High Pressure Operation Research Articles

Unveiling the high-pressure behavior of thymol+carvone NADES: A combined experimental-computational approach

this study considers the high-pressure behavior of thymol + carvone Natural Deep Eutectic Solvent using a combined experimental and computational approach. Experimentally, PVT (pressure – volume/density - temperature) measurements were conducted to characterize the fluid volumetric behavior as well as compressibility and internal pressure, which are directly related with hydrogen bonding and nanoscopic structuring. Likewise, these measurements provide crucial insights into the thermodynamic properties of the considered fluid under high pressure, which is pivotal for scaling up and process design for high pressure operations. Computationally, the PC-SAFT equation of state was employed to predict phase equilibria and PVT behavior, Machine Learning for density predictions, while Density Functional Theory and Classical Molecular Dynamics simulations were considered for the structural and dynamic characterization. These simulations provides insights into the electronic structure, intermolecular interactions (hydrogen bonding), liquid structuring and they unveil the pressure's impact on microscopic interactions, structural organization, and transport properties. This comprehensive investigation aims to shed light on the behavior under high pressure, facilitating their optimization for applications in chemical processing, energy storage, and materials science.

Suitability of Test Procedures for Determining the Compatibility of Seal Materials with Ionic Hydraulic Fluids.

The compatibility of seal materials with the working fluid is crucial for the flawless, energy-saving, environmentally sustainable, and safe operation of any technical system. This is especially true for hydraulic systems operating under high operating pressure. The problem of materials compatibility comes into play when either a new type of seal material or a new type of fluid comes into use. The paper discusses the research findings regarding material compatibility testing of new high-tech ionic hydraulic fluids with commonly used seal materials. Due to the completely different chemical composition of these new fluids compared to the classical mineral-based oil, for these fluids, there are no standardized testing procedures. In these cases, we can only lean on the Standards that apply to classical fluids, which can lead to incorrect results. In the forefront of the paper is the discrepancy between the results obtained by the standardized test, and the test under real operating conditions. FKM, an excellent material for seals, proved to be the most suitable in the case of using ionic hydraulic fluid, according to a standardized test. However, it failed in the comparison test under real operating conditions, as the cylinder leaked. NBR seals proved to be a better solution.

The thermal-mechanical deformations of CO2 mixture gases dry gas seal based on two-way thermal-fluid-solid coupling model

PurposeThis study aims to investigate the influence mechanism of thermal-mechanical deformations on the CO2 mixture gases dry gas seal (DGS) flow field and compare the deformation characteristics and sealing performance between two-way and one-way thermal-fluid-solid coupling models.Design/methodology/approachThe authors established a two-way thermal-fluid-solid coupling model by using gas film thickness as the transfer parameter between the fluid and solid domain, and the model was solved using the finite difference method and finite element method. The thermal-mechanical deformations of the sealing rings, the influence of face deformation on the flow field and sealing performance were obtained.FindingsThermal-mechanical deformations cause a convergent gap between the two sealing end faces, resulting in an increase in the gas film thickness, but a decrease in the gas film temperature and sealing ring temperature. The axial relative deformations of rotating and stationary ring end faces caused by mechanical and thermal loads in the two-way coupling model are less than those in the one-way coupling (OWC) model, and the gas film thickness and leakage rate are larger than those in the OWC model, whereas the gas film stiffness is the opposite.Originality/valueThis paper provides a theoretical support and reference for the operational stability and structural optimization design of CO2 mixture gases DGS under high-pressure and high-speed operation conditions.

Multi-Dimensional Modelling of Bioinspired Flow Channels Based on Plant Leaves for PEM Electrolyser

The Polymer Electrolyte Membrane Water Electrolyser (PEMWE) has gained significant interest among various electrolysis methods due to its ability to produce highly purified, compressed hydrogen. The spatial configuration of bipolar plates and their flow channel patterns play a critical role in the efficiency and longevity of the PEM water electrolyser. Optimally designed flow channels ensure uniform pressure and velocity distribution across the stack, enabling high-pressure operation and facilitating high current densities. This study uses flow channel geometry inspired by authentic vine leaf patterns found in biomass, based on various plant leaves, including Soybean, Victoria Amazonica, Water Lily, Nelumbo Nucifera, Kiwi, and Acalypha Hispida leaves, as a novel channel pattern to design a PEM bipolar plate with a circular cross-section area of 13.85 cm2. The proposed bipolar design is further analysed with COMSOL Multiphysics to integrate the conservation of mass and momentum, molecular diffusion (Maxwell–Stefan), charge transfer equations, and other fabrication factors into a cohesive single-domain model. The simulation results showed that the novel designs have the most uniform velocity profile, lower pressure drop, superior pressure distribution, and heightened mixture homogeneity compared to the traditional serpentine models.

