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Flow through pasteurizer

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You could make a flow-through pasteurizer unit that might be easier to handle and store than a pasteurizer that heats a bunch of sludge up batchwise. There is also the possibility of getting power consumption down using a heat exchanger, but the average power consumption is very low anyway, because there is very little sludge produced each day.

I was just thinking about this, and I think you could do it very cheaply and pretty easily, actually.

Suppose you have some stainless steel tubing (you could use copper, too, but it might corrode). You put that through some temperature resistant plastic tubing, or some more metal tubing, to form a heat exchanger. Make the tubes wide enough that they don’t get clogged by sludge (probably not a serious issue). Now bend that around into a compact shape so it takes a manageable space, put it in a container and fill said container with Great Stuff, or similar foam insulation.

So that’s your heat exchanger, next is the pasteurizer and the pump. The pump could just be a hand squeeze pump, since the removal of sludge could be done only once every few months even, and should only take a couple minutes. Just one of those rubber bulb pumps for a couple bucks.

Next, the pasteurizing chamber per se could be a long metal or plastic tube of sufficient size wound and folded up and put into a kettle, or any other appliance that boils water, and then submersed in water. Ideally something insulated, or there is no point in the heat exchanger. The internal volume of the tube determines how fast you can pasteurize stuff, because the stuff must be held at above 70 deg c. or whatever for 5 minutes – so if the chamber is 1 liter in volume, you can do 1l per 5 minutes. Actually, I think it’s only 30 seconds or something at 90 deg c.

Now turn the appliance on, bring to a boil, and start slowly pumping the sludge through. Pretty straightforward. You need to be sure the conductivity and diameter of the tubing in the pasteurization chamber is suitable, so all the waste is being adequately treated. You also need to be sure the water surrounding it is maintained hot enough, either by watching it boil, or with a cheap oven thermometer.

You might also want to flush it with fresh water when you’re done with it, to get the sludge out. Then you can sell your “100% pasteurized liquid humanure” to a local gardener, or put it on a lawn, or wherever.

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Written by gregor

August 20, 2010 at 02:31

Posted in Uncategorized

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