阅读说明：本技术 一种降低硝酸磷肥中和料浆粘度的方法和应用 (Method for reducing viscosity of nitric phosphate neutralized slurry and application ) 是由 冯军强 李�瑞 韩冬芳 张凌云 赵国军 岳秀萍 樊彩梅 刘建新 吕瑞 席庆 于 2021-01-06 设计创作，主要内容包括：本发明公开了一种降低硝酸磷肥中和料浆粘度的方法和应用,涉及硝酸磷肥生产技术领域,该方法包括：采用螯合剂对中和料浆混合,使中和料浆中的金属离子以可溶的螯合物状态存在；其中,所述螯合剂选自EDTA、柠檬酸和草酸中的任意一种或多种的组合。本发明基于现有的冷冻法硝酸磷肥生产工艺,在中和过程中添加螯合剂,利用中和料浆中金属离子与螯合剂的螯合效应,使中和料浆中的金属离子在氨中和过程中以可溶的螯合物状态存在而不引起沉淀,以达到有效降低料浆稠度的目的,且费用低廉,操作简单,重要的是无二次污染,零排放,所得肥料物化性能好,在土壤中不易被固定,易溶于水,又不离解,能很好地被植物吸收利用。(The invention discloses a method for reducing viscosity of nitric phosphate neutralized slurry and application thereof, and relates to the technical field of nitric phosphate production, wherein the method comprises the following steps: mixing the neutralized slurry with a chelating agent to enable metal ions in the neutralized slurry to exist in a soluble chelate state; wherein the chelating agent is selected from any one or more of EDTA, citric acid and oxalic acid. The invention is based on the existing production process of the nitrophosphate fertilizer by a freezing method, a chelating agent is added in the neutralization process, and the chelating effect of metal ions in the neutralized slurry and the chelating agent is utilized, so that the metal ions in the neutralized slurry exist in a soluble chelate state in the ammonia neutralization process without causing precipitation, thereby achieving the purpose of effectively reducing the consistency of the slurry.)

1. A method for reducing viscosity of a nitrophosphate neutralized slurry, comprising: mixing the neutralized slurry with a chelating agent to enable metal ions in the neutralized slurry to exist in a soluble chelate state;

wherein the chelating agent is selected from any one or more of EDTA, citric acid and oxalic acid.

2. The method for reducing the viscosity of a nitrophosphate fertilizer neutralization slurry as recited in claim 1, wherein said chelating agent is added in an amount such that the chelating agent and Mg in the neutralization slurry²⁺、Al³⁺And Fe³⁺The theoretical chelating amount of the three metal cations is 1-2 times of the total amount required.

3. The method for reducing the viscosity of a nitrophosphate fertilizer neutralization slurry as recited in claim 2, wherein said chelating agent is added in an amount such that the chelating agent and Mg in the neutralization slurry²⁺、Al³⁺And Fe³⁺The theoretical chelating amount of the three metal cations is 1-1.5 times of the total amount required.

4. The method for reducing the viscosity of a nitrophosphate neutralized slurry of claim 1, wherein said mixing conditions are: the temperature is 100-120 ℃, and the reaction time is 0.1-2 h.

5. The method for reducing the viscosity of a nitrophosphate fertilizer neutralization slurry as recited in claim 4, wherein said temperature is 100-110 ℃.

6. The method for reducing the viscosity of a nitrophosphate fertilizer neutralization slurry as recited in claim 4, characterized in that the reaction time is 0.5-1 h.

7. The method for reducing the viscosity of a nitrophosphate fertilizer neutralization slurry as recited in claim 1, wherein the chelating agent is added to the neutralization slurry at the following time: in the ammonia neutralization process, the temperature reaches 100-120 ℃, and the pH reaches 1.0-2.6.

8. The method for reducing the viscosity of a nitrophosphate fertilizer neutralization slurry as recited in claim 1, wherein the chelating agent is added to the neutralization slurry at the following time: in the ammonia neutralization process, the temperature reaches 105-115 ℃, and the pH reaches 1.8-2.0.

