Flue gas multi-step purification and resource recovery method

Abstract

The invention relates to the field of flue gas deacidification, and discloses a flue gas multi-step purification and resource recovery method, which comprises the following steps: firstly, carrying out cloth bag dust removal on flue gas through a cloth bag dust removal module; condensing, cooling and separating water vapor from the flue gas subjected to cloth bag dust removal through a first condensing module; then discharging into a second condensation module for SO2 separation; discharging the flue gas discharged from the second condensation module into an ammonia water HCl removal module for removing HCl; the HCl-removed flue gas is discharged into a flue gas circulation module for heat exchange, and the graded deacidification process of the flue gas is achieved; sO2 sequentially enters the liquid SO2 separation module and the SO2 purification module, so that SO2 resource utilization is realized; the ammonia water sequentially enters the ammonium chloride separation module and the nitrogen fertilizer preparation module after adsorbing the HCl, so that resource utilization of the ammonia water and the HCl is realized; according to the invention, the problems of poor deacidification effect and energy consumption caused by the fact that sulfur dioxide and hydrogen chloride in the flue gas cannot be removed step by step in the prior art are solved, and recycling of sulfur dioxide and hydrogen chloride in the flue gas is realized in the process.

Description

Technical Field

[0001] The present invention relates to the field of flue gas deacidification, and in particular to a flue gas multi-step purification and resource recovery method. Background Art

[0002] Waste incineration technology is one of the most effective ways to achieve waste reduction, resource utilization, and harmlessness. While the high temperatures of the incineration process effectively control pollutants, the flue gas produced still contains a certain amount of acidic substances and waste heat. The comprehensive utilization and treatment of this flue gas can effectively reduce the harmful effects of waste incineration.

[0003] Currently, waste incineration flue gas deacidification technologies can be categorized into three types: wet, dry, and semi-dry, depending on the state of the raw materials and byproducts. Wet deacidification primarily utilizes a scrubber, where the flue gas is treated with an alkaline solution. Deacidification efficiencies can reach 99%, but these processes suffer from high power and water consumption, high operating and maintenance costs, and the need for additional wastewater treatment. Dry deacidification involves injecting lime powder into a reaction tower via a spray system, where it reacts with the acidic gases to form solid compounds. While this approach offers low initial investment and eliminates the need for a wastewater treatment system, it suffers from low deacidification efficiency, making it difficult to meet stringent emission standards. Furthermore, long-term use incurs high reagent consumption. While not as high as the wet deacidification process, this still represents a significant operating cost. Semi-dry deacidification involves injecting lime slurry into a reaction tower to react with the acidic gases. By controlling the reaction temperature and water evaporation, larger flue gas particles settle to the bottom of the tower and are discharged. Fine particles are captured in a dust collector and then stabilized. The semi-dry method is between the wet method and the dry method in terms of deacidification efficiency and operating cost, and is suitable for general emission requirements.

[0004] The acidic gases SO2 and HCl compete in flue gas, and some waste incineration power plants cannot completely remove SO2 even with excessive amounts of deacidification agents. Therefore, they seek to remove the two gases separately from the flue gas for advanced treatment. In China, many waste incineration plants still use dry deacidification processes due to their lower overall operating costs. Therefore, finding a technology that can separate SO2 and HCl at the lowest cost and with the best deacidification results remains a key research area. Summary of the Invention

[0005] The present invention aims to provide a multi-step flue gas purification and resource recovery method, which solves the problem in the prior art that sulfur dioxide and hydrogen chloride in flue gas cannot be removed separately, resulting in poor deacidification effect and energy consumption, and realizes the resource recovery of sulfur dioxide and hydrogen chloride in flue gas in the process.

[0006] In order to achieve the above object, the present invention provides the following method:

[0007] The present invention provides a multi-step flue gas purification and resource recovery method:

[0008] S1: The flue gas passes through the bag dust removal module for bag dust removal;

[0009] S2: passing the flue gas after bag dust removal through a first condensation module to condense and cool it to separate water vapor;

[0010] S3: Discharging the flue gas after passing through the first condensation module into the second condensation module for SO2 separation;

[0011] S4: Discharging the flue gas discharged from the second condensation module into an ammonia HCl removal module to remove HCl;

[0012] S5: The flue gas from which HCl has been removed is discharged into the flue gas circulation module for heat exchange, thereby realizing a graded deacidification process of the flue gas.

[0013] Preferably, the temperature of the flue gas is 130°C to 150°C.

