Feed Gas Pressure Research Articles

HYDROGEN GAS RECOVERY THROUGH THE PERMEATION MEMBRANE BASED BIMETALLIC PALLADIUM ALLOY

Generally, the H2 gas produced from the industrial processes is not in a pure state but is mixed with other compounds. For example, the off-gas produced in the oil refinery process still contains CH4, H2, and other gases. Thus, the process of separating as well as recovering the valuable H2 gas from other gas compounds is of essential process. Currently, the H2 separation process is being developed with relatively low costs with good efficiency, namely using the permeation membranes separation process, in which the compounds with high permeability tends to be more easily separated. Here we report the hydrogen recovery process from the mixed H2/N2 off-gas contains 61 % hydrogen and 39% balancing nitrogen, by using the bimetallic Pd-Ag membrane, where the effect of the gas feed pressure (1 and 2 bar) and operating temperature (373.15, 423.15, 473.15, and 523.15, 573.15 K) on the resulting permeate flux is comprehensively studied. We found that the flux and permeability increased with the increase in the gas feed pressure and temperature. Under the same gas temperature of 373.15 K, the permeation flux at the 2 bar gas feed pressure was found to be 2.047 mol.s-1.m-2, which was 166% greater than that of 1 bar pressure, i.e. 1.204 mol.s-1.m-2. Meanwhile, under the same gas feed pressure of 2 bar, the permeation flux at the operating temperature of 573.15 K was found to be 2.103 mol.s-1.m-2, which is 104,9% greater than that of 373.15 K operating temperature, i.e. 2.047 mol.s-1.m-2. These findings suggest the breakthrough advantages of the Pd-Ag alloy membrane for its high hydrogen permeability at low pressure.

Joint experimental-computational: Revealing the role of sodium poly(heptazineimide) in the selective separation of CO2 in PEBAX-based mixed matrix membranes

Mixed matrix membranes (MMMs) with the dual properties of porous materials and polymer matrix membranes have become one of the most optimal solutions to the gas separation problem. However, the adapted porous material and the explicit transport mechanism of gases within the mixed matrix membrane hinder its further commercialization. Thanks to their porous nature and tunable gas adsorption properties, heteroatom-doped porous materials, especially nitrogen-doped porous materials, are widely used to design and prepare advanced CO2 separation membranes. Herein, a layered two-dimensional nano-sheet with a nitrogen content of 44.7 % was successfully synthesized via thermal polymerization. And nano-sheets were homogeneously dispersed in a Pebax matrix to make a composite film. Since the CO2 affinity of the nitrogen functional site and the PEO flexible chain, realizing the synergistic improvement of CO2 permeability and selectivity. A comprehensive combined permeation experimental/simulation characterization reveals the CO2 transport pathway within the membrane, indicating the mechanism of action of nitrogen-doped porous packing on CO2 diffusion. Among these, the CO2 permeability of the mixed matrix film containing 5 wt% sodium poly(heptazine imide) (NaPHI) reached 153 Barrer at a feed gas pressure of 9 bar, nearly 149 % compared to the pure Pebax film. The selectivity of CO2/N2 was enhanced to 105, exhibiting a remarkable increase of 159 % and exceeding the 2019 Robeson limit. Importantly, the present work further reveals and demonstrates the gas separation mechanism of nitrogen-doped porous filler/polymer hybrid matrix membranes, which provides new ideas for the design and application of heteroatom-doped porous fillers in the field of gas separation.

Enhanced natural gas purification by a mixed-matrix membrane with a soft MOF that has a CO2-adapted nanochannel

