CN106040676A - Automatic washing method for rectifying tower pipeline - Google Patents

Abstract

The invention relates to an automatic washing method for a rectifying tower pipeline and belongs to the technical field of chemical oil refining production pipelines. According to the automatic washing method, on the basis of traditional liquid level-flow cascade control, dynamic function compensation is conducted on a tower bottom liquid level variable, that is to say, a main liquid level disturbance variable, the variable quantity of tower feed quantity, is adopted as a feed forward signal. The feed variable quantity is preset according to process requirements, the purpose is to stabilize the tower bottom liquid level, a dynamic function compensation method is adopted, effective dynamic control is conducted on the tower bottom liquid level, and thus the tower bottom liquid level can still operate stably under the circumstance of process adjusting of the feed quantity. Through the automatic washing method, stable control over the tower bottom liquid level of a rectifying tower can be achieved, and thus the influence of change of the feed quantity on normal production of the rectifying tower is reduced greatly; and meanwhile, the influence of model mismatch on the function of dynamic function compensation is lowered, a filtration module is added, and thus the system robustness is enhanced.

Description

A kind of rectifying column pipeline auto-flushing method

Technical field

The present invention relates to a kind of rectifying column pipeline auto-flushing method, belong to chemical oil refining's production flow line technical field.

Background technology

In chemical oil refining produces, rectifying column is crucial distillation operation equipment, and whether it steadily operates, be related to target The height of product purity.Wherein, tower bottom liquid position is directly connected to the material balance of whole rectifying column, the energy balance, when tower liquid level Too high being likely to result in full still, liquid level is too low is likely to result in sky still.In order to maintain the normal production of tower, tower bottom liquid position needs Control in certain safe operating range.

The tower feeding line of some rectifying column is owing to containing mink cell focus composition in charge raw material, easily to subsequent technique pipeline Result in blockage, the method being usually taken be human at periodic intervals to the tower charging amount of carrying, keep, the operation of fall amount, to downstream line Play the effect washed away, but this can cause fluctuating widely of tower bottom liquid position.But, tower bottom liquid position is generally entered by load at the bottom of tower Row regulation, takes liquid level flow Cascade Control Plan, and such regulative mode exists the problem of time lag, to tower bottom liquid position Regulation not prompt enough, this is the main cause of liquid level fluctuation.Some are controlled the tower that level requirement is high, tower bottom liquid The fluctuation of position must be paid attention to.

The at present purging method to rectifying column pipeline mostly use manually the amount of carrying, keep, fall amount, downstream line is played punching The effect of brush.

The purging method manually that prior art uses is easily caused fluctuating widely of tower bottom liquid position, and tower bottom liquid position Generally being regulated by load at the bottom of tower, take liquid level flow Cascade Control Plan, there is time lag in such regulative mode Problem, the regulation to tower bottom liquid position is not prompt enough, and this is the main cause causing tower bottom liquid position to fluctuate widely, and controls some The tower that level requirement is high, the fluctuation of tower bottom liquid position must be paid attention to.

Summary of the invention

The purpose of the present invention proposes a kind of pipeline flushing method ensureing rectifying column stable operation of novelty.The method is passing On the basis of system liquid level flow serials control, tower bottom liquid bit variable is carried out kinematic function compensation, i.e. takes liquid level mainly to do The variable quantity of the amount of disturbing tower inlet amount is as feed-forward signal.Feed variation amount is preset, with stabilizer according to technological requirement End liquid level is target, the method using kinematic function to compensate, and tower bottom liquid position carries out effective dynamically control, enters at technique adjustment In the case of doses, tower bottom liquid position remains to stable operation.

For achieving the above object, the technical solution used in the present invention is a kind of rectifying column pipeline auto-flushing method, with reality Now washing away rectifying column downstream line, the setting value of rectifying column inlet amount is adjusted by technological requirement, conventional liquid level- Add kinematic function on the basis of flow serials control to compensate, it is achieved the steady control to liquid level at the bottom of rectifying tower, be reduced or eliminated Inlet amount changes the impact of production normal on rectifying column.

As it is shown in figure 1, be the rectifying column flow chart of this method, tower inlet amount is FIC1001, its set-point FIC001.SV Being adjusted by process requirements, tower bottom liquid position LIC001 and load FIC002 realizes serials control.On this basis, according to entering The adjustment change of doses, carries out kinematic function compensation to tower bottom liquid position serials control, and it controls loop block chart as shown in Figure 2.

