Similar Process Conditions Research Articles

Thermodynamic Modeling of an Aqueous N,N-Dimethyldipropylenetriamine and Benzylamine Blend for Efficient CO2 Capture.

This study evaluates the carbon dioxide (CO2) capture capabilities of a novel aqueous blend of N,N-dimethyldipropylenetriamine (DMDPTA) and benzylamine (BA). The solvent properties such density, vapor- liquid equilibrium (VLE) of CO2 in the solvent, CO2 absorption enthalpy are evaluated experimentally for solvent composition of (5 mass% DMDPTA + 25 mass% BA), (10 mass% DMDPTA + 20 mass% BA), and (15 mass% DMDPTA + 15 mass% BA). Solvent density were measured in the temperature range of 303.15K-333.15K and correlated using Redlich-Kister excess molar volume model, with a low average absolute relative deviation (AARD) of 0.014. VLE data was measured using a custom-made stirred VLE cell, within CO2 partial pressure range of 2-200 kPa and at temperatures 313.15K, 323.15K and 333.15K. Equilibrium CO2 solubility data were correlated using a modified Kent-Eisenberg model, achieving an AARD of 1.5%. Enthalpy of CO2 absorption was measured at 313.15 K using a Meter Toledo reaction calorimeter. Results indicated that under similar process conditions and solvent composition, (DMDPTA+BA) blends exhibited significantly higher CO2 loading and low absorption enthalpy compared to aqueous BA and monoethanolamine (MEA) solvent alone indicating the potential of (DMDPTA+BA) blend as efficient CO2 capture solvent.

Single-etched fiber-chip coupler with a metal mirror on a 220-nm silicon-on-insulator platform for perfectly vertical coupling.

Vertical couplers play a pivotal role as essential components supporting interconnections between fibers and photonic integrated circuits (PICs). In this study, we propose and demonstrate a high-performance perfectly vertical coupler based on a three-stage inverse design method, realized through a single full etching process on a 220-nm silicon-on-insulator (SOI) platform with a backside metal mirror. Under surface-normal fiber placement, experimental results indicate a remarkable 3-dB bandwidth of 99 nm with a peak coupling efficiency of -1.44 dB at the wavelength of 1549 nm. This achievement represents the best record to date, to the best of our knowledge, for a perfectly vertical coupler fabricated under similar process conditions.

Safer and efficient assemblies: Harnessing real time worker movements with digital twins

This paper addresses a critical gap in digital twin simulation within manufacturing environments by focusing on the dynamic representation of worker movements during assembly processes. We introduce an innovative approach that utilises Ultra-Wideband (UWB) sensors to incorporate worker trajectory data into Siemens Process Simulate software, enabling the creation of a digital twin of assembly line operations. Our methodology involves comprehensive data collection using UWB sensors, followed by pre-processing steps such as data cleaning, interpolation, and classification of points into dwell and transit locations. Within the framework of Process Simulate, we develop the assembly process digital twin, integrating simulations of tricycle assembly alongside dynamic worker path and movement simulations. Our digital twin facilitates ergonomic analysis, process optimisation, and worker interaction analysis, offering insights for enhancing factory efficiency and safety. Notably, through visualisation of worker paths and identification of bottlenecks, our digital twin enables optimisation of resource allocation. Quantitative results demonstrate significant improvements, such as a reduction in the time of completion of six products by 11% compared to Discrete Event Simulation under similar process conditions. This study highlights the transformative potential of digital twin technology in manufacturing, providing a robust framework for simulating and optimising worker movements within real-world factory environments.

Assessing stability and performance of fluorine-doped tin oxide electrodes for peroxide formation in carbonate-based electrolytes

