RU2784567C1 - Flue gas heat recovery unit - Google Patents

Abstract

FIELD: heat power industry.

SUBSTANCE: invention can be used, in particular, for the utilization of heat from flue gases at thermal power plants (TPP) that utilize boiler systems. Flue gas heat recovery plant contains the main gas duct to which the first bypass flue is connected; the first shut-off and regulating device, the first stage of the gas-to-water surface heat exchanger, the second stage of the gas-to-water surface heat exchanger, exhaust fan and the second shut-off and regulating device are installed on the line of the duct in succession along the gas flow. The plant also contains a second bypass gas duct the inlet of which is connected to the first bypass gas duct between the first shut-off and regulating device and the first stage of the gas-to-water surface heat exchanger, and the outlet of the duct is connected to the first bypass gas duct between the second stage of the gas-to-water surface heat exchanger and the exhaust fan. Moreover, the third shut-off and regulating device is installed on the line of the second bypass gas duct; the device is connected to a resistance thermometer installed on the line of the first bypass gas duct between the second stage of the gas-to-water surface heat exchanger and the outlet of the second bypass gas duct. The plant also contains a make-up water pipeline on the line of which a pump is installed. Moreover, the outlet of the make-up water pipeline is connected to the inlet of the first discharge pipeline, on the lines of which the second stage of the gas-to-water surface heat exchanger and the first stage of the gas-to-water surface heat exchanger are installed in succession along the water flow. At the same time, the outlet of the first discharge pipeline is connected to the first inlet of the heating network feed tank. Moreover, the outlet of the make-up water pipeline is also connected to the inlet of the second discharge pipeline on the line of which at least one heat exchanger for heating water is installed. The outlet of the second discharge pipeline is connected to the second inlet of the heating network feed tank. Moreover, a hot well of the second stage of the gas-to-water surface heat exchanger is connected to the condensate pipeline.

EFFECT: automatic regulation of the flow of flue gases discharged from the main gas duct and supplied to the make-up water heating to reduce the likelihood of condensate in the first bypass gas duct in front of the exhauster, main gas duct and smoke stack, ensuring the separation of moisture from the flue gases discharged from the main gas flue.

1 cl, 1 dwg

Description

Technical field

The invention relates to the field of thermal power engineering and can be used, in particular, for the utilization of flue gas heat at thermal power plants (TPPs) operating boiler plants.

State of the art

The prior art adopted as a prototype of the claimed invention is a flue gas heat recovery device containing a gas-gas heat exchanger, a condenser, an inertial droplet eliminator, gas ducts, air ducts, fans and a pipeline. At the same time, the gas-gas surface plate heat exchanger is made according to the counterflow scheme, a surface gas-air plate heat exchanger is installed as a condenser, an additional smoke exhauster is installed in the gas flue of cold dried flue gases, a gas flue is embedded in front of the additional smoke exhauster for mixing a part of the heated dried flue gases (patent RU 2436011 C1 , publication date: 10.12.2011 (hereinafter referred to as [1])).

In the flue gas heat recovery device known from [1], it is not supposed to control the flow of flue gases discharged from the boiler plant, but blast air is used as a coolant that removes heat from flue gases using a gas-gas heat exchanger.

Disclosure of invention

The task to be solved by the patented invention is to ensure the utilization of flue gas heat at thermal power plants, and the technical results are to provide automatic adjustment of the flow of flue gases removed from the main gas duct and fed to make-up water heating in order to reduce the likelihood of condensate in the first bypass gas duct before smoke exhauster, main flue and chimney; as well as ensuring the separation of moisture from flue gases discharged from the main flue.

