Experimental Studies on Decomposing Properties of Desulfurization Gypsum in a Thermogravimetric Analyzer and Multiatmosphere Fluidized Beds

Abstract

This paper proposes a new technical process to utilize flue gas desulfurization (FGD) gypsum in fluidized beds. Gypsum is stable in the inert atmosphere and instable in the reducing atmosphere. Decomposing properties of gypsum in multiatmospheres were investigated in both a thermogravimetric analyzer (TGA) and a fluidized bed reactor. Results from the TGA showed that the initial decomposing temperatures of gypsum in all reducing atmospheres are about 800 °C; however, the ratio between CaS and CaO in the product is influenced by CO concentration ([CO]). Higher [CO] is beneficial to speeding the decomposition. The analysis of mass spectrometer showed that part of CaS was oxidized to CaO when the atmosphere was changed from the reducing one with [CO] = 2% to the oxidizing one with O2 concentration of 0.6%, which was proved by the XRD analysis of the final product with content of CaO of 91.6%. Fluidized bed experiments were done in a hot, lab scale, bubbling reactor. Results showed that CO2 can increase the CaO content in the product by restraining the side production of CaS significantly. After gypsum decomposition in the reducing atmosphere, a certain amount of air was injected to change the atmosphere to oxidizing, and more SO2 was released. The present research proves that a multistage fluidized bed system with multiatmospheres is feasible for gypsum decomposition.

Decomposing properties of phosphogypsum with iron addition under two-step cycle multi-atmosphere control in fluidised bed

“…Therefore, the research is designed as twice atmospheric conversion circulation. Based on existing research on phosphogypsum decomposition (Miao et al, 2012), the reaction temperatures were set as 900 °C, 1000 °C and 1100 °C to explore the influence of temperature on the circular reaction.…”

“…The experimental study investigated the decomposition condition of phosphogypsum decomposition with different mass ratios of phosphogypsum and coal and different molar ratios of n(C)·n(S) -1 . Some research using CO as reductant and switching the reaction atmosphere from a reducing atmosphere to an air-support oxidising atmosphere yielded a higher concentration of CaO; this has also been done in thermogravimetry (TGA) and a tubular furnace (Miao et al, 2012; Yan et al, 2014).…”

Qualitative and quantitative characterization of a coal power plant waste by TG/DSC/MS, XRF and XRD

“…In inert or reducing atmosphere, thermal decomposition of metal sulfates occurs at lower temperatures than in oxidant atmosphere [30,31].…”

Fly Ash Pollutants, Treatment and Recycling

“…FDG FA chemical composition is mainly gypsum, so the finally produce FA are called FGD FA and/or FGD gypsum. The other impurities include about 10 % of extra water, organic carbon, and limestone (Miao et al 2012). FGD FA volumes and quality were essentially influenced by power station parameters, such as mode of operation, type of fuel/ sulphur content, technology of the desulphurisation unit and absorbents type.…”