Waste heat recovery and dehumidification method and system for coal-fired boiler

Abstract

The invention relates to the technical field of waste heat recovery, and discloses a waste heat recovery and dehumidification method and system for a coal-fired boiler, and the method comprises the steps that flue gas discharged by the coal-fired boiler is introduced into an adsorption area of an adsorption rotating wheel, water vapor in the flue gas is captured by an adsorbent, released adsorption latent heat and flue gas sensible heat are absorbed by the adsorption rotating wheel, and the flue gas is discharged by the adsorption rotating wheel; cooling and dehumidification of the smoke are achieved, and low-temperature and low-humidity exhaust smoke and a saturated adsorbent are formed; a stream of low-temperature dry air from a coal-fired boiler system is used as regeneration airflow to desorb the saturated adsorbent, and a stream of high-temperature and high-humidity regeneration airflow is formed; the high-temperature and high-humidity regeneration airflow and combustion-supporting air are mixed and then enter a hearth, moisture and heat carried by the high-temperature and high-humidity regeneration airflow are recycled, the problems of flue gas waste heat recovery, dehumidification and low-temperature corrosion control are solved through the adsorption rotating wheel technology, and the double breakthrough of energy efficiency improvement and equipment protection is achieved.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology, and more specifically, to a method and system for waste heat recovery and dehumidification of coal-fired boilers. Background Technology

[0002] Coal-fired boilers occupy an important position in my country's energy system, and improving their thermal efficiency is a key aspect of energy conservation and emission reduction. Boiler flue gas temperatures are typically maintained in the range of 120-150℃, containing a significant amount of low- and medium-temperature waste heat that remains unutilized. In particular, the flue gas contains approximately 8%-15% water vapor, whose latent heat of vaporization accounts for more than 50% of the total heat loss from the flue gas, constituting a major portion of boiler energy waste.

[0003] Currently used traditional heat exchange devices such as economizers and air preheaters mainly recover sensible heat from the medium- and high-temperature ranges, but their energy recovery effect from the low-temperature range is limited. When attempting to further reduce the flue gas temperature to recover more energy, the following technical challenges arise: First, when the flue gas temperature drops to a lower level, the heat transfer temperature difference of traditional heat exchange equipment decreases significantly, leading to a sharp decline in heat exchange efficiency; second, low-temperature heat exchange requires a larger heat exchange area, significantly increasing the equipment size and cost; in addition, dust in the flue gas is more likely to adhere to the heat exchange surface in the low-temperature range, affecting the long-term stable operation of the equipment.

[0004] In existing technologies, some solutions attempt to enhance waste heat recovery by using heat pipe heat exchangers or adding low-temperature economizers, but these solutions often suffer from problems such as system complexity and long investment payback periods. Other technologies use direct contact heat exchange methods such as spraying, which can recover some latent heat, but may increase system resistance and complicate subsequent processing. Summary of the Invention

[0005] This application provides a method and system for waste heat recovery and dehumidification of coal-fired boilers, solving the long-standing problem of deep energy recovery in the waste heat recovery process of flue gas at the tail end of coal-fired boilers in the prior art. By adopting adsorption rotor technology, non-condensation dehumidification of flue gas is achieved through physical adsorption, realizing the efficient recovery of latent heat of water vapor that is difficult to utilize by traditional technologies; and by returning the recovered wet heat energy to the combustion system in the form of regenerated exhaust air, a closed-loop energy utilization is formed.

[0006] To achieve the above objectives, the present invention provides a method for waste heat recovery and dehumidification of a coal-fired boiler, comprising:

[0007] The flue gas discharged from the coal-fired boiler is passed into the adsorption zone of the adsorption rotor. The water vapor in the flue gas is captured by the adsorbent, and the latent heat of adsorption and the sensible heat of the flue gas are absorbed by the adsorption rotor, thereby achieving cooling and dehumidification of the flue gas and forming low-temperature and low-humidity flue gas and saturated adsorbent.

[0008] A stream of low-temperature, dry air from a coal-fired boiler system is used as the regeneration gas flow to desorb the saturated adsorbent, forming a high-temperature, high-humidity regeneration gas flow.

[0009] The high-temperature and high-humidity regeneration gas flow is mixed with combustion air and then enters the furnace to recover and utilize the moisture and heat carried by the high-temperature and high-humidity regeneration gas flow.

