JPS595321B2 - Evaporator control method and evaporator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for controlling the evaporator pressure of a self-compressing multiple effect evaporator and an evaporator thereof.

In order to stabilize the operation of multiple-effect evaporators, conventionally a method was used to keep the pressure on the evaporator side of the final stage evaporator constant.The pressure detection terminal for this purpose was also provided on the evaporator side of the final stage evaporator. Ta.

An example is shown in FIG.

In the same figure, 1, 2.3 are the first stage, second stage, and third stage evaporators, respectively, 4, 5° 6 is a heating chamber, 7, 8.9 is an evaporation chamber, 10 is a condenser, and 11 is a heating To steam type 12 is dilute solution inlet, 13゜14 is solution flow path, 15 is concentrated solution outlet, 16,
17° 18 is a steam flow path, 19.20 is a cooling water flow path, 21
is a condensed water outlet, and 22, 23, and 24 are drain outlets.

25 detects the pressure in the steam flow path 18 (that is, the evaporation side pressure of the third stage evaporator 3), and operates the cooling water flow rate control valve 26 to keep the evaporation side pressure of the third stage evaporator 3 at a predetermined level. This is a pressure indicator controller that maintains the set pressure.

Recently, in such multi-effect evaporators, compressors and steam boosters as shown by the two-dot chain line in Fig. 1 have been installed in order to reduce the amount of steam consumed by increasing the amount of evaporation per unit amount of input steam as an energy-saving measure. For example, a self-compression type (mechanical compression or thermal compression) multi-effect evaporator is often used, which uses a compression mechanism such as an ejector 27 to compress the vapor evaporated from the evaporator and guide it to the heating side of the same evaporator. It looks like this.

In conventional devices of this kind, in order to maintain stable operation, the evaporation side pressure of the third stage evaporator 3 at the final stage is controlled by the vapor flow path 1.
8, and in order to keep it at the set pressure [cooling water'
I was adjusting the 1itlJ control valve 26.

In general, in a multi-effect can, the balance is not determined by the heat transfer area under the processing conditions, and the internal pressure of each evaporator is also determined step by step for each evaporator.

However, due to differences in processing conditions, physical properties of the liquid, margins in heat transfer area, etc., the balance at the time of planning may deviate during actual operation. The first stage evaporator 1 to which self-compressed steam is supplied (hereinafter referred to as the evaporator to which self-compressed steam is supplied, that is, the evaporator to which the discharged steam of the ejector 27 is supplied to the heating side) is referred to as the first stage evaporator 1. It was extremely difficult to maintain the evaporation side pressure of the stage evaporator at a predetermined value.

On the other hand, the performance of compression mechanisms such as the compressor and the ejector 27 is greatly influenced by the suction side (secondary side) pressure.

That is, let the steam pressure at the heating steam supply port 28 be P, the flow rate be Ql, the steam pressure in the suction pipe 29 be P2, the flow rate be Q2, the pressure P2 at the heating steam population 11, and the flow rate be Q2 (=Q1+Q2). For example, if Pl is constant, Ql is determined by dimensions such as the nozzle diameter of the ejector 27, and Q2 is determined by P2, that is, the pressure on the evaporation side of the first stage evaporator 1. Therefore, Q2, which is Q, +Q2, is determined by the size of the nozzle diameter of the ejector 27.
If 7 is determined, it will depend on the evaporation side pressure of the first stage evaporator 1.

Since the design point of the ejector 27 is selected for the most efficient suction ratio Q2/Q1, as mentioned above, it is difficult to control the evaporation side pressure of the first stage evaporator only by controlling the evaporation side pressure of the last stage evaporator, as described above. As a result, the suction side pressure P2 of the ejector 27 fluctuates, and the operation is performed at a point different from the design point, making it difficult to fully demonstrate the performance of the compression mechanism such as the ejector 27. Moreover, the heating amount of the first stage evaporator 1 fluctuated, making it difficult to perform stable operation.

The present invention eliminates the above-mentioned drawbacks of the conventional method by detecting the evaporation side pressure of at least the first stage evaporator and manipulating the operating point in the system to maintain the same pressure at a predetermined set pressure. Even if there is a margin in the design or a difference or variation in actual conditions from the design conditions, the compression mechanism should be operated in a good condition that matches the design point, and fluctuations in the heating amount of the first stage evaporator should be avoided. This allows for stable operation.

An object of the present invention is to provide a method for controlling an evaporator and an evaporator.

In addition, in this specification, [nth (n is 1.2...
...The evaporation side line of the final stage evaporator refers to the evaporation chamber of the nth stage evaporator and the part connected to it at approximately the same pressure.For example, in Fig. The evaporation side yarn path of the can includes the evaporation chamber 7, the steam flow path 16, the heating chamber 5, and the suction pipe 29, and the ``evaporation side yarn path of the final stage evaporator'' includes the evaporation chamber 9, the steam flow path 18 , including the gas phase portion of the condenser 10.

