JPS6182803A - Multi-flash seawater desalting apparatus - Google Patents

Abstract

PURPOSE:To operate stably the process by changing rapidly a load in correspondence with the load even when the varying velocity of the load changes momentarily. CONSTITUTION:The set value of a temp. controller 21 is raised or lowered by a water production controller 37 in correspondence with the difference between the signal from a water production detector 35 and the signal from a water production setting device 36, and the temp. at the outlet from a brine heater 3 is controlled to obtain a specified load. The output of a differential arithmetic unit 38 for differentiating the output of a differential pressure detector 30 and calculating the absolute value of the differential pressure between stages of the first and the second flash chambers 1 and 2. The difference between the output of the arithmetic unit 38 and the output of a device for setting the upper limit value of said varying velocity between stages is calculated by an arithmetic unit 40, and an ON signal is outputted only when the output of the arithmetic unit 38 is lower than the output of a setting device 39. Besides, when the output of the arithmetic unit 40 is OFF, the calculation of the water production controller 37 is held, and the calculated result of the water production controller is outputted to the temp. controller 21, when said output is ON.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Medical Application) The present invention relates to a load control device for a multi-stage flash type seawater desalination device.

(Prior Art) A conventional multi-stage flash type seawater desalination apparatus is explained with reference to FIG. (3) is a brine heater, (4) is a raw seawater supply line, (5) is a raw seawater discharge line, and (6) is a raw material seawater discharge stage. Seawater supply line, (7)
is the cooling circulation line, (8) is the condenser, (9) is the heating medium supply pipe, Ql is the orifice installed at the entrance of each flash chamber, and ■ is the population a of each of the 7 flash chambers [weir installed nearby] , α2 is the demister installed in each flash chamber, (13 is the condensate tray installed in each 7-7 chamber, ■ is the produced water take-out line from the final stage flash chamber (5), (19 is the final stage flash chamber) (5) waste water extraction line, 4 is a temperature sensor installed on the outlet side of the brine heater (3), C
19 is a temperature controller that adjusts the opening degree of the flow rate regulating valve a1 installed in the heating medium supply line (9) according to the detection signal from the temperature detector The temperature sensor installed in the cooling circulation line (temperature control meter with +7 knots in the opening of the flow rate regulating valve u mallet installed on the sword, Ca in the final stage -) is detected by the detection signal from the same temperature detector. ,
(2) is a temperature controller that adjusts the opening degree of the flow rate control valve α field installed in the wastewater extraction line (151) based on the detection signal from the temperature detector (2), and the raw seawater is transferred to the raw seawater supply line (4). A part of the raw seawater is discharged to the outside from the raw seawater discharge line (5), and the remaining raw seawater is supplied from the raw seawater supply line (6) to the final stage 7, the second chamber. After joining the liquid between the final stage black chamber,
Cooling circulation line (supplied from power to heat recovery stage (At)
Becomes cooling fluid (circulating fluid). That is, each 7 of the heat recovery stages (3)
The steam boiled and evaporated in the raso/yu chambers (1), (2) and (N-2) is cooled by the cooling liquid passing through the condenser (8),
Condense. The coolant passing through the condenser (8) gradually increases in temperature before reaching the inlet of the prine heater (3), and then passes through the condenser (8) provided in the flash chamber (1). Sometimes, the temperature rises to near the temperature of the steam boiled and evaporated in the flash chamber (1), and in addition to the above cooling effect,
It has a heat recovery effect. The coolant is heated to a temperature several orders of magnitude higher than the saturation temperature of the flash chamber (1) by the heating medium (usually steam) sent from the heating medium supply line (9) in the prine heater (3). and is supplied to the flash chamber (1). This heated seawater (brine)
Flows toward each of the 72 and 7 chambers (1) to (6), but each flash chamber (1) has an orifice (il) and a weir (0υ), which causes frictional pressure loss. So,
Even if the liquid temperature decreases after passing through each flash chamber (11 to 1), the saturation pressure also decreases, so seawater is boiled and evaporated in each of the 72 chambers (1) to 72 chambers (1). 1
) to (5), the water droplets accompanied by the steam boiled and evaporated are separated by a demister a3, and the steam from which all the water droplets have been separated is:
It contacts the condenser (8) and is cooled, condensing into fresh water. This fresh water is stored in the condensate tray Q3, flows toward the final stage flash chamber, and is taken out from the produced water take-out line side. Also, the temperature of the heated seawater (brine) leaving the brine heater (3) and heading towards the flash chamber (1) is detected by the temperature detector ■, and the detection signal obtained at that time is sent to the temperature control needle Qυ. , the temperature controller (21) controls the opening degree of the flow rate regulating valve αη to control the flow rate of the heating medium flowing through the heating medium supply line (9) toward the prine heater (3). In addition, the temperature of the circulating fluid leaving the final stage flash chamber and heading for the heat recovery test in the cooling circulation line (7) is detected by a temperature detector, and the detection signal obtained at that time is sent to a temperature controller. The temperature controller adjusts the opening degree of the flow rate control valve to control the flow rate of the circulating fluid to the set flow rate corresponding to the required load (water supply amount). Also, the temperature between the final stage flash chambers is measured by a temperature detector (24
1, the detection signal obtained at that time is sent to the temperature control meter/device, and the temperature control device is connected to the flow rate control valve (11
(by adjusting the amount of waste water flowing from between the final stage flash chambers to the waste water extraction line 13), the liquid level in the final stage flash chamber (company) is controlled to be constant. There is.

