Tobacco stem processing technology

Abstract

The invention discloses a tobacco stem processing technology. The traditional tobacco stem processing mode of firstly drying and then treating is changed, the tobacco stems are finely classified by adopting a wet stem multi-stage sorting process, then the various types of tobacco stems are treated in a targeted manner, long stems are pre-pressed and dried, short stems are pre-crushed and dried, crushed stems are directly used for composting without being dried, and stem crutches are directly used for composting. By means of wet stem classification treatment, differential drying, long stem pre-pressing and short stem pre-crushing, energy waste caused by excessive drying of other types of tobacco stems except for long stems is avoided, the tobacco stem shred making and slice making technology is substantially advanced, the comprehensive utilization rate of the tobacco stems is increased, and the dual goals of turning waste into wealth, reducing cost and improving efficiency are achieved.

Description

Technical Field

[0001] The invention belongs to the field of tobacco processing, and particularly relates to a process for sorting and processing wet tobacco stems after leaf and stem separation. Background Art

[0002] In the tobacco processing industry chain, tobacco stem processing during the threshing and re-roasting phase has long been handled in a crude manner. The current process generally employs a "curing first, then screening" model: after threshing and destemming, the tobacco stems are uniformly cured and dried. The stems are then screened through a vibrating screen to remove broken stems and sorted by length into long and short stems. This model has significant economic drawbacks and technical limitations: First, energy waste. The "curing first, then screening" approach requires all tobacco stems to be cured uniformly. Compared to the "wet stem multi-stage sorting followed by directional dehydration" approach, the combined curing of broken stems and shredded stems, which could otherwise be used directly in composting without curing, results in significant energy waste. Second, there is the issue of overdrying. Due to the varying surface areas of tobacco stems of different sizes, short and shredded stems dry faster than long stems. During the uniform curing phase, in order to achieve the target moisture content for the high-value long stems, the short and shredded stems are over-dried, resulting in a low moisture content. This increased brittleness of the short stems increases the breakage rate in subsequent processing, and the shredded stems are over-carbonized, making them difficult to use directly in composting and requiring additional pretreatment (such as crushing). The third is the problem of resource mismatch. It is difficult to accurately separate tobacco stems of different shapes during the screening process of mixed stems after baking, resulting in the mixing of high-value raw materials, long stems, and low-value materials, such as short and broken stems, and bent stems. This leads to a reduction in the quality of high-value raw materials due to mixing, and thus a reduction in the utilization rate.

[0003] The 2023 "Green Manufacturing Specifications for the Tobacco Industry" explicitly mandates a comprehensive tobacco stem utilization rate of ≥85%, but current processes fall far short of this target. Furthermore, the trend toward higher-end cigarette brands is driving demand for high-purity cut stems, which are double the price of standard cut stems, forcing a shift toward more refined tobacco stem processing. This invention breaks with the "pre-drying" mindset and provides a tobacco stem processing method that combines multi-stage wet stem sorting, targeted dehydration, and classified value-added utilization. Through refined sorting, differentiated drying, and targeted utilization, this method effectively reduces energy consumption in tobacco stem processing and improves the overall utilization rate of tobacco stems. Summary of the Invention

[0004] In response to the shortcomings of existing tobacco stem processing technologies and methods, the present invention provides a green and low-carbon tobacco stem processing technology. The present invention breaks through the traditional high-energy consumption model, changes the traditional tobacco stem processing method of drying first and then processing, and adopts a wet stem multi-level sorting process to achieve fine classification of tobacco stems. Then, each category of tobacco stems is subjected to precise, low-energy targeted processing: long stems are pre-pressed and dried, short stems are pre-crushed and dried, and broken stems and bent stems are directly used for composting without drying. Through wet stem classification, differentiated drying, long stem pre-pressing and short stem pre-crushing, energy consumption is reduced, and energy waste caused by excessive drying of tobacco stems other than long stems is avoided. This process has substantially advanced the tobacco stem silk and thin sheet making processes, improved the comprehensive utilization rate of tobacco stems and resource conversion efficiency, not only reduced waste emissions, but also achieved the dual goals of resource recycling (composting) and cost reduction and efficiency improvement, providing an effective path for energy conservation, emission reduction and sustainable development in the tobacco industry.

[0005] The tobacco stem processing technology of the present invention comprises the following process steps in order: screening of mixed wet stems, pre-pressing and baking of long stems, pre-breaking and baking of short stems, and composting of broken and crushed stems.

[0006] The specific steps include:

[0007] Step 1: Sift the mixed wet stems

[0008] The mixed wet stems after threshing and leaf separation are directly classified without being baked. The low-value stem bends are screened out through the stem bend screening device. The target long stems are screened out through the long-short stem screening device and the gap between the dividing end and the dropping end is adjusted. The broken stems are screened out through the broken stem screening device. Finally, the short stems are collected separately to achieve fine classification of wet stems and improve the comprehensive utilization rate of tobacco stems.