Hydrogen peroxide (H2O2) is a valuable chemical currently produced industrially on a large scale by the anthraquinone process. Recently, carbonate and/or bicarbonate-induced selective water oxidation to hydrogen peroxide has been suggested as an environmentally friendly alternative. In this manuscript, we discuss the effect of electrolyte concentration and type of cation in selective water oxidation using carbonate-based electrolytes (i.e., Na2CO3, K2CO3 and Cs2CO3) on fluorine-doped tin oxide (FTO) electrodes. Based on the experimental observations and a techno-economic evaluation we reveal that K2CO3 is preferred over Na2CO3 and Cs2CO3 electrolytes. Using 5 M K2CO3 a Faradaic efficiency of > 60 % was achieved at industrially relevant current densities of 100 mA cm−2. Although for 5 M Cs2CO3 electrolytes lower potentials are required at otherwise similar process conditions, a lower efficiency for hydrogen peroxide formation has been observed which is assigned to higher degradation in Cs-containing electrolyte, rendering the use of potassium-based electrolytes more efficient. Independent of the electrolyte used, the electrodes suffered from stability issues as revealed by increasing concentrations of tin in the electrolyte and electrode failure after polarization for several hours. Overall, this work provides detailed knowledge about the impact of electrolyte concentration and type of cation and reveals the importance of appropriate cell design and process operation for meaningful hydrogen peroxide synthesis by mediated-anodic water oxidation.

Superconformal silicon carbide coatings via precursor pulsed chemical vapor deposition

In this work, silicon carbide (SiC) coatings were successfully grown by pulsed chemical vapor deposition (CVD). The precursors silicon tetrachloride (SiCl4) and ethylene (C2H4) were not supplied in a continuous flow but were pulsed alternately into the growth chamber with H2 as a carrier and a purge gas. A typical pulsed CVD cycle was SiCl4 pulse—H2 purge—C2H4 pulse—H2 purge. This led to growth of superconformal SiC coatings, which could not be obtained under similar process conditions using a constant flow CVD process. We propose a two-step framework for SiC growth via pulsed CVD. During the SiCl4 pulse, a layer of Si is deposited. In the following C2H4 pulse, this Si layer is carburized, and SiC is formed. The high chlorine surface coverage after the SiCl4 pulse is believed to enable superconformal growth via a growth inhibition effect.

Experimental Validation of Numerical Model for Thermomechanical Performance of Material Extrusion Additive Manufacturing Process: Effect of Process Parameters.

The material extrusion additive manufacturing (MEAM) process for polymers seems straightforward. However, several controlled and uncontrolled factors affect the 3D printed product quality, e.g., MEAM process parameters, thermomechanical properties of the material, and part design. Therefore, it is crucial to understand these interlinked factors of part geometry, material properties, and 3D printing (3DP) process parameters to optimize 3D printed product quality. The numerical models and simulation tools can predict the thermomechanical performance of the MEAM process under given input parameters (material, design, and process variables) and reduce the research and development costs significantly. However, the numerical models and tools need further exploration and validation of simulation predictions for their adaptability and reliability. Therefore, in this study, numerical simulations were performed to observe the impact of process parameters on the part quality of MEAM 3D printed components. The two crucial process parameters (i.e., extrusion temperature and layer resolution) were varied while keeping the other process parameters, part geometry (tensile testing coupon), and material properties (acrylonitrile butadiene styrene (ABS)) constant. These two process parameters were sequentially optimized for optimum part quality, first by varying the extrusion temperature and secondly by changing the printing resolution using the optimum printing temperature. The 3DP process quality was evaluated in terms of dimensional accuracy, distortions, and residual stresses. Finally, the specimens were 3D printed under similar process conditions to validate the numerical model predictions.

In-process monitoring of distortion and temperature in multi-layer laser cladding of Stellite 6 and Inconel 718 alloys

In laser cladding, the development of rapid heating and cooling cycles generates high residual stresses and thermal gradients that lead to induce unwanted distortion in the parts. The paper deals with online monitoring of temperatures and the associated distortions in multi-layer laser cladding using pyrometers and laser displacement sensors. The alloys deposited in the present work are Stellite 6 and Inconel 718, having similar thermo-mechanical properties. The results show that variation in thermal gradients due to rapid heating and cooling allows the material to expand and contract, generating substantial distortions. In the current investigations, Stellite 6 deposits generated 28%, 21%, 15% higher deflection at 12 mm/s, 16 mm/s, 20 mm/s scan speeds respectively; and 23%, 20%, 17% at 2400 W, 2900 W, 3400 W laser power compared to Inconel 718. Irrespective of the coating material, the second layer cladding induced 10% to 30% lower distortion than the first layer because of the reduction in temperature gradient. However, Inconel 718 clads measured 10% to 15% less melt pool temperatures than Stellite 6. The study reveals that different cladding materials deposited under similar process conditions have greater impact on distortion and temperature. At last, the investigations provide an optimum set of parameters to produce homogeneous cladding with moderate deflection and temperature for both the alloys.

