🧪 Carbon, hydrogen and nitrogen in solid fuels — ultimate analysis, macro method — PN-G-04571
In short
A rapid method for determining three elements of the ultimate analysis of a solid fuel — carbon, hydrogen and nitrogen — with automatic analysers in the macro variant, i. The test is performed according to PN-G-04571:1998 (wersja polska); Measured quantities: Content of carbon, hydrogen and nitrogen in a solid fuel. The procedure comprises 7 steps; it is used for: Ultimate analysis of hard coal and lignite for power generation, Calculation of combustion balances and of the calorific value of the fuel, Estimating nitrogen oxide emissions from the nitrogen content of the fuel.
At a glance
- Standard: PN-G-04571:1998 (wersja polska)
- Category: Petrochemistry
- Procedure steps: 7
- Measured quantities: Content of carbon, hydrogen and nitrogen in a solid fuel
- Variant of the method: MACRO — test portion larger than in micro analysers; the micro variant is not equivalent and a switch must be recorded
- Nature of the method: Rapid, with an automatic analyser — this is how the scope of the standard itself describes it
Overview
SCOPE FROM THE PKN CATALOGUE CARD, QUOTED VERBATIM (our translation): "A rapid method for the determination of the content of carbon, hydrogen and nitrogen in solid fuels is specified. The principle of the method, the apparatus used, reagents and materials, preparation of the sample and of the analyser for testing, the procedure of determination, calculation of results, the permissible difference between results and the final result are given."
WHAT "MACRO METHOD" MEANS AND WHY IT IS NOT A TRIFLE. The term in the title refers to the size of the test portion. Solid fuels are inherently heterogeneous — grain by grain they differ in their content of mineral matter. The larger the test portion, the smaller the influence of this heterogeneity on the result of a single determination. That is why the macro variant is sometimes more appropriate for coal than a micro analyser, even though the latter uses less sample and is sometimes faster. Switching variants is not an equivalent substitution and should be recorded.
WHAT THESE THREE NUMBERS ARE FOR. Carbon and hydrogen enter the calculation of the calorific value and combustion balances; hydrogen additionally determines the amount of water formed during combustion, and thus the difference between the gross calorific value and the net calorific value. Nitrogen is the basis for estimating emissions of nitrogen oxides. Ultimate analysis is therefore not a test "for the statistics" — its results go directly into operational and environmental calculations.
WHY THE RESULT MUST ALWAYS BE STATED WITH A REFERENCE STATE. The content of each of these elements is stated with reference to a defined state of the fuel: analytical, as-received (working), dry, or dry and ash-free. The same sample gives four different numbers depending on the state adopted. A number without a stated reference state is unclear, and comparing results in different states is a frequent error in reports.
THE CLAUSE "PERMISSIBLE DIFFERENCE BETWEEN RESULTS" IS A TOOL, NOT AN ORNAMENT. The card lists it as a separate element of the standard. It is what makes it possible to decide whether the discrepancy between two determinations is within what can be expected of the method, or indicates an error — in the sample, in the analyser or in the execution. A laboratory that does not use this clause loses the simplest tool for supervising its own work.
STATUS OF THE DOCUMENT. The standard dates from 1998. The PKN catalogue card has no "Withdrawn" heading and no "Withdrawal date" line, and also has no "Replaces" field — so it did not replace any earlier document with this number.
ONE INSTRUMENT FOR CARBON, HYDROGEN, NITROGEN AND SULPHUR. The Department of Solid Fuels Quality Assessment of the Central Mining Institute (Główny Instytut Górnictwa) lists TruSpec CHNS and CHNS628 analysers for the determination of total sulphur. The abbreviation CHNS states directly that one instrument covers carbon, hydrogen, nitrogen and sulphur — so the determinations of this standard and of PN-G-04584 are in practice carried out on the same device, although they are two separate reference documents. This matters when describing the accreditation scope: shared apparatus does not exempt from citing each of the standards separately. WHAT WE DO NOT GIVE. We did not have the text of the standard. WE DO NOT GIVE: the test portion and particle size of the sample, the combustion temperature, the type and flow of carrier gases, column packings, the method of detecting the individual combustion products, calculation formulae or the values of permissible differences between results. All of this is the content of the standard.
Method principle
A weighed sample of fuel is completely burned in a stream of oxygen in the analyser, converting carbon into carbon dioxide, hydrogen into water and nitrogen compounds into nitrogen oxides, which are then reduced to molecular nitrogen. The combustion products are separated and determined by the detectors of the analyser, and the content of carbon, hydrogen and nitrogen in the sample is calculated from their signals. We do not give the conditions of combustion, separation and detection — they are in the text of the standard.
