Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
- i,
--2--
64~ -
Urea granules are widely applied for manuring purposes, either
as such or as a component of a mixture of di~ferent fertilizers. The
size of the urea granules depends on thelr use, and is,'for example,
1.5 - 4 mm for bulk blending and 5-10 mm for forest fertilizer dressings.
Urea granules are produced by granulation of a urea melt, which is
prepared in urea synthesis units. In order to keep down capital outlays - -~
and the costs of operation, it is generally desirable for the granulation
of the entire production of a urea synthesis unit to be carried out in
one granulator unit only. This is possible ln the uréa l'prilling" process,
t7hich comprises spraying a substantially anhydrous urea melt in the top ' ';
of a tower, and cooling the resulting droplets during their fall with -'
upwardly flowing cooling gas so that they are solidified.-Urea prills
contain internal cavities, which are formed 0~7ing to the-shrinkage
.. . .
: occurring during the rather sudden solidific&tion of the material, and
-
which cause internal stresses in the'prills. As a consequence urea prills
are mechanically weak, they have a low crushing stre~th,a low i~pact
resistance,'and a tendency of for~ing fly dust owing to abrasion, which
propertiès? among other objections, render the prills unsuitable for
. . ,
~ ' pneumatic transportation~ Fly dust is an extremely Pine, hydroscopic powder ~'
j 20 which pollutes the working atmosphere, and hence is objectionable to
perso~nelin charge of handling the material. Furthermore, this dust give
' rise to problems in sealing the plastic bags in which the prills are packed. `~
;~ ~n an artlcle in "Nitrogen" 95, pp. 31-3~ (19T5), two techniques are
described for the production of urea granules having greater hardness and
' - strength and-, if desired, a larger diame-ter than urea prills. According to
~' both techniques a substantially anhydrous melt of urea is sprayed on to
urea nuclei, in one case in a can granula-tor and in the o-ther in a drum
granulator of special construction. r~ne urea gran~es produced by these
techniques have bet-ter p'nysical properties than urea prills. A disadva~age
of these techniques is, however that both can gr3n~ulators and dru.~ granulators,
~` '' ' ~
.
.. : . ., ~
j4~
when having practically feasible dimensions, only have a limited capaci-ty,
so that mostly more tllan one granulator is needed for processing the
production of a urea synthesis unit into granules.
It is an object of the present invention to provide a process
for the production of urea granules having a desired size between 1.5 and
25 mm or even larger dimensions, a good sphericity and a smooth closed
surface, a high crushing strength, a great resistance to impact and a !
slight tendency of forming fly dust through abrasion, so that for one thing
they are suitable for pneumatic transportation, and which granules remain
free flowing even after prolonged storage, have an excellent chemical `
composition: low values for moisture, biuret, free N~13 and COz contents
(low buffer capacity), are excellently suitable for technical uses, and
form an excellent substrate for the production of slow-release urea (such
as sulphur-coated urea). ~-
~his ob~ect is realized, according to the invention, by spraying ;
an aqueous urea solution having a urea concentration of 70-99.9% by weight, -
on to fluidized urea nuclei in the form of droplets having a mean drop
diameter of 20-120~m , preferably lOO~m and in particular 30-6Cm~
and a temperature at whlch the water evaporates from the solution sprayed
on the nuclei and urea cristallizes on the nuclei to form granules having
a desired size.
During the fluid-bed granulation the granules being formed are -
continuously exposed to vigorous collision and friction with other particles -~
which is apt to cause abrasion of the top layer of the granules to form
fine dust.
It has been found that this dust formation can be depressed
` by spraying the urea solution in the form of very fine droplets having
an average size of 20-120~m , which, once deposited on the granules,
` dry so rapidly that the top layer is continuously kept " dry"; this dry
i.e. anhydrous top layer is must better resistant to abrasion than a "wet",
i.e. water containing top layer.
It has further been found that the formation o~ dust can be
` substantially avoided if, in accordance with a preferred embodiment of
sd/(~ _3_
. .
3L69~L
the process according to t:he invention, there is added to the urea
solution to be sprayed a crystalliza-tion retardant for urea, which retards
the crystallization of the urea deposited on the granules, so that the -top
layer, although free of water, contains a relatively large proportion of
liquid phase for some time and thereby remains plastic, which has turned
out to considerably enhance the resistance to dust formation. This addition
is more important according as the urea concentration of the urea solution
to be sprayed is lower, in particular less than 95% by weight, and more
particularly less than 90% by weight.
