Energy-saving process for synergistically recycling hydrogen peroxide and dilute sulphuric acid in acid-making tail gas desulfurization

Abstract

The invention relates to an energy-saving process for synergistically recycling hydrogen peroxide and dilute sulphuric acid in acid-making tail gas desulfurization, which comprises the following steps: S1, tail gas desulfurization reaction: introducing tail gas discharged from a final absorption tower of an acid-making system into a tail gas desulfurization tower, and spraying a hydrogen peroxide solution from the upper part of the desulfurization tower to generate dilute sulphuric acid with the volume concentration of 20-25%; s2, graded collection of dilute sulphuric acid: when the volume concentration reaches 22%-25%, conveying the dilute sulphuric acid to a dilute acid storage tank by a dilute acid pump; when the volume concentration is lower than 22%, returning to the desulfurization tower for continuous recycling; s3, recycling and distributing dilute sulfuric acid: recycling the dilute sulfuric acid in a dilute acid storage tank in two paths: (1) conveying the dilute sulfuric acid with the volume ratio of 80-85% to an acid-making dry absorption process to prepare finished acid with the volume concentration of 93% or 98%; (2) conveying dilute sulphuric acid with the volume ratio of 15-20% to a purification process; s4, hydrogen peroxide is dynamically supplemented, and it is ensured that the residual concentration of hydrogen peroxide in dilute sulfuric acid is maintained to be 0.1%-0.5%. Accurate consumption control of hydrogen peroxide and resource recycling of dilute sulphuric acid can be realized.

Description

An energy-saving process for the co-recycling of hydrogen peroxide and dilute sulfuric acid from sulfuric acid production tail gas desulfurization. Technical Field

[0001] This invention relates to the field of copper smelting flue gas and acid production tail gas treatment technology, and in particular to an energy-saving process for the synergistic reuse of desulfurized hydrogen peroxide and dilute sulfuric acid in acid production tail gas. Background Technology

[0002] In copper smelting and sulfuric acid production, tail gas desulfurization is a key step in controlling SO2 emissions. Currently, the industry widely uses hydrogen peroxide desulfurization technology, the principle of which is H2O2 + SO2 = H2SO4, with a byproduct of 20%-25% dilute sulfuric acid. However, the existing process has the following drawbacks: serious resource waste: the dilute sulfuric acid produced as a byproduct of desulfurization is mostly discharged directly or sent to wastewater treatment processes, failing to fully utilize its acidic properties. At the same time, the dry absorption and purification processes require a large amount of fresh water to replenish the circulating liquid, resulting in water resource waste.

[0003] The consumption of hydrogen peroxide fluctuates greatly: Traditional processes rely on manual adjustment of the amount of hydrogen peroxide added, which is prone to over-addition (causing increased costs) or under-addition (causing emissions to exceed standards) due to changes in the SO2 concentration in the exhaust gas.

[0004] Therefore, there is an urgent need for a process that can achieve precise control of hydrogen peroxide consumption and resource recovery of dilute sulfuric acid to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an energy-saving process for achieving precise control of hydrogen peroxide consumption, resource recovery of dilute sulfuric acid, and synergistic recovery of hydrogen peroxide and dilute sulfuric acid from sulfuric acid tail gas desulfurization.

[0006] To address the aforementioned problems, the present invention provides an energy-saving process for the co-recycling of hydrogen peroxide and dilute sulfuric acid in the desulfurization of acid production tail gas, comprising the following steps: S1 Tail gas desulfurization reaction: The tail gas discharged from the final absorption tower of the acid production system is introduced into the tail gas desulfurization tower, and a hydrogen peroxide solution with a volume concentration of 27.5% is sprayed from the top of the desulfurization tower, controlling the gas-liquid ratio to be 1500~1800 Nm. 3 / m 3 Spray density 20m 3 / (m 2•h) A counter-current contact reaction occurs within the packing layer to generate dilute sulfuric acid with a volume concentration of 20%~25%; S2 Dilute sulfuric acid is collected in stages: the dilute sulfuric acid at the bottom of the desulfurization tower flows into the circulation tank, and the concentration is monitored in real time by a density meter. When the volume concentration reaches 22%~25%, it is pumped to the dilute acid storage tank by a dilute acid pump; when the volume concentration is below 22%, it is returned to the desulfurization tower for continued recycling; S3 Dilute sulfuric acid reuse distribution: the dilute sulfuric acid with a volume concentration of 22%~25% in the dilute acid storage tank is reused in two ways: ① 80%~85% by volume The dilute sulfuric acid is transported to the acid-making dry absorption process, where it is mixed with concentrated sulfuric acid of 98.5% or 93.5% by volume through an acid mixer to obtain a finished acid with a volume concentration of 93% or 98%; ② Dilute sulfuric acid with a volume ratio of 15%~20% is transported to the purification process to replenish the circulating liquid in the gas cooling tower, maintaining it at a 3% dilute acid concentration; S4 Hydrogen peroxide dynamic replenishment: Based on the online continuous monitoring data of SO2 in the tail gas and the feedback of dilute sulfuric acid concentration, the hydrogen peroxide replenishment amount is automatically adjusted through a regulating valve: when the SO2 concentration is >70mg / Nm 3 When the SO2 concentration is <50mg / Nm³, increase the hydrogen peroxide dosage to 0.45~0.5 tons / shift; 3 At the same time, reduce the amount of hydrogen peroxide added to 0.3~0.35 tons / shift to ensure that the residual concentration of hydrogen peroxide in dilute sulfuric acid is maintained at 0.1%~0.5%.

