Microwave wet torrefaction: A catalytic process to convert waste palm shell into porous biochar

Yek, Peter Nai Yuh; Osman, Mohd Shahril; Wong, Chee Chung; Kong, Shuying; Sie, Teck Sung; Foong, Shin Ying; Lam, Su Shiung; Liew, Rock Keey

doi:10.1016/j.mset.2020.08.004

Cited by 12 publications

(11 citation statements)

References 36 publications

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“…Therefore, the search for innovative heating methods that are able to decrease the energy consumption for processing and improve the yield and quality of the product is an urgent task. One of these approaches-the use of microwave (MW) irradiation at the frequency of 2.45 GHz-is an alternative source of energy instead of conventional heating at thermal conversion of lignocellulosic biomass [14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Characteristics of the Main- and Side-Stream Products of Microwave Assisted Torrefaction of Lignocellulosic Biomass of Different Origination

et al. 2022

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In this paper, the yields and composition of solid and condensable products that were obtained by microwave-assisted torrefaction of softwood, wheat straw, and peat fuel pellets, defined as main- and side-stream torrefaction products, were studied. The torrefaction process, at temperatures varied in the range of 200–300 °C, was performed using a laboratory-scale torrefactor of original construction. Water-enriched fractions were distilled off from condensable products to isolate tar fractions, the fuel characteristics of which were compared with those of solid fractions. Py-GC/MS/FID, GC/MS/FID, thermal analysis, elemental analysis, and wet chemistry methods were used to characterize the main- and side-stream torrefaction products, with a focus on their valorization according to the biorefinery approach. The simultaneous development of the destruction and condensation processes in lignocarbohydrate complexes during microwave treatment leads to an increase in the relative portion of aromatic compounds in torrefied biomass, increasing the higher heating value (HHV) of the solid fractions. The increase up to 60% of the heat amount that was liberated due to the thermal oxidative conversion of solid fractions vs. that of the non-treated ones was established by DSC tests. The heat that was liberated by the combustion of the tar fractions was much lower than that of solid fractions, which was explained by the composition of tars, influencing their thermal conversion.

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Section: Introductionmentioning

confidence: 99%

Characteristics of the Main- and Side-Stream Products of Microwave Assisted Torrefaction of Lignocellulosic Biomass of Different Origination

et al. 2022

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“…The wheat and barley straw in a microwave heating system was carbonised owing to microwave irradiance, which merely increased the energy density by 14-15 % [7]. The various studies on the similar technique were conducted, but the effect of temperature was not clearly stated nor was its effect on physical traits of biomass explained [8]- [13]. From literature review, it was clear that the microwave heating system requires surplus power to produce a desirous effect.…”

Section: Introductionmentioning

confidence: 99%

Thermal Modelling of the Torrefaction Process Using the Finite Element Method

Dhaundiyal

Tóth

2021

Environmental and Climate Technologies

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This paper focuses on the thermal characteristic of the torrefied pinecone pellets. The resistivity heating system was used for torrefaction purposes. The torrefaction was conducted at 523 K for different holding times of 5, 10 and 15 minutes. The thermal behaviour of the pinecone pellet was numerically predicted using the pdepe algorithm. A parabolic 2-D heat transfer equation was used to estimate the thermal profile across the pinecone. The effect of the interactive atmosphere was on the numerical solution was also examined. The pelletisation was performed using a ring-die at the temperature of 70 °C.

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“…The physical properties of biochar were remarkably changed. The surface area of the finished material was increased by 117.97%, whereas the mass yield was reduced by 15% [10]. Torrefaction of wheat and barley straw in a microwave heating system was carbonised due to the action of microwave irradiance, which resulted in a 14-15% increase in energy density and a 29.1% increase in carbon fraction.…”

Section: Introductionmentioning

confidence: 99%

“…Notwithstanding the evidence, the overall mass loss of 64% to 66.3% proved that the effect of the microwave at a higher level did not have a significant influence on the physical characteristics of the material. It had diminished the qualitative aspects of torrefaction [10]. Similarly, dewatering of sewage sludge was performed using microwave irradiance.…”

Section: Introductionmentioning

confidence: 99%

“…Various other studies based on similar principles have shown that microwave-based technology is suitable for moisture removal [9,10,15], but the optimisation of irradiance, time and temperature was not clearly stated and its influence on the physical characteristics was not explained. Moreover, the cost of consumption and production was found to be high if an additional binding agent is used, and the interaction of the thermal history of the microwave furnace with the biomass is not considered in the study.…”

Section: Introductionmentioning

confidence: 99%

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Modelling of a Torrefaction Process Using Thermal Model Object

Dhaundiyal

Tóth

2021

Energies

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So far, the torrefaction process has been merely discussed based on the physical and chemical characteristics of the final product, but the mechanism has not been yet pondered and investigated. Thus far, microwave torrefaction has been predominately used for thermal pre-treatment; therefore, a paradigm shift in the methodology has been introduced by using a Joule heating system. The article mainly focuses on the thermal engineering aspect of the torrefaction process. The densified black pine underwent thermal pre-treatment at a temperature of 523 K. The furnace used for torrefaction was initially improvised to carry out thermal degradation at quasi-static/dynamic conditions. A 3D PDE thermal model was developed to determine the numerical solution and temperature distribution across a black pine pellet. To compare the effect of the linear ramping profile, time-dependent as well as fixed Dirichlet conditions were applied to the proposed model. The mass distribution, duration of the torrefaction process, the effect of Nusselt and Reynold’s number of inert gas, and thermal history are some of the factors whose influence on the numerical solution was investigated. The simulation of thermal pre-treatment and its effect on the heat transfer characteristic was examined with help of a PDE thermal model, whereas the numerical solution of diffusion of the product of reactions was determined by solving the partial differential equations with the help of the discretisation method (PDEPE). The densification of black pine was performed in a ring die, whereas initial milling of biomass was carried out using a 1.5 mm sieve size. The system was found to have a homogeneous distribution in energy and temperature with time, whereas the amplitude of heat flux along the radial direction was reduced by 15% if the same pellet underwent torrefaction for a duration of 5 min in dynamic mode. Similarly, a 64.46% drop in amplitude of heat flux along the azimuth plane could be seen while performing torrefaction in a time-dependent thermal history. However, the relative amplitude of the heat flux at the centre of the pellet was estimated to be lowered by 98.41% along the vertical axis for heating a pellet in a quasi-static condition. The net change in the mass fraction of carbon dioxide across the boundary film was seen to be 40% higher than that of carbon monoxide. The rate of change of mass fraction of carbon monoxide across the boundary film was increased by 7–11% with the increase in torrefaction time. A 6.8% rise in the evaporation of water was noticed during the first half interval of torrefaction (from 5 min to 10 min). In the second half, from 10 min to 15 min, it was merely increased by 5.8%. A relative drop of 17.24% in water evaporation was estimated in the dynamic state of the system.

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Microwave wet torrefaction: A catalytic process to convert waste palm shell into porous biochar

Cited by 12 publications

References 36 publications

Characteristics of the Main- and Side-Stream Products of Microwave Assisted Torrefaction of Lignocellulosic Biomass of Different Origination

Characteristics of the Main- and Side-Stream Products of Microwave Assisted Torrefaction of Lignocellulosic Biomass of Different Origination

Thermal Modelling of the Torrefaction Process Using the Finite Element Method

Modelling of a Torrefaction Process Using Thermal Model Object

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