Biomass Blends Research Articles

Co-gasification of rice husk and woody biomass blends in a CFB system: A modeling approach

In the present study, co-gasification behaviors of rice husk (RH) and blends of two woody biomasses, sawdust (SD) and bamboo dust (BD) in a circulating fluidized bed (CFB) system were studied by using ASPEN plus software. The gasifier performance was evaluated in respect of the gas yield and its higher heating value (HHV), in addition to the char conversion efficiency (CCE) and cold gas efficiency (CGE). The present study effectively showed that the blending of biomasses significantly improves the producer gas quality in terms of H2 production and energy output, as well as the gasifier performance indicators. RH + SD blend showed both the highest higher heating value (4.79 MJ/Nm3) and H2 content (12.51 vol %) at 900 °C and ER of 0.24. The simulation results also showed that the gas yield was the highest for RH + BD blend (1.75 Nm3/kg) followed by RH + SD blend (1.73 Nm3/kg) and then RH (1.41 Nm3/kg) at 900 °C. The highest HHV of RH (4.71 MJ/Nm3), RH + SD (5.17 MJ/Nm3) and RH + BD (5.39 MJ/Nm3) were also obtained at 800 °C and ER of 0.19. Change in the steam/biomass (S/B) also showed a slight variation in gasifier performance parameters.

Conversion of biomass blends (walnut shell and pearl millet) for the production of solid biofuel via torrefaction under different conditions

The torrefaction of lignocellulose biomass was conducted to produce biochar with properties compatible with coal. Two lignocellulose biomasses, pearl millet (PM) and walnut shell (WS), were torrefied at different process temperatures (230–300 °C), residence times (30–90 min), and different compositional biomass blends to improve the characteristics of the biochar product. The resulting biochar product exhibited favorable changes in their properties. The pure biomasses and their blends obtained a high biochar yield (41–91%). The gross calorific value (GCV) ranged from 22 to 27 MJ/kg, showing an increase of 22–59% compared to the raw biomass. The torrefaction temperature had the most notable effect on the biochar quantity and quality. The biochar samples obtained from the torrefaction of different blends showed a higher GCV and other physicochemical characteristics than the pure biomasses. Scanning electron microscopy showed that these products might also be used for other applications.

Effect of pretreatment and biomass blending on bio-oil and biochar quality from two-step slow pyrolysis of rice straw

This study investigated biomass blending and water washing to improve product quality from two-step pyrolysis of rice straw. Rice straw (RS) was mixed with groundnut shells (GNS) and wheat straw (WS) in different weight ratios. Blending RS with GNS/WS in a 1:1 ratio increased the total bio-oil yields by 7-9% and reduced the pyrolysis gas and char yields by 5-7% and < 2%, respectively. RS was washed with water separately to examine the effect of removing water-soluble ash elements. The optimum washing duration was 60 min; the ash removal efficiency was then 26%. The bio-oil yields from washed straw increased by 4% over unwashed straw, and pyrolysis gas yields decreased. Combining the washing and blending processes increased the levoglucosan yield by 1.6-2.1 times compared to unwashed RS, and the water content in bio-oil was reduced by ∼ 10%. Moreover, the biochar samples obtained after pyrolysis of washed biomass blends had potential fuel applications owing to low fouling or slagging propensity. They also had possible use in the soil for adsorption of soil contaminants and increasing acidic soil pH, with likely stability of ∼ 1000 years in the ground. These results provide a promising alternative for efficiently converting rice straw to multiple value-added products.

Impact of storage and blending of algae and forest product residue on fuel blendstock production

Seasonal impacts on the production of algae biomass require blending with other feedstocks such as wood to maintain consistent annual conversion capacity. Idaho National Laboratory (INL) has developed a long-term storage strategy for algae biomass using ensiling, or anaerobic wet storage, that was tested for blends of algae and wood to stabilize the feedstock supply for processing to fuels. Additionally, blending biomass (algae and wood) leverages existing biomass storage approaches commonly used by the feed and forage industry. Earlier research also has demonstrated positive results that indicate ensiling is more effective and economical in normalizing biomass feedstock supply prior to conversions such as HTL (hydrothermal liquefaction) than preserving biomass by drying.By assessing impacts beginning with upstream logistic operations and proceeding through each conversion step, this work focuses on conversion of ensiled and blended biomass to fungible liquid transportation fuel blendstocks. This is accomplished by conversion of the blended biomass (62% Chlorella sp. blended with 38% loblolly pine forest product residues [FPR]) to bio-crude through HTL and subsequent upgrading through HT (hydrotreating) with a commercial refinery catalyst analogous to a refinery process to produce hydrocarbon fuel. Results indicate that carbon retention and quality are preserved in both the bio-crude and upgraded fuel from the ensiled blend, indicating the potential of this approach for managing seasonal variations in algae biomass productivity.

