Partial Combustion Research Articles

In situ FTIR characterization of NH 3 adsorption and reaction with O 2 and CO on Pd-based FCC emission control additives

The adsorption of NH 3 and its reaction with O 2 and CO over Ce n+ /Na +/γ-Al 2O 3 and Pd/Ce n+ /Na +/γ-Al 2O 3 was examined by FTIR spectroscopy in a wide range of temperatures. Ammonia undergoes decomposition on the surfaces of these materials at elevated temperatures with a fraction of the NH 3 species being oxidized by lattice oxygen to NO x , which is trapped on the surface in the form of nitrites. The presence of O 2 in the feed accelerates the formation of surface nitrite and nitrate species. The reaction of these species with ammonia at 400 °C is fast, producing N 2. The presence of CO in the gaseous feed leads to the formation of surface isocyanates, presumably through the reaction with partially dehydrogenated surface NH x species. The PdO component mildly promotes the formation of these isocyanate species. Both the NCO and NO 3 −/NO 2 − species identified on the surfaces of these materials at elevated temperatures are active intermediates, participating in further reactions which ultimately lead to the reduction of NO x and CO emissions. The contribution of these intermediates to a possible N 2 formation reaction network should be accounted for when FCC regenerators are operating under partial or incomplete burn combustion modes.

Modelling a slow smoldering combustion process

AbstractWe present a mathematical model for the slow and partial combustion process of a sheet of paper ignited on one side and in the presence of a flow of air confined in a narrow gap above the paper. The model includes mass and thermal balance for the various components. After having introduced some simplifications, a suitable rescaling is performed and some limit cases are examined. Two classes of travelling wave solutions are analyzed, corresponding to the opposite cases of a sufficiently large or of a moderate air flow. Copyright © 2010 John Wiley & Sons, Ltd.

Production of hydrogen energy through biomass (waste wood) gasification

Biomass gasification, conversion of solid carbonaceous fuel into combustible gas by partial combustion, is a prominent technology for the production of hydrogen from biomass. The concentration of hydrogen in the gas generated from gasification depends mainly upon moisture content, type and composition of biomass, operating conditions and configuration of the biomass gasifier. The potential of production of hydrogen from wood waste by applying downdraft gasification technology is investigated. An experimental study is carried out using an Imbert downdraft biomass gasifier covering a wide range of operating parameters. The producer gas generated in the downdraft gasifier is analyzed using a gas chromatograph (NUCON 5765) with thermal conductivity detector (TCD). The effects of air flow rate and moisture content on the quality of producer gas are studied by performing experiments. The performance of the biomass gasifier is evaluated in terms of equivalence ratio, composition of producer gas, and rate of hydrogen production.

Carbon monoxide poisoning

Carbon monoxide is a colourless, odourless and tasteless gas existing in a miniscule concentration in the atmosphere (< 0.001%), and is a product of partial combustion. Carbon monoxide poisoning is associated with a high incidence of morbidity and mortality. Symptoms are usually non-specific and include fatigue, headache, dizziness, nausea and vomiting, cognitive impairment, and tachycardia; mimicking an influenza-like illness. Symptoms occurring in more than one person (belonging to the same family/office) simultaneously and the relief also occurring at the same point of time in them should sound the physician’s mind for suspected carbon monoxide poisoning. A high index of suspicion and presence of a source of generation of carbon monoxide are the diagnostic aids which can be confirmed by blood carboxyhaemoglobin levels. Removal from the source of carbon monoxide generation, moving the person to fresh air immediately is most important. In the emergency room, oxygen therapy is the key. Immediate treatment with a high fraction of inspired oxygen and careful clinical evaluation are mandatory for effective management. Patients with a carboxyhaemoglobin level of 10% or more should always be treated and 100% oxygen for 8 hours is recommended for patients requiring artificial ventilation. Hyperbaric oxygen also holds promise in select cases specially those with a history of unconsciousness, cardiovascular instability or ischemia, persistent mental and/or neurologic deficits and probably in pregnant patients.

Enhanced and irreversible sorption of pesticide pyrimethanil by soil amended with biochars

Biochar derived from partial combustion of vegetation is ubiquitous and potentially effective in sequestration of environmental contaminants. Biochars were prepared by burning of red gum ( Eucalyptus spp.) woodchips at 450 and 850°C (labeled as BC450 and BC850). These two biochars were found to possess markedly different properties in terms of surface area and porosity. Short-term equilibration tests (24 hr) were conducted to assess the sorption-desorption behavior of pyrimethanil in the soil amended with various amounts of biochar of each type, with a special focus on the desorption behavior of the sorbed pesticide through four times successive desorption by dilution. Sorption coefficient and isotherm nonlinearity of the amended soils progressively increased with the content of biochar in the soil. Biochar BC850 with higher surface area and microporosity showed a stronger effect on the reversibility of sorption pesticide. The soils amended with 5% BC450 and 1% BC850 had nearly the same sorption capacity for pyrimethanil; however, their desorption processes were very different with 13.65% and 1.49% of the sorbed pesticide being released, respectively. This study suggested that biochar in soil could be an important factor for immobilization of a pesticide and thus affecting its environment fate in soil.

