Sulfur-containing flue gas waste heat recovery system and waste heat recovery method

Abstract

The invention discloses a sulfur-containing flue gas waste heat recovery system and a waste heat recovery method, belongs to the field of waste heat recovery, solves the problem that a heat exchanger cannot be applied to a desulfurization system at low cost, and mainly adopts the technical scheme that the sulfur-containing flue gas waste heat recovery system comprises a first desulfurization device and a dust collection device, the heat exchanger is arranged at the upstream of the first desulfurization device, so that the flue gas passes through the upstream heat exchanger and then enters the first desulfurization device, the first desulfurization device desulfurizes the flue gas by mixing a first desulfurization agent and forms desulfurization powder containing calcium-based desulfurization ash, and the dust collection device is used for collecting the desulfurization powder generated by the first desulfurization device; and a feeding device is arranged at the downstream of the dust collecting device and feeds collected desulfurized powder into the upstream of the heat exchanger through a first feeding pipe, and the desulfurized powder is mixed with flue gas entering the heat exchanger and desulfurized. The application is mainly used for realizing the addition of the heat exchanger, and the heat exchanger with lower material cost is used for maintaining normal work, so that the economic benefit of the whole set of system is improved.

Description

Technical Field

[0001] The present application relates to the field of waste heat recovery, and in particular to a waste heat recovery system and a waste heat recovery method for sulfur-containing flue gas. Background Art

[0002] Coal-fired boilers and industrial kilns (such as glass kilns) widely use fossil fuels (coal, oil, natural gas), biomass / garbage, and other fuels that still have economic value. These fuels will generate complex pollutants such as dust, CO2, CO, SO2, SO3, HCl, HF, etc. after high-temperature combustion.

[0003] Gaseous SO3 reacts easily with water vapor to generate H2SO4 steam. When the flue gas temperature or the equipment surface temperature drops to the acid dew point temperature, H2SO4 condenses into liquid (fog, micro-droplets, liquid film), which will cause serious corrosion to metals. When the sulfuric acid concentration and temperature are 40%-50%&60℃ and 80%&120℃ respectively, the corrosion to metal materials is more serious. When the flue gas contains HCL, the corrosion to metals is accelerated. When there is a denitrification device in the system and ammonia, ammonia water, urea and other denitrification agents need to be sprayed, there is also excessive gaseous NH3 in the flue gas, which is easy to react with H2SO4 to generate low-melting-point ammonium bisulfate. Ammonium bisulfate has a low melting point and strong adhesion, and will adhere to the surface of the equipment together with dust, causing blockage and aggravating under-scale corrosion.

[0004] Due to the above factors, the flue gas temperature at the outlet of the waste heat boiler is mostly controlled at around 175℃~185℃, and then enters the desulfurization system, resulting in a waste of heat energy. At the same time, it also leads to an increase in the operating energy consumption of the desulfurization and dust removal system (such as desulfurizer, electricity, water, and compressed air).

[0005] In order to optimize the operating parameters of environmental protection equipment and recover flue gas heat energy at the same time, for example, a traditional tubular fin heat exchanger is installed at the outlet of the waste heat boiler. However, it is generally found that the resistance drop is large, the local eddy current of dust causes serious erosion and wear, and it is easy to form scale and blockage, resulting in serious under-scale corrosion. As a result, the heat exchange equipment has a short service life, a large maintenance workload, and a high operating power consumption. These problems cannot be solved. Summary of the invention

[0006] The present application aims to solve the problems existing in the existing desulfurization system. In the prior art, when the heat recovery system is used to quickly cool down the desulfurization system, the heat exchanger will suffer from severe corrosion. If a heat exchanger is not used, a large amount of heat in the flue gas will be wasted. If a heat exchanger is used, its material cost will increase in order to resist the corrosiveness of the flue gas. Therefore, a waste heat recovery system and a waste heat recovery method for sulfur-containing flue gas are provided, which can realize the addition of a heat exchanger and use a heat exchanger with a lower material cost to maintain normal operation, thereby improving the economic benefits of the entire system.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme: a sulfur-containing flue gas waste heat recovery system, comprising a first desulfurization device and a dust collecting device connected in sequence, and a heat exchanger arranged upstream of the first desulfurization device, so that the flue gas passes through the upstream heat exchanger and then enters the first desulfurization device. The first desulfurization device desulfurizes the flue gas by mixing in a first desulfurizer, and forms desulfurization powder containing calcium-based desulfurization ash. The dust collecting device is used to collect the desulfurization powder generated by the first desulfurization device. A feeding device is provided downstream of the dust collecting device. The feeding device feeds the collected desulfurization powder into the upstream of the heat exchanger through a first feeding pipe, where it is mixed with the flue gas entering the heat exchanger and desulfurized.

[0008] After adopting the above technical scheme, the present application has the following advantages: in order to reduce the temperature of the flue gas entering the first desulfurization device and the dust collecting device, the scheme adds a heat exchanger to quickly reduce the flue gas temperature and recycle the waste heat in the flue gas; in order to reduce the cost of the heat exchanger, the desulfurization powder after desulfurization in the dust collecting device is transported to the upstream of the heat exchanger. Since the desulfurization powder contains calcium-based desulfurization ash, the calcium-based desulfurization ash can neutralize the acidic components in the flue gas to a certain extent (such as , HCl, etc.), reducing the corrosiveness of flue gas, so that heat exchangers with lower material costs can be used and maintain their normal operation, solving the problem of having to use heat exchangers with high material costs in the past to resist corrosion, and reducing equipment investment costs and maintenance costs.

