Disadvantages Of Pulping

Pulping is a various processes by which wood or other fibrous feedstocks convert into a product mass with liberated fibers. These thermal conversions can be accomplished both chemically or mechanically, or by combining the two treatments. Although pulps are predominantly utilized for papermaking industry, some pulps are processed in various cellulose derivatives and regenerated celluloses.
Chemical pulping can be described as a method to remove lignin (delignification) from wood using chemical solution and through chemical degradation. This method also has the objective of minimizing damage to the cellulose of the wood and thus maintain the pulp strength properties. This method separated fibers by dissolving away lignin component, maintain

The main reason for the dominance of the kraft process, compared to other processes, is excellent pulp strength properties, low demand on wood species and wood quality, well-established recovery of cooking chemicals, energy, and by-products, and short cooking time. In this process, wood chips are cooked with sufficient chemicals in an aqueous solution at adequate temperature and pressure, in order to remove and dissolve away the lignin component and maintain most of the celluloses and hemicelluloses. In the conventional kraft pulping, cooking liquor called white liquor, containing mainly the active cooking chemicals of sodium sulfide (Na2S) and sodium hydroxide (NaOH), is used for cooking the wood chips. As a large amount of sodium hydroxides is used, the pH value in the initial cooking process is alkaline (about 13 to 14), and will decrease continuously during the cooking process resulted from the liberation of organic acids from lignin and carbohydrates along the pulping process. After the adequate cooking process, the spent cooking liquor called black liquor is separated from the pulp by washing. The separated black liquor is then concentrated to increase the solid content by the multiple-effect evaporators and then combusted in the recovery furnace to recover the cooking chemicals and also to generate

Dissolving pulp (DP) is used as a material for viscose rayon, cellophane, chemical additives and other cellulose derivatives. Use of dissolving pulp depends on its purity (cellulose content), which depend mainly on the production process. It requires a high quality with a pure degree (more than 90%) of -cellulose, a relatively low content of hemicellulose and an extremely low content (less than 0.05%) of lignin. To obtain products of high quality, removing hemicellulosed from the wood fiber is crucial. Several methods have been developed for producing dissolving