Gypsum and its preparation method and application

Abstract

Gypsum, its preparation method, and application, belonging to the technical field of gypsum materials. The gypsum comprises the following components: 55-65 parts of desulfurized gypsum, 29.2-38.4 parts of limestone powder, 1-3 parts of silica fume, 1-3 parts of calcium chloride, and 1.2-3.8 parts of a composite water reducer. The composite water reducer is composed of calcium ligninsulfonate, sodium aminosulfonate, and polyethylene glycol monomethyl ether in a weight ratio of 1-3:0.1-0.5:0.1-0.3. The preparation steps are: 1) mixing the calcium ligninsulfonate, sodium aminosulfonate, and polyethylene glycol monomethyl ether to obtain the composite water reducer; 2) mixing the limestone powder, silica fume, calcium chloride, and composite water reducer to obtain component A; 3) dehydrating the desulfurized gypsum and then mixing it with component A in a mixer to obtain the gypsum. The gypsum of the invention can be applied to ordinary Portland cement and composite Portland cement, and can solve the problems of high water demand, slow early strength development and poor anti-seepage performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of gypsum materials, and in particular relates to gypsum and a preparation method and application thereof. Background Art

[0002] Desulfurization gypsum, a major byproduct of flue gas desulfurization in coal-fired power plants, consists of calcium sulfate dihydrate. Due to its similar chemical properties to natural gypsum, it has become a key research area in the resource utilization of industrial solid waste. It can replace natural gypsum as a cement retarder, effectively reducing production costs, significantly alleviating the environmental pressures caused by industrial solid waste accumulation, and promoting the development of a circular economy.

[0003] However, desulfurized gypsum still faces numerous challenges in practical application. It has a high moisture content upon shipment, which increases transportation costs and causes caking during storage and transportation, hindering subsequent use. While traditional rotary kiln drying can reduce the moisture content to below 8%, it consumes a staggering 40-50 kW·h / t of energy and generates significant dust pollution. Natural airing, limited by climate and site conditions, requires a long dehydration cycle of 5-7 days, making it inadequate for continuous production.

[0004] Existing technologies mostly focus on physical dehydration, but pay insufficient attention to the problem that desulfurized gypsum has high viscosity and poor fluidity, and its direct addition can easily cause ball sticking in the grinding system and blockage of conveying equipment. At the same time, existing formulas cannot solve the problems of high water demand, slow early strength development and poor impermeability of ordinary Portland cement and composite Portland cement. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a gypsum and a preparation method and application thereof, wherein the gypsum can be applied to ordinary Portland cement and composite Portland cement and can solve the problems of high water demand, slow early strength development and poor impermeability.

[0006] In order to achieve the above object, the present invention provides a gypsum comprising the following components, measured in parts by weight: 55-65 parts of desulfurized gypsum, 29.2-38.4 parts of limestone powder, 1-3 parts of silica fume, 1-3 parts of calcium chloride, and 1.2-3.8 parts of a composite water reducer; the composite water reducer comprises calcium lignin sulfonate, sodium aminosulfonate, and polyethylene glycol monomethyl ether; and the weight ratio of calcium lignin sulfonate, sodium aminosulfonate, and polyethylene glycol monomethyl ether in the composite water reducer is 1-3:0.1-0.5:0.1-0.3.

[0007] The retarding properties of calcium ligninsulfonate combined with the strong dispersibility of polycarboxylic acid can reduce the risk of bleeding while maintaining slurry stability. Sodium aminosulfonate compensates for the fluidity loss of both at high dosages. By optimizing the ratio of the three and designing functional molecules, the three synergistically address the high water demand, slow early strength development, and insufficient impermeability of desulfurized gypsum-limestone-based materials. Calcium ligninsulfonate primarily controls retarding and basic water reduction, sodium aminosulfonate enhances dispersion efficiency, and polyethylene glycol monomethyl ether improves the microstructure through physical barriers. These three act on the hydration process, dispersion stability, and porosity control, respectively, forming a multi-dimensional regulation mechanism. The efficient water reduction of sodium aminosulfonate and the pore-filling effect of polyethylene glycol monomethyl ether synergize to reduce water demand, while the retarding effect of calcium ligninsulfonate prevents a rebound in water demand due to excessive hydration. Polyethylene glycol monomethyl ether reduces porosity, sodium sulfamate accelerates nucleation of hydration products, and calcium lignin sulfonate ensures a dense structure. The densification effect of polyethylene glycol monomethyl ether and the dispersion effect of sodium sulfamate synergize to improve impermeability. Calcium lignin sulfonate inhibits the growth of microcracks, further ensuring impermeability.

[0008] Calcium lignin sulfonate forms a double electrical layer by adsorbing on the surface of cement particles, reducing the van der Waals forces between particles, improving slurry fluidity, and delaying the rapid heat release during the initial hydration phase, thus avoiding the risk of early cracking and indirectly improving early structural density. The sulfonic acid and amino groups of sodium aminosulfonate synergistically enhance the dispersibility of cement particles, reducing the water-cement ratio and extending the fluidity of the slurry by inhibiting the agglomeration of hydration products. The long hydrophilic side chains of polyethylene glycol monomethyl ether form a three-dimensional barrier by adsorbing on the surface of cementitious particles, reducing the tendency of desulfurized gypsum and limestone powder to agglomerate and improving slurry fluidity. The steric hindrance effect allows for efficient dispersion, reduces porosity, and promotes early strength development.

