Air separation unit.1 g potassium dichromate or 2 g sodium nitrite can be added to each liter of water (not suitable for nonferrous metal degreasing); due to the toxicity or explosion of degreasing agent, attention must be paid to prevent poisoning and formation of explosive mixture. In alkaline cleaning, the pipeline with more oil stains is heated to 60-90 ℃ with 10% sodium hydroxide solution, then neutralized with 15% nitric acid and washed with clean water.Air separation unit.From the vaporization temperature (saturation temperature) of liquid oxygen, if the liquid oxygen surface is too high, the greater the static pressure difference between the upper and lower liquid oxygen surface, the higher the average pressure of liquid oxygen and the corresponding saturation temperature. In order to maintain the heat transfer temperature difference of the condensing evaporator, it is necessary to increase the pressure of the lower tower. From this point of view, we do not want to make the plate unit too high.
The extraction rate of oxygen in the process air is further reduced, and the output of oxygen is reduced. Therefore, for 1000m3 / h air separation plant, it is not suitable to extract some liquid products. For a 50m3 / h small medium pressure air separation plant, if 4 L liquid nitrogen is extracted per hour, the air pressure should be increased by 0.3-0.4 MPa.Its temperature can be lower than that of the cooled medium (chilled water, etc.), so it can absorb heat Q2 from the cooled medium in evaporator 4, and the refrigerant will evaporate into low-pressure steam and return to the compressor for circulation. Therefore, compared with the refrigeration in the oxygen generator, the common point of the refrigeration in the refrigerator is that the compressor needs to consume work.Air separation unit.The overall heating in cold state is the heating operation after parking. The main purpose is to remove the residual water, carbon dioxide, acetylene and other impurities, so as to prepare for the long-term operation or maintenance of the next cycle. Full heating in hot state is the heating operation before start-up. Its main purpose is to remove water and some solid debris.
Air separation unit.The porous fin is formed by punching many holes in the straight fin. Because of these holes in the fin, the laminar boundary layer is broken continuously to improve the heat transfer performance. This kind of fin is often used as guide fin and in the case of phase change (condensation or evaporation) of fluid.The newly installed fractionator must be thoroughly heated and purged before start-up and long-term shutdown. After putting into operation, when the suspension fault of the fractionator cannot be eliminated, or the pressure difference before and after the heat exchanger pressure is greater than 0.5MPa at the end of the operation cycle, or the purity and yield of oxygen and nitrogen are decreased, heating and blowing should be carried out.Air separation unit.Generally, the nitrogen content in the fraction should not be more than 0.01%. In a word, the operation of the crude argon column should gradually increase the load of the crude argon condenser, too fast operation will be counterproductive, making the whole system fluctuate.
Air separation unit.Due to the large heat capacity of the accumulator, when the temperature of the cold end reaches - 60 ℃, the temperature of the intermediate extraction is still above 0 ℃ after the water freezing stage. Therefore, for the process of intermediate extraction, in addition to the problem that the air at the cold end of the accumulator has passed through the freezing stage of moisture and carbon dioxide, there is also the problem that the intermediate extraction air has passed through the freezing stage of moisture.Air separation unit.When the air separation column changes from normal temperature to low temperature, the phenomena of pipe cracking and valve sticking often occur. The main reasons are that the installation prestress is too large and the cold compensation is not good. In order to reduce the installation prestress and cold deformation stress, the following measures should be taken in the installation: when piping, it should be large first and then small, difficult first and then easy, small pipe should give way to large pipe, heat pipe should give way to cold pipe.
