SU735881A1 - Method of regulating gas-mixture separation process in fractionating column - Google Patents

Description

The invention relates to a method for automatically adjusting distillation columns of gas mixture separation plants by deep cooling and can be used in the chemical and metallurgical industries.

A known method of regulating the process of separation of gas mixtures in a distillation column by changing the flow of the gas mixture depending on the flow of the gas mixture at the inlet of the apparatus and the pressure in front of the compressor and the level of the product in the lower part of the distillation column.

There is a known method for controlling Prones, gas separation of gas mixtures in the upper distillation column of an air separation unit by throttling the gas in front of the pipe expander depending on the level of the product in the column. However, such a method is not economically feasible, since it leads to underutilization of the available isoentropic heat transfer, determined by pressure in the lower and upper columns and losses in communications.

Closest to the proposed invention is a method of regulating the process of separation of gas mixtures in a distillation column by changing the cooling capacity of the expander when the level in the upper distillation column deviates from the set value.

However, control over the deviation of the level in the upper column leads to poor control quality when the unit’s de-energy is changed, since the regulator does not receive leading pulses associated with a change in air flow into the unit, and only the deviation in the upper rectification column from the set value is triggered.

The chain of the invention is improving the quality of regulation, reducing the delay time of the regulatory object, reducing the duration of the transition process when changing the performance of the installation.

I

This is achieved by the fact that the change in the cooling capacity of the expander is carried out depending on the flow rate of the gas mixture with a level correction in the upper part of the distillation column. ₅ It is known that increasing the flow rate of gas entering the separation unit requires increasing the flow rate of the expander stream. Therefore, maintaining a certain ratio of gas flow supplied to the lock 10 and allow flow of expander flow control the level of the top of the distillation column disturbances associated with the change of installation performance, without waiting for the ^level-15 deviation. But because it is difficult to accurately determine the law of variation of expander flow in response to changes in gas flow and flow for various settings, it is obtained not the same, vozni- repents θ ² need adjust the magnitude of expander flow rate in the upper level of the distillation column.

The drawing shows a diagram of an installation ²⁵ implementing the proposed method for regulating the process of separation of gas mixtures.

It consists of a block 1 of regenerators, a distillation column 2, an upper ³⁰ column 3, a flow sensor 4, a program setter 5, an adder 6, a regulator 7, an expander 8, a mechanism 9 for changing the cold performance, a flow sensor 10, a level 11 sensor, 35 of the regulator 12, the knob 13 of the motor knob '14.

The method is as follows.

The gas entering the separation unit 40 passes through the regenerator unit 1 and is supplied to the lower distillation column 2. In the steady state, the level in the upper column 3 is in the middle position. When the installation productivity changes, the I4 signal from the flow sensor 4 is fed to prog. frame adjuster 5, which realizes the relationship between the gas flow rate G _r entering the unit and the flow rate of the de-flow stream. It is known that the value of the expander stream necessary to compensate for the loss of the high-capacity air separation unit can be found from 55 expressions = 0.125 + --- (190000-G _r ) ^br 280,000 (1) where C., _T - magnitude of the expander flow

Ds. | h. 'nm ^d / h;

G is the flow rate of gas entering the installation, nm ^{3 /} h.

Expression (1) is valid when the GfB gas flow rate varies from 12,000 to 190,000 nm ⁵ / h. Consequently, the expander flow rate at a new installation capacity can be defined as

6 _Δ ρ. · Γ “ ^{0> 1254} Γ ⁺ - ^L --- (190000-Gij)

2,800,000 (2)

The program master 5 realizes the dependence (2) between the gas flow rate G _g entering the installation and the flow rate of the expander stream. The output signal of the program master 5 proportional to the value Сд> found from expression (2) is input to the adder 6. The output signal of the adder 6 is a variable 'task of the regulator 7 changes the cooling capacity of the expander 8 and is equal to ₂ M ^{+ and} s (s)

With a constant signal (Hj = cons-tl of the engine master 14, a change in the output signal I ^ of the program master 5 (associated with a change in the installation capacity) causes a change in the controller 7. The signal from the adder 6 supplied to the controller 7 causes a change in the regulatory effect on the mechanism. 9 changes in cooling capacity, in particular, rotates the blades of the guiding apparatus of expander 8 by such a value that the output signal Πρε of the adder 6 (which is the task of controller 7) is equal to the signal Id of the sensor 10 expense.

