Inlet Feed Research Articles

Long-Term Treatment of Highly Saline Brine in a Direct Contact Membrane Distillation (DCMD) Pilot Unit Using Polyethylene Membranes.

Membrane distillation (MD) is an attractive separation process for wastewater treatment and desalination. There are continuing challenges in implementing MD technologies at a large industrial scale. This work attempts to investigate the desalination performance of a pilot-scale direct contact membrane distillation (DCMD) system using synthetic thermal brine mimicking industrial wastewater in the Gulf Cooperation Council (GCC). A commercial polyethylene membrane was used in all tests in the DCMD pilot unit. Long-term performance exhibited up to 95.6% salt rejection rates using highly saline feed (75,500 ppm) and 98% using moderate saline feed (25,200 ppm). The results include the characterization of the membrane surface evolution during the tests, the fouling determination, and the assessment of the energy consumption. The fouling effect of the polyethylene membrane was studied using Humic acid (HA) as the feed for the whole DCMD pilot unit. An optimum specific thermal energy consumption (STEC) reduction of 10% was achieved with a high flux recovery ratio of 95% after 100 h of DCMD pilot operation. At fixed operating conditions for feed inlet temperature of 70 °C, a distillate inlet temperature of 20 °C, with flowrates of 70 l/h for both streams, the correlations were as high as 0.919 between the pure water flux and water contact angle, and 0.963 between the pure water flux and salt rejection, respectively. The current pilot unit study provides better insight into existing thermal desalination plants with an emphasis on specific energy consumption (SEC). The results of this study may pave the way for the commercialization of such filtration technology at a larger scale in global communities.

Using LSTM and PSO techniques for predicting moisture content of poplar fibers by Impulse-cyclone Drying.

Impulse-cyclone drying (ICD) is a new type of pretreatment method to remove the excess moisture of wood fibers (WFs) with high speed and low energy consumption. However, the process parameters are often determined by the experience of the process operators, thus the quality of WF drying lacks an objective basis and cannot be ensured. To address this issue, this study adopted the long short-term memory (LSTM) neural network, backpropagation neural network, and Central-Composite response surface method to establish a moisture content (MC) prediction model and a process parameter optimization model based on single-factor experiments. The initial MC, inlet air temperature, feed rate, and inlet air velocity were taken as the experimental factors, and the final MC was taken as the inspection index. The parameters of LSTM were optimized by particle swarm optimization (PSO) algorithm, and the predicted value of MC was fitted to the model. The PSO-optimized LSTM had higher prediction accuracy than did the typical prediction models. The optimal process for the targeted MC, which was obtained by PSO, was featured with an initial MC of 10.3%, inlet air temperature of 242°C, feed rate of 90 kg/h, and inlet air velocity of 8 m/s. PSO-LSTM could be a new approach for predicting the MC of WFs, which, in turn, could provide a theoretical basis for the application of ICD technology in the biomass composite industry.

Conceptual comparison of three novel configurations in the spherical radial flow reactor for ammonia production

Since ammonia is a powerful energy carrier of hydrogen, the attempts are considered to improve the ammonia synthesis process. Reactors are the heart of chemical units. Because of the effect of pressure on gas phase and equilibrium reactions and significant pressure drop in tubular reactors, Spherical reactors are a good alternative. Due to the importance of fluid flow in reactors, 2-dimensional ammonia tubular and three configuration of spherical radial flow reactors were simulated with computational fluid dynamics (CFD) in the present study. The tubular reactor results are verified with experimental data at the same condition to justify the suggested model accuracy. The advantages of the proposed configurations are the possibility of using a higher flow rate and less pressure drop compared to the tubular configuration. The three proposed configurations include spherical reactors with four feed inputs (Config 4F), six feed inputs (Config 6F), and eight feed inputs (Config 8F). The simulation results also show that the nitrogen conversion rate in each recommended configuration has improved by 20.96%, 20.28%, and 19.66%, respectively. The spherical radial flow reactor with four feed inlets has the best performance among the provided configurations. Furthermore, the effect of process parameters, including flow scale-up ratio and outlet temperature of intermediate coolers, on the conversion of nitrogen has been investigated.

