Part 1, Hydrocarbon Processing (Int'l Ed) Clean Fuels Technology: A Special Report.
Until the late 1960’s and early 1970, diesel fuel supplied in North America was usually classified as “above average” quality. These fuels were produced by a “straight-run” distillation process with little or no refinery-cracked components in the distillate stream. Subsequently, due to shrinking availability of high quality crude oils, the overall diesel fuel quality world- wide has shown decreasing tendencies. Since crude oil reserves are being consumed at an ever-increasing rate, a continued downward trend seems inevitable.
For oil refiners, extra processing and blending is a practical, though not always easy, option for improving some fuel properties; however, it entails compromises. For example, ignition quality can be improved by including more paraffin's, but this inclusion negatively impacts the required low-temperature operability properties. Another possibility is adding aromatics to increase the fuel’s calorific value, but aromatics generally burn poorly and tend to cause smoking. Due to these and other types of diametrical trade-offs, the scope of distillate processing and fuels blending at the refinery is often very limited. Therefore, fuel additives are rapidly becoming the only alternative for obtaining the superior quality necessary in fuel termed as “Premium Diesel Fuel”
Premium Diesel Fuel Additives
Additives targeted expressly to compliment certain fuel specifications are often an easier and much more cost-efficient means to enhance fuel quality without the negative of fuel processing and finished product blending. Premium Diesel Fuel Additive chemicals are supplied by various selling entities in North America. Although, the inherent quality of a fuel may negate the need to add all of the following chemical components, the specific parameters and how each might impart added value to the finished fuel must be seriously considered before the fuel can be marketed as “Premium”:
Detergents, Deposit Modifiers, Insoluble Dispersants, Cetane Improvers, Corrosion & Rust Modifiers, Metal Deactivators, Sludge Retardants, and De-Emulsifiers.
CHEMICAL COMPOUNDS AND PURPOSES
(diesel fuel additive components and their reasons for inclusion in formula)
Anti-Oxidants Stabilize the fuel and prevent Particulate formations
Anti-Rust Agents Reduce from oxidation in tank and fuel system
Cetane Improvers Raise Cetane to improve starting
Corrosion Inhibitors Stop Oxidation/Acid attack in fuel system
De-emulsifiers Anti-Moisture agent to break fuel and water emulsions
Deposit Modifiers Minimum non-combustion and fuel deposits
Detergents Clean fuel system components and insure
Dispersants Break up fuel insolubles and improve filterability
Metal Deactivators Counteract catylitic oxidation effects on fuel and
Pour Point Depressants Lower pour flow temperature of fuel
Wax Modifiers Reduce wax crystal size to improve fuel filterability
Each of these performance additives may be added separately to the base distillate fuel or they may be compounded into a comprehensive chemical package formulated specifically at the chemical supplier’s recommended dosage levels for making Premium Diesel Fuels. For the current low-sulfur #2D fuels (0.05% wt.) and future extremely low-sulfur (0.005% wt.), a compatible Lubricity Additive is also a necessity.
Winter poses additional fuel flowability and operational problems. Cloud Point, Pour Point, and Cold-Filter Plug Point (CFPP) Reducers are common fuel additives that should be added to premium quality diesel fuels to protect the purchaser and insure proper cold-temperature properties in the Premium Diesel Fuel.
The incorporation of the proper amounts of these chemical additives in the base diesel fuels will guarantee optimum performance and dependability at the most economical price.
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