Centrifugal absorber pumps

The urea solution leaving the stripper bottom contains about 12 wt% of NH and is further purified in the 1.8 MPa (18 bar) and 0.2 MPa (2 bar) recovery sections of the plant. The resultant NH and CO2 separated in the decomposers is absorbed and returned to the synthesis section by the high pressure centrifugal carbamate pump. 

Centrifugal pumps are made up of several components and are expected to cope in a multitude of environments, some quite hostile, fin understanding of houi they luorh, uihy they tuorh, luhy and houi they go turong and luhat to da about It can only come from a mix of theory and experience, hut the theory needs to be presented in a form which Is absorbable and Interesting if it is to he retained... 

The pressure at any point in the suction line must never be reduced to the vapor pressure of the liquid (see Equation 3-6). Both the suction head and the vapor pressure must be expressed in feet of the liquid, and must both be expressed as gauge pressure or absolute pressure. Centrifugal pumps cannot pump any quantity of vapor, except possibly some vapor entrained or absorbed in the liquid, but do not count cm it. The liquid or its gases must not vaporize in the eye/entrance of the impeller. (This is the lowest pressure location in the impeller.)... 

Centrifugal pumps, as do most other mechanical equipment, generate dynamic forces that must be absorbed by their foundation. The foundation should have a mass that is at least five times that of the installed pump and driver. In addition, the pump assembly must be properly affixed... 

Pressure drop. Good control requires a substantial pressure drop through the valve. For pumped systems, the drop through the valve should be at least 1/3 of the pressure drop in the system, with a minimum of IS psi. When the expected variation in flow is small, this rule can be relaxed. In long liquid transportation lines, for instance, a fully open control valve may absorb less than 1% of the system pressure drop. In systems with centrifugal pumps, the variation of head with capacity must be taken into account when sizing the valve. Example 7.2, for instance, illustrates how the valve drop may vary with flow in such a system. 

The gas is led to a saturator containing a soluhon of 5 to 10% sulfuric acid where the ammonia is absorbed, and crystalline ammonium sulfate is formed. The gas is fed into the saturator through a serrated distributor underneath the surface of the acid liquid. The acid concentration is maintained by the addition of sulfuric acid, and the temperature is kept at 60°C by the reheater and the heat of neutralization. The crystallized ammonium sulfate is removed from the bottom of the saturator by a compressed-air ejector, or a centrifugal pump, and drained on a table, from which the mother liquor is run back into the saturator. 

Theoretical problems with the traditional theory of the parabolic equation relate to the assumption of constant and both of which are functions of the pressure drop across the cake. The pressure drop Ap varies when centrifugal and constant rate pumps are employed. Even in constant pressure filtration, Ap varies with time. At t = 0, there is no cake, and all of the pressnre is absorbed by the medium, as shown in Fignre 22.22. As the cake builds up, the flow rate q drops and the pressure drop across the medium, p, decreases in accord with Equation (22.28) ... 

Prevention of hot spots and efficient removal of the heat of reaction are very important because of the thermal instability of hypochlorites. The continuing reaction of hypochlorite to form unwanted byproducts is part of the discussion of emergency vent scrubbers (Section 9.1.10.3A), where it is more of an issue. Here, we note that the production of high-quality bleach depends on a consistent supply of chlorine in the tail gas and on adequate temperature control. The absorbing solution is therefore circulated by titanium centrifugal pumps around the reactor(s) through titanium coolers, usually of the plate-and-frame type. The recirculation of liquor in itself provides turbulence in the reaction zone, and the volume of circulation determines the maximum temperature possible in the reactor. A gas feed or the vaporization of a liquid chlorine supply may also be used to promote turbulence. 

There are two principal classes of pumps positive-displacement and centrifugal. In positive-displacement pumps, a given volume of fluid is mechanically forced from the suction port to the discharge with every rotation of the shaft. In reciprocating pumps, this is done in a periodic fashion, such that outflow pulsates if multiple cylinders are used, they are phased so as to diminish the amplitude and period of the pulsations, smoothing the flow. Often an air chamber is attached to the discharge line to help absorb these pulsations. 

Absorbent recycle pump (3,2 +1 qwre) Centrifugal, 48,400 gpm, 66-fthead, Rubber liniiig and 316L... 

The wet solvent from the centrifuge is combined with the overflow stream from the surge tank and is pumped to a solvent stripper, where the water (3.5 wt%) is stripped from the solvent to maintain the water balance in the system. The water-vapor flow in the stripper removes unreacted H2S and most of the other gases, such as CO2, co-absotbed in the solvent. Most of the lean solvent exiting the bottom of the solvent stripper is used in the SO2 scrubber to absorb the SO2 from >he combustion gas leaving the furnace. The overhead vapor is condensed in a partial condenser. Approximately 65% of the condensate is fed to a sour-water... 

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