EP1398564A1 - Method for operating a horizontally positioned steam generator and steam generator for carrying out this method - Google Patents

Abstract

The method is for operating a turbine steam generator with a horizontal hot gas flow duct (6) having steam tubes extending across it (12). It involves feeding the flow medium such as water (W) through the generator through-flow heating surface (8) so that in the falling steam tube section (20) of each tube, a flow speed is above a preset level. The water can be partially prevaporised before passage into the steam tubes.

Description

The invention relates to a method for operating a Steam generator with one in one in an approximately horizontal Heating gas direction arranged flowable heating gas channel Evaporator continuous heating surface, which is a number of Flow through a flow medium connected in parallel Steam generator tubes, each one approximately vertical arranged, from the flow medium in the downward direction Downflow piece through which flow can flow and one on the flow medium side downstream, approximately vertically arranged and can be flowed through by the flow medium in the upward direction Have riser pipe piece, the evaporator flow heating surface is designed so that a compared to a another steam generator tube of the same evaporator flow heating surface multi-heated steam generator tube in comparison to the further steam generator tube higher throughput of the flow medium having. It also affects a steam generator to carry out the procedure.

In a gas and steam turbine plant, the is relaxed Work equipment or heating gas contained in the gas turbine Heat used to generate steam for the steam turbine. The heat transfer takes place in a downstream of the gas turbine Heat recovery steam generator, in which usually a Number of heating surfaces for water preheating, for steam generation and is arranged for steam superheating. The heating surfaces are connected to the water-steam cycle of the steam turbine. The water-steam cycle usually comprises several e.g. three, pressure levels, each pressure level an evaporator heating surface can have.

For the gas turbine as waste heat generator on the hot gas side Downstream steam generators come with several alternatives Design concepts, namely the design as a continuous steam generator or the design as a circulation steam generator. In the case of a once-through steam generator, the heating leads of steam generator tubes provided as evaporator tubes evaporation of the flow medium in the steam generator tubes in a single pass. In contrast to that in the case of a natural or forced circulation steam generator led water during a passage through the evaporator tubes only partially evaporated. The water that has not evaporated is after a separation of the steam generated for a further evaporation fed to the same evaporator tubes again.

In contrast to a natural or forced circulation steam generator, a continuous steam generator is not subject to any pressure limitation, so that for live steam pressures it is far above the critical pressure of water (P _Kri ≈ 221 bar) - where it is not possible to distinguish between the phases of water and steam and therefore no phase separation - can be interpreted. A high live steam pressure promotes high thermal efficiency and thus low CO ₂ emissions from a fossil-fired power plant. In addition, a continuous steam generator has a simple construction in comparison to a circulation steam generator and can therefore be produced with particularly little effort. The use of a steam generator designed according to the continuous flow principle as waste heat steam generator of a gas and steam turbine system is therefore particularly favorable in order to achieve a high overall efficiency of the gas and steam turbine system with a simple construction.

Special advantages in terms of manufacturing effort, but also offers required maintenance work a heat recovery steam generator in a horizontal design, in which the heating medium or heating gas, i.e. the exhaust gas from the gas turbine, in approximately horizontal flow direction the steam generator is guided. At a steam generator in The steam generator tubes of an evaporator heating surface can be constructed horizontally however depending on their positioning one exposed to very different heating. In particular if connected to a common collector on the output side Steam generator tubes of a once-through steam generator can different heating of individual steam generator tubes to merge steam streams with strong from each other deviating steam parameters and therefore undesirable Loss of efficiency, especially compared to a reduced effectiveness of the affected heating surface and one reduced steam generation. A different one Heating of neighboring steam generator tubes can also, especially in the mouth area of collectors Damage to the steam generator pipes or the collector. The desirable use of a lying construction executed continuous steam generator as heat recovery steam generator For a gas turbine this can pose significant problems with regard to a sufficiently stabilized flow guidance entail.

A steam generator is known from EP 0 944 801 B1 is suitable for a layout in horizontal construction and also has the mentioned advantages of a once-through steam generator. This is the evaporator heating surface of the known steam generator connected as a continuous heating surface and such designed that a compared to another steam generator tube same continuous heating surface multi-heated steam generator tube one compared to the other steam generator tube has higher throughput of the flow medium. Under Pass-through heating surface is generally a heating surface to understand the flow for the flow principle is designed. That of the interconnected as a continuous heating surface Flow medium supplied to evaporator heating surface is in a single pass through this continuous heating surface or by a plurality of series connected Continuous heating surface system completely evaporated.

The evaporator heating surface connected as a continuous heating surface of the known steam generator thus shows in the type of flow characteristic a natural circulation evaporator heating surface (Natural circulation characteristic) when different occur Heating individual steam generator tubes a self-stabilizing Behavior that requires no outside influence to equalize the outlet temperatures also on differently heated, fluid medium side steam generator pipes connected in parallel.

