Ships and marine technology -- Marine NOx reduction agent AUS 40

ISO 18611-2:2014 specifies test methods required for the determination of the quality characteristics of the NOx reduction agent AUS 40 (aqueous urea solution) specified in ISO 18611-1. In the remaining parts of ISO 18611, the term "NOx reduction agent AUS 40" will be abbreviated to "AUS 40". This International Standard is covering quality requirements and guidelines for AUS 40 for marine applications, irrespective of manufacturing method or technique.

Navires et technologie marine -- Agents réducteurs NOx marins AUS 40

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Published
Publication Date
22-Sep-2014
Current Stage
9093 - International Standard confirmed
Start Date
04-May-2020
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INTERNATIONAL ISO
STANDARD 18611-2
First edition
2014-10-01
Ships and marine technology —
Marine NOx reduction agent AUS 40 —
Part 2:
Test methods
Navires et technologie marine — Agents réducteurs NOx marins AUS
40 —
Partie 2: Méthodes d’essai
Reference number
ISO 18611-2:2014(E)
ISO 2014
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ISO 18611-2:2014(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2014

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Published in Switzerland
ii © ISO 2014 – All rights reserved
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ISO 18611-2:2014(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Specifications ........................................................................................................................................................................................................... 1

4 Sampling ........................................................................................................................................................................................................................ 1

5 Precision and dispute ...................................................................................................................................................................................... 2

5.1 General ........................................................................................................................................................................................................... 2

5.2 Repeatability, r .........................................................................................................................................................................................2

5.3 Reproducibility, R ...................................................................................................................................................................................2

Annex A (normative) Sampling .................................................................................................................................................................................. 3

Annex B (normative) Determination of urea content by total nitrogen .......................................................................... 5

Annex C (normative) Refractive index and determination of urea content by refractive index .............9

Annex D (normative) Determination of alkalinity ..............................................................................................................................13

Annex E (normative) Determination of biuret content ..................................................................................................................16

Annex F (normative) Determination of aldehyde content ..........................................................................................................21

Annex G (normative) Determination of insoluble matter content by gravimetric method

.....................25

Annex H (normative) Determination of phosphate content by photometric method ...................................28

Annex I (normative) Determination of trace element content (Ca, Fe, K, Mg, Na) by ICP-

OES method .............................................................................................................................................................................................................34

Annex J (informative) Determination of identity by FTIR spectrometry method ..............................................40

Annex K (informative) Precision of test methods ................................................................................................................................43

Bibliography .............................................................................................................................................................................................................................44

© ISO 2014 – All rights reserved iii
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ISO 18611-2:2014(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the meaning of ISO specific terms and expressions related to conformity

assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers

to Trade (TBT) see the following URL: Foreword - Supplementary information

The committee responsible for this document is ISO/TC 8, Ships and marine technology, Subcommittee

SC 2, Marine environment protection.

ISO 18611 consists of the following parts, under the general title Ships and marine technology — Marine

NOx reduction agent AUS 40:
— Part 1: Quality requirements
— Part 2: Test methods
— Part 3: Handling, transportation and storage
iv © ISO 2014 – All rights reserved
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ISO 18611-2:2014(E)
Introduction

In order to protect the environment and to enhance air quality, exhaust emissions regulations around

the world are continuously strengthened. For ships with large combustion engines, particulate matter

(PM), nitrogen oxide (NOx) emissions, and sulfur dioxide emissions are the main concern, and efforts

have been focused on the development of technology that can reduce them effectively with minimum fuel

economy penalty. Selective catalytic reduction (SCR) converters using a urea solution as the reducing

agent is considered to be a key technology for reducing NOx emissions. The quality of the urea solution

used for that technology needs to be specified to ensure reliable and stable operation of the SCR converter

systems. The ISO 18611 series provides the specifications for quality characteristics, for handling,

transportation, and storage, as well as the test methods needed by manufacturers of SCR converters, by

engine producers, by producers, distributors of the urea solution, and by fleet operators/ship owners.

