A method for producing sulfuric acid from desulfurization catalyst slag

Abstract

The present invention discloses a method for producing sulfuric acid from desulfurization catalyst slag, which includes: drying the desulfurization catalyst slag and then mixing it with sulfur concentrate by low-temperature ball milling; calcining the mixture in a fluidized bed furnace, and the generated sulfur dioxide is dust-removed by an electrostatic dust-removing device and then catalyzed by a catalytic contact oxidation tower to obtain a mixed gas of sulfur trioxide and partially uncatalyzed sulfur dioxide; introducing the mixed gas into a three-stage tail gas treatment system to produce sulfuric acid under the synergistic effect of ultrasonic cavitation treatment, filtering the produced sulfuric acid through a membrane filtration device, and finally recovering iron powder. The present invention can not only convert the sulfide in the waste and deactivated iron oxide desulfurization slag into sulfuric acid, but also the remaining iron oxide after treatment has a high iron content and can be used in iron and steel metallurgy and cement manufacturing. The present invention is economical, practical, green and environmentally friendly, and has great development potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization of industrial solid waste, and particularly relates to a method for producing sulfuric acid from desulfurization catalyst slag. Background Art

[0002] Activated iron oxide is a desulfurizer with good deep desulfurization effect and is widely used in petroleum and natural gas processing and some fields requiring deep desulfurization. After desulfurization, the activated iron oxide will be deactivated, and the desorbed sulfur dioxide will be released after long-term placement. A large amount of activated iron oxide desulfurizer slag is produced in China every year, which will cause serious environmental pollution if not properly disposed of.

[0003] Currently, the domestic processes for disposing of desulfurizer slag include landfill, non-fired bricks, waste power plants, calcination in coal-fired power plants, co-processing in cement kilns, sintered bricks, etc. These processes do not fundamentally solve the sulfur dioxide in the desulfurizer, and the iron oxide in the desulfurizer is not fully utilized. The present invention provides a method for producing sulfuric acid from desulfurization catalyst slag, which can not only convert the sulfide in the waste deactivated iron oxide desulfurization slag into sulfuric acid, but also the remaining iron oxide after treatment has a high iron content and can be used in iron and steel metallurgy and cement manufacturing. Summary of the Invention

[0004] An object of the present invention is to solve at least the above problems and / or defects and provide at least the advantages described hereinafter.

[0005] To achieve these and other advantages in accordance with the present invention, there is provided a method for producing sulfuric acid from desulfurization catalyst slag, comprising the following steps:

[0006] Step 1: Dry, ball-mill the desulfurization catalyst slag and mix it with a certain proportion of sulfur concentrate.

[0007] Step 2: Calcinate the mixture in a fluidized bed furnace, remove the generated sulfur dioxide through an electrostatic dust removal device, and then catalyze it through a catalytic contact oxidation tower to generate a mixed gas of sulfur trioxide and some uncatalyzed sulfur dioxide.

[0008] Step 3: Pass the mixed gas into a three-stage tail gas treatment system to produce sulfuric acid, filter the produced sulfuric acid through a membrane filtration device, and finally recover iron powder.

[0009] Preferably, in Step 1, the desulfurization catalyst slag is activated iron oxide slag, the drying temperature is 100-200 °C, the drying time is 1-3 hours, and the ball-milled particle size is 200-300 mesh.

[0010] Preferably, in Step 1, the mass ratio of the desulfurization catalyst slag to the sulfur concentrate is 1:9-10.

[0011] Preferably, in the first step, the desulfurization catalyst slag is first dried under negative pressure at low temperature, and then the dried desulfurization catalyst slag is mixed with sulfur concentrate and ground in low-temperature liquid nitrogen. The process is as follows: The desulfurization catalyst slag is dried under negative pressure at low temperature for 1 - 4 h under the conditions of a pressure of 0.2 - 0.8 MPa and a temperature of 70 - 90 °C; the dried desulfurization catalyst slag and sulfur concentrate are added to the sealed ball milling tank of the ball mill in proportion, titanium alloy balls with a diameter of 10 - 30 mm are added, the ball-to-material ratio is 10 - 20:1, and the tank is filled with liquid nitrogen, the sealed ball milling tank is closed and left standing for 10 - 30 min, and then ball milled for 2 - 6 h.

