Z. Liu, M. Hughes, Y. Tong et al.
Energy 239 (2022) 121925
Fig. 8. TPO-TG and TPO-DTG of new and used p-sludge biochars (More coke deposited on the biochar surface after repeated use.).
Fig. 9. The effect of biochar catalyst cycle number on the py-gas and bio-oil energy distribution at 800 C. 0B denotes without catalyst or sand at 500 C downstream. 0S denotes control with sand in place of catalyst. 1, 3, 5 represent cycle numbers.
biochar (from 2300 kJ/kg to 2500 kJ/kg), indicating the stable cat- alytic performance of p-sludge biochar. In contrast, due to the gradual loss of the catalytic activity of biosolids biochar, the bio-oil HHV increased from 2200 kJ/kg to 4300 kJ/kg after fi ve cycles. Since p-sludge biochar was more stable catalytically, the py-gas HHV just showed an obvious increase after the fi fth cycle of using p-sludge biochar. When wood and biosolids biochars were used for three cycles, the py-gas HHV increased greatly because these used catalysts decomposed less hydrocarbons resulting in lower H 2
3.4. Impact of catalyst cycle numbers on py-gas and bio-oil energy yields
Catalytic pyrolysis using wood, p-sludge, and biosolids biochars reduced bio-oil energy content compared to the bio-oil HHV in the 0B test (HHV fi gure is shown in SI, Figure S3). The bio-oil HHV decrease was due to the aforementioned decomposition of heavy hydrocarbons and the formation of water during catalysis [44]. The bio-oil HHV slightly increased after fi ve cycles of using p-sludge
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