Method and system for treating high-temperature flue gas

Abstract

The present invention relates to the field of environmental protection chemical engineering technology, and particularly relates to a method and a system for treating high-temperature flue gas. The method comprises the following steps: (1) burning incineration raw materials, sulfur-containing raw materials and fuel to obtain high-temperature flue gas; (2) exchanging heat between the high-temperature flue gas and air to obtain high-temperature air and flue gas; (3) subjecting the flue gas to subsequent treatment to obtain acid-making process gas; (4) exchanging heat between the high-temperature air and the acid-making process gas to obtain medium-temperature air and acid-making process conversion gas; subjecting the acid-making process conversion gas to acid-making treatment to obtain sulfuric acid; (5) dividing the medium-temperature air into A-share gas and B-share gas, the A-share gas generating saturated steam, and the B-share gas superheating the saturated steam into superheated steam. The system comprises: an incineration reaction unit, a high-temperature flue gas treatment unit, a flue gas treatment unit, an acid-making process gas treatment unit, an acid-making unit and a steam treatment unit. The method can directly recycle flue gas with a high dew point temperature and a low sulfur dioxide concentration.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection chemical engineering, and particularly relates to a method and a system for treating high-temperature flue gas. Background Art

[0002] Incineration reactors in the petrochemical, coal chemical, and smelting industries usually generate high-temperature flue gas containing sulfur dioxide. When high-temperature flue gas containing sulfur dioxide and water contains elemental impurities such as sulfur, phosphorus, fluorine, and chlorine, the dew point corrosion temperature of the high-temperature flue gas can reach 350 - 400 °C, which is very high. When recovering waste heat from high-temperature flue gas to by-product steam, a waste heat boiler is usually used. To ensure that the heat recovery equipment is not corroded, the pressure rating of the waste heat boiler must ensure that the temperature of the saturated steam is above the dew point corrosion temperature. The temperature of saturated steam at 20 MPa is only 357 °C, but the boiler with a pressure rating of 20 MPa is approaching the "supercritical" pressure, and it is very difficult to manufacture. Directly using a boiler for heat recovery is no longer applicable.

[0003] Secondly, when the heat of high-temperature flue gas containing sulfur dioxide is recovered and enters the subsequent sulfuric acid production system, the heat generated by the reaction of sulfur dioxide and oxygen to form sulfur trioxide is insufficient to maintain the heat balance of the entire process. Usually, in the process of producing sulfuric acid from high-temperature flue gas containing sulfur dioxide, when the concentration of sulfur dioxide ≤ 6%, this concentration of sulfur dioxide usually requires additional heating equipment during the sulfuric acid production process. Inevitably, using additional heating equipment will bring problems such as high energy consumption and high operating costs.

[0004] In order to make full use of the thermal energy of high-temperature flue gas, there is an urgent need to adopt a suitable and efficient heat utilization technology. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problem in the prior art that flue gas with a high dew point corrosion temperature and a low sulfur dioxide concentration cannot be directly recycled, and to provide a method and a system for treating high-temperature flue gas. This method utilizes the heat of high-temperature flue gas with characteristics of high dew point corrosion temperature and low sulfur dioxide concentration to by-product steam, and at the same time realizes sulfuric acid production with a low sulfur dioxide concentration without external heating equipment, reduces the energy consumption level of the device, and improves the resource utilization rate.

[0006] To achieve the above purpose, in the first aspect of the present invention, a method for treating high-temperature flue gas is provided, wherein the method includes the following steps:

[0007] (1) Incinerate incineration raw materials, sulfur-containing raw materials, and fuel to obtain high-temperature flue gas;

[0008] (2) Exchange heat between the high-temperature flue gas and air to obtain high-temperature air and flue gas;

[0009] (3) Perform subsequent treatment on the flue gas to obtain the gas for acid making process;

[0010] (4) Exchange heat between the high-temperature air and the gas for acid making process to obtain medium-temperature air and the converted gas for acid making process; subject the converted gas for acid making process to acid making treatment to obtain sulfuric acid;

[0011] (5) Divide the medium-temperature air into A-stream gas and B-stream gas. The A-stream gas generates saturated steam, and the B-stream gas superheats the saturated steam into superheated steam; the A-stream gas and the B-stream gas that recover the superheat amount are combined and then divided into two streams of low-temperature air C and D; the low-temperature air C is used as the combustion-supporting agent for incineration treatment, and the low-temperature air D is recycled as the recycle gas.

[0012] The second aspect of the present invention provides a system for treating high-temperature flue gas. Among them, the system includes: an incineration reaction unit, a high-temperature flue gas treatment unit, a flue gas treatment unit, a gas treatment unit for acid making process, an acid making unit, and a steam treatment unit.

