阅读说明：本技术 一种层燃锅炉结构及锅炉脱硫脱硝方法 (Layer-combustion boiler structure and boiler desulfurization and denitrification method ) 是由 郭强 徐雨贤 于 2019-10-29 设计创作，主要内容包括：本发明涉及锅炉设备技术领域,公开了一种层燃锅炉结构及锅炉脱硫脱硝方法,包括竖直安装的主炉膛以及尾部烟道,在主炉膛的顶部侧壁上设置第一喷嘴,第一喷嘴用于向主炉膛内部喷入钙粉；设置烟气再循环装置连通主炉膛内部与尾部烟道的末端、用于将尾部烟道末端的烟气引入主炉膛内部。本发明提供的一种层燃锅炉结构及锅炉脱硫脱硝方法,向炉内喷入钙粉可实现炉内脱硫；在尾部烟道的末端取部分烟气送入主炉膛中,可降低主炉膛内燃烧区的燃烧温度,减少氮氧化物的生成；满足硫氧化物和氮氧化物的环保排放要求,降低了环保设备投入及环保设备运行费用,有较好的经济效益和社会效益。(The invention relates to the technical field of boiler equipment, and discloses a layer combustion boiler structure and a boiler desulfurization and denitrification method, wherein the layer combustion boiler structure comprises a main hearth and a tail flue which are vertically installed, a first nozzle is arranged on the side wall of the top of the main hearth, and the first nozzle is used for spraying calcium powder into the main hearth; and the flue gas recirculation device is arranged to communicate the inside of the main hearth with the tail end of the tail flue and is used for introducing the flue gas at the tail end of the tail flue into the main hearth. According to the layer combustion boiler structure and the boiler desulfurization and denitrification method provided by the invention, calcium powder is sprayed into the boiler to realize in-boiler desulfurization; part of the flue gas is taken from the tail end of the tail flue and is sent into the main hearth, so that the combustion temperature of a combustion area in the main hearth can be reduced, and the generation of nitrogen oxides is reduced; the method meets the requirement of environmental protection emission of sulfur oxides and nitrogen oxides, reduces the investment of environmental protection equipment and the operating cost of the environmental protection equipment, and has better economic benefit and social benefit.)

1. A layer combustion boiler structure comprises a main hearth and a tail flue, wherein the main hearth is vertically arranged, and the tail flue is characterized in that a first nozzle is arranged on the side wall of the top of the main hearth and used for spraying calcium powder into the main hearth, wherein the calcium powder comprises calcium carbonate powder or calcium oxide powder; and a flue gas recirculation device is arranged to communicate the inside of the main furnace with the tail end of the tail flue and is used for introducing the flue gas at the tail end of the tail flue into the inside of the main furnace.

2. The grate-firing boiler structure according to claim 1, wherein an auxiliary furnace and a convection channel are sequentially arranged in parallel at the rear of the main furnace, the top end of the main furnace is communicated with the top end of the auxiliary furnace, the bottom end of the auxiliary furnace is communicated with the bottom end of the convection channel, and the top end of the convection channel is communicated with the tail flue.

3. The grate-firing boiler structure according to claim 2, characterized in that the first nozzles are provided at the top of the side walls of the primary furnace, the first nozzles being provided toward the top inlet of the secondary furnace; the first nozzle is also connected with one end of an external flue gas pipeline, the other end of the flue gas pipeline is connected with the tail flue, and a pneumatic conveying device and a water removal device are connected on the flue gas pipeline in series.

4. The grate firing boiler structure of claim 2, wherein the flue gas recirculation device comprises a flue gas recirculation main air pipe, a flue gas taking port is arranged at the tail end of the tail flue, the flue gas taking port is connected with the flue gas recirculation main air pipe, and the flue gas recirculation main air pipe is arranged at one side of the grate close to the tail.

