Combustion Of Carbonaceous Materials Research Articles

Catalytic Effect of Iron Oxide on the Combustion of Carbonaceous Materials in Mold Flux for Continuous Casting

Catalytic Effect of Iron Oxide on the Combustion of Carbonaceous Materials in Mold Flux for Continuous Casting

Extensive Soot Compaction by Cloud Processing from Laboratory and Field Observations

Soot particles form during combustion of carbonaceous materials and impact climate and air quality. When freshly emitted, they are typically fractal-like aggregates. After atmospheric aging, they can act as cloud condensation nuclei, and water condensation or evaporation restructure them to more compact aggregates, affecting their optical, aerodynamic, and surface properties. Here we survey the morphology of ambient soot particles from various locations and different environmental and aging conditions. We used electron microscopy and show extensive soot compaction after cloud processing. We further performed laboratory experiments to simulate atmospheric cloud processing under controlled conditions. We find that soot particles sampled after evaporating the cloud droplets, are significantly more compact than freshly emitted and interstitial soot, confirming that cloud processing, not just exposure to high humidity, compacts soot. Our findings have implications for how the radiative, surface, and aerodynamic properties, and the fate of soot particles are represented in numerical models.

Organic Aerosol Characterization and Source Identification in Karachi, Pakistan

With its rapidly growing population and large industrial base, the megacity of Karachi, Pakistan, has been subjected to an increasing amount of ambient particulate matter (PM). Fine particulate matter (PM2.5) in Karachi was collected every 24 hours from January 8 to January 29, 2006. The samples were extracted and analyzed by gas chromatography-mass spectrometry (GC-MS) and ultra-performance liquid chromatography (UPLC) coupled with a triple quadrupole mass spectrometric detector (TQD) and time-of-flight (TOF) mass spectrometer. The daily PM2.5 levels ranged from 99.5 to 251.1 µg m–3 with a mean of 177.4 µg m–3, averaging 4–10-fold higher than the WHO guideline for 24-hour averaged PM2.5 (25 µg m–3). We found that the day-of-the-week variations of PM2.5 demonstrate Sundays have significantly lower concentrations (with a t-based confidence level of 95%), indicating that weekly behavioral patterns affect local PM2.5 concentrations. A significant negative correlation was found between the daily concentrations of levoglucosan, a biomass burning tracer, and the average daily temperatures (r = –0.589, p = 0.004), implicating heating as a major source of biomass burning emissions. Results indicate that polyaromatic hydrocarbons, hopanes, steranes, and alkanes are mainly emitted from fossil fuels and the combustion of carbonaceous materials. Organosulfates (OSs) and sulfonates were also quantified; significant correlations between OSs and sulfonates indicate a common source and/or similar formation mechanisms, while correlations with hopanes, steranes, and levoglucosan suggest their emission from primary sources such as fossil fuels and biomass burning. Qualitative analysis suggests the presence of a C6–C9 alkyl sulfate series. Through this study, the chemical composition and origin of the organic fraction of PM2.5 in Karachi has been evaluated for the first time, and the results indicate a strong anthropogenic influence on combustion emissions, particularly those from biomass and fossil fuel burning.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in the environment - A review.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are derivatives of PAHs with at least one nitro-functional group (-NO2) on the aromatic ring. The toxic effects of several nitro-PAHs are more pronounced than those of PAHs. Some nitro-PAHs are classified as possible or probable human carcinogens by the International Agency for Research on Cancer. Nitro-PAHs are released into the environment from combustion of carbonaceous materials (e.g. fossil fuels, biomass, waste) and post-emission transformation of PAHs. Most studies on nitro-PAHs are about air (gas-phase and particulate matter), therefore less is known about the occurrence, concentrations, transport and fate of nitro-PAHs in soils, aquatic environment and biota. Studies on partition and exchange of nitro-PAHs between adjacent environmental compartments are also sparse. The concentrations of nitro-PAHs cannot easily be predicted from the intensity of anthropogenic activity or easily related to those of PAHs. This is because anthropogenic source strengths of nitro-PAHs are different from those of PAHs, and also nitro-PAHs have additional sources (formed by photochemical conversion of PAHs). The fate and transport of nitro-PAHs could be considerably different from their related PAHs because of their higher molecular weights and considerably different sorption mechanisms. Hence, specific knowledge on nitro-PAHs is required. Regulations on nitro-PAHs are also lacking. We present an extensive review of published literature on the sources, formation, physico-chemical properties, methods of determination, occurrence, concentration, transport, fate, (eco)toxicological and adverse health effects of nitro-PAHs. We also make suggestions and recommendations about data needs, and future research directions on nitro-PAHs. It is expected that this review will stimulate scientific discussion and provide the basis for further research and regulations on nitro-PAHs.

