1.4
1.3
HCRK
1.3
1.2
C H plant only
C H plant + feed preparation
1.2
1.1
1.1
1
1
0.9
0.6 0.7 0.8 0.9
0.5 0.6 0.7 0.8
C H plant + feed preparation
Heater e uent
Gasoline fractionator
Quench tower
Charge gas compressor
Refrigeration
Naphtha
HCRK(TC2C)
Figure 5 Comparison of specific energy to a naphtha cracker (HCRK = TC2C with hydrocracker)
chemicals. Although only complete crude to chemicals is dis- cussed here, partial transportation fuel production depend- ing upon the local market can also be considered. Extensive bench-scale, pilot-scale, and demo-scale feed preparation units (1 bbl/day) were operated over three years, and all relevant data were collected and modelled. A digital twin of the flow scheme was also constructed. One plant is currently under construction, which is expected to start up in 2026. There are other projects under various stages of design. TC2C not only reduces Capex but also reduces energy consumption and CO₂ emissions. The material bal - ance shown is only an example and will vary case-by-case basis to project specific objectives. Conclusion Ethylene is produced by thermally cracking hydrocarbons mixed with dilution steam in tubular reactors at high temper- atures in a short residence time. During this process, coke (a solid) deposits in the reactor and, hence, the cracking coils must be cleaned periodically using steam/air. The coking ten- dency of heavy molecules such as gasoil and vacuum gasoils is high, and the relative ethylene yield from these feeds is typically low compared with gaseous and naphtha feeds. Traditional feeds such as naphtha and gasoil to the cracker are obtained from crude through distillation in a refinery. These are made to specifications to meet the fuel stand - ards. In this transcript, crude is cracked to produce ethylene bypassing the refinery. In TC2C technology, all crude mole - cules ranging from naphtha to residue are processed to pro- duce light olefins. Detailed analysis and understanding of the crude characterisation have resulted in better catalyst and reactor systems to upgrade the crude for olefin production. Coke precursors that shorten the heater run length are reduced significantly with better characterisation and exper - imental techniques of crude characterisation. In the scheme proposed, in addition to the standard C 2 to C 6 -C 8 NA recy- cles, pyrolysis gasoil and fuel oil produced in the ethylene plant are sent to the TC2C crude conditioning section, where they are upgraded to meet ethylene plant feed requirements. By doing this, the amount of crude required to meet the design ethylene production is significantly reduced. Only a small purge is taken out as valuable IMO-compliant VLSFO. For Arab Light crude with hydroprocessing, total high-value chemicals are increased to >75%, much higher than that Figure 6 Relative capacity factors for major ethylene plant recovery section
reference naphtha cracker. In addition, major capacity factors are shown in Figure 6 relative to the naphtha cracker. Capacity factor represents the quantity of feed with that quality relative to reference feed cracking. These are based on simplified mass transfer models and sometimes based on two-component distillation models. Most of the unit capacity can be accurately predicted within +/-2%; hence, it is a standard design tool for preliminary design. Most sec- tions have less than 5% over the reference plant except the charge gas compression and quench section. Naphtha feeds have higher ultimate ethylene yields than crude. Generally, crude and in this case, Arab Light crude, has high residue, reducing the ultimate yield. However, as shown in Table 2, crude conditioning (hydroprocessing) has significantly improved the yields. The specific energy is one of the key performance parame - ters of the ethylene plant. It is defined as the energy required to produce per unit weight of ethylene after accounting for energy generated in the plant. Industry-standard energy equivalents are used for the import/export of steam, fuel, and electricity. Cooling water is another parameter. After accounting for all credits and debits, the energy to produce per unit of ethylene is calculated as specific energy. The lowest one is desirable. In the industry, pure ethane cracking has the lowest spe- cific energy value (~3,000 kcal/kg C₂H₄). In this exercise, no additional schemes are considered; hence, direct comparison with the reference plant gives a good indication of energy consumption for crude to chemicals. In the traditional way, a refinery is used to produce feeds (naphtha and gasoil) for the olefin plant. The refinery contributes additional Capex and energy. Therefore, for a proper comparison, the additional Capex and energy must be included for the naphtha plant in principle to account for the upfront naphtha production. That is based on some in-house data in Figure 6. Although the ethylene plant shows higher specific energy than the naphtha plant, including the refinery to produce that naph - tha, it clearly shows that TC2C is superior. When the specific energy is reduced, that also reduces the CO₂ emission. This clearly shows that a crude-to-chemicals configu - ration bypassing the refinery not only reduces Capex but also energy consumption. More than 10 patents have been granted and/or pending for different feed treatment/ethyl- ene plant configurations and technologies covering crude to
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PTQ Q1 2024
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