Multi-parameter adjustable five-stage flue gas waste heat utilization system

Abstract

The utility model relates to a multi-parameter adjustable five-stage flue gas waste heat utilization system which comprises an air preheater, a flue gas heat exchanger in front of an electric precipitator, a low-low temperature electric precipitator, an induced draft fan, a flue gas heat exchanger in front of an absorption tower, a desulfurizing tower and a chimney which are sequentially connected through pipelines, the air preheater is also connected with a cold primary air system and a cold secondary air heating system; the cold secondary air heating system comprises an air heater, and the air heater is further connected with a flue gas heat exchanger in front of an electric precipitator and a flue gas heat exchanger in front of an absorption tower; the air preheater is provided with a bypass system; and an expansion water tank is arranged between the electric dust remover front flue gas heat exchanger and the absorption tower front flue gas heat exchanger. The flue gas waste heat utilization system has the advantages that the flue gas waste heat utilization rate can be effectively increased, energy is saved, and consumption is reduced; and cold secondary air is heated by the air heater, so that the problem of cold end corrosion of the air pre-heater can be effectively relieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to flue gas waste heat utilization technical field, more exactly, it relates to five -stage flue gas waste heat utilization system of multiple parameter adjustable. BACKGROUND

[0002] Boiler exhaust heat loss is one of main heat losses in thermal power plant, and when the coal kind is changed, can also cause the condition that the boiler exhaust temperature all exceeds the design value. Adopting the boiler tail flue gas waste heat utilization system to recover the exhaust heat, can reduce the exhaust temperature, greatly reduce the exhaust heat loss, improve the power plant economy, is one of important ways to improve the unit heat efficiency. In order to save energy, improve the power plant economy, many domestic power plants adopt the condensate or feed water to absorb the exhaust heat in the low temperature coal economizer, reduce the exhaust temperature, after being heated, temperature is raised and then returns to the steam turbine heater system, replaces the function of part of heater, forms a component of steam turbine thermodynamic system. The low temperature coal economizer saves part of steam turbine extraction steam, under the condition that the steam turbine admission quantity is invariable, the saved extraction steam returns to the steam turbine to continue expansion and work, thus, under the condition that the power generation capacity is invariable, the energy consumption of unit can be saved.

[0003] And after part of power plant adopts seawater desulfurization system, the seawater desulfurization and limestone-gypsum wet desulfurization have a big difference, that is, the desulfurization tower has no water balance requirement, which means that compared with limestone-gypsum wet desulfurization, the flue gas temperature before entering the desulfurization tower can be reduced more, and there is more flue gas waste heat utilization space. From this point of view, the flue gas heat exchanger is arranged before the absorption tower. Because the smoke temperature is low, the heat of this part of flue gas is large, but due to the low smoke temperature, the overall heat exchange efficiency is low, after the water temperature is heated by the flue gas, the water temperature is still low, and the conventional flue gas is used to heat the cold secondary air into the furnace, the secondary air temperature is still low, and the outlet flue gas temperature of the air preheater cannot be effectively improved. UTILITY MODEL CONTENTS

[0004] The utility model aims at the deficiency of prior art, and proposes five -stage flue gas waste heat utilization system of multiple parameter adjustable, including: air preheater, electric dust collector front flue gas heat exchanger, low low temperature electric dust collector, induced draft fan, absorption tower front flue gas heat exchanger, desulfurization tower and chimney that are connected in proper order through pipeline,

[0005] Among them, the air preheater is also connected with cold primary air system and cold secondary air heating system;The cold secondary air heating system includes a warm air heater, and the warm air heater is also connected with the electric dust collector front flue gas heat exchanger and the absorption tower front flue gas heat exchanger;The air preheater is provided with a bypass system;An expansion tank is arranged between the electric dust collector front flue gas heat exchanger and the absorption tower front flue gas heat exchanger.

[0006] Preferably, the bypass system includes a bypass flue and a high-temperature economizer and a medium-temperature economizer installed on the bypass flue; the high-temperature economizer and the medium-temperature economizer are connected in series.

