1960's EFM boiler sulphur/venting problem

I am just finishing my first season with a refurbished 1960's EFM 520 boiler. Previously I had an alaska insert in a fireplace so I am ending my 3rd year of burning coal. After using the boiler this year I am now looking back at issues I have had. I use bagged coal that is sometimes wet (Blackshak). I have a huge build up of sulphur at the point where the auger tube meets the 55 gallon drum. I imagine the wet coal is drying and the sulphur is pushing out at this spot. The heat from the stoker travels through that auger tube into the storage drum/hopper and dries the coal. The problem is that as the coal gets low in the barrel fumes and exhaust begin to backflow from the stoker up through the barrel. If I don't keep the barrel really full it gets smelly in the basement and may even start to trigger the carbon monoxide detector. Any ideas on how to keep this from happening. I know it vents well because I had 4 feet of chimney added when I put in the boiler. The air flows right up the chimney and pulls hard.

thanks

How hard is hard ? was it measured with a manometer?
Could your combustion blower be pushing to much air?



Eric

Fumes in the barrel or bin is usually from too short of an auger pipe, and/or too much combustion air for the feed setting. Less likely is that the vent holes at the pot end of the auger pipe (or the air holes in the burner plates themselves) have become plugged with sludge/fines from the excessively wet coal.

I have a few questions for you.

1. How many feet of auger pipe do you have in total?

2. Does the auger pipe have a series of holes drilled about 1" from the end? See the pipes in the center of this photo:


3. Are you burning rice or buck size coal?

4. What are you using for feed and air settings?

5. Has this been a problem since you first got the EFM running or did it start later?

6. Have you checked the draft with a draft gauge?

Not uncommon when using a short worm with little coal above the worm, such as a low barrel. Rob gave good reasons. You can stop this by putting a lid, with a foam seal, on the barrel and keeping a weight on top of the lid. Or use a longer pipe and worm.

Thanks for the replies.

My auger is short, only about 4ish feet, but there are holes. As soon as I stop burning I will investigate the holes and see if they are clogged. I hadn't considered the air settings as a cause. I burn rice coal. I usually have the air setting a little above 5. If I lowered it do you think that would help? I don't really know if it has always been a problem because of the chimney issue when we first installed it. The chimney wasn't tall enough so it wasn't sucking. I had the chimney professionally heightened, cleaned, and repaired. They checked everything and made sure the boiler was venting correctly out of the chimney. Do you think if I used only dry coal it would help or wouldn't it matter. I also had not thought of a lid but that doesn't seem to address the problem, just cover it up. Where would I get a longer auger and pipe if you think that would help?

thanks again.

Having the air at 5 is OK if your feed is at 5 or 6 teeth. The easiest solution is to keep the coal drum full OR put a sealed lid on it. You need to put a number on your draft. It must read at least negative .03 while the unit and chimney are hot and while stoking. Adjusting your draft damper could help alot.

I'd bet your air feed is the root of your issue. First year EFM guy here, and I ran into the same situation. The fire burned real nice, but would blow fumes out the auger. 4 teeth, and 5 on the air, burning wet bagged rice coal. I turned the air down to 4, problem went away, and no noticeable difference in coal burn or performance. The only time I get exhaust fumes now is when I run out of coal.