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The present study focuses on the numerical modeling of the co-combustion of reject coal (RC) and sal leaves (SL) in a drop tube furnace (DTF) under different conditions, including air-fuel and oxy-fuel environments. The numerical results highlight the significant influence of replacing the N2 atmosphere with CO2 on the temperature profiles of individual fuels and their blends. For instance, when exposed to a 21%O2/79%CO2 atmosphere, Blend SL3 and Blend SL5 experience a decrease in temperature from 1372 K to 1559 K to 1327 K and 1395 K, respectively. Conversely, increasing the O2 concentration to 35% leads to a temperature rise. Furthermore, the combustion analysis reveals that the addition of 10% SL to RC in a 21%O2/79%N2 environment enhances the devolatilization rate from 1.41 × 10−12 kg/s to 1.77 × 10−12 kg/s. Additionally, the char combustion process for all blends is completed closer to the DTF inlet at 0.28 m, compared to 0.32 m for RC alone. These findings indicate that blending SL with RC promotes a favorable combustion process. Moreover, increasing the O2 concentration to 35% in oxy-fuel conditions enhances the temperature profiles. The numerical analysis demonstrates good agreement with experimental data within a range of ±5%–11%. This suggests that the developed model can be effectively utilized for optimizing and designing biomass co-firing systems in industrial applications, considering both air-fuel and oxy-fuel conditions. [ABSTRACT FROM AUTHOR]

This work presents the combustion behavior of different mean relative densities (MRD) of Indian thermal coal. Coal of different MRD in the range of 1.25 to 2.20 was prepared using the density separation method. Essential characterization of all MRD fraction coals was done by proximate analysis, ultimate analysis, gross calorific value, BET analysis, and ash analysis. The combustion behavior of all coal samples was carried out by a thermogravimetric analyzer (TGA). Combustion characteristics parameters such as ignition temperature (TIG), peak temperature (Tmax), burnout temperature (TBT) and maximum combustion rate (DTGmax) were evaluated using TGA-DTG data. Results show that with the increase of MRD from 1.25 to 2.20, TIG and Tmax increase from 324°C and 451°C to 426°C and 462°C, respectively, while DTGmax reduces from 9.52 to 1.68 mass%/min. The kinetic analysis demonstrates that coal combustion follows the first-order reaction model and can be separated into two stages. The thermodynamic parameters signify that lighter MRD coal requires lower endothermic energy than heavier MRD coal. [ABSTRACT FROM AUTHOR]

The present study performs three-dimensional (3D) numerical simulations of coal combustion of four samples with varying ash content in a drop tube furnace (DTF) to mimic the particle heating rates observed in industrial furnaces. The numerical framework adopted is validated with prior experimental and simulation results using a 3D cylindrical geometry and a very good match is obtained for the axial temperature distribution and particle burnout rate. The combustion performance of coal samples with varying ash contents of 2.3, 16.6, 24.1, and 37.2 wt%, is explored through temperature profiles, burnout rates, particle tracking, and mass fractions of various products of combustion. A user-defined function is used to specify the 14 species, 10-step solid particle combustion with a modified eddy dissipation concept model for volatile combustion. The range of ash content considered is for Indian coal which has a high degree of heterogeneity, making the evaluation of its combustion performance, a challenge. The present work aims to provide benchmark set of results showing the evolution of the evaporated, charred, and volatile mass for the three ash contents, which has not been attempted before. It is found that the high-ash content Indian coal samples have a tendency to produce less NOx . A 9:52% reduction in the NOx is obtained for the coal sample with 37:2% ash compared to that with 16:6% ash. The results suggest that the combustion performance is enhanced when the ash content falls within an optimum range of 20 35%. [ABSTRACT FROM AUTHOR]

In this work, drying characteristics and kinetic behavior of coal slurry were investigated. The drying tests were performed using natural draught tray dryer for power industry. The impacts of drying temperature (35°C to 90°C) and sample mass (5 g to 25 g) on moonidih and patherdih coal slurry samples were investigated. The results revealed that increasing the temperature from 35°C to 90°C raised the maximum drying rate from 11.20 to 38.72 g/s.min2 in 1.5 hr representing a 70% rise in the drying rate. As a result, the drying temperature and sample mass had a considerable influence on the drying process. The drying time was lowered and the drying rate was improved by raising the drying temperature. The Midilli-Kucuk model suited these drying data the best, suggesting that moisture transport in coal slurry samples was mostly regulated by internal diffusion. [ABSTRACT FROM AUTHOR]

