NMR Process Systems

From gasoline manufacturing to butter production, more than 140 online NMRs have been placed in manufacturing plants worldwide. Giammatteo will discuss installation and utilization of this technology, its application in the petroleum and petrochemical industries and the future in pharmaceuticals.

Giammatteo co-founded Process NMR Associates, based in Danbury, in 1997. He previously worked for Texaco for 17 years. Giammatteo received his doctorate in chemistry from Wesleyan University and has published and presented more than 30 papers.

For more information, contact James Kirby, associate professor of chemistry at Quinnipiac, at (203) 582-8275 or James.Kirby@quinnipiac.edu

Advanced process control (APC) schemes frequently require near real-time stream composition information to make adjustments to controls – the faster and more reliably the better. To obtain these crucial measurements of process performance, refiners have been deploying GC, boiling point, , cloud point, octane, and numerous other process analyzers. Nuclear Magnetic Resonance (NMR) spectroscopy is rapidly emerging as one of the most versatile and cost-effective technologies for process analysis.NMR offers tremendous analytical measurement flexibility, non-invasive sampling, rapid and precise analysis, and system availability exceeding 95%, thanks to dependable system components and very low maintenance requirements. Moreover, process NMR analyzers can measure numerous chemical species, because they can be tuned for hydrogen, fluorine, or phosphorous nuclei. Figure 1 identifies potential application sites for NMR-enhanced APC systems in the refinery.

How NMR Spectroscopy Works
During an NMR analysis, a sample stream is passed through a precisely controlled magnetic field, which brings the magnetic moments of all its protons into alignment with the homogeneous magnetic field. To take a reading, an NMR analyzer transmits a pulse of 60 MHz radio frequency (RF) energy, through a tuned circuit coil, into the stream. The magnetic field component of the radio frequency energy perturbs the magnetic moments of the various protons off their aligned axes. The amount of deflection and the subsequent recovery time will vary according to the length of the applied pulse. When the RF pulse is turned off the proton magnetic moments will return to alignment with the NMR magnetic field. As the magnetic moments precess back to equilibrium, protons with different chemical environments generate alternating currents at different frequencies in the NMR irradiation coil. These currents represent protons is different environments and the magnitude of the current is proportional to the amount of that chemical proton type in the sample. Fourier transformation of the raw signal generated in the coil yields a spectrum of peaks where each peak represents a proton in a unique chemical environment. In the course of one minute the analyzer averages multiple pulses into a spectrum that reveals hydrocarbon chemical make-up, and their relative concentrations.

This NMR spectrum can also be correlated with physical properties other than the chemical composition, enabling determination of multiple parameters from a single spectrum. And since NMR is not an optical technology, the analysis is essentially independent of sample state (e.g., solid, gas, or liquid) or physical condition. Small particulates or bubbles, for example, have little or no effect on the analysis. The sample passes through the magnetic field in a small tube, untouched and unchanged in any way, and is returned to process downstream.

REFINERY TUNE-UP SOLUTION SERIES
Advanced process control, utilizing technology ranging from simple multivariable control to model-based predictive control (MPC) and rigorous on-line modeling, generally requires near real-time stream quality information. The exceptional availability of the NMR analyzer enables this information to be supplied reliably for process control while the technology ensures accuracy and repeatability. Because this analyzer can be applied to numerous component quality measurements, a single analyzer can often alleviate the need for multiple analyzers to satisfy an APC application.

Recognizing that NMR technology is a winner for the petroleum refining industry, teaming the analyzer with appropriate Invensys advanced process control tools and control systems was a logical step. Thus, configurations of the process NMR analyzer with optimization/control software, control system hardware, and engineering services have been defined to resolve the more costly refinery process control and optimization problems. These configurations are being captured in the Refinery Tune-Up Solution Series, which currently include the following processes (Figure 1):

· Crude Oil Blending
· Atmospheric Crude Oil Distillation
· Fluid Catalytic Cracking
· Sulfuric Acid Alkylation
· Gasoline Blending
· Diesel/Distillate Blending

Managing Crude Transitions
Traditionally, refineries were built on the premise that crude would always come from a specific field. Supply varied little, and setpoints could be operated adequately with laboratory analysis and predictive control. Today’s market is quite different. Competitive pressure to maximize profitability is driving refiners to find new ways to leverage low-cost crude feeds. They are buying more crude on the spot market, and this crude usually differs significantly from the design-crude used when the refinery was built. Managing these variations profitably requires daily revision of production schedules and continuous profitability optimization.

Figure 2 shows how variations in crude feed quality affect production of low-value atmospheric residue. As the graph shows, a feed change from a typical Syrian Light crude to an Iranian Heavy, unaccompanied by a corresponding change in the process conditions of the crude unit, will increase production of low-value atmospheric residue by about 10 percent.

