Method and device for wet addition of a setting accelerator for construction gypsum

Abstract

The application discloses an adding method of a building gypsum accelerator wet addition, which comprises the following steps: step one, mixing and stirring ammonium sulfate with water until the ammonium sulfate is completely dissolved to prepare an ammonium sulfate solution; step two, mixing and grinding raw gypsum with a grinding aid to prepare crystal seeds; and step three, continuously feeding the ammonium sulfate solution and the crystal seeds into a container to stir and prepare an accelerator, and continuously injecting the accelerator into a mixing port of a gypsum stirrer to complete the wet addition of the gypsum accelerator. The application has the beneficial effects that the accelerator is added in a wet and external way, the product effect of the gypsum product is considered, and the negative effects caused by the addition of the accelerator into the stirrer are greatly solved, such as low slurry fluidity, short service life of the stirrer, serious wear of the stirrer and the like.

Description

Technical Field

[0001] This invention relates to the field of building materials, and specifically to a method and apparatus for wet-addition of a gypsum accelerator. Background Technology

[0002] Accelerating the setting process is crucial in gypsum product production. With continuously increasing production speeds, the only way to achieve maximum productivity is to significantly accelerate the setting of the cementitious material (β-type hemihydrate gypsum CaSO4·0.5H2O). Highly finely ground gypsum powder (dihydrate gypsum CaSO4·2H2O) is often used as a highly efficient accelerator in this setting process. However, the addition of this accelerator severely affects the setting time and fluidity of the gypsum slurry, thus impacting the mixer's operating time and the slurry's flow properties, failing to meet actual production requirements. While Chinese invention patent CN109278192B, "Method for Adding Accelerator to Gypsum Board and Gypsum Board Made Therefrom," discloses a method for adding an accelerator to gypsum board, the production process relies on ultrasonic emulsification, resulting in high production costs and relatively complex steps. Summary of the Invention

[0003] To address the issues of long setting time and poor fluidity of the aforementioned gypsum slurry,

[0004] This invention is achieved through the following technical solution:

[0005] A method for adding a wet-mixing accelerator to building gypsum includes the following steps:

[0006] Step 1: Mix ammonium sulfate with water and stir until completely dissolved to prepare an ammonium sulfate solution. Ammonium sulfate is readily soluble in water, with a solubility of 75.4 g / 100 g water at 20°C. The prepared ammonium sulfate solution can be stored at room temperature in any container for later use.

[0007] Step 2: Mix and grind the raw gypsum with the grinding aid to form seed crystals; the grinding equipment used is a raw gypsum grinding mill;

[0008] Step 3: The ammonium sulfate solution and seed crystals are continuously introduced into the container and stirred to prepare the coagulant. At the same time, the coagulant is continuously injected into the mixing port of the gypsum mixer to complete the wet addition of the gypsum coagulant. During this process, the liquid level inside the container remains constant, that is, the ratio between ammonium sulfate, seed crystals and water is maintained in dynamic equilibrium.

[0009] Furthermore, the concentration of the ammonium sulfate solution in step one above is 0.055-0.08 mol·kg⁻¹. -1 .

[0010] Furthermore, in step two above, the grinding aid is an organic compound containing one or more combinations of functional groups selected from -COOH, -NH2, -SO3H, and -OH; the specific surface area of ​​the seed crystals is greater than or equal to 8000 cm². 2 / g.

[0011] Furthermore, in step three above, water accounts for 75-85% of the total material mass in the container; the temperature of the material in the container is maintained at 34-38℃.

[0012] Furthermore, in step three above, the volume of the coagulant discharged from the container per unit time is equal to the sum of the volumes of the raw powder mixture and the seed crystals added to the container per unit time.

[0013] Furthermore, the gypsum used in step two above is recycled gypsum; using recycled gypsum can save production costs, as its composition is exactly the same as that of ordinary gypsum, both being calcium sulfate dihydrate.