Hydrogen sulphide to hydrogen via H2S methane reformation: Thermodynamics and process scheme assessment

Hydrogen Sulphide Methane Reformation (HSMR) represents a valid alternative for the simultaneous H2S valorisation and hydrogen production at the industrial scale, without direct CO2 emissions. The major concerns about the process commercialization are the possible coke formation in the reaction zone and the lack of active and selective catalysts. The study of the thermodynamics is the essential preliminary step for the reaction phenomena understanding. In this work, a deep thermodynamic analysis is performed to explore the system behaviour as a function of temperature, pressure, and inlet feed composition, using the Aspen Plus RGibbs module. In this way, the optimal process operating conditions to avoid carbon lay down can be identified.Assessed the system's thermodynamics, a preliminary process scheme is developed and simulated in Aspen Plus V11.0®, considering hydrogen production and its distribution in pipeline with methane. The process performances are discussed in terms of products' purity and process energy consumptions.

Study on dust migration law and spray dedusting technology in parallel double belt transportation

To effectively solve the problem of dust pollution caused by the parallel double-belt transportation of coal in a coal preparation plant, taking the Huangyuchuan coal preparation plant as an example, a numerical model of the air flow-dust distribution was established by means of simulation. The flow lines between the strips of tape and the tail of the tape machine will gather, and there will be backflow on the right side of the 3001 tape and left side of the 3002 tape. Under the action of wind current, most of the dust particles larger than 10 μm are distributed in the range of 0–5 m on both sides of the tape; dust particles smaller than 10 μm spread to the entire preparation workshop. Combined with field test verification, dust pollution is mainly concentrated at the guide trough, the feed inlet, the rear of the machine, and the joint of the belt corridor. Based on this, a targeted spray dust reduction treatment plan is proposed. By measuring the dust concentration before and after the treatment of dust-polluted areas, it is proven that the dust reduction efficiency of this plan can reach more than 90%.

3D CFD study of hydrodynamics and mass transfer phenomena for spiral wound membrane submerged-type feed spacer with different node geometries and sizes

Modification of the spacer geometry is a promising approach to increase the efficiency of reverse osmosis (RO) spiral wound membrane modules. Column nodes and spherical nodes are considered in this three-dimensional computational fluid dynamic (CFD) study to evaluate the hydrodynamic and mass transfer performance of submerged spacers with different node geometries and sizes. Small-scale CFD analysis results reveal that the column node has better mass transfer performance than the spherical node geometry because column nodes divert more flow to the filaments, leading to higher local velocity at the region between the filament and wall. Furthermore, when the dimensionless node diameter ratio of the column nodes increases from 0.3 to 1.2, Sherwood number and wall shear increase by 25% and 8% respectively at the expense of higher global friction factor (44%). A sea water RO full-scale analysis revealed that column node spacers yield higher average flux than spherical nodes and conventional spacers at high feed inlet velocity (> 0.1 m/s), because the mixing effects by the spacer that improve mass transfer are more prominent.

Study of the Fluid Passing through the Screen in the Three Products Hydrocyclone Screen (TPHS): A Theoretical Analysis and Numerical Simulation

