JPH0425561B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an operation control system and a control device at the time of start-up in a plant in which a large number of cascades each including a large number of separators are connected in parallel and operated.

Separation equipment that separates gaseous isotopes has a small flow rate that can be processed by a single unit, and the separation coefficient (the ratio of the concentration of a specific component contained in the supplied raw material to the concentration of the concentrated material) is low. 1, so they are connected in a piping network to form a cascade as shown in FIG. 1, and the concentration of the specific component in the gas is concentrated to a predetermined concentration.

In FIG. 1, 1 _i is the i-stage separation device, 2 _i is the i-stage feed header, 3 _i is the i-stage product head, 4 is _{the i-} stage waist header, and 5 is the raw material supply pipe. The separation device at each stage is connected in parallel to the feed header, product header, and waist header at each stage. The gas supplied to the feed header 2 _i of the i-stage is supplied to the separator 1 _i of the i-stage, and the concentrated gas is exhausted to the product header 3 _i and the depleted gas is exhausted to the waste header 4 _i . At this time, the proportion of the supplied gas that is exhausted to the product side is called cut.

Then, the gas collected in the product header 3 _i of the i stage flows to the feed header 2 _{i +1} of the i+1 stage, and similarly, the gas collected in the waist header 4 _i of the i stage flows to the feed header 2 _{i -} of the i-1 stage. Sent to ₁ . The gas supplied to the i+1 stage separation device 1i+1 is further concentrated, but if the separation coefficient for concentration and the separation coefficient for depletion of each separation device are made equal, the concentration of the depleted gas in the i+1 stage is as follows. It becomes equal to the feed concentration of stage i, and there is no mixing loss.

Figure 2 shows the configuration of a plant in which many such cascades are connected and operated in parallel. In Fig. 2, 11 _j is the j-th cascade, 12 _j is the j-th raw material supply pipe, 13 _j is the j-th product take-out pipe, and 14 _j is the j-th cascade.
15 _j is a control valve j, and 16 is a raw material supply device.

The raw material gas supplied from the raw material supply device 16 is
Raw material supply pipes 12 of each cascade connected in parallel
distributed to _j . Those gases are in each cascade 1
1 _j and taken out from the product take-out pipe 13 _j , collected and collected by a collection device (not shown).

Figures 3 and 4 show the temporal changes in flow rate and concentration when starting up this plant. FIG. 3 shows changes over time in the product and waste flow rates when the raw material supply amount is maintained at the rated value at startup. The reason why it takes a long time to reach a steady state is that the cut in the separated state changes depending on the flow rate.

FIG. 5 shows the relational expression between the flow rate and cut of the separator. As shown in this figure,
At low separator flow rates, the cut is small and therefore it takes a long time for the cascade to reach a high product flow rate.

FIG. 4 shows the change in product concentration over time corresponding to the time change in the flow rate shown in FIG. As shown in this figure, the reason why the product concentration temporarily becomes extremely high is because the separation coefficient of the separation device changes depending on the flow rate.

FIG. 6 shows the relationship between the flow rate of the separator and the separation coefficient. In this way, when the flow rate is low, the value of the separation coefficient becomes large, so when the flow rate of the separator at each stage is not high in the initial stage of startup, a small amount of transiently high concentration product is generated. .

In this way, producing a product with an unspecified high concentration may lead to a chemically or physically dangerous situation depending on the type of gas. Therefore, it has become necessary to reduce such phenomena as much as possible.

In view of the above, the present invention comprehensively controls a plurality of cascades by taking their mutual relationships into consideration, thereby controlling the waist side and product of each cascade as a transient phenomenon at startup. It is an object of the present invention to provide a cascade start-up control method that can minimize deterioration of product quality due to insufficient flow of inflow from the side.

