Choosing the Parameters of a Blast-Furnace Smelting Technology That Includes the Injection of Coal-Gasification Products

Abstract

The use of a multi-zone mathematical model developed by the Institute of Ferrous Metallurgy of the Ukrainian Academy of Sciences to study blast-furnace smelting with the injection of coal-gasification products showed that additional coke can be saved by adding flux, increasing the temperature of the blast, and evenly distributing the ore burden across the top of the furnace. Keywords: coal-gasification products, mathematical model, replacement of coke, oxygen, carbon. A previous analysis of blast-furnace smelting technologies that include the injection of coal-gasification products (CGPs) showed that it is possible to significantly increase the amount of coal that can be injected if it undergoes preliminary gasification and the ash is fluidized in tuyere-mounted gasifiers (TMGs) (1). Coke consumption can be reduced by replacing high-grade coals having an ash content of up to 10% (and used in the blast furnace in the form of pulverized-coal fuel, or PCF) with low-grade coals containing up to 25% ash (and used in the blast furnace in the form of CGPs). When CGPs obtained from low-grade coals are injected, it is important to reduce coke consumption to a minimum (190-200 kg/ton) by also injecting PCF obtained from high-grade coals (2, 3). The key to a technology which entails CGP injection with the use of a TMG is equipping the knee-nozzle section of each blast-furnace tuyere with a device that gasifies PCF. The PCF is delivered to this device (gasifier) from the bustle pipe, with the PCF having previously been injected into the hot blast carried by the pipe. The CGPs formed in the gasifier are discharged from the TMG in the tuyere region and enter the tuyere hearth. Choosing efficient parameters for the smelting operation is part of the process of determining whether or not it is feasible to reduce coke consumption by the designated amount. The following are among these parameters when the furnace is to be injected with CGPs obtained from low-grade coals: 1) the temperature of the blast and its oxygen content, as well as the method used to supply the blast and oxygen needed for the gasification of coke and coal in the TMG: 2) the molar consumption of oxygen for gasification of the carbon in the coal, this parameter being calculated as the ratio O/C and expressed in moles/mole; and 3) the method employed to add more flux to the charge in connection with the increased amount flux consumed when high-ash coals are being used. The method used to supply the oxygen and blast needed for the gasification of coke and coal in the TMG is chosen based on the control parameters of the smelting regime and their set points. It has been proposed (1) that part of the oxidiz- ing blast which is sent directly into the furnace to burn coke be delivered via a separate channel that can be constructed in one of two variants: the use of a separate pipe to take a portion of the blast from the bustle pipe and transport it to the tuyere; the feeding of unheated oxygen through a pipe directly into the body of the tuyere to replace an equivalent amount of heat- ed blast. It was shown in (1) that hot blast can be replaced by unheated oxygen when the initial and projected unit consump-