Mathematic Model of Unsteady Penetration Mass Transfer in Randomly Packed Hollow Fiber Membrane Module

Based on the membrane-based absorption experiment of CO2 into water, shell-side flow distribution and mass transfer in a randomly packed hollow fiber module have been analyzed using subchannel model and unsteady penetration mass transfer theory. The cross section of module is subdivided into many small cells which contains only one hollow-fiber. The cross sectional area distribution of these cells is presented by the normal probability density distribution function. It has been obtained that there was a most serious non-ideal flow in shell side at moderate mean packing density, and the large amount of fluid flowed and transferred mass through a small number of large voids. Thus mass transfer process is dominated by the fluid through the larger void area. The mass transfer process in each cell is described by the unsteady penetration theory. The overall mass transfer coefficient equals to the probability addition of the mean mass transfer coefficient in each cell. The comparisons of the values calculated by the model established with the empirical correlations and the experimental data of this work have been done.The predicted overall mass transfer coefficients are in good agreement with experimental data.

CFD simulation of flow field and resistance in a 19-core tandem ceramic membrane module

CFD simulation of the permeation process of a 19-core tandem ceramic membrane module was established to investigate flow field and resistance and its change in permeate flux to the membrane element position and the channel of each membrane element.The results show that when the volume flow rate changes from26 m3·h-1 to 89 m3·h-1,the resistance of each part of the membrane module increases gradually.The increase in resistance loss in the membrane element is faster than the plates and the bell mouths.In a single ceramic membrane module,the maximum difference in flow rate of each membrane tube is 7.23%.In a single membrane tube,the outer ring channels 3–5,3–6,3–7,3–8 are relatively slow.The maximum mass flow deviation from the mean is 2.7%.This work helps to clarify the flow mechanism within the modules,optimize the structure of the equipment and provide a reliable basis for the improvement of industrial ceramic membrane modules.

Evaluation of hollow fiber T-type zeolite membrane modules for ethanol dehydration

This work presents the design of hollow fiber T-type zeolite membrane modules with different geometric configurations. The module performances were evaluated by pervaporation dehydration of ethanol/water mixtures. Strong concentration polarization was found for the modules with big membrane bundles. The concentration polarization was enhanced at high temperature due to the higher water permeation flux. The increase of feed flow could improve water permeation flux for the membrane modules with small membrane bundle.Computational fluid dynamics was used to visualize the flow field distribution inside of the modules with different configurations. The membrane module with seven bundles exhibited highest separation efficiency due to the uniform distribution of flow rate. The packing density could be 10 times higher than that of the tubular membrane module. The hollow fiber membrane module exhibited good stability for ethanol dehydration.

Development of CO2 Selective Poly（Ethylene Oxide）-Based Membranes： From Laboratory to Pilot Plant Scale

Membrane gas separation is one of the most promising technologies for the separation of carbon dioxide （CO2） from various gas streams. One application of this technology is the treatment of flue gases from combustion processes for the purpose of carbon capture and storage. For this application, poly（ethylene oxide）-containing block copolymers such as Pebax or PolyActiveTM polymer are well suited. The thin-film composite membrane that is considered in this overview employs PolyActiveTM polymer as a selective layer material. The membrane shows excellent CO2 permeances of up to 4 m^3（STP）.（m^2·h·bar）^-1 （1 bar = 105 Pa） at a carbon dioxide/nitrogen （CO2/N2） selectivity exceeding 55 at ambient temperature. The membrane can be manufactured reproducibly on a pilot scale and mounted into fiat-sheet membrane modules of different designs. The operating performance of these modules can be accurately predicted by specifically developed simulation tools, which employ single-gas permeation data as the only experimental input. The performance of membranes and modules was investigated in different pilot plant studies, in which flue gas and biogas were used as the feed gas streams. The investigated processes showed a stable separation performance, indicating the applicability of PolyActiveTM polymer as a membrane material for industrialscale gas processing.

Introducing 3D-potting:a novel production process for artificial membrane lungs with superior blood flow design

Currently,artificial-membrane lungs consist of thousands of hollow fiber membranes where blood flows around the fibers and gas flows inside the fibers,achieving diffusive gas exchange.At both ends of the fibers,the interspaces between the hollow fiber membranes and the plastic housing are filled with glue to separate the gas from the blood phase.During a uniaxial centrifugation process,the glue forms the“potting.”The shape of the cured potting is then determined by the centrifugation process,limiting design possibilities and leading to unfavorable stagnation zones associated with blood clotting.In this study,a new multiaxial centrifugation process was developed,expanding the possible shapes of the potting and allowing for completely new module designs with potentially superior blood flow guidance within the potting margins.Two-phase simulations of the process in conceptual artificial lungs were performed to explore the possibilities of a biaxial centrifugation process and determine suitable parameter sets.A corresponding biaxial centrifugation setup was built to prove feasibility and experimentally validate four conceptual designs,resulting in good agreement with the simulations.In summary,this study shows the feasibility of a multiaxial centrifugation process allowing greater variety in potting shapes,eliminating inefficient stagnation zones and more favorable blood flow conditions in artificial lungs.

A Seawater Desalination Paradigm Utilizing Solar Energy

The scarcity of potable water added more pressure on the Palestinian and is considered obstacles in planning for sustainable development. It is so important to find alternatives that have no adverse effect on the environment and at the same time provide genuine solutions to the available resources. In this paper a new paradigm for desalinating brackish and seawater is introduced. The proposed system is technically descried with size optimization that may cater for providing definite amount of potable water serving small communities. The main driving energy, electrical and thermal, is converted from the all around year available solar radiation.

Fouling distribution in forward osmosis membrane process

Fouling behavior along the length of membrane module was systematically investigated by performing simple modeling and lab-scale experiments of forward osmosis （FO） membrane process. The flux distribution model developed in this study showed a good agreement with experimental results, validating the robustness of the model. This model demonstrated, as expected, that the permeate flux decreased along the membrane channel due to decreasing osmotic pressure differential across the FO membrane. A series of fouling experiments were conducted under the draw and feed solutions at various recoveries simulated by the model. The simulated fouling experiments revealed that higher organic （alginate） fouling and thus more flux decline were observed at the last section of a membrane channel, as foulants in feed solution became more concentrated. Furthermore, the water flux in FO process declined more severely as the recovery increased due to more foulants transported to membrane surface with elevated solute concentrations at higher recovery, which created favorable solution environments for organic adsorption. The fouling reversibility also decreased at the last section of the membrane channel, suggesting that fouling distribution on FO membrane along the module should be carefully examined to improve overall cleaning efficiency. Lastly, it was found that such fouling distribution observed with co-current flow operation became less pronounced in counter- current flow operation of FO membrane process.