Mengqi Wei

Direct Reduction of Copper Slag Composite Pellets Within Lignite Using Biomass as Binder

The resource utilization of copper slag is an attractive option of iron resource. Thermal energy recovery and direct reduction (TER-DR) system was proposed in this study. By theoretical analysis, the exergy efficiency of this system can reach to 57.3%. To investigate the feasibility of TER-DR system, copper slag composite pellets within lignite were prepared. As a new binder, pine sawdust was added into the pellets. The diameter of pellets was 20 mm in experiments and the compressive strength of them was up to 831 N when the addition ratio of biomass was 29%. The results showed that the overall iron recovery reached to 90% and the separated iron concentrate was up to 93.5% when the temperature is at 1423 K for 90 min with CaO addition ratio of 0.3. The process reduces the secondary environmental pollution of copper slag and will be applied well in the future.

Preparation and Characterization of Activated Carbon from Waste Ion-Exchange Resin for CO 2 Adsorption

Activated carbons, derived from waste ion-exchange resin by CO2 physical activation, were applied to separate CO2 from flue gas against global warming. The BET specific surface areas of activated carbons at different activation temperatures and times were investigated. The CO2 adsorption capacity was tested under non-isothermal and isothermal conditions. The experimental results show that when keeping the activation temperature constant, the specific surface area increases firstly and then decreases with increasing activation time. For the given activation time, the specific surface area rises firstly and then declines with increasing activation temperature. The adsorption capacity decreases with increasing temperature. The maximum adsorption capacity is 51.46 mg/g under the condition of 298 K and pure CO2. Fractional order kinetic model is the best one to describe the kinetics of CO2 adsorption. The activated carbons show the potential to be an effective adsorbent for the removal of CO2 from flue gas.

Oxidation kinetics of YBaCo 4 O 7+ δ and substituted oxygen carriers

In this paper, the relaxation kinetics of the oxidation process of the YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ and Y0.5Dy0.5BaCo4O7+δ oxygen carriers is studied with isothermal reaction data. XRD analysis for fresh samples shows that all the samples have YBaCo4O7+δ structure. Scanning electron microscopy images of samples show that the samples consist of porous agglomerates of primary particles. Isothermal TG experiments are conducted with temperatures of 290°C, 310°C, 330°C and 350°C, respectively. It is found that the Avrami-Eroféev model describes solid-phase changes in the oxygen absorption process adequately. The results show that the distributed activation energies of the oxidation process obtained by the Avrami-Eroféev model are 42.079 kJ mol−1, 42.944 kJ mol−1 and 41.711 kJ mol−1 for the YBaCo4O7+δ, Y0.95Ti0.05BaCo4O7+δ and Y0.5Dy0.5BaCo4O7+δ oxygen carriers, respectively. The kinetic model was obtained to predict the oxygen carrier conversion of oxygen absorption for different time durations. The kinetic parameters obtained here are quite vital when this material is used in reactors.

Low temperature selective catalytic reduction of nitric oxide with urea over activated carbon supported metal oxide catalysts

ABSTRACT Selective catalytic reduction of nitrogen oxides (SCR) with loaded urea is a method for removing NO under oxygen-rich and low-temperature conditions, which can solve the inhibitory effect of oxygen on the catalyst and the slip of ammonia. In present study, a series of activated carbon (wo-AC, co-AC, cs-AC and nu-AC) supported metal (Mn, Fe, Co, Cu and Zn) oxide catalysts with loading urea were prepared by ultrasonic assisted impregnation. The catalysts were used for NO removal at 50–120°C and characterized by XRD, SEM, GFAAS, EDS, XPS, BET and FTIR techniques. The effects of activated carbon type, loaded active element, metal oxides loading, temperature fluctuation on catalytic activity and the catalytic stability were also studied in this paper. The results indicated that nutshell-based activated carbon was more suitable as a carrier than other activated carbons, and urea-10Mn/nu-AC catalyst yielded a higher NO conversion than other catalysts. Besides, for used activated carbons, the larger specific surface area, more micropores distribution and the larger number of hydroxyl group and cyano terminal group are beneficial to the catalytic process. Moreover, the downward trend of NO conversion with increasing temperature suggested the adsorption of reactant gases played a crucial role in the catalytic process of urea-SCR. GRAPHICAL ABSTRACT