Gaseous emissions from co-combustion of biosolids from the meat processing industry with wood

摘要

Flotation sludge from the meat processing industry can be applied as biofuel in already existing plant-scale boilers. This biosolid is rich in oil and grease and has higher energetic content on a dry ash-free basis (22.74 and 27.71 MJ kg~(-1)) than the wood-based fuel (16.62 and 16.16 MJ kg~(-1)). Co-combustion trials were performed at a pilot-scale cyclonic combustor (100 kg h~(-1)) and at an industrial flamotubular rotatory grate-fired system (6000 kg h~(-1)), co-firing pre-dried and centrifuged flotation sludges (respectively) and wood at a mass ratio of 1:3. At a moisture content of 60.13 wt%, the lower heating value of the centrifuged sludge was 10.24% lower compared to wood, thus reducing it to at least 40 wt% would be advisable to obtain energy gains in the industrial plant when operating the co-combustion. The emissions were evaluated and compared to emission standards, including the characterization of polycyclic aromatic hydrocarbons and polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofu-rans (given as Toxicity Equivalent Factors at O_(2ref) = 7%), which have not yet been reported. The 16 target polycyclic aromatic hydrocarbons were identified at pilot and plant scales (0.582 ± 0.143 μg Nm~(-3) and 0.602 ± 0.506 μg Nm~(-3), respectively) being lower than the Danish reference standard (5.0 μg Nm~(-3)). The polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans concentrations were 0.0004 ± 0.0001 ng Nm~(-3) at pilot scale and 0.3617 ± 0.1310 ng Nm~(-3) at plant scale, both below the Brazilian and American standards but differed greatly between the scales, requiring further investigation since their formation can occur due to combustion and postcombustion conditions.