Method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by wet-process phosphoric acid residues

文档序号：282849 发布日期：2021-11-23 浏览：28次中文

阅读说明：本技术 湿法磷酸渣生产复合多元素聚磷酸盐联产氟硅酸的方法 (Method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by wet-process phosphoric acid residues ) 是由盛勇熊柏年方睿丁建朱尤能于艳敏康建姣王开珍张长明于 2021-09-07 设计创作，主要内容包括：本发明公开了名称一种湿法磷酸渣生产复合多元素聚磷酸盐联产氟硅酸的方法,包括有以下步骤：(1)混料：将磷酸渣与浮选尾矿在混料器中混合均匀,得到固形物Ⅰ；(2)煅烧：将固形物Ⅰ煅烧,煅烧得到固形物Ⅱ；煅烧产生的气体水洗回收得到氟硅酸溶液；(3)破碎：将固形物Ⅱ破碎,得到复合多元素聚磷酸盐。本发明的有益效果是：本发明实现了高值化利用湿法磷酸渣的目的,获得了经济价值高的复合多元素聚磷酸盐和氟硅酸产品,整个生产工艺无固体废弃物、废水排放,少量废气经水洗涤后达标排放,具有良好的环境效益、经济效益和社会效益。(The invention discloses a method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by wet-process phosphoric acid residues, which comprises the following steps: (1) mixing materials: uniformly mixing phosphoric acid residues and flotation tailings in a mixer to obtain a solid I; (2) and (3) calcining: calcining the solid I to obtain a solid II; washing and recovering gas generated by calcination to obtain a fluosilicic acid solution; (3) crushing: and (4) crushing the solid II to obtain the composite multi-element polyphosphate. The invention has the beneficial effects that: the invention realizes the purpose of utilizing the wet-process phosphoric acid residues with high value, obtains the composite multi-element polyphosphate and fluosilicic acid products with high economic value, has no solid waste and wastewater discharge in the whole production process, discharges a small amount of waste gas after reaching the standard after being washed by water, and has good environmental benefit, economic benefit and social benefit.)

1. A method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by wet-process phosphoric acid residues is characterized by comprising the following steps:

(1) mixing materials: uniformly mixing phosphoric acid residues and flotation tailings in a mixer to obtain a solid I;

(2) and (3) calcining: calcining the solid I to obtain a solid II; washing and recovering gas generated by calcination to obtain a fluosilicic acid solution;

(3) crushing: and (4) crushing the solid II to obtain the composite multi-element polyphosphate.

2. The method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by using wet-process phosphoric acid residues as claimed in claim 1Characterized in that: the phosphoric acid residue in the step (1) is generated in a wet-process phosphoric acid process, and the composition of the phosphoric acid residue comprises 10-40wt% of P₂O₅And 2 to 28wt% F; the composition of the flotation tailings in the step (1) comprises 2-12wt% of P₂O₅And 10-21wt% MgO.

3. The method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by using the wet-process phosphoric acid residues as claimed in claim 2, wherein the method comprises the following steps: the composition of the phosphoric acid residue in the step (1) comprises 20 to 35 weight percent of P₂O₅And 6 to 21wt% F; the composition of the flotation tailings in the step (1) comprises 3-10wt% of P₂O₅And 12-20wt% MgO.

4. The method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by using the wet-process phosphoric acid residues as claimed in claim 1, is characterized in that: in the step (1), the molar ratio of phosphorus to metal elements in the solid I is P (Mg + Ca-S) = 0.5-2.3.

5. The method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by using the wet-process phosphoric acid residues as claimed in claim 4, wherein the method comprises the following steps: in the step (1), the molar ratio of phosphorus to metal elements in the solid I is P (Mg + Ca-S) = 0.7-1.8.

6. The method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by using the wet-process phosphoric acid residues as claimed in claim 1, wherein the method comprises the following steps: the content of fluosilicic acid in the fluosilicic acid solution in the step (2) is 3-19%; the fluorosilicic acid solution is used for further processing into hydrofluoric acid, sodium fluorosilicate, sodium fluoride, potassium fluoride or ammonium fluoride.

7. The method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by using the wet-process phosphoric acid residues as claimed in claim 1, is characterized in that: the calcination temperature in the step (2) is 340-550 ℃; the calcination time is 1-4 h.

8. The method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by using the wet-process phosphoric acid residues as claimed in claim 7, wherein the method comprises the following steps: and (4) mixing and granulating the composite multi-element polyphosphate obtained in the step (3) with potassium sulfate, urea and the like to obtain the special fertilizer for sugarcane or the special fertilizer for potato.

9. The method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by using the wet-process phosphoric acid residues as claimed in claim 8, is characterized by comprising the following steps: in the step (2), when the calcination temperature reaches 380-400 ℃, the microwave radiation is performed in the calcination furnace, and when the temperature rises to 400-500 ℃, the microwave radiation is closed, and the temperature is continuously raised.

