Diesel Ribbon Burner

You are absolutely correct. My brother-in-law works for Enbrige gas. My brother-in-law pulled up the underground map and what I might be provided with before the meter/regulator. In my subdivision he stated I have a 2 inch line that has 60 PSI feeding more than 100 homes. (I am the second last home in the branch). He stated that he would rather run 2 =>1/2 inch lines to my residence(at 60 PSI) and drop in two 4 inch pipe regulators(7”WC), And run two 4 inch pipes into my residence before he would give me 60 PSI on the other side of the metre.

I got him to pull up the crematory I went to,(where I got the brick from). They are in an industrial setting and they were only given 2 psi with 4 diameter pipe for there three furnaces. There was a 2nd metre/regulator for internal heating and hot water. This one was only set at 7 inches water column.

I’m sure there is many different restrictions for NG. My brother-in-law stated in my region there is only four businesses that have more than 30 psi. They all have a natural gas certified employee on full-time. 2 of them are the nuclear plants.

If you can get more than 15 psi meter/regulator, off the grid for residential, I would do it right away.

My brother-in-law is the second last guy that has to sign off on any grid tie. He’s also about the second guy or third guy on the scene with the fire department for any accidental severing. Some of his pipes are 3 feet in diameter with 150 psi.

He has some 20-40 million dollar homes that are trying to fight him tooth and nail to bring high-pressure into the building/home. The metre needs to be on your property, he says, we will hide it in that monster bush you have out front, and bring in 2=>4 inch pipes for your six kitchens, six furnaces, 8 hot tubs, 4 pool heaters, 10 hot water tanks and your 30 fireplaces.

 

You left a lot out on your whole build. I didn’t realize you built a refractory ribbon burner. And at no time did you correct me. Forget my earlier suggestions, and port it through. Go big!

 

Just drill a hole and pressurize the oil to one of your ribbon holes. Call it a day.

Use a gear pump attached to a 3 phase motor controlled by a Vfd (or a 3 phase brushless DC motor and controller). This will hit all your needs. Do you have any other videos with your testing?

 

It would be interesting to see how many CFM of gas can be puled through the regulator with a given pipe size under vacuum? Would the regulator deliver several times what was normally passed or would internal restrictions limit the CFM?
Joe

 

In the big household regulators there is a vacuum pressure regulator. If you pull more than the regulator is equipped under allowable circumstances it sucks in outside air. The system needs to be purged or equalized before natural gas can flow again. I actually tryed to pull a vacuum on my line into a pressurized tank. It choked. To reset it, I had to go turn off my main high-pressure line and bleed vacuum pressure.

I did a second test and pressurized all the lines in my house to 15 psi. The outside pressure regulator blew off everything in my pipes in my house outside. I had a neighbour knocking on my door saying I smell a lot of natural gas, should I call 911. That is a good neighbour.... I said no, I’m just pressure testing my lines and doing a purge.

To do this properly, I should’ve shut off the main and disconnected after the regulator. Testing is fun.

I’m sure there’s definitely a safe way to pull a vacuum for storage. But not the way I was doing it with a vacuum pump. Next, the vacuum pump what is a paintball pump that I was just exhausting through a hose. I am guessing... but maybe 20 CFM. It’s a test that I probably wouldn’t do it again. Compression or exhaust.

 

My apologies. It never crossed my mind that a furnace burner would be built with anything but refractory.

Here's the only other video I have at the moment. I'll be home late Friday and plan to spend the weekend getting this baby ported and fired up.

 

I followed the same design as with my previous ribbon burners, but simply went bigger. Same with the furnace. I am running a dual propane tank setup which allowed the earlier burners to run for a couple hours without issue. But the tanks started to freeze up within 30 minutes with the new burner.

I plugged 1/4 of the burner holes, which helped some, but it seems like it's just not enough heat for the larger furnace.

I'm hopeful diesel will provide the necessary heat. If not, well, I guess I'll look at plan c, d, e or f.

 

Your testing scared me. Natural gas systems are intended to be safe under all operating conditions. Overpressuring the appliance regulators can lead to malfunction.

I'd be very surprised if any commercial regulator would pull in outside air when under vacuum. That can create and explosive and hazardous mixture. I do believe they are designed to snap closed at a vacuum.

It was really good your neighbor wasn't running his grill when he detected your excess gas.

I am a retired pipeline engineer and have designed and worked on natural gas pipelines with pressures as high as 1,440 psi in a 56" diameter pipe. That was from Kangan in southern Iran and went to Astara on the Russian border.

If you want high pressure gas (anything over 7" W.C. you should consider a completely separate meter and feed system not connected to your home gas system and not entering your home. Even a 2 psi system will deliver a lot more gas. Do the calculations and determine exactly how much pressure you need to get the volume through a big pipe. The pipe is relatively cheap since you only have to buy it one time. Don't even consider putting high pressure gas into your home and voiding your homeowners insurance. Even if you don't plan on having an explosion and fire there is no reason to have insurance if you void it by your actions. And if you have a mortgage, you have to have insurance, it's such a vicious circle.