The tower bottom liquid position major disturbances of rectifying column is the change of inlet amount, when inlet amount presses preset value change, right The interference that tower bottom liquid position is caused is very big.In former control program, to be checked measuring after liquid level changes, regulation just made by controller Action, therefore the regulation of stock solution bit traffic Cascade Control Plan has delayed, controls effect undesirable.To this end, increase inlet amount Variation delta PV compensates signal as kinematic function.When inlet amount changes, system detects inlet amount within each scan period Change, feed variation amount feeding compensation operation module is carried out calculation process, then output after filtered for compensation operation is delivered to The outfan of liquid level controller, as the increment of discharging flow controller setting value FIC002.SV, the tower bottom liquid to rectifying column Bit traffic serials control carries out kinematic function compensation, the most i.e. realizes before tower bottom liquid position changes by inlet amount and affected, root Press the change of function f (t) rule according to inlet amount, load is carried out kinematic function and compensates regulation, play the effect of stabilizer liquid level.

This kinematic function compensation scheme is: by detecting the variable quantity of inlet amount, dynamically putting down according to tower bottom liquid bit variable Weighing apparatus principle, calculates discharging variation delta PV that feed variation amount Δ PV (s) is corresponding₁(s), relation is as follows:

${\mathrm{\ΔPV}}_1\left(s\right)=\frac{G_{PD}\left(s\right)}{G_P\left(s\right)}\mathrm{\Δ}PV\left(s\right)---\left(1\right)$

Wherein, Δ PV₁S () is the Laplace transformation of load variable quantity, Δ PV (s) is that the Laplace of inlet amount variable quantity becomes Change, G_PS () is the transmission function of main object liquid level, G_PDS () is that interfering channel transmits function.

By the input/output relation of subloop:

${\mathrm{\ΔPV}}_1\left(s\right)=\frac{G_{C1}\left(s\right)G_{P1}\left(s\right)}{1+G_{C1}\left(s\right)G_{P1}\left(s\right)}\mathrm{\Δ}SV\left(s\right)---\left(2\right)$

Wherein, G_C1S () is that subloop flow controller transmits function, G_P1S () is subloop flow target transfer function, Δ SV (s) is the Laplace transformation of discharging flow set point change amount.

And then release set point change amount Δ SV (s) of this discharging flow, as shown in formula (3):

$\mathrm{\Δ}SV\left(s\right)=\frac{1+G_{C1}\left(s\right)G_{P1}\left(s\right)}{G_{C1}\left(s\right)G_{P1}\left(s\right)}{\mathrm{\ΔPV}}_1\left(s\right)=\frac{1+G_{C1}\left(s\right)G_{P1}\left(s\right)}{G_{C1}\left(s\right)G_{P1}\left(s\right)}\frac{G_{PD}\left(s\right)}{G_P\left(s\right)}\mathrm{\Δ}PV\left(s\right)---\left(3\right)$

Obtaining kinematic function compensation operation module is:

${\tilde{G}}_{FC}\left(s\right)=\frac{1+G_{C1}\left(s\right)G_{P1}\left(s\right)}{G_{C1}\left(s\right)G_{P1}\left(s\right)}\frac{G_{PD}\left(s\right)}{G_P\left(s\right)}=(1+\frac{1}{G_{C1}\left(s\right)G_{P1}\left(s\right)})\frac{G_{PD}\left(s\right)}{G_P\left(s\right)}---\left(4\right)$

Wherein,For delivery flow variable quantity transmission function at the bottom of the tower of Theoretical Calculation.

Being obtained kinematic function compensation operation module by above formula (4) needs the object model of identification to have: subloop flow object G_P1 (s), major loop level object G_P(s) and interfering channel object G_PD(s)。

In actual application, the mathematical model identification of object is inevitably present model error, i.e. model mismatch, for Reduce the model mismatch impact on kinematic function compensating action, strengthen the robustness of system, after compensation operation module, add one Rank filtration module:

$G_f\left(s\right)=\frac{1}{1+\mathrm{\α}s}---\left(5\right)$

Wherein α is adjustable filter constants, G_fS () is that filtration module transmits function.Obtain final compensation operation Module is:

$G_{FC}\left(s\right)=(1+\frac{1}{G_{C1}\left(s\right)G_{P1}\left(s\right)})\frac{G_{PD}\left(s\right)}{G_P\left(s\right)}{G}_f\left(s\right)---\left(6\right)$

Wherein, G_FC(s) be actual output tower at the bottom of delivery flow variable quantity transmission function, i.e. feedforward controller transmission letter Number.

