Study on Potassium Feldspar Potassium Extraction Process

I. Introduction

Is well known, three elements of nitrogen and potassium fertilizer phosphorus ratio of arable land unreasonable, high nitrogen, phosphorus and potassium is low ^[1]. Nitrogen fertilizer and phosphate fertilizer basically meet the needs in fertilizer production, and due to the lack of water-soluble potassium resources in China, potash fertilizer production is far from meeting the needs of agriculture, and most rely on imports ^[2] . But our non-water-soluble potassium resources are very rich, especially large potassium feldspar poorly soluble potassium reserves, wide distribution, the total amount of nearly 8 billion t ^[3]. Therefore, the development of the use of poorly soluble potassium resources, research on potassium extraction, has important practical and economic significance.

According to the characteristics of ion exchange reaction mechanism ^[4] and hydrothermal reaction method, the experimental scheme was designed to study the influence of parameter variation on potassium extraction rate, which provided a theoretical basis for the industrial application of potassium feldspar potassium extraction process.

Second, the experimental part

(1) Experimental principle

Ca ₅ (P0 ₄ ) ₃ F+5H ₂ S0 ₄ →5CaS0 ₄ +3H ₃ P0 ₄ +HF↑

2KAlSi ₃ 0 ₈ +Ca ²⁺ →CaAl ₂ Si ₂ 0 ₈ +2K ⁺ +4Si0 ₂

24HK+2KAlSi ₃ 0 ₈ +8H ⁺ →2Al ³⁺ +6SiF ₄ ↑+16H ₂ 0

(2) Experimental materials

Potassium feldspar was taken from the K-feldspar mine in the Sanmenxia area of ​​Henan Province. The composition is shown in Table 1.

Table 1 Potash Feldspar Composition %

(3) Experimental instruments

CS202-2AB electric blast dryer, CP214 optical analytical balance, hydrothermal reactor (polytetrafluoroethylene lining), D/max-γB type positive target X-ray diffractometer.

(4) Experimental operation

The crushed ball milled potassium feldspar and phosphate rock, the potassium feldspar powder and the phosphate rock powder are weighed according to a certain mass ratio, mixed uniformly and placed in a hydrothermal reaction kettle with a PTFE lining, and then a certain volume fraction of a certain volume is added. sulfuric acid, the reaction temperature taken after a certain time at a certain temperature, the heat source and allowed to cool off to room temperature and aged for 1.5h, add water leaching was filtered, volume, mass analysis of the filtrate with potassium tetraphenyl boron potassium quality Act Score, calculate the potassium dissolution rate.

Third, the results and discussion

(1) Orthogonal experiment

Select sulfuric acid mass fraction (A,%), sulfuric acid dosage (B, mL), raw material ratio (C, mass ratio of potassium feldspar to phosphate rock), reaction temperature (D, °C), reaction time (E, h) As the five influencing factors of the orthogonal experimental table, referring to the orthogonal table L ₄ ⁵ , four levels were selected for the orthogonal experiment, wherein the orthogonal experimental factor level is shown in Table 2, and the orthogonal experimental results are shown in Table 3.

Table 2 Orthogonal experimental factors level table

Table 3 Orthogonal experimental study results

The results of orthogonal experiment show that for the potassium dissolution rate, the orthogonal order of the excellent level should be 44132, that is, the sulfuric acid mass fraction is 60%, the sulfuric acid dosage is 4.0 mL, the raw material ratio is 0.8:1, the reaction temperature is 160 °C, and the reaction time is 2.5 h. The experimental result at the excellent level is that the potassium dissolution rate is 61.2%.

It can be seen from Table 3 that the order of influence of the five factors on the dissolution rate of potassium is: raw material ratio > sulfuric acid mass fraction > sulfuric acid dosage > reaction time > reaction temperature. Based on the four factors with the largest influencing factors (raw material ratio, sulfuric acid mass fraction, sulfuric acid dosage, reaction time), further optimization experiments were carried out.

(2) Effect of material ratio on potassium dissolution rate

From the ratio of materials with extremely different orthogonal experimental results, the reaction temperature was maintained at 160 ° C, the sulfuric acid mass fraction was 70%, the sulfuric acid dosage was 4 mL/g, and the reaction time was 3 h. The material ratio was changed. The experimental results are shown in Fig. 1.

Figure 1 Effect of material ratio on potassium dissolution rate

It can be seen from Fig. 1 that as the ore mass ratio increases, the potassium dissolution rate gradually decreases, because the amount of free Ca ²⁺ and hydrogen fluoride gas generated in the reaction system is constant as the ratio increases, so The amount of potassium extracted is constant, but in the formula for calculating the extraction rate of potassium, the molecule is constant, and the larger the denominator, the smaller the dissolution rate of potassium. Due to the large error in a small number of calculations, this experiment chose a material ratio of 0.8:1.

(III) Effect of sulfuric acid mass fraction on potassium dissolution rate

Under the condition of maintaining the reaction temperature of 160 ° C, sulfuric acid dosage of 4 mL / g, ore mass ratio of 0.8:1 (potassium feldspar: phosphate rock) and reaction time of 3 h, the sulfuric acid mass fraction was changed. The experimental results are shown in Fig. 2.

Figure 2 Effect of sulfuric acid mass fraction on potassium dissolution rate

It can be seen from Fig. 2 that with the increase of the mass fraction of sulfuric acid, the dissolution rate of potassium is parabolic, and when the mass fraction of sulfuric acid is 70%, the dissolution rate of potassium can reach 69.6%. Therefore, the optimal potassium extraction interval of sulfuric acid mass fraction is 65% to 70%, and after the sulfuric acid mass fraction exceeds 70%, the dissolution rate of potassium decreases with the increase of sulfuric acid mass fraction.

(4) Effect of sulfuric acid dosage on potassium dissolution rate

Maintain sulfuric acid mass fraction of 70%, reaction temperature of 160 ° C, ore mass ratio of 0.8:1 (potassium feldspar: phosphate rock), reaction time of 3 h, change the amount of sulfuric acid, the experimental results are shown in Figure 3.

It can be seen from Fig. 3 that as the amount of sulfuric acid increases, the potassium dissolution rate first rises and then decreases, because the excessive amount of sulfuric acid will lower the pH value of the solution, change the nature of the ion exchange system, and cause the exchange cations to passivate. The ion exchange capacity of K-feldspar. The amount of sulfuric acid used when the potassium dissolution rate was the maximum was 4 mL/g.

Figure 3 Effect of sulfuric acid dosage on potassium dissolution rate

(5) Effect of reaction time on potassium dissolution rate

Maintain sulfuric acid mass fraction of 70%, reaction temperature of 160 ° C, ore mass ratio of 0.8:1 (potassium feldspar: phosphate rock), sulfuric acid dosage of 4 mL, change the reaction time, the experimental results are shown in Figure 4.

Figure 4 Effect of reaction time on potassium dissolution rate

It can be seen from Fig. 4 that the prolongation of the reaction time increases the dissolution rate of potassium. The longer the time, the better the diffusion of sulfuric acid into the phosphate rock through the reaction layer, and the diffusion of cations into the inner pores of K-feldspar, which accelerates the reaction process. Higher potassium extraction rate, so the reaction time was chosen to be 4h on the basis of experiments.

Fourth, the conclusion

Experiments show that the potassium extraction process of potassium feldspar with phosphate rock and sulfuric acid is feasible. The order of influence of five factors on potassium dissolution rate is: raw material ratio > sulfuric acid mass fraction > sulfuric acid dosage > reaction time > reaction temperature . The optimum conditions for the potassium feldspar and phosphate rock co-acid leaching process were as follows: the ore mass ratio was 0.8:1, the sulfuric acid dosage was 4 mL/g, the sulfuric acid mass fraction was 70%, and the reaction temperature was 160 °C. At 4 h, the potassium dissolution rate was 74.1%.

references

[1]Huang Chunyuan, Liu Ying, Liu Ying. Analysis of the development and market forecast of compound fertilizer in China[J].大氮肥,2004,27(5):289-291.

[2] Gao Yongfeng. Development and prospects of domestic (outside) fertilizer industry [J]. Phosphate fertilizer and compound fertilizer. 2007, 22 (5): 1-5.

[3]Chen Shanji. Summary of Comprehensive Utilization of Phosphorus By-products from Electric Furnace in China[J].Sulphur Phosphorus Design and Powder Engineering,2004,(4):7-11.

[4] Chen Jialu. Development Trend of Phosphorus Chemical Industry [J]. Inorganic Salt Industry, 2004, (2): 1-3.

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