SIST-TP CEN/TR 14061:2021
(Main)Fertilizers - Determination of dust content
Fertilizers - Determination of dust content
When handling fertilizer grains, dust is at every moment generated on the surface. The fertilizer thus contains more or less free dust, and has a potential for generating more dust (abrasion dust) when subject to subsequent handling. In all existing gravitational test methods dust will be generated during the testing time, and the two types of dust will be measured simultaneously.
Düngemittel - Bestimmung des Staubgehaltes
Engrais - Détermination de la teneur en poussière
Gnojila - Določanje količine prahu
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CEN/TR 14061:2021
01-november-2021
Nadomešča:
SIST CR 14061:2002
Gnojila - Določanje količine prahu
Fertilizers - Determination of dust content
Düngemittel - Bestimmung des Staubgehaltes
Engrais - Détermination de la teneur en poussière
Ta slovenski standard je istoveten z: CEN/TR 14061:2021
ICS:
65.080 Gnojila Fertilizers
SIST-TP CEN/TR 14061:2021 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TP CEN/TR 14061:2021
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SIST-TP CEN/TR 14061:2021
CEN/TR 14061
TECHNICAL REPORT
RAPPORT TECHNIQUE
June 2021
TECHNISCHER BERICHT
ICS 65.080 Supersedes CR 14061:2000
English Version
Fertilizers - Determination of dust content
Engrais - Détermination de la teneur en poussière Düngemittel - Bestimmung des Staubgehaltes
This Technical Report was approved by CEN on 23 May 2021. It has been drawn up by the Technical Committee CEN/TC 260.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 14061:2021 E
worldwide for CEN national Members.
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SIST-TP CEN/TR 14061:2021
CEN/TR 14061:2021 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviated terms . 5
4.1 Technical Symbols . 5
4.2 Statistical symbols and abbreviations . 6
5 Calculation of the spouting bed apparatus . 6
5.1 Particle terminal velocity . 6
5.2 Spouting section . 7
5.3 Maximum spoutable bed height . 7
5.4 Design of apparatus . 7
5.5 Flowmeter . 8
6 Initial testing . 8
6.1 Determination of dust weight . 8
6.2 Setting the test time . 8
6.3 Preliminary ringtests . 8
7 Conclusive ring test . 9
7.1 General. 9
7.2 Apparatus . 9
7.3 Sample preparation . 9
7.4 Procedure, test plan . 9
7.5 Statistical methods . 9
7.5.1 Statistical model . 9
7.5.2 Outliers . 9
7.5.3 Regression analysis . 9
7.5.4 Correction for adapter-effect . 9
7.5.5 ANOVA-analysis . 9
7.6 Statistical analysis of test data . 10
7.6.1 Deviation from test plan . 10
7.6.2 Example — granulated NPK . 10
7.6.3 Summary of ANOVA . 14
8 Other methods . 15
9 Conclusion . 15
Annex A (informative) Method for the determination of dust potential . 16
Annex B (informative) Optical methods for determination of fertilizer dust . 22
Bibliography . 23
2
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SIST-TP CEN/TR 14061:2021
CEN/TR 14061:2021 (E)
European foreword
This document (CEN/TR 14061:2021) has been prepared by Technical Committee CEN/TC 260
“Fertilizers and liming materials”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes CR 14061:2000.
Significant changes between this document and CR 14061:2000 are as follows:
a) modification of the figures to contain neutral language;
b) adaption to current principles and rules for structure and drafting.
This document is published by the European Committee for Standardization. It is published for
information only and does not have the status of a European Standard.
The Annexes A and B are informative.
3
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SIST-TP CEN/TR 14061:2021
CEN/TR 14061:2021 (E)
Introduction
0.1 General
In production and handling of fertilizers dust generation is of great concern by both producers and users
of the fertilizer products. For health and environmental reasons, it is of great interest to control and
reduce the amount of dust generation. In the fertilizer industries there are a wide variety of apparatus
for dust determination, most being used as “in-house” methods in plants and laboratories.
The content of this document was developed by CEN/TC 260/WG 2 between 1991 and 2000 in order to
develop a standard dust test. A spouting bed apparatus was designed for gravimetric determination of
dust, and after two preliminary ringtests a conclusive ringtest involving six laboratories was carried out.
Not being able to develop a statistical significant method for the determination of dust, TC 260 decided
by resolution 105/1997 to change the deliverable of this work item into a CEN Technical Report. The
change of deliverable has been approved by CEN/BT with its resolution BT C172/1999.
