A pulp impregnation and pressing system and impregnation and pressing process thereof

Abstract

The invention discloses a pulp impregnation and pressing system and an impregnation and pressing process thereof. The pulp impregnation and pressing system comprises an impregnation liquid metering tank, an impregnation barrel and a diaphragm filter press which are connected in sequence. The water inlet of the diaphragm filter press is also connected with a water tank. The water tank and the water inlet pipeline of the diaphragm filter press are provided with a high-pressure water pump. The discharge end of the diaphragm filter press is connected with a pressure liquid tank. The outlet end of the pressure liquid tank is connected with the impregnation liquid metering tank. The invention uses a diaphragm filter press and uses a filter cloth to replace the filtering effect of the mesh of a mesh roller press, which completely eliminates the problem of wet material after the mesh is blocked. It only needs to fill the pipeline between the pulp pump and the diaphragm filter press. The pulp can be recovered by backblowing, which reduces the consumption of raw materials and avoids waste. Therefore, it is also suitable for intermittent small batch production with less raw materials.

Description

Technical Field

[0001] The invention relates to the technical field of viscose fiber preparation, in particular to a pulp impregnation and pressing system and an impregnation and pressing process thereof. Background Art

[0002] In the production of viscose fiber, pulp raw materials are impregnated with alkali solution to form pulp porridge. The pulp porridge pressing equipment mainly adopts mesh roller press. The structure of mesh roller press is as follows: Figure 1 As shown in the figure, it mainly includes a pulp tank 200, a frame 100, a front pressing roller 300, a rear pressing roller 400, a front scraper 500, a rear scraper 600, a front spray 700, a rear spray 800, an exhaust hood 900 and a transmission part. The pressing is completed by two front and rear pressing rollers. The pressing rollers are mesh-type, and the width is generally about 1800mm. The two pressing rollers rotate synchronously and turn in opposite directions. The pressing rollers are supported by double-row centripetal roller bearings. The roller surface is a stainless steel perforated plate with a hole diameter of about 1mm. The inside of the roller is a hollow roller with several reinforcing ribs. Multiple holes are opened on both sides of the roller to facilitate the reflux of the pressing alkali solution. Gaskets are installed between the bearing seats of the pressing rollers and between the pressing plate and the bearings, so that the spacing between the pressing rollers can be adjusted between 0-24mm. An adjustable plastic scraper is installed above the pressing roller to strip the fiber layer. A front scraper 500 is provided on one side of the front pressing roller 300, and a rear scraper 600 is provided between the front pressing roller 300 and the rear pressing roller 400. Sealing strips and hollow rubber rings are installed on the pulp tank side plates below the pressing rollers and the two ends of the pressing rollers. The hollow rubber rings are squeezed with compressed air to seal, thereby forming a closed space between the two pressing rollers and the pulp tank 200 below. In this way, two spaces are formed from the pulp porridge inlet 1000 area below and the alkali solution reflux area on both sides of the pressing rollers, which do not interfere with each other. A row of nozzles are horizontally arranged on the circumferential surfaces of the front pressing roller 300 and the rear pressing roller 400, namely the front spray 700 and the rear spray 800, so as to wash the surface of the pressing roller with alkali solution to ensure that the mesh is unobstructed.

[0003] The working process is as follows: alkali cellulose pulp enters the pulp tank 200 from the pulp inlet 1000 below at a constant pressure, and after the pulp tank is full, the pulp is squeezed into the pressing roller. The pulp is fully compressed during the process of the two pressing rollers driving the pulp through the two rollers. The squeezed alkali liquid enters the roller through the stainless steel mesh on the roller surface, and then flows out through the two ends of the roller. The squeezed alkali cellulose is squeezed upward and scraped by the rear scraper 600 onto the front pressing roller 300 and rotates with it, and then scraped by the front scraper 500 and discharged along the discharge trough. A pressure sensor is provided at the bearing seat of the pressing roller, which can feed back the pressure signal between the two pressing rollers to the pulp pump and the pressing roller, and the pressure between the two pressing rollers is kept constant by adjusting the rotation speed of the pulp pump or the pressing roller.

[0004] With the advancement of viscose fiber production technology and the industry's gradual transformation towards green and low-carbon development, higher requirements have been placed on the production capacity of the press, and the traditional mesh roller press has gradually been unable to meet the needs of technological updates. On the one hand, from the perspective of reducing production costs, it is hoped that the degree of pressing of alkali fiber will be higher, because it can increase the recovery rate of alkali solution and reduce the alkali consumption of the impregnation process. On the other hand, the traditional mesh roller press requires a high-power roller motor and pulp pump motor, which has high energy consumption, and it is necessary to seek a new, more energy-saving and efficient pressing method. In addition, the traditional mesh roller press also exposes the following shortcomings during use:

[0005] Disadvantages: 1. The mesh-type pressing roller is easily clogged by alkali cellulose and impurities due to its small mesh diameter. Sometimes wet spots can be seen on the squeezed alkali cellulose in pieces or blocks. This is because the alkali cellulose moisture at the mesh blockage cannot be discharged through the mesh, forming wet spots. Even if there are nozzles spraying on both sides of the pressing roller, in the actual production process, the effect of spray cleaning is not ideal, and it is still necessary to manually use a high-pressure flushing pump for flushing. In addition, the nozzle is easily clogged by alkali scale, which requires manual unblocking with special tools, and frequent unblocking operations will damage the nozzle channel, causing the alkali solution to be sprayed out in a columnar shape instead of a scattered shape, greatly reducing the cleaning effect.

[0006] 2. The pulp tank pressure has a great influence on the moisture content of the alkali fiber after pressing. Before the pulp enters the space between the two pressing rollers for pressing, the pulp tank under the pressing rollers needs to be filled first to ensure a sufficiently large and stable pulp feeding pressure to the pressing rollers and to ensure that the alkali fiber pressing degree is qualified. Since the pulp tank volume of the mesh roller press is large, a lot of pulp is filled in the pulp tank during the start-up and shutdown stages of the equipment, so a lot of pulp is lost without being pressed. Therefore, the mesh roller press is not suitable for intermittent small-batch pressing production process of alkali cellulose.

