JP2017056406A - Vacuum evaporation type concentrator and operation method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time of start operation from operation start-up to steady operation while suppressing running cost and equipment cost in a vacuum evaporation type concentrator equipped with a vacuum pump.SOLUTION: A concentrator is driven on heat pump system having a root type compressor 3 and a vacuum pump 4. Upon start operation, while the vacuum pump 4 is being rotated in the same condition as steady operation, the root type compressor 3 is rotated at low speed with a bypass passage 23 full-opened. Since the mixture of air in the root type compressor 3 is prevented, the root type compressor 3 is maintained to a standby state while preventing overload. When the temperature or the like of a raw liquid gets closer to a steady operation state, a bypass valve 24 is closed to switch the root type compressor 3 into high-speed rotation, which shifts into steady operation. The root type compressor 3 can be operated stably toward steady operation while the decompression of an evaporation container 1 is being progressed, so that the start operation time can be shortened.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a vacuum evaporation type concentrator (heat pump type concentrator) for concentrating various liquids and an operation method (control method) thereof. In addition, the liquid here means the fluid containing moisture, and the viscosity is not limited. Moreover, it does not interfere with containing a solid substance.

  Concentration of the liquid is performed by heating (heating) to remove moisture. However, if the generated steam is discarded as it is, the loss of energy is significant and the operation cost is increased. Therefore, a heat pump system is used in which the generated evaporation is compressed and heated to be reused for heating the raw material liquid. When steady operation is reached, it is almost unnecessary to supply heat energy from the outside. Thus, a cycle in which the raw material liquid can be heated only with the compressed and heated steam (for example, Patent Document 1).

  In Patent Document 1, the evaporation container and the steam flow path are decompressed by a vacuum pump. When the pressure is reduced in this way, the boiling point of the raw material liquid is lowered, so that the function of the heat pump is further enhanced. On the other hand, Patent Document 2 discloses an example of a type using only a vapor compressor without using a vacuum pump. In this Patent Document 2, when a roots compressor is used as a steam compressor and an electric heater is used as a heating source, a bypass passage is provided to connect the upstream side and the downstream side of the roots type compressor. An apparatus in which a bypass valve for opening and closing the passage is provided in a passage is disclosed.

  This Patent Document 2 aims to make the amount of power used constant during start-up operation and steady operation, and at the start of operation, the Roots compressor can be rotated at low speed by opening the bypass valve fully. Even if it exists, it is prevented from becoming overloaded. As the temperature of the raw material liquid is increased by the electric heater, the electric power to the electric heater is reduced, the rotational speed of the Roots compressor is gradually increased, and the on-off valve provided in the bypass passage is opened. When the amount of steam generated in the evaporation container reaches a predetermined amount, the bypass valve is fully closed and the Roots compressor is switched to the steady rotation speed, and the steam supply is shut off. doing.

  As described above, this Patent Document 2 aims to make the amount of electric power used constant from the start to the end of the operation of the apparatus. During the start-up operation, the electric power used by the heater is proportional to the amount of steam generated. The power consumption ratio of both is changed so that the power consumption of the roots compressor is increased, and finally, the power supply to the heater is turned off and the roots compressor is fully rotated. Therefore, it can be said that a large amount of electric power is not required during the start-up operation, and the power supply facility can be simplified accordingly.

JP 2008-111320 A Japanese Patent No. 180329

  In a vacuum evaporation type concentrator as in Patent Document 1, a stable concentration action is achieved during steady operation, but the start-up operation from the start of operation to the steady operation is unstable, resulting in a long start-up operation time. There is a problem.

  In other words, the vacuum inside the device gradually increases with the start of the vacuum pump operation, and continues to the steady operation by increasing the vacuum degree and heating the raw material liquid, but lean air remains in the evaporation container at the start-up operation Therefore, when the steam compressor is operated, lean air is sucked into the steam compressor, the steam compressor is overloaded and the operation is not stable. It was necessary to delay and wait for the vacuum to rise, and this increased the startup operation time.

