Low heat value, or inefficient boiler.

Good for you for making the effort. Getting a feel for what works and what doesn't, and why, will be valuable in the next design.

38 percent moisture is awful; that water has to be evaporated at the cost of the heat to do it, along with slow ignition. Worth looking for a better quality supply.

I would try to get a stronger draft by adding sections to the chimney which might allow for a greater burning mass of coal. More burning coal makes for a long burn instead of closing down the air intake or pipe damper to accomplish that long burn. Air must come from below the fuel bed with coal, but you still need some air above to cope with the large amount of gas when the coal is first heated. Best if that secondary hot air is fed by a perforated pipe just above or to the side of the fire box.

Most OWB are bad designs, but a few have secondary burn chambers that are a big improvement. Burning lignite will also need a well planned secondary burn to avoid all the smoke.

To repeat. A good design first has to burn the fuel efficiently, and then transfer that heat to the water. The two needs are separate and have to be thought of that way.

A revolution in boiler design was that of the Scotch Marine boiler which combined compactness with efficiency.
https://en.wikipedia.org/wiki/Scotch_marine_boiler

Where are you located and some pictures of your fire box and grate would be helpful.

hello, thanks for your help. it makes sense now.
that's some images I am located in romania.




Today, just for kicks, I have stuck a heat gun on cold in the bung hole (air flows from there under the grid) coal got much hotter despite moisture. I was advised not to do this as I would waste heat even faster.

Thanks again!!

I commend your skill and effort there.
I also am thinking you will keep refining this boiler as new discoveries come to you.
Best Wishes!

Thanks. I think I will design a new firebox and heat exchanger in the summer for sure. like, properly welded and designed if possible

Keep refining the present design and learning what works.

Things that stand out to me that need improvement are:

Chimney should be higher and 150 mm in diameter. Rain cap would be good as well as insulation to hold in heat for better draft, but that would be hard to do.

You must put a grill or some sort of banking bar across the front of the fire box. It is the only way to get a good deep bed of coal that has enough heat in it to support combustion easily. Leave a small space under it to slide a long flat poker the length of the fire box to clear ash.

Fire box probably needs to be shorter in length to more easily support a deep compact mass of burning coal.

Loading door needs insulation.

I know peat needs drying out before burning. Can your lignite be dried in storage, before use?

Fashion something across the front of the fire box and then gradually add coal to the fire until about 200 mm deep or higher. Use your heat gun on cold to help out with air if need be. Once going good see if it will maintain itself.

Bituminous coal if stored improperly can self ignite. Many old steam ships had fires in the coal bunkers. Even the Titanic had a fire in one of the coal bunkers when it went down. So learn the safe way to store your lignite ,and if there is any danger.

It always amazes and humbles me when so many people of Europe know English, when Americans rarely know another language.

It always amazes and humbles me when so many people of Europe know English, when Americans rarely know another language.


I found this a lot when I was coaching young men in Basketball. They came from all over the world with fluent English....

Kevin

thanks!!!
Chimney currently is 130mm. how taller should I go? another 3 foot section?
I cobbled that silly grid on the quick, but I have bought steel to make a new one with flat bars,
I already thought of having an edge of some sort to keep a "batch" of coals cobbled together and not spread everywhere.
I do know it seems firebox is too long, in fact, the bottom 10 inches never get used, the bottom there is filled with ash.
Insulation for the door is on the way
Also, there is one very good reason to buy fuels in early autumn, and not late in autumn, unless you buy bagged nuts (which i def. will next year as they are zero headache type of fuel) often both coal and wood are stored outdoors, and futile attempts are made to prevent moisture from wetting it, so it's best to buy before it starts snowing, stacking storing and properly covering. My other firewood was barely 11% moisture. I was silly to buy lignite without first trying nuts, I paid around 60$/ton, while coke nuts would've costed around 140, but when you compare how little water and how much heat they produce then the nuts are just a bit more expensive.
I don't know how would I dry the coal, currently, I put chunks around 4x4x2 or bigger on the front of the firebox to dry out, when they become crackled and are warm but not steaming anymore they get added.
Today I bought half a cord of oak, moisture level 18-22% not ideal but it'll work for sure, I will keep experimenting on warmer days (here it can get to -10C at night, but on average is -1 -3C, sometimes it stays above zero at night)
Will update with more pictures, and thanks again !!!
By the way, I'm italian and I lived in england for 5 years before

Anything you add to chimney height will help, but might need bracing. Ideal would be double wall insulated of at least 12 to 16 feet. Four to five meters.

