A wood pellet dryer

Abstract

The application relates to the technical field of drying equipment, and particularly discloses a rot-resistant wood pellet dryer, which comprises an inclined drying cylinder and a driving mechanism for driving the rolling of the drying cylinder, one end of the drying cylinder is provided with a feeder, the other end of the drying cylinder is provided with a discharging mechanism, the inner wall of the drying cylinder is provided with a plurality of material lifting plates, a combustion chamber is arranged around the outer periphery of the drying cylinder, the combustion head of a burner extends into the combustion chamber, a heat shield is arranged above the combustion head to prevent the flame from directly contacting the drying cylinder; one end of the combustion chamber is connected with a waste heat return pipeline, and the other end of the waste heat return pipeline sends hot air into the drying cylinder. The combustion chamber is arranged around the outer periphery of the drying cylinder, so that the front end and the tail end of the drying cylinder can have relatively uniform temperature, thereby improving the drying efficiency and avoiding local high temperature.

Description

Technical Field

[0001] This invention relates to the field of drying equipment technology, specifically to a preservative-treated wood pellet dryer. Background Technology

[0002] Wood particle reinforced composite flooring is a new type of special board material for railway flatcars, researched by the Institute of Metals and Chemistry of China Academy of Railway Sciences Group Co., Ltd. (Patent name: A composite wood floor for railway flatcars, patent application number: 202121405576.8). This type of board material can replace the existing wooden flooring for railway flatcars, and its strength, nail-holding power, corrosion resistance, and fire resistance are all superior to existing wooden flooring.

[0003] The main raw material of wood particle reinforced composite flooring is wood particles. After drying, the wood particles are glued together under pressure to form the flooring. The most significant characteristic of this flooring is its excellent corrosion resistance and fire resistance. These properties are primarily due to the addition of appropriate additives during the flooring's production process. For example, to enhance the flooring's corrosion resistance, the wood particles must first undergo a preservative treatment. This preservative process involves pre-drying the wood particles to reduce their moisture content to below 30%, then spraying a preservative agent and mixing it with the particles to achieve the desired corrosion effect. After this preservative treatment, the wood particles are dried again to control the moisture content to around 10%.

[0004] When drying preservative-treated wood pellets, the drying temperature should not exceed 150℃ to prevent the preservative from becoming ineffective; at the same time, the output must reach 2.5t / h according to production needs. Currently, the existing dryers in China are drum dryers and mesh belt dryers. Drum dryers use end ignition for heating, meaning the flame generated by the burner is directly injected into the drum. The temperature around the flame is the highest, resulting in local drying temperatures reaching 300℃-400℃, which cannot meet the drying requirements of preservative-treated wood pellets. Mesh belt dryers can meet the temperature requirements, but their working efficiency is very low, with a maximum capacity of only 0.5t / h.

[0005] In conclusion, none of the existing dryers can meet the drying requirements of wood pellets after preservation. Summary of the Invention

[0006] The purpose of this invention is to provide a preservative-treated wood pellet dryer to solve the problem that when using existing drum-type drying equipment to dry preservative-treated wood pellets, uneven drying temperature distribution and localized high drying temperatures can lead to the failure of preservatives.

[0007] The anti-corrosion wood particle dryer includes an inclined drying cylinder and a drive mechanism for rotating the drying cylinder. A feeder is located at the higher end of the drying cylinder, and a discharge mechanism is located at the lower end of the drying cylinder. Several lifting plates are provided on the inner wall of the drying cylinder. A combustion chamber is provided around the outer periphery of the drying cylinder. The burner head extends into the combustion chamber, and a heat insulation cover is provided above the burner head to prevent the flame from directly contacting the drying cylinder. The combustion chamber is connected to one end of a waste heat return pipeline, and the other end of the waste heat return pipeline sends hot air into the drying cylinder.

[0008] The beneficial effects of this plan are as follows:

[0009] 1. By setting a combustion chamber around the outer periphery of the drying cylinder and installing a heat insulation hood inside the combustion chamber, the flame generated by the gas generator impacts the heat insulation hood, which can prevent the flame from directly heating the drying cylinder. Since the combustion chamber surrounds the drying cylinder, under the guiding effect of the heat insulation hood on the flame, the hot airflow forms a circulation along the side wall of the combustion chamber, thereby making the temperature inside the combustion chamber tend to be uniform. Then, the heat is transferred to the inside of the drying cylinder through heat conduction. Thus, by regulating the temperature inside the combustion chamber, the temperature inside the drying cylinder can be made uniform and local high temperature can be avoided.

