Combustion Characteristics Of Biomass Research Articles

Demineralization effects on physicochemical and combustion characteristics of biomass: Insights into distributed kinetics, flue gas evolution, and slag formation

Biomass as the only carbon-bearing renewable energy has enormous potential to challenge the established energy structure dominated by fossil resources, and incineration technology is one of the most direct and efficient pathways for utilizing biomass resources, unfortunately enduring the inevitable sintering and slagging problems owing to the excessive alkali metals. Herein, we comparatively investigated the effects of five leaching solvents (water, acetic acid, wood vinegar, hydrochloric acid, and oxalic acid) on the physicochemical properties and ash-removal capabilities of wheat straw (WS) and rice husk (RH), with a view to achieving better performance in the subsequent combustion characteristics, kinetic examination, flue gas, and slag evolution. Results indicated with ionization ability increased (water < acetic acid < hydrochloric acid), the WS exhibited a strong demineralization performance (maximum 61.1%), further leading to a steep weight loss in its combustion characteristic curve at approximately 350 °C and a delayed peak temperature after the removal of alkali metal. Multiple distributed activation energy model and sensitivity analysis revealed that leaching pretreatment enhanced the activation energy (189–191.8 kJ mol−1) and optimized energy distribution at the preliminary stage of the combustion reaction. In addition, the absence of alkali metals suppressed the catalytic oxidation reaction in the flue gas, remarkably limiting the formation of CO2 but facilitating the release of CO and CH4. Meanwhile, a considerable optimal in biomass ash slagging, in which the initial temperature of the liquid phase slag for WS ash increased to 991 °C. Notably, HCl showed the strongest demineralization performance among the five leaching solvents during pretreatment, but the high-temperature slag content was still higher than that of acetic acid. Therefore, slagging performance is not only associated with the demineralization ability of leaching solvents, but also with ash composition.

Evaluation Indicator for the Spontaneous Combustion of Biomass Fuel Pellets and Its Self-Ignition Control

ABSTRACT To investigate the spontaneous combustion characteristics of biomass fuel particles, spontaneous combustion processes of 10 biomass samples were simulated by programmed-heating and continuous oxidation experiments. Analysis results indicated that during the very initial stage of spontaneous combustion (<90 °C), each biomass fuel particles merely yielded CO at 0–20 ppm, while the subsequent exponential growth of gas emissions tended to exhibit a significant variation on spontaneous liability. Due to the diversity of biomass material sources, its spontaneous combustion tendency is not only determined by internal properties, but also influenced by external factors such as particle size, ventilation rate, moisture, etc. There are many factors affecting the spontaneous combustion tendency, which cannot be analyzed accurately and quantitatively. Therefore, it is necessary to propose a stable indicator based on thermal analysis to objectively evaluate the tendency of biomass spontaneous combustion. A scientific index was proposed to precisely assess the spontaneous combustion tendency of biomass materials. Specifically, the activation energy (E) at the O2 gain stage was adopted as the priority criterion: If E < 70 kJ/mol, the biomass was defined to be highly flammable; if 70 ≤ E ≤ 80 kJ/mol, the biomass was considered to be prone to self-ignition; and if E > 80 kJ/mol, the biomass was regard as non-spontaneous combustion. Besides, data from cross-point temperature tests fundamentally support the reliability of mentioned evaluation methodology. In fire-extinguishment experiments, a conventional approach, such as suffocate by self-extinguishing, only reduced the temperature to 99.9–238.7°C. The comparison of extinguishing materials such as gaseous N2/liquid nitrogen, CO2, and C3HF7 revealed that extinguishing fire with C3HF7 exhibited a dramatic advantage at burning temperature > 500°C. However, fire extinguishing with CO2 was more suitable for the spontaneous combustion ignition of biomass at temperature ≤ 300°C.

Flamelet LES of a 40 kW[formula omitted] pulverized torrefied biomass furnace in air and oxy-fuel atmospheres

