Ka Leung Lam

Charcoal Production via Multistage Pyrolysis

Interests in charcoal usage have recently been re-ignited because it is believed that charcoal is a muchbetter fuel than wood. The conventional charcoal production consumes a large amount of energy due to the prolonged heating time and cooling time which contribute to the process completing in one to several days. Wood py-rolysis consists of both endothermic and exothermic reactions as well as the decomposition of the different components at different temperature range （hemicellulose： 200-260℃; cellulose： 240-350℃ and lignin： 280-500℃）. Inthis study we propose a multistagepyrolysis which is an approach to carry out pyrolysis with multiple heating stages so as to gain certain processing benefits. We propose a three-stage approach which includes rapid stepwise heating stage to a variable target temperatures of 250 ℃, 300℃, 350 ℃ and 400 ℃, slow and gradual heatingstage to a tinal temperature of 400℃ and adiabatic with cooling stage. The multi-stage pyrolysis process can save 30% energy and the processing time by using a first temperature target of 300 ℃and heating rate of 5℃.min-1 to produce a fixed-carbon yield of 25.73% as opposed to the base case with a fixed-carbon yield of23.18%.

Experimental and Modelling Studies of Biomass Pyrolysis

Abstract The analysis on the feedstock pyrolysis characteristic and the impacts of process parameters on pyrolysis outcomes can assist in the designing, operating and optimizing pyrolysis processes. This work aims to utilize both experimental and modelling approaches to perform the analysis on three biomass feedstocks—wood sawdust, bamboo shred and Jatropha Curcas seed cake residue, and to provide insights for the design and operation of pyrolysis processes. For the experimental part, the study investigated the effect of heating rate, final pyrolysis temperature and sample size on pyrolysis using common thermal analysis techniques. For the modelling part, a transient mathematical model that integrates the feedstock characteristic from the experimental study was used to simulate the pyrolysis progress of selected biomass feedstock particles for reactor scenarios. The model composes of several sub-models that describe pyrolysis kinetic and heat flow, particle heat transfer, particle shrinking and reactor operation. With better understanding of the effects of process conditions and feedstock characteristics on pyrolysis through both experimental and modelling studies, this work discusses on the considerations of and interrelation between feedstock size, pyrolysis energy usage, processing time and product quality for the design and operation of pyrolysis processes.

Quantifying and managing urban water-related energy use systemically: case study lessons from Australia

Abstract In this paper, three Australian case studies contribute to improved understanding of water-related energy quantification and management. A systems analysis of urban water in South East Queensland (Case Study 1) demonstrates the energy impact of water end use. In Melbourne (Case Study 2), water–energy interlinkages are explored within households. Finally, Case Study 3 in Sydney shows how abatement curves can help guide management action. Collectively, the case studies provide new information for least-cost solutions and simultaneous water and energy efficiency. The work highlights the need for frameworks to characterize and evaluate both the direct and indirect energy influences of urban water.

Optimisation of Operating Parameters in 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 optimisation of the operating parameters in multi-stage pyrolysis in order to limit the increase in completion time and also reduce the overall energy. This approach can achieve a 29 % reduction in energy usage with just 36 % increase in completion time.

Numerical study of mixed-feedstock pyrolysis

Abstract In light of the processing difficulties and constraints in pyrolysing certain types of bulk feedstock alone, a mixed-feedstock pyrolysis approach is proposed in this work. The pyrolysis progress of some common biomass and plastic materials were first studied by common thermal analysis techniques and were then modelled. Using a mix of wood and polyethylene as an example, the proposed approach was evaluated with the aid of two models - a particle pyrolysis model and a CFD rotary kiln model. Based on the evaluation of three areas - heat transfer, secondary reaction and reactor operation, the proposed approach can possibly be used to cope with certain processing difficulties and constraints by enabling a more uniform heating across a cross-section plane, promoting secondary reaction for biomass pyrolysis volatiles, increasing the solid retention time and reducing the extend of char deposition on the reactor wall.

CFD Study on the Application of Rotary Kiln in Pyrolysis

Abstract 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.

Kinetic Modelling and Analysis of Waste Bamboo Pyrolysis

In Asia, bamboo is mostly used for scaffolding because of its versatility, durability and being ecofriendly. About 50,000 t of bamboo waste are generated annually in Hong Kong. The abundance of bamboo in Asia and other parts of the world as well as its fast rate of replenishment have resulted in a global interest in bamboo as a wood substitute. To further utilise the growing waste, pyrolysis which is a promising technology for tackling waste disposal can be employed. To fully design a pyrolysis process for waste bamboo, the mass loss and heat flow kinetics as well as the effect of the various operating parameters must be known. The objective of this work therefore is to model the pyrolysis of waste bamboo and to study experimentally the effect of different operating strategies during the pyrolysis process. The influence of feed particle size, mixed – size, heating rate and target temperature on the processing time and energy usage are discussed in the study. The detailed results and analysis are presented including the overall energy usage and the processing rates.