Wheat straw ultrafine grinding method and device

Abstract

The present invention provides a method and device for ultrafine grinding of wheat straw, and relates to the technical field of straw processing. The present invention obliquely cuts wheat straw to obtain a first material with a length of less than 1 cm; the angle of the oblique cutting is 45°; the first material is rotary cut to obtain a second material with a length of 3 to 5 mm; the second material is ball milled to obtain ultrafine wheat straw with a particle size of 5 to 30 μm; the ball milling includes a primary ball milling and a secondary ball milling performed in sequence, the primary ball milling is performed under baking conditions, and the baking temperature is 60 to 70°C. The present invention adopts a two-stage ball milling process with "step-type multi-stage crushing" and "baking ball milling process" as the main body to crush wheat straw, which can achieve ultrafine grinding of wheat straw with a particle size of 5 to 30 μm, which is conducive to improving the utilization efficiency of wheat straw powder and realizing high added value production. The present invention also provides a wheat straw ultrafine grinding device, which can achieve ultrafine grinding of wheat straw with a particle size of 5 to 30 μm.

Description

Technical Field

[0001] The invention relates to the technical field of straw processing, and in particular to a wheat straw ultrafine grinding method and device. Background Art

[0002] my country is a major agricultural country and one of the countries with the richest straw resources. Wheat straw ranks third in the total crop straw output, and nearly 100 million tons of wheat straw can be produced each year. At present, there are still deficiencies in the rational use of wheat straw. A large amount of wheat straw is burned, which not only causes a waste of resources, but also pollutes the environment. Crushing and reusing wheat straw is one of the effective ways to solve this problem. Chinese patent CN201910166596.5 discloses that straw is crushed into 3-8 mm fragments by a kneading machine, and then dried and granulated into fuel columns by a granulator, and further ground into 200 mesh (74μm) fuel powder by a ball mill, which is used in coal-fired power companies to replace fuel coal for power generation.

[0003] In the further development and utilization of wheat straw, due to its advantages such as biodegradability and wide sources of raw materials, relevant studies have used wheat straw powder as a filler for plastic modification, and have successively developed biodegradable mulch, degradable garbage bags, degradable straws and other products. However, such applications have strict requirements on the particle size of wheat straw powder, because too large a particle size will cause the product processing performance, mechanical properties, and mechanical properties to deteriorate significantly, seriously affecting the product quality and limiting its application and promotion. With the development and progress of crushing equipment and crushing methods, the existing technology has been able to crush wheat straw into wheat straw particles of about 300 mesh (48μm). However, due to the specificity of wheat straw itself (long strip shape, high toughness of wood fiber on the surface), it has been difficult to break through the technical bottleneck of ultra-fine grinding at home and abroad. Summary of the invention

[0004] In view of this, the present invention aims to provide a method and device for ultrafine grinding of wheat straw. The method provided by the present invention is used to grind wheat straw, and ultrafine grinding of wheat straw with a particle size of 5 to 30 μm can be achieved.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a wheat straw ultrafine grinding method, comprising the following steps:

[0007] The straw is cut obliquely to obtain a first material with a length of less than 1 cm; the angle of the cut is 45°;

[0008] The first material is subjected to rotary cutting to obtain a second material having a length of 3 to 5 mm;

[0009] The second material is ball-milled to obtain ultrafine wheat straw with a particle size of 5 to 30 μm; the ball milling includes primary ball milling and secondary ball milling performed in sequence, the primary ball milling is performed under baking conditions, and the baking temperature is 60 to 70°C.

[0010] Preferably, the length of the wheat straw is 60 to 100 cm.

[0011] Preferably, the rotation speed of the rotary cutting is 2800-4300 r / min.

[0012] Preferably, the baking is constant temperature baking.

[0013] Preferably, the first-stage ball mill uses a first grinding ball, which is a high-alumina ceramic grinding ball; the first grinding ball includes a first diameter grinding ball, a second diameter grinding ball and a third diameter grinding ball, the diameters of the first diameter grinding ball, the second diameter grinding ball and the third diameter grinding ball are 100 mm, 80 mm and 50 mm respectively, and the mass ratio of the first diameter grinding ball, the second diameter grinding ball and the third diameter grinding ball is (2.2-3.0):(4.0-5.4):(2.4-3.0); the volume filling amount of the first grinding ball is 30-45%.

