Syed Mumtaz -
There is a renewed interest among existing and new planned refineries for the Solvent Deasphlating Process (SDA). The driving force, in my opinion, is to improve refining profitability by getting most from the Bottom-of–the Barrel and an interest in increasing the heavy oil content in the crude feed mix. SDA, as an intermediate building block of various residue processing configurations, offers an economical path forward towards realizing some of the benefits of residue conversion. In refineries with deep conversion units, like RFCCU and Resid Hydrocrackers. it allows either substitution of some existing feed-streams, or, if capacity is available, increase marginally the throughput by adding the De-asphalted Oil (DAO) and improve the overall profitability.
Among the various residue processing technologies, SDA stands out as an economical low-cost option or a stand-alone first step towards achieving the desired configuration of a zero fuel oil refinery. It is also not a new technology. It has evolved from initial use, decades earlier, in extracting Bright Stock lubricating oil base from vacuum residue using Propane as the solvent in a Rotating Disk type Extractor (RDC). It is also flexible in terms of controlling the yield and contaminants levels (metals, CCR, and sulfur) in the DAO through operating adjustments, has equipment (mixers/separators and strippers) whose operation is well understood by the refiners and the technology principles are based on conventional solvent extraction and solvent properties at or near critical conditions.
Some of the considerations that a refiner may want to consider when looking at this option is how to handle the precipitated asphaltenes and resins and potential implications of DAO components and contaminants in the downstream conversion units and associated utilities and infrastructure. As an example, DAO may include multi-ring aromatics, coke precursors and metals organo-metal compounds, power and steam requirements and management of potential incrementally higher loadings in emissions and waste streams. However, these issues, in my experience, aren’t insurmountable and usually, refiners find ways and mean to handle such situations.