Effects of Mustard Husk, Wheat Straw, and Flaxseed Residue Blending on Combustion Behavior of High Ash Coal and Petroleum Coke Blends

Abstract This present work reports the combustion studies of coal, petroleum coke (PC) and biomass blends to assess the effects of the mustard husk (MH), wheat straw (WS), and flaxseed residue (FR) blending toward improvement of coal combustion characteristics. Ignition temperature (TS), maximum temperature (TP), burnout temperature (TC), activation energy (AE), and thermodynamic parameters (ΔH, ΔG, and ΔS) were analyzed to evaluate the impact of biomass and PC blending on coal combustion. Experimental results indicate that coal and PC have inferior combustion characteristics compared to MH, WS, and FR. With the increase in WS content in blends from 10 to 30%, TS reduced from 371 to 258 °C and TP decreased from 487 to 481 °C, inferring substantial enhancements in combustion properties. Kinetic analysis inferred that blended fuel combustion could be explained mostly using reaction models, followed by diffusion-controlled and contracting sphere models. Overall, with the increase in FR mass in blends from 10 to 30%, AE decreased from 108.97 kJ/mol to 70.15 kJ/mol signifying ease of combustion. Analysis of synergistic effects infers that higher biomass addition improves coal and PC blends’ combustion behavior through catalytic effects of alkali mineral matters present in biomass. Calculation of thermodynamic parameters signified that combustion of coal and PC is challenging than biomasses; however, blending of biomass makes the combustion process easier.

Thermo-Chemical Conversion of Microwave Selectively Pre-Treated Biomass Blends

Possibilities of more efficient use of regional lignocellulosic resources (wood, wheat straw, peat) of different origin for an environmentally friendly energy production using selectively MW pre-treated blends of commercial wood or wheat straw pellets with raw peat pellets are studied. A hypothesis is proposed and tested that selective MW pre-treatment of wood or wheat straw pellets at the frequency 2.45 GHz and blending of MW pre-treated pellets with raw peat pellets can be used to enhance and control the thermo-chemical conversion of biomass blends. To test this hypothesis, a combined experimental study and mathematical modelling of the processes were performed. The thermo-chemical conversion of selectively activated blends was experimentally studied using a batch-size pilot device, which consists of a biomass gasifier and a combustor. To evaluate the effect of selective MW pre-treatment of biomass pellets on the thermo-chemical conversion of pre-treated blends, measurements of the kinetics of weight loss, yield of combustible volatiles, flame temperature, heat output of the device, and composition of emissions were made at different MW pre-treatment regimes of wheat straw and wood pellets and different mass fractions of pre-treated pellets in biomass blends. The developed novel 2D numerical model of thermo-chemical conversion of MW pre-treated straw confirmed that the pre-treatment of wheat straw pellets increases the generated heat and significantly affects the temperature distribution in the flame/bed zones. It was confirmed that MW pre-treatment leads to a faster thermal decomposition of biomass pellets, synergistically activating the non-treated parts of blends. The overall improved yield of combustible volatiles and their complete combustion provide a surplus of heat production by limiting the formation of GHG emissions, which allows promoting MW pre-treated biomass of different origin as efficient regional bioenergy resources for energy production.

