• Energy Research

Abstract Bio-oil from the fast pyrolysis of biomass can be converted to solid carbon materials, chemicals and syngas by various thermochemical conversion methods. As a first step in all of these processes, bio-oil undergoes drastic components changes due to its exposure to the elevated temperature. Understanding the effects of heating rate on bio-oil transformation during its pyrolysis is therefore crucial for effective utilization of bio-oil. In this study, a bio-oil sample produced from the fast pyrolysis of rice husk at 500 °C was pyrolyzed in a fixed-bed reactor at temperatures between 300 and 800 °C at three different heating rates: fast (≈200 °C/s), medium (≈20 °C/s), and slow (≈0.33 °C/s). In addition to the quantification of coke and tar yields, the tar was characterized with an ultraviolet (UV) fluorescence spectroscopy, a gas chromatography/mass spectrometer (GC/MS) and a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). Our results indicate that slow heating rates promote polymerization of bio-oil components, particularly at low temperatures ( 500) were also promoted at fast heating rates via the more intense secondary reactions.

Abstract Methane-fueled solid oxide fuel cells (SOFCs) are promising to achieve high energy conversion efficiency while no study focuses on the conversion efficiency of methane into power, which is greatly restrained by gas diffusion within anode supports. This study employs microchanneled anode supports to provide fast gas diffusion pathway. To confirm the advantage, the anodes with half-channels and without channels are also used for comparison. The microchannel structure increases the maximum power density up to 2.5 times because of diminishing or eliminating concentration polarization within anode supports and improving catalyst coating over anode internal surface. As a compromise of fuel utilization and power output, methane conversion efficiency is defined as power output per mol methane input in feeding gas to compare with the reported results, and the microchanneled SOFCs achieve the record high methane conversion efficiency.

Abstract Coal breakage characteristics have significant effects on the clean utilization of coal. The mechanical properties of Shenmu (SM) coal, Hongshaquan (HSQ) coal and Wucaiwan (WCW) coal under uniaxial compression were tested by a self-designed bench at 90 °C, 120 °C, 150 °C and 180 °C. The results show that the mechanical parameters overall decrease with the increase of temperature (T, °C) except that SM coal has an increasing trend from 120 °C to 180 °C due to thermal expansion of coal matrix and moisture inside closed pores. The compressive strength (σm, MPa) of SM coal at 120 °C decreased by 43% compared with it in 90 °C. By means of fractal theory, these mechanical properties can be reflected by the meso-structural characteristics of coal surface. The fractal dimension (D) generally possesses a positive correlation with the stress (σ, MPa). In initial segments, the curves of some coal samples are relatively stable due to compaction and compressive resistance. Two dimensionless parameters, relative fractal dimension (Dr) and relative stress (σr), were introduced to represent the relationship of meso-structural and mechanical properties quantitatively. It is shown that the relative fractal dimension rises quickly when the relative stress is above 0.75, and the relationship of the two dimensionless parameters can be described.

The high content of nitrogen in hydrochar produced from hydrothermal carbonization (HTC) of sewage sludge (SS) leads to serious NOx pollution when the hydrochar is used as a solid fuel. Mg-Ga layered double hydroxides (LDHs), Mg-Al LDHs and their calcined samples (layered double oxides, LDO) were prepared. The LDHs and LDO all can notably promote the removal of nitrogen element, in which organic-N was transferred to NH4+-N to cause increasing pH value. Mg-Al LDO showed the highest efficiency for the removal of nitrogen among the catalysts. The thermal decomposition of the N-organic matter with acidic sites in catalyst was the key step to release NH3. The key role of basic sites in Mg-Al LDO was that it can effectively destroy the cell wall and extracellular polymeric substances structure. The lipid-like substance did not participate in the carbonization reaction, but they can be absorbed by the hydrochar. Partial SS floc directly transformed to hydrochar according to "solid-solid" reaction. The reaction pathways of remove nitrogen were proposed.

Polyethylene is a major contributor of plastic waste, which can be converted into liquid fuel via catalytic pyrolysis. In this study, the pyrolysis of light or heavy density polyethylene (LDPE and HDPE) and their mixture with the biochar produced from gasification of poplar wood as catalyst was investigated. The results showed that, during the co-pyrolysis of LDPE and HDPE in absence or presence of biochar catalyst, cross-interaction of reaction intermediates originated from the degradation of LDPE and HDPE substantially promoted the formation of gaseous products and the evolution of heavy organics with π-conjugated structures in the tar. During the pyrolysis of HDPE, more heavy tar while less wax was produced, while it was contrary during the pyrolysis of LDPE. In the catalytic pyrolysis of LDPE, the volatiles could be effectively cracked over the biochar catalyst, forming more gases, while in the catalytic pyrolysis of HDPE, instead of catalyzing the cracking of the heavy components, the biochar catalyzed the polymerisation reactions. The properties of the biochar catalyst in terms of crystallinity, surface functionality, and internal structures also changed remarkably due to the transfer of oxygen-containing species from the polyethylene to biochar and the interaction of biochar with volatiles in the pyrolysis.

