Ping Ning

Kinetics and Thermodynamics Studies on the Decompositions of Phosphogypsum in Different Atmospheres

In this study, the decomposition of phosphogypsum at different atmospheres of pure CO, N2 and 10% of CO were investigated to gain knowledge about the thermal decomposition of phosphogypsum. It was found that the starting decomposition temperature is 820°C in pure CO, the temperatures are 1080°C for N2 and 890°C for 10% of CO, respectively. Quantitative XRD method was applied to determine the amounts of CaSO4, CaO and CaS in the residues. The results indicate that CaS was mainly formed during Phosphogypsum decomposition in pure CO. In N2 CaO is the main residue from reactions, accompanying a small amount of CaS, and there are CaO and CaS in the decomposed productions, in 10% of CO. Moreover, The Starink,Kissinger and Flynn-Wall-Ozawa methods were used to calculate the kinetic parameters, respectively. The results have shown that the activation energy is in the range of 290.84-317.34 kJ/mol for in pure CO, 335.98-360.90 kJ/mol for 10% CO, 476.39 kJ/mol for N2.

PHOSPHOGYPSUM AS A RAW MATERIAL FOR THE PRODUCTION OF SO2 AND LIME IN CIRCULATING FLUIDIZED BEDS

The primary objective of this research is to investigate the possibility of producing sulfur dioxide and lime from phosphogypsum (PG) in a circulating fluidized bed (CFB) on a pilot scale. Thermal decomposition of PG was conducted in a CFB using anthracite as the reducing agent and fuel at temperatures in the range 900–1100°C. The gaseous decomposition products, which mainly consist of sulfur dioxide, were analyzed using a gas analyzer and X-ray diffraction. The results indicate that the reaction conditions required to produce sulfur dioxide and lime are an air flow rate of 94 m3/h, a temperature of 1100°C, and a PG consumption rate of 120 kg/h. Under optimal conditions, the maximum concentration of sulfur dioxide in the flue gas reached 8.2% (vol. %), and the maximum CaO concentration in the phospholime reached 62.57% (wt. %).

Preparation and Characterization of Modified Activated Carbon and its Influencing Factors of Cd2+ Adsorption

In order to improve the Cd2+ adsorption ability, the granular activated carbon (GAC) was modified with different treatments, and the Cd2+ removal efficiencies (REs) by the treated GACs were then comparatively investigated under different conditions. The surface physical-chemical properties of these carbons were further characterized in virtue of BET and Boehm’s titration, etc. The results demonstrate that the specific surface area and surface oxy acidity functional groups of GAC changed to some certain after the different treatments, especially for that with HNO3 oxidizing. It therefore led to an improvement of Cd2+ adsorption ability, and the corresponding REs by the N-GACs that were respectively modified with 10% and 70% HNO3 were significantly higher than that by the original GAC (i.e., 41% and 57% vs. 10%). pH was found to be the most vital influencing factor for the Cd2+ adsorption, and the Cd2+ REs by the tested GACs were all increased with an elevation in the pH value.