Search

This study investigates the performance of DC corona discharge electrostatic precipitators (ESPs) for NO conversion to increase DeNOx technologies' efficiency for small-scale biomass combustion systems. Experiments were conducted using a 5 kW automatic wood pellet domestic heat source with combustion gas treated in a specially designed ESP operated in both positive and negative corona modes, resulting in a reduction in NO concentrations from 130 mg/m3 to 27/29 mg/m3 for positive/negative polarities (at 0 °C and 101.3 kPa). NO conversion efficiency was evaluated across a range of specific input energies (SIEs) from 0 to 50 J/L. The results demonstrate that DC corona ESPs can achieve up to 78% NO reduction, with positive corona demonstrating a greater energy efficiency, requiring a lower SIE (35 J/L) compared to the negative corona mode (48 J/L). A detailed analysis of reaction pathways revealed distinct conversion mechanisms between the two modes. In positive corona, dispersed active species distribution led to more uniform NO conversion, while negative corona exhibited concentrated reaction zones with about 20% higher ozone production. The reactions involving O and OH radicals were more important in positive corona, whereas ozone-mediated oxidation dominated in negative corona. The research results demonstrate that ESP technology with DC corona offers a promising, energy-efficient solution for NOx control in small-scale combustion systems. [ABSTRACT FROM AUTHOR]

An electrostatic precipitator (ESP) is an efficient device for removing fly ash from small-scale solid-fuel combustion. Under corona discharge, a gaseous medium becomes ionised, and particles become charged by colliding with ions. An electric field forces the movement of charged particles to remove gases and induces the movement of generated ions, causing secondary electrohydrodynamic flow. Thus, particle charge, the presence of neighbouring particles, an ESP electric field, and gas flow turbulence can enhance particle coagulation. Therefore, the ultrafine particle concentration in an ESP is expected to evolve under electrostatic removal and enhanced coagulation. In the present study, the contribution of coagulation is explored and confirmed using experimental measurements performed on an ESP used to control emissions from a 160-kW boiler with biomass combustion. The ESP was operated under several modes to obtain different coagulation conditions. Changes in particle concentrations were measured simultaneously using two techniques. It was found that coagulation could be responsible for up to 5% of the total removal efficiency, depending on the ESP operation parameters. The present study can promote a deeper understanding of the processes involved in electrostatic precipitation, and the obtained results can be useful for practical ESP engineering.

Electrostatic precipitators (ESPs) have shown promise in reducing particulate matter (PM) emissions, but their potential for simultaneous NOx reduction in small-scale combustion systems remains underexplored. This study focuses on using non-thermal plasma generated in a corona discharge to reduce PM and NOx emissions from small-scale combustion. ESP was specifically designed for a commercially available 15 kW boiler with wood pellet combustion and used with both positive and negative discharge polarity to control emissions without any chemical additives. ESP performance was evaluated across a range of specific input energies (SIE) in terms of particle mass and number concentrations and NOx concentrations obtained by continuous gas analysis. ESP ensured the reduction in PM concentrations from 48 mg/m3 to the magnitude of PM content in the ambient air. The highest precipitation efficiency was observed for particles in the 20–200 nm range. Concurrently, NOx emissions were reduced by up to 78%, from 178 mg/m3 to 39 mg/m3. These results were achieved at specific input energies of 36 for positive and 48 J/L for negative corona, which is significantly lower than those reported for many existing separate PM and NOx control systems. This study demonstrates the potential of ESPs as a compact, energy-efficient solution for simultaneous PM and NOx removal in small-scale combustion systems, offering promising implications for improving air pollution control technologies for small-scale combustion systems. [ABSTRACT FROM AUTHOR]

This paper investigates the removal efficiency of a honeycomb electrostatic precipitator (ESP) applied to control particulate matter (PM) emissions from a small-scale boiler with combustion lignite and hard coal. The specifics of the precipitation of emissions from small-scale boilers are discussed, and the design principles for relevant ESPs are presented and used. The ion-induced nucleation of sulfuric acid occurred, causing the drastic penetration of 19 nm particles through the ESP. Despite this, the overall collection efficiency was sufficient to meet the EU's Ecodesign Directive requirements. Back corona was not detected. The optimal ESP performance is defined with further parameters: a current density of 0.5 mA/m2 at an electric field strength of about 2.7 × 105 V/m; a minimal specific collecting area of ESP (SCA) of 60 m2/(m3/s); and Nt-product of 4.5 × 1014 s/m3. Such parameters of ESPs should ensure adequate PM emissions control for any type of boiler with similar emissions characteristics. The composition of collected fly ash particles was analysed, and a method for fly ash utilisation was proposed. This research may be helpful for designing ESPs to control PM emissions for small-scale units with fossil fuel combustion. [ABSTRACT FROM AUTHOR]

• Honeycomb ESP was designed to control NO x and PM emissions from 15-kW boiler. • ESP reduced NO x by 78 % while PM were reduced to a magnitude of ambient air. • ESP removal efficiency was studied in terms of ESP technological parameters. This work investigates the potential of corona discharge to control particulate matter and NO x emissions from small-scale biomass combustion. The electrostatic precipitator (ESP) was designed and used to suppress emissions from a 15-kW heating unit. The ESP was operated at different power modes at both polarities and demonstrated the capability to reduce NO x emissions with a removal efficiency of 78 % while PM concentration was reduced to a magnitude of particle content in ambient air. The efficiency of ESP was evaluated considering the technological parameters, namely the reduced electric field, Nt-product, and specific input energy. The growth in NO x abatement was observed when the energy input exceeded 1 J/L for both polarities and Nt-product exceeded 4.5 × 108 s/cm3/1 × 109 s/cm3 for negative/positive corona. The results of this work may contribute to understanding the processes in corona discharge and optimising corona discharge systems for various applications. [ABSTRACT FROM AUTHOR]

The main technical characteristics of the electrostatic precipitation process, which can be applied to ESPs of any type, are the electric field strength and the Nt-product (the product of ion concentration and the residence time of the particle in the electric field). The present study investigates the impact of these characteristics on the efficiency of ESP in suppressing particulate matter (PM) emissions from a 160-kW boiler with wood pellet combustion. PM concentration was reduced to 2 mg/m3, representing a removal efficiency of ∼95%. The SMPS continuously recorded changes in the particle concentration. The growth of removal efficiency was not uniform with enhancing ESP parameters. The study shows that Nt-product demonstrated a prior effect on removal efficiency until growing up to the value of 4.5 × 1014 s/m3. Exceeding this value of Nt-product had no significant impact on the cleaning efficiency, but the electric field became prior. The results of the present research can help to optimise the ESP dimension parameters, therefore they can be used in the practical engineering of any new ESP to collect ultrafine particles and promote the implementation of ESPs for small-scale boilers for global pollution. • Honeycomb ESP was used to control emissions from small-scale 160- kW boiler. • ESP reduced PM concentrations to 2 mg/m3. • ESP efficiency was studied in terms of Nt-product and electric field strength. • The specific energy consumption of electrostatic precipitation was studied. [ABSTRACT FROM AUTHOR]

• The electrostatic suppression of ultrafine PM emission is researched. • Five models were tested to predict the ESP efficiency for ultrafine particles. • The optimal model is selected and confirmed by practical measurement. • The impact of ESP technological parameters on the removal efficiency was studied. This work investigates the efficiency of electrostatic precipitation for ultrafine particulate matter (PM) emissions from small-scale heating units with solid fuel combustion. The removal efficiency for particles smaller than 50 nm was of research interest. The effect of electric parameters and operation conditions of precipitation was studied. Some appropriate models considering the impact of turbulent diffusion have been used to predict the efficiency of a specific electrostatic precipitator (ESP). The electric field in studied ESP was intensified from 1.8 × 105 V/m to 2.8 × 105 V/m, and Nt-product (the product of number concentration of ions and charging time) was varied from 1.1 × 1014 ions × s/m3 to 7.1 × 1014 ions × s/m3. The prediction correctness is considered by comparing to experimental measurements carried out at the ESP used to control emissions from a 160-kW boiler. The changes in number particle concentration were measured with two technics simultaneously. It was found that an increase in field strength in mentioned range affects the ESP removal efficiency strongly and evenly. In contrast, the effect of growing Nt-product has a limit on precipitating efficiency of 4 × 1014 ions × s/m3. The results of the present work could be helpful in the practical engineering of electrostatic precipitation. [ABSTRACT FROM AUTHOR]

