Waste heat cascade utilization system for the synergistic recovery of heat from heat exchange and milling heat

Abstract

Waste heat cascade utilization system for the synergistic recovery of heat energy from heat exchange and milling heat, characterized in that it includes a mechanical heat recovery device, a primary preheating device, a secondary steam generation device and a tertiary low-temperature utilization device; wherein the mechanical heat recovery device connects the heat-generating components of the blower mill to the dry pipe inlet air duct in order to absorb the heat generated by the heat-generating components of the blower mill and transfer it to the dry pipe inlet air duct; wherein the primary preheating device, the secondary steam generating device and the tertiary low-temperature utilization device are arranged sequentially in the flue gas duct at the dry pipe flue gas outlet; wherein the heat outlet of the primary preheating device is connected to the combustion air duct of the boiler in order to preheat the combustion air of the boiler; wherein the steam outlet of the secondary steam generating device is connected to the steam inlet of a steam turbine to assist the turbine in driving a generator for electricity generation; and wherein the tertiary low-temperature utilization device is connected to the process water line to regulate the process water temperature and to assist the plant heating.

Description

Technical area

[0001] The present utility model relates to the technical field of boiler waste heat recovery and utilization, in particular a waste heat cascade utilization system for the synergistic recovery of heat from heat exchange and milling heat. Background technology

[0002] In today's age of booming industrial development, the contradiction between energy consumption and environmental protection is becoming increasingly apparent. Industrial production, as the main source of energy consumption, not only promotes economic development but also generates large quantities of waste heat. If this waste heat is not used effectively, it not only represents an enormous waste of energy, but will also exacerbate the current energy shortage and have negative impacts on the environment.

[0003] Boilers play an irreplaceable role in many industrial sectors as core equipment for energy conversion and utilization. In electricity generation, coal-fired boilers, gas-fired boilers, and other similar devices convert the chemical energy of the fuel into thermal energy and heat water to produce high-temperature, high-pressure steam. This steam, in turn, drives a turbine, which in turn powers a generator to produce electricity. Therefore, they are the core components of thermal power plants. Biomass fuel is characterized by its renewability, low carbon content, and broad resource distribution. It is one of the most important directions in the current energy transition and response to climate change, offering wide-ranging applications in the civil, industrial, and transportation sectors.Biomass co-combustion technology in thermal power plants involves mixing biomass fuel and coal in a specific ratio and feeding them into the power plant's boiler, where they combust to generate electricity. This technology replaces a portion of the coal with biomass, leveraging the renewable and low-carbon properties of biomass fuel to achieve a low-carbon transition for thermal power plants while simultaneously improving energy efficiency and reducing fossil fuel consumption and pollutant emissions. However, if high-moisture biomass is fed directly into the boiler for combustion during the utilization phase, combustion efficiency decreases, flue gas emissions increase, and safety issues such as boiler flame failure can occur.Therefore, it is necessary to shred and dry the biomass to improve the combustion efficiency of the biomass co-combustion and to ensure the stable operation of the boiler.

[0004] As core equipment in the biomass drying process, the heat source of the drying tube is primarily based on the high-temperature flue gas produced during fuel combustion (the initial temperature can exceed 800 °C). During the drying process, the high-temperature flue gas comes into direct contact with the wet biomass, and some of the heat is used to evaporate the moisture in the material. However, due to the rapid drying process, the flue gas remains in the tube for only a very short time, and the flue gas at the drying tube outlet can still maintain a high temperature of 600–700 °C, carrying a large amount of unused waste heat. Direct venting of this heat not only results in energy waste but also causes thermal pollution on-site due to the dispersion of high-temperature flue gas.Furthermore, the shredding of biomass generates large amounts of mechanical heat, for example, during the operation of the blower mill. This mechanical heat increases the temperature inside the mill, which not only impairs the normal operation of the system and shortens its lifespan, but also causes some of the heat energy to be released into the environment via the equipment housing, resulting in energy losses. Therefore, there is an urgent need for a waste heat cascade utilization system capable of efficiently recovering and utilizing waste heat, featuring a well-designed structure and enabling synergistic interaction between its components. This would allow for the efficient recovery and utilization of the aforementioned waste heat, maximize its utilization efficiency, and reduce energy waste. Content of the utility model

[0005] To solve the problems of low waste heat utilization rates and large energy losses in the co-combustion process of thermal power plants according to the state of the art, the present utility model provides a waste heat cascade utilization system for the synergistic recovery of heat energy from heat exchange and milling heat.

