EP3252375B1 - Boiler plant, method for operating a boiler plant and use of a boiler plant - Google Patents

Description

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

In the currently changing energy market, the flexible provision of energy generation capacities is becoming more and more relevant and boiler systems have to be adapted to these conditions. Thick-walled components such as drums and collectors are significant limitations for regular, rapid start-up of boiler systems and the rapid load change capability. Wall thicknesses are dictated by operating pressure and high pressures are required to optimize efficiencies. Thick-walled components have to be heated up slowly due to the thermal stresses that occur, and this is in direct contradiction to rapid start-up and load changes. Due to their design, once-through boilers do not have a drum, but instead have thick-walled collectors. However, such systems are used almost exclusively in large power plants with supercritical steam parameters. For subcritical applications, e.g. B. Industrial technology, decentralized power generation plants, gas turbine power plants with waste heat boilers and power plants up to approx. 350 MW, the use of natural circulation and forced circulation boilers is dominant and these have thick-walled drum and collector components at high pressures.

the DE 971 951 B describes a boiler with two upper drums. This includes two separate systems, so the two drums are used in two separate water circuits. The documents FR 621 429 A , U.S.A. 4,262,637 , DE 975 718 C also disclose a boiler system with two top drums.

Description of the invention:

Claim 1 describes a boiler plant according to the invention. The invention relates to a boiler system for heating a medium, in particular natural circulation or forced circulation boilers or waste heat boilers, particularly preferably corner tube boilers, comprising downpipes, collectors, distributors and risers, which form at least part of a circuit of a medium to be heated, with at least two drums connected to the circuit are connected for separating the water-steam mixture into steam and water.

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

In order to minimize wall thicknesses, this invention proposes distributing the drum volume over at least 2 upper drums.

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

In a corner tube boiler, the boiler pressure hull is formed by a stable, rectangularly arranged framework of downcomers, collectors and distributors. The latter two are welded to smoke gas-tight pipe walls, creating a self-contained pipe body. This supports itself and all welded or separately mounted heating surfaces. The load is transferred to foundations via four downpipes at the corners and, if necessary, also via additional downpipes on the sides. The water-steam mixture is already separated in pre-separators outside the drum. From there, the steam reaches the drum through overflow pipes and the water-steam mixture flows through pre-separators directly to the drum. The remaining water bypasses the drum and goes down to the distributor via the return pipes.

A defined volume is required in a boiler to separate steam. In a corner tube boiler it is possible to split this volume into several small volumes rather than running it as one large volume. This volume is divided between the at least two arranged drums, which are fluidically connected.

More than two drums can be arranged, up to any number of drums. In this case, ready-made pipes can take over the function of the drum, resulting in a "poly drum". There are many places where the steam is separated from the water, such as the sidewall of headers.

In the system according to the invention, the pressure is the same in both or all of the drums, and all of the drums are connected to the same water circuit. Due to the connection on the water and steam side, both or all drums have the same pressure and are connected to the same pressure stage.

According to the invention, the ratio of the diameter D to the 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. The mixture collector can be designed with a front and a rear outlet. The vapor extraction from the mixture collector can take place in a vapor collector. A plurality of collectors are preferably arranged, the wall thickness of which is reduced in comparison to the conventional drum. If several mixture collectors are designed as drums, it may be possible to dispense with the arrangement of a conventional drum. In this case, the result is a drumless corner tube boiler in which the volume for steam-water separation is made available in the several mixture collectors designed as drums.

According to the invention, the drums are arranged in the high-pressure part of the boiler plant, i. 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 area. The arrangement in different pressure levels is also possible.

According to the invention, the diameter D of the drums in relation 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 in relation to the length L of the drums is: D/L = 0.1 to 0.2.

The invention also 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 the circuit and the water-steam mixture is separated into steam and water in both drums .

The invention also 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 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, since two upper drums are lighter than one large drum due to the thinner walls in each case. In addition, the two upper drums improve the descent times, i. H. same sinking time (time between maximum and minimum water level in the drum) with a smaller drum diameter and drum wall thickness.

Under certain circumstances, it is easier to use conventional, ready-made pipes, which are much simpler and cheaper to manufacture and install. It can If necessary, welded drums can be dispensed with, which reduces costs and effort. Welded drums are heavy and complex to manufacture due to their size and the necessary stability. In addition, high requirements in terms of statics and pressure stability must be met.

A low absolute wall thickness is possible, which enables rapid up and down movement in short times of up to 1 minute, since the resulting thermal stresses in the tubes are significantly lower than in thick-walled drums due to the smaller wall thicknesses. The wall thickness depends on the outer diameter.

Rapid ramping up and down is particularly important in gas and steam processes and when using solar thermal energy, since rapid load changes occur.

Better and faster vapor separation takes place since the absolute height of the water level of the water phase from which the vapor is to be separated is lower.

As a result, the use of pumps can be reduced.

Figure description:

the Figures 1 and 2 show conventional designs of corner tube boilers as the state of the art. It can be seen that different drum sizes are possible.

The corner tube boilers each comprise a drum 1 and several downcomers 2. On the upper side they comprise an overflow pipe 3 and mixture collector 4 and on the lower side distributor 5.

figure 3 shows a corner tube boiler according to the invention with two overhead drums 1. These are fluidically connected to one another and arranged in the same water-steam circuit. It can be seen that the two drums 1 provide the same volume as the large drum 1 2 , but manage with smaller wall thicknesses. Furthermore, the weight of the drums 1 is reduced here and is only 148.2 t compared to the version in 2 with 161.7 t.

4 shows a corner tube boiler according to the invention in a perspective view. Two drums 1 are visible at the top left, in the high-pressure part, while only one drum 1 is arranged at the top right, in the low-pressure part.

Also the ones in the Figures 3 and 4 The corner tube boilers shown comprise several downpipes 2. On the upper side they comprise an overflow tube 3 and mixture collector 4 and on the lower side distributor 5. In contrast to conventional corner tube boilers, however, they have two drums 1 on the upper side.

Reference List

1

drum

2

downpipe

3

overflow pipe

4

mixture collector

5

distributor

Claims (4)

1. A boiler plant for heating a medium, in particular a natural circulation or forced circulation boiler or waste heat boiler, particularly preferably a corner tube boiler, comprising downcomers, collectors, distributors and risers, which form at least part of a circuit for a medium to be heated, at least two drums (1) being connected to the circuit for separation of the water-steam mixture into steam and water, characterized in that the ratio of diameter D to wall thickness s of the drums is: D/s ≥ 15, wherein the drums (1) are arranged in the high pressure part of the boiler plant, i.e. in a part of the plant which is configured to operate at over 40 bar, and in that the diameter D of the drums in relation to the length L of the drums amounts to: D/L = 0.03 to 0.5, in particular 0.05 to 0.3.
2. The boiler plant according to any one of the preceding claims, wherein at least one of the drums (1) has a collector function.
3. A method for operating a boiler plant according to one of Claims 1 and 2, in which heat is generated in the boiler plant and transferred to a medium, in particular water, in the circuit and separation of the water-steam mixture into steam and water is carried out in both drums (1).
4. Use of a boiler plant according to one of Claims 1 and 2 to produce heat and transfer it to a medium, in particular to water.

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