Revamps 2024 Issue

0.292 0.250 0.208 0.167 0.125 0.083 0.042 0 Gas load factor at MCV inlet (m/s)

Figure 4 Gas load factor at MCV entry

The first is the selection of a vane pack type that can meet the required capacity while maintaining at least the same separation efficiency as the existing separator. The second is the improvement of the vapour distribution at the entry of the vane pack for better separation efficiency, and discussed in more detail as follows:  Selection of the right vane pack: Sulzer selected MCV H45D, as seen in Figure 5 , which has a higher gas han - dling capacity of 25-40% compared to MCV H51Z, based on operating conditions. As per hydraulic evaluation, MCV H45D can handle the high vapour loads without requir - ing an increase in the size of the vane pack. If the existing separator was to be revamped with another conventional vane pack, 1-2 tray decks below the separator would have to be removed to create more space for a new vane pack with bigger net flow area. Removal of tray decks not only increases site modification and turnaround time but may also have an adverse effect on column performance. The use of high-performance MCV H45D does not require any trays to be removed; the housing of the existing MCV H51Z can also be reused. MCV H45D has an optimised vane blade profile, which minimises possible re-entrainment of liquid droplets. The drainpipes from the Mellachevron were also modified for better liquid drainage to enhance separation. v Improvement of vapour flow at separator entry: Vapour flow distribution at gas/liquid separator entry is one of the most important issues influencing separation efficiency. As it is often difficult to evaluate vapour flow distribution quality at vane pack entry, especially for a non-standard arrangement, a baffle plate is usually installed at the entry

Figure 5 Sulzer high-performance Mellachevron

to improve the vapour flow trajectory. For this retrofit, Sulzer installed a thin mesh pad in front of MCV H45D; this also works as a pre-conditioner, improving Mellachevron oper - ation turndown and separation efficiency with negligible pressure drop increase. The pre-conditioner work principle is presented in Figure 6 . Even though the new vane pack location is maintained with no trays below the vane pack removed, the selection of the right vane pack, which can handle the higher capacity while maintaining the separation efficiency, together with the use of the mesh pad as a pre-conditioner, can signifi - cantly improve the separation performance. Installation and revamp results In this revamp of Mellachevrons from the existing MCV H51Z to the high-performance MCV H45D, the existing housing and welding attachment for the vane pack could be reused, saving the cost and installation time for the retrofit. The existing 73 tray decks below the vane pack were also maintained. The retrofit was completed in four days, fulfill - ing the plant owner’s turnaround schedule. Reabsorber C1 with the new MCV H45D was tested at full load in 2023. The methanol concentration at the outlet of heat exchanger E1 was reduced to less than 350 ppm. As a result, the methanol concentration of the tail gas exiting scrubber C2 was able to meet the process requirement of less than 35 ppm, meeting the plant owner’s expectations. Table 2 summarises the column performance before and after the revamp.

Column performance before and after revamp

Before revamp (2022)

After revamp (2023)

Vane pack type

Sulzer MCV H51Z

Sulzer MCV H45D and mesh pre-conditioner

Flow rate to reabsorber C1, as compared to original design Maximum turn-up of Mellachevron Methanol concentration at heat exchanger E1 outlet, ppm

116% 110%

116% 130%

900-1,400

<350

Table 2

Revamps 2024