Flue gas sulfur dioxide resource system and process

Abstract

The present application relates to the field of flue gas desulfurization and sulfur-containing resource processing technology, and discloses a flue gas sulfur dioxide resource processing system and process, which is used to solve the problem of insufficient connection between ammonia desulfurization process and sulfur-containing byproduct resource processing. The system comprises an ammonia desulfurization unit, a pyrolysis conversion unit and a sulfur dioxide acid making unit. The pyrolysis conversion unit comprises a first electric heating reaction unit, a second electric heating reaction unit and a gas isolation type solid transfer mechanism. Ammonium sulfate-containing material reacts with metal oxide in a first temperature range to generate solid material containing metal sulfate and release ammonia gas. The solid material enters a second temperature range under gas isolation conditions, decomposes, regenerates metal oxide and releases sulfur dioxide gas. Ammonia gas and metal oxide are recycled and used, and sulfur dioxide gas is used for acid making.

Description

Technical Field

[0001] This invention relates to the field of flue gas desulfurization and sulfur-containing resource utilization technology, and in particular to a flue gas sulfur dioxide resource utilization system and process. Background Technology

[0002] Sulfur dioxide-containing flue gas is widely generated in coal-fired boilers, smelting furnaces, sulfuric acid production, chemical roasting, and other heat treatment processes involving sulfur-containing materials. Direct emissions of sulfur dioxide have adverse environmental impacts; therefore, industrial flue gas typically requires desulfurization treatment before being released or used in subsequent processes.

[0003] Ammonia desulfurization is a common method for removing sulfur dioxide from flue gas. It typically utilizes the reaction between ammonia and sulfur dioxide in the flue gas, causing the sulfur dioxide to move from the gas phase into the absorbent or slurry system, further forming ammonium sulfate-containing materials. This method is characterized by a relatively fast absorption reaction rate and relatively mature absorbent utilization methods, and can meet the sulfur dioxide removal requirements of flue gas under certain operating conditions.

[0004] In existing ammonia-based desulfurization processes, ammonium sulfate-containing materials are typically treated as byproducts and undergo concentration, crystallization, drying, transportation, or further processing. While this method effectively removes sulfur-containing components from flue gas, the subsequent utilization of ammonium sulfate-containing materials is significantly affected by factors such as material moisture content, impurity composition, product quality, external disposal conditions, and transportation and storage conditions. When fluctuating flue gas operating conditions or unstable desulfurization byproduct quality, the subsequent disposal and resource utilization of ammonium sulfate-containing materials can easily become a bottleneck in the flue gas treatment process.

[0005] Furthermore, existing flue gas sulfur dioxide treatment routes typically focus more on achieving sulfur dioxide removal standards, while insufficiently considering the synergistic recovery and utilization of absorbent components and sulfur-containing components within the system. If the ammonium sulfate-containing material formed after ammonia absorbs sulfur dioxide relies primarily on external disposal, it can easily increase the pressure of byproduct handling. Simultaneously, if the absorbent components cannot form an effective reuse relationship with the flue gas desulfurization process, it may also increase the consumption of supplementary reagents and the complexity of operation and management.

[0006] For scenarios requiring further enhancement of sulfur-containing component utilization, it is generally desirable to more closely integrate the sulfur dioxide removal process from flue gas with subsequent sulfur-containing resource recovery processes. However, in multi-stage material processing or multi-stage heat treatment processes, different processing zones may exhibit variations in atmosphere composition, target gaseous products, and solid material states. If gases from different processing zones interfere with each other, it can easily affect the separation, recovery, and subsequent utilization of gaseous products, and may lead to a decrease in the stability of the processing process.

[0007] On the other hand, sulfur-containing materials have certain requirements regarding temperature conditions, material residence time, gas discharge, and solid transfer during heat treatment. If the heat supply and reaction process are not well matched, it can easily lead to insufficient release of the target gas, unstable conversion of solid materials, or low energy utilization efficiency. For continuously operating flue gas treatment systems, how to ensure a stable connection between the sulfur-containing material conversion process, the flue gas desulfurization process, and the subsequent acid production process is an important factor affecting the overall resource utilization effect.

[0008] The tail gas from ammonia-based desulfurization processes may contain a certain amount of escaped ammonia and water vapor. Inadequate treatment of escaped ammonia can affect the stability of tail gas emissions; excessive water vapor discharge with the tail gas can also impact the system's moisture balance and subsequent treatment load. In existing treatment processes, there is often a lack of sufficient coordination between escaped ammonia and water vapor in the tail gas and the subsequent utilization of sulfur-containing byproducts, leaving room for further coordination between tail gas treatment and the resource utilization of sulfur-containing materials.

[0009] It is evident that while existing ammonia-based desulfurization and sulfur-containing byproduct treatment methods can absorb and remove sulfur dioxide from flue gas, they still have shortcomings in areas such as the resource utilization pathway for sulfur-containing byproducts, the recovery and utilization of absorbent components, the control of atmospheric interference in different treatment zones, and the synergistic treatment of escaped ammonia and water vapor in the tail gas. These shortcomings can easily lead to insufficient connection between the flue gas desulfurization process and the subsequent resource utilization process. Summary of the Invention

[0010] The purpose of this invention is to provide a flue gas sulfur dioxide resource recovery system and process, which solves the problems in the prior art where the connection between the flue gas sulfur dioxide removal process and the sulfur-containing by-product resource recovery process is insufficient, and the recovery and utilization of absorbent components and sulfur-containing components are not well coordinated.

[0011] In one aspect, a flue gas sulfur dioxide resource recovery system is provided, comprising an ammonia desulfurization unit, a pyrolysis conversion unit, and a sulfur dioxide sulfuric acid production unit. The ammonia desulfurization unit is used to absorb sulfur dioxide in flue gas with ammonia and output ammonium sulfate-containing material. The pyrolysis conversion unit includes a first electrically heated reaction unit, a second electrically heated reaction unit, and a gas-isolated solid transfer mechanism disposed between the first electrically heated reaction unit and the second electrically heated reaction unit.

[0012] The first electrically heated reaction unit receives ammonium sulfate-containing material and metal oxide, and reacts the ammonium sulfate-containing material with the metal oxide in a first temperature range to generate a solid material containing metal sulfate and release ammonia gas. The second electrically heated reaction unit receives the solid material containing metal sulfate discharged from the first electrically heated reaction unit, and decomposes the solid material containing metal sulfate in a second temperature range higher than the first temperature range to regenerate the metal oxide and release sulfur dioxide gas.

[0013] A gas-isolated solid transfer mechanism is used to allow solid materials discharged from the first electrically heated reaction unit to enter the second electrically heated reaction unit, and to prevent sulfur dioxide-containing gas in the second electrically heated reaction unit from flowing back into the first electrically heated reaction unit. The flue gas sulfur dioxide resource recovery system also includes an ammonia recovery loop and a metal oxide circulation loop. The ammonia recovery loop returns the ammonia released from the first electrically heated reaction unit to the ammonia desulfurization unit, and the metal oxide circulation loop returns the metal oxides regenerated in the second electrically heated reaction unit to the first electrically heated reaction unit. A sulfur dioxide sulfuric acid production unit is connected to the sulfur dioxide exhaust end of the second electrically heated reaction unit, and is used to convert the sulfur dioxide gas released from the second electrically heated reaction unit into sulfuric acid.

[0014] Furthermore, the first electrically heated reaction unit is a first-stage electrically heated rotary kiln, and the second electrically heated reaction unit is a second-stage electrically heated rotary kiln. The discharge end of the first-stage electrically heated rotary kiln is connected to the feed end of the second-stage electrically heated rotary kiln through a gas-isolated solid transfer mechanism, so that the high-temperature solid material discharged from the first-stage electrically heated rotary kiln directly enters the second-stage electrically heated rotary kiln.

[0015] Furthermore, the gas-isolated solid transfer mechanism includes a double-layer butterfly valve, comprising a first-layer butterfly valve and a second-layer butterfly valve arranged sequentially along the material transfer direction. The first-layer butterfly valve and the second-layer butterfly valve are configured to open and close alternately and not simultaneously, thereby maintaining the isolation of the gas space between the first-stage electrically heated rotary kiln and the second-stage electrically heated rotary kiln during the material transfer process.