Variations in crude quality can affect cut point optimization, product quality control, feed rate maximization, and energy consumption, while also violating process equipment constraints. Without process control compensation for a crude transition, the process will experience an upset and become both less efficient and less profitable.

There are several options in managing the transition of crude feeds, although all options are typically not available at each refinery. Crude oil blending is very advantageous to those refiners receiving constant supplies from fields through pipelines or those with large tank farms. Refiners not so lucky must battle unit upset when transitions occur, unless they are made aware of a pending transition and have the capability to minimize the effects through process control.

Crude Oil Blending
The capability of accurately monitoring crude compositions enables precise blending of crude feeds. This means that the refiner can blend less expensive heavy, sour crudes with more expensive light, sweet crudes to achieve desired properties while maximizing profitability.

A crude oil blending system is shown in Figure 3. It is based on implementation of The Foxboro Company’s I/A Series NMR Process Analyzer and Foxboro’s Blend Optimization and Supervisory System (BOSS). A refinery information management system provides crude blend planning functionality that downloads total flow requirements, ratio limits for the crude blend components, and product quality constraints. These settings are based on refinery models that define optimal utilization of distillation and downstream units for various crude types.

BOSS calculates optimal ratios based on measurements of crude component quality and blended crude quality. At the lower level is a blend ratio controller similar to the type used for gasoline and diesel blending. A digital blending system (DBS) can be supplied, or an existing digital blender can be used.

Depending on physical location requirements, one or more NMR analyzers are applied to the blended crude stream and to the crude component streams. The NMR analyzer measures essential qualities such as API gravity or density, true boiling point /ASTM distillation, initial and final boiling point, and water content.

Operating the refinery at optimal and constant crude composition can generate savings for major refineries on the order of 2% to 3% of the operating margin of the whole refinery. The Crude Oil Blending solution achieves this by:

Improved distillation unit throughput. Constant attention to the distillation quality of the crude loads the crude distillation unit and all the other downstream units consistently. This allows refiners to operate their crude distillation unit closer to its limits, which increases throughput.

Improved refinery throughput. If the throughput of any refinery unit is limited, a constant and optimal distillation curve for the crude oil can push all units to their limit simultaneously. This maximizes throughput for the overall refinery.

Improved performance of downstream units. Specific characteristics of the crude will also influence performance of some of the downstream units. Changes in the ratio of paraffins to aromatics in crude, for example, will impact/affect the benzene, toluene, and xylene output of catalytic reformers.

Improved product quality and reduced energy costs. Stability of the crude composition also eliminates one of the major disturbance factors in a refinery, resulting in more stable operation. This contributes positively to overall quality, fosters efficient energy consumption, and improves equipment reliability.

Improved management of crude changes. Maintaining optimum and constant crude quality and composition enables more efficient management of changes in crude.

Atmospheric Crude Oil Distillation
In the past, refiners would manage the transition from one crude to another by manual adjustment of various controlled variables for a given time, thus relying upon prior crude transition experience in order to minimize process upset. By using NMR-enhanced control and process optimization, however, the refiner can follow the transition from one crude to another in real-time and adjust parameters as needed to maintain maximized profit. The result can be dramatic savings per crude transition, since the typical 4 – 8 hour upset due to a transition is essentially eliminated.

Figure 4 shows how process NMR Process Analyzer measurements would be deployed in an atmospheric crude oil distillation unit application. Because NMR technology can also monitor the distillate streams as well as crude feed, the cost benefits are substantial. It can replace complex traditional physical property and laboratory analyzers as well.

The crude feed analysis supplies crude characterization information to enable feed transition compensation. ROMeo, SIMSCI’s Rigorous On-line Modeling and Equation-based Optimization software, provides a completely unified and integrated environment for on-line modeling, process simulation, data reconciliation, and optimization. Newly calculated setpoints to continue an optimized unit performance are calculated and sent to Foxboro’s model-based predictive controller, Connoisseur, upon a crude transition. Connoisseur, using a dynamic multivariable model, makes the necessary process manipulations to attain the optimum control setpoints determined by ROMeo, while minimizing disturbance to the process.

ROMeo and Connoisseur maintain unit operation at optimum between crude transitions. Atmospheric tower overhead and sidecut product draw stream quality measurements provided by the Foxboro NMR are used in the Connoisseur model to monitor process operation performance and supply control feedback information. Common advanced control targets include:

· Maximizing unit throughput up to equipment constraints

· Maintaining product quality while maximizing yield of most valuable products

· Maximizing preheat train, pumparound, and fired heater heat transfer efficiencies

Including crude transition compensation and unit optimization, overall benefit can reach $0.12/bbl feed.

Fluid Catalytic Cracking
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 process 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.

Like the atmospheric crude distillation units, the FCCU has been built on the supposition that the feed composition will remain near design specifications. In today’s economic climate, this is no longer true. Figure 5 shows that as you change from one feed (crude type) to another, the optimal target severity changes also. In this case, maintaining the same optimization will actually reduce yield and increase costs (B).

