Rice Straw Pellets Research Articles

Microwave-assisted co-pyrolysis of rice straw pellets and plastic packaging wastes for value-added products and energy recovery

The sustainable utilization of agricultural residues and waste plastics to mitigate environmental pollution, while generating renewable energy through pyrolysis has achieved significant attention through the years. In this study, microwave-assisted pyrolysis and co-pyrolysis of plastic packaging wastes (PPW) and rice straw pellets (RSP) of different mixture compositions (10 % PPW, 20 % PPW, and 30 % PPW) have been carried out to evaluate the synergistic effect of the two different feedstocks on product yields, composition, energy recovery, energy and exergy efficiency. With an intention to avoid pulverization of the feedstocks to fine particle sizes, a unique configuration resembling a chocolate is adopted to mix the biomass pellet with sheets of PPW, while using activated carbon as a susceptor. The calorific value of the co-pyrolysis oil was higher (30–35 MJ kg−1) than the pyrolysis oil obtained from RSP (22–28 MJ kg−1). The maximum oil yield from co-pyrolysis was 40 wt% for a feed-to-susceptor ratio of 2.5:1 w/w, 10 % PPW at 600 °C, and 800 W microwave power. Compared to the pyrolysis of RSP, co-pyrolysis resulted in significant deoxygenation in the oil fraction (50–60 %). The oil composition data revealed an increase in aliphatic hydrocarbons from 37 % to 42 % along with increased aromatics from 13 % to 19 % when PPW content was increased from 10 % to 30 % in the feedstock. High energy recovery (∼91 %) and feed conversion efficiency (∼99 %) were recorded for 20 % PPW at 800 W and 600 °C. The net energy balance for co-pyrolysis was positive (9–16 MJ kg−1) at different reaction conditions, which proves the energetic feasibility of the process. At 800 W and 600 °C, the total exergy efficiency was maximum (57.7 %) for 10 % PPW feedstock, and the exergy efficiencies were lower than the energy efficiency values.

Preparation of novel CS/SiO2-EDTA nanocomposite from ash of rice straw pellets for enhanced removal efficiency of heavy metal ions in aqueous medium

The production valuable materials from waste for environmental treatment have attracted considerable attention worldwide. In this study, porous silica was produced from the ash of rice straw pellets. The porous silica was then modified with chitosan (CS) and ethylenediaminetetraacetic acid (EDTA) to produce novel CS/SiO2-EDTA nanocomposites for the removal of heavy metals in aqueous medium. The adsorption of Pb2+ was investigated to evaluate the effectiveness of the composite and the effects of reaction parameters on the adsorption process were extensively explored. The adsorption is fast in the initial 5 min, then almost reaches equilibrium in 10 min. The conditions for the highest adsorption capacity are an EDTA content of 1.0 M, a pH of 6, an adsorbent dosage of 0.1 g/L, and a Pb2+ concentration of 100 ppm. The removal efficiency, adsorption capacity, and rate constant are 70.39 %, 703.9 ± 21.1 mg/g, and 0.012 ± 0.003 g/mg·min, respectively. The conditions for the highest adsorption efficiency are an EDTA content of 1.0 M, a pH of 6, an adsorbent dosage of 0.5 g/L, and a Pb2+ concentration of 40 ppm, where the adsorption efficiency, adsorption capacity, and rate constant are 89.88 %, 71.91 ± 1.86 mg/g, and 0.013 ± 0.002 g/mg·min, respectively. The selectivity of the composite was investigated by using Ni2+, Cu2+ and Fe2+ ions under the same experimental conditions. In multi-metal solutions, the adsorbent showed the highest affinity for Pb2+. In addition, the adsorption isotherms and thermodynamics were investigated and an adsorption mechanism was proposed.

