Producers of biofuel often choose the acids with which they’re already familiar. Sometimes they choose certain acids for biofuel acid addition because they simply have them on hand. Working with the unfamiliar takes some work and can induce some nerves. Work will go into other fronts – finding lower-cost feedstocks and producing yield most efficiently. Yet when it comes to acids, producers of biofuel sometimes stick with a less than optimal choice.
When it comes to biofuel acid addition, each of the acids has advantages and drawbacks at different points in the process. When neutralizing biofuel, they each efficiently remove methylate catalysts and salts. They can each be used to neutralize glycerin and soap splitting in order to separate fatty acids. Let’s focus on additional work or concerns that they create.
Sulfuric acid: This has a high corrosive factor, which can wear parts out faster. Insoluble sulfates will require solids handling. The formation of these sulphates can make phase separation slow and less effective.
Citric acid: Scale formation is a concern here. This makes parts less efficient. The formation of insoluble citrates causes fouling. Over time, this makes your process slower and can interfere with the ratios you’re aiming for.
Phosphoric acid: Here, too, scale formation is a concern, creating the same problems that citric acid does.
Acetic acid: This isn’t particularly efficient in terms of phase separation. It’s also volatile. The odor also must be dealt with.
Phosphoric acid: Here, too, phase separation can be inefficient and slow.
Hydrochloric acid: While very effective, hydrochloric acid introduces considerable safety concerns. Fumes are a worry. Specialized equipment and monitoring can make it an expensive proposition. You also deal with the formation of insoluble salts, and you’re dealing with an acid that is more corrosive.
Whatever you use, there are advantages and disadvantages to it. There’s no right answer; it will be different for each situation and set-up. Costs vary, as do the costs of supporting equipment.
One of the most efficient things you can do is invest in the best corrosion resistant lined static mixers that are available. These broaden the range of what you can use. Telfon and Kynar Lined Static Mixers are ideal when conducting acid addition for biofuels.