[0012] Preferably, in the second step, the calcination temperature is 800 - 960 °C, and the calcination time is 1 - 4 h.

[0013] Preferably, in the second step, the catalytic process of sulfur dioxide in the catalytic contact oxidation tower is as follows: At a temperature of 180 - 200 °C, sulfur dioxide reacts with oxygen in the air to form sulfur trioxide. The volume ratio of sulfur dioxide gas to air is 1:1.5 - 2, and the air is dehydrated by an 88 - 98% sulfuric acid solution.

[0014] Preferably, in the third step, the three-stage tail gas treatment system includes: The first-stage absorption tower is an 88 - 98% sulfuric acid solution absorption tower, the second-stage absorption tower is a 6 - 20% sulfuric acid solution absorption tower, and the third-stage absorption tower is a mixed solution absorption tower of 2 - 10% sulfuric acid and 5 - 25% hydrogen peroxide.

[0015] Preferably, in the third step, the process of the mixed gas passing through the three-stage tail gas treatment system is as follows:

[0016] Ⅰ. The mixed gas first enters the first-stage absorption tower. Sulfur trioxide in the mixed gas reacts with water in the sulfuric acid solution of the first-stage absorption tower to form sulfuric acid, and the mass fraction of sulfuric acid is adjusted to 88 - 98% by injecting water.

[0017] Ⅱ. The remaining gas then enters the second-stage absorption tower. The unreacted residual sulfur trioxide in the remaining gas reacts with water in the sulfuric acid solution of the second-stage absorption tower to form sulfuric acid.

[0018] Ⅲ. The remaining gas then enters the third-stage absorption tower. The un-catalyzed sulfur dioxide in the remaining gas reacts with hydrogen peroxide in the third-stage absorption tower to produce sulfur trioxide, and the generated sulfur trioxide then reacts with water in the mixed solution to form sulfuric acid.

[0019] Preferably, in the third step, ultrasonic cavitation treatment is added during the process of the mixed gas being treated by the three-stage tail gas treatment system. The process is as follows:

[0020] Ⅰ. The mixed gas first enters the first-stage absorption tower. At this time, ultrasonic cavitation treatment is carried out on the sulfuric acid solution in the first-stage absorption tower. Sulfur trioxide in the mixed gas reacts with water in the sulfuric acid solution in the first-stage absorption tower to form sulfuric acid. The mass fraction of sulfuric acid is adjusted to 88-98% by injecting water;

[0021] Ⅱ. The remaining gas then enters the second-stage absorption tower. At this time, ultrasonic cavitation treatment is carried out on the sulfuric acid solution in the second-stage absorption tower. The unreacted residual sulfur trioxide in the remaining gas reacts with water in the sulfuric acid solution in the second-stage absorption tower to form sulfuric acid;

[0022] Ⅲ. The remaining gas then enters the third-stage absorption tower. At this time, ultrasonic cavitation treatment is carried out on the mixed liquid in the third-stage absorption tower. The uncatalyzed sulfur dioxide in the remaining gas reacts with hydrogen peroxide in the third-stage absorption tower to produce sulfur trioxide, and the generated sulfur trioxide then reacts with water in the mixed liquid to form sulfuric acid;

[0023] The ultrasonic frequency of the ultrasonic cavitation treatment is 30-40 kHz, the ultrasonic time is 3-5 min, and the ultrasonic interval is 3-5 min.

[0024] Preferably, the recovered iron powder in step III includes the iron powder in the electrostatic precipitator and the iron powder that has not been completely reacted in the fluidized bed furnace.

