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GB/T 17283-2014: Determination of the water dew point of natural gas -- Cooled surface condensation hygrometers
GB/T 17283-2014
Determination of the water dew point of natural gas - Cooled surface condensation hygrometers
ICS 75.060
E24
National Standards of People's Republic of China
Replacing GB/T 17283-1998
Determination of gas water dew point
Method cooling surface condensation hygrometers
Published 2014-12-05
2015-05-01 implementation
Administration of Quality Supervision, Inspection and Quarantine of People's Republic of China
Standardization Administration of China issued
Table of Contents
Introduction Ⅲ
1 Scope 1
Principle 2 1
3 1 instrument performance
General Considerations 3 of 4 sources of error operations ---
5 hydrocarbon condensate elimination 4
6 Accuracy 5
Appendix A (informative) The standard and ISO 6327. 1981 as compared to the changes in the structure of 7
Annex B (informative) amended water dew point 8
Reference 9
Foreword
This standard was drafted in accordance with rules GB/T 1.1-2009 given.
Instead of the standard GB/T 17283-1998 "water-gas dew point Cooled surface condensation hygrometers Law", and
GB/T 17283-1998 compared to the same main technical content.
This draft standard method using the reformed modified using ISO 6327. 1981 "Determination of gas cooled mirror dew point of water condensation hygrometers
Law ", ISO 6327 was confirmed in 2011.
This standard and ISO 6327. 1981 as compared with a large adjustment in the structure, A is listed in the Appendix of this standard and ISO 6327. 1981
Reg number control list.
This standard and ISO 6327. 1981 main technical differences and the reasons.
--- modify the scope of the standard, in ISO 6327. 1981 Scope "water dew point range is generally -25 ℃ ~ 5 ℃" base
Increase on the basis "under special circumstances, may also be a wider range of water dew point", because in order to adapt to the actual situation of China's natural gas production
Conditions, expanding the scope of this standard.
The standard proposed by China National Petroleum Corporation.
This standard by the National Gas Standardization Technical Committee (SAC/TC244).
This standard is mainly drafted by. China Natural Gas Research Institute, Southwest Oil and Gas Field Company, Chengdu Tianke limited oil and gas project
the company.
The main drafters. flat Zeng, He Bin, Gao root.
This standard supersedes the previous editions are.
--- GB/T 17283-1998.
Determination of gas water dew point
Method cooling surface condensation hygrometers
1 Scope
This standard specifies the method for measuring the cooling gas condensate water mirror dew point hygrometer analysis.
This standard applies to determination of dew point gas and similar gases water. Water pipeline gas dew point ranging generally treated
-25 ℃ ~ 5 ℃, under appropriate gas pressure, the water content range (volume fraction) of 50 × 10-6 ~ 200 × 10-6. In special circumstances
, The water dew point range may also be wider.
Principle 2
2.1 Principle Instruments
With this type of instrument, the water content is calculated by measuring the gas corresponding to the water dew point of the gas. For determination of dew point of water
Usually with a mirror hygrometer (typically metal mirror), when the sample flows through the mirror, and the temperature may be reduced and quasi artificially
Accurate measurement. When the mirror is cooled to have a temperature of condensate produced it can be observed on the mirror surface condensation begins.
When the temperature is lower than this, condensate will extend gradually increased with time; Above this temperature, the condensate is reduced until it disappears, and the mirror
Surface temperature is the dew point of the gas to be measured by the instrument.
2.2 Determination of the water vapor pressure
Sampled at a sample gas pressure by the gas pressure in line with the hygrometer case, the measured dew point corresponding to the saturated vapor pressure value,
Is the sample gas water vapor partial pressure.
For manual inspection, can be obtained the relationship between the saturation vapor pressure and temperature.
It should be noted. if the test sample gas containing methanol is determined with this method is the dew point of the mixture of methanol and water. Of course, if
Methanol content is known as an information, Appendix B gives the calculation of the actual water dew point required correction factor.
