The dried lignite is rated at 7000 BTU per pound, about the same as the wood pellet/corn mixture used in the Summer. I suspected that it was about the same. After burning for one hour straight, the total ash is less than a quart, burning at 11 teeth feed rate. I'll continue to burn the rest of the coal, about 13 gallons worth and measure the ash. I don't notice any sooting inside the boiler, but I'm sure the flyash is building up. There is no clinkering whatsoever and the ash is a fine white wood-like ash. As shown in the video, the coal pyramids and falls outward to the outer edge where it is almost immediately burned up.
The first video shows the burning fire in the 520 stokerhttp://www.youtube.com/watch?v=04jPPuzo4CM
The second video shows that there is very little or no smoke at the chimneyhttp://www.youtube.com/watch?v=dXSF96_3UVY
This picture shows the flyash produced with the boiler running at full feed capacity, 22# per hour (anthracite weight) and the air setting at 4.
This picture shows the lignite sample sent to us and is barely more than dust. Surprisingly, the dried sample cranks as easily in an 11 foot coal tube as does anthracite.
This picture shows the ash ring after burning all day.
This picture shows the ash. It's as fine as sand.
At the end of the day, with about 120 pounds of lignite burned, the quantity of ash weighed 4 pounds and displaced about a gallon sized container, compared to about 13 gallons of original lignite.
The only comments I would add are that it is not easy to start a lignite fire. Some accelerant, such as kindling or wood pellets are needed and the flue pipes should be able to be easily undone for flyash cleaning. There was no problem with the fire going out with a 30 minute rest, so the timer should take care of that. Even though the lignite easily fed through the 11 foot pipe/auger, a shorter worm will reduce the chances of breaking sheer pins. Dry lignite is a must!