ABB NGC8206/NGC8209 gas chromatograph

ABB NGC8206/NGC8209 gas chromatograph

Key technologies for improving core performance

Optimization of analysis cycle: matching the best component separation effect, balancing measurement repeatability and calorific value range.

Constant temperature detection bead circuit: The detector maintains a constant bead temperature; It can operate under no-load gas conditions without damaging the detection beads, while expanding the measurement range.

Exponential response factor calibration: Four different calibration mixtures are used to obtain the exponential response factor, which improves system linearity compared to traditional linear factors.

24 bit high-precision A/D converter: Each detection bead is independently configured with a 24 bit ADC, without the need for a preamplifier, expanding the dynamic measurement range.

Process condition remarks

The carrier gas is helium, with a typical consumption of 12-15 cc/min

Hydrogen sulfide (H ₂ S) can cause interference, and the upper limit of H ₂ S in the sample is 0.05 Mol% (500 ppm)

Two analysis application mode parameters

Unified temperature of the instrument furnace box: 140 ° F; carrier gas: helium gas, divided into two sets of analysis methods: C6+Btu and C9+Btu, with three detectors responsible for separating different components.

Mode 1: C6+Btu (detector 1+detector 2)

Detector 1 (C3-C6+heavy hydrocarbons)

Component symbol measurement range Mol% MDQ minimum detectable quantity Mol%

Propane C3 0.005-100 0.001

Isobutane iC4 0.005-15 0.001

N-Butane nC4 0.005-15 0.001

Neopentane Neo-C5 0.005-10 0.001

Isopentane iC5 0.005-10 0.001

N-pentane nC5 0.005-10 0.001

C6 and above C6+0.005-5 0.001

Detector 2 (N ₂, C1, CO ₂, C2+calorific value calculation)

Component symbol measurement range Mol% MDQ Mol%

Nitrogen N ₂ 0.01-100 0.005

Methane C1 0.01-100 0.005

Carbon dioxide CO ₂ 0.01-100 0.005

Ethane C2 0.01-50 0.005

Repeatability index of calorific value

Heating value under fixed temperature conditions (MJ/Btu): ± 0.0125

Heating value (MJ/Btu) for a wide temperature range of 0-130 ° F: ± 0.025

The document includes actual chromatograms of detector 1 and detector 2, showing the peak timing of each component.

Mode 2: C9+Btu (detector 3, analyzing C6-C9+heavy hydrocarbons)

This mode is used to analyze heavy components from hexane to nonane and above, with the interfering substance being H ₂ S, and a maximum allowable concentration of 0.05 Mol%.

Component symbol measurement range Mol% MDQ Mol% Test sample molar ratio

Hexane C6's 0.005-1 0.001 1

Heptane C7's 0.005-1 0.001 0.15

Octane C8's 0.005-0.5 0.001 0.15

Nonane and above C9+'s 0.005-0.5 0.001 0.15

Important premise: The upper limit of the measurement range is only valid when the sample remains in a gaseous state throughout the entire process. From the sampling probe, steel cylinder, conveying pipeline, sample module to the NGC chromatograph body, all links of the sample must not exhibit condensation liquefaction. The document includes the chromatogram of the C6-C9+component of detector 3.

Common troubleshooting strategies and calibration maintenance

When the chromatograph malfunctions, engineers can use its high-precision 24 bit ADC system to perform reverse inference through software chromatograms.

Baseline drift or flat peak:

Check if the constant bead temperature circuit is alarming. If the power supply of the detector circuit is abnormal, temperature fluctuations can cause baseline instability.

Insufficient purity of carrier gas or failure of purifier. Check if the carrier gas consumption (12-15 cc/min) is normal. If the flow rate drops sharply, it is necessary to investigate whether the gas path is blocked or leaking.

Deterioration of component separation (such as inability to separate C4/C5):

Check if the temperature of the chromatography column incubator is maintained at the set value of 140 ° F. Temperature fluctuations can directly alter the retention time of substances in the chromatographic column.

The valve or sample loop may be clogged with solid particles, resulting in inconsistent injection volumes. At this point, it is necessary to clean or replace the diaphragm/valve components of the injection system.

Poor repeatability of calorific value (deviation from ± 0.0125 index):

The standard gas has expired or the concentration is inaccurate. The exponential response factor of NGC is generated by four standard gases. If there is an error in the standard gas itself, the calibration will be invalidated. Four compliant mixed standard gases need to be reused to perform the calibration process.

Sample pressure fluctuations. If the pressure reducing valve of the sample processing system is not adjusted stably, causing the injection pressure to fluctuate, it will directly affect the repeatability of the measurement.

H2S interference investigation:

If a specific peak position is found to be abnormally elevated and cannot be eliminated through calibration, it is necessary to sample and test the H2S concentration in the gas source. Confirm if the tolerance limit of 500 ppm has been exceeded.