Open-hearth process

Kingdom. Adapted to steelmaking, the open-hearth process was the principal method for producing steel throughout the world until 1970. As of this writing (1996), it is stiU used in China and the CIS.  [c.374]

The manganese residue of the blown metal before ladle additions is generally higher than in an open-hearth process and is closely related to the amount of manganese in the furnace charge. High slag fluidity and good slag—metal contact promote transfer of phosphoms from the metal into the slag, even before the carbon reduction is complete. Efficiency of sulfur elimination is as good as or better than that in the basic open-hearth process because the bath action is more vigorous, the operating temperatures are higher, and the fuel does not contain sulfur.  [c.377]

Traditionally, pig-iron was converted to wrought-iron by the puddling process in which the molten iron was manually mixed with haematite and excess carbon and other impurities burnt out. Some wrought-iron was then converted to steel by essentially small-scale and expensive methods, such as the Cementation process (prolonged heating of wrought-iron bars with charcoal) and the crucible process (fusion of wrought-iron with the correct amount of charcoal). In the mid-nineteenth century, production was enormously increased by the introduction of the Bessemer process in which the carbon content of molten pig-iron in a converter was lowered by blasting compressed air through it. The converter was lined with silica or limestone in order to form a molten slag with the basic or acidic impurities present in the pig-iron. Air and appropriate linings were also employed in the Open-hearth process which allowed better control of the steel s composition, but both processes have now been supplanted by the Basic oxygen and Electric arc processes.  [c.1072]

The first gas producer making low heat-value gas was built in 1832. (The product was a combustible carbon monoxide—hydrogen mixture containing ca 50 vol % nitrogen). The open-hearth or Siemens-Martin process, built in 1861 for pig iron refining, increased low heat-value gas use (see Iron). The use of producer gas as a fuel for heating furnaces continued to increase until the turn of the century when natural gas began to supplant manufactured fuel gas (see Furnaces, fuel-fired).  [c.63]

The original process of heating coal in rounded heaps, the hearth process, remained the principal method of coke production for over a century, although an improved oven in the form of a beehive was developed in the Durham-Newcastie area of England in about 1759 (2,26,28). These processes lacked the capabiHty to collect the volatile products, both Hquids and gases. It was not until the mid-nineteenth century, with the introduction of indirectiy heated slot ovens, that it became possible to collect the Hquid and gaseous products for further use.  [c.63]

Nickel Alloying. Nickel is alloyed iato low alloy steels, ferritic alloy steels, and austenitic stainless steels through the conventional steelmaking processes, eg, open hearth, basic oxygen conversion, and the argon—oxygen decarburization (AOD) processes. The AOD process is used to produce a substantial quantity of the stainless steels ia the world. It is a highly productive process that yields cleaner products at lower operating and materials costs as compared to the older conventional electric-arc-fumace (EAF) steelmaking practice. EAF or AOD melting and air-iaduction melting (ATM) are used for some nickel-base alloys. Electro slag remelt (ESR) processiag also is used to further refine these steels and nickel alloys.  [c.6]

Typically, procedures have become less invasive as technology evolves. Eady pacemaker procedures involved open-heart surgery to attach pacemaker leads (wires) to the outside of the heart. Later, leads could be inserted in veins and pushed through to the interior of the heart, no longer necessitating opening a patient s chest. Using fluoroscopy, the physician can visualize the process, so that the only surgery needed is to create a pocket under the skin for the implantable generator to which the leads are connected.  [c.181]

Basic oxygen furnaces (BOFs) have largely replaced open hearth furnaces for steelmaking. A water-cooled oxygen lance is used to blow high-purity oxygen into the molten metal bath. This causes violent agitation and rapid oxidation of the carbon, impurities, and some of the iron. The reaction is exothermic, and an entire heat cycle requires only 30-50 min. The atmospheric emissions from the BOF process are listed in Table 30-16.  [c.507]