[0009] Furthermore, a waste heat boiler is provided upstream of the heat exchanger, and the first feeding pipe feeds the desulfurization powder upstream of the waste heat boiler to mix with the flue gas entering the waste heat boiler and desulfurize it.

[0010] By adopting the above technical solution, the desulfurization powder containing calcium-based desulfurization ash is mixed with the flue gas upstream of the waste heat boiler for desulfurization, and the acidic pollutants such as sulfur oxides can be treated at the high-temperature flue gas stage. Since the flue gas temperature is high at this time, the chemical reaction rate is relatively fast, and the calcium-based desulfurization ash and acidic gases (such as , , HCL, etc.), reducing the content of acidic gas in subsequent equipment (such as the heat exchange surface of the waste heat boiler), thereby reducing the corrosion risk of the waste heat boiler, extending the service life of the waste heat boiler, and reducing the equipment maintenance and replacement costs caused by corrosion.

[0011] Furthermore, the waste heat boiler is provided with a first inlet, a first outlet, a second inlet and a second outlet, the first feeding pipe is provided in front of the first inlet, and a high-temperature dust collector and a denitrification reactor are connected in sequence on the flue gas path between the first outlet and the second inlet, the feeding device is also provided with a second feeding pipe connected to the denitrification reactor and the second inlet, which is mixed with and desulfurized by the flue gas entering the waste heat boiler, and the waste heat boiler feeds the flue gas to the heat exchanger through the second outlet.

[0012] By adopting the above-mentioned technical solution, multiple processing units are rationally arranged in the flue gas process of the waste heat boiler, realizing the coordinated and efficient treatment of desulfurization, dust removal and denitrification. The desulfurization powder is fed into the waste heat boiler in front of the inlet through the first feeding pipe for preliminary desulfurization, which can reduce the corrosion of acidic gas to the boiler and reduce the subsequent processing load. The high-temperature dust collector effectively removes dust particles in the flue gas to avoid the wear and pollution of subsequent equipment by dust. The denitrification reactor treats nitrogen oxides, and the second feeding pipe reintroduces the desulfurization powder between the denitrification reactor and the second inlet for further desulfurization, which makes full use of the desulfurization components in the desulfurization powder and improves the whole system's resistance to multiple pollutants ( , ,dust, The comprehensive removal efficiency of

[0013] Furthermore, a second desulfurization device is provided between the second outlet and the heat exchanger to mix with the flue gas entering the heat exchanger and desulfurize the flue gas.

[0014] With the above technical solution, even after the initial desulfurization treatment (such as the initial desulfurization upstream of the waste heat boiler and possible synergistic desulfurization in other links), there may still be a small amount of sulfur oxides remaining. The second desulfurization device can carry out deep treatment of these residual sulfur oxides in a targeted manner, further reducing the sulfur content in the flue gas, greatly improving the desulfurization efficiency of the entire system, and the existence of the second desulfurization device increases the adaptability and flexibility of the entire sulfur-containing flue gas treatment system. It can flexibly adjust the desulfurization process parameters (such as the type, dosage, reaction temperature, etc. of the desulfurizer) according to the actual conditions such as different flue gas components, sulfur content and environmental protection requirements to achieve the best desulfurization effect.

[0015] Furthermore, the second desulfurization device includes a second material receiver and a second blower connected in sequence, and a second silo filled with a second desulfurizer connected to the second material receiver, so that the second blower blows the second desulfurizer in the second material receiver into the flue.

[0016] By adopting the above technical solution, the airflow generated by the second blower can quickly disperse the second desulfurizer in the flue and fully mix it with the flue gas. Compared with some traditional desulfurizer addition methods, this pneumatic conveying and blowing method can effectively break the agglomeration of the desulfurizer, increase the contact area between the desulfurizer and the sulfur oxides in the flue gas, accelerate the chemical reaction rate, improve the efficiency and speed of the desulfurization reaction, and ensure that a sufficient desulfurization reaction is achieved within a limited flue length and residence time.

[0017] Furthermore, the dust collecting device includes a dust collector and a fluidizing trough located below the dust collector for diverting the reacted materials. The fluidizing trough is provided with a discharge port connected to a feeding device, a circulation channel for passing the desulfurization powder into a desulfurization reactor, and a waste port for discharging waste. A chimney is also connected to the top of the dust collector.

[0018] By adopting the above technical solution, the setting of the fluidized tank realizes the effective diversion of the materials after the reaction. The desulfurization powder containing calcium-based desulfurization ash and other valuable materials is transported to the feeding device through the discharge port so that it can be recycled in the desulfurization process later, such as participating in the desulfurization reaction again upstream of the heat exchanger or between the denitrification reactor and the inlet of the waste heat boiler, thereby improving the utilization rate of the desulfurizer, reducing the amount of desulfurizer replenishment, and thus reducing the operating cost.

