Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Utilizing electrical or radiant energy
Reexamination Certificate
2000-12-26
2002-01-01
Nguyen, Dean T. (Department: 1731)
Paper making and fiber liberation
Processes of chemical liberation, recovery or purification...
Utilizing electrical or radiant energy
C162S263000, C250S339060
Reexamination Certificate
active
06334930
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a measurement device for quantitatively detecting constituents of a pulp/fluid mixture for paper or cardboard production and a process of using the measurement device.
2. Background and Material Information
A number of conventional processes and measurement devices for quantitatively detecting constituents are described in “Wochenblatt für Papierfabrikation”, Paper Manufacturing Weekly, No. 7, 1996, pp. 272 to 279. According to the conventional processes and measurement devices, pulp consistency measurements (percentage of total mass) in a consistency range of 1.5% and higher have been carried out based upon shear force measurements and measurement of a dielectric constant over the propagation speed of microwaves. Pulp consistency measurements in the low consistency range below 1.5% are carried out, among other ways, based upon a depolarization measurement. Polarized light is conveyed through a pulp suspension, whereupon the polarized and depolarized portions in the measured light are compared to each other.
A measurement device is also described which, for various wavelengths, measures the depolarization of emitted laser light, the damping and backscattering of laser and xenon light, and the absorption of xenon light. As a result, fifteen different optical measurement values are registered simultaneously. The fibrous solids and filler consistencies are calculated from these measurement values. The obtained depolarization signal of the penetrating light is representative of the overall consistency. Damping and backscattering are used to determine the filler consistency and the overall consistency. This known measurement device is particularly useful for optimizing a wet section. This device is able to detect a number of different constituents of the mixture. However, it is relatively complicated and thus expensive. In addition, transmitted light is a prerequisite, which involves a greater space requirement. Further, the measurement conduit must have a small diameter, especially when the pulp consistency increases. At higher pulp consistencies, the medium must be diluted.
For measurements in the low consistency range, a known device utilizes the peak value measurement method with transmitted light, wherein fibers are counted by a focused light beam and the ash content is measured by absorption. This known device can distinguish ash and fibers as a group, but is incapable of further differentiation. Moreover, transmitted light is used, thus requiring additional space. Also, the measurement conduit must have a relatively small diameter, particularly when the pulp consistency increases. Finally, at higher pulp consistencies, the medium must be diluted.
SUMMARY OF THE INVENTION
The present invention creates an improved process and an improved measurement device for quantitatively detecting constituents of a pulp/fluid mixture in which the disadvantages mentioned above are eliminated.
According to the invention, the process includes irradiating a mixture by at least one radiation source that irradiates in a number of definite, different wavelength ranges. The intensity of radiation that has been influenced by the mixture is measured by at least one sensor, each sensor measuring only one of the definite, different wavelength ranges of the radiation at a particular time. A spectrometer is therefore not required.
In this connection, radiation that has been reflected by the mixture can advantageously be detected by at least one sensor. In addition to this or alternatively, it is possible to detect radiation that has passed through the mixture by the one sensor. Detecting only radiation that has been reflected by the mixture provides the advantage of a low space requirement. A sensor can, for example, be attached to a container of the mixture, which is suspended.
In an embodiment of the invention, the mixture is irradiated by at least one optical radiation source and the intensity of the optical radiation that has been influenced by the mixture is measured by at least one photoelectric sensor. If the mixture is irradiated by a number of radiation sources of different wavelength ranges, then it is advantageous if the mixture is irradiated in chronological sequence by the individual different radiation sources and/or by different combinations of radiation sources.
In an embodiment of the present invention, a wide band sensor is used, which includes all of the different wavelength ranges. Because only one of the different wavelength ranges of the radiation is detected at one time, a spectrometer is not required.
In a particular embodiment, at least one LED is used as a radiation source, which is particularly advantageous in view of the LED's longevity and low cost. Consequently, a longstanding belief that LEDs are not suitable can be overcome.
In a wavelength range from 1300 to 2400 nm for which LEDs are not available, there are relatively pronounced peaks in the absorption spectrum, e.g., at 1450 nm water harmonic, 1930 nm water, 2100 nm cellulose fiber, 2010 nm clay, approx. 2300 nm latex and lignin, 2300 to 2400 nm polyethylene and other plastics. Thus, up to now lamps with incandescent filaments have been used. However, trials have shown that the constituents of the mixture can also easily be inferred using a number of LEDs having different wavelengths. Thus, the relative measurement precision, i.e., the response sensitivity of a sensor to very slight consistency fluctuations, is very high. A possible slight limitation of the absolute measurement precision is therefore insignificant. The considerably higher service life of LEDs in comparison to lamps with filaments is also particularly advantageous. This is particularly crucial for use in a dilution water headbox where 50 to 150 sensors are typically used simultaneously and the operator cannot reasonably be expected to continuously contend with lamp failures.
An additional inference from the absorption of different wavelengths is possible if at least two sensors are used, the sensors being disposed at different distances from the radiation sources. Fundamentally, it is also possible to associate each radiation source with its own sensor or its own pair of sensors. In this regard, more space is required. However, the fact that the measurement results obtained by the sensors can be queried simultaneously is advantageous.
The radiation sources can, for example, also be provided in a common container. Therefore, the radiation sources can be practically produced as a single radiation source, for example as a lamp with a number of different filaments. Thus, the type of radiation respectively emitted can then be changed, particularly as a function of electrical input signals.
The radiation sources and sensors can be separated from the mixture by a window. Alternatively, it is conceivable for there to be a coupling by way of a system of mirrors or fiber optic cables made of glass or plastic. The structural cost in this embodiment is somewhat greater, but it saves space.
In an exemplary embodiment, three optical radiation sources and two sensors are used. As a result, six signals are available. The required hardware can be simply integrated, for example, into a pulp density regulated headbox. It requires little space in the machine and can be produced very inexpensively.
According to the exemplary embodiment, an infrared LED (e.g., 880 nm or 950 nm), a red LED (e.g., 635 nm), and a blue LED (e.g., 480 nm, possibly a gallium nitrite LED with 430 nm) are used. The angle of radiation of the LEDs is crucial to the measurement process. At least one LED is advantageously used having an angle of radiation between approximately 12° and approximately 30°.
The switching frequency of the LEDs should be high in comparison to the time pattern in which the consistency values are required. This switching frequency is limited by the limit frequencies of the sensors and the LEDs as well as by the speed of the evaluation electronics. In actual use, for example, it is conceivable
Griech Wolfgang
Münch Rudolf
Winter Franz
Greenblum & Bernstein P.L.C.
Nguyen Dean T.
Voith Sulzer Papiertechnik Patent GmbH
LandOfFree
Measurement device for quantitatively detecting constituents... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Measurement device for quantitatively detecting constituents..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Measurement device for quantitatively detecting constituents... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2832663