Highly transparent and self-cleaning ZnO nanorods (NRs) and ZnO@TiO2 core–shell (CS) nanoarrays were fabricated using the sol–gel dip-coating technique. TiO2 nanoparticles (NPs) were coated as a shell layer over the hydrothermally grown ZnO NRs. The number of shell layers on the ZnO NRs was varied by modulating the number of dipping cycles from 1 to 3 to optimize their transmittance. The optimized CS nanoarrays with two dipping cycles display a 2% enhancement of optical transmission compared to the ZnO NRs. In addition, superhydrophilicity (contact angle ∼of 12°) stimulates the self-cleaning nature of the thin films. A water contact angle of 12° was noted for the ZnO@TiO2: 2 cycle sample, indicating their superhydrophilic nature. Moreover, the photocatalytic activity of the pristine ZnO NRs and ZnO@TiO2 CS nanoarrays was tested under UV and direct sunlight through the dye degradation of methylene blue (MB). Based upon the TiO2 morphology and accessibility of the ZnO@TiO2 heterojunction interface, CS nanoarrays with two shell layers exhibit the highest degree of dye photodegradation efficiency of 68.72% and 91% under sunlight and UV light irradiation, respectively. The CS nanoarrays demonstrate medium sunlight and excellent UV-light-driven photocatalytic activity. Our findings suggest that the ZnO@TiO2 CS nanoarrays are potential photocatalysts for dye degradation and self-cleaning applications in solar cell coverings. [ABSTRACT FROM AUTHOR]

This study reports the combustion behavior of coal, petroleum coke (PEC), wheat straw (WS), and their ternary blends to assess the impact of PEC and WS blending on coal combustion characteristics. Ignition temperature (TS), peak temperature (Tmax), burnout temperature (TB), performance indices, and combustion efficiency (η) were investigated to identify the influence of WS and PEC blending on coal combustion. Results infer that PEC has poor combustion characteristics and a higher gross calorific value of 8602 kcal/kg than coal and WS. For 10% PEC in blends, with the rise of WS from 10 to 30%, TS declined from 373 to 256°C, TB decreased from 510 to 509°C, signifying improvement in blend combustibility. At 400°C, η rose from 15.52 to 39.30% as WS increased in blends from 10 to 30%. For 15% PEC in the blend, activation energy reduced from 106.12 to 83.27 kJ/mol as WS increased from 10 to 25%. The synergistic effect is significant for higher biomass content in blends. Thermodynamics analysis inferred that PEC and coal combustion is turmoil than WS. [ABSTRACT FROM AUTHOR]

Present work reports the effects of rice husk (RH) blending on combustion characteristics of high ash Indian coal. Combustion experiments were carried out using the thermogravimetric analyzer (TGA). Combustion performance of coal, RH, and coal-RH blends were assessed through identification of ignition temperature (TI), peak temperature (TP), burnout temperature (TC) along with ignition index (IIX), combustion characteristics index (CIX), burnout index (BIX), heat intensity index (HIX), activation energy (AE), and thermodynamic parameters ( Δ H , ΔG, and ΔS) analysis. Experimental results show that with the increase in RH mass in coal up to 50%, TI decreased from 418 to 263°C, TP decreased from 468 to 450°C, TC decreased from 499 to 490°C, and AE reduced from 84.84 to 72.42 kJ/mol, inferring substantial enhancement in coal combustion performance. Δ H , ΔG, and ΔS analysis showed that with 50% RH in coal reduced from 78.66 to 67.11 kJ/mol, ΔG improved from 147.62 to 57.66 kJ/mol, ΔS varied from −92.48 to 15.99 J/mol.K, concluding blending of RH eases the combustion. [ABSTRACT FROM AUTHOR]

This work presents experimental results of combustion characteristics of low volatile Indian coal. Coal of different average relative density (ARD) varying from 1.35 to 2.0 was generated by density fractionation of the coal. Coal samples were characterized by proximate analysis, Fourier-transform infrared spectroscopy (FTIR), ultimate analysis, and gross calorific value (GCV). Combustion experiments were conducted to identify the effects of ARD and functional groups on combustion characteristics. It was observed that with the rise in ARD of coal from 1.45 to 2.0, the ignition temperature increased from 357°C to 417°C. Highest coal combustion rate was observed for 1.525 ARD coal, due to the presence of all types of hydrocarbons, alcoholic, aldehyde, and trisubstituted alkene (except primary amines) as seen from FTIR analysis. Analyses of coal combustion rate and GCV indicate that 1.45 ARD coal has the highest GCV, heat release rate, and lowest ash generation rate, properties that are best suitable for thermal utilities. [ABSTRACT FROM AUTHOR]

