Bronkhorst

A new trend in vapour generation

August 2, 2016 James Walton

Generating vapour is a perfect example of how technology trends are bringing change that can benefit multiple industries. By using mass flow metering and control technology you can control a coating or deposition process or create a stable calibration environment. To generate a vapour has always been a complex and expensive process, relying upon passing a carrier gas through a heated fluid bed. This creates a variable composition vapour that is uncontrolled in mass or vapour composition.

This technique is one that has been used for many years and in multiple industries. Just looking at the basics of the system described above you can begin to imagine the challenges and costs faced.

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Classical Bubbler System
Classical Bubbler System

If you were to change the system, the first thing you would remove would be the heated fluid bed. It creates multiple sources of variation:

  • Evaporation of the fluid can cause concentration changes in vapour
  • Differences in back pressure created by changing fluid levels
  • Flow rate changes with fluid level resulting in changing process conditions
  • Variations in thermostat accuracy can add temperature variations to the fluid
  • High energy consumption from heating a fluid bed

If you were to change the system, the first thing you would remove would be the heated fluid bed. It creates multiple sources of variation:

  • Evaporation of the fluid can cause concentration changes in vapour
  • Differences in back pressure created by changing fluid levels
  • Flow rate changes with fluid level resulting in changing process conditions
  • Variations in thermostat accuracy can add temperature variations to the fluid
  • High energy consumption from heating a fluid bed

 

 
CEM: Controlled Evaporation Mixing system
CEM: Controlled Evaporation Mixing system

By removing those sources of variation from the process and combining liquid flow control with a Coriolis instrument and gas flow control with Thermal by-pass instrument with a temperature controlled flow path you can take advantage of the following improvements:

  • Speed of response to process changes
  • Reduced raw materials costs
  • Accurate temperature control
  • Quick turnaround on substrate
  • Choice of PPM, PPB, Mole or concentration output conditions.


Applying closed loop control and combining different sensor technologies you can build a solution that will allow you to generate vapour in an accurate and controlled manner.


With direct control of the liquid and gas flows into a temperature controlled flow path it is easy to change the process conditions generated. The Coriolis liquid mass flow meter and thermal by-pass gas flow controller are directly linked to a 3-way mixing valve on top of a temperature controlled flow path. By passing the liquid and gas through an orifice the combined flow is aerosolized before being heated and this ensures complete vaporisation of the liquid in the gas stream.

Taking this a stage further, if you have a specific composition in mind then check out our on-line free to use gas database called Fluidat, go to www.fluidat.com register and you can check out yourself what is possible.

Read more about Fluidat in our blogs: