Patent Publication Number: US-9901112-B2

Title: Apparatus for producing reconstituted tobacco sheet via dry paper-making method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. national stage of PCT/CN2015/071307 filed Jan. 22, 2015, which claims priority from Chinese application 201410155207.6 filed Apr. 17, 2014, both of which are hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     This invention relates to an apparatus for producing tobacco products, more particularly, to a production line using an air-laid paper-making process to produce reconstituted tobacco leaves (TRL) and equipment used therefor. 
     BACKGROUND OF THE INVENTION 
     Reconstituted tobacco leaf, that is, tobacco sheet, also known as reconstituted tobacco or homogenized tobacco, is produced mainly from tobacco dust, stems, low-grade tobacco leaves, and additional foreign fibers, adhesives or other additives. As a kind of material widely used in tobacco product, reconstituted tobacco has the advantages of low cost, good filling performance, less tar content in the smoke, and so on. The production of reconstituted tobacco began in the &#39;50s of the 20th century. Its production processes mainly include slurry process, rolling process and paper-making process, and the paper-making process is further divided into wet paper-making process and air-laid paper-making process. However, being it wet paper-making process or air-laid paper-making process, plant fiber pulp boards have to be fiberized for further formation. The wet paper-making process uses a first-level refiner and a second-level refiner to moderately grind fibers to make them become individualized after using a hydrapulper to crush the pulp boards. These fibers will then become pulp after being beat and fibrillated in the water. The pulp will then be put in a pulp tank for use after it is processed by a high-density sand remover and a tickler. As for the air-laid paper-making process, it fiberizes the fibers in the air without water. Usually, it uses high-speed rotating needle dials, hammers, claw disks or second-level crushing devices to fiberize the fibers to make them individualized. 
     After 20 years of research and use, this technology is quite well developed and has been widely used tobacco products. However, it still has some problems. Firstly, after the processes of extracting, concentrating and refining, scent and aroma of the tobacco are significantly reduced. Secondly, the reconstituted tobacco produced by this process is structurally solid and slick on the surface. Therefore, it has lower weight gain (normally less than 40%) and lacks taste. Thirdly, it produces large amounts of wastewater. In order to overcome the disadvantages of traditional wet paper-making processes, and to reduce environmental pollution and harmful components in China, a new process and equipment in this field for improving the quality of reconstituted tobacco and reducing environment pollution has to be developed. 
     A new kind of equipment using air-laid paper-making process to produce reconstituted tobacco can not only protect the environment by reducing the large amount of sewage discharge generated during the production but also prevent aroma loss in reconstituted tobacco. Its weight gain on the base sheets can be increased to more than 200%, and both filling power and wet strength has improved. Compared with traditional paper-making process, it can also reduce more harmful aspects in the smoke. 
     The air-laid paper-making process was born in the &#39;60s of the 20th century and introduced into China at the end of the &#39;80s of the 20th century. After 20 years of development, the air-laid paper-making process has become fully mature and well-known. For example, Chinese Patent Application No. 200610117771.4 discloses a paper-making machine that uses aid-laid process. Moreover, a Chinese patent No. 201310393610.8 discloses a complete production line that uses air-laid process to produce reconstituted tobacco. Other than having two more adhesive and drying devices, the machine has no different from ordinary air-laid paper-making machine in terms of manufacturing techniques. It does not have special devices, especially fiberizing, forming, sizing and drying devices, necessary for producing reconstituted tobacco. Even the most well-known wet paper-making machine cannot be used directly to produce reconstituted tobacco, instead, corresponding devices required by the nature of reconstituted tobacco has to be designed for production of the same. Similarly, an ordinary air-laid paper-making machine cannot be used directly to produce reconstituted tobacco either; instead, corresponding devices required by the nature of reconstituted tobacco has to be designed or added for production of the same. 
     SUMMARY OF THE INVENTION 
     In order to overcome the above disadvantages, this invention provides a production line and equipment therefor that can overcome drawbacks in both the wet paper-making and air-laid paper-making processes for producing reconstituted tobacco. 
     This invention provides an apparatus that uses air-laid paper-making process to produce reconstituted tobacco, comprising a fiberizer, a base-sheet forming device, a pulp sizing device and a drying device connected in series, wherein the fiberizer comprises a rough crusher  101 , a fine crusher  102 , a fiber storage tank  103  and a fiber calculator  104  connected in series, a material inlet is arranged at a front end of the rough crusher  101 , and a material outlet of the fiber calculator  104  is connected to the base-sheet forming device of the apparatus, the fiberizer further comprises an anti-static humidifying device, the anti-static humidifying device comprises a high-moisture air generator  105  and high-moisture air pipelines, an output of the high-moisture air generator  105  is connected to the material inlet of the rough crusher  101  and the material outlet of the fiber calculator  104  via the high-moisture air pipelines respectively. 
     The base-sheet forming device comprises forming mesh belts, a mesh belt conveying device, a base-sheet forming device rack  218  arranged above the forming mesh belts, one or more sets of forming heads are arranged inside the base-sheet forming device rack  218 , a blow-off device is provided in the forming head, a negative pressure device is arranged underneath the forming mesh belts, a first screen cylinder  213  and a second screen cylinder  214  are arranged symmetrically to each other in each set of forming head, a first fiber conveying pipeline  201  and a second fiber conveying pipeline  202  are arranged along an axial direction of the first screen cylinder  213 , a third fiber conveying pipeline  203  and a fourth fiber conveying pipeline  204  are arranged along an axial direction of the second screen cylinder  214 , the first fiber conveying pipeline  201  and the second fiber conveying pipeline  202  are arranged symmetrically in an upper part of the first screen cylinder  213 , the third fiber conveying pipeline  203  and the fourth fiber conveying pipeline  204  are arranged symmetrically in an upper part of the second screen cylinder  214 , a first breaking roller  212  and a second breaking roller  211  are arranged in a lower part of the first screen cylinder  213  and a lower part of the second screen cylinder  214  respectively, the first breaking roller  212  and the second breaking roller  211  are located exactly under center points of the first screen cylinder  213  and the second screen cylinder  214  respectively, a front circular passage  215  and a rear circular passage  216  communicating internal spaces of the first screen cylinder  213  and the second screen cylinder  214  are arranged at front sides and rear sides thereof respectively. 
