Mini Boiler Project of Mine

Awesome....what's that duct taped to the furnace?

A piece of reflectix foil insulation. Without the water level being all the way to the top the temperature sensor (PT100) wants to read about 5 degrees cool so I put the insulation over that corner to keep it more accurate.

Plus it adds some protection for the leads (kept me from grabbing on to them with gloves) while I had the boiler out while working on the pumps and plumbing to put the bigger lineset in.

Big knobby protrusions, like sensor plugs, are so handy to grab onto (without thinking about the tiny wires that stick out of them) when wrestling a 400+# block of steel around.

So for how it works as you can see it uses a fairly standard fuel oil furnace burner unit but with a bit of modifications to make it work on used oil.

To start out used oil is too thick to go through the tiny injector nozzles those types of burners use so it needs a cheat to thin it out. That cheat is to heat it up to around 340 - 350 degrees Fahrenheit just before it shots out the nozzle.

To do that I designed and developed a special preheater unit that fits in the head of the burner unit.

Its basically a section of 1.25" solid copper bar stock with a 150 watt cartridge heater and thermocouple embedded in one half of it with a 1/2" fine threaded passage in the other half that has a 7/16" solid steel dowel inside it with a sold brass fuel oil burner nozzle holder bushing silver brazed to the end.

Then that has a 350 watt external band type heater around the whole outside that's held in place by two stainless steel band clamps.

The notable thing about the design is that when thick oil passes through a heated passage it apparently tend to create a odd laminating effect where the hot oil on the sides stay put and the cooler oil keeps moving through the center.

So despite having the main body at 350+ F the cold oil entering the heating passage still makes its way to the nozzle still too thick to spray properly causing flame sputter and surging.

By adding the dowel that closes the passage down it keeps the oil flow out on the edges of the passage where the threaded surface breaks up the laminating flow effect so the oil gets evenly heated before it gets to the nozzle.

It took me a good long three days and half a dozen or so redesigns of the preheater passage way to figure that little detail out.

Yeah what we used to call a "gun fired" oil furnace...I'm surprised your pump can handle that high viscosity oil, have you ever checked the pressure in the discharge line feeding the nozzle? All the gun fired oil furnaces I ever worked on used #2 fuel oil...I used to run across some old passive types we called oil pots, they just had oil drip feed into the bottom and the oil just burned from the puddle, about as low tech as you can get....good for one room....haha

I do remember the droplet size and spray pattern were important....that's a fancy bit of kit with your spray nozzle....

http://www.viscopedia.com/viscosity-tables/substances/heavy-fuel-oil-residual-fuel-oil/

Those little pumps handle anything lighter than gear oil at near room temperature and above surprisingly well.

Nozzle pressure wise I run them about 140 PSI (~100 PSI normal) to make up for the added viscosity of the oil being even at ~350 F it's still just a bit thicker than #2 fuel so it needs a bit more pressure to get the atomization up to where it will burn clean.

Ideally if I thin the oil out with diesel fuel, gasoline or even E85 fuel I can get the viscosity and nozzle temperatures down more but it's largely not worth the cost.

As for its construction it made mostly from 1/4" steel sheet with 2" schedule 40 pipe for the flues.

The firebox is ~10" x 10" x 30" ID. It works okay but after having had it in continuous operation for two months and ~ 500 gallons of used oil I have found that I should have made it larger.

The old boiler had a huge 20" x 20" x 54" firebox that could hold 2 - 3 five gallon buckets of ash without a problem but this tiny one doesn't have much space to spare and used oil makes a lot of ash due to its zinc and other micro solid additives and contaminants. ~ .5 - 1% by volume of used oil is actually microscopic solids that do not burn and leave a very fine dull grey/white rusty soot powder behind.

Given with the old boiler between the large burner box volume and the fact I regularly tossed shop garbage and old wood bits in it I never thought much about how much of the ash came from that stuff or the used oid residues. Turns out way more of the ash was from the oil than the other stuff.

At this point due to the ash issues plus the small dimensions of the firebox and flues limiting the amount of burner capacity I can run at without getting flame fluttering and blowback effects due to draft rate limitations I may take the whole thing apart and redo that part next summer or fall some time and expand them to open things up more.

Right now I am thinking I may open it up the firebox to 12" wide by 14" high and convert the flue system over from the 12 tube design (6 forward pass 6 backpass) to a open dual 2.5" x 12" box layout. The overall heated surface area will stay about the same in the change but it will make the draft flow better plus give me more ash management room.