Technical Field

The invention relates to the technical field of chemical production, in particular to a method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by using wet-process phosphoric acid residues.

Background

Phosphoric acid is an important production intermediate product in the industry of phosphorization industry, and can be used as a raw material to produce a series of national production and living necessities, such as fertilizers, industrial phosphates, feed additives, food additives and the like. Phosphoric acid is further divided into hot phosphoric acid and wet phosphoric acid, and compared with the hot phosphoric acid, the wet phosphoric acid has a larger cost advantage, so more and more enterprises choose to use the wet phosphoric acid to produce subsequent products.

At present, the wet-process phosphoric acid production process mainly adopts the reaction of phosphorite and sulfuric acid, the process can be divided into dihydrate, semi-hydrate-dihydrate and the like according to the quantity of by-product gypsum crystal water, the predominant method is dihydrate method, and the obtained phosphoric acid w (P) is₂O₅) The concentration is generally 20% -30%. In order to meet the production requirements of feed-grade calcium phosphate salt and high-concentration phosphorus compound fertilizer, the above-mentioned dilute phosphoric acid is concentrated to w (P)₂O₅) The concentration is 45-50%. As the water evaporates during the concentration process, a large amount of impurities in the phosphoric acid are precipitated, forming sludge. The concentrated phosphoric acid can be used as feed-grade calcium phosphate salt and high-concentration phosphorus compound fertilizer raw material acid after further purification treatment such as defluorination, and one can be separated out in the processQuantitative defluorination and precipitation.

The concentrated precipitate and defluorinated precipitate are collectively called wet-process phosphoric acid slag, and the main components of the slag are phosphoric acid, calcium sulfate, sodium (potassium) fluosilicate and compound salt formed by combining iron, aluminum, magnesium and phosphorus. How to properly treat wet-process phosphoric acid slag is always a difficult problem for phosphorus chemical enterprises, and some enterprises produce calcium superphosphate by using the wet-process phosphoric acid slag as a raw material, for example, Chinese patent document 'a production method for producing calcium superphosphate by using phosphoric acid slag' (application number: 201210457927.9) mixes phosphoric acid slag, phosphorite and sulfuric acid according to a certain proportion to react to obtain calcium superphosphate, for example, Chinese patent document 'a comprehensive utilization method for wet-process phosphoric acid slag' (application number: 21410263949.0) uses process water to wash phosphoric acid slag, separates solid and liquid, uses a liquid phase for an ammonium phosphate and phosphoric acid extraction process, and uses a sulfuric acid water solution and phosphorite to treat a solid phase to obtain a powdery ordinary calcium superphosphate product or to use the solid phase as a compound fertilizer raw material.

Although the two methods can treat the phosphoric acid residues, the fluorine resource in the phosphoric acid residues cannot be effectively recovered, and the main product is the superphosphate with serious surplus and low value in the prior art. Compared with the two methods, the second method adds a procedure of recovering phosphoric acid by a water washing mode, and the washed solid phase is used as a raw material for producing the ordinary calcium, which is similar to the method for treating the phosphoric acid residue in the 'method for producing the magnesium phosphate fertilizer by utilizing wet-process phosphoric acid residue' (application number: 201510530452.5), but the method for producing the magnesium phosphate fertilizer by using the washed phosphoric acid residue as the raw material is different from the method for producing the magnesium phosphate fertilizer by using the washed phosphoric acid residue as the raw material, but the two methods introduce soluble impurities in the phosphoric acid residue into a liquid phase in the process of washing and recovering the phosphoric acid, so that the quality of a fertilizer product or the phosphoric acid is influenced.

There is also a method for preparing compound fertilizer by using phosphoric acid slag as raw material, for example, Chinese patent document "a method for preparing nitro compound fertilizer by using acid slag in phosphoric acid production" (application number: 201410338769.4) firstly premixing phosphoric acid slag and water, then respectively adding nitric acid and ammonia gas, and finally carrying out procedures of granulation, drying and screening to obtain nitro compound fertilizer, although the method uses phosphoric acid slag to prepare compound fertilizer, sodium (potassium) fluosilicate in phosphoric acid slag is also brought into compound fertilizer to reduce nutrients, and simultaneously the effective phosphorus of the raw material acid slag is required to be above 40%, and the concentration of phosphoric acid slag w (P2O5) of phosphorus chemical enterprises is generally 20% -35%, so that the method has a limited popularization range.

In Chinese patent document ' method and device for preparing ammonium phosphate fertilizer by using phosphoric acid sediment ' (application number: 201310321076. X) ' w (P) is added into phosphoric acid sediment₂O₅) After 18% -20% of dilute phosphoric acid, carrying out neutralization reaction with gas ammonia and sulfuric acid, and then carrying out concentration, granulation and other processes to obtain the ammonium phosphate fertilizer.