[0019] Furthermore, the first desulfurization device includes a desulfurization reactor connected to the downstream of the heat exchanger, and a first silo connected to the desulfurization reactor and filled with a first desulfurizer.

[0020] The above-mentioned technical solution is adopted, and the desulfurization reactor is arranged downstream of the heat exchanger, so that the flue gas first passes through the heat exchanger for waste heat recovery, and then enters the desulfurization reactor for desulfurization treatment after the temperature is adjusted to a certain extent. This layout conforms to the process logic sequence of sulfur-containing flue gas treatment, which is conducive to the stable operation of the entire system and the coordinated work between various links. Recovering heat in the heat exchanger can avoid the adverse effects of high temperature on subsequent desulfurization equipment. At the same time, when the flue gas enters the desulfurization reactor after cooling, its physical and chemical properties are more conducive to the desulfurization reaction, which improves the efficiency and stability of the desulfurization reaction. The semi-dry desulfurization process used here can reduce the transportation device of the desulfurizer, and directly place the first silo on the desulfurization reactor, so that the desulfurizer and a certain liquid enter the desulfurization reactor for desulfurization operation.

[0021] Furthermore, the feeding device is a first material receiver and a first blower.

[0022] By adopting the above technical solution, the conveying flow rate of the desulfurized powder can be controlled more accurately by adjusting the air volume of the first blower and the discharge volume of the first receiving device. In the process of treating sulfur-containing flue gas, the amount of desulfurized ash added can be adjusted in real time and accurately according to factors such as the content of sulfur oxides in the flue gas, the flue gas flow rate, and the requirements for the desulfurization effect at different treatment stages.

[0023] Furthermore, the first desulfurizer in the first desulfurizer is slaked lime, and the second desulfurizer is a sodium-based or ammonium-based composite salt.

[0024] Using the above technical solution, slaked lime is a relatively common and relatively low-priced desulfurization agent raw material with a wide range of sources, easy to obtain and store. Its application in the first desulfurization device can reduce the overall cost of desulfurization operation while ensuring a certain desulfurization effect. It has significant economic advantages for the treatment of sulfur-containing flue gas from large-scale coal-fired boilers and industrial kilns, which is beneficial for enterprises to control production costs and improve economic benefits while meeting environmental protection requirements. The products such as calcium sulfite and calcium sulfate generated by the reaction have certain stability and treatability. Sodium-based or ammonium-based composite salts are used as the second desulfurizer. In the flue gas treated by the first desulfurization device, it can accurately deacidify the small amount of residual sulfur oxides.

[0025] A method for recovering waste heat from sulfur-containing flue gas, based on the above-mentioned waste heat recovery system for sulfur-containing flue gas, comprises the following steps: S100: Before the flue gas enters the first inlet of the waste heat boiler, the first feeding pipe connected to the feeding device is used to spray the desulfurization powder collected in the fluidizing tank, so that the flue gas and the calcium-based desulfurization ash are mixed in the waste heat boiler to and Conducting preliminary desulfurization to generate carbon dioxide, calcium sulfite and calcium sulfate, and performing the first heat exchange; S200: The flue gas then enters the high-temperature dust collector and the denitrification reactor in sequence from the first outlet to remove dust particles and denitrify the flue gas. Before the flue gas enters the second inlet of the waste heat boiler, the second feeding pipe connected to the feeding device is used to spray the desulfurization powder collected in the fluidizing tank, so that the flue gas and the calcium-based desulfurization ash are mixed for the second time in the waste heat boiler to remove the dust particles and denitrify the flue gas. and Carry out deep desulfurization and secondary heat exchange; S300: before the flue gas enters the heat exchanger from the second outlet, the second desulfurization device sprays the second desulfurizer into the flue gas through the second receiver and the second blower to perform precise deacidification, and then the flue gas enters the heat exchanger for three heat exchanges; S400: The flue gas then enters the first desulfurization device, and at the same time the first silo sends slaked lime into the desulfurization reactor to mix with the flue gas, so that the flue gas undergoes a semi-dry process desulfurization of NID or CFB; S500: Finally, the flue gas after desulfurization and the desulfurized substances enter the dust collector for separation, the clean air is discharged through the chimney, the desulfurized substances enter the fluidized tank, and the desulfurized powder containing calcium-based desulfurized ash is sent to the feeding device, or the desulfurized powder is re-entered into the desulfurization reactor through the circulation channel for recycling; S600: the feeding device feeds the desulfurization powder through the first feeding pipe to perform preliminary desulfurization on the flue gas, and / or, feeds the desulfurization powder through the second feeding pipe to perform deep desulfurization on the flue gas; S700: After the desulfurization operation is completed, the remaining waste is discharged through the waste port of the fluidized tank.

