SU833485A1 - Method of phosphoric acid production - Google Patents

Description

(54) METHOD FOR OBTAINING PHOSPHORIC ACID

one

The invention relates to the production of phosphoric acid from phosphate-containing ores, which is used for the production of mineral fertilizers.

Known methods. obtaining phosphoric acid from the enriched phosphate-containing ores and their ores, based on the decomposition of phosphates by sulfuric acid and the release of calcium sulfate in the presence of a dilution solution. In the existing schemes of sulfuric acid phosphate processing, decomposition is carried out in the presence of a certain amount of circulating production phosphoric acid and returned to the washing solution process.

As a result, calcium sulphate is formed, which can be isolated in the form of a dihydrate, hemihydrate or anhydrous calcium sulphate and production phosphoric acid.

The general stages of well-known methods are the stages of phosphate raw material decomposition by strong sulfuric acid (50-98%) mixed with recycled diluted phosphoric (dilution solution), at a temperature of the reaction mass of 70-120 ° C; calcium sulfate excretion; separating the resulting pulp and washing the phosphoric acid from the precipitate 1.

However, the known methods are effective for rich concentrates (28-41% PI Os), free from impurities of iron oxides and aluminum, and for the poor in phosphate (20% PjOj and below), including iron and aluminum-containing minerals, they are not suitable, due to the high consumption of sulfuric acid spent on opening impurities (up to 3-4 folds of excess stoichiometric), difficulties associated with removing large volumes of poorly filterable sludge (filtration rate drops due to gelation), contamination with impurities of the target product. All this leads to a sharp increase in cost and reduce the efficiency of the process.

There is also known a method for producing phosphorus acid by decomposing phosphorite with weak sulfuric acid at a concentration of 7-10% at 50 ° C. The ratio of solid and liquid phases in pulp is 1:30 2. The disadvantages of this method are the non-selectivity of the decomposition process — sulfuric acid at a concentration of 7-10T and a temperature of 50 ° C, in addition to calcium phosphate, decomposes other minerals that make up the ore, especially iron and aluminum, not. As a result, the production solution contains large amounts of compounds of iron, aluminum (more than 16%), significantly reducing the quality of phosphoric acid. Therefore, it becomes necessary to remove these impurities by additional time-consuming and sometimes complex operations of fractional precipitation, ion exchange, extraction. The coefficient of selectivity (the conditional coefficient, which is equal to the ratio of the percentage of extraction to the sum of the percentage of extraction of harmful impurities - FestO, etc.) is 4.0. The purpose of the invention is to reduce the content of impurities in the product. The goal is achieved by the proposed method of obtaining phosphoric acid from poor oreganized phosphorites, which consists in the decomposition of phosphorites with sulfuric acid concentration of 2-4% at a solid-to-liquid ratio in the decomposing pulp of 1: 10-1: 25 and a temperature of 10-35 ° C. The essence of the proposed method lies in the fact that dilute sulfuric acid decomposes poor ferruginous phosphorites much faster, since they have a finely dispersed structure and a correspondingly large active surface. Moreover, diluted sulfuric acid, the surface of phosphate-accompanying minerals, the passiviruate, affects the dissolution rate of the basic substance (P, O #), depending on the activity of hydrogen ions in solution, the contact time of the phases, the temperature and the diffusion rate of the resulting compounds. The acceleration of the decomposition reaction is also facilitated by the presence of carbonate compounds in the phosphate rocks, which, when interacting with acids, decompose, forming CO / E. This leads to the destruction of the dense crust of phosphogypsum on phosphorite particles and disintegration of individual phosphorite grains, which improves the conditions for the diffusion of dissolving products from the reaction zone into the solution. In general, the process under these conditions leads to a sharp increase in selectivity. The selectivity of the decomposition process depends on a combination of three parameters determining the optimal leaching conditions. Considering separately each of the parameters, it can be concluded about the degree of influence of each of them on the decomposition process. The degree of extraction of components depending on the concentration of sulfuric acid at constant temperature and phase ratio (t 20 ° C; T: W 1; 10 ) is reflected in the table. 1. From the data table. 1, it follows that the completeness of extraction of the useful component (PzOf) is achieved with an acid concentration of 2.0% and a further increase in concentration leads to a decrease in the decomposition of harmful impurities (iron, aluminum), while increasing the consumption of valuable solvent and reducing the selectivity of the process. The effect of temperature on the degree of extraction of components at a constant ratio of the concentration of sulfuric acid and the relative phase ratio (C 2%, T: W 1LO) is reflected in Table. 2. From table. 2 that the completeness of PJ.OS recovery is achieved at t 10-35 ° C, and a further increase in temperature leads to an increased dissolution of "harmful impurities of iron and aluminum, which affects the quality of the target product and the increase in energy consumption. The dependence of the degree of extraction of substances from ore on the ratio of the phases, at constant acid concentration and temperature (C 2%, t 20 ° C) is shown in Table. 3. With an increase in the phase ratio, PiQf is only partially recovered, and with a significant decrease in T: W, the acid is consumed to dissolve the impurities of iron and aluminum, with this, the selectivity of the process decreases and the acid consumption increases. In all experiments, the results of which are presented in Tables 1-3, ores containing, by weight, are used. 6.0-15.0; AUOs 2.0-10 and fetPi 5-13.0. The weight of the ore is 25 g, the leaching time is 30 minutes, the size of the ore is 1 mm. Optimization of the leaching process is assessed by selectivity. The proposed method allows to reduce the content of impurities in the acid more than 4 times with a selectivity coefficient of 18.6. Example. 100 g of ore from the Verkhnekamskoye deposit is placed in a reactor with a capacity of 2 liters ,. 1000 ml of 2% is added (T: W 1: 1 (0), stirred for 30 minutes and filtered. The filtrate and the precipitate are measured and analyzed. Then the filtrate is ammoniated. Extraction into a solution,%: 98.6; 2, 71 and A1 O 2.61. Selectivity coefficient - 18.6. Carrying out the process with other parameters gives similar results (Gtabl. 1-3). -

Table 1

at 833485g

Claims (1)

The formula of the invention for pulp is 1:10 - 1:25 and temperature The method of producing phosphoric acid is 10-35 ° C. of poor iron phosphorites by sources of information that decomposition of them with sulfuric acid, distinguished-taken into account in the examination This is due to the fact that, in order to reduce the content of i. Pozin ME zhany impurities in the product of the decomposition of the we-s salts. L., “Himi, 1974, p. 904-932. give sulfuric acid concentration. "Journal of Inorganic Chemistry, 1, when the ratio of solid to liquid in times-1956, No. 7, p. 1519 (prototype). one.