Compressor steam jet

Thermocompression Evaporators Thermocompression-evap-orator calculations [Pridgeon, Chem. Metall. Eng., 28, 1109 (1923) Peter, Chimin Switzerland), 3, II4 (1949) Petzold, Chem. Ing. Tech., 22, 147 (1950) and Weimer, Dolf, and Austin, Chem. Eng. Prog., 76(11), 78 (1980)] are much the same as single-effect calculations with the added comphcation that the heat suppied to the evaporator from compressed vapor and other sources must exactly balance the heat requirements. Some knowledge of compressor efficiency is also required. Large axial-flow machines on the order of 236-mVs (500,000-ftVmin) capacity may have efficiencies of 80 to 85 percent. Efficiency drops to about 75 percent for a I4-mVs (30,000-ftVmin) centrifugal compressor. Steam-jet compressors have thermodynamic efficiencies on the order of only 25 to 30 percent. 

Detailed design and technoeconomic calculations in close association with manufacturers of compressors, steam jet ejectors, and steam dryers and with utility companies are required to make confident conclusions regarding the optimal steam reuse and recycle systems for steam dryers. 

Simprosys 3.0 contains 20 unit operation modules and 2 utilities as displayed in Figure 60.2. The 20 unit operation modules include solid dryer, liquid dryer, burner, cyclone, air filter, bag filter, electrostatic precipitator, wet scrubber, scrubber condenser, fan/blower, compressor, steam jet ejector, pump, valve, heater, cooler, heat exchanger that can also be used as an evaporator, liquid-vapor separator. 

Steam-Jet (Ejector) Systems These systems substitute an ejector for a mechanical compressor in a vapor compression system. Since refigerant is water, maintaining temperatures lower than the environment requires that the pressure of water in the evaporator must be... 

The two principal elements of evaporator control are evaporation rate a.ndproduct concentration. Evaporation rate in single- and multiple-effect evaporators is usually achieved by steam-flow control. Conventional-control instrumentation is used (see Sec. 22), with the added precaution that pressure drop across meter and control valve, which reduces temperature difference available for heat transfer, not be excessive when maximum capacity is desired. Capacity control of thermocompression evaporators depends on the type of compressor positive-displacement compressors can utilize speed control or variations in operating pressure level. Centrifugal machines normally utihze adjustable inlet-guide vanes. Steam jets may have an adjustable spindle in the high-pressure orifice or be arranged as multiple jets that can individually be cut out of the system. 

Interstage steam pressures can be boosted with steam jet compressors of 20-30% efficiency or with mechanical compressors of 70-75% efficiency. 

Saturated steam leaves an evaporator at atmospheric pressure and is compressed by means of saturated steam at 1135 kN/m2 in a steam jet to a pressure of 135 kN/m2. If 1 kg of the high pressure steam compresses 1.6 kg of the evaporated atmospheric steam, what is the efficiency of the compressor ... 

An ejector is a simplified type of vacuum pump or compressor which has no pistons, valves, rotors, or other moving parts. Figure 10-98 illustrates a steam-jet ejector. It consists essentially of a nozzle which discharges a high-velocity jet across a suction chamber that is con-... 

Jets have been partially replaced by liquid ring-seal pumps. These are really positive-displacement compressors. The gas is squeezed between the vanes of the compressor s rotor and a pool of liquid in the compressor s case. Liquid ring-seal pumps are not interesting. They have no character. They are not as complex as steam jets. Anyway, I will discuss positive displacement compressors in later chapters. 

Steam jet ejectors are used primarily to evacuate equipment but also as pumps or compressors. They are discussed in Section 7.7. 

Application ranges of the various kinds of devices for maintenance of subatmospheric pressures in process equipment are shown in Table 7.3. The use of mechanical pumps—compressors in reverse— for such purposes is mentioned earlier in this chapter. Pressures also can be reduced by the action of flowing fluids. For instance, water jets at 40psig will sustain pressures of 0.5-2.0psia. For intermediate pressure ranges, down to O.lTorr or so, steam jet ejectors are widely favored. They have no moving parts, are quiet, easily installed, simple, and moderately economical to operate, and readily adaptable to handling corrosive vapor mixtures. A specification form is in Appendix B. 

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