Sciencemadness Discussion Board

Buss Loop Reactors

solo - 29-7-2008 at 18:36

Currently considering the purchase of a reactor.....however I had planned to do some hydrogenations on it because of the high psi availability and the volume...I since have read that there are specific type of reactors for hydrogenation called Buss Loop reactors...this are designed with hydrogenation in mind however I wonder if regular use as a reactor is also possible , making it a dual purpose unit.

Most of the units I've looked at are for the 5 gallon volume and they vary from 7-22k ...used they are all glass lined and are with an overhead stirring mechanism and some with a reflux column.

There are a couple of reactions I'm interested in but require cooling around -20 C and hence a reactor with both heating cooling coils and the design of a buss loop unit with make it a trifold purpose unit.

Has anyone had any experience with such reactor and are there any preferences over a Pfoudler glass lined unit vs a stainless steel unit.

I'm just looking around for something as mentioned to be a very useful tool in my lab....there are some out of patent phermaceuticals that demand a very good price /kg that get my interest..............solo

Magpie - 31-7-2008 at 15:35

Solo I had never heard of a BUSS loop reactor, but had heard of BUSS AG, the Swiss company who makes them. I looked on their website to see what it looked like. It has a very clever mixing device that utilizes an entrained/dissolved gas.

My career never took me to the use of these small pilot plant scale reactors, with one exception: a one-gallon stirred tank reactor with a steam jacket. It was used for the conversion of corn starch to complex sugars using alpha-amylase enzyme.

Edit: I have also used a similar pilot scale reactor to digest wood chips to pulp using the Kraft process (NaOH/Na2S).

BUSS took over the US company LCI. One plant I worked at had a large steam jacketed vertical dryer made by LCI, now BUSS. We used it to dry waste water salts such as ammonium sulfate.

[Edited on 31-7-2008 by Magpie]

Sauron - 31-7-2008 at 23:11

A loop reactor by definition is one in which the reaction mixture is recirculated by pump (often peristaltic pump or diaphragm pump) and usually this involves a main reservoir, and a catalyst bed tube. For examplee a CSLR is a Constantly Stirred Loop Reactor. This is all CE terminology so I suspect the chem engineers around here like JohnWW will be more familiar with it than I am.

A word of caution:

Many hydrogenation catalysts are very sensitive to certain catalytic "poisons" so when considering using a hydrogenation apparatus for other reactions, weigh carefully the potential for ruining the apparatus for further hydrogenation work.

Also, pressure reactors that give long service for hydrogenations may have their service life shortened by the effects of corrosion from certain kinds of reagents even if they are not poison to catalysts. Study carefully the choice of reactor material, as there are reasons why all those expensive exotic alloy reactors exist, plain old 316SS just won't do the job for everything. Glass or PTFE liners do not completely protect the metal reactor components from vapor and liquid reactants.

Never heard of BUSS AG but will look them up, I shudder to think of Swiss prices, however. Parr is bad enough!

gsd - 1-8-2008 at 01:19

Quote:
Originally posted by Sauron
A loop reactor by definition is one in which the reaction mixture is recirculated by pump (often peristaltic pump or diaphragm pump) and usually this involves a main reservoir, and a catalyst bed tube.


I may be wrong but to the best of my knowledge, the pump in the BLR is always a CENTRIFUGAL PUMP. It replaces the gas inducing stirrer of the normal hydrogenation (stirred tank) reactors. The perstaltic or Diphragm are essentially transfer pumps with very little mixing characteristics. They aid / help to maintain the "Plug Flow" of fluids in the system. Whereas centrifugal pump is as excellent mixing device as well. Which is what is required in BLS for intimate contact between 3 phases.

gsd

Sauron - 1-8-2008 at 18:50

You are right. But I wasn't referring to BUSS BLRs, but rather loop reactors generically. Peristaltic pumps have the advantage of no contact with the reaction mix (except inside the tubing) and all-PTFE diaphragm pumps also are available. But of course centifugal pumps provide better mixing, it's just problematic when the reactants are very aggressive.

For example a CSLR running SO2Cl2 through a bed of GAC while admitting Cl2 and SO2 at controlled rates using MFCs. Even Viton tubing has a short service life when handling sulfuryl chloride, I recall it is something like 6-12 hours. Replacing tubing is cheap, replacing the wetted parts of a centrifugal pump, rather costly and laborious.

