Denitration low-oxygen afterburning device of circulating fluidized bed boiler

Abstract

The utility model relates to a denitration low-oxygen afterburning device of a circulating fluidized bed boiler, and belongs to the field of circulating fluidized bed boilers. Comprising a low-oxygen afterburning spray pipe arranged at an inlet of a boiler center cylinder, the low-oxygen afterburning spray pipe enters a separator from an opening in the wall of the separator to the inlet of the boiler center cylinder, the low-oxygen afterburning spray pipe and the radial center line of the boiler center cylinder are concentrically or tangentially arranged, and the low-oxygen afterburning spray pipe is in lap joint with the lower edge of the boiler center cylinder; an SNCR reducing agent spraying gun is installed in the low-oxygen afterburning spraying pipe, and the tail end of the SNCR reducing agent spraying gun is connected with a compressed air pipeline and an SNCR reducing agent supply pipeline. According to the utility model, the CO content in boiler flue gas and the carbon content in fly ash are reduced, the heat efficiency of the boiler is improved, and the physical and chemical incomplete combustion heat loss is reduced. And the denitration efficiency of the SNCR denitration system can be improved, and the emission concentration of NOX pollutants in boiler flue gas can be reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to a circulating fluidized bed boiler denitration low oxygen supplementary combustion device belongs to circulating fluidized bed boiler field. BACKGROUND

[0002] Circulating fluidized bed boiler technology is a kind of high-efficiency low-pollution clean coal boiler that has developed rapidly in recent ten years, as an important representative of clean coal technology, it can realize direct desulfurization in the combustion process in the furnace, and due to its low-temperature staged combustion (about 900 DEG C), it can effectively inhibit the emission of nitrogen oxides, so it is widely used in industrial production enterprises, but in the actual operation process, some boilers have the problems of low SNCR denitration efficiency, the NO X emission concentration in the boiler flue gas cannot reach the ultra-low emission standard, and because the fuel of the circulating fluidized bed boiler is suspended in the furnace for combustion, the combustion is carried out in space, the flow rate is much higher than that of the usual layer combustion furnace, the combustible gas separated from small particle fuel and high volatile fuel flows rapidly with the flue gas and is quickly discharged from the combustion zone of the boiler, and the residence time in the boiler combustion zone is short, so it is difficult to fully burn, in order to reduce the NO X emission concentration of the circulating fluidized bed boiler and make the boiler flue gas meet the emission standard, it is often necessary to increase the injection amount of reducing agent, reduce the calorific value of coal and the amount of primary and secondary air, and operate at a low excess air ratio to reduce the bed temperature and the NO X emission concentration, and the above measures will cause scaling and plugging at the air preheater of the boiler, reduce the thermal efficiency of the boiler, increase the carbon content of fly ash, and increase the CO emission concentration, which reduces the economic efficiency of the boiler operation, threatens the long-period operation of the boiler, and according to the coal quality requirements of the local government in some places, the calorific value of coal used in power station boilers and industrial boilers should be greater than or equal to 21.74 MJ / Kg (5200 large cards), due to the problem of fuel adaptability, this will greatly increase the combustible content of fly ash and the CO content in flue gas of the circulating fluidized bed boiler, and increase the physical and chemical incomplete combustion heat loss.

[0003] At present, there are many methods for low-nitrogen combustion modification of circulating fluidized bed boilers, such as improving the separation efficiency by adopting a cyclone separator, low particle size modification by adopting a coal crusher, air distribution plate modification, secondary air modification, return material device modification, and use of fly ash afterburning system, etc., which have achieved certain effects, the purpose of the above modification methods is to improve the circulating ratio of the circulating fluidized bed, increase the material concentration in the furnace and the heat transfer efficiency, reduce the combustion temperature in the dense phase zone of the circulating fluidized bed boiler, increase the temperature at the upper part of the furnace, reduce the temperature difference between the upper and lower parts of the furnace, move the combustion area of the boiler backward, reduce the total air consumption of the boiler, and reduce the excess air ratio to achieve the purpose of inhibiting the generation of NO X Through the above modification, the combustion area of the boiler can continue to the inlet or even the outlet of the central cylinder of the cyclone separator.