In addition, in the method for preparing the compound fertilizer by taking the phosphate residues as the raw materials, although the fluorine overflows in a calcining mode to recover the fluorine, because the calcining condition is influenced by the cracking of phosphate molecular chains, if the temperature is too high, the polyphosphate is easy to crack, and if the temperature is too low, some heavy metal elements in tailings cannot be effectively removed, so that the obtained polyphosphate fertilizer is used for the growth of crops, the root growth of the crops is often influenced, and the emergence rate and the acre yield of the crops are influenced.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by using wet-process phosphoric acid residues.

The purpose of the invention is realized by the following technical scheme: a method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by wet-process phosphoric acid residues comprises the following steps:

(1) mixing materials: uniformly mixing phosphoric acid residues and flotation tailings in a mixer to obtain a solid I;

(2) and (3) calcining: calcining the solid I to obtain a solid II; washing and recovering gas generated by calcination to obtain a fluosilicic acid solution;

(3) crushing: crushing the solid II to obtain composite multi-element polyphosphate;

go toThe phosphoric acid slag in the step (1) is generated in a wet-process phosphoric acid process, and the composition of the phosphoric acid slag comprises 10-40wt% of P₂O₅And 2 to 28wt% F; the composition of the flotation tailings in the step (1) comprises 2-12wt% of P₂O₅And 10-21wt% MgO;

further, the composition of the phosphoric acid residue in the step (1) comprises 20 to 35 weight percent of P₂O₅And 6 to 21wt% F; the composition of the flotation tailings in the step (1) comprises 3-10wt% of P₂O₅And 12-20wt% MgO;

further, in the step (1), the molar ratio of phosphorus to metal elements in the solid I is P (Mg + Ca-S) = 0.5-2.3;

further, in the step (1), the molar ratio of phosphorus to metal elements in the solid I is P (Mg + Ca-S) = 0.7-1.8;

further, the content of fluosilicic acid in the fluosilicic acid solution in the step (2) is 3-19%; the fluosilicic acid solution is further processed into hydrofluoric acid, sodium fluosilicate, sodium fluoride, potassium fluoride or ammonium fluoride;

further, the calcination temperature in the step (2) is 340-550 ℃; the calcination time is 1-4 h;

further, mixing and granulating the composite multi-element polyphosphate obtained in the step (3) with potassium sulfate, urea and the like to obtain a special fertilizer for sugarcane or a special fertilizer for potato;

the further technical scheme is that in the step (2), when the calcination temperature reaches 380-400 ℃, the microwave radiation is performed in the calcination furnace, and when the temperature rises to 400-500 ℃, the microwave radiation is closed, and the temperature is continuously raised.

The invention has the following advantages: the wet-process phosphoric acid residues used in the invention comprise sediments in the concentration process and the defluorination process of the wet-process phosphoric acid, and how to properly treat the two wet-process phosphoric acid residues is a common problem faced by many phosphorus chemical enterprises. The wet-process phosphoric acid residue and phosphoric acid are separated by adopting conventional solid-liquid separation modes such as thickening, plate-and-frame filter pressing, centrifuging and the like, so that newly-added equipment and procedures are avoided. Meanwhile, the separated wet-process phosphoric acid residues can be directly used as a raw material for producing the composite multi-element polyphosphate, and the polyphosphate prepared from the wet-process phosphoric acid residues contains various elements required by the growth process of crops such as calcium, magnesium, sulfur, iron, manganese, zinc, silicon and the like in the wet-process phosphoric acid residues, so the polyphosphate is called as the composite multi-element polyphosphate. Compared with other treatment modes, such as water washing for extracting phosphoric acid or adding phosphoric acid for producing calcium superphosphate or compound fertilizer, the method has the advantages of simple process flow and no complex process control unit.

The invention can effectively recover fluorine resources in the wet-process phosphoric acid residues, the fluorine resources mainly come from cryolite, fluorite and phosphate rock at present, and the fluorite is restricted to be exploited as a strategic national resource. In recent years, phosphorus chemical enterprises pay attention to how to improve the recovery rate of fluorine resources in phosphorus chemical industry, and conventional measures include improving the concentration vacuum degree of wet-process phosphoric acid, adding active silicon to promote fluorine in the wet-process phosphoric acid to overflow as much as possible or replacing a fluorine washing nozzle, strengthening the washing effect and increasing the washing rate. However, about 30% of fluorine resources in the phosphate ore still exist in the concentrated sediment and the defluorination residue in the form of sodium (potassium) fluosilicate, and finally enter low-end products, such as calcium superphosphate, agricultural grade MAP and agricultural grade DAP, so that the quality of the products is influenced. In the calcining process, the calcining temperature is controlled to be 340-550 ℃ in order to decompose sodium (potassium) fluosilicate in the wet-process phosphoric acid slag as much as possible. In the above calcining temperature range, the sodium (potassium) fluosilicate is SiF₄And HF overflow, recovery is carried out by adopting a water washing mode, and meanwhile, in the temperature interval, the cracking of polyphosphate is favorably avoided by changing the calcining condition. The method can recover more than 85% of fluorine resources in the wet-process phosphoric acid residues, solves the bottleneck problem of improving the fluorine yield of phosphorus chemical enterprises, and has strong popularization and high economic value.

