Guangbo Zhao

Effect of flue gas recirculation on nitric oxide (NO) emissions during the coal grate-fired process

ABSTRACT Flue gas recirculation (FGR) is a low nitrogen oxide (NOX) combustion technology. The present study used standard gas to simulate the cycle gas (the main ingredients of which are oxygen (O2), nitrogen (N2), and carbon dioxide (CO2)). The coal grate-fired process was divided into three zones, namely (1) volatilization zone, (2) main combustion zone, and (3) char combustion and burn-out zone. The effects of FGR on coal combustion and NO emissions were investigated in these zones of a unit-boiler experimental system. An industrial test was then conducted on a chain boiler that previously used FGR. Data showed that if the cycle gas was directed into the furnace from the volatilization zone, the curve of the coal surface temperature moved backwards, the temperature peak increased, and coal ignition was delayed. When the FGR rate was 20%, NO emissions/g coal was 41.8% less than in the absence of FGR, in the overall combustion process except for the volatilization zone. An industrial test demonstrated that FGR decreased the NO emissions and incomplete-combustion loss of gas. NO and carbon monoxide (CO) emissions were reduced by 26.9 and 38%, respectively. These observations may prove to be beneficial in reducing ambient air pollution and saving energy.

Emission and Properties of NOx Generated During Coal Grate-Fired in O2/N2/CO2

With the improvement of environmental protection requirements, the problems of NOx emission from industrial boiler become more and more notable. Flue gas recirculation is a low-NOx combustion technology. It draws out a part of the flue gas from rear flue and forces it into boiler. So the flue gas can serve the combustion or flow field integration. The drawn flue gas can be forced into the boiler directly, or mixed with the primary air or secondary air. To explore a real effective method of low NOx combustion, the article discusses the influence of flue gas recirculation on the formation of NOx in the process of coal grate-fired, in the way of using the unit-boiler, measuring the temperature of coal surface and composition and other important influential parameters. Experimental studies show that under the condition of grate-fired, taking Flue gas recirculation in main combustion zone, coke combustion zone and burn-out zone could notably diminish the amount of NO. And with the promotion of flue gas recirculation rate, the effect can be more noticeable.

The Influence of Flue Gas Recirculation on the Formation of NOx in the Process of Coal Grate-Fired

With the improvement of environmental protection requirements, the problems of NOx emission from industrial boiler become more and more notable. To explore a real effective method of low NOx combustion, the article discusses the influence of flue gas recirculation on the formation of NOx in the process of coal grate-fired, in the way of using the unit-boiler, measuring the temperature of coal surface and composition and other important influential parameters. Experimental studies show that under the condition of grate-fired, the amount of NO will increase with the 25% flue gas recirculation in volatile zone, taking recirculation in coke combustion and burn-out zone could notably diminish the amount of NO.

The Research on the Formation Rules of NOx in the Coal Grate-Fired Process

With the increased requirements of environmental protection, the problem of industrial boiler NOx emissions become more and more notable. The practical coal and the same air-distribution method as the one in the actual stoker boiler were applied to study the NOx formation characteristics in a unit-boiler with the purpose of studying the NOx formation characteristics in the chain-boiler. Measuring the temperature, weightlessness and composition and other important influential parameters of the product-gas is to obtain the details of the grate-fired process and it is to know the law and main influential factors of formation rules of NOx in the grate-fired process of chain-boiler. Further, the coal layer surface temperature NOx formation, oxygen content, CO content and other parameters on different regions of a SZL10-1.25-AII symmetrical arrangement chain-grate boiler were tested. The measurements of the unit-boiler were compared with the industrial measurements to verify the reasonableness of the method of researching the actual industrial boiler combustion process by the unit-boiler. On this basis, the technical route according to the low-NOx combustion technology in chain-grate boiler is proposed and it laid the foundation for industrial demonstration.