Water selectivity feed pressure

Polymeric C02-selective membranes consisting of both mobile and fixed carriers in cross-linked PVA were synthesized. The membranes showed good C02/H2 and CO2/ CO selectivities, and high C02 permeability up to 170 °C. The effects of feed pressure, water content, and temperature on transport properties were investigated. The C02 permeability and C02/H2 selectivity decreased with increasing feed pressure,... 

A review of our recent work on the synthesis and transport properties of new C02-selective membranes follows. Transport properties of the membranes synthesized, including CO2 permeability and flux, H2 flux, CO2/H2, CO2/N2, and CO2/CO selectivities, were studied. The effects of feed pressure, water concentration, and temperature on transport properties were investigated. 

The oxidation process is carried out in the temperature range 300— 450°C, and generally studied at atmospheric pressure. Excess air is usually applied (with some exceptions) and substantial amounts of water vapour may be added to the feed. High initial selectivities (>95%) are feasible, and, although some further oxidation (combustion) of the product is unavoidable, yields of 70—90% are reported in the patent literature. The main by-products are carbon oxides, in addition to minor amounts of acrylic acid, acetaldehyde and formaldehyde. Acrylic acid may be a main product depending on specific catalyst properties and reaction conditions, as described in more detail in Sect. 2.2.3. 

Concentration polarization plays a dominant role in the selection of membrane materials, operating conditions, and system design in the pervaporation of VOCs from water. Selection of the appropriate membrane thickness and permeate pressure is discussed in detail elsewhere [50], In general, concentration polarization effects are not a major problem for VOCs with separation factors less than 100-200. With solutions containing such VOCs, very high feed velocities through... 

The reaction of l-hexene on 1/16 1 Pt/ AlaOj (Engelhard E-302) reforming catalyst extrudates was chosen as the test reaction. Figure 1 shows a schematic of the reactor unit A Waters dual piston HPLC pump rated to provide flow rates between 6 and 600 ml/h with a pressure head up to 414 bar was used to feed 1-hexene (Ethyl Corporation CAS 592-41-6 Lot 851201). By closing the liquid shut-off valve (V3) and opening the gas shut-off valve (V2), either hydrogen or nitrogen gas may be admitted to the reactor unit. The feed gas was selected by a three-way, computer-controlled solenoid valve (VI). 

Feed pressure This is the projected pressure required to the first stage of the RO system. The pressure is a function of the flow rate, water temperature, array, and fouling factor selected. 

The effects of feed pressure on C02 flux and permeability, H2 flux, and C02/H2 selectivity were investigated using a membrane with a thickness of -60pm on the BHA microporous Teflon support. The feed pressures ranged from 1.5 to 2.8atm. Temperature was maintained at 110°C, and water rates were kept at 0.03cc/min for both the feed side and sweep side. The feed gas consisted of 20% C02,40% H2, and 40% N2 (on dry basis) with a feed gas rate of about 60cc/min in the gas permeation experiments. 

Figure 9.8. C02/H2 selectivity versus water content on the sweep side (feed pressure = 2.0atm).

Figure 9.9. Effects of temperature on C02 per meability and C02/H2 selectivity (feed pressure = 2.0atm with increasing water rates at elevated temperatures).

C02, and feed pressure, 393-394 C02, and gas water content, 394—395 C02, and temperature, 397-398 C02, H2 selectivity, 402 C02, and permeability, 402-403 C02 modeling predictions, 400 -08 C02 synthesis, 388-389 C02 transport, 391 -00 commercialization, 380-382 dense metal, 358, 369-371, 381 facilitated transport, 387 failure, 375-378 HyPurium module, 368 inlet feed temperature, 403 106 inlet sweep temperature, 405 -06 integration, 378-380, 381 ion-conductive, 358 ion-exchange, 387 MEDAL, 367 metal, 372-378... 

Fig. 7.15 Membrane area versus selectivity at pressure ratios of 80 and 1000, water vapor flux fixed at 1.1x10 cm / cm s cmHg, water vapor feed concentration 0.2%, retentate concentration 0.02%, feed pressure 8 MPa.

The specification of the feed pressure takes a little thought. We will discuss the selection of column pressure in more detail later in this chapter. We know that the distillate product is propane. We will want to use cooling water in the condenser because it is an inexpensive heat sink compared with refrigeration. Cooling water is typically available at about 305 K. A reasonable temperature difference for heat transfer in the condenser is 20 K. Therefore, reflux drum temperature will be about 325 K. The vapor pressure of propane at 325 K is about 14 atm (206psia). Therefore, the column will have a pressure at the feed tray of something a little higher than 14 atm. 

