Progressive microwave heating multi-stage screening device and method

Abstract

The invention relates to the technical field of household garbage treatment, and discloses a progressive microwave heating multi-stage screening device and method.The progressive microwave heating multi-stage screening device comprises at least two sections of microwave heating mechanisms arranged in series and a metal net belt conveyor, microwave heating assemblies are fixedly connected into the microwave heating mechanisms, and a crushing mechanism is arranged at the feeding end of the metal net belt conveyor; an air guide frame, a negative pressure fan and an air nozzle assembly are arranged between the crushing mechanism and the microwave heating mechanism, and the microwave heating mechanism is provided with a vibration excitation mechanism synchronously linked with the metal mesh belt conveyor. According to the progressive microwave heating multi-stage screening device, microwave heating of a multi-section increasing temperature area is matched with negative-pressure single-layer material spreading and synchronous excitation, the difference between the softening temperature and the shrinkage rate of different plastic materials is utilized, and the synchronous excitation mechanism is matched to promote plastic sheets reaching the shrinkage criticality to fall off, so that precise screening is achieved; the treatment efficiency and the sorting purity are greatly improved, the unit energy consumption is reduced by 20% or above, and the plastic garbage coarse screening and recycling device is suitable for coarse screening and recycling of plastic garbage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of household garbage treatment, in particular to a gradual microwave heating multi-stage screening device based on temperature zone gradient control and a screening method thereof, which is suitable for coarse screening and segmented recycling of hard plastic garbage. BACKGROUND

[0002] Household garbage screening, as a core link in the garbage treatment process, its necessity is deeply reflected in the improvement of resource utilization, optimization of treatment efficiency, reduction of environmental risk and promotion of sustainable development, etc. It is not only the key link connecting the garbage source and resource utilization, but also realizes the harmonious unity of environment, economy and social benefits through scientific classification and efficient treatment technology.

[0003] As prior art, the patent with the patent number CN219503194U discloses a household garbage screening device. The household garbage screening device comprises a screening device main body, a screening structure is arranged in the interior of the screening device main body, and a dust removal structure is arranged at the front end of the screening device main body. The household garbage screening device is provided with a motor, an oval plate, a first screening plate and a second screening plate. The motor drives the rotation of the rotating rod and the oval roller. When the oval roller rotates, the two sharp ends reciprocate up and down, and impact the left end of the first screening plate and the second screening plate, so that the first screening plate and the second screening plate oscillate up and down under the support of the right end rotating seat. The household garbage on the first screening plate and the second screening plate is screened under the force, and the filtered garbage falls onto the second screening plate for secondary screening, so that the garbage screening is more precise. The garbage that is not filtered slides to the discharge port through the inclined first screening plate and the second screening plate.

[0004] The above-mentioned screening device still has some defects:

[0005] And the household garbage plastic products are complex in composition, and the materials include PET, PP, PE, PS, etc. Different materials have significant differences in chemical composition, softening temperature, shrinkage rate and other physical properties.

[0006] The above-mentioned screening device realizes physical size screening by mechanical vibration combined with multi-stage screening plates, but does not combine temperature control or material characteristics, so it cannot effectively distinguish hard plastics with significant differences in softening temperature, resulting in limited recycling efficiency and purity. SUMMARY

[0007] In view of the shortcomings of the prior art, the present application provides a gradual microwave heating multi-stage screening device and method based on temperature zone gradient control. Through microwave segmented heating, negative pressure single-layer paving and synchronous excitation, the differences in softening temperature and shrinkage behavior of different plastics are utilized to realize efficient coarse screening, improve recycling purity and reduce energy consumption.

[0008] To achieve the above object, the application provides the following technical scheme: a progressive microwave heating multi-stage screening device, comprising at least two microwave heating mechanisms arranged in series and a metal mesh belt conveyor, a microwave heating assembly is fixedly connected inside the microwave heating mechanism, a crushing mechanism is arranged at the feeding end of the metal mesh belt conveyor, left and right side supports are arranged between the crushing mechanism and the microwave heating mechanism, a gas guide frame is fixedly connected between the left and right side supports, a negative pressure fan is fixedly connected to the bottom of the gas guide frame, a fixed air deflector is fixedly connected to the top of the gas guide frame, an air nozzle assembly is fixedly connected to the upper end of the right side support, an excitation mechanism that is synchronous with the metal mesh belt conveyor is arranged on the microwave heating mechanism, the excitation mechanism comprises a sliding block, a spring, a protective baffle and a top block, a plurality of sliding grooves are formed in the two sides of the microwave heating mechanism, a sliding rod that is slidably connected with the sliding block is fixedly connected inside the sliding groove, the spring is sleeved outside the sliding rod, the inner side of the sliding block is fixedly connected with the protective baffle, the inner side of the protective baffle is fixedly connected with the top block, and a plurality of receiving grooves that match the protective baffle are formed in the inner wall of the microwave heating mechanism.