     The pulp sizing device comprises a constant pressurized storage tank  305  and a pulp distributor  322  connected to a material outlet of the constant pressurized storage tank  305 , the pulp distributor  322  has multiple pulp outlets  324 , each being connected to a pulp buffer  314  via a proportioning pump  325 , the pulp buffer  314  is connected to a pulp inlet  329  of a dual spray nozzle  328  via a check valve  319 , the dual spray nozzle  328  is further equipped with a compressed air inlet  330 , a compressed air regulating valve  331  is connected to the compressed air inlet  330  through a pipeline, the pulp sizing device further comprises a sizing device rack  304  arranged on the mesh belt, installation boxes  301  are arranged on both sides of the sizing device rack  304 , the pulp distributor  322  and the proportioning pump  325  are installed inside the installation boxes  301 , the pulp buffer  314  is installed on a pulp buffer supporting rack  334  located in the middle of the sizing device rack  304 , a nozzle supporting rack  332  is arranged in the middle of the sizing device rack  304 , a plurality of nozzle supporting racks  333  with adjustable lengths and angles are arranged on the nozzle supporting rack  332 , dual spray nozzles  328  are installed on the nozzle supporting racks  333 . 
     The drying device comprises a drying device body and a hot-air inlet  411  connected to the drying device body, wherein three fixed dampers of a first damper  401 , a second damper  402  and a third damper  403  are arranged in the drying device body, the three fixed dampers are arranged parallel to each other and distances between two neighboring dampers are equal to each other, the three fixed dampers are arranged in the drying device body and connected to the hot-air inlet  411 , an adjustable baffle is arranged at a tail end of each damper, and a moisture-discharging device  407  is arranged at a rear end of the drying device body. 
     In the invention, the rough crusher  101  of the fiberizer further has an independent material inlet arranged at the front end thereof, the material inlet comprises a fiber material inlet  112  and a particulate material inlet  113 , with independent switches arranged on the fiber material inlet  112  and the particulate material inlet  113  respectively. 
     Preferably, a movable and detachable multi-passage retainer is arranged at the material inlet of the rough crusher  101  of the fiberizer. 
     More preferably, the first screen cylinder  213  and the second screen cylinder  214  of the base-sheet forming device are of opposite rotating directions. 
     According to another preferable implementation of the invention, each screen cylinder of the base-sheet forming device and a breaking roller arranged in the screen cylinder are of opposite rotating directions. 
     In this invention, the first fiber conveying pipeline  201  and the fourth fiber conveying pipeline  204  of the base-sheet forming device are of a same length, the second fiber conveying pipeline  202  and the third fiber conveying pipeline  203  are of a same length, the first fiber conveying pipeline  201  is longer than the second fiber conveying pipeline  202 , the first fiber conveying pipeline  201  and the second fiber conveying pipeline  202  extend from a front part of the first screen cylinder  213  toward the interior of the first screen cylinder  213 , and the third fiber conveying pipeline  203  and the fourth fiber conveying pipeline  204  extend from a rear part of the first screen cylinder  213  toward the interior of the first screen cylinder. 
     Preferably, the pulp buffer supporting rack  334  of the pulp sizing device is of a   shape. 
     More preferably, the constant pressurized storage tank  305  of the pulp sizing device comprises a tank body, a pulp outlet  313  arranged at a bottom of the tank body, a pulp inlet  312  arranged on a side at an upper part of the tank body and an agitator  306  arranged inside the tank body, the constant pressurized storage tank  305  is further equipped with a pressure indicator  307 , an overpressure relief valve  308  arranged on an upper part of the tank body, a constant pressure controller  309  and a compressed air regulating valve  310 , an agitator motor  311  connected to the agitator  306  is further arranged on the upper part of the tank body. 
     In this invention, the pulp buffer  314  of the pulp sizing device has a buffer pulp inlet  317  and a buffer pulp outlet  318 , the pulp buffer inlet  317  is arranged on a side at a lower-middle part of the pulp buffer  314 , the pulp buffer outlet  318  is arranged at a bottom of the pulp buffer  314 , an exhaust valve  315  and a pressure indicator  316  are further arranged at an upper part of the pulp buffer. 
     In this invention, the adjustable baffles and the dampers of the drying device are connected through movable pins, and angles between the adjustable baffles and the dampers are adjustable. 
     Preferably, the forced moisture-discharging device  407  of the drying device comprises a negative pressure box  409  and moisture deflectors  408  arranged inside the negative pressure box  409 , the negative pressure box  409  is communicated to the body of the drying device, and connected to a negative-pressure blower  410  via a pipeline, and the negative-pressure blower  410  is connected to a controller of a frequency converter. 
     More preferably, lengths of the first damper  401 , the second damper  402  and the third damper  403  of the drying device have equal differences between one and another, and partition the drying box into four sections. 
     Technical solutions of the invention will be described in more detail in the following. 