5. The grate firing boiler structure according to claim 4, wherein the flue gas recirculation main duct is arranged in parallel with the upper surface of the grate along the width direction of the grate, the flue gas recirculation main duct is vertically connected with a plurality of second nozzles, and outlets of the second nozzles are arranged downward; a plurality of second nozzles are uniformly arranged along the width direction of the fire grate; the distance between the flue gas recirculation main air pipe and the tail part of the fire grate is 450-550 mm.

6. The grate firing boiler structure of claim 5, wherein the flue gas recirculation main duct is disposed inside the secondary furnace, and the second nozzles are inserted into the main furnace through a side wall of the secondary furnace; and two ends of the flue gas recirculation main air pipe respectively penetrate out of the hearth to be connected with the two smoke taking ports in a one-to-one correspondence manner.

7. The grate firing boiler structure of claim 2, wherein the bottom of the main furnace is provided with a grate, the bottom of the main furnace covers the grate, the cross-sectional areas of the middle part and the top of the main furnace are smaller than the cross-sectional area of the bottom, the auxiliary furnace is bent, and an adapter part is arranged between the bottom end of the auxiliary furnace and the bottom end of the convection passage.

8. A method for desulfurizing and denitrating a boiler based on the structure of the layer combustion boiler of any one of claims 1 to 7, comprising:

spraying calcium powder into the top end of the interior of the main hearth;

calcium powder is sprayed into the main hearth by adopting the tail flue gas of the boiler;

extracting the recirculated flue gas from the end of the back pass;

and introducing the recirculated flue gas into the main hearth and above the rear part of the fire grate.

9. The desulfurization and denitrification method for the boiler according to claim 8, wherein the step of spraying calcium powder into the top end of the interior of the main furnace comprises the following steps: calcium powder is sprayed into the areas with the top outlet of the main hearth and the top inlet of the auxiliary hearth and the smoke temperature of 850-950 ℃;

the method for injecting the calcium powder into the main hearth by adopting the tail flue gas of the boiler comprises the following steps: extracting the injected flue gas from the tail flue and the front side or the rear side of the economizer, mixing the injected flue gas with the calcium powder, and then injecting the mixture into the main hearth; and carrying out water removal treatment on the sprayed flue gas before mixing with the calcium powder.

10. The method for desulfurizing and denitrating boiler according to claim 8, wherein the temperature of the recirculated flue gas is 150 ℃ or lower; the proportion of the recycled flue gas in the total flue gas is 15-25%; the flow speed of the recycled flue gas introduced into the main hearth is 25-35 m/s.

Technical Field

The invention relates to the technical field of boiler equipment, in particular to a layer combustion boiler structure and a boiler desulfurization and denitrification method.

Background

China is a developing country taking coal as a main energy source, and the coal resource accounts for about 75% of the total energy production and consumption of China. During the combustion of coal, a large amount of pollutants, among which Nitrogen Oxides (NO), are produced_X) Is extremely harmful to the environment, and nitrogen oxides are formedAcid rain destroys the ecological environment and can also form photochemical smog to harm human health. High temperature combustion of coal is NO_XOne of the main sources of the coal-fired boiler, and the boiler in China mainly uses the coal as the main source, thereby reducing the NO of the coal-fired boiler_XThe discharge of (b) has important significance.

At present, various technologies and devices have been developed at home and abroad to be applied to desulfurization and denitration of boilers. The denitration technology comprises a low-nitrogen combustion technology, a flue gas denitration (SNCR) technology and the like. The reaction temperature is not controlled in place, and the reaction time is short, so that the reaction amount of nitrogen and carbon particles in the flue gas is small, and the self-separation of nitrogen oxides is not in time, so that the content of nitrogen oxides in the flue gas discharged from the tail part of the boiler is high. Various methods for desulfurizing boilers also have disadvantages.

Most of the currently used coal-fired industrial boilers are provided with desulfurization and denitrification devices, so that the environmental protection investment is large, the occupied area is large, and the economical efficiency is poor.

Disclosure of Invention

Technical problem to be solved

The invention aims to provide a layer-combustion boiler structure and a boiler desulfurization and denitrification method, which are used for solving or partially solving the problems that most of the conventional coal-fired industrial boilers are provided with desulfurization and denitrification devices, the environmental protection investment is large, the occupied area is large and the economical efficiency is poor.

(II) technical scheme

In order to solve the technical problems, in a first aspect of the invention, a layer combustion boiler structure is provided, which includes a main furnace and a tail flue, wherein the main furnace and the tail flue are vertically installed, a first nozzle is arranged on a side wall of the top of the main furnace, and the first nozzle is used for injecting calcium powder into the main furnace, and the calcium powder includes calcium carbonate powder or calcium oxide powder; and a flue gas recirculation device is arranged to communicate the inside of the main furnace with the tail end of the tail flue and is used for introducing the flue gas at the tail end of the tail flue into the inside of the main furnace.

On the basis of the scheme, the rear part of the main hearth is sequentially provided with the auxiliary hearth and the convection channel side by side, the top end of the main hearth is communicated with the top end of the auxiliary hearth, the bottom end of the auxiliary hearth is communicated with the bottom end of the convection channel, and the top end of the convection channel is communicated with the tail flue.

On the basis of the scheme, the first nozzle is arranged at the top of the side wall of the main hearth and faces the top inlet of the auxiliary hearth; the first nozzle is also connected with one end of an external flue gas pipeline, the other end of the flue gas pipeline is connected with the tail flue, and a pneumatic conveying device and a water removal device are connected on the flue gas pipeline in series.

On the basis of the scheme, the smoke recycling device comprises a smoke recycling main air pipe, the tail end of the tail flue is provided with a smoke taking port, the smoke taking port is connected with the smoke recycling main air pipe, and the smoke recycling main air pipe is arranged on one side, close to the tail, of the fire grate.

On the basis of the scheme, the flue gas recirculation main air pipe is arranged in parallel with the upper surface of the fire grate along the width direction of the fire grate, the flue gas recirculation main air pipe is vertically connected with a plurality of second nozzles, and outlets of the second nozzles are arranged downwards; a plurality of second nozzles are uniformly arranged along the width direction of the fire grate; the distance between the flue gas recirculation main air pipe and the tail part of the fire grate is 450-550 mm.

On the basis of the scheme, the flue gas recirculation main air pipe is arranged inside the auxiliary hearth, and the second nozzle penetrates through the side wall of the auxiliary hearth and is inserted into the main hearth; and two ends of the flue gas recirculation main air pipe respectively penetrate out of the hearth to be connected with the two smoke taking ports in a one-to-one correspondence manner.

On the basis of the scheme, the fire grate is arranged at the bottom of the main hearth, the bottom of the main hearth covers the fire grate, the cross-sectional areas of the middle part and the top of the main hearth are smaller than that of the bottom of the main hearth, the auxiliary hearth is bent, and a switching part is arranged between the bottom end of the auxiliary hearth and the bottom end of the convection channel.

In a second aspect of the present invention, a boiler desulfurization and denitrification method based on the structure of the grate-fired boiler includes: spraying calcium powder into the top end of the interior of the main hearth; calcium powder is sprayed into the main hearth by adopting the tail flue gas of the boiler; extracting the recirculated flue gas from the end of the back pass; and introducing the recirculated flue gas into the main hearth and above the rear part of the fire grate.

On the basis of the scheme, the step of spraying calcium powder to the top end inside the main hearth specifically comprises the following steps: calcium powder is sprayed into the areas with the top outlet of the main hearth and the top inlet of the auxiliary hearth and the smoke temperature of 850-950 ℃; the method for injecting the calcium powder into the main hearth by adopting the tail flue gas of the boiler comprises the following steps: extracting the injected flue gas from the tail flue and the front side or the rear side of the economizer, mixing the injected flue gas with the calcium powder, and then injecting the mixture into the main hearth; and carrying out water removal treatment on the sprayed flue gas before mixing with the calcium powder.

On the basis of the scheme, the temperature of the recirculated flue gas is less than or equal to 150 ℃; the proportion of the recycled flue gas in the total flue gas is 15-25%; the flow speed of the recycled flue gas introduced into the main hearth is 25-35 m/s.

