Automatic temperature and humidity regulation – Furnace controlled – Furnace controlled responsive to combustion products...
Patent
1998-03-27
1999-10-26
Tanner, Harry B.
Automatic temperature and humidity regulation
Furnace controlled
Furnace controlled responsive to combustion products...
432 17, 432 37, 374137, C21B 724
Patent
active
059712864
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for determining the gas flux distribution in the shaft of a blast furnace. The invention relates further to an arrangement for carrying out the determination.
The gas distribution in the shaft of the blast furnace is of outmost importance. Controlled gas distribution is important for the utility of the gas and for the fuel consumption. A proper gas distribution gives a uniform descent of the burden and an optimal thermal stress of the walls. In practice, a completely uniform distribution throughout the cross section of the shaft of the blast furnace is not aimed at. The object is rather a situation where the gas flux is somewhat higher in the middle of the cross section than at the periphery of the shaft.
Because it is almost impossible to carry out direct and reliable measurements of the gas velocity, one has usually been tried to estimate the gas flux distribution according to indirect methods. The blast furnaces are equipped with a probe located above or below the burden, i.e. on a beam construction extending across the shaft, wherein said beam construction is equipped with temperature probes and gas sampling devices. Said beam construction is typically a beam or star-shaped construction extending across the shaft, said construction comprising radial beams, normally three, extending from the centre of the cross section of the shaft to the periphery.
The most common method used is based on the registration of the temperatures with the probe and the assumption that these temperatures describe the velocity distribution of the gas. The higher the temperature is the greater is, the gas flux. Other methods have also been disclosed in the literature. One known method is based on the temperatures registered by the probe as well as the velocity of the burden surface descent, which is registered by a so called profile indicator. According to another known method the distribution of the burden is first calculated theoretically followed by calculation of the gas distribution by equations of flow technique.
The Russian patent SU 1330163 discloses a method for the determination of the radial distribution of the gas flux in a blast furnace. The gas composition is determined by a probe located below the burden. The temperature of the burden surface is measured at several points by the use of an IR camera. Two consecutive surface temperature measurements are taken at certain intervals after each dump. The gas flux in the different annular zones is calculated from an empirical equation on the basis of the average gas flows, temperatures, the time differences and the specific heat capacity of the burden material. This method has, however, several drawbacks. The measurement of the burden surface temperature requires the expensive IR device and the probe below the burden is prone to wear. Additionally, the determination is based on the assumption that the thickness of the burden layer and the thermal conductivity of the burden material is the same in every measurement point. This assumption differs usually considerably from the conditions encountered in practice. A calculation based on this assumption may therefore lead to very errorneous results.
The object of this invention is to eliminate the problems mentioned above and to provide a new method for the determination of the gas flux in different points of the cross section of the blast furnace shaft. The method according to the invention is accurate and simple in comparison with known methods and it does not require any expensive investments.
The method according to the invention is characterized in that passed through the burden is measured using a probe located above the burden surface, in close vicinity to said surface, at different measurement points 1, 2, 3 . . . in the cross section of the shaft, and I located further away from the burden, in which point the gas is completely mixed, and balances for a control volume V above the burden surface of the blast furnace, wherein the lower boundary of said volume V goes through the
REFERENCES:
patent: 2625386 (1953-01-01), Leone
patent: 3617037 (1971-11-01), Foch
patent: 4098122 (1978-07-01), Landman et al.
patent: 4463437 (1984-07-01), Schenck et al.
"Russian Progress in Blast Furnace Automation", Iron and Steel, vol. 42, No. 4, pp. 244-246, Aug. 1969.
Nikus Mats
Saxen Henrik
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