Low-nitrogen combustion method for coal water slurry boiler

Abstract

A low-nitrogen combustion method of a coal water slurry boiler, relates to a coal water slurry boiler, which comprises a boiler body, and a burner and a cold wall pipe are arranged on the boiler body, and the combustion method comprises the following steps: opening the primary air door of at least two burners fully, and opening the primary air door of at least two burners by 30-90%; the flame of the two burners opened fully is close to the cold wall pipe area on both sides of the furnace; so that the flame ignition positions are staggered; and the secondary air door of the four burners is fully opened. According to the practice operation, the combination of the two can inhibit the generation of about 30% of NOx.

Description

TECHNICAL FIELD

[0001] The present application relates to a water coal slurry boiler combustion method. BACKGROUND

[0002] Nitrogen oxides (NOx) are one of the main atmospheric pollutants, mainly in the form of NO and NO2 equilibrium in the atmosphere. Nitrogen oxides can cause a variety of respiratory diseases, and are one of the main pollutants that form optical smog and acid rain. Therefore, the treatment of nitrogen oxides has become a very important task in the current environmental protection. Petroleum, coal, gas and other fuel combustion will produce thermal nitrogen oxides.

[0003] Water coal slurry boiler low-nitrogen combustion technology is an important branch of NOx control technology, and the water coal slurry boiler suspension combustion mechanism is as follows: the water coal slurry and air enter the furnace through the burner in the form of jet, and the outer recirculation air and the inner recirculation air generated by the rotating jet or the bluff body flame stabilizer suck the surrounding high-temperature flue gas, so that the coal slurry gas flow and the hot flue gas are mixed strongly, and the water is evaporated quickly; at the same time, the water coal slurry gas flow is subjected to radiation from the furnace wall and the high-temperature flame, and the coal particles suspended in the gas flow are heated quickly, and the water coal slurry particles obtain enough heat and reach a certain temperature to start fire and combustion. The ignition heat changes with the fuel properties and operating conditions, and when the boiler load decreases, the average flue gas temperature in the furnace decreases, and the flue gas temperature in the burner area also decreases, which is not conducive to the ignition of the water coal slurry. Therefore, the minimum operating load of the solid slag water coal slurry boiler with atomization combustion is about 40%, otherwise, the stability of the ignition combustion will be endangered, and even the fire will be extinguished; the slurry supply pressure of this combustion method is about 1.2 MPa, and the atomized compressed air pressure is 0.7-0.8 MPa.

[0004] The water coal slurry boiler has been a research topic for researchers in the field to inhibit the generation of nitrogen oxides. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a water coal slurry boiler low-nitrogen combustion method for improving the combustion mode of the boiler body in view of the above technical status.

[0006] The technical scheme adopted by the present application to solve the above technical problem is as follows: a water coal slurry boiler low-nitrogen combustion method, the water coal slurry boiler involved includes a boiler body, the boiler body is provided with a burner and a cold wall pipe, the inside of the boiler body forms a furnace, the burner is at least four, divided into two rows, at least two in each row, the burner is arranged on one side of the boiler body, each burner has a primary air door for ignition and air distribution and a secondary air door for boiler combustion air distribution, and the cold wall pipe is arranged on the side wall of the boiler body and away from the burner; characterized in that the combustion method comprises the following steps:

[0007] ① At least two burners' primary air damper is fully opened, and another at least two burners' primary air damper is opened 30-90%; so that the flame ignition position is staggered; the secondary air damper of the burners is fully opened;

[0008] ② The two burners with fully opened flame are close to the cold wall tube of the two sides of the furnace.

[0009] Further, the two burners' primary air damper in step ① is fully opened, and the operation is as follows: when the boiler load is >60%, the two burners' primary air damper is fully opened at one time; if the boiler load is <60%, the primary air damper is slowly opened and adjusted and the combustion stability is observed before the full opening is completed step by step.

[0010] It also includes step ③ that a part of the flue gas of the water coal slurry boiler's dust collector is extracted and mixed with hot air to be sent into the furnace. A part of the flue gas not only can reduce the combustion temperature, but also can reduce the oxygen concentration, and further reduce the generation concentration of NOx.

[0011] As a preferred, the part of the flue gas accounts for 10-20% of the total flue gas.

[0012] Compared with the prior art, the advantages of the present application are that the flame ignition position is staggered, so as to prevent the flame from gathering and the combustion temperature from rising to cause the sharp generation of NOx; the generated combustion temperature can immediately absorb heat through the cold wall tube to quickly reduce the combustion point temperature, so as to inhibit the generation of NOx; according to the practical operation, the combination of the two can inhibit the generation of about 30% of NOx. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of the embodiment.

