Specialists in Detector Technology & Systems Integration since 1973


CMI Applications Note #16

Monitoring Carbon Monoxide Emissions from Stacks

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Process Analyzers, LLC, 25 Walpole Park Dr., Walpole, MA 02081

Tel. 15086605001; Fax 15086605040; email

See our home page @ - http://

Specialists in Detector Technology & Systems Integration since 1973

Carbon monoxide (CO) is produced in various combustion effluents as a product of the incomplete combustion of fossil fuels. It is frequently found at ppm to % levels. The analyzer can be used to “tune” to source to improve the efficiency and reduce the levels of CO.

Effluents generally contain high levels of water, sulfur dioxide, and fine particulate matter. Since CO is slightly soluble in water, any condensation in the lines would result in a loss of sample. Thus, a stack gas conditioning system was needed to remove water without effecting the CO. We used a “hot” (150C) filter and Permapure dryer to remove the particulate and water respectively. Now, once the water was removed from the effluent, an ambient temperature line can be run from the conditioning system to the analyzer housing. A schematic representation of the analyzer configuration is shown at the top of the next column in Fig. 1.

The analyzer was located in an instrument housing at the base of the stack and was tied into the process

controller via the 4-20 mA output from the Model 301-B Automatic GC. A photo of the analyzer in the Control Room is shown in Fig. 2 below.


Fig. 2 GC301B

After a review of the application and columns available, we chose carbosphere as a packing in order to separate methane, CO and CO2. The analysis time for CO was 1.56 minutes. The typical reproducibility obtained with the system at a concentration of 10 ppm is excellent at +/- 2.3 %. The chromatogram for this analysis is shown below in Figure 3 and Table I illustrates the reproducibility over a range from 4-200 ppm.

Fig. 3 Chromatogram of 24 ppm of CO

According to one user, “the instrument was necessary to reduce problems and complaints at the plant.

ppm / CO
Run #
1 / 4.75 / 9.75 / 24.45 / 51.33 / 104.79 / 205.53
2 / 4.09 / 9.56 / 24.98 / 50.82 / 103.96 / 202.89
3 / 4.22 / 10.0 / 25.15 / 51.47 / 103.91 / 206.94
4 / 4.71 / 9.64 / 24.54 / 51.19 / 104.73 / 206.27
5 / 4.23 / 9.88 / 24.73 / 51.55 / 104.11 / 205.82
6 / 4.34 / 9.88 / 24.41 / 50.89 / 104.15 / 205.42
7 / 4.29 / 10.2 / 24.69 / 104.37 / 205.42
Total / 30.6 / 69.0 / 173.0 / 307.3 / 730.02 / 1438.3
Ave. / 4.38 / 9.85 / 24.71 / 51.21 / 104.29 / 205.47
Std. dev. / 0.25 / 0.23 / 0.27 / 0.30 / 0.35 / 1.26
CV % / 5.81 / 2.32 / 1.11 / 0.59 / 0.34 / 0.62

The detection principle for CO involves the reduction to methane over a hot nickel catalyst (methanizer) followed by analysis by an FID. The sample is burned in a hydrogen-air flame and the resulting carbon ions are measured in an ion chamber. The ionization chamber in the FID contains a pair of electrodes. A positive potential is applied to the accelerating electrode which creates a field driving ions to the collecting electrode where the current, proportional to concentration, is measured, amplified and converted to an output signal.

Brief Specs for the 301-B

Instrument Principle: Auto GC

Detector: FID with methanizer

Other components Measured: CO2, CH4

Range: sub ppm to %; > 105

Types of Samples: stack, ambient, & exhaust

Calibration: Automatic

Sample Compartment: ambient

Dimensions:

11" H x 17" D x 19" W

Weight:

45 pounds; 20.5 Kg

Readout: High resolution VGA screen

Options

4-20 mA

X or Z purging

Other Detectors Available: PID, TCD, FUV, & ECD

New Features for the 301-B GC

  • More compact design
  • More rugged industrial design
  • Internal data storage
  • Self start after power failure
  • Optional remote control software
  • Single point, four point or eight point systems available (optional)
  • New options:

concentrator-for fenceline monitoring

Process Analyzers, LLC, 25 Walpole Park Dr., Walpole, MA 02081

Tel. 15086605001; Fax 15086605040; email

See our home page @ - http://