Water circulation system and method for producing paper-making method tobacco sheets

Abstract

The invention relates to the technical field of tobacco sheets, in particular to a water circulation system and method for paper-making process tobacco sheet production. A whole-line water system is divided into four relatively independent but associated units, independent running and non-interference of concentrated and dilute white water are achieved, municipal clean water enters the clean water unit after being heated to be applied to blanket spraying, enters the dilute white water unit after being purified, and is circularly purified in the units to form C-grade white water used for fourdrinier net spraying, extraction water and the like, and the clean water is recycled. And the water flows to the concentrated white water unit step by step for diluting and debugging the slurry, so that step-by-step use of clear water, on-demand purification of reclaimed water and tail-end discharge of sewage are realized, the requirements of all water consumption points are matched, and excessive water purification treatment capacity is avoided on the basis of meeting the water quality requirement. According to the production water circulating system disclosed by the invention, by improving the reuse proportion of reclaimed water at each stage and reasonably arranging the water demand, the clear water consumption in the production process is effectively reduced, the loss of available materials is reduced, and the sewage discharge amount is directly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of reconstituted tobacco leaves, in particular to a water circulation system and method for producing tobacco sheets by a papermaking method. Background Art

[0002] Papermaking tobacco flakes are tobacco products (hereinafter referred to as tobacco flakes) that are processed and reorganized using papermaking technology, using tobacco waste stems, flakes, etc. in cigarette production as raw materials. They have the characteristics of low density, high filling value, excellent processability, and strong plasticity of product intrinsic quality and style characteristics. Driven by the goal of improving the quality of Chinese cigarette products, the production technology and quality of tobacco flakes have developed rapidly, and in recent years, they have developed into an important raw material for Chinese cigarettes. At present, the industry adopts the "separation before combination" flake production process, that is, the tobacco raw materials are first soaked in hot water (also known as extraction) and then squeezed to achieve solid-liquid separation, and then the liquid phase (i.e., the extract) is purified, concentrated, and flavored to form a coating liquid, and the solid phase (i.e., pulp) is pulped, fiberized (mainly wood pulp) and filled (mainly light calcium carbonate), and dehydrated to form a base sheet; then the coating liquid is applied to the base sheet to achieve reorganization, and then dried and cut to form tobacco flakes for cigarette processing.

[0003] The core process of tobacco flake production line is papermaking process, which uses papermaking machine and auxiliary system which are basically the same as those in traditional papermaking industry to form the prepared pulp into paper-like flakes after molding and multi-stage dehydration. As in papermaking industry, the preparation and papermaking of pulp must be dispersed in water, and the paper machine is a dehydration process, and the dehydrated long net, blanket, etc. need to be cleaned. Therefore, a large amount of water is required in tobacco flake production. Generally, about 35-50m3 of clean water is consumed for each ton of product produced. 3 (called water consumption per ton of production, or water consumption for short); and due to the particularity of tobacco flakes, it is inconvenient to use or overuse water treatment process additives such as PAM, PAC, etc. in production, resulting in a low reuse rate of reclaimed water in the water system. In order to maintain the cleanliness of the water system (residual conditions of fine fibers, fillers, anions and cations, etc.), it is necessary to continuously replenish and replace water, further exacerbating the problems of high water consumption and high emissions; and excessive treatment brings about a series of problems such as increased loss of available materials (such as fine fibers, fillers, etc.), increased difficulty in treatment and increased costs.

[0004] In the water system of tobacco flake production line, the water removed from the pulp in the paper machine net is generally called concentrated white water. After simple purification, it is mainly used for pulp dilution and concentration adjustment, and then returned to the pulp system for recycling; the water collected after the paper machine net cleaning and the press felt cleaning is generally called dilute white water. After multi-stage purification, it is used for net cleaning again. Among them, the cleaning of the press felt mainly uses heated clean water. However, since the tobacco flake industry started and developed later than the papermaking industry, the design cognition of the water system varies from company to company, and the differences are large due to different process and equipment selection. 1) In the water system of a certain manufacturer's production line, the concentrated and dilute white water is not clearly distinguished. The water removed and collected by the paper machine is concentrated together (that is, the concentrated and dilute white water is mixed). After the first-level filtration and purification, it is used for pulp dilution and concentration adjustment, and after the second-level centrifugal purification, it is used for net cleaning. There are problems such as unclear division of the water system, accumulation of impurities in the water, water for net cleaning does not meet the water quality requirements, and low cleaning efficiency of the long net. 2) In the water system of a certain second manufacturer’s production line, there is no clear distinction between concentrated and dilute white water. After the concentrated and dilute white waters are mixed and treated at multiple stages, they are mixed with clean water in proportion to meet the water quality requirements for cleaning the mesh. There are problems such as high water consumption and complicated process flow. 3) In the water system of a certain third manufacturer’s production line, there is a distinction between concentrated and dilute white waters, but the dilute white water is purified by filtration and flotation in two stages. A certain amount of flocculation aids are used in the flotation process. Due to the problem of control over the use of aids, the process is facing elimination, and the two-stage purification still cannot meet the long mesh cleaning requirements. 4) In the water system of a certain fourth manufacturer’s production line, the cleanliness of the water used in the paper machine system is not guaranteed. The pulp is washed before it goes online to remove fine components in the pulp in advance and reduce its contamination of the paper machine’s long mesh and felts. However, this leads to problems such as increased loss of available materials, reduced product yield, and increased difficulty in sewage treatment.

