RU2715073C1 - Combined cycle gas turbine with cooled diffuser - Google Patents

Abstract

FIELD: heat power engineering.

SUBSTANCE: invention relates to heat engineering and can be used in power gas-steam units of binary type. Combined cycle gas turbine comprises gas turbine plant with outlet diffuser of optimum geometry, steam waste heat boiler, in gas duct of which there are steam generating circuits of two pressures, containing economizing and evaporation surfaces of two pressures and high pressure steam superheater, steam turbine plant with a condenser and two steam turbines, the first of which at the steam inlet is communicated with the steam high-pressure steam superheater output by steam, at the steam output is connected to the second turbine inlet by steam, second steam turbine at steam outlet is communicated with inlet of two condensers communicated at condensate outlet with heat recovery boiler input by condensate, intermediate superheater of low pressure communicated at steam inlet with outlet of drum-separator of low pressure, communicated at outlet by steam with steam turbine second input, wherein the steam superheater is in form of a steam-gas recuperator arranged on the surface of the outlet diffuser of the gas turbine, and is communicated at the inlet to the heating gases, respectively, with the gases output from the gas turbine and at the outlet to the gas inlet into the main gas duct of the heat recovery boiler.

EFFECT: invention reduces heat loss to the environment through the diffuser surface, provides ease of outer coating of the outlet diffuser by heat insulation, allows to increase total heat drop actuated in steam turbines due to reduction of pressure losses in diffuser path and intermediate steam superheater circuit.

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Description

The invention relates to a power system and can be used in binary-type power gas-steam units (GPU) containing gas turbine units (GTU) with waste-heat boilers (KU) and steam turbines, which, as you know, can improve the efficiency power plants up to 60 ... 65% instead of 33 ... 38%. The invention is applicable to cases of both horizontal and vertical location of the KU. The greatest effect can be obtained from the implementation of the invention in binary gas turbines with medium-capacity gas turbines, with a gas temperature at the outlet of 500 - 650 ° C.

A combined cycle plant contains a gas turbine unit with an outlet cooled diffuser, a steam recovery boiler, a steam turbine unit (PTU) with a condenser (K), and two steam turbines (PT). In the KU gas duct, steam generating circuits of two pressures are located, containing economizing and evaporating surfaces of two pressures and a superheater of high pressure steam (HP). The first ПТ at the steam input is communicated with the output of the steam superheater in pairs, at the output in pairs it is communicated with the input of the second PT in a couple. The second PT at the pair output is communicated with the input of a pair of capacitor, communicated at the output of the condensate with the input of the condensate condensate. An intermediate superheater of low pressure steam (ND) is communicated at the steam inlet with the output of the low pressure drum-separator, and at the steam outlet - with the second inlet of the steam inlet. Steam superheater n.d. made in the form of a gas-vapor recuperator located on the surface of the outlet diffuser GT, and communicated at the inlet for heating gases, respectively, with the outlet of gases from the GT, and at the outlet for heating gases, with their entrance to the main gas duct KU. The invention provides a reduction in heat loss to the environment through the surface of the diffuser. It allows you to replace the internal thermal insulation of the surface of the diffuser with a much cheaper and more technologically advanced external insulation coating of the surface of the output diffuser. The invention increases the total heat loss triggered in steam and gas turbines by reducing heat and pressure losses in the paths of the diffuser and the intermediate superheater.

The well-known “binary combined-cycle plant”, [Patent RU No. 156586 published 10.11.2015], containing an air compressor connected through a high-pressure combustion chamber to a high-pressure gas turbine, the high-pressure gas turbine, in turn, is connected to a low-pressure gas turbine, a low pressure gas turbine is connected to the recovery boiler using a diffuser. The combustion products passing through the waste heat boiler enter the economizer, to which feed water is supplied through the water supply from the feed pump, and steam is discharged to the low pressure steam generator through the steam pipe. The feed pump is connected to the deaerator by a water supply, to which, on the one hand, the main and secondary condensate are supplied from the low-pressure heater via the water supply, and, on the other hand, steam is supplied from the steam turbine outlets through the water supply. From the steam turbine, steam through the outlet pipe enters the condenser and through the condensate pump through the water pipe enters the low-pressure heater and then to the deaerator and feed pump. Between the gas turbines of high and low pressure, an additional superheater and a low-pressure combustion chamber are additionally installed. The pressure superheater is connected to the recovery boiler and the steam turbine on the cold side, with a high pressure gas turbine and a low pressure combustion chamber on the hot side. The low pressure combustion chamber, in turn, is connected to a pressure superheater and a low pressure gas turbine.

