Thermal Conversion Of Biomass Research Articles

Utilization of Sunflower Husk Ash in the Production of Polyurethane Materials

Energy produced from waste biomass is more environmentally friendly than that produced from fossil resources. However, the problem of managing waste from the thermal conversion of biomass arises. The overarching goal of this article was to propose a method of utilizing biomass ash (sunflower husk) as a filler that positively affects the properties of rigid polyurethane foams. The scope of the presented research is to obtain and characterize rigid polyurethane foams (RPUFs) with the addition of two types of fillers: sunflower husks (SHs) and sunflower husk ash (SHA). First, an analysis of the fillers was carried out. The carbon content of SHs (C~49%) was ten times higher in comparison to SHA’s carbon content (C~5%). The morphology of the fillers and the particle size distribution were determined, which showed that in the case of SHs, particles with a size of 500–1000 µm predominated, while in SHA, the particles were 1–20 µm. The content of inorganic compounds was also determined. Potassium and calcium compounds were the most abundant in both fillers. The second part of the research was the analysis of polyurethane materials with the addition of fillers. The obtained results indicate that filler addition had a positive effect on the dimensional stability of the foams by eliminating the risk of material shrinkage. The biodegradation process of polyurethane materials was also carried out. The reference foam weight loss after 8 weeks was ~10%, while the weight loss of the foam containing SHA was over 28%. Physical and mechanical properties, cell structure, and thermal stability tests were also carried out. The use of bio-waste fillers creates a possibility for the partial replacement of petrochemical products with environmentally friendly and recycled materials, which fits into the circular economy strategy.

Influence mechanism of K on cellulose pyrolysis by stepwise isothermal method in-situ DRIFTS method

The influence mechanism of alkali metal potassium (K) on cellulose pyrolysis is a vague and fundamental key topic in the field of biomass thermal conversion. In this study, the pyrolysis of cellulose and K-impregnated cellulose was compared by in-situ DRIFTS (Diffused Reflectance Infrared Fourier Transform Spectroscopy) and TG (Thermal Gravimetric)–MS (Mass Spectrum) experiment, and quantum chemical calculations were used to verify the peak position and pyrolysis mechanism of infrared (IR) spectroscopy. Stepwise isothermal in-situ DRIFTS was designed to study the reaction path at high temperatures. It was found that in the early stage of pyrolysis, K accelerated the activation of cellulose by attacking the hydrogen bond (H-bond) in the crystal structure of cellulose, increased the dehydration rate between molecules, and promoted the decomposition of cellulose. Simultaneously, it weakened the epoxy–ether bond, inhibited the formation of dehydrated sugar, and promoted the formation of furan. Subsequently, K combined with carbonyl groups to form C–O–K structures, which improved the thermal stability of certain oxygen-containing functional groups such as carbonyls/aldehydes, so that these structures were retained until higher temperature. K promoted the conversion of dehydrated sugars to straight-chain ketones/aldehydes, which led to an increase in carbon conversion. During the coke generation stage, K promoted the formation of disordered carbon and residues, thereby inhibiting coke aromatization. The isothermal in-situ DRIFTS method proposed in this study was demonstrated to better inhibit the high temperature drift of IR spectrum during pyrolysis. It clarified the conversion between functional groups at high temperatures, which is expected to promote the development of other high-temperature pyrolysis mechanism.

Eulerian CFD simulation of biomass thermal conversion in an indirect slow pyrolysis rotary kiln unit to produce biochar from recycled waste wood

Producing energy and higher value bio-products from waste wood recycled from construction and demolition (C&D) debris has been proposed as an economically viable opportunity in the biomass and bioenergy sectors. However, several challenges associated with the thermal conversion processes remain to be solved. This study introduces a 3D numerical simulation to study thermal conversion of wood chips. Combined biomass combustor, and indirect pyrolysis unit is used to create a self-sustainable biomass unit which does not rely on fossil fuel. Multizone heat distribution in the rotary kiln unit is investigated by employing CFD, an analytical algorithm and measurement tools in different zones of the equipment. A multizone heat transfer concept, the overall yield rate of biochar, thermochemical conversion of the bed, the volume shrinkage in the wood chips during the pyrolysis process, as well as biomass volatile and tar composition, and finally the potential of energy savings is widely investigated. CFD results and experimental evidence confirm that at least 31 % energy saving in drying zone can be achievable if drying and pyrolysis zone are separated in the indirect slow pyrolysis rotary kiln unit. The quality of biochar improved by 21 % increase in fixed carbon content and tar condensation is controlled.

