Method for preparing building gypsum directly from industrial waste sulfuric acid and waste stone powder

Abstract

This invention pertains to the field of building gypsum production, specifically relating to a method for directly preparing building gypsum using industrial waste sulfuric acid and waste stone powder. The method involves using a normal-pressure reactor, neutralizing industrial waste sulfuric acid with waste stone powder as raw material, and directly forming a building gypsum slurry under the conditions of salt and a crystallizing agent. The resulting building gypsum slurry undergoes solid-liquid separation, washing, and drying to ultimately obtain building gypsum crystals, which are then packaged and stored. This invention, a method for directly preparing building gypsum using industrial waste sulfuric acid and waste stone powder, reduces the filtration and drying steps of dihydrate gypsum in traditional methods. By adjusting the type and amount of salt and crystallizing agent, building gypsum with crystal diameters of 10μm-30μm and aspect ratios of 10:1-1:1 can be prepared.

Description

Technical Field

[0001] This invention belongs to the field of building gypsum production, specifically relating to a method for directly preparing building gypsum using industrial waste sulfuric acid and waste stone powder. Background Technology

[0002] Building gypsum is one of the three major cementing materials in the construction industry. Its production requires low energy consumption, only 25% of that of cement and 23% of that of lime, making it a typical green and low-carbon building material. The main applications of building gypsum include paper-faced gypsum board, plastering gypsum, self-leveling gypsum mortar, and gypsum blocks. The production capacity of paper-faced gypsum board has reached 5 billion cubic meters. 2 The amount of plastering gypsum used is 6 Mt, and the amount of self-leveling gypsum mortar used is 1 Mt. In summary, building gypsum has broad market prospects and environmental value.

[0003] Waste acid not only pollutes the environment and wastes sulfur resources, but also poses significant safety hazards. Waste stone powder is scrap material generated by stone processing enterprises during sawing, grinding, and polishing processes. Most enterprises allow this waste to be discharged and accumulated, causing environmental pollution and ecological damage. How to handle and utilize stone processing waste has become a major concern for stone enterprises. The building gypsum preparation processes that have been widely adopted are roughly divided into calcination, autoclaving, and atmospheric pressure salt solution methods. These three processes mostly adopt a two-step method, that is, first using waste acid to react with calcium carbonate to generate dihydrate gypsum, and then converting the dihydrate gypsum into building gypsum. This involves large equipment investment, long production cycle, and high energy consumption. There is still a lack of reliable technology in China to directly utilize industrial waste sulfuric acid and waste stone powder to prepare building gypsum in an atmospheric pressure salt solution. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder. The method uses waste stone powder to neutralize industrial waste sulfuric acid as raw material in an atmospheric pressure reactor, and directly forms building gypsum under the conditions of salt and crystallization agent. This reduces the filtration and drying steps of dihydrate gypsum in traditional methods, and saves more on equipment investment and energy consumption.

[0005] The present invention discloses a method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder, comprising the following steps:

[0006] Step 1: Mix waste rock powder, salt, crystallizing agent and water evenly, and pump the evenly mixed slurry into an atmospheric pressure reactor;

[0007] Step 2: Add water and industrial waste sulfuric acid to an atmospheric pressure reactor and stir with the mixed slurry from Step 1; control the temperature in the atmospheric pressure reactor at 40-80℃ and the reaction time at 30-90min to obtain a reaction stock solution with a pH of 5-7;

[0008] Step 3: Heat the atmospheric pressure reactor to 90-110℃ and react for 30-240 minutes under atmospheric pressure to obtain building gypsum slurry;

[0009] Step 4: The prepared building gypsum slurry is subjected to solid-liquid separation, water washing and drying to finally obtain building gypsum crystals, which are then packaged and stored.

[0010] In step 1, the salt is one or more of sodium chloride, sodium sulfate, calcium chloride, calcium nitrate, potassium chloride, potassium sulfate, potassium nitrate, aluminum sulfate, and ferric sulfate. The concentration of the salt is 5-50 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction stock solution.

[0011] In step 1, the crystallization agent is one or more of the following: ethylenediaminetetraacetic acid, ethylenediaminetetrapropionic acid, ethylenediaminediethyl ether tetraacetic acid, cyclohexanediaminetetraacetic acid, 2-dimethylhexanoic acid, 3-methyl-2-butenoic acid, 2-amino-3-hydroxybutyric acid, succinic acid, maleic acid, tartaric acid, citric acid, chitosan, and tea polyphenols. The concentration of the crystallization agent is 0.01wt%-1.0wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction stock solution.