     The apparatus that uses air-laid paper-making process to produce reconstituted tobacco comprises a fiberizer, a base-sheet forming device, a pulp sizing device and a drying device connected in series. The first process for using the air-laid paper-making process to produce reconstituted tobacco is to fiberize plant fiber pulp boards. However, conventional production lines using air-laid paper-making process have advantages. On one hand, in order to make the tobacco taste good, two or more plant fibers are needed to be added through a metering device in the process of fibrillation to make them into multi-fiber base sheets. On the other hand, due to the nature of reconstituted tobacco produced by the air-laid paper-making machine, it is necessary to reduce the amount of foreign fibers on base sheets. To do so, when being fiberized, fiber-shaped or granule-shaped tobacco materials need to be added to be fiberized together with plant fibers simultaneously, such that reconstituted tobacco base-sheets with less foreign fibers are produced. However, the conventional fiberizer used for air-laid paper-making process can only fiberize a single kind of fiber. Other than that, static electricity is another problem. In the air-laid paper-making process, the process of fiberizing needs to be run in the air, during which static electricity will be formed when fibers are span and rubbed at high speed in the air. When there is too much static electricity accumulated on the surface of the fibers, these fibers will get together as to affect the dispersal, transmission and formation of the fibers. Usually, this phenomenon can become more serious under an ambient humidity of lower than 50%, resulting in production shutdown. 
     Therefore, in the apparatus of the invention, the fiberizer comprises a rough crusher  101 , a fine crusher  102 , a fiber storage tank  103  and a fiber calculator  104  connected in series. A material inlet is arranged at a front end of the rough crusher  101 , and a material outlet of the fiber calculator  104  is connected to the base-sheet forming device of the apparatus. The fiberizer further comprises an anti-static humidifying device, the anti-static humidifying device comprises a high-moisture air generator  105  and high-moisture air pipelines, an output of the high-moisture air generator  105  is connected to the material inlet of the rough crusher  101  and the material outlet of the fiber calculator  104  via the high-moisture air pipelines respectively. 
     The rough crusher  101  of the fiberizer further has an independent material inlet arranged at the front end thereof, the material inlet comprises a fiber material inlet  112  and a particulate material inlet  113 , with independent switches arranged on the fiber material inlet  112  and the particulate material inlet  113  respectively. 
     Preferably, the rough crusher  101  may have two or more sets of material inlets. 
     By arranging two or more sets of material inlets on sides of the rough crusher, additionally introduced fiber-shaped or granule-shaped materials can be added to the rough crusher through these inlets. These extra added materials, together with the mixed plant fiber pulp boards coming from the material inlet, will be crushed into 1-2 cm 2  chips by rolling knives of the rough crusher. After being fiberized by fluted discs of the fine crusher, these chips, mixed with fiber-shaped or granule-shaped materials, will be put into a storage tank, whose agitators will mix these materials together. Finally, these mixed materials will be delivered to the fiber forming device by the fiber calculator. The above-inlets are controlled by a frequency converter, which establishes relevant modules for speed and quantity of the material inlet to make the formulation of different kinds of fibers in line with the one required by techniques in producing reconstituted tobacco base-sheets with the air laid process. 
     Preferably, a movable and detachable multi-passage retainer is arranged at the material inlet of the rough crusher  101  of the fiberizer. 
     Through arranging the movable and multi-passage retainer at the material inlets of the rough crusher, different kinds of plant fiber pulp boards can be conveniently fed to the rough crusher to be fiberized through separate passages, which is very convenient. When a single kind of fiber needs to be fiberized, the retainer can be removed. 
     In this invention, the high-moisture air generator may be a high-pressure nozzle or an ultrasonic atomizer. Preferably, a high-moisture air generator with a capacity of 1 m 3  is arranged on an operating side of the fiberizer, so as to provide sufficient atomizing moist air with a humidity of over 80% with the high-pressure nozzles or ultrasonic atomizer. A closed loop is formed by an φ 16 mm PE pipe arranged at the outlet of the high-moisture air generator and connecting a blower at the material inlet of the rough crusher and a blower at the fiber calculator  104 . Under the influence of negative pressure of the fiberizing system, the wet air will constantly be sucked in to moisten an internal delivery system for plant fiber pulp boards. 
     By using the paper-making process, also known as wet paper-making process, to produce reconstituted tobacco, firstly, lower-grade tobacco materials are extracted with water; secondly, after insoluble matters and added natural fibers are made into fibers, these fibers will go into the paper-making machine to be made into sheets. Thirdly, after being dried, this paper will be soaked in concentrated extraction liquid and additive agent. Finally, after being dried, the paper will be the finished product. Reconstituted tobacco produced by such paper-making process has certain strength, better filling power and less tar content when being used in cigarette, but it has disadvantages, such as creating large amounts of sewage discharge when producing it, requiring a lot of equipment investment having higher running costs. 
     Base-sheet formation is the second step in using the air-laid paper-making process to produce reconstituted tobacco, with a principle as follows: after being fiberized, natural fibers will be dispersed in the air. Then, the fibers will be pneumatically sent to the forming device. Each forming head is equipped with two screen cylinders that have small openings all over their bodies. The two screen cylinders are laid horizontally on the forming belt and of opposite rotating directions. Pipelines for delivering the fibers and nail rollers for beating fibers are arranged in the screen cylinder. The nail rollers and the screen cylinder are rotating in opposite directions so that the fibers delivered by wind can be beaten. The fibers, after being beaten, drop down from the screen cylinder and fall on the forming belt. A vacuum chamber forming negative pressure is arranged beneath the forming belt. Under the protection from negative pressure, a fibrous layer is formed and the forming belt moves forward, forming a consecutive and an even fibrous layer, namely, the base sheet of the reconstituted tobacco produced by the air-laid paper-making process. And then, the next manufacturing process follows. 
