Boiler flue gas waste heat deep recovery energy-saving system

Abstract

The utility model discloses a boiler flue gas waste heat deep recovery energy-saving system. According to the system, an air spraying device is arranged on a boiler air inlet pipeline, and a flue gas humidifying and cooling device is arranged on a smoke exhaust flue; a water circulation pipeline is arranged among the flue gas heat exchanger, the air spraying device and the flue gas humidifying and cooling device, condensate water generated after waste heat of flue gas is recycled through the flue gas heat exchanger enters a condensate water tank, and then part or all of the condensate water is conveyed to the air spraying device and the flue gas humidifying and cooling device. By spraying and humidifying air and flue gas, deep recovery of flue gas waste heat is achieved, and the system is simple in structure, small in implementation difficulty and suitable for different application environments.

Description

Technical Field

[0001] The utility model relates to the fields of energy conservation, environmental protection and flue gas waste heat recovery, and in particular to a boiler flue gas waste heat deep recovery and energy-saving system. Background Art

[0002] Coal-fired boilers or gas-fired boilers are commonly used boiler equipment for heating, bathing and other purposes. Common coal-fired boilers and gas-fired boilers include hot water boilers, steam boilers, etc.

[0003] Coal-fired boilers have high sulfide content in their exhaust gas, and wet flue gas desulfurization (FGD) technology is often used to reduce this level. However, after wet FGD, the water vapor content in the exhaust gas of coal-fired boilers remains high. Gas-fired boilers, however, also have high water vapor content due to the chemical composition of the fuel. Furthermore, because the exhaust gas temperature of coal-fired or gas-fired boilers is typically at or above the saturation temperature, the water vapor in the exhaust gas contains a significant amount of latent heat. Analysis suggests that the latent heat of water vapor in the exhaust gas of coal-fired or gas-fired boilers accounts for as much as 10-11% of the calorific value of the fuel. The industry lacks effective recovery and utilization measures for this waste heat, resulting in significant energy waste. Therefore, fully recovering and utilizing the waste heat from coal-fired or gas-fired boilers, including the latent heat of water vapor, is crucial for energy conservation and emission reduction.

[0004] In order to recycle the waste heat of boiler flue gas, the current conventional practice is to use heat medium water as a carrier, and set up a heat pump and a flue gas water heat exchanger at the same time. The flue gas water heat exchanger is set on the flue gas pipeline, and the heat medium water is used to recover the waste heat of the flue gas, and then it is sent to the heat pump unit to extract the waste heat of the flue gas. However, this method has many technical problems in practice, such as (1) the heat pump needs to be driven by a high-quality heat source; (2) the heat pump is expensive, the investment is large, and the investment recovery period is long; (3) the heat pump requires additional space and is subject to large space constraints, making it difficult to use it to modify the pipeline system of an existing hot water boiler or steam boiler.

[0005] In response to practical problems, the inventors of this application have previously disclosed two improved systems: (1) Patent No. CN114278956B discloses a waste heat recovery system, which includes an air heater on the boiler air inlet duct and a flue gas heat exchanger on the boiler flue gas outlet. Heating water first enters the air heater to heat the air, then the cooled heating water enters the flue gas heat exchanger to exchange heat with the flue gas, and then the heated heating water is sent back to the boiler, thereby recovering the waste heat from the low-temperature flue gas. When the amount of flue gas waste heat recovered is small, the system does not require a heat source, that is, no heat pump is required. (2) Patent CN221464409U discloses another waste heat recovery system, which is provided with an air spray device and an air heater in the boiler air inlet duct, a flue gas heat exchanger in the boiler exhaust duct, and a heat medium water between the air heater and the flue gas heat exchanger. The heat medium water and the flue gas exchange heat in the flue gas heat exchanger, and the heat of the low-temperature flue gas is transferred to the heat medium water. The heat medium water, after absorbing the heat of the flue gas, enters the air heater to heat the air, and the heated air enters the boiler, thereby realizing deep recovery of the flue gas waste heat, that is, the flue gas waste heat is transferred to the heat medium water, and the heat medium water transfers the heat to the air and enters the boiler with the air.