For the first time, large-eddy simulations are conducted for a 40 kWth self-sustained pulverized torrefied biomass furnace in air and oxy-fuel atmospheres using an extended flamelet model. A recently developed chemical reaction mechanism specifically for oxy-fuel combustion (117 species and 840 elementary reactions) is employed. The simulation results are compared to the experimental data, including the axial and tangential velocities and selected species mass fractions. In addition to this, certain characteristics are investigated: the flame structure, thermo-chemical variable distributions and the NOx emissions in different atmospheres. The flame in the oxy-fuel atmosphere is predicted to be longer and broader than that in the air atmosphere. The main reason for this is the significantly different flow dynamics in different atmospheres that are specifically designed to achieve the same oxidizer-to-fuel ratio near the burner. Two external recirculation zones (ERZs) and a central internal recirculation zone (IRZ) exist in the air atmosphere due to the designed boundary condition with a strongly swirled flow. In contrast, only a single ERZ and a weak IRZ can be observed in the oxy-fuel atmosphere. These different flow dynamics significantly influence the torrefied biomass combustion characteristics for the two atmospheres. Overall, the combustion characteristics in the air atmosphere exhibit features which are expected for a strongly swirling flow, while the thermo-chemical variable distributions in the oxy-fuel atmosphere are similar to those of a jet flame. It is also found that the atmospheres have significant effects on the NOx emissions, particularly for the furnace studied, which features staged oxidizer combustion.

Intensive exploration of the fuel characteristics of biomass and biochar from oil palm trunk and oil palm fronds for supporting increasing demand of solid biofuels in Thailand

This investigation explored the intensive characteristics of biomass and biochar from oil palm trunk (OPT) and oil palm fronds (OPF) for supporting the increasing demand of solid biofuels in Thailand. The characteristics of these samples were also compared to low grade sub-bituminous coal (LGSBC). The results indicate that converting OPT and OPF to biochar not only enhanced the fuel ratio and atomic ratios, but it also improved the energy content. The higher heating values (HHV) of OPT and OPF biochars were 26.92 and 28.05 MJ/kg. The fuel ratio, atomic ratio and HHV of biochars were better than those of LGSBC and biomass forms. Thermal decomposition and combustion characteristics of biomass and biochar from OPT and OPF were clearly different in N2 and air atmospheres. The biomass and biochar from OPT and OPF had high contents of alkali elements, consequently their ashes had high concentrations of some oxides like SiO2 and K2O. Biomass and biochar ashes from OPT and OPF had low initial deformation temperature (IDT). The IDT of OPT biochar ash was the lowest (907 °C), while the IDT of ash from LGSBC was above 1500 °C. The slagging and fouling indexes of biochars were clearly different from the LGSBC and biomass forms. Therefore, biomass and biochar from OPT and OPF have potential for solid biofuel use, and they are promising for further upgrading and applications. The user needs to be concerned with ash related problems like ash fusion, slagging, and fouling during combustion of these solid biofuels.

Combustion characteristics of biomass fuel briquettes from onion peels and tamarind shells

Rising worldwide demand and consumption of fossil fuels have elevated wealth creation, improved undesirable impacts on climatic change from emission of greenhouse gases, and endangered communal health. In developing nations, biomass wastes, which include but are not limited to agricultural residues, are generated in huge quantities yearly. During the disposal of biomass, incomplete combustion causes people to get exposed to elevated indoor concentrations on health-damaging pollutants including particulate matter and carbon monoxide. Inefficient usage or disposed biomass wastes may cause toxic impacts on higher levels of pollution, the consequent degeneration of public health and ecological contamination. It is possible to convert these wastes into energy-efficient briquettes through densification. In this research work, the combustion characteristics were identified from biomass briquettes which were produced from Onion Peels (OP), Tamarind Shells (TS) and Cassava Starch. OP-TS were mixed sequentially and conversely with different proportions. From the total weight of biomass, 10% of cassava starch was added and briquettes were produced under 200 kN pressure from the compressed hydraulic system within the dwell time of 60 seconds. The proximate characteristics such as the presence of water content, amount of fixed carbon, ash and volatile matter were determined by using the standard procedures of the American Society for Testing and Materials (ASTM). The ultimate parameter, which is inclusive of Carbon (C), Hydrogen (H) and Oxygen (O) were diagnosed in all produced biomass briquettes and calorific values were identified for all the produced biomass briquettes as well. OP-TS have better fuel properties in comparison with pine, cotton stalk (CS), wood sawdust (WS), municipal solid waste (MSW) and cotton straw biomass briquettes (CSB). Therefore, the produced biomass briquettes could bring substantial environmental and socio-economic benefits to rural communities and are potentially worthy fuels derived from agricultural wastes.

Parameter Effects in the Preparation of Pyrolytic Carbon from Agroforestry Biomass Waste

Traditional fossil fuels are being replaced by pyrolytic carbonization fuel from agricultural and forestry biomass to address the energy shortage crisis and the environmental pollution caused by the massive burning of fossil fuels in recent years. This paper introduces the research progress in the preparation of agriculture and forestry biomass pyrolysis carbonization molding fuel. The advantages and disadvantages of different biomass conversion technology are presented. The effects of different technological parameters on the preparation of pyrolytic carbon from agricultural and forestry biomass waste were reviewed. Agriculture and forestry biomass combustion characteristics and their regularity are analyzed.

