Thermal pyrolysis characteristics of polymer flocculated waste activated sludge

Simultaneous implementation of sludge dewatering and solid biofuel production by microwave torrefaction

Sludge dewatering is a matter of great concern to reduce the volume of sludge, stabilize its organic components, and achieve resource utilization. This study investigates sludge dewatering by microwave torrefaction along with the production of sludge solid biofuel at 480-800 W combined with durations of 5-25 min. Proximate analysis, calorific value analysis, thermogravimetric analysis, and scanning electron microscopy observations are employed to evaluate the dewatering degree, fuel properties, and energy efficiency of the torrefaction process. The independent parallel reaction (IPR) model and particle swarm optimization (PSO) analysis are also adopted for sludge pyrolysis kinetics calculation. The results show that microwave torrefaction is efficient for sludge dewatering with a short duration. The produced sludge solid biofuel is similar to stone-like coal, and can be used for civil or industrial boilers after flotation or just co-firing with briquette. The ash content of sludge solid biofuel shows a declining trend and the surface characteristics change from smooth to rough and fluffy with increasing the torrefaction severity. The bio-oil is mainly composed of phenols, siloxanes, and cholesterol. In addition, hydrogen is detected in the torgas. Furthermore, it is found that lower torrefaction power with a shorter duration yields a higher energy efficiency of the torrefaction process.

Removal of Basic Red 5 on Calcined Kaolinite – Characterization and Adsorption Kinetics

Indigenous kaolin was collected from Swat district and then activated. The samples were characterized by BET surface area, FTIR, XRD, SEM, EDS, TGA/DTA, zeta potential and particle size analysis. Adsorption of basic red 5 on each sample was studied by adsorption kinetics at 20 °C, 30 °C and 40 °C. The residual concentration of the dye was determined by using UV–Vis spectrophotometer. The removal of basic red 5 from water solution was studied with respect to dye concentrations and equilibration time. Adsorption kinetics on kaolinite surface were analyzed by using parabolic diffusion, Elovich and Bangham models. Thermodynamic parameters like ΔE#, ΔH# and ΔS# were calculated from the adsorption kinetics data. The results show that the adsorption is a spontaneous and endothermic process. The negative value of entropy shows that the dye molecules take a proper position on the surface.

Thermochemical conversion of livestock wastes: carbonization of swine solids

Slow pyrolysis or carbonization promotes the conversion of animal manures such as swine manure into charcoal. In this paper, the carbonizing kinetics of swine solids taken from different treatment stages were investigated with a thermogravimetric analyzer. Compared to their biologically stabilized counterpart (lagoon sludge) with an activation energy of 160 kJ mol(-1), the activation energies for fresh swine solid samples such as homogenized flushed manure and dewatered solids were much lower between 92 and 95 kJ mol(-1). Compared to the kinetics of first order decomposition of cellulose, the pyrolytic decomposition of the swine manures were more complex with the reaction orders varying at 3.7 and 5.0. The two different mathematical methods employed in this paper yielded the similar values of activation energy (E) and pre-exponential factor (A), confirming the validity of these methods. The results of this study provide useful information for development of farm-scale swine solid carbonization process.

Incineration of a small particle of wet sewage sludge: a numerical comparison between two states of the surrounding atmosphere

The main goal of this paper is to elaborate a mathematical model that represents the physics and chemistry involved when a small particle of wet sewage sludge is incinerated. Compared to existing models, our study includes both drying and heterogenous combustion of the pyrloysis residue of the processed sludge. This model relies on the assumption of homogeneous composition and temperature for the particle under study. It includes drying, pyrolysis (controlled by a four successives steps reaction pathway) and combustion of the resulting char. The ability of the model is illustrated using it in two different process conditions (representing thermogravemetric analysis and fluidized bed conditions) in order to investigate the influence of the surrounding atmosphere. It is found, that fluidized bed conditions reduce the burnout time of a small particle by enhancing the rate at which heat is transferred to that particle. It is also shown that high heating rates enhance the tar yield.

Anaerobic digestion of polyelectrolyte flocculated waste activated sludge

This work examined how adding one of three polyelectrolyte flocculants (T3052: cationic, T2000: non-ionic, and T1052: anionic) affected the anaerobic digestion of wastewater sludge. Methane production, floc characteristics (morphology and zeta-potential) and process parameters (soluble chemical oxygen demands (SCODs) and reductive potentials) were monitored along the digestion tests. The digestion rates of T2000- and T1052-conditioned sludge resembled that for original sludge. The T3052-flocculated sludge generated methane at a higher rate during the first 6 days of digestion than did the original one. In the following stage, the digestion rate of sludge flocculated with T3052 at dosage exceeding 15 g/kg dried solids declined. For example, at 40 days of digestion the methane production amounts for original, 15 g/kg DS flocculated, and 40 g/kg flocculated sludge were of 136, 105, and 85 g/kg DS, respectively. The role of flocculants could change in different stages of digestion. The dosed polymers had no apparent toxicity to the inoculum used. The changes in SCOD, adenosintriphosphate concentrations, oxidative and reductive potential, and zeta-potentials did not correlate with the noted hindered digestion for T3052-conditioned sludge. Microphotographic observation revealed that the flocs of T3052-conditioned sludge were not only of a large size, but also were resistant to structural deterioration during digestion. Therefore, mass transfer resistance was proposed to account for the hindered digestion efficiency observed for T3052-conditioned sludge.