Outer Secondary Air Vane Angles Research Articles

Industrial Experiments on Anthracite Combustion and NOx Emissions with Respect to Swirling Secondary Air for a 300 MWe Deep-Air-Staged Down-Fired Utility Boiler

A new deep-air-staging and low-NOx technology has been introduced to a 300 MWe anthracite- and down-fired boiler with swirl burners. Industrial experiments were performed at different outer secondary air vane angles (defined as β) (i.e., 20°, 30°, 40°, and 50°) to evaluate the environmental and economic performance for the retrofitted boiler. Furthermore, combining with the previous investigations on the inner secondary air vane angle (defined as α), the influence degrees of β and α on anthracite combustion and NOx emissions for the retrofitted boiler were further analyzed and compared. The experimental results revealed that the main factors affecting the ignition and the flame fullness for β and α are different. Compared with α, β had a relatively greater influence on NOx emissions for the retrofitted boiler. Compared with the orignianl boiler, a strong reducing atmosphere was formed in the primary combustion zone for the retrofitted boiler, and for the β of approximately 30°, the arithmetic mean of NOx ...

Effect of outer secondary air vane angles on combustion characteristics and NOx emissions for centrally fuel rich swirl burner in a 600-MWe wall-fired pulverized-coal utility boiler

To solve the high NOx emissions associated with a 600 MWe utility boiler with enhanced-ignition axial control low NOx (EI–XCL) burners, continuous improvement of the previously proposed centrally fuel-rich (CFR) burner technology lies on three aspects: (1) the 36 EI–XCL burners in the original furnace were retrofitted with CFR burners; (2) the 26 over fire air (OFA) ports in two layers have been added above the burners along the top row of the furnace; (3) the designed OFA ratio was 25%. Industrial-size measurements (i.e., adjusting outer secondary air vane angle of 20–30°) uncovered that, compared with the prior EI–XCL burners, the CFR burner exhibited the same good ignition performance and the O2 concentrations near the side walls were found to be above 6% when the secondary air mass flow rate of the burner decreases about 37% for all three outer secondary air vane angles. The NOx emissions decrease from 316 to 237mg/m3 (O2=6%) when outer secondary air vane angle varies from 20° to 30°. Under the optimal outer secondary air vane angle, NOx emissions were found to decrease by 60.50% at a load of 600MWe subsequent to retrofitting of the boiler.

Study on Gas/particle Flows in a Down-Fired Boiler with Swirl Burners: Influence of Different Outer Secondary Air Vane Angle

The gas-solid multi-phase flow is measured in a 300MW down-fired bolier cold model with swirl burners by two-dimensional phase Doppler velocimetry(PDA), concluded the influence of different outer secondary air vane angles on the multi-phase flow characteristics in the furnace. For vane angles of 25°, the vertical direction average velocity is high and fluctuating velocity is low, the reach of the downward airflow is deeper, primary air and secondary air mix slowly, the horizontal direction average velocity is high and fluctuating velocity is low, solid phased particles spread slowly and mix with the rewind air weakly, this is against to the ignition of pulverized coal. For vane angles of 35°, the vertical direction average velocity decrease and decay faster, fluctuating velocity increase slightly, the horizontal direction average velocity and fluctuating velocity increased slightly, solid phased particles spread quickly and mixed with the rewind air quickly, the ignition of pulverized coal increase. For vane angles of 55°, the recirculation zone appear in the burner nozzle region, the vertical direction fluctuating velocity increase significantly, average velocity decrease and decay quickly, the downward airflow turn upwards before mixing with gas, the horizontal direction average velocity high and fluctuating velocity is higher, solid phased particles spread more quickly, mixed with the rewind air more quickly, this will erode the water wall and throat, cause the water wall slagging. Considering various factors, the best outer secondary air vane angle is 35° in the operation of boiler.

Influence of the outer secondary air vane angle on the gas/particle flow characteristics near the double swirl flow burner region

A three-component particle-dynamics anemometer is used to measure, in the near-burner region, the influence of the outer secondary air vane angle on the gas/particle flow characteristics of a double swirl flow burner, in conjunction with a gas/particle two-phase test facility. Velocities, particle volume flux profiles and normalized particle number concentrations were obtained. For three different outer secondary air vane angles, annular recirculation zones formed only in the region of r/d = 0.3–0.6 at x/d = 0.1–0.3. With a decreasing outer secondary air vane angle, the peaks of (RMS) root mean square axial fluctuation velocities, radial mean velocities near the wall, RMS radial fluctuation velocities and tangential velocities all increased, and the recirculation increased slightly. There was a low particle volume flux in the central zone of the burner. At x/d = 0.1–1.0, the profiles of particle volume flux had two peaks in the secondary air flow zone and near the wall, and the two peaks increased as the outer secondary air vane angle decreased. In the section x/d = 0.1–0.5, the particle diameter in the central zone of the burner was always less than the particle diameter at other locations.

Influence of the Outer Secondary Air Vane Angle on the Flow Field of a Down-Fired Pulverized-Coal 300 MWe Utility Boiler with Swirl Burners

Using an IFA300 constant temperature anemometer system, cold air experiments on a scale model of a down-fired pulverized-coal 300 MWe utility boiler with swirl burners were performed to investigate the influence of outer secondary air vane angles on the flow characteristics in the furnace. For a vane angle of 20°, the reach of the downward airflow is deep and the mixing with vent air and staged air is good, thereby favoring coal combustion but at the expense of airflow washing out at the entrance of the upper furnace. For vane angles of 25° and 30°, the reach of the downward airflow is short, mixing with the staged air weakens, and thus, the recirculation zone below the arches is small, although washing out at the entrance ceases. For a 35° vane angle, the reach of the airflow further shortens and the mixing of the airflow and vent air is weaker. At even larger vane angles of 40° and 50°, the recirculation zone appears in the burner nozzle region and the airflow is directed upward near the burner nozzle r...