The solution of this problem by achieving the specified technical results is ensured by the fact that the installation for utilizing the heat of flue gases contains the main gas duct, to which the first bypass gas duct is connected, on the line of which the following are installed in series along the gas flow: the first shut-off and control device, the first stage of the gas-water surface heat exchanger , the second stage of the gas-water surface heat exchanger, the smoke exhauster and the second shut-off and control device. At the same time, the installation also contains a second bypass gas duct, the inlet of which is connected to the first bypass gas duct between the first shut-off and control device and the first stage of the gas-water surface heat exchanger, and the outlet is connected to the first bypass gas duct between the second stage of the gas-water surface heat exchanger and the smoke exhauster. Moreover, on the line of the second bypass gas duct, a third shut-off and control device is installed, connected to a resistance thermometer installed on the line of the first bypass gas duct between the second stage of the gas-water surface heat exchanger and the outlet of the second bypass gas duct. In this case, the installation also contains a make-up water pipeline, on the line of which a pump is installed. Moreover, the outlet of the make-up water pipeline is connected to the inlet of the first outlet pipeline, on the line of which the second stage of the gas-to-water surface heat exchanger and the first stage of the gas-to-water surface heat exchanger are installed sequentially along the water flow. In this case, the outlet of the first outlet pipeline is connected to the first inlet of the heating network make-up tank. Moreover, the outlet of the make-up water pipeline is also connected to the inlet of the second outlet pipeline, on the line of which at least one heat exchanger is installed for heating water. At the same time, the outlet of the second discharge pipeline is connected to the second inlet of the heating network feed tank. Moreover, the condensate collector of the second stage of the gas-water surface heat exchanger is connected to the pipeline for condensate removal.

The causal relationship between the essential features of the patented invention and the achieved technical results is as follows.

The inlet of the main flue is connected to the boiler plant, and the outlet is connected to the inlet of the chimney. The first stage of the gas-water surface heat exchanger contains a tank inside which tubes are installed, the inlets and outlets of which are connected to the inlet and outlet manifolds, respectively. The second stage of the gas-to-water surface heat exchanger also contains a tank inside which tubes are installed, the inlets and outlets of which are connected to the inlet and outlet manifolds, respectively. At the same time, the second stage of the gas-to-water surface heat exchanger also contains a condensate collector in its lower part, which is connected to a pipeline for condensate removal. During the operation of the boiler plant, flue gases flow from the boiler plant into the main flue. At the same time, one part of the flue gases is removed from the main gas duct to the first bypass gas duct, through which the flue gases pass sequentially through the tanks of the first and second stages of the gas-to-water surface heat exchanger, and the other part of the flue gases from the first bypass gas duct is removed to the second bypass gas duct, bypassing the gas-to-water surface heat exchanger , after which part of the flue gases from the gas-water surface heat exchanger is mixed with a part of the flue gases from the second bypass flue and then returned to the main gas flue through the first bypass flue using a smoke exhauster. The first and second shut-off and control devices serve to regulate the flow of flue gases discharged from the main flue. The make-up water is pumped by means of a pump through the make-up water pipeline, from which one part of the make-up water flows through the first discharge pipeline sequentially into the tubes of the second and first stages of the gas-to-water surface heat exchanger, passing through the inlet and outlet collectors of the first and second stages of the gas-to-water surface heat exchanger, and the other part make-up water flows through the second outlet pipeline to at least one heater installed on its line, in which water is heated by turbine steam extractions. In this case, in the first and second stages of the gas-to-water surface heat exchanger, heat exchange occurs through the walls of the tubes between a part of the make-up water passing through the tubes and collectors of the first and second stages, and a part of the flue gases passing through the tanks of the first and second stages of the gas-to-water surface heat exchanger. The condensate resulting from the cooling of part of the flue gases passing through the tanks of the gas-to-water surface heat exchanger is removed from the condensate collector through the condensate discharge pipeline. After that, both parts of the make-up water from the first and second outlet pipelines enter the heating network make-up tank, from which the make-up water is directed to the consumer.

When testing pilot samples of the first and second stages of a gas-to-water surface heat exchanger that condenses water vapor contained in flue gases, it was found that the most effective mode of operation of a gas-to-water surface heat exchanger is when the flow rate of flue gases entering through the first bypass gas duct into the gas-water surface heat exchanger, is 20-30% of the total flow of flue gases of the boiler plant entering the main gas duct, at the nominal operating mode of the boiler plant.