9. The use of the method for reducing the viscosity of a nitrophosphate fertilizer neutralization slurry as recited in any one of claims 1 to 8 in the production of a nitrophosphate fertilizer.

10. The application of the method for reducing the viscosity of the nitrophosphate fertilizer neutralization slurry in the nitrophosphate fertilizer production according to claim 9, wherein the phosphate ore used for the nitrophosphate fertilizer production is a medium-low grade phosphate ore;

except the ignition loss, the medium and low grade phosphorite comprises the following components in percentage by weight: p₂O₅28 to 31 percent of CaO, 41 to 43 percent of CaO, 17 to 19 percent of acid insoluble AI, 2.4 to 2.6 percent of F, and Fe₂O₃1.10％～1.24％、Al₂O₃1.20-1.36 percent, MgO 0.70-0.80 percent, and the balance of carbon dioxide, water and organic matters.

Technical Field

The invention relates to the technical field of nitrophosphate fertilizer production, in particular to a method for reducing viscosity of nitrophosphate fertilizer neutralization slurry and application thereof.

Background

The production process of nitrate phosphate fertilizer by freezing method is a production process which converts phosphate rock into nitrate-base compound fertilizer by the procedures of nitric acid decomposition, precipitation separation of acid insoluble substance, calcium nitrate freezing crystallization, calcium nitrate filtration, mother liquor neutralization, evaporation, granulation, drying and cooling. The nutrient structure and performance of the nitrogen and phosphorus fertilizer accord with the development direction of the fertilizer industry in the world, and the nitrogen and phosphorus fertilizer is widely used for the production of grain crops and economic crops.

However, the nitrophosphate fertilizer freezing process has high requirement on the grade of raw material phosphorite, and gradually exposes some technical problems under the situation that the grade of the phosphorite is continuously reduced in recent years and the content of metals such as calcium, iron, magnesium, aluminum and the like in the phosphorite is continuously increased.

Among the technical problems, the most prominent problem is represented by the neutralization process, wherein the mother liquor can undergo a gas-liquid phase chemical reaction involving multiple components in the ammonia neutralization process, and simultaneously generate multiple solid precipitates, so that the viscosity of the slurry in the ammonia neutralization process is obviously changed, particularly when the content of impurities in the phosphate ore is high, a large amount of gelatinous substances can be generated in the neutralization process, the viscosity of the neutralized slurry is rapidly increased, the viscosity of the slurry is high, the neutralization and evaporation cannot be normally carried out, and the system is forced to be shut down due to the fact that the slurry almost loses fluidity in severe cases, so that great economic benefit loss can be brought to a factory, a large amount of manpower and material resources are consumed for cleaning the equipment, and the normal production of the nitrophosphate fertilizer and the quality positioning of a final product can be directly influenced.

At present, most factories adopt a three-stage neutralization process to neutralize ammonia, but the method has high cost, complex operation and harsh process conditions required to be controlled.

In view of this, the invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a method for reducing viscosity of a nitric phosphate neutralized slurry and application thereof.

The invention is realized by the following steps:

in a first aspect, the present invention provides a method for reducing viscosity of a nitrophosphate fertilizer neutralized slurry, comprising: mixing the neutralized slurry with a chelating agent to enable metal ions in the neutralized slurry to exist in a soluble chelate state;

wherein the chelating agent is selected from any one or more of EDTA, citric acid and oxalic acid.

In a second aspect, the present invention provides the use of a method for reducing viscosity of a neutralized slurry of a nitrophosphate fertilizer as described in the preceding examples in the production of a nitrophosphate fertilizer.

