Imperial Stout and 10gal MLT - Mashing and Sparging

So I just got my ingredients for my Imperial Stout, 22lbs worth of grains, and I am wondering what would be the best way to go about Mashing and Sparging. It would obviously be a very small grain/water ratio. I am kind of thinking about just fly sparging slow and long, like 90 minutes. How long should I Mash for? I typically Mash for 90min and Sparge for 40min. At 1.5 qt/lb I got 84% efficiency twice in a row last weekend (also changed a few others things). Thanks for any help. I want to do this right. It wasn't a cheap recipe either.

im in the same boat for the same type of recipe...Im using 1.3qrt/lb and im going to split the sparge into multiple batch sparges. the thinner mash would be nice but it will depend how much room im going to have left over in the mlt

I actually asked essentially the same question last week, here are a few answers which may help. Imperial Stout Question
I ended up brewing a hefe for a friend but am doing the imperial this weekend, in a 10 gal mlt also. I will try and help after I do mine if I can.

I copied a post in the attached link...I would make a small beer w/ the grist after collecting the runnings for your stout...can we say partigyle?

"As far as gravity & sparging, take the runnings as-is with a sparge to hit your volume, then parigyle that ****!"

Tossing 22 lbs of mashed grain that still has available wort potential seems kind of silly.

I made my first imperial stout the other day and ended up about 9 gallons preboil, boiled for two hours, filled a carboy and put the rest in some big jars to boil down later. That one had 24 pounds of grain.. We'll see how that goes.

Well I went ahead and did it, at 1.0 qt/lb. I could have fit 1 more gallon of water, but not much more. I mashed for 90+ minutes and sparged for 90 minutes. I ended up with 60% efficiency and 1.091 OG. I was kind of disappointed, but I guess it's not terrible. I think my qt/lb ratio really determines my efficiency. I'll add another gallon of water next time and see what I get.

ODaniel said:

Well I went ahead and did it, at 1.0 qt/lb. I could have fit 1 more gallon of water, but not much more. I mashed for 90+ minutes and sparged for 90 minutes. I ended up with 60% efficiency and 1.091 OG. I was kind of disappointed, but I guess it's not terrible. I think my qt/lb ratio really determines my efficiency. I'll add another gallon of water next time and see what I get.

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for a 10lb mlt thats not bad

60% is not bad for a big beer like that. I mashed 22 lbs. at 1.33 qts. per lb. in a 10 gallon MLT - batch sparged and got 68% - usually get 75-80%. Crush a little finer next time - that increases my efficiency several points.