Inlet Gas Pressure Research Articles

Enhancing mixing characteristics of MgCl2 solution within atomization nozzles: A computational fluid dynamics investigation of structural parameter

Efficient dispersion of MgCl2 solution is crucial in saline lake industries. Understanding how structural variables influence atomization can improve nozzle design. This study uses Computational Fluid Dynamics (CFD) modeling to examine the effects of key structural parameters on MgCl2 solution mixing in atomization nozzles. It focuses on the impact of liquid injection hole size, number of air injection holes, and mixing chamber length on the nozzle's fluid dynamics. The analysis covers variations in internal velocity and MgCl2 volume fraction. Simulations show that increasing the liquid injection hole diameter reduces liquid flow resistance, while adding more air injection holes leads to a more uniform air distribution, though with a slight increase in atomization efficiency. A longer mixing chamber reduces gas phase velocity. Optimal mixing efficiency is achieved with 4 air injection holes, a 1.5 mm liquid injection hole, a 7 mm mixing chamber, a 2 mm nozzle outlet, 0.3 MPa inlet gas pressure, and an 80 L/h solution flow rate. This study provides insights into key parameters for improving performance and refining industrial applications.

Two-phase flow pattern recognition inside tubes by a novel diagnostic technique

Abstract A two-phase (liquid-gas) flow represents a highly complex regime influenced by factors such as the mass flow rate of each phase, fluid dynamic and thermal conditions, viscosity, density, and surface tension. The presence and distribution of bubbles within the liquid phase significantly impact heat transfer mechanisms and the performance of components like pumps, valves, and nozzles. This study aims to develop and validate a method for identifying the flow regime within a horizontal duct and accurately quantifying flow parameters. The authors have developed a sensing methodology and instrumentation capable of detecting and analysing the vibrational modes of ducts. This approach enables the identification of flow patterns and serves as a sensor for two-phase flow in Direct Steam Generation (hereafter DSG) solar fields. In the experimental by regulating the pump’s rotational speed, inlet gas pressure, and volumetric flow rate, various two-phase flow configurations were replicated. The flow patterns were characterized using independent statistical indices such as crest factors, shape factors, medians, and modes, to define an objective function capable of describing bubble cluster behaviour on a phase diagram (Poincare map), in which more than 76 % of cases were correctly processed. This analysis employs Poincare’s topological theory and the “within-between approach” in multivariate analysis.

Experimental study of voltage uniformity and stability of H2/O2 PEM fuel cell stack with dead-end anode and recirculation cathode

Dead-end anode and recirculation cathode is an operating mode effectively improving the gas reactant utilization of hydrogen–oxygen proton exchange membrane fuel cell (H2/O2 PEMFC) stack. However, the difference of single cells in the stack, will be further expanded due to the flooding and impurities and necessary purge for removing them. In this work, the voltage uniformity and stability of H2/O2 PEMFC under different operating conditions are investigated based on a dead-end anode and recirculation cathode PEMFC stack. Research indicates that enhancing the current density and temperature, lowering the inlet gas pressure will diminish the uniformity in stack voltage. The analysis of the experimental pattern reveals a positive correlation between the voltage uniformity and stability. This is due to the water flooding or membrane dehydration phenomenon of the single-cell leading to a reduction of the single-cell voltage and the voltage uniformity of the stack, while the water flooding or membrane drying phenomenon makes the stack more unstable and the purge interval shorter. Based on these experimental results, the best operating scheme for the designed stack is proposed, which is of some guidance and reference value for the practical application of air-cooled PEMFC in the hundred-watt class.

Modelling of a continuous sorption-enhanced methanation process in an adiabatic packed-bed reactor system

The present study investigates a sorption-enhanced methanation process and successive solid regeneration stages using a dual-function catalyst containing nickel as a catalyst and zeolite 13X for water removal. An adiabatic packed bed, modelled by a dynamical and heterogeneous model, has been considered, and a five-stage sequence describes the sorption-enhanced methanation and successive solid regeneration. First, methanation occurs with in-situ water removal; then, the catalyst drying using a pressure and temperature swing approach implemented by blowdown, purge, cooling, and pressurisation stages. In adiabatic operation, heat management is crucial; on the other hand, the heat produced can be efficiently used to dry the zeolite. Process intensification is pursued by addressing the effect of gas inlet temperature, pressure, and GHSV on system performance. Achieving an average purity of 99 % of the methane for pressures greater than 2 bar is possible for long-time operation, with productivity averaging 0.8 mol/(kgads min) at the highest gas hourly space velocity investigated.

