Aggressive reaction conditions: Coatings or lined reactors vs Exotic MOCs
One question that often arises during MOC selection is whether to go for a exotic MOC (e.g. Hastelloy) or a coated reactor e.g. glass on stainless steel. We thought it may be a good idea to summarize our advice to customers as a blog post:
- Cost: Reactors made of exotic MOCs like Hastelloy, Monel, Inconel, etc. will usually be more expensive than a lined MOC. However, the life of integral reactors is longer than lined or coated reactors. Even with the best coatings periodically a reactor will require to be re-lined or coating to be recoated.
- Abrasion due to Slurries and crystals: Another question arises when slurries, crystals or other abrasive products are involved. Normally linings are thin and will not withstand abrasion very well. The behaviour of linings under such conditions can be difficult to predict and hence integral reactors are a better choice.
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- Cleaning procedures: A similar situation was encountered by us in the past when the chemical product was sticky and the customer was used to using a sharp tool to scrape off the product. Such activities are usually incompatible with coatings or linings since invariably the operating procedures will damage the linings.
- Uncertain operating conditions are better suited for integral reactor MOCs (e.g. Hastealloy) than linings. A small corrosion rate can be tolerated since typically a corrosion allowance is present. A few mils per year will not be a problem if encountered. Linings on the other hand are very thin and they can get eaten away rather fast.
- Temperature shock: In the case of glass linings temperature shock is another parameter to carefully consider. Rapid chilling or quenching can lead to a cracked lining. Refer to operating instructions very carefully. Similar situations are also encountered with fluride-containing impurities which can have a drastically corrosive effect on glass linings.
Linings can also be very sensitive to a single spot of damage or corrosion. Once the corrosive chemicals penetrate behind the lining they will then destroy the whole underlying base. Solid MOCs usually do not have to worry about this failure mode.
Consult this excellent post by De Deitrich on how to identify glass lining damage on larger reactors: https://www.ddpsinc.com/blog/that-doesnt-look-right-how-to-evaluate-glass-lining-damage-part-2
We hope the above advice will help you choose your next MOC rationally. Again, do reach out to us for more detailed advice at [email protected]
Stay tuned for part 2 of this post for some more advice