When the flow of flue gases through the first and second stages of the gas-to-water surface heat exchanger is below the range of 20-30% of the total flow of flue gases entering the main gas duct, the thermal power of the gas-to-water surface heat exchanger decreases due to a decrease in the heat flow entering the gas-to-water surface heat exchanger. In this connection, the positive effect of flue gas heat recovery is reduced. When the flow of flue gases through the gas-water surface heat exchanger is more than 30% of the total flow of flue gases entering the main gas duct, the thermal power of the gas-water surface heat exchanger remains almost at the same level, however, the power consumption of the smoke exhauster drive increases without a significant increase in thermal power. At the same time, with an increase in the flow of flue gases through the gas-water surface heat exchanger, the flow of flue gases through the main gas duct decreases, which leads to a decrease in their flow rate. That is, in this case, the amount of heat in the main flue is reduced, which in winter can lead to the formation of condensate from flue gases in the chimney.

One of the problems in the utilization of flue gas heat is the possibility of condensate formation in the gas ducts and the chimney after cooling part of the flue gases in the gas-water surface heat exchanger. To eliminate the possibility of condensate in the main flue and chimney, the design of the proposed installation provides for a second bypass flue, through which part of the uncooled flue gases is sent to the first bypass flue in front of the smoke exhauster, bypassing the gas-water surface heat exchanger in order to maintain the temperature of the flue gases in front of the smoke exhauster above 50 ° C - dew points when burning natural gas with a sulfur content of not more than 160 ppm. At the same time, to control the flow of flue gases entering the second bypass gas duct, a third shut-off and control device is provided, connected to an electric drive and a resistance thermometer installed on the line of the first bypass gas duct between the second stage of the gas-water surface heat exchanger and the outlet of the second bypass gas duct. The signal for automatic opening/closing of the third shut-off and control device comes from the aforementioned resistance thermometer. At the nominal operating mode of the flue gas heat recovery plant, the third shut-off and control device is in the 50% open position, corresponding to the passage through the second bypass flue of 5% of the total flue gas flow through the main flue. When the flue gas temperature, measured by a resistance thermometer, in front of the smoke exhauster is below 30 ° C, according to a signal from the resistance thermometer, the third shut-off and control device is automatically transferred to the 100% open position, corresponding to the passage of 10% of the total flow through the second bypass flue flue gases through the main flue. The tests carried out showed the absence of drip moisture in front of the smoke exhauster, as well as the absence of drip moisture in the main flue and chimney under the above operating modes of the flue gas heat recovery unit.

Thus, in view of the foregoing, during the operation of the inventive installation for flue gas heat recovery, automatic adjustment of the flow of flue gases removed from the main gas duct and fed to make-up water heating is ensured in order to reduce the likelihood of condensate in the first bypass flue in front of the smoke exhauster, the main gas duct and the flue pipe; as well as ensuring the separation of moisture from flue gases discharged from the main flue.

Brief description of the drawing

The drawing shows a diagram of the installation for waste heat recovery.

Description of figure positions

1 - main flue;

2 - boiler plant;

3 - chimney;

4 - the first bypass flue;

5 - the first shut-off and control device;

6 - the first stage of the gas-water surface heat exchanger;

7 - the second stage of the gas-water surface heat exchanger;

8 - smoke exhauster;

9 - second shut-off and control device;

10 - second bypass flue;

11 - the third shut-off and control device;

12 - resistance thermometer;

13 - make-up water pipeline;

14 - pump;

15 - the first discharge pipeline;

16 - tank for feeding the heating network;

17 - the second discharge pipeline;

18 - heat exchangers for heating water;

19 - pipeline for condensate removal.

Implementation of the invention

Below is a particular example of an installation for flue gas heat recovery and the principle of its operation.

