Combustion Of Biochar Research Articles

Thermal analysis of St. John's Wort wastes and biochars: A study of combustion characteristics and kinetics

St. John's wort, extensively utilized in industries such as food, medicine, and cosmetics, generates substantial biomass waste. Utilizing these wastes is crucial to reducing environmental harm and making an economic contribution. This study aimed to determine the potential of St. John's wort wastes and biochar forms produced from these wastes to be used as solid fuel. In this context, the combustion behavior of the biomass and biochar were determined by thermogravimetric analysis method. Additionally, the Kissenger-Akahira-Sunosa and Flynn-Wall-Ozawa techniques were used to compute the combustion activation energies of these samples. According to the analysis, biomass combustion commenced at approximately 250°C and occurred in two stages, whereas biochar combustion initiated at around 400°C and proceeded in a single stage. Furthermore, over 90% of the mass from both samples was observed to decompose during combustion, with average combustion activation energies ranging between 70.08 and 203.86 kJ/mol for biomass and biochar, respectively. These findings suggest that biomass exhibits more readily combustible characteristics compared to biochar but is less energy efficient. In conclusion, optimizing the biochar production process could enhance its energy efficiency and potentially narrow the performance gap between biomass and biochar. Additionally, further research into alternative methods or additives to improve the energy efficiency of biomass combustion is warranted.

Applicability of genetic algorithm in biochar combustion kinetics with double distributed activation energy model

Applicability of genetic algorithm in biochar combustion kinetics with double distributed activation energy model

Combustion and co-combustion of biochar: Combustion performance and pollutant emissions

Biomass is a renewable and clean energy source, offering the potential to reduce fossil fuel consumption and greenhouse gas emissions when it is used as a biofuel. However, the disadvantages of raw biomass such as poor grindability, high moisture content, and low calorific value hinder its widespread industrial combustion. Thermochemical conversion techniques are widely used to convert biomass to biochar, which serves not only as an adsorbent and soil amendment but also as solid fuels alternative to fossil energy. The upgraded biochar exhibits better physicochemical properties and improved combustion performance. This paper focuses on the properties and combustion behavior of biochar as a solid fuel, reviewing common production techniques of biochar and their effects on yields and properties of biochar. It also examines the combustion characteristics and kinetics of biochar in single- and co-combustion scenarios with other fuels, such as coal, sludge, and petroleum coke, analyzing the influencing factors of combustion behavior and kinetic parameters. This study further investigates the emission characteristics during the combustion of biochar, including gaseous pollutants (such as CO, NOx, SOx, and HCl), ash-related issues, and particulate matter (PM) emissions. Additionally, a new fuel type named “bioslurry”, which is developed with biochar as a main material, is introduced. Furthermore, this paper discusses the techno-economic and environmental aspects of biochar application, exploring the feasibility of its industrial production and utilization.

Catalytic hydrothermal carbonization of corn and rice straws with citric acid: Implications for charcoal production and combustion performance

Hydrothermal carbonization represents a promising environmental approach for converting biomass into high-quality biochar fuel. Despite extensive discourse, limited research has focused on fuel properties and combustion performances of biochar as well as reaction mechanisms under catalysts. This study scrutinized properties of biochar from citric acid-catalyzed carbonization. Straw (corn/rice) was hydrothermally carbonized in 5 % citric acid solution with a solid-liquid ratio of 1:10 g/mL at 190–250 °C for 3 h. Results revealed an increase in C and a decrease in O with elevated temperature and citric acid concentration. The calorific values for corn and rice straw biochar ranged from 23.53 MJ/kg to 29.81 MJ/kg and from 23.14 MJ/kg to 26.98 MJ/kg, respectively. This study highlighted diverse impacts of hydrothermal reaction temperature and citric acid concentration on biochar attributes, calorific value, energy density, mass yield, energy yield, and thermal stability. It elucidated the influence of citric acid concentration on biochar burnout temperature and the role of hydrothermal reaction temperature and heating rate in biochar combustion characteristics. Citric acid effectively reduced biochar activation energy in low-temperature areas and prolonged the biochar combustion reaction time, achieving highly favorable comprehensive combustion characteristics at 47.56×10−7. The findings present the potential for biochar production with enhanced performance for integrating and co-firing with conventional fuels.

