• Energy Research
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AbstractLow‐concentration gas is one of the most realistic and reliable supplementary or alternative energy sources of conventional natural gas, which has a wide range of applications. However, this gas is flammable and explosive during pipeline transportation and easily causes an explosion. In order to achieve safe transmission, the explosion characteristics and propagation law of low‐concentration gas are systematically studied through a large‐scale pipeline experimental system. We found that the peak pressure of low‐concentration gas explosion in pipeline has a quadratic function relationship with the propagation distance. Moreover, the peak pressure of gas explosion initially decreases from the explosion source, and then a turning point appears after a certain distance of propagation, which is followed by a sharp increase of peak pressure of gas explosion. The explosion pressure becomes maximum at the outlets of a pipeline. The arrival time of explosion flame is logarithmically relevant to propagation distance, while the speed of flame propagation gradually increases along with the increase of propagation distance. The flame propagation is faster at the exit point. In addition, the diameter of pipeline has also an important influence on the explosion propagation process of low‐concentration gas. So, the larger the diameter, the higher the explosion pressure. The explosion pressure of DN700 pipeline is obviously higher than that of DN500, and the explosion pressure rises faster; the speed of flame propagation of gas explosion in DN700 pipeline is also higher than that in DN500 pipeline. This study provides a theoretical reference for the prevention and control of explosion accidents in low‐concentration gas pipelines.

Abstract Polyimide hollow fiber membrane module has been tested under low temperature for efficient CO2 separation. Parametric study was carried out to evaluate separation performance of the designed cryogenic-membrane hybrid system. In detail, the effect of stage cut, feed pressure, operating temperature and CO2 concentration on gas permeance, CO2/N2 selectivity, CO2 purity and recovery were investigated. The experimental results indicated that operating temperature played an important role in the separation performance. Reducing stage cut would result in the increase of permeance (up to 302 GPU), CO2/N2 selectivity (up to 20) and CO2 purity (up to 59%), especially under the low temperature (−20 °C). The variation of gas permeance depended on the competition between the compression and swelling effect of the free volume. When the operating temperature and feed pressure were set at −20 °C and 700 kPa, the CO2 recovery could be improved to 93%. Although the permeance, CO2/N2 selectivity and recovery adversely decreased with the increase of feed CO2 concentration, the CO2 purity could be increased to 40% with the feed pressure of 400 kPa. The cryogenic-membrane hybrid system presented a potential in enhancing the CO2 removal efficiency.

Conventional historical data based material and energy balance analyses are static and isolated computations. Such methods cannot embody the cross-coupling effect of energy flow, material flow and information flow in the process industry; furthermore, they cannot easily realize the effective evaluation and comparison of different energy transfer processes by alternating the model module. In this paper, a novel method for material balance and energy conservation analysis of process industry energy transfer system is developed based on model property. Firstly, a reconfigurable energy transfer process model, which is independent of energy types and energy-consuming equipment, is presented from the viewpoint of the cross-coupling effect of energy flow, material flow and information flow. Thereafter the material balance determination is proposed based on both a dynamic incidence matrix and dynamic balance quantity. Moreover, the model-weighted conservation determination theorem is proved, and the energy efficiency analysis method is also discussed. Results confirmed the efficacy of the proposed methods, confirming its potential for use by process industry in energy efficiency analyses.

Abstract Many organizations in the world are interested in waste management problems and their potential solutions. In order to solve these problems, a Japanese venture company has developed an innovative thermal decomposer for organic wastes called ERCM (Earth-Resource-Ceramic-Machine). The ERCM reactor employs electron injected air to promote the thermal decomposition reaction, while the effect of electron injection into air has not yet been clarified. An experimental work was performed using a fixed bed reactor to explore the effects of different parameters of electron injection into air, the reaction temperature and different feedstock on the syngas generation. The main purpose of this study is to clarify the phenomena occurring in the ERCM reactor where a direct current electric field is produced in the flame reaction zone to enhance the thermal decomposition of wastes. In this regard, a mathematical model for simulating the thermal decomposition of solid waste in the presence of an electric field have been developed. The equations of aero-thermochemistry are coupled to the balance equations for densities of charged species, and the Poisson equation for the electrical potential is solved. The model was validated by the experimental data and showed a good agreement. The results showed that the electric field significantly improves the stabilization of the flame. From the release behavior of CO and CO2, it is noted that the electron injection would affect the char combustion process significantly. Finally the effect of the flame reaction zone generated by the field induced ion wind on the thermal decomposition was investigated.

