The story began in 1985; the first report presenting the application of first patented model was published in 1986: S. Laugier, D. Richon. New apparatus to perform fast determinations of mixture vapor-liquid equilibria up to 10 MPa and 423 K. Rev. Sci. Instrum., 57, 469-472 (1986).

 

Continuous improvment has been achieved all along the series of ROLSI and all of their modifications.

This model was developed to perform VLE measurements in a large range of temperatures and pressures. The main purposes were:

1. to extract representative samples of small sizes (less than 1 mg) not to disturb studied equilibria and consistent with GC analyses.
2. not to disturb thermal equilibrium inside equilibrium cell which can be operated at low temperatures while liquid samples need high temperatures to be vaporized.

The successful use of this instrument allowed publishing several new accurate data in international journals with peer- reviewing.

We see on the left picture the two stems allowing sealing of the two capillaries through strong springs.
Expansion chambers are heated, for convenient vaporization of liquid samples, through a wounded heating resistance. To take samples the masses, visible on the right part of the photo, are manually moved quickly to achieve a shock displacing slightly the stems and consequently allowing samplings. Just above, we see a photo of the sampling system connected to an equilibrium cell.

The picture on the left corresponds to another design of the ROLSI I sampler.

The main problem with the ROLSI I versions is that the size of withdrawn samples highly depends on how the masses are handled by operators.

The Rolsi II was designed to make easier the samplings by using levers that can be moved within two ajustable stopping bounds. Sealing is still achieved though stems pushed against capillaries with strong springs.

ROLSI ™ III is major improvement allowing monitoring through compressed air. This latter acts on the bellows to push the stem against the capillary achieving perfect sealing.

By reducing pressure of compressed air, the bellows moves back allowing opening of capillary and flowing of sample into expansion chamber. Samples sizes are easily adjusted through the stroke of the belows controlled by one differential screw, and by time of reduction of compressed air pressure, controlled by accurate timers.

Two ROLSI ™ III valves, have been used at the university of Karlsruhe to withdraw samples from an equilibrium cell working with supercritical water (operationg conditions of the two ROLSI™ III valves were 100 MPa and 873 K).

However ROLSI™ III valves have important drawback concerning safety conditions: if pressurizing circuit fails, the ROLSI ™ III valve opens. This is why we decided to work on the next ROLSI™ generation, an electromagnetic one, which is normally closed if not powered.

ROLSI™ IV (see www.rolsi.com) is the last generation developed by TEP. However, we are already working on a modified version of ROLSI™ IV that will allow withdrawing samples at high pressures (up to 140 MPa and high temperatures (up to 800 K) for various components that can be corrosive and/or toxic.

Currently, ROLSI™ IV can be used up to 530 K and 60 MPa when samples are free of water. When samples are water containing, the operating limits are reduced to 480 K and 20 MPa.

This picture on the right is internal representation of electromagnetic ROLSI™ IV

Besides broad applications of ROLSI samplers for VLE, VLLE and also SLE and SLVE measurements, it has been used as injector-atomizer (V. De Stefani, A. Baba-Ahmed, D.Richon, Experimental determination of carbon dioxide and nitrous oxide co-solubility in liquid oxygen. Fluid Phase Equilib., 207, 131-142, (2003)) and is under development for being connected online to mass spectrometers.

ROLSI samplers have been already sold in 15 countries.