Encoded Photometric Infrared Technology
by Jim Yano, VP Marketing, Aspectrics Inc.
The process monitoring industry faces major challenges to maximize product yield, improve product quality and quickly respond to the ever-changing environment in the face of increasing industrial competitiveness within a global economy. Process monitoring needs to be much more efficient, rugged, safer and flexible. This article aims to offer an insight into the capability of Encoded Photometric Infrared (EP-IR) technology to meet these challenges.
Conventional Technologies
Conventional infrared wavelength generation technologies fall short when it comes to the measurement of multiple chemical species. NDIR is fairly sensitive and very rugged but lacks the ability to measure multiple constituents effectively and is subject to false positives due to spectrally overlapping interferences. FT-IR and FT-NIR offer excellent wavelength coverage and high resolution. However, they lack ruggedness in vibration-prone environments and can be rather expensive to acquire and operate.
Other NIR techniques are limited to operating in the short wavelength region below 2100 nm and do not capture the rich combination overtone region between 2100 to 2700 nm. In addition, some NIR technologies offer only a very narrow spectral range, which limits their practical capabilities. Process-based gas chroma-tography (GC) has also been traditionally used for many process monitoring applications, but this technology requires the use of expensive consumables that need to be maintained or replaced peri-odically, making the cost of ownership quite high.
There is an obvious need for technology capable of overcoming these challenges. Aspectrics' patented EP-IR spectroscopy has been specifically designed to address the needs of the process monitoring industry. It is positioned to potentially replace conventional methods for many process monitoring applications, as well as to create new markets inaccessible to NDIR, FT-IR, FT-NIR and GC.
The Advantages of EP-IR
EP-IR spectroscopy is a breakthrough technology for the process monitoring industry. In the past, samples were taken from the process line and run on a laboratory-based analytical instrument. Unfortunately, this process consumes a lot of the manufacturer's valuable time. Operating at an ultra-fast scan rate of 100 scans/second, the EP-IR can provide unprecedented sensitivity through signal averaging, allowing it to measure multiple gas components in the ppb to ppm range simultaneously, which allows for near real-time monitoring of processes. This same speed advantage can be applied to EP-NIR applications, producing extremely accurate measurements. EP-IR analyzers are faster than traditional FT-IR systems, providing more information than NDIR systems, and do not require the use of consumables like process-based GC systems. The inherent stability and ruggedness of the EP-IR encoder disk technology means that it is ideally suited for harsh online process monitoring applications. EP-IR technology covers a spectral range from 4000 to 1800 cm-1, thus is ideal for many industrial and hazmat gas phase applications. EP-NIR spectroscopy has a unique spectral range covering 1375 to 2750 nm compared to the more limited, conventional NIR-based systems while taking advantage of the inherent rugged design aspects. With a built-in OPC client, EP-IR spectroscopy takes on more of a "transmitter role" than a hardened laboratory instrument. This results in easy tie-in to virtually all process control systems. The ability to remotely access the sensor to collect data for calibration development and to deploy these calibrations to the sensor negates the need to be on site at all times. Multiple instruments can be monitored with one console, further reducing cost.
Compared with FT-IR systems, EP-IR analyzers do not have an internal laser or hydroscopic components. As a result, EP-IR systems are able to maintain performance under conditions that would severely limit or damage other spectroscopic technologies. Additionally, EP-IR systems are compact in size, enabling them to be located in either general-purpose or hardened enclosures at a fraction of the size required for FT-IR-based analyzers.
Principle of Operation
EP-IR spectroscopy relies upon a simple yet process-rugged design whereby the incoming beam from a sample is imaged onto a diffraction grating. The dispersed radiation from the grating is then imaged onto the surface of the encoder disk, which is spinning at 6000 rpm (100 Hz), providing spectral modulation and ultra fast real-time detection. A pattern of reflective tracks produces a reflective beam with a unique sinusoidal modulation for each individual wavelength. The reflective beam is brought to an image on a single detector, which generates a signal that forms a discrete interferogram. Applying the Fourier transform to the interferogram produces intensities for each wavelength.
Performance Characteristics
Aspectrics' EP-IR analyzer. |
The whole EP-IR process results in ultra-fast data acquisition, full spectrum data across the wavelength range and network real-time data streaming. Vibration-insensitive operation is also achieved. In fact, EP-IR analyzers have received the Military 202G Method 204D certification for vibration resistance. The analyzers were submitted to strong vibration sweeps ranging in frequencies from 0.5 to 30 Hz and demonstrated that electronic and photometric performance integrity had been preserved. In addition, the photometric performance of EP-IR analyzers was further tested by collecting spectra as vibrations were applied to the instruments. Even under the extreme stress of such vibrations, EP-IR analyzers retained photometric performance integrity, still meeting the manufacturing specification of 60-sec RMS signal-to-noise greater than 50,000:1 with no spectral artifacts from the vibrations being observed.
Applications
The real-time capabilities of EP-IR spectroscopy make the method well suited for a range of applications, including continuous emissions monitoring (CEMS), automobile emissions to meet the 2007-2010 new emission standards, solvent processing streams, specialty gases (blend ratios and purity) and environmental monitoring. Also the ultra-fast scan speed of 100 scans/second allows researchers to use EP-IR ana-lyzers to monitor fast kinetic-type reactions, including explosions and combustions in real-time, as well as end-point and fast polymer reactions such as RIM.
EP-IR analyzers are capable of processing CO, CO2, CH4 and total hydrocarbons falling within a 2.5- to 5.0-mm (4000- to 2000-cm-1) spectral range. Additionally, they measure NOx, HCl and NH3 2.85- to 5.50-mm (3500- to 1818-cm-1) spectral range.
EP-NIR systems are uniquely suited for applications in the 1375- to 2750-nm spectral range. Some of these applications include protein purification and separation analysis for HPLC-type applications, gas analysis, pharmaceutical production, food stuffs monitoring and petrochemical applications.
Future Developments
Improved sensitivity together with size reduction and battery operation for remote sensing are the main developments that Aspectrics plans to initiate. The smaller size will enable EP-IR analyzers, as one example, to be placed into shipping containers for chemical monitoring. A further area of development will be designing the packaging so that the units are capable of existing in a hazardous environment without the necessity for any additional enclosure. This will result in significantly lower integration costs for customers.
For more information, contact Jim Yano, VP marketing, Aspectrics Inc., at info@aspectrics.com or by phone at 925-931-9270 or visit www.aspectrics.com.