Steam generator flue gas heat feedback type waste heat recovery heat exchanger structure

Abstract

The application discloses a flue gas heat feedback type waste heat recovery heat exchanger structure of a steam generator, and belongs to the technical field of waste heat recovery.The structure comprises a plurality of independent steam generation cavities which are arranged in series in a heat exchanger shell body, the outlet of each cavity is connected to a steam collecting pipe through a pressure control valve, the bottom is connected to a water supplement collecting pipe through a one-way valve, a pressure feedback adjusting mechanism is arranged between the steam collecting pipe and the water supplement collecting pipe, the outlet of the steam collecting pipe is connected to a generator for power generation through a speed-increasing nozzle driving impeller, a speed-increasing mechanism, an inertial flywheel and an overrunning clutch, and the flue gas waste heat is utilized in stages and the pressure is self-adaptively and feedback-regulated.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology for steam generators, and specifically to a structure of a waste heat recovery heat exchanger for flue gas heat feedback in steam generators. Background Technology

[0002] Steam generators are widely used heat conversion devices in industrial fields, especially in continuous production scenarios such as steel sintering machines, glass kilns, and chemical cracking furnaces, where flue gas temperatures typically reach 180-250℃, carrying a large amount of recoverable waste heat. Existing technologies mostly recover waste heat from flue gas through direct heat exchange devices to preheat boiler feedwater or directly generate steam, thereby improving energy utilization efficiency.

[0003] However, in the above-mentioned typical industrial waste heat recovery applications, conventional flue gas waste heat recovery steam generators have the following two most specific drawbacks: First, the lack of heat storage and buffering capacity leads to drastic fluctuations in steam production with flue gas, making it difficult to maintain a stable steam supply.

[0004] For example, in steel sintering machines, when changing carriages or material layers, the flue gas temperature can drop sharply from 250°C to below 120°C within minutes, and then quickly rise again; in glass kilns, due to periodic fire-changing operations, flue gas parameters fluctuate significantly every 20-30 minutes. Existing equipment lacks a heat storage structure, so heat cannot be effectively stored. During low-load periods, steam pressure drops rapidly, and during high-load periods, steam pressure becomes instantaneously overpressured, making it impossible to provide a continuous and stable steam source for subsequent steam-using equipment (such as waste heat power generation systems and steam dryers), and even forcing frequent start-ups and shutdowns.

[0005] Second, the heat exchange intensity cannot be adaptively adjusted according to the heat source intensity, resulting in insufficient heat recovery under high load and excessive cooling under low load.

[0006] When flue gas rises sharply, the heat exchange area remains fixed, and a large amount of waste heat is discharged into the atmosphere without being absorbed. When flue gas drops sharply, the heat exchanger absorbs excessive heat, leading to excessively low medium temperature and condensation. This not only reduces overall thermal efficiency but also accelerates low-temperature corrosion. Existing solutions rely on manual adjustment or electric valves to control water replenishment, resulting in severe response lag and an inability to match the drastic heat source changes during the ignition and heating phase of the sintering machine or the recovery phase after kiln firing. Summary of the Invention

[0007] The purpose of this invention is to provide a structure for a waste heat recovery heat exchanger for flue gas heat feedback in a steam generator, thereby addressing the technical problem.

[0008] The objective of this invention can be achieved through the following technical solution: This application provides a structure for a waste heat recovery heat exchanger for flue gas heat feedback in a steam generator, including a heat exchanger shell, a steam generation chamber, a pressure control valve, a steam collection pipe, a water supply collection pipe, a feedback adjustment mechanism, a speed-increasing nozzle assembly, an impeller, a speed-increasing transmission mechanism, an inertial flywheel, an overrunning clutch, and a generator; The heat exchanger shell is horizontally arranged and is a sealed pressure-bearing structure. One end of the heat exchanger shell is provided with a flue gas inlet and the other end is provided with a flue gas outlet. The outer top wall is provided with a steam collection pipe and the outer bottom wall is provided with a water supply collection pipe. The heat exchanger shell is provided with at least three independent steam generating chambers at intervals along the direction from the flue gas inlet to the flue gas outlet. A flue gas passage is formed between the outer wall of each steam generating chamber and the inner wall of the heat exchanger shell. The flue gas passages are connected in series, so that the flue gas flows in from the flue gas inlet, flows sequentially through the flue gas passages corresponding to each steam generating chamber, and then is discharged from the flue gas outlet. The steam generating chamber is a sealed pressure vessel. Each steam generating chamber has a liquid storage tank at the bottom, which is filled with liquid heat exchange medium. A gas phase space is left at the top, a water supply interface with a one-way valve is provided at the bottom, and a steam outlet is provided at the top. Each steam generating chamber has heat exchange fins on its outer wall. The steam outlet at the top of each steam generating chamber extends to the outside of the heat exchanger shell. A normally closed pressure control valve is installed at the steam outlet. The inlet of the pressure control valve is connected to the gas phase space of the steam generating chamber. The pressure control valve has an opening pressure threshold and a closing pressure threshold, and the opening pressure threshold is greater than the closing pressure threshold. The outlet of each pressure control valve is connected to a steam collection pipe. The inlet end of the one-way valve at the bottom of each steam generating chamber extends to the outside of the heat exchanger shell and is connected to the water supply manifold. A feedback adjustment mechanism is provided between the steam collection pipe and the water supply collection pipe to adjust the amount of water supplied from the water supply collection pipe to each steam generating chamber, thus forming a pressure feedback loop. The outlet of the steam collection pipe is connected to a speed-increasing nozzle assembly; the speed-increasing nozzle assembly is fixed to the outside of the heat exchanger shell, and an impeller is provided at the outlet of the speed-increasing nozzle assembly, with the outlet end of the speed-increasing nozzle assembly facing the blades of the impeller; the impeller is connected to a speed-increasing transmission mechanism, and the output end of the speed-increasing transmission mechanism is connected to an inertial flywheel, which is connected to a generator via an overrunning clutch.

