NO126676B - - Google Patents

Description

Method for producing a compound fertilizer preparation.

The present invention relates to a

method for the production of fertilizer preparations.

Compound fertilizer preparations contain two or more of the elements nitrogen, phosphorus and potassium that are required for plant growth and are produced in liquid form

or powder form and usually in granulated form

shape. Such compound fertilizing preparations consist, for example, of of superphosphates, ammonium sulphate and potassium chloride, and becomes as

usually produced by mixing together materials that contain the desired ones

elements.

The inventors have found that compound fertilizing preparations can be more appropriately produced by allowing

potassium chloride and nitric acid react together so that a liquid product is formed

containing free nitric acid, below which

the formed gaseous chlorine is removed

and nitrosyl chloride, and then treating

the resulting product with phosphoric acid

or with a phosphate-containing rock. That on

the compound fertilizer preparation obtained in this way can be more concentrated

than can be achieved in any other way.

The present invention consists

therefore in a method of manufacture

of a compound fertilizer preparation which

is distinguished by allowing potassium chloride

and nitric acid react to form

a product containing free nitric acid,

that the nitrosyl chloride formed is removed

and chlorine and treats the thus obtained

product with phosphoric acid and/or with phosphate-containing rock.

It is preferred to carry out the method using an excess of nitric acid, as this, among other things, a. causes a complete reaction with the potassium chloride, so that you get a fertilizer preparation that is practically completely chlorine-free, while at the same time the chlorine can be completely recovered.

Nitric acid is preferably used in excess of the theoretical ratio of 4 mol nitric acid to 3 mol potassium chloride.

According to one embodiment of the invention, the resulting product is then treated with a neutralizing agent, preferably ammonia. If desired, sulfuric acid can be added to the reaction mixture in addition to the phosphoric acid and/or the phosphate-containing rock.

The use of an excess of nitric acid in the treatment of potassium chloride is important, as the presence of an excess of nitric acid greatly accelerates the reaction and means that the process can be carried out continuously.

The excess of nitric acid can vary within wide limits, and it has been found desirable to use at least 10 per cent, preferably 20-200 per cent excess of nitric acid over the ratio of 4 mol of nitric acid per 3 moles of potassium chloride. It has been shown that, as a rule, the use of nitric acid in an excess of more than 100 per cent has little effect with regard to further acceleration of the reaction rate. The amount of nitric acid used therefore ultimately depends on the composition you want the fertilizer preparation to have. The potassium chloride used may be of any commercially available type and may be of greater or lesser purity. The material can be used in solid • form, preferably finely divided, or in solution, depending on what is desired. The nitric acid should have a concentration within the range. 50r > -95 per cent, appropriate, approx. 7.0> percent. The phosphoric acid is preferably used in concentrated <: form, e.g. within the range of 50-70 percent. Sulfuric acid is also used in concentrated form, preferably within the range of 50-100 percent by weight.

Phosphate-containing rock that can be used according to the invention can be any of the commonly used ones. types, f., e.g. those that contain calcium phosphate, which can be obtained from e.g. Morocco, Rhodesia, Florida and various Pacific islands, or they may be of the type which contains aluminum phosphate and which is obtained e.g. from Senegal. Preferably, phosphate rock containing calcium phosphate is used.

Ammonia is preferably used as a neutralizing agent, as this is the cheapest source of nitrogen, but other materials such as e.g. potassium hydroxide, potassium carbonate and the like. If ammonia is used as a neutralizing agent, this can be used in the form of aqueous ammonia, e.g. in a concentration of 25-33 per cent, or you can use anhydrous ammonia.

