A flue gas acid production system

Abstract

This utility model discloses a flue gas acid production system, belonging to the field of flue gas acid production technology. The system includes an electrostatic precipitator, a drying tower, a sulfuric acid circulation tank, a sulfur dioxide fan, a preheater, and a converter. This utility model constructs a multi-stage synergistic demisting process mode of parallel electrostatic precipitators followed by series wire mesh precipitators, achieving deep removal of acid mist particles of different sizes, especially submicron-sized particles. This utility model integrates leaked gas resource utilization and online equipment repair technology, deeply coupling SO2 fugitive emission control with acid production process parameter optimization. This utility model adds a pressure relief control device between the inlet and outlet pneumatic butterfly valves of the faulty electrostatic precipitator. Through adjustment of the main pressure relief valve and interlocking with the fan frequency conversion system, the negative pressure inside the electrostatic precipitator can be controlled, enabling maintenance without shutting down the system.

Description

Technical Field

[0001] This utility model relates to the field of flue gas acid production technology, specifically to a flue gas acid production system, which is particularly suitable for balancing negative pressure in the process of producing acid from smelting flue gas and for using negative pressure to extract and treat flue gas containing sulfur dioxide and acid mist. Background Technology

[0002] In the flue gas acid production industry, leaks of sulfur dioxide-containing flue gas and acid mist are unavoidable. The negative pressure generated by the sulfur dioxide fan can effectively recover leaked gases, reducing harmful gas leakage. However, due to the negative pressure in the electric field of the electrostatic precipitator located upstream of the fan, manholes cannot be opened for inspection and maintenance. When the electrostatic precipitator malfunctions, the fan must be stopped to access it, negatively impacting production continuity. Acid mist from the circulating acid tank enters the drying tower, where the composite wire mesh demister at the top of the drying tower does not completely remove this portion of acid mist, potentially causing corrosion to downstream equipment.

[0003] In the current technology for sulfuric acid production from smelting flue gas, acid mist generated in the sulfuric acid circulating tank enters a composite wire mesh demister at the top of the drying tower for primary demisting. However, this method has limited efficiency in removing submicron acid mist particles. Furthermore, the composite wire mesh demister operates under high load for extended periods, resulting in susceptibility to clogging, high resistance, and high energy consumption. Additionally, in existing smelting flue gas sulfuric acid production processes, the preheater, a critical preheating device during start-up and shutdown, employs a shell-and-tube heat exchange structure. Frequent temperature increases and decreases cause significant temperature stress concentration, leading to fatigue tearing of the tube sheet welds and resulting in the uncontrolled release of SO2 gas within the system. Under current technology, such leaks require system shutdown for welding repairs, disrupting system continuity, causing sulfur resource loss, and lacking effective control over uncontrolled releases. Finally, in existing smelting flue gas sulfuric acid production systems, the electrostatic precipitator operates with a negative pressure environment of -6 to -12 kPa at the inlet due to the suction effect of the SO2 fan. When equipment experiences faults such as cathode wire breakage or electric field insulation breakdown, traditional maintenance methods suffer from the problem of negative pressure interlock. The negative pressure inside the equipment causes the manhole door to be subjected to axial suction, making it impossible to open the maintenance manhole door, resulting in system interruption and losses. Shutdown maintenance requires a 6-12 hour process of load reduction, pressure relief, and replacement, leading to technical bottlenecks such as loss of acid production capacity.