[0010] 2. In traditional drum dryers, the burner flame is typically injected from the feed end of the drying drum, causing the hot airflow to move axially from the beginning to the end of the drum. This results in a gradual decrease in temperature from the beginning to the end of the drum, with extremely high temperatures at the beginning and low temperatures at the end. The high temperature at the beginning can easily lead to the failure of the preservative, while the drying efficiency at the end is low. In this design, the combustion chamber surrounds the outer circumference of the drying drum, allowing for a relatively uniform temperature at both the beginning and end, thereby improving drying efficiency.

[0011] 3. After the combustion chamber transfers heat to the drying cylinder through heat conduction, the airflow in the combustion chamber still has a large amount of residual heat. This airflow enters the drying cylinder through the waste heat return pipeline to reuse the heat and improve drying efficiency. Secondly, the hot airflow undergoes heat conduction in the combustion chamber and then in the drying cylinder, thereby reducing the temperature of the hot airflow entering the drying cylinder and preventing ultra-high temperature airflow from entering the drying cylinder, which could lead to the failure of the corrosion inhibitor.

[0012] Preferred Option 1: As a further optimization of the basic option, the waste heat recovery pipeline introduces hot airflow into the drying cylinder from the higher end of the drying cylinder. The higher end of the drying cylinder is the feed end, i.e., the beginning end of the drying cylinder. The wood particles move from the beginning to the end of the drying cylinder. From the beginning to the end, the moisture content of the wood particles gradually decreases, and their heat requirement also gradually decreases. Therefore, introducing hot airflow from the beginning end of the drying cylinder through the waste heat recovery pipeline helps improve drying efficiency.

[0013] Preferred Option 2: As a further optimization of Preferred Option 1, the feeder includes a cover fixed to the ground and covering the end of the drying cylinder, and a feed hopper located on the upper part of the cover; an air supply duct is connected to the cover, and the end of the waste heat return pipe is connected to the air supply duct. Since the drying cylinder is rotating and the feed hopper is in a feeding state, the cover facilitates the installation of the feed hopper and can seal the end of the drying cylinder; secondly, the hot airflow first gathers in the air supply duct after passing through the waste heat return pipe before entering the drying cylinder. Since the air supply duct has a larger cross-sectional area and space than the waste heat return pipe, it is beneficial for the hot airflow to enter the drying cylinder evenly.

[0014] Preferred Option 3: As a further optimization of Preferred Option 2, the combustion chamber is provided in several sections and evenly distributed along the axial direction of the drying cylinder. The segmented arrangement of the combustion chamber facilitates the installation of the combustion chamber and the drying cylinder, and also makes it easier to install the support structure for the drying cylinder. Furthermore, segmenting the combustion chamber reduces the combustion chamber space, which is beneficial for the uniform distribution of airflow inside the combustion chamber.

[0015] Preferred Option 4: As a further optimization of Preferred Option 3, the top sidewall of the combustion chamber is an arc surface coaxial with the drying cylinder, and the bottom sidewall of the combustion chamber is square. The burner head extends into the combustion chamber from the bottom sidewall. The arc surface of the top of the combustion chamber facilitates airflow circulation within the combustion chamber; while the square bottom of the combustion chamber facilitates burner installation and allows for the installation of a heat insulation hood to block the flame inside the combustion chamber.

[0016] Preferred Option 5: As a further optimization of Preferred Option 4, one end of the waste heat recovery pipeline is connected to the top of the combustion chamber. Since the hot airflow flows upward in the combustion chamber and reaches the top after heat conduction, connecting the end of the waste heat recovery pipeline to the top of the combustion chamber facilitates the airflow entering the waste heat recovery pipeline; at the same time, it prevents high-temperature airflow from entering the waste heat recovery pipeline.

[0017] Preferred Option Six: As a further optimization of Preferred Option Five, the burner adopts a 300,000-500,000 kcal burner.

