Effect of the benzene ring of the dispersant on the rheological characteristics of coal-water slurry:Experiments and theoretical calculations

In this study,low-rank coal-water slurry(LCWS)was prepared using polyoxyethylene dodecylphenol ether(PDPE)and polyoxyethylene lauryl ether(PLE),respectively.A combination of experiments and simulations was used to investigate the pulping properties and microscopic mechanism of the LCWS samples prepared using the two agents,so as to explore the influence of benzene ring on the performance of dispersant.The results of the LCWS preparation experiments revealed that the pulp-forming performance of PDPE exceeded that of PLE.When LCWS concentration is 62%,64%,and 66%,the apparent viscosity corresponding to PDPE is 247.80,504.17,and 653.10 mPa·s,and the apparent viscosity corresponding to PLE is 548.10,1470.61,and 1549.98 mPa·s,respectively.The C_(1000)(When the apparent viscosity is 1000 mPa·s,the corresponding concentration of LCWS is defined as C_(1000))values of PDPE and PLE are 67.60%and 62.95%,respectively.In addition to the van der Waals forces and hydrogen bonds between the PDPE and/or PLE molecules and coal,the benzene rings of PDPE presentπ-πstacking effect with the aromatic rings of coal.That could facilitate and strengthen the adsorption of PDPE on coal,which would be conducive to further improving the dispersion of coal particles.The two dispersants have no significant difference in effect on the pyrolysis of LCWS.The simulation results indicated that the times for PDPE and PLE molecules to reach flat adsorption state on coal are approximately 290 and 565 ps,respectively.The self-diffusion coefficient(D)of the PDPE and PLE on coal is 3.16 x 10^(-6)and6.57×10^(-6)m~2/s,respectively,and their interaction energies with coal are 785.71 and 648.60 kcal/mol,respectively.The results of the simulation calculations demonstrated that PDPE adsorbed on coal easier than PLE,and its binding is more stable than that of PLE owing to theπ-πstacking effect,which is conducive to uniform dispersion of coal in solution.The simulation results confirmed the experimental results.

Cation exchange for mercury and cadmium of xanthated,sulfonated,activated and non-treated subbituminous coal,commercial activated carbon and commercial synthetic resin:effect of pre-oxidation on xanthation of subbituminous coal

A subbituminous coal was oxidized with air at 150℃on a fixed bed for 4 h and xanthated with carbondisulfide in a basic solution,at 30 or 5-10℃.This xanthated coal was evaluated for the removal of Hg^(2+)and Cd^(2+)from 7,000 mg/L aqueous solutions;metal concentrations were detemmined by atomic absorption spectrometry.The ionexchange of the xanthated coal was compared against those of the original subbituminous coal,a sulfonated subbituminouscoal,activated carbon,commercial activated carbon,and commercial synthetic resin.The commercial synthetic resinshowed the highest exchange capacity(concentration factor 98%)followed by the xanthated coal(concentration factor 96%).The retention of cadmium on the sulfonated subbituminous coal was lower(exchange capacity 0.56 meq/g)thanthat of xanthated coals(1.85±0.09 meq/g).Our xanthated coal showed a better Cd^(2+)removal(8l%o against 15%)than anon preoxidized 40-h-xanthated coal,which shows that oxidation of coal increased the amount of oxygenated groups whichenhanced xanthation.

Coal Seam Correlation in Terrestrial Basins by Sequence Stratigraphy and Its Implications for Paleoclimate and Paleoenvironment Evolution

Coal correlation cannot only guide coal and coalbed methane exploitation,but may also provide valuable information for the evolution of the paleoclimate and paleoenvironment during coalaccumulation periods.It is difficult to undertake coal correlation in a terrestrial basin due to multiple superimposed coal seams and a lack of effective marker beds.In this study,based on the analyses of coal-bearing sedimentary environments and the observations of field outcrops and drilling cores,three key sequence surfaces of the Middle Jurassic Xishanyao Formation were identified in the middle part of the southern Junggar Basin.Three third-order sequences(S.Ⅲ1,S.Ⅲ2 and S.Ⅲ3)and ten fourth-order sequences were divided within the Xishanyao Formation.Regional coal correlation was finally identified,combined with the layered vertical pattern coal and its interval thickness,coal maceral,and coal quality data.In terms of the coal correlation within a specific sequence set,the interval of the B2–B3 coals was approximately three times thicker than that of the B3–B5 coals,which was the main marker for regional coal correlation in the Lower Xishanyao Formation.Furthermore,the phenomena of steadily developed B4 coal seam(2–3 m in thickness)across the Liuhuanggou coal mining area(eastern study region)and the large-small-large variation for intervals between the B8 and B9,B9 and B10,and B10 and B11 coal seams in the Manasi coal mining(western study region)were also an effective means for local coal correlation.Increasing vitrinite and sulphur content and decreasing inertinite content in a third-order sequence were found,which were likely to be closely related to lake level fluctuations.Based on the variation of coal macerals,the wildfire frequency gradually decreased from the bottom to the top of the Xishanyao Formation.The predicted O2level of the S.Ⅲ1,S.Ⅲ2,and S.Ⅲ3 of the Xishanyao Formation was 26.36%,24.22%,and 22.51%,respectively.Except for global paleoclimate effects,the provenance direction changes caused by the Bogda Mountains uplifts would result in a regular variation of coal maceral and coal quality across the study region.

Coalbed methane enrichment model of low-rank coals in multi-coals superimposed regions: a case study in the middle section of southern Junggar Basin

The Middle Jurassic Xishanyao Formation in the central section of the southern Junggar Basin has substantial amounts of low-ranked coalbed methane(CBM)recourses and is typically characterized by multi superimposed coal seams.To establish the CBM enrichment model,a series of experimental and testing methods were adopted,including coal maceral observation,proximate analysis,low temperature nitrogen adsorption(LTNA),methane carbon isotope determination,porosity/permeability simulation caused by overburden,and gas content testing.The controlling effect of sedimentary environment,geological tectonic,and hydrogeological condition on gas content was analyzed in detail.The results demonstrate that the areas with higher gas content(an average of 8.57 m3/t)are mainly located in the Urumqi River-Santun River(eastern study area),whereas gas content(an average of 3.92 m3/t)in the Manasi River-Taxi River(western study area)is relatively low.Because of the combined effects of strata temperature and pressure,the gas content in coal seam first increases and then decreases with increasing buried depth,and the critical depth of the inflection point ranges from 600 m to 850 m.Affected by the changes in topography and water head height,the direction of groundwater migration is predicted from south to north and from west to east.Based on the gas content variation,the lower and middle parts of the Xishanyao Formation can be divided into three independent coalbearing gas systems.Within a single gas-bearing system,there is a positive correlation between gas content and strata pressure,and the key mudstone layers separating each gas-bearing system are usually developed at the end of each highstand system tract.The new CBM accumulation model of the multi-coals mixed genetic gas shows that both biological and thermal origins are found in a buried depth interval between 600 m and 850 m,suggesting that the coals with those depths are the CBM enrichment horizons and favorable exploration regions in the middle section of the southern Junggar Basin.An in-depth discussion of the low-rank CBM enrichment model with multi-coal seams in the study region can provide a basis for the optimization of CBM well locations and favorable exploration horizons.