Number Of Hollow Fibers Research Articles

Multiobjective optimization of membrane in hybrid cryogenic CO2 separation process for coal-fired power plants.

Post-combustion carbon dioxide (CO2) capture is considered a potential method to mitigate CO2 emissions from fossil fuels burned in power plants. In recent years, combining two different methods of post-combustion CO2 capture such as membrane and cryogenic distillation has been explored for availing the advantages of each method. This study focuses on the optimization of membranes for developing the membrane-cryogenic distillation process. For this purpose, a process flow sheet is developed, and simulation with model components such as compressor, heat exchanger, turbo expander, and distillation column is carried out using Aspen Plus. A membrane model is developed using in-house MATLAB code, and optimization is done to achieve higher concentration and recovery of CO2 using the MOJAYA algorithm. The membrane model is coupled to Aspen Plus through component object model (COM) technology. In this investigation, a hollow fiber membrane is considered. The optimized specifications of membrane modules are length, number of hollow fibers, feed pressure, and permeate pressure which are 0.3 m, 100,000, 5.76 bar, and 0.1 bar, respectively. This analysis results in the purity and recovery of the process of 99.8 and 90%, respectively, and an energy penalty of around 1.74 MJ/kg of CO2. A comparison of other processes available in the literature reveals that the current study renders maximum purity and recovery with a minimum energy penalty.

Modeling of CO2 absorption in a membrane contactor containing 3-diethylaminopropylamine (DEAPA) solvent

Among the pollutants known as greenhouse gasses, carbon dioxide (CO2), although it is less toxic than the others, has by far the most significant amount of pollution in the earth's atmosphere. Also, it is one of the typical components of natural gas, which is removed due to the increase in fuel value and the adjustment of pipeline standards to prevent acid corrosion. There are various techniques for CO2 removal, among which membrane processes are a new and applied technology with many advantages in industrial separation. 3-diethylaminopropylamine (DEAPA) is a new amine absorbent with good interaction with CO2 molecules and increased absorption capacity, which shows good potential for CO2 separation. This study aims to investigate the performance potential of CO2 absorption by an aqueous solution of DEAPA as an absorbent in a hollow fiber membrane contactor (HFMC) with hydrophobic porous polytetrafluoroethylene (PTFE) fibers. A two-dimensional mathematical model was presented and solved based on the finite element method (FEM) to evaluate the CO2 removal efficiency. The effect of different parameters such as amine concentration, liquid and gas flow rate, liquid temperature, CO2 partial pressure, membrane tortuosity, number of hollow fibers, and packing density on CO2 absorption performance was investigated. The model results showed that increasing the gas flow rate and membrane tortuosity has a negative effect on CO2 removal. Also, increasing the amine concentration, packing density, the number of hollow fibers, DEAPA concentration, liquid temperature, and CO2 partial pressure improve the CO2 separation efficiency.

Molecular investigation into the effect of carbon nanotubes interaction with CO2 in molecular separation using microporous polymeric membranes

The use of nanofluids has been recently of great interest to separate acidic contaminants such as CO2. The main objective of this research is to assess the influence of carbon nanotubes (CNTs) addition to distilled water on enhancing the CO2 molecular separation through a porous membrane contactor (PMC). For this aim, a comprehensive model is developed based on non-wetted and counter-current operational modes to evaluate the principal mass and momentum transport equations in tube, membrane and shell compartments of PMC. Consequently, a CFD-based axisymmetrical simulation is implemented according to finite element technique (FET) to prognosticate the results. It is found from the results that the addition of 0.1 wt% carbon nanotubes (CNTs) particles to water significantly enhances the mass transfer and consequently the CO2 molecular separation efficiency from 38 to 63.3%. This considerable enhancement can be justified due to the existence of two momentous phenomena including Brownian motion and Grazing effect, which enhance the mass transport of CO2 molecules in the PMC. Moreover, the effect of CNTs concentration, some membrane's parameters such as number of hollow fibers and porosity and also some module's design parameters including module radius and length on the CO2 separation performance are investigated in this paper as another highlight of the current work.