[0010] Furthermore, the released latent heat of adsorption and sensible heat of the flue gas are absorbed by the adsorption rotor, specifically including:

[0011] When the flue gas flows through the adsorption zone, the water vapor molecules in the flue gas are adsorbed into the pore structure of the adsorbent, changing from a gaseous state to an adsorbed state and releasing the latent heat of adsorption.

[0012] The flue gas transfers its sensible heat to the adsorption rotor through convective heat exchange with the solid frame of the adsorption rotor.

[0013] The latent heat of adsorption and the sensible heat of flue gas are absorbed by the adsorbent of the adsorption wheel, stored as thermal potential energy, and transported to the regeneration zone as the wheel rotates.

[0014] Furthermore, water vapor molecules in the flue gas are adsorbed into the pore structure of the adsorbent, changing from a gaseous state to an adsorbed state and releasing the latent heat of adsorption, specifically including:

[0015] The adsorbent has nanoscale pore channels inside and hydroxyl or amino polar functional groups distributed on its surface. Through hydrogen bonding and van der Waals forces, it strongly adsorbs polar water molecules in flue gas.

[0016] The gaseous water vapor molecules in the flue gas are captured by the polar functional groups on the pore surface of the adsorbent under the action of van der Waals forces and hydrogen bonds, and the molecular motion freedom is restricted, transforming from the high-energy gas phase to the low-energy adsorbed phase.

[0017] During physical adsorption and phase transition, the latent heat inherent in water molecules is released, which is the latent heat of adsorption.

[0018] The latent heat of adsorption is absorbed by the adsorbent.

[0019] Furthermore, the adsorbent has nanoscale pore channels inside, specifically including:

[0020] The adsorbent is silica gel, alumina, or molecular sieve that has undergone physical or chemical activation processes.

[0021] The nanoscale pore channels are three-dimensional network-like interconnected channels with pore sizes ranging from 0.3 to 2 nanometers, formed in situ within a solid matrix during the preparation and activation of the adsorbent by controlling the pyrolysis temperature, reaction atmosphere, or using a template agent.

[0022] Furthermore, the flue gas undergoes convective heat exchange with the solid frame of the adsorption rotor, specifically including:

[0023] The internal tortuous channels of the adsorption rotor are determined, a solid skeleton that meets the conditions is determined, and the flue gas is transferred to the solid skeleton according to the internal tortuous channels.

[0024] Determine the temperature difference between the flue gas and the solid skeleton, and set the convective heat transfer strategy for the flue gas based on the temperature difference;

[0025] Based on the aforementioned convective heat transfer strategy, the solid skeleton absorbs a portion of the sensible heat.

[0026] Further, determining the temperature difference between the flue gas and the solid skeleton specifically includes:

[0027] A first temperature sensor is installed at the flue gas inlet section of the adsorption zone to detect the temperature of the flue gas entering the adsorption rotor in real time.

[0028] A second temperature sensor is embedded inside the solid skeleton of the adsorption wheel to detect the bulk temperature of the solid skeleton in real time.

[0029] The flue gas temperature detected by the first temperature sensor and the solid skeleton phase temperature detected by the second temperature sensor are compared in real time, and the difference is the real-time temperature difference between the flue gas and the solid skeleton.

[0030] Based on this real-time temperature difference, the flue gas flow rate and rotor speed are dynamically adjusted to optimize the convective heat transfer efficiency.

[0031] Furthermore, based on this real-time temperature difference, the flue gas flow rate or rotor speed is dynamically adjusted to optimize convective heat transfer efficiency, specifically including:

[0032] Establish a coordinated control relationship between the real-time temperature difference and the flue gas flow rate and impeller speed:

[0033] The upper and lower threshold values ​​of the real-time temperature difference are preset;

[0034] When the real-time temperature difference is higher than the upper limit threshold, the flue gas flow rate is increased and the rotor speed is reduced simultaneously to enhance the intensity of a single heat exchange and prolong the heat exchange time.

[0035] When the real-time temperature difference is lower than the lower threshold, the flue gas flow rate is reduced and the rotor speed is increased simultaneously to avoid overcooling and maintain the desorption efficiency of the regeneration zone.

[0036] The deviation between the real-time temperature difference and the target temperature difference is converted into the opening signal of the flue gas regulating valve and the speed signal of the rotary drive motor by the PID controller, so as to realize the closed-loop linkage control of flue gas flow and rotary speed.

[0037] The conversion relationship follows the principle of negative correlation between heat transfer intensity and contact time, ensuring that the overall heat transfer efficiency of the adsorption zone is maintained at its optimal state when the temperature difference changes.