The ionic liquid (IL) 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) was selected as an appropriate entrainer for the extractive distillation of the methanol–ethanol-water mixture. The COSMO-RS model was applied to screen out the appropriate solvents considering selectivity and solvent capacity together. Isobaric vapor–liquid equilibrium (VLE) experiments for the two systems of methanol–water and ethanol–water with different amounts of [EMIM][DCA] added were conducted at 101.3 kPa. The experimental data showed that [EMIM][DCA] exhibits an obvious salting effect for the methanol (or ethanol)-water mixture and eliminates the azeotropic point of ethanol–water. Moreover, the predicted values by UNIFAC-Lei model coincide well with experimental data. The separation mechanism was further explained in combination with surface charge density distribution (σ-profiles), excess enthalpy (HE), and binding energy. In addition, the flow charts were designed to evaluate the improvement of energy consumption with [EMIM][DCA] as the entrainer when compared to ethylene glycol (EG). The simulation results demonstrated that [EMIM][DCA] is more energy efficient than EG.

Abstract The effects of the operating conditions on the performance of metal hydride hydrogen storage tanks are complicated and need detailed investigations for further optimization. In this study, a mathematical model is developed to understand the effects of the various operating conditions on the hydrogen absorption processes in a LaNi 5 metal hydride tank. The numerical results indicate that the quickest charging process occurs within the first 20 s, and the quickest charging rate and duration are mainly affected by the charging pressure and initial temperature, respectively. The effect of cooling level on this process is insignificant. For both the short-time charging (2 min) and long-time charging, the hydrogen fueling performance is significantly affected by the cooling level (the heat transfer coefficient and surrounding temperature) and charging pressure. In order to ensure sufficiently quick hydrogen charging, the charging pressure needs to be kept enough higher than the equilibrium pressure, and due to the fast heating of the metal hydride, the influence of the initial temperature is less significant than the cooling condition. The general distributions of the absorbed hydrogen fraction and temperature are similar under the different operating conditions.

