FIELD: chemical industry. SUBSTANCE: present invention describes reactor and method of whitening highly consistent cellulose which are intended for producing high quality uniformly whitened cellulose. In reactor highly consistent cellulose is whitened with gaseous whitening ozone containing mixture to increase degree of whiteness of cellulose from first degree GE to second higher degree GE. Cellulose particles and gaseous whitening mixture are mixed in first step with great shear forces for mixing and contacting cellulose particles with gaseous whitening mixture to react some cellulose particles with first step gaseous whitening mixture. Cellulose particles react with unreacted ozone in second retaining step for further uptake of ozone from gaseous whitening mixture and for preparing whitened cellulose having second whiteness degree GE. All of available ozone from gaseous whitening mixture is substantially desorbed. EFFECT: more efficient whitening method. 27 cl, 18 dwg , 3 ex, 2 tbl