The invention has the characteristic of treating wastes with wastes, adopts the raw materials which are common waste residues of phosphorus chemical enterprises, does not need to add other raw materials, and embodies the environmental protection and the economical efficiency of the process flow of the invention. The elements such as phosphorus, calcium, magnesium and the like in the composite multi-element polyphosphate produced by the method have good slow release property.

The method comprehensively analyzes the classification and the composition of the wet-process phosphoric acid residues universally existing in phosphorus chemical enterprises, and finds out the common points of different wet-process phosphoric acid residues. The method avoids the existing wet-process phosphoric acid residues as low-end product raw materials or adopts a complex process for treatment, polyphosphate generated by calcining the wet-process phosphoric acid residues and tailings contains various crop nutrient elements such as calcium, magnesium, sulfur, silicon, iron, manganese, zinc and the like from the wet-process phosphoric acid residues, and meanwhile, by utilizing the characteristic that the calcining temperature of the polyphosphate accords with the decomposition condition of fluorine-containing compounds in the wet-process phosphoric acid residues, increasingly scarce fluorine resources are recovered, and the maximization of resource utilization is successfully realized.

The method can obtain the powdery composite multi-element polyphosphate product and the fluorosilicic acid water only by three steps of material mixing, calcining, water washing, absorbing and crushing, and has the advantages of short process flow and low investment and operation cost.

The raw materials adopted by the invention are wet-process phosphoric acid residues and flotation tailings, the characteristics of 'treating wastes with wastes' are realized, the produced composite multi-element polyphosphate covers various elements required in the growth process of crops such as calcium, magnesium, sulfur, silicon, iron, manganese, zinc and the like in the wet-process phosphoric acid residues, the elements such as phosphorus, calcium, magnesium and the like have good slow release property and good economical efficiency, and the low-end products produced by adopting the wet-process phosphoric acid residues are avoided.

The method can effectively recover more than 85% of fluorine resources in the wet-process phosphoric acid residues, and obviously improves the fluorine yield of phosphorus chemical enterprises.

The invention realizes the purpose of utilizing the wet-process phosphoric acid residues with high value, obtains the composite multi-element polyphosphate and fluosilicic acid products with high economic value, has no solid waste and wastewater discharge in the whole production process, discharges a small amount of waste gas after reaching the standard after being washed by water, and has good environmental benefit, economic benefit and social benefit.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention.

FIG. 2 shows a sugarcane special fertilizer prepared from the composite multi-element polyphosphate prepared by the invention.

FIG. 3 shows a potato special fertilizer prepared from the composite multi-element polyphosphate prepared by the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

In addition, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, or orientations or positional relationships that the products of the present invention conventionally lay out when in use, or orientations or positional relationships that are conventionally understood by those skilled in the art, which are merely for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

Example 1: a method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by wet-process phosphoric acid residues comprises the following steps:

(1) mixing materials: uniformly mixing phosphoric acid residues and flotation tailings in a mixer to obtain a solid I;

(2) and (3) calcining: calcining the solid I to obtain a solid II; washing and recovering gas generated by calcination to obtain a fluosilicic acid solution;

(3) crushing: crushing the solid II to obtain composite multi-element polyphosphate;

the phosphoric acid residue in the step (1) is generated in a wet-process phosphoric acid process, and the composition of the phosphoric acid residue comprises 10-40wt% of P₂O₅And 2 to 28wt% F; the composition of the flotation tailings in the step (1) comprises 2-12wt% of P₂O₅And 10-21wt% MgO;

the composition of the phosphoric acid residue in the step (1) comprises 20 to 35 weight percent of P₂O₅And 6 to 21wt% F; the composition of the flotation tailings in the step (1) comprises 3-10wt% of P₂O₅And 12-20wt% MgO;

in the step (1), the molar ratio of phosphorus to metal elements in the solid I is P (Mg + Ca-S) = 0.5-2.3;

in the step (1), the molar ratio of phosphorus to metal elements in the solid I is P (Mg + Ca-S) = 0.7-1.8;

the content of fluosilicic acid in the fluosilicic acid solution in the step (2) is 3-19%; the fluosilicic acid solution is further processed into hydrofluoric acid, sodium fluosilicate, sodium fluoride, potassium fluoride or ammonium fluoride;

the calcination temperature in the step (2) is 340-550 ℃; the calcination time is 1-4 h;

mixing and granulating the composite multi-element polyphosphate obtained in the step (3) with potassium sulfate, urea and the like to obtain a special fertilizer for sugarcane or a special fertilizer for potato;

in the step (2), when the calcination temperature reaches 380-400 ℃, the microwave radiation is performed in the calcination furnace, and when the temperature rises to 400-500 ℃, the microwave radiation is closed, and the temperature is continuously raised.

