CN111765475A

CN111765475A - Circulating fluidized bed waste incineration boiler based on fire grate and working method thereof

Info

Publication number: CN111765475A
Application number: CN202010732987.1A
Authority: CN
Inventors: 蒋敏华; 高洪培; 袁野; 时正海; 王海涛; 孙献斌; 肖平
Original assignee: Huaneng Clean Energy Research Institute
Current assignee: Huaneng Clean Energy Research Institute
Priority date: 2020-07-27
Filing date: 2020-07-27
Publication date: 2020-10-13

Abstract

The invention discloses a circulating fluidized bed waste incineration boiler based on a grate and a working method thereof, and belongs to the technical field of household waste incineration flue gas treatment. The feeding system is connected with the grate drying section, the fluidized combustion section and the grate burnout section are sequentially connected, and the lower parts of the grate drying section, the fluidized combustion section and the grate burnout section are respectively connected with the primary air system through the air volume adjusting device; the fire grate burnout section is connected with the slag discharge pipe; the front arch of the fire grate is positioned above the drying section of the fire grate, and the rear arch of the fire grate is positioned above the burnout section of the fire grate; the hearth is connected with a secondary air system, the upper part of the hearth is connected with a horizontal flue, the horizontal flue is connected with an inlet of a material returning system, a material returning outlet of the material returning system is connected with a material returning port of the boiler through a material returning pipe, and a smoke outlet of the material returning system is connected to a tail flue. The stability of feeding and slag discharging is improved, so that the combustion is uniform and stable, the emission of harmful pollutants is reduced, the combustion efficiency of the boiler is improved, and the risk of blowing out is avoided.

Description

Circulating fluidized bed waste incineration boiler based on fire grate and working method thereof

Technical Field

The invention belongs to the technical field of household garbage incineration flue gas treatment, and particularly relates to a circulating fluidized bed garbage incineration boiler based on a grate and a working method thereof.

Background

A large amount of garbage and solid wastes bring great harm to the environment, and the environment mainly represents that the garbage and the solid wastes occupy land and pollute the atmosphere, soil and water. Compared with landfill and composting, the burning method has the characteristics of volume reduction, weight reduction, on-site treatment, high treatment speed, heat energy recovery, high harmless degree and the like. Therefore, various countries have used waste incineration power generation as an important way to develop new energy and waste disposal.

Under the urgent need of the garbage harmless disposal technology and the great trend of national environmental protection and energy conservation, the garbage incineration industry faces various challenges of technology, energy consumption, environmental protection and the like. The main waste incineration systems on the market today are fluidized bed and grate boilers. The grate furnace has the greatest advantages of stable and reliable operation, small fly ash amount and capability of directly feeding most of solid garbage into the furnace for combustion without any pretreatment. However, the problems of high investment cost of equipment, large floor area, unstable temperature distribution and combustion conditions of a grate and a hearth above the grate, low burnout rate, high original emission concentration of pollutants such as NOx generation and dioxin, complex tail flue gas environment-friendly equipment, high operation cost and the like still exist at present. In contrast, fluidized bed waste incineration techniques can effectively address these problems. The fluidized bed garbage furnace has strong fuel variety adaptability, can provide a large amount of heat required by garbage drying, pyrolysis and starting combustion, and has high combustion efficiency. Meanwhile, the smoke emission performance is good, and because the circulating fluidized bed adopts low-temperature and staged combustion, the thermal type and combustion are limitedFormation of material NOx. And secondly, the SNCR, the in-furnace dry method system and the deacidification system are simple, efficient and reliable. If the conventional pollutant index of the waste incineration plant is further reduced, compared with a grate furnace, the fluidized bed waste furnace is used for producing NOx and SO₂And the removal of pollutants such as HCl and the like has great advantages in investment and operation cost. However, the existing fluidized bed garbage furnace still has some problems, and the problems of high ash content, unstable combustion, high CO emission and the like still need further research.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a circulating fluidized bed waste incineration boiler based on a fire grate and a working method thereof, which improve the stability of feeding and deslagging, thereby enabling the combustion to be uniform and stable, reducing the emission of harmful pollutants, improving the combustion efficiency of the boiler and avoiding the risk of furnace shutdown.

