Study of the memory effect of PCDD/F during the combustion of several biomasses in a moving grate boiler.

The objective of this work was to study the influence of temperature on the PCDD/Fs behavior stored in biomass ashes issued from an automatic pilot-scale wood boiler. A mixture of these ashes with a dioxin mass ratio dry based of 5.9 µg kg-1 was used for thermal treatment at temperatures ranging between 200 and 500°C. First tests were carried out in a macro thermogravimetric analysis instrument while a couple of other tests were carried out in a quartz-lined crossed fixed-bed reactor. These treated ashes were afterwards analyzed and their dioxin mass ratio was determined. Results obtained from these both experiments are radically different: ashes treated in macro-TGA contain 18 times more PCDD/Fs than the initial non-treated ashes while those from the reactor have 84% less of PCDD/Fs. Ninety-one percent of stored PCDD/Fs in the initial ashes were eliminated after 1h at 400°C in crossed fixed-bed reactor. Macro-TGA experiments are a representation of what happens during the shutdown and cooling phase of the boiler, some areas reaching temperatures for which the formation of PCDD/Fs is optimal. Without cleaning the boiler, a memory effect on further tests is observed.

Use of biomass ash from different sources and processes in cement.

Substitution of cement clinker with suitable excess materials from other processes is an effective way to reduce CO2 emissions of cement production. Moreover, specific properties of the resulting mortar or concrete can be designed with different clinker replacement materials and their mixing ratios. In this study, bottom and fly ashes from six biomass power plants with different power scales and various flue-gas treatment strategies were admixed to mortars, whose properties (influence of water requirement and final compressive strength) were then assessed in the laboratory by following industrial standard procedures. Results reveal that fly ash from a cyclone of a medium-scale combustor burning Miscanthus straw amended with 2 wt % Ca(OH)2 (to prevent slagging during combustion) turned out to be well suited as a clinker replacement material, even boosting final compressive strength of the mortar. Wood-chip bottom ashes and fly ash from a cyclone exhibited acceptable results, whereas fly ash from electrostatic precipitators (ESPs) and baghouse filters lowered final compressive strength of the mortar when admixed. The scale of the power plant is positively correlated with final compressive strength in the case of ESPs. Cenospheres, typical fly ash particles present in cyclone ash, seem to have a positive effect on water-to-binder ratio and final compressive strength. In contrast, potassium salts, which are most abundant in ash from ESPs and baghouse filters, appear to have a negative influence on these properties. Grinding of the biomass ashes to a typical Portland cement fineness had a positive effect on mortar quality. All fly ashes had high contents of Cd, and baghouse filter ash contained As in amounts about four times the Swiss limit value for cement of 30 ppm; only bottom ash and cyclone ash from Miscanthus exhibited concentrations below respective limit values for all critical trace elements. To assess the immobilization potential of contaminating elements during the cement hardening process, blended mortars were crushed and subjected to multistep leaching, followed by subsequent analysis of the leachates by atomic absorption spectroscopy. Immobilization of Cd by the mortar was particularly effective. Our results indicate that fly ash from wood-chip combustion is most suitable as an amendment to cement when it was trapped by a cyclone rather than by the ESPs or baghouse filters.

Combustion of hydrolysis lignin in a drop tube furnace and subsequent gaseous and particulate emissions.

The aim of the study was to analyze the combustion of hydrolysis lignin in industrial plants which use pulverized combustible and which are characterized by very high heating rates (up to 105 K/min). Pulverized samples of hydrolysis lignin and of spruce bark or spruce trunk for comparison were injected in a drop tube furnace under an oxidative flow (synthetic air) and under an isothermal temperature (between 800 and 1200 °C) in the reaction zone. The gaseous and particulate emissions were analyzed. Ash was collected at the bottom of the drop tube furnace and analyzed. The fly ash were collected in an electrical low-pressure impactor and analyzed. Whatever the sample, the number of particles PM2.5 was sensitive to the temperature and a minimum was observed which is reached at 900 °C for hydrolysis lignin and spruce bark and at 1100 °C for spruce trunk.

