When I was involved in pre-FEED of well production and gas treatment, one of key deliverable is compressor study. In 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.
Differences Between Compressor Types
Compressor used widely in industry are reciprocating, centrifugal, and axial-flow. Rotary compressors are sometimes used for special purpose. Table below shows differences between those compressor types.
| Criteria | Reciprocating compressor | Centrifugal compressor | Axial-flow compressor |
|---|---|---|---|
| Application | Low-flow, high pressure service | ||
| Flow range | 10-5000 acfm (inlet) | 500-200,000 acfm (inlet) | 75,000-600,000 acfm (inlet) |
| Pressure range | 60,000 psia for small machine. 3000 psia for large machine | 10,000 psia for small machine. 100 psia for large machine | 10-100 psia |
| Pressure ratio | Max 3:1 to 4:1 per stage | ||
| Mechanical design limit | 350-450 deg F or lower | 400-450 deg F | 600 F |
| Overall adiabatic efficiency | Typically 0.75-0.85 |
Performance of centrifugal compressor and axial-flow compressor is usually expressed in polytropic efficiency. Polytropic efficiency is often considered as small stage efficiency or hydraulic efficiency. The value is higher than adiabatic efficiency.
A centrifugal or axial-flow compressor is usually designed to operate at its highest efficiency at the design flow rate. The operating range of centrifugal compressor at fixed speed is ranging from 50% to 100% design flow. The bottom end of this range is set by surge point. Range of operation actually can be varied by using variable speed drive.
As for axial-flow compressor, operating range is narrower because the surge point is at 85% to 95% design flow.
Check my previous post about how to calculate centrifugal compressor power.
Reference:
- What Process Engineers Need to Know about Compressors – William Dimoplon
- Rule of Thumbs for Chemical Engineers – Branan
- Perry’s Chemical Engineers’ Handbook