## 3 Results and Discussion
From this perspective, based on the behavior of the main compounds that make up the biomass of vegetable origin as the temperature rises, as shown in Figure 21, the definition of torrefaction should be assumed to be a thermo-chemical conversion technology for biomass, which occurs in a temperature range between 220 and 320 \({}^{\circ}\)C, under conditions of atmospheric pressure and in the absence of oxygen, where hemicellulose disintegrates, keeping lignin and cellulose in structural states very close to the original. In other words, with this definition, the torrefaction process takes place within the temperature range where only, or at least mostly, the disintegration of hemicellulose occurs, without affecting, or affecting very little, the other main biomass compounds, lignin and cellulose. Based on the above and as presented in the previous sections, it can be said that the correct definition of the torrefaction parameters is the main factor that leads to obtaining products with different qualities. An example is given Figure 22, where it is possible to observe on the left side of the figure, pellets produced before the measures related to the extraction of torrefaction gases and post-pelletizing cooling have been corrected, and the temperature and residence time intervals to be used as the basis for the operational procedure defined for the process, and, on the right side of the figure, other pellets produced after implementing these measures during the third testing phase. Obviously, it is still essential to correct any problems related to the operation of the equipment, which are almost always caused by the lack of knowledge and mastery of the torrefaction process, because only after these corrections is it possible to fine-tune the process for a certain type of raw material, with its own specificities and characteristics, referring to the chemical and structural composition of the biomass in question in each case. Figure 21: Exemplary model of the behavior of the main components of biomass of vegetal origin with the increase of the temperature. Blue square figure represents the temperature range where torrefaction occurs, when considered the definition of torrefaction as being a thermochemical conversion process occurring in a temperature range between 220 and 320 \({}^{\circ}\)C, under atmospheric pressure conditions and in the absence of oxygen, where the molecular disintegration of the hemicellulose occurs, maintaining lignin and cellulose in its original state and structures. This definition was developed during the development to refine the torrefaction process in the pilot unit under analysis. Throughout the different phases of testing and fine-tuning the process, data were collected on the product characterization, which are summarized in Table 1. In Table 2 are presented the results obtained from the analysis of the raw materials used to serve as a point of comparison. Another outcome resulting from the performance of these tests was to be able to create an operational procedure that would lead to production in a continuous and repeatable form of pellets of torrefied biomass with good quality, as defined in ISO/TS 17225-8: 2016 (Solid biofuels--Fuel specifications and classes--Part 8: Graded thermally treated and densified biomass fuels). This being the only standard that addresses the technical characteristics of thermally treated biomass for energy applications, it is very important that the material produced meets the parameters established in this regulatory document since, most likely, when the market for torrefied products for energy purposes develops, producers will be asked to prove that they meet these requirements. There are still few data available on the quality of industrially produced torrefied biomass pellets, as there are still very few successful cases on an industrial scale [29; 31; 34; 47; 48].