sterilize in place a bioreactor

[hyposmurf]

In a bio reactor I need to steam heating up to 1 barg to sterilize it.

First I will allow the steam to flow trough all openings , then close all it , and let the steam to build up at 1barg for 15 minutes.

After it I will shut off the steam.

Here it cames my concern, how quick will the pressure down , and how much sterile air I have to supply to allow the internal pressure not to drop bellow 200 mm water column.

I have all the tank sizes and material and other features.

Reactor volume is 2.5 m3

Material is Stainless Steel grade 416

The air is from a blower at 0.700 barg , normally the piping will allow a 2 m3/min .

Other supply of sterile is an opening where a exhaust filter is suited to allow the same flow 2 m3/min .

One way to handle this task is, I think, to close the steam step by step down the pressure to be little less than the aviable sterile air pressure , guess to 0.600 or 0.500 barg , then open the incoming sterile air and the exhaust filter, so the pressure shall be always over the 200 mm water column.

Please guide me in this task , I have no much experience on it .

 

[sreid]

Is there some reason you can't gas steilize using Ethylele Oxide?

http://en.wikipedia.org/wiki/Ethylene_oxide

 

[hyposmurf]

It is not my chemical project, steam is stated as the mean to sterilize.
I was ask to furnish the sterile air supply , and the avoinding the pressure to be below the limit stated, fall on my hea. and I guess such method , but I can not show it by any formula ,or procedure.
The bioreactor will grow RIZOBACTERIA , or soya seed inoculant.

But despite it, can you give me the pros of using Ethylene Oxide.?

 

[danw2]

ETO has its own challenges, since it is so highly flammable. See thread at

http://www.eng-tips.com/viewthread.cfm?qid=143038&page=10

The US Chemical Safety Board has a video of what happened at one facility that practiced unsafe operational procedures with ETO.

http://www.chemsafety.gov/index.cfm?folder=video_archive&page=index

 

[quark]

First of all, 1 barg is insufficient. The saturation pressure corresponding to 121C is 1.05 barg and you will see it as 1.2 barg in practice (i.e to reach 121C). Secondly, you shouldn't close all the outlets and then raise the pressure inside as the condensate builds up inside and the purpose of sterilization gets defeated.

You should, first, identify the cold point in the system and then design your sterilization cycle to get 121C at the cold point for 15 minutes. You should keep all outlets open during the entire sterilization cycle (all the outlets should be connected to trap/traps)

You shouldn't have problems if your exhaust valve is designed for 2cu.mtr/min for a 2.5cu.mtr vessel.