High-efficiency incineration coupled flue gas ultra-low emission system and control method thereof

Abstract

The present invention discloses a high-efficiency incineration coupled flue gas ultra-low emission system and a control method thereof, wherein the system comprises a garbage incinerator, a waste heat boiler, a high-efficiency dust removal, denitration and dioxin removal system, a low-temperature waste heat utilization system, a flue gas purification system, a fan and a chimney connected in sequence; wherein the high-efficiency dust removal, denitration and dioxin removal system is externally connected to a high-temperature heat circulation air supply system at its outlet, and the low-temperature waste heat utilization system is externally connected to a medium-temperature heat circulation air supply system at its outlet, and the two circulating airs of the high-temperature heat circulation air supply system and the medium-temperature heat circulation air supply system are mixed in the pipeline and then transported back to the drying section of the garbage incinerator through the pipeline. The present invention starts from the overall garbage incineration process system and establishes a coupling relationship between each link, so as to achieve the purpose of improving the adaptability and stability of the incineration system, reducing pollutant emissions and reducing energy consumption. According to detection, the dust content in the flue gas treated by the system reaches 5mg / Nm 3 Below, NOx content reaches 50mg / Nm 3 the following.

Description

Technical Field

[0001] The present invention belongs to the field of environmental protection technology, and relates to a method for fully utilizing heat in a domestic waste treatment process, specifically a high-efficiency incineration coupled flue gas ultra-low emission system and a control method thereof. Background Art

[0002] A complete waste incineration system needs to achieve stable and efficient combustion and secondary pollutant reduction, so as to achieve continuous harmlessness and reduction. Unstable combustion not only affects the efficiency of waste disposal, but also increases the operating cost due to frequent shutdowns, and produces a large amount of flue gas pollutants. Existing domestic waste has the problems of high moisture content and low calorific value, so it is difficult to incinerate continuously. The traditional method generally uses a mechanical grate furnace for incineration, which is divided into a drying section, a combustion section and a burnout section on the grate. High-temperature primary air is used to dry the waste as much as possible, so that its calorific value increases, which is conducive to subsequent stable and efficient combustion. The primary air temperature is generally in the range of 150-220℃. The higher the temperature, the more conducive it is to drying the waste and increasing the calorific value of the combustion section; therefore, the lower the calorific value of the waste, the higher the required primary air temperature. The heating methods of primary air generally include steam heating, biogas heating, hot flue gas heating, etc. However, the above heating methods have the disadvantages of high energy consumption, slow response speed, poor adjustability, insufficient temperature rise, etc., especially when the calorific value of the waste is low, it is often difficult to incinerate stably due to insufficient primary air temperature. Increasing the air volume of the primary air can also improve the drying effect. However, if air is used as the primary air, the oxygen content will increase after the air volume is increased. Although it is helpful for incineration, it will also cause the concentration of some pollutants to increase.

[0003] At the same time, with the increasing requirements for flue gas emission indicators of waste incineration, more efficient flue gas purification technologies need to be adopted, among which denitrification is particularly difficult. Conventional SNCR technology has low efficiency, and flue gas recirculation technology can only be used as an auxiliary. To achieve higher emission standards, SCR denitrification technology is generally still required. However, since waste incineration fly ash contains more alkali metal elements, low-temperature SCR technology is generally used for waste incineration, which is placed after the bag filter. Although this technology has a good denitrification effect, the flue gas needs to be heated, and the operating energy consumption is extremely high, which greatly affects the economic benefits of the project.

[0004] In the existing published patent documents:

[0005] 1) The prior art of application number 202110624474.3 extracts part of the high-temperature flue gas in the waste heat boiler and passes through a cyclone separator and other equipment to enter the furnace as part of the primary air and secondary air. On the one hand, a low-oxygen environment is formed, which is conducive to reducing NOx generation. On the other hand, it partially replaces the primary air, reduces the demand for steam heating, and appropriately improves the economy. However, since the flue gas in the waste heat boiler section contains a lot of dust, acidic gases, and especially pollutants such as dioxins, it is necessary to add a cyclone separator before the air extraction. On the one hand, it increases the equipment; on the other hand, the efficiency of the cyclone is low, and it cannot completely solve the problem of dust clogging, wear and leakage of the subsequent pipelines, valves and pumps under positive pressure operation; furthermore, the presence of a cyclone separator on the pipeline will also lead to a decrease in the regulation performance of the circulating flue gas volume.