[0004] Therefore, providing a flue gas acid production system is a problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0005] In view of this, the present invention provides a flexible and practical flue gas acid production system and method that utilizes the negative pressure generated by the operation of a sulfur dioxide fan to recover sulfur dioxide and acid mist from flue gas, and achieves negative pressure balance in flue gas acid production. It can balance the negative pressure of the electrostatic precipitator, enabling maintenance without shutting down the system.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A flue gas sulfuric acid production system includes an electrostatic precipitator, a drying tower, a sulfuric acid circulation tank, a sulfur dioxide fan, a preheater, and a converter; The top outlet of the electrostatic precipitator is connected to the feed inlet of the drying tower; the top outlet of the drying tower is connected to the sulfur dioxide blower; the outlet of the sulfur dioxide blower is connected to the preheater or external air; and the lower outlet of the preheater is connected to the converter. The bottom outlet of the drying tower is connected to the sulfuric acid circulation tank; the sulfuric acid circulation tank is provided with two discharge ports, the first discharge port of the sulfuric acid circulation tank is connected to the upper inlet of the drying tower, and the second discharge port of the sulfuric acid circulation tank is connected to the inlet of the electrostatic precipitator through an acid mist recovery pipe. The top outlet of the preheater is connected to the feed inlet of the drying tower via a negative pressure drainage pipe.

[0007] Furthermore, at least two electrostatic precipitators are provided, and any two electrostatic precipitators are connected in parallel and communicate with the feed inlet of the drying tower.

[0008] Furthermore, each of the aforementioned demisters is equipped with a main pressure relief valve and an auxiliary balance valve.

[0009] In this invention, a DN1500 pneumatic butterfly valve and a DN200 main pressure relief valve are installed at the inlet and outlet of the electrostatic precipitator to form a pressure regulating circuit; a DN80 auxiliary balancing valve is installed in parallel to maintain a slight negative pressure inside the equipment during maintenance. The main pressure relief valve and the auxiliary balancing valve constitute a pressure relief control device.

[0010] The pressure relief control device is interlocked with the sulfur dioxide fan. During maintenance, if the internal negative pressure of the faulty electrostatic precipitator drops below -6 kPa, the main pressure relief valve automatically opens first. After the main pressure relief valve is fully open, the auxiliary balancing valve is finely adjusted to precisely regulate the internal negative pressure to -2 to -3 kPa. The opening and closing states of the main pressure relief valve and the auxiliary balancing valve are interlocked with the state of the electrostatic precipitator and with the inlet and outlet valves of the electrostatic precipitator. When the main pressure relief valve or the balancing valve is open, the electrostatic precipitator cannot be powered, and the inlet and outlet valves are not allowed to open. Furthermore, an oxygen-to-sulfur ratio adjustment node is provided between the electrostatic precipitator and the drying tower.

[0011] An online gas analyzer is installed in the oxygen-sulfur ratio adjustment node to monitor the O2 / SO2 molar ratio of the mixed gas in real time and automatically adjust the pumping rate of the negative pressure drainage pipe to achieve a resource utilization rate of ≥95% for leaked gas.

[0012] Furthermore, a composite wire mesh demister is provided at the top outlet of the drying tower.

[0013] This utility model also provides a method for producing acid from flue gas under negative pressure balance, using the above-mentioned system, including the following steps: (1) Start the sulfur dioxide fan to form a negative pressure for air extraction at its front end; the sulfuric acid mist flue gas and the acid mist flue gas generated above the sulfuric acid circulation tank are introduced into the electrostatic precipitator, and the high voltage electrostatic field of the electrostatic precipitator is used to realize the charging, condensation and collection of acid mist particles; (2) The flue gas after electrostatic precipitation is introduced into the drying tower and treated by a composite wire mesh demister. The treated sulfur dioxide-containing gas passes through a sulfur dioxide fan, a preheater and a converter in sequence to complete the acid production. (3) When SO2 leakage occurs in the system, the leaked gas is transported to the oxygen-sulfur ratio adjustment node at the inlet of the drying tower through the negative pressure diversion pipeline, and then mixed with the flue gas after electrostatic precipitator treatment to participate in the acid production reaction. (4) When the equipment is under maintenance, adjust the negative pressure inside the electrostatic precipitator to -2~-3 kPa to maintain continuous operation of the system.

[0014] Furthermore, the high-voltage electrostatic field input voltage of the electrostatic precipitator is 380V and the current is 250A, while the output voltage is 72kV and the current is 1000mA.

