Inherent Moisture Research Articles

CHARACTERISTICS AND LIQUEFACTION OF COAL FROM WARUKIN FORMATION, TABALONG AREA, SOUTH KALIMANTAN–INDONESIA

Since the coal characteristic is the main controlling factors in coal liquefaction, thus five coal seams with different coal rank from Warukin Formation in Tabalong Area, South Kalimantan have been used in this study. Three seams were low rank coal (Wara 110, Wara 120, Wara 200) while two seams were medium rank (Tutupan 210 and Paringin 712). The objectives of this study was to investigate the effect of coal rank on the rate of coal conversion factor. Coal liquefaction was conducted in an autoclave on low pressure (14.7 psi) and temperature 120°C. Experiments were designed with time intervals 30, 60 and 90 minutes, respectively. The average coal properties of seam Wara 110, Wara 120 and Wara 200 were 26.65%, 5.08%, 46.26% and 30.60% for inherent moisture, ash content, volatile matter and. fixed carbon, respectively. In contrast, coal properties for seam Tutupan 210 and Paringin 712 were 18.42%, 1.81%, 23.02% and 35.76% for inherent moisture, ash content, volatile matter and fixed carbon, respectively. The maximum yields for Wara 110, Wara 120 and Wara 200 were 48.60% (30 minutes), 51.27% (60 minutes) and 46.72% (90 minutes). In comparison, Tutupan 210 and Paringin 712 resulted maximum yields of 8.22% (30 minutes), 18.35% (60 minutes), 6.23% (90 minutes). In conclusion, low rank coal has higher yield conversion compared to medium rank coal since it has higher H/C ratio. Keywords: Coal liquefaction, low rank coal, Kalimantan.

Clarifying the influence of moisture on the ignition and combustion of wet Victorian brown coal in air-firing and oxy-fuel modes: Part 2: Contribution of gasification reaction to char oxidation rate

This paper is the second part of the study to clarify the influence of moisture in Victorian brown coal oxy-fuel combustion, with a focus on char oxidation and gasification reaction through experimental and modelling efforts. An in-situ high-speed two-colour pyrometer with the wavelength band of 0.85–1.05μm was employed to measure particle temperature in the flat flame burner reactor. The combustion stage of carbon particle was simulated for the transient phenomena with particle heating and radiative heat transfer. The multiple surface reaction single-film approach, including char–O2, char–CO2 and char–steam reactions, was employed and the contribution of individual reactions to carbon consumption rate was determined via matching with the measured particle temperature. Irrespective of the initial moisture content, the extent of char–steam gasification reaction was found to account for ~15% in the air-firing case. This reaction was mainly triggered by the external steam in the reactor, rather than the inherent moisture that resided preferentially as volatile cloud on char particle surface. The combined effect of both char–CO2 and char–steam gasification was significant in oxy-fuel combustion mode, especially for the wet coal. In the oxy-21 case, these two reactions have a total extent of around 8% and 18% on the burning char surface of dried and wet coal, respectively. The char–CO2 gasification is insignificant, because the char particle temperature was low. Increasing the oxygen percentage to 31% in CO2 enhanced the total extent of these two gasification reactions to 28%, based on the mass of total carbon. Such an extent is comparable with the literature. However, the steam gasification rate for brown coal char was far higher, ~26% relative to ~10% for high-rank bituminous coal reported in the literature. This substantiates the strong steam gasification reactivity of Victorian brown coal char. The contribution of inherent moisture to char–steam gasification reaction is crucial in the combustion of wet coal in the oxy-21 case, accounting for ~10%. This is due to the long residence of the unevaporated steam as a thick cloud on the char surface. Increasing the oxygen concentration in CO2 enhanced the char–O2 reaction, the release rate of volatiles and inherent moisture. Therefore, the char–steam reaction caused by the inherent moisture within coal matrix was minimised and eventually diminished in the oxy-31 case.

