JP2945199B2 - Reboiler temperature control method for rectification tower, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reboiler temperature at the time of switching the type of feed oil supplied to a rectification column or the like (in this specification, the rectification column and the distillation column are collectively referred to as a rectification column or the like). It relates to a control method.

[0002]

2. Description of the Related Art In a rectifying tower, for example, a rectifying tower for desulfurization of kerosene gas oil, when the kind of feedstock is changed, the rectifying tower receiving tank level and the reboiler temperature greatly change. Therefore, it is necessary to control the amount of reflux, the amount of slop, and the amount of fuel in the reboiler. For example, in the rectification column system shown in FIG. 6, the raw material to be supplied to the rectification column 1 is converted from KERO (unwashed kerosene) to LGO.
When the temperature is changed to (unwashed light oil), the level of the receiving tank 2 is rapidly lowered because the temperature of the reboiler 3 is low. In such a case, a skilled operator conventionally has a level meter 11 in the receiving tank 2 and a rectification tower 1.
While watching the top thermometer 12
(The slop amount control valve 22 is adjusted as needed) to control the reflux flow rate, and further, while watching the reflux flow meter 13, the fuel control valve 23 of the reboiler 3 is controlled to control the reboiler temperature. Was. In FIG. 6, reference numeral 14 denotes a reboiler thermometer.

[0003]

As described above, conventionally, when the oil type of the raw material supplied to the rectification column is switched, the amount of reflux is manually adjusted by a skilled operator based on intuition based on many years of experience. Control and reboiler temperature control. For this reason, there is a problem that a great deal of labor is required for the operator, an erroneous control error cannot be avoided, and the amount of slop increases more than necessary. Such a problem also occurs when a feedstock type (for example, crude oil) is switched in a distillation column.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has an advantage that the reboiler temperature can be automatically controlled at the time of changing the feedstock type, thereby saving labor and minimizing the amount of slop. Accordingly, it is an object of the present invention to provide a method for controlling a rectification tower or the like in which product properties are stabilized.

[0005]

In order to achieve the above object, a method for controlling the temperature of a reboiler such as a rectification tower according to the present invention comprises the steps of: The opening of the reflux amount control valve is adjusted based on the detection data of the receiving tank level, the reflux flow rate changed by the opening adjustment is detected, and the temperature corresponding to the change in the reflux flow rate is obtained. On the other hand, the time change of the reboiler temperature at the time of changing the feedstock type is statistically processed and compiled into reference data, a temporary next reboiler set temperature is obtained from the reference data, and then the temporary next reboiler set temperature is calculated. The next reboiler set temperature is obtained by correcting with the temperature corresponding to the change in the reflux flow rate, and the reboiler temperature is controlled to be the reboiler set temperature.

[0006]

An embodiment of the method of the present invention will be described below. FIG. 1 is a block diagram of a control system for implementing the method of the present embodiment for controlling the temperature of a reboiler in a rectification column. In the figure, a rectification tower 1, a rectification tower receiving tank 2, a reboiler 3, a receiving tank level meter 11, a top thermometer 12, a reflux flow meter 13,
The reboiler thermometer 14, the reflux amount control valve 21, the slop amount control valve 22, and the fuel control valve 23 are the same as the conventional one shown in FIG.

In FIG. 1, reference numeral 31 denotes a reflux amount / slop amount control means. The reflux amount control valve 21 and the slop amount control valve 31 are based on detection signals from the tower top thermometer 12 and the receiving tank level meter 13. Adjust the opening of 28. Reference numeral 32 denotes a reflux flow rate-temperature conversion means for converting the reflux flow rate (change amount) into a temperature, and obtains a change in the reflux flow rate based on a detection value from the reflux flow meter 13 and corresponds to the change. Find the temperature.