     The base-sheet forming device of the invention comprises forming mesh belts, a mesh belt conveying device, a base-sheet forming device rack  218  arranged above the forming mesh belts, one or more sets of forming heads are arranged inside the base-sheet forming device rack  218 , a blow-off device is provided in the forming heads, a negative pressure device is arranged underneath the forming mesh belts, a first screen cylinder  213  and a second screen cylinder  214  are arranged symmetrically to each other in each set of forming heads, a first fiber conveying pipeline  201  and a second fiber conveying pipeline  202  are arranged along an axial direction of the first screen cylinder  213 , a third fiber conveying pipeline  203  and a fourth fiber conveying pipeline  204  are arranged along an axial direction of the second screen cylinder  214 , the first fiber conveying pipeline  201  and the second fiber conveying pipeline  202  are arranged symmetrically in an upper part of the first screen cylinder  213 , the third fiber conveying pipeline  203  and the fourth fiber conveying pipeline  204  are arranged symmetrically in an upper part of the second screen cylinder  214 , a first breaking roller  212  and a second breaking roller  211  are arranged in a lower part of the first screen cylinder  213  and a lower part of the second screen cylinder  214  respectively, the first breaking roller  212  and the second breaking roller  211  are located exactly under center points of the first screen cylinder  213  and the second screen cylinder  214  respectively, a front circular passage  215  and a rear circular passage  216  communicating internal spaces of the first screen cylinder  213  and the second screen cylinder  214  are arranged at front sides and rear sides thereof respectively. 
     Preferably, the first screen cylinder  213  and the second screen cylinder  214  are of opposite rotating directions, each set of screen cylinders and the breaking roller arranged therein are of opposite rotating directions. 
     More preferably, the first fiber conveying pipeline  201  and the fourth fiber conveying pipeline  204  of the base-sheet forming device are of a same length, the second fiber conveying pipeline  202  and the third fiber conveying pipeline  203  are of a same length, the first fiber conveying pipeline  201  is longer than the second fiber conveying pipeline  202 . 
     Especially preferably, the first fiber conveying pipeline  201  and the fourth fiber conveying pipeline  204  are 50-60 cm, and the second fiber conveying pipeline  202  and the third fiber conveying pipeline  203  are 30-40 cm. 
     More preferably, the first fiber conveying pipeline  201  and the second fiber conveying pipeline  202  extend from a front part of the first screen cylinder  213  toward the interior of the first screen cylinder  213 , and the third fiber conveying pipeline  203  and the fourth fiber conveying pipeline  204  extend from a rear part of the first screen cylinder  213  toward the interior of the first screen cylinder. 
     In this invention, two or more delivery pipelines may be arranged in the screen cylinder of the base-sheet forming device. 
     For the purpose of further improving the uniformity of fiber distribution, more openings may be made on the fiber delivery pipelines. 
     In this invention, by arranging two fiber conveying pipelines with different lengths inside each screen cylinder, the fibers will have more exits, thereby improving the accuracy of the delivery of fibers. 
     A front and rear circular passages communicating internal space of one forming head are arranged between two screen cylinders in the forming head, reducing accumulation of fibers at both ends of the screen cylinders. 
     After going through the base-sheet forming device, paper webs are formed after the fibrous layer is pre-pressed, which is the so-called reconstituted tobacco base sheets. The base sheets are laid on the belt. The sizing device sizes sizing agents on the base sheets. Negative pressure on the reverse side of the base sheets helps to protect base sheets from tilting and pulp from spilling when sizing, such that the sizing agents can easily penetrate the base sheets. A quantity for the sizing agents on the base sheets can be adjusted as required. After being sized with sizing agents, the base sheets go into the drying box to be dried under a drying temperature of 105° C.-110° C. After the drying, one side of the base sheet has sizing agents on its surface. Then the base sheets is transferred to lower side of the sizing drying mesh through the belt, where the other side will be sized with sizing agents. Negative pressure protection is also present on the other side, preventing the base sheets from tilting and the pulp from spilling, which also facilitates the penetration of the sizing agents to the base sheets. The quantity for the sizing agents on the base sheets can be adjusted as required. After being sized with sizing agents, the base sheets go into the drying box to be dried under a drying temperature of 105° C.-110° C. After drying, the base sheets is transferred to the upper side of the sizing drying mesh through the belt where, once again, the first side will be sized with sizing agents. There is negative pressure protecting the reverse side of the sizing side to prevent base sheets from tilting and pulp from spilling. After four times of sizing and drying, the base sheet becomes reconstituted tobacco which, through the delivery mesh, is transported to the cutting machine, where the reconstituted tobacco is cut into pieces of a certain size, becoming the finished product. 
     The pulp sizing device of the invention comprises a constant pressurized storage tank  305  and a pulp distributor  322  connected to a material outlet of the constant pressurized storage tank  305 , the pulp distributor  322  has multiple pulp outlets  324 , each being connected to a pulp buffer  314  via a proportioning pump  325 , the pulp buffer  314  is connected to a pulp inlet  329  of a dual spray nozzle  328  via a check valve  319 , the dual spray nozzle  328  is further equipped with a compressed air inlet  330 , a compressed air regulating valve  331  is connected to the compressed air inlet  330  through a pipeline. 
