On the one hand, it increases the saturated water content when the air leaves the spray tower; on the other hand, it decreases the adsorption capacity of molecular sieve; when the spray tower is cut off or the water level is too high, the temperature of molecular sieve adsorber will rise or water carrying accident will occur.If the leakage occurs in the local position of the pipeline, valve and even equipment, the cold capacity of the leaked part of low temperature gas or liquid can not be recovered, which not only greatly increases other cold loss items Q1, but also condenses and freezes inside and outside the cold insulation box, increasing the cold loss Q3.DEAR Biogas purification unit.The higher the air pressure into the device, the greater the power consumption of the air compressor, and the higher the requirements for the safety and strength of the pipeline and equipment. Moreover, with the increase of pressure, the increase of cooling capacity also decreases. Therefore, the maximum pressure of small high-pressure oxygen generator is generally not more than 20MPa, and in normal production, the working pressure should be reduced as much as possible. When the temperature of air entering the unit increases, the cooling capacity of throttling effect decreases slightly.
DEAR Biogas purification unit.There is a flow resistance when the gas flows through the switching heat exchanger. The resistance is usually expressed by the pressure drop of backflow gas, which is about 10KPA. The resistance is not only related to the amount of gas flow, but also related to the manufacturing quality of the equipment and the accumulation of water or carbon dioxide. Air leakage in the automatic valve box will also increase the resistance.The temperature of liquid oxygen at the bottom of the upper tower is about - 180 ℃. In the process of gasification, it exchanges heat and mass with the liquid on the tray. The nitrogen component evaporates and the gas temperature decreases. When the gas passes through dozens of trays and rises to the top of the tower, the gas has reached pure nitrogen and the temperature drops to the same level as the liquid temperature (- 193 ℃). Therefore, the formation of the lowest temperature in the tower is the result of liquid throttling expansion and gas-liquid heat and mass exchange.
DEAR Biogas purification unit.The packed tower is a round steel vessel filled with packing (porcelain ring, or plastic ring, etc.). The cooling water is sprayed from the top of the tower and mixed with the air flowing from bottom to top for heat and mass exchange. The air transfers the heat to the cooling water, so that the temperature of the air decreases and the water temperature increases.DEAR Biogas purification unit.When the temperature of the backflow gas out of the accumulator decreases, the temperature difference at the hot end will be larger. The cooling capacity absorbed by positive flow air is more than that absorbed by return flow and positive flow air, so the temperature of air out of the accumulator decreases, resulting in the reduction of temperature difference at the cold end.DEAR Biogas purification unit.In order to avoid the increase of hydrocarbon concentration in liquid oxygen, according to the material balance, it is necessary to extract part of liquid oxygen from the main cooler and extract part of hydrocarbon from the main cooler. The minimum amount of liquid oxygen extracted is equal to 1% of the gas oxygen output, and then gasified separately.