[0016] Furthermore, the feed end of the first-stage electrically heated rotary kiln is equipped with a feeding screw for adding ammonium sulfate-containing materials and metal oxides into the first-stage electrically heated rotary kiln. The feed end of the second-stage electrically heated rotary kiln is equipped with a pushing screw, which connects to the discharge end of the gas-isolated solid transfer mechanism to push the solid materials entering the second-stage electrically heated rotary kiln into the second-stage electrically heated rotary kiln. The ammonia exhaust end of the first-stage electrically heated rotary kiln is located at the discharge end of the first-stage electrically heated rotary kiln, and / or, the sulfur dioxide exhaust end of the second-stage electrically heated rotary kiln is located at the discharge end of the second-stage electrically heated rotary kiln.

[0017] Furthermore, the flue gas sulfur dioxide resource recovery system also includes a dilute sulfuric acid tail gas scrubbing unit, which is located after the tail gas outlet of the ammonia desulfurization unit. The dilute sulfuric acid tail gas scrubbing unit is used to scrub the tail gas discharged from the ammonia desulfurization unit with dilute sulfuric acid, absorbing the escaped ammonia in the tail gas to form ammonium sulfate, and condensing the water vapor in the tail gas into the scrubbing liquid. The ammonium sulfate-containing output end of the dilute sulfuric acid tail gas scrubbing unit is connected to the pyrolysis conversion unit to send the washed ammonium sulfate-containing material into the first electrically heated reaction unit.

[0018] Furthermore, the heating method of the first and / or second electrically heated reaction units is resistance heating and / or electromagnetic induction heating. The metal oxide is ferric oxide, manganese monoxide, or copper oxide. When the metal oxide is ferric oxide, the first temperature range is 360℃-460℃, and the second temperature range is 600℃-700℃; when the metal oxide is manganese monoxide, the first temperature range is 365℃-406℃, and the second temperature range is 800℃-900℃; when the metal oxide is copper oxide, the first temperature range is 400℃-500℃, and the second temperature range is 700℃-800℃. The mass concentration of the dilute sulfuric acid used in the dilute sulfuric acid tail gas scrubbing unit is 5%-15%, and the dilute sulfuric acid is obtained by diluting the sulfuric acid produced by the sulfur dioxide acid production unit.

[0019] Secondly, a process for the resource recovery of sulfur dioxide from flue gas is provided, comprising: absorbing sulfur dioxide from flue gas with ammonia to form an ammonium sulfate-containing material; feeding the ammonium sulfate-containing material and metal oxides into a first electrically heated reaction stage, causing the ammonium sulfate-containing material and metal oxides to react in a first temperature range to generate a solid material containing metal sulfates and release ammonia gas; feeding the solid material containing metal sulfates discharged from the first electrically heated reaction stage into a second electrically heated reaction stage under gas isolation conditions, and suppressing the sulfur dioxide-containing gas generated in the second electrically heated reaction stage from flowing back into the first electrically heated reaction stage; in the second electrically heated reaction stage, decomposing the solid material containing metal sulfates in a second temperature range higher than the first temperature range to regenerate metal oxides and release sulfur dioxide gas; returning the ammonia gas released in the first electrically heated reaction stage for absorbing sulfur dioxide from flue gas; returning the metal oxides regenerated in the second electrically heated reaction stage to the first electrically heated reaction stage for recycling; and feeding the sulfur dioxide gas released in the second electrically heated reaction stage into an acid production step to produce sulfuric acid.

[0020] Furthermore, the solid material containing metal sulfate discharged from the first electric heating reaction stage is fed into the second electric heating reaction stage under gas isolation conditions, which includes: transferring the solid material containing metal sulfate through a double-layer butterfly valve, wherein the first and second butterfly valves of the double-layer butterfly valve open and close alternately and do not open at the same time; after the solid material containing metal sulfate enters the feed end of the second electric heating reaction stage, the solid material containing metal sulfate is pushed into the reaction zone of the second electric heating reaction stage by a pusher screw.

[0021] Furthermore, after absorbing sulfur dioxide from the flue gas with ammonia, the process includes a step of washing the desulfurized tail gas with dilute sulfuric acid. In this washing step, escaped ammonia in the tail gas is absorbed by the dilute sulfuric acid to form ammonium sulfate, and water vapor in the tail gas condenses and enters the washing liquid. The ammonium sulfate-containing material formed in the washing step is combined with the ammonium sulfate-containing material formed from the absorption of sulfur dioxide from the flue gas with ammonia and then fed into the first electrically heated reaction stage.

[0022] Furthermore, the first and / or second electrically heated reaction stages employ resistance heating and / or electromagnetic induction heating. The metal oxide is ferric oxide, manganese monoxide, or copper oxide. When the metal oxide is ferric oxide, the first temperature range is 360℃-460℃, and the second temperature range is 600℃-700℃; when the metal oxide is manganese monoxide, the first temperature range is 365℃-406℃, and the second temperature range is 800℃-900℃; when the metal oxide is copper oxide, the first temperature range is 400℃-500℃, and the second temperature range is 700℃-800℃. The mass concentration of the dilute sulfuric acid is 5%-15%. The sulfur dioxide gas released in the second electrically heated reaction stage is subjected to dust removal, cooling, and / or drying before entering the acid production step. The sulfuric acid produced in the acid production step is concentrated sulfuric acid, and a portion of the concentrated sulfuric acid is diluted and used as dilute sulfuric acid.

[0023] The aforementioned flue gas sulfur dioxide resource recovery system and process generate ammonium sulfate-containing material through an ammonia desulfurization unit, and then perform segmented conversion of the ammonium sulfate-containing material through a first and second electric heating reaction unit. This allows the sulfur-containing components in the ammonium sulfate-containing material to further enter the sulfur dioxide acid production unit in the form of sulfur dioxide gas, thereby improving the connection between the flue gas sulfur dioxide removal process and the subsequent sulfur-containing resource recovery process.

[0024] Ammonia is released through the first electrically heated reaction unit and returned to the ammonia desulfurization unit via the ammonia recycling loop, thus establishing a correspondence between the ammonia absorption process and the ammonia recycling process. This helps reduce the dependence of the ammonia desulfurization unit on external ammonia supplementation and improves the continuity of absorbent component utilization in the flue gas sulfur dioxide resource recovery system.

[0025] The metal oxides are regenerated by the second electric heating reaction unit and returned to the first electric heating reaction unit through the metal oxide circulation loop. This allows the metal oxides to continue to be recycled after participating in the conversion of ammonium sulfate-containing materials, which helps to reduce the discharge of solid reaction media and helps to maintain the continuous operation of the pyrolysis conversion unit.

[0026] The solid material discharged from the first electrically heated reaction unit is transferred to the second electrically heated reaction unit by a gas-isolated solid transfer mechanism, and the sulfur dioxide-containing gas in the second electrically heated reaction unit is prevented from flowing back to the first electrically heated reaction unit. This helps to reduce atmospheric interference between different reaction zones and improves the stability of the separate recovery and utilization of ammonia and sulfur dioxide gas.

[0027] When the first electrically heated reaction unit is a first-stage electrically heated rotary kiln and the second electrically heated reaction unit is a second-stage electrically heated rotary kiln, it can meet the requirements of continuous heating, turning, and conveying of ammonium sulfate-containing materials and solid materials containing metal sulfates. When the gas-isolated solid transfer mechanism includes a double-layer butterfly valve, the first and second layer butterfly valves open and close alternately and do not open at the same time, which can take into account both material passage and gas isolation during the solid material transfer process. When a feeding screw and a pushing screw are set, it is beneficial to improve the stability of ammonium sulfate-containing materials, metal oxides, and solid materials containing metal sulfates entering the corresponding reaction areas.