In order to be particularly useful in a steam generator of this type low stress due to thermal stresses especially with regard to the water and / or steam side Distribution of the flow medium kept particularly low To achieve manufacturing and assembly costs can Evaporator continuous heating surface of the steam generator in the manner a U-shaped construction from a number of for flow of the flow medium, steam generator tubes connected in parallel be formed, each approximately vertical arranged, through which the flow medium can flow in the downward direction Downpipe piece and this one on the flow medium side downstream, approximately vertically arranged and from Flow medium riser pipe that can be flowed through in the upward direction exhibit. As it turned out, is with one such a construction the flow through the continuous heating surface favorable - flow promoting - pressure contribution about the geodetic pressure in the downpipe section of the respective Steam generator tube located water column usable.

However, such a construction could basically do that Occurrence of flow instabilities when operating the evaporator continuous heating surface favor that too operational Disadvantages. Because of the feeding the the continuous heating surface-forming steam generator tubes with comparatively low mass flow density and through that associated comparatively low loss of friction pressure a natural circulation characteristic of the flow in the steam generator tube achievable, which has a stabilizing effect on the flow. Nevertheless, it is desirable, especially with such Construction with downward flowable pipe section in particularly to stabilize the flow conditions to contribute to the operation of the evaporator continuous heating surface.

The invention is therefore based on the object of a method to operate a steam generator of the type mentioned above, with the one in a comparatively simple way high degree of flow stability when operating the Evaporator flow heating surface is accessible. Furthermore is said to be a particularly suitable one for carrying out the method Steam generators of the type mentioned above can be specified.

With regard to the method, this object is achieved according to the invention solved in that the flow medium of the evaporator flow heating surface is fed such that it is in the downpipe piece a flow velocity of the respective steam generator tube of more than a predetermined minimum speed having.

The invention is based on the consideration that a particularly high flow stability and therefore a special one high level of operational safety for the steam generator The above type is achievable by possible causes consequently suppressed flow instabilities become. As it turned out, it can be seen as one of these possible causes an occurrence of steam bubbles in the Downpipe section of the respective steam generator tube viewed become. If steam bubbles form in the downpipe section should, this could be in the downpipe section located water column and thus a movement perform against the direction of flow of the flow medium. To such a, the flow direction of the flow medium opposite movement of possibly existing Consistently preventing steam bubbles should be done by a suitable specification of the operating parameters a forced Entrainment of the steam bubbles in the actual flow direction of the flow medium can be ensured. This is achievable by feeding the evaporator continuous heating surface with flow medium in a suitable manner, wherein a sufficiently high flow velocity of the flow medium the desired entrainment effect in the steam generator tubes on the possibly existing or emerging Steam bubbles causes.

The flow rate is advantageous of the flow medium in the downpipe section of the respective steam generator pipe set such that in the permissible operating range in any case, take away any that may be present Steam bubbles are guaranteed. This will be advantageous as the minimum velocity for the flow velocity of the flow medium in the downpipe section of the respective Steam generator tube to take the steam bubbles required flow rate, increased if necessary by a suitably chosen safety margin.

The setting of a sufficiently high flow rate of the flow medium in the downpipe section of the respective Steam generator tube is possible in a particularly simple manner, by the flow medium the piece of downpipe of each Steam generator tube in the partially evaporated state and / or with a certain minimum enthalpy is supplied. This will be Flow medium advantageously before it enters the Evaporator continuous heating surface partially pre-evaporated in such a way that it is entering the evaporator once-through heating surface a vapor content and / or an enthalpy of more than one predetermined minimum vapor content or a predetermined minimum enthalpy having.

With regard to the steam generator, the stated task is thereby solved that the evaporator flow heating surface on the flow medium side another evaporator continuous heating surface is connected upstream.

The evaporator system of the steam generator is thus of the type a multi-stage design, the further Evaporator continuous heating surface in the manner of a pre-evaporator for suitable conditioning of the flow medium its entry into the actual evaporator continuous heating surface is provided. The actual evaporator continuous heating surface serves, however, in the manner of a second evaporator stage to complete the evaporation of the flow medium.

The further evaporator once-through heating surface is also expedient taken for a self-stabilizing Flow behavior through consistent use of a natural circulation characteristic designed in the respective steam generator tubes. For this purpose, the further evaporator continuous heating surface includes advantageously a number of to flow through the Flow medium steam generator tubes connected in parallel. It is expediently designed such that a comparison to another steam generator tube of the further evaporator continuous heating surface multi-heated steam generator pipe a higher compared to the other steam generator tube Has flow rate of the flow medium.

