top of page

Development of an ultra-supercritical water boiler


The boiler was developed and designed by our company on behalf of Kerogoil Zrt, and was successful in approving the design documentation by TÜV.


Basic equipment data:


Maximum constant supercritical water capacity: 12 t / h (3.3333 kg / sec)


Nominal constant supercritical water capacity: 10 t / h (2.7778 kg / sec)


Minimum constant supercritical water capacity: 5 t / h (1.389 kg / sec)


Design pressure: 420 barg.


Approved pressure: 420 barg.


Max. Operating medium pressure: 415 barg


Water outlet pressure: 400 barg


Water outlet temperature: 600 ° C


Max. Feed water inlet temperature: 45 ° C


Fuel: Natural gas


The minimum amount of feed water flowing through the boiler is 5 t / h


The quality of the feed water required for the operation of the boiler must be ensured according to the specification of the water treatment plant.


General description of the boiler:


Boiler inlet design data 


Medium: Water

Temperature: + 5… + 45 ° C 

Pressure: ≤415barg


In order to minimize logistics costs, the boiler has been designed to have a horizontal layout and size of approx. 20 'standard container, with heat-insulation.


The flue gas duct at the top of the boiler can be dismantled in one piece for easier transport.


The burners are located in the 7110x2438 mm base frame of the container.


The base frame is divided into 5 sections. There are 2 burners facing each other in the sections.


Ceramic walls rest on the section boundaries, which have a dual role: to support the lower two pipe bundles (so-called evaporator and superheated pipe bundles) and to ensure adequate flue gas flow.


The longer walls of the container are covered with relatively small, easy-to-install, thermally insulated sheet metal panels that enable easy maintenance and inspections.


There are doors that can be opened at the ends of the container, which house the collectors, the pipes connecting them and the pipe turns.


For the heating of the boiler 10-10 pieces of gas-fired Premix carpet burners per side are used. The combustion air is supplied by 1 + 1 fan (1 operating and 1 spare) per side.

A dust separator is placed on the suction side of the fans, to prevent contaminants entering the system.


The speed of the fans is controlled by pressure, thus ensuring proper pressure at the exhaust end.


After the fans the backbone is D800, the connections per burner are size DN125 and 1-1 motorized and manually operated butterfly valves are installed in front of each burner. There are DN125 size connections to the burners with flexible hoses equipped with an air pressure switch for preventing hose blockage.


The burners’ gas supply backbone is DN100 per side. The burners are connected to the backbone via DN40 taps. Each gas manifold is equipped with a double-acting solenoid valve and a motor-operated butterfly valve. After the fittings, DN40 / DN32 concentric pipe reducers are installed and connected to the burners with DN32 flexible pipes.


Above the burners is a bundle of pipes connected in three rows, of which the lower two rest on a high-strength heat-resistant ceramic wall, while the upper bundle is secured to the steel frame. The flue gas flowing out of the burners passes through all three bundles of pipes and then enters the chimney through the removable flue gas collection duct, to which it is connected with a non-metallic compensator, the role of which is to compensate for deformations caused by thermal expansion and vibration damping. The technological sequence and role of the pipe bundles during normal operation from the water supply to the outlet port are as follows:


Feed water preheater:


The feed water from the High-Pressure Pump unit enters the feed water collector through flexible pipes and then flows through the pipe bundle manifold made of the uppermost finned tubes made of Ø26.9x4, 1.4903 (P91) farthest from the burners. Finally the preheated medium continues to flow through the collector to the next process stage.


At the end of the process stage, the parameters of the flowing medium are as follows:


Medium: water

Outlet temperature: + 365 ° C

Pressure: 410 barg




From the feedwater preheater, through the feedwater preheater manifold the medium enters the “evaporator” collector through the lowest, partially irradiated pipe of Ø26.9x5 1.4903 (P91) material, which is close to the burners.


At the end of the process step, the parameters of the flowing medium are as follows:


Medium: supercritical water

Temperature: + 455 ° C

Pressure: 420 barg




The medium arrives from the “evaporator” manifold to the superheater manifold, then passes through a centralized bundle of Ø26.9x6 1.4990 (Sanicro 25) tube material, passes through the superheater manifold to the discharge port.


At the end of the process step, the parameters of the flowing medium are as follows:


Medium: supercritical water

Temperature: + 600 ° C

Pressure: 420 barg


Strength calculation:

The abstract result of the strength calculation is included in the document KTH-044-011-001 “Strength calculation”. Due to the very high design pressures and temperatures, the creep strength for 100,000 hours has been taken into account in several cases for materials built into the pressure equipment with a safety factor of 1.25! The elements calculated with the creep strength value are shown separately in the strength table. Due to the high stress and the calculation of the creep strength, the service life of the boiler is correspondingly lower. Normally the lifespan is 25 + 15 years. In this case, the boiler life is 10 + 5 years and 80,000 h + 40,000 h, respectively. In accordance with the above, the increased used / operated parts of the boiler must be checked continuously and the changes in the materials of the boiler must be checked after 80,000 operating hours or after 5,000 starts. The testing procedure is prepared by the lead designer as a separate document. The arrangement of the control warts required to check the creep is given in the drawing "Exit line KTH-044-214-017", and the instructions related to the creep measurements are included in the operating instructions.

bottom of page