Physicochemical and mineralogical characterization of biomass ash from different power plants in the Upper Rhine Region.

Bottom and fly ash samples from six biomass power plants with different power scales and various flue gas treatment strategies were collected and analyzed in regard to their mineralogical composition, and their bulk major and trace element contents, all of which are of concern for regulations on biomass ash for further utilization. Furthermore, individual ash particles were investigated by scanning electron microscopy to characterize their physicochemical microstructures. Thermal behavior of wood-pellet ash, i.e. decomposition processes and mineral transformations during combustion, was indicated by thermogravimetric analysis and X-ray diffraction. Results reveal extensive variation of physicochemical features across the different ash types: wood-chip fly ash from electrostatic precipitators mainly consisted of water-soluble salts, whereas wood-chip fly ash from cyclones contained predominantly cenospheres (hollow spherical fly ash particles) and higher heavy metal concentrations. In addition, the fuel type and admixture had influences on ash compositions; some fuels like Miscanthus straw require a liming agent such as calcium hydroxide to be admixed to prevent fouling, which is then predominantly found in the ash. Furthermore, boiler size had an influence on fly ash composition. Cadmium concentrations were elevated in some fly ash samples at levels of concern for further utilization, whereas concentrations of troublesome Cr(VI) were below the detection limit for all investigated ash samples. Other contaminating elements such as Ni, Pb and Zn were variable but below limit values. Results clearly show that the nature of biomass ash calls for careful analyses prior to further application as, e.g., cement clinker replacement material.

Characterization and in vitro biological effects of ambient air PM10 from a rural, an industrial and an urban site in Sulaimani City, Iraq.

High urban atmospheric pollution is caused by economic and industrial growth, especially in developing countries. The objective of this study was to assess possible relationships between in vitro effects on human alveolar epithelial cells of source-related dust types collected at Sulaimani City (Iraq), and to determine their mineralogical and chemical composition. A passive sampler was used to collect dust particles at a rural, an industrial and an urban sampling site during July and August 2014. The samples were size-fractionated by a low-pressure impactor to obtain respirable dust with aerodynamic diameters of less than 10 µm. The dust was mainly composed of quartz and calcite. Chrysotile fibres (white asbestos) were also found at the urban site. Dust from the industrial and urban sites triggered cytotoxic and genotoxic effects in the cells, whereas only minor effects were observed for the sample from the rural site.

Cytotoxic and genotoxic responses of human lung cells to combustion smoke particles of Miscanthus straw, softwood and beech wood chips.

Inhalation of particulate matter (PM) from residential biomass combustion is epidemiologically associated with cardiovascular and pulmonary diseases. This study investigates PM0.4-1 emissions from combustion of commercial Miscanthus straw (MS), softwood chips (SWC) and beech wood chips (BWC) in a domestic-scale boiler (40 kW). The PM0.4-1 emitted during combustion of the MS, SWC and BWC were characterized by ICP-MS/OES, XRD, SEM, TEM, and DLS. Cytotoxicity and genotoxicity in human alveolar epithelial A549 and human bronchial epithelial BEAS-2B cells were assessed by the WST-1 assay and the DNA-Alkaline Unwinding Assay (DAUA). PM0.4-1 uptake/translocation in cells was investigated with a new method developed using a confocal reflection microscope. SWC and BWC had a inherently higher residual water content than MS. The PM0.4-1 emitted during combustion of SWC and BWC exhibited higher levels of Polycyclic Aromatic Hydrocarbons (PAHs), a greater variety of mineral species and a higher heavy metal content than PM0.4-1 from MS combustion. Exposure to PM0.4-1 from combustion of SWC and BWC induced cytotoxic and genotoxic effects in human alveolar and bronchial cells, whereby the strongest effect was observed for BWC and was comparable to that caused by diesel PM (SRM 2 975), In contrast, PM0.4-1 from MS combustion did not induce cellular responses in the studied lung cells. A high PAH content in PM emissions seems to be a reliable chemical marker of both combustion efficiency and particle toxicity. Residual biomass water content strongly affects particulate emissions and their toxic potential. Therefore, to minimize the harmful effects of fine PM on health, improvement of combustion efficiency (aiming to reduce the presence of incomplete combustion products bound to PM) and application of fly ash capture technology, as well as use of novel biomass fuels like Miscanthus straw is recommended.

