Production method and device of α-type superheated gypsum

Abstract

The invention discloses a production method and device of α-type superheated gypsum, wherein the dihydrate gypsum raw material is mixed with a crystal conversion agent, and then loaded into an autoclave and heated; saturated steam at 170°C to 180°C is input into the autoclave; when the temperature in the autoclave reaches 125°C to 130°C, autoclave for 2.5 to 3 hours; the temperature is continuously raised to 145°C to 150°C, and autoclave for 0.5 to 1 hour; the steam pressure in the autoclave is removed, and when the pressure in the autoclave is zero, the exhaust device is started to quickly exhaust the steam in the reactor and cool down; the autoclave is heated again to keep the drying temperature in the reactor at 100°C to 145°C until the α-type superheated gypsum generated in the reactor is dried. The invention can produce a high-strength gypsum material suitable for preparing building mortar and casting building products, wherein the ratio of α-type hemihydrate gypsum to α-type slow-dissolving anhydrite (α-type CaSO4Ⅱs) is 9:1 to 6:4.

Description

Technical Field

[0001] The invention relates to the technical field of plaster of Paris processing, and in particular to a production method and device for alpha-type superheated gypsum. Background Art

[0002] At present, the β-burned gypsum product on the market is obtained by calcining dihydrate gypsum at a higher calcination temperature or time than general β-hemihydrate gypsum (also known as building gypsum). It is basically composed entirely of β-hemihydrate gypsum and β-soluble anhydrous gypsum (AⅢ, also known as β-hard gypsum Ⅲ). Compared with ordinary β-hemihydrate gypsum, it has a longer solidification time and higher strength.

[0003] α-type hemihydrate gypsum, also known as high-strength gypsum, is more than twice as strong as building gypsum. Its setting time is faster than that of β-type hemihydrate gypsum. During use, it is often necessary to add a retarder to reduce the strength (the strength can be reduced by 20% to 30%).

[0004] To this end, this application proposes an α-type superheated gypsum (α-type CaSO4·1 / 2H2O+α-type CaSO4Ⅱs), or α-type hemihydrate gypsum+α-type slow-dissolving anhydrite, according to the characteristics of different dehydrated phases of dihydrate gypsum. Since the production process of α-type hemihydrate gypsum is completely different from the normal pressure calcination of β-type hemihydrate gypsum, it is obtained by recrystallization in the process of removing one and a half crystal water under saturated steam pressure; therefore, α-type gypsum cannot be called overburned, but can only be called overheated. This α-type superheated gypsum not only retains the high strength characteristics of α-type hemihydrate gypsum, but also has the characteristics of adjustable setting time, which can meet the production requirements of gypsum mortar and products.

[0005] Since this α-type superheated gypsum has not yet been sold on the market or recorded in the literature; therefore, it is urgent to develop a production method and device for α-type superheated gypsum to meet the production requirements of gypsum mortar and products. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method and device for producing α-type superheated gypsum to meet the production needs of α-type superheated gypsum products.

[0007] In order to solve the above technical problems, according to one aspect of the present invention, a method for producing α-type superheated gypsum is provided, which comprises the following steps:

[0008] Step 1, dihydrate gypsum raw material and crystal conversion agent are mixed, loaded into an autoclave and heated;

[0009] Step 2, inputting saturated steam at 170°C to 180°C into the autoclave;

[0010] Step 3: When the temperature in the autoclave reaches 125°C to 130°C, autoclave for 2.5 to 3 hours; continue heating to 145°C to 150°C and autoclave for 0.5 to 1 hour;

[0011] Step 4: Open the exhaust valve of the autoclave to release the steam pressure in the autoclave; when the steam pressure in the autoclave drops to zero, start the exhaust device to quickly discharge the remaining water vapor in the reactor;

[0012] Step 5, when the temperature in the autoclave drops below 100°C, the autoclave is heated again to keep the drying temperature in the reactor at 100°C to 145°C until the α-type superheated gypsum generated in the reactor is dried;

[0013] Step six, the dried α-type superheated gypsum is discharged from the reactor and ground into a finished product.

[0014] Furthermore, in step one, the crystal conversion agent is a composition of aluminum sulfate and potassium sodium tartrate, and the mass ratios of the crystal conversion agent components to the dihydrate gypsum raw material are: aluminum sulfate 1-2%, potassium sodium tartrate 0.1-0.2%.