[0014] Preferably, the secondary ball mill uses second grinding balls, which are high-alumina ceramic grinding balls; the second grinding balls include fourth diameter grinding balls, fifth diameter grinding balls and sixth diameter grinding balls, the diameters of the fourth diameter grinding balls, the fifth diameter grinding balls and the sixth diameter grinding balls are 80 mm, 60 mm and 40 mm respectively, and the mass ratio of the fourth diameter grinding balls, the fifth diameter grinding balls and the sixth diameter grinding balls is (2.0-2.5):(3.5-4.5):(3.5-4.0); the volume filling amount of the second grinding balls is 25-40%.

[0015] Preferably, the rotation speeds of the primary ball mill and the secondary ball mill are 600-850 r / min respectively.

[0016] The present invention provides a straw ultrafine grinding device, comprising a 45° step-by-step cutter 1, a rotary cutter 2, a primary ball mill 3 and a secondary ball mill 4 which are connected in sequence;

[0017] The inner lining surface of the cylinder of the first-stage ball mill 3 and the second-stage ball mill 4 is provided with a continuous spiral structure protrusion 5, the longitudinal section of the spiral structure protrusion 5 is trapezoidal, the two side edges of the trapezoid are straight lines inclined inward, and the top ends of the two side edges are connected in an arc shape; the outer cylinder of the first-stage ball mill 3 is wrapped with a temperature control sleeve 6.

[0018] Preferably, the pitch of the spiral structure protrusion 5 is 8 to 15 cm; the angle between the two sides of the trapezoid and the bottom is 75°; the ratio of the bottom length, the side length and the height of the trapezoid is 2:3:2.3.

[0019] Preferably, a spiral feed control valve is provided at the front feed port of the first-stage ball mill 3, a temperature control sleeve controller is provided on the temperature control sleeve 6, and the spiral feed control valve and the temperature control sleeve controller are connected to a temperature sensor.

[0020] The invention provides a wheat straw ultrafine grinding method, comprising the following steps: beveling the wheat straw to obtain a first material with a length of less than 1 cm; the beveling angle is 45 degrees; the first material is rotary cut to obtain a second material with a length of 3 to 5 mm; the second material is ball milled to obtain ultrafine wheat straw with a particle size of 5 to 30 μm; the ball milling comprises primary ball milling and secondary ball milling which are carried out in sequence, the primary ball milling is carried out under baking conditions, and the baking temperature is 60 to 70°C. The present invention cuts the wheat straw at an angle of 45° to maximize the cross-sectional area of ​​the wheat straw coarse material, which can be more conducive to drying the wheat straw and better destroy the valence bond of the wheat straw surface structure; the present invention performs rotary cutting on the wheat straw coarse material, which can destroy the compact crystal structure of the outer surface of the wheat straw, and the heat energy generated during the rotation can dehumidify and dry the wheat straw; the present invention performs primary ball milling on the rotary cut wheat straw coarse material under baking conditions, and strictly controls the baking temperature, which can soften the outer surface structure of the wheat straw while reducing the moisture content of the wheat straw, making the material looser, and reduce the order of cellulose, destroy the hydrogen bonds and secondary valence bonding forces in the cellulose molecules, and weaken the lignin-carbohydrate complex structure, thereby reducing the toughness and hardness of the wheat straw as a whole, making the material easier to crush; and then further crushing by secondary ball milling to obtain ultrafine wheat straw. The method provided by the present invention is used to crush the wheat straw, and ultrafine grinding of 5-30 μm particle size of the wheat straw can be achieved, which is conducive to improving the utilization efficiency of wheat straw powder and realizing high value-added production.

