Denitration device and method for flue gas of waste incinerator

Abstract

The present invention relates to the technical field of flue gas purification, and particularly to a denitration device and a denitration method for the flue gas of a waste incinerator, including a flue gas recirculation pipeline, a nozzle, and a secondary air pipeline. The nozzle is a Venturi nozzle. One end of the Venturi nozzle is connected to the secondary air pipeline, and the other end communicates with the furnace of the waste incinerator. One end of the flue gas recirculation pipeline is connected to the flue gas discharged from the waste incinerator, and the other end is connected to the throat position of the Venturi nozzle. The recirculation flue gas in the flue gas recirculation pipeline and the secondary air in the secondary air pipeline are mixed at the throat position of the Venturi nozzle. A pressure difference is formed between the throat position of the Venturi nozzle and the inside of the furnace of the waste incinerator. The recirculation flue gas and the secondary air enter the combustion chamber of the waste incinerator. The structure of the present invention is simple and the cost is low. By reducing the oxygen content in the local area of the waste incinerator, the nitrogen oxides generated by the flue gas are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas purification, and particularly to a denitration device and a denitration method for the flue gas of a waste incinerator. Background Art

[0002] The common denitration processes for waste incineration plants mainly include Selective Non-Catalytic Reduction (SNCR) and Selective Catalytic Reduction (SCR). The SNCR denitration technology can meet the NOx emission requirements of GB18485-2014 and EU 2010 / 75 / EU. The system is simple and the investment cost is low. It is the most widely used denitration technology at present, but it also has the disadvantages of a narrow reaction temperature window, a low denitration rate, and a high ammonia slip rate. The SCR denitration technology is a technology that uses a catalyst to reduce the reaction activation energy to achieve efficient denitration at low temperatures. It has the advantages of high denitration efficiency and low ammonia slip rate. However, the SCR catalyst has high requirements for operating conditions, is easily poisoned and deactivated, and the waste catalyst after deactivation needs to be treated as hazardous waste. Moreover, to reach the reaction temperature range of the catalyst, steam is usually required to heat the flue gas, resulting in low economic benefits and poor environmental protection. Summary of the Invention

[0003] The purpose of the present invention is to provide a denitration device and a denitration method for the flue gas of a waste incinerator, which have a simple structure, low cost, and can denitrate the flue gas by reducing the oxygen content in a local area of the waste incinerator.

[0004] To achieve the above purpose, a denitration device for the flue gas of a waste incinerator according to the present invention includes a flue gas recirculation pipeline, a nozzle, and a secondary air pipeline. The nozzle is a Venturi nozzle. One end of the Venturi nozzle is connected to the secondary air pipeline, and the other end communicates with the furnace of the waste incinerator. One end of the flue gas recirculation pipeline is connected to the flue gas discharged from the waste incinerator, and the other end is connected to the throat position of the Venturi nozzle. The recirculated flue gas in the flue gas recirculation pipeline and the secondary air in the secondary air pipeline are mixed at the throat position of the Venturi nozzle. A pressure difference is formed between the throat position of the Venturi nozzle and the inside of the waste incinerator furnace. Under the action of the pressure difference, the recirculated flue gas and the secondary air enter the combustion chamber of the waste incinerator.

[0005] Further, a plurality of Venturi nozzles are provided. The plurality of Venturi nozzles are arranged in sequence along the width direction of the waste incinerator. One end of each Venturi nozzle is respectively connected to different positions along the length direction of the nozzle header of the secondary air pipeline, and the throat position of each Venturi nozzle is respectively connected to different positions along the length direction of the nozzle header of the flue gas recirculation pipeline.

[0006] Further, it further includes a flue gas filtering device, and the flue gas filtering device is arranged on the flue gas recirculation pipeline.

[0007] Further, it also includes a flowmeter, a flow regulating valve, and a control unit. The flowmeter and the flow regulating valve are both arranged on the flue gas recirculation pipeline. The flowmeter and the flow regulating valve are both located downstream of the flue gas filtering device, and the flowmeter and the flow regulating valve are both connected to the control unit.

[0008] Further, a heat preservation material layer is arranged on the outer wall of the flue gas recirculation pipeline.

[0009] Further, the flue gas recirculation pipeline is connected to the rear arch of the waste incinerator, and the Venturi nozzle is connected to the front arch of the waste incinerator.