Computational investigation on the effect of [Bmim][BF4] ionic liquid addition to MEA alkanolamine absorbent for enhancing CO2 mass transfer inside membranes

Nowadays, various types of liquid solutions have been applied to remove acidic contaminants such as CO2 with the aim of mitigating their pernicious emission to atmosphere. Ionic liquids are recently of tremendous attention as promising solutions for CO2 molecular removal from disparate gaseous mixtures due to their superior characteristics such as regeneration simplicity, low volatility and negligible environmental toxicity. The main objective of this paper is to mathematically implement a model based on finite element approach (FEA) to analyze the governing mass and momentum partial differential equations inside the domains of polytetrafluoroethylene-co-perfluorinated alkyl vinyl ether membrane contactor (PFAMC). Also, a computational fluid dynamics (CFD) simulation is carried out to analyze the CO2 molecular removal percentage using MEA absorbent and a mixed solution containing 30% 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) ionic liquid and 70% MEA amine solution. The results show that although MEA has been able to remove only 18% of CO2 from the inlet gas, the addition of 30% [Bmim][BF4] ionic liquid to MEA significantly improved the CO2 mass transfer performance and consequently its removal efficiency to 79%. Study on the effect of some operational parameters such as inlet feed gas flow rate, packing density and number of hollow fibers on removing the CO2 molecules is another objective of this paper.

Automated bundled hollow fiber array-liquid-phase microextraction with liquid chromatography tandem mass spectrometric analysis of perfluorinated compounds in aqueous media

An automated bundled hollow fiber array (BHF)-liquid-phase microextraction (LPME) methodology in combination with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) has been developed for the determination of perfluorinated compounds (PFCs) in environmental aqueous matrices. Eight PFCs were considered, including perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid. Experimental parameters influencing extraction efficiency, such as number of hollow fibers in the BHF extraction device, type of extraction and desorption solvent, extraction conditions (stirring rate, temperature and duration), elution conditions and the salting out effect were examined. Under the most favourable conditions, enrichment factors of between 9 and 40 were achieved for the target compounds when extracting from 10 mL of sample. Good intra and inter-day precision were obtained with relative standard deviations of less than 12%. The linearity range investigated was between 5 and 10,000 ng L−1, with coefficients of determination (r2) ≥ 0.991. The developed method was applied for the UHPLC-MS/MS determination of environmental PFCs in industrial water discharge samples. The automation of BHF-LPME together with UHPLC-MS/MS rendered the method efficient, rapid and sensitive to determine PFCs, with the possibility of on-site real-time monitoring of contaminants in environmental waters.

Renewable CO2 absorbent for carbon capture and biogas upgrading by membrane contactor

Abstract This study employs novel renewable absorbents derived from biogas slurry (BS) for biogas upgrading via membrane contactors. CO2 absorption capacity of biogas slurry can be enhanced by adding alkali solutions, vacuum regeneration or vacuum membrane distillation (VMD). These methods are used to produce four types of renewable CO2 solvents, including vacuum regenerated BS, recovered aqueous ammonia (RAA) from BS by VMD, calcium oxide treated BS and potassium hydroxide treated BS. These renewable absorbents for CO2 capture from biogas by membrane contactors are investigated. CO2 removal efficiency reduces but absorption rates increase with the rise in CO2 volume fraction in the feed gas stream. Absorption temperature has a limited effect on CO2 absorption rates of the renewable absorbents. RAA shows the best CO2 absorption performance among the four types of renewable absorbents in the membrane contactor. RAA flowing on the tube side leads to a 50% higher CO2 removal efficiency compared with RAA on the shell side. At low gas flow rates, partial absorbents and hollow fibers may not be utilized. Thus, selection of membrane module parameters, including the length of module, the number of hollow fibers, biogas flow rates and absorption performance, should be carefully considered when using membrane contactors for biogas upgrading.

