| OCR Text |
Show Off gasses from cupola melting require afterburners to reduce emissions to acceptable levels. Typically these are na~~l gas fired, very inefficient (without heat recovery devices), and combustion is difficult to sustain. ComposItIOn of th.e off gas is variable and needs to be better defined to reduce the amount of cover gas used to ensure complete ~estruchon. Fundamental research needs to be perfonlled to establish heating values based on chemical structur~, unproved combustion geometries and zoning, and emissions destruction efficiencies. Although not within the cOm?US~IOn program realm, the use of waste heat recovery devices should be studied for low-temperature direct ~pphcahons or for the use of electrical generation where burnout of the carbon monoxide can be used. The study must mclude effects of particulate and gas composition suitability for generation equipment. A significant amount of energy is lost in transfer processes as the hot metal is conveyed to casting areas. Based 0!l the fOlmdry site location and age, the material must be moved several times and kept hot during the transfer. Integra~on studies to minimize these transfers would be useful. The avoidance of reheating the metal will reduce the ener~ mput per ton of metal produced. Combustion-related processes to replace electrical induction, or electric arc heatmg would be more efficient. Competition from alwninwn and other products is forcing the industry to reduce wall thickness for weight ~eduction. Heat treating of the castings becomes increasingly important to achieve acceptable metal attributes. The tron carbide precipitates that fonn when iron castings are cooled are typically burned off during heat treating processes. Improved methods to reduce these precipitates and achieve the appropriate heat treatment for thin castings are an area requiring further study. Optimization of this process will reduce the amount of combustion energy. The exhaust gases from cupolas lead to difficulties in the use of current-generation combustion sensors. Sensors to monitor oxygen, carbon monoxide, and carbon dioxide content would optimize combustion. Appropriate filters should be developed to allow the use of current-generation sensors, or new sensors suitable for gas analysis in dirty environments need to be developed. Continuous measurement of the liquid metal flow out of cupolas cannot be monitored, yet this would give one necessary data point needed to optimize combustion. Monitoring of oxygen in foundries is typically accomplished with a single-use oxygen probe. Although costs for the probes are low and are used in the steel industry, they do not see use in the foundry industry because of smaller tonnage rates. The net cost of the sensor per ton of metal produced is considered too high by the metal casting industry. 4.4 Chemical Industry The chemical industry is sometimes called the keystone industry because its products improve the productivity and quality of goods manufactured by so many other industries . It is the largest U.S. exporting industry: in 1993, exports were $42.7 billion. The chemical industry must retain its strong competitive stance or risk aggravating the chronic U.S. trade deficit. The chemical industry uses about 2.7 quads of fuel annually. Four of the industry's segments-inorganics, organics, plastics, and fertilizers-use almost 90% of the industry 's fuel and electricity. Energy efficiency in the chemical industry has improved 51 % since 1974. Much of the growth in the chemical industry is in the specialty chemical sector. As fmns in the commodity chemical market shift to the specialty market, some modifications of production practices are necessary because the sales in the specialty market are tied more closely to product quality and performance. Research developments should address these types of process improvements. In addition to improvements relating to changes in products and processes, there is always a need to reduce regulated emissions and ~educe waste p~oduction . Recommendations for research to address process improvements, as they relate to combustlOn processes, mclude (a) development of advanced control algoritluns for thennal reactors (fluidized-bed reactors, fluid heaters, and distillation reactors) in which combustion is used to supply energy to the process ~ (b) development of enhanced heat transfer methods for the transfer of combustion heat to processes such as those described above; and (c) development of high-temperature separation processes to partition the components of the combustion off-gas stream. These three topics are discussed in greater detail below. 4.4.1 Development of Advanced Control Algorithms and Equipment for Thermal Reactors Product quality and efficiency are closely related to processing conditions, especially in the growing specialty chemical market· consequently, process control is imperative for successful production operations. Improved control algorithms are n~eded to meet the need for combustion processes. For externally heated fluidized-bed reactors, fluid 12 |