[0012] In step 1, the waste stone powder comprises loss on ignition, SiO2, Al2O3, Fe2O3, CaO, MgO, and R2O, wherein the loss on ignition accounts for 25-40%; SiO2 accounts for 5-25%; Al2O3 accounts for 0.5-5.0%; Fe2O3 accounts for 0.3-2.0%; CaO accounts for 30-50%; MgO accounts for 0.3-5.0%; and R2O accounts for 0.4-2.0%.

[0013] In step 2, the stirring speed is 300 rpm to 3000 rpm.

[0014] In step 4, the solid-liquid separation method is any one of centrifugal separation, gravity sedimentation, or plate and frame filtration.

[0015] In step 4, the water washing temperature is 95-100℃ and the water washing time is 3 minutes.

[0016] In step 4, the drying method is any one of spray drying, flash drying, or centrifugal airflow drying; the inlet temperature of the drying method is 105℃-150℃, and the outlet temperature of the drying method is 95℃-105℃.

[0017] In step 4, the crystal diameter of the building gypsum is 10μm-30μm, and the aspect ratio is 10:1-1:1.

[0018] The method of directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder has the following advantages:

[0019] 1. Shorten the production cycle, reduce equipment investment, and lower energy consumption;

[0020] 2. To realize the resource utilization of industrial waste sulfuric acid and waste stone powder, turning waste into treasure;

[0021] 3. Only crystallization conversion agent and salt crystallization aid are needed; the operation process is simple and the production cost is low.

[0022] 4. During the reaction, by adjusting the type and amount of salt and crystallizing agent, building gypsum with crystal diameter of 10μm-30μm and aspect ratio of 10:1-1:1 can be prepared. Attached Figure Description

[0023] Figure 1 The present invention provides a process flow diagram of a method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder.

[0024] Figure 2 Crystal form image under a microscope in Example 1 of this invention;

[0025] Figure 3 Crystal form image under a microscope in Example 2 of this invention;

[0026] Figure 4 Crystal form image under a microscope in Example 3 of this invention;

[0027] Figure 5 Crystal form image under a microscope in Example 4 of this invention;

[0028] Figure 6 Crystal form image under a microscope in Example 5 of this invention;

[0029] Figure 7 Crystal form image under a microscope in Example 6 of this invention; Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1:

[0032] like Figure 1 , Figure 2 As shown, the present invention discloses a method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder, comprising the following steps:

[0033] Step 1: Mix waste stone powder, salt, crystallizing agent, and water evenly. Pump the evenly mixed slurry into an atmospheric pressure reactor. The waste stone powder consists of loss on ignition, SiO2, Al2O3, Fe2O3, CaO, MgO, and R2O, with a loss on ignition percentage of 38.06%, SiO2 of 7.23%, Al2O3 of 2.65%, Fe2O3 of 1.52%, CaO of 46.48%, MgO of 3.22%, and R2O of 0.84%. The salt includes calcium chloride and potassium chloride, with the salt content being 15 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution. The calcium chloride content is 10 wt%, and the potassium chloride content is 5 wt%. The crystallizing agent includes tea polyphenols and 3-methyl-2-butenoic acid, with the crystallizing agent concentration being 0.5 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution. The tea polyphenol content is 0.2 wt%, and the 3-methyl-2-butenoic acid content is 0.3 wt%.

[0034] Step 2: Add water and industrial waste sulfuric acid to an atmospheric pressure reactor and stir with the mixed slurry from Step 1 at a stirring speed of 400 rpm; control the temperature in the atmospheric pressure reactor at 50℃ and the reaction time at 80 min to obtain a reaction stock solution with a pH of 7.

[0035] Step 3: Heat the atmospheric pressure reactor to 100℃ and react for 120 minutes under atmospheric pressure to obtain building gypsum slurry;

[0036] Step 4: The prepared building gypsum slurry is centrifuged, washed with water, and spray-dried. The washing time is 3 minutes, the washing temperature is 98℃, the spray drying inlet temperature is 120℃, and the outlet temperature is 95℃. Finally, building gypsum crystals with a diameter of 10μm and an aspect ratio of 4:1 are obtained, and then packaged and stored.

