JP4256684B2 - Gas supply method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for stably supplying gas generated from a gas manufacturing factory or the like to a consumption area. More specifically, the present invention relates to control of opening / closing operation of a control valve installed in a gas flow path in order to cope with fluctuations in gas supply amount and gas consumption.
[0002]
[Prior art]
Hydrogen gas generated as a by-product gas in the production of ethylene is used as a raw material and utility in manufacturing factories of various industries using the characteristics of the gas. As an absolute condition, hydrogen gas used in manufacturing factories of various industries is required to be stably supplied continuously. In particular, when gas supplied from a plurality of gas supply sources is distributed and supplied to a plurality of gas consuming areas, gas supply control for balancing the supply and demand is complicated, resulting in a decrease in responsiveness to fluctuations in gas pressure. .
[0003]
Therefore, a gas mixer is installed in the supply system, and even if there is a change in the gas supply amount of any one of the plurality of gas supply sources, the other gas supply source is changed to the gas mixer. There has been proposed a control device that stably supplies gas by quickly replenishing gas and supplying gas through the gas mixer (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-261847 [0005]
However, in the above apparatus, it is necessary to secure an installation space for the gas mixer, and it is necessary to replenish the gas to the gas mixer. Therefore, it is not applicable when the gas supply amount from the gas supply source cannot be adjusted. There was a problem.
[0006]
In an actual plant, normally, gas is stably supplied by PID-controlling the opening of a gas pressure control valve or a gas flow rate control valve installed in the gas flow path. As the control variables when performing PID control of the opening degree of these control valves, an appropriate control variable is obtained by trial and error in an operating plant, and the control valve is quickly and smoothly controlled.
[0007]
However, it is very difficult to determine an appropriate PID control variable in an operating plant. This is because, in the process of obtaining the control variable by trial and error, the variables P, I and D are made too large or too small, and the hydrogen gas supply amount to each consumption area is reduced. This is because there is a risk of a large fluctuation.
[0008]
[Problems to be solved by the invention]
The present invention is intended to solve the above-mentioned problems of the prior art, and does not change the amount of gas supplied to each gas consumption area, and a gas mixer, a buffer tank, etc. are installed in the gas supply system. It is an object of the present invention to provide a method capable of stably and continuously supplying gas from a plurality of gas supply sources to a plurality of gas consumption areas.
[0009]
[Means for Solving the Problems]
The present invention for solving the above problems is a method for stably supplying hydrogen gas generated as a by-product gas during ethylene production from a plurality of gas supply sources to a plurality of gas consumption areas through gas flow paths. The gas flow path of the gas supply system is provided with a gas pressure measuring device for measuring the gas pressure, a gas pressure adjusting valve for adjusting the gas pressure, and a gas flow rate adjusting valve for adjusting the gas flow rate to store hydrogen gas. The gas pressure control valve control variables (variable P, variable I) with respect to the time change of the gas temperature and flow rate on the simulation software that reproduces the gas supply system without the gas mixer and buffer tank for And a variable D) is determined to determine a control variable such that the fluctuation in the pressure of the gas flow path obtained by the gas pressure measuring instrument is less than ± 0.2%, and the gas supply system is determined using this control variable. Gas pressure It is characterized in the degree of opening of the control valve to PID control.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the gas supply method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a gas supply system to which a gas stable supply method according to an embodiment of the present invention is applied.
[0011]
This gas supply system includes the first to fourth gas consuming factories 20a under the control of a hydrogen gas generated from the ethylene manufacturing plant 10, the second manufacturing plant 11a, and the third manufacturing plant 11b by a control device (not shown). ˜20d and distributed to fuel gas system.
A first gas consumption factory 20a is connected to the ethylene manufacturing factory 10 via a gas flow rate measuring device 3a and a gas flow rate adjusting valve 1a, and a gas flow rate measuring instrument 3b, a gas flow rate adjusting valve 1b, and a gas are connected to the ethylene manufacturing factory 10. A second gas consumption factory 20b is connected via the flow rate measuring device 3d and the gas flow rate control valve 1d. Similarly, a third gas consuming factory 20c is connected to the ethylene manufacturing factory 10 via a gas flow path 5a, a gas pressure measuring instrument 4a, a gas flow measuring instrument 3c, and a gas flow regulating valve 1c, and further a gas pressure measuring instrument 4a. The fourth gas consuming factory 20d is connected via the gas pressure control valve 2d, the gas pressure measuring device 4d, and the gas flow path 5d. A gas pressure control valve 2a is branched from the gas pressure measuring instrument 4a, and a fuel gas system is connected to the gas pressure adjusting valve 2a via the gas flow path 5c, the gas pressure measuring instrument 4c and the gas pressure adjusting valve 2c. It is connected.