The application of this preferred embodiment of the process
according to the invention is productive of urea granules having an
exceptionally high resistance to dust formation.
~ Preferred crystalli~ation retardants for the urea are
formaldehyde and water-soluble addition and/or condensation products of
formaldehyde and urea. The production of water-soluble addition products
of formaldehyde and urea is known, for example, from U.S. patent 3,067,177, ;~
and the production of water-soluble condensation products of formaldehyde
and urea is disclosed in U.S. patent 3,112,343. It is also possible to use
~` addition products of formaldehyde and urea produced in the first place in an
alkaline medium and then condensed in an acid medium to form thin-liquid
to syruppy liquids, such as the liquid adhesives used in the chipboard
~ industry. The crystallization retardant is preferably added in a proportion
?~ of~o~l-2~o%~ preferably 0.1-1.0%, most preferably 0.5-1.0%, calculated
as formaldehyde on the weight of the urea solutibn.
- The aqueous urea solution sprayed on to the fluidized urea
:. :
nuclei has a urea concentration f ?0-99 9% by weight, preferably 85-96%
`` by weight. The use of a solution having a urea concentration oP 85-96%
by weight offers various advantages.
;` In the first place, in the urea synthesis unit, it is no longer
necessary to apply the rather expensive concentration of -the solution to
a substantially anhydrous product, as is required in the prilling process
-~ and in granulation with can or drum granulators. In the second place, such
a solution may have a low biuret content, as this content increases markedly
- sd/~ ~~~
: . ,:,
especially upon evaporation of the solution to a subs-tantial anhydrous
produced. In spite of the fact that, in this preferred ernbodiment of the
p~ocess according to the invention the solution to be granulated is not
anhydrous, but contains 4-156 of water, it has been found that a high
specific granulation capacity tthe quantity of urea by weight that can be
granulated per unit of bed surface area) of 2-4 ton per hour per m2 bed -;
surface aFea can be achieved- ~
- The urea solution is sprayed with a gas, such as air. Preferably ;
the solution is sprayed within the fluidized bed of urea nuclei, as spraying
on to the bed involves the risk of the sprayed droplets being entrained
by the fluidization air issuing from the bed. The pressure of the spraying
air is preferàbly 147-392 kPa (1.5-4 ata). This pressure has a highly
important effect on the size of the sprayed droplets. The higher the
pressure, the smaller are the sprayed droplets. The mean drop diameter
can be calculated on the basis of empirical formulae which according to
W.R. Marschall, "Atomization and Spray Drying", A.I.Ch. Monograph, Vol. 50
- pp 74-7S, can be developed in dependence upon the size of the air sprayers
used. In the case of sprayers for granulatlon, the following formula
by Nukiyama and Tanasawa applies~
D 54~4 ~ ~ 597~ loooQl ~1 5
V ~ d ~ s.d. J ~ Q2
wherein- -
D = the mean drop diameter in ~m
V = the relative velocity of the alr relative to the liquid in m/sec. ;;~
s - the surface tensi.on in dynes/cm -~
v = the Viscoslty of the liquid poises
d = the specific gravity of the liquid g/cnl3 and
Ql/Q2 = the ration of the volume of liquid to the volume of gas.
.
sd/~ -5-
6~ $
,
The speci*ic ~ravity can be determined with reference to
M.Frejaques, "Les bases t~éorlque de la synthèse industrielle ae
l'urée ", Chimie et Industrie 60 (1948), pp.22-35.
The surface tension is calculated according to the formula:
s1/4 = k.d. (S.Glasstone, Textbook of Physical Chemistry, 2nd Edition,
(1956), page 494). The surface tension at boiling point is
Sbp = 21 Tbpdbp (J.H.Perry,~Chemical Engineers Handbook, 4th Edition,
(1963) pp. 3-221 and 223). The surface tension/trial conditions ;s~
S - Sb q d ) 4 qhe viscoslty o~ the urea solution is determined by m~s~s
of International Critical Tablès. The temperature T is 'expressed in
Kelvin in all instances. ' ' '~
.
; The air flow rate after adiabatic expansion at a temperature T '
: . , .
from a supercrltlcal inltial pressure P is given bij Q2 = k.P. ~.