[0006] 2) The prior art of announcement number CN215892366U extracts high-temperature flue gas (above 300°C) from the economizer and mixes it with normal-temperature primary air, thereby raising the temperature of the primary air to about 300°C, improving the drying effect in the furnace and reducing the energy consumption required to heat the primary air. The draft point of this scheme is similar to that of comparative patent 1), but no cyclone separator and other equipment are set, which will cause the subsequent flue, valves, and fans to be eroded by high-temperature, high-dust, and highly acidic gases for a long time, resulting in a very short equipment life and low technical feasibility. In addition, the air is not equipped with a heating system, and the temperature of the high-temperature flue gas drops after mixing with the normal-temperature air. If it is lower than the acid dew point, acid dew will be formed, corroding the equipment.

[0007] 3) The prior art with announcement number CN211260819U adopts an indirect heating method, which uses a flue gas air preheater placed in the waste heat boiler to heat the primary air, avoiding problems such as flue gas leakage and corrosion and blockage of the primary air flue. However, there are many indirect heating systems, low efficiency, and poor temperature increase effect.

[0008] 4) The prior art of application number 201910444331.7 provides a highly efficient denitrification and dust removal system and method for a waste power plant, which uses a high-temperature metal dust collector combined with SCR technology to achieve deep denitrification. However, this process mainly solves the problem of denitrification and does not involve the combustion process.

[0009] 5) The prior art with application number 201611267020.0 provides an ultra-low emission purification system for waste incineration flue gas, which uses low-temperature SCR technology to achieve ultra-low emission of NOx. However, since the low-temperature SCR is arranged behind the bag filter, the flue gas needs to be heated before it can operate, resulting in increased operating costs.

[0010] Waste incineration technology is relatively mature at present and is gradually developing towards higher efficiency, greater stability and lower emissions. The existing technology has the following problems:

[0011] 1) The existing waste incineration system has insufficient synergy between related technologies, which requires multiple sets of processes to be connected in series to meet the needs of actual use, especially the lack of effective connection between the incineration system and the flue gas purification system. In addition, in order to solve problems such as dust blockage in the circulating air, it is forced to add a dust removal system or use indirect heating, while the entire system lacks coupling effect, resulting in a lengthy process chain.

[0012] 2) As for denitrification technology, among the conventional methods, SNCR technology and flue gas recirculation technology have low efficiency; low-temperature SCR technology has defects such as high operating costs;

[0013] 3) For primary air heating technology, common technologies either have low heating temperatures and cannot cope with conditions where the calorific value of garbage is low; or have high heating energy consumption; or have unreasonable heating methods, etc. Summary of the invention

[0014] Technical problem to be solved: In order to overcome the shortcomings of the existing technology, in view of the current problems of low calorific value, high moisture content, large volatility of domestic waste, and the lengthy process chain of combustion, denitrification and heat recovery in the existing technology, the present invention starts from the overall waste incineration process system and establishes a coupling relationship between each link, so as to achieve the purpose of improving the adaptability and stability of the incineration system, reducing pollutant emissions and reducing energy consumption; in view of this, the present invention provides a high-efficiency incineration coupled flue gas ultra-low emission system and a control method thereof.

[0015] Technical solution: High-efficiency incineration coupled flue gas ultra-low emission system, the system includes a garbage incinerator, a waste heat boiler, a high-efficiency dust removal, denitrification and dioxin removal system, a low-temperature waste heat utilization system, a flue gas purification system, a fan and a chimney connected in sequence; wherein, the high-efficiency dust removal, denitrification and dioxin removal system is connected to a high-temperature hot circulating air supply system at its outlet, and the low-temperature waste heat utilization system is connected to a medium-temperature hot circulating air supply system at its outlet. The two circulating airs of the high-temperature hot circulating air supply system and the medium-temperature hot circulating air supply system are mixed in the pipeline and then transported back to the drying section of the garbage incinerator through the pipeline.

