Sulfur dioxide adding system for adjusting pH of paper pulp

Abstract

The invention discloses a sulfur dioxide adding system for adjusting the pH value of paper pulp, and relates to the technical field of papermaking equipment. A bleaching agent tank is connected with an outlet section of a medium-concentration pump, a flow guide mechanism is arranged at the outlet end of the bleaching agent tank in a penetrating manner, a premixing mechanism is arranged at the outlet end of the flow guide mechanism in a penetrating manner, and a feeding mechanism is arranged on the premixing mechanism in a penetrating manner; the feeding mechanism is arranged at the outlet end of the medium-concentration pump in a penetrating manner; a premixing structure and a circulating feeding structure are arranged, and a valve structure with adjustable flux is arranged between a circulating plastic structure and an chemi-mechanical pulp conveying structure, so that a bleaching agent and chemi-mechanical pulp can be uniformly stirred and mixed, and the feeding amount of the bleaching agent can be controlled; a valve and a waste discharge structure are additionally arranged between the sulfur dioxide steel cylinder and the equipment, so that the bleaching agent can be stably and hermetically conveyed, and the residual waste sulfur dioxide bleaching agent can be cleaned when the sulfur dioxide steel cylinder is replaced.

Description

Technical Field

[0001] The invention relates to the technical field of papermaking equipment, and in particular to a sulfur dioxide adding system for adjusting the pH value of pulp. Background Art

[0002] The pH value of paper determines the image forming effect of the paper during writing and printing. A too high pH value will make it difficult for the ink to adhere during writing and printing, while a too low pH value will make the surface of the paper rough and difficult to print. Sulfur dioxide bleach is a commonly used bleach in industry. It is easy to obtain, low cost and has excellent bleaching effect, especially for natural fibers. However, the existing papermaking industry rarely uses sulfur dioxide bleach when bleaching raw materials. In the early invention experiments, the inventor adopted the method of connecting sulfur dioxide bleach to the riser of the medium-concentration pump. The sulfur dioxide bleaching agent is mixed with the chemical-mechanical pulp to realize the bleaching process of the chemical-mechanical pulp. This process directly uses a connecting pipe to connect the steel cylinder storing the sulfur dioxide bleaching agent with the lower end of the medium-consistency pump standpipe, which makes it easy to leak when adding the bleaching agent, and the amount of addition is not easy to control. In the subsequent actual production, it is found that the mixing of the sulfur dioxide bleaching agent and the chemical-mechanical pulp is not uniform enough, which makes part of the chemical-mechanical pulp unable to be completely bleached, resulting in the problem of color spots in the later paper products. For this, certain structural improvements are now made on the basis of the above structure. Summary of the invention

[0003] The purpose of the present invention is to address the defects and shortcomings of the prior art and provide a sulfur dioxide addition system for adjusting the pH of pulp. The system provides a premix structure and a circulating feeding structure, and a flux-adjustable valve structure between the circulating plastic structure and the chemical-mechanical pulp transmission structure, so that the bleaching agent and the chemical-mechanical pulp can be evenly stirred and mixed, and the feeding amount of the bleaching agent can be controlled. A valve and a waste discharge structure are added between the sulfur dioxide cylinder and the equipment to achieve stable and sealed bleaching agent transportation, and the residual waste sulfur dioxide bleaching agent can be cleaned when the sulfur dioxide cylinder is replaced.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The bleaching agent tank comprises a medium-concentration pump and a bleaching agent tank, wherein the bleaching agent tank is connected to the outlet section of the medium-concentration pump, and further comprises:

[0006] A flow guiding mechanism, wherein the flow guiding mechanism is disposed through the outlet end of the bleaching agent tank;

[0007] A premixing mechanism, wherein the premixing mechanism is disposed through the outlet end of the flow guiding mechanism;

[0008] The feeding mechanism is arranged on the premixing mechanism, and the feeding mechanism is arranged on the outlet end of the medium-consistency pump.

