Flow Measurement of Ammonia Gas used as a Cooling Agent

Cooling demand in chemical production is often significant: be it to dissipate the waste heat of exothermal reactions or to liquefy gases in distillation plants. However, in order to also ensure stable low temperatures in logistics areas or data centres, connection to a central supply network is cost-effective.

The necessary cooling supply is often generated by a closed circuit with the coolant ammonia (NH3). The cold compressors and evaporators are normally in separate locations:
The ammonia gas is compressed and liquefied in a central cooling plan and then fed via pipeline to the customer plant where it is then evaporated and asorbing thermal energy.

For volume control of the compressors, the flow rate of the warm ammonia gas must be measured. In the here described case, the process control engineers looked specifically for a measuring solution that had as little impact as possible on the uninterrupted operation of the supply plant. Measuring orifices in particular proved to be unreliable as their thin differential pressure transducers often became clogged up with oil droplets carried in the gas flow. Maintenance work which involves opening the pipeline is extremely complicated due to the toxicity of the ammonia and at least one day of preparatory work is needed to drain the pipeline. During the maintenance work, the respective compressor is unavailable. The plant operators obviously wanted to avoid shutdowns of this kind.

Non-invasive flow measurement with FLUXUS proves to be the ideal solution in this case. The stationary FLUXUS ultrasonic gas flow meters installed on the compressors, confirm the longstanding positive previous experience with FLEXIM's FLUXUS flowmeters at this site. Since clamp-on ultrasonic transducers are simply mounted on the outside of the pipe, they are not subject to wear and tear by the medium flowing inside the pipe and there is never any need to open the ammonia pipeline. Since the FLUXUS flow meters were installed, they have been working reliably and smoothly.

Advantages

  • Reliable flow measurement from outside
  • No wear and tear
  • No risk of leakage
  • No pressure loss
  • No need to open the pipeline system – next to no effort required for possible maintenance work compared to wetted measuring instruments
  • Complete plant availability

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