Optimal Dynamic Regimes for CO Oxidation Discovered by Reinforcement Learning.

Metal nanoparticles are widely used as heterogeneous catalysts to activate adsorbed molecules and reduce the energy barrier of the reaction. Reaction product yield depends on the interplay between elementary processes: adsorption, activation, desorption, and reaction. These processes, in turn, depend on the inlet gas composition, temperature, and pressure. At a steady state, the active surface sites may be inaccessible due to adsorbed reagents. Periodic regime may thus improve the yield, but the appropriate period and waveform are not known in advance. Dynamic control should account for surface and atmospheric modifications and adjust reaction parameters according to the current state of the system and its history. In this work, we applied a reinforcement learning algorithm to control CO oxidation on a palladium catalyst. The policy gradient algorithm was trained in the theoretical environment, parametrized from experimental data. The algorithm learned to maximize the CO2 formation rate based on CO and O2 partial pressures for several successive time steps. Within a unified approach, we found optimal stationary, periodic, and nonperiodic regimes for different problem formulations and gained insight into why the dynamic regime can be preferential. In general, this work contributes to the task of popularizing the reinforcement learning approach in the field of catalytic science.

Artificial neural network modelling of natural gas dehydration process

A multi-input–multi-output artificial neuron network (MIMO-ANN) model has been developed for process monitoring and improvement on a natural gas glycol dehydration process. The MIMO-ANN model was based on a steady-state process simulation model constructed in commercial software Aspen HYSYS. A set of training data was generated with the converged simulation model for the training of the MIMO-ANN model in Python. The process input of the model includes lean glycol recirculation rate and purity along with wet gas inlet pressure. On the other hand, the process output considered includes dehydrated gas water and aromatics content, dehydrated gas hydrate formation temperature and water dew point, stripping gas flow rate as well as reboiler duty. The overall mean squared error (MSE) of the MIMO-ANN model was calculated as 1.79. The best-fit line that highly overlaps with a 45° diagonal line is constructed with a correlation coefficient (R2) score of more than 0.999 for all studied process output testing datasets. The mean absolute percentage error (MAPE) of the predicted outputs is generally less than 1%, except for dehydrated gas water dew point (16.63%) and stripping gas flow rate (11.55%), due to error predictions attempted on pseudo-zero values. This successfully displays an exceptional predictive performance of the MIMO-ANN model developed in this work which can be further deployed as an online dashboard for real-time monitoring tool.

Calculation of the required methanol consumption during the flow of wet hydrocarbon gas in a horizontal pipeline

One of the main problems that have to be solved during the development of hydrocarbon deposits is the formation of gas hydrates in pipelines. In this regard, the article presents a preventive method to struggle against the formation of gas hydrate deposits on the pipes inner walls associated with the supply of a hydrate formation inhibitor to the gas stream. The research was conducted on the basis of a mathematical model of the wet hydrocarbon gas flow in a horizontal pipeline. The research object is to determine the minimum required consumption of methanol, in which there is no formation of gas hydrate deposits on the channel inner walls. The practical significance of this study is that it is aimed at reducing the risks associated with the formation of gas hydrates in pipelines. The numerical implementation of a mathematical model of natural gas flow in a horizontal channel is based on a sequential solution of a system of four differential equations by the Runge-Kutta method of 4 orders of accuracy, followed by a search for sequential approximations of the minimum inhibitor flow rate, in which the "gas + water ↔ gas hydrate phase" transition process does not occur on the inner surface of the channel. The article presents a calculation of the proportion of a hydrate formation inhibitor in the liquid phase by solving a cubic equation using the Cardano method. Based on the computational experiments results, graphs were constructed and interpreted of the dependencies of the minimum inhibitor consumption on the soil temperature, inlet gas pressure, total water concentration in the gas flow, initial gas temperature and total gas flow rate.