[0009] Further, positioning shafts are fixedly connected to the two sides of the microwave heating mechanism, an inner side synchronous wheel is rotatably connected to the side of the positioning shaft close to the microwave heating mechanism, a limiting shaft is fixedly connected to the side of the inner side synchronous wheel away from the shaft center, a roller that is rotatably connected with the limiting shaft is sleeved outside the limiting shaft, a yielding slot is formed in the outer wall of the two sides of the microwave heating mechanism, a connecting rod is slidably connected inside the yielding slot, the sliding blocks are fixedly connected with the connecting rod, a protruding block is fixedly connected to the side of the connecting rod close to the inner side synchronous wheel, the position of the protruding block matches the position of the roller, the microwave heating assembly is a magnetron or a solid-state microwave source, the working frequency is 2.45GHz, the power density is 0.5-2.0W / cm², and continuous or pulse mode heating is adopted.

[0010] Further, driving synchronous wheels are rotatably connected to the two sides of one end of the metal mesh belt conveyor, the driving synchronous wheels are fixedly connected with the rollers of the metal mesh belt conveyor, outer side synchronous wheels are arranged on the two sides of the two microwave heating mechanisms close to the crushing mechanism, the outer side synchronous wheels are rotatably connected to the ends of the positioning shafts away from the microwave heating mechanisms, the outer side synchronous wheels are fixedly connected with the inner side synchronous wheels, the outer sides of the two outer side synchronous wheels are sleeved with synchronous belts that engage with them, one inner side synchronous wheel close to the crushing mechanism is connected with the driving synchronous wheel through the synchronous belt, and the other two inner side synchronous wheels are connected through the synchronous belt.

[0011] Further, a movable air deflector is slidably connected to the upper end of the gas guide frame, a threaded rod is threadedly connected to the middle position of the movable air deflector, and the threaded rod is rotatably connected with the gas guide frame.

[0012] Further, the threaded rod is fixedly connected with a hand wheel at one end away from the air guide frame.

[0013] Further, the lower end of the air guide frame is slidingly connected with a pull frame, the pull frame is fixedly connected with the air guide frame through bolts, the inner side of the pull frame is fixedly connected with an intercepting filter screen, the intercepting filter screen is arranged obliquely, the air guide frame is provided with a waste discharge outlet at the side close to the lower side of the intercepting filter screen, the pull frame is provided with a gripping groove at the side away from the air guide frame, the intercepting filter screen has a mesh number of 20-60 meshes and is made of a high-temperature-resistant and corrosion-resistant material.

[0014] Further, the pull frame and the movable air deflector are both sleeved with sealing pads at one end away from the air guide frame, and the sealing pads are fixedly connected with the air guide frame.

[0015] Further, the air guide frame is fixedly connected with a waste guide plate at the side close to the waste discharge outlet, the air guide frame is rotatably connected with a rotating shaft at the middle position of the waste discharge outlet, the air guide frame is fixedly connected with a motor at the side close to the crushing mechanism, the rotating shaft is fixedly connected with the output end of the motor, and the outer wall of the rotating shaft is fixedly connected with a plurality of equally spaced push blades.

[0016] Further, the lower end of the microwave heating mechanism is fixedly connected with a main collecting plate arranged obliquely, the microwave heating mechanism is fixedly connected with a secondary collecting plate at one end away from the crushing mechanism, and the main collecting plate is fixedly connected with the secondary collecting plate.

[0017] A progressive microwave heating multi-stage screening device and a screening method, comprising the following steps:

[0018] Step one: hard plastic type household garbage is put into the crushing mechanism, the garbage is crushed by the crushing mechanism to become plastic pieces with similar sizes, and then the plastic pieces are conveyed to the direction of the microwave heating mechanism by the metal mesh belt conveyor;

[0019] Step two: when the plastic pieces pass through the air guide frame, the air nozzle assembly connected with the external air source blows the plastic pieces, and at the same time, the negative pressure air blower works to form a negative pressure at the bottom of the metal mesh belt conveyor, so that only one layer of plastic pieces is reserved on the metal mesh belt conveyor;

[0020] Step three: after the plastic pieces enter the microwave heating mechanism, the microwave heating assembly heats the plastic pieces, the plastic pieces shrink, the area of the plastic pieces becomes smaller, and since the mesh size of the metal mesh belt conveyor can only ensure that the just crushed plastic pieces do not fall off, after the plastic pieces shrink due to heating, they will fall into the main collecting plate and finally flow out from the secondary collecting plate;

[0021] Step four: the temperature inside each microwave heating mechanism is different, gradually increasing from the front end to the rear end of the metal mesh belt conveyor, and various plastic pieces will shrink and fall in different microwave heating mechanisms;

[0022] Step five: during the operation of the metal mesh belt conveyor, the driving synchronous wheel drives the inner synchronous wheels outside each microwave heating mechanism to rotate through the synchronous belt and the outer synchronous wheel. When the inner synchronous wheels drive the rollers to move downward, the rollers will squeeze the protrusions, thereby driving the connecting rods, sliding blocks, protective baffles and top blocks to move downward. After the rollers pass the lowest point, the protrusions lose the restriction, and the spring pushes the connecting rods, sliding blocks, protective baffles and top blocks upward, so that the top blocks hit the metal mesh belt conveyor, thereby causing the metal mesh belt conveyor to vibrate, so that the shrunk plastic pieces fall onto the main collection plate.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The gradual microwave heating multi-stage screening device gradually heats different hard plastic waste of different materials through multiple microwave heating mechanisms, so as to facilitate subsequent recycling and improve the coarse screening efficiency.