Use of CO2 in Pressurized, Fluidized Bed Gasification of Waste Biomasses

This research discusses the results of experiments performed on a large-scale gasification installation to determine the influence of total system pressure and partial pressure of CO2 on the efficiency of conversion and the quality of the produced gas. The three tested feedstocks were bark, lignin and a blend of bark and wheat straw, while softwood pellet (SWP) was used as a reference fuel. A mixture of O2/CO2/H2O was used as a gasification agent. The tests were devised to validate the previously proposed process parameters, verify whether similar ash agglomeration problems would occur and compare the thermal behaviour of the feedstocks converted in close-to-industrial process conditions. An understanding of the effect of using CO2 for gasification was further deepened, especially regarding its influence on the yield of H2 and temperature profiles of the fluidized bed. The influence of gasification pressure was predominantly visible in higher yields of all hydrocarbons (including CH4) and lower overall production of producer gas. At the process development unit (PDU), all tested feedstocks were converted at similar process conditions and no signs of potential bed agglomeration could be noticed. This opposes the findings observed in smaller-scale bubbling fluidized bed (BFB) tests. The discussion behind these discrepancies is also presented.

Morphological descriptors of agglomerates produced in continuously operated spray fluidized beds

This work presents the results of a systematic investigation of structural and morphological descriptors of agglomerates produced in continuously operated fluidized bed spray agglomeration. Experiments with glass beads as primary particles and a water-based HPMC mixture as top sprayed binder solution were carried out within a cylindrical fluidized bed of pilot plant scale. Characterization of all agglomerates was performed by X-ray micro-computed tomography. Investigated descriptors include number of primary particles, radius of gyration, coordination number and angle distribution as well as porosity and fractal properties. Utilizing these descriptors, a comparison regarding morphology of agglomerates produced in batch and continuous operation under similar process conditions and process times is drawn.

Influence of fibre type and dipping cycle on graphene adsorption and electrical conductivity of fibres

The influence of fibre type and dipping cycle on the graphene oxide (GO) add-on and the resultant mass-specific resistance has been studied for different fibres. Seven commonly used fibres, viz cotton, viscose, silk, wool, nylon, acrylic and polyester, are selected for the study. A comparative evaluation of GO add-on and the resultant mass-specific resistance of all these fibres are carried out under similar process conditions. Fibres are treated separately with 1% w/v GO solution up to 10 consecutive dipping cycles. Graphene oxide enriched fibres are reduced with sodium dithionite to restore graphene structure. Use of fibre as substrate for experiment eliminates the effect of other structural parameters of either yarn or fabric form. FTIR and UV-vis spectra confirm successful exfoliation of graphite to GO. FTIR study reveals significant chemical interaction of GO with cotton, viscose, nylon, and silk. SEM micrographs show that the graphene sheets are uniformly deposited on the cotton, silk, and nylon. Cotton yields maximum GO add-on and acrylic yields the lowest in all dipping cycles. Lowest mass-specific resistance is obtained in case of cotton, while highest values are obtained in case of acrylic after 10 dipping cycles. Nylon needs lowest amount to GO to achieve the same level of conductivity.

Transport mechanisms behind enhanced solute rejection in forward osmosis compared to reverse osmosis mode

Forward osmosis (FO) as emerging technology for water treatment was reported to exhibit higher solute rejections compared to reverse osmosis (RO). In this work, the rejection of two uncharged organic compounds (nicotinamide, caffeine) were investigated the first time in low-pressure reverse osmosis (LPRO) mode and FO under similar process conditions utilizing the same hollow fiber forward osmosis membrane modules. FO consistently showed higher rejection than LPRO mode for both nicotinamide (FO: 94.8%, LPRO: 85.5%) and caffeine (FO: 99.9%, LPRO: 99.2%). To elucidate the influence of draw solute on the rejection, different salts (NaCl, MgCl2, MgSO4), concentrations, and draw flow rates were investigated. A rise in draw concentration increased rejection in FO for all salts (RNaCl:94.1→97.2%,RMgCl2:94.5→97.5%,RMgSO4:90.0→94.7%) indicating an enhancement of rejection due to the presence of salt on the permeate side of the membrane. Two theories are proposed: While the resistance for feed solute transport could be increased due to the counter-directed reverse solute flux and the presence of salt in the support layer, the driving force for feed solute diffusion might be lowered due the presence of an ionic compound on the permeate side of the membrane.