[0026] The above-mentioned technical scheme is adopted to carry out preliminary, deep and precise deacidification and semi-dry process desulfurization by using different methods and desulfurizers (calcium-based desulfurization ash, sodium-based or ammonium-based composite salt, slaked lime) before the inlet of the waste heat boiler, before the inlet of the waste heat boiler after dust removal and denitrification, before entering the heat exchanger, and when entering the first desulfurization device. The synergistic effect of multiple links can achieve the desulfurization of flue gas. , Efficient removal of acidic gases such as sulfuric acid and so on ensures that the flue gas can meet strict environmental protection standards; and multiple heat exchanges are carried out using waste heat boilers and heat exchangers to fully recover the waste heat in the sulfur-containing flue gas, improve energy utilization, help other industrial links to use energy, reduce energy costs, and meet the needs of energy conservation and emission reduction. After desulfurization, the desulfurization powder containing calcium-based desulfurization ash is circulated through fluidizing troughs, feeding devices, etc., and can be repeatedly involved in desulfurization operations at different stages, reducing the use of new desulfurizers, saving resources and reducing operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present application is further described below in conjunction with the accompanying drawings: Figure 1 This is a schematic diagram of a waste heat recovery system and a waste heat recovery method for sulfur-containing flue gas in the present application.

[0028] Description of the drawings: 1. First desulfurization device; 11. Desulfurization reactor; 12. First silo; 2. Dust collecting device; 21. Dust collector; 22. Fluidizing trough; 23. Chimney; 3. Heat exchanger; 4. Feeding device; 41. First feeding pipe; 42. Second feeding pipe; 43. First receiving container; 44. First blower; 5. Waste heat boiler; 51. First inlet; 52. First outlet; 53. Second inlet; 54. Second outlet; 55. High-temperature dust collector; 56. Denitrification reactor; 6. Second desulfurization device; 61. Second receiving container; 62. Second blower; 63. Second silo; 7. Metering valve; 8. Kiln; 9. Ball valve. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0030] The terms "first", "second", etc. (if any) in the specification and claims of this application are used to distinguish similar objects, rather than to describe a specific order or sequence. Even if "second" is used to distinguish before a certain technical feature, it does not necessarily indicate that it has "first". It should be understood that in this application, "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. It should be understood that in this application, "multiple" refers to two or more. "And / or" is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, X and / or Y can represent: X exists alone, X and Y exist at the same time, and Y exists alone. The character " / " generally indicates that the related objects before and after are in an "or" relationship. "Contains X, Y and Z", "Contains X, Y, Z" means that X, Y, and Z are all included, "Contains X, Y or Z" means that one of X, Y, and Z is included, and "Contains X, Y and / or Z" means that any one, any two, or three of X, Y, and Z are included.

[0031] The following specific embodiments are used to describe the technical solution of the present application in detail. The following specific embodiments can be combined or replaced with each other according to actual conditions, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0032] Embodiment 1: like Figure 1 As shown, the present application provides a sulfur-containing flue gas waste heat recovery system and a waste heat recovery method, comprising a first desulfurization device 1 and a dust collecting device 2 connected in sequence, and a heat exchanger 3 arranged upstream of the first desulfurization device 1, so that the flue gas passes through the upstream heat exchanger 3 and then enters the first desulfurization device 1. The first desulfurization device 1 desulfurizes the flue gas by mixing in a first desulfurizer, and forms a desulfurization powder containing calcium-based desulfurization ash. The dust collecting device 2 is used to collect the desulfurization powder generated by the first desulfurization device 1. A feeding device 4 is provided downstream of the dust collecting device 2. The feeding device 4 feeds the collected desulfurization powder upstream of the heat exchanger 3 through a first feeding pipe 41, and mixes and desulfurizes the flue gas entering the heat exchanger 3.

[0033] After adopting the above technical scheme, the present application has the following advantages: in order to reduce the temperature of the flue gas entering the first desulfurization device 1 and the dust collecting device 2, the scheme adds a heat exchanger 3 to quickly reduce the flue gas temperature and recycle the waste heat in the flue gas; in order to reduce the cost of the heat exchanger 3, the desulfurization powder after desulfurization in the dust collecting device 2 is transported to the upstream of the heat exchanger 3. Since the desulfurization powder contains calcium-based desulfurization ash, the calcium-based desulfurization ash can neutralize the acidic components in the flue gas to a certain extent (such as , HCl, etc.), reduces the corrosiveness of the flue gas, so that a heat exchanger 3 with lower material cost can be used and its normal operation can be maintained, solving the problem that a heat exchanger 3 with high material cost has to be used in the past to resist the corrosiveness, and reducing the equipment investment cost and maintenance cost.

[0034] Specifically, the material of the heat exchanger 3 can be selected from metal sheets such as ND steel, 316L, 2205, etc., which are excellent in economy and corrosion resistance, and are laser welded, bulged, and have a wavy surface on both sides. The thickness of the sheet is 0.5mm to 3.0mm, preferably 1.0mm to 2.5mm; When the wall temperature of the coolant of the heat exchanger 3 is too low, the metal surface can be sprayed / brushed with a resin coating that has good thermal conductivity, heat resistance, wear resistance, and good adhesion to the base metal. The recommended thickness is 120~320μm, preferably 240μm. When the surface is melt-sprayed with metal, the recommended thickness is 120~320μm, preferably about 150μm.

[0035] Furthermore, a waste heat boiler 5 is provided upstream of the heat exchanger 3 , and the first feeding pipe 41 feeds the desulfurization powder upstream of the waste heat boiler 5 , where the desulfurization powder is mixed with the flue gas entering the waste heat boiler 5 and desulfurized.

