Scale-up Batch Chemical Reactors

PW,

Thanks for the reply. Fortunately, the reactants are innocuous, mainly food-grade. But you point is still well-taken.

If we hold the diameter constant, the heat released would be a linear function of the length; that is, double the length, double the volume, double the reactants, double the heat released.

But I think you are putting me on the right track. I will try to get my volume increase by longer length more than larger diameter.

RM

No. Stop. Hire someone.

PW,

I am re-reading my original post. Where do you get the idea "stop holly cow before something blows up"? Wow, over-reacting (pardon the pun).

It was an innocent basis information gathering question. Nothing to blow up quite yet, no smoldering ruins burning to the core of the earth, limbs flying everywhere. Like a Godzilla movie, perhaps worse. Oh, the humanity.

"all else being equal"

If you increase the size of the reactor all isn't equal any more. you may get away with increasing the length and keeping all else equal.

I agree with PWSlack, you need the help of a chemist or process person.

The reaction rate is a critical unknown here.

longer still means that the heat generated will exceed the interior surface area to transfer the heat to the cooling jacket. you need to go smaller diameter and longer, or insert some kind of cooling loop inside the reactor vessel. listen to these guys and hire someone who knows what he is doing. Even food grade reactants in an exothermic reaction can cause a fire or explosion due to overheating.

It's all about heat transfer rates. Hire someone experienced.

THANK you for an informed answer. This addressed my question. It is very helpful.

To the others, "listen to these guys and hire someone who knows what he is doing. " I see that answer and the answer to do an internet search all the time. The assumption in the "listen to these guys and hire someone who knows what he is doing. " answer is that I am going to fire up the old reactor maker and build one for cheap. I am going to build a reactor, never did it before, but hey what could go wrong? That is gotta be in the mind of someone writing "listen to these guys and hire someone who knows what he is doing. "

I suspect a lot of OP's posting questions on topics they don't know about is they are trying to get to the background considerations. They themselves are not building the equipment they are asking about. they want to learn about the considerations behind a design.

So lets try to not use the "you are a dummy, get someone competent" response.

OK, gurus ?

Thanks

There are numerous ways that additional heat reduction can be provided for chemical reactors. Some are: additional agitation (although you didn't say if agitation is used); different materials of construction to one with greater heat conduction if acceptable with materials present and produced such as glass lined to Stainless Steel; use of chilled water instead of ambient; use of a coolant with a higher latent heat capacity; constructing with internal "coolant wings" but only if agitated; increasing coolant surfaces; circulation of the materials through an external heat exchanger in addition to jacket cooling (be very cautious with this method); changing the design of the contact points of the reactor to the jacket (stay bolts vs. dimpled for an example); slower addition of materials if possible; and several others.

I have purposely not given any more than brief details since these decisions should and must be made by a chemical engineer qualified in process engineering. Caution, not all ChE's have this knowledge!

War story to make you very cautious--- I once had to do an accident investigation for a run away exothermic reaction. 10,000gal reactor went exo and operators couldn't dump it in time. It exploded, wiped out the control room and other distant structures. One operator was found in several pieces and the wedding ring of the other was all they could find. Caution, caution, caution! Let the qualified make the recommendations and design decisions.

Good Luck, Old Salt

Ha, another helpful response. Thank you indeed Mr Salt, all points are well taken. I will see that these points are addressed by the actual designer/manufacturer.

Absolutely agree to have the qualified make the detailed design. I am simply at the preliminary design stage and only trying to see the effects of scale-up. I am not, repeat not, building a reactor.

I do appreciate your emphasis on the inherent hazards of reactors, without the heavy hand of derision. Perhaps we could learn from your comments in more ways than one.

Rock

RockM....

You are getting some very good advice from those who have posted above, and I agree with those comments.

But I also think it is probably important to discuss a bit the nature of your question and the background of the CH4 discussions.

First, and most importantly, mention an exothermic reaction to most chemical engineers and they get a bit nervous and excited. These types of reactions are responsible for the most deadly, spectacular and career ending accidents in history. So you are treading on sensitive ground.

Secondly, you should know that these for a are littered with newbee technical questions from those who are WAY< WAY over their heads ! ( e.g. I used to weld bicycles, now I want to weld nuclear reactors.... tell me how ?)

Chem-Es feel that the combination of these two things can cause disaster !

Hope that you can understand ???!!

RockM

Agree with you. Also some Chem-E's are not smart enough to realize they have neither of the two points you have listed. A good Chem-E knows the limitations of his/her knowledge and experience, admits it, sticks to it and only does work is qualified for. Additional education/experience is the way to expand his/her pool of knowledge and skills. Fewer exothermal "Oh $hits" that way.

An analogy to this is: In the medical fields, I wouldn't want a proctologist doing cardiac surgery on me!

Good Luck, Old Salt