  In this regard, it can be said that the vacuum degree should be increased in a short time by increasing the capacity of the vacuum pump. However, this requires an expensive vacuum pump for the start-up operation, so that the equipment cost is reduced. A new problem of bulkiness occurs. In addition, in order to obtain a stable compression / temperature increase state of the steam by the steam compressor, it is necessary to run the steam compressor for a certain period of time to stabilize it. However, it does not lead to steady operation immediately, and the start-up operation time cannot be shortened in this respect as well.

  On the other hand, Patent Document 2 is understood that the internal pressure of the evaporator is lower than the atmospheric pressure because the vapor is sucked from the evaporator by the roots compressor. Therefore, it can be said that evaporation is promoted by lowering the boiling point of the raw material liquid. However, since the pressure is reduced only by the suction of the roots compressor, the necessary degree of vacuum and steam are required without using a large roots compressor. It can be said that it is difficult to ensure the temperature rise, and thus the equipment cost may increase.

  Moreover, since patent document 2 changes the ratio of the electric power of both gradually while maintaining the sum of the electric power of an electric heater and a roots type compressor constant, it is to an electric heater and a roots type compressor. The power supply control is troublesome.

  Further, regarding the start-up operation time, in Patent Document 2, in the steady operation state, the evaporator is decompressed by the vapor compressor, but during the start-up operation, the upstream side and the downstream side of the Roots-type compressor are connected via the bypass passage. Because it is connected, it seems that the evaporator is hardly depressurized during start-up operation, so it is necessary to wait for the temperature rise by the electric heater to reach steady operation, thus shortening the start-up operation time. Is not expected.

  The present invention has an object to shorten the start-up operation time in the vacuum evaporation type concentrator under such a current situation without incurring equipment costs.

  The present invention includes a vacuum evaporation type concentrator and a method for operating the same, the typical of which is specified in each claim.

  Among these, the invention of claim 1 relates to a vacuum evaporation type concentrating device, the vacuum evaporation type concentrating device comprising an evaporation container into which a raw material liquid is charged, a heating means for the raw material liquid to be charged into the evaporation container, A vapor compressor that compresses and raises the temperature of the vapor generated in the evaporation container; and a vacuum pump that depressurizes the inside of the evaporation container and the discharge path of the vapor, and is compressed by the vapor compressor The basic configuration is that steam is sent to the heating means.

  Then, a bypass passage is provided to connect the upstream side and the downstream side of the steam compressor, and the bypass passage is opened only during the start-up operation from the start of operation after starting the vacuum pump to the steady operation. A bypass valve that is closed during steady operation is provided, and during the start-up operation, the bypass passage is held in a reduced pressure state by the vacuum suction action of the vacuum pump, so that the upstream side and the downstream side of the steam compressor While making the negative pressure uniform, the steam compressor is operated at a starting rotation speed lower than the rotation speed during steady operation.

  The invention of claim 2 is a preferred embodiment of the invention of claim 1, and in this invention, the bypass valve is a system that can be switched between two stages of full open and full close, while the steam compressor Is a system that can be switched to a two-stage rotation speed, a steady operation rotation speed and a lower startup rotation speed.

  A third aspect of the present invention is a preferred embodiment of the first or second aspect, wherein the vapor compressor is a Roots type compressor, while the heating means is a thin film upflow system, By reducing the pressure, the raw material liquid is automatically sucked into the evaporation container from the supply passage.

  The invention of claim 4 is directed to a method for operating a vacuum evaporation type concentrator. First, the vacuum evaporation type concentrator includes an evaporation container into which a raw material liquid is charged, and heating of the raw material liquid into the evaporation container. Means, a vapor compressor for compressing and raising the temperature of the vapor generated in the evaporation container, a vacuum pump for depressurizing the inside of the evaporation container and the discharge path of the vapor, and upstream and downstream of the vapor compressor And a bypass valve that opens and closes the bypass passage, and the vacuum pump is always operated at a constant rotational speed.

And the start-up operation from the start of operation to the transition to steady operation is
a: The bypass valve is opened before or after the start of operation of the vacuum pump, or the vacuum pump is started with the bypass valve opened in advance.
b: Start supplying the raw material liquid to the evaporation container in a state where the bypass valve is opened and the vacuum pump is operated.
c: Start operation of the vapor compressor at a starting rotational speed lower than the rotational speed during steady operation after the supply of the raw material liquid is started.
d: After the operation of the vapor compressor is started, heating of the raw material liquid by the heating means is started.
Including the procedure
When the internal pressure and / or temperature of the evaporation container reaches a preset reference value, the bypass valve is fully closed and the steam compressor is switched to a steady operation rotational speed.

