Sulfur dioxide near zero emission and tail sulfur recycling utilization method and device for producing sulfuric acid

Abstract

The application provides a sulfur dioxide near-zero emission and tail sulfur recycling method and device for acid production. The sulfur dioxide near-zero emission and tail sulfur recycling method for acid production comprises the following steps: burning sulfur-containing raw materials, three-stage catalytic conversion and one-stage absorption for acid production, adsorbing and removing sulfur dioxide in tail gas, regenerating and desorbing the desulfurizer after adsorption to obtain sulfur dioxide gas, and returning the sulfur dioxide gas to the outlet of the sulfur burning furnace to mix with the furnace gas and re-enter the catalytic system for reaction. The sulfur dioxide near-zero emission and tail sulfur recycling method for acid production has the advantages of short conversion and absorption process, low energy consumption, near-zero emission of sulfur dioxide in purified tail gas and the like.

Description

Technical Field

[0001] This invention relates to the field of sulfuric acid manufacturing, specifically to a method and apparatus for producing sulfuric acid with near-zero sulfur dioxide emissions and tail sulfur recycling. Background Technology

[0002] Sulfuric acid is a crucial basic chemical raw material, widely used in many industrial fields such as fertilizer production, metallurgical processing, fine chemicals, and electronics manufacturing. Currently, the mainstream industrial sulfuric acid production process is the contact process, which uses sulfur, pyrite, or smelting flue gas as raw materials, first reacting sulfur dioxide (…) with… ) undergoes catalytic oxidation to produce sulfur trioxide ( Then, the finished sulfuric acid is prepared by absorption with concentrated sulfuric acid.

[0003] Since its industrial application in 1964, the two-stage conversion and two-stage absorption process has long been the core mainstream technology for sulfuric acid production due to its excellent conversion efficiency. This process generally adopts a "3+1" or "3+2" multi-stage conversion architecture, which can achieve… With a total conversion rate of over 99.7%, it effectively reduces exhaust emissions. The emission concentration has significantly improved the utilization rate of sulfur resources. In recent years, the industry has continuously iterated and improved the process in areas such as optimizing the performance of acid production catalysts, utilizing low-temperature waste heat resources, developing new corrosion-resistant materials, and scaling up production equipment, further enhancing the industrial adaptability of the two-conversion-two-absorption process.

[0004] However, the existing traditional two-conversion two-absorption sulfuric acid production process still has the following defects: (1) There is a bottleneck in the utilization rate of sulfur resources. The inherent limitations of reversible chemical equilibrium in catalytic oxidation, and the limitations of existing multi-stage conversion processes. The overall conversion rate is difficult to exceed 99.9%, and a small amount of residue remains in the exhaust gas. This section Most of the sulfuric acid is directly emitted with the exhaust gas or removed through the downstream alkaline washing process, which cannot be effectively recycled and utilized, resulting in the loss of sulfur resources and restricting the further improvement of the resource utilization rate of the acid production system. (2) The exhaust gas treatment has high operating costs and the by-products are difficult to treat. According to the "Emission Standard of Pollutants for Sulfuric Acid Industry" (GB 26132-2010), under normal operating conditions The emission limit is 400 mg / Nm³, and the special emission limit under special operating conditions is as low as 200 mg / Nm³. Environmental emission requirements are becoming increasingly stringent. Existing acid production units need to be equipped with sodium alkali method, ammonia method and other tail gas desulfurization facilities at the back end of the second absorption tower in order to meet the emission standards. However, such desulfurization processes have problems such as large consumption of absorbent, high long-term operating costs and difficulty in resource utilization of desulfurization by-products, which greatly increases the production and maintenance burden of enterprises. (3) Insufficient utilization rate of low-grade waste heat. Traditional two-conversion two-absorption process can recover most of the high-temperature waste heat through waste heat boilers and conventional low-temperature heat recovery systems. However, due to process bottlenecks such as acid dew point corrosion, a large amount of low-grade waste heat in the system cannot be effectively recovered and utilized, resulting in obvious heat energy waste and high overall system energy consumption. (4) The process is complicated and the equipment investment and land cost are high. Existing processes generally adopt a "3+1" or "3+2" multi-stage conversion structure, with multiple catalyst layers in the converter, complex system heat exchange network, a large number of supporting equipment, and low device integration. This not only leads to a lengthy production process, but also significantly increases equipment investment, plant area, and subsequent operation and maintenance costs.

[0005] Therefore, how to provide a method for producing acid with a short process flow, low energy consumption, and near-zero sulfur dioxide emissions in the exhaust gas has become a technical problem that needs to be solved. Summary of the Invention

[0006] This invention provides a method and apparatus for producing sulfuric acid with near-zero sulfur dioxide emissions and tail sulfur recycling. While completing the sulfur-containing raw material sulfur production reaction, the method recovers the unabsorbed sulfur-containing components in the tail gas and allows them to re-participate in the front-end sulfur production process. Continuous laboratory operation tests show that this process can achieve near-zero sulfur dioxide emissions from purified tail gas and reduction and regeneration of desulfurizing agent, and has the advantages of short process flow and low energy consumption.

[0007] This invention provides a method for producing acid with near-zero sulfur dioxide emissions and tail sulfur recycling, comprising the following steps:

[0008] S1. The sulfur-containing raw material and the first oxygen-containing gas are burned in a sulfur incinerator to generate furnace gas containing sulfur dioxide; the furnace gas is introduced into a catalytic system for catalytic oxidation reaction to obtain conversion gas containing sulfur trioxide; the conversion gas enters an absorption tower and undergoes an absorption reaction with concentrated sulfuric acid to generate sulfuric acid and absorption tail gas containing residual sulfur dioxide.

[0009] S2. The resulting absorption tail gas is treated, including the following process:

[0010] The absorption tail gas and the second oxygen-containing gas are fed into the reactor, heated, and then fed into the fluidized bed reactor. The sulfur dioxide in the absorption tail gas is oxidized to generate sulfur trioxide, which then undergoes an adsorption reaction with the desulfurizing agent to obtain a sulfate-containing desulfurizing agent and purified flue gas after sulfur dioxide removal.

