| dc.description.abstract | This study investigates the co-gasification of wastewater sludge (WS) and anaerobic digestate (AD) using a laboratory-scale fluidized bed gasifier, focusing on enhancing gas production quality and assessing the feasibility of heavy metal removal via a hot gas cleaning system. The experiments were conducted at gasification temperatures of 700, 800 and 900℃, an equivalence ratio (ER) of 0.3, and blending ratios of WS to AD at 3:1, 1:1 and 1:3. The hot gas cleaning system was equipped with three adsorbents: zeolite, calcined dolomite and activated carbon.
For WS gasification, the study revealed a significant enhancement in hydrogen production, from 1.40 vol.% at 700℃ to 5.21 vol.% at 900℃, with a corresponding rise in cold gas efficiency (CGE) from 8.96% to 18.71%. The heating value of the product gas also saw a substantial improvement, from 1.79 MJ/Nm3 to 3.69 MJ/Nm3. In the case of AD gasification, a similar trend was observed, with hydrogen production increased from 3.07 vol.% at 700℃ to 6.57 vol.% at 900℃, and CGE rising from 9.55% to 16.27%. The heating value of the product gas also saw a significant increase, from 2.04 MJ/Nm3 to 3.43 MJ/Nm3. These results, underscore the efficiency of the gasification process, with higher gasification temperatures favoring endothermic reactions and leading to more combustible gas production and a higher heating value of the produced gas. During the co-gasification of WS and AD at 900℃, hydrogen production ranged from 4.99 to 5.80 vol.%, with the highest yield observed at a WS:AD = 1:3. The heating value of the product gas varied between 3.56 and 3.65 MJ/Nm3; while CGE ranged from 16.96 to 17.46%. A blending ratio of 1:1 was found to optimize the heating value of the product gas.
The gasification tests incorporating the hot gas cleaning system revealed a notable increase in the syngas composition ratio. For AD gasification, the syngas′ hydrogen content surged to 7.79 and 9.52 vol.%, surpassing the results obtained without the hot gas cleaning system. The heating value of the product gas also saw a significant increase, ranging from 3.96 to 4.16 MJ/Nm³. Most importantly, the hot gas cleaning system played a pivotal role in effectively removing heavy metals from the gas phase products, with impressive removal rates of 10.83% to 28.31% for copper (Cu), 19.77% to 40.10% for chromium (Cr), 18.76% to 28.84% for zinc (Zn), 54.80% to 70.85% for gallium (Ga), and 30.76% to 49.57% for indium (In).
Overall, the study underscores the promising potential of WS and AD for co-gasification. The hot gas cleaning system emerges as a significant player, enhancing gas production quality and enabling the removal of heavy metals. These preliminary findings provide a beacon of hope for future engineering applications in the field of waste management and environmental engineering. | en_US |