  The invention of claim 5 is a preferred embodiment of claim 4 in which the bypass valve is kept fully open during start-up operation, and the internal pressure and / or temperature of the evaporation container is preset. When the reference value is reached, the steam compressor is fully closed, while the steam compressor is operated at a constant starting rotation speed during the starting operation.

  The invention of claim 6 is a preferred development of claim 4 or 5, wherein a roots compressor is used as the vapor compressor, and a thin film upflow system is used as the heating means. The invention of a seventh aspect is the invention according to any one of the fourth to sixth aspects, wherein the switching of the bypass valve to the fully closed state and the switching to the steady operation rotational speed of the steam compressor are performed by the internal pressure of the evaporation container or the raw material liquid. The temperature or both are performed at the timing before reaching the internal pressure and / or temperature during steady operation.

  Now, in the vacuum evaporation type concentrator, the capacity of the vacuum pump is not so much required in the steady operation, and the running cost required for driving the vacuum pump is not so much. This is one of the advantages of the vacuum evaporation type concentrator. However, as described above, if a large-capacity vacuum pump is used to shorten the start-up operation time, the equipment cost increases accordingly. In addition, if the steam compressor is suddenly started at the rotation speed during steady operation, the air accumulated in the evaporation container is sucked into the steam compressor, which overloads the steam compressor and damages the steam compressor. Or the operation may become unstable.

  In contrast, in the present invention, during start-up operation, the vacuum pump is operated at a steady rotational speed, and the air in the evaporation container is excluded from the bypass passage so that the steam compressor does not trip due to overload. Since the number of rotations can be increased, the time to reach the number of rotations in the subsequent steady operation is shortened, and the startup operation time can be shortened. In other words, the bypass passage is maintained in a reduced pressure state by a vacuum pump, and air accumulated in the evaporation container is quickly removed from the bypass passage, thereby preventing air from entering the steam compressor. It is possible to quickly shift to the full rotation state of steady operation while stably operating the machine without any load.

  In addition, in Patent Document 2, the evaporator is depressurized by a steam compressor, and since the bypass passage is in communication during start-up operation, basically the depressurizing action of the evaporator by the steam compressor does not occur. However, in the present invention, since the suction action of the vacuum pump is also working in the bypass passage, the vapor pressure reduction of the evaporation container is promoted by the operation of the vapor compressor, thereby promoting the transition to the steady operation. It can be said.

  As described above, the invention of the present application is to increase the degree of vacuum inside the apparatus over time during the start-up operation, and the steam compressor shifts to the steady operation via the stable run-up operation. It is possible to smoothly shift to steady operation while shortening the start-up operation time while using only a compatible small vacuum pump. As a result, equipment costs and running costs can be suppressed, and the operating rate can be increased to improve productivity.

  Since the bypass passage is for equalizing the pressure on the upstream side and the downstream side of the steam compressor, in the present invention, the bypass passage is called a pressure equalizing passage, and the bypass valve is called a pressure equalizing valve. It is also possible.

  In the first and fourth aspects, the bypass valve can be switched to three or more stages, for example, fully open, intermediate open (intermediate close), and fully closed, and the steam compressor is also rotated in the starting operation. The number can be switched between two or more speeds of low speed rotation and medium speed rotation, but the bypass valve adopts a two-stage switching method of full opening and full closing as in claims 2 and 5. At the same time, if the start-up operation speed is set to one kind of speed, the steam compressor is linked to a sensor or switch for detecting the internal pressure (vacuum level) or temperature of the evaporation container, and a bypass valve or steam. Since a simple control method (for example, control using a relay) for switching the compressor can also be adopted, the control mode of the apparatus can be simplified.

  In this case, the vacuum pump is driven at a constant speed at the same rotational speed as in the steady operation, but the steam compressor is driven at a rotational speed lower than the steady operation rotational speed, so that even if air is sucked, it is overloaded. Never become. For this reason, the degree of vacuum inside the apparatus can be quickly increased while rotating the steam compressor at a constant speed, and as described above, the decompression of the evaporation container can be promoted by the steam compressor. Accordingly, it is possible to reduce the start-up operation time by fully driving the steam compressor while stably driving the steam compressor.

