阅读说明：本技术 一种磷石膏除杂及制备白色无水磷石膏的方法 (Method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum ) 是由 刘荣荣 侯美顺 李山山 于 2021-09-15 设计创作，主要内容包括：本发明提供了一种磷石膏除杂及制备白色无水磷石膏的方法,所述方法包括以下步骤：将磷石膏进行第一煅烧处理得到半水磷石膏,将所述半水磷石膏依次进行酸处理和第二煅烧处理后得到白色无水磷石膏。本发明可有效去除磷石膏中的难溶物,大大提高了磷石膏的白度,所述方法操作简单、成本低、增白效果好,为废弃磷石膏的工业无害化处理和综合利用开辟新途径。(The invention provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: carrying out first calcination treatment on phosphogypsum to obtain semi-hydrated phosphogypsum, and carrying out acid treatment and second calcination treatment on the semi-hydrated phosphogypsum in sequence to obtain white anhydrous phosphogypsum. The method can effectively remove insoluble substances in the phosphogypsum, greatly improves the whiteness of the phosphogypsum, has simple operation, low cost and good whitening effect, and opens up a new way for the industrial harmless treatment and comprehensive utilization of the waste phosphogypsum.)

1. The method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum is characterized by comprising the following steps of: carrying out first calcination treatment on phosphogypsum to obtain semi-hydrated phosphogypsum, and carrying out acid treatment and second calcination treatment on the semi-hydrated phosphogypsum in sequence to obtain white anhydrous phosphogypsum.

2. The method as claimed in claim 1, wherein the temperature of the first calcination treatment is 100-200 ℃;

preferably, the time of the first calcination treatment is 2 to 6 hours.

3. The method according to claim 1 or 2, wherein the acid concentration in the acid treatment is 1-30% by mass;

preferably, the acid in the acid treatment comprises any one or a combination of at least two of hydrochloric acid, phosphoric acid or sulfuric acid.

4. A process according to any of claims 1 to 3, characterised in that the mass to volume ratio of the phosphogypsum hemihydrate to the acid in the acid treatment is 1: (3-10) g/mL.

5. The process according to any one of claims 1 to 4, wherein the acid treatment is carried out under stirring conditions;

preferably, the stirring speed is 250-500 rpm;

preferably, the stirring time is 1-3 h.

6. The method according to any one of claims 1 to 5, wherein the mixed solution obtained after the acid treatment is subjected to solid-liquid separation, washing and drying in this order.

7. The method according to any one of claims 1 to 6, wherein the solid-liquid separation mode comprises any one or at least two of filtration, suction filtration or centrifugation;

preferably, the washing is 3 times or more washing with deionized water.

8. The method according to any one of claims 1 to 7, wherein the temperature of the drying treatment is 50 to 80 ℃;

preferably, the drying treatment time is 6-12 h.

9. The method as claimed in any one of claims 1 to 8, wherein the temperature of the second calcination treatment is 600-1000 ℃;

preferably, the time of the second calcination treatment is 1 to 3 hours.

10. Method according to any of claims 1-9, characterized in that the method comprises the steps of: calcining phosphogypsum at 100-200 ℃ for 2-6h, mixing the obtained semi-hydrated phosphogypsum with acid with the mass concentration of 1-30%, wherein the mass-volume ratio of the semi-hydrated phosphogypsum to the acid in the acid treatment is 1: (3-10) g/mL; stirring at 500rpm of 250-; calcining the dried phosphogypsum for 1-3h at the temperature of 600-1000 ℃ to obtain the white anhydrous phosphogypsum.

Technical Field

The invention belongs to the field of comprehensive utilization of solid wastes, and relates to a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum.