Characterization and kinetic analysis of lignocellulosic and algal biochar combustion

The combustion characteristics of biochar obtained from barley straw (BS) and brown algae (BA) are explored. Four different heating rates are utilized to determine the respective activation energies. A master plot analysis is used to identify the appropriate reaction model. The results show that the activation energies vary in the ranges of 6.86–48.36 and 46.34–77.51 kJ mol−1 for BS and BA biochar combustion, respectively. As the heating rate increases, most of the combustion characteristic parameters increase, while the combustion stability index decreases. These observations help provide a deeper understanding of the combustion of lignocellulosic and algal biomass-derived biochar.

The Experimental Analysis of Biochar Combustion in a Traveling Grate Furnace

The current energy policy targets reducing energy dependence and minimizing pollutant emissions. Therefore, with the growing interest in using biomass as an alternative energy source, conducting scientific studies on its behavior and optimizing the respective conversion systems has become imperative. The present study focuses on investigating the combustion of biochar pellets in a laboratory-scale traveling grate furnace at three different bed temperatures: 700, 750, and 800 °C. The biochars were obtained via the carbonization process of Pinus pinaster, Acacia dealbata, and Cytisus scoparius pellets. The biochar combustion was studied using a moving-bed carbon particle burning model, supported by kinetic information which was obtained via the combustion of the same biochars in a bubbling fluidized bed. The diffusive parameter which was representative of this traveling grate combustion technology was determined, particularly the bed bypass factor. The combustion tests were carried out with the incomplete combustion of the char pellets. In general, the increase in biochar size led to a decrease in the bypass factor. However, the furnace temperature did not influence this parameter.

Gasification of solid biomass or fast pyrolysis bio‐oil: Comparative energy and exergy analyses using AspenPlus®

AbstractThe conversion of biomass residues into syngas through gasification is attractive for energy and process industry applications. However, transportation, storage, and operational challenges limit the conventional direct solid biomass gasification process. To address these issues, the intermediate conversion of biomass to bio‐oil has emerged as a promising alternative. Bio‐oil offers improved transport and storage capabilities due to its higher mass and energy density, enabling the decoupling of solid biomass supply and syngas demand. This study compares two routes for syngas production: direct gasification of solid biomass and indirect gasification using bio‐oil from biomass pyrolysis as an intermediate with biochar and pyrolysis gas supplying thermal energy to the pyrolysis stage. Biochar combustion provides about 1.4 MJ kg−1 of dry biomass to maintain the pyrolysis temperature at 480°C. Using AspenPlus® simulations, the composition and Low Heating Value of the syngas produced by both routes are analyzed. Energy and exergy analysis at different equivalence ratios and temperatures revealed that direct gasification has higher efficiencies than indirect gasification. At 1000°C and an equivalence ratio of 0.4, the highest energy and exergy efficiencies occurred in direct gasification processes. The energy efficiency of direct and indirect gasification amounted to 62% and 53%, respectively. At the same time, the corresponding exergy efficiencies were 65% and 61%. The syngas of direct and indirect gasification processes is a starting point to produce energy, synthetic fuels, and chemicals; this study provides insights for designing and optimizing biomass gasification processes.

An Evaluation of the Contribution of Cellulose, Hemicellulose and Lignin to Bio-Char Combustion and Adsorption Properties

The present work focuses on the contribution of cellulose, hemicellulose, and lignin for bio-char application in two aspects: fuels and adsorbent. The pyrolysis behaviors were studied at 300 to 700 °C, and the yields and characterization of bio-chars were compared. The results showed that in the three components, lignin was responsible for the formation of bio-char products, representing the main source of bio-char characterized by high heating value. Lignin was the strongest support for prepared bio-char as fuel decided by physico-chemical properties and combustion reactivity, while cellulose was the major contributor for bio-char products as ignition fuel. Scanning electron microscopy (SEM) and surface area analysis of bio-char showed that, in the three components, cellulose derived bio-chars exhibited a distinctive fibrous structure and the surface area was the largest at the same pyrolysis temperature. Compared with lignin, hemicellulose was a better precursor for adsorption, it is mainly determined by complex and abundant pore structure. Further adsorption tests of toxic substances in soil showed that, cellulose represented major adsorption donator for phenol, all bio-char samples had better adsorption capacity for Pb(II) than Cu(II), the rule on adsorption capacity of three different precursors for Cu(II) was as follows: cellulose>hemicellulose>lignin, for Pb(II): hemicellulose> cellulose> lignin.

