Takayuki Takarada

Relation between functional forms of coal nitrogen and NOx emissions from pulverized coal combustion

Abstract NOx emissions during pulverized coal combustion, the thermal decomposition behaviour of fuel-bound nitrogen during rapid pyrolysis and the functional forms of coal nitrogen were investigated to develop the general index estimating NOx levels for coals covering a wide range of rank. NOx levels under excess air and two-stage combustion strongly depended on coal type. The effect of nitrogen content in the parent coal on NOx levels was not a continuous relationship, seemingly because of the yields of volatile nitrogen species which evolve during the early stage of combustion. An improved model of NOx formation was proposed to explain the influence of coal type. The dominant factors for NOx reduction were derived on the basis of the improved model. The volatile nitrogen yield and the NH 3 HCN ratio strongly affect NOx formation. An NOx index to predict NOx levels was proposed based on the relation between the functional forms of coal nitrogen and the yields of nitrogen-containing species. The index involves the proportion of quaternary, pyrrole- and pyridine-type nitrogen.

Volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and gasification of Victorian brown coal. Part V. Combined effects of Na concentration and char structure on char reactivity

Abstract A set of NaCl-loaded Loy Yang brown coal was pyrolysed in a thermogravimetric analyser between 600 and 900 °C. The char sample after pyrolysis was cooled down directly for in situ reactivity measurement with air. The results indicated that the volatilisation of Na during pyrolysis is an important reason for the existence of catalyst loading saturation level with Na as a catalyst in char because the char prepared at high temperature had a limited holding capacity for Na. Under the experimental conditions in this study, the char reactivity showed good linear correlation with the Na concentration in the reacting char. Peak pyrolysis temperature, affecting the release of Cl and distribution of Na in char, is an important factor governing the correlation between the char reactivity and Na concentration in char. The catalytic activity of Na is a result of the interaction between Na and char and thus is greatly dependent on the char/carbon structure. At high char conversion levels where the char structure is more inert and highly condensed, the catalytic activity of Na is reduced compared with its activity at low char conversion levels. The catalytic activity of Na depends on the structure of char.

Two-stage steam gasification of waste biomass in fluidized bed at low temperature: Parametric investigations and performance optimization

Steam gasification of waste biomass has been studied in a two-stage fluidized bed reactor, which has the primary pyrolysis fluidized bed using silica sand as bed material and the secondary reforming fixed bed with catalyst. The main objectives are parametric investigation and performance improvement especially at low temperature of around 600 °C using the wood chip and the pig manure compost as feedstock. Main operating variables studied are pyrolysis temperature, catalytic temperature, steam/biomass-C ratio, space velocity and different catalyst. Reaction temperatures and steam/C ratio have important role on the gasification process. About 60 vol.% H2 (dry and N2 free) and about 2.0 Nm3/kg biomass (dry and ash free basis) can be obtained under good conditions. Compared to Ni/Al2O3, Ni/BCC (Ni-loaded brown coal char) has a better ability and a hopeful prospect for the stability with coking resistance.

Fractionation and identification of organic nitrogen species from bio-oil produced by fast pyrolysis of sewage sludge

Pyrolysis of sewage sludge was performed at 500 degrees C and a sweeping gas flow rate of 300 cm(3)/min in a drop tube furnace. Liquid fraction (i.e., bio-oil) from the sewage sludge pyrolysis was separated by silica-gel column chromatography (SGCC) with different solvents, including mixed solvents, as eluants. A series of alkanenitriles (C(13)-C(18)), oleamide, alkenenitrile, fatty acid amides and aromatic nitrogen species were fractionated from the bio-oil by SGCC and analyzed with a gas chromatography/mass spectrometry (GC/MS). Most of the GC/MS-detectable organic nitrogen species (ONSs) are lactams, amides and N-heterocyclic compounds, among which acetamide is the most abundant. N-heterocyclics with 1-3 rings, including pyrrole, pyridine, indole, benzoimidazole, carbazole, norharman and harman, were observed. The lactams detected include pyrrolidin-2-one, succinimide, phathalimide, glutarimide, piperidin-2-one and 3-isobutylhexahydropyrrolo[1,2-a]pyrazine-1,4-dione, all of which should be formed via decarboxylation and cyclization of gamma- and delta-amino acids. Such a procedure provides an effective approach to fractionation and identification of ONSs from bio-oil produced by fast pyrolysis of sewage sludge.

Preparation and characterization of bio-oils from internally circulating fluidized-bed pyrolyses of municipal, livestock, and wood waste

Fast pyrolyses of sewage sludge (SS), pig compost (PC), and wood chip (WC) were investigated in an internally circulating fluidized-bed to evaluate bio-oil production. The pyrolyses were performed at 500 °C and the bio-oil yields from SS, PC, and WC were 45.2%, 44.4%, and 39.7% (dried and ash-free basis), respectively. The bio-oils were analyzed with an elemental analyzer, Karl-Fischer moisture titrator, bomb calorimeter, Fourier transformation infrared spectrometer, gel permeation chromatograph, and gas chromatography/mass spectrometry. The results show that the bio-oil from SS is rich in aliphatic and organonitrogen species, while the bio-oil from PC exhibits higher caloric value due to its higher carbon content and lower oxygen content in comparison with that from SS. The bio-oils from SS and PC have similar chemical composition of organonitrogen species. Most of the compounds detected in the bio-oil from WC are organooxygen species. Because of its high oxygen content, low H/C ratio, and caloric value, the bio-oil from WC is unfeasible for use as fuel feedstock, but possible for use as chemical feedstock.

