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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE 5 Research and Development Opportunities This chapter discusses the R&D opportunities for select IOF industries and for crosscutting R&D (using refractories as an example). After the materials needs of selected IOF industries are described, the R&D opportunities are discussed. In keeping with the crosscutting theme of this report, the committee focused on materials technologies that would enable or improve the understanding and processing of existing and new products used by more than one IOF industry rather than on the development of industry-specific products. ALUMINUM INDUSTRY Identified Needs Oxidation-Resistant and Corrosion-Resistant Materials In the Bayer process (used to convert bauxite to alumina), yields are relatively low; therefore, productivity (output and rate of production) is a key issue. Productivity could be improved if the process could be operated at high caustic concentrations, but this would require low-cost, high-temperature, abrasion-resistant, corrosion-resistant materials or coatings. Materials Processing Smelting. The primary aluminum sector would benefit from an alternative to the prebaked carbon anodes now used in the smelting process. The new, nonconsumable anode material would have a longer life than carbon and, at the same time, would avoid carbon-dioxide emissions (an OIT project to develop this material
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE has already been funded). A related project is the development of wettable cathode materials to improve cell efficiency. The industry would benefit from a better understanding of the relationship between changes in raw materials used to make carbon anodes and their performance in the electrolytic cell. The object of this project would be to minimize dross and skim losses during melt/remelt operations through a better understanding of molten metal/oxygen reactions and the identification of new additives or procedures for preventing oxidation. Melting. Melting and casting of aluminum, in both the primary and secondary (remelt or recycling) sectors, requires durable materials, especially more durable refractories, for the containment and transfer of molten metal. Solidification. The aluminum industry would benefit from a better means of removing impurities, such as inclusions, from molten metal. Better filtration media and alternative filtration methods would be useful. Forming. The understanding of metal flow (e.g., modeling of metal flow in hollow extrusion dies) and the formability characteristics of wrought aluminum alloys (e.g., spring-back of sheet, distortion in joined components, such as laser welds), as well as test methods, could be greatly improved. R&D could focus on advanced forming processes (e.g., hydroforming, electromagnetic forming, superplastic forming) and advanced casting processes (e.g., semisolid casting and spray forming). Joining. The industry needs improved aluminum joining technologies, such as resistance spot welding, and improved materials to extend electrode tip life. Modeling Better modeling is a common need of the IOF industries and has crosscutting potential, although models are likely to have specific applications. Existing models could be improved for the solidification process, control of solidification during the casting process, and determining the relationship between composition, casting process, microstructure, surface properties, and stress/strain behavior at high temperatures. In the fabrication of wrought products, constituent models for alloys and the formability of automotive sheet could be improved, as well as modeling of the complex relationship between product behavior, structural properties, materials composition, and manufacturing processes (e.g., the relationship between mechanical properties and the formability of aluminum sheet, composition, microstructure, and thermomechanical history).
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE Other Needs Current tooling and die steels do not fully satisfy the industry’s needs. Better tool and die materials with improved heat-extraction capabilities would be useful. Scrap is an intrinsic by-product of aluminum fabrication, and the industry needs new, recycle-tolerant alloys with specifications that are better matched with scrap composition, thereby optimizing scrap utilization. The industry also needs robust, continuous-casting technology 5xxx and 6xxx alloys. The industry would benefit greatly from a searchable materials database that includes processing, microstructure, and properties to identify existing or tailored solutions to meet these challenges. Opportunities Current Programs 1 Three interrelated programs are focused on improving the energy and environmental efficiency of electrolysis cells used to smelt primary aluminum. The production of aluminum is extremely energy intensive, and the use of consumable carbon anodes gives rise to emissions of greenhouse gases. Inert anode and cathode technology for electrowinning of aluminum in primary electrolysis cells is the subject of extensive ongoing research. The market-pull for these technologies has increased with growing concerns about, and the need for, reductions of greenhouse gases. A parallel program is addressing the development of wettable ceramic-based materials for retrofitting existing cells to provide a stable, molten-aluminum, wetted cathode surface on top of the existing carbon cathode blocks, thereby improving efficiency. Another program is addressing the addition of compounds to the components of pot-cell linings to improve cell efficiency and cathode performance and improve the end-of-life disposal of spent potlining. Three programs are under way in the area of semifabricated products. One is addressing the development of improved grain refiners for reducing energy utilization and scrap generation and increasing furnace productivity. The other two are investigating the forming of aluminum: (1) spray forming for the direct production of (strip) products and (2) the semisolid forming of castings into near-net-shaped products. 1 Based on workshop presentations by Sara Dillich, U.S. Department of Energy Office of Industrial Technology, (Dillich, 1999) and John Green, The Aluminum Association (Green, 1999).