The reaction between nitric acid and potassium chloride. is preferably carried out by a . elevated temperature.,, appropriately above ; 80° C,. and. it can be carried out at normal, reduced or increased pressure. It has proven most appropriate to carry out the process at or around the boiling point of the reaction mixture, and. when working on wood. normally. pressure is preferred. to use a temperature in the area. 100:—120° C. At a . such. temperature takes place, the reaction between potassium chloride. and, nitric acid fast according to the following equation:

The formed nitrosyl chloride and chlorine are released from the liquid product and can be collected on a! any suitable way. The. thereby obtained liquid, product, is treated with finely divided phosphate. rock and/or phosphoric acid,. as well as, if desired, with sulfuric acid.

The quantity, of phosphoric acid. and/or phosphate-containing. rock, which is used, depends on the ratio of N:P:K i, it. end product you want to produce. The. preferred, to apply so. very phosphoric acid and/or phosphate-containing rock that the total amount of added phosphorus, expressed as phosphoric acid^, amounts to at least 15% by weight, preferably 30-200% by weight calculated on the weight of the potassium chloride used in the process.

Similarly, the amount of neutralizing agent introduced into the liquid product depends on the product one wishes to obtain. If liquid fertilizer products are to be obtained, the amount of neutralizing agent can vary within a large range, and the neutralizing agent can be added either in aqueous or anhydrous form. Wish, man. on the other hand to get. a solid fertilizing product, will preferably be that for. neutralization of the acid necessary substance added in anhydrous form1,, like this. that it. becomes less water that needs to be removed from the product. During the neutralization it should be stirred vigorously. The heat developed during the neutralization is considerable and is used to aid in dewatering the mixture.

In the embodiment where the reaction mixture is treated with phosphoric acid, the reaction mixture can be treated with a neutralizing agent before and/or after the addition of phosphoric acid. If. in this embodiment, ammonia is used as a neutralizing agent. it is preferred to add ammonia to a pH. of 4.4,. this is how you get monoammonium phosphate, but if desired you can add additional ammonia, so that you get diammonium phosphate or a mixture of the ammonium phosphates.

The product can be used either as a liquid fertilizer or as an available fertilizer. To obtain a solid fertiliser, the liquid product can be evaporated to dryness, so. it can be obtained in powder form, or in a semi-solid state in which it can be granulated.

If phosphate-rich rock is used, the product will not be. completely, water-soluble, although most of it is soluble in water. If it is used, phosphoric acid but not containing phosphate, Bergart, the product will be completely water-soluble.

in If that. wanted,, can. the product is mixed with. others, substances, as' usual; introduced- in ^j.destructive agents,, which. f... e.g. phosphates, superphosphates, potassium salts or aluminum salts or fillers such as e.g. lime, gypsum, brick powder and the like. The method according to the invention can be used to produce products which have a very different ratio between. N.:.P2ps:KgP. The desired: f-hold is obtained by appropriate selection of the amounts of the reaction participants used.

The? nitrosulfioride-containing1 gases which. obtained in the first step of the process becomes appropriate: used, for recycling the Moret, and. decomposition of the nitrosyl chloride into nitrogen oxides and chlorine, eg by oxidation with nitric acid. , and- the nitrogen oxides: are- returned: to the system; either as- such! or oxidized: to nitric acid. Ehi preferred embodiment. of the invention is: a, cyclic: process; which. consists in mani lar- potassium chloride; and nitric acid react, when the nitric acid is used; in, an excess! is rejected moll per.. 3 mol of potassium chloride,, after which the. formed^ nitrosyl chloride and: Mother; are removed, treating the. liquid; product with phosphoric acid' and/or containing phosphate: rock- and; processes the gases, which: contain nitro-sy/lMoride and chlorine;, so that the nitrosyl chloride is split into nitrogen oxides- and: chlorine; isolates the Moret and: returns the nitrogen oxides as such or in the form of nitric acid to the first work step of the process.

In Norwegian patent no. 17,975, a method1 is described which consists in bringing potassium chloride to react: with nitric acid, such that: potassium nitrate and an aqueous product are formed, which consists of a mixture: of hydrochloric acid, nitric acid and: alpha chloride, and; this aqueous product is mixed with: phosphate rock then. it: is obtained em solution, which, contains soluble compounds of lime,, nitrogen, potassium and phosphoric acid. ,

The method according to the invention is illustrated by the following examples.

