CN109134154B

CN109134154B - Red mud silicon calcium potassium fertilizer and preparation method thereof

Info

Publication number: CN109134154B
Application number: CN201811312551.6A
Authority: CN
Inventors: 张健伟; 甘可; 冷杰彬
Original assignee: China Nonferrous Metal Guilin Geology and Mining Co Ltd
Current assignee: China Nonferrous Metal Guilin Geology and Mining Co Ltd
Priority date: 2018-11-06
Filing date: 2018-11-06
Publication date: 2021-08-10
Anticipated expiration: 2038-11-06
Also published as: CN109134154A

Abstract

The invention discloses a red mud silicon calcium potassium fertilizer and a preparation method thereof. The preparation method of the red mud silicon calcium potassium fertilizer comprises the following steps: 1) weighing 20-50% of red mud, 30-60% of fly ash and 5-30% of desulphurization slag according to the mass percentage, and uniformly mixing to obtain a mixture; 2) weighing potassium hydroxide which accounts for 2-30% of the mass of the mixture, preparing a solution by taking water as a solvent, adding the solution into the mixture, uniformly mixing, and granulating the obtained material to obtain a granular material; 3) placing the obtained granules in dry powder to make the granules fully contact with the dry powder, and coating a layer of dry powder on the surfaces of the granules to obtain the granules after powder makeup; 4) roasting the obtained powdery granule at a temperature of more than or equal to 450 ℃, and cooling after roasting is finished to obtain the powdery cosmetic. The method is simple and easy to control, the cost is low, and the prepared red mud silicon calcium potassium fertilizer has low free sodium content and high restricted solubility silicon content.

Description

Red mud silicon calcium potassium fertilizer and preparation method thereof

Technical Field

The invention relates to a red mud silicon calcium potassium fertilizer and a preparation method thereof, belonging to the field of comprehensive utilization of solid wastes.

Background

Aluminum metal is widely used due to its light weight, good electrical and thermal conductivity, high reflectivity, and oxidation resistance, and its yield is second only to steel and occupies the first place of non-ferrous metal yield. The yield of the aluminum oxide serving as the aluminum metal raw material is continuously innovative and high in recent years, according to the commercial power network, the daily average yield of the global aluminum oxide is about 33 ten thousand tons basically in 2018, wherein the yield of the aluminum oxide reaches 590 ten thousand tons in 2018 and stably stays at the first global position in China.

Red mud is known for its red-like character. Alumina production enterprises usually produce alumina by using Bayer process, sintering process or combination process, but no matter which process is used for producing alumina, red mud, fly ash, desulphurization slag and other solid waste residues are discharged, and 0.7-1.7 tons of red mud is discharged when 1 ton of alumina is produced. The existing red mud treatment method is usually to build an open warehouse for stockpiling, and a small part of enterprises adopt a sea drainage mode to treat the red mud. The red mud has fine particles and high alkali content (wherein Na)₂O+K₂2-9%) and the radioactivity of most of red mud is obviously much higher than that of raw ore, such as red mud of three main alumina production enterprises in China monitored by Queenshang²²⁶Ra、²³²Th and⁴⁰the average specific activity of K is 477Bq/Kg, 705Bq/Kg and 153Bq/Kg, and the specific activity values of Th, K and Ra are 28 times, 3.06 times and 2.49 times of the typical value of world soil (red mud and red mud water)Radioactivity levels of mud and their dose to the public, "environmental sciences" (J)1992, phase 5). Therefore, the stockpiling of the red mud not only needs expensive warehouse construction cost and management cost, but also has high free sodium content and high radioactive element content and has great potential harm to the ecological environment.

