Process for the production of heavy calcium carbonate

Abstract

The present application belongs to the technical field of non-metallic mineral preparation, and provides a preparation method of heavy calcium carbonate, comprising the following steps: mixing calcite and a grinding aid solution, then performing ball milling and drying to obtain the heavy calcium carbonate. The present application uses a combination of a high molecular dispersant and an anionic dispersant as the grinding aid solution, which increases the viscosity and interface wetting performance of the material, improves the friction between the materials during grinding, and improves the grinding efficiency. The path of the feeding system is extended to allow the grinding aid solution to fully contact the material, further improving the grinding efficiency. In the product collection stage, the path of the air conveying system is extended to allow the material to stay in the air pipe for a longer time, further drying the material. The preparation process of the present application can meet various product indicators while reducing energy consumption by more than 25% compared with the traditional process, and has a significant energy saving and consumption reduction effect.

Description

Technical Field

[0001] This invention relates to the field of non-metallic mineral preparation technology, and in particular to a method for preparing heavy calcium carbonate. Background Technology

[0002] Calcium carbonate, a non-metallic mineral widely found in nature, is widely used in coatings, plastics, papermaking, adhesives and other fields due to its advantages such as high whiteness, low oil absorption, high grindability and low price.

[0003] Currently, the processing technology of heavy calcium carbonate is mainly divided into two categories: dry grinding and wet grinding. Dry grinding, using air as the grinding medium, has a certain grinding limit. When the fineness exceeds 3000 mesh, a large amount of energy is lost as heat, resulting in low grinding efficiency and high energy consumption. Therefore, dry grinding is generally used for grinding ultrafine products below 3000 mesh. Wet grinding uses water as the grinding medium, resulting in less energy loss as heat during the grinding process. Therefore, it is mainly used for grinding ultrafine calcium carbonate above 3000 mesh. However, wet grinding requires consideration of slurry viscosity and other factors, leading to lower solid content and higher drying costs. Furthermore, the slurry produced by wet grinding requires further treatment, resulting in high energy consumption and production costs in actual production. Therefore, effectively reducing the energy consumption in the production of ultrafine calcium carbonate products has become one of the most pressing issues for the industry. Summary of the Invention

[0004] The purpose of this invention is to overcome the deficiencies in the prior art and provide a method for preparing heavy calcium carbonate.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing heavy calcium carbonate, comprising the following steps:

[0007] The heavy calcium carbonate is obtained by mixing calcite and grinding aid solution, ball milling, and drying.

[0008] Preferably, the calcite has a diameter of 5–20 mm.

[0009] Preferably, the grinding aid solution comprises a polymeric dispersant solution and an anionic dispersant solution.

[0010] Preferably, the polymeric dispersant solution comprises a polymeric dispersant and water; the anionic dispersant solution comprises anionic dispersant and water.

[0011] Preferably, the mass ratio of the polymeric dispersant to water is 1:8 to 12; and the mass ratio of the anionic dispersant to water is 1:5 to 8.

[0012] Preferably, the polymeric dispersant is an aqueous solution of sodium hydroxyethyl cellulose and / or an aqueous solution of sodium carboxymethyl cellulose; the anionic dispersant solution is a sodium polyacrylate solution and / or a sodium dodecyl sulfonate solution.

[0013] Preferably, the mass ratio of the polymeric dispersant to the anionic dispersant is 1:5 to 10.

[0014] Preferably, the total mass of the polymeric dispersant and the anionic dispersant is 2 to 8‰ of the mass of calcite.

[0015] Preferably, the ball milling is a first ball milling and a second ball milling performed sequentially.

[0016] Preferably, the grinding media filling rates of the first ball mill and the second ball mill are independently 25-35%;

[0017] Preferably, the grinding media of the first ball mill includes steel balls with a diameter of 25-35 mm, steel balls with a diameter of 45-55 mm, and steel balls with a diameter of 55-65 mm.

[0018] Preferably, the mass ratio of the steel balls with a diameter of 25-35 mm, the steel balls with a diameter of 45-55 mm, and the steel balls with a diameter of 55-65 mm is 1-3:2-4:3-7.

[0019] Preferably, the grinding media of the second ball mill includes steel balls with a diameter of 5-15 mm, steel balls with a diameter of 15-25 mm, and steel balls with a diameter of 25-35 mm.

[0020] Preferably, the mass ratio of the steel balls with a diameter of 5-15 mm, the steel balls with a diameter of 15-25 mm, and the steel balls with a diameter of 25-35 mm is 3-6:2-4:1-2.