Design of a novel tubular membrane reactor with a middle annular injector for enhancement of dry reforming towards high hydrogen purity: CFD analysis

This study introduces a novel design of a tubular porous membrane catalytic reactor (TPMCR) with a middle annular injector, which aims to improve the performance of a dry reforming of methane (DRM) process. A computational fluid dynamics (CFD) model is developed for a fundamental configuration and subsequently verified using experimental data. The validated CFD model is utilized to examine the influence of different parameters, such as feed composition, inlet gas temperature and pressure, and injection rate, on the reactor performance. The study findings reveal that the introduction of a secondary gas during the injection process has the potential to regulate the process and positively affect the production rates of hydrogen and carbon monoxide. The optimal inlet temperature to attain the highest rate of hydrogen production is determined to be 900 K. The hydrogen selectivity is found to increase from 0.96 to 1.60 with the injection of pure steam when the injection rate is increased from 50 to 500 kg/(m2.s). In addition, the carbon monoxide selectivity is decreased from 6.30 to 2.67. The implementation of a middle annular injector within the proposed TPMCR design offers the potential for enhancing the efficiency and sustainability of chemical reactors. Consequently, the introduced modification leads to more efficient and environmentally friendly chemical processes, specifically in the realms of syngas and hydrogen production through the DRM process, resulting in improved purity levels.

Energy, economic, and environmental analysis: A study of operational strategies for combined heat and power system based on PEM fuel cell in the East China region

This study introduces a combined heat and power (CHP) system primarily based on proton exchange membrane (PEM) fuel cells, which can provide electricity and heat for residential buildings in the East China region under two operating strategies. The analysis and discussion focus on the impact of parameters such as current density and gas inlet pressure on the system's output power and efficiency. The results indicate that excessively high current density decreases the system's electricity generation efficiency, while a moderate increase in hydrogen inlet pressure contributes to greater heat generation. Considering energy, economic, and environmental factors, the system operates with the thermal-led strategy in parallel with the grid, resulting in a substantial 73.3 % reduction in fuel costs. The annual greenhouse gas (GHG) emissions and the amount of emission reduction are lowered to 6.96 × 107 g and 3.39 × 107 g, respectively.

Optimizing the CO2 capture and removal process to recover energy and CO2 from the flue gas of boilers and gas turbines outlet with considering the techno-economic analysis

This research aims to evaluate, simulate, and model the CO2 capture process for removing CO2 from the flue gas outlet flow of boilers and gas turbines. To the best of the knowledge Aspen HYSYS was employed to simulate these processes, enabling the analysis of technical conditions and evaluation of the problems and advantages associated with various designs from a technical perspective. Additionally, Aspen Capital Cost Estimator (ICARUS) was utilized for economic analysis.Initially, the CO2 capture process was examined for the removal of CO2 in the flue gas outlet flows of gas turbines and boilers. Subsequently, the process was simulated in the software to explore different optimal modes. Moreover, the feasibility of using a compressor, blower, ejector, and a combination of ejector and compressor was considered so as to provide the necessary pressure for absorption. Finally, the optimal design was selected, and more detailed studies were conducted on its absorption process, taking into account major variables. Among the important factors affecting absorption, were the number of trays, diameter, height, the amount of inlet gas and amine flow rate entering from the top of the tower, as well as the inlet gas pressure.

In-field experimental study and multivariable analysis on a PEMFC combined heat and power cogeneration for climate-adaptive buildings with taguchi method

Due to overwhelming advantages in high power density, stability in long-term storage and clear by-product water, application of hydrogen energy in buildings has attracted global interests for sustainable and low-carbon transformation, especially with the fast technology development of proton exchange membrane fuel cell (PEMFC) combined heat and power (CHP) cogeneration system. However, the cost-effective operating control of PEMFC CHP cogeneration system has not been investigated, comprehensively considering intermittence and stochasticity of building energy demands in different climate regions under extreme climates. In this study, in-field experimental study following the orthogonal method is conducted for underlying mechanism analysis of operating parameters on electric power, total power, and electric/thermal (E/T) power ratio of a PEMFC stack, considering energy losses by convection, radiation and exhausted reactant gas flow. Sensitivity analysis of operating parameters on PEMFC output performances is conducted based on Taguchi Method. For climate-adaptive applications of PEMFC CHP cogeneration systems in Guangzhou (cooling-dominated area) and Beijing (heating-dominated area), two operating strategies with electricity- and heat-dominated outputs have been proposed and compared. Results indicate that, the PEMFC output performances are influenced by internal factors, including reaction rate, substance transportation, membrane hydration level and energy losses. Electric power and total power are mainly dependent on coolant inlet temperature, inlet gas pressure and coolant flux, while E/T power ratio is mainly controlled by inlet coolant temperature, inlet gas pressure and cathode stoichiometric ratio. Furthermore, based on the proposed cost-effective operating control (the electricity-dominated output control strategy under extreme hot weather in Guangzhou and heat-dominated output control strategy under extreme cold weather in Beijing), the PEMFC could save 0.246 kg hydrogen with 2.137 × 103 kJ surplus thermal energy one day in Guangzhou, and save 2.763 kg hydrogen with 3.527 × 103 kJ surplus electric energy one day in Beijing. This study could provide a guideline for operating parameter selections of PEMFC CHP cogeneration system in variable climate areas.