[0013] In the present invention, for the high-temperature flue gas containing specific components (containing elements such as sulfur, phosphorus, fluorine, and chlorine), heat exchange treatment is carried out. Using the high-temperature flue gas as the heat source, the heat of the high-temperature flue gas is fully utilized to heat up the flue gas for acid making, so as to improve the conversion rate of the acid making conversion process, reduce energy consumption and acid making cost. At the same time, using ambient air as the heat exchange carrier and taking advantage of the advantage that the high-temperature air has no requirement for the dew point corrosion temperature characteristic, the hot air directly by-produces steam, improving the resource utilization rate, which is worthy of industrial production. Description of the Drawings

[0014] Figure 1 is the process flow schematic diagram of Embodiment 1 of the present invention;

[0015] Figure 2 is the process flow schematic diagram of Embodiment 5 of the present invention;

[0016] Figure 3 is the process flow schematic diagram of Comparative Example 1 of the present invention.

[0017] Description of the Reference Numerals

[0018] 1 Incineration reaction furnace 2 High-temperature flue gas cooling unit

[0019] 3 Waste heat boiler 4 Steam superheater

[0020] 5 Economizer 6 Air blower

[0021] 7 Purification unit 8 High-temperature heat exchanger for the gas for acid making process

[0022] 9 Low-temperature heat exchanger for the gas for acid making process 10 Converter

[0023] 11 Drying unit 12 Main blower

[0024] 13 Converter Unit Heat Exchanger 1 14 Converter Unit Heat Exchanger 2

[0025] 15 Primary Absorption System 16 Converter Unit Heat Exchanger 3

[0026] 17 Secondary Absorption System 18 Tail Gas Treatment Unit

[0027] 19 Air Cooler 20 Air Cooler

[0028] 21 One - stage Electric Heating Microwave Oven 22 Four - stage Electric Heating Furnace Detailed Implementation Manner

[0029] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0030] The first aspect of the present invention provides a method for treating high - temperature flue gas, wherein the method comprises the following steps:

[0031] (1) Incinerate the incineration raw materials, sulfur - containing raw materials and fuel to obtain high - temperature flue gas;

[0032] (2) Exchange heat between the high - temperature flue gas and air to obtain high - temperature air and flue gas;

[0033] (3) Perform subsequent treatment on the flue gas to obtain acid - making process gas;

[0034] (4) Exchange heat between the high - temperature air and the acid - making process gas to obtain medium - temperature air and acid - making process conversion gas; subject the acid - making process conversion gas to acid - making treatment to obtain sulfuric acid;

[0035] (5) Divide the medium - temperature air into air stream A and air stream B. Air stream A generates saturated steam, and air stream B superheats the saturated steam into superheated steam; the air stream A and air stream B that recover the heat quantity are combined and then divided into two air streams, low - temperature air C and D; low - temperature air C is used as the combustion aid for incineration treatment, and low - temperature air D is recycled as recycle gas.

[0036] The method provided by the present invention is used for sulfuric acid production from flue gas with a high corrosion dew point temperature and a dry-based sulfur dioxide concentration of less than 5% by volume. Taking the high-temperature flue gas generated by incineration treatment as the heat source, the flue gas for sulfuric acid production is heated up to improve the conversion rate of the sulfuric acid production conversion system. In this process, no additional electric heater is required, which reduces energy consumption and sulfuric acid production costs, and can achieve the heat exchange balance in the sulfuric acid production flue gas. At the same time, taking ambient air as the heat exchange carrier, using the advantage that high-temperature air has no requirement for dew point corrosion temperature characteristics, hot air is directly used to by-product steam.

[0037] Meanwhile, the present invention makes full use of the heat of the high-temperature flue gas and the heat of each stage of hot air. It not only reduces the energy consumption in the sulfuric acid production process, with remarkable energy-saving effect, but also the by-product steam can create certain economic value.

[0038] It should be noted that the "high-temperature air" and "medium-temperature air" mentioned in the present invention only require a temperature difference of 40 - 80 degrees between steps (2) and (4).

[0039] In the present invention, there is no specific limitation on the types of components in the high-temperature flue gas. Preferably, the high-temperature flue gas contains sulfur dioxide, sulfur trioxide, water, and optionally at least one of phosphorus, fluorine, and chlorine elements; the advantage of adopting this preferred implementation is to avoid equipment corrosion and increase heat energy utilization.

[0040] In the present invention, there is no specific limitation on the content of each component in the high-temperature flue gas. Preferably, sulfur trioxide exists in the high-temperature flue gas in the presence of unsaturated water, and the volume of sulfur trioxide is less than 0.1% by volume.

[0041] In the present invention, there is no specific limitation on the concentration of each element in the high-temperature flue gas. Preferably, the phosphorus content in the high-temperature flue gas > 100 ppm by mass, the fluorine content > 100 ppm by mass, and the chlorine content > 50 ppm by mass.

[0042] In the present invention, the high-temperature flue gas contains sulfur dioxide, and there is no specific limitation on the concentration of sulfur dioxide. Preferably, the dry-based concentration of sulfur dioxide in the high-temperature flue gas is 1 - 5% by volume, and further preferably 2.5 - 5% by volume. The advantage of adopting this preferred implementation is that it is easier to obtain 98% sulfuric acid product with low energy consumption and low cost.

