Denitration device and denitration method for flue gas of garbage incinerator

Abstract

The invention relates to the technical field of flue gas purification, in particular to a denitration device and method for flue gas of a garbage incinerator, the denitration device comprises 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 with the secondary air pipeline, the other end of the Venturi nozzle is communicated into a hearth of the garbage incinerator, and the flue gas recirculation pipeline is communicated with the secondary air pipeline. One end of the flue gas recirculation pipeline is connected with flue gas exhausted by the garbage incinerator, the other end of the flue gas recirculation pipeline is connected to the throat position of the Venturi nozzle, and recirculated flue gas in the flue gas recirculation pipeline and secondary air in the secondary air pipeline are mixed at the throat position of the Venturi nozzle; and pressure difference is formed between the throat position of the Venturi nozzle and the interior of the hearth of the garbage incinerator, and the recycled flue gas and the secondary air enter a combustion chamber of the garbage incinerator. The device is simple in structure and low in cost, and nitric oxide generated by flue gas is reduced by reducing the oxygen content of a local area in the garbage incinerator.

Description

Technical Field

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

[0002] The commonly used denitrification processes in waste incineration plants mainly include selective non-catalytic reduction technology (SNCR) and selective catalytic reduction technology (SCR). SNCR denitrification technology can meet the NOx emission requirements of GB18485-2014 and EU 2010 / 75 / EU. It has a simple system and low investment cost. It is the most widely used denitrification technology at present, but it also has the disadvantages of narrow reaction temperature window, low denitrification rate and high ammonia escape rate; SCR denitrification technology is a technology that uses catalysts to reduce the activation energy of the reaction to achieve efficient denitrification at low temperature. It has the advantages of high denitrification efficiency and low ammonia escape rate, but SCR catalysts have high requirements for operating conditions and are easily poisoned and deactivated. After deactivation, the discarded catalyst needs to be treated as hazardous waste. In addition, in order to reach the reaction temperature range of the catalyst, steam is usually required to heat the flue gas, which has low economic benefits and poor environmental protection. Summary of the invention

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

[0004] To achieve the above-mentioned purpose, the present invention provides a denitrification device for flue gas from a waste incinerator, comprising a flue gas recirculation pipe, a nozzle, and a secondary air pipe, wherein the nozzle is a Venturi nozzle, one end of the Venturi nozzle is connected to the secondary air pipe, and the other end is connected to the furnace of the waste incinerator, one end of the flue gas recirculation pipe 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 recycled flue gas in the flue gas recirculation pipe and the secondary air in the secondary air pipe 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, and under the action of the pressure difference, the recycled flue gas and the secondary air enter the combustion chamber of the waste incinerator.

[0005] Furthermore, a plurality of the Venturi nozzles are provided, and the plurality of the Venturi nozzles are arranged in sequence along the width direction of the waste incinerator, one end of each of the Venturi nozzles is respectively connected to a different position of the secondary air duct nozzle mother pipe along the length direction, and the throat position of each of the Venturi nozzles is respectively connected to a different position of the flue gas recirculation duct nozzle mother pipe along the length direction.

[0006] Furthermore, it also includes a smoke filtering device, which is arranged on the smoke recirculation pipeline.

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

[0008] Furthermore, a thermal insulation material layer is provided on the outer wall of the flue gas recirculation duct.

[0009] Furthermore, 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] Furthermore, the first Venturi straight pipe of the Venturi nozzle is connected to the secondary air duct and the first Venturi inlet reducer, the flue gas recirculation duct is connected in the middle of the first Venturi throat, the two 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, and the diameter of the first nozzle is larger than the diameter of the first Venturi throat.

[0011] Furthermore, the second Venturi first straight tube of the Venturi nozzle is connected to the second Venturi second straight tube, the second nozzle is connected to the end of the second Venturi first straight tube and the second nozzle is located in the second Venturi second straight tube, and the flue gas recirculation duct is connected to the second Venturi second straight tube.