[0005] Therefore, it is of great significance to optimize and improve the existing water system, reduce the waste of available materials, avoid problems such as excessive treatment of reclaimed water, and at the same time achieve water conservation and ensure that water quality meets standards. Summary of the invention

[0006] In view of the problems existing in the prior art, such as complex process, inability to balance water consumption and water quality, material waste and excessive treatment of reclaimed water, the purpose of the present invention is to provide a water circulation system and method for papermaking tobacco sheet production, to optimize and improve the existing water system, to achieve process goals such as independence of each unit in the water system and water conservation through a simpler process path and more economical equipment investment.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a water circulation system for producing tobacco sheets by a papermaking method, comprising a clean water unit, a dilute white water unit, a concentrated white water unit and an extraction and concentration water unit;

[0009] The clean water unit comprises a hot water tank, a squeeze white water tank and a squeeze white water filter; the hot water tank is connected to each spray point of the felt of the press section of the paper machine; the squeeze white water tank is used to collect the separated spray water of each spray point of the felt of the press section of the paper machine after use; the water inlet of the squeeze white water filter is connected to the water outlet of the squeeze white water tank;

[0010] The dilute white water unit comprises a dilute white water tank, a dilute white water purification device and a Class C white water tank which are fluidly connected in sequence; the inlet of the dilute white water tank is respectively connected to the water outlet of the squeeze white water filter of the clean water unit and the dilute white water outlet of the white water disk of the paper machine wire section; the dilute white water purification device comprises a white water centrifuge, a Class B white water tank, a membrane filtration water supply tank and a white water membrane filter which are fluidly connected in sequence, the inlet of the white water centrifuge is connected to the outlet of the dilute white water tank, the outlet of the white water membrane filter is connected to the inlet of the Class C white water tank; the outlet of the Class C white water tank is connected to the spray system of the paper machine wire section;

[0011] The concentrated white water unit includes a Class A white water tank and a concentrated white water tank; the Class A white water tank is used to provide water for pulp dilution and concentration adjustment, and the inlet of the Class A white water tank is connected with the water outlet of the broke filter and the water outlet of the squeeze white water filter; the concentrated white water tank is used to collect concentrated white water from the paper machine wire; the water outlet of the concentrated white water tank and the Class C white water outlet after the paper machine wire is sprayed are connected with the water inlet of the broke pool; the broke pool is connected with the broke filter, and the water outlet of the broke filter is connected with the inlet of the Class A white water tank;

[0012] The extraction and concentration water unit includes an extraction hot water tank, an extraction liquid tank, a concentration evaporator and an evaporation and condensation water tank which are fluidically connected in sequence; the inlet of the extraction hot water tank is connected to the outlet of the Class C white water tank of the dilute white water unit; the outlet of the evaporation and condensation water tank is connected to the inlet of the Class B white water tank of the dilute white water unit.

[0013] A second aspect of the present invention provides a water circulation method for producing tobacco sheets by a papermaking process, comprising the following steps:

[0014] (1) Clean water process: The hot water in the hot water tank is transported to each spray point of the felt in the paper machine press section. The used spray water is collected and transported to the press white water tank and filtered to obtain filtered water;

[0015] (2) Dilution white water process: a portion of the water filtered in step (1) enters a dilution white water tank, the effluent of the dilution white water tank is centrifuged to obtain Class B white water and transported to the Class B white water tank, the effluent of the Class B white water tank is membrane filtered to obtain Class C white water and transported to the Class C white water tank, the effluent of the Class C white water tank is used for spraying the paper machine wire section, and the spraying water collected by the white water tray of the paper machine wire section is returned to the dilution white water tank;

[0016] (3) Concentrated white water process: the rest of the water filtered in step (1) is transported to the Class A white water tank. The water from the Class A white water tank is used to dilute and concentrate the pulp, and finally forms the pulp on the screen and forms it in the paper machine wire section. The concentrated white water from the paper machine wire section enters the concentrated white water tank. The water from the concentrated white water tank and the Class C white water sprayed by the paper machine wire roller enter the broke pool together, and mix with the broke to form broke pulp. The broke pulp is filtered to form Class A white water and flows back to the Class A white water tank.