Thermal degradations of wood biofuels, coals and hydrolysis lignin from the Russian Federation: Experiments and modeling.

The thermal degradation of wood biofuels (spruce, pine), of coals from different fields of the Russian Federation and of hydrolysis lignin is investigated using a thermogravimetric analyzer under different heating conditions and under non-oxidative or oxidative atmospheres. The samples are indeed submitted to a linear temperature ramp of 10K/min or to a temperature ramp of 200K/min up to a residence temperature between 250 and 450°C where they are maintained during 4h (isothermal conditions). The values of the kinetic parameters are determined for these different samples in both thermal conditions, either using the differential isoconversional method or by means of an Extended Independent Parallel Reaction (EIPR) model. The values of the kinetic parameters obtained with this EIPR model for spruce trunk are also compared with that of its main constituents (hemicellulose, cellulose and lignin).

Particle-bound PAHs quantification using a 3-stages cascade impactor in French indoor environments.

Cascade Impactor is a powerful sampling method to collect airborne particles as a function of their size. The 3-stages Cascade Impactor used in this study allowed to sample simultaneously particles with aerodynamic diameter Dae>10 µm, 2.5 µm

Experimental investigation on gaseous emissions from the combustion of date palm residues in laboratory scale furnace.

Emissions characteristics from the combustion of five date palm residues, DPR, (Date Palm Leaflets, Date Palm Rachis, Date Palm Trunk, Date Stones and fruitstalk prunings) in a laboratory scale furnace were investigated. Release of gaseous products such as CO2, CO, VOC, NOx and SO2 were measured at 600-800°C. The main goal was to analyze thermal behaviors and gaseous emissions in order to select the most convenient biofuel for an application in domestic boiler installations. Regards to biofuel characteristics, date stone have the highest energy density (11.4GJ/m(3)) and the lowest ash content (close to 1.2%). Combustion tests show that among the tested date palm residues, date stone may be the promising biofuel for the design of combustion processing system. However, a special attention to the design of the secondary air supply should be given to prevent high emissions of CO and volatile matters.

Combined process for the treatment of olive oil mill wastewater: absorption on sawdust and combustion of the impregnated sawdust.

Olive oil mill wastewater (OMWW) generated by the olive oil extraction industry constitutes a major pollutant, causing a severe environmental threats because of the high chemical oxygen demand and the high content of polyphenol. This work studied a combined process of absorption on sawdust, a low-cost renewable absorbents, and an energetic valorisation via combustion was studied. The thermal behaviour of different OMWW/sawdust blends was studied under inert and oxidative atmosphere from 20 to 900 degrees C using thermogravimetric analysis (TGA). Gaseous emissions such as CO(2), CO and volatile organic compounds (VOCs) were measured under oxidative conditions at 600 degrees C in a fixed-bed reactor. Kinetic parameters were obtained and compared for the different mixtures of OMWW and sawdust. The absorption of the organic content of OMWW on sawdust improves the decomposition of cellulosic compounds at low temperatures in both atmospheres. Compared to sawdust, absorption of the organic content of OMWW on sawdust favours a combustion process with lower molar ratio of CO/CO(2) in the exhaust. Combustion of an impregnated sawdust containing 40 wt.% of the organic content of the OMWW generates the same amount of gas in the exhaust as sawdust. OMWW/sawdust blends may therefore be a promising biofuel with low environmental impacts.

Thermogravimetric analysis and emission characteristics of two energy crops in air atmosphere: Arundo donax and Miscanthus giganthus.

