removal of nitrogen purge from mixers

[BNaomi]

the nitrogen purge is used to prevent fire and explosion.
but the cost is every high.
so I 'd like to find an alternative.

I would like to know if anybody already made it?
how did you make for risks assessment

 

[mrtangent]

BNaomi,

To answer your question more info is required. You can reduce nitrogen purges or even elliminate them but.
What are your

Chemicals used in the mixer.
Flash points
Operating temperatures.
Operating pressure.
Design pressure of the vessel.
Explosion front data for chemicals. (ie if an explosion occurs what will be the pressure rise).

I have successfully reduced the nitogen flow into a vacuum process for inerting by 80 % by assessment of the above and sampling of the system details.

I used a frequence based risk assessment and hazop to determine the potential consequence of the n2 reduciton

 

[25362]

One may consider CO₂ if it doesn't adversely affect the system.

 

[StoneCold]

We just buy motors that are Class 1 Div 1 Grp C+D to avoid this problem.

 

[BNaomi]

I give you more details about it,

We use a nitrogen purge in order to avoide an explosive atmosphere in mixers (20000L).
The problem is that some products (Solvents, acetone, MEK)are loaded automaticaly. but to load pigments (powder), we use a hatch to add it to the mixture.
So we have to purge with nitrogen each times that the hatch is open more than 5 minutes. The purge lasts 30 minutes. Lot of products are loaded manually. So lot of purges are done. This procedure costs lot of times and money.

So we want to change the procedure and show that we don't need to purge when we load using hatch.

 

[25362]

Would you consider "in-line" pre-mixing the powders with some solvent while pumping the solvent to the mixers, as done in the pharmaceutical and food industries, minimizing air entrance ? Surely a Google search would show you a variety of these in-line mixers and their makers.

 

[StoneCold]

I guess my first post was way off base I thought we were talking about the agitator.
We end up doing the same thing some times.

However De Dietrich makes a system that sucks up the solid, purges it with N2 and then dumps the purged material into the reactor. (mixer) This would eliminate the need for purging the reactor. We have not purchased it because it seemed rather expensive at the time. I can not remember the numbers.

Good luck

 

[Stresfree1]

Adding solids through an open hatch make solving the problem more difficult. A few potential options to consider.

1) Can the nitrogen purge rate be reduced and still do the job? Sounds like you may be flowing a high rate of N2.
2) Is there a non flammable liquid that the solid can be mixed with in a separate tank under air? This can then be pumped in.
3) Consider adding the solid through a hopper and rotary style valve. This would decrease the need for purge and allow you to use a blanket instead.
4) Is the solid highly soluble? If so, you may be able to add the solid first, followed by the flammable liquids.
5) I have inerted vessels before with CO2 produced from small carefully controlled boilers. You cannot use a standard boiler for this - stoichiometry is important and the steam rate cannot vary.

Good luck.