[0017] (4) Extraction and concentration process: The water from the Class C white water tank is heated by steam to form extraction hot water, which is then subjected to three-stage continuous countercurrent extraction to form an extract, which enters the concentrator to form a concentrated solution. During the concentration process, excess water is collected and returned to the Class B white water tank.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The water circulation system and method for producing tobacco sheets by the papermaking method provided by the present invention divides the water system of the whole line into 4 relatively independent but related units, so as to realize independent operation of concentrated and dilute white water without interfering with each other. The municipal clean water is used for blanket spraying after heating, enters the dilute white water unit after purification, and circulates and purifies in the unit to form Class C white water, which is used for long net spraying, extraction water, etc., and flows to the concentrated white water unit step by step for pulp dilution and debugging, so as to realize the step-by-step use of clean water, on-demand purification of reclaimed water and terminal discharge of sewage, and cooperate with the needs of each water use point. On the basis of meeting the water quality requirements, the water purification treatment volume is not excessive; by increasing the reuse ratio of reclaimed water at each level and reasonably arranging the water demand, the clean water consumption in the production process is effectively reduced, the loss of available materials is reduced, and the sewage discharge is directly reduced.

[0020] 2. The water circulation system and method for producing tobacco sheets by the papermaking method of the present invention are as follows: the main water replenishment point of the whole system is the hot water tank added with municipal clean water, and other points are not replenished unless there is an abnormality or the opening shift; the main drainage (sewage) points are, in sequence, the continuous sewage discharge of Class A white water tank, the continuous sewage discharge of concentrated white water tank, the continuous sewage discharge of concentrated water from the white water membrane filter, the continuous sewage discharge of the slag phase of the white water centrifuge, etc.; the purification process in the whole water system adopts the physical mode, and does not use any water flocculation (such as polyaluminium chloride PAC, polyacrylamide PAM, chitosan and modified chitosan, etc.) treatment agents.

[0021] 3. The water circulation system and method for producing tobacco flakes by the papermaking method of the present invention have the characteristics of clear process path, low clean water consumption, high reuse / recycling ratio, and less sewage discharge, and have good application value and economic value for the current production of tobacco flakes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a schematic diagram of a water circulation system for producing tobacco sheets by a papermaking method according to an embodiment of the present invention.

[0023] Figure markings: 1-hot water tank; 2-vacuum gas-liquid separation device; 3-squeezed white water tank; 4-squeezed white water filter; 5-diluted white water tank; 6-white water centrifuge; 7-B-grade white water tank; 8-membrane filtration water supply tank; 9-white water membrane filter; 10-C-grade white water tank; 11-A-grade white water tank; 12-concentrated white water tank; 13-extraction hot water tank; 14-extraction liquid tank; 15-concentrating evaporator; 16-evaporation condensation water tank; 17-concentrated liquid tank; 18-condensation water transition tank; Ⅰ-clean water unit; Ⅱ-diluted white water unit; Ⅲ-concentrated white water unit; Ⅳ-extraction concentrated water unit. DETAILED DESCRIPTION

[0024] The water circulation system and method for producing tobacco sheets by papermaking method of the present invention are described in detail below.

[0025] In order to reduce the waste of available materials and avoid problems such as excessive treatment of grey water, the inventor divided the entire water system into four relatively independent but related units, so that concentrated and dilute white water can operate independently without interfering with each other, and the step-by-step use of clean water, purification of grey water on demand and terminal discharge of sewage can be achieved without excessive water purification. By increasing the reuse ratio of grey water at all levels and rationally arranging water demand, the consumption of clean water in the production process can be effectively reduced, the loss of available materials can be reduced, and the sewage discharge can be directly reduced.