Mathematical models for predicting the higher heating value and ultimate analysis of biomass

The higher heating value (HHV) and elemental composition are important properties of biomass and they are necessary to perform computer simulations of the biomass thermal conversion processes. Both properties require equipment to measure that can be expensive, while the proximate analysis required equipment that is typically found in a laboratory. This work presents a general correlation, based on proximate analysis of biomass, to calculate elemental composition and two new correlations, based on proximate and ultimate analyses of biomass and char used for prediction of the higher heating value. The correlations based on ultimate analysis and proximate analysis show an average absolute error (AAE) of 5.59% and 6.81%, respectively, an average bias error (ABE) of 0.17% and 1.52%, a mean bias error (MBE) of − 0.09 and − 0.06, and root mean square error (RMSE) of 1.52 and 1.98 concerning the value of HHV. To calculate the elemental composition from proximate analysis, the correlations were proposed of C, H and O. The AAE of these correlations were 3.86%, 7.49%, and 5.68%, the ABE were − 1.10%, − 0.22%, − 2.23%, the MBE were 0.58, 0.06, and 1.14 while the RMSE were 2.65, 0.6, 3.45 with respect to measured values of C, H, O, respectively. The AAE values of the correlation proposed in this study using ultimate analysis are lower than those found for the other studied correlations.

Insights into the influence and mechanism of biomass substrate and thermal conversion conditions on Fe[sbnd]N doped biochar as a persulfate activator for sulfamethoxazole removal

Fe-N-doped biochar is a promising material for advanced-oxidation heterogeneous catalysis, but its adsorption-catalytic performance is significantly affected by biomass feedstock compositions and thermal conversion conditions and is not yet conclusive. In this paper, four lignocellulosic biomasses (rice straw, bamboo, poplar wood, and corn stover) were selected as raw materials to prepare Fe-N-biochar as persulfate activators by hydrothermal-thermolysis composite. Their lignocellulosic fractions and elemental contents were detected, and a variety of thermal conversion conditions were investigated for the rice straw-based Fe-N-biochar with the best activation performance among them. It was found that the holocellulose and lignin contents of the biomass affected the catalytic activity of the prepared catalysts with correlation coefficients of 0.57 and −0.93, respectively. Increasing the pyrolysis temperature from 500 °C to 800 °C could increase the ratio of Fe2+/Fe3+ and the relative amounts of CC, graphitized N, and oxidized N in the catalyst by 0.17 %, 7 %, 12 %, and 18 %, respectively. Extending the pyrolysis time from 0.5 to 2 h was able to increase the relative content of CC, graphitized N, and oxidized N by 0.18 %, 3 %, 9 %, and 4 %, respectively. The most catalytically active rice straw-derived Fe-NRBC was able to remove 91.7 % of sulfamethoxazole (SMX) and 93.07 % of TOC mainly via ·SO4− and ·OH in an adsorption-catalytic reaction of 60 min with a k of 0.047 min−1 and the main active sites are FeN, Fe0, pyridine N, oxidized N and CO. Finally, degradation intermediates and pathways were also characterized. This paper is expected to provide a basis for the future targeted regulation of Fe-N biochar for water pollution treatment.

The deoxygenation mechanism of biomass thermal conversion with molten salts: Experimental and theoretical analysis