[0016] Preferably, the waste incinerator is externally connected to a waste bin, and a combustion and burnout air supply system is provided between the two.

[0017] Furthermore, the combustion and burnout air supply system is connected to the combustion section and the burnout section of the waste incinerator.

[0018] Preferably, a temperature monitoring system is provided on the pipeline through which the two circulating air streams are mixed and transported back to the waste incinerator.

[0019] Preferably, the high-efficiency dust removal, denitrification and dioxin removal system is located at the outlet temperature of the waste heat boiler at 300-320°C.

[0020] Preferably, the high-efficiency dust removal, denitration and dioxin removal system includes a high-temperature metal or ceramic dust collector and is filled with an SCR denitration and de-dioxin removal catalyst.

[0021] Preferably, the pipeline of the high-temperature hot circulating air supply system is externally connected to the outlet temperature of the high-efficiency dust removal, denitrification and dioxin removal system at 290-310°C.

[0022] Preferably, the pipeline of the medium-temperature hot circulating air supply system is externally connected to the outlet temperature of the low-temperature waste heat utilization system at 160-200°C.

[0023] Preferably, the high-temperature heat circulating air supply system and the medium-temperature heat circulating air supply system are provided with a switch valve, a check valve, a flow meter and a variable frequency fan in sequence near their own air outlets, and corresponding pipelines and manual valves may also be additionally provided. According to the required drying air temperature and flow, the fan air volume and ratio are adjusted to meet the drying requirements. The check valve and the switch valve can block the two gases to avoid internal circulation.

[0024] The control method of any of the above-mentioned high-efficiency incineration coupled flue gas ultra-low emission systems comprises the following steps:

[0025] S1. Domestic garbage is burned in the garbage incinerator, which is divided into drying section, combustion section and burnout section. The required primary air is provided by high-temperature hot circulation air supply system, medium-temperature hot circulation air supply system and combustion burnout air supply system respectively;

[0026] S2. The flue gas after incineration enters the waste heat boiler, the high-efficiency dust removal, denitrification and dioxin removal system and the low-temperature waste heat utilization system in sequence. The start and stop of the high-temperature heat circulation air supply system and the medium-temperature heat circulation air supply system, the flue gas extraction volume, the flow rate and the temperature of the mixed dry air in the pipeline are controlled by adjusting the switch valve, check valve, flow meter and variable frequency fan of the high-temperature heat circulation air supply system and the medium-temperature heat circulation air supply system; the temperature of the dry air in the pipeline is 160-310℃, and the flue gas extraction volume can account for a maximum of 40% of the total flue gas discharged by the high-efficiency dust removal, denitrification and dioxin removal system; the dry air is transported back to the drying section of the garbage incinerator through the pipeline as the primary air of the drying section;

[0027] S3. Flue gas that has not been extracted by the high-temperature hot circulating air supply system and the medium-temperature hot circulating air supply system is deacidified by the flue gas purification system and then discharged through the fan and chimney;

[0028] S4. The garbage incinerator draws air from the external garbage bin through the combustion and burnout air supply system to provide a negative pressure environment for the garbage bin and provide primary air for the combustion section and burnout section of the garbage incinerator.

[0029] The design idea of ​​the high-efficiency incineration coupled flue gas ultra-low emission system of the present invention is that the system sets the high-temperature dust removal, denitration and dioxin removal system downstream of the waste heat boiler, realizes dust removal, denitration and dioxin removal in the high temperature section through high-temperature dust removal coupled with high-temperature SCR technology, and cooperates with the downstream flue gas purification system to realize ultra-low emission of flue gas. The system innovatively couples the high-temperature heat circulation air supply system and the medium-temperature heat circulation air supply system at the outlet of the high-temperature dust removal, denitration and dioxin removal system at 290-310℃ and the outlet of the low-temperature waste heat utilization system at 160-200℃, and returns part of the flue gas treated with dust removal, denitration and dioxin removal to the waste incinerator as the primary air of the drying section to provide the drying efficiency of the waste in the incinerator, thereby improving the overall incineration efficiency and adaptability to the waste. Furthermore, a temperature monitoring system is set in the system to adjust the temperature range of the drying air to 160-310℃ as needed. In addition, the system transports the gas in the garbage bin to the combustion section and burnout section of the garbage incinerator through the combustion and burnout air supply system, providing a negative pressure environment for the garbage bin to prevent odor leakage. According to tests, the dust content in the flue gas treated by the system is less than 5mg / Nm3, and the NOx content is less than 50mg / Nm3.