[0026] The present invention provides a water circulation system and method for producing paper-making tobacco sheets, and the specific technical scheme is as follows:

[0027] The first aspect of the present invention provides a water circulation system for producing tobacco sheets by papermaking method, such as Figure 1 As shown, it includes clean water unit I, dilute white water unit II, concentrated white water unit III and extraction concentrated water unit IV;

[0028] The clean water unit I comprises a hot water tank 1, a squeeze white water tank 3 and a squeeze white water filter 4; the hot water tank 1 is connected to each spray point of the felt of the press section of the paper machine; the squeeze white water tank 3 is used to collect the separated spray water of each spray point of the felt of the press section of the paper machine; the squeeze white water filter 4 is used to filter the water output from the squeeze white water tank;

[0029] The dilute white water unit II comprises a dilute white water tank 5, a dilute white water purification device and a Class C white water tank 10 which are fluidically connected in sequence; the inlet of the dilute white water tank 5 is respectively connected to the water outlet of the squeeze white water filter 4 and the dilute white water outlet of the white water disk of the paper machine wire section; the dilute white water purification device comprises a white water centrifuge 6, a Class B white water tank 7, a membrane filtration water supply tank 8 and a white water membrane filter 9 which are fluidically connected in sequence, the inlet of the white water centrifuge 6 is connected to the outlet of the dilute white water tank 5, the outlet of the white water membrane filter 9 is connected to the inlet of the Class C white water tank 10; the outlet of the Class C white water tank 10 is connected to the spray system of the paper machine wire section;

[0030] The concentrated white water unit III includes a Class A white water tank 11 and a concentrated white water tank 12; the Class A white water tank 11 is used to provide water for pulp dilution and concentration adjustment, and the inlet of the Class A white water tank 11 is connected with the outlet of the broke filter and the outlet of the squeeze white water filter 4; the concentrated white water tank 12 is used to collect the concentrated white water from the paper machine wire; the outlet of the concentrated white water tank 12 and the Class C white water outlet after the paper machine wire is sprayed are connected with the water inlet of the broke pool;

[0031] The extraction and concentration water unit IV includes an extraction hot water tank 13, an extraction liquid tank 14, a concentration evaporator 15 and an evaporation and condensation water tank 16 which are fluidically connected in sequence; the inlet of the extraction hot water tank 13 is connected to the outlet of the Class C white water tank 10; the outlet of the evaporation and condensation water tank 16 is connected to the inlet of the Class B white water tank 7.

[0032] In some embodiments of the present invention, the hot water tank 1 is connected to a condensate transition tank 18, and the condensate transition tank 18 is used to collect condensate from various steam usage points. The collected condensate is transported to the hot water tank 1 and mixed with municipal clean water for spray cleaning of the felt in the paper machine press section.

[0033] In some embodiments of the present invention, the clean water unit I further includes a vacuum gas-liquid separation device 2, which is used to perform gas-liquid separation on the spray water after use at each spray point of the felt in the press section of the paper machine. The vacuum gas-liquid separation device 2 includes a vacuum box and a vacuum separator connected by fluids, and the vacuum box is used to vacuum-suction the felt in the press section of the paper machine after spraying, and dehydrate the felt through vacuum suction, and at the same time, the dirt is sucked out to dry and clean the felt, and the material after suction is obtained, and then the obtained material after suction is separated into gas and liquid through the vacuum separator, and the gas is transported to the vacuum pump group, and the liquid is collected and transported to the pressing white water tank 3.

[0034] In some embodiments of the present invention, the white water membrane filter 9 is selected from a ceramic membrane filter.

[0035] In some embodiments of the present invention, the concentrated white water unit III also includes a return pipeline for providing water for flushing the white water tray of the paper machine wire section.

[0036] In some embodiments of the present invention, the concentrating evaporator 15 is connected to a concentrated liquid tank 17 for collecting concentrated liquid.

[0037] A second aspect of the present invention provides a water circulation method for producing tobacco sheets by a papermaking process, comprising the following steps:

[0038] (1) Clean water process: The hot water in the hot water tank is transported to each spray point of the felt in the paper machine press section. The used spray water is collected and transported to the press white water tank and filtered to obtain filtered water;

[0039] (2) Dilution white water process: a portion of the water filtered in step (1) enters a dilution white water tank, the effluent of the dilution white water tank is centrifuged to obtain Class B white water and transported to the Class B white water tank, the effluent of the Class B white water tank is membrane filtered to obtain Class C white water and transported to the Class C white water tank, the effluent of the Class C white water tank is used for spraying the paper machine wire section, and the spraying water collected by the white water tray of the paper machine wire section is returned to the dilution white water tank;

[0040] (3) Concentrated white water process: the rest of the water filtered in step (1) is transported to the Class A white water tank. The water from the Class A white water tank is used to dilute and concentrate the pulp, and finally forms the pulp on the screen and forms it in the paper machine wire section. The concentrated white water from the paper machine wire section enters the concentrated white water tank. The water from the concentrated white water tank and the Class C white water sprayed by the paper machine wire roller enter the broke pool together, and mix with the broke to form broke pulp. The broke pulp is filtered to form Class A white water and flows back to the Class A white water tank.

