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Special Report: Modelling the future of ethylene

by Arabian Oil & Gas Staff on Dec 14, 2016

Luc Chantepy, Regional Sales Vice President, MENA, AspenTech.
Luc Chantepy, Regional Sales Vice President, MENA, AspenTech.

Olefins products are manufactured in highly energy intensive processes. In particular, ethylene plants are inherently complex, flexible processing systems that have the ability to adjust raw material availability in response to market demand.

Advanced technologies along with best practice methodologies used in olefins plants today can dramatically improve plant performance and result in best-in-class production, consistent product quality and swift return on investment. For the Middle Eastern manufacturers, optimising assets plant-wide will reinforce the region’s standing as a global leader in the petrochemicals industry.

The capacity for change

Ethylene is one of the most versatile and widely used petrochemicals in the world today. It is widely used in the production of goods, such as plastics or polymers, solvents, fibres for apparel, cosmetics, detergents, paints, packaging and many other products.

According to Gulf Petrochemicals and Chemicals Association (Dubai, UAE), Saudi Arabia accounts for 64% of the Gulf Cooperation Council states’ ethylene capacity of 24.1 million m.t./year. Saudi Arabia’s chemical producers are assessing the impact of the energy, feedstock and utility price hikes announced by the Saudi government in its state budget on 29th December 2015. The increases include 133% for ethane, 67% for methane, 40% for electricity and water, and 50% for gasoline. The government has also reduced the discount on LPG and naphtha feedstock from 28% to 20% and will track to the respective price in Japan. Sabic estimates that the price hikes will increase its annualised costs by about 5% before minority interests.

The petrochemicals game has clearly changed for the Middle East. Optimisation is no longer an option; it is now a commercial necessity. Having a comprehensive overview of strategic plant operations provides decision-makers with the opportunity to respond quickly to changes in product demand and feedstock availability. Adopting a model-based approach delivers a design-to-plan-to-execution methodology that allows companies to quickly scale their operations in accordance with the dynamics of business objectives and ensures production aligns to plan.

Energy, economics and efficiency form the bond to operational excellence. Using a full-lifecycle modelling environment, engineers can design plants through integrated processes and rigorous and scalable designs to predict physical plant behaviours like pressure, fluid flow and operating constraints. This approach can also be used for pressure safety-valve sizing and heat exchanger performance analysis.

The model for plant operations

The separation of ethylene from ethane is an expensive process both in capital and operating costs. The increasing production trend has been to build larger plant units and consequently the ethylene splitter (C2 splitter) has also increased in size. In the olefin business, reducing energy consumption is, therefore, an important incentive for companies. Advanced technology can help the Middle Eastern companies differentiate themselves to optimise process design, plant design and manufacturing production.

The design of an ethylene splitter is determined by several factors, including process requirements, economics and safety. Through robust models integrated with plant data, engineers can gain greater visibility into operational constraints. The process model drives value in plant operations and, by being detailed enough, can robustly predict real plant behaviour over an expected range of conditions linked to process data. The data itself is conditioned to smooth out measurement errors with an execution environment to run the model whether on-demand, scheduled or event-driven.

The C2 splitter separates ethylene as a high purity overhead product from ethane, which is combined with propane and recycled for cracking. The C2 splitter (ethylene and ethane) separation often requires large distillation columns (splitters), including a heat exchanger and compressor, and is a critical system in all ethylene plants, although it can be difficult to operate. This is because there is a limit on full system capability due to the lack of visibility on operating constraints. Also, longer plant disruptions can occur due to manual troubleshooting. Building a simulation to model the C2 splitter section using an advanced process simulation tool and matching variables with actual plant data means that engineers can predict the feed composition to the C2 splitter, tray efficiency and compressor efficiency. The use of a powerful rate-based distillation column modelling tools ensures more accurate simulations and maximises production over a wider range of operating conditions, whilst calculating the flooding factor and compressor loading based on actual plant data.


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