An industrial flue gas waste heat recycling system

Abstract

This invention belongs to the field of industrial energy-saving technology and discloses an industrial flue gas waste heat recovery and utilization system, including a flue gas pipeline and a water pipeline; a first heat exchange unit is installed on the flue gas pipeline; the first heat exchange unit has a first flue gas side and a first water side, the first flue gas side is connected in series in the flue gas pipeline, and the first water side is connected in series in the water pipeline. The first heat exchange unit is used to heat the water flowing through its first water side to partial vaporization using flue gas to produce a steam-water mixture; a separation unit is connected to the outlet of the first water side, the separation unit is used to separate the steam-water mixture into steam and water; the separation unit is connected to a steam pipe for discharging steam; a third heat exchange unit is connected downstream of the steam pipe, the third heat exchange unit has a steam side and a medium side, the steam side is connected to the steam pipe; this invention effectively solves the problem in the prior art that the steam generated when high-temperature flue gas heats water cannot be actively, continuously and safely discharged, and the discharged steam is directly wasted and not effectively utilized.

Description

Technical Field

[0001] This invention belongs to the field of industrial energy conservation technology, and specifically relates to an industrial flue gas waste heat recovery and utilization system. Background Technology

[0002] In industrial flue gas waste heat recovery systems, heat exchangers are typically used to heat water from the flue gas. Industrial flue gas temperatures are high, typically between 200°C and 600°C, far exceeding the boiling point of water. Therefore, the water inside the heat exchanger is easily heated to boiling, generating a large amount of steam. If this steam cannot be discharged in time, it will accumulate inside the heat exchanger, causing a rapid increase in pressure. Prolonged operation with this steam can lead to heat exchanger rupture, posing a serious safety hazard.

[0003] To address this issue, existing technologies typically install pressure relief valves on heat exchangers, which automatically open to release steam when the internal pressure exceeds a set value. However, this method has the following drawbacks: The pressure relief valve operates under high temperature and high pressure conditions for extended periods, causing the springs and seals to age and fail, leading to valve jamming or malfunction, resulting in poor reliability; the steam released after the pressure relief valve opens directly into the atmosphere, and the large amount of latent heat it carries is not recovered, resulting in energy waste; the pressure relief valve only opens passively when the pressure exceeds the limit, which is a reactive measure and cannot achieve active and continuous steam discharge, making it difficult to fundamentally eliminate safety hazards. Therefore, existing technologies suffer from the problem that steam generated when high-temperature flue gas heats water cannot be actively, continuously, and safely discharged, and the discharged steam is directly wasted and not effectively utilized. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide an industrial flue gas waste heat recovery and utilization system, which solves the problem that the steam generated when high-temperature flue gas is heated with water cannot be actively, continuously and safely discharged, and the discharged steam is directly wasted and not effectively utilized.

[0005] The objective of this invention can be achieved through the following technical solutions: An industrial flue gas waste heat recovery and utilization system includes flue gas pipelines and water pipelines; The flue gas duct is equipped with a first heat exchange unit; The first heat exchange unit has a first flue gas side and a first water side. The first flue gas side is connected in series in a flue gas pipe, and the first water side is connected in series in a water pipe. The first heat exchange unit is used to heat the water flowing through its first water side to partial vaporization using flue gas to produce a steam-water mixture. The outlet on the first water side is connected to a separation unit, which is used to separate the steam-water mixture into steam and water. The separation unit is connected to a steam pipe for discharging steam; Downstream of the steam pipe is a third heat exchange unit, which has a steam side and a medium side. The steam side is connected to the steam pipe, and the medium side is used to introduce the medium to be heated. The third heat exchange unit is used to heat the medium to be heated in the medium side using the steam in the steam side.

[0006] Furthermore, multiple second heat exchange units are installed on the flue gas duct, and these multiple second heat exchange units are connected in series downstream of the first heat exchange unit along the flue gas flow direction. The second heat exchange unit has a second flue gas side and a second water side, with the second flue gas side connected in series in the flue gas duct and the second water side connected in series in the water duct.

[0007] Furthermore, the water flow direction in the water pipe is opposite to the flue gas flow direction in the flue gas pipe. The water in the water pipe flows sequentially through the second water side of each second heat exchange unit, is preheated step by step by each second heat exchange unit, and then enters the first water side of the first heat exchange unit.

[0008] Furthermore, the cooling medium introduced into the medium side of the third heat exchange unit is water.

[0009] Furthermore, a branch water pipe is connected downstream of the medium side in the third heat exchange unit, and the other end of the branch water pipe merges into the water pipeline, with the merging point located upstream of the first water side in the water pipeline.

