Unfired ceramsite and preparation method thereof

Abstract

The present invention discloses an unfired ceramsite and a preparation method thereof, belonging to the field of building materials technology. The unfired ceramsite comprises the following raw materials in parts by weight: 20-50 parts of limestone powder, 50-80 parts of industrial by-product gypsum, 0.1-0.4 parts of gypsum retarder, 0.5-1.75 parts of acid, and 25-35 parts of water. The preparation method is as follows: S1: evenly mix the limestone powder, industrial by-product gypsum, and gypsum retarder to obtain a mixed powder; S2: add acid to water and mix evenly to obtain an acid solution; S3: add the acid solution to the mixed powder, mix well, and then granulate to obtain spherical particles; S4: cure the spherical particles for 1 day; S5: dry the cured spherical particles to obtain the product. The method can synergistically solve the problem of low utilization rate of limestone powder and industrial by-product gypsum, realize the reuse of solid waste resources, innovate resource utilization methods, and increase the added value of resources.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to unfired ceramsite and a preparation method thereof. Background Art

[0002] Limestone powder, phosphogypsum, desulfurized gypsum, and titanium gypsum are all industrial byproducts. Limestone powder comes from the production of limestone crushed stone and manufactured sand. Its main component is CaCO3, and its particle size is less than 75μm, which does not meet the standards for construction crushed stone and sand, and is therefore considered an industrial waste. Phosphogypsum is produced in the acid-based phosphorus production process and refers to the solid waste residue generated when calcium raw materials are used to treat acidic wastewater in phosphoric acid production. Desulfurized gypsum is primarily a byproduct of wet flue gas desulfurization in power plants. Titanium gypsum is a waste residue composed primarily of dihydrate gypsum, produced when lime (or carbide slag) is added to neutralize large amounts of acidic wastewater during the sulfuric acid process for titanium dioxide production. These three types of gypsum are the three largest types of industrial byproduct gypsum produced and stockpiled in my country. In addition, my country also produces citric acid gypsum, fluorinated gypsum, copper gypsum, salt gypsum, and monosodium glutamate gypsum.

[0003] Unfired ceramsite is a lightweight porous material that does not require calcination and hardens and generates strength through the gelling properties of the raw materials themselves. In the existing technology, cement is often used as the main gelling material, and some additives are used in combination to prepare unfired ceramsite. Its production process is relatively complicated and energy consumption is high. It also has the disadvantages of a long maintenance period and high cost. On the one hand, hemihydrate gypsum has high gelling properties and can replace cement to prepare unfired ceramsite; on the other hand, a large number of different types of industrial by-product gypsum are produced and stored as solid waste, which not only wastes a lot of resources, but also poses a serious threat to the environment. For this reason, it is necessary to propose a solution that can reasonably utilize the existing industrial by-product gypsum on a large scale and produce positive economic and social benefits. Summary of the Invention

[0004] In response to the above-mentioned existing technologies, the present invention provides a fire-free ceramsite and a preparation method thereof, which has the advantages of a simple preparation method and can absorb a large amount of solid waste residue. It can synergistically solve the problem of low utilization rate of limestone powder and industrial by-product gypsum, realize the recycling of solid waste resources, innovate resource utilization methods, and increase the added value of resources.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: providing an unfired ceramsite, comprising the following raw materials in parts by mass: 20 to 50 parts of limestone powder, 50 to 80 parts of industrial by-product gypsum, 0.1 to 0.4 parts of gypsum retarder, 0.5 to 1.75 parts of acid and 25 to 35 parts of water.