Dielectric Properties and Conductivity of (ZnO/CdO) Mixed Oxide Nanocomposite

Nanoparticles of zinc oxide and zinc-cadmium oxide were prepared from their respective metal acetates, and ammonium carbonate using ethylenediaminetetraacetic acid (EDTA) as capping agent followed by decomposition. The heat treatment of the precursor powders at their decomposition temperature and beyond, results in the evolution of heat from the combustion of carbonaceous material. This facilitates the reaction among the constituent metal ions and the desired oxide phase is formed at low temperature. The particle size was determined by X-ray diffraction and the diffractogram was compared with JCPDS data to identify the crystallographic phase. The shift in the ‘d’ value and elastic micro strain was calculated.The FTIR studies were used to confirm the formation of metal oxide. The absorption spectra of samples were recorded and band gap calculated. It is observed that band gap tuning of ZnO is possible by addition of cadmium. The effect of temperature and frequency on the dielectric behaviour and ac conductivity of the samples were studied. The dielectric permittivity is evaluated from the observed values of capacitance in the range of 1 kHz to 10 MHz, in the temperature range 300 K to 403 K. It is seen that with the decrease in frequency, the dielectric constant increases much more obviously than that in conventional materials due to space charge polarisation and rotation direction polarization. Due to the incorporation of cadmium both capacitance and conductivity increased by an order of 103. Cole-Cole plots are drawn and dispersion parameters are calculated

Absorption of carbon dioxide into N-methyldiethanolamine in a high-throughput microchannel reactor

Global warming due to greenhouse effects is on the rise, and many efforts to reduce emissions of CO2 which is a major greenhouse gas from combustion of carbonaceous materials are being made. In this study, chemical absorption of CO2 into N-methyldiethanolamine (MDEA) solution combined with effective activator piperazine (PZ), from a gas mixture containing N2 was carried out in a high-throughput microporous tube-in-tube microchannel reactor (MTMCR). As a novel microreactor, MTMCR greatlyintensifies gas–liquid mass transfer due to its large gas–liquid interfacial area. The effects of different parameters on the overall volume mass transfer coefficient and CO2 removal efficiency were investigated. The results showed that both mass transfer coefficient and CO2 removal efficiency increased with an increase in the liquid flow rate, temperature and concentration of liquid solvent. Also, the gas–liquid mass transfer efficiency increased with a decrease in the size of the micropore and annular channel of MTMCR. The volume mass transfer coefficient and CO2 removal efficiency reached 1.70s−1 and 97%, respectively, at flow rates of 100L/h and 5.32L/h for gas and liquid respectively, with alkanolamine solutions containing 10wt.% MDEA and 4wt.% PZ.

Microwaves in extractive metallurgy: Part 2 – A review of applications

In metal extraction processes, such as reduction or smelting, a source of energy is required for the endothermic reactions. This energy is often supplied by the combustion of carbonaceous materials or hydrocarbons or by inputting some electrical energy. Typically, large-scale reactors are used and the energy is transported to the reacting materials from the heat source via convective, conductive and radiative processes. Additionally, considerable heat is transferred to the containment vessel, the surroundings and the off-gases and this energy is difficult to recover. On the other hand, microwave heating systems can be designed such that only the material to be processed absorbs the microwaves, since microwave radiation is deposited directly in the material to be heated. Other potential advantages of microwave processing include; high energy densities, selective heating, improved control, environmental benefits and minimal off-gas generation. In the present research, the utilization of microwaves as an energy source in metal extraction and, in particular the pyrometallurgical processing of oxide ores, is reviewed.

