TWI459998B - Diagnostic method of gas separation system - Google Patents

Description

Diagnostic method for gas separation system

The present invention relates to a diagnostic method, and more particularly to a diagnostic method for a gas separation system.

The operation principle of the distillation column is to utilize a separation technique in which the difference in boiling points of the constituent materials in the mixture and the distribution ratio in the vapor/liquid phase are different for the purification of the substance. The cryogenic distillation gas separation system is the main method used in the industry to produce a large amount of high-purity nitrogen, oxygen and hydrogen.

Referring to Fig. 1, a conventional cryogenic distillation gas separation system 1 includes a pressurized distillation column 11, a first heat exchanger 12, a second heat exchanger 13, a low pressure distillation column 14, and a first crude argon distillation column 15, A second crude argon distillation column 16 having a first condenser 17, and a fine argon distillation column 18 having a second condenser 19.

The pressurized distillation column 11 enables compressed air 100 cooled to a set temperature to form high pressure steam 111 flowing to the first heat exchanger 12 and oxygen-enriched liquid air 112 flowing to the second heat exchanger 13.

The oxygen-enriched liquid air 112 passes through the second heat exchanger 13 to form a secondary liquid to be treated 131 flowing to the fine argon distillation column 18, and flows to the first condenser 17 and the second condenser 19, respectively. Condensate 132.

The high pressure steam 111 forms a nitrogen gas 121 through the first heat exchanger 12, and a liquid to be treated 122 flowing to the low pressure distillation column 14, the liquid to be treated 122 forms oxygen gas 141 through the low pressure distillation column 14, and flows to the first crude argon distillation. An argon-rich argon fraction 142 of column 15 and refluxed to the first heat exchanger 12 The first reflux gas 143.

The argon fraction 142 forms a crude argon 161 flowing to the refined argon distillation column 18 via the first crude argon distillation column 15 and the second crude argon distillation column 16. The crude argon 161 and the liquid to be treated 131 pass through the purified argon distillation column 18 to form argon gas 181 and a second reflux gas 182 which is refluxed to the second heat exchanger 13.

However, since the nitrogen contained in the argon fraction 142 has a low boiling point and cannot be condensed by the first condenser 17, as long as the concentration of nitrogen contained in the argon fraction 142 exceeds 1000 ppm, nitrogen is continuously accumulated in the argon fraction 142. The top end of the second crude argon distillation column 16 is such that the pressure at the top of the second crude argon distillation column 16 is too high to cause insufficient rising gas flow, which not only causes poor separation efficiency, but also causes nitrogen blocking of the crude argon column. This second crude argon distillation column 16 is inoperable.

From the above, it is understood that the concentration of nitrogen contained in the argon fraction 142 must be strictly controlled in order to avoid the occurrence of a nitrogen argon plug in the crude argon column. However, the analysis technique for the nitrogen composition in the argon fraction 142 is not yet mature, resulting in the argon fraction 142. The analysis results of the nitrogen concentration are highly variable and difficult to apply effectively.

In general, the distribution of the composition in the low-pressure distillation column 14 has a correspondence with the temperature distribution. Therefore, the temperature of the low-pressure distillation column 14 is often reversed, and the nitrogen composition in the low-pressure distillation column 14 is reversed to avoid the occurrence of a nitrogen argon plug in the crude argon column. However, during operation, the temperature varies depending on the operating conditions, and only the temperature of the low pressure distillation column 14 is considered, and it is not sufficient to completely react the nitrogen concentration in the low pressure distillation column 14, and it is often waited until the temperature of the low pressure distillation column 14 is lower than the set. The value will be processed, but at this point the crude argon column nitrogen plug has occurred.

Accordingly, it is an object of the present invention to provide a diagnostic method for a gas separation system that effectively avoids nitrogen plugging of a crude argon column.

Thus, the diagnostic method of the gas separation system of the present invention is applicable to a gas separation system comprising a low pressure distillation column for separating oxygen and a first crude argon distillation column in communication with the low pressure distillation column.

