Reluctant Poster
Tech Sergeant
- 1,690
- Dec 6, 2006
My first job out of university was working on a lignite fueled power station which is where I found out how difficult a fuel it is to burn and to handle. It is a mine mouth plant, as they all are, due to the weight of extraneous material (water and ash) that you must transport. For this plant the lignite is carried by train 14 miles from the mine. The fact that they justified building a railway for such a short haul shows how uneconomic it is to ship. In fact very short railways are quite popular for mine mouth lignite plants. Three large lignite plants in Texas used dedicated railways: Oak Grove 13 miles, Monticello 40 miles (decommissioned), Martin Lake 42 miles. They even justified the expense of electrifying the last two.
This is what the US Environmental Protection Agency has to say on the subject
One of the other issues with transporting lignite is that it tends to disintegrate after exposure to air giving it a short shelf life. At the power station the reserve coal pile has to be carefully compacted to prevent air from getting. This also helps with lignite's tendency for spontaneous combustion. The coal to be used is kept in silos
Here is the ultimate analysis for a similar coal to that is burned in the plant I worked on (Saskatchewan)
In comparison here is the proximate analysis for Welsh coal. It is indeed as good as it gets. Note the extremely low content of water and ash. Other British coals are almost as good. The Sentinel steam wagon was designed to burn Welsh or hard coal.
Here is the analysis for German brown coal. Note the extraordinarily high water content. The ash content is quite high as well. Its actually a worse coal than the one I have experience with.
Before anyone gets too excited the heating value show is higher heating value which does NOT include water and ash.
For the record the Sentinel was designed for high quality coal
"The boiler design is suitable for burning either coke or Welsh coal (ref. 1)." From:
The Sentinel Steam Waggon at Riverside Museum ____________________________
By Andrew C. Whyte, BSc, MSc, CEng, M.I.Mech.E.
Copyright April 2016, January 2021
Web site: A Chartered Mechanical Engineers Web Site
A copy is attached.
The high water content has a large effect on boiler efficiency. This is due to the unfortunate fact that you are converting water into steam on the wrong side of the boiler tubes. Instead of producing steam for the engine you are sending steam directly up the stack.
Power stations mitigate this effect by recovering waste heat from the flue gases to preheat the air going to the boiler. The air going to the coal pulverizers is heated enough to convert the water to vapour before it enters the boiler. This requires large heat exchangers to do so which are not practical on a rail locomotive let alone one for the road.
Ash has a lesser effect on boiler efficiency but is still presents a heat loss.
The Germans did use lignite for domestic purposes. To lower the extremely high moisture content they pulverized it and then heated it. They used high pressure presses to compact it into the briquettes. They are still available today. The result is a product that still had a very low heating value and a relatively high ash content. The following document describes the briquette process in India.
https://nopr.niscpr.res.in/bitstream/123456789/17781/1/JSIR 59%285%29 413-416.pdf
The Germans did experiment with both pulverized lignite and lignite briquettes in steam locomotives without success. However they exigencies of war did result in the use of a mixture of hard and soft coal:
"Officially, the performance of the 52 class was rated at 1,400 tons at 37.5mph on level track with coal of 12,650 BTU, but as their steaming capacity was on the shy side it was not always achieved. Until the end of 1943 hard coal was usually available, but subsequently it was mixed with 50 per cent soft brown coal (lignite) or briquettes, which increased fuel consumption by 30 to 40 per cent and required the services of two firemen on the footplate for all heavy long-distance trains. The use of the mixed fuel of only 9,000 BTU had a serious effect on performance by reducing drawbar horsepower while increasing the fuel consumption to 125 lb per mile."
The Kriegslokomotiven - Railway Wonders of the World
If was difficult to accomplish something as large as a railway locomotive the chances of doing it in a much smaller vehicle are slim.
After the war it seems that some pulverized coal locomotives were built.
"It has long been recognised that brown coal, even when briquetted, is an unsuitable fuel for locomotives if only because of the fire hazard associated with funnel sparks. In Germany, where successful use of brown coal briquettes on main line operation would be a major economic achievement, there has never been more than small local utilization -principally in or about open cuts. If brown coal is to partly or wholly displace black coal in Victoria's State railway system, no other solution is in sight than its use in the form of dried dust."