[0007] 3. The pulp processing capacity of the mesh roller press can be adjusted by adjusting the distance between the front and rear pressing rollers. However, the equipment must be disassembled during shutdown for maintenance to adjust the spacing of the pressing rollers, which is very inconvenient.

[0008] 4. The pressure between the rollers of the traditional mesh roller press is limited to less than 1.0 bar, so the methyl fiber content of the squeezed alkali fiber also has an upper limit. The purpose is to avoid excessive pressure in the pulp tank, which may damage the pulp tank seal and cause pulp splashing accidents. The pressure sensor is interlocked with the pulp pump, and the pulp pump automatically stops when the pressure rises to the set upper limit.

[0009] 5. Under the same pulp concentration, the fluctuation of pressing pressure causes the unstable composition of alkali cellulose after pressing (low pressing pressure makes the methyl cellulose low and the alkali content high, while high pressing pressure makes the methyl cellulose high and the alkali content low), which makes the polymerization degree of cellulose unstable after aging, directly leading to the instability of viscose viscosity and affecting the quality of viscose. Although the pressing pressure can be adjusted by feedback, the adjustment process has hysteresis and the pressure fluctuation cannot be completely eliminated.

[0010] 6. The change of pulp porridge concentration has a great influence on the pressing effect. A low pulp porridge concentration will cause the pulp porridge to flow fast between the two rollers, the pressing pressure is low, and the pressed alkali fiber is too wet. A high pulp porridge concentration will make pressing difficult, the power of the press and the pulp tank pressure will increase, and it is easy to cause equipment damage. Specifically, when the pulp porridge concentration is too low, one situation is that the particularly thin material will be directly sprayed out from between the two pressing rollers and cannot be pressed at all; another situation is that the pulp porridge consistency ensures that the material will not be sprayed out from between the rollers, but it is easy to leak from the side seal of the press roller. If not discovered in time, the leaking pulp porridge will block the return pipeline of the pressing liquid, causing the press to fail to operate normally, and once the leaking pulp porridge enters the aging and yellowing system with the alkali cellulose, waste glue will be produced. When the pulp porridge concentration is too high and the pressure is not adjusted in time, the pressed alkali cellulose is easy to be squeezed between the two rollers of the press, causing the press to jam and stop.

[0011] 7. In actual production, the roller mesh is prone to damage and fall off. The fallen iron fragments will enter the subsequent process sections with the alkali fiber, especially into the yellowing machine, which may easily cause explosion accidents and have an adverse impact on production safety. Summary of the invention

[0012] In view of the above problems, the purpose of the present invention is to provide a pulp impregnation and pressing system and its impregnation and pressing process to solve the problems of easy clogging of the mesh of the existing mesh roller press, waste of pulp, high energy consumption and changes in pulp concentration affecting the pressing effect.

[0013] The present invention is achieved in that:

[0014] A pulp impregnation and pressing system comprises an impregnation liquid metering tank, an impregnation barrel and a diaphragm filter press which are connected in sequence. The water inlet of the diaphragm filter press is also connected with a water tank. A high-pressure water pump is provided on the water inlet pipeline between the water tank and the diaphragm filter press. The discharge end of the diaphragm filter press is connected with a liquid pressure tank, and the outlet end of the liquid pressure tank is connected with the impregnation liquid metering tank.

[0015] Furthermore, it also includes an air compressor. The diaphragm filter press is provided with a first air inlet, a second air inlet, a first air outlet and a second air outlet. The air compressor is connected with the first air inlet and the second air inlet through a first air pipeline and a second air pipeline respectively. The first air outlet is connected with the impregnation barrel through a third air pipeline, and the second air outlet is connected with the pressure liquid tank through a fourth air pipeline. Control valves are provided on the first air pipeline, the second air pipeline, the third air pipeline and the connecting pipeline between the second air pipeline and the fourth air pipeline.

[0016] Furthermore, the impregnation barrel is connected to the diaphragm filter press through a first liquid pipeline, and a slurry pump is provided on the first liquid pipeline.

[0017] Furthermore, an electric contact pressure gauge is provided on the first liquid pipeline, and the electric contact pressure gauge is electrically connected to the porridge pump.

[0018] Furthermore, the liquid pressure tank is connected to the impregnation liquid metering tank via a second liquid pipeline, a liquid pressure pump and a cumulative flow meter are provided on the second liquid pipeline, and the liquid pressure pump is electrically connected to the cumulative flow meter.

[0019] Furthermore, the impregnation liquid metering tank is provided with a first liquid inlet for adding dilute alkali solution and a second liquid inlet for adding concentrated alkali solution. A first motor is fixedly provided on the top of the impregnation liquid metering tank, and a first stirring paddle is fixedly provided at the output end of the first motor. The first stirring paddle penetrates the top of the impregnation liquid metering tank and extends into the interior thereof.

[0020] Furthermore, a heating circulation machine is also provided on the outside of the impregnation liquid metering tank.

[0021] Furthermore, a first feed port for adding pulp is provided on the impregnation barrel, a second motor is fixedly provided on the top of the impregnation barrel, a second stirring paddle is fixedly connected to the output end of the second motor, and the second stirring paddle passes through the top of the impregnation barrel and extends into the interior thereof.

