"Nuisance dust": unprotective limits for exposure to coal mine dust in the United States, 1934-1969

Molecular Mechanism Study on the Effect of Microstructural Differences of Octylphenol Polyoxyethylene Ether (OPEO) Surfactants on the Wettability of Anthracite

Inhalable coal dust poses a serious threat to coal mining safety, air quality, and the health of miners. Therefore, the development of efficient dust suppressants is crucial for addressing this issue. This study evaluated the ability of three high-surface-active OPEO-type nonionic surfactants (OP4, OP9, and OP13) to improve the wetting properties of anthracite via extensive experiments and a molecular simulation and determined the micro-mechanism of different wetting properties. The surface tension results show that OP4 has the lowest surface tension (27.182 mN/m). Contact angle tests and wetting kinetics models suggest that OP4 exhibits the strongest wetting improvement ability on raw coal with the smallest contact angle (20.1°) and the fastest wetting rate. In addition, FTIR and XPS experimental results also reveal that OP4-treated coal surfaces introduce the most hydrophilic elements and groups. UV spectroscopy testing shows that OP4 has the highest adsorption capacity on the coal surface, reaching 133.45 mg/g. The surfactant is adsorbed on the surface and pores of anthracite, while the strong adsorption ability of OP4 results in the least amount of N₂ adsorption (8.408 cm³/g) but the largest specific surface area (1.673 m²/g). In addition, the filling behavior and aggregation behavior of surfactants on the anthracite coal surface were observed using SEM. The MD simulation results indicate that OPEO reagents with overly long hydrophilic chains would produce spatial effects on the coal surface. Under the influence of the π-π interaction between the hydrophobic benzene ring and the coal surface, OPEO reagents with fewer ethylene oxide quantities are more prone to adsorb onto the coal surface. Therefore, after the adsorption of OP4, both the polarity and the water molecule adhesion ability of the coal surface are greatly enhanced, which helps to suppress dust production. These results provide important references and a foundation for future designs of efficient compound dust suppressant systems.

Establishment and application of an index system for prevention of coal workers' pneumoconiosis: a Delphi and analytic hierarchy process study in four state-owned coal enterprises of China

OBJECTIVE

To explore the difference of cumulative incidence rate of coal workers' pneumoconiosis (CWP) among four large state-owned coal enterprises in northern China, we created an index system for evaluating the quality of comprehensive measures against CWP and applied the system to evaluate and compare the measures of the four coal enterprises.

METHODS

A two-round Delphi investigation was conducted to identify the indicators in the index system. The weight values of the indicators were calculated with analytic hierarchy process methods. Measures of CWP, mine annals, records and other information in each coal mine of the four enterprises were collected. The evaluation scores, which ranged from 0 to 100, were calculated and compared with.

RESULTS

A three-grade index system with 3 first-grade indicators, 9 second-grade indicators and 44 tertiary-grade indicators was established. The expert authority coefficient (C_r ) was 0.75 and the Kendall's coefficient of concordance (Kendall's W) was 0.15 (χ²=193.30, P<0.001). The weight value of 'Geological conditions' was 0.43, equal to 'Dust control engineering technology', and that of 'Occupational health management' was 0.14. The medians and quartiles of the evaluation scores of comprehensive measures against CWP of the four enterprises were 58.38 (54.60~63.02), 64.63 (60.83~67.06), 72.99 (68.92~77.67) and 75.07 (70.73~79.20), respectively.

CONCLUSIONS

The index system could be effectively used for evaluation and comparison of the comprehensive measures against CWP among different enterprises. The geological conditions and dust control engineering technology played an important role in preventing and controlling CWP.