Reference numeral 33 denotes a reference data calculating means, which statistically processes the operation method of the skilled operator, that is, the method of adjusting the temperature of the reboiler of the skilled operator at the time of switching the type of feedstock, and calculates a reference value for control (modeling). ). In other words, the temporal change of the reboiler temperature at the time of the past change of the feedstock type is statistically processed and converted into a mathematical expression to be used as a reference model. 34 is a tentative next reboiler temperature estimating means, a reference value obtained by the reference data calculation means 33 (data), provisional next (t _2: after t ₁ Delta] t time) to estimate the reboiler temperature T _2. 35 is a provisional next reboiler temperature setting means, which corrects the provisional next reboiler estimated temperature estimated by the next reboiler temperature estimation means 34 with the actual reboiler temperature detected by the reboiler thermometer 14, and sets the provisional next reboiler set temperature. Ask for.

Reference numeral 36 denotes a next reboiler temperature setting means,
The provisional next reboiler temperature set by the provisional next reboiler temperature setting means 35 is converted to the reflux amount-temperature conversion means 32.
Then, the set value of the next reboiler temperature is determined. The next reboiler temperature setting means 36 adjusts the opening of the fuel control valve 23 so as to control the temperature of the reboiler 3 to the set temperature.

Next, a control method according to an embodiment of the present invention, which is performed by a control system including the above-described units, will be described with reference to a flowchart of FIG. A change in the temperature at the top of the rectification column 1 due to the change of the type of feed oil supplied to the rectification column 1 and the level of the receiving tank 2 are detected (201, 202). Add the output. Then, a relationship diagram between the reflux flow rate and the valve opening is created (see FIG. 3), and based on the relationship diagram, the reflux amount adjusting valve 2 is set.
1 and the opening degree of the slop amount control valve 22 are obtained.
Adjustment of the opening degree of 1 and 22 is performed to control the reflux flow rate and the slop flow rate. When the opening degree of the reflux amount control valve 21 and the slop amount control valve 22 is adjusted, the reflux flow rate changes. Therefore, the change in the reflux flow rate at this time is obtained (204).

The temperature corresponding to the detected change in the flow rate of the flux is obtained based on the previously obtained relationship between the flow rate of the flux and the temperature change shown in FIG. 4 (205). For example,
Assuming that the reflux flux increases by 100 Kl / d, the reboiler temperature needs to be lowered by a ° C.
At this time, the temperature corresponding to the reflux flow rate +100 Kl / d is -a ° C. Calculated (converted) in this way
The set temperature is used for correcting the reboiler set temperature described later.

On the other hand, the operation method (temporal change of reboiler temperature) by a skilled operator at the time of changing the type of feed oil is statistically processed by means such as a neural network, and this is represented by a logistic function, and the reboiler temperature control is performed. A reference value is set (206). Here, it is expressed by one function from the start to the end of the switching of the oil type. Logistic function y (t) = K / (1 + exp (a) × exp (b ×
t)) y: reboiler temperature K: scheduled end temperature t: time (minutes) a, b: constants The constants of a and b are finally determined by tuning according to the processing amount, but the logistic function is obtained by changing a and b. The shape of the reboiler temperature curve obtained by the method (see FIG. 5) changes. That is, the shape shifts to the right as the constant a increases, and the inclination of the shape increases as b increases.
The constants a and b are automatically calculated from the past results based on the charge flow rate, specific heat, specific gravity, and the like. The scheduled end temperature K is also automatically calculated from the charge flow rate, specific heat, specific gravity, actual results, and the like. As a method for obtaining the reference data, an interval linear method or the like can be used in addition to the logistic function method described above.

Next, a provisional next reboiler temperature is estimated from the reference data (207). That is, at the present time t ₁
Then, the temperature T ₂ (T ₁ + ΔT) at the next control time point t ₂ after the control interval Δt is estimated from the reference data as shown in FIG. Provisional in next control time t ₂ a next reboiler estimated temperature T _2, is corrected actually at reboiler temperatures T ₀ the current measured (208). That is, the correction is performed as ΔT + T ₀ , and the provisional next reboiler temperature T ₃ is set. The tentative next reboiler temperature T ₃ is set this way, only the temperature corresponding to the change of the reflux flow rate as described above is corrected, sets the final next reboiler temperature (209). The reason why the provisional next reboiler temperature is corrected by the temperature corresponding to the change in the reflux flow rate is to prevent the receiving tank level from being changed by the change in the reflux flow rate.