[0009] The wet stems refer to the main veins of tobacco leaves after threshing and separation from the leaves, which generally have the following characteristics: the moisture content is significantly higher than that of the finished tobacco stems, which is 16-20%, and they are irregular cylindrical in shape, with different lengths and thicknesses. Different shapes have different drying rates and their use values vary greatly.

[0010] Furthermore, when removing stems through the stem screening device, the gap between the stem screening rollers is set to 5.4-6.4mm. When screening stems, tobacco stems from major production areas are divided into two categories: the Huanghuai tobacco production area and the non-Huanghuai tobacco production area. The Huanghuai tobacco production area refers to the two major production areas of Henan and Shandong, where the stems are relatively coarse, so the stem screening roller gap is 6.4mm. The non-Huanghuai tobacco production area refers to other production areas, where the stems are relatively fine, so the stem screening roller gap is 5.4mm.

[0011] Furthermore, when passing through the long and short stem screening device, the long and short stem screening gap is set to 20 mm.

[0012] The target long stem length is >20 mm (industry standard YC / T 147-2023).

[0013] Furthermore, when passing through the stem crushing and screening device, the plane sieve hole diameter is 6 mm.

[0014] The length of the broken stem is ≤10mm, and the length of the short stem is 10mm<≤20mm (industry standard YC / T 147-2023).

[0015] Step 2: Pre-press and bake the long stems

[0016] The obtained long stems are processed and subjected to moisture-retention treatment by taking advantage of their moisture content to increase the moisture and temperature of the tobacco stems so that they meet the requirements of the stem pressing process. Flat strips of stem pieces are then obtained through processes such as posture adjustment, stem pressing, baking, stem crushing and screening, which are used as raw materials for subsequent stem shreds.

[0017] Furthermore, the tobacco stem temperature is raised to 55-65°C through tempering treatment, and the moisture content is increased to 28-30%.

[0018] Furthermore, during the stem pressing process, two rounds of pressing were performed, and the gaps between the pressing rollers were set to 1.2 mm and 0.8 mm, respectively.

[0019] Furthermore, during the baking process, the baking temperature of the stems is set to 80-85°C, and the moisture content of the stems after baking is controlled to be 10-13%.

[0020] Step 3: Pre-crush and bake the short stems

[0021] The obtained short stems are washed, mechanically crushed, sprayed with enzyme preparations, stored for a short time, and then baked and packaged to be used as raw materials for subsequent flake making.

[0022] Furthermore, the length of the tobacco stems is controlled to 2-6 mm by mechanical crushing to ensure their uniformity.

[0023] Furthermore, the enzyme preparation is composed of cellulase, pectinase and hemicellulase in a mass ratio of 1:1:0.5.

[0024] Furthermore, after spraying the enzyme preparation, the temperature is raised to 50-70°C and kept warm for 2 hours for short-term storage to promote the degradation of cellulose and pectin macromolecules in the tobacco stems and improve the sensory quality of the tobacco stems.

[0025] Furthermore, the baking refers to baking the enzymatically hydrolyzed tobacco stems in a drum dryer at a temperature of 70-80° C. for 15-20 minutes, and controlling the final moisture content to be 10-13%.

[0026] Step 4: Compost the stems

[0027] Without drying treatment, the sieved stems and broken stems can be directly composted and fermented to produce organic fertilizer.

[0028] Furthermore, the stems collected by screening are crushed and mixed with broken stems, and conventional high-nitrogen auxiliary materials are added to balance the C / N ratio to 25-30:1. The materials are piled for fermentation, and then detoxified through long-term composting to produce organic fertilizer.

[0029] During the long stem pre-pressing and baking process, in order to ensure the long stem pre-pressing effect, improve the thickness uniformity of the stem slices, and enhance the usability of the stem slices after pressing, the posture adjustment is achieved by a method comprising the following steps:

[0030] After conditioning, the long stems pass through a vibrating conveyor trough. Spaced protrusions perpendicular to the conveying direction and periodic vibrations within the conveying surface achieve bidirectional uniformity in both longitudinal stratification and lateral dispersion during conveying. The evenly distributed stems then pass through a W-shaped vibrating guide trough, where high-frequency, micro-amplitude excitation and directional vibrations achieve high-precision dynamic directional correction. This aligns the stems with the linear cutting direction of the rollers upon entry into the stem press, minimizing slippage and overlap between the rollers. This improves the uniformity of the stem thickness and ensures the stability of the stem pressing process. This process utilizes conventional equipment, operating parameters: the vibrating conveyor trough has a frequency of 470-520 Hz, an amplitude of 20-24 mm, a protrusion length of 40 mm, a lateral spacing of 20 mm, and a longitudinal spacing of 20 mm. The W-shaped guide trough has a guide span (the lateral spacing between the tops of adjacent vibrating units) of 40 mm and a vertical height of 10 mm. The high-frequency, micro-amplitude vibrations of the W-shaped guide trough, combined with the height difference of the conveying path, achieve uniform and directional distribution of the material.

