Production and Characterization of Bio-Chars from Biomass via Pyrolysis

This article deals with slow pyrolysis of oak wood and agricultural residues such as hazelnut shell and wheat straw at high temperature (950–1250 K) in a cylindrical reactor. The aim of this work is to study the effect of the treatment conditions such as temperature, particle size, and lignin and inorganic matter contents on bio-char yield and reactivity. When the pyrolysis temperature increased, the bio-char yield decreased. A high temperature and smaller particles increase the heating rate resulting in a decreased bio-char yield. The higher lignin content in hazelnut shell results in a higher bio-char yield in comparison with oak wood and wheat straw. Bio-chars from hazelnut shell and wheat straw are more reactive in gasification than bio-chars from oak wood because of the higher ash content. The bio-char obtained are carbon rich, with high heating value and relatively pollution-free potential solid biofuel.     

Characterization of biochar and bio-oil samples obtained from carbonization of various biomass materials

Apricot stone, hazelnut shell, grapeseed and chestnut shell are important biomass residues obtained from the food processing industry in Turkey and they have a great importance as being a source of energy. In this study, the characteristics of bio-oil and biochar samples obtained from the carbonization of apricot stone, hazelnut shell, grapeseed and chestnut shell were investigated. It was found that the biochar products can be characterized as carbon rich, high heating value and relatively pollution-free potential solid biofuels. The bio-oil products were also presented as environmentally friendly green biofuel candidates.     

Fixed-Bed Pyrolysis of Hazelnut (Corylus Avellana L.) Bagasse: Influence of Pyrolysis Parameters on Product Yields

Fixed-bed slow pyrolysis experiments have been conducted on a sample of hazelnut bagasse to determine particularly the effects of pyrolysis temperature, heating rate, particle size and sweep gas flow rate on the pyrolysis product yields. The temperature of pyrolysis, heating rate, particle size and sweep gas flow rate were varied in the ranges 350–550° C, 10 and 50° C/min, 0.224–1.800 mm and 50–200 cm³/min, respectively. Under the various pyrolysis conditions applied in the experimental studies, the obtained char, liquid, and gas yield values ranged between 26 and 35 wt%, 23 and 34.40 wt%, and 25 and 32 wt%, respectively. The maximum biooil yield of 34.40% was obtained at the final pyrolysis temperature of 500°C, with a heating rate of 10° C/min, particle size range of 0.425–0.600 mm and a sweep gas flow rate of 150 cm³/min.     

Rapid and slow pyrolysis of pistachio shell: effect of pyrolysis conditions on the product yields and characterization of the liquid product

This study reports the experimental results for the pyrolysis of pistachio shell under different conditions in a tubular reactor under a nitrogen flow. For the different conditions of pyrolysis temperature, nitrogen flow rate and heating rate, pyrolysis temperature of 773 K gave the highest bio-oil yield with a value of 27.7% when the heating rate and carrier gas flow rate were chosen as 300 K min⁻¹ and 100 cm³ min⁻¹, respectively. Column chromatography was applied to this bio-oil and its subfractions were characterized by elemental analysis, FT-IR and ¹H-NMR. Aliphatic subfraction was conducted to gas chromatography–mass spectroscopy for further characterization. The results for the characterization show that using pistachio shell as a renewable source to produce valuable liquid products is applicable via pyrolysis. Copyright © 2006 John Wiley & Sons, Ltd.     

Structural Analysis of Pyrolysis Products From Pyrolysis of Hazelnut (Corylus Avellana L.) Bagasse

Fixed-bed pyrolysis biooils of hazelnut (Corylus Avellana L.) bagasse have been identified for their structures. The condensed biooils were analyzed for their properties as fuels and compared with petroleum-derived products. The biooil was analyzed by Fourier Transform infrared spectroscopy (FTIR) and ¹H-NMR spectra. The biooils were fractionated into pentane solubles and insolubles. Pentane solubles were then solvent fractionated into pentane, toluene and methanol subfractions by fractionated column chromatograpy. The aliphatic subfractions of the biooils were then analyzed by capillary column gas-liquid chromatography (GC). In addition, the physical properties, higher heating value and elemental analysis of the biooil were determined. The empirical formula of biooil that has a heating value of 34.57 MJ/kg was established as CH_1.45O_0.33N_0.127. Chromatographic and spectroscopic studies on the biooil showed that the oil obtained from hazelnut bagasse could be used as a renewable fuel and chemical feedstock.     