[0028] The tail gas discharged from the ammonia desulfurization unit is treated by a dilute sulfuric acid tail gas scrubbing unit or scrubbing step, so that the escaped ammonia in the tail gas is absorbed to form ammonium sulfate, and the water vapor in the tail gas is condensed into the scrubbing liquid. The ammonium sulfate-containing material formed by scrubbing can be sent to the first electric heating reaction unit or the first electric heating reaction stage, which helps to reduce the impact of escaped ammonia on the stability of tail gas emissions and facilitates the inclusion of the ammonium sulfate-containing material obtained from tail gas scrubbing into the subsequent resource recovery process.

[0029] By employing resistance heating and / or electromagnetic induction heating in the first electric heating reaction unit, the second electric heating reaction unit, the first electric heating reaction stage, and the second electric heating reaction stage, and by setting corresponding first and second temperature ranges according to the type of metal oxide, it is beneficial to ensure that the conversion of ammonium sulfate-containing materials, the decomposition of solid materials containing metal sulfates, the regeneration of metal oxides, and the release of sulfur dioxide gas are all under suitable temperature conditions, thereby improving the controllability of the pyrolysis conversion process.

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of an embodiment of the flue gas sulfur dioxide resource recovery system of the present invention.

[0032] Figure 2 for Figure 1 A schematic diagram of the pyrolysis conversion unit in the flue gas sulfur dioxide resource utilization system.

[0033] The diagram is marked as follows: 1-Ammonia-based desulfurization unit; 2-Pyrolysis conversion unit; 21 - First-stage electrically heated rotary kiln; 22 - Second-stage electrically heated rotary kiln; 23 - First-level butterfly valve; 24 - Second layer butterfly valve; 25 - First layer butterfly valve on the discharge side; 26 - Second layer butterfly valve on the discharge side; 3-Sulfur dioxide acid production unit; 4-Dilute sulfuric acid tail gas scrubbing unit. Detailed Implementation

[0034] The present invention will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. The following embodiments are only used to illustrate some implementations of the present invention and do not constitute an undue limitation on the scope of protection of the present invention. Technical features in the various embodiments can be combined with each other without conflict.

[0035] The terms "including," "comprising," and "having" used in this specification are open-ended and do not exclude the possibility of other unlisted structures, units, steps, or process conditions. The temperature ranges, material states, heating methods, gas treatment methods, circulation methods, and washing liquid concentrations mentioned in this specification can be adjusted according to the flue gas composition, sulfur dioxide concentration, treatment scale, equipment capacity, and continuous operation requirements, as long as the reaction between ammonium sulfate-containing materials and metal oxides in the first electric heating reaction unit or the first electric heating reaction stage, and the decomposition of solid materials containing metal sulfates in the second electric heating reaction unit or the second electric heating reaction stage, are all acceptable.

[0036] like Figure 1 As shown, this embodiment provides a flue gas sulfur dioxide resource recovery system, including an ammonia desulfurization unit 1, a pyrolysis conversion unit 2, and a sulfur dioxide sulfuric acid production unit 3. The ammonia desulfurization unit 1 receives flue gas containing sulfur dioxide and absorbs the sulfur dioxide in the flue gas with ammonia, forming and outputting ammonium sulfate-containing material. The pyrolysis conversion unit 2 is located after the ammonia desulfurization unit 1 and receives the ammonium sulfate-containing material from the ammonia desulfurization unit 1, performing segmented conversion of the ammonium sulfate-containing material with the participation of metal oxides. The sulfur dioxide sulfuric acid production unit 3 is connected to the pyrolysis conversion unit 2 and receives the sulfur dioxide gas released from the pyrolysis conversion unit 2, converting the sulfur dioxide gas into sulfuric acid.

[0037] In one specific embodiment, the ammonia desulfurization unit 1 may include a desulfurization absorption tower, an ammonia supply pipeline, a flue gas inlet, a tail gas outlet, an absorbent circulation pipeline, an ammonium sulfate-containing material output pipeline, and corresponding pumps, valves, and level control components. Sulfur dioxide-containing flue gas enters the ammonia desulfurization unit 1 through the flue gas inlet. Ammonia enters the ammonia desulfurization unit 1 through the ammonia supply pipeline and contacts the sulfur dioxide in the flue gas in the absorbent or slurry system, causing the sulfur dioxide to transfer from the gas phase to the liquid or slurry phase, forming an ammonium sulfate-containing material. The ammonium sulfate-containing material may be an ammonium sulfate solution, an ammonium sulfate slurry, a concentrated ammonium sulfate slurry, hydrated ammonium sulfate solid, or one or more mixtures of the above materials.

[0038] The pyrolysis conversion unit 2 includes a first electrically heated reaction unit, a second electrically heated reaction unit, and a gas-isolated solid transfer mechanism disposed between the first and second electrically heated reaction units. The first electrically heated reaction unit receives ammonium sulfate-containing material and metal oxides, and reacts the ammonium sulfate-containing material with the metal oxides in a first temperature range to generate a solid material containing metal sulfates and release ammonia gas. The second electrically heated reaction unit receives the solid material containing metal sulfates discharged from the first electrically heated reaction unit, and decomposes the solid material containing metal sulfates in a second temperature range higher than the first temperature range to regenerate the metal oxides and release sulfur dioxide gas.

[0039] The ammonia gas released from the first electrically heated reaction unit is returned to the ammonia desulfurization unit 1 via an ammonia reuse loop. The ammonia reuse loop may include an ammonia collection pipeline, condensation or dust removal components, a buffer tank, an induced draft or conveying component, a pressure regulating component, and a reuse inlet connected to the ammonia desulfurization unit 1. After returning to the ammonia desulfurization unit 1 via the ammonia reuse loop, the ammonia gas released from the first electrically heated reaction unit can be reused to absorb sulfur dioxide in the flue gas, thus creating a cyclical relationship between the ammonia release process in the first electrically heated reaction unit and the ammonia absorption process in the ammonia desulfurization unit 1.

[0040] The metal oxides regenerated in the second electrically heated reaction unit are returned to the first electrically heated reaction unit through a metal oxide circulation loop. This circulation loop may include a high-temperature solid conveying device, a cooling or heat-insulating conveying section, a metering feeder, a buffer silo, and a return pipeline connected to the feed end of the first electrically heated reaction unit. The regenerated metal oxides can return to the first electrically heated reaction unit after cooling, or they can return in a heat-insulating state, provided the feed conditions of the first electrically heated reaction unit are met. The specific form of the metal oxide circulation loop can be selected based on the metal oxide particle size, material temperature, processing scale, and layout height, using methods such as screw conveying, bucket elevator, pneumatic conveying, scraper conveying, or gravity discharge from a closed silo.

[0041] like Figure 2As shown, in one specific embodiment, the first electrically heated reaction unit is a first-stage electrically heated rotary kiln 21, and the second electrically heated reaction unit is a second-stage electrically heated rotary kiln 22. The first-stage electrically heated rotary kiln 21 and the second-stage electrically heated rotary kiln 22 may each include a kiln body, a transmission mechanism, a sealing structure, an electrically heated structure, a temperature detection component, a feed end, and a discharge end. The discharge end of the first-stage electrically heated rotary kiln 21 is connected to the feed end of the second-stage electrically heated rotary kiln 22 via a gas-isolated solid transfer mechanism, allowing the high-temperature solid material discharged from the first-stage electrically heated rotary kiln 21 to directly enter the second-stage electrically heated rotary kiln 22. Here, "directly entering" means that after the high-temperature solid material is discharged from the first-stage electrically heated rotary kiln 21, it does not need to be discharged as an external by-product system, but is continuously or intermittently transferred into the second-stage electrically heated rotary kiln 22 via the gas-isolated solid transfer mechanism.

[0042] The first-stage electrically heated rotary kiln 21 is used to mix, heat, agitate, and react the ammonium sulfate-containing material with the metal oxide. After entering the first-stage electrically heated rotary kiln 21, the ammonium sulfate-containing material and the metal oxide move axially along the kiln body as the kiln rotates, and react within a first temperature range. The rotation of the first-stage electrically heated rotary kiln 21 increases the contact between the ammonium sulfate-containing material and the metal oxide, and facilitates the evaporation of moisture, the release of ammonia, and the formation of solid materials containing metal sulfates.