[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 pipe is connected to the third Venturi second straight pipe, and 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, and the flue gas recirculation pipe is connected to the fourth Venturi second straight pipe.

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

[0014] The present invention discloses a denitration device for flue gas from a garbage incinerator. Since one end of a flue gas recirculation pipe is connected to the flue gas discharged from the garbage incinerator and the other end is connected to a Venturi nozzle, part of the flue gas discharged from the garbage incinerator is mixed with the secondary air in the secondary air pipe through the flue gas recirculation pipe and then sprayed into the garbage incinerator. Therefore, the recycled flue gas is fully disturbed and mixed with the flue gas in the furnace, the oxygen content in the local area is reduced, a reducing atmosphere is formed, and the generation of NOx in the garbage incineration process is suppressed, thereby achieving the purpose of denitration. No additional catalyst needs to be added, the operation cost is low, and the device is more environmentally friendly. Furthermore, since the nozzle is a Venturi nozzle, the pressure difference between the nozzle throat and the furnace chamber is used to form a self-circulation of the flue gas, and there is no need to set up a separate recirculation fan. The device has a simple structure and further reduces the cost.

[0015] The denitration device for flue gas from a garbage incinerator of the present invention will be described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0019] Figure 4 It is the venturi nozzle type 1;

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

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

[0022] Figure 7 It is the fourth type of Venturi nozzle. DETAILED DESCRIPTION

[0023] like Figure 1 , Figure 3 , Figure 4As shown, a denitration device for flue gas from a waste incinerator of the present invention comprises a flue gas recirculation pipe 6, a nozzle 7, and a secondary air pipe 2. The nozzle 7 is a venturi nozzle, one end of the venturi nozzle is connected to the secondary air pipe 2, and the other end is connected to the furnace of the waste incinerator 1. One end of the flue gas recirculation pipe 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 pipe 6 and the secondary air in the secondary air pipe 2 are mixed at the throat position of the venturi nozzle, and 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. The present invention discloses a denitration device for flue gas from a waste incinerator. Since one end of a flue gas recirculation pipe 6 is connected to the flue gas discharged from the waste incinerator 1 and the other end is connected to a Venturi nozzle, part of the flue gas discharged from the waste incinerator 1 is mixed with the secondary air in the secondary air pipe 2 through the flue gas recirculation pipe 6 and then sprayed into the waste incinerator 1. Therefore, the recycled flue gas is fully disturbed and mixed with the flue gas in the furnace, the oxygen content in the local area is reduced, a reducing atmosphere is formed, and the generation of NOx in the waste incineration process is suppressed, thereby achieving the purpose of denitration. No additional catalyst needs to be added, the operation cost is low, and the device is more environmentally friendly. Furthermore, since the nozzle 7 is a Venturi nozzle, the pressure difference between the nozzle throat and the furnace chamber is used to form a self-circulation of the flue gas, and there is no need to set up a separate recirculation fan. The device has a simple structure and further reduces the cost.

[0024] Optional, such as Figure 2 As shown, a plurality of venturi nozzles are provided, and the plurality of venturi nozzles are sequentially arranged along the width direction of the waste incinerator 1, one end of each venturi nozzle is respectively connected to a different position of the nozzle mother pipe of the secondary air duct 2 along the length direction, and the throat position of each venturi nozzle is respectively connected to a different position of the nozzle mother pipe of the flue gas recirculation duct 6 along the length direction. The recirculated flue gas is sprayed into the furnace through the plurality of venturi nozzles, so that the recirculated flue gas is mixed more evenly with the flue gas in the furnace.

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

[0026] Optionally, a flue gas filter device 3 is further included, and the flue gas filter device 3 is arranged on the flue gas recirculation pipe 6. After the flue gas generated by burning garbage is filtered by the flue gas filter device 3, the dust content of the flue gas is reduced, which is beneficial to reduce the wear of the recirculation pipe and the subsequent heating surface of the waste heat boiler, and can reduce the workload of the tail flue gas purification system.