In order to achieve the desired effect of consistently taking im Downpipe section of a steam generator tube of the evaporator continuous heating surface possibly existing vapor bubbles reliably the additional evaporator continuous heating surface must be ensured appropriately dimensioned such that in Operation in the downstream evaporator heating surface inflowing flow medium a flow velocity of more than that to take the vapor bubbles required minimum speed.

During the evaporator flow heating surface of the steam generator from the aforementioned, U-shaped steam generator tubes is formed, the further evaporator flow heating surface to avoid disabilities from there possibly existing vapor bubbles expediently from essentially vertically aligned, for the flow through the flow medium steam generator tubes provided from bottom to top educated. In particular, the further evaporator flow heating surface thus exclusively from riser pipe pieces educated.

In such a configuration of the steam generator additional evaporator flow heating surface expediently with a number of outlet collectors arranged above the heating gas duct provided for the flow medium. For a special one simple concept regarding the exit side Homogenization of the further evaporator continuous heating surface outflowing flow medium is the this outlet manifold downstream of the fluid medium advantageously with its longitudinal axis essentially aligned parallel to the heating gas direction.

In such an embodiment, the one that is provided anyway Property of the further evaporator continuous heating surface, namely a self-stabilizing circulation characteristic, consistently used to simplify distribution. Just because of the self-stabilizing circulation characteristics namely now seen in succession in the heating gas direction arranged and thus differently heated steam generator tubes on the output side with approximately the same steam conditions lead to a common outlet collector. In this becomes the flow medium flowing out of the steam generator tubes mixed and for forwarding to a subsequent one Heating surface system without affecting the mixture achieved homogenization. So a separate, downstream of the further continuous heating surface and comparatively complex distribution system is not required.

Included for a comparatively simple design the further evaporator flow heating surface preferably in type of a tube bundle a number of in the direction of the heating gas seen one behind the other pipe layers, each of which seen from a number of side by side in the heating gas direction arranged steam generator tubes is formed. That of the others Evaporator continuous heating surface on the flow medium side subsequent distribution of the flow medium with savings a complex distribution system can be particularly simple be carried out by in a further advantageous embodiment the other evaporator flow heating surface one of the number corresponding to the steam generator pipes in each pipe position Number of with their longitudinal axis substantially parallel to Assigned outlet manifolds to the heating gas direction is. This leads to each outlet collector Steam generator tube of each tube layer. The exit collectors are advantageously arranged above the heating gas duct.

Due to the substantially U-shaped configuration of the Evaporator continuous heating surface forming steam generator tubes is their inflow area in the upper area or above the heating gas duct. With consistent use of the assigned to the further evaporator continuous heating surface, arranged above the heating gas duct and with its longitudinal direction each essentially parallel to the direction of flow of the heating gas aligned outlet collector is there an interconnection of the evaporator flow heating surface with the further evaporator flow heating surface with a particularly small Effort is made possible by the or each exit collector the further evaporator flow heating surface in an advantageous Design with an associated entry collector the downstream of the fluid medium Evaporator continuous heating surface in one structural unit is integrated.

Such an arrangement enables direct overflow from the further evaporator continuous heating surface escaping flow medium in the flow medium side downstream steam generator tubes of the first-mentioned evaporator continuous heating surface. In this arrangement there is one Continuation of the further evaporator continuous heating surface flowing medium into the evaporator flow heating surface almost without affecting the in the outlet collector the further evaporator continuous heating surface by mixing achieved homogenization possible. Elaborate distribution or connecting lines between the outlet header the further continuous heating surface and the inlet collector of the Continuous heating surface and assigned mixing and distribution elements can thus be omitted, and in general the Cable routing comparatively simple.

In a further advantageous embodiment, the steam generator tubes the evaporator flow heating surface on the inlet side in a common, perpendicular to the longitudinal direction of the collector units aligned level at the respective assigned Entry collector connected. By such Arrangement ensures that the partially evaporated, the Flow medium to be supplied to evaporator continuous heating surface, starting from as an outlet collector for the further evaporator continuous heating surface used part of the integrated unit, first against the bottom of the as an entry collector for the evaporator continuous heating surface used part of the constructive Unit bounces, there is again swirled and then with almost the same two-phase proportions in the steam generator tubes connected to the respective inlet header the evaporator flow heating surface flows out. by virtue of seen in the direction of flow of the collector units symmetrical arrangement of the outflow points from the respective Entry collectors are given a particularly homogeneous feed the continuous heating surface with flow medium.

The steam generator is expediently used as a waste heat steam generator a gas and steam turbine plant used. there the steam generator is advantageously one on the hot gas side Downstream gas turbine. This circuit can be used expediently Additional firing to increase the gas turbine the heating gas temperature may be arranged.