[0006] The beneficial effects of the above-mentioned technical solution of the present invention are as follows: the main components of industrial by-product gypsum are anhydrous gypsum, hemihydrate gypsum, or dihydrate gypsum, of which anhydrous gypsum and hemihydrate gypsum have gelling properties, and dihydrate gypsum can be calcined at a temperature of approximately 160°C to form hemihydrate gypsum with gelling properties. Limestone powder, phosphogypsum, desulfurized gypsum, titanium gypsum, etc. are all industrial by-products. Based on the characteristics of industrial by-product gypsum and limestone powder, they can be prepared into unfired ceramsite, which can achieve the reuse of solid waste resources, innovate resource utilization methods, and increase resource added value. Limestone powder can react with acid to produce CO2 gas, which can act as a pore-forming agent in the ceramsite preparation process; gypsum is used as a gelling material to harden the ceramsite. If the limestone powder content is too high, the gypsum content is low, the gelling properties are weak, and the ceramsite strength is low. If the gypsum content is too high, the limestone powder content is too low, the amount of pores generated is small, and the hardening is too rapid, making porous ceramsite impossible to obtain. If the water content is too low, the raw materials will be too dry after mixing and harden too quickly, preventing pelletization. If the water content is too high, the slurry will be too fluid, also preventing pelletization. Gypsum hardens quickly, requiring the addition of a retarder to slow down the setting process and allow sufficient time for the chemical reaction between the acid and limestone powder to form sufficient pores. The acid reacts with the limestone powder to produce CO2, which creates pores. If the acid content is too low, the CO2 generated is too low, making it difficult to form lightweight, porous ceramsite. If the acid content is too high, the CO2 is released violently, which can cause the ceramsite to crack.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows.

[0008] Furthermore, the following raw materials are included in parts by mass: 35 parts of limestone powder, 65 parts of industrial by-product gypsum, 0.195 parts of gypsum retarder, 0.9 parts of acid and 30 parts of water.

[0009] The beneficial effects of the above-mentioned further technical solution adopted by the present invention are as follows: gypsum is used as a cementitious material to harden the ceramsite; limestone powder reacts with acid to generate CO2, which plays a pore-forming role; the proportions of limestone powder, industrial by-product gypsum, gypsum retarder, acid and water are appropriate, and unfired ceramsite with appropriate particle size, high strength, light weight and porosity can be prepared.

[0010] Furthermore, the specific surface area of ​​limestone powder is ≥300m 2 / kg, of which the carbonate content is ≥80%.

[0011] The beneficial effects of the above-mentioned further technical solution adopted in the present invention are: the large specific surface area can increase the contact area between the limestone powder and the acid, and the carbonate content directly determines the amount of reaction between the limestone powder and the acid, ultimately ensuring that the limestone powder can react with the acid to produce sufficient CO2 gas, and fully exerting the pore-forming effect of the reaction between the limestone powder and the acid.

[0012] Furthermore, the industrial by-product gypsum is calcined phosphogypsum, desulfurized gypsum or titanium gypsum.

[0013] The beneficial effect of the above-mentioned further technical solution adopted in the present invention is that phosphogypsum, desulfurized gypsum and titanium gypsum are the three types of industrial by-product gypsums with the largest production and stockpiling in my country. These three types of gypsums are used as raw materials, and their reserves are sufficient and easy to obtain. Converting these three types of industrial by-product gypsums with the largest production and stockpiling into building materials can dispose of a large amount of solid waste, realize the reuse of solid waste resources, increase the added value of resources, and solve the environmental resource problems caused by large-scale stockpiling.

[0014] Furthermore, the content of hemihydrate gypsum in the industrial by-product gypsum is ≥85%.

[0015] The beneficial effect of the above-mentioned further technical solution adopted by the present invention is that the unfired ceramsite is a lightweight porous material that does not require calcination and is hardened and generates strength through the gelling property of the raw material itself. The semi-hydrated gypsum in the industrial by-product gypsum has gelling properties. The content of the semi-hydrated gypsum in the raw material is limited to ≥85% in order to exert its good gelling effect in the preparation process of the ceramsite.

[0016] Furthermore, the gypsum retarder is a protein gypsum retarder, sodium citrate or potassium citrate.

[0017] The beneficial effects of the present invention's further technical solution are as follows: sodium citrate and potassium citrate can complex calcium ions, hindering the dissolution of gypsum, reducing liquid supersaturation, and slowing the rate of crystal nucleation during the hydration induction phase of gypsum, thereby achieving a retarding effect. The protein-based gypsum retarder forms a colloid upon dissolution in water, adsorbing onto the gypsum surface to form a colloid film that hinders further growth of gypsum crystals. Furthermore, due to the adsorption and protective effects of the protein colloid, the crystal morphology remains unchanged, minimally impacting the gypsum's strength. The retarding time of the protein-based gypsum retarder exhibits a good linear relationship with the amount of retarder added, making it easy to use.

