Note: Descriptions are shown in the official language in which they were submitted.
L29~.
,
T~l~ prcsent invention r~:l.ates to NPK ~ertilisers
comprislng ~u~ous solutions oE nitrogenous compounds (e g.
ammonium salts, urea), phosphorus compounds (e,g ammonium
s phosphates, phosphoric acid) and potassium compounds (nearly
alw~ys potassium chloride) Such NPK fertiliser solutions
are w.idely used throughout the world, but in general their
plant nutrient levels are severely limited by solubility
consiclerations, which place certain restrictions on their
. storage, transport and application.
. 10 There have been many ~ttempts to improve the
~` concentrations of such fertiliser solutions by employing
raw materials such as ammonium polyphosphates, but these
~ . have hi~herto had very little impact on those grades of
.. : fertiliser which contain substantial quantities of potassium
~. chloride Efforts have therefore been directed towards
:.~ making use of compounds which contain both potassium and
~`~; phosphorus, but hitherto such materials have not been
~7 available at economic prices,
~:, . We have now discovered that conventional ~PK
; 20 fertilisers con~aining ammonium, phosphate, and potassium
~ ions and comprising aqueous solutions of nitrogenous
7~ ' compounds, phosphorus compounds, and potassium chloride
¦~ under conditi.ons of mild acidulation , will deposit
t ' . crystals of a solid solution of mono-ammonium orthophosphate
,~ in monopotassium orthophosphate. These crystals, when
separated from the supernatant liquor and dissolved, can
.. be mixed with further nitrogen-, phosphorus- and/or potassium-
containing plant nutrients, to yield a more concentrated
5~ fertiliser solution than a conventional solution with the
7.. ~ 30 same plant nutirent ratio. This more concentrated solution
~ 2-
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contains proportionately less chlorlde than the original
sol.ution. It .is a hypochlorid.ic solution and as such
may be especially useful for application to crops which
are sensitive to chloride~
The acidulated supernatant liquor, after
separation of the crystals therefrom, contains more
chloride and less potassium than the original s~lution,
but its composition can be adjusted by ~he addition ~hereto
of further NPK plant nutrients to give a hyperchloridic
fertiliser solution suikable for use where the presence of
, extra chloride is not detrimental to the crop.
The pre~ent invention accordingly provides a
- process for the conversion of a ~PK fertiliser containing
ammonium, p~osphate, and potassium ions and comprising an
; a~ueous solution of a nitrogenous compound(s), a phosphorus
compound(s) and potassium chloride into a first ~PK
fertiliser fraction having a lower chloride content than
the original solution and a second NPK ~ertiliser fraction
, having a higher chloride content than the original solution, .
t~: 20 which comprises the steps of treating the solution with an
~ .
,;~ acid, allowing crystals o a solid solution of monoammonium
orthophosphate in monopotassium orthophosphate to crystallise
. out of the resultant mixture, separating the crystals from
the supe.rnatant liquor and redissolving them to form the
;:: ..................................................................... . .
'~ said first ~raction having a lower chloride content than . :the original solution,and the supernatant liquor comprising
the second fraction having a higher chloride content than
' the original solution.
,, .~. The acid is suitably phosphoric acid, polyphosphoric
i~ 30 acid or a mixture thereof.
~ ~3
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.. .. . ~ . . .. . . ~ .
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Pre:Eerably, tlle sepa~at~?d crystals ar~ re-
, dissolved a:l.ong w.i~h ad~lltional prese].ected plant nutrients
~o produce a more concentrated ~irst fraction which is a
hypochloridic NPI~ Eertiliser solution of predet~rmined
composition.
Preferably, the supernatant liquor i.s mi.xedwith additional preselected plant nutrients to produce a
.i~ second frac~ion which is a hyperchloridic NPK fertiliser
.. solution of predetermined composition.
io The invention is hereinafter described with
reference to the accompan~ing drawings, wherein:-
Fig. 1 is a schematic diagram illustrating the
process of the invention; and Fig. 2 is a more complete block
diagram illustrating the process of the invention in greater
,~;' detail.
; , Referring to Fig. 1, twelve experiments were
.~j .. . .