The advantages achieved with the invention are in particular in that by the now provided, at least partial pre-evaporation of the flow medium before it enters into the essentially U-shaped steam generator tubes Continuous heating surface formed according to specifiable Criteria a desired vapor content and / or a desired one Enthalpy of the flow medium is adjustable. By a suitable choice of the steam content and / or the enthalpy of the flow medium flowing to the continuous heating surface above a predetermined minimum vapor content and / or one given minimum enthalpy can be sufficient Flow velocity of the flow medium in the downpipe section of the respective steam generator tube of the continuous heating surface be ensured. The flow rate of a Water-steam mixture is namely at the same mass throughput the higher the proportion of steam and thus the higher is the specific volume of the mixture.

The flow rate of the water-steam mixture can in particular be set so high that possibly in the downpipe section of the respective steam generator pipe existing vapor bubbles are reliably carried away and in the riser pipe downstream of the respective downpipe section can be transferred. Even with the U-shaped design the steam generator tubes of the evaporator continuous heating surface is therefore one of the flow direction of the flow medium opposite movement of the vapor bubbles safely excluded, so that a particularly high flow stability and thus a particularly high level of operational security for the steam generator with such an evaporator flow heating surface is guaranteed.

Figur 1

in vereinfachter Darstellung im Längsschnitt die Verdampfersektion eines Dampferzeugers in liegender Bauweise,

Figur 2

den Dampferzeuger nach Figur 1 ausschnittweise in Aufsicht,

Figur 3

den Dampferzeuger nach Figur 1 im Ausschnitt entlang der in Figur 2 dargestellten Schnittlinie,

Figur 4

den Dampferzeuger nach Figur 1 im Ausschnitt entlang der in Figur 2 darstellten Schnittlinie, und

Figur 5

ein Enthalpie- bzw. Strömungsgeschwindigkeits-Massenstromdiagramm.

An embodiment of the invention is explained in more detail with reference to a drawing. In it show:

Figure 1

in a simplified representation in longitudinal section the evaporator section of a steam generator in a horizontal construction,

Figure 2

1 of the steam generator according to FIG. 1 in supervision,

Figure 3

1 in detail along the section line shown in FIG. 2,

Figure 4

the steam generator according to Figure 1 in a section along the section line shown in Figure 2, and

Figure 5

an enthalpy or flow velocity mass flow diagram.

The same parts have the same reference symbols in all the figures Mistake.

The steam generator shown in FIG. 1 with an evaporator section 1 is one in the manner of a heat recovery steam generator Gas turbine, not shown, connected downstream on the exhaust gas side. The steam generator 1 has a surrounding wall 2 which one in an approximately horizontal one, indicated by the arrows 4 Hot gas direction x hot gas duct through which flow 6 forms for the exhaust gas from the gas turbine. In the heating gas duct 6 is a number - in the exemplary embodiment two - from after Flow principle designed evaporator heating surfaces 8, 10 arranged, the for the flow of a flow medium W, D are connected in series.

That formed from the evaporator continuous heating surfaces 8, 10 multi-stage evaporator system is with undevaporated flow medium W acted upon by a single pass the evaporator flow heating surfaces 8, 10 evaporate and after the exit from the evaporator flow heating surface 8 as Steam D removed and usually for further overheating Superheater heating surfaces is supplied. That from the evaporator continuous heating surfaces 8, 10 formed evaporator system is in the water-steam cycle, not shown Steam turbine switched. In addition to this evaporator system are in the water-steam cycle of the steam turbine Number of further heating surfaces, not shown in FIG. 1 which are, for example, superheaters, Medium pressure evaporator, low pressure evaporator and / or can be preheaters.

The evaporator flow heating surface 8 of the steam generator 1 comprises in the manner of a tube bundle a variety of Flow through the flow medium W connected in parallel Steam generator tubes 12. There is a plurality of each Steam generator tubes 12 to form a so-called tube layer arranged next to each other in the direction of the heating gas x, so that in Figure 1 only one of the side by side arranged steam generator tubes 12 of a tube layer visible is. The steam generator tubes arranged side by side in this way 12 is an associated one on the flow medium side Entry collector 14 in front and a common exit collector 16 downstream.

The evaporator continuous heating surface 8 is designed such that they are used for feeding the steam generator tubes 12 comparatively low mass flow density is suitable, wherein the steam generator tubes 12 have a natural circulation characteristic exhibit. With this natural circulation characteristic, an im Comparison to another steam generator tube 12 of the same Evaporator flow heating surface 8 more heated steam generator tube 12 one compared to the other steam generator tube 12 higher throughput of the flow medium W. To do this with particularly simple constructive means on particularly reliable Way, includes the evaporator flow heating surface 8 two in line on the flow medium side switched segments. In the first segment, each steam generator tube comprises 12 of the continuous heating surface 8 approximately vertically arranged, from the flow medium W in the downward direction Flowable downpipe section 20. In the second Each steam generator tube 12 comprises a segment of the downpipe segment Approximately 20 downstream of the fluid medium vertically arranged and from the flow medium W in the upward direction Flowable riser pipe section 22.

