Nov-2022

Future refinery complexes built using an integrated approach

Minimise risks of project design changes at later stages using process digital twins during the design phase.

Amit Sarna and Sachin Srivastava
KBC

Article Summary

The refining industry is going through unprecedented times. Industry players are confronted by numerous challenges, including volatile crude prices, diminishing demand for transportation fuel, and stringent regulations to meet decarbonisation targets to produce cleaner fuels. At the same time, the growing economies in Asia will continue to propel the demand for petrochemicals. The future comprises a world of fuel refineries, refinery-integrated petrochemical complexes, and crude oil to chemicals. Through this energy transition, the latter two will undoubtedly be more resilient toward future demand and supply-side dynamics.

With the increasing complexity and size of investment for new capital projects, owners are seeking holistic technical and operational guidance to make better investment decisions and minimise costly rework with EPC (engineering, procurement, and construction). As shown in Figure 1, a conventional project execution approach requires information sharing amongst different advisors through various project phases. During each transition, there is often productivity and information loss, resulting in project scope and schedule overrun.

Initial study phases of capital projects are critical and, despite constituting a small portion of the total project costs, they can potentially reduce overall project costs by up to 20% and improve integrated complex margins by USD 2 to 3 per barrel of crude. The owner’s project team often has limited subject matter expertise and skills to cover these aspects. The concept of an owner’s technical advisor (OTA) for capital projects is increasingly becoming common to address such gaps with respect to technical, operational, and organisational experience.

With a large multi-disciplined project, the owner may enlist the assistance of third parties to review the project aim and objectives as well as basic engineering. A PMC may be engaged to help guide and manage the efforts of other contractors. In addition, licensors used for each specific technology are intertwined in the project. The interaction of the owner, PMC, and licensors require an understanding of the multiple aspects of the project. In this conventional approach, licensors work in silos where their focus gets restricted to the unit inside the battery limit.

Meanwhile, the PMC focuses on other interfaces and drives the schedule/cost optimisation. In this way, the focus on the overall complex-wide optimisation and integration is compromised. The OTA’s role is to provide the owner with an independent review and analysis to keep the project’s goals and objectives as the focal point. The OTA bridges the goals and objectives between different owner groups and appointed agencies (licensors, EPC, PMC) into a more efficient and streamlined process, as depicted in Figure 2.

This includes analysing critical concerns in the early stages of the project; reviewing licensor packages and optimising all licensed units; optimising utility consumption of all process units; solving issues outside of the licensor remit, such as various operation scenarios and turnaround issues to protect the owner’s objective. The OTA provides a holistic view and develops an integrated approach using subject matter expertise for various technologies supplemented with rigorous simulation modeling tools. Additionally, the OTA integrates into the owner’s team, allowing seamless knowledge transfer to the owner’s project and operating teams for building long-term capabilities. The OTA’s critical insights run across unit and system boundaries to ensure proper integration at the different interfaces to minimise recycling work at later stages, which helps bring significant cost savings and schedule delays at later stages of the project.

As an OTA, KBC employs an integrated approach based on three pillars: subject matter expertise, proven methodologies, and robust tools, such as process digital twins. The KBC Petro-SIM process digital twin is a complex-wide rigorous simulation model that builds kinetic reactor models for all process units across the enterprise. A digital twin is useful across the asset’s entire lifecycle, as shown in Figure 3.

Ideally, it should be created during the initial study to evaluate the feasibility and process model of the asset. During the design and EPC phases, the digital twin is used and further developed to facilitate the most optimal design of the asset as well as training its operators. Furthermore, it can be used to optimise and predict maintenance during the bulk of a plant’s lifecycle, operation, and maintenance.

A complex-wide process digital twin is used for several key activities during the design stage of a project. Following are some key uses of a complex-wide digital twin during the project stage: 

Improved design definition
Traditionally, linear programming (LP) models have been used to derive key stream flows and quality information to determine the basis of process unit design. The limitation of this method often results in inaccurate feed definitions and other critical information. A rigorous complex-wide digital twin can close this gap and ensure a robust foundation for process design by providing better stream property definition for design.

Updating the LP model
The LP model at the feasibility stage typically marginalises the definition and is generally built with a fit-for-purpose approach using limited unit parameters in a sub-model representation. The same model can be upgraded with relevant parameters for each unit based on the selected licensor data. When the tuned digital twin model is calibrated using the licensor data, it can generate accurate LP vectors to predict the right response about feed quality or operating parameter changes.

The updated LP model can be used for various optimisation sensitivity studies related to feedstock selection and operational mode changes. By conducting these sensitivity studies, the owner can identify unit operating and blending constraints at the design stage and provide the required design cushion to process different operating scenarios and opportunity feeds.

Integrated complex optimisation
The potential from incremental improvement with increased conversion capabilities of a fuel refinery with added petrochemical integration is USD 1.5 to 2 per bbl of processed crude. The value gained from effective molecular management is significant. Figure 4 shows the typical feed preference and selection criteria for key refineries and petrochemical processes.
A rigorous complex-wide process digital twin enables effective molecular management at the design stage by providing detailed carbon number breakdowns from crude assays through blending and petrochemical units for the whole integrated complex. These enhanced capabilities allow site-wide optimisation opportunities to be identified across the integrated complex. Such opportunities can be easily implemented at the design stage and lead to improved project economics.

Steam and power system optimisation
Refineries and petrochemical facilities face increasing pressure from regulators to decarbonise their current and future facilities. KBC includes the complex-wide steam and power system optimisation with net zero vision (see Figure 5). Using this model with KBC’s proprietary Best Technology methodology for energy optimisation, a holistic analysis is performed to optimise the entire system and identify energy-saving opportunities for each process unit. Thus, the complex saves energy and enjoys higher cash margins. Additionally, improving energy efficiency is the most cost-effective way to mitigate CO2. Reducing CO2 emissions also reduces the capital investment required for carbon capture facilities.

Scenario analysis
Off-design cases, such as start-ups, ramp-up, feed and operating mode change, are often not evaluated as part of a complex design and may result in unforeseen challenges and delays during operation. Such delays can result in severe economic penalties. The complex-wide flowsheet can be used to analyse such scenarios to identify critical constraints and plan mitigation strategies in a timely manner.