JPS61209086A - Load control apparatus in multistage flash type seawater desalting apparatus - Google Patents

Abstract

PURPOSE:To stably obtain made-up water so as to deal with disturbance, by respectively detecting the temp. of brine at the first stage inlet of an evaporation chamber and that of brine at the final stage of the evaporation chamber and operating the temp. difference between both detection terminals. CONSTITUTION:A final stage brine temp. detector 31, a subtractor 32 and a flash range controller 33 are provided and a flash range is operated by the subtractor 32 while the temp. difference corresponding to a set made-up water amount is calculated by a function device and a heating supply amount is controlled so as to allow the output signal of the subtractor 32 to coincide with that of the function device. By this method, even if an external operational condition changes, control can be performed so as to make the given flash range constant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a multi-stage flash-type seawater desalination device (hereinafter referred to as a seawater desalination device), in which changes in supply seawater temperature and aging changes in cooling tube heat transfer coefficients are used. The present invention relates to a load control device for a seaweed apparatus that can stably and continuously obtain a predetermined amount of produced water even when external operating conditions such as the above change.

[Conventional technology]

For example, as shown in FIG. 3, a conventional sea salt apparatus includes a heat recovery section 1 (stage /I61 to stage N-2 in FIG. 3) and a heat release section 2 (stage /I6N- in FIG. 3). It consists of a multi-stage evaporation chamber consisting of 1 stage and /16N stage) and a brine heater 3.

In FIG. 3, raw seawater is supplied from a supply line 4 to a heat release section 2. In FIG. The refractory portion is discarded through the discharge line 5, while a portion is supplied as a replenisher to the seawater system through the seawater replenishment line 6. This liquid and the brine in the final stage of the evaporation chamber are combined and passed through the brine circulation line 7 to 9.
, is supplied to the heat recovery section l as a cooling liquid. In the heat recovery section 1, the vapor evaporated in flash in each stage of the evaporation chamber is cooled and condensed by the brine passing through the condenser 8 of each evaporation chamber, and the brine in the condenser 8 is flushed in each stage of the evaporation chamber. At the inlet of the brine heater 3, the temperature is raised almost to the saturation temperature of the first stage of the evaporation chamber. In other words, it provides a heat recovery effect.

The brine is heated by the brine heater 3 to a temperature several degrees higher than the saturation temperature of the first stage of the evaporation chamber. The line 9 is a line that supplies a heating medium used in the brine heater 3. Steam is generally used as the heating medium.

The heated brine is led to the first stage evaporation chamber. In this way, the brine flows down through each stage of the evaporation chamber, and an orifice IO and a weir 11 are installed at the entrance of each stage. As the brine flows down each stage, the temperature of the brine decreases as fluff and g are emitted, but the friction pressure fi due to the orifice 10 and the weir 11 [Thus, the saturation pressure of the brine also decreases, so flash evaporation can be performed at each stage. . The vapor generated in the evaporation chamber is separated from entrained droplets by a demister 12, contacts a condenser 8, is cooled and condensed, and becomes fresh water.

This liquid is stored in a condensate tray 13, and this liquid also descends through each stage and is taken out from a line 14 and sent to a manufactured water tank.

A method of controlling the conventional device will be explained.

The items that are usually controlled by the conventional device are the brine temperature at the outlet of the brine heater 3 (that is, the first stage inlet of the evaporation chamber/I61), the circulating fluid flow rate, the final stage liquid level, and the seawater supply flow rate.

The first-stage inlet brine temperature is determined by a temperature detection end 20 provided at the outlet of the brine heater 3, and a temperature controller 21 that measures the temperature of the heating medium (
(usually using water vapor).

The circulating flow rate is controlled to be constant by a flow rate detection end 25 and a flow rate controller 22 to a set flow rate corresponding to a required load (water amount).

Seawater replenisher is also supplied according to the required amount of fresh water. The material balance of the liquid in the device with respect to the replenishment amount is controlled by the amount of water drawn from the waste water line 15 from the final stage (N stage) of the evaporation chamber. The amount of waste water is controlled by a level controller 23 that controls the final stage liquid level in the evaporation chamber to be constant.

The amount of seawater supplied from the supply line 4 to the heat release section 2 is controlled to be constant by a heat release section cooling seawater flow rate controller 24 .

