DE1926395A1 - Ventilation device for exhaust steam condensers of steam turbines - Google Patents

Description

Venting device for exhaust steam condensers of steam turbines "Die The invention relates to ventilation devices for exhaust steam condensers of steam turbines, consisting of two pumps connected in series - devices of this type are used to to keep the condensation pressure low in exhaust steam condensers of steam turbines, in order to be able to utilize the greatest possible pressure gradient in the turbine. Limits are drawn by the temperature of the available cooling medium (water or air), the economically feasible exhaust cross-sections of the turbine and the size of the capacitors. In general, turbine systems are used for condensation pressures designed from 0.02 to 0.1 ata.

Through leaks in the turbine glands and through others Air from the atmosphere and possibly other gases enter the condenser and there build up a partial pressure corresponding to their mass. The resulting higher total pressure reduces the pressure available for the turbine and heat gradient and thus leads to a loss of power in the turbine. If with constant power is due to the lower pressure gradient in the turbine has a higher steam requirement and a higher heat content of the steam at the turbine outlet. this in turn also brings a stronger one Loading of the capacitor with itself, resulting in an increase in the mean Expresses temperature difference in the condenser. The resulting higher condensation pressure then results in a higher total pressure with the partial pressure of the air and the gases in the condenser and leads to a further reduction in the amount available for the turbine standing pressure gradient and thus further loss of power in the turbine.

It can be seen from the foregoing that exhaust steam condensers must first be evacuated in order to obtain a low condensation pressure, but then a bleeding device can still be connected during operation must, in order to avoid the increase in the course of operation due to the ingress of air and gases To keep the condensation pressure constant at a low level.

For use as condenser ventilation devices, one and multi-stage steam jet pumps with and without intermediate condenser, single and multi-stage Water jet pumps, positive displacement blowers with gas pump, screw pumps as well Finally, water ring pumps with an upstream gas jet pump or steam jet pump, in the latter case also known with a pulse capacitor.

The choice of one of these pumps is made essentially below the aspects of operational safety, suction capacity and the work area. A depending on the amount of steam to be condensed is assumed Mass of penetrating air run out. According to a rule that has been in common practice for a long time It is then a matter of consistently having such a large volume of steam-air mixture from the condenser a «to suck, that the initial pressure of the air is constant at the equivalent of 3 or 40 C cooling of the steam is kept below the saturated steam temperature corresponding to the total pressure will. The pump types specified above can be designed accordingly for this purpose Use with a satisfactory result so far, but no one has said it so far has thought, -whether the usual rule of thumb also affects the efficiency of the entire, the turbine enclosing unit optimized.

It is the object of the present invention to provide a ventilation device To create the type mentioned at the beginning, which may be more expensive in itself is than the previously known devices with the usual capacity, related with the steam turbine, however, represents the technically and economically optimal unit.

The object of the invention is achieved in that the first Phmpenstufe of the ventilation device is formed by a centrifugal compressor. This construction has the advantage that it has a much lower specific energy requirement (KW / m3 / min) than the currently known systems and that if one considers the general Common rule of thumb for condenser venting performance discarded and for the first time by minimizing the total power losses of the turbine as a result of higher Condensation pressure and the ventilation device as a result of its energy requirements - allows by far the best overall efficiency. The capacity of the known ventilation systems would have to under the pressure, not the part, but the total loss if possible to keep small, are increased so that now also their power requirements is much higher than with venting devices with a centrifugal compressor in the first stage.

The suction capacity of the ventilation device proposed according to the invention should be determined according to the formula developed below To According to Dalton's law, the partial air pressure in the condenser is: PL = ML # RL # TL where: Mg = mass of air VL in kg / min RL = the gas constant for air in mkg / kg ° = = temperature of the air in kelvin VL = volume of the air in m3 / min.

The annual cost of turbine power losses as a result of Partial pressure of the air are: KV = #T # NT ML # RL # TL: xd (in DM / year) VL where mean: NT: the turbine power in kw #T = the specific power loss of the turbine in kw # m2 / kg # kw xd = the specific power loss costs in DM / kw Year.

The investment costs of the ventilation device are as follows Formula described: IE = VL # f (in DM) with f = contemporary factor for the ratio between capacity and acquisition costs in DM / m5 / min.

The annual costs of the ventilation device are KI = IE (a + w) (in DM / year) where: a = the depreciation in% / year w = the maintenance costs in% / year.

