阅读说明：本技术 一种用于低氮锅炉上的烟气再循环系统 (Flue gas recirculation system for low-nitrogen boiler ) 是由 常栩生 谭超 陶思凡 于 2019-10-31 设计创作，主要内容包括：本发明涉及一种用于低氮锅炉上的烟气再循环系统,包括风机、燃烧器、锅炉、省煤器,所述风机的空气入口处连接有混合筒,所述锅炉的烟气出口管线上设有烟气循环管道,该烟气循环管道与所述混合筒连接；所述烟气循环管道上设有流量调节机构；该流量调节机构包括平行于所述烟气循环管道的横截面的中轴线上的转轴、与所述烟气循环管道的横截面匹配的挡板、以及控制所述转轴轴向旋转的伺服电机；所述转轴的两端穿过所述烟气循环管道管壁上的两个位置对应的圆孔,所述挡板置于烟气循环管道内部。与现有技术相比,本发明具有烟气循环量调节准确方便,有效降低氮氧化物排放值等优点。(The invention relates to a flue gas recirculation system for a low-nitrogen boiler, which comprises a fan, a combustor, a boiler and an economizer, wherein an air inlet of the fan is connected with a mixing cylinder, a flue gas outlet pipeline of the boiler is provided with a flue gas circulation pipeline, and the flue gas circulation pipeline is connected with the mixing cylinder; the flue gas circulating pipeline is provided with a flow regulating mechanism; the flow regulating mechanism comprises a rotating shaft, a baffle plate and a servo motor, wherein the rotating shaft is parallel to the central axis of the cross section of the flue gas circulating pipeline, the baffle plate is matched with the cross section of the flue gas circulating pipeline, and the servo motor controls the rotating shaft to rotate axially; the two ends of the rotating shaft penetrate through the round holes corresponding to the two positions on the pipe wall of the flue gas circulation pipeline, and the baffle is arranged inside the flue gas circulation pipeline. Compared with the prior art, the invention has the advantages of accurate and convenient adjustment of the flue gas circulation amount, effective reduction of the emission value of nitrogen oxides and the like.)

1. A flue gas recirculation system used on a low-nitrogen boiler comprises a fan (3), a burner (4), a boiler (1) and an economizer (5), and is characterized in that,

the air inlet of the fan (3) is connected with a mixing drum (2), a flue gas circulating pipeline (13) is arranged on a flue gas outlet pipeline of the boiler (1), and the flue gas circulating pipeline (13) is connected with the mixing drum (2); a flow regulating mechanism is arranged on the flue gas circulating pipeline (13); the flow regulating mechanism comprises a rotating shaft, a baffle plate (6) and a servo motor (8), wherein the rotating shaft is parallel to the central axis of the cross section of the flue gas circulating pipeline (13), the baffle plate (6) is matched with the cross section of the flue gas circulating pipeline (13), and the servo motor controls the rotating shaft to rotate axially; two ends of the rotating shaft penetrate through two round holes corresponding to the two positions on the pipe wall of the smoke circulating pipeline (13), and the baffle (6) is arranged inside the smoke circulating pipeline (13).

2. The flue gas recirculation system for a low-nitrogen boiler according to claim 1, wherein the flue gas recirculation pipe (13) is a circular pipe, and the baffle (6) is a circular baffle.

3. The flue gas recirculation system for the low-nitrogen boiler according to claim 1, wherein the casing of the servo motor (8) is fixed outside the pipe wall of the flue gas recirculation pipe (13), and the output shaft of the servo motor (8) is connected with the rotating shaft.

4. The flue gas recirculation system for a low-nitrogen boiler according to claim 1, wherein a connecting rod (9) is fixed on a rotating shaft outside the flue gas recirculation pipe (13), and the connecting rod (9) is perpendicular to the rotating shaft; a connecting bolt (10) is fixed below the end part of the connecting rod (9), and the connecting bolt (10) is parallel to the rotating shaft; the smoke circulating pipeline (13) is fixedly connected with a fan-shaped connecting plate (12), and the surface of the fan-shaped connecting plate (12) is provided with a strip-shaped through hole (14) which is arranged along the arc direction of a fan shape; the connecting bolt (10) penetrates through the long strip-shaped through hole (14) and is fixed on the fan-shaped connecting plate (12) through matched nuts (11) positioned on the upper surface and the lower surface of the fan-shaped connecting plate (12).