[0006] How to further optimize the boiler flue gas waste heat recovery and utilization system so that it can not only deeply recover the boiler flue gas waste heat, but also have realistic engineering feasibility and can be effectively used to transform the existing boiler pipeline system, while also being able to improve boiler efficiency, reduce fuel consumption, simplify system structure, reduce investment, and improve return on investment is still the direction that this field is striving to pursue. Utility Model Content

[0007] The present application aims to provide a flue gas waste heat deep recovery system, which can not only ensure the recovery amount of flue gas waste heat, but also greatly simplify the system structure and can be adapted to different industrial equipment and application scenarios.

[0008] To achieve the above objectives, according to one embodiment of the present invention, the technical solution provided is as follows:

[0009] A boiler flue gas waste heat deep recovery energy-saving system, comprising:

[0010] An air spray device and an air heater are sequentially installed on the boiler air inlet pipe;

[0011] A flue gas heat exchanger is installed on the boiler exhaust duct;

[0012] After being sprayed and humidified by the air spray device, the air enters the air heater for heat exchange and temperature increase, and finally enters the boiler;

[0013] All or part of the heating water enters the air heater to heat the air, and the cooled heating water enters the flue gas heat exchanger to exchange heat with the flue gas;

[0014] The heated heating water enters the boiler or the heating network heater to be heated again;

[0015] A water circulation pipeline is set between the flue gas heat exchanger and the air spray device. The condensed water generated after the flue gas recovers the waste heat through the flue gas heat exchanger enters the condensed water tank, and then part or all of the condensed water is transported to the air spray device.

[0016] Preferably, the boiler flue gas waste heat deep recovery and energy-saving system further includes: a flue gas humidification and cooling device and a flue gas heat exchanger are sequentially arranged on the boiler's exhaust flue; after the flue gas is humidified by the flue gas humidification and cooling device, the water vapor content in the flue gas increases or reaches saturation, and then enters the flue gas heat exchanger to exchange heat with cold water to recover the flue gas waste heat; the flue gas is discharged after the waste heat is recovered.

[0017] In the present invention, the humidifying and cooling device is used to atomize and / or vaporize the spray water, and then spray it into the flue gas, so as to increase the water vapor content in the flue gas or make it saturated, thereby increasing the water dew point temperature of the flue gas.

[0018] Preferably, in the boiler flue gas waste heat deep recovery energy-saving system, a water circulation pipeline is set between the flue gas heat exchanger and the flue gas humidification and cooling device. The condensed water condensed from the flue gas in the flue gas heat exchanger enters the condensed water tank, and then part or all of the condensed water is transported to the flue gas humidification and cooling device, reducing the need for additional configuration of spray water.

[0019] More preferably, the condensed water generated after the flue gas recovers waste heat through the flue gas heat exchanger enters a condensate tank, with some of the condensed water then being delivered to the air spray device and some to the flue gas humidification and cooling device. By using the condensate tank to collect the condensed water in the flue gas and then using it to spray and humidify the air and flue gas, the need for additional spray water is reduced.

[0020] In the present invention, the air heater and the flue gas heat exchanger are partition-type heat exchangers, such as plate heat exchangers and tube heat exchangers.

[0021] Preferably, the air heater and the flue gas heat exchanger are plate heat exchangers.

[0022] Plate heat exchangers have the characteristics of high heat transfer coefficient, compact structure, small footprint and flexible layout. During use, they are not restricted by the structure and layout of the boiler exhaust duct and air inlet duct. They have strong engineering adaptability and can well meet the renovation needs of various new and old boiler systems.

[0023] In the utility model, the heating network heater is a partition type heat exchanger.

