The Torrefaction of Pulp Industry Waste to Manufacture Solid Biofuel
Date Issued
2014
Date
2014
Author(s)
Huang, Chun
Abstract
The pulp industry in Taiwan produce tons of organic wastewater sludge and wood waste per year. These biowastes were then converted to organic fertilizers for agriculture uses or soil conditioners. The biowaste can also be used in different ways to mitigate the energy shortage. This study investigates a biowaste-to-energy (BTE) method to convert pulp industry waste into solid biofuel via torrefaction. The pulp waste examined is the mixture of wood waste and secondary sludge obtained from a virgin pulp factory in eastern Taiwan (denoted as wood with pulp sludge, WPS).Two batches of WPS were received and tested, namely, WPS1 and WPS2, which contain about 95 and 80 wt.% combustibles in dry basis.
The biowaste WPS has a high content of organic compounds with the dry basis high heating value of 3,757 to 4,374 kcal/kg and can be used as raw materials for producing primary solid biofuel. However, the wet WPS bears high water (>50 wt.%) and volatiles contents and needs de-watering, drying and upgrading. The results of this study show that after 20 min torrefaction at 300 °C, the HHVD of WPS1 can be promoted to 6,570 kcal/kg, while after 20 min torrefaction at 320 °C, the HHVD of WPS2 increases to 4,718 kcal/kg. Both cases also have better combustion performance. The results also indicate that the energy densification of torrefied solid biofuel can rise to 1.26-1.50 time than the raw biowaste. The condensable gaseous by-products portions of were condensed and collected as liquid products which is essentially an organic acid liquid (wood vinegar) having highly economic value. Both condensable liquid and non-condensable gaseous by-products were analyzed. The liquid product of case WPS1 include some esters and amides, while those of case WPS2 consist of some alkanes and alcohols. The carbon numbers of alkanes in liquid of case WPS2 are above 10, which indicate that the liquid products can use for liquid fuels after purification. From this study, WPS1 and WPS have different characteristics due to different operation, collection and handling conditions when producing pulp sludge at different times. Therefore, some characteristics analysis should be conducted before mixing the pulp sludge and wood waste in order to provide information for choosing better torrefaction conditions. Moreover, because the combustion performance of torrefied WPS is similar to that coal, the torrefied solid biofuel can be mixed with coal and used in power plant directly. This thus reduces the usage of fossil fuels.
Subjects
生質物
紙漿廢棄物
固態生質燃料
焙燒
木醋酸液
SDGs
Type
thesis
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