[0043] In the present invention, there is no specific limitation on the temperature of the high-temperature flue gas, as long as the object of the present invention can be achieved. Preferably, the temperature of the high-temperature flue gas is 900 - 1300 °C, and further preferably 950 - 1100 °C. The advantage of adopting this implementation is low energy consumption and higher heat energy utilization rate.

[0044] In the present invention, there is no specific limitation on the dosages of the respective raw materials in step (2). Preferably, the molar ratio of high-temperature flue gas to air is 0.7 - 1:1, and more preferably 0.85 - 0.9:1. The advantage of adopting this preferred embodiment is higher heat utilization efficiency and greater energy conservation.

[0045] In the present invention, there is no specific limitation on the temperature of the high-temperature air. Preferably, the temperature of the high-temperature flue gas is 690 - 850 °C, and more preferably 750 - 800 °C. The advantages of adopting this embodiment are that the material selection of the heat exchange equipment is economically reasonable, with high energy efficiency, and theoretically it will not cause an increase in steam.

[0046] In the present invention, there is no specific limitation on the temperature of the flue gas. Preferably, the temperature of the flue gas is 300 - 500 °C, and more preferably 350 - 450 °C. The advantage of adopting this embodiment is to avoid the dew point corrosion temperature.

[0047] In the present invention, there is no specific limitation on the types of the respective components in the flue gas. Preferably, the flue gas contains sulfur dioxide, sulfur trioxide, water, and optionally phosphorus element.

[0048] In the present invention, there is no specific limitation on the types of the respective components in the acid-making process gas in step (3). Preferably, in step (3), the acid-making process gas contains sulfur dioxide and sulfur trioxide.

[0049] In the present invention, there is no specific limitation on the temperature of the acid-making process gas, as long as the acid-making process can be completed. Preferably, the temperature of the acid-making process gas is 410 - 470 °C, and more preferably 420 - 465 °C. The advantage of adopting this preferred embodiment is that the conversion rate of sulfur dioxide can be > 99.8%.

[0050] In the present invention, there is no specific limitation on the dosages of the respective substances in step (4). Preferably, the molar ratio of high-temperature air to acid-making process gas is 1.4 - 2.1:1, and more preferably 1.45 - 1.9:1. The advantage of adopting this preferred embodiment is that, under the condition of a certain total heat exchange amount, the heat exchange area of the heat exchange equipment is smaller and the heat exchange efficiency is higher.

[0051] In the present invention, there is no specific limitation on the temperature of the medium-temperature air, as long as the subsequent process can be completed. Preferably, the temperature of the medium-temperature air is 600 - 760 °C, for example, it can be 600 - 700 °C, 701 - 760 °C, and any value between the two. The advantage of adopting this preferred embodiment is that, under the condition of a certain total heat exchange amount, the heat exchange area of the heat exchange equipment is smaller and the heat exchange efficiency is higher.

[0052] In the present invention, there is no specific limitation on the temperature of the conversion gas in the acid-making process, as long as the acid-making can be completed. Preferably, the temperature of the conversion gas in the acid-making process is 430 - 590 °C. The advantage of adopting this preferred embodiment is that the conversion gas in the acid-making process obtains the highest conversion rate, which can be > 99.8%.

[0053] In the present invention, the medium-temperature air is divided into two gas streams, namely stream A gas and stream B gas, and there is no specific limitation on the content of the two gas streams. Preferably, the volume ratio of stream A gas to stream B gas is 3 - 4:1. The advantage of adopting this preferred embodiment is to make full use of heat to increase the production of superheated steam.

[0054] In the present invention, there is no specific limitation on the temperature of the low-temperature air in step (5). Preferably, in step (5), the temperature of the low-temperature air is 100 - 200 °C, and more preferably 130 - 180 °C. The advantage of adopting this preferred embodiment is to save fuel consumption and reduce the energy consumption per unit product.

[0055] In the present invention, the low-temperature air is used as a combustion aid for incineration treatment to control the oxygen concentration in the incineration treatment process. Preferably, in step (5), the oxygen concentration in the incineration treatment process is controlled to be 1 - 3 vol% by adding the combustion aid. The advantage of adopting this preferred embodiment is to save fuel consumption and increase the dry-based concentration of sulfur dioxide in the reaction furnace as much as possible.

[0056] The second aspect of the present invention provides a system for treating high-temperature flue gas, wherein the system includes: an incineration reaction unit, a high-temperature flue gas treatment unit, a flue gas treatment unit, an acid-making process gas treatment unit, an acid-making unit, and a steam treatment unit.

[0057] In a preferred embodiment, the incineration reaction unit is used for incinerating incineration raw materials, sulfur-containing raw materials, and fuel to obtain high-temperature flue gas.

[0058] In the present invention, the dosages of the incineration raw materials, sulfur-containing raw materials, and fuel have been described in the first aspect and will not be elaborated here.

