At the end of June 1958, pure oxygen was, for the first time, successfully injected into the hot blast pipe of Higashida No. 5 blast furnace. In summer 1959 the furnace was run again with oxygen-enriched blast, and the operating data were analysed. The results then obtained were briefly reviewed in this paper.
The test run was started on May 26th 1956 and was terminated on July 11th. In the coures of the test period, O2-content, as well as humidity, of blast was increased step by step; iron production increased correspondingly, untill, at the beginning of July, the furnace, with its volume of 646m3, produced a maximum of 805 t/d.
(Production rate: 1·25t/m3/d., “throughgut” rate: 16·7t/mm2/d)
The coke rate, ranging between 600 and 630 kg/t, was not affected by an O2-enrichment of blast, nor by a strong humidification.
It was found that the increased iron production could be preliminarily calculated on the basis of a stoichiometric equation. The following equation was given for the calculation, which showed that 1% of O2-enrichrnent was equivalent to an increase in blast rate of 4·76%.
Where; P: Praductio……t/d
L: Blast valume……Nm3/mn
S: O2 flow-rate……Nm3/mn
w: Humidity of blast……g/m3
K1: A constant characteristic of the furnace
C. R. : Coke rate……t/t
A set of material balances and heat balances was worked out. They were compared with each other, and the following conclusions were drawn: (1) O2-enrichment and humidification of blast decreased solution losses and correspondingly increased the calorific value of coke in the furnace. (2) Decrease in the sensible heat of blast, which was due to decreased volume of N2, could well be compensated by the corresponding decrease in the heat carried out by top gas. (3) When blast was strongly humidified (e. g. 40g/m3), major fraction of H2, which was evolved at tuyere-combustion-zones, could be effectively used to reduce the iron ores charged. (4) The volumes of blast, bosh gas and top gas per ton of pig iron were proportionately decreased by O2-enrichment.
