SOx Release Research Articles

Deep extractive and oxidative removal of 2- and 3-methylthiophene using a hierarchical architecture of α-Keggin-type polyoxotungstate

2-methylthiophene (2 MT) and 3-methylthiophene (3 MT) are two pollutants that are not removed through the usual purification in the gas refineries and lead to the release of SOX after combustion. A novel active hierarchical architecture of Fe2O3 hollow nanospindle coated by polyaniline-Zinc(II)-substituted α-Keggin type polyoxotungestate (Fe2O3NHS@PA/αSiW11Zn composites) is presented for removal of 2-methylthiophene (2 MT) and 3-methylthiophene (3 MT) as representative of alkylthiophenes. In this research, using a combined method based on simultaneous extraction techniques, 99.1% of 2 MT and 98.7% of 3 MT were successfully removed. The process involves the simultaneous use of ultrasound-assisted extraction phenomenon by an ionic liquid and catalytic oxidation by the heterogeneous hybrid nanocatalyst (UA-ECODS). The advantages of this process include the possibility of producing ultra-clean fuels, mild operational conditions, and cost-effectiveness. For this purpose, Box-Behnken Design (BBD) and response surface methodology (RSM) were used to design experiments and study the parameters. The affecting factors were optimized in terms of removal efficiencies by response surface methodology. The oxidation progress was studied more closely based on a pseudo-first-order kinetic model at different temperatures for various ultrasonic times. The Fe2O3NHS@PA/αSiW11Zn nanocomposite can be used as an efficient and recyclable phase-transfer heterogeneous catalyst to remove mercaptans from gas refinery products.

Experimental and numerical investigation on sulfur transformation in pressurized oxy-fuel combustion of pulverized coal

Pressurized oxy-fuel combustion, as a novel and promising technology for CO2 capture from power plants, has attracted worldwide attentions. The high partial pressure of CO2 induces significant changes to the SOx release characteristic. Properly addressing these fundamental issues and technological challenges is beneficial for reducing SOx emissions and complementing pressurized oxy-fuel combustion technology. In this study, experimental and numerical investigations are carried out to explore the sulfur transformation mechanism under different operation parameters in the pressurized oxy-fuel combustion of pulverized coal. The experimental results reveal an obvious decline of 50% in SO2 emissions as the operating pressure increased from 0.1 MPa to 1.6 MPa, which is ascribed to the enhanced oxidation from SO2 to SO3 and the reduction of SO2 to elemental sulfur. As the operation temperature increased from 700 °C to 1100 °C, the SO2 concentration first decreased and then increased, and the minimum SO2 emission was observed at 900 °C. Additionally, when the oxygen concentration increased from 10% to 60%, the SO2 emissions were significantly reduced by 74%. The simulation results show great agreement with experimental data and indicate that SO2 emissions were synergistically affected by seven elementary reactions in which HSO, SO, SH and other intermediate species were involved. The key reaction paths from fuel-S to different S products were revealed, where SO and HSO act as the major precursors to form SO2, and SH is an important intermediate product that participates in the sulfur transformation of both H2S and COS.

Elucidation of the annealing process required in the preparation of the thermoluminescence phosphor of CaSO4:Tm

The thermoluminescence phosphor of CaSO4:Tm was subjected to physicochemical studies. Careful thermo mass spectrometry and thermogravimetry/differential thermal analysis studies for a solid sample prepared by 200°C evaporation of a sulfuric acid medium without annealing by an extremely slow speed of temperature elevation were carried out. The data revealed, along with an initial weight loss corresponding to a small, nonstoichiometric amount of crystal water at 200°C, evidence for reaction with H2O vapor in air between 300 and 500°C and a 550°C and a subsequent release of SOx at higher temperatures until the beginning of bursting decomposition of CaSO4 bulk above 700°C. H1 NMR study revealed a broad signal at 9.9ppm, which was easily assigned to the crystal water involved. This initial solid has no thermostimulated luminescence (TL) efficiency. The first signal at 9.9ppm disappeared at 200°C. A new signal appeared at 13.1ppm by annealing from 300°C and increased significantly in intensity during annealing up to 600°C, which could be assigned to the intermediate produced by the reaction with H2O vapor in air. The intensity of this signal in turn was reduced by annealing at temperatures higher than 600°C and almost disappeared at 800°C. The solid by annealing at 700°C has the best TL efficiency. Several lines of the present physicochemical evidence suggest that the energy trap on irradiation of ionizing radiation is related to the concentration of O2− produced by the decomposition of SO42− during the annealing process in the course of the preparation of CaSO4:RE.

Orimulsion fly ash in clay bricks—part 1

Abstract A bitumen-in-water emulsion (Orimulsion) is currently used as a fuel in several thermal power plants worldwide. Orimulsion combustion produces a fly ash rich in S, Mg, V and Ni, which is processed to recover metals. In order to assess the feasibility of a recycling in clay brick production, a characterization of the physico-chemical and thermal properties of ash was performed by ICP–OES, XRPD, SEM, BET and TGA–DTA techniques. Orimulsion ash resulted in fine-grained (aggregates of submicronic particles), highly hygroscopic, constituted mainly of magnesium sulphate, vanadyl sulphates and magnesium and nickel oxides, and thermally unstable in the usual brick firing conditions. These features can affect the brickmaking process, particularly the plasticity of the clay body and its drying and firing behaviour; furthermore, a mobilization of sulphates could occur, promoting the formation of efflorescence and/or the SOx release during firing.