Water jacket capacity wise as it is presently designed it holds ~ 90 gallons and uses two small pumps. One is a Taco #9 that sends ~ 6 GPM to the house and the other is a Grundfos UP 15-42 set on low speed that puts about 3 - 4 GPM to the shed floor circuit.

Impressive! Good job. Being someone that maintains a boiler at work, I am curious on what safety features you have built into it.

My next question is, how the hell to you put tires in that to burn?

The burner has a CAD cell that the PLR uses to see the flame and make decisions from there.

The filter also has a Murphy switch that tells the PLR that the filter is plugging up if it sees more than ~ 7 PSI suction.

I wonder if that thing has enough torque to take scales off of a fish.

well,,.... mink ranches have found that it works great for dead cattle.

Hmmm, hamburger

My demented self would like to see a dead cow go through that.

*** WARNING MORBID CONTENT, NOT TO BE VIEWED BY SNOWFLAKES ***

Things people fall into...,

its surprising how often this happens... So,... next time you eat a hamburger or something with cheese on it.... Bon Appétit

That's looking great! Who would have thought the used oil would produce so much ash? I guess it's high calorie oil. I had to put a new boiler in and take mine out.. at about 700 lbs.. it was a chore. That's pretty wild that the core is 7/16" inside a 1/2". Tight.

On Thursday I modified a pail pump that will now dispense white lithium grease from a five gallon pail at a rate of 10 grams per pull. (+/-~.5) It's very satisfying working with grease and oil.

So are you going to add 5-10 gallon's of ash catcher?

The control system is designed around SG2-20HR-D Teco PLR (Programmable Logic Relay), a simpler low cost PLC of sorts, (still runs circles around most 1980's and 90's PLC tech though!)

Teco PLR units.

This model is a 24 VDC unit with 8 digital (on/off) inputs, 4 analog 0 -10 volt inputs and 8 digital relay outputs which for most DIY project work is pretty convenient to work with. Especially given its fairly robustly built and ruggedized making it able to handle some pretty rough environmental applications that any home built uC device based control system would take a lot of additional parts and work to get up to handling and working as a near plug and play setup.

This one is one of the earlier V2 models that did not have the programing capacity for doing dedicated temperature sensor inputs or any degree of PID loop control (at least not easily and not with this model anyway) so I had to do a bit of cheating to make it work.

I used a basic PT100 converter/transmitter module that takes the PT100 sensor signal and converts it into a 0 - 10 volt signal that this PLR's analog input system works with.

Also for the burner unit I use a bit of a cheat for flame detection as well. I pull off the 24 VDC power and run that through a 1.5K resistor then through a 50 - 5000 ohm CAD cell then back through a 1K resistor to ground that has a 1000 uf capacitor across it to stabilize the voltage signal. By using one of the PLR analog inputs to read the point between the CAD cell and the 1K resistor for the flame detect signal it can see if there is a problem with the burner.

With that a proper burning flame reads about 6 - 7 volts and a weak flame is less than 3 volts which at that point the PLR knows that the nozzle is plugging up or there is a oil quality issue (water most often) and shuts the burner down if it doesn't go away after 20 seconds. Simple effective burner monitoring and safety interlock.

Now as for the oil feed that comes from a 550 gallon tank that sits beside the shed. Given that our winters get way cold and -30 F is an expected low every year I set the system up with 3/4" steel pipe for the oil feed and have it passing right beside the back of the boiler to help heat it up before it gets to the filter.

For the filter I used a common Omni whole house water filter unit (blue thing on the wall) with a basic mesh type sediment screen. Unfortunately at 100 mesh the screen is too coarse to catch the fine debris in the oil and the next available filter they have is a 50 micron which catches too much and plugs up way too fast plus at ~ $3 - $4 each they cost to much for my cheap ass to be replacing every week or less.

My surprisingly effective and dirt cheap solution to the filtering problem was to simply wrap the mesh screen sediment filter in 2 - 3 layers of common paper towels. Perfect filtering range plus costs nothing! Also there is a vacuum switch on the filter system that sends a signal to the PLR telling it if the filter gets plugged up. At ~ -7 PSI it shuts the burner down.

For general service since it needs the flues and firebox cleaned out every week and being that the burner nozzles do plug up now and then the whole burner unit is mounted on a steel plate that's held in place by wing nuts. Plus the wiring is through a Amphenol multi pin plug and the oil supply is connected to the filter though a Pioneer hydraulic coupler so the whole burner assy can be disconnected and taken off or put back on in about 30 seconds.