Efficient expanding of the use of urea SCR technology requires a consolidated framework that can be

followed by producers, end users, OEMs, and catalyst suppliers.
© ISO 2014 – All rights reserved v
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INTERNATIONAL STANDARD ISO 18611-2:2014(E)
Ships and marine technology — Marine NOx reduction
agent AUS 40 —
Part 2:
Test methods
1 Scope

This part of ISO 18611 specifies test methods required for the determination of the quality characteristics

of the NOx reduction agent AUS 40 (aqueous urea solution) specified in ISO 18611-1. In the remaining

parts of ISO 18611, the term “NOx reduction agent AUS 40” will be abbreviated to “AUS 40”.

This International Standard is covering quality requirements and guidelines for AUS 40 for marine

applications, irrespective of manufacturing method or technique.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 3675, Crude petroleum and liquid petroleum products — Laboratory determination of density —

Hydrometer method
ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 4259, Petroleum products — Determination and application of precision data in relation to methods of

test

ISO 5661, Petroleum products — Hydrocarbon liquids — Determination of refractive index

ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples

ISO 12185, Crude petroleum and petroleum products — Determination of density — Oscillating U-tube

method
3 Specifications

Compliance with the limits specified in ISO 18611-1, Table 1 shall be determined by the test methods

specified in Annexes B through J of this part of ISO 18611. Determination of the density shall be conducted

in accordance with ISO 3675 or ISO 12185.

NOTE For the purposes of this International Standard, the terms “%(m/m)” and “%(V/V)” are used to

represent the mass fraction and the volume fraction of a material respectively.
4 Sampling
Samples shall be taken in accordance with Annex A.
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ISO 18611-2:2014(E)
5 Precision and dispute
5.1 General

All test methods referred to in this part of ISO 18611 include a precision statement according to ISO 4259.

In cases of dispute, the procedures described in ISO 4259 shall be used for resolving the dispute, and

interpretation of the results based on the test method precision shall be used. The test methods described

in this International Standard has been adopted from ISO 22241-2. Some minor changes have been made

to the ISO 22241 test methods in order to adapt it to the specifications as described in ISO 18611-1, Table

The precision of the test methods has been adopted from ISO 22241-2. In ISO 22241-2, the precision was

determined by statistical examination in accordance with ISO 4259 with the exception of the methdods

for determination of density that was taken from ISO 3675 and ISO 12185. The precision of the test

methods is specified in each annex. Additionally, this information is summarized in Annex K for all test

methods for the convenience of the user of this part of ISO 18611.

The statistical significance of the precision quoted in this part of ISO 18611 is generically defined in 5.2

and 5.3, in which the “xx (unit)” stands for the repeatability and reproducibility in question.

5.2 Repeatability, r

The difference between two test results obtained by the same operator with the same apparatus under

constant operating conditions on identical test material should, in the long run, in the normal and correct

operation of the test method, exceed xx (unit) in only one case in 20.
5.3 Reproducibility, R

The difference between two single and independent test results obtained by different operators working

in different laboratories on identical test material would, in the long run, in the normal and correct

operation of the test method, exceed xx (unit) in only one case in 20.
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ISO 18611-2:2014(E)
Annex A
(normative)
Sampling
A.1 General

The sampling method specified in this annex is valid for each sampling of AUS 40 throughout the supply

chain after the shipment from the manufacturer’s site to the AUS 40 containers on board the vessels.

A.2 Principle

The limits for the quality characteristics of AUS 40, which are specified in ISO 18611-1, are the

representative analytical results that can only be obtained when the sample is protected from any

contamination before the analysis.

Therefore, suitable bottles shall be used for sampling, which do not contaminate the sample, especially

regarding the trace elements, and which minimize the risk of algae or bacteria growth.

NOTE The sampling method specified in this annex is based on ISO 5667-2 and ISO 5667-3.

A.3 Possible contaminants

During the sampling process, foreign matter may lead to contamination of the sample. Under realistic

conditions, the following sources of contamination will pose a major hazard:
— residues of process aids used for the production of the sampling bottles;

— contaminants which have been deposited in the empty bottles during the time they are stored

empty;

— contaminants from the air, i.e. dust or any foreign matter from the surrounding, during the sampling;

— residues of cleaning agents, which have been used for cleaning the sampling equipment and the

bottles as well;
— fuel.
A.4 Apparatus
A.4.1 Sampling bottles

1000-ml wide neck bottles shall be used. Suitable materials for these bottles are HD-polyethylene, HD-

polypropylene, polyfluorethylene, polyvinylidenedifluoride, and tetrafluoroethylene-perfluoroalky

vinyl ether copolymer (PFA). In case of dispute, PFA bottles should be used.