[0031] During the long stem pre-pressing and baking process, in order to promote the baking effect of the stem slices, improve the moisture uniformity of the roasted stem slices, and reduce the leakage rate of the baking feeding process, the baking is achieved by a method including the following steps:

[0032] Based on the shape and moisture changes of tobacco stems, and taking into account the high adhesion brought by the flat shape and high moisture content of the stems, a swing-arm feeder is used to gently convey the stems to avoid the stems from being broken or agglomerated due to mechanical extrusion or friction; the reciprocating swing of the fan-shaped trajectory realizes the uniform distribution of the stem roasting machine mesh belt, providing a guarantee for the uniform moisture content of the stems after roasting, and at the same time preventing sticking and blocking, effectively reducing the leakage and blockage of traditional scraper feeding.

[0033] During the short stem pre-crushing and roasting process, in order to achieve the purpose of fine classification and utilization of short stems, a process pre-processing method based on the demand for thin slices is adopted, including the following steps:

[0034] Magnetic separation equipment is used to remove metal from wet short stems on the conveyor belt of the redrying plant to prevent metal impurities from damaging the crushing equipment in the subsequent process; running water is used to rinse to remove colloid, sand and other impurities on the surface of the tobacco stems; mechanical pre-crushing is used to reduce the particle size of the tobacco stems and increase the specific surface area by taking advantage of the moisture content; the compound enzyme preparation is evenly sprayed and then heated and kept warm, and short-term storage is used to promote the degradation of large molecular substances in the tobacco stems and reduce the negative effects of the tobacco stems on the sensory organs; finally, the tobacco stems are baked to the target moisture content and packaged.

[0035] This invention changes the traditional tobacco stem processing model of drying before processing, instead employing a multi-stage wet stem sorting process to achieve refined stem classification. In the tobacco processing industry, wet stem screening faces significant technical bottlenecks: 1) stem ends easily become stuck on the screen bars / rollers, causing mechanical blockage; 2) wet stems with leaves on them result in irregular material shape, making traditional bar screening inefficient.

[0036] The stem-breaking screening device used in the wet stem screening process of this invention is a vibrating rotary screening and rejection device. It uses a wave-like tobacco stem screening method to remove stem breaking. It employs a flat-segment + three-wave-segment composite curved surface design, increasing the screening stroke by 1.3 times through path optimization. It also utilizes the gravitational potential energy conversion generated by the wave surface drop to achieve a self-cleaning function, improving the screening effect. The vibrating rotary screening and rejection device used in this process is described in detail in the specific embodiment.

[0037] The beneficial effects of the present invention are embodied in:

[0038] Compared with the existing tobacco stem processing methods, the present invention has the following innovations and significant economic benefits: 1. It provides a processing technology for multi-stage sorting-directional dehydration-classification utilization of wet stems after threshing, forming a complete wet stem classification and refined processing process, which saves energy and improves efficiency at the source. The tobacco stems are directly separated after the leaves and stems are separated, and different tobacco stems are customized according to subsequent usage scenarios, which changes the traditional tobacco stem processing technology, improves the efficiency of tobacco stem utilization, avoids unnecessary drying links or over-drying from the source, and reduces overall processing energy consumption; 2. The shape of the tobacco stems is changed and delivered to industrial enterprises in the form of stem slices. This processing model is highly replicable and popularizable in leaf threshing and re-drying enterprises, and can be used for The redrying enterprises create profits and increase revenue, and the delivery mode of stem slices reduces the reprocessing links (such as crushing and screening) of industrial enterprises, indirectly reduces the energy consumption and carbon emissions of the downstream of the industrial chain, and improves the green level of the overall supply chain; 3. The introduction of the posture adjustment of long stems before pressing and the swing arm feeding method before baking the stem slices effectively ensures the stem pressing effect and the uniformity of the moisture content of the stem slices after baking, reduces the rework or over-drying caused by uneven moisture content, thereby avoiding additional energy waste and improving the energy efficiency of the drying link; 4. The wet stems are refinedly classified, differentially dried, and targetedly utilized, especially the stem bends and broken stems are directly used for composting without baking, which essentially reduces the energy consumption of tobacco stem processing and optimizes processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flow chart of the post-threshing wet stem classification processing process of the present invention.

[0040] Figure 2 This is the process flow chart for pre-pressing and baking wet long stems.

[0041] Figure 3 This is the process flow chart of enzymatic hydrolysis of wet short stem pre-breaking.