(III) advantageous effects

According to the layer combustion boiler structure and the boiler desulfurization and denitrification method provided by the invention, calcium powder is sprayed into the boiler to realize in-boiler desulfurization; part of the flue gas is taken from the tail end of the tail flue and is sent into the main hearth, so that the combustion temperature of a combustion area in the main hearth can be reduced, and the generation of nitrogen oxides is reduced; the requirements of the sulfur oxide and the nitrogen oxide on the environmental protection emission are met, the investment of environmental protection equipment and the operation cost of the environmental protection equipment are reduced, and better economic benefit and social benefit are achieved; and the flue gas is introduced into the main hearth again, so that the full and complete combustion of fuel is facilitated, the heat utilization rate is further improved, and the heat efficiency is improved.

Drawings

FIG. 1 is a first schematic view of a layer-fired boiler configuration according to an embodiment of the present invention;

FIG. 2 is a first schematic view of a chain grate boiler configuration in an embodiment of the present invention;

FIG. 3 is a second schematic view of a layer-fired boiler configuration according to an embodiment of the present invention;

FIG. 4 is a second schematic view of a chain grate boiler configuration in an embodiment of the present invention;

FIG. 5 is a second schematic top view of a layer-fired boiler configuration in accordance with an embodiment of the present invention;

FIG. 6 is a schematic view of a flue gas recirculation ductwork in an embodiment of the present invention;

FIG. 7 is a schematic view of a second nozzle in an embodiment of the invention.

Description of reference numerals:

1-a drum;	2-main furnace chamber;	3, a grate;
			4, an auxiliary hearth;	5-convection heating surface;	6-tail flue;
7-a coal economizer;	8-air preheater;	9 — a first nozzle;
			10-convection channel;	11-a transfer part;	12-flue gas recirculation means;
121-flue gas recirculation main air pipe;	122 — second nozzle.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

The embodiment of the invention provides a layer combustion boiler structure, and referring to fig. 1, the layer combustion boiler structure comprises a main hearth 2 and a tail flue 6 which are vertically installed, wherein a first nozzle 9 is arranged on the side wall of the top of the main hearth 2, and the first nozzle 9 is used for spraying calcium powder into the main hearth 2; calcium oxide powder is sprayed into a proper area of a hearth and can react with acidic substances in smoke, and the calcium oxide powder is neutralized by acid and alkali and oxidized and reduced to realize in-furnace desulfurization. Referring to fig. 3, a flue gas recirculation device 12 is provided to communicate the interior of the main furnace 2 with the end of the back flue 6 for introducing the flue gas at the end of the back flue 6 into the interior of the main furnace 2. The starting end of the tail flue 6 is connected with the outlet of the hearth. The end of the back pass 6, i.e. the part through which the flue gas flows, is closer to the end of the back pass 6, the lower the temperature of the flue gas.

According to the layer combustion boiler structure provided by the embodiment, calcium oxide powder or calcium carbonate powder is sprayed into the boiler, so that the desulfurization in the boiler can be realized; part of the flue gas is taken from the tail end of the tail flue 6 and is sent into the main hearth 2, so that the combustion temperature of a combustion area in the main hearth 2 can be reduced, and the generation of nitrogen oxides is reduced; the requirements of the sulfur oxide and the nitrogen oxide on the environmental protection emission are met, the investment of environmental protection equipment and the operation cost of the environmental protection equipment are reduced, and better economic benefit and social benefit are achieved; and the flue gas is introduced into the main hearth 2 again, thereby being beneficial to the full and complete combustion of the fuel, further improving the heat utilization rate and improving the heat efficiency.

Furthermore, the grate-firing boiler structure can adopt calcium carbonate powder for in-furnace desulfurization and can also adopt calcium oxide powder for in-furnace desulfurization. The following description will specifically take the example of using calcium oxide powder.