DESIGN OF RICE HUSK ROTARY DRYER USING WASTE HEAT ELECTROSTATIC PRECIPITATOR OF THE CEMENT INDUSTRY

ESP or electrostatic precipitator is a device used to capture particulate matter, such as dust, in exhaust gases using electrostatic principles. In the cement industry, ESP is commonly placed after the clinker cooler to clean the exhaust air from the cooling process, ensuring it is free from clinker dust. The clinker cooler is a device that cools down the clinker using air, reducing its temperature from an initial temperature of around 1450°C to approximately 100°C - 120°C. The exhaust air from the clinker cooler is then passed through the ESP at temperatures ranging from around 237°C to 311°C. Based on the temperature data, the exhaust air from the ESP has the potential for heat reuse for other processes, including as a heat source for drying rice husk, which is a common alternative fuel used in the cement industry and typically has a moisture content of around 25%-37%. The results of this design indicate that the exhaust heat from the ESP, with an input temperature of 275°C, is capable of drying rice straw pellets from a moisture content of 25% to 14.73% using a designed rotary dryer with a capacity of 21.6 t/h, a length of 41.58 m, and a diameter of 2.92 m. It is constructed using ASTM 283 C material with a thickness of 8.76 mm and is insulated with a 15.6 mm thick layer of aluminum foil.

Techno-economic analysis of integrated torrefaction and pelleting process

ABSTRACT In this work, a techno-economic analysis of an integrated torrefaction and pelleting process is conducted. The proposed integrated process is a single-step process to produce torrefied rice straw pellets. The proposed process shall work as an alternative to the existing multi-step/multi-site process that has multiple disadvantages. Like the conventional process, the proposed process consists of cutting, drying, grinding, torrefaction, and pelleting unit. However, the proposed process doesn’t involve any external binder as the pelleting and torrefaction steps are merged. The binding is achieved by utilizing the lignin present naturally in the biomass and softens during the torrefaction step. The techno-economic assessment estimates that the briquetting process with a production capacity of 30,000 tons briquette/annum could be very profitable and shows a return on investment (ROI) of 30%, payout time of 2.4 years and break-even point of 42% at a selling price of briquette of 73 $/ton.

Combustion and mass loss behavior and characteristics of a single biomass pellet positioning at different orientations in a fixed bed reactor

This study aims to investigate the combustion characteristics and mass loss behaviors of rice straw and wheat straw biomass pellets experimentally in a laboratory fixed bed combustor under various operating conditions. High-speed photography was used to record images of the combustion process, and a sensitive balance was utilized for recording the particle mass history during the combustion process in addition to K-type thermocouples for temperature measurements. For both materials, the single pellet was exposed to various air temperatures and different flow rates of air. The orientation of the biomass pellet was positioned at various angles from 0 (horizontal), 30°, 45°, 60° (inclined), and 90° (parallel) to the hot air stream at different flow rates. Both glowing reactions and flameless ignition have been noticed in all experiments at all pellet orientations. All pellets experienced low and high luminosity volatiles without flames, followed by a bright radish color and short-lived combustion of the chars. Although the volatile contents of the two materials are identical, the volatile combustion duration of wheat straw (17–258 s) is less than that of rice straw (20–300 s), which could be due to differences in particle sizes, shapes, and structural compositions. The results also show that increased air temperatures lessen the time it takes for volatile and char to ignite and burn off. It also raises the temperature of surface ignition. Starting from the horizontal position and increasing the orientation angle of the pellet, the volatile and char ignition times increase up to 30° and then drop up to 90°, with angle 45° giving the lowest value. The same pattern was also noticed for volatile and char burnout times. The pellet horizontal position (0°) exhibits reduced combustion and mass loss (%) time intervals. The order of increasing the maximum temperature at the pellet surface was 30° > 60° > 90° angles. Increasing the air temperature reduces the times of char combustion, devolatilization, volatile burnout, and char burnout. As the air flow rate increases, the effect on the combustion parameters alternates between increasing and decreasing values.

ENERGY AND EXERGY ANALYSIS OF RICE STRAW GASIFICATION

In this study, energy and exergy analyzes were performed in the gasification of rice straw pellets prepared in 5 different blends. The heating value (LHV) of the pellets ranged from 12.45MJ/kg to 12.93MJ/kg. The calorific values of the obtained syngas samples were between 3885.5MJ/Nm3 and 4427.7MJ/Nm3. The energy efficiency of the pellet samples in gasification ranged from 53.44% to 58.01% and exergy efficiency varied from 49.19% to 53.48%. In all pellet samples used in gasification, the efficiency of exergy was lower than energy efficiency. The lowest irreversibility value in the gasification process was 36.74kW in PC5 pellet, the highest irreversibility value was 44.21kW in PRF pellet. As a result of the thermodynamic analysis of the pellet samples in gasification, it was concluded that there is no need to add any additives in the pelletization of the rice straw.

