Characteristics of single wood particle pyrolysis using particle image velocimetry

This study examines the pyrolysis of a single cylindrical wood particle using particle image velocimetry (PIV). The pyrolysis was conducted inside a pyrolysis reactor designed for this purpose. The experimental setup presented in this paper is capable of effectively characterizing the intensity of pyrolysis based on velocity distribution in the vicinity of wood particles. The results of the gas velocity distribution show that evaporation of moisture has as a major impact on the formation of the gas cushion as devolatilization

Design and distribution of air nozzles in the biomass boiler assembly

Due to energy crisis as well as increasing pollution of the enviroment, renewable energy sources usage increases all over the world. These facts encouraged authors to start research over developing a uniform biomass boiler calculation model. Paper presents the design of biomass boiler assembly created for the organic Rankine cycle unit since these systems could achieve strong position in energy industry. To achieve optimal performance of boiler assembly, two additional devices have been designed: the economizer and air preheater. Such installation allows to reach the assembly efficiency of 82%. The research over the air nozzles placement in the combustion chamber in order to ensure the best firebox efficiency is also presented. Modeling is based on computational fluid dynamics simulations of pyrolysis on the moving grate. Released gases are being transported to the combustion chamber, mixed with air from the nozzles and combusted. Furthermore, the model assumes different distribution and composition of gases across the moving grate

Measurements of the dependence of wood’spermeability to air on the temperature of the pyrolysis

The paper deals with the wood’s (in this case pine) longitudinal permeability to air and its possible dependence on the temperature of the pyrolysis. The measurement of permeability was indirect and conducted on the original stand constructed solely for this purpose. Before every measurement a special sample preparation procedure was conducted for each sample group. Every group of samples was preheated up to the temperature previously set in the oxygen-less environment. After that, samples were cooled down to the room temperature. The following parameters were measured directly: sample length and diameter, pressure difference, and time. After numerous measurements of the mentioned values, the permeability of wood to air was calculated using the Darcy’s law for a given pyrolysis temperature. The results show a distinct dependence between the wood’s permeability to air and the pyrolysis temperature. The minimum value of the permeability is on the level of 0.56 D for temperature of 50 ◦C and is growing up to the value of 5.8 D (over ten times of the initial value) for the temperature of 350 ◦C

Review on modelling approaches based on computational fluid dynamics for biomass pyrolysis systems

Modelling is a complex task combining elements of knowledge in the field of computer science, mathematics and natural sciences (fluid dynamics, mass and heat transfer, chemistry). In order to correctly model the process of biomass thermal degradation, in-depth knowledge of multi-scale unit processes is necessary. A biomass conversion model can be divided into three main submodels depending on the scale of the unit processes: the molecular model, single particle model and reactor model. Molecular models describe the chemical changes in the biomass constituents. Single-particle models correspond to the description of the biomass structure and its influence on the thermo-physical behaviour and the subsequent reactions of the compounds released during decomposition of a single biomass particle. The largest scale submodel and at the same time, the most difficult to describe is the reactor model, which describes the behaviour of a vast number of particles, the flow of the reactor gases as well as the interaction between them and the reactor. This chapter contains a basic explanation about which models are currently available and how they work from a practical point of view