The invention has the following beneficial effects:

the invention provides a method for reducing viscosity of nitric phosphate neutralized slurry and application thereof, wherein the method comprises the following steps: mixing the neutralized slurry with a chelating agent to enable metal ions in the neutralized slurry to exist in a soluble chelate state; wherein the chelating agent is selected from any one or more of EDTA, citric acid and oxalic acid. The inventor adds a chelating agent in the neutralization process based on the prior production process of the nitrophosphate fertilizer by a freezing method, and utilizes the chelating effect of metal ions and the chelating agent in the neutralized slurry to ensure that the metal ions in the neutralized slurry exist in a soluble chelate state without causing precipitation in the ammonia neutralization process, thereby achieving the purpose of effectively reducing the viscosity of the slurry. The method provided by the invention effectively reduces the viscosity of the neutralized slurry, and has the advantages of low cost, simple operation, no secondary pollution, zero emission, good physical and chemical properties of the obtained fertilizer, difficult fixation in soil, easy water dissolution, no dissociation and good absorption and utilization by plants. Can also be mixed with other solid or liquid fertilizers for application without chemical reaction, and can improve the quality of agricultural products without reducing the fertilizer efficiency of any fertilizer.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.

FIG. 1 is a process flow diagram of a production process of a nitrophosphate fertilizer by a freezing method.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The features and properties of the present invention are described in further detail below with reference to examples.

The prior process for producing the nitrophosphate fertilizer by a freezing method has high requirements on the quality of raw material phosphorite. The inventors have found that when a phosphate ore containing a large amount of impurities (a low-or medium-grade phosphate ore) is used, a large amount of a gel-like substance is formed in the ammonia neutralization process, and the viscosity of the neutralized slurry is rapidly increased.

The high viscosity of the neutralized slurry hinders the diffusion of ammonia under agitation and the slurry flows through the channels and pipes of the plant system, when using low to medium grade phosphate ores, although after the freezing crystallization and calcium nitrate separation process, most of the calcium nitrate (about 70%) in the acidolysis solution will be in the form of Ca (NO)₃)₂·4H₂The O crystal form is separated, but the mother liquor still contains certain amounts of calcium nitrate, magnesium nitrate, ferric nitrate, aluminum nitrate. The content of the metal ions such as calcium, iron, magnesium, aluminum and the like is increased along with the continuous reduction of the grade of the phosphorite, which inevitably brings more difficulty to the neutralization operation.

In order to solve the technical problem, the embodiment of the invention provides a method for reducing viscosity of a nitrophosphate fertilizer neutralized slurry, which comprises the following steps: mixing the neutralized slurry with a chelating agent to enable metal ions in the neutralized slurry to exist in a soluble chelate state;

wherein the chelating agent is selected from any one or more of EDTA, citric acid and oxalic acid.

By adding the chelating agent in the neutralization process, the impurity ions in the neutralized slurry exist in a soluble chelate state without causing precipitation in the ammonia neutralization process by utilizing the chelating effect between the metal ions in the solution and the coordination atoms in the chelating agent, thereby achieving the purpose of reducing the viscosity of the slurry.

The metal atom or ion reacts with a ligand containing two or more coordinating atoms to form a complex having a cyclic structure, which is called a chelate. Such ligand substances capable of forming chelates are called chelating agents.

In the embodiment of the present invention, the chelating agent may be any one of EDTA, citric acid and oxalic acid, or may be any one of EDTA, citric acid and oxalic acidIs the combination of any two of EDTA, citric acid and oxalic acid, or the combination of three components of EDTA, citric acid and oxalic acid. The three components can neutralize Mg in slurry under the condition of strong acid²⁺、Al³⁺And Fe³⁺The three metal cations are chelated, thereby effectively reducing the viscosity of the slurry in the neutralization process.

Preferably, the chelating agent is added in an amount that the chelating agent and Mg in the neutralized slurry²⁺、Al³⁺And Fe³⁺The theoretical chelation of the three metal cations is 1-2 times of the total dosage, specifically 1.1 times, 1.3 times, 1.5 times, 1.7 times, 1.9 times and 2 times.

Preferably, the chelating agent is added in an amount that the chelating agent and Mg in the neutralized slurry²⁺、Al³⁺And Fe³⁺The theoretical chelating amount of the three metal cations is 1-1.5 times of the total amount required.