[0036] By adopting the above-mentioned technical solution, the desulfurization powder containing calcium-based desulfurization ash is mixed with the flue gas upstream of the waste heat boiler 5 for desulfurization, and the acidic pollutants such as sulfur oxides can be treated at the high-temperature flue gas stage. Since the flue gas temperature is relatively high at this time, the chemical reaction rate is relatively fast, and the calcium-based desulfurization ash can be more efficiently used to react with acidic gases (such as SO3, SO2, HCL, etc.), reducing the content of acidic gases in subsequent equipment (such as the heat exchange surface of the waste heat boiler 5), thereby reducing the risk of corrosion to the waste heat boiler 5, extending the service life of the waste heat boiler 5, and reducing the equipment maintenance and replacement costs caused by corrosion.

[0037] Specifically, the concentration of the desulfurized ash added before the waste heat boiler 5 is 0.5-4.0 g / nm3, preferably 0.5-1.5 g / nm3, and the calcium-based desulfurizer reacts with SO2 and SO3 in a high-temperature chemical desulfurization reaction.

[0038] Furthermore, the waste heat boiler 5 is provided with a first inlet 51, a first outlet 52, a second inlet 53 and a second outlet 54. The first feeding pipe 41 is provided in front of the first inlet 51. A high-temperature dust collector 55 and a denitration reactor 56 are sequentially connected to the flue gas path between the first outlet 52 and the second inlet 53. The feeding device 4 is also provided with a second feeding pipe 42 connected to the denitration reactor 56 and the second inlet 53, which is mixed with the flue gas entering the waste heat boiler 5 and desulfurized. The waste heat boiler 5 sends the flue gas to the heat exchanger 3 through the second outlet 54.

[0039] By adopting the above-mentioned technical solution, multiple processing units are rationally arranged in the flue gas flow of the waste heat boiler 5, realizing the coordinated and efficient treatment of desulfurization, dust removal and denitrification. The first feeding pipe 41 is used to feed desulfurization powder for preliminary desulfurization in front of the inlet of the waste heat boiler 5, which can reduce the corrosion of acidic gases to the boiler and reduce the subsequent processing load. The high-temperature dust collector 55 effectively removes dust particles in the flue gas to avoid the wear and pollution of subsequent equipment by dust. The denitrification reactor 56 processes nitrogen oxides, and the second feeding pipe 42 reintroduces desulfurization powder between the denitrification reactor 56 and the second inlet 53 for further desulfurization, which makes full use of the desulfurization components in the desulfurization powder and improves the whole system's resistance to multiple pollutants ( , ,dust, The comprehensive removal efficiency of

[0040] Specifically, the denitration reactor 56 is an SCR type denitration reactor, and the denitration agent used is ammonia, ammonia water, urea, etc. The amount of desulfurized ash added after the denitration reactor 56 is 0.5-4.0 g / , preferably 1.5 to 2.5 g / , wherein the content of slaked lime is 15% to 18%, and the calcium-based desulfurizer reacts with SO2 and SO3 in a high-temperature chemical desulfurization reaction; the flue gas temperature in the high-temperature dust collector 55 area is 300°C to 380°C, and the types of the high-temperature dust collector 55 include electrostatic precipitator, ceramic filter cartridge, and metal filter cartridge, and the electrostatic precipitator is preferred.

[0041] Preferably, the flue gas temperature at the first inlet 51 is 450°C-550°C, the flue gas temperature from the first outlet 52 to the second inlet 53 is 300°C-400°C, the temperature from the second outlet 54 to the inlet of the heat exchanger 3 is 150°C-250°C, and the outlet temperature of the heat exchanger 3 is 90°C-110°C.

[0042] Furthermore, a second desulfurization device 6 is provided between the second outlet 54 and the heat exchanger 3 to mix with the flue gas entering the heat exchanger 3 and desulfurize the flue gas.

[0043] With the above technical solution, even after the initial desulfurization treatment (such as the initial desulfurization upstream of the waste heat boiler 5 and possible synergistic desulfurization in other links), there may still be a small amount of sulfur oxides remaining. The second desulfurization device 6 can carry out deep treatment of these residual sulfur oxides in a targeted manner, further reducing the sulfur content in the flue gas, greatly improving the desulfurization efficiency of the entire system, and the presence of the second desulfurization device 6 increases the adaptability and flexibility of the entire sulfur-containing flue gas treatment system. It can flexibly adjust the desulfurization process parameters (such as the type, dosage, reaction temperature, etc. of the desulfurizer) according to the actual conditions such as different flue gas components, sulfur content and environmental protection requirements to achieve the best desulfurization effect.

[0044] Furthermore, the second desulfurization device 6 includes a second receiver 61 and a second blower 62 connected in sequence, and a second silo 63 connected to the second receiver 61 and filled with a second desulfurizer, so that the second blower 62 blows the second desulfurizer in the second receiver 61 into the flue.