[0011] The obtained desulfurizing agent is sent to the regenerator for regeneration and analysis to obtain regenerated desulfurizing agent and sulfur dioxide-rich gas. The sulfur dioxide-rich gas is then transported to the outlet of the sulfur incinerator and mixed with the sulfur dioxide-containing furnace gas produced by the sulfur incinerator. The mixture then enters the catalytic system and participates in the catalytic oxidation and absorption reactions in step S1.

[0012] According to one embodiment of the present invention, the process of introducing the furnace gas into a catalytic system for catalytic oxidation to obtain sulfur trioxide-containing converted gas includes: the furnace gas entering a first waste heat boiler for heat exchange, then entering a first catalyst layer for a first catalytic oxidation reaction to obtain first-stage converted gas; the first-stage converted gas entering a second catalyst layer for heat exchange after passing through a first heat exchanger, then entering a second catalyst layer for a second catalytic oxidation reaction to obtain second-stage converted gas; the second-stage converted gas entering a third catalyst layer for heat exchange after passing through a second waste heat boiler for a third catalytic oxidation reaction to obtain sulfur trioxide-containing converted gas;

[0013] And / or, the process of the converted gas entering the absorption tower and undergoing an absorption reaction with concentrated sulfuric acid includes: the converted gas is cooled sequentially by the second heat exchanger and the first economizer before entering the absorption tower and undergoing an absorption reaction with concentrated sulfuric acid.

[0014] According to one embodiment of the present invention, the temperature of the absorption reaction is 170°C to 220°C;

[0015] And / or, in the sulfur dioxide-rich gas after regeneration and analysis, the volume percentage of sulfur dioxide is 40% to 60%;

[0016] And / or, the purified flue gas after sulfur dioxide removal is discharged in compliance with emission standards after gas-solid separation and heat exchange cooling.

[0017] According to one embodiment of the present invention, when the absorption tower carries out the absorption reaction, it utilizes the low-temperature heat released by the absorption reaction to produce low-pressure saturated steam with a pressure of 0.6~1.0MPa as a byproduct.

[0018] According to one embodiment of the present invention, the process of sending the obtained desulfurizing agent to a regenerator for regeneration and analysis includes: sending the obtained desulfurizing agent to a regenerator to react with a reducing agent, so that the sulfur element in its sulfate is reduced to sulfur dioxide by the reducing agent, thereby obtaining a regenerated desulfurizing agent.

[0019] And / or, the temperature of the adsorption reaction is 600~700℃.

[0020] According to one embodiment of the present invention, the reducing agent comprises elemental sulfur.

[0021] According to one embodiment of the present invention, the temperature of the regeneration reaction is 500~630°C.

[0022] According to one embodiment of the present invention, the dry basis sulfur dioxide content in the purified flue gas is ≤1 mg / Nm³. 3 ;

[0023] And / or, the dry basis particulate matter content in the purified flue gas is ≤30 mg / Nm³. 3 .

[0024] This invention also provides an acid production apparatus for implementing step S1 of the above-mentioned acid production method for near-zero sulfur dioxide emissions and tail sulfur recycling, comprising a sulfur incinerator, a catalytic system, and an absorption tower connected in sequence.

[0025] The catalytic system includes a first waste heat boiler, a first catalyst layer, a first heat exchanger, a second catalyst layer, a second waste heat boiler, a third catalyst layer, a second heat exchanger, and a first economizer connected in sequence; the outlet of the sulfur incinerator is connected to the inlet of the first waste heat boiler, and the outlet of the first economizer is connected to the inlet of the absorption tower.

[0026] According to one embodiment of the present invention, it further includes a tail gas treatment device for implementing step S2 of the above-described method for producing acid with near-zero sulfur dioxide emissions and tail sulfur recycling. The tail gas treatment device includes a reactor, a regeneration furnace, a regenerator, and a fresh desulfurizing agent storage tank.

[0027] The gas inlet of the reactor is connected to the tail gas outlet of the first heat exchanger in the above-mentioned acid production device, and the gas outlet of the reactor is connected to the tail gas inlet of the reactor.

[0028] The reactor is equipped with a fresh desulfurizing agent inlet, a desulfurizing agent outlet, a regenerated desulfurizing agent inlet, a desulfurization tail gas outlet, a circulating desulfurizing agent inlet, and a circulating desulfurizing agent outlet;

[0029] The fresh desulfurizing agent storage tank is connected to the fresh desulfurizing agent inlet of the reactor;

[0030] The regeneration furnace is equipped with an air inlet and a reducing agent inlet, and the regeneration furnace is connected to the regenerator for heating.

[0031] The desulfurizing agent outlet of the reactor is connected to the desulfurizing agent inlet of the regenerator, and the desulfurizing agent outlet of the regenerator is connected to the desulfurizing agent inlet of the reactor, forming a regenerating desulfurizing agent circulation.

[0032] The regenerator is provided with a regenerated gas outlet, which is connected to a second hydrocyclone, and the second hydrocyclone is connected to the gas outlet of the sulfur incinerator of the above-mentioned acid production unit.

[0033] The desulfurization tail gas outlet of the reactor is connected to the tail gas heat exchange and purification unit.

[0034] Preferably, the exhaust gas heat exchange and purification unit includes a steam superheater, a third waste heat boiler, a first cyclone separator, a second economizer, and an air preheater connected in sequence. The air preheater is provided with a purified flue gas exhaust channel at its end. The first cyclone separator is provided with a waste desulfurizing agent outlet.