The invention is realized by the following technical scheme:

the invention discloses a circulating fluidized bed waste incineration boiler based on a grate, which comprises a primary air system, a feeding system, a grate drying section, a fluidized combustion section, a grate burnout section, a grate front arch, a grate rear arch, a slag discharge pipe, a hearth, a return pipe, a secondary air system, a horizontal flue and a return system, wherein the primary air system is connected with the feeding system through the grate drying section;

the feeding system is connected with the head end of the fire grate drying section, the tail end of the fire grate drying section is connected with the head end of the fluidized combustion section, the tail end of the fluidized combustion section is connected with the head end of the fire grate burnout section, and the tail end of the fire grate burnout section is connected with the slag discharge pipe; the lower parts of the grate drying section, the fluidized combustion section and the grate burnout section are respectively connected with a primary air system through an air quantity adjusting device, and the fluidized combustion section is used for realizing fluidized combustion of garbage materials; the front arch of the fire grate is positioned above the drying section of the fire grate, and the rear arch of the fire grate is positioned above the burnout section of the fire grate; the hearth is connected with a secondary air system, the upper part of the hearth is connected with a horizontal flue, the horizontal flue is connected with an inlet of a material returning system, a material returning outlet of the material returning system is connected with a material returning port of the boiler through a material returning pipe, and a smoke outlet of the material returning system is connected to a tail flue.

Preferably, the space between the grate drying section and the grate front arch is gradually expanded from the head end to the tail end of the grate drying section; the space between the fire grate burnout section and the fire grate rear arch gradually expands from the tail end to the head end of the fire grate burnout section.

Further preferably, the included angle between the drying section of the fire grate and the front arch of the fire grate ranges from 25 degrees to 40 degrees, and the included angle between the burnout section of the fire grate and the rear arch of the fire grate ranges from 25 degrees to 40 degrees.

Preferably, the feeding system comprises a feeding grab bucket and a horizontal reciprocating feeding device, wherein the feeding grab bucket is arranged above the horizontal reciprocating feeding device, and the horizontal reciprocating feeding device is connected with the grate drying section.

Preferably, the fluidized combustion section is grate-type or fixed hood-type.

Preferably, the secondary air system comprises a first secondary air pipe and a second secondary air pipe, and the first secondary air pipe and the second secondary air pipe are respectively arranged on two sides of the hearth.

Preferably, the material returning system comprises a separator, an outlet flue and an external bed heat exchanger; the central cylinder of the separator is connected with the outlet flue, and the outlet flue is connected with the tail flue; the inlet of the separator is connected with the horizontal flue, the outlet below the separator is connected with the external bed heat exchanger, and the external bed heat exchanger is connected with the material returning port of the boiler through the material returning pipe.

Preferably, the return port of the boiler is arranged above the fire grate burnout section.

The invention discloses a working method of the circulating fluidized bed waste incineration boiler based on the fire grate, which comprises the following steps:

the garbage materials are fed into a hearth through a feeding system and sequentially pass through a grate drying section, a fluidized combustion section and a grate burnout section, a primary air system respectively acts on the grate drying section, the fluidized combustion section and the grate burnout section through an air volume adjusting device, so that the garbage materials are dried and preheated in the grate drying section and then fluidized and combusted in the fluidized combustion section, a secondary air system enters the hearth for supporting combustion, dust-containing flue gas enters a return system through a horizontal flue in the combustion process and is treated, the flue gas enters a tail flue through a flue gas outlet, and return materials return to the grate burnout section through a return pipe to promote the garbage fuels to be burned out and then are discharged through a slag discharge pipe.