On the basis of the above embodiment, further, the rear portion of the main furnace 2 is sequentially provided with the auxiliary furnace 4 and the convection channel 10 side by side, the top end of the main furnace 2 is communicated with the top end of the auxiliary furnace 4, the bottom end of the auxiliary furnace 4 is communicated with the bottom end of the convection channel 10, and the top end of the convection channel 10 is communicated with the tail flue 6.

The rear part of the main hearth 2 is the rear side in the flow direction of the flue gas, i.e. the part to which the flue gas flows backwards. The auxiliary furnace 4 and the convection channel 10 are also vertically arranged and are connected with the main furnace 2 in sequence side by side. The layer combustion boiler is additionally provided with an auxiliary hearth 4 and a convection channel 10 at the rear side of a main hearth 2. Flue gas generated by combustion of fuel in the main furnace 2 flows into the auxiliary furnace 4 through a top outlet, then flows from the top to the bottom of the auxiliary furnace 4 into the convection channel 10, and then flows into the tail flue 6.

According to the layer combustion boiler structure, the auxiliary hearth 4 and the convection channel 10 are sequentially arranged behind the main hearth 2 side by side, the top of the main hearth 2 is communicated with the auxiliary hearth 4, and the bottom of the auxiliary hearth 4 is communicated with the convection channel 10, so that the main hearth 2, the auxiliary hearth 4 and the convection channel 10 form an S-shaped three-return-stroke flue gas channel, the flow distance of flue gas can be effectively increased, the combustion time of fuel, namely pulverized coal, in a boiler is increased, and the combustion efficiency is improved; the products which are not fully combusted in the flue gas are reduced, the emission of sulfur oxides is favorably reduced, the environmental protection investment is reduced, and the economical efficiency is improved.

Furthermore, membrane type water-cooled walls are attached to the peripheral side walls of the main hearth 2 and the auxiliary hearth 4; the side wall of the convection channel 10 is also provided with a membrane water-cooling wall, and a convection heating surface 5 is arranged in the convection channel 10 to improve the use efficiency of heat. The membrane water-cooled wall is communicated with a downcomer which is connected with the boiler barrel 1.

On the basis of the above embodiment, further, the first nozzles 9 are arranged at the top of the side wall of the main furnace 2, and the first nozzles 9 are arranged towards the top inlet of the auxiliary furnace 4; the present embodiment proposes that calcium oxide powder can be injected at the outlet of the main furnace 2 and at the inlet of the auxiliary furnace 4. For the grate-fired boiler, the smoke temperature at the outlet of the main furnace 2 and the inlet of the auxiliary furnace 4 is generally 850-:

CaO+SO₂+1/2O₂→CaSO₄；

CaO＋SO₃→CaSO₄；

furthermore, the calcium oxide powder can be ground to 200 meshes and sprayed into the hearth, which is beneficial to improving the reaction efficiency. The calcium oxide powder can be placed in a storage box, the storage box is connected with the first nozzle 9, and a certain amount of calcium oxide powder is conveyed to the first nozzle 9 every time and enters the hearth through air flow injection.

The first nozzle 9 is also connected with one end of an external flue gas pipeline, the other end of the flue gas pipeline is connected with the tail flue 6, and a pneumatic conveying device and a water removal device are connected on the flue gas pipeline in series. The calcium oxide powder is sprayed into the hearth by adopting tail flue gas, and the tail flue gas has a certain temperature, so that the influence on combustion in the hearth due to too low temperature can be avoided, the temperature of the hearth can be properly reduced, and the generation of nitrogen oxides can be reduced; meanwhile, tail flue gas is introduced into the hearth and can be combusted again, so that the combustion efficiency is improved, and the fuel is fully and completely combusted.

Further, the pneumatic conveying device can be an air pump and is used for providing conveying power for the flue gas.

Because calcium oxide powder is hygroscopic, reacts with water to form alkali, is corrosive and generates a large amount of heat, and has the specific reaction formula: CaO + H₂O→Ca(OH)₂. Therefore, the water removal device is arranged, the introduced tail flue gas passes through the water removal device before being mixed with the calcium oxide powder, and the problem that the tail flue gas carries water to influence acid-base neutralization and redox reaction of the calcium oxide powder is avoided.