[0018] Preferred Option Seven: As a further optimization of Preferred Option Six, the inclination of the drying cylinder is 1.5-3%. This inclination promotes the sliding of wood particles from the first end to the last end inside the drying cylinder, which is beneficial for material discharge; however, the inclination should not be too large, otherwise the wood particles will still slide from the first end to the last end even when the drying cylinder is not rotating, making it impossible for the wood particles to stay in the drying cylinder for a sufficient time and failing to achieve the desired drying effect.

[0019] Preferred Option 8: As a further optimization of Preferred Option 7, the discharge mechanism includes a discharge hopper that connects to the discharge port of the drying cylinder, a discharge outlet at the bottom of the discharge port, and a cyclone separator connected to the top of the discharge hopper. The cyclone separator prevents wood particles from being discharged with the airflow and reduces dust emissions.

[0020] Preferred Option Nine: As a further optimization of Preferred Option Eight, the outlet of the cyclone separator is connected to the bottom of the spray tower, and the airflow is sprayed inside the spray tower before being discharged from the top. The airflow discharged after separation by the cyclone separator still contains a large amount of sawdust and dust. Redirecting the airflow into the spray tower for spraying, followed by sedimentation treatment, can prevent the sawdust and dust from being released into the air and causing pollution. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0022] Figure 2 This is a cross-sectional view of the drying cylinder and combustion chamber in Embodiment 1 of the present invention;

[0023] Figure 3 This is a cross-sectional view of the drying cylinder and combustion chamber in Embodiment 2 of the present invention;

[0024] Figure 4 This is a cross-sectional view of the air supply duct in Embodiment 2 of the present invention;

[0025] Figure 5 This is a cross-sectional view of the air supply duct in state 1 in Embodiment 2 of the present invention;

[0026] Figure 6 This is a cross-sectional view of the air supply duct in state 2 in Embodiment 2 of the present invention. Detailed Implementation

[0027] The following detailed description illustrates the specific implementation method:

[0028] The reference numerals in the accompanying drawings include: drying cylinder 10, roller ring 11, driven gear 12, air duct 14, lifting plate 15, combustion chamber 20, burner 21, heat insulation cover 22, cover body 30, feed hopper 31, material chute 32, air supply duct 40, waste heat return pipe 41, flexible wire mesh 43, memory spring 44, rigid wire mesh 42, drive motor 50, discharge hopper 61, cyclone separator 62, and spray tower 70.

[0029] Example 1:

[0030] As attached Figure 1As shown, the anti-corrosion wood pellet dryer includes an inclined drying cylinder 10 and a drive mechanism for driving the drying cylinder 10 to rotate. The drying cylinder 10 is horizontally placed on a support roller, and the support roller has a roller ring 11 welded to the outer circumference of the drying cylinder 10 at a corresponding position. The drive mechanism includes a drive motor 50, a driven gear 12 welded to the outer circumference of the drying cylinder 10, and a drive gear meshing with the driven gear 12 and fixed to the output shaft of the drive motor 50. A concrete platform is provided on the ground, and the support roller and drive motor 50 are installed on the platform to raise the height of the drying cylinder 10 above the ground, facilitating the feeding and discharging of wood pellets, and also facilitating the inclined installation of the drying cylinder 10. The inclination angle of the drying cylinder 10 is set to 3%.

[0031] The right end of the drying cylinder 10 is the feeding end, and the left end is the discharging end. The height of the feeding end is higher than that of the discharging end. A feeder is provided at the feeding end of the drying cylinder 10. The feeder includes a cover 30 covering the right end of the drying cylinder 10, that is, the right end of the drying cylinder 10 extends into the cover 30. The cover 30 is fixed to the ground by a steel frame. A feeding hopper 31 is provided at the top of the cover 30. An inclined sliding groove 32 is welded to the inner wall of the cover 30, located below the feeding hopper 31 and extending into the drying cylinder 10.

