Esther Loop. Operation, instrumentation and measurements of thermodynamic properties of sulphur

To improve the efficiency of thermal or nuclear power plants, Electricite de France (EDF) has considered introducing a sulfur cycle as a head cycle to replace the water vapour boiler, the sulfur cycle yielding its condensation heat to the already existing water cycle. A sulfur loop has been built at the CEA to: - verify the thermodynamic diagram of sulfur established during a theoretic study. - estimate the harshness of the chemical transformations that are established when expanding in a nozzle. - measure the thermal exchange coefficients between the walls and the boiling and steam sulfur. - check the corrosion of a tube internally coated with aluminum-titanium, under conditions of industrial use. The Esther experience (divided into two loops, one in liquid sulphur, the other in steam sulphur) is then presented and described. This experience is fully piloted by two multi-tasking microcomputers. The instrumentation used for temperature, pressure, level, flowrate is described as well as the calibrations of these various devices. An original method of calibrating the thyristors blocks used to supply the heating elements of the steam loop has been developed, allowing to know the power provided to each area of the coil by knowing the control voltage of each thyristors block. Various tests have been carried out, with a good agreement between the experimental results and theoretic calculation of the thermodynamic diagram of sulphur. Two methods of calculating exchange coefficients are proposed, one for a nucleated boiling, - the other for a liquid film boiling. (author)