[0007] Preferably, the flue gas heat exchanger before the electrostatic precipitator includes a high-temperature heat exchanger and a low-temperature heat exchanger. The high-temperature heat exchanger is used to exchange heat between the flue gas output from the air preheater and the low-temperature water output from the flue gas heat exchanger before the absorption tower, and the low-temperature heat exchanger is used to exchange heat between the flue gas treated by the high-temperature heat exchanger and the condensate.

[0008] Preferably, a variable frequency pump for adjusting the water volume is provided on the condensate input side of the low-temperature heat exchanger before the electrostatic precipitator.

[0009] Preferably, the high-temperature heat exchanger before the electrostatic precipitator, the flue gas heat exchanger before the absorption tower, and the air heater are all equipped with variable frequency pumps for controlling the outlet temperature of the cold secondary air; the high-temperature heat exchanger before the electrostatic precipitator is also equipped with a bypass for controlling the amount of heat absorbed.

[0010] Preferably, the high-temperature economizer is used to heat the feedwater, and the medium-temperature economizer is used to heat the condensate output from the low-temperature heat exchanger before the electrostatic precipitator; the condensate output end of the medium-temperature economizer is connected to the deaerator.

[0011] Preferably, the medium-temperature economizer is provided with a bypass for adjusting the heat exchange.

[0012] The beneficial effects of this utility model are:

[0013] 1. The flue gas waste heat utilization system provided by this utility model can effectively improve the utilization rate of flue gas waste heat and save energy and reduce consumption.

[0014] 2. This utility model can effectively alleviate the cold end corrosion problem of the air preheater by heating the cold secondary air with a warm air heater.

[0015] 3. The flue gas heat exchanger provided by this utility model has a certain interception effect on dust, reducing the dust concentration entering the seawater desulfurization tower.

[0016] 4. This invention can further reduce the temperature of flue gas entering the desulfurization tower and improve the efficiency of seawater desulfurization. Attached Figure Description

[0017] Figure 1 A schematic diagram of a five-stage flue gas waste heat utilization system with adjustable multi-parameter parameters provided by this utility model;

[0018] Figure 2 A flowchart of a five-stage flue gas waste heat utilization method with adjustable multiple parameters provided by this utility model;

[0019] Explanation of reference numerals in the attached diagram: 1. Air preheater; 2. Flue gas heat exchanger before electrostatic precipitator; 201. High-temperature heat exchanger before electrostatic precipitator; 202. Low-temperature electrostatic precipitator; 3. Exhaust fan; 4. Flue gas heat exchanger before absorption tower; 5. Desulfurization tower; 6. Chimney; 7. High-temperature economizer; 8. Medium-temperature economizer; 9. Air heater; 10. Expansion tank; 11. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that, for those skilled in the art, several modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0021] Example 1:

[0022] Embodiment 1 of this application provides a five-stage flue gas waste heat utilization system with adjustable multi-parameter parameters, including: an air preheater 1, a flue gas heat exchanger 2 before an electrostatic precipitator, a low-temperature electrostatic precipitator 3, an induced draft fan 4, a flue gas heat exchanger 5 before an absorption tower, a desulfurization tower 6, and a chimney 7 connected in sequence through pipelines.

[0023] The air preheater 1 is also connected to a cold primary air system and a cold secondary air heating system; the cold secondary air heating system includes a heater 10, which is also connected to the flue gas heat exchanger 2 before the electrostatic precipitator and the flue gas heat exchanger 5 before the absorption tower; the air preheater 1 is equipped with a bypass system; and an expansion tank 11 is provided between the flue gas heat exchanger 2 before the electrostatic precipitator and the flue gas heat exchanger 5 before the absorption tower.

[0024] The bypass system includes a bypass flue and a high-temperature economizer 8 and a medium-temperature economizer 9 installed on the bypass flue; the high-temperature economizer 8 and the medium-temperature economizer 9 are connected in series.

[0025] Example 2:

[0026] Based on Example 1, Example 2 of this application provides a more specific five-stage flue gas waste heat utilization system with adjustable multiple parameters, such as... Figure 1 As shown, it includes: an air preheater 1, a flue gas heat exchanger 2 before the electrostatic precipitator, a low-temperature electrostatic precipitator 3, an induced draft fan 4, a flue gas heat exchanger 5 before the absorption tower, a desulfurization tower 6, and a chimney 7, which are connected in sequence by pipes.