[0018] Furthermore, the acid is hydrochloric acid with a concentration of 1 to 5 wt % or formic acid with a concentration of 50 to 90 wt %.

[0019] The present invention employs the above-mentioned further technical solution, which has the beneficial effect of producing CO2 through the reaction of acid with limestone powder, thereby generating pores. By using hydrochloric acid at a concentration of 1-5 wt% or formic acid at a concentration of 50-90 wt%, the CO2 gas generation rate and amount are kept within an appropriate range, thereby controlling the formation of pores in the unfired ceramsite and ultimately producing a high-strength, lightweight, porous material.

[0020] Furthermore, the preparation method of the unfired ceramsite comprises the following steps:

[0021] S1: Weigh the raw materials of each component according to the mass ratio, mix the limestone powder, industrial by-product gypsum and gypsum retarder evenly to obtain a mixed powder;

[0022] S2: Add acid to water and mix well to obtain acid solution;

[0023] S3: adding acid solution to the mixed powder, mixing well and granulating to obtain spherical particles;

[0024] S4: Place the spherical particles in an environment with an air humidity of 50-70% and a temperature of 18-22°C for 1 day;

[0025] S5: The cured spherical particles are placed in an environment with a temperature of 40 to 50° C. for drying or natural drying.

[0026] The beneficial effects of the above-mentioned further technical solution of the present invention are: the curing time allows for full hydration of the gypsum and for the carbonate to react with the acid to fully form pores. The drying temperature is controlled at 40-50°C or natural drying is used because higher temperatures can cause the resulting dihydrate gypsum to decompose and the ceramsite to crack. The entire preparation process does not require stringent conditions, is simple and easy to operate, and consumes low energy, making it suitable for industrial production and widespread dissemination.

[0027] Furthermore, the granulation in S3 is carried out in a disc granulator. During the granulation process, the disc granulator has an inclination angle of 40 to 44 degrees and a rotation speed of 36 to 40 r / min.

[0028] Furthermore, the particle size of the spherical particles is 15 to 35 mm.

[0029] The beneficial effect of the above-mentioned further technical solution of the present invention is that the disc granulator squeezes and cuts the raw materials by rotating the disc to form particles, and the inclination angle and rotation speed are controlled to form spherical particles with appropriate particle size.

[0030] The beneficial effects of the present invention are as follows: the main components of industrial by-product gypsum are anhydrous gypsum, semi-hydrated gypsum or dihydrate gypsum. Anhydrous gypsum and semi-hydrated gypsum have gelling properties and can harden ceramsite; limestone powder can react with acid to produce CO2 gas, which acts as a pore-forming agent in the preparation process of ceramsite. Gypsum retarder can appropriately delay coagulation, provide sufficient time for the chemical reaction of calcium carbonate, and form enough pores. The process of collaboratively preparing unfired ceramsite using limestone powder and industrial by-product gypsum as raw materials does not have strict conditions, is simple and easy to operate, has low energy consumption, and is convenient for industrial production and large-scale promotion; using limestone powder and industrial by-product gypsum as the main raw materials, industrial waste is reused, solid waste resources are reused, resource utilization methods are innovated, and the added value of resources is increased. This plan for large-scale and rational utilization of existing industrial waste can produce positive economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 To avoid burning ceramsite cross-section picture;

[0032] Figure 2 To avoid burning ceramsite appearance picture. DETAILED DESCRIPTION

[0033] The specific implementation methods of the present invention are described in detail below with reference to the embodiments.

