Fouling pressure drop

POLARISATION PHENOMENA AND MEMBRANE FOULING pressure drop over the cake are equal. 

Tubular reactors with catalytically- Cheap and simple Could foul. Pressure drop may be high ... 

The values of h, and AP, calculated by this procedure are for clean exchangers and are intended to be as accurate as possible, not conservative. A fouled exchanger will generally give lower heat-transfer rates, as reflected by the dirt resistances incorporated into Eq. (11-2), and higher pressure drops. Some estimate of fouling effects on pres-... 

In the case of particulate fouling, one of the more common types, insuring a sufficient flow velocity and minimizing areas of lower velocities and stagnant flows to help keep particles in suspension is the most common means of deahng with the problem. For water, the recommended tubeside minimum velocity is about 0.9 to 1.0 m/s. This may not always be possible for moderate to high-viscosity fluids where the resulting pressure drop can be prohibitive. 

Pressure Drop Flow resistance depends on flame arrester channel arrangement and on a time-dependent fouling fac tor due to cor-... 

Not easily fouled Lower skirt height than vertical Less pressure drop than vertical Longer tubes possible Ease of maintenance Less cost than kettle High skirt height... 

Horizontal natl. circ. Ease of maintenance Lower skirt height than vertical Less pressure drop than vertical Longer tubes possible Less cost than kettle No theoretical tray Extra space and piping as compared to vertical Fouls easier as compared to vertical Accumulation of higher boiling point components in feed line, i.e., temperature may be slightly higher than tower bottom... 

Mesh strainers finer than 100 mesh/inch (<150 /rm) should be treated as microfilters. Coarser strainers up to 50 mesh/inch (300 /rm) may generate significant static when fouled with accumulated debris, so should be treated as microfilters except in cases where fouling is not expected or may be rapidly identified by either periodic inspection or monitored pressure drop. Clean strainers should nevertheless be placed as far upstream as practical for nonconductive liquid service. A theoretical model for the charging process in strainers (screens) is given in [119-120]. Viscous nonconductive liquids (5-2.5.4) may produce unusually high charging currents in strainers. 

Metering flare gas is important for loss accounting and for control of steam injection. A special requirement for flare gas meters is low pressure drop and the ability to continue functioning in fouling conditions. The flare gas metering methods listed below have been used with varying degrees of success. 

Continnons monitoring of pressure drop and temperature should be carried out. Pressure drop should be monitored if fouling and subsequent plugging is suspected or has previously occurred. Temperature monitoring should be provided if it is possible for a standing flame to occur on the flame arrester face and subsequently destroy the element (see Chapter 7). 

The major factors governing the proper design far clearance under the downcomer (see Figure 8-63), and the distance between the bottom of the downcomer and the tray it is emptying onto are [190] (a) downcomer sealing, (b) downcomer pressure drop, and (c) fouling and/or corrosive nature of the fluids. TTie smaller the clearance, the more stable will be the tray start-up due to the greater restriction to vapor flow into and up the empty liquid downcomer. 

Figure 9-6RR. Intalox Grid-type packing useful for fouling, solids and heat transfer high-strength, low-pressure drop, high capacity, better efficiency than most structured and random packing. Used by permission of Norton Chemical Process Products Corp., Bull. IG-1.

Figure 10-148 presents a recommended pressure drop correlation for low-fin tubes in shells and is based on clean tube pressure drop with no dirt sealing the leakage clearances between tubes and baffle holes or baffle-to-shell clearances. A fouled condition pressure drop may be an indeterminate amount greater. The authors state that this University of Delaware correlation has some lactors built in that limit the deviations to a relatively small range. Figure 10-148 has... 

Reviewing the overhead water wash most overhead condensers are washed continually to minimize fouling. Since multiple bundles are common, solenoids and a PLX3 can be used to wash one bundle at a time, for approximately ten minutes each. This can lower the pressure drop and increase the available cooling with minimal impact. 

Check the recirculating CW pressure. An increase in pressure drop indicates fouled or plugged tubes, or a fouled tube sheet. 

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