Novel bypass ventilation dechlorination system and method for cement plant

Abstract

The invention discloses a novel bypass ventilation dechlorination system and method for a cement plant, and the system comprises a bypass ventilation pipeline connected with a smoke chamber, the other end of the bypass ventilation pipeline is connected with a settling chamber, the other end of the settling chamber is connected with a separated heat pipe heat exchanger, and a gate plate is arranged between the settling chamber and the separated heat pipe heat exchanger. The bottom of the separated heat pipe exchanger is connected with the pneumatic conveying system; one end, far away from the settling chamber, of the separated heat pipe exchanger is connected with the decomposing furnace; the separation type heat pipe heat exchanger comprises a condensation section, a first evaporation section and a second evaporation section, according to the invention, the temperature of the flue gas without harmful components is about 850-950 DEG C, a proper amount of pulverized coal is sprayed through the combustor to generate a reduction zone, NOx in the flue gas is reduced into N2, the consumption of SNCR ammonia water of a sintering system can be reduced, and the problem of NOx emission of bypass flue gas is solved; the flue gas with the temperature of 850-950 DEG C enters the decomposing furnace and is equivalent to the temperature in the decomposing furnace, so that the influence on a cement sintering system is very small; and crusts are reduced by adopting a separated heat pipe heat exchanger.

Description

Technical Field

[0001] The present invention relates to a chlorine removal system and method, and particularly to a new bypass air extraction chlorine removal system and method for a cement plant. Background Art

[0002] With the development of society, in the process of cement production, in order to reduce operating costs, the quality of raw fuels will decline, and at the same time, waste materials are co-disposed. The raw fuels or co-disposed waste materials will introduce harmful components such as potassium, sodium, sulfur, and chlorine into the firing system. When the harmful components exceed the standard, they will not only circulate and accumulate in the firing system, causing crusting and blockage, thus affecting the stable operation of the system, but also have an adverse impact on the quality of clinker. Therefore, measures such as bypass air extraction are required to discharge excessive harmful components such as potassium, sodium, sulfur, and chlorine from the system.

[0003] There are mainly two conventional bypass air extraction cooling processes: One is to extract high-temperature flue gas at about 1100°C from the smoke chamber, enter the mixing chamber, mix with normal-temperature air and directly cool it to about 200°C. After the waste gas passes through the bag filter, the harmful components are collected with the dust and discharged externally, and the purified waste gas is discharged to the atmosphere by the exhaust fan; the other is to extract high-temperature flue gas at about 1100°C from the smoke chamber, enter the mixing chamber, cool it to about 350°C by air cooling, and then cool it to about 200°C through an indirect heat exchanger. After the waste gas is purified by the bag filter, the harmful components are collected with the dust and discharged externally, and the purified waste gas is discharged to the atmosphere by the exhaust fan.

[0004] The existing conventional bypass air extraction system for cement clinker firing system has problems of excessive NOx emissions in the flue gas and large heat loss in the system energy.

[0005] In the existing bypass air extraction method, since the high-temperature flue gas needs to be rapidly cooled from 1100°C to 350°C or 200°C, there is a lack of suitable temperature and time window (880°C - 920°C) required for the SNCR denitration reaction during the process. The SNCR denitration efficiency is low. If the flue gas is directly discharged into the atmosphere, there is a problem of excessive NOx emissions. The current solutions are mainly: First, introduce the flue gas to the front end of the grate cooler, and then into the kiln to re-enter the firing system. Since the oxygen content in the flue gas is relatively low (oxygen content is about 15%), when it enters the firing system as the secondary and tertiary air, it will affect the burner capacity, the stability of the system will decline, the waste gas volume will increase, and the system resistance will increase; Second, introduce the flue gas to the SCR inlet. From the on-site situation, the SCR is far from the bypass air extraction system and there is a large height difference, so the transportation difficulty is large and the cost is increased. Considering the energy utilization rate of the whole system, the high-temperature flue gas needs to be rapidly cooled from 1100°C to 350°C or 200°C by mixing a large amount of cold air (normal-temperature air), and then discharged into the atmosphere after being treated by the bag filter. The heat of the flue gas is not utilized, and the heat loss of the system is large. Summary of the Invention

[0006] Objective of the Invention: The objective of the present invention is to provide a new bypass air extraction and chlorine removal system and method for a cement plant, which can directly recover the heat of the flue gas without using cold air.

