Behaviour of electric arc in plasma chemical reactor during hazardous waste treatment

BACKGROUND: Research was performed to reveal the main peculiarities of an operating electric arc in a plasma chemical reactor (PChR) for hazardous waste processing. The experimental study was performed in a model of PChR using thermal plasma as a heat source. Investigations described are conducted to study the voltage–current characteristics (VCC) and heat transfer between an electric arc and a flat anode during the free arc operation in an ambient nitrogen (N₂) atmosphere. RESULTS: Plasma torch (PT) parameters varied in the range of I = 100–600 A, U = 50–450 V, x = 0–400 mm, G = 2–4 g s⁻¹ at atmospheric pressure using N₂ as plasma‐forming gas. It was found that the power value of the laminar arc increased with increasing arc current and length. With increasing arc length, its initial part started to operate in a turbulent regime. It was observed that the region of laminar regime appeared in the area where arc power was inversely proportional to arc current. The dependence of the heat flux transferred by the electrons to the anode on arc current was determined. The distribution of convective heat flux density over the anode heating spot was analyzed and generalized. The experimental data on convective heat transfer in the anode (mean and critical point) were discussed. CONCLUSION: This confirmed that plasma technology has several advantages over conventional incineration including higher temperatures, independence of heat source from the waste being destroyed or additional fuel, and shorter exposure time of hazards in the high‐temperature area. © 2019 Society of Chemical Industry