INDUSTRY & BUSINESS
Steel keeps pressure on oxygen capacity Steelmakers may be using oxygen at the rate of 8 million tons a year by the end of 1967, 2 million more than last year Mention oxygen to steelmakers or to oxygen producers today and the universal response is "capacity is going up." Last week, for instance, the Linde division of Union Carbide said it would add a fourth 1200 ton-per-day oxygen unit at its Lakeside works near Gary, Ind. Earlier Linde announced plans for the third unit at Lakeside, which, with two 1200 ton-per-day units, is already the largest oxygen facility in the industry. In the next 12 months about 5800 tons per day of additional capacity, mostly high-purity ( 9 9 . 5 < A )
gaseous
oxygen, is scheduled to go on stream for use by steel firms. That's nearly a 25% increase over the present on-site capacity—24,000 tons per day—installed for steel firms. The U.S. steel industry used about 6 million tons of oxygen last year. Total production of oxygen in the U.S. was about 7.6 million tons last year. By the end of 1967 the steel industry's use of oxygen could reach 8 million tons annually. High-purity gaseous oxygen is in growing demand today for use in basic oxygen process (BOP) furnaces. They use high-purity oxygen at a prodigious rate; a 300-ton furnace, for instance, takes up to 24,000 cubic feet of oxygen a minute. Last year 23 million ingot tons of steel were produced in the U.S. in BOP furnaces; total U.S. steel production was about 131 million ingot tons. In February 1966 the BOP annual operating rate was in excess of 30 million ingot tons. By the end of the year it will reach about 40 million ingot tons (installed BOP furnace capacity will be about 42 million ingot tons). By the end of 1967 BOP furnace capacity may well be up to 60 million tons. The oxygen requirement for last year's 23 million tons of BOP steel was about 1.8 million tons. To supply 1967's 60 million tons of BOP steel capacity would require from 4.2 to 5 million tons of oxygen at the current rate of use, which is about 1700 to 2000 cubic feet of oxygen per ingot ton of steel. The basic oxygen process isn't the steel industry's only use for oxygen. Nor is it even the biggest. Last year, about 2.3 million tons of oxygen were used in open-hearth steelmaking. 34 C&EN MAY 9, 1966
Sometime this year, the total use of oxygen in BOP furnaces will probably overtake the total used in open-hearth furnaces. Other uses of oxygen are in finishing operations and in oxy-fuel gas cutting and welding. There are four major suppliers of oxygen to the steel industry: Linde, Air Products and Chemicals, Air Reduction, and National Cylinder Gas (a division of Chemetron). The bulk of the 24,000 tons per day of on-site capacity now installed is owned and operated by the oxygen firms; they supply the gaseous oxygen to the steel plants. This on-site capacity is divided about as follows: Linde, 5 3 % ; Air Products, 20%; Air Reduction,
BOP SHOP. At Bethlehem Steel's new basic oxygen facilities at Sparrows Point, Md., shop superintendent R. F. Urban uses control room intercom
Cheap, pure oxygen cha ged BOP steel from old i In 1950, the open-hearth process accounted for about 9 0 % of the steel made in the U.S. Its principal competitors were the electric furnace and the Bessemer process, each of which accounted for about 5 % of the steel produced. Today, the Bessemer process accounts for perhaps 1 % and the electric furnace for about 1 0 % . In 1954, however, a new technology arrived on the commercial scene as McLouth Steel began producing steel in the basic oxygen process (BOP) furnace. The BOP furnace, known abroad as the L-D (for Linz-Donawitz) furnace, was developed in Europe. The goal was a method faster than the open-hearth process and able to produce steels lower in phosphorus and nitrogen than Thomas steel. (In the World War II period, about half of Continental Europe's steel was Thomas steel, steel made in a Bessemer converter with a basic lining instead of an acid lining.) In pre-oxygen open-hearth furnaces a charge of scrap metal, iron ore, limestone, and hot metal (usually molten pig iron) is melted. Phosphorus, sulfur, silicon, manganese, and undesirable materials are adjusted to an acceptable level. After the solid part of the charge is melted and ore reactions start, the limestone calcines to lime and be-
comes part of a slag layer on top of the molten metal. The oxygen required for decarburizing (removing carbon from) the iron is supplied from the iron ore and the oxidizing atmosphere above the slag layer. Much of the oxygen must diffuse into the slag layer from the atmosphere and then from the slag into the metal below. Diffusion of enough oxygen takes considerable time. In addition, carbon reacts with iron ore highly endothermically. Increased thermal requirements of this process also contribute to lengthy heat (batch) times. Typical decarburization times in an openhearth furnace were three to six hours, and charge-to-tap time was about nine to 13 hours. An obvious way to speed the decarburizing reaction is to increase the rate of oxygenation. Bessemer suggested the idea in 1856. But the lack of high-purity oxygen in quantity, its high cost, and poor refractory life precluded its use. Nevertheless, experiments with oxygen began in Europe shortly before World War II. In 1949, a pilot plant was erected in Linz, Austria, and commercial plants were built within a short time at Linz and Donawitz, Austria. The first commercial heat was poured at Linz in November 1952.