On the basis of the above embodiment, further referring to fig. 3 and 5, the flue gas recirculation device 12 includes a flue gas recirculation main air duct 121, a smoke extraction port is arranged at the end of the tail flue 6, the smoke extraction port is connected to the flue gas recirculation main air duct 121, and the flue gas recirculation main air duct 121 is arranged on one side of the fire grate 3 close to the tail.

The smoke taking port can be arranged on the side wall at the tail end of the tail flue 6 and used for leading out smoke. The flue gas recirculation main air pipe 121 is used for guiding the flue gas taken out from the flue gas taking port to one side of the fire grate 3 close to the tail part. The flue gas can contact with the ash at the tail part of the fire grate 3, thereby reducing the temperature of the ash, reducing the heat loss of the ash and improving the boiler efficiency.

Further, referring to fig. 2, the boiler structure and the desulfurization and denitrification installation structure described in the above embodiments are also applicable to a chain boiler. Referring to fig. 4, the specific arrangement of the flue gas recirculation device for the chain grate boiler is the same as that of the grate firing boiler shown in fig. 3.

On the basis of the above embodiment, further, the main flue gas recirculation duct 121 is arranged in parallel with the upper surface of the grate 3 along the width direction of the grate 3, and the main flue gas recirculation duct 121 is arranged along the width direction of the grate 3, so that the recirculated flue gas is distributed in the width direction of the grate 3, that is, both the recirculated flue gas and the flue gas are located on one side of the grate 3 close to the tail, thereby facilitating the reduction of the temperature of the ash at the tail.

Referring to fig. 6 and 7, a plurality of second nozzles 122 are vertically connected to the main flue gas recirculation duct 121, and outlets of the second nozzles 122 are arranged downward; i.e. the second nozzles 122 spray recirculated flue gas towards the grate 3 above the grate 3. Further, the outlet of the second nozzle 122 should be located in the main combustion zone inside the main furnace 2; so as to effectively reduce the combustion temperature and reduce the generation of nitrogen oxides.

A plurality of second nozzles 122 are uniformly arranged along the width direction of the grate 3; the temperature of the main combustion area in the main hearth 2 and the temperature of the ash can be uniformly reduced, so that the denitration effect is improved, the heat loss of the ash is fully reduced, and the heat efficiency is improved. The distance between the flue gas recirculation main air pipe 121 and the tail part of the fire grate 3 is 450-550 mm. So that the flue gas recirculation main air pipe 121 corresponds to the position of ash on the fire grate 3.

On the basis of the above embodiment, further, the bottom of the main furnace 2 is provided with the grate 3, the bottom of the main furnace 2 covers the grate 3, the cross-sectional areas of the middle part and the top of the main furnace 2 are smaller than the cross-sectional area of the bottom, the auxiliary furnace 4 is bent, and a transition part 11 is arranged between the bottom end of the auxiliary furnace 4 and the bottom end of the convection channel 10.

That is, the fire grate 3 is completely positioned in the main hearth 2, the fire grate 3 has an unchanged structure compared with the original single hearth, the cross sections of the middle part and the top part of the main hearth 2 are reduced so as to reduce the occupied width of the main hearth 2, and the auxiliary hearth 4 and the convection passage 10 are arranged side by side.

The auxiliary hearth 4 and the convection channel 10 are arranged side by side with the top and the middle part of the main hearth 2, and the bottom of the auxiliary hearth 4 can be bent to enable the outlet to face one side above the fire grate 3; the convection channel 10 can also be arranged side by side with the auxiliary furnace 4 at the top and the middle part, and the bottom can be bent to enable the outlet to face to one side; the outlet at the bottom of the convection channel 10 can be located above the outlet at the bottom of the secondary hearth 4. In order to facilitate the communication between the bottom of the auxiliary hearth 4 and the bottom of the convection channel 10, the switching part 11 can be arranged to be communicated with the auxiliary hearth and the convection channel 10 respectively, and the flue gas turns at the switching part 11 and flows into the convection channel 10.

