EP3252375A1 - Boiler plant, method for operating a boiler plant and use of a boiler plant - Google Patents

Abstract

Boiler system for heating a medium, in particular natural circulation or forced circulation or waste heat boiler, particularly preferred Eckrohrkessel comprising downpipes, collectors, manifolds and risers forming at least part of a cycle of a medium to be heated, characterized in that the circuit at least two drums for a separation of the water-steam mixture in steam and water are connected.

Description

The invention relates to a boiler system with at least two overhead drums, which is also referred to as a quick-start boiler.

In today's changing energy market, the flexible provision of power generation capacity is becoming increasingly relevant and boiler systems need to be adapted to these conditions. The main limitations for regular, fast start-up of boiler systems or fast load change capability are thick-walled components such as drums and accumulators. The wall thicknesses are determined by the operating pressure and high pressures are required to optimize efficiencies. Thick-walled components must be slowly heated due to the occurrence of thermal voltages and this is in direct contradiction to the fast start-up and load changes.

Due to their design, forced-circulation boilers do not have a drum, but thick-walled collectors, but such systems are used almost exclusively in large power plants with supercritical steam parameters. For subcritical applications, e.g. For example, industrial technology, decentralized power generation plants, gas turbine power plants with waste heat boilers and power plants up to 350 MW, the use of natural circulation and forced circulation boilers is dominant and they have thick-walled drum and header components at high pressures.

The DE 971 951 B describes a kettle with two overhead drums. This includes two separate systems, so the two drums are used in two separate water circuits.

Description of the invention:

The invention relates to a boiler system for heating a medium, in particular natural circulation or forced circulation or waste heat boiler, particularly preferred Eckrohrkessel comprising downpipes, collectors, manifolds and risers, which form at least part of a cycle of a medium to be heated, characterized in that the circuit at least two drums are connected for separation of the water-steam mixture into steam and water.

The invention relates in particular to natural and forced circulation boilers with firing of solids and / or liquid and / or gaseous fuels and to waste heat boiler plants with one or more pressure stages.

To minimize wall thicknesses, this invention proposes distributing the drum volume to at least 2 top drums.

It is preferably a two-drum system, which is used in particular for heating water for the purpose of generating hot water and / or water vapor.

In a corner tube boiler, the boiler pressure vessel is formed by a stable, rectangularly arranged framework of downpipes, collectors and distributors. The latter two are welded with smoke-gas-tight tube walls, whereby a self-contained tubular body is formed. This carries itself and all welded or separately supported heating surfaces. The load is removed via four downpipes at the corners possibly also on additional downpipes on the sides on foundations. The separation of the water-steam mixture already takes place in pre-separators, outside the drum. From there, the steam passes through overflow pipes to the drum and the water-steam mixture flows through pre-separator directly to the drum. Remaining water, bypassing the drum, passes down the return pipes to the distributor.

It takes a defined volume in a boiler to separate off steam. In a Eckrohrkessel it is possible to distribute this volume to several small volumes and not run as a large volume. This volume is divided between the at least two arranged drums, which are in fluid communication.

It can be arranged more than two drums, to any number of drums. In this case, prefabricated tubes can take over the function of the drum, so that a "poly drum" is created. There are many places where the steam is separated from the water, such as the sidewalls of collectors.

In the system according to the invention in particular in the two or all drums of the same pressure and all drums are connected to the same water cycle.

Due to the water and steam side connection both or all drums have the same pressure and are connected to the same pressure level.

Preferably, the ratio of diameter D to wall thickness s of the drum is: D / s ≥ 15.

D / s ≥ 18 is preferred. In one embodiment of the invention, D / s is 20 to 22.

Preferably, at least one of the drums has a collector function.

This means that at least one mixture collector is designed as a drum. In this case, the mixture collector can be designed with a front and a rear drain. The steam extraction from the mixture collector can take place in a vapor collector. There are preferably arranged a plurality of collectors whose wall thickness is reduced compared to the conventional drum. If several mixture collectors are designed as a drum, it may be possible to dispense with the arrangement of a conventional drum. In this case, a drumless Eckrohrkessel results in which the volume is provided for steam-water separation in the several designed as drums mixture collectors.

Preferably, the drums are arranged in the high pressure part of the boiler system, d. H. in a part of the plant designed for operation above 40 bar.