[0006] To achieve the above-mentioned purpose, the present utility model adopts the following technical solution: The present utility model provides a waste heat cascade utilization system for the synergistic recovery of heat energy from heat exchange and milling heat, comprising a mechanical heat recovery device, a primary preheating device, a secondary steam generation device and a tertiary low-temperature utilization device; wherein the mechanical heat recovery device connects the heat-generating components of the blower mill to the dry pipe inlet air duct in order to absorb the heat generated by the heat-generating components of the blower mill and transfer it to the dry pipe inlet air duct; wherein the primary preheating device, the secondary steam generating device and the tertiary low-temperature utilization device are arranged sequentially in the flue gas duct at the dry pipe flue gas outlet; wherein the heat outlet of the primary preheating device is connected to the combustion air duct of the boiler in order to preheat the combustion air of the boiler; wherein the steam outlet of the secondary steam generating device is connected to the steam inlet of a steam turbine to assist the turbine in driving a generator for electricity generation; and wherein the tertiary low-temperature utilization device is connected to the process water line to regulate the process water temperature and to assist the plant heating.

[0007] Optionally, the mechanical heat recovery device includes a finned heat tube array mounted on the blower mill, wherein the finned heat tube array comprises several heat tubes and several fins connected to the heat tubes; wherein the evaporation segment of the heat tube is connected to the heat-generating components of the blower mill, and the condensation segment of the heat tube is connected to the dry tube inlet air duct.

[0008] Optionally, the heat pipes are copper water heat pipes with a diameter of 10 to 15 mm; the fins are aluminum fins with a fin spacing of 5 to 10 mm and a fin height of 20 to 30 mm.

[0009] Optionally, the primary preheating device is located in the high-temperature segment of the flue gas duct at the dry-tube flue gas outlet, the secondary steam generating device is located in the medium-temperature segment of the flue gas duct at the dry-tube flue gas outlet, and the tertiary low-temperature utilization device is located in the low-temperature segment of the flue gas duct at the dry-tube flue gas outlet; wherein the temperature of the high-temperature segment is 600 °C to 700 °C, the temperature of the medium-temperature segment is 200 °C to 400 °C, and the temperature of the low-temperature segment is less than 150 °C.

[0010] Optionally, the primary preheating device includes a ceramic heat storage element located in the flue gas duct at the dry-tube flue gas outlet, wherein the ceramic heat storage element is a ceramic heat storage element with a honeycomb structure; wherein the flue gas at the dry-tube flue gas outlet circulates through the cell channels of the honeycomb structure within the ceramic heat storage element, while the combustion air of the boiler circulates to the boiler after heat exchange outside the ceramic heat storage element.

[0011] Optionally, the ceramic heat storage body is made of cordierite ceramic and the cell channel spacing of the honeycomb structure of the ceramic heat storage body is 10 to 15 mm.

[0012] Optionally, the secondary steam generating device includes a spiral tube evaporator arranged in the flue gas duct at the dry tube flue gas outlet, wherein the flue gas from the dry tube flows through the spiral tube of the spiral tube evaporator and exchanges heat with the water contained therein before entering the tertiary low-temperature utilization device; wherein the water in the spiral tube evaporator is converted into steam after heat exchange and directed to the steam turbine to assist the steam turbine in driving the generator for power generation.

[0013] Optionally, the tertiary low-temperature utilization device includes a heat exchanger located in the flue gas duct at the dry tube flue gas outlet, wherein the medium in the heat exchanger exchanges heat with the flue gas from the dry tube to heat the process water.

[0014] Optionally, the heat exchanger can be a plate heat exchanger, which is made of an aluminum alloy.

[0015] The present utility model provides a waste heat cascade utilization method that uses the above-mentioned waste heat cascade utilization system for the synergistic recovery of heat energy from heat exchange and milling heat, comprising: collecting the mechanical heats generated by the blower mill and directing them to the drying tube for preheating;

[0016] Preheating of the flue gas at the outlet of the drying tube by the primary preheating device to generate combustion air, and subsequent routing to the secondary steam generating device and routing of the preheated combustion air to the boiler for combustion;

[0017] Directing the flue gas emitted by the primary preheating device, after heat exchange through the secondary steam generating device, to the tertiary low-temperature utilization device, and using the steam generated by the secondary steam generating device for power generation;

