Bypass filtration

The volume filtered in 15 min on a 47 mm diameter, 0 45 p-m Millipore membrane is measured at a vacuum pressure of 0.5 bar. Tlie volume can vary from 1 to 5 liters. Tlie most important factor to monitor is the way it changes with time in the system and downstream from bypass filtration whose efficiency can thereby be estimated. 

Another purpose of removing ionic species from the water or coolant loop is to maintain the desirable low ionic conductivity of these fluids to avoid shunt current, which is an internal short current (ionic) and also accelerates local corrosion. Typically, a bypass filtration loop through a deionizing (demineralizing) filter is used to continuously clean up a portion of the liquid. Replacement or regeneration of the ion filter or other filters is necessary to ensure the effectiveness of those filters. 

Anodizing solutions are not generally filtered on non-automated plants, although periodic batch filtration is desirable. Seal solutions benefit from continuous or bypass filtration, and may also require periodic carbon treatment to remove discolouration from the dyes used. A filtration system comprising a main filter element and an activated carbon chamber can provide continuous protection throughout the life of the element and carbon content. Ideally, a separate filter should be used on the seal tank. 

Four cycle diesel engines generally need fuU-fiow and bypass filters together. Bypass filtration helps to reduce rod and main bearings wear and piston ring wear. A bypass system is shown in Figure 5.10. Here, the oil pump feeds the main gallery... 

With bypass filtration in use by itself, only a proportion of the main flow is filtered and therefore the general level of contamination in the system would rise. The filter element life would generally be short, particularly if a smaller filter is matched to the lower flow rate. For example, if an electrohydraulic servo valve is being protected by its own small fine filter, the system must also include additional filtration. 

Batch filtration is similar to bypass filtration in that fluid is drawn from the reservoir and passed through a filter before being returned for further use. This is carried out by an independent unit, which may be used to batch filter any number of separate systems. 

The primary water specifications for a PWR are given in Table 1 (4). Rigid controls are appHed to the primary water makeup to minimise contaminant ingress into the system. In addition, a bypass stream of reactor coolant is processed continuously through a purification system to maintain primary coolant chemistry specifications. This system provides for removal of impurities plus fission and activated products from the primary coolant by a combination of filtration (qv) and ion exchange (qv). The bypass stream also is used both to reduce the primary coolant boron as fuel consumption progresses, and to control the Li concentrations. 

The gas quality feeding the dry faee seal should be elean and dry. Due to the possibility of eondensation of the proeess gas in the seal eavity, it was deeided to use a seal gas heater. The heater eontrol was set to provide warm gas at 15°C above the dew point to ensure no eondensate entered the seal eavity. Also, a dual filter in series with 5 and 2 p filtration elements was ehosen to provide an ideal sealing environment and maintain the optimum performanee of the seal. To reduee the risk of seal damage during reverse rotation of the turboexpander, programming logie was set to open the eompressor bypass valve whenever a shutdown impulse was initiated. 

Improper filtration plugged filters bypassing of filters... 

Biomass Production. Biomass is usually measured by dry weight of viable cells per unit volume X. We bypass the sometimes tricky problems associated with this measurement except to say that it is the province of the microbiologist and usually involves plate cultures and filtration followed by drying. Suppose there is one limiting nutrient S, and that all other nutrients are available in excess. Then the Monod model for growth is... 

Figure 4 shows the radon produced with the filter bypassed and Figure 5 shows the radon in air and water use with the data analyzed for average radon before and after filtration by averaging the radon in air. The average value for filter bypassed is 2.39 pCi/1 for days 1 and 2, and 2.67 pCi/1 for days 5, 6, and 7. The radon in air for the days with the filter connected (days 8, 9, 10) is 1.00 pCi/1. 

The mobility of very slowly degradable compounds or persistent metabolites present in surface water or bank filtration-enriched ground water is of particular interest for the production of potable water. In common with many other compounds, certain surfactants, and especially their polar metabolites, have the potential to bypass the technical purification units used, which may include flocculation (active charcoal) filtration, ozonation or chlorination, and thus can be found ultimately in drinking water destined for human consumption (see Chapter 6.4). 

A hyperfiltration process developed by Mobil Oil, now ExxonMobil, for this separation is illustrated in Figure 5.28(b). Polyimide membranes formed into spiral-wound modules are used to separate up to 50 % of the solvent from the dewaxed oil. The membranes have a flux of 10-20 gal/ft2 day at a pressure of 450-650 psi. The solvent filtrate bypasses the distillation step and is recycled directly to the incoming oil feed. The net result is a significant reduction in the refrigeration load required to cool the oil and in the size and energy consumption of the solvent recovery vacuum distillation section. 

To a solution of 1 mmol of (-)-/V-bcnzyloxycarbonylnorcphcdrinc in 10 mL of dry benzene is added 0.3 mmol of pyridinium tosylate and 1.1 mmol of methyl 4 4-dimethoxy-2-butenoate. The mixture is refluxed for 12 h with a bypassed dropping funnel filled with 4 A molecular sieves placed between the flask and the reflux condenser. The mixture is cooled, 10 mL of Et20 arc added, the filtrate washed with 5% aq NaHCOj and sat. aq NaCl and finally dried over Na2S04. The mixture is then filtered and the solvent evaporated in vacuo. GC analysis of the crude product gives a d.r. of 94 6. Chromatographic purification gives the 2-alkenyloxazolidine 1 in 88% yield. [a]D —81.6 (c = 1, CHCf,). 

Filters. Proper filtration is necessary to protect the equipment, the environment, and to prevent recontamination of the work. Good filtration adds to the initial cost, but saves maintenance cost as well as increasing overall system reliability. The filters must be compatible with the temperature and pressure of the system and installed with bypass circuits to facilitate periodic replacement. They must be fabricated from material compatible with the carbon dioxide in the supercritical, gaseous and liquid forms as well as any cosolvent and the contaminant to be removed. There are four areas where filtration is required for the safe and efficient operation of the cleaning system ... 

Leaves should be rigid and free from flexing as filtration pressure increases. Any movement of the leaf during filtration will form cracks in the filter cake and permit unfiltered hquid and filter aid to bypass the precoat. 

---