The costs of the energy consumption of the ventilation device must also be taken into account. They are KB = VL. #E Xe (in DM / year) which means: #E = the specific energy consumption / volume unit in kw / min / m3, Xe = the specific power loss costs of the ventilation device in DM / kW year The total annual costs KT of the ventilation device are: KT = KI + KB = IE # (a + w) + VL # #E # xe KT = Vt. f. (a + w) + 9E JE Xe (in DM / year) The suction capacity of the ventilation device is optimally selected when the sum of Kv + Km is a minimum: dK #T # NT # ML # RL # TL # xd = - + f (a + w) + #E # xe dVL VI2 K is a minimum at 3 = 0 This results in the optimal suction capacity of the ventilation device: This formula can be expanded to include the influence of the partial pressure of the air on the performance of the turbine as a result of the increase in the mean temperature difference in the condenser.

As can be seen from the above calculation, is with the optimal Design with a lower specific power requirement çE a greater suction capacity assigned what, according to Dalton's law first mentioned, leads to a lower one partial air pressure leads, so that a higher reduction in power loss results.

An embodiment of the invention is in the accompanying drawing shown. For a more detailed explanation, reference is made to it below.

According to the drawing, the exhaust steam from a steam turbine flows to a condenser 1, from which the condensate is derived. To the partial pressure of air and gases that have penetrated into the condenser on the calculated value To keep the level at a low level, a mist eliminator 2 steam / air mixture sucked off by a centrifugal compressor 3 from the condenser, compressed and Required in an intercooler 6. D.r centrifugal compressor 3 is used in Example case driven by an electric motor 5 via a gear 4.

In the intercooler 6, the extracted steam-air mixture, which is overheated as a result of the compression, cooled, with a large part of the water vapor condenses, so that the volume is greatly reduced. Now all you need is this relatively small volume through the second pump stage, which in the exemplary embodiment consists of the combination of an air jet 7 with a water ring pump 8, to be sucked off and compressed to atmospheric pressure. Let it be at this point emphasized that intermediate capacitors so far only in ventilation devices with a Steam jet pump are known in the first stage. There they have the purpose to condense steam used as a propellant. In the present case, however the vapor extracted from the condenser 1 largely condenses, so that the capacity the second pump stage can be kept correspondingly small.

A water separator 9 is connected to the water ring pump 8, in which the extracted air separates from the sealing water of the water ring pump and escapes into the atmosphere.

The condensate from the intercooler 6 is via a baro-6a metric Downpipevabgesaugt and from the water ring pump 8 together with the condensate of the Steam that reaches the air jet 7 in the water ring pump, in the water separator 9 promoted and shined there by an overflow.

As cooling water for the intercooler 6 and another cooler 10 for the sealing water of the water ring pump 8 is expediently condensate the turbine condenser 1 used, which by means of a centrifugal pump 21 is fed to the two coolers. In this way it can be part of the Recover heat.

The inventive provided centrifugal compressor 3 is with a Suction pressure control system, which consists of a power consumption remote transmitter 12, a power consumption regulator 13 and a power consumption regulating valve 14.

This allows the suction pressure of the centrifugal compressor 3 to be regulated in such a way that that the maximum power consumption of his drive motor 5 even at higher Pressure in capacitor 1 is not exceeded.

The centrifugal compressor 3 is also equipped with a bypass control system equipped, which consists of a suction pressure remote transmitter 15, a delivery pressure remote transmitter 16, a ratio calculator 17, a bypass controller 18 (setpoint input) and in sequence working valves, namely a bypass control valve 19 and an intermediate pressure control valve 20 exists.

This control loop is used to adjust the pressure ratio between the input and to keep the output pressure of the centrifugal compressor 3 constant, with control valve 19 the return line of compressed steam-air mixture from the outlet to the inlet side of the centrifugal compressor 3 and the control valve 20 through the coolant circuit regulates the intercooler 6 and the coolant lines 6b and 6c and thus over the cooling influences the pressure on the outlet side.

Between the condenser 1 and the droplet separator 2 was a pipe arranged through which the separated liquid enters the condenser 1 can flow back.

The ventilation system proposed according to the invention can preferably also for the pre-evacuation of the condenser 1, namely the venting from atmospheric pressure on the operating pressure prior to the start-up of the turbine, where before switching on the centrifugal compressor s with the help of the compressor of the second Pump stage the pressure initially to the maximum permissible suction pressure the centrifugal compressor is brought.

In order to reduce the time required for pre-evacuation, the An auxiliary pump 11 is provided as an exemplary embodiment of the system. she works in parallel to do the second stage compressor and is activated after reaching the operating pressure switched off in capacitor 1. As such auxiliary pumps, water ring pumps, water jet pumps, Steam jet pumps etc.

can be used.

A temporal shortening of the pre-evacuation can be done with a ventilation device can be achieved according to the invention without the use of an auxiliary pump when the Centrifugal compressor including gearbox and motor for greater performance as required for normal operation, so that the centrifugal compressor pump to atmospheric pressure in one stage, i.e. without using the second pump stage can. The suction pressure control system sets the pressure at the compressor inlet to a value that inevitably results from the delivery pressure (= atmospheric pressure) and the compression ratio (with a compression ratio of 1: 3 the suction pressure is 760/3 = 255 Torr).

