A supercritical carbon dioxide phase balance instrument and its application method

Abstract

The invention discloses a supercritical carbon dioxide phase balancing apparatus. The supercritical carbon dioxide phase balancing apparatus comprises a phase balance measuring device, a carbon dioxide gas source, a first middle container, a storage tank, a balance, a second middle container, a six-way valve, a water storage tank, a pump, a first pressure meter, a second pressure meter, a third pressure meter, a fourth pressure meter and a safety valve. The invention also discloses a use method of the supercritical carbon dioxide phase balancing apparatus. The phase behavior and the density of a system are evaluated by adopting a cloud point pressure curve technology, so the influence of polymer swelling on an experiment result in the extraction technology measurement process is avoided. Carbon dioxide or a liquid to be detected is continuously added through the middle containers under a constant pressure at a constant temperature in the experiment process to realize continuous determination of the phase behavior and the density of same components and various ratios and avoid measurement result inaccuracy caused by repeated dismounting of devices and measurement condition disunity caused by addition of a medium to be measured of routine measurement methods.

Description

technical field [0001] The invention relates to the technical field of fluid phase balance measurement, in particular to a supercritical carbon dioxide phase balance instrument and a method for using the same. Background technique [0002] Supercritical fluid refers to the fluid at a state higher than the critical temperature and critical pressure. Supercritical fluid has the characteristics of low viscosity and easy diffusion of gas, high density and easy dissolution of liquid. Among the common gases, the critical temperature (31.1°C) and critical pressure (7.38MPa) of carbon dioxide are moderate, and it is easy to reach the supercritical state in actual production, and has the advantages of non-toxicity and low price, so that supercritical carbon dioxide is widely used in Extraction materials, desiccants, cleaning agents, oil extraction, etc. [0003] Since carbon dioxide is a non-polar molecule with a low dielectric constant, its carbon-oxygen double bond length is only ...

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Problems solved by technology

Both literature (Journal of Jiangnan University, 2006, 5, 92-95) and literature (Petrochemical Industry, 2013, 42, 303-307) have reported the use of visible phase reactors for supercritical carbon dioxide phase behavior research. This device is The volume of the visible kettle is changed by manually rotating the piston, so as to obtain the cloud point pressure. This method has the following problems: first, the experiment is carried out by manually rotating the piston. Once the pressure is greater than 10MPa, the rotation of the piston will be very difficult. Time-consuming and labor-intensive; secondly, the visible window area of ​​the equipment is large, and the highest pressure it can withstand cannot exceed 20MPa. Once the pressure is higher than 20MPa, the sealing of the device will be difficult to guarantee, and the underground pressure of the oilfield site is often as high as 40-50MPa ; Again, this method can only measure the cloud point pressure under a kind of proportioning once in an experiment, can't operate continuously; The 4th, the requirement to the supercritical carbon dioxide system density of oil field is higher, this method can't get the density of the system

Therefore, the existing technology is difficult to meet the needs of oilfield field application

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