Infrared carbon monoxide detector

Long-term (>1000 h) tests were performed in a separate reactor equipped with a sohd-state on-line hydrogen sensor and infrared carbon monoxide and carbon dioxide detectors. Batch sampling was performed at the exit stream. This system allowed us to determine the durabihty of the autothermal reforming catalyst and to determine if there are any long-term problems (poisoning, coking) caused by the fuel components. 

Reference methods for criteria (19) and hazardous (20) poUutants estabHshed by the US EPA include sulfur dioxide [7446-09-5] by the West-Gaeke method carbon monoxide [630-08-0] by nondispersive infrared analysis ozone [10028-15-6] and nitrogen dioxide [10102-44-0] by chemiluminescence (qv) and hydrocarbons by gas chromatography coupled with flame-ionization detection. Gas chromatography coupled with a suitable detector can also be used to measure ambient concentrations of vinyl chloride monomer [75-01-4], halogenated hydrocarbons and aromatics, and polyacrylonitrile [25014-41-9] (21-22) (see Chromatography Trace and residue analysis). 

The primary reference method used for measuring carbon monoxide in the United States is based on nondispersive infrared (NDIR) photometry (1, 2). The principle involved is the preferential absorption of infrared radiation by carbon monoxide. Figure 14-1 is a schematic representation of an NDIR analyzer. The analyzer has a hot filament source of infrared radiation, a chopper, a sample cell, reference cell, and a detector. The reference cell is filled with a non-infrared-absorbing gas, and the sample cell is continuously flushed with ambient air containing an unknown amount of CO. The detector cell is divided into two compartments by a flexible membrane, with each compartment filled with CO. Movement of the membrane causes a change in electrical capacitance in a control circuit whose signal is processed and fed to a recorder. 

Elemental composition C 42.88%, O 57.12%. Carbon monoxide may be identified and determined quantitatively at low ppm level by infrared sensors. Such CO detectors are commercially available. Also, it can be analyzed by GC using TCD or FID or by GC/MS. The characteristic ion mass for CO identification is 28 (same as N2 or ethylene, both of which can interfere). 

Continuous analysis instruments equipped with flame ionization, chemiluminescence, and infrared detectors were used to measure the concentrations of total hydrocarbons, nitrogen oxides and carbon monoxide, respectively. The concentration of total hydrocarbons was measured by a JUM FID 3-300 hydrocarbon analyzer with a flame ionization detector. NO, NO2 and NOx was measured by an ECO Physics CLD 700 EL-ht chemiluminescence detector. CO was measured with either a Beckman Industrial Model 880 non-dispersive infrared instrument or an NDIR instrument from Maihak (UNOR 6N). 

There are a few common methods of measuring oxygen concentration in the gas phase. Electrochemical sensors and paramagnetic sensors are typically used to measure oxygen concentration on a wet and dry basis, respectively. Carbon monoxide (CO) is most commonly measured using a nondispersive infrared technique. A gas sample flows between an infrared radiation source and an infrared detector. Carbon monoxide absorbs infrared radiation, hence the difference in intensity proportional to the concentration of CO in the gas sample. 

Catalyst activity was usually measured in a bench test assembly (Figure 1). The reactor included a preheat section containing tabular alumina just above (upstream from) the 30 cm3 of catalyst in the center of the reactor. Water was pumped by a minipump (Milton-Roy) to the steam generator. From a three-temperature profile around the catalyst bed, it was determined that the midpoint data were most useful and reliable. The analytical equipment consisted of an infrared device (Mine Safety Appliances) for carbon monoxide, a flame ionization detector (Beckman) for hydrocarbons, and a paramagnetic oxygen analyzer (Beckman). The entire assembly except for Telex printer and computer is pictured in Figure 2. 

Carbon monoxide may be determined over a wide range of concentration via infrared analysis [25]. Good results are achieved at concentrations as low as 1.25 to 2.5 mg m . The main disadvantage of this technique is the non-linear response, as well as possible interference by CO2, water vapour and hydrocarbons. The use of the gas chromatography for determining CO includes a catalytic reduction system, which converts carbon monoxide quantitatively to methane and a flame ionization detector. For a rapid CO determination, indicator tubes with palladium salt as a catalyst and silicomolybdate complex, which yields a blue colour with carbon monoxide, are used. The CO determination can also be carried out on the basis of its reaction with the radioactive kryptonate of palladium chloride [18, 25]. 

Relatively inexpensive portable colorimetric indicators are now commonly used to detect the presence of a variety of contaminant gases in the atmosphere. These are normally specific for one or perhaps a series of gases. For example, the NBS colorimetric detector uses an indicator tube that contains a 15-mm section of yellow palladous silico-molybdate gel the gel changes color when exposed to carbon monoxide at concentrations as low as 0.001 vol. % in air. Figure 52 shows one version of a commercial unit used for carbon monoxide as well as carbon dioxide, the unsaturated hydrocarbons, and a variety of other gases this unit can also be used to determine the approximate concentrations of contaminants in liquid oxygen. Precise determinations can be made with a variety of analytical tools, including infrared... 

Many different kinds infrared instruments of various sizes are available for quantitative and qualitative vapor analyses. Some are manufactured specifically for detection of only one chemical, such as the carbon monoxide (CO), using a specific wavelength. Others can be very complicated, such as Fourier transform-based infrared (FT-IR) detectors that scan the entire IR wavelength for both chemical identification and concentration determination. 

Carbon monoxide presents problems in mass spectrometry. This is because nitrogen has the same mass number as carbon monoxide, and in most mass spectrometers ghost peaks of nitrogen may be present. The solution is probably to use infrared detector devices for analysis of carbon monoxide. 

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