[0015] Furthermore, in step one, the mass ratios of the crystal conversion agent component and the dihydrate gypsum raw material are: 1.5% aluminum sulfate and 0.15% potassium sodium tartrate.

[0016] Furthermore, in step 2, if the dihydrate gypsum raw material itself does not contain attached water, when the temperature in the autoclave rises to 50°C, saturated steam is input into the autoclave in an input amount of 15% of the mass of the raw material.

[0017] Furthermore, in step 2, if the dihydrate gypsum raw material itself contains attached water, when the steam pressure in the autoclave rises to 0.02 MPa, saturated steam is input into the autoclave according to the input amount of raw material mass × (15% - raw material attached water ratio).

[0018] Furthermore, in step 2, the temperature in the autoclave is maintained below 125°C.

[0019] According to another aspect of the present invention, there is provided an apparatus for the production method of the above-mentioned α-type superheated gypsum, comprising an autoclave, which is a horizontal stirring reactor, and the autoclave is equipped with a steam exhaust device for quickly exhausting the steam in the reactor.

[0020] Furthermore, the autoclave is equipped with an air flow conveying device for outputting the dried α-type superheated gypsum.

[0021] Furthermore, the discharge port and the discharge valve of the autoclave are arranged on the end surface of the autoclave.

[0022] Furthermore, it comprises a mill for grinding the α-type superheated gypsum to obtain a finished product.

[0023] The present invention makes the water content of the dihydrate gypsum raw material be between 15% and 18% by directly adding steam. During the reaction, the autoclave temperature changes in a step-by-step manner. After the steam in the autoclave is discharged to relieve the steam pressure, the exhaust device outside the autoclave is started to quickly discharge the steam and reduce the temperature. There is secondary heating in the process, and the drying temperature is controlled until the α-type overburned gypsum in the reactor is dried.

[0024] The invention can produce a high-strength gypsum material suitable for preparing building mortar and casting building products, wherein the ratio of α-type hemihydrate gypsum to α-type slow-dissolving anhydrite (α-type CaSO4Ⅱs) is 9:1-6:4. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of the autoclave of the present invention.

[0026] In the figure, 1-discharge valve, 2-feed valve, 3-stirring blade, 4-support, 5-motor, 6-stirring shaft. DETAILED DESCRIPTION

[0027] A typical embodiment of the present invention provides a method for producing α-type superheated gypsum. The α-type superheated gypsum α-type is CaSO4·1 / 2H2O+α-type CaSO4Ⅱs, and its preparation method mainly includes the following steps.

[0028] Step 1: The dihydrate gypsum raw material is mixed with a crystal conversion agent, placed in an autoclave and heated.

[0029] Wherein, in step 1, the crystal conversion agent is a composition of aluminum sulfate and potassium sodium tartrate, and the mass ratio of the crystal conversion agent component to the dihydrate gypsum raw material is: aluminum sulfate 1-2%, potassium sodium tartrate 0.1-0.2%. Preferably, the mass ratio of the crystal conversion agent component to the dihydrate gypsum raw material is: aluminum sulfate 1.5%, potassium sodium tartrate 0.15%.

[0030] Step 2: Input saturated steam at 170°C to 180°C into the autoclave.

[0031] Since the gypsum raw material needs to have a water content of 15% to 18%, water cannot be added directly. In this step, saturated steam is directly introduced into the autoclave, and the amount of saturated steam introduced is controlled to make the water content of the dihydrate gypsum raw material 15% to 18%, and to avoid the formation of raw material precipitation.

[0032] If the dihydrate gypsum raw material itself does not contain attached water, when the temperature in the autoclave rises to 50°C, saturated steam is input into the autoclave according to the input amount of raw material mass × 15%.

[0033] If the dihydrate gypsum raw material itself contains attached water, when the steam pressure in the autoclave rises to 0.02 MPa, saturated steam is input into the autoclave according to the input amount of raw material mass × (15% - raw material attached water ratio).

[0034] During the input of saturated steam, the temperature in the autoclave was kept below 125°C.

[0035] Step 3: When the temperature in the autoclave reaches 125°C to 130°C, autoclave for 2.5 to 3 hours; continue to heat up to 145°C to 150°C and autoclave for 0.5 to 1 hour.

[0036] Autoclaving under the above-mentioned temperature and time conditions can obtain the best match between α-hemihydrate gypsum and α-slow-dissolving anhydrite, while having a good cost-effectiveness.