One of the biggest issues with the project was that I had never planned to ever put a boiler in the workshed to begin with!

Originally when I moved the old house to where it is now, so that I could put the new house where it used to sit, I simply extended the old hot water lines from the old boiler at the shop down to the location the old house is at now. Roughly 350 feet each way on 1" PEX.

Also I had never intended to have a workshed here either. Let alone a heatable one.

When I got the shed two summers ago I decided that I might as well make it a man cave (to hide from the not yet Ex) and thusly heatable so I tied it into the old house hot water feed line through a liquid to liquid heat exchanger.

From that being I only needed about 15 - 20 K BTU tops I fed the shed through 3/4" PEX line which worked great for that heat load. Downside is when I put the mini boiler in the shed and tried to back feed the house heating system the ~120 foot loop of 3/4" PEX was too small to supply volume of water the house heat exchanger needed.

Initially I had to cheat it by putting two high head high volume circulator pumps (~ 245 watts each) on it to get the flow rate up to an acceptable level.

That's where the line change out came in. By switching over to 1" PEX for the loop plus eliminating all the splices and elbows the 3/4" lineset had I can now circulate the same volume of water with a ~ 90 - 100 watt pump.

Now that it's in and the old boiler system lines are still under the house I did design the control system to interface with the old boiler controls so that someday when that gets redone to heat the new house this system can be set to draw off it.

All I need to do that now is tie in a larger 120 - 150K BTU liquid to liquid heat exchanger in under the house similar to how the smaller 60 K unit was and it's good to go.

Also given I picked up a 6 person hot tub a while back for free, due to a bad heater and plumbing (it froze), and never got it going last summer I did give the new system some thought and designed it so that the old 60 K heat exchanger can be put in the new line set and the hot tub heater system can be tied into it and the boiler controls so that when I get the hot tub fixed up I can heat it off the mini boiler for next to nothing.

Seems like I do a lot of planning and work just to be cheap and lazy.

Planning and work = hiding in man cave = success!

One of the other minor issues I had with the design was that initially I placed the boiler on a 2" thick piece of extruded polystyrene insulation to help keep the heat from the base of the boiler from heat soaking and possibly cracking the concrete under it.

The problem I found was then exposed to oil polystyrene insulation board starts to decompose!

When I had the boiler out to do the feedline replacement I found that about 1/3 of the insulation panel had decomposed into nothing but dirty pink slime from oil exposure due to several times where the nozzle plugged up to the point it would not spray yet it would still pass oil at a much slower rate thus filling the firebox with enough oil to leak out onto the floor. (main reason the flame detection system was added.)

On the reinstall I made the new base out of 3" x 4" oak which by the IR thermometer is providing more than sufficient thermal separation distance between the boiler base and concrete.

Another issue was with the control system design regarding the oil preheater control.

Being the Teco PLR unit i have cant work directly with thermocouple signals plus has limited programing capacity for handling more complex analog work I simplified its job by adding the dedicated Mypin TA4 PID controller to the system to handle that function.

That's how the old boiler system oil burner add on was done and it worked well so it made for a justifiable carry over onto this one. Plus being a dedicated control systems it's way easier to make adjustments to as well.

When the boiler temperature is below operating range (<180F on, >195F off) the PLR activates a relay that send power to the PID's SSR.

From there if the PID sees that the oil preheater is below operating temperature it activates the SSR. Plus if the preheater is more than 20 degrees cooler than its set for it activates its alarm output which sends a signal back to the PLR unit telling it not to run the burner.

As long as that standby signal is active the PLR does not start the burner or the flame detect time out functions. If however when the PID tells it it can start the burner if the flame detect does not see a sufficient flame signal in 5 seconds it stops the burner then waits 10 seconds and tries again.

It will do this 4 times in an attempt to clear a partially plugged nozzle before locking the burner controls and oil preheat functions out and can only be reset manually. Also when that happens it gives me a "Flame detect fault" message on the PLR's screen so that I can see what caused it to shutdown.

There are also other display messages for other actions that the PLR has control over like if it shut down due to a filter related issue or one of the analog inputs going too far out of range.

Mostly it just tells me what the temperature is, what pump is running and what the burner run time since the last filter or nozzle service was.

This is a really cool build and I am personally impressed, but you still have not explained how you put tires in this.

No tires to burn any more. I sold them all to the DAP protesters for them to burn their 'environmental protest' activities.

(they're better tire burners than I could ever hope to be. )

It would seem that you are absolutely right.

So for those wondering where all my used oil comes from, it's all local.

