Power for compression

Reciprocating Compressors. Prior to 1895, when Linde developed his air Hquefaction apparatus, none of the chemical processes used industrially required pressures much in excess of I MPa (145 psi) and the need for a continuous supply of air at 20 MPa provided the impetus for the development of reciprocating compressors. The introduction of ammonia, methanol, and urea processes in the early part of the twentieth century, and the need to take advantage of the economy of scale in ammonia plants, led to a threefold increase in the power required for compression from 1920 to 1940. The development of reciprocating compressors was not easy Htfle was known about the effects of cycles of fluctuating pressure on the behavior of the... 

Equation (6-95) is valid for incompressible flow. For compressible flows, see Benedict, Wyler, Dudek, and Gleed (J. E/ig. Power, 98, 327-334 [1976]). For an infinite expansion, A1/A2 = 0, Eq. (6-95) shows that the exit loss from a pipe is 1 velocity head. This result is easily deduced from the mechanic energy balance Eq. (6-90), noting that Pi =pg. This exit loss is due to the dissipation of the discharged jet there is no pressure drop at the exit. 

Classification The separation of fine particles from coarse can be effected by use of a fluidized bed (see Drying ). However, for economic reasons (i.e., initial cost, power requirements for compression of fluidizing gas, etc.), it is doubtful except in special cases if a fluidized-bed classifier would be built for this purpose alone. 

Calculate the theoretical power for each case (1) no intercooling, (2) one intercooler, (3) two intercoolers, (4) isothermal compression. 

People often lack respect for the power in compressed air because air is so common, and it is viewed as harmless. At sufficient pressures, compressed air can cause damage if an accident occurred. To minimize the hazards of working with compressed air, all safety precautions should be followed closely. Reasons for general precautions follow. 

It may be noted that energy will be required for compressing the air to the injection pressure which must exceed the upstream pressure in the pipeline. The conditions under which power-saving is achieved have been examined by DZIUB1NSKI(25j. who has shown that the relative efficiency of the liquid pump and the air compressor are critically important factors. 

The power requirement is then that for compression of the gas from pressure Pi to P3 and for imparting the necessary kinetic energy to it. Under normal conditions, however, the kinetic energy term is negligible. Thus for an isothermal efficiency of compression 17. the power required is ... 

Equations B.49 and B.47 minimize the overall compression power for an A-stage compression. However, the basis is for adiabatic ideal gas compression and therefore not strictly valid for real gas compression (see Appendix B). It is also assumed that intermediate cooling is back to initial conditions, which might not be the case with real intercoolers. The power for the corresponding expression for a poly tropic compression is given by ... 

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