[0059] In a preferred embodiment, the high-temperature flue gas treatment unit is used for cooling the high-temperature flue gas to obtain high-temperature air and flue gas. The advantage of adopting this preferred embodiment is to cool the high-temperature flue gas to the flue gas dew point corrosion temperature through the cooling treatment, avoid the corrosion of equipment caused by elements such as sulfur, phosphorus, and fluorine in the high-temperature flue gas, facilitate the treatment of the high-temperature flue gas, and recover heat.

[0060] In a preferred embodiment, the high-temperature flue gas treatment unit includes one or more fixed tube sheet heat exchangers, and the high-temperature flue gas treatment unit reduces the temperature of the high-temperature flue gas to a temperature above the dew point corrosion temperature of the flue gas. The advantage of adopting this preferred embodiment is to control the flue gas temperature at the outlet of the high-temperature flue gas treatment unit through a control loop formed by the regulating valve on the air pipeline bypass entering the high-temperature flue gas treatment unit and the temperature on the flue gas pipeline at the outlet of the high-temperature flue gas treatment unit, so as to ensure that the flue gas temperature can meet the process requirements of the dew point corrosion temperature.

[0061] In the present invention, the types, contents, and temperatures of the components of the high-temperature flue gas have been described in the first aspect, and will not be elaborated here again.

[0062] In a preferred embodiment, the flue gas treatment unit is used to perform subsequent treatment on the flue gas to obtain the acid-making process gas.

[0063] In a preferred embodiment, the flue gas treatment unit includes a purification unit, a drying system, a main blower, and a converter heat exchanger I. The flue gas undergoes subsequent treatment by the flue gas treatment unit to obtain the acid-making process gas.

[0064] In the present invention, the dosage and treatment conditions of the flue gas have been described in the first aspect of the present invention, and will not be elaborated here again.

[0065] In a preferred embodiment, the acid-making process gas treatment unit is used to perform heat exchange treatment on the acid-making process gas to obtain medium-temperature air and the acid-making process conversion gas.

[0066] In a preferred embodiment, the acid-making process gas treatment unit includes a high-temperature heat exchanger for the acid-making process gas and a low-temperature heat exchanger for the acid-making process gas. The advantage of adopting this preferred embodiment is that the high-temperature air undergoes heat exchange treatment with the acid-making process gas through two heat exchange devices of the acid-making process gas treatment unit to obtain medium-temperature air and the acid-making process conversion gas, and the amount of high-temperature air entering the heat exchange device is controlled through a control loop formed by the regulating valve and the temperature to control the temperature of the acid-making process gas rising to the process requirement temperature.

[0067] In a preferred embodiment, the acid-making process gas treatment unit further includes a converter, and the converter is used to convert the acid-making process gas into the acid-making process conversion gas.

[0068] In the present invention, the components, dosages, and treatment conditions of the high-temperature air and the acid-making process conversion gas have been described in the first aspect of the present invention, and will not be elaborated here again.

[0069] In a preferred embodiment, the acid-making unit is used to treat the acid-making process conversion gas to obtain sulfuric acid.

[0070] In a preferred embodiment, the sulfuric acid production unit includes the second heat exchanger of the conversion unit, the primary absorption system, the third heat exchanger of the conversion unit, the secondary absorption system, and the tail gas treatment unit. The converted gas in the sulfuric acid production process is processed by the sulfuric acid production unit to obtain sulfuric acid.

[0071] In the present invention, the dosage and treatment conditions of the converted gas in the sulfuric acid production process have been described in the first aspect, and will not be elaborated here.

[0072] In a preferred embodiment, the steam treatment unit is used to process medium-temperature air to obtain low-temperature air, superheated steam, and saturated steam.

[0073] In a preferred embodiment, the steam treatment unit includes a waste heat boiler, a steam superheater, and an economizer.

[0074] In a preferred embodiment, the medium-temperature air is divided into A-type gas and B-type gas, and the waste heat boiler is used to by-product saturated steam from the A-type gas.

[0075] In a preferred embodiment, the steam superheater is used to by-product superheated steam from the B-type gas.

[0076] In a preferred embodiment, the economizer is used to exchange heat between the medium-temperature air leaving the steam superheater and the boiler feed water through the economizer, so that the boiler feed water becomes superheated water, further increasing the steam production and making the most of the gas temperature.

[0077] In a preferred embodiment, the temperature of the boiler feed water is 140 - 150 °C. The advantage of adopting this preferred embodiment is to produce more saturated steam.

[0078] In a preferred embodiment, the system further includes an air blower, and the air blower is used to recycle the low-temperature air D as circulating gas. The advantage of adopting this preferred embodiment is that the air after heat utilization returns to the inlet of the air blower for recycling, further saving energy and improving the conversion rate.

[0079] The present invention will be described in detail below through examples.