The inlet of the main gas duct 1 is connected to the boiler plant 2, and the outlet is connected to the inlet of the chimney 3. The installation for utilizing the heat of flue gases includes the main gas duct 1 made of steel 12X18H10T, to which the first bypass gas duct 4, made of steel 12X18H10T, is connected, on the line of which in series along the gas flow are installed: the first shut-off and control device 5, the first stage of the gas-to-water surface heat exchanger 6, the second stage of the gas-to-water surface heat exchanger 7, the smoke exhauster 8 and the second shut-off and control device 9. At the same time, the installation also contains a second bypass gas duct 10 made of steel 12Kh18N10T , the inlet of which is connected to the first bypass flue 4 between the first shut-off and control device 5 and the first stage of the gas-to-water surface heat exchanger 6, and the outlet is connected to the first bypass flue 4 between the second stage of the gas-to-water surface heat exchanger 7 and the smoke exhauster 8. Moreover, on the line of the second bypass gas path 10, a third shut-off and control device 11 is installed, connected by means of a cable to a resistance thermometer 12 installed on the line of the first bypass gas duct 4 between the second stage of the gas-water surface heat exchanger 7 and the outlet of the second bypass gas duct 10. The third shut-off and control device 11 is controlled by a thermometer signal resistance 12. The first stage of the gas-water surface heat exchanger 6 contains a tank made of steel 12X18H10T, inside which tubes are installed, the inlets and outlets of which are connected to the inlet and outlet manifolds, respectively. The second stage of the gas-water surface heat exchanger 7 also contains a tank made of steel 12X18H10T, inside which tubes are installed, the inlets and outlets of which are connected to the inlet and outlet manifolds, respectively. At the same time, the second stage of the gas-to-water surface heat exchanger 7 also contains a condensate collector in its lower part. The tubes of the first and second stages of the gas-water surface heat exchanger 6 and 7 are finned tubes made of steel 12X18H10T. Resistance thermometer 12 has a Pt100 characteristic and a current signal of 4…20 mA. The first, second and third shut-off and control devices 5, 9 and 11 are gates. At the same time, the installation also contains a make-up water pipeline 13 made of steel 12X18H10T, on the line of which a pump 14 is installed. Moreover, the outlet of the make-up water pipeline 13 is connected to the inlet of the first outlet pipeline 15 made of steel 12X18H10T, on the line of which the second stage is installed sequentially along the water flow gas-to-water surface heat exchanger 7 and the first stage of the gas-to-water surface heat exchanger 6. At the same time, the outlet of the first outlet pipeline 15 is connected to the first inlet of the heating network make-up tank 16 made of steel 12X18N10T. 17, on the line of which there are two surface heat exchangers made of steel 12X18H10T for heating water 18, connected to pipelines for extracting steam from the turbine (not shown in the drawing). At the same time, the outlet of the second outlet pipeline 17 is connected to the second inlet of the heating network make-up tank 16. Moreover, the condensate collector of the second stage of the gas-water surface heat exchanger 7 is connected to a pipeline made of steel 12Kh18N10T for condensate removal 19.

The operation of the installation for waste heat recovery is carried out as follows.

The inlet of the main flue 1 is connected to the boiler plant 2, and the outlet is connected to the inlet of the chimney 3. During the operation of the boiler plant 2, the flue gases flow from the boiler plant 2 to the main flue 1. In this case, part of the flue gases, which is 30% of the total flue gases through the main flue 1 is discharged into the first bypass flue 4. Moreover, from the above part of the flue gases entering the first bypass flue 1, one part of the flue gases, constituting 25% of the total flue gas flow through the main flue 1, is sent to the tanks of the first and the second stage of the gas-water surface heat exchanger 6 and 7, and the other part of the flue gases, which is 5% of the total flue gas flow through the main gas duct 1, is sent to the second bypass pipeline 10, bypassing the first and second stages of the gas-water surface heat exchanger 6 and 7. After that, part flue gases from the first and second stages of the gas-water surface heat exchanger 6, 7 is mixed with part of the flue gases from the second bypass flue 10 and then through the first bypass flue 4 with the help of a smoke exhauster 8 returns to the main gas flue 1. The first and second shut-off and control devices 5, 9 serve to regulate the flow of flue gases discharged from the main flue 1, and the third shut-off and control device 11 is used to regulate the flow of flue gases entering the second bypass flue 10. Make-up water is pumped by means of a pump 14 through the make-up water pipeline 13, from which one part of the make-up water flows through the first outlet pipeline 15 successively into the tubes of the second and the first stages of the gas-water surface heat exchanger 6 and 7, passing through the inlet and outlet collectors of the first and second stages of the gas-water surface heat exchanger 6 and 7, and the other part of the make-up water enters through the second outlet pipeline 17 into the heaters 18 installed on its line, in which the water is heated by selections steam turbine. At the same time, in the first and second stages of the gas-to-water surface heat exchanger 6, 7, heat exchange occurs between a part of the make-up water passing through the tubes and collectors of the first and second stages 6 and 7, and part of the flue gases passing through the tanks of the first and second stages of the gas-to-water surface heat exchanger 6 and 7. The condensate resulting from the cooling of part of the flue gases passing through the tanks of the first and second stages of the gas-to-water surface heat exchanger 6 and 7 is discharged from the condensate collector through the condensate discharge pipeline 19 into the condensate storage tank (not shown in the drawing). After that, both parts of the make-up water from the first and second outlet pipelines 15, 17 enter the heating network make-up tank 16, from which the make-up water is directed to the consumer.

