Stable And Dynamic Simulation Of Rectification Column Iminating Oxygen And Nitrogen And Intelligent Control In LCBG Equipment

Natural gas is a kind of clean and high-quality fuel with incomparable predominance over other kinds of energy sources when it comes to environmental protection, combustion efficiency and so forth. Therefore, natural has bright prospects. The pivotal techniques for exploiture of natural gas are how to store and transport it conveniently and safely. LNG (liquefied natural gas) has much advantage with respect to storage and transportation. So the technology of liquefying natural gas becomes a research focus at present.CBG (coal bed gas) is one of main sources of natural gas. One way with a good future and important sense in coal safety to exploit CBG is liquefying, storing and transporting it by means of liquefaction technology of natural gas. With the project of LCBG (liquefied coal bed gas) as the background and the oxygen and nitrogen wash rectifying column in cold box as the research plant, this paper does the following work:1. Calculation of physical properties is the foundation of process simulation, the key part in the process simulation. This paper gives a detailed discussion of how to calculate the involved primary physical properties, phase equilibrium constant and multi-component enthalpy ready for following calculation.2. This paper does research on the steady-state work mode of the oxygen and nitrogen wash rectifying column in cold box and its dynamic work mode and then establishes the corresponding mathematical models to describe several questions related to heat transfer and mass transfer. The steady-state part of the models realizes Thiele-Geddes iterative algorithm by using C program language, calculates the temperature and the composition each equilibrium stage。The dynamic part of the models was solved by using MATLAB program language and provided integral solution function, gives an detailed account of how the bottom product of rectifying column reaches the requirements of component separation on the condition that the bottom liquid-level keeps stable and of how the holdup in ordinary tray and bottom tray space exerts influence on the time needed for separation.3. The bottom liquid-level of the rectifying column is of much impact on the normal of work of the rectifying column. However, it is difficult to work out an exact mathematically model for the bottom liquid-level, which justifies the unsatisfactory results of regular control methods based on modeling. The fuzzy control method is a new intelligent control method. It is of much inborn superiority to control those plants which cannot be exactly mathematically modeled. As a result, this paper designs a fuzzy controller to control the bottom liquid-level of the rectifying column. The results of simulation based on the fuzzy control toolbox of MATLAB show that this control scheme can make good accomplishment.