The problem of the red mud has already attracted the attention of governments and technical workers in various countries, and since the last 50 century, many researches on the comprehensive utilization of the red mud have been carried out at home and abroad, and various ways and methods for the comprehensive utilization of the red mud are provided. In 2010, China has called up the national field technical exchange for the comprehensive utilization of alumina red mud, and has come out of the instructional document "red mud comprehensive utilization guidance opinions" which promotes the comprehensive utilization of red mud in China; in 2011, 12 months, the national development and reform Commission organization compiles a large solid waste comprehensive utilization embodiment, and plans to 2015, so that the comprehensive utilization rate of smelting slag (containing red mud) is improved to 70%; in the implementation scheme of important resource recycling engineering (technical popularization and equipment industrialization) jointly issued by ministerial committees such as the 2014 reform committee and the financial department (the development and modification ring fundation No. 2014 3052), red mud is specially listed in key tasks and fields, and key technologies and equipment research and development (including research and development of red mud low-cost dealkalization technology, high-iron red mud and red mud iron concentrate deep iron selection technology and the like) supporting red mud utilization, advanced technologies and equipment popularization (including red mud cemented filling technology, red mud preparation novel coal desulfurizer technology, red mud preparation industrial kiln refractory heat-insulating material technology and the like) are supported. However, the existing comprehensive utilization technology of red mud has the defects of high cost, complex process, poor economic benefit or unstable product quality, and the like, for example, when the red mud is used as a building material, because the radioactive internal irradiation index and the radioactive external irradiation index of the red mud both exceed the radioactive nuclide limit (GB6566-2001) requirement of the building material, the addition amount of the red mud usually cannot exceed 30%, and meanwhile, because of the high alkali content, the phenomena of blooming, strength reduction and the like appear in the later period of the product, the technology of using the red mud as the building material is difficult to popularize. Until now, the large-scale utilization of the red mud is not realized in the world, the comprehensive utilization rate of the red mud is still below 10%, and the problems of comprehensive utilization and resource utilization of the red mud are still difficult in the world.

The existing research shows that the biochemical action of the silicon element on crops is only second to that of nitrogen, phosphorus and potassium, and the silicon element is confirmed as the fourth plant nutrient element following nitrogen, phosphorus and potassium by the international soil academy. After the silicon fertilizer is applied to the soil, the effects of lodging resistance, drought resistance, disease and pest resistance and the like of crops can be enhanced. However, according to the investigation of the nineties of the last century, 60% of cultivated land in China is lack of silicon, and 70% of soil in Yangtze river basin is lack of silicon, with the development of agriculture in recent years, crops have continuous high yield, the content of effective silicon in soil is reduced, and the content of effective silicon in soil needs to be supplemented urgently. On the other hand, the red mud, the fly ash and the desulphurization slag contain higher content of silicon, iron, calcium and other elements required by plant growth, the content of heavy metals is low, the leaching mass concentration of the heavy metals is lower than the standard limit value of hazardous wastes, and the heavy metals of the red mud, the fly ash and the desulphurization slag are applied to soil and cannot endanger the health of human beings through a food chain. Although the test of using the red mud and the fly ash as the silicon fertilizer respectively has been used, the test does not achieve the expected effect, but the reason for the effect is that most of silicon in the red mud and the fly ash is vitreous and mineral silicon, and the content of effective silicon absorbed by plants is very low, such as SiO in the fly ash component₂Up to 50-60%, but the effective silicon absorbed by the plant is only 1-2%. Therefore, the problem that mineral state and glass state silicon in the red mud and the fly ash are converted into the dissolution silicon must be solved firstly when the red mud and the fly ash are used as silicon fertilizers, and the problem that the content of free sodium in the red mud is high must be solved secondly.

Disclosure of Invention

The invention aims to solve the technical problem of providing the red mud silicon calcium potassium fertilizer which has low free sodium content, high restricted solubility silicon content and low production cost and the preparation method thereof.

In order to solve the technical problems, the preparation method of the red mud silicon calcium potassium fertilizer comprises the following steps:

1) weighing 20-50% of red mud, 30-60% of fly ash and 5-30% of desulphurization slag according to the mass percentage, and uniformly mixing to obtain a mixture;

2) weighing potassium hydroxide which accounts for 2-30% of the mass of the mixture, preparing a solution by taking water as a solvent, adding the solution into the mixture, uniformly mixing, and granulating the obtained material to obtain a mixed material granule;

3) placing the obtained granules in dry powder to make the granules fully contact with the dry powder, and coating a layer of dry powder on the surfaces of the granules to obtain the granules after powder makeup; wherein the dry powder is red mud and/or fly ash, or a composition of red mud, fly ash and desulphurization slag;

4) roasting the obtained powdery granules at the temperature of more than or equal to 450 ℃, and cooling after roasting to obtain the red mud silicon calcium potassium fertilizer.

