Separators pressure loss

The separator pressure losses are defined as the difference between the sums of static and dynamic pressure before and after the separator. To express the characteristic parameter corresponding to the pressure loss of a separator, the pressure loss coefficient is frequently used where the subscript D is related to the characteristic dimensions of the separator. The pressure loss coefficient depends on the pressure loss of the separator, gravitational acceleration, flow rate gas density and separator dimensions. 

Pressure Drop. The prediction of pressure drop in fixed beds of adsorbent particles is important. When the pressure loss is too high, cosdy compression may be increased, adsorbent may be fluidized and subject to attrition, or the excessive force may cmsh the particles. As discussed previously, RPSA rehes on pressure drop for separation. Because of the cychc nature of adsorption processes, pressure drop must be calculated for each of the steps of the cycle. The most commonly used pressure drop equations for fixed beds of adsorbent are those of Ergun (143), Leva (144), and Brownell and co-workers (145). Each of these correlations uses a particle Reynolds number (Re = G///) and friction factor (f) to calculate the pressure drop (AP) per... 

Absorber oil units offer the advantage that Hquids can be removed at the expense of only a small (34—69 kPa (4.9—10.0 psi)) pressure loss in the absorption column. If the feed gas is available at pipeline pressure, then Httle if any recompression is required to introduce the processed natural gas into the transmission system. However, the absorption and subsequent absorber-oil regeneration process tends to be complex, favoring the simpler, more efficient expander plants. Separations using soHd desiccants are energy-intensive because of the bed regeneration requirements. This process option is generally considered only in special situations such as hydrocarbon dew point control in remote locations. 

As the filter accumulates dust, the pressure loss increases, and the dust removed improves the normal separation. Another effect can be seen with electrostatically charged filter material. During operation, the impurities neutralize the material, and the filter s capacity to separate is reduced. Figure 9.3" shows exam-... 

Equation (14.91) contains only the mass flow ratio /u as a characteristic number of the mechanics of similitude of the mixture. All the other irnpor rant factors, such as particle size, solid density, etc., are contained in the additional pressure-loss coefficient of the solid particles, A, which is determined separately for each material. 

The backpres.sure created by this drum is an additive to the pipe manifold pressure drops and the pressure loss through the separator. Therefore, it cannot be independently designed and not integrated into the backpressure system. The flow capacity of the relief valve(s) must... 

As the process model is made more accurate and complicated, you can lose the possibility of obtaining an analytical solution of the optimization problem. For example, if (1) the pressure losses through the pipe fittings and valves are included in the model, (2) the pump investment costs are included as a separate term with a cost exponent (n) that is not equal to 1.0, (3) elevation changes must be taken into account, (4) contained solids are present in the flow, or (5) significant changes in density occur, the optimum diameter will have to be calculated numerically. 

The volume flow in a typical miniplant is of the order of 101 h 1. The limiting factor is the gravity-driven flow in the separation units, for example, a rectification column. As separation units usually accompany a chemical process, this flow limit dominates the overall capacity of a miniplant. It is surprising that the flow rate is not limited here by the pressure loss. 

One solution to the problem mentioned above is not to rely solely on flow symmetry, but to achieve equidistribution by pressure-loss adjustment by means of flow resistors (see Figure 4.98) [140, 141, 148). In the flow sequence consisting of a main stream tube, fluid inlet, damping tank, distribution tubes and micro device such as a micro mixer, the main pressure drop is nearly always on the last side. The separation layer mixer acts here as a pressure restrictor similar to the sparger mentioned above. This requires accurate control over structural precision of micro fabrication. 

Each of these pressure losses is given derived equations, and each is a separate entry to be added as an algebraic sum for the total pressure loss. This of course is similar to Eqs. (6.14) and (6.15). 

Liquid-gas or solid-gas separation exergy loss can usually be neglected as long as the saturation vapour pressure of the liquid (solid) phase is low (and kinetics fast enough). 

Brine Staging Velocity past the membrane is important. If too low, polarization is excessive, local O rises, and rejection declines. Fouling occurs faster. If too high, pressure losses are higher than they need be, and the osmotic pinch is premature. Since the volume of feed declines continuously, the hydraulic design needs periodic rearrangement. This is commonly done as shown in Fig. 22-64, sometimes known as a Christmas tree. This design is commonly used where the fluid is pumped once, as in RO, NF, and gas-separation systems, but not where recirculation is practiced, as in ultrafiltration. 

The hollow-fiber module is often used when the feed stream is relatively clean, such as in gas separation and pervaporation. It has also been used in the case of seawater desalination, but pretreatment is needed. The module construction given in Fig. 15 A is a typical RO module, where a central pipe is used to uniformly distribute the feed solution throughout the module. This is to avoid the problem of channelling in outside-in model, which means the feed has a tendency to flow along a fixed path, thus reducing the effective membrane surface area. In gas separation, as shown in Fig. 15B, the outside-in model is used to avoid high pressure losses inside the fiber and to attain a high membrane area (13). 

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