HCN反应器的计算机优化控制研究

分析了HCN固化床反应器的反应机理和生产工艺特点,针对氨气的流量和压强、甲烷的流量和压强、空气的流量和压强、混合气预热温度、反应器温度、反应器输出温度、催化荆的活性等影响生产的主要因素,对生产工艺进行了机理建模,设计了一套基于Hammerstein模型的非线性多量预测函数控制器,实现其生产过程的全自动和优化控制,并进行了可行性分析.     

城市生活污水排水管道内硫化氢和甲烷产生机制综述

城市生活污水排水管道通常处于厌氧状态,管道内气液相物质交换频繁,可视为一个庞大的气体排放系统,排出的污染气体包括硫化氢、甲烷、氨气和二氧化碳等十几种气体。其中硫化氢和甲烷浓度较高,受到学术界重视,并已经在管道内厌氧环境中硫化氯和甲烷的生成机制、影响因素、相互作用、静态模型等方面取得了很大的进展。其中主要的影响因素包括管道内污水的pH、水力停留时间、产甲烷细菌和硫酸盐还原细菌的食物竞争、某些对生化反应起抑制作用的盐类等。     

甲烷+氨水体系水合物生成条件实验测定及计算

甲烷在氨水体系中生成水合物的实验数据对于开发水合法回收合成氨驰放气工艺以及操作条件的确定具有重要意义。本文测定了氨摩尔分数为1.018、3.171、5.278氨水溶液中甲烷气体水合物的生成条件。结果表明：氨的加入对甲烷水合物的生成起着明显抑制作用,而且随着氨浓度的增加,生成压力越高。采用Chen-Guo模型对甲烷在氨水中生成水合物的数据进行了计算,得到了较为满意的计算结果,平均误差为2.71%,说明Chen-Guo模型能够较好地预测该类体系的水合物的生成条件。     

Low-Temperature Coupling of Methane

Methane is the main component of natural gas and its utilization amounts to ca. 1.7 × 10⁹ tons of oil equivalent per year [1]. Since the present reserve of methane is located in remote places, its transportation is a major problem. Methane coupling to form C₂₊ hydrocarbons is, therefore, of a primary importance because before transportation methane should be converted into hydrocarbons with higher boiling points, such as ethane, propane, etc. The catalytic conversion of methane can be carried out in several ways which have excellently been reviewed in Refs. 1 and 2. Basically, three routes exist: (i) the indirect route in which methane is first converted into syngas in presence of water (steam reforming), CO₂ (carbon dioxide reforming), or oxygen (partial oxidation) and the resultant syngas can be utilized in the traditional way; (ii) direct coupling in the presence of oxygen (oxidative coupling of methane, OCM) or hydrogen (two-step polymerization); and (iii) direct conversion in the presence of oxygen to oxygenates (CH₃OH, HCOH), in the presence of Cl₂, HCI to methane chlorides, in the presence of ammonia to HCN, etc.     

Effect of hydrogen addition on formation of hydrogen and carbon from methane decomposition over Ni/Al2O3

The effects of hydrogen addition on the formation of hydrogen and carbon from methane decomposition over Ni/Al₂O₃ were studied. The results show that the added hydrogen in methane greatly affects the methane conversion, hydrogen output rate, and the properties of the carbon deposits on the surface of the Ni/Al₂O₃. The methane conversion and hydrogen output rate are significantly improved by the addition of hydrogen. As the flowrate of hydrogen increases from 0 to 25 mL/min, the initial activity of Ni/Al₂O₃ decreases sharply, while the stability increases first and then decreases due to the suppression of hydrogen to CH₄ decomposition in the thermodynamics equilibrium. When the addition flowrate of the hydrogen is 15 mL/min, that is, 37.5% of the methane flowrate, a much higher methane conversion and the best stability of Ni/Al₂O₃ are obtained. The addition of a specific amount of hydrogen benefits the methane decomposition; however, the excessive hydrogen will suppress the decomposition. Most of the carbon that deposits on the surface of Ni/Al₂O₃ is filamentous carbon when hydrogen is added to the methane, however, encapsulated carbon is mainly produced when no hydrogen is added. In addition, the formation of encapsulated carbon, which deactivates the catalyst, is inhibited by the added hydrogen.     

利用吸收-水合耦合法从氨弛放气中回收氢气的研究(英文)

In this work, the absorption-hydration hybrid method was used to recover (hydrogen + nitrogen) from (hydrogen + nitrogen + methane + argon) tail gas mixtures of synthetic ammonia plant through hydrate forma-tion/dissociation. A high-pressure reactor with magnetic stirrer was used to study the separation efficiency. The in-fluences of the concentration of anti-agglomerant, temperature, pressure, initial gas-liquid volume ratio, and oil-water volume ratio on the separation efficiency were systematically investigated in the presence of tetrahydro-furan (THF). Anti-agglomerant was used to disperse hydrate particles into the condensate phase for water-in-oil emulsion system. Since nitrogen is the material for ammonia production, the objective production in our separation process is (hydrogen + nitrogen). Our experimental results show that by adopting appropriate operating conditions, high concentration of (hydrogen + nitrogen) can be obtained using the proposed technology based on forming hydrate.     

