Shell Thermal Conversion Technologies

Comparison with other technologies

Comparison Shell Soaker Visbreaker Technology vs. Coil Visbreaking

The Shell Soaker Visbreaking Process is a low-temperature, long residence time cracking technique. It offers significant advantages over conventional heater coil cracking in operational flexibility, investment and operating cost.

The Shell Soaker Visbreaking process is a mature and proven technology. It is currently applied in over 80 units throughout the world, for a variety of feedstocks and in different configurations. The process produces a residue, which after final blending yields fuel oils that meet all commercial stability requirements.

The Shell Soaker Visbreaking process has proven to offer many benefits that have made it the leading Visbreaker technology in the world:

	Up to 15% Capital Investment Savings The major part of the thermal conversion takes place in the soaker drum. This soaker enables a lower temperature, leading to capital investment savings of up to 15% or even more, when compared to conventional coil visbreakers. The lower temperature downstream the heater results in a smaller heater, and smaller heat exchange equipment.
	Up to 30% Fuel Savings The lower heater outlet temperature results in a fuel saving of up to 30% compared to conventional coil visbreakers. Due to the lower heater outlet temperature, also less waste-heat steam is generated. Typically, refineries have little demand for low-level steam. Therefore, the value of low-level steam is not very favorable under these conditions. Overall, economics are best when fuel consumption is small, and the amount of steam generation is minimal
	Longer Run-lengths Lower temperatures mean lower heater tube wall temperatures. This results in reduced coking, extended tube life and run lengths that are at least three times the run length of conventional visbreakers. Run lengths of more than a year in a Shell Soaker Visbreaker are common, compared to a run length of 3 to 6 months for a Coil type Visbreaker. The improved run length gives the Shell Soaker Visbreaker the same onstream factor as the upstream crude and Vacuum Distillation units. In contrast, the Coil Visbreaker is down for decoking for at least two times per year for five days. During these extra ten days of downtime each year, the vacuum residue has to be blended to fuel viscosity without visbreaking.

	Enhanced Operating Flexibility Soaker visbreakers have both the heater outlet temperature and the soaker pressure (i.e. reactor residence time) as variables for process control. This provides more flexibility in the operation of the visbreaker.
	High Turndown Ratio The enhanced operating flexibility ensures stable and controlled operation at 50% of the design capacity. ABB Lummus has licensed a Shell Soaker Visbreaker to a European client that was designed to run at a turndown of 44% of design capacity.
	Up to 2% Higher Gasoil Gain The configuration and the internals of the Shell Soaker ensure an optimal flow pattern. It minimizes back mixing and hence gives an optimal residence time distribution to get a higher conversion at constant residue stability. As a result of the application of these internals, the gasoil gain of the Shell Soaker Visbreaker process is 1-2% higher than that in a process using soakers without internals at the same residue stability.
	Well-proven Technology The large number of designs made for Shell Soaker Visbreaker units and the continuing feedback received in many operating units have built up vast experience on soaker cracking. It is this experience which provides a guarantee for both advanced designs and practical advice on operational matters.

Comparison with Solvent De-asphalting technologies

The most remarkable difference between Solvent Deasphalting technology and Shell Thermal Conversion technologies is that residue is converted to lighter products with Thermal Conversion technologies, whereas residue and lighter products are only separated by extraction with Solvent Deasphalting technologies. In an integrated refinery scheme, this results in lower investment costs.

The following example, where a comparison is given between routing vacuum residue to the Shell Deep Thermal Conversion process and to the Solvent Deasphalting process, illustrates the difference:

In the case of the Solvent De-asphalting process, deasphalted oil (DAO) is routed to a Hydrocracker, and solvent deasphalted pitch is routed to a Gasifier, Similarly, in the case of the Deep Thermal Conversion process, vacuum gasoil (VGO) is routed to a Hydrocracker, and liquid residue is routed to a Gasifier.

Because residue is upgraded to lighter products in the Deep Thermal Conversion process, the amount of vacuum gasoil is smaller than the amount of deasphalted oil, and the amount of liquid residue is smaller than the amount of solvent deasphalted pitch. As a result, the load to the Hydrocracker, and the load to the Gasifier is higher in the case of the Solvent De-asphalting process. For a new refinery, this results in a smaller Hydrocracker, and a smaller Gasifier. Given that the investment cost for the Solvent Deasphalting process is similar to that of a Shell Deep Thermal Conversion process, the total investment cost (including Gasifier, Hydrocracker) is lower for the option utilizing Shell Deep Thermal Conversion technology.

Comparison with Delayed Coking technologies

The most remarkable difference between Delayed Coking technology and Shell Thermal Conversion technology is that the heavy product from the Delayed Coking process is a solid product, while the heavy product from the Shell Thermal Conversion processes are liquid products. The Delayed Coking technology is very often selected for the intentional production of cokes. However, in cases where the residue outlet could be either a liquid or a solid product, like feed to a gasifier, or a boiler, Shell Deep Thermal Conversion technologies provide a good alternative.

Traditional Visbreaking technologies typically produce a commercial fuel oil product, that is either used in the own refinery, or exported. The newly developed Shell Deep Thermal Conversion technology produces a liquid pumpable residue product, that can be used in the own refinery, or that is routed to a Gasifier.

When the refiner has the option to select either a liquid or solid residue product, Shell Thermal Conversion technologies offer distinct advantages:

	The investment cost of the Shell Thermal Conversion technologies are 50% of less of the investment required for a Delayed Coker.
	Processing of the liquid residue product from Shell’s Thermal Conversion processes is easier than processing of a solid coke product. This results in better onstream time, lower maintenance costs, and lower operating costs for Shell Thermal Conversion processes.
	Shell’s Thermal Conversion processes yields more high-value products, resulting in a better refining margin.

The graph below shows the advantage of Shell’s Thermal Conversion technologies relative to other technologies.