Cellular Automata Modelling for Simulating Segregation of Wood Pellets in Silo Filling and Discharge
Wood pellets are widely used in power generation, often co-fired in traditional coal fired power stations. Wood pellets are a low carbon energy resource which can naturally be replenished. Wood pellets are handled often by conventional coal handling equipment such as conveyer belts, pneumatic conveyors, and frequently stored in large silos and domes. During handling and storing, wood pellets degrade into fines and dust. Wood pellets mixed with fines and dust have a tendency to segregate in handling, especially silo filling and discharge. This causes spikes in fines and dust level which result in suboptimal pneumatic conveying (high energy consumption). Due to variable operational conditions, dust tend escape from processes can be more problematic, leading to dust accumulation in the environment, requiring more intense cleaning. Moreover, it leads to increased risk of fire and explosion. Unsteady unit operations including particle milling may consume excess amount of energy, resulting in additional cost in parasitic load.
In this study, segregation during silo filling and discharge is modelled using Cellular Automata (CA) approach. CA modelling is a mechanistic, deterministic approach, in this case using a simple set of rules derived based on close observation of particle heap formation and free surface segregation. The aim of this study is to test the suitability of CA modelling for estimating segregation in bulk material handling. 2-D simulations have been developed using Excel VBA and tested against laboratory scale test rigs. These CA models have shown an excellent capability to predict segregation in silo filling and discharge. All key features of behaviour seen in the experiments are captured in the model; in filling, due to free surface segregation, higher level of fines was predicted under the feeding point (usually the centre of the silo), and in discharge the tendency for fines to sift downwards through the moving layer is also captured. This paper discusses the modelling technique, the logical rules required to achieve the desired behaviour and the validation against experimental observations.
(Jeff) Susantha Dissanayake Reading for PhD, AFHEA
The Wolfson Centre for Bulk Solid Handling Technology, UNIVERSITY OF GREENWICH, CENTRAL AVENUE, CHATHAM MARITIME, KENT ME4 4TB Susantha Dissanayake is a PhD research student working at the Wolfson Center for Bulk Solid Handling Technology, University of Greenwich, United Kingdom. He is studying segregation of wood pellets during silo filling and discharge using a Cellular Automata (CA) modelling approach. CA modelling is a discrete modelling approach which consists of simple set of rules: which were developed by close observation of free surface segregation occurring during particle heap formation. In his study, the suitability of CA modelling for bulk material handling is tested and a control methodology is to be developed to assist with blending pellets to control fines level in actual handling systems at a leading power generation plant in the UK. Susantha finished his bachelor’s special degree in Science and Technology and finished his master’s degree in sustainable process development from University of Moratuwa Sri Lanka. He worked in academia for three years before he joined the University College of Southeastern Norway (UCSN) for his second master’s degree in process technology. After completion of his master’s degree he again joined academia and continued his teaching and research career in Norway. He started his doctoral studies at University of Greenwich UK in December 2017. Currently, he is in his second year of the study. During his research career he has worked in modelling and simulation field and has published more than 10 research papers. His teaching qualifications were recognized by UK Professional Standard Framework (UKPSF) and awarded Associate Fellow of the Higher Education Academy (AFHEA) in July 2019. EDUCATION & CREDENTIALS BSc (special)., University of Sri Jayewardenepura, Sri Lanka, 2009 MSc., (Sustainable Process Development) University of Moratuwa, Sri Lanka, 2011 MSc., (Process Technology), University Collage of Southeast Norway, 2016 PhD., (Reading) University of Greenwich.