Blast furnace processes

Opera.tlon, Because of the long residence time of the materials (8—10 h), the blast furnace process can exhibit considerable inertia, and control is usually appHed where the goal is maintaining smooth, stable input conditions. One of the most important aspects of blast furnace control is supply of consistent quaUty raw materials, which is why there is a strong emphasis on quaUty control at coke plants, peUeti2ing plants, and sinter plants (see Quality ASSURANCE/QUALITY control). 

The most common method of converting iron ore to metallic iron utilizes a blast furnace wherein the material is melted to form hot metal (pig iron). Approximately 96% of the world s iron is produced this way (see Iron). However, in the blast furnace process energy costs are relatively high, pollution problems of associated equipment are quite severe, and capital investment requirements are often prohibitively expensive. In comparison to the blast furnace method, direct reduction permits a wider choice of fuels, is environmentally clean, and requires a much lower capital investment. 

These formerly involved the use of banks of externally heated, horizontal retorts, operated on a batch basis. They were replaced by continuously operated vertical retorts, in some cases electrically heated. Unfortunately none of these processes has the thermal efficiency of a blast furnace process (p. 1072) in which the combustion of the fuel for heating takes place in the same chamber as the reduction of the oxide. The inescapable problem posed by zinc is that the reduction of ZnO by carbon is not spontaneous below the boiling point of Zn (a problem not encountered in the smelting of Fe, Cu or Pb, for instance), and the subsequent cooling to condense the vapour is liable, in the presence of the combustion products, to result in the reoxidation of the metal ... 

Formally no explanations have been given for these decisions. However, it is widely believed that the Veba process could not compete economically with the S VZ and blast furnace processes. 

Brassert A modified blast furnace process for making iron. Less limestone is added than in the usual process, so the product contains more sulfur. The molten iron product is mixed with sodium carbonate, with which the ferrous sulfide reacts yielding sodium sulfide and iron oxide. These float on the molten iron and are skimmed off. 

At present this method is excluded by a more economical process of methane reforming (considered in Section XIV). The exhaustion of natural gas resources may, however, restore the importance of coal gasification. In addition, reaction (377) is a constituent part of the blast furnace process. Reaction (378) is employed in the production of activated charcoal. 

Stankiewicz A. Between the chip and the blast furnace. Process intensification in industry and in academia. UEF Conference Refocusing Chemical Engineering, Barga, Italy, May 27-June 1, 2001. 

One of the most important characteristics of iron products, which enable the spectrum of properties to be achieved is the concentration of carbon present. Ordinary steels are iron-carbon alloys, which are simply referred to as steel, and are so important that this alloy comprises more than 98% of all iron alloys produced. In most iron-carbon alloys, the carbon is present as iron carbide, FesC, also called cementite. Since the carbon content of cementite is only 6.69%, a small change in the carbon content of an iron causes a large change in the concentration of the cementite present in the iron. Cementite is soluble in molten iron, one of the reasons why carbon is accumulated in the product of the blast furnace process for reduction of iron ores. This is an advantage, since the melting point of the iron-cementite mixture is depressed... 

In the eighteenth century, the blast furnace process was further developed so that iron could be made commercially. This process can be traced to the region around... 

The metallurgy of iron most common method for reduction uses a blast furnace process involves iron ore, coke, and limestone... 

We therefore obtain a value for Tr of 900 K. Extra coal is needed for the furnace to reach this temperature. The chemical drive of the whole blast furnace process, beginning and ending with all substances at room temperature, is strongly positive because of the additional consumption of carbon ... 

Table III - CO2 Emissions for the Sinter Machine -Blast Furnace Process and the...

The lead plant in Nordenham used the conventional two-stage sinter machine-blast furnace process until the development of bath smelting technology in 19%. 

In a blast furnace, coke is used to reduce the ore (iron oxide) to iron. Large quantities of gas, top gas , are formed at the top of the blast furnace as a result of the reduction of iron ore and the combustion of injected coal by injected blast air. Gas analysis is used to optimize the blast furnace process, including reducing the consumption rate of coke and controlling the temperatures inside the furnace. Analysis of hydrogen is very important for early detection of cooling water leaks which can be a considerable hazard. 

H -ll Phosphoric Acid Production by the Blast-Furnace Process.350... 

There are two basic types of processes for the production of phosphoric acid furnace processes and wet processes. Furnace processes include the blast-furnace process and the electric-furnace process. The blastfurnace process has not been used commercially since 1938. Tlie electric-furnace process is used extensively to make elemental phosphorus, most of which is converted to phosphoric acid for nonfertilizer uses. SirKe it is unlikely that furnace processes wll be competitive for producing phosphoric acid for fertilizer use, except possibly in unusual circumstances, these processes will be described only briefly. 

A flow diagram of a TVA pilot plant for producing phosphoric acid by the blast-furnace process is shown in Figure 11.34. The scale of the pilot plant was about 1 tonne of P2O5 per day [431. ---------... 

In general, the blast-furnace process differs from the electric furnace in the following aspects ... 

The blast-furnace process was used commercially to produce phosphoric add for industrial and chemical products from 1929 to 1938 by the Victor Chemical Works, now Stauffer Chemical Company. The plant was located at Nashville, Tennessee (United States). 

Conventional blast furnace process. The graded sintered calcine obtained earlier is mixed with coke and limestone acting as flux and fed into the top of the blast furnace, where it is smelted using preheated air introduced at the bottom. The reduction processes yields a lead bullion, that is, an impure lead metal containing gold and silver as well as antimony, arsenic, copper, tin, and zinc. Lead bulhon is tapped off from the bottom of the furnace and either cast into ingots or collected molten in ladles for transfer to the refining process. 

---