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Distillation and separation technologies
Improve performance and minimise expenditure.
Shell Calming Section and Shell HiFi‡ trays offer a strong combination of capacity and efficiency; there have been more than 2,000 applications since the 1980s.
At present, the industry is focusing on revamping and debottlenecking existing units by making low-cost modifications and minimising capital expenditure with a view to securing short-term payback. Consequently, there is much emphasis on non-intrusive modifications such as replacing internals without modifying column width.
The Shell Group (“Shell”) has particular strengths in fluid science and technology: separation vapour–liquid relationships, flow regimes and phase mixing. Shell Global Solutions provides technical support in primary distillation, phase separation and membrane technology.
Our expertise has been developed from extensive operational experience within Shell in exploration and production, and in more than 40 refineries and gas and chemical plants across the world.
About the technology
The high-vacuum process lies at the core of the Shell Global Solutions offering. Our deep-flash, high-vacuum units help to maximise the recovery of distillate (waxy distillate or vacuum gas oil) from long residue. This fraction has beneficial properties as feedstock for a catalytic cracker or hydrocracker unit. A fraction suitable for the refinery diesel pool is also produced.
Shell Global Solutions’ technology enables operators to blend condensate with normal crude for running in their refineries or for processing in condensate splitters, which helps them meet the demand for premium fuels. When condensate is processed through a splitter, it produces around 50% naphtha and a large portion of diesel.
Shell ConSep trays have been applied in 10 distillation unit revamps. Shell HiFi trays have been used in more than 100 applications for super-fractionators and other olefin processes.
Figure 1: The Shell Global Solutions deep-flash, high-vacuum process.
In our deep-flash, high-vacuum process (Figure 1), the long-residue feed is preheated in a furnace to reach typical flash zone conditions of 410°C and 22 mbara. We produce a tailor-made design for each application in which opportunities for process optimisation and integration with other units are developed.
The proprietary downcomer layouts of the Shell Calming Section and Shell HiFi trays help to provide the largest possible capacities with the best efficiencies. These trays can be applied to high-performance crude distillation units and high-performance distillation sections for catalytic cracker and hydrocracker units.
Figure 2: The truncated downcomers in these trays are arranged for simultaneous maximisation of active area, weir length, flow path and distribution.
The ultra-low pressure drop of the empty spray sections in Shell Global Solutions’ deep-flash, high-vacuum process gives a lower flash zone pressure compared with pump-around sections that contain packing. Typically, this increases waxy distillate yield by 4% weight, based on the feed to the column. Shell Global Solutions’ technology can achieve separation with little or no packing.
Shell ConSep trays offer a 30–100% higher capacity than most other trays (Figure 2). A revamp with these trays can help refinery operators to increase throughput without making major changes to the plant.
Shell Calming Section and Shell HiFi tray technology can be used to increase existing plant capacity and have been found, through operating experience feedback, to have excellent reliability. If required, Shell Calming Section and Shell HiFi trays are available with enhanced jet-flood and downcomer capacity.
PetroChina has increased its processing capacity with the start-up of a new 10-Mt/y crude distillation train at Dalian Petrochemical refinery. The new unit has increased the total crude processing capacity at the refinery to 20.5 Mt/y to make it among the largest in China. The design incorporates Shell’s deep-flash technology process to help produce more valuable products and reduce short residue volumes. The crude distillation train is designed to be fully heat integrated and ranks among the most efficient in the world in terms of energy efficiency and carbon footprint.
The design features of our high-vacuum-unit furnace helped to prevent excessive cracking and can facilitate a five-year run length before decoking in certain applications. The application of empty spray sections lowers the structured packing volume substantially, which represents reduced capital expenditure and maintenance costs.
In one refinery, using Shell HiFi trays expanded the capacity of a fractionation plant by 40% without requiring any new distillation towers or extra energy input.
‡Shell ConSep and Shell HiFi are Shell trademarks.