[0014] Preferably, an atomization chelation module is included before the bag dust removal to spray the chelating agent, improve the dust removal efficiency, and reduce the particles and heavy metals in the flue gas. The flue gas outlet of the bag dust removal module is connected to a flue gas chelation and curing device to perform a chelation and curing process on the flue gas to increase the stability and strength of the flue gas. The conditions of the chelation and curing process are: the moisture content is between 10%-20%, the mass ratio of the chelating agent added is 2%-5% of the incineration flue gas generated by the bag dust removal, and the reaction time is 3-5 minutes.

[0015] Preferably, the temperature of the first condensation module is controlled at 30°C to 60°C; the flue gas in the first condensation module is discharged into the flue gas self-condensation module for condensation and cooling; the condensed water vapor is discharged into the condensate collection module for collection, and then the condensate is discharged into the water treatment module for back-end resource utilization.

[0016] Preferably, after the flue gas after passing through the first condensation module is discharged into the second condensation module for SO2 separation step, it also includes: discharging the separated SO2 into the liquid SO2 separation module for liquid SO2 separation, and finally discharging the liquid SO2 into the SO2 purification module for further purification, and then performing back-end resource utilization.

[0017] Preferably, the reaction reagent used in the ammonia water de-HCl module is an ammonia solution.

[0018] Preferably, the flue gas discharged from the second condensation module reacts with HCl in the flue gas in the ammonia de-HCl module to generate ammonium chloride; and the generated ammonium chloride is separated by an ammonium chloride separation module to obtain purified ammonium chloride.

[0019] Preferably, the purified ammonium chloride is transported to a nitrogen fertilizer production module for nitrogen chloride recovery and utilization, and is then made into nitrogen fertilizer for back-end resource utilization.

[0020] Preferably, the flue gas from which HCl has been removed is discharged into a flue gas circulation module and heat exchanged with an ammonia solution.

[0021] Preferably, the flue gas after tail gas treatment in the flue gas circulation module is discharged into the heat recovery module and discharged to the outside through an induced draft fan. The temperature of the flue gas after coming out of the heat recovery module is 60-80°C.

[0022] The beneficial effects of the present invention are as follows: the present invention adopts the hierarchical condensation design of the first condensation module and the second condensation module, which not only reduces the temperature of the high-temperature flue gas and avoids the influence of excessive temperature on subsequent absorption, but also separates water vapor from the flue gas, thereby avoiding the influence of dilution on the concentration of the reactants in the subsequent deacidification treatment and improving the deacidification efficiency of the reactants; by using ammonia solution in the ammonia water de-HCl module, hydrogen chloride is absorbed in a targeted manner, ensuring that hydrogen chloride can be most effectively treated under optimal conditions; the desulfurization unit can also perform denitrification to achieve NO x Ultra-low emissions then use a tail gas absorption tower to treat the residual tail gas, forming a multi-stage absorption mechanism, which effectively improves the deacidification efficiency and effect, and significantly reduces the emission of harmful gases; through the combined design of graded condensation and multi-stage absorption, the separation of water vapor and sulfur dioxide makes the deacidification treatment more efficient, thereby reducing the consumption of reaction reagents. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0024] Figure 1 A schematic flow chart of a multi-step flue gas purification and resource recovery method provided by an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of the process structure of a flue gas multi-step purification and resource recovery method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to help those skilled in the art better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0027] The terms "first," "second," and so on, in the description and claims of the present invention and the accompanying drawings are used to distinguish between different items, not to describe a specific order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, apparatus, product, or end comprising a series of steps or elements is not limited to the listed steps or elements but may optionally include steps or elements not listed therein, or may optionally include other steps or elements inherent to such process, method, product, or end.

[0028] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute a separate or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0029] Currently, waste incineration flue gas deacidification technologies can be categorized into three types: wet, dry, and semi-dry, depending on the state of the raw materials and byproducts. Wet deacidification primarily utilizes a scrubber, where the flue gas is treated with an alkaline solution. Deacidification efficiencies can reach 99%, but these processes suffer from high power and water consumption, high operating and maintenance costs, and the need for additional wastewater treatment. Dry deacidification involves injecting lime powder into a reaction tower via a spray system, where it reacts with the acidic gases to form solid compounds. While this approach offers low initial investment and eliminates the need for a wastewater treatment system, it suffers from low deacidification efficiency, making it difficult to meet stringent emission standards. Furthermore, long-term use incurs high reagent consumption. While not as high as the wet deacidification process, this still represents a significant operating cost. Semi-dry deacidification involves injecting lime slurry into a reaction tower to react with the acidic gases. By controlling the reaction temperature and water evaporation, larger flue gas particles settle to the bottom of the tower and are discharged. Fine particles are captured in a dust collector and then stabilized. The semi-dry method is between the wet method and the dry method in terms of deacidification efficiency and operating cost, and is suitable for general emission requirements.