[0007] Technical Solution: The present invention includes a bypass air extraction pipeline connected to the smoke chamber. The other end of the bypass air extraction pipeline is connected to a settling chamber. The other end of the settling chamber is connected to a separated heat pipe heat exchanger. A gate is provided between the settling chamber and the separated heat pipe heat exchanger. The bottom of the separated heat pipe heat exchanger is connected to a pneumatic conveying system. One end of the separated heat pipe heat exchanger away from the settling chamber is connected to a decomposition furnace. The separated heat pipe heat exchanger includes a condensation section and a first evaporation section and a second evaporation section arranged in parallel.

[0008] A first gate is provided between the first evaporation section and the settling chamber, and a second gate is provided between the second evaporation section and the settling chamber. During operation, one gate is open and the other is closed, mainly to control the passage of flue gas into the separated heat pipe heat exchanger and the speed and flow rate of the flue gas.

[0009] One end of the first evaporation section and the second evaporation section is connected to the condensation section through a riser pipe, and the other end is connected to the condensation section through a downcomer pipe.

[0010] Throttle valves and external pipelines are provided on the connecting pipelines of the first evaporation section and the second evaporation section to the condensation section. During operation, the flow direction of the medium in the heat pipe is controlled through the throttle valves to ensure that one evaporation section is working and the other is closed.

[0011] The separated heat pipe heat exchanger is connected to the decomposition furnace through a flue gas riser pipe to form a circulation loop.

[0012] A soot blowing device is provided at the top of the separated heat pipe heat exchanger for cleaning the scale.

[0013] A burner is connected to the flue gas riser pipe. An appropriate amount of pulverized coal is sprayed through the burner to generate a reduction zone to reduce NOx in the flue gas to N2.

[0014] The bottom of the settling chamber is connected to the decomposition furnace. After the raw meal powder carried by the flue gas is settled in the settling chamber, it enters the decomposition furnace.

[0015] The pneumatic conveying system is connected to a dust bin. The collected dust is transported to the dust bin through the pneumatic conveying system and used as a cement admixture.

[0016] A new bypass air extraction and chlorine removal method for a cement plant includes the following steps:

[0017] S1. Extract bypass high-temperature flue gas from the front side of the smoke chamber, enter the settling chamber through the bypass air extraction pipeline. After the raw meal powder carried by the flue gas is settled in the settling chamber, it enters the decomposition furnace.

[0018] S2. After passing through the damper, the relatively clean flue gas enters the first evaporation section or the second evaporation section of the separated heat pipe heat exchanger for heat exchange. The condensation section of the separated heat pipe heat exchanger heats the steam from waste heat power generation. The temperature of the bypass flue gas drops from 1100°C to 850 - 950°C. The harmful components in the flue gas undergo a liquefaction reaction and adhere to the separated heat pipe heat exchanger. After the liquid absorbs the raw meal powder in the flue gas, under the action of gravity, it leaves the separated heat pipe heat exchanger and is transported to the ash bin by the pneumatic conveying system;

[0019] S3. The flue gas enters the flue gas rising pipe. In the flue gas rising pipe, pulverized coal is injected through the burner to generate a reduction zone, reducing the NOx in the flue gas to N2. Finally, the flue gas enters the decomposition furnace.