About 5 years ago I worked for a place that had a fair sized rental fleet that produced around 1000+ gallons a year of old oil and bad fuel from servicing their and their customers equipment.

They had to pay to get rid of it so the company manager at the time said that if I wanted it that I could have it. The problem was at that point I had no real way to transport or store it.

No problem! he got me a pair of 250 gallon tote tanks and said fill them up and take them home! just to get our bulk tank emptied out without having to pay!

That's where it started. I had a bunch of 55 gallon drums and one old 250 gallon fuel tank so tha'st where it went until I got a rough burner design worked out.

From there a buddy of mine with a big scrap yard traded me a days labor for a heavy gauge 2000 gallon fuel tank that had been pulled out of the ground some place due to having pinholes rusted in the bottom.

I got it home and cleaned it up then cut a 24" square access hatch in it and spent a very long day welding all the pinholes shut so it could sit bottom side up without leaking.

Once I had a main bulk tank to put it in and a regular source, that turned into multiple sources pretty fast by word of mouth so I needed to come up with an effective way to transport it. For that I set up my 97 Ford F super duty flatbed truck with the, at the time two 250 gallon tote tanks, plus a old engined powered hydraulic pump I tossed together out of old parts I had around.

Initially 500 gallons and a small ~4 - 5 GPM (on a good day) hydraulic pump driven by a worn out 3.5 HP B&S engine (that burned more oil than gas) was the transfer system. With cold heavy diesel engine oil a 500 gallon load up could easily be a 3+ hour job. (like moving molasses with a bent fork fast.)

Shortly after word got around I collected used oil it tended to just find me. In fact it started becoming available in large enough quantities at times that I had to redo the little transfer pump and add a pair of 330 gallon totes to the flatbed truck.

That took me up to my present transport system design with a ~ 20 - 25 GPM 6.5 HP Honda powered transfer pump system and the ability to carry up to around 1200 gallons at a time. plus I have since acquired about 8 more 250 - and 330 gallon tote tanks and a 3000 gallon above ground horizontal bulk tank to expand my home storage capacity.

Given the far more efficient use of oil now I am running out of storage space at home and will need to fix up the old 3000 gallon tank to add more room. I started out this winter with ~2600 gallons on hand, burned ~500, and presently am at ~3000 if not more with another 500 - 1000 to pick up before summer.

I think that I am going to clean up the 3000 gallon tank and set it up on a concrete pad as a vertical tank plus pick up the twin to it that is still available and do the same since no one has claimed it either. Hopefully by next fall I can have at least 10,000 gallons of working storage capacity and close to 4000 gallons of oil on hand going into winter.

Long term plans now are to someday build a new large central boiler system for the whole place that can burn oil and coal (and anything else) with the capacity to heat both houses, the work shed plus the main shop (if I ever get the concrete floor and insulation in it).

I think you need someone like me to design a water separation system and recovery tank for you.

Once you start getting tanks that size with unknown quantities of water you should set up 3 small tanks or possibly barrels. Plumb a water draw off line with a large sight glass from the bottom of your tank (_{add a sump for faster water extraction if you find large quantities}) send the water mixture to a settling tank. Once the water mixture has separated draw the water off that tank into the second tank until you get pure oil, then pump the oil back to main storage. Let the second tank accumulate oil and water until it has sufficient water to pump off water only to the third tank, as soon as you see the least bit of oil in the water, cut it off and start filling it with oil and water again. Once you get enough oil in the middle tank, drain off the pure water then pump the rest of the oil/water back to the first tank and start the process again.

The system should have mostly oil in the first tank, a mixture in the middle and almost all water in the third tank. You may need to dispose of the water as contaminated but there are more complex systems that can recover that water so it can be considered treated and can be released into the environment but it has to be tested and monitored...and you shouldn't go through enough in a year for that to be a problem. In a large tank farm with floating pan tanks (that need water drawn off daily) the third water tank took months to fill. At your quantities it may take several years to fill it.

Drew K

Actually I already have methods to deal with water collection issues being I tend to get at least 50 - 100 gallons of it a year and more at times being most places don't put caps on their collection tanks or it comes in with whatever source their oil came from which oftentimes has antifreeze and other unwanted water based contaminants in it as well.

I have a small hand draw pump that was originally made for pulling liquids out of 55 gallon drums. I put a longer tube on it and just stick it down into the lowest point of the tanks and suck out whatever water and water/oil sludge is there.