[0030] Beneficial effects:

[0031] (1) A high-temperature dust removal coupled SCR denitrification and dioxin removal system is set up in the high-temperature section (290-320°C). The flue gas can be denitrified efficiently without heating, achieving ultra-low emissions of dust and NOx while reducing the operating cost of denitrification.

[0032] (2) The high-temperature hot flue gas after the high-temperature dust removal, denitrification and dioxin removal system is used as the drying air, which has a high cleanliness level. The hot circulating air system at the back end does not need to be equipped with purification equipment. The system is simple, requires little maintenance, and has a long service life. There is no need to worry about the impact of flue gas leakage on the environment. In addition, by mixing two streams of hot flue gas at higher temperatures, the drying air temperature can be flexibly adjusted, and the problem of acid dew forming when flue gas is mixed with low-temperature air, which causes equipment corrosion, can be avoided;

[0033] (3) Set circulating air as drying air, and set two-stage mixed circulating air. The high-temperature hot circulating air extraction point is located after the high-temperature dust removal, denitrification and dioxin removal system, with a temperature of about 280-310°C, and the flue gas contains extremely low dust and dioxin. The medium-temperature hot circulating air extraction point is located after the economizer, with a temperature of about 160-200°C, and the flue gas contains extremely low dust and dioxin;

[0034] (4) Drying air is mainly used for drying and does not require high oxygen content; while combustion burnout air is mainly used for combustion and requires high oxygen content. In this system, the drying air and combustion burnout air operate independently. The drying air uses high-temperature hot flue gas and has a large flow adjustment range; the combustion burnout air uses hot air, which on the one hand ensures the negative pressure of the garbage bin, and on the other hand does not need to be heated to too high a temperature, saving energy consumption, while providing sufficient oxygen required for combustion to ensure stable combustion.

[0035] (5) The heat circulation air temperature is controllable at 160-310℃, with wider and faster adjustability. It can run at low temperature during normal operation to avoid high temperature damage to the grate. When the calorific value of the garbage is low, it can quickly reach 310℃, which is higher than the primary air temperature of general steam heating. It can effectively and quickly dry the garbage and promote stable combustion. In addition, the heat circulation air system has no large resistance equipment and strong flow regulation performance. It can quickly increase the air volume according to the combustion conditions and increase the drying effect. At the same time, due to the use of pure flue gas for air distribution, the oxygen content in it is lower than that in air, and the increase in air volume has little effect on the increase in oxygen content in the incineration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a structural diagram of a high-efficiency incineration coupled flue gas ultra-low emission system;

[0037] Among them, 1 is a waste incinerator, 2 is a waste heat boiler, 3 is a high-efficiency dust removal, denitrification and dioxin removal system, 4 is a low-temperature waste heat utilization system, 5 is a flue gas purification system, 6 is a high-temperature hot circulating air supply system, 7 is a medium-temperature hot circulating air supply system, 8 is a temperature monitoring system, 9 is a combustion burnout air supply system, and 10 is a garbage bin. DETAILED DESCRIPTION

[0038] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and essence of the present invention, modifications and substitutions made to the method, steps or conditions of the present invention all belong to the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0039] Example 1

[0040] A high-efficiency incineration coupled flue gas ultra-low emission system, the system comprises a garbage incinerator 1, a waste heat boiler 2, a high-efficiency dust removal, denitrification and dioxin removal system 3, a low-temperature waste heat utilization system 4, a flue gas purification system 5, a fan and a chimney connected in sequence; wherein, the high-efficiency dust removal, denitrification and dioxin removal system 3 is externally connected to a high-temperature hot circulating air supply system 6 at its outlet, and the low-temperature waste heat utilization system 4 is externally connected to a medium-temperature hot circulating air supply system 7 at its outlet, and the two circulating airs of the high-temperature hot circulating air supply system 6 and the medium-temperature hot circulating air supply system 7 are mixed in the pipeline and then transported back to the drying section of the garbage incinerator 1 through the pipeline.