Utilizing molten salt for biomass pyrolysis has emerged as a pivotal technology for enhancing product value and has become a crucial alternative to traditional pyrolysis methods. However, there remains a dearth of research on the deoxygenation mechanism of biomass during molten salt thermal treatment. This study focuses on investigating the deoxygenation characteristics of biomass during molten salts thermal treatment through a comprehensive analysis involving experimental and density functional theory (DFT) study. Our experimental results revealed that, compared to traditional pyrolysis, molten salt (NaNO3–NaNO2) significantly increased oxygenated gas products, favoring deoxygenation during biomass conversion. Formic acid was employed as a simplified oxygen-containing model compound to investigate the decomposition characteristics with and without the presence of molten salts using DFT calculations. DFT studies of formic acid decomposition revealed lower activation energies on NaNO3 (234.39 kJ/mol) and NaNO2 (84.11 kJ/mol) surfaces compared to homogeneous reactions (234.63 kJ/mol). This indicates that NaNO2 has a more pronounced promotional effect, facilitating formic acid decomposition. Furthermore, kinetic calculations show that both homogeneous and heterogeneous reaction rate constants for formic acid decomposition increase with temperature. The reaction rate constants on the surface of NaNO3 are similar to homogeneous reactions, while it is much higher two on NaNO2 surfaces. These findings highlight the critical role of NaNO2 in formic acid decomposition within the NaNO3–NaNO2 molten salt system. The experimental and computational results elucidate the deoxygenation mechanism of biomass thermal conversion using molten salts and establish a theoretical foundation for the high-value utilization of pyrolysis products.

On the Stability of a Convective Flow with Nonlinear Heat Sources

The linear stability of a convective flow in a vertical fluid layer caused by nonlinear heat sources in the presence of cross-flow through the walls of the channel is investigated in this paper. This study is relevant to the analysis of factors that affect the effectiveness of biomass thermal conversion. The nonlinear problem for the base flow temperature is investigated in detail using the Krasnosel’skiĭ–Guo cone expansion/contraction theorem. It is shown that a different number of solutions can exist depending on the values of the parameters. Estimates for the norm of the solutions are obtained. The linear stability problem is solved numerically by a collocation method based on Chebyshev polynomials. It is shown that the increase in the cross-flow intensity stabilizes the flow, but there is also a small region of the radial Reynolds numbers where the flow is destabilized.

Distribution of PAHs, PCBs, and PCDD/Fs in products from full-scale relevant pyrolysis of diverse contaminated organic waste

Biomass pyrolysis is the anoxic thermal conversion of biomass into a carbon rich, porous solid, often called biochar. This could be a better waste management alternative for contaminated organic wastes than incineration, due to the useful properties of biochar and potential for carbon sequestration. There are, however, concerns about the potential formation/destruction of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). Six organic wastes, including digested sewage sludges, wood wastes, and food waste reject, were pyrolyzed (500–800°C) in a full-scale relevant unit (1–5 kg biochar hr−1). Removal efficiencies for PCBs and PCDD/Fs were > 99% in the produced biochars. Biochar PAH-content (2.7–118 mgkg−1) was not significantly correlated to feedstock or temperature. PAHs (2563–8285 mgkg−1), PCBs (22–113 µgkg−1), and PCDD/Fs (1.8–50 ngTEQ kg−1) accumulated in the pyrolysis condensate, making this a hazardous waste best handled as a fuel for high temperature combustion. Emission concentrations for PAHs (0.22–421 µgNm−3) and PCDD/Fs (≤2.7 pgTEQ Nm−3) were mainly associated with particles and were below the European Union’s waste incineration thresholds. Emission factors ranged from 0.0002 to 78 mg tonne−1 biochar for PAHs and 0.002–0.45 µgTEQ tonne−1 biochar for PCDD/Fs. PCDD/F-formation was negligible during high temperature (≥500 °C) biomass pyrolysis (69–90% net loss)

Experimental study on the regulation of NOX in co-pyrolysis of maize straw and woody biomass

The NOX emissions from biomass as a carbon–neutral energy source during thermal conversion are of great concern. The research on the transformation law of NOX precursors in the thermal conversion process of biomass is an effective measure to regulate the nitrogen migration path of raw biomass and reduce the emission of NOX pollutants. In this study, maize straw was mixed with Eucalyptus wood chips and apple wood chips, respectively, and the slow pyrolysis experiment was carried out at 700 °C to control the nitrogen-containing products, the properties of char-N, tar-N and NOX precursor were studied by TGA, XPS, GC-MS and spectrophotometry, respectively.The results showed that, compared with the theoretical value of pyrolysis nitrogen products of maize straw and woody biomass alone, the addition of Eucalyptus wood chips increased the char-N yield, and the synergistic effect was the strongest under the condition of 50 wt.% addition ratio of +0.2980, the yield of char-N was 32.06 wt.%, apple wood chips was only observed to promote char-N at the addition ratio of 25 wt.%, the synergy intensity was +0.2013, the yield of char-N was 30.27 wt.%, and other experimental groups showed inhibition effect. At the same time, the co-pyrolysis system has a significant inhibitory effect on the NOX precursor nitrogen (NH3-N + HCN-N), among which the Eucalyptus wood chips addition test group has a more obvious inhibitory effect on NH3-N, the synergistic intensity reached the strongest at −0.5926 when the addition ratio was 25 wt.%; while the apple wood chips addition test group had a more obvious inhibitory effect on HCN-N, and the synergistic strength reached the strongest at −0.5798 when the addition ratio was 50 wt.%. In summary, regulating the migration path of nitrogen in the process of thermal conversion of biomass is helpful for cleaner utilization of biomass resources.

