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In this work, we study the gasification of pellets produced, after densification, by blending olive mill solid wastes, impregnated or not by olive mill waste water, and pine sawdust under different steam/nitrogen atmospheres. The charcoals necessary for the gasification tests were prepared by pyrolysis using a fixed bed reactor. The gasification technique using steam was chosen in order to produce a hydrogen-enriched syngas. Gasification tests were performed using macro-thermogravimetric equipment. Tests were carried out at different temperatures (750 °C, 800 °C, 820 °C, 850 °C and 900 °C), and at different atmospheres composed by nitrogen and steam at different percentages (10%, 20% and 30%). Results show that the mass variation profiles is similar to the usual lingo-cellulosic gasification process. Moreover, the increase of temperatures or water steam partial pressures affects positively the rate of conversion and the char reactivity by accelerating the gasification process. The increase of the gasification yields demonstrates the promise of using olive mill by-products as alternative biofuels (H 2 enriched syngas). • 4 chars were prepared under slow pyrolysis. • Gasification tests under steam/Nitrogen were performed with pellet/powder states. • Steam molar fraction and temperature influences positively the process. • Impregnation process is advantageous for gasification yields. • Olive mill wastewater is converted from a pollutant to a renewable energy source. [ABSTRACT FROM AUTHOR]

Abstract This work investigates the reactivity of chars produced from Turkish biomass and lignite fuels using a wire mesh reactor at high temperature and high heating rate. The fuels studied were olive residue, almond shell, and Soma lignite. Blends of Soma lignite-olive residue and Soma lignite-almond shell were prepared in proportions of 75:25 and 50:50 wt%, respectively. A wire mesh reactor is used for the pyrolysis of the samples in a controlled inert atmosphere at a uniform temperature of 1600 °C and at a heating rate of above 103 °C s−1. The resulting volatile yields from the wire mesh reactor were compared with those from the proximate analyses. Volatile yield of Soma lignite obtained from wire mesh reactor (53 wt%) was higher than that of the proximate analysis (31 wt%); however, biomasses showed similar yields from both techniques. The morphology and structural changes of the chars were investigated using Scanning Electron Microscopy. Biomass chars displayed a high level of macro-porosity. Combustion reactivity and burnout times of the char samples were determined from thermogravimetric analysis. Biochars had about three times shorter burnout times and three times higher reactivity values compared to those of Soma lignite. First-order kinetic rate constants were determined for all individual chars and blends. Rate constants of the blends showed minor synergistic effect with an increase in the olive residue content, and a pronounced deactivation effect observed with an increase in almond shell content. Highlights • Volatile yields from fast pyrolysis were greater than those from proximate analysis. • Reactivities of the biomass chars were higher when compared to those of the lignite. • Blends with 25% biomass displayed a combustion behavior similar to neat lignite char. • Blends with 50% olive – 50% lignite showed a synergistic effect. • Blends with 50% almond – 50% lignite presented a deactivation effect. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The effect char porosity and metal content have on its reactivity is analyzed. • At 900 °C the porosity is faster developed, attaining high S BET at lower conversion. • Porous structure influenced the reaction rate mainly at early stages. • For X > 0.6 the increase in reactivity is related to the catalytic effect of Ca and K. Abstract A study was carried out on the effect the evolution of the porous structure and metal content have on the gasification rate during char gasification in a conical spouted bed reactor. Partially gasified samples at different temperatures (800–900 °C range) were collected at various conversion levels and characterized by different techniques (N 2 adsorption-desorption, ultimate/proximate analysis and X-ray Fluorescence). At 900 °C there is a fast development of the porous structure, attaining the highest BET specific surface area (S BET) (633 m2 g−1) at low conversion. Char reactivity profiles revealed that the development of the porous structure influenced the reaction rate mainly at early stages, whereas the increase in the gasification rate for conversions higher than 60% (especially at 900 °C) was attributed to the catalytic effect of Ca, K and Fe (the main metals in the ashes). [ABSTRACT FROM AUTHOR]