[0018] Discharge of the flue gas after heat exchange in the secondary steam generation device, after heat exchange in the tertiary low-temperature utilization device, and use of the medium after heat exchange in the tertiary low-temperature utilization device to heat process water to support the heating of the plant area, thereby completing the cascade utilization of waste heat. Compared to the prior art, the present utility model has the following advantageous effects: The present utility model provides a waste heat cascade utilization system for the synergistic recovery of heat energy from heat exchange and milling heat, wherein the system comprises a mechanical heat recovery device, a primary preheating device, a secondary steam generation device and a tertiary low-temperature utilization device, whereby the mechanical heat generated by a blower mill is collected and used to preheat a drying tube and the energy loss during the drying of the biomass in the drying tube is reduced;Simultaneously, a new waste heat cascade utilization system is created through the stepwise heat exchange of the primary preheating device, the secondary steam generation device and the tertiary low-temperature utilization device, enabling comprehensive recovery and cascade utilization of waste heat and mechanical heat in different temperature segments, with the primary preheating device utilizing the high-quality waste heat of the flue gas at the dry tube outlet to preheat the combustion air, which is then directed into the boiler for combustion, thereby improving the combustion efficiency of the boiler by utilizing the relatively high waste heat temperature;wherein the secondary steam generation device utilizes waste heat in the medium temperature segment to generate steam, which assists the steam turbine in driving the generator to produce electricity, thereby converting thermal energy into electrical energy, increasing the company's power output and providing additional economic benefits; wherein the tertiary low-temperature utilization device utilizes low-temperature waste heat to regulate the process water temperature, assist the plant heating, and reduce the plant's energy consumption and heating costs in winter; compared to conventional waste heat recovery systems, this system enables the efficient use of waste heat of varying qualities, improves the overall waste heat utilization rate, and; maximizes the improvement of waste heat utilization and the reduction of energy consumption, This reduces the company's energy procurement costs and improves the company's economic benefits, making it of great importance for promoting a company's sustainable development. The mechanical heat recovery device comprises a finned heat tube array mounted on the blower mill. The finned heat tube array includes multiple heat tubes and multiple fins connected to the heat tubes. The evaporation segment of the heat tube is connected to the heat-generating components of the blower mill, and the condensation segment of the heat tube is connected to the dry tube inlet air duct. A heat tube is a heat transfer element with extremely high thermal conductivity, enabling rapid heat transfer through the phase change (evaporation and condensation) of the working medium inside. The finned heat tube array combines multiple heat tubes and is equipped with fins, which significantly increases the heat exchange surface area.The evaporation section of the heat pipe is connected to the heat-generating components of the blower mill and is able to quickly absorb the heat generated by these components. It then utilizes the evaporation of the working fluid to rapidly transfer the heat to the condensation section, thus achieving mechanical heat recovery. Compared to conventional heat recovery methods, the finned heat pipe array can dissipate heat from the blower mill's heat-generating components more efficiently, reduce heat loss during the transfer process, and improve heat recovery efficiency. The heat pipes are copper-water heat pipes with a diameter of 10 to 15 mm; the fins are aluminum fins with a fin spacing of 5 to 10 mm and a fin height of 20 to 30 mm.Copper has extremely high thermal conductivity, and water has a high specific heat capacity, allowing it to absorb or release large amounts of heat during phase changes. Copper-water finned heat pipes combine the high thermal conductivity of copper with the excellent heat capacity of water, enabling rapid heat transfer from the evaporation to the condensation zone. Compared to finned heat pipes made of other materials, such as aluminum-ammonia heat pipes, copper-water finned heat pipes are able to transfer the heat generated by the fan and heat-generating components more quickly, significantly reducing the thermal response time and improving heat recovery efficiency. A pipe diameter of 10 to 15 mm ensures sufficient space inside the heat pipe for the circulation of the working fluid, thereby reducing thermal resistance and improving heat transfer efficiency.At the same time, a rib spacing of 5 to 10 mm ensures a uniform airflow between the ribs, thus reducing flow resistance.

[0019] The primary preheating device is located in the high-temperature segment of the flue gas duct at the dry-pipe flue gas outlet, the secondary steam generation device is located in the medium-temperature segment of the flue gas duct at the dry-pipe flue gas outlet, and the tertiary low-temperature utilization device is located in the low-temperature segment of the flue gas duct at the dry-pipe flue gas outlet;where the temperature of the high-temperature segment is 600 °C to 700 °C, the temperature of the medium-temperature segment is 200 °C to 400 °C, and the temperature of the low-temperature segment is less than 150 °C. Due to the different heat quality requirements of various devices, the primary preheating device is located in the high-temperature segment (600 °C to 700 °C), where the flue gas in this temperature segment has a high heat quality, is suitable for preheating the combustion air of the boiler, and is able to quickly raise the air temperature to an appropriate level and improve the combustion efficiency of the boiler.The secondary steam generation device is located in the medium temperature range (200 °C to 400 °C), where the thermal conditions required for steam generation are met and this portion of the waste heat can be effectively used to assist the steam turbine in driving the generator for power generation. The tertiary low-temperature utilization device is located in the low-temperature range (below 150 °C) and, despite the relatively low temperature, can be used to adjust the process water temperature and to support plant heating. This method of precisely matching the heat requirements of different devices according to temperature ranges achieves efficient, staged waste heat utilization and significantly improves energy efficiency.

