DD143365A3 - MEHRNAEHRSTOFFDUENGEMITTEL - Google Patents

Description

• 1

The invention relates to multi-nutrient complex or * mixed fertilizers with improved stability to thermal stress »

Multi-constituent fertilizers with a high content of the three main nutrients nitrogen, phosphorus and potassium are generally obtained by further processing the solutions of nitric acid digestion of raw phosphates or by mixing and granulating suitable single nutrient fertilizers such as super and double superphosphate, ammonium phosphates, ammonium nitrate and potassium salts, before, all potassium chloride, won

 It is known that mixtures containing not only high concentrations of ammonium and nitrate ions but also considerable amounts of chlorides, at temperatures above 150 C, z. B, when evaporating the residual water and drying, can undergo an exothermic and autocatalytic decay, in which almost all of the nitrogen contained in the product escapes in the form of gaseous decomposition products such as nitrous oxide and elemental nitrogen. This thermal decomposition can be • initiated after a period of induction dependent on product composition and temperature, much lower than the actual decomposition temperature observed during linear heating. Although the mechanism of the reactions occurring in the induction period is not fully understood, it is highly probable

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It can be assumed that in the course of redox processes with the participation of ammonium, nitrate and chloride ions, a critical concentration of free acid is formed in which the reaction passes from the slow induction phase into the rapid decomposition phase. Experimental studies prove that small amounts of heavy metal ions - especially ions of iron, copper, manganese, molybdenum and cobalt, which are often components of commercially produced whole fertilizers - both the leading to the formation of stationary acid level during the induction period reactions and the actual decomposition reactions strongly catalyze. For the stabilization of HPK fertilizers against thermal decomposition of the specified type it has already been proposed to add to the fertilizer chemical inhibitors such as amines, urea, urea salts, urea-aldehyde condensation products, carboxylic acid amides and borates and condensed phosphates in comparatively low concentrations.

In the process of production of complex fertilizers, often acidic solutions occur which CaO and 2 ° 5 ³ * - ⁿ molar ratios of 1.5 to 3 »5 included. In the ammoniation of these solutions, it often leads to reversion of the phosphate digestion with deposition of plant cacliumphosphates available. It is known that these reversion can be prevented by adding fatty acids, alkylsulfonic or aminocarboxylic acids. It is also known that said additives are capable of reducing the hygroscopicity of calcium ammonium nitrate by complex binding of the contained calcium nitrate.

Further, mixtures of urea-formaldehyde condensates and ethylenediaminotetraacetic acid are slow acting

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highly concentrated nitrogen fertilizers used.

The mode of action of the previously known decomposition inhibitors is based primarily on the fact that they intercept the free-radical and ionic intermediates occurring during the induction reaction or keep the effective concentration of free acid in the fertilizer low by buffering. However, they do not have any specific influence on the catalyzation of the induction and decomposition reactions caused by heavy metal ions, and some of the described inhibitor systems themselves undergo thermal decomposition reactions, so that their inhibitory action decreases relatively rapidly on prolonged heating to relatively high temperatures.

The purpose of the invention is highly concentrated Mehrnährst off fertilizers u. a. Ammonium, 'Hitrat and possibly chloride ions contain' with increased resistance to thermal stress and less prone to self-heating produce.

The invention is based on the _object's to slow or in the decomposition of ITPK-complexing "~ te Mischdungera.it In particular and containing trace nutrients Yolldüngern the reactions by addition of chemical inhibitors or to suppress completely.

According to the invention a Mehrnährst offdüngemittel, the u'a _e Ammonium-j ITitrat- and possibly chloride ions ent, as chelate complexing suitable, amine groups and

Hydroxy- or carboxy-containing compounds, in particular alkanolamines or aminocarboxylic acids, added as a decay inhibitor. So come as inhibitors z. B, ß-amino alcohols such as ethanolamine and N-alkyl-substituted ethanolamines, diethanolamine and triethanolamine into consideration. Of the aminocarboxylic acids are, for example, © ^ -Aminopolycarbonsauren such as iminodiacetic acid, methyliminodiacetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, etc. It proves to be particularly advantageous to use chelating ^ Aminopolycarbonsauren in the form of their alkali metal salts, since this additional buffer effects against pH change occur. The extent of the inhibitory effect is mainly dependent on the amount of added substance; in general, it is convenient to weight the fertilizer 0.1 to a maximum of 5 -.%, preferably to add 0.2 to 1% _t the decay inhibitor. In investigating the thermal behavior of heavy metal ion-containing multicomponent fertilizers, it has been found that the inhibitors are already effective in concentrations which

- are below the Chelatligandmengen required for a complete complex fixation of the heavy metals.

The chelating ligands used apparently act in two ways. * Once the heavy metal ion catalyzed decomposition reactions are inhibited by complex masking of the catalyst; on the other hand, the substances used as potential pH buffers counteract an increase in the concentration of free acid and the associated acceleration of the onset of the decomposition reaction.