  If a roots compressor is used for the steam compressor as in claims 3 and 6, the temperature difference when raising the temperature of the steam generated in the evaporator can be increased by a high compression ratio. It can also be applied to liquids. In addition, by adopting the thin film ascending flow method, the quality change due to the heat load on the raw material liquid can be reduced, making it suitable for the food field, and a thin film ascending method that requires a relatively large temperature difference and a high temperature rising function. A high concentration efficiency can be realized by a combination with a roots type compressor having Furthermore, since the suction of the raw material liquid is performed by a vacuum action, a pumping pump is not required, and not only can the equipment cost be reduced, but also the transition from start-up operation to steady operation becomes smooth.

  When the steam compressor is operating at the starting rotational speed and the inside of the device is completely moved to the steady operating state and then the steam compressor speed is increased to the steady rotational speed, the inside of the device is temporarily excessive. There is a possibility that a large pressure fluctuation occurs due to a negative pressure state or steam heating state.

  On the other hand, as in claim 7, the steam compressor is shifted to the full rotation state in a state slightly before the negative pressure and temperature during the steady operation (for example, the degree of reach to the steady operation is 90 to 95%). Then, even if there is a large pressure reduction and steam compression due to the full rotation of the steam compressor, it shifts to a steady operation with sufficient decompression capacity, so there is no large pressure fluctuation or temperature change, and steady operation Very smooth transition. This is one of the features of the present invention.

It is a typical block diagram in the steady operation state of this invention. It is a typical block diagram in the initial stage at the time of start-up operation of this invention. It is a typical block diagram in the middle period at the time of starting operation of this invention. It is a typical block diagram in the last stage at the time of start-up operation of this invention. It is a flowchart of starting operation.

(1). Configuration of Apparatus Next, an embodiment of the present invention will be described with reference to the drawings. First, the configuration of the vacuum evaporation type concentrator will be described with reference to FIG. The vacuum evaporation type concentrator includes, as main elements, an evaporation container (evaporation tank, evaporator) 1 for evaporating a raw material liquid (concentrated liquid), a steam heating unit 2 as an example of a heating means for the raw material liquid, and evaporation A Roots type compressor 3 as an example of a compressor for compressing and raising the temperature of steam generated in the container 1 and a vacuum pump 4 for decompressing the evaporation container 1 and the steam discharge path are provided.

  The Roots compressor 3 can be switched between a steady operation rotational speed and a two-stage rotational speed that is lower than the starting rotational speed. However, the specific numbers of the steady operation rotational speed and the startup rotational speed vary, and for example, the steady operational rotational speed may be 3000 rpm, 2500 rpm, or 1500 rpm. Therefore, the steady operation rotational speed and the startup rotational speed are relative concepts, and no suitable absolute value exists. The relationship between the steady operation rotational speed and the startup rotational speed is also different depending on the capability of the vacuum pump 4. For example, when the steady operation rotational speed is 1200 rpm, the startup rotational speed is set to 600 rpm. Thus, it can be said that the startup rotational speed may be 40 to 60% of the steady operation rotational speed.

  The evaporation container 1 is a cylindrical vertical type, and the inside is hollow. The steam heating unit 2 has a configuration in which a thin film rising heat exchange unit 8 is disposed between the inflow header 6 and the outflow header 7, and the raw material liquid is vaporized in the process of flowing from the inflow header 6 to the outflow header 7. Is indirectly heated (heated). As the heating / evaporating means, various other systems such as a shell and tube type and a plate type can be adopted.

  A raw material liquid supply pipe (raw material liquid supply passage) 9 is connected to the inflow header 6 of the steam type heating unit 2, and the raw material liquid supply pipe 9 is provided with a raw material liquid supply valve 10. In addition, the inflow header 6 of the steam type heating unit 2 and the lower end of the evaporation container 1 are connected by the raw material liquid return pipe 11, and the outflow header 7 of the steam type heating unit 2 and the vertical halfway height position of the evaporation container 1 are Are connected by a raw material liquid feed pipe 12.