Kumar et al. [40] reported interesting data for membranes where MCM-48 supports (pore size 2.4 mn) were modified with polyethyleneimine (PEI). They reported an N2/CO2 selectivity of 1.31 ( 293 K) in the absence of water, 17.6 ( 293 K) in the presence of water, and 1.35 ( 363 K) in the presence of water for a feed mixture of 80/20 N2/CO2 and feed pressure of 20 psi (103.4 cm Hg). In the presence of water, the size of the diffusing unit (CO2) increased due to the clustering of water molecules, which in turn reduced the CO2 diffusivity at room temperature, and hence, the PEI-MCM 48 membranes were highly N2 selective in the presence of water. This is opposite to what we and others [10, 12, 13] observe (CO2 selective membrane), and it may be due to the fact that in our case, the amine groups are readily accessible to the CO2 molecules (since they form a brush-like structure) for reactive separation whereas the PEI approach, in contrast, may be dominated by a solution-diffusion mechanism rather than reactive or facilitated transport. 

Figure 6.4.23 Single-pressure nitric acid plant (high pressure) using selective catalytic reduction (SCR) for NO f abatement (BFW boiler feed water). Adapted from Moulijn, Makkee, and Van Diepen (2004).

In this work, a Motor-Operated Valve (MOV) of the Auxiliary Feed Water System (AFWS) has been selected based on several arguments. First, the basic event representing MOV fails to remain open is one of the most important contributors to the CDF based on the standard PSA available. Second, equipment aging, preventive maintenance and surveillance requirements are meaningful for this MOV. This basic event is modelled as a standby-related failure. This valve is normally open and its function is to control the flow from AFWS until Steam Generators on the secondary of a typical Pressurized Water Reactor (PWR) NPP. 

Open a new case in Hysys, select water as the pure component, ASME steam for the fluid package, and then enter the simulation environment. Select the pipe segment from the object palette, double click on the pipe and fill in the connection page. Click on the Worksheet tab set the feed and product stream temperatures to 20°C (isothermal condition) and the feed pressure to 20 atm. Click on the Rating tab then click on Append segment and specify the parameters of the pipe as shown in Figure 2.29. 

One can easily infer from Eq. (13.2) that to maintain the same flux rate (7) at a given temperature, one needs to increase dp to reduce AP (NDP), which is related to the feed pressure by Eq. (13.1). Largerporediameters will allow a higher passage of ionic impurities into the permeate water, and as a result one can see a deterioration in the permeate quahty. Designers of UPW systems should pay adequate attention to this issue when selecting the RO membrane modules. Especially, one needs to ensure that the RO permeate quality should be acceptable for the downstream EDI devices in any UPW system. 

Figure 28.11 Effect of feed pressure on CO2/H2 selectivity. At 110°C with water rates = 0.03/0.03 cm /min (feed/sweep) (Zou and Ho, 2006).

COa-selective membranes containing both mobile and fixed carriers in cross-linked poly(vinyl alcohol) have been synthesized. The membranes have shown high CO2/H2, CO2/N2, and CO2/CO selectivilies and high CO2 permeability up to 170°C. The CO2 permeability and CO2/H2 selectivity decreased with increasing feed pressure, which could be explained with the carrier saturation phenomenon. Both the permeability and selectivity increased significantly with increasing water contents in both feed and sweep. 

A flow diagram for the system is shown in Figure 5. Feed gas is dried, and ammonia and sulfur compounds are removed to prevent the irreversible buildup of insoluble salts in the system. Water and soHds formed by trace ammonia and sulfur compounds are removed in the solvent maintenance section (96). The pretreated carbon monoxide feed gas enters the absorber where it is selectively absorbed by a countercurrent flow of solvent to form a carbon monoxide complex with the active copper salt. The carbon monoxide-rich solution flows from the bottom of the absorber to a flash vessel where physically absorbed gas species such as hydrogen, nitrogen, and methane are removed. The solution is then sent to the stripper where the carbon monoxide is released from the complex by heating and pressure reduction to about 0.15 MPa (1.5 atm). The solvent is stripped of residual carbon monoxide, heat-exchanged with the stripper feed, and pumped to the top of the absorber to complete the cycle. 

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