Flue gas treatment device and flue gas treatment method

Abstract

The present invention provides a flue gas treatment device and method. The flue gas treatment device includes: a CO combustion chamber for burning CO; a denitrification chamber for mixing a first amount of flue gas that has undergone electrostatic precipitation with the flue gas that has passed through the CO combustion chamber to achieve flue gas denitrification; and a mixing chamber for mixing the flue gas denitrified by the denitrification chamber with all the flue gas that has undergone electrostatic precipitation to remove dioxins from the flue gas. This device can improve denitrification efficiency and effectively remove dioxins.

Description

Technical Field

[0001] The present invention relates to the field of flue gas purification and treatment, and more particularly to a flue gas treatment device and a flue gas treatment method. Background Art

[0002] Stainless steel sludge typically contains valuable metal elements such as iron, nickel, and chromium, as well as fluorine, chlorine, nitrogen, and sulfur. The "drying → rotary kiln drying → alloy furnace (electric furnace)" process is used to treat hazardous waste materials primarily consisting of stainless steel sludge, producing nickel-iron alloy and water-quenched slag, effectively achieving resource utilization and harmless treatment of hazardous waste materials. However, the "drying → rotary kiln drying → alloy furnace (electric furnace)" process for stainless steel sludge disposal may contain large amounts of pollutants such as HF, HCl, SO2, and NOx, as well as the regeneration of dioxins during the combustion process, making the flue gas treatment process complex, energy-efficient, and costly.

[0003] Therefore, it is now necessary to provide a flue gas treatment device and a flue gas treatment method, which can at least solve the above-mentioned problems existing in the prior art. Summary of the Invention

[0004] In order to solve at least one of the above problems, according to one aspect of the present invention, a flue gas treatment device is proposed, including: a CO combustion chamber for burning CO; a denitrification chamber for mixing the flue gas with a first amount that has been subjected to electrostatic precipitator with the flue gas that has passed through the CO combustion chamber to achieve flue gas denitrification; and a mixing chamber for mixing the flue gas after denitrification in the denitrification chamber and all the flue gas that has been subjected to electrostatic precipitator to remove dioxins in the flue gas.

[0005] In some embodiments, the denitrification chamber is a dust precipitation denitrification chamber.

[0006] In some embodiments, the dust settling and denitrification chamber includes a temperature sensor and a regulating valve, and wherein the regulating valve regulates the amount of electrostatically precipitated flue gas having the first amount entering the denitrification chamber based on the temperature measured by the temperature sensor.

[0007] In some embodiments, a defluorination chamber is further included for defluorination.

[0008] According to another aspect of the present invention, a flue gas treatment method is proposed, comprising the steps of: subjecting the flue gas to electrostatic dust removal; burning the flue gas in a CO combustion chamber; mixing a first amount of flue gas subjected to electrostatic dust removal with the flue gas passed through the CO combustion chamber in a denitrification chamber to achieve flue gas denitrification; and mixing the flue gas denitrified by the denitrification chamber with all the flue gas subjected to electrostatic dust removal in a mixing chamber to remove dioxins from the flue gas.

[0009] In some embodiments, the denitrification chamber is a dust precipitation denitrification chamber.

[0010] In some embodiments, the dust settling and denitrification chamber includes a temperature sensor and a regulating valve, and wherein the regulating valve regulates the amount of electrostatically precipitated flue gas having the first amount entering the denitrification chamber based on the temperature measured by the temperature sensor.

[0011] In some embodiments, the method further includes allowing the flue gas to enter a defluorination control room for defluorination before performing electrostatic dust removal on the flue gas.

[0012] The present invention provides an economical and environmentally friendly flue gas treatment device and method, which adds a denitrification chamber and a mixing chamber between the CO combustion chamber and the waste heat boiler, thereby improving the denitrification efficiency and effectively removing dioxins. At the same time, the distribution of the rotary kiln drying and roasting flue gas entering the denitrification chamber is adjusted to adjust the distribution of the temperature field in the denitrification chamber, thereby further improving the denitrification efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and other objects, features, and advantages of the present invention will become more apparent through a more detailed description of the embodiments of the present invention with reference to the accompanying drawings. The accompanying drawings are provided to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and are not intended to limit the present invention. In the drawings, the same reference numerals generally represent the same components or steps.