Preferably, the primary air volume of the grate drying section is 10% -15% of the total primary air volume, the primary air volume of the fluidized combustion section is 75% -80% of the total primary air volume, and the primary air volume of the grate burnout section is 5% -10% of the total primary air volume.

Compared with the prior art, the invention has the following beneficial technical effects:

the existing fluidized bed domestic garbage boiler has the problems of unstable feeding and slag discharging and the like due to the nature of garbage fuel, and the unstable material circulation process can cause unstable combustion, overhigh CO emission, unsmooth slag discharging, hardened materials and even the risk of furnace shutdown. According to the circulating fluidized bed waste incineration boiler based on the fire grate, the advantages of the fire grate on the feeding and deslagging system are utilized, the household garbage fuel enters the fire grate, is conveyed to the burnout section through the material returning system after being combusted, and is discharged under the action of the fire grate, and the fire grate can well convey and discharge the household garbage fuel. Meanwhile, the fluidized combustion is realized by utilizing the air quantity regulation of the fluidized combustion section, the uniformity of the temperature of the whole hearth is greatly improved by the fluidized bed hearth form and the trapping effect of a material returning system on large particles, the retention time of fuel is prolonged, the full combustion of the fuel is facilitated, and the boiler efficiency is improved.

On the environment-friendly level, the uniformity and the residence time of the overall temperature of the hearth are very important for the formation of dioxin. In general, PCDD/Fs (dioxins) are formed by two mechanisms. One is from homogeneous reaction and the temperature range is 500-800 ℃. The main processes are the rearrangement of chlorinated precursors, such as Chlorophenol (CP) and chlorobenzene (CBz). The PCDD/Fs in this process is called homogeneous PCDD/Fs or high-temperature PCDD/Fs. The PCDD/Fs can also form a reaction through a heterogeneous reaction, and the temperature range is 200-400 ℃. Heterogeneous reactions are mainly formed by CP, CBz, or carbon in fly ash, i.e. de novoprocess (source generation), under the catalytic action in fly ash. For different dioxin generation mechanisms, the high-temperature environment can realize the complete decomposition and damage of dioxin and precursors thereof, thereby achieving the purpose of reducing dioxin. At present, the widely used 3T (temperature, time, turbulence) + E (excess air factor) control technology mainly means that the hearth can reach 850 ℃, 2s or more harsh treatment working conditions. In terms of turbulence intensity, the product of the geometry of the high-temperature zone of the fluidized bed and the flow velocity of the flue is greater than that of the grate furnace, and thus the turbulence is more severe. In addition, for the coupling of temperature and residence time, the combustion mode of the fluidized bed also has the advantages that the furnace is chamber combustion and depends on high-concentration materials for heat and mass transfer, the adjustability of the temperature of the furnace cavity is stronger, the integral uniformity is better, higher temperature is easily obtained, and the decomposition of dioxin and precursors thereof is further facilitated. The more uniform the temperature of the hearth is, the longer the residence time of the high-temperature area is, and the decomposition rate of dioxin can be remarkably improved. In conclusion, the invention adopts the fire grate to convey and discharge the fuel, and fluidized combustion is carried out through the fluidized bed hearth and the material returning system, so that the temperature of the hearth can be ensured to be uniform. Meanwhile, the decomposition of dioxin and precursors thereof can be ensured by the uniform high-temperature environment and the long retention time in the fluidized bed boiler. On the premise of not adding a tail activated carbon adsorption device, the standard emission of dioxin generated by burning household garbage under different loads is realized.

Furthermore, the space between the fire grate drying section and the fire grate front arch is gradually expanded from the head end to the tail end of the fire grate drying section; the space between the fire grate burnout section and the fire grate rear arch is gradually expanded from the tail end to the head end of the fire grate burnout section to form a combustion space with a triangular-like section, so that the heat insulation effect is good, and meanwhile, smoke generated by combustion can smoothly enter a hearth.

