Characterization and pre-treatment of Jatropha curcas seed cake for co-firing with coal

In the light of growing concern over greenhouse gas emissions and limited fossil fuels, the use of renewable energy sources such as biomass is becoming more vital. Jatropha curcas seed cake, which is a waste product of biodiesel production, has been identified as a potential candidate to be co-fired with coal in existing boilers. There is a dearth of information on the effective utilisation of Jatropha curcas seed cake in this manner, and this research work contributes to bridging this knowledge gap. The seed cake received was divided into two distinct classes based on appearance and texture, identified as type A (harder and lower oil content) and type B (the more abundant class). As an initial step, the fundamental fuel properties of the seed cake were determined; these include the proximate and ultimate analyses, higher heating value (HHV) and inorganic content. The HHV of type A and type B was 20.76 MJ/kg and 24.06 MJ/kg, respectively; their dry ash content was 5.9% and 4.4%, respectively. K was the most abundant inorganic element present. The main hindrances to co-firing of a typical biomass with coal arise due to the difference in properties of biomass and coal. Torrefaction and leaching were carried out with the aim of bringing the thermochemical (primarily the HHV) and chemical (inorganic content) properties, respectively, of the seed cake closer to those of coal. An envelope of torrefaction conditions was recommended –~250°C for 45-60 min for the type A, and 280°C to >45 min at 220°C-250°C for the type B. These conditions ensured that the HHV of the type A and type B were enhanced to >24.5 MJ/kg and >27 MJ/kg, respectively, while not compromising excessively on the energy yield. Leaching at 20°C for <24 h was considered adequate in the case of the untorrefied seed cake, and this result ed in a reduction of the potassium content (the most abundant and critical inorganic element in the seed cake) by 85%. Leachability of the torrefied biomass was markedly reduced, and leaching at least at 50°C was deemed necessary. Combustion modelling using Ansys Fluent 14.0 was carried out to assess the combustion and co-firing characteristics of untorrefied and torrefied Jatropha curcas seed cake. The effect of torrefaction on the devolatilisation characteristics, flame properties and consequently NOx pollutant formation was established. Compared to the torrefied biomass, the untorrefied seed cake devolatilised earlier, had a more dispersed flame and higher NO formation. The higher reactivity of the biomass was shown to have a positive effect on the devolatilisation rate of the less reactive coal under co-firing simulations

An investigation into the use of CFD to model the co-firing of Jatropha curcas seed cake with coal

Jatropha curcas seed cake is a potential candidate for co-firing with coal. Combustion modelling using Ansys Fluent 14.0 was carried out to assess the combustion and co-firing characteristics of untorrefied and torrefied Jatropha curcas seed cake. The effect of torrefaction on the devolatilisation characteristics, flame properties and consequently NOx pollutant formation was established. Compared to the torrefied biomass, the untorrefied seed cake devolatilised earlier, had a more dispersed flame and higher NO formation. The higher reactivity of the biomass was shown to have a positive effect on the devolatilisation rate of the less reactive coal under co-firing simulations

Thermochemical and structural changes in Jatropha curcas seed cake during torrefaction for its use as coal co-firing feedstock

Jatropha curcas seed cake is a viable feedstock for co-firing with coal as it has the advantages of being renewable, carbon-neutral and sourced from a versatile plant. Torrefaction, a mild pyrolysis treatment by heating in a N2 atmosphere, was investigated as a technique to improve the thermochemical properties of the biomass, primarily the HHV (higher heating value). The temperature and holding time were varied in the ranges of 200–300 °C and 0–60 min, respectively, to form a 5-level full-factorial experimental matrix. An optimum envelope of torrefaction parameters was identified in the range of 280 °C to >45 min at 220–250 °C under a heating rate of 10 °C/min. This results in an enhancement of the HHV from 24 MJ/kg to more than 27 MJ/kg, which is within the range of coal, while maintaining an energy yield higher than 90%. The relationships between the HHV and the proximate fixed carbon content as well as the elemental CHO content were also investigated. Through 13C NMR (nuclear magnetic resonance) spectroscopy, hemicellulose was determined as the most volatile component, undergoing decomposition before 250 °C while cellulose only degraded fully in the 250–300 °C range and lignin decomposition spanned from 200 °C to beyond 300 °C

Characterization and pre-treatment of Jatropha curcas seed cake for co-firing with coal

In the light of growing concern over greenhouse gas emissions and limited fossil fuels, the use of renewable energy sources such as biomass is becoming more vital. Jatropha curcas seed cake, which is a waste product of biodiesel production, has been identified as a potential candidate to be co-fired with coal in existing boilers. There is a dearth of information on the effective utilisation of Jatropha curcas seed cake in this manner, and this research work contributes to bridging this knowledge gap. The seed cake received was divided into two distinct classes based on appearance and texture, identified as type A (harder and lower oil content) and type B (the more abundant class). As an initial step, the fundamental fuel properties of the seed cake were determined; these include the proximate and ultimate analyses, higher heating value (HHV) and inorganic content. The HHV of type A and type B was 20.76 MJ/kg and 24.06 MJ/kg, respectively; their dry ash content was 5.9% and 4.4%, respectively. K was the most abundant inorganic element present. The main hindrances to co-firing of a typical biomass with coal arise due to the difference in properties of biomass and coal. Torrefaction and leaching were carried out with the aim of bringing the thermochemical (primarily the HHV) and chemical (inorganic content) properties, respectively, of the seed cake closer to those of coal. An envelope of torrefaction conditions was recommended –~250°C for 45-60 min for the type A, and 280°C to >45 min at 220°C-250°C for the type B. These conditions ensured that the HHV of the type A and type B were enhanced to >24.5 MJ/kg and >27 MJ/kg, respectively, while not compromising excessively on the energy yield. Leaching at 20°C for <24 h was considered adequate in the case of the untorrefied seed cake, and this result ed in a reduction of the potassium content (the most abundant and critical inorganic element in the seed cake) by 85%. Leachability of the torrefied biomass was markedly reduced, and leaching at least at 50°C was deemed necessary. Combustion modelling using Ansys Fluent 14.0 was carried out to assess the combustion and co-firing characteristics of untorrefied and torrefied Jatropha curcas seed cake. The effect of torrefaction on the devolatilisation characteristics, flame properties and consequently NOx pollutant formation was established. Compared to the torrefied biomass, the untorrefied seed cake devolatilised earlier, had a more dispersed flame and higher NO formation. The higher reactivity of the biomass was shown to have a positive effect on the devolatilisation rate of the less reactive coal under co-firing simulations

Leaching as a pretreatment process to complement torrefaction in improving co-firing characteristics of Jatropha curcas seed cake

The presence of certain inorganic elements in biomass causes issues such as slagging, fouling and corrosion when co-firing with coal for power generation. In this work, the efficacy of leaching to remove these elements from Jatropha curcas seed cake was investigated. Leaching of both untorrefied and torrefied seed cakes was carried out in Milli-Q water at temperatures of 20, 35 and 50 °C. At 20 °C, the two critical elements, potassium and chlorine, decreased by as much as 85 and 97 %, respectively. Leaching at higher temperatures was only beneficial for the more intensely torrefied biomass, since they were more resistant to leaching. The electrical conductivity and ion content of the leachates were measured, as were the inorganic elemental content, dry ash content, volatile matter content and higher heating value (HHV) of the solid seed cake. A secondary benefit of the leaching was an increase in the HHV by up to 10 %