AISI-EPA-Battelle Coke Oven Door Sealing Program

The problem of coke oven door leakage is generally recognized as one for which no proven solution exists. In 1974 the United States Environmental Protection Agency and the American Iron and Steel Institute entered into a jointly funded research project with Battelle Columbus Laboratories. The initial project was to define the problem by literature search, operator interviews and profile measurements of jambs and doors.

Numerous concepts of seal designs were developed and then rated by industry and Battelle reviews. It was determined that a metal-to-metal seal offered the greatest probability of success. It was felt that jamb warpage was the most serious problem to be solved.

In the fall of 1976 another contract was signed by EPA and AISI assigning Battelle the task of developing to the point of fabrication a system to eliminate or significantly reduce leakage from coke oven end closures. This program included mathematical modeling, physical modeling, field data collecting, analysis, and full scale unit design.

A retrofittable door seal design has been developed and preparations are underway for operating evaluation at eight steel plants. The design is retrofittable to the two principal coke oven doors in service and should accommodate the worst jamb warpage usually found.     

Sensitivity Studies of the Effects of Model Formulation on the Evaluation of Control Strategies for Photochemical Air Pollution Formation in the United Kingdom

In the OZIPP (ozone isopleth plotting package, developed by United States Environmental Protection Agency) a number of model specific assumptions with respect to chemical and physical processes are made. These assumptions are introduced into an alternative model developed at AERE Harwell, United Kingdom, in which a detailed chemistry and mixture of organic emissions is included. The impact on the AERE Harwell model results of the assumptions made in OZIPP of omitting ground removal of ozone (O₃) and peroxyacetylnitrate (PAN) and of employing an incomplete PAN chemistry and adopting a reaction rate coefficient of the key reaction NO + HO₂ → NO₂ + OH which is a factor 10 lower than the accepted value, are discussed. The composition of the organic emissions is an important model parameter, and it is shown how grouping of nonmethane hydrocarbon (NMHC) emissions into a small group of NMHC thought to be representative, often implies that O₃ and other pollutants are overestimated. The O₃ isopleth diagram for London constructed using the AERE Harwell model gives a somewhat different picture from that obtained with OZIPP. OZIPP in general predicts that NO_x control or combined hydrocarbon(HC) and NO_x control is efficient with respect to O₃ reduction whilst the AERE Harwell model predicts that HC control alone usually is more efficient than combined HC and NO_x control. Furthermore NO_x control alone may often increase the O₃ burden downwind in the AERE Harwell model.     

Resource Recovery from Flue Gas Desulfurization Systems

The cost effective benefits of yielding a flue gas desulfurization (FGD) sludge predominantly composed of CaSO₄·2H₂O, have been previously established. The recovery of this material as FGD by-product gypsum has been demonstrated abroad. Recently U.S. wallboard manufacturers have recognized the viability of this recovery practice. Such techno-economic decision making variables as a) by-product specification, b) transportation costs, and c) location of suitable FGD systems enable the recognition of FGD by-product recovery. Recent investigations of resultant solids content and chloride washing reflect the technical possibility of delivering a suitable product. Commercial and economic factors favor recovery based upon rising disposal and transportation costs. Existing and near term proposed systems surface the technical and commercial problems faced by utilities considering recovery.

Generation of an oxidized FGD sludge consisting of 90⁺% CaSO₄·2H₂O and dewatered to 80⁺% solids is technically achievable by air sparging within the FGD system. Although the product is suitable for land disposal, electric power utilities should consider and evaluate by-product recovery. U.S. wallboard manufacturers have established technical criteria for FGD by-product gypsum. Percent CaSO₄·2H₂O, final solids content, particle size, and chloride content are primarily technical parameters. Technology exists within the FGD industry to satisfy these criteria and results are discussed.

Economic factors comparing mining costs, transportation costs, and disposal costs are developed for specific utility projects. Such comparison established generalized financial criteria for a given utility to develop the economic reasonableness of considering FGD byproduct recovery.

End product user perspectives are presented providing electric utilities with a realistic appreciation for by-product recovery potential. Location of existing wallboard plants highlight potential recovery regions. Quality control problems are discussed in terms of generating a by-product rather than a disposable material.     

