# CEN/TR 14061:2021

(Main)## Fertilizers - Determination of dust content

## Fertilizers - Determination of dust content

This document is applicable to crushing strength measurement as applied to grains of fertilizer obtained in prilling or wet-granulation process. Compacted or crystalline materials were not considered.

## 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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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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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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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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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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