Large air separation FAQ

With the development trend of large-scale air separation plant, the column support of its matching cold box equipment tends to be large-scale. The traditional support structure has complex structure and poor bearing capacity. Through the use of finite element analysis software, DEAR air separation carries out finite element analysis and optimization on the commonly used experienced column of air separation plant, so as to improve the bearing capacity of support and reduce the processing difficulty, to reach the purpose of saving material cost.

According to the adsorption characteristics of molecular sieve, there are two kinds of air purification process, one is pressure swing adsorption molecular sieve purification process, the other is temperature swing adsorption molecular sieve purification process. Pressure swing adsorption can simplify the process, save air cooling column, low temperature water pump, regeneration heater and other equipment, and save steam. However, its disadvantages can not be ignored, such as short switching cycle, frequent valve action which could cause default, high switching loss, increased energy consumption, adsorption is not completely compared with temperature swing adsorption, which has an impact on the safety of large-scale air separation, and the total investment is slightly greater than that of temperature swing adsorption. Therefore, we mostly use the temperature swing adsorption molecular sieve purification process.

1. The requirements of molecular sieve adsorber, electric heater and other equipment in place are the same as those of air cooling column of pre cooling system. 2. Process piping shall be constructed in strict accordance with relevant specifications and design and construction drawings. 3. The air tightness test shall be conducted before the valve is installed, and the test pressure and inspection standard shall be carried out according to the technical requirements of corresponding valves. 4. Pay attention to the direction of switch valve installation. V1201, V1202, V1207 and V1208 are front mounted valves, while V1203, V1204, V1205 and V1206 are reverse mounted valves. When the switch valve is installed, its shaft should be in a horizontal position, and the flange bolts should be evenly cross tightened. 5. The pipeline of pressure equalizing valve V1209 should have compensating bend.

The principle of expander with motor brake in air separation plant is to control the speed of expander by braking torque generated by motor generator braking state. Once the brake motor fails, the expander speed will lose control and overspeed will occur. At this time, it is necessary to automatically open the protection and control system. The principle is that the speed measuring motor will send out the overspeed signal to cut off the three-way solenoid valve. The three-way solenoid valve directly controls the air open pneumatic butterfly valve at the inlet of the expander, so that the butterfly valve is quickly closed and the air inlet is cut off. At the same time, the rotation of the valve rod touches the stop and limit switch, so that the power supply of the expander motor is cut off and the safe shutdown is realized.

In the operation of air separation plant, in order to ensure the accuracy of DCS control system monitoring and the safety and stability of operation, it is necessary to do well of DCS system grounding.

After a long-term operation of the air separation plant, the components in the cryogenic equipment and pipelines in the distillation system will be blocked due to ice or mechanical powder, which will increase the resistance of the fractionator. When the air separation plant has been in normal operation for about 2 years, the fractionator system should be heated and thawed to remove these deposits. When the molecular sieve adsorber and the main heat exchanger have water inflow or other faults, it is also necessary to stop and heat up. In general, the following methods will be used for heating and thawing.

After a long-term operation of the air separation plant, the components in the low-temperature equipment and pipelines of the distillation system will be blocked due to the internal precipitation of icing or mechanical powder, which will increase the resistance of the fractionating column. Therefore, after the normal operation of the air separation plant for about 2 years, the fractionating column system should be heated and thawed to remove these sediments. When the molecular sieve adsorber and the main heat exchanger have water or other faults, they must also be stopped for heating. The following describes several heating and thawing operation methods: