Integrated straw briquette preparation device and process based on low-temperature carbonization

Abstract

The application relates to a low-temperature carbonization-based integrated straw briquetting fuel preparation device and process. The device comprises a feeding unit for providing straw raw materials to a low-temperature carbonization unit, which comprises a horizontal furnace for low-temperature carbonization treatment of the straw raw materials. A feeding mechanism in the horizontal furnace is used to transport materials during the carbonization reaction and deliver the carbonization products to an extrusion molding unit. The extrusion molding unit comprises a sealed shell connected to the material outlet of the horizontal furnace, which is provided with a double-screw extruder and a molding die. The double-screw extruder is used to shear, grind and extrude the carbonization products to the molding die, so as to form high-density fuel under high temperature and high pressure. The output flue gas of the low-temperature carbonization unit is used by a waste heat recovery unit to obtain high-temperature flue gas, which is used to heat the low-temperature carbonization unit and / or the extrusion molding unit. The application solves the technical problems of low preparation efficiency, high energy consumption, many transfer links and low quality of the obtained straw fuel in the prior art.

Description

Technical Field

[0001] This invention relates to the field of biomass fuel preparation technology, and in particular to an integrated straw pellet fuel preparation device and process based on low-temperature carbonization. Background Technology

[0002] The annual production of straw-based biomass is substantial, necessitating its reduction, harmless disposal, and high-value utilization. Combustion is the simplest and most effective way to utilize straw-based biomass, suitable for heating, gas supply, and power generation. However, straw-based biomass has relatively low bulk density and energy density, resulting in low efficiency for large-scale direct combustion. Preparing it into briquettes can effectively address this issue. Compared to raw straw, straw briquettes have higher bulk density and energy density, with a calorific value equivalent to low-rank coal.

[0003] The vast majority of existing straw briquette production processes employ a "drying-crushing-moisture balancing-forming" process. This involves first drying the straw raw material, then crushing it into pellets suitable for subsequent forming, then absorbing moisture from the crushed straw pellets to a certain level, and finally extruding them to obtain briquettes. The energy consumption for straw drying, crushing, and forming is very high, resulting in high production costs and low economic efficiency for straw briquettes. Furthermore, the above process only involves the physical treatment of the crushed straw; while the density and calorific value of the resulting briquettes are improved, the overall quality still has significant room for improvement. The forming process also requires high temperatures or the addition of additional binders, further increasing energy consumption and costs. Traditional production lines require multiple sets of equipment connected in series, with frequent material transfers between stages, resulting in significant heat loss and a complex process. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an integrated straw briquette fuel preparation device and process based on low-temperature carbonization, which solves the technical problems of low straw fuel preparation efficiency, high energy consumption, multiple transportation links, and low quality of straw fuel obtained in existing technologies.

[0005] The technical solution adopted in this invention is as follows: This invention provides an integrated straw briquette fuel preparation device based on low-temperature carbonization. The preparation device includes a feeding unit, a low-temperature carbonization unit, an extrusion molding unit, a waste heat recovery unit, and a central control unit. The feeding unit is used to continuously and evenly transport the chopped straw raw materials to the low-temperature carbonization unit; The low-temperature carbonization unit includes a horizontal furnace, which is used to perform low-temperature carbonization treatment on straw raw materials at 150-300℃ and in a low-oxygen or inert atmosphere to remove moisture and light volatiles; the horizontal furnace is equipped with a feeding mechanism, which is used to transport materials during the carbonization reaction and transport the carbonization products to the extrusion molding unit. The extrusion molding unit includes a sealed outer shell for providing a hot environment of 100–150°C. The inlet of the sealed outer shell is connected to the material outlet of the horizontal furnace to receive the carbonized products, and the outlet is connected to a storage silo. The sealed outer shell houses a twin-screw extruder and a molding die. The twin-screw extruder shears, grinds, and extrudes the carbonized products to the molding die, which is used to mold high-density fuel under a pressure of 60–90 MPa. During the molding process, thermoplastic lignin in the straw melts and acts as a binder to tightly bind the broken particles, eliminating the need for external binders. After molding, the fuel is transported to the storage silo. The waste heat recovery unit uses the combustible components and waste heat in the flue gas output by the low-temperature carbonization unit to obtain high-temperature flue gas, and uses the high-temperature flue gas to heat the low-temperature carbonization unit and / or the extrusion molding unit. The central control unit includes monitoring and automation control equipment, which is used to monitor and coordinate with other units to achieve efficient and stable operation of the preparation device.

