| Nowadays with the development of natural gas industry,its proportion in the energy market is expanding every year.Liquefied natural gas(LNG)known as natural gas in liquid formation wins the reputation of updated energy with cleanliness,efficiency and low pollution.With the increasing burden of environment pollution,in order to improve air quality,optimize the structure of energy,realize strategy of economic development,enhance people living standard and satisfy social development,it’s very necessary and having important strategic meaning to develop LNG technology.The core section of producing LNG is the process liquefaction,which directly affects the efficiency of LNG plant production.Cooling capacity for Natural gas liquefaction is provided from outside cooling circle,the function of which is by increasing pressure and cooling down the mixed refrigerants to obtain the refrigerant mass to liquidize natural gas when it’s evaporating.In the whole process,the refrigerant compressor as the core device is operated for increasing the refrigerant pressure.Because of it’s the basis of long-term safe operation of the liquefaction process,Therefore,it is particularly important to design a compressor control system with high reliability and security.In this thesis,the refrigerant compressor unit used in a chemical plant is set an example as the research object to study its model selection,design,logic control of field instruments,and control system.Based on the CCS(Compressor Control System)control concept,and Tricon control system produced by Triconex company,the thesis provides possible hardware configuration and software development environment,and realizes the logic control of LNG compressor under a simple,clear operation condition,including:steam turbine gear turning logic,compressor start permissive logic,steam turbine speeding up logic,compressor common alarm logic,interlock logic,shutdown Logic.The thesis also provides the solution for compressor control logic and anti-surge logic.The main purpose of the thesis aims at optimizing the control program and control logic to achieve safety,stability,high efficiency and energy saving for the compressor.The project studied in this thesis is actually put into production.The feedback indicates that all the measured figures meet the requirements under stable operating.The control system enhances the unit working efficiency and saves energy,meantime improves quality of the products with less maintenance and guarantees smooth operating to ensure the plant’s profit growing. |