(Problems to be Solved by the Invention) In the multi-stage flash type seawater desalination apparatus shown in FIG. There is peace of mind in keeping it safe. It is not easy to keep the level of seawater (brine) in each chamber constant when the operating conditions change, such as when the load changes or when starting up the equipment. That is, although this device generally has about 20 stages of flash chambers, the above control is limited to the 7 flash chambers at both ends, and the level of seawater (brine) in each of the 7 flash chambers is controlled. It is not easy to keep it constant. Moreover, the response is poor when the operating conditions change, such as when the load changes or when the entire device starts up.

Equipment load (produced water: i) F'p is the flow rate of circulating fluid F
IRN If the temperature difference between the flash chamber (1) and the flash chamber (6) is 'I', and the proportionality constant determined by the plant is K, then FIP=KaFRIITF). It is clear from this equation that in order to increase the amount of VC produced water, either the flow rate of the circulating fluid can be increased or the outlet temperature of the pline heater (3) can be increased.
In order to perform stable operation, it is necessary to maintain the liquid level in each of the seven rush chambers within a predetermined range, and at the same time increase the circulating fluid flow rate and the outlet temperature of the pline heater (3) while keeping them in harmony. and this condition is not satisfied,
That is, when only the flow rate of the circulating fluid is increased, or when the flow rate of the circulating fluid is increased from the viewpoint of process responsiveness, the outlet temperature of the line heater (3) is increased simultaneously, but the outlet temperature of the line heater (3) is increased. If the amount of increase in the flow rate of the circulating fluid is greater than the increase in the outlet temperature in 3), the following problem occurs.

In other words, if the flow rate of the circulating fluid increases, the flow rate of the seawater flowing through each of the two chambers (brine) will also increase in proportion to the increase, or the balance of matter and the balance of heat will go out of order. However, unless the outlet temperature of the brine heater (3) increases in proportion to it, that is, the saturation pressure is not increased to increase the pressure difference between each flash chamber, the temperature difference between each flash chamber will increase. The flow rate at the upstream side does not increase, and the brine stays in the upstream flash chamber, causing the liquid level in the upstream flash chamber to rise, resulting in an unstable operating condition. Heater (3
), if the circulating flow rate is insufficient for the same temperature, the liquid level in the upstream flash chamber will drop abnormally. As is clear from the above, in order to operate stably, it is important to maintain the flow rate of the circulating fluid and the outlet temperature of the brine heater (3) at a ratio that corresponds to the load (amount of produced water). Although this ratio differs from plant to plant, it can be known in advance by calculation. However, calculations can only be used to determine static conditions, and during transient conditions such as when the load is fluctuating or when the plant is started or stopped, the flow rate of the circulating fluid and the outlet temperature of the brine heater (3) can be determined. It is insufficient to simply maintain the ratio of Conventionally, the rate of change in load is reduced to reduce the deviation from the static balance, and the following operations are performed.

First, while making sure that there is no instability, change the manipulated variable in small increments and slowly, or change the independent variable to a predetermined heating rate or cooling rate based on existing data that allows stable operation, and change the independent variable over time. The set value is a function whose dependent variable is the set value of the outlet temperature of the brine heater (3),
The same temperature is changed in accordance with load fluctuations, or the circulating fluid flow rate is changed in proportion to the above temperature, but these methods do not have an appropriate feedback function and do not respond quickly to the conditions. There were problems in that the operation could not be performed, the load change speed had to be slow, and there was no ability to respond to external disturbances, resulting in an unstable operating state.

