Method and device for pelletizing unprocessed cellulosic fibrous material

Abstract

The present invention relates to a method and a device for pelletizing unprocessed cellulosic fibrous material on an industrial scale, and in particular to the use of said unprocessed cellulosic fibrous material pellets as a combustible fuel product.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 60 / 721,358, filed Sep. 28, 2005. The subject application also claims priority to European Patent Application No. 05021213.3, filed Sep. 28, 2005.FIELD OF THE INVENTION [0002] The present invention relates to a method and a device for pelletizing unprocessed cellulosic fibrous material, in particular sugar-cane bagasse, on an industrial scale, and in particular to the use of said unprocessed cellulosic fibrous material pellets as a combustible fuel product. BACKGROUND OF THE INVENTION [0003] Since fossil fuel has become a finite energy source, in the last decades many efforts have been put into the production of alternative energy materials. These alternative materials should not only be affordable and readily available, they also should be preferably derived from renewable sources. Among the existing renewable alternatives to fossil fuels, biomass has raised great i...

AI Technical Summary

Benefits of technology

[0045] In another preferred embodiment of the method of the present invention, said spinning tube dryer is fitted with deflectors positioned at an angle of about 45° attached to the tube bundles, in order to increase efficiency in the transportation and drying of bagasse inside the dryer.

[0129] Most preferred is a pelletized combustible cellulosic fibrous material according to the present invention, wherein said bagasse has an upper calorific content of about 4,500 to about 5,500 kcal / kg, a lower calorific content of about 3,500 to about 4,500 kcal / kg, a density of about 500 to about 600 kg dry matter / m3, and a humidity of about 10% to about 15%. Further preferred is a pelletized combustible cellulosic fibrous material according to the present invention, wherein said pelletized combustible cellulosic fibrous material is further blended with coal. This will even further improve the combustion properties of the inventive pellets.

Problems solved by technology

It is simple to imagine that these sources are also finite sources, and that an increase of wood fuel consumption would not only lead to an increase in the price of these raw materials but also to the loss of many forests since a tree needs a long growth period, which decreases the desirability of wood as a renewable energy source.

However in this state, the bagasse cannot be transported elsewhere as a fuel due to the low calorific value (8-9 Giga Joules per metric ton), and transporting issues.

This process makes use of the wasted heat or the heat wrongly used in sugar cane and alcohol factories by drying or dehydrating the bagasse, increasing its lower heat power (Kcal / Kg).

Thus, this method can only be used for the pelletization of some materials.

However, their use with unprocessed sugar-cane bagasse had never been performed on an industrial scale without the use of the hot flue gases from the boilers.

While the literature mentions the production of pellets from unprocessed sugar-cane bagasse, the manner in which this method is described is not feasible to solve the particular problems and needs that derive from the secure industrial production perspective.

However, in all these tests production was way below the pelletizers' nominal capacity.

Another aspect analyzed was the high bagasse drying temperature, which rendered operations unsafe because of the fire risk.

This technology also faced operational difficulties in relation to the air-bagasse counter-flow, mainly frequent clogging of the system.

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