Thermal and electrochemical behaviour of C/Li xCoO 2 cell during safety test

Thermal and electrochemical processes in a 1000 mAh lithium-ion pouch cell with a graphite anode and a Li x CoO 2 cathode during a safety test are examined. In overcharge tests, the forced current shifts the cell voltage to above 4.2 V. This causes a cell charged at the 1 C rate to lose cycleability and a cell charged at the 3 C rate to undergo explosion. In nail penetration and impact tests, a high discharge current passing through the cells gives rise to thermal runaway. These overcharge and high discharge currents promote joule heat within the cells and leads to decomposition and release of oxygen from the de-lithiated Li x CoO 2 and combustion of carbonaceous materials. X-ray diffraction analysis reveals the presence of Co 3O 4 in the cathode material of a 4.5 V cell heated to 400 °C. The major cathode product formed after the combustion process cells abused by forced current is Co 3O 4 and by discharge current the products are LiCoO 2 and Co 3O 4. The formation of a trace quantity of CoO through the reduction of Co 3O 4 by virtue of the reducing power of the organic solvent is also discussed.

High catalytic activity of SCS-synthesized ceria towards diesel soot combustion

Nano-sized particles of ceria with high surface area were processed by solution combustion synthesis (SCS) and their catalytic activity towards combustion of carbonaceous materials was compared with that obtained by simple thermal decomposition of cerium nitrate, exhibiting the same specific surface area. These two kinds of ceria powders were tested by DTA and temperature-programmed combustion of diesel soot and a commercial carbon.Ceria processed by SCS was found to be more active than its counter part since it could decrease significantly both the combustion activation energy (from 115 to 111kcal/mol) and the TPC-plot peak temperature of diesel soot (from 466 to 405°C).The mechanism of the catalytic reaction of combustion was investigated by TPD/R experiments. Likewise other combustion catalysts acting as oxygen pumps, ceria can exchange limited amounts of oxygen even below 300°C, the SCS-synthesized one showing a superior O2 release at low temperatures (≤450°C). Moreover, the SCS-ceria exhibited a microstructure (i.e. a foam of nano-sized crystals) particularly suitable for maximizing the number of contact points between catalyst and carbon. Finally, the effect of specific aging protocols (thermal treatment at 600°C for 96h) in the presence of potentially deactivating species present in diesel exhaust gases (SO2 and water) was also studied showing that the here proposed material suffers from less significant ageing than Ce(NO3)3-derived ceria.

Removal of carbon dioxide by a spray dryer

With the global warming due to greenhouse effects becoming serious, many efforts are carried out to decrease the emissions of CO 2 from the combustion of carbonaceous materials. In Taiwan, there are 19 large-scale municipal solid waste incinerators running and their total emission of CO 2 is about 16 950 kton y −1. Spray dryer is the most prevailing air pollution control devise for removing acid gas in waste incineration; however, the performance of spray dryer on the removal of CO 2 is seldom studied. This study employs a laboratory-scale spray dryer to investigate the removal efficiency of CO 2 under different operating conditions. The evaluated parameters include different absorbents mixed with Ca(OH) 2, operating temperature, the concentration of absorbent, and the inlet concentration of CO 2. Experimental results show that the best removal efficiency of CO 2 by a spray dryer is 48% as the absorbent is 10%NaOH + 5%Ca(OH) 2 and the operating temperature is 150 °C. Comparing this result with previous study shows that the performance of spray dryer is better than traditional NaOH wet scrubber. For NaOH + Ca(OH) 2 spray dryer, the removal efficiency of CO 2 is decreased with the inlet concentration of CO 2 increased and the optimum operating temperature is 150 °C. Except NaOH + Ca(OH) 2, absorbents DEA + Ca(OH) 2, TEA + Ca(OH) 2, and single Ca(OH) 2 are not effective in removing CO 2 by a spray dryer.

Combustion of carbon particulate catalysed by mixed potassium vanadates and KI

A K–V–I‐containing catalyst for low‐temperature combustion of carbonaceous materials was studied so as to check its potential in diesel particulate removal. X‐ray diffraction (XRD) and scanning electron microscopy (SEM‐EDS) showed that its main constituting compounds are KVO3, KI and K4V2O7. Differential scanning calorimetry (DSC) and temperature‐programmed oxidation (TPO) tests enlightened that the catalyst is active well below 400 °C (peak combustion temperature: Tp= 380 °C). Thermal treatments carried out at this temperature with dry or humid air did not entail detrimental effects on the catalyst performance. Similar treatments at higher temperatures (600 and 750 °C) resulted in a modification of the catalyst composition and in a slight decrease of its activity (Tp increases of about 60 °C). These last treatments caused the progressive loss of active components due to either evaporation of eutectic liquid formed at about 450 °C or production of gaseous iodine through a reaction between KI and KVO3, which also gave rise to the formation of K4V2O7. However, the consequent deactivation was moderate owing to the high intrinsic activity displayed by the formed potassium pyrovanadate.

