Improvement of Efficiency and Emissions from Wood Log Stoves by Retrofit Solutions

Abstract

Biomass combustion systems contribute to the use of renewables, whereby wood log stoves have a high share for domestic heating. Promotion of renewables and efforts for lower air pollution require an improvement of technology. Short-term effects can be achieved with the help of various retrofit systems. Apart from a survey of available systems, two measurements have been analyzed: additional heat exchange and emission reduction by catalysis. During normal operation of three low-cost stoves, high levels of carbon monoxide (CO), volatile organic compounds (VOCs), and particulate matter (PM) concentration have been observed, having a major influence of the operator's behavior. The best case scenario with the retrofit systems resulted in a significant efficiency increase and as well a reduction of CO, VOCs, and PM.

Characterization and integration of oxidation catalysts at small-scale biomass combustion furnaces

“…However, there is only rare documentation of the long-term stability and no comprehensive analysation of the behaviour from the used catalysts during the manifold conditions occurring in stoves and boilers. The major part of described research in literature deals with the effect of catalysts at single-room heaters [9,[13][14][15][16][17][18][19][20]. Only some results have been presented from boilers with catalysts [21][22][23].…”

“…Even though the catalytic oxidation of carbon monoxide can already take place at room temperature [24], the so far at biomass combustion systems applied catalysts show a considerable reduction at temperatures above 250-300 °C [14,20,23]. Beside a preferably low reaction temperature the catalysts in small-scale stoves and boilers also have to feature a wide range and frequent changes in temperature.…”

“…Beside a preferably low reaction temperature the catalysts in small-scale stoves and boilers also have to feature a wide range and frequent changes in temperature. If the catalyst is applied downstream of a stove, temperatures between 250 and 500 °C can be present [14,16,20]. When the catalyst position is inside the furnace, the temperature can rise up to 750-850 °C [9,17,22], dependent on the distance to the flame.…”

“…The often applied noble metal catalysts based on platinum and palladium provide a high activity for CO oxidation. With a good dimensioned and active catalyst reduction rates over 90 % can be realized [19,20,21]. Nevertheless, very high pollutant concentrations [13,18], catalyst bypassing due to leakages [15] or insufficient process temperatures [23] can restrict the performance of the applied catalysts.…”

“…This is especially critical when alternative non-wood fuels with a higher particle formation are combusted [23]. Nevertheless, several described research results with single-room heaters have shown that a reduction of 30 -50 % PM is possible [13,19,20]. An important issue for the use of catalysts in practical operation is their long-term stability.…”