(Means for Solving the Problems) The present invention addresses the above problems, and includes a controller for controlling the outlet temperature of the brine heater or the circulation flow ffi' of the pline, and a stage for each of the seven chambers. A differential pressure detector that detects the pressure difference between stages, a differential calculator that completely differentiates the detection signal from the differential pressure detector and calculates the absolute value of the rate of change of the differential pressure between stages, and a differential calculator that calculates the absolute value of the rate of change of the differential pressure between stages, A multi-stage flash desalination system is characterized in that it is equipped with a control device that outputs output to the controller within a range that does not exceed a set value, and its purpose is to control the rate of change of load from time to time. There is a point VC that provides an improved multi-stage flash type fresh water desalination device that can quickly change the load in response to minute changes and can operate the process stably. (Example) Next, the present invention An example of a multi-stage flannel type seawater desalination apparatus will be explained using an example shown in FIGS. 1 and 2.
)~u51(17)~(c) is the same as +1+1, and (31J1 is the first stage flash chamber (
1) and the second stage flash chamber (2), a differential pressure detector that detects the submerged pressure encounter, 0D is a signal processing circuit that processes the differential pressure detection signal from the differential pressure detector (to), (to) is the manufactured water flow rate detector, B is the manufactured water amount setting device that sets the target load (target manufactured water it,), and C37+ is the manufactured water amount controller. Temperature control meter (2)
The outlet temperature of the brine heater (3) is adjusted by increasing or decreasing the set value of 11 to achieve a predetermined load. The above devices (to) no η have been used up to now, but in order to stably change the load, the speed of change when changing the setting value of the temperature controller (211) is an issue. The present invention adds the above-mentioned differential pressure detector (2). Also, (to) is a differential calculator that calculates the absolute value of the differential pressure by differentiating the output r of the differential pressure detector (2). ) is the absolute value of the rate of change in pressure difference between the first stage flash chamber (1) and the second stage flash chamber (2).In addition, the output of the stage difference between the stages that allows G!J to stably change the load A tail device that sets the upper limit of the pressure change rate,
ta is an arithmetic unit, and the arithmetic unit 141J calculates the difference between the output of the differential operator (to) and the output of the setter G91, and the output of the differential operator (to) is set by the setter (31). It is designed to output ONN harmonics only when it is smaller than the output, and output an OFF'F signal at other times.
4υ is a controller that controls the calculations performed by the manufactured water control meter c3n, and the same controller f4G holds the calculation of the calculation unit (when the output of 11 is OFF, the manufactured water control meter l37) is turned ON. At this time, the calculation result of the produced water control meter 1371 is output to the temperature control meter (21).

- (Function) Next, we will discuss the function of the multi-stage flash type seawater desalination apparatus shown in Fig. 1.2. Assuming that the plant is currently operating stably at the 60th load, there is no change in the differential pressure between the first-stage flash chamber (1) and the second-stage flash chamber (2), so the differential calculator The output on the side is zero. In this state, if the load setting between the produced water volume setting devices is set to 80%, the set value of the temperature controller (2D) will increase due to the production water volume control needle ON, and the outlet temperature of the brine heater (, 3) will rise. , the load also tends to rise.As a result, the output of the differential calculator side gradually increases, and at a certain point, the set value C3G
exceeds the set value. At this time, the output of computing unit +40 is O
FF', and the temperature rise signal from the produced water flow rate controller c3n is interrupted. As a result of the above-described effects, the rate of increase in flow between stages can be suppressed within a predetermined range and can be changed as quickly as possible. Note that the same effect is performed when the output of the controller (In) is used as the set value of the circulating fluid flow rate, that is, when the output of the controller (41) is used as the set value of the temperature controller (to). .

(Effects of the Invention) As described above, the multi-stage flash type seawater desalination apparatus of the present invention includes a controller that controls the outlet temperature of the prine heater or the circulating flow rate of brine, and a differential pressure that detects the pressure difference between stages in each flash chamber. The output of the detector, the differential calculator that calculates the absolute value of the interstage differential pressure change rate by differentiating the detection signal from the differential pressure detector, and the differential calculator, so that the output does not exceed a preset value. and a control device that outputs to the above controller within a range,
Since the above-mentioned action is performed, even if the rate of change in load changes from moment to moment, the load can be quickly changed accordingly, resulting in the effect that the process can be operated stably.

Although the present invention has been described above with reference to cases of leprosy, the present invention is of course not limited to such embodiments, and may be modified in various ways without departing from the spirit of the present invention. It is something.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an actual example of a multi-stage 7-flush type seawater desalination apparatus according to the present invention, Fig. 2 is a system diagram showing its signal processing circuit, and Fig. 3 is a system diagram showing a conventional multi-stage flash type seawater desalination system. FIG. (1) (21~(3)--7Ratsu7U room, (3)--
・Brine heater. +21)...Controller for outlet temperature of brine heater (3), (c)...Controller for brine circulation flow rate, C31
J...Differential pressure detector. (To) --- Differential calculator, Qj (il (41)...
・Control equipment. Provisional agent Patent attorney Okamoto Hon 3 people outside of the text Figure 1, cause 2''

Claims (1)

[Claims] A controller that controls the outlet temperature of the brine heater or the circulation flow rate of brine, a differential pressure detector that detects the pressure difference between stages in each flash chamber, and a differential pressure detector that differentiates the detection signal from the differential pressure detector to determine the difference between stages. A multi-stage device characterized by comprising a differential calculator that calculates the absolute value of the pressure change rate, and a control device that outputs the output of the differential calculator to the controller within a range that does not exceed a preset value. Flash type seawater desalination equipment.