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Besides, it could be reasonably expected that mercury in FGD gypsum might be released in the gas phase during the calcination process of wallboard production, based on the release curves of FGD gypsum samples from TPD, even though the temperature in the industrial process (about 160°C) is lower than the peak temperature of the …
Gases evolved at the decomposition temperature of gypsum were analyzed chemically and sample residues were anelyzed by X-ray diffraction A slight amount of decomposition was observed when gypsum ...
The direct decomposition temperature of CaSO 4 is extremely high (Dewing and Richardson, 1959; Liu et al., 2007), which causes a severe sintering of CaO, resulting in the reduced activity of CaO ... In the initial step, a blend of CaS and CaO is generated through the low-temperature reductive decomposition of gypsum. Subsequently, the ...
The dehydration temperature depends on the measurement method, the gypsum origin (natural, FGD), the type of required calcium sulfate hemihydrate (α, β), …
At high temperatures, gypsum dehydrates to other calcium sulfate phases ... Figs. 3, 5) showed a significant mass decrease caused by the decomposition of anhydrite at temperatures between 1100 and 1500 °C, when calcium oxide and sulfur oxide are products of the reaction. The occurence of free lime was also proved by the …
the decomposition characteristics haven been studied by Parker et al. [19]. Decomposition/Phase change temperatures A summary of temperatures at which phase changes occur in anhydrous and hydrated cement are shown in Table 1 in general ranges of 50°C, while in Table 2 the decomposition range for the various compounds is given.
lowing the decompositions of impurities of gypsum.17 At 1000 C, gypsum plasterboard density ρ is 71% to 90% of their value at ambi-ent temperature. So, the literature data …
Comparing the TG curves in Fig. 3, it seems that there was a considerable change in the starting temperature of the decomposition reaction of the FGD gypsum with addition of anthracite that took place at 670 °C. Therefore, addition of carbon caused the decomposition reaction to proceed at lower temperature.
So, the decomposition of gypsum occur at ${text{120}}{,^{text{o}}}{text{C}}$ to give P.O.P and back interconversion of P.O.P to gypsum is take place by treating the P.O.P with water. ... The temperature of heating is important because heating gypsum at different temperatures leads to the formation of …
In this work, we have reinvestigated the thermal degradation kinetics of synthetic gypsum (CaSO 4 ·2H 2 O) using a novel approach based on peak deconvolution followed by the application of Model-Free isoconversional method. Gypsum was prepared using wet chemical route and characterized by conventional X-ray diffraction, in situ high …
The chemical formula of Gypsum is CaSO4 ∙ 2H2O (Calcium Sulfate Dihydrate). There are a large number of uses for gypsum as a building material. ... The sulfate decomposition can be seen in a further mass loss at temperatures above 1250°C. Calcium sulfate converts into calcium oxide. The melting of a eutectic mixture of calcium …
The results indicated that the factors of the final reaction temperature and the reaction atmosphere have significant influences on the decomposition of gypsum, in the condition of 850–1,050°C, the total decomposition rate of three gypsums increases and the time-consumption of reaching decomposition equilibrium of three gypsums …
High-Temperature Release of SO2 from Calcined Cement Raw Materials. Energy & Fuels 2011, 25 (7) ... Insight into the reaction characteristics of H2-reduction decomposition of gypsum: Experimental and isothermal kinetic analysis. International Journal of Hydrogen Energy 2024, 49, 1344-1360.
From the point of view of a sustainable and environment-friendly society based on the recycling of material resources, it is preferable to utilize waste gypsum as a substitute for lime, which is currently produced by the calcination of limestone. In the present work, the reductive decomposition of CaSO4 was investigated under an …
Zhu et al. [20] used temperature programmed decomposition and sequential chemical extraction method to explore the fate of mercury in FGD gypsum, which concluded that mercury was mainly retained ...
The formation of beta-hemihydrate starts at around 85°C and is shifted into the formation of anhydrite III. Due to this, it is tricky to measure the mass loss of wet …
However, the impurity components within gypsum have been observed to reduce the self-decomposition temperature of CaSO 4 and facilitate its decomposition reaction under an inert atmosphere [37, 38]. Furthermore, according to the SO 2 curve, a higher maximum concentration of SO 2 was observed during the reduction and …
Previous studies have also concluded that the decomposition of gypsum and ettringite and the dehydration of some carbo aluminate hydrates occur in the temperature range of 60-200 • C.
The temperature of gypsum decomposition was lowered to below 1000°C under a coexisting condition with C or CO–CO 2 gas. Furthermore, it was reported that Fe 2 O 3 promoted gypsum decomposition 13). Based on these findings, a two-step heat treatment—(1) ...
the application of temperature-dependent thermal properties under natural fire especially for the cooling phase. 2 | STATE OF THE ART 2.1 | Thermal decomposition of gypsum plasterboards In general, gypsum plasterboards consist of a porous solid core of primar-ily calcium sulfate dihydrate CaSO 4 2H 2O between two layers of paper.
Due to microwave heating and calcium ferrite formation, the decomposition temperature of FGD gypsum decreased to around 800°C in air atmosphere. Based on the XRD patterns and SEM images, the ...
Gypsum plaster is considered a sustainable binder, produced by the calcination of gypsum (calcium sulfate dihydrate: CaSO4∙2H2O) in a dry process at temperatures that range from 125 °C to 180 °C (Borrachero et al., 2008; Gartner, 2009).
transition from hemihydrate gypsum to crystalline gypsum (dihydrate gypsum). This brief presents examples of TG/DTA and DSC measurements of the thermal changes of gypsum.
Concerning the thermal stability of ettringite crystals, many studies have suggested that the decomposition temperature of ettringite is generally considered to be 70–80 °C ... (CaSO 4 ·2H 2 O, hemihydrate gypsum, hard gypsum, etc.) at room temperature reacts with C 3 A hydration to form ettringite, which will later be converted …
The thermal behaviour of gypsum was frequently investigated due to its use as construc-tion material. The thermal decomposition of gypsum depends on the experimental condi …
Gypsum at High Temperature Xiaoling Ma1 · Hongbin Tan1 · Faqin Dong2 · Feihua Yang3 Received: 17 August 2021 / Accepted: 8 December 2021 / Published online: 3 February 2022 ... desulfurization behavior of red gypsum is systematically investigated by high-temperature decomposition. In the absence of
No decomposition occurred at 114°C but complete decomposition to a mixture of gypsum and hemihydrate, together with amorphous material, occurred at 120°C. Upon stepwise reduction of temperature to 115°C, some reformation of ettringite occurred together with hemihydrate, while nearly complete reformation of ettringite occurred at …
This would tend to increase the decomposition temperature[7]. Such problems can be avoided by using a fluidized bed reactor, where temperature homogenit.v and high mass and heat transfer rates can be obtained. 3.2 Gypsum decomposition Gypsum (CaSO~. 2H20) becomes anhydrous at temperatures above 160: CaSOa" …
On the TG curve of the binary (gypsum-lime) binder, the decomposition of residual calcium hydroxide, (which was not entirely consumed by carbonation at after 28 days) can be seen in the interval 370–475 °C. ... when exposed to high temperatures, gypsum-lime-silica fume material exhibited worse performance than pure gypsum, …
Due to microwave heating and calcium ferrite formation, the decomposition temperature of FGD gypsum decreased to around 800°C in air atmosphere. Based on the XRD patterns and SEM images, the ...