Predicting and Managing the Health Risks of Sour-Gas Wells

The development of sour-gas resources in Canada and the United States has prompted concerns about the public health risks of accidental releases of gas contaminated with hydrogen sulfide (H₂S) from wells. This paper focuses on methods for improving the prediction and management of those risks. Data associated with the health effects of hydrogen sulfide are examined, and it is suggested that sublethal effects should be addressed in risk assessments of sour-gas wells along with the life-threatening effects normally considered. The demarcation of hazard zones around wells can be improved by using a statistical approach for estimating an upper-bound H₂S release rate; this rate can then be used in an atmospheric dispersion model to estimate maximum distances to downwind concentrations for lethal (300 ppmv) and sublethal (50 ppmv) effects resulting from an accidental release. A vertical release is found to have little impact, especially under stable atmospheric conditions; horizontal releases, on the other hand, result in the greatest downwind distances for health impacts. Management of health risks depends on a mix of safety technologies and contingency actions, such as well-ignition options and provision for post-release monitoring and assessment of ambient H₂S concentrations.     

The Feasibility of Wet Scrubbing for Treating Waste-to-Energy Flue Gas

The selection of Hue gas treatment processes in the waste-to-energy industry has generally followed the trend of the coal-fired power industry. The highly favored process for both industries is the dry scrubber (spray absorber) followed by a fabric filter. As more attention is focused upon increasingly greater efficiencies, lower outlet concentrations, heavy metals emissions, and toxic organic pollutant emissions, the advantages of wet scrubbing become more pronounced. This paper provides an objective technical and economic evaluation of selected wet scrubbing and dry scrubbing systems for a generic waste-to-energy facility. The advantages and disadvantages of wet scrubbing are discussed and translated into cost benefits or penalties.     

Speciation and transport of arsenic in an acid sulfate soil-dominated catchment, eastern Australia

Factors controlling the transport of geogenically-derived arsenic from a coastal acid sulfate soil into downstream sediments are identified in this study with both solid-phase associations and aqueous speciation clearly critical to the mobility and toxicity of arsenic. The data from both sequential extractions and X-ray adsorption spectroscopy indicate that arsenic in the unoxidised Holocene acid sulfate soils is essentially non-labile in the absence of prolonged oxidation, existing primarily as arsenopyrite or as an arsenopyrite-like species, likely arsenian pyrite. Anthropogenically-accelerated pedogenic processes, which have oxidised this material over time, have greatly enhanced the potential bioavailability of arsenic, with solid-phase arsenic almost solely present as As(V) associated with secondary Fe(III) minerals present. Analyses of downstream sediments reveal that a portion of the arsenic is retained as a mixed As(III)/As(V) solid-phase, though not at levels considered to be environmentally deleterious. Determination of arsenic speciation in pore waters using high performance liquid chromatography/Inductively Coupled Plasma-Mass Spectrometry shows a dominance of As(III) in upstream pore waters whilst an unidentified As species reaches comparative levels within the downstream, estuarine locations. Pore water As(V) was detected at trace concentrations only. The results demonstrate the importance of landscape processes to arsenic transport and availability within acid sulfate soil environments.     

Hydrogen peroxide stabilization in one-dimensional flow columns

Rapid hydrogen peroxide decomposition is the primary limitation of catalyzed H(2)O(2) propagations in situ chemical oxidation (CHP ISCO) remediation of the subsurface. Two stabilizers of hydrogen peroxide, citrate and phytate, were investigated for their effectiveness in one-dimensional columns of iron oxide-coated and manganese oxide-coated sand. Hydrogen peroxide (5%) with and without 25 mM citrate or phytate was applied to the columns and samples were collected at 8 ports spaced 13 cm apart. Citrate was not an effective stabilizer for hydrogen peroxide in iron-coated sand; however, phytate was highly effective, increasing hydrogen peroxide residuals two orders of magnitude over unstabilized hydrogen peroxide. Both citrate and phytate were effective stabilizers for manganese-coated sand, increasing hydrogen peroxide residuals by four-fold over unstabilized hydrogen peroxide. Phytate and citrate did not degrade and were not retarded in the sand columns; furthermore, the addition of the stabilizers increased column flow rates relative to unstabilized columns. These results demonstrate that citrate and phytate are effective stabilizers of hydrogen peroxide under the dynamic conditions of one-dimensional columns, and suggest that citrate and phytate can be added to hydrogen peroxide before injection to the subsurface as an effective means for increasing the radius of influence of CHP ISCO.