[0010] Further, the first Venturi straight pipe of the Venturi nozzle is connected to the secondary air pipeline and the first Venturi inlet reducer. The flue gas recirculation pipeline is connected in the middle of the first Venturi throat. Both ends of the first Venturi throat are respectively connected to the first Venturi inlet and the first outlet reducer. The other end of the first outlet reducer is connected to the first straight pipe section. The other end of the first straight pipe section is connected to the first outlet nozzle reducer. The other end of the first outlet nozzle reducer is connected to the first nozzle. The other end of the first nozzle is connected to the incinerator. The diameter of the first nozzle is larger than the diameter of the first Venturi throat.

[0011] Further, the second Venturi first straight pipe of the Venturi nozzle is connected to the second Venturi second straight pipe. The second nozzle is connected to the end of the second Venturi first straight pipe and the second nozzle is located inside the second Venturi second straight pipe. The flue gas recirculation pipeline is connected to the second Venturi second straight pipe.

[0012] Further, the third Venturi throat of the Venturi nozzle is connected to one end of the third Venturi outlet reducer. The other end of the third Venturi outlet reducer is connected to the third nozzle. The other end of the third nozzle is connected to the incinerator. The flue gas recirculation pipeline is connected to the third Venturi second straight pipe. The diameter of the third nozzle is slightly larger than the diameter of the third Venturi throat. Or, the fourth Venturi first straight pipe of the Venturi nozzle is connected to the fourth nozzle. Part of the fourth Venturi first straight pipe and the fourth nozzle extend into the fourth Venturi second straight pipe. The diameter of the fourth Venturi second straight pipe is slightly larger than the diameter of the fourth Venturi first straight pipe. The flue gas recirculation pipeline is connected to the fourth Venturi second straight pipe.

[0013] The denitration device for the waste incinerator flue gas of the present invention has at least the following beneficial effects:

[0014] A denitration device for the flue gas of a waste incinerator according to the present invention. Since one end of the flue gas recirculation pipeline is connected to the flue gas discharged from the waste incinerator and the other end is connected to the Venturi nozzle, a part of the flue gas discharged from the waste incinerator is mixed with the secondary air in the secondary air pipeline through the flue gas recirculation pipeline and then sprayed into the waste incinerator. Therefore, the recirculated flue gas and the flue gas in the furnace are fully disturbed and mixed, reducing the oxygen content in the local area, forming a reducing atmosphere, inhibiting the generation of NOx during the waste incineration process, achieving the purpose of denitration, without the need to additionally add a catalyst, having low operating costs and being more environmentally friendly. And because the nozzle is a Venturi nozzle, a flue gas self-circulation is formed by using the pressure difference between the throat of the nozzle and the furnace, without the need to separately install a recirculation fan, with a simple structure and further cost reduction.

[0015] The following specifically describes the denitration device for the flue gas of the waste incinerator of the present invention in conjunction with the attached drawings. Brief Description of the Drawings

[0016] Figure 1 is a schematic structural diagram of the denitration device for the flue gas of the waste incinerator of the present invention;

[0017] Figure 2 is a schematic installation structure diagram of the nozzle in the denitration device for the flue gas of the waste incinerator of the present invention;

[0018] Figure 3 is another schematic installation structure diagram of the nozzle in the denitration device for the flue gas of the waste incinerator of the present invention;

[0019] Figure 4 is the first form of the Venturi nozzle;

[0020] Figure 5 is the second form of the Venturi nozzle;

[0021] Figure 6 is the third form of the Venturi nozzle;

[0022] Figure 7 is the fourth form of the Venturi nozzle. Detailed Embodiments

[0023] Such as Figure 1 、 Figure 3 、 Figure 4As shown in the figure, a denitration device for the flue gas of a waste incinerator according to the present invention includes a flue gas recirculation pipeline 6, a nozzle 7, and a secondary air pipeline 2. The nozzle 7 is a Venturi nozzle. One end of the Venturi nozzle is connected to the secondary air pipeline 2, and the other end communicates with the furnace of the waste incinerator 1. One end of the flue gas recirculation pipeline 6 is connected to the flue gas discharged from the waste incinerator 1, and the other end is connected to the throat position of the Venturi nozzle. The recirculated flue gas in the flue gas recirculation pipeline 6 and the secondary air in the secondary air pipeline 2 are mixed at the throat position of the Venturi nozzle. A pressure difference is formed between the throat position of the Venturi nozzle and the inside of the furnace of the waste incinerator 1. Under the action of the pressure difference, the recirculated flue gas and the secondary air enter the combustion chamber of the waste incinerator 1. For the denitration device of the flue gas of the waste incinerator according to the present invention, since one end of the flue gas recirculation pipeline 6 is connected to the flue gas discharged from the waste incinerator 1 and the other end is connected to the Venturi nozzle, a part of the flue gas discharged from the waste incinerator 1 is mixed with the secondary air in the secondary air pipeline 2 through the flue gas recirculation pipeline 6 and then sprayed into the waste incinerator 1. Therefore, the recirculated flue gas and the flue gas in the furnace are fully disturbed and mixed, the oxygen content in the local area is reduced, a reducing atmosphere is formed, the generation of NOx during the waste incineration process is inhibited, and the purpose of denitration is achieved. There is no need to additionally add a catalyst, the operating cost is low, and it is more environmentally friendly. And because the nozzle 7 is a Venturi nozzle, a flue gas self-circulation is formed by using the pressure difference between the throat of the nozzle and the furnace, and there is no need to additionally set a recirculation fan, the structure is simple, and the cost is further reduced.