Using the process NMR to characterize the feed and coupling it to the ROMeo process model (Figure 6) helps optimize the process in the following ways:

1. If the feed has changed, the NMR analyzer provides near real-time data on changing feed properties to enable the most economical conversion of the available feed.

2. If the feed remains unchanged, the on-line analysis of the feed enables the operator to run the process closer to equipment constraints; for example, near the limits of the LPG compressor at the back end of the process. This increases the throughput of the unit at very little additional cost.

3. As with feed transitions to a crude distillation unit, ROMeo and Connoisseur maintain FCCU operation at optimum. The main fractionator overhead and sidecut product draw stream quality measurements provided by the process NMR are used in the Connoisseur dynamic model to monitor process operation performance and supply control feedback information.

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

· Maximizing unit capacity
· Maintaining product quality while maximizing yields of most valuable products
· Optimizing energy utilization
· Controlling conversion
· Improving safety and reliability via operational stability

Total economic benefit can approach $0.30/bbl feed.

Sulfuric Acid Alkylation
The alkylation unit control system provides composition measurement and control solutions to reduce or eliminate problems characteristic of sulfuric acid alkylation unit operation. The system applies NMR technology for stream composition analyses with tightly integrated advanced process control to deliver optimum unit performance.

The process NMR analyzer is used to determine acid strength for the optimization of acid use, the emulsion character (acid-to-HC ratio), the isoparaffin-to-olefins ratio, and the acid-soluble oil content. Secondary applications include safety, quality control, and additional chemometrics uses.

Connoisseur is applied to improve the control of total feed composition and operating conditions to reduce the production of side products such as acid-soluble oil and heavy alkylate. Control improvements in the distillation section assure RVP control of the alkylate product, reduce propane and normal butane diluents in the reactor recycle streams, reduce isobutane losses in product streams, and reduce utility costs. In general, distillation column controls are enhanced to accommodate changing feed composition, temperature, and flow rates, with minimum disturbance to product quality. Reboilers, preheaters, and particular condensers are controlled to maintain required heat transfer rate, thus aiding column operation stability and preserving product yield. Furnace firing controls reduce fuel consumption.

Model-based predictive control targets include:

· Maintaining isoparaffin-to-olefins ratio at optimum
· Maintaining acid-to-hydrocarbon ratio at optimum
· Maintaining optimum overall reactor temperature profile
· Maximizing throughput within feed availability, fractionation capacity, or other constraints

Connoisseur’s LP optimizer can be used to drive the process towards an economically optimum set of process constraints. The optimum strategy is determined by the product and utility costs applied in the LP objective function. These costs can be adjusted on line to reflect changing market conditions.

Achieving the following objectives maximizes alkylation unit profitability:

· Maximize alkylate make
· Maximize isobutane/olefin ratio
· Maximize the use of low cost feed in preference to higher cost feed when alternative fresh feedstocks are available
· Maximize propane recovery
· Minimize isobutane losses in product streams

The benefit contributed by the NMR analyzer alone can amount to 10 – 15% of acid costs. The additional benefits acquired from the Connoisseur application range from $0.10 to $0.20 per barrel of feed.

Refinery Blending Systems
To satisfy new gasoline reformulation requirements, blend header complexity is increasing with the increasing number of blend components. Diesel and other blended fuels are also subjected to more severe blending requirements in order to comply with environmental mandates. As a result, refiners are compelled to evaluate the effectiveness of their blending operations and are adding or improving blend optimization to boost profitability. Common blending operation targets are:

· to reduce reblends and improve profitability
· to meet product specifications while conforming to environmental requirements
· to enhance effective inventory capability
· to lower risk of missed export schedules
· to improve refinery planning/scheduling accuracy

To realize the greatest profitability in refinery blending operations, a blend optimization system is used to provide management of the component and product tanks, blend header, on-line and laboratory analytical systems, and planning/scheduling activities. This optimizer, Foxboro’s Blend Optimization and Supervisory System (BOSS), produces blended products with a high degree of precision to meet specifications while minimizing quality giveaway, maximizing the use of the lowest cost components in the blend, increasing the flexibility of the tank farm operation, and minimizing the frequency of reblends. A flexible objective function permits component cost, inventory constraints, or product specification to direct the optimizer.

Providing BOSS with near real-time component stream and blended product chemical quality information is the NMR analyzer – Figures 7 and 8.
This information enables multivariable analyzer-directed control including:

· Feedforward control for component quality variations
· Feedback control for product quality variations
· Quality integration of product and component tanks
· Projected product qualities at the blend header

Actual process manipulations are made by existing digital blend controllers or a Digital Blending System (DBS). DBS features include uniform ramping, continuous pacing, analyzer trim, temperature-compensated flow measurement, and flexible loop configurations. It may be configured to include an automated procedure for manipulating the equipment involved in blending, transfer, flushing, and pigging operations.

