Comparison of Characteristics of Poultry Litter Pellets Obtained by the Processes of Dry and Wet Torrefaction

Abstract

Torrefaction is a technology for the preliminary thermochemical treatment of biomass in order to improve its fuel characteristics. The aim of this work is to conduct comparative studies and select the optimal operating conditions of fluidized bed torrefaction for the processing of poultry litter (PL) into an environmentally friendly fuel. PL torrefaction was evaluated according to three different process configurations: (1) torrefaction of PL pellets in a fixed bed in a nitrogen medium at temperatures of 250 °C, 300 °C and 350 °C (NT1, NT2 and NT3); (2) torrefaction of PL pellets in a fluidized bed of quartz sand in a nitrogen medium at temperatures of 250 °C, 300 °C and 350 °C (NT4, NT5 and NT6); and (3) torrefaction of PL pellets in a fluidized bed of quartz sand in an environment of superheated steam at temperatures of 250 °C, 300 °C and 350 °C (ST1, ST2 and ST3). The duration of the torrefaction process in all experiments was determined by the time required for completion of CO2, CO, H2, and CH4 release from the treated biomass samples. The gas analyzer (Vario Plus Syngaz) was used to measure the concentration of these gases. The torrefaction process began from the moment of loading the PL sample into the reactor, which was heated to the required temperature. After the start of the torrefaction process, the concentration of CO2, CO, H2, and CH4 in the gases leaving the reactor initially increased and, subsequently, dropped sharply, indicating the completion of the torrefaction process. The chemical composition of the obtained biochar was studied, and it was found that the biochar contained approximately equal amounts of oxygen, carbon, nitrogen, hydrogen and ash, regardless of the torrefaction method. Furthermore, the biogas yield of the liquid condensate, obtained from the cooling of superheated steam used in the torrefaction process, was evaluated. The results highlight the efficiency of fluidized bed torrefaction, as well as the performance of superheated steam as a fluidization medium.

Prediction of the Behavior of Sunflower Husk Ash after Its Processing by Various Torrefaction Methods

“…As shown by our previous experiments [20], at a temperature of 300 °С, the process of biomass torrefaction proceeds most intensively. On the other hand, as the temperature rises, the biomass gasification process begins, the purpose of which, as is known, is to produce combustible gases.…”

“…Superheated steam can also be used as a gas medium in which the torrefaction process is carried out [18][19][20]. In such a biomass pre-treatment, it would probably be possible to combine water washing and torrefaction processes, which would dramatically simplify the process.…”

Agricultural Waste Valorization: Exploring Environmentally Friendly Approaches to Bioenergy Conversion

“…Water is the most prevalent component of bio-oil, which also contains other ingredients, such as acids, phenols, and other compounds [133]. Throughout torrefaction, a minor quantity of biogas, primarily CO 2 , is formed, along with CH 4 and other gases [134]. Torrefaction produces biogas that can be burned to provide heat for cracking, but it is not useful in engineering fields because of its poor heating value [135].…”

A comprehensive comparative study on the energy application of chars produced from different biomass feedstocks via hydrothermal conversion, pyrolysis, and torrefaction

“…Biochars are stable, homogeneous, have higher energy densities and calorific values compared to the original biomass feedstock [25,45,46,53]. Torrefaction is conducted at 200-300 • C under lowoxygen or inert atmospheres and removes moisture and low energy volatiles [45,[54][55][56]. The cost of biomass torrefaction process (drying and torrefaction) could be minimised by using the energy released via the volatiles.…”