Automatic Switch Design And Optimum Control Of The Molecular Sieve Purifiers In Air Separate Unit

In most purification systems, the molecular sieve purifiers are always equipped in the cryogenic air separation process. The stability and the safety of the air separation unit both depend on them. Therefore, the switch control of the purifiers is critical to the operation of the large-scale air separate unit. And the switch is the reason to the flow instability. The switch quality directly decides the stability, efficiency of the air separation unit, and it even decides the output of the liquid argon. In that case, it is significant to study the purifier switch control.With the popularity and the development of the molecular sieve purification process, different companies adopt different switch control strategies, such as curve control or PID control on pressure change to narrow the fluctuation during the switch, enhance the system stability, decrease the energy cost and reduce the working intensity.Besides studying the network attributes and hardware features of the IA series control system, the thesis further analyzes the process, switching procedures and the condition of the purification system.Meanwhile, it also analyzes the ICC sequential control and parameter function with the research on ICC program software features, compound structure and integrated control block parameters. With the help of all the above mentioned study, the author designs the molecular sieve automatic switch program, its subroutine and the control program based on ICC programming software.Moreover, the paper studies the optimum control on the pressurization which is the biggest disturbance factor during the purifier switching process, and analyzes the reason to air flow fluctuation after the molecular sieve purifiers during the pressurization by combining the programming. The paper also presents a new control model by analyzing the shortcoming of the original one and builds up the flow change model to solve the unmeasurable flow problem through balancing valve in the pressurization process. At the end of the paper, the established model is tested with right data and improves the validity of the model by introducing the relative compensation.