Studies on the kinetics of catalytic combustion of deuterium using 0.5% platinum loaded on Dixon ring catalyst

When hydrogen isotopes are present in stoichiometric ratio of 2:1 with oxygen in inert gas such as helium, catalytic combustion is the most promising option to reduce the concentration of hydrogen isotopes and to minimize the associated safety hazards. This is the case, when deuterium and oxygen is formed during radiolysis of heavy water in moderator circuit of Pressurized Heavy Water Reactors (PHWR) and mixed with helium in the cover gas system. In order to design the catalytic reactor for recombination of deuterium and oxygen, the data on catalytic combustion kinetics under the similar process conditions are essential. However, the catalytic combustion data is generally reported for combustion of hydrogen in air, where oxygen is available in excess. The studies on the kinetics of catalytic combustion of deuterium where oxygen is present in stoichiometric ratio of 2:1 in an inert gas medium such as helium, is very scarce. In the present study, the multi-step reaction mechanism of catalytic combustion of hydrogen in presence of platinum catalyst is analyzed for the present process conditions. Based on the analysis, a simple rate expression is proposed for the present process conditions of catalytic combustion of deuterium. Further, 0.5% platinum catalyst is prepared on a stainless steel Dixon ring support with an objective to achieve better heat transfer characteristics and lesser reduction in the catalytic activity due to water adsorption. The kinetic data is generated using a differential packed bed reactor operating in a closed loop. The experiments were conducted at different temperatures using a stoichiometric mixture of deuterium and oxygen in helium. The rate constant for the above proposed model is estimated based on the experimental data at different temperatures. Further, the activation energy and frequency factor are determined and the activation energy for the present catalyst is found to be on the lower side in comparison to literature data.

Deformation Behavior of Longitudinal Surface Flaws in Flat Rolling of Steel Wire

The deformation behavior of a longitudinal V-shaped surface flaw was investigated during the flat wire rolling process using finite element analysis. The effects of process conditions, material properties, and initial position of the flaw on the deformation behavior of surface flaws were evaluated to understand the deformation behavior of flaws and to find solutions to decrease flaws. The surface flaw, that is, the ratio of the depth and width of the surface flaw (r), decreased with increasing reduction in height per pass, roll diameter, and friction coefficient. Unfortunately, the surface flaw and strain homogeneity of the wire simultaneously decreased under similar process conditions. The surface flaw slightly decreased with the strain hardening exponent (n) by increasing the width of the surface flaw. However, the effect of n value on the deformation of the surface flaw was not crucial. Higher strain at the flat surface induced an overlap-type surface flaw, whereas a small strain in the free surface induced an open-type surface flaw during the flat wire rolling process, which means that the surface flaw on the flat surface was much more detrimental than the surface flaw on the free surface. The deformation behavior of the surface flaw in flat-rolled wire was highly related to the strain inhomogeneity and lateral spreading of the wire. As the strain inhomogeneity of the flat-rolled wire increased, the lateral spreading of the wire increased, resulting in a decrease in the surface flaw, i.e., the r value.

Chemical Kinetics Modeling and Analysis of Monomethylamine for Power Plants Selective Non-Catalytic Reduction (SNCR) Systems