[0006] The preferred technical solution is as follows: The twin-helix extruder includes two sets of twin-helix blades rotating in opposite directions. The blade gap of the twin-helix blades is adjustable to control the crushing particle size and forming pressure.

[0007] The central control unit is used to monitor the carbonization reaction temperature, oxygen content, and feeding mechanism status in the low-temperature carbonization unit, as well as the rotation speed of the twin-screw extruder, the blade gap of the twin-screw blades, the particle moisture content, and the extrusion pressure in the extrusion molding unit, and to achieve automatic linkage adjustment based on the monitoring results.

[0008] The horizontal furnace is provided with a first air inlet, which is used to introduce protective gas into the furnace to maintain the low oxygen or inert atmosphere required for the carbonization reaction. The horizontal furnace is provided with a second air inlet, which is used to connect to the high-temperature flue gas outlet of the waste heat recovery unit, so that the carbonization reaction material can directly exchange heat with the high-temperature flue gas. The horizontal furnace is provided with an outlet for outputting the flue gas generated by the carbonization reaction to the waste heat recovery unit.

[0009] The sealed outer shell of the extrusion molding unit includes an outer shell body and a heating sleeve wrapped around it. The heating sleeve is provided with a sleeve inlet, which is connected to the high-temperature flue gas outlet of the waste heat recovery unit to realize indirect heat exchange.

[0010] The preparation device also includes an exhaust gas treatment unit, which is connected to the outlet of the heating sleeve to treat the flue gas after the heat exchange between the walls, ensuring that the emissions meet the standards.

[0011] The feeding mechanism includes a screw propeller whose rotational speed is adjustable to control the material residence time.

[0012] A sealing device is provided between the sealed housing inlet of the extrusion molding unit and the material outlet of the horizontal furnace to prevent atmosphere crosstalk between the two units.

[0013] The high-temperature flue gas generated by the waste heat recovery unit is transported to the low-temperature carbonization unit and the extrusion molding unit by two hot air ducts and corresponding induced draft fans. The central control unit controls the two induced draft fans to prioritize the use of the high-temperature flue gas to maintain the stable operation of the horizontal furnace, and the remainder is used for the extrusion molding unit. When the heat is insufficient, the waste heat recovery unit supplements the heat by burning externally supplied gas.

[0014] The present invention also provides a preparation process for the integrated straw briquette fuel preparation device based on low-temperature carbonization, the preparation process comprising: Feeding: The feeder configured in the feeding unit is used to continuously and quantitatively feed the chopped straw raw material into the horizontal furnace, and to prevent outside air from entering during the feeding process; Low-temperature carbonization: The horizontal furnace provides a low-oxygen or inert atmosphere and a temperature of 150-300°C, so that the straw raw material undergoes a low-temperature carbonization reaction during the gradual pushing process of the feeding mechanism. The carbonization product is fed into the extrusion molding unit by the feeding mechanism. Crushing and molding: The carbonized product is sheared and ground by the opposing rotating double helical blades of the twin-screw extruder, and finally compacted and conveyed to the molding die. It is pressed and molded at a pressure of 60-90 MPa and a temperature of 100-150°C to obtain high-density fuel. No external binder is required during the molding process. Waste heat recovery: The waste heat recovery unit is used to burn the flue gas generated during the carbonization process to obtain high-temperature flue gas, and the high-temperature flue gas is used to heat the low-temperature carbonization unit and / or extrusion molding unit according to heat demand. Collaborative control: The central control unit monitors the carbonization reaction temperature, oxygen content, and feeding mechanism status in the low-temperature carbonization unit, as well as the rotation speed of the twin-screw extruder, the blade gap of the twin-screw blades, the particle moisture content, and the extrusion pressure in the extrusion molding unit, and performs linkage adjustment of each unit based on the monitoring results.