[0034] Example 1:

[0035] A fire-free ceramsite, comprising the following raw materials in parts by weight:

[0036] 35 parts of limestone powder, 65 parts of calcined phosphogypsum, 30 parts of water, 0.195 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 0.9 parts of formic acid with a concentration of 70wt%; wherein the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0037] The preparation method of the unburned ceramsite in the present embodiment is:

[0038] S1: Weigh the raw materials of each component according to the above mass ratio, mix the limestone powder, industrial by-product gypsum and gypsum retarder evenly to obtain a mixed powder;

[0039] S2: Add acid to water and mix well to obtain acid solution;

[0040] S3: Apply a layer of machine oil evenly on the inner wall of the disc of the disc granulator to prevent material adhesion; pour the mixed powder into the disc granulator, slowly add acid, control the inclination angle of the disc granulator to 42°, and the speed to 38r / min to form spherical particles of about 20mm;

[0041] S4: The spherical particles were placed in an environment with an air humidity of 60% and a temperature of 20°C for 1 day;

[0042] S5: Dry the cured spherical particles naturally to obtain the product.

[0043] The cross section of the unfired ceramsite obtained by this formula and preparation method is as follows Figure 1 As shown, the appearance is Figure 2 As shown, its bulk density is 1200kg / m 3 , the cylinder pressure strength is 5.5MPa and the porosity is 52%.

[0044] Example 2:

[0045] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0046] 45 parts of limestone powder, 55 parts of calcined phosphogypsum, 30 parts of water, 0.165 parts of sodium citrate, 0.9 parts of formic acid with a concentration of 90wt%; wherein the specific surface area of ​​the limestone powder is about 350m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0047] The preparation method of the unburned ceramsite in the present embodiment is:

[0048] S1: Weigh the raw materials of each component according to the above mass ratio, mix the limestone powder, industrial by-product gypsum and gypsum retarder evenly to obtain a mixed powder;

[0049] S2: Add acid to water and mix well to obtain acid solution;

[0050] S3: Apply a layer of machine oil evenly on the inner wall of the disc of the disc granulator to prevent material adhesion; pour the mixed powder into the disc granulator, slowly add acid, control the inclination angle of the disc granulator to 40°, and the speed to 40r / min to form spherical particles of about 25mm;

[0051] S4: The spherical particles were placed in an environment with an air humidity of 70% and a temperature of 18°C ​​for 1 day;

[0052] S5: drying the cured spherical particles in an environment at a temperature of 45°C.

[0053] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1350kg / m 3 , cylinder pressure strength is 6.3MPa and porosity is 45%.

[0054] Example 3:

[0055] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0056] 45 parts of limestone powder, 55 parts of calcined phosphogypsum, 30 parts of water, 0.165 parts of potassium citrate, 1.2 parts of formic acid with a concentration of 80wt%; wherein the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 85%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0057] The preparation method of the unburned ceramsite in the present embodiment is:

[0058] S1: Weigh the raw materials of each component according to the above mass ratio, mix the limestone powder, industrial by-product gypsum and gypsum retarder evenly to obtain a mixed powder;

[0059] S2: Add acid to water and mix well to obtain acid solution;

[0060] S3: Apply a layer of machine oil evenly on the inner wall of the disc of the disc granulator to prevent material adhesion; pour the mixed powder into the disc granulator, slowly add acid, control the inclination angle of the disc granulator to 44°, and the speed to 36r / min to form spherical particles of about 30mm;

[0061] S4: The spherical particles were placed in an environment with an air humidity of 50% and a temperature of 22°C for 1 day;

[0062] S5: drying the cured spherical particles in an environment at a temperature of 40°C.

[0063] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1150kg / m 3 , the cylinder pressure strength is 5.3MPa and the porosity is 51%.

[0064] Example 4:

[0065] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0066] 45 parts of limestone powder, 55 parts of calcined phosphogypsum, 30 parts of water, 0.165 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 1.5 parts of formic acid with a concentration of 50wt%; wherein the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 89%.

