JPH029841B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling an indirect pressurization type evaporator that uses fluorocarbons, ammonia, or the like as a working fluid.

When controlling the load in an indirect compression evaporator, it is necessary to adjust the opening of the suction vane of the compressor,
The load is controlled by changing the air volume by controlling the rotational speed of the compressor, but fine adjustment is difficult in both methods, and the rotational speed control method in particular has the disadvantage of requiring complicated equipment and being expensive. Especially when there are multiple concentrate cans, various problems arise. Normally, only one compressor is provided in common for a plurality of concentration cans, and in such a case, it is impossible to adjust the capacity of each concentration can by controlling the air volume of the compressor.
In addition, if you try to control the load by adjusting the amount of working fluid heating vapor in each concentrator, it will be possible to control the load by adjusting the discharge amount of the compressor. This also affected the capacity of individual cans, making it impossible to control the capacity of each individual can.

On the other hand, in order to improve the performance of the concentrator, the liquid to be concentrated is generally preheated to the evaporation temperature of the concentrator (which is under reduced pressure) or several degrees higher than this.
This preheating temperature was assumed based on predictions of heat balance and heat transfer coefficient, and there were few cases where it was controlled because it did not cause any major problems in practice.

On the other hand, the operating temperature range (evaporated liquid temperature) of an indirect pressurization type evaporator is often a low temperature range, and there is an upper limit to the heating temperature of the liquid to be concentrated, such as fruit juice, and exceeding this temperature will cause the components in the liquid to be concentrated to be heated. There is a risk of decomposition, denaturation, etc., and the upper limit heating temperature is strictly limited.

One possible way to control the preheating temperature of the liquid to be concentrated is to directly control the amount of vapor in the heated working fluid. It has a large impact on the process. In addition, the working fluid condensate concentrated by condensation heat transfer enters the evaporator via the expansion valve, but this control changes the amount and saturation pressure of the working fluid condensate, so the expansion valve also changes. At the same time, detailed control was required, and the control mechanism was complicated.

As described above, in the conventional systems, it is difficult or impossible to control the capacity of the concentrator and the preheating temperature of the liquid to be concentrated independently for each concentrator, which is a major drawback. Ta.

The present invention eliminates the above-mentioned drawbacks of the conventional method and can perform reliable load adjustment or reliable preheating temperature adjustment, and when there are multiple concentrators, load control or preheating temperature of the liquid to be concentrated can be adjusted. It is an object of the present invention to provide a control method for an indirect pressurization type evaporator that can be performed independently for each concentrator.

The present invention provides an indirect pressure evaporator having a working fluid cycle in which a working fluid repeatedly circulates between a gas phase and a liquid phase via a compressor between a heating side of a concentrator and an evaporating side of a working fluid evaporator. In the control method of
A part of the working fluid, using its heat of condensation as a heat source, preheats the liquid to be concentrated in a preheater and then supplies it to the concentrator, and stores the working fluid condensate on the heating side of the preheater, and is stored. A condensate pipe that connects the working fluid condensed in the concentrator to a lower liquid chamber of the evaporator or a circulation pipe communicating with the lower liquid chamber by adjusting the liquid level height of the working fluid condensate. This is a control method for an indirect pressurization type evaporator, characterized in that load control is performed by adjusting a control valve provided in the concentrator to adjust the heat transfer area of the concentrator.

These methods make it possible to reliably perform load control or preheating temperature control of the liquid to be concentrated, and to make fine adjustments. Furthermore, even when there are a plurality of concentrating cans, load control or preheating temperature control of the liquid to be concentrated can be reliably performed individually for each concentrating can without affecting other processes.

Embodiments of the present invention will be described using the drawings.

FIG. 1 is an example of a single-effect indirect pressurization type evaporator using fluorocarbon or ammonia as the working fluid.

1 is a concentrator using a thin film falling type evaporator, 2 is a working fluid evaporator using a thin film falling type evaporator, 3 and 4 are gas-liquid separators, 5 is a compressor, and 6 is a compressor 5. A cooler 7 is a plurality of upright heat exchanger tubes for adjusting the temperature of the working fluid that has been pressure-heated. forms a thin film along the
The working fluid enters from the steam inlet 10 of the working body and contacts the outside of the heat exchanger tube 7. The working fluid is heated and concentrated by the heat of condensation.

