Recirculation of Dry Hop/Ruh tanks

[classic_brad]

Hello All,

Long time listener, first time caller... Hope this is in the appropriate section, but:

At the brewery in which I work, we centrifuge beer at the end of its fermentation into pre-dry hopped and co2 purged storage tanks in order to dry hop for 7-10 days. We are a contract brewery and our customer has a recirculation schedule in which they have requested we follow: recirculate after 72 and 120 hours on hops, letting the hops settle back down in time to filter after 168 hours.

Our current method is to hook up a co2 line to the bottom valve of the tank (horizontal cylindrical) and vent from the CIP line in order to fluff up the bed of hops and optimize hop surface contact with the liquid-- I know, I know... this screams loss of aroma, but it is the lesser of two evils compared to recirculating the liquid through a pump and picking up dissolved oxygen.

I have read that some breweries add the hops in phases through a top port above the liquid level, but that isn't really an option for us with the tanks we are using.

We are currently looking for a better process in which to do this and some of the ideas I have been kicking around are to either look into a way to deaerate the pump and possibly bleed some liquid down the drain in order to purge all oxygen from the line. Let me know what else you might have in mind.

Thanks!

[gitchegumee]

Imho....

...I believe you have chosen the greater of the two evils. I'll try to explain; beer is pumped every day in almost every brewery. If you do it right, there is negligible O2 pickup, negligible CO2 breakout, and negligible beer damage. (Less O2 pickup than a centrifuge, I believe) By taking a suction on, say your racking port and discharge through the tank drain, you can probably rouse the whole hops (I assume) to have the effect you desire. Especially if done by packing deaerated water in the pump lines and a gentle VFD transfer. On the other hand, it is my humble opinion that bubbling CO2 through a pressurized column of beer while venting is misguided. You are stripping the very aromas that you are trying to capture. (And I'm not convinced that this rousing is adding much, if anything to the aroma profile of your beer--surface area of a submerged hop is already 100%. You're not going to get more surface area contact with beer by rousing). Add to this the fact that bubbling through a column of pressurized beer will foam your beer and kill your foam-positive proteins--leaving your beer less capable of fine tracing/lacing. So I think you are actually hurting your beer with both sides of this double-edged sword. I would strongly encourage you to use a pump on a VFD; use hoses with a proper pitch-and-catch setup at the racking arm and the tank drain; and then pack the pump and the lines with deaerated water and use a gentle rousing action without disturbing your resting beer. Just my way of doing it. Good luck!

[dick murton]

The only thing I would add is that if you have dished bottom tanks, you are likely to simply punch a hole through the settled hops, and probably more cleanly than using gas. And if you can use something other than a high speed centrifugal pump, but still get good flow rates then this would be preferable as the centrifugal will mascerate any roused hops drawn into the pump and they may not settle as well. Having said that, if you can take of at highish level, then the amount of hops broken up will probably not be high unless you leave circulating for hours.

As noted already - make sure the recirc loop through the pump is fully clean, sterile and deaerated, ideally with deaerated water.

[Matt Dog]

Another way to do it without Deaerated water is to set it up so you have a valve and T at the highpoint and chase the sani out with beer from the low point. You waste a bit of beer but the O2 pickup should be pretty low.

[dick murton]

True, but that means they are likely to run hops into the recirc main, and if they use a PD pump, they won't be able to flood fill it backwards, so it will not be effectively deaerated. For me, the right way is to flush through from the high level takeoff, through the pump and to drain at a Tee at the bottom inlet.

Even if you use towns water in the right direction, providing the water is purged out properly this is going to reduce the DO pickup enormously - not perfect, but if you haven't got dearated liquor (or boiled water) this is a damned good second best.

[cpelz]

Phillip-

What do you mean by"proper pitch-and-catch setup"?

Dick-

No sanitization concerns using a towns water flush?

Thanks guys.

[dick murton]

Towns water should be "potable", i.e. free from pathogenic bacteria, viruses, and other harmful chemicals, and clean. So it should be OK to use. The downside is that it normally contains comparatively high levels of chlorine, which if allowed to come into contact with beer may result in chlorophenolic taints. However, if you flush through the pipework at sufficient flow rate to eliminate all air bubbles and reduce the oxygen level to the normal dissolved oxygen level, circa 8 - 10 ppm, then flush out at similar flow, i.e. turbulent flow rate, 2 metres / sec (about 7 ft / sec) and allow some beer to run to the floor before diverting into the tank, then you shouldn't have a problem.

Using boiled water has three main benefits

- the residual oxygen level is much lower than 8 ppm - if boiled for sufficient time it should be virtually zero
- the water is sterile, not just potable. But note that it can be recontaminated if the rest of distribution system is not sterile
- much if not most of the chlorine is flashed off, so reducing the risk of chlorophenolic taints

The downside is of course the cost of boiling it. But cooled brewing liquor from the cooling side of the wort chiller should also pretty much fulfil these benefits.

[dick murton]

What do you mean by"proper pitch-and-catch setup"?

This is how I would set it up. I have shown a CCV and butterfly valves. I would actually prefer to put the water on at the lowest point, but providiong the flow rate is high enough, particularly for short runs such as this, as shown is fine.

[dick murton]

Wow. I didn't expect the diagram to practically fill the screen !!

[cpelz]

Thanks for breaking it down Dick.

I've always avoided introducing tap water post sanitization. OTH my pipe purging has probably been sub optimal. I bet the benefits of the latter outweigh the risks of the former.

[nohandslance]

Free State Brewing.

The most impressive whole hop recirc loop I have seen is at Free State Brewing in Lawrence, Kansas. Give them a call.
Produces great hop beers, and is a nice compact unit.

Lance
Rebel Malting
Reno, Nevada USA

[classic_brad]

The most impressive whole hop recirc loop I have seen is at Free State Brewing in Lawrence, Kansas. Give them a call.
Produces great hop beers, and is a nice compact unit.

I shot them an email including your utmost recommendation for their products. Thank you very much to everybody for your responses.

Cheers!