[0025] The present invention has at least the following beneficial effects: The present invention provides a method for producing sulfuric acid from desulfurization catalyst slag, which can not only convert sulfides in waste active iron oxide desulfurization slag into sulfuric acid, but also the remaining iron oxide after treatment has a high iron content and can be used in iron and steel metallurgy and cement manufacturing. The present invention makes use of waste and the product is pollution-free.

[0026] Other advantages, objectives and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. Detailed Embodiments

[0027] The following further detailed description of the present invention is provided so that those skilled in the art can implement it with reference to the text of the specification.

[0028] It should be understood that the terms such as "having", "comprising" and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0029] <Example 1>

[0030] A method for producing sulfuric acid from desulfurization catalyst slag of the present invention includes the following steps:

[0031] Step 1: Dry the desulfurization catalyst slag at 150°C for 2 hours, grind it to 200 mesh, and mix the desulfurization catalyst with sulfur concentrate in a mass ratio of 1:9 (1 ton of desulfurization catalyst is mixed with 9 tons of sulfur concentrate).

[0032] Step 2: Place the mixture in a fluidized bed furnace and calcine it at 900°C for 2 hours; remove the generated sulfur dioxide through an electrostatic precipitator; then pass it through a catalytic contact oxidation tower, where sulfur dioxide reacts with oxygen in 1.6 times its volume of air at 180°C. The air is dehydrated by 98% concentrated sulfuric acid to generate a mixed gas of sulfur trioxide and some un-catalyzed sulfur dioxide.

[0033] Step 3: Pass the mixed gas into a three-stage tail gas treatment system. The mixed gas first enters the first absorption tower, where sulfur trioxide in the mixed gas reacts with water in the 98% sulfuric acid solution in the first absorption tower to form sulfuric acid, and the mass fraction of sulfuric acid is adjusted to 98% by injecting water; the remaining gas then enters the second absorption tower, where the unreacted residual sulfur trioxide in the remaining gas reacts with water in the 10% sulfuric acid solution in the second absorption tower to form sulfuric acid; the remaining gas then enters the third absorption tower, where the un-catalyzed sulfur dioxide in the remaining gas reacts with hydrogen peroxide in the mixed solution of 8% sulfuric acid and 10% hydrogen peroxide in the third absorption tower to produce sulfur trioxide, and the sulfur trioxide then reacts with water in the mixed solution to form sulfuric acid; filter the sulfuric acid with a mass fraction of 98% through a membrane filtration device; finally, recover the iron powder in the dust removal device and the unreacted iron powder in the fluidized bed furnace; a total of 12.7082 tons of sulfuric acid with a mass fraction of 98% and 7.2584 tons of iron powder are collected.

[0034] <Example 2>

[0035] A method for preparing sulfuric acid from desulfurization catalyst slag according to the present invention comprises the following steps:

[0036] Step 1: Dry the desulfurization catalyst slag at 150°C for 2 hours, grind it to 200 mesh, and mix the desulfurization catalyst with sulfur concentrate in a mass ratio of 1:9 (1 ton of desulfurization catalyst is mixed with 9 tons of sulfur concentrate).

[0037] Step 2: Place the mixture in a fluidized bed furnace and calcine it at 900°C for 2 hours; remove the generated sulfur dioxide through an electrostatic precipitator; then pass it through a catalytic contact oxidation tower, where sulfur dioxide reacts with oxygen in 1.7 times its volume of air at 180°C. The air is dehydrated by 98% concentrated sulfuric acid to generate a mixed gas of sulfur trioxide and some un-catalyzed sulfur dioxide.

