Method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller-milled iron tailings

Abstract

The invention discloses a method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller-milled iron tailings, and belongs to the technical field of comprehensive utilization of iron tailings. The method comprises the following steps: adding water into high-pressure roller-milled iron tailings to prepare high-pressure roller-milled iron tailing slurry, selecting stone powder particle slurry of which the total amount of stone powder particles is more than 50%, dehydrating the residual particle slurry which is not selected to be used as sand for construction, flocculating, settling and concentrating the stone powder particle slurry to obtain a stone powder particle filter cake, and filtering the stone powder particle filter cake to obtain the high-pressure roller-milled iron tailings. The preparation method comprises the following steps: fully mixing the raw materials with a mixture 1 of calcium bentonite, sodium bentonite and a nitrogen source to obtain a mixture 2, determining a forming mode and adjusting the water content of the mixture 2 to obtain a slow-release fertilizer material, and granulating, drying and cooling the slow-release fertilizer material to obtain the high-pressure roller milling iron tailing slow-release nitrogen fertilizer. The method makes the best use of the particles of each size fraction of the high-pressure roller milling iron tailings, exerts respective advantages, effectively solves the problem of large-amount stockpiling of the high-pressure roller milling iron tailings, and generates huge economic, environmental and social benefits at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive utilization of iron tailings, and particularly relates to a method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings. Background Art

[0002] Iron tailings are fine-grained solid wastes remaining after valuable components such as iron are selected through processes such as crushing and separation of iron ore. With the development of beneficiation technology, more and more iron mines adopt the high-pressure roller mill process for ore crushing, and then adopt the pre-grinding tailing discarding process to discard the high-pressure roller mill iron tailings, so as to reduce the feeding particle size of the ball mill and improve the ball milling efficiency. The production volume of high-pressure roller mill iron tailings shows a rapid growth trend, occupying a large amount of land and seriously polluting the environment at the same time. For the vast majority of high-pressure roller mill iron tailings, as described by Cao Kejie, Zhan Renli, Chen Tiejun, and Jiang Xiangbo in "Mining & Processing Equipment" (2024, 52(02): 38-43), "Research on Optimization of the Separation Process of Qijiaojing Mine by High-Pressure Roller Mill Superfine Crushing" and Li Genghui and Xiao Qifei in "Modern Mining" (2024, 40(06): 170-175), "Experimental Study on the Beneficiation Process of Beishan Ore in Nanfen Concentrator", the effect of wet magnetic separation is better than that of dry magnetic separation. Therefore, most mines adopt wet magnetic separation, making the high-pressure roller mill iron tailings mostly produced in a slurry state, which brings difficulties to storage and utilization. If the high-pressure roller mill iron tailings are utilized by appropriate methods, great economic, environmental, and social benefits can be generated while eliminating the hazards.

[0003] Using it as construction sand is one of the main utilization methods of iron tailings at present. According to the regulations in GB / T 14684-2022 "Construction Sand", various tailings can be classified as "manufactured sand", and the "particles with a particle size less than 75 μm in the manufactured sand" are called "stone powder", and the "stone powder content" limits of different types of manufactured sand are also specified. GB / T 14684-2022 "Construction Sand" also stipulates the content limits of "hazardous substances in manufactured sand produced from mine waste rock and tailings, etc.", and the "hazardous substances" herein refer to "mica, light substances, organic matter, sulfides and sulfates, chlorides, shells", and the "shell" limit only applies to "purified sea sand". Therefore, the hazardous substances in the manufactured sand produced from high-pressure roller mill iron tailings are "mica, light substances, organic matter, sulfides and sulfates, chlorides". The hardness of mica, light substances, sulfides and sulfates, chlorides, etc. in iron ore is small, and they are more easily broken into small particles, so their content in "stone powder" is higher. Considering the restrictive regulations on the "stone powder content" and "hazardous substance content" of manufactured sand, when using high-pressure roller mill iron tailings as construction sand, the "stone powder" part should be selected to reduce the "stone powder content" and "hazardous substance content". However, the selected "stone powder" has fine particles, which will cause serious dust hazards in the dry state and is easily washed away during rainfall, increasing its fluidity and bringing greater difficulties to storage and utilization.