[0037] Step 4: Open the exhaust valve of the autoclave to release the steam pressure in the autoclave; when the steam pressure in the autoclave drops to zero, start the exhaust device to quickly discharge the remaining water vapor in the reactor to ensure and maintain a better ratio between the hemihydrate gypsum and the anhydrous gypsum.

[0038] Step 5: When the temperature in the autoclave drops below 100°C due to exhaust steam, the autoclave is heated again to keep the drying temperature in the reactor at 100°C to 145°C until dry α-type superheated gypsum is generated in the reactor.

[0039] In this step, the drying speed is accelerated by continuing to heat, while preventing a portion of the anhydrous gypsum from being reduced to hemihydrate gypsum.

[0040] Step six, the dried α-type superheated gypsum is discharged from the reactor and ground into a finished product. The ratio of α-type hemihydrate gypsum to α-type slow-dissolving anhydrite (α-type CaSO4Ⅱs) in the finished product is 9:1 to 6:4, wherein the higher the ratio of α-type slow-dissolving anhydrite, the longer the time required for solidification.

[0041] Another typical embodiment of the present invention provides a device for the above-mentioned α-type superheated gypsum production method, comprising an autoclave, which is a horizontal stirring reactor, and a heating coil is provided on the outside of the reactor wall for heating the material in the reactor. The above-mentioned autoclave is provided with an exhaust device on the outside for quickly exhausting the steam in the reactor. It is preferred to use an exhaust device that can withstand high temperature and high humidity.

[0042] In a preferred embodiment, the autoclave is equipped with an air flow conveying device for outputting the dried α-type superheated gypsum.

[0043] In a preferred embodiment, the discharge port and discharge valve 1 of the autoclave are arranged on the end face of the autoclave. In the prior art, the discharge valve of the autoclave is at the bottom of the autoclave body. Since there is no heating coil at the location of the discharge valve, the gypsum deposited at the discharge valve is less heated and easily forms a half-cooked gypsum block that affects the discharge. In this embodiment, the discharge valve at the bottom is replaced by being installed on the end face of the horizontal stirred reactor, which can effectively prevent the gypsum block from affecting the discharge and speed up the heating speed.

[0044] In addition, the device also includes a grinder for grinding the α-type superheated gypsum to obtain a finished product.

[0045] The technical scheme claimed in the present invention is further described below by some examples. However, the examples are used to explain the embodiments of the present invention and do not exceed the scope of the subject matter of the present invention. The protection scope of the present invention is not limited by the examples. Unless otherwise specified, the materials and reagents used in the present invention can be obtained from commercial products in the art.

[0046] The following Examples 1 and 2 use flue gas desulfurization gypsum from a thermal power plant in Shanxi Province, whose crystal water content is 18.41% and the adhering water content is 13.6%. At the same time, assuming that the mass of (dihydrate) gypsum is 100, the measured crystal water content is X%, and the theoretical crystal water content of hemihydrate gypsum is Y. The calculation formula for the theoretical crystal water content of hemihydrate gypsum is: Y=(1 / 4)X÷[100-(3 / 4)X]=X÷(400-3X)(%);

[0047] According to this formula, the theoretical crystal water ratio of the desulfurized gypsum used in the specific implementation and converted into α-hemihydrate gypsum is 5.34%. Example 1

[0048] The powdered desulfurized gypsum raw material and the crystal conversion agent accounting for 1.65% of the mass of the desulfurized gypsum raw material (including 1.5% aluminum sulfate and 0.15% potassium sodium tartrate) are charged into a side-discharge horizontal stirring autoclave while stirring, the feed valve is closed, and heating is performed at the same time; when the steam pressure in the reactor rises to 0.02 MPa, saturated steam at 170°C is input into the autoclave according to the mass of the raw material × (15%-13.6%).

[0049] When the temperature in the autoclave reaches 125°C, the temperature is raised to 145°C after 2.5 hours of autoclaving and the autoclave is continued for 0.5 hours. The steam is exhausted to relieve the pressure. When the steam pressure in the autoclave is zero, the feed valve is opened, the retractable exhaust pipe is moved to the upper part of the feed valve, the exhaust device is started, and the steam is quickly exhausted.

[0050] When the temperature in the autoclave drops below 100°C due to exhaust steam, the autoclave is heated again to keep the drying temperature at 110°C until the α-type superheated gypsum inside the reactor is dried.

[0051] Finally, the dried α-type superheated gypsum is discharged to the mill through an air flow conveying device, and the α-type superheated gypsum is ground into a finished product by the mill.