[0009] Preferably, the flow guiding mechanism comprises:

[0010] A flow guide pipe, which is arranged on the outlet end of the bleaching agent tank through a flange connection;

[0011] An exhaust pipe, wherein the exhaust pipe is arranged in series on the flow guide pipe through a tee pipe;

[0012] A pressure relief pipe, wherein the pressure relief pipe is arranged in series on the flow guide pipe through a tee pipe, and the pressure relief pipe is arranged between the bleaching agent tank and the drain pipe;

[0013] A waste discharge pipe, wherein the waste discharge pipe is arranged in series on the guide pipe through a tee pipe, and the waste discharge pipe is arranged between the emptying pipe and the pressure relief pipe;

[0014] Opening and closing valves, there are three opening and closing valves, and the three opening and closing valves are respectively arranged in series on the drain pipe, the pressure relief pipe, and the waste discharge pipe;

[0015] The throttle valves are four in number and are all arranged in series on the flow guide pipe, wherein one throttle valve is arranged between the pressure relief pipe and the bleaching agent tank, one throttle valve is arranged between the emptying pipe and the waste pipe, and the other two throttle valves are arranged on the side of the emptying pipe opposite to the waste pipe.

[0016] Preferably, the premixing mechanism comprises:

[0017] A mixing box, wherein the mixing box is arranged in front of the bleaching agent tank, and the outlet end of the guide pipe is inserted and fixed on the lower part of the side plate of the mixing box;

[0018] A mounting frame, wherein the mounting frame is arranged on the side of the mixing box;

[0019] A reflux pipe, wherein the reflux pipe is fixedly arranged on the mounting frame, and the lower end of the reflux pipe is connected to the mixing box through a pipeline;

[0020] The reflux pump is fixedly arranged on the top plate of the mixing box, and the outlet end of the reflux pump is inserted and fixed on the upper side plate of the mixing box, and the upper end of the reflux pipe is connected in series with the inlet end of the reflux pump through a pipeline.

[0021] Preferably, two stirring rollers are provided in the mixing box, and the upper end shafts of the two stirring rollers are screwed through the upper side plate of the mixing box through bearings, and a driving unit is fixedly provided on the top plate of the mixing box, and the output shaft of the driving unit is transmission-connected to the upper end shafts of the two stirring rollers.

[0022] Preferably, a partition is fixedly provided on the inner wall of the mixing box, the outlet end of the flow guide pipe is arranged on one side of the partition, and the outlet end of the reflux pump is arranged on the other side of the partition.

[0023] Preferably, the feeding mechanism comprises:

[0024] A mixing tube, wherein the mixing tube is fixedly arranged on a mounting frame;

[0025] A connecting pipe, wherein the connecting pipe is arranged in series at the lower end of the mixing pipe, and the other end of the connecting pipe is fixed to the bottom plate of the mixing box;

[0026] A discharge pipe, wherein the discharge pipe is fixedly arranged in series on the outlet end of the medium-consistency pump, and the storage tank is connected to the connecting pipe through a three-way joint;

[0027] Valve assembly, the valve assembly is multiple and fixedly arranged on the mounting frame, and the return pipe and the wedding mixing pipe are connected through the valve assembly;

[0028] The guide plate is fixedly arranged on the inner wall of the mixing tube, and the guide plate and the valve assembly are arranged one by one.

[0029] Preferably, a one-way valve unit is arranged in series on the connecting pipe, and the discharge pipe is arranged between the one-way valve unit and the mixing pipe.

[0030] Preferably, the valve assembly comprises:

[0031] A valve body, wherein the valve body is fixedly arranged on the mounting frame, the upper end of the valve body is connected to the mixing pipe through a pipeline, and the lower end of the valve body is connected to the return pipe through a pipeline;

[0032] A valve core, wherein the valve core is screwed onto the valve body through a bearing;

[0033] A handle is fixedly arranged on the outer side wall of the valve core.