[0007] In step S1, the SO2 volume concentration of the exhaust gas is 0.016%~0.043%, and the temperature is 77℃.

[0008] In step S1, the tail gas desulfurization tower is made of fluorine-resistant FRP material. The tower contains a two-stage packing layer with a total height of 3500mm. The lower layer consists of φ76mm PP Heil rings, and the upper layer consists of φ50mm PP Heil rings. An electrostatic precipitator with an acid mist removal rate ≥99.9% is installed at the top to ensure that the outlet acid mist concentration is ≤5mg / Nm³. 3 .

[0009] In step S3, the mixing process of the acid mixer is monitored using an acid concentration meter.

[0010] In step S4, the hydrogen peroxide replenishment system is equipped with a flow regulating valve, and the hydrogen peroxide storage tank is set to automatically remind the user to replenish when the liquid level is ≥20%. At the same time, the storage tank area is equipped with a human static electricity elimination device and a temperature sensor, and the temperature inside the tank is controlled to be ≤35℃.

[0011] Compared with the prior art, the present invention has the following advantages: 1. By optimizing the reaction parameters of the desulfurization tower and designing a staged reuse path for dilute sulfuric acid, the present invention achieves the dual goals of precise control of hydrogen peroxide consumption and resource utilization of dilute sulfuric acid, thereby reducing the overall energy consumption and environmental protection costs of the acid production system.

[0012] 2. This invention establishes a dynamic hydrogen peroxide replenishment mechanism to reduce hydrogen peroxide consumption per unit volume.

[0013] 3. Improved resource utilization: This invention can increase the recycling rate of dilute sulfuric acid produced by desulfurization to over 85%, reduce fresh water consumption in the dry absorption process by 30%, and reduce wastewater discharge by approximately 12,000 tons per year (based on a sulfuric acid production capacity of 1310 kt / a).

[0014] 4. Cost reduction: This invention reduces hydrogen peroxide consumption by 15% to 20%, saving approximately RMB 120,000 in hydrogen peroxide procurement costs annually; it also reduces electricity consumption for dilute sulfuric acid cooling by approximately 80,000 kW·h / year.

[0015] 5. Environmental compliance guarantee: This invention can ensure that the SO2 emission concentration in the exhaust gas is consistently ≤90mg / Nm³. 3 Acid mist emissions ≤5mg / Nm 3 It complies with GB26132-2010 "Emission Standard of Pollutants for Sulfuric Acid Industry" and is suitable for tail gas desulfurization and resource recycling of high-concentration SO2 flue gas acid production systems. Detailed Implementation

[0016] The core of this invention lies in the closed-loop design of "reaction-collection-reuse-consumption control", namely: optimization of tail gas desulfurization reaction: using a high-efficiency packed tower and precise gas-liquid ratio control to improve SO2 absorption efficiency and ensure that the concentration of by-product dilute sulfuric acid is stable at 20%~25%, laying the foundation for subsequent reuse; dilute sulfuric acid staged reuse path: according to the acid concentration requirements of each process in the acid production system (the dry absorption process requires low-concentration water replenishment, and the purification process requires dilute acid circulation), the dilute sulfuric acid is reused in separate paths to avoid process fluctuations caused by single reuse; dynamic hydrogen peroxide replenishment logic: combining online SO2 monitoring and dilute sulfuric acid concentration feedback to form a "concentration-dosage" linkage adjustment to avoid hydrogen peroxide waste.