Mixed-matrix membranes, which are fabricated by incorporating dispersed fillers into continuous polymers, have been considered as a promising and feasible platform for highly efficient gas separation. However, few have impurity-adapted nanochannels. Herein we present a group of mixed-matrix membranes (MMMs) incorporating a soft metal-organic framework (NTU-88c, activated NTU-88) into 6FDA-DAM. The rotation of the pyridyl rings of the ligands in NTU-88c creates a nanochannel with an aperture size of 3.4 Å, which falls between the kinetic parameters of CO2 (3.3 Å) and CH4 (3.8 Å). The membrane shows enhanced CO2 permeability (1140 Barrer) at 60 °C, accompanied by a good separation factor of 45. In addition, an increase in feed gas pressure 1.0 MPa (25 °C) resulted in a notable enhancement in CO2 permeability (645 Barrer), accompanied by a high CO2/CH4 separation factor (41). More importantly, the MMM has demonstrated durable and stable CO2/CH4 separation performance in long-term test, exceeding the Robeson upper-bound, suggesting a promising potential for natural gas purification. Moving forward, the findings of this work not only demonstrate the importance of porous fillers that have impurity-adapted nanochannels for membrane separation, but also offer a route to design and construct high-performance MMMs for feasible applications.

Enhancement of CO2 separation efficiency in mixed matrix membranes through zinc ion modified g‐C3N4 nanosheets

AbstractThis study employed modified graphitic carbon nitride (g‐C3N4) nanosheets and polyether block amide (Pebax) to prepare mixed matrix membranes (MMMs) aiming to enhance CO2 separation efficiency. Through sulfonation and zinc ion (Zn2+) modification of g‐C3N4 nanosheets, high Zn2+ loaded nanofillers (SCN‐Zn2+) were synthesized. Compared to g‐C3N4, MMMs with SCN‐Zn2+ as nanofiller showed a CO2 permeance of 462 Barrer as well as the CO2/N2 selectivity of 47.5 at the feed gas pressure of 2 bar, which surpassed the 2008 Robeson upper bound. Additionally, the Pebax/SCN‐Zn2+(30) membrane was subjected to continuous gas permeability experiments for 70 h and showed good stability. The results showed that SCN‐Zn2+ nanosheets played an important role in enhancing the gas selectivity of the membranes. SEM confirmed that the SCN‐Zn2+ nanosheets had good compatibility with the Pebax substrate and the presence of hydrophilic sulfonic acid groups effectively suppressed the interfacial defects. The increase in the free volume fraction of the membranes as well as the solubility and diffusion coefficient suggested that the introduction of g‐C3N4 nanosheets led to more tortuous gas transport paths, which enhanced the permeability and selectivity of CO2.

Heat integration analysis based on recycle split vapor ethane recovery process

AbstractRecovering ethane from natural gas involves significant energy consumption. Globally, the recycle split vapor process (RSV) is widely adopted as an efficient method for ethane recovery. Nonetheless, one major challenge faced by the RSV process is the lack of adequate heat integration, despite its overall effectiveness. In this article, we investigate the heat integration of the RSV process and propose two novel ethane recovery processes: the recycle split vapor process with direct heat integration of the feed gas (RSV‐DTI) and the recycle split vapor process with split heat integration of the feed gas (RSV‐SHI). A comparative analysis is conducted among these three processes, focusing on integrated energy consumption, exergy efficiency, and economic investment. The study's findings reveal the following: (1) The RSV‐DTI process distinguishes itself with its reduced energy consumption, enhanced stability, and minimized refrigerant usage. In comparison to the RSV process, the RSV‐DTI process achieves a reduction of over 15% in total compression duty and a remarkable decrease of 68% in propane usage. (2) Electricity emerges as the predominant energy consumed in the ethane recovery process, and the RSV‐DTI process significantly improves upon this aspect. Notably, the RSV‐DTI process incurs the lowest investment cost, yielding a swift payback period of approximately 1 year for the plant. The characteristics of the RSV‐DTI process are investigated, and the effect of changes in feed gas conditions on the heat integration of the RSV‐DTI process is analyzed. The characteristics of the RSV‐DTI process show the following: (1) Different pressures of feed gas existing in the main cold box have different minimum heat integration temperatures (MHIT). When the feed gas temperature is lower than the MHIT, heat integration becomes difficult, and the heat energy can be supplied by hot liquid propane at 48°C. When the feed gas temperature is higher than the MHIT, changes in feed gas temperature have little effect on the process, only affecting the external gas temperature. (2) The heat transfer duty of the demethanizer sideline outlet stream is affected by the feed gas pressure. To enhance heat integration, it is recommended to set the heat transfer duty of the low‐temperature sideline outlet stream (DLTSS) between 40% and 90% of the reboiler duty and the heat transfer duty of the high‐temperature sideline outlet stream (DHTSS) between 40% and 75% of the reboiler duty.