[0035] This invention provides a method and apparatus for producing sulfuric acid with near-zero sulfur dioxide emissions and tail sulfur recycling. A simplified flow chart of the sulfuric acid production method is provided below. Figure 1 and Figure 3 This acid production method first incinerates sulfur-containing raw materials to generate sulfur dioxide-containing furnace gas. The furnace gas then undergoes a three-stage catalytic oxidation and a single absorption process to produce sulfuric acid. For residual sulfur dioxide in the exhaust gas from the absorption tower, a desulfurizing agent is used for adsorption and removal. The high-concentration sulfur dioxide gas generated by the regeneration and desorption of the desulfurizing agent is transported to the outlet of the sulfur incinerator, mixed with the high-temperature sulfur-containing furnace gas, and then re-enters the catalytic system to participate in the acid production reaction. This process is called the three-stage conversion, single absorption, and tail sulfur recycling process. The acid production method of this invention, which involves near-zero sulfur dioxide emissions and tail sulfur recycling, has advantages such as a short process flow, low energy consumption, and near-zero sulfur dioxide emissions from the purified exhaust gas. Attached Figure Description

[0036] Figure 1 This is a simplified process diagram of an acid production method for near-zero sulfur dioxide emissions and tail sulfur recycling according to an embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram of the overall process of an acid production method for near-zero sulfur dioxide emissions and tail sulfur recycling according to one embodiment of the present invention.

[0038] Figure 3 This is a schematic diagram of the tail gas treatment process of an acid production method for near-zero sulfur dioxide emissions and tail sulfur recycling according to an embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] This invention provides a method for producing sulfuric acid with near-zero sulfur dioxide emissions and tail sulfur recycling, comprising the following steps: S1, sulfur-containing raw materials and a first oxygen-containing gas are burned in a sulfur incinerator to generate furnace gas containing sulfur dioxide; the furnace gas is passed into a catalytic system for catalytic oxidation reaction to obtain conversion gas containing sulfur trioxide; the conversion gas enters an absorption tower and undergoes an absorption reaction with concentrated sulfuric acid to generate sulfuric acid and absorption tail gas containing residual sulfur dioxide;

[0041] S2. The absorption tail gas obtained in step S1 is treated in the following ways: the absorption tail gas and the second oxygen-containing gas are introduced into the reactor, heated and then introduced into the fluidized bed reactor. The sulfur dioxide in the absorption tail gas is oxidized to generate sulfur trioxide. The sulfur trioxide then undergoes an adsorption reaction with the desulfurizing agent to obtain a sulfate-containing desulfurizing agent and purified flue gas after the removal of sulfur dioxide. The obtained desulfurizing agent is sent to the regenerator for regeneration and analysis to obtain a regenerated desulfurizing agent and sulfur dioxide-rich gas. The sulfur dioxide-rich gas is sent to the outlet of the sulfur incinerator and mixed with the sulfur dioxide-containing furnace gas produced by the sulfur incinerator. They then enter the catalytic system together and participate in the catalytic oxidation reaction and absorption reaction in step S1 in a cyclical manner.

[0042] In this invention's acid production method, residual sulfur dioxide in the exhaust gas is no longer directly discharged. Instead, it is recovered through selective adsorption and regeneration desorption by a desulfurizing agent, forming a closed-loop recycling pathway for sulfur components. The sulfur dioxide produced by desorption is transported to the outlet of the sulfur incinerator and mixed with the furnace gas before re-entering the catalytic system to participate in catalytic oxidation and absorption acid production reactions again. This effectively improves the system's sulfur resource utilization rate and total sulfur dioxide conversion efficiency, significantly reducing the environmental pressure of sulfur dioxide emissions from the exhaust gas, reducing the consumption of end-of-pipe desulfurization agents, and improving the overall economic efficiency of the acid production process.

[0043] like Figure 1 As shown, this invention eliminates the entire existing acid production process (four-stage conversion, five-stage conversion, second adsorption tower, and alkali washing tower within the purple dashed box), retaining only the sulfur incinerator, first to third-stage conversion, and first adsorption tower to form a basic acid production line of one conversion and one adsorption. Simultaneously, a tail gas treatment unit (shown in the red dashed box) is added. All sulfur-containing tail gas discharged from the first adsorption tower is sent to the tail gas treatment unit for adsorption and regeneration: the purified flue gas directly meets emission standards, and the high-concentration sulfur dioxide desorption gas released during regeneration is returned to the front end of the sulfur incinerator for recycling and acid production. This eliminates the traditional secondary absorption, multi-stage conversion, and alkali washing desulfurization steps, shortens the process flow, and achieves a closed-loop recycling of sulfur resources.

[0044] The sulfuric acid production method of this invention is also known as the ZQ Sulfuric Acid Process, or ZQ SAP for short. After sulfur-containing feedstock is incinerated to generate furnace gas, it undergoes a three-stage catalytic bed sulfur dioxide conversion process with a conversion rate of approximately 93%–96%. Unconverted residual sulfur dioxide is completely recovered through a matching tail gas treatment unit (including a reactor). The recovered sulfur dioxide is returned to the sulfur incinerator outlet and fed into the main process pipeline, constructing a closed-loop sulfur resource recycling system, ultimately achieving nearly 100% conversion and utilization of sulfur dioxide. The ZQ Sulfuric Acid Process is not a partial improvement on the traditional two-stage conversion and two-stage absorption process, but rather a complete reconstruction of the entire sulfuric acid production system architecture: the process design abandons the traditional approach of relying on multi-stage conversion to pursue a single-stage maximum conversion rate, instead adopting a "main process basic conversion + tail gas" approach. This invention presents an integrated system optimization scheme for "enrichment and recycling". Compared with the existing two-conversion and two-absorption acid production technology, the conversion and absorption process of this invention is significantly shortened, while the system's low-temperature waste heat recovery efficiency is significantly improved, the overall energy consumption is lower, and the sulfur dioxide emission in the exhaust gas can be achieved to near zero, making it of outstanding value for industrial application.

[0045] In some embodiments, both the first oxygen-containing gas and the second oxygen-containing gas include air.

[0046] In this embodiment of the invention, the chemical reaction formula for the catalytic oxidation reaction is as follows: .

[0047] In this embodiment of the invention, the chemical reaction formula for the absorption reaction is as follows: .