A study was performed to investigate monomethylamine (MMA) as an alternative or supplementary reagent for selective non-catalytic reduction (SNCR) of nitrogen oxides (NOx) for power plants especially the coal-fired type. A detailed chemical kinetics mechanism for MMA, related to the SNCR NOx reduction process, was modeled using a simplified plug flow reactor (PFR) approach using the CHEMKIN software. Model validation results were in line with reported experimental results. A model sensitivity analysis showed that the normalized MMA/NO stoichiometric ratio (NSR) and the initial NOx concentration are the most critical parameters that significantly affect MMA-based process performance. Additionally, a reduced reaction mechanism and its mechanism tree for this particular process are proposed, consisting of only 18 reactions and 21 species. Simulation comparisons with three other reagents (ammonia, urea, and cyanuric acid), under similar process conditions, indicate that MMA-based SNCR NOx reduction process has a superior performance at much lower temperatures (under 800 K) than conventional SNCR processes, with the added benefit that it does not suffer from ammonia slip problems. The MMA-based SNCR NOx removal system could be applied in cascade mode with other post-combustion NOx removal approaches to extend NOx control to lower temperatures and eliminate the temperature window limitation and potential ammonia slip of conventional SNCR systems. The cascade design is a perfect solution for coal power plants especially at partial load modes of operation which provides more flexibility in performance for such plants. The results of the simulations in this study show that the potential of MMA for SNCR NOx reduction systems at full-scale power plants has significant merit.

Improving recovery of iron using column flotation of iron ore slimes

In general, the industrial flowsheets for the beneficiation of itabirite iron ores from the Quadrilátero Ferrífero (Minas Gerais state) in Brazil involves grinding, desliming, magnetic separation and cationic reverse flotation using both mechanical and columns flotation cells. At Brazilian plants, it is estimated that Fe losses generated at the slimes stage range between 8% reaching values higher than 20%. Slimes generated at hydrocyclone containing particle sizes of approximately 99% < 45 μm, 25% > 10 μm, 45% < 5 μm and 15% < 1 μm, 3% of solids by weight and between 35% and 45% of Fe grade. This work aims at evaluating the technical feasibility of concentration of two slimes samples from two different plants in operation at the Quadrilátero Ferrífero using the column flotation technology without prior desliming. Despite the similarity in terms of mineralogy, grade and particle size distribution, the flotation results indicate a very distinct behavior considering similar process conditions, including variables such as collector type and dosage, depressant dosage, pH and circuit configuration. A final concentrate containing an Fe grade higher than 60%, 4% SiO2 and 3.1% Al2O3 with an Fe recovery up to 75% in rougher column flotation can be obtained from Sample 1 with 45.2% Fe, 28.6% SiO2 and 3.1% Al2O3, when a collector type amide-amine (Flotinor 5530) was used in substitution of a conventional amine collector. On the other hand, it was not possible to obtain a final concentrate containing an Fe grade higher than 55% from Sample 2 with 39.6% Fe, 33.4% SiO2 and 5.1% Al2O3, using both types of collector (amide-amine and amine) even when applying different types of column flotation circuits (rougher or rougher/cleaner). Based on literature review and the results obtained in this study, it can be observed the non-existence of a standard solution for an efficient slimes processing in the iron ore industry. Considering flotation as the most suitable technology for the treatment of such type of material, future research should focus on a deep fundamental study of the collector-depressant mechanism interaction with the iron-bearing and gangue minerals, especially in those ores with a high amount of alumina-containing minerals. Considerations about the effect of bubble generator device to flotation columns and its impact on the metallurgical performance are also discuss regarding to application at industrial scale to slimes concentration.

VLE of Carbon Dioxide-Loaded Aqueous Potassium Salt of L-Histidine Solutions as a Green Solvent for Carbon Dioxide Capture: Experimental Data and Modelling

In this study, vapour-liquid equilibrium of CO2-loaded aqueous potassium salt of L-histidine was studied for a wide range of temperature (313.15–353.15 K), pressure (150–4000 kPa), and solvent concentrations (1–2.5 molar). The experimental results show that L-histidine has an excellent absorptive capacity for carbon dioxide. When compared to conventional solvent (monoethanolamine) and amino acid salt (potassium L-lysinate) at similar process conditions, L-histidine has superior absorption capacity. Moreover, modified Kent–Eisenberg model was used to correlate the VLE of the studied system with excellent agreement between the model and experimental values. The model exhibited an AARE% of 7.87%, which shows that it can satisfactorily predict carbon dioxide solubilities in aqueous potassium salt of L-histidine at other process conditions. Being a biological component in origin, almost negligibly volatile, and highly resistant to oxidative degradation, L-histidine offers certain operational advantages over other solvents used and has a promising potential for carbon dioxide capture.