The liquid to be treated enters the lower liquid chamber 11 and accumulates at the bottom, and a part of it is circulated to the supply port 9 of the upper liquid chamber 8 by the circulation pump 12, and a part is sent to the valve 16 and the pipe line 14 as a product. It is taken out of the system through the

In order to raise the temperature of the liquid to be treated, the circulation pipe 15 for the liquid to be treated is provided with a preheater 17 that uses the heat of condensation of the high-pressure working fluid as a heat source, so that the temperature of the liquid to be treated is lower than the evaporation temperature. In this case, this preheater 1
7, the temperature of the liquid to be treated can be raised as appropriate. Note that it is desirable that the temperature of the liquid to be treated at the outlet of the preheater 17 be slightly (2 to 3° C.) higher than the evaporation temperature.

Reference numeral 13 denotes a supply pipe line 14 for the liquid to be treated, and a pipe line 14 for extracting the product. Reference numeral 18 denotes a condensate outlet pipe for the working fluid, which connects the high-pressure side liquid storage tank 19 and the control valve 20 in series, and is connected to the lower liquid chamber 26 of the evaporator 2 for the working fluid. Note that this concentrated liquid outlet pipe 18 does not necessarily need to be connected to the lower liquid chamber 26 as shown in the figure, and may be connected to the circulation pipe 21 or the upper liquid chamber 25. 22 is a paper outlet pipe for the liquid to be treated, one end of which is connected to the evaporator 2.

The evaporator 2 is provided with a plurality of upright heat transfer tubes 23, and the working fluid is supplied to the inner wall side of the heat transfer tubes 23 via a working fluid supply port 24 and an upper liquid chamber 25. While the liquefied working fluid flows down along the inner wall of the heat transfer tube 23, it is heated by the vapor from the concentrator 1 introduced to the outside of the heat transfer tube 23, evaporating a part of it, and the remaining part flows into the lower liquid chamber 26. It accumulates in This unevaporated working fluid is extracted from the lower liquid chamber 26 through the extraction port 27, and is drawn out from the working fluid circulation pipe 21.
The liquid is again supplied to the upper liquid chamber 25 via the supply port 24. Note that the working fluid circulation pipe 21 is provided with a working fluid circulation pump 28 .

Further, the working fluid from the control valve 20 is supplied above the liquid level of the working fluid accumulated in the lower liquid chamber 26 of the evaporator 2; It is controlled by a liquid level gauge 30 and a liquid level regulator 31.

Drain condensed outside the heat exchanger tube 23 can be extracted through the drain extraction tube 29 and then used as a preheat source for the liquid to be treated.

The vapor of the working fluid separated by the gas-liquid separator 4 is pressurized and heated by the compressor 5, and is used as a heating heat source in the concentrator 1.

33 is a liquid level controller that detects the liquid level height of the working fluid condensate stored on the heating side of the concentrator 1;
A flow rate control valve 34 provided in the outlet pipe line 18 compares the liquid level height with a set value and matches the set liquid level height.
The outflow flow rate is controlled by However, the set value of the liquid level height is determined by the flow rate of the drain extracted from the drain extraction pipe 29 of the evaporator 2 (since all the steam that enters the heating side of the evaporator 2 is condensed,
The amount of steam generated in the concentrator 1 can be determined by the drain flow rate) is detected by the flow rate controller 35 and changed by a signal corresponding to the drain flow rate, so that cascade control is performed. There is. For example, when the drain flow rate decreases below the set flow rate (the amount of steam generated decreases), the set value of the liquid level height is lowered, the heat transfer area in the heat transfer tube 7 is increased, and the amount of steam generated is restored. The opposite effect occurs when the drain flow rate increases. Further, when the evaporation capacity is intentionally increased or decreased, this liquid level height setting value is changed manually or by other signals.

The liquid storage tank 19 has a flow rate control valve 34 and a regulating valve 20.
Two types of control are used to buffer against changes in flow rate.

A part of the high-pressure working fluid gas from the compressor 5 is branched and supplied to the preheater 17, and the liquid to be concentrated is heated with sensible heat and condensation heat, and the working fluid itself becomes a condensed liquid and is supplied to the preheater 17. It is designed to be stored in a heated side chamber. A flow control valve 36 is provided in the working fluid outlet line from the preheater 17. 37 is a displacement controller that detects the liquid level height of the working fluid condensate stored on the heating side of the preheater 17, compares it with the liquid level height set value, and adjusts the liquid level so that it matches the set liquid level height. A flow control valve 36 controls the outflow flow rate. The set value of the liquid level height is changed in a cascade manner by detecting the outlet temperature of the liquid to be concentrated coming out of the preheater 17 by the temperature controller 38 and by a signal corresponding to the obtained outlet temperature. control is in place. For example, if the outlet temperature becomes lower than the set temperature, lower the set value of the liquid level and
The heat transfer area of the preheater 17 is increased to restore the outlet temperature. If the outlet temperature is high, the opposite effect will occur. Further, when the preheating temperature is intentionally raised or lowered, the set value of the liquid level height is changed manually or by other means.