The riser pipe piece 22 is associated with it Downpipe piece 20 connected via an overflow piece 24.

Each steam generator tube 12 of the evaporator continuous heating surface 8 has, as can be seen in FIG. 1, an almost U-shaped one Form on, with the legs of the U through the downpipe 20 and the riser pipe 22 and the connecting bend are formed by the overflow piece 24. With one like that designed steam generator tube 12 generates the geodetic Pressure contribution of the flow medium W in the area of the Downpipe section 20 - in contrast to the area of the riser section 22 - a flow promoting and not a flow restricting Pressure contribution. In other words: the one in the downpipe section 20 water column located on unevaporated flow medium W "pushes" the flow of the respective Steam generator tube 12 still on instead of hindering them. As a result, the steam generator tube 12 has one overall comparatively low pressure loss.

With the approximately U-shaped design, each steam generator tube is 12 each in the entry area of his downpipe section 20 and in the outlet area of its riser 22 in the Kind of a suspended construction on the ceiling of the heating gas duct 6 hung or fastened. The lower ends spatially of the respective downpipe piece 20 and the respective riser pipe piece 22, through their overflow piece 24 with each other connected, however, are not directly spatially on Heating gas channel 6 fixed. Elongations of these segments of the Steam generator tubes 12 can thus be tolerated without risk of damage, the respective overflow piece 24 as an expansion curve acts. This arrangement of the steam generator tubes 12 is thus mechanically particularly flexible and with regard to thermal Stresses insensitive to differential expansion.

With the steam generator 1 in a horizontal construction and using the evaporator flow heating surface 8 with essentially However, U-shaped steam generator tubes 12 occur generally in the downpipe 20 of a steam generator tube 12 steam bubbles on. These vapor bubbles could go against the Flow direction of the flow medium W in the respective downpipe section 20 rise and thus the stability of the flow and also hinder the reliable operation of the steam generator 1. To reliably prevent this, the steam generator is 1 for feeding the evaporator continuous heating surface 8 with already partially evaporated flow medium W designed.

In this case, the flow medium D, W is fed into the Evaporator flow heating surface 8 is provided such that the Flow medium D, W in the downpipe section 20 of the respective steam generator tube 12 a flow rate of more than has a predefinable minimum speed. This is again dimensioned such that due to the sufficiently high Flow velocity of the flow medium D, W in each Downpipe piece 20 the vapor bubbles present there reliable in the direction of flow of the flow medium D, W entrained and over the respective overflow piece 24 in the each downstream pipe section 22 are transferred. Maintaining a sufficiently high flow rate for this purpose the flow medium D, W in the downpipe pieces 20 of the steam generator tubes 12 is ensured that the supply of the flow medium D, W in the Evaporator flow heating surface 8 with a sufficient for this high steam content and / or with a sufficiently high level Enthalpy is provided.

To supply the flow medium D, W with suitable for this Parameters in the already partially vaporized state enable, the evaporator flow heating surface 8 of the Steam generator 1 on the flow medium side as a further continuous heating surface the evaporator continuous heating surface 10 upstream. The evaporator continuous heating surface 10 is thus in the Kind of a pre-evaporator designed so that the evaporator system through the further evaporator continuous heating surface 10 and the evaporator flow heating surface connected downstream of this on the flow medium side 8 is formed. The kind of Additional evaporator once-through heating surface provided for the pre-evaporator 10 is spatially colder Area of the heating gas channel 6 and thus on the heating gas side arranged downstream of the evaporator continuous heating surface 8. The Evaporator flow heating surface 8, however, is larger Proximity to the entry area of the heating gas channel 6 for the from the Gas gas flowing out of the gas turbine is arranged and thus during operation a comparatively strong heat input exposed to the heating gas.

The further evaporator continuous heating surface 10 is in turn also by a number of to flow through the flow medium W steam generator tubes 30 connected in parallel educated. The steam generator tubes 30 are with her Longitudinal axis aligned essentially vertically and for one Flow through the flow medium W from a lower inlet area to an upper exit area, i.e. from below upwards, laid out. To also for the further evaporator continuous heating surface 10 in the manner of a self-stabilizing Operating behavior a particularly high stability of the The through-flow heating surface is to ensure flow 10 also designed such that a comparison to another steam generator tube 30 more heated Steam generator tube 30 in comparison to the other steam generator tube 30 has higher throughput of the flow medium W.