[0043] The second-stage electrically heated rotary kiln 22 is used to further heat, agitate, and decompose the solid material containing metal sulfates. After entering the second-stage electrically heated rotary kiln 22, the solid material containing metal sulfates decomposes within a second temperature range to regenerate metal oxides and release sulfur dioxide gas. Because the second temperature range is higher than the first temperature range, the first and second electrically heated reaction units respectively undertake reaction tasks under different temperature conditions, allowing the conversion of ammonium sulfate-containing material to solid material containing metal sulfates, and the conversion of solid material containing metal sulfates to metal oxides and sulfur dioxide gas, to occur in stages.

[0044] A gas-isolated solid transfer mechanism is disposed between the first and second electrically heated reaction units. It allows solid material discharged from the first electrically heated reaction unit to enter the second electrically heated reaction unit and prevents sulfur dioxide-containing gas from the second electrically heated reaction unit from flowing back into the first electrically heated reaction unit. In one specific embodiment, the gas-isolated solid transfer mechanism includes a double-layer butterfly valve. The double-layer butterfly valve includes a first-layer butterfly valve 23 and a second-layer butterfly valve 24 arranged sequentially along the material transfer direction. An intermediate transition cavity can be formed between the first-layer butterfly valve 23 and the second-layer butterfly valve 24. The first-layer butterfly valve 23 and the second-layer butterfly valve 24 are configured to open and close alternately and not simultaneously.

[0045] During material transfer, the first-layer butterfly valve 23 can be opened first and the second-layer butterfly valve 24 closed, allowing the solid material containing metal sulfates discharged from the first-stage electrically heated rotary kiln 21 to enter the intermediate transition chamber between the first-layer butterfly valve 23 and the second-layer butterfly valve 24. Then, the first-layer butterfly valve 23 is closed, and the second-layer butterfly valve 24 is opened again, allowing the solid material containing metal sulfates in the intermediate transition chamber to enter the feed end of the second-stage electrically heated rotary kiln 22. Because the first-layer butterfly valve 23 and the second-layer butterfly valve 24 are not opened simultaneously, the gas space between the first-stage electrically heated rotary kiln 21 and the second-stage electrically heated rotary kiln 22 remains isolated during material transfer, thereby preventing sulfur dioxide-containing gas in the second-stage electrically heated rotary kiln 22 from flowing back into the first-stage electrically heated rotary kiln 21.

[0046] In another specific embodiment, the gas-isolated solid transfer mechanism can also be used in conjunction with a sealing material sealing section, an inert gas purging section, a high-temperature resistant feed pipe, an airlock valve, or a material level detection component. The sealing material sealing section can form a material seal by maintaining a certain height of solid material, and the inert gas purging section can purge the intermediate transition chamber with a small amount of nitrogen or other inert gas to further reduce the possibility of sulfur dioxide-containing gas diffusing towards the first electrically heated reaction unit. The above structure can be used as an auxiliary structure for a double-layer butterfly valve, or it can be selectively set according to the equipment layout and sealing requirements.

[0047] The first-stage electrically heated rotary kiln 21 is equipped with a feeding screw at its feed end. The feeding screw is used to add ammonium sulfate-containing material and metal oxides into the first-stage electrically heated rotary kiln 21. In one specific embodiment, the ammonium sulfate-containing material can first enter a metering silo or a mixing silo, and the metal oxides can return to the same metering silo or another metering feeder via a metal oxide circulation loop. The ammonium sulfate-containing material and metal oxides are fed into the first-stage electrically heated rotary kiln 21 by the feeding screw according to a predetermined feeding ratio. The feeding screw can be driven by a frequency converter to adjust the feed rate of the ammonium sulfate-containing material and metal oxides.

[0048] The feed end of the second-stage electrically heated rotary kiln 22 is equipped with a pusher screw, which connects to the discharge end of the gas-isolated solid transfer mechanism. This pusher screw pushes the solid material entering the feed end of the second-stage electrically heated rotary kiln 22 into the kiln. The pusher screw can be installed within the sealed feed shell of the feed end of the second-stage electrically heated rotary kiln 22, allowing the solid material containing metal sulfates transferred from the gas-isolated solid transfer mechanism to enter the reaction zone of the second-stage electrically heated rotary kiln 22 in a sealed state. By installing the pusher screw, the possibility of solid material accumulation or backflow at the feed end of the second-stage electrically heated rotary kiln 22 can be reduced, and it is beneficial to maintain continuous feeding of the second electrically heated reaction unit.

[0049] The ammonia exhaust end of the first-stage electrically heated rotary kiln 21 can be located at the discharge end of the first-stage electrically heated rotary kiln 21. Since the ammonium sulfate-containing material and metal oxides gradually heat up and react within the first-stage electrically heated rotary kiln 21 along the material movement direction, the release of ammonia is relatively concentrated near the discharge end. Therefore, placing the ammonia exhaust end of the first-stage electrically heated rotary kiln 21 at its discharge end facilitates the discharge of ammonia from the first electrically heated reaction unit and its entry into the ammonia recycling loop. The sulfur dioxide exhaust end of the second-stage electrically heated rotary kiln 22 can be located at its discharge end, allowing the sulfur dioxide gas released after the solid material containing metal sulfates completes its decomposition within the second-stage electrically heated rotary kiln 22 to be discharged from the sulfur dioxide exhaust end and enter the sulfur dioxide acid production unit 3. The ammonia exhaust end of the first-stage electric heating rotary kiln 21 and the sulfur dioxide exhaust end of the second-stage electric heating rotary kiln 22 can also be set in other locations that are conducive to gas discharge, depending on the kiln body inclination angle, material movement direction, gas flow direction and equipment layout.

[0050] like Figure 2 As shown, the discharge end of the second-stage electrically heated rotary kiln 22 can also be equipped with a gas-isolated solid discharge mechanism on the discharge side. This gas-isolated solid discharge mechanism can include a first-layer butterfly valve 25 and a second-layer butterfly valve 26 arranged sequentially along the solid material discharge direction. The first-layer butterfly valve 25 and the second-layer butterfly valve 26 are configured to open and close alternately and not simultaneously, allowing the solid material containing metal oxides discharged from the second-stage electrically heated rotary kiln 22 to be discharged through the gas-isolated solid discharge mechanism on the discharge side. This reduces the possibility of sulfur dioxide-containing gas escaping from the second-stage electrically heated rotary kiln 22 along with the solid material discharge channel, and also reduces the possibility of external gas entering the second-stage electrically heated rotary kiln 22.

[0051] The heating methods for the first and second electric heating reaction units can be resistance heating and / or electromagnetic induction heating. When using resistance heating, resistance heating elements, insulation layers, and temperature control components can be installed on the outside of the kiln body of the first-stage electric heating rotary kiln 21 and / or the second-stage electric heating rotary kiln 22. The resistance heating power is controlled by feedback from the temperature detection components. When using electromagnetic induction heating, induction coils can be installed on the outside of the kiln body of the first-stage electric heating rotary kiln 21 and / or the second-stage electric heating rotary kiln 22, causing the kiln body or its associated magnetic and conductive components to generate heat, thereby heating the material inside the kiln. Resistance heating and electromagnetic induction heating can be used individually or in combination in different reaction units or different temperature zones.

[0052] The metal oxide can be ferric oxide, manganese monoxide, or copper oxide. In this invention, the metal oxide is not used merely as a common filler or heat transfer medium, but as a solid reaction medium participating in the staged conversion of ammonium sulfate-containing materials. After the ammonium sulfate-containing material enters the first electrically heated reaction unit, it reacts with the metal oxide in a first temperature range. The ammonium ion component in the ammonium sulfate-containing material is released in the form of ammonia, while the sulfur-containing component combines with the metal oxide to form a solid material containing metal sulfate. Subsequently, the solid material containing metal sulfate enters the second electrically heated reaction unit and decomposes in a second temperature range higher than the first temperature range, regenerating the metal oxide and releasing sulfur dioxide gas. Thus, the first electrically heated reaction unit mainly undertakes the functions of ammonia release and solid-phase transfer of sulfur-containing components, while the second electrically heated reaction unit mainly undertakes the functions of metal oxide regeneration and sulfur dioxide gas release.

