• Energy Research

Abstract Ashes were prepared by annealing selected types of solid fuels (biomass: corn cobs, sunflower husks, olive pomace, hay pellets and rice husks; coal: lignite and bituminous; and alternative fuel: paper sludge) at different temperatures (550°C, 815°C and 975°C). Based on X-ray fluorescence spectra, the slagging/fouling indexes were used to study the effects of the type of ash and the ashing temperature on the ash fouling and slagging properties. Slagging indexes were compared with the ash fusion temperatures. Ash fusion temperatures were measured by a LECO AF-700. The lowest deformation temperature (below 1000°C) was seen for the ashes prepared from hay pellets and corn cobs. On the other hand, the deformation temperature exceeded 1500°C for ashes prepared from paper sludge, sunflower husks and rice husks. By calculating the different slagging/fouling indexes, all the ashes exhibited slagging/fouling problems of varying degrees.

There are several published studies evaluating the potential of platinum and palladium-based catalysts for real flue gas purification, however, the need to reduce the mass fraction of precious metals and the effect of this process is often neglected. This study aimed to assess the influence of two catalysts on the overall flue gas composition formed during combustion in a pellet burner operated to mimic the operation of a real wood log stove. Commercial Pt–Pd-based (CAT A) and Pt-based (CAT B) catalysts with innovative sol-gel coatings and a reduced amount of active substance were used. The CO, OGC and PM conversion rates of CAT A reached 87.8%, 37.0% and 25.2%, while the removal efficiency of CAT B reached 85.8%, 37.8% and 18.8%, respectively. The decrease of organic carbon by the catalysts ranged from 28% to 49% in the case of CAT A and from 13% to 60% in the case of Cat B. The concentrations of PAHs emitted seem to indicate a less carcinogenic composition when catalytic converters are used than without these flue gas treatment units. The preparation of this article was co-financed by The Technology Agency of the Czech Republic within the Sigma DC2 Programme, project: “TQ03000511 - Innovative catalysts for household stationary heating units”. This work was also co-financed by the Recovery and Resilience Facility within the National Centre for Energy II, reg. no. TN02000025. The financial support to CESAM by FCT/MCTES (UIDP/50017/2020+UIDB/50017/2020+ LA/P/0094/2020), through national funds, is acknowledged. The catalysts were designed, prepared and tested in cooperation with Whitebeam d. o.o. company. Departamento de Geología

Bioethanol burners are significantly expanding devices in Europe, still considered preferably as the design element while its possible importance in the energy system of the household used to be neglected. The aim of this study was to determine the operating techno-environmental parameters as the heat output and the flue gas composition of the bioethanol fireplace with vortex flame. The measurement methodology was based on actual valid standard EN 16647 Fireplaces for Liquid Fuel. In general, three ethanol-based fuels were tested in combination with one bioethanol burner equipped with different regulation rings changing burner opening area. The average reached heat energy output ranged between 3.97 and 2.22 kW with maximal burner opening area (without the usage of regulation rings) for different fuels. By usage of the regulation rings, the heat energy output was reduced to 35 – 40 % of the nominal average heat output. Simultaneously the time of the burning of one fuel dose can be increased by regulation ring usage up to 195 % of the combustion time without the regulation ring. By placing the regulation rings on the burner bowl opening area, the flue gas composition was affected positively in terms of CO and negatively in terms of NOx.

Five different domestic heating boilers (automatic, over-fire, with down-draft combustion and gasification) and three types of fuel (lignite, wood and mixed fuel) were examined in 25 combustion tests and correlated with the emissions of particulate matter (PM), carbon monoxide (CO), total organic carbon (TOC) and 12 polycyclic aromatic hydrocarbons (PAHs with MW = 178-278 g/mol) focusing on particle phase. However, the distribution of 12 PAHs in gas phase was considered as well due to the presence mainly of lighter PAHs in gas phase. The PAHs, as well as the CO and TOC, are the indicators of incomplete combustion, and in this study PAH emission increased significantly with increasing emissions of CO and TOC. The PAHs were mainly detected on PM2.5, their contents were increasing linearly with increasing PM2.5 emissions. The highest emission factors of PAHs were measured for boilers of old construction, such as over-fire boiler (5.8-929 mg/kg) and boiler with down-draft combustion (3.1-54.1 mg/kg). Modern types of boilers produced much lower emissions of PAHs, in particular, automatic boiler (0.3-3.3 mg/kg) and gasification boilers (0.2-6.7 mg/kg). In general, the inefficient combustion at reduced output of boilers generated 1.4-17.7 times more emissions of PAHs than the combustion at nominal output of boilers. It is recommended to operate boilers at nominal output with sufficient air supply and to use the proper fuel to minimise PAHs emissions from domestic heating appliances.