To follow the intended concept for that through the evaporator continuous heating surface 8 and through the flow medium side upstream further evaporator continuous heating surface 10 evaporator system formed, namely in the design case the supply to the evaporator flow heating surface 8 with partially pre-evaporated, a sufficiently high Steam content and / or a sufficiently high enthalpy To ensure flow medium D, W, is the further evaporator flow heating surface 10 suitably dimensioned. A suitable choice of material is particularly important and a suitable dimensioning of the steam generator tubes 30, possibly also different from each other, but also a suitable one Positioning of the steam generator tubes 30 relative to one another considered. Especially with regard to these parameters the further evaporator continuous heating surface 10 is dimensioned in such a way that in the operating case that in the downstream Evaporator flow heating surface 8 flowing fluid D, W a flow rate greater than that for taking along existing in the respective downpipe pieces 20 Vapor bubbles have the required minimum speed.

As it turned out, the design is aimed at high operational security achievable to a particular degree, by essentially absorbing heat during operation equal to the evaporator flow heating surface 8 and distributed to the further evaporator once-through heating surface 10 is. The evaporator flow heating surfaces 8, 10 and this forming steam generator tubes 12, 30 are therefore in the embodiment dimensioned such that the total heat input into the evaporator continuous heating surface 8 forming steam generator tubes 12 approximately the heat input into which the further evaporator continuous heating surface 10 forming steam generator tubes 30 corresponds. Considering of the mass flows occurring shows the further evaporator once-through heating surface 10 one in view to the number of steam generator tubes 12 on the flow medium side downstream flow heating surface 8 suitable selected number of steam generator tubes 30.

Which form the further evaporator continuous heating surface 10 Steam generator tubes are for a flow through the flow medium W designed from bottom to top. The further evaporator flow heating surface 10 in the manner of a Pipe bundle a number of consecutively as seen in the heating gas direction x arranged pipe layers 32, each of which one Number of juxtaposed seen in the heating gas direction x Steam generator tubes 30 is formed, and of which only one steam generator tube 30 is visible in FIG. 1 is. The steam generator tubes 30 of each tube layer 32 are included each a common one, with its longitudinal direction essentially aligned perpendicular to the heating gas direction x Entry collector 34 upstream. Entry collectors 34 are in this case only schematically indicated in FIG Water supply system 36 connected, which is a distribution system for the needs-based distribution of the inflow of flow medium W may include the entry collector 34.

On the output side and therefore in an area above the heating gas duct 6 open the further evaporator continuous heating surface 10 forming steam generator tubes 30 in a number of associated exit collectors 38. Each of the essentially outlet collectors arranged parallel to one another and next to one another 38, of which only one is visible in FIG. 1 is, with its longitudinal axis substantially parallel to Hot gas direction x aligned. The number of exit collectors 38 is 30 in the number of steam generator tubes adapted to each tube layer 32.

Each outlet header 38 is an entry header 14 which is the another evaporator flow heating surface 10 on the flow medium side downstream evaporator flow heating surface 8 assigned. Due to the u-shaped design of the evaporator continuous heating surface 8 is the respective entry collector 14 as well as the respective outlet collector 38 above the heating gas channel 6. The fluid medium side-by-side connection the evaporator flow heating surface 8 with the further evaporator continuous heating surface 10 is on particularly easy way possible by each exit collector 38 with the entry collector 14 assigned to it integrated into a structural unit 40. Due to the structural or constructive unit 40 is an immediate overflow of the flow medium W from the further evaporator once-through heating surface 10 in the evaporator continuous heating surface 8, without a comparatively complex distribution or connection system would be required.

As shown in FIG. 2 in a cutout, are the steam generator tubes 30 each two adjacent Pipe layers 32 in a direction perpendicular to the heating gas direction x seen offset from each other, so that regarding the arrangement of the steam generator tubes 30 essentially diamond-shaped basic pattern results. With this arrangement are the outlet collectors 38, of which in FIG. 2 only one is shown, positioned so that in each Outlet collector 38 from each tube layer 32, one each Steam generator pipe 30 opens. It is also recognizable that each exit header 38 with an associated entry header 14 for that of the other evaporator continuous heating surface 10 downstream evaporator heating surfaces 8 is integrated into a structural unit 40.

Figure 2 can also be seen that the evaporator flow heating surface 8 forming steam generator tubes 12 also a number of consecutively seen in the heating gas direction x form lying pipe layers, the in the direction of the heating gas x seen first two pipe layers from the riser pipe pieces 22 of the steam generator tubes 12 are formed, the output side in the outlet header 16 for the vaporized Flow medium D open. The seen in the heating gas direction x The next two pipe layers, however, are from the downpipe pieces 20 of the steam generator tubes 12 formed, the input side connected to an associated entry collector 14 are.

