Handling sludge through thermal conversion is environmentally friendly, which, however, requires sludge drying. This work proposed to use the waste heat of flue gas (FG) to dry sludge. The integration of sludge drying in biomass fueled combined heat and power (CHP) plants can clearly affect the performance of downstream processes in FG cleaning, such as flue gas quench (FGQ) and flue gas condenser, and further affect the energy efficiency of CHP. In order to understand the influence, a mathematical model and an Aspen PLUS model were developed to simulate the drying process and the CHP, respectively. Based on simulations, it is found that the increase of feeding rate of sludge and the moisture content of sludge after drying can decrease the water evaporation in FGQ. An increase in the feeding rate of sludge in combination with a drop of moisture content of sludge after drying can decrease the heat recovery from FG. When using dried sludge to replace biomass, the amount of saving could be influenced by the moisture content after drying and the flow rate of sludge. Simulation results show that drying sludge to a moisture content of 40% leads to the maximum biomass saving.
In this study, halloysite nanotubes polyaniline (HNT-PANI) nanocomposite was synthesized by using an ultrasound-assisted method. Because of high conductivity, ease of synthesis, low cost, nanosize tubular structure and improved structural/electrochemical properties, HNT-PANI had been used for the electrode fabrication of a supercapacitor. The dispersion of halloysite nanotubes in polyaniline was prepared by following an ultrasound approach. The structural and morphological studies of the HNT-PANI nanocomposite were investigated by X-ray diffraction, Fourier Transform Infrared Spectroscopy, Raman and transmission electron microscopy. The length of the halloysite nanotubes varied from 200 to 1000 nm and the composite nanoparticles possessed tubular hallow shaped structure. The electrochemical performance of the HNT-PANI nanocomposite electrode was analyzed after performing potentiodynamic and electrochemical impedance spectroscopic studies. The crystallite size of HNT-PANI composite was calculated and the average size ranged from 30 to 100 nm. HNT-PANI composite electrode exhibited the highest specific capacitance of 282.5 F/g at a current density of 0.5 A/g.
Carbon spheres (CS) were synthesized by simple hydrothermal route and further modified with TiO2 shell (CSTS) to demonstrate photocatalytic reduction of Cr(VI). The bare CS and CSTS were characterized with X-ray diffraction, Raman spectroscopy, field emission scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy and steady-state photoluminescence. The hybrid CSTS photocatalyst showed improved visible light photocatalytic reduction toward Cr(VI), compared with pristine TiO2 and commercial TiO2 (P25). Porous CS catalysts when modified with TiO2 shell shows 100% reduction of Cr(VI) in 4 h under visible light illumination. Also enhanced visible light photocurrent (~ threefold) is observed for CSTS photocatalyst as compared to bare CS photocatalyst. Modification of TiO2 shell on carbon sphere suppresses the recombination of photogenerated excitons (e−/h+) as revealed from the photoluminescence study and enhanced light absorption due to scattering of light by the sphere framework of TiO2 shell and CS, thus enhancing the overall photocatalytic activity.
Ethylene diamine tetraacetic acid (EDTA) and citric acid are two different chelants that have been used in several studies to enhance the phytoremediation process. Though numerous reports are available to prove the efficacy of these chelants toward enhancing the metal uptake and translocation, there are very few studies focusing on the minimization of hazards posed by the chelants. EDTA is an effective synthetic chelant that aids phytoremediation, whereas citric acid, an organic chelant, poses minimum level of toxicity to the soil. Application of a single chelant may be effective for pollutant removal but poses toxic symptoms on the soil as well as plants at higher concentrations. Nevertheless, a combination of two different chelants may prove to be effective both in terms of pollutant removal and safety. This may be attributed to the alleviating effect of one chelant over the other, which needs further investigation. The number of reports on the combined treatment of chelants, their overall effects on plant growth and soil enzymes are also limited. The present study was conducted to evaluate the individual as well as the combined effects of EDTA and citric acid on the soil enzyme activities and plant growth parameters on Talinum triangulare. The soil was treated with chelants, and plants were grown over this soil for 50 days. Growth parameters such as leaf count, shoot length, root length and girth were analyzed. The activity of three soil enzymes—amylase, invertase and cellulase—was examined. The study revealed the toxicity of chelants themselves when used in excess. Though it was found that 250 mg kg−1 concentration of EDTA has the best performance in terms of plant growth, it has been noticed that plant growth and soil enzymes were least affected at 500 mg kg−1 concentration of mixed chelants.