Microwave‐assisted torrefaction and pyrolysis of rice straw pellets for bioenergy

The highlights of this study involve the use of microwave heating for torrefaction and pyrolysis of pelletized rice straw for the generation of high-quality bio-char pellets, and thorough energy assessment of the process. The effects of microwave power and final temperature on the product yields and their quality were thoroughly assessed. At 600 W power, the bio-char yield followed the trend: 33.7 wt.% (800°C) < 35.5 wt.% (600°C) < 55.6 wt.% (300°C). Bio-char yield was unaffected by microwave power at the final temperature of 300°C. High yield of moisture (23.5 wt.%) with a minimal amount of bio-oil (10.5 wt.%) and gases (10.7 wt.%) were obtained at 600 W and 300°C. The major functional groups in the bio-oil were phenols (∼40%), cyclic oxygenates (∼16%), furan derivatives (∼20%) and aliphatic oxygenates (16%). Bio-char obtained from torrefaction at 600 W and 300°C possessed a calorific value of 17.2 MJ/kg with limiting oxygen index of 36.7%, and power generation potential of 4.8 kWh/kg. Overall, microwave-assisted torrefaction is shown to be a promising process intensification strategy to derive high-quality bio-char in a short time of 5–10 min with high process efficiency (51–56%) and comparable biomass conversion efficiency (∼83%) with respect to conventional pyrolysis.

Effect of in-situ torrefaction and densification on the properties of pellets from rice husk and rice straw

The research on preparing high-quality pellets by combining torrefaction and densification of biomass has received widespread attention. This paper investigated the influence of torrefaction temperature on biomass and evaluated the quality of three kinds of pellets (raw pellets, ex-situ torrefied densified pellets and in-situ torrefied densified pellets). When the torrefaction temperature was raised to 300 °C, the energy yield of rice straw (RS) and rice husk (RH) quickly decreased to 71.08% and 77.62%, and the cellulose was decomposed significantly. The results proved that 250 °C was an optimum temperature for RS and RH torrefaction. The densities of RS and RH in-situ torrefied densified pellets were 1236.84 kg/m3 and 1277.50 kg/m3 under 150 MPa, respectively. The density, Meyer hardness, hydrophobicity, and mechanical specific energy consumption of the pellet increased with the increase of molding pressure. The in-situ pellets had higher Meyer hardness, hydrophobicity, and lower mechanical specific energy consumption under the same molding pressure than raw pellets and ex-situ torrefied densified pellets. In addition, the bonding mechanism was studied by using scanning electron microscopy and ultraviolet auto-fluorescence. In-situ torrefaction and densification facilitated the formation of self-locking and the migration of lignin between particles. Compared with RH pellets, RS pellets had higher quality due to the higher hemicellulose content, which was necessary for forming stable hydrogen bonds.

Agricultural wastes co-densification: A solution for seasonal feedstock storage and anaerobic digestion performance improvement

Rice straw and pig manure pellets (RPP) and sorghum straw and pig manure pellets (SPP) were used to identify their competition as the flexible feedstock of anaerobic digestion with one-year indoor storage. The results indicated the effect of time on their characteristic was tiny during storage period, such as density, calorific value, total solid, volatile solid, ratio of carbon and nitrogen, and lignocellulosic components. Biogas yields of stored RPP and SPP were 8.8% and 26.7% lower than that of fresh pig manure (PM), and 45.4% and 56.1% higher than the sum of corresponding straw and PM digestion alone, respectively. Improvements in biodegradability were observed in co-densified biomass anaerobic digestion. Net biogas yield of RPP was 24.2% higher than that of rice straw, considering volatile matter loss and biogas yield decline during densification and storage stage. Priority of manure and supplement of co-densified biomass were proposed for feedstock supply on demand.

Influence of organic binders on the pyrolysis performance of rice straw pellets

Organic additives, which are generally used as binders, play an important role in pelletization technology. However, they influence the pyrolysis performance of pellets. In this study, pea starch (PS) and carboxymethyl cellulose (CMC) were added to rice straw pellets (RS) to investigate their influence on the pyrolysis performance. The results demonstrated that when PS was added, the yield of bio-oil and the proportion of CO were higher. When the temperature was higher than 600 °C, the pyrolysis of PS was complete, and the pyrolysis behavior of the pellets with PS was similar to that of the straw pellets without binders. CMC had no obvious effects on the pyrolysis of RS, but introducing Na (in form of Na2CO3 in the bio-char) had apparently positive synergistic effects on the gasification of bio-char. This study could serve as a reference for selecting binders and for the industrial gasification of pellets from biomass.