[0025] The gradual microwave heating multi-stage screening device blows the plastic pieces through the air nozzle assembly connected with the external air source before the plastic pieces enter the microwave heating mechanism, and the negative pressure fan creates a negative pressure environment at the bottom of the metal mesh belt conveyor, so that only one layer of plastic pieces is retained on the metal mesh belt conveyor, avoiding the accumulation of plastic pieces to cause uneven heating of some plastic pieces and prevent them from shrinking.

[0026] The gradual microwave heating multi-stage screening device, during the operation of the metal mesh belt conveyor, the driving synchronous wheel drives the inner synchronous wheels outside each microwave heating mechanism to rotate through the synchronous belt and the outer synchronous wheel. When the inner synchronous wheels drive the rollers to move downward, the rollers will squeeze the protrusions, thereby driving the connecting rods, sliding blocks, protective baffles and top blocks to move downward. After the rollers pass the lowest point, the protrusions lose the restriction, and the spring pushes the connecting rods, sliding blocks, protective baffles and top blocks upward, so that the top blocks hit the metal mesh belt conveyor, thereby causing the metal mesh belt conveyor to vibrate, so that the shrunk plastic pieces fall onto the main collection plate. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of the whole application;

[0028] Figure 2 It is a front view of the whole application;

[0029] Figure 3 It is a partial sectional view of the microwave heating mechanism of the application;

[0030] Figure 4 For the invention Figure 3 The local enlarged structure schematic view of A in the invention;

[0031] Figure 5 The sectional view of the microwave heating mechanism of the invention;

[0032] Figure 6 The connection structure schematic view of the air guide frame and the negative pressure fan of the invention;

[0033] Figure 7 The three-dimensional structure schematic view of the air guide frame when viewed from the right of the invention;

[0034] Figure 8 The local sectional view of the air guide frame of the invention;

[0035] Figure 9 For the invention Figure 8 The local enlarged structure schematic view of B in the invention;

[0036] Figure 10 For the invention Figure 8 The local enlarged structure schematic view of C in the invention;

[0037] Figure 11 The structure schematic view of the movable air deflector of the invention;

[0038] Figure 12 The connection structure schematic view of the inner side synchronous wheel and the connecting rod of the invention.

[0039] In the figure: 1, crushing mechanism; 2, microwave heating mechanism; 3, microwave heating assembly; 4, metal mesh belt conveyor; 5, left side support; 6, right side support; 7, air nozzle assembly; 8, air guide frame; 9, negative pressure fan; 10, fixed air deflector; 11, movable air deflector; 12, threaded rod; 13, hand wheel; 14, sealing gasket; 15, pulling frame; 16, intercepting filter screen; 17, gripping groove; 18, rotating shaft; 19, pushing blade; 20, motor; 21, waste guide plate; 22, driving synchronous wheel; 23, synchronous belt; 24, positioning shaft; 25, inner side synchronous wheel; 26, outer side synchronous wheel; 27, sliding slot; 28, sliding rod; 29, sliding block; 30, spring; 31, protective baffle; 32, top block; 33, accommodation slot; 34, connecting rod; 35, protruding block; 36, limiting shaft; 37, roller; 38, main collecting plate; 39, auxiliary collecting plate; 40, storage slot. DETAILED DESCRIPTION

[0040] The embodiments of the present disclosure will be described in further detail below with reference to the drawings and examples. The following detailed description of the examples and the accompanying drawings are provided to illustrate the principles of the present disclosure, and should not be taken in a limiting sense. The present disclosure can be implemented in numerous ways, including, but not limited to, the specific embodiments described in this document. Rather, any number of variations and modifications of the described embodiments can be used to implement the present disclosure, and each such variation and modification is intended to fall within the scope of the present disclosure.

[0041] The present disclosure provides these examples in order to more completely explain the present disclosure and to further enable its practitioners to practice the present disclosure. It is not intended that the examples recited herein be exhaustive or limiting of the present disclosure. Skilled artisans will understand that modifications of the described examples, as well as other examples, can be employed in the practice of the present disclosure without departing from the scope thereof. Accordingly, the description is not to be considered as limiting the scope of the disclosure.

[0042] It should be noted that, in the description of the present disclosure, unless otherwise specified, the meaning of "a plurality of" is greater than or equal to two; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer" and the like is only for ease of description of the present disclosure and simplification of description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be understood as limiting the present disclosure. When the absolute position of the described object changes, the relative positional relationship can also change accordingly.

[0043] In addition, the "first", "second", and similar words used in the present disclosure do not indicate any order, number, or importance, but are only used to distinguish different parts. "Vertical" is not strictly vertical, but within the allowable range of error. "Parallel" is not strictly parallel, but within the allowable range of error. "Include" or "contain" and similar words mean that the elements before the word cover the elements listed after the word, and do not exclude the possibility of also covering other elements.

[0044] It should also be noted that, in the description of the present disclosure, unless otherwise specified and limited, the terms "mounting", "connecting", "connection" should be interpreted broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present disclosure can be understood according to the specific circumstances. When it is described that a specific device is located between a first device and a second device, there can be an intermediate device between the specific device and the first device or the second device, or there can be no intermediate device.

