Biomass Blends Research Articles

Experimental study on ash morphology, fusibility, and mineral transformation during co-combustion of antibiotic filter residue and biomass

An ever-increasing attention has been paid to the treatment of antibiotic filter residue (AFR) due to its serious hazard and growing production. Duo to the unique features of AFR, the ash properties of AFR are still unclear. The effects of biomass blending on ash characteristics of AFR have yet to be sufficiently understood. In addition, little work has been performed on ash morphology, fusibility and mineral transformation during co-combustion of AFR and biomass. The present study dealt with the ash characteristics of AFR and its blends with biomass at various combustion temperatures and blended ratios. Experimental results indicate that the ash compositions in blended fuel AFR/poplar (PL) are generally identical as those in AFR but nearly independent of PL portion. Nevertheless, the mineral distributions in the blends of AFR and peanut shell (PS) vary greatly with the blended ratio, especially minerals containing calcium and silicon. There are more species of minerals in AFR/PS blends in comparison to individual fuels, but the condition of AFR/PL blends is significantly different. The present study was helpful to understand of ash behaviors of AFR and its blends during co-combustion, and further promoted the safe, clean and efficient utilization of AFR by co-firing technology.

A kinetic study of microalgae, municipal sludge and cedar wood co-pyrolysis

In the present study, pyrolysis kinetics of the pure and blends of cedar wood (CW), algal biomass (AB), and digested sludge (DS) with and without the catalyst ZSM–5 were examined. Both Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) model-free methods were used to calculate the total activation energy (Ea), change in enthalpy (ΔH), and change in Gibb’s free energy (ΔG) of 18 different biomass combinations. The highest Ea (548.52 kJ/mol) and ΔH (532.22 kJ/mol) were found for the CW. The biomass blend of AB: CW at weight ratios of 2:1 with catalyst (2:1 catalyst to biomass weight ratio) resulted in the lowest Ea (57.03 kJ/mol) and ΔH (50.11 kJ/mol) with a ΔG value of 243.25 kJ/mol. Statistically significant response surface models were developed to describe the effect of biomass blend composition on Ea and ΔH. This study demonstrated that catalytic pyrolysis of biomass blends from different sources can be used to significantly reduce the energy requirement for the process.

Evaluation of the energy generation potential by an experimental characterization of residual biomass blends from Córdoba, Colombia in a downdraft gasifier

An experimental characterization of crop residue biomass blends to evaluate their energy potential was conducted using an experimental approach in a commercial scale downdraft gasifier. Corncobs, rice husks, sesame stalks and cotton gin refuse were used to study the effect of mixture proportions on equivalence ratio, gasification temperature, syngas lower heating value (LHV), and cold gas efficiency (CGE). Using an experimental mixture design, thirty-two sample blends were evaluated in an Ankur WBG-30 downdraft gasifier with 30 kg/h feed supply coupled with a syngas purification system, temperature sensors and a gas chromatograph. Syngas composition CO, H2, CH4, N2 and CO2 are presented for each blend. It was found that temperature, syngas composition, syngas lower heating value and cold gas efficiency were negatively affected as the proportion of rice husks in the mixture was increased. It was possible to reach CGE values up to 57.91% and LHV up to 4460 kJ/kg under certain blending conditions. A higher percentages of rice husks caused a considerable increase in the variability of the equivalence ratio resulting in suboptimal gasification conditions.

Co–pyrolysis of biomass blends: Characterization, kinetic and thermodynamic analysis

