What is the function of the air liquide return of the crude argon tower condenser to the upper tower

There are generally two types of crude argon extraction process using Air Liquide as a cold source, depending on the amount of Air Liquide: one is that all Air Liquide in the lower tower is sent to the condenser of the crude argon tower, part of the air vapor is evaporated, and the air vapor and the unevaporated air are returned to the upper tower respectively. This kind of process is called full reflow type, which is characterized by sufficient cooling capacity of the crude argon tower condenser and a large temperature difference of the condenser, but a large amount of air evaporation, which has a certain impact on the rectification conditions of the upper tower.

the other is to go down to the tower and return directly to the upper tower after a part of the air is throttled; The other part of the coargon tower condenser, most of the liquid air evaporates, the liquid air vapor and a small part of the liquid air that has not evaporated returns to the upper tower. This kind of process is called semi-reflux type, which is characterized by not only ensuring the normal operation of the crude argon tower, but also reducing the influence on the distillation conditions of the upper column, but the temperature difference of the condenser is small, which is the commonly used crude argon extraction process. Both types of crude argon extraction processes have one thing in common, namely that the liquid air in the crude argon column condenser needs to be in a flowing state like the liquid oxygen in the main condensing evaporator to prevent the accumulation of hydrocarbons in the liquid air inside the condenser.

The liquid-air return flow rate of the switched process air separation plant is about 10 of the liquid-air volume required for the coarse argon tower condenser, and the liquid-air return flow rate of the molecular sieve adsorption process air separation unit is about 2. For example, when the return flow rate of the air liquide is 2, the temperature difference of the condenser is about 1 3k, and when the return flow rate of the air liquide is increased to 10, the temperature difference of the condenser can be increased to about 2k. This is because after the increase of the reflux of the air liquid, the low boiling point nitrogen component in the reflux liquid air increases, and the average temperature of the evaporation side of the air liquide decreases, resulting in the expansion of the temperature difference of the condenser, the increase of the heat load, the increase of the resistance of the argon tower, and the decrease of the oxygen content in the crude argon.

Therefore, regulating the return flow of liquid air can be used as an important means to regulate the heat load of the coarse argon tower condenser. For the full return crude argon extraction process, Air Liquide must all return to the upper tower, the flow rate of which is uncontrollable. In the semi-reflux crude argon extraction process, only a small part of the liquid air is returned to the upper tower, so it is possible to set up a liquid air control valve on the pipeline of the air liquide return to control the amount of liquid air reflux.

The air separation plants designed by Linde and Hangyang are equipped with a special constant flow valve to control the air volume of the return liquid. Under normal working conditions, the constant flow valve is closed, and the liquid air can be quantified back to the upper tower through two small holes on the valve head; If necessary, the constant flow valve can be opened slightly to adjust the return flow of liquid-air.

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One may have a nitrogen plug, and if there is a venting point, it can be opened to expel the nitrogen, and in addition, is the argon column reboiler completely submerged? What is the oxygen content of the column under the crude argon (%)

1. Control the oxygen production and increase the argon content of the fraction.

2. Reduce the amount of argon taken out of the process.

3. Appropriately increase the load of the argon tower.

If the liquid level is too high and the cooling capacity is too large, the more coarse argon gas is condensed, the return ratio increases, and the pressure decreases. If the liquid level is too low and the cooling capacity is insufficient, the less crude argon gas will be condensed, the reflux ratio will be reduced, and the pressure will increase. The amount of pressure directly affects the distillation condition, and we need to keep the pressure at a stable and appropriate value to ensure the stable purity of the crude argon production.

Therefore, the liquid level should not be too high or too low. Hand hit,,Don't know to keep asking me!

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If the top condensation effect becomes worse, the non-condensable gas increases, and the reflux temperature rises, then the top pressure will rise, the liquid level of the reflux tank will decrease, and the recombinant component in the roof product will increase.

Distillation is a typical unit operation for separating mutuality mixtures in chemical production, and its essence is multi-stage distillation, that is, under a certain pressure, the boiling point or saturated vapor pressure of each component of the mutuality mixture is used to vaporize the light components (components with lower boiling point or higher saturated vapor pressure), and the concentration of light components in the gas phase and recombinant components in the liquid phase is gradually increased after multiple partial liquid phase vaporization and partial gas phase condensation, so as to achieve separation.

The main equipment of the distillation process includes: distillation tower, reboiler, condenser, reflux tank and conveying equipment. The distillation column is bounded by a feed plate, the upper part is the rectification section, and the lower part is the retention section.

After the feed liquid at a certain temperature and pressure enters the distillation column, the light components are gradually concentrated in the rectification section, and after leaving the top of the column, all of them are condensed into the reflux tank, part of which is used as the top product (also called distillate), and the other part is sent into the column as the reflux liquid. The purpose of the reflux fluid is to replenish the light components on the tray so that the liquid composition on the tray is composed.

Crude argon tower "nitrogen plug" when the method of quickly improving the purity of oxygen:

1. Reduce oxygen production; This is the most conventional method, according to the severity of the "nitrogen plug", the minimum amount is a few hundred, and the more oxygen production is about 5; At the same time, the nitrogen production and the amount of sewage nitrogen taken out should be appropriately increased to reduce the pressure of the upper tower, which is conducive to the recovery of working conditions;

2. Appropriately raise the argon liquid level of crude liquid at the bottom of the second tower of crude argon; In order to reduce the amount of argon circulation in crude liquid, it is beneficial to improve the purity of oxygen;

3. Appropriately open the valve to remove the large liquid nitrogen to the storage tank and take more liquid nitrogen; The amount of liquid nitrogen distilled into the upper column is reduced to reduce the reflux ratio of the upper column, and the oxygen level of the main cold liquid can be reduced, which is conducive to improving the oxygen purity.

4. The height of the liquid air level of the lower tower can be appropriately increased; Reducing the amount of liquid air driven into the upper column to reduce the reflux ratio of the upper column lifting the distillation section, which is beneficial to improving the oxygen purity.

5. Try to control the main refrigerant level not to increase; Properly controlling the level of the main refrigerant is 200 300mm lower than that in the usual operation, increasing the distillation space, which is conducive to appropriately increasing the heat exchange temperature difference of the main refrigerant and restoring the oxygen purity.

6. Try to control the resistance of the second tower of crude argon not to decrease, increase the amount of crude argon, and open the release valve of large argon at the same time to keep the amount of crude argon not reduced; May alleviate oxygen purity;

7. According to the working conditions at that time, the expansion amount can be appropriately reduced and the cooling production can be reduced; to reduce the nitrogen content in the argon distillate;

8. Appropriately increase the raw material air entering the tower, and generally control the increase between the amount to increase the heat load of the main cooling, which is conducive to improving the oxygen purity;

9. If there is liquid suspension, the amount of air entering the tower can be appropriately reduced;