Influence of inherent moisture on the ignition and combustion of wet Victorian brown coal in air-firing and oxy-fuel modes: Part 1: The volatile ignition and flame propagation

This study for the first time reported the volatile ignition and oxidation for wet Victorian brown coal in both air-firing and oxy-fuel modes. The aim is to quantitatively understand the evaporation of inherent moisture and its overlapping with the subsequent volatile ignition and oxidation steps during pulverised coal combustion. A wet Victorian brown coal sample with the moisture content up to 30wt.% and a size range of 63–104μm has been tested. Its ignition, volatile flame propagation and char oxidation have been diagnosed optically in a laboratory-scale flat-flame burner reactor (FFBR) coupled with a high-speed camera. 1-D modelling was also conducted to predict coal ignition based on the classic coal drying theory and coal devolatilisation rate. As has been confirmed, the release of moisture on the initial drying stage is incomplete prior to the subsequent volatile ignition. The fraction of moisture released upon drying only accounted for 10% of its original amount in wet brown coal prior to ignition. This is due to a firm residence of the moisture within coal capillaries, and a rapid heat feedback from hot gas to the dried particle surface that was ignited instantaneously prior to the release of the remaining moisture. The unevaporated moisture was observed to be released with the volatiles together to form a thick cloud layer in the vicinity of the coal particle, thereby enlarging the sizes of the volatile flame remarkably, which are approximately twice the size of the dried coal flame. However, the intensity of the wet coal flame was much weaker than dried coal, due to the dilution effect of the inherent moisture on the volatile cloud. In the oxy-fuel combustion mode, the inherent moisture interrelated with CO2, a tri-atomic gas with a larger specific heat capacity than N2 to significantly delay the ignition of the wet coal particle and its flame intensity and propagation velocity.

Influence of the hydrothermal dewatering on the combustion characteristics of Chinese low-rank coals

This study investigates the influence of hydrothermal dewatering performed at different temperatures on the combustion characteristics of Chinese low-rank coals with different coalification maturities. It was found that the upgrading process significantly decreased the inherent moisture and oxygen content, increased the calorific value and fixed carbon content, and promoted the damage of the hydrophilic oxygen functional groups. The results of oxygen/carbon atomic ratio indicated that the upgrading process converted the low-rank coals near to high-rank coals which can also be gained using the Fourier transform infrared spectroscopy. The thermogravimetric analysis showed that the combustion processes of upgraded coals were delayed toward the high temperature region, and the upgraded coals had higher ignition and burnout temperature. On the other hand, based on the higher average combustion rate and comprehensive combustion parameter, the upgraded coals performed better compared with raw brown coals and the Da Tong bituminous coal. In ignition segment, the activation energy increased after treatment but decreased in the combustion stage. The changes in coal compositions, microstructure, rank, and combustion characteristics were more notable as the temperature in hydrothermal dewatering increased from 250 to 300 °C or coals of lower ranks were used.

Effect of magmatic intrusion on coal pore characteristics and fractal research

The pore characteristics in magmatic intruded coals are closely related to the absorption-desorption and the flow of Coalbed Methane (CBM) in coal seams. Coal samples with different degrees of magmatic intrusion are tested using the method of mercury intrusion porosimetry (MIP). A number of parameters, such as the pore diameter, the volume, the connectivity and the specific surface area, are investigated. In addition, the fractal theory is introduced as a new approach to characterize the pore characteristics in intruded coals by calculating the fractal dimensions. The correlation between the fractal dimension and the inherent moisture content is also discussed. The results indicate that 1) when the coal approaches the magma, the pore size, the pore volume, the open pores and pore connectivity increase, but the total specific surface area exhibit decline trends; 2) the calculated fractal dimension can demonstrate the above characteristics; 3) a significant relationship between the inherent moisture content and the fractal dimension can be established. The research findings in this paper provide a useful fundamental knowledge to guide future studies of CBM development or gas outburst for intruded coals.