[0021] Preferably, the rotational speed of the first ball mill is 70-80 r / min; the rotational speed of the second ball mill is 70-80 r / min.

[0022] Preferably, the first ball milling time is 12-18 minutes; the second ball milling time is 12-18 minutes.

[0023] Preferably, the drying method is wind drying; the power of the wind drying fan is 230-250KW.

[0024] The present invention has the following advantages:

[0025] This invention provides a method for preparing heavy calcium carbonate, comprising the following steps: mixing calcite particles and a grinding aid solution, followed by ball milling and drying to obtain the heavy calcium carbonate.

[0026] This invention uses a combination of polymeric dispersants and anionic dispersants as grinding aids. The polymeric dispersant mainly increases the viscosity of the material, thereby improving the friction between materials and increasing grinding efficiency during the grinding process. The anionic dispersant improves the interfacial wetting properties and prevents adsorption and aggregation between new interfaces generated during the grinding process, which would reduce grinding efficiency.

[0027] This invention improves grinding efficiency by adding compound grinding aids, which increases the viscosity of the material and the friction of the material in the mill. Extending the path of the feeding system facilitates full contact and uniform dispersion of the grinding aids with the material, allowing the grinding aids to more easily and quickly penetrate the newly formed interface during the grinding process, thereby further improving grinding efficiency. In the finished product collection stage, extending the path of the pneumatic conveying system prolongs the time the material spends in the air duct, further drying the material and ensuring that the moisture content of the final product meets the standards without additional drying processes. Compared with the traditional production process of ultrafine calcium carbonate (above 3000 mesh, D50 < 2um, D97 < 5um), energy consumption is reduced by more than 25%. Attached Figure Description

[0028] Figure 1 This is a flowchart of Example 1. Detailed Implementation

[0029] This invention provides a method for preparing heavy calcium carbonate, comprising the following steps:

[0030] The heavy calcium carbonate is obtained by mixing calcite and grinding aid solution, ball milling, and drying.

[0031] In this invention, the calcium carbonate content of the calcite is preferably ≥95%, more preferably ≥96%, and even more preferably ≥97%.

[0032] In this invention, calcite ore is obtained by washing, drying and two-stage jaw crushing.

[0033] In this invention, the diameter of the calcite is preferably 5-20 mm, more preferably 8-17 mm, and even more preferably 10-15 mm.

[0034] In this invention, calcite is fed into a ball mill via a spiral cutter.

[0035] In this invention, the length of the conveying system of the spiral cutter is preferably 16-20m, more preferably 17-19m, and even more preferably 18m.

[0036] In this invention, the spiral cutters are preferably evenly distributed in a zigzag pattern.

[0037] In this invention, extending the spiral auger conveying system facilitates full contact and uniform dispersion of the grinding aid solution and the material. During the grinding process, the grinding aid can more easily and quickly penetrate the newly formed interface, thereby improving the grinding efficiency.

[0038] In this invention, a grinding aid solution is added while the spiral auger is conveying calcite, and the two are mixed in the spiral auger.

[0039] In this invention, the grinding aid solution is preferably added by spraying.

[0040] In this invention, the addition method of spraying allows the additives to be more fully dispersed in the material.

[0041] In this invention, the grinding aid solution comprises a polymeric dispersant solution and an anionic dispersant solution.

[0042] In this invention, the polymeric dispersant solution comprises a polymeric dispersant and water; the mass ratio of the polymeric dispersant to water is preferably 1:8 to 12, more preferably 1:9 to 11, and even more preferably 1:9.5 to 10.5.

[0043] In this invention, the anionic dispersant solution comprises anionic dispersant and water; the mass ratio of the anionic dispersant to water is preferably 1:5 to 8, more preferably 1:6 to 7, and even more preferably 1:6.2 to 6.8.

[0044] In this invention, the polymeric dispersant is preferably sodium hydroxyethyl cellulose and / or sodium carboxymethyl cellulose.

[0045] In this invention, cellulose is selected as a polymeric dispersant to increase the viscosity of the material, which can improve the friction between materials during the grinding process and improve the grinding efficiency.

[0046] In this invention, the anionic dispersant is preferably sodium polyacrylate and / or sodium dodecyl sulfonate.

[0047] In this invention, selecting a low molecular weight anionic dispersant can improve the interfacial wetting performance and prevent adsorption and aggregation between new interfaces during the grinding process.