Biomass resources and thermal conversion biomass to biofuel for cleaner energy: A review

Biofuel is considered as one of the solutions to future energy problems. Unlike fossil fuels, biofuel is a renewable fuel source produced from biomass. Biomass comes from a wide variety of plants and animals and even waste. Therefore, the production of biofuel from biomass is promising not only to solve energy problems but also to solve other social problems. This study will present some of the most potential biomass sources and thermal conversion processes of biomass for biofuel production. 

Tailor-made biochar-based nanocomposite for enhancing aqueous phase antibiotic removal

In the present study, an innovative biochar-based metal(loid) oxide nano-matrix doped hybrid nanocomposite (nMOC) from kitchen waste-derived biochar (KWB) and ZnO/SiO2 was used for aqueous phase tetracycline removal. It involved a three-stage process, entailing thermal conversion of biomass to KWB, synthesis of ZnO/SiO2 nano-matrix, and nMOC fabrication via ball-milling. Advanced characterizations were employed to determine surface chemistry, surface morphology, surface area, and elemental composition, exhibited thermostable, mesoporous, heterogeneous, ZnO/SiO2-doped matrix with rich active surface-functional groups. The nMOC showed excellent performance (95.27 ± 0.304 %) for TC removal through batch mode adsorption study for 7.0 mg L−1 aqueous TC solution at ambient temperature. The sorption data were statistically evaluated through linear and non-linear isotherms, kinetics, and thermodynamics modelling incorporating error function analysis, suggested spontaneous, exothermic, and multilayer chemisorption with complex diffusional adsorption phenomenon. The adsorption mechanisms were governed by, electrostatic interaction, H-bonding, π-π stacking interactions, and pore-filling. Regeneration study demonstrated the maximum efficiency using EDTA (81.39 ± 1.234 %). Experiments on interference by co-existing ions suggested lesser impact by monovalent anions (NO3−) than divalent anions (SO42−), and monovalent cations (NH4+). The nMOC showed enhanced TC adsorption and excellent reusability along with dual benefits of minimization of solid kitchen waste and very effective antibiotic removal from (waste)water.

Model of Residence Time Distribution, Degree of Mixing and Degree of Dispersion in the Biomass Transport Process on Various Grate Systems

Biomass includes diverse raw materials of plant or animal origin that are biodegradable. It also constitutes a significant fraction of municipal waste burned in waste incineration plants. Grate technology is one of the more commonly used technologies in the thermal conversion of biomass. The mass transport of material on the grate is a complex issue. The article presents a model for determining selected mass flow parameters on the grate, primarily the distribution of residence time, degree of mixing, and dispersion. The model is a description of mechanical mass transport on the grates of thermal waste conversion devices and represents the kinetics of the processes occurring on the grate. It allows for the design of the details of the specific movement of the material particles on the grates depending on their size and density. In addition, experimental tests of flow parameters realized on a laboratory stand simulating the operation of the grate are presented. Tests were conducted on different types of grates and with selected types of biomass materials. They included variants of the operating parameters of the grates, such as the speed and pitch of the grates an their inclination, simultaneously with the fulfillment of the 1:1 scale condition of the size of the laboratory stand to the actual size of the industrial grate (its section). A general trend can be seen in the mean residence time of the material on the grate, which is higher in the case of a reciprocating grate. The degree of dispersion is mainly influenced for moving and reciprocating grates by the inclination angle of the grate. The analysis of the test results made it possible to clarify the mechanism of material mass transport on different types of grates. It is also proposed to use the results in modeling the process of biomass combustion in grate chambers as well as their design and operation.

