Sampling systems infrared analyzers

The sampling system consists of a condensate trap, flow-control system, and sample tank (Fig. 25-38). The analytical system consists of two major subsystems an oxidation system for the recovery and conditioning of the condensate-trap contents and an NMO analyzer. The NMO analyzer is a gas chromatograph with backflush capabihty for NMO analysis and is equipped with an oxidation catalyst, a reduction catalyst, and an FID. The system for the recovery and conditioning of the organics captured in the condensate trap consists of a heat source, an oxidation catalyst, a nondispersive infrared (NDIR) analyzer, and an intermediate collec tion vessel. 

Where is it possible or desirable to locate the near-infrared analyzer modnle What hazardous area certification requirements apply to both analyzer and sampling system ... 

The emission measurements during this testing included N0X, smoke, particulate and PNA. N0X was determined by a non-disper-sive infrared analyzer, and smoke by the Bacharach test. Both the particulates and PNA were sampled by a source assessment sampling system (SASS). The SASS system isokinetically samples a fraction of the stack gas and traps particulates in a series of cyclones, which classify the particulate by size. Final filtration is through a fiberglass filter mounted in an oven heated to 200°C to prevent condensation of acids. In this program, the cyclones were not used, since previous work (3) had shown the particulate from coal-derived fuel oils to be small, with an average diameter on the order of 0.4 /um. The PNA which is not deposited on the particulate is collected on XAD-2 resin after the gas has been cooled to 15-20°C. PNA analyses were carried out on a combined extract from the particulate, XAD-2 resin, other condensates in the system, and the solvent rinses used to clean the SASS system. 

The product gas is cleaned of char particles using a cyclone. The liquid products and water are retained in a system of two condensers and a cotton filter. The gas flow rate is then measured using a dry testmeter, and the CO and CO concentrations are continuously determined by an infrared analyzer. In addition, gas samples are taken at regular time intervals and analyzed by chromatography to determine the percentages of Hj. CO, CO2, CH4 and Cj (CjHi, CjH, CjHj) in the product gas. Reaction temperature. 

Often the physical state of the sample (gas, liquid, or solid) is dictated by the physical principle upon which the measurement is based, and a phase conversion may be required. Some instruments (for example, gas chromatographs and infrared analyzers) utilize either gas or liquid samples the appropriate phase may be chosen to optimize any of the instrumental parameters discussed earlier. If the measurement is temperature sensitive and the sample temperature may vary, temperature compensation or temperature control must be provided. Temperature compensation is usually supplied as part of the measuring system the sample temperature is continuously monitored and the measurement signal electrically corrected to offset the temperature effects. When temperature control is required, a batch sample or a sample side-stream is used, and the sample temperature is adjusted prior to measurement. This procedure adds dead-time to the measurement because the sample has to be in the temperature converter long enough to come to thermal equilibrium. 

Thermogravimetry (TG) was performed on a Perkin-Elmer TGA 7 system. Infrared spectra of the evolved gases during the TG heating, were obtained with a Perkin-Elmer TG/FTIR system consisting of a TGA 7 analyzer coupled to an external optical bench of a Perkin-Elmer 17(X)-X FTIR interface. The samples were analyzed in bulk form, directly from the drying oven. 

In the most common method, the solution is irradiated with near-ultraviolet radiation (200-400 nm) to decompose organic matter by means of a radical formation mechanism. Then the generated CO2 is transported toward the detector with a carrier gas. In order to eliminate some ionic compounds that can interfere with the measurement, a membrane is placed before the detector. The detection is carried out either by the measurement of conductivity via a sensor or by a nondispersive infrared analyzer. In this online system, the sample analysis takes aroimd 6 min. Other systems based on the same principle have also been described. In this case the oxidation and detection are produced in the same chamber. In this "batch" apparatus the sample is trapped and analyzed for 3-30 min. With this latter system, some ionic species other than H and HCO3 can interfere with the conductivity readings. Species such as Ti02 [85,90] and persulfate [91,121] have been used as catalysts present as a diluted suspension in water. The TOC is obtained from the difference between the conductivities for the irradiated and nonirradiated samples. 

In the infrared detection system, the sample is weighed into a special ceramic boat which is then placed into a combustion furnace at 1371°C (2500°F) in an oxygen atmosphere. Most of the sulfur present is converted to sulfur dioxide, which is then measured with an infrared detector after moisture and dust are removed by traps. The calibration factor is determined using standards approximating the material to be analyzed. 

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