Applications
- Ultimate analysis of hard coal and lignite for power generation
- Calculation of combustion balances and of the calorific value of the fuel
- Estimating nitrogen oxide emissions from the nitrogen content of the fuel
- Quality control of solid fuels and secondary fuels
- Testing of coke and solid biomass, if the documentation cites this standard
Key parameters
| Parameter | Value |
|---|---|
| Measured quantities | Content of carbon, hydrogen and nitrogen in a solid fuel |
| Variant of the method | MACRO — test portion larger than in micro analysers; the micro variant is not equivalent and a switch must be recorded |
| Nature of the method | Rapid, with an automatic analyser — this is how the scope of the standard itself describes it |
| Reference state | The result always with an indication of the state (analytical, as-received, dry, dry ash-free) — the same sample gives different numbers |
| Supervision of the result | The standard contains a clause on the permissible difference between results — the basic control tool |
| Status of the document | PKN card without a "Withdrawn" heading, without a "Withdrawal date" line and without a "Replaces" field (checked on 22.09.2026) |
| Test portions, temperatures, gases, formulae, precision | WE DO NOT GIVE THEM — we did not have the text of the standard |
Standard
- Standard number
- PN-G-04571:1998 (wersja polska)
- Title (PL)
- Paliwa stałe — Oznaczanie zawartości węgla, wodoru i azotu automatycznymi analizatorami — Metoda makro
- Title (EN)
- Solid fuels — Determination of carbon, hydrogen and nitrogen content by automatic analysers — Macro method
Step-by-step procedure
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Checking the variant of the method
This standard describes the MACRO variant. If the laboratory works with a micro analyser, citing this standard requires checking whether the instrument meets its requirements — the variants are not equivalent.
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Preparation of the analysis sample
Crushing and dividing in accordance with the standards on the preparation of fuel samples. WE DO NOT GIVE THE PARTICLE SIZE OR TEST PORTION.
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Preparation of the analyser
Calibration on a certified reference material and leak check. The card lists this step as a separate clause of the standard.
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Combustion and determination
Complete combustion of the sample in oxygen and determination of the products. WE DO NOT GIVE THE CONDITIONS OF COMBUSTION, SEPARATION AND DETECTION.
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Calculation of results
Conversion of the signals into element contents and to the adopted reference state. WE DO NOT GIVE THE FORMULAE.
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Checking the permissible difference
Compare the results of parallel determinations with the permissible difference given in the standard; exceeding it means repeating, not averaging.
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Recording the result
State the C, H and N contents together with the reference state and indicate the macro variant. Without a reference state the numbers are unclear.
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Automatic CHN analyser in the macro variant | Combustion furnace, product separation system and detectors; we do not give the operating parameters | — |
| Analytical balance | Weighing the sample into the analyser containers | — |
| Cylinders of oxygen and carrier gas | Supply of the analyser; we do not give the types and flow rates | — |
| Laboratory mill and sample divider | Preparation of the analysis sample | — |
| Combustion boats and capsules | The requirements are in the text of the standard | — |
Reagents, media and consumables
| Reagent | CAS | Details |
|---|---|---|
| Oxygen | — | Oxidant in the combustion of the sample; we do not give the required purity |
| Carrier gas | — | Transport of the combustion products to the detection system |
| Column and reactor packings | — | Post-combustion oxidation and reduction of nitrogen oxides; we do not give the composition — it is in the text of the standard |
| Certified solid fuel reference material | — | Calibration of the analyser and checking of the series |
Health and safety (OHS)
- The analyser operates at high temperature and under gas pressure — do not open the chamber before it has cooled down
- Oxygen under pressure violently intensifies burning — protect fittings from grease and oils
- Combustion products contain carbon monoxide and nitrogen oxides — work with an efficient extraction system
- Coal dust is combustible and explosive in suspension — avoid dust formation when weighing
- Secure gas cylinders against tipping over; carrier gas displaces oxygen in the room
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-G-04571:1998 (wersja polska) — “Solid fuels — Determination of carbon, hydrogen and nitrogen content by automatic analysers — Macro method”.
How does this method work?
A weighed sample of fuel is completely burned in a stream of oxygen in the analyser, converting carbon into carbon dioxide, hydrogen into water and nitrogen compounds into nitrogen oxides, which are then reduced to molecular nitrogen. The combustion products are separated and determined by the detectors of the analyser, and the content of carbon, hydrogen and nitrogen in the sample is calculated from their signals.
What is the measuring range and accuracy?
Measured quantities: Content of carbon, hydrogen and nitrogen in a solid fuel; Variant of the method: MACRO — test portion larger than in micro analysers; the micro variant is not equivalent and a switch must be recorded; Nature of the method: Rapid, with an automatic analyser — this is how the scope of the standard itself describes it; Reference state: The result always with an indication of the state (analytical, as-received, dry, dry ash-free) — the same sample gives different numbers.
How long does the test take?
The procedure comprises 7 steps. The standard does not give a duration for every stage — the laboratory's own procedure decides.
What equipment is required?
Automatic CHN analyser in the macro variant, Analytical balance, Cylinders of oxygen and carrier gas, Laboratory mill and sample divider, Combustion boats and capsules.
Where is this test used?
Ultimate analysis of hard coal and lignite for power generation; Calculation of combustion balances and of the calorific value of the fuel; Estimating nitrogen oxide emissions from the nitrogen content of the fuel; Quality control of solid fuels and secondary fuels; Testing of coke and solid biomass, if the documentation cites this standard.
What safety precautions apply?
The analyser operates at high temperature and under gas pressure — do not open the chamber before it has cooled down; Oxygen under pressure violently intensifies burning — protect fittings from grease and oils; Combustion products contain carbon monoxide and nitrogen oxides — work with an efficient extraction system; Coal dust is combustible and explosive in suspension — avoid dust formation when weighing; Secure gas cylinders against tipping over; carrier gas displaces oxygen in the room.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-G-04571.