Furthermore, the included angle between the drying section of the fire grate and the front arch of the fire grate is 25-40 degrees, compared with the traditional structure, the height of the front arch 9 of the fire grate and the height of the rear arch 10 of the fire grate are reduced, the included angle between the burnout section of the fire grate and the rear arch of the fire grate is 25-40 degrees, and the gathering effect of smoke can be effectively improved.

Furthermore, a horizontal reciprocating type feeding device is adopted for feeding, the efficiency is high, the stability is high, and the feeding speed is controllable.

Furthermore, the fluidized combustion section adopts a grate type, so that fluidized air distribution is easy to realize, and a good conveying and slag discharging effect is achieved; the fluidized combustion section adopts a fixed hood type so as to better control the flow velocity of local small holes, the fluidized effect can be obviously improved, and the combustion efficiency is further improved.

Furthermore, the material returning system adopts a mode of combining the separator and the external bed heat exchanger, and the problem of insufficient heating surface in the hearth can be solved by the high-temperature superheater in the external bed heat exchanger. Meanwhile, most of corrosive atmosphere and elements prone to coking exist in the form of gas phase and submicron particles, and cannot be trapped by the separator and enter the external bed. Therefore, the problems of high-temperature corrosion and coking of the flue gas in the process of burning the household garbage can be well solved by using the external bed heat exchanger.

Furthermore, a material return port of the boiler is arranged above the fire grate burnout section, so that burnout of unburned garbage materials is further promoted.

The working method of the circulating fluidized bed waste incineration boiler based on the fire grate improves the feeding and slag discharging stability, thereby ensuring uniform and stable combustion, reducing the emission of harmful pollutants, improving the combustion efficiency of the boiler, avoiding the risk of blowing out and having good application prospect.

Furthermore, the primary air volume of the drying section of the fire grate is 10-15% of the total primary air volume, and the fire grate cooling and garbage material preheating and drying functions are mainly realized; the primary air quantity of the fluidized combustion section is 75% -80% of the total primary air quantity, and the fluidized combustion section is used for realizing fluidized combustion of garbage materials; the primary air quantity of the fire grate burnout section is 5% -10% of the total primary air quantity, and the garbage materials are guaranteed to be burnt out.

Drawings

FIG. 1 is a schematic view of the overall structure of embodiment 1 of the present invention;

FIG. 2 is a top view of the internal structure of the grate-based circulating fluidized bed waste incineration boiler of the present invention;

fig. 3 is a schematic view of the overall structure of embodiment 2 of the present invention.

In the figure: 1-a grate drying section air quantity adjusting device, 2-a fluidized combustion section air quantity adjusting device, 3-a grate burnout section air quantity adjusting device, 4-a grate drying section, 5-a fluidized combustion section, 6-a grate burnout section, 7-a feeding grab bucket, 8-a horizontal reciprocating feeding device, 9-a grate front arch, 10-a grate rear arch, 11-a slag discharge pipe, 12-a hearth, 13-a return pipe, 14-a first secondary air pipe, 15-a second secondary air pipe, 16-a horizontal flue, 17-a separator, 17-1-a first separator, 17-2-a second separator, 18-an outlet flue and 19-an external bed heat exchanger.

Detailed Description

The invention will now be described in further detail with reference to the following drawings and specific examples, which are intended to be illustrative and not limiting:

example 1

According to the circulating fluidized bed waste incineration boiler based on the fire grate, as shown in fig. 1, in the embodiment, a feeding system adopts a mode of combining a feeding grab bucket 7 and a horizontal reciprocating type feeding device 8, the feeding grab bucket 7 is arranged above the horizontal reciprocating type feeding device 8, the horizontal reciprocating type feeding device 8 is connected with the head end of a fire grate drying section 4, the tail end of the fire grate drying section 4 is connected with the head end of a fluidized combustion section 5, the tail end of the fluidized combustion section 5 is connected with the head end of a fire grate burnout section 6, the tail end of the fire grate burnout section 6 is connected with a slag discharge pipe 11, and the fluidized combustion section 5 adopts the same fire grate form as the fire grate drying section 4 and the fire grate burnout section 6.

