Sampling and Online Analysis of Alkalis in Thermal Process Gases with a Novel Surface Ionization Detector

Abstract

When using biomass or waste as a feedstock for power production, alkalis are a major concern because of their negative effects on equipment. To investigate the release behavior of alkalis and the effectiveness of countermeasures, it is indispensable to quantify alkali emissions with a high time resolution (less than 1 min). This paper presents a newly developed alkali detector based on the principle of surface ionization. The detector includes a number of improvements compared to previous designs that enable a reproducible measurement of alkalis in heavily tar-and particle-laden product gases. Our redesigned alkali detector has demonstrated high sensitivity and improved characteristics for making measurements of tar-and particle-laden process gases. Using an ultrasonic nebulizer as a source for alkali aerosols, we could conduct a calibration of the alkali detector over 4 orders of magnitude. In combination with a dilution setup and a sampling lance, we could take online measurements of gasifier producer gas with a high degree of reproducibility and a high time resolution of 1 s. The measurements of product gas have proven the feasibility of using the detector for field measurements.

Online elemental analysis of process gases with ICP-OES: A case study on waste wood combustion

“…The nebulizing efficiency is measured as mass flow output of analyte per mass flow input of the analyte. For the parameter settings of the USN used in this study an efficiency of 10% has been determined (Wellinger et al, 2011). The analysis of peaks using a background correction that automatically corrects for changes in the level of background noise (Poole et al, 2005).…”

“…The gaseous particles that enter the condensation interface are limited in their growth by rapid quench with cold argon gas in excess, which generates aerosols suitable to transportation through sampling lines. For a more detailed description of the gas quench system see Wellinger et al, 2011.…”

“…The time lag for this method depends on the length of the sampling line, which is determined by the nearest placement of the mobile spectrometer to the sampling location (see also Section 2.3.1). A similar sampling technique has been documented elsewhere (Kowalski et al, 2011;Wellinger et al, 2011). For the field measurements the calibration has been conducted with standards based on the same water-solvent mixture as used for the laboratory measurements.…”

“…Therefore detection of alkalis in flue gases has a potential to be used as a proxy variable for heavy metal emissions. In this context inexpensive online methods like surface ionization (Wellinger et al, 2011) that enable a monitoring of alkali emissions could be of value.…”

Development and application of a rapid sampling technique for identification and quantification of compounds in high temperature process gas streams produced from biomass gasification and pyrolysis

“…Pressure reduction, gas dilution, or some other means to reduce the dew point of tar compounds is generally required to avoid analyte condensation prior to reaching the analytical device [22,24,25]. One recently developed technique immediately quenches the heated slipstream with an alcohol to form a biphasic mixture of analytes: a non-condensable gas stream free of particulates and heavy tars that can be analyzed by micro-GC, and a liquid phase that can be analyzed using on-line density measurements for water concentration and UV-vis spectroscopy to provide real time tar concentration [22,25].…”