Study on turbine blade overall cooling effectiveness under thermal radiation and non-uniform inlet temperature

As the inlet temperature of the turbine continues to rise, if only heat conduction and convective heat transfer are considered, the temperature difference between numerical simulation and experimental will become apparent. The overall cooling effectiveness is generally used to evaluate the effect of cooling structures. However, the overall cooling effectiveness of turbine blades is difficult to measure directly due to the high temperature and pressure operating conditions. If the analogy method is established, the measurement of the overall cooling effectiveness of turbine blades under engine conditions can be carried out under experimental conditions. Therefore, it is important to study the analogy method of overall cooling effectiveness under thermal radiation. The analogy method of the overall cooling effectiveness under thermal radiation was established through one-dimensional coupled heat transfer analysis, which proposed to match the radiation term by Burger number and Boltzmann number. The matching characteristics under non-uniform inlet temperature were analyzed using numerical simulation. The results show that the method of matching the radiation term of overall cooling effectiveness is verified by numerical results. The effect of non-uniform inlet temperature on the overall cooling effectiveness matching is strongly correlated with temperature ratio, so the matching of temperature ratio should be prioritized.

Ferritic–Martensitic Steels in Power Industry: Microstructure, Degradation Mechanism, and Strengthening Methods

Ferritic–martensitic (F–M) steels are widely used for high‐temperature pressure vessels and reactor cladding structures in power plants. The high operating temperatures and pressures, as well as the radiation environment, significantly challenge the mechanical stability of these steels. Here, the degradation mechanisms in F–M steels during creep and thermal aging under these harsh environments are reviewed. The exceptional mechanical properties of F–M steels are mainly attributed to their well‐constructed microstructures and chemical compositions. Microstructural barriers such as dislocations, solid solution atoms, and precipitates play key roles in resisting degradation. During the long‐term service, the microstructures undergo gradual evolution, resulting in a deterioration of mechanical properties at the macrolevel. In addition to the degradation mechanisms, some recent advancements in strengthening methods, including microalloying strengthening, thermomechanical treatment (TMT), and oxide dispersion strengthening, are summarized, aimed at the development of next‐generation F–M steels. The strengthening of the F–M steels is mainly achieved by enhancing the thermal stability of their microstructures. Insight into both the deterioration mechanisms and strengthening methods of F–M steels may pave the way for new approaches in developing high‐performance steels for applications in next‐generation power plants operating at ultrahigh operating temperatures and pressures.

A Review of Catalyst Integration in Hydrothermal Gasification

Industrial scale-up of hydrothermal supercritical water gasification process requires catalytic integration to reduce the high operational temperatures and pressures to enhance controlled chemical reaction pathways, product yields, and overall process economics. There is greater literature disparity in consensus on what is the best catalyst and reactor design for hydrothermal gasification. This arises from the limited research on catalysis in continuous flow hydrothermal systems and rudimentary lab-scale experimentation on simple biomasses. This review summarizes the literature status of catalytic hydrothermal processing, especially for continuous gasification and in situ catalyst handling. The rationale for using low and high temperatures during catalytic hydrothermal processing is highlighted. The role of homogeneous and heterogeneous catalysts in hydrothermal gasification is presented. In addition, the rationale behind certain designs and component selection for catalytic investigations in continuous hydrothermal conversion is highlighted. Furthermore, the effect of different classes of catalysts on the reactor and reactions are elaborated. Overall, design and infrastructural challenges such as plugging, corrosion, agglomeration of the catalysts, catalyst metal leaching, and practical assessment of catalyst integration towards enhancement of process economics still present open questions. Therefore, strategies for catalytic configuration in continuous hydrothermal process must be evaluated on a system-by-system basis depending on the feedstock and experimental goals.