Therefore, when changing the performance of the installation, the controller 7 set a new value for the flow rate of the expander stream in accordance with expression (2). If the law of variation of the expander flow depending on the change in gas flow rate to the separation unit is set correctly, then the level in the upper column will not change. Indeed, the dependence of the level in the upper column on the flow rate of the expander stream can be approximately described by the following relationships: when the gas flow rate to the separation unit is equal to 170,000 nm ³ / h

Н = ф400 + - ~ (G20000) (4) at a gas flow rate in the separation unit equal to 180,000 nm ^ / h

Η = 1350 + γ = · (Gdet. 20,000) (5)

I 'where W is the level in the upper pile kgf / m ²

P ^askhoy Expander flow, nm ^ / h.

Dependencies (4) and (5) were obtained when the expander flow changed in the range from 20,000 to 26,000 nm ^ / h.

According to expression (2), when the air flow into the unit is 170000 nm ^ / h, 22460 nm ^ / h of expander flow is required, and when the air flow into the block is equal to 180,000 nm Vh, 23140hm 3/4 ^{of the} expander flow is required. From the expressions (4) and (5) it follows that the level in the upper column will not change.

Otherwise, ae (when the law of variation of the expander flow depending on the change in gas flow rate to the separation unit is not set exactly), the level will change, and the signal I ^ from the level sensor 11 to the controller 12 will differ from the signal of the transmitter 13. Pulse the signal of controller 12 and ₇ = k ₇ (and ₅ and ₆ ) '(6) is proportional to the value of the difference of the signals I ^ · and Ip will go to the motor master 14, which changes the value of the analog signal that it tracks, supplied to the adder 6 according to the following law. ₀ and ₈ = and _{a +} k ₁ and ₇ where AND ° is the value of the monitored analog signal before the arrival of the pulse signal And ₇₂ - ³⁵ ,

(7)

K2 - gain;

Ηθ is the new value of the monitored analog signal.

The signal from the adder 6 is fed to the regulator 7, which causes a change in the regulatory effect on the mechanism 9.

The correction loop for the level deviation in the upper pile will be included in the work also with other disturbances (for example, when switching the loop flow adsorbers), which affect the level in the upper column.

The proposed method of automatic stabilization of the level in the upper column significantly stabilizes the rectification process in the upper column, reduces the loss of separation products. The expected economic effect of the use of the invention will be 1OOOO rub. per year for one air separation unit, with a productivity of 30,000-35,000 m ^ oxygen per 1 h.

Claims (2)