[0004] On the other hand, nitrogen nutrition in the soil is prone to loss. Therefore, slow-release nitrogen fertilizers are often manufactured in the fertilizer field to slow down nitrogen release and improve the utilization effect of nitrogen by crops. It should be noted that for the total nutrient mass fraction specified in GB / T 23348-2009 "Slow-release Fertilizers", that of high concentration should be greater than or equal to 40%, and that of medium concentration should be greater than or equal to 30%. The standard was formulated relatively early. With the development of slow-release nitrogen fertilizer technology, the difference in the total nitrogen content of slow-release nitrogen fertilizers prepared by different technical solutions has become more obvious. For example, in the enterprise standard Q_DS 4-2019 "Slow-release Nitrogen Fertilizer" of Dongguan Desheng Fertilizer Technology Co., Ltd., the total nitrogen content is set to be greater than or equal to 20%; Wen Peng disclosed in the paper "Preparation and Performance Study of Water-retaining Slow-release Nitrogen Fertilizer Based on Bentonite" (Shihezi University, 2017) that a water-retaining slow-release nitrogen fertilizer of poly(acrylic acid-co-acrylamide) / bentonite / urea (p(AA-co-AM) / Bent / urea) with a nitrogen content of 14.98% was synthesized by inverse suspension polymerization; as described in the paper "Development of Urea-formaldehyde-Gypsum-Bentonite-based Soybean Slow-release Fertilizer and Evaluation of Its Nutrient Release Performance" published by Ma Chunxue, Deng Yuequan, Dong Faqin et al. in "Soybean Science" (2013, 32(02): 220-223), low-formaldehyde urea-formaldehyde resin-gypsum-bentonite-based soybean slow-release nitrogen fertilizer (nitrogen content 16.21%, sulfur content 1.54%), coated slow-release nitrogen fertilizer (nitrogen content 13.23%, sulfur content 1.07%), slow-release compound fertilizer (nitrogen content 3.26%, phosphorus content 4.64%, potassium content 5.37%, sulfur content 0.43%), and coated slow-release compound fertilizer (nitrogen content 3.64%, phosphorus content 4.54%, potassium content 5.25%, sulfur content 0.45%) were obtained respectively; it can be seen that the diversification of slow-release nitrogen fertilizer products has led to a significant decrease in the minimum limit of the total nitrogen content. The common manufacturing methods of slow-release nitrogen fertilizers are the film coating method and the clay method. The film coating method has high manufacturing costs, complex processes, and low granulation efficiency; in the clay method during the granulation process, it is easy for particles to adhere to each other between the contact surfaces of particles and between particles and granulation equipment, resulting in difficult granulation. Moreover, the unreasonable composition of nitrogen fertilizer materials will deteriorate the soil structure, and farmland soil also requires certain natural mineral nutrients as a supplement to soil nutrients.Fei Qiou, Jia Yanjie, Liu Shudong, et al., published "Research Progress on Resource Utilization of Iron Tailings and Soil Remediation Technology in Iron Mining Areas" in Chemical Minerals and Processing (2024, 53(07): 37-46), and Hou Xiaojie, Liu Xuan, Zhang Yanle, et al., published "Effects of Iron Tailings Soil Conditioners on Soil Remediation and Its Mechanism" in Environmental Science and Management (2024, 49(09): 169-173), pointing out that iron tailings have a structural improvement effect on many types of soils; Zhang Zhenguo, Wang Yue, Chen Jundian, et al., published "Science and Technology Review" (2024, 49(09): 169-173). ,42(2):90-103), "Current Status and Development Strategy of Iron Tailings Resource Utilization", "Study on Engineering Properties and Activity of Shanxi Iron Tailings" published by Guo Yongjun in Shanxi Transportation Science and Technology (2024(04):9-13), and "Experimental Study on Comprehensive Recovery of Low-Grained Sulfur and Phosphorus Resources in Fine-Grained Iron Tailings" published by Li Jianjuan, Xie Haiyun and Chen Haijun et al. in Nonferrous Metals (Ore Dressing) (2025(01):75-80,96) pointed out that iron tailings also contain silicon, iron, calcium, potassium, sulfur, phosphorus and other nutrients that can be used as soil nutrient supplements.

[0005] Therefore, according to the properties of HPGR tailings, they are used to manufacture slow-release nitrogen fertilizer and construction sand, so that all particle sizes of HPGR tailings can be fully utilized and give play to their respective advantages, effectively solving the problem of large-scale storage of HPGR tailings, while improving the product quality and production efficiency of slow-release nitrogen fertilizer and construction sand, which has very important economic, environmental and social benefits. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill tailings. The method can make full use of the high-pressure roller mill tailings, so that particles of each particle size of the high-pressure roller mill tailings can be fully utilized and their respective advantages can be brought into play, thereby effectively solving the problem of large-scale storage of high-pressure roller mill tailings; at the same time, it can effectively reduce the manufacturing cost of slow-release nitrogen fertilizer, improve granulation efficiency, and solve the problem of mutual adhesion between particles or between particles and the contact surface of granulation equipment; it can also effectively improve the product quality of construction sand, improve production efficiency, and reduce production costs.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for producing slow-release nitrogen fertilizer and construction sand by high-pressure roller grinding of iron tailings, comprising the following steps:

[0009] Step 1: adding water to the high pressure roller mill iron tailings to prepare high pressure roller mill iron tailings slurry, and sorting the high pressure roller mill iron tailings slurry to select the "stone powder particle slurry" containing more than 50% of the total amount of "stone powder particles" in the high pressure roller mill iron tailings slurry;

[0010] Step 2: Dehydrate the "remaining particles" slurry that was not selected in Step 1 and use it as construction sand; the "remaining particles" that were not selected are a mixture of "unselected stone powder particles" and "non-stone powder particles".

[0011] Step 3: Flocculate, settle, and concentrate the "stone powder particle slurry", recycle the overflow, filter and dehydrate the underflow to obtain "stone powder particle filter cake", which is used to manufacture slow-release nitrogen fertilizer.

[0012] Step 4: Grind and fully mix calcium-based bentonite, sodium-based bentonite, and nitrogen source in a dry state to obtain "Mixture 1".

[0013] Step 5: Fully mix the "stone powder particle filter cake" with "Mixture 1" to obtain "Mixture 2".

[0014] Step 6: Determine the forming method based on the material ratio and water content of "Mixture 2", and adjust the water content of "Mixture 2" according to the water content applicable to the forming method to obtain "slow-release fertilizer material".

[0015] Step 7: Granulate, dry, and cool the "slow-release fertilizer material" to obtain "high-pressure roller mill iron tailings slow-release nitrogen fertilizer".

[0016] Further, in Step 1, the mass concentration of the high-pressure roller mill iron tailings slurry is 16%-22%, and the separation is carried out by the hydrocyclone method or the wet screening method.

[0017] Further, in Step 2, the dehydration treatment is carried out by filtration dehydration, and the water content of the "remaining particles" is controlled to be 10%-20%; the filtration dehydration is carried out by pressure filtration or vacuum belt filtration; further natural air drying dehydration and / or drying dehydration are carried out according to the usage requirements.

[0018] Further, in Step 3, the flocculant is polyacrylamide; the filtration dehydration is carried out by pressure filtration or vacuum belt filtration, and the water content of the "stone powder particle filter cake" is controlled to be 12%-20%.