[0022] The present invention also discloses a pulp impregnation and pressing process, which uses the aforementioned pulp impregnation and pressing system and comprises the following steps:

[0023] S1. The impregnation liquid is placed in the impregnation liquid metering tank;

[0024] S2, sending all the prepared impregnation liquid into the impregnation barrel, adding pulp into the impregnation barrel, and using the second stirring paddle to stir and form pulp porridge;

[0025] S3, start the porridge pump to transport the porridge in the immersion barrel to the diaphragm filter press for a squeeze, and the squeezed liquid flows into the liquid pressure tank;

[0026] S4, close the porridge pump, open the valves on the first air pipeline and the third air pipeline, start the air compressor and blow the unpressed porridge in the feed pipe of the diaphragm filter press back into the impregnation barrel, then close the valve on the third air pipeline, blow the porridge in the feed small channel of the filter plate of the diaphragm filter press into the filter cake, and the squeezed liquid flows into the liquid pressure tank;

[0027] S5, turn off the air compressor, close the valve on the first air pipeline, start the high-pressure water pump, inject high-pressure water into the diaphragm filter press for secondary pressing, and the pressed liquid flows into the liquid pressure tank;

[0028] S6. After the second pressing is completed, the water pressure in the diaphragm chamber of the diaphragm filter press is released, and then the valve on the second air pipeline is opened, and the air compressor is started to blow the filtrate remaining in the discharge pipe of the diaphragm filter press into the liquid pressure tank;

[0029] S7. Turn off the air compressor and discharge the squeezed alkali fiber filter cake from the filter chamber of the diaphragm filter press.

[0030] Furthermore, during the first pressing in step S3, the pulp inlet pressure is less than or equal to 0.8 MPa, and the pressure of the second pressing in step S5 is 0.5 MPa to 2.0 MPa.

[0031] The beneficial effects of the present invention are:

[0032] 1. The pulp impregnation and pressing system of the present invention uses a diaphragm filter press, and the filtering effect of the mesh of the mesh roller press is replaced by the filtering of the filter cloth. The alkali fiber squeezed out has uniform moisture content, and the filter cloth is very convenient to replace and clean, which completely eliminates the problem of wet material after the mesh of the roller press is clogged.

[0033] 2. Compared with the mesh roller press that needs to fill the pulp tank for pressurization, the pulp impregnation and pressing system of the present invention only needs to pump the pulp porridge to fill the pipeline between the diaphragm filter press, and the pulp porridge can be recovered by backblowing, which reduces raw material consumption and avoids waste. Therefore, it is also suitable for intermittent small-batch production with less raw materials.

[0034] 3. The porridge processing capacity can be adjusted by increasing or decreasing the number of filter plates, which is very convenient to operate.

[0035] 4. The diaphragm filter press is used for porridge squeezing. The squeezing degree of porridge of different concentrations can be controlled by adjusting the feed amount of the press, the squeezing time and the pressure of the secondary squeezing high-pressure water. The control method is simple and convenient, which overcomes the shortcomings of the traditional mesh roller press, such as the difficulty in adjusting the squeezing roller spacing, the narrow applicable porridge concentration range and the insufficient squeezing degree.

[0036] 5. Whether the pulp concentration is too low or too high, it can be squeezed normally, which overcomes the shortcomings of mesh roller press that high-concentration pulp is easy to get stuck and low-concentration pulp is easy to leak.

[0037] 6. The squeezing degree of the diaphragm filter press is significantly higher than that of the traditional mesh roller press. On the one hand, it is helpful to reduce the consumption of impregnation alkali solution and power consumption; on the other hand, the alkali fiber after squeezing contains less alkali, which can reduce the consumption of raw material carbon disulfide in the subsequent yellowing reaction, reduce side reaction products, and improve the quality of viscose while reducing raw material costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a structural diagram of a mesh roller press of the prior art;

[0039] Figure 2 is a process flow chart of the present invention;

[0040] Figure 3 is a schematic diagram of a filter plate of a membrane filter press of the present invention;

[0041] Figure 4 It is a comparison diagram of power consumption of two pressing methods under different feed slurry concentration conditions of the present invention;

[0042] Figure 5 This is a comparison chart of power consumption of two pressing methods under different discharge methyl fiber contents of the present invention.

[0043] Description of reference numerals:

[0044] 1. Impregnation liquid metering tank; 101. First liquid inlet; 102. Second liquid inlet; 103. Third liquid inlet; 104. First motor; 105. First stirring paddle; 106. Glass tube liquid level gauge; 107. Heating circulation machine; 108. Jacket;

[0045] 2. Dipping barrel; 201. First feed port; 202. Second motor; 203. Second stirring paddle;

[0046] 3. Diaphragm filter press; 300. Filter plate; 3001. Small feed channel; 301. First air inlet; 302. Second air inlet; 303. First air outlet; 304. Second air outlet; 305. First air pipeline; 3051. Second valve; 306. Second air pipeline; 3061. Third valve; 307. Third air pipeline; 3071. First valve; 308. Fourth air pipeline; 3081. Fourth valve; 309. Fifth air pipeline;

[0047] 4. Water tank; 5. High-pressure water pump; 6. Pressure liquid tank; 7. Second liquid pipeline; 701. Pressure liquid pump; 702. Cumulative flow meter; 8. First liquid pipeline; 801. Porridge pump; 802. Electric contact pressure gauge; 9. Water inlet pipeline; 10. Pressure relief pipeline; 11. Air compressor; 12. Hydraulic station; 13. Electrical control box;

[0048] Existing technology: 100, frame; 200, pulp tank; 300, front pressing roller; 400, rear pressing roller; 500, front scraper; 600, rear scraper; 700, front spray; 800, rear spray; 900, exhaust hood; 1000, pulp porridge inlet. DETAILED DESCRIPTION

[0049] The technical scheme in the embodiment of the present invention is described clearly and completely below in conjunction with the accompanying drawings in the embodiment of the present invention. In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0050] like Figure 2 The figure shows the pulp impregnation and pressing system of the present invention, comprising an impregnation liquid metering tank 1, an impregnation barrel 2 and a diaphragm filter press 3 which are connected in sequence, the water inlet of the diaphragm filter press 3 is also connected with a water tank 4, a high-pressure water pump 5 is provided on the water inlet pipeline 9 between the water tank 4 and the diaphragm filter press 3, the discharge end of the diaphragm filter press 3 is connected with a liquid pressure tank 6, and the outlet end of the liquid pressure tank 6 is connected with the impregnation liquid metering tank 1.