A refinery blending system upgrade project is often more expansive than blend optimization. Blend optimization demands accurate tank information, and automating the tank farm is prerequisite in order to gain most benefit. Then, to maximize blend operation performance, Foxboro can complement blend optimization with the Tank Information System (TIS) and the Oil Movement Information System (OMIS) software applications.

TIS provides tank inventory information, tank monitoring functions, and tank status and information reports that satisfy internal and regulatory information reporting requirements. This system compiles data provided by tank gauging systems, and is usually an integral part of a blend optimization control scheme.

The tank information system database contains static and dynamic configuration data as well as calculated and measured data. Static data includes information such as tank ID, tank contents ID, API table ID, reference temperature, and tank strapping table values. Dynamic data includes level and temperature alarm limits, and calculated data includes volume correction factor, tank volume, thermal expansion coefficient, dry volume, available volume, ullage, net weight, and more. Accurate tank information allows operation with lower inventories, and the material balancing capability can be used to detect tank leakage. Particularly useful for blend scheduling, it can alert the planner of a potential conflict.

OMIS supplies the engine for automating the tank farm. This system provides resource management of equipment, sequencing and logic functions to control equipment, and flow path selection. System functions include movement planning, automatic movement control, equipment monitoring and management, and product movement and storage reporting and archiving. The equipment database covers tanks, pumps, valves, pipelines, and mixers.

An expert system-based guidance system directs the operator to minimize the potential for human error, protecting equipment from damage, and avoiding stream cross-contamination. The system’s “illegal” tank level change information provides a leak detection capability, using both level and flow measurement data. Another system feature is the option to select a swing tank or another pump without the need of a shutdown.

Setting up an oil movement involves selecting the appropriate tanks, pumps, pipelines, etc. from an oil movement planning display. Once the selection is made and the selected path and equipment is validated by the system, the flow path is established. Operation of the flow path equipment can be performed in either an automatic or semi-automatic mode, depending on a need for operator intervention.

A refinery gasoline blending system upgrade project including blend optimization can provide benefits amounting to $0.10 to $0.25/bbl gasoline. Including the cost of engineering studies, new field equipment, and new instrumentation in a tank farm automation and blend optimization project, the payback period is typically less than 18 months. This is true for gasoline, diesel, and fuel oil blending operations.

Mobility Detected NMR - 6479994 6549007 6744251 6828892
Blending Control by NMR - 5796251
Ex-Situ NMR - 20030052677
Oil-Water Emulsion Compositions by NMR - 6794864
Bitumen Content by NMR - 6630357
Mobile NMR Analyzer – 5994903
Detection of Spoilage – 5270650
Microcoil Benchtop NMR - 5654636 6097188
Control of Process by NMR Gas Analyzer – 5265635

To search and get adobe acrobat pdf versions of patents go to Freepatentsonline.com
http://www.freepatentsonline.com/#.pdf
where # is patent number without commas patent 5,265,635 is 5265635.pdf

On-Line Process NMR Relaxometry – Based on Auburn International/Oxford Instruments/Progression Technology – Polymer Qualities
The Analyst – Review Paper on Process NMR Spectrometry Covering Mainly Relaxometry Applications
Magritek – Low Field Portable and Specialty NMR Equipment
Minispec Analyzer from Bruker – Application Note Web Page
Maran NMR Analyzer from Universal Systems Inc – Applications Page
On-Line TD-NMR – Progression Inc
Applications of NMR Relaxometry – Process Control Technologies Inc

Time Domain Process NMR Spectrometers – NMR MOUSE
A handheld NMR surface analyzer is now available from Bruker or the collaborative research group that developed the technology.
NMR Mouse – Aachen Group Bruker Minispec MOUSE
Applications of NMR Mouse More Applications

Time Domain Process NMR Spectrometers – NMR Logging Tool
NMR logging tools have been developed for down-hole profiling of oil well pore structure and fluid reservoir structure and composition. This is NMR 1 mile down a hole.
Schlumberger NMR Logging Tool Description
Overview Paper – Trends in NMR Logging
Overview Paper – How to Use Down-Hole NMR
Lecture on Down-Hole NMR Logging

3. Shim Control Unit
The Shim control unit converts the digital shim signals from the computer and generates the current for the 50-shim coil pairs. It contains a communication board for coms to the computer, 50 ADC’s and 50 current generators.

