Green energy-saving treatment system for low-temperature flue gas containing low-concentration SO2
By designing a low-temperature flue gas green energy-saving treatment system with low concentration SO2, the reaction heat self-heating and heat exchange are used to solve the problem of high energy consumption of low-temperature flue gas treatment, and efficient and low-cost SO2 recovery and concentrated sulfuric acid production are achieved.
Patent Information
- Application Number
- CN202422562555.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-23
- Publication Date
- 2025-08-26
- Estimated Expiration
- 2034-10-23
AI Technical Summary
In the metal mine smelting industry, low-temperature flue gas treatment with low concentration SO2 has problems of high energy consumption and high cost, especially because the flue gas temperature is low, additional fuel or electricity is required to heat up to reach the starting point of the SO2 oxidation catalyst.
A green energy-saving treatment system for low-temperature flue gas containing low-concentration SO2 is designed, and the heat during the reaction is used to heat up self-heating, and the SO2 oxidation reactor and glass tube form an acid heat exchanger to realize the self-heating and heat exchange of the flue gas. Combined with a built-in heat exchanger and a catalytic oxidation bed layer, the catalyst start-up temperature is reached.
It realizes efficient treatment of low-temperature flue gas, reduces energy consumption and carbon emissions, reduces fuel and electricity consumption, and can recover and produce concentrated sulfuric acid, which has the advantages of low energy consumption, short process, low investment, simple operation and stable operation.
Smart Images
Figure CN223271689U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of smelting flue gas treatment and chemical industry, and in particular to a green energy-saving treatment system for low-temperature flue gas containing low-concentration SO2. Background Art
[0002] In many metal 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 method is to use the WSA wet sulfuric acid production solution. Due to the low flue gas temperature, 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 include incinerator heating and electric heater heating. Regardless of which method is used, it will lead to continuous large-scale fuel or electricity consumption, and the processing cost is high, which puts mining and smelting manufacturers under tremendous economic pressure to deal with low-concentration SO2 in the flue gas. Utility Model Content
[0004] The utility model is a new process treatment route designed for the treatment of the low-temperature flue gas containing low-concentration SO2, which uses the heat generated in the reaction process to achieve energy saving, consumption reduction, low carbon emission reduction and other effects.
[0005] The purpose of the utility model can be achieved through the following technical solutions:
[0006] A green and energy-saving treatment system for low-temperature flue gas containing low-concentration SO2, the system comprising a SO2 oxidation reactor and a glass tube acidification heat exchanger, wherein 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 acidification 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 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 heat exchanger, and the sulfuric acid circulation pump is connected to the sulfuric acid cooler. Part of the sulfuric acid from the sulfuric acid cooler is output as finished product, and the other part is connected to the output end of the glass tube acid heat exchanger.
[0013] A green and energy-saving treatment method for low-temperature flue gas containing low-concentration SO2 is achieved by using the above-mentioned system. The method is to preheat the purified low-concentration SO2 flue gas using a flue gas preheater, and then the flue gas enters the built-in second heat exchanger and the built-in first heat exchanger of the SO2 oxidation reactor in sequence 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 enters the second bed layer and the first bed layer of the SO2 oxidation reactor in sequence for reaction. After the reaction is completed, it is output from the bottom of the SO2 oxidation reactor and transported to the glass tube acid heat exchanger.
[0014] In the above method: the flue gas preheater preheats the flue gas to 170-185°C; the temperature of the SO2 flue gas 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 SO2 catalytic oxidation reaction and 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 acidification heat exchanger is transported to the flue gas preheater for gas preheating.
[0019] In the above method, the sulfuric acid output from the glass tube acid heat exchanger enters the sulfuric acid circulation tank, a portion of the sulfuric acid passes through the matching sulfuric acid cooler and returns to the sulfuric acid circulation tank for temperature adjustment, and the remaining portion 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, to ensure that the temperature of the flue gas entering the first bed of the SO2 oxidation reactor reaches the catalyst ignition point; a secondary line is led from the air blower to the electric heating furnace for supplying air 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 utility model, 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 heat exchange reaches the catalyst ignition point temperature of 390 to 420°C.
[0025] This utility model 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, it adopts a new process that consumes no or as little fuel and electric energy as possible, realizes the recovery and treatment of SO2 in the flue gas and makes it meet emission standards.
[0026] This process fully utilizes the reaction heat and condensation heat released during the catalytic oxidation of SO2 to SO3, the reaction of SO3 with water to form H2SO4, and the condensation of SO3 into acid to heat the low-temperature flue gas to a temperature that meets the catalyst ignition requirements. This not only significantly reduces the energy consumption of mining and smelting plants in treating flue gas containing low concentrations of SO2, but also allows SO2 in the flue gas to be recovered and used to produce concentrated sulfuric acid. This process offers significant advantages such as low energy consumption, a short process flow, 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 will be further described below with reference to the following embodiments, but the scope of protection of the present invention is not limited thereto:
[0030] like Figure 1 A green and energy-saving system for treating low-temperature flue gas containing low-concentration SO2, 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 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.
[0031] The output end of the flue gas preheater 1 is connected to the bottom end of the SO2 oxidation reactor 4. 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 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.
[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 . 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 In the specific implementation case of smelting flue gas purification with a SO2 volume fraction of 2.9% per hour:
[0039] The purified low-temperature smelting flue gas can be preheated to 180°C 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 the 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 embodiment, the SO2 content is 2.9%. 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, with application in smelting 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 some low-temperature cesium-containing catalysts need to be loaded 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 catalysts.
[0043] When the SO2 content in the smelting gas is lower than 2.4%, the high-temperature SO3 flue gas generated in the two catalytic beds of the SO2 oxidation reactor is not enough to heat the preheated purified flue gas to above 390°C. The electric heater needs to be turned on to assist in heating. The 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 utility model provides a green energy-saving treatment method for low-temperature flue gas containing low-concentration SO2, which can be used to treat 22000Nm 3 Taking the smelting purified flue gas containing 2.9% SO2 volume fraction per hour as an example, comparative calculations are carried out.
[0045] 1) Dry Acid Production Process: Due to the low SO2 volume fraction, dry sulfuric acid production cannot achieve self-heating equilibrium. Electric heaters must be operated continuously. This gas volume requires heating power of approximately 1,800 to 2,200 kW, resulting in significant electricity consumption. At 0.65 yuan per kilowatt-hour, the annual electricity cost for the electric heaters alone would reach 9.36 million to 11.44 million yuan. Furthermore, there is no profit from byproducts such as medium- and low-pressure steam to offset the electricity costs. Due to this high electricity consumption, this process has relatively poor carbon emissions 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 natural gas incinerator to heat the flue gas to raise the flue gas temperature 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. Assuming a natural gas price of 4.0 yuan per cubic meter, the natural gas cost for flue gas heating would reach 6.4 million to 8 million yuan, in addition to the costs of the incinerator, burner, supporting instrumentation and pipelines, and civil engineering and utility works. This method utilizes the exothermic heat of the conversion process to recover some medium-pressure steam, producing approximately 3.5 to 4.5 tons / h. The profit from selling the steam can offset some of the natural gas costs, but overall, natural gas costs remain higher. Furthermore, burning natural gas results in high carbon emissions.
[0047] 3) The utility model 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 a flue gas temperature of about 180°C 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 in order 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 provided in the glass tube acid heat exchanger (7). The sulfuric acid circulation pump (10) is connected to the sulfuric acid cooler (9). A portion of the sulfuric acid from the sulfuric acid cooler (9) is output as a finished product, and the other portion is connected to the output end of the glass tube acid heat exchanger (7).