RU2486404C1 - Steam recovery boiler with assembly of afterburning devices - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: largest effect may be achieved in heating steam turbine units, where an assembly of afterburning devices is used to cover peak thermal loads in cold period with simultaneous compensation of steam turbine capacity reduction due to increased pressure in heating steam bleeds in this period. A steam recovery boiler is proposed with an assembly of afterburning devices, which comprises the following serially arranged sections along the stream of heating gases: a steam reheating section and an evaporation section. The assembly of afterburning devices is installed along with the gas stream between the steam-reheating and the evaporation sections. The steam recovery boiler may be equipped with screening evaporating surfaces, being a part of the evaporation section and installed on the walls of the gas tract of the recovery boiler between the assembly of afterburning devices and the evaporator.

EFFECT: invention provides for compactness, reduced heat losses and costs for heat insulation and thermal protection.

2 cl, 2 dwg

Description

The invention relates to the field of power engineering and can be used in combined cycle power plants (CCGT) with gas turbine engines, steam turbines and waste heat boilers (KU) equipped with afterburner units (BDU).

The greatest effect can be achieved in cogeneration CCGT units, where BDUs are used to cover peak thermal loads in the cold period with simultaneous compensation for a decrease in steam turbine power due to an increase in pressure in cogeneration steam extraction during this period.

A well-known steam recovery boiler, in which a typical solution is used, consisting of a block of afterburning devices located at the inlet of the boiler for heating gases, in front of the superheater section (L.V. Arsenyev, V.G. Tyryshkin. Combined units with gas turbines. - L .: Engineering, Leningrad branch, 1982, p. 59, fig. II.I, b).

The disadvantages of the known device are the increase in the size of the KU, the increase in losses for external cooling and the cost of thermal insulation and thermal protection, as well as the relatively small range of changes in the steam capacity of the KU due to the air conditioner.

Known steam KU with BDU, used in the cogeneration CCGT Nossener Brücke in Dresden, Germany, containing sequentially located along the heating gases steam superheater and evaporator sections PE and I, equipped with two BDU, the first of which is installed at the entrance to the KU for heating gases, in front of the steam superheater section ПЕ, the second - in front of the gas heater of the mains water supply system (Tsanev S.V., Burov V.D., Remezov A.N. Gas-turbine and combined-cycle plants of thermal power plants: Textbook for universities under the editorship of S.V. Tsanev - M .: Publishing house M And 2002 - s.426, ris.9.32)

This known technical solution for the totality of features is the closest to the claimed and taken as a prototype.

The disadvantages of the device adopted for the prototype are associated with the placement of the BDU in the boiler before the superheater. This is, firstly, the need to maintain a distance from the BDU burners to the heating surfaces of the superheater tube bundle for at least 5 m - to equalize the temperature and gas flow rate (ibid., P. 287) - and, accordingly, increase the overall dimensions of the boiler, increase losses external cooling and costs of thermal insulation and thermal protection. Secondly, the relatively small range of changes in the steam capacity of the KU due to the BDU due to restrictions on the permissible temperature of the walls of the pipes of the superheater (taking into account the temperature scan in the cross section of the gas path behind the BDU and the inevitable increase in the temperature development of the steam in the pipes of the superheater), according to the temperature of the walls of the gas path of the KU directly behind the BDU (for reasons of thermal protection of the load-bearing structures of the KU and reduction of heat loss due to external cooling), as well as due to restrictions on the permissible value iyam temperature and vapor pressure E in front of a steam turbine.

The analysis of the prior art by the applicant, including a search by patent and scientific and technical sources of information, as well as the identification of sources containing information about analogues of the claimed invention, allowed to establish that the applicant did not find a technical solution characterized by signs identical or equivalent to those proposed, while the invention does not follow explicitly for the specialist in the manner of the prior art and determined by the applicant.