[0053] When the main sulfur-containing component in ammonium sulfate-containing materials is ammonium sulfate, the reaction between metal oxides and ammonium sulfate can be understood as a sulfation reaction of the metal oxides by ammonium sulfate. In one reaction pathway, ferric oxide, manganese monoxide, or copper oxide react with ammonium sulfate to form the corresponding ferric sulfate, manganese sulfate, or copper sulfate, releasing ammonia and moisture. For example, the reaction relationship can be illustrated as follows: Fe2O3 + 3(NH4)2SO4 → Fe2(SO4)3 + 6NH3+ 3H2O; MnO + (NH4)2SO4 → MnSO4 + 2NH3 + H2O; CuO + (NH4)2SO4 → CuSO4 + 2NH3 + H2O.

[0054] The above reaction formula is used to illustrate the main transformation relationship between ammonium sulfate-containing materials and metal oxides. It does not exclude the possibility that intermediate salts, basic salts or small amounts of by-products may exist in actual ammonium sulfate-containing materials due to differences in moisture, impurities, oxygen content or material residence time.

[0055] The purpose of setting the first temperature range is to ensure sufficient contact and sulfation reaction between the ammonium sulfate-containing material and the metal oxide, allowing ammonia to be released from the ammonium sulfate-containing material, while minimizing premature decomposition of the metal sulfate-containing solid material in the first electrically heated reaction unit, thus releasing sulfur dioxide gas. If the first temperature range is too low, insufficient evaporation of moisture, decomposition of ammonium salts, and sulfation reaction of metal oxides in the ammonium sulfate-containing material may occur, resulting in incomplete ammonia release and incomplete formation of the metal sulfate-containing solid material. If the first temperature range is too high, the already formed metal sulfate-containing solid material may decompose prematurely, causing sulfur dioxide gas to mix with the ammonia gas released from the first electrically heated reaction unit, which is detrimental to the stable recovery of ammonia gas in the ammonia recycling loop. Therefore, the first temperature range needs to meet the requirements of ammonia release and metal oxide sulfation reaction, while also forming a temperature division with the second temperature range.

[0056] The purpose of setting the second temperature range is to allow the solid material containing metal sulfates formed in the first electrically heated reaction unit to undergo thermal decomposition, releasing sulfur dioxide gas and regenerating the metal oxides. If the second temperature range is too low, the solid material containing metal sulfates will not decompose sufficiently, the release of sulfur dioxide gas will be insufficient, and the regeneration of metal oxides will be reduced, thus affecting the continuous operation of the metal oxide circulation loop. If the second temperature range is too high, it may cause sintering of metal oxides, decreased particle activity, increased equipment heat load, or decreased stability of solid material conveying. Therefore, the second temperature range needs to ensure the decomposition of the solid material containing metal sulfates and the release of sulfur dioxide gas while balancing the requirements of metal oxide recycling and continuous equipment operation.

[0057] In this specification, the sulfur dioxide gas released by the second electrically heated reaction unit can be understood as a sulfur-containing oxide gas containing sulfur dioxide, and it is not required that the gas consists only of sulfur dioxide. Depending on the type of metal oxide, the composition of the solid material containing metal sulfate, the second temperature range, the reaction atmosphere, and the material residence time, the gas released by the second electrically heated reaction unit may also contain sulfur trioxide, water vapor, inert gases, dust, or other accompanying components. The aforementioned sulfur-containing oxide gas can enter the sulfur dioxide acid production unit 3 after dust removal, cooling, drying, absorption, conversion, and / or gas conditioning. Therefore, the description of "sulfur dioxide gas" in this specification is intended to indicate that the gas is a sulfur-containing gas that can enter the sulfur dioxide acid production unit 3 for acid production, and does not exclude the presence of sulfur trioxide or other accompanying gas components.

[0058] The first and second temperature ranges differ for different metal oxides because the temperature conditions for the reaction of ferric oxide, manganese monoxide, and copper oxide with ammonium sulfate to form their respective metal sulfates differ, and the thermal decomposition temperatures of these metal sulfates also differ. When the metal oxide includes ferric oxide, the first temperature range is set to 360℃-460℃, which is conducive to the sulfation reaction between ammonium sulfate and ferric oxide, releasing ammonia gas. The second temperature range is set to 600℃-700℃, which is conducive to the decomposition of solid materials containing ferric sulfate and the regeneration of ferric oxide, while simultaneously releasing sulfur dioxide gas. When the metal oxide includes manganese monoxide, the first temperature range is set to 365℃-406℃, which is conducive to the reaction between ammonium sulfate and manganese monoxide, forming solid materials containing manganese sulfate and releasing ammonia gas. The second temperature range is set to 800℃-900℃, which is conducive to the decomposition of solid materials containing manganese sulfate and the release of sulfur dioxide gas. When the metal oxide includes copper oxide, the first temperature range is set to 400℃-500℃, which is conducive to the reaction of ammonium sulfate and copper oxide to form a solid material containing copper sulfate and release ammonia gas; the second temperature range is set to 700℃-800℃, which is conducive to the decomposition of the solid material containing copper sulfate and the regeneration of copper oxide, while releasing sulfur dioxide gas.

[0059] It should be noted that when the metal oxide is manganese monoxide, during the cycle between the first and second electrically heated reaction units, the oxide corresponding to the manganese element can undergo valence or phase changes depending on the reaction atmosphere, temperature conditions, and material residence time. The regenerated metal oxide discharged from the second electrically heated reaction unit may include manganese monoxide, or it may include manganese trioxide, manganese tetroxide, or other manganese-containing oxide phases. As long as this manganese-containing oxide phase can return to the first electrically heated reaction unit through the metal oxide circulation loop and continue to participate in the sulfation reaction of ammonium sulfate-containing materials within the first temperature range, it can be considered as the recycling of metal oxides in this invention. Therefore, the description of "manganese monoxide" in this specification is mainly used to describe the form of manganese-containing oxide that enters the first electrically heated reaction unit and participates in the sulfation reaction, and does not exclude the formation of other manganese-containing oxide phases during the circulation process.

[0060] Therefore, the aforementioned first and second temperature ranges are not simply selections of heating temperatures, but rather process windows that match the type of metal oxide, the conversion path of the ammonium sulfate-containing material, ammonia release, the formation of solid materials containing metal sulfates, metal oxide regeneration, and sulfur dioxide gas release. By placing the first and second electrically heated reaction units within these temperature ranges, the ammonia and sulfur components in the ammonium sulfate-containing material can be released and recovered separately at different reaction stages, thereby improving the operational stability of the ammonia reuse loop and the sulfur dioxide acid production unit 3. These temperature ranges can be jointly controlled by the temperature detection components, heating power adjustment components, and material residence time adjustment components of both the first and second electrically heated reaction units.

[0061] To ensure sufficient contact between the ammonium sulfate-containing material and the metal oxide in the first electrically heated reaction unit, and to provide sufficient decomposition conditions for the resulting solid material containing metal sulfate in the second electrically heated reaction unit, the ratio of the ammonium sulfate-containing material to the metal oxide can be controlled. When determining the ratio, the dry molar amount of ammonium sulfate in the ammonium sulfate-containing material can be used as the calculation basis. Let the dry molar number of ammonium sulfate in the ammonium sulfate-containing material be n. If the metal oxide is ferric oxide, then according to the stoichiometric relationship Fe2O3 + 3(NH4)2SO4 → Fe2(SO4)3 + 6NH3 + 3H2O, the theoretical molar number of ferric oxide is n / 3. If the metal oxide is manganese monoxide, then according to the stoichiometric relationship MnO + (NH4)2SO4 → MnSO4 + 2NH3 + H2O, the theoretical molar number of manganese monoxide is n. If the metal oxide is copper oxide, then according to the stoichiometric relationship CuO + (NH4)2SO4 → CuSO4 + 2NH3 + H2O, the theoretical molar number of copper oxide is n. In actual continuous operation, in order to compensate for impurities in ammonium sulfate-containing materials, metal oxide circulation losses, uneven solid contact, and some incomplete reactions, metal oxides can be added at 1.05 to 1.30 times the theoretical molar amount; preferably, metal oxides can be added at 1.10 to 1.20 times the theoretical molar amount.