Sooting characteristics of isolated droplet burning in heated ambients under microgravity

This paper presents an investigation into the sooting characteristics of isolated droplets (for fuel n-decane) burning in heated ambients in microgravity. A backlit video view of the droplet was taken to determine the soot shell size and to judge the transient soot generation according to qualitative amount of soot. The independent experiment variables were the ambient temperature and initial droplet diameter. Soot generation was higher for initially larger droplets when compared at the same burning time normalized with the initial droplet diameter squared (called normalized burning time). At the same absolute burning time there existed an obvious initial transient period after ignition in which the stated relationship was not satisfied. This transient time increased with increasing the ambient temperature. There was a peak in the soot generation at about 1000 K throughout the lifetime of the droplet. The soot shell size was generally larger for an initially bigger droplet at the same instantaneous droplet diameter or normalized burning time. At the same absolute burning time, however, an initially smaller droplet exhibited larger relative soot shell sizes (the soot shell size normalized with the initial droplet diameter). The soot shell size increased monotonically with increasing ambient temperature. This is due to the increase in the Stefan flow drag with the larger burning rate at the higher temperature. The consequent result is that the soot shell sizes are much larger for droplets burning in heated ambients than for droplets burning in room-temperature ambients.     

Comparison of catalytic and noncatalytic pyrolysis and product yields of some waste biomass species

The products obtained by fast pyrolysis of biomass can be used as an energy source or chemical raw material. In this study, samples of hazelnut shells, tea bush, and hazelnut knot selected as waste biomass were from the cities of Trabzon and Rize in the Eastern Black Sea Region. Firstly, the waste biomass samples were granulated into four different particle sizes by milling and sieving operations. Fast pyrolysis of the samples with specific mixing rates was carried out in a fixed bed reactor. Additionally, 2 wt% vanadium (V) oxide (V₂O₅) was used as catalyst to maximize the yield of pyrolysis liquid products. The influence of temperature, heating rate, and particle size on fast pyrolysis yields under both catalytic and noncatalytic conditions were investigated and compared. While the amount of liquid product increased with the addition of catalyst, the amount of solid products decreased. It has been found that the temperature and heating rate parameters are very effective in liquid product yield. In all experiments, the maximum liquid yield was acquired at the same heating rate of 450°C min^?1 and the temperature of 450°C with particle size of 0.5 to 1.0 mm. The maximum pyrolysis liquid (bio‐oil) was obtained with catalytic pyrolysis, and this value was 60.58 wt%.     

Producing Bio-oil from Olive Cake by Fast Pyrolysis

Abstract

This article reports on physico-chemical properties of olive cakes to evaluate them as a raw material in energy production through thermo-chemical pyrolysis conversion process. The present study focuses on the actions related to the possibilities to utilize in particularly olive cake as an agricultural residue. Olive cake is a very promising material for the production of bio-oil. Liquid, solid, and gaseous products were obtained from olive cake by pyrolysis. If the purpose were to maximize the yield of liquid products resulting from biomass pyrolysis, a low temperature, high heating rate, and short gas residence time process would be required. Flash pyrolysis gives high oil yields. The heating was carried out from 298 K to 1,050 K in the absence of oxygen. The yields of liquid products were obtained from the olive cake by pyrolysis for the runs of different heating rates: 10 K/s, 20 K/s, and 40 K/s. The highest bio-oil yields from the olive cakes were 31.0% at 700 K, 36.0% at 700 K, and 41.0% at 700 K obtained from 10 K/s, 20 K/s, and 40 K/s heating rate runs, respectively. The highest bio-oil yields olive stone shells were 27.0% at 700 K, 31.0% at 700 K, and 34.5% at 750 K obtained from 10 K/s, 20 K/s, and 40 K/s heating rate runs, respectively.     

Comparison of hazelnut and peanut shells combustion in bubbling fluidized-bed combustor

The combustion of peanut and hazelnut shells was studied in an atmospheric bubbling fluidized bed. The impact of the enrichment of air with oxygen and the flow rate of fluidizing gas on CO₂ and CO concentrations was analyzed. It was stated that in air enriched with oxygen up to 25% the mole ratios of CO₂ to CO were improved by 15–30%, depending on the flow rate used. For the peanut shell the combustion of volatiles with a hematite as an oxygen carrier was also studied. The effects were observed above ~ 450°C.     

