Gas Compressor: Types, Sizes and Functions
During my visit to Rokan Block in Duri, Riau, I encounter a couple of ’’Ariel” type gas compressor. It is used to move the natural gas through pipe from well to consumer by increases he pressure of a gas by reducing its volume. Compressor itself are the prime movers of gas and air in process industries. They are used to increase static pressure of the gas and deliver it at specified pressure and flow rate in a process application.
The working principle of compressors are similar to pumps, both increase the pressure on a fluid and both transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of gas. Liquids are relatively incompressible, so the main action of a pump is to transport liquids.
Types of Gas Compressors
As described in chart, compressors fall into two separate and distinct categories: Dynamic and Positive displacement.
Positive Displacement Compressors
In all positive displacement machines, a certain inlet volume of gas is confined din a given space and subsequently compressed by reducing this confined space or volume. At this elevated pressure, the gas is next expelled into the discharge piping or vessel system.
Although positive displacement compressors include a wide spectrum of configurations and geometries, the most important process machines are piston compressors and helical screw rotating machines. Though there are a number of other, including diaphragm and sliding vane compressors, the overwhelming majority of significant process gas-positive displacement machines are clearly reciprocating piston and twin helical screw-rotating or rotary screw machines.
Reciprocating compressor
Reciprocating or piston compressor is a positive displacement compressor that uses the movement of a piston within a cylinder to move gas from one pressure level to another (higher) pressure level.
Reciprocating compressors types include the following:
a) Simple Single-Cylinder: As single cylinder has one suction, compression and discharge area. Double acting cylinder designs have two suction, compression and discharge areas.
b) Multi-Cylinder: Some reciprocating compressors can have up to six cylinders. Pistons connected to crankshaft are utilized to compress the gas.
c) Multi-stage Design: Multi-stage compression stage take the vapour and compress it into
Rotary compressors
Screw compressor is a positive displacement machine and has a distinct working phases: suction, compression and discharge. Two counter rotating helical screw are arranged in a compressor casing; gas inlet and discharge nozzles are at opposite ends.
rotary screw compressors are very likely the equipment of choice for either oil-free or oil-wetted compression of air in mining, construction, industrial refrigeration or a host of other applications where their relative simplicity, general reliability and high availability are appreciated. Rotary screw compressors are equally suited to compress process gases.
Dynamic Compressors
Imparting velocity to a gas stream and then converting this velocity energy into pressure energy. These compressors are frequently called turbo compressors, and centrifugal machines comprise perhaps 80% or more of dynamic compressors. The remaining 20% or less is axial flow machines intended for higher-flow, lower-pressure applications.
Rotary Compressor
Centrifugal Compressor
The centrifugal compressor is a dynamic machine that achieves compression by applying inertial forces to the gas (acceleration, deceleration and turning) by means of rotating impellers. The centrifugal compressor is made up
Axial Flow Compressor
Axial-Flow Compressors can handle large flow volumes in relatively small casings and with favourable power requirements. Pressure range for axial compressor is low to medium.
Turbo-Expander Compressor Assembly
A Turboexpander, also referred to as an expansion turbine, is a centrifugal or axial, flow turbine through which a high pressure gas is expanded to produce work that is used to drive a compressor.
The term “Turboexpander”, as shown is normally used to define an Expander/Compressor machine as a single unit. It consists of two primary components; the Radial Inflow Expansion an a Centrifugal (Booster) Compressor combined as an assembly. Its wheels are connected on a single Shaft. The expansion turbine is the power unit and the Compressor is the driven unit.
In a Gas Processing Plant, the purpose of Turbo-expander is to efficiently perform two distinctly different, but complimentary, functions in a single machine. The primary function is to efficiently generate refrigeration in the process gas stream. This is done at the expansion turbine end by efficiently extracting the
