scholarly journals The Migration and Transformation of Heavy Metals in Sewage Sludge during Hydrothermal Carbonization Combined with Combustion

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Meng Liu ◽  
Yufeng Duan ◽  
Kagiso Bikane ◽  
Liang Zhao
Keyword(s):  
Heavy Metals ◽  
Sewage Sludge ◽  
Residence Time ◽  
Combustion Process ◽  
Hydrothermal Carbonization ◽  
Positive Influence ◽  
Arsenic Compounds ◽  
Weakly Bound ◽  
Residual Rate ◽  
Leaching Risk

The migration and transformation behaviors of heavy metals (HMs), including Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb, during the hydrothermal carbonization (HTC) of sewage sludge (SS) were investigated. The immobilization of HMs during the combustion of solid residual (SR) produced from HTC of SS was also analyzed. With increasing HTC temperature and residence time, the majority of HMs (except As) accumulated in the SR. The residual rate of As in the SR decreased from 73.95% to 56.74% when the residence time was increased from 1h to 3h and reduced significantly from 73.95% to 37.48% when the temperature increased from 220°C to 280°C, implying that numerous arsenic compounds dissolved into liquid phase products. Although the HTC process has a positive influence on the transformation of HMs from weakly bound fractions to the more stable fractions, the exchangeable and reducible fractions of Mn, Zn, As, and Cd in the SR were still high. In addition, the leached amounts of Zn and As were high (14.61 and 6.16 mg/kg, respectively) and showed a high leaching risk to the environment. An increase in HTC temperature and residence time led to an increase of the residual rate of HMs in the combustion residual of SR, implying that the HTC process promotes the stabilization of HMs in the combustion process.

Hydrothermal carbonization of sewage sludge: The effect of feed-water pH on fate and risk of heavy metals in hydrochars

2016 ◽  
Vol 218 ◽  
pp. 183-188 ◽  
Author(s):  
Yunbo Zhai ◽  
Xiangmin Liu ◽  
Yun Zhu ◽  
Chuan Peng ◽  
Tengfei Wang ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Sewage Sludge ◽  
Hydrothermal Carbonization ◽  
Feed Water ◽  
Water Ph

scholarly journals Assessing the effect on the generation of environmentally persistent free radicals in hydrothermal carbonization of sewage sludge

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yuhan Zhu ◽  
Jia Wei ◽  
Yitao Liu ◽  
Xiaohui Liu ◽  
Jun Li ◽  
...  
Keyword(s):  
Free Radicals ◽  
Sewage Sludge ◽  
Residence Time ◽  
Hydrothermal Carbonization ◽  
Paramagnetic Resonance ◽  
Hydrothermal Temperature ◽  
Initial Ph ◽  
Long Time ◽  
Constituent Elements ◽  
The Impact

AbstractEnvironmentally persistent free radicals (EPFRs) have attracted increasing research interest in recent years. Herein, the generation of EPFRs during the hydrothermal carbonization of sewage sludge (SS) was studied. First, the surface morphology, functional groups, constituent elements and free radicals were characterized for a holistic description of the raw SS and the selected hydrochar obtained from hydrothermal carbonization of SS (SHC). Then, the impact of hydrothermal temperature, residence time and initial pH on the formation of EPFRs was explored in detail through the investigation of g-factors and intensities of EPFRs identified in SHC. The results have shown that the formation of EPFRs was affected by the factors mentioned above, in which the impact of temperature is the greatest. Two types of EPFRs were spotted in the hydrochar, oxygen-centered (O-centered) and carbon-centered (C-centered) EPFRs, which were caught in 120–150 °C and 260–280 °C, respectively. Moreover, the intensities of Electron Paramagnetic Resonance (EPR) signals enhanced with increasing hydrothermal temperature. Whereas, residence time and initial pH only affected the amount of EPFRs in a manner. Additionally, the half-life of the O-centered EPFRs and the C-centered EPFRs was determined as long as 160.45 days and 401.10 days, respectively, indicating that EPFRs are stable in a long time.

Syngas as a Reburning Fuel for Natural Gas Combustion

2014 ◽  
Vol 35 (2) ◽  
pp. 181-190 ◽  
Author(s):  
Małgorzata Wilk ◽  
Aneta Magdziarz ◽  
Monika Zajemska ◽  
Monika Kuźnia
Keyword(s):  
Sewage Sludge ◽  
Natural Gas ◽  
Residence Time ◽  
Nox Reduction ◽  
Combustion Process ◽  
Combustion Products ◽  
Experimental Investigations ◽  
Gas Combustion ◽  
Numerical Tests ◽  
Natural Gas Combustion

Abstract The paper aims to confirm the syngas application as a reburning fuel to reduce e.g. NO emission during natural gas combustion. The main aim of this modelling work was to predict pollutants generated in the exhaust gases and to indicate the influence of the syngas on the natural gas combustion process. The effect of residence time of fuel-air mixture was also been performed. Calculations were made with CHEMIKN-PRO for reburning process using syngas. The boundary conditions of the reburning process were based on experimental investigations. The addition of 5, 10, 15 and 19% of reburning fuel into natural gas combustion was studied. The effects of 0.001 to 10 s of residence time and the addition of 5, 10, and 15% of syngas on combustion products were determined. The performed numerical tests confirmed that co-combustion of the natural gas with syngas (obtained from sewage sludge gasification) in the reburning process is an efficient method of NOx reduction by c.a. 50%. Syngas produced from sewage sludge can be utilised as a reburning fuel.

Effect of hydrothermal carbonization on migration and environmental risk of heavy metals in sewage sludge during pyrolysis

2018 ◽  
Vol 247 ◽  
pp. 282-290 ◽  
Author(s):  
Tingting Liu ◽  
Zhengang Liu ◽  
Qingfu Zheng ◽  
Qianqian Lang ◽  
Yu Xia ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Sewage Sludge ◽  
Environmental Risk ◽  
Hydrothermal Carbonization
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