A process for thermally treating granular solid waste in an incinerator installation comprising i) a generally vertical riser pipe having an inside, an upper end, and a lower portion, ii) a vertically extending chamber adjacent to the riser pipe, having a lower portion, and containing a bed of granular material, and iii) a burner for producing an upwardly extending flame in the lower portion of the riser pipe and flue gas flowing upwardly in the riser pipe, said process comprising:
- a) supplying said bed with untreated granular solid waste;
- b) supplying granular solid waste and bed material from the lower portion of said chamber directly in the flame produced in the lower portion of the riser pipe;
- c) by means of the flame produced by the burner, burning the granular solid waste and heating the inside of the riser pipe;
- d) by means of the flue gas, pneumatically transporting the granular solid waste and bed material upwardly from the lower portion of the riser pipe to the upper end of said pipe so as to create turbulence in the riser pipe to thereby increase absorption of heat by the granular solid waste and oxidation of combustible components of the granular solid waste;
- e) discharging the granular solid waste and bed material in said chamber through the upper end of the riser pipe;
- and
- f) evacuating the flue gas from the incinerator installation.