5. The flue gas recirculation system for the low-nitrogen boiler is characterized in that the two sets of the fan (3), the burner (4), the boiler (1), the economizer (5) and the flue gas circulation pipe (13) are arranged symmetrically.

6. The flue gas recirculation system for the low-nitrogen boiler according to claim 1, wherein the flow regulating mechanism is arranged at one end of the flue gas recirculation pipe (13) close to the mixing drum (2).

7. The flue gas recirculation system for the low-nitrogen boiler as recited in claim 1, wherein the flue gas recirculation pipe (13) is provided with an insulating layer.

8. The flue gas recirculation system for the low-nitrogen boiler is characterized by further comprising a PLC (programmable logic controller), wherein a nitrogen oxide sensor is arranged on a smoke exhaust pipeline of the boiler (1), and the PLC is in signal connection with the servo motor (8) and the nitrogen oxide sensor.

9. The flue gas recirculation system for the low-nitrogen boiler is characterized in that an air inlet of the mixing drum (2) is connected with an air heater, a tube side of the air heater is filled with air, a shell side inlet of the air heater is connected with a water outlet pipe of the boiler (1), and a shell side outlet of the air heater is connected with a water inlet pipe of the boiler (1).

Technical Field

The invention relates to the field of heat energy power and boilers, in particular to a flue gas recirculation system for a low-nitrogen boiler.

Background

In order to effectively control the emission of nitrogen oxides of a gas boiler and reduce the secondary generation of PM2.5, the emission standard of nitrogen oxides in boiler flue gas is not higher than 50 mg/cubic meter in many areas, and the emission temperature of the boiler flue gas is preferably lower than 110 ℃. Most of the existing boiler emission standards can not reach the emission standards specified in the latest regions, the exhaust gas temperature is difficult to be reduced below the standard value, the most basic technology at present is to integrally replace a boiler or a burner, and on the one hand, the reconstruction cost of the integral replacement equipment facility is high, and the construction period is long; on the other hand, the exhaust gas temperature of the boiler is too high, which causes waste of heat energy. In addition, the flue gas circulation volume of the existing boiler cannot be flexibly adjusted in the circulating device, the flue gas circulation volume cannot be adaptively adjusted according to different emission standards, or some circulating devices adjust the circulating flue gas volume through butterfly valves, but the butterfly valves are poor in adjustment accuracy, the valves with high accuracy are expensive, and the economical and practical requirements cannot be met.

Disclosure of Invention

The invention aims to overcome the defect of difficult flue gas quantity regulation in the prior art and provide a flue gas recirculation system which is easy to regulate flue gas and is used for a low-nitrogen boiler.

The purpose of the invention can be realized by the following technical scheme:

a flue gas recirculation system for a low-nitrogen boiler comprises a fan, a burner, a boiler and an economizer, wherein an air inlet of the fan is connected with a mixing cylinder, a flue gas outlet pipeline of the boiler is provided with a flue gas circulation pipeline, and the flue gas circulation pipeline is connected with the mixing cylinder; the flue gas circulating pipeline is provided with a flow regulating mechanism; the flow regulating mechanism comprises a rotating shaft, a baffle plate and a servo motor, wherein the rotating shaft is parallel to the central axis of the cross section of the flue gas circulating pipeline, the baffle plate is matched with the cross section of the flue gas circulating pipeline, and the servo motor controls the rotating shaft to rotate axially; the two ends of the rotating shaft penetrate through the round holes corresponding to the two positions on the pipe wall of the flue gas circulation pipeline, and the baffle is arranged inside the flue gas circulation pipeline.

The invention is designed on the original burner, and by additionally arranging the Flue Gas Recirculation (FGR) device, the effect of effectively controlling the emission value of the nitrogen oxide can be achieved without integrally replacing equipment and facilities, thereby greatly saving the cost.

According to the invention, the adjusting plate with a simple structure is designed, the flow cross section of the flue gas circulation pipeline is changed through the rotation angle of the adjusting plate, the rotation angle of the adjusting plate is controlled through the servo motor, the characteristics of high control speed and high position precision of the servo motor are utilized, the accurate adjustment of the flue gas circulation quantity is realized, and the adjustment precision is favorably improved.

