Large air separation FAQ

More than half of all air separation equipment accidents were the explosion caused by the main cooling system. When processing air, all the impurities which have not been completely removed will finally gather in the main cooling liquid oxygen.

In the air separation plant, the main heat exchanger is the key equipment to ensure the performance of the whole set of equipment. The function of the main heat exchanger in the molecular sieve pre purification process air separation equipment is to ensure the temperature difference at the hot end to be kept at the design value by recovering the cold quantity of the backflow gas, provide sufficient expander gas to expander, make up for the cold quantity loss of the equipment, and provide the raw gas under the design condition for the lower tower.

At the installation site of the air separation plant, we may see a variety of operation methods. We may be a little surprised when we first see it. We may get used to it if we see it many times. However, many accidents are caused by our negligence and carelessness. The following are some common sense of safe construction, hoping to be helpful to everyone: 1. Workers must wear safety helmets correctly when entering the construction site, because the construction site is often chaotic. Some equipment installation site, several construction teams are constructing at the same time, it is impossible to completely guarantee that there is no falling objects. 2. Use personal protective equipment correctly, and seriously implement safety protection measures. Safety belts must be fastened when constructing on high places, cliffs and steep slopes without protective facilities. 3. It is forbidden to climb the scaffold, safety protection facilities, etc. It is strictly prohibited to take the ele...

The expansion air volume entering the upper tower increases, and the reflux ratio of the distillation section decreases correspondingly. In order to achieve the required purity of nitrogen products, more tower plates need to be set. When the reflux ratio is reduced to countless Tower plates needed to be set to make the purity of nitrogen reach the required value, then the reflux ratio is called the minimum reflux ratio. The expansion air volume entering the upper tower is first limited by the minimum reflux ratio. The closer the reflux ratio is to the minimum reflux ratio, the faster the number of tower plates needed to ensure the product purity increases, which will lead to the increase of investment, the increase of tower plate resistance, the increase of Operation pressure and the increase of energy consumption. Therefore, the reflux ratio after the inflated air enters the tower should be larger than the minimum reflux ratio. When the purity of nitrogen is required to be low, the...

There are mainly the following factors that affect the output of oxygen: 1) insufficient processing air volume. The reasons for the shortage of air volume include: ① the ambient temperature is too high; ② the atmospheric pressure is too low; ③ the air suction filter is blocked; ④ the low voltage or the frequency of the power grid will reduce the rotating speed; ⑤ the cooling effect of intermediate cooler is not good; ⑥ internal leakage exists between levels; ⑦ air leakage of valve and pipeline, and leakage of automatic valve or switching valve; ⑧ for the purification process of molecular sieve, it may be the air leakage of switching butterfly valve. 2) the average purity of nitrogen is too low. The reasons are: ① the efficiency of the distillation column is reduced; ② the expansion air volume is too large due to too much cold loss; ③ the purity of liquid nitrogen is too low and the liquid nitrogen volume is too large; ④ the liquid nitrogen volume is too small; ⑤ leakage of liquid ai...

The Feed gas and cold source of the crude argon tower come from the main tower and return to the main tower, so the crude argon Tower and the main tower are closely related and affect each other. The input of crude argon tower should have the following conditions: 1) the working condition of main tower is stable; 2) the output and quality of oxygen and nitrogen products are close to or reach the normal value; 3) the argon content of argon fraction is close to normal; 4) the main cooling liquid level is relatively high with sufficient cooling capacity. In the process of the crude argon tower being put into use, first lead out the argon distillation to precool the crude argon Tower, and then gradually send the liquid air to the crude argon condenser. With the chilling of the crude argon Tower, the rectifying working condition is gradually established in the crude argon tower. Its mark is that the resistance of the crude argon Tower, the purity of the crude argon and the extraction amo...

