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  • 8/9/2019 Roadmap Chap4


    Steel Technology Roadmap 83 Chapter 4: Environmental Leadership

    Through the promotion of responsible policies that conserve energy and natural resources while sustaining a sound economic environment, the steel industry is committed to the protection of human health and the environment.

    The steel industry has invested more than $7 billion in environmental controls over the past 30 years in order  to meet the challenge of compliance with national health-based standards. In a typical year, iron and steel plants spend roughly 15% of their capital expenditures on environmental projects. In fact, the industry’s discharge of  air and water pollutants has been reduced by well over 90% since the early 1970s. Despite this significant  progress, further improvements in pollution prevention technologies are needed for iron and steel plants to reduce costs, improve profitability, and facilitate compliance with changing federal regulations.

    Recently promulgated and impending air and water pollution control regulations pose a daunting challenge for  the U.S. steel industry. In accordance with requirements of the Clean Air Act, EPA has established Maximum Achievable Control Technology (MACT) standards for hazardous air pollutant emissions. Under this program, EPA established standards for coke oven door and topside leaks and charging emissions in 1992 and placed cokemakers on a timetable to achieve progressively more stringent standards between 1995 and 2020. In 2001, additional MACT standards are proposed for coke oven pushing and quenching operations and coke battery combustion stacks. Also in 2001, MACT standards are proposed for blast furnaces, sinter plants, basic oxygen shops, and ancillary operations.

    In addition to these industry-specific regulations, EPA has also revised the ambient air quality standards for fine  particulate matter (PM-2.5) and for ozone. As regulatory programs are implemented over the next few years to achieve these ambient standards, additional control requirements are possible for iron and steel industry sources emitting fine particles or gases that contribute to the formation of urban smog, including NOx, SOx, and VOCs. Also, the federal air permitting process under Title V of the Clean Air Act will require additional administrative controls and monitoring obligations.

    4 Environmental Leadership

  • 8/9/2019 Roadmap Chap4


    Chapter 4: Environmental Leadership 84 Steel Technology Roadmap

    The industry also faces substantially tighter regulations under the Clean Water Act. EPA has proposed revisions to Effluent Limitations Guidelines (ELGs) for the Iron and Steel Point Source Category that have been in place since the early 1980s. The EPA is on schedule to issue these rules in final form by April 2002. The new limits are dramatically lower than the existing ELGs and would require significant increases in recycling and more efficient treatment for the full range of iron and steel processes. Many steel plants are already required to reduce effluents below the previously established ELG limits because of the need to meet state and federal water quality

    standards, particularly in the Great Lakes area as a result of the Great Lakes Water Quality Initiative.

    Meeting these new and changing regulations requires effective R&D efforts throughout many different aspects of the steelmaking process. To target future research, it is useful to examine the various processes and the  pollutants they produce. Although the coking process has been widely considered to pose the biggest environmental challenge, environmental regulations affect all stages of the manufacturing and forming process. The following sections discuss the potential pollutant output and development needs of each of the major   processes: cokemaking, ironmaking, steelmaking, refining, casting, forming, and finishing.

    4.1 Cokemaking

    Cokemaking represents perhaps the greatest environmental concern to the steel industry. Although much  progress has been made, cokemaking emissions continue to be a target of federal environmental regulations. Continual efforts to reduce emissions are necessary to ensure the stability of U.S. cokemaking; some by-products  present an additional concern. Figure 4-1 illustrates the cokemaking process with its major inputs and outputs.

    Strict environmental regulations in the United States, including the Clean Air Act Amendments of 1990, threaten the economic viability of domestic coke production. While improvements to contain emissions have been incorporated into recent oven designs, many older cokemaking facilities cannot be retrofitted economically to meet current and proposed environmental standards. Tighter environmental regulations threaten to accelerate  plant closures, in turn reducing domestic production capacity by approximately 30% by the year 2003. Other  developed and developing nations are expected to follow the lead of the United States with tighter environmental regulations that will affect worldwide coke production. At present, no new by-product cokemaking technology

    is guaranteed to be environmentally compliant. In fact, new MACT standards provide an incentive for non- recovery coke ovens for new facilities. In the future, U.S. dependence on foreign sources is expected to increase.