     The pulp sizing device further comprises a sizing device rack  304  arranged on the mesh belt, installation boxes  301  are arranged on both sides of the sizing device rack  304 , the pulp distributor  322  and the proportioning pump  325  are installed inside the installation boxes  301 , the pulp buffer  314  is installed on a pulp buffer supporting rack  334  located in the middle of the sizing device rack  304 , a nozzle supporting rack  332  is arranged in the middle of the sizing device rack  304 , a plurality of nozzle supporting racks  333  with adjustable lengths and angles are arranged on the nozzle supporting rack  332 , dual spray nozzles  328  are installed on the nozzle supporting racks  333 . 
     Preferably, the pulp buffer supporting rack  334  of the pulp sizing device is of a   shape. 
     The constant pressurized storage tank  305  comprises a tank body, a pulp outlet  313  arranged at a bottom of the tank body, a pulp inlet  312  arranged on a side at an upper part of the tank body and an agitator  306  arranged inside the tank body, the constant pressurized storage tank  305  is further equipped with a pressure indicator  307 , an overpressure relief valve  308  arranged on an upper part of the tank body, a constant pressure controller  309  and a compressed air regulating valve  310 , an agitator motor  311  connected to the agitator  306  is further arranged on the upper part of the tank body. 
     More preferably, the pulp buffer  314  of the pulp sizing device has a buffer pulp inlet  317  and a buffer pulp outlet  318 , the pulp buffer inlet  317  is arranged on a side at a lower-middle part of the pulp buffer  314 , the pulp buffer outlet  318  is arranged at a bottom of the pulp buffer  314 , an exhaust valve  315  and a pressure indicator  316  are further arranged at an upper part of the pulp buffer. 
     In this invention, the proportioning pump  325  may be screw proportioning pump, a peristaltic proportioning pump or a diaphragm proportioning pump. A single proportioning pump of each of the above or combinations thereof may be used. 
     In this invention, the pulp distributor  322  has four to eight pulp outlets  324  of. Through the pulp distributor, a constant pressurized storage tank may be connected to multiple sets of sizing devices to realize stable and synchronized sizing. 
     Preferably, two sets of nozzle supporting racks  332  are arranged symmetrically from each other in the installation box. Each nozzle supporting rack  332  has 4 to 10 nozzle supporting racks  333  arranged on an external side. 
     In this invention, the check valve  319  may be an angle seat valve, an electric check valve or a pneumatic check valve. A single check valve of each of the above or combinations thereof may be used. 
     Preferably, an adhesive receiving device  303  is arranged beneath the installation box  301 . The adhesive receiving device  303  comprises an adhesive receiving tank and an adhesive receiving fence arranged on the adhesive receiving tank. An adhesive scraping device comprises a drive motor, an adhesive scraping roller connected to the drive motor, and an adhesive wiping board arranged on one end of the adhesive scraping roller. 
     The drying device comprises a drying device body and a hot-air inlet  411  connected to the drying device body, wherein three fixed dampers of a first damper  401 , a second damper  402  and a third damper  403  are arranged in the drying device body, the three fixed dampers are arranged parallel to each other and distances between two neighboring dampers are equal to each other, the three fixed dampers are arranged in the drying device body and connected to the hot-air inlet  411 , an adjustable baffle is arranged at a tail end of each damper, and a moisture-discharging device  407  is arranged at a rear end of the drying device body. 
     The adjustable baffles and the dampers of the drying device are connected through movable pins, and angles between the adjustable baffles and the dampers are adjustable. Preferably the angle is between 60° to 150°. 
     In this invention, there may be three or more pieces of dampers. 
     Preferably, in this invention, two sets of identical drying devices are connected via the forced moisture-discharging device. 
     The forced moisture-discharging device  407  comprises a negative pressure box  409  and moisture deflectors  408  arranged inside the negative pressure box  409 , the negative pressure box  409  is communicated to the body of the drying device, and connected to a negative-pressure blower  410  via a pipeline, and the negative-pressure blower  410  is connected to a controller of a frequency converter. 
     Preferably, lengths of the first damper  401 , the second damper  402  and the third damper  403  of the drying device have equal differences between one and another. The three adjustable baffles are of different lengths, and differences between two neighbouring adjustable baffles are equal to each other and the drying box is partitioned into four sections. 
     More preferably, the distance between the three dampers is 8-15 cm. 
     Three or more fixed dampers with equal difference in length and connected to respective adjustable dampers with movable pins are arranged inside the oven. The angle between fixed dampers and adjustable dampers can be adjusted based on actual needs during operation. 
     Forced moisture discharging device is arranged between every two sets of ovens. The forced moisture discharging device comprises a deflector, a negative pressure box, which is connected to a negative pressure blower. The negative-pressure blower controlled by a frequency converter, forming a low temperature, fast drying system through drying, moisture discharging, second drying, and second moisture discharging. 
     Compared with conventional technologies, this invention has the following advantageous effects. 
     First of all, the fiberizer is equipped with different interfaces for various materials and an internal humidifying pipeline, such a configuration helps to, in the first place, overcome defect of utilizing a single fiber as raw material of the conventional technologies, and multi-fiber and additives help to improve the taste of reconstituted tobacco leaves. In the second place, it helps to reduce static electricity generated in the process of fiberizing, eliminating the need of adding antistatic agent, preventing the negative influence of antistatic agent on the taste of reconstituted tobacco leaves. 
     In comparison with low basis weight of forming device and conventional technologies, this invention has the following advantages: A. It overcomes problem of utilizing a single feed pipe by the conventional technology; instead, multiple pipes are used to improve uniformity and controllability of feed material. B. Circular passages can prevent fiber accumulating in the box, making formed reconstituted tobacco leave base sheet of good uniformity. C. Weight of traditional dry sheet is around 40 g/m 2 , and grams below 40 g/m 2  is difficult to achieve. According to the invention, a better controllability is achieved as a result of accurate measure of the fiber during transportation, moreover, uniform distribution of the fiber is realized during transportation, together with uniform blowing air, good controllability of negative pressure box, and uniform adjustability of negative pressure, basis weight of less than 20 g/m 2  for base sheet can be achieved. 