[0020] Beneficial effects: The present invention has the following advantages:

[0021] 1. The new type of bypass air release system does not require a fan, and no cooling air enters the system. After the flue gas returns to the firing system, the flue gas volume of the firing system will not increase. At the same time, the negative pressure at the flue gas extraction opening in the smoke chamber is about 400 Pa, and the negative pressure returning to the decomposition furnace is about 1100 Pa. Under this pressure difference, the flue gas can flow, and basically no additional power consumption will be incurred.

[0022] 2. The temperature of the flue gas after removing harmful components is about 850°C - 950°C. By injecting an appropriate amount of pulverized coal through the burner to generate a reduction zone, reducing the NOx in the flue gas to N2, the consumption of SNCR ammonia water in the firing system can be reduced, and the problem of NOx emission from the bypass flue gas is solved; The flue gas at 850°C - 950°C enters the decomposition furnace, which is equivalent to the temperature in the decomposition furnace, and has little impact on the cement firing system.

[0023] 3. The temperature of the flue gas is very high and the quality is good. The recovered heat heats the steam of the waste heat power generation system, which can improve the quality of the waste heat power generation steam and increase the efficiency of the steam turbine.

[0024] 4. The separated heat pipe heat exchanger is adopted, which has high thermal conductivity, excellent isothermal property, variable heat flux density, strong environmental adaptability, etc. Through the coupled operation of the first evaporation section and the second evaporation section, when operating at high temperature, the influence of scaling is reduced, and the system stability is better.

[0025] 5. A part of the heat carried by the flue gas of the new type of bypass air release system is absorbed by the waste heat power generation system, and the remaining heat returns to the firing system. The heat is utilized in large quantities, and the standard coal consumption of the cement production line will increase slightly. Description of the Drawings

[0026] Figure 1 is the overall structural schematic diagram of the present invention;

[0027] Figure 2 is the schematic diagram of the settling chamber and the separated heat pipe heat exchanger of the present invention;

[0028] Figure 3 Schematic diagram of the separated heat pipe heat exchanger of the present invention. Specific embodiments

[0029] The present invention will be further described below with reference to the accompanying drawings.

[0030] Embodiment 1

[0031] As Figure 1 shown, the new bypass air extraction and chlorine removal system for a cement plant in this embodiment includes a bypass air extraction pipeline 1, a sedimentation chamber 2, a gate 3, a separated heat pipe heat exchanger 4, a flue gas rising pipeline 5, a pneumatic conveying system 6, a burner 7, and a soot blowing device 8. One end of the bypass air extraction pipeline 1 is connected to the kiln tail flue gas chamber, and the other end is connected to the sedimentation chamber 2. The other end of the sedimentation chamber 2 is connected to a separated heat pipe heat exchanger 4. The bottom of the sedimentation chamber 2 is connected to the decomposition furnace. The sedimentation chamber 2 is mainly used to separate the raw meal powder in the flue gas, reduce the raw meal consumption in the cement firing system, and at the same time, reduce the wear, corrosion, and crust formation on the separated heat pipe heat exchanger 4. A gate 3 is provided between the sedimentation chamber 2 and the separated heat pipe heat exchanger 4. The bottom of the separated heat pipe heat exchanger 4 is connected to the pneumatic conveying system 6 through a feed pipe. The pneumatic conveying system 6 is connected to a ash bin. The collected dust is transported to the ash bin through the pneumatic conveying system 6 and used as a cement admixture. A soot blowing device 8 is provided at the top of the separated heat pipe heat exchanger 4. One end of the separated heat pipe heat exchanger 4 away from the sedimentation chamber 2 is connected to the decomposition furnace through a flue gas rising pipeline 5 to form a circulation loop. A burner 7 is connected to the flue gas rising pipeline 5.

