| 摘要 |
The removal of bleaching chemical-consuming metals from treatment fluids in a cellulose pulp mill is facilitated by treating the pulp in an acidic or neutral stage to dissolve metals, washing or thickening the pulp to produce a filtrate containing dissolved metals, and then using an alkali liquid to adjust the pH of the filtrate to cause dissolved metals to precipitate. The alkali liquid is pretreated with carbon dioxide to reduce the sulfide content and increase the carbonate content thereof, preferred alkali liquids being green liquor and white liquor. The reduced-metal content filtrate is used in the bleach plant of the pulp mill, to make bleaching chemicals, as a wash liquid, etc. Treatment of the alkali liquid with carbon dioxide is typically practised dy scrubbing the liquor with carbon dioxide gas, for example, using a plate column scrubber or a stationary packing scrubber. |