[0015] The technical solution of the present invention can achieve at least some of the following beneficial effects: This invention optimizes the preparation process through structural improvements to the preparation device, resulting in a significant improvement in the performance of straw-based briquettes, specifically offering the following advantages: 1. No pretreatment required, simplifying the process: Existing straw briquette fuel preparation processes typically require prior crushing, relying on specialized crushing equipment, resulting in high energy consumption and short die life. This invention directly embrittles the straw raw material through low-temperature carbonization, eliminating the need for pre-crushing. The straw can then be crushed and shaped in a hot state using a twin-screw extruder that combines crushing and extrusion functions, avoiding independent crushing units and significantly reducing energy consumption.

[0016] 2. Integrated design, compact structure, and reduced losses: Traditional "drying-pulverizing-moisture balancing-forming" processes require multiple devices connected in series, resulting in large footprints, complex processes, and high energy consumption. The device of this invention features an integrated design, directly connecting the low-temperature carbonization unit and the extrusion molding unit. The screw propeller is used for both feeding material into the horizontal furnace and conveying carbonized products to the extrusion molding unit. The two units can be installed as a whole within a unified frame and sealed outer shell, forming a continuous integrated device. This design reduces heat loss and dust emission during material transfer and facilitates device relocation. Furthermore, the fuel prepared by this invention has a bulk density ≥1.20 g / cm³ and a lower heating value ≥25 MJ / kg, significantly superior to traditional processes.

[0017] 3. Utilizing lignin as a natural binder: Unlike the process of fully carbonizing biomass such as straw and then adding binders for extrusion molding to produce briquettes, this invention employs a low-temperature carbonization process, removing only some organic oxygen from carbohydrates while preserving the lignin content and thermoplasticity of the straw. Under molding conditions, lignin can act as a natural binder, allowing particles to bond directly without the need for additional additives, further reducing system energy consumption and production costs.

[0018] 4. Partial Energy Self-Sufficiency: While the drying process in existing technologies is purely energy-intensive, the low-temperature carbonization described in this invention, although energy is required, is achieved through a complementary waste heat recovery unit that burns and recovers combustible components from the flue gas, providing heat for the carbonization and forming zones, thus achieving partial energy self-sufficiency. As a further improvement, this invention also includes an exhaust gas treatment unit to purify the low-temperature carbonization flue gas, ensuring emissions meet standards.

[0019] Other features and advantages of the invention will be set forth in the following description or may be learned by practicing the invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the preparation apparatus according to an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached drawings: 1. Feeding unit; 2. Hopper; 3. Screw feeder; 4. Sealed feed valve; 5. Low-temperature carbonization unit; 6. Horizontal furnace; 7. Feeding mechanism; 8. Temperature sensor; 9. Extrusion molding unit; 10. Twin-screw extruder; 11. Molding die; 12. Heating sleeve; 13. Twin-screw blades; 14. Storage hopper; 15. Waste heat recovery unit; 16. Burner; 17. Hot air duct; 18. Exhaust fan; 19. Exhaust gas treatment unit; 20. Central control unit; 21. Sealing device; 22. Screw feeder outlet; 23. First air inlet; 24. Air outlet; 25. Flue gas inlet; 26. Second air inlet; 27. First outlet; 28. Second outlet; 29. ​​Sleeve inlet; 30. Sleeve outlet; 31. Exhaust gas inlet; 32. Exhaust gas outlet. Detailed Implementation

[0022] The specific embodiments of the present invention are described below with reference to the accompanying drawings. Example 1