[0024] The present invention has no particular restrictions on the types of air spray devices and flue gas humidification and cooling devices, which can be spray devices commonly used in the prior art, such as tube sprayers, shower head sprayers, ring tube multi-hole sprayers, nozzles with liquid atomization function, etc.

[0025] Preferably, the air spray device and the flue gas humidification and cooling device are nozzles, which have the function of atomizing the liquid.

[0026] In the present invention, there is no restriction on the number of the air spray device, the flue gas humidifying and cooling device, the flue gas heat exchanger, and the heating network heater, which can be one or more.

[0027] The utility model has no particular restrictions on the type of boiler and is applicable to coal-fired boilers, gas-fired boilers or oil-fired boilers. In practical applications, it can be a hot water boiler, a steam boiler or a garbage incinerator.

[0028] The utility model has no special restrictions on the exhaust flue of the boiler. The utility model is applicable to various types of boiler exhaust flues. The exhaust flue can be a vertical exhaust flue or a horizontal exhaust flue, and can be the original exhaust flue of the boiler or a modified exhaust flue.

[0029] The utility model has no special restrictions on the air inlet duct of the boiler. The utility model is applicable to various types of boiler air inlet ducts. The air inlet duct can be a vertical air inlet duct or a horizontal air inlet duct, and can be the original air inlet duct of the boiler or a modified air inlet duct.

[0030] Beneficial effects of the utility model:

[0031] Compared with the existing technical problems of low flue gas waste heat recovery rate, high cost of heat pump unit, high operation and maintenance cost, complex structure, large floor space, strong space and environmental constraints, and poor engineering adaptability, this utility model has the following advantages and technical effects:

[0032] (1) Spraying humidification on the boiler inlet air increases the water content in the air, which in turn increases the heat capacity of the air. This allows the air to recover more heat from the heating water return. With this increase in water content, the water vapor content of the flue gas produced by boiler combustion also increases, increasing the heat release capacity of the flue gas. With this increase in heat release capacity, 50-90% more heat can be recovered from the flue gas under the same flue gas temperature drop.

[0033] (2) A flue gas humidification and cooling device is installed in front of the flue gas heat exchanger to increase the water vapor content in the flue gas, increase the water dew point temperature, reduce the amount of waste heat recovery in the first heat exchange stage (cooling section), and increase the amount of waste heat recovery in the second heat exchange stage (condensation section), thereby improving the heat transfer coefficient of the flue gas heat exchanger, reducing the heat exchange area, reducing the weight of the equipment, reducing equipment investment, saving floor space and space, and thus facilitating equipment installation.

[0034] (3) The system structure is simple, the implementation is easy, and the waste heat recovery efficiency is high.

[0035] (4) While deeply recovering the waste heat from boiler flue gas, it improves boiler efficiency and reduces fuel consumption.

[0036] (5) The utility model adopts a partition-type heat exchanger, which has the characteristics of compact structure, small footprint and flexible layout. It is not restricted by the boiler exhaust duct, air inlet duct structure and layout during use. It has strong engineering adaptability and can well meet the renovation needs of various new and old boiler systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 : Schematic diagram of the structure of the flue gas waste heat deep recovery and energy-saving system in Example 1 of the present utility model.

[0038] Figure 2 : Schematic diagram of the structure of the flue gas waste heat deep recovery and energy-saving system in Example 2 of the present utility model.

[0039] Figure 3 : Schematic diagram of the structure of the flue gas waste heat deep recovery and energy-saving system in Example 3 of the present utility model.

[0040] Figure 4 : Schematic diagram of the structure of the flue gas waste heat deep recovery and energy-saving system in Example 4 of the present utility model.

[0041] Figure 5 : Schematic diagram of the structure of the flue gas waste heat deep recovery and energy-saving system in Example 5 of the present utility model.

[0042] Figure 6 : Schematic diagram of the structure of the flue gas waste heat deep recovery and energy-saving system in Example 6 of the present utility model.