Validation of a biomass conversion mechanism by Eulerian modelling of a fixed-bed system under low primary air conditions

This work presents a three-dimensional Computational Fluid Dynamics study of a small-scale biomass combustion system operating with low primary air ratios. The Eulerian Biomass Thermal Conversion Model (EBiTCoM) was adapted to incorporate a pyrolysis mechanism based on the detailed Ranzi-Anca-Couce (RAC) scheme. Two scenarios were simulated using woodchips with 8% and 30% moisture content, and the results were validated against experimental data, including in-flame and bed measurements. The model accurately predicted bed temperature profiles and the influence of fuel moisture content on the pyrolysis and drying fronts, as well as on the distribution of volatiles and temperatures above the solid fuel bed. For the 8% moisture content case, the average gas temperature above the bed is approximately 700 °C, while for the 30% case, it drops to around 400 °C. The lower temperatures hinder the tar cracking reaction, resulting in a 25% higher tar content in the producer gas for the 30% moisture content fuel. The lower part of the bed consists of a thick layer of char undergoing reduction reactions, similar to that of an updraft gasifier. The developed model can accurately simulate biomass combustion systems with solid fuel beds consisting of numerous particles, while maintaining low computational requirements.

Study Examines Ability of Macroalga To Produce Green Hydrogen

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210809, “Pyrolysis of Macroalga Macrocystis pyrifera for Production of Green Carbon-Negative Hydrogen,” by Carolina A. Gallego, Shashank S. Nagaraja, and Mani Sarathy, King Abdullah University of Science and Technology. The paper has not been peer reviewed. _ The macroalga Macrocystis pyrifera is a giant brown seaweed characterized by its fast growth rate and photosynthetic metabolism that generates carbon sources from atmospheric CO2. This alga is a potential biomass to be applied in bioenergy with carbon capture and storage (BECCS), which enables carbon-negative biofuels to avoid greenhouse emissions from biomass processing and use. The study described in the complete paper is related to the thermal conversion of this alga and serves as an opening to the study of the thermal conversion of biomass commonly found in desertic or semidesertic climates. BECCS and M. pyrifera The relevance of BECCS and carbon-negative fuels is in the ability of plants and algae to capture atmospheric CO2 and simultaneously be a source of carbon. Second-generation biofuels—fuels derived from nonedible terrestrial crops or waste such as miscanthus, wheat straw, or paper waste—are a promising alternative. The disadvantages of their generation, however, include the high cost of related technologies and the risk of compromising food security in some areas because of the amount of land devoted to energy crops. Algae are classified as microalgae or macroalgae (also called seaweed). The harvesting methods of macroalgae are less energy-intensive and expensive than the methods used for microalgae. M. pyrifera, a brown macroalgae, presented several advantages because of its large size (12–22 m long), fast growth rate (7–30 cm/day), its high gas yield, and its potential sustainable cultivation. Its cultivation, however, currently takes place only in Pacific Rim countries. Thus, this alga must be imported in dry form to the Middle East. With thermal conversion methods a suboptimal choice for dry M. pyrifera, a conventional method for the thermal conversion of the algae and production of hydrogen as pyrolysis was applied. Pyrolysis is a thermochemical process for decomposition of biomass in absence of oxygen to produce oil, char, and gases; it is detailed in the complete paper. The carbon-capture process involves technologies that separate the CO2 from the products of reaction. In this way, greenhouse emissions can be reduced through the storage of captured CO2. When high quantities of CO2 compose the products of thermal conversion, the most-efficient applicable technology is physical absorption by Selexol or Rectisol.