From this the constant k can be calculated, as the sprayers used in the
: . .
examples, at room temperature (20C) and an initial pressure o~ 216 kPa
(2.2 ata)~ provide a flow rate of 30 m3/hour. There~ore k = o.oo8 m3/ ~ -
h.kPa.E (0.80'm3/h.at.K). From this air flow rate7 the air velocity is-
calculated, ~ith a head diameter of 5.8 m~: air velocity = Q2 (in m3/hour/
. 3600.surfacé area (~in m ). As the Ii~uid velocity is negllgible rela~ive to ;
the air veloci-ty, V can be equalized to the air velocity. The urea flow rate
per sprayer is k~own. The calculation of the mean drop size will be
elucidated further in EY~ample I.
The size of the urea nuclei supplied to the :'luidized bedin
which the granulation takes place generaIly r~ingeS be-tweenO.2 and ~ mm, and
, . ,
may be larger within this range according as larger urea granules are
' to be made.
The temperature of the fluidized bed of urea nuclei generally ranges
between 70 and 110C, preferably between 80 and 100 C. ~Jithin -these
limits, the temperature may be lower according as the urea concentra-tion of
the solution sprayed on to the nuclei is higher. ~he temperature of the
fluidized bed can be controlled by a suitable selection of the temperatures
of -the fluidization air and of the urea solution being sprayed.
,
i - ~ . . ;, ' '
;41
-7
' . - ' , .
The urea solution is spra~ed over the urea nuclei in the form of
very fine droplets having an average dia~eter oP 20-120 ~m. Under the
in-~luence o~ the temperature preva~ing in the fluidized bed, the water
- , - ' : ..
is evaporated from the solution and the urea crystallizes on the sur~ace
~ ..
of the urea nucleus. O~ting to the small size of'the droplet these will
generally be able to cover a~portion of the surface of the indlvidual ~ s
urea nuclei only. It is thus prevented that an onion-like structure of
the granules is formed, in which the nucleùs is coated in succession uith
~ . . , : - , . ~ .
essentiaIl~superimposed layers. As a consequence, the granules according
to the present invention do not exhibit the stresses inherent in an
onion-like structure. It is considered that the excellent mecha~ical ~'
properties of the urea granules according to this invention are due to~
the absence of these stresses ~'A further advantage of the minnte~drop
size of the sprayed urea solution is -that the water can be fully~
~ . , .: . .. . .
evaporated from it in a short time. ' ~
.
~or the purpose of removing superficial moisture, the resultlng granules-
can be subjected, if so desired, to subsequent drying for about 5-10 minutes '
with air of 100 to 150 C, s~ that the temperature of the granules ;s ~
- maintained between 70 and 90 C.-T`nereafter the granu~es~are pre~erably ~ ;
cooled to a temperature of appro~imately-30 C or lower.~Cooling can be
. .
effected in any suitable cooling apparatus, for example, in a fluidized-
. ,
bed cooler.
The product produced by the prccess according ~o the present invention
contains only small ~uantitles of free ~3~ C02, moisture and biuret7
t and has such mechanical properties that it is suitable for pneuma~ic trans-
..~
portation, and remains free flowing even after prolongea storage.
A particular advantage of the process according to thé invention is that
.
the forma-tion of biuret during the granulation can be prevented a-lmos-t
; entirely by spraying a urea solution whose ch~ystallization point is
below 100. Thus by spra~ing a urea solution havin~ a urea content of, ~or
example, ~5-85% by welght and a biuret content'~less than 0.1%,
.
,; . ,:
.. . .. .
6~L~
.
urea granules wit~l a biuret content of less than 0.1~ can be obtained.
Such urea granules are particularly desirable for certain crops, such
as tobacco and tomatoes.
The urea granules produced by the process of this invention are
highly suitable for being coated with, for e~ample, sulphur, to form slow-
release granules, as, owing to their excellent sphericity and their closed
surface, the required amount of coating material is minimized,
The process according to the present invention can be carried
out in any type of fluid-bed granulator. One example of suitable apparatus
is diagrammatically shown in the accompanying drawing, which shows a
granulator l divided into a plurality of compartments 2, 3, 4, 5 for the
granulation, and a compartmen-t 6 for the subsequent drying of the urea
granules. The compartment last mentioned is optional as subsequent drying
will only be used if the granules still contain superficial water, which '~'
may be the case if a relatively dilute urea solution is used. Granulator 1
comprises a grid 7, which supports the fluidized bed and transmits the ', ~,.