[0019] Further, in Step 4, the dry mass ratio of calcium-based bentonite, sodium-based bentonite, and nitrogen source is (2-3):(2-3):(2-6).

[0020] Further, in Step 4, the raw material of calcium-based bentonite is in fine powder form with a water content of less than 2%; the raw material of sodium-based bentonite is in fine powder form with a water content of less than 2%; the nitrogen source is urea, ammonium sulfate, or ammonium chloride.

[0021] Further, in Step 5, the dry mass ratio of the "stone powder particle filter cake" to "Mixture 1" is (2-4):(3-6).

[0022] Further, in Step 6, the water content of the "slow-release fertilizer material" is adjusted to be 4%-16% by air drying or spraying water.

[0023] Furthermore, in step 6, the molding method is extrusion granulation or extrusion granulation. When the moisture content of the "slow-release fertilizer material" is 4%-8%, extrusion granulation is performed, and when the moisture content of the "slow-release fertilizer material" is 8%-16%, extrusion granulation is performed.

[0024] The invention provides an application of high pressure roller mill iron tailings, and the high pressure roller mill iron tailings are used for collaboratively manufacturing slow-release nitrogen fertilizer and construction sand.

[0025] Compared with the prior art, the method of producing slow-release nitrogen fertilizer and construction sand by high-pressure roller grinding of iron tailings of the present invention has the following beneficial effects:

[0026] (1) The present invention classifies the HPR iron tailings, and the selected "stone powder particles" are used to manufacture slow-release nitrogen fertilizers, and the "remaining particles" are used as construction sand, so that particles of each size fraction of the HPR iron tailings can be fully utilized and give play to their respective advantages, effectively solving the problem of large-scale storage of HPR iron tailings, while generating huge economic, environmental and social benefits.

[0027] (2) The present invention selects "stone powder particles" to reduce the "stone powder" content in the construction sand, reduces the content of "harmful substances", and improves the quality of the construction sand. At the same time, the reduction of "stone powder particles" makes the construction sand easier to dehydrate, improves production efficiency, and reduces production costs.

[0028] (3) The present invention uses the selected "stone powder particles" to manufacture slow-release nitrogen fertilizer, thereby reducing the manufacturing cost of the slow-release nitrogen fertilizer.

[0029] (4) The present invention only uses polyacrylamide to flocculate and settle the "stone powder particle slurry", and the "remaining particles" do not contain flocculant components, thereby avoiding the adverse effects of the flocculant on the quality of construction sand.

[0030] (5) The present invention uses polyacrylamide to flocculate and settle the "stone powder particle slurry"; polyacrylamide is a water-soluble high molecular polymer, insoluble in most organic solvents, and has good flocculation properties. Polyacrylamide can also be used as a soil structure improver to increase the cohesion between particles on the soil surface, maintain a good soil structure, prevent soil crusting, increase soil water infiltration, prevent soil erosion, inhibit soil water evaporation, and improve rainwater utilization. It has the functions of water conservation, soil conservation, fertilizer conservation, heat preservation, and increased production; polyacrylamide can also improve the utilization rate of fertilizers and improve the ecological environment; polyacrylamide is used to flocculate and settle the "stone powder particles", so that the "stone powder particle filter cake" also contains a certain amount of polyacrylamide, which can improve the soil structure after being applied to the soil, and can also provide nitrogen and carbon nutrients for crops after degradation.

[0031] (6) The "stone powder particles" of the present invention have distinct edges and corners, irregular shapes, numerous open pores and fissures on their surfaces, and have a certain ability to adsorb nitrogen. At the same time, a large number of broken surfaces of mineral crystals contribute to the activation and release of nutrients such as silicon, iron, calcium, potassium, sulfur, and phosphorus in the "stone powder particles".

[0032] (7) The "stone powder particles" selected in the present invention have a smaller particle size, a larger specific surface area, and a stronger ability to adsorb nitrogen than the unselected "stone powder particles", and are more suitable for manufacturing slow-release nitrogen fertilizers.

[0033] (8) The present invention selects a proportional combination of "stone powder particles", calcium-based bentonite, and sodium-based bentonite, avoiding the adverse effects of excessive sodium ions on the soil caused by excessive use of sodium-based bentonite; both large and small particles are present in the mixed material and the particle size distribution is reasonable, and it will not cause adverse effects on the original soil structure.

[0034] (9) Calcium-based bentonite and sodium-based bentonite are added in proportion in the present invention. The adsorption of nitrogen by calcium-based bentonite is stronger than that of "stone powder particles", and the adsorption of nitrogen by sodium-based bentonite is stronger than that of calcium-based bentonite, enabling the prepared slow-release nitrogen fertilizer to have a stepped release ability for nitrogen, and improving the controllability of the release rate of nitrogen nutrition.

[0035] (10) The particle sizes of the ground calcium-based bentonite and sodium-based bentonite in the present invention are further reduced, increasing the specific surface areas of the calcium-based bentonite and sodium-based bentonite, enhancing the ability of the calcium-based bentonite and sodium-based bentonite to adsorb nitrogen, and at the same time, the release rate of the nitrogen nutrition adsorbed by the calcium-based bentonite and sodium-based bentonite can be adjusted by controlling the grinding fineness.

[0036] (11) In the present invention, the ground calcium-based bentonite, sodium-based bentonite, and nitrogen source are first fully mixed, and then mixed with the "stone powder particle filter cake", making the material mixing more uniform and avoiding the phenomenon of uneven material mixing caused by the agglomeration of calcium-based bentonite, sodium-based bentonite, or nitrogen source when encountering water.

