Study And Application Of Denitration Technique Combined LNB & SCR In Coal-fired Boiler

After the introduction of fossil-fuel power plant atmospheric pollutant emission standard (GB13223-2011) in 2001, the emission of NOx is further restricted which should be below 100mg/m3. The emission standards of air pollutants for boiler (GB13271-2001) has also strengthened the control of NOx emission, the maximum emission of NOx should be below 300mg/m3. The increasingly stringent emission standard reveals that the influence of NOx is highly concerned by public. The emission of most old coal-fired boilers will exceed the new standard. In order to reach the current emission standard, old boilers need to carry out the denitration transformation.A coal-fired boiler of 160t/h in a thermal power plant located at northwestern China was studied in the thesis. By studying the working condition of boiler and the gas composition, analyzing the current boiler NOx-control technique, establishing two transformation scheme, the denitration technique combined low NOx burning technology(LNB) and selective catalytic reduction(SCR) was adopted to improve the current ineffective boiler.The low nitrogen combustion boiler is designed according to the technical principles of low nitrogen combustion, SCR denitrition technology is initially designed according to the amount and compositions of gas. The catalyst type and the arrangement form, the main structure and the dimension of SCR reactor, the installment site of SCR reactor, the set of soot blower and the proposed scheme of flue upgrading are determined in the design. Actual monitoring data during the runtime is collected for statistical analysis, followed by the analysis of factors which are able to have influence on the denitrogen system, and then proposes the suggestion of optimizing adjustment according to received abnormal results.Through the practice of engineering design, the production of NOx can reduce 30% by applying the low-NOx burning system retrofits and the flue gas denitrification efficiency of SCR reactor is at least 80%. The application effect of hybrid denitrification technology combined LNB&SCR is obvious and the NOx emission concentration has decreased from 650mg/m3 to 90mg/m3. The combined denitrifiaction technology applied to greatly reduce emissions of nitrogen oxides is proved to be effective, reliable and feasible. The application of combined denitrification technology can meet the existing requirements of emissions in old coal-fired boilers.