[0067] The preparation method of the unburned ceramsite in the present embodiment is:

[0068] S1: Weigh the raw materials of each component according to the above mass ratio, mix the limestone powder, industrial by-product gypsum and gypsum retarder evenly to obtain a mixed powder;

[0069] S2: Add acid to water and mix well to obtain acid solution;

[0070] S3: Apply a layer of machine oil evenly on the inner wall of the disc of the disc granulator to prevent material adhesion; pour the mixed powder into the disc granulator, slowly add acid, control the inclination angle of the disc granulator to 42°, and the speed to 38r / min to form spherical particles of about 20mm;

[0071] S4: The spherical particles were placed in an environment with an air humidity of 60% and a temperature of 20°C for 1 day;

[0072] S5: drying the cured spherical particles in an environment at a temperature of 50°C.

[0073] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1030kg / m 3, the cylinder pressure strength is 4.8MPa and the porosity is 56%.

[0074] Example 5:

[0075] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0076] 20 parts of limestone powder, 80 parts of calcined phosphogypsum, 25 parts of water, 0.16 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 0.5 parts of formic acid with a concentration of 70wt%; wherein, the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0077] The preparation method of the unfired ceramsite in this embodiment is the same as that in Example 1.

[0078] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1300kg / m 3 , the cylinder pressure strength is 5.8MPa and the porosity is 46%.

[0079] Example 6:

[0080] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0081] 50 parts of limestone powder, 50 parts of calcined phosphogypsum, 35 parts of water, 0.2 parts of sodium citrate, 1.75 parts of 1wt% hydrochloric acid; wherein the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0082] The preparation method of the unfired ceramsite in this embodiment is the same as that in Example 1.

[0083] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1130kg / m 3 , the cylinder pressure strength is 4.9MPa and the porosity is 51%.

[0084] Example 7:

[0085] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0086] 20 parts of limestone powder, 80 parts of desulfurized gypsum, 25 parts of water, 0.4 parts of potassium citrate, and 0.5 parts of 5wt% hydrochloric acid; wherein the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in desulfurization gypsum is about 85%.

[0087] The preparation method of the unfired ceramsite in this embodiment is the same as that in Example 1.

[0088] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1270kg / m 3 , the cylinder pressure strength is 6.1MPa and the porosity is 49%.

[0089] Example 8:

[0090] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0091] 50 parts of limestone powder, 50 parts of desulfurized gypsum, 25 parts of water, 0.1 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 0.75 parts of hydrochloric acid with a concentration of 3.5wt%; wherein the specific surface area of ​​the limestone powder is about 340m 2 / kg, the carbonate content is about 82%; the content of hemihydrate gypsum in desulfurization gypsum is about 88%.

[0092] The preparation method of the unfired ceramsite in this embodiment is the same as that in Example 1.

[0093] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1110kg / m 3 , cylinder pressure strength is 4.5MPa and porosity is 55%.

[0094] Example 9:

[0095] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0096] 20 parts of limestone powder, 80 parts of titanium gypsum, 33 parts of water, 0.28 parts of sodium citrate, 1.75 parts of formic acid with a concentration of 70wt%; wherein the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in titanium gypsum is about 85%.

[0097] The preparation method of the unfired ceramsite in this embodiment is the same as that in Example 1.

[0098] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1290kg / m 3 The cylinder pressure strength is 5.1MPa and the porosity is 52%.

[0099] Example 10:

[0100] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0101] 50 parts of limestone powder, 50 parts of titanium gypsum, 30 parts of water, 0.25 parts of potassium citrate, 1.2 parts of formic acid with a concentration of 80wt%; wherein the specific surface area of ​​the limestone powder is about 330m 2 / kg, the carbonate content is about 85%; the content of hemihydrate gypsum in titanium gypsum is about 89%.

[0102] The preparation method of the unfired ceramsite in this embodiment is the same as that in Example 1.

[0103] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1080kg / m 3 , the cylinder pressure strength is 4.3MPa and the porosity is 57%.

[0104] Comparative Example 1:

[0105] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0106] 10 parts of limestone powder, 90 parts of calcined phosphogypsum, 30 parts of water, 0.27 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 0.9 parts of formic acid with a concentration of 70wt%; wherein, the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0107] The preparation method of the unfired ceramsite in this comparative example is the same as that in Example 1.

