Bologa, A.

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Study of corona discharge characteristics of an ionizer for a compact electrostaticallyenhanced condensation system for pyrolysis gasesA.Bologa, H.-J. Gehrmann, K. Woletz, D. StapfInstitute for Technical Chemistry, Karlsruhe Institute of Technology,  76344, Eggenstein-Leopoldshafen, Germany Keywords: condensation system, gas composition, ionizer, corona discharge, current-voltage characteristicsPresenting author email: andrei.bologa@kit.eduIn the modern society, the increase amount of plasticwastes has a negative impact on the environment. Thepyrolysis technology is an effective way to upgradeplastic wastes.The current study is focused on the developmentof a compact electrostatically enhanced condensationsystem for pyrolysis gases. Instead of separatelymaintained coolers and electrostatic precipitators it issupposed to design a compact system, which usescondensers equipped with corona discharge ionizers.Such design allows the lowing of the costs of thecondensation system and the reduction of size andsystem complexity. The discussed results are focused onthe optimization of design and operation parameters ofthe non-thermal plasma (NTP) ionizer for a compactcondensation system. The NTP allows gas moleculesactivation in an energy-efficient way, as the gas doesnot have to be heated as a whole. Non-thermal plasmarequires no pre-heating, long stabilization and cool-down times. NTP can be quickly turned on and off.The developed pilot corona discharge ionizerincluded a tube grounded electrode, which simulatedthe condenser inner tube. A high voltage (HV) rod wasaxially installed inside the grounded tube, beingequipped with star-form HV electrodes used forgeneration of corona discharge. The current-voltagecharacteristics (CVC) of the corona discharge weremeasured in air, pure gases (He, N2, CO2) and gasmixtures. Study was carried out for positive andnegative polarity of applied voltage. The “direct” and“indirect” CVCs were measured assuming increase anddecrease of applied voltage at constant operationconditions. Taking into consideration, that the ionizershould be operated in hot pyrolysis gases, the testswere carried out for variable temperatures of thegrounded tube electrode, which was electrically heated.The test facility allowed the experiments to be carriedout at the temperature of the ionizer up to 650°C andvariable gas pressure inside the facility. The Fourier-transform infrared spectrometer was used to controlgas composition inside the test facility.The results of the tests show, that during thesame time interval, the negative polarity corona allowshigher discharge energy densities, than the positive one.The increase of air pressure results in decrease ofcorona current at constant applied voltage. The gascomposition plays a decisive role for corona dischargecharacteristics. It was defined, that in the gas mixture N2is “responsible” for hysteresis and He “moves” thehysteresis curves to higher gas pressures. The use ofhysteresis allows the optimization of ionizer operationparameters taking into consideration the variability ofapplied voltage, corona current and powerconsumption. For the CVCs, measured in the gasmixture CO2:He:N2 (Figure 1), at constant appliedvoltage, the current for “indirect CVC” was higher thanfor “direct” CVC. At constant applied voltage, at thebeginning, corona discharge power consumptionincreases and then exponentially decreases (Figure 2).After 1 h, the corona discharge power consumptionwas 4 times lower, than previously measuredmaximum value, what means the change of gascomposition inside the facility.Figure 1. Negative polarity corona discharge CVC,CO2 19,0%: He 10,3%: N2 70,7%Figure 2. Time dependence of corona discharge powerconsumption, CO2 68,7%: He 16,4%: N2 14,9%The results of tests are used for the design of the ionizerof the compact electrostatically enhanced condensationsystem for pyrolysis gases.11th INTERNATIONAL AEROSOL CONFERENCE (IAC) | 4-9 September 2022 | 1364VIRTUAL POSTER SESSION | AT-eP2 Electrical effects | AT-eP2_002

Study of corona discharge characteristics of an ionizer for a compact electrostatically enhanced condensation system for pyrolysis gases

https://publikationen.bibliothek.kit.edu/1000151202/149420164

Study of corona discharge characteristics of an ionizer for a compact electrostatically enhanced condensation system for pyrolysis gases

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