With the consistent changes to the crude supply being processed across the globe, refiners are facing new challenges to ensure the safe and reliable operation of their entire facility. Crudes that are considered opportunistic due to their low cost are highly desired for refiners, but without proper treatment these crudes can severely damage downstream units and equipment. Furthermore, with the large variety of crude available, refiners are seeking the ideal blends of various crudes to economically optimize their refineries while resisting solid and salt accumulation, corrosion and fouling to essential equipment (due mainly to acidic compounds and asphaltene deposition). Whether it is heavy, high TAN crudes or blends of various crude sources, these feedstocks require treatment prior to reaching the CDU to keep operations smooth throughout processing. This is where pretreatment methods such as desalting and the use of chemical additives play a major role.
Preparing crude for the CDU mainly involves electrostatic desalting, which removes water and water-soluble salts. This process is also supported by additional techniques including the upstream removal of hydrogen sulfide by the addition of so-called "H2S scavengers," metal-removal additives, asphaltene dispersants, base addition to reduce naphthenic acid content of high-acid crudes (HACs), solids filtration, and chemical demulsifiers. Improved crude blending operations upstream of the desalter may help alleviate some of the difficulties associated with these preparation steps, and at the very least, a more thorough understanding of the crude feedstock slate will be beneficial for optimizing crude treating and desalting activities.
The ability to predict crude blend properties has proven to be the most efficient means of preventing damage to refining equipment, as refiners can determine which ratios offer the ideal properties for their refinery, or they can optimize the crude pretreatment process to combat the expected issues. This involves the use of both software-related solutions and testing/analysis of crude samples. Both approaches have seen new developments in recent years, and can be used together to optimize a blend for a particular refinery. There are a growing number of chemical products available to assist refiners with overcoming desalting problems. Chemical companies market a range of emulsion breakers tailored for desalter operations as well as extensive chemical treatment packages to aid in metals removal; inhibit corrosion, fouling, and scaling; prevent foaming; and remove sulfur. A number of chemical companies also provide reverse emulsion breakers to treat oily brine effluent upstream of the wastewater treatment plant. Corrosion control technologies that include monitoring and predictive technique are also available to be used when processing high-acid crudes. The crude blending, treating, and desalting also features the latest trends and technology offerings, including:
- Updated market information on crude quality and diversity of crude oil properties that directly impact the blending, desalting, and pretreatment of crude at refineries;
- ABB's Advanced Blend Control (ABC) package and Control IT Regulatory Blend Control (RBC);
- Haverly Systems's Crude Assay Management System (H/CAMS) and Crude Oil Management and Evaluation Tool (H/COMET);
- Modcon-Systems software for both blend optimization and analysis of oil properties;
- Princeps Compass software for crude oil blending and scheduling;
- Cameron's JetMix with power mixers for complex blends that may include opportunity crudes;
- Baker Hughes's Field ASIT (asphaltene stability index test) services and chemical additives for pretreatment;
- GE's Turbiscan technology for stability analysis and variety of chemical additives to improve desalting;
- Intertek's two‐stage electrical (AC) desalter;
- Alfa Laval's Compabloc high-pressure spiral heat exchanger;
- Emerson's Rosemount Guided Wave Radar (GWR) for desalter control; and
- A discussion of the latest patent applications and research papers regarding crude blending, treating, and desalting technology, including crude oil scheduling when accounting for crude blends; methods to both measure and predict the properties of crude oil blends; control systems for inline crude blending that keep properties within defined specs; electrostatic desalting hardware and equipment; chemical additives used as demulsifiers, metal removers, asphaltene inhibitors, and neutralizers; simulation and control methods; and more.