[0009] Preferably, the steam generating chambers are arranged sequentially along the flue gas flow direction, and a partition plate is provided between two adjacent steam generating chambers. The partition plate divides the interior of the heat exchanger shell into multiple independent flue gas passage spaces. Each partition plate is provided with a vent hole, so that the flue gas flows from the previous flue gas passage space into the next flue gas passage space through the vent hole, thereby realizing the series connection of the flue gas passages.

[0010] Preferably, the heat exchange fins include multiple sets of fin units, each set of fin units consisting of multiple radial fins, which are evenly distributed along the circumference of the steam generating cavity; the multiple sets of fin units are arranged at intervals along the axial direction of the steam generating cavity; and the heat exchange fins are fixedly connected to the outer wall of the steam generating cavity.

[0011] Preferably, the pressure control valve is sealed to the steam outlet, and a manual reset handle is provided on the valve body of the pressure control valve. The manual reset handle and the valve core of the pressure control valve are linked by a one-way push rod structure. The one-way push rod structure only pushes the valve core to open when the handle is manually pressed. After the handle is released, the push rod automatically resets and disengages from the valve core. When the pressure control valve is working normally, its automatic opening and closing is independently controlled by the hysteresis characteristic formed by the opening pressure threshold and the closing pressure threshold, and is not affected by the manual reset handle.

[0012] Preferably, the feedback regulating mechanism includes a pressure feedback pipe connecting the steam collection pipe and the water supply collection pipe, and a pressure-driven flow control valve disposed on the pressure feedback pipe; the pressure-driven flow control valve includes a pressure input port, a flow output port, a valve core, and a return spring; the pressure input port is connected to the steam collection pipe, and the flow output port is connected to the water supply collection pipe; the valve core is slidably disposed in the valve body of the pressure-driven flow control valve, one end of the valve core bears the pressure of the pressure input port, and the other end of the valve core abuts against the return spring, and the valve core moves with the pressure change of the pressure input port, thereby controlling the opening degree of the flow output port.

[0013] Preferably, the speed-increasing nozzle assembly includes a nozzle body and a fixed bracket; one end of the nozzle body is sealed and connected to the outlet of the steam collection pipe, and the other end of the nozzle body is a steam injection outlet; one end of the fixed bracket is fixedly connected to the outer wall of the heat exchanger shell, and the other end of the fixed bracket is fixedly connected to the nozzle body.

[0014] Preferably, the nozzle body is a Laval nozzle, which consists of a converging section, a throat section, and an expanding section in sequence along the steam flow direction. The cross-sectional area of ​​the throat section is smaller than the cross-sectional area of ​​the inlet of the converging section and smaller than the cross-sectional area of ​​the outlet of the expanding section.

[0015] Preferably, the steam injection outlet is arranged opposite to the center of the windward side of the impeller blades, and a gap is left between the steam injection outlet and the impeller.

[0016] Preferably, the inertial flywheel includes a flywheel disc and a flywheel shaft. One end of the flywheel shaft is fixedly connected to the output end of the speed-increasing transmission mechanism, and the other end of the flywheel shaft is connected to the input end of the overrunning clutch. The output end of the overrunning clutch is drively connected to the input shaft of the generator.

[0017] Preferably, the inertial flywheel includes a hub, spokes, and rim, the thickness of the rim being greater than the thickness of the spokes, the hub being fixedly connected to the output end of the speed-increasing transmission mechanism via a key or flange, and the input end of the overrunning clutch being fixedly connected to the flywheel shaft via a key or flange.

[0018] The beneficial effects of this invention are as follows: The system utilizes at least three independent steam generating chambers and their internal storage tanks to store sensible heat using liquid working fluid. Each chamber is equipped with a normally closed pressure control valve at the top (with an opening pressure threshold greater than the closing pressure threshold) to pressurize and store energy when there is excess flue gas and maintain pressure to continue steam production when there is insufficient flue gas. At the same time, the multiple chambers are connected in series to coordinate and smooth the total steam output, thereby achieving effective buffering of flue gas fluctuations and stable steam supply.

[0019] Through the feedback regulation mechanism (pressure feedback pipe and pressure-driven flow control valve) between the steam manifold and the water supply manifold, the steam manifold pressure directly drives the water supply flow opening. When the pressure increases, the water supply automatically increases to enhance heat exchange; when the pressure decreases, the water supply automatically decreases to avoid excessive heat exchange, forming a purely mechanical negative feedback loop, realizing real-time adaptive matching of heat exchange intensity to the flue gas heat source.

