Influence Of Feed Temperature Research Articles

Hydrophobic ZSM-5/styrene-butadiene-styrene (SBS) membrane for the removal of pyridine from aqueous solutions via pervaporation

New mixed matrix membranes (MMMs) of poly(styrene-butadiene-styrene) (SBS) incorporated with hydrophobic ZSM-5 zeolite (calcinated and non-calcinated) were prepared and characterized by various analyses. The performance of fabricated membranes was investigated in a pervaporation (PV) experimental setup for removing pyridine from aqueous solutions and the results indicated a notable increase in total flux. The influence of feed temperature (25–55ºC) on the pure SBS membrane performance was studied and the results were compared. It was found that an increase in feed temperature increased the permeation flux and decreased the separation factor. Incorporating ZSM-5 into the membrane matrix substantially influenced the separation performance of the fabricated membranes. The sample with 20 wt% calcinated zeolite (C.ZSM-5) represented the highest separation factor. C.ZSM-5 loading up to 20 wt% reduced total flux while it was increased with further increments in zeolite content. The highest separation factor and pervaporation separation index (PSI) for 20 wt% C.ZSM-5 sample at 45ºC feed temperature obtained at about 72 and 80,223 (g/m2h), respectively.

Hysis Simulation Optimization of Distillation Desulfurization for Mixed Light Hydrocarbons in Tahe Oil Field

In order to improve the performance of distillation desulfurization unit for mixed light hydrocarbons in Tahe Oil Field, HYSIS simulation investigation was performed. The influences of feed temperature, operation pressure, reboiler temperature and plate number on sulfur content of bottom product, flow rate of product, energy consumption and saturated vapor pressure of light hydrocarbons were carefully discussed. It is indicated that the total energy consumption can be reduced by 45.78% if the unit is operated at the optimized conditions. Meanwhile, the sulfur content of the bottom product will be less than 0.05% and the flow rate of bottom product can be increased by 2.04 t/d while the flow rate of top gas product can be decreased up to 754.11 Nm3/d. In addition, the saturated vapor pressure of light hydrocarbons is lower than the operation pressure.

Pervaporation as an alternative for adding value to residues of oyster (Crassostrea gigas) processing

The recovery of volatile organic compounds from oyster boiling juice was investigated by pervaporation with PDMS membrane. The effects of feed flow rate, pervaporation temperature, and permeate pressure on the pervaporation of aroma compounds of the juice were studied. No differences in the total permeate flux for the different feed flow rates was observed. This behavior was described by computational fluid dynamics simulation, which showed the flow was laminar for all cases. The influences of feed temperature and permeate pressure on the permeate flux were described by the solution-diffusion model. The main aroma compounds of oyster boiling juice could be successfully concentrated by pervaporation, and an enrichment factor of 35 was reached for 1-octen-3-ol at permeate pressure 1750 Pa and 30 °C.

Influence of Feeding Temperature of Biofuels on Agricultural Engine Performance

The search for alternative energy sources to reduce the use of diesel in the national energy matrix has been studied in a gradual way, with partial insertions of biodiesel to diesel. Parameters such as viscosity change when biodiesel is added to diesel, as this factor directly influences the atomization of the fuel. This paper aimed to evaluate the behavior of renewable biofuels in a 61 hp agricultural engine, by means of dynamometric tests, operating with mixtures of type A diesel S500 and biodiesel, including an analysis of pure diesel (0% biodiesel) and diesel blend with 20% biodiesel, heated with a system before the injection pump, at temperatures of 45 °C, 65 °C, and 85 °C. The highest values were maximum torque of 208.7 N m, maximum power of 55.3 KW, and specific consumption of 236.9 g KW h-1 at 45 °C. The viscosities of the mixtures were also determined using the 40 °C test temperature, as suggested by ASTM D 445, followed by the ANP, as well as temperatures studied, and the cSt values of the blends at 65 °C and 85 °C were below the minimum limit established by ANP.