The present study has dealt with characterization and co–pyrolysis of binary and ternary blends of three biomass, viz. water hyacinth (WH), Thevetia peruviana (TP) and sugarcane bagasse (SCB). The biomass blends were characterized for proximate and ultimate analysis, surface morphology and functional groups. Co–pyrolysis of blends was carried out using a thermogravimetric analyzer (TGA) at heating rates of 8, 10, 15 and 30 °C min−1. TGA data was analysed using Ozawa–Flynn–Wall (OFW), advanced isoconversional model of Vyazovkin (Vyazovkin _AIC) and distributed activation energy model (DAEM). The dominant reaction mechanism of co–pyrolysis at different stages of conversions was deduced using Criado plots. The kinetic parameters of activation energy and pre–exponential factor, and thermodynamic parameters of ΔH and ΔS showed large variation with conversion, which is indicative of complex chemistry of thermal conversion of various structural components of biomass with synergistic interactions. The activation energies for binary blends WH SCB, WH TP, TP SCB were in the range 122.90–237.53, 127.93–272.92, and 124.80–235.94 kJ mol−1, respectively. For ternary blends WH 111, WH 211 and WH 311, activation energy varied in the range 119.64–194.31, 123.40–246.80, and 121.65–194.75 kJ mol−1, respectively. The predominant reaction mechanism for all blends was ordered reaction (F1) in lower conversion range (α ≤ 0.25), and diffusion limited process (D1 or D2 or D3) in higher conversion range (α = 0.35–0.55). Positive ΔH for all blends indicated endothermic nature, while positive ΔS indicated more disordered system after reaction – typical of pyrolysis.

Experimental and numerical investigation of the combustion characteristics and NO emission behaviour during the co-combustion of biomass and coal

As a promising technology for pollutant reduction, biomass-coal co-combustion has attracted worldwide attention. In this study, experiments combined with simulations were conducted to explore the combustion characteristics and NO emission behaviour, as well as their interrelations during the co-combustion process of biomass and coal. The experimental results reveal an obvious decrease in the NO concentration with an increased biomass blending ratio by weight. A maximum NO reduction of 24% was found when 50% biomass was blended with coal, which mainly occurred in the stage of stable char combustion and was attributed to non-catalytic effect related to free radicals. Moreover, the higher biomass blending ratio led to a more violent combustion reaction during the devolatilization stage, while the reaction remained constant during the char combustion stage. As the temperature increased from 800 °C to 1000 °C, the fuel-N/NO conversion ratio increased for the blend with 30% biomass and 70% coal, which resulted from the combined contributions of devolatilization and char combustion. Although the rise in temperature also led to an increase in the combustion rates of the fuel samples, the effect of the temperature on NO emission turned out to be more sensitive than that on the combustion rate. Additionally, when the oxygen concentration increased from 6 vol% to 21 vol%, the NO conversion ratio decreased, which is attributed to the promotion effect of the higher O2 concentration on homogeneous NO reduction. The simulation data were in good agreement with the experimental results, and demonstrated that there were six elementary reactions dominating the NO transformation. Moreover, homogeneous NO reduction plays a vital role in decreasing NOx emissions.

A thermogravimetric assessment of the tri-combustion process for coal, biomass and polyethylene

Thermogravimetric analysis (TGA) was applied to evaluate the combustion behaviour of combining three feedstocks coal, biomass and polyethylene as a tri-fuel for various blend ratios. The feed materials assessed were bituminous coal (BC), anthracite coal (AC), camphor wood (CW), wheat straw (WS) and polyethylene-terephthalate (PET). The kinetic parameters of the tri-fuel blends were assessed using a Coats-Redfern integral method. The kinetic analysis indicates that the tri-fuel combustion mechanisms follow the diffusion model (D1 & D4) and can be separated in to three distinct stages. TGA analysis demonstrated that an increase in the blend ratio of biomass (CW/WS) and plastic (PET) enhances the combustion properties with respect to lowering the ignition (Ti) and burnout (Th) temperatures, along with an increase in the combustion stability indices (Cs/Csi). This enhancement of the combustion behaviour is more evident for the lower volatile anthracite coal tri-fuel blends. As the blend ratio of the anthracite coal is lowered the overall hydrocarbon-volatile content is increased as a function of increasing the biomass and plastic blend ratios. Laboratory scale analytical analysis of blending biomass, plastic with either bituminous coal or anthracite coal demonstrates a synergistic influence which is observed to benefit the overall combustion behaviour (enhanced mass loss rate and burnout). However, further investigation of tri-fuel blending streams assessing the combustion performance (Ti, Th, Ci, Csi, Ea, flue gas emissions and ash chemistry) is required at pilot and plant scale.