[0041] The garbage incinerator 1 is externally connected to a garbage bin 10, and a combustion and burnout air supply system 9 is arranged between the two.

[0042] The combustion and burnout air supply system 9 is connected to the combustion section and the burnout section of the garbage incinerator 1 .

[0043] A temperature monitoring system 8 is provided on the pipeline where the two circulating air streams are mixed and transported back to the garbage incinerator 1 .

[0044] The high-efficiency dust removal, denitrification and dioxin removal system 3 is located at the outlet temperature of the waste heat boiler 2 at 300-320℃.

[0045] The high-efficiency dust removal, denitration and dioxin removal system 3 includes a high-temperature metal or ceramic dust collector and is filled with an SCR denitration and dioxin removal catalyst.

[0046] The pipeline of the high-temperature hot circulating air supply system 6 is externally connected to the outlet temperature of the high-efficiency dust removal, denitrification and dioxin removal system 3 at 300°C.

[0047] The pipeline of the medium-temperature hot circulating air supply system 7 is externally connected to the outlet temperature of the low-temperature waste heat utilization system 4 at 160°C.

[0048] The high-temperature heat circulating air supply system 6 and the medium-temperature heat circulating air supply system 7 are provided with a switch valve, a check valve, a flow meter and a variable frequency fan in sequence near their own air outlets.

[0049] The above high-efficiency incineration coupled flue gas ultra-low emission system is controlled by the following methods:

[0050] S1. Domestic garbage is burned in a garbage incinerator 1. The garbage incinerator 1 is divided into a drying section, a combustion section and a burnout section. The required primary air is provided by a high-temperature hot circulating air supply system 6, a medium-temperature hot circulating air supply system 7 and a combustion and burnout air supply system 9 respectively;

[0051] S2, the flue gas after incineration enters the waste heat boiler 2, the high-efficiency dust removal, denitrification and dioxin removal system 3 and the low-temperature waste heat utilization system 4 in sequence, and the start and stop of the high-temperature heat circulation air supply system 6 and the medium-temperature heat circulation air supply system 7, the flue gas extraction amount, the flow rate and the temperature of the mixed dry air in the pipeline are controlled by adjusting the switch valve, check valve, flow meter and frequency conversion fan of the high-temperature heat circulation air supply system 6 and the medium-temperature heat circulation air supply system 7; when the calorific value of the garbage is high, the temperature of the dry air in the pipeline is set to 180°C, and the flue gas extraction amount is 15% of the total flue gas discharged by the high-efficiency dust removal, denitrification and dioxin removal system 3; the dry air is transported back to the drying section of the garbage incinerator 1 through the pipeline as the primary air of the drying section;

[0052] S3, the flue gas that has not been extracted by the high-temperature hot circulating air supply system 6 and the medium-temperature hot circulating air supply system 7 is deacidified by the flue gas purification system 5 and then discharged through the fan and chimney;

[0053] S4. The waste incinerator 1 draws air from the external waste bin 10 through the combustion and burnout air supply system 9 to provide a negative pressure environment for the waste bin 10 and provide primary air for the combustion section and the burnout section of the waste incinerator 1.

[0054] Example 2

[0055] The difference from Example 1 is that:

[0056] The pipeline of the medium-temperature hot circulating air supply system 7 is externally connected to the outlet temperature of the low-temperature waste heat utilization system 4 at 200°C.

[0057] When the calorific value of the garbage is low, in the system control method, the temperature of the dry air in the pipeline is controlled to be 250°C, and the flue gas extraction volume reaches 30% of the total flue gas discharged by the high-efficiency dust removal, denitrification and dioxin removal system 3.

[0058] Example 3

[0059] The difference from Example 1 is that:

[0060] The pipeline of the high temperature heat circulating air supply system 6 is externally connected to the outlet temperature of the high efficiency dust removal, denitration and dioxin removal system 3 at 310°C. The pipeline of the medium temperature heat circulating air supply system 7 is externally connected to the outlet temperature of the low temperature waste heat utilization system 4 at 200°C.

