batch sparging and efficiency

[Junket]

Anyone have a calculation for how much water a pound of grain sucks up and holds onto? I want 7 gallons of wort, so with two runoffs I want to target 3.5 gallons per runoff. For the first runoff, I know the amount of water that I used in my mash, say 3 gallons. I need to know how much of that initial 3 gallons will be retained by the grain, so that I can determine how much mash out/sparge water to add so that when I do my first runoff, I'll yeild 3.5 gallons.

I'd guess that the grain holds on to about one third of the mash water, so my initial 3 gallons is reduced to 2 runoff gallons and I need to add 1.5 gallons for the first runoff. How does this estimate sound?

Then for my second runoff, I simply need to add 3.5 gallons to the grain, because the grain has already sucked up what it is going to keep, and what I put in should equal what I get out.

[rich]

Anyone have a calculation for how much water a pound of grain sucks up and holds onto?

I let ProMash figure that out for me. Hasn't failed me yet. I have my grain absobtion rate set to 0.12 gallons per pound. Of course different grains will have different moisture content, but 0.12 gal/lb should give a pretty happy medium.

[Kaiser]

ok, I took the time and analyzed the efficiency of the model system that I mentioned above. I saved the data on the spreadsheet as PDF (http://www.troesterfamily.com/brewing/batch_sparging_efficiency.pdf). The first diagram shows the efficiency for different amounts of wort left in the grain (1 through 10) across the ratio of the 1st run-off volume to the total boil volume. The second diagramm shows the efficiencies for 1, 2, 3, 4, and 5 batch sparges which each result in the same boil volume.

One can make the following conclusions:
- when only 2 sparges are done, the maximum efficiency is achieved when both runnings are the same volume. But the curve is very flat on top and it doesn't make much of a difference if the 2 runnings are not of the same volume (as Denny said)
- the less wort that remains in the grain/deadspace the better the efficiency. This is obvious
- The more times you sparge the better will be the efficiency. Even if you are going for the same boil volume and are collecting less wort for each sparge. But from a practical point of view, only 2-3 sparges make actually sense due to the overhead and the dropping wort gravity

But don't worry to much. This is only FYI for brewers who want to know about this.

Kai[/url]

[bub]

Ok so that is cool..... and DAMN you are anal
BUB

[Kaiser]

Ok so that is cool..... and DAMN you are anal
BUB

I'd rather be brewing though. But it is something brewing releated, that I can do w/o having to brew. Time to get into the new house and get back to the regular brewing schedule that I had 3 months ago

Kai

[Junket]

Great info, K.

Two final questions:

When we talk about stirring a batch sparge up (which I'm led to believe is the most vital step), how long are we talking? 5 minutes?

In a batch sparge, should I drain both runoffs completely, ie. until air comes through my runoff tubing?

Thanks for making my experiment with and possible conversion to batch sparging easier.

[Bugeater]

Yes and yes.

Actually, the five minute thing is not set in stone. It takes about that long for the temperature to stabilize, especially if you did not preheat your mashtun. If you did preheat, then it might only take 2 or 3 minutes. Just make sure there are no cold spots or lumps left. This is also the amount of time it takes for the ph to stabilize assuming you are in a position to measure it and make any necessary corrections.

Wayne
Bugeater Brewing Company

[John F]

One can make the following conclusions:
- when only 2 sparges are done, the maximum efficiency is achieved when both runnings are the same volume.

- The more times you sparge the better will be the efficiency.
Kai[/url]

I've been trying to figure this out.

Would two runnings of 3 gal each result in a higher gravity than 3 runnings of 2 gal each?

John F