[0041] (4) Extraction and concentration process: The water from the Class C white water tank is heated by steam to form extraction hot water, which is then subjected to three-stage continuous countercurrent extraction to form an extract, which enters the concentrator to form a concentrated solution. During the concentration process, excess water is collected and returned to the Class B white water tank.

[0042] In some embodiments of the present invention, calculated by volume percentage, 20% to 35% of the filtered water in step (1) is delivered to the Class A white water tank, and 65% to 80% is delivered to the dilute white water tank; for example, 25% can be delivered to the Class A white water tank, and 75% can be delivered to the dilute white water tank.

[0043] In some embodiments of the present invention, in step (4), the three-stage continuous countercurrent extraction further includes pre-extracting the tobacco stems with the extraction hot water, and the tobacco stem liquid formed by the pre-extraction is discharged to a sewage station.

[0044] In some embodiments of the present invention, in step (1), the water inlet to the hot water tank includes municipal clean water and condensed water from various steam usage points, which is collected and the heat energy is recovered.

[0045] In some embodiments of the present invention, in step (1), the used spray water is collected and then transported to the white water tank after being used, specifically comprising: using a vacuum box to vacuum-suction the felt of the press section of the paper machine after spraying to obtain the material after suction, and then separating the obtained material after suction by gas and liquid through a vacuum separator, and the gas is transported to the vacuum pump group, and the liquid is collected and transported to the white water tank after being transported. Preferably, the gas-liquid separation is achieved by a vacuum box and a vacuum separator, specifically, using a vacuum box to vacuum-suction the felt of the press section of the paper machine after spraying (the felt of the press section of the paper machine wetted by the spray water) to obtain the material after suction (a mixture of gas and liquid), and then separating the obtained material after suction by gas and liquid through a vacuum separator, and the gas is transported to the vacuum pump group, and the liquid is collected and transported to the white water tank after being transported.

[0046] In some embodiments of the present invention, in step (1), the filtration is mesh filtration. Preferably, the mesh number of the mesh is 150 to 200.

[0047] In some embodiments of the present invention, in step (2), the membrane filtration is ceramic membrane filtration.

[0048] In some embodiments of the present invention, the effluent from the dilute white water tank is centrifuged to obtain Class B white water having a solid suspended matter content of 300 to 500 ppm.

[0049] In some embodiments of the present invention, the content of suspended solids in the Class C white water obtained by filtering the effluent from the Class B white water tank is 5 to 10 ppm.

[0050] In some embodiments of the present invention, in step (3), a portion of the effluent from the concentrated white water tank flows back to the paper machine wire section to rinse the white water tray of the paper machine wire section.

[0051] In some embodiments of the present invention, in step (3), a portion of the concentrated white water removed from the paper machine wire section is transported to the pulping white water bucket for secondary pulping. Specifically, the water from the Class A white water tank is mixed with the solid phase material formed by extraction and squeezing, and is diluted by the dilution water pump and concentrated by the concentration adjustment water pump to obtain the pre-sheet pulp and transported to the pre-sheet pulp tank. Then, the pre-sheet pulp is mixed with the concentrated white water removed from the paper machine wire section, and secondary pulping dilution is performed to obtain the web pulp. A portion of the concentrated white water removed from the paper machine wire section for the web pulp is transported to the pulping white water bucket for secondary pulping, and the rest enters the damaged paper pool.

[0052] In some embodiments of the present invention, in step (3), the solid suspended matter content in the Class A white water formed after the broken pulp is filtered is 3000-4000 ppm.

[0053] Below in conjunction with preferred embodiment, specific embodiment of the present invention is described in further detail.When embodiment gives numerical range, it should be understood that, unless otherwise specified in the present invention, the two endpoints of each numerical range and any numerical value between the two endpoints can be selected.Unless otherwise defined, all technical and scientific terms used in the present invention are identical with the meanings commonly understood by those skilled in the art.Unless otherwise defined, the equipment or device used in the present invention are conventional equipment or devices in the field of papermaking tobacco sheets, such as various types of spraying devices, delivery pumps, centrifuges, liquid metering and control, etc.Except the specific method, equipment, materials used in the embodiment, as those skilled in the art grasp the prior art and record of the present invention, any method, equipment and materials of the prior art similar or equivalent to the method, equipment, materials in the embodiment of the present invention can also be used to realize the present invention.