[0032] The outer circumference of the drying cylinder 10 is provided with combustion chambers 20, which are arranged in four sections at intervals. Roller rings 11 and driven gears 12 are disposed in the gaps between the combustion chambers 20. (See attached diagram) Figure 2 As shown, the combustion chamber 20 surrounds the outer periphery of the drying cylinder 10, meaning the drying cylinder 10 passes through the middle of the combustion chamber 20, thus making the combustion chamber 20 annular. The lower sidewall of the combustion chamber 20 is connected to the burner 21, meaning the burner head of the burner 21 extends through the sidewall of the combustion chamber 20 into the combustion chamber 20, with the flame jet direction perpendicular to the axis of the drying cylinder 10. To prevent the flame from the burner 21 from directly hitting and heating the drying cylinder 10, a heat insulation cover 22 is provided inside the combustion chamber 20 corresponding to the burner head position. The heat insulation cover 22 is made of refractory bricks and covers the flame. An opening is provided on the sidewall of the heat insulation cover 22, through which the hot airflow inside the heat insulation cover 22 enters the combustion chamber 20 and flows along the sidewall of the combustion chamber 20 to heat the drying cylinder 10. The top sidewall of the combustion chamber 20 is an arc surface coaxial with the drying cylinder 10 to guide the hot airflow; while the lower part of the combustion chamber 20 is square, facilitating the installation of the heat insulation cover 22 and the burner 21, and also facilitating the use of a steel frame structure to fix the combustion chamber 20 to the ground. In this embodiment, the burner 21 uses natural gas as fuel and is a 400,000 kcal burner to ensure that the combustion chamber 20 has sufficient heat for continuous heating.

[0033] As attached Figure 1As shown, an air supply duct 40 is fixedly connected to the right side of the cover 30. The air supply duct 40 penetrates the right side wall of the cover 30 and connects to the feed end of the drying cylinder 10. The air supply duct 40 is connected to the combustion chamber 20 through a waste heat return pipe 41. One end of the waste heat return pipe 41 connects to the top of the combustion chamber 20, and the other end connects to the side of the air supply duct 40. The four waste heat return pipes 41 send the hot airflow after heat conduction from each combustion chamber 20 into the air supply duct 40 for mixing before entering the drying cylinder 10. This facilitates uniform heat distribution within the drying cylinder 10, achieving uniform drying of the wood particles. (See attached diagram) Figure 1 As shown, the waste heat return pipe 41 is parallel to the horizontal section of the drying cylinder 10 and is in the same vertical plane. The vertical plane is located in front of or behind the drying cylinder 10, which makes it easy to set up a steel frame to support the waste heat return pipe 41.

[0034] In this design, the heat carried by the flame injected by the gas burner 21 is dispersed within the combustion chamber 20 and then heated to the drying cylinder 10 via heat conduction. This avoids localized high temperatures, ensuring a relatively uniform temperature on the sidewalls of the drying cylinder 10 and promoting uniform internal temperature. Even if the heat carried by the flame is not completely uniformly distributed within the drying chamber, the combination of the combustion chamber 20 and the drying cylinder 10 prevents excessively high localized temperatures on the sidewalls of the drying cylinder 10, as the drying cylinder 10 is rotating and heat conduction requires time to raise the temperature. Secondly, after the hot airflow in the combustion chamber 20 conducts heat to the drying cylinder 10 once, the temperature will decrease. The waste heat return pipe 41 is connected to the drying chamber at the top, which is relatively far from the burner 21. Therefore, the top of the burner 21 is the location with a relatively low internal temperature. That is, the temperature carried by the flame has been reduced after being dispersed and transferred once in the combustion chamber 20, and then enters the drying cylinder 10 through the air supply duct 40. This can avoid the temperature inside the drying cylinder from being too high, while making full use of heat and reducing gas consumption.

[0035] The inner wall of the drying cylinder 10 is equipped with several lifting plates 15. During the rotation of the drying cylinder 10, the lifting plates 15 have a scattering effect on the wood particles, thereby facilitating uniform heating of the wood particles. Secondly, the scattering effect of the lifting plates 15 on the wood particles, combined with the inclination of the drying cylinder 10, can gradually drive the wood particles to move from the front end to the rear end within the drying cylinder 10. In addition, to reduce heat loss, the side walls of the combustion chamber 20 are filled with a heat insulation layer, and the portion of the side wall of the drying cylinder 10 outside the combustion chamber 20 is also filled with a heat insulation layer.

