WO2012041649A2

WO2012041649A2 - Steam turbine with reheating

Info

Publication number: WO2012041649A2
Application number: PCT/EP2011/065283
Authority: WO
Inventors: Richard Geist
Original assignee: Siemens Aktiengesellschaft
Priority date: 2010-09-29
Filing date: 2011-09-05
Publication date: 2012-04-05
Also published as: EP2606205B1; DE102010041627A1; EP2606205A2; WO2012041649A3

Abstract

The invention relates to a steam turbine comprising at least one high-pressure part (1) and at least one low-pressure part (2), wherein at least one control valve (3) is arranged between the high-pressure part (1) and the low-pressure part (2). The control valve (3) can be made to move, preferably infinitely variably, between two end positions, wherein, in a first end position of the control valve, the volumetric steam flow V can be fed via the at least one control valve (3) completely to the low-pressure part (2), in a second end position the entire volumetric steam flow V can be fed initially to a reheater (4) and, in at least one further switching position that is located between the first and second positions, a first partial volumetric flow can be fed to the reheater (4) and a second partial volumetric flow can be fed to the low-pressure part (2) without reheating. The invention also comprises a method for controlling the moisture content on entry into the low-pressure part (2) of a steam turbine, wherein the turbine comprises a switchable control valve (3).

Description

description

Steam turbine with reheating The invention relates to a steam turbine according to the preamble of claim 1 and a method for controlling the moisture content of a steam turbine according to the preamble of Pa ^¬ tentanspruchs 5. Conventional steam turbines have at least one high-pressure section and a low pressure part. With the low-pressure part, the temperature of the steam drops very sharply, resulting in partial condensation of the steam. However, the low-pressure part is very sensitive to the moisture content of the steam. Reaches the vapor in the low pressure part of the turbine ei ^¬ ne wetness of approximately 8 to 10 percent, measures to ergrei ^¬ fen, which reduce the moisture content of the steam prior to entering the low pressure part to an acceptable level is. Usual ^¬ example, the steam is supplied for this purpose before entering the low-pressure part of a reheatening. In the reheat, the steam is heated, so that the moisture content decreases. In this reheating of the vapor mass flow to the high pressure part of the turbine is taken ^¬ ent, the reheat fed and raised to approximately the temperature of the live steam. Subsequently, the steam is then fed to the low-pressure part. Without a sol ^¬ che reheat steam turbine would have to be stopped because condensed water droplets may impinge on the rotating turbine blades and thus would cause damage to the turbine.

Especially for turbines with widely fluctuating steam parameters, such as in biomass or solar applications, the wetness in the steam causes great problems. However, the supply of the entire steam volume flow for reheating and the heating of the entire steam flow rate lead to a significant reduction in the efficiency of the steam turbine ^¬ . Starting from the prior art, it is therefore an object of He ^¬ invention to provide a steam turbine, in which the wet content is limited in an energetically advantageous manner when entering the low pressure part of the steam turbine to an acceptable level. It is another object of the present invention to provide a method for operating such a steam turbine.

The object is achieved with respect to the steam turbine by the features of independent claim 1. ^¬ Lich respect of the process for controlling the moisture content in a ^¬ enters the low-pressure part of the steam turbine, the Aufga be ^¬ is solved by the features of the independent claim. 5 Further advantages of the invention, which can be combined individually or in combination, are the subject of the subclaims.

The steam turbine according to the invention with at least one high-pressure section and at least one low-pressure part, wherein Zvi ^¬ rule, a control valve is arranged the high pressure part and the low pressure part at least, is characterized in that the control valve between two end positions is movable and wherein

- in the first end position of the control valve of the steam flow through the valve ^¬ a rule be fed the low pressure part completely at least

- In the second end position, the total steam flow is first fed to a reheat and - in at least one other switching position, which is located between the first and second end position, a first partial volume flow of the reheat is supplied and a second partial volume flow without reheat the low pressure part can be fed.

Compared to the prior art, the steam turbine is improved to the effect that by the control valve and its design no longer the entire steam flow rate must be supplied to the intermediate overheating when reaching a certain moisture content, but that only a partial volume flow is removed and this is the intermediate superheating is supplied. Subsequently, the temporarily heated partial volume flow is fed together with the remaining steam volume flow to the low-pressure part of the steam turbine.