Combustion characteristics of biomass and bituminous coal co-firing in non-isothermal and isothermal conditions

A thermogravimetric method was used to study the combustion of bituminous coal (BC), diverse biomass (wood chips: WC, chaff: CH), and their blends under non-isothermal conditions and isothermal conditions. A higher blending amount of WC or CH under non-isothermal conditions resulted in a lower ignition temperature, burnout temperature, and a greater comprehensive combustion characteristic index. Meanwhile, the co-combustion of BC, WC, and CH all showed inhibiting effects. The inhibition effect was prominent when the blending ratio of WC was below 30%. Under isothermal conditions, with the increase of oxygen concentration and blending amount, the combustion performance of BC improved gradually. The synergistic effect between BC and biomass dominated, and the interaction was more distinct when WC content exceeded 50%. Under both non-isothermal and isothermal conditions, the interaction between CH and BC did not vary at diverse blending ratios. The dynamic results suggested that the chemical reaction model O1 was suitable for stage 1 of the co-combustion of WC and BC, the model diffusion controlled D4 controlled the co-combustion of CH and BC and stage 2 of the co-combustion of WC and BC. The blending ratio of WC or CH with the lowest activation energy was 50%.

Predicting the macroscopic combustion characteristics of diverse forms of biomass in p. p. firing

This study validates a transient, zero-dimensional analysis for suspension firing of biomass in cylindrical shapes with specified particle density and aspect ratio (AR). The associated heat transfer coefficients determine the thermal histories for devolatilization which govern both ignition delays and volatiles combustion times for raw and torrefied biomass forms. The analysis accurately interprets ignition delays for four woods and two agricultural residues (AgRes), including two torrefied samples. It is also accurate for volatiles combustion times for six woods, two grasses, and two AgRes, including four torrefied samples. Simulations for a single biomass form with uniform moisture level over the ranges of density and AR for all biomass forms display enormous variations in the volatiles combustion times, even though the same devolatilization kinetics were implemented with all sets of particle properties. Char burnout times were insensitive to char oxidation kinetics from 850 to 1500 °C and from 5 to 100% O2. All cases gave burning rates limited by film diffusion of O2, and thermal annealing and ash encapsulation had to be omitted from CBK/E to match the predicted and measured char burnout times. Very large variations in the combustion characteristics of biomass in p. f. firing are inherent, because neither particle density nor AR are uniform throughout any biomass sample. These inhomogeneities are apparent in the spreads in reported ignition delays for different size cuts for a single biomass form, which were half as large as the spreads predicted for the complete ranges of density and AR over all biomass forms.

Moisture adsorption and spontaneous combustion characteristics of biomass wastes after degradative solvent extraction

The inherent disadvantages such as high oxygen content, low energy density, high moisture adsorption propensity and high spontaneous combustion tendency, have limited the widespread utilization of lignocellulosic biomass. A novel degradative solvent extraction (DSE) method has been recently developed to deoxygenate and upgrade biomass into two high-quality extracts (Soluble and Deposit) with various high-value applications. However, the moisture adsorption and spontaneous combustion characteristics of Soluble and Deposit still remain unclear, which are important for the safe storage, transportation and subsequent application of Soluble and Deposit. Therefore, in this study, the moisture adsorption and spontaneous combustion characteristics of Soluble, Deposit as well as raw biomass were investigated and compared. The moisture adsorption ratios of Soluble and Deposit were lower than 1.5% and 2.5% respectively, which were significantly lower than that of raw biomass, indicating that degradative solvent extraction greatly inhibited the moisture adsorption propensity of biomass. The ignition temperatures of Soluble and Deposit were at least 110 °C higher than that of raw biomass, and the activation energy of low temperature oxidation of Soluble and Deposit were 1.2–2.0 times higher than that of raw biomass. Soluble and Deposit had much higher weight loss temperature, heat release temperature, ignition temperature and higher activation energy of low temperature oxidation, revealing that the spontaneous combustion tendency of Soluble or Deposit was also significantly suppressed in comparison with raw biomass. The physicochemical properties of raw biomass, Soluble and Deposit were detailedly characterized, and it can be concluded that the low content of oxygen-containing functional groups, poor pore structure and dense surface structure jointly suppressed the moisture adsorption propensity and spontaneous combustion tendency of biomass after degradative solvent extraction. This research proves that degradative solvent extraction could not only achieve the upgrading of biomass but also inhibit the moisture adsorption propensity and spontaneous combustion tendency of biomass.