[0037] (12) The particle size of the "stone powder particles" in the present invention is much larger than that of calcium-based bentonite and sodium-based bentonite; the proportional mixing of the "stone powder particles" with calcium-based bentonite and sodium-based bentonite makes the prepared "mixture 2" have an appropriate plasticity index, and the "slow-release fertilizer material" prepared after adjusting the moisture of the "mixture 2" is easy to form during the granulation process, improving the granulation efficiency and solving the problem of mutual adhesion between particles or between the particle and the granulation equipment contact surface.

[0038] (13) The "stone powder particles" of the present invention act as a hard skeleton during and after the granulation process. Their sharp edges, irregular shapes, and a large number of open pores on the surface enable them to be tightly combined with other components. The calcium-based bentonite and the sodium-based bentonite play a role in bonding the components. The combined effect of the "stone powder particles", calcium-based bentonite, and sodium-based bentonite improves the particle strength of the "high-pressure roller-milled iron tailings slow-release nitrogen fertilizer".

[0039] (14) The present invention can achieve flexible control of the nitrogen nutrient release rate by adjusting the fineness and mixing ratio of the "stone powder particles", calcium-based bentonite and sodium-based bentonite powders, selecting extrusion granulation or extrusion granulation, and adjusting the moisture content of the "slow-release fertilizer material" and the molding pressure of extrusion granulation or extrusion granulation. DETAILED DESCRIPTION

[0040] The present invention is described in detail below with reference to the embodiments.

[0041] Example 1

[0042] A method for producing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings, wherein the high-pressure roller mill iron tailings are taken from the Waitoushan Iron Mine of Benxi Iron and Steel Group, comprising the following steps:

[0043] Step 1: Add water to the high pressure roller mill iron tailings to prepare a high pressure roller mill iron tailings slurry with a mass concentration of 20%, and use the hydrocyclone method to sort the high pressure roller mill iron tailings slurry to select the "stone powder particle slurry" containing more than 80% of the total amount of "stone powder particles" in the high pressure roller mill iron tailings slurry.

[0044] Step 2: The "remaining particles" slurry not selected in step 1 is subjected to filter pressing and dehydration treatment, and the moisture content of the "remaining particles" is controlled to be 10%, and is further dried and dehydrated before being used as construction sand; the "remaining particles" not selected are a mixture of "unselected stone powder particles" and "non-stone powder particles";

[0045] Step 3: Use polyacrylamide to flocculate, settle and concentrate the "stone powder particle slurry", reuse the overflow, and perform vacuum belt filtration and dehydration on the underflow to obtain a "stone powder particle filter cake" with a moisture content of 20%, which is used to manufacture slow-release nitrogen fertilizer;

[0046] Step 4: fine powdered calcium bentonite with a moisture content of 1.5%, fine powdered sodium bentonite with a moisture content of 1.5%, and commercial urea (total nitrogen content of 45%, moisture content of 0%) were mixed in a dry weight ratio of 2.5:2.5:6 and then ground to obtain a "mixture 1";

[0047] Step 5: Fully mix the "stone powder particle filter cake" and "mixture 1" with a dry weight ratio of the two materials of 2:3 to obtain "mixture 2", the moisture content of which is 9%;

[0048] Step 6: The material ratio and moisture content of "Mixture 2" are suitable for extrusion molding, and the moisture content does not need to be adjusted to obtain "slow-release fertilizer material".

[0049] Step 7: Extrude and granulate the "slow-release fertilizer material" using a flat die granulator, and after drying and cooling, make "high-pressure roller mill iron tailing slow-release nitrogen fertilizer".

[0050] Product analysis:

[0051] Using the detection method specified in GB / T 14684-2022 "Construction Sand", the methylene blue value (MB) of the construction sand obtained by dehydrating the "remaining particles" in this application is 0.9, the stone powder content is 8%, the mica content is 0.4%, the light substance content is 0.4%, the sulfide and sulfate content (calculated by the mass of SO3) is 0.3%, the chloride content (calculated by the mass of chloride ions) is 0.006%, the soundness index - mass loss rate is 5%, the crushing index - single-stage maximum crushing index is 15%, the flaky particle content is 6%, and the apparent density is 2850 kg / m 3 , and the loose bulk density is 1710 kg / m 3 , and the porosity is 40%, meeting the technical requirements of Class I construction sand in the GB / T 14684-2022 standard.

[0052] Using the method specified in GB / T 22923-2008 "Determination Method of Nitrogen, Phosphorus and Potassium in Fertilizers by Automatic Analyzer", the total nitrogen content of the high-pressure roller mill iron tailing slow-release nitrogen fertilizer prepared in this example is 14.7%, the initial nutrient release rate is 13%, the 28-day cumulative nutrient release rate is 60%, and the 60-day cumulative nutrient release rate is 85%, achieving a good nitrogen slow-release effect.

[0053] Example 2

[0054] A method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings. The high-pressure roller mill iron tailings are taken from the Waitoushan Iron Mine of Benxi Iron and Steel Group, and the method includes the following steps:

[0055] Step 1: Add water to the high-pressure roller mill iron tailings to prepare a high-pressure roller mill iron tailing slurry with a mass concentration of 18%, and use the hydrocyclone method to separate the high-pressure roller mill iron tailing slurry to select a "stone powder particle slurry" containing more than 70% of the total amount of "stone powder particles" in the high-pressure roller mill iron tailing slurry;

[0056] Step 2: Perform vacuum belt filtration and dehydration treatment on the "remaining particle" slurry not selected in Step 1, control the moisture content of the "remaining particle" filter cake to 20%, and use it as construction sand after further natural air drying and dehydration; the "remaining particles" not selected are a mixture of "unselected stone powder particles" and "non-stone powder particles";

