1、Il F November 2001 I N T E R NATI ON A L Alumina Technology Roadmap Sponsors Alcan Inc. Alcoa World Alumina Aluminium Pechiney Comalco Aluminium Limited Hindalco Industries Ltd Hydro Aluminium Metal Products Kaiser Aluminum v Needs Ud his roadmap represents a concerted look by the global alumina ind
2、ustry at its technology challenges T over the next 20 years. While most of the R the supply of economical gibbsitic ore is not as large as ores requiring more vigorous treatment. Improvements in resource utilization create benefits that ripple through to plant efficiency and environmental performanc
3、e. By maximizing the alumina extracted per ton of bauxite, refiners reduce the input of impurities per ton of alumina and also the quantity of residue generated. The energy efficiencyof the Bayer process can be improved directly or indirectly through the use of cogeneration, waste heat utilization,
4、and synergies with nearby industries, as well as through equipment advances or process changes. Alumina Technology Roadmap 5 The non-utilization of waste heat within some refineries represents one of the biggest energy inefficiencies in the industry. Opportunities for utilizing the waste heat of nea
5、rby power generators should also be considered. Reducing residence time in the Bayer process equipment also reduces energy consumption, losses, and capital costs while increasing production. Any operating change that increases productivity essentially reduces the unit energy requirements of producin
6、g alumina. Improving the thermal efficiency of refinery operations also reduces emissions of greenhouse gases. The alumina industry is not as advanced as the chemical and some other industries in its use of process management techniques, particularly models and control systems. Refiners often use mo
7、dels that have not been tailored for the specific conditions found in a refinery and therefore do not work particularly well. Increased use of Bayer-specific models and automation reduces process variation while reducing human exposure to the caustic environment. Knowledge management systems are als
8、o critically lacking in the alumina industry, leading to repeated mistakes, particularly at the operations level. Benchmarking is a mechanism by which individual refineries can gauge their performance and practices against each other, and the industry can measure itself against other industries. Ben
9、chmarking tends to be most successful in those industries where an information infrastructure already exists. The alumina industry has been investigating options for residue treatment and utilization for years with limited success. The economics of using the residue in most applications are not curr
10、ently favorable. Inventories of this byproduct represent a liability for the industry that extends well into the future, and technology is needed to find economically viable alternative uses. Reducing human exposure to safety risks can be accomplished through many of the topics already discussed, in
11、cluding reducing scale and increasing plant automation. The push for full automation is a common goal throughout the industry and would promote the awareness of refineries as well-run, modern, and safe. Industry-wide standards and criteria for safety in plant design and operation, as well as standar
12、dized training, would help establish a culture of operating safety within the refining industry. The ensuing pages highlight the twelve pfiofity R capital cost; energy consumption; environment, safety, and health; and product quality * - Following the highest priority needs is a discussion of thirte
13、en Rm Energy Environment, Safety, lower maintenance costs Fewer pfecipitators; lower capital cost per ton of alumina for brownfield and greenf e I d projects Increased yield is equivalent to lower unit energy , requirements I Fewer energy-related emissions per ton of alumina See comments under “Desc
14、ription“ 8 Alumina Technology Roadmap PRIORITY R improved sustainability and environmental responsibility Alumina Technology Roadmap 9 PRIORITY R fewer heaters required Energy savings associated with moving to low- temperature d gestion Fewer energy-related emissions; reduced odor Improved alumina p
15、roperties with fewer impurities 10 Alumina Technology Roadmap PRIORITY R reduced energy requirements; reduced manpower requirements Elimination of Bayer process equipment Substantial reduction in energy requirements of producing aluminium Unknown ?!$J pt Unknown Alumina Technology Roadmap 11 PRIORIT
16、Y R automation reduces process upsets requiring human intervention in potentially dangerous environments. Automation can also lead to better product quality and consistency. Potential Partners Alumina companies, academia, research organizations, equipment and instrument suppliers Potential Payoff Mo
17、derate Technical/Economic Risk Time Frame Challenges 2001 Description Impacts , - Negligible impact Small savings from better control of digestion and calcination Reduced human interaction in potentially dangerous I environments Better product quality and consistency through improved I process contr
18、ol and I predictive modeling 12 Alumina Technology Roadmap PRIORITY R&D NEEDS Impurity ion Efficient use of the worlds bauxite resources requires maximizing both the quantity and quality of the alumina that is extracted. A major cause of Bayer process inefficiency is the introduction of impurities c
19、ontained in the bauxite. The industry lacks technically and economically viable methods for controlling and removing these impurities. The trend toward lower grades of bauxite available in the future will only exacerbate this problem. Potential Partners Potent al Payoff Technical/Economic Risk Time