The structure of the arrangement structure can reduce the structural change of the existing boiler grate 3, the auxiliary hearth 4 and the convection channel 10 can be additionally arranged on the basis of the arrangement of the existing grate 3, the combustion efficiency can be improved on the basis of the original fuel combustion amount, and the pollutant emission can be reduced.

Further, the bottom and middle of the main hearth 2 may be bent.

On the basis of the above embodiment, further, the convection heating surface 5 is arranged inside the convection channel 10, and the economizer 7 and the air preheater 8 are sequentially arranged on the tail flue 6 along the flowing direction of the flue gas. The heat use efficiency is improved.

On the basis of the above embodiment, further, the flue gas recirculation main duct 121 is arranged inside the auxiliary furnace 4, and the second nozzle 122 is inserted into the main furnace 2 through the side wall of the auxiliary furnace 4; two ends of the flue gas recirculation main air pipe 121 respectively penetrate out of the hearth to be connected with the two smoke taking ports in a one-to-one correspondence manner. Because the main furnace 2 is bent, the sectional area of the middle part is smaller than that of the bottom part, so that the space of the main furnace 2 corresponding to the upper part of the tail part of the fire grate 3 is smaller, the flue gas recirculation main air pipe 121 can be arranged in the auxiliary furnace 4, and the second nozzle 122 can penetrate through the membrane type water-cooled wall between the main furnace 2 and the auxiliary furnace 4.

Smoke taking ports can be respectively arranged on two opposite sides of the tail end of the tail flue 6, so that two ends of the flue gas recirculation main air pipe 121 are connected with the two smoke taking ports in a one-to-one correspondence manner, the flue gas recirculation main air pipe 121 can be conveniently and fixedly installed, and the recirculated flue gas can be uniformly fed above the grate 3. Further, a fan can be disposed on a connection pipeline between the flue gas recirculation main air pipe 121 and the flue gas taking port to provide conveying power for recirculated flue gas.

On the basis of the foregoing embodiments, further, the present embodiment provides a method for removing sulfur and nitrogen from a boiler based on the structure of the grate-fired boiler described in any of the foregoing embodiments, including: spraying calcium oxide powder into the top end inside the main hearth 2; calcium oxide powder is sprayed into the main hearth 2 by adopting the tail flue gas of the boiler; drawing the recirculated flue gas from the end of the back pass 6; the recirculated flue gas is introduced into the main furnace 2 and above the rear part of the grate 3.

Calcium oxide powder is sprayed into the hearth, so that in-furnace desulfurization can be realized through acid-base neutralization and redox reaction, the operation is simple and convenient, the environmental protection investment is small, and the economical efficiency is high. The calcium oxide powder is injected into the hearth by adopting tail flue gas, so that the calcium oxide powder is conveniently and fully mixed and reacted in the furnace, the temperature of the hearth can be reduced, and the generation of nitrogen oxides is reduced.

On the basis of the above embodiment, further, the step of injecting calcium oxide powder into the top end of the interior of the main hearth 2 specifically includes: calcium oxide powder is sprayed into the areas with the top outlet of the main hearth 2 and the top inlet of the auxiliary hearth 4 and the smoke temperature of 850-950 ℃; the temperature of the area is proper, the mixing reaction of calcium oxide powder is facilitated, and sulfur oxides in the flue gas at the temperature are more, so that the desulfurization effect is improved. Furthermore, the calcium oxide powder can be ground to 200 meshes and injected into the hearth, so that the mixing reaction efficiency can be improved.

The calcium oxide powder is sprayed into the main hearth 2 by adopting the tail flue gas of the boiler, and the method specifically comprises the following steps: extracting the injected flue gas from the tail flue 6 and the front side or the rear side of the economizer 7, mixing the injected flue gas with the calcium oxide powder, and then injecting the mixture into the main hearth 2; and carrying out water removal treatment on the sprayed flue gas before mixing with calcium oxide powder.