Compared with prior art, the present invention has the advantages that.

(1) on the basis of original rectifying column pipeline flushing method, tower bottom liquid bit traffic Cascade Control Plan is increased Add kinematic function compensation, when inlet amount is changed by predetermined function, tower bottom liquid bit traffic tandem is carried out kinematic function Compensate and control, it is achieved the steady control to liquid level at the bottom of rectifying tower, greatly reduce inlet amount and change production normal to rectifying column Impact.

(2) in the present invention program, in order to reduce the model mismatch impact on kinematic function compensating action, filtering mould is increased Block, strengthens the robustness of system.

Accompanying drawing explanation

Fig. 1 rectifying column base level control flow chart.

Liquid level control loop block chart at the bottom of Fig. 2 rectifying tower.

In figure:

G_C(s): the transmission function of liquid level controller

G_P(s): the transmission function of major loop level object

G_C1(s): the transmission function of subloop flow controller

G_P1(s): the transmission function of subloop flow object

G_FC(s): the transmission function of feedforward controller

G_PD(s): interfering channel transmission function

SV (s): the Laplace transformation of level set value

The Laplace transformation of L (s): liquid level output

Δ PV (s): the Laplace transformation of interference volume

Δ SV (s): the Laplace transformation of Front Feed Compensation

Detailed description of the invention

In order to verify the effectiveness of such scheme, in conjunction with industry actual production case, carry out in Yokogawa CS3000 system The simulating, verifying of such scheme.

As it is shown in figure 1, in ethylene industry produces, in order to prevent the light-weight fuel oil stripper discharging downstream tube of quench zone Road is blocked by follow-up mink cell focus, be usually taken periodically to the light-weight fuel oil tower charging amount of carrying, keep, the means of fall amount, Downstream line is played the effect washed away, but this can cause fluctuating widely of light-weight fuel oil tower bottom liquid position, and tower bottom liquid position Generally by controlling load, liquid level-flow Cascade Control Plan is taked to be adjusted, owing to level object exists delayed asking Topic, so using such control strategy often governing speed the slowest.For this problem, above-mentioned kinematic function is taked to compensate control Scheme processed is controlled.

Before scheme is implemented, as in figure 2 it is shown, pick out the object model needed for kinematic function compensation scheme.

$G_{P1}\left(s\right)=\frac{1}{1+1.4s};G_P\left(s\right)=\frac{1}{1+1.9s}{e}^{-1s};G_{PD}\left(s\right)=\frac{1}{1+2.5s}{e}^{-3s}$

Subloop flow controller parameter is: proportionality coefficient P=100, the time of integration I=10, derivative time D=0, ?Filter parameter α=2, i.e.According to (6) formula feedforward controller is:

$G_{FC}\left(s\right)=(1+\frac{10s}{1+10s}\×(1+1.4s\left)\right)\×\frac{1+1.9s}{1+2.5s}\×e^{-2s}\×\frac{1}{1+2s}$

Model parameter and controller parameter according to above-mentioned offer emulate, and former control program and the present invention program are entered Row contrast, feed rate increases to 50t/h from 40t/h, presses ramp function change with the speed of 900t/h, treats that inlet amount rises to After 50t/h, keep 2 minutes, carry out fall amount with the speed of 900t/h the most again.

By Case Simulation, when inlet amount is controlled by traditional liquid level flow Cascade Control Plan, level fluctuation scope is SV ± 6.14% (SV is setting value)；The present invention program level fluctuation scope is SV ± 0.3%.Visible, on the basis of former scheme After increasing kinematic function compensation scheme, when the fall amount that carries carrying out tower charging operates, the impact on tower liquid level is greatly reduced, effect Significantly.