[0034] Preferably, a limit frame is rotatably provided on the mounting frame via a rotating shaft, the handle is movably supported on the limit frame, a torsion spring is sleeved on the rotating shaft of the limit frame, one end of the torsion spring is fixedly provided on the limit frame, and the other end of the torsion spring is fixedly provided on the mounting frame.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The device is provided with a mixing box, the bleaching agent tank is connected to the mixing box through a guide pipe, and the medium-consistency pump is connected to the mixing box through a connecting pipe, so that the bleaching agent dilution liquid is mixed and then sent into the mixing pipe to achieve secondary mixing with a large amount of chemical-mechanical pulp, thereby achieving bleaching of the chemical-mechanical pulp;

[0037] 2. The device is provided with an emptying pipe and a waste pipe on the guide pipe, so that when cleaning the bleach waste, the waste can be discharged into the air or into a water bucket;

[0038] 3. The device is provided with a plurality of valve bodies and valve cores, and the return pipe is connected to the mixing pipe through the valve body, so that the flux of the mixture in the return pipe sent into the mixing pipe can be adjusted by adjusting the opening degree of each valve core respectively;

[0039] 4. The device is provided with a mixing box, and a loop connected with the mixing box is provided through a reflux pump and a reflux pipe, so as to achieve flux adjustment of the mixture that can be fed into the mixing pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the home structure of the present invention.

[0041] Figure 2 yes Figure 1 Lower side view.

[0042] Figure 3 yes Figure 1 The rich test view.

[0043] Figure 4 It is a structural schematic diagram of the flow guide pipe, mixing pipe and valve assembly in the present invention.

[0044] Figure 5 It is a schematic diagram of the structure of the call and stirring rollers of the present invention.

[0045] Figure 6 It is a structural schematic diagram of the valve body and valve core in the present invention.

[0046] Figure 7 It is a structural schematic diagram of the mounting frame and the limiting frame in the present invention.

[0047] Figure 8 It is a structural schematic diagram of the mixing tube and the guide plate in the present invention.

[0048] Description of reference numerals:

[0049] Medium-consistency pump 1, bleaching agent tank 2, diversion mechanism 3, diversion pipe 3-1, drain pipe 3-2, pressure relief pipe 3-3, waste pipe 3-4, opening and closing valve 3-5, throttle valve 3-6, premixing mechanism 4, mixing box 4-1, mounting frame 4-2, reflux pipe 4-3, reflux pump 4-4, feeding mechanism 5, mixing pipe 5-1, connecting pipe 5-2, discharge pipe 5-3, guide plate 5-4, valve assembly 6, valve body 6-1, valve core 6-2, handle 6-3, stirring roller 7, drive unit 8, partition 9, one-way valve unit 10, limit frame 11, torsion spring 12. DETAILED DESCRIPTION

[0050] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. The preferred embodiments in the description are only used as examples, and all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of the present invention.

[0051] like Figure 1-8 As shown, this specific implementation adopts the following technical solutions:

[0052] The bleaching agent tank 2 comprises a medium-concentration pump 1 and a bleaching agent tank 2, wherein the bleaching agent tank 2 is connected to the outlet section of the medium-concentration pump 1, and further comprises:

[0053] A flow guiding mechanism 3, wherein the flow guiding mechanism 3 is disposed through the outlet end of the bleaching agent tank 2;

[0054] A premixing mechanism 4, wherein the premixing mechanism 4 is disposed through the outlet end of the flow guiding mechanism 3;

[0055] A feeding mechanism 5, wherein the feeding mechanism 5 is disposed through the premixing mechanism 4, and the feeding mechanism 5 is disposed through the outlet end of the medium-consistency pump 1;

[0056] The flow guiding mechanism 3 comprises:

[0057] A flow guide pipe 3-1, wherein the flow guide pipe 3-1 is disposed on the outlet end of the bleaching agent tank 2 through a flange connection;

[0058] An exhaust pipe 3-2, wherein the exhaust pipe 3-2 is arranged in series on the flow guide pipe 3-1 through a tee pipe;