[0015] The beneficial effects of this utility model are as follows: 1. This invention constructs a multi-stage synergistic demisting process mode of parallel electrostatic precipitators followed by series wire mesh demisters, achieving deep removal of acid mist particles of different sizes, especially submicron-sized particles, increasing the overall sulfuric acid mist removal efficiency from approximately 95% in traditional processes to over 99.9%. This invention introduces the acid mist generated in the circulation tank into the inlet of the electrostatic precipitator via an extraction system. The acid mist-containing flue gas is then introduced into the honeycomb electrostatic precipitator, where a high-voltage electrostatic field causes the acid mist particles to sequentially complete the charging, condensation, and efficient capture processes. The flue gas, after pretreatment by the electrostatic precipitator, is then passed through a drying tower and a composite wire mesh demister for further fine treatment, ensuring that the flue gas purification indicators meet the standards.

[0016] 2. This invention breaks through the traditional "passive plugging" treatment model. Through integrated technology of leaked gas resource utilization and online equipment repair, it deeply couples the control of fugitive SO2 emissions with the optimization of acid production process parameters. This invention directs leaked gas from the preheater to the oxygen-sulfur ratio adjustment node at the inlet of the drying tower via a negative pressure extraction system. The process airflow at the drying tower inlet is used to mix and adjust the composition of the leaked gas, achieving resource utilization and enabling online welding operations on the equipment, ensuring continuous and efficient system operation.

[0017] 3. This invention can also perform online maintenance of the dynamic negative pressure balance of the electrostatic precipitator. This invention adds a pressure relief control device (including a main pressure relief valve and an auxiliary balancing valve) between the inlet and outlet pneumatic butterfly valves of the faulty electrostatic precipitator. Through adjustment of the main pressure relief valve and interlocking with the fan frequency conversion system, the negative pressure inside the equipment can be precisely adjusted to -2 to -3 kPa, breaking through the technical bottleneck of "inoperable under negative pressure" in electrostatic precipitators. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the flue gas acid production system provided by this utility model.

[0020] The structures represented by each number in the attached diagram are listed below: 1-Electrostatic precipitator, 2-Drying tower, 3-Sulfuric acid circulation tank, 4-Sulfur dioxide fan, 5-Start-up preheater, 6-Converter, 7-Acid mist recovery pipe, 8-Negative pressure diversion pipe, 9-Main pressure relief valve, 10-Auxiliary balancing valve, 11-Oxygen-sulfur ratio adjustment node, 12-Composite wire mesh precipitator. Detailed Implementation

[0021] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this utility model, and should not be construed as limiting this utility model. In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified. In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances. In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. Example 1 A flue gas acid production system includes an electrostatic precipitator 1, a drying tower 2, a sulfuric acid circulation tank 3, a sulfur dioxide fan 4, a preheater 5, and a converter 6; The top outlet of the electrostatic precipitator 1 is connected to the feed inlet of the drying tower 2; the top outlet of the drying tower 2 is connected to the sulfur dioxide blower 4; the outlet of the sulfur dioxide blower 4 is connected to the preheater 5 or external air; and the lower outlet of the preheater 5 is connected to the converter 6. The bottom outlet of the drying tower 2 is connected to the sulfuric acid circulation tank 3; the sulfuric acid circulation tank 3 is provided with two discharge ports. The first discharge port of the sulfuric acid circulation tank 3 is connected to the upper inlet of the drying tower 2, and the second discharge port of the sulfuric acid circulation tank 3 is connected to the inlet of the electrostatic precipitator 1 through the acid mist recovery pipe 7. The top outlet of the preheater 5 is connected to the feed inlet of the drying tower 2 through the negative pressure diversion pipe 8.

[0022] In some embodiments, at least two electrostatic precipitators 1 are provided, and any two electrostatic precipitators 1 are connected in parallel and communicate with the feed inlet of the drying tower 2.

