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The desulfurization performance of magnesium slag has been improved by the modified method of quenching hydration, but it still cannot meet the industrial requirements. Based on the research of additives for calcium-based desulfurizer, NaCl, CaCl2, Na2SO4, CaSO4, Na2CO3, K2CO3, acetic acid and adipic acid are used for modification of quenching hydrated magnesium slag. TGA are used for analysis of magnesium slag desulfurization performance; XRD, SEM, EDS and BET are used for analysis of modified magnesium slag composition, surface morphology and microscopic characteristics, respectively, obtaining the modification mechanism of different additives on the quenching hydrated magnesium slag. The results showed that: the best desulfurizer was 2% Na2SO4 modified magnesium slag, and the calcium conversion rate reached 40.16%. Cl− and SO42− mainly improve the desulfurization performance of magnesium slag by improving the specific surface area and pore volume of magnesium slag, and the modification effect of SO42− was better than Cl−. CO32− mainly through the reaction with Ca(OH)2 to produce CaCO3 that could crystalize on the surface of magnesium slag, thus improving the desulfurization performance of magnesium slag. Organic acids enhanced the transmission of H+ in hydrated slurry and promoted the dissolution of Ca2SiO4.

To provide a theoretical basis for the development of future mercury removal methods, two types of biochars modified by the coprecipitation method were investigated: undoped iron-based biochars modified with FeCl3 and iron-based biochars doped with Cu and Mn from CuSO4, Mn(CH3COO)2, and KMnO4. The crystal phase compositions, pyrolysis characteristics, pore structures, microscopic morphologies, elemental speciations, and functional groups of the modified biochars were characterized. The adsorption mechanism was further explored by temperature-programmed desorption (TPD). The results showed that the mercury adsorption of the modified biochars was significantly enhanced. The mercury adsorption performances first increased and then weakened with increased loading. The modification decreased the graphitization degree. Spinel structure solid solutions of MnFe2O4 and CuFe2O4 were formed in the modified biochars, generating many cation vacancies on the biochar surface. After biochar modification, the pore structu...

A series of quenching hydration experiments of magnesium slag were carried out under different conditions (quenching and hydration temperatures, hydration time, liquid/solid ratio, and continuous/non-continuous process). During the hydration process, the electrical conductivity, pH, and hydration degree were obtained to characterize the reaction. Combined with the hydration degree, kinetic models were used to analyze the hydration kinetics and obtain the relevant parameters. To further understand the desulfurization performance of the hydrated magnesium slag, and the relationship between hydration and desulfurization, desulfurization experiments were carried out in a thermal gravimetric analyzer. Further, changes in the material composition and morphology after hydration were investigated by X-ray diffraction and scanning electron microscopy, respectively. The results showed that the non-continuous hydration could be described by a modified Krstulovic-Dabic model. The highest hydration degree (0.16) was achieved at the quenching temperature of 950 °C and hydration temperature of 80 °C. Orthogonal tests established the optimum conditions for continuous hydration: quenching temperature of 950 °C, liquid/solid ratio of 8, and hydration time of 8 h. In decreasing order, these three factors are ranked as hydration time > quenching temperature > liquid/solid ratio. The desulfurization performance of samples treated with continuous hydration was better than that treated with non-continuous hydration, with the calcium conversion rates of 30.3% and 13.3%, respectively.

Biochars prepared in three pyrolysis atmospheres of N2, O2, and CO2 were investigated. The pyrolysis characteristics, pore structures, and functional groups of the biochars were characterized by thermogravimetric analysis (TGA), specific surface area and porosity analyses, and Fourier transform infrared (FTIR) spectroscopy. The adsorption mechanism was further explored by the temperature-programmed desorption (TPD) technique in combination with the adsorption kinetics. The results showed that the Hg0 adsorption capacities of the biochars produced in an O2 pyrolysis atmosphere were worse than those of the biochars obtained in a N2 atmosphere, whereas CO2 significantly promoted the adsorption capacity. The biochar prepared in 20% CO2 had the highest adsorption capacity. Three pyrolysis reaction pathways were possible in the O2 atmosphere. In addition, a critical concentration existed between O2 concentrations of 5 and 7%. Above 750 °C, CO2 could react directly with the biochar through the Boudouard reaction...

Modified magnesium slag could be used as a kind of practical desulfurizer. Four modification methods were studied in this paper, which were magnesium slag hydration, magnesium slag/fly ash hydration, magnesium slag quenching hydration and magnesium slag/additives hydration. The desulfurization performance of modified magnesium slag was characterized by its calcium conversion rate. The desulfurization experiments were carried out in Thermal Gravimetric Analyzer. Based on hydration kinetics and fractal theory, the relationship between desulfurization performance and hydration degree or fractal characteristics were, respectively, analyzed. The results showed that the optimal temperature of desulfurization reaction was 920 °C. When the mass ration of fly ash and calcium silicate of magnesium slag (MR) was 20, hydration time (tH) was 8 h, hydration temperature (TH) was 90 °C, the desulfurization performance was the best. The most efficient additive in hydration reaction was H2C2O4, the calcium conversion rate reached to 73.7% by adding 0.5% H2C2O4. The optimal hydration conditions for quenching magnesium slag/fly ash were also MR = 20, tH = 8 h, and the relationship between fractal dimension and calcium conversion rate was similar to parabolic. The activation energy of this hydration reaction was 72.37 kJ mol− 1. The relationship between hydration degree and calcium conversion rate was a positive correlation in the condition.

Biomass chars (bio-chars) prepared under two pyrolysis modes and with four particle size ranges were investigated. The pyrolysis modes included isothermal pyrolysis and non-isothermal pyrolysis with three heating rates (5 °C/min, 10 °C/min, and 15 °C/min). The particle size ranges were 58-75 μm, 75-106 μm, 106-150 μm, and 150-270 μm. The pyrolysis characteristics, pore structures, surface morphologies, and functional groups of the bio-chars were characterized by TGA, specific surface area and porosity analyses, SEM, and FTIR. The mercury adsorption was further explored by the adsorption kinetics. The results established the optimum pyrolysis conditions for mercury adsorption: pyrolysis temperature of 600 °C, heating rate of 10 °C/min, and particle size of 58-75 μm. In addition, the mercury adsorption processes were affected by both physical adsorption and chemical adsorption. Furthermore, the rate constants of the pseudo-first-order and pseudo-second-order models gradually increased with decreasing particle size.