Research On Mercury Removal From Low Temperature Flue Gas By Cerium Modified Catalyst

Mercury is a kind of heavy metal pollutant which is concerned and controlled worldwide,the atmospheric mercury emissions in China have been severe over the years.But with the official entry into force of the world convention "Minamata convention",China's mercury pollution control is also accelerating.In addition to controlling the consumption of coal resources,replacing old boilers,installing and popularizing air pollution control equipment and other existing measures,using catalysts to remove mercury from flue gas is also an effective method.The main purpose of this paper is to explore the metal catalysts for the mercury removal of flue gas at low temperature in coal-fired power plants.The main research object of this paper is the cerium base catalyst,which is widely studied for its powerful catalytic properties,and it has the ability to store oxygen and resist S02.In this paper Ce-Mo/Al catalyst and Ce-Cu/Al catalyst of different load ratios were prepared by using incipient-wetness impregnation method,then the experiment was conducted in the atmosphere of oxygenation.The optimal negative load of Ce was 2%in the catalyst,and 8%for matching Mo and 4%for matching Cu.2Ce-8Mo/Al catalyst has effect of mercury removal among 250?350 ? temperature range,and mercury oxidation rate reaches as high as 92.1%at 300 ?,while under the condition of 150?,8%O₂ 2Ce-4Cu/Al catalyst can still maintain the catalytic activity about 80%after 80 h reaction.2Ce-4Cu/Al catalyst is better at removing mercury in low temperature,and better than 2Ce-8Mo/Al when flue gas contains S02.Therefore,the following experiment was studied with 2Ce-4Cu/Al catalyst.To discuss the influence of 2Ce-4Cu/Al catalyst preparation,the impregnation sequence and roasting temperature of catalyst were changed respectively.The experiments show that the mixing of the two kinds of active components of Ce and Cu can be fully integrated with the method of incipient-wetness impregnation method,the catalytic performance of the calcined temperature at 500 ? is better than that of 400 ?and 600 ?.At the same time,the 2Ce-4Cu/Al catalyst was tested for characterization,including SEM,BET,XRD.The result is that the addition of active ingredients can reduce the specific surface area and pore volume of the carrier,and the crystal phase structure of 2Ce-4Cu/Al catalyst is fully developed.The distribution of Cu is in good condition,Cu dispersed in the carrier surface with the substratum and single-layer state,while the Ce02 may be reunited,showing the diffraction peak.In the end,the influence of the composition of the flue gas on the 2Ce-4Cu/Al catalyst oxidation was studied.It was found that 02,HCl and NO are effective in removing mercury from flue gas,the higher the content,the better the mercury's oxidation.The influence of SO₂ is more complex,oxidative efficiency of the catalyst was reduced when SO₂ was passed alone,but performance turned into promotion when O₂ is entered at the same time.Under the condition of 800 ppm SO₂ and 6%O₂,the oxidation efficiency of the catalyst was up to 95.3%,and the effect of sulfur resistance was stable during the reaction time.Under the condition of 150? and simulated flue gas,2Ce-4Cu/Al catalyst has good effect on mercury removal,which can reach 99%during the 3 h reaction time,and the effect of SO₂ in gas components plays a decisive role on the removal of mercury.