木質バイオマス由来の発生炉ガス中のタール改質除去 : 部分燃焼条件における逆拡散火炎の適用(熱工学,内燃機関,動力など)

Experimental study for clarifying the effect of combustion mechanism on reforming of producer gas was carried out. The inverse diffusion flame was formed in the actual gas reformer by partial combustion of producer gas. Direct observation and laser diagnostics were applied to the inverse diffusion flame formed in the modeled gas reformer. Experimental parameters are steam concentration in supplied model producer gas (X_<steam>) corresponding to moisture content of wood, and the flame configuration (flame at the nozzle and lifted flame). The main results are as follows. In the condition of 20% concentration of oxygen, flames at the nozzle and lifted flames were formed in the same supply condition. One might identify a type of hysteresis in flame formation that determines its configuration. When the flames at the nozzle were formed, the exergy yield was increased with the increase of X_<steam> because soot formation was suppressed and steam reforming of model tar can be promoted. In contrast, when the lifted flames were formed, the exergy yield was decreased with the increase of X_<steam> because of formation of the particulate matter such as the soluble organic fraction and the young soot.

Effect of Magnesite as Bed Material in a 100 kWthSteam−Oxygen Blown Circulating Fluidized-Bed Biomass Gasifier on Gas Composition and Tar Formation

Because of the fibrous nature of woody and herbaceous biomass and the widely distributed appearance of the feedstock with respect to its size, the circulating fluidized bed (CFB) is a very suitable type of reactor for thermal conversion of this potentially renewable and sustainable energy source. Of the thermal conversion processes, combustion and gasification are the most well-known. The advantage of gasification above combustion is that it produces a secondary gaseous energy carrier (i.e., product gas or syngas) from solid biomass. This secondary energy carrier can subsequently be upgraded to, for example, hydrogen-rich fuel gas for fuel cells, converted to liquid transportation fuels [such as Fisher−Tropsch (FT) diesel or dimethyl ether (DME)], or used for synthesis of other chemicals. During operation, the CFB internally recirculates a certain amount of inert material, also referred to as “bed material”. This bed material accumulates a part of the energy released during (partial) combustion of biomass...

Regeneration of CuO-ZnO-Al2O3/γ-Al2O3 catalyst in the direct synthesis of dimethyl ether

This paper deals with the regeneration of a CuO-ZnO-Al2O3/γ-Al2O3 catalyst used in the direct synthesis of dimethyl ether. When coke combustion (subsequent to aging treatment) is performed in a thermobalance, two coke fractions with different combustion kinetics are identified. One coke fraction, deposited on the metallic sites and whose combustion is activated by these sites, has a kinetic constant of combustion 7–26 times higher than that corresponding to the coke located at the Al2O3 support. Uninterrupted operation is feasible in reaction–regeneration cycles in a fixed bed reactor as long as the reaction and regeneration steps are carried out at 325°C, which are limiting conditions in order to avoid irreversible deactivation by sintering of the metallic function. The regeneration with O2 diluted with He (5% of O2) allows the complete combustion of coke. Under conditions of partial coke combustion it is observed that the removal of the fraction deposited on the metal makes it possible to recover the initial activity of the catalyst, which subsequently undergoes fast deactivation.

Pressure rise generated by the expansion of a local gas volume in a closed vessel

Experiments were conducted to determine the pressure rise that results from either the combustion of a localized gas volume or the expansion of a pressurized gas volume adjacent to an inert gas in a closed vessel. The experiments consisted of either pressurized air or the combustion of stoichiometric and fuel-lean hydrogen–air mixtures compressing an inert gas. The pressure rise in the inert gas was measured as a function of either the volume fraction or the initial pressure of the expanding gas. Helium, nitrogen, air and carbon dioxide were tested to explore the effect of inert gas heat capacity on the pressure rise. The final pressure of the inert gas increased with the volume fraction and initial pressure of the expanding gas, and was influenced to a lesser extent by the heat capacity of the inert gas. A model was assessed using the experimental data, and the theoretical results were consistent with the observed trends. This model and other published models were assessed and compared using prior data for localized gas combustion surrounded by an inert gas and the partial combustion of homogeneous methane–air mixtures.