The well-known "Combined-cycle plant" [Patent RU No. 2561780, 09/10/2015], comprising a gas turbine unit connected by a gas duct to a recovery boiler, which is equipped with a gas duct for exhausting gases into the chimney, and into which are connected interconnected heating surfaces of the economizer, evaporator and a superheater, which is connected by a steam line to a high pressure steam turbine, the first recuperator being connected by a steam line to a condenser-evaporator, which is connected by a water line to the first pump, and a low pressure steam turbine by one steam it is connected by a wire through the first recuperator to a condenser-evaporator, and to another through a second recuperator to a condenser, which is connected to a second recuperator through a second pump, characterized in that the heating boiler is additionally equipped with heating surfaces of an intermediate superheater, and a high-pressure steam turbine an intermediate superheater is connected by a steam line to a medium-pressure steam turbine, which is connected by a steam line to the first recuperator, the cooler being heated l water pipes connected to the first pump and the economizer heat recovery boiler and steam - with the condenser-evaporator and the second heat exchanger, the steam turbine of high, medium and low pressure via a common shaft connected to an electric generator.

The claimed analogues have a common drawback, which is that they do not use the possibility of heat transfer to superheat the steam in front of the low pressure steam turbine through the surface of the GTU outlet diffuser. Such an approach would reduce the temperature of the walls of the diffuser, reduce the volume occupied by the heat exchange surfaces inside the KU path, and, in addition, increase the total heat difference triggered in steam and gas turbines by reducing heat and pressure losses in the paths of the diffuser and the superheater.

As a prototype of the claimed invention, the patent "Combined-cycle plant" [Patent RU No. 2391517] containing a gas turbine installation, a steam recovery boiler with steam generating circuits of two pressures and a steam turbine installation is selected. Steam generating circuits contain economizer and evaporative surfaces of two pressures and a steam superheater. The steam turbine installation contains a condenser and two steam turbines: high and low pressure (PTVD and PTND). A high-pressure steam turbine inlet at a steam input is communicated by a steam line with the output of a steam superheater; The capacitor is communicated at the output of the condensate with the input of the condensate condensate. The intermediate steam superheater, communicated at the steam inlet with a steam line with the outlet of the high-pressure turbine engine, and at the steam outlet with the inlet of the high pressure steam pump, is characterized in that the intermediate low-pressure steam superheater is designed as a water superheater and communicated at the steam input with the exit of the high-pressure turbine , and also - with the exit from the water superheater n.d. (VPND) of a waste heat boiler. At the inlet of a couple of VPND connected to the output of a pair of drum-separator n.d. At the inlet and outlet of the heating water, this superheater is connected respectively to the outlet and inlet of the economizer. KU on water. In GPU, made according to the presented scheme for overheating of the steam stream n.d. steam-water heat exchangers are also used. One for preheating steam n.a., the second is an intermediate steam superheater in front of the turbine n.d. and communicated at the steam inlet with the KU output at the steam of the steam engine; at the steam outlet with the turbine at the steam engine; at the inlet and outlet of the heating water it is communicated with the exit and entrance of the economizer on water. The advantage of the prototype is the use of compact steam-water superheaters, and a significantly simpler installation scheme than in analogues. However, in the selected prototype there is a drawback noted earlier in the analogues: the surface of the GTU outlet diffuser is not used to superheat low pressure steam, cool the diffuser and increase the total heat difference triggered in steam and gas turbines due to the reduction of heat and pressure losses in the output paths diffuser and intermediate superheater.

Thus, the technical problem is the creation of a gas turbine unit, in which an intermediate superheater in which is removed from the gas path of the compressor unit and located on the surface of the gas turbine outlet diffuser. This arrangement of the intermediate superheater allows one to solve several problems: reduce the temperature of the diffuser walls, avoid the need to insulate the diffuser from the inside, reduce heat losses to the environment, reduce gas pressure losses in the diffuser, and increase the triggered heat transfer in steam and gas turbines.

The solution to this technical problem is achieved by the fact that in a gas-steam installation containing a gas turbine installation, a waste heat boiler with steam generating circuits of two pressures containing economizing and evaporating surfaces of two pressures and a steam superheater, a steam turbine installation with a condenser and two steam turbines, the first of which is coupled at the steam inlet to the outlet of the steam superheater in steam, in steam output with the input of the second turbine in steam, the second steam turbine in the output of steam is connected to the steam input of the condenser communicated at the condensate output to the KU input of the condensate, and the intermediate steam superheater communicated at the steam input with the steam output of the drum-separator n.d., the steam output - with the input of the second steam turbine in pairs. A feature of the proposed GPU is that the intermediate steam superheater is made in the form of a gas-steam recuperator located on the surface of the GTU outlet diffuser and communicated at the steam input with the output of the KU drum-separator for a couple of n.a., at the steam output - with the input of the second steam turbines, at the inlet and outlet for heating gases - respectively, with the exit from the gas turbine and the entrance to the main KU gas duct.

