Reduction of Nitrogen Oxide Emissions by Combustion Process Modification in Oil and Gas Flames PDF Download

Author: János Miklós Beér
Publisher:
ISBN:
Category :
Languages : en
Pages : 54

Get Book

Book Description
Results of an experimental-computational investigation to establish the design principles of a low-NOx burner of novel design are reported. The burner is designed to achieve staged combustion by a combination of radial density gradients and rotating flow in the flame. Fuel/air mixing is suppressed by radial density stratification close to the burner but is promoted by a toroidal recirculating flow further downstream of the burner. This design is referred to as the "Radially Stratified Flame Core" (RSFC) Burner. All experimental results described in this report are obtained with the RSFC Burner. Parametric and detailed experimental studies carried out with natural gas and fuel oil flames in the pilot scale flame tunnel of the MIT Combustion Research Facility (CRF) served for the optimization of the burner for low-NOx and CO emissions. The results showed that for several operational modes of the burner input variables, highly stable flames with low-NOx and CO emission levels were attainable. The primary operating variables were found to be the radial distributions of the air flow and the swirl velocity at the exit from the burner, and the central fuel injection velocity and angle. Minimum values of NOx and CO emissions obtained in the first phase of our investigation were: 70 ppm NOx (at 3% 0) and 56 ppm CO for natural gas, 54 ppm NOX and 23 ppm CO for No. 2 fuel oil and 97 ppm NOx and 32 ppm CO for No. 6 fuel oil. These results were obtained without staging of combustion air and without flue gas recirculation. In a further stage of the investigation, flue gas was recirculated through the natural gas flame and small amount of steam (12 wt. % of the fuel mass flow rate) was injected into the fuel, resulting in significant additional reduction of NOx to the level of 15 ppm. In heavy fuel oil flames, NOX emissions of less than 60 ppm were reached with small amounts of overfire air (10%). The time frame of the experiments described in this report is from August 1989 through December 1991. In the summer of 1991 ABB-Combustion Engineering announced plans to develop the RSFC concept towards a commercialized burner for utility use. The primary thrust of the planned development was for a gas-fired burner, but it was recognized that successful commercialization would call for a dual-fuel capability, i.e., the burner should yield low NO, emissions when burning either natural gas or No. 6 fuel oil. Thus, while some further work is required to establish optimum operating conditions for the RSFC Burner with natural gas, the primary focus of future investigation at MIT will be on improvement of the burner's fuel oil firing performance. This will involve both modeling and experimental studies