SU990079A3 - Method for preparing suspension - Google Patents

Abstract

Prodn. of slurries for the mfr. of NP or NPK fertilisers comprises digesting rock phosphate with HNO3 and then neutralising the resulting slurry with ammonia while adding additional acid. The process is modified in that (a) part of the rock phosphate is replaced by H3PO4; (b) only two neutralisation stages are employed; and (c) at least a major part of the H3PO4 is added in the 2nd neutralisation stage. The process employs fewer neutralisation stages then prior art processes while still avoiding excessive thickening of the slurry.

Description

54) METHOD OF OBTAINING SUSPENSION

The invention relates to methods for preparing a suspension suitable for processing into complex fertilizers containing nitrogen, phosphorus and possibly 5 potassium. To form a suspension, the crude phosphate is leached with a yawing acid and then neutralized with ammonia while phosphoric acid is added. 10

A method is known for producing a suspension suitable for processing on complex fertilizers, by decomposing the phosphate stock with nitric acid. In the interaction between the crude phosphate and nitric acid, phosphoric acid and calcium nitrate are formed, KOTOixie is then neutralized with ammonia along with the added phosphoric acid. In this case, neutralization is carried out 20 in several steps to the required pH, since the suspension is highly prone to paste formation 13.

A disadvantage of the known method 25 is the complexity of the process due to the need for a multi-stage automation.

The purpose of the invention is to simplify the process by reducing the steps 30

ammonization to two while simultaneously forming a flowable suspension.

This goal is achieved by the fact that according to the method of obtaining a suspension suitable for. processing into complex fertilizers by decomposing the phosphate raw material with nitric acid, followed by neutralization of the resulting product with gaseous ammonia in the presence of phosphoric acid, 10-40% of phosphoric acid is first introduced into the decomposition product and neutralized to a pH of 2.5-4.5, followed by the rest amounts of phosphoric acid and neutralization to pH 5.0-6.0 at 110-130 ° C at both stages of the process.

The method is carried out in the following manner.

Claims (2)

