GB1317826A - Method of controlling a blast furnace - Google Patents

Abstract

1317826 Controlling blast furnace operation NIPPON KOKAN K K 28 May 1970 [28 May 1969] 25867/70 Heading C7D [Also in Division G3] A blast furnace 1, which, for more precise control may be monitored in each of four sectors, Fig. 5 (not shown) is controlled to keep the silicon, Si, content and outlet temperature T p of the tapped iron near desired values by keeping the height (H), Fig. 1 (not shown) of the coke reserve between the direct reduction zone (6) and the tuyered (2) substantially constant by calculating the rate of coke consumption, R and tuyere flame temperature F as functions of the moisture, fuel, oil content, and blast temperature of the tuyere blast gas, and the chemical composition of the furnace top gases, and hence controlling R and F, as follows: - Calculator C3, on the basis of the chemical composition; CO, CO 2 , H 2 (N 2 ); of the furnacetop gases, and the moisture and fuel oil content; M, "Oil"; of the tuyere gases provides to calculator C-2 using empirical algelbraic relations, quantities #,γ representative of the indirect and hydrogenous reducing amounts. The moisture content is measured by a lithium chloride hygrometer, the oil being measured by rotameter. C2 also receives the ratio O/C of ore to coke in the burden, as well as, from a calculator Cl, a measure O x of the reducing requirement of the iron ore and provides as output to C4 a signal L representing oxygen content in the direct reduction zone (6) and C 4 calculates, on the basis of empirically founded linear algelbraic relations, with coefficients h i , f i , and inputs T p , Si, as well as corresponding desired values (Si), (T p ), theoretical values of coke consumption (R) and tuyere flame temperature (F). Calculator C5, on the basis of the total reduction α, determined empirically from the top gas composition, and the actual values M, "Oil", of moisture of oil, contents of the tuyere gas, provides other calculated values of these quantities, the two such sets of quantities being processed in C6, also receiving upper limit constraints Muc, Oil uc, Tuc, and which provides corresponding calculated values Teal, Oilcal, Mcal, which, in C7 are compared with lower limit constraint values MLL OilLL and TLL and maximum allowable fluctuations #M, #Oil, #T, the outputs of C7 setting the servocontrollers MRC, OilRC, TRC. The calculated values are also fed to C8, which compares them with desired values (M), (Oil), (T), and in dependence upon excessive deviation calculated from desired values, causes the coke composition of the burden to be changed, at the succeeding charging, by increasing or decreasing the charge of coke by a weight #C to correct the deviation. Operation:- The furnace is set to be operated at nominal given rates of coke and oil consumption, and moisture content of the tuyere gases, and the algelbraic relations, and linear programming coefficients are empirically suited to operation about such rates. In practice Tcal is set to a maximum permitted value with Oilcal, Mcal and coke consumption (C) varying in accordance with the above control scheme. Typical nominal settings for the furnace are (i) M is set high, maximizing production. (ii) M is set low, minimizing coke consumption and hence costs, perhaps by additionally setting the oil consumption high. To determine the composition of the furnace-top gases, an infrared gas analyser is used for CO and CO 2 , a thermal conductivity gas analyser for H 2 , the remainder of the gas being assumed nitrogen. The tapping temperature T p is measured by immersion thermometry, or by a two colour pyrometer. Silicon content is determined by optical spectrometry.