[0037] Example 2:

[0038] like Figure 1 , Figure 3 As shown, the present invention discloses a method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder, comprising the following steps:

[0039] Step 1: Mix waste rock powder, salt, crystallizing agent, and water evenly. Pump the uniformly mixed slurry into an atmospheric pressure reactor. The waste rock powder consists of loss on ignition (LOI), SiO2, Al2O3, Fe2O3, CaO, MgO, and R2O, with LOI accounting for 38.06%, SiO2 7.23%, Al2O3 2.65%, Fe2O3 1.52%, CaO 46.48%, MgO 3.22%, and R2O. 2O accounts for 0.84%; the salt includes sodium chloride and potassium chloride, with the salt content being 20 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction stock solution, sodium chloride accounting for 10 wt% and potassium chloride accounting for 10 wt%; the crystallization agent includes chitosan and 2-amino-3-hydroxybutyric acid, and the concentration of the crystallization agent is 0.4 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction stock solution, of which chitosan accounts for 0.2 wt% and 2-amino-3-hydroxybutyric acid accounts for 0.2 wt%;

[0040] Step 2: Add water and industrial waste sulfuric acid to an atmospheric pressure reactor and stir with the mixed slurry from Step 1 at a stirring speed of 500 rpm; control the temperature in the atmospheric pressure reactor at 55℃ and the reaction time at 70 min to obtain a reaction stock solution with a pH of 7.

[0041] Step 3: Heat the atmospheric pressure reactor to 105℃ and react for 160 minutes under atmospheric pressure to obtain building gypsum slurry;

[0042] Step 4: The prepared building gypsum slurry is subjected to plate and frame filter press, water washing, and flash drying. The water washing time is 3 minutes, the water washing temperature is 95℃, the inlet temperature of flash drying is 125℃, and the outlet temperature is 105℃. Finally, building gypsum crystals with a diameter of 12μm and an aspect ratio of 5:1 are obtained, and then packaged and stored.

[0043] Example 3:

[0044] like Figure 1 , Figure 4 As shown, the present invention discloses a method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder, comprising the following steps:

[0045] Step 1: Mix waste stone powder, salt, crystallizing agent, and water evenly. Pump the evenly mixed slurry into an atmospheric pressure reactor. The waste stone powder consists of loss on ignition, SiO2, Al2O3, Fe2O3, CaO, MgO, and R2O, with a loss on ignition percentage of 38.06%, SiO2 of 7.23%, Al2O3 of 2.65%, Fe2O3 of 1.52%, CaO of 46.48%, MgO of 3.22%, and R2O of 0.84%. The salt includes sodium sulfate and potassium sulfate, with the salt content being 20 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution, and sodium sulfate and potassium sulfate accounting for 10 wt%. The crystallizing agent includes maleic acid and 2-dimethylhexanoic acid, with the concentration of the crystallizing agent being 0.5 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution, and maleic acid accounting for 0.3 wt% and 2-dimethylhexanoic acid accounting for 0.2 wt%.

[0046] Step 2: Add water and industrial waste sulfuric acid to an atmospheric pressure reactor and stir with the mixed slurry from Step 1 at a stirring speed of 600 rpm; control the temperature in the atmospheric pressure reactor at 60℃ and the reaction time at 60 min to obtain a reaction stock solution with a pH of 6.

[0047] Step 3: Heat the atmospheric pressure reactor to 98°C and react for 200 minutes under atmospheric pressure to obtain building gypsum slurry;

[0048] Step 4: The prepared building gypsum slurry is subjected to gravity settling, water washing, and centrifugal air drying. The water washing time is 3 minutes, the water washing temperature is 98℃, the inlet temperature of the centrifugal air drying is 120℃, and the outlet temperature is 100℃. Finally, building gypsum crystals with a diameter of 10μm and an aspect ratio of 5:1 are obtained, and then packaged and stored.

[0049] Example 4:

[0050] like Figure 1 , Figure 5 As shown, the present invention discloses a method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder, comprising the following steps:

[0051] Step 1: Mix waste rock powder, salt, crystallizing agent, and water evenly. Pump the uniformly mixed slurry into an atmospheric pressure reactor. The waste rock powder consists of loss on ignition (LOI), SiO2, Al2O3, Fe2O3, CaO, MgO, and R2O, with LOI accounting for 38.06%, SiO2 7.23%, Al2O3 2.65%, Fe2O3 1.52%, CaO 46.48%, MgO 3.22%, and R2O. The 2O content is 0.84%; the salts include calcium nitrate and potassium chloride, with the salt content being 25 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the original reaction solution, calcium nitrate accounting for 20 wt%, and potassium chloride accounting for 5 wt%; the crystallization agents include maleic acid and 3-methyl-2-butenoic acid, with the crystallization agent concentration being 0.3 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the original reaction solution, maleic acid accounting for 0.05 wt%, and 3-methyl-2-butenoic acid accounting for 0.25 wt%.

