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What technology and strategies can resolve the huge gaps between ethylene and propylene production in certain markets?

Apr-2024

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Francy Barrios, Axens, Francy.Barrios@axens.net

Ethylene and propylene are fundamental in the petrochemical industry and have a wide range of applications across numerous industries, such as packaging, automotive, construction, and textiles. The market for these chemicals is growing due to the global demand for plastics and expanding end-use industries. For this, it is important to solve the huge gaps between ethylene and propylene production in certain markets.

An increase in ethylene and propylene production can be reached by applying simple strategies to existing technologies in the industry. For instance, increasing the severity in FCC units and/or using specific catalyst technologies and additives like ZSM-5 zeolite with high selectivity to olefins provides the product flexibility required by market demand. Even investment in additional and new technologies can be evaluated to maximise olefins production, like the integration of FlexEne technology, which is an innovative combination of two well-proven technologies – FCC and oligomerisation – to expand the capabilities of the FCC process to maximise olefins production, especially propylene.

This flexibility is achieved by selective oligomerisation of light FCC alkenes (olefins) for recycle cracking in the FCC unit. Another important technology to be considered is High Severity Fluid Catalytic Cracking (HS-FCC), an excellent prospect for olefins maximisation. It is an evolution of the well-known FCC process to reach a considerably higher level of light olefins production, in particular propylene. This technology is, therefore, bridging the gap between the refining and petrochemicals industries.

Apr-2024
Hernando Salgado, BASF Refining Catalysts,

One strategy to adapt to changing market conditions, such as seasonal changes in ethylene and propylene demand, is having flexible process technologies that can adapt their product slate to the changing demand of both products. One of these process technologies is the always resilient work-horse of the refining industry (and becoming increasingly important to the petrochemical industry) – the fluid catalytic cracking (FCC) process. The FCC process is characterised by its inherent flexibility to manipulate severity, and therefore, it can have the flexibility to shift between types of light olefins produced.

This is particularly true for FCC units specially designed to maximise light olefins – these can operate at very high severity (with reactor outlet temperatures higher than 540°C/1,000°F) and are equipped with special hardware, such as an additional riser to crack naphtha recycles or other light streams, and/or special riser terminations to maximise these secondary cracking reactions. Also, some units are designed to crack naphtha streams exclusively instead of conventional vacuum gasoil (VGO) or resid stock. These specialised FCC designs combined with the appropriate FCC catalyst and additive systems are very effective in maximising a variety of light olefins products.

The presence of this kind of process unit in a refining or petrochemical complex can provide huge flexibility to play between propylene and ethylene production by changing operating conditions, particularly severity. In addition, the selection of a proper catalyst, such as BASF MPS, MPS-R, Fourte, Fourtune or Fourtitude, in combination with an olefins additive to crack naphtha range material, such as ZIP, will contribute to enhanced flexibility in the FCC unit, allowing adjustment to shifting demand for propylene and ethylene.

Apr-2024
Ujjal Mukherjee, Lummus Technology,

When there is an abundance of cheap gas such as ethane, producing ethylene from ethane is the most cost-effective production pathway. However, the product slate is severely tilted towards ethylene. Excess ethylene can be combined with 2-butene to produce propylene using metathesis, a low-cost energy-neutral process. Lummus’ olefins conversion technology is the most widely used route to convert ethylene to propylene to balance product slates in the most economic manner. When both ethane and propane are in abundance, we see a growing need for propane or propane/butane dehydrogenation technology to produce a very high yield of propylene. This approach has been adopted in the US, the Middle East, and even in China with imported propane from the US.

The other way to reduce ethylene and propylene production gaps is using mixed feed crackers designed to handle a wide range of feedstocks from ethane, liquefied petroleum gas (LPG), naphtha, gasoils, and conditioned crudes and condensates. Mixed feed steam crackers have specially designed furnaces that can handle a wide range of liquids while maintaining long heater run lengths. Mixed feed crackers are particularly useful in the crude-to-chemicals strategy being adopted in many regions of the world.

Apr-2024
Jeffery Nichols, HSB Solomon Associates,

The boom over the past 15 years in demand for olefinic derivatives, most notably polyolefin plastics, has ushered in a supply deficit in multiple markets, leaving producers scrambling to capitalise on incremental margins. While the introduction of new production lines has been realised, with multiple fleet operators executing major capital projects since 2010, existing facilities are examining their options for squeezing every possible pound from their units.

The keys to maximising olefin production from any facility – whether a new, world-scale complex or a vintage cracker, and regardless of feed or technology – fall into four foundational areas:
• Shrinking or eliminating losses
• Increasing yield
• Increasing capacity
• Sustaining high availability and minimising slowdowns and downtime.

As intuitive as these strategies for maximising production may seem, applying them in the real world may not be straightforward. In addition, they are likely to involve initial costs that hinge on the strategy or strategies adopted. Furthermore, no action exists in a vacuum. In some cases, improvement in one area will be complemented by positive results in another, but sometimes there are trade-offs.

Robust mechanical maintenance programmes, including sound predictive and preventive maintenance components, are critical to increasing unit availability. Higher availability, almost without fail, translates into reductions in losses within a particular plant. Operational risk analysis that takes into account a facility’s tolerance for approaching critical plant limits or constraints is another essential element. Key points to consider include excess utility capacity, redundancy in contaminant removal, and safe operating limits for major equipment such as compressors. Consider this: For a 1,500-kiloton-per-year facility with a 98.5% service factor, a four-day reliability event translates into a production impact of more than 15 kilotons of product. Solomon can assist plant operators in evaluating the critical balance between maintenance cost and reliability to improve long-term performance.

Some loss mitigation programmes are not focused specifically on increasing plant reliability. These include capital-intensive projects aimed at recovering flare gas, taking advantage of improved separation technologies (for example, tower internals), and purifying recycle/fuel gas (and thereby minimising olefin loss).

Frequent objectives such as improving plant yields or expanding capacity can involve everything from unit operational debottlenecking to incremental marginal yield shifts. Economic feasibility is a major factor in executing any programme in these areas. Recent technological advances in furnace coil design and metallurgy are having a significant positive impact on once-through yields, with the bonus of considerably extended run lengths. For furnace-limited plants, a 50% average run length increase could translate into an increase of 1-2% in annual furnace availability. Another option is adding furnace capacity, but this can be considerably more cost-intensive, at least initially.

Though attractive in principle, incorporating flexibility into a plant’s operation to take advantage of changes in demand or price disparities for ethylene, propylene, or another co-product may or may not be a practical pursuit. One must consider not only market demand but also supply-side factors. For plants equipped to handle multiple feed types, shifting to heavier feedstocks to increase propylene production is an intuitive response. Other options for increasing propylene production include the incorporation of metathesis units (at the expense of ethylene production) and propane dehydrogenation (PDH). The current focus on sustainability has also brought attention to methanol-to-olefins (MTO) technology, especially when integrated with blue hydrogen production from steam methane reforming and with processes for carbon capture, utilisation, and storage (CCUS).

The overriding takeaway is that there are numerous options available for any particular producer to consider when attempting to address deficiencies in olefins demand vs supply. However, regardless of the technology considered or the strategies employed, an intense focus on availability must be maintained to keep the unit running and running well. Solomon Advisors can assist plant operators in achieving best-in-class performance.

Apr-2024