10%; National Cylinder Gas, 6%. Hydrocarbon Research, Inc., has about 3 % and the remainder—8%—is owned by the steel firms. High-purity gaseous oxygen for steelmaking is made by low-temperature fractionation. The liquid air is passed through a distillation column to separate oxygen, nitrogen, and byproduct fractions. The high-purity oxygen is warmed and vaporized through a heat exchange against incoming air. The nitrogen may be handled in a similar way and marketed as product gas or it may be used as a "waste stream" to cool incoming air. The gaseous oxygen from the heat exchanger is supplied to the steel plant by pipeline. Oxygen makers are pushing to keep pace with demand from steelmakers. Air Reduction says new plants scheduled to come on-stream within the next 12 months will increase its oxygen output to steel mills by 850 tons a day. Air Products has just completed construction of a 900 ton-a-day plant at Bethlehem Steel's Sparrows Point, Md., plant, and is currently building new capacity for Armco Steel, the
to modern reality In the BOP, high-purity oxygen is jetted directly through the slag into or onto (the choice of the preposition being one of the matters at issue in a legal dispute between Kaiser and the rest of the steel industry) the metal via a water-cooled lance above the surface of the melt. The lance oxygen is fed into the metal at supersonic speed—lance head pressure is from 140 to 180 p.s.i. The oxygen reacts with the iron producing an iron oxide which oxidizes the carbon to carbon monoxide. In the U.S., the time from chargeto-tap in BOP furnaces has been as short as 38 minutes, much below that required in the open-hearth. Furnace sizes vary from 100 to 300 tons and they take about an hour per heat (compared with 20 to 25 tons per hour with the older openhearth furnaces and 40 to 50 tons in those converted to use oxygen). The third type of steel furnace of importance today is the electric furnace. It can accept an all-scrap charge. In this, it is unlike present BOP furnaces, which are limited to charges with about 3 5 % scrap because too much scrap would cool the charge excessively. In electric furnaces the temperature and composition of the metal bath can be regulated with high precision but the cost of power limits their use.
Weirton division of National Steel, and Granite City Steel. As the size of the air separation plants has increased, the unit cost of oxygen has decreased. But the increase in size of the air separation plants has been predicated on increased oxygen demand from steelmakers; this demand, in turn, was predicated on less expensive oxygen. The first-generation oxygen plants (those built before the early 1950's) produced up to 60 tons of oxygen per day, some of it gaseous but mostly liquid. The price of oxygen fluctuated from about $80 per ton in the midthirties down to about $25 a ton in the early fifties. Next, in the mid-fifties, came 110 to 140 ton-a-day plants. They produced gaseous oxygen for sale at about $15 a ton. Third-generation plants, introduced in the late fifties, were up to 400 to 600 tons a day in capacity. The present fourth-generation plants are in the 900 to 1200 ton-a-day class. From these new, larger plants, high-purity gaseous oxygen is sold for $7.50 to $10 per ton. Oxygen is used in open-hearth steelmaking to speed up decarburiza-
tion. The oxygen is generally added via a water-cooled roof lance, similar to the lance used in BOP furnaces. Also, experimental work is under way on using a high-temperature, oxy-fuel flame to accelerate scrap melting in open hearths. Possible uses of oxygen in the near future are for blast-furnace air enrichment in iron production and scrap melting in open-hearth, BOP, and electric furnaces. In the more distant future, 1970 and beyond, even greater use of oxygen in steelmaking and metallurgy is foreseen. A. L. Hodge, associate manager of gas products development for Linde, says it's conceivable that in the next 25 years oxygen requirements for metallurgical use—iron, steel, and alloy production and finishing—could reach an annual total of 3000 to 5000 cubic feet of oxygen per ton of finished steel. (The rate in 1965 was about 1150 cubic feet per ton of finished steel.) This rate of use would require an annual production of 20 to 40 million tons of oxygen for steelmaking. Studies by Air Products and Air Reduction Co. confirm this estimate.
ON-SITE. Oxygen capacity installed for steelmakers will increase by nearly 2 5 % in the next 12 months, reaching close to 30,000 tons a day. This on-site plant serves Armco Steel at Ashland, Ky., belongs to Air Products
REACTION. Oxygen reacts with impurities in the molten iron and steel scrap in BOP furnace at U.S. Steel's Duquesne Works. By 1967, BOP furnace capacity may total 60 million tons, require 5 million tons of oxygen