[0054] Example 1

[0055] A water circulation system for producing tobacco sheets by papermaking method:

[0056] The water system of the whole line is divided into four relatively independent and related units: clean water unit I, dilute white water unit II, concentrated white water unit III, and extraction and concentration water unit IV. The relevant capacity of the paper machine is a speed of 160m / min, a width of 1880mm, and a base sheet weight of 58±2gsm, that is, the paper machine capacity is about 1.05t / h (calculated based on absolute dry base sheet). According to the coating rate of 36±2% and the product moisture of 11.0±1.5%, the production line capacity is about 1.84t / h (calculated based on normal products).

[0057] 1) Clean water unit I starts with hot water tank 1, which is mainly used for spray cleaning of felts in the press section of the paper machine. After the condensed water from each steam point is collected and heat energy is recovered (flash evaporation), it enters hot water tank 1 with municipal clean water, and after being heated to 70±5°C by steam, it is pumped to each spray point of the felt in the press section of the paper machine for spray cleaning of the felt in the press section of the paper machine. The felt after spray cleaning is vacuum-sucked by a vacuum box (to remove moisture and impurities on the felt) to obtain the material after suction (gas-liquid mixture), and then the obtained material after suction is separated into gas and liquid by a vacuum separator, and the gas is transported to the vacuum pump group, about 50m 3 / hThe liquid is collected and transported to the white water pressing tank 3. The effluent after being filtered by the white water pressing filter 4 (the mesh size is 150 mesh) is divided into about 75% of the dilute white water unit and about 25% of the concentrated white water unit, and the slag phase is discharged; the clean water unit is a one-way mode, and water does not circulate in the unit.

[0058] 2) The dilute white water unit II is centered on the C-class white water tank 10, which is mainly used for spray cleaning of the paper machine wire section; the effluent from the press white water filter 4 and the dilute white water collected by the wire white water tray enter the dilute white water tank 5 for mixing and are purified by the white water centrifuge 6 (flow rate is about 60-62m 3 / h) to a solid suspended matter content of 300-500ppm to form Class B white water, which is then filtered through a ceramic membrane filter 9 to a solid suspended matter content of 8-10ppm to form Class C white water that enters a Class C white water tank 10, thereby realizing the recycling and renewal of the dilute white water.

[0059] 3) Concentrated white water unit III is centered on the Class A white water tank 11, which is used for dilution and concentration of the slurry; the effluent from the squeezed white water filter 4 of the clean water unit I and the effluent (white water) from the broken paper filter enter the Class A white water tank 11, and the outlet of the Class A white water tank 11 is connected to the dilution water pump and the concentration water pump in sequence through pipelines. The solid phase material formed by extraction and squeezing is diluted once and concentrated five times (total flow rate is about 43-45m 3 / h) to form pre-papermaking pulp, which is transported to the pre-papermaking pulp tank. The pre-papermaking pulp is then subjected to secondary pulping to form on-net pulp (the water for secondary pulping comes from the pulping white water bucket, which is connected to the concentrated white water outlet of the paper machine wire section). The concentrated white water (excluding the water for secondary pulping) discharged from the paper machine wire section enters the concentrated white water tank 12. The Class C white water discharged from the concentrated white water tank 12 and sprayed by the couch roll of the paper machine wire section enters the broke pool, mixed with the broke to form broke pulp, filtered through a broke filter (80 meshes) until the solid suspended matter content is 3500-4000ppm, formed into Class A white water, which flows back to the Class A white water tank 11, so as to realize the recycling and renewal of the concentrated white water.

[0060] 4) The extraction concentration water unit IV is centered on the extraction hot water tank 13 and is used for extracting tobacco raw materials to form an extract; the Class C white water coming out of the Class C white water tank 10 of the dilute white water unit II is heated by steam in the extraction hot water tank 13 to form extraction hot water, and is subjected to three-stage continuous countercurrent extraction in the extraction liquid tank 14 to form an extract, which enters the concentration evaporator 15 for concentration, and the formed concentrate is collected in the concentrate tank 17. The excess water in the extract is collected in the form of evaporated condensed water in the evaporation condensed water tank 16, and then refluxed to the Class B white water tank 7 of the dilute white water unit II, and is recycled and renewed with the dilute white water unit II.

[0061] The main water replenishment point of the entire system is the hot water tank 1 where municipal clean water is added. Other points will not be replenished unless there is an abnormality or the start of the shift. The main drainage (sewage) points are the Class A white water tank 11 for continuous sewage discharge, the concentrated white water tank 12 for continuous sewage discharge, the ceramic membrane filter 9 for continuous sewage discharge of concentrated water, and the white water centrifuge 6 for continuous sewage discharge of slag phase.

