United States Environmental Protection Agency EPA/540/S-97/501 August 1997 &EPA SUPERFUND INNOVATIVE TECHNOLOGY EVALUATION Emerging Technology Summary Vitrification of Soils Contaminated by Hazardous and/or Radioactive Wastes A performance summary of an ad- vanced multifuel-capable combustion and melting system (CMS) for the vitri- fication of hazardous wastes is pre- sented. Vortec Corporation has evaluated its patented CMS for use in the remediation of soils contaminated with heavy metals and radionuclides under the EPA's SITE program and other waste treatment technology evalu- ation programs. The Vortec CMS has successfully demonstrated the ability to effectively treat hazardous and/or ra- dioactive soils and produce a stable vitrified product with excellent leach resistance. The ability to process con- taminated soils either as dry granular solids or in the form of a slurry has been demonstrated with a ORE of greater than 99.99% for organic com- pounds. All the glass produced passed the TCLP test with the concentration of contaminants in the leachates signifi- cantly reduced from those of the corre- sponding feedstocks which did not pass TCLP. The vitrified product also demonstrated superior radionuclide leach resistance, as no detectable quan- tities of the surrogate radionuclide were found by an ANSI/ANS-16.1 test. This Summary was developed by the National Risk Management Research Laboratory's Sustainable Technology Division, Cincinnati, OH, to announce key findings of the SITE Emerging Tech- nology program that is fully docu- mented in a separate report (see Project Report ordering information at back). Introduction Vortec Corporation has developed an advanced multifuel-capable combustion and melting system (CMS) for the vitrifica- tion of hazardous wastes. Vortec has evaluated the CMS for the remediation of soils contaminated with heavy metals un- der the EPA's SITE Programs, and for the remediation of soils contaminated with heavy metals, organic compounds, and radionuclides under other waste treatment technology evaluation programs. The soil remediation programs focused on demonstrating the ability of the Vortec CMS to immobilize heavy metals and ra- dionuclides by incorporating these con- taminants into the matrix of a glassthe vitrified product. The glass is formed by the vitrification of the soil which contains the hazardous constituents. Depending upon the composition of the contaminated soil, the addition of inexpensive glass-forming agents may be required. The Vortec CMS produces a vitrified product which has long-term stability, reduces the teachabil- ity of the heavy metals (and radionuclides) below regulatory limits, and results in a volume reduction of the waste material. In the vitrification of contaminated soils that are hazardous by characteristic and do not contain radionuclides, the vitrified prod uct would no longer be classified as a hazardous waste. The Vortec CMS also completely oxidizes any organic compo- nents (hazardous or not) in the waste. The Vortec CMS has demonstrated a de- struction removal efficiency (ORE) greater than 99.99% for all organic compounds in the soil. The unique features of the CMS make it particularly suitable for the rapid and efficient heating of fine granular materials, and subsequent vitrification into a glass product. A process diagram of the Vortec CMS-based soil vitrification system is shown in Figure I. The basic components of the system include: the Vortec multifuel-capable CMS, consisting of a counter-rotating vortex combustor and a cyclone melter; an upstream storage and feeding sub- system; a separator/reservoir assembly; AWBERG LIBRARY U.S. ------- DATE DUE Fuel Oil or Water Wet Grinding Crusher Dryer/ Grinder Dry Soil Bin Transport Air Gla Agitator Tank Glass-Forming Additives Figure 1. Vortec's CMS-based contaminated soil vitrificatic -r" Stack ID Fan Recycled to CMS System Vitrified Product Storage The Library Store #47-0106 a cullet handling subsystem; a heat recoverysubsystem; a flue gas conditioning assembly; and an air pollution control subsystem. Except for the CMS and the separator/ reservoir, all other subsystems or assem- blies are commercially available or modi- fied versions of commercially available equipment. The basic CMS can be modified