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CN-224228736-U - Energy closed efficiency improving system for smoke recycling composite low-order regenerative steam extraction

CN224228736UCN 224228736 UCN224228736 UCN 224228736UCN-224228736-U

Abstract

The utility model discloses an energy closed efficiency improving system for smoke recycling composite low-order regenerative steam extraction, wherein a low-pressure regenerative steam extraction pipeline is connected to a middle pressure cylinder and/or a low pressure cylinder of a steam turbine, the low-pressure regenerative steam extraction pipeline is correspondingly connected with a low-pressure heater, a recycling smoke pipeline is led out from a boiler smoke pipeline between the downstream of a dust remover and the upstream of a desulfurizing device, the output end of the recycling smoke pipeline is connected to a hearth of the boiler, one or more smoke steam heaters connected in series are arranged in the recycling smoke pipeline, a smoke heating steam extraction pipeline is led out from the low-pressure regenerative steam extraction pipeline, and the output end of the smoke heating steam extraction pipeline is connected with the smoke steam heater. According to the scheme, low-temperature flue gas is used as a carrier for heating the extraction latent heat, the low-temperature flue gas enters the hearth in a circulating mode, the extraction latent heat of the steam turbine is fully utilized by arranging the steam flue gas heater, the cold source loss is reduced, and the heat economy of low load and even rated load in the unit is improved.

Inventors

  • ZHANG GUANGWEN
  • ZHAO HONGWEI
  • SHAO YIMING
  • WANG JIANSHAN
  • NIU MIAOREN
  • LI YUANYUAN

Assignees

  • 中国电力工程顾问集团华北电力设计院有限公司

Dates

Publication Date
20260512
Application Date
20250519

Claims (8)

  1. 1. The energy closed efficiency improving system for the smoke recycling composite low-order regenerative steam extraction is characterized by comprising a boiler (1), wherein the boiler (1) is connected with a boiler water supply pipeline (11) and a boiler smoke pipeline (12); the medium pressure cylinder (22) and/or the low pressure cylinder (23) of the steam turbine are connected with a low-pressure regenerative steam extraction pipeline (31), and the low-pressure regenerative steam extraction pipeline (31) is correspondingly connected with the low-pressure heater; An air preheater (121), a dust remover (122), an induced draft fan (123), a desulfurization device (124) and a chimney (125) are sequentially arranged in a boiler flue gas pipeline (12) along the flue gas conveying direction, a recycling flue gas pipeline (4) is led out from the boiler flue gas pipeline (12) between the downstream of the dust remover (122) and the upstream of the desulfurization device (124), the output end of the recycling flue gas pipeline (4) is connected to a hearth of the boiler (1), one or more flue gas steam heaters (41) connected in series are arranged in the recycling flue gas pipeline (4), a flue gas heating steam extraction pipeline (32) is led out from the low-pressure heat recovery steam extraction pipeline (31), and the output end of the flue gas heating steam extraction pipeline (32) is connected with the flue gas steam heaters (41).
  2. 2. The energy closed efficiency improving system of the flue gas recirculation composite low-order regenerative extraction according to claim 1, wherein the input end of the recirculation flue gas pipeline (4) is positioned between the induced draft fan (123) and the desulfurization device (124).
  3. 3. The energy closed efficiency improving system of the smoke recycling composite low-order regenerative extraction according to claim 1, wherein the input end of the recycling smoke pipeline (4) is positioned between the dust remover (122) and the induced draft fan (123), and a variable frequency recycling fan (5) is arranged in the recycling smoke pipeline (4).
  4. 4. The energy closed efficiency improving system of the flue gas recirculation composite low-order regenerative extraction according to claim 1, wherein the output end of the recirculation flue gas pipeline (4) is positioned on the front and rear walls of the furnace below the lowest-layer burner of the boiler (1) and above the inflection point of the ash cooling hopper, or the output end of the recirculation flue gas pipeline (4) is positioned on the front and rear walls of the furnace above the uppermost-layer burner of the boiler (1) and near the overfire air.
  5. 5. The energy closed efficiency improving system of the smoke recycling composite low-order regenerative extraction according to claim 1, wherein an output electric adjusting baffle (42) is arranged at the output end of the recycling smoke pipeline (4).
  6. 6. The energy closed efficiency improving system of the smoke recycling composite low-order regenerative extraction according to claim 1, wherein an input electric shutoff baffle (43) is arranged at the input end of the recycling smoke pipeline (4), and a valve is arranged in the smoke heating extraction pipeline (32).
  7. 7. The energy-closed efficiency improving system for recycling flue gas and compounding low-order regenerative steam extraction according to any one of claims 1 to 6, wherein the number of the flue gas steam heaters (41) is N, N is a positive integer, the low-pressure regenerative steam extraction pipeline (31) is an N-stage steam extraction pipeline at the tail end of the medium pressure cylinder (22), the flue gas steam heaters (41) are in one-to-one correspondence with the low-pressure regenerative steam extraction pipeline (31), and the N low-pressure regenerative steam extraction pipelines (31) are sequentially connected with the N flue gas steam heaters (41) arranged along the flue gas conveying direction in the order of low steam extraction pressure.
  8. 8. The energy closed efficiency improving system of the smoke recycling composite low-order regenerative steam extraction according to claim 7 is characterized in that a multi-stage low-pressure heater, a deaerator (6), a water feed pump (7) and a multi-stage high-pressure heater are sequentially arranged in a boiler water feed pipeline (11) along the water conveying direction; The multistage low-pressure heater comprises a nine-low-pressure heater (85), a eight-low-pressure heater (84), a seven-low-pressure heater (83), a six-low-pressure heater (82) and a five-low-pressure heater (81) which are sequentially arranged along the water conveying direction, and the multistage high-pressure heater comprises a three-high-pressure heater (93), a two-high-pressure heater (92) and a first-high-pressure heater (91) which are sequentially arranged along the water conveying direction; the number of the smoke steam heaters (41) is three, and the low-pressure backheating steam extraction pipeline (31) is five sections of steam extraction pipelines, six sections of steam extraction pipelines and seven sections of steam extraction pipelines of the medium-pressure cylinder (22); The five-section steam extraction pipeline is connected with a five-section low-pressure heater (81), the six-section steam extraction pipeline is connected with a six-section low-pressure heater (82), the seven-section steam extraction pipeline is connected with a seven-section low-pressure heater (83), the smoke heating steam extraction pipeline (32) led out of the five-section steam extraction pipeline is connected with the smoke steam heater (41) at the most downstream side of the three smoke steam heaters (41), the smoke heating steam extraction pipeline (32) led out of the six-section steam extraction pipeline is connected with the smoke steam heater (41) in the middle of the three smoke steam heaters (41), and the smoke heating steam extraction pipeline (32) led out of the seven-section steam extraction pipeline is connected with the smoke steam heater (41) at the most upstream side of the three smoke steam heaters (41).