[0009] Adding too much calcium lignin sulfonate intensifies the retarding effect, prolonging the initial setting time of concrete, affecting the construction process and hindering early strength development in environments below 12°C. Adding too little calcium lignin sulfonate reduces concrete workability, increases slump loss, and requires additional water to maintain fluidity, resulting in reduced early strength.

[0010] Adding too much sodium sulfamate can lead to excessive chloride ion content, increasing the risk of steel corrosion. Excessive water reduction can cause bleeding and segregation, reducing concrete homogeneity. Adding too little sodium sulfamate reduces water reduction efficiency, failing to effectively lower the water-cement ratio and resulting in lower 28-day compressive strength. It also fails to suppress the early hydration heat peak of cement, increasing the risk of volumetric concrete cracking. Sodium sulfamate synergizes with calcium chloride to accelerate calcium ion release, promoting nucleation of hydration products, shortening setting time and enhancing early strength.

[0011] Adding too much polyethylene glycol monomethyl ether results in an overly dense molecular structure, leading to an overly strong steric hindrance effect, causing a sudden increase in slurry viscosity and increased pumping resistance. Adding too little polyethylene glycol monomethyl ether fails to effectively control the pore structure, resulting in a decrease in impermeability.

[0012] Limestone powder and desulfurized gypsum together form the cementitious framework, calcium chloride and silica fume enhance early performance, and a composite water reducer balances rheological properties and strength development. The synergistic effect of the various ingredients in this application's formula creates a highly effective composite system, enabling the application of desulfurized gypsum in cement while addressing issues such as high water demand, slow early strength development, and insufficient impermeability. The gypsum in this application has an impermeability of ≥ P14.

[0013] The main component of desulfurized gypsum is calcium sulfate dihydrate. After calcination, desulfurized gypsum is converted into hemihydrate gypsum. Desulfurized gypsum increases sulfur trioxide and generates calcium aluminate during the hydration reaction. It compensates for shrinkage through the expansion effect and improves early strength. In addition, desulfurized gypsum can also adjust the setting time and balance the hardening process of the cement system.

[0014] As a base material, limestone powder has a dual function: it neutralizes free moisture in desulfurized gypsum, reducing system porosity and increasing density; it also reacts with aluminum-phase minerals to form carbon aluminates, enhancing the cement's later strength and impermeability. Its microcrystalline effect also refines the structure of the hydration product and optimizes its mechanical properties.

[0015] The mass ratio of calcium chloride to silica fume is 0.8-1.2:1. The silica fume and calcium chloride, synergistically with the nucleation effect of silica fume nanoparticles and the calcium chloride's accelerated setting, accelerate CSH gel formation, addressing the problem of insufficient early strength. Furthermore, the alkali-aggregate reaction is inhibited, reducing microcrack propagation and synergistically improving impermeability. The ultrafine amorphous silica in the silica fume fills the gaps between cement particles, while calcium chloride, acting as an early strength agent, accelerates the hydration rate of tricalcium silicate and tricalcium aluminate, shortening the setting time and improving early strength and hardening speed.

[0016] According to another aspect of the present invention, there is also provided a method for preparing the above-mentioned gypsum, comprising the following steps:

[0017] (1) Calcium lignin sulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether are mixed to obtain a composite water reducing agent;

[0018] (2) Mix limestone powder, silica fume, calcium chloride and composite water reducer to obtain component A;

[0019] (3) Desulfurized gypsum is first dehydrated and then mixed with component A in a mixer to obtain gypsum.

[0020] In step (1), calcium lignin sulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether are preferentially mixed to form a composite water reducer, mainly for the following reasons:

[0021] Calcium chloride and calcium lignosulfonate have potential synergistic and antagonistic effects. The calcium ions produced by the dissolution of calcium chloride accelerate the hydration reaction of tricalcium silicate and promote early strength development. However, excessive calcium ion concentrations can easily chelate with water reducer molecules, especially calcium lignosulfonate and sodium aminosulfonate, causing the water reducer to fail. Therefore, it is crucial to pre-mix calcium lignosulfonate, sodium aminosulfonate, and polyethylene glycol monomethyl ether to form a composite water reducer. The sulfonic acid group of sodium aminosulfonate can preferentially bind to some calcium ions to form a stable sulfonic acid-calcium chelate, reducing the risk of excessive chelation during subsequent contact with calcium chloride. At the same time, sodium aminosulfonate itself has the effect of delaying the hydration of tricalcium aluminate, while calcium chloride accelerates hydration, ultimately forming a staged hydration regulation effect that balances early strength development and setting time.

[0022] In step (1), calcium lignin sulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether are preferentially mixed to form a composite water reducer, which optimizes the efficiency of the composite water reducer and the reaction sequence of the materials, and ultimately achieves the comprehensive effects of low water content, reasonable sulfur distribution and high early strength.

[0023] The phased mixing design of step (2) and step (3) is mainly based on the following functional synergy and process stability requirements:

[0024] Prevent premature activation of desulfurized gypsum hydration: Limestone powder and silica fume have high surface activity and should be combined with a composite water reducer first. The dispersion and coating effects of the water reducer reduce friction between particles, forming a stable suspension system and providing fluidity for subsequent mixing with desulfurized gypsum. Desulfurized gypsum rapidly dissolves and releases calcium ions upon contact with water. If directly mixed with a water reducer and calcium chloride, its hydration reaction can initiate prematurely, resulting in a rapid loss of slurry fluidity and affecting the homogeneity of the final product.

