Modeling and Simulation of Various Startup Scenarios of Compressors

Background: Dynamic simulation has been finding extensive application in modeling and simulation of various chemical processes. With the availability of high speed computers it has become customary to use Dynamic simulation to analyze various operating scenarios which not only include steady state scenarios but also dynamic situations like startup, planned shutdown and emergency shutdown. In this present work, various methods used to startup a compressor have been simulated. These scenarios were analyzed to find optimal power consumption and time requirements for startup of a model LNG compressor. This work gives some insight into how dynamic simulation can be used to evaluate different start up scenarios of a centrifugal compressor. Methods: We have modelled and simulated centrifugal compressor start up scenarios using Aspen Hysys and in each case made sure that compressor does not enter the surge region. We have compared the compressor power consumption in each scenario. Results: Based on the analysis of Dynamic Simulation we found that optimization of compressor power consumption is possible by studying different start up procedures. Conclusions: As shown in the above cases the compressor start up scenarios can be studied to optimize many parameters like power consumption, control valve opening time and discharge pressure variation. Out of the 3 cases studied with similar setup, the variable speed drive case with ASV being 60% initially and then reducing as the compressor starts, seems to consume lesser power and better discharge pressure. All these simulations exemplify the benefits of using dynamic simulation when designing and optimizing these kinds of systems. However, caution must be taken while selecting proper anti surge valve opening timings and compressor map characteristics.