[0014] Figure 1 A block diagram of a flue gas treatment device according to an embodiment of the present invention is shown;

[0015] Figure 2 A block diagram showing a denitration chamber and a mixing chamber according to an embodiment of the present invention; and

[0016] Figure 3 A flow chart of a flue gas treatment method according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more apparent, exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described in the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

[0018] In the process of treating stainless steel sludge using the traditional "drying → rotary kiln drying → alloy furnace (electric furnace)" process, there may be a large amount of pollutants such as HF, HCl, SO2, NOx, as well as the problem of dioxin regeneration during the combustion process, making the flue gas treatment process complex, energy-efficient and costly.

[0019] The present invention provides an economical and environmentally friendly flue gas treatment device and method, which adds a denitrification chamber and a mixing chamber between the CO combustion chamber and the waste heat boiler, thereby improving the denitrification efficiency and effectively removing dioxins. At the same time, the distribution of the rotary kiln drying and roasting flue gas entering the denitrification chamber is adjusted to adjust the distribution of the temperature field in the denitrification chamber, thereby further improving the denitrification efficiency.

[0020] The following combination Figure 1 The flue gas treatment device according to an embodiment of the present invention will be described in detail.

[0021] like Figure 1 As shown, the present invention provides a flue gas treatment device, comprising: a CO combustion chamber for burning CO; a denitrification chamber for mixing the flue gas having a first amount that has been subjected to electrostatic precipitator with the flue gas that has passed through the CO combustion chamber to achieve flue gas denitrification; and a mixing chamber for mixing the flue gas after denitrification in the denitrification chamber and all the flue gas that has been subjected to electrostatic precipitator to remove dioxins in the flue gas.

[0022] In some embodiments, the flue gas treatment device further includes a defluorination chamber for defluorination.

[0023] Specifically, if Figure 1 The device, shown here, demonstrates an economical and environmentally friendly flue gas treatment system. The device includes a baffle settling chamber, a defluorination chamber, an electrostatic precipitator, a denitrification chamber, a waste heat boiler, a quenching tower, a bag filter, and a two-stage wet deacidification tower. Flue gas from the rotary kiln drying and roasting process is de-dusted in the baffle settling chamber before entering the defluorination chamber for defluorination. The defluorinated flue gas then enters the electrostatic precipitator for dust removal. The remaining flue gas is then mixed with the flue gas from the CO combustion chamber in the denitrification chamber. The amount of rotary kiln flue gas entering the denitrification chamber is adjusted to maintain a temperature of approximately 1050°C. Denitrification is carried out using the SNCR process within this temperature range. The remaining flue gas from the rotary kiln enters the mixing chamber. The flue gas temperature in the mixing chamber is approximately 850°C, and then passes through the waste heat boiler for waste heat utilization. The flue gas outlet temperature of the waste heat boiler is designed to be approximately 500°C. The slag is then rapidly cooled to 200°C in a quenching tower, and then slaked lime and activated carbon are sprayed for deacidification and dioxin removal. The slag is then subjected to bag dust removal and two-stage Ca(OH)2 wet deacidification, and finally discharged through a chimney. The smoke 1 generated in the baffle settling chamber is returned to the rotary kiln for drying and roasting, and the smoke 2 from the electrostatic dust removal is outsourced for disposal. The smoke 3 collected by the bag dust removal is identified, and if the content of CaF2 and CaCl2 therein is low (less than 1wt.%), it can be returned to the rotary kiln, otherwise it can be outsourced for disposal. The present invention provides an economical and environmentally friendly flue gas treatment device to overcome the shortcomings of the "drying → rotary kiln drying → alloy furnace (electric furnace)" process for treating stainless steel sludge, such as complex flue gas treatment, high energy efficiency, and high cost.

[0024] The denitrification process can be selected based on the amount of flue gas from the rotary kiln and the amount of NOx produced, including but not limited to SNCR, PNCR or a combination of SNCR and PNCR.

[0025] The optimal denitration temperature for SNCR is 1050°C. In this invention, the exhaust temperature of the CO combustion chamber flue gas is between 1200°C and 1300°C, and the exhaust temperature of the rotary kiln flue gas is around 400°C. Through the denitration chamber and mixing chamber, the amount of low-temperature flue gas (the amount of rotary kiln exhaust gas) is regulated to keep the mixed flue gas temperature around 1050°C, thereby improving denitration efficiency. Furthermore, the separate denitration chamber increases the residence time of the reaction, thereby improving denitration efficiency. 1050°C is the optimal reaction temperature for SNCR denitration, and 850°C is the temperature at which dioxins begin to decompose significantly.

