Opposite-firing boiler combustion system suitable for changing meagre coal into bituminous coal
By setting up multi-layer swirl burners and staggered burners in the lean coal boiler, the combustion flame dispersion control and multi-stage graded combustion are achieved, which solves the coking problem after the lean coal boiler is mixed with bituminous coal and improves the safety and economy of boiler operation.
Patent Information
- Application Number
- CN202510654228.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-21
- Publication Date
- 2025-09-12
AI Technical Summary
When lean coal boilers are mixed with bituminous coal, there are problems such as the risk of furnace coking and insufficient temperature, which affect the safety and economy of boiler operation. The existing technology has poor adjustment flexibility and high cost.
Multi-layer swirl burners are installed in the secondary air box of the boiler. The swirl burners are arranged in layers and staggered. Combined with burners of different powers and air dampers, the combustion flame dispersion control and multi-stage combustion are realized, and the flue gas mixing and temperature regulation are enhanced.
It effectively reduces the average flue gas temperature in the main burner area of the furnace, controls the heat load to be evenly distributed, prevents coking of the water-cooled wall, and improves combustion stability and economy.
Smart Images
Figure CN120627062A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a combustion system of a boiler, in particular to a combustion system of a hedge boiler suitable for replacing lean coal with bituminous coal. Background Art
[0002] Lean coal, a preferred power coal, accounts for a significant portion of my country's total coal reserves. Its low volatility, high calorific value, long-lasting combustion, high ignition temperature, short flame, slow burnout, and low coking properties make it widely used in coal-fired power plants. On the one hand, to achieve the "dual carbon" goals as soon as possible, increasingly stringent national environmental protection policies have led to challenges such as high nitrogen oxide emissions in units burning lean coal. On the other hand, from an economic perspective, the current high raw coal price and transportation costs of lean coal have put significant pressure on coal-fired power plants. To enhance their viability, meet environmental protection requirements, and improve economic efficiency, many lean coal boilers have begun to blend or exclusively burn more affordable bituminous coal.
[0003] Compared to lean coal, bituminous coal has higher volatility, slightly lower calorific value, easier ignition and burnout, lower ash melting point, and higher coking potential. Shenhua coal, for example, is a bituminous coal with strong coking properties. Based on the combustion characteristics of lean and bituminous coal, lean coal boilers have higher burner area heat loads and a leaner furnace than bituminous boilers. Lean coal boilers employing a high proportion of blended or all-bituminous coal combustion offer significant advantages in terms of reduced pollutant emissions, lower costs, enhanced combustion stability, and improved economic efficiency. However, they present significant challenges such as the risk of coking in the furnace and insufficient air temperature, severely impacting the safety and economic efficiency of boiler operation.
[0004] In order to alleviate or solve the problem of furnace coking in lean coal boilers after burning bituminous coal, the following two methods are commonly used: Method 1: Use refined combustion adjustment to reduce the occurrence of furnace coking. Due to the difference in fuel characteristics between lean coal and bituminous coal, there are also design differences in the boiler combustion system. Therefore, when a lean coal boiler burns bituminous coal, it is necessary to adjust the primary and secondary air rates, wind speed and air-coal ratio in the furnace to maintain the center of the flame in the middle and avoid the flame sticking to the wall; adjust the coal powder fineness, control the oxygen content, weaken the combustion intensity, reduce the furnace heat load, and thus alleviate furnace coking. However, this method needs to be repeatedly adjusted according to the unit's combustion conditions to the operating conditions suitable for each condition. The combustion adjustment has the disadvantage of poor flexibility and limited adjustment capabilities, and is only suitable for small-proportion blending; Method 2: Blackbody spraying technology is used to improve the performance of the heating surface itself to reduce furnace coking. Blackbody material with relatively low thermal conductivity is sprayed onto the water-cooled wall surface to improve the furnace's heat absorption capacity and reduce the risk of contamination and coking on the heating surface. However, this method has issues such as high technical costs and a short protection period. It does not fundamentally solve the boiler coking problem and is only suitable for small-scale blending. Summary of the Invention
[0005] The purpose of the present invention is to address the above-mentioned shortcomings of the prior art and provide a hedge boiler combustion system suitable for converting lean coal to bituminous coal. It can realize decentralized control of combustion flames and multi-stage graded combustion, effectively reduce the average temperature of flue gas in the main burner area of the furnace and control the overall heat load distribution of the furnace combustion area to be more uniform, thereby effectively preventing and controlling coking of the furnace water-cooled wall.