Abstract The firing of biomass or co-firing of biomass with coal has become a common practice in power generation industry worldwide as a cost-effective means to move towards lower carbon footprint. However, the relationship between the properties of biomass and combustion behaviour is not well understood, yet. In this study, we investigated the links between biomass lignocellulosic composition and plant cell wall types, and how they would collectively influence char morphology and reactivity. Five different biomass, i.e. pinewood, distiller dried grains with solubles (DDGS), miscanthus, wheat straw and wheat shorts, in two size fractions were thermochemically pre-treated to alter their lignocellulosic compositions resulting in 50 different samples with varying compositions. Plant cell type and morphology of raw biomass particles were examined using SEM. Biomass char samples were prepared using a fast heating drop tube furnace (DTF) and a slow heating muffle furnace. The morphology of char particles was examined using an oil-immersion microscope whilst the intrinsic reactivity of chars was studied using a thermogravimetric analyser (TGA). Pre-treatments affected most biomass tested in similar trends but to varying degrees, particularly in terms of lignocellulosic composition, cell wall structure and char morphology. Results show that lignocellulosic composition (and plant cell wall types) of biomass correlated well with char morphology and char reactivity. Therefore, it is possible to predict aspects of combustion behaviour from biomass lignocellulosic composition for this selection of samples tested. This work provides a base study for establishing lignocellulosic composition as a key indicator in fuel selection. Highlights • The type of plant cell wall has significant impact on char morphology and reactivity. • The influence of lignocellulose on biomass char morphology is established. • Pre-treatments have profound impacts on lignocellulosic composition and char morphology. • Amount of lignin and cellulose indicates the presence (or absence) of secondary walls. • The combined amount of lignin and cellulose can be used to predict char reactivity. [ABSTRACT FROM AUTHOR]

In this work, single particle combustion of raw and torrefied 4 mm wood particles with different potassium content obtained by KCl impregnation and washing was studied experimentally under a condition of 1225 °C, 3.1% O 2 and 26.1% H 2 O. The ignition time and devolatilization time depended almost linearly on the fuel particle mass. The char conversion time was influenced by both the char mass and char reactivity. Both KCl impregnation and torrefaction promoted char yield, while washing slightly inhibited char formation. The char reactivity was increased by KCl impregnation, decreased by washing, and unchanged by torrefaction. Compared to the raw wood particle, the char conversion time was increased by torrefaction, decreased by washing, and almost unchanged by KCl impregnation due to its promoting effect on both char yield and reactivity. [ABSTRACT FROM AUTHOR]

A critical review and analysis of co-gasification of coal/biomass blends is presented. Initially, the chemistry of gasification of coal and biomass has been described along with different models for pyrolysis of cellulose/biomass. The mechanistic issues of catalytic effect of alkali metals on coal char gasification have been reviewed. This is followed by literature review on gasification of coal/biomass blends in two parts, viz. thermogravimetric and fluidized bed gasification. First part deals with effects of operational parameters on char reactivity. Second part analyzes influence of these parameters on gasification chemistry and producer gas. Factors governing tar content in producer gas have been discussed. Finally, the literature on kinetic modeling of coal/biomass blends has been analyzed. Some new approaches in kinetic modeling of solid-state reactions have been discussed. [ABSTRACT FROM AUTHOR]

Gasification is one route to produce chemicals and liquid fuels from biomass. The gasification of the char is catalyzed by alkali and alkaline earth metals in the biomass. In this work the catalytic effect of calcium (Ca) and potassium (K) on CO 2 gasification of spruce wood was studied using a thermo gravimetric analyzer (TGA). The ash-forming elements were first removed from the wood using an acid leaching method. Then, various concentrations of K and Ca were absorbed to the wood by ion-exchange to carboxylic and phenolic groups, impregnation of K 2 CO 3 or physically mixing of CaC 2 O 4 . The prepared spruce samples were placed in a mesh holder and gasified in the TGA at 850 °C in 100% CO 2 . The results demonstrate that the gasification rate of the char increased linearly with an increase in the concentration of Ca or K. Crystalline CaC 2 O 4 distributed only at the surface of the wood particles resulted in low catalytic activity. The catalytic activity of Ca was higher than K in the beginning of char gasification but the catalytic effect of Ca decreased earlier than the catalytic effect of potassium. Further, the char structure was investigated by SEM–EDX. The SEM analysis from interrupted gasification experiments showed the formation of CaCO 3 and K 2 CO 3 layer on the char surface. By adding corresponding levels of Ca and K as the original spruce to the acid washed sample, a similar gasification reactivity was obtained at 850 °C. [ABSTRACT FROM AUTHOR]