[0057] Step 3: The "stone powder particle slurry" is subjected to flocculation, sedimentation and concentration using polyacrylamide, the overflow is reused, and the underflow is subjected to vacuum belt filtration and dehydration to obtain a "stone powder particle filter cake" with a moisture content of 16%, which is used to manufacture slow-release nitrogen fertilizer;

[0058] Step 4: Grind fine powdered calcium bentonite with a moisture content of 1%, fine powdered sodium bentonite with a moisture content of 1%, and commercial urea (total nitrogen content of 45%, moisture content of 0%) separately, and mix them thoroughly in a dry mass ratio of 2:3:5 to obtain a "mixture 1";

[0059] Step 5: Fully mix the "stone powder particle filter cake" and "mixture 1", the dry mass ratio of the two materials is 2.5:5, and obtain "mixture 2", the moisture content of "mixture 2" is 6%;

[0060] Step 6: The material ratio and moisture content of "Mixture 2" are suitable for extrusion molding, and the moisture content does not need to be adjusted;

[0061] Step 7: The "slow-release fertilizer material" is extruded and granulated using a double-roll extrusion granulator, and after drying and cooling, it is made into "high-pressure roller-milled iron tailings slow-release nitrogen fertilizer".

[0062] Product Analysis:

[0063] Using the testing method specified in GB / T 14684-2022 "Construction Sand", the construction sand obtained by dehydrating the "residual particles" in this application has a methylene blue value (MB) of 1.1, a stone powder content of 9%, a mica content of 0.5%, a light matter content of 0.5%, a sulfide and sulfate content (measured by SO3 mass) of 0.4%, a chloride (measured by chloride ion mass) of 0.012%, a firmness index-mass loss rate of 6%, a crushing index-single-stage maximum crushing index of 21%, a flaky particle content of 7%, and an apparent density of 2800kg / m 3 , loose bulk density is 1652kg / m 3 The porosity is 41%, which meets the technical requirements for Class II construction sand in GB / T 14684-2022 standard.

[0064] By adopting the method specified in GB / T 22923-2008 "Automatic Analyzer Determination of Nitrogen, Phosphorus and Potassium in Fertilizers", the high-pressure roller-milled iron tailings slow-release nitrogen fertilizer prepared in this application has a total nitrogen content of 15%, an initial nutrient release rate of 11%, a 28-day cumulative nutrient release rate of 55%, and a 60-day cumulative nutrient release rate of 83%, achieving a very good nitrogen slow-release effect.

[0065] Example 3

[0066] A method for producing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings, wherein the high-pressure roller mill iron tailings are taken from the Waitoushan Iron Mine of Benxi Iron and Steel Group, comprising the following steps:

[0067] Step 1: adding water to the high pressure roller mill iron tailings to prepare a high pressure roller mill iron tailings slurry with a mass concentration of 18%, and separating the high pressure roller mill iron tailings slurry by a hydrocyclone method to select a "stone powder particle slurry" containing more than 60% of the total amount of "stone powder particles" in the high pressure roller mill iron tailings slurry;

[0068] Step 2: The "remaining particles" slurry not selected in step 1 is subjected to filter pressing and dehydration treatment, and the moisture content of the filter cake of the "remaining particles" is controlled to be 12%, and is further naturally air-dried and dehydrated before being used as construction sand; the "remaining particles" not selected are a mixture of "unselected stone powder particles" and "non-stone powder particles";

[0069] Step 3: Use polyacrylamide to flocculate, settle and concentrate the "stone powder particle slurry", reuse the overflow, and perform vacuum belt filtration and dehydration on the underflow to obtain a "stone powder particle filter cake" with a moisture content of 20%, which is used to manufacture slow-release nitrogen fertilizer;

[0070] Step 4: Grind fine powdered calcium bentonite with a moisture content of 1%, fine powdered sodium bentonite with a moisture content of 1%, and commercial urea (total nitrogen content of 45%, moisture content of 0%) separately, and mix them thoroughly in a dry mass ratio of 3:3:5 to obtain "mixture 1";

[0071] Step 5: Fully mix the "stone powder particle filter cake" and "mixture 1", the dry mass ratio of the two materials is 3:5, and obtain "mixture 2", the moisture content of "mixture 2" is 9%;

[0072] Step 6: Spray water on the "mixture 2" and stir it to obtain a "slow-release fertilizer material" with a moisture content of 12%;

[0073] Step 7: Use a flat die granulator to extrude and granulate the "slow-release fertilizer material", and make it into "high-pressure roller-milled iron tailings slow-release nitrogen fertilizer" after drying and cooling.

[0074] Product Analysis:

[0075] Using the testing method specified in GB / T 14684-2022 "Construction Sand", the construction sand obtained by dehydrating the "residual particles" in this application has a methylene blue value (MB) of 1.2, a stone powder content of 9.2%, a mica content of 1.2%, a light matter content of 0.6%, a sulfide and sulfate content (measured by SO3 mass) of 0.5%, a chloride (measured by chloride ion mass) of 0.014%, a firmness index-mass loss rate of 6.6%, a crushing index-single-stage maximum crushing index of 22%, a flaky particle content of 8%, and an apparent density of 2780 kg / m 3, loose bulk density is 1612kg / m 3 The porosity is 42%, which meets the technical requirements for Class II construction sand in GB / T 14684-2022 standard.

[0076] By adopting the method specified in GB / T 22923-2008 "Automatic Analyzer Determination of Nitrogen, Phosphorus and Potassium in Fertilizers", the high-pressure roller-milled iron tailings slow-release nitrogen fertilizer prepared in this application has a total nitrogen content of 12.8%, an initial nutrient release rate of 11%, a 28-day cumulative nutrient release rate of 55%, and a 60-day cumulative nutrient release rate of 84%, achieving a very good nitrogen slow-release effect.

