Large air separation FAQ

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...

Air separation plant is one of the important production devices in petrochemical, metallurgy and other industries. Due to its special structure and physical and chemical properties of media, the risk of explosion is relatively high. In recent years, due to manufacturing defects and poor management of air separation plant, there have been many explosion accidents of air separation plant. According to incomplete statistics, there have been more than 100 explosion accidents of small air separation plant all over the country, there are more than 30 accidents of large and medium-sized air separation plant, especially the explosion caused by excessive hydrocarbon substances in the evaporator of air separation main condensing is the main reason for frequent accidents in recent years, which not only affects the smooth operation of production unit, and cause great economic losses to enterprises and the country. The following is a brief discussion on the explosion mechanism and explosion-proo...

The start-up of the air separation plant includes three stages: cooling, hydrops and purification. For a certain equipment, the start-up time is roughly certain. As for the low-pressure air separation equipment, there is no room to adjust the pressure of the air compressor. Generally, it depends on two expansion machines working at the same time to increase the refrigerating capacity in the start-up stage and shorten the start-up time. Even so, according to the maximum refrigeration capacity and the cooling required by cooling and Hydrops of the device, the start-up time of the device needs to be more than 36 hours. Large air separation plants are generally equipped with liquid oxygen storage tanks as emergency standby oxygen. If necessary, can liquid oxygen be filled into the tower to shorten the start-up time of the air separation plant? Theoretically, it is completely possible. For example, if filling 1M3 liquid oxygen into the main cooling, it is equivalent to providing 0.47 × 1...

When the working condition of the air separation plant is stable, the cooling capacity of the unit keeps balance with the cooling capacity consumption, and the temperature, pressure, liquid level and other parameters of each part in the unit no longer change with time. The main cooling is the bond connecting the upper tower and the lower tower. The rising nitrogen from the lower tower is heated and condensed in the main cooling, and the reflux liquid oxygen from the upper tower is absorbed and evaporated in the main cooling. When the amount of recirculation liquid is equal to the evaporation, the liquid level remains unchanged. When the processed air enters the tower, it has certain "moisture content", that is, a small part of it is liquid. Most of the air will be liquefied in the main cooling. As for the low-pressure air separation equipment, the air going into the tower is composed of the air at the cold end of the main heat exchanger and the air passing through the liquid purifie...