Experimental And Numerical Studies Of Denox Retrofit And Slaging Properties At Utility Boilers

China is a large coal producer as well as a large coal consumer. It has been a long-term and challenging task to utilize coal more efficiently and cleanly, and improve the safety and efficiency of power generation. The present work focuses on the combustion and NOx control in power plant boilers. Laboratory experiments, numerical simulations and field tests were carried out to investigate the combustion and NOx control methodologies. And attempts were made to explore a new set of optimization techniques for power plants.In view of the large NOx emission of the#1boiler in a Guangdong power plant, the denox retrofit scheme with air staged combustion was proposed in this work. The nozzle in the primary combustion zone is retrofitted with the addition of a SOFA nozzle and the retrofit of the mill separator. Field test results showed that the NOx emission at the rated load was decreased to298mg/m3and denitrification rate was as high as50%. In order to further investigate the temperature and major gas composition distributions after the retrofit, CFD simulation was carried out to simulate the flow and combustion situations before and after retrofit. The simulation results showed that air staged combustion is more stable and the NOx emission was significantly reduced. And the simulated results math well with measured ones. Therefore the expected results are attained.Dry slag disposal is a technology which can save water and energy and enhance the utilization value of ash and slag in power plants. Thus this technology can increase the economic benefits for power plants. The principle and outline of the dry slag disposal system is introduced in this work. CFD simulations were carried out to study the temperature and NOx distributions in a200MW pulverized coal-fired boiler after the introduction of dry slag disposal technology. The results showed that the height of the flame center and temperature were basically unchanged, while the NOx concentration at the boiler outlet was increased. The increase of NOx can be attributed to that the air leakage at the boiler bottom increased the oxygen concentration at the lower part of boiler and weakened the effect of lean-oxygen combustion and increased the formation of fuel NOx. Study on the piecewise coal field showed that the blending situation is highly related to the arrangement and operation sequences of the coal fields. The penetration depth of different coal fields is1-2cm, which is equivalent to the penetration depth of2-4m for practical coal fields. This means that the mixing effect of coal fields has a large impact on the stability of coal supply. The inner water of coal has a obvious influence on the pile angle.Based on the particle coalescence models of combustion models, the present work simulated the slagging conditions before and after the denox retrofit. The simulation was carried out on the combustion of blended coals in Shajiao A power plant. The simulated results showed that coal blending can reduce slagging and change the areas which are easy to form slag. As to the study of slagging prevention, the present work used Neutral network and genetic algorithms to optimize the maximum and minimum melting points for the ash oxides.The pipe gas-solid two phase online measurement has a significant influence on the safe and optimized operation of utility boilers. The present work studied the two phase concentration measurement. The ultrasonic wave receptor was set on the outside of the pipe elbow. The ultrasonic signals produced on the collision between the two phase flow and the pipe elbow was sent to the computer and processed. The two phase concentration was therefore analyzed and obtained. The experimental tests showed that online measurement is possible by using this method.