Effects of Bed Height and Particle Size on Drying of a Turkish Lignite

Drying of coarse lignite particles, because of high inherent moisture content, is very important for the lignite user. An effective drying process is necessary to utilize coarse lignite particles effectively. Fixed-bed drying experiments were carried out for a Turkish lignite (Konya-Ilgın). Effects of bed height and particle size were investigated. Drying experiments were carried out at 80, 130, and 150 mm bed heights and 20, 35, and 50 mm particle sizes. It was found that increasing the bed height increased the drying time and decreased the drying rate, and particles of larger sizes have lower drying rates and higher drying times. Additionally, it was also found that Konya-Ilgın lignite does not show a constant drying rate and has a long falling drying rate. As a result of this study, drying characteristics of Konya-Ilgın lignite were presented for different drying conditions.

Comparative studies on the effect of mineral matter on physico-chemical properties, inherent moisture and drying kinetics of Chinese lignite

The comparative study between the high-ash lignite (HAS) and low-ash lignite (LAS) demonstrated great effects of mineral matter on physico-chemical properties, inherent moisture and drying kinetics of Chinese lignite. The physico-chemical properties were characterized by X-ray diffraction (XRD), N2 physisorption, fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and thermoanalytical methods. Raw and treated samples (screening, dry beneficiation, and flotation) were analyzed for inherent moisture content. Drying kinetic experiments were performed by isothermal thermogravimetry in combination with thin-layer models. In comparison with LAS, HAS had less cohesive features with higher amounts of heterogeneous crystalline minerals, less quantity of O-containing functional groups, and smaller surface areas as well as lower pore volumes, as evidenced by characterization analysis. Less cohesive features could allow the moisture to move easily through the lignite, which thus resulted in a lower inherent moisture contained in HAS. On the other hand, due to higher thermal conductivity and poorer holding-moisture structures resulted from the presence of abundant minerals, HAS revealed more promising drying kinetics with lower activation energies, which were determined by the combination of isothermal experiments and Page model analyses.

Numerical Modeling and Experimental Investigation on the Use of Brown Coal and Its Beneficiated Semicoke for Coal Blending Combustion in a 600 MWe Utility Furnace

In this paper, coal blending combustion performance in a 600 MWe supercritical boiler has been investigated through a series of on-site measurements and computational fluid dynamic modellings. A bituminous coal was used as reference, which was blended with brown coal or brown coal semicoke in an indirect way, i.e., different coals being fed separately into the boiler without prior mixing in the mill. The coal blending combustion behavior was assessed upon varying brown coal injection location, brown coal blending ratio, air staging ratio, and the use of brown coal pyrolysis-derived semicoke. ANSYS FLUENT 15.0 was employed for numerical simulations. Upon a successful validation, the model was further used to predict the influence of individual variables. The main conclusions achieved include (1) the bituminous coal-designed mill can be used safely for brown coal, at the expense of an increased mass ratio of primary air to coal, a decreased temperature for the outlet of the mill, and an incomplete drying of brown coal. (2) The allocation of brown coal in the middle burner zone is the best option that ensures a relatively long residence time of bituminous coal particles in the boiler, as well as provides sufficient heat to bituminous coal particles for a quicker ignition and burnout. (3) The 50 wt % blending ratio for brown coal is optimum, striking a good balance between the feeding amounts of combustible hydrocarbons and inherent moisture into the burner. (4) The separate over fire air of 30% ratio is beneficial in reducing total NOx emission through increasing the unburnt char quantity in the NOx reduction zone. (5) The high heating value of beneficiated Victorian brown coal and its semicokes ensures a lower feeding rate for each of them to be used as a substitute fuel. The high volatile-O2 and char-O2 oxidation reactivity of these samples also ensured a strong heat provision from their flame to the bituminous coal allocated in both the bottom and top of the burner zones. (6) The use of brown coal and semicoke is in favor of the reduction in NOx, particularly fuel-NOx, due to the generally low nitrogen content within these samples, relative to bituminous coal.