[0059] A pressure relief pipe 3-3, wherein the pressure relief pipe 3-3 is arranged in series on the flow guide pipe 3-1 through a tee pipe, and the pressure relief pipe 3-3 is arranged between the bleaching agent tank 2 and the emptying pipe 3-2;

[0060] The waste pipe 3-4 is connected in series to the flow guide pipe 3-1 through a tee pipe, and the waste pipe 3-4 is arranged between the drain pipe 3-2 and the pressure relief pipe 3-3;

[0061] The opening and closing valve 3-5 is three in number, and the three opening and closing valves 3-5 are respectively arranged in series on the drain pipe 3-2, the pressure relief pipe 3-3, and the waste pipe 3-4;

[0062] Throttle valve 3-6, there are four throttle valves 3-6 and they are all arranged in series on the guide pipe 3-1, one throttle valve 3-6 is arranged between the pressure relief pipe 3-3 and the bleaching agent tank 2, one throttle valve 3-6 is arranged between the emptying pipe 3-2 and the waste pipe 3-4, and the other two throttle valves 3-6 are arranged on the side of the emptying pipe 3-2 opposite to the waste pipe 3-4;

[0063] The premixing mechanism 4 comprises:

[0064] A mixing box 4-1, wherein the mixing box 4-1 is arranged in front of the bleaching agent tank 2, and the outlet end of the flow guide pipe 3-1 is inserted and fixed at the lower part of the side plate of the mixing box 4-1;

[0065] A mounting frame 4-2, wherein the mounting frame 4-2 is arranged on the side of the mixing box 4-1;

[0066] A return pipe 4-3, wherein the return pipe 4-3 is fixedly arranged on the mounting frame 4-2, and the lower end of the return pipe 4-3 is connected to the mixing box 4-1 through a pipeline;

[0067] The reflux pump 4-4 is fixedly arranged on the top plate of the mixing box 4-1, and the outlet end of the reflux pump 4-4 is inserted and fixed on the upper side plate of the mixing box 4-1, and the upper end of the reflux pipe 4-3 is connected in series with the inlet end of the reflux pump 4-4 through a pipeline.

[0068] Stirring rollers 7, there are two stirring rollers 7 and both are arranged in the mixing box 4-1, and the upper end shafts of the stirring rollers 7 are screwed through the bearings to the upper side plate of the mixing box 4-1;

[0069] A driving unit 8, wherein the driving unit 8 is fixedly arranged on the top plate of the mixing box 4-1, and the output shafts of the driving unit 8 are both connected to the upper shafts of the two stirring rollers 7 in a transmission manner;

[0070] A partition 9, wherein the partition 9 is fixedly arranged on the inner wall of the mixing box 4-1, and the partition 9 is arranged between the port of the guide pipe 3-1 and the port of the return pipe 4-3;

[0071] The feeding mechanism 5 comprises:

[0072] A mixing tube 5-1, wherein the mixing tube 5-1 is fixedly arranged on the mounting frame 4-2;

[0073] A connecting pipe 5-2, wherein the connecting pipe 5-2 is arranged in series at the lower end of the mixing pipe 5-1, and the other end of the connecting pipe 5-2 is fixed to the bottom plate of the mixing box 4-1;

[0074] The discharge pipe 5-3 is fixedly arranged in series on the outlet end of the medium-consistency pump 1, and the storage tank is connected to the connecting pipe 5-2 through a three-way joint;

[0075] Valve assembly 6, the valve assembly 6 is multiple and fixedly arranged on the mounting frame 4-2, and the return pipe 4-3 and the wedding mixing pipe 5-1 are connected through the valve assembly 6;

[0076] The guide plate 5-4 is fixedly arranged on the inner wall of the mixing tube 5-1, and the guide plate 5-4 and the valve assembly 6 are arranged one by one.

