I need to handle large quantities of $\ce{KOH}$; close to 1000 liters of 85 % conc $\ce{KOH}$ for about an hour. Any suggestions on how I go about doing it? Also the temperature during the process might touch 500 degrees Celsius.

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    $\begingroup$ why are you doing this? $\endgroup$ – bon Feb 21 '15 at 17:43
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    $\begingroup$ I'm voting to close this question as off-topic because it asks about safety advice. We are not here for that (and should not IMHO). Please consult a professional company for advice. $\endgroup$ – Jori Feb 21 '15 at 19:37
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    $\begingroup$ @Jori I disagree that safety should be off-topic. Though I can agree that this particular case is asking about a scale where I'm rather uncomfortable having it here. Anyone handling reactions on a thousand liter scale shouldn't ask the internet for help, they should have people that know this stuff already. Anyting else would be dangerous and very likely illegal. $\endgroup$ – Mad Scientist Feb 21 '15 at 19:49
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    $\begingroup$ @Jori Safety, covering advices on personal protection during the handling on particular compounds, suggestions for alternative and less toxic reagents and the advice to better not do something at all always had their place here - for good reason. Consequently, I voted to leave the question open. $\endgroup$ – Klaus-Dieter Warzecha Feb 21 '15 at 20:10
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    $\begingroup$ Ok just to clear the air. I am planning to leave my job to open a manufacturing company of my own. And yes i will be hiring professionals to help me out, but i dont think it would hurt to know a few things before so that when they start talking at least i understand a bit of they are saying. to reiterate I am not crazy enough to handle such large amounts on internet advice. No its not one large 1000 liter container. Actually I will be needing only 500 liters and i plan on dividing it in 5 containers. The facility will be in a industrial area with nothing around within a 700m radius. $\endgroup$ – cryptex Feb 22 '15 at 5:55

Various stainless steels resist boiling saturated aquous $\ce{KOH}$, such as DIN X6CrMo17 (ASI 434), DIN X5CrNi1911 (ASI 305).

Dont't forget about a suitable and sufficiently large reservoir around the tank in case of spills, valve breaks, etc.

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    $\begingroup$ ya sure safety first. i will be using only 500 liters but just to be safe i am going for a larger container. would you by any chance know of some reliable suppliers for these tanks? $\endgroup$ – cryptex Feb 21 '15 at 18:29
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    $\begingroup$ Unfortunately not. Btw, don't forget about the (local) legal aspects of running such a facility ;) $\endgroup$ – Klaus-Dieter Warzecha Feb 21 '15 at 18:32
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    $\begingroup$ I know in New Jersey you are required to have a holding tank around an open reaction that is 110% the size of the reacting vessel, or that's at least what my Chem prof said was required when he worked in an industrial lab. Edit: 110% the size of aka 10% larger. $\endgroup$ – Mike Feb 22 '15 at 12:38
  • $\begingroup$ This "stainless" and (expensive=ferritic) steels are a bad choice, and moreover superfluous. Any lye above ph 9 can be stored safely in mild steel. KOH it seems is sold at 45 % maximum, so most of this thread is nonsensy. And first of all, why KOH instead of much cheaper NaOH? Last not least 1000 ltrs is not a big amount, only to an amateur. 50 % NaOH is shipped in 1000 ltr PE containers or in Tank trucks/waggons/barges. If this cryptex has the company of a chem master, why does he ask here? $\endgroup$ – Georg Feb 22 '15 at 12:55
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    $\begingroup$ @Georg there is a difference between Sodium and Potassium. Ever had Potassium Chloride as table salt? Having potassium instead of sodium imparts specific properties to the final product. Hope you are smart enough to understand why not 'Na'OH. It doesn't hurt to ask around, especially when none of us have any solid industrial experience. The one with among the 3 of us who has a degree in chem is on an extended holiday in Norway. So until he comes I am doing some ground work. $\endgroup$ – cryptex Feb 22 '15 at 19:42

The first thing to clear up is – Why do you need to store 1000 L of KOH in liquid form? It is as others have pointed out, very concerning that someone who is planning to store this quantity needs to ask on the internet.

My advice is don't store 1000 L of liquid KOH, store 40 × 25 L of liquid KOH. This will reduce the risk considerably, and help ensure that a single leak isn't a catastrophic event, but is something you can deal with. This is a common philosophy, and is used, for example, in trailers of dangerous gases, which are organized into racks of 20 smaller gas bottles instead of one large tank.

Keep your 25 L containers off the floor in a bunded area for spill containment, and have appropriate means to deal with a spill. I'm not going to tell you the best way to handle a spill because I don't know. – You need to find out. Also, make sure the store is properly monitored to detect any problems.

Now, going back to my initial point: Let's accept that, for whatever reason, you need to store 1000 L of KOH (as you haven't shared with us what you are doing.) Solid KOH is much safer than liquid KOH, so why do you even need to mix up the solution all at once?