[0042] Figure 4 This is the flow chart of the composting fermentation process of wet crushed stems and stem ends.

[0043] Figure 5 This is a schematic structural diagram of the vibrating rotary screening and rejection device used in the present invention.

[0044] Figure 6 This is a structural schematic diagram of the rotating roller mechanism, the exciting mechanism and the discharging mechanism in the vibrating rotary screening and rejecting device used in the present invention.

[0045] Figure 7 This is a schematic structural diagram of the rotating roller mechanism and the excitation mechanism in the vibrating rotary screening and rejecting device used in the present invention.

[0046] Figure 8 This is a schematic structural diagram of the rotating roller, chain and positioning sleeve in the vibrating rotary screening and rejecting device used in the present invention.

[0047] Figure 9 This is a schematic structural diagram of the vibration excitation mechanism in the vibrating rotary screening and rejection device used in the present invention.

[0048] Figure 10 This is a schematic structural diagram of the bidirectional conveying mechanism in the vibrating rotary screening and rejection device used in the present invention.

[0049] In the figure: 11. Upper frame, 12. Lower frame; 2. Roller mechanism, 21. Roller, 211. Core shaft, 212. Sleeve, 22. Chain, 23. Driving wheel, 24. Reversing wheel, 25. Tensioning wheel, 26. Positioning sleeve; 3. Vibration mechanism, 31. Vibration base, 32. Flexible connecting part, 33. Vibration bracket, 34. Vibration motor, 35. Contact plate; 4. Bidirectional conveying mechanism, 41. Conveyor belt, 411. Stop edge, 42. Conveyor motor, 43. Dropping port; 5. Discharging mechanism. DETAILED DESCRIPTION

[0050] The technical solution of the present invention is further analyzed and explained below through specific embodiments.

[0051] In the following embodiments, the stem screening device used in the wet stem screening process is a vibrating rotary screening and rejection device, such as Figures 5-10As shown, the structure is as follows: the upper frame 11 is connected to the top of the lower frame 12 via an elastic component. It is equipped with a roller mechanism 2 comprising side plates, rollers 21, chains 22, drive wheels 23, reversing wheels 24, and positioning sleeves 26. The rollers 21, each with a positioning sleeve 26 in the middle, are closely spaced with their axes parallel to each other. A pair of chains 22 are mounted and fixed to each end of each roller 21, forming a roller belt with a closed annular structure. The positioning sleeves 26 are axially restrained on the rollers 21, with adjacent positioning sleeves 26 in close contact, forming sieve holes between adjacent rollers 21. The rollers 21 are radially positioned by positioning sleeves 26, with an outer diameter tolerance of ±0.05mm, to precisely control the width of the sieve holes. The positioning sleeves 26 are preferably axially restrained on the rollers 21 by retaining springs to achieve axial positioning of the positioning sleeves 26. The sieve hole width is preferably 5.4-6.4mm.

[0052] The driving wheel 23 and the reversing wheel 24 are symmetrically arranged in pairs on both sides of the roller belt, and are rotatably mounted on a pair of side plates arranged on both sides of the roller belt, and the side plates are fixed to the upper frame 11; the roller belt is tensioned on the driving wheel 23 and each reversing wheel 24, and can rotate around the driving wheel 23 and each reversing wheel 24 under the action of the driving wheel 23 connected to the roller motor; the frequency of the roller motor is preferably 50Hz±2%; the top surface of the roller belt is in the form of a plane and at least one upward inclined surface in its own movement direction.

[0053] In addition, an excitation mechanism 3 and a discharge mechanism 5 are provided; the fixed end of the excitation mechanism 3 is fixedly mounted on the upper frame 11, and its output end contacts and acts on the roller belt; a discharge mechanism 5 is provided between the top and bottom surfaces of the roller belt, and below the roller belt, respectively, for conveying the materials screened and sieved by the roller belt.

[0054] Preferably, each plane and each upward inclined surface is correspondingly provided with a vibration mechanism 3 serving as a screening drive mechanism.

[0055] The excitation mechanism 3 includes an excitation base 31, an excitation bracket 33, an excitation motor 34 and a contact plate 35; the contact plate 35 and the excitation motor 34 are both mounted and fixed on the excitation bracket 33, and the excitation bracket 33 is mounted and fixed to the upper frame 11 through the excitation base 31 which serves as the fixed end of the excitation mechanism 3; the contact plate 35 of the screening drive mechanism serves as the output end of the excitation mechanism 3, is located above the plane or upward inclined surface, and can, under the action of the excitation motor 34, periodically contact at least one positioning sleeve 26 in a corresponding plane or upward inclined surface.

[0056] The pendulum angle of the excitation motor 34 is preferably 70°±0.5°, and the frequency is preferably 50 Hz±2%.