The invention enables impurity ions in the neutralized slurry to exist in a soluble chelate state better without causing precipitation during the ammonia neutralization process by controlling the addition amount, the addition time and the reaction conditions of the chelating agent.

Preferably, the mixing conditions are: the temperature is 100-120 ℃, and the time is 0.1-2 h. The temperature is any of 100 ℃, 110 ℃ and 120 ℃. The time is any one of 0.1h, 0.5h, 1.0h, 1.5h and 2.0 h.

Preferably, the mixing temperature is 100-110 ℃.

Preferably, the reaction time is 0.5-1 h.

Preferably, the adding of the chelating agent to the neutralized slurry is performed at the following time: in the ammonia neutralization process, the temperature reaches 100-120 ℃, and the pH reaches 1.0-2.6. The temperature can be any of 100 deg.C, 105 deg.C, 110 deg.C, 115 deg.C, and 120 deg.C, and the pH can reach any of 1.0, 2.0, and 2.6. If add after pH surpasses 2.6, the first viscosity peak can appear in the ground paste of neutralization when pH 2.7, and then leads to neutralization, evaporation to go on normally, and the ground paste loses mobility almost when serious and causes the system to be forced to shut down, not only can bring very big economic benefits loss for the mill like this, consumes a large amount of manpower and materials and is used for cleaning equipment, can directly influence the normal production of nitrophosphate fertilizer and the positioning of quality of final product moreover.

Preferably, the adding of the chelating agent to the neutralized slurry is performed at the following time: in the ammonia neutralization process, the temperature reaches 105-115 ℃, and the pH reaches 1.8-2.0.

In addition, the embodiment of the invention also provides the application of the method for reducing the viscosity of the neutralized slurry of the nitrophosphate fertilizer in the production of the nitrophosphate fertilizer.

Preferably, the phosphorite used for producing the nitrophosphate fertilizer is medium-low grade phosphorite;

except for ignition loss, the medium and low grade phosphorite mainly comprises the following components in percentage by weight: p₂O₅28 to 31 percent of CaO, 41 to 43 percent of CaO, 17 to 19 percent of acid insoluble AI, 2.4 to 2.6 percent of F, and Fe₂O₃ 1.10％～1.24％、Al₂O₃1.20-1.36 percent, MgO 0.70-0.80 percent, and the balance of carbon dioxide, water and organic matters.

In some embodiments, except for the loss caused by ignition, in the middle-low grade phosphorite, the proportion of carbon dioxide is 2.91-4.91 percent and the proportion of organic matters is 0.01-1.00 percent by weight percent; the proportion of water is 0.08-2.08%.

"loss on ignition" refers to the mass lost to the original sample mass as a percentage of the mass burned at a high temperature for a sufficient period of time. The total amounts given herein are the sum of the percentages of the other components except for the appropriate amount on ignition, and in some embodiments, the middle and low grade phosphate ore components can be found in Table 1.

TABLE 1 phosphate rock compositions

Components	Content (wt.)	Components	Content (wt.)
				P2O5	28.98％	Fe2O3	1.14％
Al2O3	1.26％	F	2.59％
				CO2	3.91％	AI	18.71％
H2O	1.08％	CaO	42.05％
				MgO	0.74％	Organic matter	0.63％
-	-	Total amount of	101.09％

Preferably, the application adopts a freezing method to produce the nitrophosphate fertilizer. The method for producing the nitrophosphate fertilizer by the freezing method mainly comprises the following steps: adding nitric acid into phosphorite for acidolysis, precipitating and separating acid insoluble substances, freezing and crystallizing calcium nitrate, filtering the calcium nitrate, removing fluorine from mother liquor, deeply removing calcium from the mother liquor, neutralizing the mother liquor, evaporating, granulating, drying and cooling.

The embodiment is based on the improved production process of the prior nitrophosphate fertilizer by a freezing method, a chelating agent is added in a neutralization process, and the process flow diagram is shown in figure 1.

