Experimental Study On The Effect Of Microwave Discharge On The Regeneration Performance Of Desulfurization And Denitrification Activated Coke

Microwave heating is the process in which the polar molecules inside the absorbing object collide with each other and the electromagnetic energy is converted into thermal energy.Microwave not only promotes the chemical reaction by thermal effect,but also has non-thermal effect induction and catalytic reaction,which is widely used in flue gas desulfurization and denitrification.The activated coke has a small specific surface area,but has high mechanical strength,good anti-wear performance,can be recycled,and has stable physical and chemical properties.It is a high-quality material for joint removal of various pollutants.Microwaves act on carbonaceous materials such as activated charcoal?carbon?and coal char to generate electricity,and discharge can generate low-temperature plasma to reduce the activation energy of chemical reactions and promote chemical reactions.The microwave-induced desulfurization and denitrification activated coke discharge cycle regeneration is carried out in a microwave reactor.The discharge intensity is detected by a voltmeter.The microwave power and the regeneration temperature?denitration temperature?are changed by the temperature control mode and the controlled power mode to study the discharge intensity and the product.The microstructure of activated coke before and after removal of contaminants was analyzed by BET and FT-IR analysis,and the effects of microwave discharge on the regeneration products of desulfurization and denitrification activated coke and the recycling performance were further analyzed.The main conclusions are as follows:?1?The higher the power,the stronger the alternating electric field,the higher the density of the energetic electrons at the activated coke tip,and producing low temperature plasma,the stronger the microwave discharge and the faster the temperature rise.Microwave-induced activated coke discharge accelerates the cracking,volatilization analysis,oxygen-containing functional groups and C-O compound release or conversion of activated coke,optimize pore structure and form C=C and N=O functional groups which are favorable for adsorption of NO/SO₂.?2?The yields of SO₂ after 200 W,300 W,400 W,350°C,450°C,and 550°C discharge regeneration were maintained at 70%,50%,25%,77%,53%,and 40%,respectively.The adsorption capacity of activated coke SO₂ after microwave discharge cycle regeneration under 200W condition is improved;The adsorption capacity of active coke SO₂ after microwave discharge cycle regeneration under300W condition shows a downward trend;microwave discharge cycle regeneration under 400W condition,the adsorption capacity of post-active coke SO₂ decreased significantly;The adsorption capacity of activated coke SO₂ after microwave discharge cycle regeneration increased first and then decreased under350°C conditions;the adsorption of active coke SO₂ after microwave discharge cycle regeneration under 450°C conditions,the capacity first rises,then falls and then rises;the adsorption capacity of active coke SO₂ decreases after microwave discharge cycle regeneration under 550°C conditions.?3?As the discharge intensity increases,the stable state of SO₂ molecules adsorbed by activated coke is converted into SO₂ in the excited state,and the local high temperature and low temperature plasma are generated by the discharge to promote the reduction reaction of C-SO₂ to form CO₂,CO,sulfur,and-S=O and S-C-O and other sulfur-containing functional groups;microwave discharge regeneration destroys the pores of the activated coke,which is unfavorable for removing SO₂.After microwave discharge regeneration,the active sites of SO₂adsorption in the activated coke increased;The activated coke surface functional groups have a greater effect on the SO₂ adsorption capacity than the pore structure.?4?As the discharge intensity increases,the efficiency of microwave-induced activated coke discharge to remove NO increases,the amount of CO production increases,and the mass loss increases.The stable state NO molecule adsorbed by the activated coke is converted into an excited state NO,which promotes the reduction reaction of C-NO at a high temperature to form CO₂,CO,N₂,and a nitrogen-containing compound.Microwave discharge denitration in O₂atmosphere is more likely to occur in oxidation reaction.The NO in the adsorption state is directly converted into nitrogen-containing functional groups such as-C-NO₂,-NO₃,N=O,and-C-NO₂.After strong discharge,most of the-C-NO₂,N=O and-NO₃ functional groups are directly released in the form of N₂ and CO,CO₂;In the absence of O₂ atmosphere,the microwave discharge denitrification first converts NO into the-C-NO₂ vibration peak,and the weak discharge mainly exists in the form of nitrogen-containing functional group.The strong discharge-C-NO₂vibrational peak can be rapidly converted by pyrolysis to N=O and-NO₃functional groups or directly desorbed in the form of N₂ and CO.?5?After microwave discharge regeneration combined with desulfurization and denitrification activated coke,the activated coke pore structure is optimized with respect to separate desulfurization-regeneration and separate denitrification.The nitrogen-containing functional group formed by activated coke after microwave discharge denitration is the active site for adsorbing and oxidizing SO₂.When the desulfurization activated coke is regenerated,these functional groups redeem SO₂ to a sulfur-containing compound,S elemental substance,and release the active site to complete regeneration.?6?By contrast analysis of strong discharge and weak discharge,microwave strong discharge can accelerate the progress of chemical reaction,and optimization of activated coke is beneficial to adsorb SO₂ and NO surface functional groups,but it will cause activated coke pore damage.The weak discharge of NO/SO₂ is mainly through the oxidation of NO/SO₂ by oxygen-containing functional groups to form sulfur-containing?nitrogen?compounds;the strong discharge removes part of NO/SO₂ and oxidizes with oxygen-containing functional groups to form sulfur-containing?nitrogen?compounds,reductive pyrolysis occurs at high temperatures.The other part produces a C-NO/SO₂reduction reaction in the local high temperature and low temperature plasma generated by microwave discharge.