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| NMR
Application
- Fluid
Catalytic Cracking Control and Optimization View Application Note PDF |
| The
fluid catalytic cracking unit (FCCU) is one of the most important units
in the refinery. Few FCCUs have real-time process optimization
implemented, since feeds typically have been measurable only in the
laboratory. These measurements take many hours, with reports available
only once or twice a day. Even the measurement of PIONA (paraffins,
isoparaffins, olefins, naphthenes, and aromatics) and the distillation
properties of the rundowns are difficult to achieve on-line.
The Donahue Process Systems NMR now provides a means of obtaining these measurements near real-time, thus enabling significant economic benefit to the refiner through APC and process optimization. |
FCCU
controls and optimization include feed preparation, the
reactor/regenerator, the main fractionator, the wet gas compressor, and
the downstream gas plant. Typical operating objectives are:
Total economic benefit can
approach $0.30/bbl feed. |
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Product 1: NMR Prediction of FCC Feed Characteristics
In this application the process NMR unit provides control parameters based on the needs of the plant.
Different plants have different chemical and parameters of the FCC Feedstream to control or optimize the FCC unit.
Typical parameters requested for the NMR are:
 | Density |
| Sulphur ** |
| Total Nitrogen ** |
| Basic Nitrogen ** |
| Metals ++ |
| Micro Conradson Residue |
| Aniline Point |
| Refractive Index |
| Total Aromatics |
| Aromatic Breakdown (Mono, di, tri, tetra+ rings) |
| Distillation (D1160) |
| Viscosity |
| Hydrogen Content |
| Asphaltenes |
** Secondary correlation
++Cannot be determined by NMR directly-Relaxation studies may allow quantification of Total Metals (No discernment between metal types).
All the above parameters can be modeled (except metals). Sulphur and nitrogen numbers will be secondary correlations that can be used only for gross estimation. These are poorer correlations because the NMR does not observe N or S directly, instead correlation is found in H chemistry that is elated to these heteroatoms. The remaining parameters can be modeled to an error of prediction somewhere between ASTM repeatability and reproducibility for the ASTM tests depending on the validation procedure that is followed.
Process NMR Associates is also developing large databases that correlate 1H NMR spectra with 13C NMR parameters that are more useful and technically accurate than the above tests many of which simply correlate to the 13C NMR parameters of carbon aromaticity (FA), carbon paraffinicity (FP) and carbon naphthenicity (FN). These parameters would be the preferred parameters for online control and optimization.
A seperate description of these 13C NMR parameters is given here.
Product 2: NMR Prediction of FCC Product Characteristics
Characteristics of these streams (FCC gasoline and Cycle Oils) are closely related to other applications such as gasoline blending and gas oil blending. Relevant information can be found in the description of these applications.
For further process details follow the following
links: UOP
Technical Sheet , The FCC Network
For more information on this topic please contact:
Manager, Process and Analytical NMR Services
Process NMR Associates LLC,
87A Sand Pit Rd
Danbury, CT 06810, USA
Tel: (203) 744-5905