0.2 General background
When handling fertilizer grains, dust is at every moment generated on the surface. The fertilizer thus
contains more or less free dust, and has a potential for generating more dust (abrasion dust) when subject
to subsequent handling.
In all existing gravitational test methods dust will be generated during the testing time, and the two types
of dust will be measured simultaneously. The scope of the method is expressed in Annex A and the aim is
to:
“.specify a method for the determination of the dust potential of solid fertilizers and is applicable to
granular and prilled fertilizers.
Dust particles, which cause reduced visibility in air are too small to be determined by this method.”
0.3 Background for choice of method
Fluidized particle powders are generally divided into four characterizing groups (A, B, C, D) [1]. Group C
particles are small, cohesive and are difficult to fluidize. Aeratable powders belong to group A, and many
fluidized bed catalysts characterize this group. Sand typifies group B, in which inter-particle forces are
negligible, in contrast with group A powders. Large and/or dense particles in general belong to group D,
and fertilizer particles (2 mm to 4 mm) in air are in this group. A flow diagram can be used to broadly
identify flow regimes appropriate to combinations of gas velocity and particle properties. It can be shown
that the fertilizer system is in the lower part of the spouted bed regime.
A criterion that can be used to distinguish between group B and D is the numerical inequality that
classifies a powder as spoutable if:
1,24
(ρ – ρ ) ⋅ d > 0,23
p f p
For a typical fertilizer this value will be about 1,4 and about 0,5 for an urea prill.
From previous experiments with other methods based on a fluidized bed and the above calculations, it
was decided to base the method upon the spouted bed principle.
4
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SIST-TP CEN/TR 14061:2021
CEN/TR 14061:2021 (E)
1 Scope
This document is applicable to the determination of dust potential of solid fertilizer, obtained in prilling
or granulation process. Compacted or crystalline materials were not considered.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
4 Symbols and abbreviated terms
4.1 Technical Symbols
C drag coefficient
D
d particle diameter, expressed in metres (m)
p
d average spout diameter, expressed in metres (m)
s
D average particle diameter, expressed in metres (m)
p
D diameter of spouting section, expressed in metres (m)
D inner orifice diameter, expressed in metres (m)
i
2
g gravity, expressed in kilograms per metres per square seconds (kg/m s )
H bed height, expressed in metres (m)
Re Reynolds number
v terminal velocity, expressed in metres per seconds (m/s)
t
v minimum spouting height
ms
3
ρ particle density, expressed in kilograms per metres to the third power (kg/m )
p
3
ρ fluid density, expressed in kilograms per metres to the third power (kg/m )
f
2
μ viscosity, expressed in Newton seconds per square metres (Ns/m )
5
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CEN/TR 14061:2021 (E)
4.2 Statistical symbols and abbreviations
df degrees of freedom
F mean square between groups/mean square within groups
F tabulated value form the F-distribution for a significance level of 0,05 confidence interval
crit
MS mean square
P-value significance level corresponding to a given F (should be less than 0,05 to reject the null-
hypothesis)
SS sum of squares
5 Calculation of the spouting bed apparatus
5.1 Particle terminal velocity
A particle falling freely in a fluid will finally reach its terminal velocity. The forces acting on it are
gravitational, accelerating, buoyancy force and drag (friction) force. The drag force can be expressed by
a drag coefficient C , which is expressed by Formula (1):
D
ρρ− dg
( )
p f p
4
C = (1)
D
2
3
ρ v
ft
By calculation and plotting log C against log Re (Reynolds number) the so-called “standard drag-curve”
D
can be obtained which has three broad regions:
— Laminar region, Re < 0,2;
— Transitional region (tr), 0,2 < Retr < 1000;
— Turbulent region, Re > 1000.
2 2 2 2
The drag coefficient equation can be multiplied with ρ v d /μ and rearranged as:
f t p
3
ρρ− dg
( )
p f p
4
2
C Re = (2)
D t
2
3
µ
2
The group C Re is dimensionless containing only the physical properties of the particle/fluid system
D tr
including the particle diameter d . The Re-number and the terminal velocity (v ) can be estimated by
p t
graphical methods.
Calculations prove that transitional flow describes the system of fertilizer dust in air, thus giving Table 1.
Table 1 — System of fertilizer dust in air
2
Particle size d C Re Re v
p D tr tr t
µm m/s
100 88 3,0 0,5
150 300 7,7 0,8
200 704 15,0 1,3
6
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CEN/TR 14061:2021 (E)
The air velocity was chosen to be 0,75 m/s in the classification section (110 mm ⌀) of the apparatus, and
irregular particles less than 150 μm will then be carried over, according to calculations.