The three products hydrocyclone screen (TPHS), a branch of the hydrocyclone, effectively removes the fish-hook effect, which has been used in the industrial field. The current cylindrical screen in the TPHS generates the characteristic flow known as the screen underflow, which has a significant impact on device performance. To investigate the flow behaviour of the fluid passing through the screen, a combination of a dynamic analysis and a numerical simulation was used. The permeating process in the TPHS was abstracted by a simple fan mode in this work to generate the flow-rate equations and the driving-force models. The pressure difference was the driving force for the screen penetration in the ideal fluid, but it also included a viscous force in the viscous fluid. Furthermore, at the same inlet velocity, the viscous fluid had a higher flow rate than the ideal, indicating that the viscosity promoted the fluid penetration. Meanwhile, as the inlet velocity increased, the mass flow of the screen backflow increased, while the corresponding proportion first rose to a peak then dropped and then gradually stabilised. Furthermore, a flow equation for the screen underflow in the TPHS was developed, which is related to the structural parameters (the rotation radius, the length of the cylindrical screen, the aperture size, and the open-area percentage) and the process parameters (the dynamic viscosity of the fluid and the pressure difference between the feed inlet and the screen outlet).

Numerical study on supercritical water partial oxidation of ethanol in a continuous reactor

Supercritical water partial oxidation (SCWPO) is a green technology favorable for low-carbon organic waste resource conversion and utilization. At present, there is a lack of reasonable optimization methods for the SCWPO reactor. In this paper, a numerical model was established for the SCWPO reactor based on ethanol. Herein, a numerical study on SCWPO of ethanol in a continuous reactor was carried out. On the basis, the fluid flow, heat transfer, and gas products distribution in the SCWPO reactor were analyzed in detail, and the influence of different operating parameters was also discussed. The results showed the carbon gasification efficiency (CE) and gas yield increased with the wall temperature, ethanol concentration, and the equivalent ratio of oxidant (ER). The lower feed inlet height and the lower flow rate of feed inlet and preheated water could extend residence time and improve CE and gas yield. In particular, CE was 98.6% when the wall and preheated water temperature were 700 °C, and the height of the feed inlet was 500 mm. Under the current operating condition, the SCWPO reactor could achieve auto-thermal with ER = 0.25. Given the above, this numerical study would provide an effective method for SCWPO reactor optimization.

Performance investigation of solar-powered direct-contact membrane distillation and humidification–dehumidification hybrid system

This study proposes a novel integrated direct-contact membrane distillation (DCMD) and humidification–dehumidification (HDH) desalination system driven by a solar flat-plate collector (FPC). In this approach, seawater heated by the FPC system is fed to the DCMD system to recover freshwater. The DCMD brine is subsequently processed by the HDH system to recover additional energy and produce freshwater. The DCMD system is incorporated prior to the HDH, as high concentrations of the feed solution can cause membrane fouling and pore wetting. The performance modeling of the FPC, DCMD, and HDH systems utilizing real-time solar irradiation data of Gizan city, Saudi Arabia is considered. The effects of FPC area, solar irradiation, inlet seawater temperature, feed salinity, humidifier dehumidifier effectiveness, and inlet feed flow rate on the FPC outlet seawater temperature, distillate rate (m˙d), recovery ratio (RR), and gain output ratio (GOR) are investigated. The monthly temperature of the seawater output from the FPC is in the range of 53–78 °C with a collector area of 16 m2 and inlet feed flow rate of 1.8 L/min. The highest m˙d, RR, and GOR values are 9.1 kg/h, 8.4%, and 1.3, respectively, under temperature and flow conditions of 78 °C and 1.8 L/min, respectively.

A methodology for structure dependent global kinetic models: Application to the selective catalytic reduction of NO by hydrocarbons

Global kinetic models capable of capturing experimentally observed features of catalytic reactions are vital in design and optimization studies. In this work, a detailed analysis of the selective catalytic reduction of NO and NO2, particularly in automotive exhaust control is undertaken. The prominent metal based catalysts for this reaction range from Pt, Au & Rh to cheaper options including Cu, Ag & Co supported on Al2O3, SiO2, and occasionally, zeolites. Here, we focus on Ag & Co supported on Al2O3 catalysts, and propose a computationally tractable kinetic model capable of capturing the observed SCR features across a range of catalyst synthesis and reactor operating conditions. In particular, the effects of metal loading on catalyst performance are closely examined. In SCR, an important aspect is the catalytic activity at higher inlet O2 concentrations. The global kinetic model proposed here is shown to predict the trends with respect to reactor temperature and inlet feed compositions (including O2), well, for both catalysts.