[0077] Example 4

[0078] A method for producing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings, wherein the high-pressure roller mill iron tailings are taken from the Waitoushan Iron Mine of Benxi Iron and Steel Group, comprising the following steps:

[0079] Step 1: adding water to the high pressure roller mill iron tailings to prepare a high pressure roller mill iron tailings slurry with a mass concentration of 20%, and separating the high pressure roller mill iron tailings slurry by a hydrocyclone method to select a "stone powder particle slurry" containing more than 80% of the total amount of "stone powder particles" in the high pressure roller mill iron tailings slurry;

[0080] Step 2: The "remaining particles" slurry not selected in step 1 is subjected to vacuum belt filtration and dehydration treatment, and the moisture content of the filter cake of the "remaining particles" is controlled to be 18%, and is further naturally air-dried and dehydrated before being used as construction sand; the "remaining particles" not selected are a mixture of "unselected stone powder particles" and "non-stone powder particles";

[0081] Step 3: Use polyacrylamide to flocculate, settle and concentrate the "stone powder particle slurry", reuse the overflow, and filter press and dehydrate the underflow to obtain a "stone powder particle filter cake" with a moisture content of 12%, which is used to make slow-release nitrogen fertilizer;

[0082] Step 4: fine powdered calcium bentonite with a moisture content of 1%, fine powdered sodium bentonite with a moisture content of 1%, and commercial ammonium sulfate (total nitrogen content of 21%, moisture content of 0%) were mixed in a dry weight ratio of 2:3:5 and then ground to obtain a "mixture 1";

[0083] Step 5: Fully mix the "stone powder particle filter cake" and "mixture 1", the dry mass ratio of the two materials is 2.5:5, and obtain "mixture 2", the moisture content of "mixture 2" is 4%;

[0084] Step 6: The material ratio and moisture content of "Mixture 2" are suitable for extrusion molding, and the moisture content does not need to be adjusted;

[0085] Step 7: Extrude and granulate the "slow-release fertilizer material" using a pair-roll extrusion granulator, and after drying and cooling, produce the "high-pressure roller mill iron tailing slow-release nitrogen fertilizer".

[0086] Product analysis:

[0087] Using the detection method specified in GB / T 14684-2022 "Sand for construction", the methylene blue value (MB) of the construction sand obtained by dehydrating the "remaining particles" in this application is 0.9, the stone powder content is 8%, the mica content is 0.4%, the light material content is 0.4%, the sulfide and sulfate content (calculated by the mass of SO3) is 0.3%, the chloride content (calculated by the mass of chloride ions) is 0.006%, the soundness index - mass loss rate is 5%, the crushing index - single-stage maximum crushing index is 15%, the flaky particle content is 6%, and the apparent density is 2850 kg / m 3 , and the loose bulk density is 1710 kg / m 3 , and the porosity is 40%, meeting the technical requirements of Class I construction sand in the GB / T 14684-2022 standard.

[0088] Using the method specified in GB / T 22923-2008 "Determination method for nitrogen, phosphorus and potassium in fertilizers by automatic analyzer", the total nitrogen content of the high-pressure roller mill iron tailing slow-release nitrogen fertilizer prepared in this application is 7%, the initial nutrient release rate is 12%, the cumulative nutrient release rate in 28 days is 55%, and the cumulative nutrient release rate in 60 days is 82%, achieving a good nitrogen slow-release effect.

[0089] Example 5

[0090] A method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings. The high-pressure roller mill iron tailings are taken from the Waitoushan Iron Mine of Benxi Iron and Steel Group, and include the following steps:

[0091] Step 1: Add water to the high-pressure roller mill iron tailings to prepare a high-pressure roller mill iron tailing slurry with a mass concentration of 22%. Use the wet screening method to separate the high-pressure roller mill iron tailing slurry, and select the "stone powder particle slurry" containing more than 50% of the total amount of "stone powder particles" in the high-pressure roller mill iron tailing slurry;

[0092] Step 2: Perform vacuum belt filtration and dehydration treatment on the "remaining particle" slurry not selected in Step 1, control the moisture content of the "remaining particle" filter cake to be 14%, and use it as construction sand after further natural air-drying dehydration; the "remaining particles" not selected are a mixture of "unselected stone powder particles" and "non-stone powder particles";

[0093] Step 3: Use polyacrylamide for flocculation, sedimentation and concentration of the "stone powder particle slurry", recycle the overflow, and perform pressure filtration and dehydration on the underflow to obtain a "stone powder particle filter cake" with a moisture content of 16% for manufacturing slow-release nitrogen fertilizer;

[0094] Step 4: fine powdered calcium bentonite with a moisture content of 1%, fine powdered sodium bentonite with a moisture content of 1%, and commercial ammonium sulfate (total nitrogen content of 21%, moisture content of 0) were mixed in a dry weight ratio of 2:2:6 and then ground to obtain a "mixture 1";

[0095] Step 5: Fully mix the "stone powder particle filter cake" and "mixture 1", the dry mass ratio of the two materials is 2:6, and obtain "mixture 2", the moisture content of "mixture 2" is 5%;

[0096] Step 6: The material ratio and moisture content of "Mixture 2" are suitable for extrusion molding, and the moisture content does not need to be adjusted;

[0097] Step 7: The "slow-release fertilizer material" is extruded and granulated using a double-roll extrusion granulator, and after drying and cooling, it is made into "high-pressure roller-milled iron tailings slow-release nitrogen fertilizer".

[0098] Product Analysis:

[0099] Using the testing method specified in GB / T 14684-2022 "Construction Sand", the construction sand obtained by dehydrating the "residual particles" in this application has a methylene blue value (MB) of 1.3, a stone powder content of 12%, a mica content of 1.6%, a light matter content of 0.6%, a sulfide and sulfate content (measured by SO3 mass) of 0.4%, a chloride (measured by chloride ion mass) of 0.016%, a firmness index-mass loss rate of 9%, a crushing index-single-stage maximum crushing index of 26%, a flaky particle content of 9%, and an apparent density of 2770 kg / m 3 , loose bulk density is 1579kg / m 3 The porosity is 43%, which meets the technical requirements for Class III construction sand in GB / T 14684-2022 standard.

