The fate of main gaseous and nitrogen species during fast heating rate devolatilization of coal and secondary fuels using a heated wire mesh reactor

The effect of ultra-fast heating on the microstructures of steel has been thoroughly studied over the last year as it imposes a suitable alternative for the production of ultra high strength steel grades. Rapid reheating followed by quenching leads to fine-grained mixed microstructures. This way the desirable strength/ductility ratio can be achieved while the use of costly alloying elements is significantly reduced. The current work focuses on the effect of ultra-fast heating on commercial dual phase grades for use in the automotive industry. Here, a cold-rolled, low-carbon, medium-manganese steel was treated with a rapid heating rate of 780 °C/s to an intercritical peak temperature (760 °C), followed by subsequent quenching. For comparison, a conventionally heated sample was studied with a heating rate of 10 °C/s. The initial microstructure of both sets of samples consisted of ferrite, pearlite and martensite. It is found that the very short heating time impedes the dissolution of cementite and leads to an interface-controlled α → γ transformation. The undissolved cementite affects the grain size of the parent austenite grains and of the microstructural constituents after quenching. The final microstructure consists of ferrite and martensite in a 4/1 ratio, undissolved cementite and traces of austenite while the presence of bainite is possible. Finally, it is shown that the texture is not strongly affected during ultra-fast heating, and the recovery and recrystallization of ferrite are taking place simultaneously with the α → γ transformation.

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Variable‐heating‐rate wire‐mesh pyrolysis apparatus

Review of Scientific Instruments ◽

10.1063/1.1140327 ◽

1989 ◽

Vol 60 (6) ◽

pp. 1129-1139 ◽

Cited By ~ 86

Author(s):

J. R. Gibbins ◽

R. A. V. King ◽

R. J. Wood ◽

R. Kandiyoti

Keyword(s):

Heating Rate ◽

Wire Mesh

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Evaluation of Hydrogen Yield Evolution in Gaseous Fraction and Biochar Structure Resulting from Walnut Shells Pyrolysis

Energies ◽

10.3390/en13236359 ◽

2020 ◽

Vol 13 (23) ◽

pp. 6359

Author(s):

Elena David

Keyword(s):

Heating Rate ◽

Pyrolysis Temperature ◽

Walnut Shell ◽

Hydrogen Yield ◽

X Ray Diffraction ◽

Fast Heating ◽

X Ray ◽

Walnut Shells ◽

Water Vapors ◽

Gaseous Fraction

Conversion experiments of wet and dry walnut shells were performed, the influence of moisture content on the hydrogen yield in the gas fraction was estimated and the resulted biochar structure was presented. Measurements of the biochar structures were performed using X-ray diffraction and scanning electron microscopy methods. The results demonstrate that heating rate played a key role in the pyrolysis process and influenced the biochar structure. Under fast heating rate, the interactions between the water vapors released and other intermediate products, such as biochar was enhanced and consequently more hydrogen was generated. It could also be observed that both biochar samples, obtained from wet and dry walnut shells, had an approximately smooth surface and are different from the rough surface of the raw walnut shell, but there are not obvious differences in shape and pores structure between the two biochar samples. The increasing of the biochar surface area versus pyrolysis temperature is due tothe formation of micropores in structure. The biochar shows a surface morphology in the form of particles with rough, compact and porous structure. In addition the biochar structure confirmed that directly pyrolysis of wet walnut shells without predried treatment has enhanced the hydrogen content in the gas fraction.

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Simulation of the Agro-Biomass(Olive Kernel) Fast Pyrolysis in a Wire Mesh Reactor Considering Intra-Particle Radial and Temporal Distribution of Products

International Journal of Chemical Reactor Engineering ◽

10.2202/1542-6580.1833 ◽

2009 ◽

Vol 7 (1) ◽

Author(s):

Theodoros Damartzis ◽

Margaritis Kostoglou ◽

Anastasia Zabaniotou

Keyword(s):

