Investigation on characterization of different types of coals and preparation of coal-derived activated carbon

Mongolia possesses substantial coal resources (173 billion tons), which include high-rank bituminous coals, subbituminous coals, and brown coals. Based on these coal types, a manufacturer of activated carbon can be developed using comparatively simple technology. The consumption of activated carbon is continuously increasing due to its use in waste and drinking water treatments, atmospheric pollution control, gas mixture separation, and solvent recovery. Currently, Mongolia imports 700–800 tons of activated carbon annually at a price of 700–900 USD per ton. For this study, we have selected several high-rank coals from Mongolia, including Tavan Tolgoi IV and Nariin Sukhait (both bituminous coking coals from Southern Mongolia), as well as the Saikhan-Ovoo deposit (a high-rank stone coal from Northern Mongolia). The selected coals were enriched with a zinc chloride solution and subjected to semicoking (carbonization) to produce the primary raw material for activated carbon production. Activated carbon was obtained from the carbonized coal by activation with preheated water steam within 120 minutes. The main technical characteristics of the initial coal samples and activated carbons, along with their microporous properties such as iodine number, methylene blue adsorption, and surface area (BET), have been determined. Additionally, a technological scheme for activated carbon production from high-rank coal has been proposed.

For commercialization of coal liquefaction processes, blending of various types of raw coal will be an important consideration. In this report, Shin-Yubari coal, Taiheiyo coal, Sohyakoishi coal and Yallourn brown coal were blended in various ratios to investigate the effects of a mixture of two types of coal on the hydrogenation reaction. The conversion of the blended coals were compared to conversion obtained for each pure coal. A blend of Yallourn brown coal and Shin-Yubari coal exhibited a clear deviation from additivity and a positive synergism was observed. Brown coal requires hydrogen donor solvent to enhance its hydrogenation capability. It is considered that hydroaromatics derived from Shin-Yubari coal promote the hydrogenation reaction of Yallourn brown coal.

Implementing a co-combustion technology in coal-fired plants using biomass waste is a promising option to alleviate environmental pollution, reduce fuel costs, and minimize waste. The considerable potential of palm oil waste is believed to be able to substitute coal as a raw material in a coal-fired power plant. However, since each coal has different compositions and biomass generally has a high alkali content, the propensity of slagging and fouling during co-combustion needs to be clarified. This research evaluates the co-combustion ash characteristics of different types of coal, which is co-combusted with 25% palm oil biomass waste. The combustion test employs a drop tube furnace, where the produced ash composition and its morphology are investigated using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction. The results show that the ash melting temperature of the three types of coal mixed with biomass is reduced, although insignificant. Bituminous coal has a low potential for slagging and fouling since SiO2 and Al2O3 dominate the coal ash composition. In addition, lignite coal has low SiO2 and Al2O3 contents but high alkali contents (K and Na). As confirmed by SEM-EDS analysis, probe observations also show that lignite coal co-combustion with empty fruit bunch and frond waste has higher slagging and fouling risks.