[0038] Step 3: Pass the mixed gas into a three-stage tail gas treatment system. The mixed gas first enters the primary absorption tower, where sulfur trioxide in the mixed gas reacts with water in the 98% sulfuric acid solution in the primary absorption tower to form sulfuric acid, and the mass fraction of sulfuric acid is adjusted to 98% by injecting water; the remaining gas then enters the secondary absorption tower, where the unreacted residual sulfur trioxide in the remaining gas reacts with water in the 15% sulfuric acid solution in the secondary absorption tower to form sulfuric acid; the remaining gas then enters the tertiary absorption tower, where the uncatalyzed sulfur dioxide in the remaining gas reacts with hydrogen peroxide in the mixed solution of 10% sulfuric acid and 18% hydrogen peroxide in the tertiary absorption tower to produce sulfur trioxide, and the sulfur trioxide then reacts with water in the mixed solution to form sulfuric acid; the sulfuric acid with a mass fraction of 98% is filtered through a membrane filtration device; finally, the iron powder in the dust removal device and the unreacted iron powder in the fluidized bed furnace are recovered; a total of 12.7081 tons of sulfuric acid with a mass fraction of 98% and 7.2585 tons of iron powder are collected.

[0039] <Example 3>

[0040] A method for producing sulfuric acid from desulfurization catalyst slag according to the present invention comprises the following steps:

[0041] Step 1: Dry the desulfurization catalyst slag at 150°C for 2 h, grind it to 250 mesh, and mix the desulfurization catalyst and sulfur concentrate in a mass ratio of 1:9 (1 t of desulfurization catalyst is mixed with 9 t of sulfur concentrate).

[0042] Step 2: Place the mixture in a fluidized bed furnace and calcine it at 900°C for 2.2 h; remove dust from the generated sulfur dioxide through an electrostatic dust removal device; then pass it through a catalytic contact oxidation tower, where sulfur dioxide reacts with oxygen in 1.8 times its volume of air at 180°C, and the air is dehydrated by 98% concentrated sulfuric acid to generate a mixed gas of sulfur trioxide and partially uncatalyzed sulfur dioxide.

[0043] Step 3: Pass the mixed gas into a three-stage tail gas treatment system. The mixed gas first enters the primary absorption tower, where sulfur trioxide in the mixed gas reacts with water in the 98% sulfuric acid solution in the primary absorption tower to form sulfuric acid, and the mass fraction of sulfuric acid is adjusted to 98% by injecting water; the remaining gas then enters the secondary absorption tower, where the unreacted residual sulfur trioxide in the remaining gas reacts with water in the 15% sulfuric acid solution in the secondary absorption tower to form sulfuric acid; the remaining gas then enters the tertiary absorption tower, where the uncatalyzed sulfur dioxide in the remaining gas reacts with hydrogen peroxide in the mixed solution of 8% sulfuric acid and 20% hydrogen peroxide in the tertiary absorption tower to produce sulfur trioxide, and the sulfur trioxide then reacts with water in the mixed solution to form sulfuric acid; the sulfuric acid with a mass fraction of 98% is filtered through a membrane filtration device; finally, the iron powder in the dust removal device and the unreacted iron powder in the fluidized bed furnace are recovered; a total of 12.7083 tons of sulfuric acid with a mass fraction of 98% and 7.2583 tons of iron powder are collected.

[0044] <Example 4>

[0045] A method for producing sulfuric acid from desulfurization catalyst slag according to the present invention comprises the following steps:

[0046] Step 1: Place the desulfurization catalyst slag under the conditions of a pressure of 0.6 MPa and a temperature of 90 °C, and dry it under low temperature and negative pressure for 4 h; mix the dried desulfurization catalyst with sulfur concentrate sand at a mass ratio of 1:9 (mix 1 t of desulfurization catalyst with 9 t of sulfur concentrate sand); then add it to the sealed ball mill tank of the ball mill, add titanium alloy balls with a diameter of 10 mm, with a ball-to-material ratio of 15:1, fill the tank with liquid nitrogen, seal the sealed ball mill tank and let it stand for 10 min, and ball mill for 2 h until the particle size reaches 200 mesh.

