At a large petrochemical production plant in The Netherlands, ethylene and propylene are produced from naphta through steam cracking. Ethylene and propylene are among the most important molecules in the chemical industry. They are precursors for plastics, paints, solvents, pesticides, vitamins and much more. Numerous companies at the site depend on a constant supply from the steam crackers.
At one of the steam crackers, propylene gas flow measurement relied on a differential pressure measurement which was installed on the DN200 pipe since the construction of the plant. It measures the gas flow from the discharge side of the propylene compressor towards an energy exchanger (i.e. cooler). The propylene flow data is required for correct pre-heating of the de-ethaniser feed. The energy for this heating and evaporation is extracted from the propylene vapour (temperature ~45 °C), condensing in the cooler. Furthermore, the flowmeter plays an important role regarding energy consumption. The better the operators of the plant control the propylene flow through the energy exchanger, the less steam is needed in the reboiler system.
When starting up the process after a plant shutdown, the operators encountered severe issues with the old orifice measurement. There was no option to stop the process again in order to exchange the orifice plate. Steam crackers are typically only shut down every five to six years when a complete turnaround of the whole plant is executed. Therefore, the operators looked for an alternative method of flow measurement without any need to stop the process for opening of the pipe.
Easy retrofit
Non-invasive flow measurement with FLUXUS® proves to be the ideal solution. E & I engineers at the plant have been working with FLEXIM’s clamp-on ultrasonic systems for many years. Therefore, they turned to FLEXIM Benelux to find out if there is a possibility to bypass the obsolete Dp measurements by means of non-invasive ultrasonic technology. FLEXIM Benelux issued an application checklist in order to be able to quote the right alternative. Because of the age of the Dp meter, the operators could not retrieve all necessary data. However, based on the data provided, FLEXIM was able to provide an offer, consisting of a FLUXUS® G 721 dual-channel transmitter and two pairs of low-frequency Lamb wave transducers. This kind of instrumentation has been developed by FLEXIM especially for gas flow measurements at lower pressures.
In order to achieve the highest possible degree of measurement accuracy, it was decided to install the transducers in an X-configuration on the pipe. This configuration effectively eliminates the effects of swirl disturbances. Furthermore, each pair of transducers was mounted in a 3-path configuration. This allows for high accuracy because of the longer signal path and consequently a longer transit time.
Through this easily retroffited propylene gas flow measurement, the operators of the plant were able to continue production without any interruption and therefore have no production losses.
Advantages
- Ensuring supply of propylene to the site by simply retrofitting the measuring point with non-invasive clamp-on ultrasonic technology
- Achieved measuring accuracy matches original Dp flowmeter
- Excellent cooperation between the customer’s E & I department and FLEXIM’s sales and service team.
Measuring Points and Instrumentation
Medium: Propylene gas (C3H6)
Pipelines: DN200, carbon steel
Pressure: 12 barg
Measuring device: 1 stationary clamp-on ultrasonic FLUXUS® G721 dual-channel gas flowmeter 2 pairs of GRH1N52 clamp-on ultrasonic Lamb wave transducers, mounted in VARIOFIX C
“Our clamp-on gas flow measurement enabled our customer to replace the obsolete Dp measurement and therefore continue production without interrupting the process.”
Hugo van der Stoep, Account Manager, FLEXIM Benelux.
FLEXIM Benelux
127 Berkelse Poort
2651 JX Berkel en Rodenrijs
Netherlands
+31 10 24 92 333
benelux@flexim.com
