This paper deals with experimentation of the unsteady-state fixed-bed reactor with flow reversal for SO2 conversion. A laboratory reactor with compensatory heating coils has been set up, resulting in 96-99% conversion for SO2 = 2.62-9.52 vol%, and u = 0.2 m/s. The results were from agreement with simulation of a really adiabatic unsteady-state reactor, but agreed well with modelling by considering the radial heat transfer. A three-stage pilot-scale converter has also been run with the M-typed temperature profile produced by heat loss from the chamber between stages. Good agreement was achieved with modelling by taking into account this feature. The results show that, while the adiabatic requirement is difficult to fulfill in the well-accepted experimental reactors, simulation and modelling are powerful means for compensation.