The aim of this work was to study the thermal behavior of two herbaceous crops (Miscanthus giganthus, Arundo donax) obtained from energy plantations. Thermogravimetric analyses were performed at 5 degrees C min(-1) under air atmosphere. The thermal degradation rates in devolatilization and combustion steps, the initial degradation temperature, and the residual weight were determined. The gas emissions and Particle Matter (PM) were also quantified. The thermal behavior of energy crops depends on the chemical composition. In fact, the initial degradation temperature for A. donax under air atmosphere was lower than for M. giganthus. However, the thermal degradation rate was higher for M. giganthus. Kinetic expressions for the degradation rate in devolatilization and combustion steps have been obtained for both energy crops. The comparison of the gas and PM emissions showed the same order of magnitude for both energy crops. In fact, 26.8 mmol/g of CO, CO(2), VOC and 1.8 x 10(13) particles/g were mainly emitted.

Pyrolysis characteristics and kinetics of Arundo donax using thermogravimetric analysis.

The increase of the price of fossil means, as well as their programmed disappearing, contributed to increase among appliances based on biomass and energy crops. The thermal behavior of Arundo donax by thermogravimetric analysis was studied under inert atmosphere at heating rates ranging from 5 to 20 degrees C min(-1) from room temperature to 750 degrees C. Gaseous emissions as CO(2), CO and volatile organic compounds (VOC) were measured and global kinetic parameters were determined during pyrolysis with the study of the influence of the heating rate. The thermal process describes two main phases. The first phase named active zone, characterizes the degradation of hemicellulose and cellulose polymers. It started at low temperature (200 degrees C) comparatively to wood samples and was finished at 350 degrees C. The pyrolysis of the lignin polymer occurred during the second phase from 350 to 750 degrees C, named passive zone. Carbon oxides are emitted during the active zone whereas VOC are mainly formed during the passive zone. Mass losses, mass loss rates and emission factors were strongly affected by the variation of the heating rate in the active zone. It was found that the global pyrolysis of A. donax can be satisfactorily described using global independent reactions model for hemicellulose and cellulose in the active zone. The activation energy for hemicellulose was not affected by a variation of the heating rate with a value close to 110 kJ mol(-1) and presented a reaction order close to 0.5. An increase of the heating rate decreased the activation energy of the cellulose. However, a first reaction order was observed for cellulose decomposition. The experimental results and kinetic parameters may provide useful data for the design of pyrolytic processing system using A. donax as feedstock.

Size distributions of fine and ultrafine particles in the city of Strasbourg: correlation between number of particles and concentrations of NO(x) and SO(2) gases and some soluble ions concentration determination.

An Electrical Low Pressure Impactor (ELPI) was used during spring and autumn 2003 in the centre of Strasbourg for the measurement of atmospheric aerosols size distribution. The concentration of NO(x) and SO(2) in air was simultaneously measured with specific analysers. Samples were collected in the range 0.007-10 microm in equivalent aerodynamic diameter size. Number distributions are representative of a pollution originating from urban traffic with a particle size distribution exhibiting a nucleation mode below 29 nm and an accumulation mode around 80 nm in size. A mean particle density equal to 39000+/-35000 total particles per cm(3) with a size ranging from 7 to 10 microm was obtained after a sampling period of 2 weeks in spring. About 86.9% of the number of particles have an aerodynamic diameter below 0.1 microm and 13.1% between 0.1 and 1 microm. Correlation coefficients between the number of particles impacted on each ELPI plate and gas concentrations (SO(2) and NO(x)) showed that the numbers of particles with diameter between 0.10 and 0.62 microm are highly related to the NO(x) concentration. This result indicates that particles are traffic induced since NO(x) is mainly emitted by cars as shown by measurements on various sites. Particles are less clearly correlated to the SO(2) concentration. Particle analysis on different ELPI plates for a sampling period of 2 weeks in autumn showed high level of soluble NO(3)(-), SO(4)(2-) and NH(4)(+) ions. Indeed, up to 90% b.w. of these three species were found in the particle range 0.1-1 microm. The formation of particulate NH(4)NO(3) is favoured by high NO(x) concentration, which induces the formation of gaseous HNO(3).