[0023] See Figure 1 The integrated straw molding fuel preparation device based on low-temperature carbonization in this embodiment includes a feeding unit 1, a low-temperature carbonization unit 5, an extrusion molding unit 9, a waste heat recovery unit 15, and a central control unit 20. The feeding unit 1 can continuously and evenly transport the chopped straw raw materials to the low-temperature carbonization unit 5; The low-temperature carbonization unit 5 includes a horizontal furnace 6, which is used to perform low-temperature carbonization treatment on straw raw materials at 150-300℃ and in a low-oxygen or inert atmosphere to remove moisture and light volatiles; the horizontal furnace 6 is equipped with a feeding mechanism 7, which is used to stir and transport the material along the length of the horizontal furnace and transport the carbonized product to the extrusion molding unit 9. The extrusion molding unit 9 includes a sealed outer shell, which provides a hot environment of 60-90 MPa and 100-150°C. The inlet of the sealed outer shell is connected to the material outlet of the horizontal furnace 6 to receive the carbonized products, and the outlet is connected to the storage silo 14. The sealed outer shell is equipped with a twin-screw extruder 10 and a molding die 11. The twin-screw extruder 10 is used to shear, grind and extrude the carbonized products to the molding die 11, which is used to form high-density fuel. During the forming process, the thermoplastic lignin in the straw melts and acts as a binder, making the crushed particles tightly bound together without the need for external binders. After forming, the fuel is transported to the storage silo 14. The waste heat recovery unit 15 utilizes the combustible components and waste heat in the flue gas output by the low-temperature carbonization unit 5 to obtain high-temperature flue gas, and uses the high-temperature flue gas to heat the low-temperature carbonization unit 5 and / or the extrusion molding unit 9. The central control unit 20 includes monitoring and automation control equipment, which is used to monitor and coordinate other units to achieve efficient and stable operation of the preparation device.

[0024] This embodiment of the device adopts an integrated design concept. First, the straw raw material is directly brittled through low-temperature carbonization, eliminating the need for pre-crushing. Then, it is crushed and shaped under hot conditions using a twin-screw extruder that combines crushing and extrusion functions. This avoids the need for a separate crushing unit, making the device structure more compact and significantly reducing energy consumption. The low-temperature carbonization unit is directly connected to the extrusion molding unit. The feeding mechanism in the low-temperature carbonization unit handles both horizontal furnace feeding and conveying carbonized products to the extrusion molding unit, reducing heat loss and dust emission during material transfer and facilitating device relocation. Furthermore, this embodiment incorporates waste heat recovery, achieving partial energy self-sufficiency, thereby further reducing energy consumption.

[0025] As a preferred embodiment, the feeding unit 1 comprises a hopper 2, a sealed feed valve 4, and a screw feeder 3. The hopper 2 stores the chopped straw raw material. The hopper 2 is equipped with a sealed feed valve 4, through which the straw raw material enters the screw feeder 3, preventing outside air from entering the hopper 2 and improving sealing. The sealed feed valve 4 is preferably a multi-stage slide gate valve. The screw feeder 3's feed outlet 22 is connected to the horizontal furnace 6 of the low-temperature carbonization unit 5, continuously and uniformly feeding the straw raw material into the low-temperature carbonization unit 5.

[0026] As a preferred embodiment, the twin-screw extruder 10 includes two sets of twin-screw blades 13 rotating in opposite directions. The blade gap of the twin-screw blades 13 is adjustable to control the crushing particle size and forming pressure.

[0027] As a preferred embodiment, the central control unit 20 is used to monitor the carbonization reaction temperature, oxygen content, and feeding mechanism 7 in the low-temperature carbonization unit 5, as well as the rotation speed of the twin-screw extruder 10 and the blade gap of the twin-screw blades 13, the particle moisture content, and the extrusion pressure in the extrusion molding unit 9, and to achieve automatic linkage adjustment based on the monitoring results.

[0028] Specifically, the carbonization reaction temperature, i.e. the furnace temperature inside the horizontal furnace, is collected by temperature sensors 8 installed on the horizontal furnace 6. The number and location of temperature sensors 8 are set according to the size of the horizontal furnace and actual needs.

