The facility THERMOPROP is one element of the CTP, research center of the Common Center DR to ARMINES and MINES ParisTech, which is competent in the field of thermodynamics of fluid phase equilibria (VLE, VLLE, LLE, SLE, density, heat capacity, etc…) and determination of thermophysical properties. In our research group, two ways are applied: modeling (and simulation) and experimental work. Data are particularly important to define thermodynamic models, which will be used by engineers in charge of the design and development of new processes (for CO2 capture and transport), gas reservoirs modelling, etc... The new regulations regarding energetic and environmental aspects lead industry to get exactly accurate information on the physics and the chemistry of their systems and so to use more and more sophisticated models. In THERMOPROP, 4 equipments are available and described below for VLE measurements (solubility and bubble pressure), density and critical point.
Health and Safety
Strict laboratory policies are in place, in addition to general practices, for safe work practices in the CTP and so in the facility. The research group follows the recommendations of INRS (http://en.inrs.fr/) for experimental activities particularly with toxic fluids and the certifications of equipments and experimental procedures (particularly for H2S). Since 2002, the Centre is equipped with a high Safety laboratory (http://www.ctp.mines-paristech.fr/Recherche/Moyens/Laboratoire/). Moreover, the workshop of the CTP maintains the equipment in good working conditions.
(See picture 1.)
Picture of fume hood of THERMOPROP facility.
Measuring high-pressure gas solubility is not an easy task from a technical and safety point of view. For an accurate quantification of the different constituents using the different analytical methods, phase sampling is necessary. However, during sampling, disturbance of the thermodynamic equilibrium must be avoided, which is not easy due to the high pressure. Several techniques exist to minimize the disturbance of equilibrium during sampling or even circumvent this problem by using synthetic methods. A classification of high pressure phase equilibria measurement methods is given by Dohrn and coworkers.
Analytical methods: As indicated by its designation, these methods consist of the determination of phase equilibria with or without sampling, using analytical techniques such as chromatography, titration, volumetric and gravimetric methods, or Raman spectroscopy.
Synthetic methods: These methods consist of the determination of phase equilibria by material balance without phase change, or by visual or non-visual detection of phase change starting with a single-phase system.
(See picture 2.)
Classification of high-pressure phase equilibria measurement techniques.
Moreover, our high safety laboratory allowing the measurements of toxic fluids such as mercaptans, H2S, SO2, CO, NOx, etc… but also H2, CO2. The laboratory also develops its own software tools to check the reliability of data, using thermodynamic models like cubic Equations of State (EoS), PC SAFT EoS, Virial EoS, etc. The main topics addressed at the Centre include: CO2 capture and storage, gas processing, LNG, fluorinated compounds, energetic optimization and green chemistry. The Centre has also acquired knowledge about supercritical fluids and in the cryogenic field. For further details, please refer to our web site: http://www.ctp.mines-paristech.fr/Accueil/.
In 2018, we welcomed a PhD student from NTNU - Norway. She used our equipment and worked on phase diagram on system including amine solvent and H2S. The data were published in FPE journal: E Skylogianni, I Mundal, DDD Pinto, C Coquelet, HK Knuutila, Hydrogen sulfide solubility in 50 wt% and 70 wt% aqueous methyldiethanolamine at temperatures from 283 to 393 K and total pressures from 500 to 10000 kPa, Fluid Phase Equilibria, 2020, 112498.
Areas of research
The main areas of research include chemical engineering (thermophysical properties for design and operation of CCS process) but also underground storage (solubility of gas in brine and determination of thermophysical properties for design of gas reservoir. In chemical engineering, solvents and research of solvents are essential for the separation of chemicals. The methods of selection of solvent require the knowledge of thermophysical properties but they are also based on chemical engineering criterion like partition coefficient.
Installations
List of equipments available in the facility for the study of thermophysical properties in the context of CCS.
Gas solubility in brine
This apparatus developed within the framework of the ANR SIGARRR project (ANR-13-SEED-006) and improved in this work (especially on the analytical part: boosted TCD detector, addition of a pre-column to stop the salt) is described in detail in Chabab et al. 2019). It consists of an equilibrium cell positioned in an oven for temperature control, and equipped with pressure transducers, temperature probes and two ROLSI® (Rapid On-Line Sampler-Injector, French patent number 0304073) capillary samplers for each phase (liquid and vapor).
(See picture 3.)
Simplified schematic representation of the "static-analytic" apparatus for phase equilibria measurement.
After setting the temperature and charging the cell with the saline solution and the gas up to the desired pressure, the thermodynamic equilibrium is reached in some dozens of minutes after continuous agitation, assuming that the equilibrium is verified by the stabilization of the temperature and pressure in the cell. Several samples (for repeatability check) are then taken by the liquid ROLSI® and sent through a transfer line to GC to determine the mole fraction of gas and water. This last step depends on GC detector calibration, which is carried out under the same measurement conditions, to convert the areas obtained by integration of the chromatogram peaks into numbers of moles. Using the mole number of gas (๐๐๐๐ ) and H2O (๐๐ป2๐), the gas solubility in the saline solution in terms of “salt-free” mole fraction ๐ฅ๐๐๐ can be determined.