[0045] All terms used herein have the same meaning as those understood by those having ordinary skill in the art to which the present disclosure belongs, unless otherwise specifically defined. It should also be understood that terms defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and not in an idealized or overly formal sense, unless expressly so defined herein.

[0046] Techniques, methods, and devices known to those of ordinary skill in the relevant art can not be discussed in detail herein, but should be considered as part of the specification, where appropriate.

[0047] Please refer to Figures 1-12 A progressive microwave heating multi-stage screening device, comprising at least two microwave heating mechanisms 2 arranged in series and a metal mesh belt conveyor 4, a microwave heating assembly 3 is fixedly connected inside the microwave heating mechanism 2, a crushing mechanism 1 is arranged at the feeding end of the metal mesh belt conveyor 4, a left side support 5 and a right side support 6 are arranged between the crushing mechanism 1 and the microwave heating mechanism 2, a gas guide frame 8 is fixedly connected between the left side support 5 and the right side support 6, a negative pressure fan 9 is fixedly connected to the bottom of the gas guide frame 8, a fixed air deflector 10 is fixedly connected to the top of the gas guide frame 8, an air nozzle assembly 7 is fixedly connected to the upper end of the right side support 6, a vibration excitation mechanism is arranged on the microwave heating mechanism 2 and is in synchronous linkage with the metal mesh belt conveyor 4, which is used to trigger the separation of the plastic pieces that reach the shrinkage critical point, the vibration excitation mechanism comprises a sliding block 29, a spring 30, a protective baffle 31 and a top block 32, a plurality of sliding grooves 27 are arranged on both sides of the microwave heating mechanism 2, a sliding rod 28 is fixedly connected inside the sliding groove 27 and is in sliding connection with the sliding block 29, the spring 30 is sleeved outside the sliding rod 28, the inner side of the sliding block 29 is fixedly connected with the protective baffle 31, and the inner side of the protective baffle 31 is fixedly connected with the top block 32, and a plurality of receiving grooves 40 matched with the protective baffle 31 are arranged on the inner wall of the microwave heating mechanism 2.

[0048] As Figures 1 to 12 shown, the progressive microwave heating multi-stage screening device in the present application comprises the following steps when in use:

[0049] Step one: put the hard plastic type of household garbage into the crushing mechanism 1, crush the garbage through the crushing mechanism 1, so that the garbage becomes plastic pieces with similar sizes, and then transport the plastic pieces to the direction of the microwave heating mechanism 2 through the metal mesh belt conveyor 4;

[0050] Step two: when the plastic pieces pass through the gas guide frame 8, the air nozzle assembly 7 connected with the external air source will blow the plastic pieces, and at the same time, the negative pressure fan 9 will work to form a negative pressure at the bottom of the metal mesh belt conveyor 4, so that only one layer of plastic pieces is reserved on the metal mesh belt conveyor 4;

[0051] Step three: after the plastic pieces enter the inside of the microwave heating mechanism 2, the microwave heating assembly 3 will heat the plastic pieces, which will shrink, making the area of the plastic pieces smaller. Since the mesh size of the metal mesh belt conveyor 4 can only ensure that the just broken plastic pieces do not fall off, after the plastic pieces shrink due to heating, they will fall into the main collection plate 38 and finally flow out from the auxiliary collection plate 39;

[0052] Step four: the temperature inside each microwave heating mechanism 2 is different, gradually increasing from the front end to the rear end of the metal mesh belt conveyor 4, and various plastic pieces will also shrink and fall in different microwave heating mechanisms 2.

[0053] Step five: during the operation of the metal mesh belt conveyor 4, the driving synchronous wheel 22 will drive the inside synchronous wheel 25 outside each microwave heating mechanism 2 to rotate through the synchronous belt 23 and the outside synchronous wheel 26. When the roller 37 moves downward under the rotation of the inside synchronous wheel 25, the roller 37 will press the protrusion 35, thereby driving the connecting rod 34, the sliding block 29, the protective baffle 31 and the top block 32 to move downward together. After the roller 37 passes the lowest point, the protrusion 35 loses the restriction, and the spring 30 will push the connecting rod 34, the sliding block 29, the protective baffle 31 and the top block 32 upward together, so that the top block 32 hits the metal mesh belt conveyor 4, thereby causing the metal mesh belt conveyor 4 to vibrate, so as to facilitate the falling of the shrunk plastic pieces onto the main collection plate 38.

[0054] Working principle: the hard plastic type of household waste is first broken by the breaking mechanism 1, and after breaking, plastic pieces with similar sizes are formed. These plastic pieces will fall onto the metal mesh belt conveyor 4 and be sequentially sent to each microwave heating mechanism 2. In the microwave heating mechanism 2, the plastic pieces will shrink (the principle is that when the temperature exceeds the glass state of the plastic pieces, the molecular chain segment obtains enough energy, starts to shrink from the oriented "stretching state" to the more disordered "curling state", resulting in the overall shrinkage of the plastic pieces). Since the temperature inside each microwave heating mechanism 2 is different, and the temperature of the microwave heating mechanism 2 gradually increases from the front end to the rear end of the metal mesh belt conveyor 4, various plastic pieces will also shrink and fall in different microwave heating mechanisms 2 to the main collection plate 38, and the plastic pieces that do not shrink will enter the next microwave heating mechanism 2, and so on. In addition, the excitation mechanism is connected with the belt speed to trigger vibration, so as to promote the plastic pieces that reach the shrinkage critical point (the shrinkage critical size d is calculated by the formula d = k(T)·d0, where d0 is the initial particle size of breaking, and k(T) is the temperature-dependent shrinkage coefficient) to fall from the mesh belt of the metal mesh belt conveyor 4 to the collection plate. A mechanical top block can also be used to hit or an external electromagnetic / eccentric excitation.