     In comparison with the conventional technologies, the sizing device with high viscosity and high solid content of this invention has the following advantages. A. In conventional technologies, a solid content of the sized adhesive is around 6%, while the pulp of this sizing device has a solid content of above 15%, making it of poor mobility. By utilizing this sizing device, pulp with high solid content can be evenly distributed to reach an accurate measure. B. It overcomes the defect that only sizing material of lower viscosity can be applied in the conventional sizing device for air-laid paper-making process technology. Sizing material for the present device contains more tobacco dusts, tobacco extract, and adhesive agent, which can be evenly distributed by using the present apparatus. C. The present sizing device also overcomes the problem that only weight gain of up to 40% can be achieved by utilizing the conventional device, while weight gain for the current device can reach above 80%, with 200% weight gain to the base sheet (In this invention, weight gain is interpreted as increased weight of the base sheet after the base sheet is sized, dried. Ratio between additional weight to the original base sheet is weight gain. This index is a calculation for tobacco component contained in RTL, which is also an important index for RTL). 
     In comparison with the conventional technologies, forced moisture elimination drying device at low temperature has the following 2 advantages. A. Moisture content after drying of the conventional dried sheet is low, allowing a drying oven of low drying efficiency to achieve a good drying effect. With the present invention, moisture content in the final sheet is above 7 times that of the base sheet. To prevent tobacco components loss during drying process, temperature of drying oven cannot be increased without limitation. This invention adopts forced moisture elimination device which is installed between 2 sections of drying ovens to speed up air circulation to remove moisture in RTL. B. In the drying device a deflector is introduced, which is different from the conventional drying oven without flow guide device leading to over drying caused by uneven distribution of inside hot air. The drying device of the present invention is equipped with the deflector, which can be adjusted as needed to ensure the whole sheet is dried synchronously, and to avoid tobacco aroma loss caused by partially overheated and generating burnt taste. 
    
    
     
       DESCRIPTION OF DRAWING 
         FIG. 1  is a front view of a fiberizer and a count and converging system 
         FIG. 2  is a top view of a rough crusher. 
         FIG. 3  schematically illustrates a base sheet forming device. 
         FIG. 4  schematically illustrates an arrangement of two fiber conveying pipelines in a forming head. 
         FIG. 5  schematically illustrates an arrangement of three fiber conveying pipelines in a forming head. 
         FIG. 6  schematically illustrates a breaking roller in a forming head. 
         FIG. 7  schematically illustrates a screen cylinder and circular passages in a forming head. 
         FIG. 8  schematically illustrates a pulp sizing device of the invention. 
         FIG. 9  is a top view of a rack and installation boxes. 
         FIG. 10  schematically illustrates a single set of pulp sizing device. 
         FIG. 11  schematically illustrates a constant pressure storage tank. 
         FIG. 12  schematically illustrates a pulp distributor. 
         FIG. 13  schematically illustrates proportioning pump. 
         FIG. 14  schematically illustrates a pulp buffer. 
         FIG. 15  schematically illustrates a check valve. 
         FIG. 16  schematically illustrates dual spray nozzle. 
         FIG. 17  schematically illustrates a compressed air regulating valve. 
         FIG. 18  schematically illustrates an arrangement of dual spray nozzles. 
         FIG. 19  is a front view of an adhesive receiving fence. 
         FIG. 20  is a top view of an adhesive receiving fence. 
         FIG. 21  is an internal structure of a drying oven. 
         FIG. 22  schematically illustrates a drying oven 
         FIG. 23  is a top view of a drying oven. 
     
    
    
     NUMERAL REFERENCES 
       101  rough crusher,  102  fine crusher,  103  fiber storage tank,  104  fiber calculator,  105  high humidity air generator,  106  air inlet of rough crusher,  107  air inlet of fiber calculator,  108  movable retainer,  109  feeding channel separated by movable retainer,  112  fiber material inlet,  113  particulate material inlet,  114  material inlet of rough crusher 
       201  first fiber conveying pipeline,  202  second fiber conveying pipeline,  203  third fiber conveying pipeline,  204  fourth fiber conveying pipeline,  205  fifth fiber conveying pipeline,  206  sixth fiber conveying pipeline,  207  seventh fiber conveying pipeline,  208  eight fiber conveying pipeline,  209  ninth fiber conveying pipeline,  210  tenth fiber conveying pipeline,  211  first breaking roller,  212  second breaking roller,  213  first screen cylinder,  214  second screen cylinder,  215  front circular passage,  216  rear circular passage,  217  negative pressure box,  218  base sheet forming device rack,  219  mesh belt 
       301  installation box,  302  negative pressure box for sizing device,  303  adhesive receiving device,  304  sizing device rack,  305  constant pressure storage tank,  306  agitator,  307  pressure indicator,  308  overpressure safety valve,  309  constant pressure controller,  310  compressed air regulating valve,  311  agitator motor,  312  pulp inlet,  313  pulp outlet,  314  pulp buffer,  315  pressure relieve valve,  316  pressure indicator,  317  pulp inlet,  318  pulp outlet,  319  check valve,  320  pulp inlet,  321  pulp outlet,  322  pulp distributor,  323  pulp inlet,  324  pulp outlet,  325  proportioning pump,  326  pulp inlet,  327  pulp outlet,  328  dual spray nozzle,  329  pulp inlet,  330  compressed air inlet,  331  compressed air regulating valve,  332  main nozzle supporting rack,  333  movable nozzle supporting rack  334  pulp buffer supporting rack,  335  adhesive receiving fence,  336  rotating shaft,  337  adhesive scraper,  338  rotary motor 
       401  first damper,  402  second damper,  403  third damper,  404  first adjustable baffle,  405  second adjustable baffle,  406  third adjustable baffle,  407  forced moisture discharging device,  408  deflector,  409  negative pressure box,  410  negative pressure blower,  411  hot air inlet 
     Detail Description of the Embodiments 
     The invention will be described more detail in the following in connection with detailed embodiments. The embodiments are for illustrative purpose only and do not intend to limit the technical scope of the invention, which is defined by the appended claims. 