The lower parts of the grate drying section 4, the fluidized combustion section 5 and the grate burnout section 6 are respectively connected with a primary air system through a grate drying section air quantity adjusting device 1, a fluidized combustion section air quantity adjusting device 2 and a grate burnout section air quantity adjusting device 3, and the fluidized combustion section 5 is used for realizing fluidized combustion of garbage materials.

The fire grate front arch 9 is positioned above the fire grate drying section 4, and the fire grate rear arch 10 is positioned above the fire grate burnout section 6; the space between the grate drying section 4 and the grate front arch 9 is gradually expanded from the head end to the tail end of the grate drying section 4; the space between the fire grate burnout section 6 and the fire grate rear arch 10 gradually expands from the tail end to the head end of the fire grate burnout section 6. Specifically, the included angle between the drying section of the fire grate and the front arch of the fire grate can be set to be 25-40 degrees, the included angle between the burnout section of the fire grate and the rear arch of the fire grate can be set to be 25-40 degrees, compared with the traditional structure, the structure reduces the heights of the front arch 9 and the rear arch 10 of the fire grate, and the heat preservation and the gathering effect of smoke gas are enhanced.

The hearth 12 is connected with a secondary air system, the secondary air system comprises a first secondary air pipe 14 and a second secondary air pipe 15, and the first secondary air pipe 14 and the second secondary air pipe 15 are respectively arranged at two sides of the hearth 12; the upper part of the hearth 12 is connected with a horizontal flue (16), the horizontal flue 16 is connected with an inlet of a material returning system, and the material returning system comprises a separator 17, an outlet flue 18 and an external bed heat exchanger 19; the central cylinder of the separator is connected with an outlet flue 18, and the outlet flue 18 is connected with a tail flue; the inlet of the separator 13 is connected with the horizontal flue 16, the outlet below the separator 13 is connected with the external bed heat exchanger 19, the external bed heat exchanger 19 is connected with the material returning port of the boiler through the material returning pipe 13, and preferably, the material returning port of the boiler is arranged above the fire grate burnout section 6.

Example 2

As shown in fig. 3, in this embodiment, the feeding system adopts a mode of combining a feeding grab bucket 7 and a horizontal reciprocating feeding device 8, the feeding grab bucket 7 is arranged above the horizontal reciprocating feeding device 8, the horizontal reciprocating feeding device 8 is connected with the head end of a fire grate drying section 4, the tail end of the fire grate drying section 4 is connected with the head end of a fluidized combustion section 5, the tail end of the fluidized combustion section 5 is connected with the head end of a fire grate burnout section 6, the tail end of the fire grate burnout section 6 is connected with a slag discharge pipe 11, the fluidized combustion section 5 adopts a fixed hood type, and a plurality of fixed hoods are arranged on an air distribution plate, so as to better control the flow rate of local small holes and simultaneously realize fluidized combustion of materials.

The hearth 12 is connected with a secondary air system, the secondary air system comprises a first secondary air pipe 14 and a second secondary air pipe 15, and the first secondary air pipe 14 and the second secondary air pipe 15 are respectively arranged at two sides of the hearth 12; the upper part of the hearth 12 is connected with a horizontal flue (16), and the horizontal flue 16 is connected with an inlet of a material returning system.

The material returning system comprises two sets of separators 17, an outlet flue 18 and an external bed heat exchanger 19 which are arranged in parallel; the central cylinder of the separator is connected with an outlet flue 18, and the outlet flue 18 is connected with a tail flue; as shown in FIG. 2, the inlets of the first separator 17-1 and the second separator 17-2 are respectively connected with 1 horizontal flue 16, the outlets below the first separator 17-1 and the second separator 17-2 are respectively connected with 1 external bed heat exchanger 19, the external bed heat exchanger 19 is connected with a return port of the boiler through a return pipe 13, and preferably, the return port of the boiler is arranged above the fire burnout section 6.