[0055] It needs to be particularly pointed out here that the number of microwave heating mechanisms 2 can be selected according to requirements, and the more the number of microwave heating mechanisms 2, the more refined the classification of plastic sheets is. However, the device is mainly used for coarse screening of plastic sheets, so the number of microwave heating mechanisms 2 does not need to be too much to avoid causing energy waste. At the same time, the mesh belt of the metal mesh belt conveyor 4 can adopt a straight shaft type mesh belt, which has more fluent mesh and slightly larger mesh size than the critical size of the plastic sheet shrinkage, facilitating the screening of the plastic sheet. In addition, since the crushing mechanism 1, the microwave heating mechanism 2 and the microwave heating assembly 3 are all products of existing mature technology, they will not be described in detail here, and the figure also does not show them in detail.

[0056] As a preferred scheme of the present application, the two sides of the microwave heating mechanism are fixedly connected with positioning shafts, the side close to the microwave heating mechanism of the inner side synchronous wheel is rotatably connected with a limiting shaft, the limiting shaft is rotatably connected with a roller outside the limiting shaft, the outer wall of the two sides of the microwave heating mechanism is provided with a letting slot, the letting slot is slidably connected with a connecting rod, a plurality of sliding blocks are fixedly connected with the connecting rod, the side close to the inner side synchronous wheel of the connecting rod is fixedly connected with a protrusion, the position of the protrusion matches the position of the roller, the microwave heating assembly is a magnetron or a solid-state microwave source, the working frequency is 2.45GHz, the power density is 0.5-2.0W / cm², and continuous or pulse mode heating is adopted.

[0057] As a preferred scheme of the present application, the two sides of the metal mesh belt conveyor 4 at one end are rotatably connected with driving synchronous wheels 22, the driving synchronous wheels 22 are fixedly connected with the rollers of the metal mesh belt conveyor 4, the two sides of the two microwave heating mechanisms 2 close to the crushing mechanism 1 are provided with outer side synchronous wheels 26, the outer side synchronous wheels 26 are rotatably connected with the ends of the positioning shafts 24 away from the microwave heating mechanisms 2, the outer side synchronous wheels 26 are fixedly connected with the inner side synchronous wheels 25, the outer sides of the two outer side synchronous wheels 26 are sleeved with synchronous belts 23 engaged therewith, one inner side synchronous wheel 25 close to the crushing mechanism 1 is connected with the driving synchronous wheel 22 through the synchronous belt 23, and the other two inner side synchronous wheels 25 are connected through the synchronous belt 23.

[0058] More specifically, during the operation of the metal mesh belt conveyor 4, the driving synchronous wheel 22 drives the inner synchronous wheel 25 outside each microwave heating mechanism 2 to rotate through the synchronous belt 23 and the outer synchronous wheel 26. When the inner synchronous wheel 25 rotates, the roller 37 moves towards the lower end of the microwave heating mechanism 2, and the roller 37 extrudes the protrusion 35, thereby driving the connecting rod 34, the sliding block 29, the protective baffle 31 and the top block 32 to move downwards. After the roller 37 passes the lowest point, the protrusion 35 is no longer limited, and the spring 30 pushes the connecting rod 34, the sliding block 29, the protective baffle 31 and the top block 32 upwards, so that the top block 32 hits the mesh belt of the metal mesh belt conveyor 4 at a certain speed, thereby causing the mesh belt of the metal mesh belt conveyor 4 to vibrate, so that the shrunk plastic pieces fall onto the main collecting plate 38.

[0059] As a preferred scheme of the present application, the upper end of the air guide frame 8 is slidingly connected with a movable air deflector 11, and a threaded rod 12 is threadedly connected to the middle position of the movable air deflector 11, and the threaded rod 12 is rotationally connected with the air guide frame 8.

[0060] As a preferred scheme of the present application, a hand wheel 13 is fixedly connected to the end of the threaded rod 12 away from the air guide frame 8, for adjusting the position of the movable air deflector 11 to change the negative pressure state at the top of the air guide frame 8.

[0061] More specifically, when it is necessary to adjust the movable air deflector 11, the threaded rod 12 is rotated through the hand wheel 13, so as to change the area of the air inlet at the upper end of the air guide frame 8, and change the negative pressure state at the top of the air guide frame 8, which is suitable for adsorbing and fixing plastic pieces of different sizes.

[0062] As a preferred scheme of the present application, a pull-out frame 15 is slidingly connected to the lower end of the air guide frame 8, and the pull-out frame 15 is fixedly connected with the air guide frame 8 through bolts, and an intercepting screen 16 is fixedly connected to the inner side of the pull-out frame 15, the intercepting screen 16 is arranged obliquely, the air guide frame 8 is provided with a waste discharge outlet near the side with lower horizontal height of the intercepting screen 16, the pull-out frame 15 is provided with a gripping groove 17 away from the air guide frame 8, and the intercepting screen 16 has a mesh number of 20-60 meshes and is made of high-temperature-resistant and corrosion-resistant material.

