| 摘要 |
The present invention is a method of measuring the temperature of a hot crystalline material. It is especially well adapted for measuring the temperature of mineral products within or being discharged from rotary or other types of kilns. The mineral material entering the kiln is doped with a rare earth compound at a level of at least 0.001 molar percent, preferably about 0.01 molar percent. During the process of calcination in the kiln, the rare earth is incorporated into the crystal lattice of the host mineral to form a phosphor. This is excited by laser light of an appropriate wavelength. The flourescence emitted by the excited hot material is then measured and can be accurately related to the temperature. In one version of the invention the mineral material is used in a chemical process where it is recycled to the kiln for recovery. The lime cycle in a kraft pulping operation is such a process. In this way there is minimal loss of the rare earth material and all that need be added is a sufficient amount to make up process losses. Under such operating conditions the cost is minimum and is minor when compared to the potential savings in fuel by avoiding overburning. However, the amounts of rare earth dopant used are sufficiently small so that the process can be used with other calcined materials, such as cement, which are not recycled through the process. Praseodymium is a preferred dopant for use with lime kilns.
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