The invention is further illustrated below with reference to the working method of example 1:

the domestic garbage is sent into a horizontal reciprocating type feeding device 8 by a feeding grab bucket 7, and under the reciprocating pushing action of the horizontal reciprocating type feeding device, garbage fuel enters a grate. The front arch 9 and the rear arch 10 of the furnace type fire grate are lower, so that the flue gas can enter the hearth 12 while the heat preservation effect is ensured. The garbage fuel passes through the grate drying section 4, the fluidized combustion section 5 and the grate burnout section 6 in sequence under the conveying action of the grate. The primary air is controlled by a grate drying section air quantity adjusting device 1, a fluidized combustion section air quantity adjusting device 2 and a grate burnout section air quantity adjusting device 3 to respectively enter the lower parts of a grate drying section 4, a fluidized combustion section 5 and a grate burnout section 6. In the actual operation process, the air volume of the drying section 4 of the fire grate accounts for 10-15% of the total air volume, the air volume of the fluidized combustion section 5 accounts for 75-80% of the total air volume, and the air volume of the burnout section of the fire grate accounts for 5-10% of the total air volume. The air quantity of the drying section 4 of the fire grate is small, and the drying section mainly plays a role in cooling and preheating the fire grate. Fluidized combustion section) air volume accounts for most of primary air, and under the action of an independent fluidized combustion section air volume adjusting device 2, fluidized combustion of fuel can be realized, and in the combustion process, part of small particles can enter the upper part of a hearth 12 along with flue gas and enter a first separator 17-1 and a second separator 17-2 from a horizontal flue 16. In the whole design process, the furnace type grate mainly plays a role in conveying materials and discharging slag, the area of the grate is lower than that of a grate furnace with the same treatment scale, and specific design parameters are determined according to garbage characteristics. After the dust-containing flue gas passes through the two separators 17, large particles are collected by the separators 17 and then return to the fire grate burnout section 6 through the return pipe 13 by the external bed heat exchanger 19 at the lower part, and then enter the slag discharge pipe 11 under the conveying action of the fire grate. In order to ensure complete decomposition of dioxin and precursors thereof, the hearth 12 can be properly designed for thermal insulation of parts, and the combustion temperature in the furnace is ensured to be maintained at 950-1000 ℃. Here, the high temperature ash particles may further promote the burnout of the unburnt waste fuel. The flue gas discharged from the central cylinder of the separator 17 is converged and then discharged from the outlet flue 18 for tail heat exchange. The secondary air is introduced into the hearth 12 from the first secondary air pipes 14 and the second secondary air pipes 15 on the left side and the right side for afterburning, so that the fuel combustion efficiency is ensured.

It should be noted that the above description is only one embodiment of the present invention, and all equivalent changes of the system described in the present invention are included in the protection scope of the present invention. Persons skilled in the art to which this invention pertains may substitute similar alternatives for the specific embodiments described, all without departing from the scope of the invention as defined by the claims.

Claims

1. A circulating fluidized bed waste incineration boiler based on a grate is characterized by comprising a primary air system, a feeding system, a grate drying section (4), a fluidized combustion section (5), a grate burnout section (6), a grate front arch (9), a grate rear arch (10), a slag discharge pipe (11), a hearth (12), a material return pipe (13), a secondary air system, a horizontal flue (16) and a material return system;

