Feed pumps suction side

Feed-water Heaters.—Types include the open heater (Cochrane, Webster) in which the exhaust steam and water mix, and the closed heater, in which the water circulates in tubes surrounded by exhaust steam. Open heaters give slightly higher feed temperatures at the same back pressure, or slightly less back pressure at the same feed temperature. Filters, separators, etc., are provided to remove oil from the exhaust. The open heater forms a convenient receptacle for various drips, for the automatic introduction of any cold water make-up supply and for certain forms of feed-water treatment and purification. It may be of the thoroughfare type in which all exhaust steam in the pipe passes through the heater, or of the draw in type in which a branch from the auxiliary exhaust leads to the heater as a dead end. Open heaters must be located on the suction side of the feed pump and above (preferably 3 ft. or more above) the level of the feed-pump suction valves. 

Black Liquor Soap Recovery. Black Hquor soap consists of the sodium salts of the resin and fatty acids with small amounts of unsaponifiables. The soap is most easily separated from the black Hquor by skimming at an intermediate stage, when the black Hquor is evaporated to 25% soHds (7). At this soHds level, the soap rises in the skimmer at a rate of 0.76 m/h. At higher soHds concentrations, the tall oil soap is less soluble, but higher viscosity lowers the soap rise rate and increases the necessary residence times in the soap skimmer beyond 3—4 hours. The time required for soap recovery can be reduced by installing baffles, by the use of chemical flocculants (8,9), and by air injection into the suction side of the soap skimmer feed pump. Soap density is controUed by the rate of air injection. Optimum results (70% skimmer efficiency) are obtained at a soap density of 0.84 kg/L (7 lb/gal). This soap has a minimum residual black Hquor content of 15% (10—12). 

Severe cavitation damage on the suction side of the pump reveals insufficient water supply to the pump (insufficient net-positive suction head). Such a circumstance could be caused by partially clogged filters or screens upstream of the pump, or simply by insufficient feed of water to the pump. 

Where air bubbles and other gases are entrained in turbulent FW and an abrupt reduction in pressure takes place, cavitation may occur. The result of the extremely rapid formation and collapse of steam bubbles on the suction side of feed pumps or the discharge side of valves produces erosive microjets that over time may promote severe cavitation-al metal wastage. 

Feed points for AVT treatments vary, usually hydrazine is added to the base of the deaerator but it also can be added to the base of the condensate extraction pump. Ammonia (where used) or amine is injected into the suction side of the boiler feed pump. 

An RO feed pump requires a certain volume and pressure of make-up water to the suction side of the RO feed pump so as not to... 

The still for this system is a simple flash still with a forced circulation reboiler. The saponified, crude glycerine stream is fed into the recirculation pump on the suction side. The recirculation rate is in the range of 40-50 times of the crude glycerine feed rate. The top of the stiU vessel is equipped with a pad style entrainment separator to eliminate carryover. 

The sample can be injected ahead of the column, either on the suction side or on the pressure side of the pump. Injection on the suction side is performed by a three-way magnetic valve, which switches between the eluent and the feed. Some pumps have an additional pump head for the injection of the feed. If the sample is injected on the pressure side a switch valve is used. The sample is injected into a sample loop, which is connected to the six-port valve. The volume of the sample loop is adapted to the maximum injection volume of the process (see Tab. 5.1). 

In configurations Figure 5.16b as well as 5.16c and d the fluid loop is broken at the eluent line. Therefore the highest pressure is located at the entrance of the column connected to the pressure side of the pump and the lowest pressure at the outlet of the column connected to the suction side respectively the process outlet. In these cases, the pump operates at constant flow rate. When the eluent line is switched from one column to the next the points of high and low pressures are switched by one column as well. In configuration 5.16a, the pressure all along the system is more or less constant, irrespective of the position of the eluent, extract, feed, and raffinate lines. However, the pump has to change its flow rate if it enters a different zone of the SMB process. 

An RO feed pump requires a certain volume and pressure of make-up water to the suction side of the RO feed pump so as not to cavitate the pump, as discussed above. Low pressure and volume to the suction side of a pump are typically caused by one of the following three problems ... 

Increase the diameter of the suction line (feed pipe to punp). This reduces the velocity and the frictional loss term, thereby increasing iVPSJT. It is standard practice to have larger-diameter pipes on the suction side of a pump than on the discharge side. 

Figure 7-6 shows a plan of the feed gas compressor area for a 200,000 tons per year ethylene unit. Main pipe runs are also shown. It is an In-Line-Layout with equipment in process flow sequence. The large diameter gas lines directly interconnect process equipment. On the complete plot plan, equipment (including compressors) is arranged on both sides of a central yard in process flow sequence. Pumps are located at their point of suction and are lined up under the yard. A parallel road is arranged to every line of equipment for convenient construction and maintenance access. 

Submerged membranes are operated with the feed in a vessel at atmospheric pressure. To obtain a TMP, the permeate side has to be below atmospheric pressure, and this is achieved by suction provided by permeate pumping. The pressure on the permeate side will be determined by the TMP defined by Eq. (10.3) as well as a presstrre drop due to permeatc-side (lumen) flow, which may be significant for hollow fibers. This situation has been analyzed for vertical submerged hollow fibers closed at the bottom and with suction at the top. The situation is depicted in Figure 10.18a for a clean water feed, and the axial flux distribution can be estimated from (Chang et al., 2000)... 

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