[0048] In this invention, the mass ratio of the polymeric dispersant to the anionic dispersant is preferably 1:5 to 10, more preferably 1:6 to 9, and even more preferably 1:7 to 8.

[0049] In this invention, the mass of the polymeric dispersant and the anionic dispersant is preferably 2-8‰ of the mass of calcite, more preferably 3-7‰, and even more preferably 4-6‰.

[0050] In this invention, the ball mill is preferably a two-compartment ball mill.

[0051] In this invention, the preferred size of the two-compartment ball mill is 2.4 × 8 m.

[0052] In this invention, the two-compartment ball mill is divided into a front compartment and a rear compartment by a partition; the partition has holes, and the material first passes through the front compartment for the first ball milling, and then enters the rear compartment for the second ball milling through the gaps in the partition.

[0053] In this invention, the length ratio of the front compartment to the rear compartment is preferably 2:3.

[0054] In this invention, the ball milling is a first ball milling and a second ball milling performed sequentially.

[0055] In this invention, the first ball milling is performed in the front chamber, and the second ball milling is performed in the rear chamber.

[0056] In this invention, the grinding media filling rate of the first ball mill and the second ball mill is preferably 25-35%, more preferably 28-32%, and even more preferably 29-31%.

[0057] In this invention, the grinding media of the first ball mill preferably includes steel balls with a diameter of 25-35 mm, steel balls with a diameter of 45-55 mm, and steel balls with a diameter of 55-65 mm; more preferably, it includes steel balls with a diameter of 28-32 mm, steel balls with a diameter of 48-52 mm, and steel balls with a diameter of 58-62 mm; and even more preferably, it includes steel balls with a diameter of 29-31 mm, steel balls with a diameter of 49-51 mm, and steel balls with a diameter of 59-61 mm.

[0058] In this invention, the preferred mass ratio of the steel balls with a diameter of 25-35 mm, the steel balls with a diameter of 45-55 mm, and the steel balls with a diameter of 55-65 mm is 1-3:2-4:3-7, more preferably 1.2-2.8:2.2-3.8:3.5-6.5, and even more preferably 1.5-2.5:2.5-3.5:4-6.

[0059] In this invention, the grinding media of the second ball mill preferably includes steel balls with a diameter of 5-15 mm, steel balls with a diameter of 15-25 mm, and steel balls with a diameter of 25-35 mm; more preferably, it includes steel balls with a diameter of 8-12 mm, steel balls with a diameter of 18-22 mm, and steel balls with a diameter of 28-32 mm; and even more preferably, it includes steel balls with a diameter of 9-11 mm, steel balls with a diameter of 19-21 mm, and steel balls with a diameter of 29-31 mm.

[0060] In this invention, the preferred mass ratio of the steel balls with a diameter of 5-15 mm, the steel balls with a diameter of 15-25 mm, and the steel balls with a diameter of 25-35 mm is 3-6:2-4:1-2, more preferably 4-5:2.5-3.5:1.2-1.8, and even more preferably 4.4-4.6:2.8-3.2:1.4-1.6.

[0061] In this invention, the rotational speed of the first ball mill is preferably 70-80 r / min, more preferably 72-78 r / min, and even more preferably 74-76 r / min; the rotational speed of the second ball mill is preferably 70-80 r / min, more preferably 72-78 r / min, and even more preferably 74-76 r / min.

[0062] In this invention, the first ball milling time is preferably 12-18 min, more preferably 13-17 min, and even more preferably 14-16 min; the second ball milling time is 12-18 min, more preferably 13-17 min, and even more preferably 14-16 min.

[0063] In this invention, the drying method is preferably wind drying.

[0064] In this invention, the product obtained from grinding is processed through a multi-head grading system to obtain a product with qualified fineness, and then air-dried before entering the collection system.

[0065] In this invention, the preferred path of the hierarchical system is 8 to 15 meters.

[0066] In this invention, the power of the fan used for air drying is preferably 230-250KW, more preferably 235-245KW, and even more preferably 238-242KW.

[0067] In this invention, the number of dampers opened during wind drying is preferably 2 to 4.

[0068] In this invention, extending the path of the air drying process allows for further drying of the material.

[0069] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0070] Example 1

[0071] 100 kg of calcite ore with a calcium carbonate content ≥ 95% was selected, washed and naturally dried, and then crushed in two stages to obtain calcite with a diameter of 18 mm.

