Experimental and numerical investigation of development, rearrangement and detachment of reactive-inert particle structures on cylindrical collectors in gaseous environment

• Applicants: Professor Dr.-Ing. Achim Dittler; Professor Dr.-Ing. Uwe Janoske
• Subject Area: Mechanical Process Engineering
• Term: from 2019 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 434784957

Reactive-inert particle structure depositions on collectors in gas flow fields occur in several applications. Soot (reactive) and ash (inert) in porous filter media used to remove particles from exhaust gases or process gases, but also coal dust (reactive), ash (inert) and fractured packing material (inert) in fixed bed reactors for coal dust gasification, are examples for such particle structures. Deposited structures can detach from the collector and penetrate through the porous media. Examples are the penetration of ash through soot particle filters or the transport of coal dust in fixes bed reactors.Re-entrainment of deposited particles is necessary for the occurrence of transport phenomena. Inert particles can detach from single fibres at gas velocities higher than 1 m/s according to Löffler 1972. The influence of reacting particle structures on detachment is not known jet.First experiments with soot and 4 – 20 micrometer glass spheres deposited on a 40 micrometer thick metal fibre confirm the result by Löffler. In these experiments the particle structures detach at more than 3,5 m/s (superficial velocity) if the temperature was 22°C. At 410°C the soot reacted and re-entrainment took place at only 48 cm/s. In addition the particle structures shrank and deformed at elevated temperatures. These experiments shows that reactive components in particle structures can cause detachment from collectors at lower flow velocities. In this research project the detachment of reactive-inert particle structures in dependence of gas velocity, temperature, diameter of the collector, amount of particles on the collector, percentage of reactive/inert particles, structure of particle deposits, size of inert particles, size of reactive particles and process procedure should be investigated. Single cylindrical collectors should be used in order to achieve fundamental understanding of detachment phenomena independent of the concrete structure of the used porous media.Experimental research of the detachment of reactive-inert particle structures from cylindrical collectors should be made at the Karlsruher Institute of Technology. The deposited particle structure should be characterized by weighing and microscopy. For quantification of particle detachment an rearrangement image analysis and a light-sheet-technique should be used.Also the detachment should be modelled at the Bergische Universität Wuppertal. These models enhance further understanding and allow calculation of detachment from other geometries and applications after the model is verified.The aim of this research project is to investigate re-entrainment of inert-reactive particle structures. Dependence of the number, distribution and structure of re-entrained particles on the airflow velocity, temperature, process procedure, particle size distribution of separated structures, inert- and reactive- fraction is of special interest. Models of this dependence will be developed and verified experimentally.

• DFG Programme: Research Grants