INVESTIGATION OF THE COMBUSTION OF BIOCHAR OBTAINED BY HYDROTHERMAL CARBONISATION AND TORREFACTION OF SAWDUST

The effect of the temperature regimes of hardwood sawdust thermochemical treatment (hydrothermal carbonization and torrefaction) on biochar properties and combustion characteristics are investigated. The mass yields of biochars were considered from the viewpoint of the processes that take place during thermochemical treatment, along with the changes in the elemental composition resulting from these processes. The optimal method and temperature regime of thermochemical treatment were determined. The effect of the method and temperature of sawdust thermochemical treatment on the composition of gaseous products from biochar combustion was assessed by FTIR spectroscopy combined with thermogravimetric analysis. Two main stages of biochar combustion were detected: the phase of removal and combustion of volatile substances (up to 400 °C) and the phase of semi-coke combustion (above 400 °C). The analysis carried out by means of FTIR spectroscopy during combustion allowed us to determine the released components of the gaseous mixture and to observe thermochemical decomposition of biochar components in the real time mode. Investigation of biochar combustion showed that an increase in sawdust processing temperature reduces the formation of gaseous products at the first stage of combustion and promotes an increase in the amount of carbon dioxide at the second stage.

Influence of phosphorus based additives on nitrogen and sulfur pollutants emissions during densified biochar combustion

Influence of phosphorus based additives on nitrogen and sulfur pollutants emissions during densified biochar combustion

Ash fouling behavior during the combustion of bituminous coal and high-Ca pyrolytic biochar under air and oxyfuel atmosphere

Co-combustion of coal and pyrolytic biochar under oxy-fuel atmosphere is a promising option for addressing CO2 problems in power plants, where the issue of ash fouling during combustion was considered in this study. A high-Ca pyrolytic biochar from pilot-scale trail and a high-Si Utah bituminous coal were selected for single- and co-combustion on a drop tube furnace (DTF) coupled with fouling sampling system under the atmosphere of air and oxy50 (CO2:O2 = 50:50 vol%) at 1300 ℃. The fouling deposits were collected and characterized by various techniques to investigate the formation mechanism of ash deposits. The results indicated that the combined effects of impaction and capture resulted in the different deposition propensity from coal and biochar combustion under both air and oxy50 conditions. Besides, co-firing can inhibit the formation of ash deposits during coal combustion under air atmosphere when the blended biochar was greater than 50%, while the deposition propensity of the blend with 80% biochar rapidly aggravated under oxy50 atmosphere. The fine particles act as “glue” to fix coarse particles from impaction were the main source of the inside deposits from coal combustion, whereas the inside deposits from biochar combustion were dominated by agglomerated and sintered fine particles. Co-firing can weaken the “glue effect” from coal combustion, and finally presented as mitigated deposition propensity of inside deposits. Switching to oxy50 condition, the enhanced sulfidation of deposits and scavenging of alkali metal suppressed the growth of inside deposits from coal combustion, while that had minor impact on biochar. The inhibitory effect of co-firing on inside deposits diminished with the increased biochar under oxy50, where the deposition propensity of the blend containing 80% biochar was higher than that in air-firing.