[0014] A wet-addition device for gypsum accelerator includes a pre-mixing tank, a stirring mechanism, a raw powder mixture feeding mechanism, a raw powder mixture inlet, a seed crystal inlet, and a discharge mechanism. The stirring mechanism is installed inside the pre-mixing tank, and the raw powder mixture inlet and seed crystal inlet are provided on the pre-mixing tank. The material outlet of the raw powder mixture feeding mechanism is connected to the raw powder mixture inlet. The discharge mechanism is located at the bottom of the pre-mixing tank.

[0015] Furthermore, the aforementioned seed inlet is connected to the seed feeding mechanism, which is a screw conveyor, belt conveyor, or powder pneumatic conveying system; the material conveying volume per unit time of the raw powder mixture feeding mechanism, plus the material conveying volume per unit time of the seed feeding mechanism, equals the material conveying volume per unit time of the discharge mechanism.

[0016] Furthermore, the aforementioned raw starch mixture feeding mechanism includes a conveying pump, a flow meter, and a connecting pipe. Ammonium sulfate solution is introduced into the material inlet of the conveying pump, and the material outlet of the conveying pump is connected to the raw starch mixture inlet via the connecting pipe. A flow meter is installed on the connecting pipe. The discharge mechanism includes a discharge pump, a discharge pipe, and a flow meter. The material inlet of the discharge pump is connected to the inside of the pre-mixing tank, and the material outlet of the discharge pump is connected to the discharge pipe. The discharge pipe is connected to the mixing port of the gypsum mixer. A flow meter is installed on the discharge pipe. The two flow meters can measure the material conveying volume of their respective pipes to adjust the feed and discharge volumes, thereby ensuring that the material in the pre-mixing tank maintains a dynamic balance.

[0017] Furthermore, the aforementioned stirring mechanism includes a stirring motor, a stirring shaft, and stirring blades. The stirring motor is fixedly connected to the upper outer part of the pre-mixing tank. One end of the stirring shaft is coaxially fixedly connected to the output end of the stirring motor, and the central axis of the stirring shaft coincides with the central axis of the pre-mixing tank. Several sets of stirring blades are evenly arrayed along the axial direction on the stirring shaft. The circumferential wall of the pre-mixing tank is configured as a double-layered structure. A heating device and a thermocouple are installed inside the pre-mixing tank, and the thermocouple is electrically connected to the heating device. The thermocouple monitors the material temperature inside the pre-mixing tank and transmits the signal to the heating device. When the material temperature is higher than the preset temperature, the heating device stops working; when the material temperature is lower than the preset temperature, the heating device starts working. The heating device can adopt a direct heating method using heating rods or heating coils, or an indirect heating method using steam or a heat transfer medium introduced into the jacket of the pre-mixing tank.

[0018] The beneficial effects of this invention are as follows: the coagulant of this invention is added wet and externally, which, while taking into account the finished product effect of gypsum, greatly solves the negative effects caused by adding the coagulant inside the mixer, such as low slurry fluidity, short service life of the mixer, and severe wear of the mixer. Attached Figure Description

[0019] Figure 1 : A three-dimensional structural diagram of the device for wet addition of gypsum accelerator;

[0020] Figure 2 : Front view of the device for wet addition of gypsum accelerator;

[0021] Figure 3 Cross-sectional view of the device for wet addition of gypsum accelerator;

[0022] Figure 4 : A three-dimensional sectional view of the pre-mixed tank;

[0023] Figure 5 Solubility curve of calcium sulfate dihydrate in ammonium sulfate solution;

[0024] In the diagram: 1-Premixing tank, 2-Stirring mechanism, 3-Raw starch mixture feeding mechanism, 4-Raw starch mixture inlet, 5-Seed inlet, 6-Discharge mechanism. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0026] Example:

[0027] In the production of gypsum products, the raw material used is β-type hemihydrate gypsum (CaSO4·0.5H2O). The process is as follows: First, it dissolves in water, then precipitates as dihydrate gypsum (CaSO4·2H2O). As hydration continues, the number of colloidal particles of the dihydrate gypsum (CaSO4·2H2O) increases. These particles are finer than before, have a large specific surface area, and adsorb a lot of water. At the same time, the free water in the slurry decreases due to hydration and evaporation, the consistency of the slurry increases, and the adhesion between the colloidal particles gradually strengthens. Friction and adhesion forces are generated between the particles, causing the slurry to gradually lose its plasticity, that is, the slurry gradually solidifies. Continued hydration transforms the colloid into crystals. The crystal particles gradually grow, causing the slurry to completely lose its plasticity and gain strength, that is, the slurry hardens. This process continues until the slurry is completely dry and the strength no longer increases. At this point, the slurry has hardened into artificial stone.

[0028] Specifically, because the solubility of β-type hemihydrate gypsum (CaSO4·0.5H2O) is much greater than that of gypsum (CaSO4·2H2O) below 100℃, this difference becomes even more pronounced below 50℃ (i.e., the ambient temperature for conventional gypsum processing). Therefore, when β-type hemihydrate gypsum (CaSO4·0.5H2O) is mixed with water, the hemihydrate dissolves rapidly, forming a supersaturated gypsum solution. Then, the dihydrate gypsum begins to deposit, crystallizing from the nucleation points, which may be fine dihydrate gypsum particles or impurities acting as seeds. As the gypsum crystallizes, the saturation of the slurry with the hemihydrate decreases, thus more hemihydrate dissolves and deposits as gypsum until all the hemihydrate is converted into gypsum crystals.

[0029] This invention discloses a method for wet-adding a precipitant to building gypsum. The precipitant is added wet-addition during the setting and crystallization of the aforementioned β-type hemihydrate gypsum, aiming to reduce setting time while maintaining the fluidity of the slurry. The specific method is as follows:

[0030] A method for adding a wet-mixing accelerator to building gypsum includes the following steps:

[0031] Step 1: Mix ammonium sulfate with water and stir until completely dissolved to prepare an ammonium sulfate solution; the concentration of the ammonium sulfate solution is 0.055–0.08 mol·kg⁻¹. -1 ;

[0032] Step 2: Mix and grind the recycled gypsum with the grinding aid to form seed crystals; the grinding aid is an organic compound containing one or more combinations of functional groups such as -COOH, -NH2, -SO3H, and -OH; the specific surface area of ​​the seed crystals is greater than or equal to 8000 cm². 2 / g; Similarly, the seed crystals composed of raw gypsum powder (calcium sulfate dihydrate) and grinding aid powder, when added together to gypsum, both serve as nucleation sites to promote coagulation.

[0033] Step 3: Continuously introduce the ammonium sulfate solution and seed crystals into the container and stir to prepare the coagulant. Simultaneously, continuously inject the coagulant into the mixing port of the gypsum mixer to maintain a constant liquid level inside the container, thus completing the wet addition of the gypsum coagulant. The volume of coagulant discharged from the container per unit time is equal to the sum of the volumes of the raw powder mixture and seed crystals added to the container per unit time, ultimately ensuring that water accounts for 75-85% of the total material mass in the container. Simultaneously, maintain the temperature of the material inside the container at 34-38℃.

[0034] In the above process, since a large amount of sulfate ions are present in the solution after the ammonium sulfate dissolves, the presence of sulfate ions will inhibit the formation of new sulfate ions when the powdered gypsum in the seed crystal is added to the ammonium sulfate solution. This is based on the solubility curve of calcium sulfate dihydrate in ammonium sulfate solution (see...). Figure 5 It can be seen that when the concentration of ammonium sulfate solution is between 0.055 and 0.08 mol·kg⁻¹ -1 The inhibition of calcium sulfate dihydrate dissolution is most pronounced when the concentration is between 100 and 1000 ppm.

[0035] Therefore, a large amount of powdered gypsum (calcium sulfate dihydrate) exists in solid form in the prepared coagulant. After being added to gypsum, it acts as a nucleation point during gypsum setting, serving as a seed coagulant to accelerate setting. At the same time, ammonium sulfate, as a soluble sulfate, can improve the hydration efficiency of gypsum, reduce hydration time, and improve setting efficiency. Furthermore, due to the wet addition method, it does not significantly reduce the fluidity of gypsum and does not affect subsequent processing.

