Green energy-saving treatment method and system for low-temperature flue gas containing low-concentration SO2
By designing a green energy-saving treatment system combining SO2 oxidation reactor and glass tube acid heat exchanger in the metal mine smelting industry, the flue gas preheating is solved by using the catalytic oxidation reaction and the heat during the condensed acid process. The problem of the difficulty in recycling and utilization of low-temperature flue gas at concentration SO2 has achieved efficient, low-cost and low-carbon emission treatment effects.
Patent Information
- Application Number
- CN202411483149.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-23
- Publication Date
- 2024-12-10
AI Technical Summary
In the metal mine smelting industry, low-temperature flue gas with low concentrations of SO2 is difficult to efficiently recycle and utilize. Conventional treatment methods require a large amount of fuel or electricity consumption, resulting in high costs and high carbon emissions.
A green energy-saving treatment system was designed, including an SO2 oxidation reactor and a glass tube-forming acid heat exchanger. The flue gas is preheated by catalytic oxidation reaction and heat released during the condensation process, and combined with an electric heater to assist in heating, the flue gas is achieved. Effective recycling and treatment of SO2 in flue gas.
It significantly reduces energy consumption and carbon emissions, realizes efficient recycling and management of low-concentration SO2 flue gas, reduces the treatment costs of mining and smelting plants, and can produce concentrated sulfuric acid, which has low energy consumption, short process, small investment and land occupation Small, simple operation and stable operation.
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Figure CN119103875A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of smelting flue gas treatment and chemical industry, and in particular to a green energy-saving treatment method and system for low-temperature flue gas containing low-concentration SO2. Background Art
[0002] In many metal ore smelting industries, the flue gas roasted in the ore powder decomposition kiln contains low-concentration SO2, which needs to be recovered and processed. Due to the high dust content in the flue gas, it must be purified after electrostatic precipitator treatment. The flue gas temperature after acid washing or water washing is about 36-40°C, and the SO2 content is about 2.0%-3.0% (vt). Under such working conditions, it is difficult and costly to recover the SO2 in the flue gas.
[0003] For materials with low SO2 concentration, the conventional solution is the WSA wet sulfuric acid production solution. Since the flue gas temperature is very low, the flue gas needs to be heated to reach the ignition point of the SO2 oxidation wet process catalyst. The heating methods that can be used are incinerator heating and electric heater heating. No matter which method is used, it will lead to continuous large amounts of fuel or electricity consumption, and the processing cost is high, which makes mining and smelting manufacturers bear huge economic pressure to deal with low concentrations of SO2 in the flue gas. Summary of the invention
[0004] The present invention designs a new process route for treating the low-temperature flue gas containing low-concentration SO2, and utilizes the heat generated in the reaction process to achieve energy saving, consumption reduction, and low-carbon emission reduction effects.
[0005] The purpose of the present invention can be achieved through the following technical solutions:
[0006] A green energy-saving treatment system for low-temperature flue gas containing low-concentration SO2, the system comprising a SO2 oxidation reactor and a glass tube acid-forming heat exchanger, the output end of the low-concentration SO2 is connected to a flue gas preheater, and the output end of the heat exchange gas of the glass tube acid-forming heat exchanger is connected to the flue gas preheater;
[0007] The output end of the flue gas preheater is connected to the bottom end of the SO2 oxidation reactor, and the SO2 oxidation reactor is provided with a built-in second heat exchanger, a second catalytic oxidation bed, a built-in first heat exchanger and a first catalytic oxidation bed from bottom to top; the built-in second heat exchanger is connected to the built-in first heat exchanger through a pipeline, and the output end of the built-in first heat exchanger is connected to the top of the SO2 oxidation reactor;
[0008] The output end of the air duct is connected to the upper part of the SO2 oxidation reactor and the glass tube acid-forming heat exchanger; the output end of the bottom of the SO2 oxidation reactor is connected to the glass tube acid-forming heat exchanger.
[0009] In the above system, the output end of the air duct is connected to the upper part of the SO2 oxidation reactor through an electric heater.
[0010] In the above system, the output end of the built-in first heat exchanger is connected to the input end of the electric heater.