Effects of length-to-diameter ratio, pinewood sawdust, and sodium lignosulfonate on quality of rice straw pellets produced via a flat die pellet mill

Poor pelleting ability of rice straw (RS) discourages its production and utilization as a biofuel. Woody biomass and lignin are believed to improve the quality of herbaceous and agro-residual pellets. This study investigated the influence of length-to-diameter ratio (L/φ = 6 and 10), pine sawdust (PS) (0, 20, and 40 wt%) and sodium lignosulfonate (SL) (0, 10 and 20 wt%) on the quality of RS pellets produced via a mini-pilot scale flat-die pellet mill. L/φ positively affected quality of RS pellets and specific energy consumption (SEC) of pelleting process. PS improved significantly the energy content and reduced the ash content of the RS pellets simultaneously, however, it decreased the true, bulk densities and tensile strength of RS pellets. SL positively influenced pellet physical properties for SL up to 10%. Average unit, bulk, tapped densities and tensile strength of RS pellets were 1272–1330 kg m−3, 596–687 kg m−3, 661–760 kg m−3, and 4.4–5.6 MPa in L/φ = 6 and L/φ = 10, respectively. PS remarkably affected combustion behavior of RS pellets, however the effect of SL was not critical. The SEC of pelleting process ranged between 1.9 and 2.7 GJ t−1 in L/φ = 6 and 2.4–3.6 GJ t−1 in L/φ = 10. The corresponding energy ratios were 3.1–4.4 and 2.5–3.6, respectively. The optimal heating value and energy density were 15.79 MJ kg−1 and 9102.81 MJ m−3 in L/φ = 6, and 15.27 MJ kg−1 and 10818.08 MJ m−3 in L/φ = 10.

Experimental and numerical modelling of solid and hollow biomass pellets high-temperature rapid oxy-steam combustion: The effect of integrated CO2/H2O concentration

Oxy-steam combustion behaviour of rice straw (RS) pellets was studied at high temperatures experimentally in a new plasma combustion system and numerically using an upgraded one-dimensional unsteady-state single particle combustion model with a new homogeneous devolatilization volatile combustion and heterogeneous char oxidation sub-models under different O2/H2O/CO2/N2 gas compositions. Experimental results showed that the temperature gradient profiles for both the surface and center decreased significantly when the steam was added to the gas mixture at 20 and 40%. At 30% H2O, the heat consumption of the gasification reaction decreased which resulted in a higher particle temperature and a higher char oxidation reaction rate. Combustion characteristics for heating, ignition, devolatization, and combustion stages were obtained and confirmed through the time of recorded pictures by high-speed camera. The obtained experimental results were validated through fitting the measured values of surface and center temperature-time profiles, ignition time, final pellet diameter, and time for the maximum amount of released volatiles, under different H2O and CO2 concentrations, with those predicted from the model solution. Also, the mass of the released volatiles and pellet diameter history were predicted from the model solution. Results of the model solution proved the reality and credibility of the measured and calculated experimental findings.

Mechanical Characteristics and Energy Consumption of Solid and Hollow Biomass Pellet Production Using a Statistical Analysis of Operating Parameters

Biomass pelletization technology overcame the poor utilization and handling properties of loose materials. The quality of pellets is sensitive to the pelletization conditions. In this work the impact of the operating parameters as pressure, temperature, and moisture content on the mechanical characteristics as the compression strength ( $${\sigma }_{max}$$ ) and durability ( $$Du$$ ) and energy consumption for both production ( $${E}_{c,p}$$ ) and ejection ( $${E}_{c,ej}$$ ) of rice straw (RS) pellets was studied. Furthermore, the synergic effect of these parameters on the pellet characteristics was evaluated at the optimum conditions. The operating parameters were optimized using a multi-objective optimization approach of Response Surface Method (RSM) based on the predicted significant models that describe the physical characteristics of the pellets. The optimization results showed that high quality pellets could be produced at a pressure of 68.4 MPa, temperature of 110.0 °C, and moisture of 8.2% for solid pellets and 63.6 MPa, 110.0 °C, and 8.7% for hollow pellets. Significant individual and interaction effects of all independent parameters on the pellets characteristics were investigated using statistical analysis results, main plot curves and 2D interaction contour plots. New significant empirical dimensionless relationships that correlate the characteristics of pellets were proposed. These relationships can be generalized for any type of pellets that produced under various operating conditions. Hollow pellets are recommended to be used in the industrial sector due to their enhanced heat transfer which resulted from the high surface to volume ratio besides their ease production at normal operating condition similar to that required for solid pellets.

