jt0119

Lining for a waste oil forge

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Hey guys,

My dad and I are working on putting together a waste oil forge just to get started as we have most of the pieces needed and plenty of fuel already available. We know the dangers the products created by burning it, and are planning on using the forge outside for now. My main concern is the lining. Our current plan is to have 2" of kaowool and 1" refractory as the base, and 1 1/2" kaowool and 1/2" refractory in the upper shell. The more i'm thinking about it, the more I'm thinking we might need 1" of refractory in the shell. Our burner is going to be mounted into the side of the forge, so instead of blasting the floor, it'll be aimed at the opposite wall. Actual heated area will be ~385 cubic inches. 

 

Thanks in advance!

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What are you going to do with the nasty stuff in the exhaust?  

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We're going to be feeding the oil through a filter before burning it, but aside from that, we're working in a well ventilated area. We have respirators as well if we feel like they're necessary.

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Most oil fueled forges I have seen have a hard firebrick liner for rough usage.

When you say "waste oil"  is it motor oil or vegetable oil?

Motor oil would be hard to filter all the nasties out of---benzine for instance!

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Good mixing and accurate control of flame temperature tends to be much more difficult with oil than it is with gaseous fuels. Hard firebrick is a good idea because it is pretty tolerant of the temperature gradients you are likely to have where the flame hits the wall, and is resistant to erosion. If you are going with hard refractory, a properly hard one with a high temperature rating would seem wise. Check the manufacturers data sheet for whatever you intend to use. Some have a minimum recommended thickness and others have a maximum.

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I've been working on an oil burning forge.  My inner shell is hard firebrick for the floor (because that's easy to replace) and kast-o-lite 30 for the upper shell.

I'm very interested in what you're using as your burner.  I've been using Delavan siphon nozzles and I think I'm close to a working burner.  There's been a lot of trial and error.  Mostly error.

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First a disclaimer:  I only ran a waste oil forge using a siphon nozzle for a short period of time, so take all of what I have to say with a grain of salt.

I built my own siphon nozzle from commonly available hardware parts and some solder.  It pulled the fuel into the air stream and did a good job atomizing the fuel, so no complaints there.  I used the blower from a power vent hot water heater for the forced air source and typically ran 20 to 60 psi from the air compressor to run the siphon nozzle. If you're using a commercially available siphon nozzle you shouldn't need as much pressure to get good results.  However, there are some challenges specific to using a siphon nozzle in this application that you have to deal with.   The viscosity of used oils varies with the type of oil, the amount of contaminants, and also significantly with temperature.  That affects the rate at which your siphon nozzle will draw the fuel in for a given air pressure.

My recommendations if you are going that route has 3 main parts, which you may have already dealt with:

1) Always filter the used oil. It takes very little solids to plug up your nozzle.

2) Heat your feed container to a level that is higher than any ambient temperature your region will experience.  120 degrees F should suffice in your area.  Warmer may be even better.  You don't want the temperature outside to cause fluctuations in the viscosity of your oil.

3) Design your feed container so that it always has a consistent level of oil in it.  Otherwise as the level drops in your container the hydraulic pressure will change and that will affect the rate at which fuel is pulled into the siphon nozzle.  This normally requires a 2 tank system and/or a float/valve setup.

If you can't maintain a constant fuel flow to your nozzle you may find that you spend as much or more time adjusting the fuel to air ratio as you do beating on hot steel.

Were I to attempt a used oil forge again I would look into a constant pressure pump system and a good spray nozzle to eliminate the siphon nozzle.

FWIW, I usually started up the forge using kerosene or diesel fuel and then switched over to used oil once the forge started glowing.  Otherwise I had a lot of flameouts during the startup period.

Good luck with your project and let us know how it turns out.

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I appreciate the advice.  I've read some of your previous posts on the topic.  I plan on doing a complete write-up on it once I've got everything working.

I've got a big horizontal fuel tank such that I should only see a change in fuel level of about half an inch per hour.  Mounting that close enough in height required finding a scrap of very tall I beam at my steel supplier.  I would like to setup a pump/return system to a miniature tank so instead of refilling a 5 gallon tank periodically, I can just set an oil drum nearby and never have to deal with it.  As it is, I should only see a 10% change in fuel output over the course of 4 hours.

The Delavan nozzles are designed to run at 3-5 PSI.  They're calibrated at 4 PSI and 4 inches of lift.  At that range, they produce a fantastic fine mist of fuel.

I ran it successfully tonight on kerosene and once I got the air/fuel flow rates adjusted, wow did it get hot.  It's been a long journey to get to this point.  Now that I've got most of the bugs out, I think it's time to rebuild parts of the forge, particularly the shell and fuel inlet.  It's a huge upgrade over my previous under powered and under insulated propane forge.

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I sure hoping you're playing with this thing a long way from your or anybody's house or structures. Have you done ANY research into how many waste oil heating systems are in use? Typically just the chemistry and hazmat disposal of the necessary treatment chemicals and residues makes it prohibitively expensive.

Be VERY careful. Maybe build or buy a good propane forge.

Frosty The Lucky.

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6 hours ago, Frosty said:

Typically just the chemistry and hazmat disposal of the necessary treatment chemicals and residues makes it prohibitively expensive.

FWIW we have a commercial waste oil boiler in our building at work that supplies the in-floor heat.  There are no required treatment chemicals and the only residue left is a fine gray/white ash buildup on the inside of the flame chamber that has to be cleaned out about every 700 hours of use.  The exhaust is pretty similar to anything else that releases heated gases.  It exits through the roof of the building and is a few feet taller than the tallest part of the building it's in.  The boiler can burn any type of (filtered and water-separated) fuel between number 1 diesel and 90 weight lube.  It mostly burns used motor oil from the vehicles at work, which are running 10w 30 or 15w 40.  As I understand it the combustion chamber is hot enough so that most of the nasty stuff is broken down into far less harmful compounds in the exhaust.  I wouldn't want to breathe the concentrated exhaust, but it appears that complete combustion at high temperatures reduces the toxicity of the exhaust fumes, and the remaining ash residue is far from scary. It's also likely that it runs a slightly lean mix to ensure as complete of combustion as possible.

Regardless, that applies to my state and it may be different elsewhere. It would probably also be hard to fully replicate the combustion efficiency of that commercial product in a DIY forge.

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The shop boiler was some high tech thing rather than usual. I only have hearsay to go on but boy did building maintenance HATE that thing. The diesels ran 15-40 and the gassers 10-40. Gear oil, ATF, etc. were nothing special and the State fleet was always well maintained. You'd better have a good reason for missing the service sched by much.

DOT actually spent a bunch to have nat gas run in and switched to vented overhead burner type heaters and gradually changed all the heat in that complex to gas.

I just get jumpy when someone tries building a blue flame waste oil forge or heck anything. Had a neighbor almost 40 years ago now who used to fire pottery with waste oil. To be fair it was a crude oil drip burner but it flamed out more than once and neighbors evidently told him to cut it out or they'd fix it for him. Close neighbors there were on 5 acre lots so he wan't endangering their homes but the neighborhood kids were all about watching when he fired up a kiln.

Like I say it just makes me jumpy.

Frosty The Lucky.

 

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