Combustion of carbonaceous materials by Cu [sbnd]K [sbnd]V based catalysts : II. Reaction mechanism

In Part I the chemical and microstructural nature of Cu K V catalysts for diesel soot combustion was assessed. In this second communication the reaction mechanism of these catalysts is studied by testing their activity through either differential scanning calorimetry (DSC) or temperature-programmed oxidation (TPO), performed on catalyst-carbon mixtures. The following parameters were varied: the particle size of both the catalyst and the carbon powders, the catalyst-to-carbon weight ratio, the catalyst composition (besides the standard Cu K V catalyst defined in Part I, binary catalysts based on a single copper or potassium vanadate + KCl were also considered). On the basis of the obtained results the presence of liquid eutectic phases (whose formation was detected via DSC runs performed in the absence of carbon) is found to be a key factor in determining the catalytic activity of all tested catalysts since it dramatically improves the catalyst-carbon contact. Once liquid phases are formed at suitable temperatures (ranging from 330 to 480°C depending on the catalyst nature), the catalytic combustion likely proceeds according to redox mechanisms.

95/05880 Furnace for generating water gas by combustion of carbonaceous materials with ultrasonic wave

95/05880 Furnace for generating water gas by combustion of carbonaceous materials with ultrasonic wave

Modelling gasification reactions including the percolation phenomenon

The analysis of percolative fragmentation for noncatalytic gas—solid reactions, with special emphasis on gasification and combustion of carbonaceous materials, is presented. The description of pore surface area and pore surface enlargement during reaction is based on the random pore model developed by Bhatia and Perlmutter (1980), A.I.Ch.E. J. 26, 379–386; 1981, A.I.Ch.E. J. 27, 247–254). Different reaction regimes between intraparticle diffusion and chemical kinetics control are considered. The inclusion of percolative fragmentation in the Bathia—Perlmutter random pore model allows a more realistic description of changes during gasification of porous solids to be made. The results include the variation of local properties (porosity, surface area and gas concentration) within the particle at different reaction stages as well as the modification of the overall particle properties (particle conversion, percolated mass fraction and reaction rate) with reaction progress.

The Twilight Zone: Death on a Sunday Morning

If it weren't for one peculiar twist of physical chemistry, carbon monoxide might be the least interesting of all the organic compounds. Its ubiquitous production results from the incomplete combustion of carbonaceous materials. More than 90% of atmospheric carbon monoxide is produced from automobile emissions, hundreds of millions of tons per year.1While pollution alerts may indicate transient elevations in carbon monoxide, in the general environment, carbon monoxide levels are so low as to be clinically insignificant. The colorless, odorless, and tasteless gas is the most frequent cause of chemical asphyxiation. Although carbon monoxide itself is nonirritating and apparently nontoxic to cells, almost 50% of all deaths from poisoning are due to its inhalation.2Carbon monoxide is lethal because of its occult nature and because at a normal pH, it has an affinity for hemoglobin 210 to 270 times greater than that of oxygen. When inhaled, most carbon

小型燃焼炉によるレースウェイ再現実験における各種炭材の燃焼温度

小型燃焼炉によるレースウェイ再現実験における各種炭材の燃焼温度

As Clunkers Die, Carboxyhemoglobin Levels in Chicago Blood Donors Continue to Fall

To the Editor.— Carbon monoxide (CO), produced by incomplete combustion of carbonaceous material, is a major air pollutant with well-described adverse effects on human health. In a national survey of the range of carboxyhemoglobin (COHb) levels in blood donors representing various segments of the American population conducted in 1970, Stewart et al 1 found a mean COHb level for nonsmokers living in Chicago of 2.04% (90% confidence limits, 1.0% to 3.2%), with 74% having a level in excess of the 1.5% limit of the Air Quality Standards of 1971. By 1974-1975, the mean COHb level for Chicago nonsmokers had fallen to 1.53% (90% confidence limits, 0.7% to 2.4% ), a difference that was statistically significant ( P 2 The greatest reduction in COHb levels occurred in downtown Chicago, the area of highest automobile density, leading the authors to speculate that reduction in CO in automobile exhaust due to emission control laws

Combustion of Carbonaceous Material in Porous Solid

Combustion of Carbonaceous Material in Porous Solid