[0063] More specifically, the small particle plastic pieces falling down are intercepted by the intercepting screen 16, so as to avoid the small particle plastic pieces from entering the negative pressure fan 9 and causing damage to the negative pressure fan 9.

[0064] As a preferred scheme of the present application, the end of the pull-out frame 15 and the movable air deflector 11 away from the air guide frame 8 is sleeved with a sealing gasket 14, and the sealing gasket 14 is fixedly connected with the air guide frame 8, so as to improve the sealing effect.

[0065] More specifically, the outer side of the pulling frame 15 and the movable air deflector 11 is sealed by the sealing gasket 14 to improve the sealing effect of the air guide frame 8.

[0066] As a preferred scheme of the present application, the air guide frame 8 is fixedly connected with a waste guide plate 21 on the side close to the waste discharge port, a rotating shaft 18 is rotatably connected with the air guide frame 8 at the middle position of the waste discharge port, a motor 20 is fixedly connected with the air guide frame 8 on the side close to the crushing mechanism 1, the rotating shaft 18 is fixedly connected with the output end of the motor 20, and a plurality of equally spaced push blades 19 are fixedly connected with the outer wall of the rotating shaft 18.

[0067] More specifically, the waste discharge port is blocked by the push blades 19, so that the inside of the air guide frame 8 is always in a negative pressure state, and the motor 20 can drive the push blades 19 to rotate, thereby pushing out the small plastic sheet impurities intercepted by the intercepting filter screen 16, avoiding the blockage of the intercepting filter screen 16 by the impurities, and affecting the negative pressure fan 9.

[0068] As a preferred scheme of the present application, a main collecting plate 38 is fixedly connected with the lower end inside the microwave heating mechanism 2 and is arranged obliquely, a secondary collecting plate 39 is fixedly connected with the end of the microwave heating mechanism 2 away from the crushing mechanism 1, and the main collecting plate 38 is fixedly connected with the secondary collecting plate 39.

[0069] More specifically, the main collecting plate 38 collects the shrunk plastic sheets, and the secondary collecting plate 39 guides the plastic sheets collected by the main collecting plate 38, so as to facilitate subsequent waste treatment.

[0070] It is worth noting that, in terms of mechanical structure: the microwave heating mechanism 2 is provided with an excitation mechanism that is synchronously linked with the metal mesh belt conveyor 4, for promoting the plastic sheets reaching the shrinkage critical point to fall off the metal mesh belt conveyor 4, and the plurality of microwave heating mechanisms 2 are incremental temperature zones, each section of the microwave heating mechanism 2 is provided with an independent temperature control system and a power modulation unit, and the temperature control precision is ±3℃; the temperature zones are increased from front to back, for example, 60-90℃, 90-120℃, 120-160℃, which can be adjusted according to the material characteristics; the negative pressure surface wind speed range is 0.3-1.8m / s, and the negative pressure range is -200-600Pa; the excitation frequency of the excitation mechanism and the belt speed are matched according to the preset logic, so that the particles of the shrinkage critical size preferentially fall off at the corresponding section.

[0071] The metal mesh belt conveyor 4 passes through each heating section, and the inlet and outlet are provided with shielding and wave-absorbing material lining to prevent microwave leakage, and the mesh aperture a of the metal mesh belt conveyor 4 satisfies a > k(T)·d0 and a < d0, so as to ensure that the material does not fall off before shrinking and automatically falls off after shrinking.

[0072] The feeding end is provided with a crushing mechanism 1 for crushing the hard plastic into a target particle size d0 (e.g. 30-50 mm). A gas guide frame 8 and a negative pressure fan 9 are arranged between the crushing mechanism 1 and the first heating section, so that the crushed plastic pieces form a single layer under negative pressure. The inclined intercepting screen 16 has a mesh size of 20-60 meshes, the negative pressure range is controlled to be -200 to -600 Pa, the air speed on the top surface of the gas guide frame 8 is 0.3-1.8 m / s, and the unit area paving thickness is ≤15 mm.

[0073] A main collecting plate 38 (with an inclination range of 15°-30°) and a secondary collecting plate 39 are arranged below each microwave heating mechanism 2. The main collecting plate 38 and the secondary collecting plate 39 are made of 304 or 316 stainless steel. The metal mesh belt conveyor 4 is provided with a synchronous excitation mechanism on both sides, which is matched with the belt speed. After triggering vibration, the plastic pieces that reach the critical size of shrinkage can be caused to fall off. The excitation can also be achieved by mechanical top block impact or cavity electromagnetic / eccentric exciter through support coupling. The latter avoids metal movement in the microwave cavity.