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE Future Opportunities Although many of the R&D needs identified in this report, such as the demand for chemically inert materials for electrolytic cells, are specific to the aluminum industry, a number of needs overlap with the needs of other IOF industries. Materials and materials process modeling was cited in all of the IOF road maps (see Table 1-2 ). Because IOF industries often face materials challenges unrelated to their fields of expertise, the development of tools to help identify materials solutions would be extremely useful. A comprehensive, internet-accessible, searchable database of material specifications and properties would be a valuable tool for determining the availability of existing solutions or highlighting the need for further development. The aluminum industry needs models for understanding the relationship between product materials characteristics (e.g., microstructure and properties) and processing (e.g., casting, rolling, and extrusion forming of sheet). Although these models are likely to be industry specific, the methodology used in their development may have wider applications. The Bayer process for the production of alumina from bauxite, a well established chemical process, could be improved with new materials. In the Bayer process, bauxite is crushed, ground, mixed with a solution of sodium hydroxide, and pumped into large autoclaves. In these vessels, under pressure and at temperatures in the range of 220°C to 350°C degrees, the caustic dissolves the alumina in the bauxite to form sodium aluminate. The yields from this process are relatively low, and the industry would like to increase output by operating at higher caustic concentrations. Research opportunities include the selection, adaptation, or development of corrosion-resistant coatings (e.g, ceramic-based coatings) for the containment vessels. These coatings would also be useful for other IOF industries. The aluminum industry could use more durable refractory materials for melting, holding, and handling molten aluminum. Melting furnaces use salts to help break down the surface oxide during melting and chlorine for fluxing and magnesium control. Although the temperature requirements will differ for the aluminum industry and other industries, the chemical conditions are similar. A range of alkali-resistant and halogen-resistant coatings would be of interest to several IOF industries. CHEMICAL INDUSTRY Needs The chemical industry has three high-priority needs: new materials that would expand the limits of process operating conditions (e.g., higher temperatures and pressures); a better understanding of the operating limits within which existing and
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE new materials could be safely and reliably used; databases and models as tools for reliable, cost-effective predictions of the performance of materials under expected process conditions (e.g., aqueous and nonaqueous conditions and high-temperature processes). The technology road map developed by the Materials Technology Institute provides more details on the materials needs of this industry (MTI, 1998). Opportunities The committee identified several research opportunities to meet the needs of the chemical industry. The industry would benefit from improved materials capable of withstanding aggressive process environments (e.g., improved thermal spray coatings resistant to corrosive liquid environments; more cost-effective, reliable techniques of cladding exotic materials over a steel substrate; materials with improved resistance to high-temperature, high-dew point, and liquid halogen-containing environments; and materials resistant to metal dusting). Other opportunities for R&D are the fundamental understanding of process/materials interactions, predictive tools (e.g., computational process modeling; reliable tools for predicting material performance without costly testing; and modeling/predicting the performance of high-temperature materials), data acquisition (e.g., user-friendly databases on thermophysical, kinetic, and mechanical data), and monitoring and inspections (e.g., nonintrusive, nondestructive, on-line inspection methods and corrosion probes for high-temperature environments). FOREST PRODUCTS INDUSTRY Current Projects Composite Tubes in Kraft Recovery Boilers The recovery boiler is used in a kraft pulp mill to incinerate the unwanted organics (mainly lignin) that were removed from pulped wood. More than 50 million tons of kraft pulp are produced in the United States each year, and a roughly equivalent amount of organic material is incinerated in the recovery boilers of kraft mills. Therefore, this is a significant energy conversion process. The capital investment for a recovery boiler, the most costly unit in a kraft pulp mill, is about $200 million. The walls of the most recent units, especially at the floor of the recovery boiler (consisting of tubes through which cooling water circulates), have been made from stainless-steel clad carbon-steel tubes instead of the older studded carbon-steel tubes. The walls of the lower portion of the furnace are covered with a