., .
` air of fluidization, preheated in one or more heaters not shown and ~-
supplied through conduit 8. The space below the grid can be divided in
the same way as the space above it, into compartments, in which case the air ' ,
`` 20 of fluidization is supplied to each of these compartments. Granulator 1 is
~'~ further provided at the bottom with pneumatic sprayers 9, 10, 11, 12, which ~-,' ,
` e~tend to a level above grid 7. It is also possible to use two or more
'~ sprayers in each compartment. Through these sprayers, the urea solution
supplied through conduit 13, to which a crystallization retardant may have
been added, is sprayed with the 'spraying air supplied through conduit 14
.~. . .
into the granulation compartments 2, 3, 4, 5. The fluidized bed is
constituted by urea nuclei, which are supplied by means of a screw
conveyor 15. For the subsequent drying of the granules in compartment 6,
granulator 1 is equipped with a conduit 16 for supplying drying air.
For the removal of air and possibly entrained dust particles,
granulator 1 has discharge conduits 17, 18, which are connected to a
)~ ' , -
sd/~,~
:
.
L6~1
cyclone 19, in which very small granules, of a size o~ approximately
100-500 micron, are separated, which are supplied throuyh condult 20 to
screw conveyor 15. The air from cyclone 19 is conducted through discharge
conduit 21 to a device 22, in which the air is washed with a dilute urea
solution to remove fine dust and possibly remaining very small granules.
In order that a high washing efficiency may be achieved, water may be ~ -
sprayed into the air through a sprayer 23. The air stripped of dust ; ~ -
can escape through discharge conduit 2~, and the dilute urea solution
formed is discharged through conduit 25.
Granulator 1 further comprises a bottom outlet 26 for urea
granules, terminating over a vibratory chute 27, whence the granules are
transported to a sieving device 28, in which they are separated into a
number of fractions, namely into an undersize fraction, a fraction having
the desired slzes, and an oversize fraction. The fraction having the ;~
desired sizes is passed through a cooler 29 to a storage site, where
further separation into fractions for different purposes can be effected.
If desired, the cooler may be arranged upstream of the sieving device. ;~
The fraction of oversize granules separated in sieving device 28 is
transported after cooling to a crusher 30 in which this fraction is
crushed to the same sizes as, or smaller sizes than, those of the -
undersize fraction. The undersize fraction separated in sieving device 28 -
is passed through conduit 32 to conduit 31, in which it is conducted to
screw conveyor 15 together with the fraction from crusher 30.
~ The process according to the present invention can be carried
out both continuously and batchwise. A urea solution is supplied through
- conduit 13 and sprayed by means of the spraying air supplied -through
conduit 14 via sprayers 9, 10, 11, 12 into the fluidized bed of urea nuclei
in compartments 2, 3, ~, 5 of granulator 1.
The quantity of urea granules removed from the fluidized bed
via compartment 6, in which no urea solution is sprayed, and discharge
conduit 26 is replaced by urea nuclei supplled by screw conveyor 15.
sd/~ .9_
The size of the product granules depends on a number of
factors, such as the number of urea nuclei in the fluidi~ed bed, the size
of these nuclei, the quantity of urea solution sprayed per unit of time,
and the residence time of -the nuclei in the bed. Thus, for example,
larger product granules will be obtained, if the number of nuclei in the
fluidized bed is reduced and the residence time is prolonged. In order
that a predetermined particle siæe distribution of the product may be
maintained, it is necessary for the bed contents to be kept as constant
as possible as regards both the particle size distribution and the number
of nuclei. This can be achieved by ensuring that the quantity by weight
of the urea nuclei, with the correct particle size distribution, to be
added to the fluidized bed is at all times in agreement with the quantity
by weight of the product granules removed from the bed.
~ If, through one cause or another, deviations in the desired!` product sizes occur during the granulation process, these deviations will
be automatically corrected in the above-described embodïment of the process:
;~. if the product become too coarse, a larger oversize fraction will be
separated in sieving device 28, the load of crushe~ 30 will be increased,
and a larger number of nuclei will be supplied through line 31 and screw
conveyor 15 to the fluidized bed in granulator 1, whereby the average
diameter of the granules is reduced. The operation of crusher 30 should
be properly controlled: if -the broken product is too fine, too much dust
is supplied to the fluidized bed, where it either entrained by the
fluidization gas, or causes agglomeration; if the broken product is
too coarse, too few nuclei are supplied to the fluidized bed.