Pilot-Scale Pelleting Tests on High-Moisture Pine, Switchgrass, and Their Blends: Impact on Pellet Physical Properties, Chemical Composition, and Heating Values

In this study, we evaluated the pelleting characteristics of southern yellow pine (SYP), switchgrass (SG), and their blends for thermochemical conversion processes, such as pyrolysis and gasification. Using a pilot-scale ring-die pellet mill, we specifically assessed the impact of blend moisture, length-to-diameter (L/D) ratio in the pellet die, and ratio of pine to SG on the physico-chemical properties of the resulting pellets. We found that an increase in pine content by 25–50% marginally affected the bulk density; however, it also led to an increase in calorific value by 7% and a decrease in ash content by 72%. A moisture content of 25% (wet basis) and an L/D ratio of 5 resulted in poor pellet durability at &amp;lt;90% and bulk density values of &amp;lt;500 kg/m3, but increasing the L/D ratio to 9 and lowering the moisture content to 20% (w.b.) improved the pellet durability to &amp;gt;90% and the bulk density to &amp;gt;500 kg/m3. Blends with ≥50% pine content resulted in lower energy consumption, while a lower L/D ratio resulted in higher pelleting energy. Based on these findings, we successfully demonstrated the high-moisture pelleting of 2.5 ton of pine top residues blended with SG at 60:40 and 50:50 ratios. The quality of the pellets was monitored off-line and at-line by near infrared (NIR) spectroscopy. Multivariate models constructed by combining the NIR data and the pelleting process variables could successfully predict the pine content (R2 = 0.99), higher heating value (R2 = 0.98), ash (R2 = 0.95), durability (R2 = 0.94), and bulk density (R2 = 0.86) of the pellets. Thus, we established how blending and densification of SYP and SG biomass could improve feedstock specifications and that NIR spectroscopy can effectively monitor the pellet properties during the high-moisture pelleting process.

Effects of Cofiring Coal and Biomass Fuel on the Pulverized Coal Injection Combustion Zone in Blast Furnaces

CO2 emissions are a major contributor to global warming. Biomass combustion is one approach to tackling this issue. Biomass is used with coal combustion in thermal power plants or with blast furnaces (BFs) because it is a carbon-neutral fuel; therefore, biomass provides the advantage of reduced CO2 emissions. To examine the effect of co-firing on pulverized coal injection (PCI) in BFs, two coals of different ranks were blended with the biomass in different proportions, and then their combustion behaviors were examined using a laminar flow reactor (LFR). The PCI combustion primarily functions as a source of heat and CO to supply the upper part of the BF. To create a similar PCI combustion environment, the LFR burner forms a diffusion flat flame with an oxygen concentration of 26% with a flame temperature of ~2000–2250 K at a heating rate of 105 K/s. The combustion characteristics, such as the flame structure, burning coal particle temperature, unburned carbon (UBC), and CO and CO2 emissions were measured to evaluate their effect on PCI combustion. With the increase in the biomass blending ratio, the brightness of the volatile cloud significantly increased, and the particle temperature tended to decrease. The fragmentation phenomenon, which was observed for certain coal samples, decreased with the increase in the biomass blending ratio. In particular, with an increase in the biomass blending ratio, the optimum combustion point occurred, caused by the fragmentation of coal and volatile gas combustion of biomass.

Computational fluid dynamics modeling of biomass co-firing in a 300 MW pulverized coal furnace

Biomass energy is one of the most accessible and readily available carbon-neutral energy options as a RES. It is regarded as a viable alternative fuel for coal combustion, particularly for biomass co-firing with pulverized coal, with numerous applications. The CFD can provide reasonably accurate solutions to complex thermo-chemical-fluid interactions, which is useful for understanding the design or retrofit of boilers and can save time, money, and effort. In this study, a CFD simulation of a 300 MW pulverized coal boiler with biomass co-firing was performed to investigate the impact of biomass co-firing with coal, considering the biomass co-firing ratio, mixing effect, and feeding temperature. The results show that the flow field in the furnace does not change significantly under different bio-mass blending ratio. Biomass co-firing can reduce peak temperatures in the furnace and make the temperature distribution more uniform. The concentration of unburned carbon in the furnace decreases as the biomass blending ratio increases. Furthermore, biomass blending has a significant impact on nitrogen oxide reduction, with NOx emissions reduced by 20% and 28%, respectively, when the biomass blending ratio is 15% and 30%. The change of parameters inside the furnace caused by the reduction of biomass powder feeding temperature about 80 K is not significant. On the other hand, co-firing biomass with coal, reduces the risk of biomass spontaneous combustion while maintaining the furnace combustion stability and boiler combustion efficiency. The optimum ratio of biomass co-firing ration is deduced in this study is up to 20%.

