Linear blending is a concept, often used in industries dealing with mixtures like petroleum or chemicals, where the final property of a blend is a direct, weighted average of the properties of its components. Simply put, when someone refers to a test or product blending linearly, they are basically saying 1 + 1 = 2. This means the property of the mixture behaves in a straightforward, additive manner.
Understanding the Concept
In linear blending, the assumption is that mixing two components with specific characteristics results in a blend where that characteristic is directly proportional to the amount of each component used. There are no unexpected interactions or non-linear effects that would cause the blended property to be higher or lower than predicted by a simple average.
Consider the example provided:
For example: you are asked to deliver a gasoline cargo meeting a 30 ppm max sulfur specification. Currently in inventory you have two tanks.
If you have Tank A with X ppm sulfur and Tank B with Y ppm sulfur, and sulfur blends linearly, the sulfur content of a blend consisting of 'a' parts of Tank A and 'b' parts of Tank B would be calculated directly:
- Sulfur in Blend = (a X + b Y) / (a + b)
This simple formula works because the sulfur blends linearly.
Linear vs. Non-Linear Blending
Not all properties of substances blend linearly. Some properties exhibit non-linear blending behavior, meaning the final property is not a simple weighted average.
| Feature | Linear Blending | Non-Linear Blending |
|---|---|---|
| Core Concept | 1 + 1 = 2 (Simple Additivity) | Result is not a simple weighted average |
| Calculation | Weighted average of component properties | Requires complex models or blend rules |
| Example Props | Sulfur (often), Density (often) | Octane Number, Vapor Pressure, Viscosity (can be) |
| Predictability | Highly predictable with simple math | Less predictable, requires specific blend data |
Practical Implications
In the context of the gasoline example:
- If sulfur blends linearly, a simple calculation is sufficient to determine the required proportions of your two tanks to meet the 30 ppm specification.
- If sulfur blended non-linearly (which is generally not the case for sulfur), you would need more complex blend rules or empirical data to determine the proportions.
Industries rely on understanding which properties blend linearly and which do not to perform accurate blending calculations and ensure final products meet strict quality specifications.
Conclusion
Linear blending simplifies the process of predicting the properties of a mixture based on its components, adhering to the straightforward principle that the whole is equal to the sum of its parts for that specific property.
