Ethylene treatment using nanosecond pulsed discharge

Abstract

Ethylene, a gas released from fruits and vegetables, has an effect to hasten ripening. Modern shipping has fruits and vegetables of various types transported together by container ship; however, the amount of ethylene released and the sensitivity of various produce toward ethylene vary. As such, if products with high ethylene release such as apples are mixed with those with high ethylene sensitivity such as persimmons, the latter will ripen excessively. Non-thermal plasmas (NTP) such as dielectric barrier discharges (DBD) and corona discharges have been investigated as a way to decompose ethylene. Nanosecond (ns) pulsed discharge, a type of NTP, is known to generate O3, treat exhaust gases and decompose VOCs with higher energy efficiency. However, many issues still remain prior to industrial implementation, including increasing energy efficiency for the removal of formic acid (HCOOH), CO, and O3 resulting as byproducts; there are also decomposition limitations in areas of low ethylene concentration. Overcoming these limitations is the purpose of this work. The output voltage of our ns pulse generator was 30 kV–50 kV in amplitude, 10 pulse/s–100 pulse/s in repetition rate, and 5 ns in pulse width. 100 ppm ethylene diluted with dried air was employed as gas simulating that of a transportation container. The gas mixture was fed into the coaxial cylinder type reactor for evaluation of decomposition efficiency. Ethylene concentration decreased to less than 0.1 ppm after ns pulsed discharge treatment at 30 J/L in input energy density. O3, CO, NO, HCOOH, HNO3 were generated as byproducts; byproduct concentrations were measured.