Estimation of fuel burning rate and heating value with highly variable properties for optimum combustion control

Estimating solid residue gross burning rate and heating value burning in a power plant furnace is essential for adequate manipulation to achieve energy conversion optimization and plant performance. A model based on conservation equations of mass and thermal energy is established in this work to calculate the instantaneous gross burning rate and lower heating value of solid residue fired in a combustion chamber. Comparing the model with incineration plant control room data indicates that satisfactory predictions of fuel burning rates and heating values can be obtained by assuming the moisture-to-carbon atomic ratio (f/a) within the typical range from 1.2 to 1.8. Agreement between mass and thermal analysis and the bed-chemistry model is acceptable. The model would be useful for furnace fuel and air control strategy programming to achieve optimum performance in energy conversion and pollutant emission reduction.     

Nanoparticle-based approach for the formation of CIS solar cells

In this study, nanoparticle-based approach was suggested for the formation of CuInSe₂ (CIS) layer. Nanoparticles with core–shell structure were used as the precursor material, and binary phases were used as core and shell material in the core–shell structure to maximize the kinetics of CIS formation reaction. From the investigation of the effect of heating rate on Se-loss, it was concluded that Se-loss could be minimized by using high heating rate and core–shell structure with a binary compound. By minimizing Se-loss before and during CIS formation reaction, it was shown that CIS layer could be formed without Se overpressure. CIS solar cell made in this study showed the highest efficiency of 1.11%, which showed a CIS layer for the device could be obtained without selenization process.     

Do nanoenergetic particles remain nano-sized during combustion?

It is axiomatic that the burning time dependence on particle size follows an integer power law dependence. However, a considerable body of experimental data show a power dependence less than unity. In this paper, we focus on what might be responsible for the fractional power dependence observed for the burning time for nanoparticles (e.g. Al and B). Specifically we employ reactive molecular dynamics simulations of oxide-coated aluminum nanoparticles (Al-NPs). Since most nanomaterials experimentally investigated are aggregates, we study the behavior of the simplest aggregate – a doublet of two spheres. The thermo-mechanical response of an oxide coated Al-NP is found to be very different than its solid alumina counterpart, and in particular we find that the penetration of the core aluminum cations into the shell significantly softens it, resulting in sintering well below the melting point of pure alumina. For such coated nanoparticles, we find a strong induced electric field exists at the core–shell interface. With heating, as the core melts, this electric field drives the core Al cations into the shell. The shell, now a sub-oxide of aluminum, melts at a temperature that is lower than the melting point of aluminum oxide. Following melting, the forces of surface tension drive two adjacent particles to fuse. The characteristic sintering time (heating time + fusion time) is seen to be comparable to the characteristic reaction time, and thus it is quite possible for nanoparticle aggregates to sinter into structures with larger length scales, before the bulk of the combustion can take place. This calls into question what the appropriate ‘effective size’ of nanoparticle aggregates is.     

Oily Products from Mosses and Algae via Pyrolysis

In this study, the fuel properties of mosses and algae, and the effect of pyrolysis temperature on the yield of bio-oil from moss and alga samples, were investigated. The yield of bio-oil from pyrolysis of the samples increased with temperature. The yields were increased up to 750 K in order to reach the plateau values at 775 K. The maximum yields were 39.1, 34.3, 33.6, 37.0, 35.4, 48.2 and 55.3% of the sample for Polytrichum commune, Dicranum scoparium, Thuidium tamarascinum, Sphagnum palustre, Drepanocladus revolvens, Cladophora fracta and Chlorella protothecoides, respectively. The bio-oil yield for Chlorella protothecoides (a microalga sample) rose from 5.7 to 55.3% as the temperature rose from 525 to 775 K, and then gradually decreased to 51.8% and was obtained at 875 K with a heating rate of 10 K/s. Formulas can be developed to calculate higher heating value (HHV) of different moss and alga samples. The calculated HHV using these new correlations showed mean differences ranging from ?2.3% to +0.06%. The equation developed in this study showed good agreement with experimental results on moss and algae samples. The HHVs for bio-oils from mosses 21.5–24.8 MJ/kg and the HHVs for bio-oils from algae and microalga 32.5 and 39.7 MJ/kg, respectively, were obtained at temperature ranging from 775 to 825 K. In general, algae bio-oils are of higher quality than bio-oils from mosses. In general, microalgae bio-oils are higher quality than bio-oil from wood.     