[0038] Furthermore, the recovery and utilization of moisture and heat carried by the high-temperature and high-humidity regeneration airflow specifically includes:

[0039] The moisture carried by the high-temperature and high-humidity regeneration gas flow undergoes a phase change transformation in the high-temperature environment of the furnace, transforming from liquid water into high-temperature steam and becoming a component of the flue gas. It is condensed and precipitated when passing through the condensing heat exchanger in the coal-fired boiler system, and the released latent heat of vaporization is recovered by the circulating working fluid.

[0040] The latent heat of adsorption and the sensible heat of flue gas are partially recovered in the boiler as the flue gas cools down.

[0041] Furthermore, the latent heat of adsorption and the sensible heat of flue gas are partially recovered in the boiler as the flue gas cools, specifically including:

[0042] The high-temperature and high-humidity regeneration gas flow first flows through the boiler economizer, where it undergoes convective heat exchange with the feedwater in the economizer tubes. Part of the sensible heat of the flue gas is recovered, and the temperature is initially reduced.

[0043] The initially cooled regenerated gas flow continues to flow through the flue gas condenser heat exchanger located behind the economizer, where its temperature drops further below the water dew point, causing some of the water vapor in the flue gas to condense and release the adsorbed latent heat.

[0044] The latent heat of adsorption released by condensation and the residual sensible heat of flue gas are absorbed by the circulating working fluid in the flue gas condenser heat exchanger through convection and condensation phase change heat transfer, thus completing the deep recovery and utilization of the latent heat of adsorption and the sensible heat of flue gas.

[0045] To achieve the above objectives, the present invention also provides a waste heat recovery and dehumidification system for a coal-fired boiler, comprising:

[0046] The flue gas treatment module is used to pass the flue gas discharged from the coal-fired boiler into the adsorption zone of the adsorption rotor. The water vapor in the flue gas is captured by the adsorbent, and the latent heat of adsorption and the sensible heat of the flue gas are absorbed by the adsorption rotor, thereby achieving cooling and dehumidification of the flue gas and forming low-temperature and low-humidity exhaust gas and saturated adsorbent.

[0047] Adsorbent regeneration module: used to desorb the saturated adsorbent by using a stream of low-temperature dry air from the coal-fired boiler system as a regeneration gas flow, and to form a high-temperature and high-humidity regeneration gas flow.

[0048] Energy recovery module: used to mix the high-temperature and high-humidity regeneration gas flow with combustion air before entering the furnace, and to recover and utilize the moisture and heat carried by the high-temperature and high-humidity regeneration gas flow.

[0049] Compared with existing technologies, the advantages of this invention are as follows: By employing an adsorption rotor with a nanoscale porous structure, the latent heat and sensible heat of water vapor in the flue gas of a coal-fired boiler are synergistically recovered, breaking through the energy efficiency bottleneck of traditional heat exchange technology in the low-temperature range. The polar functional groups on the surface of the functionalized adsorbent enable the directional capture of water molecules, simultaneously completing latent heat absorption and sensible heat transfer during physical adsorption. This solves the problem of ineffective recovery of latent heat of water vapor in traditional technologies. Furthermore, by establishing an intelligent control model of temperature difference and operating parameters, the adsorbent regeneration process is dynamically optimized, ensuring that the system maintains optimal heat exchange efficiency under different operating conditions. A complete energy cascade utilization path is constructed, returning the recovered energy to the boiler system in the form of a high-temperature, high-humidity medium, significantly reducing the flue gas temperature while effectively improving energy quality. Attached Figure Description

[0050] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0051] Figure 1 A schematic flowchart of a waste heat recovery and dehumidification method for a coal-fired boiler is shown in an embodiment of the present invention.

[0052] Figure 2 A schematic diagram of a waste heat recovery and dehumidification system for a coal-fired boiler is shown in an embodiment of the present invention. Detailed Implementation

[0053] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0054] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0055] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0056] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0057] The following is a description of preferred embodiments of the present invention in conjunction with the accompanying drawings.

[0058] S110: The flue gas discharged from the coal-fired boiler is passed into the adsorption zone of the adsorption rotor. The water vapor in the flue gas is captured by the adsorbent, and the latent heat of adsorption and the sensible heat of the flue gas are absorbed by the adsorption rotor, thereby achieving cooling and dehumidification of the flue gas and forming low-temperature and low-humidity flue gas and saturated adsorbent.