(54) METHOD FOR REGULATING THE PROCESS OF SEPARATION OF GAS MIXTURES IN RECTIFICATION The invention relates to a method for automatically regulating the rectification of ion columns of gas mixture separation installations by the method of deep cooling and can be applied in the chemical and metapurgical industry. There is a known method for regulating the process of separation of gas mixtures in a distillation column by changing the gas mixture flows depending on the flow rate of the gas mixture at the inlet to the apparatus and the pressure before the compressor to the product level in the lower part of the distillation column. There is a known method of controlling the ttpoueks of separation of gas mixtures in the upper distillation column of an air separation plant by r eselling gas before the expander depending on the level of the product in the column. However, this method is not economically economical, since it leads to under-expansion of the available isentropic heat-drop, which is determined by the pressure of the spill column in the lower and upper columns and losses in communications. Closest to the first invention, a method for regulating the process of separation of gas mixtures in a distillation column by changing the cooling capacity of the expander when the level in the upper distillation column deviates from a predetermined value. However, the control of the level deviation in the upper column leads to poor quality control when the plant capacity changes, since the controller does not receive leading pulses associated with changes in air flow to the unit, and triggers only 1FI. Deviation of the level in the upper rectification column given value. The purpose of the invention is to improve the quality of regulation, reduce the lag time of the control object, shorten the duration of the transient process when the installation performance changes. 7 This is achieved by changing the cooling capacity of the expander, depending on the flow rate of the gas mixture, with a level correction in the upper part of the distillation column. It is known that increasing the flow rate of gas entering the separation unit requires an increase in flow rate of the expander flow. Therefore, maintaining a certain ratio of the flow rate of gas entering the lock and the flow rate of the dendief flow will make it possible to control the level in the upper distillation column by disturbance associated with a change in the plant capacity without waiting for the level deviation. But since it is difficult to accurately determine the law of change of the expander flow B depending on the change in the flow rate of gas into the unit and for different installations it does not turn out to be the same, it becomes necessary to correct the flow rate of the expander flow by level in the upper distillation column. The drawing is a diagram of an installation implementing the proposed method for regulating the process of separation of gas mixtures. It consists of a unit 1 of regenerators, a distillation column 2, an upper column 3, a flow sensor 4, a programming unit 5, a combiner b, a regulator 7, a dendief 8, a cooling capacity changing mechanism 9, a flow sensor 10, a level sensor 11, a regulator 12 , the setting device 13 of the engine setting device 14. The method is carried out as follows. The gas entering the separation unit passes through the unit 1 of the regenerator and is fed to the lower distillation column. 2. In the steady state, the level in the upper column 3 is in the middle position. When the installation performance is changed, the signal from the flow sensor 4 is fed to the software setting device 5, which realizes the relationship between the gas flow rate G, which stumbles into the installation, and the flow rate of the back-end flow. It is known that the size of the decanding flow, necessary to compensate for the cold air of the air-handling installation of a large capacity, can be found from the expression; i9oooo-Gr 0.125 + 280000 1 | .p - aenTRjffla of the expander flow, G 1- is the flow rate of the gas entering the installation,. The expiry of (1) is valid when the gas consumption of GrB changes from 12,000 to 19,100. Consequently, the flow of the expander flow with the new capacity of the installation can be defined as Sett ° 2 g + - {190000- (2,800,000 (2) Software setting unit 5 realizes the relation (2) between the flow rate of gas Q entering the plant and the flow of the detander flow) The signal from the program setting device 5, proportional to the value found from expression (2), is applied to the input of the adder 6. The output signal of the adder 6 is the reference setting of the regulator 7 for changing the x output of the expander 8 and is equal to I2 And + I5. In the (From sos8-b) motor setting unit 14, a change in the output signal of an I. signal and a programming setting unit 5 (associated with a change in the performance of the installation) causes a change in the reference of the regulator 7. The signal from the adder 6 applied to the control 7 causes a change in the regulating Changes in the cooling capacity, in particular, rotates the vanes of the guide apparatus of the expander 8 by such a value that the output signal HQC of the adder 6 (which is the task of the regulator 7) is compared with the signal Id of the sensor 1 consumption. Consequently, when changing the plant performance, the regulator 7 established a new value for the flow of the expander Flow in accordance with expression (2). If the law of change of the flow expander depending on the change in gas flow in the separation unit is set correctly, the level in the upper column will not change. Indeed, the dependence of the magnitude of the level in the upper head on the flow rate of the expander flow can be approximately described as follows: if the gas flow rate in the separation unit is equal to 17OOOO nm + g (Odet - 20000) (4) when the gas flow in the unit the separation is equal to 180 ooo nmz / h (Det 20,000) (5) H 1350 + gr. where C is jT jODGHb at the upper end of the kgf / m flow rate of the expander flow,. Dependencies (4) and (5) were obtained by changing the expander flow in the range from 2OOOO to 260OO. According to expression (2), when air flow to the unit is equal to 170,000, 22,460 flow-through current is required, and with air flow to the unit, equal to 1,800OOHMV4, 23140nm / h of flow is required. From expressions (4) and (5) it follows that the level in the upper column does not change. Otherwise, when the law of change of the expander flow, depending on the change in the gas flow rate in the separation unit, is not set exactly, changes from the level, and the signal Id from the sensor AND level supplied to the regulator 12 will differ from the signal AND setpoint 13. The 12 К K regulator pulse signal () (6) g is the reference signal of the difference between the IS and AND signals and goes to the motor setting device 14, which changes the value of the analog signal monitored by it, sent to cyri-iMaTOp 6 along the next law. . where Id is the value of the monitored analog signal before the arrival of the pulsed signal K2 is the gain; And .. is the value of the monitored analog signal. The signal from adder 6 is fed to the heel 7, which causes a change in the regulating effect on the mechanism 9. The level deviation correction loop in the upper column will also work on other disturbances (for example, when switching the loop flow adsorbers), affecting t & level in the top column. G%) The proposed method of automatic stabilization of the level in the upper column substantially stabilizes the process of rectification in the upper column, reducing the loss of separation products. The expected economic effect from the use of the invention will be 1OOOO rub. per year per air separation plant, with a capacity of 35,000 m of oxygen per hour. Formula of the invention. Method for controlling the process of separation of gas mixtures in a distillation column by the method of deep cooling by changing the cooling capacity of the expander, due to the fact that to increase the cooling capacity of the expander, to change the cooling capacity of the expander The productivity of the detector is carried out depending on the flow rate of the gas mixture with the qJpection in terms of the level in the upper part of the distillation column.