Drainage air-water capillary-pressure curves were obtained for Pittsburgh and Pocahontas coals at various overburden pressures. Capillary-pressure data were used to investigate pore-size characteristics. Results were indicative of the complex pore structure of coal, consisting primarily of a network of macro- and microfractures. In most cases, however, displacement pressure and residual water saturation increased at higher overburden pressure. Reasonable agreement between measured relative permeabilities and those calculated from capillary-pressure data with Purcell's model was obtained for only a few samples. Fracture permeabilities computed from pore-size distribution were lower than permeabilities pore-size distribution were lower than permeabilities actually measured at the same overburden pressure. Helium porosity was considerably higher than porosity determined by water saturation, indicating porosity determined by water saturation, indicating inaccessible pore volume to water. Pore compressibility was determined under triaxial stress-loading conditions. Changes in porosity with overburden pressure were more significant at pressures below 1,500 psig. Above this pressure, pore compressibility appeared to approach a pressure, pore compressibility appeared to approach a constant value averaging about 0.5 × 10(−4) psi(−1) for the coal samples studied. Introduction Increased interest in underground coal gasification and coal-seam degasification for the purpose of producing clean energy stimulated fundamental producing clean energy stimulated fundamental research into the phenomena of multiphase fluid flow through coal. Two previous papers presented results of investigation of the air- and water-permeability and relative-permeability characteristics at various overburden pressures for two different types of coal. However, to understand the mechanisms of two-phase flow (usually gas and water) through a complex porous system such as coal, one needs a clear insight into the internal pore structure of coal and the interaction between pore structure of coal and the interaction between this structure and the associated fluids. Such knowledge of the make-up of the pore structure helps in modeling fluid flow through the system and in interpreting permeability and relative-permeability data. Interaction between the pore structure and fluids results in the capillary-pressure phenomena. Capillary-pressure data have been used extensively to determine the pore characteristics of many petroleum reservoir rocks and to relate these petroleum reservoir rocks and to relate these characteristics to the single- and two-phase flow behavior in the rock. It is also known that natural fracture systems are the principal source of flow capacity of many petroleum reservoir rocks and contribute materially petroleum reservoir rocks and contribute materially to the storage capacity of some. Changes in fracture capacity resulting from changes in net overburden pressure have an important influence on the flow pressure have an important influence on the flow properties of the rock, as reported by Jones. In our properties of the rock, as reported by Jones. In our previous work with coal, which is a naturally previous work with coal, which is a naturally fractured system, absolute and effective permeabilities were found to be highly sensitive to overburden pressure (pov). Thus, it would be expected that the pressure (pov). Thus, it would be expected that the effect of Pov on the fracture flow capacity, capillary pressure, and pore compressibility is more dramatic pressure, and pore compressibility is more dramatic for coal. The internal structure of coal has been studied by microscopic methods, gas sorption measurements, and by mercury porosimetry. Data on helium porosity of different types of coal also can be porosity of different types of coal also can be found in Ref. 5. However, we are not aware of any determinations of capillary pressure in coal at different overburden pressures. In this paper gas-liquid capillary-pressure relationships for coal at different overburden pressures are presented. pressures are presented. SPEJ P. 261

An analysis was conducted on the relationship between the calorific value of different types of coal and the theoretical air requirement. It was found that the theoretical air volume required for generating the same amount of heat during combustion is the same for different types of coal. The concept of the air/coal ratio was improved by proposing the concept of the air/carbon ratio, which refers to the ratio of the mass of air to the mass of carbon during complete combustion; the ratio is approximately 11.5 kg/kg (mass ratio), being roughly constant for different types of coal, unlike the air/coal ratio showing a significant change with coal types. The total air flow rate in a boiler changed with load demand, and the influence of different fuel types can be neglected at the same load level. On this basis, an air flow rate control strategy for coal-fired utility boilers was proposed and implemented in the boiler in which the air flow rate required to the furnace is a function of the unit load. Experiments conducted in a 300 MWe coal-fired utility boiler confirm that the use of the control strategy of the air flow rate for the combustion optimization improves the stability of the main steam pressure and mitigates the fluctuations of the coal flow. These results provide a foundation for the implementation of a new strategy of air/coal decoupling and independent control of boiler combustion.

Influence of coal types on overlying strata movement and deformation in underground coal gasification without shaft and prediction method of surface subsidence

Laboratory investigation of drying process of Illinois coals

A general method for determining chemical kinetic parameters during ignition of coal char particles

