Geochemistry

Catalysis

Adsorption

Metamorphic rock

Engineering

Mesoporous material

Materials science

Mineralogy

Intrusion

Biochemistry

Computer science

Chemical engineering

Nitrogen

Classification scheme

Geology

Coal

Porosity

Physical chemistry

Thermodynamics

Fractal

Physics

Organic chemistry

Mathematics

Macropore

Fractal dimension

Porosimetry

Mathematical analysis

Porous medium

Composite material

Chemistry

Mercury intrusion porosimetry

Piecewise

Machine learning

Powder Technology

The pore structure of different metamorphic coal was analyzed by mercury intrusion porosimetry and N2 adsorption. Combined with the fractal dimension models of the Frenkel-Halsey-Hill and Menger, the pore size range of the experiment was spliced reasonably. A new pore classification scheme is put forward by fractal dimensions, revealing the pore structure and fractal characteristics of different metamorphic coal. The results suggest that pores exhibit piecewise fractal characteristics. A new pore classification scheme is put forward by piecewise fractal dimensions: I (0–2.0 nm, corresponding to D1); II (2.0–50 nm, corresponding to D2); III (50–2000 nm, corresponding to D3); IV (2000–20,000 nm, corresponding to D4); V (>20,000 nm, corresponding to D5). It is not inconsistent with the international union of pure and applied chemistry for pore classification, which shows that the new pore classification scheme is reliable.

Experimental analysis of the pore structure and fractal characteristics of different metamorphic coal based on mercury intrusion‑nitrogen adsorption porosimetry