to ac- commodate the use of a variety of fuels, including pulverized coal, coal slurry fu- els, natural gas, oil, waste oils, and waste solvents. The CMS is also capable of us- ing any combination of these fuels. Natu- ral gas is customarily used in demonstration testing because of its con- venience. Complete combustion and in-flight sus- pension preheating of the contaminated soils, and any glass-forming additives, takes place in the combustor. The feed- stock ingredients are introduced into the combustor through an injector and are rapidly heated in the flame zone. Any carbon-based materials are rapidly volatil- ized and oxidized. The inert materials are heated to nominally 230OF to 280OF, depending on the characteristics of the soil, prior to entering the cyclone melter. Since combustion air is preheated to nomi- nally 100OF to 140OF, high local flame temperatures of more than 400OF can be achieved in the combustor. However, due to the rapid temperature quenching of the combustion products by the inert soil par- ticles and the staged combustion inherent in the CMS design, the NOx emissions have been demonstrated in pilot scale test- ing to be lower than DOE's boiler emis- sions standard of 0.6 Ibs NOx/MMBtu. NOx emissions lower than 2 Ibs NOx/ton glass have also been demonstrated. The preheated solid materials from the combustor enter the cyclone melter, where they are distributed to the chamber walls by the cyclone action of the combustion products, thus forming a molten layer of vitrified soil (glass). The glass and the combustion products exit the cyclone melter through a tangential exit channel and enter the separator/reservoir. The separator/reservoir separates the combus- tion products from the molten glass and provides additional residence time for the completion of glass-forming reactions. The glass exits the separator/reservoir through either a tap hole in the floor or an over- flow weir along a side wall. The combus- tion products exit through an exhaust port, which discharges into a conventional radiation-type recuperator for combustion air preheating. A flue gas conditioning assembly re- duces the temperature of the flue gas exiting the radiation recuperator to satisfy the temperature requirements of particu- late control devices. Commercially avail- able paniculate control devices are incor- porated into the design as dictated by local environmental regulations. A high ef- ficiency venturi scrubber can be used for particulate control in some applications. Wet or dry electrostatic precipitators (ESPs) or baghouses can be used to achieve higher levels of particulate emis- sions control. Additional air pollution con- trol, such as acid gas scrubbers, may be easily incorporated if required. Two different techniques for transport- ing the contaminated soil into the CMS have been investigated. In one feed sys- tem, the soil was pneumatically fed to the CMS as dry granular solids. However, many soils found at contaminated sites are not in this preferred (dry) form. There- fore, a second feed system was devel- oped to handle wet soils in the form of a slurry. The slurry feed system provides a means of mixing the wet contaminated soil and a liquid (water), and then deliver- ing and atomizing this slurry into the CMS. By processing wet soils in a slurry form, the preparation and blending of the wet soil and the glass-forming materials, as well as the introduction of the resulting mixture into the CMS, are simplified. The Vortec CMS process demonstrated its abil- ity to process both the dry and slurried feed materials, while forming a fully-reacted vitrified product. ------- Procedure Laboratory melts were conducted by Vortec on EPA's Synthetic Soil Matrix (SSM) to determine whether the addition of glass-forming agents is required to pro- duce a vitrified product that will consis- tently pass the Toxic Characteristic Leaching Procedure (TCLP). Table 1 pre- sents the composition of EPA's SSM and the resulting feedstock formulation used in Vortec's SITE testing. Vortec, in coop- eration with DuPont Chemicals, estab- lished the types and quantities of heavy metal compounds (shown later in Table 2) that were used to produce the contami- nated surrogate soil. Blending of the sur- rogate soil, limestone and the heavy metal