[0048] In this embodiment of the invention, the process of obtaining sulfur trioxide-containing converted gas by sequentially passing the furnace gas through a catalytic system for catalytic oxidation includes: the furnace gas enters a first waste heat boiler for heat exchange, then enters a first catalyst layer for a first catalytic oxidation reaction, obtaining first-stage converted gas; the first-stage converted gas enters a second catalyst layer for a second catalytic oxidation reaction after heat exchange in a first heat exchanger, obtaining second-stage converted gas; the second-stage converted gas enters a third catalyst layer for a third catalytic oxidation reaction after heat exchange in a second waste heat boiler, obtaining sulfur trioxide-containing converted gas. By sequentially feeding the furnace gas into multiple catalyst layers and setting waste heat boilers and heat exchangers between each layer, the furnace gas temperature can be gradually adjusted to the appropriate range for the corresponding catalytic oxidation reaction, thereby balancing the reaction rate and conversion equilibrium, allowing sulfur dioxide to be more fully converted into sulfur trioxide. The furnace gas after the second stage reaction enters the third catalyst layer after heat exchange in the second waste heat boiler, which helps stabilize subsequent reaction conditions and further improves the conversion efficiency of sulfur dioxide.

[0049] In some embodiments, the process of the converted gas entering the absorption tower and reacting with concentrated sulfuric acid includes: the converted gas is cooled sequentially by a second heat exchanger and a first economizer before entering the absorption tower to react with concentrated sulfuric acid. The converted gas is further cooled by the second heat exchanger and the first economizer before entering the absorption tower, which makes the gas temperature more suitable for the absorption of sulfur trioxide by concentrated sulfuric acid. This helps to improve absorption efficiency and reduce the residual sulfur dioxide content in the tail gas, allowing for better integration between the upstream acid production process and the subsequent tail gas recovery and utilization.

[0050] In some embodiments, taking sulfuric acid production as an example, sulfur-containing raw materials are fed into a sulfur incinerator for combustion to generate sulfur dioxide-containing flue gas. The flue gas then undergoes catalytic oxidation reactions in a catalytic system to obtain sulfur trioxide-containing converted gas. The process includes: liquid sulfur is incinerated in a sulfur incinerator to produce high-temperature sulfur-containing flue gas; after the flue gas is heated by a first waste heat boiler, it enters a first catalyst layer at 400°C to 440°C for a first catalytic oxidation reaction, with the temperature rising to approximately 600°C to 620°C; after being cooled by a first heat exchanger to approximately 420°C to 460°C, it enters a second catalyst layer for a second catalytic oxidation reaction, with the temperature rising to approximately 500°C to 540°C; after being heated by a second waste heat boiler, it enters a third catalyst layer at approximately 420°C to 460°C for a third catalytic oxidation reaction, with the temperature rising to approximately 450°C to 470°C, thus obtaining sulfur trioxide-containing converted gas.

[0051] In some implementations, the converted gas enters the absorption tower and reacts with concentrated sulfuric acid to produce sulfuric acid and residual sulfur dioxide-containing tail gas. The process includes: the converted gas is cooled to 180°C~230°C via a second heat exchanger and a first economizer before entering the absorption tower to absorb sulfur trioxide. The absorption tower employs two independent acid circulation systems (high and low temperatures) to achieve countercurrent absorption: the lower section uses high-temperature acid for countercurrent absorption. The high-temperature acid enters the absorption tower at 170°C~190°C, while the upper section uses low-temperature concentrated sulfuric acid for fine absorption to prevent acid entrainment in the flue gas. After absorption by the low-temperature acid in the upper section, the converted gas leaves the absorption tower at approximately 85°C. After heat exchange in the second heat exchanger (shell side) and the first heat exchanger (shell side), it enters the reactor at approximately 590°C.

[0052] In some embodiments, the first and second waste heat boilers produce 6.4 MPa medium-pressure steam for waste heat recovery, and utilize the reaction heat released by the high-temperature acid in the absorption tower when absorbing sulfur trioxide to produce 0.6~1.0 MPa low-pressure steam as a byproduct.

[0053] In some embodiments, the process of sending the absorption tail gas obtained in step S1 into a reactor to undergo an adsorption reaction with a desulfurizing agent to remove residual sulfur dioxide from the absorption tail gas, thereby obtaining a ready-to-use desulfurizing agent and purified flue gas after sulfur dioxide removal, includes: the absorption tail gas obtained in step S1 first enters a reactor using natural gas as fuel, and after being heated, it enters the bottom of a fluidized bed reactor, where it mixes with a regenerated desulfurizing agent from a regenerator and a circulating desulfurizing agent from an adsorption reaction settling tank. During the lifting process, the sulfur dioxide in the tail gas is adsorbed off, resulting in purified flue gas after sulfur dioxide removal and a ready-to-use desulfurizing agent. Gas-solid separation is achieved in the settling tank through a two-stage hydrocyclone, and the desulfurized tail gas exits the reactor.

[0054] In this embodiment of the invention, the absorption reaction temperature is 170℃~220℃, which is beneficial to balance the sulfur trioxide absorption efficiency and the system operation stability, thereby ensuring continuous and stable acid production in the absorption section.

[0055] In some embodiments, the adsorption reaction temperature is 600~700℃. This is beneficial for improving the adsorption efficiency of the desulfurizing agent for residual sulfur dioxide in the exhaust gas. In some embodiments, during the absorption reaction in the absorption tower, low-temperature heat released from the absorption reaction is used to produce low-pressure saturated steam with a pressure of 0.6~1.0 MPa as a byproduct.

[0056] In some embodiments, the purified flue gas after sulfur dioxide removal passes sequentially through a steam superheater, a third waste heat boiler, an external cyclone separator, a second economizer, and an air preheater. The temperature of the purified flue gas drops to 90°C~110°C before being discharged. The third waste heat boiler produces 6.4MPa medium-pressure steam.

[0057] In some implementations, the sulfur dioxide volume percentage in the sulfur dioxide-rich gas after regeneration and analysis is 40% to 60%.

[0058] In some implementations, the purified flue gas after sulfur dioxide removal is discharged in compliance with emission standards after gas-solid separation and heat exchange cooling. This can reduce the adverse effects of entrained particulate matter and high-temperature flue gas on subsequent emissions. Therefore, it can reduce environmental emission pressure while achieving exhaust gas treatment, and together with the aforementioned recycling cycle, improve the resource utilization efficiency and operational economy of the acid production process.

