This article presents a modular open chamber stand which simulates the densification process that occurs in a single channel of a pelletising die. The results of the verification tests confirmed the suitability of this stand for determining the optimal geometry of the channel. The test material was the biomass of Miscanthus x giganteus which is considered to be a difficult material for pressure densification; therefore, it was decided that it would be a good material for verifying the stand. The stand consists of four modules: an introductory section with a diameter of D = 12 and 10 mm, a conical part with an angle of alpha = 10 degrees, 20 degrees, 30 degrees, 40 degrees, a cylindrical part with lengths L = 5, 15, 25, 35, 45 mm and diameter d= 8 mm and a pellet receiving module. The stand is able to heat the densification channel. Individual modules can be assembled into test combinations; this results in a change in channel geometry without the necessity to manufacture many singular channels. The optimum geometry of the channel for miscanthus with a moisture content of 13%, densified at 100 degrees C was determined. It should be a channel with D = 10 mm, alpha = 40 degrees and L = 18 mm.