Benzene removal using spruce wood char as catalyst was investigated. The influence of pyrolysis temperature and activation with CO2 on the char structure and reactivity for benzene adsorption and cracking was analyzed. The structural features of the char were examined by the CO2 adsorption technique and Fourier transform infrared spectroscopy (FTIR). The reactivity for benzene removal was investigated using a fixed bed quartz reactor. Surface analysis showed that the microporous char surface area was influenced by the pyrolysis temperature and was almost doubled by activation with CO2. The benzene adsorption capacity of the char decreased with increasing pyrolysis temperature. Activation with CO2 however, increased the fraction of adsorbed benzene by a factor of two and 10 for char produced at 500 and 800 °C, respectively. The total microporous surface above 700 m²/g was found to be a good indicator for the reactive char surface for benzene cracking at high temperatures. At 1050 °C the main mode of benzene conversion was homogeneous thermal decomposition. We confirmed that wood char has the potential to serve as an effective catalyst for benzene removal. However, benzene decomposed over the charcoal by carbon deposition which led to a fast deactivation of the wood char catalyst. [ABSTRACT FROM AUTHOR]

Abstract: The influence of initial water content and temperature on the pyrolysis product distribution as well as on the structure and reactivity of the pyrolysis char was investigated. Spruce wood chips with 2.4%, 16.4%, and 55.4% initial water content were pyrolyzed in a tubular batch reactor at 500 and 800°C with a heating rate between 4 and 12.6°C/min. The structural features of the char samples were examined with scanning electron microscopy, Brunauer–Emmett–Teller (BET) method, and mercury porosimetry. The reactivity in CO2 was investigated using thermo-gravimetric analysis and a fixed bed quartz reactor. It could be seen that higher water content led to a higher yield of condensable products and a lower amount of char. At a pyrolysis temperature of 500°C the CO-content of the product gas did increase significantly with increasing water content. Moreover, initial water content had no significant effect on the microscopic structure of wood chars. The specific char surface area did increase with increasing initial water content up to the fiber saturation point. It was also observed that the specific char surface area was strongly influenced by the pyrolysis temperature. When the pyrolysis temperature increased from 500 to 800°C, the BET surface area became at least 200 times smaller and the average size of micropores became about 10 times smaller. Most likely, pyrolysis at 800°C induced more secondary reactions that were responsible for the occlusion of the micropores within the char [1]. Finally, it was found that reactivity in CO2 significantly decreased with increasing pyrolysis temperature. However, initial wood water content did not have a significant effect on char reactivity in CO2. [Copyright &y& Elsevier]

Abstract: Recently, international research is aiming at developing gasification and pyrolysis processes for the cost-effective thermochemical conversion of non-food biomass to biofuels. Gasification produces a mixture of carbon monoxide and hydrogen, known as syngas. Pyrolysis produces a liquid bio-oil. Both syngas and bio-oil can be used directly or can be converted to clean fuels and other valuable chemicals. Catalysis is central to achieving this aim. This study presents results from lignocellulosic biomass pyrolysis, air and steam gasification in the presence of Fe. Noncatalytic and catalytic pyrolysis and gasification experiments were carried out at temperature range of T =500–760°C under an inert helium atmosphere for pyrolysis and at T =750–1050°C with air and steam as the gasification agents for gasification. The effect of temperature (°C), heating rate (°C/min), gasification medium (steam or air), air ratio (λ), steam to biomass ratio (S/B) as well as the catalytic effect of Fe naturally dispersed in the biomass char were studied. The influence of the iron traces originated from the native biomass and ending up in the char residue is mostly studied. Moreover, experiments were performed and results discussed of Fe residues utilization mixed with the bed material to act as catalyst for the conversion of biomass. The results of the performed study showed that olive kernel pyrolytic char is highly reactive comparing to cellulosic biomass char, due to its porous structure, increased surface area and ash content rich in metals. In combination, the presence of metals in olive kernel ash (especially Fe metal) can play an active catalytic role in tar cracking. Additional results have also shown that the addition of Fe residue as in bed catalyst for upgrading non edible residual biomass, favorises the production of H2 rich gas (syngas) due to Fe pronounced catalytic activity. [Copyright &y& Elsevier]

