Improved Compressor Efficiency, Reduced Surge

Margin, with Micro Motion Specific Gravity Meter

CHEMICAL

RESULTS

• Reduced operating costs through improved system efficiency

through accurate process control

• Reduced risk of compressor bearing, seal, blade damage or

catastrophic failure

• Reduced down time due to maintenance or repair of damaged

compressors

APPLICATION

A leading chemical producer in Belgium uses the Catofin propane

dehydrogenation (PDH) process to produce propylene, which in

turn is used to produce polypropylene. Polypropylene is used in a

variety of applications, including packaging, textiles, plastic parts

and reusable containers of various types, and laboratory equipment

to name a few. Axial gas turbine compressors are an integral part

of the propylene production process.

CHALLENGE

It is a common occurrence to experience surge when compressors

are operated near their peak-efficiency point. Surge is a sudden

reduction in flow combined with a high differential pressure across

the compressor that may result in a reversed back flow through

the gas compressor. As the system recovers from a surge, the

compressor speed may momentarily increase. This unstable

behaviour can result in an increase of stresses, damage to the

compressor parts, or at the worst, complete catastrophic failure

of the compressor. For this reason, gas compressors must be

protected from surge.

To avoid surge, the compressor should operate below a given

surge limit, or within an operating margin with anti-surge control.

Operating within this margin will result in reduced operating

efficiency, so it is to the benefit of the customer to operate as

close to the surge limit as possible. To determine the surge limit,

you must consider a number of factors, such as the gas composition

which in turn determines the gas molecular weight. If the gas

molecular weight can be accurately determined then anti-surge

control can be implemented.

For more information:

www.MicroMotion.com/chemical

www.MicroMotion.com

CHEMICAL

SOLUTION

The refinery chose to install a Micro Motion

Gas Specific

Gravity meter because of its ability to provide a continuous,

fast online molecular weight measurement. Gas Specific Gravity

is critical because surge is a volumetric flow phenomena.

As the composition might fluctuate, the volume flow might

fluctuate unexpectedly as measured by other devices.

This meter provided the molecular weight and specific gravity

measurements, independent of process conditions. The meter

enabled them to more accurately determine the surge limit,

and operate with increased efficiency and reduced risk of

damage due to surge.

Micro Motion Specific Gravity Meter with

Sample Conditioning System