JPH06184547A - Control of specific gravity of pitch discharged from depitching tower - Google Patents

Abstract

PURPOSE:To improve the precision of the quality of the discharged pitch by estimating the specific surface gravity of the discharged pitch in high precision from the measured value of the feed absorbing oil and the measured value of the bottom temperature and regulating the amount of the feed oil according to this estimation. CONSTITUTION:This figure shows a depitching tower in a process for recovering crude gas oil in a coke oven gas. An absorbing oil is fed for depitching through a feed pipe 12 to the upper side surface of a depitching tower 8. Steam is blown into the tower through a steam pipe 13 from the lower side surface of the depitching tower 8 and heats the oil to effect its depitching. The absorbing oil is separated, and the soft fraction absorbing oil is recovered from a recovery pipe 14 on the top of the tower 8, and the heavy fraction absorbing oil, namely the discharged pitch, is withdrawn from a recovery pipe 15. A temperature sensor 21 is provided at the bottom of the tower 8, automatically detects the bottom temperature, and the detected value is sent to a temperature indicator/controller 22 in the feed pipe 12 to perform automatic control. When the bottom temperature is higher than the target temperature, the amount of the feed absorbing oil is increased, and on the contrary, when it is lower than the target value, this amount is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the specific gravity of the discharge pitch of a depitching tower in a crude light oil recovery process in coke oven gas.

[0002]

2. Description of the Related Art By-products generated with a gas from a coke oven are first cooled, and then the gas is mainly used for fuel, and tar, light oil, and ammonia are recovered as by-products.

FIG. 5 is a diagram showing an example of a crude light oil recovery process. In the absorption tower 1, the crude gas is sprayed with absorption oil such as creosote from the top of the absorption tower 1, and the crude light oil in the crude gas is absorbed. The crude light oil is sent to the circulation tank 2 and becomes an absorbing oil (hereinafter referred to as benzene oil) containing about 4% of the crude light oil. The oil containing benzen passes through the vapor oil heat exchanger 3 and the oil heat exchanger 4 and enters the dehydration tower 5 to be dehydrated. The components discharged from the tower enter the stripping tower 6 as they are, and the components from the bottom of the tower are heated in the heating furnace 7. After being heated by, it enters the stripping tower 6. A part of the components from the bottom of the stripping tower 6 enters the depitching tower 8, and the pitch-removed depitching component enters.

The gas oil component is distilled in the stripping tower 6, heat-exchanged in the vapor oil heat exchanger 3, cooled in a gas oil cooler 9, and then converted into crude gas oil in a separation tank 10 to collect a fractionation residue. Part of the components from the bottom of the stripping tower 6 is recirculated as debened oil, and enters the absorption tower 1 via the oil heat exchanger 4 and the oil cooler 11 (JP-A-3-7893). ).

The depitching tower 8 removes heavy components accumulated in the absorbing oil, that is, pitch, to prevent aging of the absorbing oil. Here, the specific gravity of the discharged pitch is batchwise (for example, daily). (3 times), by manual analysis, the amount of absorbed oil supplied is adjusted to control the specific gravity of the discharge pitch so that the specific gravity of the discharge pitch falls within the set range.

[0006]

However, in the above-described manual measurement of the pitch specific gravity, it is difficult to grasp the pitch property and quick action cannot be taken, so that the accuracy of pitch quality control is poor. In this case, if the pitch specific gravity rises excessively, there is a problem of blockage. Therefore, the specific gravity is controlled to be low for safety. Therefore, more oil is used than necessary and the loss is large.

The present invention is intended to solve the above-mentioned problems, and an object of the present invention is to provide a method capable of promptly obtaining the specific gravity value of the discharge pitch of a depitching tower and controlling it at a set specific gravity. .

[0008]

In order to achieve the above object, the present invention provides a method for controlling the specific gravity of the discharge pitch of a depitching tower in a crude light oil recovery process in coke oven gas, wherein the depitching tower is supplied. Using the regression line by the relationship between the viscosity of the absorbing oil, the tower bottom temperature, and the specific gravity of the discharge pitch,
The viscosity of the absorption oil supplied to the depitching tower and the tower bottom temperature are measured, the specific gravity of the discharge pitch is estimated from the regression line, the supply amount of the supplied absorption oil is controlled, and the specific gravity of the discharge pitch is managed. This is a method for controlling the specific gravity of the discharge pitch of the depitching tower, which is characterized in that it is carried out.