Densitometer
The Vibrating Tube Densitometer (VTD), Anton Paar DMA 512P is currently used to measure the densities. See picture 4, from Rivollet et al., presents a schematic diagram of the apparatus.
(Picture 4.)
Flow diagram of the equipment, from Rivollet et al.: 1, loading cell; 2a and 2b, regulating and shut-off valves; 3, DMA 512 P densitometer (Anton Paar); 4, heat exchanger; 5, bursting disk; 6, inlet and outlet of the temperature regulating fluid; 7a and 7b, regulating and shut-off valves; 8, pressure sensors maintained at constant temperature (373 K); 9, to vacuum pump; 10, vent; 11, vibrating cell temperature sensor; 12, HP 53131A unit; 13, HP 34970A unit; 14, bath temperature sensor; 15, liquid bath.
The main part of the setup is the U-shaped vibrating tube densitometer provided by Anton Paar. The specifications of the equipment are: pressure up to 140 MPa and temperature between 263 – 473 K. The tube material is made of Hastelloy. The temperature is controlled by fluid (silicon oil Kryo 20 from Lauda, Germany) that circulates in a jacket (small liquid bath) around the densitometer. The sample fluid is introduced from the gas reservoir into the densitometer through the tube. The whole connection tubes are fully immersed in the temperature controlled liquid bath. Four-wire 100-Ω platinum resistance probes (Pt100) (PP) measure the temperature at each part of the equipment. There are two thermostated pressure transducers (PT) to measure different levels of pressure. The pressure and the temperature were recorded using Agilent HP34970A data acquisition unit and the vibration period, τ, also was recorded using a HP53131A data acquisition unit.
PVT cell
The variable volume cell technique can be cited as a static-synthetic method. The components of the mixture are introduced separately and the composition is known by weighing procedure or after analysis. The volume of the cell is modified with a piston to study bubble points. At fixed temperature, saturating properties (pressure and saturated molar volume) of the mixture are determined through the pressure vs volume curve recorded that display a break point.
(See picture 5.)
Example of equipment which can be used for bubble point measurement. DAU: Data Acquisition Unit; DDD : Digital Displacement Display ; DT : Displacement Transducer ; GC : Gas Cylinder ; LB : Liquid Bath ; LVi: Loading Valve; P: Piston; PM: Piston Monitoring; PN : Pressurized Nitrogen ; PP : Platinum Probe ; PT: Pressure Transducer; PV (VP): Vacuum Pump; R: Gas Reservoir; SD: Stirring Device; SB: Stirring Bar; ST: Sapphire Tube; TR: Thermal Regulator; Vi: Valve; VVCM: Variable Volume Cell.
Critical point
The technique is based on dynamic-synthetic method where the mixture is circulating through the equilibrium cell under specific conditions of temperature and pressure. A critical point can be determined by visually observing the critical opalescence and the simultaneous disappearance and reappearance of the meniscus i.e. of the liquid-vapor interface from the middle of the view cell.
(See picture 6.)
Schematic diagram of the critical point measurement apparatus. DAU: Data Acquisition Unit ; FV: Flow Regulation Valve ; HE: Heat Exchanger ; MR: Magnetic Rode, O: Oven; PN: Pressurized Nitrogen; PP: Platinum Probe; PT: Pressure Transducer; ST: Sapphire Tube; SP: Syringe Pump; TR: Temperature Regulator; Vi: Valve; VVC: Variable Volume Cell; VP: Vacuum Pump; W: Waste.
In order to operate in good condition or to adapt the procedure to the characteristics of the system, the workshop team is available to modify the equipment in THERMOPROP.
(See picture 7.)
View of our workshop and mechanist.
State of the Art, uniqueness & specific advantages
We offer the following services:
• Design, commissioning of equipments (ex: in 2011 and in 2015, we sold two equipments to SINTEF in Norway) and training. Equipment can be realized according to specifications (with separate quotation).
• Determination of thermophysical properties: carrying out research work from A to Z: utilisation of equipment adapted to the measurement conditions (temperature, pressure and nature of the compounds), manufacturing or adaptation of existing equipment, definition of experimental procedure and measurement in compliance with safety conditions, data treatment and modelling. with a strong awareness of industrial issues.
• Lectures on measurement of thermophysical properties and fluid thermodynamics (see our MOOC: https://www.fun-mooc.fr/en/cours/thermodynamique-experimentale/about Title: «Thermodynamique expérimentale»)
• Training of technical staff of companies on the measurement of phase equilibrium properties
Scientific Environment
• Three scientific experts in the domain of CCS and the determination of thermophysical properties (experimental work and modelling).
• Two mechanists for equipment maintenance and design of new equipments
• Two technicians for measurement and definition of experimental procedure
• One engineer responsible of experimental platform and expert in measurement
In addition, some research team members have a first aid certificate.