  A concentrated liquid take-out pipe 13 is connected to the middle part of the raw material liquid return pipe 11, and a concentrated liquid take-out control valve 14 is provided in the concentrated liquid take-out pipe 13. The concentrate extraction control valve 14 is controlled to be opened and closed by a control signal from a control device (not shown).

  An external steam introduction pipe 15 is connected to the upper part of the heat exchange unit 8 in the steam heating unit 2, and an external steam introduction valve 16 is provided in the external steam introduction pipe 15. Needless to say, the external steam introduction pipe 15 is connected to an external steam generation source such as a boiler. Further, a condensed water discharge pipe 17 is connected to the lower part of the heat exchanging unit 8 in the steam heating unit 2, and the condensed water discharge pipe 17 is provided with a condensed water pot 18 and a condensed water pump 19. . The water level inside the condensate pot 18 is maintained within a certain range by an automatic valve.

  The upper end portion of the evaporation container 1 and the suction chamber of the roots compressor 3 are connected by a steam take-out pipe 21, and the discharge chamber of the roots compressor 3 and the heat exchange unit 8 of the steam heating unit 2 are They are connected by a steam return pipe 22. The steam take-out pipe 21 and the steam return pipe 22 constitute a steam discharge passage. The steam take-out pipe 21 and the steam return pipe 22 are connected by a bypass passage 23, and a bypass valve 24 for opening and closing is provided in the bypass passage 23. The bypass valve 24 can be switched between two stages of fully open and fully closed, and can be operated with a simple actuator such as a solenoid valve, a pneumatic cylinder, or an electric motor.

  The bypass passage 23 mainly removes air to the steam return pipe 22 during the start-up operation, and is connected to an upstream portion of the steam return pipe 22. The starting end of the bypass passage 23 can be connected to the evaporation container 1 without being connected to the vapor take-out pipe 21. The bypass passage 23 is intended to remove air remaining in the evaporation container 1, but the amount of residual air is small, and air is more fluid than steam and is easily sucked. The diameter may be much smaller than that of the take-out pipe 21 and the steam return pipe 22.

  The roots compressor 3 and the vacuum pump 4 are connected by a first vacuum passage 25. The vacuum pump 4 is also connected to the condensed water pot 18 through the second vacuum passage 26. The first vacuum passage 25 is connected to a bearing portion of the casing of the Roots-type compressor 2, and reduces the load on the oil seal by reducing the pressure outside the oil seal to which the rotary shaft is attached. The second vacuum passage 26 is provided with a vacuum switching valve 27 for releasing the vacuum passage to the atmosphere. The vacuum switching valve 27 may be provided in any part of the vacuum path.

  The lower portion of the evaporation container 1 is a conical portion 1a (conical portion) with a narrowed bottom, a temperature sensor 28 is provided at the lower end portion, and a liquid level sensor 29 is provided at the upper end portion. Further, a pressure sensor (vacuum degree sensor) 30 is provided at the upper end of the evaporation container 1.

  The temperature sensor 28 controls the external steam introduction valve 16 and the bypass passage 23, the pressure sensor 30 controls the raw material supply valve 10, and the pressure sensor 30 controls the rotation of the Roots compressor 3. The These control relationships are indicated by dotted lines. However, the actuators of the sensors 28 to 30 and the valves 10, 13, 16, and 23 are actually connected to a control device (not shown), and each valve 10 is based on an input signal from the sensors 28 to 30. , 13, 16, and 23 are controlled via the control device.

(2). Control Mode The present invention is characterized by control during start-up operation. This point will be described with reference to FIGS. 2 to 4 while focusing on the flowchart of FIG. 2 to 4, the white arrow indicates the flow direction of the raw material liquid, and the black arrow indicates the flow direction of the vapor generated in the evaporation container 1. Regarding the rotation of the Roots compressor 3, for the sake of convenience, the rotation at start-up is called low-speed rotation, and the rotation at steady state is called high-speed rotation. As for the valve, the open state is indicated by a white square, and the closed state is indicated by a black square.

  In the present embodiment, it is assumed that the bypass valve 23 is closed and the vacuum control valve 27 is open during operation stop. However, these are arbitrary settings, and the bypass valve 23 may remain open and the vacuum control valve 27 may remain closed.

