First of all, the steam pressure and flow rate required for the molecular sieve heating should meet the requirements of process design. Heating regeneration process can be judged by regeneration temperature curve. Pressure relief stage: due to the decrease of pressure, the adsorption capacity of molecular sieve decreases, and the water and carbon dioxide molecules that were originally adsorbed are partially desorbed, resulting in the decrease of temperature.When other conditions are the same, the larger the average temperature difference is, the greater the heat transfer is, and the better the heat transfer effect is. For the same amount of heat transfer, the required heat transfer area can be reduced. The temperature of the heat flow in the same section of the heat exchanger must be higher than that of the cold fluid. If the downstream arrangement is adopted, the final temperature of the hot fluid outlet should still be higher than that of the cold fluid outlet;DEAR Air separation plant.At present, a new type of packed tower is used in 6000-0000m3 / h air separation plant, which adopts alpha Bauer ring, conjugate ring and step ring. It has the advantages of large flow rate, small resistance, good heat transfer effect and good strength. The temperature difference of heat transfer at the hot end is about 0.5 ℃, and the negative temperature difference of effluent (water temperature is lower than nitrogen temperature) can reach 4 ~ 9 ℃, depending on the gas-liquid ratio.
The valve is the place where the airflow is disturbed and impacted most severely. For safety, the material of pressure or flow control valve with working pressure of 0.1MPa or above shall be stainless steel or copper base alloy, or the combination of the above two materials. The sealing packing of valve shall be graphite treated asbestos or polytetrafluoroethylene, or expanded graphite. The materials used for other valves vary with the working pressure.The heat transfer of the fin is transferred to the cold fluid gradually from the root to the upper part of the fin. If there is a certain temperature drop inside the fin, the effect of the fin will be reduced, that is, the efficiency of the fin will be lower. Therefore, in order to effectively play the role of fins, so that it has a higher fin efficiency, in the case of large surface heat transfer coefficient, such as liquid channel, select short and thick fins.DEAR Air separation plant.The measures to control the temperature behind the expander are as follows: first, circulating current is used in advance to increase the temperature in front of the expander and make the air entering the expander in an unsaturated state; second, throttling in front of the expander is adopted to reduce the temperature drop of the expander. The latter method reduces the cooling capacity of expander and prolongs the start-up time, so it is generally not suitable.
DEAR Air separation plant.The main way to adjust the temperature of the heat exchanger is to adjust the middle temperature and keep the deviation as small as possible. It is the most common and effective method to adjust the middle temperature by changing the ring flow (or middle pumping).DEAR Air separation plant.Because of the increase of expansion, the amount of air entering the lower tower decreases, so that the heat load of the condensing evaporator decreases, and the liquid oxygen evaporated decreases relatively, which shows that the liquid oxygen level rises; if the expansion remains unchanged, only the unit cooling capacity is increased, that is, the temperature before expansion is increased (the bypass volume is reduced), the cooling capacity of the circulating gas in the switching heat exchanger will increase.DEAR Air separation plant.Using external cold source is also an effective way to shorten the start-up time. When the main cooling is over and liquid appears, liquid oxygen, liquid air or liquid nitrogen are input from the outside. The infusion method is to connect the liquid source with the liquid oxygen discharge valve, open the liquid oxygen discharge valve, and inject the external liquid into the main cooler.