Enhanced reactivity of nano-B/Al/CuO MIC's

Aluminum is traditionally used as the primary fuel in nanocomposite energetic systems due to its abundance and high energy release. However, thermodynamically boron releases more energy on both a mass and volumetric basis. Kinetic limitations can explain why boron rarely achieves its full potential in practical combustion applications, and thus has not replaced aluminum as the primary fuel in energetic systems. In particular, the existence of the naturally formed boron oxide (B₂O₃) shell is believed to play a major role in retarding the reactivity by acting as a liquid barrier if it cannot be efficiently removed. In this paper we demonstrate from constant-volume combustion experiments that nanoboron can be used to enhance the reactivity of nanoaluminum-based Metastable Intermolecular Composites (MICs) when the boron is <50 mol% of the fuel. It was also observed that an enhancement was not achieved when micronboron (700 nm) was used. Thermodynamic calculations showed that the aluminum reaction with CuO was sufficient to raise the temperature above ∼2350 K in those mixtures which showed an enhancement. This is above both the boiling point of B₂O₃ (2338 K) and the melting point of boron (2350 K). A heat transfer model investigates the heating time of boron for temperatures >2350 K (the region where the enhancement is achieved), and includes three heating times; sensible heating, evaporation of the B₂O₃ oxide shell, and the melting of pure boron. The model predicts the removal of the B₂O₃ oxide shell is fast for both the nano- and micronboron, and thus its removal alone cannot explain why nanoboron leads to enhancement while micronboron does not. The major difference in heating times between the nano- and micronboron is the melting time of the boron, with the micronboron taking a significantly longer time to melt than nanoboron. Since the oxide shell removal time is fast for both the nano- and micronboron, and since the enhancement is only achieved when the primary reaction (Al/CuO) can raise the temperature above 2350 K, we conclude that the melting of boron is also necessary for fast reaction in such formulations. Nanoboron can very quickly be heated relative to micronboron, and on a timescale consistent with the timescale of the Al/CuO reaction, thus allowing it to participate more efficiently in the combustion. The results indicate that sufficiently small boron can enhance the reactivity of a nanoaluminum-based MIC when added as the minor component (<50% by mole) of the fuel.     

Combustion Characteristics of 24 Lignite Samples

Abstract

In this study, the combustion characteristics such as thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA), burning profile, ignition temperature, and peak temperature were analyzed for 24 lignite samples from different areas of Turkey. The samples were heated up to 900°C at a constant rate of 10°C/min in a 5 mL/min flow of dry air. The burning profiles of the samples studied, combined with proximate, sulfur analysis and calorimetry results, contribute to a clearer identification of lignite samples' structure and a better understanding of the coalification process. The lignite samples have been tested with particle size of 0–0.05 mm. Ignition temperatures of the samples have been determined from their burning profiles.     

Study of the plasma and heating effect on hydrogen permeation through Pd0.60-Cu0.40 membrane in a micro-channel plate reactor

The diffusion of hydrogen through palladium and palladium-copper alloys membrane have been provided the highest hydrogen selectivity and permeance. In this study the composite Pd_0.60-Cu_0.40 wt% membrane foil with thickness 20 μm was measured in the micro-channel plate reactor (MPR) with gap length 4.5 mm. The hydrogen permeation flux was measured at atmospheric feeding pressure for 100% H₂ concentration in the temperatures range of 423–573 K under heating only and plasma-heating experiments. The plasma firing high voltage source ranges of 10–18 kV are tested. The hydrogen permeation flux and hydrogen permeability have been calculated according to Fick's and Sieverts combining laws with power exponent n-value 0.5. It was found that the maximum hydrogen flux, hydrogen permeability and Permeation rate percent of the heating only experiment at MPR heating temperature of 573 K and flow rate 0.1 l/min. In the plasma heating experiment, it was observed that the maximum hydrogen flux, hydrogen permeability, and permeation rate percent at MPR heating temperature of 573 K and plasma firing voltage of 14 kV. Also, the hydrogen permeation rate percent decreased due to the hydrogen reverse reaction even though the plasma firing voltage increased to 16 kV and 18 kV. The results also reveal that the activation energy and Pre-exponential constant factor decreased with increasing the feeding H₂ flow rate while the linear regression R² decreased with increasing H₂ feeding flow rate that in the heating only experiment, in contrast, the plasma-heating experiment showed non-linearity values. A comparison between both experiments showed the hydrogen permeation flux of the plasma-heating experiment is higher than that obtained from the heating only experiment, additionally; the plasma effect increased at low hydrogen flow rates. In contrast, the energy efficiency of heating only experiment was higher than that obtained from the plasma-heating experiment due to the total energy consumption of plasma experiment is high.     