[0047] Step 2: Place the mixture in a fluidized bed furnace and calcine it at 900 °C for 2 h; remove dust from the generated sulfur dioxide through an electrostatic dust removal device; then pass it through a catalytic contact oxidation tower, and sulfur dioxide reacts with oxygen in air with a volume 1.6 times that of sulfur dioxide at 180 °C. The air is dehydrated by 98% concentrated sulfuric acid to generate a mixed gas of sulfur trioxide and partially uncatalyzed sulfur dioxide.

[0048] Step 3: Pass the mixed gas into a three-stage tail gas treatment system. The mixed gas first enters the first absorption tower, and sulfur trioxide in the mixed gas reacts with water in the 98% sulfuric acid solution in the first absorption tower to generate sulfuric acid, and the mass fraction of sulfuric acid is adjusted to 98% by injecting water; the remaining gas then enters the second absorption tower, and the unreacted residual sulfur trioxide in the remaining gas reacts with water in the 10% sulfuric acid solution in the second absorption tower to generate sulfuric acid; the remaining gas then enters the third absorption tower, and the uncatalyzed sulfur dioxide in the remaining gas reacts with hydrogen peroxide in the mixed solution of 8% sulfuric acid and 10% hydrogen peroxide in the third absorption tower to produce sulfur trioxide, and sulfur trioxide then reacts with water in the mixed solution to generate sulfuric acid; filter the sulfuric acid with a mass fraction of 98% through a membrane filtration device; finally, recover the iron powder in the dust removal device and the iron powder that has not reacted completely in the fluidized bed furnace; a total of 12.7084 tons of sulfuric acid with a mass fraction of 98% and 7.2585 tons of iron powder are collected.

[0049] In this embodiment, in Step 1, two treatment methods of low-temperature negative-pressure drying and low-temperature liquid-nitrogen ball milling are adopted. The desulfurization catalyst slag is dried under low temperature and negative pressure to prevent the sulfides in the desulfurization catalyst slag from volatilizing due to high-temperature heating and drying, which not only ensures the availability of the desulfurization catalyst slag but also avoids environmental pollution caused by the volatilization of toxic sulfides; after mixing the dried desulfurization catalyst slag and sulfur concentrate sand, perform low-temperature liquid-nitrogen ball milling, which makes the grinding and mixing more uniform, and under low-temperature conditions, the sulfides in the desulfurization catalyst slag will not volatilize due to excessive heating during the ball milling process. Compared with Comparative Example 1, the mass of the collected sulfuric acid and iron powder is greater.

[0050] <Example 5>

[0051] A method for producing sulfuric acid from desulfurization catalyst slag according to the present invention comprises the following steps:

[0052] Step 1: Dry the desulfurization catalyst slag at 150°C for 2 hours, grind it to 200 mesh, and mix the desulfurization catalyst and sulfur concentrate in a mass ratio of 1:9 (1 ton of desulfurization catalyst is mixed with 9 tons of sulfur concentrate).

[0053] Step 2: Place the mixture in a fluidized bed furnace and calcine it at 900°C for 2 hours; remove dust from the generated sulfur dioxide through an electrostatic precipitator; then pass it through a catalytic contact oxidation tower, where sulfur dioxide reacts with oxygen in air with a volume 1.6 times that of sulfur dioxide at 180°C. The air is dehydrated by 98% concentrated sulfuric acid to generate a mixed gas of sulfur trioxide and partially uncatalyzed sulfur dioxide.