[0006] In order to achieve the above-mentioned purpose, the present invention is suitable for the combustion system of the hedge boiler for burning lean coal instead of bituminous coal, including secondary air boxes respectively arranged on the front and rear walls of the furnace, and the two secondary air boxes are divided into the uppermost burnout air chamber and the 3-5 layers of secondary air chambers below by several partitions, and each layer of air chamber is provided with air door baffles on both sides; the characteristics are as follows: the burnout air chamber is provided with 4-8 middle burnout air nozzles located in the upper layer and 2 side burnout air nozzles located in the lower layer; the lowermost secondary air chamber is provided with m swirl combustion nozzles The swirl burners in the secondary air chambers of the lowermost layer are arranged in a staggered manner with those in the secondary air chambers of the lowermost layer (4<m<10), and n swirl burners (3<n<9) are arranged in the secondary air chambers of the other layers, with m>n. The swirl burners in the secondary air chambers of the lowermost layer are arranged in a staggered manner in the horizontal direction, and each swirl burner is provided with a primary air duct. The swirl burners in the two second-layer secondary air chambers on the front and rear walls are arranged in a staggered manner in the height direction. The swirl burners in the secondary air chambers of the adjacent layers on the front and rear walls are arranged in a non-uniform spacing with respect to the height difference between the layers.
[0007] The present invention arranges multiple swirl burners in layers in the secondary air boxes on the front and rear walls, and sets the number of burners in each layer at intervals. The burners in the bottom layer are low-power burners, and the burners in the layers above them are high-power burners. The rated output ratio of the low-power burners to the high-power burners is 0.8. The number of burners in the bottom layer is greater than the number of burners in each layer above it and they are staggered in the horizontal direction. In addition, the height difference of the swirl burners in the secondary air chambers of the adjacent layers on the front and rear walls is arranged at non-uniform intervals, which can realize the dispersed control of the combustion flame and the multi-stage combustion, so that the furnace flame is more full and the heat load is more evenly distributed. The layered middle burnout air spray The swirl burners in the two second-layer secondary air chambers on the front and rear walls are staggered in height to enhance the flue gas entrainment disturbance in the main combustion area of the furnace, making the flue gas in the furnace evenly mixed, avoiding local high temperatures, and achieving uniform heat load distribution in the upper main burner area. The air dampers can then adjust the amount of hot air entering each layer of the air chamber, adjust the air distribution for combustion organizations with different loads, effectively reduce the average flue gas temperature in the main burner area of the furnace, and control the overall heat load distribution of the furnace combustion area to be more uniform, thereby effectively preventing and controlling coking of the furnace water-cooled wall. As a further improvement of the present invention, the outermost swirl burners in each layer of secondary air chamber above the lowest secondary air chamber on the front and rear walls are arranged inwardly, with an inward deflection angle α of 5 to 10 degrees. By deflecting the outermost swirl burners inward, the risk of combustion flames brushing the wall and the heat load in the side wall area can be reduced, thereby reducing the risk of coking of the side wall water-cooled wall. As a further improvement of the present invention, the height difference between the middle overburnt air nozzle and the swirl burner in the uppermost secondary air chamber, and the height difference between the swirl burners in two adjacent secondary air chambers from top to bottom, decrease successively; this can make the flue gas in the furnace more fully mixed and the heat load in the furnace more uniform; As a further improvement of the present invention, the height difference between the unequally spaced swirl burners in the secondary air chambers of adjacent layers on the front and rear walls is as follows: the interlayer spacing LB of the upper two layers of swirl burners is greater than the interlayer spacing LA of the upper two layers of swirl burners, and LB:LA = 1.2-1.5. This allows the combustion flame to be dispersed and burned in stages along the furnace height, resulting in more complete mixing of the flue gas in the furnace and further reducing the average flue gas temperature in the main burner area of the furnace. As a further improvement of the present invention, among the swirl burners in each layer of the secondary air chamber, the distance between the outermost swirl burner and the adjacent secondary air chamber side wall, the distance between the two outermost swirl burners, and the distance between the swirl burners located in the middle decrease in sequence; the distance between the flames of the burners on the same layer is increased from the middle to the outside, which can reduce the flue gas temperature level in the main burner area of the furnace and avoid the occurrence of local high-temperature areas; As a further improvement of the present invention, the two adjacent middle overburnt air nozzles and the two side overburnt air nozzles in each layer of the overburnt air chamber are swirl nozzles with opposite rotation directions; this can enhance the disturbance of the high-temperature flue gas in the furnace, make the mixing more intense, and make the combustion more complete; As a further improvement of the present invention, the rotation directions of the two adjacent swirl burners in each secondary air chamber are opposite, which can make the flame filling degree in the furnace more uniform and full; In summary, the present invention can realize the dispersed control of combustion flame and multi-stage graded combustion, effectively reduce the average temperature of flue gas in the main burner area of the furnace and control the overall heat load distribution of the furnace combustion area to be more uniform, thereby effectively preventing coking of the furnace water-cooled wall. BRIEF DESCRIPTION OF THE DRAWINGS
[0008] Figure 1 It is a front view of an embodiment of the present invention.
