KR790001375B1 - Manufacture of solid ammopium phosphate - Google Patents

Abstract

at. ratio of 0.95-1.10 was prepd. by 1st adding NH3 to H3PO4 to produce a slurry with an N:P ratio of 1.3:1.5, passing to a mixer where 15-85% of the sceondary H3PO4 needed to produce the final product was added, and then passing the slurry to a final mixer and demoisturizer where the final amt. of acid was added.

Description

Preparation of Ammonium Phosphate

The accompanying drawings are a manufacturing process diagram of the ammonium phosphate of the present invention.

The present invention relates to a process for the preparation of solid ammonium phosphate, in particular primary ammonium phosphate.

Solid ammonium phosphates such as first ammonium phosphate, NH ₄ H ₂ PO ₄ (hereinafter abbreviated as MAP), second ammonium phosphate, (NH ₄ ) ₂ HP O ₄ (hereinafter abbreviated as DAP) and mixtures of these salts are plant It supplies phosphorus of nitrogen, two elements necessary for growth, making it an important component of fertilizer.

It is known that ammonium phosphate, which is used as a conventional fertilizer, can be prepared by a method of reacting wet phosphoric acid with ammonia.

Ammonium phosphate is characterized by an atomic ratio of nitrogen to phosphorus contained, commonly referred to as an N: P atomic ratio, i.e., the first ammonium phosphate has an N: P atomic ratio of 1.0, and the first ammonium phosphate and the second ammonium phosphate The molar equivalent mixture has an N: P atomic ratio of 1.5.

For mixtures containing nitrogen or phosphorus compounds other than ammonium phosphate, the N: P atomic ratio is expressed only as a ratio in ammonium phosphate.

Impurities present in wet phosphoric acid are important for producing ammonium phosphate, especially MAP, used as a solid fertilizer into a good granular material. In the case of solid products containing ammonium phosphate prepared by the method of British Patent No. 951,476, a large amount of impurities are present in the amorphous gelloche. For the best granulation properties, most of the impurities must be present in this form.

The most important impurities are iron, aluminum, magnesium and fluorine. As the effects of these elements correlate, small changes in the proportion and amount of only one of these elements can have a significant impact on the production and physical properties of the product. For example, acidifying the MAP / DAP slurry as described in British Patent 951,476 may alter the size and shape of the precipitated MAP crystals. For example, it has been found that the average size of the crystals is 100 μm when in the form of a solid powder of MAP that is well suited for granulation of mixed NPK fertilizer products.

메쉬 표준 철망 스크린을 통과함)로 얻기 위하여 제품을 특수 분쇄(milling) 시킬 수 있다. 영국 특허 제 951,476호의 방법은 미세하게 분쇄해여 선별해서 공정에 재차 공급하는데 비용이 많이드는 결점이 있다.Products according to the method of British Patent No. 951,476 have good granulation properties but are of some kind of wet acids containing the above-mentioned impurities in undesirable amounts and / or proportions, such as khouribga and Gafsa phosphate. That is, wet phosphoric acid produced from North African phosphate is difficult to aggregate into small crystals, so that the desired size (generally at least 90%)

The product can be specially milled to obtain a mesh standard wire screen). The method of British Patent No. 951,476 has the disadvantage of being costly to finely pulverize, screen and re-feed to the process.

Therefore, the present inventors have improved the above-mentioned drawbacks, and most of the MAP crystals have a size of 30-200 μm (average 100 μm) and reduce the agglomeration of the crystals to impart powdery hair appearance to the solid product. Discovered a method for producing ammonium phosphate products characterized by. The ammonium phosphate thus obtained has good granulation properties suitable for use in the manufacture of NPK compounded fertilizers.

범위의 제품 크기로 얻어지는 입상화 효율을 의미한다.Good granulation properties mean high yields, for example more than 60% of the desired NPK product size range.

Granulation efficiency obtained with a range of product sizes.

The present inventors found that a portion of a MAP / DAP slurry formed by ammoniaating wet phosphoric acid is mixed with a second acid raw material as described below before entering a dehumidification apparatus such as, for example, a pin shofted U-shaped mixer. It was found that crystal growth was greatly improved. Mixing a portion of the MAP / DAP slurry with the second acid feedstock well controls the sedimentation of some MAPs, forming nuclei for crystal growth in the dehumidifier.

This improvement is achieved by mixing 20-80% by volume of the first MAP / DAP slurry with the second acid raw material to precipitate some MAP. The remainder of the MAP / DAP is added separately to the dehumidifier at one or more points after delaying crystal formation for a while.