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE protective layer of frozen kraft smelt when the furnace is in operation. Without this protective layer, the tubes would quickly fail. One of the projects in the AIM Program is to elucidate the causes of composite tube cracking in the floor of recovery boilers. Cracking is happening more and more frequently and is of great concern to the industry in terms of safety and capital effectiveness. A multi-institutional team, including ORNL, the Institute of Paper Science and Technology, the Pulp and Paper Research Institute of Canada, and a large number of pulp and paper companies and suppliers is involved in this project. Computer modeling and experimentation has shown that the washing process of the recovery boiler is a significant source of corrosion and the subsequent failure of composite tubes (Adams, 1997). Identified Needs A study of the materials needs of the pulp and paper industry was issued in August 1995 (Angelini, 1995). Since then, other needs have been identified, especially in the area of low-effluent processing. An important factor for the pulp and paper industry is the extraordinary capital intensity of the process. Therefore, even though materials that could solve a given problem may be readily available in the marketplace, they may be prohibitively expensive. As a result, R&D to define the operating window for existing and installed materials may be more useful than R&D on new materials, which may be most useful for new processes, such as black-liquor gasification (i.e., high-temperature, gas-separation membranes to separate sulfurous gases, refractories, and erosion-resistant materials) (Harriz, 1999). Opportunities for new applications of existing materials (based on a database), unit operations, separations, and surface properties are described below. Wood Preparation Logs must be processed into chips that are then converted to pulp by chemical and/or mechanical means. Improving the erosion and abrasion resistance of cutting tools and surfaces of transport equipment would be a significant improvement. This could be achieved by surface treatments or the use of ceramics. Improvements in cutting and chipping tools and machinery for transporting logs would increase the effectiveness of existing capital equipment by reducing down time and maintenance requirements.
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE Kraft Pulping Conventional corrosion problems occur throughout the recovery area. However, as mills strive to produce less effluent, process conditions and the chemical composition of liquors change. As a result, chloride and potassium build up in the recovery system of many mills. Problems include increased corrosion due to these changes in concentration. These problems could clearly be solved by switching to materials that are readily available in the marketplace, such as duplex steels. However, the capital costs of the changeover are usually prohibitive. Therefore, the industry would benefit from new applications that can be used safely with existing capital equipment. Problems with conventional recovery boilers include: corrosion at air ports, the lack of on-line monitoring to detect impending failures, and water-side corrosion cracking. Recycled Paper One of the pressing issues for the pulp and paper industry is sticky polymer residues in the recycled paper stream. These residues (from adhesives used on envelopes, labels, stamps, etc.) interfere with equipment by adhering to metal surfaces and can be very detrimental to the final product because they cause imperfections visible to the human eye. Separation is quite difficult because the density of these materials is close to the density of water. They also clog screens and filters. Opportunities for R&D include water-soluble adhesives and surface treatments that would reduce or eliminate the fouling of machinery by sticky adhesives. Bleaching The technologies of choice that meet current environmental regulations are substituting chlorine dioxide for chlorine and using oxygen delignification. An evaluation of using current materials with chlorine dioxide would be beneficial. Papermaking More wear-resistant materials and improved surface materials (mostly polymers) used to produce felts (for pressing) and wires (the continuous belt on which the paper slurry is sprayed in the first step of papermaking) would reduce down time. Other R&D areas of interest to the industry are: improved mechanical properties of the high-speed processes used in papermaking; improved surface
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE properties and durability of metallic surfaces (e.g., rolls and headbox); bearing materials, especially ceramic bearings, that do not require lubrication and can operate at higher speeds. Low-Effluent Processing in Pulp and Paper The buildup of chloride and potassium are problems in low-effluent kraft pulping. The buildup leads to plugging in the recovery boiler and may lead to corrosion. More rugged ultrafiltration and electrodialysis membranes and systems would be useful for separation processes to segregate the contents (both organic and inorganic) of bleach effluents before recycling the majority of the water. Membrane systems must be tolerant of small amounts of cellulose fibers to avoid the need for maintenance-intensive prefiltration. Current electrodialysis stacks are not fiber tolerant. The advantages of electrodialysis for recycling acidic bleach effluent have already been shown in DOE/OIT-sponsored research (Tsai and Pfromm, 1999). Inorganic elements in the pulping, bleaching, and papermaking operation can cause scaling and corrosion; the industry would benefit from a comprehensive