as Si content increased, which is inconsistent with the results predicted by the chemical reaction. Si caused a delay in the rate of H₂ production. Energy dispersive spectrometry showed that a large amount of unreacted Si remained in the matrix, and the unreacted fraction increased as the Si content increased. As the evolution reaction of Al and Al-Si alloys is exothermic, the temperature of all the specimens increased. Si addition reduced the hydroxide removal rate, which decreased the average H₂ production rate. The initiation time for H₂ evolution depends on the elimination rate of the oxide film formed during production of the powder. On increasing the Si content, SiO₂ was formed, which is harder to eliminate than Al₂O₃; this delayed the initiation.     

Effect of Mg3MnNi2 on the electrochemical characteristics of Mg2Ni electrode alloy

Mg₂Ni–x mol% Mg₃MnNi₂ (x = 0, 15, 30, 60, 100), the novel composite alloys employed for hydrogen storage electrode, have been successfully synthesized by a method combining electric resistance melting with isothermal evaporation casting process (IECP). X-ray diffraction (XRD) analysis results show that the composite alloys are composed of Mg₂Ni phases and the new Mg₃MnNi₂ phases. It is found on the electrochemical studies that maximum discharge capacities of the composite alloys increase with the increasing content of the Mg₃MnNi₂ phase. The discharge capacity of the electrode alloy is effectively improved from 17 mAh g⁻¹ of the Mg₂Ni alloy to 166 mAh g⁻¹ of the Mg₃MnNi₂ alloy. Among these alloys, the Mg₃MnNi₂ phase possesses a positive effect on the retardation of cycling capacity degradation rate of the electrode materials. Cyclic voltammetry (CV) results confirm that the increasing content of the Mg₃MnNi₂ phase effectively improves the reaction activity of the electrode alloys. Surface analyses indicate that the Mg₃MnNi₂ phase can enhance the anti-corrosive performance of the particle surface of these composite alloys.