Soda locomotive
The soda locomotive is a fire-free steam locomotive . It was developed by Moritz Honigmann in 1883 and is based on a principle that is rarely used for steam generation.
The process was protected by Honigmann on May 8, 1883 under patent number 24993 in Berlin. The title of the patent was: About the process for developing pressurized steam by absorbing the outgoing machine steam in caustic soda or caustic potash by Moritz Honigmann in Grevenberg near Aachen.
functionality
Steam is passed into a strong sodium hydroxide solution , in principle other solutions are also conceivable. The steam is completely absorbed into the solution at temperatures of 130 ° C and above. The dissolution process (the lye is diluted by the water) simultaneously releases heat ( heat of condensation and enthalpy of solution ) and the solution heats up. This heated solution is then used to heat the actual steam boiler. The solution becomes warmer and more watery over time, until it can no longer absorb water and begins to boil itself.
The standard enthalpy of formation of solid sodium hydroxide (NaOH) is −426.7 kJ / mol ; that of dissolved NaOH −469.6 kJ / mol. When NaOH is completely dissolved, 42.9 kJ / mol are released in the form of heat. Solid NaOH has a molar mass of 39.997 g / mol (corresponds to 25.002 mol / kg). So per kilogram of completely dissolved solid 1072.6 kJ (= 0.298 kWh) are released. However, only part of this energy could be used because the sodium hydroxide was already in solution when the locomotive was filled .
At the filling station, the locomotive was filled with 900 kg, 83% sodium hydroxide solution at 180 ° C. The energy content was later described as “ a filling weight of 20 kg per horsepower hour”. From this information, however, it is not clear whether it is the mechanical output of the steam engine or the thermal output of the boiler . The value corresponds to an energy density of approx. 36.8 Wh / kg of caustic solution, at 900 kg this results in a "tank capacity" of around 33.1 kWh. A modern lead-acid battery can reach up to 60 Wh / kg, compared to petrol, it has an energy density of 12 kWh / kg, i.e. more than three hundred times as much.
In addition to the heat obtained from the solution, the heat of condensation of the exhaust steam was used and was not lost. In this way, the heat of evaporation of the feed water could be obtained from the exhaust steam and only the energy required to carry out work had to be provided by the storage tank.
Honigmann installed a soda kettle a (picture on the right) on his locomotives , over which a kettle b stands. From the bottom of the kettle a large number of boiler tubes c extend almost to the bottom of the soda kettle . A pipe d leads from the upper, steam-filled part of the kettle to the steam cylinders f, a second e leads from these to the lower part of the soda kettle. If the steam pressure in b is high enough from the outset to drive the machine, the used steam gets through e into the caustic soda, where it dissolves and heats the solution by giving off heat. This in turn allows enough water to evaporate in b to keep the machine running through the heat transfer through the boiler pipes c . The heating of the water boiler regulates itself. The more the machine does, the more steam it consumes, the more steam is also added to the caustic soda and the more heat is generated.
After about four to five hours, the sodium hydroxide solution became ineffective through dilution. Then it had to be drained and evaporated again. The kettle was filled with fresh, concentrated solution. The water evaporating in b was replaced by a steam jet pump from a water storage box g .
Soda boilers, boiler pipes and steam pans must be made of corrosion-resistant material (at that time it was mainly copper ) because iron is attacked by the caustic soda solution at high temperatures. Compared to the steam storage locomotive, the soda locomotive has a more complicated boiler that is more expensive to manufacture and a water reservoir. On the other hand, it is not only fire-free and smokeless, but also does not emit steam. It is also characterized by a longer service life after filling, so that at the same time the risk of the vehicle getting stuck in the middle of the route is reduced.
history
Honigmann had a machine of this type built for the Aachen and Burtscheider horse-drawn railway company in Aachen . It was operated from June 1884 to March 1885 on a one-kilometer route. Two such locomotives were used in coal mining near Aachen. In Berlin-Charlottenburg , a tram with a soda locomotive was also running on a trial basis . The Leipziger horse railway company resulted from the end of February 1886 trial runs between downtown and the depot in Plagwitz with the Halle Maschinenfabrik "System Honigmann" supplied soda locomotive with 11 tonnes operating weight by.
Like the trial run in Leipzig, the results of the trial run in Aachen were actually quite positive. So it is said: “The movement of the machine was so calm and steady that the passengers liked to ride it.” Unlike the horse-drawn tram, the soda locomotive mastered the 3% gradient without any problems. While one kilometer of travel on the horse-drawn tram cost the operator 25 pfennigs, the Natronbahn only cost 16 pfennigs.
Obviously there were problems with re-evaporation of the diluted caustic soda. In Aachen, copper kettles were used for this, which are said to have been dissolved by the caustic soda over time. However, experiments on this were carried out by Prof. Alois Riedler, who was entrusted with the assessment of the technology, and his assistant Gutermuth from the Technical University of Munich with a cast iron boiler . There was a certain reduction in the wall thickness due to the caustic soda, from which the two calculated that the boiler of the evaporation plant would have to be replaced every one to two years. Those responsible shied away from these costs. However, Honigmann developed a system to evaporate the caustic soda under vacuum. About 80 ° C would have been sufficient for this. At this temperature, the cast-iron kettles should last four thousand times longer. Such an apparatus was used to evaporate the caustic soda in the Honigmann's soda factory.
Those responsible also referred to a track system that could not sustain the weight of the soda locomotive in the long term, and stopped the experiment after eight months.
Despite its advantages, especially compared to the competition from horse-drawn trams and early steam locomotives at the time, whose use in built-up areas was not without problems due to smoke and steam emissions, this type of construction could not prevail.
However, this form of thermochemical heat storage is used for heat storage, e.g. B. in connection with solar systems , was used again at the end of the 20th century.
literature
- Journal of the Association of German Engineers , year 1883, p. 730.
- Journal of the Association of German Engineers , year 1884, p. 69 and p. 978.
- Engineering dated February 27, 1885.
- Journal for the entire local and tram system , year 1885, p. 74.
- Christian Mähr : The soda locomotive. In: Forgotten Inventions. 1st edition, 2002. / 2nd edition, DuMont Buchverlag , Cologne 2006, ISBN 978-3-8321-7744-7 , pp. 27-46.
Web links
Individual evidence
- ↑ a b c d Christian Mähr: Forgotten inventions. Dumont, Cologne 2002, ISBN 3-8321-7816-3 , p. 27 ff.
- ^ Conrad Matschoss : Men of Technology. A biographical manual. Berlin 1925. / Reprint (with an introduction by Wolfgang König): Düsseldorf 1985, ISBN 3-18-400662-X .
- ↑ Deutsche Bauzeitung , Vol. 20, 1886, No. 18 (from March 3, 1886), p. 107.