~ carried out to exemplify the invention, Each experiment
'; ~ resulted in one hypochloridic fertiliser and one hyperchlor-
. idic fertiliser, making a total of twenty-four. The general
procedure followed in the experiments is outlined hereunder,
~- General procedure for Exper:iments 1-12
.i To T gms of a conventional fertiliser solution
~ .:
(composition A-B-C) were added M gms of phosphoric acid
, (0-65-0), The resultant mixture was allowed to ~ature for
i: at least 20 minutes under ambient conditions before filter-
:; .
~ ing off S gms of
, . ~
:,~ . .
- . .
:s"
~'
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: which is a hyperchloridic NPK fertiliser solu-tion of predeter-
mined compositlon.
The invention is hereinafter described with re~erence
to the accompanying drawings, wherein:-
Fig. 1 is ~ schematic diagram illustrating the process
of the invention; and Fig. 2 is a more complete block diagram ~:
: ~ illustrating the process of the invention in greater detail.
, ~ Referring to Fig~ 1, twelve experiments were carried
.~ out to exemplify the invention. Each experiment resulted in one
hypochloridic ~ertiliser and one hyperchloridic fertiliser,making a total of twenty-four~ The general procedure followed
. .
in the experiments is outlined hereunder~
General procedure for Experiments 1-12
To T gms of a conventional fertiliser solution (com-
~ . position A-B-C~ were addea M gms o phosphoric acid (0-65-0).
:~ ~ The resultant mixture was allowed to mature or at least 20 min~
., utes under ambient conditions before filtering of S gms of
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Z~ 28376
1(~84;~:9
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;i crystalline monoammonium phosphate-monopotassium phospha-te solid solution
~composition D-E-F) from a ~upernatant liquor (composition J-K-~) weighing
gm8.
~- To the S gms of wet cxystals were added Vl gms of = onium phosphate
solution (8-24-0), Wl gms of urea, ~1 gm8 of po-tassium chloride, hl gms of
-~ aqueou~ ammonia (26-o-o) and nl gms of water, producing 100 gm~ of a more
concentrated, hypochloridic fertiliser eolution (co~position P-Q-R).
Similarly, to the ~ gms of supernatant liquor were added V2 gms of
` ammonium pho=phate solution (8-24-0) or = onium polypho~phate =olution (10-
34-0~, W2 gm~ of urea, ~2 gms of potassium chloride, h2 gme of aqueous am~onia
(26-o-o) and n2 gm~ of water thereby producing 100 gms of a hyperchloridic
.~ fertiliser ~olution (compo~ition X-Y-Z).
Numerical values of the parameters A, ~, C, etc. are summarised in the
~ followin~ ~able 1.
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t will b~a observed th~-t, in these samples the chlo-
. ride content o the hypochloridic solution P-Q-R has been
decreased by up to about one-third as compared with the original
.. solution A-B-C, whereas the chloride content of the hyperchlo-
ridic solution X-Y-Z has been increased by an average of about
. 30%.
The weight and composition of the raw materials added
; to the wet crystals and supernatant li~uor may be varied as
required to provide final hypochloridic and hyperchloridic
solutions of predetermined compositionf.
- In the block diagram of Fig. 2 the upper portion
illustrates a conventional method of preparing a conventional
.,.
;........... NPK fertiliser solution (i.e. the solution A-B-C). Phosphoric ~.
.. or polyphosphoric acid is neutralised with ammonia in a neutra-
liser, gaseous ammonia is dissolved in water, and these two
~ constituents are mixed, together with additional water, potas-
f sium chloride and urea in a mixer A. ~ ~
The mixture ~rom mixer A is led to a crystalliser : :
' . where it is treated with phosphoric or polyphosphoric acid, and
~ 20 the resultant mixture is allowed to mature for at least 20 min- :
.~ utes at ambient temperature, during which time a solia solution
of monoammonium orthophosphate in monopotassium orthophosphate
crystallises out. The wet crystals are separated from the
.~ mother liquor, and are led to a mixer B, the mother liquor
; being led to a mixèr C. To each of these two mixers there are
added, in preselected quantit.ies, plant nutrients from the
. earlier stages of the process, for example phosphoric or poly-
: phosphoric acid~ ammonium phosphate or ammonium polyphosphate, ~.
aqueous ammonia, potassium chloride, urea, together with further -~:
water. As shown, s~me of the original fertiliser solution
:,
. (A~B-C) produced in mixer A can be added to mixer B and/or
mixer C.
8 -
