MVR (Mechanical Vapor Recompression) evaporation and concentration system for caustic alkali

Abstract

The invention discloses a caustic alkali MVR (mechanical vapor recompression) evaporation and concentration system which comprises a first-effect evaporator, a second-effect evaporator, a third-effect evaporator, a steam exhaust header pipe and a steam inlet header pipe. The second-effect evaporator is provided with a second steam inlet branch pipe and a second steam exhaust branch pipe used for exhausting secondary steam. The third-effect evaporator is provided with a third steam inlet branch pipe and a third steam exhaust branch pipe used for exhausting secondary steam. One end of the steam exhaust header pipe is communicated with a first steam exhaust branch pipe, a second steam exhaust branch pipe and a third steam exhaust branch pipe, and one end of the steam inlet header pipe is communicated with a first steam inlet branch pipe, a second steam inlet branch pipe and a third steam inlet branch pipe; the other end of the steam exhaust header pipe is sequentially communicated with the steam buffer tank, the steam compressor and the other end of the steam inlet header pipe. The device can heat, evaporate and concentrate alkali liquor again, so that the latent heat of secondary steam can be reused, and the purpose of improving the utilization rate of the latent heat of the secondary steam is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of caustic soda concentration production, and in particular relates to a caustic soda MVR evaporation concentration system. Background Art

[0002] At present, the three-effect countercurrent process used in the production of caustic soda concentration requires a large amount of steam to be continuously provided by the outside world to heat the alkali solution, and a vacuum pump is required to generate a high negative pressure on the evaporator. In addition, the secondary steam produced by the first-effect evaporator is generally condensed by a surface condenser, and then treated by a vacuum pump to extract non-condensable gas and create a high vacuum to form condensed water; however, the latent heat of low-temperature steam is not effectively utilized, and circulating cooling water is required for cooling, which consumes a lot of electricity. Summary of the invention

[0003] In order to overcome the defects of the prior art, the present invention provides a caustic soda MVR evaporation concentration system, which can improve the utilization rate of latent heat of secondary steam.

[0004] The object of the present invention is achieved through the following technical solutions:

[0005] A caustic soda MVR evaporation concentration system, comprising:

[0006] A first-effect evaporator, wherein the first-effect evaporator is provided with a first steam inlet branch pipe and a first steam exhaust branch pipe for exhausting secondary steam;

[0007] A second-effect evaporator, which is provided with a second steam inlet branch pipe and a second steam exhaust branch pipe for exhausting secondary steam;

[0008] A triple-effect evaporator, which is provided with a third steam inlet branch pipe and a third steam exhaust branch pipe for exhausting secondary steam;

[0009] An exhaust main pipe, one end of which is connected to the first exhaust branch pipe, the second exhaust branch pipe and the third exhaust branch pipe;

[0010] A steam buffer tank, the input end of which is connected to the other end of the exhaust main pipe;

[0011] A steam compressor, wherein an input end of the steam compressor is connected to an output end of a steam buffer tank;

[0012] A steam inlet main pipe, one end of which is connected to the output end of the steam compressor, and the other end of which is connected to the first steam inlet branch pipe, the second steam inlet branch pipe and the third steam inlet branch pipe.

[0013] The beneficial effects of adopting the above technical scheme are as follows: a steam compressor is set to extract the secondary steam discharged from the first-effect evaporator, the second-effect evaporator and the third-effect evaporator, so as to form a higher negative pressure to meet the negative pressure requirement; in addition, after the secondary steam is heated and pressurized by the steam compressor, the saturation temperature of the secondary steam is increased, and the secondary steam can enter the first steam inlet branch pipe, the second steam inlet branch pipe and the third steam inlet branch pipe respectively after passing through the steam inlet main pipe, so as to enter the first-effect evaporator, the second-effect evaporator and the third-effect evaporator respectively, thereby heating the steam of the first-effect evaporator, the second-effect evaporator and the third-effect evaporator, and then heating and evaporating the concentrated alkali solution again, so as to facilitate the reuse of the latent heat of the secondary steam, that is, to achieve the purpose of improving the utilization rate of the latent heat of the secondary steam, and realize the MVR technology in the caustic soda production process, which greatly reduces the demand of the evaporation and concentration device for external energy.

[0014] Furthermore, a first pressure sensor, a first temperature sensor and a first atomizing nozzle are provided on the exhaust main pipe, and both the first pressure sensor and the first temperature sensor are interlocked with the first atomizing nozzle.