To explain the operation status, liquids to be processed (liquids to be concentrated) such as fruit juice raw material liquid and sugar raw material liquid are routed from the liquid to be processed supply pipe 13 to the circulation pipe 1 for the liquid to be processed.
The liquid is supplied to the liquid chamber 5, heated by the preheater 17, and guided to the upper liquid chamber 8 via the supply port 9. Further, it flows down from the upper liquid chamber 8 along the inner wall of the heat transfer tube 7, and during this time it is heated and concentrated by the heat of condensation of the working fluid, and the concentrated liquid to be treated accumulates in the lower liquid chamber 11, and the gas-liquid mixture is The vapor and the liquid to be treated are separated by the gas-liquid separator 3, and the liquid to be treated is sent to the circulation pump 12.
A part of it is extracted from the system as a product,
The remainder is circulated to the upper liquid chamber 8 through the circulation pipe 15. Note that the liquid to be treated that is extracted as a product can also be used to preheat the liquid to be treated that flows into the concentrator 1.

On the other hand, a part of the working fluid that has been concentrated by removing heat in the heat transfer tube 7 is stored on the heated side of the concentrator 1, and the rest passes through the condensate outlet pipe 18 and the flow rate control valve 34 and is stored on the high pressure side. The liquid is introduced into the tank 19 and further flows into the lower liquid chamber 26 of the evaporator 2 via the control valve 20. Here, the liquid level of the working fluid in the lower liquid chamber 26 is determined by the liquid level gauge 30.
The control valve 20 is adjusted by a signal from the liquid level regulator 31 so that the level of the working liquid is always constant. The working fluid accumulated in the lower liquid chamber 26 is extracted from the extraction port 27 by the circulation pump 28, guided again to the upper liquid chamber 25 via the supply port 24, and further flows down along the inner wall of the heat transfer tube 23. During this time, the vapor generated in the concentrator 1 and separated in the gas-liquid separator 3 is heated and evaporated. Here, the upper liquid chamber 2 of the evaporator 2
5, heat transfer tube 23, lower liquid chamber 26, circulation pump 2
8. The circulating flow rate of the working fluid that sequentially circulates through the circulation pipes 21 is at least 5 times, preferably at least 10 times, the amount of working fluid evaporated in the evaporator 2, so that it is effective in the heat transfer tubes 23. Heat transfer is taking place. Reference numeral 32 denotes a valve, which adjusts the amount of circulating fluid.

Although the evaporator 2 in the figure is a multi-tube thin film descending type evaporator, the effects unique to the present invention can also be achieved by using a thin film descending type evaporator made of an inclined or upright flat plate.

The load control system using the flow rate control valves 34 and 36 and the preheating temperature control system for the liquid to be concentrated are schematically shown in the second diagram.
As shown in the figure. In this figure, the flow control valve 34 also functions as a pressure reducing valve.

Figure 3 shows an apparatus using a plurality of concentrators 1A, 1B, and 1C, and the numbers A, B, and C in the figure are the same as those with the same numbers in Figure 2. show something In addition, flow rate/liquid level controller 3
9A, 39B, and 39C are abbreviated combinations of the flow rate controller 35 and liquid level controller 33 in FIG. 2, and their functions are the same as those in FIG. 2, and perform cascade control. In addition, temperature/liquid level controller 40A, 4
0B and 40C are temperature controllers 38 in Fig. 2.
This is an abbreviation of the combination of the liquid level controller 37 and the liquid level controller 37, and the configuration and operation are the same as those shown in FIG. 2, and cascade control is performed.

The evaporator 2 has one chamber on the working fluid side (evaporation side), but the heating side is partitioned into chambers for the number of concentrators 1A, 2A, and 3A (that is, three in this example). Separately from the drain extraction chambers 29A, 29B, 2
9C, each drain flow rate is detected by flow rate/liquid level controllers 39A, 39B, 39C, and the amount of steam generated in each concentrator 1A, 1B, 1C is independently controlled by flow rate control valves 34A, 34B, 34C. to control. Flow control valve 34A, 3
The outlet sides of 4B and 34C merge and are connected to the evaporation side of the evaporator 2.

Steam generated from the liquid to be concentrated in each of the concentrators 1A, 1B, 1C is passed through outlet pipes 22A, 22B,
It is guided to the evaporator 2 through 22C and 41 (one outlet pipe 41 is shown in the figure, but actually there are three).