[0014] Figure 2 It is Figure 1 It is a three-dimensional structural schematic diagram of the boiler body. DETAILED DESCRIPTION

[0015] The present application will be further described in detail below in combination with the embodiment and the drawings.

[0016] In combination Figure 1 and Figure 2 shown, the water coal slurry boiler process includes a boiler body 1, an SCR (denitration) reactor 2, an air preheater 3, a dust collector 4, a desulfurization tower 7, a wet electric dust collector 8 and a chimney 9. A part of the tail gas from the dust collector 4 returns to the furnace through a recirculation fan 5, and most of it is discharged from the chimney 9 after being desulfurized and dusted by an induced draft fan 6.

[0017] The boiler body 1 is provided with burners 11 and cold wall pipes 12, and a hearth is formed inside the boiler body 1. The burners 11 are four in number, arranged in two rows, two in each row, and are arranged on one side of the boiler body 1. Each burner 11 is provided with a primary air door 111 for ignition and air distribution, and a secondary air door 112 for boiler combustion air distribution. When the primary air door 111 is opened, the ignition point of the coal water slurry is lengthened, and the flame is pushed backward. The secondary air door 112 is used for boiler combustion air distribution, and the coal water slurry is normally sprayed and burned. The cold wall pipes 12 are arranged on the side wall of the boiler body 1 and are arranged away from the burners 11. The boiler body 1 is not provided with cold wall pipes 12 on the side where the burners 11 are arranged. The cold wall pipes 12 can be water-cooled or oil-cooled.

[0018] The combustion method comprises the following steps:

[0019] The primary air doors 111 of two burners 11 are fully opened, and the primary air doors 111 of the other two burners 11 are opened by 30-90%. The flame ignition positions are staggered. The flames of the two burners 11 that are fully opened are close to the cold wall pipes 12 on both sides of the hearth. The secondary air doors 112 of the four burners 11 are fully opened. The flame ignition positions are staggered to prevent the flames from gathering and the combustion temperature from rising, which would cause the rapid generation of NOx. The generated combustion temperature would immediately absorb heat through the cold wall pipes to rapidly reduce the combustion point temperature, thereby inhibiting the generation of NOx.

[0020] A part of the flue gas of the dust collector of the coal water slurry boiler is extracted and mixed with hot air to be sent into the hearth. In this embodiment, the volume percentage of the part of the flue gas is 10-20% of the total flue gas, which can replace 30% of the hot air. Not only can the combustion temperature be reduced, but also the oxygen concentration is reduced, thereby reducing the concentration of the generated NOx.

[0021] The primary air doors 111 of two burners 11 are fully opened in step ①, and the operation is as follows: when the boiler load is >60%, the primary air doors 111 of two burners 11 are fully opened at one time. If the boiler load is <60%, the primary air doors 111 are slowly opened and adjusted, and the combustion stability is observed before the primary air doors 111 are fully opened.

[0022] This embodiment is more suitable for a boiler with four or more burners 11 for coal water slurry suspension (atomization) combustion.

Claims

1. A low-nitrogen combustion method for a coal-water slurry boiler, the coal-water slurry boiler comprising a boiler body, wherein the boiler body is provided with burners and cold wall pipes, the inside of the boiler body forms a furnace, the burners are four, two in each of the upper and lower rows, the burners are arranged on one side of the boiler body, each burner is provided with a primary air door for ignition and air distribution and a secondary air door for boiler combustion and air distribution, and the cold wall pipes are arranged on the side wall of the boiler body and away from the burners; characterized in that The combustion method comprises the following steps: Two burners are fully opened, and the other two burners are opened by 30%-90%; the flame ignition positions are staggered, the flames of the two fully opened burners are close to the cold wall pipe area on both sides of the furnace; the secondary air doors of the burners are fully opened; The two burners are fully opened, and the operation is as follows: when the boiler load is greater than 60%, the primary air doors of the two burners are fully opened at one time; if the boiler load is less than 60%, the primary air doors are slowly opened and adjusted, and the combustion stability is observed before the primary air doors are fully opened step by step.

2. The low NOx combustion method for a coal water slurry boiler according to claim 1, characterized by The method further comprises the following steps: a part of flue gas in the dust remover of the coal water slurry boiler is extracted, mixed with hot air, and then sent into the furnace.

3. The method of low NOx combustion for a coal water slurry boiler according to claim 1, characterized in that The part of flue gas accounts for 10%-20% of the total flue gas.

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