[0054] Step 3: Pass the mixed gas into a three-stage tail gas treatment system. The mixed gas first enters the first absorption tower, where ultrasonic cavitation treatment is performed on the 98% sulfuric acid solution in the first absorption tower. Sulfur trioxide in the mixed gas reacts with water in the 98% sulfuric acid solution in the first absorption tower to form sulfuric acid, and the mass fraction of sulfuric acid is adjusted to 98% by injecting water; the remaining gas then enters the second absorption tower, where ultrasonic cavitation treatment is performed on the 10% sulfuric acid solution in the second absorption tower. Residual sulfur trioxide in the remaining gas that has not reacted reacts with water in the 10% sulfuric acid solution in the second absorption tower to form sulfuric acid; the remaining gas then enters the third absorption tower, where ultrasonic cavitation treatment is performed on the mixed solution of 8% sulfuric acid and 10% hydrogen peroxide in the third absorption tower. Uncatalyzed sulfur dioxide in the remaining gas reacts with hydrogen peroxide in the mixed solution of 8% sulfuric acid and 10% hydrogen peroxide in the third absorption tower to produce sulfur trioxide, and sulfur trioxide then reacts with water in the mixed solution to form sulfuric acid; the ultrasonic frequency of the ultrasonic cavitation treatment is 40 kHz, the ultrasonic time is 5 minutes, and the ultrasonic interval is 5 minutes; filter the sulfuric acid with a mass fraction of 98% through a membrane filtration device; finally, recover the iron powder in the dust removal device and the iron powder that has not reacted completely in the fluidized bed furnace; a total of 12.7085 tons of sulfuric acid with a mass fraction of 98% and 7.2584 tons of iron powder are collected.

[0055] In this embodiment, in Step 3, continuous ultrasonic cavitation treatment is performed on the solutions in the three absorption towers of the three-stage tail gas treatment system. By using the cavitation effect generated by ultrasonic vibration in the solution, the reaction between the mixed sulfur-containing gas and the solution in the absorption tower is promoted, enabling the absorption tower to capture the sulfur-containing gas more fully. Compared with Comparative Example 1, more sulfuric acid and iron powder are collected.

[0056] <Example 6>

[0057] A method for preparing sulfuric acid from desulfurization catalyst slag according to the present invention comprises the following steps:

[0058] Step 1: Place the desulfurization catalyst slag under the conditions of a pressure of 0.6 MPa and a temperature of 90 °C, and dry it at low temperature and negative pressure for 4 h; mix the dried desulfurization catalyst with sulfur concentrate in a mass ratio of 1:9 (1 t of desulfurization catalyst is mixed with 9 t of sulfur concentrate); then add it to the sealed ball mill tank of the ball mill, add titanium alloy balls with a diameter of 10 mm, with a ball-to-material ratio of 15:1, fill the tank with liquid nitrogen, close the sealed ball mill tank and let it stand for 10 min, and ball mill for 2 h until the particle size reaches 200 mesh.

[0059] Step 2: Place the mixture in a fluidized bed furnace and calcine it at 900 °C for 2 h; remove the dust of the generated sulfur dioxide through an electrostatic dust removal device; then pass it through a catalytic contact oxidation tower, and sulfur dioxide reacts with oxygen in air with 1.6 times its volume at 180 °C. The air is dehydrated by 98% concentrated sulfuric acid to generate a mixed gas of sulfur trioxide and partially uncatalyzed sulfur dioxide.

[0060] Step 3: Pass the mixed gas into a three-stage tail gas treatment system. The mixed gas first enters the first absorption tower. At this time, ultrasonic cavitation treatment is carried out on the 98% sulfuric acid solution in the first absorption tower. Sulfur trioxide in the mixed gas reacts with water in the 98% sulfuric acid solution in the first absorption tower to form sulfuric acid, and the mass fraction of sulfuric acid is adjusted to 98% by injecting water; the remaining gas then enters the second absorption tower. At this time, ultrasonic cavitation treatment is carried out on the 10% sulfuric acid solution in the second absorption tower. The unreacted residual sulfur trioxide in the remaining gas reacts with water in the 10% sulfuric acid solution in the second absorption tower to form sulfuric acid; the remaining gas then enters the third absorption tower. At this time, ultrasonic cavitation treatment is carried out on the mixed solution of 8% sulfuric acid and 10% hydrogen peroxide in the third absorption tower. The uncatalyzed sulfur dioxide in the remaining gas reacts with hydrogen peroxide in the mixed solution of 8% sulfuric acid and 10% hydrogen peroxide in the third absorption tower to produce sulfur trioxide, and sulfur trioxide then reacts with water in the mixed solution to form sulfuric acid; the ultrasonic frequency of the ultrasonic cavitation treatment is 40 kHz, the ultrasonic time is 5 min, and the ultrasonic interval is 5 min; filter the sulfuric acid with a mass fraction of 98% through a membrane filtration device; finally, recover the iron powder in the dust removal device and the unreacted iron powder in the fluidized bed furnace; a total of 12.7088 tons of sulfuric acid with a mass fraction of 98% and 7.2589 tons of iron powder are collected.

