CN102494329A - Device for utilizing flue gas waste heat of boiler comprehensively - Google Patents

Abstract

The invention is a boiler flue gas waste heat comprehensive utilization device, which uses condensed water or heating network water as a heat transfer medium to absorb the flue gas waste heat. Part of the waste heat of the flue gas is used as the heat source of the heater to heat the cold air through recirculation. On the one hand, the temperature of the cold air is increased to avoid low-temperature corrosion of the preheater, and on the other hand, the temperature of the inlet water of the heat exchanger in the flue gas is increased to avoid low-temperature corrosion; Waste heat replaces extraction steam to heat condensed water or heating network water. This boiler flue gas waste heat comprehensive utilization device can recover the waste heat in the boiler flue gas and convert it into condensed water or heating network water heating source. When the heater is running, part of the waste heat is converted into the heater heat source, reducing the heat recovery system of the steam turbine. The amount of steam extracted can improve the efficiency of the unit, increase the output of power generation, and reduce the coal consumption of power generation.

Description

Boiler flue gas waste heat comprehensive utilization device

technical field

The invention relates to a boiler flue gas waste heat comprehensive utilization device, and mainly relates to the technical field of boiler flue gas waste heat utilization.

Background technique

Heat exchange equipment that transfers the heat released by burning coal, oil, natural gas, biomass and other fuels or other heat energy to purified water through the metal heating surface, and heats it to a certain pressure and temperature of water or steam, called a boiler . The power plant boiler sends the heated steam to the steam turbine to do work, and the steam turbine transfers the energy to the generator to generate electricity, thus completing the energy conversion process. Among them, the boiler efficiency can be improved by increasing the inlet air temperature, and the steam turbine can increase the relative internal efficiency of the steam turbine by adding a reheating system and a feedwater recuperation system. The exhaust heat loss is a large proportion of the heat loss of the boiler. Due to the limitation of the low-temperature corrosion of the air preheater, the design value of the boiler exhaust temperature is usually high, and the condensed water or hot water is used as the cold source to absorb the flue gas. Waste heat, here the condensed water refers to the condensed water from the steam turbine condenser, and the hot water refers to the hot water used for heating in winter. Since the inlet water temperature of the flue gas heat exchanger of this device is higher than the cold air temperature of the air preheater, it can effectively avoid low-temperature corrosion, thereby reducing the exhaust gas temperature, improving boiler efficiency, reducing the steam extraction volume of the steam turbine recovery system, and increasing power generation output , reduce coal consumption for power generation.

The water temperature at the inlet of the flue gas heat exchanger should not be too low, otherwise it will cause low-temperature corrosion of the flue gas heat exchanger. In the present invention, a recirculation pump is provided to heat the water at the outlet of the flue gas heat exchanger into the inlet of the flue gas heat exchanger to Increase the inlet water temperature. When the external ambient temperature of the boiler is actually low, in order to avoid low-temperature corrosion caused by the low temperature of the cold air at the inlet of the air preheater, it is necessary to put in a heater to heat the cold air. Generally, steam extraction is used to heat the cold air. This invention uses a recirculation pump to draw flue gas After the outlet of the heat exchanger is heated, the water is used to heat the cold air, so that the heat required by the air heater is completely replaced by the waste heat of the flue gas.

