Major Breweries mix their mash?

Ok after watching numerous videos on youtube showing how the big breweries make their beer, I noticed they all use these giant mash tuns with big mixers inside slowly stirring the mash about 6 RPM.

My question is why do they mix their mash? Why dont they use recirc pumps like the rest of us? Seems like that's the best way to get maximum efficiency.

I read they use big mixers and false bottoms. I'm also wondering if they sparge or do they just boil some hot water, turn the mixer on,, pour in the mash and walk away.

Any info would be greatly appreciated since im in the middle of designing my system. Heres what I have so far. Please excuse the chickenscratch drawing that looks like a ten year old drew it.. I drew it up in a matter of seconds and dont have fancy design apps on my computer. Let me know what you think.

im going to use hoses with tri clamp and barb ferrules instead of piping. the little box on the bottom right of the photo running from the boiler is the hop filter and the other lil drawing next to that is the fermentation vessel. The water comes in through the line on the bottom left corner which splits into two lines one going to the chiller inside the boiler and the other to the water filter which then runs to the HLT. I use valves all over the place to control the flow of course just not sure what valves to use. Or is there any easier way to set this up instead of having all the valves? the valves seem the easiest route after looking at other setups on here which looked like they ran more lines than they needed. Im going to put use two elements. one in the BK and one in the HLT. 5500w in the BK, 4500 in the HLT. false bottom in the hlt and a HERM. or is having a mixer in the mash tun too overkill? since im recirculating through a herm as well?

I cannot imagine a big brewery conducting a mash in a 10g MLT. They wouldn't be a big brewery for long if they did.
"Why dont they use recirc pumps like the rest of us?"
What is applicable to a home brewer making small batches is not necessarily right for a commercial brewer making large batches. I'm sure that their procedures produce a better return on investment than would a home brewers procedures.

-a.

Breweries actually do recirc the mash for 15 minutes before the sparge and transfer, it is called a vorlaf. They do it to set the grain bed and clear the beer. If they were to recirc much longer, the bed would compact and the brewer will risk a stuck sparge. The equipment is much larger, with a grain bed depth much much deeper than a homebrewers. The mixing paddles, or rakes as they call them, are used to stir the mash to ensure all the grain is hydrated, and the temperature is even through out, just like you would use a spoon. I dont have experience with a herms, I use like to play with fire, it I like the fact there are fewer parts, and it is easier to clean. [/url][/IMG]

Big breweries will have a three part brewhouse: the mash mixer, the lauter tun and the boil kettle. The mash mixer is used to keep the entire mash at the same temperature. If there was no mixing mechanism then there is a good chance that the mash wouldn't be a consistent temperature. All mash mixers will have a steam jacket around it to adust the temperature as well. After the mash is complete, everything is pumped to the lauter tun which is a very wide tank with a false bottom. The mash is spread over the false bottom at around 1.5 to 3 feet deep. Wort runoff starts as well as a sparging. After this step is finished all the wort is in the kettle and the boil begins. With this setup a large brewery is looking to get 98% efficiency. Hope this clears things up.