CS248991B1 - Method of monophosphate-type liquid nitrogen-phosphoric fertilizers' continuous production - Google Patents

Description

(54) Method for the continuous production of mono-phosphate-type liquid nitrogen-phosphorus fertilizers

It is an object of the invention to provide a continuous process for the production of mono-phosphate-type liquid nitrogen-phosphorus fertilizers.

Liquid nitrogen-phosphorus fertilizers of monophosphate of the orthophosphate type are aqueous solutions or suspensions of ammonium dihydrogen phosphate (NH4H2PO4) and dibasic hydrogen phosphate [(NH4) 2HPO4.

They are prepared by neutralization of trihydrogenphosphoric acid or an aqueous solution, respectively. a suspension of a mixture of ammonium monophosphates of the type Amofos, MAP, M-DAP and the like, with ammonia. In the neutralization of H3PO4 produced by the decomposition of phosphates by mineral acids - so-called. In the extraction acid, impurities such as Mg, Al, Fe, Ca, SiF6 < ^{2 >} achieved in the acid precipitate in the form of gel-like, and usually chemically significant, precipitates. The amount of these haloforming precipitates, their structure as well as their physical form are dependent on how the neutralization reaction is conducted. In this context, the presently known processes for the preparation of liquid nitrogen-phosphorous-249999 so-called " NP fertilizers can be divided into processes in which precipitated impurities are separated (USA Pat. 3 264 087; Chemical Enginneering Progress, Vol. 58, No. 9, 1962, pages 89-93) and technologies in which precipitated impurities impurities do not detach, but the halofluoric impurities stabilize in the product in various ways to prevent sedimentation of sludge (Agricultural and Food Chemistry, Sep.-Oct. 1961, pp. 343-34; U.S. Pat. Nos. 3,160,495, 3,179,496, 3). 519,413, 3,563,723, 3,579,321, 4,066,432; Cs. AO No. 200,671).

The manufacturing process and the device for preparing liquid monophosphate fertilizers are also contained in U.S. Pat. According to this process, ammonia water, H3PO4 and process water are fed into the neutralization reactor, where the hot solution is pumped out in two streams and fed to a cooling system.

A method for producing a mono-phosphate type liquid NP-fertilizer using a tubular reactor is the subject of US Pat. no. The reactor consists of two zones, H3PO4 being added to the first zone and ammonia water to the second. Also disclosed is an apparatus and method of cooling the reaction mixture in which 50-75% of the cooled circulating product is mixed with the freshly prepared reaction mixture.

Stage US Pat. No. 2,917,380, a mono-phosphate-type liquid fertilizer can be prepared with a predetermined N-P2O5-K2O ratio by the manner in which phosphoric acid, ammonia and a mixture consisting of water and a cooled reaction product are metered into a stirred tank-type reactor. The temperature of the reaction mixture is kept below 71 ° C by cooling, while the preparation of the 8-24-0 fertilizer is complete when the pH of the reaction mixture reaches 6.85. In our conditions, during several years of operation of the production of liquid fertilizer type 8-24-0, the production method in terms of Cs, AO no. 202 154, in which H 3 PO 4 and ammonia water are fed to a reaction medium that circulates at a rate 10- to 500-fold higher than the phosphoric acid feed rate.

In the wake of the global energy crisis, especially in the second half of the 1970s, attention has been paid to technological research on liquid fertilizers to develop products that can be matched by conventional liquid multi-component fertilizers based on condensed phosphates but at least energy. Thus, monophosphate (NP) suspensions of the monophosphate type have become the subject of research in this field. At the beginning of research in this field, the maximum concentration of the suspension, while maintaining its acceptable handling and storage properties, was the type 10-30-0 ("New Developments in Fertilizer Technology" - 8 th Demonstration NFDC-TVA, October 6-7, 1970; Tennessee Valley Authority, Muscle Shoals, Alabama; Bulletin Y-12). It turned out later that if the acid is neutralized in several stages, more concentrated NP-suspensions can be prepared.

In two-stage technology, the acid was neutralized with ammonia gas first to pH 4.5 (about 75% of the total NFIs requirement), at the boiling point of the reaction mixture and the residence time of the reaction mixture in a stirred boiler-type neutralizer about 30 minutes. The neutralization of the acid was completed in the second step, while cooling the reaction mixture.