[0010] Furthermore, there are multiple branch water pipes, the number of which is equal to and corresponds one-to-one with the number of second heat exchange units. One end of each branch water pipe is connected to the medium-side outlet of the third heat exchange unit, and the other end of each branch water pipe is connected to the downstream of the second water side of each second heat exchange unit. Each branch water pipe is equipped with a valve section, and each valve section is connected to a monitoring and control module, which is used to control the opening or closing of the corresponding valve section.

[0011] Furthermore, the monitoring and control module includes a first temperature sensor, a second temperature sensor, and a controller; The first temperature sensor is one, which is set at the medium-side outlet of the third heat exchange unit to collect the water temperature at the medium-side outlet; The number of second temperature sensors is equal to that of branch water pipes and they correspond one-to-one. The second temperature sensors are installed at the junction of the corresponding branch water pipe and the water pipeline to collect the downstream water temperature of the second water side of the corresponding second heat exchange unit. The number of controllers and valves are equal and correspond one-to-one. Each controller is electrically connected to the corresponding valve. Each controller is used to control the opening or closing of the corresponding valve based on the water temperature collected by the first temperature sensor and the water temperature collected by the corresponding second temperature sensor.

[0012] Furthermore, the separation unit is a steam-water separator.

[0013] Furthermore, the first heat exchange unit is an evaporator, and the third heat exchange unit is a steam heater.

[0014] Furthermore, the second heat exchange unit is an economizer.

[0015] The beneficial effects of this invention are: 1. By setting up a first heat exchange unit, high-temperature flue gas is used to heat the water flowing through its first water side to partial vaporization. The separation unit connected to the outlet of the first water side promptly extracts the generated steam-water mixture and separates it into steam and water. The steam is discharged through a steam pipe, effectively avoiding the risk of explosion caused by the accumulation of steam in the heat exchanger. At the same time, the discharged steam is introduced into the steam side of the third heat exchange unit, and the latent heat of the steam is used to heat the medium to be heated in the medium side. On the basis of eliminating safety hazards, the secondary recovery and utilization of steam energy is realized, achieving a technical effect that unifies safety and economy. It effectively solves the problem in the existing technology that the steam generated when high-temperature flue gas heats water cannot be actively, continuously and safely discharged, and the discharged steam is directly wasted and not effectively utilized. 2. By setting up multiple second heat exchange units in series downstream of the first heat exchange unit in the flue gas duct, and making the water in the water pipe flow through each second heat exchange unit in sequence to be preheated step by step before entering the first heat exchange unit, and at the same time, the water flow direction is opposite to the flue gas flow direction, so that the water is gradually preheated and heated when entering the first heat exchange unit, thus realizing the stepwise utilization of flue gas heat. 3. By setting up multiple branch water pipes corresponding one-to-one with the second heat exchange unit, one end of each branch water pipe is connected to the medium side outlet of the third heat exchange unit, and the other end is connected to the downstream of the second water side of the corresponding second heat exchange unit. A valve is set on each branch water pipe. The monitoring and control module controls the opening or closing of the corresponding valve based on the comparison results of the outlet water temperature of the third heat exchange unit collected by the first temperature sensor and the downstream water temperature of each second heat exchange unit collected by the second temperature sensor. This ensures that the preheated hot water flows into the position with the closest temperature, thereby minimizing irreversible losses when mixing hot and cold water and improving the thermodynamic efficiency of the system. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a block diagram of the overall system structure of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] like Figure 1 As shown, an industrial flue gas waste heat recovery and utilization system includes flue gas pipelines and water pipelines. The flue gas duct is equipped with a first heat exchange unit; The first heat exchange unit has a first flue gas side and a first water side. The first flue gas side is connected in series in a flue gas pipe, and the first water side is connected in series in a water pipe. The first heat exchange unit is used to heat the water flowing through its first water side to partial vaporization using flue gas to produce a steam-water mixture. The outlet on the first water side is connected to a separation unit, which is used to separate the steam-water mixture into steam and water. The separation unit is connected to a steam pipe for discharging steam; Downstream of the steam pipe is a third heat exchange unit, which has a steam side and a medium side. The steam side is connected to the steam pipe, and the medium side is used to introduce the medium to be heated. The third heat exchange unit is used to heat the medium to be heated in the medium side using the steam in the steam side. When high-temperature flue gas heats the water flowing through the first water side of the first heat exchange unit, the water boils rapidly, generating a large amount of steam. If the steam accumulates in the heat exchange unit, it will cause a sharp increase in pressure, leading to an explosion risk. Existing technologies lack effective countermeasures for this problem. This application connects a separation unit to the outlet of the first water side of the first heat exchange unit to promptly extract and separate the steam-water mixture into steam and water, allowing the steam to be discharged through a steam pipe. This effectively solves the technical problem in existing technologies where the risk of heat exchanger explosion due to steam accumulation when high-temperature flue gas heats water. At the same time, the discharged steam is not directly wasted but is introduced into the steam side of the third heat exchange unit through a steam pipe, utilizing the latent heat of the steam to heat the medium to be heated on the medium side. This further realizes the secondary recovery and utilization of steam energy while eliminating safety hazards, achieving a technical effect that unifies safety and economy.