A method for producing a granular solid product containing ammonium phosphate having an N: P atomic ratio of 0.95-1.05 is already known, and this known method has a fluidity roughness at the operating temperature of the first phosphoric acid-containing raw material and ammonia. The amount of the aforementioned slurry corresponding to that produced by the addition of phosphoric acid and ammonia in the form of a large amount of slurry having the same composition, concentration and fluidity roughness when added to an aqueous slurry of ammonium phosphate having an N: P atomic ratio in the range of 1.3-1.5. After the removal, the removed slurry was mixed with a second acid raw material (i.e., wet phosphoric acid) to reduce the N: P atomic ratio to 0.95-1.05.

In contrast, the process of the present invention comprises a large amount of the same composition, concentration and fluidity roughness formed by adding a first phosphoric acid-containing raw material and ammonia to an aqueous slurry of ammonium phosphate having a fluidic roughness at an operating temperature and having an N: P atomic ratio of 1.3 to 1.5. The slurry was removed in an amount corresponding to the slurry formed by the addition of phosphoric acid and ammonia, and then the removed slurry 20-80 = volume% was mixed with the second acid raw material and then added to the remaining mixture of the slurry to form N: The atomic ratio of P is in the range of 0.95-1.05, and the water content of the removed aqueous slurry and the second acid raw material is such that the resulting product is allowed to begin to solidify in the dehumidifying apparatus which is treated for a time sufficient to solidify at room temperature.

When the N: P atomic ratio is 0.95 or less, due to the presence of free phosphoric acid, the ammonium phosphate becomes acidic to have corrosiveness and hygroscopicity. And since this invention mainly concerns manufacture of MAP, the upper limit of N: P atomic ratio is set to 1.05. Aqueous slurries of ammonium phosphate with N: P atomic ratios of about 1.6 or more usually lose ammonia, and when the aqueous slurries of ammonium phosphate with N: P atomic ratios of about 1.2 or less, the temperature rises and the mixture of the mixture with the second acid raw material There are deficiencies in which the effect is generally insufficient to promote the evaporation and crystallization required to produce the desired solid product at room temperature. These facts suggest that ammonium phosphate has the highest solubility in MAP / DAP slurries when the N: P atomic ratio is about 1.4, which is related to a pH of about 6.5. If at least one other ammonium salt, such as ammonium nitrate sulfate and / or urea, is to be blended into the granular solid ammonium phosphate, these salts may be added during the process, such as ammonia being added to the mixed acid containing phosphoric acid and sulfuric acid. It can be added to form an aqueous slurry of ammonium phosphate and ammonium sulfate with fluidity roughness at the operating temperature.

"Solid" refers to a homogeneous mixture of solid particles with a saturated aqueous solution of soluble components, in which case the proportion of the solution can be separated from the product only by a small amount of liquid at a pressure of 6 psig, close to normal storage conditions. It is enough. The maximum level of water content varies with crystal size, and the higher the impurity content of ammonium phosphate, the lower. The maximum level of water content is also lower when at least one other ammonium salt is blended into solid ammonium phosphate as described above. For example, a MAP having an N: P atomic ratio of 0.95 having a crystal size of 30-200 μm made from ore with 72% BPL grade kuribga, has a maximum moisture content of 16% under pressure of 6 psig, as defined above. Is the same "solid".

As can be appreciated from the foregoing, the moisture content introduced into the process of the invention is not so high that the final product does not become solid at room temperature. Ammonia is also added in gaseous or anhydrous form, but ammonia solutions may also be used as long as the water introduced thereby exceeds the product moisture limit and does not interfere with the product becoming solid at room temperature.

As mentioned above, the MAP / DAP slurry is formed by ammonialation of wet phosphoric acid to be the "first acid" raw material.

The "second acid" raw material described above is an acid used to lower the N: P atomic ratio of the slurry. "Secondary acid" raw materials include, for example, inorganic acids such as phosphoric acid (particularly wet phosphoric acid), nitric acid or sulfuric acid, mixed acids thereof. These acids themselves are partially ammoniaized. The use of such partially ammoniad acid is particularly suitable for the process of the invention for producing a product which is solid at room temperature and has, for example, an N: P ₂ O ₅ weight ratio of 1: 2, 1: 1 or 2: 1.

In addition, for example, a product having a weight ratio of 1: 2, 1: 1, 2: 1 by weight of N: P ₂ O ₅ may be prepared by introducing ammonium salts in the form of a solid or an aqueous solution at or after the addition of the "second acid" raw material. have.

Nitrogen compounds, such as urea, can also be introduced as solids or in the form of aqueous solutions upon or after addition of the "second acid" raw material.

The proportion of the final solid product by the process of the invention is introduced before, during or after the mixing of the second acid with the MAP / DAP slurry, ie by recycling it to change the roughness of the acid and slurry mixture so that the surface of the mixture is dehumidifying. The more exposure at, the faster the water is released from the mixture. Moreover, other solid materials, such as potassium chloride, can be added at or after the addition of the second acid to obtain a solid product containing nitrogen, phosphorus and potassium.

