Catalysis 2026 Issue

Lifting handle of core assembly

Lifting ring of core assembly

Magnetic bar ring

Filter housing cover

Flush uid inlet

Process stream inlet

Filter housing

Magnetic bar sleeve holder

Filter basket

Magnetic bar

Perforated screen for lter assembly

Process stream outlet

Propriety packing rings

Flush uid outlet

Figure 2 Schematic diagram of the MagAFS filter

from entering the HDS reactor, hydrocracker, and other fixed-bed reactors. Coal tar feed stream clean-up The magnetically induced MagAFS filter is capable of pref- erentially removing smaller particles from process streams. In fact, it removes more than 95% of solid particles of any size (down to 10 nm [0.01 µm]) at substantially reduced costs and simpler operations. In previous commercial tests on light coal tar liquid, it allowed only less than 5% solid particles to enter the reactor, preventing a significant pres- sure drop caused by plugging in the top macro-pore pack- ings and the catalyst bed. Minimising smaller particles in the filtered liquid feed stream also reduces catalyst pore plugging, helping to maintain its activity.1 , 2 As shown in Figure 2 , the process stream entering the MagAFS filter travels through a perforated metal cage. It contacts the proprietary packing substances under the influence of a suitable magnetic field generated by the per- manent magnetic bar assemblies. Magnetism of the para- magnetic and diamagnetic solids in the process stream is induced by the ferromagnetic solids in the process stream and the proprietary packing substances in the filter. As a result, most ferromagnetic, paramagnetic, and diamag- netic solid particles in the process stream are attracted to the sleeve holders and the proprietary packing substances. The treated process stream passes through the perforated metal cage and exits the filter housing. In the clean-up cycle, the filter cover plate is opened, and the entire core assembly, including permanent magnetic bar assemblies, the top supporting plate, along with sleeve holders, and the perforated metal cage containing pro- prietary packing substances, is withdrawn from the filter

housing. Thereafter, permanent magnetic bar assemblies are withdrawn from the sleeve holders to remove the mag- netic field from the interior, thereby releasing the attracted solids from the outer surface of the sleeve holders and the surfaces of the proprietary packings. The core assembly is washed with water or other suita- ble fluid before the magnetic bar assemblies are reinserted into the sleeve holders. The cleaned core assembly is then re-positioned into the filter housing, and the top opening is closed and sealed with the cover plate and fitted gas- ket. Before starting the operation cycle, control valves are opened to briefly introduce high-pressure fluid, such as water, a process stream, or air, to flush out residual solids from the filter housing. With this filter, conventional RTM packings used in the HDS reactor can be replaced with thinner, low-cost mac- ropore packings for liquid distribution only, leaving more space to allow a significantly expanded active catalyst bed. The only requirement is that the solid particles in the feed stream contain certain amounts (at least 10% or more) of ferromagnetic substances, such as FeO, FeS, Fe₂O₃, Ni, NiO, Co, and CoO. The solid particles in most fresh feed streams (including coal tar naphtha) to the HDS reactors or hydrocrackers meet this requirement. Commercial demonstrations A schematic process diagram of the MagAFS filter for treat- ing a light coal tar stream is shown in Figure 3 . It replaced both the front-end basket filter and the cartridge filter, eliminating the need for top RTM packings in the HDS reac- tor and allowing more room for an expanded catalyst bed. The coal tar naphtha stream fed to the HDS reactor con- tained 0.24-0.26 wt% sulphur, 200-300 ppmw nitrogen,

Catalysis 2026