Different strategies of a Cryogen Process control by real time sizing sensor system working under insitu and in line conditions.


Different strategies of a Cryogen Process control by real time sizing sensor system working under insitu and in line conditions.


Key words:

  • insitu particle measurement in Cryogen high pressure application
  • In line sizing of precipitation under cryogen conditions under explosion proof conditions


Benefits of an insitu disperse phase control system

  • Improvement of process stability prediction during R&D projects
  • Faster development of new process kinetics
  • Scale up scale down Information
  • Optimisation of process equipment and energy
  • Continues control of size and number depending reaction



  1. in any viscosity or concentration where material can flow in a pipeline or reactor under flow conditions
  2. for solids in liquid systems
  3. for liquids in liquid systems
  4. for „clear“ particles in „clear“ solutions with a different refractive index
  5. at elevated temperature from minus 120°C up to 300°C
  6. at elevated pressure vacuum up to 300 bar
  7. within process flow up to 30 m/ sec
  8. Detecting ranges 500 nm up to 3000 micron


Summary of Objectives:

  • The application department, founded in 1989, measured more than 6000 products, a lot of them were confidential, and acquire a substantiated knowledge of cryogen application.
  • This experience generated a lot of efforts for the partners of the combined technologies.
  • We have met several cryogen fields where the knowledge of the particle, crystal and droplet sizes where essential for understanding of the process and the control of it as well.
  • Nature gas resources are mostly contaminated. They can be cleaned by a precipitation under high pressures in low temperatures.



Installation of the in line measuring sensor devices

  • The PAT insitu sensor for cryogen application has been directly installed inside the process line.
  • The sensor follows the precipitation / extraction of gas components during a 60 bar and minus 60°C operation
  • The system consist of a high speed electronic which counts the number of particles which are founded during the precipitation and measured inside the focus of the sensor system.
  • During the measurement the temperature and pressure could be changed. The system is capable to follow these changes over the full process, with its different reaction steps of precipitated droplets and particles flawless.
  • The sensor was installed in a pipeline with DN 400. Therefore the sensor dip was directly in contact with the steam of founded particles/droplets.


Results out of experiences in Plant and operation control


Contribution of the measured result during the variation of the process is shown in Fig.01below. The measured sizes are related to temperature modifications.




Fig. 01: Formation of droplet over time during different temperatures and pressures

During the insitu measurements the operated system measured the total number of droplet/ or particles in the liquid gas system which has been inside the system based on the P/T ratio.

Therefore we could always see follow the habit of the precipitation during the different reaction kinetics.

All this kinetic could be observed in reversed mode of the process of gas cleaning.



Fig. 02: shows the distribution of counted particles in a normalized contribution of measured droplets during different kinetic phases of the reaction


It was also useful to see the different fractions over the time in Fig.03



Fig. 03: Fraction 1 – as function of changes of the reaction conditions

1 to 3 µm    blue line

8 to 12 µm  red line

During the same time we have also got access to the total number of measurement related to the amount of precipitated particles or and droplets in Fig.04




Fig. 04: shows the change of number of precipitated droplets or particles, if temperature and pressure are changing


During the reaction time it was questionable, what is the habit of the amount of fine particles. Based on fact that the insitu measuring sensor system takes all measured and counted signals as row data in store – it was easily to display it in a report -shown in Fig.05.


Fig. 05: D10/2 over time of total reaction in liquid gas during the precipitation


Summaries Control of a selective process system

  1. All steps of process operation could be confirmed as reproducible.
  2. The measurements could be done under insitu and real time conditions.
  3. The sensor system could be installed under in line condition directly in side the process pipe work.
  4. The operated sensor has been also installed inside reactor vessels and autoclaves.
  5. The sensor system can be operated in a large various range of temperature and pressure based on customer requirements.