Prior to the invention, the inventors of the present invention have studied and found that
It was obtained that there was a correlation between the bottom temperature and the specific gravity of the discharge pitch.
This is shown in FIG. The solid line shows the specific gravity, and the dotted line shows the tower temperature.
Here, it can be seen that the temperature and the specific gravity have a correlation.

However, when the viscosity of the supplied absorption oil changes, the relationship may be broken. Therefore, further study is conducted and it is found that there is a relationship between the viscosity of the supplied absorption oil, the tower bottom temperature and the discharge pitch specific gravity. The present invention has been reached.

[0011]

Embodiments of the present invention will be described with reference to the drawings. The regression line used in the present invention can be obtained by the regression equation represented by the following equation (1). That is, it is a regression equation between the viscosity N of the supplied absorbing oil, the tower bottom temperature T, and the discharge pitch specific gravity D. Specific gravity D = 0.0037 ・ T-0.375 ・ N + 1.03 (1)

FIG. 1 is a diagram showing a regression line when the viscosity of the supplied absorption oil is changed by using the regression equation (1). The regression line a has a viscosity of the supplied absorption oil N = 1.28, the regression line b has a viscosity of the supply absorption oil N = 1.32, and the regression line c has a viscosity of the supply absorption oil N = 1.36.

[0013]

[Table 1]

Table 1 shows a comparison between the case of the regression line and the measured value, and the difference from the measured specific gravity is 2/1000.
˜3 / 1000, which is sufficiently reliable. FIG. 2 is a view showing a depitching tower used in the method of the present invention.

Absorbing oil is supplied for depitching from the upper side surface of the depitching tower 8 through a supply pipe 12. Here, steam is blown into the tower from the lower side surface of the depitching tower 8 through the steam pipe 13 to heat the depitched oil to perform the depitching process. Here, the absorbing oil is separated, and the soft absorbing oil is taken out from the recovery pipe 14 in the upper part of the depitching tower 8. Then, the heavy component absorption oil, that is, the discharge pitch portion is taken out from the recovery pipe 15.

Here, a temperature sensor 21 is provided at the bottom of the depitching tower 8 to automatically measure the temperature of the bottom, and the value is transmitted to a temperature indicating controller (TIC) 22 of the supply pipe 12. , Perform automatic control. Here, when the tower bottom temperature is higher than the target temperature, the supplied absorbed oil amount is increased, and when it is smaller than the target value, the supplied absorbed oil amount is decreased.

FIG. 3 shows the result of the present invention. As is clear from the figure, the method of the present invention enables accurate management. Therefore, it is possible to reduce the amount of absorbed oil, the specific gravity is for confirmation, and only once / day is required.

As a comparison, FIG. 4 shows the result of the conventional management of the specific gravity of the discharge pitch. Here, in order to maintain safety in consideration of measurement error, control is performed on the side lower than the set range. The variation is also large.

[0019]

According to the method of the present invention, the specific gravity of the discharge pitch with high accuracy is estimated from the measured values of the viscosity and the bottom temperature of the supplied absorbed oil, and the amount of supplied oil is adjusted based on the estimated values to determine the discharge bite. The accuracy of quality can be improved. Moreover, since an appropriate amount of absorbed oil can be used, resources are saved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a regression line used in the present invention.

FIG. 2 is a diagram showing an example of a depitching tower used in the present invention.

FIG. 3 is a diagram showing an example of an experimental result of the present invention.

FIG. 4 is a diagram showing a relationship between a specific gravity of a discharge pitch and a tower bottom temperature.

FIG. 5 is a diagram showing an example of a crude light oil recovery process.

[Explanation of symbols]

 21 Temperature Sensor 22 Temperature Indicator Controller for Supply Pipe

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Shinji Hatahira 1-2, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. (72) Minor Miyake 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Co., Ltd. (72) Inventor Shoji Kobayashi 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Tube Co., Ltd.

Claims (1)

[Claims] 1. A method for controlling the specific gravity of the discharge pitch of a depitching tower in a crude light oil recovery process in coke oven gas, comprising:
The viscosity of the absorbed oil supplied to the depitching tower, the tower bottom temperature, and the regression line based on the relationship of the specific gravity of the discharge pitch are used to measure the viscosity of the absorbed oil supplied to the depitching tower and the furnace bottom temperature, and the regression A method for managing the specific gravity of the discharge pitch of the depitching tower, which comprises estimating the specific gravity of the discharge pitch from the line, controlling the supply amount of the supplied absorbing oil, and managing the specific gravity of the discharge pitch.