[0077] A one-way valve unit 10, wherein the one-way valve unit 10 is arranged in series on the connecting pipe 5-2, and the one-way valve unit 10 is arranged to pass through the discharge pipe 5-3 to one side of the mixing box 4-1;

[0078] The valve assembly 6 comprises:

[0079] A valve body 6-1, wherein the valve body 6-1 is fixedly mounted on the mounting frame 4-2, the upper end of the valve body 6-1 is connected to the mixing pipe 5-1 through a pipeline, and the lower end of the valve body 6-1 is connected to the return pipe 4-3 through a pipeline;

[0080] A valve core 6-2, wherein the valve core 6-2 is screwed onto the valve body 6-1 through a bearing;

[0081] A handle 6-3, wherein the handle 6-3 is fixedly disposed on the outer side wall of the valve core 6-2;

[0082] A limit frame 11, wherein the limit frame 11 is rotatably mounted on the mounting frame 4-2 via a rotating shaft;

[0083] The torsion spring 12 is sleeved on the rotating shaft of the limiting frame 11, wherein one column foot of the torsion spring 12 is arranged on the limiting frame 11, and the other column foot of the torsion spring 12 is fixedly arranged on the mounting frame 4-2.

[0084] When the device is used, the chemical mechanical pulp is sent to the discharge pipe 5-3 through the medium-consistency pump 1, and then the chemical mechanical pulp is sent to the mixing box 4-1 through the discharge pipe 5-3 and the connecting pipe 5-2. The chemical mechanical pulp is sent to the mixing pipe 5-1 through the discharge pipe 5-3, and the bleaching agent in the bleaching agent tank 2 is sent to the mixing box 4-1 through the guide pipe 3-1. The two stirring rollers 7 are driven to rotate by the driving unit 8, and then the two stirring rollers 7 stir the bleaching agent and chemical mechanical pulp sent to the mixing box 4-1. When the height of the stirred mixture exceeds the partition plate 9, the mixture flows to the partition plate 9. On the other side of the plate 9, the mixture in the mixing box 4-1 is extracted by the reflux pump 4-4, so that the mixture circulates in the reflux pipe 4-3, and the handle 6-3 is pushed to drive the valve core 6-2 to rotate, and then the valve assembly 6 is adjusted to open, so that the mixture in the reflux pipe 4-3 is sent into the mixing pipe 5-1 through the valve assembly 6, and the chemical mechanical pulp sent into the mixing pipe 5-1 in the discharge pipe 5-3 moves from the lower end of the mixing pipe 5-1 to the upper end of the mixing pipe 5-1, and the chemical mechanical pulp in the mixing pipe 5-1 is mixed with the mixture when passing through the guide plate 5-4. The bleaching agent is mixed into the chemical-mechanical pulp for bleaching. When the bleaching agent tank 2 is replaced, the throttle valve 3-6 between the pressure relief pipe 3-3 and the bleaching agent tank 2 is closed to replace the bleaching agent tank 2. When the bleaching agent waste is processed, the bleaching agent waste is directly discharged into the air by opening the opening and closing valve 3-5 on the emptying pipe 3-2, or the opening and closing valve 3-5 on the waste discharge pipe 3-4 is opened to discharge the bleaching agent waste into the water bucket. When adjusting the flux of the mixture in the reflux pipe 4-3 entering the mixing pipe 5-1, the valve core is pushed by the handle 6-3. 6-2 rotates, thereby realizing the size of the opening opened by the cooperation of the valve core 6-2 and the valve body 6-1. By opening one valve assembly 6 or multiple valve assemblies 6, the flux of the mixture entering the mixing tube 5-1 is regulated. When it is necessary to close all the valve cores 6-2, the limit frame 11 is directly pushed, and the handles 6-3 on all the valve cores 6-2 are pushed to move at the same time through the limit frame 11, so as to realize pushing all the valve cores 6-2 to rotate and close at the same time. After closing the valve assembly 6, the limit frame 11 is loosened, and the yellow push button is twisted to push the limit frame 11 to rotate and reset.

