Pumps, centrifugal metering

Booster Pump. Use of a centrifugal booster pump avoids a low intake pressure, particularly for large, high volume units. A low pressure (>26.6 kPa (200 mm Hg)) on the iatake of a timing pump can cause vaporization of the product. The booster pump is ia the circuit ahead of the timing pump and operates only when the FDV is ia forward flow, the metering pump is ia operation, and the pasteurized product is at least 7 kPa (1 psi) above the maximum pressure developed by the booster pump (Fig. 8). 

Positive Pumps. Positive pumps employed by the food industry have a rotating cavity between two lobes, two gears that rotate in opposite directions, or a crescent or stationary cavity and a rotor. Rotary positive pumps operate at relatively low speed. Fluid enters the cavity by gravity flow or from a centrifugal pump. The positive pump also may use a reciprocating cavity, and may be a plunger or piston pump. These pumps are not truly positive with respect to displacement, but are used for metering product flow. 

The centrifugal pump is the type most widely used in the chemical industiy for transferring liquids of aU types—raw materials, materials in manufacture, and finished produc ts—as well as for general services of water supply, boiler feed, condenser circulation, condensate return, etc. These pumps are available through avast range of sizes, in capacities from 0.5 mVh to 2 X 10 mVh (2 gal/min to 10 gaJ/min), and for discharge heads (pressures) from a few meters to approximately 48 MPa (7000 Ibf/iu"). The size and type best suited to a particular apphcation can be determined only by an engineering study of the problem. 

FIG. 10-28 Characteristic curve of a centrifugal pump operating at a constant speed of. 3450 r/min. To convert gallons per minute to cubic meters per hour, multiply hy 0.2271 to convert feet to meters, multiply hy 0..3048 to convert horsepower to kilowatts, multiply hy 0.746 and to convert inches to centimeters, multiply hy 2.54. 

Air samples are typically collected by passing a known volume of air for a specific time period through Chromosorb 102 air sampling mbes (e.g. l.SLmin for 2h) using a Gilian or similar pump and a flow meter. For extraction, the contents of the tube are emptied into a 15-mL distillation receiver and extracted with 10 mL of toluene briefly at 5-min intervals for 15 min. After centrifugation, a portion of the toluene is removed and analyzed using GC/ECD. 

Kinetic Studies. Peracetic Ac id Decomposition. Studies with manganese catalyst were conducted by the capacity-flow method described by Caldin (9). The reactor consisted of a glass tube (5 inches long X 2 inches o.d.), a small centrifugal pump (for stirring by circulation), and a coil for temperature control (usually 1°C.) total liquid volume was 550 ml. Standardized peracetic acid solutions in acetic acid (0.1-0.4M) and catalyst solutions also in acetic acid were metered into the reactor with separate positive displacement pumps. Samples were quenched with aqueous potassium iodide. The liberated iodine was titrated with thiosulfate. Peracetic acid decomposition rates were calculated from the feed rate and the difference between peracetic acid concentration in the feed and exit streams. 

The mixed acid (72), brought to the nitration house by means of a centrifugal pump, is fed into the nitrator via a metering pump. The flow of the two reacting liquids is maintained in the correct proportion by means of speed controller. 

The preneutralizer slurry is pumped at a controlled rate to a rotary-drum, ammoniator-granulator there it is distributed onto a rolling bed of recycled solids. The most commonly used metering system for the preneutralized slurry is a variable-speed centrifugal pump with automatic control from a magnetic flowmeter. Some plants have had success with a magnetic flowmeter and automatic control valve of a special ball type. 

The basic experimental equipment for FFF is, except for the channel and its support, in general identical to the equipment used for liquid chromatography. It is usually composed of a solvent reservoir, a pump, and an injection system the chromatographic column is replaced by the FFF channel, followed by a detector. The FFF channel can require additional supporting devices, such as a centrifuge for sedimentation FFF or a power supply, and other electronic regulation devices for electrical FFF. If necessary, this basic equipment is complemented by a flow meter at the end of the separation system. For special semipreparative purposes, a fraction collector can be attached to the system. 

FIG. 29-51 Application areas for centrifugal pump turbines. Curves apply between the following minimum and maximum limits inlet pressure, 100 to 3000 psig pressure differential, 100 to 2800 Ibl in flow of motive fluid, 200 to 4000 gal/min horsepower, 50 to 3000 hp. Curve horsepower is based on a speed of 3600 r/min and a fluid of 1.0 specific gravity for other fluids, multiply the curve horsepower by specific gravity to get the actual horsepower. To convert pounds-force per square inch to megapascals, multiply by 6.89 X 10" to convert gallons per minute to cubic meters per minute, multiply by 3.79 x 10" and to convert horsepower to kilowatts, multiply by 0.746. 

PPDS works on the principle of metering pumps and employs diaphragm, bellows, centrifugal, or vacuum-pressure-dispense pumps. These systems may be used for slurries including shear-sensitive slurries and cause minimal recirculation during slurry usage and replenishment. 

Ancillary equipment, designed for at least 2.5 MPa (25 bar) meters and flow controls for pressurized ammonia feed and effluent streams centrifugal pumps for discharging into liquid ammonia supply piping and for liquid ammonia loading equipment for safe pressure relief for ammonia vapor and inerts (see Fig. 118 and [1268]). Design of pressure storage tanks and the related safety aspects are discussed in [1270]. 

In continuous systems, preheated crude oil (80°C) and water are metered into an in-dwell pipeline agitator, or a large agitated tank, and held only for a short period. In both systems, the oil is then pumped to a centrifuge for separation of the lecithin sludge from the oil (33, 118, 125-126). Water with a low concentration of calcium and magnesium is preferred (115). 

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