Blast furnace with top-gas recycle

Abstract

A blast furnace where coke is combusted with oxygen, instead of air, and where a top gas comprising CO, CO2, H2, and without excess nitrogen is withdrawn from the upper part of the blast furnace, cleaned of dust, the H2 / CO volume ratio adjusted to between 1.5 to 4.0 in a water shift reactor, water and CO2 are removed (increasing its reduction potential), heated to a temperature above 850° C. and fed back to the blast furnace above where iron starts melting (thereby increasing the amount of metallic iron reaching the dead-man zone and decreasing the amount of coke used for reduction). Also carbon deposit problems caused by heating the CO-containing recycled gas are minimized by on-line cleaning of the heater tubes with steam without significantly affecting the reduction potential of the recycled reducing gas.

Description

technical field [0001] The present invention relates to the field of the iron and steel industry, and more particularly to a more efficient method and apparatus for the production of molten iron in blast furnaces, which reduces coke consumption by recycling reformed top gas, The upgraded top gas has an adjusted H 2 / CO ratio. Background technique [0002] In blast furnaces for making pig iron, iron ore is charged with coke and flux. Hot blast air is blown through tuyeres in the bottom of the furnace, thereby generating heat by burning the carbon in the coke, which melts the filler. The molten iron and slag are periodically discharged from the furnace. Combustion gases flow up through the furnace and reduce the iron oxides and leave the furnace as a hot dust-laden gas stream, the heat being recovered for preheating the blast and generally used as fuel in other areas of the steelworks. [0003] Metallurgical coke is required in the charging of blast furnaces because this m...

AI Technical Summary

Problems solved by technology

Another problem is that the recirculated gas needs to be reheated before entering the reduction zone of the blast furnace, because the high CO content will lead to carbon formation, which may cause blockage and fouling of the reheating equipment and heating path equipment

The disadvantage of this method is that a cryogenic plant is required to separate the nitrogen contained in the top gas

[0016] None of the above patents or patent applications teach or suggest the use of a CO shift reactor to improve the composition of the circulating top gas to significantly reduce the problem of heater coking of the circulating gas

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