Place a mixture of 25 g. of phenol, 50 ml. of formalin and 3 ml. of 40 per cent, sodium hydroxide solution in a 500 ml. conical flask. Attach a reflux condenser to the flask and reflux gently. As the heating proceeds, the mixture acquires a red coloration and becomes increasingly more viscous. After 60-75 minutes the contents of the flask are so viscous that the bubbles which rise through the mass encounter great difficulty in escaping from the surface. At this point remove the flame and immediately pom the viscous mass into a wide test-tube ( boiling tube ) upon coohng, an opaque white solid is obtained. (Immediately clean the reaction flask with 40 per cent, sodium hydroxide solution if it is allowed to stand, the hardened product lining the flask is difficult to remove.) To complete the preparation, place the boiling tube in an air oven for 1 hour at 50° and for 4 hours at 60-75° when the baking process is complete, a hard pink mass of plastic is obtained.  [c.1023]

Creep Feed Wheels. Abrasive machining in which the grinding wheel does not merely finish the surface of a machine part but actuaHy forms it by removing a significant amount of metal is a relatively new grinding procedure caHed creep feed grinding. In this process, a shape is generated in the face of an open-stmcture vitrified grinding wheel by diamond tooling or cmsh-form roHer. The profiled wheel is then fed into the metal to be ground in a deep cut, ranging from 1 to 10 mm, at a very slow rate under a flood of coolant. In normal grinding, cuts are shaHow, from 0.025 to 0.13 mm, and formed at a fast travel rate. Creep feed grinding finds its greatest use in the aerospace industry where hard-to-grind, heat-resistant aHoy parts must be ground without surface damage. The intricate "Christmas tree" shape at the base of a turbine blade can be ground in one pass using this process and there is less wheel wear, better retention of form, and higher overaH productivity than with other shaping methods. Reference 46 provides a complete treatment of the creep feed grinding process.  [c.15]

Ores are mined (6) by open-pit, underground, alluvial, and solution mining methods. The first two are forms of hard rock mining. Open-pit mining is preferred because it is more economical and practical, especially when the ore grade is low and large tonnages have to be handled. It can, however, be practiced only when the ore body is close to the surface. Underground mining, the most expensive method of mining, has to be used when the ore body is at a considerable depth from the surface. Often a combination of open-pit and underground mining is used on the same ore body. Alluvial and solution mining are iaexpensive, but can be used only on sedimentary, alluvial, or placer deposits such as river beds, dried-up oceans, and lakes. Dredges or water pressure are used to extract the ore. Unlike subsequent processiag, the mining method has comparatively Htde dependence on the mineralogical nature of the valuable minerals ia the ore although the nature of the gangue minerals may affect the actual method of hard rock mining used.  [c.394]

Manufacture and Processing. The largest volume of coal is carbonized in batch coke ovens to produce a hard coke suitable for blast furnaces for the reduction of iron ore. Oven temperatures, as measured in the flues, are between 1250 and 1350° and residence time varies between 17 and 30 h. The gas made in this process is mainly used as fuel and other appHcations in the steel works (see Fuels, synthetic).  [c.336]

The role of baker s yeast Saccharomyces cerevisiae) in producing leavened bread depends on two factors the abUity of yeast to generate carbon dioxide and alcohol through the breakdown of simple sugars, and the unique abUity of wheat flour proteins to form films in dough that trap evolved gases (see Eermentation Yeast). Basic bread is made with flour, water, salt, and yeast. Product variety is achieved by incorporating varying amounts of additional ingredients by altering the breadmaking process by shaping or cutting or putting toppings on the dough prior to baking or by the method of baking. Each of these practices may be utilized alone or in combination to produce a virtually limitless number of yeast-raised products. Thus raisin bread is made from a white-type bread dough with the addition of raisins and possibly spice. Erench bread is made from a lean white dough, shaped into a cylinder and baked on the hearth of a steam-filled oven. Pita bread is also made from a lean white dough, but it is shaped into thin, round pieces before baking in a very hot (400°C) oven, to achieve the typical pocket formation. Sweet roU doughs are made with relatively high levels of sugar, fat, eggs, and yeast, compared to ordinary bread dough, and are shaped in various ways, with additional fillings and toppings to obtain the desired product.  [c.460]

