Gregory Shahnovsky, Tal Cohen
Modcon Systems Ltd.
1 Bornshtein str., South Akko Ind. Park, Akko Israel


KEYWORDS
Process Analyzer, Validation, Spectrometry, NIR, NMR, Modeling, ASTM, ATEX

 

ABSTRACT
Petroleum process analyzers based on standard ASTM methods are not dependent on crude quality and other factors, but their response time is longer and maintenance is expensive. Nearinfrared (NIR) spectroscopy requires close attention to the modeling efforts, but an innovative solution discussed in this paper enables automatic model correction. Nuclear magnetic resonance (NMR) technology does not have the continual model maintenance issue and the main advantage of this technology is the linear spectral response which enables models to be extrapolated accurately. Application of all three technologies are presented and discussed to reach the optimize performance, accuracy and availability in petroleum process analysis.

 

INTRODUCTION
The objective of a modern process plant is manufacturing the high value and on-specification products at optimal cost and minimal environmental burden. Therefore on-line qualitative and quantitative measurements of physical properties and chemical composition are indisputable requirements. Successes that can be attributed to the use of process analyzers include reduced cost of production, decreased product giveaway, operating manpower and energy conservation.

 

NIR PROCESS ANALYZER TECHNOLOGY
Much has been written on the subject of NIR and Mid-IR spectroscopy which requires close attention to the modeling efforts. Over the past 15 years repeated attempts have been made to validate these on-line systems. The conclusion is that the systems validate when close attention is paid to the modeling effort. Continuous model updates are required after each crude slate change (the analyzer is not available until the new gasoline has been produced and placed in the model). The project will fail and the analyzer will never be validated if on-site expertise is not continuously available.


NIR analyzers are usually simple to install, very reliable and requires minimum maintenance. However, this technique is not linear and not all components in the sample are clearly resolved, so that any change in stream composition or process conditions requires model updating. The new innovation represents NIR Analyzer located in the control room and connected via telecommunication fiber optics to the field units installed as needed in the process or on blending collectors.


This technology enables the facility to connect of up to 15 process stream sensors which uses no electricity and contains no moving parts, to a single main analyzer situated in the control room. The special software installed on the analyzer compares analyzer readings with the laboratory results and enables the automatic correction of models if systematic disagreement between results is determined. The use of standard telecommunication fiber optics has resulted in multiple analyzers installations in petroleum industries worldwide, which did not require any manual model updates during the last five years.


The main drawback of NIR is not related to the hardware but to finding the resources (time and money) to build the models and maintaining the model robustness. For the most economical incentive applications, such as CDU and blending, a successful implementation of NIR can last up to 12 months. The bottleneck is not the NIR spectrometer accuracy or the limits on laboratory resources, but the fact that the model has to be robust. The model has to cover all possible variations of the product composition, which is constantly changing over time. Therefore, although very powerful, current NIR systems are not “plug and play” devices. If changing crude influences the analyzer's behavior, the refinery operators will lose their confidence in the
analyzer.

 

NMR PROCESS ANALYZER TECHNOLOGY
The NMR analyzer is quite different to the NIR for the modeling side of an analyzer project. It does not have the continual model maintenance issue caused by spectral changes seen with crude composition changes. An NMR analyzer provides a continuous flow-through, accurate chemical and physical analysis of multiple components in dense and opaque materials. It allows various process industries such as chemicals, biotechnology and food to explore new ways of increasing profits by controlling and optimizing the production process. The main advantage of this innovative process technology is linear spectral response across a broad range, which enables models to be extrapolated accurately. The

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