[0074] In terms of the screening method, the steps are as follows:

[0075] 1. Crushing: crushing the mixed hard plastic to a target particle size d0 in the range of 15-55 mm;

[0076] 2. Paving: under the action of negative pressure, the plastic pieces are paved to form a uniform single layer, ensuring that the unit area thickness is ≤15 mm, and preferably 5-8 mm;

[0077] 3. Step-by-step heating: sequentially passing through multiple microwave heating sections with increasing temperature, heating at the set temperature and power;

[0078] 4. Synchronous excitation: triggering excitation at the end of each section to cause the plastic pieces with a critical size d = k(T)·d0 of shrinkage to fall off. The critical size formula is d = k(T)·d0, wherein:

[0079] ① k(T) is the shrinkage coefficient, which is related to temperature and plastic material

[0080] ② PET: k(90℃)≈0.9, k(120℃)≈0.7

[0081] ③ PP: k(90℃)≈0.95, k(120℃)≈0.8

[0082] ④ PE: k(90℃)≈0.97, k(120℃)≈0.85

[0083] The range of k(T) is 0.6-1.0, and the specific value depends on the heating section temperature and the material quality, which is determined through experiments or a database;

[0084] 5. Segmented collection: The main and auxiliary collection plates under each segment receive the corresponding products, respectively;

[0085] 6. Subsequent processing: The materials in each segment enter different recovery paths to achieve high-purity recovery.

[0086] Among them, the following safety measures need attention:

[0087] ① All metal moving parts are grounded, and the grounding resistance is ≤4Ω;

[0088] ② The edges of the metal parts in the cavity are rounded with a radius ≥2mm to prevent sharp corner discharge;

[0089] ③ The labyrinth shielding structure at the inlet and outlet is equipped with wave-absorbing material to ensure that the microwave leakage is ≤ the national standard limit;

[0090] ④ A microwave leakage detection and interlock shutdown system is provided.

[0091] Compared with the prior art, the present application has the following beneficial effects:

[0092] 1. Precise control of segmented temperature zones: Taking advantage of the difference in softening temperature of different plastics, the screening precision and recovery purity are improved;

[0093] 2. Negative pressure single-layer paving: Ensures uniform heating and avoids uneven heating caused by accumulation;

[0094] 3. Synchronous excitation and material falling: Reduces the screening dead angle caused by static accumulation and improves the separation efficiency;

[0095] 4. Energy saving and high efficiency: Compared with traditional pure mechanical screening, the unit energy consumption can be reduced by more than 20%.

[0096] The technical principles of the present application are described above in conjunction with specific embodiments. These descriptions are only to explain the principles of the present application and cannot be interpreted in any way as a limitation on the scope of protection of the present application. Based on the explanations here, those skilled in the art can think of other specific embodiments of the present application without creative labor, and these embodiments will fall within the scope of protection of the claims of the present application.

Claims

1. A progressive microwave heating multi-stage screening device, comprising at least two microwave heating mechanisms (2) arranged in series and a metal mesh belt conveyor (4), the inside of the microwave heating mechanism (2) is fixed with a microwave heating assembly (3), characterized in that: The feeding end of the metal mesh belt conveyor (4) is provided with a crushing mechanism (1), the crushing mechanism (1) and the microwave heating mechanism (2) are provided with a left side support (5) and a right side support (6) between them, the left side support (5) and the right side support (6) are provided with a gas guide frame (8) fixedly connected thereto, the bottom of the gas guide frame (8) is fixedly connected with a negative pressure fan (9), the top of the gas guide frame (8) is fixedly connected with a fixed air deflector (10), the upper end of the right side support (6) is fixedly connected with an air nozzle assembly (7), the microwave heating mechanism (2) is provided with an exciting mechanism which is in synchronous linkage with the metal mesh belt conveyor (4), the exciting mechanism comprises a sliding block (29), a spring (30), a protective baffle (31) and a top block (32), a plurality of sliding grooves (27) are formed in the two sides of the microwave heating mechanism (2), the inside of the sliding groove (27) is fixedly connected with a sliding rod (28) which is in sliding connection with the sliding block (29), the spring (30) is sleeved outside the sliding rod (28), the inside of the sliding block (29) is fixedly connected with the protective baffle (31), the inside of the protective baffle (31) is fixedly connected with the top block (32), and a plurality of accommodating grooves (40) matched with the protective baffle (31) are formed in the inner wall of the microwave heating mechanism (2).

2. The multi-stage classification device for progressive microwave heating according to claim 1, characterized in that: The two sides of the microwave heating mechanism (2) are fixedly connected with positioning shafts (24), the side of the positioning shaft (24) close to the microwave heating mechanism (2) is rotatably connected with an inside synchronous wheel (25), the inside synchronous wheel (25) is fixedly connected with a limiting shaft (36) at a position away from the shaft center of one side of the microwave heating mechanism (2), the outside of the limiting shaft (36) is sleeved with a roller (37) which is rotatably connected therewith, the outer wall of the two sides of the microwave heating mechanism (2) is provided with a giving slot (33), the inside of the giving slot (33) is in sliding connection with a connecting rod (34), a plurality of sliding blocks (29) are fixedly connected with the connecting rod (34), the side of the connecting rod (34) close to the inside synchronous wheel (25) is fixedly connected with a protruding block (35), the position of the protruding block (35) is matched with the position of the roller (37), the microwave heating assembly (3) is a magnetron or a solid-state microwave source, the working frequency is 2.45GHz, the power density is 0.5-2.0W / cm², and continuous or pulse mode heating is adopted.