[0061] Under extreme working conditions, the temperature of dry air in the control pipeline is 310℃, and the flue gas extraction volume accounts for 40% of the total flue gas discharged by the high-efficiency dust removal, denitrification and dioxin removal system 3.

Claims

1. High-efficiency incineration coupled flue gas ultra-low emission system, characterized by: The system comprises a waste incinerator (1), a waste heat boiler (2), a high-efficiency dust removal, denitration and dioxin removal system (3), a low-temperature waste heat utilization system (4), a flue gas purification system (5), a fan and a chimney, which are connected in sequence; wherein the high-efficiency dust removal, denitration and dioxin removal system (3) is externally connected to a high-temperature hot circulating air supply system (6) at its outlet, and the low-temperature waste heat utilization system (4) is externally connected to a medium-temperature hot circulating air supply system (7) at its outlet, and the two circulating air streams of the high-temperature hot circulating air supply system (6) and the medium-temperature hot circulating air supply system (7) are mixed in a pipeline and then transported back to the drying section of the waste incinerator (1) through the pipeline; The garbage incinerator (1) is externally connected to a garbage bin (10), and a combustion burnout air supply system (9) is provided between the two. The combustion burnout air supply system (9) is connected to the combustion section and the burnout section of the garbage incinerator (1); A temperature monitoring system (8) is provided on the pipeline for conveying the two circulating air streams back to the waste incinerator (1) after mixing; The high-efficiency dust removal, denitrification and dioxin removal system (3) is installed at the outlet temperature of the waste heat boiler (2) at 300-320°C; The high-efficiency dust removal, denitrification and de-dioxin removal system (3) includes a high-temperature metal or ceramic dust collector and is filled with an SCR denitrification and de-dioxin removal catalyst; The pipeline of the high-temperature hot circulating air supply system (6) is externally connected to the outlet temperature of the high-efficiency dust removal, denitrification and dioxin removal system (3) at 290-310°C; The pipeline of the medium temperature hot circulating air supply system (7) is externally connected to the outlet temperature of the low temperature waste heat utilization system (4) at 160-200°C; The high-efficiency incineration coupled flue gas ultra-low emission system is controlled by the following method, including the following steps: S1. Domestic waste is burned in a waste incinerator (1). The waste incinerator (1) is divided into a drying section, a combustion section and a burnout section. The primary air required is provided by a high-temperature hot circulating air supply system (6), a medium-temperature hot circulating air supply system (7) and a combustion and burnout air supply system (9), respectively. S2, the flue gas after incineration enters the waste heat boiler (2), the high-efficiency dust removal, denitrification and dioxin removal system (3) and the low-temperature waste heat utilization system (4) in sequence, and the start and stop of the high-temperature heat circulation air supply system (6) and the medium-temperature heat circulation air supply system (7), the flue gas extraction amount, the flow rate and the temperature of the mixed dry air in the pipeline are controlled by adjusting the switch valve, the check valve, the flow meter and the variable frequency fan of the high-temperature heat circulation air supply system (6) and the medium-temperature heat circulation air supply system (7); wherein the temperature of the dry air in the pipeline is 160-310°C, and the flue gas extraction amount accounts for up to 40% of the total flue gas discharged by the high-efficiency dust removal, denitrification and dioxin removal system (3); the dry air is transported back to the drying section of the waste incinerator (1) through the pipeline as the primary air of the drying section; S3, the flue gas that has not been extracted by the high-temperature hot circulating air supply system (6) and the medium-temperature hot circulating air supply system (7) is deacidified by the flue gas purification system (5) and then discharged through the fan and chimney; S4. The garbage incinerator (1) draws air from an external garbage bin (10) through a combustion and burnout air supply system (9), thereby providing a negative pressure environment for the garbage bin (10) and providing primary air for the combustion section and the burnout section of the garbage incinerator (1).

2. The high-efficiency incineration coupled flue gas ultra-low emission system according to claim 1 is characterized in that: The high-temperature heat circulation air supply system (6) and the medium-temperature heat circulation air supply system (7) are provided with a switch valve, a check valve, a flow meter and a variable frequency fan in sequence near their air outlets.

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