simulation system for liquors and process conditions in pulping and papermaking, including the complex interactions of wood fibers with inorganic dissolved ions. Available databases are mostly tailored for other industries. Expanding these databases to include the thermodynamics of multicomponent, aqueous mixtures, including organics as they occur in papermaking, will require fundamental research. Lumber and Structural Wood More durable, resistant high-speed cutting tools used in lumber production would prevent catastrophic failures of equipment. Modifications of surface materials would help prevent the adhesives used in “engineered lumber” from disturbing processing operations. Research Opportunities The forest products industry offers several high-priority R&D opportunities. First, the industry would benefit from computer-searchable databases and simulations for modeling. Simulations of the behavior of multicomponent inorganic mixtures in pulping and papermaking will require fundamental research. Simulations would be useful for predicting the effects of low-effluent processing on the operation. Second, the industry needs better refractories that can withstand the conditions in new black-liquor gasification units. R&D in this area should focus on defining and assessing the
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE process conditions and determining desirable properties. Third, once fundamental data have been obtained, they must be integrated into existing databases and process simulation software. Fourth, the industry needs ways to increase the corrosion resistance and wear resistance of existing materials in the changing chemical and physical environment. Fifth, the industry would benefit from surface modification to prevent detrimental interactions with adhesives, improve wear resistance, and improve corrosion resistance. GLASS INDUSTRY Industry Needs The glass industry is dependent on materials technology for both products and manufacturing. Most of the industry’s products are melted in high-temperature furnaces fired by gas or petroleum or heated electrically. Process technology, which is primarily dependent on high-temperature material properties, then shapes, molds, pulls, stretches, grinds, polishes, or otherwise manipulates the product to give it its final form. Glass can also be produced by chemical synthesis, usually by sol-gel or chemical vapor deposition. As traditional “hot-melt” methods of producing glass have come under intense competitive pressure from competing materials and technologies, these methods are becoming economically significant. The industry as a whole is struggling to reduce costs because most glass products are commodities. To reduce the high capital and energy costs of “hot-melt” glass tanks, the industry has turned to more efficient processes, such as oxygen firing, which produces more heat and fewer pollutants per pound of fuel. However, these new techniques have revealed a need for better, lower cost refractory materials and melting processes. The industry is in need of any technology that can lower costs. Like most manufacturing industries, the glass industry as a whole has many technical needs because the business model for commodity businesses requires that costs be cut to the bone and overheads (including R&D) be ruthlessly slashed to underprice competition. Therefore, most glass companies do minimal research internally and depend on suppliers, consultants, and consortia to meet their research needs. The IOF Program has provided the industry with an excellent opportunity to make its needs known to the research community. At first glance, many of the industry’s needs appear to be common to other IOF industries, but there is usually a unique twist that makes the needs of this industry different. In cooperation with OIT, the entire industry working together for the common good has undertaken a refractories development program. Most glass products are manufactured using “hot-melting” processes, which entails putting a mix of sand, certain minerals, and fluxing agents together and melting them at very high
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE temperatures. The molten glass is then formed into shape, cooled, annealed, and sometimes ground and polished to produce the finished product. The industry produces a myriad of products, each with a unique composition and manufacturing process. All of them require high-temperature materials. Glass, which is loosely defined as any noncrystalline solid, can have an almost infinite number of compositions. Even if we limit our discussion to silica glasses, which includes most of the economically important glass products, nearly 100,000 different formulations are possible. These compositional differences, along with different melting temperatures and properties, have very different chemical reactivities resulting in different corrosion rates. The selection of refractory materials has always involved economic trade-offs between cost and lifetime, and even modest improvements in these materials will have a great impact on entire segments of the industry. Research Opportunities The glass industry has traditionally been very conservative in adopting new technologies because of the high capital costs of production and low profit margins of most glass products. Economic survival has dictated this approach, and the marketplace has ruthlessly enforced this discipline. Therefore, the