Integration of Visbreaking Units with Other Refinery Processes

Refining worldwide is undergoing a quickening transformation. To the degree that shrinking market demand for heavy fuel oil and more stringent environmental rules are pushing refiners to optimize their operations and extract every last drop of value out of each barrel of crude, the visbreaking unit has been an ever more attractive choice.

By mild thermal cracking, visbreaking reduces the viscosities of heavy residues and upgrades them to lighter, more desirable products. Used in combination with other refinery units such as FCC, hydrocracking, or delayed coking, economic and environmental benefits can be even more significant. The following presents the relevance of visbreaking in modern refineries, the operations best suited to employ it, and the key factors for success.

The Role of Visbreaking in Modern Refineries

Modern refineries are designed to maximize production from each crude oil category, and visbreaking is a primary solution for making this achievable. Visbreaking is, in effect, a controlled thermal cracking process that lowers the viscosity of vacuum residue to enhance fluidity and ease of further processing. Unlike heavier refitting technologies, the visbreaker system operates under milder conditions, which minimizes coke formation at the expense of lighter, salable products such as gas oil and naphtha.

One of the major uses of visbreaking today is to reduce the production of low-cost heavy fuel oil, a product that is losing world demand. Residue upgrading to light fractions enables refiners to increase their middle distillate yields and improve refinery margins without assuming the large fixed capital of delayed coking or hydrocracking.

In addition, visbreaking enhances refinery flexibility. Refiners can adjust severity levels based on crude quality and product demand, giving them more control over the output slate. Such flexibility to respond quickly is especially critical in fuels with varying fuel regulations and varying consumption trends. For the majority of plants, the visbreaking unit provides a cost-efficient trade-off between investment, process complexity, and product value recovery.

Key Refinery Processes That Benefit from Visbreaking Integration

Visbreaking is not a standalone asset; its value is only derived through its synergistic relationships with other principal refinery processes. Strategic integration matures it from a simple viscosity reducer to a key unit optimizing the efficiency and flexibility of the overall refinery process. The principal integration points are:

1. Crude and Vacuum Distillation Units: These are the sources of visbreaker’s feedstock. The visbreaking unit is integrated primarily to process the heavy, viscous bottoms—atmospheric residue or, more commonly, vacuum residue—from these units. Successful integration allows the direct routing of this hot feedstock, with optimum recovery of heat and total energy efficiency.

2. Delayed or Fluid Coking Units: Of all the strong synergies, one of the most prevalent is between visbreaking and coking. The visbreaking unit in this instance is a high-technology pre-treating step. By reducing viscosity and mild cracking of the largest molecules, visbreaking yields a more pumpable and tractable feed to the coker. This has the capability of providing increased coker capacity, reduced recycling of heavy streams, and potential quality improvements in coke.

3. Fluid Catalytic Cracking (FCC) Unit: The visbreaking unit is a supplemental feed provider to the FCCU. The visbreaker gasoil stream is produced during visbreaking and can be sent to the FCCU following appropriate hydrotreatment. This facilitates the increasing of the feedstock available for conversion into value-added transportation fuels such as diesel and gasoline, thus improving overall refinery yield.

4. Hydrotreating Units: The integration of hydrotreating is paramount for the product quality and stability. The unsaturated naphtha and gasoil product, as well as the sulfur containing, from the visbreaking unit, is unstable and cannot be directly blended into finished products. They can only be incorporated into the refinery hydrotreating network, to sulfonate olefins and remove sulfur, to be able to fulfill the minimum fuel specification requirements.

5. Sulfur Recovery Unit (SRU): The visbreaking unit, though, does produce a small but fairly significant amount of acid gas, such as H₂S, that needs to be captured and handled. This can be done by the amine gas treating and Sulfur Recovery Unit, which is integrated within the SRU. This is important for fulfilling the regulatory requirements, as it allows elemental sulfur to be sold or disposed of, as well as converted from its compounds.

6. The Fuel Oil Blending Pool: The main product of a visbreaking unit is a tar of stabilizing with much lower viscosity. This direct integration visbreaking unit with the fuel oil blending pool is fundamental. It drastically diminishes the volume of light distillate (diluent) which has appreciable value needed to market heavy fuel oil to table specifications and liberates those distillates for more profitable applications.

Advantages of Integrating a Visbreaking Unit in Your Refinery

Integrating a visbreaking unit with an existing refinery setup comes with many benefits, most of which are economically prudent.

1. The visbreaking unit remains one of the best economic optimization strategies. By converting heavy residues into gas oil and naphtha, refiners reduce the production of fuel oil, hence increasing profitability. The refinery does not have to spend on heavy delayed coking or hydrocracking to meet market demand to produce light and clean fuels.
2. A visbreaking unit provides operational flexibility, which remains a crucial advantage. The unit allows refiners to vary the processing intensity depending on the quality of crude and the products to be achieved. Balance is achieved since the refinery does not hold excess production of products that are not in high demand. Instead, the unit allows the refinery to respond to market and regulatory changes that may be aggressive.
3. In addition, integrating into the refinery visbreaking helps in meeting the necessary environmental stipulations. This results in reduced emitting of SOx, which comes from the burning of heavy fuel oils. By lowering emissions, a refinery can keep in stride with environmental rules such as IMO 2020 and the rest of the world’s sustainable goals.
4. A well-planned visbreaking unit can also improve ROI. Visbreaking ROI is simplified operationally throughout the Value Chain while still retaining the mid-capex structure. This ensures that refiners spend far less while garnering improved yield. Energy, product, and cost efficiencies get the visbreaking unit integrated further down the value chain.

Design Considerations for Successful Integration

Integrating a visbreaking unit in a refinery is a complex process that requires both careful engineering and planning for visbreaking performance and reliability.

• One important aspect is the compatibility of the unit. Different oils, which will be used as feedstock for the visbreaking process, will be different in viscosity, Vacuum resid, and sulphur will all affect the Viscosity of the Oil. Thus, different configurations will be optimal for the different units, such as a soak or coil visbreaking.
• Capacity planning is another essential factor. Integrating a visbreaking unit with downstream units such as FCC, hydrocracking, or delayed coking will eliminate bottlenecks and help plan for smooth flows of products. Incorporating the visbreaking unit capacity into the rest of the refinery is important to prevent bottlenecks.
• Safety and Operational reliability are the most important considerations. Incorporating robust control systems and proper heat integration and safety systems will relieve much of the Operational backup.
• Finally, attention to flexibility and maintainability allows the refinery to adjust to changing market demands, process different crudes, and optimize product slates over time. By addressing these design considerations, a visbreaking unit can seamlessly enhance refinery performance and maximize economic returns.

Summary

A visbreaking unit is a valuable addition to the refinery of today by converting heavy residues into light, higher-value products and enhancing operating flexibility and efficiency. Integration of visbreaking with FCC, hydrocracking, and delayed coking processes allows refiners to optimize yields, reduce fuel oil production, and comply with environmental regulations. By incorporating a well-engineered visbreaking unit, refineries can maximize profitability, address market demands, and achieve maximum value from every barrel of crude cost-effectively and in an environmentally friendly manner.

If your business also needs the inclusion of a visbreaking unit in your refinery, you can contact us for a customized solution!