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在二氧化氯漂白中,弱碱(如氢氧化镁)是一种较好的pH控制替代品,它可以在整个漂白过程中,保持pH变化相对平缓。实验结果表明,由于氢氧化镁的缓冲效应,所以从浆料白度和黏度看,二氧化氯增白段采用氢氧化镁替代氢氧化钠来控制pH,可以提升二氧化氯的效能。在一段二氧化氯增白段(D_1)采用氢氧化镁作为pH控制剂,可以在相同二氧化氯用量的情况下获得更高的浆料白度,或者在给定成品漂白浆目标白度下,减少二氧化氯用量高达30%。当D_1段的pH控制剂氢氧化钠采用氢氧化镁替代时,D_1段浆料和最终漂白浆的黏度都较高。氢氧化镁用于二段二氧化氯增白段(D_2),也可以类似地改善浆料白度和黏度。氢氧化镁的缓冲效应可以减少二氧化氯增白段常常遇到的二氧化氯碱性分解现象,进而减少了氯酸盐和亚氯酸盐的形成。结果,使用氢氧化镁的二氧化氯增白工艺的漂白效率得以改善。使用氢氧化镁的另外一种好处是漂白车间水系统中的Mg~(2+)增多,进而减少草酸类结垢现象。
In chlorine dioxide bleaching, a weak base, such as magnesium hydroxide, is a good pH control alternative that maintains a relatively gentle pH change throughout the bleaching process. The experimental results show that due to the buffering effect of magnesium hydroxide, from the whiteness and viscosity of the slurry, the use of magnesium hydroxide instead of sodium hydroxide to control pH in the whitening stage of chlorine dioxide can improve the chlorine dioxide performance. In a chlorine dioxide brightening section (D_1) using magnesium hydroxide as a pH control agent, the same amount of chlorine dioxide can be used to obtain a higher slurry whiteness, or bleach pulp in a given target target whiteness , Reduce the amount of chlorine dioxide up to 30%. When the pH control agent in the D 1 section was replaced with magnesium hydroxide, the viscosity of the D 1 section slurry and the final bleached pulp were both higher. Magnesium hydroxide for the second phase of chlorine dioxide whitening (D_2), can also be similar to improve the whiteness and viscosity of the slurry. The buffering effect of magnesium hydroxide can reduce the alkaline decomposition of chlorine dioxide, which is often encountered in the chlorine dioxide whitening stage, thus reducing the formation of chlorate and chlorite. As a result, the bleaching efficiency of the chlorine dioxide whitening process using magnesium hydroxide is improved. An additional benefit of using magnesium hydroxide is the increased Mg 2+ content in the bleaching plant water system, which in turn reduces oxalate scaling.