Your grate will need the help of a riddling or slicing poker to clear ash. A flat piece of steel 6 or more mm thick and maybe 35 t0 50 mm wide, to slide under the front grate and over the inner grate. With it you can skip a shaking grate for easier construction.

This boiler is a learning experience, but with improvements it just might do the job you want. Some payback for all the work, effort, and thought. Congratulations on your excellent English.

A further thought on the grate. Cast iron is much more heat and warp resistant than steel. You might be able to adapt part of a cast iron basket intended for fire places or for some grills.

hello guys.
I have built shaker grates. What do you think? bars are spaced 1 inch apart and in between I put 1/4 in rebar sections. the coal I am currently using makes both dust and tiny bits so if the bars in betweens are in the way I can easily remove them.

I would gear them together so that moving one can move all 3.

Nice work! You have been busy there.
And I wish we had your sunshine here

Just bought a Bosch 4.5 in. angle grinder...it was made in Chiner.

There is no silly question. Not many would take on such an endeavor, including myself. Fortunately money is a little easier to come by than time for me (not much but a little).

I simply would never have the time to attempt a boiler. Congratulations even though it doesn't burn lignite well. At least it burns wood well.

Grates work fine. for some reason, I suspect its either the fuel itself, or the combustion process, some pieces create "bone" aka flakes of ash that don't shake off and clogs air flow, but by the time they clogged all good it's morning and it's clean-up time. it looks like the flaky chunks tend to do this more than the solid blocks that don't flake.
I also didn't have the time to put insulation on the door, a week ago I started placing a 4 inch glasswool insulation over the door the heat recovery improved a lot. Soon i'll be welding a proper counter-door with insulation in.
this summer i'll build a new boiler with a full water jacket and heat recovery on the chimney pipe as well.

Coal likes to burn with air that originates from below the grates.

To answer my own question on the "low heat value", it is sure now that it's low heat value.
I did the following reasoning.
1. Why 30kg wood, at an estimated 6,000 btu/lb keep my home warm no problem, and 40kg of that coal does not?
regardless of the efficiency of the boiler this is simple logic.
2. I saw on the local "craiglist" the following. Coke/anthracite nuts (these not available here in like buy 1 sack off) rated at 14500 btu/lb, 1200 lei (300 usd/ton). Lignite briquettes rated at 7000 btu/lb 600 lei (150 USD ton) and then this chunks of coal that I bought unrated, apparently coming from neighbouring bulgaria, 300 lei per ton (75 USD ton)
Some ads for the briquettes wrote "twice the heat value of bulgarian coal". My Logic on all this is that the carbon content is quoted in the stock market, so what costs less has less btu, simple as that. logic is the blocks I bought have an approximate heat value of 3500/4000 btu/lb, which would make point #1 make total sense.
3. I placed 50 grams (approx 2 ounces) of the coal in a tin can, placed in the firebox but away from the flames, tin can being hot but not so hot to burn, and let all the water evaporate. sample weight went down to 28g, making water content 44%. That's about 1 pound of water every 1kg of fuel.
Now, I read that to evaporate 1 pound of water you would require approx 1,000 btu, but I suspect this is not so simple as "you have a 7000 btu fuel and you lose 1,000". It's more like trying to make a fire burn while you douse it with water, hence losing a LOT more energy
Also, I did a previous test and estimated ash content being 20% but it could be more. so 20% ash, 44% water, what is left? 36% (what? all pure carbon?)
even if that is all pure carbon, on 10lb of raw material, I am left with 3.6lb of pure carbon. 3.6 * 14000 btu = 50,000 btu. Hence, 5,000 btu per pound. 5,000-1000 btu to evaporate water? 4,000 btu/lb

Sorry for the long winded post

Thanks