[0021] The present invention provides a straw ultrafine grinding device, comprising a 45° step-by-step cutter 1, a rotary cutter 2, a primary ball mill 3 and a secondary ball mill 4 connected in sequence; the surface of the inner lining plate of the cylinder of the primary ball mill 3 and the secondary ball mill 4 is provided with a spiral structure protrusion 5, the longitudinal section of the spiral structure protrusion is trapezoidal, the two sides of the trapezoid are straight lines inclined inward, and the tops of the two sides are connected in an arc shape; the cylinder of the primary ball mill 3 is wrapped with a temperature control sleeve 6. The device provided by the present invention can achieve ultrafine grinding of 5-30μm grain size of wheat straw, especially the surface of the inner lining plate of the cylinder of the primary ball mill 3 and the secondary ball mill 4 is provided with a spiral structure protrusion, the longitudinal section of the spiral structure protrusion is trapezoidal, compared with the traditional triangular and trapezoidal structures, it has the advantages of high sample rate, impact resistance, high strength and good grinding efficiency, and is more conducive to achieving ultrafine grinding of materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a process flow chart of ultra-fine grinding of wheat straw;

[0023] Figure 2 It is a schematic diagram of the ultrafine grinding device provided by the present invention;

[0024] Figure 3 It is a schematic diagram of the structure of the inner lining plate of the cylinder of the first-stage ball mill 3 and the second-stage ball mill 4 in the present invention. Figure 3 (a) is a three-dimensional view of the liner, (b) is a view of the liner when it is unfolded, looking toward A, and (c) is a view of the liner when it is unfolded, looking toward B;

[0025] Figure 2-3 Middle, 1-45° step-type cutter, 2-rotating cutter, 3-first-stage ball milling chamber, 4-second-stage ball milling chamber, 5-spiral structure protrusion, 6-temperature control sleeve;

[0026] Figure 4 It is a schematic diagram of a ladder-like structure. DETAILED DESCRIPTION

[0027] The present invention provides a wheat straw ultrafine grinding method, comprising the following steps:

[0028] The straw is cut obliquely to obtain a first material with a length of less than 1 cm; the angle of the cut is 45°;

[0029] The first material is subjected to rotary cutting to obtain a second material having a length of 3 to 5 mm;

[0030] The second material is ball-milled to obtain ultrafine wheat straw with a particle size of 5 to 30 μm; the ball milling includes primary ball milling and secondary ball milling performed in sequence, the primary ball milling is performed under baking conditions, and the baking temperature is 60 to 70°C.

[0031] First, the material properties of wheat straw are explained. The length, thickness, hardness and thickness of the stalk wall of wheat vary greatly with the wheat variety, planting environment and planting method. Most of the wheat varieties widely used in production have a plant height of 70-85 cm, and there are also a small number of short-stalked high-yield varieties of 60-70 cm and a small number of tall-stalked high-yield varieties with strong resistance to lodging of more than 90 cm. Therefore, the overall length of wheat straw is distributed between 60 and 100 cm. Wheat straw is mainly composed of cellulose, hemicellulose and lignin. Among them, cellulose accounts for about 45%, hemicellulose accounts for about 30%, and lignin has the lowest content of about 20%. Cellulose is a natural polymer compound formed by glucose as a unit; hemicellulose is a heteropolymer composed of several different types of monosaccharides such as xylose, arabinose and galactose; lignin is mainly a complex polymer formed by three alcohol monomers (coniferyl alcohol, sinapyl alcohol and p-coumaryl alcohol). In the plant cell wall on the outer surface of wheat straw, lignin is filled between cellulose and hemicellulose. There is only a secondary binding force between cellulose and hemicellulose. In addition to the secondary binding force, hemicellulose and lignin are also connected by chemical bonds to form a lignin-carbohydrate complex (LCC). The inner surface of wheat straw is mainly composed of thin-walled cells with a loose structure and a clear fiber skeleton. Therefore, the outer surface structure of wheat straw is the main factor affecting the toughness and hardness of wheat straw. The high toughness of the outer surface structure of wheat straw is also one of the main reasons why wheat straw is difficult to achieve ultra-fine grinding.

[0032] Figure 1 The process flow chart of the present invention for ultrafine grinding of wheat straw is shown below. Figure 1 The present invention is described in detail.

