Under the condition of 3 ℃ temperature difference at the hot end of a large capacity air separation plant, the incomplete heat exchange loss accounts for about half of the total cooling loss. If the temperature difference increases by 1 ℃, the total cooling loss will increase by about 16%. In order to make up for the increased cold loss, it is required to increase the expansion capacity of the expander, which will affect the work of the whole device. In the process of operation, pay attention to the change of temperature difference at the hot end, and take corresponding measures to prevent the expansion of temperature difference and avoid exceeding the design value.General spray cooling tower is equipped with automatic water level regulation device. When the water level is too high, the pneumatic diaphragm valve which controls the drainage automatically opens. Some devices are controlled manually. If the inspection is not enough or the instrument and valve are in trouble, the water level will rise.
By several different gases evenly mixed together, the composition of the gas mixture is called "mixed gas". Air is a mixture of gases. Each component of the gas mixture is called "component". In the mixed gas, the gas molecules of various components occupy the same volume (that is, the total space of the container) and have the same temperature.Due to the hard work of valve opening and closing, the valve stem is often twisted and the hand wheel is broken. Therefore, after the maintenance of the valve, the packing should be installed evenly and tightly, and the compression nut should be tightened. During the overall leakage test of air separation unit, the leakage at the valve rod packing should also be checked, and this problem should be solved before cold start-up.Air separation unit.For the internal compression process, the liquid oxygen is compressed to the required pressure in the device and then reheated and gasified in the high-pressure heat exchanger. If the compression pressure of liquid oxygen is lower than the critical pressure (for example, the pressure of oxygen for steelmaking is 3.0MPa), there is a gasification stage in which the heat is absorbed and the temperature remains unchanged, and then the superheating stage when the gas temperature rises;
Air separation unit.It can be seen that in this case, it is better to stop an expander, which can not only reduce the impact of expansion on distillation conditions, but also make the switching heat exchanger work under normal conditions, so as to prevent cold end supercooling or low temperature after expander.Air separation unit.The purity of product oxygen is improved, that is to say, the concentration of oxygen in gas phase and liquid phase on each tray of stripping section is increased, and the sum of oxygen, argon and nitrogen is 100%, so the content of argon and nitrogen is bound to decrease.Air separation unit.In normal operation, the biggest influence on the operation cycle is the temperature difference control of the cold end of the switching heat exchanger. If the temperature is not well controlled, on the one hand, the self-cleaning effect of the switching heat exchanger will be poor, and carbon dioxide will accumulate in the heat exchanger and increase its resistance; on the other hand, a small amount of carbon dioxide will be brought into the tower.
In energy industry, in order to maintain the temperature of oxidation layer in the furnace, enough oxygen must be supplied during coal pressurized gasification. The purity of oxygen is not less than 95%, and the oxygen consumption per kilogram of coal varies with the type and quality of coal. It is 0.14-0.18m3/kg for lignite and 0.17-0.22m3/kg for bituminous coal. The oxygen pressure is determined by the production process requirements. The higher the pressure, the less oxygen consumption. For the IGCC unit, the oxygen demand of 1kW is about 5.6m.Air separation unit.At this time, the flow rate of the central extraction or ring will automatically decrease, so that the middle temperature will increase. After the main cooler is cooled and the middle temperature is increased, start the expander. If the temperature of central extraction or circulating current is not much lower than the specified value, the method of throttling in front of the unit can also be adopted to reduce the cooling capacity and increase the temperature after the unit. Or use part of the cooling capacity to cool the adsorber.