[0011] In the above system, the bottom output end of the glass tube acid forming heat exchanger is connected to the sulfuric acid circulation tank.
[0012] In the above system, a sulfuric acid circulation pump is provided in the glass tube acid forming heat exchanger, and the sulfuric acid circulation pump is connected to a sulfuric acid cooler. Part of the sulfuric acid from the sulfuric acid cooler is output as a finished product, and the other part is connected to the output end of the glass tube acid forming heat exchanger.
[0013] A green and energy-saving treatment method for low-temperature flue gas containing low-concentration SO2 is achieved by utilizing the above-mentioned system. The method comprises the following steps: preheating the purified low-concentration SO2 flue gas using a flue gas preheater, and then sequentially allowing the flue gas to enter the built-in second heat exchanger and the built-in first heat exchanger of the SO2 oxidation reactor for heat exchange and temperature increase; then the flue gas is output from the second heat exchanger and enters from the top of the SO2 oxidation reactor, and sequentially enters the second bed layer and the first bed layer of the SO2 oxidation reactor for reaction, and after the reaction is completed, the flue gas is output from the bottom of the SO2 oxidation reactor and transported to the glass tube acid-forming heat exchanger.
[0014] In the above method: the flue gas preheater preheats the flue gas to 170-185°C; the SO2 flue gas temperature output by the built-in first heat exchanger is 390-420°C.
[0015] In the above method: the temperature of the purified low-concentration SO2 flue gas is 36-40°C, and the volume concentration of the low-concentration SO2 flue gas is <4%;
[0016] When the concentration of SO2 is lower than 2.4%, the heat generated by the catalytic oxidation reaction and condensation into acid is not enough to heat the low-temperature SO2 flue gas to the catalyst ignition point temperature, and an electric heater needs to be turned on to assist in heating;
[0017] When the concentration of SO2 in the flue gas is above 2.4%, the reaction heat of the SO2 catalytic oxidation reaction and the SO3 hydration reaction as well as the condensation heat released during the condensation into acid process can be fully utilized to heat the low-temperature SO2 flue gas to the temperature required for catalyst ignition.
[0018] In the above method: the hot air from the air outlet of the glass tube acidifying heat exchanger is transported to the flue gas preheater for preheating the gas.
[0019] In the above method: the sulfuric acid output from the glass tube acid heat exchanger enters the sulfuric acid circulation tank, a part of the sulfuric acid passing through the matching sulfuric acid cooler returns to the sulfuric acid circulation tank for temperature adjustment, and the remaining part is sent to the boundary area.
[0020] In some more preferred technical solutions, an electric heater is provided for supplementary heating, which is activated when the SO2 concentration in the flue gas is low, so as to ensure that the temperature of the first bed layer of the flue gas entering the SO2 oxidation reactor reaches the catalyst ignition point; a secondary line is led from the air fan to the electric heating furnace for air supply during the start-up heating stage;
[0021] Due to the low SO2 concentration, the SO2 oxidation reactor can achieve a total conversion rate of about 99.4% by setting up two catalyst beds.
[0022] In the technical solution of the present invention, the temperature of the flue gas to be treated is lower than the ignition point temperature of the conventional SO2 catalyst, and the temperature of the flue gas after purification is even lower, about 36 to 40°C.
[0023] In the technical solution of the present invention, the concentration of SO2 in the flue gas to be treated is relatively low, and the concentration is <4%.
[0024] In the technical solution of the present invention, a built-in heat exchanger is used to exchange heat between the high-temperature SO3 flue gas generated after the catalytic oxidation reaction and the low-temperature SO2 flue gas in the tube of the built-in heat exchanger, thereby improving the heat exchange efficiency. The temperature of the SO2 flue gas after the heat exchange reaches the catalyst ignition point temperature of 390 to 420°C.
[0025] The present invention starts from the direction of reducing energy consumption and carbon emissions. Aiming at the low-temperature flue gas containing low-concentration SO2 commonly found in mining and smelting plants, a new process is adopted, which consumes no or as little fuel and electric energy as possible, and realizes the recovery and treatment of SO2 in the flue gas and makes it meet the emission standards.
