Compression horsepower

Figure 10-11. Curve for estimating compression horsepower. (Reprinted with permission from GPSA Engineering Data Book, lOtb Ed. ...

To obtain the most efficient use of an economizer, studies are needed to balance economizer pressure, condenser pressure and temperature, evaporator surface area, and compression horsepower. These are all interrelated, and horsepower can be saved at the expense of surface areas, and vice-versa. 

The actual horsepower input to the compressor shaft is the sum of the gas compression horsepower plus losses from the compressor wheel friction, fluid friction, gas turbulence, gas hy-passing internally, and seal and hearing friction. 

The optimization of compressor horsepower must be weighed against this type of overall weight/space penalty to the penalties of minimizing compression horsepower by having several stages of oil-gas separation. 

Bill has asked you to calculate the new compression horsepower output from the compressor. Using Eq. (18.1), we note... 

Acid gas behaves differently from sweet gas inside the compressor. Simulation of the actual compression horsepower and temperature rise inside the compressor must be given careful consideration. Of course, the cooling is also an important consideration. Not properly accounting for water condensation and non-aqueous phase changes (especially in final stage) can result in undersized coolers. 

Ghp = gas horsepower, actual compression horsepower, excluding mechanical losses, hp H = head, (ft. lbf)/lb ... 

A rule of thumb for compression troubleshooting is that the theoretical increase of gas due to compression is linearly proportional to a compression horsepower. A useful application of this rule of thumb is the approximation ... 

In every physical solvent process, a portion of the most valuable constituent of the process gas—ordinarily either CH4 or H2—is unavoidably dissolved in the rich solvent. With CH4 this potential loss can be as high as 10% of the total CH4. Standard practice is to flash the rich solvent to an intermediate pressure, M to M of the absorber pressure, and to recompress the flash gas and recycle it to the feed gas. This additional step can reduce CH4 losses to typically 2 or 3% of the CH4 present in the feed gas. The CH4 (or H2) loss is clearly a function of the pressure at which the flash is conducted and standard optimization procedures can be followed to determine this pressure. In some cases, several intermediate flashes, rather than a single flash, are used to reduce compression horsepower. Another method of reducing compression horsepower that has been proposed is to scrub CO2 from the flash gas in a reab-... 

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