[0062] In one specific embodiment, the ammonium sulfate-containing material and the metal oxide can be premixed, pre-dried, or preheated before entering the first electrically heated reaction unit. Premixing can be completed in a mixing silo to ensure a more uniform distribution of the ammonium sulfate-containing material and the metal oxide. Pre-drying can be performed using system waste heat, low-temperature hot air, or heat from the inlet section of the first electrically heated reaction unit to reduce the free water content of the ammonium sulfate-containing material upon entering the first electrically heated reaction unit. Preheating can reduce the temperature rise load at the inlet section of the first electrically heated reaction unit. The aforementioned premixing, pre-drying, or preheating treatments are all optional measures and do not affect the basic reaction process between the ammonium sulfate-containing material and the metal oxide in the first temperature range.

[0063] The flue gas sulfur dioxide resource recovery system may also include a dilute sulfuric acid tail gas scrubbing unit 4. The dilute sulfuric acid tail gas scrubbing unit 4 is located after the tail gas outlet of the ammonia desulfurization unit 1 and is used to scrub the tail gas discharged from the ammonia desulfurization unit 1 with dilute sulfuric acid. This allows the escaped ammonia in the tail gas to be absorbed, forming ammonium sulfate, and the water vapor in the tail gas to condense and enter the scrubbing liquid. The dilute sulfuric acid tail gas scrubbing unit 4 may include a tail gas scrubbing tower, a dilute sulfuric acid circulation tank, a circulation pump, a spray layer, a demister, a cooler, an acid replenishment pipeline, a water replenishment pipeline, and an ammonium sulfate-containing output terminal. The tail gas enters the dilute sulfuric acid tail gas scrubbing unit 4 from the tail gas outlet of the ammonia desulfurization unit 1. After contacting the sprayed dilute sulfuric acid, the escaped ammonia in the tail gas is absorbed by the dilute sulfuric acid to form ammonium sulfate, and some of the water vapor in the tail gas condenses during the scrubbing process and enters the scrubbing liquid.

[0064] The ammonium sulfate-containing output end of the dilute sulfuric acid tail gas scrubbing unit 4 is connected to the pyrolysis conversion unit 2 to feed the ammonium sulfate-containing material formed by scrubbing into the first electrically heated reaction unit. In one specific embodiment, the ammonium sulfate-containing material formed by the dilute sulfuric acid tail gas scrubbing unit 4 can be combined with the ammonium sulfate-containing material output from the ammonia desulfurization unit 1 and then fed into the same ammonium sulfate-containing material buffer tank, and then fed into the first electrically heated reaction unit via a feeding screw or other feeding equipment. In another specific embodiment, the ammonium sulfate-containing material formed by the dilute sulfuric acid tail gas scrubbing unit 4 can be metered separately and fed into the first electrically heated reaction unit together with the metal oxide. The mass concentration of the dilute sulfuric acid used in the dilute sulfuric acid tail gas scrubbing unit 4 can be 5%-15%, and the dilute sulfuric acid can be obtained by diluting the sulfuric acid produced by the sulfur dioxide acid production unit 3.

[0065] The sulfur dioxide acid production unit 3 is connected to the sulfur dioxide exhaust end of the second electrically heated reaction unit, and is used to convert the sulfur dioxide gas released by the second electrically heated reaction unit into sulfuric acid. The sulfur dioxide acid production unit 3 may include dust removal equipment, cooling equipment, drying equipment, conversion equipment, absorption equipment, and a sulfuric acid output pipeline. The sulfur dioxide gas released by the second electrically heated reaction unit can first undergo dust removal, cooling, and / or drying before entering the acid production step. The dust removal equipment can be used to remove solid dust entrained in the sulfur dioxide gas, the cooling equipment can be used to adjust the sulfur dioxide gas to a temperature range suitable for subsequent processing, and the drying equipment can be used to reduce the moisture content in the sulfur dioxide gas. The treated sulfur dioxide gas enters the conversion and absorption equipment to form sulfuric acid.

[0066] In one specific embodiment, the sulfuric acid produced in the acid production step is concentrated sulfuric acid. A portion of the concentrated sulfuric acid is output as sulfuric acid product, while the other portion is diluted and used as dilute sulfuric acid in the dilute sulfuric acid tail gas scrubbing unit 4. The water used to dilute the concentrated sulfuric acid can come from system makeup water or at least partially from water condensed into the scrubbing liquid during the tail gas scrubbing process. Thus, the sulfuric acid produced by the sulfur dioxide acid production unit 3 can form a material relationship with the dilute sulfuric acid tail gas scrubbing unit 4, allowing the dilute sulfuric acid required for tail gas scrubbing to be provided by the sulfuric acid produced within the system.

[0067] This embodiment also provides a flue gas sulfur dioxide resource recovery process based on metal oxide circulation and electric heating. This flue gas sulfur dioxide resource recovery process can be implemented using the aforementioned flue gas sulfur dioxide resource recovery system, or it can be implemented using a combination of other equipment capable of achieving the same material flow direction and reaction process. The process for the resource recovery of sulfur dioxide from flue gas includes: absorbing sulfur dioxide from flue gas with ammonia to form ammonium sulfate-containing material; feeding the ammonium sulfate-containing material and metal oxides into a first electrically heated reaction stage, where the ammonium sulfate-containing material and metal oxides react in a first temperature range to generate a solid material containing metal sulfates and release ammonia gas; feeding the solid material containing metal sulfates discharged from the first electrically heated reaction stage into a second electrically heated reaction stage under gas isolation conditions, and preventing the sulfur dioxide-containing gas generated in the second electrically heated reaction stage from flowing back into the first electrically heated reaction stage; in the second electrically heated reaction stage, decomposing the solid material containing metal sulfates in a second temperature range higher than the first temperature range to regenerate metal oxides and release sulfur dioxide gas; returning the ammonia gas released in the first electrically heated reaction stage to absorb sulfur dioxide from the flue gas; returning the metal oxides regenerated in the second electrically heated reaction stage to the first electrically heated reaction stage for recycling; and feeding the sulfur dioxide gas released in the second electrically heated reaction stage into an acid production step to produce sulfuric acid.

[0068] In the step of absorbing sulfur dioxide from flue gas with ammonia, ammonia can enter the ammonia desulfurization unit 1 in the form of ammonia gas, ammonia water, or ammonia-containing absorbent. After the sulfur dioxide-containing flue gas comes into contact with the ammonia-containing absorbent medium, the sulfur dioxide in the flue gas is absorbed and forms ammonium sulfate-containing material. The ammonium sulfate-containing material can enter the first electrically heated reaction stage after sedimentation, filtration, concentration, or slurry preparation, or it can directly enter the first electrically heated reaction stage if the feed requirements are met.

[0069] In the first electrically heated reaction stage, the ammonium sulfate-containing material reacts with metal oxides within a first temperature range. The metal oxides, acting as a solid reaction medium, participate in the conversion of the ammonium sulfate-containing material, transforming the sulfur-containing components into solid materials containing metal sulfates, while simultaneously releasing ammonia. The ammonia released in the first electrically heated reaction stage is collected and returned to absorb sulfur dioxide in the flue gas. The first electrically heated reaction stage can be adjusted by regulating the feed rate, kiln speed, heating power, and material residence time to maintain sufficient contact and reaction time between the ammonium sulfate-containing material and the metal oxides within the first temperature range.

