Centrifugal pump degassing device and pulp conveying system

Abstract

The present invention discloses a centrifugal pump degassing device and a pulp conveying system. The centrifugal pump degassing device includes a pulp inlet pipeline connecting a pulp pool and a centrifugal pump, wherein the pulp inlet pipeline is provided with at least one variable diameter section, and the inner diameter of the variable diameter section is smaller than the inner diameter of the pulp inlet pipeline located upstream of the variable diameter section; at least one of the variable diameter sections is provided with an exhaust port, and an exhaust pipe is installed at the exhaust port. By comparison, after exhausting the gas through the centrifugal pump degassing device of the present invention, the cyclone at the center of the centrifugal pump impeller disappears, and the pumping capacity of the centrifugal pump is increased by 30%; at the same time, under the same flow rate and head, the output power of the centrifugal pump is significantly reduced, and the power saving reaches 30%.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking, and in particular relates to a centrifugal pump degassing device and a pulp conveying system. Background Art

[0002] A centrifugal pump is a pump that transports liquid by the centrifugal force generated by the rotation of an impeller. Its structure generally includes a volute, in which an impeller is rotatably installed, and a motor is provided outside the volute to drive the impeller to rotate. A liquid inlet is provided in the axial center of the volute, which is opposite to the impeller, and a liquid outlet is provided on the circumference of the volute.

[0003] The working principle of the centrifugal pump is as follows: the fluid entering the centrifugal pump rotates with the impeller, and is thrown from the center of the impeller to the periphery under the action of inertial centrifugal force and gains energy, which increases the static pressure of the fluid flowing to the periphery of the impeller and increases the flow rate; the fluid leaving the impeller is thrown onto the volute of the centrifugal pump. Since the flow channel in the volute gradually expands, the flow rate of the fluid gradually slows down during the flow along the flow channel, and part of the kinetic energy of the fluid is converted into static pressure energy. Therefore, the liquid with a higher pressure enters the discharge pipeline from the discharge port of the pump and is transported to the required piping system.

[0004] In the papermaking industry, centrifugal pumps and other conveying equipment are often needed to evenly convey pulp to various downstream processes. However, unlike other fluids, the papermaking industry requires that pulp maintain a uniform concentration during transportation, so it is often necessary to set up a stirring process upstream of the centrifugal pump. After the pulp is evenly stirred, it is conveyed to the downstream process by the centrifugal pump.

[0005] However, the violent stirring in the stirring process will cause a large amount of air to mix into the pulp. When the pulp mixed with a large number of bubbles enters the centrifugal pump, the impeller pushes the pulp to be transported. During the rotation of the impeller, the bubbles will be separated from the pulp. Because air is extremely light, the separated bubbles will gather in the center of the impeller to form a cyclone. The cyclone reduces the conveying capacity of the centrifugal pump by more than 30%.

[0006] In order to remove bubbles in paper pulp and avoid affecting the conveying capacity of the centrifugal pump, a Chinese utility model patent with publication number CN205401148U discloses a centrifugal pump, which includes a volute provided with a pump chamber, a pump shaft and an impeller located in the pump chamber, a driving device for driving the pump shaft to rotate, and an air extraction device located outside the volute, wherein the impeller is sleeved on the pump shaft, the pump shaft is provided with a first exhaust hole, the impeller is provided with at least one second exhaust hole connected to the first exhaust hole and the pump chamber, and one end of the first exhaust hole away from the second exhaust hole is connected to the air extraction device.

[0007] The disadvantage of the centrifugal pump is that pulp can easily flow into the first exhaust hole and the second exhaust hole, so that the exhaust holes are blocked by solid matter in the pulp, and the original air extraction function is lost.

