Transferring caustic soda flakes for dilution

[dan78er]

Hi,

Can anybody advise me on the safest and most reliable way to transfer 100 kg of caustic soda flakes (in the hopper) into a large mixing tank filled with water? I try to avoid having an operator bring the bags onto the platform and sprinkling the flakes slowly from the manhole. I was thinking of having a vacuum transfer into the tank bottom, but the risk of vacuum pump failure make me have to think other solution. Is pneumatic (vacuum or compressed air) conveying to the top then let the flakes fall quite reliable?

regards,

Dan

 

[sshep]

Hey Dan,
Since you didn't get any bites, i'll give you my 1 cent. In most of these operations there has to be manual transfer of some sort, and you try to make it as easy and safe as possible via good access, platforms, and lifting devices (elevators, drum lifts, etc). Rather than a vacuum transfer, consider maybe a screw feeder. Instead of flake you could try pellets or balls which have better flow properties.
Anyway, best of luck,
Sshep

 

[moltenmetal]

Presume that this is an operation which doesn't like water, or likes water too much. Otherwise, you SHOULD buy caustic solution as it will be far, far easier and safer for you to do so. It's available at 50 wt% and apparently even at 73#. 50% freezes at a higher temperature than water, so watch for freezing.

Sodium hydroxide deliquesces strongly, i.e. it picks up moisture from the atmosphere to an absolutely extreme degree. In the lab, you could literally watch the stuff gain weight on a humid day. Deliquescence makes the pellets or flakes sticky. The film of liquid on the surface is saturated hydroxide solution- very hazardous to skin. If this is going to be some kind of manual transfer operation, selecting the right PPE is going to be important.

You'll need to transfer full bags into a hopper which can be sealed and purged with DRY air. As to what sort of metering device (screw, rotary valve etc.) is best to gradually feed the material into your mixed vessel, best to speak to the vendors of both caustic and these transfer devices to see what works.