In the switching heat exchanger, moisture and carbon dioxide cannot be completely and thoroughly removed. Although the remaining amount is very small, it will gradually block the switching heat exchanger over time. In the production, it shows that the resistance of switching heat exchanger increases continuously, the free section of gas flow decreases, and the air volume cannot enter. In addition, in the cold section of the switching heat exchanger, carbon dioxide has been basically cleaned up theoretically, but due to the clamping effect of air flow, the amount of carbon dioxide brought into the tower is much more than the theoretical content. Apart from being partially cleared by the adsorption filter, the rest of the carbon dioxide will gradually accumulate in the tower and block the tower plates, pipelines and valves. In addition, the air also contains a small amount of acetylene and hydrocarbon. Although adsorbed by acetylene adsorber, its adsorption efficiency can only reach a...

1) The station can only be built after the review and approval of relevant departments according to the regulations on the safety management of chemical dangerous materials and the regulations on the safety supervision of gas cylinders issued by the State Council; 2) filling station should go through the registration formalities of Boiler and Pressure Vessel Safety Supervision Agency of Labor Department, and can only be engaged in gas filling work after passing the on-site examination; 3) the production devices, buildings and safety facilities of the filling station must conform to the provisions of fire prevention, explosion prevention and environmental protection; 4) the filling station must establish a management system to ensure the quality and safety of the filling station, such as safety education, training, fire prevention and explosion prevention, storage and transportation, equipment maintenance and other systems, and have the relevant standards, specifications and other te...

Switching purification process air separation equipment refers to self-cleaning of moisture and carbon dioxide in the passageway of switching Plate-fin Heat Exchanger (or cooler) through switching valve. Switching purification process the air separation equipment mostly adopts the method of circulation or extraction to reduce the temperature difference of the cold end of the Plate-fin Heat Exchanger (or the cooler); it adopts the expansion heat exchanger to recover the cooling, further reduce the temperature of the expansion gas; use the liquid supercooler to further reduce the liquid temperature of the throttle entering the upper tower. Therefore, when switching purification process air separation plant restarts and starts after short-term parking, attention should be paid to: 1) before recovery, the start-up circuit should be determined according to the recovery situation of cold end temperature; 2) for the air separation equipment with liquid supercooler, a part of the liquid fro...

On the one hand, the expansion heat exchanger is to reduce the temperature of the air after expansion by utilizing the cooling amount of the sewage nitrogen returned from the upper tower, so as to reduce the superheat of the air after expansion into the upper tower; on the other hand, it plays a role in distributing the cooling capacity of the upper and lower towers. Through it, the cooling amount of dirty nitrogen from the outlet supercooler to the switch-type heat exchanger (or the cooler) is partly returned to the upper tower, which improves the rectification of the upper tower. The location of the expansion heat exchanger can be placed in front of or behind the expansion machine, which is determined by the process design. The large air separation equipment in our country is often set in front of the machine, using part of the dirt nitrogen from the supercooler to cool the air in front of the expansion machine, so that the temperature behind the expansion machine is not too high,...

As the air of the air separation plant of the molecular sieve purification process removes impurities such as moisture and carbon dioxide through the adsorption of the molecular sieve, compared with switching the purification process, the start-up operation is simple and easy to control. It doesn't need to consider the complex influences such as self-cleaning of water and carbon dioxide, precipitation of water and carbon dioxide in the expansion machine, and the attention of starting process mainly focuses on giving full play to the refrigeration capacity of the expansion machine, reasonably allocate cooling capacity and fully cool the equipment. It can be divided into three stages: cooling equipment, accumulation of liquid and adjustment of rectification working condition. Compared with the start-up mode of switching process, it can be called "comprehensive cooling method" or "one-time cooling method ". The following points should be paid attention to when starting the operation: 1...

Nitrogen-water precooler is generally installed in all low-pressure air separation plant. It mainly uses the unsaturation of the water in the nitrogen to make part of the water evaporate. When the water evaporates, it absorbs the latent heat of vaporization to lower the cooling water temperature, and then uses it to cool the processed air to lower the air temperature entering the tower. Therefore, it includes air cooling tower and water cooling tower. The fundamental purpose of setting nitrogen-water precooler is to reduce the temperature of air entering the air separation tower and avoid the sharp fluctuation of the temperature entering the tower. Because the air temperature in the tower directly affects the working condition of switching heat exchanger and distillation column and the economy of the whole air separation plant. When designing, the temperature of air entering the tower is generally set at 30℃. When the inlet temperature of the tower is higher than the design index du...