Question
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Considering the enormous amounts of thermal energy and stripping steam required for crude distillation unit (CDU) throughputs, are there any new crude oil processing schemes for reducing CDU operating costs?
Dec-2022
Answers
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Jagannadh Sripada, KBC (A Yokogawa Company), Jagannadh.Sripada@kbc.global
Due to the high-energy consumption of crude distillation units (CDU) and vacuum distillation units (VDU), energy reduction is essential to meet emission targets and reduce energy costs in the refining industry. Three key aspects of a new design or future revamp scenario(s) are as follows:
Configuration Recent developments in progressive crude distillation methodology make it a viable process to be considered during the design stage to potentially save utility and perhaps better yields. However, the initial Capex could be higher for such configurations, and the sensitivity of benefits on the type of crude should also be kept in mind.
Depending on location and pricing, refineries should evaluate their overhead vacuum configuration. Replacing the last stage of ejectors with liquid ring vacuum pump (LRVP) has been beneficial for refineries in the past, and the configuration is to be carefully evaluated and selected based on steam, cooling water and, electricity prices.
Heat integration Optimising heat recovery from the preheat train via a revamp could include utilising spiral and plate and frame heat exchangers at select locations, adding extra heat transfer surface area to existing heat exchangers, installing new exchangers, and more.
Process integration between CDU and VDU to save fuel, periodic re-evaluation of minimum approach temperature based on energy costs, and utilisation of pinch technology to identify opportunities should be beneficial to refineries. Monitoring heat exchanger fouling, online cleaning, and an optimised cleaning schedule will minimise fuel costs and emissions. Evaluating opportunities to utilise the product heat can include providing hot feed to downstream units or using that heat to preheat the crude at CDU.
Distillation column optimisation Reduce the operating pressure of the atmospheric column during winters to benefit from lower temperature cooling water. APC can be used to automate the minimisation of pressure to great effect.
The latest high efficiency and low DP trays and the replacement of tray sections with packings usually help refiners increase throughput, but small gains in energy can also be achieved via such modifications.
Dec-2022
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