The Combustion Characteristics of Waste Liquor from Renewable Plant-Derived Chemical Polyol Processing

An experimental study was carried out to investigate the combustion characteristics of plant-derived polyol liquor waste using thermogravimetric analyzer and vertical tube furnace tests. The research results showed that the waste liquor combustion reaction comprised four processes: evaporation, pyrolysis, combustion, and inorganic salt reaction, and that a wave peak exists for each process. The pyrolysis process, which is the most violent reaction, exhibited the maximum peak weight-loss rate and weight-loss ratio and had the lowest activation energy and frequency factor. The peak weight-loss rate of inorganic salt reaction process was less than that during the combustion process, but sodium alkali has catalytic effect at high temperature, which makes the activation energy and the frequency factor of inorganic salt reaction process less than that of the combustion process. The ignition temperature of the waste liquor in the vertical tube furnace was lower than the temperature in the thermogravimetric analyzer. The ignition temperature of pyrolysis volatiles measured in a vertical tube furnace was less than 700 °C but the ignition temperature of carbon combustion as measured with TG – DTG was 718 °C. When the temperature inside vertical tube furnace was higher than 800 °C, the waste liquor combustion process becomes almost instantaneous (about 8 s) and is violent, which produces more residual carbon content in the combustion products as a longer holding time is necessary to ensure that the reaction is completed.

Diffusion of F and Cl in dry rhyodacitic melt

Chemical diffusion of F and Cl has been experimentally determined in a rhyodacitic melt obtained from remelting a sample of Hekla pumice (Iceland). Diffusion couple experiments were conducted in a vertical tube furnace over a temperature range of 750–950 °C and in air for durations of 1 to 35 days. Concentration profiles of F and Cl were obtained for the quenched samples using an electron microprobe. Fluorine and chlorine exhibit Arrhenian behavior over the range of temperature investigated here. The pre-exponential factors of F and Cl are D0(F) = 4.3 × 10−4 and D0(Cl) = 1.6 × 10−5 m2/s. Fluorine diffusion coefficients vary in the order of 1 × 10−15 to 1 × 10−13 m2/s, whereas Cl diffusivity is up to two orders of magnitude slower. The activation energies for F and Cl diffusivities are equal within error at 223 ± 31 and 229 ± 52 kJ/mol, respectively. The difference in diffusivity between F and Cl is particularly pronounced in the melt of our study, compared to results obtained for other magmatic melt compositions. This means that the potential for diffusive fractionation exists and may occur especially under conditions of magma ascent and bubble growth, as this would favor partitioning of the relatively fast-diffusing halogens into growing bubbles, due to H2O exsolution. A dependence of diffusivity on atomic radius observed here is enhanced over that observed in more basic, less viscous melts, indicating that diffusive fractionation is more likely to be pronounced in more silicic, more viscous systems. A proper parameterization and modeling of diffusive fractionation of halogens in actively degassing volcanic systems thus holds the potential of serving as a tool for quantifying the processes responsible for volcanic unrest.

Experimental Studies on Co-Combustion of Sludge and Wheat Straw

This work presents studies on the co-combustion of sludge and wheat straw (30 wt % sludge + 70 wt % wheat straw). Prior to the combustion experiment, thermogravimetric analysis was performed to investigate the combustion characteristic of the blended fuel. Results indicated that the blended fuel could remedy the defect of each individual component and also promote the combustion. Co-combustion experiments were conducted in a lab-scale vertical tube furnace and the ash samples were analyzed by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES), X-ray Diffraction (XRD), and Scanning Electron Microscope (SEM). Thermodynamic calculations were also made to study the interactions that occurred. Addition of sludge could raise the melting point of wheat straw ash and reduce the slagging tendency. Co-combustion also restrained the release of K and transferred it into aluminosilicate and phosphate. Transfer of Pb and Zn in the co-combustion was also studied. The release and leaching toxicity of the two heavy metals in the co-combustion were weakened effectively by wheat straw. PbCl2(g) and ZnCl2(g) could be captured by K2SiO3 in wheat straw ash particles and generate silicates. Interactions that possibly occurred between K, Zn, and Pb components were discussed at the end of the paper.

Use of colemanite in ferronickel smelting

Use of colemanite in metal-slag systems aims primarily to decrease the viscosity of slag and, therefore, achieve better metal-slag separation. Enhanced metal-slag separation is helpful to decrease the number of suspended metal/alloy droplets in slag, i.e. the physical losses. In the literature, successful use of colemanite was reported both in steelmaking and copper matte smelting processes. Ferronickel smelting slags contain nickel in the range of 0.1-0.2% and correspondingly, metal-slag distribution ratio values of nickel are reported even above 200. On the contrary, nickel recoveries are hard to exceed 95%. This can be mostly attributed to the physical losses of nickel due to very high slag volume in ferronickel smelters; for 1 ton of ferronickel, 10-15 tonnes of slag are generated regardless of the type of the laterite, which contains significant quantity of gangue components. The authors thought that use of colemanite could be a solution to decrease physical losses. Therefore, the use of colemanite in ferronickel smelting was investigated in the present work. Laboratory-scale smelting experiments were conducted using calcined and prereduced laterites in a vertical tube furnace under different gas atmospheres. The amount of colemanite added was in the range of 0 - 2.5% of the total charge. The experiments were also performed using ferronickel and slag samples obtained from a ferronickel smelter.

Carbothermic Reduction of Misamis Oriental Chromite Ores

This study was conducted to determine the non-isothermal and isothermal reduction of chromium ores in the solid-state by reductants like solid carbon under argon and hydrogen-argon atmosphere. Two different chromite ores from local sources , sandy chromite ore from Opol, Misamis Oriental (SCO) and lumpy chromite ore from Manticao, Misamis Oriental (LCM) were used in the study. Isothermal and non-isothermal experiments were conducted in a fixed bed reactor heated in a vertical tube furnace in the temperature range 800 to 1000°C. Raw chromite and reduced samples were subjected to phase analysis and morphology characterization using X-ray flourescence (XRF), X-ray diffraction (XRD), and energy dispersive x-ray spectroscopy (EDX). It was found that reduction does not go to completion at this temperature range. The early stage of reduction of iron was controlled by nucleation and the later by nucleation or chemical reaction or both. The activation energy at the early stage of reduction is estimated to be 44.76 kJ/mol and the later stage of reduction is 144 kJ/mol for SCO and 76.5 kJ/mol for LCM. The reduction of chromium was controlled by chemical reaction.