industry has been very adverse to taking risks, which has slowed the pace of improvement. Nevertheless, many research areas would be beneficial for modernizing the industry’s aging infrastructure. Industry-wide data on high-temperature materials are not readily available. Research in this area could standardize high-temperature materials data and enable the industry to compile an industry-wide handbook. In this case (and others), the IOF Program can play an extremely important role for the glass industry. Research to develop technology to reduce energy costs, improve yield and/or quality, create new products, and improve product characteristics would all be very useful. Improvements might include smaller, more efficient glass tanks, faster flow through (more “pull” from) furnaces, better refractories, more efficient burners, cheaper oxygen technologies, better sensors, more useful modeling, better energy recovery from melting operations, faster product forming, lower cost raw materials, and better glass compositions. This list is certainly not all inclusive, and the reader is directed to the glass industry technology road map for more information (Energetics. 1997a ). Some crosscutting R&D areas are listed below: refractory materials (compilation of properties and performance parameters) high-temperature material (glass) properties measurements of electroconductivity
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE combustion research low-cost oxygen production modeling (including glass flow) sensor applications corrosion effects new product applications MINING INDUSTRY Needs The mining industry (including the extraction processing of all metals but aluminum and steel) has been the subject of recent studies by the National Research Council (NRC, 2001) and others (e.g., RAND, in press). In 1992, the amount of energy used by the mining industry was: 77 trillion BTUs for the extractive processing of nonferrous metals and 582 trillion BTUs for excavating and hauling. The first mining industry road map on crosscutting technology deliberately excluded nonferrous metals in favor of technologies that would benefit both coal and hardrock mining (NMA, 1998). The next road map will address processing technologies for coal and extractive metallurgy. A future road map will cover specific mining technologies for coal and hard rock, which may address materials for wear and fatigue in more detail, as well as an energy and environment profile for mining, which will include more information on process technologies and materials needs. Research Opportunities Extractive industries for copper, nickel, cobalt, zinc, lead, gold, silver, and platinum group metals should be included in future mining industry road maps. These industries have limited funding for research but represent a broad segment of the mining industry, which is sorely in need of technical and financial support. STEEL INDUSTRY Needs The needs of the steel industry form a very long list (AISI, 1998). At the CEO level, the dominant problems for an integrated company are: the level of imports (routinely described as unfairly priced), which affects the whole price structure of this commodity material and thus the ability to remain competitive; and the supply of
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE new iron units to replace coke ovens and blast furnaces in the long run (one or two decades). Electric-melting carbon-steel companies have similar worries, with fewer concerns about imports because of their customer lists but equal concerns about finding high-quality melt stock (scrap or alternative iron units) at an affordable price to enable them to enter new markets. Specialty producers are also heavily impacted by imports. These factors explain why the industry is often characterized as not very forward looking. Limited cash flow has severely limited the implementation of new materials, and many important developments are the result of local initiatives by individual plants to reduce costs. Improved materials rarely result in higher prices in the market. Since about 1980, the actual average price of steel has not increased although quality and service have been vastly improved. In a “normal” environment, the profit on an average $500/ton steel might be $50. Normal environments are rare, however, and profits are often lower than this and may even be negative. It is generally accepted that replacing ingots by continuous casting was worth about $50/ton. A possible measure of an R&D program would be the potential of saving several dollars per ton (e.g., $10) and improving quality. Research Opportunities Corrosion Corrosion is an ubiquitous problem in steel plants. Aqueous corrosion occurs wherever water is used for cooling. Oxidation occurs whenever a product is exposed to high-temperature oxidizing gases (e.g., reheat furnaces and caster runout tables). If a scale is cracked in the roughing mill and washed away by high-pressure water, the result is lower yield. Conserving some of the heat in a slab by hot charging minimizes the chances of cracking a scale and also saves energy but requires careful scheduling when several different grades of steel are made in consecutive heats. Oxidation also occurs when hot gases are contained (e.g., in the off-take from a basic oxygen furnace). The melting of refractories into the oxide in which they are immersed also lowers productivity and increases costs. This problem has been mitigated in recent years but is still a serious concern. Currently, all of these problems must be solved locally, and incremental improvements continue to be made. Wear The machinery used in steel production, which is exposed to high loads and high temperatures (frequently nonuniform), takes a great deal of abuse. Hard coatings