[0085] Compared with the prior art, the present invention has the following beneficial effects:

[0086] 1. The device is provided with a mixing box 4-1, the bleaching agent tank 2 is connected to the mixing box 4-1 through a flow guide pipe 3-1, and the medium-consistency pump 1 is connected to the mixing box 4-1 through a connecting pipe 5-2, so that the bleaching agent dilution liquid is mixed and then sent into the mixing pipe 5-1 to achieve secondary mixing with a large amount of chemical-mechanical pulp, thereby achieving bleaching of the chemical-mechanical pulp;

[0087] 2. The device is provided with an emptying pipe 3-2 and a waste pipe 3-4 on the guide pipe 3-1, so that when cleaning the bleach waste, the waste can be discharged into the air or into a water bucket;

[0088] 3. The device is provided with a plurality of valve bodies 6-1 and valve cores 6-2, and the reflux pipe 4-3 is connected to the mixing pipe 5-1 through the valve body 6-1, so that the flux of the mixture in the reflux pipe 4-3 sent to the mixing pipe 5-1 can be adjusted by adjusting the opening degree of each valve core 6-2 respectively;

[0089] 4. The device is provided with a mixing box 4-1, and a loop connected with the mixing box 4-1 is provided through a reflux pump 4-4 and a reflux pipe 4-3, so as to achieve flux adjustment of the mixture that can be fed into the mixing pipe 5-1.

[0090] For those skilled in the art, they can modify the technical solutions described in the aforementioned embodiments and make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A sulfur dioxide addition system for adjusting the pH value of pulp, comprising a medium-consistency pump (1) and a bleaching agent tank (2), wherein the bleaching agent tank (2) is connected to the outlet section of the medium-consistency pump (1); characterized in that: It also contains: A flow guiding mechanism (3), wherein the flow guiding mechanism (3) is arranged through the outlet end of the bleaching agent tank (2); A premixing mechanism (4), wherein the premixing mechanism (4) is disposed through the outlet end of the flow guiding mechanism (3); A feeding mechanism (5), wherein the feeding mechanism (5) is disposed through the premixing mechanism (4), and the feeding mechanism (5) is disposed through the outlet end of the medium-consistency pump (1).

2. A sulfur dioxide addition system for adjusting the pH value of pulp according to claim 1, characterized in that: The flow guiding mechanism (3) comprises: A flow guide pipe (3-1), wherein the flow guide pipe (3-1) is arranged on the outlet end of the bleaching agent tank (2) through a flange connection; An exhaust pipe (3-2), wherein the exhaust pipe (3-2) is arranged in series on the flow guide pipe (3-1) via a tee pipe; A pressure relief pipe (3-3), wherein the pressure relief pipe (3-3) is arranged in series on the flow guide pipe (3-1) via a tee pipe, and the pressure relief pipe (3-3) is arranged between the bleaching agent tank (2) and the drain pipe (3-2); A waste discharge pipe (3-4), wherein the waste discharge pipe (3-4) is arranged in series on the flow guide pipe (3-1) through a tee pipe, and the waste discharge pipe (3-4) is arranged between the drain pipe (3-2) and the pressure relief pipe (3-3); On-off valves (3-5), there are three on-off valves (3-5), and the three on-off valves (3-5) are respectively arranged in series on the exhaust pipe (3-2), the pressure relief pipe (3-3), and the waste discharge pipe (3-4); A throttle valve (3-6), wherein four throttle valves (3-6) are arranged in series on the flow guide pipe (3-1), wherein one throttle valve (3-6) is arranged between the pressure relief pipe (3-3) and the bleaching agent tank (2), one throttle valve (3-6) is arranged between the emptying pipe (3-2) and the waste discharge pipe (3-4), and the other two throttle valves (3-6) are arranged on the side of the emptying pipe (3-2) opposite to the waste discharge pipe (3-4).