Background

Phosphogypsum is solid waste residue generated in the production process of wet-process phosphoric acid, and when the phosphoric acid is produced by adopting the wet-process, every 1 ton of phosphoric acid is produced along with 4.5-5 tons of phosphogypsum. The main component of the phosphogypsum is CaSO₄·2H₂O, and various impurities such as chlorosilicate, incompletely decomposed phosphate ore and phosphoric acid-like substances, fluoride, iron-aluminum compound, organic matter, etc. At present, phosphogypsum is mainly subjected to stockpiling treatment, but the accumulation of a large amount of phosphogypsum not only occupies land resources, but also diffuses and permeates harmful components such as soluble phosphorus, fluoride and the like to the surrounding environment in the stockpiling process, so that potential safety and environmental protection hazards exist, and huge environmental burden is brought to the storage of the phosphogypsum. Phosphogypsum can also be used asBuilding gypsum and raw materials of building gypsum products, but the requirement on the whiteness of the phosphogypsum is high, and the phosphogypsum is grey white or grey black due to the existence of carbon-based impurities and non-ferrous metal compounds, so that the application of the phosphogypsum in industry is greatly limited. The harmless treatment and utilization of the phosphogypsum are the main problems of the current research.

At present, various documents have carried out researches on impurity removal and decoloration of phosphogypsum, and CN109180036A discloses a method for decoloring and whitening phosphogypsum, which comprises the steps of adding ammonium salt and water into the phosphogypsum, stirring and soaking at room temperature to obtain a solid-liquid mixture, filtering, washing and drying filter residues after filtration to obtain the decolored and whitened phosphogypsum.

CN111792663A discloses a phosphogypsum whitening method, which comprises the steps of calcining phosphogypsum and a calcining auxiliary agent at high temperature, soaking the obtained calcined material in a sulfuric acid solution, cooling after reaction, carrying out suction filtration, washing, carrying out suction filtration and drying to obtain the whitened phosphogypsum.

In view of the problems in the prior art, the phosphogypsum has some technical problems in impurity removal and whitening, and with the application and popularization of the phosphogypsum in various industries, the demand of the phosphogypsum is more and more large, and the requirement on the whiteness of the phosphogypsum is also more and more high. Therefore, there is a need to develop a method for removing impurities and whitening phosphogypsum, which can not only solve the influence of impurities in the phosphogypsum on whitening, but also improve the resource utilization rate of the phosphogypsum.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides the method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which can remove impurities in the phosphogypsum, improve the whiteness of the product, realize the harmless treatment of phosphogypsum waste and provide a technical basis for the industrialization of the waste phosphogypsum.

In order to achieve the technical effect, the invention adopts the following technical scheme:

the invention provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: carrying out first calcination treatment on phosphogypsum to obtain semi-hydrated phosphogypsum, and carrying out acid treatment and second calcination treatment on the semi-hydrated phosphogypsum in sequence to obtain white anhydrous phosphogypsum.

According to the method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, the semi-hydrated phosphogypsum obtained through the first calcination treatment can fully contact and react with non-ferrous metals in the phosphogypsum in the acid treatment process by utilizing the hydration characteristic of the semi-hydrated phosphogypsum, so that the non-ferrous metals in the phosphogypsum can be effectively leached, the impurity removal effect of the acid treatment is improved, the color influence of impurities on the phosphogypsum in the second calcination process is reduced, and the whiteness of the product is improved.

In a preferred embodiment of the present invention, the temperature of the first calcination treatment is 100-200 ℃, and may be, for example, 100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃ or 200 ℃, but is not limited to the recited values, and other values not recited in the numerical ranges are also applicable.

Preferably, the time of the first calcination treatment is 2 to 6 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours, etc., but is not limited to the recited values, and other values not recited in the range of values are also applicable.

In a preferred embodiment of the present invention, the acid concentration in the acid treatment is 1 to 30% by mass, for example, 1%, 5%, 15%, 20%, 25%, or 30%, but the present invention is not limited to the above-mentioned values, and other values not shown in the numerical ranges are also applicable.

Preferably, the acid in the acid treatment comprises any one or a combination of at least two of hydrochloric acid, phosphoric acid or sulfuric acid, typical but non-limiting examples of which are: a combination of hydrochloric acid and phosphoric acid, a combination of hydrochloric acid and sulfuric acid, or a combination of phosphoric acid and sulfuric acid, and the like.