[0108] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1470kg / m 3 The cylinder pressure strength is 5.4MPa, the porosity is 19%, and no porous structure is formed.

[0109] Comparative Example 2:

[0110] A kind of unfired ceramsite, comprising the following raw materials in parts by weight:

[0111] 60 parts of limestone powder, 40 parts of calcined phosphogypsum, 30 parts of water, 0.12 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 0.9 parts of formic acid with a concentration of 70wt%; wherein the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0112] The preparation method of the unfired ceramsite in this comparative example is the same as that in Example 1.

[0113] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1250kg / m 3 , the cylinder pressure strength is 3MPa, the strength is too low, and the porosity is 45%.

[0114] Comparative Example 3:

[0115] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0116] 35 parts of limestone powder, 65 parts of calcined phosphogypsum, 30 parts of water, 0.195 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 0.9 parts of formic acid with a concentration of 70wt%; wherein, the specific surface area of ​​the limestone powder is about 200m 2 / kg, the carbonate content is about 50%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0117] The preparation method of the unfired ceramsite in this comparative example is the same as that in Example 1.

[0118] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1380kg / m 3 The cylinder pressure strength is 5.5MPa and the porosity is 21%, and no porous structure is formed.

[0119] Comparative Example 4:

[0120] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0121] 35 parts of limestone powder, 65 parts of calcined phosphogypsum, 30 parts of water, 0.195 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 0.9 parts of formic acid with a concentration of 70wt%; wherein, the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 55%.

[0122] The preparation method of the unfired ceramsite in this comparative example is the same as that in Example 1.

[0123] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1190kg / m 3 The cylinder pressure strength is 2.9MPa, the strength is too low, and the porosity is 48%.

[0124] Comparative Example 5:

[0125] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0126] 35 parts of limestone powder, 65 parts of calcined phosphogypsum, 30 parts of water, 0.9 parts of formic acid with a concentration of 70wt%; wherein the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0127] The preparation method of the unfired ceramsite in this comparative example is the same as that in Example 1.

[0128] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1450kg / m 3The cylinder pressure strength is 5.9MPa and the porosity is 25%. During the preparation, the ceramsite hardening process is relatively fast and no porous structure is formed.

[0129] Comparative Example 6:

[0130] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0131] 35 parts of limestone powder, 65 parts of calcined phosphogypsum, 10 parts of water, 0.195 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 0.3 parts of formic acid with a concentration of 70wt%; wherein the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0132] The preparation method of the unfired ceramsite in this comparative example is the same as that in Example 1.

[0133] The unfired ceramsite of this formula and preparation method is too dry after the raw materials are mixed during the preparation process, and spherical particles cannot be formed, so the unfired ceramsite cannot be obtained.

[0134] Comparative Example 7:

[0135] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0136] 35 parts of limestone powder, 65 parts of calcined phosphogypsum, 50 parts of water, 0.195 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 1.5 parts of formic acid with a concentration of 70wt%; wherein, the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0137] The preparation method of the unfired ceramsite in this comparative example is the same as that in Example 1.

[0138] During the preparation process of the unfired ceramsite prepared with this formula and preparation method, the slurry formed after the raw materials are mixed has too high fluidity to form spherical particles, and thus the unfired ceramsite cannot be obtained.

[0139] Comparative Example 8:

[0140] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0141] 35 parts of limestone powder, 65 parts of calcined phosphogypsum, 30 parts of water, 0.195 parts of SGR-1801 gypsum retarder (protein gypsum retarder); the specific surface area of ​​limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0142] The preparation method of the unfired ceramsite in this comparative example is the same as that in Example 1.

[0143] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 1270kg / m 3 , the cylinder pressure strength is 5.6MPa, the porosity is 5%, and no porous structure is formed.

[0144] Comparative Example 9:

[0145] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0146] 35 parts of limestone powder, 65 parts of calcined phosphogypsum, 30 parts of water, 0.195 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 2.4 parts of formic acid with a concentration of 70wt%; wherein, the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0147] The preparation method of the unfired ceramsite in this comparative example is the same as that in Example 1.