  First, when the operation is started, the vacuum control valve 27 is closed (step 1), then the bypass valve 24 is opened (step 2), and then the operation of the vacuum pump 4 is started (step 3). Of course, when the bypass valve 24 is open before the start of operation, step 2 is not necessary. After the operation of the vacuum pump 4 is started, the raw material liquid supply valve 10 is opened (step 4).

  FIG. 2 shows the initial state during start-up operation after step 4. That is, in this state, the concentrate pump control valve 14, the vacuum control valve 27, and the external steam switching valve 16 are closed, and the vacuum pump 4 is driven with the raw material liquid supply valve 10 and the bypass valve 24 opened. Yes. In this state, since the evaporation container 1 is depressurized, the raw material liquid is gradually sucked up and flows into the evaporation container 1.

  After the raw material liquid supply valve 10 is opened, the liquid level control is performed as a set (step 4). This liquid level control is performed by controlling the raw material liquid supply valve 10 based on a signal from the liquid level sensor 29, and a liquid level within a certain range is maintained. This liquid level control is continuously performed even during steady operation.

  Whether the internal pressure (vacuum) inside the evaporation container 1 is lower than a preset pressure (negative pressure) by comparing the value detected by the pressure sensor 30 with a preset value in conjunction with the liquid level control ( It is determined whether or not the pressure is high (step 5). If the internal pressure is lower than the set pressure (reduced pressure), the Roots compressor 3 is driven at a low speed (step 6). ). FIG. 3 shows the state after step 6. If the internal pressure inside the evaporation container 1 is higher than the set pressure on the atmospheric pressure side, the determination in step 5 is repeated.

  The specific value of the degree of vacuum for starting the low-speed operation (operation at the rotation speed at startup) of the Roots compressor 3 may be, for example, about 20 to 30 kPa. Since the vacuum suction by the vacuum pump 4 acts on the evaporation container 1 via the bypass passage 23, the degree of vacuum of the evaporation container 1 increases with time even before the operation of the Roots compressor 3. .

  It is impossible to start rotation of the vacuum pump 4 and the Roots compressor 3 at the same time, or start the operation of the Roots compressor 3 first, and start the operation of the vacuum pump 4 slightly later than this. However, in terms of stabilizing the operation by suppressing the suction of air into the Roots compressor 3, the operation of the Roots compressor 3 is started after the operation of the vacuum pump 4 as shown in the flowchart. In addition, it is preferable that the inside of the evaporation container 1 has reached a certain degree of vacuum.

  By driving the roots type compressor 3, decompression of the evaporation container 1 is promoted. That is, the inside of the evaporation container 1 is depressurized by both the suction action by the vacuum pump 1 and the suction action by the roots compressor 3. For this reason, the supply of the raw material liquid is also promoted, and the transition to the steady operation is promoted.

  After starting the low speed operation of the Roots compressor 3, the external steam introduction valve 16 is opened to introduce external steam into the heat exchange section 8 of the steam heating unit 2 (step 7). The introduction of the external steam can be performed in tandem with the operation of the roots compressor 3, but if the steam is introduced in a state where the raw material liquid is not accumulated, the raw material liquid may be excessively heated. As shown in the flowchart, after the operation of the roots compressor 3, it is preferable that the raw material liquid is introduced into the evaporation container 1 after the same amount of water has accumulated in the evaporation container 1 as in the steady operation.

  Since the external steam introduction valve 16 is opened, the temperature of the raw material liquid is monitored by the temperature sensor 28, and the temperature of the raw material liquid (retained liquid temperature) inside the evaporation container 1 is set in advance. The difference from the set temperature is determined (step 8). If the retained liquid temperature is equal to or higher than the first set temperature, the bypass valve 24 is fully closed (step 9), and then the roots compressor 3 Is switched to the same high-speed operation as in the steady operation (step 10). If the retained liquid temperature is lower than the first set temperature, step 8 is continuously repeated. FIG. 4 shows the state after step 10.

  In Step 8, the first set temperature is set to a temperature slightly lower than the evaporation temperature at which steady operation is performed. Specifically, it is set to a value about 5 ° C. lower than the evaporation temperature. Although the evaporation temperature differs depending on the degree of vacuum, for example, when the degree of vacuum is 20 to 30 kPa, the evaporation temperature (saturated vapor temperature) is about 60 to 70 ° C. Therefore, the first set temperature is higher than this. The temperature is set to about 55 to 65 ° C. which is lower by about 5 ° C. (As a more specific example, when the degree of vacuum is 30 kPa, the first set temperature is set to 60 ° C.).