Effectiveness of Gas Recombination Catalyst Layers in Mitigating H2 Crossover in PEM Water Electrolyzers Operating at High Differential Pressure

Gigawatt-scale deployment of proton exchange membrane water electrolyzers (PEMWE) to produce green hydrogen at $1/kg of H2, the US department of energy’s (DOE) ultimate cost target, requires the use of thinner membranes to reduce ohmic losses at high current densities as well as differential pressure operation to improve the overall system efficiency.1 High differential pressure operation results in significant hydrogen crossover through PEMs leading to safety concerns due to the formation of a flammable gas mixtures at anode (> 4% H2 in O2).2 Therefore, the successful deployment of PEMWEs at scale relies on successful implementation strategies to reduce the hydrogen concentration at anode to enable safe operation at high efficiency. These strategies include incorporating gas recombination catalyst (GRC) in the membrane, PTL or downstream in the anode gas outlet. However, the impact of GRC layers on PEMWE performance and hydrogen crossover rates at high differential pressure is not well understood.In this work, we employ in-operando gas chromatography coupled with thermal conductivity detector along with PEMWEs operating at differential pressures (up to 30 bar) to quantify hydrogen crossover rates through PEM at differential pressure. Using this setup, we evaluate the effectiveness of gas recombination layers incorporated in PEMWE membrane electrode assemblies (MEA) in mitigating the risk of formation of the flammable gas mixture. Further, we will also discuss implications of high differential pressure operation on PEMWE performance, durability, and operational safety.

Numerical Investigation on Two-Phase Flow-Electrochemical Reaction Coupling in PEM Water Electrolyzers Porous Transport Layer Under High Operating Pressures

Proton exchange membrane water electrolyzers (PEMWEs) operated at high pressures have advantages such as lower energy consumption, reduced noise, and absence of component slippage. They have a more robust potential for commercial applications than other electrolyzers. The transport characteristics of two-phase flow within the porous transport layer (PTL) and channels are not well understood, especially under high-pressure conditions. The gas bubbles generated in the catalyst layer (CL) pass through the PTL and reach the flow channel. However, oxygen evolution reaction in the anode CL may be limited if these bubbles block the pathway of liquid water, causing reactant starvation. The interaction between electrochemical reactions and gas bubbles thus directly impacts a PEMWE's efficiency. This study aims to investigate the coupling between the two-phase flow and electrochemical reactions under high-pressure conditions.A two-dimensional (2D) CFD model was developed to simulate the bubbly flow through a reconstructed PTL. The volume of fluid (VOF) method was employed to capture bubble growth, movement, and detachment, as illustrated in Figure 1. The coupling of bubble transport and electrochemical reactions was achieved through the application of a weighted averaging method. A cross-section of a stochastically reconstructed titanium felt model was generated as the computational domain; see Fig. 1(a). The computation domain consists of a liquid water channel, a PTL, and a simplified CL interface at the bottom. The CL's reaction rate is modeled as a function of local bubble coverage on the CL interface. Transient simulations of the two-phase flow of the PEMWE anode side were carried out for pressures ranging from 1 bar to 200 bar. The simulation results elucidate the flow characteristics of liquid water in the PTL under high-pressure conditions and quantitatively reveal the coupling between two-phase flow and electrochemical reactions. The behavior of the two-phase flow in PEMWE is found to be sensitive to operating pressure. As the operating pressure increases, the size of bubbles generated on the CL interface decreases, resulting in a higher permeability of liquid water than that under low pressures. When the flow rate of liquid water in the channel is sufficiently high, bubbles do not fully develop and are rapidly removed from the domain. This phenomenon significantly shifts the two-phase flow regime within the channels,. Furthermore, the activation overpotential is substantially reduced under high-pressure conditions. The present study demonstrates a numerical simulation tool for high-pressure PEMWE. A future study of a full 3D PTL model is currently underway. Figure 1