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE of various types, preferably renewable coatings, would help greatly. Progress is made currently by incremental improvements. The combination of wear with chemical attack at high temperatures and thermal cracking makes testing new materials difficult. Refractories The industry uses enormous quantities of refractory materials as structural containers, protective coatings, and fluxes, especially in continuous casting. The recycling or disposal of refractories is a serious problem. Although incremental improvements could be made with new materials, reductions in costs are not likely to be revolutionary. Sensors Many automatic measurements of variables (e.g., dimension, temperature, composition, stress, and surface quality [including cracks and other imperfections]) are being pursued. The American Iron and Steel Institute has supported joint R&D on these difficult problems, sometimes with support from DOE, for many years. Much progress has been made, and further progress is expected. Improvements in sensors could also be useful for other metal producing industries. Monitoring transformations as they occur, either liquid-solid or solid-solid, is a primary goal, especially the simultaneous measurement of local stresses and/or strains. Numerous sensors to measure variables during casting are already available, but other apparently simple problems, such as exact location of the metal-slag interface, could be investigated. HEAT-TREATING INDUSTRY Needs The business environment for a heat-treating facility is quite different from that of a steel plant although the two industries employ an equal number of workers. A typical commercial plant is a job shop, frequently quite small and with limited technical staff. International competition is not often an issue but satisfying customers (who have a wide choice of suppliers) is. Input material may not be well characterized because heat treaters are primarily service providers. The sequence of operations can be described simply. Material is received, usually as machined parts. Each material has a temperature-time sequence for producing specific properties, which may or not be dependent on position. Chemical
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE changes in the surface can be part of the process, intentionally (e.g., carburizing or nitriding) or unintentionally (e.g., if control of the atmosphere in the furnace is inadequate). The parts are then cleaned, inspected, and shipped. Research Opportunities R&D opportunities include new equipment and hardware, such as design devices to ensure temperature uniformity and magnitude and to control heat losses and quenching devices to ensure uniform treatment of large volumes of material, reduce costs, improve disposal methods, and control cooling rates. Cooperative R&D in the industry could include the development of databases, sensors, and instrumentation and the creation of networks for the dissemination of nonproprietary information. Other opportunities are in new construction materials, the development of models to predict responses of parts throughout the production cycle (including efforts to shorten heat-treating times by increasing temperatures without adversely effecting material properties) and a better understanding of computational fluid dynamics. R&D to help the industry meet current pollution-prevention requirements is crucial. An economic analysis of issues likely to increase profits would help to set priorities for R&D projects. REFRACTORIES: AN ILLUSTRATIVE CROSSCUTTING AREA Refractories have been identified as a technology important to all nine IOF industries (see Table 2-1 ). The refractories industry itself, like many of the IOF industries, is undergoing a consolidation. Since 1990, several buyouts in this industry have resulted in the closing of R&D laboratories, greatly reducing the resources being devoted to research. In addition, the steel industry has greatly reduced its R&D and evaluation of refractories over the last several decades. Only a few U.S. universities have active programs in refractories research (J.D. Smith, 1999). The disproportion between the need for improved refractories by the IOF industries and the greatly reduced resources dedicated to R&D on refractories could limit improvements. All of the IOF industries use heat in at least one step in their manufacturing processes. The industries for which improved refractories would be most beneficial are aluminum, chemicals, glass, oil refining, and steel. Although refractories are not mentioned in every road map, often the need identified could only be met by improving the refractories or other materials involved in the process. The largest consumer of refractories is the iron and steel industry, which consumes approximately 50 percent of all of the refractories produced in the United States. The steel industry’s dependence on refractory materials has two key ramifications: (1)