Another option is to consider installing a small compressor to boost the pressure into a storage tank. Determine how many standard cubic feet you need to burn in order to run your furnace for a couple of heats, then add 50% and buy a pressure vessel like a propane tank large enough to hold your charge. for instance, if you want 500,000 BTU/hr, that is 500 cu ft per hr (roughly, most gas is 1,100 BTU/cu ft, not 1,000). That is 500 cu ft at 14.7 psi, standard conditions. If you want two 45 minute runs that equates to 750 cu ft, if you add 50% you need storage for 1,125 cu ft. If you choose a propane tank for storage then you should limit your pressure to around 200 psi. 200 psi is about 13.6 atmospheres, so if you divide 1,125 by 13.6 you need a vessel with an internal volume of 83 cubic feet. So in this instance you would need a propane tank of 750 gallons (100 cu ft). Perhaps a 500 gallon propane tank would serve (67 cu ft, or 911 standard cubic feet, a 21% margin over the estimated 750 cu ft). You would need double check valves from the compressor to the tank and a regulator (probably double regulators in series) to let the pressure down from 200 psi to 5 psi or whatever you want to your burners. Natural gas is easy to compress with an air compressor but you need to consider safety controls to make sure you're not venting natural gas or can control it when the compressor starts leaking. Even a 10 cfm compressor would recharge your storage in two hours.

It makes propane look cheaper. I have a 200 gallon propane tank to feed my burner and it never freezes However I do all my melting with a super simple waste oil drip burner and only use my propane for warmup and to burn off excess oil at the end of a run.

 

It wasn’t too scary for me. I had all the ball valves turned off to each and every appliance including the main, (before the main regulator. And all the appliances I did a burn off). I was only traditionally testing psi with pressure test. But I also pulled a vacuum pressure test. I learned something that the regulator shouldn’t be part of the pressure testing!

Under vacuum it took about 30 seconds before there was locked pressure, And vacuum continued. I Pressurized to 15 psi (testing) trunk, this is when, exhausted truck fuel went outside.

I was told this was normal by my brother-in-law.

At no time do I advocate pressurizing NG with uncertified equipment for home use! Unsafe compression could lead to combustion if not done properly. What I was doing was somewhat dangerous with the vacuum pull.

My brother-in-law‘s, Company truck runs on natural gas. I asked him if it was worth while to switch a vehicle to natural gas. His simple explanation was no! There was on the map, six natural gas filling stations in 100 km radius of me. And to compress it properly/safely it would cost almost $10,000 for a residential pump and his guess was a two hour fill.

 

I spent the day adapting my ribbon burner for diesel. I started with a gravity fed system into 1/4" id tubing, through a couple of ball valves, and ending with a run of 1/4" od copper tubing into the furnace through one of the middle burner holes. I left the tube sticking into the furnace about 1/4" while testing, allowing fuel to drop directly in front of the burner.

I installed a thermocouple near the bottom of the furnace to get an idea of the temperature. I fired things up on propane until around 550c, then started switching over to diesel. There was nothing else in the foundry except a small plinth.

I spent about an hour trying to tune things, and found it difficult to burn diesel without it flaring up, then a puff of smoke, then more flaring. I know it burns different than propane, but this isn't what I was expecting. I included some videos below showing my testing.

First, I suspect my vent hole at the top may be too small. I can reach a better burn with the top cracked open a couple of inches.

A normal rise in temperature seemed to stop around 770c, at which time I started adding more fuel... and air. I found that I could drastically speed up the temperature increase, but at a cost of a lot of smoke. I found a balance where the smoke was lower, but it took 20 minutes to bump the temp another 200 degrees.

I increased fuel and air once again, and reached 1200+ celsius in a much shorter time, but had to back off due to the attention I was drawing from neighbors. There's just too much smoke.

Here are a few videos I captured at various temperatures:








I'm happy that it's running on diesel, which is a very positive step forward! But now I need to look at tuning it. What modifications would you suggest to get this baby purring?

 

It might be worth having a small nozzle like a MIG electrode nozzle (1/16"?) and having the fuel tank as high as you can get it to go: like up a tree hoisted by rope for some gravity assist pressure, 21' gets you 9 PSI pressure. That way you'd get a consistent squirt of fuel instead of a rich-lean pulsating mixture that would make tuning easier. A crucible will have an effect on combustion by reducing the furnace chamber volume.

Edit: Also experiment with 1/2" tube for any long/high distance runs to improve flow rate/reduce friction. Without a fuel pump of some kind, these physics factors matter, I went from 1/4 to 1/2" tube for my earlier gravity feed experiments and there was a significant improvement.

 

You need more air to cut down on that smoke or lean it out... Your exhaust hole looks big enough from where I sit. If it's around the 3-4" in diameter, you're good.
You may be burning diesel, but it's really unstable. I would try Marks idea, as is, you'll never turn it consistently.

 

I couldn't find a happy fuel/air ratio. Less fuel and the temp started dropping rapidly. More fuel and the instability became much worse.

I think your feedback is spot on. The pulsating must be coming from a surge in fuel. I'll add the mig tip, and work on a solution to pressurize the fuel. Give me a few days and I'll be back with the next report.