4. Power Supply I/O Unit
The Power Supply I/O unit contains digital output modules for sample stop and sample switching valve control, digital input modules for enclosure alarms. A RS-485 Field Point connection for analog outputs and a RS-485 Modbus connection for digital connection to a DCS. It also provides all dc operating voltages for the system. The voltages are:
+15 volts ( Main & lock Tx,)
–15 (Heater and Shim)
+15 (Heater and Shim)
–15 (Heater and Shim)
+9 (Shim Coils)
–9 (Shim Coils)
+28 ( Main & lock Tx)
AUX (24 VDC)

5. Magnet
The magnet is permanent and built from multiple segments of neodymium- boron-iron. This material is used because its very high field strength-to-mass ratio achieves the desired flux density in a small, compact package. Because the flux must be extremely uniform over the entire air gap, construction of the magnet is complex. The magnet is fabricated from several segments bonded together to form the basic assembly. In addition to the bonded segments of magnetic material, each magnet also contains 50 coils of wire arranged about a Shimming Unit mounted in the center of the magnet between the pole pieces. These coils are used as small electromagnets; the strength and polarity of which can be controlled by varying the current through them so as to improve uniformity of the overall field of the magnet assembly.
Prior to assembly in the manufacturing plant, each magnet segment is “cured” at a high temperature to stabilize its field strength. In the fabrication process, the absolute field strength of each individual segment of the magnet is measured. A computer analysis of this data then determines the best placement of each segment in the final assembly to achieve a consistent, uniform field for the assembled magnet. The segments are then bonded together to form the final magnet assembly. The assembly is placed inside a soft iron cylinder, the ‘envelope’, which constrains the magnetic flux and prevents the magnetic field outside the magnet housing from exceeding a value of as little as 5 gauss. More importantly, the iron cylinder raises field strength in the center of the magnet by pushing the flux toward the center; a process called “condensing the field”. There are electric heater strips and thermistors on the magnet and envelope to heat the assembly to the desired temperature.

6.Probe
The sample probe is mounted inside the permanent magnet in the air gap between the magnet poles. The probe contains two coils; the first, the ‘Main Coil’ is wound around a ceramic or molybdenum tube that is inserted in a hole through the shimming unit in the center of the gap between pole pieces of the magnet. The second coil, the ‘Lock Coil’ is wound on a sealed capsule of lithium chloride beside the main coil in the sample probe inside the permanent magnet. This is provided as a reference standard for setting the frequency of the main transmitter.
The constant magnetic field of the permanent magnet is perpendicular to the axis of the transmitter coil in the sample probe. Since the pulsed ac field introduced by the coil around the sample tube coincides with the vertical axis of the probe, the pulsed magnetic field is therefore perpendicular to the constant magnet field of the permanent magnet.

7. Heater Control Unit
The Magnet Heater Control Unit controls the temperature of the magnet and the envelope. The temperature of the magnet is set at 41°C and the temperature of the envelope is maintained at 37°C. The Heater Control Unit is mounted on the interior wall of the Magnet Enclosure Cabinet and has two PID loops that accept measurement input signals from the thermistors mounted on the magnet itself and the envelope. The outputs of these two PID loops control the currents to electric heater strips.

8. Enclosure
The NMR analyzer is housed in a two-door NEMA Type 4 enclosure approximately 48 inches high, 44 inches wide and 30 inches deep. Floor stands are approximately 12 inches high and are welded to the body to make it a freestanding enclosure.

The enclosure with equipment installed weighs approximately 1500 pounds and is equipped with transportation eyebolts. It is fabricated from 304 stainless steel, with all seams continuously welded and ground smooth. A center partition divides the enclosure into Magnet (left) and Electronics (right) compartments.

The magnet side is home to the gas leak detector and the ambient temperature is maintained at 72°F ±1°F. This is accomplished by means of an air conditioner on the outside left wall of the enclosure working in conjunction with a bank of five 500-watt strip heaters and a PID Controller. The ambient temperature in the Electronics side is controlled by an air conditioner on the outside right wall with an internal thermostat set at approximately 70°F.

Principle of Operation
The Donahue Process Systems NMR Analyzer

A sample is selected via the sample switching control and the S.C.S. (Sample Control System) and is flowed through the Main probe, through the Magnet. After a specified time the sample stop valve locks the sample in the magnet and holds it, we then have a specified time until the Main circuit then Pulses the sample, waits and receives the signal. This signal that is received is called a F.I.D. (Free Induction Decay).

The FID is read in the time domain, meaning the Y axis is time and in this time domain we can perform various processing functions, the FID is then Fast Fourier Transformed (F.F.T.) into the frequency domain.

The signal is then digitally processed passed though the prediction models to obtain a prediction, the prediction is then transmitted to a DCS or receiver via analog or modbus outputs. After this has happened the sample stop valve is opened and the cycle is repeated. The lock circuit is constantly performing a NMR experiment on the Lithium Chloride, this is done as a reference. The frequency of Lithium in the NMR magnet is around 22 MHz and therefore does not interfere with observing hydrogen at 60 MHz. Because the magnet is highly dependent on temperature it is impossible to maintain a constant temperature and there for, as we know where the Lithium Chloride peak should be we can reference the main circuit to the same as the Lithium Chloride peak is away from where is should be.