The technical result consists in lowering the temperature of the walls of the diffuser, there is no need to insulate the diffuser from the inside, reducing heat losses to the environment, reducing gas pressure losses in the diffuser, increasing the triggered heat drop in steam and gas turbines.

The drawings attached to the invention are diagrams illustrating the essence of the invention.

FIG. 1 is a diagram of a GPU with a cooled diffuser:

claim 1 - gas turbine installation; item 2 - a cooled diffuser; Clause 3 - the main flue of the recovery boiler; p. 4 - economizer of low pressure; p.5 - low pressure evaporator; p.6 - low pressure drum separator; p. 7 - economizer of high pressure; p.8 - high pressure evaporator; p. 9 - high pressure drum-separator; p.10 - high pressure superheater; p. 11 - steam condenser; p.12 - high pressure steam turbine; p.13 - low pressure steam turbine; p. 14 - low pressure condensate pump; p.15 - intermediate steam superheater (PPP) of low pressure; p.16 - high pressure condensate pump; Clause 17 - a turbogenerator;

Figure 2 - diagram of the IFR 15 located on the surface of the diffuser:

p.18 - the heat transfer surface of the diffuser from gases to steam; p.19 - the outer surface of the steam channels (diffuser cover); p.20 - wall of the steam channel; p.21 - thermal insulation of the diffuser; p.22 - gas flow from the gas turbine; p.23 - input steam collector; p.24 - output collector.

The invention is illustrated by the graphic materials presented in FIG. 1 — FIG. 2.

In FIG. 1. presents the GPU, which contains a gas turbine 1 with a continuously cooled output diffuser 2, a steam compressor, in the main gas duct 3 of which there are two pressure steam circuits containing an economizer n.d. 4, low pressure evaporator 5 with n.a. 6, economizer r.p. 7, evaporator 8 with a drum separator 9 and steam superheater 10, a steam turbine unit with a condenser 11 and two steam turbines 12 and 13, the first of which is an east-west steam turbine (PTVD) 12 - at the steam input it is communicated with the output of the steam superheater 10 for a couple at the outlet for a couple communicated with the entrance of the second turbine, the second steam turbine n.d. (ПТНД) 13 - at the steam output it is communicated with the steam input of the capacitor 11, communicated at the condensate output through the condensate pump 14 with the condensate pump input 4, and ППП 15 located on the surface of the output diffuser 2, communicated at the steam input with steam generator output n.d. 6, coupled at the steam outlet with the inlet of the steam turbine ПТНД 13 at the couple, communicated at the inlet for heating gases - respectively, with the gas outlet from the gas turbine and at the gas outlet with gas inlet to the main gas duct KU 3. Economizer v.d. 7 at the water inlet is communicated with the exit of the economizer n.d. 4 by water through a feed pump 16, output communicated with the drum separator E 9, communicated by the steam output with the input of the main superheater 10, communicated by the steam output with the input of the anti-theft valve 12, communicated by the steam output also with the input of the high pressure heat pump 13.

The RFP circuit 15 is shown in FIG. 2.

Between the surface of the outlet diffuser 18 and the cover 19 there are steam channels separated by partitions-ribs 20. The cover 19 is covered with a layer of heat-insulating material 21. Saturated steam from the drum-separator 6 enters the channels from the inlet manifold 23, superheated steam is fed to the input of the low pressure turbine 13 from collector 24.

GPU works as follows. GTU 1 does the work of driving a turbogenerator 17. In the KU 3 gas duct, steam from two pressures is generated by the heat of the GTU exhaust gases. Vp fed from the superheater steam 9 in the high-pressure turbine engine 12, where it expands to a pressure in the n.d. circuit, performing work on the drive of the turbogenerator 17. Next, the spent steam of the high-pressure turbine engine 12 together with superheated steam coming from the n.d. circuit, in this example, from the SPP 15 , enters the PTND 12, where the steam expands to a pressure in the condenser 14, while doing the job of driving a turbogenerator. Since the steam in the high pressure tube 12 expands to a pressure in the n.a. When mixed saturated steam with steam n.d., superheated in the RFP 15, superheated steam is obtained, the superheat temperature of which depends on the ratio of steam consumption n.d. and East, and on the degree of overheating of low pressure steam in the PPP 15. Regulation of condensate flow in the circuits of the East and n.a. allows you to get the optimal overheating of the steam supplied to the PTND 13. This is especially important when the GPU is in variable modes.

