For the unit group with lower intermediate temperature, the air separation unit manufacturer can close the small product control valve to reduce the product flux, that is, reduce the cooling capacity, which can make the intermediate temperature rise. The product flux distribution is adjusted according to the central temperature, but the total product quantity cannot be changed to adjust the central temperature. When the temperature of each group is unbalanced, the highest and lowest central temperature should be adjusted first. When the air separator manufacturer measures the temperature, pull the thermometer out of the casing and read it again. The proper installation and use method is: firstly, the air inlet pipe and return pipe about 1.6 meters above the ground are respectively perforated, and the thermometer joint of 45 ° is welded with the main pipe. When using platinum resistance thermometer or glass rod thermometer with metal shell, the thermometer should be inserted into 1 / 3 ~ 1 / 2 of the main pipe diameter to align the thermometer with the fluid.

Water supply and drainage systems are independent circulation systems. Due to the large temperature rise of cooling water in the tower, high drainage temperature and serious scaling, the make-up water of the system is required to use low hardness or soft water as far as possible, and its temporary hardness is generally not greater than 8.5 ℃ DH. Other requirements are the same as that of compressor cooling water. Distilled water or softened water shall be used as the lubricating water after the cylinder of high pressure oxygen compressor is inflated. With the increase of expansion capacity, the amount of air entering the lower tower decreases, so that the heat load of the condensing evaporator decreases, and the liquid oxygen evaporated decreases relatively, which shows that the liquid oxygen level rises; if the expansion capacity does not change, and the unit cooling capacity increases, that is, the temperature before expansion is increased (the bypass flux is reduced), then the cooling capacity of the circulating gas discharged from the switching heat exchanger will inevitably increase.

The total refrigerating capacity QP (kJ / h) of expander of air separation plant is related to the expansion capacity V (m3 / h) and unit refrigerating capacity ah (kJ / KMOL): q = V △ H / 22.4 = vaht · η P / 22.4, in which unit cooling capacity △ ^ is equal to the product of unit theoretical cooling capacity △ HT and expander efficiency η P. The theoretical cooling capacity is determined by the pre expansion pressure, expansion temperature and post expansion pressure. When the heat exchanger is removed, the total heat transfer capacity of one component is reduced. If the air flow rate remains unchanged, the air can not be cooled to the set temperature, and the temperature difference at the cold end will also increase, which is not conducive to self-cleaning, and the resistance will increase rapidly.

The temperature difference of heat transfer rises, but it is impossible to return to the temperature difference of heat transfer before the change of working conditions, which is larger than the original, so the cooling capacity of backflow gas will still increase. However, due to the increase of air volume, the amount of cold absorbed per 1 kg air is reduced, otherwise it is impossible to reach a new heat balance. This will inevitably lead to the expansion of the temperature difference at the cold end and the decrease of the temperature difference at the hot end. The air separation plant manufacturer should first 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.

In the process of molecular sieve purification of pressurized process, the flow rate of pressurized channel should be reduced, and the nearby reflux channel should be sufficient, so as to avoid the channel can not be fully used due to the large start-up expansion. As for the specific layout of the return channel, due to the fact that there is no production gas at the time of start-up, and the vent valve is opened small, the discharge of sewage nitrogen is large, so more sewage nitrogen channels should be set near the return channel. The hollow tower of hollow equipment manufacturer is simpler, smaller, less resistance and better cooling effect than packing and sieve plate tower. Hollow tower has high requirements for spray equipment and water quality. It must ensure that the spray water can be atomized well to make gas-liquid contact fully.