compounds was performed just prior to the initiation of testing, thus minimizing the possibility of further contamination in the feedstock. The Vortec SITE program has con- ducted two tests at Vortec's nominal 15-20 tons per day pilot facility using surrogate soil spiked with heavy metal compounds. The first test employed the pneumatic feed system to process dry feedstock, while the second test used the slurry feed sys- tem to process an aqueous slurry contain- ing contaminated surrogate soil. Prior to the slurry feed test, an initial combustion stability test was successfully completed and demonstrated the ability of the com- bustor to accept the designated water flow rate of 400 pounds per hour. Additional combustion stability testing was performed using a slurry of 60% cullet (ground waste glass) and 40% water. Cullet was used as the sole constituent, rather than clean soil, to avoid contamination of the materials being used in concurrent testing. The sta- bility testing using the cullet/water slurry was also successful and verified the slurry system design parameters. Finally, a slurry containing 60% contaminated surrogate soil/limestone mixture and 40% water was used to perform the second of Vortec's contaminated soil SITE tests. Sampling and chemical analyses of the influent and effluent streams from both pilot scale con- taminated soil tests were performed by DuPont's Water Quality Laboratory, Cham- bers Works, NJ; and Geraghty and Miller, Inc., Pittsburgh, PA. Under other demon- stration programs, the feedstocks con- sisted of different SSMs, glass-forming additives, surrogate heavy metal com- pounds, organic compounds, and surro- gate radionuclides. Results and Discussion The tests conducted under the EPA SITE Program, as well as all tests per- formed under other demonstration pro- grams, have satisfied all technical and data quality objectives. Table 2 presents the metal concentrations in the feedstocks and the vitrified products produced during the Vortec SITE tests. Table 2 also in- cludes the results of the TCLP tests per- formed on the feedstocks and the vitrified products. Due to the high cadmium con- tent in the dry feedstock leachate and the high cadmium and lead content in the slurried feedstock leachate, both feed- stocks failed TCLP testing. Therefore, these feedstocks would be considered haz- ardous if classified as waste products. However, all of the glass produced during Vortec's testing passed TCLP testing, with the concentration of heavy metals in the leachates significantly reduced from those of the corresponding feedstocks. The el- evated chromium content in the vitrified products is due to the leaching of this element from the refractory present in the CMS during the SITE testing. Under other demonstration programs, the vitrified prod- uct was also evaluated by the ANSI/ ANS-16.1 test for the leachability of the surrogate radionuclide. No detectable quantities of the surro- gate radionuclide were found in any of the leachates collected during the ANSI/ ANS-16.1 test procedures. Table 3 presents system mass balances and emission data for the Vortec SITE tests. The production of carbon dioxide, Table 1. EPA's Synthetic Soil Matrix (SSM) and the Feedstock Compositions used during Vortec's SITE Program SSM Si02 A1203 K20 Na20 CaO Fe203 MgO Other oxides Composition wt% 57.43 11.74 1.55 0.84 20.26 2.32 5.29 0.57 Feedstock SSM Limestone Water Dry feed test wt% 80.0 20.0 0.0 Slurry feed test wt% 48.0 12.0 40.0 water vapor and the volatilization of other materials present in the feedstock resulted in the loss on ignition displayed in the table. Both uncontrolled and controlled stack particulate loadings are presented. During the SITE testing, a venturi scrub- ber was used as the pollution control de- vice in the CMS exhaust system. A wet ESP has since been placed in the sys- tem, and based on subsequent testing of a variety of materials, the anticipated emis- sions under the conditions that existed during the SITE tests would be lower than 0.003 gr/dscf. As the contaminated soils are processed within the CMS, the metal contaminants partition to either the carryover stream or the glass stream. The volatility of the met- als and their oxides is the primary factor controlling the partitioning of these