CN110805923A - A steam-air preheater system based on energy cascade utilization - Google Patents

Abstract

The invention discloses a steam-air preheater system based on energy cascade utilization, comprising 3 steam heating stages and 6 hydrophobic heating stages; the 3 steam heating stages are respectively a low-pressure steam heating stage, Medium-pressure steam heating stage, high-pressure steam heating stage; the 6 hydrophobic heating stages include 3 hydrophobic low-temperature heating stages, 2 hydrophobic medium-temperature heating stages, and 1 hydrophobic high-temperature heating stage. According to the quality of different heat sources, the invention uses 9 heating stages to heat the air, realizes the cascade utilization of energy, and improves the utilization efficiency of energy; after the thermal energy of the steam at all levels is used in a cascade, the thermal load impact of the drain on the deaerator is reduced. , effectively preventing the self-boiling of the deaerator and reducing the risk of boiler operation; the cold air is heated by multi-stage, low temperature rise, which effectively alleviates the impact of load fluctuations on the air temperature and ensures the stable operation of the incineration system.

Description

A steam-air preheater system based on energy cascade utilization

technical field

The invention relates to the technical field of waste incineration power generation, in particular to a steam-air preheater system.

Background technique

Air preheater is an air heating device that uses waste heat to increase the temperature of the air entering the furnace to facilitate combustion. Its main function is to increase the theoretical combustion temperature of the fuel, ensure the furnace temperature, and improve the combustion efficiency. Since there are more acid gases in the boiler flue gas of waste incineration power plants, it is easy to cause low-temperature corrosion at low temperatures, so a steam-air preheater that heats air with steam is generally used. The steam-air preheater system has a great influence on the stable combustion of garbage, the stability of the thermal system, and the thermal efficiency of the whole plant.

The conventional steam-air preheater in the waste incineration power plant is heated in two stages: the first stage is the low-pressure heating section, and the heat source is the first-stage extraction steam of the steam turbine; the second stage is the high-pressure heating section, and the heat source is the superheated main steam or the saturated steam of the steam drum. Conventional steam air preheaters have the following disadvantages: 1) Two-stage heating is used, energy is not fully utilized, thermal efficiency is low, and energy is wasted; 2) When the boiler load changes, the air temperature of each heating section often cannot reach the design temperature; 3) The heat of the hydrophobicity is not fully utilized, and a large amount of heat carried in the hydrophobicity is vaporized and directly enters the deaerator, resulting in spontaneous boiling of the deaerator, which reduces the deoxygenation effect and affects the safe operation of the boiler.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a high-efficiency and stable steam-air preheater system based on energy cascade utilization.

The concrete technical scheme of the present invention is:

A steam air preheater system based on energy cascade utilization includes 3 steam heating stages and 6 hydrophobic heating stages. The three steam heating stages are respectively a low pressure steam heating stage, a medium pressure steam heating stage, and a high pressure steam heating stage along the air inlet direction. , Boiler drum saturated steam; the 6 hydrophobic heating stages, including 3 hydrophobic low temperature heating stages, 2 hydrophobic medium temperature heating stages, 1 hydrophobic high temperature heating stage, along the air inlet direction are low pressure hydrophobic low temperature heating stage, Medium-pressure hydrophobic low-temperature heating stage, high-pressure hydrophobic low-temperature heating stage, medium-pressure hydrophobic medium-temperature heating stage, high-pressure hydrophobic medium-temperature heating stage, and high-pressure hydrophobic high-temperature heating stage. The arrangement relationship between each steam heating stage and the hydrophobic heating stage along the air inlet direction is as follows: 3 hydrophobic low temperature heating stages are followed by a low pressure steam heating stage, 2 hydrophobic medium temperature heating stages are arranged after a medium pressure steam heating stage, 1 A high pressure steam heating stage is arranged after the hydrophobic high temperature heating stage. The steam heat exchange process at all levels is as follows: the saturated steam from the boiler steam drum is discharged through the high-pressure steam heating stage and then condensed into saturated hydrophobicity. The superheated steam from the first-stage extraction steam from the steam turbine is condensed into saturated hydrophobicity after passing through the medium-pressure steam heating stage, and the saturated hydrophobicity enters the middle The medium-temperature heating stage of pressure drainage will further release heat to form sub-cooled drainage, and the sub-cooled drainage will pass through the medium-pressure drainage and low-temperature heating stage to release heat and then enter the deaerator; the superheated steam from the secondary extraction of the steam turbine will be released through the low-pressure steam heating stage. After condensing into saturated hydrophobicity, the saturated hydrophobicity enters the low-pressure hydrophobic low-temperature heating stage for further heat release, and then forms supercooled hydrophobicity and enters the deaerator.

