# Influences of the Pretreatments of Residual Biomass on
## 1 Introduction
[18] reported that biomass torrefaction improves its physical properties, such as: grindability; particle size and distribution; pelletability; proximate and ultimate composition (moisture, carbon, and hydrogen content); calorific value; storability, thanks to increased resistance towards biological degradation. [PERSON] et al. [19] investigated physicochemical characteristics of fast-growing poplar, torrefied at 200, 225, 250, 275, and 300 \({}^{\circ}\)C; they found that: (i) torrefaction reduced biomass hemicellulose content because of dehydration, deacetylation, and cleavage of ether linkages; (ii) H/C decreases while O/C and heating value increase as the torrefaction temperature is increased. [PERSON] et al. [20] focused on the correlation between wheat straw torrefaction (in the range 150-300 \({}^{\circ}\)C) and pelletizing properties, concluding that the pelletizing process results in mechanically strong pellets (with higher heating value and reduced moisture adsorption) for torrefaction temperature lower than or equal to 250 \({}^{\circ}\)C. [PERSON] et al. [15], thanks to the research carried out at CENER (Centro Nacional de Energias Renovables), found that torrefaction was effective in the removal of Cl from wheat straw, therefore suggesting this pretreatment as a de-chlorinating operation, which prevents the formation of pollutants derived from Cl and the accelerated corrosion issues in facilities for thermochemical processes, such as CLG. The washing pretreatment may be used to remove alkali and alkaline earth metals (AAEM) [15; 21]. [PERSON] et al. [21] studied the AAEM content and the pyrolytic behavior of rice straw, washed with water, aqueous HCl solution or aqueous phase bio-oil; they found that K, Ca, Mg, and Na were removed thanks to washing by each of the three liquids, with removal efficiencies always between 90-100% as to the HCl solution and aqueous phase bio-oil, while quite lower with water (~80% for K, ~10% for Ca, ~25% for Mg, and ~75% for Na); with regard to the pyrolytic behavior of washed rice straw, they found that the pretreatment with water had little effect on developed non-condensable gases. This work thoroughly investigates the influence of some pretreatments on the thermochemical decomposition of wheat straw and the produced syngas. In this regard, experiments were carried out involving devolatilizations in a fluidized bed made up of sand. Devolatilization is a key step of a generic gasification process, and strongly influences the amount and composition of the produced gas [22], so devolatilization results may detect possible primary effects of pretreatments on the thermochemical behavior of wheat straw. The fluidized bed made up of inert sand was chosen in so that: (i) biomasses could be studied in a reactor configuration similar to that of CLG developed in the CLARA project; (ii) possible redox effects from solids (such as OC) could be excluded and only those influences strictly due to biomass pretreatments could emerge. Devolatilization tests were performed on pellets of differently pretreated biomasses, firstly elaborating data by methods described elsewhere [10; 23]. In addition, a further analysis of the same data was introduced, based on information taken from the instantaneous peaks of gas release during devolatilizations, treated by simple regressions with straight lines. This represents a point of novelty, since the introduced method is quite straightforward as far as both experimental and mathematical approaches are concerned.