the feeding system is connected with the head end of the grate drying section (4), the tail end of the grate drying section (4) is connected with the head end of the fluidized combustion section (5), the tail end of the fluidized combustion section (5) is connected with the head end of the grate burnout section (6), and the tail end of the grate burnout section (6) is connected with the slag discharge pipe (11); the lower parts of the grate drying section (4), the fluidized combustion section (5) and the grate burnout section (6) are respectively connected with a primary air system through an air quantity adjusting device, and the fluidized combustion section (5) is used for realizing fluidized combustion of garbage materials; the fire grate front arch (9) is positioned above the fire grate drying section (4), and the fire grate rear arch (10) is positioned above the fire grate burnout section (6); furnace (12) and overgrate air headtotail, furnace (12) top is connected with horizontal flue (16), and horizontal flue (16) are connected with the entry linkage of returning the material system, and the returning charge export of returning the material system is connected with the returning charge mouth of boiler through returning charge pipe (13), and the exhanst gas outlet of returning the material system is connected to the afterbody flue.

2. The grate-based circulating fluidized bed waste incineration boiler of claim 1, wherein the space between the grate drying section (4) and the grate front arch (9) is gradually enlarged from the head end to the tail end of the grate drying section (4); the space between the fire grate burnout section (6) and the fire grate rear arch (10) is gradually enlarged from the tail end to the head end of the fire grate burnout section (6).

3. The circulating fluidized bed waste incineration boiler based on the grate of claim 2, characterized in that the included angle between the grate drying section (4) and the grate front arch (9) is 25-40 °, and the included angle between the grate burnout section (6) and the grate rear arch (10) is 25-40 °.

4. The grate-based circulating fluidized bed waste incineration boiler of claim 1, wherein the feeding system comprises a feeding grapple (7) and a horizontally reciprocating feeding device (8), the feeding grapple (7) being disposed above the horizontally reciprocating feeding device (8), the horizontally reciprocating feeding device (8) being connected to the grate drying section (4).

5. The grate-based circulating fluidized bed waste incineration boiler of claim 1, wherein the fluidized combustion section (5) is grate-type or fixed hood-type.

6. The grate-based circulating fluidized bed waste incineration boiler of claim 1, wherein the secondary air system comprises a first secondary air duct (14) and a second secondary air duct (15), the first secondary air duct (14) and the second secondary air duct (15) being respectively disposed on both sides of the furnace (12).

7. The grate-based circulating fluidized bed waste incineration boiler of claim 1, wherein the return system includes a separator (17), an outlet flue (18), and an external bed heat exchanger (19); the central cylinder of the separator is connected with an outlet flue (18), and the outlet flue (18) is connected with a tail flue; an inlet of the separator (17) is connected with the horizontal flue (16), an outlet below the separator (17) is connected with the external bed heat exchanger (19), and the external bed heat exchanger (19) is connected with a material returning port of the boiler through a material returning pipe (13).

8. The grate-based circulating fluidized bed waste incineration boiler of claim 1, wherein the return port of the boiler is positioned above the grate burnout section (6).

9. The method of any one of claims 1 to 8, wherein the method comprises:

the garbage materials are fed into a hearth (12) through a feeding system, and sequentially pass through a grate drying section (4), a fluidized combustion section (5) and a grate burnout section (6), a primary air system respectively acts on the grate drying section (4), the fluidized combustion section (5) and the grate burnout section (6) through an air quantity adjusting device, so that the garbage materials are dried and preheated in the grate drying section (4) and then fluidized and combusted in the fluidized combustion section (5), a secondary air system enters the hearth (12) for supporting combustion, dusty smoke enters a return system through a horizontal flue (16) in the combustion process for treatment, the smoke enters a tail flue from a smoke outlet, and the return material returns to the grate burnout section (6) through a return pipe (13) to promote the garbage fuel to be burnt out and then is discharged through a slag discharge pipe (11).

10. The operating method of the grate-based circulating fluidized bed waste incineration boiler according to claim 9, wherein the primary air volume of the grate drying section (4) is 10% -15% of the total primary air volume, the primary air volume of the fluidized combustion section (5) is 75% -80% of the total primary air volume, and the primary air volume of the grate burnout section (6) is 5% -10% of the total primary air volume.