[0072] 5g of sodium hydroxyethyl cellulose and 5g of sodium carboxymethyl cellulose were dissolved in 40g of water respectively, and then mixed to prepare a polymeric dispersant solution. 45g of sodium polyacrylate and 45g of sodium dodecyl sulfonate were dissolved in 225g of water respectively, and then mixed to prepare an anionic dispersant solution. The polymeric dispersant solution and the anionic dispersant solution were then mixed to prepare a grinding aid solution.

[0073] Take 50 kg of the above-mentioned calcite and put it into an 18 m spiral auger conveyor system with evenly distributed spiral cutters. Add 630 g of the above-prepared grinding aid solution at the front end of the conveyor system by spraying. The material enters a two-compartment ball mill with a specification of 2.4 m × 8 m through the spiral cutter. The first ball milling is carried out in the front compartment and the second ball milling is carried out in the rear compartment.

[0074] First ball milling: The first ball milling was carried out at a speed of 70 r / min for 12 min in a filling medium with a filling rate of 30% and a filling medium consisting of steel balls with a diameter of 30 mm, 50 mm, and 60 mm in a mass ratio of 1:2:3.

[0075] Second ball milling: In a filling medium with a filling rate of 30% and a mass ratio of 10mm diameter steel balls: 20mm diameter steel balls: 30mm diameter steel balls of 3:2:1, the second ball milling was carried out at a speed of 70r / min for 12min.

[0076] After ball milling, the product is classified by a 6-head classifier to obtain a product with qualified fineness (D50 1.53um, D97 4.12um). Under the condition that the number of air dampers is 3 and the fan power is 240KW, it is conveyed into the bag collection system for sieving, testing and packaging.

[0077] The specific process of this embodiment is as follows: Figure 1 As shown.

[0078] Example 2

[0079] 100 kg of calcite ore with a calcium carbonate content ≥95% was selected, washed and naturally dried, and then crushed in two stages using an ordnance crusher to obtain calcite particles with a diameter of 18 mm.

[0080] 12.5g of sodium hydroxyethyl cellulose and 12.5g of sodium carboxymethyl cellulose were each dissolved in 125g of water, and then mixed to prepare a polymeric dispersant solution. 87.5g of sodium polyacrylate and 87.5g of sodium dodecyl sulfonate were each dissolved in 613g of water, and then mixed to prepare an anionic dispersant solution. The polymeric dispersant solution and the anionic dispersant solution were then mixed to prepare a grinding aid solution.

[0081] Take 50 kg of the above-mentioned calcite and put it into an 18 m spiral auger conveyor system with evenly distributed spiral cutters. Add 1676 g of the above-prepared grinding aid solution at the front end of the conveyor system by spraying. The material enters a two-compartment ball mill with a specification of 2.4 m × 8 m through the spiral cutter. The first ball milling is carried out in the front compartment and the second ball milling is carried out in the rear compartment.

[0082] First ball milling: The first ball milling was carried out at a speed of 76 r / min for 15 min in a filling medium with a filling rate of 30% and a filling medium consisting of steel balls with a diameter of 30 mm, 50 mm, and 60 mm in mass ratio of 1:3:5.

[0083] Second ball milling: In a filling medium with a filling rate of 30% and a mass ratio of 10mm diameter steel balls: 20mm diameter steel balls: 30mm diameter steel balls of 5:3:1, the second ball milling was carried out at a speed of 76r / min for 15min.

[0084] After ball milling, the product is classified by a 6-head classifier to obtain a product with qualified fineness (D50 1.51um, D97 4.01um). Under the premise that the number of air dampers is 4 and the fan power is 240KW, the product is conveyed into the bag collection system for sieving, testing and packaging.

[0085] Example 3

[0086] 100 kg of calcite ore with a calcium carbonate content ≥ 96% was selected, washed and naturally dried, and then crushed in two stages using an Ochre-type crusher to obtain calcite particles with a diameter of 17 mm.

[0087] 20g of sodium hydroxyethyl cellulose and 20g of sodium carboxymethyl cellulose were dissolved in 240g of water respectively, and then mixed to prepare a polymeric dispersant solution. 180g of sodium polyacrylate and 180g of sodium dodecyl sulfonate were dissolved in 1440g of water respectively, and then mixed to prepare an anionic dispersant solution. The polymeric dispersant solution and the anionic dispersant solution were then mixed to prepare a grinding aid solution.

[0088] Take 50 kg of the above-mentioned calcite and put it into an 18 m spiral auger conveyor system with evenly distributed spiral cutters. Add 3760 g of the above-prepared grinding aid solution at the front end of the conveyor system by spraying. The material enters a two-compartment ball mill with a specification of 2.4 m × 8 m through the spiral cutter. The first ball milling is carried out in the front compartment and the second ball milling is carried out in the rear compartment.