[0051] In this embodiment, the impregnation liquid metering tank 1 is arranged above the impregnation barrel 2, and the liquid outlet of the impregnation liquid metering tank 1 is connected to the top of the impregnation barrel 2. The impregnation liquid metering tank 1 is made of 304 stainless steel, and is provided with a first liquid inlet 101 for adding a dilute alkali solution and a second liquid inlet 102 for adding a concentrated alkali solution. The first liquid inlet 101 and the second liquid inlet 102 are respectively connected to the dilute alkali solution storage tank and the concentrated alkali solution storage tank (not shown in the figure) through pipelines. The second liquid inlet 102 can be set as a hand hole, and the concentrated alkali solution can be manually added to the impregnation liquid metering tank 1 through the second liquid inlet 102. The top of the impregnation liquid metering tank 1 is also provided with a third liquid inlet 103 for adding squeezed liquid. The squeezed liquid tank 6 is connected to the impregnation liquid metering tank 1 through the second liquid pipeline 7. The inlet end of the second liquid pipeline 7 is connected to the outlet of the squeezed liquid tank 6, and the outlet end of the second liquid pipeline 7 is connected to the third liquid inlet 103 of the impregnation liquid metering tank 1, so as to transport the filtered squeezed liquid to the impregnation liquid metering tank 1 to avoid energy waste. The second liquid pipeline 7 is provided with a squeezed liquid pump 701 and a cumulative flow meter 702, and the squeezed liquid pump 701 is electrically connected to the cumulative flow meter 702. The inlet of the squeezed liquid pump 701 is connected to the liquid outlet of the squeezed liquid tank 6, and the outlet of the squeezed liquid pump 701 is connected to the impregnation liquid metering tank 1. The cumulative flow meter 702 is interlocked with the squeezed liquid pump 701, and the cumulative delivery amount of the squeezed liquid can be set. When the total amount of squeezed liquid delivered by the squeezed liquid pump 701 reaches the set value, the squeezed liquid pump 701 automatically stops.

[0052] A first motor 104 is fixedly provided on the top of the impregnation liquid metering tank 1. A first stirring paddle 105 is fixedly provided on the output end of the first motor 104. The first stirring paddle 105 penetrates the top of the impregnation liquid metering tank 1 and extends to the inside thereof. The first stirring paddle 105 is used to fully stir and mix the solution in the impregnation liquid metering tank 1. A glass tube level gauge 106 is also provided on the impregnation liquid metering tank 1. The volume of the added dilute alkali solution, concentrated alkali solution and squeezed liquid can be measured by observing the liquid level height of the glass tube level gauge 106. A heating circulation machine 107 is also provided on the outside of the impregnation liquid metering tank 1. A jacket 108 is fixedly provided on the outer wall of the impregnation liquid metering tank 1. The jacket 108 and the impregnation liquid metering tank 1 are heated by the heating circulation machine 107 with water or heat transfer oil as the medium.

[0053] In this embodiment, the material of the impregnation barrel 2 is 304 stainless steel, and a first feed port 201 for adding pulp is provided on the impregnation barrel 2. The first feed port 201 can be set as a hand hole, and pulp can be manually added through the first feed port 201. A second motor 202 is fixedly provided on the top of the impregnation barrel 2, and a second stirring paddle 203 is fixedly connected to the output end of the second motor 202. The second stirring paddle 203 penetrates the top of the impregnation barrel 2 and extends into the inside thereof. The second stirring paddle 203 is used to fully stir and mix the pulp and the impregnation liquid in the impregnation barrel 2 to form pulp porridge.

[0054] The impregnation barrel 2 is connected to the diaphragm filter press 3 through the first liquid pipeline 8, and a slurry pump 801 is provided on the first liquid pipeline 8. An electric contact pressure gauge 802 is also provided on the first liquid pipeline 8, and the electric contact pressure gauge 802 is arranged near the liquid inlet of the diaphragm filter press 3, and the electric contact pressure gauge 802 is electrically connected to the slurry pump 801. The slurry pump 801 is an ordinary three-leaf cam rotor pump, and the material is 316 stainless steel. The slurry pump 801 can be frequency-controlled, and the slurry pump 801 is overpressure interlocked with the electric contact pressure gauge 802 at the liquid inlet of the diaphragm filter press 3, and the overpressure value can be set to protect the diaphragm filter press 3. At the beginning of filtration, the slurry enters each filter chamber of the diaphragm filter press 3 under the push of the slurry pump 801, and solid-liquid separation is performed with the help of the pressure generated by the slurry pump 801.

[0055] Among them, the diaphragm filter press 3 in this embodiment can adopt mature products currently sold in the market, and its product model is not limited here. The diaphragm filter press 3 includes a frame, a hydraulic station 12, a filtration system and an electrical control box 13. The frame is the basic component of the filter press, and is mainly composed of a beam, a clamping plate, a thrust plate, a filter plate, a diaphragm filter plate, a filter cloth, a hydraulic system, etc. The filtration system includes a plurality of filter plates, filter cloths and a pressing diaphragm plate. The filter plate is covered with a filter cloth, and the filter plate and the filter cloth are arranged alternately. The filtered material enters each filter chamber from the feed hole. The solid particles are intercepted in the filter chamber because their particle size is larger than the pore size of the filter cloth, and the filtrate is discharged from the liquid outlet below the filter plate. Among them, the structural diagram of the filter plate 300 is shown in FIG. Figure 3 As shown, it includes a first air inlet 301 and a first air outlet 303 located at the upper part, and a second air inlet 302 and a second air outlet 304 located at the lower part. Among them, the first air outlet 303 is connected to the small feed channel 3001 opened inside it. The hydraulic station 12 includes a motor, an oil pump, a relief valve regulating pressure reversing valve, a pressure gauge, an oil circuit, a clamping plate and an oil tank. The electrical control box 13 is the control center of the diaphragm filter press 3. By controlling the hydraulic station 12, the entire diaphragm filter press 3 is controlled. The working principle of the diaphragm filter press 3 mainly includes the steps of feeding and pre-pressing, filtering, squeezing, flushing and dehydration, and diaphragm squeezing. The structure and working principle of the diaphragm filter press 3 are all prior art and will not be repeated here.