FIG. 3 shows a partial side view of the entry area the steam generator tubes 12 and the outlet area of the steam generator tubes 30 in the respectively assigned structural unit 40, which on the one hand the outlet header 38 for a number of the further evaporator continuous heating surface 10 forming steam generator tubes 30 and the other Entry collector 14 for two of the evaporator continuous heating surface 8 forming steam generator tubes 12 comprises. It is particularly clear from this illustration that flowing out of the steam generator tubes 30 into the outlet header 38 entering flow medium D, W on direct Path in the assigned to the evaporator continuous heating surface 8 Entry collector 14 can overflow. When overflowing of the flow medium D, W initially strikes one Base plate 42 of the structural comprising the inlet header 14 Unit 40. As a result of this impact, swirling takes place and particularly intimate mixing of the flow medium D, W, before this from the entry collector 14 into the Downpipe pieces 20 of the associated steam generator tubes 12 transgresses.

As in the illustration according to FIG. 3, it is also particularly special what is clear is that as an inlet header 14 for the steam generator tubes 12 designed end part of the structural Unit 40 designed such that the outflow of the flow medium W into the steam generator tubes 12 for everyone Steam generator tubes 12 perpendicular from a single plane to the longitudinal direction of the structural unit 40 out. In order to make this possible for two steam generator tubes 12 as well, those with regard to their actual spatial positioning two different, seen in the heating gas direction x pipe layers arranged one behind the other are to be assigned each overflow piece 46 is assigned to each steam generator tube 12. Each overflow piece 46 runs obliquely to Heating gas direction x and connects the upper area of each assigned steam generator tube 12 with the respective Outlet opening 48 of the inlet header 14. By this arrangement can all outlet openings 48 of the inlet collector 14 in a common plane perpendicular to the cylinder axis the structural unit 40 be positioned so that already due to the symmetrical arrangement of the outlet openings 48 in relation to the flow path of the flow medium D, W an even distribution of the in the steam generator tubes 12 entering flow medium D, W guaranteed is.

To further clarify the pipe guides in the area of their Entries into and out of the building unit 40 in FIG. 4 is a number of such structural units 40 shown in front view, the one designated by IV in FIG Cutting line is used. It can be seen that the two structural elements shown on the left in FIG Units 40, which in the area of their entry collectors 14 trained for the downstream steam generator tubes 12 Are shown at the end, each over the overflow pieces 46 the downstream downpipe pieces 20 of the steam generator tubes 12 are connected.

In comparison, the two are shown on the right in FIG structural units 40 each in the area of their as Outlet collector 38 for the steam generator tubes 30 of the others Evaporator continuous heating surface 10 trained front Area shown. The illustration shows that the pipe layers 32 lying one behind the other in the structural unit 40 merging steam generator tubes 30 in simply angled shape introduced into the structural unit 40 are.

The steam generator 1 according to Figure 1 and with the special configurations according to Figures 2 to 4 is special for one safe operation of the evaporator continuous heating surface 8. For this purpose, when the steam generator 1 is operating, it is ensured that that the essentially U-shaped evaporator continuous heating surface 8 with flow medium D, W with a flow rate of more than a given one Minimum speed is applied. This will achieved that in the downpipe pieces 20 of the continuous heating surface 8 forming steam generator tubes existing steam bubbles entrained and in the downstream pipe section 22 are spent. To a sufficiently high one Flow rate in the evaporator flow heating surface 8 flow medium D, W ensure the evaporator flow heating surface is fed 8 using the additional evaporator flow heating surface upstream of this 10 such that that in the evaporator flow heating surface 8 inflowing flow medium D, W is a vapor content or enthalpy of more than one specifiable minimum vapor content or more than a specifiable Has minimum enthalpy. More suitable to comply with this The operating parameters are the evaporator continuous heating surfaces 8,10 designed or dimensioned so that in all Operating points are the steam content or the enthalpy of the flow medium D, W when entering the evaporator continuous heating surface 8 lies above suitably specified characteristic curves, as exemplified in Figures 5a, 5b.

FIGS. 5a, 5b show, in the manner of a family of curves with the operating pressure as a family parameter, the functional dependency of the minimum amount of steam X _{min to be set} or the minimum enthalpy H _{min to be set} as a function of the mass flow density m ˙ selected according to the design. Shown here as curve 70 is the design criterion for an operating pressure of p = 25 bar, whereas curve 72 is provided for an operating pressure of p = 100 bar.

It can be seen from these families of curves, for example, that in partial load operation with a design mass flow density m ˙ of 100 kg / m ² s and an intended operating pressure of p = 100 bar, it should be ensured that the steam content X _min in the flow medium W flowing into the continuous heating surface 8 has a value of at least 25%, preferably about 30%. In an alternative representation of this design criterion, it can also be provided that the enthalpy of the flow medium W flowing to the continuous heating surface 8 should have at least a value of H = 1750 kJ / kg under the mentioned operating conditions. The further continuous heating surface 10, which is designed to comply with these conditions, is dimensioned, i.e., for example, with regard to the type, number and design of the steam generator tubes 30 which form it, taking into account the heat available within the heating gas duct 6, which is designed for its spatial positioning, to these boundary conditions customized.

