Continuous steam generator

Abstract

A continuous steam generator is provided. The continuous steam generator includes a number of burners for fossil fuels, the outside wall thereof being fully or partially formed from steam generator tubes welded together in a gas-tight manner. The burners are arranged in a combustion chamber, and a vertical gas duct is mounted downstream of the combustion chamber above a horizontal gas duct on the hot gas side. A first part of the steam generating tubes forms a system of evaporation tubes mounted upstream of a water separator system, on the flow medium side, and a second side, and a second part of the steam generating tubes forms a system of superheater tubes mounted downstream of the water separator system on the flow medium side. Superheater tubes adjacent and parallel to evaporation tubes are mounted directly downstream of the water separator system on the flow medium side.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is the US National Stage of International Application No. PCT / EP2009 / 061468, filed Sep. 4, 2009 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 08015871.0 EP filed Sep. 9, 2008. All of the applications are incorporated by reference herein in their entirety.FIELD OF INVENTION[0002]The invention relates to a once-through (“continuous”) steam generator comprising a number of burners for fossil fuel, the surrounding wall thereof being completely or partially formed from steam generator tubes welded together in a gas-tight manner. Said burners are disposed in a combustion chamber downstream of which a vertical gas duct is mounted above a horizontal gas duct on the hot gas side, a first part of the steam generator tubes being implemented as a system of evaporator tubes mounted upstream of a moisture separation system on the flow medium side, and a secon...

AI Technical Summary

Benefits of technology

"The invention is about a new design for a once-through steam generator that reduces repair costs and increases service life. It achieves this by mounting superheater tubes in parallel contiguity with evaporator tubes immediately downstream of the moisture separation system on the flow medium side. This minimizes temperature differences between the tubes caused by high temperature differences between them, which can lead to damage and overloading. The design also prevents flow stagnation and damage caused by overfeeding of the moisture separation system. Overall, this design reduces the need for repairs and increases the longevity of the steam generator."

Problems solved by technology

Advantages of this design are, for example, the lower installed height and the resulting reduced manufacturing costs.

However, particularly in startup mode, the above mentioned concept causes high temperature differences between evaporator tubes and superheater tubes: during cold starting, as yet unevaporated flow medium flows in the evaporator tubes at saturation temperature, while steam at higher temperature is still present in the superheater tubes.

This can result in overloading and damage of the materials due to the differential thermal expansion.

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