JohnWW - 1-8-2008 at 19:38

"Loop reactors" can be either of two components of process units:
(a) A liquid- or gas-phase reaction proceeds inside a pipe into which the reagents are continuously introduced, mixed, and through which the reaction mixture moves in turbulent-flow mode during the reaction (which is complete when the mixture exits the pipe into a tank); while concentrically outside this pipe is another pipe through which flows (either countercurrently or cocurrently depnding on the reaction) a cooling or a heating fluid in a continuous closed loop, with this fluid being either recooled (e.g. water in a cooling tower) or reheated to the required temperature before reentering the cooling or heating pipe; or
(b) Some sort of continuous liquid- or gas-phase reaction in which one of the reagents (e.g. an homogenous catalyst) emerges unchanged after the reaction and is somehow continuously recovered and recycled in a loop, eg. by its forming an immiscible liquid which can be pumped off and reused in the reaction.

gsd - 2-8-2008 at 01:05

@ Sauron

We are discussing the same subject on different wavelengths :). You have lab scale on your mind where peristaltic / diaphragm pumps definately have an edge. However on industrial scale the good old CP beats them hands down.

Also now-a-days Material of Construction for pumps is not an issue at all. From glass and exotic polymers to esoteric metals or even Cement Concrete (!), every imaginable material is successfully used as a MOC for Centrifual pumps.

gsd

Sauron - 2-8-2008 at 18:07

OK but then the question becomes:

What does industrial scale process equipment have to do with amateur home chemistry?

I own some pilot scale stuff like 72L RB flasks and a 20L Buchi but have never actually USED them. In fact my bench scale kit stops at 5 liters. Rarely do I feel the need for 12-22 L glass and too rarely to have ever purchased any. (The big stuff I do have was bought for liquor making.)

I think process equipment is fascinating, but just a little OT for this forum, isn't it?

[Edited on 3-8-2008 by Sauron]

Magpie - 2-8-2008 at 18:32

Quote:

What does industrial scale process equipment have to do with amateur home chemistry?


Sauron, I agree with you that process equipment is fascinating in it's own right. Since it has to do with chemistry I think discussions of it are fun and worthwhile.

Besides, who says we might not be able to scale down some clever feature we find on industrial scale equipment to a lab or at least a pilot scale. I would say that the gas mixing jet on the BUSS loop reactor might even be a posibility for scale down. Chemists perhaps have a mindset that they can only run batch reactions. When you use a tube furnace with continuous feed aren't you just using a small continuous flow plug reactor?

[Edited on 2-8-2008 by Magpie]

Sauron - 3-8-2008 at 03:52

I was not proposing that we rule the thread out of bounds, merely arching an eyebrow, so to speak about the delineation between industrial scale and bench scale. I have a lot of kit that is not "typical" home lab stuff, e.g. pressure reactors. However they are definitely bench scale (like, 1 liter) and not something enormous that is fed by process pipe.

Scaling down is fine where feasible.

dapper - 6-8-2008 at 09:33

I personally would love to hear more about pilot scale reactors and gear because its interesting and not-often discussed. You're certainly lucky to have the larger stuff, I'm sure it wasn't cheap.

Sauron - 6-8-2008 at 12:23

Cheap? Nope. Two 72 liter GlasCol TM's purchased new from their agent here. Two Kontes 72 L single neck 45/50 flasks, same, new from local agent. That's about $6000 US right there.

Two used 72 L four neck flasks purchased second hand in USA and shipped to Thailand, these were $750 each not including the ocean freight and import fees. These are 100 mm center necks with Schott flanges, side necks are 45/50 on one and 55/50 on the other. I sleeves those to 45/50 and set up one with a stirrer and water cooled bearing and the other for distillation or reflux. So far have never used any of this stuff and have near $10K in it.

The 20 L Buchi is a R-152 with E-type glassware (descending condenser, foam trap etc.) I paid $6500 for this in Alabama and shipped it to Thailand. 20 L flask and 10 L receiving flask came with it. Also have not had use for it yet.

All this was purchased for liquor making (absinthe) which project I pulled out of for complex reasons.

gsd - 6-8-2008 at 16:42

Isn't all this discussion completely off-topic?

I think PM is a great tool available on this forum but unfortunately it seems it is grossly under utilized.

gsd

Sauron - 6-8-2008 at 20:04

Ah, the volunteer auxiliary post police are active, I see.

I was responding to post above. My response is no more off topic than any other discussion of process equipment on a forum dedicated to AMATEUR HOME chemistry.

gsd - 7-8-2008 at 05:55

Since when merely pointing out something-which is not only completely off-topic but is hijacking a good thread from scientific discussion (albeit about process equipments but scientific never-the-less) into a personal life monologue of a member-has become policing?

I don't know how can anyone see BLR as anything other than a process equipment.

