scholarly journals Preparation and Performance of Supercritical Carbon Dioxide Thickener

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 78
Author(s):  
Bin Liu ◽  
Yanling Wang ◽  
Lei Liang
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Molecular Design ◽  
Simulation Method ◽  
Capillary Viscometer ◽  
Low Viscosity ◽  
New Ideas ◽  
And Performance ◽  
Core Displacement ◽  
Supercritical Carbon

The low sand-carrying problem caused by the low viscosity of supercritical carbon dioxide (SC–CO2) limits the development of supercritical CO2 fracturing technology. In this study, a molecular simulation method was used to design a fluorine-free solvent-free SC–CO2 thickener 1,3,5,7-tetramethylcyclotetrasiloxane (HBD). Simulations and experiments mutually confirm that HBD-1 and HBD-2 have excellent solubility in SC–CO2. The apparent viscosity of SC–CO2 after thickening was evaluated with a self-designed and assembled capillary viscometer. The results show that when the concentration of HBD-2 is 5 wt.% (305.15 K, 10 MPa), the viscosity of SC–CO2 increases to 4.48 mPa·s. Combined with the capillary viscometer and core displacement device, the low damage of SC–CO2 fracturing fluid to the formation was studied. This work solves the pollution problems of fluoropolymers and co-solvents to organisms and the environment and provides new ideas for the molecular design and research of SC–CO2 thickeners.

Effect of Turbulence and Flow Distortion on the Performance of Conical Diffusers Operating on Supercritical Carbon Dioxide

2013 ◽  
Author(s):  
A. López ◽  
B. Monje ◽  
D. Sánchez ◽  
R. Chacartegui ◽  
T. Sánchez
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Static Pressure ◽  
Pressure Rise ◽  
Working Fluid ◽  
Flow Distortion ◽  
Inlet Flow ◽  
Conical Diffuser ◽  
And Performance ◽  
Supercritical Carbon

A rapidly growing interest in the supercritical carbon dioxide power cycle has been observed in the last years due to the superb performance of this system in concentrated solar and nuclear applications; a sample of this interest is the number of technical publications submitted to Turbo Expo in the last couple of years. As active members of the supercritical carbon dioxide (SCO2) community, the authors of this work have lately studied the fundamentals of SCO2 flows. The approach followed has nevertheless been different to that of most researchers since it has concentrated on simple devices rather than on an entire turbomachinery. Thus, recent contributions by the authors have shown that major differences are to be expected when air and SCO2 diffuse through simple conical divergent ducts at subsonic speeds, most of which derive from the very different characteristics and performance of the boundary layer when adverse pressure gradients are faced. In particular, the effects of geometry (i.e. divergence angle) and aerodynamic blockage on the static pressure rise coefficient of such a conical diffuser have been reported by the authors in recent technical works. This work presents the effects of other aerodynamic features of the inlet flow to a conical diffuser on the capacity to convert kinetic energy into static pressure. Two flow features are studied: (i) the distortion of the inlet velocity distribution and (ii) the turbulence intensity of the inlet flow. A parallel analysis is developed for air and SCO2 showing that the effects of both distortion and turbulence on diffuser performance are sensitive to the working fluid of choice.

Preparation and Studies of Polymer/Polymer Composites Prepared Using Supercritical Carbon Dioxide

2004 ◽  
Author(s):  
Edward Kung ◽  
Alan J. Lesser
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Polymer Composites ◽  
Substrate Surface ◽  
Solid Polymer ◽  
Ambient Conditions ◽  
Swelling Agent ◽  
Low Viscosity ◽  
Supercritical Solution ◽  
Supercritical Carbon

Because of the recent emphasis on green chemistry, there has been interest in using supercritical carbon dioxide (sc CO2) as a solvent or swelling agent to aid in polymer processing and polymer chemistry (Adamsky and Beckman, 1994; DeSimone et al., 1992; Hayes and McCarthy, 1998; Kung et al., 1998; Mistele et al., 1996; Romack et al., 1995; Watkins and McCarthy, 1995). Supercritical CO2 is a very weak solvent for most polymers (some fluoropolymers and silicones are exceptions); however, it swells most polymers and dissolves many small molecules (Berens and Huvard, 1989). The density of a supercritical fluid (SCF), and thus its solvent strength, is continuously tunable as a function of temperature or pressure up to liquidlike values. This provides the ability to control the degree of swelling in a polymer as well as the partitioning of small-molecule penetrants between a swollen polymer phase and the fluid phase. The low viscosity and zero surface tension of SCFs allows for fast transfer of penetrants into swollen polymers. The lack of vapor/liquid coexistance in SCFs allows the sorption to proceed without the penetrant solution wetting the substrate surface. Since most of the common SCFs are gases at ambient conditions, the removal and recovery of the solvent from the final product is extremely facile. All of these factors aid in a new method we have developed for preparing polymer composites. This method involves the absorption of a supercritical solution of a monomer, initiator, and CO2 into a solid polymer substrate and subsequent thermal polymerization of the monomer to yield a composite system of the two polymers. We have focused on radical polymerization of styrene within various solid semicrystalline polymer substrates (Hayes and McCarthy, 1998; Kung et al., 1998; Watkins and McCarthy, 1995). Table 10.1 lists a number of systems that we have studied to make polymer–polystyrene composites. The method for preparing the polymer blends listed in Table 10.1 involves the soaking of the substrate polymer in a supercritical solution of styrene, a thermal radical initiator, and CO2 at a temperature where the initiator decomposes very slowly (half-lives of hundreds of hours).

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