[0089] First ball milling: The first ball milling was carried out at a speed of 80 r / min for 18 min in a filling medium with a filling rate of 30% and a filling medium consisting of steel balls with a diameter of 30 mm, 50 mm, and 60 mm in mass ratio of 1:4:7.

[0090] Second ball milling: In a filling medium with a filling rate of 30% and a mass ratio of 10mm diameter steel balls: 20mm diameter steel balls: 30mm diameter steel balls of 6:4:1, the second ball milling was carried out at a speed of 80r / min for 18min.

[0091] After ball milling, the product is classified by a 6-head classifier to obtain a product with qualified fineness (D50 1.48um, D97 3.99um). Under the conditions of 3 air dampers open and 240KW fan power, it is conveyed into the bag collection system for sieving, testing and packaging.

[0092] The heavy calcium carbonate prepared in Examples 1-3 above was tested for relevant indicators according to HG / T 3249-2013, and compared with the same type of product produced by traditional process. The results are shown in Table 1.

[0093] Table 1 Results of tests in Examples 1-3

[0094] detection indicators Example 1 Example 2 Example 3 Traditional ball mill Stirred mill Whiteness 96.3 96.2 96.3 96.2 96.1 D50(um) 1.53 1.51 1.48 1.54 1.51 D97(um) 4.12 4.01 3.99 4.23 4.11 Oil absorption (ml / 100g) 25 24 23 27 25 Moisture (%) 0.21 0.22 0.21 0.20 0.29 Installed capacity / kW 550 550 550 520 690 Production capacity (t / h) 3.55 3.51 3.62 2.51 3.21 Energy consumption per unit (t / kW) 155 157 152 207 215

[0095] As can be seen from the above embodiments, the present invention provides a method for preparing heavy calcium carbonate, comprising the following steps: mixing calcite and a grinding aid solution, followed by ball milling and drying to obtain the heavy calcium carbonate. As can be seen from Table 1 above, the product prepared by the method of the present invention meets all the required indicators while reducing energy consumption per unit capacity by more than 25%, demonstrating significant energy-saving and consumption-reducing effects.

[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing heavy calcium carbonate, characterized in that, Includes the following steps: The heavy calcium carbonate is obtained by mixing calcite and grinding aid solution, followed by ball milling and drying. The ball milling is a first ball milling and a second ball milling performed sequentially. The grinding media filling rates of the first and second ball mills are independently 25% to 35%; The grinding media of the first ball mill include steel balls with a diameter of 25-35 mm, steel balls with a diameter of 45-55 mm, and steel balls with a diameter of 55-65 mm; The mass ratio of the steel balls with a diameter of 25-35mm, the steel balls with a diameter of 45-55mm, and the steel balls with a diameter of 55-65mm is 1-3:2-4:3-7; The grinding media of the second ball mill include steel balls with a diameter of 5-15 mm, steel balls with a diameter of 15-25 mm, and steel balls with a diameter of 25-35 mm; The mass ratio of the steel balls with a diameter of 5-15mm, the steel balls with a diameter of 15-25mm, and the steel balls with a diameter of 25-35mm is 3-6:2-4:1-2; The rotational speed of the first ball mill is 70~80 r / min; the rotational speed of the second ball mill is 70~80 r / min; The first ball milling time is 12-18 minutes; The second ball milling time is 12-18 minutes; The grinding aid solution comprises a polymeric dispersant solution and an anionic dispersant solution; The polymeric dispersant solution comprises a polymeric dispersant and water; The mass ratio of the polymeric dispersant to water is 1:8~12; The anionic dispersant solution comprises an anionic dispersant and water; The mass ratio of the anionic dispersant to water is 1:5~8; The polymeric dispersant is sodium hydroxyethyl cellulose and / or sodium carboxymethyl cellulose; The anionic dispersant is sodium polyacrylate and / or sodium dodecyl sulfonate; The mass ratio of the polymeric dispersant to the anionic dispersant is 1:5~10; The total mass of the polymeric dispersant and the anionic dispersant is 2-8‰ of the mass of calcite.

2. The preparation method according to claim 1, characterized in that, The diameter of the calcite is 5~20mm.

3. The preparation method according to claim 2, characterized in that, The drying method is wind drying; The fan power for the air dryer is 230~250KW.

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