Furthermore, "detection of the pressure on the evaporation side of the n-th stage evaporator" refers to the detection of the pressure in the evaporation-side line path of the n-th stage evaporator.

The present invention includes a plurality of evaporators, guides the steam generated from the final stage evaporator to a condenser, and connects the evaporator or its In a control method for a self-compressing multi-effect evaporator in which a part of the vapor generated in an evaporator downstream of the evaporator is compressed and guided, at least the evaporator to which self-compressed vapor is supplied is used as pressure detection. Detecting the pressure on the evaporator side of the can and operating a predetermined operating point in the system to control the pressure so that the pressure on the evaporator side of the evaporator to which the self-compressed steam is supplied becomes a predetermined set pressure. A method for controlling an evaporator and an evaporator characterized by the following.

To explain the present invention with reference to the drawings in accordance with an embodiment, as shown in FIG. Detected by the detection end 30 at , a signal is issued when the variation permissible range for the set value is exceeded, and the pressure indicator controller 25 operates the flow rate control valve 26 as an operating point to adjust the amount of cooling water.
The temperature and pressure of the evaporation chamber 9 are changed, and the heating chamber 6,
By changing the temperature and pressure of the evaporation chamber 8, the pressure of the heating chamber 5,
That is, the pressure on the steam side of the first stage evaporator 1 is changed to a predetermined set pressure, the suction side pressure of the ejector 27 is adjusted to the predetermined design conditions, and the ejector 27 is operated with good efficiency to ensure the capacity. A predetermined amount of steam is supplied to the heating chamber 4I to ensure stable operation.

For pressure detection, in addition to the detection end 30, a detection end 31 is provided to detect, for example, the evaporation side pressure of the third stage evaporator 3 at the final stage, for example, in the steam flow path 18. 31 may be switched to operate.

For example, when operating under specification conditions (design conditions), the detection end 30 is activated to control the pressure in this area, and when operating conditions differ, the pressure on the evaporation side of the third stage evaporator 3 at the final stage is If it is better to control the detection end 31, the detection end 31 is activated.

FIG. 3 shows another embodiment, in which the detection end 30 in FIG.
．． Instead of 31, pressure guide pipes 32 and 33 are branched from that position via control valves 34 and 35, and a detection end 36 is provided.

The control valve 34 or 35 is switched depending on the operating conditions and the pressure of the opened valve is detected, and has the same effect as the previous example.

These switching pressure controls make it easy to deal with a wide range of operating conditions, and sharing a control device simplifies the structure.

FIG. 4 shows another embodiment in which a detection end 30 is placed inside the evaporation chamber 7.
is provided, and a pressure indicating controller 25 operates a control valve 37 as an operating point.

The evaporation chamber 8 has a negative gauge pressure, and when the on-off valve 37 is opened, the atmosphere is introduced into the evaporation chamber 8 and the partial pressure of the air increases.

Due to the increase in air partial pressure, the overall heat transfer coefficient U decreases, the amount of heat transferred to the evaporation chamber 8 changes, and the pressure inside the heating chamber 5, that is, the pressure on the evaporation side of the first stage evaporator 1, changes to a predetermined level. Adjust the pressure to the set pressure.

A regulating valve 38 or 39 may be provided in the evaporation chamber 9 or the vapor flow path 18 to change the pressure within the evaporation chamber 9.

The above is an embodiment of the present invention in which steam self-compressed by the ejector is supplied to the first stage of the multi-effect canister, that is, the first stage evaporator. However, the present invention is applicable even in such a case, since it is not only possible to supply to the first stage evaporator, but it can be supplied to any evaporator other than the final stage evaporator. can.

In addition, water is not the only cooling source used in condensers.
Any fluid with a temperature lower than that of the incoming steam can be used as a cooling medium within the range allowed by the material.

Furthermore, means for adjusting the amount of heat transfer in the evaporator other than that shown in FIG. 4 are possible.

For example, it is also an effective means to configure the system so that non-condensable gas can be supplied to the steam flow path leading to the condenser, and to adjust the supply amount of this non-condensable gas as appropriate.

FIG. 5 shows another embodiment. In this embodiment, one control valve 40 and on-off valves 41, 42, 43 provided in any flow path are combined to form one control valve. The control valve 40 allows atmospheric air to be introduced into a desired flow path.