[0036] The above-mentioned method for wet-addition of building gypsum accelerator is achieved through the following device:

[0037] like Figure 1-4 As shown, a wet addition device for gypsum accelerator includes a pre-mixing tank 1, a stirring mechanism 2, a raw powder mixture feeding mechanism 3, a raw powder mixture inlet 4, a seed crystal inlet 5, and a discharge mechanism 6. The stirring mechanism 2 is installed and connected inside the pre-mixing tank 1, and the raw powder mixture inlet 4 and the seed crystal inlet 5 are provided on the pre-mixing tank 1. The material outlet of the raw powder mixture feeding mechanism 3 is connected to the raw powder mixture inlet 4. The discharge mechanism 6 is located at the bottom of the pre-mixing tank 1.

[0038] The seed inlet 5 is connected to the seed feeding mechanism, which is a screw conveyor, belt conveyor, or powder pneumatic conveying system. The material conveying volume of the raw powder mixture feeding mechanism 3 per unit time, plus the material conveying volume of the seed feeding mechanism per unit time, is equal to the material conveying volume of the discharge mechanism 6 per unit time.

[0039] The raw starch mixture feeding mechanism 3 includes a conveying pump, a flow meter, and a connecting pipe. The material inlet of the conveying pump is fed with ammonium sulfate solution, and the material outlet of the conveying pump is connected to the raw starch mixture inlet 4 via the connecting pipe. A flow meter is installed on the connecting pipe. The discharge mechanism 6 includes a discharge pump, a discharge pipe, and a flow meter. The material inlet of the discharge pump is connected to the interior of the pre-mixing tank 1, and the material outlet of the discharge pump is connected to the discharge pipe. The discharge pipe is connected to the mixing port of the gypsum mixer. A flow meter is installed on the discharge pipe.

[0040] The stirring mechanism 2 includes a stirring motor, a stirring shaft, and stirring blades. The stirring motor is fixedly connected to the upper part of the pre-mixing tank 1. One end of the stirring shaft is coaxially fixedly connected to the output end of the stirring motor, and the central axis of the stirring shaft coincides with the central axis of the pre-mixing tank 1. Several sets of stirring blades are evenly arrayed along the axial direction on the stirring shaft. The circumferential wall of the pre-mixing tank 1 is set as a double-layered structure. A heating device and a thermocouple are installed inside the pre-mixing tank 1, and the thermocouple is electrically connected to the heating device.

[0041] During use, the raw starch mixture is continuously fed into the pre-mixing tank 1 by the raw starch mixture feeding mechanism 3, and at the same time, the seed crystals are also continuously fed into the pre-mixing tank 1. All materials are quickly and evenly mixed by the stirring mechanism 2, and then fed into the gypsum mixer through the discharge mechanism 6 to complete the wet addition of the coagulant.

[0042] The following are the results of comparative experiments on the standard consistency and setting time of the gypsum product produced by adding a setting accelerator according to the present invention, compared with those of a blank sample and the traditional method of dry addition of setting accelerator:

[0043] Add method Addition amount (g / m²) Standard viscosity % Initial setting time Final setting time blank sample 0 67 3′40″ 6′30″ Dry processing 35 101 3′50″ 5′20″ Wet mixing for 30 seconds 35 81 3′10″ 5′50″ Wet mixing 1 minute 35 86 3′10″ 6′00″ Wet mixing for 2 minutes 35 84 3′00″ 5′40″ Wet mixing for 5 minutes 35 85 3′10″ 6′20″ Wet mixing for 10 minutes 35 84 3′10″ 6′10″

[0044] The results show that, according to the wet addition method and apparatus for accelerator of building gypsum provided by the present invention, the standard consistency of gypsum slurry is much lower than that of traditional dry addition method, and the setting time is also reduced to a certain extent.