Performance of proton exchange membrane fuel cell integrated with direct contact membrane distillation for electricity and fresh water productions

This paper develops a new hybrid system composed of direct contact membrane distillation (DCMD) and proton exchange membrane fuel cell (PEMFC), which generates fresh water from brine by utilizing waste heat from the PEMFC to improve the system energy efficiency. The mathematical model of the hybrid PEMFC-DCMD system is established to explore the influence of feed inlet temperature, feed and permeate inlet flow rates of DCMD on the hybrid system performance. To achieve the optimal system performance, the genetic algorithm (GA) is used to search for the optimal feed and permeate inlet flow rates of DCMD with the transmembrane water flux as the objective function. The optimization results illustrate that transmembrane water flux of DCMD is 15.24 kg/(m2·h), while feed and permeate inlet flow rates are 1.83 L/min and 8.98 L/min. In addition, the optimal overall energy efficiency of the proposed system is 72.96%, which is increased by 54.48% compared with a single PEMFC system.

Control strategy for multi-column continuous periodic counter current chromatography subject to fluctuating inlet stream concentration

Fluctuations of the inlet feed stream concentration are a challenge in controlling continuous multi-column counter current chromatography systems with standard methods. We propose a new control strategy based on calculated product column breakthrough from UV sensor signals by neglecting an impurity baseline and instead using the impurity to product ratio. This calculation is independent of the inlet feed concentration. In-silico simulation showed that the proposed method can calculate the product column breakthrough perfectly even with fluctuating and highly unstable inlet feed concentration during a loading cycle. Applying the proposed method to control a three column periodic counter current chromatography process with fluctuating inlet feed concentration resulted in constant column loading in each cycle, while using the standard method failed to do so. Unavoidable band broadening caused by diffusion and dispersion has been identified as an inherent limiting factor for accurate calculation of column breakthrough comparing inlet and outlet UV signals. The proposed advanced calculations increase the robustness of periodic counter current chromatography and extend the capability to process unstable inlet streams.

Spray dried extract of Callophyllum brasiliense Cambés produces a potent hypoglycemic effect and improves total serum cholesterol and triglycerides in diabetic rats

The species Calophyllum brasiliense Cambés (Calophyllaceae) is widespread throughout Central and South America. The stem bark infusion is used for lowering blood glucose. Aim: To optimize the spray dry extract of this plant using a D-optimal experimental design. Materials and methods: As factors were used the air-drying speed (3.5-4.5 m3/h), the feed flow rate of the suspension (5-11 mL/min), and the inlet air temperature (90-130 °C). The dried extract was character-ized by measuring the phenolics and flavonoids content, moisture, the water activity, apparent densities, flowability, and compressibility. The antioxidant activity, the inhibitory activity of lipase and alpha-glycosidase, and the antiglycant activity of the spray dried extract (SDE) were evaluated. Subsequently, the hypoglycemic activity was evaluated in rats by monitoring the blood glucose level, triglycerides, and choles-terol. Results: Inlet air temperature and feed flow rate were the factors that most affected the yield and phenolic content. SDE showed a potent antioxidant effect (IC50 1.83 μg/mL), a potent α-glycosidase (IC50 74.45 μg/mL) and pancreatic lipase (IC50 27.33 μg/mL) inhibition. A potent antiglycation effect (IC50 9.45μg/mL) was also observed. Conclusion: the SDE showed a potent hypoglycemic effect at 100 mg/kg. These results suggest that SDE could activate four important pathways that can contribute to diabetes control.

