CS265805B1 - A method of making a composition comprising predominantly phosphoric acid or NP or HPK fertilizers - Google Patents

Abstract

The essence of the method is that "during the decomposition of phosphate raw material with nitric acid or to the already decomposed slurry, a raw material is added which forms a precipitate with the slurry, such as ammonium, potassium, magnesium sulfate, which, together with the difficultly decomposed components of the phosphate raw material, is separated from the resulting suspension before adjusting the ratio between calcium and phosphorus pentoxide by direct freezing. In the case of the production of NP or NPK fertilizers, this phase can be added back to the produced fertilizer in one of the other operations, after adjusting the ratio between calcium and phosphorus pentoxide, /leading to the formation of the final product. The effect of the proposed production method is to limit the formation of so-called villi and the associated technological difficulties when mixing the organic and inorganic phases during direct freezing of the decomposed slurry.

Description

The invention relates to a process for the preparation of a mixture comprising, predominantly, phosphoric acid and / or NP and / or NPK fertilizers.

In the manufacture of fertilizers of the NP or NPK-based nature these phosphates uses to adjust the ratio between calcium and. Congealing phosphorus pentoxide direct way in which the system removes the Ca / NO? / ^ G ^ l ^{is extended, and <3-} phosphate rock The principle of direct freezing consists in the hypothermia of the decomposed slurry being in direct contact with the cooled and immiscible liquid, such as gasoline.

For more details on this technology, see books by I. Harmaniak: Industrial Fertilizers, Alfa 1975 and V. Lakota: Production of Combined Fertilizers, SNTL 1964. Under operating mode conditions, so-called villi are clogged during freezing, which clog the freezing equipment by preventing separation phases. One of the causes of this difficulty is the poorly degradable admixtures contained in the phosphate feedstock, the removal of which from the decomposed slurry is a very demanding process, since these are particles of very small size, some of which are colloidal in nature.

As is evident, the drawback of the direct freeze-drying methods used hitherto is primarily that there is no effective purification of the decomposed slurry from the hardly decomposable impurities contained in the phosphate feedstock prior to the calcium-phosphorus ratio preparation.

265 805

This disadvantage is solved by a process for producing a mixture containing predominantly trihydrogenphosphoric acid and / or NP and / or NPK fertilizers, including the decomposition of phosphate feedstock with nitric acid, adjusting the ratio between calcium and phosphorus pentoxide by direct freezing. Ammoniacalization and hardening of the frozen slurry, which consists in adding to the starting material and / or starting materials and / or partially or / and completely decomposed slurry a raw material which forms a precipitate with the slurry as raw materials containing sulphates, ammonium sulphate, potassium sulphate magnesium sulfate, which, together with the hardly decomposable components of the phosphate feedstock, is separated from the resulting suspension before adjusting the ratio between calcium and phosphorus pentoxide.

The basic effect of the process according to the invention is that the formation of so-called villi is reduced when the organic and inorganic phases are mixed. As a result, the process according to the invention becomes more advantageous than the hitherto known processes.

For example, the proposed process involves adding nitric acid and a phosphate feedstock to a first reactor of a decomposition plant consisting of four sequential reactors. Ammonium sulfate is added to the fourth reactor. The resulting calcium sulphate together ^- with hardly decomposable components of the phosphate rock is separated from the resulting suspension by filtration, and the manufacture of solid fertilizers it can be added back to the manure in some others, the following operations after adjusting the ratio of calcium to phosphorus oxide.

The above process is described in more detail below with reference to specific embodiments.

Example 1

In a batch stirred reactor, apatite Kola was decomposed at a temperature of ca 60 ° C with a concentration of 54% by weight in an amount corresponding to a 10% excess over the consumption

- 3 265 805 standard. After 60 minutes of decomposition, ammonium sulfate was added in an amount corresponding to 10% of the calcium present. The resulting calcium sulfate was further separated from the resulting slurry together with the hardly decomposable components from the Apatite Kola by filtration. The remaining vigorous filtrate after cooling was mixed and further shaken with cooled gasoline. The freezing temperature was maintained at about -10 ° C. After shaking, gasoline spontaneously separated without the formation of a villous phase from the remaining suspension, containing predominantly phosphoric acid and calcium nitrate tetrahydrate crystals. These were separated by filtration. The product was a solution containing mainly trihydrogen phosphoric acid, non-frozen calcium nitrate and the remaining nitric acid.

During the freeze-up of sludge without addition of ammonium sulphate and separation of the solid phase, so-called villi are formed in the amount of about 0.5 Λ vol. Since the industrial process is continuous, the volume of these villi is gradually increased and technological problems arise. in the freezer.

Example 2

The process was conducted as in Example 1 except that Senegal phosphate was used instead of the Wheel apatite.

Due to the continuous process of the process, the volume of these villi is rapidly increased and the freezing equipment is gradually clogged.

Example 3

The process was conducted as in Example 1 except that the filtered calcium sulfate along with the hardly decomposable components from the apatite was added to the purified frozen and ammonia to neutralize the slurry to pH = 4.6.

265 805

After drying, the product was a fertilizer containing predominantly calcium hydrogen phosphate, ammonium dihydrogen phosphate and ammonium nitrate. The physical properties of the obtained NP fertilizer were approximately comparable to the corresponding types of industrially produced fertilizers.

Example 4

The process was conducted as in Example 1 except that the filtered calcium sulfate along with the hardly decomposable components from apatite. The wheels were added to the purified frozen and ammonia to ρΗ = 4, β neutralized slurry along with potassium chloride. The product was fertilizer after drying the NPK. The physical and chemical properties of the obtained fertilizer were comparable to the corresponding types of industrially produced fertilizers.

Claims (1)

Process for producing a mixture containing predominantly trihydrogenphosphoric acid and / or NP and / or NPK fertilizers, including the decomposition of phosphate raw material with nitric acid, adjusting the ratio between calcium and phosphorus pentoxide by direct freeze drying, NP fertilizers and freeze slurry for NPK fertilizers a frozen slurry, characterized in that a feedstock which precipitates with the slurry is added to the feedstock and / or to the feedstock and / or partially or / and to the fully decomposed slurry, such as those containing sulphates, ammonium sulphate, potassium sulphate, magnesium sulphate, which, together with the hardly decomposable components of the phosphate feedstock, is separated from the resulting suspension before adjusting the ratio between calcium and phosphorus pentoxide.