The Synthesis of CME (Coconut Methyl Ester) With Organic Catalyst: Experiments, Data Analysis and Kinetics Model

Biodiesel is one of the biomass materials or renewable energy, which is needed today to replace fuel from fossil energy, which can reduce global warming and has a high renewability cycle. Biodiesel is obtained from plants, so it is also known as biofuel. One type of biodiesel group is CME (Coconut Methyl Ester) which is biodiesel obtained from coconut oil as raw material. In this study, a synthesis of used coconut oil and methanol has been carried out with an organic catalyst based on coconut coir called the ASK catalyst. The results of transesterification have provided some important information, including: the yield are 15-19,5% after usage of the ASK catalyst consisting of amorphous phase and crystalline phase ClK0,8Na0,2, with the density and viscosity of products are 790-800 kg/m3 and 0,6-1 mm2/s. Yield data obtained are then used to build the kinetics equation. The equation is 𝑌 = 1 − e^(-k'tn), with the value of n = 1 and k' for temperatures of 50oC and 60oC were 0,20 and 0,21, respectively, and a minimum activation energy of Q = 1,1 kJ/mol, which can determine reaction time needed at a specified temperature to achieve a certain yield value.

Study of Modified Dry Desulfurization Ash in a Power Plant for Sequestering CO2 from a Micron-Nanoscale Perspective

To improve the CO2 fixation ability of dry desulfurization ash (DDA), a DDA must be modified by chemical methods. At the micron level, the changes in microstructure and chemical composition before and after DDA modification were analysed by Scanning Electron Microscope (SEM) and Energy Dispersive Spectroscopy (EDS), and the reaction mechanism of the modification process was inferred. On the other hand, the chemical and mineral phase compositions of the modified DDA and its solid products were analysed by X ray Fluorescence (XRF) and X-ray diffraction (XRD). In addition, the microstructure of the modified DDA before and after sequestration at nanometre resolution was studied by SEM-EDS so that the curing mechanism of the modified DDA was clearly defined. Then, the effects of the solid–liquid ratio, temperature, pressure and reaction time on the sequestration of CO2 in the modified DDA were studied with aqueous carbonation. The results showed that the higher the temperature is, the higher the solid–liquid ratio, and the lower initial pressure is, the less the CO2 sequestered in the modified DDA and the less the carbon sequestration capacity of the modified DDA. Under the experimental conditions, the carbonation efficiency of the modified DDA could reach 94.42%, and 1 ton of modified DDA could sequester up to 50.61 kg CO2. Compared with conventional DDA, the carbon sequestration capacity is effectively improved. The kinetic data confirmed that the fitting correlation of the quasi-first-order kinetics equation is more significant. The smaller the solid–liquid ratio is, the lower the temperature, the higher the initial pressure, and the higher the rate constant of the quasi-first-order kinetics equation.

Application of Stiffness Confinement Method in Transient Transport Calculation

Stiffness confinement method (SCM) can effectively alleviate the stiffness in the neutron kinetics equation and can use larger time steps to obtain the same calculation accuracy and improve the computational efficiency. However, the existing SCM is mainly used to solve two group transient diffusion equations. In this paper, the SCM is employed to solve the multigroup transient transport calculation. On the basis of the original method of characteristics (MOC) code PEACH, the transient function is added, and the PEACH-K program is developed. Based on the numerical results of the latest published OECD/NEA C5G7-TD benchmark, it shows that the PEACH-K program developed in this paper has both high computing precision and good numerical stability.

Adsorption of cadmium and lead in wastewater by four kinds of biomass xanthates

This study determined the adsorption of Cd2+ and Pb2+ (100 mg·L−1 of each) in simulated wastewater by biomass xanthates made from starch, chitosan, wheat stalk and corn stalk. The results showed that the adsorption efficiency of Pb2+ and Cd2+ ions followed the order: corn stalk xanthate > wheat stalk xanthate ≥ chitosan xanthate > starch xanthate. The results of kinetic modeling showed that the adsorption process was characterized by physical-chemical adsorption, and that a second-order kinetics equation described the adsorption process well. The optimum conditions for the adsorption of Cd2+ and Pb2+ by corn stalk xanthate were: adsorption time 2 hours, temperature 20–25 °C, and pH 6–8. The results serve as a reference for treating wastewater containing Cd2+ and Pb2+.

Kinetics of Siderite Ore Roasting in the Shaft Furnace

Kinetics of the siderite ore roasting in the air, helium and hydrogen flows has been studied in a gasometrical unit with continuous mass variation logging. We have derived the expression for determination of an apparent degree of calcination and identified its dependence on the size of the prill, the heat treatment duration, and gas-phase composition. Using a generalized chemical kinetics equation, we have obtained a formula for calculation of the decomposition period for siderite ore samples. It has been found that calcination rate increases with the temperature rise, irrespective of the sample size and atmospheric composition. Calcination process has been studied at low temperatures. We have demonstrated that it is feasible to describe the process of siderite ore thermal dissociation by a first-order kinetics equation. We have obtained the expression to calculate the duration of this process depending on different parameters. Using a generalized chemical kinetics equation, we have obtained a formula for checking the expressions that describe the experimental data. We have studied kinetics of the reduction of roasted ore samples at various temperatures using different sizes of the samples. The obtained results have been applied for optimization of the design values and operating conditions of the siderite ore roasting in shaft furnaces. These will also be used for designing a shaft furnace consisting of a calcination zone, reduction zone (metallization zone) and metallized product cooling zone, which will increase iron content in the end-product to 65-70%.

Determining the relationship between critical conditions of detonation propagation and the average decomposition rates of explosives in detonation waves

The study introduces a model of steady propagation of non-ideal detonation of open cylindrical charges with diameters close to critical ones. The model was obtained in the quasi-one-dimensional approximation with the use of analytical methods. We found a solution for the model’s closing equation, which directly relates the average decomposition rate in the detonation front, determined by the parameters of the formal kinetics equation and dependent on the detonation rate, the gas-dynamic parameters of the initial explosive and its reaction products (isentropic exponents), the duration of the chemical peak and ideal detonation velocity, and also the ratio of the charge diameter to the duration of the chemical peak of the ideal detonation. We obtained an equation which reflects the dependence of the non-ideal detonation velocity on the charge diameter. The critical diameter is determined as the range boundary of the charge diameter values at which this equation still has a solution. The study shows that the expression for the fundamental characteristics of the detonation process, i.e. the ratio of the spread time and the reaction time of the explosive, differs from the expression used in the Khariton principle when taking into account the divergence of the reacting flow in the curved detonation front. As for the critical value of this ratio, in general it is different from the unity and is a variable value depending on the characteristics of the kinetics of decomposition of a substance in shock waves. Based on the calculations, we draw a conclusion that changes in the microstructure of the explosive charge of the same composition, displayed by changes in the parameters of the formal kinetics equation, are accompanied by relative changes in the critical diameter, many times greater than the relative changes in the duration of the chemical peak of ideal detonation