[0057] Preferably, a vibration mechanism 3 serving as a screening drive mechanism is provided below the roller belt.

[0058] The contact plate 35 of the screening drive mechanism serves as the output end of the excitation mechanism 3 , is located below the bottom surface of the roller belt, and can periodically contact at least one positioning sleeve 26 in the bottom surface of the roller belt under the action of the excitation motor 34 .

[0059] The contact plate 35 is preferably a nylon contact plate. Nylon material has the advantages of excellent strength, good wear resistance, chemical resistance, high volume resistivity and high breakdown voltage, light weight, and easy processing.

[0060] Preferably, the excitation mechanism 3 further includes a flexible connection portion 32 .

[0061] A flexible connection portion 32 is connected between the excitation bracket 33 and the excitation base 31. The flexible connection portion 32 can isolate vibration transmission, reduce structural resonance, absorb excitation energy, and convert the rigid coupling between the excitation mechanism 3 and the upper frame 11 into an elastic buffer connection, thereby reducing the transmission efficiency of the periodic excitation force to the upper frame 11, preventing the periodic excitation force generated by the excitation mechanism 3 from being rigidly transmitted to the upper frame 11 and the parts connected to the upper frame 11, thereby avoiding problems such as loosening of threaded connections and cracking of welds caused by overall structural resonance, which is conducive to extending the service life and maintenance cycle of the device; the flexible connection portion 32 is preferably a rubber pad.

[0062] Preferably, the excitation mechanism 3 is provided with a pair of parallel excitation brackets 33, the excitation bracket 33 is a U-shaped structure with the middle part bent toward the roller belt, and a vibration base 31 is respectively installed and fixed at both ends, and a flexible connecting part 32 is padded between the end and the excitation base 31; the excitation motor 34 is located between the pair of excitation brackets 33 and is installed and fixed to the middle part of the pair of excitation brackets 33.

[0063] Preferably, the end of the contact plate 35 that contacts the positioning sleeve 26 serves as the terminal end and is in the form of a long strip of plate structure, and a frame structure with increasing width from the front end to the terminal end.

[0064] Preferably, the roller 21 includes a core shaft 211 and a sleeve 212. The ends of the core shaft 211 are respectively fitted with a pair of chains 22, and the sleeve 212 is fitted around the center of the core shaft 211. One end of the core shaft 211 is provided with a stopper for axial positioning, while the other end is provided with a stopper pin for axial positioning. When using the vibrating rotary screening and rejection device to screen materials, the screen aperture width can be adjusted by replacing sleeves of different diameters.

[0065] Preferably, the roller mechanism 2 further includes a tensioning wheel 25 ; the tensioning wheels 25 are symmetrically arranged in pairs on both sides of the roller belt, are rotatably mounted and connected to the side plates, and tension the roller belt in a direction opposite to the driving wheel 23 and the reversing wheel 24 .

[0066] The tensioning wheel 25 is preferably arranged in the middle of the bottom surface of the roller belt and tensions the roller belt from bottom to top.

[0067] Preferably, it also includes a bidirectional conveying mechanism 4, which is located between the top and bottom surfaces of the roller belt and above the discharge mechanism 5; the bidirectional conveying mechanism 4 includes a pair of conveying belts 41 arranged side by side and a pair of conveying motors 42 respectively used to drive the conveying belts 41 to rotate.

[0068] A pair of conveyor belts 41 form blanking ports 43 at opposite ends that are respectively connected to the discharge mechanism 5; the movement direction of the top surface of the conveyor belt 41 is parallel to the movement direction of the top surface of the roller belt, and the pair of conveyor belts 41 and the pair of blanking ports 43 cover the connecting section between the top surface and the bottom surface of the roller belt.

[0069] Preferably, skirt-shaped retaining edges 411 are integrally provided on both sides of the conveyor belt 41 .

[0070] The specific use includes the following process:

[0071] In the first step, according to the size and shape of the material to be screened, a sleeve 212 with a suitable outer diameter is selected, and each sleeve 212 on the roller belt is installed or replaced.

[0072] In the second step, the tobacco stems enter the roller mechanism from the flat surface of the roller belt. The flat surface vibrates at a high frequency and low amplitude under the action of the corresponding excitation mechanism 3, so that the tobacco stems are evenly spread on the flat surface and transported forward along with the movement of the flat surface.

[0073] During this process, part of the target stems pass through the sieve holes in the plane and fall to the bidirectional conveying mechanism 4, and are sent to the downstream process via the bidirectional conveying mechanism 4 and the corresponding discharging mechanism 5.

