Alkali Monitoring of Industrial Process Gas by Surface Ionization─Calibration, Assessment, and Comparison to In Situ Laser Diagnostics

Abstract

In this work, we present rigorous calibration and assessment of a surface ionization detector (SID) for alkali monitoring in industrial process gases and compare it to an in situ laser diagnostic method called collinear photofragmentation and atomic absorption spectroscopy (CPFAAS). The side-by-side comparison of the time-resolved alkali concentration was performed in a technical-scale gas burner seeded with selected alkali salts, corresponding to alkali molar fractions of 10–100 ppm in the flue gas. The SID operates at room temperature and relies on extraction, dilution, and conditioning of the sample gas, whereas CPFAAS provides in situ molecular data. During KCl addition, the instruments were in good agreement: 80.1 ppm (SID) and 88.5 ppm (CPFAAS). In addition to the field measurements, internal validation of SID performance parameters (flow, electric field strength, and filament temperature) and external parameters (particle size and salt composition) was performed. The difference in sensitivity toward different alkali salts was found to be considerable, which limits the quantitative assessment for a sample gas of unknown composition. The results demonstrate the capability and limitations of the SID and show that a SID can satisfactory monitor KCl levels in a process gas over several days of continuous measurements. However, for heterogeneous fuels with deficient characterization of the gas composition, the obtained SID signal is difficult to interpret without supportive diagnostics. The generic ability of the SID to detect Na and K in both gas and particle phases makes it a valuable complement to alkali diagnostics, such as spectroscopic techniques.

Effects of Temperature, Operation Mode, and Steam Concentration on Alkali Release in Chemical Looping Conversion of Biomass─Experimental Investigation in a 10 kWth Pilot

“…Henceforth, the discussion focuses on K as the key alkali element of concern, and the terms “alkali” and “potassium/K” are used interchangeably. SID response to predominant K species that occur in combustion systems was explored in a recent study by Gall et al 39 and was further validated during pre-campaign calibration of the SID instrument. The approximate signal response factors are summarized in Table 5 .…”

“…The random error of the SID instrument was measured to be ±1.9% in a previous study. 39 A systematic error of ±4% that is associated with the maximum instrument drift that occurs within a day of operation was estimated from comparison of the pre- and post-operation calibrations. From the combination of these two errors, the overall SID measurement uncertainty for days 4–6 of operation was estimated to be ±6%.…”

“…The exact impact of losses when sampling high-temperature combustion aerosols is difficult to determine and take into account 40 but were shown to be low in a recent campaign using the sampling system implemented in the current study. 39 As such, no corrections were implemented to account for sampling losses.…”

Recirculation of NOx and SOx Scrubber Effluent to an Industrial Grate Fired MSW Boiler─Influence on Combustion Performance, Deposition Behavior, and Flue Gas Composition

“…However, alkali sulfates may form alkali chlorides in the presence of chlorine by the reversed sulfation reaction. The chemistry is described in , and experimentally shown in a recent injection study …”

“…The chemistry is described in 32,33 and experimentally shown in a recent injection study. 34 The increased level of sulfur seen in the depositions is benign from corrosion aspects if chloride is substituted by sulfates. 10,14 Further tests with injections at different temperatures and compositions would be interesting to explore as options to recirculate sulfur to the scrubber process and reduce the chemical costs for the gas scrubber.…”