The effect of feed temperature on biofouling development on the MD membrane and its relationship with membrane performance: An especial attention to the microbial community succession

The influence of feed temperature on biofouling of membrane distillation (MD) with respect to the microbial community composition developed on the membrane surface was detailedly investigated in this study. The microbial community profile of MD-membrane biofilm was elucidated during the treatment of Xuanwu Lake water in a flat-sheet bench-scale direct contact membrane distillation (DCMD) system operated under higher feed temperature (60 °C) and lower feed temperature (40 °C), respectively. The fouling data showed that a more severe flux decline was observed under 60 °C, which exhibited a three-phase decline pattern. Comparatively, the normalized flux (NF) of 40 °C continuously demonstrated a higher value than that of 60 °C, and rather less variations were observed for its decline rate. The combination of SEM-EDS and EEM analysis revealed that more obvious deposition of salt crystals and protein-like substances was observed for the MD membrane operated under 60 °C. Phylogenetic analysis using next-generation sequencing of 16S rDNA showed that rather significant shifts of microbial community were observed for the 60 °C developed biofilm, while the 40 °C formed biofilm bacteria were relatively stable during the MD operation process. Finally, a three-phase model was suggested for the biofilm formation on the MD membrane.

A study on optimal schedule of membrane cleaning and replacement for spiral-wound SWRO system

In this work, the optimal schedule of membrane cleaning and replacement of spiral-wound SWRO (seawater reverse osmosis) system was studied and analyzed under different feed conditions. Firstly, the spiral-wound RO process model described by differential and algebraic equations was established with the consideration of membrane fouling. Then the optimization problem was formulated to minimize the daily cost of the SWRO system, and a new method by which the optimization problem was transformed as an NLP problem was proposed to solve the problem effectively and quickly. The method was used for SWRO case study and was compared with the traditional method in the form of MINLP. Computing results demonstrate that the proposed method has the advantages of efficiency and stability. Moreover, it can get schedule of membrane cleaning and replacement with lower operational cost as well as give more detailed information of membrane channel. Lastly, influence of feed temperature and feed concentration of seawater was analyzed with the new method. Computing results show the stability of the new method and lead to new profiles of optimal operational variables and performance when feed temperature and salt concentration change, which are quite different from those in designed conditions.

Effect of Feed Temperature on the DCMD Performances in Treating Synthetic Textile Wastewater

This article discussed the effect of feed temperature on the performance of direct contact membrane distillation (DCMD) in treating synthetic textile wastewater containing dissolved dye and salt. The DCMD experiments were conducted using an in-house made composite hollow fiber membrane made of organic polyvinylidene fluoride (PVDF) and inorganic Cloisite 15A. Prior to dyeing solution treatment process, the influence of feed temperature on membrane permeability was first investigated using deionized water. Then, the membrane was tested using synthetic solution containing 50 mg L-1 acid red 1 and 60 g L-1 sodium chloride. The inlet temperature of the feed solution was varied in the range of 50 to 90°C while the temperature of permeate solution was kept constantly at 20°C. The results showed that the vapor fluxes of membrane increased with increasing the feed temperature and maximum flux (Jv = 20.88 kg m-2 h-1) was obtained at 90°C.This is mainly due to the higher water vapor pressure sensitivity at the feed side of a higher operating temperature. With respect to separation performance, it is reported that DCMD process could easily achieve excellent rejection for both dye compound and dissolved salts, recording more than 99% rejection.

The influence of feed temperature and composition on the conversion of KCl into KHSO4 in a membrane reactor combined with direct contact membrane distillation

The studies of a conversion of KCl with H2SO4 into KHSO4 were performed using a chemical reactor coupled with direct contact membrane distillation. The feed temperature at the inlet of the membrane distillation (MD) module amounted to 333 or 343K and the permeate temperature was 293K. The concentration of solutions with various initial molar ratios of KCl to H2SO4, in the MD membrane reactor resulted in the formation and periodical precipitation of KHSO4 in the feed tank. The application of the membrane reactor enabled a continuous removal of HCl from the reaction mixture through the polypropylene membrane to shift the equilibrium of the conversion. Pure hydrochloric acid reaching a concentration of 43g/dm3 was obtained.It was found that higher feed temperature and excess of sulphuric acid in relation to KCl was profitable. In the case of the conversion at 343K with the reaction mixture containing KCl and H2SO4 in the molar ratio of 1:2, the efficiency of KHSO4 production was high. The potassium conversion coefficient was about 93%. Pure KHSO4 was precipitated from the concentrated solution.

A novel model based on cluster formation for pervaporation separation of polar components from aqueous solutions

Abstract This study investigates pervaporation performances for the separation of ethanol–water mixtures using composite polydimethylsiloxane (PDMS). The probability of cluster formation into PDMS matrix was analyzed by molecular dynamics simulation (MD) technique. Cluster formations within water–water and ethanol–ethanol molecules into PDMS were not observed, but ethanol–water dimerization was evidenced by MD simulation. When molecules aggregate, their average sizes increase; hence, diffusion coefficients of components decrease. Based on these assumptions, a new semi-empirical model for diffusion coefficients of penetrants in membrane was proposed. Then using this theory, the solution–diffusion model was modified and the process was simulated. Diffusion coefficient parameters were obtained by minimization error between simulation and experimental results at different concentrations. The behaviour of pervaporation experimental results as a function of concentration has confirmed the proposed model. Influences of feed temperature, feed flow rate, membrane thickness and permeate-side pressure on the membrane separation performance were predicted by the model. Simulation results showed excellent agreement with the experimental data.

