Steam Sterilizer Cabinet Venting

Newfie

Hi All;
I have built a walk through double door plywood and insulation steam cabinet that takes 2,000 pounds of material at a time to sterilize . I have attached two 6Kw steam generators. This is a zero pressure cabinet sterilizer. My issue is the exhaust and condensate handling while still trying to keep the material I place in the sterilizer fairly sterile and free of dirty air during the cool down (cool down will take about 2 days). The cool down will try and suck in air via the vent/drain pipe. The floor inside the cabinet has a slight slope and I have a 1.5" drain pipe as the two steam inlets are 1/2" each. The cabinet is about 7'x7'x6' (R 32 high temp resistant insulation - isocyanurate and fibreglass). I can vent it outside but that will have to be after a rise of >2 feet up a concrete wall and then out through the building wall - so the condensate will also need to be drained to prevent it blocking the exhaust/drain pipe at the elbow at the bottom of the wall aka 2 foot rise. I can put a float valve in a sealed bucket in the drain at the base of this 2' rise via a T joiner set in a hole in the concrete floor that contains a sump pump. This will drain the condensate and let the steam vent up and out the wall via a steam pipe...but, when the cabinet starts the cool-down cycle it will start to suck in dirty air from outside the building and up the 10 foot long drain pipe and into the sterilizer cabinet. The stuff in the cabinet will be in polypropylene bags with hepapatches but I'd like to avoid the system drawing in that dirty air as it cools. I have the walk through steam/sterilizer cabinet attached to a Class B sterile air positive pressure lab via one of the two cabinet doors. So, my thought is that once the cool off cycle starts I'd immediately open the lab door side of the double door sterilizer cabinet and let rip with one of two massive (2'x4' each) 90cfm hepafilters (laminar flowhoods) that clean the lab air before it enters the lab and flood the cabinet with cool sterile air. Thoughts?

EBEBRATT-Ed

Don't know much about this but sounds like your only alternative. Would a trap in the drain line make a seal and prevent the back entry of dirty air?

Newfie

Yes, but then as the 2000 pounds of material cools it would make a tremendous vacuum as it went from 96C to 20C.

mushroommatt

Newfie, how did this work out for you? i am trying to design a similar system for my smaller mushroom op. i have a single 6kw unit and i am trying to determine how large a vessel i can use with it for superpasturizing. you can hit me up on here or Facebook under Matt Wanasek or Matts wild foods. Thanks and mush love

mushroommatt

another thought on your problem as well, i am sure you have come up with a solution by now, but just in case you are still thinking about options. You could get a small HEPA filter unit that is used for rodent cages. they have a small 3-4inch outlet to feed into chambers that house the cages and turn that on during your cooldown cycle. incorporate some kind of shutoff of check valve as well to avoid steam going into the unit during your heating cycle. this would also speed up your cooldown significantly i would think. I cant take credit for the idea, i have seen others use it on proofer cabinets used for steam boxes. IF your box is 7x7x6 thats 294 ft3 that use are processing in. would it be safe to assume that if i had one 6kw unit i could do half that volume? i really need to figure out what, and how to build a processing unit for my substrate. I am 8 months into my building lease and still have not made a dime, my HVAC is going in soon for the grow area, i have to start making some money on this before i run out lol.