Dynamic investigation on potassium migration and transformation during biochar combustion and its correlation with combustion reactivity

For agricultural biomass combustion, K migration and transformation is a key factor affecting boiler operation and reaction characteristics. In this study, dynamic K migration and transformation characteristics during rice straw char combustion process under different O2 concentrations were studied using chemical fractionation analysis (CFA), X-ray diffraction (XRD) and scanning electron microscopy coupled with energy dispersive X-ray (SEM-EDX). Furthermore, the correlation between K migration/transformation and char combustion reactivity was discussed. The results showed that most of K in rice straw char was H2O-soluble K. And the main forms of H2O-soluble K and insoluble K are KCl and KAlSi3O8, respectively. As reaction proceeded, the contents of H2O-soluble K and insoluble K decreased but those of NH4Ac-soluble K and HCl-soluble K increased. Most of the released K is H2O-soluble K. H2O-soluble K would be transformed into NH4Ac-soluble K and HCl-soluble K, and some insoluble K would be transformed into H2O-soluble K. The increase of O2 concentration would stimulate the transformation of H2O-soluble K into NH4Ac-soluble K, HCl-soluble K and released K. However, the reaction to form K-aluminosilicate was hardly found during the combustion process at 400 ℃. Ultimately, it is found that H2O-soluble K is the key occurrence form K affecting the combustion characteristics of rice straw char.

Computational fluid dynamics analysis of biochar combustion in a simulated ironmaking electric arc furnace

The most urgent concern confronting the steel industry in the twenty-first century is climate change. The Electric Arc Furnace (EAF) is the second most common process in steelmaking, accounting for 29% of the total global production of crude steel in 2018. More than 40% of energy in current EAFs originates from chemical sources of fossil fuels: natural gas and coal. Reducing greenhouse gas emissions (GHG) in the steelmaking process necessitates the development of breakthrough technologies and operational strategies. The use of biochar from torrefaction, slow pyrolysis and hydrothermal carbonisation (HTC) of biomass as a substitute for fossil coal in EAF was investigated in this research. A three-dimensional computational fluid dynamics (CFD) model for combustion and electrode radiation inside an EAF was developed by assuming particle surface and gas-phase reactions to predict injected biochar particle combustion. The effect of the combustion reaction on the temperature distribution inside the EAF and the influence of intermediate gas release was analysed. Results showed that the use of biochars instead of fossil coal in the EAF steelmaking process did not involve significant negative differences. CFD can be a useful and reliable support for guiding adequate EAF process and injection design in a more eco-friendly scenario.

Analytical assessment of the behavior of biochar, as an additionally injected fuel, under conditions of blast-furnace smelting

The relevance of the issue of using carbon-neutral types of raw materials in metallurgical production is considered. One of the promising directions is the use of biomass pyrolysis product - biochar, which has a high carbon content and, as a result, a calorific value relative to biomass. A comparative analysis of the main characteristics of biochar and pulverized coal injected fuel (PCI) produced from "T" and "G" coal grades was carried out. Biochar contains less carbon and ash with a higher content of volatile substances compared to PCI. To study the combustion process of biochar in the blast furnace tuyere zone, a study of the kinetics of its combustion in a laboratory installation for the solid fuel combustion was carried out. In order to adapt the obtained biochar combustion kinetics to the conditions of the blast furnace tuyere zone, a similar study was carried out for the considered types of pulverized coal. The results of the experimental study of the combustion kinetics of the studied types of fuel are presented, according to which the fuel combustion process in front of the tuyeres consists of two phases: the first one is accompanied by a high oxygen consumption for the combustion of volatile substances; the second one is characterized by slow afterburning of the carbon residue. The longest burning time of 0.6 g fuel at a temperature of 1200 °C is 762 s for T-grade PCI. Pulverized coal grade “G” and biochar have the similar combustion kinetics, but the latter burns faster: grade “G” pulverized coal burns in 369 s, and biochar in 162 s. The conclusion is made about a higher degree of biochar afterburning in the conditions of the blast furnace tuyere zone in comparison with pulverized coal fuel.

