nozzle 18 and is subsequently subjected to the sucking action of a further means 19 or intaking lip tube so that on said cloth 14 a determined amount of chlorinated solvent remains the woolen cloth 14 moist with solvent subsequently travels on a further set of rollers 10 and enters through an opening provided with seal elements 20 the second processing chamber 12 in which a desired and predetermined amount of aqueous solution of sulphuric acid is applied by means of nozzles 21 the woolen cloth 14 thus impregnated by the resulting mixture of chlorinated solvent and of acidic aqueous solution passes through a further opening provided with seal elements 22 and enters third chamber 13 where the cloth travels slidingly guided on a further set of rollers 10 the third chamber 13 being i e the thermal treatment chamber inside third chamber 13 the drying and the true carbonization of the cloth take place by means of the evaporation of the above said mixture and the carbonization of the vegetable impurities due to the combined effect both of temperature and of the residual sulphuric acid finally the woolen cloth 14 passing through a last opening provided with seal elements 23 is extracted in a dry and carbonized state from the third chamber 13 preferably inside said third chamber 13 a means is provided to accomplish a closed loop circulation of hot air e g by a thermo fan 24 which is provided with a delivery duct 25.