In the calcining process, the calcining temperature is controlled to be 340-550 ℃ in order to decompose sodium (potassium) fluosilicate in the wet-process phosphoric acid slag as much as possible. In the above calcining temperature range, the sodium (potassium) fluosilicate is SiF₄And HF overflow, recovery is carried out by adopting a water washing mode, and meanwhile, in the temperature interval, the cracking of polyphosphate is favorably avoided by changing the calcining condition. The method can recover more than 85% of fluorine resources in the wet-process phosphoric acid residues, solves the bottleneck problem of improving the fluorine yield of phosphorus chemical enterprises, and has strong popularization and high economic value.

The method can effectively recover more than 85% of fluorine resources in the wet-process phosphoric acid residues, and obviously improves the fluorine yield of phosphorus chemical enterprises.

Example 2: (small) a method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by wet-process phosphoric acid residues, which comprises the following steps:

(1) mixing materials: uniformly mixing phosphoric acid residues and flotation tailings in a mixer to obtain a solid I;

(2) and (3) calcining: calcining the solid I to obtain a solid II; washing and recovering gas generated by calcination to obtain a fluosilicic acid solution;

(3) crushing: crushing the solid II to obtain composite multi-element polyphosphate;

the phosphoric acid residue in the step (1) is generated in a wet-process phosphoric acid process, and the composition of the phosphoric acid residue comprises 10wt% of P₂O₅And 2wt% F; the composition of the flotation tailings in the step (1) comprises 2wt% of P₂O₅And 10wt% MgO;

the composition of the phosphoric acid residue in the step (1) comprises 20wt% of P₂O₅And 6 to 21wt% F; the composition of the flotation tailings in the step (1) comprises 3wt% of P₂O₅And 12wt% MgO;

in the step (1), the molar ratio of phosphorus to metal elements in the solid I is P (Mg + Ca-S) = 0.5;

in the step (1), the molar ratio of phosphorus to metal elements in the solid I is P (Mg + Ca-S) = 0.7;

the calcination temperature in the step (2) is 340 ℃; the calcination time is 1 h;

in the step (2), when the calcining temperature reaches 380 ℃, microwave radiation is carried out in the calcining furnace, and when the temperature rises to 400 ℃, the microwave radiation is closed, and the temperature is continuously raised.

The method can effectively recover more than 85% of fluorine resources in the wet-process phosphoric acid residues, and obviously improves the fluorine yield of phosphorus chemical enterprises.

Example 3: a method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by wet-process phosphoric acid residues comprises the following steps:

(1) mixing materials: uniformly mixing phosphoric acid residues and flotation tailings in a mixer to obtain a solid I;

(2) and (3) calcining: calcining the solid I to obtain a solid II; washing and recovering gas generated by calcination to obtain a fluosilicic acid solution;

(3) crushing: crushing the solid II to obtain composite multi-element polyphosphate;

the phosphoric acid residue in the step (1) is generated in a wet-process phosphoric acid process, and the composition of the phosphoric acid residue comprises 40wt% of P₂O₅And 28wt% F; the composition of the flotation tailings in the step (1) comprises 12wt% of P₂O₅And 21wt% MgO;

the composition of the phosphoric acid residues in the step (1) comprises 35wt% of P₂O₅And 21wt% F; the composition of the flotation tailings in the step (1) comprises 10wt% of P₂O₅And 20wt% MgO;

in the step (1), the molar ratio of phosphorus to metal elements in the solid I is P (Mg + Ca-S) = 2.3;

in the step (1), the molar ratio of phosphorus to metal elements in the solid I is P (Mg + Ca-S) = 1.8;

the calcination temperature in the step (2) is 550 ℃; the calcination time is 4 h;

in the step (2), when the calcining temperature reaches 400 ℃, microwave radiation is carried out in the calcining furnace, and when the temperature rises to 500 ℃, the microwave radiation is closed, and the temperature is continuously raised.

The method can effectively recover more than 85% of fluorine resources in the wet-process phosphoric acid residues, and obviously improves the fluorine yield of phosphorus chemical enterprises.

Example 4:

the detection indexes of the wet-process phosphoric acid residues (concentrated residues) and the flotation tailings are shown in the following table 1.

TABLE 1 indexes for detection of wet process phosphoric acid sludge (concentrate sludge) and flotation tailings used in example 4

	Total P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	SO₃（wt%）	F（wt%）
						Phosphoric acid slag	23.53	7.92	2.87	14.41	12.31
Flotation of tailings	6.12	29.89	13.89	1.55	1.66

Uniformly mixing the wet-process phosphoric acid residues and the flotation tailings according to the weight ratio of 5:1 to obtain a solid I, wherein P: the molar ratio of (Mg + Ca-S) was 1.71. And (3) calcining the solid I in a rotary drying kiln at the temperature of 360 ℃ for 1.2h to obtain a blocky solid II. Collecting gas generated in the calcining process, and absorbing and treating the gas by adopting a water washing mode to obtain fluorosilicic acid water containing 11% of fluorosilicic acid.