[0020] The primary preheating device comprises a ceramic heat storage element located in the flue gas duct at the dry-tube flue gas outlet. The ceramic heat storage element has a honeycomb structure; the flue gas at the dry-tube flue gas outlet circulates through the cell channels of the honeycomb structure within the ceramic heat storage element, while the boiler's combustion air, after heat exchange outside the ceramic heat storage element, circulates back to the boiler. The honeycomb-structured ceramic heat storage element features numerous small channels, and this structure significantly increases the contact area between the ceramic heat storage element and the flue gases and air.Compared to conventional flat-plate or tube heat exchangers, the honeycomb structure provides a larger heat exchange surface for the same volume. This larger surface area means that the heat from the exhaust gas is transferred more effectively to the ceramic heat storage element, which in turn transfers the heat more efficiently to the air used for combustion in the boiler. Simultaneously, the regular arrangement of the cell channels in the honeycomb structure ensures that the flue gas and air flow smoothly within the ceramic heat storage element. This orderly flow reduces turbulence and dead zones in the fluid, lowers flow resistance, and improves heat exchange efficiency.

[0021] The ceramic heat storage element is made of cordierite ceramic, and the cell channel spacing of its honeycomb structure is 10 to 15 mm. Cordierite ceramics have an extremely low coefficient of thermal expansion, and their volume changes only minimally with temperature variations. Using cordierite ceramic for the heat storage element effectively prevents stress concentrations and cracking caused by thermal expansion and contraction, thus improving the stability and lifespan of the element. The 10-15 mm cell channel spacing provides a sufficient number of cells while ensuring the structural strength of the ceramic heat storage element, thereby increasing the contact area with the flue gas and air and improving heat exchange efficiency.

[0022] The secondary steam generation device comprises a spiral tube evaporator located in the flue gas duct at the dry tube flue gas outlet. The flue gas from the dry tube flows through the spiral tube of the spiral tube evaporator, exchanging heat with the water it contains before entering the tertiary low-temperature utilization device. After heat exchange, the water in the spiral tube evaporator is converted into steam and directed to the steam turbine to assist the turbine in driving the generator for power generation. The spiral structure of the spiral tube evaporator significantly increases the contact area between the tube and the flue gas.In comparison to the straight tube evaporator, the spiral tube can offer a greater tube length with the same space requirement, so that flue gas and water in the tube have more contact points, which allows the heat from the flue gas to be transferred better to the water in the tube, accelerating the rise in water temperature and improving heat exchange efficiency.

[0023] The tertiary low-temperature utilization device comprises a heat exchanger located in the flue gas duct at the dry tube flue gas outlet. The medium in the heat exchanger exchanges heat with the flue gas from the dry tube to heat the process water. After passing through the primary preheating device and the secondary steam generation device, the dry tube flue gas still contains a certain amount of low-temperature waste heat. The heat exchanger is able to absorb this otherwise wasted heat and transfer it to the medium within the heat exchanger. This medium then heats the process water, thus maintaining a relatively stable process water temperature.The heat exchanger is able to adapt to flue gas and process water conditions with different temperatures, pressures and flow rates, while at the same time the media flow in the heat exchanger is relatively uniform, thus reducing the risk of equipment damage from fluid turbulence and shocks.

[0024] The heat exchanger is a plate heat exchanger made of aluminum alloy. Aluminum alloys have high thermal conductivity and can quickly transfer heat from one medium to another. In the plate heat exchanger, heat is exchanged between the flue gas from the drying tube and the process water via the plates. The high thermal conductivity of the aluminum alloy accelerates this heat transfer. Simultaneously, the plate design of the heat exchanger ensures a uniform fluid flow across the heat exchange surface. Furthermore, the aluminum alloy plates are easily machinable and can be formed into various complex flow channel shapes to further optimize fluid distribution.