 

A month worth of testing, tweaking, retesting, and retweaking, and I'm finally back with a positive report.

As suspected, the primary issue was related to the fuel pressure. I went about solving it in a few different ways, but finally settled on an inline fuel pump to drive the pressure.

I also swapped out my fuel nozzle with a couple of different mig tips, and found that the stream was solid and squirting directly into the refractory wall. I don't know if this was actually causing a problem, but I machined a stainless steel tip with a 1mm nozzle angled into the oncoming airflow, and she seems to be working much better.

I've been struggling with tuning the fuel/air mixture tho. As far as reading the burn, it seems to generate the most heat when a couple inches of flame is shooting out the top. Adding a smidgen of air may accelerate the temperature increase without changing the flame, or it may start a temperature decline. it's very touchy, but I'm figuring it out a little more with each burn,

Here are a couple of videos I captured while she was heating up tonight. Temps were probably passing the 1000c mark, but i slowed her down to keep from melting my phone.




I was able to reach 1,450c tonight, but she is very temperamental at this temp and the slightest adjustment to either air or fuel sends the temperature in the wrong direction.

Would a misting or atomizing nozzle help at these higher temps? It sounds like fuel is hitting the wall or base when I crank it up any higher, and wondering if atomizing the fuel would make any difference.

I also found that after increasing both fuel and air multiple times, the flame seemed to be burning properly, but I actually gained more heat by turning down both fuel and air. It sounds like the amount of burn was saturated, but I'll spend a little more time tweaking and gaining a better understanding of what's really going on.

Thanks for your patience and pointers! It's been a fun project and I've learned a great deal.

 

It might be worth having a second thermocouple just inside the lid to see if there's a delay in combustion making things hotter up high, even looking at the exhaust temps just above the lid hole. Also see if a disc of refractory sat on top of the plinth boosts the recirculation/swirling of the flame: the disc is sized so that the surface area of the air gap exceeds the cross sectional area of the tuyere/burner pipe. Is the top of your plinth higher than the tuyere so that a round disc doesn't block the tuyere opening?. The goal of the disc is to swirl the flames back onto the fuel spray to aid pyrolosis and increase turbulence which then increases flame propagation speeds.

 

I’ve heard that from other people too. Seems the geometry of a burner-furnace-crucible combination sets a maximum temperature achievable inside the furnace, and the common burner designs are quite capable of maxing that out.

 

For my last attempt, I placed a crucible full of brass on the plinth and a second thermocouple above the lid hole. Unfortunately life is busy right now and I haven't been able to dedicate the time I want to this, but I'll drill a second hole for another thermocouple near the top later this week.

I captured the following temperatures while heating, which I found a bit surprising:

Lower temp: 1034c, above lid 852
Lower temp: 1024c, above lid 895
Lower temp: 1228c, above lid 945

I can bring the temperature above the lid to a much higher number, but that typically caused the lower temperature to dive.

The swirl seems to be very effective, although the following video doesn't properly show the way it looks with the naked eye. The plinth is below the entire burner. I can slow down the air flow, which allows the flame to make a couple of loops around before reaching the top, but I'm still experimenting to find an optimal air flow/fuel mixture. I'm currently tweaking the mixture by watching the temperature and (mostly) adjusting the airflow.


I realize I'm getting some flame impingement on the crucible, but I'm waiting until I better understand what going on before adding a flame block.

 

Interesting. I hadn't thought of this. I sure hope I can find a way around this. Does the process require more area for the burn, or could I have too much?

I can increase the airflow to the point where the swirl is only a couple of inches in diameter. This appears to effectively burn the fuel, but doesn't produce the expected heat and destabilizes the flame at higher flow rates. Or I can increase the fuel to where it's squirting against the wall, but this causes its own set of problems.

 

It's good that you have real-time temp data for your particular furnace and that the combustion is happening where you expect it to be. A rich mixture burns faster than a lean mixture too which means a rich mixture should be hotter at a lower point than a lean flame all other things being equal. So that's yet another factor adding complexity to the situation. My thinking is that if you can make the flame take a longer path by swirling more, then it has more dwell time inside the furnace to transfer heat to the crucible. This compensates for the faster flow of the flames at higher rates of burn. At present I have a furnace with a relatively high rate of burn: without a long swirling path, iron only gets soft in the crucible but iron resting on the lid in the exhaust gas stream has liquid iron blowing off it in three minutes. With extra swirling it melts iron in the crucible at the same fuel burn rates. So with no swirl: iron gets soft in the crucible but doesn't melt no matter how long you run the furnace, with swirl, the iron melts readily in the crucible in under an hour.

 

Great information. Thanks!

My first goal is to build a new crucible that will fill up more of the volume in the furnace. If I leave less than an inch between the wall and crucible, as well as extend the crucible height, I should be able to extract more burn time with a slower swirl before it exhausts. I'll also create a taller base to sit on the plinth to help keep the crucible at a reasonable height. Hopefully it will be ready before the new year.

I've also been thinking about extending the exhaust port into the furnace, with the intent of forcing the heat to swirl another round or so. I'm not sure if the airflow would bounce around a little longer or just create a shorter path to the exit. Any thoughts or experience with this idea?