(Invited) Targeted Research to Develop Next Generation PEM Water Electrolyzers

The utilization of low-carbon intensity hydrogen as an energy carrier promises a path to the decarbonization of sectors including electricity, heavy-duty transportation, and industry at scale. The United States Department of Energy is investing into this opportunity by heavily supporting research and development efforts for hydrogen production at scale. In recent years, the DOE has established the H2NEW consortium which consists of nine national labs and additional partners to focus on the advancement of water electrolysis. It also launched the Hydrogen Energy Earthshot in 2021, targeting the reduction of clean hydrogen production cost by 80% from $5 to $1 per 1 kg H2 produced in 1 decade. For these efforts to be successful, techno-economic analyses are used to identify the research and development areas with the greatest impact, supporting targeted studies on scalable manufacturing and materials that lower capital costs, produce hydrogen efficiently, and enable durable operation over the system lifetime.In this presentation the challenges and trade-offs of electrolyzer operation for renewable hydrogen generation will be reviewed, and results from targeted NREL studies on components, materials and interfaces will be discussed in detail, including for example PTL morphology, PTL coatings, and PTL/catalyst layer interactions and their effect on operation with thin membrane materials, hydrogen crossover and voltage loss contributions. The presentation also touches on any advanced in-situ diagnostic development that was required for the studies, such as high pressure operation, hydrogen crossover quantification, high throughput testing, and spatial diagnostics.

Thin Film Based Membrane Electrode Assemblies for Solid-State Ammonia Synthesis

Ammonia is the of the most crucial chemicals and currently primarily produced through the Haber-Bosch process causing the industrial ammonia production to emit more CO2 than any other chemical-making reaction. While the current primary function of ammonia lies within the fertilizer production, it can also be directly used as a fuel for power generation or in the maritime industry. Compared to hydrogen, ammonia has superior storage and transportation capabilities due to its greater volumetric energy density and mild conditions for liquefication. Given the need of reducing global carbon emissions, ammonia could be synthesized electrochemically using air, water and electricity by the Solid-State Ammonia Synthesis (SSAS). Protonic ceramic cells operate within an intermediate temperature regime of around 450 - 550 °C which is well suited for this process. Within our work, we present a tubular membrane electrode unit entirely made of ceramic components based on a barium zirconate thin film electrolyte. An ammonia production rate of 9.06 × 10-10 mol s-1 cm-2 and a Faradaicefficiency of 6.58% were achieved using a NiO-BaZr0.7Ce0.2Y0.1O3- δ | BaZr0.8Y0.2O3- δ | Ru@Ba0.5Sr0.5TiO3-δ cell.A key innovation lies in the production of dense BaZr0.8Y0.2O3-δ electrolyte layers, ranging from 1 to 5 µm in thickness, utilizing a Closed-Field Unbalanced Magnetron Sputtering (CFUMS) process. This technique allows precise adjustments of stoichiometric ratios within the perovskite structure, offering improved sputtering yields compared to conventional methods. Furthermore, the crystallinity, phase purity, and microstructure of sputter-deposited thin films are enhanced through selective laser annealing (SLA), resulting in high-density films composed of single-phase BaZr0.8Y0.2O3-δ with average crystallite sizes of 200 nm while avoiding substrate damage from thermal stress. Electrochemical performance was evaluated through impedance spectroscopy, half-cell tests and full cell tests providing insights into the efficacy of the developed tubular membrane reactor for the electrochemical synthesis of ammonia. The results demonstrate the feasibility of utilizing ceramic proton conductors in SSAS, particularly highlighting the potential of high-pressure operation up to 80 bars in tubular cells at relatively low temperatures around 450 °C, thereby achieving attractive NH3 production rates.This research contributes to the evolving landscape of sustainable ammonia synthesis by presenting a novel approach that integrates advanced materials and manufacturing techniques. Electrification and decentralization of the ammonia supply chain will expand the market by supporting its current use as fertilizer source and enable a new route as green energy carrier paving the way for an ammonia-based economy. Figure 1

