Refiners that sell diesel in regions that experience severe winters must ensure that it meets demanding cold flow specifications for cloud point, pour point and cold filter plugging point. This can be achieved in various ways. One approach is to add kerosene, but when kerosene commands a relatively high price, this can detract from the bottom line. Cold flow additives? That can be an ineffective and high-cost solution. Instead, many refiners are using catalytic dewaxing, which can often be implemented at a low cost for a large margin uplift.
In recent years, catalytic dewaxing, which changes the product properties in order to prevent the wax compounds from crystallising out in diesel at low temperatures and causing engine problems, has emerged as a powerful process for improving the cold flow properties of diesel and lubricating oils. More than 90 refineries worldwide apply or have applied this technique, and many more could enhance their margins by using it.
Whether kerosene blending, additivation or catalytic dewaxing offers the most profitable solution for your operation to produce winter diesel depends on your specific circumstances and constraints. There is no definitive answer, as it also depends on local factors such as the price of naphtha, gasoline and kerosene.
If the cold flow plugging or pour point is the blocking factor, additivation may be appropriate: these properties can improve significantly with small amounts of additives.
However, additivation cannot achieve large improvements in cloud point: it only improves the cloud point by 2–4°C. Kerosene blending is also of limited effectiveness here; it requires the addition of about 10% of kerosene to improve the cloud point by 1°C, though it also improves the pour point by about 3°C.
In general, catalytic dewaxing tends to be the most-economic solution if the cloud point needs improving by more than 5–7°C.
A low-cost, flexible solution
Catalytic dewaxing technology continues to improve. For example, Criterion Catalysts & Technologies (Criterion) has recently introduced more selective catalysts that enable deeper dewaxing, improved yields and longer cycle lengths, and Shell Global Solutions has improved the heat integration and reliability of the process.
Potentially, it is an extremely valuable opportunity for many refiners. Nevertheless, it may not be the most economic option for all refiners, so they should carefully evaluate the benefits against other cold flow improvement techniques.