257
edits
Difference between revisions of "Torrefaction"
Jump to navigation
Jump to search
m
→Product
Bas Davidis (talk | contribs) |
Bas Davidis (talk | contribs) m (→Product) |
||
| Line 4: | Line 4: | ||
=== Origin and composition === | === Origin and composition === | ||
In general, woody biomass and other lignocellulosic biomass are used for torrefaction. Heat transfer to the biomass lies at the heart of the torrefaction process as the temperature of the biomass must be increased sufficiently to allow the thermochemical degradation reactions to take place. In case biomass is not predried, moisture evaporation creates an additional heat demand. Since the heat requirement for drying is much larger than for torrefaction, and the heat used in drying the biomass cannot be readily recovered, applying dry torrefaction for upgrading biomass feedstock with high inherent moisture levels is typically less attractive. | In general, woody biomass and other lignocellulosic biomass are used for torrefaction. Heat transfer to the biomass lies at the heart of the torrefaction process as the temperature of the biomass must be increased sufficiently to allow the thermochemical degradation reactions to take place. In case biomass is not predried, moisture evaporation creates an additional heat demand. Since the heat requirement for drying is much larger than for torrefaction, and the heat used in drying the biomass cannot be readily recovered, applying dry torrefaction for upgrading biomass feedstock with high inherent moisture levels is typically less attractive. For this reason, moisture content of incoming biomass should normally not exceed 15%. | ||
=== Pre-treatment === | === Pre-treatment === | ||
| Line 18: | Line 18: | ||
=== Torrefaction technologies === | === Torrefaction technologies === | ||
* Rotary drum reactor | |||
* Screw reactor | |||
* Multiple Hearth Furnaces (MHF) | |||
* Torbed reactor | |||
* Moving bed reactor | |||
* Belt reacor | |||
* Microwaves reactor | |||
== Product == | |||
Torrefaction has been employed to improve on biomass properties, such as lower moisture content, higher energy density, improved hydrophobicity, and better grindability. | |||
{| class="wikitable" | |||
|+Properties of biomass before and after torrefaction | |||
!Raw biomass | |||
!Torrefied biomass | |||
|- | |||
|Higher moisture | |||
|Lower moisture | |||
|- | |||
|Higher O/C and H/C ratios | |||
|Lower O/C and H/C ratios | |||
|- | |||
|Lower heating value | |||
|higher heating value | |||
|- | |||
|Hygroscopic | |||
|Hydrophobic | |||
|- | |||
|Poor grindability | |||
|Better grindability | |||
|- | |||
|Non uniform properties | |||
|More uniform properties | |||
|- | |||
|Energy density: 1 MJ/kg | |||
|Energy density: 1.28 MJ/kg | |||
|} | |||
Torrefaction process essentially aimed at making biomass suitable for subsequent processes such as pyrolysis, hydrolysis and densification. It can also be employed in gasification and iron-making processes. | |||