[0032] As Figure 2 and Figure 3 shown, the separated heat pipe heat exchanger 4 includes a condensation section 4-3 and a first evaporation section 4-1 and a second evaporation section 4-2 arranged in parallel. A first gate 3-1 is provided between the first evaporation section 4-1 and the sedimentation chamber 2, and a second gate 3-2 is provided between the second evaporation section 4-2 and the sedimentation chamber 2. During operation, one gate is opened and the other is closed, mainly to control the channel for the flue gas to enter the separated heat pipe heat exchanger and the speed and flow rate of the flue gas. Both the first evaporation section 4-1 and the second evaporation section 4-2 are connected to the flue gas rising pipeline 5. One end of the first evaporation section 4-1 and the second evaporation section 4-2 is connected to the condensation section 4-3 through a riser pipe 4-4, and the other end is connected to the condensation section 4-3 through a downcomer pipe 4-5. A first throttle valve 9-1 and a first external pipeline 10-1 are respectively provided on the connecting pipeline between the first evaporation section 4-1 and the condensation section 4-3. A second throttle valve 9-2 and a second external pipeline 10-2 are respectively provided on the connecting pipeline between the second evaporation section 4-2 and the condensation section 4-3. During operation, the flow direction of the medium in the heat pipe is controlled by the throttle valve to ensure that one evaporation section works and the other is closed.

[0033] In the evaporator section of the separated heat pipe heat exchanger 4, the medium inside the pipes absorbs heat and vaporizes. The generated steam enters the condenser section 4-3 through the riser pipe 4-4. In the condenser section 4-3, the medium inside the pipes condenses and liquefies, releasing heat to heat the steam from waste heat power generation, and then returns to the evaporator section through the downcomer 4-5. The medium inside the heat pipe undergoes vaporization and liquefaction to complete a cycle, transferring the heat in the flue gas to the steam from waste heat power generation. The temperature of the bypass flue gas drops from 1100 °C to 850 - 950 °C. The harmful components in the flue gas undergo a liquefaction reaction and will adhere to the heat pipe. The liquid will absorb the raw meal powder in the flue gas, resulting in accumulation. Finally, under the action of gravity, it leaves the heat pipe, is collected through the blanking pipe, and is transported to the ash bin by the pneumatic conveying system 6. The flue gas leaving the separated heat pipe heat exchanger enters the flue gas riser pipe 5. In the flue gas riser pipe, an appropriate amount of pulverized coal is injected through the burner 7 to generate a reduction zone, reducing the NOx in the flue gas to N2. Finally, the flue gas enters the decomposition furnace.

[0034] A certain proportion of bypass high-temperature flue gas is extracted from the front side of the smoke chamber above the rotary kiln and enters the settling chamber 2 through the bypass air release pipe 1. After the raw meal powder carried by the flue gas settles in the settling chamber 2, it enters the decomposition furnace, reducing the raw material consumption of the cement firing system. The relatively clean flue gas enters the first evaporator section 4-1 or the second evaporator section 4-2 of the separated heat pipe heat exchanger 4 for heat exchange after passing through the gate 3. In the condenser section 4-3 of the separated heat pipe heat exchanger 4, the steam from waste heat power generation is heated. The temperature of the bypass flue gas drops from 1100 °C to 850 - 950 °C. The harmful components in the flue gas undergo a liquefaction reaction and will adhere to the separated heat pipe heat exchanger 4. The liquid will absorb the raw meal powder in the flue gas, resulting in accumulation. Finally, under the action of gravity, it leaves the separated heat pipe heat exchanger 4, is collected through the blanking pipe, and is transported to the ash bin by the pneumatic conveying system 6 to be used as a cement admixture. The flue gas enters the flue gas riser pipe 5. In the riser pipe, an appropriate amount of pulverized coal is injected through the burner 7 to generate a reduction zone, reducing the NOx in the flue gas to N2. Finally, the flue gas enters the decomposition furnace. This system does not require a cooling fan and will not increase the flue gas volume. After passing through the separated heat pipe heat exchanger, the flue gas temperature is 850 - 950 °C, and then self-denitrification treatment is carried out. Finally, it returns to the decomposition furnace, with a temperature equivalent to that in the decomposition furnace, having little impact on the cement firing system. At the same time, the ammonia water consumption can be reduced after self-denitrification treatment.

