DEVELOPMENT AND PROSPECTS FOR DRYING BAGASSE BY STEAM

摘要

Drying of bagasse offers the advantage of an increase in calorific value and an improvement in boiler efficiency. Recovery of steam from the dryer for process heating increases the availability of bagasse as a fuel for cogeneration. A comparison of the impacts on the overall energy demand of a cane sugar plant employing flue gas drying and steam drying is given. The possibilities for integration of a bagasse steam dryer in the steam system of a cane factory are discussed. First test results and experiences gained with a steam drying pilot plant of 0.3 t/h water evaporation capacity are presented. Test conditions include drying of bagasse and fresh sugarcane to below 10% moisture. The plant has been operated for more than 1000 hours. In contrast to flue gas and low temperature drying, the steam dryer offers the advantage of a closed system. Air emissions can be reduced to a minimum by employing this technology. Steam drying of bagasse is also a measure to increase the electrical power production (cogeneration). The gross calorific value of bagasse can be increased from 9000-10 000 kJ/kg (50% moisture) up to 18 000-19 600 kJ/kg. The boiler efficiency can be increased by up to 15% and the total electrical surplus power production by approx. 40-50 kWh/t cane. Impacts on the handling of dry bagasse, storage, boiler feeding and boiler design have to be considered and to be investigated further.