Boron removal from aqueous solution by direct contact membrane distillation

The removal of boron from aqueous solution by direct contact membrane distillation (DCMD) was studied with self-prepared polyvinylidene fluoride (PVDF) hollow fiber membranes in the present work. The effect of pH, boron concentration, temperature and salt concentration of the feed solution on the boron rejection was investigated. The experimental results indicated that boron rejection was less dependent on the feed pH and salt concentration. DCMD process had high boron removal efficiency (>99.8%) and the permeate boron was below the maximum permissible level even at feed concentration as high as 750 mg/L. Although the permeate flux was enhanced exponentially with the feed temperature increasing, the influence of feed temperature on the boron rejection could be neglected. Finally, the natural groundwater sample containing 12.7 mg/L of boron was treated by DCMD process. The permeate boron kept below 20 μg/L whether the feed was acidified or not, but pre-acidification was helpful to maintain the permeate flux stability. All the experimental results indicated that DCMD could be efficiently used for boron removal from aqueous solution.

Application of hydroxy sodalite films as novel water selective membranes

Supported hydroxy sodalite (H-SOD) membranes were prepared on α-alumina disks using direct hydrothermal synthesis at 413 K for 3.5 h. The continuity of the membranes was verified using single gas permeation of He and N 2 at ambient conditions. The membranes were impermeable to N 2 and He, which validated absence of defects in the membrane structure. The membranes were used in dewatering several organic alcohol/water mixtures (organic alcohol being: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, and 2-pentanol). The influence of feed temperature (303–473 K), feed concentration (0–100 mol% alcohol in the feed), and absolute feed pressure (1.6–2.4 MPa) on the water flux were analyzed. The absolute feed pressure had no effect on the water permeance. The membrane exhibited a water/alcohol separation factor larger than 10 6 and showed excellent thermal, mechanical, and operation stability in continuously dehydrating a water/ethanol mixture (72 mol% water) by pervaporation at 473 K and 2.2 MPa for 125 h. The normalized water flux correlated well with the water feed concentration for the primary alcohols. Below 40 mol% water in mixtures with secondary alcohols the water flux was three orders of magnitude lower. The water mobility through the membrane had an activation energy of ∼15 kJ/mol.

Transport of Binary Mixtures in Pervaporation through a Microporous Silica Membrane: Shortcomings of Fickian Models

This study explores the applicability of the adsorption‐diffusion mechanism to describe the transport of binary “methanol‐water” and “ethanol‐water” mixtures in pervaporation through a commercial microporous silica membrane. Two different adsorption‐diffusion models are considered: one based on Fick's diffusion equation and another based on the Maxwell‐Stefan formulation. Basic models (Fick) assume concentration independent parameters; more complex models (Maxwell‐Stefan) incorporate flux coupling and other non‐idealities. The influence of feed temperature (40°C–90°C) on permeation flux was analysed in terms of activation energy for flux, permeability and diffusion, and heat of adsorption and vaporization. Also the occurrence of coupling effects was studied by determining the effect of feed composition (entire composition range) on permeation flux, permeability and selectivity. Adsorption‐diffusion models based on Fick's diffusion equation can be used to describe coupling effects if they are modified with concentration dependent diffusion and/or sorption coefficients. They are incapable of describing drag effects by water on alcohols. These drag effects should be modeled through models based on the Maxwell‐Stefan theory.