[0043] Description of reference numerals:

[0044] 1-Boiler; 2-Fan; 3-Air heater; 4-Air spray device; 5-Flue gas heat exchanger I; 6-Condensate tank; 7-Spray water pump; 8-Flue gas humidification and cooling device; 9-Flue gas heat exchanger II; 10-Heating network heater. DETAILED DESCRIPTION

[0045] The inventors of this application have previously disclosed two improved systems to address existing technical problems in practice: (1) Patent No. CN114278956B discloses a waste heat recovery system, which includes an air heater installed on the boiler air inlet duct and a flue gas heat exchanger installed on the boiler flue gas outlet. Heating water first enters the air heater to heat the air, then enters the flue gas heat exchanger to exchange heat with the flue gas after cooling, and then enters the boiler after heating, thereby recovering the waste heat in the low-temperature flue gas. (2) Patent CN221464409U discloses another waste heat recovery system, which is provided with an air spray device and an air heater in the boiler air inlet duct, a flue gas heat exchanger in the boiler exhaust duct, and a heat medium water between the air heater and the flue gas heat exchanger. The heat medium water and the flue gas exchange heat in the flue gas heat exchanger, and the heat of the low-temperature flue gas is transferred to the heat medium water. The heat medium water, after absorbing the heat of the flue gas, enters the air heater to heat the air, and the heated air enters the boiler, thereby realizing deep recovery of the flue gas waste heat, that is, the flue gas waste heat is transferred to the heat medium water, and the heat medium water transfers the heat to the air and enters the boiler with the air.

[0046] The system disclosed in patent No. CN114278956B is more suitable for industrial devices with a small amount of flue gas waste heat recovery. When the amount of flue gas waste heat recovery is large, a supporting heat pump technology is required.

[0047] The system disclosed in Patent No. CN221464409U can ensure the recovery of flue gas waste heat, has a wider range of applicable scenarios, and eliminates the need for a heat pump and a driving heat source compared to conventional systems, but requires a heat medium water system.

[0048] The present invention is based on previous inventions and creations, further optimizes the waste heat recovery system, and proposes the technical solution of the present invention.

[0049] The technical solution provided by the utility model is to arrange an air spray device on the air inlet duct of the boiler. After the air is sprayed and humidified by the air spray device, the water content in the air increases, and the heat absorption capacity of the air increases. Under the condition of the same air temperature rise, the air can absorb more heat from the heating water. After the air enters the air heater and is heated by the heating water, the temperature of the air increases, and at the same time, the liquid water in the air is vaporized into gaseous water. After the air enters the boiler and is burned in the boiler, flue gas is generated. The water vapor content in the flue gas will also increase, and the heat release capacity of the flue gas will be increased. That is, under the condition of the same flue gas temperature drop, 50-90% more heat can be recovered from the flue gas.

[0050] All or part of the heating water enters the air heater to heat the air. The cooled heating water then enters one or more flue gas heat exchangers to exchange heat with the flue gas, absorbing the flue gas's waste heat. The heated heating water is then further heated by the boiler or heat network heater before being supplied externally. This recovers waste heat from the flue gas and raises the temperature of the boiler's inlet air and the heating water.

[0051] Furthermore, a flue gas humidification and cooling device is set in front of the flue gas heat exchanger. Before the flue gas exchanges heat with the heat exchanger, the flue gas is first sprayed to humidify and cool it, so that the water vapor content in the flue gas increases or reaches saturation, and then enters the flue gas heat exchanger for heat exchange. The first heat exchange stage (cooling section) is partially or completely converted into the second heat exchange stage (condensing section), which greatly improves the heat exchange capacity. When recovering the same amount of heat, the heat exchange area of ​​the heat exchanger can be significantly reduced.

[0052] The principle of setting up the flue gas humidification and cooling device is: the flue gas water heat exchange to recover the flue gas waste heat includes two heat exchange stages:

[0053] The first heat exchange stage is the cooling stage. During the flue gas cooling process, no liquid water is precipitated, that is, there is no phase change until the temperature reaches the water dew point.