[0033] The present invention obliquely cuts the wheat straw to obtain a first material with a length of less than 1 cm; the oblique cutting angle is 45°. Before oblique cutting, the present invention preferably pre-treats the wheat straw, and the pre-treatment includes removing residual soil and impurities on the wheat straw, drying, and baling the wheat straw. The present invention obliquely cuts the wheat straw at an angle of 45° to maximize the cross-sectional area of ​​the wheat straw coarse material, which can be more conducive to drying the wheat straw and better destroying the valence bonds of the surface structure of the wheat straw. After the oblique cutting, a coarse material with a length of less than 1 cm, an inclined cross-section, a uniform texture, and a hollow structure with exposed straw ends is obtained, that is, the first material.

[0034] After obtaining the first material, the present invention performs rotary cutting on the first material to obtain a second material with a length of 3 to 5 mm. In the present invention, the rotation speed of the rotary cutting is preferably 2800 to 4300 r / min. The rotary cutting can destroy the compact crystal structure of the outer surface of the straw, and the heat energy generated during the rotation can dehumidify and dry the straw.

[0035] After obtaining the second material, the present invention ball-mills the second material to obtain ultrafine wheat straw with a particle size of 5 to 30 μm. In the present invention, the ball milling includes primary ball milling and secondary ball milling performed sequentially, and the primary ball milling is performed under baking conditions, and the baking temperature is 60 to 70°C; the baking is preferably constant temperature baking, specifically 60°C or 70°C. In the present invention, the primary ball mill preferably uses a first grinding ball, and the first grinding ball is preferably a high-aluminum ceramic grinding ball, and the high-aluminum ceramic grinding ball is specifically a highly wear-resistant 95% high-aluminum ceramic grinding ball. Compared with traditional grinding balls made of steel, iron and other materials, high-aluminum ceramic grinding balls have the advantages of high density, high mechanical strength, and good wear resistance. In the present invention, the first grinding balls preferably include first diameter grinding balls, second diameter grinding balls and third diameter grinding balls, the diameters of the first diameter grinding balls, the second diameter grinding balls and the third diameter grinding balls are preferably 100 mm, 80 mm and 50 mm respectively, the mass ratio of the first diameter grinding balls, the second diameter grinding balls and the third diameter grinding balls is preferably (2.2-3.0):(4.0-5.4):(2.4-3.0), more preferably 3.0:4.0:3.0; the volume filling amount of the first grinding balls is preferably 30-45%, more preferably 40%. In the present invention, the rotation speed of the primary ball mill is preferably 600-850 r / min, more preferably 800-850 r / min. The present invention makes the primary ball mill have grinding specificity for 3-5 mm wheat straw materials by specially setting the filling amount, volume size and quantity ratio of the grinding balls used in the primary ball mill. In the present invention, the first-stage ball milling adopts the "baking ball milling process", and the wheat straw is subjected to the first-stage ball milling under the condition of baking at 60-70°C. While reducing the moisture content of the wheat straw, the outer surface structure of the wheat straw is softened to make the material looser, and the order of cellulose is reduced, the hydrogen bonds and secondary valent binding forces in the cellulose molecules are destroyed, and the lignin-carbohydrate complex structure is weakened, thereby reducing the toughness and hardness of the wheat straw as a whole, making the material easier to crush. If the baking temperature is too low, the internal valent bonds of the wheat straw structure cannot be fully destroyed, resulting in a larger final crushing particle size. If the baking temperature is too high, the safety risk of the crushing process increases and the energy consumption increases.

[0036] In the present invention, the secondary ball mill uses a second grinding ball, and the second grinding ball is a high-aluminum ceramic grinding ball, specifically a highly wear-resistant 95% high-aluminum ceramic grinding ball. In the present invention, the second grinding ball preferably includes a fourth diameter grinding ball, a fifth diameter grinding ball and a sixth diameter grinding ball, and the diameters of the fourth diameter grinding ball, the fifth diameter grinding ball and the sixth diameter grinding ball are preferably 80mm, 60mm and 40mm respectively, and the mass ratio of the fourth diameter grinding ball, the fifth diameter grinding ball and the sixth diameter grinding ball is preferably (2.0-2.5): (3.5-4.5): (3.5-4.0), more preferably 2.0: 4.0: 3.5; the volume filling amount of the second grinding ball is preferably 25-40%, more preferably 35%. In the present invention, the rotation speed of the secondary ball mill is preferably 600-850r / min, more preferably the same as the rotation speed of the primary ball mill. The present invention makes the secondary ball mill have grinding specificity for the straw material after baking and grinding in the primary ball mill by specially setting the filling amount, volume size and quantity ratio of the grinding balls used in the secondary ball mill. During the primary and secondary ball milling, the centrifugal force generated by the primary and secondary ball milling rotates the grinding balls to a certain height and then leaves the cylinder track, generating impact and friction forces on the material below in a parabolic shape, and finally the material is fully ground by the double-stage ball mill to obtain ultra-fine material.