[0056] The water inlet of the diaphragm filter press 3 is also connected to a water tank 4, and a high-pressure water pump 5 and a control valve (not shown in the figure) are provided on the water tank 4 and the water inlet pipeline 9 of the diaphragm filter press 3. By passing high-pressure water into the filter assembly of the diaphragm filter press 3, the filter cake is further squeezed to reduce the moisture content. Preferably, a pressure relief pipeline 10 is also connected to the water tank 4 and the water inlet pipeline 9, and a control valve is also provided on the pressure relief pipeline 10. The setting of the pressure relief pipeline 10 is used to relieve the water pressure in the diaphragm chamber of the diaphragm filter press 3.

[0057] The discharge end of the membrane filter press 3 is connected to a pressure tank 6, and the outlet end of the pressure tank 6 is connected to the impregnation liquid metering tank 1. Preferably, the height of the pressure tank 6 is lower than the membrane filter press 3 to ensure that the filtrate can flow into the pressure tank 6 by gravity.

[0058] The pulp impregnation and pressing system of the present invention further comprises an air compressor 11, and the diaphragm filter press 3 is provided with a first air inlet 301, a second air inlet 302, a first air outlet 303 and a second air outlet 304. The first air inlet 301 is connected to its liquid inlet, and the second air inlet 302 is connected to its liquid discharge port. The air compressor 11 is connected to the first air inlet 301 and the second air inlet 302 through the first air pipeline 305 and the second air pipeline 306 respectively, the first air outlet 303 is connected to the impregnation barrel 2 through the third air pipeline 307, and the second air outlet 304 is connected to the liquid pressure tank 6 through the fourth air pipeline 308. The first air pipeline 305 and the third air pipeline 307 are connected through the fifth air pipeline 309, and the fifth air pipeline 309 is located at the end of the air compressor 11 away from the liquid inlet. Control valves are provided on the first air pipeline 305, the second air pipeline 306, the third air pipeline 307 and the connecting pipeline between the second air pipeline 306 and the fourth air pipeline 308. The control valve on the third air pipeline 307 is defined as the first valve 3071, the control valve on the first air pipeline 305 is defined as the second valve 3051, the control valve on the second air pipeline 306 is defined as the third valve 3061, and the control valve on the connecting pipeline between the second air pipeline 306 and the fourth air pipeline 308 is defined as the fourth valve 3081.

[0059] Start the air compressor 11, and then introduce compressed air into the diaphragm filter press 3 for backblowing. Specifically, open the first valve 3071 and the second valve 3051, and the compressed air passes through the first air pipeline 305, the liquid inlet channel of the diaphragm filter press 3, the fifth air pipeline 309 and the third air pipeline 307 in sequence, and then blows the porridge in the liquid inlet channel of the diaphragm filter press 3 back to the impregnation barrel 2; switch the compressed air inlet valve, that is, close the first valve 3071, the second valve 3051 and the fourth valve 3081 and open the third valve 3061, and the compressed air passes through the second air pipeline 306, the liquid discharge pipe of the diaphragm filter press 3 and the fourth air pipeline 308 in sequence, and then blows the residual filtrate in the liquid discharge pipe of the diaphragm filter press 3. The purpose of using compressed air for backblowing is to reduce the loss of raw materials, and to prevent the water from being reabsorbed by the filter cake when the diaphragm filter press 3 is depressurized or unloaded, so as to ensure that the moisture content of the alkali fiber obtained by squeezing is qualified.

[0060] The present invention also discloses a pulp impregnation and pressing process, which uses the aforementioned pulp impregnation and pressing system and comprises the following steps:

[0061] S1. Prepare the impregnation liquid in the impregnation liquid metering tank 1, that is, mix the dilute alkali solution, the squeeze solution and the concentrated alkali solution in an appropriate proportion. In this embodiment, 200L of impregnation liquid with a sodium hydroxide concentration of 230g / L is prepared in the impregnation liquid metering tank 1 for pulp impregnation. There are two specific cases:

[0062] A. Before the first start (prepare the impregnation solution with dilute alkali solution and concentrated alkali solution)

[0063] According to the concentration of dilute alkali solution and concentrated alkali solution, calculate the amount of dilute alkali solution and concentrated alkali solution needed to prepare a can of impregnation solution.

[0064] The amount of dilute alkali solution and concentrated alkali solution is calculated according to the following formula:

[0065] 210*N(amount of dilute alkali solution)+432*Y(amount of concentrated alkali solution)=230*(N+Y)

[0066] N+Y=200L (immersion liquid volume)

[0067] Calculated N = 182L, Y = 18L

[0068] Add dilute alkali solution and concentrated alkali solution into the impregnation liquid metering tank 1. After the addition is completed, close the manual valve for the dilute alkali solution, start the first stirring paddle 105 for stirring, turn on the heating circulation machine 107, and heat the impregnation liquid to not less than 50°C, so that the pulp can react with the alkali in the impregnation liquid to generate alkali fiber during the impregnation process. Then adjust the set temperature of the heating circulation machine 107 for insulation.

[0069] B. Conventional operation (preparing the impregnation solution with pressing liquid, concentrated alkali solution and diluted alkali solution)

[0070] The required amount of concentrated alkali solution and diluted alkali solution is calculated according to the concentration and amount of the squeezed liquid. When the concentration of the impregnation liquid changes, the amount of diluted alkali solution and concentrated alkali solution is adjusted accordingly.

[0071] The amount of dilute alkali solution and concentrated alkali solution is calculated according to the following formula:

[0072] c(pressing liquid concentration)*X(pressing liquid volume)+210*N(dilute alkali liquid volume)+432*Y(concentrated alkali liquid volume)=230*(N+Y)

[0073] X+N+Y=200L (immersion liquid volume)

[0074] Set the volume value of the squeezed liquid on the cumulative flow meter 702, start the squeezed liquid pump 701 to deliver the squeezed liquid to the impregnation liquid metering tank 1, until the cumulative amount reaches the set value, the squeezed liquid pump 701 automatically stops the pump, and closes the pump outlet manual valve. Add dilute alkali solution and concentrated alkali solution to the impregnation liquid metering tank 1, close the dilute alkali solution manual valve after the addition is completed, start stirring, turn on the heating circulation machine 107, heat the impregnation liquid to not less than 50°C, and then adjust the set temperature of the heating circulation machine 107 to keep it warm.