[0027] The air preheater 1 is also connected to a cold primary air system and a cold secondary air heating system; the cold secondary air heating system includes a heater 10, which is also connected to the flue gas heat exchanger 2 before the electrostatic precipitator and the flue gas heat exchanger 5 before the absorption tower; the air preheater 1 is equipped with a bypass system; and an expansion tank 11 is provided between the flue gas heat exchanger 2 before the electrostatic precipitator and the flue gas heat exchanger 5 before the absorption tower.

[0028] The flue gas discharged from the boiler needs to be cooled before the electrostatic precipitator. This part has a large amount of heat, and if it is all used to heat the secondary air entering the furnace after heat exchange in the heater, the air temperature will be too high. Therefore, this part is optimized to be divided into two sections. Specifically, the flue gas heat exchanger 2 before the electrostatic precipitator includes a high-temperature heat exchanger 201 and a low-temperature heat exchanger 202. The high-temperature heat exchanger 201 is used to exchange heat between the flue gas output from the air preheater 1 and the low-temperature water output from the flue gas heat exchanger 5 before the absorption tower. The low-temperature heat exchanger 202 is used to exchange heat between the flue gas treated by the high-temperature heat exchanger 201 and the condensate.

[0029] The condensate input side of the pre-static precipitator low-temperature heat exchanger 202 is equipped with a variable frequency pump for adjusting the water volume, thereby adjusting the heat exchange ratio between the pre-static precipitator high-temperature heat exchanger 201 and the pre-static precipitator low-temperature heat exchanger 202.

[0030] The high-temperature heat exchanger 201 before the electrostatic precipitator, the flue gas heat exchanger 5 before the absorption tower, and the air heater 10 are all equipped with variable frequency pumps for controlling the outlet temperature of the cold secondary air. The high-temperature heat exchanger 201 before the electrostatic precipitator is also equipped with a bypass for controlling the amount of heat absorbed. The heat absorbed by the high-temperature heat exchanger 201 before the electrostatic precipitator can be controlled by the bypass, and the heat exchange of the heat exchangers 5 before the tower, 201 before the electrostatic precipitator, and 10 before the air heater can be controlled by the variable frequency pumps, thereby controlling the outlet temperature of the secondary air.

[0031] The high-temperature economizer 8 is used to heat the feedwater, and the medium-temperature economizer 9 is used to heat the condensate output from the low-temperature heat exchanger 202 before the electrostatic precipitator; the condensate output end of the medium-temperature economizer 9 is connected to the deaerator.

[0032] The medium-temperature economizer 9 is equipped with a bypass for adjusting the heat exchange, which ultimately regulates the temperature entering the deaerator.

[0033] It should be noted that the parts in this embodiment that are the same as or similar to those in Embodiment 2 can be referred to each other, and will not be repeated in this application.

[0034] Example 3:

[0035] Based on Examples 1 and 2, Example 3 of this application provides a five-stage flue gas waste heat utilization method with adjustable multiple parameters, such as... Figure 2 As shown, it includes:

[0036] Step 1: Input flue gas, cold primary air and cold secondary air heated by heater 10 into air preheater 1.

[0037] Step 1 also includes: inputting flue gas into the bypass system of air preheater 1, heating feedwater through the high-temperature economizer 8 of the bypass system, and heating the condensate output from the low-temperature heat exchanger 202 before the electrostatic precipitator through the medium-temperature economizer 9. For example, the feedwater pump outlet inlet temperature connected to the high-temperature economizer 8 is 186.2°C, and the temperature after heating by the high-temperature economizer 8 is 330°C. The outlet inlet temperature of the No. 9 low-temperature heater connected to the medium-temperature economizer 9 is 101.8°C, and the temperature after heating by the high-temperature economizer 8 is 165°C. Furthermore, the outlet flue gas temperature of air preheater 1 is 131°C.

[0038] The heating method for the cold secondary air is as follows: the heat of the flue gas in front of the desulfurization tower is used to heat the water temperature through the flue gas heat exchanger 5 in front of the absorption tower. The water temperature, which is still relatively low after heating, is further heated by the high temperature heat exchanger 201 in front of the electrostatic precipitator before being reheated into the cold secondary air of the furnace.