[0015] The beneficial effect of adopting the above technical solution is: such an arrangement can reduce the temperature of the superheated secondary steam discharged from the first-effect evaporator, the second-effect evaporator or the third-effect evaporator to saturated steam.

[0016] Furthermore, a liquid level meter and a first valve for controlling drainage are provided on the steam buffer tank, and the liquid level meter is interlocked with the first valve.

[0017] The beneficial effect of adopting the above technical solution is: by setting it in this way, drainage can be carried out in time when the liquid level in the steam buffer tank is too high, thereby reducing the liquid level in the steam buffer tank in time.

[0018] Further, the first pressure sensor and the first temperature sensor are both interlocked with the steam compressor.

[0019] The beneficial effect of adopting the above technical solution is: in this way, when the pressure and temperature in the exhaust main pipe cannot meet the requirements for the stable operation of the steam compressor, the steam compressor can be shut down in time for protection.

[0020] Furthermore, a second valve is provided on the pipeline between the steam buffer tank and the steam compressor, a third valve is provided on one end of the steam inlet main pipe close to the steam compressor, and the steam compressor is interlocked with the second valve and the third valve.

[0021] The beneficial effect of adopting the above technical solution is: by setting it in this way, the second valve and the third valve can be closed in time when the steam compressor is shut down, thereby avoiding the steam backflow phenomenon of the secondary steam entering the steam compressor and the steam inlet main pipe.

[0022] Furthermore, a second pressure sensor, a second temperature sensor and a second atomizing nozzle are provided on the steam inlet main pipe, and the second pressure sensor and the second temperature sensor are interlocked with the second atomizing nozzle.

[0023] The beneficial effect of adopting the above technical solution is: such an arrangement can cool the superheated steam coming out of the steam compressor into saturated steam.

[0024] Furthermore, the steam inlet main pipe is connected to an external steam delivery pipe, and the external steam delivery pipe is provided with a fourth valve interlocked with the second pressure sensor.

[0025] The beneficial effect of adopting the above technical solution is: by setting it in this way, when the steam pressure in the steam inlet main pipe is high, the fourth valve can be opened in time to send the steam out.

[0026] Furthermore, the steam inlet main pipe is connected to a vent pipe, and the vent pipe is provided with a fifth valve interlocked with the second pressure sensor.

[0027] The beneficial effect of adopting the above technical solution is: by setting it in this way, when the steam pressure in the steam inlet main pipe is too high, the fifth valve can be opened in time to discharge the steam.

[0028] Furthermore, a return pipe is connected between the exhaust main pipe and the steam inlet main pipe, a sixth valve is arranged on the return pipe, and a flow sensor interlocked with the sixth valve is arranged on the steam inlet main pipe.

[0029] The beneficial effect of adopting the above technical solution is: by setting it in this way, the sixth valve can be opened in time when the steam flow in the steam inlet main pipe is low, thereby preventing the steam compressor from surging and protecting the steam compressor.

[0030] Furthermore, a steam transmission pipe for inputting raw steam is arranged on the steam inlet main pipe, and a seventh valve is arranged on the steam transmission pipe.

[0031] The beneficial effect of adopting the above technical solution is that raw steam can be input and supplemented through the steam transmission pipe, thereby ensuring that the first-effect evaporator, the second-effect evaporator and the third-effect evaporator can operate normally.

[0032] The beneficial effects of the present invention are:

[0033] A steam compressor is set up to extract the secondary steam discharged from the first-effect evaporator, the second-effect evaporator and the third-effect evaporator, which can form a higher negative pressure to meet the negative pressure requirement; in addition, after the secondary steam is heated and pressurized by the steam compressor, the saturation temperature of the secondary steam is increased, and it can pass through the steam inlet main pipe and enter the first steam inlet branch pipe, the second steam inlet branch pipe and the third steam inlet branch pipe respectively to enter the first-effect evaporator, the second-effect evaporator and the third-effect evaporator respectively, so as to heat the steam of the first-effect evaporator, the second-effect evaporator and the third-effect evaporator, and then heat the evaporated alkali solution again, so as to reuse the latent heat of the secondary steam, that is, to achieve the purpose of improving the utilization rate of the latent heat of the secondary steam, and realize the MVR technology in the caustic soda production process, which greatly reduces the demand of the evaporation and concentration device for external energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings, wherein:

[0035] Figure 1 A schematic structural diagram of an embodiment of the present invention is shown;

[0036] In the drawings, like reference numerals are used for like parts. The drawings are not necessarily to scale.

