Interstage cooling

Problems with blade fatigue are common. When interstage cooling is used, water from the cooler is carried over to the blades. These water particles... 

Figure 12-36. Benefits of interstage cooling for air compression system. (Used by permission Skrotzki, B. G. A. Power, p. 72, Jan 1958. McGraw-Hill, Inc. All rights reserved.)...

Figure 8.41. Multistage compression cycle with interstage cooling...

A three-stage compressor is required to compress air from 140 kN/m2 and 283 K to 4000 kN/m2. Calculate fee ideal intermediate pressures, the work required per kilogram of gas, and fee isothermal efficiency of fee process. Assume the compression to be adiabatic and the interstage cooling to cool the air to the initial temperature. Show qualitatively, by means of temperature-entropy diagrams, fee effect of unequal work distribution and imperfect intercooling, on the performance of the compressor. 

Fig. 9. Invariant cycling state temperature profiles for a three-stage, 800 mm diameter pilot plant S02 converter with interstage cooling. Profiles were measured just before switching of the flow direction and are for S02 at 7.6 vol% and a superficial velocity of 0.07 m/s. Catalyst was a commercial potassium-promoted vanadia, Type S101. (Figure adapted from Xiao and Yuan, 1996, with permission of the authors.)...

Techniques for approaching optimum temperature profiles for exothermic reaction, (a) Adiabatic operation of reactors with interstage cooling, (b) Countercurrent heat exchange. (Adapted from Chemical Reaction Engineering, Second Edition, by O. Levenspiel. Copyright 1972. Reprinted by permission of John Wiley and Sons, Inc.)... 

That is, the total work is minimized if the compression ratio for each stage is the same. This result can easily be generalized to any number (ri) of stages (with interstage cooling to the initial temperature), as follows ... 

If there is no interstage cooling or if there is interstage cooling to a temperature other than 7), it can be shown that the optimum compression ratio for each stage (z) is related to the temperature entering that stage (7)) by... 

You want to compress air from 1 atm, 70°F, to 2000 psig, using a staged compressor with interstage cooling to 70°F. The maximum compression ratio per stage you can use is about 6, and the compressor efficiency is 70%. 

A natural gas (methane) pipeline is to be designed to transport the gas at a rate of 50,000 scfm. The pipe is to be 6 in. ID, and the maximum pressure that the compressors can develop is 10,000 psig. The compressor stations are to be located in the pipeline at the point at which the pressure drops to 100 psi above that at which choked flow would occur (this is the suction pressure for the compressors). If the design temperature for the pipeline is 60°F, the compressors are 60% efficient, and the compressor stations each operate with three stages and interstage cooling to 60°F, determine... 

Natural gas (CH4) is transported through a 6 in. ID pipeline at a rate of 10,000 scfm. The compressor stations are 150 mi apart, and the compressor suction pressure is to be maintained at lOpsig above that at which choked flow would occur in the pipeline. The compressors are each two stage, operate adiabatically with interstage cooling to 70°F, and have an efficiency of 60%. If the pipeline temperature is 70°F, calculate ... 

Figure 21.9 Extreme cases for FBCR, both requiring relatively large W(catalyst) (a) approach to equilibrium (b) extent of interstage cooling...

Optimal Multistage Operation with Interstage Cooling... 

Note that fAoi < /a,-i- That is, the mixing of fresh feed with the effluent from stage i - 1 results in a decrease in fA as well as in T. This is a major difference between cold-shot cooling and interstage cooling, in which /A does not change between stages. 

A number of factors may influence the choice of cold-shot cooling rather than interstage cooling in adiabatic operation of an FBCR. (Some of these are explored in... 

Suppose the operating conditions for a four-stage S02 converter, with adiabatic operation within each stage and interstage cooling, are as given in the table below. The other conditions are P = 1 bar feed is 9.5 mol % SO2,11.5% 02,79% N2. 

With packed towers it is considerably more difficult to arrange for cooling, and it is usually necessary to remove the liquid stream at intervals down the column and to cool externally. Coggan and Bourne149 have presented a computer programme to enable the economic decision to be made between an adiabatic absorption tower, or a smaller isothermal column with interstage cooling. 

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