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  • Please HELP!!

    This is going to be a long post , so bear with me here as we need some real life experience to help us. So we are getting to the point where we can see a little light at the end of the tunnel with our startup and we have run into a big road block.

    Our brewhouse is an oversized 3.5 bbl custom built system which we have designed to be direct fired by NG. WE are looking into Midco Burners and particularly model # 4400 DS which runs btwn 130,000 to 400,000 BTU's.

    BK is 175 gal and measures 33"w x 48" T. dished bottom with 1 1/2" tc wort out the side of the kettle just above the dish. There is a 4" trub clean out in the bottom center w/ triclover and gasket.

    HLT is 125 gal and measures 30"w x 40"t. dished bottom with 1 1/2" water out in the center of the dish.

    MT is not fired!

    We wanted to achieve wort boil in roughly 30 min after we turn on the burners. Which means, if our MT run off enters the BK at roughly 155 deg and needs to hit 212 that's a diff of 57 deg. Starting with a pre boil volume of 130 gal. Using on line BTU calcs we came up with a need of 140,000 BTU's to achieve this. But, that's 100% heat transfer efficiency, and we know we aren't going to get that. So assuming 75% efficiency we added 25% more BTU's to the original 140,000. So now we are at 175,000 BTU's to heat our wort to boil in 1/2 hr.

    Now ? #1: Is this all making sense? #'s right?

    Now, we will roughly be heating 100 gal of water in our HLT from our tap temp of 50-60 deg up to 190 deg ( sparge , strike water). This done in the same amount of time. This calculation came out to 260,000 BTU's at 100% eff. Add 25% and we get 325,000 BTU's.

    These BTU #'s are all well within this burners capability.

    Now ? #2: Assuming our calculations are right, where does one get the fire box to contain this burner and safely remove spent gases?

    #3 If one were to have this box fit to a dish bottom tank, should it sit up snug and tight to the curve of the tank, have a hole for the burner tube to fit in and a hole to have the vent pipe fit in ?

    I picture a round box that fits tight to the tank, has the burner hole set up down lower on the box and the vent hole higher on the box and off to the side. Baffles inside would slow the heat down as it's being blown in and circles the bottom of the tank and help it transfer over to the wort inside the kettle.

    As the exhaust (carbon monoxide) gases came around the kettle they would exit the box and be blown out our brewery walls to the outside via a 6" vent pipe.

    As far as the design goes for the box, we are thinking 12-14 gauge SS, lined with fire cloth from Mc Master Carr, baffles would also be 12 Gauge and we would use some sort of gasket to seal the box where it meets the tank.

    Would we need to vent the box to the brewery room for oxygen needs of the burner? If so what kind of exhaust quantities would we be looking at coming from the vent and rising up through our catwalk? Deadly amounts?

    This has been driving us mad for 2 weeks and we need to move on with the brewery, but this is very very important part and we don't want to do it wrong the first time around. Give us your best shot and try to get us over this hump.

    We are very handy at coming up with ideas, can weld, problem solve and keep things moving, but this is a matter of employee health and brewery safty so we need some real life experience. We only have a 200 amp panel so electric is out of the ?.

    Thanks for listening, Gabe

  • #2
    Hi Gabe,

    for the oxygen needs of the burner, you could run a vent/fan from the exterior of the building to the box. Actually, you need to have a large container/room between the inlet and the burner to buffer atmospheric pressure changes (like the airbox on a motorcycle) but the notion is to draw your air from outside, and vent the spent gases up a stack.Preferably outside, through a b vent or something.

    That's the first thing I thought of. But then again, I'm not a combustion engineer (or an inspector)

    Then again, if the hot gases are going out the flue, the burner should draw from the air in the brewery. Just like a fireplace, as long as the stack is long enough and gets velocity as the heat increases, there should be no CO coming out these holes as the stiff breeze of make up air enters the airbox. Barring drastic atmospheric changes. And I think most vents are buffered from those.

    Wiser men than me may have a better suggestion.

    Nat
    Last edited by Natrat; 05-27-2010, 05:23 PM.

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    • #3
      I would not trust 75% efficiency. On a good day with an ideally designed firebox, 50% could be a good number. There is much to the design of a firebox, and I have designed a few. I will try to get you a more to get you a more thorough answer in a couple days.

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      • #4
        When you do your math don't forget the btu's needed to make up for system inefficiencies are subject to the same inefficiencies. Based on equation 1, increasing your btu's by a third, to 187k, is the number your looking for.

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