Study of the Process of Winding Hollow Fibers

The processes which take place during the winding of hollow fibers are analyzed. The article describes a unit that has been developed to receive flows of hollow fibers of polysulfone (for example) created on equipment designed for forming, finishing, and drying. A bundle is formed by a certain number of hollow fibers having a certain length. As a hollow fiber is wound on the reel of the unit, it is subjected to tensile, centrifugal, and bending forces and the external pressure exerted by other fibers. The method that is described for calculating the stresses which develop in hollow fibers during their winding onto a reel makes it possible to determine the diameter of the reel’s working spokes that is optimum from the standpoint of keeping the stresses at an acceptable level.

Numerical Approach for Optimal Design of a Hollow Fiber Dialyzer System

A numerical approach for an optimal designing of a countercurrent hollow fiber dialyzer has been proposed by utilizing the membrane transport model based on the porous media theory. The three-dimensional numerical computations have been conducted to capture individual concentration fields, namely, blood, dialysate and membrane phases within a hollow fiber dialyzer. Clearances for the Creatinine and Vitamin B12 obtained from present numerical simulations are compared against available experimental date so as to examine the validity of the present method. Subsequently, the effects of housing of countercurrent hollow fiber dialyzers on the mass transfer rate have been also investigated by utilizing several types of hollow fiber dialyzers. Furthermore, a series of calculations have been carried out with variation of the number of hollow fibers so as to find the effective hollow fiber dialyzer for given pumping power. The present numerical methods based on the membrane transport model can be useful for optimization of hollow fiber dialyzer systems.

Continuous Cometabolic Transformation of 4-Chlorophenol in the Presence of Phenol in a Hollow Fiber Membrane Bioreactor

An immobilized cell hollow fiber membrane bioreactor was operated continuously for the cometabolic transformation of 4-cp in the presence of phenol. In contrast to the batch operation of the bioreactor in which the immobilized cells were exposed to decreasing substrate concentrations, at high substrate concentrations, under continuous operation, dissolved oxygen was found to be a limiting nutrient. It was found that substrate degradation was enhanced by aerating the feed with pure oxygen. It was also found that the optimum number of hollow fibers in the bioreactor was 25, ca. 30% bioreactor volume. This occurred due to a balance of the pore space available for cell immobilization in the fibers against the extracapillary space available for suspension cell growth. During continuous operation, regardless of feed rate (21–60 mL∙ h−1 ) , the maximum substrate loading was found to be 9 mg∙ h−1 each of phenol and 4-cp in order that both substrates were completely transformed. In anticipation of reduced provisio...

Neonatal Hemodialysis and Continuous Renal Replacement Therapy

After completing this article, readers should be able to: 1. Describe catheters, dialyzers, and blood lines in hemodialysis for neonates. 2. Explain the blood prime and hemodialysis prescription in hemodialysis for neonates. 3. List potential complications of hemodialysis for neonates. 4. Identify the types of continuous renal replacement therapy (CRRT) in neonates. 5. Explain the dialysis prescription and anticoagulation options for CRRT in neonates. 6. List potential complications of CRRT in neonates. Since the mid-1980s, when dialysis manufacturers began making dialyzers and blood circuit paths that required smaller extracorporeal volumes, hemodialysis has been used successfully to manage renal failure in neonates and infants. Compared with peritoneal dialysis (PD), which is analogous to the “family sedan” in the world of dialysis (slower, more predictable, easier to operate), hemodialysis is the “race car.” Hemodialysis is capable of removing fluids and solutes much more rapidly than is PD. Unlike PD, hemodialysis uses catheters that access the intravascular space directly. Despite the advantages of hemodialysis, the process in neonates is technically more challenging than PD due to the very attributes that make it so effective. Rapid removal of intravascular fluids, exceeding the rate of refill from the extravascular space, causes problems with hypotension due to direct reduction in intravascular volume. Similarly, rapid rates of solute clearance can cause problems with increased intracranial pressure. Catheter placement and maintenance of catheter function can constitute a significant obstacle to hemodialysis. Hemofiltration is very similar to hemodialysis in that patient blood is circulated through an artificial kidney. However, hemofiltration differs from hemodialysis in three significant aspects. First, the hemofilter has larger pore sizes than the standard dialyzer, which allows for excellent fluid removal, even with low blood flow rates, and better larger molecule clearance. Second, hemofiltration runs continuously without the continuous presence of a dialysis nurse. Third, typical hemofiltration uses a pre- or postdilution …

