Air separation parts FAQ

The temperature condition adjustment of the cooler (or switching heat exchanger) is based on the central temperature. The "middle" mentioned here does not refer to the central position of geometric dimension, but refers to the temperature on the barrel (or switching channel) near the central air extraction or the outlet of circulation. It is also related to the location where the thermometer is installed. The purpose of temperature condition adjustment is to keep the temperature difference between cold end and hot end within the specified range. Then, why should the temperature in the middle prevail? We need to take a look at the relationship between the temperature of the middle part and the temperature difference of the cold end and the temperature difference of the hot end, and what rules the temperature changes along the height direction of the cooler (or the switching heat exchanger) follow. The temperature condition change of the cooler (or switching heat exchanger) is general...

The start-up phase of the whole low-pressure oxygen generator is that liquid empty appears first in the lower tower, and then liquid oxygen appears in the upper tower. The cold energy needed to accumulate liquid in the tower mainly comes from the expansion machine, which uses the low temperature gas after expansion to make part of the air liquefaction in the liquid purifier. But the upper tower itself can not produce liquid, it mainly depends on the liquid from the lower tower into the upper tower. In the phase of hydrops, in order to accumulate the liquid level as soon as possible, the cooling volume should be transferred to the tower as much as possible, the phenomena of overcooling, temperature difference at the hot end and cold loss increase caused by excess cooling of switching heat exchanger should be avoided. As for how to recycle and transfer the cold volume of the air expansion into the tower, whether it is by the liquid purifier to transfer the cold volume to the lower tow...

Saturation temperature and saturation pressure are terms in gas-liquid equilibrium. If it is not filled with liquid in a sealed container, part of liquid molecules will enter the upper space, which is called "evaporation ". As the number of vapour molecules in space increases, the pressure of vapour generated by it also increases. At a certain time, the number of vapour molecules in space will not increase any more. At this time, the number of molecules leaving the liquid and the number of molecules returning the liquid from Space reach a dynamic balance, which is also called "saturated state ". At this time, the pressure generated by vapour is called "saturated pressure ". For the same substance, the saturation pressure is related to the temperature. The higher the temperature is, the greater the energy the molecule has, the easier it is to get rid of the liquid and gasification, and the corresponding saturation pressure is also higher. A certain temperature corresponds to a certai...

In the air separation plant, the adsorption capacity of the adsorbents is expressed by static adsorption capacity and dynamic adsorption capacity. The static adsorption capacity is the largest amount of adsorbed substance when the adsorbents per unit mass (or unit volume) reach the adsorption equilibrium under certain temperature and certain concentration of absorbed components, that is the ratio of the maximum adsorptive capacity (equilibrium value) that can be reached by the adsorbents to the adsorbents. The dynamic adsorption capacity is the adsorptive capacity when the absorbents reach the "conversion point" (expressed by the average adsorptive capacity per unit of absorbents in the adsorber ). Generally, it is calculated by "conversion time", that is, the time from the fluid contacting the absorbents layer to the "conversion point. "Turning effect point" is the point where the concentration of absorbed component increases obviously when fluid flows out of the absorption layer. ...

Before starting, the following preparations should be done first: 1) Check whether the unit has the starting conditions (including the reason of last stop and the condition of overhaul; check whether there are obstacles around the unit; whether the starting tools, listening needles, recording tables and so on are ready); 2) Check whether the motor, electric, instrument and lighting signal are normal, especially whether the accident chain system can act correctly (including water break, low oil pressure, axial displacement, etc.); 3) oil supply lubrication system is normal (fuel tank oil level, fuel tank bottom whether the water, auxiliary oil pump and oil circuit normal); 4) conditions of cooling system and cooling water (including whether the cooler valve is flexible, water supply pressure and water volume, etc.); 5) whether various valves are flexible and easy to use, and whether they can be closed or opened as required; 6) turn the wheel before starting, check whether the rotatin...

Air compressor intermediate cooler is generally shell-tube structure. Water is supplied inside the pipe, and gas is supplied between the pipes, which plays a cooling role through the heat exchange of fluid inside and outside the pipe. The reasons that affect the cooling effect of compressor intermediate cooler include: 1) insufficient cooling water. The heat of the air is not enough to be taken away by the cooling water, resulting in the increase of the next level of suction temperature, the decrease of gas density, and finally the reduction of exhaust volume. Therefore, the water supply pressure of cooling water should be closely monitored during operation to control the water supply. The process generally requires that the cooling water pressure should be greater than 0.15MPa (surface pressure); 2) the cooling water temperature is too high. High water temperature reduces the temperature difference between water and gas, and reduces the effect of heat and cooling. Even if the amoun...