Measurement of Soil Moisture Content at Microwave Frequencies

This paper discusses the measurement of moisture content present in soil by computing the dielectric constant of soil samples at three frequencies, using microwave free-space transmission technique. This leads to the determination of inherent moisture content in the samples by applying Topp's Equation. The change in the value of dielectric constant and the subsequent increase in the moisture content for each of the soil samples with added moisture levels at 20%, 23.1% and 28.6% are noted. Dielectric constant of some common materials such as free-space, FR4, acrylic and water are measured to check the efficacy of the proposed method.

Physicochemical characterizations for improving the slurryability of Philippine lignite upgraded through microwave irradiation

Philippine lignite with high inherent moisture and oxygen was upgraded by improving the slurryability through microwave irradiation.

Influence of relative humidity on the structure and electrochemical performance of sustainable LiFeSO4F electrodes for Li-ion batteries

Tavorite-type LiFeSO4F is used to demonstrate the inherent moisture sensitivity issue of sulfate-based materials for Li-ion batteries.

Synthesis and thermal properties of polyimides containing azomethine linkage for processable high-performance engineering plastics

A new series of polyimides having azomethine functionality in backbone was synthesized by two-steps polycondensation method. Five substituted aromatic diamines—N-(4-aminobenzylidene)-2chloro-6-methylbenzene-1,4-diamine (DA1), N-(4-aminobenzylidene)-2-methoxybenzene-1,4-diamine (DA2), N-(4-aminobenzylidene)-2-methylbenzene-1,4-diamine (DA3), N-(4-aminobenzylidene)-3-methylbenzene-1,4-diamine (DA4) and N,(4-aminobenzylidene)-2-hydroxybenzene-1,4-diamine (DA5)—were prepared and condensed with 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) to obtain poly(azomethine imide). All synthesized polyimides PI(1–5) were fully characterized by elemental analyses, FTIR, 1H-NMR, having amorphous nature and are soluble in dmac, dmf, and dmso, m-cresol due to presence of azomethine functionality. The inherent viscosities and moisture absorption of all polyimides lie in the range of 0.65–0.85 dL gm−1 and 0.68–0.82% respectively. Thermal stability was assessed by 10% weight loss temperature and the degradation temperature of the resultant polymers falls in the ranges from 480–535 °C in nitrogen. The glass transition temperature was in the range of 225–330 °C. Due to above mentioned attractive properties, polyimide-based material are attractive for processable high-performance engineering plastics and starting material for fabrication of new polymers.

Pyrolysis of Hailar Lignite: Experiments with a Tubular Reactor and a Continuous Screw Kiln Reactor

Pyrolysis of Hailar lignite (moisture content ~ 34.81 wt%) was investigated at temperatures ranging from 700 °C to 900 °C in two different reactors: A tubular reactor (TR) and a continuous screw kiln reactor (CSKR). Under temperature programmed-heating conditions in the TR reactor, the auto-generated steam from the lignite moisture was vaporized and swept out of the reactor by the N2flow during the long heating process, leading to a weakened effect on the subsequent reactions. However, in the CSKR tests all the volatiles was generated continuously while avoid the carrier gas dilution , significant interactions between the in situ steam and the intermediate products occurred. Upon comparing the two pyrolysis processes, it was found the CSKR process exhibits higher H2yield of 23.23 mol/kg, H2proportion of 49.82 vol % than those (16.97 mol/kg, 41.51 vol %) from the TR process. The results demonstrated that inherent moisture in Hailar lignite had a significant influence on the product yield, depending on the pyrolysis conditions. It was also shown that increase in temperature led to rising dry gas yield and H2yield.

Nanostructured self-cleaning lyocell fabrics with asymmetric wettability and moisture absorbency (part I)

A single-faced superhydrophobic lyocell fabric maintaining its inherent high moisture absorbing bulk property was produced by oxygen plasma-based nanostructuring and a subsequent coating with a low-surface-energy material. After 5 minutes of oxygen plasma etching, followed by 30 seconds of a plasma polymerized hexamethyldisiloxane coating, the treated surface of lyocell turned into a superhydrophobic surface with a static contact angle greater than 160° and a sliding angle less than 2°; however, the backside was hydrophilic, untreated lyocell fabric. As a result of oxygen plasma etching, dual hierarchical roughness was formed on the lyocell fabric as nano scale pillars or hairs were added onto the lyocell fabric surface with micro scale roughness. Extremely opposite wetting behavior was observed, when a water droplet was deposited on the face and backside of the plasma-treated lyocell fabric. A water droplet was immediately absorbed and spread out on the untreated backside, while it rolled off the treated surface, demonstrating a bouncing effect.