[0025] Controlling calcium ion release and water-reducing agent synergy: Calcium ions generated by the dissolution of calcium chloride accelerate the hydration reaction. Direct mixing with desulfurized gypsum can lead to localized hydration heat concentration. Preliminary combination with sodium aminosulfonate in the composite water-reducing agent in step (2) can form a stable sulfonic acid-calcium chelate, balancing the accelerating and retarding effects of setting. Calcium lignin sulfonate preferentially adsorbs on the surface of limestone powder, slowing the calcium ion release rate through hydroxyl and sulfonic acid groups, thus avoiding the instantaneous hydration peak caused by direct contact with desulfurized gypsum.

[0026] Optimizing microstructure and interface bonding: The silica fume in step (2) is preferentially dispersed in the gaps between the limestone powder and is evenly distributed through the steric hindrance effect of the water reducer. When subsequently mixed with desulfurized gypsum, a gradient pore structure is formed, improving early strength. The long side chains of polyethylene glycol monomethyl ether must first be adsorbed on the limestone powder in a low-calcium environment to form a directional steric hindrance layer, preventing the side chains from curling up and failing due to high calcium concentration after the desulfurized gypsum is introduced.

[0027] Through the staged mixing process of step (2) and step (3), the fluidity, early strength and microstructure of the desulfurized gypsum-based material are optimized, while the risk of water-reducing agent failure in a high-calcium system is avoided.

[0028] The desulfurized gypsum described in step (3) is dehydrated in a dehydration device before being mixed with component A. The dehydration device includes three walls and a drain plate. The three walls are vertically arranged to form a space with an opening for placing the desulfurized gypsum. The drain plate is horizontally arranged on the lower side of the space and is connected to the three walls respectively. The lower side of the drain plate forms a drainage space on the three walls. A guide groove is provided on the drain plate, and a through hole is provided on the lower side of the guide groove. The guide groove is connected to the through hole, and the through hole is connected to the drainage space to form a complete drainage channel. The dehydration plant consists of 5 to 6 dehydration devices. The three walls of the dehydration device are 3m high concrete solid walls. The drain plate of the dehydration device is provided with a guide groove and a through hole. The through hole is at the bottom of the guide groove and is connected to the drainage space below. The through hole is Φ12mm, the size of the drainage space is 220mm×220mm, and the guide groove is a V-shaped guide groove.

[0029] When the desulfurized gypsum fills the dehydration device, it is repeatedly rolled over by a loader or vehicle. After the desulfurized gypsum is compacted, the water is separated under the action of its own weight and pressure. The water flows into the diversion groove and is discharged into the drainage space through the through hole, thus achieving solid-liquid separation. The moisture content of the desulfurized gypsum is 17% to 22% when it enters the factory. The dehydration described in step (3) uses extrusion dehydration to reduce the moisture content of the desulfurized gypsum to 10% to 12%. The dehydration cycle of a single dehydration device in this method is 2 to 3 days, which is much more efficient than the traditional drying method. By rotating 5 to 6 dehydration devices, continuous production is achieved. The material's own weight and mechanical energy are used for synergistic dehydration, which is more energy-efficient than hot air drying and has the dual advantages of high efficiency and energy saving.

[0030] In step (3), the desulfurized gypsum is first dehydrated, and then the desulfurized gypsum hopper is unloaded and measured by a belt scale. The measured desulfurized gypsum is directly transported to the mixer discharge port by a belt conveyor; the belt scale is equipped with a 1.2m wide belt, and the desulfurized gypsum hopper discharge port is widened to 0.8m.

[0031] The desulfurization gypsum hopper described in step (3) is provided with a desulfurization gypsum hopper vibrator on the outside and a vibrating rod on the inside. A limit switch is provided on the outside of the desulfurization gypsum hopper, and both ends of the trigger arm are connected to the limit switch and the belt respectively. When there is desulfurization gypsum on the belt of the belt scale, the trigger arm contacts the desulfurization gypsum; when there is no desulfurization gypsum on the belt of the belt scale, the trigger arm contacts the belt, the trigger arm falls, and the limit switch triggers the vibrating rod and the desulfurization gypsum hopper vibrator to work simultaneously, thereby making up for the limitations of a single vibration mode.

[0032] During the desulfurization gypsum batching process, in order to solve the problem of poor discharge of high-humidity materials, a combination of desulfurization gypsum hopper discharge and belt scale measurement is adopted. The belt scale is equipped with a 1.2m wide belt, and the desulfurization gypsum hopper discharge port is widened to 0.8m to ensure smooth discharge of high-humidity desulfurization gypsum. The measured materials are directly transported to the mixer discharge port by the belt conveyor.

[0033] The original width of the desulfurized gypsum discharge port was 0.5-0.6m, but this application has increased it to 0.8m to reduce the risk of clogging with high-moisture materials. The wide belt also reduces the risk of clogging with high-moisture desulfurized gypsum at the discharge port by expanding the material flow cross-section, ensuring stable gravity-driven discharge. A dual vibration anti-clogging device is designed to address the propensity of desulfurized gypsum to cling to the silo wall and bulge. High-frequency vibration dislodges material adhering to the silo wall. A vibrating rod within the desulfurized gypsum hopper acts directly on accumulated material to break up internal bulges. Furthermore, a limit switch monitors material flow in real time. A trigger arm on the limit switch engages the material when there is material on the belt and drops when there is no material. Upon detecting a material discharge anomaly, the limit switch automatically triggers the vibrating rod and the desulfurized gypsum hopper vibrator to operate simultaneously. These two devices work together to simultaneously address both material clinging to the silo wall and bulges, addressing the limitations of a single vibration method.

[0034] The desulfurization gypsum hopper adopts the desulfurization gypsum discharge port widening and dual vibration coordinated control technology. Through physical structure optimization and intelligent linkage control, it solves the problems of high-humidity material blockage and warehouse bloating, and ensures stable material supply in the batching process.