Preheaters 17A, 17B, 17C are for each concentration can 1
A, 1B, and 1C are provided, and each independently performs the same control as in FIG. are doing.

Since the upper embodiment is configured and operates as described above, the following effects can be achieved.

(1) Concerning the control of the evaporation capacity of the concentrator: (i) Working fluid condensate was stored on the heating side of the concentrator, and the load was controlled by changing the heat transfer area by adjusting the liquid level. (a) Reliable load control including fine adjustment is possible.

(b) Since the amount of evaporation is directly detected and controlled using this, it is easy to understand the capacity and easy to operate.

(c) By using it in conjunction with suction vane control, a wide range of capacity control is possible.

(d) It is possible to operate several concentrators using one compressor and evaporator, and in this case, the load can be controlled independently without affecting the processes in other concentrators. You can definitely do it.
In addition, the number of equipment is reduced, the cost is reduced, the space is reduced, and maintenance is easy.

(ii) Since the operation end for liquid level control is also used as a pressure reducing valve, only one controller is required, and at least two controls are performed with one operation amount, so control against disturbances is reliable.

(iii) Flow control valves are provided in each concentrator, allowing complete independent control over other processes.

(2) Concerning preheating temperature control of the liquid to be concentrated: (i) By controlling the preheating temperature, product decomposition and deterioration due to rise in liquid temperature can be avoided and a high quality product can be obtained.

(ii) By storing the working fluid concentrate on the heating side and controlling the stored liquid level, the heat transfer surface can be adjusted to control the load and the preheating liquid temperature, thereby affecting other processes. It is possible to independently and reliably control only the target part without applying any pressure.

(iii) Since the operation end of the liquid level control also serves as a pressure reducing valve, only one controller is required, and at the same time, at least two controls can be performed with one operation amount, allowing for appropriate control against disturbances. is possible.

(iv) Since the piping after the control valve is connected to the refrigerant evaporator independently (each control valve is provided separately), completely independent control can be performed reliably without affecting other processes. .

(3) Regarding the structure of evaporator 2 and concentrator 1: (i) Since they are vertical, the cross section of the liquid storage part is uniform, and the liquid level and storage volume are in a proportional relationship, making it easy to control the LIC. It is.

(ii) Since it is a vertical type, the liquid level of the storage liquid and the heat transfer area are in a proportional relationship, making it easy to control.

(iii) Since a thin film drop type evaporator is used as the working fluid evaporator, the boiling point does not increase due to liquid depth and the working fluid can be evaporated even with an extremely low heat source. In the case of a type concentrator, there is no increase in boiling point due to liquid depth in both the evaporator for the working fluid and the concentrator for the liquid to be concentrated, so that concentration can be performed at a lower temperature. In addition, since the thin-film descending evaporator has little hold-up of the working fluid in the heat transfer section, it can quickly respond to load fluctuations and maintain the entire system in an optimal operating state at all times. Particularly in concentration operations at low temperatures, it is not possible to rapidly adjust large amounts of heat due to the low temperatures, so it is a great advantage to employ a system with an extremely quick response as in this example.

(iv) Furthermore, even if a working fluid with poor heat transfer such as fluorocarbon is used, the heat transfer in a drop-down evaporator is
The heat transfer efficiency is dramatically higher than that of calandria and thin film rising evaporators, so it transfers heat effectively without any negative effects.
Thermal energy can be quickly recovered from the polarized paper.

(v) Furthermore, since the working fluid is circulated and supplied to the thin film falling type evaporator, the amount of evaporation can be easily adjusted by adjusting the amount of circulation.

Adjusting the amount of evaporation of the working fluid in the evaporator by adjusting the circulating amount of the working fluid becomes more reliable by stabilizing the discharge amount of the circulation pump. In order to stabilize the discharge amount, a liquid level gauge is provided in the lower liquid chamber at the bottom of the evaporator, and a control valve is adjusted based on this detection signal so that the liquid level is always constant.

(vi) Furthermore, since the high pressure side liquid storage tank is provided upstream of the control valve, the control valve always operates stably.

(vii) Furthermore, the working fluid from the control valve can be introduced into the lower liquid chamber of the evaporator, the working fluid circulation line, or the upper liquid chamber of the evaporator, but in particular, the working fluid in the lower liquid chamber If the liquid is introduced above the surface, this liquid level control will be more stable. By doing so, there is no fluctuation in the flow of the circulation pump and cavitation is also eliminated.

