Effect of composite ratio of composite crystal modifiers on …

Flue-gas desulfurization gypsum (FGD gypsum), as a type of solid waste, can be recycled to prepare calcined gypsum by low temperature heat-treatment. The properties of calcined gypsum reached the best as calcining FGD gypsum at 170 ℃ for 2 h. ... Effect of modifiers on crystalizing habit and mechanical strength of α-hemihydrate gypsum ...

WhatsApp: +86 18221755073

Preparation of α-hemihydrate gypsum from phosphogypsum in …

The α-hemihydrate gypsum (α-HH) is a kind of high value-added binding material due to the favourable workability and high mechanical strengths [15], [16]. It has gained much acceptance in the building material field. ... The results show that the dehydration of PG to β-hemihydrate gypsum depends on calcination temperature …

WhatsApp: +86 18221755073

Fast in-situ X-ray scattering reveals stress sensitivity of …

In the US, 47% of the domestically mined and synthesised gypsum supplies are calcined to hemihydrate to be used as plaster 14.

WhatsApp: +86 18221755073

Formation of α-Hemihydrate Inside of a Gypsum …

Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world. During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water …

WhatsApp: +86 18221755073

Gypsum plaster waste recycling: A potential environmental …

Zhixin et al. (2016) made a recycled gypsum plaster by milling gypsum waste in a steel ball mill for 2 min, after which, it was calcined at a temperature of 180 °C for 3 h. Thereafter, the material was cured in air for 2 days.

WhatsApp: +86 18221755073

Dehydration behaviors and properties of anhydrite II …

Li and Zhang [21] investigated the dehydration behavior and impurity changes of PG at 120°C, concluding that PG could be converted into β-hemihydrate gypsum at this temperature, but the morphology of calcined gypsum became rough and many cracks formed, founding the impurity content did not decrease significantly and the eutectic …

WhatsApp: +86 18221755073

Dehydration behaviour and impurity change of phosphogypsum during

Studies on the calcination process of PG show that calcination temperature (high and low temperatures) and time are the most important parameters affecting the conversion of PG into β-hemihydrate gypsum or anhydrite [20], [21].Geraldo et al. [17] evaluated calcination temperature and kiln residence time of PG, and found …

WhatsApp: +86 18221755073

Calcination Processes | Gypsum: Connecting Science and …

The preparation of natural and synthetic gypsum prior to calcination, such as drying and grinding. The various calcination methods for β-hemihydrate and α-hemihydrate are reviewed, such as batch kettle, continuous kettle, submerged combustion kettle, conical kettle, and other calcination equipment.

WhatsApp: +86 18221755073

Gypsum hydration: a theoretical and experimental study

volume ratio of hemihydrate/free water (0.36 for α- and 0.38 for β-hemihydrate), vn/vw the specific volume ratio of crystal water/free water (0.81 for α- and 0.71 for β-hemihydrate), w the water/hemihydrate ratio, and w0 the water requirement for the hydration reaction (0.186 for both α- and β-hemihydrate).

WhatsApp: +86 18221755073

Gypsum hydration: a theoretical and experimental study

Calcium sulphate dihydrate (CaSO4·2H2O or gypsum) is used widely as building material because of its excellent fire resistance, aesthetics, and low price. Hemihydrate occurs in …

WhatsApp: +86 18221755073

Changes of Mineralogical Properties and Biological Activities …

Calcination at different temperatures, three phase CG structures, namely, bassanite, anhydrite III, and anhydrite II, may be generated. We herein investigated the …

WhatsApp: +86 18221755073

The Dehydration Kinetics of Gypsum in a Fluidized Bed Reactor

The calcined particle porosity and average pore radius wereestimated from BET analysis to be 11% and 35nm respec-tively. Thus, under the reaction conditions most appropriateto the industrial calcination of desulphurized gypsum (e.g. bed temperature of 1408 C) the effective diffusivity of thewater vapour in the calcined particle is 0.004cm2s±1.

WhatsApp: +86 18221755073

Controlled-hemihydrate gypsum calcining system

PDF | On Nov 30, 1952, Wolf G. published Controlled-hemihydrate gypsum calcining system | Find, read and cite all the research you need on ResearchGate ... calcination temperature, the age ...

WhatsApp: +86 18221755073

Preparation of α-High Strength Gypsum from Flue Gas …

The synthesis of α -calcium sulfate hemihydrate (α -CSH) from flue gas desulfurization (FGD) gypsum is a good way to realize the comprehensive utilization of …

WhatsApp: +86 18221755073

Dehydration Pathways of Gypsum and the Rehydration …

The dehydration products of gypsum under different temperature and water vapor pressure were investigated by thermodynamic theory. Additionally, the rehydration mechanism of soluble anhydrite was also studied by Monte Carlo (MC) simulations. The thermodynamic calculation results reveal that the dehydration mechanism of gypsum …

WhatsApp: +86 18221755073

Calcining processes for natural and synthetic …

The roller mill is a short-time calcining system. Both natural gypsum and mixtures of natural and synthetic raw materials can be ground, dried, calcined and classified in this kind of mill. Bundling several process …

WhatsApp: +86 18221755073

Gypsum Properties and Applications Quiz

Involves heating gypsum to produce different forms, namely β-hemihydrate (Plaster of Paris) and α-hemihydrate (Dental Stone). Open Calcination occurs at 110-120°C, producing β-hemihydrate with irregularly shaped particles, characterized by large crystal size and capillary pores. Closed Calcination utilizes an autoclave at 16 PSI and 120-130 ...