[0035] During operation, by reducing the amount of steam from waste heat power generation, the surface temperature of the separated heat pipe heat exchanger 4 is increased, or when it is stabilized at an unreasonably high temperature (the reason is that the scale area is very large and the scale cannot be removed by self-heating), the dechlorination effect drops sharply at this time. By controlling the gate 3, for example, closing the first gate, opening the second gate, and at the same time opening the throttle valve connecting the riser and downcomer of the second evaporation section, and closing the throttle valve connecting the riser and downcomer of the first evaporation section, the second evaporation section is allowed to work. At this time, the external pipeline connecting the riser and downcomer of the first evaporation section is connected to the normal temperature medium pipeline, and the normal temperature medium is slowly introduced into the first evaporation section to rapidly cool the first evaporation section. The scale will be cracked, and the scale will be cleaned under the action of the soot blower. Finally, an appropriate medium is filled into the first evaporation section for the next use. Through the coupled operation of the first evaporation section and the second evaporation section, the influence of the scale is reduced during high-temperature operation, and the system stability is better.

[0036] This bypass system utilizes the characteristics of the separated heat pipe heat exchanger, such as high thermal conductivity, excellent isothermal property, variable heat flux density, and strong environmental adaptability, to directly recover the heat of the flue gas. The flue gas temperature drops from about 1100 °C to about 850 - 950 °C (the known melting point temperature of KCl is about 770 °C, and the melting point temperature of NaCl is about 800 °C). The harmful components in the flue gas undergo a liquefaction reaction and will adhere to the heat pipe. The liquid will absorb the raw meal powder in the flue gas, accumulate and gather, and finally leave the heat pipe under the action of gravity. After being collected by the feeding pipe, it is transported to the ash bin by the pneumatic conveying system. The condensing section of the separated heat pipe heats the steam from waste heat power generation to improve the steam quality for power generation. After the harmful components are removed from the flue gas leaving the separated heat pipe heat exchanger, an appropriate amount of pulverized coal is sprayed into the rising pipe to form a reduction zone for denitrification, and finally it enters the decomposition furnace. The new type of bypass air release system does not require a cooling fan, greatly reducing the system heat loss. The recovered heat heats the steam of the waste heat power generation system to improve the steam quality of the waste heat power generation. At the same time, after the flue gas is self-denitrified, it is recycled back to the decomposition furnace system, reducing the ammonia water consumption. Through measures such as the main system SNCR, the problem of NOx emissions from the bypass flue gas is solved, providing a basic guarantee for the cement kiln to use raw fuels containing harmful components or co-dispose of waste. The oxygen content of the flue gas recycled back to the decomposition furnace system is low, solving the problem of dust emissions.

[0037] Example 2

[0038] The new type of bypass air release dechlorination method for the cement plant in this embodiment includes the following steps:

[0039] A certain proportion of bypass high-temperature flue gas is extracted from the front side of the smoke chamber above the rotary kiln and enters the settling chamber 2 through the bypass air release pipeline 1. After the raw meal powder carried by the flue gas is settled in the settling chamber 2, it enters the decomposition furnace.

[0040] After passing through the damper 3, the relatively clean flue gas enters the first evaporation section 4-1 or the second evaporation section 4-2 of the separated heat pipe heat exchanger 4 for heat exchange. At the condensation section 4-3 of the separated heat pipe heat exchanger 4, the steam from waste heat power generation is heated. The temperature of the bypass flue gas is reduced from 1100 °C to 850 - 950 °C, and the harmful components in the flue gas undergo a liquefaction reaction, which will adhere to the separated heat pipe heat exchanger 4. The liquid will absorb the raw meal powder in the flue gas, resulting in accumulation and aggregation. Finally, under the action of gravity, it leaves the separated heat pipe heat exchanger 4, is collected through the blanking pipe, and is transported to the ash bin by the pneumatic conveying system 6;

[0041] The flue gas enters the flue gas rising pipe 5. In the rising pipe, an appropriate amount of pulverized coal is injected through the burner 7 to generate a reduction zone, reducing the NOx in the flue gas to N2. Finally, the flue gas enters the decomposition furnace.