[0035] Limestone powder is stored in a steel silo and accurately measured by a rotor scale at the bottom. It is then conveyed via an air chute to an elevator and ultimately transferred to the mixer's discharge port. Silica fume, composite water reducer, and calcium chloride are metered by a pneumatic conveying pump and then injected into the limestone powder's air chute. After mixing with the limestone powder, they are lifted and conveyed by an elevator to the mixer's discharge port, achieving coordinated multi-material conveying and efficient batching.

[0036] The mixer in step (3) comprises three interconnected parts, namely, a mixing part, a dispersing part, and a discharging part, from top to bottom. The volume of the mixing part is smaller than that of the dispersing part, so that the relatively rotating reamer can fully mix the materials within a limited space, and avoid uneven mixing caused by excessive space. The space of the mixing part needs to be designed to be smaller so that the reamer can fully mix the materials; if the space is too large, the reamer will not be able to function effectively.

[0037] The mixer offers the following advantages: First, it incorporates a three-stage mixing structure. In addition to the mixing section, the dispersing and discharging sections also have mixing functions. Through multi-dimensional agitation and material movement, uniform mixing is achieved throughout the entire process. Second, dispersing, dehydration, and dust removal are integrated. The dispersing section is equipped with a dispersing disc and a hot air system. Mechanical dispersing and heat exchange synergize to efficiently remove moisture from the material, and a dust collector effectively controls dust. Third, a vibrator is installed on the outside of the discharging hopper, using intermittent vibration to ensure smooth discharging. Combined with a bracket spring damper and flexible connection design, this optimizes vibration transmission efficiency and ensures continuous and stable material output.

[0038] The mixing part consists of a mixing shell and two relatively rotating reamers. Under the action of gravity, the material passes through the two relatively rotating reamers from top to bottom for sufficient mixing; the two reamers adopt a relative rotation design to form a countercurrent shearing effect, and the centrifugal force generated by high-speed rotation and the collision force generated by reverse motion greatly increase the contact frequency between materials; when the material flows from top to bottom under the action of gravity, it is affected by the spiral propulsion and reverse throwing of the reamers, forming a multi-dimensional motion trajectory in the longitudinal, transverse and radial directions, breaking the planar mixing limitations of traditional single-axis stirring and realizing all-round uniform distribution of material particles; the material falls naturally under the action of gravity, and the reamers only need to provide auxiliary shear force to complete the mixing, which reduces energy consumption compared to the traditional fully mechanical stirring mode.

[0039] The dispersing part is composed of a dispersing shell, two dispersing disks, an air inlet and a dust collector, and the dispersing disk is arranged in the dispersing shell. After the material is mixed in the mixing part, it is dispersed in the dispersing shell by the two dispersing disks. Part of the moisture comes into contact with the air during the dispersing process and is extracted by the dust collector, while the material is further mixed. The dust collector has the triple functions of dust removal, auxiliary dehydration and improving the mixing effect. It realizes efficient and clean production through the coordination of multiple systems. An air inlet is provided on the dispersing shell of the dispersing part, on which an electric heating wire is installed. The external air is heated to form hot air and enters the dispersing part to fully contact with the material. The hot air accelerates the evaporation of moisture, and the dust collector simultaneously extracts moisture and dust, and effectively removes moisture from the material.

[0040] The discharging section includes a hopper and a reamer conveyor, with a vibrator installed outside the hopper. This ensures uniform material discharge. The discharging section also includes a flexible connection, a bracket, and a spring damper on the bracket. The spring damper on the bracket and the flexible connection optimize vibration transmission efficiency. The reamer conveyor facilitates material transport and further mixing, ensuring uniform and fully mixed discharging.

[0041] According to another aspect of the present invention, there is also provided the use of the above-mentioned gypsum or the gypsum prepared according to the above-mentioned method in ordinary Portland cement and composite Portland cement. Ordinary Portland cement is designated PO in GB 175-2023, in which clinker and gypsum account for 80-94% of the total components; composite Portland cement is designated PC in GB 175-2023, in which clinker and gypsum account for 50-79% of the total components.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. This application optimizes the ratio of calcium ligninsulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether in the composite water-reducing agent and the functionalized molecular design, and the three synergistically reduce the water demand to a minimum; sodium aminosulfonate accelerates the nucleation of hydration products, polyethylene glycol densifies the pores, and lignin inhibits microcracks to improve the impermeability; through the regulation of the hydration process, dispersion stability and microstructure optimization, the three synergistically improve the early performance. The synergistic effect of calcium chloride and silica fume can enhance the early strength and improve the impermeability. The synergistic effect of various ingredients in the formula of this application forms a high-efficiency composite system. The gypsum of the present invention can be applied to ordinary Portland cement and composite Portland cement, and can solve the problems of high water demand, slow early strength development and poor impermeability of ordinary Portland cement and composite Portland cement.

[0044] 2. This application effectively solves the problems of high humidity and viscosity of desulfurized gypsum, uneven mixing, dust pollution, long dehydration cycle and high dehydration energy consumption by squeezing dehydration, increasing the width of the desulfurized gypsum hopper outlet, and combining the mixing and dehydration integrated function of the mixer. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a diagram of the dehydration device.

[0046] Figure 2 for Figure 1 A partial enlarged view of point A in the middle.

[0047] Figure 3 This is a top view of the dehydration device.

[0048] Figure 4 This is the front view of the desulfurization gypsum hopper.

[0049] Figure 5 This is a side view of the desulfurization gypsum hopper.