Renal Replacement Therapy: Physical Properties of Hollow Fibers Influence Efficiency

Physical properties of filters for continous renal replacement therapy have a great impact on biocompatibility. According to Poiseuille's law, a filter with more and shorter hollow fibers should offer a decreased pressure drop and, therefore, lower transmembrane pressure (TMP). The aim of this study was to study the effect of a new filter configuration in terms of TMP and clotting compared with the standard configuration. In a prospective randomized cross-over study 2 polysulphone hollow fiber hemofilters, one handmade, which differed only in length and number of hollow fibers were compared. In each group 12 filters were investigated during continous venovenous hemofiltration in patients with acute renal failure due to septic shock. Pressures were measured every 3 hours and running time until filter clotting was documented. Mediators before and after the filter, at the end of treatment and in filtrate were assessed. The standard filter with longer hollow fibers had significantly lower TMPs (106 vs. 194 mmHg, p=0.02) and longer running times (1276 vs. 851 min, p=0.04). There were no differences in hematocrit, total protein, cellular and plasmatic coagulation or blood temperature. No significant elimination of mediators was shown. In contrast to our expectations, the filter with the longer hollow fibers had a better performance, as it ran longer and had lower TMP This may be due to slower blood flow leading to an increase in blood viscosity in a filter with a larger cross section.

Microporous Membrane Solvent Extraction in Multiple-Fiber Passes and One-Shell Pass Hollow-Fiber Modules

ABSTRACT The performance for solvent extraction in microporous membrane hollow—fiber modules with various fiber passes, but with a specified total number of hollow fibers, has been calculated. Increasing the fiber passes, as well as decreasing the total cross—section area of flowing channels inside the hollow Fibers, will increase the fluid velocity, thereby leading to an increased mass-transfer coefficient. Considerable improvement in the mass—transfer rate is obtainable if multiple—fiber passes, instead of a one—fiber pass, are arranged in a hollow—fiber module with a total number of fixed hollow fibers.

Adverse events in breastfed infants exposed to antihistamines in maternal milk

An automated bundled hollow fiber array (BHF)-liquid-phase microextraction (LPME) methodology in combination with ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) has been developed for the determination of perfluorinated compounds (PFCs) in environmental aqueous matrices. Eight PFCs were considered, including perfluoroheptanoic acid, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, perfluorododecanoic acid, perfluorotridecanoic acid, perfluorotetradecanoic acid. Experimental parameters influencing extraction efficiency, such as number of hollow fibers in the BHF extraction device, type of extraction and desorption solvent, extraction conditions (stirring rate, temperature and duration), elution conditions and the salting out effect were examined. Under the most favourable conditions, enrichment factors of between 9 and 40 were achieved for the target compounds when extracting from 10 mL of sample. Good intra and inter-day precision were obtained with relative standard deviations of less than 12%. The linearity range investigated was between 5 and 10,000 ng L−1, with coefficients of determination (r2) ≥ 0.991. The developed method was applied for the UHPLC-MS/MS determination of environmental PFCs in industrial water discharge samples. The automation of BHF-LPME together with UHPLC-MS/MS rendered the method efficient, rapid and sensitive to determine PFCs, with the possibility of on-site real-time monitoring of contaminants in environmental waters.

Optimization of hemofilters for the development of implantable artificial kidneys.

The concept of developing an implantable artificial kidney demands, in addition to the regeneration of endogenous filtrate, a small hemofilter with a high filtration rate. Conventional capillary filters are limited in their capacity to yield adequate filtrate, even if the number of capillaries is increased. To improve filter design so as to modify flow conditions for filtration rate augmentation, it is necessary to consider such factors as blood flow through a single capillary, wall shear rate, and transmembrane pressure (ptm) in in vivo applications, where such biological considerations as blood pressure, blood flow, and flow characteristics of blood are important. These requirements lead to a completely new filter type, the "curl filter," characterized by a large effective filtration surface in a relatively small number of hollow fibers in which optimal flow conditions prevail.