Designing Automatic Control System Base On ITCC For The LNG Refrigerant Compressor

The refrigeration cycle is used to liquefy natural gas. In the refrigeration cycle mixed refrigerant is compressed and cooled down to obtain low temperature. After that the natural gas is liquefied through the evaporation of the refrigerant. Throughout the liquefaction process, the refrigerant compressor which increases the pressure of mixed refrigerant is the core device of the refrigeration cycle. The long-term operation of the entire liquefaction process is based on the safety and stable running of refrigerant compressor. so the design of a set of high reliability compressor instrumentation and control system with a high level of security is particularly important.In this thesis, a refrigerant compressor which is running in a plant is the object of study; the thesis shows the design of compressor instrumentation & control system in the following topics.(1) To give the idea of steam turbine, dry gas seal, oil system, cooling separation system in centrifugal compressor train and explain the key point of centrifugal compressor train control and research targets.(2) According to the research targets, the thesis shows the cause and harm of compressor surge. A practical anti-surge control system and anti-surge control thinking are finalized. At the same time, the performance tuning is studied in depth to match require of the liquefaction process.(3) According to the characteristics of the refrigerant compressor train, to select the local instruments (sensors) and final elements.(4) As to the control requirements and design principles of the compressor,to design a control system based on the ITCC (Integrated Turbine & Compressor Control) concept, to indicate the control system network architecture, hardware, software, screen, etc., to complete the logic of permissive start, turbine speed-up, common alarm and emergency shutdown.The development of the LNG refrigerant compressor automation control system based on the ITCC control concept comes from the actual project. Through above content of research, the design of an advanced and reasonable instrument & control system was completed, the control system programming and debugging was carried out. Finally the end user approve the result of development.The result of development is a guarantee of compressor stable running in site, at the meantime it is also a good compressor reference and engineering practice for other foreign LNG project in the future.