NOVELTY - The method involves comprising a swirl chamber (2) with a conical upper portion (8). A tangential inlet (6) is provided at bottom of swirl chamber, and an outlet (7) is provided at upper end of swirl chamber. A layer of feedstock particles is formed on wall (3) of conical upper portion of swirl chamber. The feedstock is converted into gaseous compounds in swirl chamber at elevated temperature. The conversion is performed in layer of feedstock particles on wall of conical upper portion of swirling chamber. A stream comprising the gaseous compounds is discharged through the outlet.    USE - Method for converting feedstock comprising solid carbonaceous particles into gaseous compounds in reactor.    ADVANTAGE - The control of residence time of feedstock particles is improved as a function of the particle size, and the control of residence time of gaseous products is improved, and the over-reaction and secondary cracking reactions are avoided. Gaseous compounds are rapidly separated from the particles and discharged from the chamber through the empty reaction space in the centre of the chamber.    DETAILED DESCRIPTION - The wall of the lower portion of the swirl chamber is provided with a second angle with the vertical that is smaller than the first angle. The ratio of the length of the lower portion and the length of the upper portion is below 1. The first angle with the vertical is in the range of from 10-60 degrees. The reactor is comprised of a conical insert contained in the swirl chamber, centrally located at the bottom of the swirl chamber and defining an annual flow path at the bottom of the swirl chamber. The ratio between the length and the largest diameter of the swirl chamber is in the range of from 2-8. The feedstock and the carrier gas are tangentially supplied to the swirl chamber through tangential inlet. The carbonaceous feedstock is paper sludge. The non-condensable gas separated from the stream is recycled to the swirl chamber as portion of the carrier gas. The catalyst particles are tangentially supplied to the swirl chamber through the inlet.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic cross-sectional view of a reactor.    Swirl chamber (2)    Wall (3)    Tangential inlet (6)    Outlet (7)    Conical upper portion (8)