Two different stockpiles, one loose and another compact, in the open air were formed using approximately 500 tons of less than 200 mm size run of mines thermal coal on a concrete floor. Coal samples from the stockpile were collected at 30 days interval (from June 2016 to May 2017) for analysis of various chemical properties: proximate analysis, ultimate analysis, gross calorific value (GCV), and various burning profile temperatures such as ignition temperature, peak temperature, and burnout temperature. Experimental results show that, due to weathering of coal, elemental carbon decreased from 43% to 37%, hydrogen decreased from 4% to 3%, and GCV decreased from 3,769 to 3,211 kcal/kg during 330 days of storage of coal in an open atmosphere. Ash content of coal increased from 34% to 42.5% due to loss of combustibles. Sulfur was found to increase from 0.25% to 0.60% during storage. Variation in combustion parameters signifies that weathering has a significant negative impact on coal combustion properties as coal becomes difficult to ignite. Economic analysis infers that due to weathering of coal, for generation of 10,000 kcal heat, coal consumption may increase from 2.65 to 3.13 kg, while ash generation increases from 0.9 to 1.30 kg. [ABSTRACT FROM AUTHOR]

Presents work aims at the results obtained from experimental studies on utilization of eucalyptus leaves (ECL) to enhance the burning performance of a coal cleaning plant reject well known as reject coal (RC). Different parameters of combustion like; temperature of ignition (Ti), peak temperature (Tp), temperature of burnout (Tb), peak combustion rate (DTGmax), index of ignition (Di), index of burnout (Df), index of combustion performance (S), and index of rate intensity (Hf) were obtained from TGA-DTG experiments to optimize the blending ratio of ECL and RC. Experimental results showed that there is improvement in combustion performance of RC when 20% by mass of ECL is blend with 80% by mass of RC and reducing Ti from 449℃ to 429℃, Tp from 511℃ to 509℃, and Tf from 567℃ to 552℃. Addition of higher quantities of ECL up to 90% mass, reduces Ti, Tp, Tb further down to 234℃, 476℃ and 508℃ respectively and increases DTGmax from 3.64 to 4.73 wt%/minute. Considering the various parameters of combustion, maximum of 20% mass of ECL having 78% volatile matter, 6985 kcal/kg GCV are recommended to blend with 80% by mass of RC having 11% volatile matter and 3105 kcal/kg GCV for thermal utilities. Experimental results confirmed that, ECL can be burned with coal to reduce the overall coal consumption, thus decreases the carbon footprint of coal fired utilities. [ABSTRACT FROM AUTHOR]

Presence of arsenic ion [As(V)] in ground water at different locations of India is a big health concern in present days. In this work, effort was made to remove As(V) ions from tap water by electrocoagulation (EC) using iron (Fe) electrodes having an effective surface area of 38.67 m2/m3. Investigation was focused on studying the effects of various process parameters of EC like solution pH, current density (CD), inter-electrode distance (IED) initial arsenic concentration (Co), electrical conductivity of water on removal of As(V) in efficient ways. Experimental results reveal that initial pH of 7, CD of 0.431 mA/cm2, IED of 0.5 cm, agitation speed of 200 rpm and NaCl dose of 0.33 g/L are optimal conditions to reduce As(V) ion concentration from 100 µg/L to below 10 µg/L. Overall, 99.4% As(V) removal was achieved at 30 minutes of EC treatment. Different quality parameters for drinking water such as TDS, turbidity, salinity, electrical conductivity were also assessed during the EC, to verify drinking water quality in several aspects. Kinetic analysis infers that As(V) removal by EC follow the first order reaction model. Present study affirms that, EC is an effective technique for efficient As(V) removal from drinking water with an estimated energy consumption of 8.33 × 10−3 Kwh/m3, electrode utilization of 0.0486 kg/m3, and operational cost of 0.0488 US$/m3. [ABSTRACT FROM AUTHOR]