[0075] S2. Open the exhaust valve of the impregnation barrel 2 and the feed port connected to the impregnation liquid metering tank 1, send all the prepared impregnation liquid into the impregnation barrel 2, and add pulp into the impregnation barrel 2. The weighed pulp can be manually poured into the impregnation barrel 2 through the first feed port 201. The absolute dry weight of the pulp is 10kg. Among them, the first feed port 201 can be set as a hand hole to facilitate manual addition of pulp. In order to improve the reaction performance of pulp, 0.03%-0.2% of V388 additive is manually added into the impregnation barrel 2. Observe the mixing state of the materials in the impregnation barrel 2. If it is normal, close the first feed port 201, start the second motor 202, and the second motor 202 rotates to drive the second stirring paddle 203 to rotate. Use the second stirring paddle 203 to mix and stir the pulp and the impregnation liquid in the impregnation barrel 2 to form a porridge. The reaction is stirred for 30-40 minutes, the temperature of the impregnation liquid is about 50-55° C., and the volume of the impregnation liquid and the weight of the pulp are calculated based on 1 kg of absolute dry pulp corresponding to 20 L of impregnation liquid.

[0076] S3, start the slurry pump 801, and transport the slurry in the immersion barrel 2 to the membrane filter press 3 for a first pressing, and squeeze out the excess alkali liquid, and the pressed liquid flows into the liquid pressure tank 6. During the first pressing, the slurry inlet pressure is less than or equal to 0.8Mpa.

[0077] S4. After the slurry is fed, the slurry pump 801 is closed, the valves on the first air pipeline 305 and the third air pipeline 307 are opened, and the air compressor 11 is started. The compressed air passes through the first air pipeline 305, the liquid inlet channel of the membrane filter press 3, the fifth air pipeline 309 and the third air pipeline 307 in sequence, and the unpressed slurry in the feed channel of the membrane filter press 3 is blown back into the impregnation barrel 2. Then, the valve on the third air pipeline 307 is closed, and the compressed air passes through the first air inlet 301, the first air outlet 303 and the small feed channel 3001 in sequence, so as to blow the slurry in the small feed channel 3001 of the filter plate 300 of the membrane filter press 3 into the filter cake, and the squeezed liquid flows into the liquid pressure tank 6.

[0078] S5, turn off the air compressor 11, close the valve on the first air pipeline 305, start the high-pressure water pump 5, and inject high-pressure water into the diaphragm filter press 3 for secondary pressing. The pressure of the secondary pressing is 0.5MPa~2.0Mpa, and the pressed liquid flows into the liquid pressure tank 6.

[0079] S6. After the second squeezing is completed, that is, when the flow rate of the squeezed filtrate is extremely small, close the control valve on the water inlet pipeline 9, open the control valve on the pressure relief pipeline 10, and release the water pressure in the diaphragm chamber of the diaphragm filter press 3. Open the valve on the second air pipeline 306, close the control valve on the connecting pipeline between the second air pipeline 306 and the fourth air pipeline 308, that is, open the third valve 3061 and close the fourth valve 3081, start the air compressor 11, and compress the air through the second air inlet 302 and the second air outlet 304 in sequence, and blow the filtrate remaining in the discharge pipe of the diaphragm filter press 3 into the liquid pressure tank 6.

[0080] S7, turn off the air compressor 11, control the hydraulic station 12 to loosen the clamping plate, and discharge the squeezed alkali fiber filter cake from the filter chamber of the membrane filter press 3. The product index of the squeezed alkali cellulose is: 30%-35% methyl cellulose content, 13.5%-14.5% caustic soda content.

[0081] The present invention conducted the following experiments on the effects of the traditional mesh roller press and the membrane filter press 3 of the present embodiment. In the embodiment, the power consumption of the two presses is compared. The power consumption of the traditional mesh roller press includes the power consumption of the pulp pump 801 and the press roller, and the power consumption of the membrane filter press includes the power consumption of the pulp pump 801 and the high-pressure water pump 5. Because the working principles of the two presses are different, the pressure data of the two presses only serve as auxiliary explanations, and the advantages and disadvantages of the two pressing processes cannot be judged by comparing this data.

[0082] Example 1

[0083] Under different pulp concentration conditions, the pressing pressure was adjusted to make the methyl fiber content in the squeezed alkali fiber reach 30%. The power consumption of the two pressing methods was compared. The specific experimental data are shown in Table 1.

[0084] Table 1 Pressing power of two pressing methods at different porridge concentrations when the methyl cellulose content is 30%

[0085] Porridge concentration 3.0％ 3.5％ 4.0％ 4.5％ 5.0％ 5.5％ 6.0％ 6.5％ 7.0％ 7.5％ 8.0％ Power consumption of mesh roller press (kWh / ton alkali fiber) / 25.45 20.48 17.65 15.37 14.66 13.46 12.93 12.54 12.06 11.77 Power consumption of membrane filter press (kWh / ton alkali fiber) 9.87 8.96 8.03 7.24 6.51 6.23 6.03 5.72 5.59 5.48 5.37 Mesh roller press pressure (bar) Spraying 0.62 0.59 0.57 0.56 0.56 0.55 0.53 0.52 0.52 0.51 Diaphragm filter press pressure (bar) 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73

[0086] When the porridge concentration is less than or equal to 3.0%, the material of the mesh roller press directly sprays out from between the two pressing rollers and cannot be squeezed, while the present invention can squeeze. As can be seen from Table 1, under different porridge concentration conditions, the power consumption of the diaphragm filter press is much lower than that of the mesh roller press.