Claims (13)

Method for operating a steam generator (1) with an evaporator flow-through heating surface (8) arranged in a heating gas channel (6) through which the heating gas channel (x) can flow in an approximately horizontal direction (x) and which has a number of steam generator tubes (12) connected in parallel to flow through a flow medium (W). each comprising an approximately vertically arranged downpipe piece (20) through which the flow medium (W) can flow in the downward direction and an approximately vertically arranged riser pipe piece (22) arranged downstream of this on the flow medium side and through which the flow medium (W) can flow in the upward direction, the evaporator continuous heating surface (8) is designed in such a way that a steam generator pipe (12) which is more heated than a further steam generator pipe (12) of the same evaporator once-through heating surface (8) has a higher throughput of the flow medium (W) compared to the further steam generator pipe (12), characterized in that , the s the flow medium (W) is fed to the evaporator continuous heating surface (8) in such a way that it has a flow velocity of more than a predetermined minimum velocity in the downpipe section (20) of the respective steam generator tube (12). The method of claim 1, wherein the minimum speed to take in the respective downpipe section (20) generated steam bubbles required flow rate is specified. The method of claim 1 or 2, wherein the flow medium (W) before entering the evaporator continuous heating surface (8) is partially pre-evaporated in such a way that when Entry into the evaporator continuous heating surface (8) Vapor content and / or an enthalpy of more than a given one Minimum vapor content or a predetermined minimum enthalpy having. Steam generator (1), in which an evaporator flow heating surface (8) is arranged in a heating gas channel (6) through which an approximately horizontal heating gas direction (x) can flow and which comprises a number of steam generator tubes (12) connected in parallel to flow through a flow medium (W) , each of which has an approximately vertically arranged downpipe piece (20) through which the flow medium (W) can flow in the downward direction and an approximately vertically arranged downpipe piece (22) arranged downstream of this on the flow medium side and through which the flow medium (W) can flow in the upward direction, the evaporator continuous heating surface ( 8) is designed in such a way that a steam generator pipe (12) which is more heated in comparison to a further steam generator pipe (12) of the same evaporator once-through heating surface (8) has a higher throughput of the flow medium (W) compared to the further steam generator pipe (12),
characterized in that a further evaporator flow heating surface (10) is connected upstream of the evaporator flow heating surface (8) on the flow medium side. Steam generator (1) according to claim 4, the further evaporator flow heating surface (10) a number of to flow through a flow medium (W) steam generator tubes connected in parallel (30) comprises and is designed such that a compared to another steam generator tube (30) another evaporator continuous heating surface (10) more heated Steam generator tube (30) compared to the other steam generator tube (30) higher flow rate of the flow medium (W) having. Steam generator (1) according to claim 4 or 5, the other Evaporator continuous heating surface (10) is dimensioned in such a way that in the event of operation, the downstream evaporator heating surface (8) inflowing flow medium (W) a flow rate greater than that to take with you The minimum speed required for the resulting vapor bubbles having. Steam generator (1) according to one of Claims 4 to 6, characterized in that an outlet header (38) connected downstream of the flow generator on the flow medium side of the steam generator pipes (30) of the further evaporator once-through heating surface (10) is aligned with its longitudinal axis essentially parallel to the heating gas direction (x). Steam generator (1) according to one of claims 4 to 7, the further evaporator continuous heating surface (10) a number of Arranged one behind the other as seen in the heating gas direction (x) Pipe layers, each of a number of in Hot gas direction (x) seen side by side steam generator tubes (30) is formed. Steam generator (1) according to claim 8, the further evaporator flow heating surface (10) one of the number of steam generator tubes (30) corresponding number of in each tube layer with its longitudinal axis essentially parallel to the heating gas direction (x) aligned outlet collectors (38) with a steam generator tube in each outlet header (38) (30) each pipe layer opens. Steam generator (1) according to one of claims 7 to 9, in that of the or each outlet collector (38) of the further evaporator once-through heating surface (10) with one assigned to each Inlet collector (14) downstream of the fluid medium Evaporator continuous heating surface (8) in a constructive Unit is integrated. A steam generator (1) according to claim 10, wherein the steam generator pipes (12) the evaporator continuous heating surface (8) in a common, perpendicular to the heating gas direction (x) Level at the entry collector assigned to them (14) are connected. Steam generator (1) according to one of claims 7 to 11, the Outlet collector (38) arranged above the heating gas duct is or are. Steam generator (1) according to one of claims 4 to 12, the a gas turbine is connected upstream of the heating gas.

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