Because of the low pressure, it is impossible to increase the air volume arbitrarily to provide more cooling capacity. In view of this characteristic, the backflow gas channel on the pressurization channel side should be arranged more (the product channel should also be considered), and it can be cooled down when the expansion volume increases.In case of temperature deviation in the middle part, it should be adjusted as soon as possible. Because when the deviation is small, as long as a little adjustment, it will soon return to normal. If the deviation develops to a large extent and measures are taken, the adjustment will become difficult. In the process of adjustment, a small number of times should be taken, that is, the amount of each adjustment should be less, but the number of times can be more, so that the middle temperature tends to be uniform smoothly. In the process of regulation to prevent irritability, so as not to produce new interference factors.The middle temperature difference between the control units is generally not greater than 3 ~ 5 ℃; the middle temperature should not be too low, and the cooling capacity should not be too much concentrated in the main heat exchanger, resulting in the increase of the temperature difference at the hot end. When the temperature of the cold end reaches the air liquefaction temperature, the cooling capacity should be transferred to the distillation system to make the distillation system cool enough, accumulate liquid as soon as possible and establish the distillation system;
DEAR Biogas purification unit.The temperature drop of air from 0.6MPa throttling to 0.1MPa is only about 1 ℃, while the temperature drop can reach 80 ~ 90 ℃ theoretically through expansion of expander, and the effect of temperature drop is much better than that of throttling. The reason is that the throttling process does not output work, and the decrease of temperature is caused by the increase of molecular potential energy.DEAR Biogas purification unit.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 Biogas purification unit.Stop pressure test can be carried out only after external leakage is eliminated. After the heat exchanger is raised to the maximum working pressure and stopped for 1 hour, it is qualified if the pressure does not drop obviously. Pressure test of lower tower system. Close the liquid nitrogen throttle valve, liquid air throttle valve and liquid air to argon tower valve.
DEAR Biogas purification unit.There is a certain amount of argon in the rising steam of stripping section and the steam after liquid air throttling. In the process of rising, some steam will condense into liquid after encountering downflow cold liquid. Oxygen and argon, which are difficult to volatilize, condense more into the liquid phase than nitrogen.DEAR Biogas purification unit.The reasons for this situation may be as follows: the adsorption performance of molecular sieve decreases after long-term use; the regeneration of molecular sieve is incomplete, or the steam regeneration heater leaks, and the regeneration gas is wet; or the adsorption water load of molecular sieve is too large, which affects the adsorption of carbon dioxide;The heat transfer coefficient K increases with the increase of fluid velocity. However, increasing the flow rate will increase the flow resistance and increase the energy consumption of conveying fluid, so we can not unilaterally emphasize increasing the flow rate. The strength of heat conduction through the wall is not only related to the material and thickness of the wall, but also related to the pollution of the wall.