[0020] The liquid working fluid inside each steam generating chamber undergoes phase change heat transfer, stabilizing the temperature of the outer wall of the chamber near the saturation temperature corresponding to the current working fluid pressure. Pressure control valves maintain the chamber pressure within a set range, causing the wall temperature to fluctuate slowly only within the saturation temperature range. In addition, multiple chambers connected in series share the total temperature drop of the flue gas, thereby isolating the heat exchange wall from the thermal shock of fluctuating flue gas and significantly reducing the risk of thermal fatigue damage. Attached Figure Description

[0021] To better understand and implement this application, the technical solution is described in detail below with reference to the accompanying drawings.

[0022] Figure 1 A schematic diagram of a waste heat recovery heat exchanger for flue gas heat feedback of a steam generator provided in this application; Figure 2 A partial cross-sectional schematic diagram of a waste heat recovery heat exchanger structure for flue gas heat feedback of a steam generator provided in this application; Wherein: 1-Heat exchanger shell; 2-Steam manifold; 3-Water supply manifold; 4-Steam generating chamber; 6-One-way valve; 7-Pressure control valve; 8-Feedback regulating mechanism; 9-Increasing speed nozzle assembly; 10-Impeller; 11-Flue gas inlet; 12-Flue gas outlet; 13-Generator; 14-Overrunning clutch; 15-Increasing speed transmission mechanism; 16-Inertia flywheel; 41-Liquid storage tank; 42-Gas phase space; 43-Water supply interface; 44-Steam outlet; 45-Heat exchange fins; 71-Manual reset handle. Detailed Implementation

[0023] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, exemplary embodiments will be described in detail below, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0024] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0025] The following detailed description of the specific implementation methods, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided in detail.

[0026] Example 1 Please see Figures 1-2 This embodiment provides a structure for a waste heat recovery heat exchanger for flue gas heat feedback in a steam generator, including a heat exchanger shell, a steam generation chamber, a pressure control valve, a steam collection pipe, a water supply collection pipe, a feedback adjustment mechanism, a speed-increasing nozzle assembly, an impeller, a speed-increasing transmission mechanism, an inertial flywheel, an overrunning clutch, and a generator.

[0027] The heat exchanger shell 1 is horizontally arranged and is a sealed pressure-bearing structure, providing a sealed channel for flue gas. One end has a flue gas inlet 11, and the other end has a flue gas outlet 12. A steam collection pipe 2 is fixed to the outer top wall, and a water supply collection pipe 3 is fixed to the outer bottom wall. The heat exchanger shell 1 is made of sulfuric acid dew point corrosion-resistant steel and is wrapped with an insulation layer. High-temperature flue gas enters the heat exchanger shell 1 through the flue gas inlet 11 and flows sequentially through the series flue gas channels formed between the outer walls of each chamber and the inner wall of the shell, gradually transferring heat to each steam generating chamber, thus achieving the cascade utilization of flue gas heat.

[0028] Furthermore, the steam generating chambers 4 are arranged sequentially at intervals along the flue gas flow direction, and a partition is provided between two adjacent steam generating chambers (4). The partition divides the interior of the heat exchanger shell into multiple independent flue gas channel spaces. Each partition has at least one vent hole for connecting adjacent flue gas channels in series, allowing flue gas to flow from one flue gas channel space to the next. The vent hole is located near the upper part or central area of ​​the partition, and the opening area of ​​the vent hole is not less than 50% and not more than 80% of the cross-sectional area of ​​the flue gas channel, so as to ensure smooth flue gas flow and maintain an appropriate flow velocity, thereby improving heat exchange efficiency while avoiding excessive pressure drop. By setting up partitions and vent holes, the original spaced gap structure is replaced, which more effectively prevents flue gas short circuits and realizes the orderly guidance of flue gas between the chambers.

[0029] The steam generating chamber 4 is a sealed pressure vessel, making the steam generating chamber an independent steam generator; the lower part of the steam generating chamber 4 is provided with a liquid storage tank 41, which is filled with liquid heat exchange medium to absorb the heat of flue gas and then boil to generate steam; a gas phase space 42 is left at the top, a water supply interface 43 with a one-way valve 6 is provided at the bottom, and a steam outlet 44 is provided at the top; during operation, the heat of flue gas is conducted to the internal liquid through the chamber wall, the liquid absorbs heat and boils, and the steam accumulates in the gas phase space (42), causing the pressure inside the chamber to gradually increase. By utilizing the heat capacity of the liquid heat exchange medium itself and the hysteresis characteristics of the pressure control valve, heat storage and buffering of flue gas fluctuations are achieved. Multiple sets of heat exchange fins 45 are welded to the outer wall of the steam generating chamber to significantly increase the heat exchange area on the flue gas side and enhance turbulence, enabling the liquid heat exchange medium to quickly absorb heat and boil, thereby supporting the rapid response of the multi-chamber series-connected cascade high-efficiency heat exchange and heat feedback loop. The main body of the steam generating chamber is made of stainless steel (316L) to resist high-temperature corrosion.

