Corner tube boiler

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A corner tube boiler is a special type of natural circulation boiler , which differs from other water tube boilers by its characteristic water-steam cycle. A separation of the water-steam mixture already takes place outside the drum.

principle

Corner tube boilers were developed for small steam outputs. The boiler was based on two important design criteria. On the one hand, stable water circulation should ensure that all heated riser pipes are adequately cooled, even with low partial loads. On the other hand, emphasis was placed on a self-supporting boiler construction. This manifests itself in the self-supporting shell construction , i.e. the unheated drum downpipes and return pipes (the downpipes not connected to the drum), which are located in the corners of the boiler, form the support structure, hence the name corner tube boiler .

In addition, the piping system is also responsible for managing the water distribution in the riser pipe and downpipe, collecting the steam-water mixture and in order to separate the steam-water mixture from a certain amount. The water circulation takes place simultaneously through the drum and through the return pipes in the pipeline system.

history

During the Second World War, and especially towards the end, there was a shortage of fuels such as gasoline and diesel in Germany. However, the demand for fuels continued to grow. Heinrich Vorauf developed a solution to this problem by designing the concept of a new type of boiler that could meet demand with substitute fuels such as wood. In 1944, the first corner tube boiler developed by Heinrich Vorauf was installed on a truck.

effect

Water circulation in the corner tube boiler

The water flows from the drum through the downpipes in the distributor, where it is distributed in the various risers. The steam-water mixture circulates (in the area heated by radiation) through the pre-separator (also known as cross-collector), where the separated steam flows through overflow pipes to the drum and the steam-water mixture flows through the collector to the drum. The rest of the water flows through the return line into the rear wall distributor, which is directly connected to the longitudinal distributor, and thus back to the riser pipe, where it is then heated.

The water flows from the unheated drum downpipes to the side distributor and the rear wall distributor and supplies the heated riser pipes with water. A separation of the water-steam mixture already takes place in the collector through the connected overflow pipe. Part of the water flows back down from the collector through the so-called return pipes, while the rest of the water-steam mixture flows through the collector to the drum.

advantages

  • The boiler expands from the fixed point in all directions and adapts to the different operating conditions without locking in additional tension or tightness, ie the boiler can expand in a vertical direction without any problems.
  • The shorter waterways for supplying the riser pipes enable the boiler to be operated quickly at partial loads.
  • Thanks to the system of return pipes, the heating surfaces are not only supplied with water from the drum. The heating surfaces can thus be located relatively far away from the drum. Large boilers, as is common in waste incineration plants, can thus be implemented without great effort.
  • The permissible temperature gradients can therefore be much higher, which enables the boiler to be started up quickly. The wall thickness of the drum over the entire circumference can be constant, so that the deformation of the drum remains small.
  • Relatively few pipes are connected to the drum, which is why there are no material weaknesses and the drum can be designed with the same wall thickness over its entire circumference.
  • Low risk of foaming. Since the water and the steam-water mixture that is fed into the drum, keep the same constant level all the time it leaves the space above the water level in the drum.
  • The downpipes and return pipes have such a large diameter that vapor bubbles do not endanger the circulation in the event of pressure drops or high load change speeds.
  • Small pressure fluctuations with load changes.
  • Load fluctuations in the shortest possible time are possible without the vapor pressure changing significantly. Even with load fluctuations, the water level in the drum remains calmer than with other boiler types.

disadvantage

  • Bad feed water with high salt concentrations of e.g. B. Magnesium, calcium etc. can lead to salting out, which can clog the boiler tubes.
  • The design and design concept of the boiler is complex and therefore expensive.

Fuels

The most common fuels used in Europe, America and the Pacific are: Bagasse , Biomass , Lignite , Coal , Bark , Natural Gas , Industrial Waste, Khuff Gas MFO, Mineral Oil , Organic Materials, Litter, Rice Husk, Rubber Tree , Sludge, Wood , Wood chips, household waste, hazardous waste.

Individual evidence

  1. ^ A b Karl J. Thome-Kozmiensky: Thermal waste treatment . EF for energy and environmental technology, Germany 1994, ISBN 3-924511-77-2 , p. 393-394 .
  2. ↑ a b Fritz Mayr (Ed.): Boiler operating technology . Resch, Graefelfing / Munich 1986, ISBN 3-87806-033-5 , p. 99 .
  3. ↑ F Block, LaLone, Girouard, Letendere: Designing a boiler for Waste Fuels . In: Power . , USA, May 1977, p. 75.
  4. ↑ Lars Josefsson: corner pipe boiler . Steam Esteem. Retrieved March 11, 2013.
  5. ^ Henrich Vorauf: The water circulation in corner tube boiler . Energie, Germany 1957, p. 3 .
  6. ^ Wolfgang Noot: From suitcase boilers to large power plants; The development in boiler construction . Vulkan Verlag, Germany 2011, ISBN 978-3-8027-2558-6 , pp. 345 .
  7. ↑ Henrich Preemption: The Eckrohrkessel . In: VDI magazine . 93, No. 14, 1951, pp. 395-397.