[0050] Figure 6 This is a diagram of a mixer.

[0051] Figure 7 A top view of the mixer.

[0052] Figure 8This is the process flow chart of gypsum production.

[0053] Among them: 1. Wall; 2. Leakage plate; 3. Diversion trough; 4. Through hole; 5. Drainage space; 6. Desulfurization gypsum hopper vibrator; 7. Vibrating rod; 8. Desulfurization gypsum hopper discharge port; 9. Limit switch; 10. Trigger arm; 11. Belt; 12. Mixing shell; 13. Reamer; 14. Scattering shell; 15. Scattering plate; 16. Air inlet; 17. Dust collector; 18. Receiving hopper; 19. Reamer conveyor; 20. Receiving hopper vibrator; 21. Flexible connection; 22. Bracket; 23. Spring shock absorber; 24. Desulfurization gypsum shed; 25. Product shed; 26. Silica fume; 27. Composite water reducer; 28. Calcium chloride; 29. ​​Steel silo. DETAILED DESCRIPTION

[0054] Figures 1 to 8 The best embodiment of the present invention is shown below in conjunction with the attached Figures 1 to 8 The present invention is further described.

[0055] Reference Figures 1-3 The dehydration device consists of three vertical walls 1 and drain panels 2. The three walls 1 are 3m tall concrete walls, forming a space for the desulfurized gypsum. These walls 1 are 3m tall, ensuring the device's structural strength and stability. The drain panels 2 are horizontally positioned below the desulfurized gypsum space and are connected to each of the three walls 1. Drainage spaces 5 are formed below the three walls 1, measuring 220mm x 220mm.

[0056] A V-shaped diversion groove 3 is provided on the drain plate 2, facilitating rapid water collection and diversion. A through hole 4 is provided below the diversion groove 3, connecting the diversion groove 3 to the through hole 4, which in turn connects to the drainage space 5, forming a complete drainage channel. The through hole 4 is 12 mm in diameter, ensuring smooth drainage and preventing clogging by desulfurized gypsum particles.

[0057] When in use, the dehydration unit is filled with desulfurized gypsum. A loader or vehicle then repeatedly rolls over the compacted gypsum. The water in the compacted gypsum is quickly separated under its own weight and pressure. The water flows through holes 4 into diversion troughs 3 and is discharged through drainage space 5, achieving solid-liquid separation. The dehydration plant consists of five to six such dehydration units, which rotate in operation to achieve continuous production.

[0058] Reference Figures 4 and 5 The desulfurization gypsum hopper is equipped with a desulfurization gypsum hopper vibrator 6 on the outside and a vibrating rod 7 on the inside, which together form a dual vibration anti-blocking device. The desulfurization gypsum hopper vibrator 6 generates high-frequency vibrations; the vibrating rod 7 is vertically set in the center of the desulfurization gypsum hopper and can penetrate deep into the accumulated materials.

[0059] The desulfurized gypsum hopper is also equipped with a limit switch 9 on the outside, equipped with a trigger arm 10. The trigger arm 10 is L-shaped, with one end connected to the limit switch 9 and the other end maintaining a specific distance from the belt 11 of the belt scale. When desulfurized gypsum is present on the belt 11 of the belt scale, the trigger arm 10 contacts the surface of the desulfurized gypsum. When the belt 11 is empty, the trigger arm 10 loses its support and contacts the belt 11, falling down. At this point, the limit switch 9 triggers the desulfurized gypsum hopper vibrator 6 and vibrating rod 7 to activate simultaneously. The high-frequency vibration generated by the vibrator 6 acts on the hopper wall, causing any material adhering to the wall to fall off. The internal vibrating rod 7 also directly acts on the accumulated material through high-frequency vibration, effectively preventing the problem of bulging hoppers. The two work together to fully overcome the limitations of a single vibration method and ensure smooth desulfurized gypsum discharge.

[0060] Reference Figures 6 and 7 The mixer includes three interconnected parts, namely, a mixing part, a dispersing part and a discharging part from top to bottom; among them, the volume of the mixing part is smaller than that of the dispersing part. The purpose is to enable the relatively rotating reamer 13 to fully mix the materials within a limited space to avoid uneven mixing due to excessive space.

[0061] The mixing part consists of a mixing shell 12 and two relatively rotating reamers 13; the material passes through the two relatively rotating reamers 13 from top to bottom under the action of gravity. The two reamers 13 adopt a relative rotation design to form a countercurrent shearing effect. The high-speed rotation of the reamers 13 generates centrifugal force, and the reverse motion generates collision force, which greatly increases the contact frequency between the materials. When the material flows from top to bottom, the spiral propulsion and reverse throwing action of the reamers 13 form a multi-dimensional motion trajectory in the longitudinal, transverse and radial directions, breaking through the planar mixing limitations of traditional single-axis stirring and achieving all-round uniform distribution of material particles. In addition, the material falls naturally due to gravity, and the reamers 13 only need to provide auxiliary shear force to complete the mixing, which effectively reduces energy consumption compared to the traditional fully mechanical stirring mode.

[0062] The scattering part is composed of a scattering shell 14, two scattering discs 15, an air inlet 16 and a dust collector 17. The scattering disc 15 is arranged in the scattering shell 14. After the material is mixed in the mixing part, it enters the scattering part and is fully dispersed in the scattering shell 14 through the scattering effect of the two scattering discs 15. During the scattering process, part of the moisture comes into contact with the air and is extracted by the dust collector 17, while the material is further mixed. The dust collector 17 has the triple functions of dust removal, auxiliary dehydration and enhancing the mixing effect, and realizes efficient and clean production through the coordination of multiple systems. In addition, an air inlet 16 is provided on the scattering shell 14, and the air inlet 16 is equipped with an electric heating wire. The external air is heated to form hot air and enters the tank, fully contacts with the material, and efficiently removes moisture from the material.

