CN218065982U

CN218065982U - Cement kiln waste gas discharge system for reducing content of nitrogen oxides

Info

Publication number: CN218065982U
Application number: CN202222104621.7U
Authority: CN
Inventors: 公丕峰
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-08-11
Filing date: 2022-08-11
Publication date: 2022-12-16
Anticipated expiration: 2032-08-11

Abstract

The utility model relates to a reduce cement kiln exhaust emission system of nitrogen oxide content, including exhaust-heat boiler, dust precipitator and SCR device in advance, the last entry of hot-medium of exhaust-heat boiler first part communicates with the exhanst gas outlet of cement kiln, the hot exhanst gas outlet of lower part of exhaust-heat boiler first part communicates with the air intake of dust precipitator in advance, the air outlet of dust precipitator and the air intake intercommunication of SCR device in advance, the air outlet of SCR device and the air intake intercommunication of exhaust-heat boiler second part, the air intake and the first flue intercommunication of exhaust-heat boiler second part, install the third valve on the third flue. The utility model sets the waste heat boiler into a split structure, and efficiently and deeply removes nitrogen oxides by leading out flue gas with higher temperature from the first part of the waste heat boiler; the SCR matched pre-dust collector is arranged between the SCR device and the first part of the waste heat boiler, so that adverse effects on waste heat power generation are reduced; and the denitrated flue gas is subjected to heat exchange through the second part of the waste heat boiler, so that the heat emission is further reduced.

Description

Cement kiln waste gas discharge system for reducing content of nitrogen oxides

Technical Field

The utility model relates to a cement kiln's exhaust-gas treatment technical field especially involves a cement kiln exhaust emission system who reduces nitrogen oxide content.

Background

Technical guidelines (revised 2020) established by emergency emission reduction measures in severe-pollution weather major industries require that the environmental performance A level of cement clinker enterprises reaches: cement kiln and kiln tail waste heat utilization system smokeGas particle matter is less than or equal to 10mg/Nm ³ (ii) a Sulfur dioxide: 35 mg/Nm or less ³ (ii) a Nitrogen oxides less than or equal to 50 mg/Nm ³ (ii) a Ammonia escape: less than or equal to 5 mg/Nm ³ . Zibo city proposes ammonia escape: less than or equal to 3PPm/Nm ³

Thus cement kiln NO _x Emission reduction is deeply realized, and the work of accurately controlling ammonia escape is imperative.

The outlet temperature of the primary preheater of the advanced energy-saving cement kiln is lower than 260 ℃, so that a low-temperature catalyst becomes necessary in use. Under the strategy of low carbon, the cement kiln treats hazardous waste in a synergistic manner, the trend is to use alternative fuels, and acidic components in the smoke of the cement kiln are increased.

The cement kiln flue gas has high dust content, fine dust particle size and most of the components of CaO and CaCO ₃ 、SiO ₂ The catalyst is easy to wear and block; the dust contains CaO and Na ₂ O、K ₂ O, and the like, and the smoke components of the cement kiln partially mixed with the burned garbage or the solid waste are more complicated, and the catalyst is easy to be poisoned by alkali metals.

SO in flue gas when medium-temperature SCR and low-temperature SCR are adopted ₂ 、SO ₃ The catalyst can be poisoned, so that the catalyst is deactivated at low temperature; in the production process, due to the reasons of low-load operation, ammonia escape, low ammonia spraying temperature, uneven temperature field and the like, ammonium bisulfate is condensed into liquid and adhered to the catalyst, so that the activity of the catalyst is reduced until the activity is lost, the normal use of the catalyst is influenced, and the activity of the catalyst can be recovered only by changing the liquid ammonium bisulfate into gas in time.

At present, no complete scheme is available in the industry, the method is suitable for low-temperature flue gas in an energy-saving cement kiln, is suitable for a waste heat boiler and a power generation system, is suitable for acid flue gas, and can stably, reliably and long-term realize that the emission concentration of nitrogen oxides discharged by waste gas of the cement kiln is less than or equal to 50 mg/Nm ³ And ammonia escape: not more than 3PPm/Nm ³ 。

Disclosure of Invention

The utility model discloses to prior art's is not enough, provides a cement kiln exhaust emission system who reduces nitrogen oxide content, has realized nitrogen oxide emission reduction, has avoided catalyst poisoning to the waste heat utilization of denitration flue gas has been realized.