[0037] Reference numerals:

[0038] 1-single-effect evaporator, 2-second-effect evaporator, 3-triple-effect evaporator, 4-first steam inlet branch, 5-first steam exhaust branch, 6-second steam inlet branch, 7-second steam exhaust branch, 8-third steam inlet branch, 9-third steam exhaust branch, 10-exhaust main pipe, 11-steam inlet main pipe, 12-first pressure sensor, 13-first temperature sensor, 14-first atomizing nozzle, 15-steam buffer tank, 16-first valve, 17-liquid level meter, 18-second valve, 19-steam compressor, 20-third valve, 21-second atomizing nozzle, 22-second temperature sensor, 23-flow sensor, 24-reflux pipe, 25-sixth valve, 26-vent pipe, 27-fifth valve, 28-second pressure sensor, 29-external steam pipe, 30-fourth valve, 31-steam transmission pipe, 32-seventh valve. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings.

[0040] The present invention provides a caustic soda MVR evaporation concentration system, such as Figure 1 As shown, it includes:

[0041] A first-effect evaporator 1 is provided with a first steam inlet branch pipe 4 and a first steam exhaust branch pipe 5 for exhausting secondary steam;

[0042] A second-effect evaporator 2, on which a second steam inlet branch pipe 6 and a second steam exhaust branch pipe 7 for exhausting secondary steam are provided;

[0043] A triple-effect evaporator 3, on which a third steam inlet branch pipe 8 and a third steam exhaust branch pipe 9 for exhausting secondary steam are provided;

[0044] An exhaust main pipe 10, one end of which is connected to the first exhaust branch pipe 5, the second exhaust branch pipe 7 and the third exhaust branch pipe 9;

[0045] A steam buffer tank 15, the input end of the steam buffer tank 15 is connected to the other end of the exhaust main pipe 10;

[0046] A steam compressor 19, wherein the input end of the steam compressor 19 is connected to the output end of the steam buffer tank 15;

[0047] The steam inlet main pipe 11 has one end connected to the output end of the steam compressor 19 , and the other end connected to the first steam inlet branch pipe 4 , the second steam inlet branch pipe 6 and the third steam inlet branch pipe 8 .

[0048] It can be understood that, by setting up a steam compressor 19 to extract the secondary steam discharged from the first-effect evaporator 1, the second-effect evaporator 2 and the third-effect evaporator 3, a negative pressure of -59 kPa can be formed to meet the negative pressure requirement; in addition, after the secondary steam is heated and pressurized by the steam compressor 19, the saturation temperature of the secondary steam can be increased from 75°C to 127°C, and can enter the first steam inlet branch pipe 4, the second steam inlet branch pipe 6 and the third steam inlet branch pipe 8 respectively after passing through the steam inlet main pipe 11, so as to enter the first-effect evaporator 1, the second-effect evaporator 2 and the third-effect evaporator 3 respectively, so as to heat the steam of the first-effect evaporator 1, the second-effect evaporator 2 and the third-effect evaporator 3, and then heat the evaporated alkali solution again, so as to be conducive to the reuse of the latent heat of the secondary steam, that is, to achieve the purpose of improving the utilization rate of the latent heat of the secondary steam, and realize the MVR technology in the caustic soda production process, which greatly reduces the demand of the evaporation and concentration device for external energy.

[0049] It should be noted that valves are also provided on the first steam inlet branch pipe 4 , the second steam inlet branch pipe 6 , the third steam inlet branch pipe 8 , the first steam exhaust branch pipe 5 , the second steam exhaust branch pipe 7 and the third steam exhaust branch pipe 9 .

[0050] In one embodiment, the exhaust main pipe 10 is provided with a first pressure sensor 12 , a first temperature sensor 13 and a first atomizing nozzle 14 , and both the first pressure sensor 12 and the first temperature sensor 13 are interlocked with the first atomizing nozzle 14 .

[0051] It can be understood that this arrangement is used to reduce the temperature of the superheated secondary steam discharged from the first-effect evaporator 1, the second-effect evaporator 2 or the third-effect evaporator 3 to saturated steam.

