1、附表 A 英文文献 Coal Flow Measurement and FlowBalancingfor Improving Combustionand Emissions on Coal Fired Boilers S. Laux, J. Grusha Foster Wheeler Energy Corporation Clinton, NJ08809-4000, USA Stefan_L T. Rosin TR-Tech Int. Oy FIN-20100 Turku, Finland TR Abstract The performance of pulverized coal combu
2、stion systems commonly suffers from air and fuel imbalances at the burners. Stoichiometries local to the burners must be maintained in order to achieve ultra low NOx performance without significantly sacrificing combustion efficiency. In addition to the emission benefits, improvement of the air and
3、fuel balance results in less slagging and reduced furnace wall corrosion. He paper presents results and benefits associated with operating coal fired boilers using Foster Wheeler and TR-Techs Electric Charge Transfer (ECT) coal flow measurement technology. ECT systems provide boiler operators with c
4、ontinuous on-line indication of coal flow distribution, conduit velocity and particle fineness. The paper will show devices that control the coal flow balance. ECT technology in conjunction with Foster Wheelers solutions for coal flow balancing is opening up an entire new spectrum in operational ass
5、essment and improvement as well as emission control. Ultra Low NOx Combustion New NOx regulations demand drastically reduced NOx emissions from fossil fired boilers. With a few exceptions, the NOx limits for ozone control during the summer months require a post-combustion control method such as SCR
6、on coal fired boilers, because Low NOx firing systems alone can not achieve compliance. However, investment costs and ammonia costs of an SCR DeNOx catalyst can be reduced, if the output NOx from the firing system is low. Thus, more stringent emission limits and the addition of post combustion NOx c
7、ontrol create the need for improvements of NOx emissions from the existing Low NOx coal firing systems. Regardless of the NOx reduction approach, many current low NOx systems are limited in their ability to provide significant additional reductions in NOx. New multi air zone burner designs, special
8、coal nozzle tips, etc dont provide the reductions being sought by utilities wanting tominimize or eliminate post combustion systems. In anticipation of these requirements, Foster Wheeler has been developing new technologies to go beyond just “burner components”. Our evaluation of operating LNB syste
9、ms shows that many are limited from further NOx reduction by “non burner“ barriers. By addressing and eliminating each of these, significant reductions are possible. One of the most common barriers to lower NOx is related to poor coal and air distribution. These can include high unburned carbon, hig
10、h CO, furnace slagging, oxygen and/or steam temperature imbalance, corrosion, etc. All low NOx firing systems depend on a defined balance of the air and coal at the burners. By monitoring and controlling the air and coal flow to the burners, existing as well as new systems greatly benefit from lower
11、 emissions and improved boiler operation. Or, if you use the following analogy for boiler emission improvement: This trend is comparable to the change from carburetors to fuel injection systems seen over time in the car industry. Foster Wheeler strongly believes that future ultra low NOx firing syst
12、ems need a tight control of the air and fuel balance at each burner in the system, regardless whether it is tangential, wall or arch fired /1/. Many pulverized coal boilers experience some of the problems associated with poor air and fuel distribution: * Poor emission performance * Increased ammonia consumption of SCR and SNCR systems * Increased unburned carbon in the fly ash * Distorted oxygen profile at boiler outlet * Uneven steam temperature profiles * Flame impingement