To stabilize the product-NP suspension, atapulgite powder was used, which was added to the reaction mixture after the second neutralization step, in an amount of 1.5 wt. % dry matter. Two-stage neutralization allowed to increase the concentration of NP-suspension based on monophosphates from floods 10-30-0 to 11-33-0 and late to 11-39-0. It was later shown that even the proposed two-stage process of neutralizing the extraction H3PO4 with ammonia gas does not guarantee the necessary stability of the NP suspension type 11-39-0. After extensive tests using different additives affecting the fertilizer properties (e.g. 0.3 to 0.5% H2S1F6 addition), the composition of the developed suspension finally stabilized on the 13-38-0 type. Three-stage neutralization was proposed for the continuous process of preparing liquid fertilizer suspension 13-38-0 ("New Developments in Fertilizer Technology", 12 th Demonstration NFDC-TVA, October 18-19, 1978, Tennessee Valley Authority Muscle Shoals, Alabama; Bulletin Y- 136).

The currently known and industrially used technological processes for the production of liquid NP-fertilizers, although they allow the preparation of pumpable and storable liquid fertilizers, are relatively demanding in terms of mechanical and technological equipment, whether this is due to multistage neutralization, complicated handling, storage and dosing of nitrogen a complex and often inefficient, operationally unreliable and energy-intensive way of cooling the reaction mixture, or in some cases also the preparation and dosing of the stabilizing additive used.

It has now been found that the drawbacks of some of the processes described can be largely remedied by the continuous production of liquid NP-fertilizers according to the invention.

According to this process, the continuous reaction of trihydrogenphosphoric acid in aqueous medium with directly liquid ammonia is continuously fed into the liquid reaction medium consisting of a mixture of the product and the starting materials, in one or more places, so that the point of entry of the liquid ammonia to the reaction medium is at least 320 millimeters away from the surface interface and contact of the reactants takes place with vigorous stirring, characterized by a Reynolds criterion value of Re 1.7.10 ³ , while the pH of the reaction mixture is constantly maintained during the reaction by dosing the reactants within 5.7 to 7.4 and enthalpy of the liquid ammonia metered into the reaction medium is used to remove heat from the reaction medium. Additives improving the physical-handling properties of the product are also continuously added to the reaction medium.

It has been found to be particularly advantageous if the continuous reaction between trihydrogenphosphoric acid and concentrated liquid ammonia is carried out by dosing the reactants into the circulating reaction medium, while maintaining the pH of the reaction mixture continuously during the reaction by dosing the reactants in a relatively narrow range (pH 5.7). to 7.4).

Under these conditions, it has proven to be particularly advantageous if the acid to be fed into the reaction medium is supplied before the circulation pump and the liquid ammonia has entered the liquid circulating reaction medium at the displacement part of the circulation path, at one or more locations. the inlet of liquid ammonia was at least 320 mm from the surface interface.

By using the continuous process for the production of mono-phosphate type phosphate-nitrogen liquid fertilizers according to the invention, the following benefits are achieved in comparison with the industrial processes used today:

- the technological process itself will be simplified as well as the transport, storage, handling and dosing of nitrogenous raw material (liquid ammonia can be processed according to the invention without the need to build a costly stock management directly from a transport container - for example railway or automobile tank etc. .j;

- the operating costs for the removal of the heat of reaction are significantly reduced, since a considerable high vapor enthalpy of concentrated liquid ammonia (about 1,400 kj / l kg of ammonia) is used directly to cool the reaction mixture in the production process;

- a substantial reduction in ammonia emissions as well as improved culture and hygiene at work will be achieved;

the energy requirements for the handling, storage and transport of nitrogenous raw material to production are removed;

- even in the treatment of heavily contaminated extractive H3PO4, only a fine, homodisperse, gel-like precipitate is formed which, after stabilization with a suitable stabilizing additive, does not impair the rheological properties, manipulability and pumpability of the liquid NP-fertilizer.

The following examples illustrate but do not limit the invention in any way.

Example 1

The process for preparing mono-phosphate-type liquid nitrogen-phosphorous fertilizers of the present invention has been tested for a long time on a model quarter operating apparatus consisting of a circulating neutralization reactor consisting of a reactor storage tank equipped with a heat sink (ZV-40, FORMAN type). The pipeline (Ms 40) on the suction side 1 of the centrifugal vertical glandless pump 2 was supplied with a feed of treated phosphoric acid, which was fed to the reactor by means of a peristaltic-hose metering pump from an acid reservoir placed on the scale.

