Experimental and theoretical investigation of wood pellet shrinkage during pyrolysis

Paulauskas, Rolandas; Džiugys, Algis; Striūgas, Nerijus; Garšvinskaitė, Lina; Misiulis, Edgaras

doi:10.6001/energetika.v60i1.2867

Cited by 8 publications

(4 citation statements)

References 10 publications

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“…While the pyrolysis operating at low temperatures produces a large amount of bio-charcoal production with low caloric value and ash content of the bio-charcoal. The results of this simulation are comparable to the results of previous studies, the higher pyrolysis operating temperature causes the evaporation process to be higher, causing the bio-charcoal to lose mass (Paulauskas et al, 2014). The simulation results show agreement with previous studies.…”

Section: Resultssupporting

confidence: 88%

Coconut Waste Pyrolysis Simulation Using Aspen Plus Software

Hasan,

Widayat,

Suedi

2023

tjp

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Currently, in the world are trying to substitute fossil energy for renewable energy. One of the renewable energy is biomass energy. Biomass is a renewable natural resource derived from biological nature. Biomass from palm shells has been successfully used by the Tembilahan PLTU as an effort to substitute coal. The results of technical evaluation and monitoring show operating parameters within normal limits. Palm shells are known to have a lower sulfur content than coal so that the emissions produced are less than coal. When viewed from the characteristics based on the analysis of proximate, ultimate and calorific value, it shows that the characteristics of biomass from coconut waste, especially coconut shells, are not significantly different from biomass from palm shells. This means that coconut shells can be considered as a renewable energy source. To improve the quality of the calorific value of biomass, a pyrolysis process is carried out to produce bio-charcoal. Modeling using Aspen Plus software has a difference average of less than 6%. Simulation results of coconut shell pyrolysis with maximum yield of bio-charcoal occurring at an operating temperature of 600°C which produces a total of 30.35% bio-charcoal, a calorific value (LHV) of 33.03 MJ/kg, and an ash content of 18.99%. While the simulation results of coconut shell pyrolysis with maximum syngas yield occurred at an operating temperature of 800°C which produced 82.43% syngas, high H2 49.67% and low CO2 2.90%.

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Section: Resultssupporting

confidence: 88%

Coconut Waste Pyrolysis Simulation Using Aspen Plus Software

Hasan,

Widayat,

Suedi

2023

tjp

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“…The initial dimensions of the char were accepted as equal to those of the pellet. This position correlates with the results described in [22] devoted to thermal shrinkage of pellets at pyrolysis in the inert atmosphere, indicating its insignificance at 600-700°C during 30-50 s. The char of a cylindrical pellet (with the diameter d = 2R 0 and the length l = 2δ 0 ) was regarded as a result of the infinite cylinder, with the initial radius R 0 , intersection with the endless plate, with half-thickness δ 0 , see Fig. 1.…”

Section: Methodssupporting

confidence: 92%

Carbon burnout from the char of a single cylindrical pellet

Zhovmir¹

2023

energetika

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In countries with limited wood fuel resources, the use of straw for energy should be increased to comply with environmental commitments. Boiler houses burning whole straw bales have limited application because of unfavourable straw logistics and obstacles to their construction in most densely built-up settlements. Straw pellets are more convenient for transportation and safer for storage. Boilers with pellet burning can be operated in fully automatic mode. However, burning straw pellets instead of wood pellets is complicated with increased ash content and lower ash melting temperature. Approaches for low-temperature burning of straw pellets at temperatures below the initial deformation temperature of their ash are of practical interest. At low temperatures, burning is slowing and incomplete burnout with energy loss is possible. The rate of burnout also depends on the form and dimensions of the particle. It was common to accept the rate of carbon burnout as uniform on the reacting surface of the particle. This work aimed to study the low-temperature carbon burnout from the char of the cylindrical pellets of various lengths and to estimate the energy loss with unburned carbon. The aim was achieved by the mathematical description of pellet char burning, in which the actual cylindrical char was regarded as the infinite cylinder intersecting with the endless plate. The burnout of fixed carbon was accepted as layered, the carbon burning fronts as infinitely thin, and different rates of carbon burning in radial and axial directions were accepted. An experimental study of the low-temperature burning of fixed carbon from the char of wood and straw pellets was conducted at free air access at 700°C in the furnace, i.e., the temperature around a single pellet was certainly lower than the possible initial deformation temperature of the pellet ash. The duration of carbon burnout from the char of single cylindrical pellets depending on their lengths was studied. The research findings are as follows. Equations in a dimensionless form, describing changes in the remaining share of unburned fixed carbon in pellet char in time, were deduced analytically. At the experimental burning of single straw pellets, loose particles of ash with no signs of melting formed, but they contained unburned carbon. The share of unburned fixed carbon in ash was 0.016–0.020. The coefficient of determination of calculated and experimental duration of complete burnout of fixed carbon from wood pellet char was R2 = 0.96, and R2 = 0.87–0.91 at incomplete burnout from straw pellet char. The most significant scientific result is that for long pellets, the fixed carbon burnout is controlled mainly by its slower burnout rate in the radial direction, and for the shortest pellets by more intensive burnout rate in the axial direction. The practical value of the results obtained is that the use of shorter pellets, which are characterised by faster burnout, may become purposeful for intensive combustion. Conversely, for slow combustion, and especially with the aim of arranging low-temperature burning of straw pellets, it may be feasible to use longer pellets with extended burnout. In the given conditions of straw pellet burning, the unburned carbon presents in ash, but losses of the pellet energy with unburned carbon were estimated at 0.61–0.72%, which is acceptable for boiler burners.

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“…The reduction in particle diameter was then calculated be 28%, 24% and 21%. These values are in line with several studies focused on particle shrinkage of pelletized biomass during pyrolysis, with a temperature range of 300-800°C [24,25].…”

Section: Bed Compactionsupporting

confidence: 91%

Oxidative pyrolysis of pine wood, wheat straw and miscanthus pellets in a fixed bed

Pham

Piriou

Salvador

et al. 2018

Fuel Processing Technology

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Oxidative pyrolysis is a key step in the autothermal operation of many fixed-bed reactors for staged gasification and advanced carbonisation. In these reactors, biomass is converted into charcoal, condensates and permanent gases inside a moving Oxidation Zone (OZ) which also produces energy to self-sustain the process. Oxidative pyrolysis of three different biomass types: pine wood, miscanthus and wheat straw pellets, was performed in a batch 20 cm diameter fixed bed reactor. Results showed that the OZ consumed 11% to 14% of the stoichiometric air to self-sustain the process and reached a peak temperature around 720°C whatever the biomass. The propagation velocity and thickness of the OZ were inversely proportional to the ash content and to the bulk density of the biomass. Ash was also shown to influence the yield and composition of the resulting products due to a catalytic effect on primary and secondary pyrolysis reactions.

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Experimental and theoretical investigation of wood pellet shrinkage during pyrolysis

Cited by 8 publications

References 10 publications

Coconut Waste Pyrolysis Simulation Using Aspen Plus Software

Coconut Waste Pyrolysis Simulation Using Aspen Plus Software

Carbon burnout from the char of a single cylindrical pellet

Oxidative pyrolysis of pine wood, wheat straw and miscanthus pellets in a fixed bed

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