Further, the second manufacturing factory 11a is connected to the gas flow path 5d, and the third manufacturing factory 11b is connected to the gas flow path 5c via the gas pressure measuring instrument 4b and the gas pressure control valve 2b.
The third manufacturing factory 11b is also connected to the downstream side of the gas flow rate control valve 1b interposed between the ethylene manufacturing factory 10 and the second gas consumption factory 20b.
[0012]
Further, the control device (not shown) is configured to adjust the gas flow rate adjusting valves 1a to 1d and the gas pressure based on the input control variables and control target values based on the pressure signals obtained by the gas pressure measuring devices 4a to 4d. It is a device having a function of calculating the opening degree of the valves 2a to 2d, outputting the result as an electric or air signal, and performing PID control of the opening degree of these control valves.
[0013]
Here, PID control refers to control that uses the control variables P (proportional action), I (integral action), and D (differential action) to bring the indicated value of the controlled object closer to the target value. Say.
[0014]
In such a gas supply system, for example, when the gas consumption amount of the fourth consumption factory 20d varies, the pressure of the gas flow path 5d varies. The opening degree of the gas pressure control valve 2d is PID controlled so that the pressure in the gas flow path 5d is constant, and the amount of hydrogen gas delivered to the gas flow path 5d is increased or decreased. The opening of the gas pressure control valve 2a is PID-controlled so that the pressure of the gas flow path 5a does not fluctuate with the adjustment of the opening of the gas pressure control valve 2d, and the amount of hydrogen gas sent to the gas flow path 5c is increased or decreased. . Next, the opening of the gas pressure control valve 2c is PID controlled so that the pressure of the gas flow path 5c does not fluctuate with the adjustment of the opening of the gas pressure control valve 2a, and the amount of hydrogen gas supplied to the fuel gas system is increased or decreased. To do. Further, even if the pressure of the gas flow path 5c varies, the opening degree of the gas pressure control valve 2b is PID controlled so that the pressure of the gas flow path 5b does not vary, and the gas flow path 5c from the gas pressure control valve 2b. Ensure that the amount of hydrogen gas delivered to the air does not fluctuate. That is, the gas pressure control valves 2a to 2d finally adjust the fluctuation of the gas consumption amount of the fourth consumption factory 20d by increasing or decreasing the supply amount to the fuel gas system to stabilize the pressure in the gas supply system. ing.
[0015]
In the present embodiment, the control variables P, I and D of the control valve respectively correspond to the following operations.
P action: When a difference R [%] occurs between the target value and the indicated value, a control action I instantaneously moves the valve opening S [%] by a value obtained by multiplying the difference R by the variable P. I action: the target value and When the difference R [%] continues to occur in the indicated value, the control operation D moves the valve opening S [%] by the value obtained by multiplying the difference R by the variable P over the time of the variable I [minute]. Action: When the difference R [%] between the target value and the indicated value increases by 1 [%] per minute, the control action moves the valve opening S [%] instantaneously by the value obtained by multiplying the variable P by the variable D [0016]
As can be seen from the above description, the variable P is a control variable that determines the speed of the valve operation. If it is too large, the valve operation is too early and causes vibration. If it is too small, the valve operation is too slow and the target value is set as the target value. It becomes impossible to control to the value. The variable I is a control variable that determines the smoothness of the valve operation. If it is too large, it takes too much time to bring the indicated value closer to the target value, and if it is too small, it approaches the P operation and the smoothness that is the aim of the I operation is reduced. It will disappear. Therefore, in order to realize fast and smooth control of the control valve, it is necessary to make the variable P as large as possible and the variable I as small as possible within a range where vibration does not occur.
[0017]
Further, the variable D is a control variable that determines a characteristic for suppressing the vibration because the valve operation is determined according to the rate of change per unit time of the instruction value. Therefore, the D operation may amplify the vibration with respect to the high-frequency vibration. Generally, in this type of PID control, the variable D = 0 is often set.
When the variable D = 0, if the variables P and I of the gas pressure control valves 2a to 2d are not appropriate, for example, the following problem occurs when the gas consumption of the fourth consuming factory 20d fluctuates.