Example 1:

M7 parts of potassium chloride were added to 905 parts 69-.5 percent; nitric acid, and the mixture was heated to 100'°' Cl The reaction was complete: ii in a few minutes, and the evolved: nitrosyl chloride and chlorine were collected.. To', the liquid: product was, added 34'5 parts 40: pst.s phosphoric acid; and 97/.1 deTer gaseous; ammonia- was' irm^ carried under stirring-..

The. resulting: liquid' product was evaporated so that a semi-solid sludge was obtained which was granulated, il em sludge granulator, whereby a solid product was obtained which was water-soluble: and. contained 430' parts of ca-limrmltrate;. 163: parts monoammonium phosphate and; 344 f. parts ammonium nitrate, r which the ratios Nl:i?^0^::K20 were 21i,4:1GH.7:2'1.4.

Berr evolved gas,, which consists, of nitrosyl chloride and Mor, bfe' treated with

'nitric acid1,- and: it. resulting gaseous product was fractionated and: yielded 151 'parts cro.. The recovered nitrogen dioxide was: oxidized to nitric acid1,

t EExample 2:

The apparatus used in the process here consists of two stages, where each stage orders a number; reactors- with agitators in sequence. To the first three reactors; the first" step bite' it per hour ;con.timuerli'g trllfed 1*0-6 kg- 56- pst.s nitric acid and 5.2'; kg potassium chloride. The reaction temperature in the first step was kept at 115-1!20°C and the residence time in; each reactor was 1.5 minutes. The reaction mixture flowed from one reactor to the other; next li row, and- that. which flowed forth from it; third reactor contained: less than 1% chloride, corresponding to 95% of the lithium chloride having been converted. ! It evolved- chlorine and: nitrosylMoride. was cooled to remove the nitric acid and the varna jaom was returned to the first reactor. .NitrosylMoride. was treated so that chlorine was recovered as elemental chlorine, and the nitrogen was returned: to the first reactor in form. of nitric acid. The first reactor was stirred sufficiently to ensure rapid dissolution of the potassium chloride in the nitric acid and rapid removal; of the gases as these became. formed. The product: from. them third: reactor in the .first, stage: was: led to two in order ;arranged' reactors as (True it. second stage. To each reactor in the second stage, 4.25 kg 60 per cent was added per hour. s phosphoric acid. Anhydrous ammonia was added to each of the reactors in this step with stirring during the stirring so that the product from the last: reactor had an ipH-, of 4;5>;, tii this: was used 0.8; kg [ammonia per hour.

While; the ammonia', was added was. The reaction heat was used to concentrate the mixture, like this. that the product, from. the last, stage jhad the desired consistency for granov clay, or for the production: of flakr. The final product contained, less than; 0.5% chloride <..

IN

in ETcsempeV 3>:

in

The apparatus used in this example consisted of two stages, each of which contained a number of reactors with agitators arranged in sequence. To the first of the three reactors in: it. first: step was per hour 'continuously supplied H', 11 kg 65 per cent nitric acid and 2.7 kg potassium chloride (60 per cent K20). The reaction temperature in the first stage was kept at 100-110° C and the residence time in each reactor was 10 minutes. The reaction mixture flowed from one reactor to the next in the series, and the product from the third reactor contained less than 0.3 percent chloride, which corresponds to 98 percent of the potassium chloride having been converted.

The evolved chlorine and nitrosyl chloride were cooled to remove nitric acid and water which was returned to the first reactor. The nitrosyl chloride was treated to recover the chlorine as elemental chlorine, and nitrogen was returned to the first reactor in the form of nitric acid. The first reactor was agitated sufficiently to ensure rapid dissolution of the potassium chloride in the nitric acid as well as rapid removal of the gases as they were formed.