Effect of co-liquefaction of lignin and laminaria saccharina on optimization of bio-oil yield

• Co-liquefaction of Laminaria saccharina with lignin is studied. • The synergistic effect is negative in most mild and lignin-rich conditions. • The synergistic effect is positive in severe and lignin-poor conditions. • Residence time showed an impact on bio-oil quality. • Co-liquefaction synergistically enhanced the bio-oil quality at specific conditions. Hydrothermal liquefaction (HTL) is a valuable technology to convert and use wet biomass feedstocks. Lignin, waste from the paper industry and the main component of lignocellulosic biomass, is co-liquefied with laminaria saccharina, a commonly available seaweed in Norway. The aim is to conduct statistical analysis and investigate the possibility of increasing bio-oil yield while lowering the char yield through a synergistic effect. The bio-oil and char yields are measured with different operating temperatures, residence times, and blending ratios (mass ratio of laminaria saccharina to the total mass) to find out the optimized process conditions for better outputs statistically. Response surface methodology (RSM) with a Box Behnken design methodology is used to optimize the liquefaction yields of laminaria saccharina, lignin, and the different blends of the two biomasses. The results explicitly revealed that the biomass blend's optimal bio-oil and char yields are 0.2513 (w/w 0 ) and 0.1791 (w/w 0 ) respectively at 573 K, 20 min with the blending mass ratio of 0.2. The synergistic effects on the bio-oil yield are detected at comparatively severe reaction conditions. According to the RSM, residence time does not affect bio-oil and char yields as much as the operating temperature and the blending ratio. Nevertheless, temperature, residence time, and blending ratio have different impacts on the functional groups. The temperature increase has helped increase the alcohol and phenolic compounds production while the residence time consumes the C-O bonds. The increase of laminaria saccharina mass ratio in the feedstock has improved the phenolic compounds, long-chain aliphatic hydrocarbons, carboxylic acids, ketones, aldehydes, and esters in the bio-oils. Co-liqueafctio has produced bio-oil with significantly lower N content than from bio-oil produced from laminaria saccharina liquefaction.

Understanding the Pyrolysis Synergy of Biomass and Coal Blends Based on Volatile Release, Kinetics and Char Structure

Understanding the Pyrolysis Synergy of Biomass and Coal Blends Based on Volatile Release, Kinetics and Char Structure

Understanding the Pyrolysis Synergy of Biomass and Coal Blends Based on Volatile Release, Kinetics and Char Structure

Understanding the Pyrolysis Synergy of Biomass and Coal Blends Based on Volatile Release, Kinetics and Char Structure

Investigation of the pollutant emission characteristics of blends of biomass and coal gangue in a fluidized bed

The composite fuel of coal gangue and biomass is expected to increase the utilization rate of solid waste and compensate for the disadvantages of separate fuels. However, the NO and SO2 emissions from this composite fuel during the combustion process are a concern, but there are few studies on it. In this paper, corn cobs and wheat straws, typical agricultural biomass discarded in North China, and coal gangue from the mine in Xilingol, China, were selected for co-combustion in a fluidized bed. The emission characteristics of NO and SO2 were studied by changing the ratio of biomass to coal gangue and the combustion temperature. Studies had shown that: to a certain extent, mixing biomass, and coal gangue can reduce the NO and SO2 emissions, and mixing 20% of biomasses had the best effect on NO and SO2 emissions reduction. The SO2 emission reduction effect of wheat straws was better than that of corn cobs, and the NO emission reduction effect of corn cobs was better than that of wheat straws. The NO emissions of wheat straws and corn cobs added to the coal gangue were 6.45% and 7.93% less than those of coal gangue alone. The SO2 emissions of wheat straws and corn cobs added to the coal gangue were 27.45% and 25.94% less than those of coal gangue alone. Both NO and SO2 emissions decreased with the growth of the biomass rate; NO and SO2 emissions increased with the growth of the combustion temperature.

Study on the treatment of phenol-containing wastewater by doping coal char

The single blending of biomass and S-TiO2 and the mixed modification of coal char were obtained by the method of coking with coal pyrolysis furnace. The adsorption performance of biomass and S-TiO2 was investigated by the adsorption experiment of phenol solution. The results show that under the optimal conditions the best performance of MCC-2 can achieve 94% removal efficiency of phenol. The adsorption efficiency is 20% higher than that reported in the literature, and the adsorption equilibrium time is several times shorter than that reported in the literature. The modified coal char has broad prospects as a substitute for activated carbon in practical application.