1. If the variables P and I of the gas pressure control valve 2d are not appropriate, the pressures of the gas flow path 5a and the gas flow path 5d are not stable, and the delivery amount to the first consuming factory 20a and the pressure of the gas flow path 5b are It will fluctuate. Further, the amount of delivery to the second consuming factory 20b also varies with the pressure variation of the gas flow path 5b.
2. If the variables P and I of the gas pressure control valve 2a are not appropriate, the pressure fluctuation in the gas flow path 5a cannot be accommodated. Further, the pressure of the gas flow path 5c also varies.
3. If the variables P and I of the gas pressure control valve 2b are not appropriate, the pressure fluctuation in the gas flow path 5b cannot be accommodated. Further, the pressure of the gas flow path 5c also varies.
4). If the variables P and I of the gas pressure control valve 2c are not appropriate, the pressure fluctuation in the gas flow path 5c cannot be accommodated.
[0018]
In the present invention, dynamic pressure fluctuation analysis is used in order to obtain control variables that do not cause the above problems. The dynamic pressure fluctuation analysis is a method of calculating the pressure change of the supply system with respect to time-varying temperature, flow rate, etc. in time series. For example, the analysis can be executed using general-purpose simulation software “HYSYS”. . Appropriate control variables P, I and D obtained by this analysis are input to the control device.
[0019]
【Example】
An embodiment of the present invention will be described using a gas supply system similar to that shown in FIG. A total of 200 [capacity unit / h] of hydrogen gas generated from the ethylene production factory 10, the second production factory 11a, and the third production factory 11b is distributed to the first to fourth consumption factories 20a to 20d and the fuel gas system. Supply. The amount of hydrogen gas supplied from each manufacturing plant and the amount of hydrogen gas consumed in each consuming plant and fuel gas system are as follows. However, the hydrogen gas supply amount is constant, and the hydrogen gas consumption amount in the consumption factories 20a, 20b and 20c is also constant.
<Hydrogen gas supply>
Ethylene production plant 10: 160 [capacity unit / h]
Second manufacturing factory 11a: 20 [capacity unit / h]
Third manufacturing factory 11b: 20 [capacity unit / h]
<Hydrogen gas consumption>
1st consumption factory 20a: 1 [capacity unit / h]
Second consumption factory 20b: 6 [capacity unit / h]
Third consumption factory 20c: 5 [capacity unit / h]
Fourth consumption factory 20d: 100 [capacity unit / h]
Fuel gas system: 88 [capacity unit / h]
[0020]
The hydrogen gas of 160 [volume unit / h] generated from the ethylene production factory 10 is 1 [volume unit / h] to the first consumption factory 20a via the gas flow rate measuring device 3a and the gas flow rate control valve 1a. Hydrogen gas of 5 [capacity unit / h] is supplied to the third consuming factory 20c through the passage 5a, the gas pressure measuring device 4a, the gas flow measuring device 3c and the gas flow regulating valve 1c, and the gas flow measuring device 3b and 1 [volume unit / h] through the gas flow rate control valve 1b, 73 [volume unit / h] through the gas flow path 5a, the gas pressure measuring instrument 4a and the gas pressure control valve 2a, the gas flow path 5a, the gas pressure 80 [volume unit / h] of hydrogen gas is sent out through the measuring instrument 4a, the gas pressure control valve 2d, and the gas pressure measuring instrument 4d.
The 20 [capacity unit / h] hydrogen gas generated from the second manufacturing plant 11a merges with 80 [capacity unit / h] hydrogen gas sent from the gas pressure measuring instrument 4d in the gas flow path 5d, and the total amount 100 [capacity unit / h] of hydrogen gas is supplied to the fourth consumer factory 20d.
Of the 20 [capacity unit / h] hydrogen gas generated from the third manufacturing plant 11b, 5 [capacity unit / h] are 1 [capacity unit / h] hydrogen gas sent from the gas flow rate control valve 1b. A total of 6 [capacity unit / h] hydrogen gas is supplied to the second consumption factory 20b through the gas flow rate measuring device 3d and the gas flow rate control valve 1d, and the remaining 15 [capacity unit / h] h] hydrogen gas merges with 73 [volume unit / h] of hydrogen gas sent from the gas pressure control valve 2a through the gas pressure measuring device 4b and the gas pressure control valve 2b in the gas flow path 5c, A total of 88 [volume unit / h] of hydrogen gas is sent to the fuel gas system through the gas pressure measuring device 4c and the gas pressure control valve 2c.