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE research that improves the performance of refractory materials or reduces installation time will benefit the steel industry; and (2) R&D on steel making will be affected by the performance of refractory/containment materials. The development of new processes for the production of iron and steel has been limited by refractories that do not perform well in the proposed environments. The steel industry has identified the following specific needs: prevention of the clogging of transfer nozzles improved monolithic products and installation methods (including dewatering) improvements in electric furnace delta sections and sidewalls better high-temperature data improved ladle, tundish, and mold refractories (including slide plates and shrouds) improved basic oxygen furnance taphole mixes improved stirring elements economical recycling methods for refractories Some of the results of R&D in these areas could be transferred directly to other IOF industries. For example, the aluminum, metalcasting, and glass industries also use nozzles in their processes. The dewatering of monolithic refractories obviously applies to any industry that uses these materials. Knowledge of high-temperature properties would also be valuable to all of the IOF industries. Like the steel industry, the glass industry is highly dependent on refractories. In fact, molten glass is sometimes referred to as a universal solvent. Keeping refractory stones from getting into the glass bath is extremely important in the quality control of glass. In addition to the molten glass, the atmosphere above the glass bath is extremely corrosive to refractories. As a result of recent technological advances in the oxyfuel method of glass making, this atmosphere is even more corrosive to refractories than it had been. In general terms, the glass industry road map has identified a need for improved refractories for melting systems that use oxygen combustion. In fact, improved refractories for the crown and breast walls is one of the highest priorities in the glass technology roadmap (Energetics, 1997a). A fundamental understanding of the corrosion mechanisms of refractory compositions is another high priority need. It is safe to say that a better understanding of corrosion mechanisms will benefit more than one of the IOF industries. The Aluminum Industry Technology Roadmap also mentions refractories, for the reduction cell (Aluminum Association, 1997). For many years, the refractories industry, in conjunction with the aluminum industry, has been conducting research on various kinds of refractories specifically for the aluminum industry. Other areas of the aluminum process that require significant amounts of refractories are the anode baking pit furnaces, melting and holding furnaces, and troughs and runner systems.
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE Recently, the aluminum industry has begun using stirring elements in the melting and holding furnaces. Improvements in stirring elements would also be valuable to the steel industry. The Technology Roadmap for Materials of Construction, Operation, and Maintenance in the Chemical Process Industries identifies refractories as a high-priority need with the potential to impact many chemical industries that use furnaces in the manufacturing process (MTI, 1998). The highest priority is for materials with high-temperature capabilities and corrosion resistance. Related needs include materials for halogen-based processes, high-temperature refractory coatings, high-temperature materials (> 3,000°F), and longer life, field-repairable refractories. The needs of the petrochemical industry and the plant/crop-based renewable resources industry are generally similar to those of the chemical process industry; and these industries would benefit directly from improved refractories. Although the mining industry does not have significant uses for refractories, the nonferrous metals industries do. The operating conditions of refractories in nonferrous metals processing are demanding. Nonferrous metals, such as copper, lead, zinc, and magnesium, are very hostile to refractories. A better understanding of chemical attack at high temperatures would be helpful to these industries. In other words, R&D on refractories for the steel, glass, and aluminum industries would also benefit the nonferrous metal industries. The forest products industry has identified a key need for refractories for the treatment of black liquor that can withstand high-temperature chemical attack. This industry is particularly interested in chromium-free refractories. Any advances in corrosion-resistant or erosion-resistant materials would benefit this industry. The forging and heat-treating industries use refractories but at lower temperatures and in less demanding environments than other metal industries. Neither the forging nor the heat-treating industry identified a need for improved refractories. Research Opportunities Although the committee identified many opportunities for crossscutting research from the IOF industry road maps, the one need common to all of the road maps is for a database on high-temperature materials. Very little reliable data are available for refractories. In recent years, government agencies have been reluctant to support R&D that generates data that may not lead to a new theory or scientific model, and industry has been unable to support this R&D. Nevertheless, the IOF representatives have clearly identified a need for a high-temperature database to advance their process efficiencies. The steel industry has identified a need for improved monolithic refractories, including installation methods; R&D in this area would benefit all of the IOF