Optimization of process variables during torrefaction of coal/biomass/waste tyre blends: Application of artificial neural network & response surface methodology

Torrefaction models to predict solid yield (SY), enhancement factor (EF) and higher heating value (HHV) of blends of coal and biomass, and waste are limited in the literature. In this study, Artificial Neural Network (ANN) and Response Surface Methodology (RSM) were used to determine the optimum torrefaction process conditions (temperature, time, and blend ratio) and optimum fuel blend based on the torrefaction variables (HHV, EF, and SY). Pine sawdust (PSD), sugarcane bagasse (SCB), and corn cob (CC) were the biomass materials used. Three torrefaction temperatures (200, 250, & 300 OC), torrefaction times (30, 45, and 60 min), and blend ratios (50:50, 71:29, & 80:20) for coal/biomass/waste-tyre blends were studied. The HHV of the fuels that was determined experimentally was used to estimate the EF and SY. A Levenberg-Marquardt back-propagation algorithm ANN and RSM, Box-Behnken Design (BBD) techniques were applied to study the torrefaction process. Coal-to-Torrefied fuel ratio of 50:50 at 300 OC and 45 min was the optimum process condition, while Coal + Torrefied PSD was the optimum fuel with the HHV and EF of 28.27 MJ/kg and 1.41, respectively. The HHV of the optimum fuel (torrefied) is around 10% higher than the raw fuel. Fuel quality enhancement of Coal + Torrefied WT via torrefaction was not promising. A second-order polynomial and ANN models were developed for each fuel, but the ANN model was more reliable than RSM model considering the R2, AAD and PRE results.

Experimental tests on co-firing coal and biomass waste fuels in a fluidised bed under oxy-fuel combustion

The co-firing of coal and biomass waste in oxy-fuel fluidised beds is an important oxy-fuel combustion technology for CO2 capture and waste disposal. However, practical experience regarding co-firing in an oxy-fuel fluidised bed is still limited. In this study, a 10 kWth oxy-fuel fluidised bed with continuous fuel-feeding and real-time flue gas measurements was developed. The combustion stability and dynamic response during the switch in combustion states were examined. The effect of the combustion atmosphere (air or oxy-fuel combustion), inlet O2 concentration (V0o2), combustion temperature, fuel type, and biomass blending mass ratio (Mb) on the combustor temperature distribution, CO2 enrichment, carbon conversion, and combustion residues were systematically investigated. The results indicated that the combustion state can switch quickly during the co-firing process (similar to the rapid switch in combustion states during oxy-coal or oxy-biomass combustion), and stable combustion in the fluidised bed can be maintained when V0o2 is increased to 30% or more. The optimal range of Mb, which is directly related to the fuel type and combustion mode, contributes to a highly uniform temperature distribution, increased CO2 generation, and decreased amount of unburnt carbon in the fly ash. The bottom slag had a honeycomb structure, which became larger than quartz sand (bed material) after 120 h of combustion. Furthermore, no agglomeration of bottom slag, quartz sand, and fly ash was detected during the tests.

Gasification of municipal solid waste blends with biomass for energy production and resources recovery: Current status, hybrid technologies and innovative prospects

This paper critically reviews the current status of utilization of municipal solid waste and biomass blends for energy and resources recovery together with identifying the opportunities for future development in technological equipment and physicochemical waste compositions involved in such complex processes. Among numerous thermochemical conversion techniques, gasification of municipal solid waste with different biomass blends has unveiled as an auspicious technology to develop a sustainable waste management system that would substantially reduce pollution and maximize energy and materials recovery. Municipal solid wastes and biomass have different properties and elemental compositions and are abundantly available. These materials have the potential to produce various types of value-added products in terms of energy and chemicals through the gasification process. Recently, hybrid systems have been introduced with simple gasification technologies in terms of fuel oxidation system, plasma torch, or some biochemical conversion systems to enhance the process efficiency, energy, economics, quality, the yield of syngas, and to alter the composition of gaseous products. Consequently, gasification of biomass and waste would be the most suitable option to reduce toxic elements and harmful gases for the surroundings. For instant, ecological influence is not the real issue for limitation of biomass and waste gasification development, while a feasible economic return could appeal to investors and initiate its commercialization. Energy and resource recovery is assessed as an integrated approach to overcoming limitations. Also, techno-economic and environmental impact, life cycle assessment, and their implications are discussed in detail. Key bottlenecks that need urgent attention to facilitate global recognition of hybrid technology are highlighted.