Plasma control for the step prototype power plant

In 2019 the UK launched the Spherical Tokamak for Energy Production (STEP) programme to design and build a prototype electricity producing nuclear fusion power plant, aiming to start operation around 2040. The plant should lay the foundation for the development of commercial nuclear fusion power plants. The design is based on the spherical tokamak principle, which opens a route to high pressure, steady state, operation. While facilitating steady state operation, the spherical design introduces some specific plasma control challenges: (i) All plasma current during the burn phase should to be generated through non-inductive means, dominated by bootstrap current. This leads to operation at high normalised plasma pressure βN with high plasma elongation, which in turn imposes effective active stabilisation of the vertical plasma position. (ii) The tight aspect ratio means very limited space for a central solenoid, imposing that even the current ramp up must be non-inductively generated. (iii) The compact design leads to extreme heat loads on plasma facing components. A double null design has been chosen to spread this load, putting strict demands on the control of the unstable vertical plasma position. (iv) The heat pulses associated with unmitigated ELMs are unlikely to be acceptable imposing ELM free operation or active ELM control. (v) To reduce and spread heat loads, core and divertor radiation and momentum loss has to be controlled, aiming to operate with simultaneously detached upper and lower divertors. (vi) High pressure operation is likely to require active resistive wall mode (RWM) stabilisation. (vii) The conductivity distribution in structures near the plasma must be carefully selected to reduce the growth rates for the vertical instability and the RWM without damping the penetration of the of magnetic fields from active control coils too much. This article describes the initial work carried out to develop a STEP plasma control system.

Engineered loose nanofiltration membrane for efficient dye/salt separation by starting from poly(ether sulfone) powder modification

Loose nanofiltration (LNF) is increasingly considered as the powerful technique for dye desalination due to its clear advantages at energy efficiency, selectivity and low pollution. But the membrane materials for loose nanofiltration process still suffer from the low permeance, unsatisfactory selectivity, membrane fouling and high cost. Herein, we propose a new three-step route to fabricate efficient poly(ether sulfone) (PES) LNF membrane, which starts from PES powder modification via mutual radiation-induced grafting polymerization and ensues immersion precipitation phase inversion and amination processes. The obtained PES-based LNF membrane possessed a thinner skin layer and an unusual irregular vesicular pore structure in sublayer instead of the finger-like macrovoids of conventional PES membrane. Thus, it achieved larger filtration permeance (35.5 L m–2 h−1 bar−1), high dye rejection (93.7 % to Congo Red) but low salt rejection (2.9 % to NaCl) during the filtration process of Congo red-containing saline water. It also showed excellent separation stability at high operation pressure and tolerance to acidic, alkaline and chlorine-oxidative conditions. Therefore, such a three-step strategy could endow the PES membrane with both loose and thinner skin layer in a reliable and scalable way, enlightening the development of high-performance LNF membrane for wastewater treatment and resource recovery.

Selective anion exchange adsorption of molybdenum(VI) at low concentrations from an acid leached vanadium shale solution containing aluminium and phosphorus

With a decline in high-grade molybdenum reserves, the development of other types of molybdenum resources have received increasing attention. Vanadium shale is a multi-metal shale and fine-grained sedimentary rock comprising small grains and various minerals. After leaching and extracting vanadium, the solution often contains a low concentration of molybdenum. However, because of the low molybdenum concentration, many processing plants treat it as an acidic wastewater, which wastes molybdenum resources and carries the risk of environmental pollution. The leaching process of vanadium shale mostly involves high-temperature and high-pressure operations, which greatly increase the content of impurity ions such as aluminium and phosphorus in the pregnant leach solution. These impurity ions increase the difficulty in separating and recovering molybdenum. In this study, the adsorption and separation of molybdenum at leach liquor of low molybdenum concentration were investigated. The effects of different factors such as: (i) pH of feed solution, (ii) adsorption time, and (iii) presence of impurity ions, aluminium and phosphorus, on the adsorption and separation of molybdenum using five different anion-exchange resins, D201, D296, D301, D314, and D301R, were investigated. The static adsorption and desorption test results showed a molybdenum adsorption capacity of 222 mg/g at pH = 1.5 by the D301 resin. The desorption efficiency using 20% NH₄OH was 96.1%. The adsorption efficiencies of aluminium and phosphorus were 1.31% and 3.10%, respectively. This is a better choice for separating molybdenum from complex solutions. The experimental results from spectra and theoretical calculations showed that the -NH group of D301 resin was combined with the O atoms of MoO3·3H2O, Al(SO4)2−, and H2PO4− by electrostatic attraction. The binding energies of these three species were − 311 kJ/mol, −231 kJ/mol, and − 62.0 kJ/mol respectively, indicating that D301 resin preferentially adsorbed MoO3·3H2O. Based on the above results, the D301 resin can adsorb molybdenum(VI) in complex solutions under low pH conditions, and this study is expected to promote the comprehensive recovery of valuable metals from vanadium shale.

