The determination of the operation cycle of air separation unit is mainly based on the time interval when the trace carbon dioxide is gradually accumulated after it is brought into the air separation tower until it cannot continue to operate due to blockage. Under normal conditions, the continuous operation time of the full low pressure oxygen generator should be more than one year, and the continuous operation time of the new molecular sieve adsorption process can be more than two years.DEAR Air separation plant.For medium pressure process small air separation unit, the pressure after air throttling is lower tower pressure, about 0-6MPa. The specific enthalpy of saturated liquid and saturated vapor is - 2450j / mol and 2550j / mol respectively. If the specific enthalpy of the gas before throttling is less than the specific enthalpy of the saturated steam corresponding to the pressure after throttling, it will partially liquefy after throttling.Part of the liquid air is sent to the condensing evaporator of the crude argon tower and evaporated completely, then the steam is sent to the upper tower. Its characteristics are opposite to the first one. Generally, the third way between the two ways is adopted, that is, part of the liquid air passes through the crude argon tower, but not all of it evaporates. This can not only ensure the normal operation of the crude argon column, but also reduce the impact on the main column.
For users with external activation conditions, follow the following steps: 1) thoroughly activate the molecular sieve to be filled; 2) remove the air inlet pipe and filter pipe at the top of the purifier to be filled; 3) load the activated molecular sieve into the purifier until it is full, and note the number of molecular sieves to be filled. In order to fill compactly, wooden hammer can be used to knock on the head of the cylinder; 4) after the molecular sieve is installed, the pipeline, filter pipe and valve can be installed again. And attention should be paid to: the screws of connecting flange should be tightened evenly and symmetrically; the valve should be degreased before packing; the packing of nitrogen heating valve should also use high temperature resistant expanded graphite or asbestos wire.DEAR Air separation plant.Since the subcooler and liquefier can fully recover the cooling capacity of the expansion air, it is unnecessary to send air to the upper tower too early. When the main cooling liquid area is enough, the normal distillation condition is established, it is appropriate to stop one expander and then send gas to the upper tower.
DEAR Air separation plant.For the medium pressure process air separation unit, the high pressure air is divided into two channels after passing through the first heat exchanger: one is cooled continuously through the second heat exchanger, and then throttled to enter the lower tower; the other is expanded by the expander, and then enters the lower tower. The expansion amount has no direct relationship with the oxygen extraction rate.When the unit is in normal operation, the cooling capacity is mainly to balance the cooling capacity loss of the unit and the cooling capacity needed to produce a small amount of liquid products. Generally speaking, according to the design conditions, an expander can meet the requirements. When an expander can not maintain normal liquid level, there must be abnormal cooling loss such as internal leakage. At this time, it can't solve the fundamental problem to increase the refrigeration capacity only by increasing the expander. But we should first find out the reason for the increase of cooling loss.
The sieve plate column is similar to the sieve plate column of distillation column, but the number of plates is small (generally about 5), and the diameter and spacing of sieve holes are large (about 5mm in diameter and 9mm in spacing). The cooling water is ejected from the top through the spray device and flows down the tray through the sieve hole layer by layer. The air flows counter current through the sieve hole from the bottom of the tower and bubbles up.At present, the air cooling tower of large-scale air separation plant in our country adopts the upper section as the packed tower with new plastic rings, and the lower section as the sieve plate tower (aperture 12mm, spacing 24mm), which has achieved good results. The heat transfer temperature difference at the top is only 0.5 ℃, and the scaling problem is completely solved.DEAR Air separation plant.The fault occurs at each connection. The causes of this kind of failure include cold and freezing of valve packing, leakage of connecting flange between valve seat and pipeline, leakage of tin filling thread at both ends of valve screw sleeve, etc. The valve stem packing is generally in the packing groove where the valve stem is close to the wall of the cold box.