Effect of pressure and supply configuration on mixing efficiency through Venturi effect for co2/h2- ch4/h2 mixtures in Power-To-Gas process: CFD analysis

Introduction: The present article is one of the outcomes of the project “Desarrollo de un sistema “power to gas” (PTG) en el contexto de las fuentes de energía renovables y convencionales disponible en la Guajira” This project was carried out by the University of Antioquia and the University of La Guajira during the period 2019-2023. Problem: Efficiency and uniformity in gas mixing for Power-to-Gas applications are influenced by pressure varia- tions and supply configurations. Objective: To assess the impact of pressure variations and supply configurations on the efficiency of the Venturi mixing process, utilizing indicators such as the Z-factor and the coefficient of variation (CoV). Methodology: Numerical simulations were conducted for four mixer configurations. For CO2/H2 mixtures, pressures of 1 bar (case i) and 4 bars (case ii) were considered; for CH4/H2 mixtures, pressures of 3 bars (case i) and 35 bars (case ii) were studied. Results: As the inlet gas pressure increases, uniformity decreases for both mixtures. Horizontal H2 feeding improves CO2/H2 uniformity, while vertical feeding benefits CH4/H2 mixing. The mixer reduces CoV by an average of 80% for CO2/H2. For CH4/H2 mixtures at 3 bars, there is a 60% reduction, but at 35 bars, coefficients increase by 56%. Conclusion: Pressure and supply configuration significantly influence the mixing process, underscoring the impor- tance of considering these factors in Power-to-Gas applications. Originality: The study explores the Venturi mixing process in specific gas mixtures for Power-to-Gas applications. Limitations: The studied conditions and configurations may not encompass all possible scenarios in Power-to-Gas applications.

Flexible carbon capture using MOF fixed bed adsorbers at an NGCC plant

Novel carbon capture systems are necessary to help natural gas power plants approach net zero CO2 emissions. We propose a hybrid carbon capture system attached to a natural gas combined cycle (NGCC) power plant that consists of a membrane system and a solid sorbent system, with this work focusing on the design of the solid sorbent system. We modeled fixed bed adsorbers that are packed with metal-organic framework (MOF) solid sorbents that adsorb CO2 and undergo temperature swing desorption using steam from the power plant. Parametric simulation of adsorber conditions showed that ten 5-m diameter beds adsorbing in parallel with 4.9 bars inlet gas pressure and 1.5 bars of steam pressure at a flow rate of 0.15 kmol/s led to optimized performance. This study enabled us to determine that the MOF bed adsorber can attain 86.6 % and 85.4 % carbon capture during peak and off-peak operation, respectively. When combined with the membrane capture system, this results in overall capture rates of 98.4 % and 98.9 % during peak and off-peak operation, respectively. Although we were unable to attain net-zero or net-negative emissions in this study, we are confident that net-negative operation could be obtained in future work by selecting a solid sorbent better suited to direct air capture conditions so that more air could be processed by the solid sorbent system.