[0087] Example 2

[0088] Under different pulp concentration conditions, the pressing pressure was adjusted to make the methyl fiber content in the squeezed alkali fiber reach 35%. The power consumption of the two pressing methods was compared. For specific experimental data, see Table 2.

[0089] Table 2 Pressing power of two pressing methods at different porridge concentrations when the methyl cellulose content is 35%

[0090] Porridge concentration 3.0％ 3.5％ 4.0％ 4.5％ 5.0％ 5.5％ 6.0％ 6.5％ 7.0％ 7.5％ 8.0％ Power consumption of mesh roller press (kWh / ton alkali fiber) / / 29.71 27.54 22.91 19.97 18.11 18.03 17.59 16.93 16.88 Power consumption of membrane filter press (kWh / ton alkali fiber) 14.99 13.71 13.04 12.33 11.80 11.52 11.34 11.31 10.96 10.82 10.64 Mesh roller press pressure (bar) Spraying Spraying 0.84 0.83 0.83 0.81 0.81 0.79 0.79 0.78 0.75 Diaphragm filter press pressure (bar) 1.17 1.17 1.17 1.17 1.17 1.17 1.17 1.17 1.17 1.17 1.17

[0091] When the porridge concentration is less than or equal to 3.5%, the material of the mesh roller press directly sprays out from between the two pressing rollers and cannot be squeezed, while the present invention can squeeze. As can be seen from Table 3, under different porridge concentration conditions, the power consumption of the diaphragm filter press is much lower than that of the mesh roller press.

[0092] Figure 4 The figure is a comparison of the power consumption of the mesh roller press and the membrane filter press under different feed slurry concentrations (slurry concentrations) in Example 1 and Example 2. The mesh roller press in the figure is a traditional mesh roller press, and the plate press is a membrane filter press in the present invention. Figure 4 It can be seen that under different pulp concentration conditions, the power consumption of the diaphragm filter press is much lower than that of the mesh roller press.

[0093] Example 3

[0094] Using 5% porridge raw material, by adjusting the pressing pressure, alkali fibers with different methyl fiber contents were obtained, and the power consumption of the two pressing methods was compared. The specific experimental data are shown in Table 3.

[0095] Table 3 Pressing power of two pressing methods to obtain alkali fibers with different methyl fiber contents when the porridge concentration is 5%

[0096] Adipose tissue content 30.0％ 31.0％ 32.0％ 33.0％ 34.0％ 35.0％ 36.0％ 37.0％ 38.0％ 39.0％ 40.0％ Power consumption of mesh roller press (kWh / ton alkali fiber) 15.37 17.97 19.51 20.23 21.66 22.91 24.29 / / / / Power consumption of membrane filter press (kWh / ton alkali fiber) 6.51 7.11 7.82 8.70 10.50 11.80 12.26 13.70 15.35 18.05 20.48 Mesh roller press pressure (bar) 0.56 0.59 0.63 0.68 0.74 0.81 0.90 Overpressure Overpressure Overpressure Overpressure Diaphragm filter press pressure (bar) 0.73 0.79 0.87 0.96 1.06 1.17 1.30 1.45 1.63 1.85 2.08

[0097] As can be seen from Table 3, when the methyl cellulose content is greater than 36%, the pressure of the mesh roller press is close to the upper limit, and it is impossible to obtain an alkali fiber product with an methyl cellulose content of more than 37% by increasing the pressing pressure, while the membrane filter press can continue to press to obtain an alkali fiber product with a higher methyl cellulose content. Moreover, within the methyl cellulose content range in this embodiment, under the condition of obtaining an alkali fiber product with the same methyl cellulose content, the power consumption of the membrane filter press is much lower than that of the mesh roller press.

[0098] Example 4

[0099] Using 8% porridge raw material, by adjusting the pressing pressure, alkali fibers with different methyl fiber contents were obtained, and the power consumption of the two pressing methods was compared. The specific experimental data are shown in Table 4.

[0100] Table 4 Pressing power of two pressing methods to obtain alkali fibers with different methyl fiber contents when the porridge concentration is 8%

[0101] Adipose tissue content 30.0％ 31.0％ 32.0％ 33.0％ 34.0％ 35.0％ 36.0％ 37.0％ 38.0％ 39.0％ 40.0％ Power consumption of mesh roller press (kWh / ton alkali fiber) 11.77 12.35 13.02 14.63 15.40 16.88 18.13 20.64 / / / Power consumption of membrane filter press (kWh / ton alkali fiber) 5.37 6.38 7.56 8.42 9.63 10.64 11.79 12.96 14.32 15.97 17.84 Mesh roller press pressure (bar) 0.51 0.53 0.56 0.60 0.66 0.75 0.84 0.94 Overpressure Overpressure Overpressure Diaphragm filter press pressure (bar) 0.73 0.79 0.87 0.96 1.06 1.17 1.30 1.45 1.63 1.85 2.08

[0102] As can be seen from Table 4, when the methyl cellulose content is greater than 37%, the pressure of the mesh roller press is close to the upper limit, and it is impossible to obtain an alkali fiber product with an methyl cellulose content of more than 37% by increasing the pressing pressure. However, the present invention can continue pressing to obtain an alkali fiber product with a higher methyl cellulose content. Moreover, within the methyl cellulose content range of this embodiment, under the condition of obtaining an alkali fiber product with the same methyl cellulose content, the power consumption of the diaphragm filter press is much lower than that of the mesh roller press.

[0103] Figure 5 The figure is a comparison of the power consumption of the mesh roller press and the membrane filter press under different discharge methyl cellulose contents in Example 3 and Example 4. The mesh roller press in the figure is a traditional mesh roller press, and the plate press is the membrane filter press in the present invention. Figure 5 It can be seen that under different conditions of discharge methyl methacrylate content, the power consumption of the diaphragm filter press is much lower than that of the mesh roller press.

