removal using the MagAFS filter contain preferably 10% or more FeS or FeO/Fe₂O₃ particles. According to the pre - vious problem description, the fresh feed stream and RO stream to the hydrocracker contain a significant amount of FeS particles. For solving the resulting major pressure drop (or plugging) problems for the hydrocracker with min - imal investment and low operating costs while maximising throughput, filtration technology has provided the follow - ing benefits for an HDS reactor for coal tar naphtha (one of the most difficult feed streams): • The filter removed and prevented up to 97.6% of the solid particles in the coal tar naphtha stream from entering the HDS reactor. • The filter (more efficient for smaller particle removal) prevented particles ranging from 260 to 1,000 nm (mostly around 400 nm) particles in the coal tar naphtha stream from entering the HDS reactor to protect the catalyst pores and maintain catalytic activity. • The filter effectively removed not only Fe (99%) and S (96%), but also other substances, including Mn (100%), Hg (100%), Al (88%), Cr (90%), Mo (100%), Ni (74%), Cu (100%), and Cl (64%), producing an ultra-clean feed stream for the HDS reactor. • Essentially no pressure drop change in the front-end heat exchanger and the HDS reactor, as well as no unscheduled shutdown in more than five years of continuous operations. • Weight average bed temperature (WABT) of the HDS reactor increased only 1ºC (or essentially no change), demonstrating minimal catalyst deactivation during more than five years of operation. Figure 5 presents a schematic process diagram of a hydrocracker (without showing the heat exchangers) for converting the fresh feed, including distillates and FCC unit light cycle oil (LCO), into aromatics and light/heavy naphtha. The fresh feed containing particles with 10% or more FeS/ FeOx is fed through the filter upstream of the hydrocracker to remove up to 98% of solid particles. The filtered fresh feed enters the top of the hydrocracker through a thinner layer of low-cost macropore packings for liquid distribution only. Without RTM packings or other sophisticated parti - cle-trapping materials, the active catalyst bed can be expanded significantly to increase the process through - put. Plugging in macropore packings and the catalyst bed is minimised due to significantly reduced solid particles introduced with the reactor feed, especially the small - er-sized particles. Catalyst life can be extended through minimising catalyst pore plugging caused by nanometer particles. The RO stream from the bottom of the product fraction - ator is a major source of FeS particles, causing plugging problems in the hydrocracker. FeS particles are the corro - sion product generated by high-temperature sulphidation in the fractionator. The RO stream contains many more FeS particles than the fresh feed stream, with mostly smaller particles. However, this is the ideal process stream to be effectively treated by a high-temperature MagAFS filter (up to 300ºC), in terms of FeS content, particle size, and stream temperature.
MagAFS lter
Hydrogen & gases
Fresh feed
Macropore packings for liquid feed distributors only
Light naphtha
Aromatics
High - temp MagAFS lter
Heavy naphtha
Expanded bed catalyst
Fractionator
Hydrocracker
Non-converted bottoms
Recycle feed
The particles in the fresh feed stream also contain sig- nificant amounts of corrosion products from reactions between the process fluids and the plant equipment, typ - ically FeS, which, in fact, is the root cause of the pressure drop problem in the hydrocracker. A sample analysis of particles taken out of the reactor bed during skimming indicated that they were virtually 100% FeS. The PSD measured on the catalyst bed material suggests that the FeS particles agglomerated at the process conditions in the catalyst bed. Another major source of FeS particles causing plugging problems in the reactor is coming from the RO stream from the bottom of the product fractionator. The corrosion products, mainly FeS particles, are generated by high-tem - perature sulphidation in the fractionator. The RO stream contains many more particles (mainly FeS) than the fresh feed stream, with problematic smaller sizes. Feed filters, such as a basket filter followed by a cartridge filter, are typically used in front of the reactor to remove larger particles (larger than 25-50 µm), while inlet grad - ing materials in the reactor are used to control fouling. A conventional grading bed arrangement has been used with a large-diameter catalyst size on the top to produce a low inherent bed pressure drop, allowing fine particles to migrate through the reactor bed. Although the grading bed provided a large volume for storing contaminants, it does not have the capability to catch the fine particles, causing the plugging problem in this case. Recently, improvements have been made using RTM for trapping 1 to 1,500 µm particles to minimise pres - sure drop and improve flow distribution. However, the RTM packings do take up significant valuable catalyst bed space, so the amount of this trapping material needs to be limited. Also, RTM packings cannot protect the catalyst pores of active sites from plugging, as they are unable to remove particles smaller than 1 µm (1,000 nm). Solid particle removal from HDS feed streams The most favourable process streams for solid particle Figure 5 MagAFS filter for cleaning up hydrocracker feed streams
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PTQ Q2 2026
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