The utility model discloses a through following technical scheme realization, a reduce nitrogen oxide content's cement kiln exhaust emission system is provided, including exhaust-heat boiler, dust precipitator and SCR device in advance, the last entry of hot medium of exhaust-heat boiler first part is through advancing the exhanst gas outlet intercommunication of tobacco pipe way and cement kiln, the hot exhanst gas outlet of lower part of exhaust-heat boiler first part is through the air intake intercommunication of first flue and dust precipitator in advance, the air outlet of dust precipitator and the air intake intercommunication of SCR device in advance, the air outlet of SCR device passes through the air intake intercommunication of second flue and exhaust-heat boiler second part, the air intake of exhaust-heat boiler second part passes through third flue and first flue intercommunication, install the third valve on the third flue, install the sixth valve that is located between third flue and the dust precipitator on the first flue.

When the scheme is used, flue gas discharged by the cement kiln enters the first part of the waste heat boiler through the smoke inlet pipeline for primary heat exchange and cooling, then is led out from a hot flue gas outlet at the lower part of the first part of the waste heat boiler, can directly enter the second part of the waste heat boiler for heat exchange, can also enter the SCR device after being dedusted by the pre-deduster, and enters the second part of the waste heat boiler for secondary heat exchange after the waste gas exits the SCR device, so that the low-temperature catalyst can tolerate higher sulfate and sulfite in use; firstly, the flue gas is dedusted by the pre-deduster, then SCR denitration is carried out, and alkali metals in the flue gas are removed, so that the low-temperature catalyst is possible in use, the SCR denitration efficiency can reach 90 percent, and corresponding NO is _x The discharge concentration is reduced to 28-40mg/Nm ³ And the ammonia escape can be well controlled.

Preferably, the SCR device is equipped with a catalyst thermal desorption system. The SCR device of this optimization scheme communicates catalyst thermal desorption system, utilizes the kiln flue gas that is heated to erode the catalyst, and the temperature rise is fast, makes liquid ammonium bisulfate more timely to gaseous transformation, can resolve at any time.

And as optimization, the waste heat boiler further comprises a first short-circuit flue, one end of the first short-circuit flue is communicated with the smoke inlet pipeline, the other end of the first short-circuit flue is communicated with the first flue, a first valve is installed on the first short-circuit flue, and a second valve located between the first short-circuit flue and a hot medium upper inlet of the first part of the waste heat boiler is installed on the smoke inlet pipeline. The arrangement of the optimized scheme realizes the short circuit of the first part of the waste heat boiler, so that the flue gas discharged by the cement kiln directly enters the pre-dust collector, the application range is expanded, the cement kiln is suitable for more working conditions, the emission reduction of nitrogen oxides is ensured normally when the first part of the waste heat boiler is overhauled, and the use working condition with higher drying temperature requirement can be met.

And optimally, the first flue is provided with a high-temperature fan, and a communication point of the third flue and the first flue is positioned at the downstream side of the high-temperature fan. The high-temperature fan is arranged before pre-dedusting in the optimized scheme, so that the working negative pressure of the pre-dedusting and the SCR device is reduced, and the air leakage rate of the pre-deduster and the SCR device is reduced.

And as optimization, the waste heat boiler further comprises a second short-circuit flue and a smoke exhaust pipeline communicated with an air outlet of the second part of the waste heat boiler, one end of the second short-circuit flue is communicated with the third flue, the other end of the second short-circuit flue is communicated with the smoke exhaust pipeline, and a seventh valve is installed on the second short-circuit flue. The short circuit of dust precipitator, SCR device and exhaust-heat boiler second part in advance has been realized for the flue gas that the cement kiln discharged or directly get into subordinate's use system with the flue gas after the first part heat transfer of exhaust-heat boiler, satisfied more use operating modes equally, especially when overhauing dust precipitator, SCR device or exhaust-heat boiler second part in advance, guarantee the normal emission of cement kiln furnace flue gas and the normal operating of exhaust-heat boiler first part.

As optimization, the smoke exhaust pipeline is communicated with the material drying system. The arrangement of the optimized scheme realizes the further utilization of waste heat, and the flue gas discharged by the waste heat boiler is used for drying the raw materials, so that the further energy conservation and emission reduction are realized, and the heat waste is reduced.

And as optimization, the waste heat boiler further comprises a pre-dust collector arranged on the first flue, the pre-dust collector is positioned between the sixth valve and the SCR device, an air inlet of the pre-dust collector is communicated with a hot flue gas outlet at the lower part of the first part of the waste heat boiler, and an air outlet of the pre-dust collector is communicated with an air inlet of the SCR device.