Almost all motors commonly used in the air separation plant are three-phase AC motors. Three-phase AC motor can be divided into asynchronous motor and synchronous motor. The rotating speed of the synchronous motor and the frequency of the power grid keep a strict relationship, namely: N = 60f/P in the formula P -- magnetic pole logarithm; f -- grid frequency, the normal situation is 50Hz; n -- motor speed, r/min. For example, for two-pole (P = 1) synchronous motor, the synchronous speed is 3000r/min; for four-pole motor, P = 2, n = 1500r/min. While the rotating speed of asynchronous motor is always less than that of synchronous motor, and it generates rotating torque by its phase difference. Asynchronous motor is most widely used. It consists of a stator and a rotor, and has a stator and a rotor winding respectively. The stator winding is made of copper (aluminum) wire with outsourcing insulation. With the difference of rotor winding, asynchronous motor can be divided into squirrel ...

When the general motor in the air separation plant is started, the current that the stator of the motor takes from the power grid is about 5 ~ of the rated current of the motor ~ 7 times. After starting the small motor for one or two seconds, the current decreases rapidly as the rotating speed of the rotor gradually rises; while the large motor needs more than ten seconds, even dozens of seconds before the rotor reaches the stable rotating speed. That is, until the start-up ends, the current drops to the rated value. If the starting current of asynchronous motor is high, what problems will it bring to the use? If this motor starts frequently when it is used, the motor will heat severely due to the influence of starting current, which will affect the normal service life of the motor. In addition, if the starting times of the motor used are not frequent, when its capacity exceeds 30% of the power transformer capacity, due to the large starting current, it will cause the overvoltage dr...

When the power supply of the air separation unit of the molecular sieve adsorption purification process is resumed after the power failure, the operation should be conducted according to the following steps: 1) the possible influence on the mechanical equipment such as the air compressor when the power is suddenly cut off should be judged. If there is no influence, start-up preparation of the air compressor according to the operation specification of the air compressor; 2) check and confirm the switch state of the chain shutdown equipment valve; 3) check and confirm the alarm chain project of the air separation plant. Re-check and confirm the chain control of failure during power failure; 4) start the air compressor and air precooling system according to regulations; 5) start the molecular sieve adsorber according to regulations. Continue to complete the process before shutdown. If the downtime is long (more than 24 hours), the molecular sieve adsorber should recycle for one cycle; ...

The forced valve is opened and closed by the air source pressure pushing the piston. Its faults include the faults in the cylinder and the valve body. The faults in the cylinder are mainly caused by the slow switching action, the valve is not easy to open or close badly. This is caused by low gas source pressure, dirty gas source or excessive pipeline resistance. It is also possible that the piston ring is worn and the amount of lubricating oil is too small, which causes air leakage of the piston. When the sealing packing is too tight, it will also cause the phenomenon of slow movement. In order to prevent air leakage, in addition to checking whether the seal is in good condition frequently during overhaul, you should also pay attention to keeping enough lubricating oil in the cylinder. Rust on the inner wall of the cylinder or foreign matters entering may also cause the phenomenon of jam, causing the forced valve not to move. The main failure in the valve body is the phenomenon tha...

Under the design working condition, the positive and return air volume of the Heat section of the switching heat exchanger (or cooler) is basically equal. While in the cold section, the return flow volume must be larger than the positive flow air volume, and keep a certain proportion relationship, so that the temperature difference of the cold end is within the required range of moisture and carbon dioxide self-elimination, and the temperature difference of the hot end should be appropriate. In actual operation, when the temperature condition fluctuates, the method of changing the air volume or the distribution of product gas volume is also often used to adjust. When the middle temperature deviation occurs between two groups of switching heat exchanger (or between two groups of refrigerators), air inlet stop valve (or thin film butterfly valve) can be used for adjustment. The group with lower temperature in the middle part is larger, increasing air ventilation. In this way, the requ...

There are many types and types of low temperature valves. Now taking the low temperature stop valve as an example, the common failures can be divided into three categories: the first category: the failures occurring on the top of the valve. The valve top (valve head) of this kind of valve is connected with the valve stem by movement, so that when the valve is closed, the two sealing surfaces can be "corrected automatically ". After long-term use, sometimes the lock nut is loosened due to the damage of anti-back gasket, and finally the top of the valve falls off when opening the valve. At this time, the valve will lose its function of closing. Sometimes the damage of the lock nut is caused by the improper material and the replacement of cold and fragile metal. Another common fault is that the valve top is not closed strictly, that is, the valve leaks. The common reason is that the sealing surface of the valve top and the valve seat is crushed by hard objects (such as hard objects suc...