Fresh air and circulating flue gas are mixed through the mixing cylinder and then enter the combustor, so that the uniformity of the gas entering the combustor is improved, and the combustion quality is ensured; the oxygen content of combustion air is reduced after the flue gas and the fresh air are premixed, so that the combustion temperature is reduced, the flue gas emission temperature is reduced, and the heat energy waste is reduced.

The flue gas circulating pipeline is a circular pipeline, and the baffle is a circular baffle.

The shell of the servo motor is fixed on the outer side of the pipe wall of the flue gas circulation pipeline, and an output shaft of the servo motor is connected with the rotating shaft.

A connecting rod is fixed on the rotating shaft positioned outside the flue gas circulating pipeline and is vertical to the rotating shaft; a connecting bolt is fixed below the end part of the connecting rod and is parallel to the rotating shaft; the smoke circulating pipeline is fixedly connected with a fan-shaped connecting plate, and the surface of the fan-shaped connecting plate is provided with a strip-shaped through hole which is arranged along the arc direction of a fan shape; the connecting bolt penetrates through the strip-shaped through hole and is fixed on the fan-shaped connecting plate through the matched nuts positioned on the upper surface and the lower surface of the fan-shaped connecting plate.

After servo motor accomplished the location, realize the fixed of connecting rod and pivot through connecting bolt and supporting nut to make the baffle keep at fixed rotation angle, prevent that servo motor from opening the atress for a long time, influence servo motor's life-span.

The fan, the burner, the boiler, the economizer and the flue gas circulating pipe are provided with two sets, and the two sets of devices are symmetrically arranged.

The flow regulating mechanism is arranged at one end of the flue gas circulating pipeline close to the mixing cylinder.

The flue gas circulating pipeline is provided with a heat preservation layer, heat preservation treatment is carried out on FGR, and flue gas condensate water is effectively prevented from being generated.

The invention also comprises a PLC controller, wherein a nitrogen oxide sensor is arranged on the smoke exhaust pipeline of the boiler, and the PLC controller is in signal connection with the servo motor and the nitrogen oxide sensor. Through the PLC controller, the system can be automatically adjusted according to the content of the discharged nitrogen oxide sensor.

An air inlet of the mixing cylinder is connected with an air heater, a tube pass of the air heater is filled with air, a shell pass inlet of the air heater is connected with a water outlet pipe of the boiler, and a shell pass outlet of the air heater is connected with a water inlet pipe of the boiler.

Compared with the prior art, the invention has the following advantages:

(1) the servo motor drives the adjusting plate to realize efficient and accurate adjustment of the flue gas circulation amount, the flue gas circulation amount is accurately adjusted, the adjustment precision is improved, and different emission requirements can be met by controlling the recirculation amount of the flue gas;

(2) the circulating flue gas and air are premixed, so that the gas entering the combustor is more uniform, the combustion uniformity is facilitated, and the combustion quality is improved;

(3) when the system is stable, the position of the adjusting plate is fixed through the matched connecting rod, connecting bolt, nut and fan-shaped connecting plate, and energy waste and damage of the servo motor caused by long-time work of the servo motor are avoided;

(4) the flue gas circulating pipeline FGR is subjected to heat preservation treatment, so that flue gas condensate water is effectively prevented from being generated;

(5) the hot water or steam generated by the boiler is utilized to preheat the fresh air, so that the temperature of the gas entering the combustor is ensured, and the combustion effect is improved.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic diagram of the operation of the present invention;

FIG. 3 is a schematic front view of the flow regulating mechanism of the present invention;

FIG. 4 is a schematic view of the fan-shaped connecting plate according to the present invention;

in the figure, 1 is a boiler, 2 is a mixing drum, 3 is a fan, 4 is a burner, 5 is an economizer, 6 is a baffle, 7 is a rotating shaft, 8 is a servo motor, 9 is a connecting rod, 10 is a connecting bolt, 11 is a nut, 12 is a fan-shaped connecting plate, 13 is a flue gas circulating pipeline, 14 is a long-strip-shaped through hole, 15 is an air inlet, 16 is flue gas, and 17 is circulating flue gas.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.