[0024] Optionally, as Figure 2 shown, there are multiple Venturi nozzles, and the multiple Venturi nozzles are arranged in sequence along the width direction of the waste incinerator 1. One end of each Venturi nozzle is respectively connected to different positions along the length direction of the nozzle header of the secondary air pipeline 2, and the throat positions of each Venturi nozzle are respectively connected to different positions along the length direction of the nozzle header of the flue gas recirculation pipeline 6. The recirculated flue gas is sprayed into the furnace through multiple Venturi nozzles, so that the recirculated flue gas and the flue gas in the furnace are mixed more evenly.

[0025] Optionally, the flue gas recirculation pipeline 6 can not only be connected to the flue gas discharged from the incinerator 1 as Figure 2 shown, but also can be selected to draw out the flue gas from any position of the waste heat boiler according to the on-site layout, such as the positions before and after the evaporator, superheater, and economizer.

[0026] Optionally, it further includes a flue gas filtration device 3, and the flue gas filtration device 3 is arranged on the flue gas recirculation pipeline 6. After the flue gas generated by burning waste is filtered by the flue gas filtration device 3, the dust content of the flue gas is reduced, which is beneficial to reducing the abrasion of the recirculation pipeline and the subsequent heating surface of the waste heat boiler, and can also reduce the working load of the tail flue gas purification system.

[0027] Optionally, it further includes a flowmeter 5, a flow regulating valve 4, and a control unit. The flowmeter 5 and the flow regulating valve 4 are both arranged on the flue gas recirculation pipeline 6. The flowmeter 5 and the flow regulating valve 4 are both located downstream of the flue gas filtering device 3 and are both connected to the control unit. The flowmeter 5 collects the flow information of the recirculated flue gas in the flue gas recirculation pipeline 6 and transmits it to the control unit. The control unit controls the opening degree of the flow regulating valve 4 according to the flow information to control the flow of the recirculated flue gas.

[0028] Optionally, a heat preservation material layer is provided on the outer wall of the flue gas recirculation pipeline 6 to prevent the temperature of the recirculated flue gas from being too low. When the air temperature entering the furnace of the waste incinerator 1 is low and the calorific value of the waste entering the furnace is also low, in order to meet the requirement of a flue gas residence time of 2 s at 850 °C or above, it may cause the waste incinerator 1 to stop operating. By providing a heat preservation material layer on the outer wall of the flue gas recirculation pipeline 6, the risk of shutdown can be reduced.

[0029] Optionally, the flue gas recirculation pipeline 6 is connected to the rear arch 9 of the waste incinerator 1 or a selected position of the waste heat boiler. The Venturi nozzle is connected to the front arch 8 of the waste incinerator 1. The recirculated flue gas is led out from the rear arch 9 of the waste incinerator 1 and enters the furnace through the nozzle of the front arch 8 of the waste incinerator 1. It uses fewer pipelines and is convenient for on-site layout. Moreover, the recirculated flue gas contains unburned CO near the rear arch of the incinerator, which enters the furnace with the secondary air and burns more fully, improving the combustion efficiency of the incinerator. The temperature of the recirculated flue gas led out from the rear arch of the waste incinerator 1 is about 1000 °C, enabling the incinerator to operate stably under low calorific value conditions and further reducing the risk of shutdown.