[0030] Furthermore, the heat exchange fins are arranged along the axial direction of the steam generating cavity and are evenly distributed along the circumference of the steam generating cavity, and can be spiral fins or H-shaped fins; the heat exchange fins are fixedly connected to the outer wall of the steam generating cavity.

[0031] The pressure control valve 7 is a normally closed pressure control valve, installed at the steam outlet 44 at the top of each steam generating chamber. It is used to maintain the pressure inside each steam generating chamber within a set range, realizing the buffer working mode of "pressure increase and energy storage → centralized steam exhaust → pressure reduction and valve closure". The steam outlet extends to the outside of the heat exchanger shell. The inlet end of the pressure control valve is connected to the gas phase space of the chamber, and the outlet end is connected to the steam collection pipe 2. The pressure control valve is provided with an opening pressure threshold and a closing pressure threshold. When the pressure inside the chamber rises to the opening threshold due to heat absorption, the valve automatically opens and steam is discharged into the steam collection pipe (2). When the pressure drops to the closing threshold after steam exhaust, the valve closes and the chamber re-accumulates pressure. In order to achieve orderly steam exhaust from multiple chambers and maintain the pressure stability of the steam collection pipe, the opening pressure threshold of the pressure control valve of each steam generating chamber decreases sequentially along the flue gas flow direction. That is, the high temperature side chamber near the flue gas inlet has the highest threshold, and the low temperature side chamber near the flue gas outlet has the lowest threshold. The threshold difference between adjacent chambers is set to 0.05~0.15MPa. Specifically, taking three chambers as an example, the opening threshold of the first chamber is set to 0.8~1.0MPa, and the closing threshold is set to 0.6~0.8MPa; the opening threshold of the second chamber is set to 0.65~0.85MPa, and the closing threshold is set to 0.45~0.65MPa; the opening threshold of the third chamber is set to 0.5~0.7MPa, and the closing threshold is set to 0.3~0.5MPa. In this way, the high-temperature side chamber first pressurizes and stores energy, and after reaching a higher pressure, it discharges high-pressure steam. Then, the low-temperature side chamber discharges steam at a lower pressure, avoiding pressure fluctuations caused by simultaneous steam discharge, and keeping the pressure of the steam collection pipe within the range of 0.5~0.8MPa. The pressure control valve adopts a spring-loaded safety valve or a pilot-operated pressure control valve. For the pilot-operated pressure control valve, its hysteresis characteristic is achieved through the area difference between the main valve core and the pilot valve core and the spring preload force. After the pilot valve opens, the upper chamber of the main valve is depressurized, and the main valve core opens rapidly under the inlet pressure. The opening pressure is determined by the spring preload force of the pilot valve. When the pressure drops to the closing threshold, the pilot valve closes, the upper chamber of the main valve is repressurized, and the main valve core closes under the spring force. The closing pressure is lower than the opening pressure. The difference can be set within the range of 0.1~0.3MPa by adjusting the pilot valve return spring or the size of the damping orifice. A manual reset handle 71 is provided on the valve body. This handle is only used to manually open the valve core to depressurize during system maintenance or failure. During normal operation, the handle is in a free state and does not interfere with the automatic hysteresis action of the valve core. A non-self-locking push rod structure is used between the handle and the valve core. After being released, the handle automatically resets, and the valve core returns to the spring preload state.

[0032] Furthermore, the pressure control valve is sealed to the steam outlet, and a manual reset handle is provided on the valve body of the pressure control valve. The manual reset handle is linked to the valve core of the pressure control valve.

[0033] The one-way valve 6 is located at the water supply interface 43 at the bottom of each steam generating chamber to prevent high-pressure steam or hot water in the chamber from backflowing into the water supply manifold, ensuring the one-way flow of the water supply system and the stability of the heat feedback loop; the inlet end of the one-way valve extends to the outside of the heat exchanger shell and is connected to the water supply manifold 3; the one-way valve 6 is a swing valve or a lift valve, with an opening pressure ≤0.05MPa and a zero reverse leakage rate after closing.

[0034] The steam collection pipe 2 collects the steam discharged from all pressure control valves, and its internal pressure reflects the total steam production; the water supply collection pipe 3 connects to an external water source and distributes water to each check valve; a feedback adjustment mechanism 8 is provided between the steam collection pipe 2 and the water supply collection pipe 3. Furthermore, the feedback adjustment mechanism includes a pressure feedback pipe connecting the steam collection pipe 2 and the water supply collection pipe 3, and a pressure-driven flow control valve mounted on the pressure feedback pipe, used to form a purely mechanical negative feedback loop to achieve real-time adaptive matching of heat exchange intensity to the flue gas heat source; one end of the pressure feedback pipe is connected to the steam collection pipe 2, and the other end is connected to the pressure input port of the pressure-driven flow control valve; the flow output port of the pressure-driven flow control valve is connected to the water supply collection pipe 3; the valve core of the pressure-driven flow control valve is slidably mounted in the valve body, one end of which bears the pressure of the pressure input port, and the other end abuts against a return spring, and the flow is controlled by the preload of the return spring and the pressure input... The valve core position is controlled by the balance of inlet pressure, thereby adjusting the opening of the flow output port. When the pressure in the steam manifold increases, the valve core moves against the spring force, the opening increases, and the water supply increases. When the pressure decreases, the spring pushes the valve core to move in the opposite direction, the opening decreases, and the water supply decreases. The stiffness of the reset spring is designed according to the working pressure range of the steam manifold (0.5~0.8MPa) and the required flow regulation. The typical stiffness value is 10~50N / mm. The initial pre-compression makes the valve core at the middle opening (about 50%) at 0.5MPa, thus forming a stable negative feedback. This forms an adaptive closed loop of "steam production → steam pressure → water supply → steam production", without the need for external control signals.