[0026] The exhaust temperature of CO combustion chamber flue gas is generally between 1200°C and 1300°C, sometimes even reaching 1400°C. In the present invention, the exhaust temperature of the rotary kiln is 400°C, and the highest amount of dioxin generation occurs in the exhaust gas of the rotary kiln. Dioxins begin to decompose in large quantities at 850°C, with higher temperatures leading to more complete decomposition. Therefore, mixing high-temperature flue gas (1200°C to 1300°C) with low-temperature flue gas (400°C) to a mixed temperature of approximately 1050°C can significantly decompose dioxins in the low-temperature flue gas.

[0027] The rotary kiln uses a countercurrent method for drying and calcining. To reduce dioxin formation, the kiln flue gas outlet temperature is controlled above 400°C. The quench tower can use industrial water or a combination of industrial water and lime slurry for rapid cooling. Dust collected from the denitrification chamber and waste heat boiler is returned to the rotary kiln for drying and calcining.

[0028] The waste heat boiler is clad with welding, and the cladding material can be Inconel 686, HR160 NI-Co-Cr alloy, etc. The bag filter shell is made of carbon steel + PTFE, the bag cage is made of 316L, and the flower plate is made of Monel alloy with a thickness of not less than 6mm.

[0029] In some embodiments, the denitrification chamber is a dust settling denitrification chamber. A typical denitrification chamber is merely a section of flue gas without a temperature regulating device.

[0030] In some embodiments, the dust settling and denitrification chamber includes a temperature sensor and a regulating valve, and wherein the regulating valve regulates the amount of electrostatically precipitated flue gas having the first amount entering the denitrification chamber based on the temperature measured by the temperature sensor.

[0031] Next, combine Figure 2 The structures of the denitration chamber and the mixing chamber according to an embodiment of the present invention will be described.

[0032] Figure 2 The temperature control method of the denitrification chamber is shown. A temperature sensor is installed below the mixing point of the flue gas from the electrostatic dust removal in the denitrification chamber and the flue gas from the alloy furnace. The temperature sensor automatically adjusts the opening of the regulating valve, thereby controlling the amount of flue gas entering the denitrification chamber and further controlling the temperature of the denitrification chamber.

[0033] like Figure 2 As shown in the figure, the temperature of the alloy furnace flue gas (i.e., the flue gas from the CO combustion chamber) is between 1200 and 1300°C, and the temperature of the electrostatic precipitator flue gas is at 400°C. Therefore, the temperature of the denitrification chamber needs to be controlled at 1050°C (the optimal reaction temperature for SNCR denitrification). The control valve opening is adjusted by the temperature sensor. When the temperature is higher than 1050°C, the control valve opening increases, allowing more low-temperature flue gas (400°C flue gas) to enter, thereby lowering the temperature of the mixed gas. When the sensor temperature is lower than 1050°C, the control valve opening decreases, reducing the amount of low-temperature flue gas (400°C flue gas) entering, thereby achieving the purpose of temperature regulation.

[0034] Example 1

[0035] The flue gas treatment device of the present invention is used to treat stainless steel sludge (water content 60% to 70%) with the composition described in Table 1. The flue gas dried and roasted in the rotary kiln is dedusted in the baffle settling chamber and enters the defluorination control room for defluorination. The defluorinated flue gas enters the electrostatic dust removal equipment for dust removal. The flue gas temperature at the rotary kiln outlet is designed to be 400°C.