[0052] Step 2: Add water and industrial waste sulfuric acid to an atmospheric pressure reactor and stir with the mixed slurry from Step 1 at a stirring speed of 500 rpm; control the temperature in the atmospheric pressure reactor at 40℃ and the reaction time at 80 min to obtain a reaction stock solution with a pH of 5.

[0053] Step 3: Heat the atmospheric pressure reactor to 102℃ and react for 100 minutes under atmospheric pressure to obtain building gypsum slurry;

[0054] Step 4: The prepared building gypsum slurry is centrifuged, washed with water, and spray-dried. The washing time is 3 minutes, the washing temperature is 95℃, the spray drying inlet temperature is 125℃, and the outlet temperature is 105℃. Finally, building gypsum crystals with a diameter of 14μm and an aspect ratio of 3:1 are obtained, and then packaged and stored.

[0055] Example 5:

[0056] like Figure 1 , Figure 6 As shown, the present invention discloses a method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder, comprising the following steps:

[0057] Step 1: Mix waste stone powder, salt, crystallizing agent, and water evenly. Pump the evenly mixed slurry into an atmospheric pressure reactor. The waste stone powder consists of loss on ignition, SiO2, Al2O3, Fe2O3, CaO, MgO, and R2O, with a loss on ignition percentage of 38.06%, SiO2 of 7.23%, Al2O3 of 2.65%, Fe2O3 of 1.52%, CaO of 46.48%, MgO of 3.22%, and R2O of 0.84%. The salt includes calcium nitrate and potassium nitrate, with the salt content being 30 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution. The calcium nitrate content is 29 wt%, and the potassium nitrate content is 1 wt%. The crystallizing agent includes tea polyphenols and ethylenediaminetetraacetic acid, with the crystallizing agent concentration being 0.8 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution. The tea polyphenol content is 0.3 wt%, and the 3-methyl-2-butenoic acid content is 0.5 wt%.

[0058] Step 2: Add water and industrial waste sulfuric acid to an atmospheric pressure reactor and stir with the mixed slurry from Step 1 at a stirring speed of 600 rpm; control the temperature in the atmospheric pressure reactor at 70℃ and the reaction time at 45 min to obtain a reaction stock solution with a pH of 6.

[0059] Step 3: Heat the atmospheric pressure reactor to 104℃ and react for 80 minutes under atmospheric pressure to obtain building gypsum slurry;

[0060] Step 4: The prepared building gypsum slurry is subjected to plate and frame filter press, water washing, and flash drying. The water washing time is 3 minutes, the water washing temperature is 98℃, the flash drying inlet temperature is 115℃, and the outlet temperature is 100℃. Finally, building gypsum crystals with a diameter of 12μm and an aspect ratio of 2:1 are obtained, and then packaged and stored.

[0061] Example 6:

[0062] like Figure 1 , Figure 7 As shown, the present invention discloses a method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder, comprising the following steps:

[0063] Step 1: Mix waste stone powder, salt, crystallizing agent, and water evenly. Pump the evenly mixed slurry into an atmospheric pressure reactor. The waste stone powder consists of loss on ignition, SiO2, Al2O3, Fe2O3, CaO, MgO, and R2O, with a loss on ignition percentage of 38.06%, SiO2 of 7.23%, Al2O3 of 2.65%, Fe2O3 of 1.52%, CaO of 46.48%, MgO of 3.22%, and R2O of 0.84%. The salt includes calcium nitrate and sodium chloride, with the salt content being 40 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution, calcium nitrate of 35 wt%, and sodium chloride of 5 wt%. The crystallizing agent includes chitosan and cyclohexanediaminetetraacetic acid, with the concentration of the crystallizing agent being 0.7 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution, chitosan of 0.5 wt%, and cyclohexanediaminetetraacetic acid of 0.2 wt%.