[0148] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 980kg / m 3 , the cylinder pressure strength is 3.3MPa, the porosity is 65%, and cracking problems occur.

[0149] Comparative Example 10:

[0150] A fired-free ceramsite, comprising the following raw materials in parts by weight:

[0151] 35 parts of limestone powder, 65 parts of calcined phosphogypsum, 30 parts of water, 0.195 parts of SGR-1801 gypsum retarder (protein gypsum retarder), 0.9 parts of formic acid with a concentration of 70wt%; wherein the specific surface area of ​​the limestone powder is about 300m 2 / kg, the carbonate content is about 80%; the content of hemihydrate gypsum in calcined phosphogypsum is about 85%.

[0152] The preparation method of the unfired ceramsite in this comparative example is:

[0153] S1: Weigh the raw materials of each component according to the above mass ratio, mix the limestone powder, industrial by-product gypsum and gypsum retarder evenly to obtain a mixed powder;

[0154] S2: Add acid to water and mix well to obtain acid solution;

[0155] S3: Apply a layer of machine oil evenly on the inner wall of the disc of the disc granulator to prevent the material from sticking; pour the mixed powder into the disc granulator, slowly add acid, control the inclination angle of the disc granulator to 42°, and the speed to 38r / min to form spherical particles of about 20mm;

[0156] S4: Place the spherical particles in an environment with an air humidity of 60% and a temperature of 20°C for 1 day;

[0157] S5: drying the cured spherical particles in an environment at a temperature of 70°C.

[0158] The bulk density of the unfired ceramsite obtained by this formula and preparation method is 950kg / m 3 , the cylinder pressure strength is 3.5MPa, the porosity is 58%, and cracking problems occur.

[0159] Although the specific embodiments of the present invention have been described in detail in conjunction with the embodiments, this should not be construed as limiting the scope of protection of this patent. Within the scope described by the claims, various modifications and variations that can be made by those skilled in the art without creative work still fall within the scope of protection of this patent.

Claims

1. A kind of unburned ceramsite, characterized in that, Including the following raw materials by weight: 20-50 parts of limestone powder, 50-80 parts of industrial by-product gypsum, 0.1-0.4 parts of gypsum retarder, 0.5-1.75 parts of acid and 25-35 parts of water; the industrial by-product gypsum is calcined phosphogypsum, desulfurized gypsum or titanium gypsum, and the hemihydrate gypsum content in the industrial by-product gypsum is ≥85%; the specific surface area of ​​the limestone powder is ≥300m 2 / kg, of which the carbonate content is ≥80%.

2. The unburned ceramsite according to claim 1, characterized in that Including the following raw materials by weight: 35 parts of limestone powder, 65 parts of industrial by-product gypsum, 0.195 parts of gypsum retarder, 0.9 parts of acid and 30 parts of water.

3. The unfired ceramsite according to claim 1 or 2, characterized in that: The gypsum retarder is a protein gypsum retarder, sodium citrate or potassium citrate.

4. The unfired ceramsite according to claim 1, characterized in that: The acid is hydrochloric acid with a concentration of 1-5 wt% or formic acid with a concentration of 50-90 wt%.

5. The method for preparing the unfired ceramsite according to any one of claims 1 to 4, wherein: The following steps are involved: S1: Weigh the raw materials of each component according to the mass ratio, mix the limestone powder, industrial by-product gypsum and gypsum retarder evenly to obtain a mixed powder; S2: Add acid to water and mix well to obtain acid solution; S3: adding the acid solution to the mixed powder, mixing well and granulating to obtain spherical particles; S4: curing the spherical particles in an environment with an air humidity of 50-70% and a temperature of 18-22° C. for 1 day; S5: The cured spherical particles are placed in an environment with a temperature of 40-50°C for drying or natural drying.

6. The method for preparing unfired ceramsite according to claim 5, wherein: In S3, granulation is carried out in a disc granulator. During the granulation process, the disc granulator has an inclination angle of 40-44° and a rotation speed of 36-40 r / min.

7. The method for preparing unfired ceramsite according to claim 5, wherein: The particle size of the spherical particles is 15-35 mm.

Images