Owing to the subdivision.of the fluidiz~d bed into compartments,
a fractlonation of the growing granules can be realized. In each
compartment the granules having the largest dimensions will mainly be
present in the bottom part of the fluidized bed and easily pass to the
next compartment.
,
~g~
The invention is illustrated in and by the follo~ing examples.
Example I
In apparatus simllar to that shown in the drawing, but having
one granulation compartment, in which two spra~ers were disposed, 16
granulation tests were performed batchwise. The sprayers used had an
air-head diameter of 5.8 mm, a liquid-tube diameter of 3 mm and an air
capacity of 500 l/min. at an air pressure of 216 kPa (l.2 ats overpressure).
In all tests, the fluidi~ed bed was approximately 30 cm high. In each
test 35 kg urea nuclei was used as the starting material. The other data
as well as the results are shown in Table A. In said Table, Formurea
80 is mentioned as one of the crystalli~ation retardants. Formurea 80
is a commercially available product, the preparation of which is ~ ~
described in U.S. patent 3!067,177, and is an aqueous solu-tion consisting -
of approximately 20 parts by weight of water, 23 parts by weight of urea
and 57 parts by weight of formaldehyde, with approximately 55% of the
formaldehyde being substantially bonded as trimethylolurea, and the
balance oE the formaldehyde being present in non-bonded condition!
In order to show the effect of the pressure of the spraying
air, the concentration of the urea solution used, and other factors
on the mean drop diameter, and of the mean drop diameter on the physical
properties of the product granules, the mean drop diameter has been
calculated for all tests. The data required for this calculation and
the calculated mean drop diameter values are listed in Tables B and C.
The properties of the product granules are specified in Table D.
: .
,
..
sd ~ -ll-
The TVA abrasion test is described in Specia] Report S-444
~1970) of ~pplied Research Branch, Division of Chemical Development,
Tennessee Valley ~uthority, Alabama.
Example II
In the same apparatus as used in Example I, in two continuous
process granulation tests, 30-35 kg urea nuclei having a grain size of
0.5-2.0 mm were fluidized in a granulator with approximately 700 m~ air of
fluidization of 120C per hour. As soon as the urea nuclei had reached a
temperature of approximately ]00C, an 80% aqueous urea solution to ~
which 0.5% by weight of Formurea 80 had been added was sprayed by two r
sprayers at a rate of 120 kg/hour with spraying air of 120C and 245 kPa
~ ,
(2.5 ata). The mean drop diameter of the sprayed urea solution was
approximately 80~m . In the granulator, the temperature assumed a value
of 90-100C owing to the evolved heat of crystallization of the urea and
~` the evaporation of water from the urea solution.
The average size of the product granules is a function of the
size of the urea nuclei supplied and of the quantity of sprayed urea
,
solution. In test 17, granules of 2.5-4 mm were made and in test 18
granules of 4-6 mm.
The size distribution of the product granules in the fluidized
bed was as follows: :
Test 17 18
diameter <2.5 mm, % 30 15
2.5-4 mm, ~ 60 25
>4 mm, % 10 60 (of which 10% of
diarneter ?6 mrn)
product of desired sizes, ~ 60 50
By continuously removing approximately 170 kg product granules
per hour, the quantity of granules in the fluidized bed was kept constant.
The product granules were divided by sieving into three fractions:
.
sd~ -12-
-;
Test _17 _ _ 18
`~ product from granulator, kg/h 170 200
of desired size, kg/h 102 100
undelsize, kg/h 51 80
oversiæe, kg/h 17 20
The oversiæe granules were crushed in a crusher and resupplied to ~ :
the granulator together with the undersize fraction. In this manner the
size distribution of the granules in ~the granulator was kept constant.
The product granules ha~ing the desired sl~e were subjected to
subsequent drying for 5-10 minutes with air of 100-150C to a product
temperature of between 70 and 90C. Subsequently the product granules
were cooled to approximately 30C. ;~
During the granulation, 2.8% by weight of fine fly dust was formed,
calculated bn the sprayed quantity of urea solution.