20、Frame Challenges Al um i na com pan es , research organ izat ions, govern ment, su p pl ers High Moderate 2001 2005 2010 2020 Description Impacts , Increased refinery output and a lower capital cost per ton of alumina Better energy efficiency from increased caustic concentration Maximized use of bau
21、xite reserves Less degradation of alumina quality mina Technology Roadmap , 13 PRIORITY R&D NEEDS Almost all organic compounds enter the Bayer circuit with the bauxite. Inorganic impurities also are introduced via bauxite as well as caustic and makeup water. The presence of significant concentration
22、s of impurities in the liquor has a detrimental effect on almost every aspect of the Bayer process, including digestion and precipitation capability, liquor productivity, and product quality. Potential Partners Alumina companies, academia, research organizations, government Potential Payoff Moderate
23、ly high Technical/Economic Risk Time Frame C ha I I enges 2001 Description . .- * I Impacts Increased liquor productivity (lower caustic consumption) Increased refinery output and a lower capital cost per ton of alumina Better energy efficiency from increased caustic concentration Fewer residues, in
24、creased use of lower-grade bauxites Less degradation of alumina quality 14 Alumina Technology Roadmap PRIORITY R&D NEEDS nowled The alumina industry lags behind the chemical and some other industries in terms of its use of process modeling to optimize operations, the sophistication of its control sy
25、stems, its handling and treatment of raw materials and byproducts, and its safety culture. Poor knowledge management, particularly at the operations level, inhibits the industrys ability to improve its performance. Benchmarking may help the refining industry identify potential solutions to some of i
26、ts key problems by learning from other industries. Potential Partners Potential Payoff Technical/Economic Risk Time Frame Alumina companies, government, suppliers Moderately high Low C ha I I enges 2001 2005 2010 Description 2020 Impacts Potentiat for more elegant processes, fewer unit operations Po
27、tential for more efficient operation Potential to reduce human exposure for desea I ing Potential to improve product through better process control and predictive modeling Alumina Technology Roadmap 15 PRIORITY R&D NEEDS Major Reduction in Caustic Consumption The caustic soda used in Bayer liquor re
28、presents one of the largest operating costs in an alumina refinery. Major factors influencing caustic requirements are the composition of the bauxite being processed and the chemistry of the desilication product (DSP) formed during digestion. Much of the caustic soda content of DSP is currently unre
29、covered. Potential Partners Potential Payoff Technical/Economic Risk Time Frame C h a I I enges Industry, academia, research organizations, government High 2001 2005 2010 2020 Description Large cost savings from reduced caustic requirements No impact 61 No impact Reduced handling of a dangerous subs
30、tance, less likelihood of spills No impact i l i l I I 16 Alumina Technology Roadmap PRIORITY R&D NEEDS Scale manage men The precipitation of sodium aluminosilicate crystals from spent Bayer liquor leads to scaling of heat exchanger vessels and piping. Other types of scale can occur elsewhere in the
31、 plant (e.g., calcium titanate-containing scale and alumina trihydrate scale). Maintenance personnel are required to remove scale manually, presenting a serious risk for injury because of the corrosive environment and enclosed space. Scale leads to a significant reduction in heat transfer efficiency
32、 and liquor throughput, resulting in increased energy and caustic soda consumption and loss of productivity. Potential Partners Potential Payoff Technical/Economic Risk Time Frame Challenges Alumina companies, academia, research organizations, su p pl ers , govern ment High Moderately high _I 2001 2
33、005 Description Impacts / Fewer heaters required I Savings from higher heat transfer efficiency in the heat exchangers Reduced human interaction in descaling (enclosed space, caustic environment I Small benefit through better control of silica Alumina Technology Roadmap 17 PRIORITY R&D NEEDS Tecnica
34、l Solutions for inery Releases The issue of refinery releases (including air emissions, effluents, and solid wastes) is becoming more prominent and must be viewed from a broader perspective than in the past. Cost-effective solutions are needed to deal with caustic, organics, trace metals, particulat
35、es, and other releases. Insufficient attention has been given to groundwater contamination in particular. Potential Partners Research organizations, government, refineries, industry trade associations Potential Payoff Moderately high Technical/Economic Risk High Time Frame Challenges Descri pt ion I
36、mpacts , Small reduction in caustic consumption No impact Small opportunity to recover low-grade waste heat from flue gas Reduction in air pollutant emissions, spills, and groundwater contamination Provide “green“ alumina to customers , 18 Alumina Technology Roadmap PRIORITY R&D NEEDS The alumina in
37、dustry is a large sink for low-grade heat and presents significant opportunity for cogeneration. The industry is currently not taking advantage of available waste heat, mainly because of economic and regulatory reasons. The initial focus should be on recovering waste heat generated in the refinery.