The product from the third reactor in the first stage was fed to two reactors arranged in series which formed the second stage. For each reactor in the second stage, per hour added 3.9 kg 60 percent phosphoric acid. Anhydrous ammonia was added to each of the reactors in this step while stirring, so that the product from the first reactor had a pH of 4.5, which corresponds to a consumption of ammonia of 1.45 kg per hour.

During the ammonia addition, the heat of reaction was used to concentrate the mixture, so that the product from the last step had a desired consistency for granulation or for the production of flakes. The chloride content in the final product was below 0.1 per cent.

Example 4:

The apparatus used in this example consists of three stages and each stage contains a number of stirring reactors arranged in series. To the first of the three reactors in the first stage, it was continuously per hour added 11.1 kg 65 pct.s nitric acid and 2.7 kg potassium chloride (60 pct. K20). The reaction temperature in the first stage was kept at 100-110° C and the residence time in each reactor was 5 minutes. The reaction mixture overflowed from one reactor to the next in the series and the overflow from the third reactor contained less than 0.3 percent chloride, which corresponds to 98 percent of the potassium chloride. was <p>little traded.

The evolved chlorine and nitrosyl chloride were cooled to remove nitric acid and water which was returned to the first reactor. The nitrosyl chloride was treated to remove the chlorine as elemental chlorine, and nitrogen was returned to the first reactor in the form of nitric acid. In the first reactor, sufficient stirring is done to ensure rapid dissolution of the potassium chloride in the nitric acid and also rapid development of the gases as they are formed.

The overflow from the third reactor in the first stage was led to two reactors in series, which constituted the second stage. For each reactor in the second stage, per hour added 3 kg 60 percent phosphoric acid. Anhydrous ammonia was added to each of the reactors in this stage while stirring, so that the overflow from the last reactor had a pH of 4.5, which corresponded to an ammonia consumption of 1.45 kg per hour.

During the ammonia addition, the heat of reaction was used to concentrate the mixture, so that the overflow from the first burn had the desired consistency for granulation or the production of fiak. The final concentration of chloride was below 0.1 percent.

Example 5:

Potassium chloride (60 percent K20) and 65 percent nitric acid were continuously added to a stirred reaction system in an amount of 356 resp. 653 kg per hour. The reaction system was maintained at a temperature of 115-120° C, and nitrosyl chloride and chlorine were evolved. The gas mixture was treated so that it was converted into nitric acid and chlorine, the latter being withdrawn as a by-product, and the former being continuously returned to the reaction system;

In the second stage of the process, the liquid product from the first-mentioned reaction system containing nitric acid was mixed continuously with 383.5 kg per hour phosphate rock from Morocco (33.3 percent P2Os;

50.3 percent CaO) and 245 kg of sulfuric acid which contained 94 percent by weight H2S04.

In the third stage of the process, the porridge from the second stage was treated with gaseous ammonia under vigorous stirring, so that the product obtained a pH of 4.5; for this, approx. 38.3 kg of ammonia per hour.

The porridge from the third step in the process was taken to a granulation plant for the production of a granulate product, 1270 kg per hour, and the product' contained 10 percent N, 10 percent P2O5 and 16.6 percent K20. The phosphate content in the product was 97 per cent soluble in water under normal test conditions.

Example<1-> 6- r

Chlorpotassium. (<60 psts.s'K,©)<1> and 65-psts-nitric acid were continued-llg-conducted tiPetom:-stirred reaction system: in' one- amount1 of-1 35'6 resp; 6534 kg' per: hour. The reaction system car kept on one. temperature of 11'5<;>—1-20'° G, and; it' Bie developed nitrosyl chloride- and" chlorine: The gas mixture was treated' so that it was1, converted into' nitric acid1 and chlorine, the latter? was' taken out as> by-product, and' the- former; was- continuously1- returned- to " the reaction system,

IN! that-other ; step- of the process- bled- the liquid product from the first step: continuously mixed: with* 63£,&kg; per: hour of phosphate rock fisa Morocco- (33l,3<l> pst'. P2Og; 50]3ipst CåO)-and-405^ kg-per-, hour sulfuric acid which contained- 94 weight percent H2S04.

