Measurement and Testing Table I - Comparisons between NIR and NMR Technology Parameter Applicable streams to measure NIR/ FT-IR / RAMAN
Raw Crude Oil Blended Crude Oil Desalted Crude Oil Light Naphtha Heavy Naphtha Kerosene Light Gas Oil Heavy Gas Oil Atmospheric Residue Vacuum Gas Oil Vacuum Residue
Alkylation (name of the acid?) Refi nery applications
Crude Custody Transfer Crude Blending CDU (Partial) CDU (Full) FCCU
Delayed Coker Alkylation Unit Light Product Blending
Figure 2: Implementation of NIR/FT-IR and NMR Analysers in Crude Oil Distillation
implementation in refi ning and process industries.
OP-NMR technology can be applied to any process stream involving organic molecules, allowing for correlations between the physical properties of process feeds and product streams. It provides an effective means of making real-time adjustments to process conditions, which is essential for optimising process unit utilisation.
Physical properties of process streams result from the combined properties and concentrations of individual components. Optical methods like NIR/FT-IR/RAMAN spectrometry offer the advantage of measuring at distant locations via fi xed fi eld probes or fl ow cells connected by fi ber optics. However, their applicability is limited by the transparency of the process stream, and they rely on chemical composition “fi ngerprints” without molecular structure specifi city.
In contrast, NMR distinguishes between molecular structures and chemical bonds precisely, enabling quantitative and qualitative assessment of molecular structures with high certainty. Its linear response allows accurate correlation between spectral data and physical properties, even for compositions not included in the calibration curve of the chemometric model.
Optical spectrometric methods require chemometric models to encompass a wide range of expected compositions to enhance accuracy due to overlapping and weak spectral bands and a lack of linear spectral response. NMR’s linear response allows extrapolation for quantifying physical properties of compositions not included in the model.
Crude oils contain various hetero-atomic substances at different levels depending on their origin. These substances can partially distill alongside distillation products, impacting the accuracy of analytical results with optical methods like NIR/FT-IR. NMR spectrometry, as a fundamental method, is not affected by the presence of these hetero-atomic molecules and can specifi cally assess hydrocarbon molecules. This is crucial for its application in crude oil distillation, covering crude oil, naphtha, diesel, kerosene, heavy distillates, vacuum distillates, and bottom products.
Figure 2 illustrates the application of NMR process analysers in a crude distillation unit of a refi nery. Light distillates can be measured by NIR/FT-IR or OP-NMR analysers. Monitoring of kerosene and diesel can also be performed by both, but under the restrictions that process streams are transparent, and that crude switching is omitted. Otherwise, NMR is the method of preference. Heavy distillates, vacuum distillates and bottom product can only be monitored by NMR.
Full monitoring of all refi nery streams is essential to the most effi cient performance of the crude unit. However, temperature differences between distillate streams prevented previous generation of NMR analysers to switch between the distillate streams without losing accuracy. The enhanced temperature insulation between magnet and probe in the third generation eliminated these drawbacks.
Analysis of feed and product streams by the same analytical method and the same analyser is the preferred strategy to accurately correlate between physical properties of process
Modeling simplicity and robustness Low (non-linear response) Sample lag time
Immediate (Fiber optics, optical switching) Sample Conditioning complexity
Deployment complexity (civil work) Maintenance overhead
Higher (Water removal, higher temp sensitivity)
Lower (fi ber optics) Higher
streams. Boiling ranges of different distillates partially overlap. Effi cient and stringent adjustment of the temperature profi le in the distillation to optimise cut points between distillates increases its production capacity of the most required distillates. It enables the optimisation of its capacity towards the distillates that will have the highest profi t on the market.
Crude switching is a common practice in many refi neries. Implementation of NMR process analysers reduces the impact of the transition period, until optimised process conditions are restored.
Beside petroleum industries, chemical process industries can benefi t from OP-NMR process analysers. NMR technology can provide accurate information about the substances available in the process stream. As a molecular determining method, NMR distinguishes between and enables quantifi cation of raw materials, intermediates and fi nal products. It provides an effi cient tool for analyses of reaction proceedings and failure analyses in chemical processes. NMR spectra can be analysed by chemist throughout the entire production process.
Other applications of NMR analysers can be found in the pharmaceutical industries, the food industries, fermentation processes in biotechnology industries, in all other processes, where organic substances are available with NMR distinguishable chemical compositions.
Process NMR can be applied for at many locations within refi nery processes. Its ability to not be restricted to transparent streams provide an effected tool to continuously monitor the feed and product streams of refi nery units, especially those units where optical spectrometry methods fail.
In other process chemical industries, NMR technology can provide accurate information about the substances available in the process stream. As a molecular determining method, NMR enables quantifi cation of raw materials, intermediates and fi nal products.
The incorporation of NMR analyser in process stream monitoring prevents the production of border-line and off-spec materials and avoids the investment of time and money to upgrade these products.
Summary: Comparison between NIR and 3rd Generation NMR Technology
A comparison between the characteristics of NIR and third generation NMR technology is summarised in table I.
Lower
Higher, deployment specifi c (fl uids tubing) Lower
Conclusions
The successful application of on-line process analyses is dictated by its stability, its feasibility to provide reliable analytical results process streams and its capability to switch without any impact between different process streams.
Previously, its high sensitivity towards temperature fl uctuations, its lack of stability of the magnetic systems and its defi cient reliability harmed the reputation of NMR process analysers in refi neries and process industries. The conclusions of a thorough and all including failure analyses of fi rst and second generation on-line NMR process analysers were implemented in the entirely new design of the third generation. Incorporation of innovative hardware and software has eliminated the drawbacks of previous generations and increased its stability accuracy and reliability. The cost of human resources required for calibration and maintenance is reduced. It will benefi t chemical industries and refi neries to effectively monitor and control its entire process. It enables the entire production unit to run at maximum effi ciency and profi tability.
Stability, Reliability and accuracy of the third generation of NMR process analysers is the major challenge in restoring the reputation of NMR technology for process control in the chemical and petroleum industries.
References
1. Giammatteo, Paul J., Edwards John C., Cohen Tal, “Integrated analyses and control to enhance clean fuel production”, ISA 54th Analysis Division Symposium, 2009
2. Shahnovsky, Gregory “Innovation in Petroleum Process Analysers Technology”, ISA 53th Analysis Division Symposium, 2008.
3. McMahon, Terrence K., Process Analytical Technology, John Wiley & Sons, Inc, 2005.
4. Clevett, Kenneth J., Process Analyser Technology, John Wiley & Sons, Inc, 1986.
5. Giammatteo, Paul J., “More from the Barrel - On-line NMR Increased Diesel Production and Quality”, presented to the NMR symposium at the Eastern Analytical Symposium in Somerset New Jersey, November 12-15, 2007 (
www.nmr-automation.com)
OP-NMR
Raw Crude Oil Blended Crude Oil Desalted Crude Oil Light Naphtha Heavy Naphtha Kerosene Light Gas Oil Heavy Gas Oil Atmospheric Residue Vacuum Gas Oil Vacuum Residue Alkylation Unit
Crude Custody Transfer Crude Blending CDU (Partial) CDU (Full) FCCU
Delayed Coker Alkylation Unit Light Product Blending
High (linear response) Deployment specifi c (tubing, streams switching)
5
Author Contact Details Tal Cohen - CTO, 4IR Solutions Ltd. • Email:
tal@4irsolutions.com • Web:
www.4irsolutions.com
WWW.PETRO-ONLINE.COM
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