The evaluation of Wood Ash as a potential preventive measure against alkali-silica reaction induced expansion and deterioration

Over the past decades, a wide number of research programs were conducted and demonstrated the efficiency of supplementary cementing materials (SCMs) to mitigate alkali-silica reaction (ASR)-induced expansion and deterioration. However, the anticipated depletion in the coming years of some of the most common SCMs used in concrete makes imperative the finding of new potential SCMs sources. This research aims to study the performance of wood ash (WA), a by-product of biochar combustion, as a preventive measure against ASR. Two highly reactive aggregates (i.e., fine and coarse) and different WA replacement levels (i.e., 10%, 20%, 50% and 60%) were selected for this research and accelerated tests were performed in the laboratory (i.e., accelerated concrete prism test – ACPT and the accelerated mortar bar test – AMBT). AMBT results indicated a potential benefit of using WA to mitigate ASR-development whereas the ACPT yielded completely opposite results, which highlights important inconsistencies of these test procedures to appraise preventive measures against ASR. Furthermore, the microscopic damage features and mechanical properties losses of ASR-affected concrete incorporating WA at distinct replacement levels were studied through the Damage Rating Index and Stiffness Damage Test, showing an agreement with the induced expansion results obtained through the ACPT. • Wood ash (WA) was evaluated as an alternative for sustainable and durable concrete. • WA performance inconsistencies against ASR are observed as per the method adopted. • WA was observed to be effectible if tested in mortars and ineffective in concrete. • In concrete, higher WA replacement leads to higher ASR-induced deterioration. • Further analyses using distinct WA types in concrete are still required.

Occurrence of dissolved black carbon in source water and disinfection byproducts formation during chlorination

Dissolved black carbon (DBC), the water-soluble component of black carbon, which is formed by incomplete combustion of fossil fuels or biochar, takes up about 10% of dissolved organic matter (DOM) in river water. However, the distribution of DBC in water environment especially in source water is not clear and as an important component of DOM, whether DBC can produce disinfection byproducts (DBPs) like other DOM during disinfection remains unknown. In this study, the DBC concentrations in seventeen source water samples from East China were measured. The concentrations of DBC in the source water samples ranged from 60 to 270 μg/L, which were positively correlated with UV254 absorbance and chemical oxygen demand. The levels of DBC in wet season were higher than that in dry season. The average concentrations of DBC in different types of source water samples followed the order of reservoir > canal > lake > river. DBC could only be removed by 20% during the simulated coagulation, and further generate different categories of DBPs during chlorination, among which the concentrations of haloacetic acids (HAA) were the highest. The results indicated that DBC widely distributes in source water and is an important precursor of HAAs and THMs during chlorination.

The origin of potential precursors of secondary organic aerosols during combustion of biochar and softwood in residential heating

Compounds that are potential precursors of secondary organic –aerosols account for up to 33.4 ± 7.1 mg/m3 in softwood combustion emissions, while biochar can be considered zero-emission fuel (0.18 ± 0.06 mg/m3). The characteristic feature of gaseous emissions from biochar combustion is the presence of n-alkanes (70.3 ± 6.6 µg/m3), which arise from the thermal degradation of waxes, cuticles, and plant lipids. In addition to alkanes, carboxylic acids (4.9 ± 0.2 µg/m3) are present in biochar emissions at significantly lower concentrations. In deposits from biochar combustion (6.1 ± 0.8 g/kg), the internal parts of the boiler capture 20% more organic compounds than in wood-burning deposits (4.84 ± 0.91 g/kg). The greater uptake of organic compounds in biochar combustion deposits (513.8 ± 6.2 g/kg) than in softwood (382.7 ± 27.3 g/kg) is related to the higher elemental carbon content in biochar. The organic compounds present in deposits from biochar are mainly methyl ketone, fatty acids such and alkanes. In deposits from softwood, the compounds of chemical groups of phenols, anhydrosaccharides and acetic acids are present. The novelty lies in identifying and determining the quantity of organic compounds that form precursors of the solid organic aerosols in the combustion of biochar.

