Research On The Flow Field Optimization Before Denitrification And Harmless Disposal Of Waste SCR Catalysts

Selective catalytic reduction(SCR)with high denitrification efficiency is often employed in various industrial equipment,such as coal-fired power plants and iron and steel industries.It has been recognized as the most widely used among lots of the flue gas denitrification technology.However,with the diversification of the system structure of coal-fired power plants in China,the requirements for SCR flue gas denitrification devices are different.For example,it needs to be solved of serious nonuniform distribution of NH3/NO,within a short distance of flue gas duct.In the present work,the SCR gradient uneven ammonia injection system was proposed to meet the technical requirements of coal-fired power stations.And,the key issues encountered in the denitration process of low-temperature sintering flue gas were studied.Firstly,this work presents the effects of various inclined jet angles including 0°,30° and 45° to enhance mixing performance and optimize concentration uniformity.The flow field and tracer gas mixing performances are quantitatively analyzed by using the root mean square deviation coefficient.From results,mixing enhancement between jet and crossflow for the inclined injection grid is achieved.It is also indicated that the inclined angle plays an important effect on jet rigidity and tracer gas dilution.Multiple jets with an inclined angle of 30° achieved the best mixing performance.Then,an SCR gradient non-uniform ammonia injection system designed on the basis of 30°ammonia injection grid pattern is introduced.By comparing the distribution of NOx for the flue gas before and after the installation of the system,it is proved that the SCR gradient non-uniform ammonia injection system has shown effective NOx control performance in industrial utility furnace.Secondly,experimental investigations have been conducted to promote turbulent thermal mixing of hot gas and cold airflow in a simulated sintering gas preheating unit.Mixing performance was analyzed by measuring velocity,temperature,and concentration fields.Results show that the perforated pipes with an obtuse jet angle achieve the better mixing performance than those of others.Moreover,the inclined angle performs an important role in jet penetration and hot gas dilution.The jet penetration and flow deviation have a great effect on thermal mixing for perforated pipes at a short distance.The jet hole configuration of 120° achieves the best mixing performance.However,the configuration with an obtuse angle shows inferior average velocity because of the collision momentum loss caused by the reverse jet.Finally,to study the effects of different additives on high-temperarure melting treatment of waste SCR catalyst at 1 300 ?,an analysis was conducted on the composition of molten slag respectively obtained by using three different additives of different mass fractions.Results show that the waste SCR denitration catalysts can be effectively stabilized by the way of high-temperature melting at 1300 0C.When the mass fraction of additives is 40%(Fe2O3 31.2%?SiO2 2.64%?CaO 5.2%and Al2O3 0.96%),the leaching toxicity of heavy metals Ni,As,Se,Cu and Mn can be reduced by 98.6%,68.0%,96.8%,11.1%and 77.3%,respectively.