[0045] By adopting the above technical solution, the airflow generated by the second blower 62 can make the second desulfurizer disperse rapidly in the flue and fully mix with the flue gas. Compared with some traditional desulfurizer adding methods, this pneumatic conveying and blowing method can effectively break the agglomeration of the desulfurizer, increase the contact area between the desulfurizer and the sulfur oxides in the flue gas, accelerate the chemical reaction rate, improve the efficiency and speed of the desulfurization reaction, and ensure that a sufficient desulfurization reaction is achieved within a limited flue length and residence time.

[0046] Furthermore, the dust collecting device 2 includes a dust collector 21, and a fluidizing trough 22 located below the dust collector 21 for diverting the reacted materials. The fluidizing trough 22 is provided with a discharge port connected to the feeding device 4, a circulation channel for passing the desulfurization powder into the desulfurization reactor 11, and a waste port for discharging waste. The dust collector 21 is also connected to a chimney 23 at the top.

[0047] By adopting the above technical solution, the setting of the fluidizing tank 22 realizes the effective diversion of the reacted substances. The desulfurization powder containing calcium-based desulfurization ash and other valuable materials is transported to the feeding device 4 through the discharge port so as to be subsequently recycled in the desulfurization process, such as participating in the desulfurization reaction again upstream of the heat exchanger 3 or between the denitrification reactor 56 and the inlet of the waste heat boiler 5, thereby improving the utilization rate of the desulfurizer, reducing the amount of desulfurizer replenishment, and thus reducing the operating cost.

[0048] Specifically, the dust collector 21 is a bag-type or electric bag composite dust collector 21, an interface of the desulfurization ash fluidizing trough 22 at the bottom is connected to the desulfurization ash deacidification metering valve 7, and an induced draft fan is also provided between the chimney 23 and the dust collector 21 to discharge the air after dust removal.

[0049] Furthermore, the first desulfurization device 1 includes a desulfurization reactor 11 connected to the downstream of the heat exchanger 3 , and a first silo 12 connected to the desulfurization reactor 11 and filled with a first desulfurizing agent.

[0050] By adopting the above-mentioned technical solution, the desulfurization reactor 11 is arranged downstream of the heat exchanger 3, so that the flue gas first passes through the heat exchanger 3 for waste heat recovery, and then enters the desulfurization reactor 11 for desulfurization treatment after the temperature is adjusted to a certain extent. This layout conforms to the process logic sequence of sulfur-containing flue gas treatment, which is conducive to the stable operation of the entire system and the coordinated work between various links. Recovering heat in the heat exchanger 3 can avoid the adverse effects of high temperature on subsequent desulfurization equipment. At the same time, when the flue gas after cooling enters the desulfurization reactor 11, its physical and chemical properties are more conducive to the desulfurization reaction, which improves the efficiency and stability of the desulfurization reaction. The semi-dry desulfurization process used here can reduce the transportation device of the desulfurizer, and directly place the first silo 12 on the desulfurization reactor 11, so that the desulfurizer and a certain liquid enter the desulfurization reactor 11 for desulfurization operation.

[0051] Furthermore, the feeding device 4 includes a first material receiver 43 and a first blower 44 .

[0052] By adopting the above technical solution, the conveying flow rate of the desulfurized powder can be controlled more accurately by adjusting the air volume of the first blower 44 and the discharge volume of the first receiving device 43. In the process of treating sulfur-containing flue gas, the amount of desulfurized ash added can be adjusted in real time and accurately according to factors such as the content of sulfur oxides in the flue gas, the flue gas flow rate, and the requirements for the desulfurization effect at different treatment stages.

[0053] Furthermore, the first desulfurizer in the first desulfurizer 1 is slaked lime, and the second desulfurizer is a sodium-based or ammonium-based composite salt.

[0054] Using the above technical solution, slaked lime is a relatively common and relatively cheap desulfurization agent raw material with a wide source, easy to obtain and store. Its application in the first desulfurization device 1 can reduce the overall cost of desulfurization operation while ensuring a certain desulfurization effect. It has significant economic advantages for the treatment of sulfur-containing flue gas from large-scale coal-fired boilers and industrial kilns 8, which is beneficial for enterprises to control production costs and improve economic benefits while meeting environmental protection requirements. The products such as calcium sulfite and calcium sulfate generated by the reaction have certain stability and treatability. Sodium-based or ammonium-based composite salts are used as the second desulfurizer. In the flue gas treated by the first desulfurization device 1, a small amount of residual sulfur oxides can be accurately deacidified.

[0055] Specifically, the first desulfurizing agent in the first desulfurizing device 1 contains 20% to 35% slaked lime.

[0056] The second desulfurizer is a cheap and easily decomposable sodium-based and / or ammonium-based complex salt, such as baking soda, ammonium bicarbonate, etc., and the concentration is 0.3-1.5 g / nm3, preferably 0.5-1.0 g / nm3. The second desulfurizer undergoes chemical desulfurization reaction and physical adsorption with SO3.