The beneficial effects of the utility model are that: the flue gas with higher temperature is led out from the first part of the waste heat boiler, and the SCR catalyst is used to work at 160-280 ℃, so that the acid poisoning resistance of the catalyst can be improved, the nitrogen oxide can be efficiently and deeply removed, the ammonia escape can be reliably controlled, the emission reduction concentration of the nitrogen oxide is stably and reliably realized for a long time and is not higher than 50 mg/cubic meter, and the flue gas is suitable for low-temperature flue gas in an energy-saving cement kiln; the SCR matched pre-dust collector is arranged between the SCR device and the first part of the waste heat boiler, so that adverse effects on waste heat power generation are reduced, and the SCR matched pre-dust collector is suitable for the waste heat boiler and a power generation system; the denitrated flue gas is subjected to heat exchange by the second part of the waste heat boiler, so that the heat emission is further reduced; flue gas after denitration is used for drying raw materials, so that deep utilization of waste heat is realized; the method is suitable for the existing cement production process, has little influence on waste heat utilization, and has good application prospect.

Drawings

FIG. 1 is a flow chart of the present invention;

FIG. 2 is an enlarged view of a portion of FIG. 1;

shown in the figure:

1. a smoke inlet pipeline 2, a second valve 3, a first short-circuit flue 4, a first valve 5, a first part of a waste heat boiler 6, a fifth valve 7, a high-temperature fan 8, a third valve 9, a third flue 10, a first flue 11 and a fourth valve, 12, a smoke exhaust pipeline, 13, a second part of the waste heat boiler, 14, an SCR device, 15, a pre-dust collector, 16, a sixth valve, 17, a catalyst thermal desorption system, 18, a second short-circuit flue, 19, a seventh valve, 20 and a second flue.

Detailed Description

In order to clearly illustrate the technical features of the present solution, the present solution is explained below by way of specific embodiments.

As shown in figure 1, the cement kiln waste gas emission system for reducing the content of nitrogen oxides comprises a waste heat boiler, a pre-dust collector 15 and an SCR device 14, wherein the SCR device is provided with a catalyst thermal desorption system 17, the pre-dust collector, the SCR device and the catalyst thermal desorption system are integrated, and the heating surface of the waste heat boiler is divided into two main parts, namely a first part of the waste heat boiler and a second part of the waste heat boiler. The first part of the waste heat boiler is connected with the second part of the waste heat boiler through a flue, so that equipment or parts can be conveniently arranged between the first part and the second part, the middle upper part of the waste heat boiler in the prior art is used as the first part 5 of the waste heat boiler, and the lower part of the waste heat boiler is used as the second part 13 of the waste heat boiler.

An upper inlet of a heat medium of the first part 5 of the waste heat boiler is communicated with a flue gas outlet of the cement kiln through a flue gas inlet pipeline 1, as a preferred scheme, the flue gas outlet of the cement kiln of the embodiment is a waste gas outlet of a primary preheater, a lower hot flue gas outlet of the first part 5 of the waste heat boiler is communicated with an air inlet of a pre-dust collector 15 through a first flue 10, an air outlet of the pre-dust collector is communicated with an air inlet of an SCR device 14, an air outlet of the SCR device is communicated with an air inlet of a second part 13 of the waste heat boiler through a second flue 20, an air inlet of the second part 13 of the waste heat boiler is communicated with the first flue 10 through a third flue 9, a third valve 8 is installed on the third flue 9, a sixth valve 16 located between the third flue and the pre-dust collector is installed on the first flue, and a fourth valve 11 is installed on the second flue 20.

An air outlet of the second part of the waste heat boiler is communicated with a smoke exhaust pipeline 12, and the smoke exhaust pipeline 12 is communicated with a material drying system. In order to improve the efficiency of the flue gas flow, a high-temperature fan 7 is installed on the first flue 10, the high-temperature fan 7 is used for providing power for the flue gas flow, and the communication point of the third flue 9 and the first flue is positioned on the downstream side of the high-temperature fan. The upstream side and the downstream side of the present embodiment are based on the description of the flow direction of the flue gas, that is, the flue gas flows from upstream to downstream.