The temporary next reboiler temperature is estimated from the reference data, and the temporary next reboiler set temperature T ₃ (= T ₂ ) is directly calculated without correcting the temporary next reboiler estimated temperature with the actual reboiler temperature. Can be predicted, a provisional next reboiler temperature estimation step (means 34),
The correction step based on the actual reboiler temperature can be omitted.

In this manner, the next reboiler set temperature is obtained, and the fuel supply amount to the reboiler 3 is controlled by the fuel control valve 23 so that the reboiler temperature becomes the set reboiler temperature.

The present invention is not limited to the above embodiment, and can be applied to the case of switching the oil type from LGO to KERO. In this case, the shape of the reboiler temperature curve in the reference data decreases with the passage of time. Shape.

[0017]

As described above, according to the present invention, the control of the reboiler temperature at the time of switching the type of feedstock oil in the rectification tower or the like can be automated, thereby saving labor in control and preventing product slop down due to operation errors. However, it is possible to minimize the amount of slop drawn from the receiving tank.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control system for implementing a method according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a method according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram for obtaining opening degrees of a reflux amount control valve and a slop amount control valve from a change in a receiving tank level and a tower top temperature.

FIG. 4 is a graph showing a relationship between a change in a reflux flow rate and a temperature conversion.

FIG. 5 is a reboiler temperature curve diagram showing a reboiler temperature transition at the time of changing the feedstock type, which is obtained by a logistic function method.

FIG. 6 is a block diagram showing a control system of a conventional rectification column.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Rectification tower 2 ... Receiving tank 3 ... Reboiler 11 ... Receiving tank level meter 12 ... Tower thermometer 13 ... Reflux flow meter 14 ... Reboiler thermometer 21 ... Reflux amount control valve 22 ... Slop amount control valve 23 ... Fuel control Valve 31 ... Reflux amount / slop amount control means 32 ... Reflux amount-temperature conversion means 33 ... Reference data calculation means 34 ... Temporary next reboiler temperature estimating means 35 ... Temporary next reboiler temperature setting means 36 ... Next reboiler temperature setting means

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G05D 23/00-23/32

Claims (2)

(57) [Claims] An opening of a reflux amount control valve is adjusted based on a change in the temperature of the top of a rectifying tower or the like at the time of feedstock type switching and detection data of a receiving tank level of the rectifying tower or the like. Detect the reflux flow rate changed by the adjustment, and find the temperature corresponding to the change in the reflux flow rate. On the other hand, statistically process the reboiler temperature over time when the feedstock type is changed, and process the reference data. From this reference data, a tentative next reboiler set temperature is obtained, and then the tentative next reboiler set temperature is corrected by a temperature corresponding to a change in the reflux flow rate to obtain a next reboiler set temperature. A reboiler temperature control method for a rectification tower or the like, wherein 2. An opening of a reflux amount control valve is adjusted based on a change in the temperature of the top of the rectification tower or the like at the time of switching the feedstock type and detection data of a receiving tank level of the rectification tower or the like. Detect the reflux flow rate changed by the adjustment, and find the temperature corresponding to the change in the reflux flow rate. On the other hand, statistically process the reboiler temperature over time when the feedstock type is changed, and process the reference data. The provisional next reboiler estimated temperature is obtained from the reference data, and then the provisional next reboiler estimated temperature is corrected by the actual reboiler temperature to obtain a provisional next reboiler set temperature. The reboiler set temperature is corrected by the temperature corresponding to the change in the reflux flow rate to determine the next reboiler set temperature. A reboiler temperature control method for a rectification column or the like, characterized in that the temperature is controlled as follows.