[0035] The outlet of the steam collection pipe 2 is connected to a speed-increasing nozzle assembly 9. The speed-increasing nozzle assembly is fixed to the outside of the heat exchanger shell. An impeller 10 is located at the outlet of the speed-increasing nozzle assembly, and the outlet end of the speed-increasing nozzle assembly 9 faces the blades of the impeller. The impeller 10 includes a hub and multiple twisted blades, used to receive the impact of the high-speed steam jet, converting the steam kinetic energy into rotational mechanical energy to drive the subsequent transmission system. The impeller is connected to the input shaft of the speed-increasing transmission mechanism. The speed-increasing transmission mechanism 15 is a gear speed-increasing box, used to increase the low speed of the impeller to the high speed required by the generator, matching the optimal operating range of both. The impeller's design speed is 500~1500 rpm, and the generator's rated speed is 1500 rpm (four-pole) or 3000 rpm (two-pole), therefore the gear... The gearbox transmission ratio is set to 1:2 to 1:6 (i.e., output speed / input speed), using single-stage or two-stage helical cylindrical gear transmission, with a gear precision grade of not less than 6, and employing splash lubrication or forced oil injection lubrication; the bottom of the speed-increasing transmission mechanism is equipped with a shock-absorbing base, and the output end of the speed-increasing transmission mechanism is connected to an inertial flywheel, which is connected to a generator via an overrunning clutch; the overrunning clutch 14 is a roller type or wedge type, used for unidirectional transmission, with its input end fixedly connected to the flywheel shaft of the inertial flywheel 16, and its output end connected to the input shaft of the generator 13; the generator 13 is a synchronous generator or an asynchronous generator, and its output end is rectified and inverted before being connected to the grid or supplied to the local load, ultimately converting mechanical energy into electrical energy, realizing the conversion of waste heat into high-grade energy.

[0036] Furthermore, the speed-increasing nozzle assembly 9 includes a nozzle body and a fixed bracket; one end of the speed-increasing nozzle body is sealed and connected to the outlet of the steam collection pipe 2, and the other end is a steam injection outlet; one end of the fixed bracket is fixedly connected to the outer wall of the heat exchanger shell 1, and the other end is fixedly connected to the nozzle body; the inner wall of the speed-increasing nozzle body is electropolished.

[0037] Furthermore, the speed-increasing nozzle body is a Laval nozzle, consisting of a converging section, a throat section, and a diffusing section along the steam flow direction. The throat cross-sectional area is smaller than the inlet area of ​​the converging section and smaller than the outlet area of ​​the diffusing section. This is used to accelerate the pressurized steam output from the steam manifold 2 to supersonic speed, converting the pressure energy of the steam into the kinetic energy of the high-speed jet, providing a high-energy-density jet for subsequent kinetic energy recovery. To prevent shock wave losses due to back pressure mismatch, the area ratio of the nozzle outlet diffusing section is designed to match the working pressure range of the steam manifold (0.5~0.8MPa, absolute pressure) with the environmental pressure inside the impeller cavity. The environmental pressure inside the impeller cavity is designed to be slightly lower than atmospheric pressure (0.08~0.1MPa absolute pressure). By calculating the nozzle expansion ratio, the difference between the nozzle outlet static pressure and the back pressure is kept within ±10%, or a diffuser section is set between the nozzle outlet and the impeller for pressure recovery, thereby ensuring the stable impact efficiency of the supersonic jet.

[0038] Furthermore, the steam injection outlet is arranged opposite to the center of the windward side of the impeller blades 10, and a gap of 10-30mm is left between the steam injection outlet and the impeller.

[0039] Furthermore, the inertial flywheel 16 includes a flywheel disc and a flywheel shaft. One end of the flywheel shaft is fixedly connected to the output end of the speed-increasing transmission mechanism, and the other end of the flywheel shaft is connected to the input end of the overrunning clutch. The output end of the overrunning clutch is drively connected to the input shaft of the generator.

[0040] Furthermore, the flywheel includes a hub, spokes, and rim, with the rim thickness greater than the spoke thickness to provide sufficient rotational inertia; the flywheel is fixedly connected to the output shaft of the speed-increasing transmission mechanism 15 via a key or flange.