[0037] The existing wheat straw crushing process has a crushing particle size of only millimeters, and the purpose is to use the coarse crushing of wheat straw for the production of feed, papermaking, biomass energy power generation, etc. The present invention adopts a two-stage ball milling process with targeted "step-type multi-stage crushing" and "baking ball milling process" as the main body, aiming at the length characteristics of the wheat straw and the compact structural characteristics of the outer surface of the wheat straw, which solves the problem of high toughness of wheat straw and difficulty in ultrafine crushing, and realizes ultrafine crushing of wheat straw with a particle size of 5 to 30 μm. It is suitable for the production of ultrafine powder particles of wheat straw of different types, lengths, humidity, etc., and the resulting product has a wider range of uses and better performance.

[0038] The present invention also provides a straw ultrafine grinding device, comprising a 45° step-by-step cutter 1, a rotary cutter 2, a primary ball mill 3 and a secondary ball mill 4 connected in sequence;

[0039] The inner lining surface of the cylinder of the first-stage ball mill 3 and the second-stage ball mill 4 is provided with a continuous spiral structure protrusion 5, the longitudinal section of the spiral structure protrusion 5 is trapezoidal, the two side edges of the trapezoid are straight lines inclined inward, and the top ends of the two side edges are connected in an arc shape; the outer cylinder of the first-stage ball mill 3 is wrapped with a temperature control sleeve 6.

[0040] Figure 2 The schematic diagram of the ultrafine grinding device provided by the present invention is shown below in combination with Figure 2 The ultrafine grinding device provided by the present invention is described in detail.

[0041] The ultrafine grinding device provided by the present invention includes a 45° step-by-step cutter 1. The present invention has no special requirements for the specific structure of the 45° step-by-step cutter 1, and the corresponding equipment familiar to those skilled in the art can be used. When in use, the 45° step-by-step cutter 1 preferably adopts a step-by-step feed with a length of 1 cm. In the present invention, the 45° step-by-step cutter 1 cuts the wheat straw, which is conducive to obtaining wheat straw coarse materials with good length uniformity, and beveling the wheat straw at a 45° angle can maximize the cross-sectional area of ​​the wheat straw coarse materials; in addition, when working, the equipment has the characteristic of stable operation.

[0042] The ultrafine grinding device provided by the present invention includes a rotary cutter 2 connected to the discharge end of the 45° step-by-step cutter 1. In the present invention, the discharge end of the 45° step-by-step cutter 1 is preferably provided with a conveyor belt, which is connected to the rotary cutter 2 through the conveyor belt, that is, the material cut by the 45° step-by-step cutter 1 is fed into the rotary cutter 2 through the conveyor belt. The present invention has no special requirements for the specific structure of the rotary cutter 2, and a rotary cutter familiar to those skilled in the art can be used. In the present invention, the blade of the rotary cutter 2 is preferably a steel blade. In the present invention, the rotary cutter 2 can destroy the compact crystal structure of the outer surface of the straw; and the rotary cutter has the characteristics of high working efficiency.

[0043] The ultrafine grinding device provided by the present invention adopts a "step-by-step cutting" system composed of a 45° step-by-step cutter 1 and a rotary cutter 2. Compared with the traditional "one-step hammering cutting", it has the advantages of materials not being easy to get knotted or blocked at the cutting device, high sampling efficiency, simple equipment structure, and low maintenance cost.