[0025] The present utility model provides a waste heat cascade utilization process that uses the aforementioned waste heat cascade utilization system for the synergistic recovery of thermal energy from heat exchange and milling heat. The process collects the mechanical heat generated by a blower mill and uses it to preheat a drying tube, thereby reducing the thermal energy loss of the drying tube during biomass drying. The flue gas at the outlet of the drying tube is preheated with combustion air in a primary preheating device and then directed to a secondary steam generating device. The preheated combustion air is then directed to the boiler for combustion, thereby improving the combustion efficiency of the boiler and reducing combustion losses.The flue gas discharged from the primary preheating device is directed to a tertiary low-temperature utilization device after heat exchange with the secondary steam generating device, and the steam generated by the secondary steam generating device is used for power generation, thereby reducing the turbine's output energy consumption and increasing the company's power output;The flue gas is discharged after heat exchange in the secondary steam generation unit and then in the tertiary low-temperature utilization unit. The medium after heat exchange in the tertiary low-temperature utilization unit is used to heat process water to support the heating of the plant area, thus completing the cascade utilization of waste heat. This process enables the cascade utilization of waste heat of varying qualities, improves energy utilization efficiency, reduces dependence on external energy, avoids irrational distribution and waste of energy, and improves the energy conversion efficiency of the entire system. Figures Fig. Figure 1 is a schematic structural representation of a waste heat cascade utilization system for the synergistic recovery of heat energy from heat exchange and milling heat according to the present utility model. Fig. Figure 2 is a schematic representation of the principle of recovering the mechanical heat generated by the operation of the blower mill according to the present utility model. Fig. Figure 3 is a three-dimensional structural representation of the ceramic heat storage body with honeycomb structure according to the present utility model. Fig. Figure 4 is a schematic representation of the heat exchange structure of the primary preheating device. Fig. Figure 5 is a three-dimensional structural representation of the spiral tube evaporator. Fig. Figure 6 is a schematic representation of the heat exchange process of the tertiary preheating device. Fig. Figure 7 is a flowchart of a waste heat cascade utilization process that uses the above-mentioned waste heat cascade utilization system for the synergistic recovery of heat energy from heat exchange and milling heat, according to the present utility model.

[0026] In the figures: 1 - heat-generating component of the blower mill, 2 - mechanical heat recovery device, 3 - dry pipe inlet air duct, 4 - dry pipe flue gas outlet, 5 - primary preheating device, 6 - secondary steam generating device, 7 - tertiary low-temperature utilization device, 8 - boiler, 9 - steam turbine, 10 - generator, ceramic heat storage body 20, cell channel of the honeycomb structure 21, spiral tube 30, fin 31. Specific embodiments

[0027] To clarify the purpose, technical solution, and advantages of the embodiments of this utility model, the technical solutions in these embodiments are described below in full, in conjunction with the accompanying drawings. It is evident that the described embodiments represent some of the embodiments of this utility model, not all of them. The components of the embodiments of this utility model, which are typically described and shown in the accompanying drawings, can be arranged and designed in a variety of different configurations.

[0028] Therefore, the following detailed description of the embodiments of the present utility model in the drawings is not intended to limit the scope of the claimed utility model, but merely to present selected embodiments of the present utility model. Based on the embodiments in the present utility model, all other embodiments obtained by general technical personnel without creative work fall within the scope of protection of the present utility model.

[0029] It should be noted that similar designations and letters in the following drawings refer to similar concepts, so that an object defined once in one drawing does not need to be further defined and explained in subsequent drawings.

[0030] In describing this utility model, it is necessary to point out that any azimuth or positional relationship referred to in terms such as "top," "bottom," "horizontal," "inside," and the like, is based on the drawing and is intended to facilitate and simplify the description of this utility model, rather than indicating or implying that the device or component in question must have a specific orientation, be designed, or be operated in a specific orientation. Therefore, they must not be understood as limiting this utility model. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying a relative meaning.

[0031] Furthermore, the use of the term "horizontal" does not mean that the part must be perfectly level, but rather that it can be tilted slightly. For example, "horizontal" simply means that its orientation is relatively more horizontal compared to "vertical," and it does not mean that the structure must be completely horizontal, but that it can be slightly inclined.

[0032] In the present utility model, it is necessary to point out that the terms "arrange," "install," "connect," and "link" are to be understood in a broad sense, unless expressly stated otherwise or limited. For example, it may refer to a permanent connection, a detachable connection, or a connection in one piece; it may be a mechanical connection or an electrical connection; it may be a direct connection, an indirect connection via an intermediate medium, or a connection within the two elements themselves. For general technical personnel in this field, the specific meaning of the aforementioned terms in the present utility model may be understood depending on the specific circumstances.

[0033] The present utility model is described in more detail below with reference to specific embodiments which are intended to explain, but not limit, the present utility model. With reference to Fig. 1 The present utility model discloses a waste heat cascade utilization system for the synergistic recovery of heat energy from heat exchange and milling heat, comprising a mechanical heat recovery device 2 connected to the heat-generating components of the blower mill 1, as well as a primary preheating device 5, a secondary steam generation device 6 and a tertiary low-temperature utilization device 7, which are arranged sequentially in the flue gas duct at the dry-tube flue gas outlet 4; the primary preheating device 5 is located in the high-temperature segment of the flue gas duct at the dry-tube flue gas outlet 4, the secondary steam generation device 6 in the medium-temperature segment of the flue gas duct at the dry-tube flue gas outlet 4 and the tertiary low-temperature utilization device 7 in the low-temperature segment of the flue gas duct at the dry-tube flue gas outlet 4;wherein the temperature of the high-temperature segment is 600 °C to 700 °C, the temperature of the medium-temperature segment is 200 °C to 400 °C and the temperature of the low-temperature segment is less than 150 °C.