According to the method of the present invention, solid ammonium phosphate having a N: P atomic ratio in the range of 0.95 to 1.05 can be prepared by mixing aqueous phosphoric acid having a P ₂ O ₅ content of 30 to 54% and ammonia gas to prepare an aqueous slurry of ammonium phosphate. The N: P atomic ratio of the slurry is limited to the range 1.3-1.5 and the moisture content of the slurry is limited to the range 10-20%. And a fixed moisture content), a large amount of slurry is formed.

Thus, the amount corresponding to the slurry formed by mixing phosphoric acid and ammonia is removed from the formed slurry, and 20-80% by volume, preferably 25-75% by volume, of the removed amount of the slurry is mixed again with wet phosphoric acid. The remaining product of the slurry is then added to the solidified product mainly by evaporative cooling in the dehumidifier so that the desired N: P atomic ratio is obtained, but the moisture content of the product is due to evaporation due to the use of heat of reaction, heat of crystallization and sensitive heat. By adding the remainder of the slurry under conditions where the product can be obtained at room temperature so that a solid as described above is obtained.

Referring to the method of the present invention in detail based on the accompanying drawings as follows. In the drawing, the slurry shredder box 2 is a device for dividing the MAP / DAP slurry stream 7 from the reaction vessel 1, for example, a compartment capable of dividing the slurry stream at a desired ratio by having an outlet that can be opened and closed, It is a container having two or more separation parts (not shown) composed of channels, walls, and the like.

The mixing device 3 for mixing the MAP / DAP slurry 7 'and the second acid raw material 4 consists of, for example, one tank or several tanks arranged in series, which contain slurry and "secondary". Acid "Raw material is fitted with a device (not shown) for vigorous stirring. In order to vigorously stir in a mixing apparatus, it is sufficient to stir with a propeller, for example.

Hereinafter, the present invention will be described in detail with reference to Examples. The following example describes a method of advancing crystal growth by mixing a portion of the slurry stream with a "secondary acid" raw material to form the nucleus of the MAP to impart crystal precipitation points.

Example 1

A solid product as described above, i.e., a solid product of ammonium phosphate having an average composition of N 10.9%, P ₂ O ₅ 48%, H ₂ O 7.6%, and N: P atomic ratio of 1.00, has a P ₂ O ₅ 40% wet-phosphoric acid (5) (prepared from the will Koh ribs phosphate rock) 442kg per hour and ammonia gas (6) to (not more than 130 ℃) at a temperature of 120-125 ℃ to 66kg per hour composition of P ₂ O ₅ 44%, H ₂ O was added to the reaction vessel (1) containing a slurry of 14%, N: P atomic ratio 1.4 was prepared at a rate of 516kg per hour.

은 핀혼합기(8)의 일단 근처에 장설된 수증기 가열 슬러리/산 혼합장치(3)에서 P₂O₅48.0% 습식인산("제 2 산"원료)(4)의 시간당 147kg과 예비 혼합된다. 이와 같이 처리된 슬러리는 도관(9)을 통해서 핀 혼합기(8)에 유입된다.The amount of hot slurry corresponding to the slurry formed in the reaction vessel is introduced through the conduit 7 into the slurry cleaner box 2, that is, the feed box for cutting the slurry feed. MAP / DAP (7 ') capacity

The silver is premixed with 147 kg per hour of P ₂ O ₅ 48.0% wet phosphoric acid ("second acid" raw material) 4 in a steam heated slurry / acid mixer 3 installed near one end of the pin mixer 8. The slurry thus treated enters the fin mixer 8 through the conduit 9.

는 도관(7")을 통해서 1개 이상의 지점(A, A', A"), 예컨대 도면에서 표시된 A지점에서 핀 혼합기에 직접 가해진다.Rest of MAP / DAP Slurry Capacity

Is applied directly to the pin mixer at one or more points A, A ', A ", for example at point A indicated in the drawing, through conduit 7".

This process will have a total effect on the precipitation of some MAP in the steam heated slurry / acid mixer (3), so that the formation of nuclei for crystal growth in the fin mixer (8) when the remainder of the slurry is applied through the conduit (7 ") The product of this reaction is solidified as it passes along the mixer 8 and the bursting is repeated so that a new surface is exposed by the action of the blade 10 attached to the rotating shaft 11, thus producing a new surface. As a result of this exposure, moisture dissipation is assisted by an aeration ventilator (not shown) to obtain the final solid product described above at 12. The product thus obtained has a temperature of 33 ° C. and H ₂ O 7.6%.

All parts are expressed in parts by weight except for the chopped slurry feed expressed in volume.

The MAP thus obtained was tested and compared to a control sample prepared in the same manner, except that a part of the slurry stream and the step of mixing the "second acid" raw material were omitted. At 1.0, a large amount of flow slurry and large crystals were obtained, and the product obtained by the method described in this Example was a mixture of finely divided hairy material and extremely soft granule, whereas the control sample was hard. It was a rough product.