[0080] Example 1

[0081] Taking a 25,000-ton / year 50% by mass concentration waste sulfuric acid regeneration device as an example, high-temperature flue gas at 1100 °C is generated after the waste sulfuric acid and fuel are mixed and incinerated. The high-temperature flue gas mainly contains sulfur dioxide, water, carbon dioxide, nitrogen, oxygen, and impurities such as fluorine (about 8000 ppm by mass), phosphorus, and chlorine. The wet-based molar amount of the high-temperature flue gas is 625.72 kmol / h, the dry-based molar amount is 432.24 kmol / h, and the sulfur dioxide concentration is 3.6% by volume. The process flow is as Figure 1 shown.

[0082] The high-temperature flue gas at 625.72 kmol / h at the outlet of the incineration reactor 1 directly enters the high-temperature flue gas cooling unit 2. The high-temperature flue gas cooling unit 2 consists of two fixed tube-sheet heat exchangers. The high-temperature flue gas flows through the tube side, and the air flows through the shell side. The temperature of the high-temperature flue gas is reduced from 1100 °C to 400 °C and then enters the flue gas treatment unit. 625.72 kmol / h of air is heated from 88 °C to 800 °C to become high-temperature air. 82% by volume of the high-temperature air leaving the high-temperature flue gas cooling unit 2 enters the high-temperature heat exchanger 8 for the acid-making process gas, raising the temperature of the acid-making process gas from the outlet of the first-stage bed of the converter 10 by 62 °C. 18% by volume of the high-temperature air leaving the high-temperature flue gas cooling unit 2 enters the low-temperature heat exchanger 9 for the acid-making process gas, raising the temperature of the acid-making process gas that needs to enter the converter 10 for the secondary conversion reaction by 15 °C.

[0083] After passing through the acid-making process gas treatment unit, the high-temperature air is cooled to 750 °C. Among them, 76% by volume of the medium-temperature air at 750 °C directly enters the waste heat boiler 3 of the steam treatment unit and is cooled to 180 °C to become low-temperature air. 24% by volume of the medium-temperature air at 750 °C enters the steam superheater 4. The oxygen concentration in the incineration reactor 1 is controlled to make 58.8% of the low-temperature air at 180 °C after being cooled by the waste heat boiler 3 enter the incineration reactor 1 for combustion support, so that the oxygen concentration in the incineration reactor is 2.93% by volume. The waste heat boiler 3 generates 4.3 t / h of saturated steam at 0.5 MPa (G). In the steam superheater 4, the heat of 24% by volume of the medium-temperature air at 750 °C is used to superheat the saturated steam at 0.5 MPa (G) into superheated steam at 330 °C. The air at 380 °C leaving the steam superheater 4 enters the economizer 5 and is cooled to 180 °C to heat the boiler feed water. The 4.52 t / h of boiler feed water is heated from 104 °C to 150 °C and then enters the steam drum of the waste heat boiler 3. All the low-temperature air after the heat is used, except for that entering the incineration reactor 1 for combustion support, returns to the inlet of the air blower 6 for recycling.

[0084] Example 2

[0085] Taking a 25,000-ton / year 35% concentration waste sulfuric acid regeneration device as an example, high-temperature flue gas at 1100 °C is generated after the waste sulfuric acid and fuel are mixed and incinerated. The high-temperature flue gas mainly contains sulfur dioxide, water, carbon dioxide, nitrogen, oxygen, and impurities such as fluorine (about 7000 ppm by mass), phosphorus, and chlorine. The wet-based molar amount of the high-temperature flue gas is 679 kmol / h. The dry-based molar amount is 456.82 kmol / h, and the sulfur dioxide concentration is 2.41% by volume.

[0086] The high-temperature flue gas at 679 kmol / h at the outlet of the incineration reactor 1 directly enters the high-temperature flue gas cooling unit 2. The high-temperature flue gas cooling unit 2 consists of two fixed tube-sheet heat exchangers. The high-temperature flue gas flows through the tube side, and the air flows through the shell side. The temperature of the high-temperature flue gas is reduced from 1100 °C to 400 °C and then enters the flue gas treatment unit. 748.8 kmol / h of air is heated from 88 °C to 750 °C to become high-temperature air. 81% of the high-temperature air leaving the high-temperature flue gas cooling unit 2 enters the high-temperature heat exchanger 8 for the acid-making process gas, raising the temperature of the acid-making process gas from the outlet of the first-stage bed of the converter 10 by 80 °C. 19% of the high-temperature air leaving the high-temperature flue gas cooling unit 2 enters the low-temperature heat exchanger 9 for the acid-making process gas, raising the temperature of the acid-making process gas that needs to enter the converter 10 for the secondary conversion reaction by 20 °C.