Catalytic Co-Pyrolysis of Blended Biomass - Plastic Mixture Using Synthesized Metal Oxide(Mo)-Dolomite Based Catalyst

Catalytic Co-Pyrolysis of Blended Biomass - Plastic Mixture Using Synthesized Metal Oxide(Mo)-Dolomite Based Catalyst

Ash Aerosol and Deposit Formation from Combustion of Coal and Its Blend with Woody Biomass at Two Combustion Scales: Part 1─1.5 MWTH Pilot-Scale Combustor Tests

There is great interest worldwide in repurposing electric utility boilers designed to fire pulverized coal to fire, instead woody biomass or blends of woody biomass with coal. In this investigation, two prepared biomass/coal blends and the pure parent coal were fired in a 1500 kW pulverized coal combustor with a primary objective of elucidating the mineral particle behavior. The results reported here, although complete in themselves, comprise the first part of a two-part systematic study to investigate the effects of combustion scale on ash deposition rates at scales of 1500 kW (this study), and 1.2 × 106 kW (471 MWe) using identical coal and coal/biomass fuels and similar analytical techniques. The woody biomass of interest was composed of materials collected in a Utah National Forest and was prepared using a torrefaction technique (for both combustion scales) and a separate steam explosion technique (for the 1500 kW pilot scale only, described here). Biomass samples were blended in 15 wt % biomass with a Utah bituminous coal and were pulverized along with samples of pure coal at a specification of 70 wt % passing through 200 mesh. To sample entrained and deposited mineral matter, a water-cooled extractive probe for ash aerosol and an air-cooled ash deposit probe were designed, constructed, and implemented. The probes were inserted into sample ports at gas temperatures in the range of 1200–1370 K with a deposit coupon surface temperature of 811 K, conditions representative of a utility boiler vertical reheater and of a fouling deposit mechanism. Aerosol size distributions were determined using a scanning mobility particle sizer (SMPS) and an aerodynamics particle sizer (APS), and a Berner low-pressure Impactor (BLPI) collected size-segregated aerosol samples for subsequent elemental analysis. A laser diffraction particle size analyzer (Beckman Coulter LS230) was used to determine the size distributions of ash deposit samples. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS) was used to determine the morphology and composition of ash deposit samples. For the pilot-scale tests reported here, the experimental results suggested little difference in mineral matter behavior between pure coal and biomass blends. The measured aerosol PSDs showed nearly identical behaviors, with modes at approximately 20 nm and 3 μm. The size-segregated aerosol particles were slightly enriched in Na, K, and Ca and deficient in Si and Al for biomass blends compared to the pure coal. The deposition rates were 60% greater in port 7 than in port 10 at 106 vs 65 g/(m2 h). Deposit samples collected for 90 min showed essentially the same deposition rate for coal and the two biomass blends, while short deposition times (30 min) suggested higher initial deposition rates for the biomass blends. The deposit composition and morphology were nearly identical for all three fuels.

Pyrolysis of pellets prepared from pure and blended biomass feedstocks: Characterization and analysis of pellets quality

Recently, pyrolysis integrated with pelletization has received great attention. In the current study, various physical, mechanical, chemical and thermal characteristics of furfural residue pellets (FRPs), sewage sludge pellets (SSPs), furfural residue-sewage sludge pellets (FRSSPs) were studied at different pyrolysis temperature (200–850 °C) and residence time (15–45 min). The mass and energy yields of pellets dropped drastically with increasing pyrolysis temperature. Higher heating values (HHV) of pyrolysed furfural residue pellets (PYFRPs) and furfural residue-sewage sludge pellets (PYFRSSPs) increased from 22.22 to 26.76 MJ/kg, and 20.59–23.72 MJ/kg, respectively with increasing temperature from 200 to 850 °C. However, the HHV of pyrolysed sewage sludge pellets (PYSSPs) decreased with increasing temperature. The lowest pellet density and strength were found at 850 °C and residence time of 45 min. The pellets remained dimensionally stable during the water immersion test and after a storage time of 2 weeks, the relaxed densities and strength remained unchanged. The volumetric energy density of PYFRPs (30.35 kJ/m3) was found to be higher than PYSSPs (8.92 kJ/m3) and PYFRSSPs (23.85 kJ/m3) at the same process conditions. Thermal treatment enhanced the hydrophobicity of pellets. The lowest moisture uptake of 1.14 wt%, 1.8 wt%, and 1.58 wt% for the corresponding PYFRPs, PYSSPs and PYFRSSPs were observed at pyrolysis temperature of 300 °C. The maximum methylene blue and iodine adsorption values (i.e. 96 and 244.8 mg/g), (191 and 314.7 mg/g) and (121.6 and 263 mg/g) for PYFRPs, PYSSPs and PYFRSSPs were found, respectively, at temperature of ≥ 450 °C. Pyrolysis at higher temperature significantly reduced the heavy metals in PYFRSSPs and PYSSPs.