When I get a lot of water in a tote I just let it sit for a few weeks then hold it up with my forklift and open the drain valve and let it go in the driveway then work the sludgy mess in with the tractor and blade to make poor man's asphalt.

One thing I have started seriously considering now since I seem to have more oil coming in than I can use in a year is to set up a miro refinery of sorts and start processing my used oils into more suitable boiler fuel by using simple distillation processes.

Kind of thinking that if I take all my old oils as I get them and run them through a ~750 - 800 F single pass distillation system what I can get back from it should be good clean heavy fuel oil without the water and other micro solids contaminants in it.

You might be able to do that with simple filtration. The refining process would take a tremendous amount of heat and possibly a superheated steam system to transfer that heat.

I would set up a test with filtration media, run it through a coarse then fine mesh basket strainer then try a coalescer filter that separates water and finish with a micronic filter. You might need a few progressive filters upstream of the coalescer.

Drew K

Rough numbers say for a heavy fuel oil distillation process assuming zero heat recovery it would take about 1 gallon of oil for every 10 processed.

Or about one cord of wood per 1000 gallons of oil for a wood fired heavy fuel oil still.

Those are numbers I can work with given filters cost money (especially multiple large ones) and wood and oil for me largely don't.

The thing is I tried the filtering before and it didn't pan out. Initially I started with common large capacity spin on filters but they don't go very far 50 - 100 gallons tops before before they started to bypass. 20 - 30 cents a gallon filtering costs.

Then I went with gravity feeding through large 7" x 32" sock filters of various micron ratings while unloading from the truck totes to the bulk tank and any of them that were fine enough to do any good made it maybe 200 gallons at most before becoming so clogged that they could sit full up for a week and not lose half a gallon of their contents.

Purchase price plus shipping with those was putting that method at the high side of 15 cents a gallon to filter anything.

That's where the Omni whole house filter with paper towels design came in. 50 - 100 gallons on ~5 sheets worth of a 75 cent roll of paper towels.

You would get more life if you pumped it through the filter. The real problem I see is removing the sludge, I wonder is there is some sort of vortex separation system for high viscosity fluids?

The fuel cost for refining might be manageable but the overhead for building it will be high. If you could come up with filtration medium that could be cleaned and re-used that would be cost effective.

Drew K

I've been looking at the various small scale systems on Youtube people have built and pretty much everything that would go into making one I already have.

So for me no overhead but time and I have a fair amount of that to waste on self education experimentation projects.

pretty interesting stuff.

don't know because of the smaller size,... would it be more efficient with a vacuum column in the process?.

I'm not sure really. Given I have all the fuel I can use efficiency is not much of a concern. That and the energy usage to heat the stuff is way lower than the latent heat of vaporization value for a given mass is so even if I reduce the boiling point by 100 - 200 F that energy savings isn't all that great.

At ~ .5 BTU/LB per degree F specific heat Vs ~ 800 - 900 BTU/LB latent heat of vaporization it's not that big of concern.

As long as I can boil the stuff off and recondense something that's cleaner than what I started with I would call it good enough.

Mostly any major energy savings would likely be best had from simple heat exchange between incoming and outgoing flows and adequate insulation on hottest parts of the system.

Well,... maybe I should have waited till you had it done, completed and running... then I could have told you how you should have done it...

lol

nice... how big will your surge tank be?...

Around 4 gallons. It's designed to be an open system so it will never have any system pressures to deal with.

Although when I built it I did do a air pressure test to ~ 8 - 10 PSI to find any pinholes.

No body panel bending issues despite the box design being it has internal bracing to counter any of that. (Brick shyte house design engineering.)

(Brick shyte house design engineering.)

Nice qualities in a boiler,... and a woman.

My first boiler was all 10 ga mild sheet (cheapest I could find of course!) and I never expected it to last more than 5 years. It made it 15!

This ones almost entirely high carbon 1/4" with a primer paint lining to cut down on corrosion issues that did in the old boiler after 15 years of running with nothing but untreated tap water.

Rather hoping that this one outlasts me even if I somehow make it another 50 years.

I looked pretty stout. way back when I was in High school, my industrial arts teacher made a boiler out of lighter gauge material, 12 ga I believe.

I think his dampers weren't set right, or weren't working and was left open. When he fired it up and beyond, it got cherry red and warped. He only noticed it when his pressure relief valve blew.... I don't think he had any firebrick in it either...

I like it when teachers demonstrate what not to do.

Fortunately my shop teachers always had it together. Same with the cooks and the custodial staff.

The rest of the teachers and school faculty however not so much.