And crushing the massive solid II to obtain powdery composite multi-element polyphosphate, wherein the detection indexes are shown in the following table 2.

Table 2 detection index of composite multi-element polyphosphate obtained in example 4

	Total P₂O₅（wt%）	Effective P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	F（wt%）	MnO（wt%）	SiO₂（wt%）	Zn（wt%）	S（wt%）
										Composite multi-element polyphosphate	37.24	36.61	18.42	10.33	1.10	0.2	6.29	0.006	3.24

Through fluorine balance calculation and product detection, the fluorine yield in the wet-process phosphoric acid residue is 86.42%, the polymerization rate of the composite multi-element polyphosphate is 82%, and the polymerization degree is 2.81.

Example 5:

the detection indexes of the wet-process phosphoric acid residues (defluorination residues) and the flotation tailings are shown in the following table 3.

TABLE 3 index for wet process phosphoric acid sludge (defluorination sludge) and flotation tailings used in example 5

	Total P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	SO₃（wt%）	F（wt%）
						Phosphoric acid slag	28.31	4.46	3.01	3.68	20.49
Flotation of tailings	4.47	37.71	18.22	1.29	1.47

Uniformly mixing the wet-process phosphoric acid residues and the flotation tailings according to the weight ratio of 3:1 to obtain a solid I, wherein P: the molar ratio of (Mg + Ca-S) was 0.88. And (3) calcining the solid I in a rotary drying kiln at the temperature of 430 ℃ for 1.5h to obtain a blocky solid II. Collecting gas generated in the calcining process, and absorbing and treating the gas by adopting a water washing mode to obtain fluorosilicic acid water containing 13% of fluorosilicic acid.

And crushing the massive solid II to obtain powdery composite multi-element polyphosphate, wherein the detection indexes are shown in the following table 4.

TABLE 4 detection index of the composite multielement polyphosphate obtained in example 5

	Total P₂O₅（wt%）	Effective P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	F（wt%）	MnO（wt%）	SiO₂（wt%）	Zn（wt%）	S（wt%）
										Composite multi-element polyphosphate	42.28	41.90	19.26	11.32	0.98	0.16	9.41	0.004	3.01

The fluorine yield of the wet-process phosphoric acid residue is 88.27%, the polymerization rate of the composite multi-element polyphosphate is 85%, and the polymerization degree is 3.11, which is measured by fluorine balance calculation and product detection.

Example 6:

the detection indexes of the wet-process phosphoric acid residues (defluorination residues and defluorination residues) and the flotation tailings are shown in the following table 5.

TABLE 5 indexes for detection of wet process phosphoric acid sludge (defluorination sludge and defluorination sludge) and flotation tailings selected in example 6

	Total P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	SO₃（wt%）	F（wt%）
						Phosphoric acid slag	25.81	5.74	2.99	8.90	15.26
Flotation of tailings	8.35	33.76	13.53	5.28	1.72

Uniformly mixing the wet-process phosphoric acid residues and the flotation tailings according to a weight ratio of 4:1 to obtain a solid I, wherein P: the molar ratio of (Mg + Ca-S) was 1.36. And (3) calcining the solid I in a rotary drying kiln at the temperature of 450 ℃ for 2 hours to obtain a blocky solid II. Collecting gas generated in the calcining process, and absorbing and treating the gas by adopting a water washing mode to obtain fluorosilicic acid water containing 12% of fluorosilicic acid.

And crushing the massive solid II to obtain powdery composite multi-element polyphosphate, wherein the detection indexes are shown in the following table 6.

TABLE 6 detection index of composite multielement polyphosphate obtained in example 6

	Total P₂O₅（wt%）	Effective P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	F（wt%）	MnO（wt%）	SiO₂（wt%）	Zn（wt%）	S（wt%）
										Composite multi-element polyphosphate	43.32	42.98	20.01	10.99	0.84	0.18	8.72	0.0072	3.85

The fluorine yield of the wet-process phosphoric acid residue is 86.26%, the polymerization rate of the composite multi-element polyphosphate is 87%, and the polymerization degree is 3.24, which is measured by fluorine balance calculation and product detection.

Example 7:

the detection indexes of the wet-process phosphoric acid residues (concentrated residues) and the flotation tailings are shown in the following table 7.

TABLE 7 indexes for wet-process phosphoric acid residue (concentrate residue) and flotation tailings detection

	Total P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	SO₃（wt%）	F（wt%）
						Phosphoric acid slag	30.74	6.33	2.01	13.12	11.26
Flotation of tailings	5.01	35.20	17.45	4.79	2.02

Uniformly mixing the wet-process phosphoric acid residues and the flotation tailings according to a weight ratio of 4:1 to obtain a solid I, wherein P: the molar ratio of (Mg + Ca-S) was 0.94. And (3) calcining the solid I in a rotary drying kiln at the temperature of 510 ℃ for 3 hours to obtain a blocky solid II. Collecting gas generated in the calcining process, and absorbing and treating the gas by adopting a water washing mode to obtain fluorosilicic acid water containing 15 percent of fluorosilicic acid.