Blending of waste biomass for cost-effective chitosan-based biosorbents for removal of reactive dye from aqueous solution

Chitosan (CS) is an attractive natural and biodegradable cationic adsorbent material for treatment of anionic pollutants. For chitosan-based sorbents to be practicable, their price should be low. This study aims at cost reduction of chitosan-based sorbent through making of composite chitosan beads with industrial fermentation waste biomass of Escherichia coli. The maximum biomass content for maintaining stable composite bead structure was approximately 70.4% (w/w). The adsorption properties of the bacterial biomass-chitosan composite beads (BCCB) were evaluated using an anionic dye material, Reactive Yellow 2 (RY 2). At pH 4, the maximum uptake of BCCB was 679.13±23.76 mg/g, whereas those of pristine CS bead (CSB) and raw E. coli biomass were 934.71±50.97 mg/g and 200.77±4.51 mg/g, respectively. However, considering bound amount of RY2 to CS molecules in the CS-based beads, the BCCB showed the 2.1 times higher dye sorption capacity of CS than that of the CS in the CSB. In addition, the cost of RY2 treatment process using BCCB is expected to be shortened by 58% compared to CSB. Therefore, this study suggests that compositing CS with biomass waste can be a practical way to design cost-effective adsorbents.

A Comparison of Combustion Properties in Biomass-Coal Blends Using Characteristic and Kinetic Analyses.

This paper presents comparative research on the combustion of coal, wheat, corn straw (CS), beet residues after extracting sugar (BR), and their blends, coal–corn straw blends (CCSBs), coal–wheat blends (CWBs), and coal–beet residue blends (CBRBs), using thermogravimetric (TG) analysis under 10, 20, 30, 40 and 50 °C/min. The test results indicate that CS and wheat show better combustion properties than BR, which are recommended to be used in biomass combustion. Under the heating rate of 20 °C/min, the coal has the longest thermal reaction time when compared with 10 and 30 °C/min. Adding coal to the biomass can improve the burnout level of biomass materials (BM), reduce the burning speed, and make the reaction more thorough. The authors employed the Flynn–Wall–Ozawa (FWO) method and the Kissinger–Akahira–Sunose (KAS) method to calculate kinetics parameters. It was proven that overall, the FWO method is better than the KAS method for coal, BM, and coal–biomass blends (CBBs), as it provides higher correlations in this study. It is shown that adding coal to wheat and BR decreases the activation energy and makes conversion more stable under particular α. The authors selected a wider range of biomass raw materials, made more kinds of CBB, and conducted more studies on different heating rates. This research can provide useful insights into how to choose agricultural residuals and how to use them.

EXPERIMENTAL STUDY ON BED-TO-TUBE HEAT TRANSFER COEFFICIENTS IN BUBBLING FLUIDIZED BED

The overall bed-to-tube heat transfer coefficients of the blends of Lafia-obi coal and coconut shells have been investigated in a bubbling fluidized bed combustor. Experiments were performed at five different particle sizes of coal (5, 10, 15, 20 and 25 mm) and five different particle sizes of coconut shells (2, 6, 10,14 and 18 mm) for different blend proportions of 10%, 20%, 30%, 40% and 50%. Results obtained showed that the overall bed-to-tube heat transfer coefficient decreased with increasing coconut shell particle size in the blends. Combined effects of high radiation from large particle size of coal (25 mm) and high convection heat from small particle size of coconut shell (2 mm) at blend proportion of 10 and 50% produced the maximum bed-to-tube heat transfer coefficient. Due to the importance of heat exchange in the fluidized bed, it is observed that the contribution of biomass co-firing with coal is significant, hence, co-firing at optimal particle size and biomass blend ratio is imperative for achieving higher bed-to-tube heat transfer in the fluidized bed boiler.