[0054] The second heat exchange stage is the condensation stage, where the flue gas starts to cool down from the water dew point temperature. Liquid water precipitates during the process, which means there is a phase change.

[0055] For example, the flue gas temperature drops from 75°C to 30°C, and the flue gas water dew point temperature is 40°C. In the first heat exchange stage (cooling section), the flue gas temperature drops from 75°C to the dew point temperature of 40°C, and there is no phase change in the flue gas; in the second heat exchange stage (condensation section), the flue gas temperature drops from the dew point temperature of 40°C to 30°C, condensed water precipitates in the flue gas, and the water in the flue gas undergoes phase change.

[0056] In the first heat exchange stage (cooling stage), the heat exchange between the flue gas and water is a heat exchange between the flue gas and water without phase change. Since the gas phase heat transfer coefficient is very small, the total heat transfer coefficient in the first heat exchange stage is very small.

[0057] In the second heat exchange stage (condensation section), the heat exchange between the flue gas and water is the flue gas condensation and water heat exchange with phase change. The flue gas condensation heat transfer coefficient is much larger than the gas phase cooling heat transfer coefficient in the first heat exchange stage (cooling section). Therefore, the total heat transfer coefficient of the second heat exchange stage (condensation section) is about ten times larger than the total heat transfer coefficient of the first heat exchange stage (cooling section).

[0058] The technical concept of this application differs from conventional wisdom in the field. Traditionally, the greater the temperature difference between the flue gas entering the heat exchanger and the cooling medium, the greater the heat transfer capacity, or the smaller the heat transfer area. Water spraying and humidification lower the flue gas inlet temperature, which traditionally would be interpreted as reducing the heat transfer capacity of the heat exchanger or requiring a larger heat transfer area to recover the same amount of heat. This is, in fact, a misunderstanding.

[0059] The utility model reduces the flue gas temperature through a humidification and cooling spray device, and at the same time increases the water vapor in the flue gas or makes it reach a saturated state, thereby raising the water dew point temperature of the flue gas. The effect is that the first heat exchange stage (cooling section) is partially or completely transformed into the second heat exchange stage (condensation section). Since the condensation heat transfer coefficient is about ten times greater than the cooling heat transfer coefficient, and is much greater than the amplitude of the reduction in heat transfer temperature difference caused by the reduction in flue gas temperature, the heat exchange area required to recover the same amount of heat after humidification and cooling is significantly reduced; after the utility model adopts spray humidification and cooling, the heat exchange area of ​​the flue gas heat exchanger is reduced by more than 30% compared with the heat exchange area of ​​the traditional flue gas heat exchanger.

[0060] In the present invention, the air spray device and the flue gas humidification and cooling device work together to improve the heat exchange capacity of the entire system. The air spray device is used to increase the water content in the air entering the boiler, increase the air heat capacity, and improve the air heat carrying capacity. The air heater heats the air after spraying and humidification, and at the same time evaporates the liquid water into gaseous water. The water vapor entering the boiler with the air is heated by combustion and cooled by heat transfer before being discharged from the boiler with the flue gas. The temperature of the added water vapor in the flue gas is increased, the flue gas saturation is increased, and the dew point temperature of the flue gas is also increased. The discharged flue gas is further cooled and humidified by the flue gas humidification and cooling device, the flue gas temperature is reduced, the water vapor content is further increased, and the water dew point temperature is further increased. Before the flue gas enters the heat exchanger, the water in the flue gas has completed the vaporization state, and the heat exchange capacity of the entire system is comprehensively improved. When recovering the same amount of heat, the demand for the heat exchange area of ​​the flue gas heat exchanger is reduced.

