On the influence of an added fraction of hygroscopic salt particles on the operating behaviour of surface filters for dust separation by moisture-induced deliquescence and efflorescence

• Applicant: Dr.-Ing. Qian Zhang
• Subject Area: Mechanical Process Engineering
• Term: from 2015 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 281470635

The basis for targeted manipulation of the operating behaviour of surface filters is, as a rule, always attributable to the fact that a favorable performance adjusts itself at long cycle times. These are obtained by a slow increase in pressure drop during the filtration phase and by a low residual pressure drop after the regeneration. Technically, such states can be realized by so-called raw gas conditioning. Here the particle characteristics in the flight phase or in the dust cake are selectively modified by dosing additives or introducing energies. It is known that the particle adhesion is generally strengthened with increasing gas humidity. While an increase of particle adhesion in the dust cake reduces/prevents the compression of the dust cake in the filtration phase and promotes the cohesion of the cake layer during the regeneration, an increase of adhesion between the cake layer and the filter medium surface impedes the detachment of the dust cake during the regeneration. A separate influence of these two effects is not possible by a permanent change of the gas humidity during the filtration.The deliquescence and efflorescence properties of hygroscopic salt particles, which can be induced by a transient increase in gas humidity, can be considered as possibilities for the formation of solid bridges between dust particles in the filter cake. With this raw gas conditioning concept, a flexible and targeted strengthening of the cohesion in the filter cake without an accompanied modification of the adhesion between the cake layer and the filter medium is theoretically possible. Within the scope of the proposed research project, it is being studied experimentally and theoretically, which effects an added fraction of hygroscopic salt particles with their deliquescence and efflorescence properties in the dust cake has on the operating behaviour of surface filters, in particular with the aim of a targeted manipulation of the operating behaviour of surface filters by periodic dosing of hygroscopic salt particles. The observed positive effects will be checked by systematic examinations with standard test filters from needle felts on a laboratory filter testing apparatus. In addition, critical boundary conditions for a possible technical implementation of the method are to be investigated experimentally by extended screening tests. Based on this, a quantitative assessment of the new conditioning process is made.

• DFG Programme: Research Grants