A petrochemical plant in Israel uses on-line NIR (Near Infra Red) analysis to monitor its processes and provide real-time data for Advanced Control Software. A sketch of the plant is shown below. The NIR instrument is a PetroMetriX Beacon 2000 – II Analyzer. The Analyzer is located in control room and is connected to the 12 Field Units via telecommunication fiber optic cable. Field Units are installed at a distance of 150 – 450 meters. Measurement sequence is controlled by optical multiplexer. The system interfaces to a Honeywell TDC-300 using Modbus protocol and PLC.
The NIR analyzer monitors the streams at specific points where there is a need for a round-the-clock real time quantification.
The NIR analysis has a much faster response time and lower maintenance requirements than other instruments such as on-line gas chromatographs that have been traditionally used for these applications. Continuous data is provided by the analyzer and used for Advanced Process Control and by optimization software.
Table 1: Properties measured with the NIR instrument
|Field Unit #|
|p – Xylene||+||+||+||+||+||+||+||+||+||+||+|
|o – Xylene||+||+||+||+||+|
|2 – Methylpentane||+|
|3 – Methylpentane||+|
|n – Hexane||+||+|