[0070] When the solid material containing metal sulfate discharged from the first electrothermal reaction stage is fed into the second electrothermal reaction stage under gas isolation conditions, the solid material containing metal sulfate can be transferred via a double-layer butterfly valve. The first butterfly valve 23 and the second butterfly valve 24 of the double-layer butterfly valve open and close alternately and do not open simultaneously, so that a continuous gas channel is not formed between the first and second electrothermal reaction stages during the transfer of solid material. After the solid material containing metal sulfate enters the feed end of the second electrothermal reaction stage, it can be pushed into the reaction zone of the second electrothermal reaction stage by a pusher screw.

[0071] In the second electrically heated reaction stage, the solid material containing metal sulfates decomposes in a second temperature range to regenerate metal oxides and release sulfur dioxide gas. The temperature of the second electrically heated reaction stage is higher than that of the first electrically heated reaction stage, allowing the solid material containing metal sulfates to be converted under suitable decomposition temperature conditions. The metal oxides regenerated in the second electrically heated reaction stage are returned to the first electrically heated reaction stage for recycling via a metal oxide recycling loop. The sulfur dioxide gas released in the second electrically heated reaction stage is discharged through the sulfur dioxide exhaust end and then enters the acid production step.

[0072] After absorbing sulfur dioxide from the flue gas with ammonia, the process may include a step of washing the desulfurized tail gas with dilute sulfuric acid. In this washing step, escaped ammonia in the tail gas is absorbed by the dilute sulfuric acid to form ammonium sulfate, and water vapor in the tail gas condenses and enters the washing liquid. The ammonium sulfate-containing material formed in the washing step can be combined with the ammonium sulfate-containing material formed from the absorption of sulfur dioxide from the flue gas with ammonia and then fed into the first electrically heated reaction stage. The mass concentration of the dilute sulfuric acid can be 5%-15%. When the sulfuric acid obtained in the acid production step is concentrated sulfuric acid, a portion of the concentrated sulfuric acid can be diluted and used as dilute sulfuric acid in the washing step.

[0073] In the acid production step, the sulfur dioxide gas released in the second electrically heated reaction stage can be subjected to dust removal, cooling, and / or drying before entering the acid production step. Dust removal can be achieved using cyclone dust collectors, bag filters, ceramic filters, or high-temperature filters; cooling can be achieved using heat exchangers, quench towers, or indirect cooling equipment; drying can be achieved using concentrated sulfuric acid drying or other drying methods suitable for the pretreatment of sulfur dioxide gas before acid production. The aforementioned dust removal, cooling, and drying methods can be selected and used in one or more combinations depending on the dust content, temperature, and moisture content of the sulfur dioxide gas.

[0074] Figure 1 In the embodiment of the flue gas sulfur dioxide resource recovery system shown, the flue gas sequentially passes through an ammonia desulfurization unit 1 and an optional dilute sulfuric acid tail gas scrubbing unit 4. The ammonium sulfate-containing material enters the pyrolysis conversion unit 2. The ammonia gas released by the pyrolysis conversion unit 2 returns to the ammonia desulfurization unit 1 via an ammonia gas recycling loop. The sulfur dioxide gas released by the pyrolysis conversion unit 2 enters the sulfur dioxide acid production unit 3. The metal oxides regenerated by the pyrolysis conversion unit 2 return to the first electrically heated reaction unit via a metal oxide recycling loop. Figure 1 This is used to describe the material and gas flow directions between each unit. The specific number of equipment, pipeline layout, valve location, and control method can be adjusted according to the engineering conditions.

[0075] Figure 2 In the embodiment of the pyrolysis conversion unit 2 shown, a gas-isolated solid transfer mechanism is provided between the first-stage electric heating rotary kiln 21 and the second-stage electric heating rotary kiln 22. The ammonium sulfate-containing material and metal oxide enter the first-stage electric heating rotary kiln 21 through the feeding screw. The solid material containing metal sulfate discharged from the first-stage electric heating rotary kiln 21 enters the feed end of the second-stage electric heating rotary kiln 22 through the gas-isolated solid transfer mechanism and is pushed into the reaction zone of the second-stage electric heating rotary kiln 22 by the pushing screw. Figure 2 This description is intended to illustrate the relative connection between the first electrically heated reaction unit, the second electrically heated reaction unit, and the gas-isolated solid transfer mechanism, and does not limit the specific dimensions, installation angles, or driving methods of the first-stage electrically heated rotary kiln 21, the second-stage electrically heated rotary kiln 22, the feeding screw, the pushing screw, and the double-layer butterfly valve.

[0076] In one combined implementation, the flue gas sulfur dioxide resource recovery system may simultaneously include a first-stage electrically heated rotary kiln 21, a second-stage electrically heated rotary kiln 22, a double-layer butterfly valve, a feeding screw, a pushing screw, a dilute sulfuric acid tail gas scrubbing unit 4, an ammonia recovery loop, a metal oxide circulation loop, and a sulfur dioxide acid production unit 3. After being treated by the ammonia desulfurization unit 1, the sulfur dioxide-containing flue gas forms ammonium sulfate-containing material. The desulfurized tail gas is then treated by the dilute sulfuric acid tail gas scrubbing unit 4 to form supplementary ammonium sulfate-containing material. The two ammonium sulfate-containing materials are combined and then enter the first-stage electrically heated rotary kiln 21 with the metal oxides, reacting in the first temperature range and releasing ammonia. The solid material containing metal sulfates discharged from the first-stage electrically heated rotary kiln 21 enters the second-stage electrically heated rotary kiln 22 via the double-layer butterfly valve and the pushing screw, decomposing in the second temperature range and releasing sulfur dioxide gas. The ammonia gas returns to the ammonia desulfurization unit 1, the sulfur dioxide gas enters the sulfur dioxide acid production unit 3, and the regenerated metal oxides return to the first-stage electrically heated rotary kiln 21.

[0077] The first and second electric heating reaction units can employ different heating methods. For example, the first electric heating reaction unit can use resistance heating, while the second electric heating reaction unit can use electromagnetic induction heating; or the first electric heating reaction unit can use electromagnetic induction heating, while the second electric heating reaction unit can use resistance heating; or both the first and second electric heating reaction units can be equipped with both resistance heating and electromagnetic induction heating. The combination of different heating methods can be determined based on the material heating rate, temperature control accuracy, equipment materials, and operating and maintenance conditions.

[0078] The specific structures, equipment forms, process conditions, and parameter ranges in the above embodiments are all illustrative of the present invention. Those skilled in the art can adjust the specific forms of the first electrically heated reaction unit, the second electrically heated reaction unit, the gas-isolated solid transfer mechanism, the ammonia recovery circuit, the metal oxide circulation circuit, the dilute sulfuric acid tail gas scrubbing unit 4, and the sulfur dioxide acid production unit 3 without departing from the technical concept of the present invention. As long as such adjustments still achieve the synergistic relationship between the reaction of ammonium sulfate-containing materials and metal oxides in the first temperature range, the decomposition of solid materials containing metal sulfates in the second temperature range, ammonia recovery, metal oxide circulation, and sulfur dioxide gas acid production, it should be understood as falling within the scope of the present invention.

[0079] The foregoing has described the relevant content of the present invention. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the foregoing content of this specification without inventive effort should fall within the scope of the present invention.

Claims

1. A flue gas sulfur dioxide resource recovery system, comprising an ammonia desulfurization unit, a pyrolysis conversion unit, and a sulfur dioxide acid production unit, characterized in that: The ammonia desulfurization unit is used to absorb sulfur dioxide in flue gas with ammonia and output ammonium sulfate-containing material. The pyrolysis conversion unit includes a first electrically heated reaction unit, a second electrically heated reaction unit, and a gas-isolated solid transfer mechanism disposed between the first electrically heated reaction unit and the second electrically heated reaction unit; The first electrically heated reaction unit is used to receive the ammonium sulfate-containing material and the metal oxide, and to react the ammonium sulfate-containing material with the metal oxide in a first temperature range to generate a solid material containing metal sulfate and release ammonia gas; The second electric heating reaction unit is used to receive the solid material containing metal sulfate discharged from the first electric heating reaction unit, and to decompose the solid material containing metal sulfate in a second temperature range higher than the first temperature range, so as to regenerate metal oxides and release sulfur dioxide gas. The gas-isolated solid transfer mechanism is used to allow the solid material discharged from the first electric heating reaction unit to enter the second electric heating reaction unit, and to prevent the sulfur dioxide-containing gas in the second electric heating reaction unit from flowing back into the first electric heating reaction unit. It also includes an ammonia recycling circuit and a metal oxide circulation circuit. The ammonia recycling circuit is used to return the ammonia released by the first electric heating reaction unit to the ammonia desulfurization unit, and the metal oxide circulation circuit is used to return the metal oxide regenerated by the second electric heating reaction unit to the first electric heating reaction unit. The sulfur dioxide acid production unit is connected to the sulfur dioxide exhaust end of the second electrically heated reaction unit, and is used to convert the sulfur dioxide gas released by the second electrically heated reaction unit into sulfuric acid.