The phosphorus in the raw phosphate, for example, in apatite, is converted into a plant-friendly form by conversion between nitric acid and apatite, in which the apatite phosphorus is released in the form of phosphoric acid. A portion of the phosphorus is added directly in the form of phosphoric acid. Slurry spraying The amount of phosphorus supplied during neutralization can be avoided if part of the crude phosphate is replaced by phosphoric acid, most of which is fed during the second stage of neutralization with a high pH. . In the first neutralization stage, the pH is 2.5-4.5, and in the second neutralization stage - 5.0-6.0 The suspension during the neutralization is cooled to 110-130 ° C. In order to obtain water-soluble phosphorus at the stage of neutralization, phosphoric acid and, possibly, sulfuric acid are added predominantly in an excess amount, while the concentration of phosphoric acid is 30-50 wt.%. Thus, the costs of calcium nitrate go to the formation of calcium phosphate or gypsum. The general reaction is carried out according to the following scheme: P, 05-3.35 CaO + 6.8 HNOa + 6.8 NH + 1, 35 1.675 (P205-2 CaO) + + 6.8 + 2NH4N03. PjOj-3.35 CaO + 6.8 HNOj + 6.8 NH 3 + 1.35 H2SO4-P O -ZSaO + l, 35CaS0 + 6.8 NH4N03. The phosphorus thus obtained is poorly soluble, but soluble in ammonium citrate, and thus, it is in a form that can be used by plants. In order to become water soluble, the phosphorus in the fertilizer must be in the form of ammonium phosphate, which is achieved by working with an excess of phosphoric and sulfuric acid. Ammonization of phosphorus is carried out to the place of inter mono and diammonium phosphate. By using an excess, the concentration of which is P, j05, P, j05-3.35 CaO + 6.8 HNO + ll, 825NH + 4.7 H2O., 675 (P205-2CaO) + + 1.675 (P205- 3 NHg) + 6.8. When working with an excess, P 0 0c-3.35 CaO + 6.8 then + 8.3 NH, + 2.35 H 50 504- 0.5- {P ,, 05-2СаО) + + 0.5 are obtained. (PjOj -3 NH) 2.55 SAZOC + + 6.8. Fluorine contained in apatite is treated as hydrogen fluoride (HF) by treatment with nitric acid. Upon ammonization, the remaining part of the solution turns into calcium fluoride and remains in the fertilizer. CaF2 + 2HN05 - CaCNOj), + HF Ca {N03i2 2HF + 2NH ,, + 2NHN Example 1. Use sphe,% Apatite P-j05) 39 Nitrogen KiSlota (HNOj) 60-65 Phosphoric acid (PjOs) 40-50 Sulfuric acid ( Well 50) Ammonia Kaliev salt IKjO) Trace elements Borat fertilizer. When receiving 42 t / h (15:20:15 N: PgOs KgO) of the fertilizer, 118 kg of apatite is passed through the pipeline to the leaching reactor. 253 kg of nitric acid are fed into the same reactor through a pipe duct at. Then, the acidic suspension is conducted to the first ammoniation (neutralization) reactor, in which 10% phosphoric acid is fed through the tube, and ammonia gas is in several nozzles at the bottom of the reactor so that the pH of the suspension is 3.5. Using external cooling and evaporation of water, the temperature in the reactor is maintained at 125 ° C. In this reactor also serves water washing gas from the absorber. From the reactor, the slurry flows into the second ammoniation reactor, into which the residual phosphoric acid is also fed through the pipeline. Sulfuric acid is not used. A total of 160 kg of phosphoric acid is consumed. After several nozzles at the bottom, ammonia is fed into the reactor through the pipeline so that the pH of the slurry in the reactor rises to 5.5. Then in the reactor serves water washing the gas from the scrubber. The total ammonia consumption for both reactors is 114 kg. The temperature in the reactor is 125 ° C. Next, another 260 kg of potassium salt and 2.2 kg of borate fertilizer are fed into the reactor (the indicated quantities of raw materials are considered per ton of product). RK slime (slurry), which has a water content of 18% and is suitable for further processing, is obtained as a product. according to the traditional granulation method. Example 2. Moroccan phosphate is taken as crude phosphate, and an anti-foam agent is added to eliminate foaming. Raw materials are used,%: Moroccan phosphate (P2O5) 34 Nitric acid (NNOZ) 40-65 Phosphoric acid (PjOs) 40-50 Sulfuric acid (N5504 ). 93 Ammonia. Calcium salt gas (K2O) 60 as magnesium trace elements add magnesium sulfate and borate fertilizer; N: P205: KgO 20: lO: 10 .. 62 kg / h of Moroccan phosphate and 608 nitric acid, as well as 0.6 kg of water at 67 ° C are fed into the targeting reactor. The suspension of this reactor is carried out in the first neutralization reactor, in which 10 phosphoric acid and ammonia are added in such a way that the pH of the suspension rises to 3, S. Temperature in the reactor 110 ° From the first reactor, the neutralization of the suspension is fed to the second reactor, into which the rest of the ammonia and 90% of phosphoric acid is fed, with the suspension rising to 5.6. The temperature is controlled by appropriate regulation (water is maintained at the jacket at 100 ° C. The suspension has a water content of 18%. In addition, 78 kg / h of sulfuric acid, 167 kg / h of csc salt, and trace elements (, 43 kg / Sulfate magnet and 2.2 kg / h of borate fertilizer K. Water is used to flush gases into both neutralization reactors. The product, containing 18% water, is further processed in a Blyunger granulator.Good quality granular fertilizer is obtained. 3 (comparative). Use raw materials,%: Apatite (PgrOj) 39 Nitric Acid (HNOj) Phosphoric Acid (PjOs Sulfuric Acid (H 2 SO)) Ammonium Potassium Salt 12 kg / h of apatite and 45.8 kg of nitric acid are fed to the leaching reactor. The acidic suspension is passed to the first neutralization reactor. wherein 50% phosphoric acid and ammonia are fed in such a way that the pH of the suspension rises to 4. The temperature in the reactor is then the suspension is fed to the second neutralization reactor, to which the remaining substances are added, i.e. 50% phosphoric acid, 2.2 kg / h of sulfuric acid, 25.1 kg / h of potassium salt and ammonia, so that the pH rises to L, 6. The remaining water must be supplied to the neutralization reactors, since the suspension is prone to thickening in the second neutralization reactor .. Although the water content is 30% (very high), the suspension flows poorly or does not flow at all, so that the method cannot be used for industrial production. fertilizer. Thus, the proposed method is much simpler and more economical compared to the known while maintaining the quality of the product. The method of obtaining a suspension suitable for processing into complex fertilizers by decomposing a phosphate raw material with nitric acid, followed by neutralizing the resulting product with gaseous ammonia in the presence of phosphoric acid, characterized in that, c. in order to simplify the process, 1040% phosphoric acid is first introduced into the resulting decomposition product and neutralization is carried out to a pH of 2.5-4.5, followed by addition of the remaining amount of phosphoric acid and neutralization to pH 5.0-6.0 at 110-130 ° C at both stages of the process. Sources of information taken into account in the examination 1. Technical and conference. The Hague (Netherlands), September, 1976, p. 234-ZbJ.