The temperature of the flue gas at the outlet of the first part of the waste heat boiler is higher, SCR denitration is carried out, and the poison of sulfate and sulfite is reduced. The flue gas is dedusted and then SCR denitration is carried out to remove alkali metals in the flue gas, so that the use of a low-temperature catalyst becomes possible. The denitration efficiency of SCR can reach 90 percent, and the corresponding NO _x The discharge concentration is reduced to 28 to 40mg/m ³ And the ammonia escape can be well controlled. The SCR device is communicated with a catalyst thermal desorption system, and inevitably generates ammonium bisulfate in the flue gas, and the catalyst is preparedThe catalyst thermal analysis system utilizes the heated kiln flue gas to wash the catalyst, the temperature rises quickly, the liquid ammonium bisulfate is converted into gas in time, and the analysis can be carried out at any time. The catalyst is divided into bins, an active smoke recovery flow is established, and the smoke used for activity recovery is heated by using the heat of hot smoke or steam or electricity or flame of a kiln. The hot flue gas gets into the catalyst storehouse that stops use through the bypass pipeline, erodes the catalyst surface, becomes gaseous state with liquid ammonium bisulfate, and gaseous state ammonium bisulfate is directed into the flue and is purified again. The specific structure of the catalyst thermal desorption system can be realized by adopting the prior art, such as the patent scheme of the patent number 2019204371511 and the name of 'a device for recovering the activity of the selective catalytic reduction catalyst'.

As shown in fig. 2, the abatement system of the present embodiment also comprises a first short circuit stack 3 and a second short circuit stack 18.

One end of a first short-circuit flue 3 is communicated with a flue inlet pipeline 1, the other end of the first short-circuit flue is communicated with a first flue 10, a first valve 4 is installed on the first short-circuit flue, a second valve 2 located between the first short-circuit flue and a hot medium upper inlet of a first part of the waste heat boiler is installed on the flue inlet pipeline, and a fifth valve 6 located between a hot flue gas outlet of the lower part of the first part of the waste heat boiler and the first short-circuit flue is also installed on the first flue 10.

One end of the second short-circuit flue 18 is communicated with the third flue 9, the other end of the second short-circuit flue is communicated with the smoke exhaust pipeline 12, a seventh valve 19 is installed on the second short-circuit flue, and a sixth valve 16 located between the third flue 9 and the pre-dust collector is installed on the first flue.

The drying system of this embodiment selects for the stoving of material, specifically is to grind the air intake intercommunication with raw materials drying system's raw materials, and raw materials grinds the air-out and gets into afterbody dust remover, makes waste gas get into equipment such as raw materials mill and dries the raw materials, then gets into afterbody dust remover, discharges to the chimney at last.

The outlet temperature of a first-stage preheater of an advanced energy-saving cement kiln is lower than 260 ℃, flue gas enters a waste heat boiler for heat exchange, generally passes through a steam superheater, then an evaporator and then an economizer, and the specific using method of the embodiment comprises the following aspects:

1. closing a first valve 4, a third valve 8 and a seventh valve 19, opening a second valve 2, a fifth valve 6, a sixth valve 16 and a fourth valve 11, allowing flue gas to enter a first part of the waste heat boiler for primary cooling, reducing the temperature to 200-250 ℃, then leading out from a hot flue gas outlet at the lower part of the first part of the waste heat boiler, performing dust removal treatment by a pre-dust remover, allowing the flue gas to enter an SCR (selective catalytic reduction) device, providing a catalyst thermal desorption system for the SCR device, allowing waste gas to exit the SCR and then enter a second part of the waste heat boiler for heat exchange, allowing the waste gas to exit the second part of the waste heat boiler for deep waste heat utilization, allowing the waste gas to enter a raw material drying system through a smoke exhaust pipeline, and drying raw materials;

2. closing the second valve 2, the fifth valve 6, the sixth valve 16 and the fourth valve 11, opening the first valve 4, the seventh valve 19 and the third valve 8, short-circuiting the SCR device, the first part of the waste heat boiler and the second part of the waste heat boiler, and directly feeding the waste gas of the cement kiln into a smoke exhaust pipeline;

3. closing the second valve 2, the third valve 8, the seventh valve 19 and the fifth valve 6, opening the first valve 4, the sixth valve 16 and the fourth valve 11, carrying out short circuit on the first part of the waste heat boiler, directly feeding the flue gas into the pre-dust collector 15 through the flue gas inlet pipeline, carrying out SCR treatment and denitration on the flue gas, then feeding the flue gas into the second part of the waste heat boiler for heat exchange, and feeding the flue gas into the flue gas exhaust pipeline, wherein when the first part of the waste heat boiler does not operate, the flue gas denitration treatment can also be carried out;

4. and closing the first valve 4, the sixth valve 16, the seventh valve 19 and the fourth valve 11, opening the second valve 2, the fifth valve 6 and the third valve 8, carrying out short circuit on the SCR device, and allowing the flue gas to enter the second part of the waste heat boiler after heat exchange of the first part of the waste heat boiler and then enter a smoke exhaust pipeline, so that the flue gas bypasses the SCR device, and the SCR device can be conveniently split.