[0036] As attached Figure 1As shown, the discharge end of the drying cylinder 10 is equipped with a discharge mechanism, including a discharge hopper 61 and a cyclone separator. The discharge hopper 61 is a four-sided enclosed structure, with the discharge end of the drying cylinder 10 extending into it. A discharge port is located at the bottom of the discharge hopper 61 for the wood particles to be discharged. A moisture outlet is located at the top of the discharge hopper 61, connected to the cyclone separator 62. The outlet of the cyclone separator 62 is connected to the bottom of the spray tower 70, meaning that moisture flows upward from the bottom within the spray tower 70 while being sprayed, thereby adsorbing wood chips and dust. A sedimentation tank is located at the bottom of the spray tower 70 to settle the wood chips and dust. The sprayed gas is discharged from the top of the spray tower 70.

[0037] Example 2:

[0038] The difference between Example 2 and Example 1 is as follows: (See attached) Figure 4 As shown, an arc-shaped rigid wire mesh 42 is provided at the corresponding position where the air supply duct 40 connects to the waste heat return pipe 41, and is located inside the air supply duct 40. The rigid wire mesh 42 can be made of iron wire mesh; the iron wire mesh is fixed to the inner side wall of the air supply duct 40. The hot airflow discharged from the waste heat return pipe 41 enters the air supply duct 40 after passing through the iron wire mesh. Since the temperature of each combustion chamber 20 entering the waste heat return pipe 41 may be different, there is a certain resistance when the hot airflow passes through the iron wire mesh, which promotes a certain degree of mixing of the hot airflow inside the iron wire mesh, and then the hot airflow enters the air supply duct 40 evenly after being distributed by the iron wire mesh, thus promoting the formation of a uniform hot airflow inside the air supply duct 40.

[0039] As attached Figure 5 As shown, a flexible wire mesh 43 is provided inside the left end of the air supply duct 40. The flexible wire mesh 43 can be made of fine stainless steel wire mesh. The flexible wire mesh is woven from narrow strips of stainless steel, with a width of 3-6 mm and a thickness of 0.2-0.3 mm. After being stretched, the stainless steel wire mesh forms a conical shape, and its outer edge is fixed to the side wall of the air supply duct 40. A memory spring 44 (a spring made of shape memory alloy wire) is connected to the center of the stainless steel wire mesh, and the other end of the memory spring 44 is fixed to the side wall of the air supply duct 40. When the temperature inside the air supply duct 40 is below 120℃, the length of the memory spring 44 shortens, and the stainless steel wire mesh is stretched to the right; as shown in the attached diagram. Figure 6As shown, when the temperature inside the air duct 40 exceeds 120℃, the length of the memory spring 44 elongates. At this time, due to the airflow flowing to the left, the stainless steel wire mesh expands to the left. Since the stainless steel wire mesh is woven from narrow strips of stainless steel, the area projected onto the cross-section of the drying cylinder is smaller for holes near the edge of the wire mesh and larger for holes near the center. After being distributed by the stainless steel wire mesh, the airflow inside the air duct 40 enters the drying cylinder 10. When the stainless steel wire mesh stretches to the right into a conical shape, due to the tendency of fluids to adhere to the surface of an object, more hot airflow will flow out from the outer edge of the wire mesh, while less will flow out from the center. Conversely, when the stainless steel wire mesh expands to the left, due to the tendency of fluids to adhere to the surface of an object, more hot airflow will flow out from the center of the wire mesh, while less will flow out from the outer edge.

[0040] As attached Figure 3 , 5 As shown, a duct 14 is provided at the center of the drying cylinder 10. The duct 14 is fixed to the inner wall of the drying cylinder 10 by spokes. The duct 14 is open at one end facing the air supply duct 40 and closed at the other end. Several air holes are provided on the duct 14 corresponding to the part outside the combustion chamber 20 (i.e., the installation area of ​​the roller ring 11 and the driven gear 12).