       FIGS. 1 and 2  illustrates a fiberizer, which comprises a rough crusher  101 , a fine crusher  102 , a fiber storage tank  103  and a fiber calculator  104  connected in series. A material inlet is arranged at a front end of the rough crusher  101 , and a material outlet of the fiber calculator  104  is connected to the base-sheet forming device for producing reconstituted tobacco by using air-laid paper-making process. The fiberizer further comprises a high-moisture air generator  105  and high-moisture air pipelines, an output of the high-moisture air generator  105  is connected to the material inlet of the rough crusher  101  and the material outlet of the fiber calculator  104  via the high-moisture air pipelines respectively. 
     The rough crusher  101  further has an independent material inlet arranged at the front end thereof, the material inlet comprises a fiber material inlet  112  and a particulate material inlet  113 , with independent switches arranged on the fiber material inlet  112  and the particulate material inlet ( 113 ) respectively. A movable and detachable multi-passage retainer is arranged at the material inlet. 
     By arranging two or more sets of material inlets on sides of the rough crusher, additionally introduced fiber-shaped or granule-shaped materials can be added to the rough crusher through these inlets. These extra added materials, together with the mixed plant fiber pulp boards coming from the material inlet, will be crushed into 1-2 cm 2  chips by rolling knives of the rough crusher. After being fiberized by fluted discs of the fine crusher, these chips, mixed with fiber-shaped or granule-shaped materials, will be put into a storage tank, whose agitators will mix these materials together. Finally, these mixed materials will be delivered to the fiber forming device by the fiber calculator. The above-inlets are controlled by a frequency converter, which establishes relevant modules for speed and quantity of the material inlet to make the formulation of different kinds of fibers in line with the one required by techniques in producing reconstituted tobacco base-sheets with the air laid process. 
     The high-moisture air generator has a capacity of 1 m 3  and provide sufficient atomizing moist air with a humidity of over 80% with the high-pressure nozzles or ultrasonic atomizer. A closed loop is formed by an φ 16 mm PE pipe arranged at the outlet of the high-moisture air generator and connecting a blower at the material inlet of the rough crusher and a blower at the fiber calculator  104 . Under the influence of negative pressure of the fiberizing system, the wet air will constantly be sucked in to moisten an internal delivery system for plant fiber pulp boards. 
     Fiberized fiber will be sent into a base sheet forming device. As shown in  FIGS. 3-7 , the base-sheet forming device comprises forming mesh belts, a mesh belt conveying device, a base-sheet forming device rack  218  arranged above the forming mesh belts, one or more sets of forming heads are arranged inside the base-sheet forming device rack  218 , a blow-off device is provided in the forming head, a negative pressure device is arranged underneath the forming mesh belts, a first screen cylinder  213  and a second screen cylinder  214  are arranged symmetrically to each other in each set of forming head, a first fiber conveying pipeline  201  and a second fiber conveying pipeline  202  are arranged along an axial direction of the first screen cylinder  213 , a third fiber conveying pipeline  203  and a fourth fiber conveying pipeline  204  are arranged along an axial direction of the second screen cylinder  214 , the first fiber conveying pipeline  201  and the second fiber conveying pipeline  202  are arranged symmetrically in an upper part of the first screen cylinder  213 , the third fiber conveying pipeline  203  and the fourth fiber conveying pipeline  204  are arranged symmetrically in an upper part of the second screen cylinder  214 , a first breaking roller  212  and a second breaking roller  211  are arranged in a lower part of the first screen cylinder  213  and a lower part of the second screen cylinder  214  respectively, the first breaking roller  212  and the second breaking roller  211  are located exactly under center points of the first screen cylinder  213  and the second screen cylinder  214  respectively, a front circular passage  215  and a rear circular passage  216  communicating internal spaces of the first screen cylinder  213  and the second screen cylinder  214  are arranged at front sides and rear sides thereof respectively. 
     The first fiber conveying pipeline  201  and the fourth fiber conveying pipeline  204  are of a same length, the second fiber conveying pipeline  202  and the third fiber conveying pipeline  203  are of a same length, and the first fiber conveying pipeline  201  is longer than the second fiber conveying pipeline  202 . 
