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Aggregating structure in coal water slurry studied by eDLVO theory and fractal dimension

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Abstract

Coal water slurry gasification is a main source of hydrogen in the developing hydrogen economy. Moreover, biomass and waste can be added, making gasification process greener. To expand the application of coal water slurry and gasification process, it is necessary to understand the micro-structure in this large particle suspension system. In this paper, the micro-structure in coal water slurry was studied by extended DLVO (eDLVO) theory and fractal dimension, which is used to explain the mechanism of stability in large particle suspension systems. The interaction between two coal particles was characterized from the interparticle potential and energy barrier based on the eDLVO theory. The rheology and stability between different types of coals are measured and explained by the aggregating structure and fractal dimension in coal water slurry. The results indicated that there would be an aggregating structure in high rank coals, due to the interparticle potential caused by the surface properties, but probably not in low rank coals. This aggregating structure can be described and characterized by fractal dimension. The aggregation of particles is the source of the stability for high rank coals, as the close-packed 3D network structure in large particle suspension can support coal particles from settling down. The results have demonstrated that the combination of the eDLVO theory and rheological measurement is an effective way to investigate the stability of large particle suspension systems.

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Abbreviations

a :

Diameter of particle

A 121 :

Hamaker constant of material 1 in medium 2 with material 1

d p :

Distance of glass rod traveled

d s :

Length of the supernatant above the mud line

d t :

Height of the total slurry

D :

Fractal dimension of aggregation structure

H :

Distance between two particles

k :

Boltzmann constant

K :

Consistency coefficient

K 121 :

Hydrophobic constant of material 1 in medium 2 with material 1

n :

Rheological index

R :

Radius of agglomeration structure

T :

Temperature

V D :

Van der Waals force/potential

V E :

Double layer force/potential

V H :

Hydrophobic force/potential

V T :

Total potential energy

β :

Structural coefficient

ε :

Dielectric constant

θ :

Contact angle

\({\rm{\dot \gamma}}\) :

Shear rate

κ :

−1 Debye screening length

ρ :

Material density

σ :

Shear stress

σ :

0 Yield stress

ϕ :

v Volume fraction of particles

ψ :

δ Stern potential

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Authors and Affiliations

  1. Key Laboratory for Thermal Science and Power Engineering of the Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing, 100084, China

    Qiang Li, Jian Hou, Jiansheng Zhang & Yang Zhang

  2. Energy and Electricity Research Center, Jinan University, Zhuhai, 519070, China

    Qian Wang

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  1. Qiang Li
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Correspondence to Jiansheng Zhang.

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Li, Q., Wang, Q., Hou, J. et al. Aggregating structure in coal water slurry studied by eDLVO theory and fractal dimension. Front. Energy 17, 306–316 (2023). https://doi.org/10.1007/s11708-021-0736-1

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