[0063] The discharge section consists of a hopper 18 and a reamer conveyor 19. A hopper vibrator 20 is installed outside the hopper 18. The hopper vibrator 20 uses intermittent vibration to ensure uniform material discharge. The spring damper 23 on the bracket 22 and the flexible connection 21 optimize vibration transmission efficiency. While conveying the material, the reamer conveyor 19 further mixes it, ensuring uniform and fully mixed discharge, resulting in consistent and stable material discharge.

[0064] Reference Figure 8 , Figure 8 This is a gypsum production process flow chart. Desulfurized gypsum is stored in a desulfurized gypsum shed 24. The desulfurized gypsum is first dehydrated and then conveyed directly to the mixer discharge port by a belt conveyor using a combination of desulfurized gypsum hopper discharge and belt scale metering. Limestone powder is stored in a steel silo 29 and accurately metered by a rotor scale at the bottom of the steel silo 29. The metered limestone powder is conveyed through an air chute. Silica fume 26, composite water reducer 27, and calcium chloride 28 are metered separately by pneumatic conveying pumps and injected into the air chute for limestone powder transportation to mix with the limestone powder. The mixed materials are lifted and conveyed to the mixer discharge port by an elevator, realizing multi-material coordinated transportation and efficient batching. The finally prepared gypsum is stored in a product shed 25.

[0065] The above devices are used in this application.

[0066] Embodiment 1 is the best embodiment of the present invention. The present invention will be further described below with reference to specific embodiments and comparative examples.

[0067] The chemical additives used in the examples and comparative examples of the present invention are all commercially available, and their specific information is as follows:

[0068] Desulfurization gypsum: industrial grade, purchased from Huadian Laiwu Power Plant Co., Ltd.

[0069] Limestone powder: industrial grade, purchased from Zibo Baiyuanxiang Trading Co., Ltd.

[0070] Silica fume: industrial grade, purchased from Zibo Zi'an Trading Co., Ltd.

[0071] Calcium chloride: Calcium chloride is anhydrous calcium chloride, industrial grade, purchased from Zibo Zi'an Trading Co., Ltd.

[0072] Calcium lignin sulfonate: industrial grade, model, AR250G, purchased from Zibo Zi'an Trading Co., Ltd.

[0073] Sodium sulfamate: industrial grade, purchased from Zibo Zi'an Trading Co., Ltd.

[0074] Polyethylene glycol monomethyl ether: industrial grade, purchased from Zibo Zi'an Trading Co., Ltd.

[0075] Example 1

[0076] A gypsum comprising the following components: 60 parts of desulfurized gypsum, 31.5 parts of limestone powder, 2.5 parts of silica fume, 3 parts of calcium chloride, and 3 parts of a composite water reducer; the composite water reducer comprises 2.5 parts of calcium lignin sulfonate, 0.3 parts of sodium aminosulfonate, and 0.2 parts of polyethylene glycol monomethyl ether, respectively; and a mass ratio of calcium chloride to silica fume of 1.2:1.

[0077] The preparation method comprises the following steps:

[0078] (1) Calcium lignin sulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether are mixed to obtain a composite water reducing agent;

[0079] (2) Mix limestone powder, silica fume, calcium chloride and composite water reducer to obtain component A;

[0080] (3) The desulfurized gypsum is first dehydrated by extrusion in a dehydration device, and then mixed with component A in a mixer to obtain gypsum.

[0081] Example 2

[0082] A gypsum comprising the following components: 65 parts of desulfurized gypsum, 29.2 parts of limestone powder, 1 part of silica fume, 1 part of calcium chloride, and 3.8 parts of a composite water reducer; wherein the composite water reducer comprises 3 parts of calcium lignin sulfonate, 0.5 parts of sodium aminosulfonate, and 0.3 parts of polyethylene glycol monomethyl ether; and a mass ratio of calcium chloride to silica fume of 1:1.

[0083] The preparation method comprises the following steps:

[0084] (1) Calcium lignin sulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether are mixed to obtain a composite water reducing agent;

[0085] (2) Mix limestone powder, silica fume, calcium chloride and composite water reducer to obtain component A;

[0086] (3) The desulfurized gypsum is first dehydrated by extrusion in a dehydration device, and then mixed with component A in a mixer to obtain gypsum.

[0087] Example 3

[0088] A gypsum comprising the following components: 55 parts of desulfurized gypsum, 38.4 parts of limestone powder, 3 parts of silica fume, 2.4 parts of calcium chloride, and 1.2 parts of a composite water reducer; wherein the composite water reducer comprises 1 part of calcium lignin sulfonate, 0.1 part of sodium aminosulfonate, and 0.1 part of polyethylene glycol monomethyl ether, respectively; and a mass ratio of calcium chloride to silica fume of 0.8:1.

[0089] The preparation method comprises the following steps:

[0090] (1) Calcium lignin sulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether are mixed to obtain a composite water reducing agent;

[0091] (2) Mix limestone powder, silica fume, calcium chloride and composite water reducer to obtain component A;

[0092] (3) The desulfurized gypsum is first dehydrated by extrusion in a dehydration device, and then mixed with component A in a mixer to obtain gypsum.

[0093] Comparative Example 1

[0094] The preparation method of gypsum described in this comparative example is the same as that in Example 1, except that the water reducing agent in this comparative example is 3 parts of calcium lignin sulfonate.

