Creosote removal

Approximately 50—55% of the product from a coal-tar refinery is pitch and another 30% is creosote. The remaining 15—20% is the chemical oil, about half of which is naphthalene. Creosote is used as a feedstock for production of carbon black and as a wood preservative. Because of modifications to modem coking processes, tar acids such as phenol and cresyUc acids are contained in coal tar in lower quantity than in the past. To achieve economies of scale, these tar acids are removed from cmde coal tar with a caustic wash and sent to a central processing plant where materials from a number of refiners are combined for recovery. 

The coal tar first is processed through a tar-distillation step where ca the first 20 wt % of distillate, ie, chemical oil, is removed. The chemical oil, which contains practically all the naphthalene present in the tar, is reserved for further processing, and the remainder of the tar is distilled further to remove additional creosote oil fractions until a coal-tar pitch of desirable consistency and properties is obtained. 

PermeOx is also used to improve the bioremediation of soils contaminated with creosote or kerosene (see Bioremediation (Supplement)), to deodori2e sewage sludges and wastewater (see Odormodification), and to dechloriaate wastewater and effluents. A special formulation of calcium peroxide, made by FMC and sold ia the United States under the trademark Trap2ene, is used for removing metal ions from acidic waste streams such as coal ash leachate and acid mine drainage (see Wastes, industrial). 

The water is then pumped through series operated sand filters, which provide the final stage of suspended solids removal and protect the garnualr activated carbon (GAC) filters from particulate contamination. Series operated GAC filters are then used to remove the dissolved creosote and pesticides from the water. To achieve compliance with specifications levels, water should be sampled and analyzed after leaving the first GAC filter. The second GAC filter normally serves as a guard bed. 

Middaugh, D.P., S.E. Lantz, C.S. Heard, and J.G. Mueller. 1994a. Field-scale testing of a two-stage bioreactor for removal of creosote and pentachlorophenol from ground water chemical and biological assessment. Arch. Environ. Contam. Toxicol. 26 320-328. 

Three types of closely related cresols exist ortho-cresol (o-cresol), meta- cresol (m-cresol), and para-cresol (p-cresol). Pure cresols are colorless chemicals, but they may be found in brown mixtures such as creosote and cresylic acids (e.g., wood preservatives). Because these three types of cresols are manufactured separately and as mixtures, they can be found both separately and together. Cresols can be either solid or liquid, depending on how pure they are pure cresols are solid, while mixtures tend to be liquid. Cresols have a medicinal smell (odor) and when dissolved in water, they give it a medicinal smell and taste. Cresols do not evaporate quickly from water, but in rivers and lakes, they can be removed quickly by bacteria. Dissolved cresols can pass through soil into underground water sources. This may be a problem at hazardous waste sites where cresols are buried. Once cresols are in the water table, they may stay there for months without changing. Cresols in air quickly change and break down into smaller chemicals, some of which irritate the eyes. Cresols can also irritate the eyes. 

The "tar" stream which is highly aromatic is made up of tar naphtha, creosote and pitch. The tar naphtha is hydrofined to remove N, S and 0 compounds. It consists mainly of toluenes and xylenes. The creosote can either be sold as such (eg for wood preservation) or be hydrofined to yield a product rich in higher aromatics. The tar pitch is used for impregnating cellulose fibre pipes or is converted to high quality coke (for the production of carbon electrodes). 

The 7-7, Inc. (7-7) liquefication process was used at the Broderick Wood Products Superfund site, a former wood treating plant near Denver, Colorado. More than 3200 yd of creosote sludge were removed and recovered. The on-site liquefication of the sludge cost approximately 1,000,000. No information was available as to what these costs covered (D16170G). 

CESAR was developed to address the problem of locating, characterizing, and removing dense non-aqueous-phase liquids (DNAPLs) from contaminated aquifer systems. The process is particularly suited to remediating groundwater contaminated with chlorinated solvents, such as trichloroethylene (TCE), tetrachloroethene (PCE), trichloroethane (TCE), and carbon tetrachloride (CCE). According to the vendor, CESAR can also be applied to sites contaminated with creosote, polychlorinated biphenyls (PCBs), Freon 113, volatile organic compounds (VOCs),... 

Chemical contaminants for which full-scale treatment data exist include primarily volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs). These SVOCs include polychlorinated biphenyls (PCBs), pentachlorophenol (PCP), pesticides, and herbicides. Extremely volatile metals, such as mercury and lead, can be removed by higher temperature thermal desorption systems. The technology has been applied to refinery wastes, coal tar wastes, wood-treating wastes, creosote-contaminated soils, hydrocarbon-contaminated soils, mixed (radioactive and hazardous) wastes, synthetic mbber processing wastes, and paint wastes. 

Expectorants are the drugs which increase the production of bronchial secretion and reduce its viscosity to facilitate its removal by coughing. Expectorants can stimulate the expulsion of respiratory secretion either directly or reflexly. Certain volatile oils of plant origin such as oil of lemon, anise, eucalyptus by steam inhalation route increase the respiratory secretion by its direct action. Another compound, guaiacol, which is obtained from wood creosote or synthetically prepared, directly increase bronchial secretion and syrup tolu (Tolu balsum) act in same way. 

Relying on the activity of the indigenous microfiora, Tremaine et al. (1994) comparatively evaluated three solid-phase treatment strategies according to their ability to remove PAHs from creosote-contaminated soil. These efforts culminated in an initial biodegradation rate 06) of 122 mg total PAH per kg of soil per day with a starting soil total PAH concentration of 500-14 000 mg/kg. However, when biodegradation data are considered over the entire 12-week incubation period, PAH removal appears to be less extensive removal of the HMW PAHs was not described. 

Tremaine et al. (1994) conducted pilot-scale studies to compare the effect of a suspended-growth reactor and a fixed-film bioreactor with a constructed wetland environment in removing creosote-PAHs from contaminated water recovered from a wood-preserving facility. Mass balanced chemical analysis of 5 PAHs used as model constituents of creosote showed that the wetland yielded between 20 and 84% removal, whereas the fixed-film reactor yielded 90 to 99% PAH removal. Biodegradation accounted for >99% of the losses observed in the fixed-film reactor, but only 1-55% of the compounds removed in the artificial wetland was attributable to biodegradation. Again, physical sorption of PAHs, especially HMW PAHs, was found to be significant. 

Starch and Bakelite were obtained from stock supplies and were used as-received for pyrolysis studies of blends. Hydrogenated creosote was prepared in the laboratory by catalytically hydrotreating a 270°-355°C. creosote fraction to remove all heterocyclic impurities and to saturate completely the ring systems. 

Figure 1. Relationship between weight of activated carbon and removal of COD ana phenols from a creosote wastewater...

Middle oils, or creosote oils, generally are the fraction from 200 to 250°C, which contain naphthalene, phenol, and cresols. The naphthalene settles out on cooling, is separated by centrifuging, and is purified by sublimation. After the naphthalene is removed, phenol and other tar acids (phenol and its homologs) are obtained by extraction with 10% caustic soda solution and neutralization, or springing by carbon dioxide. These are fractionally distilled. 

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