Numerical investigation of the influence of particle shape, pretreatment temperature, and coal blending on biochar combustion in a blast furnace

Using carbon-neutral from biomass is a promising solution to achieve carbon neutrality in pulverized coal injection (PCI) technology in an ironmaking blast furnace (BF). In this paper, a 3D CFD model, including the whole region of lance-blowpipe-tuyere-raceway surrounding coke bed, is improved to describe the in-furnace phenomena related to biochar injection under industrial-scale BF conditions. The factors such as particle shape, carbonization temperature, and coal blending are considered to determine the influence on flow and thermochemical behaviors of biochar particles. The results show that, in comparison to spherical particles, the cylindrical particles show a slower gas conversion rate and smaller burnout as a result of the shorter traveling time in the raceway; High carbonization temperature decreases the burnout of biochar in the raceway. From the perspective of the economy, BC-773 has an appropriate ratio of volatile matter (VM) to fixed carbon, which burns more fully and releases a large amount of heat in a limited time, and has the potential to better replace PCI coals in BF practice. The overall gas temperature and burnout of the biochar/coal blend show a non-additivity, indicating there is a synergistic effect during the co-combustion process. This model provides an effective way for understanding and optimizing biomass injection technology in BF practice.

Smoke Particle, Polycyclic Aromatic Hydrocarbons and Total Benzo[a]pyrene Toxic Equivalence Emitted by Palm Oil Sewage Sludge Bio-Char Combustion

The size distribution, total particle mass concentration (TPMC), polycyclic aromatic hydrocarbons (PAHs) value, and total Benzo[a]pyrene Toxic Equivalence (BaPTE) concentration of smoke particles from palm oil sewage sludge (POSS) bio-char combustion were studied. In this experiment, temperature data of the POSS bio-char combustion were recorded in two parts: particle temperature (Tp) by using a two-color pyrometer and temperature at 300, 500 and 800 mm, respectively, above the fire base by using K-type thermocouples. The POSS bio-char moisture content, clean air speed values, and burning period affected the change of temperature above the fire base. The mass median aerodynamic diameter (MMAD) values of the POSS bio-char combustion were found to be 0.44 to 1.05 micron at various moisture contents and burning periods. The MMAD, TPMC, and PAHs values increased with increasing moisture content and decreased the POSS bio-char combustion period. For the total BaPTE values, the results showed that the decrease in moisture content of the POSS bio-char samples had a prime influence in decreasing the total BaPTE values. Meanwhile, with decreases in the clean air speed values, the total BaPTE values were increased. Comparing the total BaPTE data between the experimental results and predicted values, the first-degree model had a better fit in predicting than the zero-degree model; this result was confirmed by the higher mean of the coefficient of determination.

Combustion Behavior of Algal Biochars Obtained at Different Pyrolysis Heating Rates.

In this work, the combustion performance of Chlorella vulgaris (CV), Dunaliella salina (DS), and Haematococcus pluvialis (HP) algal biochars was analyzed based on the multicomponent method. The biochars were obtained via nonisothermal pyrolysis of raw algal biomasses at three different heating rates (i.e., 30, 40, and 50 °C/min), and biochar combustion was performed from 200 to 700 °C at a heating rate of 5 °C/min. The complex oxidative reaction of algal biochar was resolved into combined reactions of multiple pseudo-components based on the peak deconvolution method using a bi-Gaussian model. The activation energies (Ea) for each pseudo-component (PC) of all biochar samples were calculated by the Coats–Redfern isoconversional method and four kinetic models (i.e., diffusion, nucleation, order-based, and shrinking core models). The results showed that the highest Ea values were predicted by the diffusion model. Except that the Ea for the first PC of CV biochar decreased by 16.45%, the Ea values for all other biochar samples generally increased with increasing the pyrolysis heating rate. Moreover, when the diffusion model was used, the Ea for the second PC of CV biochar increased by 50.87%, that for the first PC of DS biochar increased by 16.85%, and those for the first and third PCs of HP biochar increased by 4.66 and 11.66%, respectively. In addition, the combustibility index (Sn) was evaluated based on the ignition and burnout temperatures as well as the mean and maximum weight loss rates. Generally, the combustion performance of all biochar samples was good at a low temperature but deteriorated toward a high temperature. As the pyrolysis heating rate increases, an overall increase in the combustion quality was also seen for the second PC of CV biochar and the first PCs of DS and HP biochars because their Sn increased from 2.70 × 10–15 to 3.07 × 10–15 °C–5, 2.53 × 10–13 to 3.88 × 10–13 °C–5, and 3.00 × 10–13 to 3.26 × 10–13 °C–5, respectively.