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Application Range of Variety of Compressors and Compressor Selection

When I was involved in pre-FEED of well production and gas treatment, one of key deliverable is compressor studyIn this post, I want to share you about application range of variety of compressors (reciprocating, compressor, and axial-flow). In addition, I will also share the differences between those compressors.

Application Range of Variety of Compressors

Figure below can estimate application range of variety of compressors. It is a function of inlet flow in actual cubic feet per minute and discharge pressure in psia. 

Application range of variety of compressors
Application range of variety of compressors (source: Rules of Thumb of Chemical Engineers, Branan)

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Centrifugal Compressor Power Calculation

In this post I want to share you how to calculate centrifugal compressor power since there are so many process engineers are looking for it (and I also don’t know how).

To calculate centrifugal compressor power, we need these gas properties: compressibility factor (Z), molecular weight (MW), inlet gas temperature, inlet gas pressure, outlet gas pressure, adiabatic component (Cp/Cv), and mass flow rate.

Let’s start with an example while I show you step-by-step of the calculation method. In this example, we have these gas properties (I use US units).

Compressibility factor (Z) = 0.9972

Molecular weight (MW) = 18.15

Gas constant (R) = 1544/molecular weight

Inlet temperature (T1)  = 546 deg R

Inlet pressure (P1) = 15 psia (don’t forget to use absolute pressure)

Outlet pressure (P2) = 60 psia

K (Cp/Cv) = 1,274

Flow (W) = 0,184 lb/min

The required data to calculate centrifugal compressor power is head. We can use either adiabatic head or polytropic head as long as we use adiabatic efficiency and polytropic efficiency in companion. (more…)