In the preparation method, the red mud, the fly ash and the desulfurization slag are solid wastes generated in the process of preparing the alumina, the granularity of the red mud, the fly ash and the desulfurization slag before use preferably meets the condition that-200 meshes in the materials account for 70-90 percent of the total amount, and the red mud, the fly ash and the desulfurization slag are dried before use.

In step 2) of the preparation method, the potassium hydroxide aqueous solution plays a role of a binder, and when the potassium hydroxide aqueous solution is prepared, the amount of water can be determined according to needs, and is preferably 20-30% of the mass of the mixture. In this step, the amount of potassium hydroxide is more preferably 8% to 20% of the mass of the mixture. During granulation, spherical or cylindrical or other irregular particles can be prepared according to the requirement, and when the particles are spherical or cylindrical, the diameter of the particles is preferably 2 mm-20 mm.

In the step 3) of the preparation method, when the dry powder is a composition of red mud, fly ash and desulfurized slag, the dry powder is preferably prepared according to the composition in the step 1).

In the step 4) of the preparation method, the sintering time (i.e. the holding time after reaching the set temperature) of the roasting is usually more than or equal to 10 min. The calcination is preferably carried out at 500 to 950 ℃, more preferably at 500 to 700 ℃, and in this case, the calcination time is preferably 15 to 50min, more preferably 15 to 30 min.

In the preparation method, after roasting and cooling, the cooled material is further crushed and subpackaged for the convenience of subsequent use, wherein the crushed material preferably accounts for more than 80 percent of the total amount by-250 microns according to the requirement of national standard silicon fertilizer granularity, and the crushing operation is preferably carried out in a dry crusher; the specification of the subpackage can be determined according to the requirement, and the crushed red mud silicon calcium potassium fertilizer is usually packaged by a composite plastic woven bag or a plastic woven bag lined with a polyethylene film, and the specification can be 5 Kg/bag, 10 Kg/bag, 25 Kg/bag or 50 Kg/bag according to the net weight.

The invention also discloses the red mud silicon calcium potassium fertilizer prepared by the method.

Compared with the prior art, the invention is characterized in that:

1) the raw materials are all solid wastes generated in the process of producing alumina, and except that the fly ash has certain market price, the red mud and the desulphurization slag also need to pay the warehouse construction cost, the warehouse storage management cost and the like of the warehouse storage at present, so the cost of the raw materials is extremely low and can be almost ignored;

2) utilizing free alkali (Na) in red mud₂O、K₂O) is used as a fluxing agent, red mud dealkalization treatment is not needed in the manufacturing process, and the cost expenditure for roasting the fluxing agent is saved;

3) the red mud, the fly ash and the desulphurization slag generated in the process of producing alumina have very fine granularity, for example, the red mud-200 meshes generated by the Bayer process in the plain alumina plant are about 90 percent, and the fired finished product is a loose porous block, so the energy consumption of crushing (fine grinding) is low; on the other hand, the red mud contains certain alkaline substances, and the fine grinding and dust-raising capability is low; the whole manufacturing process does not produce waste residue and waste water, and has the characteristics of energy conservation and environmental protection;

4) after granulation, a layer of dry powder is directly coated on the surface of the granules without drying, so that the drying process and the cost of the blank are saved, and the purposes of simplifying the process and reducing the cost are achieved; on the other hand, the obtained particle material after powder making up effectively avoids the problem that KOH exposes and corrodes a kiln, so that the particle material after powder making up can be placed in a conventional roasting furnace to finish roasting operation without a special kiln, and the production cost is further reduced;

5) the roasting is carried out under the condition of relatively low medium temperature, the time is shorter, and the method has the obvious advantage of low energy consumption;

6) the red mud silicon-calcium-potassium fertilizer prepared by the method has high content of limited soluble silicon and low content of free sodium, wherein the content of limited soluble silicon dioxide is more than or equal to 15 percent, the content of potassium oxide is more than or equal to 5 percent, the content of calcium oxide is more than or equal to 20 percent, the content of free sodium is reduced by more than 50 percent compared with the content of the original red mud, and the red mud silicon-calcium-potassium multi-element fertilizer can be used as a silicon-calcium-potassium multi-element compound fertilizer for plant growth, and can adjust the acidity of acid soil due to the alkalinity (the pH value is 9-12).

