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CRUDE BLENDING/TREATING/DESALTING, AND ISOMERIZATION
Publication date:1Q 2010
The 1Q 2010 issue of the Review features updates on market/technology trends and opportunities, state-of-the-art technology offerings, discussions on plant operations and practices, and a look into research and development work in the areas of Crude Blending, Treating, and Desalting and Isomerization.
As crude quality changes and worldwide refining demand grows, treating and desalting crude before it enters the crude distillation unit (CDU) will become a pivotal step to ensure efficient downstream operation and prolonged equipment life. Without proper treating and desalting, corrosion, catalyst poisoning, and fouling can become major concerns for the refinery. Additionally, the increasing presence of opportunity crudes makes a focus on crude compatibility issues a must when blending. Opportunity crudes may offer a large discount in crude cost, but due to the increased prevalence of asphaltene compatibility issues crude blends must be carefully analyzed to prevent major fouling episodes.
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 worldwide increase in crude processing capacity, coupled with the diversification of crude sources (and in some cases a degradation of crude quality) has led to an increased focus on crude blending, treating, and desalting technologies. Specifically, an increase in the processing of heavier and/or high-acid crudes with increasing quantities of contaminants (e.g., calcium) from Canada, South/Latin America, and Africa is occurring throughout the world. Also, crude capacity expansion in developing nations (e.g., India, China) is outpacing the decline in processing seen in Western Europe and North America resulting in an overall increase in refining capacity.
Overall, crude capacity expansion is seen in many regions throughout the world, and even in those countries in which crude capacity is contracting, a trend toward crude diversification can be seen. More detailed information in terms of transportation fuel supply and demand; capacity additions; crude variability and diversification; and technology competition/development are discussed as part of the Market/Technology Trends and Opportunities section in this issue of the Review. Furthermore, the section covering Crude Blending, Treating, and Desalting technology features new catalysts, processes, and topics including:
C4 isomerization provides a suitable feedstock for the alkylation process. C5-C6 isomerization, also known as light naphtha isomerization, aims to increase the octane number of light naphtha streams while also helping refiners manage benzene and open naphthenic rings. The process is capable of raising the octane number of the C5-C6 cut by as much as 25 points for blending into the gasoline pool, where isomerate accounts for 3-4% of the total pool. With the Mobile Source Air Toxics (MSAT) Phase 2 regulation on benzene being lowered to 0.62 vol% in the US beginning on Jan. 1, 2011, C5-C6 isomerization will become even more integral to helping US refiners manage benzene in the gasoline pool.
The main factors affecting the future of isomerization technology include a decrease in demand for gasoline coupled with growing dieselization around the globe, a continued rise in vehicle fuel efficiency, and increased ethanol blending into the gasoline pool. Environmental factors, specifically, lower benzene content in gasoline and lower RVP limits, will also play a key role as refiners look to meet these new specifications without sacrificing product yield or quality.
As worldwide alkylation capacity continues to increase (up 91.6K b/d from Jan. 09 to Jan. 10) alkylation feedstock produced from a C4 isomerization unit will continue to be in demand. Isomerate produced from the C5-C6 isomerization unit faces a far more uncertain future with decreasing gasoline demand globally coupled with increased ethanol blending and tighter environmental regulations. The C5-C6 unit can be used to help reduce the amount of benzene in the gasoline pool through hydrogenation. However, the isomerization unit can only handle a small amount (max. 5 vol%) of benzene precursors in the feed. Another option for refiners is to route naphtha from the C5-C6 isomerization unit to a steam cracker to produce petrochemicals (i.e. ethylene and propylene). Cheaper feedstocks (natural gas) are now available in certain parts of the world (US) making naphtha a less attractive option for steam cracker feed. If gasoline margins continue to decline and natural gas remains at a discount to naphtha, refiners will need to adjust the operation of the C5-C6 isomerization unit to adapt to the changing market conditions or shut the unit down. Global isomerization capacity declined 2.22% in 2010 to 1.74MM b/d with decreases in overall isomerization capacity being seen in both the United States (22.9K b/d) and Canada (16.5K b/d).
The impact that supply, demand, and pricing for isomerization products (i.e., alkylation feedstock and isomerate) will have on the refined products market, and the future role for isomerization technology are further examined in the Market/Technology Trends & Opportunities sections. Additionally, state-of-the art technologies, process operations and considerations, and research developments are presented. New products and topics include:
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