Top fermentation is used in Great Britain for production of ale and stout. The yeast is usually a blend of pure strains of S. cerevisiae. Fermentation takes place in open vessels provided with equipment for harvesting the yeast from the surface. Figure 9 shows a time profile for a typical fermentation process in the traditional production of ale. After an initial phase, "the lag phase," the yeast begins to pick up nourishment from the wort for growth and fermentation, and the next phase involves a logarithmic growth of the yeast cells. Reproduction goes on until there is a lack of nourishment, ie, oxygen, amino acids, or minerals. Then fermentation continues until the fermentable substrate is exhausted. During reproduction, the temperature rises from 15 to 22°C. At this point, cooling is started to maintain a constant temperature. After 3—4 d the desired degree of fermentation is attained and the green beer is cooled from 22 to 14°C and is thus ready for secondary fermentation. Primary fermentation takes about six days and has four phases. In the first phase, a thin, white layer of foam is formed on the surface. In the second phase, this growth is thicker, higher, and darker because of hop resins. This layer is skimmed to prevent it from being mixed with the yeast that surfaces in the third phase. This yeast is pure, composed of fresh yeast cells, and it is also skimmed for later use for the brews to foUow. In the last phase, the yeast turns to a hard, leathery layer at this stage the beer is clearing.  [c.23]

Immersion in aqueous media open to air Solutions in which tin is cathodic to steel cause corrosion at pores, with the possibility of serious pitting in electrolytes of high conductivity. Porous coatings may give satisfactory service when the corrosive medium deposits protective scale, as in hard waters, or when use is intermittent and is followed by cleaning, as for kitchen equipment, but otherwise coatings electrodeposited or sprayed to a sufficient thickness to be pore-free are usually required.  [c.503]

Fluorspar has been used as a flux ia the steel iadustry siace the iatroduction of the open-hearth process. Historically, hydrogen fluoride was used ia limited quantities for glass etching, polishing, scale removal, and smaH-volume production of fluorides. In the 1930s the first significant commercial HF production was appHed toward the production of aluminum (see Aluminumand aluminum alloys) and chlorofluorohydrocarbons for refrigerants (see Refrigeration and refrigerants). During World War 11 HF was used ia alkylation catalysis to produce aviation gasoHne and ia the manufacture of fluorine to produce volatile UF for isotopic enrichment of the uranium essential for nuclear devices. The use of the very corrosive UF also stimulated development of fluoiinated organic compounds for lubricants and seals that are resistant to UF (see Lubrication and lubricants). Anhydrous HF is used both as a reactant and as a solvent (4) ia the manufacture of inorganic fluorides.  [c.137]

Significant mining of fluorspar began in England about 1775 and in the United States after 1820. Substantial use of fluorspar began about 1880 in the basic open-hearth process for making steel (qv). Large increases in demand came with the need for fluorides in the aluminum industry, starting about 1900. A large fluorine chemicals industry based on hydrogen fluoride made from fluorspar followed in production of refrigerants (see Refrigeration and refrigerants) (1930), alkylation (qv) catalysts for gasoline (1942), materials for nuclear energy (ca 1942), aerosol propellants (see Aerosols) (ca 1942), fluoroplastics (ca 1942), and fluorocarbons for sod-repeUant surface treatments (early 1950s). Fluorspar is used directly in the manufacture and finishing of glass (qv), in ceramics (qv) and welding (qv) fluxes, and in the extraction and processing of nonferrous metals (see Metallurgy, extractive).  [c.171]

Steel produced by the converter process contains dissolved nitrogen and oxygen. The steel is usually deoxidized by small additions of elements like aluminum, manganese, and siUcon. Vacuum degassing is used to remove residual oxygen, nitrogen, and hydrogen. The Siemens-Martin or open-hearth process, developed ca 1880, used a reverberatory furnace which is charged with soHd steel scrap, limestone, iron ore, and molten pig iron. As of the 1990s, electric-arc furnaces are used. These provide the higher temperatures and flexibiUty of operation requited for the production of alloy steels.  [c.170]

Shordy after Wodd War II, the top-blown converter was invented in Austria (L-D process), and oxygen lancing was appHed to the open-hearth process. Top-blown oxygen steelmaking, common practice in the 1990s, reduces the time for processing of high carbon iron into steel from hours to minutes. The process is autogeneous. Larger (250—300 t capacity) converters can handle 25—35% scrap. Rotating converters like the Kaldo and Rotor processes have also been developed (4). The invention of the Savard/Lee gas-shielded tuyere made possible the injection of oxygen through tuyeres in the bottom of a steel converter. The bottom injection of argon is another improvement in the production of stainless steel by the argon—oxygen decarburization process.  [c.170]