Gasification of blended coal, biomass and plastic wastes to produce hydrogen (DOE)

Gasification of blended coal, biomass and plastic wastes to produce hydrogen (DOE)

Radiocarbon Determination of the Carbon-Based Biomass Blending Ratio by Analysing Flue Gas Emitted from Coupled Combustion

The determination of carbon-based biomass blending ratio was a prerequisite for the large-scale development of the coupled combustion technology of biomass and coal. In this study, the experimental system of the radiocarbon method to detect the carbon-based biomass blending ratio by analyzing the flue gases produced during coupled combustion was built, and the calculation model of the carbon-based biomass blending ratio was proposed, and the accuracy and precision of the radiocarbon method were evaluated. The results showed that there was a good linear relationship between the 14C concentration of CO2 samples and biogenic fractions in flue gas. The application of the new calculation model improved the accuracy of the 14C determination method, and the relative error increased as the carbon-based biomass blending ratio decreased in the 14C method: the minimum relative error of the carbon-based biomass blending ratio with carbon-based assay was 15.16%,12.21%, 9.61%, 7.96% and 3.13% when considering coal and air simultaneously in AMS analysis. This further validated the 14C determination method as an accurate method for identifying the carbon-based biomass blending ratio in biomass and coal coupled combustion.

Synergistic co-pyrolysıs of polyolefin plastics with wood and agricultural wastes for biofuel production

Renewable lignocellulosic biomass is a promising energy resource since its co-pyrolysis with hydrogen-rich plastics can produce high-yield and high-quality bio-oil. In this study, co-pyrolysis of agricultural wastes (i.e. corn stover) and wood wastes (i.e. narra, Pterocarpus indicus and ipil, Intsia bijuga) with polyolefin plastics (i.e. polypropylene, low-density polyethylene, and high-density polyethylene) were examined via thermogravimetric analyses. Unlike previous co-pyrolysis studies which had focused on the improvement of product yield or cumulative weight loss, herein, we present the synergistic effects on the mass decomposition rate or rate of generation of products during co-pyrolysis. The main objective of this study is to evaluate the effects of temperature, and biomass-to-plastic ratio on rate synergy during co-pyrolysis. Rate synergy values up to 10% per min were obtained for biomass and plastic blends. Activation energy and pre-exponential factor of the reactions in the co-pyrolysis process were evaluated using the Coats-Redfern method. Activation energies for agricultural waste and plastics blends ranged from 45 to 82 kJ mol−1 while that for wood wastes and plastic blends ranged from 53 to 112 kJ mol−1. Interestingly, the activation energy of the thermal decomposition of plastic was found to be lower during co-pyrolysis with biomass than in pure form. Moreover, biomass-plastic co-pyrolysis followed a two-stage degradation: biomass degradation from 200 to 400 °C and thereafter plastic degradation from 400 to 500 °C. Overall, the use of lignocellulosic biomass and waste plastics for biofuel production can also minimize the volume of solid wastes for landfills.

Thermogravimetric Analysis of Fuel Blends of Biomass and High-Ash Coal-Containing Waste

An investigation of co-combustion characteristics of the two-component mixed fuel was carried out using methods of thermogravimetric analysis. As feedstock, there were used two types of biomass and the high-ash coal-containing waste, which were ash-slag waste from a coal-fired power plant and coal concentrate obtained by their enrichment. The experiments were carried out in an inert (nitrogen) and oxidizing (air) medium. It is shown, that in the temperature range characteristic for biomass burning the additivity principle cannot be used for evaluation of combustion characteristics of the blends. The presence of a coal-containing component in the mixture leads to a disproportionate decrease in the mass loss rate both in the temperature range characteristic for yield and oxidation of biomass volatile products, and in the temperature range in which its solid residue is oxidized. The effect of biomass on the oxidation rate of the coal-containing component was not found.