2. The flue gas sulfur dioxide resource recovery system according to claim 1, characterized in that: The first electrically heated reaction unit is a first-stage electrically heated rotary kiln, and the second electrically heated reaction unit is a second-stage electrically heated rotary kiln; The discharge end of the first-stage electric heating rotary kiln is connected to the feed end of the second-stage electric heating rotary kiln through the gas-isolated solid transfer mechanism, so that the high-temperature solid material discharged from the first-stage electric heating rotary kiln directly enters the second-stage electric heating rotary kiln.

3. The flue gas sulfur dioxide resource recovery system according to claim 2, characterized in that: The gas-isolated solid transfer mechanism includes a double-layer butterfly valve, which includes a first-layer butterfly valve and a second-layer butterfly valve arranged sequentially along the material transfer direction. The first-layer butterfly valve and the second-layer butterfly valve are configured to open and close alternately and not at the same time, so that the gas space between the first-stage electric heating rotary kiln and the second-stage electric heating rotary kiln remains isolated during material transfer.

4. The flue gas sulfur dioxide resource recovery system according to claim 2, characterized in that: The first-stage electrically heated rotary kiln is equipped with a feeding screw at the feed end for adding the ammonium sulfate-containing material and the metal oxide into the first-stage electrically heated rotary kiln; The feeding end of the second-stage electric heating rotary kiln is provided with a pusher screw, which is connected to the discharging end of the gas-isolated solid transfer mechanism to push the solid material entering the feeding end of the second-stage electric heating rotary kiln into the second-stage electric heating rotary kiln. The ammonia exhaust end of the first-stage electric heating rotary kiln is located at the discharge end of the first-stage electric heating rotary kiln, and / or the sulfur dioxide exhaust end of the second-stage electric heating rotary kiln is located at the discharge end of the second-stage electric heating rotary kiln.

5. The flue gas sulfur dioxide resource recovery system according to claim 1, characterized in that: It also includes a dilute sulfuric acid tail gas scrubbing unit, which is located after the tail gas outlet of the ammonia desulfurization unit. The dilute sulfuric acid tail gas scrubbing unit is used to scrub the tail gas discharged from the ammonia desulfurization unit with dilute sulfuric acid, so that the escaped ammonia in the tail gas is absorbed to form ammonium sulfate, and the water vapor in the tail gas is condensed into the scrubbing liquid. The ammonium sulfate-containing output end of the dilute sulfuric acid tail gas scrubbing unit is connected to the pyrolysis conversion unit so as to send the ammonium sulfate-containing material formed by scrubbing into the first electrically heated reaction unit.

6. The flue gas sulfur dioxide resource recovery system according to any one of claims 1 to 5, characterized in that: It also includes at least one of the following features: The heating method of the first electric heating reaction unit and / or the second electric heating reaction unit is resistance heating and / or electromagnetic induction heating; The metal oxide is ferric oxide, manganese monoxide, or copper oxide; when the metal oxide is ferric oxide, the first temperature range is 360℃-460℃, and the second temperature range is 600℃-700℃; when the metal oxide is manganese monoxide, the first temperature range is 365℃-406℃, and the second temperature range is 800℃-900℃; when the metal oxide is copper oxide, the first temperature range is 400℃-500℃, and the second temperature range is 700℃-800℃. When the flue gas sulfur dioxide resource recovery system includes a dilute sulfuric acid tail gas scrubbing unit, the mass concentration of the dilute sulfuric acid used in the dilute sulfuric acid tail gas scrubbing unit is 5%-15%, and the dilute sulfuric acid is obtained by diluting the sulfuric acid produced by the sulfur dioxide acid production unit.

7. A process for the resource recovery of flue gas sulfur dioxide based on metal oxide recycling and electric heating, characterized in that: include: Ammonia absorbs sulfur dioxide in flue gas to form ammonium sulfate-containing materials; The ammonium sulfate-containing material and the metal oxide are fed into the first electrically heated reaction stage, so that the ammonium sulfate-containing material and the metal oxide react in the first temperature range to generate a solid material containing metal sulfate and release ammonia gas. The solid material containing metal sulfate discharged from the first electric heating reaction stage is sent into the second electric heating reaction stage under gas isolation conditions, and the sulfur dioxide gas generated in the second electric heating reaction stage is prevented from flowing back into the first electric heating reaction stage. In the second electrothermal reaction stage, the solid material containing metal sulfate is decomposed in a second temperature range higher than the first temperature range to regenerate metal oxides and release sulfur dioxide gas. The ammonia gas released in the first electric heating reaction stage is returned to absorb sulfur dioxide in the flue gas; The metal oxides regenerated in the second electrothermal reaction stage are returned to the first electrothermal reaction stage for recycling. The sulfur dioxide gas released in the second electric heating reaction stage is fed into the acid production step to produce sulfuric acid.

8. The flue gas sulfur dioxide resource recovery process according to claim 7, characterized in that: The solid material containing metal sulfate discharged from the first electrically heated reaction stage is then fed into the second electrically heated reaction stage under gas-isolated conditions, including: The solid material containing metal sulfate is transferred through a double-layer butterfly valve, wherein the first and second layer butterfly valves of the double-layer butterfly valve open and close alternately and do not open at the same time; After the solid material containing metal sulfate enters the feed end of the second electrically heated reaction stage, the solid material containing metal sulfate is pushed into the reaction zone of the second electrically heated reaction stage by a pusher screw.

9. The flue gas sulfur dioxide resource recovery process according to claim 7, characterized in that: After absorbing sulfur dioxide from the flue gas with ammonia, the process includes a step of washing the desulfurized tail gas with dilute sulfuric acid. In the washing step, the escaped ammonia in the exhaust gas is absorbed by dilute sulfuric acid to form ammonium sulfate, and the water vapor in the exhaust gas condenses and enters the washing liquid. The ammonium sulfate-containing material formed in the washing step and the ammonium sulfate-containing material formed by absorbing sulfur dioxide in flue gas with ammonia are combined and then sent to the first electrically heated reaction stage.

10. The flue gas sulfur dioxide resource recovery process according to any one of claims 7 to 9, characterized in that: It also includes at least one of the following process conditions: The first electric heating reaction stage and / or the second electric heating reaction stage employ resistance heating and / or electromagnetic induction heating; The metal oxide is ferric oxide, manganese monoxide, or copper oxide; when the metal oxide is ferric oxide, the first temperature range is 360℃-460℃, and the second temperature range is 600℃-700℃; when the metal oxide is manganese monoxide, the first temperature range is 365℃-406℃, and the second temperature range is 800℃-900℃; when the metal oxide is copper oxide, the first temperature range is 400℃-500℃, and the second temperature range is 700℃-800℃. When the flue gas sulfur dioxide resource recovery process includes a step of washing the desulfurized tail gas with dilute sulfuric acid, the mass concentration of the dilute sulfuric acid is 5%-15%; The sulfur dioxide gas released in the second electric heating reaction stage is then removed from dust, cooled and / or dried before entering the acid production step; When the flue gas sulfur dioxide resource recovery process includes a step of washing the desulfurized tail gas with dilute sulfuric acid, the sulfuric acid produced in the acid production step is concentrated sulfuric acid, and a portion of the concentrated sulfuric acid is diluted and used as the dilute sulfuric acid.

Images