[0017] An energy-saving process for the co-recycling of hydrogen peroxide and dilute sulfuric acid in the desulfurization of acid production tail gas includes the following steps: S1 Tail gas desulfurization reaction: The tail gas discharged from the final absorption tower of the acid production system is introduced into the tail gas desulfurization tower. The SO2 volume concentration of the tail gas is 0.016%~0.043%, and the temperature is 77℃. A 27.5% hydrogen peroxide solution is sprayed from the top of the desulfurization tower, controlling the gas-liquid ratio at 1500~1800 Nm. 3 / m 3 Spray density 20m 3 / (m 2 ·h), in the packing layer, a reverse contact reaction is carried out to generate dilute sulfuric acid with a volume concentration of 20%~25%.

[0018] The exhaust gas desulfurization tower is made of fluorine-resistant FRP material. It features a two-stage packing layer with a total height of 3500mm. The lower layer consists of φ76mm PP Heil rings, and the upper layer consists of φ50mm PP Heil rings. An electrostatic precipitator with an acid mist removal rate of ≥99.9% is installed at the top to ensure that the outlet acid mist concentration is ≤5mg / Nm³. 3 .

[0019] S2 dilute sulfuric acid is collected in stages: the dilute sulfuric acid at the bottom of the desulfurization tower flows into the circulation tank, and the concentration is monitored in real time by a density meter. When the volume concentration reaches 22%~25%, it is pumped to the dilute acid storage tank by the dilute acid pump; when the volume concentration is lower than 22%, it is returned to the desulfurization tower for continued recycling.

[0020] S3 Dilute Sulfuric Acid Recycling and Distribution: The 22%~25% volume concentration dilute sulfuric acid in the dilute acid storage tank is recycled in two ways: ① Dilute sulfuric acid with a volume concentration of 80%~85% is transported to the acid production dry absorption process, where it is mixed with concentrated sulfuric acid with a volume concentration of 98.5% or 93.5% through an acid mixer to obtain a finished acid with a volume concentration of 93% or 98%. The mixing process in the acid mixer is monitored using an acid concentration meter.

[0021] ② Dilute sulfuric acid with a volume ratio of 15%~20% is transported to the purification process to replenish the circulating liquid in the gas cooling tower, so as to maintain a 3% dilute acid concentration.

[0022] This invention can adjust the dilute sulfuric acid reuse ratio according to sulfuric acid production fluctuations (e.g., <1000 tons / shift): when production is low, the reuse ratio of the dry absorption process is reduced and the reuse ratio of the purification process is increased to ensure stable acid concentration in each process; at the same time, by adding a dilute sulfuric acid buffer tank, short-term fluctuations in tail gas SO2 concentration can be addressed, further enhancing the system's anti-interference capability.

[0023] S4 Hydrogen Peroxide Dynamic Replenishment: Based on online continuous monitoring data of SO2 in the exhaust gas and feedback from the dilute sulfuric acid concentration, the hydrogen peroxide replenishment amount is automatically adjusted via a regulating valve: when SO2 concentration > 70 mg / Nm³ 3 At this time, increase the hydrogen peroxide dosage to 0.45~0.5 tons / shift (corresponding to a sulfuric acid production of 1000~1500 tons / shift); when the SO2 concentration is <50mg / Nm 3 At the same time, reduce the amount of hydrogen peroxide added to 0.3~0.35 tons / shift to ensure that the residual concentration of hydrogen peroxide in dilute sulfuric acid is maintained at 0.1%~0.5%.

[0024] The hydrogen peroxide replenishment system is equipped with a flow regulating valve, and the hydrogen peroxide storage tank has an automatic level alarm that alerts the user when the liquid level is ≥20%. Additionally, the storage tank area is equipped with a static electricity elimination device and a temperature sensor, and the internal temperature is controlled to ≤35℃ to prevent hydrogen peroxide decomposition. Example

[0026] Taking the sulfuric acid production system of the 1310kt / a sulfuric acid production capacity of the chemical branch of Jinchuan Group Yongchang Copper Company as an example, the following process is implemented: 1. Equipment configuration: The tail gas desulfurization tower is a φ8000×16000mm fluorine-resistant FRP tower, equipped with two 1200m³ / h flow rate towers. 3 A dilute acid circulation pump with a capacity of [number] h (one in operation, one on standby); the dilute acid storage tank is a 50m [unit]. 3 Q345R carbon steel tank (with insulation layer); hydrogen peroxide electric flow regulating valve (flow rate 0~100L / h, accuracy ±1%).

[0027] 2. Process parameter control: Exhaust gas treatment capacity: 193275 Nm 3 / h (dry basis), SO2 inlet concentration 0.016%.

[0028] Hydrogen peroxide dosage: 0.35~0.4 tons / shift (corresponding to sulfuric acid production of 1200 tons / shift), with the concentration of dilute sulfuric acid kept stable at 23%~24%.