[0100] By adopting the method specified in GB / T 22923-2008 "Automatic Analyzer Determination of Nitrogen, Phosphorus and Potassium in Fertilizers", the high-pressure roller-milled iron tailings slow-release nitrogen fertilizer prepared in this application has a total nitrogen content of 9.5%, an initial nutrient release rate of 14%, a 28-day cumulative nutrient release rate of 70%, and a 60-day cumulative nutrient release rate of 85%, achieving a very good nitrogen slow-release effect.

[0101] Example 6

[0102] A method for producing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings, wherein the high-pressure roller mill iron tailings are taken from the Waitoushan Iron Mine of Benxi Iron and Steel Group, comprising the following steps:

[0103] Step 1: adding water to the high pressure roller mill iron tailings to prepare a high pressure roller mill iron tailings slurry with a mass concentration of 18%, and separating the high pressure roller mill iron tailings slurry by a hydrocyclone method to select a "stone powder particle slurry" containing more than 70% of the total amount of "stone powder particles" in the high pressure roller mill iron tailings slurry;

[0104] Step 2: The "remaining particles" slurry not selected in step 1 is subjected to filter pressing and dehydration treatment, and the moisture content of the "remaining particles" filter cake is controlled to be 14%. After further natural air drying and dehydration, it is used as construction sand. The "remaining particles" not selected are a mixture of "unselected stone powder particles" and "non-stone powder particles";

[0105] Step 3: The "stone powder particle slurry" is subjected to flocculation, sedimentation and concentration using polyacrylamide, the overflow is reused, and the underflow is subjected to vacuum belt filtration and dehydration to obtain a "stone powder particle filter cake" with a moisture content of 16%, which is used to manufacture slow-release nitrogen fertilizer;

[0106] Step 4: Grind fine powdered calcium bentonite with a moisture content of 1%, fine powdered sodium bentonite with a moisture content of 1%, and commercial ammonium chloride (total nitrogen content of 24%, moisture content of 0%) separately, and mix them thoroughly in a dry mass ratio of 2:3:5 to obtain a "mixture 1";

[0107] Step 5: Fully mix the "stone powder particle filter cake" and "mixture 1", the dry mass ratio of the two materials is 2.5:5, and obtain "mixture 2", the moisture content of "mixture 2" is 6%;

[0108] Step 6: The material ratio and moisture content of "Mixture 2" are suitable for extrusion molding, and the moisture content does not need to be adjusted;

[0109] Step 7: The "slow-release fertilizer material" is extruded and granulated using a double-roll extrusion granulator, and after drying and cooling, it is made into "high-pressure roller-milled iron tailings slow-release nitrogen fertilizer".

[0110] Product Analysis:

[0111] Using the testing method specified in GB / T 14684-2022 "Construction Sand", the construction sand obtained by dehydrating the "residual particles" in this application has a methylene blue value (MB) of 1.1, a stone powder content of 9%, a mica content of 0.5%, a light matter content of 0.5%, a sulfide and sulfate content (measured by SO3 mass) of 0.4%, a chloride (measured by chloride ion mass) of 0.012%, a firmness index-mass loss rate of 6%, a crushing index-single-stage maximum crushing index of 21%, a flaky particle content of 7%, and an apparent density of 2800kg / m 3 , loose bulk density is 1652kg / m 3 The porosity is 41%, which meets the technical requirements for Class II construction sand in GB / T 14684-2022 standard.

[0112] By adopting the method specified in GB / T 22923-2008 "Automatic Analyzer Determination of Nitrogen, Phosphorus and Potassium in Fertilizers", the high-pressure roller-milled iron tailings slow-release nitrogen fertilizer prepared in this application has a total nitrogen content of 8%, an initial nutrient release rate of 11%, a 28-day cumulative nutrient release rate of 55%, and a 60-day cumulative nutrient release rate of 83%, achieving a very good nitrogen slow-release effect.

[0113] Example 7

[0114] A method for producing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings, wherein the high-pressure roller mill iron tailings are taken from the Waitoushan Iron Mine of Benxi Iron and Steel Group, comprising the following steps:

[0115] Step 1: adding water to the high pressure roller mill iron tailings to prepare a high pressure roller mill iron tailings slurry with a mass concentration of 16%, and separating the high pressure roller mill iron tailings slurry by a hydrocyclone method to select a "stone powder particle slurry" containing more than 70% of the total amount of "stone powder particles" in the high pressure roller mill iron tailings slurry;

[0116] Step 2: The "remaining particles" slurry not selected in step 1 is subjected to filter pressing and dehydration treatment, and the moisture content of the "remaining particles" filter cake is controlled to be 12%. After further natural air drying and dehydration, it is used as construction sand. The "remaining particles" not selected are a mixture of "unselected stone powder particles" and "non-stone powder particles";

[0117] Step 3: The "stone powder particle slurry" is subjected to flocculation, sedimentation and concentration using polyacrylamide, the overflow is reused, and the underflow is subjected to vacuum belt filtration and dehydration to obtain a "stone powder particle filter cake" with a moisture content of 16%, which is used to manufacture slow-release nitrogen fertilizer;

[0118] Step 4: Grind fine powdered calcium bentonite with a moisture content of 1%, fine powdered sodium bentonite with a moisture content of 1%, and commercial urea (total nitrogen content of 45%, moisture content of 0%) separately, and mix them thoroughly at a dry mass ratio of 2:2:2 to obtain "mixture 1";

[0119] Step 5: Fully mix the "stone powder particle filter cake" and "mixture 1" with a dry weight ratio of the two materials of 4:5 to obtain "mixture 2", the moisture content of which is 7.8%;

[0120] Step 6: The material ratio and moisture content of "Mixture 2" are suitable for extrusion molding, and the moisture content does not need to be adjusted;

[0121] Step 7: The "slow-release fertilizer material" is extruded and granulated using a double-roll extrusion granulator, and after drying and cooling, it is made into "high-pressure roller-milled iron tailings slow-release nitrogen fertilizer".