This suction pressure also corresponds to the maximum that can be achieved in one stage Pressure in the condenser. Before this pressure is reached, the second pump stage is activated switched on. ts In the case of the last-mentioned system, the arrangement is one thing not valve shown on the exhaust pipe of the centrifugal compressor that the pumped Allows air to escape into the atmosphere. After switching on the second stage, this valve closed. The Bzpass control system has the required pressure ratio upright.

In order to avoid excessively high temperatures when the bypass valve is open Return of the conveyed and heated air to the entry To avoid the centrifugal compressor, deviating from the illustrated embodiment the air via the bypass control valve into condenser 1 (not into the connection line between condenser 1 and mist eliminator 2) are returned so that they can cool there.

Finally, a calculation example is given which illustrates how small the capacity of the second pump stage in the system according to the invention can be measured: A steam-air mixture of 100kg / h is assumed Steam and 2.5kg / h of air at a total pressure of 300kg / m2 and a temperature of 23 ° C at the inlet of the centrifugal compressor has a volume of: MD # RD # T ML # RL # T VG = + PG PG 100 # 42.06 # 296 2.5 # 29.27 # 296 = = 78.5 m3 / min, 60 # 300 60 # 300 The indices used in the general formula mean: G = total D = steam L = air In the centrifugal compressor there should then be a compression in the ratio 1: 3 take place with subsequent cooling in the intercooler to 300 C. The total pressure PG is then PG = 3 # 300 = 900kg / m in the intercooler and the Partial pressure of the air PL is calculated as the difference to PL = PG - PD300 C PL = 900 - 430 = 470kg / m2.

This means that the total volume calculated from the air fraction becomes which From the intercooler 6 to the second pump stage, VG = ML flows. RL. U = 2.5 @ 29.27 @ 303 = 0.8 m @ / min.

PL 60 # 470 Due to this considerable volume reduction (from 78.5 to 0.8 m3 / min), the compressor of the second stage can be small and therefore energy-saving to get voted.

Expectations /

Claims (8)

Claims 1. Ventilation device for exhaust steam condensers of steam turbines, Consists of two pumps connected one behind the other, which is not possible notices that the first pump stage is operated by a centrifugal compressor (3) is formed and between the first and the second pump stage in known per se Way an intermediate capacitor (6) is arranged. 2. Ventilation device according to claim 1, d a d u r c h g e k e n n z e i c h e t that the second pump stage by a water ring compressor (8) is formed with an air jet (7). 3. Ventilation device according to claim 1 or 2, d a -d u r c h g e k It is noted that the centrifugal compressor (3) has a suction pressure control system (12, 13, 14) is equipped, whereby the suction pressure can be regulated such that the permissible power consumption of the drive motor (5) is not exceeded. 4. Ventilation device according to claim 1, 2 or 3, d a -d u r c h g e It is not possible to say that the centrifugal compressor (3) has a pressure ratio Equipped with a constant bypass control system (15 to 20) between inlet and outlet is. 5. Ventilation device according to one or more of the preceding claims, D a d u r c h e k e n n n z e i chn e t that the centrifugal compressor (3) by Choice of a suitably powerful drive motor designed as a pre-evacuation device is, the second pump stage is short-circuited and that in the capacitor (1) vacuum created by the centrifugal compressor's maximum compression ratio (3) is determined. 6. Ventilation device according to one or more of the preceding claims, d a d u r c h e k e n n n z e i c h -n e t that for use as a pre-evacuation device two compressors (7, 8 and 11) are connected in parallel in the second pump stage, one of which can be switched off automatically if the other one does the necessary Maintain intermediate pressure between the first and second pump stage in is able to. 7. Ventilation device according to one or more of the preceding claims, dadurchgekennzeic hn et that the centrifugal compressor has a suction capacity where: = = the specific power loss of the turbine in kw # m2 / kg # kw NT = the turbine power in kw ML = mass of the air in kg / min. RL = the gas constant for air in mkg / kg ° TL = temperature of the air in ° Kelvin Xd = the specific DM / kW # year f = contemporary factor for the ratio between capacity and acquisition costs in DM / m3 / min. a = the depreciation in% / year w = the maintenance costs in% / year #E = the specific energy consumption / volume unit in kw / min / m3 xe = the specific Power loss costs of the ventilation device in DM / kw year. 8. Ventilation device according to claim 7, d a d u r c h g e k e n n z e i c h e t that the suction capacity (VL) of the centrifugal compressor (3) also after the temperature increase caused by the partial pressure of the air in the condenser (1) certainly.