[0052] It has been tested that the ratio of α-type hemihydrate gypsum and α-type slow-dissolving anhydrite in the α-type superheated gypsum produced under the above process conditions is about 9:1, that is, the actual measured crystallization water is 4.79%, slightly lower than 90% of the theoretical crystallization water of 5.34%. Its setting time is 28 minutes and the dry compressive strength is 38.2 MPa. Example 2

[0053] The powdered desulfurized gypsum raw material and the crystal converter accounting for 1.65% of the mass of the desulfurized gypsum raw material (including 1.5% aluminum sulfate + 0.15% potassium sodium tartrate) are charged into a side-discharge horizontal stirring autoclave while stirring, the feed valve is closed, and heating is performed at the same time; when the steam pressure in the reactor rises to 0.02 MPa, saturated steam at 180°C is input into the autoclave according to the mass of the raw material × (15%-13.6%).

[0054] When the temperature in the autoclave reaches 125°C, heat it up to 145°C after 3 hours of autoclaving and continue autoclaving for 45 minutes to exhaust the steam and relieve the pressure. When the steam pressure in the autoclave is zero, open the feed valve, move the retractable exhaust pipe to the upper part of the feed valve, start the exhaust device, and quickly exhaust the steam.

[0055] When the temperature in the autoclave drops below 100°C due to exhaust steam, the autoclave is heated again to keep the drying temperature at 110°C until the α-type superheated gypsum inside the reactor is dried.

[0056] Finally, the dried α-type superheated gypsum is discharged to the mill through an air flow conveying device, and the α-type superheated gypsum is ground into a finished product by the mill.

[0057] It has been tested that the ratio of α-type hemihydrate gypsum and α-type slow-dissolving anhydrite in the α-type superheated gypsum produced under the above process conditions is about 8:2, that is, the actual crystallization water is 4.3%, slightly lower than 80% of the theoretical crystallization water of 5.34%. Its setting time is 1 hour and 12 minutes, and the dry compressive strength is 36.8 MPa. Example 3

[0058] The powdered desulfurized gypsum raw material and the crystal conversion agent accounting for 1.65% of the mass of the desulfurized gypsum raw material (including 1.5% aluminum sulfate and 0.15% potassium sodium tartrate) are charged into a side-discharge horizontal stirring autoclave while stirring, the feed valve is closed, and heating is performed at the same time; when the steam pressure in the reactor rises to 0.02 MPa, saturated steam at 180°C is input into the autoclave according to the mass of the raw material × (15%-13.6%).

[0059] When the temperature in the autoclave reaches 130°C, heat it up to 150°C after 3 hours of autoclaving and continue autoclaving for 1 hour to exhaust the steam and relieve the pressure. When the steam pressure in the autoclave is zero, open the feed valve, move the retractable exhaust pipe to the upper part of the feed valve, start the exhaust device, and quickly exhaust the steam.

[0060] When the temperature in the autoclave drops below 100°C due to exhaust steam, the autoclave is heated again to keep the drying temperature at 110°C until the α-type superheated gypsum inside the reactor is dried.

[0061] Finally, the dried α-type superheated gypsum is discharged to the mill through an air flow conveying device, and the α-type superheated gypsum is ground into a finished product by the mill.

[0062] It was tested that the ratio of α-type hemihydrate gypsum and α-type slow-dissolving anhydrite in the α-type superheated gypsum produced under the above process conditions was about 2.4:7.6, that is, the actual crystallization water was 1.27%, slightly lower than 23.8% of the theoretical crystallization water of 5.34%. Its setting time was 12 hours and the dry compressive strength was 36.1 MPa. Example 4

[0063] The powdered desulfurized gypsum raw material and the crystal conversion agent accounting for 1.1% of the mass of the desulfurized gypsum raw material (including 1% aluminum sulfate and 0.1% potassium sodium tartrate) are mixed and loaded into a side-discharge horizontal stirring autoclave, the feed valve is closed, and heating is performed at the same time; when the steam pressure in the reactor rises to 0.02 MPa, saturated steam at 180°C is input into the autoclave according to the mass of the raw material × (15%-13.6%).

[0064] When the temperature in the autoclave reaches 130°C, heat it up to 150°C after 3 hours of autoclaving and continue autoclaving for 1 hour. Exhaust the steam to relieve the pressure. When the steam pressure in the autoclave is zero, open the feed valve, move the retractable exhaust pipe to the upper part of the feed valve, start the exhaust device, and quickly exhaust the steam.