An insight into the performance of CNT-based membrane with the application of electric field for distillation process

The main drawbacks of conventional membrane distillation (MD) are particularly related to the membrane fouling, wherein the fouling development on the hydrophobic membrane surface was greatly affected by the decrement of temperature along the flow-direction. In this study, a composite membrane was fabricated by coating carbon nanotubes (CNT), and an electric-enhanced direct contact MD was developed subsequently with the application of alternating current potential (AC). Systematical analysis showed that the conventional MD system exhibited a great difference of fouling morphology from the feed inlet to outlet, and the variation of dominant communities from the Deinococcus − thermus to Proteobacteria. The AC application on the composite membrane exhibited a simultaneous anti-fouling and flux-enhancing property, which overcame the temperature drop and effectively maintained the membrane stability. Less foulants including the crystals and organics were observed, and the microbial richness and diversity obviously decreased, and the dominant bacteria composition was quite similar and single. Under the electrical field, better performance was expected due to the effects of hydrophilic surface, Joule heating and electrical function. We believe that the electrically conducting membrane has a promising potential in water treatment, paving the way for the smart design of novel MD systems.

Modeling and simulation of a multi-bed industrial reactor for renewable diesel hydroprocessing

The complexity of designing and optimizing vegetable oil hydrotreating reactors lies in describing multiple phenomena, including heat and mass transfer, hydrogen consumption, pressure drop, and a complicated network of highly exothermic reactions. This study intends to analyze the behavior of a vegetable oil hydroprocessing unit in a commercial environment via modeling and simulation techniques. In order to describe the three-phase (gas-liquid-solid) system in a detailed manner, a commercial-scale reactor model having multiple catalyst beds and inter-bed quench gas injections was constructed accounting for the heat and mass transfer between phases, the dynamic response of the system, the variation in gas phase velocity, and intraparticle effects. Based on dynamic reactor simulations, quench gas injection strategies were proposed to control the reactor temperature profile and yield of the desired products. Simulation results showed that the selection of a feed inlet temperature plays a major role in reactor overheating and quench injections must start as soon as the reactant stream reaches the inter-bed quench zone to stabilize reactor temperature more rapidly during start-up. In addition, the lengths of the catalyst beds need to be adjusted such that the heat released by chemical reactions is properly distributed along the reactor. The results overall provide useful information for the design and optimization of commercial-scale catalyst bed configurations for hydrotreating renewable feedstock. In particular, it is highlighted that by means of an appropriate gas quenching configuration, reactor temperature can be adequately controlled, allowing higher yields of green diesel.

ADSORPTION OF Cd(II) IN A SEMI-CONTINUOUS PROCESS BY RESIDUAL CHARCOAL FROM THE PYROLYZED OIL PALM SHELLS

This study aims to evaluate the utilization of residual charcoal from the pyrolysis of oil palm shells as activated carbon for the adsorption of cadmium metal ions in a semi-continuous process. The charcoal was crushed with a ball mill to a size of 80-100 mesh and its activation was carried out chemically using 0.1 N NaOH. Cadmium metal ions were adsorbed in a semi-continuous operation using a cylindrical packed bed column, with variations in the inlet feed concentration, pH, column inside diameter, bed height, and flow rate. The initial concentration of cadmium before and after the adsorption was tested on an atomic absorption spectrophotometer. The adsorption isotherms were evaluated using the Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherm models. The results showed that the best adsorption capacity was obtained at an initial concentration of 120 mg/L, pH 5, inside diameter of 26 mm, bed height of 50 cm, and flow rate of 10 ml/min. The isotherm model of cadmium metal ion adsorption followed the Langmuir isotherm with R2 = 0.99.

The Functionality of Probiotic Bacteria Microencapsulation by Spray Drying: A Literature Review

Probiotic-based products are associated with many health benefits. The viability of probiotics is necessary to provide health benefits, but it is lost during processing, storage, and gastrointestinal tract. The viability of probiotics can be maintained by applying the spray drying encapsulation technique. This review article discusses probiotic bacteria, encapsulant ingredients, the principle of spray drying in microencapsulation, and the functional properties of spray drying probiotic microcapsules. This article uses a non-research method with a literature review of various sources such as research journals and related books. Based on existing studies, the viability of probiotic spray drying results is influenced by the bacterial culture used, the type and concentration of the encapsulated material, and the spray drying conditions (feed temperature, inlet temperature, and outlet temperature). Probiotic microcapsules spray drying has excellent potential in functional food formulations, and its commercial applications will benefit both the industry and consumers.