Main Circuit
The crystal oscillator outputs a 36 MHz signal, which is sent to the DDS card. The DDS unit multiplies, divides, and/or phase shifts the signal and outputs a 51 MHz signal that is used as the main transmitter and receiver local oscillators (MAIN_TX_LO and MAIN_RX_LO). A 9 MHz signal from the DDS unit is added to the MAIN_TX_LO signal to produce the main transmitter frequency of 60 MHz, which is transmitted to the diplexer and then switched to the main transmitter coil in the probe. After the main transmitter pulse is removed, the nuclei relax and generate a 60 MHz signal in the coil, which flows to the diplexer, where it is automatically switched to the receiver input. The received signal is amplified and then mixed with the MAIN RXLO signal (51 MHz) to produce an Intermediate Frequency (IF) of 9 MHz. This signal is then mixed with 9 MHz from the DDS card to produce an audio frequency of approximately 1 kHz. The audio signal is then split into two equal channels, I and Q, phase separated by 90°. The I and Q signals are then input to the ADC, where they are converted to digital form for input to the PC.

Lock Circuit
The purpose of the lock system is to provide control of the frequency of the main transmitter pulse, automatically compensating for any minor variations in magnet field strength and temperature. The lock system continuously detects the resonant frequency of the nuclei in a known sample fluid, lithium chloride, and then sets the frequency of the main transmitter to be a fixed ratio to this reference. Since the reference fluid capsule is located inside the main probe, it is subjected to the same magnetic field and temperature as the main transmitter/receiver. Therefore, a change in one affects the other. The lock system functions in the same general way as the main transmitter system, except that the basic transmitter frequency is approximately 22 MHz, the resonance frequency of lithium in a magnetic field of 1.5 tesla. The frequency of the lock transmitter is swept over a range of about 1 MHz (22-23 MHz) as it searches for the resonance frequency of lithium. When it first detects a resonant response (significant increase in signal level) as it increases frequency during the search, it stores this value and then jumps to a higher frequency and approaches resonance from the other direction. When it detects a resonance response as it approaches from the other direction, it stores this frequency and then jumps to a frequency at the mid point between the two stored values and then “locks” on this frequency as the resonance frequency of lithium. The output of the lock system is used as the set point of the main transmitter circuit, which maintains the main transmitter frequency in a fixed ratio to this “lock” frequency.

Shimming
To obtain a rough magnetic field, the field homogeneity of the permanent magnet is adjusted by mechanical alignment of the magnet pole faces. The more parallel the pole faces, the more homogeneous the magnetic field. The first step in the process of adjusting magnetic homogeneity is to adjust the position of the magnet’s pole faces by turning adjustment bolts which hold the pole faces in position. Adjusting these bolts tilts the pole faces relative to each other with the aim of making the pole faces more parallel. In old electromagnetic magnets, if the bolts ran out of range, thin pieces of brass were placed between the magnet yoke and the pole pieces to move the pole pieces as parallel as possible. These thin pieces of brass were also placed in other strategic locations to make the pole faces parallel in a manner not addressed by the adjustment bolts. The metal pieces were called shim stock and the seemingly endless process of placing and removing pieces of shim stock acquired the name “shimming”. This is, however, a simple mechanical adjustment that only gets the NMR to a symmetric half height of 700 Hz. To increase performance, reduce the difficulty of adjusting magnetic homogeneity, and reduce the manufacturing difficulty of the magnets, an electronic “shimming” process is used, which uses a series of small electromagnets (essentially shaped coils) having very specific magnetic field contours. These small coils are placed around the sample area in different orientations. Each small coil can be used to adjust the shape of the magnetic field gradients by simply passing different currents through the coil. A complete series of these coils can be used to adjust the magnetic field homogeneity to a given level of “purity”. The process of adjusting the magnetic field homogeneity by adjusting the current in each of the coils has retained the name “shimming” and the small coils assumed the name “shims”.

Systems are marketed through NMR Process Systems Inc

Contact John Edwards for details and visit the Process NMR Associates web page for application examples.

Repeatability – the measurement of the spread around a test result from a single analyst and/or single analyzer at the same site on the same sample. However, this does not mean that the result is accurate (produces the true value).

Precision – the level to which any measurement can be accurate. That is, 46 or 46.259.

Bias – a definite offset from the true value. Consecutive single point measurements can be biased.

Model Definitions

Global Model: Any chemometric based prediction that incorporates lab analyses and samples from multiple locations on multiple streams, multiple processes, and multiple stream sources (i.e. crudes). By definition then, the prediction is accurate (predicting the true value) to within reproducibility. In order to compare a global model prediction to any single point lab measurement, the lab must first validate that the lab can meet the reproducibility requirements of the method, or ascertain it’s actual reproducibility by as described in ASTM D3764. Once the lab measurements are validated, single point lab measurement comparisons to the chemometric prediction should be within reproducibility limits. Global models are less prone to bias errors and drift.