The definition from the list of identified analogues of the prototype, as the closest technical solution for the totality of features, allowed to identify in the claimed device a combination of significant distinctive features in relation to the applicant's perceived technical result, set forth in the following claims.

The invention provides a compact arrangement of the BDU in the waste heat boiler, reducing heat loss for external cooling and the cost of thermal insulation and heat protection, expanding the range of variation in steam production due to the BDU within the existing restrictions on the temperature of the walls of the heat exchange surfaces and the temperature and pressure of the steam in front of the steam turbine.

A steam recovery boiler with a block of afterburning devices is proposed, including steam superheater and evaporator sections arranged sequentially along the heating gases, while the block of afterburners is placed along the gas between the steam superheater and evaporative sections.

The steam recovery boiler can be equipped with shielding evaporation surfaces that are part of the evaporation section and are installed on the walls of the gas path of the recovery boiler between the afterburner unit and the evaporator.

The distance from the BDU burners to the evaporator package in the inventive KU can be reduced to the size of the torch, since the sweep and temperature fluctuations along the cross section of the gas path behind the BDU will not lead to the development of water and steam-water mixture temperatures in the evaporator pipes, because the water temperature in the pipes of the evaporator is constant and the same, and as gas passes through the evaporator, gas temperature jumps are leveled due to an increase in local heat fluxes at elevated gas temperatures and, conversely, a decrease in heat fluxes where local gas temperatures during passage of the evaporator are below average level.

A more compact placement of the control unit with the possibility of shielding the boiler walls, if necessary, with evaporative surfaces, can significantly reduce heat loss due to external cooling of the boiler and the cost of thermal insulation and thermal protection.

).The range of KU steam capacity changes due to the BDU when it is placed in front of the evaporator can also be significantly increased, firstly, because the afterburning of the fuel begins at a lower gas temperature behind the superheater, and secondly, due to the guaranteed not exceeding the maximum allowable temperature level of the walls of the water-cooled surfaces (which are the surfaces of the evaporator), thirdly, due to the decrease (and not increase) of the temperature of the steam in front of the steam turbine when using the remote control and, as a result, a more gradual increase in pressure in front of the steam turbine (P), which varies in approximately proportional dependence on the product of the steam consumption (G) by the square root of the temperature (T) in degrees Kelvin ( $$P\sim G\cdot \sqrt{T}$$

)

The invention is illustrated by the presented in figure 1 and figure 2 schematic drawings illustrating embodiments of the invention according to both claims by the example of using the inventive KU as a part of a combined-cycle unit similar to the prototype. The drawings show:

- figure 1 - steam recovery boiler with gas turbine engine and steam boiler with a block of afterburning devices. Option with water supply to the shielding surfaces from the drum;

- figure 2 - steam recovery boiler with gas turbine engine and steam boiler with a block of afterburning devices. Variant with water supply to the shielding surfaces from the economizer.

The steam recovery boiler contains a gas turbine engine 1 with a turbogenerator 2 and a steam boiler 3 with a boiler 4. The steam boiler is designed to generate steam of the same pressure using residual heat to heat the mains water and contains steam superheater and evaporator sections 5 and 6 sequentially located along the heating gases. According to the invention, the BDU 4 is placed along the gas paths between the superheater and vaporization sections 5 and 6. According to claim 2, KU 3 can also be equipped with shielding vaporization surfaces 7, which are part of and paritelnogo portion 6 and mounted on the walls of the gas path between the NOS 3 KU 4 and the evaporator 6.

In the above example, the control unit is vertical and contains a drum 8 with a circulation pump 9, as well as an economizer 10 with a control valve (PK) 11 installed at the outlet of the economizer 10 for feed water. The screening evaporation surface 7 at the outlet of the steam-water mixture is communicated through the output manifold 12 with the inlet of the drum 8 through the steam-water mixture. At the water inlet, the shielding surfaces 7 are connected:

- in the embodiment shown in figure 1 - with the output of the drum 8 through the water through the circulation pump 9;

- in the embodiment shown in figure 2 - with the release of the economizer 10 through RK 11 for feed water.

