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Blending biodiesel with diesel fuel isn't a picnic in the winter

Posted by: Erik Bjornstad

The practice of mixing up to 5% biodiesel into diesel fuel without the necessity of labeling it as such is one of the reasons biodiesel use is higher than ever.  A lot of facilities are buying biodiesel and mixing it themselves on site. But while biodiesel has some wonderful qualities, storing it and using it on medium and large scales can pose a problem in the colder months.  So we put together some comments to help guide you through.

blend biodiesel with dieselIf you don’t mix it yourself

We said a lot of companies are getting it on bulk, putting it in dedicated tanks and mixing it with their stored diesel fuel.  That’s not to say everyone’s doing that. For those who buy it pre-mixed, you want to make sure the supplier knows what your cold weather fuel operability specifications are.  They have options to meet those goals (cold flow fuel treatment, kerosene blending) but they have to know what your expectations are.

Blending It Into Your System

Blending biodiesel with diesel to make a desired Bxx blend involves a little more consideration than just dumping a quantity of one on top of the other.

Should you do in-line or splash blending? Heat is important.

In-line blending (also called wild stream) is a good way for optimal homogenization, but requires that the biodiesel be kept at least 10 degrees (F) warmer than its cloud point. And for some tropical bio feedstocks that are really bad in the cold (like palm oil), the recommendation is 20 degrees warmer.  If you remember to do this, it makes it much easier to successfully blend the biodiesel into the diesel base.

Not everyone can do in-line blending, though. Splash blending is their only option. Here, it’s doubly important that the biodiesel be warm enough. Remember that you’ll be putting cold-sensitive biodiesel into a cold tank or tanker truck. If the biodiesel isn’t warm enough, it will flash freeze before you can ever complete the mixing process. It’s not unusual for blenders to warm the biodiesel past 100 degrees F.  The warm you get it, the more successful you’ll be at blending.

Lastly, when you’re done, be sure to test your final blend for operability. And once it is blended, you still have to consider how to keep the blend from unduly freezing in the winter.  The general rule is that putting 20% biodiesel into diesel will make that blend gel at a temperature 10 degrees higher than before. Not good.  To combat this, you can use a combination of cold flow fuel treatment s and also kerosene blending.  Kerosene is most effective when the expected temperatures approach -30 to -40 degrees.

You may be interested in these posts:

Storing Diesel and Biodiesel Cheatsheet Bundle

Bio Cold Flow Improver

This post was published on December 17, 2015 and was updated on December 17, 2015.

Topics: Biodiesel, winter