A method and reaction kettle for rapidly preparing ultra-high-strength α-hemihydrate gypsum

Abstract

The invention discloses a method and a reaction kettle for rapidly preparing ultra-high-strength alpha semihydrate gypsum. The method disclosed by the invention comprises the following steps of preparing a salt solution of which the concentration is 0.5-5% from water, a crystal modifier (0.2-1%) and easily soluble calcium salt or sulfate; preparing slurry from the salt solution and powdered dihydrate gypsum at a mass ratio being 1 to (0.5-2) and heating the slurry to 90-100 DEG C; adding the slurry to the reaction kettle internally equipped with a baffle, reacting and preserving heat for 0.2-1.0 hour at 110-150 DEG C at a rotation speed of 100-800 revolutions per minute; and dehydrating and drying reacted semihydrate gypsum crystal slurry to obtain the ultra-high-strength alpha semihydrate gypsum finished product. According to the method disclosed by the invention, due to the adoption of easily soluble calcium salt or sulfate, the energy consumption in the production is reduced, the growth rate of the crystals is increased, and the reaction period becomes shorter; since the baffle is introduced inside the reaction kettle, the rate of the secondary nucleation of semihydrate gypsum is increased, the fineness is reduced, the distribution of the particle size is optimized and the compressive strength of the finished product after the semihydrate gypsum is dried for 2 hours is raised to above 50Mpa.

Description

technical field [0001] The invention relates to the preparation of α-hemihydrate gypsum, in particular to a method for rapidly preparing super-high-strength α-hemihydrate gypsum and a reaction kettle. Background technique [0002] Gypsum material has a long history of use and is still an important cementitious material. Hemihydrate gypsum is the raw material for preparing gypsum-based products, and there are two kinds of α hemihydrate gypsum and β hemihydrate gypsum. Among them, the output of β hemihydrate gypsum is large, but the strength of the products prepared by it is very low, while α hemihydrate gypsum can have a regular shape, and the water requirement of standard consistency is much lower than that of β hemihydrate gypsum. The product structure is dense, porosity, strength High, so it has more and more extensive applications, especially in the field of model, precision casting and other fields has an irreplaceable role. At present, there are three main problems in...

AI Technical Summary

Problems solved by technology

At present, there are three main problems in α hemihydrate gypsum: one is that they basically focus on the control of crystal morphology, that is, the preparation of short columnar crystals. However, according to research, the performance of α hemihydrate gypsum is not only related to particle morphology, but also It is closely related to the particle size and gradation of the crystals; secondly, although the α hemihydrate gypsum prepared by the existing technology and equipment has an ideal shape, the particles are coarse, which makes the strength of the prepared gypsum products not too high, only 30Mpa The fineness of the gypsum products prepared with it is not enough; third, when the crystal modifier is added to control the morphology, the transformation start temperature is increased by nearly 30°C, which leads to increased energy consumption and higher requirements for the reactor. At the same time, the heating time is greatly increased, which prolongs the production cycle and increases the cost.

Therefore, the existing preparation process of α hemihydrate gypsum, on the one hand, controls the morphology of α hemihydrate gypsum to make it have a regular shape and reduce the water demand for standard consistency; on the other hand, in order to reduce the particle size and optimize the particle size distribution, After the preparation of hemihydrate gypsum, grinding is required to destroy the regular shape of some crystals, so that the water demand for standard consistency tends to increase, and the strength is limited.

In order to reduce the conversion temperature, a high-concentration salt solution such as NaCl solution is used, the concentration of which is as high as 20%. On the one hand, the production cost increases, and in addition, the prepared α-hemihydrate gypsum needs to be cleaned. The process is complicated and the product quality is difficult to guarantee.

Images