Coal Dust Powered Steam Engines
Here's some additional websites on the Sentinel waggon
Sentinel Waggon Works, Sentinel Steam Lorry
Steam Wagon - Sentinel Waggon Works Ltd, Super Sentinel, circa 1924 Archive & drawings
This is what the US Environmental Protection Agency has to say on the subject
One of the other issues with transporting lignite is that it tends to disintegrate after exposure to air giving it a short shelf life. At the power station the reserve coal pile has to be carefully compacted to prevent air from getting. This also helps with lignite's tendency for spontaneous combustion. The coal to be used is kept in silos
Here is the ultimate analysis for a similar coal to that is burned in the plant I worked on (Saskatchewan)
In comparison here is the proximate analysis for Welsh coal. It is indeed as good as it gets. Note the extremely low content of water and ash. Other British coals are almost as good. The Sentinel steam wagon was designed to burn Welsh or hard coal.
Here is the analysis for German brown coal. Note the extraordinarily high water content. The ash content is quite high as well. Its actually a worse coal than the one I have experience with.
Before anyone gets too excited the heating value show is higher heating value which does NOT include water and ash.
For the record the Sentinel was designed for high quality coal
"The boiler design is suitable for burning either coke or Welsh coal (ref. 1)." From:
The Sentinel Steam Waggon at Riverside Museum ____________________________
By Andrew C. Whyte, BSc, MSc, CEng, M.I.Mech.E.
Copyright April 2016, January 2021
Web site: A Chartered Mechanical Engineers Web Site
A copy is attached.
The high water content has a large effect on boiler efficiency. This is due to the unfortunate fact that you are converting water into steam on the wrong side of the boiler tubes. Instead of producing steam for the engine you are sending steam directly up the stack.
Power stations mitigate this effect by recovering waste heat from the flue gases to preheat the air going to the boiler. The air going to the coal pulverizers is heated enough to convert the water to vapour before it enters the boiler. This requires large heat exchangers to do so which are not practical on a rail locomotive let alone one for the road.
Ash has a lesser effect on boiler efficiency but is still presents a heat loss.
The Germans did use lignite for domestic purposes. To lower the extremely high moisture content they pulverized it and then heated it. They used high pressure presses to compact it into the briquettes. They are still available today. The result is a product that still had a very low heating value and a relatively high ash content. The following document describes the briquette process in India.
https://nopr.niscpr.res.in/bitstream/123456789/17781/1/JSIR 59%285%29 413-416.pdf
The Germans did experiment with both pulverized lignite and lignite briquettes in steam locomotives without success. However they exigencies of war did result in the use of a mixture of hard and soft coal:
"Officially, the performance of the 52 class was rated at 1,400 tons at 37.5mph on level track with coal of 12,650 BTU, but as their steaming capacity was on the shy side it was not always achieved. Until the end of 1943 hard coal was usually available, but subsequently it was mixed with 50 per cent soft brown coal (lignite) or briquettes, which increased fuel consumption by 30 to 40 per cent and required the services of two firemen on the footplate for all heavy long-distance trains. The use of the mixed fuel of only 9,000 BTU had a serious effect on performance by reducing drawbar horsepower while increasing the fuel consumption to 125 lb per mile."
The Kriegslokomotiven - Railway Wonders of the World
If was difficult to accomplish something as large as a railway locomotive the chances of doing it in a much smaller vehicle are slim.
After the war it seems that some pulverized coal locomotives were built.
"It has long been recognised that brown coal, even when briquetted, is an unsuitable fuel for locomotives if only because of the fire hazard associated with funnel sparks. In Germany, where successful use of brown coal briquettes on main line operation would be a major economic achievement, there has never been more than small local utilization -principally in or about open cuts. If brown coal is to partly or wholly displace black coal in Victoria's State railway system, no other solution is in sight than its use in the form of dried dust."
https://www.advanced-steam.org/wp-content/uploads/2017/07/Brown-Coal-Dust-Firing-for-Locomotives.pdf
Coal Dust Powered Steam Engines
Here's some additional websites on the Sentinel waggon
Sentinel Waggon Works, Sentinel Steam Lorry
Steam Wagon - Sentinel Waggon Works Ltd, Super Sentinel, circa 1924 Archive & drawings