Thermodynamic Equilibrium Model and Exergy Analysis of a Biomass Gasifier

Biomass gasification involves the production of a gaseous fuel by partial oxidation of a solid fuel. Clean synthesis (syn) gas, produced from partial combustion of biomass, can be burnt in a gas turbine combustion chamber to run a biomass based combined cycle power plant. A thermochemical model has been developed to predict the gas composition and performance of a biomass gasifier based on thermodynamic equilibrium concept for different biomass materials. A simplified numerical method is applied to solve the thermochemical equilibrium reactions. The system consists of a pressurized circulating fluidized bed to produce the syn gas from the biomass. The effect of the relative air fuel ratio (RAFR), steam fuel ratio (SFR), and gasifier pressure has been examined on the gas composition, gasifier temperature, lower heating value of syn gas, and exergy efficiency of biomass gasifier to obtain a high yield from the biomass. It has been found that at lower values of RAFR and SFR, the heating value of the syn gas and the exergy efficiency of gasifier is high.

Hydrogen Sulfide from the Black Sea for Hydrogen Production

The Black Sea is a unique sea. Its water contains hydrogen sulfide (H2S). The Black Sea is the world's largest water body containing H2S and its hydrogen sulfide layer begins about 200 meters below the surface. H2S potential in the Black Sea is investigated as a source of hydrogen. The total sulfide pool in the Black Sea is believed to be around 4.6 × 109 tons. H2S, an acid gas, is generally considered to be an environmental pollutant. As an industrial by-product, it is produced mostly during fuel processing. One-step thermal decomposition methods appear to be more suitable for hydrogen production from H2S. Superadiabatic partial combustion is an encouraging process for the near future. Environmentally, H2 production based on this H2S-splitting cycle is carbon free.

Control of insect pests under ware-house conditions using smoke generated from partial combustion of rice (paddy) husk

Adult Sitophilus oryzae and Rhyzopertha dominica , two major devastating insect pests of stored paddy in Sri Lanka, included in cloth sacks with rice medium inside were placed at three locations of the poly sack stacks containing paddy viz. outside, just inside and centremost. They were then exposed to smoke generated from partial combustion of paddy husk for 2 1/2-3 hours {where carbon monoxide (CO) concentration was higher than 5000ppm} and sealed for 18, 36, 54 and 72 hours in the first step and repeated for a similar time period with a subsequent smoking in between as against the control. Results revealed that increasing CO 2 concentrations in smoke caused no significant mortality on the target insects. Smoke generated by partial combustion of paddy husk where CO concentration was above 5000ppm was directly responsible for insect mortality. Insect mortality was increased with the increase in the sealed period up to 72 hours irrespective of both the location of insect (outside, just inside and centermost) and species. However, a significant difference in the mortality levels of insects was observed among the above 3 locations, outside the poly sack bag recording the highest mortality. This indicates that the poly propylene membrane acts as a physical barrier for the penetration of smoke into the poly sacks. Experiments under ware-house conditions also revealed that there was no significant difference among the treatments smoked once a week, once in two weeks and once a month in terms of percentage weight loss due to insect attack which all differed significantly with the control stack which was not smoked. This study shows the possibility of using smoke generated from partial combustion of paddy husk for the control of stored product insect pests as an alternative to the chemical insecticides.

Catalytic combustion of volatile organic compounds in binary mixtures over MnOx/Al2O3 catalyst

In this work the catalytic performance of an alumina supported manganese oxide catalyst in ethanol, ethyl acetate, toluene and mixtures of them was studied. The reactivity of each VOC investigated increased in the following order: ethanol>ethyl acetate>toluene. Toluene affects acetaldehyde yields, favoring partial combustion of ethanol and ethyl acetate. There is a competition for the adsorption sites between ethanol and ethyl acetate because both are polar molecules. Mixture effect decreases when the conversion temperature range of each component in the mixture is different, as in the case of ethanol–toluene and ethyl acetate–toluene mixture, consequently, the total conversion temperature is determined by the temperature at which the most difficult molecule is oxidized, in this case toluene.