In order to achieve the above object, the present invention includes a cascade configured using a large number of gaseous isotope separation devices, a pressure gauge installed in a feed header of a raw material distribution pipe of the cascade, and a pressure gauge provided in a feed header of a raw material distribution pipe of the cascade. A device that uses a plurality of flow meters and flow control valves installed in the distribution pipe, and a calculation device that determines the opening degree of each flow control valve based on the signals from these pressure gauges and flow meters. , a first process of comparing the signal measured by the pressure gauge provided in the cascade with a preset pressure setting value and outputting a pressure deviation signal whichever is larger; and a second process of comparing the signal with a preset flow rate setting value and outputting a pressure deviation signal that is larger; and comparing the pressure deviation signal and the flow rate deviation signal for one of the cascades; A third controller that adjusts the opening degree of the flow rate regulating valve of the cascade based on the larger deviation signal.
The pressure deviation signal and the flow rate deviation signal are compared for the remaining cascades among the plurality of cascades, and the gas state to be supplied to the remaining cascades is set based on the larger deviation signal. a fourth process of comparing the total flow rate of the isotopes with an upper limit value that the raw material supply device can supply; and cascading some of the remaining cascades so that the flow rate is within the upper limit value. a fifth process of adjusting the opening degree of the flow rate regulating valve of the remaining stopped cascade so as not to exceed the upper limit when the raw material supply flow rate to the starting cascade decreases; This is composed of a sixth process of sequentially adjusting the opening degree of the flow rate regulating valve.

In other words, by starting multiple cascades in sequence based on the optimal operation control method for a single cascade, it is possible to prevent the product concentration in the plant from increasing.

An embodiment of the present invention will be described below.

FIG. 7 shows a single cascade control system. In the figure, 17 _j is the pressure gauge provided in the j-th cascade, 18 _j is the j-th flow meter,
20 is an adder, 21 _j is the j-th pressure set value, 22 _j is the j-th flow rate set value, 23 _j is the j-th high value selector, 24 _j
is the jth operator.

The pressure gauge _17j is provided at the feed header of the raw material supply stage of the j-th cascade. Pressure gauge 1
The signal measured at _7j is compared with the pressure setpoint _21j and the deviation signal is input to the high value selector _23j .
Similarly, the signal from the flowmeter _18j is compared with a set value _22j , and a deviation signal is input to the high value selector _23j .
In the high value selector, after each input signal is exchanged with a valve opening degree signal, one of the larger values is set as an output signal.

At startup, of the gas flowing into the feed header _2i , the flow rate from the waist side of stage i+1 and i
- Since the amount of light from the product side of the first stage is not large, the gas flow rate supplied through the raw material supply pipe _12j reaches several times as large. Therefore, the raw material supply flow rate is controlled so as to keep the pressure of the feed header 2 _i constant.

In that case, the feed flow rate of the raw material supply stage is at the rated value, so the cut and separation coefficients are also approximately at the rated values. Therefore, the product concentration will no longer reach an extremely high value. FIG. 8 shows temporal changes in flow rate and concentration. As shown in the figure, the product waste flow rate also reaches a steady state within a short time, which can reduce the production of high concentration products.

Next, an example of multiple cascade flow rate control will be described.

In FIG. 9, reference numeral 25 is a valve opening degree controller, and the others are those already explained. In the figure,
The signals from the raw material supply stage feed header pressure gauge 17 _j and the raw material supply flow meter 18 _j of each cascade are input to the valve opening controller, and after being internally processed, the signals are sent to the control valve 15 as operation signals for each valve. _j
sent to.

The operation of each cascade is as shown in Figure 8.
Although it is sufficient if the raw material supply flow rate can be controlled, the supply capacity of the raw material supply device 16 is generally designed to be close to the rated value. However, since it is necessary to flow several times the rated value to each cascade, all cascades cannot be activated at the same time. Therefore, some cascades will be started at the same time, but others will be left in a stopped state and on standby. Then, when the flow rate to be supplied to the activated cascade decreases, the remaining cascades are activated one after another.

FIG. 10 shows the signal arithmetic processing within the valve opening degree control device, which realizes the above-mentioned starting method. In the figure, 31 _j is the j-th plate pressure setting device, 32 _j is the j-th plate flow rate set value, 33
is a raw material supply upper limit value, 34 is a high value selector, and 35 is a low value selector. Here, the pressure signal 17 _j of each cascade is compared with the pressure set value 31 _j and a deviation signal is inputted to the high value selector 34, and the flow rate signal 18 _j is also compared with the flow rate set value 32 _j and the deviation signal is inputted to the high value selector 34. The signal is input to high value selector 34. Each of these signals is converted into a valve opening signal, and then a large value signal is output. The output signals of the high value selector 34 are the same as those of the low value selector 3 except for the first cascade.
5 is input.