A novel model of a hydrogen production in micro reactor: Conversion reaction of methane with water vapor and catalytic

This study presents a comprehensive investigation of a thermally integrated membrane micro reactor for efficient hydrogen production through the conversion of methane with water vapor. The reactor design incorporates a catalytic Au/ZnO system to enhance performance. The effects of key operational variables, including inlet gas flow rate, pressure, temperature, water-to-methane ratio, and membrane thickness, were examined. Optimal conditions were sought to maximize methane conversion, hydrogen yield, and minimize carbon monoxide production. As feed flow increases, methane conversion decreases due to reduced retention time in the reactor. This decrease is almost six times greater at 240 °C than at 270 °C. Higher water-to-methane ratios improved methane conversion and reduced hydrogen and carbon monoxide production. Shell pressure affected methane conversion, with higher pressures resulting in decreased rates and carbon monoxide levels. As shell airflow velocity increases, methane conversion rises about 0.96 %. Tube pressure influenced hydrogen passage through the membrane, causing decreased hydrogen output from the tube section and increased output from the shell section, while reducing carbon monoxide emissions. These findings contribute to the optimization of a thermally integrated membrane micro reactor for efficient hydrogen production through water vapor-methane conversion.

Effects of temperature, inlet gas pressure and humidity on PEM water contents and current density distribution

The liquid water content directly affects the performance of the proton exchange membrane fuel cell (PEMFC). However, the liquid water content is influenced by the temperature, inlet gas pressure and humidity, so this investigation seeks to explore the relationship among the operating parameters, liquid water content and the current density distribution that used to characterize the cell performance. Firstly, a three-dimensional monomer model of PEMFC was established for numerical simulation based the COMSOL software to study the effect of temperature and inlet gas parameters on cell performance. Then the PEMFC reactor performance test used control variable method was carried out on the 15 kW test bench to verify the research. From the simulation and test results, we can acquire that the liquid water content and current density distribution of fuel cell are the maxima under the condition of 0.2 MPa pressure and 100% humidification. Finally, the experiment confirmed that when the temperature is 353 K, the liquid water content is the highest, and when the temperature remains constant, the higher inlet gas pressure and humidity was given, the higher liquid water content will be generated in the proton membrane which can increase the current density on the membrane to a certain extent, hence to improve the cell performance.

Process analysis and optimization of high-N2 natural gas liquefaction

The demand for natural gas (NG) is increasing rapidly due to the world energy crisis. Liquefied Natural Gas (LNG) technology is one of the most flexible and reliable supply solutions, which has already been a major research hotpot in energy use. However, NG with high-N2 content lowers the gas calorific value and value of the gas and increases the energy consumption for production and transport. To address this issue, this study established nitrogen removal from the NG process using a single-column cryogenic distillation process based on Aspen HYSYS® in this study. An expanding refrigeration process using N2-CH4 was selected to provide the required cold energy for this plant, and the process power consumption and LNG specific power consumption was used as evaluation indicators. Results from sensitivity analysis showed that by the increase of natural gas feed temperature T1, the distillation column operation pressure Pc, and refrigerant high pressure P3, the LNG specific power consumption also demonstrated an increasing trend. The variables of natural gas inlet pressure P1, the outlet temperature of natural gas from pre-cooler T2, the ratio of return RR, the methane content ZCH4, the temperature of refrigerant after pre-cooler T4 and refrigerant low pressure P5 had a negative impact on the LNG specific power consumption. After conducting an optimization algorithm, the minimum LNG specific power consumption was determined to be 56.17 kJ/mol. Exergy analysis demonstrated that the total exergy destruction was 2076.13 kW. The compressor and expander components accounted for 31.57% and 26.29% of the total exergy losses respectively. This research provides valuable insights into optimizing LNG production processes by mitigating the impact of high nitrogen content, and it contributes to the advancement of LNG technology and energy efficiency in the industry.

Temperature drop for CO2 gas flowing through multilayer micro-pin fin arrays

A reasonable theoretical calculation model is established, and an appropriate correlation formula is selected to calculate the flow and heat transfer of CO2 gas flowing through micro-pin fin arrays in a micro-cooler respectively under different working conditions. The inlet pressure of CO2 gas is 1.0 MPa, 1.5 MPa, and 2.0 MPa respectively, and the inlet temperature is 12 °C and 16 °C respectively. The results show that the cold end temperature of the gas decreases with the increase of CO2 gas inlet pressure and the decrease of inlet temperature, and the lowest temperature reaches -29.93 °C. The calculated results have the same trend as the experimental data, and the calculated values are consistent with the experimentally measured values, which demonstrates the calculation model’s logic.