Pyrolysis of Hailar lignite in an autogenerated steam agent

An in situ pyrolysis process of high moisture content lignite in an autogenerated steam agent was proposed. The aim is to utilize steam autogenerated from lignite moisture as a reactant to produce fuel gas and additional hydrogen. Thermogravimetric analysis revealed that mass loss and maximum mass loss rate increased with the rise of heating rates. The in situ pyrolysis process was performed in a screw kiln reactor to investigate the effects of moisture content and reactor temperature on product yields, gas compositions, and pyrolysis performance. The results demonstrated that inherent moisture in lignite had a significant influence on the product yield. The pyrolysis of L R (raw lignite with a moisture content of 36.9 %, wet basis) at 900 °C exhibited higher dry yield of 33.67 mL g−1 and H2 content of 50.3 vol% than those from the pyrolysis of the predried lignite. It was also shown that increasing reaction temperature led to a rising dry gas yield and H2 yield. The pyrolysis of L R showed the maximum dry yield of 33.7 mL g−1 and H2 content of 53.2 vol% at 1,000 °C. The LHV of fuel gas ranged from 18.45 to 14.38 MJ Nm−3 when the reactor temperature increased from 600 to 1,000 °C.

Development of a CO2 emission factor in Korea from sub-bituminous coal by the classification method

While the Intergovernmental Panel on Climate Change classifies coal as anthracite, bituminous coal, and sub-bituminous coal, Korea only distinguishes coal as anthracite and bituminous coal while sub-bituminous coal is considered bituminous coal. As a result, Korea conducted research in the CO2 emission factors of anthracite and bituminous coal, but largely ignored sub-bituminous coal. Therefore, the purpose of this research is to develop the CO2 emission factor of sub-bituminous coal by classifying sub-bituminous coal from resources of bituminous coal activities collected in Korea between 2007 and 2011. The 2007–2011 average carbon content of sub-bituminous coal was analyzed to be 69.63 ± 3.11 %, the average hydrogen content 4.97 ± 0.37 %, the inherent moisture 12.60 ± 4.33 %, the total moisture 21.91 ± 5.45 %, and the dry-based gross calorific value was analyzed to be 5,914 ± 391 kcal/kg; using these analyzed values, the as-received net calorific value was found to be 20.75 ± 7.59 TJ/Gg and the CO2 emission factor was found to be 96,241 ± 4,064 kg/TJ. In addition, the 62.7 million ton amount for the 2009 greenhouse gas emission from sub-bituminous coal as estimated with the analyzed value of this study is an amount that is equivalent to 11.1 % of the 2009 total greenhouse gas emission amount of 564.7 million tons, and this amount is larger than the 9.3 % for the industrial processes sector, 3.3 % for the agricultural sector and 2.5 % for the waste sector. Therefore, it is important to reflect the realities of Korea when estimating the greenhouse gas emission from such sub-bituminous coals.

UV‐cured cellulose nanofiber composites with moisture durable oxygen barrier properties

ABSTRACTNanocomposites based on 10 to 60 vol % cellulose nanofibers (NFC) in a photopolymerizable hyperbranched acrylate matrix were prepared. Unmodified NFC and NFC chemically modified with a silane coupling agent and with ceric ammonium nitrate for direct polymer grafting from the cellulose surface were used. A homogeneous dispersion of NFC in the matrix was obtained in each case, leading to a marked improvement in oxygen barrier (up to nine times) and thermomechanical properties (storage modulus increased up to seven times). The mechanisms involved in the permeability reduction were investigated, revealing non‐monotonic trends in the evolution of the solubility and diffusion coefficients with NFC content. Most significantly, the inherent moisture sensitivity of the oxygen permeability of the NFC was found to be drastically reduced when it was dispersed in the polymer matrix, particularly after chemical modification, underlining the promise of the present approach for the production of robust, high barrier organic films. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40604.