And crushing the massive solid II to obtain powdery composite multi-element polyphosphate, wherein the detection indexes are shown in the following table 8.

TABLE 8 detection index of composite multielement polyphosphate obtained in example 7

	Total P₂O₅（wt%）	Effective P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	F（wt%）	MnO（wt%）	SiO₂（wt%）	Zn（wt%）	S（wt%）
										Composite multi-element polyphosphate	44.25	44.01	21.32	11.03	0.77	0.19	8.13	0.006	4.12

The fluorine yield of the wet-process phosphoric acid residue is 89.32%, the polymerization rate of the composite multi-element polyphosphate is 90%, and the polymerization degree is 4.05, which is measured by fluorine balance calculation and product detection.

Example 8 field test 1

The field test is carried out in the test field of Jiang Haote Wuchuan county in inner Mongolia 4 months in 2020.

The raw materials used in the test are all common commercial products: potassium sulfate (K)₂O52 percent, urea (total N46.4 percent), potassium humate (organic matter 75 percent), zinc sulfate heptahydrate (Zn 21.5 percent), triple superphosphate (effective P)₂O₅44%), calcium superphosphate (available P)₂O₅18%）。

The test procedure was as follows:

test set # 1: 30kg of heavy calcium superphosphate, 33kg of urea, 38kg of potassium sulfate, 0.5kg of potassium humate and 0.1kg of zinc sulfate heptahydrate are applied as base fertilizers.

Test set # 2: 30kg of calcium superphosphate, 33kg of urea, 38kg of potassium sulfate, 0.5kg of potassium humate and 0.1kg of zinc sulfate heptahydrate are applied as base fertilizers.

Test set # 3: 28kg of the composite multi-element polyphosphate prepared in example 4, 33kg of urea, 38kg of potassium sulfate, 0.5kg of potassium humate and 0.1kg of zinc sulfate heptahydrate were applied as base fertilizers.

Test set # 4: 28kg of the composite multi-element polyphosphate prepared in example 7, 33kg of urea, 38kg of potassium sulfate, 0.5kg of potassium humate and 0.1kg of zinc sulfate heptahydrate were applied as base fertilizers.

The potato type used in the test is Hissen No. 6, each group of tests is repeated for 4 times, the emergence rate and the acre yield of the test are counted, and the statistical result is shown in the following table 9.

TABLE 9 statistical results of field test 1

	Rate of emergence (%)	Rate of increase in emergence (%)	Mu yield (Kg)	Proportion of increase in production
					Test group No. 1	80.14	---	2980	---
Test group No. 2	81.45	1.63	3148	5.64
					Test group No. 3	85.79	7.05	3463	16.21
Test group 4#	87.11	8.70	3592	20.54

The data in the table show that the composite multi-element polyphosphate prepared by the invention has the effects of obviously increasing the rate of emergence and increasing the yield compared with triple superphosphate and superphosphate. In addition, since the polyphosphate used in test 4 has a higher polymerization rate than that used in test 3, the rate of increase of emergence and the yield per mu were more advantageous.

And (3) fluosilicic acid yield test:

the test is completed on a small test device built by Zhonghuayunlong Co., Ltd, Hongming county, in 2020 and 10 months, and the device is an equal-proportion reduction of the existing whole plant production device, and the reduction rate is more than 95%.

Fluorine yield to 1 ton per P produced₂O₅And (wet-process phosphoric acid) is recycled, and the quantity of the recovered 100% fluorosilicic acid is calculated.

The test data shows that:

experiment 1 is a reduction simulation of the existing wet-process phosphoric acid production and subsequent product processes, and the yield of fluosilicic acid is 58.9kg/tP₂O₅The actual production data are matched;

experiment 2 on the basis of reducing the existing process, the wet-process phosphoric acid slag (concentrated slag and defluorination slag) generated in the experiment process is used as the raw material to prepare the compound multi-element polyphosphate and recover the fluosilicic acid, and the yield of the fluosilicic acid is 93.7kg/tP₂O₅。

The data show that the yield of the fluosilicic acid is obviously increased and the increase rate reaches 59.08 percent when the invention is adopted to comprehensively treat the wet-process phosphoric acid slag.

Example 9:

the procedure used to prepare the powdered multi-element polyphosphate salt was carried out as in example 7, except that during calcination, microwave irradiation was stopped when the temperature was raised to 400 ℃ in the calciner, and then the temperature was raised to 500 ℃ and then the temperature was maintained at 510 ℃ for 3 hours to obtain the bulk solid ii.

And crushing the blocky solid II to obtain powdery composite multi-element polyphosphate, wherein the detection indexes are shown in the following table 10.