[0036] Table 1 Dry basis composition of stainless steel sludge

[0037]

[0038] Part of the flue gas from the electrostatic precipitator is mixed with the flue gas from the CO combustion chamber in the denitrification chamber. By adjusting the amount of flue gas entering the denitrification chamber, the temperature of the mixed flue gas is maintained at approximately 1050°C. Within this temperature range, the SNCR process is used for denitrification. The remaining flue gas from the rotary kiln enters the mixing chamber. The flue gas exiting the mixing chamber has a temperature of approximately 850°C. The flue gas is then recycled through a waste heat boiler (HRSG) to utilize waste heat. The flue gas outlet temperature is designed to be around 500°C. It is then rapidly cooled to 200°C in a quenching tower. Slaked lime and activated carbon are then sprayed for deacidification and dioxin removal. The flue gas then undergoes bag filter dust removal and two-stage Ca(OH)2 wet deacidification before being discharged through the chimney. Dust 1 generated in the baffle settling chamber is returned to the rotary kiln for drying and calcination. Dust 2 from the electrostatic precipitator is outsourced for disposal. Dust 3 collected by the bag filter is identified and returned to the rotary kiln. This process meets the emission requirements shown in Table 2.

[0039] Table 2 Flue gas emission design values

[0040]

[0041] Example 2

[0042] The invented flue gas treatment device is used to treat stainless steel sludge (water content 60% to 70%) with the composition as described in Table 1. The flue gas dried and roasted in the rotary kiln is dedusted in the baffle settling chamber and then enters the defluorination control room for defluorination. The defluorinated flue gas enters the electrostatic dust removal equipment for dust removal. The flue gas temperature at the rotary kiln outlet is designed to be 400°C.

[0043] Part of the flue gas from the electrostatic precipitator is mixed with the flue gas from the CO combustion chamber in the denitrification chamber. By adjusting the amount of flue gas entering the denitrification chamber, the mixed flue gas temperature is maintained at approximately 1050°C. Denitrification is carried out using a combined SNCR and PNCR process. The remaining flue gas from the rotary kiln enters the mixing chamber. The flue gas exiting the mixing chamber is approximately 850°C, while the exhaust gas temperature at the waste heat boiler outlet is designed to be around 500°C. It is then rapidly cooled to 200°C in a quenching tower. Slaked lime and activated carbon are then sprayed for deacidification and dioxin removal. The flue gas then undergoes bag filter and two-stage NaOH wet deacidification before being discharged through the chimney. Dust 1 generated in the baffle settling chamber is returned to the rotary kiln for drying and calcination. Dust 2 from the electrostatic precipitator is outsourced for disposal. Dust 3 collected by the bag filter is identified and returned to the rotary kiln. This process meets the emission requirements shown in Table 3.

[0044] Table 3 Flue gas emission design values

[0045]

[0046] The present invention provides an economical and environmentally friendly flue gas treatment device. Compared with the prior art, the present invention can provide the following beneficial effects: the present invention mixes the flue gas from the rotary kiln with the flue gas from the CO combustion chamber, which can decompose dioxins that may be generated in the flue gas from the rotary kiln; a separate defluorination control chamber is set up, which can effectively remove HF and avoid HF corrosion to subsequent systems. At the same time, an emergency spray gun can be used in the chamber to avoid flue gas overheating, which is an emergency protection for electrostatic dust removal equipment; the use of a dust reduction and denitrification chamber can ensure an optimal denitrification temperature window and significantly improve the denitrification efficiency of the flue gas; and the mixing of the flue gas from the rotary kiln with the flue gas from the CO combustion chamber reduces the temperature of the flue gas entering the waste heat boiler, making the selection of cladding welding materials for the waste heat boiler wider and reducing the high-temperature corrosion rate of the waste heat boiler.

[0047] Next, refer to Figure 3 The flue gas treatment method according to an embodiment of the present invention is described below.

[0048] like Figure 3As shown, a flue gas treatment method includes the following steps: subjecting the flue gas to electrostatic dust removal; burning the flue gas in a CO combustion chamber; mixing the flue gas having a first amount that has been subjected to electrostatic dust removal with the flue gas that has passed through the CO combustion chamber in a denitrification chamber to achieve flue gas denitrification; and mixing the flue gas that has been denitrified in the denitrification chamber with all the flue gas that has been subjected to electrostatic dust removal in a mixing chamber to remove dioxins in the flue gas.

[0049] In some embodiments, the denitrification chamber is a dust precipitation denitrification chamber.

[0050] In some embodiments, the dust settling and denitrification chamber includes a temperature sensor and a regulating valve, and wherein the regulating valve regulates the amount of electrostatically precipitated flue gas having the first amount entering the denitrification chamber based on the temperature measured by the temperature sensor.

[0051] In some embodiments, the method further comprises allowing the flue gas to enter a defluorination control room for defluorination before performing electrostatic dust removal on the flue gas.