[0059] In some implementations, a steam generator is integrated inside the absorption tower to heat the feedwater using the low-temperature heat released during the high-temperature absorption process, and to produce low-pressure saturated steam at a pressure of 0.6~1.0 MPa as a byproduct. By integrating a steam generator inside the absorption tower, the heat released when sulfur trioxide is absorbed by concentrated sulfuric acid can be directly recovered and used to heat the feedwater and produce 0.6~1.0 MPa low-pressure saturated steam, thereby converting the originally dispersed low-temperature heat into usable steam energy. This structure tightly couples the absorption unit and the heat recovery unit, reducing additional heat exchange equipment and heat loss, thus reducing system energy consumption. The byproduct steam can also be used for regeneration and desorption, thus improving overall thermal efficiency and operational economy while achieving coordinated operation of acid production and tail gas recovery.

[0060] In this embodiment of the invention, sulfur dioxide is adsorbed onto the desulfurizing agent in the reactor, thereby purifying the tail gas and reducing the acid dew point, which is beneficial for subsequent low-temperature heat recovery.

[0061] In some embodiments, the obtained desulfurizing agent is regenerated and analyzed to obtain regenerated desulfurizing agent and sulfur dioxide gas. The desulfurizing agent enters a regenerator and undergoes a regeneration reaction with a reducing agent, causing the sulfur element in the sulfate of the desulfurizing agent to be reduced to sulfur dioxide by the reducing agent, thus obtaining the regenerated desulfurizing agent. After the desulfurizing agent comes into contact with the reducing agent in the regenerator, it can convert the sulfur element in the adsorbed sulfate into sulfur dioxide gas, and at the same time restore the activity of the desulfurizing agent, so that the regenerated desulfurizing agent can be returned to the adsorption stage for reuse, thereby reducing the amount of desulfurizing agent replenishment and reducing the emission of solid by-products.

[0062] In some implementations, the reducing agent includes elemental sulfur.

[0063] In some implementations, under the action of a desulfurizing agent, the exhaust gas contains... It reacts with oxygen to produce , The desulfurizing agent reacts with the sulfurizing agent to form sulfate. Specifically, the desulfurizing agent may include alkaline oxides, and generally may also include trace amounts of non-alkaline oxides to improve the reduction performance of the desulfurizing agent and make it easier to regenerate; wherein, alkaline oxides include, for example, oxides of alkaline earth metals, preferably including active magnesium oxide. This desulfurizing agent is particularly effective at removing sulfates present in the exhaust gas under high-temperature conditions. Oxidized to and rapid adsorption It generates stable sulfates and can react with reducing agents to achieve rapid decomposition and reduction, especially at high temperatures (such as the regeneration reaction temperature described below) to achieve regeneration.

[0064] The main reaction equations for the adsorption reaction are shown below:

[0065]

[0066] (XO represents a basic oxide, where X represents a metal).

[0067] The regeneration reaction formula is shown below:

[0068] .

[0069] In this embodiment of the invention, the regeneration reaction temperature is 500~630℃. This is beneficial for balancing the reactivity of elemental sulfur, the decomposition and reduction efficiency of sulfate, and the structural stability of the regenerated desulfurizing agent, making the regeneration process more complete and suppressing side reactions, thereby improving the concentration of sulfur dioxide obtained from the desorption and the recovery efficiency.

[0070] In this embodiment of the invention, fluctuations in the inlet sulfur content are addressed by adjusting the desulfurizing agent circulation rate. Even when the sulfur dioxide concentration in the flue gas at the absorber outlet increases, the dry basis sulfur dioxide concentration in the purified flue gas is kept below 1 mg / Nm³.3 When the upstream incineration load, the sulfur content of the feedstock, or the amount of sulfur dioxide returned from regeneration changes, the sulfur dioxide load entering the reactor will fluctuate. By synchronously adjusting the desulfurizing agent circulation rate, the dry basis sulfur dioxide concentration in the tail-end purified flue gas is kept consistently below 1 mg / Nm³. 3 Because this regulation method directly affects the supply of circulating desulfurizing agent, it can reduce the impact of emission fluctuations on the system's compliance, thereby improving the operational stability of the entire acid production and tail gas recovery process and the sulfur resource recovery effect.

[0071] In some embodiments, the dry basis sulfur dioxide content in the purified flue gas is ≤1 mg / Nm³. 3 .

[0072] In this embodiment of the invention, the dry basis particulate matter content in the purified flue gas is ≤30mg / Nm³. 3 .

[0073] This invention also provides an acid production apparatus for implementing step S1 of the above-described acid production method, comprising a sulfur incinerator, a catalytic system, and an absorption tower connected in sequence.

[0074] In some embodiments, the catalytic system includes, in sequence, a first waste heat boiler, a first catalyst bed, a first heat exchanger, a second catalyst bed, a second waste heat boiler, a third catalyst bed, a second heat exchanger, and a first economizer. The first heat exchanger has an exhaust gas inlet and an exhaust gas outlet.

[0075] In this embodiment of the invention, a tail gas treatment device is also included for step S2 of the above-mentioned acid production method for near-zero sulfur dioxide emissions and tail sulfur recycling. The device includes a reactor, a regeneration furnace, a regenerator, and a fresh desulfurizing agent storage tank. The inlet of the reactor is connected to the tail gas outlet of the first heat exchanger in the acid production device, and the outlet of the reactor is connected to the tail gas inlet of the reactor. The reactor is provided with a fresh desulfurizing agent inlet, a desulfurizing agent outlet, a regenerated desulfurizing agent inlet, a desulfurized tail gas outlet, a circulating desulfurizing agent inlet, and a circulating desulfurizing agent outlet. The fresh desulfurizing agent storage tank is connected to the fresh desulfurizing agent inlet of the reactor; the regeneration furnace is equipped with an air inlet and a reducing agent feed inlet, and the regeneration furnace is connected to the regenerator for heating; the desulfurizing agent outlet of the reactor is connected to the desulfurizing agent inlet of the regenerator, and the regenerated desulfurizing agent outlet of the regenerator is connected to the regenerated desulfurizing agent inlet of the reactor, forming a solid-phase circulation of regenerated desulfurizing agent; the regenerator is equipped with a regeneration gas outlet, which is connected to a second hydrocyclone, and the second hydrocyclone is connected to the gas outlet of the sulfur combustion furnace of the acid production unit; the desulfurization tail gas outlet of the reactor is connected to the tail gas heat exchange unit.