[0059] In some embodiments of the present invention, the released latent heat of adsorption and sensible heat of flue gas are absorbed by the adsorption rotor, specifically including:

[0060] In this embodiment, when the flue gas flows through the adsorption zone, the water vapor molecules in the flue gas are adsorbed into the pore structure of the adsorbent, changing from a gaseous state to an adsorbed state and releasing the latent heat of adsorption.

[0061] The flue gas transfers its sensible heat to the adsorption rotor through convective heat exchange with the solid frame of the adsorption rotor.

[0062] The latent heat of adsorption and the sensible heat of flue gas are absorbed by the adsorbent of the adsorption wheel, stored as thermal potential energy, and transported to the regeneration zone as the wheel rotates.

[0063] In this embodiment, water vapor molecules in the flue gas are adsorbed into the pore structure of the adsorbent, changing from a gaseous state to an adsorbed state and releasing the latent heat of adsorption, specifically including:

[0064] The adsorbent has nanoscale pore channels inside and hydroxyl or amino polar functional groups distributed on its surface. Through hydrogen bonding and van der Waals forces, it strongly adsorbs polar water molecules in flue gas.

[0065] The gaseous water vapor molecules in the flue gas are captured by the polar functional groups on the pore surface of the adsorbent under the action of van der Waals forces and hydrogen bonds, and the molecular motion freedom is restricted, transforming from the high-energy gas phase to the low-energy adsorbed phase.

[0066] During physical adsorption and phase transition, the latent heat inherent in water molecules is released, which is the latent heat of adsorption.

[0067] The latent heat of adsorption is absorbed by the adsorbent.

[0068] In this embodiment, the adsorbent has nanoscale pore channels inside, specifically including:

[0069] The adsorbent is silica gel, alumina, or molecular sieve that has undergone physical or chemical activation processes.

[0070] The nanoscale pore channels are three-dimensional network-like interconnected channels with pore sizes ranging from 0.3 to 2 nanometers, formed in situ within a solid matrix during the preparation and activation of the adsorbent by controlling the pyrolysis temperature, reaction atmosphere, or using a template agent.

[0071] In this embodiment, the flue gas undergoes convective heat exchange with the solid frame of the adsorption rotor, specifically including:

[0072] The internal tortuous channels of the adsorption rotor are determined, a solid skeleton that meets the conditions is determined, and the flue gas is transferred to the solid skeleton according to the internal tortuous channels.

[0073] Determine the temperature difference between the flue gas and the solid skeleton, and set the convective heat transfer strategy for the flue gas based on the temperature difference;

[0074] Based on the aforementioned convective heat transfer strategy, the solid skeleton absorbs a portion of the sensible heat.

[0075] In this embodiment, the adsorption rotor mainly consists of a honeycomb porous matrix, a high-performance adsorbent material uniformly loaded on the matrix surface, and core structural components supporting the rotor's operation. The honeycomb matrix forms a solid skeleton with a large specific surface area and tortuous channels, providing ample contact space and a stable convective heat transfer interface for the flue gas and the adsorbent. The adsorbent material is silica gel, alumina, or molecular sieve treated with physical or chemical activation processes. It possesses a precise pore structure of 0.3-2 nanometers and abundant surface polar functional groups, serving as a key functional layer for efficient moisture capture and adsorption heat storage. The core structural components ensure continuous and stable rotation between the adsorption and regeneration zones under the action of the drive device, completing the periodic transfer and regeneration of energy and matter.

[0076] In this embodiment, determining the temperature difference between the flue gas and the solid skeleton specifically includes:

[0077] A first temperature sensor is installed at the flue gas inlet section of the adsorption zone to detect the temperature of the flue gas entering the adsorption rotor in real time.

[0078] A second temperature sensor is embedded inside the solid skeleton of the adsorption wheel to detect the bulk temperature of the solid skeleton in real time.

[0079] The flue gas temperature detected by the first temperature sensor and the solid skeleton phase temperature detected by the second temperature sensor are compared in real time, and the difference is the real-time temperature difference between the flue gas and the solid skeleton.

[0080] Based on this real-time temperature difference, the flue gas flow rate and rotor speed are dynamically adjusted to optimize the convective heat transfer efficiency.