Experimental study on charging and discharging characteristics of copper finned metal hydride reactor for stationary hydrogen storage applications

With the shift in power generation methods from conventional to renewable, the need for energy storage has increased, and hydrogen as a carrier has great potential. The storage of hydrogen is one of the main obstacles to the effective deployment of the hydrogen economy. Since metal hydride offers a higher energy density than conventional methods, it can potentially be used to store and deliver hydrogen. Also, the metal hydride hydrogen storage system is the primary element of the energy storage system that connects hydrogen production and consumption. Therefore, the present study is focused on the development and testing of a metal hydride reactor. In the present experimental study, 9 kg of La0.7Ce0.1Ca0.3Ni5 is loaded in a single tube copper finned reactor attached to an external jacket, and the charging and discharging characteristics related to hydrogen storage are analysed along with variations in its thermal performance under various operating conditions. Also, the effect of HTF temperature on the hydrogen release performance of the copper finned reactor is studied under constant discharge pressure and constant discharge flow rate. Further, a comparison has been made between the copper and aluminium finned reactors. This fabricated copper finned reactor attained volumetric and gravimetric storage densities of 21.78 kg per m3 of H2 and 0.77%, respectively. The results indicated that La0.7Ce0.1Ca0.3Ni5 filled within the copper finned reactor stores 1.45 wt.% (130.7 g) of hydrogen in 680 s, corresponding to 25 bar feed gas pressure. At the HTF temperature of 60 °C, the copper-finned reactor discharged 1.42 wt.% (127.3 g) of hydrogen in 1450 s, showing the release of 98% of the stored mass of hydrogen. Further, the developed copper finned MH reactor could supply hydrogen at a constant rate of 13 lpm with a capability of 90% discharge even at a discharge temperature of 30 °C. Beside this, the comparative results showed that adding copper fins showed a considerable improvement over aluminium fins during discharging compared to the charging process. The copper-finned reactor consumed 20.9% and 23.6% less time to release 1 wt.% of hydrogen than the aluminium-finned reactor at discharge temperatures of 40 °C and 50 °C, respectively.

Optimizing carbon capture efficiency with direct capturing and amine: Insights from exegetic analysis

AbstractWith climate change concerns on the rise, finding efficient and sustainable ways to separate carbon dioxide from industrial gas mixtures has become increasingly important. Membrane‐based gas separation technologies offer a promising solution due to their low energy consumption, low emissions, and ease of operation. In this study, we dug deep into theoretical energy consumption and practical optimization strategies for CO2 separation using such technologies. Our results showed that CO2 separation can be achieved with relatively low specific energy consumption, ranging from 0.09 to 0.27 MJe/kg CO2, depending on feed CO2 concentration. By conducting process simulations, we determined the optimal feed gas pressure and membrane surface area required to achieve a CO2 absorption ratio of 90% (mol). We also analyzed the effects of CO2 permeation and selectivity on energy consumption and membrane area, revealing that increasing both can significantly reduce energy consumption, albeit with more membrane surface area required. Using seepage flow circulation was found to be a particularly effective way to improve feed CO2 concentration and reduce energy consumption. To optimize and improve the capturing process, we conducted exergy analysis in each of the five stages of optimization, reporting Cooling Utilities (MW), Heating Utilities (MW), and Total Utilities (MW) for each step. Our results showed that in the optimal mode, Total Utilities (MW) were reported as 228.1, highlighting the potential of membrane‐based CO2 separation for carbon capture and storage applications. This study provides valuable insights and practical strategies for achieving efficient and sustainable CO2 separation.