The implementation uses SCR to deeply remove nitrogen oxides with high efficiency, reliably control ammonia escape, and stably and reliably realize the emission reduction concentration of the nitrogen oxides not higher than 50 mg/cubic meter for a long time. And the SCR matched dust remover and the SCR are arranged between the first part and the second part of the waste heat boiler, so that the influence on waste heat power generation is small. The temperature of the denitrated flue gas is still suitable for drying the raw materials, and the waste heat is continuously and deeply utilized. The system is suitable for the existing cement production process, has small influence on waste heat utilization, and has good application prospect.

The utility model is also suitable for other industrial kilns. Of course, the above description is not limited to the above examples, and the technical features of the present invention that are not described in the present application can be implemented by or using the prior art, which is not described herein again; the above embodiments and drawings are only used for illustrating the technical solutions of the present invention and are not intended to limit the present invention, and the present invention has been described in detail with reference to the preferred embodiments, and it should be understood by those skilled in the art that changes, modifications, additions or substitutions made by those skilled in the art within the spirit of the present invention should not depart from the spirit of the present invention, and shall also belong to the protection scope of the claims of the present invention.

Claims

1. The utility model provides a reduce cement kiln exhaust emission system of nitrogen oxide content which characterized in that: the cement kiln waste heat recovery device comprises a waste heat boiler and an SCR device (14), an inlet of a hot medium of a first part (5) of the waste heat boiler is communicated with a smoke outlet of a cement kiln through a smoke inlet pipeline (1), a lower hot smoke outlet of the first part (5) of the waste heat boiler is communicated with an air inlet of the SCR device (14) through a first flue (10), an air outlet of the SCR device is communicated with an air inlet of a second part (13) of the waste heat boiler through a second flue (20), an air inlet of the second part (13) of the waste heat boiler is communicated with the first flue through a third flue (9), a third valve (8) is installed on the third flue (9), and a sixth valve (16) located between the third flue and the SCR device is installed on the first flue.

2. The cement kiln exhaust gas emission system for reducing nitrogen oxide content according to claim 1, wherein: the SCR device is equipped with a catalyst thermal desorption system (17).

3. The cement kiln exhaust emission system for reducing nitrogen oxide content according to claim 2, wherein: still include first short circuit flue (3), the one end and the advancing tobacco pipe way (1) intercommunication of first short circuit flue (3), the other end and first flue (10) intercommunication of first short circuit flue, install first valve (4) on the first short circuit flue, advance and install second valve (2) that are located on the tobacco pipe way between the hot-medium of first short circuit flue and exhaust-heat boiler first part and enter the mouth.

4. The cement kiln exhaust gas emission system for reducing nitrogen oxide content according to claim 1, wherein: the high-temperature fan (7) is installed on the first flue (10), and the communication point of the third flue (9) and the first flue is located on the downstream side of the high-temperature fan.

5. The cement kiln exhaust gas emission system for reducing nitrogen oxide content according to claim 1, wherein: the waste heat boiler is characterized by further comprising a second short-circuit flue (18) and a smoke exhaust pipeline (12) communicated with an air outlet of the second part of the waste heat boiler, one end of the second short-circuit flue is communicated with a third flue (9), the other end of the second short-circuit flue is communicated with the smoke exhaust pipeline (12), and a seventh valve (19) is installed on the second short-circuit flue.

6. The cement kiln exhaust gas emission system for reducing nitrogen oxide content according to claim 1, wherein: the exhaust-heat boiler further comprises a pre-dust collector (15) arranged on the first flue (10), the pre-dust collector is located between the sixth valve (16) and the SCR device (14), an air inlet of the pre-dust collector (15) is communicated with a hot flue gas outlet at the lower part of the first part (5) of the exhaust-heat boiler, and an air outlet of the pre-dust collector is communicated with an air inlet of the SCR device (14).