v-/EPA United States Environmental Protection Agency EPA/540/MR-94/507 April 1994 SUPERFUND INNOVATIVE TECHNOLOGY EVALUATION Demonstration Bulletin I ,i , ., I, Thermal Desorpticn System Clean Berkshires, Inc. Technology Description: A thermal desorption system (TDS) has been developed by Clean Berkshires, Inc. (CBI), Lanesboro, Massachusetts for ex-situ treatment of soils and other media contaminated with organic pollutants. The TDS uses heat as both a physical separation mechanism and as a means to destroy contaminants. The process is continuous and is com- posed of three different operations: feed preparation, contami- nant volatilization, and gas treatment. Feed preparation begins with a sequence consisting of crushing, shredding, and screening excavated or dredged waste material to reduce maximum particle size to 3/4-inch. Next, using a front- end loader, the waste is repeatedly folded into itself in an attempt to distribute moisture and pollutants evenly. This step is particu- larly important since it helps protect the system from severe, sudden thermal shocks caused by "hot spots" in the waste. The prepared material is then dumped into surge bins and fed into a kiln through a two-stage conveyor belt system. Contaminant volatilization begins after the prepared material en- ters the kiln. The temperature of the soil is increased through contact with an air stream heated by a natural gas burner located at the entrance of the kiln. The kiln is equipped with specially designed flights which lift and veil the soil, exposing greater surface area to the hot gases, improving volatilization. Treated soil exits the kiln and enters a pug mill which combines the material with solid residuals from gas treatment. Water recycled from the quench tower is added at this time to cool the treated materials and to control fugitive dust emissions. The solids are deposited onto a discharge conveyor and stockpiled. Gas treatment begins when the gas stream from the kiln, which contains volatilized contaminants and entrained paniculate, en- ters a multi-stage treatment sequence. The sequence uses the following: a cyclone to remove coarse particulate, a high-effi- ciency afterburner to destroy organics, a quench tower to cool the gas stream, and a baghouse to remove filterable particulate still suspended in the gas stream. A scrubber could be added to remove sulfur dioxide if levels are high enough to impact air quality standards. Treated gases exit the system through a 75- foot high stack. Solid residuals from gas treatment are trans- ferred by a screw auger to the pug mill and are combined with the treated waste material. The TDS is transportable and is monitored and controlled by a computer-based data acquisition system. Waste Applicability: The CBI TDS process has been successfully applied at two sites processing soils from throughout New England and New York. To date, over 250,000 tons of solid wastes have been treated using this technology. The CBI TDS can remove volatile organic compounds (VOCs), semivolatile organic compounds (SVOCs), organometallic complexes, and total petroleum hydrocarbons (TPHs). Full-scale CBI TDS opera- tions] have been used to remove VOCs such as benzene, tolu- ene, ethylbenzene, and xylene (BTEX); SVOCs such as naphtha- lene, phenanthrene, chrysene, benzo(a)pyrene, and other poly- nuclear aromatic hydrocarbons (PAHs); organometallic complexes such; as ferricyanides; and TPHs in the range of C4 toC,'. Demonstration Results: The CBI TDS Demonstration took place at the Niagara Mohawk Power Corporation's Reme- diation Technologies Demonstration Facility at Harbor Point in Uticaj New York between November 15 and December 13,1993. Figure 1 is a photo of the TDS used at this site. Harbor Point is the site of a former manufactured gas plant (MGP) and is con- taminated with BTEX and PAHs, ferricyanide compounds, and a variety of heavy metals. Four different types of MGP solid wastes were tested: (1) coke plant residuals; (2) purifier wastes; (3) water gas plant residuals; and (4) Utica Terminal Harbor sediments. Maximum pollutant concentrations were 320 milli- grams per kilogram (mg/kg) BTEX; 3500 mg/kg PAHs; 1200 mg/ kg cyanide; 60 mg/kg arsenic; and 320 mg/kg lead. Three 4-hr replicate runs were conducted for each waste type. For each run, samples were collected from feed soil, treated soil, cyclone solids, baghouse solids, quench water, intake water, and stack gases. Samples were analyzed for PAHs, BTEX, cyanide and metals. Feed soil samples were also analyzed for other chemical and geotechnical parameters. Critical operating parameters were optimized and monitored for each {waste type. Soil feed rate and kiln soil exit temperature were varied for each waste stream, based on preliminary results from an experimental test phase. The range for each parameter was as follows: feed rate, 16 to 22 tons per hour; kiln soil exit temperature, 620 to 860 °F; afterburner residence time, 0.82 to 0.87 seconds; and afterburner temperature, 1810 to 1820°F. Printed on Recycled Paper ------- Hgure 7. Ctean Berkshlres, Inc. Thermal Desorption System Preliminary results from the SITE Demonstration are summarized below: * • The CBITDS achieved DREs of 99.99 percent or better in alt 12 runs using total xylenes as a volatile principal or- ganic hazardous constituent (POHC). * DREs of 99.99 percent or better were achieved in 11 of 12 runs using naphthalene as a semivolatile POHC. * Average concentrations for critical pollutants in treated soils were 0.066 mg/kg, BTEX; 12.4 mg/kg, PAHs; and 5.4 mg/kg total cyanide. • Comparison of the dry weight basis concentration of pollut- ants in the feed and treated soil showed the following average removal efficiencies: 99.8 percent, BTEX; 986 percent, PAHs; and 97.4 percent total cyanides. ""' > ' " ..... n" "" ' ' ' " " . J i ' " " ' ' ' ' ' ' ' ' ' ! ' ' ' ' ' ' n v !» ...... I" 5 !, , t "SI ' pi ' . 'i . ...... ' ii* f • The CBI TDS showed good operating stability during the Demonstration with only a minor amount of down time. An Innovative technoiogyEvaiuatiori Report describing the com- plete Demonstration will be available in the Fall of 1994. For Further Information: • i, '., ;"'1 , .in1 ii!, , , i1 "'i"" i iri1'1"1:11'1! ..... .'iih;-!''"!.!,!:; '"iiij.!.;!1 v:i t ..p .in „ iii'iwr i1 w».ii: ' ,,i, ,i ' ! "'«,,,,, ,„ : i ' w, ...... H? "ir, .1,, !,• ...... B, .m , uttri't,,, ,u nn 'i|!i.i,i.: EPA Project Manager Ronald F. Lewis U.S Environmenta.1 Protection Agency Risk Reduction Engineering Laboratory 26 W. Martin Luther King Drive Cincinnati, OH 45268 (513) 569-7856 -u.S. Government Printing Office: 1994— 650-067/80267 United States Environmental Protection Agency Center for Environmental Research Information Cincinnati, OH 45268 Official Business Penalty for Private Use $300 BULK RATE POSTAGE & FEES PAID EPA PERMIT No. G-35 EPA/540/MR-94/507 ------- |