Claims

1. A new bypass air extraction chlorine removal system for a cement plant, characterized in that, It includes a bypass air bleed pipeline connected to a smoke chamber. The other end of the bypass air bleed pipeline is connected to a sedimentation chamber. The other end of the sedimentation chamber is connected with a separated heat pipe heat exchanger. A sluice gate is arranged between the sedimentation chamber and the separated heat pipe heat exchanger. The bottom of the separated heat pipe heat exchanger is connected to a pneumatic conveying system. The end of the separated heat pipe heat exchanger far from the sedimentation chamber is connected to a decomposition furnace. The separated heat pipe heat exchanger includes a condensation section and a first evaporation section and a second evaporation section arranged in parallel.

2. The novel bypass air extraction and chlorine removal system for a cement plant according to claim 1, wherein A first sluice gate is arranged between the first evaporation section and the sedimentation chamber, and a second sluice gate is arranged between the second evaporation section and the sedimentation chamber.

3. The novel bypass air extraction chlorine removal system for a cement plant according to claim 2, characterized in that, One ends of the first evaporation section and the second evaporation section are connected to the condensation section through riser pipes, and the other ends are connected to the condensation section through downcomer pipes.

4. The novel bypass air extraction chlorine removal system for a cement plant according to claim 3, wherein, Throttle valves and external pipelines are arranged on the connecting pipelines of the first evaporation section and the second evaporation section with the condensation section.

5. The novel bypass air release chlorine removal system for a cement plant according to claim 1, wherein The separated heat pipe heat exchanger is connected to the decomposition furnace through a flue gas rising pipeline.

6. The novel bypass air extraction chlorine removal system for a cement plant according to claim 1, characterized in that, A soot blowing device is arranged at the top of the separated heat pipe heat exchanger.

7. The novel bypass air extraction chlorine removal system for a cement plant according to claim 5, characterized in that, A burner is connected to the flue gas rising pipeline.

8. The novel bypass air extraction chlorine removal system for a cement plant according to claim 1, wherein, The bottom of the sedimentation chamber is connected to the decomposition furnace.

9. The novel bypass air extraction chlorine removal system for a cement plant according to claim 1, wherein, The pneumatic conveying system is connected to a ash bin.

10. A chlorine removal method for the novel bypass air release chlorine removal system of a cement plant according to any one of claims 1 to 9, characterized in that, It includes the following steps: S1. Extract bypass high-temperature flue gas from the front side of the smoke chamber, enter the sedimentation chamber through the bypass air bleed pipeline. After the raw meal powder carried by the flue gas is sedimented in the sedimentation chamber, it enters the decomposition furnace. S2. The relatively clean flue gas enters the first evaporation section or the second evaporation section of the separated heat pipe heat exchanger for heat exchange after passing through the sluice gate. The condensation section of the separated heat pipe heat exchanger heats the steam from waste heat power generation. The temperature of the bypass flue gas is reduced from 1100 °C to 850 - 950 °C. The harmful components in the flue gas undergo a liquefaction reaction and adhere to the separated heat pipe heat exchanger. After the liquid absorbs the raw meal powder in the flue gas, under the action of gravity, it leaves the separated heat pipe heat exchanger and is transported to the ash bin by the pneumatic conveying system. S3. The flue gas enters the flue gas rising pipeline. In the flue gas rising pipeline, pulverized coal is injected through the burner to generate a reduction zone to reduce NOx in the flue gas to N2. Finally, the flue gas enters the decomposition furnace.

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