OPTIMIZING THE ELECTRONIC CONTROL OF SUCTION VALVES FOR GAS COMPRESSION UNITS

In certain compression stations where twin-screw compressors assemblies are installed, certain operational problems have been observed when starting the assembly again after it was shut down. The downtime can vary from several minutes to a few days, depending on the shutdown causes. The gases accumulated in the compressor suction pipe can cause the inlet gas pressure to be above the typical pressure values ranging from atmospheric pressure (1 bar) to 1.5 bar. The compressor is automatically shut down via the sequences implemented in the automation control system if the pressure at the inlet of the compression unit exceeds 1.5 bar, this value being the maximum suction pressure that the compressor unit is designed to withstand. The solution introduces a potentiometer for providing feedback on the suction valve opening angle and thus optimizing the valve control to prevent the occurrence of higher pressures which may lead to failed start-ups or emergency shutdowns.

A new apparatus for investigating gas transport property in geomaterials with ultralow permeability

The gas flow in geological materials with ultra-low permeability can vary dramatically, i. e., from almost no measurable quantity of gas before breakthrough to a massive gas flux at breakthrough. It is a great challenge to realize the whole process measurement of gas transport in saturated geomaterials with ultra-low permeability. In this work, a newly designed temperature-controlled triaxial apparatus was developed. In which, a water-to-gas-exchanger was designed for precise injection of gas at a constant pressure or constant injection rate, due to that water is less compressible and much more difficult to leak through the seal of a regulator. Meanwhile, eddy current sensors and displacement transducer with high resolutions were utilized to accurately measure the specimen deformation at different locations in a non-contact way to explore the mechanism of gas entry and breakthrough. In addition, a gas flow detection device that contains four gas flowmeters with different measurement ranges and can automatically switch between these flowmeters was developed to monitor the gas outflow of the whole process. To validate the performance of the developed apparatus, systematic gas injection tests on Gaomiaozi (GMZ) bentonite were conducted, during which the helium gas was injected in a constant rate. Real-time data on inlet gas pressure, gas outflow rate, stress state (both isotropic and axial stresses) and volume deformation (both axially and radially) were monitored. Results show that the developed apparatus could successfully capture the gas entry and the subsequent breakthrough points of the compacted bentonite with ultralow permeability. For compacted bentonite with high saturation, capillary flow, dilatant flow and interfacial leakage could co-exist during the gas transport process and the dominated mechanism was closely related to the gas injection pressure.

A Pilot Demonstration of Flaring Gas Recovery during Shale Gas Well Completion in Sichuan, China

Summary As one of the largest emitters in the world, the oil and gas industry needs to apply more effort to greenhouse gas (GHG) reduction. Methane, as a potent GHG, could largely determine whether natural gas could serve as a bridging energy toward a sustainable future. In the past decade, oil and gas companies in China have significantly enhanced casing gas recovery and reduced large volume flaring (>2×104 m3/d). However, the remaining low- to mid-volume flaring gas was left for further recovery. Shale gas production in China has met a surge in the number of drilling wells. Those new wells were characterized by a relatively low gas production rate (<1×106 m3/d) in comparison with shale gas wells in the US. As a result, flaring gas during well completion needs to be recycled or used to enhance the gas recovery rate. In this study, we carried out a pilot demonstration project of flaring gas recovery to reduce GHG emissions in the Weiyuan shale gas region in Sichuan Province, China. We adopted the technical route of dehydration and natural gas compression. The recycled natural gas was transformed into compressed natural gas (CNG) and transported to the nearest CNG station for further use. The inlet gas pressure was between 2.85 and 5.82 MPa, and the outlet pressure was kept stable at around 20 MPa to meet the standard of CNG. The manufactured device also showed sound flexibility with the recovery rate between 523.22 and 1224.38 m3/h, which was 28–157% of the designed capacity. The combination of the molecular sieve with high capacity, post low-pressure dehydration, and the application of hydraulic piston in the compression system have guaranteed the equipment to meet the designed performance. The equipment applied in the pilot demonstration has well matched with the local transportation, gas composition, and surface engineering of the well completion. It has the potential of popularization and application in the shale gas tight gas regions in China. Other technical routes, such as small-scale gas to chemicals or natural gas hydrate, should be considered for industrial application for gas flowing rate less than 2×104 m3/d to ensure a further drive down of methane emission along the value chain.