Due to the reheating of the partial volume flow, the total volume flow is brought to a permissible moisture content. However, only a comparatively low energy is needed to heat the partial volume flow. Thus the invention ^shown SSE steam turbine provides an energetically more favorable operation. Advantageously, the control valve can be infinitely adjusted between the first and the second end position, so that the partial volume flow supplied to the reheat can be selected steplessly.

Is According to the invention that is formed at least one Regelven ^¬ til than inboard control valve. As a result, the internal control valves that have been the volume flow between the high pressure and low pressure part of the

Steam turbine regulate, be used and need only be provided with the appropriate supply and discharge lines for reheating. The internal control valves also have the advantage that they can be accommodated very space-saving in the housing of the steam turbine.

A further advantageous embodiment of the invention provides that the steam volume flow, which is supplied to the intermediate overheating, is dependent on the moisture and / or the temperature of the steam after the high-pressure part. It is as described previously necessary that the Nässege holding does not exceed ^¬ the steam before entering the low-pressure part of a permissible value. This value is übli ^¬ cherweise at a moisture content of 8 to 10 percent. The wetness describes the water content, ie in the steam. To ensure that this does not exceed the permissible value, the moisture content is preferably at the outlet of the high-pressure part by measuring the temperature and / or Moisture content determined by itself. The measurement after the high ^¬ pressure part does not mean that necessarily must be measured directly at the outlet of the high pressure part, but only that the measurement between the end of the high pressure part and the supply must be made for reheating, so that a corresponding partial volume flow of the reheat can be supplied. The control valve can preferably be connected to a Re ^¬ geleinheit, which makes a corresponding adjustment of the Re ^¬ gelventils due to the measured temperature and / or humidity, so that the necessary partial volume flow of the reheatening is supplied.

A further advantageous embodiment of the invention provides that the steam, which is supplied to the reheat, is heated to a temperature at which the moisture in the steam is lowered to a value permissible for the low-pressure part. Conveniently, the steam is not heated above this level, otherwise more energy is consumed for reheat than is necessary. This would the efficiency of the steam turbine unnecessarily verschlech ^¬ ter.

The inventive method for controlling the moisture content on entering the low-pressure part of a steam turbine where ^¬ particular includes a switchable control valve in the steam turbine, is characterized by the following steps:

Determination of the moisture content and / or the temperature of the steam after the high-pressure part,

if a predetermined moisture content of the steam is exceeded and / or falls below a predetermined steam temperature, removal, at least one partial volume flow,

- heating of the extracted partial volume flow to a front ^¬ certain moisture and / or temperature, and

- Supplying the entire steam flow to the low pressure part of the steam turbine. The method thus differs from the prior art in that really only the necessary partial volume flow of the reheat is supplied and not as previously the total steam volume flow. By removing a previously determined partial volume flow, a particularly efficient operation of the steam turbine can be ensured. As a result, the efficiency of the steam turbine over the prior art is significantly improved. Further advantages and embodiment of the invention will be described below with reference to FIGS.

It shows:

Figure 1 is a circuit diagram of a steam turbine according to the invention;

Figure 2 is a sectional view of the steam turbine according to the invention in operation without reheat and

Figure 3 is a sectional view of the turbine according to the invention during operation with reheat.

The figures each show highly simplified representations of the invention, in which only the essential components of the invention are shown. Identical or functionally identical components are all figures with the same reference numerals ^¬.

