Electric heating – Heating devices – With power supply and voltage or current regulation or...
Reexamination Certificate
1999-10-06
2001-09-25
Paschall, Mark (Department: 3742)
Electric heating
Heating devices
With power supply and voltage or current regulation or...
C219S121550, C219S121540, C219S121480, C110S250000, C588S900000
Reexamination Certificate
active
06294764
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to the field of automated controls and more particularly to multi-component process analysis and control of operations within applicable industrial segments.
Compositional evaluation of industrial process streams currently involves sampling followed by laboratory evaluation. Normally, specific locations along the process stream are selected. Samples may be gathered in the exhaust stack to confirm that the facility is in permit compliance. Other evaluation points may be after specific operations or directly prior to packaging and are used to gauge process efficiency and/or product purity. One problem with this approach concerns the time lag between the actual sampling event and attainment of the desired analytical information. Sample integrity may also be a concern if deleterious reactions are possible or if chemical reactions have not proceeded to completion.
Basing decisions upon delayed-time data can lead to deficiencies in process control, especially when hours or tens of minutes are needed for the analysis. In such a situation, the process would continue to operate under the same conditions until the new sample information was received. Assuming that the chemical information was unacceptable, the plant operators would proceed to systematically change process control variables (temperatures, feed rate, etc.) until a desirable process condition was obtained. Tuning a large-scale process in this manner can be inefficient and product yields during the out-of-specification period would be lower than expected, which would translate into lost revenues (lower profit margins) and an increase in process emissions (reactant byproducts). Furthermore, once the process is tuned, slight changes in raw material feed stocks can effect product yields. These input changes would normally go unnoticed and the process would not be operating at peak efficiency.
The most appropriate means for assuring high product yields while controlling process emissions would be to rapidly determine the necessary chemical information and transmit the results to, for example, the facility control computer, wherein decisions based on a specified process model could be automatically implemented.
The use of Fourier Transform Infrared (FTIR) spectroscopy allows determination of the concentrations of multiple gas phase constituents in near real time. Simply interfacing an FTIR at appropriate facility locations, either in an extractive (sampling) or in an on-line (non-intrusive) configuration, i.e., across a process channel, followed by communication of the results is, however, insufficient. In order to produce a reliable, effective, and robust process control scheme, a system (or protocol) of instrumental and measurement guidelines and quality assurance/quality control (QA/QC), must be adopted. Without such validations system implementation can be rendered ineffective and may result in erroneous observations leading to the misapplication of controls. The use of a protocol also allows for numerous checks on the performance of the instrument and the data obtained. The concept disclosed herein is intended to eliminate the obstacles associated with the lack of a viable QA/QC plan and with other deficiencies, noted in the prior art, regarding process specificity.
Chapple-Sokol et al. (Chapple-Sokol), U.S. Pat. Nos. 5,431,734, and 5,665,608, describe a system for control of the addition of aluminum oxide to a chemical vapor deposition reactor based on the use of FTIR to detect product degradation. The technology employs an in-line analysis cell and a single valve operated to either permit the chemical to flow into the reactor or to bypass the reactor altogether if the chemical has been found to have degraded. Improved product yield is expected. However, Chapple-Sokol do not disclose or suggest quality assurance/quality control and are targeted to the evaluation of a single chemical and the associated degradation products. Application of the developed technology would be limited to gas stream temperatures consistent with preservation of the materials and components used in the sample cell.
Holt (U.S. Pat. No. 5,457,260) discusses the use of near-infrared spectroscopy to control a simulated moving absorbent bed separation process. The target application is specific and a QA/QC framework for imposing regulation on the measurements, thereby assuring the acceptability of the data, is lacking.
Le Feber et al. (U.S. Pat. No. 5,430,295) describes a process for the controlled mixing of petroleum components. The specific embodiment relies on a control process based on a specific model for the generation of the product of choice. The foremost method for detection of the specific target molecule in the mixture was noted as near-infrared spectroscopy although other means for the determination of the given molecule or final product parameter are claimed. Again, a QA/QC frame work was not considered.
Lange et al. (U.S. Pat. No. 5,151,474) describe the use of a multi-component analyzer (FTIR spectrometer) in the context of controlling a polymerization process for polyolefins. The spectrometer is directed toward the quantification of 1-octene, ethylene, and propylene. Lange et al. does not refer to a standard means for assuring and controlling the quality of the measurements. Moreover, applications to processes other than olefin polymerization were not considered.
Reagen (U.S. Pat. No. 5,777,735) describes an in-situ gas analyzer consisting of the basic functional components of an FTIR spectrometer. A traceable QA/QC protocol is cited but the gas analyzer does not consider the direct control of industrial and/or manufacturing processes. The cited invention is specific for evaluating trace concentrations in ambient air samples (there is no sample pre-processing involved), thus the objectives and scale of the instrumentation are directly applicable to the field of industrial hygiene and not process control where typically larger molecular concentrations are encountered.
SUMMARY OF THE INVENTION
The present invention overcomes the aforementioned limitations of the prior art to a great extent by providing an apparatus and method for multiple component process analysis and control comprising the steps of obtaining a sample from a process stream, interrogating the sample using Fourier transform infrared spectroscopy according to an established QA/QC protocol to determine the concentration(s) of a single or multiple constituents which indicate the state of the process, transmitting the determined concentration(s) to a control computer, determining control system response based upon the determined concentration(s) and a process model, implementing at least one facility action based on the control system response, and repeating the obtaining, interrogating, transmitting, determining and implementing steps. Furthermore, the MPAC system extends the technology of multi-component analytical instrumentation to direct use in a controller suitable of a wide variety of processes encountered in waste remediation, chemical manufacturing, combustion, and other industrial operations.
An object of the invention is to provide an automated controller which is based upon a method suitable for quantification of multiple components inherent to a process stream sample coupled with a viable and traceable quality assurance/quality control (QA/QC) routine thereby permitting rapid temporal quantification of multiple components enabling a high level of process control.
Another object of the invention is to provide a control system that is versatile enough so as not to be restricted to a specific application.
Another object of the invention is to provide a controller which allows for incorporation of various control scheme architectures.
A further object of the invention is to provide a control system based upon reliable technology.
Yet another object of the invention is to provide a control system capable of increasing product yields as opposed to traditional control systems.
Still yet another object of the in
Hamilton Jason M.
Lindner Jeffrey S.
Toghiani Hossein
Kelber, Esq. Steven B.
Mississippi State University
Paschall Mark
Piper Marbury Rudnick & Wolfe
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