[0074] In the third step, the tobacco stems follow the plane to the end of the plane and enter at least one upward inclined surface. The upward inclined surface vibrates at a high frequency and low amplitude under the action of the corresponding excitation mechanism 3, screening the tobacco stems. The selected target stems pass through the sieve holes in the upward inclined surface and fall to the bidirectional conveying mechanism 4. They are then conveyed to the downstream process via the bidirectional conveying mechanism 4 and the corresponding discharge mechanism 5. The removed stems and unscreened stems are conveyed forward along the movement of the upward inclined surface until the tobacco stems are screened.

[0075] During this process, when the sieve hole with the embedded stem runs to the end of the upward slope (i.e. the highest position of the upward slope), the inclination angle of the roller belt surface near the sieve hole produces a gravity-centrifugal force composite decoupling effect, causing the embedded stem to break away from the sieve hole and fall.

[0076] In the fourth step, the stems follow the upward slope to the end of the last upward slope, and then most of the stems are separated from the roller belt under the action of gravity and fall to the corresponding discharge mechanism 5 for delivery.

[0077] In the fifth step, a small part of the stems are stuck in the sieve holes and move with the roller belt to the bottom of the roller belt; the bottom surface of the roller belt vibrates at a high frequency and low amplitude under the action of the corresponding excitation mechanism 3, so that the stems stuck in the sieve holes are separated from the bottom surface of the roller belt and fall to the corresponding discharge mechanism 5 for delivery.

[0078] The top surface of the roller belt of the above-mentioned vibrating rotary screening and rejection device is in the form of a plane and at least one upward inclined surface arranged in sequence. The plane is conducive to the uniform spreading of tobacco stems under the action of periodic excitation force, and the upward inclined surface has an extension effect, which extends the screening path compared to the plane with the same projection length. The upward inclined surface also has a clearing effect. When the screen hole with the stems embedded in it runs to the end of the upward inclined surface, the inclination angle of the roller belt surface near the screen hole produces a gravity-centrifugal force composite decoupling effect, so that the embedded stems are separated from the screen hole and fall, so as to reduce the false rejection rate of the device and eliminate the attenuation of screening efficiency caused by the stems stuck in the screen hole, thereby improving the screening effect and ensuring the continuity and stability of the screening process. It is particularly suitable for the screening of stems with irregular shapes.

[0079] The contact plate of the screening drive mechanism of the above-mentioned vibrating rotary screening and rejection device uses a periodic direct contact excitation method to periodically transmit the excitation force to the top surface of the roller belt, thereby enhancing the vibration efficiency during the screening process and thus improving the screening efficiency of the material. In addition, the contact plate uses a periodic direct contact excitation method to periodically transmit the excitation force to the bottom surface of the roller belt, which can also effectively solve the problem of material hanging on the stems, so that the stems stuck in the screen holes can be separated from the screen holes and fall to the corresponding discharge mechanism for delivery. The screened material is transported in both directions through a two-way conveying mechanism to prevent local accumulation and blockage of the material, ensuring that the material is efficiently and smoothly transported to the downstream discharge mechanism.

[0080] In actual operation, the vibrating rotary screening and rejection device demonstrated excellent results in separating broken stems from tobacco stems in various regions, including Sichuan, Hunan, Fujian, Jiangxi, and Jilin. The equipment operated stably and reliably, further demonstrating its adaptability to a wide range of production areas and process stability. Table 1 below compares the effectiveness of different devices in separating broken stems from tobacco stems in Sichuan.

[0081]

[0082] *Missing rate %: The ratio of the weight of the stem crescent in the target stem after screening to the total weight of the target stem sample.

[0083] * False rejection rate %: The ratio of the weight of non-stem agarwood in the sieved agarwood to the total weight of the agarwood sample.

[0084] The following uses the actual processing of high-quality tobacco stems in central Sichuan during the 2024 tobacco season at a threshing and redrying company as an example. The application of a refined processing technology for wet stem classification, including post-threshing wet stem screening, long stem pre-pressing and baking, short stem pre-crushing and baking, and stem and crushed stem composting, is compared with tobacco stem processing that is baked first and then screened. The specific implementation steps are as follows:

[0085] Example 1: New tobacco stem processing technology (including posture adjustment, stem baking and swing-arm feeding)

[0086] Step 1: After the leaf stems are separated, the mixed wet stems (moisture content 16-18%) are sequentially passed through a vibrating rotary screening and rejection device, a W-shaped diversion screening device, and a flat circular hole screening device to screen out and collect wet stems, long stems, short stems, and broken stem tobacco. The gap between the rollers of the stem screen is 5.4mm, the gap between the long and short stem screen is 20mm, and the diameter of the short broken stem screen is 6mm.

[0087] Step 2: The long stems are sent into the rehumidification drum at a flow rate of 2500kg / h, with a circulating air temperature of 80℃, a heating and humidification rate of 100%, and a front water flow rate of 315L / h. The temperature of the long stems is raised to 55-65℃, and the moisture content is increased to 28-30%. The speed of the rehumidification drum is appropriately slowed down to ensure the rehumidification effect of the long stems.