In the j-th cascade, the sum of the flow rates of the cascades up to the j-1st is calculated, and if that value does not reach the upper limit of the raw material supply device, the raw material can also be supplied to the j-th cascade. It can be supplied within the deviation from Therefore, the sum of the flow rates up to the j-1st flow rate and the deviation signal of the supply capacity upper limit value 33 are input to the low value selector 35, and the smaller value of the value converted to the valve opening degree and the output of the high value selector 34 is input. Each valve 1 uses the value as the actual valve opening signal.
5 Operate _j .

These signal processes can be expressed by the following equation.

V _j = min(max(f _P (P _j , _j ), f _g (g _j , _j )), f _g ( _j-1 〓 ^i-1 where V _j is the j-th valve opening signal P _j is the j-th pressure signal _j is the j-th pressure set value g _j is the j-th flow rate signal _j is the j-th flow rate set value g _F is the raw material supply upper limit value f _P (P,) is the deviation from the set value A function that converts (-P) into a valve opening signal.

f _g (g,) is a function that converts the deviation (-g) from the set value into a valve opening signal.

It is.

FIG. 11 shows temporal changes in the cascade raw material supply flow rate, the whole plant raw material supply flow rate, and product concentration at the time of plant start-up according to the present invention. Cascades 1 through j-1 are activated simultaneously, but the j-th cascade can increase its supply flow rate as the supply flow rate of the j-1 cascades decreases. Then, after reaching the maximum value and starting to decrease, the j+1th cascade can be activated.

By starting up in this manner, the product concentration increases somewhat initially, but does not become extremely high. In addition, products with high concentrations that occur in the j-th and subsequent cascades have a small effect on the whole and can be almost ignored because their amounts are small.

The arithmetic unit in the embodiments described above can be realized by an analog arithmetic circuit, but it can also be controlled by a digital computer.

According to the present invention, since each cascade reaches a steady state within a short time, the amount of product with a concentration other than the standard can be reduced, which is economically advantageous.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the relationship between the cascade piping network and centrifuges, Fig. 2 is a schematic diagram showing the connection relationship of multiple cascades, Fig. 3 is a diagram showing the time change in flow rate due to the conventional startup method, Figure 4 is a diagram showing the change in product concentration over time due to the conventional startup method, Figure 5 is a diagram showing the relationship between the flow rate and cut of the separation device, and Figure 6 is a diagram showing the relationship between the flow rate and cut of the separation device.
The figure is a diagram showing the relationship between the separation coefficients of separation devices.
The figure is a schematic diagram showing an example of a control system for a single cascade, Figure 8 is a diagram showing time changes in flow rate and concentration at startup using the control system in Figure 7, and Figure 9 is a diagram showing flow rate control meters for multiple cascades. Fig. 10 is a schematic diagram showing the signal processing of the valve opening controller of the flow rate regulating valve of each cascade, Fig. 11 is a diagram showing the raw material supply flow rate of each cascade according to the control method of Fig. 10, and the flow rate of the entire blunt. FIG. 2 is a diagram showing temporal changes in raw material supply flow rate and product concentration. DESCRIPTION OF SYMBOLS 1... Separation device, 2-4... Header, 5... Raw material supply pipe, 11... Cascade, 15... Control valve.

Claims (1)

[Scope of Claims] 1. A cascade configured using a large number of gaseous isotope separation devices, a pressure gauge installed in the feed header of a raw material distribution pipe of the cascade, and a pressure gauge installed in the raw material distribution pipe of the cascade. The following process is used in a device that uses a plurality of flowmeters and flow control valves, and an arithmetic device that determines the opening degree of each flow control valve based on the signals from those pressure gauges and flowmeters. A cascade startup control method consisting of. a first process of comparing a signal value measured by the pressure gauge provided in the cascade with a preset pressure setting value and outputting a pressure deviation signal that is larger; a second process of comparing the detected signal with a preset flow rate setting value and outputting a larger flow rate deviation signal; a third process of comparing the signals and adjusting the opening degree of the flow rate regulating valve of the cascade based on whichever is the larger deviation signal; A step of comparing the flow rate deviation signals and comparing the total flow rate of the gaseous isotope supplied to the remaining cascades, which is set based on the larger deviation signal, with an upper limit value that the raw material supply device can supply. a fifth process of adjusting the opening degrees of the flow rate regulating valves of some of the remaining cascades so that the flow rate is within the upper limit value; A sixth process of sequentially adjusting the opening degrees of the flow rate regulating valves of the remaining stopped cascades so as not to exceed the upper limit when the raw material supply flow rate decreases.