Peran Apron Movement Control (AMC) Dalam Menerapkan Kedisiplinan Kerja Karyawan Di Bandar Udara Internasional Sultan Hasanuddin Makassar

Air transportation is the primary choice due to its speed, safety, and comfort. Airports are places where aircraft land and take off and conduct various activities related to passengers and cargo, categorized into domestic and international. The Apron Movement Control (AMC) unit at PT Angkasa Pura I oversees movements in the apron area and provides services to airport users. Strict supervision is required to maintain safety and discipline on the apron. However, observations at the AMC at Sultan Hasanuddin International Airport in Makassar show a lack of discipline among staff, such as oil spills on the apron, which pose a safety hazard. This research aims to understand the role of AMC in enforcing employee discipline and the challenges faced at Sultan Hasanuddin International Airport in Makassar. This research employs a qualitative approach to understand the phenomena in the Apron Movement Control unit at PT Angkasa Pura I, Sultan Hasanuddin International Airport in Makassar, from June 1 to July 31, 2024. Primary data were collected through interviews and direct observations, while secondary data were obtained from company documents and literature studies. Data analysis involves reduction, presentation, and conclusion drawing, with data validity tested through source, technique, and time triangulation. Research steps include interviews, observations, data analysis, and conclusion drawing.The results show that the Apron Movement Control (AMC) unit at Sultan Hasanuddin International Airport in Makassar plays a crucial role in maintaining security, order, and discipline on the apron. They control the movements of aircraft, vehicles, and personnel and ensure operations follow safety procedures. AMC also acts as disciplinarian and educator through regular training. However, they face challenges such as a lack of employee understanding of procedures, limited communication equipment, communication challenges due to noise, and high operational pressure. To overcome these challenges, AMC needs to strengthen training, improve communication and coordination, enhance facilities, and increase employee welfare. These measures are expected to improve AMC's performance and instill a strong work discipline culture, making them the front line in maintaining airport security and operational efficiency.

Direct ESI-MS of Ionic Liquids Using High-Pressure Electrospray From Large-Bore Emitters Made of Micropipette Tips.

Electrospray ionization mass spectrometry of neat undiluted ionic liquid (IL) and the analysis of protein with the doping of IL were performed using high-pressure electrospray. The use of disposable micropipette tips as emitters eased the handling of viscous and easy-to-clog samples and improved the reproducibility of the measurement. A high-pressure operation enabled the stable electrospray of the highly conductive IL from these relatively large bore emitters. The measurement of the current-voltage relationship of 1-ethyl-3-methylimidazolium tetrafluoroborate (Emim BF4) revealed an unusual negative differential resistance that has not been seen in the typical atmospheric or high-pressure electrospray. Mass spectrometric analysis of this IL also showed the characteristic response of various ion species with the emitter voltage. When added to the commonly used protein solution, the mass spectrum also showed protein peaks that correspond to the adduction of fluoroboric acid molecules (HBF4).

3D volume construction methodology for cold spray additive manufacturing

Cold spraying has proved as an attractive and rapidly developing solid-state material deposition process that allows for fast formation of high quality, large 3D volume objects. Low risks of undesirable heat effects lead to increased interest in cold spraying based rapid additive manufacturing. However, by continuous powder spraying and high-pressure gas operation, cold spray additive manufacturing in terms of shape building is sensitive to operating parameters and imposes high requirements on the control of process conditions and locally needed kinematics. Every step of the manufacturing process therefore needs to be meticulously conceived and planned, especially the toolpath planning and implementation. This is not only essential to meet basic performance requirements, but also needed for the desired geometric accuracy. To address these needs, this study presents a new implementation method for cold spray additive manufacturing to improve manufacturing accuracy and flexibility. The workflow and principles of the proposed method are explained and strategies are presented for building up various component types, including rotational geometries as well as freestanding parts. The developed algorithms for 3D applications can be well integrated into the cold spray additive manufacturing process for toolpath planning and path parameter determination. Reliable and accurate robot programs were developed to make the process easy to repeat and to follow. Toolpath planning and robot programming are supported and performed by applying virtual cells to simulate the automation process for the real scenario. Path parameter adjustment and kinematic optimization can then be conducted according to the feedback from the simulation result. Applied benchmarking tests prove acceptable shape accuracy and demonstrate that the current method can enhance the capabilities of cold spray additive manufacturing for near-net shape construction. This implies that careful planning and manufacturing strategies should enable overcoming the challenges associated with cold spray additive manufacturing.