[0039] For example, the temperature of the primary cold air is 27°C, the temperature of the secondary cold air before heating is 22°C, and the temperature of the secondary cold air after heating is 100°C.

[0040] Step 2: The flue gas output from the air preheater 1 undergoes heat exchange treatment through the flue gas heat exchanger 2 before the electrostatic precipitator.

[0041] For example, the temperature of the flue gas after heat exchange treatment is 85°C.

[0042] Step 3: The flue gas output from the flue gas heat exchanger 2 before the electrostatic precipitator passes through the low-temperature electrostatic precipitator 3 and the induced draft fan 4 in sequence to the flue gas heat exchanger 5 before the absorption tower for heat exchange treatment.

[0043] For example, the flue gas temperature output by the induced draft fan 4 is 95°C, and the flue gas temperature after treatment by the flue gas heat exchanger 5 in front of the tower is 68°C.

[0044] In addition, in steps 2 and 3, the condensate input of the low-temperature heat exchanger 202 before the electrostatic precipitator and the cold secondary air outlet temperature are adjusted by the corresponding variable frequency pump.

[0045] Step 4: The flue gas output from the flue gas heat exchanger 5 in front of the absorption tower is treated by the desulfurization tower 6 and then discharged through the chimney 7.

[0046] It should be noted that the method provided in this embodiment is the same as the method of the system provided in Embodiments 1 and 2. Therefore, the parts that are the same as or similar to those in Embodiments 1 and 2 in this embodiment can be referred to each other, and will not be repeated in this application.

Claims

1. A multi-parameter adjustable five-stage flue gas waste heat utilization system, characterized in that, The application relates to a flue gas heat recovery system of a circulating fluidized bed boiler. The air preheater (1) is connected with a cold primary air system and a cold secondary air heating system; the cold secondary air heating system comprises a warm air heater (10) which is further connected with the electric dust collector front flue gas heat exchanger (2) and the absorption tower front flue gas heat exchanger (5); the air preheater (1) is provided with a bypass system; the electric dust collector front flue gas heat exchanger (2) and the absorption tower front flue gas heat exchanger (5) are provided with an expansion water tank (11). The bypass system comprises a bypass flue and high-temperature and medium-temperature economizers (8) and (9) arranged on the bypass flue; the high-temperature and medium-temperature economizers (8) and (9) are connected in series.

2. The multi-parameter adjustable five-stage flue gas waste heat utilization system according to claim 1, characterized in that, The electric dust collector front flue gas heat exchanger (2) comprises an electric dust collector front high-temperature heat exchanger (201) and an electric dust collector front low-temperature heat exchanger (202); the electric dust collector front high-temperature heat exchanger (201) is used for heat exchange between flue gas output by the air preheater (1) and low-temperature water output by the absorption tower front flue gas heat exchanger (5), and the electric dust collector front low-temperature heat exchanger (202) is used for heat exchange between flue gas treated by the electric dust collector front high-temperature heat exchanger (201) and condensate water.

3. The multi-parameter adjustable five-stage flue gas waste heat utilization system according to claim 2, characterized in that, The electric dust collector front low-temperature heat exchanger (202) is provided with a variable frequency pump for adjusting water quantity at a condensate water input side.

4. The multi-parameter adjustable five-stage flue gas waste heat utilization system according to claim 3, characterized in that, The electric dust collector front high-temperature heat exchanger (201), the absorption tower front flue gas heat exchanger (5) and the warm air heater (10) are all provided with variable frequency pumps for controlling cold secondary air outlet temperature; the electric dust collector front high-temperature heat exchanger (201) is further provided with a bypass for controlling heat absorption.

5. The multi-parameter adjustable five-stage flue gas waste heat utilization system according to claim 4, characterized in that, The high-temperature economizer (8) is used for heating feed water, and the medium-temperature economizer (9) is used for heating condensate water output by the electric dust collector front low-temperature heat exchanger (202); a condensate water output end of the medium-temperature economizer (9) is connected with a deaerator.

6. The multi-parameter adjustable five-stage flue gas waste heat utilization system according to claim 5, characterized in that, The medium-temperature economizer (9) is provided with a bypass for adjusting heat exchange quantity.

7. The multi-parameter adjustable five-stage flue gas waste heat utilization system according to claim 6, characterized in that, ​

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