Range-resolved detection of potassium chloride using picosecond differential absorption light detection and ranging.

A laser diagnostic concept for measurement of potassium chloride (KCl) and potentially other alkali compounds in large-scale boilers and furnaces of limited optical access is presented. Single-ended, range-resolved, quantitative detection of KCl is achieved by differential absorption light detection and ranging (DIAL) based on picosecond laser pulses. Picosecond DIAL results have been compared experimentally with line-of-sight measurements using a commercial instrument, the in situ alkali chloride monitor (IACM), utilizing differential optical absorption spectroscopy. For centimeter-scale range resolution and a collection distance of 2.5 m, picosecond DIAL allowed for measurement of KCl concentrations around 130 ppm at 1200 K, in good agreement with values obtained by IACM. The DIAL data indicate a KCl detection limit of around 30 ppm for the present experimental conditions. In addition, a double-pulse DIAL setup has been developed and demonstrated for measurements under dynamic conditions with strong Mie scattering. The picosecond DIAL results are discussed and related to possible implementations of the method for measurements in industrial environments.

The effect of isosaccharinic acid (ISA) on the mobilization of metals in municipal solid waste incineration (MSWI) dry scrubber residue.

Co-landfilling of incineration ash and cellulose might facilitate the alkaline degradation of cellulose. A major degradation product is isosaccharinic acid (ISA), a complexing agent for metals. The impact of ISA on the mobility of Pb, Zn, Cr, Cu and Cd from a municipal solid waste incineration dry scrubber residue was studied at laboratory using a reduced 2(5-1) factorial design. Factors investigated were the amount of calcium isosaccharinate (Ca(ISA)(2)), L/S ratio, temperature, contact time and type of atmosphere (N(2), air, O(2)). The effects of pH and Ca(ISA)(2) as well as other factors on the leaching of metals were quantified and modelled using multiple linear regression (alpha=0.05). Cd was excluded from the study since the concentrations were below the detection limit. The presence of Ca(ISA)(2) resulted in a higher leaching of Cu indicating complex formation. Ca(ISA)(2) alone had no effect on the leaching of Pb, Zn and Cr. A secondary effect on the mobilization was predicted to occur since Ca(ISA)(2) had a positive effect on the pH and the leaching of Pb, Zn and Cr increased with increasing pH. The leaching of Pb varied from 24 up to 66 wt.% of the total Pb amount (1.74+/-0.02 g(kgTS)(-1)) in the dry scrubber residue. The corresponding interval for Zn (7.29+/-0.07 g(kgTS)(-1)) and Cu (0.50+/-0.02 g(kgTS)(-1)) were 0.5-14 wt.% of Zn and 0.8-70wt.% of Cu. Maximum leaching of Cr (0.23+/-0.03 g(kgTS)(-1)) was 4.0 wt.%. At conditions similar to a compacted and covered landfill (4 degrees C, 7 days, 0 vol.% O(2)) the presence of ISA can increase the leaching of Cu from 2 to 46 wt.% if the amount of cellulose-based waste increases 20 times, from the ratio 1:100 to 1:5. As well, the leaching of Pb, Zn, and Cr can increase from 32 to 54 wt.% (Pb), 0.8-8.0 wt.% (Zn), and 0.5 to 4.0 wt.% (Cr) depending on the amount of cellulose and L/S ratio and pH value. Therefore, a risk (alpha=0.05) exists that higher amounts of metals are leached from landfills where cellulose-containing waste and ash are co-disposed. This corresponds to an additional 29 t of Pb and 17 t of Cu leached annually from a compacted and covered landfill in the north of Sweden.

Principle, calibration, and application of the in situ alkali chloride monitor.

The extended use of biomass for heat and power production has caused increased operational problems with fouling and high-temperature corrosion in boilers. These problems are mainly related to the presence of alkali chlorides (KCl and NaCl) at high concentrations in the flue gas. The in situ alkali chloride monitor (IACM) was developed by Vattenfall Research and Development AB for measuring the alkali chloride concentration in hot flue gases (less than or approximately 650 degrees C). The measurement technique is based on molecular differential absorption spectroscopy in the UV range. Simultaneous measurement of SO(2) concentration is also possible. The measuring range is 1-50 ppm for the sum of KCl and NaCl concentrations and 4-750 ppm for SO(2). This paper describes the principle of the IACM as well as its calibration. Furthermore, an example of its application in an industrial boiler is given.