Influence of Different Outer Secondary Air Vane Angles on Flow and Combustion Characteristics and NOxEmissions of a New Swirl Coal Burner

Measurements were taken for a 300 MWe wall-fired pulverized-coal utility boiler installed with eight centrally fuel rich swirl coal combustion burners in the bottom row of the furnace during experiments. For various outer secondary air vane angle settings, flow characteristics, gas temperature and gas species concentrations in the burner region were measured. The results show that with decreasing outer secondary air vane angle, the swirl intensity of air, divergence angles and maximum length and diameter of the central recirculation zone all increased; the turbulence intensity of the jet flow first increased and then quickly decreased. With decreasing outer secondary air vane angle, the rate of increase in the gas temperature in the early stage and the rate of decrease in the later stage increased along the jet flow direction. For outer secondary air vane angle of 25°, the O2 concentration along the jet flow direction in the burner region was low, and the CO concentration decreased with increasing outer s...

Study of the influence of vane angle on flow, gas species, temperature, and char burnout in a 200 MW e lignite-fired boiler

We measured various operational parameters of a 200-MW e, wall-fired, lignite utility boiler under various outer secondary air vane angles. The parameters measured were gas temperature, gas species concentrations, char burnout, and component release rates (C, H and N). Cold air experiments of a single burner were conducted in the laboratory. A double swirl flow pulverized-coal burner has a single ring recirculation zone that forms in the secondary air region in the burner. By decreasing vane angles, maximum values of radial velocity, tangential velocity and turbulence intensity all increase. Moreover, swirl intensity of air flow and recirculation zone size increase. Concomitantly, in the central region of the burner, decreasing the vane angles of outer secondary air increases gas temperatures, CO concentrations, char burnout and component release rates of C, H, and N, while O 2 and NO x concentrations decrease, and an early ignition of pulverized-coal occurs. Meanwhile, in the secondary air region of the burner, conditions are similar except that NO x mean concentrations are reversed showing instead an increase. In the side wall region, gas temperatures increase, O 2 and NO x concentrations decrease, but CO concentrations vary only slightly.

Fractal and turbulence characteristics of aerodynamic fields of swirl burners

Turbulence intensities at the exit of a centrally fuel rich (CFR) burner were measured employing a probe with hot-film sensors. In addition, using glycol as a smog tracer, optical images of the highlighted primary airflow were taken with a CCD camera and contrast-enhanced by computer. Profiles of the interface between primary and secondary air were obtained from which fractal dimensions (FDs) of the primary air boundary were estimated. Results indicate that FDs of this air boundary are in the range of 1.10–1.30 depending on burner conditions. As the FD and mean turbulence intensities of the primary air boundary have uniform distributions, they can be used to analyze coal combustion and NOx formation characteristics of the burner. When either decreasing the outer secondary air vane angle or increasing either the inner secondary air vane angle or total mass flow rate of the secondary air, the burner swirl number increases which subsequently shows up as an increase in the FD and mean turbulence intensities of the primary air boundary. Increasing the ratio of the mass flow rate of inner to outer secondary air decreases the burner swirl number, but increases the FD and mean turbulence intensities of primary air boundary.

Influence of outer secondary-air vane angle on combustion characteristics and NOx emissions of a down-fired pulverized-coal 300MWe utility boiler

Abstract Industrial experiments were performed on a down-fired pulverized-coal 300 MWe utility boiler with swirl burners. Gas temperature, concentrations of gas components (O 2 , CO, CO 2 and NO x ) in the burning region and carbon content in the fly ash were measured with outer secondary-air vane angles of 25°, 32.5° and 50°. Results indicate that with increasing vane angle, NO x emission and boiler efficiency decrease. Overall evaluation boiler efficiency and NO x emission, the vane angle of 32.5° is optimum. Using an IFA300 constant-temperature anemometer system, cold air experiments on a quarter-scaled burner model were also carried out to investigate the influence of various outer secondary-air vane angles on the flow characteristics in the burner nozzle region. No central recirculation zone appeared for vane angles of 25° and 32.5°. Most of the pulverized-coal was ignited in the external recirculation zone. For vane angles of 45° and 55°, a central recirculation zone could be observed, and air flow rigidity and axial velocities decreased rapidly.

New low NO<SUB>x</SUB>, low grade coal fired swirl stabilised technology

AbstractA centrally fuel rich (CFR) swirl coal combustion technology was developed to burn low grade coal with low NOx emissions. The enhanced ignition dual register (EIDR) burners were used in an opposite wall, low grade coal fired 1025 ton per hour boiler. Eight EIDR burners in the bottom row were retrofitted with the new burners. Both cold air flow and reacting flow experiments were performed in an industrial boiler. The jet border, the central recirculation zone boundary, and the performance of two types of burners were investigated. The run parameters used were: the ratio of the largest diameter and length of the central recirculation zone to the outer diameter of the outer secondary air duct of the CFR burner is over 1˙40 and 1˙89, and the EIDR burner has no central recirculation zone. The influence of the outer secondary air vane angle, the primary air and the secondary air on the air flow field of the two types of burners was examined. The influence of different positions of the secondary air damp...