[0061] Furthermore, the flue gas waste heat deep recovery system is equipped with a condensation water tank and a spray water pump to collect the condensation water precipitated by the flue gas in the flue gas heat exchanger when it is cooled into the condensation water tank, and then send it to the air spray device and / or the flue gas humidification and cooling device through the spray water pump, so as to realize the recycling of the condensation water and reduce the need for additional spray water.

[0062] The present invention will now be further described with reference to the accompanying drawings, but the following embodiments do not constitute a limitation to the present invention.

[0063] Example 1

[0064] Figure 1 The utility model shows a flue gas waste heat deep recovery system provided by the present invention, comprising:

[0065] An air spray device 4, an air heater 3, and a fan 2 are sequentially arranged on the air inlet pipe of the boiler 1;

[0066] A flue gas heat exchanger I5 is installed on the boiler exhaust duct;

[0067] After being sprayed and humidified by the air spray device 4, the air enters the air heater 3 for heat exchange and temperature increase, and finally enters the boiler 1;

[0068] All the heating water enters the air heater 3 to heat the air. The cooled heating water enters the flue gas heat exchanger I 5 to exchange heat with the flue gas, recovers the waste heat of the flue gas, and then heats up and enters the boiler 1.

[0069] A water circulation pipeline is set between the flue gas heat exchanger I5 and the air spray device 4. The condensed water generated after the flue gas recovers the waste heat through the flue gas heat exchanger I5 first enters the condensed water tank 6, and then part or all of the condensed water is transported to the air spray device 4 through the spray water pump 7.

[0070] After the air is humidified by the air spray humidification device, the water content in the air increases, and the air's heat absorption capacity increases. The air then enters the air heater, where all the heating water enters the air heater to heat the air. After being heated by the heating water, the air temperature rises, and the liquid water in the air vaporizes into gaseous water. The air then enters the boiler, where it is burned and produces flue gas. This flue gas also contains more water vapor, which increases its heat release capacity.

[0071] In some embodiments, a condensate treatment device is provided at the outlet of the condensate tank, and the treated condensate is fully or partially transported to the air spray device.

[0072] This system uses a condensate tank to collect condensate from the flue gas, and then uses the condensate to spray and humidify the air. This not only improves the utilization rate of the condensate, but also reduces the need for additional spray water devices, achieving the effect of simplifying the system, reducing costs and increasing efficiency.

[0073] Example 2

[0074] Figure 2 This example shows another deep flue gas waste heat recovery system provided by the present invention. Compared to Example 1, the two differ in that: a portion of the heating water enters the air heater 3 to heat the air. The cooled heating water then enters the flue gas heat exchanger I 5 to exchange heat with the flue gas, recovering the flue gas waste heat before being heated and then entering the boiler 1. The remaining portion of the heating water enters the boiler 1 directly.

[0075] Example 3

[0076] Figure 3 This figure shows another deep flue gas waste heat recovery system provided by the present invention. Compared to Example 1, the two differ in that a flue gas humidification and cooling device 8 is installed before the flue gas heat exchanger I5; the flue gas is sprayed, humidified, and cooled by the flue gas humidification and cooling device 8. During this process, the spray water enters the flue gas after being atomized and / or vaporized, or atomized and / or vaporized after entering the flue gas, thereby increasing the water vapor content in the flue gas or reaching saturation. The flue gas then enters the flue gas heat exchanger I5 to exchange heat with heating water, recovering the flue gas waste heat. After the waste heat is recovered, the flue gas is discharged.

[0077] A water circulation pipeline is set between the flue gas heat exchanger I5 and the flue gas humidification and cooling device 8. The condensed water condensed from the flue gas in the flue gas heat exchanger I5 first enters the condensed water tank 6, and then part of the condensed water is transported to the air spray device 4 through the spray water pump 7, and part of the condensed water is transported to the flue gas humidification and cooling device 8.