[0041] In this embodiment, the main workflow during operation is as follows: High-temperature flue gas enters the casing through the inlet and flows sequentially through the outer walls and fins of each steam generating chamber. Heat is conducted through the walls to the liquid inside the chamber. The liquid absorbs heat and boils to generate steam, gradually increasing the pressure in the gas phase space. Due to differences in flue gas temperature, the steam generation rates differ between chambers: the high-temperature chamber heats up and generates steam quickly, and its pressure control valve has the highest opening threshold, so it first raises the pressure to a higher threshold before venting steam, which then enters the main steam pipe. The low-temperature chamber has a lower threshold; when the pressure in the main steam pipe rises to its opening threshold due to the high-temperature side's steam venting, it also vents steam, but due to its lower threshold, the venting pressure is lower. Through differentiated threshold design, the high-temperature chamber primarily undertakes the high-pressure energy storage function, while the low-temperature chamber replenishes steam in a timely manner when the pressure in the main steam pipe drops, jointly maintaining the main steam pipe pressure stable within the range of 0.5~0.8 MPa. When the pressure in a chamber reaches the opening threshold of its pressure control valve, the valve automatically opens, and steam is discharged into the main steam pipe; after venting, the valve closes when the pressure drops to the closing threshold. Each chamber vents steam independently and intermittently, working together to maintain a stable pressure in the steam collection pipe.

[0042] To ensure normal steam discharge from all chambers connected to the same steam manifold, this embodiment employs a dynamic matching design to achieve orderly circulation: the speed-increasing nozzle assembly 9 and generator 13 serve as continuous steam consumption loads, with their rated steam consumption designed to exceed the maximum instantaneous steam discharge flow rate of any single chamber. When the high-temperature chamber discharges steam, the manifold pressure rises instantaneously, but due to the steam consumption exceeding the inflow, the pressure quickly drops, resulting in a periodic fluctuation of "peak-rapid fall" in the manifold pressure. The opening threshold (absolute pressure) of the low-temperature chamber is designed to be lower than the trough of the manifold pressure drop, thus obtaining an opening window within each cycle. By adjusting the volume of the liquid storage tank in each chamber (designed based on the maximum steam production rate of 5-10 minutes), the opening and closing difference of the pressure control valve (0.1-0.3 MPa), and the downstream steam consumption rate, the pressure fluctuation range of the manifold can cover the opening pressure of all chambers, achieving coordinated operation of high-pressure energy storage steam discharge from the high-temperature chamber and low-pressure steam replenishment from the low-temperature chamber. Those skilled in the art can obtain a stable cycle of exhaust gas based on the flue gas fluctuation amplitude through conventional engineering calculations.

[0043] The pressure from the steam manifold is transmitted to the pressure-driven flow control valve via a pressure feedback pipe. The valve core moves under the combined action of pressure and a return spring, changing the opening of the flow output port: the opening increases when the pressure rises, increasing the water supply; the opening decreases when the pressure falls, reducing the water supply. The water supply enters the respective storage tanks through check valves, maintaining a stable water level and forming an adaptive closed loop of "steam production → steam pressure → water supply → steam production".

[0044] Steam in the steam collection pipe enters the speed-increasing nozzle and is accelerated to supersonic speed, impacting the impeller blades and driving them to rotate. After being accelerated by the speed-increasing transmission mechanism, it drives the inertial flywheel to rotate, and then drives the generator to generate electricity in one direction through the overrunning clutch.

[0045] When a shutdown for maintenance is required, first shut off the flue gas source. After the system has cooled down, manually operate the manual reset handle of each pressure control valve to open the valve core and release pressure. For long-term shutdowns, dry nitrogen should be introduced into the shell to purge and replace residual acidic gases to prevent shutdown corrosion.

[0046] It should be noted that the specific models and specifications of components such as pressure sensors, level sensors, pressure control valves, check valves, and pressure-driven flow control valves need to be selected and determined based on the actual operating parameters of the device. The specific selection and calculation methods adopt existing technologies in this field, so they will not be described in detail here.

[0047] Example 2 Based on the structure described in Example 1, this embodiment further describes the adaptive working mode of the heat exchanger structure under flue gas condition fluctuations, which is particularly suitable for industrial waste heat recovery applications such as steel sintering machines and glass kilns where flue gas temperature and flow rate fluctuate frequently.

[0048] When the flue gas inlet temperature and flow rate are stable near the design conditions, each steam generating chamber operates according to the differentiated threshold setting rules described in Example 1: the high-temperature side chamber intermittently exhausts steam at a high threshold, the low-temperature side chamber supplements steam exhaust at a low threshold, the steam collection pipe pressure is maintained in the range of 0.5~0.8MPa, and the feedback adjustment mechanism makes the water supply and steam production match in real time, so that the system is in a balanced state.

[0049] When the flue gas inlet temperature suddenly rises or the flue gas flow rate increases (such as during the ignition and heating stage of a sintering machine), the heat absorption of the high-temperature side cavity increases sharply, the steam generation rate accelerates, and the pressure inside the cavity rises rapidly. Since the opening thresholds of each pressure control valve are fixed, the high-temperature side cavity reaches its opening threshold first and discharges steam, causing the pressure in the steam manifold to rise rapidly. At this time, the pressure-driven flow control valve in the feedback regulation mechanism detects the increase in the manifold pressure, the valve core moves against the force of the return spring, the flow output port opening increases, and the amount of water supplied to each cavity from the water manifold increases, enhancing the circulation of the heat exchange medium and suppressing excessive pressure surges in the cavity. Simultaneously, the low-temperature side cavity, due to the passive increase in manifold pressure, may reach its opening threshold earlier and participate in steam discharge, sharing the steam discharge load of the high-temperature side cavity, forming a multi-cavity coordinated pressure relief. The above process requires no external control signal; pure mechanical feedback achieves automatic capacity expansion under high load.