[0088] Step 3: After rehydration, the long stems are split in half and the direction of the stems entering the stem press is adjusted by the posture correction device so that the direction is basically consistent with the linear cutting direction of the pressing rollers;

[0089] Step 4: The long stems are pressed in two rounds by a tandem stem press, with roller gaps of 1.2mm and 0.8mm respectively;

[0090] Step 5: After pressing, the stem pieces are fed into the stem roasting machine by a swing arm feeder and roasted to a moisture content of 10-13%. The temperature of the stem roasting machine is 85℃, 80℃, and 80℃.

[0091] Step 6: After roasting, the stem slices are passed through a flat circular hole vibrating sieve to remove broken stems and tobacco powder, and the long stem slices are bagged;

[0092] Step 7: The screened wet short stems are screened again in the redrying plant to remove large-sized debris, and an electromagnetic iron remover and a permanent magnetic iron remover are used to remove ferrous metals.

[0093] Step 8: Rinse the short stems after metal removal with running water at a ratio of 1:8-12 for 30-45 seconds to remove impurities such as colloid and sand on the surface of the short stems and improve the cleanliness of the short stems;

[0094] Step 9: After cleaning, the short stems are sent to the crusher for pre-crushing to reduce the particle size of the short stems, and the stems of different particle sizes are sieved and separated to control the target stem size to 2-6mm to ensure its uniformity;

[0095] Step 10: Using a spray device, evenly add a composite enzyme preparation at a weight ratio of 0.8%-1.2% (the ratio here is calculated as the mass percentage of the composite enzyme preparation to the tobacco stems, and when adding the composite enzyme preparation, it is sprayed in the form of a solution), wherein the cellulase + pectinase + hemicellulase are compounded at a mass ratio of 1:1:0.5, and the temperature is raised to 50-70°C and maintained for 2 hours to promote the degradation of cellulose and pectin macromolecules in the tobacco stems and improve the sensory quality of the tobacco stems;

[0096] Step 11: After enzymatic hydrolysis, the tobacco stems are dried in a drum dryer at a temperature of 70-80°C for 15-20 minutes, and the final moisture content is controlled to be 10-13%;

[0097] Step 12: The sieved wet stems are mechanically crushed into small particles, and the wet crushed stems are evenly mixed in simultaneously, and high nitrogen auxiliary materials are added to balance to 25-30:1;

[0098] Step 13: The materials after C / N balance are piled and fermented under ventilation conditions, and fermented twice after the high temperature period. Then, the materials are piled and composted for a long time to achieve detoxification treatment and produce organic fertilizer.

[0099] Comparative example: baking first and then sorting processing technology

[0100] Step 1: After the leaves and stems are separated, the mixed wet stems are scraped and fed into the stem roasting machine with a flow rate of 4000-4200kg / h and roasted to a moisture content of 10-13%. The roasting machine temperatures are 100℃, 95℃, and 95℃.

[0101] Step 2: After roasting, the mixed stems are sequentially screened through a flat steel bar screening device with a gap of 8 mm, a φ3 mm stainless steel perforated plate screening device, a 5×25 mm stainless steel perforated plate screening device, and a φ6 mm stainless steel perforated plate screening device to screen out and collect the dried stems, broken pieces, long stems, short stems, and broken stems;

[0102] Step 3: After drying, the short stems are packaged and sent to the sheet mill to be made into tobacco sheets by papermaking;

[0103] Step 4: After drying, the stems and broken stems are mechanically crushed into small particles, and high nitrogen auxiliary materials are added to balance to 25-30:1;

[0104] Step 5: Same as step 13 of Example 1.

[0105] In terms of economic indicators, the weight of each type of tobacco stems screened out before and after roasting was weighed and measured, and their proportions were calculated as shown in Table 2 below.

[0106]

[0107] As can be seen from Table 2, compared with the method of the comparative example, the method of the present invention screens out a larger amount of long stems of high-value raw materials, and the proportion of non-target stems (crooked stems and broken stems) is 21.44%. No forced baking is required, which effectively saves energy consumption.

[0108] In terms of quality indicators, YC / T 147-2023 was used to detect the tobacco stem structure of various samples as shown in Table 3 below. The detection method was to first classify them into long stems, short stems, and broken stems based on the length dimension, and then classify them into stem bends and non-stem bends based on the morphology dimension. Those with contact points with the tobacco stems were counted as stem bends.

[0109]

[0110] *After classification by length, the long stem rate + short stem rate + broken stem rate = 100%. The industry standard YC / T 147-2023 clearly defines the requirements for the long stem rate and broken stem rate of tobacco stem products, so only the long stem rate and broken stem rate need to be tested.

