Even much worse, you would ruin your vacuum pump. Let us think: why do we use vacuum to facilitate evaporation? Because evaporation is an equilibrium process , so lowering the activity (concentration, pressure) of the product of that reaction moves the equilibrium to the right side. Please note therefore that for evaporation it makes little difference whether the activity of the vapors is lowered by applying vacuum, or by dilution with another gas. Flowing air or an inert gas through your tube can be as effective as applying vacuum. Proof: Steam distillation. Beside: There exist stainless steel vacuum vessels, double-walled, which you can fill with e.g. a zeolite, and a chilling agent (separated) which needs to be placed between your tube and the vacuum pump. The connection between the evaporation tube and that vessel - yes, it would need to be heated and/or purged. Diaphragm pumps seem to be a good choice. If applicable to your situation, a water-ejection pump might help yo wit disposing of the condensate. I happen to have several such stainless steel vessels, and no need for them. If you want meto send you one for free, please write an email to: [email protected]

Thank you Jerry P. Czarnecki for the response. The purpose of having a vacuum along with gas flow is to have another degree of control over growth kinetics (the powder is evaporated onto a substrate), and to evacuated excess reactants.

The double walled stainless steel vessels seem like an interesting solution, is there any catalog/site that I can look at for reference?

Lastly, are diaphragm pump more resistant to contaminates? if so that too can be a good solution for me.

Many thanks!

Hello,

I have never used a diahragm pump, but that principle makes me think the damage from contamination or possibly cleaning, would be less devastating. Your condensate would ruin the oil in an oil vacuum pump, to say nothing of a complete destruction of a turbo pump. Generally, for your application, only primary-vacuum pumps can be considered. You do not really need vacuum, right? All you probably need is some suction; but I may be wrong. Should I be right, did you consider a water-ejection pump? Way simpler, much higher flow rate, but the negative pressure may be insufficient.

About the double walled stainless steel vessels: Thee price normally is about $1200, I do not have any catalog, but this weekend I will take a picture of what I have, and will send you that picture, if you provide me your email address; mine is [email protected] If you have a use for it, and if you are in the USA, I can send it to you for free. Jerry Czarnecki, La Habra, CA, ph. 714-296-4004

Hello Eyal,

don't be afraid too much.The problem is quite common to the vacuum industry. Traditional suppliers of vacuum equipment such as Leybold, Edwards, and Preiffer should have solutions ready.

The solution will depend on evaporation pressure and the nature of the powder you want to evaporate.

The lower the pressure in the pump line the easier to catch your evaporated matierial by some obstacle within the gas flow such as some baffle in high vacuum conditions. Under gross vacuum, you need to offer lot of surface in an adsorbent trap or some cold trap. If the cold trap is made from glass, you may notice that clogging is not so rapid.

In any case, trouble arises if your powder is hazardous. Then you need to get rid of it without endangering yourself or your colleagues.

Best from

Heinrich