Centrifugal pumps are increasingly being used as a safer and more effective alternative to the traditional roUer pump in open-heart surgery and Hver transplants. As of the mid-1990s, about 45% of open-heart procedures use a centrifugal pump. In the latter 1980s, that number was less than 10%. The market would likely change over more rapidly to centrifugal pumps except for the higher price ( 125— 175) of each disposable centrifugal pump compared to the lower cost for roUer pump tubing. A strong case can be made that the centrifugal pump is less expensive in the long mn because the pump causes less damage to blood and may reduce recovery time. Use of the pump is also a safer method and thus may reduce the HabiUty risk of this procedure.  [c.182]

Supply and demand of scrap is affected by a variety of factors, including technological advances ia iroa- and steelmaking and scrap processiag, war-time effects such as price controls and export restrictions, economic depressions, and foreign trade ia scrap. The opea-hearth furnace, which was oace a primary part of steelmaking ia an iategrated plant, was capable of melting up to 100% scrap or any combination of hot metal (molten pig iron) and scrap. Open-hearth steelmaking declined rapidly ia the 1980s and was phased out ia 1991 ia the United States. The lost demand for scrap by this process has been offset by advances ia electric arc furnace (EAF) and basic oxygen furnace (BOF) processes. Developments impacting scrap iaclude minimills, coatiauous castiag, and minimill thin-slab casting.  [c.552]

The various steelmaking processes were all eventually supplanted (3,4). The first of the newer techniques was the historic pneumatic or Bessemer process, introduced in 1856. Shortiy thereafter, the regenerative-type furnace, known in the 1900s as the open-hearth furnace, was developed in the United  [c.373]

Calcium Aluminate Cements. These cements are manufactured by heating until molten or by sintering a mixture of limestone and bauxite with small amounts of Si02, FeO, and Ti02 (see Aluminum compounds, aluminum oxide, calcined, tabular, and aluminate cet nts). In Europe the process is usually carried out ia an open-hearth furnace having a long vertical stack iato which the mixture of raw materials is charged. The hot gases produced by a blast of pulveri2ed coal and air pass through the charge and carry off the water and carbon dioxide. Fusion occurs when the charge drops from the vertical stack onto the hearth at about 1425—1500°C. The molten Hquid mns out continuously iato steel pans on an endless belt ia which the melt solidifies. Special rotary kilns, provided with a tap hole from which the molten Hquid is drawa intermittently, and electric arc furnaces have also been used.  [c.294]

Industrial boilers are employed over a wide range of applications, from large power-generating units with sophisticated control systems, which maximize efficiency, to small low-pressure units for space or process heating, which emphasize simplicity and low capital cost. Although their usual primary func tion is to provide energy in the form of steam, in some applications steam generation is incidental to a process objec tive, e.g., a chemical recoveiy unit in the paper industry, a carbon monoxide boiler in an oil refineiy, or a gas-cooling waste-heat boiler in an open-hearth furnace. It is not unusual for an industrial boiler to serve a multiplicity of functions. For example, in a paper-pulp mill, the chemical-recoveiy boiler is used to convert black liquor into useful chemicals and to generate process steam. At the same plant, a bark-burning unit recovers heat from otherwise wasted material and also generates power.  [c.2397]

Direct-Fired Equipment Direct-fired combustion equipment transfers heat by bringing the flame and/or the products of combustion into direct contact with the process stream. Common examples are rotary Idlns, open-hearth furnaces, and submerged-combustion evaporators. Table 27-23 gives the average energy consumption rates for various industries and processes that use direct heat. Section 11 of this handbook describes and illustrates rotary dryers, rotaty Idlns, and hearth furnaces. Forging, heat treating, and met milhng hirnaces are discussed by Mawhinney (Marks Standard Handbook for Mechanical Engineers, 9th ed., McGraw-HJl, New York, 1987, pp. 7.47-7.52). Other direct-fired furnaces are described later in this section.  [c.2401]

