| Central heating is the main way of heating for urban residents in vast areas of northern China.It is also an important part of urban public utilities.Heating in winter can increase local PM2.5concentration significantly.Nitrogen oxides are important precursors of PM2.5 formation.Small space occupation and high security requirements are characteristics for central heating centers adjacent to a city's concentrated residential areas;at the same time,the operation condition of central heating boiler is affected by the change of thermal load demand.during the heating periods early,middle and at the end of the day,as well as the fluctuation between day and night are large and form a huge challenge to the secure,stable and reliable operation of the denitration facilities.Therefore,in view of the characteristics of the central heating boiler,the research and development of the adaptive denitrification technology has important engineering significance and practical value.Regarding the characteristics of the central heating boiler load change rate and high frequencies,we developed a fast response control technology of reducing agent and invented sleeve cage type ammonia spraying flow regulating device,formed with the opening percentage and linear flow response curve,that overcomes the existing technical flow change lags behind the opening adjustment of the problem,greatly improving the regulation properties;we form urea feedforward feedback flow control strategy based on fuzzy control to import NOx concentration of the flue gas volume.Ammonia is used as feedforward input variables,output control for urea flow regulation through the material balance and the PI controller operation,to realize the fast tracking of the load;we export NOx and use the concentration of deviation and its change rate as input variables of fuzzy feedback flow control,using urea as fuzzy incremental output variables,build a two-dimensional fuzzy controller,overlay control output and the output signal of the feedforward control,the feedforward control achieve modified fine Denitration Process control precision and stability.The above results are applied to the flue gas denitrification project of more than 10 central heating boiler,and the automatic control of spray ammonia is realized in a stable operation.In view of the wide range of load variation and the low efficiency of commercial catalysts under low load conditions,the preparation and modification of manganese based catalysts were studied.We prepare Mn-Fe and Mn-Ti catalysts and study its activity by four kinds of processes.The results show that for temperatures higher than 180°C there is a two system activity and for temperatures lower than180?Mn-Fe the activity that the Mn-Ti catalyst prepared by coprecipitation of Mn-Fe active window range is much larger than the citric acid method,the surface area,the adsorption of NH3 acid site and stability are relatively high;we then explore the transition metal?Cr,Zr,Mo?effect on the denitrification performance and found that the incorporation of Cr can significantly increase the activity of Mn-Fe-Cr,the specific surface area,active component dispersion,adsorption of NH3 acid sites,resistance to water vapor and SO2 poisoning ability and redox properties.based on the study of Mn-Fe-Cr powder catalyst,we prepare honeycomb catalysts coated with industrial size method in actual industrial flue gas under the conditions of exploration for honeycomb catalyst's optimal operation parameters in industrial flue gas.The results show that Mn-Fe-Cr catalyst at a temperature of 140?and a speed of 4000h-1,the export NOx concentration can be reduced to below 50 mg/m3.Aiming at the difficulty of retrofit or retrofit the heating surface of some central heating boilers,we explored the new method of denitrification after the dust removal and desulphurization of the boilers.We made a basic research and pilot study on the new biofilm degradation process of NOx.The sludge was used to domesticate denitrification bacteria,the biofilm culturing and denitrification performance of denitrifying bacteria on four kind fillers were investigated,the results show,light-weight ceramics with high denitrification efficiency and low resistance were the best fillers,on this basis,the effects of various process parameters on the denitrification efficiency were studied,and the optimal operation range of the denitrification of the biotrickling filter was obtained.Based on the results of nitrogen balance and microbial Miseq sequencing,the mechanism hypothesis of nitrification/denitrifying bacteria in the process of denitrification of biological droplet was proposed.The effects of organic carbon sources,inorganic nitrogen sources,metal ions,and rare earth elements on the denitrification performance of nitrification/denitrification coexisting microbial systems were systematically studied,and the optimal combination of enhancers was obtained.The efficiency increased by 14.6%to 78.9%when the intake volume was 500 L/h.The application of the above technology was designed to build a denitrification pilot plant to process 500 m3/h coal-fired boiler flue gas,and the 46-day trial operation results showed that the average denitration efficiency reached67.3%and the performance was stable.this process has engineering application value in non-priority discharge area?NOx requires emission concentration of 100-200mg/m3?. |
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