7) By popularizing and using the method, the purposes of greatly absorbing and quickly recycling the red mud can be achieved, and economic benefits and environmental ecological benefits of agriculture and forestry are created at the same time.

Drawings

FIG. 1 is an X-ray diffraction pattern of a final product obtained in example 1 of the present invention;

FIG. 2 is an X-ray diffraction pattern of a final product obtained in example 2 of the present invention;

FIG. 3 is an X-ray diffraction pattern of the final product obtained in example 3 of the present invention.

Detailed Description

The present invention will be better understood from the following detailed description of specific examples, which should not be construed as limiting the scope of the present invention.

In the following examples, the red mud, fly ash and desulfurized slag used in examples 1 to 4 are solid wastes generated in the production of alumina by alumina plants of Guangxi aluminum division, Middling aluminum, wherein the red mud is Bayer process red mud; the red mud used in examples 5 to 6 was the red mud from the sintering process discharged from alumina plants of Guizhou division, Middling aluminum, and the fly ash and the desulfurized slag were still produced from alumina plants of Guangxi aluminum division, Middling aluminum. They were analyzed and the results were as follows:

bayer process red mud: the granularity is less than or equal to 0.02mm and accounts for 72.8 percent, wherein the granularity is less than or equal to 0.002mm and accounts for 24.05 percent, the inter-granular pores are small, the viscoplasticity is strong, the hardening is easy, and the physical property is very close to that of silt clay soil. The mineral types mainly comprise hydrated garnet, cancrinite, perovskite, hematite, calcite, calcium aluminum garnet, goethite, calcium iron ore, calcium hydroxide stone, diaspore and the like. The results of analyzing the main chemical components are shown in table 1 below. The component analysis result shows that the red mud component has the characteristics of low potassium, low silicon and high sodium relatively.

TABLE 1 Multi-element chemical analysis results of Bayer process red mud

Composition (I)	Fe₂O₃	CaO	Na₂O	Al₂O₃	SiO₂	K₂O
							Content (%)	28.83	14.55	5.09	23.48	10.41	0.11

Sintering red mud: the red mud discharged from the alumina plant 2009 from the aluminum industry division, Guizhou, aluminum stocks, was consolidated into blocks during the test. The analysis of the main chemical components is shown in the following table 2. The component analysis result shows that the red mud component has the characteristics of high silicon and high calcium relatively.

TABLE 2 Multi-element chemical analysis results of sintering process red mud

Composition (I)	Fe₂O₃	CaO	Na₂O	Al₂O₃	SiO₂	K₂O
							Content (%)	9.87	40.97	3.13	7.91	21.47	0.84

The particle size of the fly ash is-200 meshes, the particle size of the desulphurization slag is-200 meshes, and the analysis results of the main chemical components of the fly ash and the desulphurization slag are shown in the following table 3:

TABLE 3 analysis results of main components of fly ash and desulfurized fly ash

Example 1

1) According to the proportion of 27%: 53%: weighing 20% of red mud, fly ash and desulfurization slag by mass percent, and uniformly mixing to obtain a mixture;

2) weighing potassium hydroxide which accounts for 8% of the mass of the mixture, dissolving the potassium hydroxide in water which accounts for 20% of the mass of the mixture, adding the obtained potassium hydroxide solution into the mixture obtained in the step 1), uniformly mixing, and granulating the obtained material (the manufactured granules are cylindrical, the thickness of the granules is 3mm, and the diameter of the granules is 1cm) to obtain granules;

3) placing the obtained granules into dry powder (comprising 27% of red mud, 53% of fly ash and 20% of desulfurized slag by mass percent) to ensure that the granules are fully contacted with the dry powder, and coating a layer of dry powder on the surfaces of the granules to obtain the powdered granules;

4) and placing the particle material after powder making up in a ceramic crucible, then placing the ceramic crucible in a muffle furnace for roasting, setting the highest furnace temperature to 600 ℃, then preserving the temperature for 30min after the temperature reaches 600 ℃, and naturally cooling to obtain the red mud silicon calcium potassium fertilizer.

The red mud silicon calcium potassium fertilizer prepared by the embodiment is a loose porous block and is not adhered to a crucible. The weight is not damaged before and after the ceramic crucible is sintered, and the inner wall is not damaged by naked eyes.