TABLE 10 detection index of composite multielement polyphosphate obtained in example 9

	Total P₂O₅（wt%）	Effective P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	F（wt%）	As（wt%）
							Composite multi-element polyphosphate	58.6 5	56.0 1	19.32	16.03	1.81	0.00012

Example 10:

powdered composite multielement polyphosphate was prepared by the method of example 7, the only difference is that during calcination, microwave irradiation was carried out in the calciner when the temperature was raised to 400 ℃, the microwave irradiation was stopped when the temperature was raised to 540 ℃, and calcination was carried out for 3h at this temperature after the temperature was raised to 550 ℃ to obtain a bulk solid ii.

And crushing the massive solid II to obtain powdery composite multi-element polyphosphate, wherein the detection indexes are shown in the following table 11.

TABLE 11 detection of the composite multielement polyphosphate obtained in example 10

	Total P₂O₅（wt%）	Effective P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	F（wt%）	As（wt%）
							Composite multi-element polyphosphate	44.6 5	43.0 1	19.22	14.08	1.03	0.00010

Example 11:

a powdery composite multi-element polyphosphate was prepared in the same manner as in example 10 except that the microwave irradiation was not performed in the calciner during the calcination. After the temperature is raised to 550 ℃, the temperature is kept for calcining for 3 hours, and the blocky solid II is obtained.

And crushing the massive solid II to obtain powdery composite multi-element polyphosphate, wherein the detection indexes are shown in the following table 12.

TABLE 12 detection of composite multielement polyphosphate obtained in example 11

	Total P₂O₅（wt%）	Effective P₂O₅（wt%）	CaO（wt%）	MgO（wt%）	F（wt%）	As（wt%）
							Composite multi-element polyphosphate	38.26	38.0 1	16.29	10.08	1.01	0.00025

It can be known from examples 10, 11, and 12 that too high temperature of calcination affects the cracking of polyphosphate, thereby being not beneficial to the generation of polyphosphate, but in the process of raising the temperature, the microwave radiation in the calcination furnace is performed when reaching a certain high temperature, so that the cracking of polyphosphate can be favorably hindered, arsenic can be favorably overflowed, and the content of arsenic in tailings in polyphosphate can be favorably reduced.

Example 13 field test 2

The same field test method as in example 8 was used

The test procedure was as follows:

test set # 1: 30kg of heavy calcium superphosphate, 33kg of urea, 38kg of potassium sulfate, 0.5kg of potassium humate and 0.1kg of zinc sulfate heptahydrate are applied as base fertilizers.

Test set # 2: 30kg of calcium superphosphate, 33kg of urea, 38kg of potassium sulfate, 0.5kg of potassium humate and 0.1kg of zinc sulfate heptahydrate are applied as base fertilizers.

Test set # 3: 28kg of the composite multi-element polyphosphate prepared in example 9, 33kg of urea, 38kg of potassium sulfate, 0.5kg of potassium humate and 0.1kg of zinc sulfate heptahydrate were applied as base fertilizers.

Test set # 4: 28kg of the composite multi-element polyphosphate prepared in example 10, 33kg of urea, 38kg of potassium sulfate, 0.5kg of potassium humate and 0.1kg of zinc sulfate heptahydrate were applied as base fertilizers.

Test group 54 #: 28kg of the composite multi-element polyphosphate prepared in example 11, 33kg of urea, 38kg of potassium sulfate, 0.5kg of potassium humate, and 0.1kg of zinc sulfate heptahydrate were applied as base fertilizers.

The potato type used in the test is the Hessen No. 6, each group of tests is repeated for 4 times, the emergence rate and the acre yield of the test are counted, and the statistical results are shown in the following table 12.

Table 12 field trial 2 statistical results

	Rate of emergence (%)	Rate of increase in emergence (%)	Mu yield (Kg)	Proportion of increase in production
					Test group No. 1	80.14	---	2980	---
Test group No. 2	81.45	1.63	3148	5.64
					Test group No. 3	92.87	11.70	4092	20.54
Test group 4#	88.79	9.05	3569	16.21
					Test group 5#	80.94	1.34	2997	5.98

From the results in table 12, it can be seen that, in the temperature rise process of the calcination process, after microwave radiation is performed in the calcination furnace, the overflow of arsenic is facilitated, and the prepared composite multi-element polyphosphate salt is used for preparing the fertilizer special for potatoes, which is more conducive to the improvement of the rate of emergence and the per mu yield. The composite multi-element polyphosphate prepared in the example 9 has high content, namely, the composite multi-element polyphosphate depends on the proper control of the raw material ratio, is also derived from proper calcining temperature and calcining condition, is favorable for protecting the polyphosphate from cracking, and simultaneously, arsenic contained in tailings is removed under the environment of high temperature and microwave radiation, so that the composite multi-element polyphosphate is favorable for the growth of potato seedlings.

Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and/or modifications of the invention can be made, and equivalents and modifications of some features of the invention can be made without departing from the spirit and scope of the invention.

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Method for producing composite multi-element polyphosphate and co-producing fluosilicic acid by wet-process phosphoric acid residues

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