[0029] Specifically, the feeding mechanism 7 preferably adopts a screw propeller. The central control unit 20 monitors the status of the feeding mechanism 7, including the rotational speed of the screw propeller. By controlling the rotational speed of the screw propeller, the residence time and degree of pyrolysis of the material in the horizontal furnace 6 are ensured to meet the process requirements.

[0030] As a preferred embodiment, a sealing device 21 is provided between the sealed housing inlet of the extrusion molding unit 9 and the material outlet of the horizontal furnace 6 to prevent atmosphere crosstalk between the two units.

[0031] Specifically, the sealing device 21 can be a sealing gasket or other mechanical seal, which is set at the contact position of the housing between the two units to prevent crosstalk between the atmospheres of the two units during material conveying.

[0032] As a preferred method, the shaped fuel blocks obtained by the molding die 11 fall into the storage bin 14 under the action of gravity. Appropriate molds can be selected according to requirements to prepare shaped fuels of different shapes, such as columnar, blocky, or honeycomb shapes.

[0033] As a preferred embodiment, the horizontal furnace 6 is provided with a first air inlet 23, which is used to introduce a protective gas, such as nitrogen, carbon dioxide or a mixture of inert gases, into the furnace to maintain the low oxygen or inert atmosphere required for the carbonization reaction and to prevent oxidative combustion.

[0034] As a preferred embodiment, the horizontal furnace 6 is provided with a second air inlet 26, which is used to connect to the high-temperature flue gas outlet of the waste heat recovery unit 15, so that the carbonization reaction material can directly exchange heat with the high-temperature flue gas.

[0035] As a preferred embodiment, the horizontal furnace 6 is provided with an outlet 24, which is used to output the flue gas generated by the carbonization reaction to the waste heat recovery unit 15.

[0036] Specifically, the horizontal furnace 6 is cylindrical.

[0037] As a preferred embodiment, the sealed outer shell of the extrusion molding unit 9 includes an outer shell body and a heating sleeve 12 wrapped around it. The heating sleeve 12 is provided with a sleeve inlet 29, which is connected to the high-temperature flue gas outlet of the waste heat recovery unit 15 to introduce high-temperature flue gas. Heat exchange between the heating sleeve 12 and the material is achieved through the wall.

[0038] As a preferred embodiment, the waste heat recovery unit 15 comprises a combustion chamber and a burner 16. The combustion chamber has a flue gas inlet 25, a first outlet 27, and a second outlet 28. The flue gas inlet 25 is connected to the outlet 24, introducing the flue gas (containing combustible components) generated during the carbonization process, which is then ignited and burned by the burner 16 to form high-temperature flue gas. The first outlet 27 and the second outlet 28 are respectively connected to the second inlet 26 and the jacket inlet 29 via hot air ducts 17, thereby conveying a portion of the high-temperature flue gas to the horizontal furnace 5 and another portion to the heating jacket 12.

[0039] Each of the two hot air ducts 17 is equipped with an induced draft fan 18. In a preferred manner, the central control unit 20 controls the two induced draft fans 18 to prioritize the use of high-temperature flue gas to maintain the stable operation of the horizontal furnace 6, with the remainder used for the extrusion molding unit 9; when the heat is insufficient, the waste heat recovery unit 15 can supplement the heat by burning externally supplied gas.

[0040] As a preferred embodiment, the preparation apparatus further includes an exhaust gas treatment unit 19, which is connected to the sleeve outlet 30 of the heating sleeve 12 via an exhaust gas inlet 31, for treating the flue gas after heat exchange between the partition walls, and the treated flue gas that meets the standards is discharged through the exhaust gas outlet 32.

[0041] Specifically, the exhaust gas treatment unit 19 is used to remove dust, tar and acidic gases from the flue gas to ensure that the exhaust gas meets the standards. Example 2

[0042] This embodiment provides a preparation process using the integrated straw briquette fuel preparation device based on low-temperature carbonization as described in Embodiment 1. The preparation process includes: S1. Feeding: The feeder 3 configured in the feeding unit 1 is used to continuously feed the chopped straw raw material into the horizontal furnace 6 in a quantitative manner, and to prevent outside air from entering during the feeding process.