Nitrogen evolution during rapid hydropyrolysis of coal

The behavior of nitrogen evolution during rapid hydropyrolysis of coal has been investigated at temperatures ranging from 923 to 1123 K and hydrogen pressure up to 5 MPa using a continuous free fall pyrolyzer. Three coals have been tested in this study. The dominant nitrogen gaseous species is ammonia, together with a little amount of HCN because most of HCN is converted to NH₃ through secondary reactions. The results show that the evolution of nitrogen in coal is caused mainly by devolatilization at temperatures below 973 K, while the evolution of volatile nitrogen in char is accelerated with increasing temperature and hydrogen pressure. The mineral matter in coal act as catalysts to promote the evolution of volatile nitrogen in char to N₂ apparently at high temperatures of 1123 K, as found during pyrolysis of coal by Ohtsuka et al. A pseudo-first-order kinetic model was applied to the evolution of nitrogen in coal during rapid hydropyrolysis. The model shows the activation energy for the nitrogen evolution from coal is 36.6–58.6 kJ/mol while the rate of the nitrogen evolution depends on hydrogen pressure in the order of 0.16–0.24.     

Investigation of the gas-dynamic characteristics of hollow semipermeable fibres

Conclusions A scheme of a laboratory set-up for measuring the gas-dynamic resistance of hollow fibre channels over a wide range of temperatures and pressures has been described.A procedure for performing experiments and the results of experimental measurements of the flow rate of nitrogen, ammonia, argon, hydrogen, helium, and methane through the channels of polypropylene fibres from 20 to 0.2 m in length at 293°K and a pressure drop from 0.098 to 2.124 MPa have been presented.It has been found that the flow rate of the investigated gases increases regularly on increasing the pressure drop and decreases with increase in the length of the hollow fibre specimen. For hydrogen, helium, nitrogen, and argon, under otherwise equal conditions, flow rate decreases with increase in molecular weight of the gas. For ammonia and methane, a deviation from this relationship is observed, since the flow rate of these gases exceeds that of helium.Translated from Khimicheskie Volokna, No. 6, pp. 13–14, November–December, 1985.     

气氛、温度对煤热解过程中NH3和HCN释放的影响

为了实现煤的洁净转化,研究煤热解过程中N转移的机理,实验在固定床反应器上采用程序升温法对云南煤在不同温度下进行了氩、甲烷、15%水蒸气/氩和15%水蒸气/甲烷气氛下的煤加氢热解研究,主要对热解过程中产生的No2主要前驱物NH3和HCN的释放规律进行了考察,实验表明云南煤热解释放的NH3随热解温度的升高而增加,但是HCN...     

Sulphur poisoning of nickel-based hot gas cleaning catalysts in synthetic gasification gas II. Chemisorption of hydrogen sulphide

The effect of different components of gasification gas on sulphur poisoning of nickel catalysts were studied. In addition, the sulphur distribution and content of nickel catalyst beds were analysed to account the poisoning effect of sulphur on the activity of catalysts to decompose tar, ammonia and methane. The desorption behaviour of chemisorbed sulphur from the bed materials was monitored by temperature programmed hydrogenation (TPH). It was established that bulk nickel sulphide was active in decomposing ammonia in high-temperature gasification gas-cleaning conditions. The decomposing activity of methane was not affected by bulk nickel sulphide formation, but that of toluene was decreased. The activity of the catalyst regained rapidly when H₂S was removed from the gas. However, the conversion of ammonia was not regained at as high a level as before sulphur addition, most probably due to irreversible sulphur adsorption on the catalyst. The temperature increase could also be used to regenerate the catalyst performance especially in respect to methane and toluene. Sulphur adsorbed on nickel catalysts in different chemical states depends on the process conditions applied. At >900°C the sulphur adsorbed on the catalyst formed an irreversible monolayer on the catalyst surfaces, while at <900°C the adsorbed sulphur, probably composed of polysulphides (multilayer sulphur), was desorbed from the catalyst in sulphur-free hydrogen containing atmosphere. However, a monolayer of sulphur still remained on the catalyst after desorption. The enhanced effect of high total pressure on sulphur-poisoning of nickel catalysts could be accounted for the increased amount of sulphur, probably as a mode of polysulphides, adsorbed on the catalyst.     

