Developmental Study of Soot-Oxidation Catalysts for Fireplaces: The Effect of Binder and Preparation Techniques on Catalyst Texture and Activity

Efficiency of Emission Reduction Technologies for Residential Biomass Combustion Appliances: Electrostatic Precipitator and Catalyst

Residential biomass combustion has been pointed out as one of the largest sources of atmospheric pollutants. Rising awareness of the environmental effects of residential biomass combustion emissions boosted the development of different emission reduction devices that are currently available on the market for small-scale appliances. However, detailed studies on the efficiency of these devices in different combustion systems available in Southern European countries are lacking. In this study, two pollution control devices (catalytic converter and electrostatic precipitator) were tested in two different combustion systems (batch mode operated woodstove and automatically fed pellet stove) in order to assess the emission reduction potential of the devices. Pine firewood was used to fuel the woodstove. One commercial brand of pellets and an agricultural fuel (olive pit) were taken for the experiments in the pellet stove. While the efficiency of the electrostatic precipitator in reducing PM10 was only recorded for woodstove emissions (29%), the effect of the catalyst in decreasing gaseous emissions was only visible when applied to the pellet stove flue gas. For wood pellet combustion, reductions of CO and TOC emissions were in the range of 60–62% and 74–77%, respectively. For olive pit combustion, a lower decrease of 59–60% and 64% in CO and TOC emissions, respectively, was recorded.

Selective Deposition of Candle Soot on a Cellulose Membrane for Efficient Solar Evaporation

Owing to their natural abundance, seawater together with sunlight has a potential to meet the global challenges in terms of water scarcity and energy crisis. Herein, we demonstrate a solar vapor generator composed of an inner flame candle soot (IFCS) deposited on a cellulose filter paper (FP) prepared by a simple two-step process. The resultant IFCS/FP device exhibits a high photothermal conversion ability owing to the broadband solar absorption of the IFCS layer along with the multiple scattering of the incoming sunlight in the porous microstructure of the cellulose FP. Additionally, the low thermal conductivity of the IFCS effectively localizes the photothermally generated heat at the IFCS/FP surface, thereby significantly suppressing the conduction heat losses to the underlying bulk water. Meanwhile, the capillary action of the FP supplies an adequate amount of water to the heated surface for accelerating the evaporation process. Benefitting from the synergistic effect of these characteristics, the IFCS/FP achieves high evaporation rates of ∼1.16 and ∼4.09 kg m^-2 h^-1 and their corresponding efficiencies of ∼75.1 and 90.9% under one and three sun illumination, respectively. Moreover, the IFCS/FP device presents an excellent longevity owing to the persistent performance over 15 repeated cycles under one and three sun illumination. Hence, the facile fabrication, fine mechanical strength, desalination, and the salt-resistance ability of our IFCS/FP make it a suitable candidate for practical applications.

Na2WO4/Mn/SiO2 Catalyst Pellets for Upgrading H2S-Containing Biogas via the Oxidative Coupling of Methane

Biogas is a promising renewable energy source; however, it needs to be upgraded to increase its low calorific value. In this study, oxidative coupling of methane (OCM) was selected to convert it to a higher fuel standard. Prior to establishing the scaled-up OCM process, the effect of organic/inorganic binders on catalytic activity was examined. The selection of the binders and composition of the catalyst pellet influenced the pore structure, fracture strength, and catalytic activity of the catalyst pellets. It was also observed that the O2 supply from the inorganic binder is a key factor in determining catalytic activity, based on which the composition of the catalyst pellets was optimized. The higher heating value increased from 39.9 (CH4, Wobbe index = 53.5 MJ/Nm3) to 41.0 MJ/Nm3 (OCM product mixture, Wobbe index = 54.2 MJ/Nm3), achieving the fuel standard prescribed in many countries (Wobbe index = 45.5–55.0 MJ/Nm3). The reaction parameters (temperature, gas hourly space velocity, size of the reaction system, and the CH4/O2 ratio) were also optimized, followed by a sensitivity analysis. Furthermore, the catalyst was stable for a long-term (100 h) operation under the optimized conditions.

High Temperature Electrical Charger to Reduce Particulate Emissions from Small Biomass-Fired Boilers

New particulate matter (PM) filtering technologies are needed to meet the emission regulations for small combustion appliances. In this work, we investigate the performance of a novel electrical particle filtration system, the single needle shielded corona charger (SCC), which offers an advantageous solution for PM control in boilers by enhancing particulate deposition within existing boiler sections. Experiments under different operating conditions of a wood-fired boiler were performed, wherein the SCC was installed upstream of either a condensing heat exchanger (CHX) or a cyclone. PM reduction was found to be strongly affected by the SCC temperature and the following collection surface area, and reached its highest reduction efficiency of >90% at the temperature range of 400–500 °C when operating in combination with a CHX. The SCC–cyclone combination was less efficient, providing a 27% PM reduction, as a result of the low surface area and residence time in the cyclone. These results indicate that the SCC can feasibly provide particle filtration when combined with a CHX, wet scrubber, or a cyclone to meet the new emission regulation requirements. The system is best suited for small-scale boilers but can be scaled up to larger boilers by increasing the number of corona chargers.