[0043] S2. Low-temperature carbonization: The horizontal furnace 6 provides a low-oxygen or inert atmosphere and a temperature of 150–300°C, allowing the straw raw material to undergo a low-temperature carbonization reaction during the gradual pushing process of the feeding mechanism 7. The carbonized product is then fed into the extrusion molding unit 9 by the feeding mechanism 7. The preferred carbonization reaction time is 30–240 minutes.

[0044] S3. Crushing and molding: The carbonized product is sheared and ground by the opposing rotating double helix blades 13 of the twin helix extruder 10, and finally compacted and conveyed to the molding die 11. It is pressed and molded at a pressure of 60-90MPa and a temperature of 100-150℃ to obtain high-density fuel. No external binder is required during the molding process.

[0045] S4. Waste heat recovery: The waste heat recovery unit 15 is used to burn the flue gas generated during the carbonization process to obtain high-temperature flue gas. According to the heat demand, the high-temperature flue gas is used to heat the low-temperature carbonization unit 5 and / or the extrusion molding unit 9.

[0046] S5. Collaborative Control: Throughout the entire preparation process, the central control unit 20 monitors the carbonization reaction temperature, oxygen content, and feeding mechanism 7 in the low-temperature carbonization unit 5, as well as the rotation speed of the twin-screw extruder 10, the blade gap of the twin-screw blades 13, the particle moisture content, and the extrusion pressure in the extrusion molding unit 9, and realizes the linkage adjustment of each unit based on the monitoring results.

[0047] The straw briquette fuel prepared by the process in this embodiment has a bulk density ≥1.20 g / cm³ and a lower heating value ≥24.5 MJ / kg, which is significantly higher than that of traditional straw briquette fuel.

[0048] To further verify the effectiveness of the preparation process in this embodiment, sub-examples and comparative examples under different conditions are set up as follows to verify the quality of the obtained shaped fuel.

[0049] Example 2.1 Using the preparation process described in this example, cotton stalks were used as raw material, carbonized at 200 °C for 90 min, then crushed in an extrusion molding unit, and extruded into molded fuel at 150 °C and 60 MPa. The density of the obtained cotton stalk molded fuel was 1.23 g / cm³. 3 Its calorific value is 24.8 MJ / kg.

[0050] Example 2.2. Using the preparation process of this example, corn stalks were used as raw material, carbonized at 200℃ for 60 min, then fed into an extrusion molding unit for crushing, and extruded into shaped fuel at 140℃ and 60 MPa. The density of the obtained corn stalk shaped fuel was 1.25 g / cm³. 3 Its calorific value is 25.6 MJ / kg.

[0051] Example 2.3. Using the preparation process of this example, rice straw was used as raw material, carbonized at 220℃ for 75 min, then fed into an extrusion molding unit for crushing, and extruded into shaped fuel at 130℃ and 75 MPa. The density of the obtained rice straw shaped fuel was 1.26 g / cm³. 3 Its calorific value is 25.1 MJ / kg.

[0052] Example 2.4. Using the preparation process of this example, rapeseed stalks were used as raw material, carbonized at 300℃ for 30 minutes, then fed into an extrusion molding unit for crushing, and extruded into shaped fuel at 100℃ and 90MPa. The density of the obtained rapeseed stalk shaped fuel was 1.31 g / cm³. 3 Its calorific value is 27.2 MJ / kg.

[0053] Example 2.5. Using the preparation process of this example, sorghum stalks were used as raw material, carbonized at 280℃ for 40 minutes, then fed into an extrusion molding unit for crushing, and extruded into shaped fuel at 120℃ and 75MPa. The density of the obtained sorghum stalk shaped fuel was 1.28 g / cm³. 3 Its calorific value is 26.7 MJ / kg.

[0054] Example 2.6. Using the preparation process of this example, wheat straw was used as raw material, carbonized at 260℃ for 50 min, then fed into an extrusion molding unit for crushing, and extruded into shaped fuel at 110℃ and 90 MPa. The density of the obtained wheat straw shaped fuel was 1.30 g / cm³. 3 Its calorific value is 25.9 MJ / kg.