Monitoring, modeling, and optimization of parameters affecting the recovery efficiency of acid gases from a sweetening unit

Amine processes are the advanced technology available today for the removal of carbon dioxide (CO2) and hydrogen sulfide (H2S) acid gases. Methyldiethanolamine (MDEA) is a well-known tertiary amine used selectively for the removal of carbon dioxide from natural gas. There are many parameters that can affect the efficiency of separating these acid gases from natural gas. In this paper, we have studied, modeled, and optimized different operating parameters of sour gas feed and MDEA solution which affect the CO2 recovery efficiency from an existing sweetening unit. These operating parameters are the sour gas feed temperature and pressure, volume ratio (%) of carbon dioxide in the feed gas, amine inlet temperature, and amine circulation rate. Actual data were collected from an industrial CO2 sweetening unit over one year. These data were used to study the effect of the studied operating parameters on the recovery efficiency of CO2 from the sweetening unit. All studied operating parameters were found to have an impact on the recovery efficiency of the removed gases. A response surface methodology approach was used in Design-Expert software version 13 to model the relationship between considered operating parameters and CO2 recovery efficiency. In addition, Design Expert numerical optimization has been used to maximize CO2 recovery efficiency. The results showed that the optimal range of sour gas feed temperature is 34.71 to 45.56 °C, sour gas feed pressure is 8.32 to 10.04 barg, the volume ratio (%) of carbon dioxide in the sour gas feed is 8.51 to 10.15, the temperature of the amine is 38.03 to 43.96 °C, and the amine circulation rate is 788.39 to 1122.35 m3/h. The presented work can be considered as a guideline for increasing the recovery efficiency of CO2 for both new and existing sweetening units.

An SDBD plasma-based source for efficient degradation of VOCs in an enclosed environment

In this work, a surface dielectric barrier discharge (SDBD) plasma-based source powered by a bipolar pulsed power supply is reported. This source has been tested for the decomposition of toluene and benzene in an enclosed environment of size 12 ft3. Study has been performed to compare decomposition of toluene and benzene on various combinations of the applied voltages and frequencies. For about 60 min of continuous operation of the SDBD source, a decomposition efficiency of 99.7% (toluene) and 74.8% (benzene) has been achieved. For the effective generation of reactive species, the ground electrode of the SDBD source is coated with TiO2 nanoparticles. Optical emission spectroscopy diagnostic has also been used to estimate the electron temperature, which is found to be in the range of 3–6 eV. Consequently, the high energetic electrons produced via the SDBD source are the primary reason to activate the catalyst instead of ultra-violet (UV) light. The results further showed that the developed SDBD source produces powerful, immediate discharge and energetic electrons, which could be efficiently used for volatile organic compounds (VOCs) degradation. The need for feed gas, pellets and/or differential pressure has been eliminated by the developed SDBD source from the known conventional methods for VOCs decomposition.

Efficient deactivation of aerosolized pathogens using a dielectric barrier discharge based cold-plasma detergent in environment device for good indoor air quality

Air pollution is one of the top 5 risks causing chronic diseases according to WHO and airborne transmitted pathogens infection is a huge challenge in the current era. Long living pathogens and small size aerosols are not effectively dealt with by the available indoor air purifiers. In this work, a dielectric barrier discharge (DBD) based portable cold-plasma detergent in environment device is reported and its disinfection efficiency has been analyzed in the indoor environment of sizes up to 3 × 2.4 × 2.4 m3. The deactivation efficiency of total microbial counts (TMCs) and total fungal counts (TFCs) is found to be more than 99% in 90 min of continuous operation of the device at the optimized parameters. The complete inactivation of MS2 phage and Escherichia coli bacteria with more than 5 log reduction (99.999%) has also been achieved in 30 min and 90 min of operation of the device in an enclosed environment. The device is able to produce negative ions predominantly dominated by natural plasma detergent along with positive ions in the environment similar to mother nature. The device comprises a coaxial DBD geometry plasma source with a specially designed wire mesh electrode of mild steel with a thickness of 1 mm. The need for feed gas, pellets and/or differential pressure has been eliminated from the DBD discharge source for efficient air purification. The existence of negative ions for more than 25 s on average is the key advantage, which can also deactivate long living pathogens and small size aerosols.