Example 2

The solid product as described above, i.e. solid product of ammonium phosphate having an average composition of N 11.8%, P ₂ O ₅ 46.6%, H ₂ O 5.5% and N: P atomic ratio 0.98, is P ₂ O ₅ 39% wet phosphoric acid (5 9.77 tons / hour and 6.63 tons / hour of ammonia gas (6) were added to a reaction vessel (1) containing a pre-formed slurry having an N: P atomic ratio of 1.4 at a temperature of 125 ° C. Made at a speed of 11.4 tonnes per hour. Hot slurry of an amount corresponding to the slurry formed in the reaction vessel is initially in a slurry / acid mixing device 3, once installed in the vicinity of the pin mixer 8 through a conduit (7) MAP / DAP slurry of 25% by volume of P ₂ O ₅ 48% wet phosphoric acid 3.16 tons / hour (second acid raw material) is introduced into the slurry fine box (2) premixed, the treated slurry is introduced into the pin mixer (8) through the conduit (9), 75 volume% residual of the MAP / DAP slurry was added directly to the pin mixer at point A indicated in the drawing through conduit 7 ". A slurry weight of approximately 15-75% was added to the" second The portion was added via conduit (7 ') to treat the acid "raw material (4). In this way, a number of separately shredded slurry feeds were tested within the range of 25-75 volume% and the remainder of the MAP / DAP slurry The capacity was applied directly to the pin mixer 8 through the conduit 7 "as described above.

The method of the present invention was compared to a control sample prepared in the same manner, except that in each case the obtained MAP was tested and the step of mixing a portion of the slurry stream with all “secondary acid” raw materials was omitted. When the ratio was 1.0, a large amount of flow slurry and a large proportion of large crystals were obtained, and the product obtained by the method described in this example was a mixture of finely divided hairy substance and extremely soft granule, whereas the control sample was obtained. Was a hard and rough product.

Example 3

313 kg / hr of wet phosphoric acid (5) containing 40% of P ₂ O ₅ made from ore of Gafsa was treated at 36 kg / hr of ammonia gas (6) in a separate reaction vessel (1). At a temperature of 126 ° C. (not more than 130 ° C.), a slurry having an N: P atomic ratio of 1.4 and a moisture content of 15% by weight of H ₂ O was formed, and then the amount of hot slurry corresponding to the slurry formed in the reaction vessel was removed. Introduced into the season box (2). 50% by volume of the MAP / DAP slurry is wet phosphoric acid (secondary acid raw material) containing 51% P ₂ O ₅ made from the same phosphate to reduce the N: P atomic ratio to 1.0 through conduit (7). The mixture was premixed with 86 kg / h of (4), and this step was carried out in the heat slurry / acid mixing device 3 with steam installed near one end of the pin mixer 8. The 50 volume% residue of the MAP / DAP slurry was added directly to the pin mixer at one or more points (A, A ', A ") such as point A shown in the drawings through a conduit 7".

The dehumidifier, i.e. the pin mixer 8, served to release moisture as the product passed along the pin mixer.

The production rate of MAP during the operation was 319 kg per hour, and the final product had an N: P atomic ratio of 1.05 and an average composition of N 10.4% P ₂ O ₅ 53.0% (total) and H ₂ O 7.86%.

The MAP thus obtained was tested and compared to a control sample prepared in the same manner except for omitting the step of mixing a portion of the slurry stream with the "second acid" raw material (all acids and slurry were mixed simultaneously). In the case of N: P atomic ratio of 1.0, a large amount of flow slurry and a large ratio of large crystals were obtained. The product obtained by the method described in this example was also a mixture of finely divided hair-bearing material and extremely soft granules, whereas the control sample was a hard and rough product.

Claims (1)

As described above and shown in the drawing, the first phosphate-containing raw material and ammonia were added to an aqueous slurry of ammonium phosphate having fluidity roughness at an operating temperature and having an N: P atomic ratio of 1.3 to 1.5, and the same composition and concentration. And forming a large amount of slurry having fluidity roughness, removing the amount corresponding to the slurry formed by adding phosphoric acid and ammonia from the slurry, and then mixing the removed slurry with the second acid raw material to obtain an N: P atomic ratio of 0.95-1.05. In preparing a granular solid product containing ammonium phosphate having 20-80% by volume of the removed slurry with the second acid raw material, the mixture is added to the remaining amount of the slurry to The N: P atomic ratio is 0.95-1.05, and the water content of the removed aqueous slurry and the second acid raw material are treated for a time sufficient to cure the product produced at room temperature. Method for producing a solid ammonium phosphate, characterized in that it contains the above-described product in the dehumidifier to start to solidify.

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