[0078] In some embodiments, the system is equipped with a dust removal device and a water scrubber. After dust removal and water scrubbing, the flue gas undergoes deep heat recovery. These devices can be tube-type sprayers, showerhead sprayers, loop-tube multi-hole sprayers, or nozzles capable of atomizing liquids. Their function is to use water to flush away pollutants or dust. However, their purpose is completely different from the humidification and cooling devices described in this application. The type, state, and method of liquid sprayed differ, resulting in different effects.

[0079] In some embodiments, after being discharged from the boiler, the flue gas first enters a flue gas humidification and cooling device, and then enters one or more flue gas heat exchange devices.

[0080] In other embodiments, after being discharged from the boiler, the flue gas first enters one or more flue gas heat exchange devices, then enters one or more flue gas humidification and cooling devices, and then enters one or more flue gas heat exchange devices.

[0081] In other embodiments, a condensate treatment device is provided at the outlet of the condensate tank, and the treated condensate is transported to the air spray device and / or the flue gas humidification and cooling device.

[0082] Example 4

[0083] Figure 4 This example shows another deep flue gas waste heat recovery system provided by the present invention. Compared to Example 3, the two differ in that: Part of the heating water enters the air heater 3 to heat the air. The cooled heating water then enters the flue gas heat exchanger I 5 to exchange heat with the flue gas, recovering the flue gas waste heat before being heated and then entering the boiler 1. The remaining heating water enters the boiler 1 directly.

[0084] Example 5

[0085] Figure 5 The present invention provides another deep flue gas waste heat recovery system. Compared to Example 3, the difference between the two is that a flue gas heat exchanger II 9 is added between the boiler 1 and the flue gas humidification and cooling device 8. The heating water sequentially enters the flue gas heat exchanger I 5 and the flue gas heat exchanger II 9 to recover the flue gas waste heat before entering the boiler 1.

[0086] In this embodiment, both the flue gas heat exchanger I and the flue gas heat exchanger II are plate heat exchangers.

[0087] Example 6

[0088] Figure 6 The present invention provides another deep flue gas waste heat recovery system. Compared to Example 3, the two differ in that: the deep flue gas waste heat recovery system includes a heat network heater 10. Heating water is heated by the flue gas heat exchanger before entering the heat network heater 10. Within the heat network heater 10, the heating water exchanges heat with steam generated by the boiler 1, and the heated waste water is then supplied externally.

[0089] In this embodiment, the boiler 1 is a steam boiler, and the heating network heater is a partitioning heat exchanger.

[0090] Test Case

[0091] The flue gas waste heat deep recovery system in Example 3 was tested. When recovering the same amount of flue gas waste heat, the present invention was compared with the conventional process. In this system, the flue gas temperature was 98°C, the flue gas water dew point was 41°C, the cold water inlet temperature was 22°C, and the cold water outlet temperature was 34°C. After waste heat recovery, the flue gas temperature dropped to 38°C.

[0092] Test 1: Traditional process, without humidification and cooling device.

[0093] Without humidification and cooling device, the heat transfer temperature difference is 30℃ and the heat transfer coefficient is 74W / m 2 ℃, the heat exchange area required for the flue gas heat exchanger is about 2200m 2 .

[0094] Test 2: A humidifying and cooling device was added, and the water vapor content in the flue gas increased, but did not reach saturation.

[0095] The flue gas temperature before humidification and cooling was 98°C, and the flue gas temperature after humidification and cooling was 60°C, and the flue gas water dew point temperature increased to 46°C.

[0096] The results show that the heat transfer temperature difference is 16℃ and the heat transfer coefficient is 218W / m 2 ℃, the heat exchange area required for the flue gas heat exchanger is about 1300m 2 .

[0097] Test 3: Add a humidifying and cooling device to saturate the water vapor content in the flue gas.

[0098] The temperature of the flue gas before humidification and cooling is 98°C, and the temperature after humidification and cooling is 48°C, which is the water dew point temperature of the flue gas.