5.2 Spouting section
The spouting section is characterized by the “minimum spouting height”, v , that depends on the particle
ms
(fertilizer) properties, spouting column geometry and the inlet orifice diameter:
12/
13/
2gH ρρ−
d
( )
D
pf
p
i
v = (3)
ms
D D ρ
f
Based on 500 g fertilizer, v = 1,0 m/s and diameter D = 85 mm of spouting section, the theoretical
ms
expression of v [1] was rearranged. Inner orifice diameter D :
ms i
1/3 −4
D = 5,645 10 d
i p
thus giving the figures:
d 2,0 mm 3,0 mm 4,0 mm
p
D 22,5 mm 6,6 mm 2,8 mm
i
Depending on the average particle diameter (d ) the inner orifice diameter (D ) should thus be varied,
p i
according to the theory.
5.3 Maximum spoutable bed height
The maximum spoutable bed height (H ) can be estimated from the correlation:
s
2 2 0,384 −1,384
H = 0,345 (D − d ) ⋅ D ⋅ d (4)
s s s
where d is the average spout diameter. D = 85 mm and estimated d = 15 mm gives H ~ 38 mm, which is
s s s
higher than the chosen bed height. However, the calculation assumes spherical particles, and practical
maximum spoutable depth will therefore be lower than the theoretical value.
Based on the calculations above the spouting bed apparatus was designed and tested.
5.4 Design of apparatus
The column was designed with the dimensions according to Table 2.
Table 2 — Design of apparatus
Classification section Spouting section
Column diameter 110 mm Column diameter 85 mm
Column height 400 mm Column height 120 mm
Outlet diameter 40 mm Cone height 85 mm
Air velocity 1 m/s Total height (incl. bottom inlet) 220 mm
b
Fertilizer mass 400 g Cone inlet diameter 23 mm
3 a
Air rate 25 m /h Air velocity (overall) 1,2 m/s
a
The air velocity in the classification section was chosen to be 0,75 m/s in order to carry 150 m particles over
(see 5.1).
b
Adapters with diameters 7, 8, .,18 mm were made to include most fertilizers. A 440 m grid was fitted into the
adapter inlet.
7
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CEN/TR 14061:2021 (E)
5.5 Flowmeter
A calibrated flowmeter is connected to the column. The flowmeter should have a capacity of approximate
3
40 m /h.
6 Initial testing
6.1 Determination of dust weight
Initially the dust was collected by a filter at the outlet of the apparatus. However, because of safety
(pressurized air in the glass apparatus) and inaccuracy in measurements due to accumulation of dust on
column walls, it was decided to record the difference in weight of the fertilizer sample during the test.
6.2 Setting the test time
Initial tests were carried out in order to set the test-time. Dust generation of selected NP/NPK-fertilizers
were measured at increasing time intervals.
Figure 1 shows a decreasing slope at approximate 0,5 min test time which is due to a change from free
dust to abrasion dust. In order to include approximately the same amount of free dust as abrasion dust,
a 2 min test time was chosen.
Key
X time (min)
Y dust (mg/kg)
1 blended NPK
2 granulated NP
3 granulated NPK
4 prilled NPK
Figure 1 — Dust generation as function of time
6.3 Preliminary ringtests
Two preliminary ring tests were run in order to improve the method.
8
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CEN/TR 14061:2021 (E)
7 Conclusive ring test
7.1 General
A final and conclusive ring test was run with six participating laboratories involved. Ten replicates of five
fertilizers were tested at each laboratory and statistical results calculated by ANOVA.
7.2 Apparatus
The apparatus is described in Annex A.
7.3 Sample preparation
The ring tests were conducted using the following five types of homogenous fertilizer products:
granulated urea; granulated CAN; granulated PK; granulated NPK; prilled NPK. The relevant producer of
each fertilizer sent 12 separate samples (10 as required for the tests plus 2 spares in case a test had to be
aborted) to the participant laboratories.
7.4 Procedure, test plan
The drafted test procedure is enclosed in Annex A. Ten replicates were tested for all five fertilizers.
7.5 Statistical methods
7.5.1 Statistical model
Each test result, y, is the sum of four components: y = m + A + B + e
where m is the general average, A is the adapter diameter used, B is the between-laboratory variation and
e is the random error occurring in every test.
