Study of Flow Patterns in Two-Stage Mode of Moving Granular Bed Filter

Abstract

The use of moving granular bed filters (MGBFs), which hold an important role in the gasification or combustion of coal and biomass, has been growing. Furthermore, these filters have great potential to be developed for the high-temperature gas cleanup of advanced power generation systems. However, the creation of a stagnant zone due to defective designs in MGBFs can cause serious issues such as plugging. Therefore, in order to minimize these problems, flow-corrective inserts for filter vessels have been researched, most of which use mono-sized filter granules. This study proposed a new method that introduced two granule sizes in one filter vessel, called the two-stage filtration mode. Nevertheless, the design theory of a mass flow vessel by Johanson could not be satisfied by using two sizes of filter granules to diminish the stagnant zone. The flow patterns in a two-dimensional and cross-flow moving granular bed were evaluated in six test configurations based on different geometric designs in a filter. The two kinds of filter granules consisted of coarse and fine silica sands. The findings revealed that the flow patterns of filter granules were influenced by the vessel geometry. The optimal design for two-stage filtration diminished the stagnant zone in 165 minutes.

A New Approach of Dedusting for IGCC by a Two-Stage Moving Granular Bed Filter

“…Model: PPC-P), as shown in Figure 2. The designed MGBF was based on quasi-two-dimensional tests reported in our previous study [21]. The dimensions were 1570 mm (height), 380 mm (width), and 500 mm (depth).…”

“…Conversely, the F group included various mass flow rates (110, 330, 440, 550, and 1100 g/min) of fine granules (ṁ F ) and a fixed mass flow rate of coarse granules (for F1, F2, F3, F4, and F5, respectively). A mass flow rate of 330 g/min was concluded to be the optima setup, as determined in our previous study [21]. These coarse and fine granules were controlled by two variable-frequency conveyers located under the MGBF.…”

“…This study introduced a novel concept for the three-dimensional movement and continuity of filtering granules. The two-stage moving granular bed filter (MGBF) in our previous study [21] used a two-dimensional asymmetrical geometric design for two granule sizes, which vertically flow from the upper hopper to the lower filter, thus diminishing stagnant zones. The three-dimensional apparatus of the two-stage MGBF was built from a two-dimensional setup for cold filtration tests (Figure 1).…”

On the Special Issue for the 12th World Filtration Congress

“…• Recognizing the high potential of moving granular bed filters (MGBFs) in facilitating high-temperature gas cleaning for advanced power-generation systems, Chang et al (2017) proposed and tested a new method that placed two filter-granule sizes in one vessel, called the two-stage filtration mode, and proved that vessel geometry influenced the flow pattern profiles of the granules. The optimal design diminished the filter's stagnant zone in 165 minutes.…”