Syngas methanation over a metal hydride catalyst: Technology performance, efficiency and economic profitability

In the last decade, biomass has been considered one of the main renewable energy sources to replace fossil fuels and consequently, biomass conversion technologies for the production of alternative fuels will play a specific role in the future energy as green biofuels for the transport sector or a power generation at small-scale distributed plants. During the thermal conversion - gasification, biomass is converted into more valuable products - syngases which could be used for biomethane production. Though, some challenges still exist related to the broad applicability of the thermal conversion of biomass to biomethane: costly short-life catalysts and a low conversion efficiency due to the high amount of carbon monoxide/dioxide in syngas.To overcome these challenges, an innovative biomethane production concept based on the plasma-assisted gasification and conversion of synthetic gases to biomethane was developed and tested, including research on the adaptability of two catalysts, magnesium nickel and magnesium nickel hydride, for raw syngas conversion. The performance of catalysts was investigated in a fixed bed type reactor using raw syngas obtained from plasma-assisted gasification.The results indicate the magnesium nickel hydride catalysts' good activity and functionality for converting carbon dioxide and carbon monoxide-containing syngas. A high conversion of 0.997 is reached. Determined that the surplus of hydrogen promotes the conversion of carbon oxides, though the volumetric concentration of methane (the maximum of 86.4 vol%) in product gas is reduced. Considering that the developed technology concept can be integrated into small combined heat and power plants, bio-waste generating plants, or decentralized areas as an additional source of renewable energy or biofuel production, the energy-mass balance and economic analysis for the optimization of 1 MWh bio-CH4 production concept was provided.

Aluminosilicate Clay Minerals: Kaolin, Bentonite, and Halloysite as Fuel Additives for Thermal Conversion of Biomass and Waste

The current focus on renewable energy sources and the circular economy favors the thermal conversion of low-quality fuels, such as biomass and waste. However, the main limitation of their usability in the power sector is the risk of slagging, fouling, ash deposition, and high-temperature corrosion. These problems may be avoided or significantly mitigated by the application of aluminosilicate clay minerals as fuel additives. In this paper, the three most commonly occurring aluminosilicates are reviewed: kaolin, halloysite, and bentonite. Their application has been proven to minimize combustion-related problems by bonding alkalis in high-melting compounds, thus increasing ash melting temperatures, reducing ash deposition tendencies, and decreasing the particulate matter emission. Due to excellent sorption properties, aluminosilicates are also expected to fix heavy metals in ash and therefore decrease their emissions into the atmosphere. The application of aluminosilicates as fuel additives may be a key factor that increases the attractiveness of biomass and other low-quality fuels for the power sector.

Review of Phosphorus Chemistry in the Thermal Conversion of Biomass: Progress and Perspectives

Phosphorus is vital for all life, which means that phosphorus is present in all biomass to some extent. Some types of biomass, such as certain agricultural residues, animal biomass, and sewage sludge, contain high levels of phosphorus. In thermal conversion of biomass, high levels of phosphorus can cause various operational problems. Extensive work has been carried out to understand the phosphorus chemistry taking place at higher temperatures. However, until now, knowledge about transformation chemistry and fate of phosphorus during thermal conversion of biomass was not easily accessible in one place. In this work, the outcome of an extensive literature review has been summarized. First, an introduction to the role of phosphorus in biomass, and in what forms it may be present, is given. Different analytical techniques relevant for characterization of phosphorus in biomass, biomass char, and biomass ash are described. A classification of phosphorus-rich biomass is proposed, and the potential of different phosphorus-rich biomass types is presented. To provide a common basis for the field of high-temperature phosphorus chemistry, fundamental chemistry relevant for thermal conversion of biomass is first discussed. This includes the gas phase chemistry and reaction pathways of light phosphorus species, pyrolysis, and combustion of organophosphorus compounds, and solid, liquid, and gaseous interactions with other ash-forming elements. Thereafter, an in-depth review of phosphorus transformations in biomass, including decomposition of organic phosphorus, ash transformations in the condensed phase, release to the gas phase, and formation of particulate matter in the flue gas follows. Finally, the review covers research focusing on phosphorus in different application aspects, such as the use of phosphorus as an additive to mitigate operational problems related to slag and deposit formation, the behavior of phosphorus in fluidized bed technologies, corrosion, and the deactivation of SCR catalysts.

