• Energy Research

Despite many advantages of the utilization of biomass as a renewable energy source, certain bottlenecks during biomass plant operation can be identified. Transport and collection of biomass as well as non-uniform material characteristics are issues related to decreasing efficiency of logistics and fuel manipulation which can also cause economic problems with biomass collection, transport, and storage. Since biomass is an especially reactive fuel, this has raised concerns over its safe handling and utilization. Fires, and sometimes explosions, are a risk during all stages of fuel production as well as during handling and utilization of the product. This paper presents a novel method for assessing ignition risk and provides a ranking of relative risk of ignition of biomass fuels. Tests within this method include physical and chemical properties of biomass, thermal analysis measurements, and the calculation procedure steps which were made using characteristic temperatures from thermogravimetry recordings. The results of thermogravimetry analysis were used for determination of tangent slope of the mass loss rate curves in devolatilization zone at considered heating rates for all tested samples. Linear interpolation of the data obtained by tangent slope analysis and used heating rates may provide unique straight line for each sample in the ignition testing. Thermogravimetry index of spontaneous ignition (TGspi) is obtained for all samples based on newly established formula. By varying gradient of linear dependence of self-heating coefficient against reference temperatures, mass and heat transfer limitations for various biomasses were discussed. The proposed method is accurate as well as relatively simple and quick, enabling determination of data necessary for design and application of appropriate measures to reduce fire and explosion hazard related to operation of biomass.

In this work, plane tree seed-based activated carbons were characterized in detail for a variety of applications. The particularly important area of application would be in the artificial photosynthesis. After carbonization process of biomass precursor at 650°C, the resulting preliminary activated carbons were activated at various temperatures. The activated carbons were characterized by oxygen functionalities (a particularly important role has ester oxygen groups) which provide a unique microstructure. The chemical compositions of as-prepared activated carbons were analyzed through Fourier transform infrared and Raman spectra as well as gas chromatography–mass spectroscopy analysis, while morphology was observed by scanning electron microscopy analysis. Applied analysis showed that detected graphite mainly becomes uniformly nanocrystalline system. The current study also explored the applicability of carbon material obtained from plane tree seed as a potential gaseous adsorbent. The characterization showed that the tested material contains both mesopores and micropores, and this should be advantageous for the gas sorption process, since mesopores may provide low-resistant pathways for the diffusion of CO2 molecules, while the micropores are the most suitable for trapping of CO2. The sorption process analysis (including adsorption/desorption isotherms behavior) shows indication that the rate-limiting step of CO2 adsorption onto activated carbon is probably governed by diffusion-controlled process, especially at temperatures below 850°C.

The development of carbon materials with desirable textures and new aqueous electrolytes is the key strategy to improve the performance of supercapacitors. Herein, a deep eutectic solvent (DES) was used for in situ templating of a carbon material. A carbon material was characterized (XRD, N2-physisorption, FTIR, SEM and EDS) and used as an electrode material for the first time in multivalent-based supercapacitors. In situ templating of carbon was performed using a novel DES, which serves as a precursor for carbon and for in situ generation of MgO. The generation of MgO and its roles in templating of carbon were discussed. Templating of carbon with MgO lead to an increase in surface area and a microporous texture. The obtained carbon was tested in multivalent-ion (Al3+ and Mg2+) electrolytes and compared with H2SO4. The charge-storage mechanism was investigated and elaborated. The highest specific capacitance was obtained for the Al(NO3)3 electrolyte, while the operating voltage follows the order: Mg(NO3)2 > Al(NO3)3 > H2SO4. Electrical double-layer capacitance (versus pseudocapacitance) was dominant in all investigated electrolytes. The larger operating voltage in multivalent electrolytes is a consequence of the lower fraction of free water, which suppresses hydrogen evolution (when compared with H2SO4). The GCD was experimentally performed on the Al(NO3)3 electrolyte, which showed good cyclic stability, with an energy density of 22.3 Wh kg−1 at 65 W kg−1.