[0030] Optionally, the Venturi nozzle can be of various forms. Form 1 is as Figure 4 shown. The first Venturi straight pipe 7-1-1 connects the secondary air pipeline 2 and the first Venturi inlet reducer 7-1-2. The flue gas recirculation pipeline 6 is connected in the middle of the first Venturi throat 7-1-3. Both ends of the first Venturi throat 7-1-3 are respectively connected to the first Venturi inlet 7-1-2 and the first outlet reducer 7-1-4. The other end of the first outlet reducer is connected to the first straight pipe section 7-1-5. The other end of the first straight pipe section is connected to the first outlet nozzle reducer 7-1-6. The other end of the first outlet nozzle reducer 7-1-6 is connected to the first nozzle 7-1-7. The other end of the first nozzle 7-1-7 directly enters the incinerator 1. To ensure sufficient pressure difference, in this form, the diameter of the first nozzle 7-1-7 should be larger than the diameter of the first Venturi throat 7-1-3. Form 2 is as Figure 5As shown in the figure, the first straight pipe 7-2-1 of the second Venturi is connected to the second straight pipe 7-2-3 of the second Venturi. The second nozzle 7-2-2 is connected to the end of the first straight pipe 7-2-1 of the second Venturi and extends into the second straight pipe 7-2-3 of the second Venturi. The flue gas recirculation pipe 6 is connected to the second straight pipe 7-2-3 of the second Venturi, and the subsequent structure is the same as that of Form 1. Form 3 is as follows Figure 6 As shown in the figure, the form before the throat 7-3-1 of the third Venturi is the same as that of Form 2. The throat 7-3-1 of the third Venturi is connected to the reduced diameter of the third Venturi outlet 7-3-2. The other end of the reduced diameter of the third Venturi outlet 7-3-2 is connected to the third nozzle 7-3-3. The other end of the third nozzle 7-3-3 directly enters the incinerator 1. In this form, the diameter of the third nozzle 7-3-3 is slightly larger than the diameter of the throat 7-3-1 of the third Venturi. Form 4 is as follows Figure 7 As shown in the figure, the first straight pipe 7-4-1 of the fourth Venturi is connected to the fourth nozzle 7-4-2. Part of the first straight pipe 7-4-1 of the fourth and the fourth nozzle 7-4-2 extend into the second straight pipe 7-4-3 of the fourth Venturi. The diameter of the second straight pipe 7-4-3 of the fourth Venturi is slightly larger than the diameter of the first straight pipe 7-4-1 of the fourth. The flue gas recirculation pipe 6 is connected to the second straight pipe 7-4-3 of the fourth Venturi, and the subsequent form is the same as that of Form 2 or Form 3. The above Venturi nozzle structures can make the wind speed at the nozzle entering the incinerator be 20-200 m / s.

[0031] A method for denitrifying the flue gas of a waste incinerator by using the above device includes the following steps:

[0032] Mix the recirculated flue gas led out from the flue gas recirculation pipe 6 and the secondary air in the secondary air pipe 2 at the throat position of the Venturi nozzle. A pressure difference is formed between the throat position of the Venturi nozzle and the inside of the furnace of the waste incinerator 1. Under the action of the pressure difference, the recirculated flue gas and the secondary air enter the combustion chamber of the waste incinerator 1, reducing the oxygen content in the waste incinerator 1 and forming a reducing atmosphere. The waste in the combustion chamber of the waste incinerator 1 burns in the reducing atmosphere to inhibit the generation of NOx during the waste incineration process.

[0033] The above-described embodiments are only used to describe the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A denitration device for the flue gas of a waste incinerator, characterized in that: It includes a flue gas recirculation pipeline (6), a nozzle (7), and a secondary air pipeline (2). The nozzle (7) is a Venturi nozzle. One end of the Venturi nozzle is connected to the secondary air pipeline (2), and the other end communicates with the furnace of the waste incinerator (1). One end of the flue gas recirculation pipeline (6) is connected to the flue gas discharged from the waste incinerator (1), and the other end is connected to the throat position of the Venturi nozzle. The recirculated flue gas in the flue gas recirculation pipeline (6) and the secondary air in the secondary air pipeline (2) are mixed at the throat position of the Venturi nozzle. A pressure difference is formed between the throat position of the Venturi nozzle and the interior of the furnace of the waste incinerator (1). Under the action of the pressure difference, the recirculated flue gas and the secondary air enter the combustion chamber of the waste incinerator (1). There are multiple Venturi nozzles, and the multiple Venturi nozzles are arranged in sequence along the width direction of the waste incinerator (1). One end of each Venturi nozzle is respectively connected to different positions along the length direction of the nozzle header of the secondary air pipeline (2), and the throat position of each Venturi nozzle is respectively connected to different positions along the length direction of the nozzle header of the flue gas recirculation pipeline (6).