The replacement of air by oxygen for blast furnace metal refining in the Basic Oxygen Process (BOF), revolutionized the rate of production of h on from blast furnace metal, as well as considerably reducing the amount of physical plant which was required. The earlier refining process, the open hearth furnace was essentially a reverberatoty furnace, in which carbon was eliminated as CO(g) which was nucleated on the furnace bottom. The original tests for the BOF process, in which an oxygen lance was used, were soon followed by injection of oxygen beneadr die metal surface, first from the side, and eventually from the bottom of the vessel. The average rate at which refined metal can be produced in modern oxygen-injected vessels is roughly 200 tonnes in 20 minutes Due to the severe agitation which is produced by the passage of oxygen and CO, the metaPslag system takes the form of an emulsion in which there are droplets of metal and slag as well as the gas phase. It is drought drat the major refining reaction for de-carburization is between carbon dissolved in the metal droplets, and FeO dissolved in the slag. The use of pure oxygen in the basic oxygen furnace, causes severe erosion of the tuyere linings due to attack by the liquid slag containing a high FeO percentage. This has been overcome by the addition of hydrocarbon gas to dre oxygen injection.  [c.337]

The Nobel Prize frequently puts so many new responsibilities and preoccupations on the shoulders of the winners that it drastically changes their lives and affects their ability (or desire) to continue active research. 1 have heard some express the opinion that having received their prize at a more advanced age was in a sense a blessing, because it did not hinder their work throughout most of their career. This indeed may be the case, although Alfred Nobel s intention was to encourage and facilitate research through his prizes. However, as 1 mentioned in Chapter 11,1 was, determined that the Prize should not affect my life, and certainly not my research, significantly. Now, six years later, and looking back on these post-Nobel years, I feel that I mostly succeeded. These were productive and in many ways most rewarding years of research. Helped by my dedicated younger colleagues and associates and by close collaboration with my colleague Surya Prakash, who increasingly took over many of the responsibilities and bnrdens associated with running our institute, I was able not only to continue my research but to extend it into new and challenging areas.  [c.188]

Structural drawings of carbohydrates of this type are called Haworth formulas, after the British chemist Sir Walter Norman Haworth (St Andrew s University and the University of Birmingham) Early m his career Haworth contributed to the discovery that carbohydrates exist as cyclic hemiacetals rather than m open chain forms Later he col laborated on an efficient synthesis of vitamin C from carbohydrate precursors This was the first chemical synthesis of a vitamin and provided an inexpensive route to its prepa ration on a commercial scale Haworth was a corecipient of the Nobel Prize for chem istry m 1937  [c.1034]

An interesting example of a large specific surface which is wholly external in nature is provided by a dispersed aerosol composed of fine particles free of cracks and fissures. As soon as the aerosol settles out, of course, its particles come into contact with one another and form aggregates but if the particles are spherical, more particularly if the material is hard, the particle-to-particle contacts will be very small in area the interparticulate junctions will then be so weak that many of them will become broken apart during mechanical handling, or be prized open by the film of adsorbate during an adsorption experiment. In favourable cases the flocculated specimen may have so open a structure that it behaves, as far as its adsorptive properties are concerned, as a completely non-porous material. Solids of this kind are of importance because of their relevance to standard adsorption isotherms (cf. Section 2.12) which play a fundamental role in procedures for the evaluation of specific surface area and pore size distribution by adsorption methods.  [c.24]

Acoustical Wall Treatments. Sound-absorbing wall treatments are sometimes required to prevent echoes (long-delayed reflections) or flutter echoes (repeated reflections between hard parallel surfaces). Prefabricated fiber glass boards 2.5 cm (1 in.) to 5.1 cm (2 in.) thick wrapped in fabric or thin perforated vinyl are widely used. Mineral fiber boards with integral facings of fabric-like material also are available. Open-ceU foam products represent another type of acoustical treatment used on walls. The foam products are available in several thicknesses and with sculptured surfaces, some of which have a sawtooth shape and others a textured appearance similar to egg cartons. They can be appHed to wall surfaces by means of a self-adhesive backing and are popular in sound studios because of their appearance as well as their properties. Porous concrete blocks with carefully designed slots and cavities, which act as resonant cavity absorbers, also are used for sound-absorbing walls. The resonant cavities provide a significant amount of low frequency absorption, and the porous concrete provides some middle and high frequency absorption.  [c.314]