The model for sample j at laboratory i is: y = m + b A + b + e
ij 0 i i ij
where b and b are regression coefficients and A is the adapter diameter used in labor
...
SLOVENSKI STANDARD
kSIST-TP FprCEN/TR 14061:2021
01-marec-2021
Gnojila - Določevanje količine prahu
Fertilizers - Determination of dust content
Düngemittel - Bestimmung des Staubgehaltes
Engrais - Détermination de la teneur en poussière
Ta slovenski standard je istoveten z: FprCEN/TR 14061
ICS:
65.080 Gnojila Fertilizers
kSIST-TP FprCEN/TR 14061:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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kSIST-TP FprCEN/TR 14061:2021
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kSIST-TP FprCEN/TR 14061:2021
FINAL DRAFT
TECHNICAL REPORT
FprCEN/TR 14061
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
January 2021
ICS Will supersede CR 14061:2000
English Version
Fertilizers - Determination of dust content
Engrais - Détermination de la teneur en poussière Düngemittel - Bestimmung des Staubgehaltes
This draft Technical Report is submitted to CEN members for Vote. It has been drawn up by the Technical Committee CEN/TC
260.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.
Warning : This document is not a Technical Report. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a Technical Report.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. FprCEN/TR 14061:2021 E
worldwide for CEN national Members.
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kSIST-TP FprCEN/TR 14061:2021
FprCEN/TR 14061:2021 (E)
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Symbols and abbreviated terms . 5
5 Calculation of the spouting bed apparatus . 6
6 Initial testing . 8
7 Conclusive ring test . 9
8 Other methods . 15
9 Conclusion . 15
Annex A (informative) Method for the determination of dust potential . 16
A.0 Introduction . 16
A.1 Scope . 16
A.2 Terms and definitions . 16
A.5 Safety . 18
A.6 Test samples . 19
A.7 Calibration of flowmeter . 19
A.8 Procedure . 19
A.9 Expression of results . 20
A.10 Test report . 21
Annex B (informative) Optical methods for determination of fertilizer dust . 22
Bibliography . 23
2
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kSIST-TP FprCEN/TR 14061:2021
FprCEN/TR 14061:2021 (E)
European foreword
This document (FprCEN/TR 14061:2021) has been prepared by Technical Committee CEN/TC 260
“Fertilizers and liming materials”, the secretariat of which is held by DIN.
This document is currently submitted to Vote on TR.
This document will supersede CR 14061:2000.
This CEN Report is published by the European Committee for Standardization. It is published for
information only and does not have the status of a European Standard.
The Annexes A and B are informative.
Significant changes between this document and CR 14061:2000 are as follows:
a) modification of the figures to be language-neutral;
b) adaption to current principles and rules for structure and drafting.
3
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kSIST-TP FprCEN/TR 14061:2021
FprCEN/TR 14061:2021 (E)
Introduction
0.1 General
In production and handling of fertilisers dust generation is of great concern by both producers and users
of the fertiliser products. For health and environmental reasons it is of great interest to control and
reduce the amount of dust generation. In the fertiliser industries there exist a wide variety of apparatus
for dust determination, most being used as “in-house” methods in plants and laboratories.
The content of this document was developed by CEN/TC 260/WG 2 between 1991 and 2000 in order to
develop a standard dust test. A spouting bed apparatus was designed for gravimetric determination of
dust, and after two preliminary ringtests a conclusive ringtest involving six laboratories was carried out.
Not being able to develop a statistical significant method for the determination of dust TC 260 decided
by resolution 105/1997 to change the deliverable of this work item into a CEN Report. The change of
deliverable has been approved by CEN/BT with its resolution BT C172/1999.
0.2 General background
When handling fertiliser grains, dust is at every moment generated on the surface. The fertiliser thus
contains more or less free dust, and has a potential for generating more dust (abrasion dust) when subject
to subsequent handling.
In all existing gravitational test methods dust will be generated during the testing time, and the two types
of dust will be measured simultaneously. The scope of the method is expressed in Annex A and the aim is
to:
“.specify a method for the determination of the dust potential of solid fertilisers and is applicable to
granular and prilled fertilisers.
Dust particles which cause reduced visibility in air are too small to be determined by this method.”
