Nano-particles re-cleaning filtres
Nowadays, renewable sources of energy have become absolutely essential in our energy consuming society. Modern, widely accepted methods for energy recovery, particularly those used for MSW, are achieved mainly through combustion that entails many potentially environmentally damaging by-products. The high temperatures that are necessary for the incinerator's operation need to fall in order to remove the off gases particles, and this is a costly procedure. In addition, the cooling process is accompanied by the production of acidic gases, dioxins and other harmful substances. Hence, there is a substantial augmentation in the incinerator operating costs due to the required increase of expenditure on contamination control. The project work was a multi-disciplinary approach aimed at developing hot gas filtration methods for preventing the synthesis of dioxins and reducing the harmfulness of gases. For this reason, new effective technical solutions were instituted to remove blocking agents, such as fly ash, at such high temperatures (around 800° C). Thus, suitable and easy methods, similar to pulse jet, vacuum pulse or coupled re-cleaning (CPP) techniques may be employed to clean the ceramic filter candles. The result of this project has initiated the production and manipulation of nano-particle coatings to ceramic filter candles for use in high temperature gas filtration applications. The nano-particle and membrane coatings ultimately optimise the surface strength and bring a micro-porous barrier layer on filter surfaces that aids the re-cleansing of filters by reducing the emission of harmful organic compounds. At the same time, they reduce operating costs and increase the potential for heat recovery and the generation of electricity. Nano particle coatings were applied by two methods: a special technique that used scattered nano-particles and a novel atmospheric pressure plasma technique that not only generated them but applied them as well. Materials specialists studied the morphology of the coatings that both techniques provided using a dust model that simulates the common gas dynamics in MSWs. The results have proven that the coatings applied with the atmospheric pressure plasma technique improved re-cleaning of filtration and decreased the pressure drop during the process by 57%. Furthermore, when the particle is enhanced with calcium sulphate, it can optimise the filter cake detachment process and this method has the potential to be industrialised. On the other side of the Atlantic, almost $20 million are spent on building pilot hot filter plants for pressurized, fluidised bed combustion systems. This project result is a successful European method of high temperature filtration processes involving ceramic filter media may become the Best Available Techniques Not Entailing Excessive Cost (BATNEEC), in treating the hot gases from MSW incineration and related processes. Incinerators, may not be the best option of energy sources, but coupled with nano-technologies, they are brought all the more closer to green-energies and hence converted to more environmentally friendly energy sources.