[0034] The mechanical heat recovery device 2 is designed to absorb the heat generated by the heat-generating components 1 of the blower mill and transfer it to the dry pipe inlet air duct 3; the finned heat tube array comprises several heat tubes and several fins connected to the heat tubes; the mechanical heat recovery device 2 comprises a finned heat tube array mounted on the blower mill, wherein the finned heat tube array comprises several heat tubes and several fins 31 connected to the heat tubes; wherein the evaporation segment of the heat tube is connected to the heat-generating components of the blower mill, and the condensation segment of the heat tube is connected to the dry pipe inlet air duct. Optionally, the heat tubes are copper-water heat tubes with a diameter of 10 to 15 mm; The ribs 31 are aluminum ribs with a rib spacing of 5 to 10 mm and a rib height of 20 to 30 mm.The evaporation segment of the heat pipe is firmly connected to the heat-generating components 1 of the blower mill via thermally conductive silica gel to ensure efficient heat transfer, and the condensation segment is fixed in the dry pipe inlet air duct and connected to the inner wall of the air duct via a bracket.

[0035] The operating principle is in Fig. Figure 2 illustrates this: When the blower mill generates mechanical heat during operation, the heat pipe in the evaporation segment absorbs the heat from the heat-generating components 1 of the blower mill, and the water it contains evaporates into steam. Due to the pressure difference, the steam flows into the condensation segment. In the condensation segment, the steam transfers heat to the air in the dryer tube inlet air duct, thus heating the air. The air then condenses into liquid and flows back into the evaporation segment due to gravity. This cycle repeats, transferring the mechanical heat generated by the blower mill to the dryer tube inlet, thereby reducing the initial heating energy consumption of the dryer tube by 20%.

[0036] As in the Fig. 3 and Fig. As shown in Figure 4, the heat outlet of the primary preheating device 5 is connected to the combustion air duct of the boiler 8 and is designed to preheat the combustion air of the boiler 8, comprising a ceramic heat storage element 20 located in the flue gas duct at the dry-tube flue gas outlet 4, wherein the ceramic heat storage element 20 is a ceramic heat storage element 20 with a honeycomb structure; wherein the flue gas at the dry-tube flue gas outlet circulates through the cell channels of the honeycomb structure within the ceramic heat storage element 20, this structure being characterized by high temperature resistance, large heat capacity and high heat exchange efficiency; the combustion air of the boiler 8 circulates to the boiler 8 after heat exchange outside the ceramic heat storage element 20;The ceramic heat storage body 20 is arranged in a multi-layered, offset structure, and the multi-layered, offset structure further increases the heat exchange surface and improves the preheating effect, wherein the diameter of the cell channels of the honeycomb structure 21 of each heat storage body layer is 5 to 8 mm, the cell channel spacing is 10 to 15 mm, the thickness of the heat storage body is 50 to 100 mm and the number of layers is 5 to 8;The ceramic heat storage element 20 is made of cordierite ceramic (which withstands high temperatures above 700 °C). The ceramic heat storage element 20 is fixed in the flue gas duct by a high-temperature-resistant bracket, which is welded to the inner wall of the flue gas duct to ensure a secure installation. The combustion air duct is located outside the ceramic heat storage element 20 and is separate from the flue gas duct. The combustion air flows through the duct outside the heat storage element, and the flue gas passes through the cellular channels of the honeycomb structure 21 of the heat storage element.

[0037] Operating principle: When the high-temperature flue gas (600 °C to 700 °C) flows through the honeycomb structure 21 of the ceramic heat storage element 20 at the dry pipe outlet, the heat is transferred to the heat storage element, which absorbs and stores it. When the combustion air flows through the outer channel of the heat storage element, the heat storage element transfers the stored heat to the combustion air by conduction and convection, preheating the combustion air to 300 °C. This improves the combustion efficiency of the boiler and can increase the thermal efficiency by approximately 10%.