[0026] The implementation of this process can fully utilize the reaction heat and condensation heat released during the catalytic oxidation of SO2 to SO3 and the generation of H2SO4 by SO3 and water and the condensation to acid, and heat the low-temperature flue gas to a temperature that meets the catalyst ignition requirements. This can not only significantly reduce the energy consumption of mining and smelting plants in treating flue gas containing low concentrations of SO2, but also recover SO2 in the flue gas to produce concentrated sulfuric acid. This process has significant advantages such as low energy consumption, short process, low investment, small footprint, simple operation, and stable operation. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 Schematic diagram of the device of the present invention.
[0028] Among them, 1- flue gas preheater, 2- thermal fan, 3- electric heater, 4- SO2 oxidation reactor, 5- built-in first heat exchanger, 6- built-in second heat exchanger, 7- glass tube acid heat exchanger, 8- air fan, 9- sulfuric acid cooler, 10- sulfuric acid circulation pump, 11- sulfuric acid circulation tank. DETAILED DESCRIPTION
[0029] The present invention is further described below in conjunction with embodiments, but the protection scope of the present invention is not limited thereto:
[0030] like Figure 1 A green energy-saving treatment system for low-temperature flue gas containing low-concentration SO2, the system comprising a SO2 oxidation reactor 4 and a glass tube acidification heat exchanger 7, the output end of the low-concentration SO2 is connected to the flue gas preheater 1, and the output end of the heat exchange gas of the glass tube acidification heat exchanger 7 is connected to the flue gas preheater 1;
[0031] The output end of the flue gas preheater 1 is connected to the bottom end of the SO2 oxidation reactor 4, and the SO2 oxidation reactor 4 is provided with a built-in second heat exchanger 6, a second catalytic oxidation bed, a built-in first heat exchanger 5 and a first catalytic oxidation bed from bottom to top; the built-in second heat exchanger 6 is connected to the built-in first heat exchanger 5 through a pipeline, and the output end of the built-in first heat exchanger 5 is connected to the top of the SO2 oxidation reactor 4;
[0032] The output end of the air duct is connected to the upper part of the SO2 oxidation reactor 4 and the glass tube acid-forming heat exchanger 7; the output end of the bottom of the SO2 oxidation reactor 4 is connected to the glass tube acid-forming heat exchanger 7.
[0033] The output end of the air duct is connected to the upper part of the SO2 oxidation reactor 4 through the electric heater 3.
[0034] The output end of the built-in first heat exchanger 5 is connected to the input end of the electric heater 3 .
[0035] The bottom output end of the glass tube acid heat exchanger 7 is connected to the sulfuric acid circulation tank 11.
[0036] A sulfuric acid circulation pump 10 is provided in the glass tube acid heat exchanger 7 , and the sulfuric acid circulation pump 10 is connected to the sulfuric acid cooler 9 . A part of the sulfuric acid from the sulfuric acid cooler 9 is output as a finished product, and the other part is connected to the output end of the glass tube acid heat exchanger 7 .
[0037] Example 1
[0038] A green and energy-saving method for treating low-temperature flue gas containing low-concentration SO2. 3 / h smelting flue gas with a SO2 volume fraction of 2.9% in a specific implementation case:
[0039] The purified low-temperature smelting flue gas can be preheated to 180°C by passing through the flue gas preheater, and then passes through the built-in second heat exchanger and the built-in first heat exchanger in sequence. The flue gas temperature rises to 416°C and can directly enter the first catalytic bed of the SO2 oxidation reactor. After two-stage reaction, the SO3 flue gas temperature is heat exchanged to about 290°C and enters the glass tube acid heat exchanger, and the output concentrated sulfuric acid concentration is about 96.8% to 97.5%.
[0040] In this implementation case, the SO2 content is 2.9%, and the heat generated during the reaction process can be fully utilized to heat the low-temperature smelting flue gas to about 416°C, reaching the ignition point of the SO2 oxidation wet process catalyst. No additional natural gas incinerator heating or electric heater heating is required, which greatly reduces operating costs.