[0041] When the temperature inside the air duct 40 is higher than 120℃, it indicates that the temperature of the side wall of the drying cylinder 10 is too high. At this time, the heat transfer efficiency of the combustion chamber 20 to the drying cylinder 10 is reduced, and the temperature near the inner side wall of the drying cylinder 10 should not be increased further. Therefore, the stainless steel wire mesh expands to the left, so that more hot airflow discharged from the air duct 40 flows out from the middle of the stainless steel wire mesh and enters the air duct 14 to increase the center temperature of the drying cylinder 10. After entering the air duct 14, the hot airflow is discharged from the air control to enter the area outside the combustion chamber 20, thereby improving the heat utilization efficiency.

[0042] When the temperature inside the air supply duct 40 is below 120℃, it indicates that the temperature of the side wall of the drying cylinder 10 is too low, and the heat transfer efficiency of the combustion chamber 20 to the drying cylinder 10 is relatively high. At this time, it is necessary to further increase the temperature near the inner side wall of the drying cylinder 10. Therefore, the stainless steel wire mesh is stretched to the right so that more hot airflow discharged from the air supply duct 40 flows out from the outer edge of the stainless steel wire mesh and enters the air duct 14, which helps to increase the temperature near the side wall of the drying cylinder 10 and improve the drying efficiency. At the same time, some hot airflow enters the middle of the drying cylinder 10 to ensure the temperature in the middle of the drying cylinder 10.

[0043] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A wood particle drying machine for preventing decay, comprising a drying cylinder body arranged obliquely and a driving mechanism for driving the drying cylinder body to roll, a feeding device arranged at a higher end of the drying cylinder body, a discharging mechanism arranged at a lower end of the drying cylinder body, and a plurality of material lifting plates arranged on an inner wall of the drying cylinder body, characterized in that: The drying cylinder is externally provided with a combustion chamber surrounding the outer periphery of the drying cylinder, the combustion head of the burner extends into the combustion chamber, and a flame barrier heat shield is arranged above the combustion head to avoid direct contact of the flame with the drying cylinder; The feeder comprises a cover body fixed to the ground and covering the end of the drying cylinder and a feeding hopper arranged on the upper part of the cover body, and the right side of the cover body is connected with a blowing cylinder; the combustion chamber is provided with a plurality of combustion chambers which are uniformly distributed along the axial direction of the drying cylinder, one end of the combustion chamber is connected with a waste heat return pipeline, and the other end of the waste heat return pipeline is connected with the blowing cylinder to mix the hot air flow after heat conduction of each combustion chamber and then send the mixed hot air flow into the drying cylinder; the corresponding position of the blowing cylinder connected with the waste heat return pipeline is provided with a hard wire mesh in the form of an arc and located in the blowing cylinder; A flexible wire mesh is arranged in the left end of the blowing cylinder, the flexible wire mesh is made of a stainless steel wire mesh, the outer edge of the stainless steel wire mesh is fixed to the side wall of the blowing cylinder, and a memory spring is connected to the center of the flexible wire mesh; when the length of the memory spring is shortened, the stainless steel wire mesh is in a conical stretching state to the right; when the length of the memory spring is elongated, the stainless steel wire mesh is expanded to the left under the influence of the air flow flowing to the left.

2. A rotting wood pellet dryer according to claim 1, characterized in that: The top side wall of the combustion chamber is an arc surface coaxial with the drying cylinder, and the bottom side wall of the combustion chamber is in the form of a square, and the combustion head of the burner extends into the combustion chamber from the bottom side wall of the combustion chamber.

3. A rotting wood pellet dryer according to claim 2, characterized in that: One end of the waste heat return pipeline connected with the combustion chamber is connected with the top of the combustion chamber.

4. A wood pellet roaster according to claim 3, wherein: The burner adopts a 300-500 W calorific value burner.

5. A rotting wood pellet dryer according to claim 4, characterized in that: The slope of the drying cylinder is 1.5-3%.

6. A wood pellet roaster according to claim 5, wherein: The discharging mechanism comprises a discharging hopper butting against the discharging port of the drying cylinder, and the bottom end of the discharging port is provided with a discharge port, and the top end of the discharging hopper is connected with a cyclone separator.

7. A wood pellet roaster according to claim 6, wherein: The air outlet of the cyclone separator is connected with the bottom of a spray tower, and the air flow is sprayed in the spray tower and then discharged from the top after the spraying treatment.

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