DEAR Biogas purification unit.When the temperature of sewage nitrogen in the cold end is reduced, the temperature difference in the hot end will be enlarged, so that the insufficient reheating will increase the cold loss, the expansion will increase, and the product quantity will decrease; liquid hammer may occur, and the automatic valve will be easily damaged. In a word, air liquefaction at the cold end is harmful but not beneficial, and the expansion of temperature difference at the cold end is the most harmful.DEAR Biogas purification unit.Other cold losses Q1 (or Q1). In addition to the above two kinds of cooling losses, when regenerating and precooling the cryogenic adsorber, when discharging the liquid, or when the device or valve leaks, an additional part of the cooling capacity will be consumed, or a part of the cooling capacity of the cryogenic liquid (or gas) will be lost. These cooling losses fall within the scope of other cooling losses.When the gas or liquid flows through a shrinkage cavity or a valve in the pipeline, the flow is hindered, and the fluid produces vortex, collision and friction at the valve. In order to flow through the valve, these resistances must be overcome. The pressure P2 behind the valve is much lower than the pressure P1 before the valve. This process of pressure drop caused by local resistance is usually called "throttling process".
DEAR Biogas purification unit.If the heating pressure of purifier is controlled lower than 1MPa (gauge pressure), the speed is twice as fast as 2MPa. With the increase of air velocity, the adsorbent is easy to turn into powder. Therefore, when the purifier is heated, the pressure is controlled to the normal working pressure (2MPa), which is conducive to extending the service life of the adsorbent. However, attention should be paid to the control of the heating inlet valve, so that the pressure entering the heating furnace is not higher than 0.5MPa, and the upper tower pressure is not higher than the normal working pressure.DEAR Biogas purification unit.In the maintenance of nitrogen water precooling system, the most important thing is to prevent nitrogen suffocation. There have been several times in China that maintenance workers died of nitrogen suffocation. During maintenance, the nitrogen is often heated at the same time, and the heated nitrogen often flows into the cooling tower through the sewage nitrogen three-way valve, resulting in too high nitrogen concentration in the tower.
The water injection hole of the chilled water distributor is blocked, which causes the water level in the chilled water return tank to overflow to the orifice of the riser, and part of the water is carried into the purifier by air; too much spray water or poor separation effect of the water separation device (including the water capture layer on the top of the tower or the separate water separator) will also cause water entrainment;The refrigeration capacity of throttling effect is due to the decrease of pressure, volume expansion and the increase of potential energy of molecular interaction, resulting in the decrease of kinetic energy of molecular motion and the decrease of gas temperature, which makes it have a certain ability to absorb heat. For the whole air separation unit, the air pressure when entering the unit is high, and the pressure when leaving the air separation unit is low. Theoretically, the temperature can be reheated to the temperature when entering the unit. At this time, the enthalpy value of the low pressure gas is greater than the enthalpy value at the inlet, and the enthalpy difference between the low pressure gas and the inlet gas is the refrigeration capacity of throttling effect, no matter whether the pressure drop is generated in the throttle valve or not.
DEAR Biogas purification unit.The heat transfer process of regenerative type is convection heat conduction convection, which is completed by two cycles. The mixed heat transfer process is very complex, including the evaporation or condensation of the carrier phase change, mass transfer process, and phase change also needs to absorb or release heat. For example, in a water cooling tower, while using nitrogen to cool water, some water absorbs heat due to evaporation into nitrogen, which further reduces the temperature of water.When the packing is not uniform or tight, or the valve stem is not straight or round, the cryogenic liquid or gas will leak out along the gap of the packing. As the cooling capacity is transmitted, the moisture in the air will freeze on the packing and freeze the valve stem. In this case, only steam or hot water can be used to heat the packing to open and close the valve. However, after the valve is opened and closed, the water accumulated in the packing will freeze again.