Abstract This study aims to investigate the importance of aromatic structures in tar to the destruction of tar itself during the volatile–char interactions. The same nascent char was subjected to interactions with two distinctly different volatiles (e.g. coal volatiles and biomass volatiles) at 700–900 °C. The results indicate that the aromatic structures in tar are more reactive with char than the non-aromatic structures, especially at high temperature (e.g. 900 °C). At lower temperatures (

Abstract Bio-oil is considered a renewable feedstock for the production of energy, fuels, chemicals and carbon materials. These specifically include the direct combustion of bio-oil as a boiler fuel, the production of biofuel from bio-oil via hydrotreatment, or the production of value-added chemicals via separation and acid-catalysis/hydrogenation or the conversion of bio-oil to carbon materials via polymerisation/cracking. So far, considerable efforts have been made to develop feasible method for utilizing bio-oil. However, it remains a challenge to find a suitable outlet for the commercial application of bio-oil. The conversion of bio-oil into the useful products has been the focus of numerous studies. Therefore, the review of the progress of this area is of importance for providing the necessary information for assessing the feasibility of the varied process for the application of bio-oil in a comparative manner. This work reviewed the progress of bio-oil as the feedstock for the use as boiler, heavy-duty engine fuel, or the use as the feedstock for the production biofuel, hydrogen, chemicals, carbonaceous materials, binder for electrode and asphalt, pesticide and fertilizer, polyurethane foam and plastics. In addition, the major issues associated with the application of bio-oil as well as the techno-economic aspects of each application were analysed as well. Suggestions were given for the future developments in each application. The analysis indicated that majority of these technologies are mainly in the initial stages of developments. Either cost or the technical issues are the major barrier for the commercial application of bio-oil in large scale.

Abstract This study investigated the transformation of N‑heterocycle compounds during sewage sludge pyrolysis process. The reaction pathways for evolution of the products especially the N-containing organics such as amino acids‑N were analyzed in detail. NH3 is the main N-containing gaseous product during the pyrolysis and its concentration was increased with the increasing temperature. Phenolic compounds, hydrocarbons and heterocyclic compounds were the main component in liquid products. The in situ FT-IR study showed that the labile inorganic ammonium salt decomposition proceeded to completion below 500 °C. Above 500 °C N‑heterocycle compound was formed and then it was decomposed, while above 600 °C nitrile started to decompose. NH3 formation main originates from the decomposition of N‑heterocyclic compounds and nitrile. Proteins during the pyrolysis, as verified by XPS, were mainly converted into inorganic nitrogen. In addition, the Py-GC–MS results showed that large amount of N‑heterocyclic compounds were found in amino acid‑N pyrolysis products. The transformation paths for the amino acids with different chemical structures were distinct. Except N‑heterocyclic amino acids, long chain aliphatic amino acid also can form N‑heterocyclic compounds through cyclization. In addition, the decomposition of the intermediates of N‑heterocyclic compounds form small molecular compounds or while the polymerization of the intermediates forms macromolecule compounds. The amino acids with heterocycle structure were disrupted to form heterocycle and aliphatic intermediate. The plausible mechanism of sewage sludge pyrolysis was proposed.

Abstract The pyrolysis of cellulose at 200–800 °C with an increment of 50 °C was conducted in this study, aiming to understand impacts of temperature on evolution of the of organics and the structures of bio-char. Extensively pyrolysis of cellulose to bio-oil initiated at 300 °C, reached maximum at 450 °C, and shifted to gasification to produce gases as the main products above 650 °C. Dehydrate sugars were the initial products formed below 350 °C, which soon dehydrated to form furans at ca. 400 °C and then generate aliphatic aldehydes, ketones and carboxylic acids at ca. 650 °C via the session of the C–C bonds. Aromatization of the volatiles initiated at 350 °C, producing phenolics and then further to aromatic hydrocarbons. The medium pyrolysis temperature (i.e. 450 °C) tended to produce the heavier bio-oil. The in situ DRIFTS characterization of cellulose pyrolysis showed that the structural reconstruction of the feedstock occurred at ca. 430–440 °C, forming abundant C O functionalities in bio-char. The increasing pyrolysis temperature led to staged change of carbon, hydrogen and oxygen contents in bio-char. The bio-char produced at the low temperature was quite aliphatic, and increasing pyrolysis temperature enhanced the formation of graphite structure, thermal stability and the porosity of bio-char. The bio-char from cellulose had a compact structure with small surface area and very limited mesopores. The results of kinetic analysis showed that the pyrolysis of cellulose was a complex multi-step reaction process.