United States Environmental Protection Agency Air and Energy Engineering Research Laboratory Research Triangle Park NC 27711 Research and Development EPA/600/S2-85/041 July 1985 v>EPA Project Summary Parametric Evaluation of VOC/HAP Destruction Via Catalytic Incineration M. A. Palazzolo, J. I. Steinmetz, D. L. Lewis, and J. F. Beltz A pilot-scale catalytic incineration unit/solvent generation system was used to investigate the effectiveness of catalytic incineration as a way to de- stroy volatile organic compounds (VOCs) and hazardous/toxic air pollu- tants (HAPs). The objectives of the study were to: (1) investigate the effects of operating and design varia- bles on the destruction efficiency of VOC/HAP mixtures, and (2) evaluate destruction efficiencies for specific compounds in different chemical classes. The study results verified that the following factors affect catalyst performance: inlet temperature, space velocity, superficial gas velocity, cata- lyst geometry, compound type, com- pound inlet concentration, and mixture composition. Tests showed that destruction efficiencies exceeding 98 percent were possible (given suffi- ciently high inlet temperatures/low space velocities) for the following com- pounds/compound classes: alcohols, acetates, ketones, cellosolves/diox- ane. aldehydes, aromatics, and ethyl- ene/ethylene oxide. Destruction efficiencies of at least 97 percent were achieved for acrylonitrile and cresol. Chlorinated hydrocarbons were not effectively destroyed with the type of catalyst used in this study. This Project Summary was devel- oped by EPA's Air and Energy Engi- neering Research Laboratory. Research Triangle Park, NC, to announce key findings of the research project that is fully documented in a separate report of the same title (see Project Report order- ing information at back). Introduction A test program has been completed to investigate on an experimental scale the effectiveness of catalytic incineration as a way to destroy volatile organic com- pounds (VOCs) and hazardous/toxic air pollutants (HAPs). A pilot-scale catalytic incineration unit and a solvent vapor gen- eration system were used for the testing. Prior to the completion of this study, limited data were publicly available on the performance of catalytic incinerators for a large number of compounds over a wide range of operating conditions. Thus, objectives of this study were to (1) inves- tigate the effects of key incinerator oper- ating and design parameters on mixture destruction efficiency, and (2) measure component specific destruction efficien- cies for compounds in different chemical classes. Test System The effects of key operating and design parameters on the destruction efficiency of a skid-mounted catalytic incinerator were investigated using a solvent vapor generation system. The vapor generation system, consisting of a pump, dry gas meter, tube furnace, glass mixing chamber, and motor-driven syringes, was used to produce a spiked air stream with the desired concentrations of organic vapors. The skid-mounted unit, leased from Englehard Industries, was equipped with a blower, preheater, mass flowmeter, catalytic reactor, and temper- ature controls. The design gas flowrate ------- Exhaust r Incinerator Catalyst Electric Heater ~] Air In Rotary Vane Vent Dry Gas Tube Furnace Mixing Chamber Pump Activated Meter Carbon Figure 1. Incinerator and solvent vapor generation system. for the catalytic test unit was 275 cfh (4.6 scfm).* Figure 1 is a schematic of the test system. Experimental Design In designing the experimental pro- gram, conditions were selected to (1) pro- vide data on a large number of solvent types, (2) give an indication of the operat- ing conditions required for destruction efficiencies near 98 or 99 percent, and (3) represent operating conditions typically used in industrial applications. The major operating parameters that were varied during the testing included: catalyst inlet temperature, compound concentration, space velocity, compound type, catalyst geometry, and catalyst volume. Much of the testing was conducted to character- ize compound destruction across the pre- heater and catalyst bed as a "system." However, heater and catalyst destruction efficiencies were also measured separ- ately at a number of conditions. Most of the test work involved the mea- surement of destruction efficiencies for low concentrations of VOC/HAP mix- tures in air. A short series of tests was also conducted with a low oxygen gas stream, intended to simulate the off-gas from an ethylene oxide production pro- cess. Components of the VOC/HAP mix- tures and compositions of the simulated ethylene oxide off-gases are shown in Tables 1 and 2, respectively. For the VOC/HAP mixtures, total system inlet concentrations were typically main- tained near 1200 ppm carbon (by volume). Mixtures were generally pre- pared to provide equal amounts of each component on a per carbon or ppm car- *1 ft3 = 28.3 L. bon (by volume) basis. At all test condi- tions, total mixture destruction efficiencies were measured with EPA Method 25A, and component specific efficiencies were determined by EPA Method 18. The ranges of incinerator operating conditions tested during this study are summarized in Table 3. As shown in Table 3, space velocities, based on total catalyst volume and standard gas flow rates, were varied from 15,000 to 80,000 hr° with catalyst inlet temperatures ranging from 500 to 800 F.