Permeate flow rate

Flow Flux, Permeability, Conversion The productivity of a membrane module is described by its flux J = volumetric permeate flow rate/membrane area with units of volume per area per time. Relatively high flux rates imply that relatively small membrane areas are required. The permeate volume is usually greater than the feed volume for a given process. Flux is also the magnitude of the normal flow velocity with units of distance per time. 

The efficiency of a membrane module is characterized by the recovery or conversion ratio CR = permeate flow rate/feed flow rate. Low conversion means that fluid has to be repeatedly cycled past the TFF module to generate permeate. High-efficienCT NFF has CR = 1. 

It is anticipated that the equilibrium filter cake mass would depend strongly on the axial velocity through the cross-flow filter assembly. The shear rate at the filter surface will increase the entrainment of the catalyst solids for a given permeate flow rate. Therefore, for each differential pressure condition, the axial velocity will be varied in order to quantify the effect of the wall shear on the filter cake resistance term. 

Permeability = (permeate flow-rate/membrane area) x pressure... 

Polymer-Assisted Ultrafiltration of Boric Acid. The Quickstand (AGT, Needham, MA) filtration apparatus is pictured schematically in Figure 3. The hollow fiber membrane module contained approximately 30 fibers with 0.5 mm internal diameter and had a nominal molecular weight cut-off of 10,000 and a surface area of 0.015 m2. A pinch clamp in the retentate recycle line was used to supply back pressure to the system. In a typical run, the transmembrane pressure was maintained at 25 psig and the retentate and permeate flow rates were 25 ml/min and 3 ml/min, respectively. Permeate flux remained constant throughout the experiments. 

Among the configurations described in that paper, the irradiation carried out on the recirculation batch seems very promising since it allows high irradiation efficiency and high membrane permeate flow rate to be obtained and also it is possible to select the membrane type depending on the photocatalytic process under study. 

At constant temperature and for gases such as 02, N2 and H20 which permeate as molecules, the permeability of a material can be expressed as a permeation flow rate (qpy vm) ... 

Another already mentioned application of membrane filtration is for the recovery of ionic liquids from wastewaters. Here the challenge is to find appropriate membranes, since rejection values that have been reported to date [136] are too low for industrial application. However, for similar ionic liquids we found a membrane that shows rejection rates above 99% throughout at considerably high permeate flow rates above 50 L m 2 h 1 in cross flow filtration. Such numbers make washing in combination with nanofiltration an interesting option. 

In some cases, the actual design permeate flow rate of the RO system may differ from the "name plate" flow rating. In most of these situations, the RO system is de-rated by design due to a poor feed water source or as a natural result of low feed water temperature. 

Permeate flow rate is entered here. Units are selected on the project info screen. 

Figure 10.18 shows the output page. This screen shows the input variables such as the selected membrane, permeate flow rates, and recovery. Calculated outputs include ... 

Performance of an RO system, specifically the permeate flow rate, salt rejection and pressure drop, is a function of membrane fouling, scaling, and degradation, as previously discussed (See Chapter 11.3). This chapter covers the detailed effects of membrane fouling, scaling, and degradation have on normalized product flow, normalized salt rejection, and pressure drop. 

Cross-flow filter performance is often characterized by a flux rate, which equates to the permeate flow rate per unit area of membrane surface. The flux rate in most biological separations is reduced by a fouling phenomenon called gel polarization, which tends to concentrate material at the surface of membrane to impose an additional resistance to transmembrane flow. The deterioration in flux rate must be well characterized for a commercial bioseparation process to ensure the correct size for the cross-flow filtration unit and avoid hold-ups at this processing stage. 

Descriptive model and its division into parts. The first steps in the model construction are related to Fig. 3.7. The pump PA assures simultaneously the suspension transport and the necessary transmembrane pressure. The excessive accumulation of the solid in the retentate is controlled by its permanent removal as a concentrated suspension from the reservoir RZ. The clear liquid (permeate) flow rate and the solid concentration in the exit suspension are permanently measured and these values are transferred to the control and command computer CE. The instantaneous values of the operation pressure and input rate of fresh suspension are established by the computer (this works with software based on the mathematical model of the process) and corrected with the command execution system CSE. 

The simulations shown in Figs. 3.10 and 3.12 were made for the following operating conditions 1, for the monodimensional model, the filter was considered to be composed of three identical membranes with a 0.5 m surface, the minimum permeate flow was imposed at 3.8 x 10 m /s, the initial value of the filtration constant ko = 33 x 10 m /m bar 2, in the second case, a 10 m long, 0.075 m high and 0.15 m wide filter was analyzed with a constant permeate flow rate while keeping the initial value of the filtration constant. A concentration of 10 kg/m was used for the fresh suspension. 

Figure 3.17 shows the evolution of the permeate flow rate when we work at constant pressure. We can observe (curves FI and FIS) that controlling the pressure pump with a precision of 0.1 bar (for instance see Table 3.2) produces a mean fluctuation of the flow rate that begins with 20% and progressively decreases to as little as 5% when we approach the total clogged state. In this case of slow surface clogging, it must be mentioned that the operating time before the total... 

If the total permeate flow rate is given by F, say, the component flow rate can be designated as... 

Q( is the crossflow flow rate 2p is the permeate flow rate Ppn is the TMP... 

A new empirical correlation was proposed and for a given permeate flow rate, the energy consumption is lower for a curved module than for a straight one... 

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