Effects of torrefaction on product distribution and quality of bio-oil from food waste pyrolysis in N2 and CO2.

Waste food utilization to produce bio-oil through pyrolysis has received increasing attention. The feedstock can be utilized more efficiently as its properties are upgraded. In this work, the mixed food waste (MFW) was pretreated via torrefaction at moderate temperatures (250-275 °C) under an inert atmosphere before fast pyrolysis. The pyrolysis of torrified MFW (T-MFW) was performed in a bubbling fluidized-bed reactor (FBR) to study the influence of torrefaction on the pyrolysis product distribution and bio-oil compositions. The highest liquid yield of 39.54 wt% was observed at a pyrolysis temperature of 450℃. The torrefaction has a significant effect on the pyrolysis process of MFW. After torrefaction, the higher heating values (HHVs) of the pyrolysis bio-oils (POs) ranged from 31.51 to 34.34 MJ/kg, which were higher than those of bio-oils from raw MFW (27.69-31.58 MJ/kg). The POs mainly contained aliphatic hydrocarbons (alkenes and ketones), phenolic, and N-containing derivatives. The pyrolysis of T-MFW was also carried out under the CO2 atmosphere. The application of CO2 as a carrier gas resulted in a decrease in the liquid yield and an increase in the gas product yield. In addition, the carbon and nitrogen content of POs increased, whereas the oxygen was reduced via the release of moisture and CO. Using CO2 in pyrolysis inhibited the generation of nitriles derivatives in POs, which are harmful to the environment. These results indicated that the application of CO2 to the thermal treatment of T-MFW could be feasible in energy production as well as environmental pollution control.

Catalytic upgrade for pyrolysis of food waste in a bubbling fluidized-bed reactor.

Biofuel production via pyrolysis has received increasing interest as a promising solution for utilization of now wasted food residue. In this study, the fast pyrolysis of mixed food waste (MFW) was performed in a bubbling fluidized-bed reactor. This was done under different operating conditions (reaction temperatures and carrier gas flow rate) that influence product distribution and bio-oil composition. The highest liquid yield (49.05 wt%) was observed at a pyrolysis temperature of 475 °C. It was also found that the quality of pyrolysis bio-oils (POs) could be improved using catalysts. The catalytic fast pyrolysis of MFW was studied to upgrade the pyrolysis vapor, using dolomite, red mud, and HZSM-5. The higher heating values (HHVs) of the catalytic pyrolysis bio-oils (CPOs) ranged between 30.47 and 35.69 MJ/kg, which are higher than the HHVs of non-catalytic pyrolysis bio-oils (27.69-31.58 MJ/kg). The major components of the bio-oils were fatty acids, N-containing compounds, and derivatives of phenol. The selectivity for bio-oil components varied depending on the catalysts. In the presence of the catalysts, the oxygen was removed from oxygenates via moisture, CO2, and CO. The CPOs contained aliphatic hydrocarbons, polycyclic aromatic compounds (such as naphthalene), pyridine derivatives, and light oxygenates (cyclic alkenes and ketones).

A general reaction network and kinetic model of the hydrothermal liquefaction of microalgae Tetraselmis sp.

In this work, the hydrothermal liquefaction (HTL) of microalgal Tetraselmis sp. was conducted at various reaction temperatures (250-350°C) and reaction times (10-60min). A general reaction network and a quantitative kinetic model were proposed for the HTL of microalgae. In this reaction network, the primary decomposition of lipids, proteins, and carbohydrates generated heavy oil (HO), light oil (LO), and aqueous-phase (AP) products. Then, reversible interconversions and further decomposition of these product fractions to produce gas product were followed. The model accurately captures the trends observed in the experimental data. Analyses of the kinetic parameters (reaction rate constants and activation energies) suggested the dominant reaction pathways as well as the contribution of the biochemical compositions to the bio-oil yield. Finally, the kinetic parameters calculated from the model were utilized to explore the parameter space in order to predict the liquefaction product yields depending on the reaction time and temperature.

Thermogravimetric characteristics and pyrolysis kinetics of alga Sagarssum sp. biomass.

Alga Sagarssum sp. can be converted to bio-oil, gas, and char through pyrolysis. In this study, the pyrolysis characteristics and kinetics of Sagarssum sp. were investigated using a thermogravimetric analyzer and tubing reactor, respectively. Sagarssum sp. decomposed below 550°C, but the majority of materials decomposed between 200 and 350°C at heating rates of 5-20°C/min. The apparent activation energy increased from 183.53 to 505.57 kJ mol(-1) with increasing pyrolysis conversion. The kinetic parameters of Sagarssum sp. pyrolysis were determined using nonlinear least-squares regression of the experimental data, assuming second-order kinetics. The proposed lumped kinetic model represented the experimental results well and the kinetic rate constants suggested a predominant pyrolysis reaction pathway from Sagarssum sp. to bio-oil, rather than from Sagarssum sp. to gas. The kinetic rate constants indicated that the predominant reaction pathway was A (Sagarssum sp.) to B (bio-oil), rather than A (Sagarssum sp.) to C (gas; C1-C4).

Pyrolysis characteristics and kinetics of the alga Saccharina japonica.

Saccharina japonica can be converted to bio-oil, gas, and char through pyrolysis. In this study, the pyrolysis characteristics of S. japonica were investigated using a thermogravimetric analyzer. Most of the materials decomposed between 200°C and 350°C at heating rates of 10-20°C/min. The apparent activation energy increased from 102.5kJmol(-1) to 269.7kJmol(-1) with increasing pyrolysis conversion. The kinetic parameters of S. japonica pyrolysis were determined using nonlinear least-squares regression of the experimental data assuming first-order kinetics. The kinetic rate constants indicated that the predominant reaction pathway was B (bio-oil) to C (gas; C(1)-C(4)), rather than A (S. japonica) to B (bio-oil) and/or to C (gas; C(1)-C(4)). The proposed lumped kinetics of S. japonica pyrolysis offers a guide for the scale-up of the process at the research and industrial level.