Cold Flow Improvers

Reduce the buildup of wax layers in vehicle and storage tanks with Dodiwax® wax anti-settling additive.

Clariant DODIWAX® Wax Anti-Settling Additive (WASA) is often used in combination with DODIFLOW® Middle Distillate Flow Improvers (MDFI) in order to improve operability significantly. Wax Anti-Settling Additives prevent crystals from agglomeration and settling of the paraffin crystals at the bottom of the fuel tank.

Using DODIWAX wax dispersants typically allows passage of modern operability tests such as sedimentation tests or LTFT. The combination of DODIWAX and DODIFLOW often lowers MDFI dosage requirements by creating a synergistic improvement of CFPP. The good solubility properties make wax dispersants suitable for terminal on top treatment and multi-component additive blends. The redissolving of paraffin crystals is also improved.

The long history of Clariant allows our experienced experts help you select and design a WASA and MDFI additive system to successfully treat a wide range of diesel fuel grades.

Typical WASA dosage rates lie within the range of 100-300 ppm and must be added at least 10°C above the CP temperature of the middle distillate.

The WASA keeps the paraffin crystals dispersed more effectively when diesel fuel is exposed to temperatures below the cloud point by:

• Further paraffin crystal size reduction
• Co-crystallization/nucleation mechanism
• Comb-Polymer anti-agglomeration effect
• Electrostatic repulsion

This helps improve vehicle operability and prevents a wax layer from developing on the vehicle tank bottom and will reduce filter cake buildup. The combination of DODIWAX and DODIFLOW also helps to prevent a wax layer forming at the bottom of diesel storage tanks.

The cloud point of a middle distillate is the temperature where upon cooling the first wax crystals appear. The Cloud Point is measured according to EN 23015/ASTM D2500.

Operability refers to the cold operating performance of a given fuel, meaning that a vehicle will operate satisfactorily down to a certain temperature until eventually the engine fails to run smoothly. When the engine will no longer run, due to extreme plugging of the fuel filter or even fuel solidification, the so called operability limit has been reached.

Vehicle field operability, as we might call it, is dependent on four important factors:

• Weather conditions (rate of cooling and lowest temperature reached)
• Vehicle construction (protected or exposed fuel lining/fuel filter)
• Diesel cold flow performance
• Length of time the vehicle is standing exposed to the cold conditions

Operability can best be tested at All Weather Chassis Dynamometer-test sites (AWCD) or alternatively in the less costly Rig-tests. In the Rig-test, just the cold flow critical parts of the engine (filter, injection pump, tank, fuel lining) are arranged in a cold box. The fuel to be tested is filled into the tank and the system cooled down repeatedly until the critical temperature is determined, whereupon filter blockage occurs. The injection pump is driven by an electric engine.

The development of Clariant flow improvers is based on profound understanding of fuel characteristics and the molecular interaction of specially designed polymers with the various types of paraffins found in diesel. Also, all aspects of a successful application, even under challenging conditions, play an important role. Clariant flow improvers efficiently interact with paraffins when they begin to drop out, thereby limiting crystal growth to an uncritical size and keeping them well dispersed within the fuel. The formation of interlocking platelet-like space-filling agglomerates that are prone to form sediments is prevented. The fuel, so treated, remains fluid and filterability to temperatures way below the original pour point temperature.

Flow improving additives do not alter the cloud point or the rate of precipitation of wax as the fuel is cooled down. The additive improves the low temperature operability just by changing physical properties of the fuel. The need for kerosene is reduced and this valuable component can be released to the jet fuel pool, creating additional value to this particular refinery stream.

Diesel fuels and heating oil contain lower molecular weight paraffins with carbon numbers up to approximately C30. Fuels within this range can differ significantly in cold flow properties. Diesel cuts coming from Coal to Liquid or Gas to Liquid procedures show higher pour points than diesel coming from crude distillation. Some high waxy crudes lead to diesel cuts with high pour points. Pipeline specifications and local requirements may require the use of PPDs for such diesel fuels. All these different middle distillates require PPD which are optimized to the individual paraffine distribution. Clariant is specialized to develop these tailored PPD, aiming to use PPD in most economic injection rates. Whatever your challenge, we have the expertise and experience to help you meet it. Our experts are on hand to develop innovative solutions just for you.

There are many different types of biodiesel on the market. Some contain fatty acid methyl esters made by trans-esterification of vegetable oils, cooking oils or animal fats with an alcohol producing fatty acid esters while others are hydrocarbon based, e.g. produced in process similar to Fischer-Tropsch. Biodiesel is mainly used in standard diesel engines as blend or as pure fuel. Blends of biodiesel and conventional hydrocarbon-based diesel are labeled with a B-factor in most cases. Pour Point Depressants are used for higher B-contents (e.g. bio content > 20%) or when handling the pure substances, e.g. before blending or when transporting or storing pure biodiesel. B100 (pure biodiesel) is also used in some engines but needs pour point and cloud point modifications. Clariant has developed specially designed biodiesel PPD’s, such as DODIFLOW 5603.