con- taminants. The non-volatile metals, chro- mium, copper, and nickel, are found primarily in the vitrified product, while the semi-volatile metals, cadmium and lead, have a significantly higher percentage par- titioning to the carryover. Table 4 summa- rizes the partitioning of the metal contaminants among all the effluent streams from the Vortec CMS. Through the use of a high efficiency particulate removal system, such as an ESP (wet or dry) or a baghouse, the carryover can be effectively recycled back into the molten vitrified product within the CMS using a proprietary technology developed by Vortec. With the implementation of this particulate-carryover recycle technology, the Vortec CMS has the potential to be- come a zero waste discharge process. While the recycling of the particulate carry-over into the vitrified product was not performed during Vortec's SITE test- ing, other programs are currently demon- strating this carryover recycle feature. Conclusions and Recommendations Pilot scale vitrification testing has dem- onstrated that, with the addition of appro- priate glass-forming additives, surrogate soils representative of EPA Superfund and other hazardous waste sites can be effec- tively vitrified by the Vortec CMS. A high capture rate of the heavy metal contami- nants into the glass product is achievable with the glass consistently passing the TCLP testing requirements for the leach- ing of RCRA metals. The CMS has dem- onstrated DREs greater than 99.99% for organic compounds. In addition, the CMS has demonstrated the ability to effectively process surrogate soil in both wet and dry forms. With the implementation of a pro- prietary particulate recycling technology, the Vortec CMS-based contaminated soil vitrification system can become a zero waste discharge process. ------- Table 2. Summary of Contaminant Concentrations and TCLP Data for the Feedstocks used and the Vitrified Products Collected under Vortec's SITE 'rogram Metal Contaminants Concentration in Feedstock Feedstock TCLP Result Concentration in Glass Glass TCLP Result TCLP RCRA Limit Dry Feed Test PPMa PPM" PPMC PPM" PPM Arsenic Cadmium Chromium Copper Lead Nickel Zinc Slurry Feed Test (dry basis) Arsenic Cadmium Chromium** Copper Lead Nickel Zinc 273 187 867 395 2132 128 2395 PPM 112 116 546 235 1106 85 1300 0.97 1.55 0.02 0.06 0.10 1.73 8.71 PPM 1.1 2.7 0.04 3.7 7.5 3.5 26.3 259 75 1615 366 872 189 1615 PPM 275 27 1209 381 505 229 1506 0.00 0.00 0.04 0.04 0.00 0.00 0.12 PPM 0.0 0.008 0.19 0.15 0.13 0.15 0.83 5. 1.0 5.0 N/ 5.0 N/ N/ PPM 5.0 1. 5.0 N/A 5.0 N/A N/A a Average of 13 samples. b Average of 19 samples. c Average of 11 samples. d Average of 18 samples. N/A - not applicable. ** Excess levels of chromium leached from refractory into glass. Table 3. CMS Performance During Vortec's SITE Program Testing Mass Dry feed test Slurry feed test Feedstock Glass produced Loss on ignition Ibs/hr Ibs/hr Ibs/hr 947 721 195 450 212 235 Emissions data Uncontrolled particulate Controlled particulate using venturi scrubber Controlled particulate estimate using wet ESP % of Feedstock % of Feedstock grains/dscf 3.3 0.3 <0.003 0.06 0.01 <0.001 Table 4. Partitioning of Heavy Metals among the CMS Effluent Streams During Vortec's SITE Program Dry feed test Slurry feed test Metal Arsenic Cadmium Chromium Copper ead .'Jickel Zinc Glass 69.9 50.9 89.4 85.4 44.7 87.5 78.0 Scrubber 27.3 24.6 9.8 12.5 31.6 12.2 16.6 Stack gas 2.8 24.5 0.8 2.1 23.7 0.3 5.4 Glass 91.0 41.2 85.5 96.0 52.7 98.5 92.7 Scrubber 5.4 16.3 11.4 2.2 23.5 0.0 3.7 Stack gas 3.6 42.5 3.1 1.8 23.8 1.5 3.6 ------- James G. Hnat Is with Vortec Corporation, Collegeville, PA 19426. Ten Richardson is the EPA Project Officer (see below). Details of the completed SITE Emerging Technology project are given in an article published in Glass Production Technology International, 1994 pp. 103-106. The EPA Project Officer can be contacted at: Sustainable Technology Division National Risk Managemet Research Laboratory U.S. Environmental Protection Agency Cincinnati, OH 45268 United States Environmental Protection Agency Center for Environmental Research Information (G-72) Cincinnati, OH 45268 Official Business Penalty for Private Use $300 BULK RATE POSTAGE & FEES PAID EPA PERMIT No. G-35 EPA/540/S-97/501 ------- |