The diagnostic method comprises the steps of: (A) drawing the temperature in the low pressure distillation column, (B) calculating a temperature change rate of the low pressure distillation column, and (C) if the temperature in the low pressure distillation column is continuously lowered, and When the temperature change rate of the low pressure distillation column is greater than 0.01 ° C / min, the temperature of the low pressure distillation column is raised.

The beneficial effects of the present invention are: using the temperature change rate of the low pressure distillation column, pushing back the nitrogen concentration in the low pressure distillation column, and when the temperature in the low pressure distillation column is continuously decreased, and the temperature change rate of the low pressure distillation column is greater than 0.01 °C/min, the temperature of the low pressure distillation column is raised, and then the nitrogen concentration in the argon fraction of the low pressure distillation column is controlled to avoid the occurrence of a nitrogen argon plug in the crude argon column.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

Referring to Figures 2 and 3, a preferred embodiment of the diagnostic method of the gas separation system of the present invention is applicable to a gas separation system 3 as shown in Figure 3, the gas separation system 3 comprising a pressurized distillation column 31, a first heat An exchanger 32, a second heat exchanger 33, a low pressure distillation column 34, a first crude argon distillation column 35, a second crude argon distillation column 36 having a first condenser 361, and a second An argon distillation column 37 of condenser 371. Due to the gas separation system 3 It is the same as the prior art of FIG. 1, and therefore, no further details are provided herein.

In the diagnostic method, first, as shown in step 21, a temperature sensor 200 is disposed on the low pressure distillation column 34, and the temperature in the low pressure distillation column 34 is taken once every fixed time interval.

Referring to FIG. 4, and referring back to FIG. 3, the low pressure distillation column 34 has an opposite tower top 341 and a bottom 342, and a tower between the top 341 and the bottom 342 and the first crude argon distillation column 35. The argon fraction withdrawal port 343 is connected to extract the argon fraction 340, and the distance between the temperature sensor 200 and the argon fraction extraction port 343 is smaller than the distance between the temperature sensor 200 and the column top 341.

It should be particularly noted that under normal operating conditions, the lower the nitrogen concentration of the low pressure distillation column 34 near the bottom 342, the higher the nitrogen concentration near the top 341, but relatively closer to the bottom of the column. The higher the argon concentration of 342, the more the argon fraction extraction port 343 is interposed. While the temperature sensor 200 is disposed adjacent to the argon fraction extraction port 343, although the temperature of the argon fraction 340 is not directly measured, the temperature change of the argon fraction 340 can be sufficiently reacted. In actual use, the argon fraction extraction port 343 is located at the 38th plate of the low-pressure distillation column 34 in the industry, and the temperature sensor 200 is installed at a plate number of 3 to 4 plates from the 38th plate. position.

Referring to Figures 2 and 3, next, as shown in step 22, the rate of temperature change of the low pressure distillation column 34 is calculated. The temperature in the low pressure distillation column 34 is taken once every fixed time interval to facilitate the calculation of the temperature change rate, and the temperature change in the low pressure distillation column 34 can be correctly grasped.

Finally, as shown in step 23, if the temperature in the low pressure distillation column 34 continues to decrease and the temperature change rate of the low pressure distillation column 34 is greater than 0.01 ° C / min, the temperature of the low pressure distillation column 34 is raised to make the low pressure distillation The temperature of column 34 is maintained between -185 ° C and -187 ° C.

According to theoretical and on-site verification, when the concentration of nitrogen in the argon fraction 340 rises, the nitrogen argon plug of the crude argon column does not immediately occur, but most of them are accompanied by unfavorable results, such as a decrease in productivity or quality.