The temperature of the flue gases in front of the smoke exhauster 8 must be above 50 ° C - the dew point when burning natural gas with a sulfur content of not more than 160 ppm. At the same time, to control the flow of flue gases entering the second bypass gas duct 10, a third shut-off and control device 11 is provided, connected to an electric drive and a resistance thermometer 12 installed on the line of the first bypass gas duct 4 between the second stage of the gas-water surface heat exchanger 7 and the outlet of the second bypass gas duct 10. The signal for automatic opening/closing of the third shut-off and control device 11 comes from the above resistance thermometer 12. At the nominal operating mode of the flue gas utilization plant, the third shut-off and control device 11 is in the 50% open position, corresponding to the passage through the second bypass flue 5% of the total flue gas flow through the main flue 1. When the flue gas temperature, measured by a resistance thermometer 12 in front of the smoke exhauster 8, drops below 30 ° C, according to a signal from the resistance thermometer 12, the third shut-off and control device 11 auto is automatically transferred to a 100% open position, corresponding to the passage of 10% of the total flue gas flow through the main gas duct 1 through the second bypass flue. under the above operating modes of the flue gas recovery plant.

Thus, in view of the foregoing, during the operation of the proposed installation for flue gas heat recovery, automatic adjustment of the flow of flue gases removed from the main gas flue 1 and supplied to the make-up water heating is provided in order to reduce the likelihood of condensate in the first bypass gas flue 4 before the smoke exhauster 8, mainly flue 1 and chimney 3; as well as ensuring the separation of moisture from the flue gases discharged from the main flue 1.

Industrial Applicability

The patented invention meets the condition of "industrial applicability". The essence of the technical solution is disclosed in the formula, description and drawing clearly enough for understanding and industrial implementation by the relevant specialists, and the means used are simple and accessible for industrial implementation in the field of thermal power engineering.

Claims (1)

Installation for flue gas heat recovery, characterized in that it contains the main gas duct, to which the first bypass gas duct is connected, on the line of which the following are installed in series along the gas flow: the first shut-off and control device, the first stage of the gas-to-water surface heat exchanger, the second stage of the gas-to-water surface heat exchanger, a smoke exhauster and a second shut-off and control device; the plant also contains a second bypass flue, the inlet of which is connected to the first bypass flue between the first shut-off and control device and the first stage of the gas-to-water surface heat exchanger, and the outlet is connected to the first bypass flue between the second stage of the gas-to-water surface heat exchanger and the smoke exhauster; moreover, on the line of the second bypass gas duct, a third shut-off and control device is installed, connected to a resistance thermometer installed on the line of the first bypass gas duct between the second stage of the gas-water surface heat exchanger and the outlet of the second bypass gas duct; while the installation also contains a make-up water pipeline, on the line of which a pump is installed; moreover, the outlet of the make-up water pipeline is connected to the inlet of the first discharge pipeline, on the line of which the second stage of the gas-to-water surface heat exchanger and the first stage of the gas-to-water surface heat exchanger are installed in series along the water flow; wherein the outlet of the first discharge pipeline is connected to the first inlet of the heating network feed tank; moreover, the outlet of the make-up water pipeline is also connected to the inlet of the second outlet pipeline, on the line of which at least one heat exchanger is installed for heating water; wherein the output of the second discharge pipeline is connected to the second input of the heating network feed tank; moreover, the condensate collector of the second stage of the gas-water surface heat exchanger is connected to the pipeline for condensate removal.

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