(viii) Furthermore, by reducing the amount supplied by the circulation pump, the entire amount of supplied working fluid can be evaporated. In this case, no circulation is performed in the circulation pipe, and the absolute amount of evaporation decreases, but the amount of evaporation can be controlled to a linimer by adjusting the supply amount.

In the above embodiments, the concentrate can has a single effect, but it may have multiple effects.
In this case, the drain flow rate is detected by detecting the total drain flow rate of the liquid to be concentrated, and adjusting the liquid level setting value of the first concentrating can according to this detected value.

According to the present invention, the load control in the concentrator or the preheating temperature of the liquid to be concentrated in the preheater can be reliably and finely adjusted, and a single compressor can be used to operate multiple concentrators. Even in such cases, it is possible to reliably control the load of each concentrator or the preheating temperature of the concentrated liquid in each preheater individually and independently without affecting other processes. It is possible to provide a control method for an indirect pressurization type evaporator that can be carried out in a number of ways, and can have extremely great practical effects.

[Brief explanation of drawings]

FIG. 1 is a flowchart of an embodiment of the present invention, FIG. 2 is a flowchart mainly showing the control system thereof, and FIG. 3 is a flowchart mainly showing the control system of another embodiment. 1... Concentrator, 2... Evaporator, 3... Gas-liquid separator, 4... Gas-liquid separator, 5... Compressor, 6... Cooler, 7... Heat exchanger tube, 8... Upper part Liquid chamber, 9... Supply port, 10... Steam inlet, 11... Lower liquid chamber, 1
2... Circulation pump, 13... Supply pipe line, 14...
Pipe line, 15...Circulation pipe line, 16...Valve, 17...
Preheater, 18...Outlet pipe line, 19...Liquid storage tank, 2
0... Control valve, 21... Circulation pipe line, 22... Outlet pipe line, 23... Heat transfer tube, 24... Supply port, 25...
... Upper liquid chamber, 26 ... Lower liquid chamber, 27 ... Extraction port, 28 ... Circulation pump, 29 ... Drain extraction pipe, 30 ... Liquid level gauge, 31 ... Liquid level regulator, 32
...Valve, 33...Liquid level controller, 34...Flow rate control valve, 35...Flow rate controller, 36...Flow rate control valve, 37...Liquid level controller, 38...Temperature controller,
39A, 39B, 39C...Flow rate/liquid level controller,
40A, 40B, 40C...Temperature/liquid level controller,
41...Exit pipe.

Claims (1)

[Claims] 1. Indirect addition having a working fluid cycle in which the working fluid repeatedly cycles through a gas phase and a liquid phase via a compressor between the heating side of a concentrator and the evaporating side of a working fluid evaporator. In a method for controlling a pressure type evaporator, a liquid to be concentrated is preheated in a preheater using a part of the working fluid as a heat source using its condensation heat, and then supplied to the concentrator, and the working fluid is supplied to the heating side of the preheater. A circulation pipe that stores condensate and communicates the flowing fluid condensed in the concentrator to the lower liquid chamber of the evaporator or the lower liquid chamber by adjusting the liquid level of the stored working fluid condensate. A method for controlling an indirect pressurization type evaporator, characterized in that load control is performed by adjusting a heat transfer area of the concentrator by adjusting a control valve provided in a condensate pipe connected to the condensate pipe. 2. A patent for controlling the preheating temperature of the liquid to be concentrated by detecting the temperature of the liquid to be concentrated at the outlet of the preheater and adjusting the liquid level of the stored working fluid condensate according to this outlet temperature. The method according to claim 1. 3. Control method for an indirect pressurization type evaporator having a working fluid cycle in which a working fluid repeatedly circulates through a gas phase and a liquid phase between the heating side of a concentrator and the evaporating side of a working fluid evaporator via a compressor. In a part of the working fluid, the liquid to be concentrated is preheated in a preheater using the heat of condensation as a heat source, and then supplied to the concentrator, and the working fluid condensate is stored on the heating side of the preheater. By storing the working fluid condensate on the heating side of the concentrator and adjusting the height of the liquid level of the working fluid condensate that has been removed, the condenser is heated. Adjusting the heat transfer area of the concentrator by adjusting a control valve provided in a condensate pipe that connects the condensed flowing fluid to a lower liquid chamber of the evaporator or a circulation pipe communicating with the lower liquid chamber. A method for controlling an indirect pressurization type evaporator, characterized in that the load is controlled by 4. By storing a working fluid on the heating side of the evaporator and adjusting the liquid level of the stored working fluid, the working fluid condensate control valve of the concentrator is adjusted to adjust the heat transfer area. The method according to claim 3.