Contents of the invention

The present invention is a comprehensive utilization device of boiler flue gas waste heat. Condensed water or hot network water absorbs the exhaust heat in the flue gas heat exchanger of the device, reduces the exhaust gas temperature, is heated by itself, and then returns to the steam turbine for low-pressure heating after the temperature is raised. Heater or heat network system, instead of some low-pressure heaters and heat network heat exchangers, is an integral part of the steam turbine thermal system. In the case of constant fuel consumption, this device will save part of the steam recovery or heating extraction of the steam turbine. When the steam intake of the steam turbine remains unchanged, the saved extraction steam will continue to work on the steam turbine to improve the efficiency of the unit. , increase the output of power generation and reduce the coal consumption of power generation. The installation position of the flue gas heat exchanger of this device is any position before the desulfurization system after the preheater, and the installation direction can be arranged horizontally or vertically. The flue gas heat exchanger of this device is installed in the original flue gas channel, the original flue duct can be modified, the cross-sectional area of the device can be increased, and the flue gas flow rate can be evenly distributed by using a flow equalizer or other flow equalization methods to reduce the flue gas flow rate. flow rate. In order to prevent the wear of the flue gas heat exchanger of this device, an anti-wear device can be added to the flue gas inlet of the flue gas heat exchanger of this device. Due to the danger of low-temperature corrosion in the flue gas heat exchanger of this device, materials with high corrosion resistance can be used for the areas with severe low-temperature corrosion of the flue gas heat exchanger, and conventional materials can be used for other parts.

Part or all of the high-temperature water at the outlet of the flue gas heat exchanger of the device in the present invention can enter the water side of the flue gas heat exchanger of the device through recirculation and the low-temperature water at the inlet of the flue gas heat exchanger through the inlet connection box or other mixing methods At the inlet, the water temperature at the inlet of the flue gas heat exchanger is controlled by the recirculation water volume, and the water temperature at the inlet of the heat exchanger in the flue gas is increased to avoid low-temperature corrosion.

The high-temperature water at the outlet of the flue gas heat exchanger of the device of the present invention can partly or completely be recirculated as the heat source of the heater to heat the cold air, and the low-temperature water at the inlet of the flue gas heat exchanger of the device enters through the inlet connection box or other mixing methods The inlet of the water side of the flue gas heat exchanger of this device reduces the heating heat of other means of the heater. The inlet water of the flue gas heat exchanger and the air temperature at the outlet of the heater are controlled by the amount of recirculated water and the amount of water flowing through the heater. On the one hand, increase the cold air temperature to avoid low-temperature corrosion of the preheater, and on the other hand, increase the inlet water temperature of the heat exchanger in the flue gas to avoid low-temperature corrosion.

Description of drawings

Fig. 1 is a schematic diagram of the system of the present invention.

In Figure 1, the numbers represent as follows: 1. Tail flue gas channel, 2. Flue gas heat exchanger, 3. Flue gas heat exchanger inlet header, 4. Heater outlet water gate, 5. Heater, 6. Air heater inlet water gate, 7 flue gas heat exchanger condensate outlet water gate, 8. flue gas heat exchanger condensate water inlet gate, 9. flue gas heat exchanger heat network water inlet gate, 10. flue gas heat exchanger outlet Water gate, 11. Recirculation pump outlet gate, 12. Recirculation pump, 13. Recirculation pump inlet gate, 14. Steam turbine, 15. Low pressure heater, 16. Condenser.

Detailed ways

As shown in the figure, condensed water or heating network water is used as a cold source to absorb the waste heat of flue gas and return to the original pipeline. The flue gas heat exchanger of this device and the original heater can be operated in parallel or in series to exchange heat with flue gas The steam generator replaces the function of part of the steam extraction heat exchanger, reduces the steam extraction volume of the steam turbine extraction system, improves the efficiency of the unit, increases the output of power generation, and reduces the coal consumption of power generation.

Condensed water or heating network water absorbs the exhaust heat in the flue gas heat exchanger of this device, reduces the exhaust gas temperature, is heated by itself, and then returns to the low-pressure heater of the steam turbine or the heating network system after the temperature is raised. The water at the outlet of the flue gas heat exchanger 2 is introduced into the recirculation pump 12 through the inlet door 13 of the recirculation pump to control the amount of water, and the water is introduced into the inlet header 3 of the flue gas heat exchanger through the outlet door 11 of the recirculation pump. The water temperature at the inlet of the flue gas heat exchanger is controlled by the recirculation water volume, and the water temperature at the inlet of the heat exchanger in the flue gas is increased to avoid low-temperature corrosion.