[Problems that the invention is not supposed to solve]

Generally, what is required in the operation of a seawater apparatus is to stably and continuously obtain a predetermined amount of produced water. However, the amount of produced water is influenced by a heating amount, b circulating fluid flow rate, c cooling pipe heat transfer coefficient, d supply seawater flow rate, e supply seawater temperature, etc.

Of these, a, b, and d can be adjusted arbitrarily, but c, e
is an external factor and a disturbance for controlling the amount of produced water. Therefore, the operator is required to perform operations corresponding to this disturbance.

For example, in response to changes in operating conditions such as large differences in the temperature of e-supply seawater between summer and winter, and changes in the heat transfer coefficient of the C cooling pipe due to aging, operators can It is necessary to adjust each set value of the circulating fluid flow rate controller 22, heat release section cooling seawater flow rate controller 24, etc. to match the predetermined amount of produced water. Furthermore, there are some things that are difficult to measure, such as dirt that changes the heat transfer coefficient of the C cooling pipe, and not all factors that influence the amount of produced water are quantitatively understood. Therefore, when changing the amount of produced water, the operator should monitor the brine temperature and level in each stage of the evaporation chamber, and change a heating amount, b circulating fluid flow rate, and d supply seawater flow rate little by little and slowly. Therefore, considerable empirical knowledge is required.

As mentioned above, the amount of water produced is affected by the heel and is expressed by the following formula:

Fp=toφFR・TF ・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・(1
) FP: Produced water volume (t/h) FR: Circulating fluid flow rate (t/h) K: Proportionality constant (-) In other words, changes in various operating conditions with respect to the produced water volume result in changes in the final stage temperature. This is something that focused on the fact that it was coming.

Here, the proportionality constant is a constant determined by the plant, but it can be considered to be approximately constant for each plant.In order to obtain the desired produced water of 1 tFp, the product of the circulating fluid flow rate Fn and the flush range TF must be controlled. good.

However, in the conventional apparatus, the control system is such that the temperature K of the lobule entering the evaporation chamber at the first stage is kept constant.

Therefore, in order to obtain the same amount of produced water, it is necessary to set this value high in the summer and low in the winter. Additionally, if you change the brine temperature at the first stage of the evaporation chamber, the liquid level at each stage will become abnormal, which may cause problems in obtaining high-quality manufactured water. It is necessary to simultaneously adjust the circulating fluid flow rate to avoid abnormalities, and the adjustment of the set value of the brine temperature at the first stage inlet of the evaporation chamber has to be done through trial and error. The produced water 11FP of the seawater apparatus is mainly determined by the circulating liquid flow @FR and the flash range TF, as shown in equation (1). However, the conventional control method has a problem in that it controls not the flash range Tp but the lobline warmer which enters the first stage of the evaporation chamber.

C Cooling pipe heat transfer coefficient, e When there is no change in the supply seawater temperature, the final stage brine temperature for the desired production water amount is almost constant, and even if only the first stage inlet brine temperature is controlled as in the past, the desired production cannot be achieved. This means that the flash range for the amount of water is controlled, but the brine heater 3 and the discharge line 5
If disturbances are unavoidable, there are problems with conventional control methods.

The present invention was proposed in order to solve the above-mentioned conventional problems, and by controlling the amount of heating by the flash range Tr, which is based on the temperature difference between two points instead of simply controlling the temperature at one point as described above, It is an object of the present invention to provide a load control device for a seaweed apparatus that can cope with disturbances such as operating conditions and always stably and continuously obtain a predetermined amount of produced water.

[Means for solving problems]

In the load control device for the seawater apparatus according to the present invention,
A calculator that detects the brine temperature at the first stage inlet of the evaporation chamber and the brine temperature at the final stage of the evaporation chamber, calculates the temperature difference between the two output ends, and outputs this temperature difference, as well as a setting signal for the production water volume setting device and the circulating fluid. A function unit that calculates a temperature difference corresponding to a set amount of manufactured water from a flow rate detection signal, and a control device that controls the heating supply amount so that the output signal of the arithmetic unit and the output signal of the function unit match are provided. It is characterized by:

[Effect]

According to the present invention, in the seawater apparatus, the difference between the first-stage inlet brine temperature of the evaporation chamber and the final-stage brine temperature of the evaporation chamber, that is, the flash range, is calculated by a subtractor, and the temperature difference corresponding to the set amount of produced water is calculated by a function unit. By controlling the amount of heating supply by a control device so that the output signal of the subtracter and the output signal of the function unit match, disturbances can be dealt with and the problems of the conventional technology can be solved. This is how it was done.