[0122] Product Analysis:

[0123] Using the testing methods specified in GB / T 14684-2022 "Sand for construction", the methylene blue value (MB) of the construction sand obtained by dehydrating the "remaining particles" in this application is 1.1, the stone powder content is 9%, the mica content is 0.5%, the light substance content is 0.5%, the sulfide and sulfate content (calculated by the mass of SO3) is 0.4%, the chloride content (calculated by the mass of chloride ions) is 0.012%, the soundness index - mass loss rate is 6%, the crushing index - single-stage maximum crushing index is 21%, the flaky particle content is 7%, and the apparent density is 2800 kg / m 3 , and the loose bulk density is 1652 kg / m 3 , and the porosity is 41%, meeting the technical requirements of Class II construction sand in the GB / T 14684-2022 standard.

[0124] Using the method specified in GB / T 22923-2008 "Determination method of nitrogen, phosphorus and potassium in fertilizers by automatic analyzer", the total nitrogen content of the high-pressure roller mill iron tailing slow-release nitrogen fertilizer prepared in this application is 8.3%, the initial nutrient release rate is 10%, the 28-day cumulative nutrient release rate is 49%, and the 60-day cumulative nutrient release rate is 80%, achieving a good nitrogen slow-release effect.

[0125] The above are only some embodiments of the present invention, and do not impose any formal limitations on the present invention. Any person skilled in the art, without departing from the scope of the technical solution of the present invention, can make many possible changes and modifications to the technical solution of the present invention by using the disclosed method content, and all belong to the scope of protection of the present invention.

Claims

1. A method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings, characterized in that, It includes the following steps: Step 1: Add water to the high-pressure roller mill iron tailings to prepare a high-pressure roller mill iron tailings slurry, and separate the high-pressure roller mill iron tailings slurry to select a stone powder particle slurry containing more than 50% of the total amount of stone powder particles in the high-pressure roller mill iron tailings slurry; Step 2: Dehydrate the remaining particle slurry not selected in Step 1 and use it as construction sand; the remaining particles not selected are a mixture of unselected stone powder particles and non-stone powder particles; Step 3: Flocculate, settle and concentrate the stone powder particle slurry, recycle the overflow, filter and dehydrate the underflow to obtain a stone powder particle filter cake for manufacturing slow-release nitrogen fertilizer; Step 4: Grind and fully mix calcium-based bentonite, sodium-based bentonite and nitrogen source in a dry state to obtain Mixture 1; Step 5: Fully mix the stone powder particle filter cake with Mixture 1 to obtain Mixture 2; Step 6: Determine the forming method according to the material ratio and water content of Mixture 2, and adjust the water content of Mixture 2 according to the water content applicable to the forming method to obtain slow-release fertilizer materials; Step 7: Granulate, dry and cool the slow-release fertilizer materials to obtain high-pressure roller mill iron tailings slow-release nitrogen fertilizer.

2. The method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller milled iron tailings as claimed in claim 1, wherein, In Step 1, the mass concentration of the high-pressure roller mill iron tailings slurry is 16%-22%, and the separation is carried out by the hydrocyclone method or the wet screening method.

3. The method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller milled iron tailings according to claim 1, characterized in that, In Step 2, the dehydration treatment is carried out by filtration dehydration, and the water content of the remaining particles is controlled at 10%-20%; the filtration dehydration is carried out by pressure filtration or vacuum belt filtration; further natural air drying dehydration and / or drying dehydration are carried out according to the use requirements.

4. The method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roll-milled iron tailings as claimed in claim 1, wherein, In Step 3, the flocculant is polyacrylamide; the filtration dehydration is carried out by pressure filtration or vacuum belt filtration, and the water content of the stone powder particle filter cake is controlled at 12%-20%.

5. The method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller milled iron tailings as claimed in claim 1, wherein, In Step 4, the dry mass ratio of calcium-based bentonite, sodium-based bentonite and nitrogen source is (2-3):(2-3):(2-6).

6. The method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings according to claim 1, characterized in that, In Step 4, the raw material of calcium-based bentonite is in fine powder form with a water content of less than 2%; the raw material of sodium-based bentonite is in fine powder form with a water content of less than 2%; the nitrogen source is urea, ammonium sulfate or ammonium chloride.

7. The method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings according to claim 1, characterized in that In Step 5, the dry mass ratio of the stone powder particle filter cake to Mixture 1 is (2-4):(3-6).

8. The method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller milled iron tailings as claimed in claim 1, wherein, In Step 6, the water content of the slow-release fertilizer materials is adjusted to 4%-16% by air drying or spraying water.

9. The method for manufacturing slow-release nitrogen fertilizer and construction sand from high-pressure roller mill iron tailings according to claim 1, characterized in that, In Step 6, the forming method is extrusion granulation or extrusion molding. When the water content of the slow-release fertilizer materials is 4%-8%, extrusion granulation is carried out. When the water content of the slow-release fertilizer materials is 8%-16%, extrusion molding is carried out.

10. Application of high-pressure roller mill iron tailings, characterized in that, Use the high-pressure roller mill iron tailings to cooperate in manufacturing slow-release nitrogen fertilizer and construction sand.