[0095] Comparative Example 2

[0096] The preparation method of gypsum described in this comparative example is the same as that in Example 1, except that the water reducing agent in this comparative example is 3 parts of sodium aminosulfonate.

[0097] Comparative Example 3

[0098] The preparation method of gypsum described in this comparative example is the same as that in Example 1, except that the water reducing agent in this comparative example is 3 parts of polyethylene glycol monomethyl ether.

[0099] Comparative Example 4

[0100] The preparation method of the gypsum described in this comparative example is the same as that in Example 1, except that the composite water reducer in this comparative example is 2.6 parts of calcium lignin sulfonate and 0.4 parts of sodium aminosulfonate.

[0101] Comparative Example 5

[0102] The preparation method of the gypsum described in this comparative example is the same as that in Example 1, except that the composite water-reducing agent in this comparative example is 2.65 parts of calcium lignin sulfonate and 0.35 parts of polyethylene glycol monomethyl ether.

[0103] Comparative Example 6

[0104] The preparation method of the gypsum described in this comparative example is the same as that in Example 1, except that the composite water-reducing agent in this comparative example is 1.8 parts of sodium sulfamate and 1.2 parts of polyethylene glycol monomethyl ether.

[0105] Comparative Example 7

[0106] The preparation method of gypsum described in this comparative example is the same as that in Example 1, except that the amount of calcium chloride in this comparative example is 4 parts, and the mass ratio of calcium chloride to silica fume is 1.6:1.

[0107] Comparative Example 8

[0108] The preparation method of gypsum described in this comparative example is the same as that in Example 1, except that the amount of calcium chloride in this comparative example is 0.5 parts, and the mass ratio of calcium chloride to silica fume is 0.2:1.

[0109] Comparative Example 9

[0110] The contents of the components of the gypsum described in this comparative example are the same as those in Example 1, except that the preparation method includes the following steps:

[0111] (1) Calcium lignin sulfonate, sodium aminosulfonate, polyethylene glycol monomethyl ether, limestone powder, silica fume, calcium chloride and composite water reducer are mixed to obtain component A;

[0112] (2) Desulfurized gypsum is first dehydrated by extrusion, and then mixed with component A in a mixer to obtain gypsum.

[0113] Comparative Example 10

[0114] The contents of the components of the gypsum described in this comparative example are the same as those in Example 1, except that the preparation method includes the following steps:

[0115] (1) Calcium lignin sulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether are mixed to obtain a composite water reducing agent;

[0116] (2) Mix limestone powder, silica fume, calcium chloride, composite water reducer and dehydrated desulfurized gypsum in a mixer to obtain gypsum.

[0117] Comparative Example 11

[0118] The preparation method of gypsum described in this comparative example is the same as that in Example 1, except that the composite water reducer in this comparative example is 1 part; the calcium lignin sulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether in the composite water reducer are 0.45 parts, 0.1 parts and 0.45 parts respectively.

[0119] Comparative Example 12

[0120] The preparation method of gypsum described in this comparative example is the same as that in Example 1, except that the composite water reducer in this comparative example is 4 parts; the calcium lignin sulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether in the composite water reducer are 3.1 parts, 0.55 parts and 0.35 parts, respectively.

[0121] Performance Testing

[0122] The performance tests were conducted on the gypsum prepared in the examples and comparative examples and the cement formed by configuring the gypsum. The specific test results are shown in Tables 1 and 2.

[0123] The gypsum described in Examples 1-3 and Comparative Examples 1-12 was ground uniformly with clinker, fly ash, and mineral powder in ratios of 6 parts, 75 parts, 13 parts, and 8 parts, respectively, using a small test mill to produce cement samples for comparative experiments. A three-day strength enhancement blank sample was prepared with natural gypsum, clinker, fly ash, and mineral powder in ratios of 6 parts, 75 parts, 13 parts, and 8 parts, respectively.

[0124] The cement obtained from the test small mill was mixed with standard sand and water, with a water-cement ratio of 0.5 and a mass ratio of cement to standard sand of 1:3. After being evenly mixed, the mortar was taken out and placed in a grinding mold (40mm×40mm×180mm) for compaction, and then maintained in a constant temperature and humidity chamber at 25°C and 98% for 3 days for curing. Performance tests were carried out in accordance with the standard GB / T19671-2223.

[0125] The sulfur trioxide content of gypsum is tested with reference to GB / T23371-2024 "Industrial by-product gypsum used in cement".

[0126] The moisture content of gypsum is tested in accordance with GB / T5484-2024 "Chemical Analysis Methods for Gypsum".

[0127] The water requirement of cement formed by gypsum configuration is tested for performance in accordance with GB / T1346-2011 "Test methods for water consumption, setting time and stability of cement of standard consistency".

[0128] The setting time of cement formed by gypsum configuration is tested for performance in accordance with GB / T1346-2011 "Test methods for water consumption, setting time and stability of cement of standard consistency".

[0129] The compressive strength of the cement formed by gypsum configuration is tested in accordance with GB / T17671-2021 "Cement mortar strength test".

[0130] The anti-seepage performance of cement formed by gypsum configuration is tested with reference to GB / T23440-2024 "Test method for anti-seepage performance of cement".

[0131] Table 1 Performance test results of gypsum of embodiment and comparative example

[0132] .

[0133] Table 2 Performance test results of cement formed by gypsum configuration of Example and Comparative Example

[0134] .