Adding nitric acid and phosphorite powder into an acidolysis tank according to the stoichiometric amount for acidolysis reaction, separating acid insoluble substances in acidolysis solution by precipitation separation, then sending the acidolysis solution from which the acid insoluble substances are separated into a freezing crystallization process, separating calcium nitrate from the acidolysis solution by freezing crystallization, and filtering the calcium nitrate to separate solid and liquid, wherein the obtained liquid is mother liquor; conveying the mother liquor to a mother liquor defluorination tank, defluorinating the mother liquor by adding potassium nitrate to react fluosilicic acid ions in the mother liquor with potassium ions to generate potassium fluosilicate crystals, discharging the potassium fluosilicate out of a system through solid-liquid separation, conveying the defluorinated mother liquor to a mother liquor deep decalcification process, adding potassium sulfate to react calcium ions in the defluorinated mother liquor with sulfate ions to generate calcium sulfate crystals, and separating the calcium-free mother liquor through solid-liquid separation; the calcium-free mother liquor firstly enters a 1# mother liquor neutralization process (neutralization slurry) according to the process of freezing the nitrophosphate fertilizer, and is subjected to neutralization reaction with added ammonia gas, ammonium nitrate and a chelating agent, after the reaction is finished, the neutralized mother liquor enters a 2# mother liquor neutralization process, and is subjected to neutralization reaction with ammonia gas continuously, and after the neutralization is finished, the nitrophosphate fertilizer is obtained by slurry evaporation, granulation, drying and cooling.

The specific process parameters in the process can be obtained by the prior art, and are not described in detail herein.

According to the invention, the chelating effect is successfully utilized to remove metal ions such as magnesium, aluminum, iron and the like in the neutralized mother liquor, the viscosity of slurry is reduced, the production load and difficulty of the neutralization process are reduced, the adaptability of the production process of the nitrophosphate fertilizer by a freezing method to the grade of the phosphate ore is improved, the cost is low, and the operation is simple; the adopted treatment technology is simple, relatively independent and self-integrated, does not need to be additionally provided with a device, and can directly realize technical transformation on the prior nitric phosphate fertilizer device by a freezing method.

The nitrophosphate fertilizer prepared after being treated by the chelating agent is applied to farmland fertilization application, the defects of low utilization rate, difficult absorption and the like of inorganic salt multi-element trace fertilizer can be overcome, beneficial synergistic effect among trace elements is enhanced, biological activity is improved, plants are further promoted to absorb nitrogen, phosphorus, potassium and the trace elements, the absorptivity and the utilization rate of the fertilizer are enhanced, heavy metals deposited in soil can be effectively absorbed by the plants in a natural enrichment mode under the action of the chelating agent, and the content of the heavy metals in the soil is reduced. In addition, the chelating agent is introduced to be combined with metal ions, so that the generation of metal phosphate precipitates in the neutralization process is avoided, the content of water-soluble phosphorus in a final product is increased, and the fertilizer efficiency, the quality and the action range of the fertilizer are improved.

Example 1

The invention provides a preparation method of a nitrophosphate fertilizer, which comprises the following steps.

The phosphorite adopted by the embodiment mainly comprises the following components in percentage by weight except ignition loss: p₂O₅28.98%, CaO 42.05%, F2.59%, acid insoluble AI 18.71%, Fe₂O₃ 1.14％、Al₂O₃1.26 percent, 0.74 percent of MgO and the balance of water, organic matters and carbon dioxide; the acid insoluble material is mainly silica. The concentration of nitric acid was 58%.

Adding nitric acid and phosphorite into an acidolysis tank for acidolysis reaction, wherein the dosage of the nitric acid is 120 percent of the theoretical dosage of the nitric acid. The theoretical amount of nitric acid used can be calculated according to equation 1.