Fluidized Bed Granulation Parameters Effect on Urea Granule Physical Properties

The aim of this study is to determine the effect of different airflow patterns and process conditions on the physical properties of granules produced using fluidized bed granulation technique. It was observed that spiral airflow was the most important factor to produce granules with required size and density under similar process conditions if compared with normal airflow. From ANOVA, binder spray pressure and bag shake duration showed the strongest influence on hardness of granules on both types of airflow patterns. Optimization studies for spiral and normal airflow proved that granules with desired density and hardness can be produced at middle level of wind velocity and binder spray pressure together with high level bag shake duration. For spiral airflow, the optimum value for wind velocity, binder spray pressure and bag shake duration was 28 m/s, 0.31 MPa and 60 s respectively; for normal airflow, it was 25 m/s, 0.20 MPa and 15 s respectively.

Experimental Investigation on Silicon Carbide Reinforced Duralumin based MMC Produced by Cold Compacting

In the present investigation, an attempt is made to fabricate the Duralumin(DA) based Silicon Carbide (SiCp-6 and 12% wt.) reinforced composite by cold compacting the ball milled powders. The mechanically mixed powders taken into the die cavity are applied with a steady axial load in the range 22-30 T to produce the cylindrical compacts. The compacts are further subjected to sintering by holding it at a constant temperature of 5800C in Muffle furnace for 5 h and allowed to cool in the same for 18 h. The hardness of sintered composite is found to have improved as compared to the sintered duralumin compact prepared under similar process conditions. The SEM images showed the uniform distribution of the reinforcements in the matrix and the elemental composition is confirmed by the EDAX spectrum. The sintered specimens were further subjected to age hardening heat treatment. Specimens were soaked at 5500C for 2 h followed by water quenching at room temperature. The quenched specimens were artificially aged in the furnace at temperatures of 100, 150, and 2000C for various durations of time. The peak hardness obtained because of aging heat treatment is found to be much better than the corresponding sintered compacts. Compacts peak aged at 1000C exhibited better tensile strength than the other category of specimens. The composites developed in the present study would be most suitable in the applications requiring high strength and resistance to heat and wear.

The Effect of Catalyst Type and Concentration on the Yield of Biodiesel from Jathropha/Moringa Oil Mix

The exhaustible nature of petroleum diesel has made biodiesel an attractive alternative to diesel, but efforts at reducing its high production costs through the use of cheap poor-quality oil feedstock are not sufficient. A careful choice of catalyst concentration and type is also necessary. Binary blends of oil-feedstock and alcohol-feedstock were used to increase the efficiency of transesterification process. The effect of changing alkaline catalysts on the yield of transesterification reactions was also examined for similar and varied process conditions. This allowed the examination of the impacts of catalyst on yield with changing feedstock type and processing condition. Results of oil and alcohol blending showed that the partial use of ethanol permitted reactions to be completed in 45 minutes instead of 60- 120 minutes common to conventional ethanolysis. Yields were comparable to those of methanolysis. Ester yield increased with increase in the concentration of KOH and CaO catalysts within the 0.5-2.5 w/w% range.

Poly (l-lactic acid) synthesis using continuous microwave irradiation–simultaneous cooling method

In this study, Poly(l-lactic acid) (PLLA) synthesis was studied using direct melt condensation polymerization (DMP) method in an experimental microwave (MW) system where external cooling was applied to keep both temperature (T) and MW power (P) continuous and constant during the polymerization. T, P, reaction time (t), catalyst type, and catalyst amount were considered to determine appropriate process conditions. In addition, some experiments were carried out under the similar process conditions using MW-assisted ring opening polymerization (MW-ROP) and conventional heating (CH) methods. These methods were compared in terms of process performance and various properties of the oligomeric PLLA. According to results, polymerization rate, polymer yield, average-molecular weight, the dispersity, and thermal properties of PLLA products were similar in both MW methods but higher than CH counterparts. Furthermore, low crystallinity of PLLA products synthesized by MW methods showed the effect of MW on the optical purity (L or D) of products. Finally, energy saving was accomplished by 73% and an increase of polymer production rate by 37.7% in MW-DMP method.