[0009] Figure 2 for Figure 1 P-direction view.
[0010] Figure 3 for Figure 1 Q-direction view.
[0011] Figure 4 for Figure 2 MM cross-sectional view.
[0012] Figure 5 for Figure 2 NN cross-sectional view. DETAILED DESCRIPTION
[0013] The present invention will be further described below with reference to the accompanying drawings.
[0014] like Figures 1 to 5 As shown, the embodiment is suitable for the combustion system of the counter-fired boiler for burning lean coal instead of bituminous coal, comprising secondary air boxes 2 and 3 respectively arranged on the front and rear walls of the furnace 1. The two secondary air boxes 2 and 3 are divided into an uppermost burnout air chamber 5 and three lower secondary air chambers 6, 7, and 8 by three partitions 4. Both sides of each air chamber are provided with air dampers 13. The burnout air chamber 5 is provided with four middle burnout air nozzles 9 located in the upper layer and two side burnout air nozzles 10 located in the lower layer. The two adjacent middle burnout air nozzles 9 and the two adjacent side burnout air nozzles 10 are swirl nozzles with opposite rotation directions, i.e., respectively. Clockwise and counterclockwise swirl nozzles; the bottom secondary air chamber 8 is provided with five swirl burners 12, the rotation directions of the adjacent swirl burners 12 are opposite, the other two layers of secondary air chambers 6, 7 are provided with four swirl burners 11, the rotation directions of the adjacent swirl burners 11 in the same layer are opposite, that is, clockwise and counterclockwise swirl burners respectively; the swirl burners 12 in the bottom secondary air chamber and the swirl burners 11 in the other two layers of secondary air chambers 6, 7 are staggered in the horizontal direction, and each swirl burner 11, 12 is provided with a primary air duct and a secondary Air distribution device; the swirl burners 11 in the two second-layer secondary air chambers 7 on the front and rear walls are staggered in height, with a height difference L2 of 1.5-4 meters; the outermost swirl burners 11 in the two-layer secondary air chambers 6 and 7 are arranged inwardly, with an inward deflection angle α = 5-10 degrees; the height difference LC between the middle burnout air nozzle 9 and the swirl burner 11 in the uppermost secondary air chamber 6, and the height differences LB and LA of the swirl burners in the two adjacent layers of secondary air chambers from top to bottom decrease in sequence, that is, LC>LB>LA, and LB:LA=1.2-1.5 ; Among the swirl burners 11 in the secondary air chambers 6 and 7, the distance L33 between the outermost swirl burner and the adjacent secondary air chamber side wall, the distance L31 between the two outermost swirl burners, and the distance L32 between the swirl burners located in the middle decrease successively, that is, L33>L31>L32; among the swirl burners 12 in the secondary air chamber 8, the distance L53 between the outermost swirl burner and the adjacent secondary air chamber side wall, the distance L51 between the two outermost swirl burners, and the distance L52 between the swirl burners located in the middle decrease successively, that is, L53>L51>L52.