38、Potential Partners Alumina companies, adjacent industries, government Potential Payoff Moderate Technical/Economic Risk Low Time Frame C ha1 lenges 2001 2005 2010 2020 Description Impacts _ Moderately lower , energy costs I h impact (fewer boilers savings from fewer boilers Moderate to high savings
39、(higher if cogeneration is used) Q Fewer combustion- % related emissions , e Noimpact Alumina Technology Roadmap 19 R&D AREAS Digestion During the digestion process, the alumina contained in the bauxite is dissolved in the Bayer liquor in the form of sodium aluminate. R&D needs in digestion focus on
40、 reducing the energy requirements (e.g., by carrying out the process at lower temperature or using biotechnology), facilitating the use of different grades of bauxite such as those with more reactive silica and reducing caustic requirements. A specific activity would be research into altered desilic
41、ation technologies that reduce sodium consumption, which would have a substantial payoff for refiners processing high-silica bauxite. The success of this effort would also significantly increase usable bauxite reserves. A true countercurrent digestion process for extracting monohydrate grades of bau
42、xite at low temperatures (using a vertical upflow vessel where the monohydrate is introduced at the top and the spent liquor at the bottom) would be a valuable progression of the “best practice” countercurrent technology currently used. The use of “free” evaporation (where entropy is used as a subst
43、itute for additional live steam) should also be investigated. Challenges process to extract m c at low temperatures ivitie i) Technology for high extraction at low temperature .(c Selective bauxite biodigestion i) New digestion system for high- silica bauxite circuit I Continuation of near- and mid-
44、 1 , term activities I I I l I i i l l l 20 Alumina Technology Roadmap R&D AREAS larific Bauxite residue is separated from the liquor containing the dissolved sodium aluminate in a settling process, after which the residue is washed to recover caustic soda and any remaining aluminate liquor. Potenti
45、al improvements to this process could include the elimination of security filtration, which would improve safety while decreasing capital and operating costs. Combining digestion and clarification into a single unit operation would improve the stability of these processes. If the combination process
46、 is continuous, it would represent a step change in current operations. An alternative to pressure decanter technology for the combined process would be a liquid/solid separation process utilizing membrane technology. both at el ow-wash soda recovery Alumina Technology Roadmap 21 R&D AREAS Alumina h
47、ydrate crystals are precipitated from Bayer liquor in a series of tanks seeded with gibbsite. The development of catalysts for reducing the activation energy for precipitation (as well as other Bayer process steps) could significantly improve productivity. Computer modeling techniques should be deve
48、loped to improve the efficiency of designing these catalysts as well as other additives. An alternative to current precipitation operations would be to focus on the yield of the precipitation process and adjust the quality of the product afterwards. cts 1 l I I l l simulation of new agitators , I l
49、I l Methods to make quality after precipitation j 22 Alumina Technology Roadmap R&D AREAS Calcination represents one of the costliest and most energyintensive operations in alumina refining. In calcination, the precipitated alumina hydrate crystals are sent to calciners or kilns where the water is removed. Several properties of the alumina product are very dependent on the conditions of the calcination process. The main focus of R&D is investigating potential means for improving the thermal energy efficiency of calcination. These efficiency gains must be su