Magnetorheological (MR) fluids are a talk of the day due to their potential applications in various fields. In the present work, six different MR fluids were prepared based on the variation in the percentage of carbonyl iron (CI) particles and carrier liquid. The smart material CI particle was well characterized by XRD, SEM-EDAX and VSM measurements. The effect of carrier fluid on sedimentation was tested using CI 50% and compared with the other carrier oil used. The Magnatec oil acts as a better candidate due to its sedimentation stability and thermal resistance. Therefore, the rheological measurement was examined for the three magnetorheological fluids (MRF) prepared, namely MRF 32, MRF 50 and MRF 80 with Magnatec oil as carrier liquid. The three various size annular gaps between the piston and the inner cylinder casing was also studied. Among the three variations, 1, 1.5 and 2 mm, the maximum damping force was obtained for 1-mm annular gap. A number of experimentations were carried out to investigate the performance of the MR fluid as well as the annular gap. Cyclic load test was performed with various annular gaps, and 0.536 kN was the maximum damping force for 1-mm annular gap.
Hydrocarbon-based solid oxide fuel cell (SOFC) is being projected as one of the possible alternatives to conventional internal combustion engines. However, the conventional Ni–YSZ anode is prone to carburization in the presence of hydrocarbon fuels. In the present study, an optimized Ni–Cu-based anode composition (Ni0.9–Cu0.1–YSZ0.95–GDC0.05) has been evolved based on accelerated carburization studies and phase analysis by X-ray diffractometry and X-ray photoelectron spectroscopy. The electrochemical parameters have been derived for the optimized anode composition, and its exchange current density is estimated to be 76.3 mA cm−2 at 780 °C. The main advantage of the optimized anode is its suitability for co-firing with the electrolyte. Using the optimized anode composition, anode-supported SOFC single cells (ASCs) have been fabricated and their electrical and electrochemical performances have been evaluated and compared with conventional ASC. The anode-supported co-cast SOFC with the optimized anode composition exhibits a power density of 436 mW cm−2 at 850 °C and 0.5 V with methane as fuel.
Briquetting process offers unique advantages such as uniformity in briquette size and shape, easy storage and transportation, thanks to the influence of binders which ensures good bonding and combustion performance. Recently, much has been discussed about the briquettes-binders system and the influence of binders on the resulting physical and combustion properties of briquettes. However, the present knowledge is insufficient on the binderless briquetting technology which is commonly used for producing lignite briquettes, as well as the resulting properties and beneficial effects when compared to briquettes produced with binders. The present review discusses the binderless briquetting technology in detail and its influence on the combustion and mechanical properties of the lignite briquettes. To a large extent, some properties of the lignite like hardness, surface structure, plasticity and elasticity can influence the binderless briquetting process. Reducing the plasticity or increasing the elasticity of lignite is advantageous to binderless briquetting. The various forms/theorems of binderless technology including capillary, adhesion, bituminous and humic acid, colloidal, denser water and cation membrane theorems were discussed. Under binderless briquetting system, the influence of briquetting parameters (temperature and pressure) and lignite coal properties (particle size distribution, moisture content, and hydrogen bonding) on briquette strength was extensively analyzed and discussed. This review study is concluded by presenting a comprehensive overview on the bonding mechanisms and several points of interest for future studies as regards the binderless technology for producing lignite briquettes.