The nature of the incorporation of the inhibitors into the fertilizer depends on the physical properties of the components. It is advisable, for example, to spray aqueous solutions of the inhibitors onto the surface of the fertilizer granules in the process of shaping and conditioning. Another possibility is the

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Additives in one of the last stages of the manufacturing process j z. B-, together with the potash component or with the trace elements, the NPK-mash add «This has the advantage that the compounds mentioned already stabilize during evaporation and drying of the mash *

The essential criterion for assessing the thermal stability of a multi-nutrient fertilizer is the exothermic decomposition of upstream temperature-dependent induction times. When investigating a large number of ITPK fertilizers, it was found that the dependence of the induction times t on the sample temperature T (in ° ¹ O in the range of about 150 to 250 ° C by a Induktionsgleiehung of the type

log t β a / T + b

can be reproduced * here are a and 1) product «specific parameters«

It is a significant advantage of the multi-nutrient fertilizers stabilized by the method according to the invention that the induction times, which are for unstabilized products depending on the test temperature a few minutes to several hours, by adding the inhibitor component by about 100 to 300 depending on the type and amount of the inhibitor % be extended. By adding the inhibitors, the limits of the thermal stability of the treated fertilizers and the decomposition temperatures can be increased by 10 to 30 ° C under otherwise identical conditions »The otherwise often observed tendency

of ITPK fertilizers for self-heating and "cigar burning" does not occur in the multi-nutrient fertilizers according to the invention.

In addition, it has been found that the inhibitors used in the invention can also be used to stabilize highly concentrated aqueous ammonium nitrate solutions.

The invention will be explained in more detail below with reference to 4 exemplary embodiments.

Example 1i

TOO parts by weight of an NPK complex fertilizer of composition 17-12-17 (calculated on N-PpO ₁₅ -KgO) are sprayed with good mixing with a solution of 1 part of ethanolamine in 2 parts Y / asser * After drying, samples of non-stabilized and The stabilized fertilizer of $ e exposed about 10 g in an electrically heated bath to defined temperatures and recorded the times required until the onset of thermal decomposition »

From the measured times, the product-specific constants of the induction equation log t = a / T + b can be calculated. In the table below and in Pig. 1, the constants obtained for both products and the induction times determined from the induction equations for 5 selected temperatures are compiled.

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Induction times (min) ο _c 180 190 200 210 220

without inhibitor 417 170 72.4 33.1 14 * 8 a = 7950; b = -14.95-

with inhibitor 1380 489 166 64.5 26.3 a = 9580? b «-18.01

Example 2

By analogy with the above provision, an NPK fertilizer of the Hährstoffzusammensetzung 18-11-15 is treated with 1 % of its mass of diethanolamine.

The following table shows a comparison of the stability criteria of the two products under thermal stress «

Induction times (min) ° C 180 190 200 .21,0. 220th

without inhibitor 115 61 _e 6 33.9 19.5 11 a = 567Ο; b = -IO.46

with inhibitor 324 141 64.5 30.2 14.5

a = 7500; b = -14.05

Example 3

A complete fertilizer of composition 13-8-13, containing about 0.5% micronutrients (manganese, copper, zinc, cobalt, molybdenum, iron), is stabilized by grinding with less than 1 % of an aminopolycarboxylic acid the following examples show the induction times found at a test temperature of 197 ° C, depending on the type and amount of the additive,

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Induction time (min)

without inhibitor 17.6

Nitrilotriacetic acid (0 * 5 %) 49.1

Nitrilotriacetic acid (0.2 %) 27.3

Ethylenediaminetetraacetic acid (0.4 %) 51 »1 disodium salt of xylenediamine« ·

tetraacetic acid (0.4 %) 62.0

Example 4

A 75 percent strength aqueous solution of ammonium nitrate _s, which is about 10 mol% free acid and 1 mol% ~ ammonium chloride and iron - containing (. III) nitrate, decomposes at a temperature of 120 C by a rate law 1st order , where for the decrease of the ammonium ion concentration, a rate constant of 6, O «1O ~ ² Stde."' ^{1 is} found.

I ¹ Ur a solution of the same composition which has been treated with 1 wt .- ^ Dinatriumsälses of the ethylenediaminetetraacetic acid, is the rate constant of NH ₄ NO ₃ -decay 2.2 * 10 ^"2 STDE."^"1.

Claims (4)

Invention claim. 1. Multi-nutrient fertilizers containing u, &, * ammonium, ITi and eTcntuell chloride ions, with improved thermal stability, characterized by a content of suitable as chelating agents, amino groups and hydroxy or carboxy groups containing compounds, in particular alkanolamines or aminocarboxylic acids , as disintegration inhibitors. 2. Multi-nutrient fertilizer according to claim 1, characterized in that the inhibitor in an amount of OjI to 5 wt .- ^, preferably 0.2 to 1 fa ~ - based on the total mass of the fertilizer - is applied. 3. Multi-nutrient fertilizer na = ch claim 1 and 2, characterized _} that are used as alkanolamines ethanol amine, diethanolamine or triethanolamine. 4 «multi-nutrient fertilizer according to claim 1 and 2, characterized in that are used as aminocarboxylic c-arabopolycarboxylic acids such as iminodiacetic acid, nitrilotriacetic acid and Xthylendianiintetraessigsäure or their alkali metal salts. For this 1 great drawings