The total heat transfer coefficient of the condensing evaporator mainly depends on the heat transfer of the evaporation side, and the high liquid level is beneficial to improve the heat transfer coefficient. Although increasing the liquid oxygen surface will slightly increase the average saturation temperature of oxygen, it is disadvantageous to the average temperature difference of heat transfer.DEAR Biogas purification unit.If the dew point temperature is measured, the water vapor content can be found from the table of water vapor saturation content. Because the water vapor content does not change in the process of temperature reduction, the determination of dew point is actually the determination of absolute humidity in the air. The lower the dew point, the less moisture in the air.When the working condition of the air separation unit is stable, the cold production and consumption of the unit keep balance, and the temperature, pressure, liquid level and other parameters of each part of the unit no longer change with time. The main cooling is the link between the upper and lower towers. The rising nitrogen from the lower tower is exothermic condensed in the main cooling, and the return liquid oxygen from the upper tower is endothermic evaporated in the main cooling. When the amount of reflux liquid is equal to the amount of evaporation, the liquid level remains unchanged.
DEAR Biogas purification unit.It can be divided into three stages: cooling equipment, liquid accumulation and rectification condition adjustment. Compared with the start-up mode of switching process, it can be called "overall cooling method" or "one-time cooling method". Attention should be paid to the following points during the start-up operation: the molecular sieve used for the first time should be activated and regenerated to remove the water and carbon dioxide absorbed in the transportation and filling process.DEAR Biogas purification unit.As a convenient cold source, liquid nitrogen is widely used in food industry, medical treatment, animal husbandry and scientific research.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;
It can be seen that in the air separation plant, throttle valve and expander have their own advantages and disadvantages, and they are used together to meet the requirements of refrigeration capacity. The refrigeration capacity is adjusted by adjusting the refrigeration capacity of the expander, and the lowest temperature (- 193 ℃) in the air separation tower is achieved by liquid throttling.In the start-up operation, attention must be paid to gradually reduce the temperature difference at the hot end of the cold accumulator or the switching heat exchanger; before accumulating enough liquid, do not rush to start the liquid oxygen pump or deliver oxygen. If the cooling loss is limited to a minimum, more cooling capacity can be used to liquefy the gas and the start-up time can be shortened.The number of molecules leaving the liquid is in dynamic equilibrium with the number of molecules returning from space, which is also called "saturated state". At this time, the pressure produced by steam is called "saturation pressure". For the same substance, the saturation pressure is related to the temperature.