• Particles from small-scale combustion require a suitable charging model. • Some charging models are used to predict the ESP efficiency. • The optimal charging model is selected and confirmed by practical measurement. • The selected charging model is useful for practical engineering. The present study investigates methods for predicting the efficiency of electrostatic precipitation for controlling particulate matter (PM) emissions from small-scale heating units, namely, solid fuel combustion boilers with heating power output less than 300 kW. The prediction correctness for particle precipitation efficiency is considered on the basis of the accuracy of the estimated charge on a particle. Prediction of the specific PM from small-scale boilers requires a relevant model of specified particle charging. Three appropriate particle charge models have been used to predict the efficiency of a specific electrostatic precipitator (ESP). The prediction results are compared on the basis of experimental measurements taken from an ESP used to control the emissions from a 160-kW boiler. The measurements are based on different physical principles and are undertaken simultaneously. The optimal method for particle charge evaluation is determined to allow the practical modeling of an ESP to control the PM emissions from small-scale units with solid fuel combustion. [ABSTRACT FROM AUTHOR]

• Particles from small-scale combustion require a suitable charging model. • Sole field or diffusion charging mechanisms are unsuitable for such particles. • The summation of these mechanisms leads to inaccurate prediction of ESP efficiency. • Some available charging models are analysed, and the most suitable are selected. Small-scale heating units with solid fuels combustion cause a global atmospheric pollution by fine particles. Electrostatic precipitation is suggested as a method of controlling fine particle emissions. The correctness of modelling for precipitation efficiency is defined by the accuracy of the evaluation of particle charges. This work focuses on reviewing the existing particle charging theories in terms of their suitability for practical engineering for the electrostatic precipitation of fly ash particles from the flue gases of small-scale boilers. Charging calculation methods were rated as a function of the particle sizes, external discharge electric field strength, and ion density-time product and compared to published experimental data. Two particle charge rating methods were identified to be suitable for the electrostatic precipitation of such particles. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the use of an electrostatic precipitator (ESP) for controlling the emissions of particulate matter (PM) from small-scale heating units, specifically boilers that combust solid fuel with a heating power output of <300 kW. The equilibrium between the required precipitation efficiency and the structural parameters of the ESP in combination with the applied voltage were determined. This study presents a method of optimising the applied voltage alongside the specific ESP structural parameters while retaining the required precipitation efficiency. The ESP was designed, optimised, and integrated into a 15-kW boiler without expanding its volume. The theoretically predicted voltages and resulting ESP efficiency (20 kV and 85% respectively) were verified by measuring the reduction in the particle number concentration. The measurements were based on different principles and simultaneously sampled. The PM concentrations were reduced below 40 mg/m3 (0 °C, 101.3 kPa; at reference O 2 = 10 % vol.) by nominal and reducing the heat power, which allowed the boiler to meet the requirements of the EU's Ecodesign Directive. The presented optimisation method can be used in the practical engineering of any type of ESP. • An ESP was encased in a 15-kW automatic boiler's body as an inseparable part. • The boiler thereby met the EU's Ecodesign Directive emissions requirements. • An optimisation method was proposed to ensure the ESP's required efficiency. • Two-type numeric concentration measurements verified this method. • The method is useful for assessing the structural potential of any ESP. [ABSTRACT FROM AUTHOR]