[0076] In this embodiment of the invention, the reactor is used to provide the temperature required for the adsorption reaction. A reducing (oxygen-free) fluidizing gas is provided, with a dry air inlet and a reducing agent inlet, and is connected to a regenerator.

[0077] In some embodiments, the exhaust gas heat exchange and purification unit includes a steam superheater, a third waste heat boiler, a first cyclone separator, a second economizer, and an air preheater connected in sequence. The air preheater is provided with a purified flue gas exhaust channel at its end. The first cyclone separator is provided with a desulfurizing agent return port, which is connected to the regenerator.

[0078] like Figure 3 As shown, the absorption tail gas generated during acid production is sent to the reactor. Air and fuel gas are introduced into the reactor to raise its temperature before it enters the fluidized bed reactor. Fresh desulfurizing agent is added to the reactor from the new agent tank, and the process is completed within the reactor. The adsorption reaction produces a desulfurizing agent that is then fed into a regenerator. Air and a reducing agent are introduced into the regenerator to achieve thermal regeneration and desorption of the desulfurizing agent. The sulfur dioxide-rich desorbed gas is separated by a second hydrocyclone and then sent to the outlet of the sulfur incinerator for circulating acid production. The regenerated desulfurizing agent is returned to the reactor for reuse. The purified flue gas discharged from the reactor passes sequentially through a heat exchanger, a third waste heat boiler, a first hydrocyclone to remove waste agent, a second economizer, and an air preheater for heat exchange and cooling before being discharged into the atmosphere.

[0079] Example 1

[0080] Adopting such Figure 2 The acid production process shown is as follows:

[0081] Liquid sulfur, as a sulfur-containing feedstock, is burned with a first oxygen-containing gas in a sulfur incinerator to generate sulfur dioxide-containing furnace gas. This furnace gas is then passed through a first waste heat boiler for heat exchange and is fed into a first-stage catalyst bed at 420°C for a first catalytic oxidation reaction, yielding first-stage converted gas. After the first catalytic oxidation reaction, the furnace gas temperature rises to approximately 610°C. The first-stage converted gas is then passed through the tube side of a first heat exchanger for heat exchange and cooling to 440°C. It then enters a second-stage catalyst bed for a second catalytic oxidation reaction, yielding second-stage converted gas. The second-stage converted gas temperature rises to approximately 52°C. The first stage of conversion gas is at 0℃. The second stage waste heat boiler recovers heat and cools the gas to approximately 440℃ before sending it to the third stage catalyst layer for a third catalytic oxidation reaction, yielding sulfur trioxide-containing conversion gas. This sulfur trioxide-containing conversion gas is then heated to approximately 460℃. The sulfur trioxide-containing conversion gas flows sequentially through the tube side of the second heat exchanger and the first economizer, where it is cooled to 200℃. It then enters the absorption tower and reacts with concentrated sulfuric acid, causing the sulfur trioxide to react with the bound water in the concentrated sulfuric acid to form sulfuric acid. Simultaneously, absorption tail gas containing residual sulfur dioxide is obtained. The first and second waste heat boilers each produce 6.4MPa medium-pressure steam as a byproduct.

[0082] The absorption tower employs a high-temperature concentrated sulfuric acid countercurrent absorption process. The temperature of the high-temperature concentrated sulfuric acid entering the absorption tower is controlled at 170~190℃. After low-temperature acid washing, the absorption tail gas leaves the absorption tower at a temperature of approximately 85℃. It then flows sequentially through the shell side of the second heat exchanger and the shell side of the first heat exchanger for heat exchange and temperature increase, finally yielding a high-temperature absorption tail gas of approximately 590℃. During this process, the high-temperature acid absorbs sulfur trioxide within the absorption tower, releasing the heat of reaction and simultaneously producing low-pressure steam at 0.6~1.0 MPa as a byproduct.

[0083] The absorption tail gas, at approximately 590°C, is fed into the reactor of the tail gas treatment unit and heated to 650°C using natural gas as fuel. The heated tail gas is then fed into the lower part of a fluidized bed reactor. Regenerated desulfurizing agent from the regenerator and circulating desulfurizing agent from the reactor's settling section are introduced into the reactor. The gas and solid phases rise and come into full contact. At the 650°C adsorption reaction temperature, the desulfurizing agent reacts with the absorption tail gas, removing residual sulfur dioxide and yielding sulfur-loaded desulfurizing agent and purified flue gas after sulfur dioxide removal. Two-stage hydrocyclones are installed in the reactor's settling section to complete preliminary gas-solid separation. The purified flue gas is discharged from the reactor's desulfurization tail gas outlet. The circulation rate of the desulfurizing agent can be adjusted by monitoring the sulfur content of the flue gas.

[0084] After being discharged from the reactor, the purified flue gas passes sequentially through a steam superheater, a third waste heat boiler, a first cyclone separator, a second economizer, and an air preheater for heat exchange and cooling. The final flue gas temperature drops to 105℃ before being discharged. The third waste heat boiler produces 6.4MPa medium-pressure steam as a byproduct of the heat exchange process. After the first cyclone separator separates and removes waste desulfurizing agent particles, the particulate matter content in the discharged purified flue gas can be controlled below 30mg / Nm³ (dry basis).

