PTQ Q1 2024 Issue

in SRT ethylene furnaces are given in Table 2 . The balances are based on Arab Light crude, and for Case 1, a typical Middle Eastern full-range naphtha is used for comparison. Acetylene and MAPD are hydrogenated with appropriate selectivities to their respective olefins. Ethane and propane are recycled to extinction. For this case study, all C5 species are fully hydrogenated and recycled to extinction. Benzene, toluene, and xylenes (BTX) are extracted and considered valuable products. C 6 -C 8 raffinate is recycled to extinction. C 9 -204°C is a heavy gasoline containing a high concentra- tion of C 9 -C 10 aromatics. It is processed in the feed prepa- ration section and recycled to heaters for crude cracking. Pyrolysis gasoil (PGO) (204°C-288°C) and pyrolysis fuel oil (PFO) (288°C+) are generally sold as products. The salient feature of TC2C technology is the ability to upgrade these materials to high-value products, as shown in Figure 4. A small amount of residue is always purged to minimise the coke precursors circulating in the system. This is taken out as VLSFO for Case 2, as shown in Figure 4. Case definitions shown in Table 2 are further discussed: • Case 1 is a standard naphtha cracker. Only C 2 /C 3 recycle, fully hydrogenated C 5 s, and hydrogenated C 6 -C 8 raffinate are recycled to extinction. • Case 2 – TC2C for the configuration shown in Figure 4. All recycles of Case 1 and recycles with C9 -204°C and pyrolysis fuel oil after treatment. Valuable chemicals include hydrogen, ethylene, propylene, butadiene, butene, and BTX. VLSFO is also valuable but not included in this study since it is considered a fuel product. Upgrading the feed (Case 2) by hydroprocessing produces the highest amount of valuable chemicals per unit of crude. The naphtha cracker is the simplest liquid cracker. When only thermal cracking (no hydroprocessing) is considered, a significant amount of residue must be rejected. In addition, vacuum gasoil range molecules must be cracked with a higher steam-to-oil ratio. They consume more crude and more energy. With hydrocracking options, residue is also used to some extent. Almost all PGO and PFO produced in the cracker are recycled after upgrading. Therefore, crude consumption is significantly reduced. The amount of high-value chemicals is also increased signifi - cantly. A cost is associated with this configuration as it requires the incorporation of select components for hydro- cracking, residue hydrocracking, and a hydrogen manufac- turing plant. Considering the reduction in crude and the increase in high-value chemicals, the increase in Capex is justified and is substantially less than a classical refinery configuration. The payout is less than two years for most locations. With light crudes, such as Permian, as high as 70% high-value chemi- cals instead of 50% for Arab Light crude can be obtained in thermal mode, 5 , 6 and with TC2C more than 80% high-value chemicals production is possible. In addition to the cracking heater, the recovery section plays a vital role in the ethylene plant. Fortunately, after the hot section, the recovery section configuration is nearly inde - pendent of the feed. Since a naphtha plant is chosen as a reference, relative factors can be used to prorate the capacity of the plant. Figure 5 shows specific energy relative to the

Cracker overall material balance summary

Case Feed

Naphtha

Crude

Feed, KTA Full-range naphtha

4,132

Naphtha from crude + TC2C crude conditioning

1,524 3,045

Gasoil from TC2C crude conditioning

LPG from crude + TC2C crude conditioning

233

Steam reacted

Total

4,136

4,807

Products, KTA H 2 product

Methane-rich off-gas

722

671

PG ethylene PG propylene

1,500

649 195 167 569

750 245 230 603 126 195 441

Butadiene Other C 4s

BTX

Heavy gasoline

90 66

PGO PFO

126

Acid gases

Total

4,136

4,807

High-value chemicals

3,119

3,351

Amount of crude, KTA

4,444 93,344

Crude, BBL/day

% HV chemicals to crude

75.4

Table 2

months. Therefore, CLG and Lummus have strict monitoring procedures for the HPNA of the cracker feeds. Optimum hydrocracker reactor operation and conversion are essential for high ethylene yield and long run length. This is achieved by passing the products of the LC reactor through the fixed bed reactor, which further improves the quality of cracker feed and reduces polynuclear aromatics (PNAs). Not only materials (chemicals and refrigerants) are exchanged between the ethylene plant and hydroprocess - ing (feed preparation) section, as heat integration (steam and fuel system) is also essential for energy conservation and CO₂ minimisation. TC2C maximises olefins from any crude. FCC is an effec - tive way to produce propylene, and Lummus has introduced both Indmax and single regenerator dual catalyst (SRDC) technology to maximise FCC propylene. Experimental data and model calculations clearly show the maximum amount of total valuable chemicals is achieved through the hydropro- cessing/steam cracker route, which also produces the high - est amount of ethylene with the lowest crude consumption. Ethylene plant The previous sections discuss how the feeds to the ethyl - ene pyrolysis reactors are prepared from crude. Since the molecular structure is altered through different processing methods, ethylene and the byproduct distributions will vary for different cases. Therefore, illustrative overall material balances for producing 1,500 KTA ethylene at high severity

PTQ Q1 2024