Coke and Steel

NH3 oxidation down to below 700 K, where NO is metastable. NO oxidation to NO2 is only favored at low temperatures. 

For ammonia oxidation, PtRh gauzes with a wire diameter of about 70p.m are used as catalyst. At temperatures above 400 °C the effective rate is completely controlled by external mass transfer, and catalytic NH3 oxidation is one of the rare cases where a non-porous solid catalyst is used. For complete NFt3 conversion, only ten gauzes are needed, which underlines the rule of thumb that about ten characteristic lengths (here the wire diameter) are needed if the kinetics are determined by external mass transfer. 

The diagram representing the sigmoidal heat production function and the line of heat removal shows that the wire ignites at a gas preheating temperature of around 150°C, which leads to a wire temperature of around 900°C. 

The NH3 into NO conversion efficiency increases with decreasing pressure, whereas the conversion of NO into NO2 and the subsequent absorption is favored by high pressures. Thus, modern nitric acid piants are duai pressure processes, that is, the product gas of ammonia oxidation (at 6 bar) is compressed to 12 bar and then fed to the absorption tower for NO oxidation and for NO2 absorption. 

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These three steps all produce significant amounts of waste. First, as discussed earlier, the nitration process results in the production of spent sulfuric acid. In the past the company had been able to sell much of this material to the coke and steel industries but declining demand meant that the acid now required disposing of, at additional cost. At the time green catalytic nitration technology was becoming available with clay, zeolite and lanthanide catalysts all providing possible alternatives to the use of sulfuric acid (see below). Improved selectivity to the desired para-isomer is an added benefit of some of these catalytic systems. However on the... 

Recovery of the various chemicals from the gas will be discussed. The mixture of iaron ore and limestone in the blast furnace is heated by the coke to form liquid pig iron. The gases liberated in the blast furnaces are used in stoves to preheat the air which is blown into the furnace to maintain combustion of the coke. The liquid pig iron is refined to liquid steel by direct reaction with oxygen in the Basic Oxygen Furnace, Some boiler ooal is used as a source of heat in boilers to produce steam used throughout the coke and steel plants. 

Hematite (Fe203), magnetite (Fe304) and pyrite (FeS) are the main ores of iron. Pig iron is produced by reduction of these ores with coke, and steel is produced by... 

Coke and Steel 595 Figure 6.5.10 Configuration of a blast furnace. 

When energy alternatives are available, a compromise between cost and quaHty is often realized. Blending of coals can be used to achieve more desirable quaHties. For example, lignite from the former Yugoslavia has been blended with, and even substituted for, the highly caking Rasa coal used for coke production in the iron (qv) and steel (qv) industries. 

Piebaked anodes aie produced by molding petroleum coke and coal tar pitch binder into blocks typically 70 cm x 125 cm x 50 cm, and baking to 1000—1200°C. Petroleum coke is used because of its low impurity (ash) content. The more noble impurities, such as iron and siUcon, deposit in the aluminum whereas less noble ones such as calcium and magnesium, accumulate as fluorides in the bath. Coal-based coke could be used, but extensive and expensive prepurification would be required. Steel stubs seated in the anode using cast iron support the anodes (via anode rods) in the electrolyte and conduct electric current into the anodes (Fig. 3). Electrical resistivity of prebaked anodes ranges from 5-6 Hm anode current density ranges from 0.65 to 1.3 A/crn. ... 

The largest consumer of coke is the iron and steel industry. In the United States, ca 600 kg of coke is used to produce a metric ton of steel. Japanese equipment and practice reduce the requirement to 400—450 kg. Coke is also used to gas from the char in one vessel. The reducing gas converts iron oxide to iron in the upper two stages of a second vessel. Steam is converted to hydrogen and reoxidizes the iron in two stages in the lower half of the vessel. 

Douglas E. Lowenhaupt, M.S., Group Leader, Coke Laboratory, CONSOL, Inc. Member, American Society for Testing and Materials, Iron and Steel Making Society, International Committee for Coal Petrology (Section 27, Energy Resources, Conversion, and Utilization)... 

General 1. Use cokeless iron- and steel-making processes, such as the direct reduction process, to eliminate the need to manufacture coke. 2. Use beneficiation (preferably at the coal mine) and blending processes that improve the quality of coal feed to produce coke of desired quality and reduce emissions of sulfur oxides and other pollutants. 

There are a large number of outputs that are produced as a result of the manufacturing of coke, iron, and steel, the forming of metals into basic shapes, and the cleaning and scaling of metal surfaces. For example ... 

Acetylene works Acrylates works Aldehyde works Aluminum works Amines works Ammonia works Anhydride works Arsenic works Asbestos works Benzene works Beryllium works Bisulfate works Bromine works Cadmium works Carbon disulfide works Carbonyl works Caustic soda works Cement works Ceramic works Chemical fertilizer works Chlorine works Chromium works Copper works Di-isocyanate works Electricity works Fiber works Fluorine works Gas liquor works Gas and coke works Hydrochloric acid works Hydrofluoric acid works Hydrogen cyanide works Incineration works Iron works and steel works... 

The production of steel begins when iron ore is fed into a blast furnace (Fig. 16.39). The furnace, which is approximately 40 m high, is continuously replenished from the top with a mixture of ore, coke, and limestone. Each kilogram of iron produced requires about 1.75 kg of ore, 0.75 kg of coke, and 0.25 kg of limestone. The limestone, which is primarily calcium carbonate, undergoes thermal decomposition to calcium oxide (lime) and carbon dioxide. The calcium oxide, which contains the Lewis base O2", helps to remove the acidic (nonmetal oxide) and amphoteric impurities from the ore ... 

Coke and by-products part of SIC 3312—"Blast furnaces (including coke ovens), steel works, and rolling 3312... 

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