Torrefaction Upgrades Sugarcane Bagasse

By:Mr Evan Wang

Position:Managing Director

Dec 22, 2021

Sugarcane bagasse is a main byproduct produced by the sugar industry. And it is consisted of about 28% of the total weight of sugarcane delivered to factories and is exported as a biomass fuel. Bagasse is also used as a bio-fuel for co-generation in producing heat and power in the factory.

Some problems of bagasse utilization are similar to other conventional biomass, such as the high moisture content, high oxygen content, hygroscopic nature, low calorific value and heterogeneous properties, causing problems in collection, storage, transportation and low energy conversion.

These problems can be overcome by thermal pre-treatment named torrefaction which is developed to upgrade the characteristics of sugarcane bagasse. SIMEC torrefaction technology for biomass is a thermo-chemical conversion process under atmospheric pressure conditions and in the absence of oxygen.

Torrefied bagasse converts the material into a coal-like solid fuel. It contains a high energy density that is similar to coal, but higher than for wood pellets.

Raw Sugarcane Bagasse

Torrefied-Bagasse-Different-Temperatures

Torrefied Sugarcane Bagasse

Under various reaction temperatures and duration times, there’ll be different mass yields and energy yields from torrefaction of the bagasse. The energy and mass yields decrease as the torrefaction temperature increases.

Typically, with the torrefaction temperature up to 275℃, the high heating value of bagasse can be increased from 14.33 MJ/kg (raw bagasse) to 24.01 MJ/kg(torrefied bagasse).

The HHV of coal is always in range of 25–35 MJ/kg . It is approximately that the HHV of torrefied bagasse is close to of coal.

Report of analysis for raw and torrefied bagasse samples:

Proximate analysis (wt % dry basis)	Raw Bagasse	Torrefied Bagasse
Fixed Carbon	14.26	44.04
Volatiles Matter	83.46	51.85
Ash Content	2.17	3.95
Sulfur	0.11	0.15
Fuel Ratio	0.17	0.85
Ultimate analysis (wt % dry-ash free basis)
Carbon	46.37	58.25
Hydrogen	6.29	2.81
Oxygen	46.79	38.68
Nitrogen	0.55	0.31
Lignocellulosic composition (wt. %)
Hemicellulose	18.81	1.37
Cellulose	23.08	0.22
Lignin	11.35	89.62

The lignocellulose or biomass composition comprises hemicellulose, cellulose and lignin. The torrefaction process can significantly affect the lignocellulose components. From the torrefaction of sugarcane bagasse, it’s found that hemicellulose and cellulose decline while lignin increases, when the torrefaction temperature increases.

Experimental data shows that a higher torrefaction temperature will lead to hemicellulose and cellulose decomposition. Lignin of the torrefied bagasse is highest at 89.62% for a torrefaction temperature of 275 ̊C. This feature means that it’s more easy to make black pellets using torrefied bagasse.

Torrefied Pellet Plant

SPM650s Torrefied Pellet Mill

Generally, torrefaction can improve the overall performance and characteristics of the torrefied bagasse as a solid fuel by increasing the High Heating Value with a rise in the carbon content, and reducing the hydrogen and oxygen contents in the torrefied bagasse.

The reactivity of the torrefied bagasse samples was lower due to their lower amount of volatile matter and the char formation of bio-polymers compared to the raw bagasse. Therefore, the torrefied bagasse can be as advanced solid fuel in heat and power applications.

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Torrefaction Upgrades Sugarcane Bagasse