Model Training: The process of enabling a global model to statistically recognize (i.e. f-test, mahalanobis distance, etc) the spectral results of a specific analyzer at a specific location. Requires no extensive lab sampling and analyses or exorbitant input of local unit and process specific spectral files to the model.

Local Models and Localization: Local models are built on data from a specific process unit, in a specific location, usually incorporating only lab analyses from the on-site laboratory. This effectively makes the model an on-line duplicate of the on-site laboratory and therefore subject to bias. Further, if a model is localized too much, it can be prone to drift (moving away from the true value) and/or fail to predict outside of the model space when the process changes or experiences an upset.

NMR Reproducibility: The limits of the differences between a valid, single point lab measurement and an NMR predicted result. This value is determined by the primary method and range of samples that the model is built on.

NMR Repeatability: The limits of the differences between successive predictions on a blocked in sample in the NMR under defined conditions. This value is determined bythe primary method and range of samples that the model is built on.

NMR Model and Application Strategies

NMR models based predictions are based on two types of applications: Process Control or Product Certification.

Process Control: Feed Forward and/or Feedback

• NMR models cover a wider sample range.
• Very Robust: continue to accurately predict over wide process ranges.
• Reproducibility differences between the NMR prediction and any single point lab measurement will be slightly higher.

Product Certification: i.e. Blending

• NMR model ranges are narrowed and confined with respect to the product (i.e. gasoline and blend components only)
• NMR validation set at product certification levels.
• Models are not as robust. That is, a gasoline blending model will not predict a diesel fuel as accurately as a more broad based model. For more information on this topic please contact:
  John Edwards

Internal Tank Farm Management
Bitumen Upgrading Process

Petroleum Exploration
Whole Crude Analysis
Custody Transfer

Petrochemical Applications
Steam Cracker
BASF Steam Cracker Application Note
Equistar ISA Presentation – Naphtha/Condensate Cracker Optimization
Aromatics Plant
Styrene-Butadiene Rubbers
Ethylene-Propylene Copolymers

Food Applications
Dairy Overview
Butter
Cream Cheese
Sour Cream, Milk, Cheeses, Yogurt
Beverages (Juices and Alcoholic)
Baby Food and Soups
Sodium Content of Food and Drink

Pulp and Paper Industry
Black Liquor Evaporation Process

LNG and Power Industry
BTU Analysis and Limited Speciation of Gas Components

The Other Aspect of Process NMR is Time Domain NMR Spectroscopy – Learn More

These Applications and Others Marketed through NMR Process Systems Inc.
For Technical Information Contact john@process-nmr.com or see the Process NMR Associates Website

Spoilage of Wine observed by NMR of Intact Bottles
A large bore superconducting magnet and specialized probe is all that is required to check that your $4500 bottle of Mouton Rothschild 1865 is not a extraordinarily expensive bottle of vinegar US Patent 6,911,822. See also this magazine atricle and the website of the company that is using the first commercial system in Morristown New Jersey – Wine Scanner Inc

Patented NMR Method for Quality Control of Medicinal Natural Products
Pattern recognition technology in conjunction with 1H and 13C NMR spectroscopy is used to determine the standard specification expected for medicinal grade natural products – see US Patent 6,806,090

Food Authentification by SNIF-NMR
Gérard Martin of Eurofins Scientific, CNRS, Nantes University, Nantes – France, writes:” Methodology: No dramatic improvement in NMR instrumentation originated during the last decade where an 11.4 T spectrometer, fitted with dedicated 2H{1H} probe and a 19F locking canal represents a good compromise between cost and efficiency. Since the main challenge for 2H-SNIF-NMR is to overcome its low sensitivity, efforts were directed in this way. The cheapest solution is to avoid the use of an internal reference that spares room in the cell for more molecules of interest and this can be done in two ways. First, the isotope ratios may be computed from the molar ratios of the deuterium isotopomeres, and the overall (D/H) value measured by Mass Spectrometry (IRMS). An alternative is to replace the chemical reference by an electronic signal conveniently generated (ERETIC method).
Wines and juices: Since 1991, the European data bank on wines has been established years after years and contains now the isotopic data of several thousands of wines from the main producing countries in Europe. Illegal enrichment of wines can be checked out and, according to the pertinence of the data bank, geographic origins of QWPSR wines can be controlled. Private ventures took also an interest in building up specific databanks of wines from third countries. The market of fruit juices has been stabilized by SNIF-NMR and the quantity of sucrose added in pure juices has been severely reduced. A joint approach using SNIF-NMR and IRMS is very useful for fighting against other sophisticated frauds.
Aromas and perfumes: The replacement of vanillin from beans (Vanilla Planifolia) by synthetic vanillin is an old practice and during thirty years, isotopic methods (IRMS and SNIF-NMR) were a nightmare to the fraudsters. Biotechnology forms the subject of the last serial of the vanillin saga: vanillin obtained from ferrulic acid by fermentation has been declared “natural” providing that all the steps and ingredients taking part in its manufacture are “natural”. The potentiality of isotopic analysis for solving the problem of the natural status of biotechnological vanillin will be discussed. Progresses in the authentication of aromatic molecules obtained from the shikimate pathway and of monoterpenes bio synthesized according to the deoxyxylulose pathway are also pointed out.
Miscellaneous applications of SNIF-NMR: During the last decade, fats and oils, fishes, dairy products and coffees received a great attention form the official and private laboratories in charge of the consumer protection. Legal (tobacco) and illegal (heroin) drugs have also been authenticated by SNIF-NMR.”
See also – Eurofins Site, and the following papers in The Chemical Educator (Elsevier), and this US Customs Service Report, explain the technique and a simple application very well.
SNIF NMR methodology has actually been patented US Patent 6,815,213, US Patent 4,550,082.
An excellent overview of where NMR analysis fits in the isotopic methods utilized in the European Union to detect fraudin food products is given by the European Commission’s Joint Research Centre
See Process NMR Associates for your NMR analysis needs.

