Research On Gravimetric Method And Temperature Control System Of Gas-liquid Two-phase CO₂ Flow Facility

Aim to combat the worldwide climate change,Carbon Capture and Storage has been adopted to enrich,compress and transport CO₂ from industrial process to specific locations,and be injected into background reservoir for storage.Recently,pipelines transportation is the primary pattern to transport CO₂.The fact that temperature and pressure affect the properties of CO₂,together with the impurities introduced from pipelines transportation,have raised severe challenges to CO₂ flow measurement in Carbon Capture and Storage process.The flow measurement plays a significant role in CO₂ trade metrology,leakage detection and so on.The development of gas-liquid two-phase CO₂ flow facility is an important part of flow measurement and performance testing of flowmeters.Focusing on the problems of CO₂ flow measurement,the major researches were completed as follows in the paper.Firstly,gravimetric method acting as original standard is an important component of facility design.In the paper,two gravimetric methods were compared and studied based on the water standard facility in Tianjin University flow lab.The closed weighing system of the medium and high pressure gas-liquid two-phase CO₂ flow rig was developed.The standing start-stop method was adopted to deal with the problems of a sudden flow change and phase-shifting.The major factors impacting the uncertainty were analyzed and revised.The uncertainty of the weighing system is better than 0.06%（k=2）.Secondly,temperature is an important procedure parameter,which affects the properties and phase of CO₂.In the paper,temperature rise and heat transfer of the closed pipelines loop were analyzed.The key equipments,such as heater,insulating layer and chiller were reasonably selected to design the temperature control system.The cascade and fixed control mode were proposed and the PID and PWM control algorithm were adopted.The stability of temperature is better than 0.5℃per hour.Thirdly,a gas-liquid two-phase CO₂ flow rig was developed,which made the above two researches application and verification.The facility offers a range of liquid,gaseous or gas-liquid two-phase flow condition in horizontal and vertical pipeline to carry out experimental researches and testing.Furthermore,various flow regimes can be simulated and Coriolis mass flowmeters were tested on the rig.The pipeline design,pressure loss calculation and lectotype of safety valves were given in the paper.Meanwhile,the hardware and software were processed and the control system including pressure,temperature and flow were discussed.