     The first fiber conveying pipeline  201  and the second fiber conveying pipeline  202  extend from a front part of the first screen cylinder  213  toward the interior of the first screen cylinder  213 , and the third fiber conveying pipeline  203  and the fourth fiber conveying pipeline  204  extend from a rear part of the first screen cylinder  213  toward the interior of the first screen cylinder. 
     a. After going through the base-sheet forming device, the base sheets are sized by the pulp sizing device, and then dried by the drying device as shown in  FIG. 8-23 . The pulp sizing device comprises a constant pressurized storage tank  305  and a pulp distributor  322  connected to a material outlet of the constant pressurized storage tank  305 , the pulp distributor  322  has multiple pulp outlets  324 , each being connected to a pulp buffer  314  via a proportioning pump  325 , the pulp buffer  314  is connected to a pulp inlet  329  of a dual spray nozzle  328  via a check valve  319 , the dual spray nozzle  328  is further equipped with a compressed air inlet  330 , a compressed air regulating valve  331  is connected to the compressed air inlet  330  through a pipeline. The pulp sizing device further comprises a sizing device rack  304  arranged on the mesh belt, installation boxes  301  are arranged on both sides of the sizing device rack  304 , the pulp distributor  322  and the proportioning pump  325  are installed inside the installation boxes  301 , the pulp buffer  314  is installed on a “ ” shaped pulp buffer supporting rack  334  located in the middle of the sizing device rack  304 . A nozzle supporting rack  332  is arranged in the middle of the sizing device rack  304 , a plurality of nozzle supporting racks  333  with adjustable lengths and angles are arranged on the nozzle supporting rack  332 , dual spray nozzles  328  are installed on the nozzle supporting racks  333 . 
     The constant pressurized storage tank  305  comprises a tank body, a pulp outlet  313  arranged at a bottom of the tank body, a pulp inlet  312  arranged on a side at an upper part of the tank body and an agitator  306  arranged inside the tank body. The constant pressurized storage tank  305  is further equipped with a pressure indicator  307 , an overpressure relief valve  308  arranged on an upper part of the tank body, a constant pressure controller  309  and a compressed air regulating valve  310 . An agitator motor  311  connected to the agitator  306  is further arranged on the upper part of the tank body. 
     The pulp buffer  314  has a buffer pulp inlet  317  and a buffer pulp outlet  318 . The pulp buffer inlet  317  is arranged on a side at a lower-middle part of the pulp buffer  314 , the pulp buffer outlet  318  is arranged at a bottom of the pulp buffer  314 , an exhaust valve  315  and a pressure indicator  316  are further arranged at an upper part of the pulp buffer. 
     The pulp distributor  322  has four pulp outlets  324  of. Through the pulp distributor, a constant pressurized storage tank may be connected to multiple sets of sizing devices to realize stable and synchronized sizing. 
     Two sets of nozzle supporting racks  332  are arranged symmetrically from each other in the installation box. Each nozzle supporting rack  332  has 8 nozzle supporting racks  333  arranged on an external side. 
     An adhesive receiving device  303  is arranged beneath the installation box  301 . The adhesive receiving device  303  comprises an adhesive receiving tank and an adhesive receiving fence arranged on the adhesive receiving tank. An adhesive scraping device is arranged on the adhesive receiving fence and comprises a drive motor, an adhesive scraping roller connected to the drive motor, and an adhesive wiping board arranged on one end of the adhesive scraping roller. 
     The drying device comprises a drying device body and a hot-air inlet  411  connected to the drying device body, wherein three fixed dampers of a first damper  401 , a second damper  402  and a third damper  403  are arranged in the drying device body, the three fixed dampers are arranged parallel to each other and distances between two neighboring dampers are equal to each other. The three fixed dampers are arranged in the drying device body and connected to the hot-air inlet  411 . An adjustable baffle is arranged at a tail end of each damper, and a moisture-discharging device  407  is arranged at a rear end of the drying device body. 
     The adjustable dampers and fixed dampers are connected with movable pins. The angles between the adjustable baffle and the damper are adjustable. 
     Two sets of identical drying devices are connected via the forced moisture-discharging device. The forced moisture-discharging device  407  comprises a negative pressure box  409  and moisture deflectors  408  arranged inside the negative pressure box  409 , the negative pressure box  409  is communicated to the body of the drying device, and connected to a negative-pressure blower  410  via a pipeline, and the negative-pressure blower  410  is connected to a controller of a frequency converter. 
     Forced moisture discharging device is arranged between every two sets of drying devices. The forced moisture discharging device comprises a deflector, a negative pressure box, which is connected to a negative pressure blower. The negative-pressure blower controlled by a frequency converter, forming a low temperature, fast drying system through drying, moisture discharging, second drying, and second moisture discharging. 
     With the above devices, on one hand, the fiberizer is equipped with different interfaces for various materials and an internal humidifying pipeline. As a result, multi-fiber and additives may be used at the same time, which helps to improve the taste of reconstituted tobacco leaves. The humidifying device helps to reduce static electricity generated in the process of fiberizing, effectively preventing the negative influence of antistatic agent on the taste of reconstituted tobacco leaves. 
     By utilizing multiple passages for material transfer and the unique design with breaking rollers, screen cylinders and annular devices, uniformity of incoming material and controllability are improved. Therefore, there will be no fiber accumulating inside the chamber, rendering a better uniformity for the formed base sheet. Since the fiber distributes evenly in the conveying pipelines with good controllability, basis weight of base sheet is less than 20 g/m 2    
     The sizing device of this invention can guarantee a higher solid content in the pulp to be evenly distributed and accurately measured. Therefore, pulp containing more tobacco dusts, tobacco extract, and adhesive agent may be sized, which has a strong adaptability. 
     In addition, the forced moisture discharging device is adopted to prevent tobacco components loss during the drying process, and to prevent significant temperature increase in the drying oven. Forced moisture elimination device is arranged between 2 sets of drying ovens to speed up air circulation to remove moisture in RTL. Drying device is installed with deflector to ensure whole sheets to dry synchronously, and to avoid tobacco aroma loss caused by partially high temperature and generating burnt taste. 
     Thus, the apparatus of the present invention can improve the overall productivity of reconstituted tobacco with obvious excellent effect.