[0038] With reference to Fig. 5 is the steam outlet of the secondary steam generating device 6 connected to the steam inlet of a steam turbine 9 and it includes a spiral tube evaporator arranged in the flue gas duct at the dry tube flue gas outlet 4, wherein the spiral tube evaporator has a larger contact area with the medium temperature flue gas and a higher heat exchange efficiency, which allows the waste heat in the medium temperature segment to be better utilized and the efficiency of power generation to be improved.The flue gas from the drying pipe flows through the spiral tube of the spiral tube evaporator and exchanges heat with the water it contains before entering the tertiary low-temperature utilization device 7. After heat exchange, the water in the spiral tube evaporator is converted into steam and directed to the steam turbine 9 to assist the turbine in driving the generator 10 for power generation. The spiral tube evaporator is a steam generating device made of high-temperature and corrosion-resistant stainless steel. The spiral tube 30 has a diameter of 20-30 mm and a pitch of 50-80 mm. The spiral tube 30 is located in the flue gas duct in the medium-temperature segment (200-400 °C). The inlet and outlet pipes of the spiral tube evaporator are connected to the pipes of the steam-driven power generation system via flanges to ensure a good seal.The installation position of the spiral tube evaporator in the flue gas duct should ensure that the medium temperature flue gas can flow completely through the spiral tube 30 to improve heat exchange efficiency.

[0039] Operating principle: After heat exchange in the primary preheating device 5, the medium-temperature (200-400 °C) flue gas passes through the spiral tube evaporator, transferring heat to the water in the evaporator. The water absorbs the heat and evaporates into steam, which is then conveyed through the pipeline to the steam turbine 9. This sets the steam turbine 9 in motion, subsequently driving the generator 10 to produce electricity, thus improving the system's power generation efficiency. The tertiary low-temperature utilization device 7 is connected to the process water line to regulate the process water temperature and support plant heating. It includes a heat exchanger located in the flue gas duct at the dry-tube flue gas outlet 4. The medium in the heat exchanger exchanges heat with the flue gas from the dry tube to heat the process water.The heat exchanger is secured in the low-temperature flue gas duct by a bracket and is tightly connected to the flue gas duct; the process water line is equipped with a circulation pump designed to circulate the process water within the system, and an intelligent temperature control is installed in the plant heating line, which can automatically adjust the heating temperature of the process water to the plant heating requirements. The operating principle is described in [reference missing]. Fig. Figure 6 illustrates the following: After the low-temperature flue gas (<150 °C) undergoes heat exchange through the secondary steam generation device 6, it transfers heat to the process water as it flows through the heat exchanger. The process water absorbs the heat, causing its temperature to rise. The circulation pump directs the heated process water to the plant's heating system, supplying the plant with heat via the heating pipes. The intelligent temperature controller automatically adjusts the flow rate and heating temperature of the process water to the set heating temperature to ensure the heating effect. The comprehensive waste heat recovery rate can exceed 90%, enabling automatic adjustment of the process water's heating temperature and real-time adaptation to the plant's heating requirements, thus improving the flexibility and efficiency of energy use.

[0040] With reference to Fig.7. The present utility model provides a waste heat cascade utilization method which utilizes the above-mentioned waste heat cascade utilization system for the synergistic recovery of heat energy from heat exchange and milling heat, comprising the following: S1. Collecting the mechanical heat generated by the blower mill and directing it to the drying tube for preheating; S2. Preheating of the flue gas at the outlet of the drying tube by the primary preheating device 5 to generate combustion air, and subsequent routing to the secondary steam generating device 6 and routing of the preheated combustion air to the boiler 8 for combustion; S3. Directing the flue gas discharged from the primary preheating device 5, after heat exchange through the secondary steam generating device 6, to the tertiary low-temperature utilization device 7, and using the steam generated by the secondary steam generating device 6 for power generation; S4. Discharge of the flue gas after heat exchange in the secondary steam generation device 6, after heat exchange in the tertiary low-temperature utilization device 7, and use of the medium after heat exchange in the tertiary low-temperature utilization device 7 to heat process water to support the heating of the plant area, thus completing the cascade utilization of waste heat. This process enables the cascade utilization of waste heat of varying qualities, improves energy utilization efficiency, reduces dependence on external energy, avoids irrational distribution and waste of energy, and improves the energy conversion efficiency of the entire system.

[0041] In summary, the present utility model provides a waste heat cascade utilization system and method for the synergistic recovery of heat energy from heat exchange and milling heat, comprising a mechanical heat recovery device 2, a primary preheating device 5, a secondary steam generation device 6 and a tertiary low-temperature utilization device 7, whereby the mechanical heat generated by a blower mill is collected and used to preheat a drying tube and the energy loss during the drying of the biomass in the drying tube is reduced;Simultaneously, a new waste heat cascade utilization system is created, enabling comprehensive recovery and cascade utilization of waste heat and mechanical heat in different temperature segments. This system allows for the efficient use of waste heat of varying qualities, improves the overall waste heat utilization rate, and maximizes the improvement of waste heat utilization and the reduction of energy consumption, thereby lowering the company's energy procurement costs and improving its economic benefits. It is therefore of great importance for promoting the sustainable development of a company.

