Strength Calculation And Stability Analysis Of Venting And Flare Stack System In Natural Gas Processing Plant

With the further development and utilization of natural gas, there are an increasing number of natural gas processing plants. Venting and flare stack system is an indispensable facility of natural gas processing plants. Since this system endures excessive impact load during the venting process, accidents such as the structure failure of vent pipe and the collapse of flare may happen. It must be guaranteed that the production units do not have any problems during the venting process. Therefore, it is necessary to analyze the pipe strap arrangement of the venting and flare stack system accurately; conduct the transient dynamic analysis under the circumstance of whole plant emergency shutdown in order to get the displacement and stress results of the vent pipes; and conduct stability analysis on the flare.This thesis sets the venting and flare stack system of the fourth natural gas processing plant in sulige gas-field as the research object. The finite element model of venting and flare stack system is established at first, including the compressor area, deoiling and dewatering area, gas gathering area and flare area. Meanwhile, the pressure drop and velocity of vent pipes under three conditions are calculated and the exciting force at bend and tee are obtained from this. Then, the static stress analytical calculations are conducted on the venting and flares stack system under the circumstance of whole plant emergency shutdown with three projects of pipe strap arrangement and determine the projects of pipe strap arrangement according to the displacement and stress results. After that, the models are modified based on the projects of pipe strap arrangement and the dynamic simulation analysis is conducted on the venting and flare stack system under three conditions, and then the rationality of the projects of pipe strap arrangement is determined based on the results. Besides, modal analysis is conducted on the flare area of the venting and flare stack system and the natural frequency and corresponding modal shape of its first three orders are extracted for fear of resonance. At last, the energy method and finite element method are used to analyze the critical conditions of the flare failure and the result shows that internal pressure decreases the stability of flare, while external pressure enhances the stability of flare. Meanwhile, the relationship between the stability of elevated venting flare and wall thickness are explored.