Influence of manure types and pyrolysis conditions on the oxidation behavior of manure char

Livestock manure can be quickly converted into valuable products (H(2), syn-gas and char) by low temperature gasification. Manure char combustion offers energy for the gasification reactions. In the paper, the influence of manure type and pyrolysis conditions on manure char reactivity is addressed. The results show that the oxidation behaviors of manure char are dependent strongly on manure type and pyrolysis conditions employed. The large difference between the oxidation behaviors of pig and hen manure chars can be attributed to the difference in the organic materials and minerals of the samples. High final temperature, flash pyrolysis and water steam atmosphere used for char preparation promote the resultant char reactivity.

Scanning electron microscope observation of the purification behaviour of carbon nanotubes

Carbon nanotubes, with their unique structure, are expected to have a variety of applications as industrial materials. However, carbon nanotubes synthesized using the laser ablation method or arc discharge evaporation method always include other carbonaceous materials. Purification is a very important step in the use of carbon nanotubes as industrial materials. For the efficient recovery of nanotubes it is very important to clarify the gasification behaviour of the nanotube-containing material during the purification step. In this study, the gasification behaviour of a nanotube-containing material with various gasification agents was investigated in detail using a fixed-point observation technique and scanning electron microscopy. The gasification manner of the carbon nanotube-containing material was clarified using oxygen, carbon dioxide and hydrogen plasma as the gasifying agents. The gasification behaviour of the sample depended on the kind of reactant gas. In hydrogen plasma, carbon nanotubes were partly purified. Under the experimental conditions examined, oxygen gasification at 1023 K was the most effective method for purification of carbon nanotubes, and nanotubes were recovered selectively.

Gasification of bituminous coal with K-exchanged brown coal prepared from potassium chloride

Abstract A new method utilizing KCl as a catalyst precursor in the gasification of high rank coal was investigated. Potassium-loaded brown coal (Yallourn coal) prepared with KCl using an ion-exchange technique was physically mixed with a higher rank coal (Liddell coal). The mixture was gasified in steam (0.03 MPa) or carbon dioxide (0.1 MPa) with a thermobalance. The gasification temperature ranged from 873 to 973 K. Incorporation of potassium catalyst into Yallourn coal significantly enhanced the reactivity not only of Yallourn char but also of Liddell char. The effectiveness of the catalyst on the gasification of Liddell coal was dependent on coal particle size and the mixing ratio of K-exchanged Yallourn coal to Liddell coal. Electron probe microanalysis showed that potassium catalyst transferred from Yallourn char to Liddell char and spread out over the Liddell char surface in the gasification stage. The remarkable rate enhancement of high rank coal char by this technique was observed in both steam and carbon dioxide gasification.

Triacetonamine formation in a bio-oil from fast pyrolysis of sewage sludge using acetone as the absorption solvent.

A sewage sludge sample was pyrolyzed in a drop tube furnace at 500 degrees C and sweeping gas flow rate of 300cm(3)/min. Triacetonamine (TAA) was detected with GC/MS as major component in the resulting bio-oil using acetone as the absorption solvent and proven to be a product from the reaction of NH(3) in the bio-oil with the absorption solvent acetone. TAA yield increased with storage time and reached a level about 28.4% (% sludge fed, daf) after 175h. Since the reaction of pure NH(3) with acetone does not proceed, some species in the bio-oil must catalyze the reaction of NH(3) with acetone. TAA was isolated in a high yield (27.9%, daf) and high purity (80.4%) by column chromatography with different solvents, including mixed solvents, as eluants. The study revealed the possibility of sewage sludge as potential resource of TAA.

Hydropyrolysis of coal in a powder-particle fluidized bed

Abstract Coal was pyrolysed in hydrogen in a powder-particle fluidized bed at atmospheric pressure. The coal powder was continuously fed into the bed, in which CoMo Al 2 O 3 catalyst particles or silica sand particles were fluidized. The effect of silica sand on the secondary reactions of volatile matter was quite small, whereas CoMo Al 2 O 3 showed high activity for the cracking of tarry materials. In the presence of CoMo Al 2 O 3 , a hydrocarbon liquid with a narrow product distribution was obtained; the main components were light aromatic hydrocarbons such as BTX and naphthalene. The product composition was quite sensitive to the pyrolysis temperature. The yields of light aromatic hydrocarbons with CoMo Al 2 O 3 increased with temperature to 590 °C and then sharply decreased above 600 °C. Maximum yields of light aromatic hydrocarbons, 7.2wt% (BTX 5.8 wt%, naphthalene 1.4 wt%), ~30 times those with silica sand, were obtained at 590 °C with a bed height of 10 cm. The yields of hydrocarbon gases increased with temperature; the CH4 yield was 32 wt% at 650 °C.