[0004] It is found through experiments that the SNCR denitration efficiency of the boiler after low-nitrogen combustion modification is obviously reduced, and the main reason is that the combustion area of the boiler is moved backward, the SNCR reducing agent injection position of the traditional circulating fluidized bed boiler is arranged at the upper part of the boiler furnace or the outlet part of the boiler furnace, that is, the accelerating section position of the cyclone separator inlet, and the reducing agent injection arrangement area of the boiler furnace outlet can process all the flue gas because the combustion area of the boiler without low-nitrogen combustion modification is located at the middle and lower part of the furnace, but the SNCR denitration system of part of the circulating fluidized bed boilers after low-nitrogen combustion modification cannot process part of the flue gas because the combustion area of the boiler after low-nitrogen combustion modification is moved to the rear of the reducing agent injection arrangement area, and the reaction time of the SNCR denitration reaction is short, so that the SNCR denitration efficiency of the SNCR denitration system of part of the circulating fluidized bed boilers after low-nitrogen combustion modification is reduced. SUMMARY

[0005] According to the problems described in the background, the problems to be solved by the utility model are:

[0006] How to ensure that the SNCR denitration efficiency of the boiler will not be reduced while low-nitrogen combustion is carried out.

[0007] In order to achieve the above-mentioned purpose, the utility model provides the following technical scheme:

[0008] A circulating fluidized bed boiler denitration low-oxygen supplementary combustion device, comprising a low-oxygen supplementary combustion nozzle arranged at the inlet of a boiler center cylinder, wherein the low-oxygen supplementary combustion nozzle enters the cyclone separator from the opening on the wall of the cyclone separator to the inlet of the boiler center cylinder, the low-oxygen supplementary combustion nozzle is arranged concentrically or tangentially with the radial center line of the boiler center cylinder and is overlapped with the lower edge of the boiler center cylinder, the low-oxygen supplementary combustion nozzle is connected with the primary hot air duct through a supplementary air pipeline, the control valve is arranged on the supplementary air pipeline, the SNCR reducing agent injection lance is arranged in the low-oxygen supplementary combustion nozzle, the tail end of the SNCR reducing agent injection lance is connected with the compressed air pipeline and the SNCR reducing agent supply pipeline respectively, the low-oxygen supplementary combustion nozzle is provided with a supplementary combustion nozzle head, a connecting pipeline, a water cooling layer, a refractory nail and a wear-resistant layer, the end of the connecting pipeline close to the boiler center cylinder is connected with the supplementary air pipeline, and the other end of the connecting pipeline is connected with the supplementary combustion nozzle head, the water cooling layer adopts a coil type and is sleeved outside the connecting pipeline and the low-oxygen supplementary combustion nozzle, the water cooling layer is wrapped by the wear-resistant layer, the wear-resistant layer is fixed by the refractory nail, and the water cooling layer participates in the natural circulation of the boiler water.

[0009] Preferably, the connecting pipeline has one or more than one.

[0010] Preferably, the low-oxygen supplementary combustion nozzle has one or more than one.

[0011] The combustion-supporting air from the primary hot air passage of the boiler enters the low-oxygen combustion-supporting nozzle through the air-supplying pipeline, is injected into the inside of the boiler central cylinder, is fully mixed with the boiler flue gas under the joint action of the high-speed rotating airflow and the injection airflow in the inside of the boiler central cylinder, and generates an oxygen-rich area in the inside space of the boiler central cylinder, so that the small particulate fuel and the combustible gas entrained in the boiler flue gas are fully combusted, the CO content and the carbon content of the fly ash in the boiler flue gas are reduced, the thermal efficiency of the boiler is improved, and the physical and chemical incomplete combustion heat loss is reduced.

[0012] The reducing agent of the SNCR denitration system of the boiler is injected into the inside of the boiler central cylinder through the reducing agent injection lance arranged in the low-oxygen combustion-supporting nozzle, is fully mixed with the boiler flue gas under the joint action of the high-speed rotating airflow and the reducing agent injection airflow in the inside of the boiler central cylinder, and is beneficial to the full mixing of the boiler flue gas and the reducing agent of the SNCR system and the improvement of the denitration efficiency of the SNCR denitration system, and the reduction of the NO X Pollutant emission concentration.

[0013] The low-oxygen combustion-supporting nozzle is provided with a combustion-supporting nozzle head, a connecting pipeline, a water cooling layer, a refractory nail and a wear-resistant layer, the connecting pipeline plays a supporting and connecting role, the water cooling layer plays a cooling role, the refractory nail plays a role of fixing the water cooling layer and the wear-resistant layer, and the wear-resistant layer plays a role of preventing the connecting pipeline and the water cooling layer from being worn.