[0065] When the temperature in the autoclave drops below 100°C due to exhaust steam, the autoclave is heated again to keep the drying temperature at 100°C until the α-type superheated gypsum inside the reactor is dried.

[0066] Finally, the dried α-type superheated gypsum is discharged to the mill through an air flow conveying device, and the α-type superheated gypsum is ground into a finished product by the mill.

[0067] It has been tested that the ratio of α-type hemihydrate gypsum and α-type slow-dissolving anhydrite in the α-type superheated gypsum produced under the above process conditions is about 9:1, that is, the actual measured crystallization water is 4.79%, slightly lower than 90% of the theoretical crystallization water of 5.34%. Its setting time is 28 minutes and the dry compressive strength is 37.8 MPa. Example 5

[0068] The powdered desulfurized gypsum raw material and the crystal conversion agent accounting for 2.2% of the mass of the desulfurized gypsum raw material (including 2% aluminum sulfate and 0.2% potassium sodium tartrate) are mixed and loaded into a side-discharge horizontal stirring autoclave, the feed valve is closed, and heating is performed at the same time; when the steam pressure in the reactor rises to 0.02 MPa, saturated steam at 180°C is input into the autoclave according to the mass of the raw material × (15%-13.6%).

[0069] When the temperature in the autoclave reaches 125°C, heat it up to 145°C after 2.5 hours of autoclaving and continue autoclaving for 0.5 hour. Exhaust the steam to relieve the pressure. When the steam pressure in the autoclave is zero, open the feed valve, move the retractable exhaust pipe to the upper part of the feed valve, start the exhaust device, and quickly exhaust the steam.

[0070] When the temperature in the autoclave drops below 100°C due to exhaust steam, the autoclave is heated again to keep the drying temperature at 145°C until the α-type superheated gypsum inside the reactor is dried.

[0071] Finally, the dried α-type superheated gypsum is discharged to the mill through an air flow conveying device, and the α-type superheated gypsum is ground into a finished product by the mill.

[0072] It has been tested that the ratio of α-type hemihydrate gypsum and α-type slow-dissolving anhydrite in the α-type superheated gypsum produced under the above process conditions is about 9:1, that is, the actual measured crystallization water is 4.79%, slightly lower than 90% of the theoretical crystallization water of 5.34%. Its setting time is 28 minutes and the dry compressive strength is 38.1 MPa.

Claims

1. A method for producing α-type superheated gypsum, characterized in that: The following steps are involved: Step 1, dihydrate gypsum raw material and crystal conversion agent are mixed, loaded into an autoclave and heated; Step 2, inputting saturated steam at 170°C to 180°C into the autoclave; If the dihydrate gypsum raw material itself does not contain attached water, when the temperature in the autoclave rises to 50°C, saturated steam is input into the autoclave at an input amount of 15% of the raw material mass; If the dihydrate gypsum raw material itself contains attached water, when the steam pressure in the autoclave rises to 0.02 MPa, saturated steam is input into the autoclave according to the input amount of raw material mass × (15% - raw material attached water ratio); Step 3: When the temperature in the autoclave reaches 125°C to 130°C, autoclave for 2.5 to 3 hours; continue heating to 145°C to 150°C and autoclave for 0.5 to 1 hour; Step 4: Open the exhaust valve of the autoclave to release the steam pressure in the autoclave; when the pressure in the autoclave is zero, start the exhaust device to quickly discharge the steam in the reactor and cool it down; Step 5, when the temperature in the autoclave drops below 100°C, the autoclave is heated again to keep the drying temperature in the reactor at 100°C to 145°C until the α-type superheated gypsum generated in the reactor is dried; Step six, the dried α-type superheated gypsum is discharged from the reactor and ground into a finished product.

2. The method according to claim 1, characterized in that: In step 1, the crystal conversion agent is a composition of aluminum sulfate and potassium sodium tartrate, and the mass ratios of the crystal conversion agent components to the dihydrate gypsum raw material are: aluminum sulfate 1-2%, potassium sodium tartrate 0.1-0.2%.

3. The method according to claim 2, characterized in that: In step 1, the mass ratios of the crystal conversion agent component and the dihydrate gypsum raw material are: 1.5% aluminum sulfate and 0.15% potassium sodium tartrate.

4. The method according to claim 1, 2 or 3, characterized in that: In step 2, the temperature in the autoclave is maintained below 125°C.

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