Gasoline is composed of a mixture of different refinery process streams obtained from the FCC naphtha, catalytic reformate, alkylates and isomerate. Each of these components compose to the overall physical property that characteristic for gasoline. Physical properties of gasoline must comply with the required specification, according the regulations and standards that are mandatory in the countries of consumption.
Most properties are quit constant values trough out the whole year, except the Reid Vapor Pressure (RVP), which depends on the environmental temperature, and differs between summer and winter seasons. In the summer the RVP that is required for a car engine, is already achieved vapor pressure resulting from of partial pressure of each of the above gasoline component. However, in winter period, and cold climates, the volatility of these components is insufficient to provide the requested RVP.
Butane is a low valued product that is obtained from the distillation of crude oils.
This, in combination with its high vapor pressure makes butane extremely attractive to increase the RVP, especially in during the cold seasons. It is the target of each gasoline blender to maximize the amount of butane incorporated in the gasoline mixture, and by that to reduce the cost of the blend, and without affecting other physical properties, such as knock properties.
The platform to achieve this goal lies in on-line process analyzers that measure continuously multiple physical properties such as the RVP, RON and MON, preferably by one single analyzer, such as NIR process analyzers. The measured analytical data is processed to continuously calculate the ratio between butane and other gasoline components that will provide gasoline with the required specification.