* Two volumes of two different catalyst types were tested. Both catalyst types had the same precious metals formulation. How- ever, the ceramic honeycomb substrates had different cell sizes and, hence, differ- ent catalyst surface areas. *5/9(°F-32) = Table 1. Lists of Components in Multi- component VOC/HAP Mixtures Mixture 1 - Control Mixture Isopropanol Methyl ethyl ketone Ethyl acetate Benzene n-Hexane Mixture 1A - Hexane Substitution Isopropanol Methyl ethyl ketone Ethyl acetate Benzene Cyclohexane Mixture IB - Hexane Substitution Isopropanol Methyl ethyl ketone Ethyl acetate Benzene Iso-octane Mixture 1C - Hexane Substitution Isopropanol Methyl ethyl ketone Ethyl acetate Benzene n-Octane Mixture 2 - Industrial Mixture Methyl ethyl ketone Toluene Mixture 3 - Alcohols/Acetates Methanol Ethanol Isopropanol n-Butanol Ethyl acetate n-Propyl acetate Isobutyl acetate Mixture 4 - Ketones/Miscellaneous Oxygenated Compounds Acetone Methyl ethyl ketone Methyl isobutyl ketone Cyclohexane Ethyl cellosolve Butyl cellosolve Dioxane Mixture 5 - Aldehydes Propionaldehyde Isobutyl aldehyde Isovaleraldehyde n-Butyl aldehyde n-Valeraldehyde Mixture 6 - Alkanes/Aromatics n-Hexane n-Octane n-Decane Benzene Toluene m-Xylene Isopropyl benzene Mixture 7 - Non-Chlorinated HAPs m-Cresol Acrylonitrile Mixture 8 - Chlorinated HAPs Methylene chloride Carbon tetrachloride Ethylene dichloride Trichloroethylene Tetrachloroethylene 1,1 -Dichloroethane 1,1,2-Trichloroethane Test Results Results from the pilot-scale catalytic incineration testing identified and/or verified the effects of a number of operat- ing and design parameters on catalytic incinerator performance. Parameters found to have the greatest effect on destruction included catalyst inlet temperature, space velocity, compound type, catalyst geometry, and catalyst volume. Other parameters generally showing a lesser effect included inlet concentration and mixture composition. ------- Table 2. Components and Concentrations in the Ethylene Oxide Off-Gas Test Parameter Conditions or Values Tested Stream Composition 1 (percent by volume) Stream Composition II (percent by volume) Ethylene Ethane Ethylene oxide Nitrogen Carbon dioxide Oxygen Ethylene Ethane Ethylene oxide Nitrogen Carbon dioxide Oxygen 0.43% 0.09% 0.01% 86.0% 12.0% 1.5% 0.64% 0.09% 0.01% 85.3% 11.5% 2.5% Table 3. Ranges of Operating Conditions Tested Catalyst Geometry/ Volume" A/0.006 ft3 B/ 0.006 ft3 A/0.012 ft3 A/0.012 ft* B/ 0.01 2 ft3 Mixture(s) Tested 1 through 8 plus pure compounds11 1,6 1,2,4,6 Ethylene Oxide Ethylene Oxide Range of Space Velocity hr~' 20,000 to 80,000 30,000 and 50,000 15,000 to 50,000 30,000 and 50,000 30,000 and 50,000 Inlet Concentrations ppmCc 1.200/6.000 10,000 1,200 1.200 /,//d /" Catalyst Inlet Temperatures °F 500 to 800 600 to 800 600 to 800 500 and 600 500 and 600 Catalyst A had a catalyst surface area of 270 ft2/ft31 and Catalyst B had an area of 660 ft2/ft3. Sixteen single components tested with this catalyst. ppmC = parts per million by volume as carbon. Compositions shown in Table 2. ft2 = 0.0929m2 The test results provided data on: (1) potential partial oxidation products, (2) carbon monoxide emissions, and (3) cata- lyst temperature rise relationships. The capability of catalytic incineration to achieve destruction efficiencies in the 98 to 99 percent range was also verified for compounds in seven different chemical classes. Multi-component mixture effects on compound specific destruction efficien- cies were evaluated by comparing pure compound destruction efficiencies with efficiencies of these compounds as com- ponents of the VOC test mixtures. In addi- tion, destruction efficiencies for compounds tested in more than one mix- ture were compared. A mixture effect was found on pure compound destruc- tion efficiencies for 6 of 13 compounds. In most cases, these compounds showed higher destruction efficiencies as mix- ture components than as pure com- pounds. However, two linear alkanes, n-hexane and n-octane, showed decreased destruction as components of one mixture. An effect of mixture composition was also found for two of five compounds tested in more than one mixture. This effect appeared to be greatest at lower catalyst inlet temperatures. The effects of catalyst inlet tempera- ture and space velocity on system de- struction efficiency are shown for Mixture 1 in Figure 2. The trends shown in Figure 2 of increasing destruction with increasing inlet temperature and decreasing space velocity are typical of those observed for the other mixtures. System destruction efficiencies for Mix- ture 3 (alcohols and acetates) showed a particularly strong dependence on cata- lyst inlet temperature at a space velocity- of 50,000 hr"1. In addition, system destruction efficiencies for Mixtures 3 and 6 (alkanes and aromatics) showed a strong dependence on space velocity. Test Mixture 5, which consisted of dif- ferent aldehyde compounds, generally showed the highest system destruction efficiencies of the mixtures