Numerical investigation the effect of air supply on the biomass combustion in the grate boiler

Abstract The burning behavior of biomass in the industrial-scale grate boiler is investigated through numerical simulation. A dynamic one-dimensional model is developed to simulate the biomass combustion in the grate bed. The three-dimension simulation is also employed to determine the radiation temperature as the boundary condition for the developed model. The model is validated with experimental measurements. The effect of air supply for biomass combustion characteristics in the grate bed is discussed based on the simulation results. It is found that the increase of air supply shortens the burning time and raises the maximum combustion temperature. Under the condition of constant excess air ratio, the fuel can be burnt out in advance by increasing primary air supply, but the radiation temperature in the zone 1 of grate bed is decreased when the ratio of primary air is larger than 43%. Based on these predicted results, the suggested ratio of primary to secondary air is 43:57 for this industrial-scale grate boiler. The effect of primary air flow distribution in different zones is also investigated to reduce the heat loss from bottom ash.

Hydrothermal Carbonization of Australian Saltbush

Hydrothermal carbonization (HTC) is a thermochemical process, wherein biomass is subjected to high-pressure, high-temperature subcritical water to improve the combustion characteristics of biomass ...

Surface Morphology and Combustion Characteristics of Biomass Micron Fuels

The surface morphology and combustion characteristics of micron-scale rice husks with different particle sizes were studied in detail by the fractal theory and thermogravimetric test. The calculation results by the box-counting dimension and erosion method were consistent with the actual data. The fractal dimensions first increased and then decreased with the rising particle sizes of rice husks. The largest fractal dimension and best combustion performance were found in 150 μm rice husk. The experiment results were verified finally by thermogravimetric tests, which were consistent with the theoretical results based on the fractal theory. The fractal theory of box-counting dimension and erosion provides a feasible method for studying biomass combustion characteristics.

Combustion behavior of coal pellets blended with Miscanthus biochar

To achieve reductions in CO2 emissions, replacing fossil fuels with biomass in thermal power generation is becoming increasingly prevalent. In general, the fuel nature and combustion characteristics of biomass are distinct from those of fossil fuels. Biomass is typically subjected to torrefaction to improve its grindability, hydrophobicity, and heating value (HV). However, the pretreatment process is accompanied by fuel property alteration and an energy penalty. This is strongly associated with the operating envelope and combustion stability of biochar cofiring with coal. Therefore, in this study, the Taguchi method was used to calculate the optimal torrefaction parameters for maximum energy yield and HV. Thermogravimetric and fuel characteristic analyses were performed to examine the pyrolysis features and combustion behavior of the studied fuels. In addition, a blend of 50% Miscanthus biochar and 50% Australia coal was produced and pressed into pellets. The pellets were placed into a free-drop furnace to observe their combustion behavior. The results demonstrated that the ignition temperature and burnout temperature of the blended fuels could be effectively reduced, and that their fuel conversion rates and combustion characteristic index could be enhanced. The results can be applied to coal cofiring in large-scale boilers in the future.

Thermogravimetric study of combustion of biomass and anthracite coal by iso-conversional method

The combustion characteristics of biomass, anthracite coal and their blends were investigated using thermogravimetry, and the kinetic parameters and combustion reaction mechanisms were tested by combining the iso-conversional method and Avrami method in order to find out the kinetics characteristics responsible for the combustion of samples. In biomass combustion, two peaks were observed at 332.3 and 472.3 °C, but the reactive rate curve of coal showed one peak with maximum mass loss rate at 552.8 °C. The ignition temperature and burnout temperature of blends decreased, and the ignition index and combustibility index increased with the increase in biomass content. Calculation of kinetic parameters showed that the values of activation energy of blends increased with increasing biomass content from 150.77 to 215.93 kJ/mol. The reaction orders of blends lay in the range of 0.44 and 0.78.

Comparative Study of the MILD Combustion Characteristics of Biomass and Brown Coal

The present paper reports a comparative study on the burning characteristics of pulverized biomass and coal under moderate or intense low-oxygen diluted (MILD) combustion conditions. Two types of biomass fuels—namely, grape marc and almond husk—and a high volatile Victorian brown coal were used as pulverized fuels to burn in a vitiated coflow inside a vertical MILD combustion furnace. The furnace walls, as well as coflow temperature, and local oxygen concentrations were controlled by a secondary swirling burner. Fuels were introduced into the furnace employing CO2 as a carrier gas with a constant velocity (i.e., bulk jet Reynolds number, Rejet = 20 000) and a fixed range of particle sizes (250–355 μm). Detailed measurements of in-furnace and exhaust temperatures and chemical species (i.e., O2, CO, CO2, and NO) are demonstrated and discussed, together with optical images at the top, middle, and bottom sections of the furnace. It was found that MILD combustion was successfully established for all of the fue...