[0044] The ultrafine grinding device provided by the present invention comprises a primary ball mill 3 and a secondary ball mill 4 which are sequentially connected to the discharge end of the rotary cutter 2, that is, the present invention adopts a double-bin ball mill system. In the present invention, the material cut by the rotary cutter 2 can be blown into the inlet of the primary ball mill 3 by the wind force generated by the high-speed rotating blade of the rotary cutter 2. In the present invention, the inner lining surface of the cylinder of the primary ball mill 3 and the secondary ball mill 4 is provided with a continuous spiral structure protrusion 5, and the longitudinal section of the spiral structure protrusion 5 is trapezoidal, and the two side edges of the trapezoid are straight lines inclined inward, and the top ends of the two side edges are connected in an arc shape. In the present invention, the inner lining of the cylinder of the primary ball mill 3 and the secondary ball mill 4 is preferably a polymer ceramic lining. Figure 3 It is a schematic diagram of the structure of the inner lining plate of the cylinder of the first-stage ball mill 3 and the second-stage ball mill 4 in the present invention. Figure 3 (a) is a three-dimensional view of the liner, (b) is a view of the liner when it is unfolded, looking toward A, and (c) is a view of the liner when it is unfolded, looking toward B; Figure 3The design of the spiral structure protrusions on the surface of the inner lining of the cylinder of the primary ball mill 3 and the secondary ball mill 4 is shown. The present invention adopts the design of the spiral structure protrusions, which can effectively drive the lateral movement of the material in the double bins, that is, the material moves laterally to the secondary ball mill 4 while being ground in the primary ball mill 3. In the present invention, the pitch of the spiral structure protrusion 5 is preferably 8 to 15 cm, more preferably 12 cm. The present invention sets the pitch of the spiral structure protrusion 5 to 8 to 15 cm, which is beneficial to control the time the material stays in the bin and to stabilize the discharge rate. In the present invention, the angle between the two side sides of the trapezoid and the bottom is preferably 75°; the ratio of the bottom length, side length and height of the trapezoid is preferably 2:3:2.3; the trapezoid is as Figure 4 As shown, a is the bottom, b is the side, and c is the height. Compared with the traditional triangular and trapezoidal structures, the present invention adopts the trapezoidal structure, which has the advantages of high sample rate, impact resistance, high strength, and good grinding efficiency, which is conducive to the realization of ultra-fine grinding of materials. When the material is actually ground, the filling amount, volume size and quantity ratio of the grinding balls loaded in the primary ball mill 3 and the secondary ball mill 4 can be set differently, so that the primary ball mill 3 and the secondary ball mill 4 can be specifically ground for materials of different sizes, and then the double-bin ball mill system formed by the primary ball mill 3 and the secondary ball mill 4 is used to perform two-stage ball milling from coarse to fine to achieve ultra-fine grinding of the material.

[0045] In the present invention, the cylinder of the first-level ball mill 3 is wrapped with a temperature control sleeve 6. In the present invention, a temperature control sleeve 6 is arranged outside the cylinder of the first-level ball mill 3 to heat the first-level ball mill 3. In the present invention, a spiral feed control valve is preferably arranged at the front feed port of the first-level ball mill 3, and a temperature control sleeve controller is preferably arranged on the temperature control sleeve 6. The spiral feed control valve and the temperature control sleeve controller are preferably connected to a temperature sensor, and the probe of the temperature sensor is preferably fixed on the inner side of the cylinder of the first-level ball mill 3; the arrangement of the spiral feed control valve, the temperature control sleeve controller and the temperature sensor is conducive to real-time maintenance of the working temperature (baking temperature) of the first-level ball mill 3. Specifically, when the temperature is too high, on the one hand, the temperature sensor can transmit an electrical signal to the feed control valve to increase the feed speed, and on the other hand, the electrical signal can be transmitted to the temperature control sleeve to stop heating the bin; when the temperature is too low, the feed rate is reduced, and the bin is heated by the temperature control sleeve. In the present invention, the first-level ball mill 3 can realize the baking of the material while grinding the material.

[0046] In the present invention, the method for ultrafinely grinding wheat straw using the device comprises the following steps:

[0047] The straw is cut obliquely by a 45° step-by-step cutter 1 to obtain a first material with a length of less than 1 cm;

[0048] The first material enters the rotary cutter 2 for rotary cutting to obtain a second material with a length of 3 to 5 mm;

[0049] The second material enters the primary ball milling chamber 3 and is subjected to primary ball milling while being baked; the material obtained by the primary ball milling enters the secondary ball milling chamber 4 for secondary ball milling to obtain ultrafine wheat straw with a particle size of 5 to 30 μm.