tested. Mix- ture 8, which contained seven chlori- nated hydrocarbons, showed by far the lowest destruction. Except for Mixture 8, all mixtures showed system destruction efficiencies ranging from 85 to 99 per- cent for the conditions tested in this study. Mixture 8 destruction efficiencies ranged from 0.0 to 80 percent. The preheater on the test unit con- sisted of a pipe or tube wrapped with a high temperature electrical resistance heater element. At low space velocities and/or high inlet temperatures with the small catalyst volumes, heater (thermal) destruction efficiencies were as high as 80 to 90 percent for some mixtures. With the larger catalyst volume, gas flow rates through the system were doubled at a given space velocity and heater destruc- tion decreased to between 10and 76 per- cent. The degree to which the heater destruction efficiencies observed on the test unit may represent destruction in the natural gas burner zones of full-scale incinerators is not known. However, burner designs that provide direct con- tact of the waste gas with the flame are expected to provide an opportunity for a significant amount of compound destruction. At a given space velocity, catalyst destruction efficiencies for the mixtures were found to be higher for the larger catalyst volume. The higher destruction for the large volume results from a higher gas velocity through the catalyst cells, which apparently improved mass transfer and increased the overall reac- tion rate. With the larger catalyst volume, catalyst destruction efficiencies of 98 percent or higher were obtained for Mix- tures 1, 3, 4, and 6. The effect of catalyst inlet temperature and space velocity on component destruction efficiencies varied consider- ably for the different compounds. Com- pounds of the same chemical class often showed similar destruction efficiencies and trends with inlet temperature. Other results from the catalytic incin- eration testing included: - Tests with the chlorinated hydrocar- bon mixture were found to have par- tially deactivated the catalyst. ------- - Higher destruction efficiencies were observed for the catalyst type with the higher surface area (catalyst B), as expected. - Inlet concentration was found to slightly affect destruction, with higher efficiencies at higher concentrations. - Tests with the simulated ethylene oxide off-gas showed VOC destruc- tion efficiencies in excess of 99 per- cent at all conditions tested. - The pilot-scale efficiencies for Mix- ture 2 agreed well with those for a full-scale unit treating this same mix- ture in exhaust gas from a foil coil coating line. - Mass spectroscopy analysis identi- fied partial oxidation products from the catalytic combustion test unit. - Carbon monoxide emissions from catalytic combustion were found to be less than 5 ppmv for most test conditions. - Catalyst bed temperature rise was found to be directly related to the mass of solvent destroyed in the cata- lyst bed. - Method 25A and Method 18 mixture destruction efficiencies were in very good agreement, with Method 25A efficiencies being 2.4 percent lower on average for the entire test effort. Conclusions Results from this study identified or verified that the following factors affect the performance of catalytic incinerators: - catalyst inlet temperature; - space velocity; - superficial gas velocity (at the catalyst inlet); - catalyst geometry; - compound type; - inlet VOC concentration; and - mixture composition. In addition, the testing verified that destruction efficiencies in the 98 to 99 percent range are achievable with cata- lytic incineration for the following com- pounds or classes at sufficiently low space velocities and/or high enough catalyst inlet temperatures: - alcohols; - acetates; - ketones; - cellosolve compounds/dioxane; - aldehydes; - aromatics; and - ethylene/ethylene oxide. Destruction efficiencies of at least 97 percent are also achievable for acryloni- trile and cresol, while chlorinated hydro- carbons appear unsuitable for control 700 _ •a 90 80 CO 70 / L © O 80.000 hr'1 A 50,000 hr'' [•] 30,000 hr~1 (•} 20,000 /ir'1 Hi Shaded - Method 25A I I Open-Method 18 Ht 500 600 700 Catalyst Inlet Temperature, °F 800 900 Figure 2. Mixture 1 system destruction efficiency vs. inlet temperature for small volume catalyst A. with the type of catalyst tested in this study. Other catalyst formulations might be more favorable for destroying chlori- nated hydrocarbons. M. A. Palazzolo, J. I. Steinmetz, D. L. Lewis, and J. F. Beltz are with Radian Corporation, Research Triangle Park, NC 27709. Bruce A. Tichenor is the EPA Project Officer (see below). The complete report, entitled "Parametric Evaluation of VOC/HAP Destruction Via Catalytic Incineration," (Order No. PB 85-191 187/AS; Cost: $25.00, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, V'A 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Air and Energy Engineering Research Laboratory U.S. Environmental Protection Agency Research Triangle Park, NC 27711 U. S. GOVERNMENT PRINTING OFFICE: 1985/559-111/20613 ------- United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 BULK RATE POSTAGE & FEES PAI EPA PERMIT No. G-35 Official Business Penalty for Private Use $300 EPA/600/S2-85/041 ------- |