0.3 Background for choice of method
Fluidized particle powders are generally divided into four characterizing groups (A, B, C, D) [1]. Group C
particles are small, cohesive and are difficult to fluidize. Aeratable powders belong to group A, and many
fluidized bed catalysts characterize this group. Sand typifies group B, in which inter-particle forces are
negligible, in contrast with group A powders. Large and/or dense particles in general belong to group D,
and fertiliser particles (2 mm to 4 mm) in air are in this group. A flow diagram can be used to broadly
identify flow regimes appropriate to combinations of gas velocity and particle properties. It can be shown
that the fertiliser system is in the lower part of the spouted bed regime.
A criterion that can be used to distinguish between group B and D is the numerical inequality that
classifies a powder as spoutable if:
1,24
(ρ − ρ ) ⋅ d > 0,23
p g p
For a typical fertiliser this value will be about 1,4 and about 0,5 for an urea prill.
From previous experiments with other methods based on a fluidized bed and the above calculations, it
was decided to base the method upon the spouted bed principle.
4
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kSIST-TP FprCEN/TR 14061:2021
FprCEN/TR 14061:2021 (E)
1 Scope
This document is applicable to the determination of dust potential of solid fertilizer, obtained in prilling
or granulation process. Compacted or crystalline materials were not considered.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
4 Symbols and abbreviated terms
4.1 Technical Symbols
C drag coefficient
D
d particle diameter, expressed in metres (m)
p
d average spout diameter, expressed in metres (m)
s
D average particle diameter, expressed in metres (m)
p
D diameter of spouting section, expressed in metres (m)
D inner orifice diameter, expressed in metres (m)
i
2
g gravity, expressed in kilograms per metres per square seconds (kg/m s )
H bed height, expressed in metres (m)
Re Reynolds number
v terminal velocity, expressed in metres per seconds (m/s)
t
v minimum spouting height
ms
3
ρ particle density, expressed in kilograms per metres to the third power (kg/m )
p
3
ρ fluid density, expressed in kilograms per metres to the third power (kg/m )
f
2
μ viscosity, expressed in Newton seconds per square metres (Ns/m )
5
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FprCEN/TR 14061:2021 (E)
4.2 Statistical symbols and abbreviations
df degrees of freedom
F mean square between groups/mean square within groups
F tabulated value form the F-distribution for a significance level of 0,05 confidence interval
crit
MS mean square
P-value significance level corresponding to a given F (should be less than 0,05 to reject the null-
hypothesis)
SS sum of squares
5 Calculation of the spouting bed apparatus
5.1 Particle terminal velocity
A particle falling freely in a fluid will finally reach its terminal velocity. The forces acting on it are
gravitational, accelerating, buoyancy force and drag (friction) force. The drag force can be expressed by
a drag coefficient C , which is expressed by Formula (1):
D
ρρ− dg
( )
4
p fp
C = (1)
D
2
3 ρ v
ft
By calculation and plotting log C against log Re (Reynolds number) the so-called “standard drag-curve”
D
can be obtained which has three broad regions:
— Laminar region, Re < 0,2
— Transitional region (tr), 0,2 < Re < 1000
tr
— Turbulent region, Re > 1000
2 2 2 2
The drag coefficient equation can be multiplied with ρ v d /μ and rearranged as
f t p
3
ρρ− dg
( )
4 p fp
2
C Re =
D t
2
3 µ
2
The group C Re is dimensionless containing only the physical properties of the particle/fluid system
D tr
including the particle diameter dp. The Re-number and the terminal velocity (vt) can be estimated by
graphical methods.
Calculations prove that transitional flow describes the system of fertiliser dust in air, thus giving Table 1:
Table 1 — System of fertiliser dust in air
2
Particle size d C Re Re v
p D tr tr t
µm m/s
100 88 3,0 0,5
150 300 7,7 0,8
200 704 15,0 1,3
6
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FprCEN/TR 14061:2021 (E)
The air velocity was chosen to be 0,75 m/s in the classification section (110 mm ⌀) of the apparatus, and
irregular particles less than 150 μm will then be carried over, according to calculations.
5.2 Spouting section
The spouting section is characterized by the “minimum spouting height”, v , that depends on the particle
ms
(fertiliser) properties, spouting column geometry and the inlet orifice diameter:
1/2
1/3
2gH ρρ−
d ( )
D
pf
p
i
v =
ms
DD ρ
f
= 1,0 m/s and diameter D = 85 mm of spouting section, the theoretical
Based on 500 g fertiliser, vms
expression of v [1] was rearranged. Inner orifice diameter D :
ms i
1/3 −4
D = 5,645 10 d
i p
thus giving the figures:
d 2,0 mm 3,0 mm 4,0 mm
p
D 22,5 mm 6,6 mm 2,8 mm
i
Depending on the average particle diameter (d ) the inner orifice diameter (D ) should thus be varied,
p i
according to the theory.
