Pyrolysis of Municipal Sewage Sludge to Investigate Char and Phosphorous Yield together with Heavy-Metal Removal—Experimental and by Thermodynamic Calculations

Naeimeh Vali, Lars-Erik Åmand, Aurélie Combres, Tobias Richards and Anita Pettersson
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Naeimeh Vali: Swedish Centre for Resource Recovery, University of Borås, 501 90 Borås, Sweden
Lars-Erik Åmand: Swedish Centre for Resource Recovery, University of Borås, 501 90 Borås, Sweden
Aurélie Combres: Swedish Centre for Resource Recovery, University of Borås, 501 90 Borås, Sweden
Tobias Richards: Swedish Centre for Resource Recovery, University of Borås, 501 90 Borås, Sweden
Anita Pettersson: Swedish Centre for Resource Recovery, University of Borås, 501 90 Borås, Sweden

Energies, 2021, vol. 14, issue 5, 1-18

Abstract: Sewage sludge is regarded as a potential source for soil fertilizer However, the direct utilization of sewage sludge in agricultural land is restricted since it also contains heavy metals, pathogens, and toxic compounds. Pyrolysis of the sewage sludge destroys the organic pollutants and partly volatilizes the heavy metals. In this study, pyrolysis of sewage sludge was carried out in order to determine the optimum residence time and temperature to recover the phosphorous and remove heavy metals from the resultant sewage sludge char (SSC). Pyrolysis was conducted on dried sewage sludge (DSS) by means of thermogravimetric analysis (TGA) and high-temperature oven with an N 2 -atmosphere. Microwave Plasma-Atomic Emission Spectroscopy (MP-AES) was used to determine the concentration of P and trace elements in the resulting solid char fraction. A combination of chemical fractionation (step-by-step leaching) of the DSS and thermodynamic equilibrium calculations were utilized to estimate the availability of phosphorous and removal of heavy metals in the SSC fraction at different temperatures. The results from the thermodynamics calculation were in line with the measured chemical composition of the SSC. Furthermore, the energy contents of the SSC obtained at different temperatures were measured. The pyrolysis evaluation results indicate that phosphorous was enriched in the char, while lead, zinc, and cadmium were significantly removed.

Keywords: sewage sludge; pyrolysis; thermodynamic equilibrium modeling; phosphorus recovery; chemical fractionation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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