Enhancing dispersibility of nanofiller via polymer-modification for preparation of mixed matrix membrane with high CO2 separation performance

Mixed matrix membrane (MMM) is now emerging as a viable and promising option for industrial separation processes due to its combination of the benefits of polymers and porous nanofillers. However, the aggregation of nanofillers at high concentrations hinders the development of MMM. Here, we introduce a simple polymeric surface post-modification method by covalently bonding polyvinylamine (PVAm) to prepare polymer-modified Schiff base network-1 (SNW-1) called SNW-P. Adjusting the post-modification time improved the dispersibility of SNW-P. Compared to SNW-1, MMMs with SNW-P4H as nanofiller achieved a significantly high CO2 permeance of 3092 GPU as well as the CO2/N2 selectivity of 184 at the feed gas pressure of 0.2 MPa, which obviously surpasses the current limit enumerated by 2019. Additionally, for CO2/CH4 and CO2/H2 separation, the optimized membrane also exhibits excellent CO2 permeance. With low-cost raw materials and superior properties, the membrane created in our research has good potential for large-scale applications.

Towards retrofitting based multi-criteria analysis of an industrial gas sweetening process: Further insights of CO2 emissions

Natural gas processing is currently facing economic and environmental challenges due to abrupt changes in oil prices and the development of an alternate source of energy. Therefore it is essential to optimize the processing unit to make it profitable and environmentally friendly. Sustainable optimization of an industrial natural gas treatment plant is carried out using the NSGA-II algorithm for the methyl diethanol amine (MDEA) process to optimize CO2 removal along with payback period and damage index. This multi-objective optimization study includes seven decision variables such as temperature and pressure of feed gas, feed flow rate, temperature and pressure of regenerator feed, lean amine temperature, and MDEA concentration. Three separate two-objective optimization study problems are developed and applied for retrofitted case and base case studies. Two different ProMax models are developed and validated the model by using actual plant data. All the retrofitted cases and base cases are solved and the Pareto optimal fronts are obtained. Trade-offs between different objectives are illustrated for all the problems. The lean vapor compression process can facilitate maximum H2S removal of 99.75% and maximum CO2 removal of 98.52% simultaneously by maintaining a DI value of 476. TOPSIS method is used to rank and find the best optimal solution. Optimization study for uncertain CO2 concentration (4%mole) in the feed gas is also analyzed and compared with normal feed conditions. The machine learning approach is used to obtain the predictions of selected objective functions for all the problem cases using the decision tree method.

Model predictive control with exogenous auto-regressive model to improve performance in the CO2 removal

Model predictive control (MPC) is used in the CO2 removal process in the Subang field to improve its control performance. MPC is used to maintain the CO2 concentration at the sweet gas output by controlling the feed gas pressure (PIC-1101), makeup water flow rate (FIC-1102), and amine flow rate (FIC-1103). The empirical model applied to MPC to represent the process model is the auto-regressive exogenous (ARX) model. The ARX model is compared with the first order plus dead time (FOPDT) model based on the root mean square error (RMSE) between the model and the actual process, then MPC parameters are tuned which include sampling time (T), prediction horizon (P) and control horizon (M) to control for the three variables. Improved control performance is measured based on the integral square error (ISE). The results show that the ARX model is the best model for the CO2 removal process with an RMSE value of 35%-91% smaller than the FOPDT model. The optimal control parameters Prediction Horizon (P), Control Horizon (M) and Sampling Time (T) in the CO2 removal process are 75, 25 and 1 on PIC-1101, 25, 10 and 1 on FIC-1102, and 30, 25 and 1 on FIC-1103. The MPC-ARX (MPC using ARX model) can improve the control performance of 33% in the servo control and 6-56% on the regulatory control. However, not all of them showed an increase in control performance improvement from previous studies even though they had used the best model (ARX). This is due to the MPC parameter setting that is not yet appropriate, so it needs to be retuning.