Back Cover Image, Volume 14, Issue 5

The back cover image is based on the Case Report Briquetting characteristics of woody and herbaceous biomass blends: Impact on physical properties, chemical composition, and calorific value by Jaya Shankar Tumuluru et al., https://doi.org/10.1002/bbb.2121. image

Design of solid biofuels blends to minimize the risk of sintering in biomass boilers

Biomass with high concentration of alkali/alkaline and silica components can lead to slagging/fouling, and sintering of the ash deposits, causing corrosion and erosion of the boilers. There are several methods to predict bed agglomeration such as slagging/fouling indexes. However, these indexes are developed to be used for coal ashes, which shows a different behaviour than biomass fuels. The aim of this work was to determine the suitable percentage of different species found in biomass blends in order to reduce the risk of slagging and sintering. We studied the ash behaviour of 24 blended biomass samples using two slagging indexes: the alkali index, and the % of bases in ashes index, and we validated these two indexes with the Bioslag test, and with the Hardness Index (%D1). There is low risk of slagging in most of the samples, as well as a low sintering risk. However, some samples present moderate risk of sintering possibly due to SiO2. The Bioslag test and the %D1 test support our results. Samples showing risk of sintering exceed 25% of the total accumulated ash weight percentage ac%_1P>25%, and show a hardness of %D1 > 0.7. These validations can be considered as useful tools for estimating slagging and sintering of woody biomass fuels in domestic pellet boilers.

Co-Pyrolysis of Rice Husk and Chicken Manure

Abstract The increase in the production scale of chicken causes an increment in the produced manure. Chicken manure is considered an excellent soil amendment due to the high nitrogen and phosphorous content. However, the high production of manure exceeds the soil requirements. Rice husk is a by-product of rice production. Approximately one hundred forty million tons of rice husk is produced per year worldwide. There are several ways to manage rice husk such as animal bedding, direct combustion, or as a soil fertilizer. The husk's ashes are suitable for construction or as reinforcing material due to the high silica content. However, rice husk has a low volatile matter and high silica content, which makes processes like direct combustion inefficient. Thermochemical processes (such as pyrolysis and gasification) are effective ways to manage waste. The present study investigates the co-pyrolysis of chicken manure and rice husk. The experiments were conducted in a non-isothermal gravimetrical analyzer using nitrogen at a flowrate of 100 ml/min at three different heating rates (5, 10, and 15 °C/min). The degradation of individual biomass and biomass blends is investigated. The kinetic parameters are calculated using the Friedman method. Results show a positive synergetic effect for mixing ratios greater than 20% rice husk. The mixing ratio of 40% of rice husk manifested the best performance among all blends. This mixture showed the minimum energy of activation (90.2 kJ/mol). Also, the 40% rice husk mixing ratio showed maximum conversion when compared with chicken manure's conversion.

Migration and transformation law of potassium in the combustion of biomass blended coal

The effects of combustion temperature and biomass blending ratio on the release of K, the occurrence form of K in the ash and the change of mineral matter were studied. It is found that combustion temperature has a significant effect on the release of K. At 600–750°C, with an increase in temperature, water-soluble K and NH4Ac-soluble K are released to the gas phase, which makes the release ratio of K fast; while at 750–850°C, water-soluble K and NH4Ac-soluble K begin to convert into other forms of K and are fixed in the ash sample, which makes the release ratio of K slow; when the temperature is higher than 850°C, as the temperature increases, the decomposition of HCl-soluble K causes the release ratio of K increase again. Through XRD analysis, it is found that the water-soluble K in ash mainly exists in the form of KCl. The production of K2SO4 is affected by both the K content in the raw material and the S/Cl ratio, the higher the content of K in raw materials, and the greater the ratio of S/Cl, the more it will promote the formation of K2SO4. At the same time, it is also found that there is a synergistic effect between biomass and coal combustion. The elements such as Al, Si in coal may react with K in biomass to generate alkaline aluminosilicate, resulting in more K remaining in the ash

Chemical looping based co-combustion of high ash Indian coal and rice straw operating under CO2 in-situ gasification mode