[0021]
First, the following values are input as control variables (variable P, variable I, and variable D) of the gas pressure control valves 2a to 2d, and the opening degrees of the gas pressure control valves 2a to 2d are PID-controlled. Gas was distributed and supplied from the gas supply source (the ethylene production factory 10, the second production factory 11a, and the third production factory 11b) to the four gas consumption factories 20a to 20d via the gas flow paths. FIG. 2 (before application) shows the pressure fluctuation in the gas flow path 5b, FIG. 3 (before application) shows the pressure fluctuation in the gas flow path 5c, and FIG. 4 (before application) shows the pressure fluctuation in the gas flow path 5d. It can be seen that the pressure fluctuations of the gas flow paths 5b to 5d exceed ± 4%, and hydrogen gas cannot be stably supplied to the gas consuming factories.
(Gas pressure control valve 2a) = (0.4, 1.0, 0.0)
(Gas pressure control valve 2b) = (1.0, 1.0, 0.0)
(Gas pressure control valve 2c) = (1.0, 1.0, 0.0)
(Gas pressure control valve 2d) = (1.5, 5.0, 0.0)
[0022]
Next, the general-purpose simulation software “HYSYS” is used to reproduce the gas supply system of FIG. 1 and change the control variables (variable P, variable I, variable D) of the gas pressure control valves 2a to 2d on the simulation software. Thus, the control variable was determined so that the pressure fluctuation in each of the gas flow paths 5a to 5d was reduced. As the control variable determined here, for example, a value as shown below is input to a control device (not shown), and the opening degree of the gas pressure control valves 2a to 2d is PID-controlled, and the gas flow paths are supplied from three gas supply sources. The gas was distributed and supplied to four gas consumption factories. FIG. 2 (after application) shows the pressure fluctuation in the gas flow path 5b, FIG. 3 (after application) shows the pressure fluctuation in the gas flow path 5c, and FIG. 4 (after application) shows the pressure fluctuation in the gas flow path 5d. By applying the method of the present invention, the pressure fluctuation in each of the gas flow paths 5b to 5d can be less than ± 0.2%, and hydrogen gas can be stably supplied to each gas consuming factory. .
(Gas pressure control valve 2a) = (0.4, 1.0, 0.0)
(Gas pressure regulating valve 2b) = (4.0, 5.0, 0.0)
(Gas pressure control valve 2c) = (7.0, 4.0, 0.0)
(Gas pressure regulating valve 2d) = (5.0, 4.0, 0.0)
[0023]
【The invention's effect】
According to the present invention, when gas is supplied from a plurality of gas supply sources to a plurality of gas consuming places through gas flow paths, the amount of hydrogen gas supplied to each gas consuming place is not changed in an operating plant. And gas can be stably supplied to each gas consumption place, without installing a gas mixer, a buffer tank, etc. in a gas supply system.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a gas supply system to which a gas stable supply method according to an embodiment of the present invention is applied.
FIG. 2 is a graph showing the pressure of the gas flow path in one embodiment.
FIG. 3 is a graph showing the pressure of a gas flow path in one embodiment.
FIG. 4 is a graph showing the pressure of the gas flow path in one embodiment.
[Explanation of symbols]
1a to 1d gas flow rate control valve, 2a to 2d gas pressure control valve, 3a to 3d gas flow rate measuring instrument, 4a to 4d gas pressure measuring instrument, 5a to 5d gas flow path, 10 ethylene manufacturing factory, 11a second manufacturing factory 11b 3rd manufacturing factory, 20a 1st consumption factory, 20b 2nd consumption factory, 20c 3rd consumption factory, 20d 4th consumption factory.

Claims (1)

A method of stably supplying hydrogen gas generated as a by-product gas during ethylene production from a plurality of gas supply sources to a plurality of gas consumption areas through gas flow paths,
The gas flow path of the gas supply system, a gas pressure measuring device for measuring the gas pressure, the gas pressure regulating valve for adjusting the gas pressure, and gas flow rate control valve for adjusting the gas flow rate is provided, hydrogen gas There are no gas mixers or buffer tanks to store,
Obtained by the gas pressure measuring instrument by changing the control variables (variable P, variable I and variable D) of the gas pressure control valve with respect to the time change of the gas temperature and flow rate on the simulation software that reproduces the gas supply system. The control variable is determined so that the fluctuation of the pressure of the gas flow path is less than ± 0.2%,
A stable gas supply method, wherein the opening of a gas pressure control valve of a gas supply system is PID controlled using this control variable.

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