[0062] According to production operation statistics, the system designed in Example 1 of the present invention consumes about 32.0 to 34.0 tons of water per ton of product produced; that is, about 32.0 to 34.0 tons of clean water (statistical data of the clean water main flow meter) is required for every ton of product produced, and about 38.0 to 40.0 tons of various types of sewage are discharged (statistical data of the flow meter after the workshop sewage collection well). The long net is used for about 140-150 days, and the blanket is used for about 55-60 days.

[0063] Note: The amount of clean water plus the amount of steam is the amount of sewage discharged. After being used in various places, the steam forms condensed water, enters the water system for circulation, and finally becomes sewage discharge.

[0064] The water system of a certain manufacturer's production line does not clearly distinguish between concentrated and diluted white water. The water removed and collected by the paper machine is concentrated together (i.e., the concentrated and diluted white water is mixed). After the first-level filtration and purification, it is used for pulp dilution and concentration adjustment, and after the second-level centrifugal purification, it is used for net cleaning. There are problems such as unclear division of the water system, accumulation of impurities in the water, water used for net cleaning does not meet the water quality requirements, and low cleaning efficiency of the long net. According to the survey, it requires about 42.0 to 44.0 tons of clean water for every ton of product produced, and discharges about 50.0 to 52.0 tons of various sewage. The long net is used for about 100-120 days, and the blanket is used for about 35-40 days.

[0065] The water system of a certain manufacturer's production line did not clearly distinguish between concentrated and diluted white water. After the concentrated and diluted white water were mixed and treated at multiple levels, they were mixed with clean water in proportion to meet the water quality requirements for cleaning water in the net part. There were problems such as high water consumption and complicated process flow. According to the survey, it takes about 46.0 to 48.0 tons of clean water to produce 1 ton of product, and discharges about 52.0 to 54.0 tons of various sewage. The long net is used for about 120-140 days, and the blanket is used for about 50-55 days.

[0066] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A water circulation system for producing tobacco sheets by papermaking method, characterized in that: It includes a clean water unit (Ⅰ), a dilute white water unit (Ⅱ), a concentrated white water unit (Ⅲ) and an extraction concentrated water unit (Ⅳ); The clean water unit (I) comprises a hot water tank (1), a squeeze white water tank (3) and a squeeze white water filter (4); the hot water tank (1) is connected to each spray point of the felt in the press section of the paper machine; the squeeze white water tank (3) is used to collect the separated spray water from each spray point of the felt in the press section of the paper machine; the squeeze white water filter (4) is used to filter the water output from the squeeze white water tank (3); The dilute white water unit (II) comprises a dilute white water tank (5), a dilute white water purification device and a Class C white water tank (10) which are fluidically connected in sequence; the inlet of the dilute white water tank (5) is respectively connected to the water outlet of the squeeze white water filter (4) and the dilute white water outlet of the white water disk of the paper machine wire section; the dilute white water purification device comprises a white water centrifuge (6), a Class B white water tank (7), a membrane filtration water supply tank (8) and a white water membrane filter (9) which are fluidically connected in sequence, the inlet of the white water centrifuge (6) is connected to the outlet of the dilute white water tank (5), the outlet of the white water membrane filter (9) is connected to the inlet of the Class C white water tank (10); the outlet of the Class C white water tank (10) is connected to the spray system of the paper machine wire section; The concentrated white water unit (III) comprises a Class A white water tank (11) and a concentrated white water tank (12); the Class A white water tank (11) is used to provide water for pulp dilution and concentration adjustment, and the inlet of the Class A white water tank (11) is connected with the outlet of the broke filter and the outlet of the squeeze white water filter (4); the concentrated white water tank (12) is used to collect concentrated white water discharged from the paper machine wire section; the outlet of the concentrated white water tank (12) and the Class C white water outlet after spraying the paper machine wire section are connected with the water inlet of the broke pool; The extraction and concentration water unit (IV) comprises an extraction hot water tank (13), an extraction liquid tank (14), a concentration evaporator (15) and an evaporation and condensation water tank (16) which are fluidically connected in sequence; the inlet of the extraction hot water tank (13) is connected to the outlet of the Class C white water tank (10); the outlet of the evaporation and condensation water tank (16) is connected to the inlet of the Class B white water tank (7).