In the third stage: of the process1, the porridge from the second stage was treated with gaseous ammonia under vigorous stirring so that a pH value of 4.5 was obtained. The porridge from the third stage of the process was sent to a granulation plant and it. was. produced- a gray zeroing product in. a quantity of 2250 kg; per... hour, with a content of 1.4; 1 percent N-, 9; 45. percent P- 2Q5' j and-, 9.4 percent <K>^O. The phosphate content in the product was 9.7 percent soluble in water under standard test conditions.

Example. 7c

Potassium chloride (60% K^Q) and 65% nitric acid were: continuous; led tii a stirred reaction system in an amount of 356 resp. 1318 kg per hour. The reaction system: was maintained at a temperature of 1>1'5r—120° G;J and there, nitrosyl chloride was evolved. and chlorine. The gas mixture. became. treated so man- of the fickle nitric acid; and, chlorine; which last: became; taken. out- as> et. by-product,, while the former, became continuous; returned to! the reaction system..

Ii that, other: step", it became. continuous? and with good stirring added 180; kg per: hour: of phosphate rock; faja-Floridai (-34.6-: percent P2Oj): and. 392f kg< per;, hour? phosphoric acid; of 38? pst.s- concentration about (fcalculated as; P2Ol)..

In the third step were; it:- under vigorous stirring added 143 kg of gaseous ammonia: per hour.. After granulation, drying and, application of a treatment, which. counteracts" caking, 1706 kg of product was obtained per hour with a content of 18.6 percent N, 12.4 percent P205 and 12.4 percent KaO. The phosphate content in the product was 98 percent water-soluble under standard test conditions.

Example<1> £J."

Potassium chloride t60ipst. KgO); and; 65- psfes= nitric acid, became; continuous; resulted; one- omr-touched. reaction system in a quantity; of NOK 356 respectively. 1318; kg per hour.. The reaction system, became. held on* one. temperature of 115':—120? G*, and, it. became; evolved nitrosyl chloride: and; chlorine: The gas mixture. became; treated as much as you could get from them. nitric acid; and. chlorine, which last; was taken as a by-product, while the first-mentioned was continuously returned to the reaction system I\ it. other, stepped became: it continuous; and under godi stirring; added per;, hour; 1265 kg; phosphate rock.as-.hadded'en! approximate formula- 3Caii,(fP04.);2 .- CaF2. and. 225 kg. prr. hour phosphoric acid of 38'. pct.s; concentration!

(calculated as- P2Of;-);.

In the third section, gaseous ammonia was added under vigorous stirring so that a pH of 4.5 was obtained.

The obtained product was granulated, -, age one got. 945. kg, granulated product per hour jned, a content of 13;3i per cent.- N-„ 13.3 per cent.. PgOg-.and 22.4; pst. K^Oi

Example- 9-.'

Potassium chloride' (.60- per cent.. K20,) and, 65; psts;

nitric acid was continuously added. a worm-stirred reaction system. L a quantity; of 225 or 608. kg: per hour. The reaction system was kept on. one. temperature of 115:—120° C-„ and. it was. developed, nitrosyl chloride and, chlorine. The gas mixture became; treated, as- one- by, it-got. nitric acid and chlorine,,; which, last was taken, out. as a by-product,, whereas. the one, the former, became. continuously returned to;

r eaks j the bns system.

In the second step of the process, the floating product from the above-mentioned reaction system, which contained an excess of nitric acid, mixed continuously with 57.7 kg per hour; of gaseous; ammonia under vigorous stirring, such that a pH was obtained. on. 4;5i

The solution from this second step was taken to a third step where it was mixed with 333 kg; per: hour of phosphoric acid |(40 percent P2p3) and. 212.5 kg 50% potassium hydrate solution.