  In step 8, the raw material liquid is in a state immediately before reaching the boiling point inside the evaporation container 1, and some steam is generated. Moreover, the air inside the evaporation container 1 has already been excluded. When the bypass valve 24 is closed and the Roots compressor 3 is rotated at a high speed, the Roots compressor 3 stands by in a compressible state by sucking a large amount of steam, but no air is present at this stage. Therefore, the Roots type compressor 3 does not trip even if it is rotated at a high speed. Note that the closing operation of the bypass valve 24 and the high-speed operation switching of the Roots compressor 3 may be performed with almost no time lag.

  After the root compressor 3 is switched to high speed rotation, when the raw material liquid is heated by the external steam and the raw material liquid reaches the evaporation temperature (boiling point), a large amount of steam is generated inside the evaporation container 1. This is compressed by the Roots compressor 3, and the steam is sent to the steam heating unit 2 in a heated state, and the steam is used to raise the temperature of the raw material liquid. Therefore, whether the drive current value (HP current value) of the Roots compressor 3 is equal to or larger than the set value in the sense of confirming the transition to steady operation after the Roots compressor 3 has shifted to high speed rotation. It is determined whether the held temperature is equal to or higher than the preset second set temperature (step 11). If either of them is YES, the external steam introduction valve 16 is closed (step 12), and the routine shifts to a steady operation. If both are NO, step 11 is repeated continuously.

  When the HP current value becomes the set value and the retained liquid temperature reaches the second set temperature, it means that the predetermined evaporation is started in a steady state (the predetermined evaporation amount is reached). doing. Accordingly, the subsequent operation is managed as a steady operation. As described above, when the degree of vacuum is 20 to 30 kPa, the second set temperature is about 60 to 70 ° C. (As a more specific example, when the degree of vacuum is 30 kPa, the second set temperature is Set to 70 ° C.).

  The HP current value (heat pump current value) monitors evaporation from the current value by utilizing the fact that the current value of the Roots compressor 3 changes according to the amount of steam to be compressed. However, since the current value consumed by the Roots-type compressor 3 varies greatly depending on various conditions, a general preferable value does not exist. As an example, a current value that is 1/3 of the rated current can be set as the HP current value.

  During the steady operation, if the temperature of the raw material liquid decreases for some reason and the raw material liquid cannot be heated to a required temperature only by the roots compressor 3 (heat pump), the external steam introduction valve 16 is turned on as in the conventional case. Open to supply external steam. The concentrated liquid may be taken out based on a concentration sensor (not shown) or intermittently based on experience values.

(4). Others The present invention can be embodied in various ways other than the above embodiment. For example, the evaporation promoting means does not need to be a thin film upward flow method, and various evaporation means such as a multistage flash method and a thin film flow method can be employed. As the compressor, various compressors such as a blower compressor, a trochoid compressor, a vane compressor, and a gear compressor can be adopted. As the external heating means, various types such as an electric heating type and a hot air type can be adopted instead of the steam type.

  It is also possible to provide a plurality of bypass passages side by side and individually control the opening and closing of the bypass valves provided in both bypass passages. In this case, the exclusion of air can be finely adjusted while using a simple ON / OFF bypass valve. It is also possible to arrange a plurality of compressors in parallel so that all of them are rotated at full speed during steady operation and part of them are rotated at full speed during start-up operation.

  It is also possible to arrange a plurality of concentrators in parallel and share one vacuum pump with each concentrator. In addition, the evaporator vessel is shared between the concentrator of another structure and the concentrator of the present invention. Usually, the concentrator of another structure is used, and when the concentrator of the other structure fails, the concentrator of the present invention is used. It is also possible to use the concentrator as an emergency (or vice versa).

  The heating means can be arranged inside or outside the evaporation container, but if the heating means is provided outside the evaporation container as in the above embodiment (that is, if the evaporation container and the heating means are configured separately), the evaporation means There is an advantage that the structure of the container can be simplified and the labor of manufacturing and maintenance can be reduced.