Formula 1:

wherein, W_CaOIs the mass percent of calcium oxide in phosphorite;

W_MgOis the mass percent of magnesium oxide in phosphorite;

is the mass percent of the alumina in the phosphorite;

is the mass percentage of the ferric oxide in the phosphorite.

Separating acid insoluble substances in the acidolysis solution by precipitation separation, then sending the acidolysis solution from which the acid insoluble substances are separated into frozen crystals, separating out calcium nitrate from the acidolysis solution by a frozen crystallization process, and filtering the calcium nitrate to perform solid-liquid separation to obtain a liquid, namely a mother solution; mother liquor is conveyed into a mother liquor defluorination tank, and defluorination is carried out on the mother liquor by adding potassium nitrate, so that fluosilicic acid ions in the mother liquor react with potassium ions to generate potassium fluosilicate crystals, the reaction conditions in the process are that the reaction temperature is 30 ℃, the reaction time is 1 hour, and the adding amount of the potassium nitrate is as follows according to the molar ratio of the potassium nitrate to the fluosilicic acid: KNO₃/H₂SiF₆3, wherein potassium fluosilicate is discharged out of the system after solid-liquid separation, defluorination neutralization mother liquor is sent into the mother liquor for deep calcium removal, calcium ions in the defluorination mother liquor and sulfate ions react to generate calcium sulfate crystals by adding potassium sulfate, the calcium sulfate crystals are separated from the calcium-free mother liquor through solid-liquid separation, the reaction conditions of the process are 65 ℃ and the reaction time is 1 hour, the adding amount of the potassium sulfate is determined according to the content of the calcium ions in the defluorination mother liquor, namely, the molar ratio of the sulfate ions to the calcium ions is 1.1: 1; the calcium-free mother liquor enters a 1# mother liquor neutralization process (neutralization slurry) according to the process of freezing nitrophosphate fertilizer, and is subjected to neutralization reaction with added ammonia gas and ammonium nitrate, when the reaction temperature reaches 110 ℃ and the pH value reaches 1.8, EDTA chelating agent is added into the reaction liquid, and the dosage of the chelating agent is that the chelating agent and Mg in the neutralization slurry²⁺、Al³⁺And Fe³⁺The theoretical chelation of the three metal cations is 1.5 times of the total dosage, the slurry is maintained to react for 1 hour at 110 ℃, and the slurry enters a 2# mother solution after the reaction is finishedAnd a liquid neutralization step, wherein the liquid neutralization step and ammonia gas continue to carry out neutralization reaction, the mass ratio of the total addition amount of the ammonia gas to the phosphorite in the two-stage neutralization step is 0.15, the ammonia gas introduced in the 1# mother liquor neutralization step accounts for about 55% of the total introduced ammonia gas, the ammonia gas introduced in the 2# mother liquor neutralization step accounts for about 45% of the total introduced ammonia gas, the mass ratio of the addition amount of the ammonium nitrate to the phosphorite is 0.6, and after the neutralization is finished, slurry evaporation, granulation, drying and cooling are carried out, so that the nitrophosphate fertilizer is obtained.

Example 2

The invention provides a preparation method of a nitrophosphate fertilizer, which has the same general steps as those of the example 1, and is different from the chelating agent, wherein the chelating agent adopted in the example is as follows: a citric acid chelating agent.

Example 3

The invention provides a preparation method of a nitrophosphate fertilizer, which has the same general steps as those of the example 1, and is different from the chelating agent, wherein the chelating agent adopted in the example is as follows: an oxalic acid chelating agent.

Comparative example 1

The invention provides a preparation method of a nitrophosphate fertilizer, which is the same as the embodiment 1 in general steps and is different from the steps of: no chelating agent was added during neutralization.

Test example 1

The nitrophosphate fertilizer is prepared by the preparation methods of the examples 1 to 3 and the comparative example 1, the viscosity change of the neutralized slurry before and after the chelating agent is added in the neutralization process is measured, and the measurement results are shown in the table 2.

Table 2 viscosity change of neutralized slurry before and after chelant addition

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.