5.3 Maximum spoutable bed height
The maximum spoutable bed height (H ) can be estimated from the correlation:
s
2 2 0,384 −1,384
H = 0,345 (D − d ) ⋅ D ⋅ d
s s s
where d is the average spout diameter. D = 85 mm and estimated d = 15 mm gives H ~ 38 mm, which is
s s s
higher than the chosen bed height. However, the calculation assumes spherical particles, and practical
maximum spoutable depth will therefore be lower than the theoretical value.
Based on the calculations above the spouting bed apparatus was designed and tested.
5.4 Design of apparatus
The column was designed with the dimensions according to Table 2.
Table 2 — Design of apparatus
Classification section Spouting section
column diameter 110 mm column diameter 85 mm
column height 400 mm column height 120 mm
outlet diameter 40 mm cone height 85 mm
air velocity 1 m/s Total height (incl. bottom inlet) 220 mm
b)
fertiliser mass 400 g cone inlet diameter 23 mm
3 a)
air rate 25 m /h air velocity (overall) 1,2 m/s
a)
The air velocity in classification section was chosen to be 0,75 m/s in order to carry 150 m particles over (see
5.1).
b)
Adapters with diameters 7, 8, .,18 mm were made to include most fertilisers. A 440 m grid was fitted into the
adapter inlet.
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FprCEN/TR 14061:2021 (E)
5.5 Flowmeter
A calibrated flowmeter is connected to the column. The flowmeter should have a capacity of approximate
3
40 m /h.
6 Initial testing
6.1 Determination of dust weight
Initially the dust was collected by a filter at the outlet of the apparatus. However, because of safety
(pressurized air in the glass apparatus) and inaccuracy in measurements due to accumulation of dust on
column walls it was decided to record the difference in weight of the fertiliser sample during the test.
6.2 Setting the test time
Initial tests were carried out in order to set the test-time. Dust generation of selected NP/NPK-fertilisers
were measured at increasing time intervals.
Figure 1 shows a decreasing slope at approximate 0,5 min test time which is due to a change from free
dust to abrasion dust. In order to include approximate the same amount of free dust as abrasion dust,
2 min test time was chosen.
Key
X Time (min)
Y Dust (mg/kg)
1 blended NPK
2 granulated NP
3 granulated NPK
4 prilled NPK
Figure 1 — Dust generation as function of time
6.3 Preliminary ringtests
Two preliminary ring tests were run in order to improve the method.
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FprCEN/TR 14061:2021 (E)
7 Conclusive ring test
7.1 General
A final and conclusive ring test was run with six participating laboratories involved. Ten replicates of five
fertilisers were tested at each laboratory and statistical results calculated by ANOVA.
7.2 Apparatus
The apparatus is described in Annex A.
7.3 Sample preparation
The ring test included various types of homogenous fertiliser products. Ten plus two fertiliser samples of
the following formulas each fertiliser were sent by the producer to the participant laboratories:
granulated urea; granulated CAN; granulated PK; granulated NPK; prilled NPK.
7.4 Procedure, test plan
The drafted test procedure is enclosed in Annex A. Ten replicates were tested for all five fertilisers.
7.5 Statistical methods
7.5.1 Statistical model
Each test result, y, is the sum of four components: y = m + A + B + e
where m is the general average, A is the adapter diameter used, B is the between-laboratory variation and
e is the random error occurring in every test.
The model for sample j at laboratory i is: y = m + b A + b + e
ij 0 i i ij
where b and b are regression coefficients and A is the adapter diameter used in laboratory i.
0 i i
7.5.2 Outliers
Assuming that the statistical model is correct, the residuals, e are normal distributed. A normal-plot is
used to check for normality.
7.5.3 Regression analysis
In the regression analysis the outliers are removed. The regression analysis gives one significant PLS
component (one-component explains model).
7.5.4 Correction for adapter-effect
After regression analysis the effect of chosen adapter was removed, and variance within laboratory and
between laboratories were analysed.
7.5.5 ANOVA-analysis
The ANOVA-analysis performs simple analysis of variance, which tests the hypothesis that means from
several samples are equal. The confidence-level is set to 95 %. Generally, analysis of variance, or ANOVA,
is a statistical procedure used to determine whether means from two or more samples are drawn from
populations with the same mean. This technique expands on the tests for two means, such as the t-test.
7.6 Statistical anal
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