When the external ambient temperature of the boiler is low and the heater needs to be put into use, the water at the outlet of the recirculation pump is controlled by the inlet valve 6 of the recirculation pump and introduced into the heater 5 as a heat source to heat the cold air, replacing the heat source of the original heater. Part of the water heats the cold air and enters the inlet header 3 of the flue gas heat exchanger through the outlet water door 4 of the air heater. When the boiler is in operation, the heating water volume of the heater 5 is controlled by the opening of the heater inlet water door 6 and the heater outlet water door 4 to adjust the cold air heating temperature.

Claims (9)

1. Boiler flue gas waste heat comprehensive utilization device, characterized in that: condensed water or heating network water is used as a cold source to absorb the waste heat of flue gas and returns to the original pipeline, and runs in parallel or in series with the original heater, using a flue gas heat exchanger Replacing the function of part of the steam extraction heat exchanger, reducing the steam extraction volume of the steam turbine regenerating system, the condensed water or the heating network water absorbs the heat of the exhaust gas in the heat pipe heat exchanger of the device, reduces the exhaust gas temperature, and is heated and raised by itself. After returning to the low-pressure heater of the steam turbine or the heating network system, the water at the outlet of the flue gas heat exchanger (2) is introduced into the recirculation pump (12) through the recirculation pump inlet door (13) to control the water volume, and then passes through the recirculation pump outlet door ( 11) Control the amount of water introduced into the inlet header (3) of the flue gas heat exchanger. The water temperature at the inlet of the flue gas heat exchanger is controlled by the recirculation water volume, and the water temperature at the inlet of the heat exchanger in the flue gas is increased to avoid low-temperature corrosion. When the external ambient temperature of the boiler is low and the heater needs to be put into use, the water at the outlet of the recirculation pump is controlled by the inlet water gate of the heater (6) and introduced into the heater (5) as a heat source to heat the cold air, replacing the original heater Heating the heat source, this part of water heats the cold air and enters the inlet header (3) of the flue gas heat exchanger through the outlet water door (4) of the air heater. When the boiler is in operation, the heating water volume of the heater (5) is controlled by the opening of the heater inlet water gate (6) and the heater outlet water gate (4) to adjust the heating temperature of the cold wind. 2. The boiler flue gas waste heat comprehensive utilization device according to claim 1, characterized in that: a flue gas heat exchanger is used to replace part of the function of the steam extraction heat exchanger to reduce the steam extraction volume of the steam turbine extraction system. 3. The boiler flue gas waste heat comprehensive utilization device according to claim 1, characterized in that: the water at the outlet of the recirculation pump is used to replace the heat source of the original heater. 4. The boiler flue gas waste heat comprehensive utilization device according to claim 1, characterized in that the device can be used independently after the recirculation system is removed. 5. The boiler flue gas waste heat comprehensive utilization device according to claim 1, characterized in that: the flue gas heat exchanger of the device is installed at any position before the desulfurization system after the preheater, and the installation direction is horizontal or vertical . 6. The boiler flue gas waste heat comprehensive utilization device according to claim 1, characterized in that: the flue gas heat exchanger of the device is installed in the original flue gas passage, and the original flue can be modified to increase the flow cross-sectional area of the device Reduce the flow rate of the flue gas, and distribute the flow rate of the flue gas evenly by using a flow equalizer or other flow equalization methods. 7. The boiler flue gas waste heat comprehensive utilization device according to claim 1, characterized in that an anti-wear device can be added to the flue gas inlet of the flue gas heat exchanger of the device. 8. The boiler flue gas waste heat comprehensive utilization device according to claim 1, characterized in that the condensed water heated by the flue gas heat exchanger of the device is taken from any position of the condensed water pipeline of the original unit according to the condition of the unit. 9. The boiler flue gas waste heat comprehensive utilization device according to claim 1, characterized in that: the flue gas heat exchanger of the device has the risk of low-temperature corrosion, and the area with severe low-temperature corrosion of the flue gas heat exchanger is made of a material with high corrosion resistance. Other parts can be used with conventional materials.

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