The vapor pressure of aluminum can be lowered by ahoying it with aluminum carbide over 40% aluminum carbide is soluble in aluminum at 2200°C (23). Thus an ahoy of aluminum and aluminum carbide was produced at 2400°C by controlling the stoichiometry of the charge (26). When the ahoy was tapped from the furnace and allowed to cool slowly, the aluminum carbide crystallized in an open lattice and the interstices fihed with pure aluminum. The aluminum was removed by leaching with molten chlorides or by vacuum distillation of the aluminum from the ahoy. The aluminum carbide residue was recycled to the arc furnace. This process has been further improved (27), going to three stages to decarbonize the aluminum— two in the hearth and one in an external holding furnace. A Hquid aluminum and a slag which was recycled were obtained. The process gave good yields and produced aluminum at less than 11 kWh/kg, but was not developed past the pilot stage.  [c.100]

Hardwoods have a more varied and complex arrangement of cells than softwoods. Figure lb is a cross section of the stmcture of yellow poplar, a typical hardwood. The main stmctural element of hardwoods is the wood fiber (F), which is significantly shorter than the softwood tracheid (1—2 mm vs 3—6 mm) and generally thinner, ca 20 pm in diameter. The tme fibers are uniform throughout the aimual ring. Hardwoods also contain a sizable proportion of short, large-diameter cells or vessels (V) through which sap is transported and which are categorized on the basis of pore (vessel) size. Ring-porous hardwoods, ie, oaks, hickory, chestnut, elm, black locust, and ash, have vessels that are larger in springwood than in summerwood. In diffuse-porous hardwoods, ie, yellow poplar, aspen, maple, gums, and basswood, the pores are fairly uniform in size and evenly distributed throughout the annual ring. Vessels have open ends or a connecting grate-like tissue called a scalariform plate (SC). Hardwood fibers have simple pits, which are smaller, and do not contain the toms system of the softwood bordered pits. This is related to the fact that the vessels perform the primary liquid-transport function in hardwoods. Thus, the cross-fiber fiquid flow is gready restricted in hardwoods in contrast with softwoods. In general, there is less differentiation in Springwood and summerwood fibers than in those of softwoods. The AR is shown by one or two layers of terminal parenchyma cells that form at the end of the growing season.  [c.247]

Several refineries use this process which was invented by Outokumpu Oy (Finland) in the 1970s. The original batch process hearth roasted a slurry of decopperized slimes and concentrated sulfuric acid. The off-gases, containing selenium dioxide and sulfur dioxide, were scmbbed using water and a venturi jet ejecter. Phelps Dodge Refining Corporation (El Paso, Texas) has converted this to a continuous process. Outokumpu has modified their process so that trays of dry decopperized slimes are contacted with a gaseous mixture of sulfur dioxide and water in an oven. Sulfur trioxide is generated in situ and converts the selenium to selenium dioxide which is volatilized from the trays into the overall gas stream. The gases pass through a venturi scmbber and selenium is precipitated as before.  [c.329]

Unfortunately chemical process plant PSA have no requirements for public disclosure, consequently examples of their PSAs are hard to find. However the following are some examples from the open literature. They are similar to nuclear PSAs except less elaborate with more empahsis on consequences than on probabilities.  [c.428]

An interesting example of a large specific surface which is wholly external in nature is provided by a dispersed aerosol composed of fine particles free of cracks and Assures. As soon as the aerosol settles out, of course, its particles come into contact with one another and form aggregates but if the particles are spherical, more particularly if the material is hard, the particle-to-particle contacts will be very small in area the interparticulate junctions will then be so weak that many of them will become broken apart during mechanical handling, or be prized open by the film of adsorbate during an adsorption experiment. In favourable cases the flocculated specimen may have so open a structure that it behaves, as far as its adsorptive properties are concerned, as a completely non-porous material. Solids of this kind are of importance because of their relevance to standard adsorption isotherms (cf. Section 2.12) which play a fundamental role in procedures for the evaluation of specific surface area and pore size distribution by adsorption methods.  [c.24]

See pages that mention the term Open-hearth process : [c.524]    [c.507]    [c.211]    [c.289]    [c.752]    [c.588]    [c.306]    [c.1034]    [c.53]    [c.164]    [c.211]    [c.236]    [c.451]   
Chemistry of the elements (1998) -- [ c.1072 ]