Influence of the Dilution System and Electrical Low Pressure Impactor Performance on Particulate Emission Measurements from a Medium-scale Biomass Boiler

Abstract

The accurate monitoring of particulate emissions from medium-scale, decentralized biomass combustion units is a major challenge for the deployment of this technology in the framework of the current energy transition. More specifically, the experimental characterization of the size of the emitted particles, i.e., using impactors, is still subject to discussions about the impact of the methodology on the measurement results. To meet these challenges, particulate emissions from a mediumscale biomass boiler (4.5 MW th ) were measured with the Electrical Low Pressure Impactor (ELPI+) using two different dilution systems-one containing a single stage and the other, dual stages-to examine the effect of dilution and the performance of the ELPI+. No statistically significant correlation was found with either system between the dilution ratio (DR) and the total particle number concentration, N tot , or between the DR and the mass concentration, m tot . However, a significant positive correlation was observed with both systems between the DR and the concentration of particles with a diameter, D p , below 0.01 µm due to measurement artefacts. With the one-stage dilution system, the condensation appeared to be enhanced when the DR was reduced. When the ELPI+ impactor was not overloaded, the number concentrations of the N <0.01 and N 0.01-0.1 size fractions decreased over time due to the premature measurement of particles. However, when the impactor was overloaded, the N <0.01 concentration was overestimated, whereas the N 0.01-0.1 and N 0.1-1 concentrations were underestimated, due to the change in the cut-off diameter.

Particulate matter emission reduction in small- and medium-scale biomass boilers equipped with flue gas condensers: Field measurements

“…The purpose of the two-stage dilution system is to minimize modifications of the particle size distribution by first diluting the flue gas sample with heated air to lower the vapour pressure of volatile species, and then decreasing the temperature by diluting at ambient temperature. A more thorough description of the two-stage dilution system can be found elsewhere [15]. The sampling was not performed isokinetic since the majority of the particles are smaller than 1 µm and thus the particles can follow the gas streamlines due their negligible inertia [17].…”

“…Medium-scale (0.5 -50 MW th ) and large-scale (> 50 MW th ) biomass boilers are often equipped with technologies to reduce particulate emissions, such as (multi-)cyclones, baghouse filters and electrostatic precipitators (ESP) [9][10][11][12][13][14][15]. Baghouse filters have a collection efficiency that can exceed 99% both in mass and number, but this can decrease for particles smaller than 1 µm [14][15][16]. Small particles are mainly captured by diffusion while large particles are mainly collected by interception and inertial impaction [17].…”

Characteristics of Chemical Composition and Particle Size Distribution from Real Coal-fired Circulating Fluidised Bed (CFB) Boiler

“…Carbonaceous aerosols, including organic carbon (OC), and elemental carbon (EC), are ubiquitous species in the atmosphere. OC is derived from the complete combustion of coal and secondary transformation (Saud et al, 2013;Cornette et al, 2020), whereas EC is mainly produced by incomplete combustion of coal (Masiello, 2004;Peng et al, 2018). The OC and EC from coal-fired coal has been reported (Ma et al, 2016).…”

Waste to Energy: Air Pollutant Emissions from the Steam Boilers Using Recycled Waste Wood

“…In order to reduce particulate matter (PM) emissions, biomass boilers are equipped with air pollution control devices (such as cyclones or multi-cyclones, fabric filters, scrubbers, and electrostatic precipitators) to reduce the particulate matter emission. (Strand et al, 2002;Pagels et al, 2003;Wierzbicka et al, 2005;Lim et al, 2015;Bianchini et al, 2016;Nussbaumer et al, 2016;Mertens et al, 2020;Cornette et al, 2020). These boilers produce small fluctuations in NOx emissions and have low DeNOx efficiency.…”