Study on the Effect of the Activity of Anthracite on the Decomposition of Phosphogypsum

Abstract

In this paper, a thermogravimetric analyzer with Fourier transform infrared spectroscopy (TG-FTIR), pyrolysis device and gas chromatography (Py-GC), and kinetic models were used to study the effect of anthracite with different activities on the decomposition of phosphogypsum (PG) and the reaction mechanism was analyzed. The results show that the decomposition rate of PG is affected by the CO partial pressure and the thickness of the decomposition product layer, and the high-activity anthracite has a high decomposition rate of PG. It mainly contains CO, CO 2 , and SO 2 in the decomposition process, while the solid products are mainly CaS, CaO, and Ca 2 SiO 4 . According to the kinetic calculation results at 800−1100 °C, it can be divided into three stages, namely, the one-dimensional diffusion model based on the solid−solid reaction, the two-dimensional diffusion based on the gas−solid reaction model, and the nucleation and growth model of CaO.

Preparation of calcium sulfide by sludge‐assisted rice husk reduction of phosphogypsum

“…The products are characterized by XRD as shown in Figure 2c. From Figure 2c, characteristic peaks of 40% RH + 20% SL and 50% RH are consistent, CaSO 4 has been completely reduced to CaS, and no obvious characteristic peaks of CaO, Ca 2 Al 2 SiO 7 , and Ca 2 SiO 4 are seen, which may be due to the low reaction temperature, CaSO 4 does not react with CaS to form CaO 10 . This indicates that the above CaS yield data are feasible.…”

“…For example, keeping the amount of 40% RH addition constant, the decomposition rate increases from 85.87% to 99.99% with SL addition increasing from 0% to 20%, which indicates that PG has been completely decomposed. In addition, by comparing the actual and theoretical decomposition rates, the predicted decomposition rate is clearly lower than the actual value 10 This indicates that the above CaS yield data are feasible. PG:RH = 2:1 (S1) and PG:RH:SL = 5:2:1 (S2) are chosen as the best ratios.…”

“…7 The type of reducing agent and the C/Ca molar ratio are the two most important factors influencing PG decomposition. The common reducing agents used for PG reduction mainly include solid reducing agents such as lignite, 8,9 anthracite, 10 high sulfur coal, 11 coke, 12 and gaseous reducing agents such as CO, 13 H 2 , 14 and H 2 S. 15 It is shown that pure graphite hardly reacted with CaSO 4 , while coal and char could effectively decompose PG. Moreover, when other conditions are the same, the PG decomposition rates of coals with low degrees of metamorphism (lignite and bituminous coal) are significantly better than those of coals with higher degrees of metamorphism (anthracite).…”

“…The type of reducing agent and the C/Ca molar ratio are the two most important factors influencing PG decomposition. The common reducing agents used for PG reduction mainly include solid reducing agents such as lignite, 8,9 anthracite, 10 high sulfur coal, 11 coke, 12 and gaseous reducing agents such as CO, 13 H 2 , 14 and H 2 S 15 . It is shown that pure graphite hardly reacted with CaSO 4 , while coal and char could effectively decompose PG.…”

Experimental study on preparation of calcium oxide by coal reduction of calcium sulfate in carbon dioxide atmosphere

“…While CaSO 4 decomposes at temperatures of up to 1400 °C, introducing reducing agents can drastically lower this temperature 6 . Common reducing agents mainly include carbon‐based (lignite, 7 anthracite, 8 coke, 9 coal gangue, 10 CO 11 ) and sulfur‐based (sulfur, 12 pyrite, 13 H 2 S 14 ). Therefore, the conversion of CaSO 4 to CaO is completely feasible in terms of process.…”