[0057] A method for recovering waste heat from sulfur-containing flue gas, based on the above-mentioned waste heat recovery system for sulfur-containing flue gas, comprises the following steps: S100: before the flue gas enters the first inlet 51 of the waste heat boiler 5, the first feeding pipe 41 connected to the feeding device 4 is used to spray the desulfurization powder collected in the fluidizing tank 22, so that the flue gas and the calcium-based desulfurization ash are mixed in the waste heat boiler 5, and the SO2 and SO3 in the flue gas are preliminarily desulfurized to generate carbon dioxide, calcium sulfite and calcium sulfate, and the first heat exchange is performed; S200: The flue gas then enters the high-temperature dust collector 55 and the denitration reactor 56 in sequence from the first outlet 52 to remove dust particles and denitrate the flue gas. Then, before the flue gas enters the second inlet 53 of the waste heat boiler 5, the second feeding pipe 42 connected to the feeding device 4 is used to spray the desulfurization powder collected in the fluidizing tank 22, so that the flue gas and the calcium-based desulfurization ash are mixed for the second time in the waste heat boiler 5, and the SO2 and SO3 in the flue gas are deeply desulfurized, and secondary heat exchange is performed; S300: before the flue gas enters the heat exchanger 3 from the second outlet 54, the second desulfurization device 6 sprays the second desulfurization agent into the flue gas through the second receiver 61 and the second blower 62 to perform precise deacidification, and then the flue gas enters the heat exchanger 3 for three heat exchanges; S400: The flue gas then enters the first desulfurization device 1, and at the same time the first silo 12 sends slaked lime into the desulfurization reactor 11 to mix with the flue gas, so that the flue gas is desulfurized by a semi-dry process of NID or CFB; S500: Finally, the flue gas after desulfurization and the desulfurized substances enter the dust collector 21 for separation, the clean air is discharged through the chimney 23, the desulfurized substances enter the fluidizing tank 22, and the desulfurized powder containing calcium-based desulfurized ash is sent to the feeding device 4, or the desulfurized powder is re-entered into the desulfurization reactor 11 through the circulation channel for recycling; S600: the feeding device 4 feeds the desulfurization powder through the first feeding pipe 41 to perform preliminary desulfurization on the flue gas, and / or, through the second feeding pipe 42 to perform deep desulfurization on the flue gas; S700: After the desulfurization operation is completed, the remaining waste is discharged through the waste outlet of the fluidizing tank 22.

[0058] The above-mentioned technical scheme is adopted to carry out preliminary, deep and precise deacidification and semi-dry process desulfurization by using different methods and desulfurizers (calcium-based desulfurization ash, sodium-based or ammonium-based composite salt, slaked lime) before the inlet of the waste heat boiler 5, before the inlet of the waste heat boiler 5 again after dust removal and denitrification, before entering the heat exchanger 3, and when entering the first desulfurization device 1. The synergistic effect of multiple links realizes the desulfurization of the flue gas. , The efficient removal of acidic gases such as sulfuric acid and sulfur dioxide ensures that the flue gas can meet strict environmental protection standards; and the waste heat boiler 5 and the heat exchanger 3 are used for multiple heat exchanges to fully recover the waste heat in the sulfur-containing flue gas, improve energy utilization, and help other industrial links to use energy, reduce energy costs, and meet the needs of energy conservation and emission reduction. Moreover, the desulfurization powder containing calcium-based desulfurization ash after desulfurization is circulated through the fluidizing trough 22, the feeding device 4, etc., and can be repeatedly involved in the desulfurization operation at different stages, reducing the use of new desulfurizers, saving resources and reducing operating costs.

[0059] Specifically, the pipelines for conveying the desulfurizing agent and the desulfurizing powder are equipped with metering valves 7 for controlling the flow rate, and the first feeding pipe 41 and the second feeding pipe 42 are provided with ball valves 9 .

[0060] It can be understood that the flue gas entering the waste heat boiler 5 comes from the coated kiln 8 .

[0061] Taking a 700t / d glass kiln 8 flue gas with a plate heat exchanger 3 added at the outlet of the waste heat boiler 5 as an example, the designed inlet flue gas volume is 170000nm3 / h (wet, standard, working oxygen), and the flue gas temperature is 179℃; the flue gas temperature after heat exchange is 135℃, and the waste heat recovered by the heat exchanger 3 is 9.56GJ / h.

[0062] Before the heat exchanger 3 is installed, the desulfurization operating temperature is 115°C.

[0063] After installing heat exchanger 3, the desulfurization operating temperature is 80℃~85℃, the total operating resistance of the system is reduced by about 500pa, the total operating power consumption of the system is reduced by about 22.0 kWh, the process water used for desulfurization is reduced by about 3.67t / h, the compressed air sprayed by the bag dust collector is reduced by about 2m3 / min, and the consumption of slaked lime is reduced by about 187.5 kg / h.

[0064] Annual economic benefit calculation (8000h)

[0065] Example 2: The difference from Example 1 is that the first feeding pipe 41 and the second feeding pipe 42 are the same, that is, the feeding device 4 does not need to feed the desulfurization powder to the first inlet 51 of the waste heat boiler 5, and can also achieve the effect of reducing the material cost of the heat exchanger 3.

[0066] In addition to the above-mentioned preferred embodiments, the present application also has other implementation modes. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making any creative work are within the scope of protection requested by the present application.