2. The denitration device for the flue gas of the waste incinerator according to claim 1, wherein: It further includes a flue gas filtration device (3), and the flue gas filtration device (3) is arranged on the flue gas recirculation pipeline (6).

3. The denitration device for the flue gas of the waste incinerator according to claim 2, characterized in that: It further includes a flowmeter (5), a flow regulating valve (4), and a control unit. The flowmeter (5) and the flow regulating valve (4) are both arranged on the flue gas recirculation pipeline (6). The flowmeter (5) and the flow regulating valve (4) are both located downstream of the flue gas filtration device (3), and the flowmeter (5) and the flow regulating valve (4) are both connected to the control unit.

4. The denitration device for the flue gas of the waste incinerator according to claim 1, characterized in that: The outer wall of the flue gas recirculation pipeline (11) is provided with a heat insulation material layer.

5. The denitration device for the flue gas of the waste incinerator according to claim 1, characterized in that: The flue gas recirculation pipeline (6) is connected to the rear arch (9) of the waste incinerator (1), and the Venturi nozzle is connected to the front arch (8) of the waste incinerator (1).

6. The denitration device for the flue gas of the waste incinerator according to claim 1, characterized in that: The first Venturi straight pipe (7-1-1) of the Venturi nozzle is connected to the secondary air pipeline (2) and the first Venturi inlet reducer (7-1-2). The flue gas recirculation pipeline (6) is connected in the middle with the first Venturi throat (7-1-3). The two ends of the first Venturi throat (7-1-3) are respectively connected to the first Venturi inlet (7-1-2) and the first outlet reducer (7-1-4). The other end of the first outlet reducer (7-1-4) is connected to the first straight pipe section (7-1-5). The other end of the first straight pipe section (7-1-5) is connected to the first outlet nozzle reducer (7-1-6). The other end of the first outlet nozzle reducer (7-1-6) is connected to the first nozzle (7-1-7). The other end of the first nozzle (7-1-7) is connected to the incinerator (1). The diameter of the first nozzle (7-1-7) is larger than the diameter of the first Venturi throat (7-1-3).

7. The denitration device for the flue gas of the waste incinerator according to claim 1, characterized in that: The first straight pipe (7-2-1) of the second Venturi of the Venturi nozzle is connected to the second straight pipe (7-2-3) of the second Venturi. The second nozzle (7-2-2) is connected to the end of the first straight pipe (7-2-1) of the second Venturi and the second nozzle (7-2-2) is located within the second straight pipe (7-2-3) of the second Venturi. The flue gas recirculation pipe (6) is connected to the second straight pipe (7-2-3) of the second Venturi.

8. The denitrification device for the flue gas of the waste incinerator according to claim 1, wherein: The throat (7-3-1) of the third Venturi of the Venturi nozzle is connected to one end of the reduced diameter at the outlet of the third Venturi (7-3-2). The other end of the reduced diameter at the outlet of the third Venturi (7-3-2) is connected to the third nozzle (7-3-3). The other end of the third nozzle (7-3-3) is connected to the incinerator (1). The flue gas recirculation pipe (6) is connected to the second straight pipe of the third Venturi. The diameter of the third nozzle (7-3-3) is slightly larger than the diameter of the throat (7-3-1) of the third Venturi. Alternatively, the first straight pipe (7-4-1) of the fourth Venturi of the Venturi nozzle is connected to the fourth nozzle (7-4-2). Part of the first straight pipe (7-4-1) of the fourth Venturi and the fourth nozzle (7-4-2) extend into the second straight pipe (7-4-3) of the fourth Venturi. The diameter of the second straight pipe (7-4-3) of the fourth Venturi is slightly larger than the diameter of the first straight pipe (7-4-1) of the fourth Venturi. The flue gas recirculation pipe (6) is connected to the second straight pipe (7-4-3) of the fourth Venturi.

9. A method for denitrifying the flue gas of the waste incinerator by using the denitrification device according to any one of claims 1-8 above, characterized in that: Including the following steps: Mix the recirculated flue gas led out from the flue gas recirculation pipe (6) and the secondary air in the secondary air pipe (2) at the throat position of the Venturi nozzle. A pressure difference is formed between the throat position of the Venturi nozzle and the interior of the furnace of the waste incinerator (1). Under the action of the pressure difference, the recirculated flue gas and the secondary air enter the combustion chamber of the waste incinerator (1), reducing the oxygen content in the waste incinerator (1) to form a reducing atmosphere, and the waste in the combustion chamber of the waste incinerator (1) burns in the reducing atmosphere.

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