Simulation of the Fast Pyrolysis of Coffee Ground in a Tilted-Slide Reactor

The fast pyrolysis of coffee ground for bio-crude oil production was simulated in a tilted-slide reactor. The biochemical composition was derived by an extended biomass characterization method based on the elemental analysis. The simulation was performed in a steady-state and a Lagrangian multiphase model was adopted to describe the transport of sand and biomass particles together with a multistep kinetic mechanism for fast pyrolysis. When the secondary tar cracking reactions were not considered the volatile yield increased monotonically with temperature. The inclusion of secondary reactions could improve the prediction of volatile yield which turn to decrease at higher temperature. It was found that not only the maximum volatile yield but also the corresponding reactor temperature agreed well with the experimental results. At the temperature higher than 550 °C the trend of volatile yield is similar to that of experiment while it is larger at lower reactor temperature. The individual species yields were compared at various reactor temperatures and the pyrolysis processes were analyzed by tracking the reference components when they were decomposed along the distance. It was found that the reactor temperature should be above 500 °C for effective pyrolysis of all reference components of coffee ground.

An Improved Comprehensive Model of Pyrolysis of Large Coal Particles to Predict Temperature Variation and Volatile Component Yields

In this work, an improved comprehensive model was developed for large coal particles to predict temperature variation and volatile component yields. The kinetics model of volatile component yields, where the volatile matters were assumed to comprise nine species, was combined with heat transfer model. The interaction between volatile yield and heat transfer during pyrolysis of large Maltby coal particles was investigated. An apparent temperature difference has been observed between the surface and core of particles at the initial heating stage. The non-uniform temperature distribution inside coal particles causes non-simultaneous volatile yields release from the surface and core area. The volatile release occurs after the coal temperature rises higher than 350 °C, and its yield steeply increases within the temperature range of 450–520 °C. The peak of volatile release rate corresponds to about 485 °C due to the rapid release of tar and H2O. The tar is almost completely released at around 550 °C. With the increasing particle size, the difference in temperature and volatile yield between the surface and core increases at the end of heating. The results are expected to provide insights into the interaction between heat transfer and volatile yields during pyrolysis of large coal particles.

Change of parameters in molecular structure of Donbas coals under the influence of external factors

The molecular structure of coal is estimated by 13 parameters of infrared spectra, electron paramagnetic resonance, volatile yield and ash content. A new criterion of hydrophobicity is applied, which has shown its informativeness in analyzing the molecular structure of coals of various ranks. It is more sensitive to changes in coal rank than the standard index of volatile yield. The coalification process leads to a significant increase in this index due to the water release and other hydroxyl-containing compounds from the substance of coal. Two-way analysis of variance showed that the influence of the metamorphism factor is significant for 9 molecular parameters. The strongest effects are manifested in the sorption capacity, the criterion of hydrophobicity and the number of paramagnetic centers. The stratigraphic factor does not have a significant impact on one of the molecular parameters. Factor analysis by the method of principal components of the molecular structure of coal showed that the most significant independent factors are metamorphism and sedimentation conditions, the latter ones include independent processes: accumulation of mineral components, decomposition of biomass and geochemical environment during the sedimentation period.

Influence of Pyrolysis Gas on Volatile Yield and CO2 Reaction Kinetics of the Char Samples Generated in a High-Pressure, High-Temperature Flow Reactor

The influence of pyrolysis atmosphere on volatile yield, structural characteristics, and CO2 reaction kinetics have been examined on chars generated from Pittsburgh No. 8 coal at 6.2 bar pressure and 1100 °C in a high-pressure, high-temperature flow reactor (HPHTFR) in Ar, N2, 50 (vol. %) CO2 and N2 (i.e., CO2/ N2) atmospheres. The chars were characterized for volatile yield, thermal swelling ratio, surface area, pore size distribution, crystallite structure, defects to graphitic intensity ratio, and char-CO2 reactivity. Coal pyrolyzed in CO2/N2 showed higher volatile yield (27%) compared to coal pyrolyzed in argon (~16%) and nitrogen (~19%). Except for volatile yield, there was no significant difference in structural properties for chars generated in different pyrolysis atmospheres. The difference in volatile yield was found to be due to presence of unconverted tetrahydrofuran (THF) soluble tar/soot. The results also showed that the intrinsic reactivity was highest for char generated in N2 atmosphere and lowest for char generated in CO2/N2 atmosphere. The kinetic parameters (activation energy and pre-exponential factor) for the char-CO2 reaction were ascertained using nth order model. The activation energies did not differ significantly among the chars generated in different pyrolysis atmospheres. The order of reaction was found to follow: CO2/N2 char > N2 char ≈ Ar char.