13C NMR Analysis for Authentification of Gum Arabic
35 samples of Gum Arabic (acacia senegal) were analyzed by 13C NMR spectroscopy and the “average 13C NMR peak relative intensities” were calculated. This average 13C NMR signature can be used to determine the authenticity of a gum arabis sample and allows for observation of adulterants which are typically gums from other tropical trees (eg. gum talha (Acacia Seyal), Combretum, etc.). 13C NMR has been suggested as a specification of Gum Arabic quality in the following paper:“Gum arabic (Acacia senegal): unambiguous identification by 13C-NMR spectroscopy as an adjunct to the Revised JECFA Specification, and the application of 13C-NMR spectra for regulatory/legislative purposes.” by Anderson DM, Millar JR, Weiping W., Chemistry Department, University, Edinburgh, UK. Published in Food Additives and Contaminants, 1991 Jul-Aug;8(4):405-21
See Process NMR Associates for your 13c analysis needs.

NMR Acronyms
Excellent NMR Acronym Summary Pages – Oxford University, University of Wisconsin

NMR on a Chip
All you need to purchase with this PCI Card NMR spectrometer is an amplifier, a magnet and probe. Details can be obtained at the Spincore RadioProcessor Page. Benchtop high resolution NMR is very close to being a reality. Combining new spectrometer design with micro-probe and sample automation such as that found at Protasis will make benchtop QA-QC spectrometers a reality and place NMR spectrometers in the hands of people who can utilize them for routine testing at an affordable price.

Fat Content of Live Salmon
MOUSE NMR application on Salmon

Mobile NMR of Polyethylene Pipes
MOUSE NMR application to polyethylene pipes.

Upcoming NMR Meetings for 2006
47th ENC Conference will be held April 23 – 28, 2006, at The Asilomar Conference Center, Pacific Grove, California – Program.
EUROMAR - York will be held July 16-21, 2006 at The University of York Main Campus, Programme
22nd International Conferences on Magnetic Resonance in Biological Systems will be held August 20-25, 2006 in Goettingen, Germany – programme
6th Colloquium on Mobile NMR will be held 6-8 September 2006 in Aachen, Germany – Program
SMASH 2006 will be held September 10-13 at the Sheraton Hotel in Burlington, Vermont – Program
The NMR Symposium of the 48th Rocky Mountain Conference on Analytical Chemistry will be held July 23 – 27, 2006. The conference site is the Beaver Run Resort & Conference Center in Breckenridge, Colorado.
21st Meeting of the Central European NMR Discussion Groups will be held April 23-26, 2006, Valtice, Czech Republic in the hotel HUBERTUS in Valtice Castle
14th ISMRM will be held 6-12 May 2006 in Seattle Washington – program
ANZMAG 2006 will be held February 12-16 at the Murramarang National Park, NSW, Australia – Programme

Fast NMR Field Cycling
Stelar s.r.l of Italy manufacture a fast field cycling NMR spectrometer that shuttles a sample in and out of a varying magnetic field to generate T1 longitudinal relaxation profiles obtained by measuring T1 at a series of different magnetic field strengths. Stelar has developed low-inductance, air-coil magnets and power supplies capable of switching the field electronically to any desired value in a matter of milliseconds while, at the same time, maintaining the high field stability and homogeneity required by NMR. This allows the link between NMR relaxation phenomena and molecular dynamics to explored initially in the following application fields: the hydration of paramagnetic metal ions and organometallic complexes, the dynamics of liquid crystals, and the dynamics of proteins.

See Process NMR Associates for more details