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

Madanayake, Buddhike Neminda (2017) Characterization and pre-treatment of Jatropha curcas seed cake for co-firing with coal. PhD thesis, University of Nottingham.

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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 <5 min at >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.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Gan, Suyin
Eastwick, Carol
Ng, Hoon Kiat
Keywords: Jatropha curcas seed, greenhouse gas, energy sources, biomass
Subjects: T Technology > TP Chemical technology
Faculties/Schools: University of Nottingham, Malaysia > Faculty of Science and Engineering — Engineering > Department of Chemical and Environmental Engineering
Item ID: 37438
Date Deposited: 26 Oct 2017 09:49
Last Modified: 07 May 2020 14:16

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