Physico-chemical assessment of torrefied Eurasian pinecones

Biomass pre-treatment is gaining attention as a standalone process to improve the qualitative aspect of the lignocellulosic material. It has been gaining ground in the power station by replacing the coal with the pre-treated biomass. In this context, this paper enlightens the operating condition of carrying out the torrefaction so that the process can be made relatively more effective. The influence of physico-chemical characteristics on the heat of reaction of pyrolysis reactions, mass loss and temperature regimes are evaluated by thermogravimetry of the pre-treated samples of the pinecone; whereas, the structural transformation in the basic constituents is determined via knowing the fractional change in cellulose, hemicellulose and acid-insoluble lignin contents of the pine cone. The thermogravimetric (TGA) and differential thermal analysis (DTA) were performed to determine the physical as well as the thermal behaviour of the thermally processed biomass. The samples had undergone thermal decomposition at heating rates of 5 °C min^-1, 10 °C min^-1 and 15 °C min^-1. Nitrogen gas was used as a purge gas for the pyrolysis of the pre-treated samples. The volumetric rate of 200 ml min^-1 was pre-set for the thermal decomposition of the samples at 600 °C; whereas, the selected torrefaction temperature range varied from 210 to 250 °C.

The heat of reaction for the pre-treated samples was found to vary from 1.04 to 1.52 MJ kg^-1; whereas, it was 0.91-1.54 MJ kg^-1 for the raw samples. The total annual production cost of processing 3.6 Mg of fuel in a year at a pilot scale was $ 36.72; whereas, the fiscal burden per kilogram of fuel during thermal degradation of the processed fuel was reduced by 0.08-1.5ȼ. The entropy of the system decreased with an increasing ramp rate. The exergetic gain in the system increased by 1-2%. The loss of energy during the energy-intensive processing of the pre-treated fuel was relatively low at a heating rate of 5 °C min^-1.

By the physico-chemical assessment, it was determined that pinecones required the highest torrefaction temperature and time to provide the upgraded pinecones. It was concluded that the duration of the torrefaction should be at least 15 min for a temperature of 250 °C so that the chemical exergy of the system, energy yield and the energy density of the processed material are qualitatively improved. The volatile and ash contents were noticed to decrease during the torrefaction process. The least fractional change in the volatile content was estimated at 210 °C for a torrefaction time of 15 min; whereas, the ash content was minimum at 210 °C for a torrefaction time of 5 min.