[0087] After passing through the acid-making process gas treatment unit, the high-temperature air is cooled to 685 °C. 79% of the 685 °C medium-temperature air directly enters the waste heat boiler 3 of the steam treatment unit and is cooled to 180 °C to become low-temperature air. 21% of the 685 °C medium-temperature air enters the steam superheater 4. The oxygen concentration in the incineration reactor 1 is controlled to make 58.8% of the 180 °C low-temperature air after being cooled by the waste heat boiler 3 enter the incineration reactor 1 for combustion support, so that the oxygen concentration in the incineration reactor 1 is 2.36%. The waste heat boiler 3 generates 4.39 t / h of saturated steam at 0.5 MPa (G). In the steam superheater 4, the heat of 21% of the 685 °C medium-temperature air is used to superheat the saturated steam at 0.5 MPa (G) into superheated steam at 320 °C. The 370 °C air leaving the steam superheater 4 enters the economizer 5 and is cooled to 180 °C to heat the boiler feed water. The 4.61 t / h of boiler feed water is heated from 104 °C to 148 °C and then enters the steam drum of the waste heat boiler 3. After the heat is utilized, all the low-temperature air except that entering the incineration reactor 1 for combustion support returns to the inlet of the air blower 6 for recycling.

[0088] Example 3

[0089] Taking a 25,000-ton / year 65% concentration waste sulfuric acid regeneration device as an example, the waste sulfuric acid and fuel are mixed and incinerated to produce high-temperature flue gas at 1100 °C. The high-temperature flue gas mainly contains sulfur dioxide, water, carbon dioxide, nitrogen, oxygen and impurities such as fluorine, phosphorus and chlorine. The wet-based molar amount of the high-temperature flue gas is 560.7 kmol / h. The dry-based molar amount is 422.97 kmol / h, and the sulfur dioxide concentration is 4.78 vol%.

[0090] The high-temperature flue gas at 560.7 kmol / h at the outlet of the incineration reactor 1 directly enters the high-temperature flue gas cooling unit 2, which consists of two fixed tube sheet heat exchangers. The high-temperature flue gas flows through the tube side, and the air flows through the shell side. The temperature of the high-temperature flue gas is reduced from 1100 °C to 400 °C and then enters the flue gas treatment unit. 625.5 kmol / h of air is heated from 91 °C to 800 °C to become high-temperature air. 85% of the high-temperature air leaving the high-temperature flue gas cooling unit enters the high-temperature heat exchanger 8 for the acid-making process gas, raising the temperature of the acid-making process gas from the outlet of the first-stage bed of the converter 10 by 50 °C. 15% of the high-temperature air leaving the high-temperature flue gas cooling unit 2 enters the low-temperature heat exchanger 9 for the acid-making process gas, raising the temperature of the acid-making process gas that needs to enter the converter for the secondary conversion reaction by 10 °C.

[0091] After passing through the acid-making process gas treatment unit, the high-temperature air is cooled to 755 °C. 78% of the 755 °C medium-temperature air directly enters the waste heat boiler 3 of the steam treatment unit and is cooled to 180 °C to become low-temperature air. 22% of the 755 °C medium-temperature air enters the steam superheater 4. The oxygen concentration in the incineration reactor 1 is controlled to make 57.14% of the 180 °C low-temperature air enter the incineration reactor 1 for combustion support after being cooled by the waste heat boiler 3, so that the oxygen concentration in the incineration reactor 1 is 2.58%. The waste heat boiler 3 generates 4.15 t / h of saturated steam at 0.5 MPa(G). In the steam superheater 4, the heat of 22% of the 755 °C medium-temperature air is used to superheat the 0.5 MPa(G) saturated steam into superheated steam at 350 °C. The 380 °C air leaving the steam superheater 4 enters the economizer 5 and is cooled to 180 °C to heat the boiler feed water. The 4.36 t / h of boiler feed water is heated from 104 °C to 148 °C and then enters the steam drum of the waste heat boiler 3. After the heat is utilized, all the low-temperature air except that entering the incineration reactor 1 for combustion support returns to the inlet of the air blower 6 for recycling.

[0092] Example 4

[0093] Compared with Example 1, taking the 25,000-ton / year 50% concentration waste sulfuric acid regeneration device using heat to produce saturated steam as an example, the waste sulfuric acid and fuel are mixed and incinerated to produce high-temperature flue gas at 1100 °C. The high-temperature flue gas mainly contains sulfur dioxide, water, carbon dioxide, nitrogen, oxygen, and impurities such as fluorine (about 8000 ppm by mass), phosphorus, and chlorine. The wet-base molar amount of the high-temperature flue gas is 665.2 kmol / h. The dry-base molar amount is 464.2 kmol / h, and the sulfur dioxide concentration is 3.38 vol%.

[0094] The high-temperature flue gas at 665.2 kmol / h at the outlet of the incineration reactor 1 directly enters the high-temperature flue gas cooling unit 2. The high-temperature flue gas cooling unit 2 consists of two fixed tube-sheet heat exchangers. The high-temperature flue gas flows through the tube side, and the air flows through the shell side. The temperature of the high-temperature flue gas is reduced from 1100 °C to 400 °C and then enters the flue gas treatment unit. 665.2 kmol / h of air is heated from 75 °C to 800 °C to become high-temperature air. 82% of the high-temperature air exiting the high-temperature flue gas cooling unit 2 enters the high-temperature heat exchanger 8 for the acid-making process gas, raising the temperature of the acid-making process gas from the outlet of the first-stage bed of the converter 10 by 62 °C. 18% of the high-temperature air exiting the high-temperature flue gas cooling unit 2 enters the low-temperature heat exchanger 9 for the acid-making process gas, raising the temperature of the acid-making process gas that needs to enter the converter 10 for the secondary conversion reaction by 15 °C.

