Study On The Mechanism Of Simultaneous Removal Of Mercury And Trichlorobenzne By Pulsed Corona Plasma

Incineration is a waste treatment technology which is widely used in countries around the world.The waste incineration process emits some pollutants.In particular,medical waste incineration is highly prone to produce mercury and dioxins which have highly toxicity and harmfulness and so on.It is uaually used a combined flue gas purification technology "Rotary spray type semi-dry washing + deacidification absorption tower + activated carbon injection + bag filter " to remove mercury and dioxins in medical waste incineration flue gas.However,this technology requires a large amount of activated carbon.In addition,the problem of treatment and regeneration after deactivation of activated carbon increases the cost of treatment,which makes the company overwhelmed.Some scholars are also committed to developing new technologies to remove mercury and dioxins,such as catalytic oxidation,electron beam technology,and plasma technology.Among them,the low temperature plasma treatment has the advantages of high efficiency,small footprint and low processing cost per unit volume.It is a cost-effective treatment method.Therefore,in this paper low-temperature plasma technology is used to simultaneouslly remove mercury and 1,2,4-trichlorobenzene,a simulated for dioxins.And the removal mechanism of the technology also had been discussed in order to provide a theoretical basis for industrial applications.In this paper,a pulsed corona discharge low temperature plasma experimental platform was built.1,2,4-trichlorobenzene(TCB),one of the main precursors of dioxins,was regarded as a dioxin mimetic.TCB and Hg0 were used as research objects.The pulsed corona discharge low temperature plasma was used to remove Hg0,TCB and"TCB+Hg0"flue gas respectively.The parameters in the process such as voltage,frequency,pulse width and rising edge parameters were investigated.The effects of removal performance were also systematically studied.The results and conclusions obtained are as follows:1.When the input frequency is 200 Hz,the pulse width is 100 ns,and the rising/falling edge is 100 ns,the adjustment pulse voltage varies from 12 kV to 15.3 kV.As the voltage increases,the Hg0 oxidation rate increases,and the voltage is greater than 13.3 kV,The Hg0 oxidation efficiency is basically stable at 90%-94%;When the input frequency is 500 Hz,the pulse width is 100 ns,and the rising/falling edge is 100 ns,the removal efficiency of trichlorobenzene increases with voltage from 12 kV to 16 kV.When the pulse voltage is 16 kV,the frequency is 300 Hz,and the pulse width is 100 ns,risiing/falling edge of 100 ns,the removal efficiency of TCB is up to about 70%.2.When the pulse voltage is 12.7 kV,the pulse width is 50 ns,and the rising/falling edge is 100 ns,the adjustment frequency is 100?800 Hz.The oxidation efficiency of Hg0 increases with the frequency increases.When the frequency is 400 Hz,the frequency continues to increase,the effect is maintained at 87?90%.Therefore there is an optimum frequency;When the pulse voltage is 14 kV and 16 kV,the pulse width is 100 ns,and the rising/falling edge is 100 ns,the regulation frequency is 100?800 Hz.The regular of TCB removal is similar to Hg0oxidation.After the frequency>300 Hz,and the removal effect is stable at 75%?78%with the frequency is increased continuously.3.When the pulse width and rising edge are within a certain range(100-600 ns),the pulse width and rising edge have little effect on the treatment effect of Hg0 and trichlorobenzene.However,when the pulse width is large(0?900000 ns),the oxidation rate of Hg0 is greatly improved with the pulse width increasing exponentially,which can be increased from 60%to 98%.4.In the process of removing Hg0by pulse corona plasma,the atmosphere has a great influence on the removal effect.This paper discusses the effects of NO,HCl,O2,SO2,HaO(g)and other components on the removal efficiency of Hgo0in flue gas.With the increase of O2 in the system,the oxidation rate of Hg0increases,and when the content reaches 5%,the oxidation rate of Hg0 is 92.31%.The oxidation effect is maintained at 92?95%with the O2 is increased continuously;The addition of H2O(g)and HCl promoted the oxidation of mercury.The water content was 4%?10%.The Hg0 oxidation decreased with the increase of H20(g);Both NO and SO2 have an inhibitory effect on Hg0 oxidation,and the reaction mechanism is also different.5.Dechlorination of trichlorobenzene by pulsed corona low temperature plasma is mainly achieved by breaking bonds by huge energy,which leads to the dechlorination and dehydrogenation of benzene ring,followed by the oxidation of hydroxyl radicals and other free radicals,and ultimately leads to complete degradation of trichlorobenzene.6.When Hg0 and TCB are synergistically removed,the highest mercuryoxidation effect is about 60%,and the trichlorobenzene removal effect is about 70%at 17 kV.In the removal of"TCB+Hg0"flue gas by pulse corona plasma,t he degradation rate of TCB was not changed much compared with the single treatment,but it had a great change on the oxidation rate of Hg0.The Hg0 oxidation mechanism has little effect on the change of TCB elimination characteristics.At the same time,through the process of co-control of TCB and Hg0 by low temperature plasma and the product analysis of the simultaneous process,it is considered that the energy competition between the two is the main factor in the synergistic treatment,and the free radical competition has little effect on the synergistic treatment.The reaction of the elements in the system is complicated,and various reactions are mutually restricted.