Description

Energy closed efficiency improving system for smoke recycling composite low-order regenerative steam extraction Technical Field The utility model belongs to the technical field of coal-fired power generation, and particularly relates to an energy closed efficiency improving system for smoke recycling composite low-order regenerative steam extraction. Background The traditional coal power mainly considers the high efficiency under the rated working condition, and the coal consumption of the unit is obviously increased under the medium-low load working condition. The unit efficiency is mainly dependent on the boiler efficiency and the absolute internal efficiency of the steam turbine. As the load decreases, the general boiler efficiency does not decrease much, while the absolute internal efficiency of the turbine tends to decrease significantly. Taking a million kilowatt wet cooling unit as an example, the boiler efficiency is reduced from 95.4% of rated working conditions to 94.63% of rated working conditions, and the absolute internal efficiency of the steam turbine is reduced from 51.4% of rated working conditions to 46.6% of 30% of rated working conditions and 44.5% of rated working conditions. From the above, the point of application for improving the low load efficiency of the unit is to improve the absolute internal efficiency of the low load of the turbine. The absolute internal efficiency of the turbine reflects the actual thermal efficiency of the thermodynamic cycle of the turbine unit. The heat input to the steam turbine by the boiler is shown as cold source loss except the part doing work and generating electricity, namely, the heat released to the environment by the condensing device from the exhaust steam of the low-pressure cylinder of the steam turbine. The absolute efficiency of the steam turbine is generally about 50%, and the cold source loss is about 50%. The steam is used for generating power in the steam turbine by acting mainly by utilizing the energy of the overheat part, and the latent heat accounts for the majority of the enthalpy value of the steam and the enthalpy value of the overheat part accounts for the minority of the enthalpy value of the overheat part. Taking supercritical main steam with parameters of 28MPa.a and 600 ℃ as an example, the enthalpy value of the main steam is 3465.7kJ/kg, the exhaust enthalpy value of the low-pressure cylinder is 2417.9 kJ/kg, the effective work-doing enthalpy drop is 1047.8, and the main steam accounts for 30% of the total enthalpy value. The exhaust steam from the low-pressure cylinder is reduced as much as possible by fully utilizing the latent heat of steam, which is an important effective direction of the coal motor group. The steam extraction and heat recovery system of the steam turbine fully utilizes the latent heat of steam to heat condensation water and feed water, and is a typical application for reducing the loss of a cold source. For how to return the latent heat of extraction steam to the boiler, for example, a mode of heating air by extraction steam, a mode of heating water supply at an inlet of an economizer by extraction steam, a mode of heating raw coal by extraction steam, and the like are generally considered, but the purposes of reducing the amount of cold end exhaust steam and reducing the loss of cold sources are difficult to achieve. Disclosure of utility model The utility model aims to solve the technical problems of providing an energy closed efficiency improving system for smoke recycling composite low-order regenerative steam extraction, solving the problem of higher coal consumption of the traditional coal motor set under medium-low load working conditions, and fully utilizing the steam extraction latent heat of a steam turbine, reducing the loss of a cold source and improving the medium-low load heat economy of the set by innovating the system structure and constructing a low-temperature carrier capable of recovering the steam extraction latent heat of the set. According to the technical scheme, the utility model provides an energy closed efficiency improving system for smoke recycling composite low-order regenerative steam extraction, which comprises a boiler, wherein the boiler is connected with a boiler water supply pipeline and a boiler smoke pipeline, a multi-stage low-pressure heater is arranged in the boiler water supply pipeline, a low-pressure regenerative steam extraction pipeline is connected to a middle-pressure cylinder and/or a low-pressure cylinder of a steam turbine, the low-pressure regenerative steam extraction pipeline is correspondingly connected with the low-pressure heater, an air preheater, a dust remover, an induced draft fan, a desulfurization device and a chimney are sequentially arranged in the boiler smoke pipeline along the smoke conveying direction, a recycling smoke pipeline is led out of the boiler smoke pipeline between the downstream of the dust remover and the upstream of the de