Abstract Slow pyrolysis characterization and kinetic modeling study of five different biomasses (corn brakes (CB), wheat straw (WS), hazelnut shell (HS), sawdust (Beech), and sawdust chemically treated (SDCT)) were performed in this work, using STA-MS techniques. Thermal decomposition of these samples was divided into three stages corresponding to removal of water, devolatilization, and formation of bio-char. Mass spectrometry (MS) showed that H2, CH4, H2O, CO2 (C3H8), CO, and C2H6 were the main gaseous products released during the pyrolysis of biomasses. It was found that H2O, CO and CO2 evolutions for all biomass samples arise from lignin source in biomass, followed by the cellulose, and hemicelluloses. It was established that the pseudo-component fraction estimated by the theoretical calculations is dependent on the heating rate. Using Gaussian multi-peak fitting and peak-to-peak approaches, regardless of the type of biomass, it was found that decomposition of lignin occurs independently of decomposition of remaining two pseudo-components and that there is no interaction between them. Namely, it was assumed that during pyrolysis process of biomasses, carbohydrate (hemicelluloses + cellulose)—lignin chemical structures most likely exist, where the variety of lignin structure units in different types of biomass affects on the level of energy required for its decomposition.

Abstract In the present study, the pyrolysis process under dynamic conditions of swine manure solids collected from rearing farm was investigated. Tested type of biomass feedstock was analyzed from the point of view of technological exploitation in order to obtain the highest possible quality and yields of bio-oil and bio-char. Furthermore, char gasification process was also examined. It was found that pyrolysis process can be described by parallel independent two-portion process model (PI-TPPM), which includes two processing state of the system (marked by processes # 1 and # 2), where process # 1 can be attributed to decomposition processes of hemicelluloses and fats/proteins, while process # 2 corresponds to pyrolyses of cellulose and lignin. Also, it was found that liquid and gas yields increase with an increase in heating rate, while approximately 40% of heavy oil yield is achieved by proposed experimental setup, which have been attained the satisfactory results for a good support in industrial extraction procedures. It was found that results associated with the presence of high reactivity at highest heating rate can be attributed to the highly porous structures formed, as we approach to the fast pyrolysis conditions.

As representative among biomass feedstocks, Poplar fluff was chosen to analyze the pyrolysis properties of this new biofuel. Thermogravimetry under inert (argon) atmosphere at the heating rates of 5, 10, 15, and 20 °C min−1 was employed in the investigation of thermal processing of studied biomass. The determination of kinetic parameters and estimation of reaction mechanism function were done through application of the state-of-the-art NETZSCH Kinetics NEO software. With this aim, the various model-free models and model-based calculations were implemented. The obtained results showed that the most appropriate kinetic model to describe the thermal decomposition of Poplar fluff sample was n-dimensional acceleratory Avrami–Erofeev model (An) for three-step consecutive reaction mechanism. Governed reaction pathway in pyrolysis process represents fragmentation reactions which arise from levoglucosan decomposing that permits permanent gases and refractory tars, where diffusion-controlled process is involved in the sample devolatilization. The modulated and multiple-step predictions of pyrolysis process were also carried out.

This study presents the experimental results of the mechanical and thermophysical properties of wood pellet samples important for their utilization in pellet stoves and boilers for heat production. The impact of operational parameters during the production process on a single pelletizer unit for three typical domestic commercial wood pellet samples (PWP110, BWP110, and BWP140) on fuel particle mechanical characteristics and related thermal properties was analyzed. It was concluded that the changes in raw material selection, as well as related operating parameters (extrusion length, i.e., die temperature during production process), have influenced the key mechanical and thermal characteristics of tested commercial wood pellets. The presented results have indicated the existence of a thin solid layer (due to waxes and subsequently lignin coating layer behaviors depending on their glass transition temperatures) on the surface of the BWP140 pellet sample. This layer leads to increasing the thermal resistance in the considered sample which can be explained by decreasing the effective thermal conductivity. Also, the forming of this layer on the surface of the wood pellet sample was caused by the production process (high-temperature impact explained by increasing friction between the die and feedstock during pellets production). It could be related to a lower value of effective thermal conductivity and specific heat capacity for considered (Beech) wood pellet sample.

The pyrolysis process of various types of biomass (agricultural and wood by-products) in non-isothermal conditions using simultaneous thermal analyses (STA) was investigated. Devolatilization kinetics was implemented through combined application of model-free methods and DAEM (distributed activation energy model) using Gaussian distribution functions of activation energies. Results obtained were used in the curve prediction of the rate of mass loss against temperature at various heating rates by numerical optimization. The possible calculation of biomass samples behavior under pyrolytic conditions as the summation of their pseudo-components, hemicelluloses, cellulose, and lignin is also explored. The differences between experimental and calculated data are less than 3.20% offering a quality test of applicability of proposed model on the kinetic studies of a wide range of biomass samples. It seems that the most physically realistic model is the decomposition of biomass in three reactions, depending on the composition of the biomass regarding hemicelluloses, cellulose, and lignin. Kinetic model applied here may serve as a starting point to build more complex models capable of describing the thermal behavior of plant materials during thermochemical processing.