Final Year Project

Digester design and construction info

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hernan83
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Joined: Sun Nov 13, 2005 8:30 am

Final Year Project

Post by hernan83 » Sun Nov 13, 2005 9:06 am

Hi.

What happened last month? My account was gone as well. I was just wondering, that day when I presented my project, I was told that the polyethylene bio-gas plant wasn't too suitable for use in Malaysia and also that it is too large to be used for a small scale facility. My supervisor has asked me to come up with a simple and small digester which is suitable for cooking, even if it can light the gas stove is good enough already for this project. I was just wondering whether a stainless steel water tank can be modified to work as the digester. If yes, what kind of modification is needed. If no, any other suggestions?

Thanks.

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nathan_lamothe
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Location: Joussard, Alberta, Canada

Post by nathan_lamothe » Sat Nov 19, 2005 8:20 pm

Unfortunately the site was hacked. Bob lost all the data back to his last backup. Which meant quite a number of posts, including our discussion of your project.

I am glad to see you found your way back though.

Did they explain In what ways was the polyethylene plant not suited for Malaysia? That might help with thinking about modifications and new directions.

I would suspect that any tank could be modified to be suitable... stainless must be pretty expensinve though?

hernan83
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Joined: Sun Nov 13, 2005 8:30 am

Post by hernan83 » Wed Nov 23, 2005 12:55 pm

What they said was the design is not compatible with my objective, which is to design a small scale facility. They said that this design is too large and will be difficult to transport the cow manure which may be far away. So that is why my supervisor suggested that I try to come up with a portable digester which can be carried around to be filled with manure. I am just unsure whether a small and portable design will be sufficient to produce enough bio-gas to light the cooking stove. I've been thinking, a rectangular polyethylene tank which is modified where there are 2 holes inlet and outlet for continuous feeding. But I wonder whether is there any alternative to the "plastic bag"? My supervisor don't seem convinced with it. One more thing is how do I measure the temperature and pH inside the digester when the "digesting process" has begun? Sorry if I am like asking too much.

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Bob
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Post by Bob » Thu Nov 24, 2005 1:46 pm

Hi Hernan,

I am so sorry that all of our previous conversation was lost. As Nathan explained, the site was hacked, and I had been negligent in keeping my database backups current. (Which reminds me. I think I'll do a backup right now. :oops: )
They said that this design is too large and will be difficult to transport the cow manure which may be far away. So that is why my supervisor suggested that I try to come up with a portable digester which can be carried around to be filled with manure.
Are you still considering John Fry's "inner tube" design? It seemed to me that that small simple design fit your stated goals about as well as anything I've seen. (Do you still have links to that information that you could post here again?)
how do I measure the temperature and pH inside the digester when the "digesting process" has begun?
The easiest way would be to install a capped port that would allow sampling the contents without allowing gas to escape.

hernan83
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Joined: Sun Nov 13, 2005 8:30 am

Post by hernan83 » Sun Nov 27, 2005 8:10 am


hernan83
Posts: 4
Joined: Sun Nov 13, 2005 8:30 am

Post by hernan83 » Tue Nov 29, 2005 9:45 am

Just want to ask a few questions on the inner tube digester. Will it work with 3 or 4 months? And when the design is complete, the manure is added into the main digester but how much of manure to add? Full or almost full or half? I need to learn on how to start the digester.

And also the scum collector. How to remove the scum removed without air entering the container.

Can the main digester be replaced with a polyethylene water tank with baffles for plug flow path instead of using tractor inner tubes? I feel that the inner tube is vulnerable to leaks and can be dangerous.

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