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The fast devolatilization of biomass is the first step of thermochemical conversion in fluidized bed boilers or gasifiers. Some advanced devolatilization models applicable to a wide range of biomasses and process conditions have been developed on the basis of a detailed description of the physico-chemical mechanisms and of biomass standard analysis. In this study, the results of a biomass devolatilization model taking into account the main physical and chemical phenomena are reported. Attention is focused on biomass thermal properties derived from its composition and density. The kinetic scheme is based on the lumped kinetic model of (Ranzi et al., 2008) and its further development. Predictions of the complete devolatilization time of biomass thick particles are compared with experimental results obtained in different high-temperature fluidized bed reactors. Experimental results obtained with biomass pellets under image furnace conditions are also used to assess the dynamic release of volatile matter predicted in transient state. The great interest of predictive model able to reduce the number of input parameters for any biomass type is finally underlined.

The simultaneous combined heat and power (CHP) production via biomass gasification is considered as one of the main alternatives to fossil energy. Yet, a major obstacle in the development of this advanced technology lies in the presence of tars in syngas that are responsible for clogging downstream process equipment. Mathematical modelling and simulation studies are powerful tools to predict the performance of new processes. Baratieri et al. (2009), Pérez-Fortes et al. (2011) or Damartzis et al. (2012) develop comprehensive models of integrated biomass gasification plant, but based on thermochemical equilibrium approach that do not take into account the formation of tars. Recently, extensive models of Dual Fluidised Bed (DFB) gasifier demonstrate the possibility of accurately predict the formation of tars in syngas (Abdelouahed et al., 2012). The work presented in this paper consists in integrating a rigorous model of a DFB gasifier capable of predicting tar and contaminants in a global biomass CHP process. Our model includes the steps of wood drying, wood gasification, syngas cleaning, and power production in gas engine. Heat integration is considered all over the process for intern consumption and extern district heating. The model is set in Aspen Plus® and external Fortran user-subroutines are used to precisely describe complex phenomena in gasification reactor and gas engine. The energey efficiency of the CHP plant is evaluated. Simulation results highlight the strong impact of the syngas cleaning step in the overall performance of the CHP plant.

In the context of waste upgrading of polyethylene terephthalate (PET) by pyrolysis, this study presents three on-line mass spectrometric techniques with soft ionization for monitoring the emitted decomposition products and their thermal dependent evolution profiles. Pyrolysis experiments were performed using a thermogravimetric analyzer (TGA) under nitrogen atmosphere with a heating rate of 5 °C/min from 30 °C to 600 °C. Single-photon ionization (SPI at 118 nm/10.5 eV) and resonance enhanced multiple photon ionization (REMPI at 266 nm) were used with time-of-flight mass spectrometry (TOF-MS) for evolved gas analysis (TGA-SPI/REMPI-TOFMS). Additionally, the chemical signature of the pyrolysis products was investigated by atmospheric pressure chemical ionization (APCI) ultra high resolution Fourier Transform ion cyclotron resonance mass spectrometry (FT-ICR MS) which enables assignment of molecular sum formulas (TGA-APCI FT-ICR MS). Despite the soft ionization by SPI, the fragmentation of some compounds with the loss of the [O-CH = CH2] fragment is observed. The major compounds were acetaldehyde (m/z 44), benzoic acid (m/z 122) and a fragment of m/z 149. Using REMPI, aromatic species were selectively detected. Several series of pyrolysis products were observed in different temperature intervals, showing the presence of polycyclic aromatic hydrocarbons (PAHs), especially at high temperatures. FT-ICR MS data showed, that the CHO 4 class was the most abundant compound class with a relative abundance of 45.5%. The major compounds detected with this technique corresponded to m/z 193.0495 (C 10 H 9 O 4 + ) and 149.0233 (C 8 H 5 O 3 + ). Based on detailed chemical information, bulk reaction pathways are proposed, showing the formation of both cyclic monomer/dimer and linear structures., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The pyrolysis of the lignocellulosic biomass is a promising process to produce biofuels or green chemicals. Specific analytical methods have to be developed in order to better understand the composition of biomass and of its pyrolysis products and therefore to optimize the design of pyrolysis processes. For this purpose, different biomasses (Douglas and Miscanthus) and one biochar were analyzed by laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (LDI FT-ICR MS). This method allowed the biomass and biochar to be analyzed without any sample preparation and with a spatial resolution of about 100 μm. The influence of LDI conditions (laser wavelength and laser irradiance) and the nature of the biomass and biochar on the obtained mass spectrum were investigated. The nature and origin of the observed ions highly depended on LDI conditions. In the softest laser-biomass interaction conditions (low laser irradiance), the detected ions were related to the nature of the investigated biomass. Indeed, the main part of the detected species came from the different biomass subunits and was produced by photolysis of covalent bonds. When more severe laser irradiation conditions were used, the obtained mass spectra gathered the ions relative to (i) the chemical components of the investigated samples, (ii) the recombination products of these species in the gas phase after their ejection from the sample surface, and (iii) the compounds produced by laser pyrolysis of the sample. This was expected to be useful to mimic thermal pyrolysis. Graphical Abstract.

Clostridium acetobutylicum, a promising organism for biomass transformation, has the capacity to utilize a wide variety of carbon sources. During pre-treatments of (ligno) cellulose through thermic and/or enzymatic processes, complex mixtures of oligo saccharides with beta 1,4-glycosidic bonds can be produced. In this paper, the capability of C. acetobutylicum to ferment glucose and cellobiose, alone and in mixtures was studied. Kinetic studies indicated that a diauxic growth occurs when both glucose and cellobiose are present in the medium. In mixtures, D-glucose is the preferred substrate even if cells were pre grown with cellobiose as the substrate. After the complete consumption of glucose, the growth kinetics exhibits an adaptation time, of few hours, before to be able to use cellobiose. Because of this diauxic phenomenon, the nature of the carbon source deriving from a cellulose hydrolysis pre-treatment could strongly influence the kinetic performances of a fermentation process with C. acetobutylicum.

Experiments are performed on a laboratory scale setup where beech wood chips are heated by gas convection and walls radiation. This study shows that it is possible to obtain high bio-oil and char yields with relatively low external heat transfer coefficients. The main advantage of this convection/radiation heat transfer mode compared to solid-solid collisions, applied in fluidized bed or twin screw reactors, is the reduction of solid attrition (char and sand). Thus tricky gas-solid separation through hot cyclones and/or hot filters could be avoided or reduced. It should be possible to recover directly bio-oil with less char particles and char free of sand dust. These qualities would allow easier use of these bio-products in different applications.