2. The water circulation system for producing paper-making tobacco sheets according to claim 1, characterized in that: Includes one or more of the following features: 1) The inlet of the hot water tank (1) is connected to a condensate transition tank (18), and the condensate transition tank (18) is used to collect condensate from various steam usage points; 2) The clean water unit (I) further comprises a vacuum gas-liquid separation device (2), wherein the vacuum gas-liquid separation device (2) is used to separate the gas-liquid of the spray water after use at each spray point of the felt in the press section of the paper machine; 3) the white water membrane filter (9) is selected from a ceramic membrane filter; 4) The thick white water tank (12) is provided with a return pipeline for providing water for flushing the white water tray of the paper machine wire section; 5) The concentrating evaporator (15) is connected to a concentrated liquid tank.

3. The water circulation system for producing paper-making tobacco sheets according to claim 2, characterized in that: The vacuum gas-liquid separation device (2) comprises a vacuum box and a vacuum separator which are fluidically connected.

4. A method for circulating water in the production of tobacco sheets by a papermaking process, characterized in that: The steps include: (1) Clean water process: The hot water in the hot water tank is transported to each spray point of the felt in the paper machine press section. The used spray water is collected and transported to the press white water tank and filtered to obtain filtered water; (2) Dilution white water process: a portion of the water filtered in step (1) enters a dilution white water tank, the effluent of the dilution white water tank is centrifuged to obtain Class B white water and transported to the Class B white water tank, the effluent of the Class B white water tank is membrane filtered to obtain Class C white water and transported to the Class C white water tank, the effluent of the Class C white water tank is used for spraying the paper machine wire section, and the spraying water collected by the white water tray of the paper machine wire section is returned to the dilution white water tank; (3) Concentrated white water process: the rest of the water filtered in step (1) is transported to the Class A white water tank. The water from the Class A white water tank is used to dilute and concentrate the pulp, and finally forms the pulp on the screen and forms it in the paper machine wire section. The concentrated white water from the paper machine wire section enters the concentrated white water tank. The water from the concentrated white water tank and the Class C white water sprayed by the paper machine wire roller enter the broke pool together, and mix with the broke to form broke pulp. The broke pulp is filtered to form Class A white water and flows back to the Class A white water tank. (4) Extraction and concentration process: The water from the Class C white water tank is heated by steam to form extraction hot water, which is then subjected to three-stage continuous countercurrent extraction to form an extract, which enters the concentrator to form a concentrated solution. During the concentration process, excess water is collected and returned to the Class B white water tank.

5. The method for circulating water for producing tobacco sheets by papermaking method according to claim 4, characterized in that: Calculated by volume percentage, 20% to 35% of the water filtered in step (1) is transported to the Class A white water tank, and 65% to 80% is transported to the dilute white water tank.

6. The method for circulating water for producing tobacco sheets by papermaking method according to claim 4, characterized in that: In step (4), before the three-stage continuous countercurrent extraction, the process also includes pre-extracting the tobacco stems with the hot extraction water, and discharging the tobacco stem liquid formed by the pre-extraction into a sewage station.

7. The water circulation method for producing tobacco sheets by papermaking method according to claim 4, characterized in that: Step (1) also includes one or more of the following features: (1a) The water inlet to the hot water tank includes municipal clean water and condensed water from various steam use points, which is collected and the heat energy is recovered; (1b) The used spray water is collected and then transported to the press white water tank, which specifically includes: using a vacuum box to vacuum-suction the felt of the press section of the paper machine after spraying to obtain a suctioned material, and then using a vacuum separator to separate the obtained suctioned material into gas and liquid, and transporting the gas to a vacuum pump group, and collecting the liquid and transporting it to the press white water tank; (1c) The filtration is mesh filtration.

8. The method for circulating water for producing tobacco sheets by papermaking method according to claim 7, characterized in that: The mesh number of the mesh cloth is 150 to 200 meshes.

9. The method for circulating water for producing tobacco sheets by papermaking method according to claim 4, characterized in that: Step (2) also includes one or more of the following features: (2a) The membrane filtration is ceramic membrane filtration; (2b) The effluent from the dilute white water tank is centrifuged to obtain a Class B white water having a solid suspended matter content of 300 to 500 ppm; (2c) The solid suspended matter content of the Class C white water obtained by filtering the effluent from the Class B white water tank is 5 to 10 ppm.

10. The water circulation method for producing tobacco sheets by papermaking method according to claim 4, characterized in that: In step (3), part of the effluent from the thick white water tank is returned to the paper machine wire section for washing the white water tray of the paper machine wire section; and / or part of the thick white water discharged from the paper machine wire section is transported to the pulp flushing white water bucket for secondary pulp flushing; and / or the solid suspended matter content of the Class A white water formed after the waste pulp is filtered is 3000-4000ppm.

Images