[0050] In the present invention, the process conditions of beveling, rotary cutting, baking, primary ball milling and secondary ball milling are the same as those in the above technical solution and will not be described in detail herein.

[0051] The wheat straw ultrafine grinding method and device provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0052] Each embodiment and comparative example adopts Figure 2 The ultra-fine grinding device shown in the figure performs ultra-fine grinding on wheat straw, and the device is composed of a 45° step-by-step cutter, a rotary cutter, a first-level ball mill (referred to as warehouse one) and a second-level ball mill (referred to as warehouse two) connected in sequence. Among them, the surface of the inner lining plate of the first-level ball mill and the second-level ball mill is provided with a continuous spiral structure protrusion, and the longitudinal section of the spiral structure protrusion is trapezoidal, and the two sides of the trapezoid are straight lines inclined inward, and the tops of the two sides are connected in an arc shape; the pitch of the spiral structure protrusion is 12cm; the angle between the two sides of the trapezoid and the bottom is 75°; the ratio of the bottom length, the side length and the height of the trapezoid is 2:3:2.3. The outer cylinder of the first-level ball mill is wrapped with a temperature control sleeve, and a spiral feed control valve is provided at the front feed port of the first-level ball mill, and a temperature control sleeve controller is provided on the temperature control sleeve, and the spiral feed control valve and the temperature control sleeve controller are connected to the temperature sensor.

[0053] Example 1

[0054] The method for ultra-fine grinding of wheat straw is as follows:

[0055] (1) Pretreatment of wheat straw: Collect the harvested wheat straw, remove the residual soil and impurities, dry it in natural conditions for 3 days, and then bundle it for later use.

[0056] (2) Obtaining crude materials:

[0057] ① The pretreated wheat straw enters a 45° step-type cutter via a conveyor belt for rough shearing with a step of 1 cm, and after rough cutting, a coarse material 1 with a length of <1 cm is obtained.

[0058] ② The coarse material 1 falls into the high-speed rotary cutter through the conveyor belt and is crushed to 3-5 mm to form the coarse material 2.

[0059] (3) The coarse material 2 is double-bin ground to obtain fine material:

[0060] Setting of grinding balls in the primary ball mill and the secondary ball mill: the diameters of the grinding balls in the primary ball mill are 100mm, 80mm and 50mm respectively, with a corresponding mass ratio of 3.0:4.0:3.0, and the volume filling amount of the grinding balls is 40%; the diameters of the grinding balls in the secondary ball mill are 80mm, 60mm and 40mm respectively, with a corresponding mass ratio of 2.0:4.0:3.5, and the volume filling amount of the grinding balls is 35%.

[0061] The coarse material 2 is ground while being baked at 70℃ in the first ball mill. The temperature is achieved by controlling the feed speed, the discharge speed and the thermal compensation of the temperature control sleeve. The coarse material 2 is driven by the built-in spiral liner in the bin, and moves horizontally to the second ball mill while being baked and ground. Ultra-fine grinding is performed on the basis of the coarse material obtained by coarse grinding in the first ball mill. The speed of the first and second ball mills is set to 850r / min. The centrifugal force generated by the rotation of the cylinder rotates the grinding balls to a certain height and then leaves the cylinder track, generating impact and friction on the material below in a parabolic shape. The particle size D is obtained after grinding in the first and second ball mills. 50 =5.761 ultra-fine wheat straw powder.

[0062] (4) Packaging and storage: The collected ultrafine wheat straw powder is packaged and stored.

[0063] Examples 2 to 4 and Comparative Examples 1 to 3

[0064] The steps of ultrafine grinding of wheat straw are the same as those in Example 1, except that the corresponding parameters are adjusted according to Table 1, and the particle sizes of the obtained wheat straw powder are listed in Table 1.