[0029] Dilute sulfuric acid recycling and distribution: 82% of the dilute sulfuric acid is sent to the dry absorption process (of which 22% is used for water replenishment in the drying tower and 60% is used for concentration of finished product acid), and 18% of the dilute sulfuric acid is sent to the purification process.

[0030] 3. Implementation Results: The SO2 emission concentration in the exhaust gas remained stable at 65~80 mg / Nm³. 3 Acid mist concentration ≤3mg / Nm 3 .

[0031] Fresh water consumption increased from the original 1.2m 3 / h decreased to 0.84m 3 / h, saving approximately 31,000 tons of fresh water annually.

[0032] The hydrogen peroxide consumption per shift has been reduced from 0.48 tons / shift to 0.38 tons / shift, resulting in annual cost savings of approximately 108,000 yuan.

Claims

1. An energy-saving process for the co-recycling of hydrogen peroxide and dilute sulfuric acid from sulfuric acid production tail gas desulfurization, comprising the following steps: S1 tail gas desulfurization reaction: The tail gas discharged from the final absorption tower of the acid production system is introduced into the tail gas desulfurization tower, and a 27.5% hydrogen peroxide solution is sprayed from the top of the desulfurization tower, controlling the gas-liquid ratio at 1500~1800 Nm. 3 / m 3 Spray density 20m 3 / (m 2 •h) A counter-current contact reaction occurs within the packing layer to generate dilute sulfuric acid with a volume concentration of 20%~25%; S2 Dilute sulfuric acid is collected in stages: the dilute sulfuric acid at the bottom of the desulfurization tower flows into the circulation tank, and the concentration is monitored in real time by a density meter. When the volume concentration reaches 22%~25%, it is pumped to the dilute acid storage tank by a dilute acid pump; when the volume concentration is below 22%, it is returned to the desulfurization tower for continued recycling; S3 Dilute sulfuric acid reuse distribution: the dilute sulfuric acid with a volume concentration of 22%~25% in the dilute acid storage tank is reused in two ways: ① 80%~85% by volume The dilute sulfuric acid is transported to the acid-making dry absorption process, where it is mixed with concentrated sulfuric acid of 98.5% or 93.5% by volume through an acid mixer to obtain a finished acid with a volume concentration of 93% or 98%; ② Dilute sulfuric acid with a volume ratio of 15%~20% is transported to the purification process to replenish the circulating liquid in the gas cooling tower, maintaining it at a 3% dilute acid concentration; S4 Hydrogen peroxide dynamic replenishment: Based on the online continuous monitoring data of SO2 in the tail gas and the feedback of dilute sulfuric acid concentration, the hydrogen peroxide replenishment amount is automatically adjusted through a regulating valve: when the SO2 concentration is >70mg / Nm 3 When the SO2 concentration is <50mg / Nm³, increase the hydrogen peroxide dosage to 0.45~0.5 tons / shift; 3 At the same time, reduce the amount of hydrogen peroxide added to 0.3~0.35 tons / shift to ensure that the residual concentration of hydrogen peroxide in dilute sulfuric acid is maintained at 0.1%~0.5%.

2. The energy-saving process for the co-recycling of hydrogen peroxide and dilute sulfuric acid in acid production tail gas desulfurization as described in claim 1, characterized in that: In step S1, the SO2 volume concentration of the exhaust gas is 0.016%~0.043%, and the temperature is 77℃.

3. The energy-saving process for co-recycling hydrogen peroxide and dilute sulfuric acid in acid production tail gas desulfurization as described in claim 1, characterized in that: In step S1, the tail gas desulfurization tower is made of fluorine-resistant FRP material. The tower contains a two-stage packing layer with a total height of 3500mm. The lower layer consists of φ76mm PP Heil rings, and the upper layer consists of φ50mm PP Heil rings. An electrostatic precipitator with an acid mist removal rate ≥99.9% is installed at the top to ensure that the outlet acid mist concentration is ≤5mg / Nm³. 3 .

4. The energy-saving process for the co-recycling of hydrogen peroxide and dilute sulfuric acid in acid production tail gas desulfurization as described in claim 1, characterized in that: In step S3, the mixing process of the acid mixer is monitored using an acid concentration meter.

5. The energy-saving process for co-recycling hydrogen peroxide and dilute sulfuric acid in acid production tail gas desulfurization as described in claim 1, characterized in that: In step S4, the hydrogen peroxide replenishment system is equipped with a flow regulating valve, and the hydrogen peroxide storage tank is set to automatically remind the user to replenish when the liquid level is ≥20%. At the same time, the storage tank area is equipped with a human static electricity elimination device and a temperature sensor, and the temperature inside the tank is controlled to be ≤35℃.