I need help on a sampling system problem

[Shaman2]

Folks

I have a problem with an online analyser sampling system.
The analyser in question is a shamadzu benchtop uv/vis, which works very well when the analyte reaches it.
The sampling system however is very problematic.

The sample is return gas from a reactor for converting TiCl4 to TiO2 and consists of ~70-80% Cl2 with O2, CO2, HCl, and some water vapor rounding out the mix. The analyser is for detecting any TiCl4 that escapes the reactor.
The sample system was designed years ago under the assumption that any TiCl4 would be gaseous, and has always had questionable results.
Recent developments have lead to the conclusion that the TiCl4 has actually converted to a powder, possibly at least partially as TiOCl2.
The sample system captures a stream of the gas and delivers it to a mixing coil where it is mixed with a liguid stream containing an excess of H2SO4 and H2O2, the liquid stream is then delivered to a flow cell in the shimadzu for reading.
As a chemist I am not really strong on the engineering side of things, but now find I have need to find a way to redesign the sample system, in order to deliver the solid as well as the gaseous sample portion to the mixing coil.
I have tried simply removing the filter, only to have the smaller lines in the sample prep system clog quickly.

Can any of you offer any suggestions as to how to proceed?

Thanks

Shaman

Balance is the prime law of the universe

 

[unclesyd]

I wont say that sample system are a black art, but it come pretty close.
It would be extremely had to come up with any ideas without seeing the physical plant and have an intimate knowledge of the process as the analyzer sees it. I've seen all types of setups for continuous analyzer from the very simple to very expensive.
If I were you I would start by contacting someone like Sentry to get an idea of what's available as starting point. You might want to search "online analyzers; process analyzer"

http://www.sentry-equip.com/Products.htm

The best I've ever seen was on of the original original IR on-stream analyzers where they had spent thousands of dollars installing pumps, filters, valves. etc and the thing still didn't perform. A mechanic who was working on a pump told the engineers if they would move their sample and return point on the process they could do away with all the mechanical equipment by using the process pressure to supply a very clean fluid at the required flow . Worked like a charm.

 

[StoneCold]

Shaman2
I have some experience with TiCl4 and I can tell you that it loves to plug lines if it is exposed to air, so I am not surprised that you are having problems. We have problems in 1/2" tubing where if it gets air exposure it turns into a nasty black tar like substance. That being said maybe you should be bubbling your gas stream through a liquid and analizing the liquid for trace amounts of TiCl4. Could be reactive liquid or just a solvent. Like on HF alky units they will sometimes spray ammonia water over a suspected leaking area. The HF will make a white cloud with the ammonia. Not very quantitative but a good go/no go test.

Hope that helps.

Regards
StoneCold

 

[Shaman2]

Thanks Stonecold

I agree this is part of what is happening, no surprise since there is both a few % of O2 and some water vapor in the mix. The other compounding problem is that the sample point is at the distal end of a return line, before the gas goes back into the process loop. This placement allows for reaction time, cooling, and plenty of surface area for solids to plate out on, and never reach the sample point.
The plant components the analyser is to help protect is at the beginning of this part of the process, the analyser at the tail end.
I have argued in the past, even before we were aware of the solids issue, that the analyser should be in the same general area as the part it protects, just to avoid lag time. There were a number of road blocks raised to doing this, however if we don't find an issue to the solids issue I may win the argument by default.

Cheers

Shaman

Balance is the prime law of the universe