[0023] In other embodiments, each electrostatic precipitator 1 is provided with a main pressure relief valve 9 and an auxiliary balance valve 10.

[0024] In some embodiments, an oxygen-to-sulfur ratio adjustment node 11 is provided between the electrostatic precipitator 1 and the drying tower 2.

[0025] In some embodiments, a composite wire mesh demister 12 is provided at the top outlet of the drying tower 2.

[0026] Example 2 A method for producing acid from flue gas under negative pressure balance, using the system of Example 1, includes the following steps: (1) After the sulfur dioxide fan 4 is started, a negative pressure is formed at its front end for air extraction. The sulfuric acid mist flue gas and the acid mist generated above the sulfuric acid circulation tank 3 are introduced into the electrostatic precipitator 1, and the acid mist is removed by the high voltage electric field.

[0027] (2) The gas is introduced into the drying tower 2 and processed by the composite wire mesh demister 12. The treated sulfur dioxide gas passes through the sulfur dioxide fan 4, the preheater 5 and the converter 6 in sequence to complete the acid production. The front end of the negative pressure diversion pipe 8 is arranged after the sulfur dioxide fan 4. When the preheater 5 and the converter 6 leak, the pipe is adjusted according to the location of the sulfur dioxide leak to achieve the best gas extraction effect.

[0028] (3) The leaked sulfur dioxide-containing flue gas and some air are drawn into the oxygen-sulfur ratio adjustment node 11 at the front end of the drying tower 2. The moisture carried in the air is absorbed by the drying tower 2, and the oxygen carried is used to adjust the conversion ratio of oxygen and sulfur dioxide.

[0029] (4) The main pressure relief valve 9 is installed on the outer shell of the electrostatic precipitator 1 and is connected to the internal space. When the electrostatic precipitator 1 malfunctions or needs to be inspected through the manhole, the power supply to the electrostatic precipitator 1 is turned off, and the flue gas inlet and outlet valves are closed. The main pressure relief valve 9 is opened, and the maintenance manhole can be opened when the negative pressure inside the electrostatic precipitator 1 is close to atmospheric pressure. During maintenance by personnel entering the electrostatic precipitator 1, the internal slight negative pressure is controlled by the main pressure relief valve 9, the auxiliary balancing valve 10, and the operating frequency of the sulfur dioxide fan 4. This allows for inspection and maintenance of the electrostatic precipitator 1 without stopping the fan.

[0030] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0031] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A flue gas acid production system, characterized in that, Includes electrostatic precipitator, drying tower, sulfuric acid circulating tank, sulfur dioxide fan, preheater and converter; The top outlet of the electrostatic precipitator is connected to the feed inlet of the drying tower; the top outlet of the drying tower is connected to the sulfur dioxide blower; the outlet of the sulfur dioxide blower is connected to the preheater or external air; and the lower outlet of the preheater is connected to the converter. The bottom outlet of the drying tower is connected to the sulfuric acid circulation tank; the sulfuric acid circulation tank is provided with two discharge ports, the first discharge port of the sulfuric acid circulation tank is connected to the upper inlet of the drying tower, and the second discharge port of the sulfuric acid circulation tank is connected to the inlet of the electrostatic precipitator through an acid mist recovery pipe. The top outlet of the preheater is connected to the feed inlet of the drying tower via a negative pressure drainage pipe.

2. The flue gas acid production system according to claim 1, characterized in that, The electrostatic precipitator is provided in at least two units, and any two electrostatic precipitators are connected in parallel and communicate with the feed inlet of the drying tower.

3. The flue gas acid production system according to claim 1 or 2, characterized in that, Each of the electric demisters is equipped with a main pressure relief valve and an auxiliary balance valve.

4. The flue gas acid production system according to claim 1, characterized in that, An oxygen-to-sulfur ratio adjustment node is provided between the electrostatic precipitator and the drying tower.

5. The flue gas acid production system according to claim 1, characterized in that, A composite wire mesh demister is installed at the top outlet of the drying tower.

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