[0027] Optionally, it further includes a flow meter 5, a flow regulating valve 4, and a control unit. The flow meter 5 and the flow regulating valve 4 are both arranged on the flue gas recirculation pipeline 6. The flow meter 5 and the flow regulating valve 4 are both located downstream of the flue gas filter device 3. The flow meter 5 and the flow regulating valve 4 are both connected to the control unit. The flow meter 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 of the flow regulating valve 4 according to the flow information to control the flow of the recirculated flue gas.

[0028] Optionally, a thermal insulation material layer is provided on the outer wall of the flue gas recirculation duct 6 to prevent the recycled flue gas temperature from being too low. When the wind temperature entering the furnace of the waste incinerator 1 is low and the calorific value of the entering garbage is also low, in order to ensure the requirement that the flue gas stays above 850°C for 2s, the waste incinerator 1 may be shut down. By providing a thermal insulation material layer on the outer wall of the flue gas recirculation duct 6, the risk of shutdown is reduced.

[0029] Optionally, the flue gas recirculation pipe 6 is connected to the rear arch 9 of the waste incinerator 1 or to a selected position of the waste heat boiler, and the Venturi nozzle is connected to the front arch 8 of the waste incinerator 1. The recycled flue gas is drawn 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. Fewer pipes are used and the on-site layout is convenient. The recycled flue gas contains unburned CO near the rear arch of the incinerator, which enters the furnace with the secondary air for combustion, and the combustion is more complete, which can improve the combustion efficiency of the incinerator. The temperature of the recycled flue gas drawn out from the rear arch of the waste incinerator 1 is about 1000°C, so that the incinerator can operate stably under low calorific value conditions, further reducing the risk of shutdown.

[0030] Optionally, the Venturi nozzle can be selected in a variety of forms, such as Figure 4 As shown, the first venturi straight pipe 7-1-1 connects the secondary air duct 2 and the first venturi inlet reducer 7-1-2, the flue gas recirculation duct 6 is connected in the middle of the first venturi throat 7-1-3, the first venturi throat 7-1-3 is connected at both ends to the first venturi inlet 7-1-2 and the first outlet reducer 7-1-4 respectively, 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, the diameter of the first nozzle 7-1-7 in this form should be greater than the diameter of the first venturi throat 7-1-3. Form 2 is as follows Figure 5As shown, the second venturi first straight pipe 7-2-1 is connected to the second venturi second straight pipe 7-2-3, the second nozzle 7-2-2 is connected to the end of the second venturi first straight pipe 7-2-1 and extends into the second venturi second straight pipe 7-2-3, the flue gas recirculation pipe 6 is connected to the second venturi second straight pipe 7-2-3, and the subsequent structure is the same as the first form. Figure 6 As shown, the front form of the third venturi throat 7-3-1 is the same as form 2, the third venturi throat 7-3-1 is connected to the third venturi outlet reducer 7-3-2, the other end of the third venturi outlet reducer 7-3-2 is connected to the third nozzle 7-3-3, and 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 third venturi throat 7-3-1. Form 4 is as shown Figure 7 As shown, the fourth venturi first straight pipe 7-4-1 is connected to the fourth nozzle 7-4-2, part of the fourth first straight pipe 7-4-1 and the fourth nozzle 7-4-2 extend into the fourth venturi second straight pipe 7-4-3, the diameter of the fourth venturi second straight pipe 7-4-3 is slightly larger than the diameter of the fourth first straight pipe 7-4-1, the flue gas recirculation pipe 6 is connected to the fourth venturi second straight pipe 7-4-3, and the subsequent form is the same as form 2 or form 3. The above-mentioned venturi nozzle structure can make the wind speed at the nozzle entering the incinerator be 20-200m / s.