[0052] It should be noted that the superheated secondary steam coming out of the first-effect evaporator 1, the second-effect evaporator 2 or the third-effect evaporator 3 has a small density and a large volume. If it is not cooled to saturated steam in the exhaust main pipe 10, the volume of the equipment required for the subsequent exhaust main pipe 10 will also be large; therefore, cooling it to saturated steam in the exhaust main pipe 10 can reduce the volume of the subsequent equipment required, thereby helping to reduce the equipment installation space.

[0053] In one embodiment, a liquid level meter 17 and a first valve 16 for controlling drainage are provided on the steam buffer tank 15. The liquid level meter 17 is interlocked with the first valve 16 so that drainage can be performed in time when the liquid level in the steam buffer tank 15 is too high, thereby reducing the liquid level in the steam buffer tank 15 in time.

[0054] In one embodiment, a liquid level meter 17 and a first valve 16 for controlling drainage are provided on the steam buffer tank 15. The liquid level meter 17 is interlocked with the first valve 16 so that drainage can be performed in time when the liquid level in the steam buffer tank 15 is too high, thereby reducing the liquid level in the steam buffer tank 15 in time.

[0055] In one embodiment, a second valve 18 is provided on the pipeline between the steam buffer tank 15 and the steam compressor 19, and a third valve 20 is provided on the end of the steam inlet main pipe 11 close to the steam compressor 19. The steam compressor 19 is interlocked with the second valve 18 and the third valve 20 so that the second valve 18 and the third valve 20 can be closed in time when the steam compressor 19 is shut down, thereby avoiding steam backflow of the secondary steam entering the steam compressor 19 and the steam inlet main pipe 11.

[0056] In one embodiment, a second pressure sensor 28, a second temperature sensor 22 and a second atomizing nozzle 21 are provided on the steam inlet main pipe 11. The second pressure sensor 28 and the second temperature sensor 22 are interlocked with the second atomizing nozzle 21 to cool down the superheated steam coming out of the steam compressor 19 into saturated steam.

[0057] It should be noted that the input end and the output end of the steam compressor 19 are also provided with atomizing nozzles, and these atomizing nozzles and the first atomizing nozzle 14 and the second atomizing nozzle 21 are all supplied with liquid by a booster water pump.

[0058] In one embodiment, the steam inlet main pipe 11 is connected to an external steam pipe 29, and a fourth valve 30 interlocked with the second pressure sensor 28 is provided on the external steam pipe 29 so that the fourth valve 30 can be opened in time when the steam pressure in the steam inlet main pipe 11 is high, thereby sending the steam out.

[0059] Specifically, when the steam pressure in the steam inlet manifold 11 exceeds 155 kPa, the fourth valve 30 is opened.

[0060] In one embodiment, the steam inlet main pipe 11 is connected to a vent pipe 26, and a fifth valve 27 interlocked with a second pressure sensor 28 is provided on the vent pipe 26 so that the fifth valve 27 can be opened in time when the steam pressure in the steam inlet main pipe 11 is too high, thereby venting the steam.

[0061] Specifically, the fifth valve 27 is opened when the steam pressure in the steam inlet manifold 11 exceeds 200 kPa.

[0062] In one embodiment, a return pipe 24 is connected between the exhaust main pipe 10 and the steam inlet main pipe 11, and a sixth valve 25 is arranged on the return pipe 24. A flow sensor 23 interlocked with the sixth valve 25 is arranged on the steam inlet main pipe 11, so that the sixth valve 25 can be opened in time when the steam flow in the steam inlet main pipe 11 is low, thereby preventing the steam compressor 19 from surging, thereby protecting the steam compressor 19.

[0063] In one embodiment, a steam delivery pipe 31 for inputting raw steam is disposed on the steam inlet main pipe 11 , and a seventh valve 32 is disposed on the steam delivery pipe 31 .

[0064] It can be understood that raw steam can be input and supplemented through the steam delivery pipe 31, so as to ensure that the first-effect evaporator 1, the second-effect evaporator 2 and the third-effect evaporator 3 can operate normally.

[0065] In summary, the present invention can fully recycle and utilize the latent heat of secondary steam of each effect evaporator, and can directly send the pressurized steam to the evaporators of each effect of the caustic soda concentration device; during the normal production period of the present invention, there is no need to supplement steam from the outside, and there is excess steam to be sent out; the unit energy consumption cost of the steam compressor 19 is much lower than the unit energy consumption cost of the boiler to produce steam, which saves production costs and reduces carbon emissions.

