<span style="font-size:14.0pt;line-height: 115%;font-family:"Times New Roman";mso-fareast-font-family:"Times New Roman"; color:black;mso-ansi-language:EN-IN;mso-fareast-language:EN-IN;mso-bidi-language: HI" lang="EN-IN">Studies on Bleaching of Alkoxygen Delignified Pulp of <i>Cajanus cajan</i></span>

Abstract

The proposed study was undertaken to assess the suitability of <i>Cajanus cajan</i>

using alkoxygen delignification process. Molecular oxygen is a specific oxidising agent for lignin but has limitations because of its low solubility in cooking liquors. The problem of mass transfer of oxygen should be far less than that of woods, because of more loose and open structure and low specific gravity of <i>Cajanus cajan, </i>makes it possible for dissolved oxygen to diffuse easily to accomplish the alkoxygen delignification. The effect of cooking variables like oxygen pressure (0, 0.5, O.S, 1.0 and 1.2 MPa), alkali charges ( 16,15 and 20 per cent as NaOH), cooking time (60,90,120,and 150 min) and cooking temperature (155,160, 165 ,and 170^oC) on pulp yield, kappa number and screen rejects were studied. The alkoxygen delignification of <i>Cajanus cajan</i>

led to significant increase in screened pulp yield, faster rate of delignification and substantial drop in kappa number due to carbohydrate stabilization. The res ults of these studies revealed that optimum process condition for alkoxygen delignification process of <i>Cajanus cajan </i>includes the following: Alkali charge = 18 per cent (as NaOH), Temperature = 165^oC, Time = 120 min and Oxygen

pressure =1.0 Mpa. The unbleached pulp of kappa number 30 and brightness 29.5 per cent, (Elrepho) shows good response towards bleaching. To attain stable and high brightness, the pulp was bleached with chlorine dioxide and oxygen. The properties of CEDED, and C(EO)DED bleached pulps were compared with CEHH bleached pulp.