12-08-2014, 10:35 AM
Water cleaning in a heterogeneous pulsed corona reactor
Water cleaning.doc (Size: 1.99 MB / Downloads: 51)
Abstract
This article discusses a new water treatment system using electrical discharges. The method is based on corona discharges in air-water reactor. The discharges are created above the water and is an effective source of ozone but also creates lots of other oxidizers, such as hydroxyradicals and UV photons. This so called CAW Reactor (Corona Above the Water) is promising to be an effective and cheap technique for water treatment.
Introduction
Although the Earth is covered in 75% by water, most of it is useless for people. Resources of potable water are shrinking in hectic pace. With the growing commitment to improve water quality, there is a need for new processes for environmental cleanup. Discovery of those processes is necessary for both existing and ongoing wastes. Studies of plasma processing of waste have shown good looking possibilities for more effective treatment and for lower treatment cost.
Plasma created in corona discharges are used nowadays for many purposes.[1,2] Its oldest applications is probably ozone generation. Water and gas cleaning experiments started in 1980’s and are becoming the biggest part of using plasma in environmental objectives. Gas and water cleaning using corona discharges makes use of the radicals created during discharges and are similar in principle to ozone generation. Existing applications concerns removal of NOx, SO2 and various VOC’s from flue gases. Water cleaning is also an option but is reported less frequent [3]. The main reason are difficulties in efficient transport radicals to treated water and relatively big cost of large scale proceses.
Recently a European project on corona discharge gas and water cleaning, called ytriD, has started.[4] Within this project the two different techniques for water cleaning will be studied. Aerosol reactor build by Soreq Israel will be compared with CAW reactor from TU/e Eindhoven. Optimisation and upscaling the system for water cleaning by pulsed corona discharges will be studied. This implies a parametric study of a reactor module and testing a large reactor system with a continuous water flow.
: Electric circuit
Repetitive pulsed power generators are the enabling technology for successful industrial applications of pulsed corona discharges. Prototypes of efficient nanosecond pulse generators are available and have been demonstrated in laboratory and in field trials [2]. These generators employ a heavy-duty spark-gap switch combined with a transmission-line-transformer. Lifetime and reliability are adequate for industrial demonstrations. Treatment of gas flows up to 100.000 Nm3/hr is possible. We expect to reach an average corona output power of 100 kW within the next year [
. Conclusions
Performed tests confirm the efficiency of CAW technique.
This technique is suitable for treatment of different kinds of water wastes. It can be used for treatment of phenol and PEG contaminated water and also for cleaning chemical wastes from different types of industries.
First measurements using LIF spectroscopy and deuterium light absorbtion are suitable for in-situ detection of model compounds decomposition and ozone creation.
After the improvements in reactor conditions, such as residence time of treated wastes, electrode configurations, additives, the increase of reactor efficiency is expected