  The present invention can actually be embodied in a concentrator. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Evaporation container 2 Steam type heating unit which is an example of heating means 3 Roots type compressor which is an example of a compressor 4 Vacuum pump 8 Thin film rising type heat exchange unit 9 Raw material liquid supply pipe (supply passage)
DESCRIPTION OF SYMBOLS 10 Raw material liquid supply valve 11 Raw material liquid return pipe 12 Raw material liquid feed pipe 15 External steam introduction pipe 16 External steam introduction valve 17 Condensate water discharge pipe 19 Condensate water pump 21 Steam extraction pipe 22 constituting steam discharge passage 22 Construct steam discharge passage Steam return pipe 23 bypass passage 24 bypass valve 25 first vacuum passage 26 second vacuum passage

Claims (7)

An evaporation container into which the raw material liquid is charged, a heating means for the raw material liquid to be charged into the evaporation container, a vapor compressor that compresses and raises the temperature of the vapor generated in the evaporation container, the inside of the evaporation container and the vapor A vacuum pump for reducing the pressure of the discharge path, and the steam compressed by the steam compressor is sent to the heating means,
A bypass passage is provided to connect the upstream side and the downstream side of the steam compressor, and the bypass passage is opened only during the start-up operation from the start of operation when the vacuum pump is started to the steady operation. There are sometimes bypass valves that are closed,
During the start-up operation, by maintaining the bypass passage in a reduced pressure state by the vacuum suction action of the vacuum pump, the steam compressor is kept steady while equalizing the negative pressure on the upstream side and the downstream side of the steam compressor. It is operated at the starting speed lower than the operating speed,
Vacuum evaporation type concentrator. The bypass valve is a system that can be switched to two stages of full open and fully closed, while the steam compressor is a system that can be switched to a two-stage rotational speed of a steady operation rotational speed and a lower starting rotational speed. Is,
The vacuum evaporation type concentrator according to claim 1. While the vapor compressor is a Roots type compressor, the heating means is a thin film upflow system, and when the evaporation container is depressurized, the raw material liquid is automatically sucked up from the supply passage to the evaporation container.
The vacuum evaporation type concentrator according to claim 1 or 2. An evaporation container into which the raw material liquid is charged, a heating means for the raw material liquid to be charged into the evaporation container, a vapor compressor that compresses and raises the temperature of the vapor generated in the evaporation container, the inside of the evaporation container and the vapor A vacuum pump for depressurizing the discharge path, a bypass passage communicating the upstream side and the downstream side of the steam compressor, and a bypass valve for opening and closing the bypass passage, the vacuum pump being always constant An operation method of a vacuum evaporation type concentrator configured to be operated at a rotational speed of
Start-up operation from start of operation to transition to steady operation
a: The bypass valve is opened before or after the start of operation of the vacuum pump, or the vacuum pump is started with the bypass valve opened in advance.
b: Start supplying the raw material liquid to the evaporation container in a state where the bypass valve is opened and the vacuum pump is operated.
c: Start operation of the vapor compressor at a starting rotational speed lower than the rotational speed during steady operation after the supply of the raw material liquid is started.
d: After the operation of the vapor compressor is started, heating of the raw material liquid by the heating means is started.
Including the procedure
When the internal pressure or temperature of the evaporation container or both reach a preset reference value, the bypass valve is fully closed to switch the steam compressor to a steady operation rotational speed.
Operation method of vacuum evaporation type concentrator. The bypass valve is kept fully open during start-up operation, and is fully closed when the internal pressure and / or temperature of the evaporation container reaches a preset reference value,
The steam compressor is operated at a constant start-up rotation speed during the start-up operation.
The operation method of the vacuum evaporation type concentrator according to claim 4. A roots type compressor is used for the vapor compressor, and the heating means uses a thin film upflow system,
The operation method of the vacuum evaporation type concentrator according to claim 4 or 5. The switching of the bypass valve to fully closed and the switching to the steady operation rotational speed of the vapor compressor are performed at the timing before the internal pressure of the evaporation container and / or the temperature of the raw material liquid reach the internal pressure and / or temperature during steady operation. Done,
The operating method of the vacuum evaporation type concentrating device in any one of Claims 4-6.

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