[0020] Multiple second heat exchange units are also installed on the flue gas duct, and these multiple second heat exchange units are connected in series downstream of the first heat exchange unit along the flue gas flow direction. The second heat exchange unit has a second flue gas side and a second water side, with the second flue gas side connected in series in the flue gas duct and the second water side connected in series in the water duct. By setting up multiple second heat exchange units connected in series downstream of the first heat exchange unit in the flue gas duct, the waste heat of the flue gas downstream of the first heat exchange unit is used to preheat the water, thereby realizing the cascade utilization of flue gas heat and improving the overall thermal efficiency of the system.

[0021] The water flow direction in the water pipe is opposite to the flue gas flow direction in the flue gas pipe. The water in the water pipe flows through the second water side of each second heat exchange unit in sequence. After being preheated by each second heat exchange unit step by step, it enters the first water side of the first heat exchange unit. By making the water flow direction opposite to the flue gas flow direction, and by having the water flow through each of the second heat exchange units in sequence to be preheated step by step before entering the first heat exchange unit, the water reaches a higher temperature when it enters the first heat exchange unit, thereby reducing the amount of heat required by the first heat exchange unit to heat the water to the target temperature and improving the heat exchange efficiency.

[0022] The cooling medium introduced into the medium side of the third heat exchange unit is water; By limiting the heated medium in the third heat exchange unit to water, the hot water heated by steam can be directly fed into the water pipes to participate in the system circulation, thus simplifying the system structure.

[0023] Downstream of the medium side in the third heat exchange unit is a branch water pipe, and the other end of the branch water pipe merges into the water pipeline, with the merging point located upstream of the first water side in the water pipeline. When the third heat exchange unit uses steam to heat water, it is limited by the steam temperature and can only heat the water to a relatively low temperature, which cannot meet the production needs. Therefore, this application connects a branch water pipe downstream of the medium side of the third heat exchange unit and merges the other end of the branch water pipe into the upstream position of the first water side of the water pipeline. This allows the water preheated by steam to mix with the preheated water from the second heat exchange unit and then enter the first heat exchange unit together. The first heat exchange unit uses high-temperature flue gas to further heat the water to the temperature required for production before outputting it. This not only makes up for the deficiency of insufficient steam temperature, but also realizes the cascade utilization of steam heat.

[0024] There are multiple branch water pipes, and the number of branch water pipes is equal to the number of second heat exchange units and corresponds one-to-one. One end of each branch water pipe is connected to the medium side outlet of the third heat exchange unit, and the other end of each branch water pipe is connected to the downstream of the second water side of each second heat exchange unit. Each branch water pipe is equipped with a valve section, and each valve section is connected to a monitoring and control module. The monitoring and control module is used to control the opening or closing of the corresponding valve section. By configuring independent branch water pipes and valve sections for each second heat exchange unit, and controlling the opening and closing status of each valve section according to actual needs by the monitoring and control module, the hot water heated by the third heat exchange unit can flow into the downstream location of any second heat exchange unit as needed, thereby realizing flexible selection and switching of hot water inflow points.

[0025] The monitoring and control module includes a first temperature sensor, a second temperature sensor, and a controller; The first temperature sensor is one, which is set at the medium-side outlet of the third heat exchange unit to collect the water temperature at the medium-side outlet; The number of second temperature sensors is equal to that of branch water pipes and they correspond one-to-one. The second temperature sensors are installed at the junction of the corresponding branch water pipe and the water pipeline to collect the downstream water temperature of the second water side of the corresponding second heat exchange unit. The number of controllers and valves are equal and correspond one-to-one. Each controller is electrically connected to the corresponding valve. Each controller is used to control the opening or closing of the corresponding valve based on the water temperature collected by the first temperature sensor and the water temperature collected by the corresponding second temperature sensor. Based on the detection of the outlet water temperature of the third heat exchange unit by the first temperature sensor and the detection of the downstream water temperature of each second heat exchange unit by the second temperature sensor, each controller compares the detection values ​​of the first temperature sensor with the corresponding second temperature sensor and controls the opening and closing state of the corresponding valve accordingly, so that the preheated hot water always flows into the position with the closest water temperature, thereby minimizing the irreversible loss when mixing hot and cold water and improving the thermodynamic efficiency of the system. Preferably, the valve section is an electric regulating valve, and the controller is a PLC controller or a microcontroller. Each controller opens the electric regulating valve on the branch water pipe with the smallest absolute temperature difference based on the absolute value of the temperature difference between the first temperature sensor and the corresponding second temperature sensor, while closing the electric regulating valves on the remaining branch water pipes.