Particle Size ◽

Heating Rate ◽

Particle Temperature ◽

Fast Pyrolysis ◽

Temporal Distribution ◽

Experimental System ◽

Product Distribution ◽

Wire Mesh ◽

Particle Model ◽

Transfer Model

In the present study, a model for the fast pyrolysis of a spherical biomass particle has been developed. The model admits the generation of data which are not accessible experimentally such as the intra-particle temperature and concentration distribution. Simulations have been carried using data from the reactor as well as from literature and the effects of the heating rate and the particle size have been examined. The kinetic model is coupled with a heat transfer model. The reaction kinetic constants have been chosen in order to match the theory to the data taken from experiments carried out in a laboratory wire mesh reactor, for a temperature range from 573 K to 873 K and a heating rate of 200 K/s. Pyrolysis temperature and product distribution profiles in both spatial and temporal directions throughout the particle are presented. The effects of the particle size and the reactor's heating rate in the final pyrolysis products and temperature are shown and discussed. Simulations were carried out using Matlab and the model has been validated against the experimental results. The heating rate, which is an important operating condition in thermal processes, seems to have a positive effect on the biomass conversion to gaseous and liquid products, an increase of the first resulting to an increase of the second. Particle size was found to have a negative effect on pyrolysis conversion as larger particles tend to give higher char yields. For the particular experimental system analyzed here, it seems that the radial non-uniformity is not very large and acceptable results can also be taken using a lumped particle model. Validation of the model with experimental data showed great accordance, thus the model could be used for the prediction of final pyrolysis yields and temperatures.

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Nano-Meter Size WC Whiskers Grown over a Compacted Pellet of Graphite/Tungsten Powder Mixture Heated with an Ultra-Fast Heating Rate by a Concentrated Solar Beam

MATERIALS TRANSACTIONS ◽

10.2320/matertrans.48.919 ◽

2007 ◽

Vol 48 (5) ◽

pp. 919-923 ◽

Cited By ~ 8

Author(s):

Susana Dias ◽

Fernando Almeida Costa Oliveira ◽

Bernard Granier ◽

Jean-Marie Badie ◽

Jorge Cruz Fernandes ◽

...

Keyword(s):

Heating Rate ◽

Powder Mixture ◽

Tungsten Powder ◽

Fast Heating

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Attempts to Measure the Inductive Element Associated with the Natural Convection of Heat

Australian Journal of Physics ◽

10.1071/ph600084 ◽

1960 ◽

Vol 13 (1) ◽

pp. 84

Author(s):

RCL Bosworth

Keyword(s):

Natural Convection ◽

Kinetic Energy ◽

Electric Current ◽

Heating Rate ◽

Heat Input ◽

Inductive Element ◽

Heated Wire ◽

The Wire ◽

Inductive Elements

A study has been made of the variation in time of the temperature of a wire immersed in a fluid and heated by a constant electric current. For a given fluid the curve obtained by plotting the ratio of the temperature of the wire to the heat input versus the time is initially the same shape for all rates �of heat input. Divergences from the lowest heating rate set in only when the system of convection currents sets in. This occurs at earlier times after the commencement of heating the higher the heating rate. Expressions already developed are used to evaluate the resistive, capacitive, and inductive elements required to fit the observed transient curves. The values of the former two types of element are consistent with an assumed stagnant film of a thickness the order of 1 mm around the heated wire, but the value of the deduced inductive element is some 10--106 greater than that associated with the kinetic energy belonging to the system of convection currents.

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The effect of heating factors on the properties of heat-induced surimi gel under ohmic heating

Can Tho University Journal of Science ◽

10.22144/ctu.jen.2021.028 ◽

2021 ◽

Vol 13 (2) ◽

pp. 32-42

Author(s):

Van Nguyen

Keyword(s):

Electrical Conductivity ◽

Heating Rate ◽

Salt Concentration ◽

Ohmic Heating ◽

Heating Time ◽

Holding Time ◽

Water Bath ◽

Heating Rates ◽

Fast Heating ◽

Water Bath Heating

Ohmic heating (OH) is a method that heat is generated within the food due to its electrical resistance, resulting in a relatively linear heating rate and uniform temperature distribution. Because surimi-based paste contains water and salts, the conductivity is sufficiently good for the ohmic effect. Gelation induced by OH greatly depends on heating conditions such as heating speed, heating time, or electrical conductivity. However, the detailed information obtained is quite limited. Therefore, in order to clarify how ohmic heating affects the physical properties of surimi gel under OH, gels from croaker surimi (SA grade) were obtained using different heating conditions (heating speed, heating time, or salt concentration - electrical conductivity). Furthermore, the gels heated by ohmic heating were compared with the gel obtained by conventional water-bath heating. The results showed that, at the same heating rates, higher salt concentration generated better surimi gels for croaker surimi. Gels cooked ohmically at a slow heating rate performed significantly better than those cooked at a fast heating rate or heated conventionally in a water bath. There was little discernible difference in protein pattern between gels heated by OH and conventional water bath heating at fast heating rates with two different salt concentrations. The results also indicated that holding time at target temperature showed no effect on the gel. These results suggested that the properties of heat-induced surimi gels by OH are affected by not only heating speed but also holding time at maximum temperature and salt content.

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