The present invention includes a plurality of evaporators, guides the steam generated from the final stage evaporator to a condenser, and connects the evaporator or its In a control method for a self-compressing multi-effect evaporator in which a part of the vapor generated in an evaporator downstream of the evaporator is compressed and guided, at least the evaporator to which self-compressed vapor is supplied is used as pressure detection. By detecting the pressure on the evaporation side of the can and manipulating a predetermined operating point in the system, the pressure is controlled so that the pressure on the evaporation side of the evaporation can to which the self-compressed steam is supplied becomes a predetermined setting. , when there is a difference between the design conditions and the actual operating conditions, the compression mechanism can be operated under efficient operating conditions, and the heating amount of the first stage evaporator can be It is possible to provide a stable and reliable high-performance evaporator control method and evaporator by keeping the temperature almost constant and performing a large heating action at the part where the temperature on the heating side is the highest, which is extremely practical in practice. It has a dog-like effect.

[Brief explanation of the drawing]

Figure 1 is a flow diagram of the conventional example, Figures 2, 3, 4,
FIG. 5 is a flow diagram of different embodiments of the present invention. 1... First stage evaporator, 2... Second stage evaporator, 3... Third stage evaporator, 4, 5, 6...
...heating chamber, I. 8.9... Evaporation chamber, 10... Condenser,
11... Heating steam inlet, 12... Dilute solution included, 13, 14... Solution flow path, 15...
...Concentrated solution out, 16,17°18...Steam flow path, 19,20...Cooling water flow path, 21...
... Condensed water outlet, 22, 23, 24 ... Drain outlet, 25 ... Pressure indicator and controller, 26 ...
...flow control valve, 27... ejector, 28.
... Heating steam supply port, 29 ... Suction pipe line, 30, 31 ... Detection port 32.33 ...
- Impulse pipe, 34, 35... Control valve, 36...
...detection end, 37, 38, 39... control valve,
40... Control valve, 41, 42, 43...
・Opening/closing valve.

Claims (1)

[Claims] 1. A device comprising a plurality of evaporators, which guides the steam generated from the final stage evaporator to a condenser, and directs the steam generated from the final stage evaporator to the heating side of any evaporator preceding the final stage evaporator. In a control method for a self-compressing multi-effect evaporator in which a part of the vapor generated in the evaporator or an evaporator downstream of the evaporator is compressed and guided, at least self-compressed vapor is supplied as compression detection. The pressure is controlled so that the pressure on the evaporator side of the evaporator to which the self-compressed vapor is supplied becomes a predetermined set pressure by detecting the pressure on the evaporator side of the evaporator to which the self-compressed vapor is supplied and operating a predetermined operating point in the system. A method for controlling an evaporator, characterized by performing the following steps. 2. The method according to claim 1, wherein the pressure detection is capable of detecting the pressure on the evaporation side of another evaporator in addition to the pressure on the evaporation side of the evaporator to which the self-compressed vapor is supplied. 3. Claim 1, wherein the operating point is a cooling medium flow path of the condenser, and the cooling medium flow rate is adjusted.
The method described in section. 4. The operating point is an evaporation side thread path of a negative gauge pressure of an evaporator other than the heating side of the evaporator to which the self-compressed vapor is supplied, and atmospheric air is introduced into the thread path to 2. The method according to claim 1, further comprising increasing the pressure on the evaporation side of the other evaporator. 5 the operating point is in the steam inlet flow path of the condenser;
2. The method according to claim 1, wherein the amount of non-condensable gas flowing into the condenser is adjusted. 6.Equipped with a plurality of evaporators, the vapor generated from the final stage evaporator is guided to the condenser, and the heating side of any evaporator in the previous stage than the final stage evaporator is connected to the evaporator or the evaporator. In a self-compressing multi-effect evaporator that compresses and guides a portion of the vapor generated in a subsequent evaporator, a pressure detection mechanism is provided at least in the evaporator line path of the evaporator to which the self-compressed vapor is supplied. An evaporation pressure detector is provided, and a predetermined operating point in the system is operated based on a signal from the evaporation pressure detector so that the pressure on the evaporation side of the evaporator to which the self-compressed vapor is supplied becomes a predetermined set pressure. An evaporator characterized by comprising a pressure control mechanism. 7. The apparatus according to claim 6, wherein the evaporator to which the self-compressing steam is supplied is the first-stage evaporator. 8. The pressure detection mechanism is such that an evaporation pressure detector is provided not only in the evaporation side line path of the evaporator to which the self-compressed vapor is supplied, but also in the evaporation side line path of other evaporators. An apparatus according to certain claim 6. 9 the operating point is a cooling medium flow path of the condenser;
7. The apparatus according to claim 6, further comprising a cooling medium flow rate adjustment mechanism. 10 The operating point is an evaporation side thread path of negative gauge pressure of another evaporator other than the heating 91U of the evaporator to which the self-compressed vapor is supplied, and an atmosphere introduction operation for introducing atmospheric air into the thread path. 7. The device of claim 6, wherein the device is provided with a mechanism. 11. The device according to claim 6, wherein the operating point is located in the steam inlet channel of the condenser, and a non-condensable gas introduction mechanism is provided for introducing non-condensable gas into the steam inlet channel. .