3. The multi-stage classification device for progressive microwave heating according to claim 2, wherein: Both sides of one end of the metal mesh belt conveyor (4) are rotationally connected with driving sprocket wheels (22), the driving sprocket wheels (22) are fixedly connected with the roller of the metal mesh belt conveyor (4), both sides of the two microwave heating mechanisms (2) close to the crushing mechanism (1) are provided with outer sprocket wheels (26), the outer sprocket wheels (26) are rotationally connected with the one end of the positioning shaft (24) away from the microwave heating mechanism (2), the outer sprocket wheels (26) are fixedly connected with inner sprocket wheels (25), the outer sides of the two outer sprocket wheels (26) are provided with synchronous belts (23) engaged with them, one inner sprocket wheel (25) close to the crushing mechanism (1) is connected with the driving sprocket wheel (22) through the synchronous belt (23), the other two inner sprocket wheels (25) are connected through the synchronous belt (23).

4. The multi-stage classification device for progressive microwave heating according to claim 3, wherein: The upper end of the air guide frame (8) is slidably connected with a movable air deflector (11), a threaded rod (12) is threadedly connected to the middle position of the movable air deflector (11), and the threaded rod (12) is rotationally connected with the air guide frame (8).

5. The apparatus according to claim 4, wherein: The end of the threaded rod (12) away from the air guide frame (8) is fixedly connected with a hand wheel (13).

6. The multi-stage classification device for progressive microwave heating according to claim 5, wherein: The lower end of the air guide frame (8) is slidably connected with a pull frame (15), the pull frame (15) is fixedly connected with the air guide frame (8) through bolts, the inner side of the pull frame (15) is fixedly connected with an intercepting screen (16), the intercepting screen (16) is arranged in an inclined manner, a waste discharge outlet is formed in the side of the air guide frame (8) close to the lower horizontal position of the intercepting screen (16), a gripping groove (17) is formed in the side of the pull frame (15) away from the air guide frame (8), the intercepting screen (16) has a mesh number of 20-60 meshes and is made of a high-temperature-resistant and corrosion-resistant material.

7. The multi-stage classification device for progressive microwave heating according to claim 6, wherein: The end of the pull frame (15) and the movable air deflector (11) away from the air guide frame (8) is sleeved with a sealing gasket (14), and the sealing gasket (14) is fixedly connected with the air guide frame (8).

8. The apparatus according to claim 7, wherein: The side of the air guide frame (8) close to the waste discharge outlet is fixedly connected with a waste guide plate (21), the middle position of the waste discharge outlet of the air guide frame (8) is rotationally connected with a rotating shaft (18), the side of the air guide frame (8) close to the crushing mechanism (1) is fixedly connected with a motor (20), the rotating shaft (18) is fixedly connected with the output end of the motor (20), and the outer wall of the rotating shaft (18) is fixedly connected with a plurality of equidistantly distributed push blades (19).

9. The apparatus according to claim 8, wherein: The lower end of the microwave heating mechanism (2) is fixedly connected with an inclined main collecting plate (38), and the end of the microwave heating mechanism (2) away from the crushing mechanism (1) is fixedly connected with a secondary collecting plate (39).

10. The method of claim 9, wherein the microwave heating is progressive. 10 The method comprises the following steps: Step one: hard plastic type household garbage is put into the crushing mechanism (1), the crushing mechanism (1) is used for crushing the garbage, so that the garbage becomes plastic pieces with similar sizes, and then the plastic pieces are conveyed to the direction of the microwave heating mechanism (2) through the metal mesh belt conveyor (4). Step two: when the plastic sheet passes through the air guide frame (8), the air nozzle assembly (7) connected with the external air source will blow the plastic sheet, and at the same time, the negative pressure fan (9) will work to form negative pressure at the bottom of the metal mesh belt conveyor (4), so that only one layer of plastic sheet is reserved on the metal mesh belt conveyor (4); Step three: after the plastic sheet enters the inside of the microwave heating mechanism (2), the microwave heating assembly (3) will heat the plastic sheet, and the plastic sheet will shrink, so that the area of the plastic sheet becomes smaller. Since the size of the mesh of the metal mesh belt conveyor (4) can only ensure that the just broken plastic sheet does not fall off, after the plastic sheet shrinks due to heating, it will fall into the main collection plate (38) and finally flow out from the auxiliary collection plate (39); Step four: the temperature inside each microwave heating mechanism (2) is different, gradually increasing from the front end to the rear end of the metal mesh belt conveyor (4), and various plastic sheets will also shrink and fall off in different microwave heating mechanisms (2); Step five: during the operation of the metal mesh belt conveyor (4), the driving synchronous wheel (22) will drive the inside synchronous wheel (25) outside each microwave heating mechanism (2) to rotate through the synchronous belt (23) and the outside synchronous wheel (26). When the inside synchronous wheel (25) rotates to drive the roller (37) to move downward, the roller (37) will press the protrusion (35), thereby driving the connecting rod (34), the sliding block (29), the protective baffle (31) and the top block (32) to move downward. After the roller (37) passes the lowest point, the protrusion (35) is no longer restricted, and the spring (30) will push the connecting rod (34), the sliding block (29), the protective baffle (31) and the top block (32) upward, so that the top block (32) hits the metal mesh belt conveyor (4), thereby causing the metal mesh belt conveyor (4) to vibrate, so as to facilitate the plastic sheet after shrinking to fall onto the main collection plate (38).

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