[0041] A green and energy-saving treatment method for low-temperature flue gas containing low-concentration SO2, and its application in smelting and purification flue gas with different SO2 concentration ranges:
[0042] The flue gas temperature entering the first catalytic bed of the SO2 oxidation reactor is related to the SO2 content in the purified smelting gas. According to calculations and process simulations, when the SO2 content in the smelting gas is between 2.4% and 2.6%, the flue gas temperature entering the first catalytic bed of the SO2 oxidation reactor can reach above 390°C, and it is necessary to load some low-temperature cesium-containing catalyst in the first catalytic bed of the SO2 oxidation reactor; when the SO2 content in the smelting gas is between 2.78% and 3.0%, the temperature can reach above 415°C, and the first catalytic bed of the SO2 oxidation reactor is loaded with conventional wet catalyst.
[0043] When the SO2 content in the smelting gas is lower than 2.4%, the high-temperature SO3 flue gas generated in the two-stage catalytic bed layers of the SO2 oxidation reactor is not enough to exchange the preheated purified flue gas to above 390°C, and the electric heater needs to be turned on to assist in heating. The turning-on power of the electric heater is related to the SO2 content in the smelting gas. The higher the SO2 content, the smaller the required heating power.
[0044] The present invention provides a green and energy-saving method for treating low-temperature flue gas containing low-concentration SO2 to treat 22000Nm 3 Taking the smelting purified flue gas containing 2.9% SO2 volume fraction / h as an example, a comparative calculation was carried out.
[0045] 1) Dry acid production process: Due to the low volume fraction of SO2, if the dry sulfuric acid production process is adopted, the entire reaction process cannot reach self-heating balance, and the electric heater needs to be turned on continuously. The heating power of this gas volume is about 1800-2200kW, and the electricity consumption is huge. At 0.65 yuan per kilowatt-hour, the electricity cost of the electric heater alone will reach 9.36 million yuan to 11.44 million yuan per year, and there will be no by-product profits such as medium and low-pressure steam to offset the electricity consumption. Due to the high electricity consumption, the process has relatively poor carbon emission indicators and energy-saving indicators.
[0046] 2) Simple WSA wet sulfuric acid production process: Since the temperature of the flue gas after purification is only 36-40°C, and can only reach about 170°C after preheating, it is necessary to set up an electric heater or a natural gas incinerator to heat the flue gas and raise the temperature of the flue gas to 390-420°C before it can enter the SO2 conversion unit for catalytic oxidation reaction. The natural gas consumption or electricity consumption at this stage is very considerable, and the natural gas consumption is about 200-250Nm 3 / h, at 4.0 yuan per cubic meter of natural gas, the cost of natural gas used to heat the flue gas will reach 6.4 million to 8 million yuan, in addition to the costs of incinerators, burners, supporting instrument pipelines, and civil engineering and public works. This method can use the heat released by the conversion to recover part of the medium-pressure steam during the conversion process, with a steam volume of about 3.5 to 4.5 t / h. The profit from the external sale of steam can offset part of the natural gas expenditure, but the overall comparison is still that the natural gas cost is higher. In addition, the carbon emissions caused by burning natural gas are relatively high.
[0047] 3) The present invention provides a green and energy-saving treatment method for low-temperature flue gas containing low-concentration SO2: the purified low-temperature smelting flue gas can be preheated to about 180°C by passing through a flue gas preheater, and then passes through a built-in second heat exchanger and a built-in first heat exchanger in sequence, and the flue gas temperature rises to about 416°C, reaching the ignition point of the SO2 oxidation wet process catalyst, and can directly enter the first catalytic bed layer of the SO2 oxidation reactor without the need for additional heating by a natural gas incinerator or an electric heater, thereby greatly reducing operating costs.