La biogazéification in situ du charbon peut être définie comme l'une des méthodes d'extraction du charbon qui utilise pleinement les bactéries méthanogènes du charbon pour examiner les résultats actuels, à savoir la digestion anaérobie des composants organiques. L'expérience suivante a été réalisée en ce qui concerne, un puits vertical et un puits horizontal à branches multiples ont été utilisés comme puits expérimentaux et deux puits verticaux ont été utilisés comme puits témoins, le test pilote a été effectué avec une méthode d'injection nutritionnelle à puits unique. En appliquant la méthode mentionnée ci-dessus, la concentration d'ion Cl- et le nombre modifié dans les Methanogen spp. ont été utilisés pour suivre la diffusion de la nutrition. En outre, l'analyse des résultats de la mise en œuvre technique a été faite avec l'observation des changements de production de CH4 et de l'évolution du biome du lit de charbon. Les taux de production de gaz dans chaque puits ont été surveillés en utilisant le flux de racines de gaz FLLQ Mete. La concentration de CH4 et de CO2 a été évaluée en utilisant le chromatographe en phase gazeuse Agilent 7890A, d'autre part, les concentrations de Cl- ont été déterminées par l'application du système de chromatographie ionique ICS-1100. La méthode de fluorescence F420 a été adoptée pour tester la présence de bactéries méthanogènes. Dans l'intervalle de la phase d'achèvement, l'étude a indiqué que la diversité bactérienne de l'eau souterraine du puits Z-7H a une séquence passe-haut avec la période expérimentale de 814 jours. Les données de production de gaz dans les puits Z-159 et Z-7H ont montré que la gazéification du charbon a duré 635 et 799 jours, produisant 74817 m3 et 251754 m3 de méthane de houille, respectivement. En outre, les données expérimentales ont montré qu'une injection nutritionnelle unique dans des puits de méthane à charbon anthracite a permis d'atteindre une moyenne de 717 jours de production continue de gaz parmi tous les puits expérimentaux. L'étude susmentionnée a consacré l'importance de la fermentation bactérienne native, car elle a prouvé le fait que l'anthracite peut être appliquée pour réaliser la biogazéification du charbon et la stimulation de la production de méthane à partir de charbon in situ. La biogasificación de carbón in situ se puede definir como una de las metodologías de biominería de carbón que utiliza completamente las bacterias metanogénicas en el carbón para revisar los hallazgos actuales, a saber, la digestión anaeróbica de componentes orgánicos. El siguiente experimento se ha realizado con respecto a, un pozo vertical y un pozo horizontal de múltiples ramas se utilizaron como pozos de experimento y dos pozos verticales se utilizaron como pozos de control, la prueba piloto se llevó a cabo con el método de inyección de nutrición de un solo pozo. Al aplicar el método mencionado anteriormente, la concentración de ion Cl- y el número alterado en Methanogen spp. se utilizaron para rastrear la difusión nutricional. Además, se ha realizado un análisis de los resultados de la implementación técnica con la observación de los cambios en la producción de CH4 y la evolución del bioma del lecho de carbón. Las tasas de producción de gas en cada pozo se monitorearon mediante el uso del medidor de flujo de raíces de gas FLLQ. La concentración de CH4 y CO2 se evaluó utilizando el cromatógrafo de gases Agilent 7890A, por otro lado, las concentraciones de Cl- se determinaron mediante la aplicación del sistema de cromatografía iónica ICS-1100. Se adoptó el método de fluorescencia F420 para evaluar la presencia de bacterias metanogénicas. En el ínterin de la etapa de finalización, el estudio indicó que la diversidad bacteriana del agua subterránea del pozo Z-7H tiene una secuencia de paso alto con el período experimental de 814 días. Los datos de producción de gas en los pozos Z-159 y Z-7H mostraron que la gasificación del carbón duró 635 y 799 días, produciendo 74817 m3 y 251754 m3 de metano en lecho de carbón, respectivamente. Además, los datos experimentales presentaron que la inyección de nutrición de una sola vez en pozos de metano de lecho de carbón de antracita logró un promedio de 717 días de producción continua de gas entre todos los pozos experimentales. El estudio mencionado anteriormente dedicó la importancia de la fermentación bacteriana nativa, ya que demostró el hecho de que la antracita se puede aplicar para lograr la biogasificación del carbón y la estimulación de la