CO2: One-Component Two-Phase System as Model Fluid for High-Pressure Hydrocarbon Systems

In the process of performing either scientific experiments or research and development related to the design and optimization of high-pressure liquid-from-gas separator units, both laboratory experiments and tests in prototypes are needed. In order to emulate the low interfacial tensions often experienced in high-pressure hydrocarbon systems, the use of carbon dioxide (CO(2)) as model fluid is studied. This paper describes how the CO(2) system behaves at saturation conditions. It describes this system and compares it with traditional laboratory systems and real fluids (from the field). CO(2) at saturation pressure under normal temperatures presents an interesting system with low interfacial tension, below 3 mN/m, while the liquid/gas-density ratio is approximately 3. The availability of the fluid (CO(2)) in research centers and academia is high. When planning a matrix of experiments as part of a database of reproducible laboratory fluids, the present system is an independent base vector ideal for studying the high-Weber/low-Reynolds-number regime. This paper shows how a dispersed CO(2)-droplet phase, representative of a hydrocarbon-gas/condensate system, can be achieved in the laboratory and used for studying collision outcomes.. Results show that it is possible to obtain streams of droplets for droplet experiments. The mean diameter in the studied regime with the particular nozzle used was on the order of 100 rim, while the smallest droplets possible to track with the presented technique were approximately 40 rim. Droplet/wall-collision experiments were focused in this work. Both coalescence and bouncing were observed on both dry and wet walls. The absence of real fluid experiments at laboratory conditions generates a lack of basic knowledge about what is happening in real scrubbers. This system is proposed to be representative for a part of the flow-property region of interest in real gas/liquid scrubbers. This basic knowledge is fundamental when designing separation units at high pressures for gas-processing stages such as subsea gas-separation concepts.