DL/T 1358-2014 PDF in English
DL/T 1358-2014 (DL/T1358-2014, DLT 1358-2014, DLT1358-2014)
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Analytical methods of steam and water in power plants determination of total organic carbon
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Standards related to (historical): DL/T 1358-2014
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DL/T 1358-2014: PDF in English (DLT 1358-2014) DL/T 1358-2014
DL
ELECTRICAL POWER INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 27.100
F 24
Registration number. 47931-2015
Analytical methods of steam and water in power
plants - Determination of total organic carbon
ISSUED ON. OCTOBER 15, 2014
IMPLEMENTED ON. MARCH 01, 2015
Issued by. National Energy Administration
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions ... 4
4 Method summary ... 4
5 Reagents ... 5
6 Instruments ... 6
7 Analytical procedures ... 6
8 Precision... 7
9 Analytical report ... 7
Appendix A (Informative) Decomposition products and potential hazards of
organics in water ... 9
Analytical methods of steam and water in power
plants - Determination of total organic carbon
1 Scope
This standard specifies the method for the determination of total organic carbon
in water steam from thermal power plants.
This standard applies to the determination of water samples with TOC and TOCi
contents in the range of 10 µg/L ~ 1000 µg/L.
2 Normative references
The following documents are essential to the application of this document. For
the dated documents, only the versions with the dates indicated are applicable
to this document; for the undated documents, only the latest version (including
all the amendments) are applicable to this standard.
GB/T 6903 Analysis of water used in boil and cooling system - General rule
3 Terms and definitions
3.1
Total organic carbon (TOC)
Total carbon content in organic matter.
3.2
Total organic carbon ion (TOCi)
The sum of the total carbon content in organic matter and the content of other
heteroatoms that produce anions after oxidation.
4 Method summary
The organics in water will, after complete oxidation, be subject to the following
reactions.
Note. M represents heteroatoms (except for carbon) in the organic matter that
may produce anions after the oxidation.
When organic matter contains only carbon, hydrogen, oxygen, and no other
heteroatoms [see formula (1)], the carbon dioxide produced after oxidation is
directly proportional to the total organic carbon content in the water. By
measuring the change in CO2 at the inlet and outlet of the oxidizer, the carbon
content (TOC) in the organic matter cab be calculated, and the measured TOC
content is consistent with the TOCi content. When organic compounds contain
other heteroatoms other than carbon atoms [see formula (2)], after oxidation,
chloridion, sulfate, nitrate, and other anions are generated in addition to carbon
dioxide (see Appendix A for details). At this time, the change in the conductivity
of all atoms that may produce anions (including carbon) in the organic matter
before and after oxidation is determined and converted to the sum of the carbon
dioxide content (in terms of carbon) as the TOCi content, whereas the
determination of the resulting carbon dioxide content only yields the TOC
content. Under such conditions, the measured TOCi content is greater than the
TOC content. The TOCi content can more accurately reflect the corrosiveness
of organic matter in water.
5 Reagents
5.1 Reagent water. It shall meet the requirements of the level 1 reagent water
as specified in GB/T 6903, the total organic carbon content shall be less than
50 μg/L.
5.2 Reagent purity. It shall meet the requirements of GB/T 6903.
5.3 TOC stock solution (1000 mg/L). Accurately WEIGH 2.3770 g of superior
grade pure sucrose (C12H22O11) which has been dried at 100°C for 2 h. USE
reagent water to dissolve it, quantitatively TRANSFER it into a 1000 mL
volumetric flask, USE reagent water to dilute it to the mark. This solution shall
be stored in the refrigerator, which is valid for three months.
5.4 TOC standard solution (10 mg/L). Accurately PIPETTE 1.00 mL of TOC
stock solution into a 100 mL volumetric flask, USE reagent water to dilute it to
the mark, the solution shall be prepared before use.
5.5 Ammonia buffer solution 1 (ammonia content approximately 1200 mg/L).
PIPETTE 10 mL of superior grade pure ammonia into a 200 mL volumetric flask,
USE reagent water to dilute it to the mark. This solution shall be stored in the
refrigerator, which is valid for three months.
Appendix A
(Informative)
Decomposition products and potential hazards of organics in water
A.1 Heat system organic material origin and potential hazards
When organic compounds do not contain halogens, sulfur, and other
heteroatoms, the decomposition products in the thermal system include formic
acid, acetic acid and other low-molecular organic acids, and carbon dioxide;
when organic compounds containes chlorine, sulfur and other heteroatoms, its
decomposition products in the thermal system include chloride, sulfate and
other anions in addition to the above anions. Studies have shown that
excessive levels of organic compounds in water steam will lead to corrosion of
the turbine's low-pressure cylinder blades. Since the corrosion of low-
molecular-weight organic acids is far less than chloride, sulfate, and other
strong-acid anions, the organic substances corrosion against equipment is
closely related to the heteroatom contents such as sulfur and chlorine in organic
materials. For example, if the seriously polluted cooling water leaks into the
condensate, the quality of the added medicine in the system is unqualified, the
feed water source is polluted seriously, the desalination system is not efficient
in removing organic matter, and the leachables of the resin are large, it may
introduce organic substances containing halogen, sulfur and other heteroatoms
into the steam system. The case of many power plants shows that when the
total organic carbon (TOC) content in the water has not exceeded the standard,
the TOCi content has exceeded the standard seriously. At this time, the steam
hydrogen conductivity has exceeded the standard and the low-pressure
cylinder blade of the turbine has severe corrosion. Therefore, to prevent the
corrosion of the turbine low-pressure cylinder blades, it shall monitor and
control the TOCi content in the water steam.
A.2 Differences between TOC and TOCi measurement indicators
A.2.1 Meaning of TOC measurement indicator
Total carbon content in organic matter. The measuring principle is to calculate
the total carbon content in organic matter by measuring the change of carbon
dioxide content before and after the complete oxidation of organic matter, and
convert it to carbon content. The measurement can be performed using the
membrane conductance method or the non-dispersive infrared detector. No
matter how the organic composition changes, the TOC content in the water
steam only expresses the total carbon content in the organic matter, and the
content of heteroatoms is not reflected.
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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