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 …
Due to the above chemical properties, the decomposition of gypsum occurs at higher temperature ranges than plaster of Paris or hemihydrate samples. For the …
This may be because the effect of silicon dioxide on the decomposition of FGD gypsum was more evident than that of alumina when the alumina–silica ratio was between 1.76 and 3.35. Results indicated that the additive in the raw material can reduce the decomposition temperature of FGD gypsum and make it less difficult to decompose.
Reductant agents such as carbon or coal on natural gypsum or PG reduced the decomposition temperature to approximately 1000 °C (Chen and Yang, 1979, ... Also, petroleum oil decomposes gypsum at a temperature between 1065 and 1163 °C, where reductive and oxidative environments are done in the same fluidized bed reactor ...
NOV.1985 Thermal Analysis of Gypsum 1. Introduction Gypsum has long been used as a building material and is used for that purpose in the following items. • Setting retarder for Portland cement • For gypsum plaster, gypsum board, ceramic molding tools, and arts …
To address the challenge of optimizing the utilization of industrial by-product gypsum, this study proposes a two-step reductive decomposition process for the production of quicklime from industrial by-product gypsum. In the initial step, a blend of CaS and CaO is generated through the low-temperature reductive decomposition 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 …
At present, due to the high decomposition temperature and complex composition of gypsum, only a small part of FGD gypsum is recycled; most of it is directly stored as solid waste. This not only causes serious pollution to the environment, but also wastes calcium and sulfur resources. ... fly ash (90%), FGD gypsum (10%); reaction …
They found that the thermal decomposition of PG took place at 1000 °C, which is much lower than the decomposition temperature (about 1250 °C) of pure gypsum and that (about 1200 °C) of natural gypsum. The results also showed that the impurities in PG can promote the decomposition of PG.
Various researchers utilize CaSO 4 ·2H 2 O nanorods [29], waste gypsum board [30], flue gas desulfurization gypsum [31] ... The optimum low-temperature thermal decomposition temperature is 140 ℃, and the thermal decomposition time is 5 h. After a 12 h reaction period, the PG displays a 90 % fluoride removal efficiency at an initial …
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 …
To recover Ca and S resources, many scholars focus on the high-temperature conversion of FGD gypsum. Through high temperature, the FGD gypsum can be converted into CaO or CaS to broaden and realize its efficient utilization [14], [15], [16].High decomposition temperature is not economical, and reduction roasting is an …
In the oxidizing atmospheres, the decomposing temperature for gypsum is over 1,350°C, while, in the reducing atmosphere, the initial temperature for starting decomposition decreases to 950–1,000°C depending on the atmosphere and impurity, which is suitable for fluidized bed operation.
The utilization rate of gypsum in sintering was calculated, and the results showed that gypsum decomposition was the limiting factor in the reaction mechanism of calcium ferrite synthesis, the optimal raw material ratio for the formation of calcium ferrite was 30.4% desulfurization gypsum produced in sintering, 31.7% iron ore, 11.1% blast ...
With the addition of gypsum (CaSO 4 ·2H 2 O), the initial decomposition temperature decreased slightly relative to that of EPS/HFR0 due to dehydration of the gypsum to form thermally stable ...
Herein, the influence of carbon and pyrite on the desulfurization behavior of red gypsum is systematically investigated by high-temperature decomposition. In the absence of …
Due to the above chemical properties, the decomposition of gypsum occurs at higher temperature ranges than plaster of Paris or hemihydrate samples. For the former, at high heating rates, decomposition occurs from 100 to about 300 °C, with overlapped peaks of the two steps .
Due to the development of CaSO 4 reductive decomposition technology in recent years, the decomposition temperature of CaSO 4 has been greatly reduced [9, 10]. Among them, CaSO 4 gas-phase reductive decomposition technology can decompose gypsum into quicklime and high concentrations of SO 2 by controlling the reaction …
The strength of gypsum-bonded investment is temperature sensitive, there being marked differences between the products tested. Overall, the strength ranking (temperature range average/MPa) was: Cristobalite (10.1)>Beauty Cast (7.8)>Novocast (5.1)>Deguvest California (3.4). ... Decomposition of gypsum investment in the …
The review covers research efforts specifically directed toward the regeneration of sulfated limestones plus those studies which have been made to investigate the decomposition of naturally occurring minerals of calcium sulfate.
In this work, we have reinvestigated the thermal degradation kinetics of synthetic gypsum (CaSO4·2H2O) 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 …
To address the challenge of optimizing the utilization of industrial by-product gypsum, this study proposes a two-step reductive decomposition process for the production of quicklime from industrial by-product gypsum. In the initial step, a blend of CaS and CaO is generated through the low-temperature reductive decomposition of …
At high temperatures, gypsum dehydrates to other calcium sulfate phases ... Figs. 3, 5) showed a significant mass decrease caused by the decomposition of …
In fact, most of the researches on the decomposition of FGD gypsum were taken in a reducing atmosphere, which can help to reduce the initial decomposition temperature and to promote of decomposition degree [28]. However, a reducing atmosphere negatively impacts the formation of mineral phase in CSA cement clinker [29].
temperatures. This decomposition is presumably responsible in part for the absence of CaSO, in many portland cement clinkers made in the ordinary way, as has been …
Using special crucibles with well-defined small holes and high heating rates (here 30 K/min), one can separate both decomposition reactions and quantify the content.
Therefore, this study uses powders in a stirred suspension at specified temperatures to determine the temperature dependence of gypsum dissolution rates. …
The anthracite can decrease the decomposition temperature of FGD gypsum, ... By adding additives, the decomposition temperature can be further reduced and PG decomposition rate and product yield can be improved. However, the use of current additives such as Fe 2 O 3 and SiO 2 brings the problem of increasing economic …
The iron and calcium elements can be reused as iron-making raw materials, but the sulfur element in the gypsum is required to be removed as it has a harmful effect on the properties of iron. Herein, the influence of carbon and pyrite on the desulfurization behavior of red gypsum is systematically investigated by high-temperature decomposition.
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 …
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