Factors affecting deposit formation in foul condensate stripping systems

In kraft pulp mills, foul condensates are often steam-stripped to produce clean condensate for use as process water. The formation of organic deposits in the stripped condensate is a common problem. A systematic study was conducted to examine the deposit composition and the most likely operating parameters responsible for stripped condensate contamination experienced at a kraft mill in Brazil. Daily averaged data of 170 operating parameters over a 15-month period were analyzed by means of multivariate discriminant analysis and random forest classification analysis. The results showed that the deposit formation is related to high temperature, pressure, and dry solids operations in various evaporator effects. These conditions, combined with the poor demisting efficiency in these effects, may have increased black liquor carryover mist in the vapor. Deposit formation also appeared to be related to increased throughput of the foul condensate stripping system and increased pressure in the stripper. Results of Fourier transform infrared spectroscopy (FTIR) and pyrolysis-gas chromatography mass spectrometry (Py-GCMS) analyses show that the deposit consists of mostly organic matter that likely originated from wood extractives and lignin.

Study on interdigital flow field structure and two phase flow characteristics of PEM electrolyzer

Proton exchange membrane (PEM) electrolytic hydrogen production has the advantages of high current density, high operating pressure, wide power regulation range and so on. It has good adaptability to wind and photovoltaic power with high volatility and recognized as an important way to solve the effective utilization of renewable energy. In PEM electrolyzer cell (PEMEC), anode flow field plate plays a crucial role in the process of water electrolysis to produce oxygen, which affects the of gas and liquid transfer. Among them, the channel blockage caused by bubble retention is an important factor limiting the performance of PEMEC. In this paper, an interdigital flow field plate is designed based on the plant leaf vein system. The two-phase flow behaviors within the interdigital flow field channel are studied. The results show that the interdigital flow field plate is superior to the traditional serpentine flow field in terms of electrolytic efficiency and voltage loss. The reaction kinetics rate is accelerated, the overall ohmic resistance is reduced by about 4.8 %, and the hydrogen production is increased by about 9.1 %. The above research can provide guidance for the structural improvement and performance improvement of PEMEC.

A hydrate-based post-combustion capture system integrated with cold energy: Thermodynamic analysis, process modeling and energy optimization

Carbon capture is a crucial part of global warming mitigation. Carbon capture via clathrate hydrate is an attractive approach due to its high capture capacity, high carbon dioxide purity, water-based benign process, ease of recycling, and robustness to contaminants. In this work, we propose a two-stage hydrate-based carbon dioxide separation system integrated with cold energy for carbon capture from flue gases. A thermodynamic cycle consisting of two sub-cycles was constructed to simulate the process. Operating conditions were optimized within the range of 274.15–282.15 K and 0.1–28.04 MPa, resulting in the lowest electricity consumption of 2.22 MJ/kg CO2 with 95.24 mol% CO2 purity and 65.97 % CO2 recovery. A higher CO2 recovery rate can be achieved by recycling the residual gas of Sub-cycle 2. Gas compression to the high operating pressure (16.01 MPa) is the major contributor to electricity consumption. By incorporating 100 % expansion work recovery from the high-pressure gases, the electricity consumption can be reduced to 0.43 MJ/kg CO2 (i.e., 0.119 kWh/kg CO2). A more realistic scenario assuming 80 % compression/pumping efficiency and 90 % expansion work recovery gives an electricity consumption of 1.16 MJ/kg CO2 (i.e., 0.322 kWh/kg CO2), representing an energy penalty of 33.1 % for a coal-fired power plant. Future direction for further improvement could be a paradigm shift to hydrate process with thermodynamic promoters, which can potentially reduce the operation pressure by over 90 % and thus cut down the energy consumption dramatically. This work established a framework to simulate the hydrate-based carbon capture process, evaluated its minimum energy consumption and examined how operating conditions affect the separation performance. The results could offer valuable guidelines for the design and optimization of real hydrate-based carbon capture systems.