Figure 1 shows schematically the block diagram of a steam turbine according to the invention. The steam turbine comprises at least one high-pressure part 1 and one low-pressure part 2. The live steam initially flows via an inlet valve 5 into the high-pressure part 1 of the steam turbine. Here, the un ^¬ ter high pressure and high temperature is standing steam relaxes and is expanded to a lower pressure and a nied- complicated temperature steam is then passed to the low pressure part 2 of the steam turbine where it is further expanded and thereby further to temperature and pressure loses. Between the high-pressure part 1 and the low-pressure part 2 is a control valve 3 is arranged, which is preferably infinitely movable between two ^¬ end positions. In the first end position of the control valve 3, the control valve 3 is fully ^¬ constantly open, whereby the entire steam flow V from the high-pressure part 2 is completely supplied via the control valve 3 to the Never ^¬ derdruckteil 2. In its second end position, the control valve 3 is completely closed, so that the entire steam volume flow V is guided by the high-pressure part 1 via a reheat 4, where it is heated and then fed to the low-pressure part 2. In the interim ^¬ rule overheating 4 is essentially a heat exchanger. By heating the steam volume flow V, the moisture in the steam volume flow V is reduced. Too high a degree of humidity, ie an excessively high water content in the steam volume flow V, would otherwise lead to the formation of individual drops of water which would impinge on the turbine blades rotating at high peripheral speed in the low-pressure part 2 and lead to severe erosion damage to the turbine blade there. In addition to the two end positions of the control valve 3 can be moved continuously between these two Endpo ^¬ sitions. In this case, depending on the position of the control valve 3, a more or less large vapor volume flow V _{z is conducted} via the reheat 4 and the remaining vapor volume flow Vo is added directly to the low-pressure part 2 via the control valve 3. Preferably, the Teilvolu ^¬ menstrum V _z is chosen only as large as necessary to achieve a certain moisture content of the total volume flow V at the entrance of the low pressure part 2. Characterized that only a partial volume flow V _z of the Zwischenüber- overheating 4 is supplied, the result is an energetically günsti ^¬ ger operation of the steam turbine. A heating of the total steam flow V as this is still necessary, can be omitted. The vapor volume flow V _z, which rule overheating of the intermediate 4 is supplied, is dependent on the moisture and / or temperature of the steam to the high pressure part 1. A moisture content of 8 to 10 percent should not be exceeded in the re ^¬ gel. The regulation takes place so that the control valve 3 is more or less open, depending on the moisture content and / or the tempering temperature ^¬ and so a more or less large part of the volume flow V _z reheat 4 is added. The steam, which is supplied to the reheat 4, is doing to a

Heated temperature at which the moisture of the total Dampfvolu ^¬ menstromes V is lowered to a permissible for the low pressure part 2 value. The crucial factor is not the Nässege ^¬ halt in the partial volume flow V _z but in the total volume flow V. This must not exceed an allowable moisture content. Although it is expedient to design the steam turbine so that the control valve 3 between the two end positions described above is movable, and thus allows complete flow of the entire steam flow V either via the intermediate overheating 4 or directly via the control valve 3 in the low pressure part 2 of the steam turbine , The Ge ^¬ thanks of the invention is not abandoned by the fact that a steam turbine is designed such that constantly a min ^¬ least amount of steam flows through the reheate 4.

Next, the method for controlling the moisture content on entering the low-pressure part of the steam turbine 2 ge ^¬ shows to be short on the basis of the shown in Figure 1 block diagram. To control the moisture content on entering the low-pressure part of the steam turbine 2, it is initially not ^¬ agile, to determine the moisture content and / or the temperature of the steam to the high pressure part. 1 The determination of the moisture content or the temperature must be carried out before the control ^¬ valve 3, so as to be able to initiate suitable steps NEN to reduce the moisture content or to increase the steam temperature.

If it is determined in the determination of the moisture content and / or the Tempe ^¬ temperature of the vapor after the high-pressure section 1, that the moisture content or the temperature of the steam is too high to low, so that a risk of drop impingement erosion is given, a part of the vapor flow rate V removed and the reheate 4 supplied. The to be removed Partial volume flow V _z depends on the wetness content and / or the temperature of the steam after the high-pressure part 1. The partial volume flow V _z , which is the reheate 4 supplied, is set via the control valve 3. If the control valve 3 is moved in the closing direction, there is a stronger throttling on the control valve 3, whereby more Dampfvolu ^¬ menstrom V _{z flows} through the reheater 4. Opening the control valve 3 ensures that a higher partial volume flow Vo flows via the control valve 3 directly into the low-pressure part 2 of the steam turbine. The partial volume flows Vo and V _z, before being supplied to the low pressure part 2 together quantitative ^¬ leads and blend, resulting in a homogeneous vapor flow rate V is obtained. Figure 2 shows an axial section through a steam turbine with a high-pressure part 1 and a low-pressure part 2. The Never ^¬ derdruckteil 2 is formed in three stages. Based on the figure 2, the vapor flow V is to be displayed at fully open control valve 3. The steam volume flow V first enters via an inlet valve 5 and the Einströmge ^¬ housing the steam turbine in the high pressure part 1 of the steam turbine ^¬ ne and is initially relaxed there. The thus relaxed steam leaves the high pressure part 2 and flows through the control ^¬ valve 3, which is formed in the embodiment as an internal control gel.