[0081] In this embodiment, based on the real-time temperature difference, the flue gas flow rate or rotor speed is dynamically adjusted to optimize the convective heat transfer efficiency, specifically including:

[0082] Establish a coordinated control relationship between the real-time temperature difference and the flue gas flow rate and impeller speed:

[0083] The upper and lower threshold values ​​of the real-time temperature difference are preset;

[0084] When the real-time temperature difference is higher than the upper limit threshold, the flue gas flow rate is increased and the rotor speed is reduced simultaneously to enhance the intensity of a single heat exchange and prolong the heat exchange time.

[0085] When the real-time temperature difference is lower than the lower threshold, the flue gas flow rate is reduced and the rotor speed is increased simultaneously to avoid overcooling and maintain the desorption efficiency of the regeneration zone.

[0086] The deviation between the real-time temperature difference and the target temperature difference is converted into the opening signal of the flue gas regulating valve and the speed signal of the rotary drive motor by the PID controller, so as to realize the closed-loop linkage control of flue gas flow and rotary speed.

[0087] The conversion relationship follows the principle of negative correlation between heat transfer intensity and contact time, ensuring that the overall heat transfer efficiency of the adsorption zone is maintained at its optimal state when the temperature difference changes.

[0088] The beneficial effects of the above scheme are as follows: Through the multi-stage adsorption-regeneration mechanism of the adsorption rotor, the adsorbent with nanoscale pore structure and polar functional groups is used to achieve directional capture of water vapor in flue gas. The latent heat of water vapor and sensible heat of flue gas are recovered simultaneously through the physical adsorption process, resulting in a significant reduction in flue gas temperature and humidity. Secondly, the latent heat and sensible heat released during the adsorption process are stored in the rotor material to form high-temperature thermal potential energy, and the rotation of the rotor realizes the spatial transfer and reuse of energy. Finally, the synergistic effect of the honeycomb matrix and the precision adsorbent ensures high heat and mass transfer efficiency, enabling the system to achieve cascaded energy recovery and utilization while completing deep dehumidification.

[0089] S120: A stream of low-temperature, dry air from a coal-fired boiler system is used as a regeneration gas stream to desorb the saturated adsorbent and form a high-temperature, high-humidity regeneration gas stream.

[0090] In some embodiments of the present invention, desorption of the saturated adsorbent specifically includes:

[0091] The regeneration gas flow enters the regeneration zone of the adsorption rotor and comes into contact with the saturated adsorbent;

[0092] The regenerated airflow exchanges heat with the adsorbent through convective heat transfer, breaking the adsorption bonds between water molecules and the adsorbent material, causing the adsorbed water to desorb and revert to gaseous water vapor.

[0093] The desorbed water vapor is carried away by the regeneration gas flow, thereby completing the drying and regeneration of the adsorbent. At the same time, the regeneration gas flow absorbs moisture and heat to form a high-temperature and high-humidity regeneration gas flow.

[0094] In this embodiment, during the heat exchange between the regeneration gas stream and the adsorbent via convective heat transfer, the heat and mass transfer processes occur simultaneously and mutually promote each other when the low-temperature, dry regeneration gas stream enters the regeneration zone and comes into contact with the saturated adsorbent. Firstly, because the partial pressure of water vapor in the regeneration gas stream is much lower than that on the surface of the saturated adsorbent, a significant concentration difference exists, and this gradient becomes the main driving force for water desorption. To overcome adsorption bonds and achieve desorption, water needs to absorb heat. At this point, although the initial temperature of the regeneration gas stream is low, the forced convection caused by its flow continuously carries away the desorbed water molecules from the adsorbent surface, thus maintaining the crucial concentration difference. Simultaneously, the temperature difference between the regeneration gas stream and the high-temperature adsorbent solid framework drives sensible heat to be transferred from the adsorbent to the regeneration gas stream via convective heat transfer. The adsorbent cools due to the loss of this sensible heat and the provision of desorption heat, and the released energy is ultimately absorbed by the regeneration gas stream, transforming it into a high-temperature, high-humidity gas stream.

[0095] The beneficial effects of the above scheme are: it achieves the dual goals of efficient adsorbent regeneration and improved energy quality through a heat and mass transfer mechanism. During the regeneration process, the desorption process is driven by the water vapor partial pressure difference between the regeneration gas flow and the saturated adsorbent, while energy transfer is achieved through convective heat transfer. This transforms the low-temperature, dry gas flow into a high-temperature, high-humidity regeneration gas flow while completing the regeneration task. This regeneration method not only significantly reduces the heat energy consumption of traditional regeneration methods, but more importantly, it converts dissipated energy into recyclable energy, laying a solid foundation for subsequent energy recycling and forming a self-circulating, energy-saving regeneration system.

