In this study, a pilot-scale Regenerative Thermal Oxidizer (RTO) was used to test its performance for volatile organic compound (VOC) destruction and degree of thermal energy conservation. The RTO is electrically heated and contains two 0.5 m ¡Ñ 0.5 m ¡Ñ 2.0 m (L ¡Ñ W ¡Ñ H) columns both packed with gravel particles of 1.0 cm in diameter to a height of 1.4 m. The bed has a void fraction of 0.415. The purpose of this study is to establish the influencing operating conditions and to improve the technique for further applications. Experiments include two phases: (1) energy conservation test with no VOC in the influent air stream , and (2) VOC destruction test with influent air streams containing one of the three VOCs: isopropyl alcohol, acetone, and xylene. Phase 1 experiments were conducted in the maximum gravel temperatures (Tmax) of 402-704 oC, superficial gas velocities (Ug, evaluated at ambient temperatures of 25-30 oC) of 0.15-0.50 m/s, and bed shift times (ts) of 0.5-2.0 min. Results indicate that the temperature raise (

In this study, two regenerative thermal oxidizers (RTO) were used to test the thermal destruction, thermal recovery efficiency and the gas pressure drop over the beds characteristics when burning, respectively, airborne chlorine- and nitrogen-containing volatile organic compounds (VOCs). First, an electrically-heated RTO containing two 0.5 m ¡Ñ 0.5 m ¡Ñ 2.0 m (L ¡Ñ W ¡Ñ H) beds, both packed with gravel particles with an average diameter of around 0.0116 m and a height of up to 1.48 m with a void fraction of 0.41 in the packed section was used to study the destruction characteristics of chlorine-containing VOCs (trichloroethane, TCE and dichloromethane, DCM). With a valve switch time (ts) of 1.5 min, preset maximum destruction temperatures (TS) of 500-800 oC and superficial gas velocity (Ug) of 0.17-0.33 m/s (evaluated at an influent air temperature of around 27 ¢J), tests on the thermal recovery efficiency (TRE) and the pressure drop for the air stream without VOC in the influent air stream have been performed. With a ts of 1.5 min, Ts of 500-800 oC and Ug of 0.17-0.24 m/s (evaluated at an influent air temperature of around 27 ¢J), tests on the degree thermal destruction of VOCs with influent air streams containing one of the two VOCs: trichloroethylene (TCE) and dichloromethane (DCM) have been done. Second, an electrically-heated RTO containing two 0.152 m ¡Ñ 0.14 m ¡Ñ 1.0 m (L ¡Ñ W ¡Ñ H) beds, both packed with gravel particles with an average diameter of around 0.0111 m and a height of up to 1.0 m with a void fraction of 0.42 in the packed section was used to study the destruction and NOx formation characteristics of DMF (N, N-dimethylformamide). With a ts of 1.5 min, Ts of 750-850 ¢Jand Ug of 0.39-0.78 m/s (evaluated at an influent air temperature of around 30 ¢J), TRE and the pressure drop for the air stream without VOC in the influent air stream have been tested. With a ts of 1.5 min, a Ug of 0.39 m/s (evaluated at an influent air temperature of around 30 ¢J), and Ts of 750-950 ¢J and, thermal destruction efficiencies and nitrogen oxides (NOx) formation characteristics in burning air streams containing either DMF or DMF mixed with methyl ethyl ketone (MEK) were performed. Results demonstrate that: (1) a RTO is suitable for destruction of low concentrations (<1,000 ppm as methane) of airborne highly chlorinated VOCs such as TCE and DCM and the destructed products contain no chlorine and only trace of COCl2 (< 1% of the influent VOC); (2) for TS = 800 oC and Ug = 0.17-0.24 m/s, complete oxidation products of TCE and DCM are HCl, CO2, and H2O, and the main intermediates are CO and COCl2; (3) with ts of 1.5 min, a Ug of 0.39 m/s (evaluated at an influent air temperature of around 30 oC) and TS of 750-950 ¢J, no NOx was present in the effluent gas from the RTO when it was loaded with DMF-free air; (4) when only DMF was present in the influent air, the average destruction efficiencies exceeded 96%, and increased with the influent DMF concentration from 300 to 750 mg/Nm3. The ¡§NOx-N formation/DMF-N destruction¡¨ mass ratios were in the range 0.76-1.05, and decreased as the influent DMF concentration increased within the experimental range; (5) when both DMF and MEK were present in the influent gas, the NOx formation ratio was almost the same and the DMF destruction efficiency increased with the influent MEK/DMF ratio from 150/300 to 4500/300 (mg/mg) and in the preset temperature range. The NOx formation ratios were in the range 0.75-0.96; (6) the TRE decreased as Ug increased but was invariant with Ts; and (7) the Ergun equation was found to suffice in the estimation of the pressure drop when the gas flowed over the packing beds.

Performance studies on the treatment of VOCs in air streams by a pilot-scale regenerative catalytic oxidizer (RCO) and a full-scale regenerative thermal oxidizer (RTO) were conducted. The pilot-scale RCO was constructed with two 20-cm x 200-cm (inside diameter x packing height) regenerative beds packed with gravel (average particle size = 1.25 cm) used as the thermal regenerative solid material. Experimental results indicate that destruction efficiencies of 97 and 90%, respectively, were obtained for methyl ethyl ketone and toluene at a superficial gas velocity of 0.372 m/s (evaluated at 25¢J) and a maximum bed temperature of 400¢J. It was estimated that an electrical thermal energy of approximately 84 kWh was required for treating 1,000 m3 of the waste air stream by the RCO. The full-scale RTO was constructed with two regenerative beds of 100-cm square x 200-cm height packed with the gravel used in the RCO. A paint solvent containing methyl ethyl ketone, ethyl benzene, xylenes, and ethyl acetate was used for the target VOCs. Experimental results indicate that, at a superficial gas velocity of 0.372 m/s (evaluated at 25¢J), VOC destruction efficiencies of 84, 92, 95 and 98% were obtained for the beds at temperature ranges of 200-300, 300-500, 400-700, and 500-700¢J. These conditions corresponded to empty gas retention times of 1.07, 0.85, 0.41, and 0.39s, respectively, for the cited temperature ranges. Finally, it was estimated that electrical watts of approximately 0.10, 0.45, 1.78, 2.43 kWh were required for treating 1,000 m3 of the waste air stream, respectively, at bed temperature ranges of 200-300, 300-500, 400-700, and 500-700¢J.