[0061] In this embodiment, in step one, two treatment methods of low-temperature negative-pressure drying and low-temperature liquid-nitrogen ball milling are adopted. The desulfurization catalyst slag is subjected to low-temperature negative-pressure drying to prevent the sulfides in the desulfurization catalyst slag from volatilizing due to high-temperature heating and drying, which not only ensures the availability of the desulfurization catalyst slag but also avoids environmental pollution caused by the volatilization of toxic sulfides. After the dried desulfurization catalyst slag and sulfur concentrate are mixed, they are subjected to low-temperature liquid-nitrogen ball milling. The grinding and mixing are more uniform, and during ball milling at a low temperature, the sulfides in the desulfurization catalyst slag will not volatilize due to excessive heat during the ball milling process. In step three, continuous ultrasonic cavitation treatment is carried out on the solutions in the three absorption towers of the three-stage tail gas treatment system. By utilizing the cavitation effect generated by ultrasonic vibration in the solution, the reaction between the mixed sulfur-containing gas and the solution in the absorption tower is promoted, enabling the absorption tower to capture the sulfur-containing gas more fully. Compared with Comparative Example 1, more sulfuric acid and iron powder are collected.

[0062] As described above, the above is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for producing sulfuric acid from desulfurization catalyst slag, characterized in that, It includes the following steps: Step 1: Dry the desulfurization catalyst slag, ball-mill it, and mix it with a certain proportion of sulfur concentrate sand; Step 2: Calcinate the mixture in a fluidized bed furnace, remove dust from the generated sulfur dioxide through an electrostatic precipitator, and then catalyze it through a catalytic contact oxidation tower to generate a mixed gas of sulfur trioxide and partially uncatalyzed sulfur dioxide; Step 3: Pass the mixed gas into a three-stage tail gas treatment system to make sulfuric acid, filter the made sulfuric acid through a membrane filtration device, and finally recover iron powder; In the above Step 1, the desulfurization catalyst slag is active iron oxide slag, the drying temperature is 100~200°C, the drying time is 1~3 hours, and the ball-milling particle size is 200~300 mesh; In the above Step 1, first subject the desulfurization catalyst slag to negative pressure low-temperature drying treatment, and then mix the dried desulfurization catalyst slag with sulfur concentrate sand for low-temperature liquid nitrogen ball-milling. The process is as follows: Place the desulfurization catalyst slag under the conditions of a pressure of 0.2~0.8 MPa and a temperature of 70~90°C for low-temperature negative pressure drying for 1~4 h; Add the dried desulfurization catalyst slag and sulfur concentrate sand into the sealed ball-milling tank of the ball-milling instrument according to the proportion, add titanium alloy balls with a diameter of 10~30 mm, the ball-to-material ratio is 10~20:1, fill the tank with liquid nitrogen, seal the sealed ball-milling tank and let it stand for 10~30 min, and ball-mill for 2~6 h.

2. The method for producing sulfuric acid from desulfurization catalyst slag according to claim 1, characterized in that, In the above Step 1, the mass ratio of the desulfurization catalyst slag to the sulfur concentrate sand is 1:9~10.

3. The method for producing sulfuric acid from desulfurization catalyst slag according to claim 1, wherein, In the above Step 2, the calcination temperature is 800~960°C, and the calcination time is 1~4 h.