The key and original element of the proposed GPU scheme is PPP 15, which is a gas-vapor heat exchanger-recuperator located on the surface of the GTU outlet diffuser. The gas heat exchanger usually has a larger volume than the water provided in the prototype. However, in this case, the existing surface of the outlet diffuser 18 is used for heat exchange, along which gas 22 moves inside the diffuser, and heat exchanger channels 20 are located outside (outside the KU gas duct), over which the superheated steam moves. The channels are formed by partitions (ribs) between the diffuser body and the outer cover 19. Outside, the cover is covered with thermal insulation 21. Thus, there is an additional volume inside the KU gas duct for organizing intermediate overheating n.d. not required.

The temperature of the steam moving through the channels of the superheater n.a. increases due to the selection of heat from the gas from 170 ° C to 250 ° C, and the temperature of the outer surface of the recuperator in the presence of thermal insulation 22 will be significantly lower (80 ° C. 100 ° C ) In the absence of a superheater on the surface of the diffuser, which in this case must be thermally insulated from the inside, its surface will have a temperature that is 80 ° C. 100 ° C lower than the gas temperature, which is 550 ° C - 600 ° C. Thus, the presence of a superheater on the surface of the outlet diffuser leads to a significant decrease in the temperature of the massive diffuser structure. The diameter of the optimal GTU diffuser with a power of 150 - 170 MW varies from ~ 3 m at the input to ~ 6 m at the output, and its length is 10 - 12 m. A decrease in the surface temperature of the diffuser reduces the heat loss on the diffuser by at least 3 times and amounts to about 0.3 - 0.4 MW for the GPU of the indicated power.

To assess the possibility of organizing overheating of low-pressure steam on the surface of the GTU outlet diffuser, we used data from CCGT-450T. Overheating of low pressure steam (7.7 bar) with a flow rate of 56 t / h is carried out from 169 to 200 ° C. The flow rate of gases leaving the gas turbine with a temperature of 537 ° C is 534 kg / s at a pressure of ~ 1 bar. In the calculations, the dimensions of the GTU SGT-5-3000E diffuser model were used: length L = 12 m, input diameter D ₁ = 3.175 m, output diameter D ₂ = 5.238 m, total diffuser surface F _Σ ≈ 91 m ² . The calculations were carried out under the condition that the diffuser is made of stainless steel 10 mm thick, heat transfer from gases to the diffuser wall was taken into account both due to convection and due to radiation. The longitudinal vapor channels on the outer surface of the diffuser 20 had a radial size l _p = 40 mm, the channel wall thickness δ _p = 4 mm, their number (n) varied from 660 to 66. In addition, a calculation was performed for the case of flow without partitions, i.e. when steam flows in an annular channel (n = 0). The result of the calculations was the diffuser surface required for superheating of the steam from 169 to 200 ° C, which is required in the CCGT-450T. The calculation results are shown in Table 1.

Table 1

n
(number of channels) F (m ² ) T _st1 (° C) T _st2 (° C) 660 48.7 264 252 132 59.0 324 310 66 61.8 336 321 0 84.1 395 385

As follows from the table, the surface area of the GTU outlet diffuser is quite sufficient for the PGU-450T low-pressure steam to overheat to a predetermined temperature. Even in the absence of edges, the required surface is smaller than the available (91m ² ), and in the presence of edges, a large margin is obtained, i.e. low pressure steam consumption can be increased.

Claims (2)

1. Combined-gas unit with a cooled diffuser, comprising a gas turbine unit, a steam recovery boiler with two-pressure steam generating circuits containing two pressure economizing and evaporating surfaces and a high-pressure steam superheater, a steam-turbine unit with a condenser and two steam turbines, the first of which is at the inlet by the steam is communicated with the output of the superheater of high pressure steam in pairs, at the output of steam with the inlet of the second turbine in pairs, the second steam turbine at the output of steam is in ohm for a pair of condenser communicated at the condensate outlet with the input of the condensate recovery boiler, and an intermediate steam superheater communicated at the pair inlet with a pair of low-pressure drum-separator (n.a.) output, at the steam outlet with an inlet a second steam turbine in steam, characterized in that the intermediate steam superheater is made in the form of a gas-steam recuperator, located on the surface of the outlet diffuser of the gas turbine unit and communicated at the steam input with the output of the recovery boiler drum-separator in a pair of bottom pressure at the steam outlet with the inlet of the second steam turbine, at the inlet and outlet of heating gases, respectively, with the exit of the gas turbine and the entrance to the main gas duct of the recovery boiler. 2. Combined-cycle plant according to claim 1, characterized in that the thermal insulation of the outlet diffuser is located on its outer surface.

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