In operation of the system, if the total pressure in the test sample is greater than or equal to atmospheric pressure, according to the present standard can be corrected without hygrometer for measuring
The water vapor pressure, the relationship between the water vapor partial pressure and dew point depends on the measured level and the method of measurement used.
If the condensate temperature test environment containing a gas in a region near or above the water dew water dew point, it is difficult to measure the water vapor condensate.
2.3 Notes
A substantially water dew point of the measurement point is the sampling line should be as short as possible, the pressure drop of a size to be generated during the assay ignorable
Slightly; In addition to the mirror, the remaining part of the instrument and the sampling line temperature should be above the dew point of water. When sampling, with reference to the specific considerations
GB/T 13609 requirements.
3 instrument performance
3.1 Overview
Instrument may be designed in different ways, the main difference is that the characteristics of condensate mirror, the mirror and the control method of cooling the temperature of the mirror,
The method of detecting temperature of the mirror and the condensate was measured. Determination of small interior mirror and corresponding components are typically in a sample of air through, at high pressure,
This measuring chamber should have the appropriate mechanical strength and sealing.
Recommended mirror easily removed for easy cleaning. Determination of the process are hydrocarbons such as dewing, should cause enough attention and take appropriate
Measures. Process can be measured manually or automatically.
Before under high pressure, the sample gas introduced into the measuring chamber, should first check the instrument instructions.
Manual and automatic dewpoint meter 3.2
Dew point analyzer designed to both samples were measured at different times, it can also be continuously measured. For the assay, respectively
The method of cooling the mirror, it is required to make the selected operator to observe the change of phase to generate aggregation with the naked eye can be continuously
Observations. If the water content of the sample gas is very low dew point rarely i.e., steam flowing through the device per unit time is small, so that the dew formation
Very slow, difficult to distinguish which is increasing or disappear. The use of a photocell or any other light-sensitive component, it is easy to dew condensate
Poly observed. When the manual control of the refrigeration holding member, but also a simple display.
In the case of the hydrocarbon condensate present case, the use of manually operated dew point will be difficult to observe the formation of water dew. In this case, the available
Liquid hydrocarbons bubbler to assist observation, however, it is important to understand the principles used in the bubbler and use limitations.
Bubbler at a certain temperature and pressure, the sample gas through the bubbler containing Ping Heng will be established between the hydrocarbon liquid in the bubbler,
Which comprises the following reaction.
a) the fresh gas flow is started by the sample liquid hydrocarbon foamer will lose part of the water when out until after Ping Heng established, the sample gas at the outlet
The water content and water content before the inlet of the sample gas are equal. Accordingly, the temperature of the bubbler gas should be higher than the measured water sample
Dew point temperature, and sufficient sample should be introduced into the gas to be measured before the sample gas and the equilibrium between the bubbler.
b) the heavy hydrocarbon components of the sample gas into the liquid hydrocarbon from the gas phase until Ping Heng is established, this exchange is to reduce the potential in the gas
Condensate amount of hydrocarbons, thereby reducing the masking effect condensate hydrocarbon liquid. With the continuous exchange of the components, the liquid hydrocarbons are condensable gas sample
Analysis of saturated hydrocarbons, the sample gas condensate hydrocarbon content may also increase. Before further testing, liquid hydrocarbon should be replaced, and
The foamed state and reaches required.
By using the output signal of the photo tubes can be stably observed on the condensate condensate mirror at the required temperature, so that the entire apparatus
Fully automated. For continuous reading or recording, automatic operation is essential.
3.3 irradiating mirror
The manual means are adapted to generate the observed visually condensate, if using a photocell, the mirror will be installed in a room of the assay
Irradiating light source. Available lamp and photocell arranged in various ways, in the direction of the specular scattering of the generated light can be mirror polished
cut back. In any case, prior to use of the mirror should be clean.
When no condensate, fall on the photocell light scattering will be reduced. If the measurement surface blackened pool, the measuring chamber can be reduced
The inner surface of the light scattering effect can also be installed via a further optical system as a complement to the above measures, such that the mirror is only
Irradiation, so that only the photocell observed mirror case.