[0008] Another example is a Chinese invention patent with the authorization announcement number CN1147342C, which discloses a centrifugal gas separation pump, including a hollow rotating barrel, one end of which is connected to a stationary fluid inlet, and the other end is connected to a stationary fluid outlet, and there is an exhaust pipe in the center, and an impeller at the inlet of the rotating barrel makes the liquid in the rotating barrel rotate; the impeller has bucket-shaped arc blades, which are used to accelerate the flow speed of the liquid at the inlet end of the rotating barrel, and make the fluid rotate at a circumferential speed higher than the circumferential speed of the inlet end of the rotating barrel; the arc blades extend inward from the inner wall of the rotating barrel, and the leading edge thereof faces the stationary inlet end and the outlet edge faces the inner wall of the rotating barrel, and there is an angle between the outlet edge and the parallel line of the center line of the rotating barrel. The centrifugal gas separation pump is large in size, complex in structure, and high in cost. Summary of the invention

[0009] The object of the present invention is to provide a centrifugal pump degassing device and a pulp conveying system. The centrifugal pump degassing device has a simple structure, is easy to construct, has a fast construction and modification speed, does not require additional power output, and can remove bubbles in the pulp without modifying the centrifugal pump, thereby improving the pumping capacity of the centrifugal pump.

[0010] To achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0011] A centrifugal pump degassing device comprises a pulp inlet pipeline connecting a pulp pool and a centrifugal pump, wherein the pulp inlet pipeline is provided with at least one variable diameter section, the inner diameter of the variable diameter section is smaller than the inner diameter of the pulp inlet pipeline upstream of the variable diameter section; at least one of the variable diameter sections is provided with an exhaust port, and an exhaust pipe is installed at the exhaust port.

[0012] In the centrifugal pump degassing device of the present invention, since the exhaust pipe is connected to the pulp pool through the pulp inlet pipeline, the pulp will flow into the exhaust pipe; the pulp flows on the pulp inlet pipeline, and the inner diameter at the variable diameter section is smaller, so the fluid pressure at the variable diameter section is smaller, causing the bubbles in the pulp to float up due to the increase in volume, and enter the exhaust pipe through the exhaust port; while in the exhaust pipe, the pulp hardly flows, so the pressure further decreases from the bottom end to the top end of the exhaust pipe, and the bubbles continue to expand and float up until they escape from the exhaust pipe, thereby achieving the purpose of exhaust.

[0013] By comparison, after exhausting the centrifugal pump degassing device of the present invention, the cyclone at the center of the centrifugal pump impeller disappears, and the pumping capacity of the centrifugal pump is increased by 30%; at the same time, under the same flow rate and head, the output power of the centrifugal pump is significantly reduced, saving electricity by 30%.

[0014] The inner diameter of the variable diameter section can be constant or gradually reduced, as long as the inner diameter of the variable diameter section is smaller than the inner diameter of the pulp inlet pipeline upstream of the variable diameter section. However, in order to further accelerate the floating speed of bubbles in the pulp, in the above-mentioned centrifugal pump degassing device, the inner diameter of the variable diameter section gradually decreases along the pulp feeding direction of the pulp inlet pipeline. In this way, the fluid pressure at the variable diameter section gradually decreases, the bubble volume increases at a uniform speed, and the bubble floating speed is further improved.

[0015] In the above centrifugal pump degassing device, the reducer is an eccentric reducer with a straight section installed on the pulp inlet pipeline. This eccentric reducer with a straight section is not only easy to install on the pulp inlet pipeline, but also easy to install the exhaust pipe on the top edge of the reducer.

[0016] In order to further improve the exhaust efficiency, in the centrifugal pump degassing device, the inner diameter of the exhaust pipe is larger than the inner diameter of the exhaust port. In this way, the pressure at the pressure change section in the exhaust pipe is smaller, and the bubbles in the pulp expand faster and float upward.

[0017] Preferably, in the above-mentioned centrifugal pump degassing device, the inner diameter of the exhaust pipe is larger than the inner diameter of the slurry inlet end of the variable diameter section.

[0018] As a further preferred embodiment, in the centrifugal pump degassing device, the inner diameter of the exhaust pipe is at least three times the inner diameter of the pulp inlet end of the variable diameter section. The larger the inner diameter of the exhaust pipe, the higher the expansion rate of bubbles in the pulp and the higher the degassing efficiency.