Claims (2)

1. a rectifying column pipeline auto-flushing method, it is characterised in that: the tower bottom liquid position major disturbances of rectifying column is inlet amount Change, inlet amount press preset value change time, the interference causing tower bottom liquid position is very big；In former control program, to be checked Measuring after liquid level changes, regulation action just made by controller, and therefore the regulation of stock solution bit traffic Cascade Control Plan has Delayed, control effect undesirable；To this end, variation delta PV increasing inlet amount compensates signal as kinematic function；Work as inlet amount During change, system detects the change of inlet amount within each scan period, feed variation amount feeding compensation operation module is carried out Calculation process, more filtered for compensation operation rear output is delivered to the outfan of liquid level controller, set as discharging flow controller The increment of definite value FIC002.SV, carries out kinematic function compensation to the tower bottom liquid bit traffic serials control of rectifying column, so i.e. real Before existing tower bottom liquid position is changed by inlet amount and affected, press function f (t) rule according to inlet amount and change, load is moved State function compensates regulation, plays the effect of stabilizer liquid level；

This kinematic function compensation scheme is: by detecting the variable quantity of inlet amount, the dynamic equilibrium according to tower bottom liquid bit variable is former Reason, calculates discharging variation delta PV that feed variation amount Δ PV (s) is corresponding₁(s), relation is as follows:

${\mathrm{\ΔPV}}_1\left(s\right)=\frac{G_{PD}\left(s\right)}{G_P\left(s\right)}\mathrm{\Δ}PV\left(s\right)---\left(1\right)$

Wherein, Δ PV₁S () is the Laplace transformation of load variable quantity, Δ PV (s) is the Laplace transformation of inlet amount variable quantity, G_P S () is the transmission function of main object liquid level, G_PDS () is that interfering channel transmits function；

By the input/output relation of subloop:

${\mathrm{\ΔPV}}_1\left(s\right)=\frac{G_{C1}\left(s\right)G_{P1}\left(s\right)}{1+G_{C1}\left(s\right)G_{P1}\left(s\right)}\mathrm{\Δ}SV\left(s\right)---\left(2\right)$

Wherein, G_C1S () is that subloop flow controller transmits function, G_P1S () is subloop flow target transfer function, Δ SV S () is the Laplace transformation of discharging flow set point change amount；

And then release set point change amount Δ SV (s) of this discharging flow, as shown in formula (3):

$\mathrm{\Δ}SV\left(s\right)=\frac{1+G_{C1}\left(s\right)G_{P1}\left(s\right)}{G_{C1}\left(s\right)G_{P1}\left(s\right)}{\mathrm{\ΔPV}}_1\left(s\right)=\frac{1+G_{C1}\left(s\right)G_{P1}\left(s\right)}{G_{C1}\left(s\right)G_{P1}\left(s\right)}\frac{G_{PD}\left(s\right)}{G_P\left(s\right)}\mathrm{\Δ}PV\left(s\right)---\left(3\right)$

Obtaining kinematic function compensation operation module is:

${\tilde{G}}_{FC}\left(s\right)=\frac{1+G_{C1}\left(s\right)G_{P1}\left(s\right)}{G_{C1}\left(s\right)G_{P1}\left(s\right)}\frac{G_{PD}\left(s\right)}{G_P\left(s\right)}=(1+\frac{1}{G_{C1}\left(s\right)G_{P1}\left(s\right)})\frac{G_{PD}\left(s\right)}{G_P\left(s\right)}---\left(4\right)$

Wherein,For delivery flow variable quantity transmission function at the bottom of the tower of Theoretical Calculation；

Being obtained kinematic function compensation operation module by above formula (4) needs the object model of identification to have: subloop flow object G_P1(s)、 Major loop level object G_P(s) and interfering channel object G_PD(s)。

A kind of rectifying column pipeline auto-flushing method the most according to claim 1, it is characterised in that: in actual application In, the mathematical model identification of object is inevitably present model error, i.e. model mismatch, for reducing model mismatch to dynamic letter The impact of number compensating action, strengthens the robustness of system, addition first-order filtering module after compensation operation module:

$G_f\left(s\right)=\frac{1}{1+\mathrm{\α}s}---\left(5\right)$

Wherein α is adjustable filter constants, G_fS () is that filtration module transmits function；Obtain final compensation operation module For:

$G_{FC}\left(s\right)=(1+\frac{1}{G_{C1}\left(s\right)G_{P1}\left(s\right)})\frac{G_{PD}\left(s\right)}{G_P\left(s\right)}{G}_f\left(s\right)---\left(6\right)$

Wherein, G_FC(s) be actual output tower at the bottom of delivery flow variable quantity transmission function, i.e. feedforward controller transmission function.