Abstract: Pyrolytic characteristics of acid hydrolysis residue (AHR) of corncob and pinewood (CAHR, WAHR) were investigated using a thermo-gravimetric analyzer (TGA) and a self-designed pyrolysis apparatus. Gasification reactivity of CAHR char was then examined using TGA and X-ray diffractometer. Result of TGA showed that thermal degradation curves of AHR descended smoothly along with temperature increasing from 150°C to 850°C, while a “sharp mass loss stage” for original biomass feedstock (OBF) was observed. Char yield from AHR (42.64–30.35wt.%) was found to be much greater than that from OBF (26.4–19.15wt.%). In addition, gasification reactivity of CAHR char was lower than that of corncob char, and there was big difference in micro-crystallite structure. It was also found that CAHR char reactivity decreased with pyrolysis temperature, but increased with pyrolysis heating rate and gasification temperature at 850–950°C. Furthermore, CAHR char reactivity performed better under steam atmosphere than under CO2 atmosphere. [Copyright &y& Elsevier]

Abstract: Data on biomass chars obtained under conditions similar to those of practical applications (high heating rate and low residence time) are required for co-combustion and gasification plants. A methodological procedure is developed and applied to two biomass fuels (cacao shells and olive cake) for producing high heating rate chars and characterizing their reactivity and morphology after the first steps of devolatilization. Different chars are produced in a drop tube reactor (rapid pyrolysis) by varying the nominal temperature and the residence time. Oxidation in air is performed to compare typical temperatures and kinetic parameters and evaluate the effect of the operating conditions on char reactivity. A detailed SEM analysis allows to assess the structural variations during the pyrolysis and detect the main phenomena (softening, swelling, melting, formation of bubbles). A quantitative morphological study is also performed to provide size and shape (important for biomasses) distributions of the parent fuel and the chars. These data are more significant than average values in advanced model to correctly simulate the fluid dynamic behaviour of each dimensional class of particles in large scale furnaces and gasifiers and predict a more reliable residence time of the particles. [Copyright &y& Elsevier]

Abstract: The knowledge of biomass char gasification kinetics is of considerable importance in the design of advanced biomass gasifiers, some of which operate at high pressures. In the present work the effects of pyrolysis temperature, total pressure and CO2 concentration on the gasification of biomass chars have been studied using the thermogravimetric approach. The chars were obtained by pyrolysis in a drop tube furnace reactor at temperatures of 1000 and 1400°C. The gasification tests were carried out in a pressurized thermogravimetric analyser (PTGA) at different temperatures, pressures and CO2 concentrations. The reactivity measurements were conducted under the kinetically controlled regime, and three nth-order kinetic models as well as the Langmuir–Hinshelwood model were applied to determine the kinetic parameters. [Copyright &y& Elsevier]

Gasification is a promising technology to dispose antibiotic mycelial dreg (AMD) which is a typical pharmaceutical hazardous bio-waste. However, the gasification of AMD is rarely studied. Since char gasification is the key step in the gasification process, the present work focused on the steam gasification of char. The influence of inorganic elements inside AMD char (mainly P, K and Ca) on the char gasification reactivity is investigated. Particularly, the effect of P on char gasification reactivity was deeply studied, and the co-effect of P, K and Ca on char gasification reactivity was firstly studied and explained. The obtained results suggested that P can deactivate the catalytic function of K and Ca on char gasification by forming K-phosphates and Ca-phosphates. The existence form of P can affect its inhibitory effect on K and Ca, and the pyrophosphate P had a stronger inhibiting effect than orthophosphate P. The deactivation of P on K is related to the ratio of K to P, and the bigger the ratio of K to P the less the deactivation of P on K. The existence of Ca can effectively eliminate the deactivation of P on K by reacting with P to form more stable Ca 3 (PO 4) 2. • Samples gasification reactivity difference mainly come from inorganic difference. • The effect of P on char gasification reactivity was deeply studied. • P can deactivate the catalytic function of K and Ca on char gasification. • The deactivation of P relates to the existence form of P and the ratio of P to K. • The existence of Ca can effectively eliminate the deactivation of P on K. [ABSTRACT FROM AUTHOR]