Research On Desulfurization Protective Material Based On Electrochemical NO_x Sensor

With the air pollution becoming more and more serious,the emission and monitoring of poisonous gas was also gaining more and more attention.For example,the lifetime and signal accuracy of the NO_x sensor is somehow affected by SO₂ that exists in the exhaust gas of the heat-engine plant.The objective of this study was to develop a desulfurizer which can be used in NO_x sensors.The desulfurizing agent can react with the SO₂ before the gas was detected by the NO_x sensors,thus protect the NO_x sensors being damaged by the SO₂.The desulfurization characteristics of the Ca-based desulfurizer?CaO and Ca?OH?₂?was studied.The test was conducted under the condition of different temperatures 300?,400?,500?and 600?with 500 ppm SO₂,200 mL/min gas flow,the reaction time is 120 minutes.The result shows that the desulfurization performance of the CaO and Ca?OH?₂ was increased by the temperature.The time for the desulfurization efficiency of the CaO reaches 90%under different temperatures is 4 min,28 min,34 min and 40 min;while the time for Ca?OH?₂ is 8 min,18 min,19 min and 61 min.Relatively speaking,the desulfurization efficiency of the Ca?OH?₂ is much better than CaO.Furthermore,the desulfurization efficiency of Ca?OH?₂ powder with different kinds of surface area was tested.The result shows that the efficiency is the highest when the surface area of the Ca?OH?₂ powder is 20 m²/g,and the efficiency decreased dramatically when the surface area is 50 m²/g.In order to enhance the SO₂ adsorption of the desulfurization materials,the desulfurization characteristics of the activated carbon loaded with Fe?Fe/AC?was also studied.The test was conducted under different temperatures at 200?,300?,and 400?with 500 ppm SO₂,200 mL/min gas flow,the reaction time is 60 minutes.The result shows that the desulfurization performance of the Fe/AC reach its best under 300?.The time for the desulfurization efficiency is nearly 90%under different temperatures is 13min,18 min and 12 min.After ball-milling for 12 hour,the powder of Ca?OH?₂ and Fe/AC was mixed at a mass ratio of 1:1.The mixture was tested under different temperatures at 200?,400?,and 600?with 500 ppm SO₂,200 mL/min gas flow,the reaction time is 120 minutes.The result shows that the desulfurization performance of the Ca?OH?₂-Fe/AC was increased by the temperature,which is the same with Ca?OH?₂.The time for the Ca?OH?₂-Fe/AC's desulfurization efficiency is nearly 90%under different temperatures is10 min,18 min and 34 min.The desulfurization effect of the two kinds of desulfurizers evenly after mixing is better than the desulfurization effect when the two layers are layered in different order,because the Fe element plays a catalytic role in calcium-based desulfurization.The mixture Ca?OH?2-Fe/AC after desulfurization was then used to test its adsorption activity of NO_x under different temperatures at 200?,400?,and 600?with 300 ppm SO₂,250 ppm NO,200 mL/min gas flow.The result shows that the mixture Ca?OH?₂-Fe/AC after desulfurized was insensible to NO_x,due to the concentration of NO_x after tested remains the same.