Dataset Information

Thermochemical and Toxic Element Behavior during Co-Combustion of Coal and Municipal Sludge.

ABSTRACT: The thermochemical and kinetic behavior of co-combustion of coal, municipal sludge (MS) and their blends at different ratios were investigated by thermogravimetric analysis. Simulation experiments were performed in a vacuum tube furnace to determine the conversion behavior of toxic elements. The results show that the combustion processes of the blends of coal and municipal sludge are divided into three stages and the combustion curves of the blends are located between those of individual coal and municipal sludge samples. The DTGmax of the sample with 10% sludge addition reaches a maximum at the heating rate of 20 °C/min, indicating that the combustion characteristics of coal can be improved during co-combustion. Strong interactions were observed between coal and municipal sludge during the co-combustion. The volatilization rates of toxic elements decrease with an increasing proportion of sludge in the blends during co-combustion, which indicates that the co-combustion of coal and sludge can effectively reduce the volatilization rate of toxic elements. The study reflects the potential of municipal sludge as a blended fuel and the environmental effects of co-combustion of coal and municipal sludge.

SUBMITTER: Chen Y

PROVIDER: S-EPMC8307717 | biostudies-literature | 2021 Jul

REPOSITORIES: biostudies-literature

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Thermochemical and Toxic Element Behavior during Co-Combustion of Coal and Municipal Sludge.

Chen Yongchun Y Gui Herong H Xia Ziwei Z Chen Xing X Zheng Liugen L

Molecules (Basel, Switzerland) 20210709 14

The thermochemical and kinetic behavior of co-combustion of coal, municipal sludge (MS) and their blends at different ratios were investigated by thermogravimetric analysis. Simulation experiments were performed in a vacuum tube furnace to determine the conversion behavior of toxic elements. The results show that the combustion processes of the blends of coal and municipal sludge are divided into three stages and the combustion curves of the blends are located between those of individual coal an ...[more]

PMID: 34299445

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Project description:Feedstocks such as coal, biomass, plastics, and their blends have the potential to serve as fuels for the thermochemical conversion process owing to their relatively high calorific values. Nevertheless, the relative proportion of these feedstock blends has a pivotal influence over the overall energy conversion efficiency. Consequently, conducting a comprehensive study to optimize the blend proportion becomes crucial in order to obtain an optimal fuel. The study aims to investigate the thermochemical characterization and kinetics of blends composed of lignite coal, southern pine biomass, and municipal waste plastic blend to optimize the blend proportion. This optimization has been achieved through an analysis of 12 distinct blends, considering factors such as combustion reaction kinetics, combustion stability, and comprehensive combustion indices. The reaction kinetics, including activation energy, pre-exponential factor, and reaction order, were estimated using various methods, including Vyazovkin, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa, Master-plot, and multidistributed activation energy methods. The investigation revealed that increasing the biomass content within the blends enhances both the combustion stability and combustion performance. The multidistributed activation energy model exhibited a good fit with both the experimental thermogravimetric and the derivative thermogravimetric curves, achieving linear regression fitness values of 0.99 and 0.95, respectively. To showcase the viability of these blends as energy generation feedstock, the optimal blend comprised of 60% biomass, 10% coal, and 30% municipal waste plastic blend, possessing the lowest activation energy (110 kJ/mol), was employed as the feedstock for the fluidized bed oxy-steam gasification process. The gasification process resulted in a synthetic gas consisting of 47.79 mol % H2, 27.96 mol % CO, 5.85 mol % CH4, and 18.38 mol % CO2 (nitrogen-free basis) with a cold gas efficiency of 72.88%. The findings of this study can offer valuable insights into global industries engaged in the thermochemical conversion of solid waste materials.

Project description:Following the nuclear accident at the Fukushima Daiichi Nuclear Power Plant in 2011, even the municipal solid waste (MSW) and sewage sludge (SS) in northeastern Japan became contaminated by radioactive nuclides such as 137Cs and 134Cs. To understand the state of radioactive cesium (r-Cs) in the incineration residues of the municipal wastes, research groups studied the concentration and the chemical form of r-Cs in the residues, as well as its water-leaching behavior. In the present study, we conducted thermodynamic equilibrium calculations to estimate the possible chemical forms of r-Cs in the incineration residues. Thermodynamic data for cesium oxides and aluminosilicates were collected and compiled into a new database to perform equilibrium calculations for systems that include Cs. The calculation results suggested that Cs (radiocesium and stable cesium) in municipal solid waste was transformed into gaseous CsCl or crystalline aluminosilicate at incineration temperatures and, when a molten aluminosilicate phase (i.e., slag phase) was generated, a proportion of the Cs species was dissolved into the slag phase. In the case of sewage sludge, Cs was calculated to be transformed mostly into crystalline aluminosilicate at incineration temperatures, whereas by analogy with the behaviors of Na and K, Ca,Cs-phosphate double salts were also potential incineration products. These results could account for the high leaching rates of r-Cs from the MSW incineration fly ash and the low leaching rates from the MSW incineration bottom ash and SS incineration fly ash reported in earlier studies. In the case of dewatered SS that included a large amount of slaked lime as a flocculant, it was exceptionally difficult for the calculation to represent the fate of Cs, and we needed to include the contribution of silica sand in a fluidized-bed combustor in the equilibrium calculation to represent the low leaching rates of alkali species from the dewatered SS fly ash. From the results of the thermodynamic equilibrium calculations and also from the calculated standard Gibbs energy of cesium aluminosilicate formation/decomposition reactions, the effects of waste composition and incineration temperature on the fate of Cs were examined: High incineration temperature and large amounts of Ca and Cl in the waste composition increased the fraction of gaseous CsCl in the furnace and thus resulted in the high distribution ratios of Cs in the fly ash of MSW and the high leaching rates of Cs from the fly ash.

Dataset Information

Thermochemical and Toxic Element Behavior during Co-Combustion of Coal and Municipal Sludge.

Publications

Thermochemical and Toxic Element Behavior during Co-Combustion of Coal and Municipal Sludge.

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