However, as long as the temperature of the argon fraction 340 is lower than the liquefaction temperature of the argon fraction 340 having a nitrogen concentration of 1000 ppm, the nitrogen argon plug of the crude argon column is surely caused, so if the temperature in the low pressure distillation column 34 continues to decrease, and the low pressure The temperature change rate of the distillation column 34 is greater than 0.01 ° C / min, and the temperature of the low pressure distillation column 34 is raised to control the nitrogen concentration in the argon fraction 340 of the low pressure distillation column 34. At a temperature change rate of more than 0.01 ° C / min as a boundary for raising the temperature of the low pressure distillation column 34, sufficient reaction time can be obtained to raise the temperature of the low pressure distillation column 34 so that the temperature of the low pressure distillation column 34 is maintained higher than the nitrogen concentration. It is the liquefaction temperature of 1000 ppm of argon fraction 340 to avoid the occurrence of crude argon nitrogen plug, and the temperature change rate is less than 0.01 ° C / min to maintain the stability of production capacity or quality.

In summary, the diagnostic method of the gas separation system of the present invention utilizes the temperature change rate of the low pressure distillation column 34 to reverse the nitrogen concentration in the low pressure distillation column 34, and has accurately determined whether a coarse argon column nitrogen plug will occur, and when The temperature in the low pressure distillation column 34 is continuously lowered, and the temperature change rate of the low pressure distillation column 34 is greater than 0.01 ° C / min, thereby raising the temperature of the low pressure distillation column 34, thereby controlling the argon fraction 340 of the low pressure distillation column 34. Nitrogen concentration In order to avoid the occurrence of a nitrogen argon plug in the crude argon column, the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

21‧‧‧Draw the temperature in the low pressure distillation column

22‧‧‧ Calculate the rate of temperature change of the low pressure distillation column

23‧‧‧If the temperature in the low-pressure distillation column continues to decrease, and the temperature change rate of the low-pressure distillation column is greater than 0.01 ° C / min, the temperature of the low-pressure distillation column is raised

200‧‧‧temperature sensor

3‧‧‧Gas Separation System

31‧‧‧Pressure distillation tower

32‧‧‧First heat exchanger

33‧‧‧second heat exchanger

34‧‧‧Low Pressure Distillation Tower

340‧‧‧Extracted argon fraction

341‧‧‧Tower

342‧‧‧Totto

343‧‧‧ argon fraction extraction

35‧‧‧First Crude Argon Distillation Tower

36‧‧‧Second crude argon distillation tower

361‧‧‧First condenser

37‧‧‧ Fine Argon Distillation Tower

371‧‧‧second condenser

1 is a schematic view showing a conventional cryogenic distillation gas separation system; FIG. 2 is a flow chart showing a preferred embodiment of the diagnostic method of the gas separation system of the present invention; and FIG. 3 is a schematic view showing the comparison of the diagnostic method A gas separation system applied by a good implementation; and FIG. 4 is a schematic diagram showing the installation position of the temperature sensor.

21‧‧‧ Capture the temperature in a low pressure distillation column

22‧‧‧ Calculate the rate of temperature change of the low pressure distillation column

23‧‧‧If the temperature in the low-pressure distillation column continues to decrease, and the temperature change rate of the low-pressure distillation column is greater than 0.01 ° C / min, the temperature of the low-pressure distillation column is raised

Claims (3)

A diagnostic method for a gas separation system comprising a low pressure distillation column and a first crude argon distillation column, the diagnostic method comprising: (A) drawing the temperature in the low pressure distillation column; Calculating a rate of temperature change of the low pressure distillation column; and (C) increasing the temperature of the low pressure distillation column if the temperature in the low pressure distillation column is continuously lowered and the rate of temperature change of the low pressure distillation column is greater than 0.01 ° C / min. The diagnostic method according to claim 1, wherein the step (A) is that the temperature in the low-pressure distillation column is taken once every fixed time interval. The diagnostic method according to claim 1, wherein the low pressure distillation column has an opposite top and a bottom, and a bottom between the top and the bottom and the first crude argon distillation tower a connected argon fraction withdrawal port, the step (A) is a temperature sensor is disposed between the argon fraction withdrawal port and the top of the column to extract the temperature in the low pressure distillation column, and the temperature sensor is The distance between the argon fraction withdrawal ports is less than the distance between the temperature sensor and the top of the tower.