PDF simulations of ethylene decomposition in tubular LDPE reactors

AbstractThe present study deals with turbulent reacting flow simulation inside low‐density polyethylene (LDPE) tubular reactors, based on a detailed computational fluid dynamics (CFD) technique—transported probability density function (PDF) methods. The ability of the PDF methods to provide an exact representation of chemical source terms is ideally suited for coupling complex LDPE chemistry with small‐scale fluid dynamic fluctuations in turbulent flow. LDPE chemistry with a total of 16 scalars provides an ideal test case for illustrating the applicability of an efficient chemistry algorithm based on in‐situ adaptive tabulation. A particle‐based Monte Carlo algorithm is used to solve the joint‐composition PDF equation, whereas a finite‐volume code is used to obtain hydrodynamic fields from the standard k–ε turbulence model. The influence of feed temperature, initiator concentration, and degree of premixing is investigated to gain detailed knowledge of micromixing effects on steady‐state reactor performance. The computational approach provides a low‐cost alternative to experimental and pilot‐plant tests for exploring a variety of design options when making important design and operational decisions, or for investigating unstable reactor operating conditions. The ability of a simplified, but otherwise equivalent multi‐environment‐presumed PDF model to predict turbulence–chemistry interactions close to physical reality is validated using the detailed transported PDF simulations. The transported PDF method is shown to be an excellent tool for obtaining fundamental information on turbulent reacting flows, as well as for deriving simplified models for faster and easier interpretation of these flows when developing safe and efficient chemical processes. © 2005 American Institute of Chemical Engineers AIChE J, 51: 585–606, 2005

Microporous polypropylene and polyethylene hollow fiber membranes. Part 3. Experimental studies on membrane distillation for desalination

Three polypropylene (PP) and one polyethylene (PE) microporous hollow-fiber membranes were used in direct contact membrane distillation (DCMD) and vacuum membrane distillation (VMD) for the desalination of simulated seawater. The influence of feed temperature and feed flow on distillate pure water flux was investigated. The comparison of the PP and PE membranes in DCMD and VMD was carried out. It was found that the water flux increased with the feed temperature and feed flow in both DCMD and VMD. The data also showed that, compared with the PP membranes, higher water flux could be obtained by using PE membranes in both the DCMD and VMD processes.

Effect of feed temperature on permeate flux and mass transfer coefficient in spiral-wound reverse osmosis systems

The objective of the present study was to analyze and model concentration polarization in spiral-wound seawater membrane elements. In particular, the influence of feed temperature, salinity and flow rate on permeate flow and salinity was evaluated. Membrane lifetime and permeate fluxes are primarily affected by the phenomena of concentration polarization (accumulation of solute) and fouling (i.e., microbial adhesion, gel layer formation and solute adhesion) at the membrane surface. Results show that the polymer membrane is very sensitive to changes in the feed temperature. There was up to a 60% increase in the permeate flux when the feed temperature was increased from 20 to 40°C. This occurred both in the presence and absence of solute. Surprisingly, the permeate flux appears to go through a minimum at an intermediate temperature. There was up to a 100% difference in the permeate flux between feed temperatures of 30 and 40°C. The differences were statistically significant ( p<0.05). A doubling of the feed flow rate increased the permeate flux by up to 10%, but only at a high solute concentration. Membrane parameters were estimated using an analytical osmotic pressure model for high salinity applications. A combined Spiegler—Kedem/film theory model described the experimental results. The modeling studies showed that the membrane transport parameters were influenced by the feed salt concentration and temperature.

Olefin/paraffin gas separations with 6FDA-based polyimide membranes

Pure gas permeation and sorption experiments were carried out for the gases ethylene, ethane, propylene and propane using polyimides based on 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA). Composite membranes and free films were used. Experiments were performed at 308 K and feed pressures up to 17 atm for ethylene and ethane and 9 atm for propylene and propane. Mixed gas permeation experiments were carried out with 50 : 50 olefin/paraffin feed mixtures. For all investigated polyimides, the ideal ethylene/ethane separation factor ranged between 3.3 and 4.4 and the ideal propylene/propane separation factor ranged between 10 and 16 at a feed pressure of 3.8 atm and 308 K. In mixed gas permeation experiments, up to 20% lower selectivity was found for the ethylene/ethane separation and up to 50% reduced selectivity for the propylene/propane separation compared to the ideal selectivity. The influence of feed temperature on separation and permeation properties will be discussed based on pure gas permeability data at 298 and 308 K.

Pervaporation of aromatic C 8-isomers

A pervaporation process was applied to the separation of different mixtures of aromatic C 8-isomers using a dense homogeneous polyethylene membrane. The influence of feed temperature and downstream pressure on the flux of pure components was investigated. For mixtures, the effect of feed composition on permeation rates and separation characteristics was determined. Molar fluxes and separation factors depend on the feed composition. Coupled transport occurs and the extent of coupling depends on the difference in the permeabilities of the pure components. p]The mass transport of pure components through the membrane was modelled for varying downstream pressures with diffusivities linearly dependent on the concentration of all the permeants in the membrane. On the basis of this model, molar fluxes of each component in the mixture of ethylbenzene and p-xylene were calculated and compared with the experimental data. The model and experimental data show good agreement.