`~ The properties of the resulting urea granules were as follows:
` Teat 17 18
moisture content, % -1~ 0.10
:~
:
biuret content, % 0.45 0.44
formaldehyde content % 0.24 0.23
si~e distribution<2.5mm 1.2 <4mm 3.4
of the 2.5-4.0mm 97.3 4-6mm 94.8
granules ? % >4.Omm 1.5 >6mm 1.8
crushing strength diameter 2.5mm 3.05 diameter 4mm >5
kg diameter 3.15mm 3.35diameter 5mm >5
diameter 4mm 4,25 diameter 6mm ~5
TVA abrasion test, % <1 <1
__
~ 30
.
jl/5~, -13-
. . ~- .. . :,, ~ : , -
6~
_ TA~LE A
Test No. 1 Z
- Concentration urea solution % 72 72
- Temperature sprayillg air C 95 95
- Pressure sprayillg air kPa(ata) 147(1.5) 147(1.5)
~ - Crystalli~ation retardant none Formurea 80
.' Granulation
- Urea nuc]ei broken broken
- Urea solution granules granules
.~ concentration % 72 72
' temperature C 90 90
¦ formaldehyde content % none 0.3
rate sprayed (total) kg/hr 60 55
.: . .
~ mean drop dia.~m 68 60
:) ,
`~ - Temperature_granules in C 70 80
`" granulator
'` - : ;~,
Final product after sieving
and cooling
temperatore ~ C 25 25
chemical analysls
- moisture % 0.06 0.10 `~
`
- formaldehyde equivalent % none 0.28
- Granulometry
- >5.0mml % 3.0 2.8
- 4.0 - 5.0mm % 6.9 4.5
2.5 - 4.0mm % 89.7 90.1 -~
¦ - <2.5mm % 0.4 2.6
! - Crushing strength
~ - ~ 2.0mm kg 0.42 0.85
¦ - 0 2.5mm kg 0.65 0.99
`- 0 3.15mm kg
` - 30
- ~ 4.Omm kg
T.V.A. abrasion test
- <1.25mm % of
3.15-4.Omm fraction
- Dust formation during granulation
% dust relative to urea solution
- sprayed 30 8
. ~
il/s~ ` -14-
3 4 4 4 7
~ .
96
125 125
147(1.5) 147(1.5) 245(2.S)147(1.5) 172(1.75)
none Formurea 80 Formurea 80 Formurea 80 Formurea 80
- micro micro broken micro micro
prills prills granules prills prills
96
115 125
none 0.3 0.3 0.3 0.3
42 85 85 85 96 `~
39 109 51 106 92
100 100 100
' '
0.06 0.15 0.09 0.08 0.33
none 0.22 0.25 0.23 0.22
0 0 0 0 15.3
0.2 0.9 15.0 17.6 54.5
82.1 98.7 84.4 77.2 28.4
17.7 0.4 0.6 5.2 2.8
20 0.50 0.98 1.6L 0.91 0.85
0~70 1.30 2.05 1.26 0.97
- - 2.35 - 1.55
- - 3.71 - 1.77
4.2 2.8 <1 1 <1
3 3 3
,
` 30
jl/ S'~' -15-
~ -
. .
~ 9 10 ~1 12
__ ___
96 96 96 96 96
120 110 105 130 130
196(2.0) 245(2.5) 270(2.75)245(2.5)245(2.5)
Formurea 80 Forn~urea 80 Formurea 80none Formurea 80 ~'
.
micro broken broken broken broken
prills granules granulesgranules granules
96 96 96 96 96
125 125 125 125 125
0.3 0.3 0.3 none 0.1 ~
84 84 72 75 75 ! ~: "
62 45 32 37 37 ~
100 100 100 100 100 ,
~`
0.21 0.12 0.08 0.03 0.09
0.23 0.24 0.28 none 0.12
3.8 20.0 5.9 5.6 1.3
14.6 43.9 42.4 53.4 55.6
79.2 31.4 44.2 37.3 41.7
2.4 5.7 ` 7.5 3.7 1.4
1.40 1.68 2.08 1.31 1.68 -
1.7~ 2.21 2.68 1.90 2.21
2.07 2.76 3.03 2.19 2.76
3.21 3.94 4.43 3.39 3.94
<1 ~ <1 <1 <1 <1 ,-~
3 1.5 1.0 2.5 1.5
' -~
~ 7D -16- !