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE industries. R&D could focus on the development of monolithic refractories that have properties equal to or better than brick, can be installed quickly and easily, and are cost effective. Significant progress in this area has been made in recent years with the introduction of low-cement/no-cement castables, self-flowing castables, and shotcreting of castables. A castable with a basic chemistry has not yet been developed. One example of the potential advantage of a castable refractory would be for the ladle. When a brick lining in a ladle is replaced, the bricks are removed and usually disposed of in a landfill. When a cast lining has worn too thin to be used it is cleaned, a mold is placed in the ladle, and the space between the worn lining and the mold is filled with a castable refractory. This method greatly reduces the environmental problem of disposing of the ladle lining. One concern associated with monolithic refractories, such as castables, is the removal of the mechanical and chemical water before it can be returned to service. This is a time-consuming process that increases the down time of the equipment and could potentially cause a catastrophic failure of the lining during the drying phase. Rapid drying castables are available, but, unfortunately, the ingredient that allows the rapid drying also degrades the properties of the castable. All of the IOF industries would benefit from R&D in this area. The steel industry road map indicated that refractories between the steel ladle and the continuous caster mold would yield major cost reductions. The industry greatly needs to reduce the cost of refractories for all equipment, from the well block and slide gate system at the ladle to the submersible entry nozzles to the tundish lining, the tundish slide plates, and the shrouds. These consumable items now represent a significant portion of the cost of producing steel. Several IOF road maps mention refractory coatings, an area in which considerable efforts have been mounted in recent years by the refractories industry and others. Although some applications have been successful, new coatings have seldom met expectations. This R&D area has a low probability of success but would have a high economic return. Another R&D area (although not specified in industry road maps) applicable to all of the IOF industries is insulating refractories, which would lead to energy savings, is one of OIT’s overall objectives. Refractory ceramic fiber is an extremely effective insulating material but is often not cost effective and has limited temperature capabilities. Health and safety concerns have also been raised about using this material. R&D in this area could focus on reducing costs, increasing service temperatures, finding a cost-effective substitute (e.g., foam), and developing a high-temperature ceramic fiber that is environmentally benign. More conventional insulating refractories (e.g., insulating firebrick) also have the potential to save energy, but very little work has been done in this area in recent years. Insulating castables could also have significant energy savings.
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MATERIALS TECHNOLOGIES FOR THE PROCESS INDUSTRIES OF THE FUTURE OPPORTUNITIES FOR MATERIALS RESEARCH AND DEVELOPMENT In keeping with the crosscutting theme of this report, the committee has focused on materials technologies that would enable or improve the understanding and processing of existing and new products used by more than one IOF industry rather than on the development of industry-specific products. The R&D opportunities are summarized in the following recommendations. Recommendation. The Office of Industrial Technologies (OIT) should focus its materials technologies programs on a few high-priority areas that would meet the needs of several member industries of the Industries of the Future Program and, when warranted, develop crosscutting programs to address these areas. Areas to consider include: corrosion, wear, high-temperature materials (including refractories), and materials models and databases. OIT should use the panel of experts to identify materials-performance requirements and process parameters for each industry as a basis for selecting crosscutting technologies. OIT should then work with the panel to develop and select programs. Recommendation. Funding by industry, universities, and the national laboratories for the development of improved refractories has been reduced although most of the members of Industries of the Future have identified a need for them. The Office of Industrial Technologies should consider starting a refractories initiative to encourage cooperative research and development agreements and other mechanisms that would promote cooperation between industry and government agencies. OIT should consider supporting research and development in the following areas: reducing corrosion/erosion high-temperature reactions between molten metal, glass, and refractories; reducing the buildup of materials on the surface of the refractories; clarifying the fundamentals of monolithic refractories (including drying mechanisms and new binder systems); and developing data for finite element analysis design.
Representative terms from entire chapter: