DEAR Air separation unit.Under certain conditions, especially under high pressure, oxygen may react with carbon in steel when encountering friction, impact and spark. Therefore, according to the pressure and laying method, except for the requirements shown in table 40, a stainless steel pipe (gb2270-80) or copper pipe with a length of more than 5 times the outer diameter of the pipe and no less than 1.5m shall be used at the downstream side of the pressure or flow control valve group Stainless steel pipe shall also be used for the oxygen release pipe section with working pressure greater than 0.1MPa at the downstream side of the oxygen release valve.DEAR Air separation unit.The control of non switching plate fin heat exchanger in molecular sieve purification pressurization process is not as strict as the temperature difference control of switching heat exchanger in self cleaning process under stable conditions. Since there is no self cleaning problem, the heat exchanger only needs to control the temperature difference at the hot end and the air extraction temperature in the middle.
When the freezing is serious, only stop to heat the accumulator (or switching heat exchanger) separately. This is the most effective way to eliminate the freeze. When the passage is completely frozen and blocked, and the heating gas can not be passed in, hot water can be poured in to make the ice melt slowly.After extracting argon fraction, it has a great influence on the working conditions from the liquid air feed port to the fraction extraction port of the main tower. Because the amount of rising steam decreases and the reflux ratio increases, more trays are needed to ensure the purity of liquid oxygen.DEAR Air separation unit.In order to prevent the pipeline from freezing and cracking in winter, insulation measures must be taken for some outdoor detection pipelines with liquid medium. In places with low ambient temperature, steam or electric heating can be used for insulation. In general, the pipeline can be wrapped with asbestos rope and other insulation materials for thermal insulation;
If the compression pressure of liquid oxygen is higher than the critical pressure (for example, the oxygen pressure for chemical industry is 6.0MPa or higher), there is no gasification stage with constant temperature in the gasification process of heat exchanger. This will affect the heat transfer performance of high-pressure heat exchanger, which should be fully considered in the design.Generally, rivers, lakes or groundwater are used as cooling water for air separation units. This kind of water usually contains suspended solids (sediment and other pollutants) and bicarbonates such as calcium and magnesium [- Ca (HCO3) 2 and Mg (HCO3) 2], which is called hard water. When there are many suspended solids, it is easy to block the channels, filters and valves of the cooler. Calcium, magnesium and other bicarbonates are easy to form calcium carbonate (CaCO3) and magnesium carbonate (MgCO3) precipitates when the water temperature rises, that is to say scale. Generally, water temperature above 45 ℃ will start to form scale, and the higher the water temperature is, the easier it is to scale.
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.DEAR Air separation unit.The mechanical water is carried out with the air and enters the molecular sieve purifier or the switching heat exchanger, which destroys the normal operation of the device. The causes of this failure are as follows: the screen hole of the sieve plate is partially blocked. The spray water of the air cooling tower flows down through the cross flow sieve plate and constantly contacts with the air.Close the regulating valves of liquid air, liquid nitrogen and sewage liquid nitrogen. Fully close the oxygen and nitrogen product delivery valve, open the vent valve, and place the waste nitrogen vent three-way valve on the vent side. Fully close the butterfly valve of the expansion air into the upper tower, and open the bypass valve.