[0014] The utility model discloses the beneficial effect is:

[0015] The utility model discloses reduce the CO content and the carbon content of fly ash in the boiler flue gas, improve the thermal efficiency of the boiler, reduce the physical and chemical incomplete combustion heat loss. X Pollutant emission concentration. DRAWINGS

[0016] Figure 1 It is the schematic diagram of the utility model

[0017] Figure 2 It is the partial enlarged view of the schematic diagram

[0018] Figure 3 It is the schematic diagram of the low-oxygen combustion-supporting nozzle

[0019] In the figure: 1 is the boiler center tube; 2 is the low oxygen afterburning nozzle; 3 is the control valve; 4 is the air supplement pipeline; 5 is the primary hot air duct; 6 is the SNCR reducing agent injection lance; 7 is the compressed air pipeline; 8 is the SNCR reducing agent supply pipeline; 9 is the afterburning nozzle; 10 is the connecting pipeline; 11 is the water cooling layer; 12 is the refractory nail; 13 is the wear-resistant layer; 14 is the separator. DETAILED DESCRIPTION

[0020] Embodiment 1

[0021] A circulating fluidized bed boiler denitration low oxygen afterburning device, comprising a low oxygen afterburning nozzle 2 arranged at the inlet of a boiler center tube 1, wherein the low oxygen afterburning nozzle 2 is arranged concentrically or tangentially with the radial center line of the boiler center tube 1 and overlaps with the lower edge of the boiler center tube 1, and opens into the separator 14 from the wall of the separator 14 to the inlet of the boiler center tube 1; the low oxygen afterburning nozzle 2 is connected with the primary hot air duct 5 through an air supplement pipeline 4, and the air supplement pipeline 4 is provided with a control valve 3; the low oxygen afterburning nozzle 2 is internally provided with an SNCR reducing agent injection lance 6, and the tail end of the SNCR reducing agent injection lance 6 is respectively connected with a compressed air pipeline 7 and an SNCR reducing agent supply pipeline 8; the low oxygen afterburning nozzle 2 is provided with an afterburning nozzle 9, a connecting pipeline 10, a water cooling layer 11, a refractory nail 12 and a wear-resistant layer 13; the low oxygen afterburning nozzle 2 is provided with the afterburning nozzle 9 near one end of the boiler center tube 1; one end of the connecting pipeline 10 is connected with the air supplement pipeline 4, and the other end is connected to the afterburning nozzle 9; the water cooling layer 11 adopts a coil type and is sleeved outside the connecting pipeline 10 and the low oxygen afterburning nozzle 2; the wear-resistant layer 13 wraps the water cooling layer 11, and the wear-resistant layer 13 is fixed by the refractory nail 12; and the water cooling layer 11 participates in the natural circulation of boiler water.

[0022] The connecting pipeline 10 has one or more than one.

[0023] The low oxygen afterburning nozzle 2 is provided with one or more.

[0024] The utility model reduces the CO content and the carbon content of fly ash in the boiler flue gas, improves the thermal efficiency of the boiler, reduces the physical and chemical incomplete combustion heat loss, is favorable for improving the denitration efficiency of the SNCR denitration system, reducing the NOx X pollutant emission concentration in the boiler flue gas.

Claims

1. A circulating fluidized bed boiler denitrification low oxygen supplementary combustion device, characterized in that: The invention comprises a low oxygen supplementary combustion nozzle (2) arranged at the inlet of the boiler central tube (1), wherein the low oxygen supplementary combustion nozzle (2) enters the separator (14) from the opening on the wall of the separator (14) to the inlet of the boiler central tube (1), and the low oxygen supplementary combustion nozzle (2) is concentrically or tangentially arranged with the radial center line of the boiler central tube (1) and overlaps with the lower edge of the boiler central tube (1); the low oxygen supplementary combustion nozzle (2) is connected to the primary hot air duct (5) through the air supply pipe (4), and the air supply pipe (4) is provided with a control valve (3); an SNCR reducing agent injection gun (6) is installed inside the low oxygen supplementary combustion nozzle (2), and the ends of the SNCR reducing agent injection gun (6) are respectively connected to the compressed air pipe (7) and An SNCR reducing agent supply pipeline (8) is provided, wherein the low-oxygen supplementary combustion nozzle (2) is provided with a supplementary combustion nozzle (9), a connecting pipeline (10), a water-cooling layer (11), a refractory nail (12) and a wear-resistant layer (13); the low-oxygen supplementary combustion nozzle (2) is provided with a supplementary combustion nozzle (9) at one end close to the boiler center tube (1); one end of the connecting pipeline (10) is connected to the air supply pipeline (4), and the other end is connected to the supplementary combustion nozzle (9); the water-cooling layer (11) is a coil type and is coiled on the outside of the connecting pipeline (10) and the low-oxygen supplementary combustion nozzle (2); the wear-resistant layer (13) wraps the water-cooling layer (11); the wear-resistant layer (13) is fixed by a refractory nail (12); and the water-cooling layer (11) participates in the natural circulation of boiler water.

2. A circulating fluidized bed boiler denitrification low-oxygen post-combustion device according to claim 1, characterized in that: There is one or more connecting pipelines (10).

3. The circulating fluidized bed boiler denitrification and low-oxygen post-combustion device according to claim 1, characterized in that: The low-oxygen supplementary combustion nozzle (2) is provided with one or more.

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