Prior to the first use with AUS 40, the bottles shall be cleaned and finally rinsed with de-ionized water

followed by AUS 40.
A.4.2 Labels

Each bottle shall be labelled using labels of approximately 10 cm × 5 cm. The labels and the writing on

these labels shall be resistant to water and to AUS 40.
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ISO 18611-2:2014(E)
A.5 Sampling

The locked wide-neck bottle shall be opened; the cap shall be put down on a clean surface with the

opening turned downward. After flushing the sampling pipe, the bottle shall be filled completely with

AUS 40 from the container. The first filling shall be discarded, and the bottle shall immediately be re-

filled with AUS 40 and closed tightly. The label shall be attached to the bottle (see A.4.2). During the

filling of the sample, due care shall be taken that neither dust nor liquid pollutants get into the bottle.

The filled bottle should reach the laboratory as soon as possible. During transportation and storage,

the sample should be kept at the lowest possible temperature, preferably between 1 °C and room

temperature (20 °C), and kept away from daylight to prevent growth of algae. Samples to be stored for

a long period of time should be stored at between 1 °C and 15 °C and should be kept away from daylight.

It is recommended to conduct the analysis within three weeks in order to take into account possible

changes in the ammonia content.
A.6 Sample quantity

The minimum quantity of sample material depends on the type of analysis conducted. Whenever

possible, make sure that a sufficient volume of sample material is available (recommendation: 1 litre),

and at least double that which is required for complete verification of AUS 40 specifications. In case of

dispute, a sufficient number of samples shall be taken according to ISO 4259.
A.7 Labelling and Chain of Custody information

Samples will be labelled and a Chain of Custody form shall be utilized in order to track the movement of

the samples as they are transferred to a laboratory for analysis.
A.7.1 Labelling
The label should contain the following information:
— sample identification number;
— product name;
— address/vessel name where the sample was taken from ;
— container/location from which the sample was taken ;
— date and time of sampling .
A.7.2 Chain of Custody information
The Chain of Custody form shall contain the following information:
— sample identification number;
— product name;
— address/vessel name where the sample was taken from ;
— container/location from which the sample was taken ;
— date and time of sampling ;
— name and signature of person who sampled
— date when the sample left the site.
1) Mandatory only in cases of dispute.
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ISO 18611-2:2014(E)
Annex B
(normative)
Determination of urea content by total nitrogen
B.1 General
This annex specifies the procedure for determining the urea content of AUS 40.

The method is applicable for the determination of the urea content in the range from 38 % to 42 %

(m/m).
B.2 Principle

The sample is combusted at high temperatures in a stream of oxygen. Following the reduction of formed

nitrogen oxides to elemental nitrogen and removal of any interfering products of combustion, nitrogen

is measured with a thermal-conductivity detector. The urea content is calculated from the determined

total nitrogen minus the nitrogen content of biuret.
B.3 Apparatus
B.3.1 Automatic nitrogen analyser
The unit to be used is based on combustion methods.
B.3.2 Analytical balance

The accuracy of the balance is a function of the analyser used and the required weighed portions.

Resolution should be 0,1 % or better of the weighed portion.
B.3.3 Auxiliary devices for sample preparation
Examples of these devices include
— tweezers with a blunt tip,
— micro-spatula with a flattened tip, and
— pipette.

The pipette is recommended for weighing in and thus does not need to be calibrated. It is important,

however, to obtain a good droplet size (small droplets). Fixed-volume pipettes or pipettes with an

adjustable volume in the range of 10 µl to 1 000 µl or single-trip Pasteur pipettes with a fine tip can also

be used.
NOTE This is customarily chemically resistant glass.
B.4 Chemicals

B.4.1 De-ionized water, conductivity less than 0,1 mS/m, according to ISO 3696, grade 2.

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ISO 18611-2:2014(E)

B.4.2 Auxiliary combustion agent and other equipments, appropriate for use with the selected

nitrogen analyser.

The following materials are merely examples. Other or similar materials can be used as required,

depending on the system that is available:
— tin capsule or similar sample containers;
— auxiliary combustion agent, non-nitrogenous, such as saccharose, cellulose;
— absorbing agent for liquids, non-nitrogenous, such as magnesium oxide.

B.4.3 Standard substances for nitrogen determination, preferably with certified nitrogen content.