[0135] The results in Table 1 show that when only a single water-reducing agent was used in Comparative Examples 1-3, a balance between water reduction rate and dispersion stability was not achieved. When any of the composite water-reducing agents in Comparative Examples 4-6 were missing, the performance results of Example 1 were not achieved. Calcium ligninsulfonate primarily controlled set retardation and basic water reduction, sodium sulfamate enhanced dispersion efficiency, and polyethylene glycol monomethyl ether improved the microstructure through a physical barrier. These three agents acted separately on the hydration process, dispersion stability, and porosity control, creating a multi-dimensional control mechanism. The high water-reduction efficiency of sodium sulfamate synergizes with the pore-filling effect of polyethylene glycol monomethyl ether to reduce water demand. The retarding effect of calcium ligninsulfonate prevented a rebound in water demand caused by excessive hydration. Polyethylene glycol monomethyl ether reduced porosity, sodium sulfamate accelerated the nucleation of hydration products, and calcium ligninsulfonate ensured a dense structure. The densification effect of polyethylene glycol monomethyl ether synergistically with the dispersion effect of sodium sulfamate improved impermeability. Calcium ligninsulfonate inhibited microcrack propagation, further ensuring impermeability. This composite water reducer achieves balanced optimization of water demand, early strength and impermeability through the functional complementarity and synergistic mechanism of its components.

[0136] From the results of Example 1 and Comparative Examples 7 and 8, it can be seen that the mass ratio of calcium chloride to silica fume affects the 3-day compressive strength and impermeability of gypsum. Microstructural defects are a common cause of decreased impermeability. Imbalance in proportion leads to decreased microstructural density. Under the conditions of an appropriate mass ratio of calcium chloride to silica fume, the nano-nucleation effect of silica fume and the accelerating coagulation effect of calcium chloride synergistically promote CSH gel formation, improving early strength and density. In Comparative Example 7, the mass ratio of calcium chloride to silica fume is too high. Too high a ratio will cause the hydration reaction rate to accelerate sharply, induce structural defects, shorten the setting time, loosen the crystal structure of ettringite, reduce the compressive strength, and reduce the impermeability. In Comparative Example 8, the mass ratio of calcium chloride to silica fume is too low, resulting in an increase in water demand and a decrease in impermeability.

[0137] Comparative Example 9 shows that mixing all components except desulfurized gypsum at once results in adsorption competition between the composite water reducer and silica fume and limestone powder, reducing the effective utilization of the water reducer and increasing fluidity loss. Comparative Example 10 shows that premature contact of desulfurized gypsum with the water reducer causes prehydration of the gypsum particle surface, increasing slurry consistency and porosity in the molded product. Comparative Examples 11 and 12 show that either excessive or insufficient addition of the composite water reducer results in increased water demand.

[0138] This application solves the problems of poor adaptability and low mixing uniformity of water reducers in desulfurized gypsum-based materials by compounding the functions of composite water reducers and optimizing the mixing sequence; solves the problems of poor adaptability, low mixing uniformity and difficult coagulation control of water reducers in desulfurized gypsum-based materials, and also effectively solves the problems of high humidity and viscosity of desulfurized gypsum, uneven mixing, dust pollution, long dehydration cycle and high dehydration energy consumption by extrusion dehydration and expanding the width of the desulfurized gypsum hopper outlet to 0.8m, in conjunction with the integrated mixing and dehydration function of the mixer.

[0139] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art can utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A gypsum, characterized in that: The preparation method comprises the following components in parts by weight: 55-65 parts of desulfurized gypsum, 29.2-38.4 parts of limestone powder, 1-3 parts of silica fume, 1-3 parts of calcium chloride, and 1.2-3.8 parts of a composite water reducer; the composite water reducer is composed of calcium lignin sulfonate, sodium aminosulfonate, and polyethylene glycol monomethyl ether in a weight ratio of 1-3:0.1-0.5:0.1-0.

3.

2. The gypsum according to claim 1, characterized in that: The mass ratio of the calcium chloride to the silica fume is 0.8-1.2:

1.

3. The method for preparing gypsum according to any one of claims 1 to 2, characterized in that: The following steps are involved: (1) Calcium lignin sulfonate, sodium aminosulfonate and polyethylene glycol monomethyl ether are mixed in a weight ratio to obtain a composite water reducing agent; (2) Mix limestone powder, silica fume, calcium chloride and composite water reducer in parts by weight to obtain component A; (3) Desulfurized gypsum is first dehydrated and then mixed with component A in a mixer to obtain gypsum.

4. The method for preparing gypsum according to claim 3, wherein: The dehydration in step (3) uses extrusion dehydration to reduce the moisture content of the desulfurized gypsum to 10-12%.

5. The method for preparing gypsum according to claim 3, wherein: The dehydration in step (3) adopts a dehydration device, which includes three walls (1) and a leaking plate (2). The three walls (1) are vertically arranged to form a space with an opening for placing desulfurized gypsum. The leaking plate (2) is horizontally arranged on the lower side of the space and is respectively connected to the three walls (1). The lower side of the leaking plate (2) forms a drainage space (5) on the three walls (1); a guide groove (3) is provided on the leaking plate (2), and a through hole (4) is provided on the lower side of the guide groove. The guide groove (3) is connected to the through hole (4), and the through hole (4) is connected to the drainage space (5).

6. The method for preparing gypsum according to claim 3, wherein: The mixer described in step (3) comprises a mixing part, a dispersing part and a discharging part from top to bottom, and the three parts are connected; the volume of the mixing part is smaller than that of the dispersing part.

7. Use of the gypsum according to any one of claims 1 to 2 or the gypsum prepared by the method according to any one of claims 3 to 6, characterized in that: Application in the fields of ordinary Portland cement and composite Portland cement.

Images