[0095] After passing through the acid-making process gas treatment unit, the air is cooled to 750 °C. 100% of the 750 °C medium-temperature air directly enters the waste heat boiler 3 of the steam treatment unit, and is cooled to 180 °C to become low-temperature air. It enters the economizer 5 and is cooled to 145 °C to heat the boiler feed water. 58.8% of the 145 °C air after being cooled by the economizer 5 enters the incineration reactor 1 for combustion support by controlling the oxygen concentration in the incineration reactor 1, so that the oxygen concentration in the incineration reactor 1 is 2.76%. The waste heat boiler 3 generates 6.1 t / h of saturated steam at 0.5 MPa(G). All the air after the heat is utilized, except for that entering the incineration reactor 1 for combustion support, returns to the inlet of the air blower 6 for recycling.

[0096] Example 5

[0097] Compared with Example 1, taking the saturated steam produced by using heat in a 25,000-ton / year waste sulfuric acid regeneration device with a concentration of 35% by mass as an example, the waste sulfuric acid and fuel are mixed and incinerated to produce high-temperature flue gas at 1100 °C. The high-temperature flue gas mainly contains sulfur dioxide, water, carbon dioxide, nitrogen, oxygen, and impurities such as fluorine (about 8000 ppm by mass), phosphorus, and chlorine. The wet-based molar amount of the high-temperature flue gas is 690.6 kmol / h. The dry-based molar amount is 466.1 kmol / h, and the sulfur dioxide concentration is 2.36% by volume.

[0098] The high-temperature flue gas at 690.6 kmol / h at the outlet of the incineration reactor 1 directly enters the high-temperature flue gas cooling unit 2. The high-temperature flue gas cooling unit 2 consists of two fixed tube-sheet heat exchangers. The high-temperature flue gas flows through the tube side, and the air flows through the shell side. The temperature of the high-temperature flue gas is reduced from 1100 °C to 400 °C and then enters the flue gas treatment unit. 690.6 kmol / h of air is heated from 85 °C to 690 °C to become high-temperature air. 81% of the high-temperature air leaving the high-temperature flue gas cooling unit 2 enters the high-temperature heat exchanger 8 for the acid-making process gas, raising the temperature of the acid-making process gas from the outlet of the first-stage bed of the converter 10 by 80 °C. 19% of the high-temperature air leaving the high-temperature flue gas cooling unit 2 enters the low-temperature heat exchanger 9 for the acid-making process gas, raising the temperature of the acid-making process gas that needs to enter the converter for the secondary conversion reaction by 20 °C.

[0099] The high-temperature air passing through the acid-making process gas treatment unit is cooled to 630 °C. 100% of the medium-temperature air at 630 °C directly enters the waste heat boiler 3 of the steam generation unit and is cooled to 180 °C to become low-temperature air. It enters the economizer 5 and is cooled to 140 °C to heat the boiler feed water. 47.62% of the air at 140 °C after being cooled by the economizer 5 enters the incineration reactor 1 for combustion support through the oxygen concentration in the incineration reactor 1, so that the oxygen concentration in the incineration reactor 1 is 2.32%. The waste heat boiler 3 generates 6.24 t / h of saturated steam at 0.5 MPa (G). All the low-temperature air after the heat is utilized, except for that entering the incineration reactor 1 for combustion support, returns to the inlet of the air blower 6 for recycling.

[0100] Comparative Example 1

[0101] Taking the 25,000-ton / year 50% concentration spent sulfuric acid regeneration device as an example, the spent sulfuric acid and fuel are mixed and incinerated to produce high-temperature flue gas at 1100 °C. The high-temperature flue gas mainly contains impurities such as sulfur dioxide, water, carbon dioxide, nitrogen, oxygen, fluorine, phosphorus, and chlorine. The wet-base molar amount of the high-temperature flue gas is 535 kmol / h. The dry-base molar amount of the conversion process gas is 357.25 kmol / h, and the sulfur dioxide concentration is 4.35%. The oxygen concentration in the incineration reactor 1 is 2.93 vol%, and the process flow is as Figure 3 shown.

[0102] The high-temperature flue gas at the outlet of the incineration reactor 1, with a flow rate of 535 kmol / h, enters the air cooler 19, which is an M-shaped heat exchanger with fins. Through air convection heat dissipation, the high-temperature flue gas is cooled down to 800 °C and then enters the air heat exchanger 20 to heat 323.5 kmol / h of normal-temperature air to 500 °C. All of them enter the incineration reactor 1 to participate in the incineration reaction. The fuel used is 34.4 kmol / h. The flue gas exiting the air heat exchanger 20 is cooled down to 400 °C and enters the sulfuric acid production system. Since the sulfur dioxide concentration in the converted process gas is only 4.35%, an electric heating furnace is required to heat the process gas. The process gas from the outlet of the first-stage bed of the converter 10 is heated by 62 °C, and the process gas that needs to enter the converter 10 for the secondary conversion reaction is heated by 15 °C. The power of the electric furnace is 250 kw / h, and no steam is generated in the entire device system. Compared with Example 1, 10% less fuel is used, but less steam is produced, and there is more power consumption. The energy consumption of the device is very high and it is not energy-saving.