producción de metano en el lecho de carbón in situ. In-situ coal bio-gasification can be defined as one of the coal bio-mining methodology that fully utilizes the methanogenic bacteria in coal to review the current findings, namely anaerobic digestion of organic components. The following experiment has been done in regards, one vertical well and one multi-branch horizontal well were used as experiment wells and two vertical wells were used as control wells, the pilot test was carried out with single well nutrition injection method. By applying the above mentioned method, the concentration of Cl- ion and number altered in Methanogen spp. were used to trace nutrition diffusion. Furthermore, technical implementation results analysis has been made with the observation of CH4 production changes and coal bed biome evolution. Gas production rates in each well were monitored by using the FLLQ gas roots flow mete. The concentration of CH4 and CO2 were evaluated by using the Agilent 7890A gas chromatograph, on the other hand, concentrations of Cl- were determined by the application of ICS-1100 ion chromatography system. The F420 fluorescence method was adopted to test for the presence of methanogenic bacteria. In the interim of the completion stage, the study stated that the bacterial diversity of underground water of Z-7H well has a high pass sequence with the experimental period of 814 days. Gas production data in Z-159 and Z-7H wells showed the gasification of coal lasted 635 and 799 days, yielded 74817 m3 and 251754 m3 coalbed methane, respectively. Furthermore, experimental data presented that one time nutrition injection in anthracite coalbed methane wells achieved an average of 717 days of continuous gas production among all experimental wells. The above fore-said study dedicated the significance of native bacterial fermentation, as it proven the fact that anthracite can be applied to accomplish coal bio-gasification and coalbed methane production stimulation in-situ. يمكن تعريف التغويز الحيوي للفحم في الموقع على أنه إحدى منهجيات التعدين الحيوي للفحم التي تستخدم بالكامل البكتيريا المولدة للميثان في الفحم لمراجعة النتائج الحالية، وهي الهضم اللاهوائي للمكونات العضوية. تم إجراء التجربة التالية فيما يتعلق، تم استخدام بئر رأسي وبئر أفقي متعدد الفروع كآبار تجريبية وتم استخدام بئرين رأسيين كآبار تحكم، وتم إجراء الاختبار التجريبي بطريقة حقن تغذية بئر واحدة. من خلال تطبيق الطريقة المذكورة أعلاه، تم استخدام تركيز الكلور والعدد المتغير في مشتقات الميثانوجين لتتبع انتشار التغذية. علاوة على ذلك، تم إجراء تحليل لنتائج التنفيذ الفني مع ملاحظة تغييرات إنتاج الميثان وتطور المجال الحيوي لطبقة الفحم. تمت مراقبة معدلات إنتاج الغاز في كل بئر باستخدام مقياس تدفق جذور الغاز FLLQ. تم تقييم تركيز CH4 و CO2 باستخدام كروماتوغراف الغاز Agilent 7890A، من ناحية أخرى، تم تحديد تركيزات Cl - من خلال تطبيق نظام كروماتوغرافيا الأيونات ICS -1100. تم اعتماد طريقة الفلورة F420 لاختبار وجود البكتيريا المولدة للميثان. في غضون مرحلة الإنجاز، ذكرت الدراسة أن التنوع البكتيري للمياه الجوفية لبئر Z -7H له تسلسل تمرير عالي مع الفترة التجريبية البالغة 814 يومًا. أظهرت بيانات إنتاج الغاز في آبار Z -159 و Z -7H أن تغويز الفحم استمر 635 و 799 يومًا، وأسفر عن 74817 متر مكعب و 251754 متر مكعب من الميثان في قاع الفحم، على التوالي. علاوة على ذلك، أظهرت البيانات التجريبية أن حقن التغذية لمرة واحدة في آبار الميثان في قاع الفحم الأنثراسايت حقق متوسط 717 يومًا من الإنتاج المستمر للغاز بين جميع الآبار التجريبية. كرست الدراسة المذكورة أعلاه أهمية التخمير البكتيري الأصلي، حيث أثبتت حقيقة أنه يمكن تطبيق الأنثراسايت لإنجاز التغويز الحيوي للفحم وتحفيز إنتاج الميثان في الموقع.

Abstract Hydration is an alternative promising method for CO2 capture and separation from either post-combustion flue gas or pre-combustion fuel gas. The present paper gathers the researches on CO2 hydrate and the hydrates of gas mixtures of CO2+N2/H2/CH4, including studies of fundamental thermo-physical properties, molecular structures and hydrate formation equilibrium conditions. Some promoters, i.e. quaternary ammonium salt etc. are usually used in CO2 hydration process to reduce the hydrate equilibrium pressure and to enhance the hydrate kinetic and stability, hence their promotion effect on CO2 hydrate and on the hydrates of gas mixture of CO2+N2/H2/CH4 are reviewed. The paper also summarizes the applications of hydrate technology in CO2 capture and separation, and the corresponding performance is summarized and the bottlenecks are discussed. It necessitates more works to promote this technology towards industrial application.