However, it is not excluded that the drums designed according to the invention are also arranged in the low-pressure region. The arrangement in different pressure levels is also possible.

Preferably, the diameter D of the drums relative to the length L of the drums is: D / L = 0.03 to 0.5, in particular 0.05 to 0.3.

Preferably, the diameter D of the drums relative to the length L of the drums is: D / L = 0.1 to 0.2.

The invention further relates to a method for operating a boiler system according to the invention, in which heat is generated in the boiler system and is transferred to a medium, in particular water, in circulation and a separation of the water-steam mixture in steam and water in both drums is performed ,

The invention further relates to the use of a boiler system according to the invention for generating heat and for transferring the heat to a medium, in particular to water.

The main advantage of the volume division according to the invention lies in the reduction of the drum diameter and consequently the drum wall thickness. Another advantage of the system is the reduced boiler weight, as two upper drums are lighter due to the smaller wall thickness than a large drum. In addition, the two top drums improve the sinking times, i. H. same settling time (time between maximum and minimum water level in the drum) with smaller drum diameter and drum wall thickness.

It may be easier to use conventional prefabricated tubes, which are much simpler and cheaper to manufacture and install. It can optionally dispensed with welded drums, which reduces costs and effort. Welded drums are difficult and expensive to manufacture due to their size and the necessary stability, in addition high requirements with regard to statics and pressure stability have to be met.

It is possible a small absolute wall thickness, which allows a rapid startup and shutdown in short periods up to 1 minute, since the resulting thermal stresses in the tubes are much lower due to the smaller wall thicknesses than in thick-walled drums. The wall thickness depends on the outer diameter.

A rapid startup and shutdown is crucial, especially in gas and steam processes as well as in the use of solar thermal, as rapid load changes occur.

There is a better and faster vapor separation, since the absolute level of the water level of the water phase is lower, from which the vapor is to be separated.

Pump insert can therefore be reduced.

Brief Description:

The Figures 1 and 2 show conventional versions of Eckrohrkesseln as prior art. It can be seen that different drum sizes are possible.

The Eckrohrkessel each comprise a drum 1 and a plurality of downcomers 2. On the upper side they comprise a transfer pipe 3 and mixture collector 4 and on the lower side distributor. 5

FIG. 3 shows a Eckrohrkessel invention with two overhead drums 1. These are fluidically interconnected and arranged in the same water-steam cycle. It can be seen that the two drums 1 provide the same volume as the large drum 1 Fig. 2 , but do it with smaller wall thicknesses. Furthermore, the weight of the drums 1 is reduced here and is only 148.2 t compared to the execution in Fig. 2 with 161.7 t.

Fig. 4 shows a Eckrohrkessel invention in a perspective view. Top left, in the high pressure part, two drums 1 are visible, while the upper right, in the low pressure part, only a 1 drum is arranged.

Also in the Figures 3 and 4 On the upper side they comprise a transfer pipe 3 and mixture collector 4 and on the lower side distributor 5. However, in contrast to conventional Eckrohrkesseln you have at the top two drums 1 on.

LIST OF REFERENCE NUMBERS

1

drum

2

downspout

3

overflow

4

mixture collectors

5

distributor

Claims (7)

Boiler system for heating a medium, in particular natural circulation or forced circulation or waste heat boiler, particularly preferred Eckrohrkessel comprising downpipes, collectors, manifolds and risers forming at least part of a cycle of a medium to be heated, characterized in that the circuit at least two drums for a separation of the water-steam mixture in steam and water are connected. Boiler plant according to claim 1, wherein the ratio of diameter D to wall thickness s of the drum is: D / s ≥15. Boiler plant according to one of the preceding claims, wherein at least one of the drums has a collector function. Boiler plant according to one of the preceding claims, wherein the drums are arranged in the high pressure part of the boiler system, d. H. in a part of the plant designed for operation above 40 bar. Boiler plant according to one of the preceding claims, wherein the diameter D of the drums with respect to the length L of the drums is: D / L = 0.03 to 0.5, in particular 0.05 to 0.3. A method for operating a boiler plant according to one of claims 1 to 5, wherein the heat is generated in the boiler plant and is transferred to a medium, in particular water, in the circulation and carried out a separation of the water-steam mixture in steam and water in both drums becomes. Use of a boiler installation according to one of Claims 1 to 5 for generating heat and transferring to a medium, in particular to water.

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