Energy efficiency: project optimisation through proven tools and practices (ERTC)
The world’s refining sector is at a pivotal inflection point where operators must evolve to remain competitive following a challenging year.
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Net-zero targets have also brought on aggressive decarbonisation goals that require critical action to meet the fast-approaching deadlines. Refineries will want to maximise the use of existing assets while minimising capital expenditure (Capex) and operating expense (Opex). While there are multiple pathways to achieve these goals, we will focus on two: refinery repurposing and refinery optimisation.
We have already witnessed a few refineries in Europe take the path of repurposing facilities to produce biofuels. Fluor recently completed the front-end engineering design (FEED) and detailed engineering for a refinery project where the client wanted to repurpose their existing facility to produce renewable diesel and meet incentive eligibility for tax benefits. A tailored plan was made which supported the project’s highly accelerated schedule with safe construction and in alignment with the client’s economic model. It was a plan that struck the right balance between schedule reduction, quality requirements, and capital investment.
Developing quality deliverables that could be adapted for late changes was deemed the best approach, and this approach was supported by and founded on a highly collaborative execution model with attractive incentives to stimulate achieving goals. During execution, several challenges associated with fast-track execution were overcome by applying practical and smart approaches such as a system of mini model reviews for early construction work fronts, designing using in-house data (vendor data was late), overdesigning certain foundations and steel members to meet the ultra-fast schedule, and collaboratively working with the constructor to address late design changes in the field.
It cannot be highlighted enough that the way the Fluor team worked in harmony and partnership with the client and other stakeholders made the difference. This creative and highly collaborative approach helped achieve a 10-month FEED plus detailed engineering schedule – a six-month reduction from the base case – which will help the client to generate an internal rate of return of 20-30% for the project.
Energy efficiency optimisation reduces a facility’s required energy consumption, which mutually delivers decarbonisation benefits and provides an economic return.
One technique to improve energy efficiency is to enhance heat integration and optimise the design of heat recovery equipment. This technique can create a huge economic benefit to any operating company and greatly helps in reducing CO2 emissions. We will discuss this further in the following three examples:
Heat exchanger design optimisation
In this first example, Fluor takes a systematic, rigorous approach to understand the client’s existing assets and needs. By leveraging our technical expertise in process and electrical engineering, we can readily determine the best options for each project and facility.
The client’s original heat exchanger design was based on the traditional approach with high fouling factors and overdesign margins.
Fluor studied a fit-for-purpose solution to reduce the fouling tendency and increase the heat exchanger’s effectiveness. The “modern - no foul” design approach manipulates and adjusts key design parameters such as velocity and shear force, impingement rods, and tube wall temperature.
As shown in Table 1, reducing the surface area resulted in reduced Capex, while increasing the velocities in the shell and tube side resulted in higher equipment thermal efficiency. Additionally, the run time between cleaning cycles was increased, which ultimately reduced the fouling tendency. Although this activity comes at the expense of increased pressure drops, the loss in energy efficiency is well compensated and recovered by the improvement in thermal performance.
Exchanger composite heat curves
This second case shows the importance of heat integration studies and involves the revamp of an existing crude distillation column. The client wanted to increase the recovery of distillates by installing a new vacuum flasher to recover the vacuum gasoil (VGO) from the bottom stream off the crude column.
In the original design, the VGO stream was cooled using a steam generator. Fluor began looking at opportunities to recover this heat by integrating it with the crude preheat train. Using composite heat curves, the team was able to better understand the heat transfer system and improve the design.
By removing one low duty heat exchanger and installing a new VGO cooler, a higher furnace inlet temperature could be achieved while still saving 25 MW of furnace duty (see Figure 1). With a carbon tax of 50 $/t of CO2, the simple investment payback is three years.
Heat integration in a crude/vacuum unit
The third example showcases the results of a feasibility study that Fluor performed for a European refiner. The objective was to maximise throughput in the operating crude distillation unit (approximately 60% higher volumetric throughput) and the vacuum distillation unit (approximately 40% higher volumetric throughput) while improving VGO recovery at the expense of vacuum residue and without increasing scope in key equipment.
The goal was achieved by:
• Plotting detailed heat exchanger composite curves to identify gaps in heat integration
• Adding new, efficient heat exchangers to fill in those gaps
• Improving the vacuum on the vacuum distillation unit column
Adding the heat exchangers created a higher total pressure drop in the crude pre-heat train, which resulted in the need for revamped pumps. The figure above shows that the specific energy consumption of the crude distillation unit and the vacuum distillation unit decreased by 11%, which indicates lower energy consumption as well as reduced emissions in the fired heaters. This investment was recouped in less than two years.
Proven Tools and Practices
Fluor’s role in energy transition is to safely design, build and maintain projects that create a better, more sustainable world. Our experience in this space is extensive, with the world’s top minds and technologies as well as a passion for innovation. Using proven tools, Fluor can optimise a project or facility’s energy efficiency to meet economic and environmental needs.
For more information contact: Ana.Casablanca.Jimenez@fluor.com
This short article originally appeared in the 2021 ERTC Newspapers, produced by PTQ / DigitalRefining.
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