MIXING CHARACTERISTICS OF SAND AND BIOMASS IN A ROTATING CONE REACTOR

Abstract

With the faster depletion of fossil fuel resources like petroleum products and coal, there is a dire need to come up with high efficiency and cost effective fuel source. Renewable energy offers a promising field to be focussed on. The search of the new energy source ends in Biomass, which can be converted to energy by pyrolysis, gasification or direct combustion. Biomass is a renewable resource with high potential, not only as a fuel source for the creation of steam and electricity, but as transportation fuel as well. It offers many promising advantages as it utilizes the waste product decreasing the concern of their disposal and has low ash and sulfur content making it a clean, renewable energy source that could improve our environment, economy and energy securities. Expensive nature and green house problems are the growing concern in its current application. Pyrolysis of biomass is the most common process for energy conversion which occurs above 430 °C in absence of oxygen. The various type of reactor used for the purpose are bubbling fluid bed, circulating fluid bed, rotating cone reactor, ablative pyrolysis, entrained flow reactor etc. Among these rotating cone reactor is recently developed by University of Twente and effectively operates as a transported bed reactor, but with transport affected by centrifugal forces in rotating cone reactor rather than gas. For the experimental work a reactor with diameter 245 mm and height 205 mm was chosen. An outer cone of 500 mm is used to collect the sand and biomass at one single point which can be collected at the bottom through a bowl shaped hole. The biomasses of coarse nature than sand were used and the type is bagasse and saw dust. These two biomasses can be differentiated on the basis of ash content and density. The results were taken as per different operating conditions (rotating speed of cone, particle size of sand and biomass, mix ratio of sand and biomass in the reactor) on the mixing characteristic of sand and biomass. The results showed that the ratio of optimum performance of the reactor as per sand/biomass ratio keeps on increasing for a particular biomass as frequency of cone increases. The experiments also showed poor mixing for cone speed less than 150 rpm. The physico-chemical analyses of the biomasses were done to find out the ash and moisture content. The results also showed that the wt % of biomass on dry feed basis should be 1- 13 % of sand in the reactor for an optimum performance. The mixing is dependent of rotational speed and the size of feeded particle and also on type of biomass used.