[0103] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for treating high-temperature flue gas, wherein, The method comprises the following steps: (1) Incinerating incineration raw materials, sulfur-containing raw materials and fuel to obtain high-temperature flue gas; (2) Exchanging heat between the high-temperature flue gas and air to obtain high-temperature air and flue gas; (3) Conducting subsequent treatment on the flue gas to obtain acid-making process gas; (4) Exchanging heat between the high-temperature air and the acid-making process gas to obtain medium-temperature air and acid-making process conversion gas; subjecting the acid-making process conversion gas to acid-making treatment to obtain sulfuric acid; (5) Dividing the medium-temperature air into A-stream gas and B-stream gas, generating saturated steam from the A-stream gas, and superheating the saturated steam into superheated steam by the B-stream gas; combining the A-stream gas and B-stream gas that recover the superheat amount and then dividing them into two streams of low-temperature air C and D; using the low-temperature air C as the combustion-supporting agent for incineration treatment and recycling the low-temperature air D as recycle gas; In step (1), the high-temperature flue gas contains sulfur dioxide, sulfur trioxide, water and optionally at least one of phosphorus, fluorine and chlorine elements; The temperature of the high-temperature flue gas is 900 - 1300 °C; The dry-based concentration of sulfur dioxide in the high-temperature flue gas is 1 - 5% by volume; The temperature of the high-temperature air is 650 - 850 °C, and the temperature of the flue gas is 300 - 500 °C; In step (3), the temperature of the acid-making process gas is 410 - 470 °C; The temperature of the medium-temperature air is 600 - 760 °C; The temperature of the low-temperature air is 100 - 200 °C.

2. The method according to claim 1, wherein there is sulfur trioxide in the high-temperature flue gas in the presence of unsaturated water, and the volume of sulfur trioxide is less than 0.1% by volume; and / or, the phosphorus content in the high-temperature flue gas > 100 ppm by mass, the fluorine content > 100 ppm by mass, and the chlorine content > 50 ppm by mass.

3. The method according to claim 1, wherein, In step (2), the molar ratio of the high-temperature flue gas to air is 0.7 - 1:1; and / or, the flue gas contains sulfur dioxide, sulfur trioxide, water and optionally phosphorus element.

4. The method according to claim 1, wherein, In step (3), the acid-making process gas contains sulfur dioxide and sulfur trioxide.

5. The method according to claim 1, wherein In step (4), the volume ratio of the high-temperature air to the acid-making process gas is 1.4 - 2.1:1; and / or, the temperature of the acid-making process conversion gas is 430 - 590 °C.

6. The method according to claim 1, wherein, In step (5), the volume ratio of the A-stream gas to the B-stream gas is 3 - 4:1; and / or, in step (5), the oxygen concentration in the incineration treatment process is controlled to be 1 - 3% by volume by adding a combustion-supporting agent.

7. A system applicable to the method for treating high-temperature flue gas according to any one of claims 1-6, wherein, The system comprises: an incineration reaction unit, a high-temperature flue gas treatment unit, a flue gas treatment unit, an acid-making process gas treatment unit, an acid-making unit and a steam treatment unit; The incineration reaction unit is used for incinerating incineration raw materials, sulfur-containing raw materials and fuel to obtain high-temperature flue gas; The high-temperature flue gas treatment unit is used for cooling the high-temperature flue gas to obtain high-temperature air and flue gas; The flue gas treatment unit is used for conducting subsequent treatment on the flue gas to obtain acid-making process gas; The acid-making process gas treatment unit is used for heat-exchanging the acid-making process gas to obtain medium-temperature air and acid-making process conversion gas; The acid-making unit is used for treating the acid-making process conversion gas to obtain sulfuric acid; The steam treatment unit is used for treating the medium-temperature air to obtain superheated steam and saturated steam.

8. The system according to claim 7, wherein, The high-temperature flue gas treatment unit includes one or more fixed tube sheet heat exchangers, and the high-temperature flue gas treatment unit reduces the temperature of the high-temperature flue gas to above the flue gas dew point corrosion temperature.

9. The system according to claim 7 or 8, wherein The sulfuric acid production process gas treatment unit includes a high-temperature heat exchanger for sulfuric acid production process gas and a low-temperature heat exchanger for sulfuric acid production process gas; And / or, the steam treatment unit includes a waste heat boiler, a steam superheater, and an economizer.

10. The system according to claim 9, wherein The medium-temperature air is divided into A-stream gas and B-stream gas, and the waste heat boiler is used to by-product saturated steam from the A-stream gas.

11. The system according to claim 9, wherein, The steam superheater is used to by-product superheated steam from the B-stream gas.

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