Claims
1. A green energy-saving treatment system for low-temperature flue gas containing low-concentration SO2, characterized in that: The system comprises an SO2 oxidation reactor (4) and a glass tube acidification heat exchanger (7), wherein the output end of the low-concentration SO2 is connected to a flue gas preheater (1), and the output end of the heat exchange gas of the glass tube acidification heat exchanger (7) is connected to the flue gas preheater (1); The output end of the flue gas preheater (1) is connected to the bottom end of the SO2 oxidation reactor (4), and the SO2 oxidation reactor (4) is provided with a built-in second heat exchanger (6), a second catalytic oxidation bed, a built-in first heat exchanger (5) and a first catalytic oxidation bed from bottom to top; the built-in second heat exchanger (6) is connected to the built-in first heat exchanger (5) through a pipeline, and the output end of the built-in first heat exchanger (5) is connected to the top of the SO2 oxidation reactor (4); The output end of the air duct is connected to the upper part of the SO2 oxidation reactor (4) and the glass tube acid heat exchanger (7); the output end of the bottom of the SO2 oxidation reactor (4) is connected to the glass tube acid heat exchanger (7).
2. The green energy-saving treatment system for low-temperature flue gas containing low-concentration SO2 according to claim 1 is characterized in that: The output end of the air duct is connected to the upper part of the SO2 oxidation reactor (4) through an electric heater (3).
3. The green energy-saving treatment system for low-temperature flue gas containing low-concentration SO2 according to claim 1 is characterized in that: The output end of the built-in first heat exchanger (5) is connected to the input end of the electric heater (3).
4. The green energy-saving treatment system for low-temperature flue gas containing low-concentration SO2 according to claim 1 is characterized in that: The bottom output end of the glass tube acid heat exchanger (7) is connected to the sulfuric acid circulation tank (11).
5. The green energy-saving treatment system for low-temperature flue gas containing low-concentration SO2 according to claim 4 is characterized in that: A sulfuric acid circulation pump (10) is arranged in the glass tube acid heat exchanger (7). The sulfuric acid circulation pump (10) is connected to the sulfuric acid cooler (9). A part of the sulfuric acid from the sulfuric acid cooler (9) is output as a finished product, and the other part is connected to the output end of the glass tube acid heat exchanger (7).
6. A green and energy-saving method for treating low-temperature flue gas containing low-concentration SO2 by using the system of claim 1, characterized in that: The method comprises the following steps: preheating the purified low-concentration SO2 flue gas using a flue gas preheater (1), and then sequentially entering a built-in second heat exchanger (6) and a built-in first heat exchanger (5) of a SO2 oxidation reactor (4) for heat exchange and temperature increase; then the flue gas is output from the second heat exchanger (6) and enters from the top of the SO2 oxidation reactor (4), and sequentially enters the second bed layer and the first bed layer of the SO2 oxidation reactor (4) for reaction, and after the reaction is completed, the flue gas is output from the bottom of the SO2 oxidation reactor and transported to a glass tube acid-forming heat exchanger (7).
7. The method according to claim 6, characterized in that: The flue gas preheater (1) preheats the flue gas to 170-185°C; the temperature of the SO2 flue gas output by the built-in first heat exchanger (5) is 390-420°C.
8. The method according to claim 6, characterized in that: The temperature of the low-concentration SO2 flue gas after purification is 36-40°C, and the volume concentration of the low-concentration SO2 flue gas is <4%; When the concentration of SO2 is lower than 2.4%, the heat generated by the catalytic oxidation reaction and condensation into acid is not enough to heat the low-temperature SO2 flue gas to the catalyst ignition point temperature, and an electric heater needs to be turned on to assist in heating; When the concentration of SO2 in the flue gas is above 2.4%, the reaction heat of the SO2 catalytic oxidation reaction and the SO3 hydration reaction as well as the condensation heat released during the condensation into acid process can be fully utilized to heat the low-temperature SO2 flue gas to the temperature required for catalyst ignition.
9. The method according to claim 6, characterized in that: The hot air from the air outlet of the glass tube acid heat exchanger (7) is transported to the flue gas preheater (1) for preheating the gas.
10. The method according to claim 6, characterized in that: The sulfuric acid output from the glass tube acid forming heat exchanger (7) enters the sulfuric acid circulation tank (11), and a part of the sulfuric acid passes through the matching sulfuric acid cooler (9) and returns to the sulfuric acid circulation tank (11) for temperature adjustment, and the remaining part is sent to the boundary area.