EXAMPLE Suitable standard substances include ethylenediamine tetraacetic acid (EDTA), nicotinic acid

amide.

Low-biuret urea of adequate purity (for example, crystalline ultra pure or analytical) or other such

standard substances recommended by and available from the equipment manufacturer can also be

used. Certified standard substances should be preferred.

NOTE Liquid standard substances (e.g. urea solutions) are not suited for calibration purposes.

B.4.4 Oxygen, min. 99,995 % O .

B.4.5 Other ultrapure gases, if required to operate the nitrogen analyser, such as helium, min. 99,996 %

He.
B.4.6 Other reagents or auxiliary agents, as required by the equipment.
B.5 Procedure
B.5.1 General

The sample should be fully dissolved and free from urea crystals. It can be heated to max. 40 °C as

required prior to further processing.

NOTE Different types of apparatus are available on the market. The resulting various resources and modes of

operation are not an object of this part of ISO 18611. Rather, activity should be based on the respective operation

manuals.
B.5.2 Reference curve

Perform calibration as required for the specific type of analyser and according to the respective operation

manuals (for example, after replacement of the combustion tube, reagent or similar) by performing

measurements as described in B.5.4. Weigh in an appropriate amount of standard substances repeatedly

as appropriate for the respective types of apparatus to obtain a reference curve.

B.5.3 Inspecting the apparatus for good working order, and the reference curve

Use an appropriate standard substance to review the good working order of the apparatus and the

reference curve. Preferably, a certified urea standard solution should be used.
Frequency of inspection is a function of the analyser used.
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ISO 18611-2:2014(E)
B.5.4 Measurement

Weigh a portion of the sample in a suitable holder (such as a tin capsule) as specified for the type of

nitrogen analyser used. The amount should be such that the absolute amount of nitrogen is in the middle

range of the reference curve.

Use approximately the threefold amount of combustion agent (for example, non-nitrogenous cellulose)

and additional binders (for example, magnesium oxide) as required.

When using liquid feeder systems, the volume used should be no less than 100 µl. The sample mass is

calculated using the density that was calculated according to ISO 12185.

Enter the required data (weighed portion, sample identification) into the analyser (or a control computer),

depending on the type of apparatus. Feed the weighed-in sample to the analyser, and start combustion.

Perform at least three (3) single determinations.
B.6 Results
B.6.1 Calculation

Prior to calculating the reference curve, drift of the baseline, or samples, determine the blank reading

value by means of blank samples, and use this value to correct the respective analytical sequences.

Use the apparatus-specific programme to calculate the reference curve or the drift correction for the

samples.

Calculate the mean value for the samples. If there is a strong dispersion of single values (relative standard

deviation RSD > 1,0 %), repeat the affected sample. After that, determine the mean value for this sample

from all single values.

Determine the urea content from the mean value from at least three nitrogen determinations:

ww=−2,1438××Fw −Fw× (B.1)
UN 12Bi NH3
where
w is the urea content [% (m/m)];
w is the mean value of the nitrogen content [% (m/m)] (to the nearest 0,01 %);
w is the mean value of the biuret content (%), determined according to Annex E;

w is the mean value of the ammonia content (%), determined according to Annex D;

NH3
F is the factor for converting the biuret content to nitrogen (0,407 6);
F is the factor for converting the ammonia content to nitrogen (0,822 5).
B.6.2 Expression of results

The result is the arithmetic mean value from at least three (3) single determinations (nitrogen

determinations).
Round off the result of the urea content calculation to the nearest 0,1 %.
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ISO 18611-2:2014(E)
B.7 Precision
See 5.2, 5.3, and Table B.1.
Table B.1 — Precision
Urea content Repeatability Reproducibility
w r R
% (m/m) % (m/m) % (m/m)
38 to 42 0,4 1,0
B.8 Test report
The report shall include the following data as a minimum requirement:
a) type and description of tested product;
b) reference to this part of ISO 18611 (i.e. 18611-2);
c) sampling method used;
d) test result (see B.6);
e) deviations from the specified mode of operation, if any;
f) test date.
8 © ISO 2014 – All rights reserved
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ISO 18611-2:2014(E)
Annex C
(normative)
Refractive index and determination of urea content by refractive
index
C.1 General

This annex specifies the procedure for the determination of the refractive index of AUS 40. The test

method is applicable to liquids having refractive indices in the range of 1,33 to 1,41 and at temperatures

of 20 °C to 30 °C.