Adsorption is a popular technique and has been investigated with many different materials for removing synthetic dyes from textile wastewater. This study compares the methylene blue (MB) adsorption capabilities of surface-modified superparamagnetic iron oxide nanoparticles, (SPION) using polyvinyl alcohol (PVA) and chitosan (CS), combined with two carbon materials, activated carbon (AC) and graphite (GR), respectively. After 9 days, depending on the initial MB loading concentration (0.015 mg/mL, 0.02 mg/mL, and 0.025 mg/mL), the MB adsorption capacities onto SPION/PVA/CS/AC and SPION/PVA/CS/GR were 7.6 ± 0.2–22.4 ± 0.05 and 6.9 ± 0.02–22.4 ± 0.05 mg/g, respectively. The cumulative release percentages of SPION/PVA/CS/AC and SPION/PVA/CS/GR after 30 days were 63.24 ± 8.77%–22.10 ± 2.59% and 91.29 ± 12.35%–24.42 ± 1.40%, respectively. Additionally, both SPION/PVA/CS/AC and SPION/PVA/CS/GR can both fit the Freundlich isotherm model. The adsorption and desorption kinetics can be fitted to the pseudo-second-order linear and zeroth-order models, respectively. At 0.020 mg/mL MB initial loading, out of SPION/PVA/CS/AC, SPION/PVA/CS/GR, and SPION/PVA/CS/GO, SPION/PVA/CS/AC is the most economical adsorbent. Compared to SPION/PVA/AC, SPION/PVA/CS/AC is less economical. Since CS has antimicrobial properties, antimicrobial activities should be investigated to conclude which adsorbent is more promising: SPION/PVA/AC or SPION/PVA/CS/AC.

An integrated process comprising ≃550 MWe (net power after CO2 capture and compression) pulverised coal-fired (PC-fired) supercritical power plant, an MEA-based post-combustion capture plant and a CO2 compression system has been modelled. The modelling was realised with Aspen Plus, V8.4, and extensive simulations of the integrated process using three different types of coal – Illinois No. 6 (bituminous coal), Montana Rosebud (sub-bituminous coal) and North Dakota (lignite coal), have been performed and the impacts of coal type on the overall performance of the integrated process have been quantified. The net plant efficiency, with CO2 capture only and with both CO2 capture and CO2 compression, is highest for Illinois No. 6 and least for North Dakota. For the state-of-the-art 30 wt% MEA solution, the optimum net plant efficiencies with only CO2 capture are 31.10, 30.60 and 30.30% for Illinois No. 6, Montana Rosebud and North Dakota, respectively, while the optimum net plant efficiencies with both CO2 capture and CO2 compression are 28.74, 28.12 and 27.74% for Illinois No. 6, Montana Rosebud and North Dakota, respectively.

The activated carbon (AC) with an exceptionally high surface area was made of silkworm excrement (SE) by microwave-assisted KOH activation (MAKA). It was investigated for the potential applications in methylene blue (MB) adsorption and a supercapacitor electrode. The effect of activation time on the AC properties and performance was studied. The physical and chemical properties of the as-prepared samples were analyzed by FE-SEM, TEM, N2 adsorption, and Raman spectroscopy. Remarkably, the AC with the largest specific surface area (SAs) of 2530.3 m2g−1 was produced by partial carbonization of SE at 400 °C (SE400-5) and then activated for only 5 min. The large SAs is attributed to the abundance of micro-pores, leading to the enhanced MB absorption performance, as equilibrium was reached within 10 min at 25 ppm of MB concentration. The maximum MB adsorption capacity for SE400-5 was 902.56 mg g−1. The adsorption isotherms revealed that the Langmuir model best fits the empirical data (R2 ≥ 0.9813), indicating monolayer adsorption. The kinetic model fitted well to the Pseudo-second-order (PSO) (R2 ≥ 0.9691). CV, GCD, and EIS measurements also evaluated the electrochemical properties of all samples. The electrodes were made without the addition of conductive material. The SE400-5 also had the lowest total resistance and highest total effective capacitance, which resulted in its highest specific capacitance (Cs) of 322 F g−1 at 0.5 A g−1. The capacitive retention of SE400-5 remained as high as 98% even after 10,000 cycles at 10 A g−1. These results demonstrate that SE is a viable source of AC for MB adsorption and a supercapacitor electrode.Graphical abstract

Micro- and mesoporous-enriched carbon materials prepared from a mixture of petroleum-derived oily sludge and biomass

Heteroatoms-doped hierarchical porous carbons: Multifunctional materials for effective methylene blue removal and cryogenic hydrogen storage

Tailored mesoporous structures of lignin-derived nano-carbons for multiple applications

Pore characterization of different types of coal from coal and gas outburst disaster sites using low temperature nitrogen adsorption approach