[0019] Since the exhaust pipe is connected to the pulp pool through the pulp inlet pipeline, the pulp will flow into the exhaust pipe. In order to prevent the pulp from overflowing from the top of the exhaust pipe, in the above-mentioned centrifugal pump degassing device, the exhaust pipe is vertically installed on the variable diameter section, and the height of the exhaust pipe is not lower than the highest liquid level of the pulp in the pulp pool.

[0020] In the above-mentioned centrifugal pump degassing device, the exhaust pipe is made of a stainless steel seamless steel pipe; a ball valve is installed on the top of the exhaust pipe.

[0021] The inner wall of the stainless steel seamless pipe is smooth and will not leave any bubbles. The ball valve installed on the top is in a normally open state. When the degassing speed needs to be further accelerated, a vacuum device can be installed at the ball valve.

[0022] In the centrifugal pump degassing device, a valve for adjusting the pulp flow is provided on the pulp inlet pipeline. Different centrifugal pumps have different output powers and different pulp delivery rates. The valve is provided to facilitate control of the pulp flow rate in the pulp inlet pipeline to avoid excessive flow rate and thus reduce the degassing efficiency.

[0023] The pulp conveying system of the present invention comprises a pulp pool for storing pulp and a centrifugal pump for conveying pulp, and also comprises the above-mentioned centrifugal pump degassing device, the pulp inlet end of the centrifugal pump degassing device is connected to the pulp pool, and the pulp outlet end of the centrifugal pump degassing device is connected to the centrifugal pump.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) In the centrifugal pump degassing device of the present invention, since the exhaust pipe is connected to the pulp pool through the pulp inlet pipeline, the pulp will flow into the exhaust pipe; the pulp flows on the pulp inlet pipeline, and the inner diameter at the diameter-changing section is smaller, so the fluid pressure at the diameter-changing section is smaller, causing the bubbles in the pulp to float up due to the increase in volume and enter the exhaust pipe through the exhaust port; while in the exhaust pipe, the pulp hardly flows, so the pressure further decreases from the bottom end to the top end of the exhaust pipe, and the bubbles continue to expand and float up until they escape from the exhaust pipe, thereby achieving the purpose of exhaust; by comparison, after exhausting the gas through the centrifugal pump degassing device of the present invention, the cyclone at the center of the centrifugal pump impeller disappears, and the pumping capacity of the centrifugal pump is increased by 30%; at the same time, under the same flow rate and head, the output power of the centrifugal pump is significantly reduced, saving electricity by 30%.

[0026] (2) In the centrifugal pump degassing device of the present invention, the inner diameter of the variable diameter section gradually decreases along the slurry delivery direction of the slurry inlet pipeline; thus, the fluid pressure at the variable diameter section gradually decreases, the bubble volume increases at a uniform rate, and the bubble floating rate is further improved.

[0027] (3) In the centrifugal pump degassing device of the present invention, the inner diameter of the exhaust pipe is larger than the inner diameter of the exhaust port, so that the pressure in the exhaust pipe is smaller than the pressure at the variable diameter section, and the bubbles in the pulp expand faster and float upward.

[0028] (4) In the centrifugal pump degassing device of the present invention, the exhaust pipe is made of a stainless steel seamless steel pipe, the inner wall of the stainless steel seamless steel pipe is smooth and no bubbles will remain; a ball valve is installed at the top of the exhaust pipe, and the ball valve is in a normally open state. When it is necessary to further speed up the degassing speed, a vacuum device can be installed at the ball valve.

[0029] (5) In the centrifugal pump degassing device of the present invention, a valve for adjusting the pulp flow rate is provided on the pulp inlet pipeline; this facilitates controlling the flow rate of the pulp in the pulp inlet pipeline and avoids a decrease in degassing efficiency due to excessive flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic structural diagram of the centrifugal pump degassing device of the present invention. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0032] Example 1

[0033] like Figure 1 As shown, a centrifugal pump degassing device of this embodiment includes a pulp inlet pipeline 1 connecting a pulp pool 100 and a centrifugal pump 200, the pulp inlet end of the pulp inlet pipeline 1 is located at the bottom of the pulp pool 100, and a stirring device 300 is installed on the side wall of the pulp pool 100 above the pulp inlet pipeline 1. The stirring device 300 is used to stir the pulp entering the pulp pool 100 from the pulp inlet 101 to ensure that the pulp entering the pulp inlet pipeline 1 maintains a relatively uniform concentration. A valve 2 is also installed on the pulp inlet pipeline 1 of this embodiment, and the valve 2 is used to adjust the pulp conveying speed.

[0034] Depend on Figure 1 It can be seen that at least one variable diameter section 3 is provided on the slurry inlet pipeline 1, and the inner diameter of each variable diameter section 3 is smaller than the inner diameter of the slurry inlet pipeline 1 upstream of the variable diameter section 3; and, at least one variable diameter section 3 is provided with an exhaust port (not shown in the figure), and an exhaust pipe 4 is installed at the exhaust port.

[0035] Since the inner diameter of the variable diameter section 3 is small (the cross section is small), the flow rate of the pulp through the variable diameter section 3 is fast, so the fluid pressure at the variable diameter section 3 is small, causing the bubbles in the pulp to float up due to the increase in volume and enter the exhaust pipe 4 through the exhaust port; while in the exhaust pipe 4, the pulp hardly flows, so the pressure further decreases from the bottom end to the top end of the exhaust pipe 4, and the bubbles continue to expand and float up until they escape from the exhaust pipe 4, thereby achieving the purpose of exhaust.

[0036] The inner diameter of the reducing section 3 can be constant or gradually reduced, as long as the inner diameter of the reducing section 3 is smaller than the inner diameter of the pulp inlet pipeline 1 upstream of the reducing section 3. However, in order to further speed up the floating speed of bubbles in the pulp, in this embodiment, the reducing section 3 is an eccentric reducer 31 with a straight section installed on the pulp inlet pipeline 1; the inner diameter of this eccentric reducer 31 with a straight section gradually decreases, and the fluid pressure changes at a uniform speed, which is conducive to ensuring that the pulp remains in a relatively stable state. At the same time, this eccentric reducer 31 with a straight section is not only easy to install on the pulp inlet pipeline 1, but also easy to install the exhaust pipe 4 on the top edge of the reducing section 3.

[0037] like Figure 1 As shown, in this embodiment, the exhaust pipe 4 is vertically mounted on the diameter-changing section 3; and the top of the exhaust pipe 4 is at a height equivalent to the highest liquid level 102 of the pulp in the pulp pool 100, or the top of the exhaust pipe 4 is at a height higher than the highest liquid level 102 of the pulp in the pulp pool 100, so as to prevent the pulp from overflowing from the top of the exhaust pipe 4. Obviously, in order to ensure that the highest liquid level 102 of the pulp in the pulp pool 100 remains unchanged, an overflow port 103 is provided in the pulp pool 100.

[0038] In this embodiment, the exhaust pipe 4 is made of a stainless steel seamless steel pipe to ensure that the inner wall of the exhaust pipe 4 is smooth and free of residual bubbles. A ball valve 5 is also installed at the top of the exhaust pipe 4. The ball valve 5 is in a normally open state. When it is necessary to further speed up the degassing speed, a suction device (not shown in the figure) can be installed at the ball valve 5.

[0039] Depend on Figure 1 It can be seen that in this embodiment, the inner diameter of the exhaust pipe 4 is larger than the inner diameter of the exhaust port; thus, the pressure in the exhaust pipe 4 is smaller at the variable diameter section 3, and the bubbles in the pulp are accelerated to expand and float up. The inner diameter of the exhaust port is affected by the inner diameter of the variable diameter section 3. Therefore, in actual operation, the inner diameter of the exhaust pipe 4 can be set to at least three times the inner diameter of the pulp inlet end of the variable diameter section 3 (three times in this embodiment). The larger the inner diameter of the exhaust pipe 4, the higher the expansion rate of the bubbles in the pulp and the higher the degassing efficiency.

[0040] The working principle of the centrifugal pump degassing device of this embodiment is as follows: pulp enters the pulp pool 100 through the pulp inlet 101, and the stirring device 300 stirs the pulp in the pulp pool 100 to ensure that the pulp entering the pulp inlet pipeline 1 maintains a uniform concentration; under the action of the centrifugal pump 200, the uniformly stirred pulp enters the pulp inlet pipeline 1, and the flow rate of the pulp in the pulp inlet pipeline 1 can be controlled by the valve 2;

[0041] When the pulp flows to the variable diameter section 3, the pulp flows into the exhaust pipe 4 through the exhaust port; since the inner diameter of the variable diameter section 3 becomes smaller, the fluid pressure at the variable diameter section 3 becomes smaller, causing the bubbles in the pulp to float up due to their increased volume, and enter the exhaust pipe 4 through the exhaust port; while in the exhaust pipe 4, the pulp hardly flows, and since the pressure further decreases from the bottom end to the top end of the exhaust pipe 4, the bubbles continue to expand and float up until they escape from the exhaust pipe 4, thereby achieving the purpose of exhaust.

[0042] Pulp was transported using a common pulp conveying system (the pulp inlet pipeline 1 was a closed pipeline without an exhaust pipe 4) and the pulp conveying system of this embodiment (an exhaust pipe 4 was provided on the pulp inlet pipeline 1), and the pumping capacity of the centrifugal pump 200 and the power consumption of the system were investigated.

[0043] By comparison, after exhausting the air through the centrifugal pump degassing device of the present invention, the cyclone at the center of the impeller of the centrifugal pump 200 disappears. In the pulp conveying system of this embodiment, the pumping capacity of the centrifugal pump 200 is increased by 30%. At the same time, under the same flow rate and head, the output power of the centrifugal pump 200 in the pulp conveying system of this embodiment is significantly reduced, saving electricity by 30%.

Claims

1. A centrifugal pump degassing device, comprising a pulp inlet pipeline (1) connecting a pulp tank (100) and a centrifugal pump (200), characterized in that: The slurry inlet pipeline (1) is provided with at least one variable diameter section (3), the inner diameter of the variable diameter section (3) being smaller than the inner diameter of the slurry inlet pipeline (1) located upstream of the variable diameter section (3); at least one of the variable diameter sections (3) is provided with an exhaust port, and an exhaust pipe (4) is installed at the exhaust port; The inner diameter of the exhaust pipe (4) is larger than the inner diameter of the exhaust port; Along the slurry feeding direction of the slurry inlet pipeline (1), the inner diameter of the variable diameter section (3) gradually decreases; The reducing section (3) is an eccentric reducing pipe (31) with a straight section installed on the pulp inlet pipeline (1); The inner diameter of the exhaust pipe (4) is larger than the inner diameter of the pulp inlet end of the diameter-changing section (3).

2. The centrifugal pump degassing device according to claim 1, characterized in that: The inner diameter of the exhaust pipe (4) is at least three times the inner diameter of the slurry inlet end of the variable diameter section (3).

3. The centrifugal pump degassing device according to claim 1, characterized in that: The exhaust pipe (4) is vertically installed on the diameter-changing section (3), and the height of the exhaust pipe (4) is not lower than the highest liquid level (102) of the pulp in the pulp pool (100).

4. The centrifugal pump degassing device according to claim 1, characterized in that: The exhaust pipe (4) is made of a stainless steel seamless pipe; a ball valve (5) is installed at the top of the exhaust pipe (4).

5. The centrifugal pump degassing device according to claim 1, characterized in that: The pulp inlet pipeline (1) is provided with a valve (2) for adjusting the pulp flow rate.

6. A pulp conveying system, comprising a pulp pool (100) for storing pulp, and a centrifugal pump (200) for conveying pulp, characterized in that: It also comprises a centrifugal pump degassing device as claimed in any one of claims 1 to 5, wherein the pulp inlet end of the centrifugal pump degassing device is connected to the pulp pool (100), and the pulp outlet end of the centrifugal pump degassing device is connected to the centrifugal pump (200).

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