[0045] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for wet-addition of a building gypsum accelerator, characterized in that: The system includes a pre-mixing tank (1), a stirring mechanism (2), a raw starch mixture feeding mechanism (3), a raw starch mixture inlet (4), a seed crystal inlet (5), and a discharge mechanism (6). The stirring mechanism (2) is installed and connected inside the pre-mixing tank (1), and the raw starch mixture inlet (4) and the seed crystal inlet (5) are provided on the pre-mixing tank (1). The material outlet of the raw starch mixture feeding mechanism (3) is connected to the raw starch mixture inlet (4). The discharge mechanism (6) is located at the bottom of the pre-mixing tank (1). The seed inlet (5) is connected to the seed feeding mechanism, which is a screw conveyor, belt conveyor, or powder pneumatic conveying system; the material conveying volume of the raw powder mixture feeding mechanism (3) per unit time, plus the material conveying volume of the seed feeding mechanism per unit time, is equal to the material conveying volume of the discharge mechanism (6) per unit time. The raw starch mixture feeding mechanism (3) includes a conveying pump, a flow meter, and a connecting pipe. The material inlet of the conveying pump is fed with ammonium sulfate solution, and the material outlet of the conveying pump is connected to the raw starch mixture inlet (4) via the connecting pipe. A flow meter is installed on the connecting pipe. The discharge mechanism (6) includes a discharge pump, a discharge pipe, and a flow meter. The material inlet of the discharge pump is connected to the inside of the pre-mixing tank (1), and the material outlet of the discharge pump is connected to the discharge pipe. The discharge pipe is connected to the mixing port of the gypsum mixer. A flow meter is installed on the discharge pipe. The stirring mechanism (2) includes a stirring motor, a stirring shaft, and stirring blades. The stirring motor is fixedly connected to the upper part of the pre-mixing tank (1). One end of the stirring shaft is coaxially fixedly connected to the output end of the stirring motor, and the central axis of the stirring shaft coincides with the central axis of the pre-mixing tank (1). Several sets of stirring blades are evenly arrayed along the axial direction on the stirring shaft. The circumferential wall of the pre-mixing tank (1) is set as a double-sided sandwich. A heating device and a thermocouple are installed inside the pre-mixing tank (1), and the thermocouple is electrically connected to the heating device.

2. A method for wet-adding a building gypsum accelerator, comprising the device for wet-adding a building gypsum accelerator as described in claim 1, characterized in that: The process includes the following steps: Step 1: Mix ammonium sulfate with water and stir until completely dissolved to prepare an ammonium sulfate solution; Step 2: Mix and grind raw gypsum with a grinding aid to prepare seed crystals; Step 3: Continuously introduce the ammonium sulfate solution and seed crystals into a container and stir to prepare a coagulant. Simultaneously, continuously inject the coagulant into the mixing port of the gypsum mixer to complete the wet addition of the gypsum coagulant; In Step 3, the material level inside the container remains constant.

3. The method for adding the building gypsum accelerator by wet application as described in claim 2, characterized in that: The concentration of the ammonium sulfate solution in step one is 0.055-0.08 mol·kg⁻¹.

4. The method for adding the building gypsum accelerator by wet application as described in claim 2, characterized in that: In step two, the grinding aid is an organic compound containing functional groups such as -COOH, -NH2, -SO3H, and -OH; the specific surface area of ​​the seed crystal is greater than or equal to 8000 cm2 / g.

5. The method for adding the building gypsum accelerator by wet application as described in claim 2, characterized in that: In step three, water accounts for 75-85% of the total material mass in the container; the temperature of the material in the container is maintained between 34-38℃.

6. The method for adding the building gypsum accelerator by wet application as described in claim 2, characterized in that: In step three, the volume of the coagulant discharged from the container per unit time is equal to the sum of the volumes of the raw powder mixture and the seed crystals added to the container per unit time.

7. The method for adding the building gypsum accelerator by wet application as described in claim 2, characterized in that: The gypsum used in step two is recycled gypsum.

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