Role of Potassium and Calcium on the Combustion Characteristics of Biomass Obtained from Thermogravimetric Experiments

This work focuses on the combustion behavior of raw and demineralized grape pomace and grape pomace doped with 0.1, 0.5, 0.82 (equal to the K concentration in the raw biomass), 3, and 6 wt % K and 0.1, 0.5, 1.08 (equal to the Ca concentration in the raw biomass), 3, and 6 wt % Ca. To identify the individual role of calcium and potassium, the biomass samples were either pyrolyzed in a N2 atmosphere or oxidized in air in a thermogravimetric analyzer (TGA) during non-isothermal runs at 10 K/min from room temperature to a maximum temperature of 1275 K. In all of the cases, the biomass pyrolysis process shows one main stage associated with the volatile matter release. This process is not significantly affected by the mineral content of biomass nor the presence of high K and Ca contents. During combustion in air, the biomass samples show two main distinct stages that are associated with the volatile matter release and the char oxidation. Whereas the main devolatilization stage is not significantly affected by t...

Control of the Development of Swirling Airflow Dynamics and Its Impact on Biomass Combustion Characteristics

Abstract The development of the swirling flame flow field and gasification/ combustion dynamics at thermo-chemical conversion of biomass pellets has experimentally been studied using a pilot device, which combines a biomass gasifier and combustor by varying the inlet conditions of the fuel-air mixture into the combustor. Experimental modelling of the formation of the cold nonreacting swirling airflow field above the inlet nozzle of the combustor and the upstream flow formation below the inlet nozzle has been carried out to assess the influence of the inlet nozzle diameter, as well primary and secondary air supply rates on the upstream flow formation and air swirl intensity, which is highly responsible for the formation of fuel-air mixture entering the combustor and the development of combustion dynamics downstream of the combustor. The research results demonstrate that at equal primary axial and secondary swirling air supply into the device a decrease in the inlet nozzle diameter enhances the upstream air swirl formation by increasing swirl intensity below the inlet nozzle of the combustor. This leads to the enhanced mixing of the combustible volatiles with the air swirl below the inlet nozzle of the combustor providing a more complete combustion of volatiles and an increase in the heat output of the device.

3-3. Effect of lignin and cellulose content on pyrolysis and combustion characteristics of biomass

3-3. Effect of lignin and cellulose content on pyrolysis and combustion characteristics of biomass

Combustion characteristics and design of hot water boiler

In order to understand the combustion characteristics of biomass, a detailed comparison with coal was made. There are many differences between biomass and coal in combustion characteristics. The burning rate of biomass is much higher than coal. The burning rate of biomass char is also higher than coal char. During biomass combustion, HCl, SO2 and NOx emissions mainly concentrate in volatile combustion stage, while CO2 emission mainly concentrates in char combustion stage. The slagging tendency of biomass ash is severer than coal ash and the adhesive force of biomass ash is higher. However, the wearing tendency of biomass ash is minor. Aiming at the particularity of biomass fuels, this paper briefly introduces the design of biomass hot water boilers. On this basis, a 2.8 MW biomass hot water boiler was developed and tested under the loads of 1.7 MW and 2.8MW. The running results show that the carbon content of bottom slag significantly decreases as the load increases. The boiler efficiency is higher than 85% under both loads.

Oxy-combustion of biomass in a circulating fluidized bed

Abstract The objective of this study was to investigate combustion characteristics of biomass (willow, Salix viminalis) burnt in air and O2/CO2 mixtures in a circulating fluidized bed (CFB). Air and oxy-combustion characteristics of wooden biomass in CFB were supplemented by the thermogravimetric and differential thermal analyses (TGA/DTA). The results of conducted CFB and TGA tests show that the composition of the oxidizing atmosphere strongly influences the combustion process of biomass fuels. Replacing N2 in the combustion environment by CO2 caused slight delay (higher ignition temperature and lower maximum mass loss rate) in the combustion of wooden biomass. The combustion process in O2/CO2 mixtures at 30% and 40% O2 is faster and shorter than that at lower O2 concentrations.