The beneficial effects of the invention are as follows: the system is safe, reliable, stable and efficient, and 9 heating stages are used to heat the air according to different heat source qualities, so as to realize the cascade utilization of energy, improve the utilization efficiency of energy, and achieve the purpose of saving energy and reducing consumption; The heat energy of the deaerator is used in a cascade, and the heat of the terminal drain is greatly reduced, which reduces the thermal load impact of the drain on the deaerator, effectively prevents the self-boiling of the deaerator, and reduces the risk of boiler operation; cold air adopts multi-stage, low temperature It can effectively alleviate the influence of load fluctuation on the wind temperature and ensure the stable operation of the incineration system.

Description of drawings

FIG. 1 is a schematic diagram of a steam-air preheater system based on energy cascade utilization according to the present invention.

FIG. 2 is a schematic diagram of the device structure of the system of the present invention.

In the figure: 1-low pressure hydrophobic low temperature heating stage, 2-medium pressure hydrophobic low temperature heating stage, 3-high pressure hydrophobic low temperature heating stage, 4-low pressure steam heating stage, 5-medium pressure hydrophobicity medium temperature heating stage, 6-high pressure hydrophobicity medium temperature heating stage stage, 7-medium pressure steam heating stage, 8-high pressure hydrophobic high temperature heating stage, 9-high pressure steam heating stage.

Detailed ways

As shown in FIG. 1, a steam air preheater system based on energy cascade utilization includes a low-pressure hydrophobic low-temperature heating stage 1, a medium-pressure hydrophobic low-temperature heating stage 2, a high-pressure hydrophobic low-temperature heating stage 3, a low-pressure steam heating stage 4, Medium-pressure draining and medium-temperature heating stage 5, high-pressure draining medium-temperature heating stage 6, medium-pressure steam heating stage 7, high-pressure draining high-temperature heating stage 8, and high-pressure steam heating stage 9. The saturated steam of the steam drum passes through the high-pressure steam heating stage 9 and then condenses into saturated hydrophobicity. The saturated hydrophobicity enters the high-pressure hydrophobic high-temperature heating stage 8 for further exothermic heat to form supercooled hydrophobicity. The low-temperature heating stage 3 releases heat in two stages and then enters the deaerator; the superheated steam from the first-stage extraction steam of the steam turbine passes through the medium-pressure steam heating stage 7 and then condenses into saturated hydrophobicity. After heat release, supercooled drain is formed, and the supercooled drain passes through the medium-pressure drain and low-temperature heating stage 2 to release heat and then enters the deaerator; the superheated steam from the secondary extraction steam of the steam turbine passes through the low-pressure steam heating stage 4 and then condenses to saturation The hydrophobic and saturated hydrophobic enter the low-pressure hydrophobic low-temperature heating stage 1 for further heat release, and then form supercooled hydrophobicity and enter the deaerator.

When in use, the cold air enters from the inlet end of the air preheater and passes through the low-pressure draining low-temperature heating stage 1, the medium-pressure draining low-temperature heating stage 2, the high-pressure draining low-temperature heating stage 3, the low-pressure steam heating stage 4, and the medium-pressure draining and medium-temperature heating stage. 5. High-pressure draining medium-temperature heating stage 6, medium-pressure steam heating stage 7, high-pressure draining high-temperature heating stage 8, high-pressure steam heating stage 9, and the air temperature at the outlet of the air preheater reaches the design value after the nine-stage heating.

Example 1, a waste incineration power generation project with a primary air temperature of 220°C and a main steam parameter of 4.0MPa/400°C. The saturated steam (5.1MPa/266℃) from the steam drum is condensed into saturated hydrophobic (5.1MPa/266℃) after exothermic through high pressure steam heating stage 9, and saturated hydrophobicity (5.1MPa/266℃) enters the high pressure hydrophobic high temperature heating stage 8 After further heat release, supercooled hydrophobicity (5.1MPa/215°C) is formed, and the supercooled hydrophobicity (5.1MPa/215°C) is depressurized to 2.1MPa, and then the medium temperature hydrophobicity (2.1MPa/140°C) is exothermic through high-pressure hydrophobicity medium-temperature heating stage 6. ℃), the medium-temperature hydrophobicity (2.1MPa/140℃) is depressurized to 1.0MPa, and then the low-temperature hydrophobicity (1.0MPa/90℃) is formed after exothermic heat release through the high-pressure hydrophobic low-temperature heating stage 3, and enters the deaerator; steam is extracted from the first stage of the steam turbine The superheated steam (1.0MPa/264°C) is condensed into saturated hydrophobicity (1.0MPa/184°C) after passing through the medium-pressure steam heating stage 7, and the saturated hydrophobicity (1.0MPa/184°C) enters the medium-pressure hydrophobic medium-temperature heating stage 5 After further heat release, supercooled hydrophobicity (1.0MPa/140°C) is formed, and the supercooled hydrophobicity (1.0MPa/140°C) is then exothermic in medium pressure hydrophobic low temperature heating stage 2 to form low temperature hydrophobicity (1.0MPa/90°C), which enters the removal process. Oxygenizer; the superheated steam (0.4MPa/186℃) from the secondary extraction steam of the steam turbine is condensed into saturated hydrophobicity (0.4MPa/151℃) and saturated hydrophobicity (0.4MPa/151℃) after exothermic heat release in the low-pressure steam heating stage 4 Enter the low-pressure hydrophobic low-temperature heating stage 1 to further release heat to form supercooled hydrophobic (0.4MPa/90°C) and enter the deaerator. The primary air-cooled air (25°C) enters from the inlet end of the air preheater and is sequentially heated to 35.4°C by the low-pressure hydrophobic low-temperature heating stage 1, heated to 38.7°C by the medium-pressure hydrophobic low-temperature heating stage 2, and heated to 38.7°C by the high-pressure hydrophobic low-temperature heating stage 3. 43.9°C, low pressure steam heating stage 4 heated to 130°C, medium pressure draining medium temperature heating stage 5 heated to 133°C, high pressure draining medium temperature heating stage 6 heated to 141°C, medium pressure steam heating stage 7 heated to 175°C, high pressure draining high temperature The heating stage 8 is heated to 180.9°C, and the high pressure steam heating stage 9 is heated to 220°C. Compared with the conventional two-stage steam-air preheater scheme, the thermal efficiency of the whole plant in this case is improved by about 0.8%; after multi-stage cooling, all the hydrophobicity finally enters the deaerator at a temperature of 90 °C. Compared with the conventional scheme, the hydrophobicity directly uses saturated water The way the state enters the deaerator, this scheme greatly reduces the thermal load impact of the drain on the deaerator; the cold air can stably reach the design value (220°C) after being heated by nine stages, which is more efficient than the conventional scheme. Strong resistance to load fluctuations.