[0050] When the flue gas inlet temperature suddenly drops or the flue gas flow rate decreases (such as during nighttime load reduction or before boiler shutdown), the heat absorption of the high-temperature side chamber decreases sharply, the steam production rate drops, and the pressure inside the chamber is difficult to reach the opening threshold. At this time, the pressure of the steam manifold gradually decreases, and the valve core in the feedback regulation mechanism closes the flow output port under the push of the return spring, reducing the amount of water replenishment and avoiding excessive water replenishment to each chamber, which would lead to excessively high liquid levels and reduce the heat storage space. At the same time, since the opening threshold of the low-temperature side chamber is already low, when the pressure of the manifold drops to within its opening threshold range, intermittent steam exhaust can still be maintained to replenish a small amount of steam to the manifold, preventing the pressure of the manifold from suddenly dropping to zero and maintaining the basic steam supply to downstream steam-using equipment. When the pressure of the manifold further drops below the closing threshold of all chambers, the system enters a low-power standby state, only maintaining the heat capacity storage of the liquid medium in the storage tank, and automatically restarting steam exhaust after the flue gas conditions recover.

[0051] During system startup, cold flue gas first enters the heat exchanger shell, and the initial pressure in each steam generating chamber is zero. As the flue gas flows, the high-temperature side chamber absorbs heat and heats up first, the liquid medium begins to boil, and the pressure rises slowly. During this period, the low-temperature side chamber heats up more slowly because some of the temperature has been absorbed by the flue gas flow through the high-temperature side, and its pressure control valve remains closed. The pressure-driven flow control valve in the feedback regulation mechanism is initially closed or slightly open, with minimal water supply. When the pressure in the high-temperature side chamber first reaches its opening threshold, steam is injected into the manifold, the pressure in the manifold is established, the feedback regulation mechanism begins to operate, and the water supply gradually increases with the pressure rise, completing the system's self-starting process. The entire startup phase requires no human intervention, achieving cold-state self-starting.

[0052] During system shutdown, after the flue gas source is shut off, each chamber stops absorbing heat, and the pressure gradually decreases. When the pressure in the main pipe falls below the closing threshold of all pressure control valves, all valves remain closed. Residual steam within the chambers condenses in the liquid storage tank, creating negative pressure, and the check valve prevents backflow of makeup water. In the feedback regulating mechanism, the valve core closes completely under spring action, cutting off makeup water. At this point, the pressure can be released manually by operating the manual reset handle of each pressure control valve, or the pressure can be allowed to return to zero after the chambers cool naturally.

[0053] This embodiment further illustrates the adaptive working mechanism of the heat exchanger structure in dynamic processes such as flue gas condition fluctuations, start-up, and shutdown through the above scenario description, and verifies its technical effect of achieving stable operation under wide operating conditions without external energy or complex control system.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A structure for a waste heat recovery heat exchanger for flue gas heat feedback in a steam generator, characterized in that, include: Heat exchanger shell, steam generation chamber, pressure control valve, steam manifold, water supply manifold, feedback regulating mechanism, speed-increasing nozzle assembly, impeller, speed-increasing transmission mechanism, inertial flywheel, overrunning clutch and generator; The heat exchanger shell (1) is horizontally arranged and is a sealed pressure-bearing structure. One end of the heat exchanger shell (1) is provided with a flue gas inlet (11) and the other end is provided with a flue gas outlet (12). The outer top wall is provided with a steam collection pipe (2) and the outer bottom wall is provided with a water supply collection pipe (3). The heat exchanger shell (1) is provided with at least three independent steam generating chambers (4) arranged sequentially from the flue gas inlet (11) to the flue gas outlet (12). A flue gas passage is formed between the outer wall of each steam generating chamber and the inner wall of the heat exchanger shell. The flue gas passages are connected in series, so that the flue gas flows in from the flue gas inlet (11), flows sequentially through the flue gas passages corresponding to each steam generating chamber, and then is discharged from the flue gas outlet (12). The steam generating chamber (4) is a sealed pressure vessel. Each steam generating chamber has a liquid storage tank (41) at the bottom, which is filled with liquid heat exchange medium. A gas phase space (42) is left at the top, a water supply interface (43) with a one-way valve is provided at the bottom, and a steam outlet (44) is provided at the top. Each steam generating chamber (4) has heat exchange fins (45) on its outer wall. The steam outlet (44) at the top of each steam generating chamber (4) extends to the outside of the heat exchanger shell. A pressure control valve (7) is installed at the steam outlet. The inlet end of the pressure control valve (7) is connected to the gas phase space (42) of the steam generating chamber. The pressure control valve (7) is provided with an opening pressure threshold and a closing pressure threshold, and the opening pressure threshold is greater than the closing pressure threshold. The outlet end of each pressure control valve is connected to the steam collection pipe (2). The inlet end of the one-way valve (6) at the bottom of each steam generating chamber (4) extends to the outside of the heat exchanger shell and is connected to the water supply manifold (3); A feedback adjustment mechanism (8) is provided between the steam collection pipe (2) and the water supply collection pipe (3) to adjust the amount of water supplied by the water supply collection pipe (3) to each steam generating chamber, thus forming a pressure feedback loop; The outlet of the steam collection pipe (2) is connected to a speed-increasing nozzle assembly (9); the speed-increasing nozzle assembly (9) is fixed to the outside of the heat exchanger shell, and an impeller (10) is provided at the outlet of the speed-increasing nozzle assembly, and the outlet end of the speed-increasing nozzle assembly (9) is directly opposite the blade of the impeller (10); the impeller (10) is connected to a speed-increasing transmission mechanism (15), and the output end of the speed-increasing transmission mechanism (15) is connected to an inertial flywheel (16), and the inertial flywheel (16) is connected to a generator (13) through an overrunning clutch (14).