Formation of NOx and SOx precursors during the pyrolysis of coal and biomass. Part III. Further discussion on the formation of HCN and NH3 during pyrolysis

The formation of HCN and NH₃ from the pyrolysis of coal (and biomass) is discussed based on our experimental data as well as the data in the literature, including the pyrolysis of N-containing pyrrolic and pyridinic model compounds reported in the literature. The pyrolysis of the model compounds and the thermal cracking of coal pyrolysis volatiles appear to be in good qualitative agreement in terms of the onset decomposition temperature, the main intermediates and the final N-containing product (HCN). The formation of NH₃ requires the presence of condensed phase(s) of carbonaceous materials rich in hydrogen. Direct hydrogenation of the N-sites by the H radicals generated in situ in the pyrolysing solid is the main source of NH₃ from the solid. The initiation of the N-containing heteroaromatic ring by radical(s) is the first step for the formation of both HCN and NH₃. While the thermally less stable N-containing structures are mainly responsible for the formation of HCN, the thermally more stable N-containing structures may be hydrogenated slowly by the H radicals to NH₃. The formation of NH₃ and the formation of HCN are controlled by the local availability of radicals, particularly the H radicals, in the pyrolysing solid. The increased yield of NH₃ (and HCN) with increasing heating rate can be explained by the rapid generation of the H radicals at high heating rates, favouring the formation of NH₃ (and HCN) over the combination of N-containing ring systems within the coal/char matrix. The size of the N-containing heteroaromatic ring systems and the types of substitutional groups also play important roles in the formation of HCN and NH₃.     

氨硼烷分解制氢及其再生的研究进展

氨硼烷具有储氢密度高（152.9g/L）、放氢条件温和、无毒以及常温下为稳定的固体而易于储运等特点而成为最有前景的储氢材料之一。本文综述了近年来氨硼烷在不同催化剂作用下,通过热解、醇解和水解这3种方式制氢以及分解后的副产物循环再生氨硼烷的研究进展。分析讨论了氨硼烷的热解制氢研究主要集中在降低温度和抑制气态副产物的生成这两方面,而水解或醇解制氢的研究热点是二元或三元非贵金属纳米核壳或负载型催化剂。与氨硼烷的热解相比,水解或醇解由于条件温和、制氢速度快而更具实用性。指出氨硼烷作为储氢材料最大的挑战是其再生问题,氨硼烷分解脱氢后的副产物不能直接氢化而再生氨硼烷,需要通过一系列反应来进行间接的离线再生,因此氨硼烷的再生将是今后的重点研究方向。     

Mechanisms for methane and ethane formation in the reaction of hydrogen with carbonaceous materials

A systematic density functional theory (DFT) study of the hydrogen reactions with carbonaceous surfaces was carried out in order to provide molecular-level understanding on the mechanisms of chemical processes involved in carbon hydrogasification. It was found that hydrogen is dissociatively chemisorbed on the active sites of zigzag and armchair configurations of carbonaceous models. In addition, mechanisms for methane and ethane production during the carbon-H₂ reaction were proposed suggesting that methane formation is exothermic and ethane formation is also possible but with a much lesser extent. These results agree with available experimental observations. Rate constants of the rate limiting steps were also calculated using the transition state theory. From both the thermodynamic and kinetic points of view, methane formation is much easier from zigzag edges rather than from armchair edges. The large activation energies for both pathways suggest that these reactions are favored at high temperatures.     

神木煤热解形成NOx前驱物的影响因素研究

热解是煤加工的重要基础过程，它是煤燃烧、气化的初始和伴随反应。通过固定床石英反应器研究了不同的热解方式、加热速率、气体流速和粒径对神木煤形成NO，的前驱物HCN和NH3，的影响规律，得出以下结论：终温和加热速率越高，形成的HCN和NH，的量越大；粒径的变化对HCN和NH3的影响规律不同；气体流速对HCN和NH3的形成受加热方式的影响。     

New aspects for heterogeneous cobalt-catalyzed hydroamination of ethanol

Gas-phase hydroamination of ethanol and ammonia over supported cobalt on silica catalysts was investigated at 103 kPa. Besides the desired products, mono-, di- and triethylamine, acetonitrile, diethylimine, and hydrocarbons (methane, ethene, ethane, propane, and propene) were identified as byproducts. The formation of hydrocarbons was found to depend on the cobalt loading of the catalyst and on the pretreatment of the catalyst. Guaranteeing a sufficient reduction of the cobalt catalyst allows a reduction in the selectivity of hydrocarbons from 25 to 10 mol% at a constant conversion of 90%. In addition, rapid deactivation of the catalyst was observed in the absence of hydrogen. The deactivation was ascribed to the interaction of ammonia with the catalyst and is largely reversible. Carbonaceous species are present on the spent catalyst, as shown by temperature-programmed reduction. These species are thought to be responsible for a slow deactivation in the presence of hydrogen.     

