The function principle of diesel coagulant(1)

Diesel fuel coagulant, also known as diesel fuel low-temperature fluidity improver or diesel fuel anti-wax settling agent, is a common additive in diesel fuel production. Diesel fuel coagulant on the refinery to increase the production of diesel fuel, improve the flexibility of production and diesel, steam ratio, improve economic efficiency has an obvious role. For the storage and transportation of diesel fuel and users, due to the application of coagulant, can significantly improve its low temperature performance.

Freezing point and cold filtering point is an important indicator to characterize the performance of diesel fuel at low temperatures. The freezing point (SP) is the highest temperature at which diesel fuel loses its fluidity in low temperature environment; the cold filtering point (CFPP) can indicate the highest temperature at which diesel fuel can cause filter blockage when passing through the diesel engine oil supply system. 

For light diesel fuel, the cold filter point is more important than the freezing point index in actual use. This is because the cold filter point is directly related to the low temperature performance of diesel fuel, while the freezing point is mainly related to the storage and transportation of diesel fuel. Adding low concentration (below 1‰) of coagulant in diesel oil can greatly improve the low temperature fluidity of diesel oil, and the method of adding agent is flexible and simple. 

Due to the small amount added, it will not change the other performance indicators of diesel fuel, and at the same time, the unit production cost of diesel fuel is much lower than the cost invested in other methods or ways to reduce coagulation and filtration.

The reason why diesel oil solidifies at lower temperature is that diesel oil contains a certain amount of waxes (i.e. n-alkanes), which will gradually precipitate out and form wax crystals when the temperature is lowered. As the temperature decreases further, the wax crystals will grow rapidly and firstly form planar crystals, these crystals are linked with each other to form a three-dimensional mesh structure, in which the oil is wrapped, so that the oil loses its fluidity and appears to be solidified.

Usually the n-alkane content in diesel oil is about 15%~30%, when the diesel oil is cooled, as long as there is about 2% of n-alkane precipitation, it can make the diesel oil solidify, the amount of wax precipitation of diesel oil at a certain temperature depends on the type of crude oil, distillation range and the processing scheme and blending ratio of each distillate of the blended diesel oil.

When the diesel engine is working, the diesel fuel is sprayed into the cylinder through the coarse and fine filters, then through the high pressure pump and injector. When the temperature of diesel oil drops to the cold filter point temperature, the wax crystal formed will block the filter and affect the normal oil supply of the oil circuit, and then affect the normal work of the engine.