[0031] The method for denitrifying flue gas from a garbage incinerator using the above device comprises the following steps:

[0032] The recirculated flue gas led out from the flue gas recirculation duct 6 and the secondary air in the secondary air duct 2 are mixed at the throat of the venturi nozzle, and a pressure difference is formed between the throat 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 garbage in the combustion chamber of the waste incinerator 1 burns in the reducing atmosphere to suppress the generation of NOx during the waste incineration process.

[0033] The embodiments described above are merely descriptions of preferred implementation modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A denitrification device for flue gas from a garbage incinerator, characterized in that: The invention comprises a flue gas recirculation pipe (6), a nozzle (7), and a secondary air pipe (2), wherein the nozzle (7) is a venturi nozzle, one end of the venturi nozzle is connected to the secondary air pipe (2), and the other end is connected to the furnace of the waste incinerator (1); one end of the flue gas recirculation pipe (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 pipe (6) and the secondary air in the secondary air pipe (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).

2. The denitration device for flue gas from a garbage incinerator according to claim 1, characterized in that: A plurality of the Venturi nozzles are provided, and the plurality of the Venturi nozzles are arranged in sequence along the width direction of the waste incinerator (1), one end of each of the Venturi nozzles is respectively connected to a different position of the nozzle mother pipe of the secondary air duct (2) along the length direction, and the throat position of each of the Venturi nozzles is respectively connected to a different position of the nozzle mother pipe of the flue gas recirculation duct (6) along the length direction.

3. The denitration device for flue gas from a garbage incinerator according to claim 1, characterized in that: It also comprises a smoke filter device (3), wherein the smoke filter device (3) is arranged on the smoke recirculation pipe (6).

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

5. The denitration device for flue gas from a garbage incinerator according to claim 1, characterized in that: The outer wall of the flue gas recirculation pipe (11) is provided with a thermal insulation material layer.

6. The denitration device for flue gas from a garbage incinerator according to claim 1, characterized in that: The flue gas recirculation pipe (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).

7. The denitration device for flue gas from a garbage incinerator according to claim 2, characterized in that: The first Venturi straight pipe (7-1-1) of the Venturi nozzle is connected to the secondary air duct (2) and the first Venturi inlet reducer (7-1-2), the flue gas recirculation duct (6) is connected to the middle of the first Venturi throat (7-1-3), the first Venturi throat (7-1-3) has two ends connected to the first Venturi inlet (7-1-2) and the first outlet reducer (7-1-4) respectively, 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), and the diameter of the first nozzle (7-1-7) is greater than the diameter of the first Venturi throat (7-1-3).

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

9. The denitration device for flue gas from a garbage incinerator according to claim 2, characterized in that: The third venturi throat (7-3-1) of the venturi nozzle is connected to one end of the third venturi outlet reducer (7-3-2), the other end of the third venturi outlet reducer (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 pipeline (6) is connected to the third venturi second straight pipe, the diameter of the third nozzle (7-3-3) is slightly larger than the diameter of the third venturi throat (7-3-1), or, The fourth Venturi first straight pipe (7-4-1) of the Venturi nozzle is connected to the fourth nozzle (7-4-2), and part of the fourth Venturi first straight pipe (7-4-1) and the fourth nozzle (7-4-2) extend into the fourth Venturi second straight pipe (7-4-3), the diameter of the fourth Venturi second straight pipe (7-4-3) is slightly larger than the diameter of the fourth Venturi first straight pipe (7-4-1), and the flue gas recirculation pipe (6) is connected to the fourth Venturi second straight pipe (7-4-3).

10. A method for denitrification using the denitrification device for flue gas from a waste incinerator as claimed in any one of claims 1 to 9, characterized in that: The steps include: The recirculated flue gas drawn out from the flue gas recirculation duct (6) and the secondary air in the secondary air duct (2) are mixed at the throat of the venturi nozzle, and a pressure difference is formed between the throat 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) and forming a reducing atmosphere. The waste in the combustion chamber of the waste incinerator (1) is burned in the reducing atmosphere.

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