The resulting resolution celebrated it

the third stage was taken to a granulation plant where 878 kg of granulated product was obtained per hour with a content of 15.3 percent N,

15.3 percent P205 and 25.7 percent K20. The resulting product was water soluble.

Example 10: Potassium chloride (60 percent K20) and 65 percent nitric acid were fed to a continuously stirred reaction system in an amount of 225 resp. 608 kg per hour. The reaction system was maintained at a temperature of 115-120° C, and nitrosyl chloride and chlorine were evolved. The gas mixture was treated so that nitric acid and chlorine were obtained from it, the latter being taken out as a by-product, while the former was continuously returned to the reaction system.

In the second step of the process, the liquid product from the aforementioned reaction system, which contained an excess of nitric acid, was continuously mixed with granular, solid potassium hydroxide under vigorous stirring, so that a pH of 4.5 was obtained. The thick porridge obtained was granulated.

Example 11: Potassium chloride (60 percent K20) and 65 percent nitric acid were continuously fed to a stirred reaction system in an amount of 356 resp. 836 kg per hour. The reaction system was maintained at a temperature of 115-120° C, and nitrosyl chloride and chlorine were evolved. The gas mixture was treated so that nitric acid and chlorine were obtained from it, the latter being removed as a by-product^ while the former was continuously returned to the reaction system.

In the second stage of the process, the liquid product from the aforementioned reaction system, which contained an excess of nitric acid, was continuously mixed with 387 kg per hour of phosphate rock from Morocco (33.3 percent P205 content). In the third step, the porridge from the second step was treated with gaseous ammonia under vigorous stirring so that a pH of 4.5 was obtained; for this, approx. 1.53 kg of ammonia per hour.

The porridge from the third stage was taken to a granulation plant where, per hour received 1028 kg of granules containing 11.1% N, 11.1% P205 and 18.5%; K20. Of the phosphate content in the product, 92 per cent was water-soluble under standard test conditions. ■ .

Example 12: Potassium chloride (60 percent K20) and 65 percent nitric acid were continuously fed into a stirred reaction system in an amount of 365 resp. 836 kg per hour. The reaction system was maintained at a temperature of 115-120° C, and nitrosyl chloride and chlorine were evolved. The gas mixture was treated so that nitric acid and chlorine were obtained from it, the latter being taken out as a by-product, while the former was continuously returned to the reaction system.

In the second stage of the process, the liquid product from the aforementioned reaction system, which contained an excess of nitric acid, was continuously mixed with 387 kg per hour of phosphate rock from Morocco (33.3 percent P203 content).

In a third step, the porridge from the second step was treated with a 50% by weight solution of potassium hydroxide with vigorous stirring, so that a pH of 4.5 was obtained. A thick porridge was obtained which was granulated.

Claims (4)

1. Process for the production of a compound fertiliser, characterized by bringing potassium chloride and nitric acid, where the nitric acid is used in excess over the theoretical ratio of 4 mol nitric acid to 3 mol potassium chloride, to react so that a liquid product containing free nitric acid is formed, ' ' ate to remove the formed nitrosyl chloride and chlorine, and treat the liquid product with phosphoric acid and/or phosphate rock. 2. Method according to claim <i>\, characterized in that the nitric acid is used in an amount of at least 10 percent and preferably 20-200 percent excess over the said ratio. 3. Method according to claim 1 or 2, characterized in that the liquid product is also treated with sulfuric acid. 4. Method according to claims 1-3, characterized in that the liquid product is treated with a neutralizing agent, preferably ammonia, before the treatment with phosphoric acid. •5. Method according to claim 1-4, characterized in that the reaction between potassium chloride and nitric acid is carried out at one temperature of approx. 100°C.