Pyrolysis of Municipal Sewage Sludge to Investigate Char and Phosphorous Yield together with Heavy-Metal Removal—Experimental and by Thermodynamic Calculations (original) (raw)
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Scientific Reports
Biochar from sewage sludge is a low-cost sorbent that may be used for several environmental functions. This study evaluates the induced effects of pyrolysis temperature on the physicochemical characteristics of sewage sludge (SS) biochar produced at 350 (SSB350), 450 (SSB450) and 600 (SSB600), based on the metal enrichment index, metal mobility index (MMI), and potential ecological risk index (PERI) of Cd, Cu, Pb, and Zn. Increased pyrolysis temperature reduced the biochar concentration of elements that are lost as volatile compounds (C, N, H, O, and S), while the concentration of stable aromatic carbon, ash, alkalinity, some macro (Ca, Mg, P2O5, and K2O) and micronutrients (Cu and Zn), and toxic elements such as Pb and Cd increased. Increasing the pyrolysis temperature is also important in the transformation of metals from toxic and available forms into more stable potentially available and non-available forms. Based on the individual potential ecological risk index, Cd in the SS a...
Waste management (New York, N.Y.), 2017
This research compares and contrasts the physical and chemical characteristics of incinerator sewage sludge ash (ISSA) and pyrolysis sewage sludge char (PSSC) for the purposes of recovering phosphorus as a P-rich fertiliser. Interest in P recovery from PSSC is likely to increase as pyrolysis is becoming viewed as a more economical method of sewage sludge thermal treatment compared to incineration. The P contents of ISSA and PSSC are 7.2-7.5% and 5.6%, respectively. Relative to the sludge, P concentrations are increased about 8-fold in ISSA, compared to roughly 3-fold in PSSC. Both PSSC and ISSA contain whitlockite, an unusual form of calcium phosphate, with PSSC containing more whitlockite than ISSA. Acid leaching experiments indicate that a liquid/solid ratio of 10 with 30min contact time is optimal to release PO4-P into leachate for both ISSA and PSSC. The proportion of P extracted from PSSC is higher due to its higher whitlockite content. Heavy metals are less soluble from PSSC b...
Characterisation of products from pyrolysis of waste sludges
Fuel, 2006
The pyrolysis of waste sludges was investigated using thermogravimetry/mass spectrometry (TG/MS) and a fixed-bed reactor. Two types of sludge were used, namely mixed sludge and oil sludge. In TGA/MS measurements, two degradation steps were observed. Degradation of organic structures, in sludge took place in the first step, while inorganic materials in sludge were mainly decomposed in a second step (above 500 °C). In a fixed-bed reactor, the catalytic effect of inorganic matter in addition to organic matter was monitored the quality and yield of products from pyrolysis. Pyrolysis of oil sludge produced a larger amount of oil containing more aliphatic compounds and a high calorific value. On the other hand, pyrolysis of mixed sludge gave a smaller amount of oil being rich in polar compounds. The gaseous products from pyrolysis consist of high amount of combustable gases. Landfilling was found to be the best alternative to dispose off the pyrolytic char obtained from pyrolysis.
PYROLYSIS OF DOMESTIC SEWAGE SLUDGE: EFFECT OF PROCESS PARAMETERS ON BIOCHAR CALORIFIC VALUE
Civil and Environmental Engineering, 2023
This research aims to look into a sustainable technique for the treatment, reuse and disposal of domestic sewage sludge (DSS). The purpose of the study was to examine the operating factors that influence the calorific value of the produced biochar from the pyrolysis of DSS. Based on the analysis of the full factorial design, the impacts of the pyrolysis conditions, specifically: temperature, heating rate, and isothermal time on the calorific value of biochar were evaluated. When the pyrolysis temperature was raised from 300 to 500 oC, the calorific value of biochar was decreased by 34%. A 14% decrease in the calorific content of the biochar was also noticed when the heating rate was increased from 5 to 35 oC/min. When the isothermal time was increased from 45 to 120 minutes, the calorific value of the biochar remained essentially unchanged. No interaction effects among process variables were found using the factorial design methodology. A first-order regression model was developed to predict the calorific value of biochar using the magnitude of the effects of the process factors and their interactions. The model predictions agreed very well with the obtained experimental results.
Journal of Chemistry
The pyrolytic conversion of domestic sewage sludge (SS) into biochar is a promising method to reduce its large volume and recycle its high-value fuel gas as renewable energy and the use of its chemicals as soil fertilizers. Even though the effects of pyrolysis temperature on energy recovery have been extensively studied, little information has been found on nutrient recovery and biochar’s phytotoxicity before its reuse as a soil amendment. This study aims to investigate the ideal pyrolysis temperature that guarantees higher fertility levels as well as meeting quality standards for land disposal. Accordingly, air-dried domestic sewage sludge has been pyrolyzed at 260°C (PSS1), at 420°C (PSS2), and at 610°C (PSS3) with a residence time of 20, 40, and 60 minutes, respectively. The raw sewage sludge and the produced biochars have been analyzed to determine their volatile organic matter (VOM), mineral content (MC), nutrients’ level (total nitrogen TN, available phosphorus P, and potassiu...