Co-Incineration of Rice Straw-Wood Pellets: A Sustainable Strategy for the Valorisation of Rice Waste

Agricultural activities produce an estimated amount of 32.7 MToe/year of residues in EU countries. They are mostly disposed in landfills, incinerated without any control, or abandoned in fields, causing severe impacts on human health and environment. Rice is one of the most consumed crops worldwide with an annual production of 782 million tons according to the Food and Agriculture Organization of the United Nations database. In this context, the EU-funded project LIFE LIBERNITRATE promotes the use of renewable residual sources (i.e., rice straw) to obtain new materials with an added value. The methodology is based on the incineration of rice straw in an own-designed and constructed valorization system. Rice straw/wood pellets are burned in optimized conditions to produce a maximized quantity of ashes with high silica content. These materials will be then used to treat water polluted with nitrates, representing an optimal example of circular economy strategy. In this work, the own-designed valorization unit is described, with special focus on its main constituting elements. The theoretical study of the co-incineration of rice straw and wood pellets identified the optimised combustion conditions. Experimental tests using the theoretical inputs confirmed the most adequate operational conditions (10 g rice straw pellets/min + 10 g wood pellets/min, 6–7 Nm3/h of air, T = 500 °C) and helped in the definition of improvements on the experimental plant.

Investigation of Steam Treatment on the Sorption Behavior of Rice Straw Pellets

Agricultural residue is a readily available biomass source for making biofuels. However, complex structure along with low calorific value makes it reluctant to be utilized. This necessitates the pretreatment of biomass to improve its accessibility. In this study, rice straws were treated with saturated steam at 180–200 °C for 5–10 min and pelletized. Results indicated that the pretreatment process could effectively improve the calorific values and enhance the hydrophobicity of the rice straws. The steam explosion process changed the content of chemical components in the biomass materials. With the increase of reaction temperature and retention time, the content of cellulose, hemicelluloses and lignin declined. Comparedwith the raw materials, there was an increase in the calorific value from 16.24 MJ/kg to 17.26 MJ/kg for the steam treated straws. For moisture sorption test under the condition of 30 °C and 90% relative humidity, the equilibrium moisture content dropped from 21% for untreated straw pellets to 14.2% for the steam treated straw pellets treated at 200 °C for 10 min. Moisture adsorption rate reduced along with the increase in steam temperature and retention time. This study demonstrated that steam explosion performed an effective way to improve the characteristics of agricultural residues.

Improvement of Biomass Fuel Properties for Rice Straw Pellets Using Torrefaction and Mixing with Wood Chips

Utilization of rice pellets as biomass fuel has many challenges compared with wood pellets, including low heating value, low bulk density, and high ash content, that cause high logistic costs and clinker formation. To solve these problems, this study focused on upgrading the quality of rice straw pellets to improve logistic efficiency by torrefaction and mixing with wood chips. Torrefaction and mixing with wood chips was effective to improve the energy density, the mechanical durability and the contents of fixed carbon, nitrogen, sulfur and ash, leading to the improvement of both logistic efficiency and combustion behavior. The burning test showed that increases in the fixed carbon content and the mechanical durability contributed to stable increases in the temperature inside the furnace during starting up and reduced the amount of ash in the exhaust gas during stable combustion.

Production, Characterization, and Evaluation of Pellets from Rice Harvest Residues

Pellets from residues from rice harvest (i.e., straw and husk) were produced and their main properties were evaluated. Firstly, rice straw pellets were produced at lab scale at varying operational conditions (i.e., load compression and wt % of feeding moisture content) to evaluate their suitability for palletization. Successively, rice straw and husk pellets were commercially produced. All the samples were characterized in terms of their main physical, chemical, and physico-chemical properties. In addition, axial/diametral compression and durability tests were performed to assess their mechanical performance. All the analyzed properties were compared with the established quality standards for non-woody pellets. In general, rice straw pellets presented suitable properties for their use as pelletized fuels. Rice husk pellets fell out of the standards in recommended size or durability and thus preliminary treatments might be required prior their use as fuels.

