Cécile Lemaitre

Degradation (or Lack Thereof) and Drag Reduction of HPAM Solutions During Transport in Turbulent Flow in Pipelines

Rules of thumb that are used in the industry for polymer-flooding projects tend to limit the distance over which hydrolyzed poly-acrylamide polymers can be transported in pipelines without under-going significant degradation. However, in sensitive environments, such as offshore facilities where footprint minimization is required, centralization of the polymer-hydration process and long-distance transport may be desirable. More-reliable rules are required to de-sign the pipe network and to estimate mechanical degradation of polymers during transport in turbulent conditions.In this work, we present evidence in the form of empirical large-scale pipeline experiments and theoretical development refuting the claim that polymer pipeline transport is limited by mechanical degradation. Our work concludes that mechanical degradation oc-curs at a critical velocity, which increases as a function of pipe di-ameter. Provided the critical velocity is not reached in a given pipe, there is no limit to the distance over which polymer solution can be transported. In addition, the drag reduction of viscous polymer solutions was measured as a function of pipe length, pipe diameter, fluid ve-locity, and polymer concentration. An envelope was defined to fix the minimum and maximum drag reductions expected for a given velocity in larger pipes. For pipes with diameters varying between 14 and 22 in. at a velocity greater than 1 m/s, the drag-reduction percentage is anticipated to be between 55 and 80%. A more- refined model was developed to predict drag reduction with less uncertainty. In conclusion, classical design rules applied for water transport (fluid velocity < 3 m/s) can be applied to the design of a polymer network. Therefore, for tertiary polymer projects, the existing water-injection network should be compatible with the mechanical requirements of polymer transportation. For secondary polymer projects, changing the rules of design by taking into account the high level of drag reduction should bring some economy to the pipe design and installation

Experimental and thermodynamic comparison of the separation of CO 2 /toluene and CO 2 /tetralin mixtures in the process of organogel supercritical drying for aerogels production

An organogel is firstly prepared by synthesizing an aminoacid-type organogelator which is able to immobilize aromatic solvents, such as tetralin or toluene. Aerogels are obtained from organogels by extracting the solvent with a stream of supercritical CO2 in an autoclave. The CO2/solvent mixture leaving the autoclave is separated in a cascade of three cyclone separators. The experimental results showed a good solvent recovery rate in the case of tetralin, exceeding 90%, but an unsatisfactory separation for toluene with a yield below 65%. A thermodynamic study was carried out to model the separation for both solvents. The Peng–Robinson equation of state with van der Waals mixing rules and temperature-dependent binary interaction coefficients was selected to predict the CO2/solvent thermodynamic behavior. Measurements of isothermal bubble points of the CO2/tetralin system were conducted using a high-pressure variable-volume visual cell confirming the relevancy of this model. Then, the first separator was simulated as a simple theoretical equilibrium stage. Simulations using PRO/II software were in good agreement with experimental solvent recovery rate for both toluene and tetralin. The best operating pressure and temperature for the separation were computed by a numerical parametric study.Graphical abstractThermodynamic study to explain theoretical recovery in organogel supercritical drying: comparison between two solvents (T=20 °C, P=50 bar).