In a preferred embodiment of the present invention, the mass-to-volume ratio of the hemihydrate phosphogypsum to the acid in the acid treatment is 1 (3-10) g/mL, for example, 1:3g/mL, 1:4g/mL, 1:5g/mL, 1:6g/mL, 1:7g/mL, 1:8g/mL, 1:9g/mL or 1:10g/mL, but is not limited to the values listed, and other values not listed in the numerical range are also applicable.

In a preferred embodiment of the present invention, the acid treatment is performed under stirring.

Preferably, the stirring rate is 250-500rpm, such as 250rpm, 300rpm, 350rpm, 400rpm, 450rpm or 500rpm, but not limited to the enumerated values, and other unrecited values within the numerical range are also applicable.

Preferably, the stirring time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc., but is not limited to the recited values, and other values not recited in the numerical range are also applicable.

In a preferred embodiment of the present invention, the mixed solution obtained after the acid treatment is subjected to solid-liquid separation, washing, and drying in this order.

As a preferred technical scheme of the invention, the solid-liquid separation mode comprises any one or at least two combinations of filtration, suction filtration or centrifugation, and the combinations are typically but not limited to: a combination of filtration and suction filtration, a combination of filtration and centrifugation, or a combination of suction filtration and centrifugation, and the like.

Preferably, the washing is 3 times or more washing with deionized water.

In a preferred embodiment of the present invention, the temperature of the drying treatment is 50 to 80 ℃, and may be, for example, 50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃ or 80 ℃, but is not limited to the recited values, and other values not recited in the numerical ranges are also applicable.

Preferably, the drying time is 6-12h, such as 6h, 7h, 8h, 9h, 10h, 11h or 12h, but not limited to the recited values, and other values not recited in the range of values are also applicable.

In a preferred embodiment of the present invention, the temperature of the second calcination treatment is 600-1000 ℃, for example, 600 ℃, 650 ℃, 700 ℃, 750 ℃, 800 ℃, 850 ℃, 900 ℃, 950 ℃ or 1000 ℃, but not limited to the recited values, and other values not recited in the numerical range are also applicable.

Preferably, the time of the second calcination treatment is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, etc., but is not limited to the recited values, and other values not recited in the numerical range are also applicable.

As a preferred technical scheme of the invention, the method specifically comprises the following steps: calcining phosphogypsum at 100-200 ℃ for 2-6h, mixing the obtained semi-hydrated phosphogypsum with acid with the mass concentration of 1-30%, wherein the mass-volume ratio of the semi-hydrated phosphogypsum to the acid in the acid treatment is 1: (3-10) g/mL; stirring at 500rpm of 250-; calcining the dried phosphogypsum for 1-3h at the temperature of 600-1000 ℃ to obtain the white anhydrous phosphogypsum.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, the semi-hydrated phosphogypsum obtained through the first calcination treatment is subjected to acid treatment, and the characteristics of hydration of the semi-hydrated phosphogypsum are utilized, so that an acid solution and impurities in the phosphogypsum are fully contacted and reacted, the dissolution of insoluble matters in the phosphogypsum is promoted, the impurity removal effect of acid washing is improved, the influence of the impurities on the whiteness of the phosphogypsum in the second calcination process is reduced, and the whiteness of the phosphogypsum is greatly improved;

(2) the preparation method disclosed by the invention is simple, low in cost and good in whitening effect, realizes harmless treatment of industrial waste, provides a higher-quality raw material for downstream application of phosphogypsum, and has good economic and social benefits.

Detailed Description

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

Example 1

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining phosphogypsum at 150 ℃ for 4h, mixing the obtained semi-hydrated phosphogypsum with sulfuric acid with the mass concentration of 15%, wherein the mass-volume ratio of the semi-hydrated phosphogypsum to the sulfuric acid is 1:7g/mL, stirring for 2h at 350rpm, filtering the obtained mixed solution, washing the solid with deionized water for more than 3 times, and drying for 6h at 80 ℃; and calcining the dried product at 800 ℃ for 2h to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 88.4.

Example 2

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining phosphogypsum at 100 ℃ for 5 hours to obtain semi-hydrated phosphogypsum, mixing the semi-hydrated phosphogypsum with sulfuric acid with the mass concentration of 1% and hydrochloric acid with the mass concentration of 2%, wherein the mass-volume ratio of the semi-hydrated phosphogypsum to the mixed acid is 1:3g/mL, stirring for 3h at 250rpm, centrifuging the obtained mixed solution, washing the solid with deionized water for more than 3 times, and drying for 12h at 50 ℃; and calcining the dried product at 600 ℃ for 3h to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 87.6.

Example 3

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining phosphogypsum at 200 ℃ for 2h, mixing the obtained semi-hydrated phosphogypsum with sulfuric acid with the mass concentration of 30%, wherein the mass-volume ratio of the semi-hydrated phosphogypsum to the sulfuric acid is 1:10g/mL, stirring at 500rpm for 1h, filtering the obtained mixed solution, washing the solid with deionized water for more than 3 times, and drying at 60 ℃ for 10 h; calcining the dried product at 1000 ℃ for 1h to obtain the white phosphorus anhydrous gypsum. The whiteness was measured to be 89.2.

Example 4

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining phosphogypsum at 150 ℃ for 4h, mixing the obtained semi-hydrated phosphogypsum with sulfuric acid with the mass concentration of 5%, wherein the mass-volume ratio of the semi-hydrated phosphogypsum to the sulfuric acid is 1:5g/mL, stirring for 2h at 350rpm, filtering the obtained mixed solution, washing the solid with deionized water for more than 3 times, and drying for 8h at 70 ℃; and calcining the dried product at 800 ℃ for 3h to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 88.2.

Example 5

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining phosphogypsum at 180 ℃ for 3 hours to obtain semi-hydrated phosphogypsum, mixing the semi-hydrated phosphogypsum with sulfuric acid with the mass concentration of 3%, wherein the mass-volume ratio of the semi-hydrated phosphogypsum to the sulfuric acid is 1:3g/mL, stirring for 2h at 350rpm, filtering the obtained mixed solution, washing the solid with deionized water for more than 3 times, and drying for 12h at 60 ℃; and calcining the dried product at 900 ℃ for 2h to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 86.2.

Example 6

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining phosphogypsum at 120 ℃ for 5 hours to obtain semi-hydrated phosphogypsum, mixing the semi-hydrated phosphogypsum with sulfuric acid with the mass concentration of 1%, wherein the mass-volume ratio of the semi-hydrated phosphogypsum to the sulfuric acid is 1:10g/mL, stirring for 2h at 350rpm, filtering the obtained mixed solution, washing the solid with deionized water for more than 3 times, and drying for 8h at 80 ℃; and calcining the dried product at 750 ℃ for 3h to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 89.2.

Example 7

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining phosphogypsum at 200 ℃ for 3h, mixing the obtained semi-hydrated phosphogypsum with sulfuric acid with the mass concentration of 3%, wherein the mass-volume ratio of the semi-hydrated phosphogypsum to the sulfuric acid is 1:4g/mL, stirring at 350rpm for 2h, filtering the obtained mixed solution, washing the solid with deionized water for more than 3 times, and drying at 70 ℃ for 10 h; and calcining the dried product at 1000 ℃ for 3h to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 87.2.

Example 8

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining phosphogypsum at 100 ℃ for 6 hours to obtain semi-hydrated phosphogypsum, mixing the semi-hydrated phosphogypsum with sulfuric acid with the mass concentration of 3%, wherein the mass-volume ratio of the semi-hydrated phosphogypsum to the sulfuric acid is 1:10g/mL, stirring for 2h at 350rpm, filtering the obtained mixed solution, washing the solid with deionized water for more than 3 times, and drying for 8h at 60 ℃; and calcining the dried product at 600 ℃ for 3h to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 90.2.

Example 9

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: except that phosphogypsum is calcined at 90 ℃ for 12h to obtain semi-hydrated phosphogypsum; the other conditions were the same as in example 1. The whiteness was measured to be 80.5.

Example 10

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: except that phosphogypsum is calcined at 300 ℃ for 3h to obtain semi-hydrated phosphogypsum; the other conditions were the same as in example 1. The whiteness was measured to be 82.5.

Example 11

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining the dried product at 400 ℃ for 2h to obtain white anhydrous phosphogypsum; the other conditions were the same as in example 1. The whiteness was measured to be 56.2.

Example 12

The embodiment provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: except that the mass-to-volume ratio of the semi-hydrated phosphogypsum to the sulfuric acid solution is 1:1 g/mL; the other conditions were the same as in example 1. The whiteness was measured to be 71.5.

Comparative example 1

The comparative example provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: mixing phosphogypsum with sulfuric acid with the mass concentration of 15%, wherein the mass-volume ratio of the phosphogypsum to the sulfuric acid is 1:7g/mL, stirring for 2h at 350rpm, filtering the obtained mixed solution, washing the solid with deionized water for more than 3 times, and drying for 10h at 60 ℃; and calcining the dried product at 800 ℃ for 2h to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 75.4.

Comparative example 2

The comparative example provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining phosphogypsum at 800 ℃ for 2h, mixing the obtained anhydrous phosphogypsum with sulfuric acid with the mass concentration of 15%, wherein the mass-volume ratio of the anhydrous phosphogypsum to the sulfuric acid is 1:7g/mL, stirring for 2h at 350rpm, filtering the obtained mixed solution, washing the solid with deionized water for more than 3 times, and drying for 6h at 80 ℃ to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 68.2.

Comparative example 3

The comparative example provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining the phosphogypsum at 800 ℃ for 3h to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 38.1.

Comparative example 4

The comparative example provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining the phosphogypsum for 2 hours at 900 ℃ to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 40.4.

Comparative example 5

The comparative example provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which comprises the following steps: calcining the phosphogypsum at 750 ℃ for 3h to obtain the white anhydrous phosphogypsum. The whiteness was measured to be 53.7.

Comparing example 1 with examples 9-10, too high or too low of the first calcination treatment temperature gives anhydrous phosphogypsum with lower whiteness; comparing example 1 with example 11, the whiteness of the anhydrous phosphogypsum obtained by excessively low temperature of the second calcination treatment is low; comparing example 1 with example 12, the weight to volume ratio of the semi-hydrated phosphogypsum to the acid in the acid treatment is too low, and the obtained anhydrous phosphogypsum has low whiteness; therefore, the temperature of the first calcining treatment and the second calcining treatment and the mass-volume ratio of the semi-hydrated phosphogypsum to the acid in the acid treatment are in proper ranges, so that the impurity removal of the phosphogypsum and the whiteness improvement of the phosphogypsum are facilitated.

Comparing the example 1 with the comparative example 1, the whiteness of the anhydrous phosphogypsum obtained by direct acid treatment and high-temperature calcination is low without first calcination treatment; comparing the example 1 with the comparative example 2, firstly calcining the phosphogypsum at high temperature, and obtaining the anhydrous phosphogypsum with low whiteness after the acid treatment; therefore, the semi-hydrated phosphogypsum obtained by the first calcination treatment is beneficial to full contact reaction between subsequent acid treatment and impurities in the semi-hydrated phosphogypsum, and is beneficial to improving the whiteness of the phosphogypsum.

Comparing the example 1 with the comparative examples 3-5, the anhydrous phosphogypsum obtained by directly calcining phosphogypsum at high temperature has low whiteness; therefore, the first calcining treatment and the acid treatment are important steps for ensuring the impurity removal of the phosphogypsum and improving the whiteness of the phosphogypsum.

In conclusion, the invention provides a method for removing impurities from phosphogypsum and preparing white anhydrous phosphogypsum, which can reduce the influence of impurities on the whiteness of the phosphogypsum and greatly improve the whiteness of the phosphogypsum; the preparation method is simple, low in cost and good in whitening effect, realizes harmless treatment of industrial waste, and can provide a higher-quality raw material for downstream application of the phosphogypsum.

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.