[0096] S130: The high-temperature and high-humidity regeneration gas flow mixes with the combustion air and enters the furnace to recover and utilize the moisture and heat carried by the high-temperature and high-humidity regeneration gas flow.

[0097] In some embodiments of the present invention, the recovery and reuse of moisture and heat carried by the high-temperature and high-humidity regeneration airflow specifically includes:

[0098] The moisture carried by the high-temperature and high-humidity regeneration gas flow undergoes a phase change transformation in the high-temperature environment of the furnace, transforming from liquid water into high-temperature steam and becoming a component of the flue gas. It is condensed and precipitated when passing through the condensing heat exchanger in the coal-fired boiler system, and the released latent heat of vaporization is recovered by the circulating working fluid.

[0099] The latent heat of adsorption and the sensible heat of flue gas are partially recovered in the boiler as the flue gas cools down.

[0100] In this embodiment, the latent heat of adsorption and the sensible heat of flue gas are partially recovered in the boiler as the flue gas cools, specifically including:

[0101] The high-temperature and high-humidity regeneration gas flow first flows through the boiler economizer, where it undergoes convective heat exchange with the feedwater in the economizer tubes. Part of the sensible heat of the flue gas is recovered, and the temperature is initially reduced.

[0102] The initially cooled regenerated gas flow continues to flow through the flue gas condenser heat exchanger located behind the economizer, where its temperature drops further below the water dew point, causing some of the water vapor in the flue gas to condense and release the adsorbed latent heat.

[0103] The latent heat of adsorption released by condensation and the residual sensible heat of flue gas are absorbed by the circulating working fluid in the flue gas condenser heat exchanger through convection and condensation phase change heat transfer, thus completing the deep recovery and utilization of the latent heat of adsorption and the sensible heat of flue gas.

[0104] In this embodiment, as the moisture carried by the high-temperature and high-humidity regeneration gas flow undergoes vaporization, heating, and ultimately becomes part of the flue gas in the furnace, firstly, the liquid water droplets rapidly vaporize by absorbing a large amount of latent heat of vaporization in the high-temperature environment of the furnace. Although this process will locally reduce the flame temperature, it stores energy in the form of latent heat in the steam. Subsequently, the formed steam continuously absorbs the sensible heat of the flue gas and heats up to the flue gas temperature through convective heat transfer as it flows with the flue gas. Finally, these high-temperature steam carrying latent and sensible heat gradually release the stored heat as they flow through the heating surfaces at the tail end of the boiler (especially the economizer and condenser heat exchanger).

[0105] The beneficial effects of the above scheme are as follows: through the synergistic mechanism of energy cascade recovery and active corrosion prevention, the energy efficiency and safety of the boiler system are improved simultaneously. Regarding energy recovery, the moisture and heat carried by the high-temperature, high-humidity regeneration gas flow complete a full energy cycle in the furnace and tail-end heating surfaces. The latent heat absorbed by moisture vaporization and the sensible heat of the flue gas are ultimately recovered by the working fluid through the economizer and condenser heat exchanger. Meanwhile, the heat of the regeneration gas flow itself directly increases the initial enthalpy of the combustion air, and this dual effect significantly reduces fuel consumption. Regarding corrosion prevention, by actively increasing the inlet air temperature, the temperature of the tail-end flue wall is kept stably above the sulfuric acid dew point, fundamentally blocking the conditions for low-temperature corrosion and forming an organic unity of energy saving and equipment protection.

[0106] To further illustrate the technical concept of this invention, the technical solution of this invention will now be described in conjunction with specific application scenarios.

[0107] Correspondingly, such as Figure 2 As shown, this application also provides a waste heat recovery and dehumidification system for a coal-fired boiler, comprising:

[0108] The flue gas treatment module is used to pass the flue gas discharged from the coal-fired boiler into the adsorption zone of the adsorption rotor. The water vapor in the flue gas is captured by the adsorbent, and the latent heat of adsorption and the sensible heat of the flue gas are absorbed by the adsorption rotor, thereby achieving cooling and dehumidification of the flue gas and forming low-temperature and low-humidity exhaust gas and saturated adsorbent.

[0109] Adsorbent regeneration module: used to desorb the saturated adsorbent by using a stream of low-temperature dry air from the coal-fired boiler system as a regeneration gas flow, and to form a high-temperature and high-humidity regeneration gas flow.