'
4~
13 14 15 16
96 96 96 96
130 130 130 130
245(2.5)245(2.5)245(2.5) 245(2.5)
Formurea 80 Formurea 80 Formaline U F -condensate
broken broken broken broken
granulesgranulesgranules granules
96 96 96 96
125 125 125 125 ! ~i
0.2 0~3 0,3 0,3
37 37 37 37
100 100 100 100
-
0.08 0.09 0.12 0~08
0.19 0.25 0.28 0.30
1.1 1,3 1.6 6,1 :~
59.5 61.2 47,2 - 42.4
37.9 37.1 43,3 44.1
l.S 0.4 7,9 7,4
1.60 1.68 1,99 1. 98
2,08 2.23 2.63 2,54
2.83 2.74 3.44 3.39
4,46 3,94 5.20 5,14
<1 <1 <1 <1
1.0 0~8 0.7 0,7
~" - .
-17-
- bm~
X
L6~ i
-18_
- ::
.
TABLE B
Concentration - ~0
urea Tb ( K~ ~ s d s v 54~4~ 59~(~~~~
solution P ~P ~r--.d
-- .
- 72~ 390.5 1.148 25.86 1.167 27.62 0.03 264.65 56.3807
.
_ 80% 396 1.166 26.64 1.187 28.61 0.03 267.o7 55.7538
90% 407 1.192 27.99 1.206 29.32 0.03 268.23 55.1643
96% I~23 1.200 29.28 1.222 31.~8 0.03 ~ 276n11 5l~.2195;
- ~ - ~ - , " ,
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.
~ 16~ :
T A B L E_ C ~ -
~] Q2 ~ 1000 Q~ 11.5 V 1st 2nd D
` ¦ 501ution ~ Q2 J m/sec. term term ~icron
. , ., _
1 72 25.723.0 1.1812 241,94 1.09 66.60 68
2 72 23.6`~ 23.01.0394 241.94 1.09 58.60 60
3 80 17,7 ~ 23,00,6751 241.94 1.10 37~64 39
4 80 35.823.0 1.9419 241.94 1.10 108.27 109
35.838.4 0.9002 403.93 0.66 50.19 51
6 90 35.223.0 1.8933 241.94 1.11 104.63 106
7 96 39.327.9 1.6718 293,48 0.94 gO.64 92
8 96 34.431.7 1.1305 333.45 0.83 61.30 62
9 96 34.439.1 0.8252 411029 0.67 44.74 45
96 29.542.8 0.5723 450.21 0,61 31,03 32
11 96 30.7 ~ ` 40.2 0.6674 422.86 0,65 36,19 37
12 96 30.7 40.2 0.6674 422.86 0.65 36,19 37
13 96 30O7 40,2 0.6674 422.86 0.65 36.19 37
14 96 30.7 40,2 0.6674 422.86 0.65 39,19 37
96 30,7 40.2 0.6674 422.86 0.65 36.19 37
~_96 ~ ~ 1 0,6674 1 422.86 10,651 36.191 ~7
'''. '.
.
-19-
.
.. .. . . ~ .
~ 1641
~ -20-
.
- T A ~ L E D
T e s t no. ~ 5 6 7 8 9 10
.. . . . . . . . . .. .. ..
Chemical analysis
- moisture, % 0.15 O.Og o.o8 0.33 0.21 0.12 o.oa
- biuret, ~o 0.54 o.so o.46 o.s8 o.sl, o.56 0.58
- ~ormurea ao~% 0.39 0.43 0.40 0.3O o.40 0.42 o.48
.Physical analysis : -~ .
~ crushing strength, kg
.. . . ..
1.75 mm ~ 0.85 o.g8 0.73 o.60 0.95 - -
2.0 mm 0 o.g8 1.61 0.91 o.85 1.~0 1.68 2.0a
2.5 mm ~ 1.30 2.05 1.26 0.97 1.78 2.21 2.68
3.15 mm ~ - 2~.35 - 1.55 2.07 2.76 3.
,
~ 4.oo m~ 3.71 _ ~ 1.77 3.21 3.94 4.43
, . .- . . .
- , . . . ~ -
- TVA abrasion test
% 1.25 mm 2.a cl 1 ~1 C 1 < 1 c 1
~ ~ :
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