Chemical looping combustion (CLC) is a promising technology paving the way for the inherent CO2 capture. As Indian coals are enriched in ash content, their utilization in the CLC technology under direct fueled condition is challenging due to the ash layer resistance in the reactivity of metal oxides. Alternatively, the blending of biomass with high ash coal (HAC) can enhance fuel reactivity with metal oxides. In this context, the present study is focused on the co-utilization of high ash Indian coal (ash 33 wt %) and rice straw (RS) in the CLC process using Fe2O3 particles as metal oxides in a fixed bed reactor under CO2 based in-situ gasification mode of operation. The intrinsic reactivity of ash, char, and volatile matter of the solid fuels with Fe2O3 is assessed individually. The obtained CLC based experimental results showed that the CO2 capture efficiency and gas conversion are found to be increased by 9.7% and 6%, respectively, during the co-utilization of HAC and RS. The reactivity of H2, CO, and CH4 with Fe2O3 is also assessed under the co-combustion mode of the CLC process. The XRD results showed that the formation of calcium ferrite (CaFe2O4) had enhanced the conversion of char during the CLC process. A higher reactivity between char and Fe2O3 (solid-solid interaction) is observed at high operating temperatures with 13% increase in the weight loss under the co-combustion mode of the CLC process. Further, the kinetic parameters are evaluated for the CLC and non-CLC based reactions under various operating temperature regimes. Among the kinetic models considered, the shrinking core model is found to be the best fit, compared to the homogenous progression model. The chemical reaction is the slowest step at the operating temperatures in the range of 200–500 °C; ash layer diffusion is found as the rate controlling step at high operating temperatures (800–1000 °C); whereas film diffusion controlled mechanism is dominant at 700–800 °C.

Fluidised Bed Gasification of Diverse Biomass Feedstocks and Blends—An Overall Performance Study

The aim of this work is to investigate the fluidised bed gasification of several pure and blended feedstock prepared in the form of pellets: oak bark, two bark/wheat straw blends (85/15 and 50/50 wt%) and lignin residue remaining from bioethanol production. Gasification conditions were defined to be representative of dual fluidised bed ones (steam gasification at 850 °C, followed by air combustion of the char). The cold gas efficiency (77–81%), gas composition and tar content (0.9–2.3 g/kgdaf) are close for the gasification of bark and the two bark/wheat straw blends. For lignin residue, the cold gas efficiency is lower (71%), and the tar content is 9.1 g/kgdaf. The agglomeration propensity is much higher for lignin residue than for the other feedstock. This was put into evidence with in-bed temperature measurements at different levels, and confirmed with post-test size screening of the bed material particles. The 50/50 wt% bark/wheat straw blend seems to undergo defluidisation in combustion, however followed by refluidisation of the bed. These findings were also well correlated with a predictive model for defluidisation.

Techno-economic analysis of forest biomass blends gasification for small-scale power production facilities in the Azores

The present work assesses the energetic valorisation of forest biomass blends in the archipelago of the Azores, to do so, a multiphase 2-D Eulerian-Eulerian model was employed to simulate forest biomass gasification in a pilot-scale fluidized bed reactor. The numerical model was validated under experimental gasification runs performed in a 250 kWth quasi-industrial biomass gasifier. The potential use of the produced syngas as a complementary energy source for small-scale power production in the Azores was assessed based on the results. The exergy efficiency and tar production of the process were determined. A techno-economic study combining the net present value (NPV), internal rate of return (IRR), and payback period (PBP) followed by a Monte Carlo sensitivity analysis was comparatively performed for two distinct application sizes (100 and 1000 kW) so to gauge which unit size carries enhanced operative feasibility and foresee the main investment risks in conducting forest biomass blends gasification for power production in small facilities. Results revealed that the 100 kW unit was economically impracticable under current market conditions, while the 1000 kW unit showed to be economically feasible with an NPV of 486 k€, IRR of 17.44% and PBP of 7.4 years. The sensitivity analysis predicted a higher risk of failure in the NPV, being highly sensitive to the electricity sales tariff and electricity production. Indeed, forest biomass gasification projects carry great potential when applied to small facilities with economic viability in some economies of scales, withal, special concerns must always be considered regarding the project attractiveness to potential investors.