[0110] Energy recovery module: used to mix the high-temperature and high-humidity regeneration gas flow with combustion air before entering the furnace, and to recover and utilize the moisture and heat carried by the high-temperature and high-humidity regeneration gas flow.

[0111] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0112] Although the invention has been described above with reference to embodiments, various modifications can be made and components can be replaced with equivalents without departing from the scope of the invention. In particular, as long as there is no structural conflict, the features in the embodiments disclosed in this invention can be combined with each other in any way. The fact that not all of these combinations are described in this specification is merely for the sake of brevity and resource conservation.

[0113] It will be understood by those skilled in the art that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for waste heat recovery and dehumidification in a coal-fired boiler, characterized in that, include: The flue gas discharged from the coal-fired boiler is passed into the adsorption zone of the adsorption rotor. The water vapor in the flue gas is captured by the adsorbent, and the latent heat of adsorption and the sensible heat of the flue gas are absorbed by the adsorption rotor, thereby achieving cooling and dehumidification of the flue gas and forming low-temperature and low-humidity flue gas and saturated adsorbent. A stream of low-temperature, dry air from a coal-fired boiler system is used as the regeneration gas flow to desorb the saturated adsorbent, forming a high-temperature, high-humidity regeneration gas flow. The high-temperature and high-humidity regeneration gas flow is mixed with combustion air and then enters the furnace to recover and utilize the moisture and heat carried by the high-temperature and high-humidity regeneration gas flow.

2. The waste heat recovery and dehumidification method for a coal-fired boiler according to claim 1, characterized in that, The released latent heat of adsorption and sensible heat of flue gas are absorbed by the adsorption rotor, specifically including: When the flue gas flows through the adsorption zone, the water vapor molecules in the flue gas are adsorbed into the pore structure of the adsorbent, changing from a gaseous state to an adsorbed state and releasing the latent heat of adsorption. The flue gas transfers its sensible heat to the adsorption rotor through convective heat exchange with the solid frame of the adsorption rotor. The latent heat of adsorption and the sensible heat of flue gas are absorbed by the adsorbent of the adsorption wheel, stored as thermal potential energy, and transported to the regeneration zone as the wheel rotates.

3. The waste heat recovery and dehumidification method for a coal-fired boiler according to claim 2, characterized in that, Water vapor molecules in the flue gas are adsorbed into the pore structure of the adsorbent, changing from a gaseous state to an adsorbed state and releasing the latent heat of adsorption, specifically including: The adsorbent has nanoscale pore channels inside and hydroxyl or amino polar functional groups distributed on its surface. Through hydrogen bonding and van der Waals forces, it strongly adsorbs polar water molecules in flue gas. The gaseous water vapor molecules in the flue gas are captured by the polar functional groups on the pore surface of the adsorbent under the action of van der Waals forces and hydrogen bonds, and the molecular motion freedom is restricted, transforming from the high-energy gas phase to the low-energy adsorbed phase. During physical adsorption and phase transition, the latent heat inherent in water molecules is released, which is the latent heat of adsorption. The latent heat of adsorption is absorbed by the adsorbent.

4. A method for waste heat recovery and dehumidification of a coal-fired boiler according to claim 3, characterized in that, The adsorbent has nanoscale pore channels inside, specifically including: The adsorbent is silica gel, alumina, or molecular sieve that has undergone physical or chemical activation processes. The nanoscale pore channels are three-dimensional network-like interconnected channels with pore sizes ranging from 0.3 to 2 nanometers, formed in situ within a solid matrix during the preparation and activation of the adsorbent by controlling the pyrolysis temperature, reaction atmosphere, or using a template agent.

5. A method for waste heat recovery and dehumidification of a coal-fired boiler according to claim 2, characterized in that, The flue gas undergoes convective heat exchange with the solid frame of the adsorption rotor, specifically including... The internal tortuous channels of the adsorption rotor are determined, a solid skeleton that meets the conditions is determined, and the flue gas is transferred to the solid skeleton according to the internal tortuous channels. Determine the temperature difference between the flue gas and the solid skeleton, and set the convective heat transfer strategy for the flue gas based on the temperature difference; Based on the aforementioned convective heat transfer strategy, the solid skeleton absorbs a portion of the sensible heat.