[0111] As shown in Table 3, the rejection rate of bent stems in wet long stems after screening is 3.86%, which is better than 18.73% of the control example. The long stem rate is 99.42%, which is higher than 83.23% of the control example. That is, the method of the present invention effectively improves the use value of the target long stems.

[0112] Example 2: New tobacco stem processing technology (no posture adjustment before pressing, stem baking and scraper feeding)

[0113] Steps 1 and 2 are the same as steps 1 and 2 of Example 1;

[0114] Step 3: After the moisture is restored, the long stems are split in half and directly sent to the stem press;

[0115] Step 4: Same as Example 1;

[0116] Step 5: After pressing, the stem pieces are fed into the stem roasting machine through a scraper and roasted to a moisture content of 10-13%. The temperature of the stem roasting machine is 85℃, 80℃, and 80℃.

[0117] Step 6: Same as Example 1;

[0118] Steps 7-13: Same as Example 1.

[0119] Three groups of 30 stems were sampled after the second pressing, and the thickness of the stems was measured using a handheld thickness gauge, and the standard deviation was calculated. The moisture content of the packaged stems and packaged long stems was sampled and tested according to YC / T 147-2023, and the coefficient of moisture variation was calculated. The results are shown in Table 4.

[0120]

[0121] It can be seen from Table 4 that, compared with the method of Example 2, adjustment of the tobacco stem posture before pressing effectively improves the thickness uniformity of the stem slices; compared with the method of the comparative example, the method of the present invention has a significant promoting effect on improving the moisture uniformity of the tobacco stems during baking.

Claims

1. A tobacco stem processing process, characterized in that The steps include: Step 1: Sift the mixed wet stems Directly classify the mixed wet stems after leaf stem separation, remove the bent stems through the stem bending screening device, separate the target long stems through the long and short stem screening device, remove the broken stems through the broken stem screening device, and finally collect the short stems separately; Step 2: Pre-press and bake the long stems The obtained long stems are subjected to a moisture conditioning treatment to increase the moisture and temperature of the long stems. Then, after posture adjustment, stem pressing, baking, stem crushing and screening, flat strips of stems are obtained, which are used as raw materials for subsequent stem shreds. Step 3: Pre-crush and bake the short stems The obtained short stems are washed, mechanically crushed, sprayed with enzyme preparations, stored for a short time, and then baked and packaged to be used as raw materials for subsequent flake production; Step 4: Compost the stems The sieved stems and broken stems are directly composted and fermented to produce organic fertilizer.

2. The tobacco stem processing process according to claim 1, characterized in that: In step 1, when the stems are screened out by the stem screening device, the gap between the stem screening rollers is set to 5.4-6.4 mm.

3. The tobacco stem processing process according to claim 1, characterized in that: In step 2, the long stem temperature is raised to 55-65°C and the moisture content is increased to 28-30% through rehumidification treatment.

4. The tobacco stem processing process according to claim 3, characterized in that: In step 2, the posture of the long stems after moisture conditioning is adjusted before pre-pressing, and the long stems are conveyed through a vibrating conveying trough, and the longitudinal stratification and transverse diffusion of the long stems are bidirectionally uniformed by blocking with transversely spaced ribs and periodic vibration; the long stems uniformly distributed in the transverse and longitudinal directions pass through a W-shaped vibrating guide trough, and high-frequency micro-amplitude excitation and directional vibration are used to achieve high-precision dynamic directional correction of the long stems, so that the long stems are consistent with the linear cutting direction of the pressing roller when entering the stem press.

5. The tobacco stem processing process according to claim 1, characterized in that: In step 2, during the stem pressing process, two rounds of pressing are performed, and the gaps between the pressing rollers are set to 1.2 mm and 0.8 mm respectively.

6. The tobacco stem processing process according to claim 1, characterized in that: In step 2, before baking, the baking feeding of the stem slices is completed by using a swing arm feeder, and the reciprocating swing of the fan-shaped trajectory is used to achieve uniform distribution of the stem baking machine mesh belt.

7. The tobacco stem processing process according to claim 1, characterized in that: In step 2, during the baking process, the baking temperature of the stems is set to 80-85° C., and the moisture content of the stems after baking is controlled to be 10-13%.

8. The tobacco stem processing process according to claim 1, characterized in that: In step 3, the short stems are mechanically crushed to control the length of the tobacco stems to 2-6 mm.

9. The tobacco stem processing process according to claim 1, characterized in that: In step 3, the enzyme preparation is composed of a compound of cellulase, pectinase and hemicellulase.

10. The tobacco stem processing process according to claim 9, characterized in that: After spraying the enzyme preparation, the temperature is raised to 50-70°C and kept warm for 2 hours to promote the degradation of cellulose and pectin macromolecules in the tobacco stems and improve the sensory quality of the tobacco stems.

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