On the basis of the above embodiment, further, the sprayed flue gas is taken from the flue gas with the temperature of 200-300 ℃ in the tail flue 6; the flow rate of the injected flue gas is determined according to the weight of the calcium oxide powder and the type of the pneumatic conveying device for injecting the flue gas; the weight of the calcium oxide powder is determined according to the desulfurization requirement of the boiler.

CaO powder is sprayed into an outlet of the main hearth 2 by adopting tail flue gas, so that the CaO powder is conveniently and fully mixed and reacted in the hearth. The flue gas is taken from the tail flue 6 and can be positioned in front of or behind the economizer 7, and the temperature is selected according to the temperature calculated by heat power and is between 200 ℃ and 300 ℃. The flue gas amount is selected according to the weight of CaO powder required by desulfurization and the type of the selected pneumatic conveying device.

After the flue gas is sprayed into the outlet of the main hearth 2, the temperature of the hearth can be reduced, and the generation of nitrogen oxides can be reduced. It is noted that CaO powder is hygroscopic, reacts with water to form alkali, is corrosive, and is associated with a large amount of heat generation. Therefore, a dewatering device is required to be arranged before the tail flue gas is mixed with the CaO powder.

The layer-combustion industrial boiler structure and the boiler desulfurization method provided by the embodiments solve the problem that the SO is controlled in the combustion process of the coal-combustion industrial boiler₂The generated problem reduces the treatment intensity of pollutants at the tail part of the boiler. The boiler structure is provided with the auxiliary hearth 4 and the convection channel 10 to form a three-return flue gas flow path, and the structure of a boiler system is simplified; the investment of desulfurization equipment and the operating cost of the desulfurization equipment are reduced while the requirement of environmental protection emission is met; has better economic benefit and social benefit.

On the basis of the above embodiment, further, the temperature of the recirculated flue gas is less than or equal to 150 ℃; the proportion of the recycled flue gas in the total flue gas is 15-25%; the flow speed of the recycled flue gas introduced into the main hearth 2 is 25-35 m/s.

Specifically, a flue gas outlet is provided in the back flue 6 after the air preheater 8, where the flue gas temperature should be below 150 ℃, and this portion of the flue gas is taken to the flue gas recirculation unit 12 above the back of the grate 3. The flue gas recirculation main air pipe 121 and the flue gas recirculation nozzles are arranged at the tail part of the rear arch, are vertically arranged downwards, are about 500mm away from the tail part of the fire grate 3, and need to ensure the cooling of furnace slag.

The maximum flue gas circulation amount is about 20 percent of the total flue gas amount. In actual operation, the frequency conversion fan can be used for adjusting the amount of the recycled flue gas so as to obtain the best effect. The size and the number of the inner openings of the flue gas recirculation nozzle are selected according to the amount of flue gas, the flue gas velocity in the flue gas recirculation nozzle is about 30m/s, and the rear arches are uniformly distributed as much as possible during arrangement. The welding mode is adopted between the flue gas recirculation main air pipe 121 and the flue gas recirculation nozzle, and the flat steel of the membrane type wall corresponding to the flue gas recirculation nozzle is provided with holes according to the size of the flue gas recirculation nozzle.

According to the layer combustion boiler structure and the boiler denitration method, part of flue gas is taken from the tail part of the boiler and is sent to the rear part of the fire grate 3, so that the combustion temperature of a main combustion area on the fire grate 3 is reduced, and the generation of nitrogen oxides is reduced. The problems of low thermal efficiency and high emission of nitrogen oxides of the grate-fired industrial boiler are solved, and the treatment intensity of pollutants (nitrogen oxides) of the grate-fired boiler can be reduced; the ash temperature is reduced, the heat loss of ash is reduced, and the boiler efficiency is improved; the combustion temperature of flame in the hearth is reduced, and the generation of nitrogen oxides is reduced; the method meets the requirement of environment-friendly emission of nitrogen oxides, reduces the investment of environment-friendly equipment and the operating cost of the environment-friendly equipment, and has better economic benefit and social benefit.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.