3.4 and a temperature control method of a refrigeration mirror
3.4.1 General
By the following methods to reduce and adjust the temperature of the mirror. Wherein the process required in 3.4.2 and 3.4.3 as described in operating personnel
Continuous observation, these methods are not suitable for automatic dewpoint meter. For automatic analyzer, available in two kinds of the 3.4.4 and 3.4.5
Refrigeration method. a refrigerant in indirect contact cooling and thermoelectric (Peltier) refrigeration effect. Whichever method is used, the cooling rate should not exceed a mirror
Over 1 ℃/min.
3.4.2 solvent evaporation method refrigeration
Reacting a volatile liquid in contact with the back of the mirror, into the air flow and vaporized refrigerant. To that end, the general manual
Blower, if low-pressure compressed air source is an adjustable throttle or other suitable gas pressurized gas source, the better, in the manual of the blower
Case, the use of ethylene oxide as a high volatile solvent, no effort can be too large temperature drop around the mirror 30 ℃,
Their toxicity is taken into account, the choice of acetone as the solvent can be, in the case of manual blower, the temperature of the mirror can be decreased left 20 ℃
Right, as by compressed air or other suitable gas under pressure, cooling effect will be even better.
3.4.3 Method adiabatic expansion refrigeration
Reacting a gas flowing through the nozzle back of the mirror, the mirror is cooled due to the gas expansion, the gas is usually filled with small cylinders
Compressed carbon dioxide, other gases may also be used, such as compressed air, compressed nitrogen, propane, or the like halogenated hydrocarbon. Law allows at least the mirror with a temperature
Used for the gas temperature drop 40 ℃.
3.4.4 indirect cooling refrigerant
The RTD is connected through a mirror and a refrigerator. Typically a copper rod is inserted into the refrigerator and a small piece of insulating material constituting a thermoelectric
Resistance and connected to the mirror, the mirror is heated by an electronic component, the current should be controlled so that the intensity of the mirror temperature can be easily and accurately
adjust. As with liquid nitrogen as a refrigerant, the temperature dropped to make the mirror -70 ℃ ~ -80 ℃; with a dry ice and acetone mixture as refrigeration
Agent, can mirror the temperature dropped to -50 deg.] C (depending on the design of the instrument); liquefied propane, the mirror temperature can drop to about -30 ℃.
3.4.5 thermoelectric (Peltier) cooling effect
Single-stage Peltier effect element is generally the maximum achievable refrigeration temperature drop of about 50 ℃. When the two-stage, obtained in about 70 ℃
Refrigeration temperature drop. By changing the current Peltier effect element, the temperature of the mirror can be adjusted, but this method is a large thermal inertia; by maintaining a
Constant current refrigeration while a heat resistor connected with the mirror, with an adjustable heating means for heating the mirror can be adjusted quickly
Mirror temperature.
3.5 Temperature Measurement
When there is formed on the exposed mirror surface, the temperature should be measured as accurately as possible at the time of condensation, the temperature difference in order to avoid specular, preferably selected
Material with high thermal conductivity of the mirror. During the temperature measurement mirror, a manual measuring instrument commonly used mercury thermometer precision for the automatic determination
Heating the probe instrument is used (e.g., resistance thermometer, thermistor or thermocouple).
General precautions when operating 4 sources of error ---
4.1 interfering substances
4.1.1 Overview
In addition to the gas or water vapor, other materials, such as solid particles, dust or the like may also enter the instrument, and can be deposited on the mirror surface, impact tester
Operating performance of the device. Other vapor except water vapor may condense on the mirror surface. In the measurement of dew point, natural or accidental sample into
Water-soluble gas will cause the measured room dew point observed actual water vapor content corresponding to a dew point vary.
4.1.2 solid impurities
If the solid impurities absolutely insoluble in water, they will not affect the observed dew point temperature, but will prevent condensation observed. In automatic loading
Centering, solid impurities, if not used for compensation means, and when exposed lower amounts, these impurities would interfere with operation of the instrument. If the mirror
Solid impurities too, will generally re...