[0065] Table 1 Process parameters of Examples 1 to 4 and Comparative Examples 1 to 3 and particle size of obtained wheat straw powder

[0066]

[0067]

[0068] As can be seen from Table 1, Examples 1 to 4 can achieve ultrafine grinding of wheat straw at the level of 5 to 30 μm by reasonably controlling the grinding ball parameters, the baking temperature of the ball mill, and the speed of the double-bin ball mill. However, in Comparative Example 1, the grinding ball filling amount is too low, and the probability of the material in the ball mill being subjected to impact force, friction, etc. is too small, the grinding force is insufficient, and the powder product D 50The target particle size requirement of 5-30 μm cannot be met. In Example 2, the baking temperature of the ball mill bin is reduced to 50°C, but it is difficult to achieve the baking conditions, and the crushing effect is poor. The target particle size requirement of 5-30 μm cannot be met by traditional ball milling alone. In Example 3, the speed of the double-bin ball mill is too low, and the arc of the grinding balls thrown out in the grinding bin is not good, which leads to insufficient impact force on the material and affects the final crushing effect.

[0069] It can be seen from the above embodiments that the method provided by the present invention can be used to grind wheat straw to achieve ultra-fine grinding of 5 to 30 μm level.

[0070] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for ultra-finely pulverizing wheat straw using an ultra-fine pulverizing device for wheat straw, characterized in that: The straw ultrafine grinding device comprises a 45° step-by-step cutter (1), a rotary cutter (2), a primary ball milling chamber (3) and a secondary ball milling chamber (4) which are connected in sequence; The inner lining surfaces of the first-stage ball mill (3) and the second-stage ball mill (4) are provided with continuous spiral structure protrusions (5), the longitudinal section of the spiral structure protrusions (5) is trapezoidal, the two sides of the trapezoid are straight lines inclined inward, and the top ends of the two sides are connected in an arc shape; the outer cylinder of the first-stage ball mill (3) is wrapped with a temperature control sleeve (6); the pitch of the spiral structure protrusions (5) is 12 cm; the angle between the two sides of the trapezoid and the bottom is 75°; the ratio of the bottom length, the side length and the height of the trapezoid is 2:3:2.3; The following steps are involved: The straw is beveled by a 45° step-by-step cutter (1) to obtain a first material having a length of less than 1 cm; the beveled angle is 45°; The first material enters a rotary cutter (2) for rotary cutting to obtain a second material having a length of 3 to 5 mm; The second material enters the primary ball milling chamber (3) for primary ball milling, and the material obtained by the primary ball milling enters the secondary ball milling chamber (4) for secondary ball milling to obtain ultrafine wheat straw with a particle size of 5.761 μm; the primary ball milling is carried out under baking conditions, and the baking temperature is 70° C. The first-stage ball mill uses first grinding balls, which include first-diameter grinding balls, second-diameter grinding balls and third-diameter grinding balls, the diameters of the first-diameter grinding balls, the second-diameter grinding balls and the third-diameter grinding balls are 100 mm, 80 mm and 50 mm respectively, and the mass ratio of the first-diameter grinding balls, the second-diameter grinding balls and the third-diameter grinding balls is 3.0:4.0:3.0; the volume filling amount of the first grinding balls is 40%; The secondary ball mill uses second grinding balls, which include fourth diameter grinding balls, fifth diameter grinding balls and sixth diameter grinding balls, the diameters of the fourth diameter grinding balls, fifth diameter grinding balls and sixth diameter grinding balls are 80 mm, 60 mm and 40 mm respectively, and the mass ratio of the fourth diameter grinding balls, fifth diameter grinding balls and sixth diameter grinding balls is 2.0:4.0:3.5; the volume filling amount of the second grinding balls is 35%; The rotation speeds of the primary ball mill and the secondary ball mill are 850 r / min respectively.

2. The method according to claim 1, characterized in that The length of the wheat straw is 60-100 cm.

3. The method according to claim 1, characterized in that The rotation speed of the rotary cutting is 2800~4300r / min.

4. The method according to claim 1, characterized in that The baking is constant temperature baking.

5. The method according to claim 1, characterized in that The first grinding balls are high-aluminum ceramic grinding balls.

6. The method according to claim 1, characterized in that The second grinding balls are high-alumina ceramic grinding balls.

7. The method according to claim 1, characterized in that A spiral feed control valve is arranged at the front feed port of the first-stage ball mill bin (3), a temperature control sleeve controller is arranged on the temperature control sleeve (6), and the spiral feed control valve and the temperature control sleeve controller are connected to a temperature sensor.

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