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Rocket Stove for Scalding Pigs?

Sasha Goldberg


Joined: Jan 07, 2012
Posts: 27
Location: Southeast Virginia, Zone 7B
Hello,

we raise pigs and do our own slaughtering. We raise American Guinea Hogs so they are significantly smaller than standard pigs. When they are very small, we use a 50 gallon drum that has been cut lengthwise to scald them. When they are larger we use an uncut 50 gallon drum and our tractor to dunk them, one half at a time. To heat the water, we place the drums on concrete blocks and make a fire underneath. With the tall barrel, this requires constantly feeding the fire as we only get 8" of clearance. We can raise the half drum higher but it has so much open surface area that we also have to feed a bunch of wood. We have plenty of wood but the smoke constantly gets in our faces and we stink from smoke after we are done and we don't feel good about the amount of wood we use and the amount of pollution we create.

For pig scalding:

It is not necessary or desirable to bring the water to a boil; we typically scald at around 150 F.

We could do without the half barrel; it was the first one we got and it can be raised higher which makes it easier to move the pig to the work table and easier to make the fire, but it is not strictly necessary and it only works well for the smaller pigs.

Using the tall drum requires using our tractor, which is compact in size, to dunk the pig and even then there is a limit to the size of the pig we can manage because of the height of the barrel with the blocks is 43".

We do the largest pigs on a table or cart and pour water on them. This requires that we fill the tall drum virtually to the top and we heat extra water in the half barrel. We also need hotter water for this method; probably around 175 F.


All of the designs for rocket stoves that I seen are either quite tall or have smallish heating areas. Tall would be okay with the half barrel but we would need a heating area of about 3' X 2'. The tall drum has a much smaller surface area but it is already difficult to use because of the height. If we have to raise it up, we will need to use one barrel for heating and another, which we would lower into the ground, for dunking.

I would appreciate any advice. Also, I live in southeast Virginia. If any experienced rocket stove designer could help us, we would trade a pig for help.

Thanks,

Sasha

Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
build it into the ground. Dont know about scalding pigs so take this for what its worth. if you are only going to 150 degrees you can run a circulation system through a coil around the first bit of exhaust ducting and hit that temp easy. this would make your barrel size mostly not relevant and you can set it up so your scalding tank is at what ever level you want.


Need more info?
Ernie and Erica
Wood burning stoves, Rocket Mass Heaters, DIY,
Stove plans, Boat plans, General permiculture information, Arts and crafts, Fire science, Find it at www.ernieanderica.info


Sasha Goldberg


Joined: Jan 07, 2012
Posts: 27
Location: Southeast Virginia, Zone 7B
So this would be, basically, a batch water heater as you wrote about in answer to Don Walker?

If you want a batch heater plumb a pipe through the tank like a gas hot water heater and run it off the heat riser. wont be as clean as a RMH but this method works well as long as you dont have a pressurized tank.
.

I have very little experience with any of this so I am not sure I have the idea right in my mind. Construct a rocket heater in the the normal fashion except instead of the curved piping that is positioned at the bottom of the heat riser and buried under thermal mass, I would use a straight pipe that goes through the side of the scalding drum where it would be joined to another tube which rises above the level of the water. Is this correct? The tube that rises through the scalding tank would have to lie against a wall or it would be in the way of the pig but we could stir the water periodically to distribute the heat. Could the pipe that heats the water be smaller than 8"; say 4"?

Sasha
Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
no you set up a coil of tubing around the first 5 feet of exhaust duct and heat the water in the tank with an open circulation system; like you would use to heat water in an old franklin stove. I am sure someone here can draw you a quick diagram. Will someone draw a quick diagram for her and others.
Sasha Goldberg


Joined: Jan 07, 2012
Posts: 27
Location: Southeast Virginia, Zone 7B
I think I understand. The water that is in the scalding tank circulates around the exhaust tube. If this is correct then this set-up would not work for this application because the water gets yucky.

Sasha
tel jetson
steward

Joined: May 17, 2007
Posts: 3098
Location: woodland, washington
    
  53
another idea:
build the stove into the ground as Ernie suggested, but instead of the rocket mass heater style, try a pit stove. somebody on the forum used one to boil birch sap with good results.

if you want to get more efficient, insulate the vertical portion of the stove, and create a skirt around your scalding barrels to direct the hot exhaust more directly around them.


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Ernie Wisner
volunteer

Joined: Oct 16, 2009
Posts: 788
Location: Tonasket washington
    
  23
Well a filter would be a good idea. and i like Tel's idea.
Sasha Goldberg


Joined: Jan 07, 2012
Posts: 27
Location: Southeast Virginia, Zone 7B
Thanks for the link. I guess I'll have to buy the book again. I have it somewhere but cannot find it. We have a high water table. In some places it's less than two feet but if I am selective where I dig I can get at least 2-2 1/2 feet. I now have some ideas to work with. Thanks much.

Sasha
tel jetson
steward

Joined: May 17, 2007
Posts: 3098
Location: woodland, washington
    
  53
the book is great. certainly worth the price. but don't buy it just to see how a pit stove is built. at its simplest, a pit stove is a vertical hole in the ground that intersects another angled hole in the ground. basically an italic "v" underground. simple and easy enough to make that you can experiment a bit to find good dimensions for your purposes.

slightly fancier would be to line both the holes with stove pipe. fancier yet: stove pipe for the angled feed hole, and stove pipe insulated with a couple inches of perlite around it for the vertical burn/exhaust hole.

the skirt I mentioned could be built above ground with flashing, bricks, earth, et cetera. or it could also be below ground, so that your scalding barrel is actually set into the ground a little bit. might make lifting the carcass in and out a bit easier.

this solution might not be the most efficient possible way to heat your water with wood, but it will be so very much better than just building a fire under a barrel. and it will be cheap and easy to make. you ought to be able to try half a dozen iterations in a day, whereas building a full on rocket stove or mass heater could take several days (or 14 months in my case) and a lot more material for one.
Sasha Goldberg


Joined: Jan 07, 2012
Posts: 27
Location: Southeast Virginia, Zone 7B
We are definitely going to try the pit stove. I am very excited especially since Jesse Corker was able to bring 30 gallons of sap to a boil. We don't even need to boil the water and we probably put only 30-35 gallons of water in the drum anyway. I am a little concerned about the structure of our soil. It is sandy clay loam but thinking about it, it's actually pretty clayey once you get below the topsoil. There is no way we can go down 3 fee like Jessee did but see how it works at 2 feet.

Sasha
tel jetson
steward

Joined: May 17, 2007
Posts: 3098
Location: woodland, washington
    
  53
just been building my own pit stove for scalding chickens. a very simple way to solve your high water table problem came to me. just build the whole thing in a mound of dirt instead of at grade. you'll still get all the benefits of the pit stove. build a platform for yourself to stand on on the mound, too, and I should think you'll be in great shape.
 
 
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