## Materials and Methods  
### Pilot Plant  
The study was conducted on an industrial-scale pilot plant reproducing the suction system commonly used in the milling industry to draw the finer particles of bran and flour out of machines and keep the working environment clean (see Figure 1).  
The system consists of a bag filter, a fan, piping, connections, flow control valves, and sensors. A schematic representation of the pilot plant is reported in Figure 2.  
The main element under study is the cyclone bag filter, which consists of a cylindrical steel body with a conical bottom, that contains 31 fabric sleeves. The airflow enters tangentially inside the separator, so that a percentage of the bran and flour dust, particularly  
Figure 1: Cyclonic bag filter pilot plat used for experimental testing.  
Figure 2: Schematic representation of the pilot plant.  
the coarser ones, are initially separated by a cyclonic effect and do not impact against the sleeves. The percentage of dust that is separated by the cyclonic effect is collected in the conical bottom and can be extracted, and recovered, thanks to a rotary valve; the remaining particles remain trapped in the fabric of the sleeves, gradually decreasing their permeability. This results in rapid clogging of the sleeves, causing the need for their rapid replacement. Indeed, a compressed air cleaning system is installed on the filter, which, at regular time intervals, flows compressed air counter currently through the sleeves to remove the dust trapped in them. This flow, however, can clean the sleeves only partially, as the dust that has penetrated deeper into the porous matrix is not removed. Moreover, since to date, it is not possible to know the actual state of each sleeve, the sequence of sleeve cleaning is decided a priori and remains unchanged throughout the entire life cycle.  
Once the permeability of the sleeves is no longer sufficient to ensure proper airflow, the sleeves must be replaced. Usually, sleeve replacement is performed when a differential pressure sensor, installed upstream and downstream of the sleeves, measures a pressure drop higher than a threshold value (generally set at about 15 mbar). The intervention of sleeve replacement is very time-expensive and requires stopping the production process for the time needed to complete the substitution. Therefore, to minimize the number of replacement interventions, all sleeves are usually replaced together. To maximize the uptime of the filter and its performance during this time interval, it is therefore highly desirable that the clogging of different sleeves occurs as uniformly as possible. On the one hand, it is therefore preferable to maximize the percentage of dust separated by the cyclonic effect and, at the same time, it is important to foresee the occurrence of abnormalities in filter operation so that timely action can be taken to restore proper operating conditions. Finally, it would be very useful to know the actual working conditions of each sleeve, since it would allow the optimization of the cleaning operations by increasing the frequency of the air jets on the sleeves most affected by airflow and decreasing the frequency on the others.