[0030] In addition to the three basic flue gas deacidification processes mentioned above, combined flue gas deacidification processes such as "semi-dry + dry" and "dry + wet" have emerged and been put into practice in recent years. The "semi-dry + dry" process is the most commonly used in the waste incineration industry. This process primarily utilizes a semi-dry method, supplemented by a dry method, and its deacidification results generally meet national standards. In China, many waste incineration plants still use dry deacidification due to its lower overall operating costs. Therefore, finding a low-cost, effective deacidification technology remains a key research priority.

[0031] The present invention aims to provide a multi-step flue gas purification and resource recovery method, which solves the problem in the prior art that sulfur dioxide and hydrogen chloride in flue gas cannot be removed separately, resulting in poor deacidification effect and energy consumption, and realizes the resource recovery of sulfur dioxide and hydrogen chloride in flue gas in the process.

[0032] like Figure 1 and Figure 2 As shown, a specific embodiment of the present invention provides a flue gas multi-step purification and resource recovery method, comprising the following steps:

[0033] S1: The flue gas passes through the bag dust removal module for bag dust removal.

[0034] In an embodiment of the present invention, the temperature of the flue gas is 130°C to 150°C; an atomization chelation module is also included before the bag dust removal to spray the chelating agent, improve the dust removal efficiency, and reduce the particles and heavy metals in the flue gas. The flue gas outlet of the bag dust removal module is connected to a flue gas chelation and curing device to perform a chelation and curing process on the flue gas to increase the stability and strength of the flue gas. The conditions of the chelation and curing process are: the moisture content is between 10%-20%, the mass ratio of the chelating agent added is 2%-5% of the incineration flue gas generated by the bag dust removal, and the reaction time is 3-5 minutes.

[0035] S2: The flue gas after bag dust removal is passed through the first condensation module for condensation, cooling and separation of water vapor.

[0036] In an embodiment of the present invention, the temperature of the first condensation module is controlled at 30°C to 60°C; the flue gas in the first condensation module is discharged into the flue gas self-condensation module for condensation and cooling; the condensed water vapor is discharged into the condensate collection module for collection, and then the condensate is discharged into the water treatment module for back-end resource utilization.

[0037] S3: The flue gas after passing through the first condensation module is discharged into the second condensation module for SO2 separation.

[0038] In an embodiment of the present invention, after the flue gas after passing through the first condensation module is discharged into the second condensation module for SO2 separation step, it also includes: discharging the separated SO2 into the liquid SO2 separation module for liquid SO2 separation, and finally discharging the liquid SO2 into the SO2 purification module for further purification, and then performing back-end resource utilization.

[0039] S4: The flue gas discharged from the second condensation module is discharged into the ammonia HCl removal module to remove HCl.

[0040] In an embodiment of the present invention, the reaction reagent used in the ammonia water de-HCl module is an ammonia solution; the flue gas discharged from the second condensation module reacts with HCl in the flue gas in the ammonia water de-HCl module to generate ammonium chloride; the generated ammonium chloride is separated by the ammonium chloride separation module to obtain purified ammonium chloride; the purified ammonium chloride is transported to the nitrogen fertilizer production module for nitrogen chloride recovery and utilization, and is then produced into nitrogen fertilizer for back-end resource application.

[0041] S5: The flue gas from which HCl has been removed is discharged into the flue gas circulation module for heat exchange, thereby realizing a graded deacidification process of the flue gas.

[0042] In an embodiment of the present invention, the flue gas from which HCl has been removed is discharged into a flue gas circulation module and subjected to heat exchange with an ammonia solution. The flue gas in the flue gas circulation module, after undergoing tail gas treatment, is discharged into a heat recovery module and exhausted by an induced draft fan. The temperature of the flue gas after exiting the heat recovery module is 60 to 80°C.