[0055] Comparative example: Commercially available briquettes were used as a comparative example. They were prepared using the commonly used "drying-crushing-moisture balancing-molding" process in existing technologies. The density was 1.11 g / cm3 and the calorific value was 16.7 MJ / kg.

[0056] The preparation process parameters and quality of the above-mentioned molded fuels are summarized in Table 1 below.

[0057] Table 1. Preparation process parameters and quality of various briquette fuels

[0058] As shown in Table 1, under the set low-temperature carbonization time, the straw raw materials in each embodiment can be carbonized well at low temperatures. Therefore, the higher the low-temperature carbonization temperature of the straw raw materials, the higher the calorific value of the resulting briquetted fuel. Under the set molding temperature and molding pressure, the crushed straw particles in each embodiment can be molded well. Therefore, the higher the molding pressure, the greater the density of the resulting briquetted fuel. Furthermore, the density and calorific value of the straw briquetted fuel prepared by the process of this invention are higher than those of the commercially available briquetted fuel in the comparative example.

[0059] It will be understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An integrated straw briquette fuel preparation device based on low-temperature carbonization, characterized in that, The preparation device includes a feeding unit (1), a low-temperature carbonization unit (5), an extrusion molding unit (9), a waste heat recovery unit (15), and a central control unit (20). The feeding unit (1) is used to continuously and evenly transport the chopped straw raw materials to the low-temperature carbonization unit (5). The low-temperature carbonization unit (5) includes a horizontal furnace (6), which is used to perform low-temperature carbonization treatment on straw raw materials at 150-300℃ and in a low-oxygen or inert atmosphere to remove moisture and light volatiles; the horizontal furnace (6) is equipped with a feeding mechanism (7), which is used to transport materials during the carbonization reaction and transport the carbonization products to the extrusion molding unit (9). The extrusion molding unit (9) includes a sealed outer shell, which provides a hot environment of 100-150°C. The inlet of the sealed outer shell is connected to the material outlet of the horizontal furnace (6) to receive the carbonized products, and the outlet is connected to the storage silo (14). The sealed outer shell is equipped with a twin-screw extruder (10) and a molding die (11). The twin-screw extruder (10) is used to shear, grind and extrude the carbonized products to the molding die (11), which is used to form high-density fuel under a pressure of 60-90 MPa. During the molding process, the thermoplastic lignin in the straw melts as a binder to make the broken particles tightly bonded, without the need for external binders. After molding, the fuel is transported to the storage silo (14). The waste heat recovery unit (15) uses the combustible components and waste heat in the flue gas output by the low-temperature carbonization unit (5) to obtain high-temperature flue gas, and uses the high-temperature flue gas to heat the low-temperature carbonization unit (5) and / or the extrusion molding unit (9). The central control unit (20) includes monitoring and automation control equipment for monitoring and coordinating the operation of other units, thereby achieving efficient and stable operation of the preparation device.

2. The integrated straw briquetting fuel preparation device based on low-temperature carbonization according to claim 1, characterized in that, The twin-helix extruder (10) includes two sets of twin-helix blades (13) rotating in opposite directions. The blade gap of the twin-helix blades (13) is adjustable to control the crushing particle size and forming pressure.

3. The integrated straw briquetting fuel preparation device based on low-temperature carbonization according to claim 2, characterized in that, The central control unit (20) is used to monitor the carbonization reaction temperature, oxygen content, and feeding mechanism (7) status in the low-temperature carbonization unit (5), as well as the rotation speed of the twin-screw extruder (10), the blade gap of the twin-screw blades (13), the particle moisture content, and the extrusion pressure in the extrusion molding unit (9), and to achieve automatic linkage adjustment based on the monitoring results.

