Middle distillates also known as Diesel Fuels are typically produced through a refining and distillation process from crude petroleum oils. The refining process separates the crude oil into mixture of its constituents i.e. paraffinic, aromatic & olefinic hydrocarbons, which are on the heavy end of the crude oil barrel.
Cold weather presents unique challenges for diesel operations. As the temperature drops below its cloud point, the normal paraffins in the C10 to C25 range present in the fuel start to come out of the solution as wax crystals. These wax crystals are about 50-250 microns in diameter. These large platelet crystals have a strong affinity for each other & readily interlock to form longer crystal agglomerates. As the temperature continues to drop, more wax will come out of the solution forming bigger interlocking structures & ultimately prevent the fuel from flowing.
In diesel vehicle fuel systems the presence of such long interlocked structures also causes operational difficulties, as crystal agglomerates quickly plug fuel lines & fuel filters. If the temperature is sufficiently low to crystallize a lot of wax, the engine would simply stop through fuel starvation.
Wax, however, is an important component in diesel, because it gives the fuel higher cetane value. Therefore, increasing the aromatics component in the fuel composition by blending lighter, kerosene type components would not be the best solution, as it would increase cost & lower its cetane value & fuel lubricity. Besides, such blends demand higher price when sold for use in aviation fuel.
CRISTOL flow improver solutions have enabled fuels to operate efficiently at temperatures below their cloud point. These additives are cost-effective solutions to ensure smooth flow of the fuel and prevent fuel filter problems caused by separated paraffins. The function of these additives is to interact with wax crystals, modify their growth, reduce their shape & size, prevent them to form agglomerates & also reduce the temperature at which they crystallize.
These additives are also known as Anti-gel additives, anti-freeze additives, pour point depressants, cold flow improvers, diesel operability additives, CFPP additives, LTFT additives, cloud point depressants, wax modifiers, wax, inhibitors etc.
The low temperature operability of diesel fuel is commonly characterized by the cloud point (CP), cloud filter plugging point (CFPP), Low temperature filterability test (LTFT) and Pour Point (PP).