STEAM EXPLOSION PULPING OF INDIAN NONWOOD FIBRES

摘要

There is an increasing trend in Indian paper based biorefinery industries for efficient utilization of its abundantly available nonwood and especially annual renewable resources, mainly for two purposes, for developing a balanced ecosystem and at the same time to meet its paper and paper products using eco-friendly technology. Interests is also being explored to produce value added chemicals and low cost biofuels. Steam explosion technology is one of the innovative processes to achieve the above objectives. An attempt has been made to produce Steam Explosion Pulp from pre-impregnated Indian sugarcane bagasse(CO variety), rice straw and bamboo(Bambusa Dendrocalamus Strictus) cooked for 2 minutes at 463K (1.26 M Pa saturated steam pressure) using reactor designed by Stake Technology, Canada with varying sodium sulphite chemical charge as primary impregnating chemical, with or without the presence of secondary chemicals and some additional swelling agents. For the sake of comparison all the three species are impregnated at the same conditions of time and chemical charge and also cooked at the same conditions and then explosively decompressed and discharged. Explosion pulp properties were evaluated for all the species obtained from a variety of conditions. As many variables are involved in the above investigation a planned statistical experimental design is used to identify selective number of experimentsMore detailed experimental investigations for bamboo, bagasse and straw were also carried out for finding out the optimum operational conditions. However for yield comparison purposes, change of pH and chemicals were studied. As bagasse and rice straw are radically different in terms of their structural openness compared to bamboo(even though all are non-wood species), the optimum conditions as expected are found to be quite different, bamboo required much more drastic impregnation and protracted time with severe chemical treatment and for the improved pulp quality the most effective pulping agents were either purely caustic soda at higher level of charge or an optimum mixture of sodium sulphite and alkali. Loss of pulp yield has been found in all species with treatment of NaOH. Total ionic content of bagasse and bamboo are comparable, being higher than straw.The optical properties of unbleached pulp are acceptable atleast for manufacture of newsprint grade pulp. Combination of sodium sulphite with low percentage of soda may be a compromise between loss of pulp yield and gain in strength properties for bamboo. Drainage characteristics of bamboo pulp are found to be much more superior to those of bagasse or straw pulp. From the detailed study, it is found that the exploded pulp is susceptible to changes in pH, the treatment of chemicals, the nature of chemicals and the concentration.The waste liquor obtained after steam explosion were analyzed and evaluated for its pollution potential.