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**Overview of Dengfeng China Resources Power Co., Ltd. 2*320MW Boiler System**
Dengfeng China Resources Power Co., Ltd. operates two 320MW units, each equipped with a subcritical pressure boiler featuring four-corner tangential firing. The boiler is designed with natural oil-burning burners arranged in four corners, consisting of 20 branches and five layers. The oil burners are simple mechanical atomization type, with 12 branches and three layers. The coal grinding system includes four steel ball mills, operating under negative pressure, with intermediate storage. The furnace features a ring steam drum, single furnace, one-stage reheat, balanced ventilation, solid slag discharge, and an all-steel frame suspension structure. The layout follows a "âˆ" type semi-open island configuration. The boiler is designed based on the B-ECR parameter. At 300MW electrical load, the rated evaporation capacity is 900t/h, while at 330MW, it reaches a maximum continuous evaporation of 1025t/h. The pulverized coal burners are DC fixed horizontal concentrated flame burners, except for the B layer of #1 and #2 furnaces, which feature a center-recirculation zone.
Despite advancements in technology, the reduction of nitrogen oxides (NOx) remains a significant challenge. NOx emissions contribute to acid rain and photochemical smog, posing serious threats to both human health and the environment. As China’s power industry expands, the issue of NOx pollution has become increasingly critical.
Since its establishment, Dengfeng China Resources Power Co., Ltd. has prioritized energy efficiency and environmental protection. The company continuously improves its equipment and facilities, aiming to achieve sustainable development and social benefits.
**Keywords:** low nitrogen burner, NOx, environmental protection, micro-pulverized coal combustion
**1. Overview**
The main technical parameters of the boiler include:
[Image: A schematic of the boiler system]
**2. Coal Characteristics and Combustion Status**
The boiler is designed to burn medium to low calorific value coal with medium volatile content, high ash, moderate moisture, low sulfur, and lean coal. The coal composition and combustion characteristics are detailed in the table below:
[Image: Coal composition and properties]
Currently, NOx emissions from the boiler are relatively high. At 250MW load, the tail gas NOx concentration measures around 1073/1055mg/m³, and at 287MW, it is approximately 1022/1021mg/m³, making further reduction challenging.
**3. Burner Design Parameters**
Design calculations were performed for both the design coal and verification coal types. Below are the relevant data:
[Image: Burner design parameters]
[Image: Additional design data]
**4. Primary Air and Pulverized Coal Concentrator**
An optimized pulverized coal concentrator was implemented to ensure low flow resistance, uniform air distribution, and high coal concentration. The system uses wear-resistant cast steel and lined with cast iron materials for durability. It is compact and suitable for on-site installation. Based on current coal quality, the concentrator was optimized to enhance ignition, burnout, and reduce NOx emissions.
[Image: Pulverized coal concentrator design]
A cooling perimeter wind is installed around the spout to cool the shutdown area. The primary air spout has a flared structure to delay mixing with the perimeter wind. A vertical baffle is placed between the primary and secondary air to further delay mixing. The circumferential nozzle offset helps reduce wall slagging and prevent high-temperature corrosion.
**5. Trace Oil Burner**
Considering the characteristics of #2 boiler and fuel combustion, the B-layer burners were upgraded to a new generation of trace oil direct ignition horizontal concentrated pulverized coal burners. These serve as both ignition and main burners, meeting start-up and shutdown requirements.
[Image: New trace oil burner design]
**6. Secondary Air Nozzles and Burnout Zones**
The secondary air nozzles use a contracted structure to delay mixing between primary and secondary air, reducing NOx formation. The area of the secondary air nozzles in the main burner zone is adjusted to maintain high secondary wind speed. Larger nozzles provide greater momentum, improving combustion efficiency and reducing slag and carbon content. The secondary air cut circle arrangement remains unchanged from the original design.
[Image: Secondary air nozzle layout]
The high-level burnout system distributes organized combustion air vertically. The air-to-fuel ratio in the main combustion zone is reduced from λp=1.25 to λp=0.875–0.9375. Four layers of 16 air nozzles are installed at 29m and 32m above the main burner, positioned at the four corners of the furnace.
[Image: Burnout air nozzle layout]
Burnout air nozzles are located at the upper part of the water-cooled walls. They account for 25%–30% of the total air volume, with a wind speed of 45–50 m/s. The nozzles can swing ±15° vertically and ±10° horizontally, allowing adjustments based on operational conditions such as NOx emissions and steam temperature deviation.
**7. Conclusion**
After implementing low-nitrogen burners and damper modifications, NOx emissions have been significantly reduced. This has also improved thermal performance and saved resources like ammonia, steam, and fuel oil. The project aligns well with the actual conditions of the Dengfeng plant.
In summary, this study has successfully modified the boiler combustion system, achieving positive results. However, further research and optimization of the combustion process and operational adjustments are needed to achieve even better outcomes. Due to time and resource limitations, some aspects remain incomplete and require additional analysis.