2. The structure of the steam generator flue gas heat feedback type waste heat recovery heat exchanger according to claim 1, characterized in that, The steam generating chambers (4) are arranged sequentially along the flue gas flow direction. A partition plate is provided between two adjacent steam generating chambers (4). The partition plate divides the interior of the heat exchanger shell into multiple independent flue gas passage spaces. Each partition plate is provided with a vent hole, so that the flue gas flows from the previous flue gas passage space into the next flue gas passage space through the vent hole, thereby realizing the series connection of the flue gas passages.

3. The structure of the steam generator flue gas heat feedback type waste heat recovery heat exchanger according to claim 1, characterized in that, The heat exchange fins (45) include multiple sets of fin units, each set of fin units consisting of multiple radial fins, which are evenly distributed along the circumference of the steam generating cavity; the multiple sets of fin units are arranged at intervals along the axial direction of the steam generating cavity; the heat exchange fins are fixedly connected to the outer wall of the steam generating cavity.

4. The structure of the steam generator flue gas heat feedback type waste heat recovery heat exchanger according to claim 1, characterized in that, The pressure control valve (7) is sealed to the steam outlet. A manual reset handle (71) is provided on the valve body of the pressure control valve. The manual reset handle (71) and the valve core of the pressure control valve are linked by a one-way push rod structure. The one-way push rod structure only pushes the valve core to open when the handle is manually pressed. After the handle is released, the push rod automatically resets and disengages from the valve core. When the pressure control valve is working normally, its automatic opening and closing is independently controlled by the hysteresis characteristic formed by the opening pressure threshold and the closing pressure threshold, and is not interfered with by the manual reset handle.

5. The structure of the steam generator flue gas heat feedback type waste heat recovery heat exchanger according to claim 1, characterized in that, The feedback regulating mechanism (8) includes a pressure feedback pipe connecting the steam collection pipe (2) and the water supply collection pipe (3), and a pressure-driven flow control valve disposed on the pressure feedback pipe; the pressure-driven flow control valve includes a pressure input port, a flow output port, a valve core and a return spring; the pressure input port is connected to the steam collection pipe, and the flow output port is connected to the water supply collection pipe; the valve core is slidably disposed in the valve body of the pressure-driven flow control valve, one end of the valve core bears the pressure of the pressure input port, and the other end of the valve core abuts against the return spring, and the valve core moves with the pressure change of the pressure input port, thereby controlling the opening degree of the flow output port.

6. The structure of the steam generator flue gas heat feedback type waste heat recovery heat exchanger according to claim 1, characterized in that, The speed-increasing nozzle assembly (9) includes a nozzle body and a fixed bracket; one end of the nozzle body is sealed and connected to the outlet of the steam collection pipe (2), and the other end of the nozzle body is a steam injection outlet; one end of the fixed bracket is fixedly connected to the outer wall of the heat exchanger shell (1), and the other end of the fixed bracket is fixedly connected to the nozzle body.

7. The structure of the steam generator flue gas heat feedback type waste heat recovery heat exchanger according to claim 6, characterized in that, The nozzle body is a Laval nozzle, which consists of a converging section, a throat section, and a diffusing section in sequence along the steam flow direction. The cross-sectional area of ​​the throat section is smaller than the cross-sectional area of ​​the inlet of the converging section and smaller than the cross-sectional area of ​​the outlet of the diffusing section.

8. The structure of the steam generator flue gas heat feedback type waste heat recovery heat exchanger according to claim 6, characterized in that, The steam injection outlet is arranged opposite to the center of the windward side of the blade of the impeller (10), and there is a gap between the steam injection outlet and the impeller (10).

9. The structure of the steam generator flue gas heat feedback type waste heat recovery heat exchanger according to claim 1, characterized in that, The inertial flywheel (16) includes a flywheel disc and a flywheel shaft. One end of the flywheel shaft is fixedly connected to the output end of the speed-increasing transmission mechanism (15), and the other end of the flywheel shaft is connected to the input end of the overrunning clutch (14). The output end of the overrunning clutch (14) is connected to the input shaft of the generator (13).

10. The structure of the steam generator flue gas heat feedback type waste heat recovery heat exchanger according to claim 9, characterized in that, The inertial flywheel (16) includes a hub, spokes and rim, the thickness of the rim is greater than the thickness of the spokes, the hub is fixedly connected to the output end of the speed-increasing transmission mechanism (15) by a key or flange, and the input end of the overrunning clutch (14) is fixedly connected to the flywheel shaft by a key or flange.

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