HOF-21 nanofillers incorporated mixed matrix membranes for high-performance N2/CH4 separation

N2/CH4 separation membranes based on N2 preferential permeation can effectively reduce the recompression cost of CH4 gas and show promising application prospects in the field of natural gas purification. However, the performance of N2/CH4 separation membranes still needs to be improved. Here, we report a kind of mixed matrix membranes (MMMs) for N2/CH4 separation via using HOF-21 as nanofiller and 6FDA-DAM polyimide as polymer matrix. In this work, the effects of HOF-21 loading, feed side pressure and temperature based on membrane performance were explored, and finally performance variation of the MMMs with operation time was tested. The incorporated HOF-21 nanoparticles with the most probable pore size of about 3.6 Å can significantly increase the diffusion rate of smaller N2 molecules and enhance the N2/CH4 diffusivity selectivity of the membrane. In addition, compared with polyimide, HOF-21 exhibits almost the same dynamic adsorption of N2 and CH4, which can weaken the solubility of CH4 and enhance the N2/CH4 solubility selectivity of the membrane. When feed gas pressure was 0.2 MPa, the optimum membrane performance was achieved at the HOF-21 loading of 7 wt%, with N2 permeance of 5.13 GPU and N2/CH4 (50/50, vol%) selectivity of 20.52 at 298.15 K. Compared with N2 permeation and N2/CH4 selectivity of the 6FDA-DAM/PAN membrane, the MMMs increased by 67% and 54%, respectively, possessing potential applications in the field of N2 removal in CH4 purification.

Characteristics of hydrogen separation and methane steam reforming in a Pd-based membrane reactor of shell and tube design

This work investigates numerically the characteristics of the two process, hydrogen separation and steam methane reforming (SMR), in a palladium-based (Inconel-supported Pd–Ag film) membrane reactor (MR) of porous reformer (30% Ni/Al2O3) shell and multi-tube design. Still parameters like reactor design and temperature, feed gas concentration and pressure, and flow configuration need more investigation to figure out their impact on hydrogen production rate at lower energy cost and minimum possible volume. This work targets optimization of reactor performance for higher hydrogen yield and coming up with a scalable optimized reactor design for industrial applications. First, an optimization study is performed under non-reforming (separation-only) conditions to optimize the MR design and operating parameters for higher hydrogen production. Then, the study is extended to consider hydrogen separation under SMR conditions to come up with a MR design for hydrogen production at the industrial scale. Hydrogen permeation is limited to small zone near the membrane surface with no effect of feed pressure, inlet gas temperature, and feed hydrogen concentration on widening such zone that necessitates reducing the pitch distance between membrane tubes below 22 mm. The results showed reduced hydrogen permeation rate under SMR conditions compared to the separation-only cases.

Process improvement and heat integration of rich gas ethane recovery

AbstractThe recovery of ethane from natural gas is an important measure to enhance the economic benefit and energy saving of oilfields. In the process of condensation, the gas‐rich ethane recovery process has the problems of high condensation, high methane content, difficult control of cold box pinch temperature, and high energy consumption. Based on the Recycle Split Vapor (RSV) process, two improved processes, Supplemental Rectification with Compression and Recycle Split Vapor (SRCR) and Recycle Split Vapor with Liquid Flashing (RSVL), are proposed. Energy consumption analysis shows that RSVL process has the lowest total compression power and lower investment cost than SRCR process. The heat integration analysis shows that the ratios R1 and R2 of the demethanizer side‐draw duty directly influence the temperature matching of the cold and hot streams in the main cold box. For rich gas, R1 is advised to set between .5 and .75, and R2 is advised to set between .6 and .8. The sensitivity analysis shows that the lower the feed gas pressure and the richer the gas, the higher the total compression power of the process, and the closer the composite curve of cold and heat in the main cold box. The higher the feed gas temperature, the greater the total compression power. The higher the CO2 content in the feed gas, the higher the total compression power of the RSVL process, and the smaller the CO2 freezing temperature in the demethanizer.

Nanohybrid Pebax/PEGDA-GPTMS membrane with semi-interpenetrating network structure for enhanced CO2 separations

Polymeric membranes containing polyethylene oxide (PEO) groups are promising CO2 separation materials, but suffer from the trade-off between separation performance and mechanical strength. To overcome this challenge, we combine the merits of semi-interpenetrating polymer network and nanohybrid to maintain a high PEO loading and robust membrane structure. The membranes were prepared by introducing in-situ formed PEO networks with silica nodes into Pebax1657 to produce a semi-interpenetrating network structure. The introduced network and in situ formed silica nanoparticles reduce the chain packing efficiency of Pebax matrix to enhance the CO2 diffusivity, while the increased PEO content enhances CO2 solubility. Under feed gas pressure of 25 bar, nanohybrid membranes containing 40 wt% polymer network display excellent gas separation performance with CO2 permeability of 272.8 Barrer and CO2/N2 selectivity of 79.6 under mixed gas separation tests, surpassing 2008 Robeson upper bound. Moreover, the hybrid membranes showed high mechanical strength, the Young's modulus increases by 1.95 times. This strategy provides a simple route for the design of nanohybrid membranes with high separation performance as well as excellent durability.