The aim of this study was to simulate a banned but widely spread practice of co-combustion of plastic with wood in a small residential boiler and to quantify its impact on emissions of gaseous pollutants, particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and 1,3,5-triphenylbenzene (135TPB), a new tracer of polyethylene plastic combustion. Supermarket polyethylene shopping bags (PE) and polyethylene terephthalate bottles (PET) were burnt as supplementary fuels with beech logs (BL) in an old-type 20 kW over-fire boiler both at a nominal and reduced heat output. An impact of co-combustion was more pronounced at the nominal heat output: an increase in emissions of PM, total organic carbon (TOC), toxic equivalent (TEQ) of 7 carcinogenic PAHs (c-PAHs) and a higher ratio of c-PAHs TEQ in particulate phase was observed during co-combustion of both plastics. 135TPB was found in emissions from both plastics both at a nominal and reduced output. In contrast to findings reported in the literature, 135TPB was a dominant compound detected by mass spectrometry on m/z 306 exclusively in emissions from co-combustion of PE. Surprisingly, six other even more abundant compounds of unknown identity were found on this m/z in emissions from co-combustion of PET. One of these unknown compounds was identified as p-quaterphenyl (pQ). Principal component analysis revealed strong correlation among 135TPB, pQ and five unknown compounds. pQ seems to be suitable tracers of polyethylene terephthalate plastic co-combustion, while 135TPB proved its suitability to be an all-purpose tracer of polyethylene plastics combustion.

Abstract In this study, two honeycomb catalysts with palladium and platina-palladium as active elements were used for an oxidation of products of incomplete combustion such as carbon monoxide (CO) and propane (C3H8) contained in flue gas produced by a small-scale stove. Catalysts were installed into the flue gas duct right behind the flue gas outlet of the wood log, and pellet stove. During the tests, the conversion rates of unburned pollutants were observed according to volume fraction of oxygen in the flue gas, space velocity of flue gas, temperature of flue gas at the catalysts inlet, and mass concentration of oxidized pollutants at the catalysts inlet. The CO conversion rates ranged between 37% and 95.4% (69% in average) in case of Cat A and 51.4% and 99.9% (96% in average) in case of Cat B. In terms of C3H8 conversion rate, Cat B proved higher effectiveness (25% in average), than Cat A (4% in average). The most significant parameters were determined. The significant influence of combustion phase on C3H8 conversion rate was observed in case of manually loaded stove.

The study describes gaseous and particulate emissions from the combustion of two types of coal (hard and brown) in three types of boilers (one modern-type and two old-type boilers) used for residential heating. The importance of the heat outputs (nominal and two reduced outputs) for the emission of pollutants was also studied. Three outputs (95-108%, 58-73% and 26-50%) covered the expected operation of these boilers in real households under different outdoor air temperatures in the winter. Gaseous components (NOx, SO2, CO, CO2, OGC) and particulate organic compounds (n-alkanes, polycyclic aromatic hydrocarbons, hopanes) were determined in the emissions. In general, the emission factors (EFs) of the products of incomplete combustion were higher from the combustion of coal in old-type boilers than from that in the modern-type boilers. The EFs of particulate matter varied between 11.6 and 17.0 g kg-1 (hard coal, the oldest-type boiler), and 0.290 and 0.544 g kg-1 (brown coal, the modern-type boiler). The trends between the EFs of particulate organic compounds and the outputs of boilers were observed only with the automatic boiler (modern-type boiler). Similar trends for old-type boilers were not observed, probably due to the high instability of the combustion process as a result of the old construction of these boilers. Diagnostic ratios of the PAHs and the homohopane index, used for source apportionment of particulate matter in ambient air, were calculated. While the calculated homohopane indexes were similar to those reported in the literature, the calculated diagnostic ratios for PAHs related to coal combustion were different.

The awareness of environmental pollution has been continuously growing in recent decades and is currently reaching its maximum. Europe and most developed countries are determined to ensure safe breathing air for their citizens, and the measures to do so are stricter than ever before. Combustion procedures remain the primary means of producing energy and warmth in Poland. Among the notable constituents of flue gases produced as a result of fuel combustion, solid particles (or particulate matter) hold significant prominence. The paper presents the chemical characterisation of particulate matter emitted from stationary and automotive emission sources. Stationary emission sources included the combustion process of fossil fuels (soft wood, bituminous coal, ecopea coal, culm) in domestic heating units and the process of combustion of bituminous coal in a power plant. Automotive emission sources included light duty and medium duty vehicles fuelled by diesel. Exhaust toxicity tests were carried out maintaining the real conditions of PM emission. In all field measurements particulate matter was gravimetrically measured and collected on quartz or glass fibre filters. Subsequently, the content of carbonaceous fraction, inorganic ions, and metals and metalloids was analyzed using different analytical techniques. The chemical composition of the particulate matter differed depending on the emission source. With respect to stationary combustion sources, the main factors determining solid particle emission are related primarily to the fuel quality. The duty of vehicles was also a factor that influenced the chemical characterisation of the particulate matter emitted from the engines.