PTQ Q1 2024 Issue

Hydrogen manufacturing

Natural gas

Hydrogen

Light oil

Heat

Cooling

Steam cracker complex

Middle oil

Tailored separation

Tricle ow reactors

HOPS

Chemicals

Crude oil

Desalter

C9+

Low-value streams

Liquid circulation reactors

Pyrolysis oil

Crude conditioning section

Tricle ow reactors

VLSFO

Stripped sour water

Sour water

Lean amine

Rich amine

Stripped sour water unit

Amine regeneration unit

Sulphur recovery unit

Sulphur

Figure 4 TC2C flow scheme with liquid circulation reactor configuration. The total yield of chemicals ranges from 70 to more than 85 wt%, depending on the nature of the crude

The qualities of gasoil and vacuum gasoil are reasonable, but when cracked they produce a significant amount of fuel oil. The intent of a crude-to-chemicals project is to maximise chemicals production and, hence, the target was to mini- mise fuel oil. Hydroprocessing will upgrade the quality of the feeds. In the previous section, various cuts are obtained by vapourising the crude at a lower temperature by adding steam in the heavy oil processing system (HOPS) tower. Dilution steam is also required for thermal cracking to reduce hydrocarbon partial pressure to increase olefin yields and suppress coking. However, though a small quantity of saturated water in oil is not harmful to hydroprocessing cat- alysts, the levels required for thermal cracking are detrimen- tal to the catalyst. TC2C utilises a novel separation device and targeted hydroprocessing of fractions to provide the right amount of hydrogenation of feeds to the steam cracker reactor for maximum crude conversion. The simplified flow scheme is shown in Figure 4 . The importance of the desalter must be stressed at this time. Crude can come from different sources and different transport methods. This will contain some debris and salts. Ppm chloride levels cause havoc on material selection, requiring equipment to be alloyed up for resistance against chloride corrosion. Ppm sodium levels are sufficient to cause significant damage to catalysts, especially when the target run lengths exceed five years. Hence, the investment in desalters and feed filter systems is worthwhile and justified. The desalted crude goes to the first-stage HOPS, where naphtha mixed with steam is separated for the steam cracker. The material heavier than naphtha in the crude enters the tailored separation section. The fixed bed hydro - cracking reactor and liquid circulation reactor technologies previously explained are used to condition the feed. Typically,

an ethylene plant turnaround exceeds five years and, hence, all sections are also designed to last that period. An important TC2C feature is the ability to utilise the pyrol- ysis oil generated by the steam cracker in the liquid circulation reaction section. The addition of pyrolysis oil with the feed to the liquid circulation reaction section where asphaltene conversion occurs permits higher conversion of asphaltenes while maintaining product stability. During research and development, several types of pyrolysis oils were tested, including very high proportions of pyrolysis oil in the feed mix, to ensure the concept was robust. Extensive pilot plant results show that at low catalyst con- sumption, heavy boiling material can be converted easily to high-quality feeds for olefins production. This is one of the major benefits of the integrated steam cracker/LC reactor system. Low-value fuel oil is upgraded to high-value chemi - cals. More than 90% of feed conversions can be achieved at very low catalyst consumption in the liquid circulation reac- tor platform. Very low sediments were also observed, improving the operation of downstream units. Many CLG-designed inte - grated LC-Fining/hydrocracker plants have been in opera - tion over the last 25 years for producing jet and diesel quality fuels and some as feed to ethylene plants. When certain cat- alysts and operating conditions are used in the hydrocracker, certain types of species are produced in the hydrocracker which are not present in the feed. A lot of research was conducted to limit the high DBE HPNA from reaching the cracker so there would be no highly condensed molecules such as coronenes (six ring) and ova- lenes (10 ring) in the steam cracker feed. These molecules deposit as solids, fouling the transfer line exchanger. 4 The resulting run length could be a few hours instead of a few

PTQ Q1 2024