GB/T 20475.2-2006Classification of the content of harmful elements in coal - Part 2: Chlorine (English PDF)
煤中有害元素含量分级 第2部分：氯
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Issued by
General Administration of Quality Supervision, Inspection and Quarantine; Standardization Administration of the PRC
Level / Type
National · Recommended
Issue date
September 12, 2006
Implementation date
February 1, 2007
Scope
GB/T 20475.2-2006 is the English-translated version of 煤中有害元素含量分级 第2部分：氯.
China's national classification of coal by chlorine content.
It is Part 2 of GB/T 20475 and specifies the ranges, names and codes into which coal is classified by its dry-basis chlorine content, together with the chlorine requirements for the production, processing and utilisation of coal, and it applies to coal exploration, production, processing, marketing and utilisation.
Chlorine is present in coal in small amounts and does damage out of all proportion to its concentration.
In a boiler it volatilises as hydrogen chloride, and where the flue gas cools below the acid dew point on the economiser, the air heater or the ductwork, it condenses and corrodes them; in a superheater it participates in the deposits that cause the high-temperature corrosion of tube surfaces, which is one of the commonest causes of unplanned outages in coal-fired plant.
It also worsens fouling by lowering the melting point of the ash deposits. In a coke oven the chlorine passes into the gas and into the by-product liquor and attacks the plant there.
And it raises the corrosivity of the residues and effluents that leave the site.
Because chlorine cannot be removed by washing to any useful degree - much of it is associated with the inherent moisture and the organic matter rather than the mineral matter - the only effective control is knowing the content in advance and blending or designing for it.
That is what a classification does: it turns a laboratory number into a category that can appear in a resource statement, a purchase specification and a boiler design basis.
The standard fixes the class boundaries, names and codes, with sampling and determination referred to the coal analysis standards. Issued on 12 September 2006 and in force since 1 February 2007.
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Document preview — GB/T 20475.2-2006
National Standard of the People's Republic of China
- ICS
- 73.040
- Classification
- D 20
Issued by: General Administration of Quality Supervision, Inspection and Quarantine; Standardization Administration of the PRC
Contents
- 1 Scope
- 2 Normative references
- 3 Terms and definitions
- 4 Classification by chlorine content
- 5 Requirements for production, processing and utilisation
- 6 Sampling and determination
1 Scope
This part of GB/T 20475 specifies the ranges, names and codes into which coal is classified by dry-basis chlorine content, and the chlorine requirements for the production, processing and utilisation of coal.
It applies to coal exploration, production, processing, marketing and utilisation.
Small quantity, large damage
In a boiler chlorine volatilises as hydrogen chloride, and where the flue gas cools below the acid dew point - on the economiser, the air heater, the ductwork - it condenses and corrodes them.
In the superheater it takes part in the deposits that cause high-temperature corrosion of the tubes, one of the commonest causes of unplanned outages in coal-fired plant.
It also makes the ash stick
Chlorine lowers the melting point of the deposits, worsening fouling.
In a coke oven it passes into the gas and the by-product liquor and attacks the plant there, and it raises the corrosivity of everything leaving the site as residue or effluent.
And washing does not remove it
Much of the chlorine is associated with the inherent moisture and the organic matter rather than the mineral matter, so cleaning the coal barely touches it.
The only effective control is knowing the content in advance and blending or designing for it - which is exactly what a classification makes possible, by turning a laboratory number into a category that can appear in a resource statement, a purchase specification and a boiler design basis.
......
This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — 15 pages — is available in the English PDF.
Referenced standards
Normative references
- GB 475[GB/T 475-2008] Method for manual sampling of commercial coal
- GB/T 482Sampling of coal seams
- GB/T 3558Determination of Chlorine in Coal
- GB/T 19494.1Mechanical sampling of coal - Part 1: Method for sampling
- GB/T 19494.2Mechanical sampling of coal - Part 2: Method for sample preparation
GB 474
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