〔Example〕

An embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention.
The same parts as those shown in the figures are given the same reference numerals.

An embodiment of the present invention shown in FIG. 1 is an improvement on the conventional device shown in FIG.
1 is a control system that operates the flow rate of the heating medium in a flash range. In Fig. 1, 3I is a final-stage brine temperature detector, and a 32-digit flash range (a control system that controls the temperature of the first-stage inlet brine and the final-stage brine temperature). 33 is a flash range controller. The structure and operation of other parts are the same as those explained with reference to FIG.

The operation of the embodiment of the present invention shown in FIG. 1 will be explained.

In FIG. 1, by providing a final stage brine temperature detector 31, a subtracter 32, and a flash range controller 33, the flash range is calculated by the subtracter 32,
- Calculate the temperature difference corresponding to the force setting produced water amount using a function unit 17, and control the heating supply amount so that the output signal of the subtractor 32 and the output signal of the function unit match. As a result, even if external operating conditions change, the given flush range can be controlled to be constant, and therefore, as long as there is no change in the circulating fluid flow rate, the amount of produced water can be maintained constant.

FIG. 2 is a diagram showing the configuration of an embodiment of a pond according to the present invention, in which the same parts as those shown in FIGS. 1 and 3 are given the same reference numerals.

The actual example shown in Figure 2 shows that for a given amount of produced water,
This is an example of automatically adjusting the flash range and circulating fluid volume to obtain a desired manufactured water load, and in Fig. 2,
41 produced water amount detector, 42 target produced water load setter,
43 is a buffer, 44 is a manufactured water load adjuster, 45 is an arithmetic unit that calculates a flash range corresponding to the manufactured water load (output value of the manufactured water load adjuster 44), and 46 is a manufactured water load (refined water load). This is a calculation unit that calculates the circulating fluid flow rate corresponding to the output value of the regulator 44.

The structure and operation of other parts are the same as those explained with reference to FIGS. 1 and 3.

The operation of another embodiment of the present invention shown in FIG. 2 will be explained.

In FIG. 2, the manufactured water load signal, which is the output signal of the manufactured water load adjuster 44, is the output signal of the target manufactured water load setter 42, which is set to a target value with a rate of change limited so that the output signal changes slowly with a buffer 43. The produced water load regulator 44 adjusts the produced water load signal so that the produced water quantity detection signal detected by the produced water quantity detector 41 becomes equal.

Calculator 46 calculates the circulating fluid flow rate corresponding to this manufactured water load signal.
is calculated and given as the setting value of the circulating fluid flow rate controller 22. Further, the calculator 45 performs the following calculation based on the produced water load signal and the circulating fluid flow rate detection signal detected by the circulating fluid flow rate detector 25, and calculates the set value of the flash range controller 33.

Therefore, the set values for the circulating fluid flow rate and the flush range can be automatically given in accordance with the output signal of the target produced water load setting device 42, and the produced water amount can be automatically adjusted even if external operating conditions change.

〔Effect of the invention〕

As described above, according to the present invention, the desired amount of produced water can be rapidly achieved by continuously changing the water supply load and automatically changing the set value in response to disturbances such as changes in operating conditions. Moreover, excellent effects such as being stably obtained can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of one embodiment of the present invention, FIG. 2 is a diagram showing the configuration of another embodiment of the present invention, and FIG. 3 is a diagram showing a conventional example. 1... Heat recovery section, 2... Heat release section, 3... Brine heater, 31... Final stage brine temperature detector, 32
...Subtractor, 33...Flash range controller, 4
DESCRIPTION OF SYMBOLS 1... Produced water amount detector, 42... Target produced water load setter, 43... Buffer, 44... Produced water load regulator, 45.46... Arithmetic unit.

Claims (1)

[Claims] In a multi-stage flash type seawater desalination device, a computing unit that detects the brine temperature at the first stage inlet of the evaporation chamber and the brine temperature at the final stage of the evaporation chamber, calculates the temperature difference between both detection ends, and outputs this temperature difference; a function unit that calculates the temperature difference corresponding to the set production water volume from the setting signal of the water volume setting device and the circulating fluid flow rate detection signal; 1. A load control device for a multi-stage flash desalination device, characterized in that it is equipped with a control device for controlling.