Effect of herbal supplementation on growth, immunity, rumen histology, serum antioxidants and meat quality of sheep

There is a wide range of feed additives deliberately designed to be used in sheep diets that can improve production performance. Whereas herbal supplementation is gaining popularity not only for improving sheep productivity and mutton quality but also for safe application without any harmful residual effects. The present study was designed to investigate the effect of plantain (Plantago lanceolata L.) and/or garlic leaf (Allium sativum) dietary supplementation on growth performance, immunity, rumen histology, serum antioxidants and meat quality of sheep. The experiment consisted of a completely randomized design with 32 one-year-old sheep (initial mean live weight 9 ± 0.2 kg) allocated to four groups (8 sheep per group). Rice straw and concentrates-based total mixed ration pellets (2390 kcal/kg DM, CP = 15.1%) were offered as a control diet (CL diet). Herbal treatment diets included (i) CL diet + 10 g DM of plantain herb (PL diet), (ii) CL diet + 10 g DM of garlic leaf (GL diet) and (iii) CL diet + 5 g DM of PL and 5 g DM of GL (PG diet). Compared with the CL diet group, the live weight gain and feed conversion ratio were 18% to 26% and 13% to 20% higher in herbal-supplemented groups, respectively. Moreover, the herbal-supplemented groups, especially the PL diet group had higher serum immunoglobulin concentration, antioxidant capacity and rumen papillae size compared to the control. Besides, the lowest caul fat and pelvic fat levels were observed in the PL diet group followed by PG, GL and CL diet groups. In addition, lower mutton ether extract and saturated fatty acid along with higher polyunsaturated fatty acid levels were found in all herbal-supplemented groups. In conclusion, dietary supplementation with PL and/or GL might be used as an alternative in sheep to promote growth, health status and lean mutton production.

Effect of amendment of biochar supplemented with Si on Cd mobility and rice uptake over three rice growing seasons in an acidic Cd-tainted paddy from central South China

To examine the effect of rice straw biochar and the synergism with silicon on Cd immobilization, a Cd-contaminated acidic sandy loam paddy, polluted from emissions from industrial activity, was chosen in central South China. A field trial was conducted over three rice growing seasons during 2016–2017. Rice straw biochar (BR), produced by the pyrolysis of rice straw pellets at 450 °C, was amended at 10 t/ha (BR1), 20 t/ha (BR2), and supplemented with 0.75 t/ha sodium silicate (SS) at 10 t/ha, (BR1 + SS) and 20 t/ha (BR2 + SS), compared to the control without biochar and sodium silicate (BR0). BR supplemented with Si enhanced Cd soil immobilization and decreased Cd accumulation in rice plant within three rice seasons. Compared to BR0, BR + SS reduced Cd concentrations in grains by 19.5–73.7%, higher than that of 8.6–50.2% following BR. Cd bio-concentration factor of the root was reduced by an average of 54.6% from BR + SS and by 19.0% from BR, compared to BR0 in last two rice seasons. BR + SS significantly increased soil pH and available Si, and soil CaCl2-Cd was negatively related to soil available Si (p < 0.05). The synergistic effect of BR and Si induced liming effect and co-precipitation of Cd with Si compounds during the aging process of biochar. Thus, we suggest that an alkaline silicon supplementation is used as an amendment to BR, which could be used as a strategic approach for tackling Cd contamination in South China rice paddies.

Experimental Study of Ignition and Combustion Characteristics of Mixed Rice Straw and Sewage Sludge Solid and Hollow Spherical Pellets in a Plasma Combustion System

In this work, the ignition and combustion characteristics of mixed rice straw and sewage sludge pellets in air atmosphere were investigated using a plasma combustion system. One common pellet shape (solid spherical pellet) and another new shape (hollow spherical) are used in this study. High-speed camera was used to record and observe ignition and combustion process of pellets. In case of hollow pellets, the shape and distribution of flame are found to be better compared to solid pellets. Also, it is clear that the values of volatile combustion times in case of hollow pellets are low compared to solid pellets. The overall heat transfer enhanced in case of hollow pellet due to the large area subjected to hot gases and the high surface to volume ratio. Hollow pellet consumed less time for internal ignition and volatiles char combustion compared to solid pellet. Volatiles and char combustion lasted for 63.05 and 61 s, respectively for hollow pellet while these values were found to be 72.8 and 83 s, respectively for solid pellet.