According to the weight of fractionator, the manufacturer of air separation unit selects appropriate steel wire rope and hangs the tower flat on the sleeper for air tightness test; Tie the steel wire rope to the lower part of the upper cylinder shell, and pad it with about 10 mm wood around to prevent deformation of the shell, and then lift it to the specified position with a crane; At the beginning of heating, it is necessary to turn down the oxygen and nitrogen vent valves, limit the discharge volume, increase the low pressure pressure, increase the gas volume of the pipeline with large resistance, and speed up the heating thoroughly. When the fractionator is heated, the molecular sieve purifier also needs to be heated. If the low pressure is too low, the regeneration of purifier will be affected. But the pressure should not exceed the normal working pressure to ensure safety.
First of all, we should make preparations before heating: 1) discharge the liquid in the tower; 2) Remove the flowmeter and thermometer at the outlet of oxygen, nitrogen and fraction, remove the upper and lower joints of liquid air and liquid oxygen level gauges, and remove all pressure gauges except low pressure gauges; 3) Close the high-pressure air main inlet valve, section-1 valve, oxygen and nitrogen product delivery valve, and heating inlet main valve; 4) Push open the push rod of the inlet and outlet valves of the expander; 5) Open all through valves, throttle valves, analysis valves, blow off valves, upper and lower valves of liquid level gauge, Pressure Gauge Valves and heating valves on the shell of fractionator; 6) Top up the heater with distilled water. The saturated liquid nitrogen pumped out by the air separation plant manufacturer is also at this temperature. The temperature of the liquid nitrogen is about 16 ℃ higher than that of the gas nitrogen in the upper tower. Therefore, when the two fluids flow through the liquid nitrogen subcooler, through heat exchange, the liquid nitrogen releases heat and is cooled into supercooled liquid, and the gas nitrogen becomes superheated steam due to heat absorption.
When measuring the temperature, take the thermometer out of the casing and read again. The correct installation and use method is: first, the air inlet pipe and the return air pipe are respectively opened at about 1.6m above the ground, and the thermometer joint with 45 ° to the main pipe is welded. If a platinum resistance thermometer or a glass rod thermometer with a metal shell is used, the temperature measuring element point should be inserted into the inner diameter of the main pipe 1 / 3 ~ 1 / 2, so that the temperature measuring element is aligned with the fluid. The adsorption method of air separation plant manufacturers makes use of the selective adsorption characteristics of adsorbents (such as molecular sieve, activated carbon, etc.) to separate or further purify rare gas components. For example, the purification of crude neon, neon, helium, krypton and xenon can all adopt this method.
Therefore, the total cooling loss of an air separation unit that does not produce liquid products is 8.1-11.4kj/m3. It can be seen that most of the total cooling loss is made up by expander cooling, and the required expander cooling capacity is 6.74-10.04kj/m3, accounting for 83% - 88% of the total cooling capacity. Annular or U-shaped condensing isolation pipe must be added to the pipeline used for the detection of steam or other condensing gas near mounted instruments to prevent overheating of measuring elements; For the positive and negative pressure detection pipelines of flow and liquid level, the length and the number of elbows should be consistent as far as possible, so that the resistance of positive and negative pressure pipelines is the same, and the instrument error caused by local resistance of pipelines can be eliminated;
The flange connection is easy to use and can bear large pressure. Flange connection is widely used in industrial pipeline. In the family, the pipe diameter is small, and it is low pressure, and the flange connection is invisible. If in a boiler room or production site, there are flange connected pipes and equipment everywhere. When the gas is expanded by external power through the expander, the internal energy will be consumed, and the effect of temperature drop is much greater than when the throttle is not expanded by external power. Especially for the low pressure air separation plant, the refrigeration capacity mainly depends on the expander. However, the higher the inlet temperature is, the greater the effect is. In addition, no liquid is allowed in the expander to avoid damaging the blades.
