Analysis Of Dynamic Properties And Seismic Responses Of Air Separation Plant Rectification Box

Air Separation Plant is the key plant for industry gas production. Rectification Box is the core part of Air Separation Plant. So it is very important to make sure Rectification Box to be safe under design. But because it is complicated inside Rectification Box structure, the dynamic properties of Rectification Box need to be study carefully. On the project normally we use approximate formula estimation for natural period of vibration and equivalent base shear methodfor calculation of Rectification Box seismic loads. But there is no further study about whether approximate formula estimation for natural period of vibration is accurate, whether equivalent base shear method is reliable or whether the perlite influence to the Rectification Box dynamic properties can be ignored.This article use FEA software and real project to do typical Rectification box seismic analysis. Try to answer above questions. The main contents include following aspects:(1) Introduce basic loads which act on Rectification box, especially lateral pressure on Rectification box due to perlite load.(2)Use FEA software ANSYSto build the Rectification box model. Consider perlite loads and stiffness in the model. Because Rectification box include Rectification column, it is different from normal silo. Use incircle to get the perlite loads act on the Rectification Box. Use spring element to model perlite stiffnessinANSYSand get the finite element model of Rectification box.(3)Do Model analysis for coldbox structure, rectification column, and the whole coldbox.Get vibration mode numbers while the modal participation mass coefficient reaches90%. And study the influence of perlite stiffness to the Rectification box natural vibration frequency. The results show that approximate formula estimation for natural period of vibration is similar to FEA result and perlite stiffness influence to the Rectification Box dynamic properties can’t be ignored.(4) Select the area of seismic precautionary intensity8degree, design basic acceleration of ground motion0.2g, site-class2. Use equivalent base shear method, response spectrum analysis and time history analysis to get the base shear and structure displacement. The results show that because the first mode shape is not control shape, it is not meet the requirement of equivalent base shear method. If we want to use equivalent base shear method, we must consider ajusted factor. According to the results of Rectification Box FE analysis, give the opinions and suggestions of Rectification Box dynamic properties calculation and seismic response calculation.