In Figure 2, the control valve 3 is in a first end position in which it is fully open. As a result, it represents only a very low flow resistance, so that the entire steam flow V flows completely through the control valve 3, directly into the low-pressure part 2 of the steam turbine ^¬ and relaxed to the ambient pressure or a slight negative pressure and then the Nie ^¬ derdruckteil 2 leaves.

The control valve 3 is always one of its first end position, ie in the fully open position, when coming from the high pressure part 1 steam flow V a permissible value in terms of its wetness and / or temperature. If the permissible temperature is exceeded or the permissible moisture content of the steam is exceeded, the control valve 3 is closed more or less strongly.

If the control valve 3 is completely closed, i. if it is in its second end position, then the entire volume flow V is fed to a reheate 4. This case is shown in more detail in FIG.

FIG. 3 shows the steam turbine shown in FIG. In this setting, the control valve 3 is completely ge ^¬ closed so that all of the vapor volume flow V of the reheat 4 is supplied and is heated there.

As a result of the heating, the moisture content in the steam is reduced to a permissible value and the steam is then supplied to the low-pressure part 2.

Between the first end position (FIG. 2) and the second end position (FIG. 3) there are preferably any number of intermediate positions in which a partial volume flow Vo of the steam is added directly to the low-pressure part 2 via the control valve 3 and a second partial volume flow V _z via the intermediate superheating 4 is first heated and then the low pressure part 3 of the steam turbine is added. The two partial volume flows Vo / V _z are mixed in the inner casing of the steam turbine and enter as a total volume flow V in the low-pressure part 2 a. In the inventive steam turbine does not need as previously the case, the entire flow of a reheat be added if the moisture content exceeds a permissible value in the volume flow or the permissible steam Tempe ^¬ temperature is not reached. Rather, it is sufficient to divert a partial volume flow from the volume flow and merely supply it to reheating and then reassemble the two partial volume flows so that the total volume flow allows permissible values with regard to the wetness flow. reached and the temperature reached before it is passed into the low pressure part of the steam turbine. By Teilent ^¬ measure the steam flow rate increase the efficiency and efficiency of the steam turbine significantly over the prior art.

The steam turbine according to the invention is very productive ago ^¬ parts in applications with widely fluctuating steam parameters, such as the case of biomass or solar application. The moisture content or the temperature of the steam can be adjusted by the fiction, ^¬ modern steam turbine very quickly to a permissible value.

Claims

claims

Steam turbine with at least one high-pressure part (1) and at least one low-pressure part (2), wherein at least one control valve (3) is arranged between the high-pressure part (1) and the low-pressure part (2),

characterized in that

the control valve (3) is movable between two end positions and wherein

in the first end position of the control valve (3) of

In the second end position, the entire steam volume flow is initially supplied to a reheat (4) and in at least one further switching position, which is located between the first and the second end position , a first partial volume flow of the reheat (4) can be supplied and a second partial volume flow without reheating the low pressure part (2) can be fed.

2. Steam turbine according to claim 1,

characterized in that

the at least one control valve (3) is designed as inboard Re ^¬ gelventil.

3. Steam turbine according to claim 1 or 2,

characterized in that

the steam volume flow which is supplied to the reheat (4) depends on the wetness and / or the temperature of the steam after the high-pressure part (1).

4. Steam turbine according to one of the preceding claims,

characterized in that

the steam supplied to the reheat (4) is heated to a temperature at which the moisture is lowered in the steam to a value permissible for the low-pressure part (2). Method for controlling the moisture content when entering the low-pressure part (2) of a steam turbine, wherein the steam turbine in particular comprises a switchable control valve (3) according to one of the preceding claims,

characterized by the following steps:

Determination of the moisture content and / or the temperature of the steam after the high-pressure part (1),

when exceeding a predetermined moisture content of the steam and / or falls below a predetermined steam temperature removal, at least a portion of the steam ^¬ volume flow,

heating the extracted steam volume flow to a predetermined humidity and / or temperature,

Supplying the steam volume flow to the low-pressure part (2) of the steam turbine.