3. A sulfur dioxide addition system for adjusting the pH value of pulp according to claim 2, characterized in that: The premixing mechanism (4) comprises: A mixing box (4-1), wherein the mixing box (4-1) is arranged in front of the bleaching agent tank (2), and the outlet end of the flow guide pipe (3-1) is inserted and fixed at the lower part of the side plate of the mixing box (4-1); A mounting frame (4-2), wherein the mounting frame (4-2) is arranged on the side of the mixing box (4-1); A return pipe (4-3), wherein the return pipe (4-3) is fixedly arranged on the mounting frame (4-2), and the lower end of the return pipe (4-3) is connected to the mixing box (4-1) through a pipeline; A reflux pump (4-4) is fixedly arranged on the top plate of the mixing box (4-1), and the outlet end of the reflux pump (4-4) is inserted and fixed on the upper side plate of the mixing box (4-1), and the upper end of the reflux pipe (4-3) is connected in series with the inlet end of the reflux pump (4-4) through a pipeline.

4. A sulfur dioxide addition system for adjusting the pH value of pulp according to claim 3, characterized in that: Two stirring rollers (7) are arranged in the mixing box (4-1), and the upper end shafts of the two stirring rollers (7) are both screwed and inserted into the upper side plate of the mixing box (4-1) through bearings. A driving unit (8) is fixedly arranged on the top plate of the mixing box (4-1), and the output shaft of the driving unit (8) is transmission-connected to the upper end shafts of the two stirring rollers (7).

5. A sulfur dioxide addition system for adjusting the pH value of pulp according to claim 4, characterized in that: A partition (9) is fixedly arranged on the inner wall of the mixing box (4-1), the outlet end of the flow guide pipe (3-1) is arranged on one side of the partition (9), and the outlet end of the reflux pump (4-4) is arranged on the other side of the partition (9).

6. A sulfur dioxide addition system for adjusting the pH value of pulp according to claim 5, characterized in that: The feeding mechanism (5) comprises: A mixing tube (5-1), wherein the mixing tube (5-1) is fixedly arranged on a mounting frame (4-2); A connecting pipe (5-2), wherein the connecting pipe (5-2) is arranged in series at the lower end of the mixing pipe (5-1), and the other end of the connecting pipe (5-2) is fixed to the bottom plate of the mixing box (4-1); A discharge pipe (5-3), wherein the discharge pipe (5-3) is fixedly arranged in series on the outlet end of the medium-consistency pump (1), and the storage tank is arranged on the connecting pipe (5-2) through a three-way joint; A valve assembly (6), wherein the valve assemblies (6) are in plurality and fixedly arranged on the mounting frame (4-2), and the return pipe (4-3) and the wedding mixing pipe (5-1) are connected through the valve assembly (6); A guide plate (5-4), wherein the guide plate (5-4) is fixedly arranged on the inner wall of the mixing tube (5-1), and the guide plate (5-4) and the valve assembly (6) are arranged in a one-to-one correspondence.

7. A sulfur dioxide addition system for adjusting the pH value of pulp according to claim 6, characterized in that: A one-way valve unit (10) is arranged in series on the connecting pipe (5-2), and the discharge pipe (5-3) is arranged between the one-way valve unit (10) and the mixing pipe (5-1).

8. A sulfur dioxide addition system for adjusting the pH value of pulp according to claim 7, characterized in that: The valve assembly (6) comprises: A valve body (6-1), wherein the valve body (6-1) is fixedly mounted on the mounting frame (4-2), the upper end of the valve body (6-1) is connected to the mixing pipe (5-1) through a pipeline, and the lower end of the valve body (6-1) is connected to the return pipe (4-3) through a pipeline; A valve core (6-2), wherein the valve core (6-2) is rotatably mounted on the valve body (6-1) via a bearing; A handle (6-3) is fixedly arranged on the outer side wall of the valve core (6-2).

9. A sulfur dioxide addition system for adjusting the pH value of pulp according to claim 8, characterized in that: A limit frame (11) is rotatably arranged on the mounting frame (4-2) via a rotating shaft, and the handle (6-3) is movably arranged on the limit frame (11). A torsion spring (12) is sleeved on the rotating shaft of the limit frame (11), wherein one end of the torsion spring (12) is fixedly arranged on the limit frame (11), and the other end of the torsion spring (12) is fixedly arranged on the mounting frame (4-2).

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