Claims

1. A waste heat recovery system for sulfur-containing flue gas, characterized in that: It includes a first desulfurization device and a dust collecting device connected in sequence, and a heat exchanger arranged upstream of the first desulfurization device, so that the flue gas passes through the upstream heat exchanger and then enters the first desulfurization device. The first desulfurization device desulfurizes the flue gas by mixing in a first desulfurizer and forms desulfurization powder containing calcium-based desulfurization ash. The dust collecting device is used to collect the desulfurization powder generated by the first desulfurization device. A feeding device is arranged downstream of the dust collecting device. The feeding device feeds the collected desulfurization powder upstream of the heat exchanger through a first feeding pipe to mix with the flue gas entering the heat exchanger and desulfurize it.

2. According to the sulfur-containing flue gas waste heat recovery system of claim 1, a waste heat boiler is also provided upstream of the heat exchanger, and the first feeding pipe feeds the desulfurization powder into the upstream of the waste heat boiler to mix with the flue gas entering the waste heat boiler and desulfurize.

3. A sulfur-containing flue gas waste heat recovery system according to claim 2, wherein the waste heat boiler is provided with a first inlet, a first outlet, a second inlet and a second outlet, the first feeding pipe is provided in front of the first inlet, and a high-temperature dust collector and a denitration reactor are sequentially connected on the flue gas path between the first outlet and the second inlet, the feeding device is further provided with a second feeding pipe connected to the denitration reactor and the second inlet, which is mixed with the flue gas entering the waste heat boiler and desulfurized, and the waste heat boiler feeds the flue gas to the heat exchanger through the second outlet.

4. According to the sulfur-containing flue gas waste heat recovery system of claim 3, a second desulfurization device is further provided between the second outlet and the heat exchanger to mix with the flue gas entering the heat exchanger and desulfurize.

5. A sulfur-containing flue gas waste heat recovery system according to claim 4, characterized in that: The second desulfurization device comprises a second material receiver and a second blower connected in sequence, and a second material bin connected to the second material receiver and filled with a second desulfurizer, so that the second blower can blow the second desulfurizer in the second material receiver into the flue.

6. A sulfur-containing flue gas waste heat recovery system according to claim 5, characterized in that: The dust collecting device includes a dust collector and a fluidizing trough located below the dust collector for diverting the reacted materials. The fluidizing trough is provided with a discharge port connected to a feeding device, a circulation channel for passing desulfurization powder into a desulfurization reactor, and a waste port for discharging waste. A chimney is also connected to the top of the dust collector.

7. A sulfur-containing flue gas waste heat recovery system according to claim 6, characterized in that: The first desulfurization device includes a desulfurization reactor connected to the downstream of the heat exchanger, and a first silo connected to the desulfurization reactor and filled with a first desulfurizing agent.

8. The sulfur-containing flue gas waste heat recovery system according to claim 1, characterized in that: The feeding device is a first material receiver and a first blower.

9. The sulfur-containing flue gas waste heat recovery system according to claim 1, characterized in that: The first desulfurizing agent in the first desulfurizing device is slaked lime.

10. A method for recovering waste heat from sulfur-containing flue gas, characterized in that: A sulfur-containing flue gas waste heat recovery system based on claim 7 above comprises the following steps: S100: before the flue gas enters the first inlet of the waste heat boiler, the desulfurization powder collected in the fluidizing tank is sprayed into the first feeding pipe connected to the feeding device, so that the flue gas and the calcium-based desulfurization ash are mixed in the waste heat boiler, the SO2 and SO3 in the flue gas are preliminarily desulfurized, carbon dioxide, calcium sulfite and calcium sulfate are generated, and the first heat exchange is performed; S200: The flue gas then enters the high-temperature dust collector and the denitration reactor in sequence from the first outlet to remove dust particles and denitrate the flue gas. Then, before the flue gas enters the second inlet of the waste heat boiler, the desulfurization powder collected in the fluidizing tank is sprayed into the second feeding pipe connected to the feeding device, so that the flue gas and the calcium-based desulfurization ash are mixed for the second time in the waste heat boiler, and the SO2 and SO3 in the flue gas are deeply desulfurized, and secondary heat exchange is performed; S300: before the flue gas enters the heat exchanger from the second outlet, the second desulfurization device sprays the second desulfurizer into the flue gas through the second receiver and the second blower to perform precise deacidification, and then the flue gas enters the heat exchanger for three heat exchanges; S400: The flue gas then enters the first desulfurization device, and at the same time the first silo sends slaked lime into the desulfurization reactor to mix with the flue gas, so that the flue gas undergoes a semi-dry process desulfurization of NID or CFB; S500: Finally, the flue gas after desulfurization and the desulfurized substances enter the dust collector for separation, the clean air is discharged through the chimney, the desulfurized substances enter the fluidized tank, and the desulfurized powder containing calcium-based desulfurized ash is sent to the feeding device, or the desulfurized powder is re-entered into the desulfurization reactor through the circulation channel for recycling; S600: the feeding device feeds the desulfurization powder through the first feeding pipe to perform preliminary desulfurization on the flue gas, and / or, feeds the desulfurization powder through the second feeding pipe to perform deep desulfurization on the flue gas; S700: After the desulfurization operation is completed, the remaining waste is discharged through the waste port of the fluidized tank.

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