SOLVENT PULPING OF BAGASSE -A PROCESS AND SYSTEM CONCEPT

摘要

Bagasse is increasingly becoming an important raw material for the pulp and paper industry in the wood deficient tropical countries. The world-wide availability is estimated to be more than 37.5 million tons per year which is equivalent to 10 million tons of pulp. The traditional pulping process has been, and continues to be, soda (or kraft). The process and system is expensive, its viability is questionable Therefore, despite availability of bagasse in large quantities, countries like Brazil and Australia are reluctant to use bagasse for pulping in any significant amount. These countries prefer to use pulp wood from planted forests. Bagasse is gaining popularity as a paper making material for all grades of paper. China, Cuba, Egypt, India and Iran look upon bagasse as the main raw material. A comparison has been made between solvent pulping of bagasse with soda and alkaline sulphite process. An analysis of the different pulping processes from a holistic point of view, using a pulping process evaluation, matrix, where the criteria like yield, power and heat consumption, chemical cost, water pollution, capital cost per ton and size of investment, are considered. Ethylene glycol which has a boiling point of 190°C under atmospheric pressure is proposed as pulping agent. The equipment for performing the process has been adapted from the beet sugar industry by modifying the feeding system. A system is proposed for regeneration of ethylene glycol for reuse while producing lignin for sale. The mixed acids from the hemicellulose is treated anaerobically to produce methane which will generate electricity by a gas turbine and produce process steam for the process. A basic flowsheet for the pulping system and a block diagram for the regeneration system is presented. As a proof of the concept laboratory trials are being conducted by two post graduate students in two universities in Sweden. Results will be presented by the end of this year. Technical feasibility study along with financial viability ol the system will be conducted with an aim to erect a pilot plant.