[0099] The results show that the heat transfer temperature difference is 15℃ and the heat transfer coefficient is 566W / m 2 ℃, the heat exchange area required for the flue gas heat exchanger is about 560m 2 .

[0100] The above tests show that the flue gas waste heat deep recovery system provided by the present invention can effectively improve the recovery rate and reduce the area of ​​the heat exchange device.

[0101] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0102] The present invention has been introduced in detail above. The principles and implementation methods of the present invention have been described in detail using specific examples in the specification. However, the examples are only used to help understand the present invention and should not be construed as limiting the present invention.

Claims

1. A boiler flue gas waste heat deep recovery energy-saving system, characterized in that: include: An air spray device and an air heater are sequentially installed on the boiler air inlet pipe; A flue gas heat exchanger is installed on the boiler exhaust duct; After being sprayed and humidified by the air spray device, the air enters the air heater for heat exchange and temperature increase, and then enters the boiler; All or part of the heating water enters the air heater to heat the air, and the cooled heating water enters the flue gas heat exchanger to exchange heat with the flue gas; The heated heating water enters the boiler or the heating network heater to be heated again; A water circulation pipeline is set between the flue gas heat exchanger and the air spray device. The condensed water generated after the flue gas recovers the waste heat through the flue gas heat exchanger enters the condensed water tank, and part or all of the condensed water is transported to the air spray device.

2. The boiler flue gas waste heat deep recovery and energy-saving system according to claim 1, characterized in that: Also includes: A flue gas humidification and cooling device and a flue gas heat exchanger are sequentially installed on the flue gas exhaust duct of the boiler; after the flue gas is humidified by the flue gas humidification and cooling device, the water vapor content in the flue gas increases or reaches saturation, and then enters the flue gas heat exchanger to exchange heat with heating water to recover the waste heat of the flue gas; the flue gas is discharged after the waste heat is recovered.

3. The boiler flue gas waste heat deep recovery and energy-saving system according to claim 2, characterized in that: A water circulation pipeline is set between the flue gas heat exchanger and the flue gas humidification and cooling device. The condensed water condensed from the flue gas in the flue gas heat exchanger first enters the condensation water tank, and then part or all of the condensed water is transported to the flue gas humidification and cooling device.

4. The boiler flue gas waste heat deep recovery and energy-saving system according to claim 3, characterized in that: The condensed water generated after the flue gas recovers waste heat through the flue gas heat exchanger first enters the condensed water tank, and then part of the condensed water is transported to the air spray device, and part of the condensed water is transported to the flue gas humidification and cooling device.

5. The boiler flue gas waste heat deep recovery and energy-saving system according to any one of claims 1 to 4, characterized in that: The air heater is a partition type heat exchanger; the flue gas heat exchanger is a partition type heat exchanger; the heat network heater is a partition type heat exchanger.

6. The boiler flue gas waste heat deep recovery and energy-saving system according to any one of claims 1 to 4, characterized in that: The air spray device and the flue gas humidification and cooling device are tube sprayers, shower head sprayers, ring pipe multi-hole sprayers or nozzles.

7. The boiler flue gas waste heat deep recovery and energy-saving system according to any one of claims 1 to 4, characterized in that: The air heater and flue gas heat exchanger are plate type heat exchangers; the air spray device and flue gas humidification and cooling device are nozzles.

8. The boiler flue gas waste heat deep recovery and energy-saving system according to any one of claims 1 to 4, characterized in that: A condensate treatment device is installed at the outlet of the condensate tank.

9. The boiler flue gas waste heat deep recovery and energy-saving system according to claim 1, characterized in that: Includes one or more air spray devices.

10. The boiler flue gas waste heat deep recovery and energy-saving system according to claim 2, characterized in that: It includes a flue gas humidifying and cooling device and a flue gas heat exchanger; or includes a flue gas humidifying and cooling device and multiple flue gas heat exchangers; or includes multiple flue gas humidifying and cooling devices and multiple flue gas heat exchangers.

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