[0026] The separation unit is a steam-water separator; The separation unit is specifically a steam-water separator, which uses mature steam-water separation technology to effectively separate steam and water, ensuring the purity of the steam used in the future. At the same time, the separated hot water has a high temperature and can be directly supplied to production as industrial hot water.

[0027] The first heat exchange unit is an evaporator, and the third heat exchange unit is a steam heater; Preferably, the evaporator adopts a shell-and-tube heat exchange structure, and the steam heater adopts a surface condensation heat exchange structure to improve heat exchange efficiency.

[0028] The second heat exchange unit is an economizer; The economizer is located downstream of the evaporator and uses the waste heat of the flue gas at the evaporator outlet to preheat the incoming water in stages, which significantly increases the water temperature entering the evaporator, thereby reducing the heat load of the evaporator. Preferably, there are multiple economizers arranged in series, and each economizer adopts a finned tube structure to enhance the heat exchange effect.

[0029] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0030] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. An industrial flue gas waste heat recovery and utilization system, comprising flue gas pipelines and water pipelines, characterized in that, The flue gas duct is equipped with a first heat exchange unit; The first heat exchange unit has a first flue gas side and a first water side. The first flue gas side is connected in series in a flue gas pipe, and the first water side is connected in series in a water pipe. The first heat exchange unit is used to heat the water flowing through its first water side to partial vaporization using flue gas to produce a steam-water mixture. The outlet on the first water side is connected to a separation unit, which is used to separate the steam-water mixture into steam and water. The separation unit is connected to a steam pipe for discharging steam; Downstream of the steam pipe is a third heat exchange unit, which has a steam side and a medium side. The steam side is connected to the steam pipe, and the medium side is used to introduce the medium to be heated. The third heat exchange unit is used to heat the medium to be heated in the medium side using the steam in the steam side.

2. The industrial flue gas waste heat recovery and utilization system according to claim 1, characterized in that, Multiple second heat exchange units are also installed on the flue gas duct, and these multiple second heat exchange units are connected in series downstream of the first heat exchange unit along the flue gas flow direction. The second heat exchange unit has a second flue gas side and a second water side, with the second flue gas side connected in series in the flue gas duct and the second water side connected in series in the water duct.

3. The industrial flue gas waste heat recovery and utilization system according to claim 2, characterized in that, The water flow direction in the water pipe is opposite to the flue gas flow direction in the flue gas pipe. The water in the water pipe flows through the second water side of each second heat exchange unit in sequence. After being preheated by each second heat exchange unit step by step, it enters the first water side of the first heat exchange unit.

4. The industrial flue gas waste heat recovery and utilization system according to claim 3, characterized in that, The cooling medium introduced into the medium side of the third heat exchange unit is water.

5. The industrial flue gas waste heat recovery and utilization system according to claim 4, characterized in that, The downstream of the medium side in the third heat exchange unit is connected to a branch water pipe, and the other end of the branch water pipe merges into the water pipeline, with the merging point located upstream of the first water side in the water pipeline.

6. The industrial flue gas waste heat recovery and utilization system according to claim 5, characterized in that, There are multiple branch water pipes, and the number of branch water pipes is equal to the number of second heat exchange units and corresponds one-to-one. One end of each branch water pipe is connected to the medium side outlet of the third heat exchange unit, and the other end of each branch water pipe is connected to the downstream of the second water side of each second heat exchange unit. Each branch water pipe is equipped with a valve section, and each valve section is connected to a monitoring and control module, which is used to control the opening or closing of the corresponding valve section.

7. The industrial flue gas waste heat recovery and utilization system according to claim 6, characterized in that, The monitoring and control module includes a first temperature sensor, a second temperature sensor, and a controller; The first temperature sensor is one, which is set at the medium-side outlet of the third heat exchange unit to collect the water temperature at the medium-side outlet; The number of second temperature sensors is equal to that of branch water pipes and they correspond one-to-one. The second temperature sensors are installed at the junction of the corresponding branch water pipe and the water pipeline to collect the downstream water temperature of the second water side of the corresponding second heat exchange unit. The number of controllers and valves are equal and correspond one-to-one. Each controller is electrically connected to the corresponding valve. Each controller is used to control the opening or closing of the corresponding valve based on the water temperature collected by the first temperature sensor and the water temperature collected by the corresponding second temperature sensor.

8. The industrial flue gas waste heat recovery and utilization system according to claim 7, characterized in that, The separation unit is a steam-water separator.

9. The industrial flue gas waste heat recovery and utilization system according to claim 8, characterized in that, The first heat exchange unit is an evaporator, and the third heat exchange unit is a steam heater.

10. The industrial flue gas waste heat recovery and utilization system according to claim 9, characterized in that, The second heat exchange unit is an economizer.

Images