Partial oxidation of methane to synthesis gas:: Elimination of gas phase oxygen

The reaction between methane and cerium oxide to produce syngas has been studied at 700°C in a pulse apparatus. The cerium oxide was supported on γ-Al₂O₃ and promoted by re-impregnation with Pt or Rh. The promoters drastically enhanced the conversion of methane. TPR with hydrogen shows that Pt and Rh also lowered the temperature necessary to reduce the cerium oxide. Studies of the reaction between methane and promoted cerium oxide showed that the selectivity to syngas depends on the degree of reduction of the cerium oxide. The promoters also led to some carbon formation. Regeneration of the reduced oxide was studied both with oxygen and carbon dioxide.     

合成氨废气综合利用制天然气工艺设计

以合成氨膜提氢尾气为原料,根据气体压力、成分条件,采用低温液化精馏技术,将膜提氢尾气中的绝大部分甲烷提取并加工为管道天然气产品,通过管道输送方式就近并入天然气管网,从而解决合成氨提氢尾气利用不充分的生产现状.     

Ammoniaksynthese als Beispiel einer stofflichen Nutzung von intermittierend erzeugtem Wasserstoff

Producing hydrogen‐rich chemicals, such as methane, ammonia or methanol, from renewable energy may foster the integration of renewables into the current energy system. Here, a flexible ammonia synthesis concept is introduced, which is then compared to the widely discussed power‐to‐gas concepts on a technical and economic level. The current ammonia prices result in comparably high hydrogen‐specific revenues, which imply the ability to operate the system more profitable under fluctuating electricity prices and thereby increase the plant capacity factor.     

The mechanism of the selective reduction of nitrogen oxides by hydrocarbons on zeolite catalysts

The mechanism of the selective catalytic reduction (SCR) of nitrogen oxides over 3d transition metal zeolites has been investigated in a variety of ways. The initial step is the abstraction of hydrogen from the hydrocarbon by adsorbed NO₂ species which is rate determining with methane but not with isobutane. The subsequent path appears to involve nitroso and/or nitro compounds. Comparative studies of the reactions of such compounds indicate that nitromethane is more likely to be an intermediate than nitrosomethane during the methane-SCR reaction over Co-MFI although the latter cannot be ruled out entirely. In both cases the predominant route to N₂ is an initial decomposition to carbon oxides and ammonia followed by the NH₃-SCR reaction. The isobutane-SCR reaction over Fe-MFI produces substantial amounts of hydrogen cyanide which disappears only at temperatures where all the hydrocarbon has been consumed. Hydrogen cyanide appears to arise from isobutyronitrile, the expected dehydration product if an initially formed nitroso compound undergoes tautomerism to an oxime. HCN is converted to N₂ largely by reaction with NO₂ which is fast well below 300°C in the absence of isobutane. The corresponding isobutane-SCR reaction over Cu-MFI gives rise to cyanogen (C₂N₂) rather than HCN. The general path is probably the same in the two systems with the difference arising from variation in the relative reactivity of HCN. The copper-containing catalyst is very effective at forming and dimerising adsorbed cyanide groups while the iron catalyst has higher activity for the oxidation of NO to the NO₂ needed to convert adsorbed cyanide to N₂. The difference between the apparent involvement of a nitro route in methane-SCR with Co-MFI, and a nitroso one with isobutane, is similarly explainable. The former reaction proceeds with simultaneous production of NO₂ which can participate in the intermediate chemistry that follows. However, the NO₂ concentration is low during the latter reaction over Cu-MFI and Fe-MFI as long as any hydrocarbon remains. This is due to the blocking of sites for NO oxidation by deposits and the recycling of NO₂ back to NO during hydrocarbon oxidation. Thus only NO is available and the nitroso route prevails. The extent to which this picture applies with other catalysts and other hydrocarbons remains to be established.     

Kinetics of the reaction of hydrogen with thin films of carbon

The kinetics of the reaction of hydrogen with thin films of carbon has been studied over the temperature range 870–1150K and at pressures of hydrogen from 50–300 Torr (6.7–40 KPa). Thin films of carbon of average thickness about 30 nm were deposited on the surface of a quartz reactor by the pyrolysis of methane at 1100 K and the kinetics were studied in a static system. The products of the reaction were methane, ethane and ethylene, formed in successive hydrogenation steps, which in the low temperature region occurred largely on the surface of the carbon. In this region the activation energy of the rate of formation of methane was 6.5 kcal/mole. At temperatures above about 1050 K the thermal dissociation of hydrogen provided a source of radicals which caused a rapid increase in the rate of hydrogenation, both heterogeneous and homogeneous, giving an activation energy for the rate of formation of methane of 51 kcal/mole. A self-inhibition was observed, probably caused by a heterogeneous polymerization reaction leading to the formation of higher molecular weight products which remained adsorbed on the surface.