Water tube boilers as SCHNEIDER-Eckrohrkessel in “corner tube design”

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The SCHNEIDER Eckrohrkessel is a state-of-the-art natural circulation boiler and it is used as a generator of steam and hot water. The tube cage of this type of boiler is constructed from prefabricated furnace and convection heating surfaces. The SCHNEIDER Eckrohrkessel design differs from the conventional bi-drum water-tube boilers with natural circulation which are still being produced for more than 100 years..

Design principle
The pressure part consists of a solid rectangular framework of downcomers, collectors and distributors, welded together to form a closed tube cage with tube walls that are flue gas proof.

1. Drum - unheated
2. Down corner tube - unheated
3. Bottom tubes - heated
4. Upper collector - unheated
5. Overflow tube - unheated
6. Return tube - unheated
7. Riser tube - heated
8. Mixture tube unheated
9.Partition wall
10. Steam outlet
11. Lower collector - unheated
Water tube boilers

The Unique Water Circulation System
The water circulation of the SCHNEIDER Eckrohrkessel has a number of special characteristics which distinguishes it from all other known natural circulation water tube boilers especially from the bi-drum design.
In the SCHNEIDER Eckrohrkessel only riser tubes (7) and bottom tubes (3) are heated while the drum (1), the down corner tubes (2), the overflow tubes (5) the return tubes (6), the mixture tubes (8) and all collectors are unheated. The steam-water mixture, which is generated in the riser tubes (7) and bottom tubes (3) rises into the unheated upper collector (4) where an almost complete separation of steam and water occurs (principle of gravity). The separated steam flows over the overflow tubes (5) into the drum area behind the partition wall (9) above the low water level LWL. Approximately 50% of the separated water flows through the unheated return tubes (6) down to the heated bottom tubes (3) and the remainding 50% via the mixture tubes (8) towards the drum (1) into the area behind the partition wall (9) and below the low water level LWL. From there the water flows down through the unheated down comer tubes (2) back into the unheated lower collector (11) from where it is distributed to the bottom tubes (3) and the riser tubes (7) and the cycle starts again.
The exceptional and unique advantages of the SCHNEIDER Eckrohrkessel are:
utilization of various fuels
short start-up time and extremely high load variation speed at stable water level
compact and self supporting design
no material stress since the tube cage and the drum expand independent of one another
generation of 100% dry and pure steam
adapts ideally to the space available