And if you can discuss finer points of Parr Bomb in this AMATURE HOME chemistry forum then so can others discuss construction features of plant scale BLR which could give some input to scaling it down to HOME scale to some enterprising member.

gsd

gsd - 7-8-2008 at 07:21

@ Solo

Here is a process description of an INDUSTRIAL SCALE BLR
(This description is mailed to me by a friend who is in this business)

"Process Description of BLR

The reaction mixture is fed into the reaction autoclave and then circulated through the reaction heat exchanger
and then back into the autoclave through a unique reaction mixer which also introduces the reaction gas (H2,
EO, NH3, etc). Mixing is intensive, constant, and with high sheer forces that produces high diffusion rates
across the catalyst boundary layer.

The intensive mixing provides optimal reaction contact. Any undissolved, dispersed gas is disengaged in the
autoclave and returns to the head space. As the reaction gas is consumed, fresh gas is introduced to maintain
a constant reaction pressure. The temperature of the reaction mixture is controlled by the reaction heat
exchanger. Catalyst is added in a suspension of raw material or solvent. The centrifugal pump used to circulate
the reaction mixture is specifically designed to handle suspended catalysts. It has a special seal system that is
protected by a pressurized flushing system."

I think this gives clear picture of the system. Given the inclination and of course resources, Any good AMATURE HOME chemist will be able to assemble a working HOME BLR based on this description.

Also I must admit that I was wrong when I presumed in my previous post that the centrifual pump does the job of mixing as well as circulation in the BLR. This description says that it is meant for circulation. A separate (static) mixer does the mixing job.

gsd

[Edited on 7-8-2008 by gsd]

Sauron - 7-8-2008 at 09:32

@solo, my Parr is 1 L nominal with a working capacity of 650 ml.

I am not the only member with this sort of equipment, and mine is not the largest owned by a member.

Pray, what is un-amateur about that?

When you factor in the mantle, and stirrer, and thermostat, and controller, the cost is of same order of magnitude as glassware setup - which is to say it is more but less than 10X more. And the ability to work at >1800 psi @ a few hundred C is something glass will never deliver.

Of course I did not buy it new.

On the other hand, I have never seen anything from BUSS AG come up for sale on used market.

You have not mentioned the size of the BLR you are contemplating to buy.

Benchtop? Or does it require a containment dome?

In any case I never intended to raise any serious objection to this thread, and I already said so upthread.

Nor was it my intention in any way to hijack or derail the discussion. A member asked or at least implied a question, I replied. End of story.

[Edited on 8-8-2008 by Sauron]

gsd - 8-8-2008 at 00:08

Here is a schematic diagram of BLR, which when read along with the process description given previously gives perfect details of BLR.

It seems it is a good candidate for scallling down to lab / small scale depending on the pressure at which you wish to operate.

You only need to find out correct centrifgual pump compatible with your reaction media, temperature and PRESSURE.

The big advantage as I see it, BLR has over Autoclave is there is no stirrer. It ofcourse has a centrifugal pump but it is available - depending on your operating conditions - in vide variety / types and prices. In an high pressure hydrogenation autoclave the mechanical seal of a stirrer is a major cost component. I remember for a 30 lit gas-inducing type hydrogenation reactor operating at 35 bar and 150 Deg C., the cost of BERGMANN double mechanical seal complete with pressure equilizing device was more than the cost of the vessel :).

gsd

[Edited on 8-8-2008 by gsd]

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Sauron - 8-8-2008 at 03:17

Lots of bench scale autoclaves, say 1 to 5 L, have either packed gland or magnetically coupled stirrers and operate to about 250 C and >100 bar. Optionally, higher, with a different vessel. The standard ones are rated for 1900 psi at the max service temp. (316SS vessel).

But you are right, the components for these things, purchased new, are absolutely outrageous in price.

Fleaker - 8-8-2008 at 10:33

Solo,

The only Pfaulder I've experienced is their glass-lined unit with the bottom tap and it wasn't meant for pressure. I know they make pressure vessels, but as you said yourself--they're extremely expensive. Convenience lies in that you have little worries about permeability of the stainless and that there are less things that react with glass than SS316--granted you won't have the same pressure capabilities. Weigh your options--spend more on higher pressure using cheaper catalysts, or spend less on lower pressure with expensive catalysts.

Recirculating Hydrogenation Apparatus

stoichiometric_steve - 17-10-2013 at 05:07

Has anybody seen or heard of this?

Some guy on another forum claims that his "company uses this type of device on a wide variety of hydrogenations since it is easy to use and does not require high pressures of hydrogen".

I have no clue as to how this device could be made up. Enlighten me! :)

Edit: Yes, i googled. The patents that came up are useless.

[Edited on 18-10-2013 by stoichiometric_steve]

gsd - 18-10-2013 at 07:31

By any chance is it Bus Loop Reactor?

Gsd


stoichiometric_steve - 18-10-2013 at 07:40

thanks man, that looks exactly like what the guy was talking about! :) there's even a thread about it here. gotta know what to search for.