Semi-pilot scale sewage sludge pyrolysis and characterization of obtained fractions by thermal analysis

Abstract

Sewage sludge pyrolysis is an alternative to incineration and presents as advantages the generation of three fractions: gas (non-condensable volatiles), liquid (condensable volatiles) and solid (carbonaceous coke). In this context, the purpose of the present study is to quantify and to characterize by thermal analysis the fractions produced by sewage sludge pyrolysis in semi-pilot scale. The semi-pilot pyrolysis was performed in two steps, the first dynamic up to 500°C, followed by an isothermal step at this temperature for 3 h. The solid and liquid fractions produced were analyzed by TG/DTG/DTA, and the volatiles were analyzed by thermogravimetry coupled to mass spectrometry (TG-MS). The influence of different pyrolysis conditions (dynamic and isothermal) was verified by differential thermal analysis (DTA) characterization and by the higher heating value (HHV) of the liquid fractions produced by sludge pyrolysis. In total, 60.1, 28.6 and 11.3 % of the sludge initial mass were obtained, respectively, as solid, liquid and gas pyrolytic fractions. The liquid fraction was composed of aqueous and oily phases. By TG-MS, the volatile compounds detected in pyrolysis were as follows: H 2 O, C 3 H 6 , CO 2 , NO 2 , C 4 H 8 , SO 2 , C 6 H 6 and C 7 H 8 . The aliquots obtained at higher time periods by isothermal pyrolysis at 500°C showed higher DTA exothermic peaks and higher HHV values as well. Sewage sludge isothermal pyrolysis at 500°C produces a liquid fraction with HHV of 36.2 MJ kg -1 , indicating that it can be used as renewable energy source. A good correlation exists between total DTA peak area of the oily fractions obtained from sewage sludge pyrolysis and respective HHV values, indicating that it can be used to estimate these values from corresponding DTA curves.

Influence of pH on hydrothermal treatment of swine manure: Impact on extraction of nitrogen and phosphorus in process water

“…Pyrolysis concentrates phosphorus in the char and this can be used as a soil additive or as a concentrated phosphorus source for further extraction and transformation. The former has been developed for treatment of sewage sludge (Bridle and Pritchard, 2004;Viana et al, 2015), however not all the phosphorus is bioavailable (Huang and Tang, 2015). Incineration of manure concentrates phosphorus in the resulting ash.…”

Impact of temperature and residence time on sewage sludge pyrolysis for combined carbon sequestration and energy production

“…Prior studies have also noted a decline in bio-oil yield beyond 600 °C, accompanied by an increase in syngas production [ 29 , 55 ]. In sewage sludge pyrolysis, some researchers have reported a peak bio-oil yield of 28.6% at 500 °C [ 56 ] after which the yield declined. Maximal oil production during pyrolysis has been highlighted within the temperature range of 450–575 °C in other investigations [ 47 , [57] , [58] , [59] ].…”

Adsorption of phosphate from aqueous solution on to pyrolyzed drinking water treatment residuals: Statistical process optimization, equilibrium, and kinetic analysis

“…Hence, to remove such impurities in DWTRs and to enhance their adsorption capability, certain pretreatment processes have been recommended. Among various approaches, a pyrolysis process in the absence of oxygen or in an oxygen‐deficient atmosphere, one of the thermal degradation process, is seems to be a more attractive and effective method because organic materials can only be effectively removed, while all inorganic elements remain in the pyrolyzed materials in contrast with conventional thermal pretreatment process . However, up to now, the pyrolysis process for removal of impurities in DWTRs has not been reported in the literature as well as removal of phosphate from aqueous solution using pyrolyzed‐DWTRs (PDRs).…”