Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Reexamination Certificate
2002-04-19
2004-08-31
Hannaher, Constantine (Department: 2878)
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
C250S343000
Reexamination Certificate
active
06784429
ABSTRACT:
FIELD OF THE INVENTION
The present invention is generally directed to an apparatus and method for in situ, real time measurements of properties of a liquid such as, for example, a molten metal. The liquid may be stationary or in a flowing state. Real time measurements may be taken from any location including inside the liquid and on the surface of the liquid. When measurements are taken below the surface of the liquid, a stable volume of an inert gas under continuous flow may be provided at the interface of the apparatus and the liquid to enable a rapid and accurate passage of a radiation beam into the liquid to generate a detectable species which is then analyzed to determine the desirable properties. Alternatively, the apparatus may operate in a passive mode without any supplied radiation by detecting species emanating from the liquid.
BACKGROUND OF THE INVENTION
The measurement of various properties of a liquid including, but not limited to, quantitative and qualitative measurements such as concentration and composition is of critical importance in a variety of industrial applications. When a liquid is contained within a vessel, measurements can be routinely taken by obtaining a sample of the liquid and transporting the sample to a remote location such as a laboratory so that the sample may be analyzed. Quantitative and qualitative measurements can be taken at the laboratory and then transmitted back to the operator of the vessel to determine if adjustments to the composition of the liquid must be made. While instrumentation is well known in the art to measure concentration and composition of a liquid, the time it takes to make such measurements and to relay the information to the operator of the vessel can be critical to productivity as in the metal (e.g. the production of steel or aluminum) and glass industries.
As an example, closely controlling the composition of steel during its manufacture is critical to the production of quality products. It is incumbent upon the operators of the steel plant to fine tune the composition of the molten steel. Currently, samples of molten steel are taken from the furnace, transported to a laboratory where spectrometric measurements are taken that determine the elemental composition of the steel. The results of the analysis are transmitted back to the furnace operator who determines whether the actual composition of the molten steel is the same as that desired. If not, adjustments to the composition may be made by adjusting the relative amounts of the components of the molten metal.
The time it takes to complete the compositional analysis of the molten product therefore is critical to the rate of production of the desired product (e.g. steel). It therefore is desirable to employ an apparatus and method for in situ analysis of liquids such as molten metals and glasses so that adjustments to the composition of the liquid may be made in a shorter period of time than through the use of outside labs. One such approach is disclosed in Carlhoff et al. (U.S. Pat. No. 4,995,723 and related U.S. Pat. No. 4,993,834) incorporated herein by reference. These references disclose a method of analyzing elements of a molten metal by providing a stationary conduit at a side wall of the vessel containing the molten metal. A laser beam is directed into the conduit and onto the surface of the molten metal. The light generated by the plasma formed by the interaction of the laser beam and the molten metal is coupled with an optical waveguide through a lens system and then introduced by the optical waveguide into a spectrometer. The system provides for measurements of the molten metal on the surface only and does so only at a fixed point due to the stationary position of the conduit.
Another stationary conduit system is disclosed in Cates (U.S. Pat. Nos. 5,830,407 and 6,071,466) incorporated herein by reference. A stationary conduit is inserted into the bottom of a vessel containing a molten metal. The center pipe of the stationary conduit carries a transparent gas under pressure to maintain an opening in the molten metal. The gas flow has a sufficiently high hydrostatic head to prevent the molten metal from entering the conduit. A sight glass assembly enables a direct view of the molten metal and an optical sensing device such as a photometer or spectrometer is employed for determining the composition of the molten metal. Here again, measurements of the molten metal are taken from a fixed position at only one location within the molten metal.
The systems described in the above-mentioned references suffer from a number of disadvantages. These prior art systems employ stationary conduits which require all measurements to be made from a fixed location either only on the surface of the molten metal or only at one location within the molten metal. Such systems are disadvantageous because the molten metal may vary in composition within a single vessel. The accuracy employed in adjusting the composition of the molten metal depends in part on getting a highly accurate reading of the entire composition of the molten bath. If only one fixed location for analysis is provided as in the above-mentioned references, the accuracy of the analysis with respect to the entire molten metal is compromised.
Further disadvantages of the above-mentioned prior art relate to the angle at which the instruments interact with the probe. Because the molten material is of higher density than the gas, the device disclosed in Carlhoff et al., cannot sustain a static bubble of gas for making measurements. The heavier molten material will flow into the hole in the furnace wall displacing any gas. Therefore, gas must be flowing continuously in order to keep the molten material out of the instrument. This continuous flow will result in a non-stationary interface between the gas and the molten material, greatly complicating the measurement process, which is most accurate when the interface is stationary so that the optics are in focus. Since constant pressure is required to keep the molten material out of the device, the loss of gas pressure due to for example, a leak in the gas supply line, may adversely affect the desired measurements and may result in damage to the instruments.
The device disclosed in the Cates references has similar disadvantages. While a vertical orientation can maintain a static surface, if pressure is lost, the device will be destroyed and the molten material lost, just as in the case of Carlhoff et al. Also, while the vertical column of gas can be stationary in Cates, it is unstable, particularly if some of the gas is released into the bath due to a disturbance of sufficient magnitude, the remainder of the gas is likely to follow, and molten material will flow into the tube.
A further disadvantage of Cates concerns the required access from the bottom of the furnace. It is typically very difficult to gain access to the bottom of commercial furnaces because of the weight of the furnace. Also, there is the potential for a disastrous leak of molten material onto the factory floor with a port located on the bottom of the furnace. When the port is on the side, material will leak out only until the level of molten material in the vessel falls below the level of the port. With the port positioned on the bottom of the vessel, and the column containing the gas extending only a short distance into the furnace, nearly the entire volume of molten metal contained in the furnace can leak out if there is a loss of gas pressure.
Another disadvantage in the Cates and Carlhoff et al., systems relates to the location where analyses are performed. Carlhoff et al., samples the molten material at the wall of the furnace, and Cates samples the molten material near the bottom of the furnace. These locations may contain molten material that is not representative of the bath as a whole. When the furnace operators introduce alloying elements into the bath, they attempt to mix them thoroughly throughout the bath. However, it is most difficult to ensure thorough mixing of the ingredients close to the si
De Saro Robert
Weisberg Arel
Energy Research Company
Watov & Kipnes P.C.
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