[0043] The beneficial effects of the present invention are as follows: the present invention adopts the hierarchical condensation design of the first condensation module and the second condensation module, which not only reduces the temperature of the high-temperature flue gas and avoids the influence of excessive temperature on subsequent absorption, but also separates water vapor from the flue gas, thereby avoiding the influence of dilution on the concentration of the reactants in the subsequent deacidification treatment and improving the deacidification efficiency of the reactants; by using ammonia solution in the ammonia water de-HCl module, hydrogen chloride is absorbed in a targeted manner, ensuring that hydrogen chloride can be most effectively treated under optimal conditions; the desulfurization unit can also perform denitrification to achieve NO x Ultra-low emissions then use a tail gas absorption tower to treat the residual tail gas, forming a multi-stage absorption mechanism, which effectively improves the deacidification efficiency and effect, and significantly reduces the emission of harmful gases; through the combined design of graded condensation and multi-stage absorption, the separation of water vapor and sulfur dioxide makes the deacidification treatment more efficient, thereby reducing the consumption of reaction reagents.

[0044] The above description is merely an embodiment of the present invention. Common knowledge such as the specific technical solutions or features of the solutions is not described in detail here. It should be noted that those skilled in the art may make several modifications and improvements without departing from the solution of the present invention, and these modifications and improvements should also be considered as the scope of protection of the present invention. These modifications and improvements will not affect the effects of the present invention and the practicality of the patent. The scope of protection claimed in this application shall be based on the content of the claims, and the specific embodiments and other descriptions in the specification may be used to interpret the content of the claims.

Claims

1. A flue gas multi-step purification and resource recovery method, characterized in that: The method comprises: S1: The flue gas passes through the bag dust removal module for bag dust removal; S2: passing the flue gas after bag dust removal through a first condensation module to condense and cool it to separate water vapor; S3: Discharging the flue gas after passing through the first condensation module into the second condensation module for SO2 separation; S4: Discharging the flue gas discharged from the second condensation module into an ammonia HCl removal module to remove HCl; S5: The flue gas from which HCl has been removed is discharged into the flue gas circulation module for heat exchange, thereby realizing a graded deacidification process of the flue gas.

2. The method for multi-step flue gas purification and resource recovery according to claim 1, characterized in that: The temperature of the flue gas is 130°C to 150°C.

3. The method for multi-step flue gas purification and resource recovery according to claim 1, characterized in that: Before the bag dust removal, an atomization chelation module is also included to spray the chelating agent to improve the dust removal efficiency and reduce the particles and heavy metals in the flue gas. The flue gas outlet of the bag dust removal module is connected to a flue gas chelation and curing device to perform a chelation and curing process on the flue gas to increase the stability and strength of the flue gas. The conditions of the chelation and curing process are: the moisture content is between 10%-20%, the mass ratio of the chelating agent added is 2%-5% of the incineration flue gas generated by the bag dust removal, and the reaction time is 3-5 minutes.

4. The method for multi-step flue gas purification and resource recovery according to claim 1, characterized in that: The temperature of the first condensation module is controlled at 30°C to 60°C; Discharging the flue gas in the first condensation module into the flue gas self-condensation module for condensation and cooling; The condensed water vapor is discharged into the condensate collection module for collection, and then the condensate is discharged into the water treatment module for back-end resource utilization.

5. The method for multi-step flue gas purification and resource recovery according to claim 1, characterized in that: After the flue gas after passing through the first condensation module is discharged into the second condensation module for SO2 separation, the method further includes: The separated SO2 is discharged into the liquid SO2 separation module for liquid SO2 separation, and finally the liquid SO2 is discharged into the SO2 purification module for further purification before being utilized as a resource at the back end.

6. The method for multi-step flue gas purification and resource recovery according to claim 1, characterized in that: The reaction reagent used in the ammonia water de-HCl module is ammonia solution.

7. The method for multi-step flue gas purification and resource recovery according to claim 6, characterized in that: The flue gas discharged from the second condensation module reacts with HCl in the flue gas in the ammonia de-HCl module to generate ammonium chloride; the generated ammonium chloride is separated by the ammonium chloride separation module to obtain purified ammonium chloride.

8. The method for multi-step flue gas purification and resource recovery according to claim 7, characterized in that: The purified ammonium chloride is transported to a nitrogen fertilizer production module for nitrogen chloride recovery and utilization, and is then made into nitrogen fertilizer for back-end resource utilization.

9. The method for multi-step flue gas purification and resource recovery according to claim 1, characterized in that: The flue gas from which HCl has been removed is discharged into the flue gas circulation module and undergoes heat exchange through an ammonia solution.

10. The method for multi-step flue gas purification and resource recovery according to claim 1, characterized in that: The flue gas after tail gas treatment in the flue gas circulation module is discharged into the heat recovery module and discharged to the outside through the induced draft fan. The temperature of the flue gas after coming out of the heat recovery module is 60-80°C.

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