Product water flow

Product water flow (after passage through membrane) in product water-side backing... 

Fig. 13. A hoUow-fibet reverse osmosis membrane element. Courtesy of DuPont Permasep. In this twin design, the feedwater is fed under pressure into a central distributor tube where half the water is forced out tadiaUy through the first, ie, left-hand, fiber bundle and thus desalted. The remaining portion of the feedwater flows through the interconnector to an annular feed tube of the second, ie, right-hand, fiber bundle. As in the first bundle, the pressurized feedwater is forced out tadiaUy and desalted. The product water flows through the hoUow fibers, coUects at each end of the element, and exits there. The concentrated brine from both bundles flows through the concentric tube in the center of the second bundle and exits the element on the right.

Eig. 19. Flow diagram of the experimental solar RO unit at Cadatache, France. Feedwater flow = 1.38 L/s, product water flow = 0.69 L/s, energy... 

Scale is caused by precipitation of dissolved metal salts in the feed water on the membrane surface. As salt-free water is removed in the permeate, the concentration of ions in the feed increases until at some point the solubility limit is exceeded. The salt then precipitates on the membrane surface as scale. The proclivity of a particular feed water to produce scale can be determined by performing an analysis of the feed water and calculating the expected concentration factor in the brine. The ratio of the product water flow rate to feed water flow rate is called the recovery rate, which is equivalent to the term stage-cut used in gas separation. 

Crude oil production from the wellhead will always have production water flowing with it. Most of this water is what we call free water. That is, it is not dissolved into the crude oil. Soluble water in crude oil has ranged as high as 1000 parts per million by volume (ppmv), and as low as 20 ppmv. No attempt to remove soluble water is ever made in field production facilities. Rather, substantial equipment and processes are dedicated to the removal of free water. This chapter shall therefore address only free water. Refiners request, and in many cases specify, a 1% free water crude content in all pipeline crude oil received. Thus, the crude oil field production facilities must meet this 1% water requirement in treated crude oil to pipeline sales. 

The product water flows through the porous material in a spiral path until it contacts and flows through the holes in the product water tube. 

The product water flow through the membrane is defined as follows ... 

The solution-diffusion model seems to represent the performance of a reverse osmosis membrane. Figure 4.3 shows the salt rejection and flux of a low pressure polyamide membrane as a function of applied pressure. The membrane was operated on a 5,000 mg/ aqueous solution of sodium chloride at 25°C. As can be seen, there was no product water flow until the applied pressure exceeded the osmotic pressure (50 psi). After this, the flux increased linearly as would be predicted by the above water flux equation. Rejection is poor at lower pressures and increases rapidly until it reaches an asymptote at an applied pressure of about 150 psig. This can be attributed to a near constant flow of salt with a rapidly increasing product water flow which results in a more dilute product or in increased rejection. These data tend to substantiate the assertion of the solution-diffusion model that flow is uncoupled. 

As a rule of thumb, the product water flow with constant net applied pressure will increase about 3% for each degree centigrade increase in feedwater temperature. Salt flux through the membrane is also directly proportional to temperature and the ratio of salt flux to water flux is essentially constant at different temperatures. This results in little or no change in rejection as a function of... 

This relationship can be modified to include product water flow Q i> by introducing recovery R into equation (8.1). 

Membrane desalination plants, especially seawater RO plants, are energy intensive. One option for reducing energy consumption is to use dual-purpose plants that provide both electricity and waste heat for heating RO feed water. Membrane productivity increases with feed water temperature albeit at a slight penalty in product water quality. Higher productivity, in turn, means fewer membrane elements to achieve the same product water flow rate, resulting in reduced Capex and Opex. 

The RO permeate flows to the EDI unit. The EDI system performance specifications are product water recovery = 90% rejection > 99% with the product water conductivity <1.0 pS/cm, and TOC < 10 ppb. The EDI product water flows through a 0.2 pm cartridge final filter and the reject flows back to the holding tank. The high-purity water flows to the point-of-use at 9 m /h. 

In the configuration shown in Figure 5.3, low salinity brackish water (TDS 3000 mg/1) flows to the BWRO system, which produces 34 m /h potable water when operating at about 75% recovery based on a feed water flow rate of 45 m /h. In order to increase the yield, the reject (TDS 12,000 mg/1) flows to the BRO unit at 11 m /h. The product water flow rate from the two RO units is 40 m /h, resulting in an overall recovery of 89%. The total energy consumption is 37 kW (Table 5.3). The integrated system SEC is 0.93 kWh/m. ... 

End of Barrel Products, Water Flow Products, Mold Accessories, Maintenance Accessories, EMI Plastics Equipment (machine and mold accessories), Jackson Center, Ohio, USA. 

Alternative SWRO Membrane fstem Configurations Reverse Osmosis membrane elements are installed in pressure vessels that usually house 6 to 8 elements per vessel (see Fig. 3.7). Multiple pressure vessels are arranged on support structures (racks) that form RO trains. Each RO train is typically designed to produce between 10 and 20% of the total amount of the membrane desalination product water flow. Figure 3.6 depicts one RO train. 

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