Mechanism and modelling of bamboo pyrolysis

Bamboo is the world's fastest growing woody plant and some species can grow up to a foot a day if the right conditions were met, therefore it can be a sustainable raw material resource for energy demand. In Asia, bamboo is mainly used for scaffolding and about 50,000 tonnes of bamboo waste is generated annually in Hong Kong. To utilise the growing bamboo waste, pyrolysis which is a promising technology for tackling waste disposal can be employed. This paper proposes the pyrolysis mechanism and develops a mathematical model for bamboo pyrolysis process using the parameters generated from the TGA/DTA analysis. This model helps to understand the bamboo pyrolysis better and it was then used to study the effects of different operating parameters on bamboo pyrolysis. (C) 2012 Elsevier B.V. All rights reserved

Optimum biomass drying for combustion - A modeling approach

Drying biomass as fuel in a combustion process can increase the combustion efficiency, reduce pollution and improve operation. On the other hand, drying biomass is an expensive process that requires huge capital investment and energy input. The difficulty of removing moisture from biomass is affected by many factors such as the moisture content and the size of the solid particles. The level of drying is therefore a very important parameter, which strongly influences the economies of the utilization of biofuel. This study utilizes a mathematical model that incorporates material and energy balances, heat transfer and drying kinetics to determine the optimum drying level of biomass. Drying kinetic based upon the Fick's second law of diffusion is used in the model to determine the energy and capital expenditures for the drying process. Case studies of wood chips drying are presented to demonstrate how the thickness of wood chips affects the optimal drying intensity and the overall economics of the process. (C) 2013 Elsevier Ltd. All rights reserved

CFD Study on the Application of Rotary Kiln in Pyrolysis

The pyrolysis of bulk feed requires the use of some alternative pyrolysis reactors other than the conventional fluidized bed reactors used in the fast pyrolysis of biomass. An indirect-fired rotary kiln was suggested to be a suitable choice subject to the need for a better thermal efficiency. An approach to utilize the Computational Fluid Dynamics (CFD) simulation and the pyrolysis kinetics for the design of pyrolysis rotary kilns with a better thermal efficiency is proposed. A case study of the internal configuration of the kiln with a qualitative discussion was used to demonstrate how the approach can be utilized for the kiln design process

Optimisation of particle size in waste tyre pyrolysis

During pyrolysis of waste tyre, the operating parameters such as tyre composition, the process temperature, the heating rate and the particle size affect the result of the pyrolysis. Some of these parameters have been closely considered but the particle size of the waste tyre is often ignored. The goal of this paper is to study the effect of particle size in waste tyre pyrolysis under different heating approaches and to use optimization techniques to determine the optimized particle size for each scenario. In this paper, the size of the waste tyre particle is considered as a major factor in determining the magnitude of the overall energy used as well as the completion time of the pyrolysis reaction. Simulations were conducted to compare the effects of the particle size on the completion time and the overall energy usage under different heating rates and operational strategies. Shredding energy needed to reduce waste tyre particles was also included into the calculation of the overall energy consumption. Optimisation of the particle size was conducted under a number of specified maximum completion times and heating rates. This study confirms the trade-off between the overall energy used and the completion time. It also shows the impact of using some optimisation techniques to determine the optimized particle size for different heating approaches. © 2012 Elsevier Ltd. All rights reserved

Co-pyrolysis of Biomass and Plastics waste: A Modelling Approach

Thermal co-processing of waste mixtures had gained a lot of attention in the last decade largely due to certain synergistic effects such as higher quantity and better quality of oil, limited supply of certain feedstock and improving the overall pyrolysis process. Many experiments have been done using the TGA analysis and different reactors to achieve the stated synergistic effects in co-pyrolysis of biomass and plastic wastes. The thermal behaviour of plastics during pyrolysis is different from that of biomass because its decomposition happens at a high temperature range (>450 degrees C) with sudden release of volatile compared to biomass which have a wide range of thermal decomposition. Therefore it is worthwhile to study the possible synergistic effects on the overall energy used during co-pyrolysis process. In this work, two different modelling approaches were used to study the energy related synergistic effect between polystyrene (PS) and bamboo waste. The results show that both modelling approaches give an appreciable synergy effect of reduction in overall energy when PS and bamboo are co-pyrolyzed together. However, the second approach which allows interaction between the two feedstocks gives a more reduction in overall energy usage up to 6.2 % depending on the ratio of PS in the mixed blend

Optimization of multi-stage pyrolysis

Pyrolysis process is considered as a beneficial option in waste treatment largely due to the products generated and the energy recovery when compared to other methods. In the conventional pyrolysis process, heat is continually supplied to the reactor until the final pyrolysis temperature is attained. The reactor is then maintained isothermally at this temperature until the pyrolysis is completed. This technique does not take into consideration the mechanism of the pyrolysis which involves both exothermic and endothermic reaction and the opportunity of gaining some processing benefits is often ignored. Multi-stage pyrolysis which is an approach to carry out pyrolysis with multiple heating stages in order to gain certain processing benefits has been introduced in our earlier works. 22.5% energy reduction was achieved in our past work with a 100% increase in completion time. This work therefore proposes the optimization of the operating parameters in multi-stage pyrolysis in order to limit the increase in completion time and also reduces the overall energy. This innovative approach can achieve a range of 24.7%-37.9% reduction in energy usage with 37%-50% increase in completion time depending on the heating rate for each heating stages. This approach has also been used for charcoal production. © 2013 Elsevier Ltd. All rights reserved