Enhancing CO2 Conversion to Methanol Using Dynamic Optimization,Applied on Shell Temperature and Inlet Hydrogen During Four Years Operation of Methanol Plant

Abstract

The investigation of dynamic optimal policies for an industrial methanol reactor experiencing exothermic, reversible reactions is the subject of this study. Optimal values of inlet hydrogen mole fraction and shell temperature have been investigated for a heterogeneous methanol reactor. Optimization has been carried out by employing the methanol production rate (MPR) as an objective function. Optimal history profiles for shell temperature (T_shell) and hydrogen inlet mole fraction has been obtained during 4 years of operation. It was found that applying obtained optimal profiles of H₂ and T_shell provides a 1.4% production benefit compared to an existing operating plant policy. This is equivalent to 1,400,000 USD during a four year operation period.     

Theoretical modeling of a compound-drop spray in premixed flames

The influence of internal heat transfer induced by dilute compound-drop sprays on one-dimensional premixed flames is investigated using large activation energy asymptotic analysis. In this study, the compound drop is composed of a single water core encased by a shell of fuel. The gasification zones of the shell fuel and the core water affect the flow and flame characteristics. A critical completely pre-vaporized burning condition, (CPB)_c, is defined as the whole compound drops finishing vaporization right at the flame and a critical shell pre-vaporized burning condition, (SPB)_c, is defined as the shell fuel of compound drops finishing vaporization right at the flame. Under the (CPB)_c and (SPB)_c conditions of lean and rich flames, the flame propagation flux, the critical values of the shell-fuel mass fraction and the initial radius vary with the water-core radius and the liquid loading. For a lean spray flame, compound drops can provide internal heat transfer in the form of heat gain from the shell fuel and heat loss from the core water. The lean spray flame may be strengthened or weakened depending on the net heat transfer. For a rich spray flame, the compound-drop spray always weakens flame propagation. An S-shaped extinction curve occurs for a rich spray flame under the (SPB)_c condition, with a sufficiently heavy liquid loading and a sufficiently large water-core size.     

Pyrolysis Kinetics of Blends of Yeni Çeltek Lignite and Sugar Beet Pulp

Abstract

Pyrolysis kinetics of the Yeni Çeltek lignite/sugar beet pulp blends prepared at different ratios (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100) were investigated by thermogravimetric analysis in the present study. All the experiments were carried out in nitrogen atmosphere under non-isothermal conditions with a heating rate range of 30 K/min in the pyrolysis temperature interval of 298–1,173 K. The Arrhenius model is applied to determine the kinetic parameters from TG/DTG curves. Apparent activation energies of the lignite and sugar beet pulp were calculated as 51.55 kJ/mol and 97.27 kJ/mol, respectively. Activation energies of the blends were also calculated and were found to vary between 54.87 and 74.83 kJ/mol. Effects of blending ratio of lignite to sugar beet pulp on kinetic parameters were investigated and the results were discussed.     

The emissions from a space-heating biomass stove

In this paper, the flue gas emissions of carbon monoxide (CO), nitrogen oxides (NO_X), sulphur dioxide (SO₂) and soot from an improved space-heating biomass stove and thermal efficiency of the stove have been investigated. Various biomass fuels such as firewood, wood shavings, hazelnut shell, walnut shell, peanut shell, seed shell of apricot (sweet and hot seed type), kernel removed corncob, wheat stalk litter (for cattle and sheep pen), cornhusk and maize stalk litter (for cattle pen) and charcoal were burned in the same space-heating biomass stove. Flue gas emissions were recorded during the combustion period at intervals of 5 min. It was seen from the results that the flue gas emissions have different values depending on the characteristics of biomass fuels. Charcoal is the most appropriate biomass fuel for use in the space-heating biomass stoves because its combustion emits less smoke and the thermal efficiency of the stove is approximately 46%.