Based on the measurement of refractive index, the method shall be used for determining the content of

urea in the range of 38 % to 42 % (m/m).
C.2 Principle

Measurement is based on the dependence of the refractive index on the concentration of urea in an

aqueous solution at a definite temperature.
The content is determined by means of a reference curve.
NOTE The method specified in this annex is based on ISO 5661.
C.3 Apparatus
C.3.1 Refractometer, measuring range 1,330 00 to 1,410 00, resolution 0,000 01.
C.3.2 Analytical balance, resolution 0,1 mg or better.
C.3.3 Thermostat, temperature-control precision 0,02 °C.
C.3.4 Drying oven.
C.3.5 150 ml beaker, tall form.
C.3.6 Typical laboratory glass.
C.4 Chemicals

C.4.1 De-ionized water, conductivity less than 0,5 mS/m, according to ISO 3696, grade 3.

C.4.2 Urea, crystalline, with biuret content less than 0,1 % (m/m).

Prior to weighing the urea to draw the reference curve, it shall be dried for 2 h at 105 °C.

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ISO 18611-2:2014(E)
C.4.3 Urea test solution, 40 % (m/m).

The test solution shall be made by exactly weighing urea and water. The desired value and the permissible

dispersion shall be established through 10 measurements.

The solution shall be kept air-tight in the refrigerator and should be used within 12 weeks maximum.

C.5 Procedure
C.5.1 General

The sample should be fully dissolved and free from urea crystals. It can be heated to ≤40 °C as required

prior to further processing.

Different types of apparatus are available on the market. The resulting various resources and modes of

operation are not an object of this part of ISO 18611. Rather, operation should be based on the respective

operation manuals.
C.5.2 Drawing the reference curve and determining the evaluation factor

The following urea solutions shall be prepared by weighing urea in glass beakers and then adding the

corresponding quantity of de-ionized water: 38,0 % (m/m) / 39 % (m/m) / 40 % (m/m) / 41 % (m/m) /

43,0 % (m/m).
The refractive index of these solutions shall be determined at 20 °C ± 0,02 °C.

The diagram shall show a stringent linear relationship between the refractive index and concentration.

An evaluation factor shall be calculated from the urea concentrations and the refractive indices:

∑ U,i
i=1
F = (C.1)
nn−
UW,i
i=1
where
F is the evaluation factor (%);
w is the urea content of the i-th reference solution [%(m/m)];
U,i
n is the refractive index of the i-th reference solution;
U,i

n is the refractive index of water and is 1,332 96 when measured with a refractometer of five-

decimal resolution.
C.5.3 Checking the instrument function and the reference curve

The instrument function shall be checked weekly using water or a reference standard. If a deviation

greater than 0,000 02 from the desired value occurs, adjust the instrument according to the instructions

provided by the manufacturer. If afterwards the desired value is not attained, then the instrument shall

be disabled for further measurements and the manufacturer’s service should be called for.

Adjust the thermostat to the desired temperature, reading this temperature on the refractometer

thermometer on the discharge side. Maintain the flow of water so that the desired temperature shall be

reached and maintained within ±0,02 °C.

Furthermore, the reference curve shall be verified weekly with urea solution [32,5 % (m/m)]. In the

process, the refractive index shall be determined and the concentration shall be calculated with the help

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ISO 18611-2:2014(E)

of the factor according to C.6. If the concentration determined deviates from the desired value by more

than 0,1 % (m/m), a new test solution shall be used. If the deviation persists, the reference curve shall

be created anew.
C.5.4 Sample preparation and measuring

The original sample shall be measured at 20 °C ± 0,02 °C without further preparation.

Measure the urea content two times with different test portions. Should the difference between the

separate values be more than 0,000 05, the measurements shall be repeated.
C.6 Results
C.6.1 Calculation
Urea content shall be calculated according to Formula (C.2):
wn=−nF×−wW− (C.2)
UP WBi NH3
where
w is the urea content [% (m/m)];
n is the refractive index of the sample (with five decimals);
n is the refractive index of water (with five decimals);
F is the evaluation factor (%);
w is the biuret content of the solution [% (m/m)]

(determined according to Annex E; biuret has the same refractive index as urea);

...

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