Example 2, a waste incineration power generation project with a primary air temperature of 220°C and a main steam parameter of 4.0MPa/450°C. The process of the air preheater system is the same as that of Case 1. Compared with the conventional two-stage steam-air preheater scheme, the thermal efficiency of the whole plant is improved by about 1.3% in this case.

Example 3, a waste incineration power generation project with a primary air temperature of 220°C and a main steam parameter of 6.4MPa/485°C. The process of the air preheater system is the same as that of Case 1. Compared with the conventional two-stage steam-air preheater scheme, the thermal efficiency of the whole plant in this case is relatively improved by about 1.1%.

Claims (3)

1. A steam air preheater system based on energy cascade utilization is characterized by comprising 3 steam heating stages and 6 hydrophobic heating stages; the 3 steam heating stages are respectively a low-pressure steam heating stage, a medium-pressure steam heating stage and a high-pressure steam heating stage along the direction of an air inlet; the 6 hydrophobic heating stages comprise 3 hydrophobic low-temperature heating stages, 2 hydrophobic medium-temperature heating stages and 1 hydrophobic high-temperature heating stage; a low-pressure hydrophobic low-temperature heating stage, a medium-pressure hydrophobic low-temperature heating stage, a high-pressure hydrophobic low-temperature heating stage, a medium-pressure hydrophobic medium-temperature heating stage, a high-pressure hydrophobic medium-temperature heating stage and a high-pressure hydrophobic high-temperature heating stage are respectively arranged along the direction of an air inlet; the heat source of each hydrophobic heating stage is respectively from the hydrophobic of the steam heating stage with corresponding pressure; the arrangement relation of each steam heating stage and each hydrophobic heating stage along the direction of the air inlet is as follows: 1 low-pressure steam heating stage is arranged behind 3 hydrophobic low-temperature heating stages, 1 medium-pressure steam heating stage is arranged behind 2 hydrophobic medium-temperature heating stages, and 1 high-pressure steam heating stage is arranged behind 1 hydrophobic high-temperature heating stage.

2. A steam air preheater system based on energy cascade utilization, as set forth in claim 1, wherein: and the steam sources of the respective heating stages of the low-pressure steam heating stage, the medium-pressure steam heating stage and the high-pressure steam heating stage are respectively from a secondary steam extraction of a steam turbine, a primary steam extraction of the steam turbine and saturated steam of a boiler drum.

3. A steam air preheater system based on energy cascade utilization, as set forth in claim 1, wherein: the heat exchange process of each stage of steam is as follows: saturated steam from a boiler drum is condensed into saturated drain after being subjected to heat release in a high-pressure steam heating stage, the saturated drain enters a high-pressure drain high-temperature heating stage for further heat release to form super-cooled drain, and the super-cooled drain enters a deaerator after being subjected to two-stage heat release in a high-pressure drain medium-temperature heating stage and a high-pressure drain low-temperature heating stage; superheated steam from the first-stage steam extraction of the steam turbine is condensed into saturated drain after being subjected to heat release by a medium-pressure steam heating stage, the saturated drain enters a medium-pressure drain medium-temperature heating stage for further heat release to form supercooled drain, and the supercooled drain enters a deaerator after being subjected to heat release by a medium-pressure drain low-temperature heating stage; superheated steam from the secondary steam extraction of the steam turbine is condensed into saturated drain after being subjected to heat release by the low-pressure steam heating stage, and the saturated drain enters the low-pressure drain low-temperature heating stage to further release heat to form super-cooled drain and enters the deaerator.

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