Rheological behavior of coal bio-oil slurries

Coal bio-oil slurries (CBSs) were prepared by blending coal with bio-oil from the fast pyrolysis, and their apparent viscosities were measured by a rotary viscometer. The influences of coal rank, solid concentration, particle size distribution and temperature on the apparent viscosity and rheological properties of slurries were investigated. Additionally, the grey relational analysis was employed to determine the order of importance of factors affecting the apparent viscosity for different rank coals. Results show that, the CBS exhibits non-Newtonian fluid behavior and can be described by Herschel–Bulkley equation. The main factors for different rank coals affecting apparent viscosity of CBS are inherent moisture and carboxyl groups. The maximum solid concentration of CBS can reach 45–47 wt. % for Shenmu bituminous coal. Appropriate solid particle size distribution and preparation temperature can provide satisfied slurries with low viscosity.

Effects of Moisture and Coal Blending on the Hardgrove Grindability Index of Pakistani Coals

The Hardgrove Grindibility Index (HGI) of coal is an indicator of its grindibility characteristics to determine the energy required for its pulverization. The present study is aimed at investigating the effect of inherent moisture and the blending behavior on HGIs of indigenous coals. Experiments were carried out using the standard Hardgrove Grindibility Machine to determine HGIs of three indigenous coals belonging to the Lakhra, Degari, and Chamalang coal deposits. In addition, the blending effect of six binary and six ternary blends of parent coals with different blending ratios were also tested for their HGIs. The Lakhra coal has shown the highest HGI value of 66 against 23% of inherent moisture, whereas the Degari and Chamalang coals respectively indicated HGI values of 53 and 32 against 10% and 6.95% of inherent moisture content. It was found that as the inherent moisture in coal increased the HGI values also increased. Lakhra coal, having the highest HGI value, was found to be easy to grind as compared to the Degari and Chamalang coals that have lower HGI values. The HGI values of the binary and ternary blends of parent coals, in various proportions, were found to be the proportionally average values of the parent coals.

Investigation of Low Rank Coal Gasification in a Two-Stage Downdraft Entrained-Flow Gasifier

Low-rank coal contains more inherent moisture, high alkali metals (Na, K, Ca), high oxygen content, and low sulfur than high-rank coal. Low-rank coal gasification usually has lower efficiency than high-rank coal, since more energy has been used to drive out the moisture and volatile matters and vaporize them. Nevertheless, Low-rank coal comprises about half of both the current utilization and the reserves in the United States and is the largest energy resource in the United States, so it is worthwhile and important to investigate the low-rank coal gasification process. In this study, the two-stage fuel feeding scheme is investigated in a downdraft, entrained-flow, and refractory-lined reactor. Both a high-rank coal (Illinois No.6 bituminous) and a low-rank coal (South Hallsville Texas Lignite) are used for comparison under the following operating conditions: 1) low-rank coal vs. high-rank coal, 2) one-stage injection vs. two-stage injection, 3) low-rank coal with pre-drying vs. without pre-drying, and 4) dry coal feeding without steam injection vs. with steam injection at the second stage. The results show that 1) With predrying to 12% moisture, syngas produced from lignite has 538 K lower exit temperature and 18% greater Higher Heating Value (HHV) than syngas produced from Illinois #6. 2) The two-stage fuel feeding scheme results in a lower wall temperature (around 100 K) in the lower half of the gasifier than the single-stage injection scheme. 3) Without pre-drying, the high inherent moisture content in the lignite causes the syngas HHV to decrease by 27% and the mole fractions of both H2 and CO to decrease by 33%, while the water vapor content increases by 121% (by volume). The low-rank coal, without pre-drying, will take longer to finish the demoisturization and devolatilization processes, resulting in delayed combustion and gasification processes.