Liquid ammonia was transferred to a circulating reactor through a shaped metal tube 4 from a pressure reservoir of liquid ammonia placed on the balance. The amount of liquid ammonia fed into the process was controlled by a needle valve built into the metallic liquid ammonia feed line (10 x 1.5 millimeter diameter). Within this group of long run tests, liquid ammonia was introduced into the reactor via a metal tube (10 x 1 5 millimeters) coaxially incorporated into the vertical portions of the reactor circulation piping (Ms 40) 3. In order to avoid the possibility of problems during commissioning and shut-down, the liquid ammonia supply was also equipped with a low-pressure steam supply 6, addition (only at start-up and shut-down) was controlled by valve 7. The pressure conditions in the discharge part of the circulating reactor during liquid ammonia dosing could be monitored by a pressure gauge 8 built into the NH3 line between the water inlet S and the inlet pipe The detailed view of the part of the neutralization circulating reactor with the solution of the liquid ammonia supply is shown in Figure no. First

The required amount of water was dispensed by means of a peristaltic-hose metering pump from a reservoir placed on the scale, through a packed end-exhaust gas absorption column connected between the circulating reaction mixture reservoir and the final fan.

Liquid ammonia containing at least 99% NH3 and extraction H3PO4 containing:

53.10 wt. % of total P2O5 (determined photometrically),

50.36 wt. % P2O5 by acidity,

0.52 wt. % Fe,

0.76 wt. % AI

0.22 wt. % Mg, less than 0.01 wt. % Ca and 3.20 wt. % sulfur expressed as SO4 ^2- .

An average of 1132 g of phosphoric acid, so-called phosphoric acid, was added to the neutralization reactor in accordance with the above specification. of a black type and of the aforementioned quality and 246 g of concentrated liquid ammonia. While cooling the reaction mixture exclusively through the flow of cooling water through the reaction vessel reservoir duplicator, the temperature of the circulating reaction mixture stabilized at 63 ° C, its pH only fluctuating on average around 6.5. An average of 1125 grams was dosed over the layer of unorganized ceramic packing in the absorption column. min ^{1 of} water, which flowed continuously through the column into the reaction vessel.

The liquid nitrogen-phosphorus fertilizer prepared in this manner continuously discharged through the side overflow in the reaction vessel reservoir, continuously monitoring the acidity value and continuously monitoring its specific gravity. More than 900 kg of liquid NP-fertilizer type 8-24-0 was prepared as described in the 6-hour experiment.

Example 2

Under the conditions specified in Example 1, the preparation of a stabilized liquid NP-fertilizer was verified during a multi-hour experiment. , at 85 ° C with sodium carbonate, in the presence of a protective colloid. The stabilizing additive prepared as described above was continuously metered in the form of an aqueous approximately 10 percent suspension (based on bentonite dry matter) in an average amount of 500 g. . min ¹ to the reaction tank. During this experiment, the amount of water dosed was reduced to 625 g. min ¹ . Thus, a stable liquid fertilizer of type 8-24-0 was prepared, characterized by very good handling-rheological properties (fluidity: 2.2 wt.% Of the residue; dynamic viscosity at room temperature: 0.2 Pa.s).

Claims (2)

SUBJECT The method of continuous production of mono-phosphate-type liquid nitrogen-phosphorous fertilizers is not interrupted by the guided reaction of trihydrogenphosphoric acid with ammonia at a temperature of 35 to 105 ° C, characterized in that the phosphoric acid is neutralized directly in concentrated water by ammonia. points continuously into the liquid reaction medium consisting of a mixture of product and starting materials, such that the point of entry of liquid ammonia into the reaction medium is at least 320 millimeters away from the surface phase of the invention and the reactants are contacted with vigorous stirring of the reaction mixture; characterized by the Reynolds criterion value Re ≥ 1.7.10 ³ , wherein the pH of the reaction mixture is maintained during the reaction by continuously dosing the reactants between 5.7 and 7.4 and for dissipating heat from the reaction medium. The enthalpy of the liquid ammonia metered into the reaction medium is used, and additives which improve the physical-handling properties of the product are also continuously added to the reaction medium.