Joining semi-closed gas turbine cycle and tri-reforming: SCGT-TRIREF as a proposal for low CO 2 emissions powerplants

Methane conversion to a rich H 2 fuel by reforming reactions is a largely applied industrial process. Recently, it has been considered for applications combined to gas turbine powerplants, as a mean for (I) chemical recuperation (i.e. chemical looping CRGT) and (II) decarbonising the primary fuel and make the related power cycle a low CO 2 releaser. The possibility of enhancing methane conversion by the addition of CO 2 to the steam reactant flow (i.e. tri-reforming) has been assessed and showed interesting results. When dealing with gas turbines, the possibility of applying tri-reforming is related to the availability of some CO 2 into the fluegas going to the reformer. This happens in semi-closed gas turbine cycles (SCGT), where the fluegas has a typical 14–15% CO 2 mass content. The possibility of joining CRGT and SCGT technologies to improve methane reforming and propose an innovative, low CO 2 emissions gas turbine cycle was assessed here. One of the key issues of this joining is also the possibility of greatly reduce the external water consumption due to the reforming, as the SCGT is a water producer cycle. The SCGT-TRIREF cycle is an SCGT cycle where fuel tri-reforming is applied. The steam due to the reformer is generated by the vaporization of the condensed water coming out from the fluegas condensing heat exchanger, upstream the main compressor, where the exhausts are cooled down and partially recirculated. The heat due to the steam generation is recuperated from the turbine exhausts cooling. The reforming process is partially sustained by the heat recovered from the turbine exhausts (which generates superheated steam) and partially by the auto thermal reactions of methane with fresh air, coming from the compressor (i.e. partial combustion). The effect of CO 2 on methane reforming (tri-reforming effect) increases with decreasing steam/methane ratio: at very low values, around 30% of methane is converted by reactions with CO 2. At high values of steam/methane ratio, the steam reforming reactions are dominant and only a marginal fraction of methane is interested to tri-reforming. Under optimised conditions, which can be reached at relatively high pressure ratios (25–30), the power cycle showed a potential efficiency around 46% and specific work at 550 kJ/kg level. When the amine CO 2 capture is applied, the specific CO 2 emissions range between 45 and 55 g CO 2 / kW h .

Mixed-mode homogeneous charge compression ignition—direct injection combustion on common rail diesel engines: An experimental characterization

In recent years, increasing attention has been given to the study of homogeneous charge compression ignition (HCCI) for automotive diesel engines, due to its potential to lower NO x and particulate matter (PM) emissions. However, controlling the combustion process and engineering a mixture preparation method that does not require significant modifications to the engine hardware are still significant barriers to a vehicle implementation. In this scenario, external mixture formation, performed through a diesel fuel atomizer, is a simple and reliable method to obtain a truly homogeneous charge, resulting in ultra-low NO x and negligible PM formation. This technology does not require any modification to the engine compression ratio or to the fuel direct injection (DI) system. The possibility of combining two separate fuelling systems allows for mixed-mode HCCI—DI combustion, where a diesel-type combustion is induced during HCCI operations, increasing the IMEP and the output engine torque. This would allow for a seamless transition from HCCI to conventional DI mode at high load, while retaining the HCCI combustion benefits on emissions at part-load engine operating conditions. Building on preliminary experimental results proving the feasibility and benefits of the HCCI combustion with external mixture preparation on a high-speed common rail diesel engine, the proposed work aims at extending the HCCI combustion characterization, in order to define an engine operating region for its application. Then, mixed-mode HCCI—DI operations were investigated as a strategy to overcome the IMEP limitations of pure HCCI combustion. The analysis of HCCI—DI combustion aims at studying the effect of important control parameters, such as EGR ratio and direct injection timing, on combustion and emissions, showing the effects of partial HCCI combustion at higher engine loads.

Geochemical evidence for combustion of hydrocarbons during the K-T impact event.

It has been proposed that extensive wildfires occurred after the Cretaceous-Tertiary (K-T) impact event. An abundance of soot and pyrosynthetic polycyclic aromatic hydrocarbons (pPAHs) in marine K-T boundary impact rocks (BIRs) have been considered support for this hypothesis. However, nonmarine K-T BIRs, from across North America, contain only rare occurrences of charcoal yet abundant noncharred plant remains. pPAHs and soot can be formed from a variety of sources, including partial combustion of vegetation and hydrocarbons whereby modern pPAH signatures are traceable to their source. We present results from multiple nonmarine K-T boundary sites from North America and reveal that the K-T BIRs have a pPAH signature consistent with the combustion of hydrocarbons and not living plant biomass, providing further evidence against K-T wildfires and compelling evidence that a significant volume of hydrocarbons was combusted during the K-T impact event.