In the above example, KU 3 also contains a tail economizer 13 installed along the gases behind the economizer 10 and communicated at the water outlet with the inlet of the economizer 10 by water, and contains a water heater for network water 14 communicated at the inlet and outlet of heating water, respectively, with an exit and an entrance - through the circulation pump 15 and RK 16 - of the tail economizer 13 by water.

Steam KU with BDU works as follows.

Water from the tail economizer 13 is fed into the economizer 10, from where it enters the drum 8 directly (Fig. 1) or through the steam-water path of the shielding surfaces 7 (Fig. 2) with regulation by the water level in the drum 8 using RK 11. The water from the tail the economizer 10 is also fed by a circulation pump 15 to the inlet of the network water heater 14 through the heating water with water temperature regulation behind the tail economizer 13 using the RC 16.

In the period when the heat supplied to the external consumer through the water heater of the mains water 14 and from the steam turbine withdrawals (not shown in the drawings) is not enough, the control unit 4 is turned on. Due to the heat of combustion of the fuel supplied to the control unit 4 and burned in residual oxygen exhaust gas turbine engine 1, the vapor productivity of the evaporator 6 increases.

The maximum range of changes in the KU steam capacity due to the BDU when it is placed in front of the evaporator is much wider than in the prototype, firstly, because the afterburning of fuel in the BDU begins at a lower gas temperature behind the superheater 5 (and not before it, as in the prototype) secondly, due to the guaranteed non-exceeding of the maximum allowable temperature level of the walls of the water-cooled surfaces of the evaporator 6 and the water-cooled shielding surfaces 7, which are part of the evaporator 6, and thirdly, due to the reduction ( does not increase as in the prototype) steam temperature in the steam superheater 5 when NOS 4.

The problem of thermal protection and thermal insulation of the walls of the gas path (if it is necessary to expand the range of gas temperature in front of the evaporator to too high values) can be solved by installing shielding surfaces 7, and the distance from the BDU 4 burners to the evaporator package 6 can be reduced to the size of the torch, since the scan and temperature fluctuations in the cross-section of the gas path behind the BDU 4 do not lead to a scan of the temperatures of the water and the steam-water mixture in the pipes of the evaporator 6, because the water temperature in the pipes of the evaporator 6 is constant and the same, while as the gas passes through the evaporator 6, gas temperature jumps are leveled due to an increase in local heat fluxes at elevated gas temperatures and, conversely, a decrease in heat fluxes where the local gas temperatures pass through the evaporator below average. This ensures a more compact placement of the control unit and a significant reduction in heat loss due to external cooling of the control unit and the costs of thermal insulation and thermal protection of the walls of the control unit associated with the use of the control panel.

The above example is presented to illustrate the claimed invention in the most visual form and does not exhaust all possible variants of its application. In particular, the recovery boiler may not be vertical, but horizontal, may contain surfaces of not one but two or more pressures, may not be of a drum but of a direct-flow type (i.e., without drums), respectively, the performance of shielding evaporation surfaces and their connection to the main package of the evaporator can also be very diverse, in addition, the boiler may not have shielding surfaces at all, given the lower initial gas temperature in front of the BDU (compared with the prototype) and a more compact size NOS displacements in CG (a slight distance from the RCU to the basic package of the evaporator tubes), etc.

Claims (2)

1. A steam recovery boiler with a block of afterburning devices, comprising successively superheating and vaporizing sections located along the heating gases, characterized in that the block of afterburning devices is placed along the gas between the steam overheating and evaporating sections. 2. The steam recovery boiler with a block of afterburning devices according to claim 1, characterized in that the steam recovery boiler is equipped with shielding evaporation surfaces that are part of the evaporation section and are installed on the walls of the gas path of the recovery boiler between the afterburning unit and the evaporator.

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