[0042] The foregoing descriptions merely represent preferred embodiments of the present utility model and are not intended to limit the technical solutions of the present utility model. Those skilled in the art should be aware that several simple modifications and substitutions can be made to the technical solution without departing from the spirit and principles of the present utility model, all of which fall within the scope of protection of the accompanying claims.

Claims

[1] Waste heat cascade utilization system for synergistic recovery of heat energy from heat exchange and milling heat, characterized by , that it includes a mechanical heat recovery device, a primary preheating device, a secondary steam generating device and a tertiary low-temperature utilization device; wherein the mechanical heat recovery device connects the heat-generating components of the blower mill to the dry pipe inlet air duct in order to absorb the heat generated by the heat-generating components of the blower mill and transfer it to the dry pipe inlet air duct; wherein the primary preheating device, the secondary steam generating device and the tertiary low-temperature utilization device are arranged sequentially in the flue gas duct at the dry pipe flue gas outlet; wherein the heat outlet of the primary preheating device is connected to the combustion air duct of the boiler in order to preheat the combustion air of the boiler; wherein the steam outlet of the secondary steam generating device is connected to the steam inlet of a steam turbine to assist the turbine in driving a generator for electricity generation; and wherein the tertiary low-temperature utilization device is connected to the process water line to regulate the process water temperature and to assist the plant heating. [2] Waste heat cascade utilization system for synergistic recovery of heat energy from heat exchange and milling heat according to claim 1, characterized by, that the mechanical heat recovery device comprises a finned heat tube array mounted on the blower mill, wherein the finned heat tube array comprises several heat tubes and several fins connected to the heat tubes; wherein the evaporation segment of the heat tube is connected to the heat-generating components of the blower mill, and the condensation segment of the heat tube is connected to the dry tube inlet air duct. [3] Waste heat cascade utilization system for synergistic recovery of heat from heat exchange and milling heat according to claim 2, characterized by that the heat pipes are copper water heat pipes with a diameter of 10 to 15 mm; the fins are aluminum fins with a fin spacing of 5 to 10 mm and a fin height of 20 to 30 mm. [4] Waste heat cascade utilization system for synergistic recovery of heat energy from heat exchange and milling heat according to claim 1, characterized by, that the primary preheating device is located in the high-temperature segment of the flue gas duct at the dry-pipe flue gas outlet, the secondary steam generating device is located in the medium-temperature segment of the flue gas duct at the dry-pipe flue gas outlet, and the tertiary low-temperature utilization device is located in the low-temperature segment of the flue gas duct at the dry-pipe flue gas outlet; wherein the temperature of the high-temperature segment is 600 °C to 700 °C, the temperature of the medium-temperature segment is 200 °C to 400 °C, and the temperature of the low-temperature segment is less than 150 °C. [5] Waste heat cascade utilization system for synergistic recovery of heat energy from heat exchange and milling heat according to claim 1, characterized by, that the primary preheating device comprises a ceramic heat storage body located in the flue gas duct at the dry-tube flue gas outlet, wherein the ceramic heat storage body is a ceramic heat storage body with a honeycomb structure; wherein the flue gas at the dry-tube flue gas outlet circulates through the cell channels of the honeycomb structure within the ceramic heat storage body, while the combustion air of the boiler circulates to the boiler after heat exchange outside the ceramic heat storage body. [6] Waste heat cascade utilization system for synergistic recovery of heat energy from heat exchange and milling heat according to claim 5, characterized by , that the ceramic heat storage body is made of cordierite ceramic and the cell channel spacing of the honeycomb structure of the ceramic heat storage body is 10 to 15 mm. [7] Waste heat cascade utilization system for synergistic recovery of heat energy from heat exchange and milling heat according to claim 1, characterized by , that the secondary steam generating device comprises a spiral tube evaporator arranged in the flue gas duct at the dry tube flue gas outlet, wherein the flue gas from the dry tube flows through the spiral tube of the spiral tube evaporator and exchanges heat with the water contained therein before entering the tertiary low-temperature utilization device; wherein the water in the spiral tube evaporator is converted into steam after heat exchange and directed to the steam turbine to assist the steam turbine in driving the generator for electricity generation. [8] Waste heat cascade utilization system for synergistic recovery of heat energy from heat exchange and milling heat according to claim 1, characterized by, that the tertiary low-temperature utilization device comprises a heat exchanger arranged in the flue gas duct at the dry tube flue gas outlet, wherein the medium in the heat exchanger exchanges heat with the flue gas from the dry tube to heat the process water. [9] Waste heat cascade utilization system for synergistic recovery of heat from heat exchange and milling heat according to claim 8, characterized by that the heat exchanger is a plate heat exchanger, the plate heat exchanger being made of an aluminum alloy.

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