The red mud silicon calcium potassium fertilizer prepared by the embodiment is tested by an X-powder crystal diffractometer of the institute of geoscience and information physics of the university of the middle and south China, and the obtained X-ray diffraction pattern is shown in figure 1. And (3) map display: mainly amorphous phase, only a small amount of crystallization. Less than 20% crystalline phases, the main crystalline phases being calcite (about 5%), hematite (8%) and a small amount of quartz (about 3%), ilmenite (less than 1%), mullite (less than 1%) and feldspar (less than 1%).

The red mud silicon calcium potassium fertilizer prepared by the embodiment is tested by key laboratories for investigation of hidden metal mineral products in Guangxi province of Guilin Ringji university, and the content of sodium oxide, the content of silicon dioxide, the content of calcium oxide and the content of potassium oxide dissolved in 0.5mol/L hydrochloric acid solution are respectively 1.82%, 15.0%, 20.02% and 6.14%.

Example 2

1) According to the proportion of 25%: 50%: weighing 25% of red mud, fly ash and desulfurization slag by mass percent, and uniformly mixing to obtain a mixture;

2) weighing potassium hydroxide which accounts for 15% of the mass of the mixture, dissolving the potassium hydroxide in water which accounts for 20% of the mass of the mixture, adding the obtained potassium hydroxide solution into the mixture obtained in the step 1), uniformly mixing, and granulating the obtained material (the manufactured granules are cylindrical, the thickness of the granules is 3mm, and the diameter of the granules is 1cm) to obtain granules;

3) placing the obtained granules in dry powder (fly ash) to make the granules fully contact with the dry powder, and coating a layer of dry powder on the surfaces of the granules to obtain the granules after powder makeup;

The red mud silicon calcium potassium fertilizer prepared by the embodiment is tested by an X-powder crystal diffractometer of the institute of geoscience and information physics of the university of the middle and south China, and the obtained X-ray diffraction pattern is shown in figure 2. And (3) map display: mainly amorphous phase, only a small amount of crystallization. Less than 20% crystalline phases, with the major crystalline phases being calcite (about 5%), hematite (8%) and small amounts of quartz (< 1%), ilmenite (less than 1%), mullite (less than 1%).

The red mud silicon calcium potassium fertilizer prepared by the embodiment is tested by key laboratories for investigation of hidden metal mineral products in Guangxi of Guilin university, and the content of silicon dioxide and the content of sodium oxide dissolved in 0.5mol/L hydrochloric acid solution are 20.6% and 1.32%.

Example 3

2) weighing potassium hydroxide which accounts for 20% of the mass of the mixture, dissolving the potassium hydroxide in water which accounts for 20% of the mass of the mixture, adding the obtained potassium hydroxide solution into the mixture obtained in the step 1), uniformly mixing, and placing the obtained material in a granulator for granulation (the prepared granules are cylindrical, have the thickness of 3mm and the diameter of 1cm) to obtain granules;

4) and placing the particle material after powder making up in a ceramic crucible, then placing the ceramic crucible in a muffle furnace for roasting, setting the highest furnace temperature to 700 ℃, keeping the temperature for 30min after the temperature reaches 700 ℃, and naturally cooling to obtain the red mud silicon calcium potassium fertilizer.

The red mud silicon calcium potassium fertilizer obtained in the embodiment is tested by an X-powder diffractometer of the institute of geoscience and information physics of the university of the middle and south China, and the diffraction of an obtained X-ray spectrum is shown in figure 3. And (3) map display: mainly amorphous phase, with less than 30% crystalline phase. The predominant crystalline phase was Megakalsilite (about 15%, a mineral-like substance of kalsilite, composition KAlSiO₄) Calcite (about 5%), hematite (8%) and mullite (less than 1%).

The red mud silicon calcium potassium fertilizer obtained in the embodiment is tested by key laboratories for investigation of Guangxi concealed metal mineral products of Guilin Ringji university, and the content of silicon dioxide and the content of sodium oxide dissolved in 0.5mol/L hydrochloric acid solution are 26.0% and 1.69%.