6. A method for waste heat recovery and dehumidification of a coal-fired boiler according to claim 5, characterized in that, Determining the temperature difference between the flue gas and the solid skeleton specifically includes: A first temperature sensor is installed at the flue gas inlet section of the adsorption zone to detect the temperature of the flue gas entering the adsorption rotor in real time. A second temperature sensor is embedded inside the solid skeleton of the adsorption wheel to detect the bulk temperature of the solid skeleton in real time. The flue gas temperature detected by the first temperature sensor and the solid skeleton phase temperature detected by the second temperature sensor are compared in real time, and the difference is the real-time temperature difference between the flue gas and the solid skeleton. Based on this real-time temperature difference, the flue gas flow rate and rotor speed are dynamically adjusted to optimize the convective heat transfer efficiency.

7. A method for waste heat recovery and dehumidification of a coal-fired boiler according to claim 6, characterized in that, Based on this real-time temperature difference, the flue gas flow rate or rotor speed is dynamically adjusted to optimize convective heat transfer efficiency, specifically including: Establish a coordinated control relationship between the real-time temperature difference and the flue gas flow rate and impeller speed: The upper and lower threshold values ​​of the real-time temperature difference are preset; When the real-time temperature difference is higher than the upper limit threshold, the flue gas flow rate is increased and the rotor speed is reduced simultaneously to enhance the intensity of a single heat exchange and prolong the heat exchange time. When the real-time temperature difference is lower than the lower threshold, the flue gas flow rate is reduced and the rotor speed is increased simultaneously to avoid overcooling and maintain the desorption efficiency of the regeneration zone. The deviation between the real-time temperature difference and the target temperature difference is converted into the opening signal of the flue gas regulating valve and the speed signal of the rotary drive motor by the PID controller, so as to realize the closed-loop linkage control of flue gas flow and rotary speed. The conversion relationship follows the principle of negative correlation between heat transfer intensity and contact time, ensuring that the overall heat transfer efficiency of the adsorption zone is maintained at its optimal state when the temperature difference changes.

8. A method for waste heat recovery and dehumidification of a coal-fired boiler according to claim 1, characterized in that, The recycling of moisture and heat carried by the high-temperature, high-humidity regeneration airflow specifically includes: The moisture carried by the high-temperature and high-humidity regeneration gas flow undergoes a phase change transformation in the high-temperature environment of the furnace, transforming from liquid water into high-temperature steam and becoming a component of the flue gas. It is condensed and precipitated when passing through the condensing heat exchanger in the coal-fired boiler system, and the released latent heat of vaporization is recovered by the circulating working fluid. The latent heat of adsorption and the sensible heat of flue gas are partially recovered in the boiler as the flue gas cools down.

9. A method for waste heat recovery and dehumidification of a coal-fired boiler according to claim 8, characterized in that, The latent heat of adsorption and the sensible heat of flue gas are partially recovered in the boiler as the flue gas cools, specifically including: The high-temperature and high-humidity regeneration gas flow first flows through the boiler economizer, where it undergoes convective heat exchange with the feedwater in the economizer tubes. Part of the sensible heat of the flue gas is recovered, and the temperature is initially reduced. The initially cooled regenerated gas flow continues to flow through the flue gas condenser heat exchanger located behind the economizer, where its temperature drops further below the water dew point, causing some of the water vapor in the flue gas to condense and release the adsorbed latent heat. The latent heat of adsorption released by condensation and the residual sensible heat of flue gas are absorbed by the circulating working fluid in the flue gas condenser heat exchanger through convection and condensation phase change heat transfer, thus completing the deep recovery and utilization of the latent heat of adsorption and the sensible heat of flue gas.

10. A waste heat recovery and dehumidification system for a coal-fired boiler, applied to the waste heat recovery and dehumidification method for a coal-fired boiler as described in any one of claims 1-9, characterized in that, include: The flue gas treatment module is used to pass the flue gas discharged from the coal-fired boiler into the adsorption zone of the adsorption rotor. The water vapor in the flue gas is captured by the adsorbent, and the latent heat of adsorption and the sensible heat of the flue gas are absorbed by the adsorption rotor, thereby achieving cooling and dehumidification of the flue gas and forming low-temperature and low-humidity exhaust gas and saturated adsorbent. Adsorbent regeneration module: used to desorb the saturated adsorbent by using a stream of low-temperature dry air from the coal-fired boiler system as a regeneration gas flow, and to form a high-temperature and high-humidity regeneration gas flow. Energy recovery module: used to mix the high-temperature and high-humidity regeneration gas flow with combustion air before entering the furnace, and to recover and utilize the moisture and heat carried by the high-temperature and high-humidity regeneration gas flow.

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