On-Line Viscometer- Anything New?

[controlnovice]

Has anyone worked with on-line viscometers recently?

We are looking for viscometers that can be installed in a batch reactor. We are not interested in the pump-around style. Also looking for something that can detect Acid Number.

We've tried IR about 10 years ago and they did not work. Have they improved since then?

Our product is Polyester resin at temperatures up to 220 deg C.

 

[sshep]

My own experience with direct process control of a viscosity spec has been dismal for the primary reason that the product spec is always at some specified temperature, which in general will not be the same as the processing temp. Use of the Andrade equation to project process viscosity on to a product specification has proved in-adequate on most occassions. If this is your situation, a pump-around sample conditioning system (i.e. to deliver a sample stream at spec temp) still offers the best general hope for something useful. As this is a type installation which you wish to avoid, there may not be any good options at this time.

Note sure what your objective is, but the temperature conditions of your reactor seem fairly challenging especially if this resin is a solid at cool reactor conditions. Best wishes in your search, sshep

 

[StoneCold]

controlnovice
There was a thread here a while back, I can't find it, but on of the suggestions was to use mixer horsepower as a measure of the viscosity of the material. They rigged their agitator to show amps. From the amp readings they deduced the correct final product viscosity.
Maybe that will help. Maybe someone else can find that thread for you.

Goodluck
StoneCold

 

[controlnovice]

Thanks StoneCold,

We've looked into that.

Unfortunately, our Chem E likes to oversize the agitators, so from beginning to end of the batch, we see very little amperage change. (Plus, you should really look at kW, not amps)

 

[controlnovice]

Has anyone worked with the (fairly) new Encoded Photometric infrared analyzers (EP-IR)?

 

[jmw]

I think that for polyesther resins the technologies are usually referred to as MFI or Melt Flow Indicators. These are often little more than a capillary style viscometer but they are intended for use at the reactor temperature.

Viscosity temperature relationships are often a problem when it is quality that you are interested in (as opposed to behaviour where the viscosity at the flowing temperature is all you are interested in).
Quality measurement usually needs the viscosity at a reference temperature.

However, the point is to discriminate between a quality measurement for quality assurance and a quality measurement for process control.
For process control all you really need is a repeatable value. If you have control of the reaction at the optimum conditions then the MFI will give a consistent and repeatable reading. This is often easier to achieve in a continuous reaction process as when it is under control the temperature should also be relatively stable.

Periodically take samples for laboratory analysis to keep track of what your on line measurement means.

In some reactions this is not practicable. For example, in methyl methacrylate batch reactions the process is initiated with heat and then, as polymerisation advances, the reaction turns exothermic and temperature rise becomes exponential. In this type of reaction you are looking for the quench point and this may be a window of only 20 seconds in a two hour batch. Tank measurement solutions have been very successful here. It is not always possible to use equation related temperature viscosity curves. The alternative is a matrix solution where you calibrate the matrix using a combination of process and lab data. The Matrix is simply a number of curves each of which represents the temperature viscosity relationship of a particular quality (e.g. molecular weight) product. The line temperature and viscosity are then ratioed to these curves to find the viscosity at a reference temperature.

If the application requires that a sample loop is necessary then the benefits can often outway the costs. Good viscoity measurement can pay dividends in reduced re-wrok and tighter quality control.

JMW

http://www.ViscoAnalyser.com