Bituminous Stoker/Lump Coal Grates

Teddy wrote:1. What is the angle of the Polish vee grates? based on the pictures I was going to set them at 35deg off horizontal
2. I will hopefully know what the klinkers are actually like. I am planning on building the furnace outside to experiment with the grates and feeding of the coal. I'll use the brick and insulation and preheat the air to try and duplicate the combustion temp. First I will run a front end loader of my coal through my 8" auger to see if it will break it up a little and use what will actually be dropping onto the bed. If the grates I have can't be used because of klinker control, I could drop the coal into a conventional stoker burner hopper - if I could find one. I looked up the Wilburt site and their smallest stoker is for 30#/hr!!! My burner needs to be max 6#/hr with a typical rate of 1.5 to 2#/hr. Do you know of any commercial burners that are that small? Not any that are currently made in the states....if you went hunting an older one this is the kind of thing you would be after https://youtu.be/N3sviUsbujw https://youtu.be/NAQaAaOIs7Q altho the coal you have is too large for them.....you might have make a coal breaker to resize your coal....not too difficult....building a test burner would be a good idea.....it will give an idea of what your going to need to deal with in the way of clinker and any swelling of the coal as it burns.....you might need to set it up to be able to run unattended and then you could leave it running for a longer test, simulating it being be run in the boiler without someone hovering over it and poking and fiddling with it
3. Slow ramp up and down will not cause problems I don't believe. I have a 1000 gallon insulated "milk tank" that the hot water will go to, so I have an enormous amount of thermal buffering, in the 600,000 BTU range. All thermal demands are withdrawn from this tank. In the summer my geothermal system cycles the compressors on at 44 Deg F and off at 40 Deg F tank temperature. The house and shop have been heavenly this summer. The house is 6600 ft2 and the shop in 2400 ft2. In heating mode, I have 3 way TC valves on each pump circuit from the tank to control the delivery temp to the radiant floor piping at around 95 Deg F. I had intended to coal heat the tank water at max fire rate to 195 Deg F and then let the demand draw it down to 100 F over a few hours to a few days. However, that means starting and stopping the burner which I am not sure will work well. Then I thought I should design the burner for 2 fire rates - max and 1/4th max. When the tank gets to100 F, go to max fire rate. When it gets to 140 to 160 F, drop to minimum fire rate. If it gets to 180 Deg F on min fire rate, open the shop doors and heat the universe, but keep the burner going. I have a lot of experience with co-generation engines burning biogas. DON'T turn them off, keep them hot and running all the time. The thermal stress of heating and cooling almost triples the maintenance costs of running the system. The joy of this project is I have never burned coal and have no experience, so I am desperately needing help understanding the pitfalls. Having that much of a thermal buffer isn't a normal coal heating system so your right, a slow ramp up and down isn't going to be too much of a problem as long as you have some way of shutting the burner off completely if your tank begins to get anywhere close to boiling.....or an automated heat dump circuit would have the same result in preventing the tank from boiling.....1000 gallons of water jumping around and trying to get out of its prison isn't alot of fun
4. What is your proposed klinker breaker made of? Stainless? Inconel? Cast? its just mainly steel flat bar as its at the end of the firebed and not actually in the fire
5. What might make more sense is to build a very small burner and run the heck out of it. If it can't keep up with demand, the geothermal will be there to keep the water at 95 degrees. Last winter the new house was finished and the geothermal did all the heating. At 8 tons or 96,000 Btu/Hr the geothermal did everything. I kept track of the minutes/hr that the compressors were on each day and the absolute worst case it ran about 40 minutes an hour or about 65,000 Btu/Hr. More typically it ran about 10 to 15 minutes per hour or about 15,000 to 20,000 Btu/Hr. I got started with this project because at the age of 73, I didn't want to split wood anymore and because the stupid "greenies" were closing down power plants due to their improper understanding of the carbon cycle, I better buy some coal before you couldn't get it any more. Also, the cost of the Illinois coal delivered to my home was $105/ton, about 1/3 the cost of firewood delivered to my home on a BTU basis. I thought, why not get about 20 years worth of coal and not have to worry about it anymore? Just load it into my hopper with my front end loader on the tractor every few days, build a large ash box and relax. So now I HAVE to finish the project!!!!65,000btu wouldn't be enough for a house that size here even if it is brand new....and we don't get anywhere near as cold as you do over there....Power Co's are are closing down the coal and gas power plants here as well.....and then jacking the power prices "Because there is a power shortage in the winter"....$0.30c per kw/hr is the current rate i'm on.....thankfully all my heating and hotwater is on coal....i know a fair number of people that think a monthly $400 power bill in winter is normal....i chuck my toys out of the cot if my power bill go's over $90....and in winter I average roughly 1/2 ton +/- of coal per month at $94 Ton picked up at the mine

I am sorry this is so long, I can't wait to get home and start burning some coal. It will take a couple days to get set up. I am at my son's home waiting for a baby to be born, we might be here for another week and then I have another vintage motorcycle race to compete in before I can get to the job at hand!!!! You have been very helpful, I am looking forward to your response of this post.

carlherrnstein wrote: you need to find out some things about the coal you plan on burning. Like is it going to clinker or will it burn to ash, and is it going to swell an stick together. Those two factors will massively effect the design of the burn pot. Those polish stoker units are built to burn anthracite, lignite, sub bituminous, and wood pellets. All of these fuels do not clinker, do not swell, and burn without much smoke. Some bituminous coal will clinker and will swell an fuse into a mass when burning however some does not but, all has a lot tars that burn with black smoke.

What you need to find out is the ash fusion temperature (this will tell you if it will clinker) and something called the coke button (this tells you how much it will swell)

If you havent already, you need to look at the many different types of stokers made. That will give you a idea of how they are made.

The polish stokers are most likely not going to burn bit coal well at all, it will smoke like a smudge pot and if the coal fuses the fire will drop off into the ash pit. I suggest searching prill stokers(they burn non swelling, non clinkering bit an sub bit. Combustioneer they burn swelling, clinkering bit.

unhippy wrote:If teddys design of burner turn out not to perform as well as is he wants/needs it to then if he could find a Combustioneer or something similar in good condition

Pacowy wrote:
I don't think he's going to find much of anything in an underfeed design that meets his spec of 6 lb/hr max feed rate. The smallest EFM I know of was 12.5; IIRC the smallest unit in the collection of Motor Stokors in my garage is 20. If an underfeed stoker turns out to be needed, I would like to know more about the sizing computations because they don't seem to align with the way equipment in the past has been designed to meet market needs.

Mike