In order to make the main cooling precooling complete, the gas in the main cooling channel must be unblocked in the cooling stage. Therefore, it is necessary to open the pure liquid nitrogen control valve, close the liquid nitrogen return valve and the sewage liquid nitrogen control valve, and use the cold air from the lower tower to cool through the main cooling nitrogen channel.With the continuous increase of the flow rate of central extraction or circulation, the circulating temperature becomes lower and lower, the cold end of the switching heat exchanger becomes colder and colder, and the temperature in front of the expander still can not be increased. Finally, the adjustment means are lost, resulting in a passive situation. The reasons for this situation are: there is no proper restriction on the flow rate of central suction or circulation before liquid accumulation; the liquefier is connected late, or the liquefying effect of liquefier is poor;The overall heating in cold state is the heating operation after parking. The main purpose is to remove the residual water, carbon dioxide, acetylene and other impurities, so as to prepare for the long-term operation or maintenance of the next cycle. Full heating in hot state is the heating operation before start-up. Its main purpose is to remove water and some solid debris.
DEAR Biogas purification unit.The purpose of controlling low pressure during fractionator heating is to speed up fractionator heating. If the low-pressure pressure is not controlled, the heated gas will be discharged from the oxygen and nitrogen discharge pipes with small resistance, and the heating gas volume of small pipes with large resistance (such as analysis valve, level gauge valve, etc.) and expander parts is very small, which is easy to cause high temperature in some pipes and incomplete heating in some pipes.DEAR Biogas purification unit.If the heat transfer surface of the condensing evaporator is insufficient, its heat load will be reduced, that is, the heat transfer will be reduced. Therefore, the evaporation of liquid oxygen will be reduced, and the condensation of gas nitrogen will be reduced accordingly. This will directly affect the distillation conditions of the upper and lower columns. At the same time, the air intake of the lower tower will be reduced, the air can not be fed, and the oxygen production will be reduced.
When the temperature at the end of oxygen filling is T1 = 313k and the gauge pressure is P1 = 14.7mpa, if the room temperature is T2 = 293k, the pressure of the cylinder will automatically drop to P2 = (14.7 + 0.1) MPa × 293k / 313k = 13.85mpa after several hours, that is, the gauge pressure will drop to 13.75mpa. Generally, the pressure in the bottle will decrease by 0.1MPa for every 2 ℃ decrease in temperature, which is a normal phenomenon. If this value is exceeded, the bottle valve may be leaking.The efficiency of expander reflects the performance of expander. The more close to the ideal enthalpy drop, the higher the efficiency. The efficiency of medium pressure piston expander is 55% ～ 60%, that of low pressure turbine expander is over 80%, and that of new high efficiency turbine expander is over 85%.DEAR Biogas purification unit.For all kinds of heat exchangers in air separation unit, the heat transfer area has been determined. However, if a part of the channel of plate heat exchanger or a part of the tube (or coil) of tube heat exchanger is blocked due to leakage in use, the heat transfer area will be reduced and the heat transfer will be reduced.