[0052] The present invention provides an economical and environmentally friendly flue gas treatment method. Compared with the existing technology, the present invention can provide the following beneficial effects: the present invention mixes the flue gas from the rotary kiln with the flue gas from the CO combustion chamber, which can decompose dioxins that may be generated in the flue gas from the rotary kiln; a separate defluorination control chamber is set up, which can effectively remove HF and avoid HF corrosion to subsequent systems. At the same time, an emergency spray gun can be used in the chamber to avoid flue gas overheating, which is an emergency protection for electrostatic dust removal equipment; the use of a dust reduction and denitrification chamber can ensure an optimal denitrification temperature window and significantly improve the denitrification efficiency of the flue gas; and the mixing of the flue gas from the rotary kiln with the flue gas from the CO combustion chamber reduces the temperature of the flue gas entering the waste heat boiler, making the selection of cladding welding materials for the waste heat boiler wider and reducing the high-temperature corrosion rate of the waste heat boiler.

[0053] Although example embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above example embodiments are merely illustrative and are not intended to limit the scope of the present invention. Various changes and modifications may be made therein by those skilled in the art without departing from the scope and spirit of the present invention. All such changes and modifications are intended to be included within the scope of the present invention as claimed in the appended claims.

[0054] In the description provided herein, numerous specific details are described. However, it is understood that embodiments of the present invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques are not shown in detail so as not to obscure the understanding of this description.

[0055] Similarly, it should be understood that in order to streamline the present invention and aid in understanding one or more of the various inventive aspects, in the description of exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this approach to the present invention should not be interpreted as reflecting the intention that the claimed invention requires more features than those explicitly recited in each claim. More precisely, as reflected in the corresponding claims, the inventive point is that the corresponding technical problem can be solved with fewer features than all the features of a single disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into the detailed description, with each claim itself serving as a separate embodiment of the present invention.

[0056] It will be understood by those skilled in the art that, except where mutually exclusive, all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or units of any method or apparatus disclosed herein may be combined in any combination. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature providing the same, equivalent, or similar purpose.

[0057] Furthermore, those skilled in the art will appreciate that although some embodiments described herein include certain features included in other embodiments but not other features, combinations of features from different embodiments are intended to be within the scope of the present invention and to form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.

[0058] The foregoing description is merely a specific embodiment of the present invention or an illustration of a specific embodiment. The scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be readily conceived by a person skilled in the art within the technical scope disclosed in the present invention are intended to be encompassed by the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A flue gas treatment device, characterized in that: include: Defluorination control room, used for defluorination and temperature control of the flue gas from the rotary kiln drying and roasting; CO combustion chamber, used to burn the flue gas and CO from the alloy furnace; The flue gas coming out of the defluorination control chamber is divided into two parts after electrostatic dust removal. A part of the flue gas after electrostatic dust removal is mixed with the flue gas coming out of the CO combustion chamber to enter the denitrification chamber to achieve flue gas denitrification. The denitrification chamber is a dust settling denitrification chamber. as well as The other part of the flue gas after electrostatic dust removal is mixed with the flue gas from the denitrification chamber in a mixing chamber to remove dioxins in the flue gas; A temperature sensor is provided in the denitrification chamber, and a regulating valve is provided on the pipeline of the portion of flue gas after electrostatic precipitator, wherein the regulating valve regulates the amount of the portion of flue gas entering the denitrification chamber based on the temperature measured by the temperature sensor; The waste heat boiler is used to utilize the waste heat of the flue gas discharged from the mixing chamber.

2. A flue gas treatment method using the flue gas treatment device according to claim 1, characterized in that: Including steps: Allowing the flue gas to enter the defluorination control room for defluorination and temperature control; subjecting the flue gas to electrostatic dust removal; burning the flue gas in a CO combustion chamber; Mixing the first amount of flue gas that has been subjected to electrostatic precipitation with the flue gas that has passed through the CO combustion chamber in a denitration chamber to achieve flue gas denitration, wherein the denitration chamber is a dust settling denitration chamber; as well as Mixing the flue gas denitrated by the denitrification chamber and part of the flue gas subjected to electrostatic dust removal in a mixing chamber to remove dioxins from the flue gas; The waste heat of the flue gas discharged from the mixing chamber is utilized.

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