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Ejectors in Sampling Systems

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Ejectors in Sampling Systems

In any reactor application, reactor media samples need to be analysed to judge the progress and state of the reaction. For reactors operating at above atmospheric pressures, samples can be readily obtained but for reactors operating at atmospheric pressure or under vacuum conditions the samples need to be extracted / pulled from the reactors.

Nature of the sampled media:
  • Sampled media can be in the form of liquids and gas mixtures.
  • In some applications, the sampled liquid or gases may contain suspended solids or particulate matter.
Requirements of the Extraction system:
  • The system must be able to generate the required flow and suction pressure to obtain the required Sampling flow at the reactor working pressures.
  • The system must not contaminate the sampled media and must be able to maintain its purity.
  • The system must be able to handle the corrosive and abrasive nature of the media.
  • Sampling being a measurement and quality control related process, it may be operated continuously or in form of batch operations. The system must be reliable enough to sustain the needs of the requirement whether continuous/batch with minimum downtime.

Ejectors for extracting the samples:

  • Ejectors can be designed to suck media from Atmospheric to high vacuum conditions.
  • Ejectors can operate with both liquid and gas media. The presence of suspended solids and particulate matter is tolerated by the Ejector without any drastic effect on performance.
  • They contain no moving parts which accounts for negligible maintenance and very high reliability. Once installed a Sampling ejector will continue to work for years with no maintenance.
  • Flexibility in choosing the Material of Construction helps to manufacture the Ejector in compatible materials, which is very useful when the sampled media is corrosive or abrasive in nature. We at Crystal TCS manufacture Sampling Ejector from Stainless steel, Hastelloys and Titanium as well as in Plastic material of construction.
  • The energy input for an Ejector is in terms of pressurized motive gas. The requirement for motive gas is generally at moderate pressures and low flow rates. The moderate pressures and low flow rates can be easily accommodated by an existing gas supply system in the factory, which eliminates the need for installing any additional equipment for running the Ejector.

Generally used Motive gases for Sampling Ejectors:

1. Compressed Air:
  • Compressed Air is non-reactive with most of the gases and liquids. Hence contact with air doesn’t contaminate the sample or bring about a physical and chemical decomposition in it.
  • Compressed Air is readily available in many plants and hence is the cheapest way to run a Sampling Ejector.
  • For best results the air must be completely dry and free of oil in order to preserve the sample purity at the highest order.
2. Nitrogen and Inert gases:
  • Nitrogen or Inert gas(Helium and Argon) operated Ejectors are used for drawing Reactor samples in processes where the media is sensitive to contact with air. Utilizing Inert gas helps conserve the exact purity of the samples and prevents any physical or chemical decomposition.
  • These motive gases are also are used for sampling gases flammable in nature.

Typical operating ranges for Sampling Ejectors:

  • Sampling Ejectors can operated with a wide range of motive pressures (3 bar(abs) and above)
  • A single stage Sampling Ejector can pull samples from pressures as low as 100 torr. Most of the
    Sampling requirements are easily satisfied by single stage Ejectors.
    In case of higher vacuum multiple stage units can also be designed.
  • Types of Sampling Systems: