FILTRATION OF NITRIC ACID DECOMPOSITION PRODUCTS OF TECHNOLOGICAL WASTE

ABSTRACT

The article determines the chemical composition of phosphorus concentrate and filtrate obtained by filtration of technogenic waste from the Central Kyzylkum phosphorite plant, processed nitrophophore porridge with nitric acid. The possibility of obtaining complex fertilizers from the resulting phosphorus concentrate and filtrate has been shown.

АННОТАЦИЯ

В статье определен химический состав фосфоконцентрата и фильтрата, полученных фильтрацией техногенных отходов Центрально-Кызылкумского фосфоритового комбината, переработанной нитрофофорной каши с азотной кислотой. Показана возможность получения комплексных удобрений из полученного фосфоконцентрата и фильтрата.

Ключевые слова: азотная кислота, азотно-фосфорная каша, минерализованная масса, техногенные отходы, фосфоконцентрат, фильтрат.

Keywords: nitric acid, nitrogen-phosphorus porridge, mineralized mass, industrial waste, phosphorus concentrate, filtrate.

Introduction. With the growth of human needs, the stage of protection of natural resources and their rational use begins to emerge. Today, the Central Kyzylkum plant is increasing the scale of production of phosphate rock, thermal concentrate and washed-dry phosphorus concentrates. However, the problem of meeting the demand for phosphate fertilizers awaits a solution. This, in turn, means that the production of phosphorus fertilizers involves industrial waste containing phosphorus and other necessary reagents. For this purpose, we set the task of obtaining liquid nitrogen-calcium fertilizers based on technogenic waste (mineralized mass) produced at the Central Kyzylkum Phosphorite Plant.

Objects and methods of research. For this purpose, experiments were carried out in laboratory conditions on a laboratory setup consisting of a tubular glass reactor equipped with a screw stirrer driven by an electric motor. To carry out laboratory work, technogenic waste (mineralized mass composition: Р₂O₅ - 12.91%; СaO - 42.88%; СO₂ - 12.84%;) generated at the Central Kyzylkum Phosphorite Plant was treated with incomplete standards of 57% nitric acid. in 25 - Decomposes in 30 minutes. The calculation of the amount of nitric acid was based on the decomposition of phosphates, free calcium oxides and calcite minerals in the mineralized mass sample, as well as the formation of monocalcium phosphate and calcium nitrate salts. The acid ratio was 30, 40, 50, 60, 70, 80, 90 and 100% relative to stoichiometry [1-3]. The temperature was 65-85°C depending on the acid standard. To prevent losses of phosphorus during the filtering process of the resulting samples of nitrogen-phosphorus acid porridge, they were neutralized with ammonia gas until the pH value pH = 5-5.5 was achieved. Porridge with nitric-phosphoric acid with a pH value of 5-5.5 was diluted with water in a 1:1 ratio and filtered using a press filter. After the filtration process, the wet residue (phosphoconcentrate) and the contents of the filtrate were subjected to chemical analysis using certain methods [4-7].

Experimental part. The results of the analysis showed that the phosphorus concentrate (wet residue) obtained from a sample with an acidity of 30% contained 10.64% total phosphorus, 29.75% total calcium and 1.39% water-soluble calcium. As the acid level in the phosphoconcentrate obtained by filtering a suspension of nitrophophoric acid increases, the content of total phosphorus, as well as total and water-soluble forms of calcium also increases (Table 1). For example, at 40-100 standards compared to a 30% acid standard, the amount of total phosphorus and water-soluble calcium increases by 1.03-1.38 and 1.20-2.76 times, respectively. Increasing the acid level during the production of wet phosphorus concentrate has a positive effect on increasing the amount of absorbed phosphorus in the samples [8]. For example, at an acidity level of 30%, the amount of phosphorus in the form absorbed by the plant is 3.61%. When the acid level increases from 40 to 100%, it increases from 4.96 to 14.69%, respectively.

Table 1.

Chemical composition of wet phosphorus concentrate obtained after filtration by diluting nitrogen-phosphorus acid pulp in a ratio of 1:1, %

In laboratory experiments, the composition of the phytrate formed during filtration was also chemically analyzed [9-11]. The results of the analysis showed that the content of total nitrogen and calcium in the filtrate obtained by filtering porridge with nitric-phosphoric acid with an acidity level of 30% was 2.57 and 5.13%, respectively (Table 2). 15.03% of the total filtrate is nitrogen-calcium fertilizer, i.e. calcium nitrate. In the filtrates obtained by filtering nitric-phosphoric acid porridge obtained at high standards, the content of total nitrogen, calcium and nitrogen-calcium fertilizers increases [12-15]. For example, when the acid level increases from 40 to 100%, the amount of nitrogen, calcium and calcium nitrate in its composition increases from 1.17 to 1.71 times, respectively.

Table 2.

Chemical composition of the filtrate obtained after filtration by diluting nitrogen-phosphorus acid slurry with water in a ratio of 1:1,%

Summary. The results of experiments carried out in laboratory conditions showed that the phosphoconcentrate produced by filtering nitrogen-phosphoric acid sludge obtained at high levels of acid has a large amount of total and plant-absorbable phosphorus, and it was found that water-soluble calcium cannot be completely separated by filtering once. It is clear from this that it is necessary to repulp the obtained phosphoconcentrate with water and filter it again. It was also found that the content of calcium nitrate is significantly higher in filtrates with a high acid level. Therefore, it is possible to use this obtained filtrate as a liquid nitrogen-calcium fertilizer in agriculture and to process it into new types of fertilizers by adding additional nutrients to it.

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