PTQ Q2 2022 Issue

towers to supply only the energy required to promote the desired separation. Figure 3 presents a basic process flow with the concept of pro - gressive distillation. The separation processes are energy intensive, and optimisation of the internals in the distillation columns and separating vessels can minimise energy consumption, rep- resenting an attractive alternative to the revamp of processing units. The use of low-pressure drop internals and divided wall distillation col- umns is effective in this sense. Optimisation and design actions can offer good results, but it is nec - essary to ensure the reliability and availability of the refining hardware before taking such actions. One of the main issues of the energy sys - tem in a crude oil refinery is steam leaks and steam condensate recov - ery. Maximising steam condensate recovery and minimising steam leaks may seem obvious, but this is fundamental and sometimes over - looked. The following questions can be used in a diagnostic process to confirm these issues are well man - aged in the refinery: 1 Has a specific maintenance pro - gramme been established for steam traps? What is the review frequency of that evaluation programme? 2 How proactive has the refinery personnel been in managing and solving condensate and steam leaks? 3 What is the response of the refin - ery for managing compressed air system leaks? 4 What are the responses if insula - tion systems are sub-par? Another key moment to reach an optimised energy system in a crude oil refinery is the planned shut - down. The participation of process engineers in the planning steps dur- ing a turnaround of the processing units is fundamental to identifying and solving inefficiency points. It is also fundamental to understanding the scenario of the crude oil refin - ery during the turnaround; which processing units will stop? How can processing units that keep running during the turnaround be optimised? Environmental driving force More relevant than the profitability issues related to the energy man-

Hydrotreating feed

Flash vessel

Kerosene

Atmospheric distillation tower

Light ATM gasoil

Petrochemical naphtha

Heavy ATM gasoil

Preash tower 1

Postash tower

Preash tower 2

Light vacuum gasoil

Heated and desalted crude oil

Deep vacuum tower

Medium vacuum gasoil

Heat exchanger

Heavy gasoil

Fired heater

Vacuum residue

Figure 3 The concept of progressive distillation

emissions. Emissions released dur- ing the production and transport of crude oil (upstream emissions) amount to 12%, emissions gener- ated in refineries during the pro - cessing of oil and transport to the petrol pump total 8%, while the majority of emissions in the oil products value chain are gener-

agement of crude oil refineries is the management of GHG emissions. Figure 4 shows that the energy sec- tor is responsible for over 70% of the world’s GHG emissions, while the industrial sector is responsible for more than 24%. The oil value chain is responsible for a significant amount of these

Agriculture, forestry & land use 18.4%

Energy 73.2%

Figure 4 GHG emissions by sector 7

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