In order to improve the drying efficiency of lignite and restrain the moisture re-adsorption of dewatered coal, the drying characteristics of typical Chinese lignite, the re-adsorption performances of dewatered samples and the change in pore structure throughout the entire processes were investigated in this study. Lignite samples with four different particle size fractions were dried in a fixed-bed reactor in the temperature range 60–160°C. The re-adsorbing moisture behaviors of dewatered coal samples containing different water contents were investigated at temperatures of 20–40°C and humidities of 55–95%. The changes in the pore structure of raw coal and different dried samples were measured by mercury intrusion porosimetry (MIP) and the relations between their re-adsorption performance and change in pore structure were explored. The moisture removal yields of lignite increased with an increase in drying time and temperature and was close to 100% above 120°C and over 100% after holding 40 and 15 min at temperatures of 140 and 160°C due to the release of CO₂ from the decomposing carboxyl group in the coal matrix. The re-adsorbed moisture content in dewatered coal was influenced by drying temperature and coal particle size through varying pore structure. The temperature and relative humidity in the re-adsorbing process were the main factors that influenced the moisture re-adsorption capacity of dewatered lignite, in which the re-adsorbing temperature mainly operated by varying the bonding ability of water on the surface of dewatered coal, and the relative humidity was connected with the pore structure as well. The mesopore was the main factor that influenced the re-adsorption of dewatered coal and the re-adsorption of moisture in dewatered coal at 100°C was highest due to the narrow range of the pore radius and because the relative volume ratio of 5 to 50 nm mesopore (above 91%) was high. The water loss yield of lignite with smaller particle size was higher due to its larger pore volume and surface area, but its re-adsorption capacity was lower because of lower volume ratio of 5 to 50 nm mesopore volume in dewatered coal obtained from the smaller size lignite.

To investigate the dewatering kinetics and mechanism of low-rank coal, the dewatering behaviors of the Chinese lignite and its moisturized sample (prepared from dewatered coal moisturized under relative humidity of 75% at 303 K for 48 h) in nitrogen and the temperature range of 333–433 K were tested. Physical structure changes of raw coal and moisturized coal before and after drying were determined. The results indicate that drying process of lignite could be divided into four stages, which are increasing rate stage, constant rate stage, relatively fast decreasing rate stage, and relatively slow decreasing rate stage. Jander model and first-order kinetics model are favorite to describe the relatively fast decreasing rate stage and relatively slow decreasing rate stage, respectively, and the corresponding dewatering mechanism equations are and y = −ln(1 − α). The effective diffusion coefficients and diffusion activation energy were calculated by Fick’s second law. The diffusion activation energy of the dewatering stages, related to the relatively fast and slow decreasing rate stages, was 35.80, 40.75 kJ/mol for raw coal and 27.80, 37.34 kJ/mol for moisturized coal, respectively. The effective diffusion coefficient was significantly affected by drying temperature through the pore structure change of coal when other drying operation parameters were fixed. These prove that the forms of readsorbed water are not entirely the same as that in raw lignite, in which the former is relatively simple and the latter is more complex.

In order to realize the resource utilization of coal gasification slag (CGS) and to effectively control the emission of nitrogen oxides (NO_x) in coke oven gas, the effect of the reaction conditions and vanadium loading over the CGS catalysts was carried out for the selective catalytic reduction (SCR) of NO by NH₃. The various vanadium loaded CGS catalysts were prepared using impregnation methods. The addition of 1% vanadium to the CGS catalyst (V1/CGS) significantly enhanced the NO conversion at a wide temperature range of 180–290 °C. The catalysts were characterized by N₂ adsorption/desorption, X-ray photoelectron spectroscopy, H₂-temperature programmed reduction, NH₃-temperature programmed desorption, Inductively coupled plasma optical emission spectrometer (ICP-OES), thermo gravimetric analyses (TGA), Fourier Transform infrared spectroscopy (FTIR), Scanning electron microscope-Energy dispersive spectrometer (SEM-EDS), and X-ray powder diffraction (XRD). The experimental results show the following: That (1) the NO removal efficiency of the sample CGS₃ was the best, and it could be up to 100% under the experimental conditions; (2) The NO removal efficiency of the catalysts was higher in the atmosphere with SO₂ than that without SO₂; (3) The XRD results indicated the active component of vanadium was homogeneously dispersed over CGS and the active component of catalyst was V₂O₅ according to the XPS results. In particular, the NH₃-TPD spectra of the vanadium loaded CGS catalyst showed that vanadium produced more acid sites, and the Lewis acid sites on the vanadium species were the active sites for the catalytic reduction of NO at 240–290 °C.