[0104] The diaphragm filter press consumes less power than the mesh roller press because the latter needs to continuously consume electrical energy to overcome the frictional resistance of the alkali fiber passing through the two rotating pressing rollers while the pulp pump is continuously feeding the material. The former, on the other hand, only needs to provide static pressure during pressing after the pulp pump is feeding the material, and does not generate the above power consumption.

[0105] By comparing the above four groups of embodiments, it can be seen that the power consumption of the diaphragm filter press is much lower than that of the mesh roller press, and the permissible concentration range of the porridge raw material used is wider, and the alkali fiber product can achieve a higher methyl fiber content. Therefore, the squeezing efficiency of the present invention is higher and the squeezing effect is better.

[0106] Although the present invention discloses preferred specific embodiments to achieve the above-mentioned objectives, it is not intended to limit the structural features of the present invention. Any person skilled in the art should know that within the technical spirit of the present invention, any easily conceivable changes or modifications are possible and are all covered by the scope of the patent application of the present invention.

Claims

1. A pulp impregnation and pressing system, characterized in that: The invention comprises an impregnation liquid metering tank (1), an impregnation barrel (2) and a membrane filter press (3) which are connected in sequence. The water inlet of the membrane filter press (3) is also connected to a water tank (4). A high-pressure water pump (5) is provided on the water tank (4) and the water inlet pipeline (9) of the membrane filter press (3). The discharge end of the membrane filter press (3) is connected to a liquid pressure tank (6). The outlet end of the liquid pressure tank (6) is connected to the impregnation liquid metering tank (1).

2. The pulp impregnation and pressing system according to claim 1, characterized in that: The invention also comprises an air compressor (11); the diaphragm filter press (3) is provided with a first air inlet (301), a second air inlet (302), a first air outlet (303) and a second air outlet (304); the air compressor (11) is connected to the first air inlet (301) and the second air inlet (302) via a first air pipeline (305) and a second air pipeline (306), respectively; the first air outlet (303) is connected to the impregnation barrel (2) via a third air pipeline (307); the second air outlet (304) is connected to the liquid pressure tank (6) via a fourth air pipeline (308); and control valves are provided on the first air pipeline (305), the second air pipeline (306), the third air pipeline (307) and the connecting pipelines between the second air pipeline (306) and the fourth air pipeline (308).

3. The pulp impregnation and pressing system according to claim 1, characterized in that: The impregnation barrel (2) and the membrane filter press (3) are connected via a first liquid pipeline (8), and a porridge pump (801) is provided on the first liquid pipeline (8).

4. The pulp impregnation and pressing system according to claim 3, characterized in that: The first liquid pipeline (8) is also provided with an electric contact pressure gauge (802), and the electric contact pressure gauge (802) is electrically connected to the porridge pump (801).

5. The pulp impregnation and pressing system according to claim 1, characterized in that: The liquid pressure tank (6) is connected to the impregnation liquid metering tank (1) via a second liquid pipeline (7). A liquid pressure pump (701) and a cumulative flow meter (702) are provided on the second liquid pipeline (7). The liquid pressure pump (701) is electrically connected to the cumulative flow meter (702).

6. The pulp impregnation and pressing system according to claim 1, characterized in that: The impregnation liquid metering tank (1) is provided with a first liquid inlet (101) for adding a dilute alkali solution and a second liquid inlet (102) for adding a concentrated alkali solution. A first motor (104) is fixedly provided on the top of the impregnation liquid metering tank (1). A first stirring paddle (105) is fixedly provided at the output end of the first motor (104). The first stirring paddle (105) passes through the top of the impregnation liquid metering tank (1) and extends into the interior thereof.

7. The pulp impregnation and pressing system according to claim 1, characterized in that: A heating circulation machine (107) is also provided on the outside of the impregnation liquid metering tank (1).

8. The pulp impregnation and pressing system according to claim 1, characterized in that: The impregnation barrel (2) is provided with a first feed port (201) for adding pulp, and a second motor (202) is fixedly provided on the top of the impregnation barrel (2), and a second stirring paddle (203) is fixedly connected to the output end of the second motor (202), and the second stirring paddle (203) passes through the top of the impregnation barrel (2) and extends into the interior thereof.

9. A pulp impregnation and pressing process, characterized in that: The pulp impregnation and pressing system according to any one of claims 1 to 8 comprises the following steps: S1. Adding impregnation liquid to the impregnation liquid metering tank (1); S2, sending all the prepared impregnation liquid into the impregnation barrel (2), adding pulp into the impregnation barrel (2), and using the second stirring paddle (203) to stir and form pulp porridge; S3, starting the porridge pump (801), conveying the porridge in the immersion barrel (2) to the membrane filter press (3) for a squeeze, and the squeezed liquid flows into the liquid pressure tank (6); S4, closing the porridge pump (801), opening the valves on the first air pipeline (305) and the third air pipeline (307), starting the air compressor (11) and back-blowing the un-pressed porridge in the feed pipe of the membrane filter press (3) into the impregnation barrel (2), then closing the valve on the third air pipeline (307), blowing the porridge in the feed small channel (3001) of the filter plate (300) of the membrane filter press (3) into the filter cake, and the squeezed liquid flows into the liquid pressure tank (6); S5, turning off the air compressor (11), closing the valve on the first air pipeline (305), starting the high-pressure water pump (5), injecting high-pressure water into the diaphragm filter press (3) for secondary pressing, and the pressed liquid flows into the liquid pressure tank (6); S6. After the second pressing is completed, the water pressure in the diaphragm chamber of the diaphragm filter press (3) is released, and then the valve on the second air pipeline (306) is opened, and the air compressor (11) is started to blow the filtrate remaining in the discharge pipe of the diaphragm filter press (3) into the liquid pressure tank (6); S7, turning off the air compressor (11), and discharging the squeezed alkali fiber filter cake from the filter chamber of the membrane filter press (3).

10. The pulp impregnation and pressing process according to claim 9, characterized in that: During the first pressing in step S3, the pulp inlet pressure is less than or equal to 0.8 MPa, and the pressure of the second pressing in step S5 is 0.5 MPa to 2.0 MPa.

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