Air separation plant.For the irreversible adiabatic process, the entropy increases. In other words, the physical quantity entropy can express the direction of the process. The spontaneous process in nature always goes in the direction of the increase of the total entropy, and the total entropy of the ideal reversible process remains unchanged. For the above two irreversible processes, the entropy of the final state must be greater than that of the initial state.Air separation plant.The heating operation is as follows: start the air compressor, when the purifier pressure rises to the normal working pressure, slowly open the heating main inlet valve, and use the valve to control the purifier pressure at the normal working pressure. After blowing with dry air for half an hour, turn on the power supply of the heating furnace, and control the air temperature at the outlet of the heating furnace between 70 ℃ and 80 ℃.The liquid level should be stable. The stability of liquid oxygen level indicates the balance of cooling capacity of the equipment. If the liquid oxygen level changes from high to low, it is very difficult to adjust the purity. The expansion volume and the opening of liquid air and liquid oxygen control valves should be adjusted reasonably to make the liquid oxygen surface stable.
Along the height of the accumulator, the air temperature of each section will increase, so the temperature difference of heat transfer will increase, and the cooling capacity will increase. When the cooling capacity of the backflow gas is more, the outlet temperature of the hot end and the temperature of each section along the height of the accumulator will also increase, and the temperature difference at the hot end will decrease (when the air inlet temperature is constant).Air separation plant.In actual operation, the heat transfer area of the heat exchanger has been fixed. If the temperature difference at the hot end is enlarged, the cooling capacity of the backflow gas can not be fully recovered in the heat exchanger. This may be due to the decrease of heat transfer performance of the heat exchanger and the decrease of heat transfer under the same heat transfer area; it may also be due to the change of air flow and air temperature. Specific analysis is needed for different processes and different heat exchanger structures.
Plate fin heat exchanger belongs to inter wall heat exchanger. It is a compact and efficient heat exchanger with all aluminum structure. Each channel is composed of partition, fin, guide fin and seal. Fins and guide fins are placed between two adjacent partitions, and both sides are sealed with seals to form a sandwich, which is called "channel".Air separation plant.N2O first penetrates the adsorption bed and enters the distillation column. In the process of CO adsorption of hydrocarbons such as H2O, CO2 and C2H2, CO2 can replace the adsorbed N2O molecules. Therefore, zeolite can not remove N2O. In the main heat exchanger, the process air is cooled to the liquefying temperature, and N2O condenses into solid first, which will block the air passage. When the processing air pressure is 0.6MPa and the N2O content is 1 × 10-6, the precipitation temperature of N2O is 113k.When the gas expands in the expander, only the enthalpy drop caused by external work is considered in calculating the refrigeration capacity of the expander. In fact, when the pressure decreases, the molecular potential energy also increases, so a part of the throttling effect should be produced, which should be the cooling capacity. This part of refrigerating capacity is not calculated separately, but the total throttling effect refrigerating capacity of the unit is expressed by the total enthalpy difference between the low-pressure gas at the time of leaving the unit and the pressure gas at the time of entering the unit. When the refrigeration capacity of expander is adjusted, the refrigeration capacity of throttling effect is not affected.