One of the causes of the Bhopal disaster (the worst industrial disaster ever, which killed many thousands of people due an uncontrolled venting event) was the unnecessary storage of a toxic and volatile compound (methyl isocyanate.) If the pesticide they were making had been synthesized via a different route, or even if the methyl isocyanate had been made only in the quantities needed, the size of the disaster could have been reduced or even eliminated (despite the extremely poor state of maintenance of the plant.)

I suggest you mix up the KOH in small batches as you need it to reduce the risk

the temperature in the process might touch 500 degrees Celsius

By "process" I assume you mean mixing solid KOH with water, and that you do not actually need to use the KOH at this temperature. If you expect to reach these temperatures, you are doing it wrong. As can be seen from https://koh.olinchloralkali.com/TechnicalInformation/Phase%20Diagram%200-80.pdf KOH solution in all compositions from 0 to 85% is liquid at below 150 °C. Note also that concentrations above 50% are solid at room temperature – so do you really mean 85% conc KOH?

The safe way to do this is to add the dangerous material to the safe material, particularly as water has such a high heat capacity and can lose heat by boiling. You are going to need either a lot of patience, or mechanical screw feeder, to perform the addition at a safe rate. You will also need decent stirring equipment. Also, I would expect most of the heat will be released in mixing the first 50% of the KOH, because after that you are effectively mixing KOH with KOH.

In any case, if you are planning to do this, you should check the thermochemistry yourself and include it in your Risk Assessment, along with any relevant details from industry experience regarding specific hazards of mixing (spattering for example?)

I really hope you make sure what you doing before you do this. Alkalis are a lot worse on human flesh than acids, partly because they turn the oils in your skin to soap, and partly because the spills won't evaporate and therefore persist until something is done about them.

It would be a good idea to dye your KOH so you know where any spills are. I personally have spilt 50L of antifreeze solution in the lab (it was intentionally dyed beforehand in case of spills, and needless to say we used propylene glycol as it is much less toxic than the ethylene glycol used in car radiators.) Whatever you intend, something in your experiment will go wrong.

Please also check the legal aspects in your area. Also, consult with your supplier! The fact that you need to ask on the internet instead of talking to them suggests you are up to something unusual. Would you care to share with us what it is?

EDIT - Now you've clarified you're an engineer, one more very important point. Keep KOH away from aluminium. Alkali will dissolve the oxide layer that protects aluminium from corrosion, and unmask the true (very high) reactivity of the metal. A lot of heat and hydrogen gas will be generated by the reaction $\ce{3 KOH + Al -> K3AlO3 + 2/3 H2}$.

I'm guessing most stainless steels should be fine (but obviously check.) I have used equipment from the catering industry in some experiments, but stay away from stainless steel cookware that has the base thickened with aluminium. Even though it is external, it's not worth the risk.

Also, note that mixtures of acids and bases with water are often most corrosive at a medium concentration, so don't assume that just because a material is OK at 90% concentration, it's going to be OK at 50% concentration.

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    $\begingroup$ Hey thanks for suggesting the idea of dyeing. As mentioned in a comment above, it is in an industrial area; the legal aspect is being worked out by another friend. The temperature will be maintained only for an hour when we add the other reactant. Why i am asking is because we have performed the process only at a laboratory level under the guidance of a prof. The prof has set us up with some of his contacts in the industry. But before we scale up, i thought it would be better to seek some advice. $\endgroup$ – cryptex Feb 22 '15 at 6:02
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    $\begingroup$ This is the kind of advice i was looking for :). Subtle points; something that is not covered in college education but only people with sharp eye catch. wish we could have you as another guide. $\endgroup$ – cryptex Feb 22 '15 at 11:36
  • $\begingroup$ @cryptex If it was not covered during college education, you went to the wrong college. Majority of these risk concerns are 1st year collage training. I am seriously concerned about people who need this advice: it is a serious red flag that they don't have any relevant knowledge and training. $\endgroup$ – Greg Feb 23 '15 at 5:54
  • $\begingroup$ @Greg I think the problem is they have the wrong degrees. They have a chemist, cryptex is an "engineer" but they don't have a chemical engineer or even an industrial chemist. Chemical engineers study two relevant subjects that are not on the curriculum for either chemists or mechanical engineers: 1. heat transfer and mass transfer (mixing,dissolution,precipitation) 2. analysis of chemical industry disasters. en.wikipedia.org/wiki/List_of_industrial_disasters divides them between "energy" and "other." Even then, there's nothing like witnessing a small incident to help you focus in future $\endgroup$ – Level River St Feb 23 '15 at 6:12
  • $\begingroup$ @steveverrill Chemists study all this or how to figure out if they don't know, it is basic lab safety. And if you don't know basic lab safety, you shouldn't do experiments, even in 10 000th of this scale. $\endgroup$ – Greg Feb 23 '15 at 6:59

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