4. The method for producing sulfuric acid from desulfurization catalyst slag according to claim 1, characterized in that, In the above Step 2, the catalytic process of sulfur dioxide in the catalytic contact oxidation tower is as follows: Under the condition of a temperature of 180~200°C, sulfur dioxide reacts with oxygen in the air to generate sulfur trioxide, the volume ratio of sulfur dioxide gas to air is 1:1.5~2, and the air is dehydrated by an 88~98% sulfuric acid solution.

5. The method for producing sulfuric acid from desulfurization catalyst slag according to claim 1, characterized in that, In the above Step 3, the three-stage tail gas treatment system includes: The first-stage absorption tower is an 88~98% sulfuric acid solution absorption tower, the second-stage absorption tower is a 6~20% sulfuric acid solution absorption tower, and the third-stage absorption tower is a mixed solution absorption tower of 2~10% sulfuric acid and 5~25% hydrogen peroxide.

6. The method for producing sulfuric acid from desulfurization catalyst slag according to claim 1, characterized in that, In the above Step 3, the process of the mixed gas passing through the three-stage tail gas treatment system is as follows: Ⅰ. The mixed gas first enters the first-stage absorption tower, and sulfur trioxide in the mixed gas reacts with water in the sulfuric acid solution in the first-stage absorption tower to generate sulfuric acid, and adjust the mass fraction of sulfuric acid to 88~98% by injecting water; Ⅱ. The remaining gas then enters the second-stage absorption tower, and the unreacted residual sulfur trioxide in the remaining gas reacts with water in the sulfuric acid solution in the second-stage absorption tower to generate sulfuric acid; Ⅲ. The remaining gas then enters the third-stage absorption tower, and the uncatalyzed sulfur dioxide in the remaining gas reacts with hydrogen peroxide in the third-stage absorption tower to produce sulfur trioxide, and the generated sulfur trioxide reacts with water in the mixed solution to generate sulfuric acid; The mixed solution is a mixed solution of 2~10% sulfuric acid and 5~25% hydrogen peroxide.

7. The method for producing sulfuric acid from desulfurization catalyst slag according to claim 1, characterized in that, In the above Step 3, ultrasonic cavitation treatment is added during the process of the mixed gas being treated by the three-stage tail gas treatment system. The process is as follows: Ⅰ. The mixed gas first enters the primary absorption tower. At this time, ultrasonic cavitation treatment is carried out on the sulfuric acid solution in the primary absorption tower. Sulfur trioxide in the mixed gas reacts with water in the sulfuric acid solution in the primary absorption tower to form sulfuric acid. The mass fraction of sulfuric acid is adjusted to 88 - 98% by injecting water; Ⅱ. The remaining gas then enters the secondary absorption tower. At this time, ultrasonic cavitation treatment is carried out on the sulfuric acid solution in the secondary absorption tower. The unreacted residual sulfur trioxide in the remaining gas reacts with water in the sulfuric acid solution in the secondary absorption tower to form sulfuric acid; Ⅲ. The remaining gas then enters the tertiary absorption tower. At this time, ultrasonic cavitation treatment is carried out on the mixed liquid in the tertiary absorption tower. The uncatalyzed sulfur dioxide in the remaining gas reacts with hydrogen peroxide in the tertiary absorption tower to produce sulfur trioxide, and the generated sulfur trioxide then reacts with water in the mixed liquid to form sulfuric acid; the mixed liquid is a mixture of 2 - 10% sulfuric acid and 5 - 25% hydrogen peroxide; The ultrasonic frequency of the ultrasonic cavitation treatment is 30 - 40 kHz, the ultrasonic time is 3 - 5 min, and the ultrasonic interval is 3 - 5 min.

8. The method for producing sulfuric acid from desulfurization catalyst slag according to claim 1, characterized in that, The recovered iron powder in step Ⅲ includes the iron powder in the electrostatic precipitator and the iron powder that has not been completely reacted in the fluidized bed furnace.