Experimental studies on producer gas generation from wood waste in a downdraft biomass gasifier

A process of conversion of solid carbonaceous fuel into combustible gas by partial combustion is known as gasification. The resulting gas, known as producer gas, is more versatile in its use than the original solid biomass. In the present study, a downdraft biomass gasifier is used to carry out the gasification experiments with the waste generated while making furniture in the carpentry section of the institute’s workshop. Dalbergia sisoo, generally known as sesame wood or rose wood is mainly used in the furniture and wastage of the same is used as a biomass material in the present gasification studies. The effects of air flow rate and moisture content on biomass consumption rate and quality of the producer gas generated are studied by performing experiments. The performance of the biomass gasifier system is evaluated in terms of equivalence ratio, producer gas composition, calorific value of the producer gas, gas production rate, zone temperatures and cold gas efficiency. Material balance is carried out to examine the reliability of the results generated. The experimental results are compared with those reported in the literature.

A C1 microkinetic model for methane conversion to syngas on Rh/Al2O3

AbstractA microkinetic model capable of describing multiple processes related to the conversion of natural gas to syngas and hydrogen on Rh is derived. The parameters of microkinetic models are subject to (intrinsic) uncertainty arising from estimation. It is shown that intrinsic uncertainty could markedly affect even qualitative model predictions (e.g., the rate‐determining step). In order to render kinetic models predictive, we propose a hierarchical, data‐driven methodology, where microkinetic model analysis is combined with a comprehensive, kinetically relevant set of nearly isothermal experimental data. The new, thermodynamically consistent model is capable of predicting several processes, including methane steam and dry reforming, catalytic partial oxidation, H2 and CO rich combustion, water‐gas shift and its reverse at different temperatures, space velocities, compositions and reactant dilutions, using the measured Rh dispersion as an input. Comparison with other microkinetic models is undertaken. Finally, an uncertainty analysis assesses the effect of intrinsic uncertainty and catalyst heterogeneity on the overall model predictions. © 2009 American Institute of Chemical Engineers AIChE J, 2009

An experimental study on air gasification of biomass micron fuel (BMF) in a cyclone gasifier

Biomass micron fuel (BMF) produced from feedstock (energy crops, agricultural wastes, forestry residues and so on) through an efficient crushing process is a kind of powdery biomass fuel with particle size of less than 250 μm. Based on the properties of BMF, a cyclone gasifier concept has been considered in our laboratory for biomass gasification. The concept combines and integrates partial oxidation, fast pyrolysis, gasification, and tar cracking, as well as a shift reaction, with the purpose of producing a high quality of gas. In this paper, characteristics of BMF air gasification were studied in the gasifier. Without outer heat energy input, the whole process is supplied with energy produced by partial combustion of BMF in the gasifier using a hypostoichiometric amount of air. The effects of equivalence ratio (ER) and biomass particle size on gasification temperature, gas composition, gas yield, low-heating value (LHV), carbon conversion and gasification efficiency were studied. The results showed that higher ER led to higher gasification temperature and contributed to high H 2-content, but too high ER lowered fuel gas content and degraded fuel gas quality. A smaller particle was more favorable for higher gas yield, LHV, carbon conversion and gasification efficiency. And the BMF air gasification in the cyclone gasifier with the energy self-sufficiency is reliable.

Relationships between composition and pulmonary toxicity of prototype particles from coal combustion and pyrolysis

The hypothesis that health effects associated with coal combustion fly-ash particles are exacerbated by the simultaneous presence of iron and soot was tested through two sets of experiments. The first set created prototype particles from complete and partial combustion, or oxygen free pyrolysis of a high iron Illinois bituminous coal in an externally heated drop-tube furnace. The second experiment created prototype particles consisting of iron and soot in various concentrations from doped ethylene Burke–Schumann flames. Size-classified samples from the coal tests were separated into coarse (>2.5 μm), fine (0.5–2.5 μm) and ultrafine (<0.5 μm) fractions, and analyzed for total carbon, elemental composition, and detailed iron and sulfur speciation. In a similar manner, ultrafine particles from the ethylene flame tests were also analyzed for total carbon and elemental composition. Pulmonary inflammatory responses were determined after intratracheal aspiration of 100 μg samples in female CD1 mice. IL-6 and neutrophil responses were monitored as markers of inflammation. With carbon present, the coal data suggested that the ultrafine particles containing soot were more toxic than fine or coarse particles containing char, even though the iron and sulfur speciation varied only slightly with particle size. Iron and sulfur chemistry were, however, dependent on the extent of carbon burnout achieved. In the absence of carbon, ultrafine particles (high in bisulfates and semi-volatile alkali metals) were less toxic than the fine fraction (high in oxidized iron and sulfates). Iron-soot particles created from ethylene flames were more toxic than an equivalent physical mixture of iron oxide and soot, and the toxicity depended primarily on the soot concentration. However, taken as whole, these data do not support the notion that iron and soot interact to enhance pulmonary inflammatory responses.