WhatsApp: +86 18221755073

The setting of gypsum plaster

QXRD results show the transformation of gypsum into hemihydrate after a residence time of 8 h and 4 h. ... at room temperature or 4°C for 21 days. ... sulphate hemihydrate made from gypsum by (a ...

WhatsApp: +86 18221755073

CN108558250B

The invention provides a process for preparing beta-semi-hydrated gypsum by calcining phosphogypsum at low temperature, which comprises the steps of uniformly mixing the phosphogypsum and a cooling agent, putting the mixture into a drying oven, calcining the mixture for 2 to 3 hours at constant temperature of 130 to 150 ℃, putting the calcined …

WhatsApp: +86 18221755073

Relationship between the evolution of organic impurities …

The higher calcination temperature resulted in higher dry bulk density. The main reason was that HPG calcined at high temperatures showed an increased water requirement for normal consistency and low content of hemihydrate gypsum, resulting in the increased combined water and reduced loss of free water. 3.4. Microstructure analysis

WhatsApp: +86 18221755073

Gypsum Calcination

The calcination is controlled by a thermocouple within the stucco bed that changes the feed to maintain a constant temperature, just like a full sized industrial calciner. Calcination temperature can be set at approximately 135-180℃ and can be tuned to minimize residual gypsum and soluble anhydrite production and maximize …

WhatsApp: +86 18221755073

Hemihydrate

Gypsum and anhydrite are naturally occurring minerals, however the hemihydrate and anhydrite can be obtained by calcination which is a process of chemical alteration by heating the dihydrated gypsum at temperatures of 125 °C-180° C and higher than 300 °C, respectively, as shown in Fig. 11 [30,31,20,32].

WhatsApp: +86 18221755073

Calcination Processes | Gypsum: Connecting Science and …

The preparation of natural and synthetic gypsum prior to calcination, such as drying and grinding. The various calcination methods for β-hemihydrate and α-hemihydrate are …

WhatsApp: +86 18221755073

Influence of the Calcination Temperature of Synthetic Gypsum …

The paper assesses the influence of the calcination temperature of synthetic gypsum binder 14 on the binding properties of innovative gypsum pastes, as well as on masonry and plastering mortars.

WhatsApp: +86 18221755073

Calcination Unit | Synthetic Gypsum Plant | LVJOE

Features of Calcination System: Low-temperature heat source is applied, to prevent gypsum from getting over heated, by controlling discharge temperature, except a small amount of dihydrate and anhydrite gypsum, the major containment of the finished product is hemihydrate gypsum, which is an ideal condition with stable physical performance.

WhatsApp: +86 18221755073

Recycling of phosphogypsum to prepare gypsum plaster: …

With the best calcination temperature of 800 °C, gypsum plaster showed a relatively quick setting and maximum strength with a compact microstructure and low ... converted impurities could hinder the hydration of anhydrite. For preparing β-hemihydrate at low calcination temperatures, Geraldo et al. [28] calcined PG at respective 120 °C, …

WhatsApp: +86 18221755073

Preparation of α-calcium sulfate hemihydrate from …

β-HH can be obtained by calcination of gypsum (Christensen et al., 2010; Schmidt et al., 2011). 170 Physicochem. Probl. Miner. ... fertilizer industries. Additionally, anhydrite and hemihydrate gypsum are unstable, with the extension of the accumulation time, they slowly hydrate into dihydrate gypsum. ... elevated temperature (above 100 °C ...

WhatsApp: +86 18221755073

Preparation of α-hemihydrate gypsum from phosphogypsum in …

The temperature was monitored by a thermocouple and maintained within ± 0.5 °C. Then, 100 g of PG was added into the mixed solutions, and the slurry was stirred by a Teflon impeller at 250 r/min. ... Promotion of conversion activity of flue gas desulfurization gypsum into α-hemihydrate gypsum by calcination-hydration treatment. J. Cent ...

WhatsApp: +86 18221755073

Calcination parameters on phosphogypsum waste recycling

The α-hemihydrate hydration results in a high dihydrate formation; therefore, this type of gypsum is applied in conditions where more significant strengths are necessary (e.g. sculptures and sanitaryware casing) [36], [37]. β-Hemihydrate is obtained through the dry calcination of gypsum in the range of 120 °C–180 °C and it is an easier ...

WhatsApp: +86 18221755073

Effect of HPO42− and brushite on gypsum reactivity and …

A mixture of gypsum and brushite was calcined at 150 °C under a nitrogen atmosphere for 5 h. At this calcination temperature, the brushite was transformed into a mixture containing 74% brushite and 26% monetite, displaying properties different from those of pure brushite and monetite.

WhatsApp: +86 18221755073

Gypsum products | PPT

9. Because of differences in crystal size, surface area, and degree of lattice perfection, the resulting powders are often referred to as α-hemihydrate for dental stone and β-hemihydrate for plaster of Paris. If the calcination process occurs under pressure in a 30% calcium chloride solution or in the presence of more than 1% of sodium …

WhatsApp: +86 18221755073

Products

Useful link

Contact Us

0086-21-58386256
0086-21-58386258
[email protected]

Hot Products

Copyright © 2024.FIXIN All rights reserved.sitemap