    4.1.1 Cokemaking Emissions

    Typical cokemaking air emissions include ammonia, benzene-soluble organics, benzene, particulates, SOx, and VOCs. Coke plant operators have initiated significant efforts to control these emissions and have spent millions of dollars on environmental control systems, improved operating and maintenance practices, and increased  personnel training. These efforts have substantially reduced cokemaking air emissions over the last three decades

  • 8/9/2019 Roadmap Chap4


    Steel Technology Roadmap 85 Chapter 4: Environmental Leadership

    Figure 4-1. Cokemaking Flow Diagram

    The industry’s efforts have reduced emissions by more than 95% for benzene and VOCs from by-product sources, particulate matter emissions from charging and pushing, and SOx emissions from the combustion of  “cleaned” coke oven gas. To reduce air emissions, the industry installed many types of new and improved environmental hardware. Training and, more importantly, the conscientious efforts of skilled operating personnel have also substantially reduced emissions of benzene-soluble organics from coke plant doors, lids, offtakes, and charging emissions sources.

    4.1.2 Cokemaking Effluents

    The typical volume of process wastewater generated at a well-controlled coke plant is approximately 150 gallons/ton of coke produced (EPA 2000). About 25 to 35 gallons/ton are generated as waste ammonia liquor  from moisture contained in the charged coal. The balance is from the steam used in distilling ammonia from the waste liquor, light oil recovery, and other processes.

    Cokemaking wastewaters contain significant levels of oil and grease, ammonia, nitrogen, cyanides, thiocyanates,  phenols, benzenes, toluene, xylene, other aromatic volatile components, and polynuclear aromatic compounds. Wastewaters also contain trace amounts of the toxic metals antimony, arsenic, and selenium. The amount of each  pollutant generated depends on the by-product process, specific facility equipment, practices, and the range of  constituents in the coals used.

  • 8/9/2019 Roadmap Chap4


    Chapter 4: Environmental Leadership 86 Steel Technology Roadmap

    4.1.3 Cokemaking By Products

    In the by-product coking process, volatile components are collected as unpurified “foul” gas containing water  vapor, tar, light oils, coal dust, heavy hydrocarbons, and complex carbon compounds. Condensable materials, such as tar, light oils, ammonia, and naphthalene are removed, recovered, and processed as gas and coal chemical  by-products. Finally, sulfur is removed, leaving clean, desulfurized coke oven gas. The cleaned, desulfurized

    gas is then used as fuel for coke ovens or other plant combustion processes, or it is sold to nearby facilities.

    Approximately 11,000 scf of coke oven gas (at about 500 Btu/scf) is produced/ton of coal charged (EPA 2000; AISE 1998). About 40% of the gas is used to heat the coke ovens.

    4.1.4 Hazardous Cokemaking Wastes

    As shown in Figure 4-1, seven listed hazardous wastes are associated with cokemaking under the Resource Conservation and Recovery Act (RCRA). These include residues from coal tar recovery, tar storage tanks, light oil processing units, wastewater sump residues, and naphthalene collection and recovery.

    Process residues from coal tar recovery (K141) are generated when uncondensed gas enters a primary cooler.

    Condensates from the primary cooler flow into the tar collecting sump and are discharged in the flushing liquor  decanter. Tar collection sump residue or sludge accumulates at the bottom of the collecting sump, and must be recycled periodically as an individual stream, through the flushing liquor decanter, or back to the coke oven. Tar storage tank residues (K142) are produced when residuals settle out of the crude coal tar collected as a coking  by-product. The residues are periodically removed from the storage tanks and are recycled to the oven or  landfilled.

    Residues from light oil processing units (K143) collect in a light-oil scrubber and light-oil stripping still. Resin is a related waste that accumulates from cleaning wash oil used in the light-oil recovery process. Wash-oil muck, residue from a wash-oil purifier or decanter, is periodically removed and recycled to the coke oven, reclaimed off-site, or used as