[0066] In addition, the prior art requires the use of equipment such as a surface condenser, a circulating water pump and a water tank, and requires the use of industrial circulating water to condense the secondary steam coming out of the first-effect evaporator 1, while the present invention will no longer use these equipment and energy, which is conducive to reducing investment and power consumption.

[0067] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "bottom", "top", "front", "back", "inside", "outside", "left", "right", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0068] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A caustic soda MVR evaporation concentration system, characterized in that: include: A first-effect evaporator (1), wherein the first-effect evaporator (1) is provided with a first steam inlet branch pipe (4) and a first steam exhaust branch pipe (5) for exhausting secondary steam; A second-effect evaporator (2), wherein the second-effect evaporator (2) is provided with a second steam inlet branch pipe (6) and a second steam exhaust branch pipe (7) for exhausting secondary steam; A triple-effect evaporator (3), wherein the triple-effect evaporator (3) is provided with a third steam inlet branch pipe (8) and a third steam exhaust branch pipe (9) for exhausting secondary steam; an exhaust main pipe (10), one end of the exhaust main pipe (10) being connected to the first exhaust branch pipe (5), the second exhaust branch pipe (7) and the third exhaust branch pipe (9); A steam buffer tank (15), wherein an input end of the steam buffer tank (15) is connected to the other end of the exhaust main pipe (10); a steam compressor (19), wherein an input end of the steam compressor (19) is connected to an output end of the steam buffer tank (15); A steam inlet main pipe (11), one end of which is connected to the output end of the steam compressor (19), and the other end of which is connected to the first steam inlet branch pipe (4), the second steam inlet branch pipe (6) and the third steam inlet branch pipe (8).

2. A caustic soda MVR evaporation concentration system according to claim 1, characterized in that: The exhaust main pipe (10) is provided with a first pressure sensor (12), a first temperature sensor (13) and a first atomizing nozzle (14); the first pressure sensor (12) and the first temperature sensor (13) are both interlocked with the first atomizing nozzle (14).

3. A caustic soda MVR evaporation concentration system according to claim 2, characterized in that: The steam buffer tank (15) is provided with a liquid level meter (17) and a first valve (16) for controlling drainage, and the liquid level meter (17) is interlocked with the first valve (16).

4. A caustic soda MVR evaporation concentration system according to claim 2, characterized in that: The first pressure sensor (12) and the first temperature sensor (13) are both interlocked with the steam compressor (19).

5. A caustic soda MVR evaporation concentration system according to claim 4, characterized in that: A second valve (18) is provided on the pipeline between the steam buffer tank (15) and the steam compressor (19), a third valve (20) is provided at one end of the steam inlet main pipe (11) close to the steam compressor (19), and the steam compressor (19) is interlocked with the second valve (18) and the third valve (20).

6. The caustic soda MVR evaporation concentration system according to claim 1, characterized in that: The steam inlet manifold (11) is provided with a second pressure sensor (28), a second temperature sensor (22) and a second atomizing nozzle (21); the second pressure sensor (28) and the second temperature sensor (22) are both interlocked with the second atomizing nozzle (21).

7. A caustic soda MVR evaporation concentration system according to claim 6, characterized in that: The steam inlet main pipe (11) is connected to an external steam delivery pipe (29), and the external steam delivery pipe (29) is provided with a fourth valve (30) interlocked with the second pressure sensor (28).

8. A caustic soda MVR evaporation concentration system according to claim 6 or 7, characterized in that: The steam inlet main pipe (11) is connected to a vent pipe (26), and the vent pipe (26) is provided with a fifth valve (27) interlocked with the second pressure sensor (28).

9. The caustic soda MVR evaporation concentration system according to claim 1, characterized in that: A return pipe (24) is connected between the exhaust steam main pipe (10) and the inlet steam main pipe (11), a sixth valve (25) is provided on the return pipe (24), and a flow sensor (23) interlocked with the sixth valve (25) is provided on the inlet steam main pipe (11).

10. The caustic soda MVR evaporation concentration system according to claim 1, characterized in that: The steam inlet main pipe (11) is provided with a steam delivery pipe (31) for inputting raw steam, and the steam delivery pipe (31) is provided with a seventh valve (32).

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