Experimental study and numerical optimization for removal of methyl orange using polytetrafluoroethylene membranes in vacuum membrane distillation process

One of the most water-intensive and environment polluting anthropogenic industries is the textile industry. Amongst textile dyes, methyl orange (MO) is an extensively used anionic azo dye that is toxic to the environment. In this study, the effect of various process parameters was studied for different operating conditions (mass flow rate, vacuum pressure, inlet feed temperature, dye concentration) to remove MO from synthetic wastewater in the vacuum membrane distillation (VMD) process. We determined the optimum conditions for operating variables using response surface methodology (RSM) and developed a regression model to describe permeate flux, dye rejection and specific energy consumption. The optimum operating parameters from the RSM study were bulk feed temperature: 70 °C, mass flowrate: 40 kg h−1, dye concentration: 60 mg l−1 and vacuum pressure: 720 mm Hg. For the optimized input process parameters, the experimentally observed values were permeate flux: 19.60 ± 1.03 l m−2 h−1, dye rejection: 99.80 ± 0.07%, and SEC: 2.04 ± 0.11 kW h m−3. Furthermore, for these optimized conditions, a 3D CFD model was developed to gain insight into the membrane module's thermal, velocity, and concentration field. The evaporation of feed at the membrane surface on the feed side and condensation of vapours at the membrane surface on the permeate side was captured in this model. The permeate flux profile and dye rejection for various cycles of VMD operation with intermittent washing were also performed to study the fouling behaviour of the membrane. The membrane's surface fouling was analyzed using SEM and FT-IR analysis. The SEM analysis of the fouled membrane indicated that the dye deposition was not severe due to high hydrophobicity, high liquid entry pressure, and high pore wetting resistance of the PTFE membrane. The FT-IR analysis showed that the fouled PTFE membrane sufficiently retained its initial structure and property.

Addressing challenges in sealing of scalable multifiber module for O2 enrichment using LSCF membranes

AbstractScalable and multifiber modules in oxygen separation face huge challenges due to difficulty in integrating all the necessary components, especially in sealing the fibers in a gas tight module. Here, we report our findings on design and fabrication of a multifiber La0.6Sr0.4Co0.2Fe0.8O3–δ (LSCF)‐based module, which can be scaled up. The focus is on sealing ceramic‐metal interfaces by layering of sealants of varying thermal properties. We have also incorporated the use of dead ended fibers to minimize ceramic‐metal interfaces in the hot zones and present a new method for dead ending by flame melting. Pressurizing the air inlet feed from either bore side or shell side is detrimental to the structural integrity of the fibers. A thorough characterization of the fresh and spent fibers is also carried out using X‐ray tomography and electron microscopy, which indicates effect of temperature and pressure on the fibers.

Modelling mass transport within the membrane of direct contact membrane distillation modules used for desalination and wastewater treatment: Scrutinising assumptions

A two-dimensional numerical model for a direct contact membrane distillation (DCMD) module, mostly used for desalination and wastewater treatment, has been created. This model has been used to explore the sensitivity of the simulated transmembrane flux of water vapour of the modelled distillation module to some of the commonly-used assumptions and simplifications related to the mass transport in the membrane, namely: equimolar diffusion; Knudsen diffusion-free mass transport; and binary gas mixture. The model has been also used to assess the impact of a slight total pressure difference across the membrane. The sensitivity of the transmembrane flux to the above assumptions has been then evaluated with relatively low and high inlet feed temperatures. The outcomes of the model have been presented, discussed and finally summarised.