[0064] Step 2: Add water and industrial waste sulfuric acid to an atmospheric pressure reactor and stir with the mixed slurry from Step 1 at a stirring speed of 400 rpm; control the temperature in the atmospheric pressure reactor at 50℃ and the reaction time at 80 min to obtain a reaction stock solution with a pH of 7.

[0065] Step 3: Heat the atmospheric pressure reactor to 108℃ and react for 50 minutes under atmospheric pressure to obtain building gypsum slurry;

[0066] Step 4: The prepared building gypsum slurry is subjected to plate and frame filter press, water washing, and centrifugal air drying. The water washing time is 3 minutes, the water washing temperature is 96℃, the centrifugal air drying inlet temperature is 125℃, and the outlet temperature is 100℃. Finally, building gypsum crystals with a diameter of 10μm and an aspect ratio of 2:1 are obtained, and then packaged and stored.

[0067] The physical properties of the prepared building plaster were tested and compared with those of a building plaster purchased from the market. The performance test results are shown in Table 1.

[0068] Table 1 Performance Test Results

[0069]

[0070] As can be seen from Table 1, the building gypsum prepared by this patent meets the requirements of standard GB / T9776-2022 "Building Gypsum" in terms of setting time, 2-hour wet strength and dry strength.

Claims

1. A method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder, characterized in that, Includes the following steps: Step 1: Mix waste rock powder, salt, crystallizing agent and water evenly, and pump the evenly mixed slurry into an atmospheric pressure reactor; The crystallization agent is tea polyphenols and 3-methyl-2-butenoic acid, with a concentration of 0.5 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution, of which tea polyphenols account for 0.2 wt% and 3-methyl-2-butenoic acid accounts for 0.3 wt%; or the crystallization agent is chitosan and 2-amino-3-hydroxybutyric acid, with a concentration of 0.4 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution, of which chitosan accounts for 0.2 wt% and 2-amino-3-hydroxybutyric acid accounts for 0.2 wt%; or the crystallization agent is maleic acid and 2-dimethylhexanoic acid, with a concentration of [missing information - likely a percentage] of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution. The total mass of the powder is 0.5 wt%, maleic acid accounts for 0.3 wt%, and 2-dimethylhexanoic acid accounts for 0.2 wt%; or the crystal conversion agent is maleic acid and 3-methyl-2-butenoic acid, and the concentration of the crystal conversion agent is 0.3 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution, maleic acid accounts for 0.05 wt%, and 3-methyl-2-butenoic acid accounts for 0.25 wt%; or the crystal conversion agent is chitosan and cyclohexanediaminetetraacetic acid, and the concentration of the crystal conversion agent is 0.7 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the reaction solution, chitosan accounts for 0.5 wt%, and cyclohexanediaminetetraacetic acid accounts for 0.2 wt%. The salt is one of several of the following: sodium chloride, sodium sulfate, calcium chloride, calcium nitrate, potassium chloride, potassium sulfate, and potassium nitrate. The concentration of the salt is 15-50 wt% of the total mass of industrial waste sulfuric acid and waste stone powder in the original reaction solution. Step 2: Add water and industrial waste sulfuric acid to an atmospheric pressure reactor and stir with the mixed slurry from Step 1; control the temperature in the atmospheric pressure reactor at 40-80℃ and the reaction time at 30-90min to obtain a reaction stock solution with a pH of 5-7; Step 3: Heat the atmospheric pressure reactor to 90-110℃ and react for 30-240 minutes under atmospheric pressure to obtain building gypsum slurry; Step 4: The prepared building gypsum slurry is subjected to solid-liquid separation, water washing and drying to finally obtain building gypsum crystals, which are then packaged and stored; the crystal diameter of the building gypsum is 10μm-30μm and the aspect ratio is 10:1-1:

1.

2. The method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder according to claim 1, characterized in that, In step 2, the stirring speed is 300rpm-3000rpm.

3. The method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder according to claim 1, characterized in that, In step 4, the solid-liquid separation method is any one of centrifugal separation, gravity sedimentation, or plate and frame filtration.

4. The method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder according to claim 1, characterized in that, In step 4, the water washing temperature is 95-100℃.

5. The method for directly preparing building gypsum from industrial waste sulfuric acid and waste stone powder according to claim 1, characterized in that, In step 4, the drying method is any one of spray drying, flash drying, or centrifugal airflow drying; the inlet temperature of the drying method is 105℃-150℃, and the outlet temperature of the drying method is 95℃-105℃.

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