[0085] The desulfurizing agent produced by the reactor is sent to the regenerator for regeneration and desorption. The regeneration furnace uses liquid sulfur as raw material and dry air as auxiliary gas source, and controls the excess of elemental sulfur to make the atmosphere inside the furnace oxygen-free, thus preparing reducing fluidized gas. After the reducing fluidized gas is heated to 700°C, it is introduced into the bottom of the regenerator. The regenerator adopts a rapid dense phase bed, and the desulfurizing agent is fully regenerated and desorbed with the reducing fluidized gas at a regeneration temperature of 580°C. The sulfur components adsorbed by the desulfurizing agent are desorbed and released, resulting in regenerated desulfurizing agent and sulfur dioxide gas. The regenerated desulfurizing agent is sent back to the reactor from the outlet of the regenerator to participate in the adsorption reaction. When the system desulfurizing agent consumption is insufficient, fresh desulfurizing agent is replenished from the fresh desulfurizing agent storage tank.

[0086] The upper section of the regenerator is equipped with two-stage hydrocyclones to complete the initial gas-solid separation. The sulfur dioxide gas is deeply dusted by an external second hydrocyclone, reducing the solid particulate matter content in the sulfur dioxide gas to below 10 mg / Nm³. The dust-removed sulfur dioxide gas is transported to the outlet of the sulfur incinerator, where it is mixed with the sulfur dioxide-containing furnace gas produced by the sulfur incinerator and then enters the catalytic system together to participate in the catalytic oxidation and absorption reactions in step S1.

[0087] Comparative Example 1

[0088] The existing 600,000 tons / year sulfuric acid production capacity was used as a comparative example 1.

[0089] Investment amount, steam production, and exhaust gas of the acid production methods in Example 1 and Comparative Example 1 Specific parameters such as emissions, sulfuric acid mist emissions, and annual benefit increments are shown in Table 1. Sulfuric acid mist in the acid production process is generated throughout the entire process of conversion, absorption, and tail gas treatment.

[0090] Table 1

[0091]

[0092] The acid production process provided in Example 1 has several significant advantages over the existing two-conversion, two-absorption acid production process in Comparative Example 1:

[0093] (1) Significantly improved economic benefits

[0094] Compared with acid production units of the same scale, such as "3+1" and "3+2" two-conversion two-absorption units, the initial investment of this process is slightly higher; however, the unit acid and steam production is significantly increased, with an annual steam production increase of up to 180,000 tons. Calculated at a steam price of 150 yuan / ton, this process can generate an additional economic benefit of 27 million yuan per year, demonstrating a clear long-term operational advantage.

[0095] (2) Exhaust gas Emissions have been significantly reduced, achieving near-zero sulfur dioxide emissions.

[0096] Purifying exhaust gas compared to existing processes (Comparative Example 1) The emission limit is ≤50mg / Nm³. The process in this embodiment can reduce the exhaust gas emissions. Emissions are controlled at ≤1mg / Nm³, significantly reducing pollutant emission levels and achieving near-zero sulfur dioxide emissions.

[0097] (3) Eliminates the constraints of sulfuric acid mist

[0098] The exhaust gas treatment uses high-temperature adsorption, which eliminates the conditions for the presence of acid mist and adsorbs sulfur trioxide, thus solving the problems of existing processes.

[0099] (4) Eliminates the hidden danger of easy agglomeration of the four- and five-stage catalyst layers.

[0100] This process adopts a three-stage conversion and one-stage absorption + tail gas treatment process, which eliminates the four-stage and five-stage low-temperature conversion in the existing two-stage conversion and two-stage absorption process, completely eliminating the hidden danger of catalyst bed agglomeration and ensuring the long-term operation of the unit.

[0101] (5) The utilization rate of sulfur resources is close to 100%.

[0102] The present invention is equipped with a tail gas adsorption regeneration circulation system, which can completely recover unconverted sulfur dioxide in the tail gas; only a small amount of sulfur components are lost with the finished sulfuric acid, and the vast majority of sulfur components are recycled back to the main conversion process to participate in the acid production reaction, with an overall sulfur resource utilization rate of nearly 100%.

[0103] (6) The desulfurizing agent consumption is 80-100 tons / year, and the operating cost is comparable to that of the existing sodium alkali method.

[0104] (7) It is compatible with the renovation of existing equipment, with high potential for capacity expansion and low renovation cost.

[0105] For the capacity expansion and renovation of existing sulfuric acid production units, this process can fully utilize the existing four-stage and five-stage catalyst layers, the second absorption tower, and supporting pipeline equipment, with only some equipment and pipelines requiring adaptive optimization and adjustment. The acid production furnace gas and the regenerated sulfur-containing gas are connected to the inlet of the four-stage catalyst layer, and the capacity is increased by relying on the "two-stage conversion + one-stage absorption" process route.

[0106] Taking the expansion of the existing plant to a scale of 750,000 tons / year as an example, the above-mentioned "two-stage conversion + one-stage absorption" process is adopted. The heat exchange process is slightly adjusted, and the other supporting facilities are only slightly modified. There is no need for large-scale demolition and reconstruction, and the amount of renovation and construction is small.

[0107] It should be noted that trace amounts of desulfurizing agent particles carried in the regenerated gas will pass through the catalyst bed, and a small amount will eventually be absorbed into the sulfuric acid and react with the sulfuric acid to form sulfate. The ash content meets the relevant requirements in "Industrial Sulfuric Acid" (GB / T534-2014), and the product meets national standards for delivery.

[0108] It should be noted that the specific temperature, flow rate, concentration, operating pressure and other limiting parameters recorded in each embodiment are the core improvement conditions of this invention. Other process operation parameters and device matching operation conditions that are not specifically limited are all common conventional technologies in the field of acid production and desulfurization processes, and those skilled in the art can reasonably select them based on conventional design experience.