[0015] The present invention arranges multiple swirl burners in layers in the secondary wind boxes 2 and 3 on the front and rear walls, and sets the number of burners in each layer at intervals. The burners 12 in the bottom layer are low-power burners, and the burners 11 in the layers above them are high-power burners. The rated output ratio of the low-power burners to the high-power burners is 0.8. The convection in the lower part of the furnace is weak. The number of burners 12 in the bottom layer is greater than the number of burners 11 in each layer above them and they are staggered in the horizontal direction. This can achieve flame dispersion control and multi-stage combustion, making the furnace flame fullness higher and the heat load distribution more uniform. The layered middle burnout air nozzle 9 and the two side burnout air nozzles 10 can enhance the high-temperature flue gas entrainment disturbance, promote the combustion of coal powder and enhance the reduction of nitrogen oxides. In addition, the front and rear burners are equipped with a plurality of swirl burners. The swirl burners 11 in the two second-layer secondary air chambers 7 on the wall are staggered in height, and the height difference between the layers is LC>LB>LA, and LB:LA=1.2~1.5. This not only avoids the fierce collision of the burner flames, but also strengthens the flue gas entrainment disturbance in the main combustion area of the furnace, and disperses the combustion flames along the furnace height and burns in stages, so that the flue gas in the furnace is mixed more fully and evenly, avoiding local high temperature and achieving uniform heat load distribution in the upper main burner area. The air dampers 13 can then adjust the amount of hot air entering the air chambers on each layer, adjust the air distribution for combustion organizations with different loads, effectively reduce the average temperature of the flue gas in the main burner area of the furnace, and control the overall heat load distribution of the furnace combustion area to be more uniform, thereby effectively preventing and controlling coking of the furnace water-cooled wall. The outermost swirl burners 11 in the secondary air chambers 6 and 7 are arranged inwardly to reduce the risk of flame brushing the wall and the heat load in the side wall area, thereby reducing the risk of coking on the side wall water-cooled wall. By arranging the spacings L33>L31>L32 and L53>L51>L52, the distance between the flames of the burners on the same layer is widened from the middle to the outside, which can reduce the flue gas temperature level in the main burner area of the furnace and avoid the occurrence of local high temperature areas; The two adjacent middle burnout air nozzles 9 and the two side burnout air nozzles 10 in each burnout air chamber 5 are swirl nozzles with opposite rotation directions, which can enhance the disturbance of the high-temperature flue gas in the furnace, make the mixing more intense, and make the combustion more complete; The rotation directions of the two adjacent swirl burners 11 or 12 in each layer of secondary air chamber 6, 7, 8 are opposite, which can make the flame filling degree in the furnace more uniform and full; The above embodiments have been used for illustration, but it should be understood that the above embodiments are only for the purpose of example and description, and are not intended to limit the present invention to the scope of the described embodiments; for example, the number of layers of secondary air chambers and the number of swirl burners in each layer of secondary air chambers can be adjusted.
Claims
1. A combustion system for an opposed boiler suitable for switching from lean coal to bituminous coal, comprising secondary air boxes respectively located on the front and rear walls of the furnace, each of which is divided by a plurality of partitions into a top burnout air chamber and three to five lower secondary air chambers, each air chamber being provided with dampers on both sides; and characterized by: Each burnout air chamber is provided with 4-8 middle burnout air nozzles located on the upper layer and 2 side burnout air nozzles located on the lower layer; each of the secondary air chambers on the lowest layer is provided with m swirl burners (4<m<10), and each of the secondary air chambers on the remaining layers is provided with n swirl burners (3<n<9), and m>n. The swirl burners in the secondary air chamber on the lowest layer and the swirl burners in the secondary air chambers on the remaining layers are staggered in the horizontal direction, and each swirl burner is provided with a primary air duct; the swirl burners in the two second-layer secondary air chambers on the front and rear walls are staggered in height; the height difference between the swirl burners in the secondary air chambers on the adjacent layers on the front and rear walls is non-uniform.
2. The counter-fire boiler combustion system suitable for switching from lean coal to bituminous coal according to claim 1, characterized in that: The outermost swirl burners in the secondary air chambers of each layer above the lowest secondary air chamber on the front and rear walls are arranged to be deflected inwards, and the inward deflection angle α is 5-10 degrees.
3. The counter-fire boiler combustion system suitable for switching from lean coal to bituminous coal according to claim 1 or 2, characterized in that: The height difference between the middle overburnt air nozzle and the swirl burner in the uppermost secondary air chamber, and the height difference between the swirl burners in two adjacent secondary air chambers from top to bottom decrease in sequence.
4. The counter-fire boiler combustion system suitable for switching from lean coal to bituminous coal according to claim 1, characterized in that: The height difference of the inter-layer spacing of the swirl burners arranged at non-uniform intervals in the secondary air chambers of adjacent layers on the front and rear walls is as follows: the inter-layer spacing LB of the upper two layers of swirl burners is greater than the inter-layer spacing LA of the upper two layers of swirl burners, and LB:LA=1.2~1.
5.
5. The counter-fire boiler combustion system suitable for switching from lean coal to bituminous coal according to claim 3, characterized in that: Among the swirl burners in each layer of the secondary air chamber, the distance between the outermost swirl burner and the adjacent secondary air chamber side wall, the distance between the two outermost swirl burners, and the distance between the swirl burners in the middle decrease in sequence.
6. The counter-fire boiler combustion system suitable for switching from lean coal to bituminous coal according to claim 5, characterized in that: The two adjacent middle overburnt air nozzles and the two side overburnt air nozzles in each layer of the overburnt air chamber are all swirl nozzles with opposite rotation directions.
7. The counter-fire boiler combustion system suitable for switching from lean coal to bituminous coal according to claim 6, characterized in that: The rotation directions of the two adjacent swirl burners in each layer of the secondary air chamber are opposite.