4. The integrated straw briquette fuel preparation device based on low-temperature carbonization according to claim 1, characterized in that, The horizontal furnace (6) is provided with a first air inlet (23), which is used to introduce protective gas into the furnace to maintain the low oxygen or inert atmosphere required for the carbonization reaction. The horizontal furnace (6) is provided with a second air inlet (26), which is used to connect with the high-temperature flue gas outlet of the waste heat recovery unit (15) so that the carbonization reaction material can directly exchange heat with the high-temperature flue gas. The horizontal furnace (6) is provided with an outlet (24) for outputting the flue gas generated by the carbonization reaction to the waste heat recovery unit (15).

5. The integrated straw briquetting fuel preparation device based on low-temperature carbonization according to claim 1, characterized in that, The sealed outer shell of the extrusion molding unit (9) includes an outer shell body and a heating sleeve (12) wrapped around its outer side. The heating sleeve (12) is provided with a sleeve inlet (29), which is connected to the high-temperature flue gas outlet of the waste heat recovery unit (15) to realize heat exchange between the walls.

6. The integrated straw briquetting fuel preparation device based on low-temperature carbonization according to claim 5, characterized in that, The preparation device also includes an exhaust gas treatment unit (19), which is connected to the sleeve outlet (30) of the heating sleeve (12) to treat the flue gas after the heat exchange between the walls and ensure that the emissions meet the standards.

7. The integrated straw molding fuel preparation device based on low-temperature carbonization according to claim 1, wherein the feeding mechanism (7) includes a screw propeller whose rotation speed is adjustable to control the material residence time.

8. The integrated straw briquette fuel preparation device based on low-temperature carbonization according to claim 1, characterized in that, A sealing device (21) is provided between the sealed housing inlet of the extrusion molding unit (9) and the material outlet of the horizontal furnace (6) to prevent atmosphere crosstalk between the two units.

9. The integrated straw briquetting fuel preparation device based on low-temperature carbonization according to claim 1, characterized in that, The high-temperature flue gas generated by the waste heat recovery unit (15) is transported to the low-temperature carbonization unit (5) and the extrusion molding unit (9) by two hot air ducts (17) and corresponding induced draft fans (18); the central control unit (20) controls the two induced draft fans (18) to prioritize the use of the high-temperature flue gas to maintain the stable operation of the horizontal furnace (6), and the remainder is used for the extrusion molding unit (9); when the heat is insufficient, the waste heat recovery unit (15) supplements the heat by burning externally supplied gas.

10. A preparation process for an integrated straw briquette fuel preparation device based on low-temperature carbonization according to any one of claims 1 to 9, characterized in that, The preparation process includes: Feeding: The feeder (3) configured in the feeding unit (1) is used to feed the chopped straw raw material into the horizontal furnace (6) in a quantitative and continuous manner, and to prevent outside air from entering during the feeding process; Low-temperature carbonization: The horizontal furnace (6) provides a low-oxygen or inert atmosphere and a temperature of 150-300°C, so that the straw raw material undergoes a low-temperature carbonization reaction during the gradual pushing process of the feeding mechanism (7), and the carbonization product is fed into the extrusion molding unit (9) by the feeding mechanism (7). Crushing and molding: The carbonized product is sheared and ground by the opposing rotating double helical blades (13) of the double helical extruder (10), and finally compacted and conveyed to the molding die (11). It is pressed and molded at a pressure of 60-90 MPa and a temperature of 100-150°C to obtain high-density fuel. No external binder is required during the molding process. Waste heat recovery: The waste heat recovery unit (15) is used to burn the flue gas generated during the carbonization process to obtain high-temperature flue gas, and the high-temperature flue gas is used to heat the low-temperature carbonization unit (5) and / or the extrusion molding unit (9) according to the heat demand. Collaborative control: The central control unit (20) monitors the carbonization reaction temperature, oxygen content, and feeding mechanism (7) status in the low-temperature carbonization unit (5), as well as the rotation speed of the twin-screw extruder (10), the blade gap of the twin-screw blades (13), the particle moisture content, and the extrusion pressure in the extrusion molding unit (9), and performs linkage adjustment of each unit based on the monitoring results.

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