Cold-end corrosion caused by hygroscopic ammonium chloride in thermal conversion of biomass and waste

Optimization of energy recovery and efficient use of the energy in flue gases is of high importance for the economy of power plants. The fuel quality and additives to mitigate corrosion may dramatically affect cold-end deposits and corrosion. Ammonium chloride may form in the cold-end of the boiler if the flue gases contain both HCl(g) and NH3(g). Ammonia may be present in the cold-end when using ammonium-based additives or operating the boiler at low load leading to an NH3(g) slip. Ammonium chloride is a hygroscopic salt, which can cause corrosion of pre-heaters and flue gas cleaning equipment NH3(g) and HCl(g) can also pass through filters and form NH4Cl(s) after the baghouse filters. In this work, the hygroscopic properties of NH4Cl were determined by measuring the conductivity of the salt during decrease of temperature at various water vapor concentrations (10–35 vol%). The corrosiveness of NH4Cl salt on carbon steel was studied at 25 vol% water vapor in the temperature range of 70–160 °C. The cross-sections were analyzed using SEM-EDX, and corrosion rates were determined from panorama SEM images by analyzing the material loss in about 50 000 points. The material loss was also determined gravimetrically after removing the corrosion products with citric acid. The work revealed that hygroscopic NH4Cl is highly corrosive on carbon steel when water is absorbed. Water uptake and corrosion occurred at relative humidities well below the deliquescence relative humidity and depended on the temperature. An empirical equation for water uptake by NH4Cl was determined for water vapor concentrations between 10 and 35 vol% H2O. As corrosion proceeded, chlorine was enriched close to the carbon steel surface due to the formation of iron chlorides. The results can be used to avoid conditions typical for NH4Cl deposit build-up and create strategies to prevent corrosion.

Temperature Evolution and Heating Rates of Biomass undergoing Ablative Pyrolysis

The ablative reactor may be employed to enable fast pyrolysis to produce bio-oil from relatively large-sized biomass samples. Ablation mainly involves direct compressive force and conductive heat transfer between a hot surface and the biomass materials. Temperature evolution and heating rates are important operating factors in the biomass thermal conversion process. In this work, experimental and analytical investigations were carried out for different vertical dimensions of the biomass samples (2-20mm) and hot plate temperatures (400-550°C). It was shown that the thermal characteristics of the biomass were mainly affected by the transient conditions. It was observed that volatile release occurred during the transient heat transfer periods. It was found that at the maximum hot plate temperature of 550°C, the highest heating rate that could be achieved by ablation was more than 600°C/min.

Release of phosphorus from thermal conversion of phosphorus-rich biomass chars – Evidence for carbothermic reduction of phosphates

Biomass can be used to generate heat, power, or biofuels in thermal conversion processes such as combustion, gasification and pyrolysis. However, some types of biomass contain high levels of phosphorus, which can be released to the gas phase and cause operational or environmental problems. The mechanism(s) responsible for phosphorus release has not been convincingly established. Understanding the high-temperature phosphorus chemistry is also important in order to enable efficient recovery of phosphorus in residues from thermal conversion of biomass. In this work, the release of phosphorus from wheat bran char and sunflower seed char in different gas environments (100 % N2, 1–20 % O2, and 10 % CO2) and temperatures (900–1100 °C) was studied. The chars were converted in a horizontal tube reactor and characterized using ICP-OES, XRD, SEM-EDS, and 31P NMR. The release of ash-forming elements was determined using ICP-OES analysis of the char and sample residues, whereas the release of carbon was determined using CO and CO2 gas analysis. In both chars, phosphorus was present primarily together with potassium and magnesium, mainly as pyrophosphates in the wheat bran char, and largely as orthophosphates in the sunflower seed char. For wheat bran char, the release of phosphorus increased from 27 % at 900 °C to 71 % at 1100 °C in N2, whereas the release was at least 20 % lower in the oxidizing atmospheres (1–20 % O2, or 10 % CO2). The sunflower seed char reached a maximum release of 55 % at 1100 °C in N2. For wheat bran char, the molar ratio of released carbon/phosphorus was close to 2.5, which fits well with the theoretical value for carbothermic reduction of phosphates (P2O5(s, l) + 5C(s) → P2(g) + 5CO(g)). At 1100 °C, in N2, the release of phosphorus, potassium and sodium occurred mainly during the first 10 min. It was shown that KMgPO4, used as a model compound, could be reduced by carbon starting from 950 °C, but that some of the phosphorus remained in the condensed phase. The work provides a better understanding of phosphorus release and presents evidence showing that carbothermic reduction reactions can be an important phosphorus release mechanism for seed- and grain-based biomass char.