[0109] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing acid with near-zero sulfur dioxide emissions and tail sulfur recycling, characterized in that, Includes the following steps: S1. The sulfur-containing raw material and the first oxygen-containing gas are burned in a sulfur incinerator to generate furnace gas containing sulfur dioxide; the furnace gas is introduced into a catalytic system for catalytic oxidation reaction to obtain conversion gas containing sulfur trioxide; the conversion gas enters an absorption tower and undergoes an absorption reaction with concentrated sulfuric acid to generate sulfuric acid and absorption tail gas containing residual sulfur dioxide. S2. The resulting absorption tail gas is treated, including the following process: The absorption tail gas and the second oxygen-containing gas are fed into the reactor, heated, and then fed into the fluidized bed reactor. The sulfur dioxide in the absorption tail gas is oxidized to generate sulfur trioxide, which then undergoes an adsorption reaction with the desulfurizing agent to obtain a sulfate-containing desulfurizing agent and purified flue gas after sulfur dioxide removal. The obtained desulfurizing agent is sent to the regenerator for regeneration and analysis to obtain regenerated desulfurizing agent and sulfur dioxide-rich gas. The sulfur dioxide-rich gas is then transported to the outlet of the sulfur incinerator and mixed with the sulfur dioxide-containing furnace gas produced by the sulfur incinerator. The mixture then enters the catalytic system and participates in the catalytic oxidation and absorption reactions in step S1.

2. The acid production method for near-zero sulfur dioxide emissions and tail sulfur recycling according to claim 1, characterized in that, The process of introducing the furnace gas into the catalytic system for catalytic oxidation to obtain sulfur trioxide-containing converted gas includes: the furnace gas entering the first waste heat boiler for heat exchange, then entering a first catalyst layer for a first catalytic oxidation reaction to obtain first-stage converted gas; the first-stage converted gas entering the second catalyst layer for a second catalytic oxidation reaction to obtain second-stage converted gas; and the second-stage converted gas entering the third catalyst layer for a third catalytic oxidation reaction to obtain sulfur trioxide-containing converted gas. And / or, the process of the converted gas entering the absorption tower and undergoing an absorption reaction with concentrated sulfuric acid includes: the converted gas is cooled sequentially by the second heat exchanger and the first economizer before entering the absorption tower and undergoing an absorption reaction with concentrated sulfuric acid.

3. The acid production method for near-zero sulfur dioxide emissions and tail sulfur recycling according to claim 1 or 2, characterized in that, The absorption reaction is carried out at a temperature of 170℃~220℃; And / or, in the sulfur dioxide-rich gas after regeneration and analysis, the volume percentage of sulfur dioxide is 40% to 60%; And / or, the purified flue gas after sulfur dioxide removal is discharged in compliance with emission standards after gas-solid separation and heat exchange cooling.

4. The acid production method for near-zero sulfur dioxide emissions and tail sulfur recycling according to any one of claims 1-3, characterized in that, When the absorption tower carries out the absorption reaction, it uses the low-temperature heat released by the absorption reaction to produce low-pressure saturated steam with a pressure of 0.6~1.0MPa as a byproduct.

5. The method for producing acid with near-zero sulfur dioxide emissions and tail sulfur recycling according to any one of claims 1-4, characterized in that, The process of sending the obtained desulfurizing agent to the regenerator for regeneration and analysis includes: sending the obtained desulfurizing agent to the regenerator to react with the reducing agent, so that the sulfur element in its sulfate is reduced to sulfur dioxide by the reducing agent, and thus obtaining the regenerated desulfurizing agent; And / or, the temperature of the adsorption reaction is 600~700℃.

6. The acid production method for near-zero sulfur dioxide emissions and tail sulfur recycling according to claim 5, characterized in that, The reducing agent includes elemental sulfur.

7. The acid production method for near-zero sulfur dioxide emissions and tail sulfur recycling according to claim 5 or 6, characterized in that, The temperature of the regeneration reaction is 500~630℃.

8. The method for producing acid with near-zero sulfur dioxide emissions and tail sulfur recycling according to any one of claims 1-7, characterized in that, The purified flue gas contains ≤1 mg / Nm³ of sulfur dioxide (dry basis). 3 ; And / or, the dry basis particulate matter content in the purified flue gas is ≤30 mg / Nm³. 3 .

9. An acid-producing apparatus, characterized in that, Step S1 of the acid production method for implementing near-zero sulfur dioxide emissions and tail sulfur recycling as described in any one of claims 1-8 includes a sulfur incinerator, a catalytic system, and an absorption tower connected in sequence. The catalytic system includes a first waste heat boiler, a first catalyst layer, a first heat exchanger, a second catalyst layer, a second waste heat boiler, a third catalyst layer, a second heat exchanger, and a first economizer connected in sequence; the outlet of the sulfur incinerator is connected to the inlet of the first waste heat boiler, and the outlet of the first economizer is connected to the inlet of the absorption tower.

10. The acid-generating apparatus according to claim 9, characterized in that, It also includes a tail gas treatment device for implementing step S2 of the acid production method of near-zero sulfur dioxide emission and tail sulfur recycling as described in any one of claims 1-8. The tail gas treatment device includes a reactor, a regeneration furnace, a regenerator, and a fresh desulfurizing agent storage tank. The gas inlet of the reactor is connected to the exhaust gas outlet of the first heat exchanger, and the gas outlet of the reactor is connected to the exhaust gas inlet of the reactor. The reactor is equipped with a fresh desulfurizing agent inlet, a desulfurizing agent outlet, a regenerated desulfurizing agent inlet, a desulfurization tail gas outlet, a circulating desulfurizing agent inlet, and a circulating desulfurizing agent outlet; The fresh desulfurizing agent storage tank is connected to the fresh desulfurizing agent inlet of the reactor; The regeneration furnace is equipped with an air inlet and a reducing agent inlet, and the regeneration furnace is connected to the regenerator for heating. The desulfurizing agent outlet of the reactor is connected to the desulfurizing agent inlet of the regenerator, and the desulfurizing agent outlet of the regenerator is connected to the desulfurizing agent inlet of the reactor, forming a regenerating desulfurizing agent circulation. The regenerator is provided with a regenerated gas outlet, which is connected to a second hydrocyclone, and the second hydrocyclone is connected to the gas outlet of the sulfur incinerator. The desulfurization tail gas outlet of the reactor is connected to the tail gas heat exchange and purification unit. Preferably, the exhaust gas heat exchange and purification unit includes a steam superheater, a third waste heat boiler, a first cyclone separator, a second economizer, and an air preheater connected in sequence. The air preheater is provided with a purified flue gas exhaust channel at its end. The first cyclone separator is provided with a waste desulfurizing agent outlet.

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