Feasibility Analysis of Typical Cryogenic Processes for Hydrogen-Mixed Natural Gas Separation

Hydrogen energy is a crucial carrier for the growth of the energy system and its low-carbon transformation. Using natural gas as a carrier of hydrogen transport and the natural gas pipeline network for transportation is a significant step toward realizing large-scale and long-distance hydrogen transport. Hydrogen-mixed natural gas is mainly separated into hydrogen and natural gas by physical methods at present. High purity of hydrogen recovery, but the recovery rate is low. At the same time, compared with natural gas, liquefied natural gas is more economical and flexible. This study analyzes three typical cryogenic separation processes. The results show that the hydrogen separation efficiency and specific energy consumption increase and the liquefaction rate and energy consumption decrease as the hydrogen ratio increases. The energy consumption and specific energy consumption of C3-MRC are lower than the MRC and the cascade liquefaction processes. Besides, as the pressure increases in the C3-MRC liquefaction process, the liquefaction and hydrogen separation efficiency increase and subsequently drop. Different hydrogen content has the highest hydrogen separation efficiency and liquefaction efficiency under different feed gas pressure conditions. The total exergy losses of the C3-MRC are the least in different hydrogen fractions, which are 37.59% and 21.77% less in the 25% hydrogen fraction, and 37.89% and 21.37% less in the 30% hydrogen fraction. Moreover, the exergy efficiency of C3-MRC are 87.68% and 88.06% when the hydrogen fraction are 25% and 30%, higher than the other two processes, which implies that in 25% and 30% fractions, making it more suitable for separate the hydrogen by the cryogenic separation.

High speed melt flow monitoring and development of an image processing algorithm for laser fusion cutting

This contribution presents high-speed camera monitoring of melt pool dynamics for steel during laser fusion cutting and compares the images with recordings in aluminum. The experiments are performed by a 4 kW multimode fiber laser with an emission wavelength of 1070 nm. To visualize the thermal radiation from the process zone during the cutting process, the kerf is captured at sample rates of up to 170 000 frames per second without external illumination with a spectral response between 400 and 700 nm, allowing measurements of the melt flow dynamics from geometric image features. The dependencies of the melt flow dynamics on laser processing parameters, such as feed rate, gas pressure, and laser power, can be evaluated. The monitoring system is placed both off-axis and mounted to a conventional cutting head, with the monitoring path aligned to the processing laser for a coaxial and lateral view of the cut kerf. The measured signal characteristics of the images captured from the melt pool are examined in the visible spectral range of the emitted thermal radiation from the process zone. Moreover, a specifically developed image processing algorithm is developed that process and analyze the captured images and extract geometric information for a measurement of the melt flow.

On the Pneumatic Hammer of Hybrid Gas Bearings: Measurements and Predictions

Abstract Hybrid bearings integrating an external pressurizing source are widely used in high-speed turbomachinery due to their notable advantages, including low friction and wear, enhanced reliability and durability, and accurate rotor positioning, as well as large static stiffness and load carry capacity even lubricated with low viscosity liquids. This paper reports experimental data and predictions to identify the characteristics of pneumatic hammer of hybrid gas bearings, 60 mm in diameter, with increasing feed gas pressures. Pneumatic hammer characteristics with static load stiffnesses and flow rates of the test bearing are recorded for increasing static loads with various shaft center positions. A computational program for modeling of hybrid gas bearings predicts static load characteristics of the test bearings. Predictions show a remarkable agreement with measurements. Comparisons of measurements and predictions reveal that calculated reduced damping factors and damping coefficients of hybrid bearings, relying on volume ratio between recess and fluid film, are reliable indicators to estimate the onset condition of pneumatic hammer instability.