Example 4

2) weighing potassium hydroxide which accounts for 8% of the mass of the mixture, dissolving the potassium hydroxide in water which accounts for 25% of the mass of the mixture, adding the obtained potassium hydroxide solution into the mixture obtained in the step 1), uniformly mixing, and placing the obtained material in a granulator for granulation (the granules are cylinders with the diameter of 5mm and the length of 5 mm-1.5 mm) to obtain granules;

3) the obtained granular material is put into dry powder (30 percent of red mud and fly ash: 70 percent of the mass percentage) of the granular material and the dry powder are fully contacted, so that a layer of dry powder is coated on the surface of the granular material to obtain the powdery granular material;

4) and placing the particle material after powder making up in a ceramic crucible, then placing the ceramic crucible in a muffle furnace for roasting, setting the furnace temperature to be 500 ℃ at most, keeping the temperature for 40min when the temperature reaches 500 ℃, and naturally cooling to obtain the red mud silicon calcium potassium fertilizer.

The red mud silicon calcium potassium fertilizer prepared by the embodiment is tested by key laboratories for investigation of hidden metal mineral products in Guangxi of Guilin university, and the content of silicon dioxide and the content of sodium oxide dissolved in 0.5mol/L hydrochloric acid solution are 20.2% and 1.81%.

Example 5

1) According to the proportion of 50%: 38%: weighing 12% of red mud, fly ash and desulfurization slag by mass percent, and uniformly mixing to obtain a mixture;

2) weighing potassium hydroxide which accounts for 2% of the mass of the mixture, dissolving the potassium hydroxide in water which accounts for 20% of the mass of the mixture, adding the obtained potassium hydroxide solution into the mixture obtained in the step 1), uniformly mixing, and placing the obtained material in a granulator for granulation (the granules are spherical) to obtain granules;

3) the obtained granular material is put into dry powder (50% of red mud and fly ash: 50 percent of the components by mass) to make the granular materials fully contact with the dry powder, so that a layer of the red mud dry powder is coated on the surface of the granular materials to obtain the powdered granular materials;

4) and placing the particle material after powder making up in a ceramic crucible, then placing in a muffle furnace, heating to 950 ℃, roasting for 20min, taking out, and cooling to obtain the red mud silicon calcium potassium fertilizer.

The red mud silicon calcium potassium fertilizer prepared by the embodiment is tested by key laboratories for investigation of hidden metal mineral products in Guangxi of Guilin Ringji university, and the content of silicon dioxide dissolved in 0.5mol/L hydrochloric acid solution is 23.2%.

Example 6

1) According to 35%: 60%: weighing 5% of red mud, fly ash and desulfurization slag by mass percent, and uniformly mixing to obtain a mixture;

2) weighing potassium hydroxide which accounts for 30% of the mass of the mixture, dissolving the potassium hydroxide in water which accounts for 30% of the mass of the mixture, adding the obtained potassium hydroxide solution into the mixture obtained in the step 1), uniformly mixing, and placing the obtained material in a granulator for granulation (the granules are spherical) to obtain granules;

4) and placing the particle material after powder making up in a ceramic crucible, then placing in a muffle furnace, heating to 450 ℃, roasting for 10min, and naturally cooling to obtain the red mud silicon calcium potassium fertilizer.

The red mud silicon calcium potassium fertilizer prepared by the embodiment is tested by key laboratories for investigation of hidden metal mineral products in Guangxi of Guilin Ringji university, and the content of silicon dioxide dissolved in 0.5mol/L hydrochloric acid solution is 20.6%.

Claims

1. A preparation method of a red mud silicon calcium potassium fertilizer comprises the following steps:

2) weighing potassium hydroxide which accounts for 2-30% of the mass of the mixture, preparing a solution by taking water as a solvent, adding the solution into the mixture obtained in the step 1), uniformly mixing, and granulating the obtained material to obtain a granular material;

2. The method of claim 1, wherein: in the step 2), when preparing the potassium hydroxide solution, the using amount of water is 20-30% of the mass of the mixture.

3. The method of claim 1, wherein: in the step 4), the sintering time during the sintering is more than or equal to 10 min.

4. The production method according to any one of claims 1 to 3, characterized in that: in the step 2), the using amount of the potassium hydroxide is 8-20% of the mass of the mixture.

5. The production method according to any one of claims 1 to 3, characterized in that: in the step 4), the particle material after powder making up is roasted at the temperature of 500-950 ℃.

6. The method of claim 5, wherein: the sintering time during the sintering is 15 min-30 min.

7. The red mud silicon calcium potassium fertilizer prepared by the method of any one of claims 1 to 6.