Low-temperature flue gas desulfurization and waste heat utilization integrated device and method

Abstract

The invention discloses a low-temperature flue gas desulfurization and waste heat utilization integrated device, which relates to the technical field of flue gas desulfurization and comprises a hot blast stove, a heat exchanger, a chimney, an air mixing device, an induced draft fan, a desulfurizer bin, a blast furnace bin, a dust remover, a dust removal fan and an exhaust funnel, an ash bin; the outlet end of the hot blast stove is connected with the inlet end of the heat exchanger and the first inlet end of the air mixing device, the outlet end of the heat exchanger is connected with the inlet end of the chimney and the second inlet end of the air mixing device, the outlet end of the air mixing device is connected with the inlet end of the induced draft fan, and the first air outlet end of the induced draft fan is connected with the inlet end of the blast furnace bin. The outlet end of the blast furnace bin is connected with the inlet end of the dust remover, the gas outlet end of the dust remover is connected with the exhaust funnel through the dust removal fan, and the bottom of the dust remover is connected with the inlet end of the ash bin. Through the gradient collaborative design of'primary catalytic desulfurization + secondary precise desulfurization + tertiary deep desulfurization ', the desulfurization purification effect is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of flue gas desulfurization technology, and in particular to an integrated device and method for low-temperature flue gas desulfurization and waste heat utilization. Background Technology

[0002] As a regenerative heat exchanger, the core function of a modern hot blast stove is to provide high-temperature hot blast for blast furnace ironmaking. The energy consumption of this hot blast accounts for approximately one-quarter of the total energy consumption of the entire ironmaking system. Its standard operating procedure is as follows: the checker bricks inside the hot blast stove are heated by combustion of coal gas, and then cold outdoor air is introduced into the high-temperature checker brick channels. After heat exchange, the temperature of the cold air rises to 1100℃~1350℃ before being sent into the blast furnace for ironmaking. The temperature of the exhaust gas after heat exchange is usually controlled below 350℃ to ensure system thermal efficiency and prevent damage to the lower structure and furnace walls of the hot blast stove due to high temperatures. To further reduce energy consumption, steel plants generally install air heat exchangers on the exhaust gas pipelines to transfer the heat of the exhaust gas below 350℃ to the coal gas and combustion air before combustion in the furnace, raising their initial temperature to recover some heat, ultimately reducing the exhaust gas temperature to 150℃~200℃. This type of low-temperature exhaust gas is characterized by huge emissions and contains a small amount of sulfur. Except for a small amount used in pulverized coal production for ironmaking pulverized coal injection systems, drying coke moisture in blast furnace silos, or low-quality heat exchange for heating / cooling, most steel plants still emit it directly through chimneys, resulting in energy waste and potential environmental pollution.

[0003] Current environmental protection policies for ultra-low emissions clearly require that the sulfur dioxide emission concentration in blast furnace hot blast stove flue gas must be below 50 mg / m³. The sulfur in this waste gas originates from the coal gas used in ironmaking, and its content fluctuates significantly depending on production conditions. Currently, most steel plants use single forced desulfurization technologies to treat this type of low-temperature waste gas, such as activated carbon desulfurization, sodium bicarbonate desulfurization, and calcium-based fixed-bed desulfurization. While these methods can achieve basic desulfurization effects, they require substantial additional environmental protection costs and do not effectively recover and utilize the waste heat contained in the low-temperature flue gas, resulting in resource waste.

[0004] The existing patent CN108671123A (an integrated device for waste heat recovery, desulfurization, and denitrification of blast furnace hot blast stove flue gas) describes a technical solution involving a waste heat recovery tower and a desulfurization and denitrification tower connected in series. The waste heat recovery tower first recovers heat from the flue gas, and then the flue gas is passed into the desulfurization and denitrification tower for purification. This technology has three significant drawbacks: First, the waste heat recovery and desulfurization processes are separated, leading to a complex system flow and high equipment investment costs. Second, the desulfurization process uses a fixed dosage of ammonia water as the desulfurizing agent, which cannot adapt to the dynamic processing requirements of different coke moisture conditions, and ammonia water is volatile and highly corrosive to the inner walls of the equipment. Third, no specific solution has been designed to address the problem of pipe adhesion between desulfurization products and coke powder, which can easily lead to pipe blockage during long-term operation, seriously affecting the stable operation of the system.

[0005] Another published patent, CN110252894B (A system for drying coke and co-desulfurizing using low-temperature flue gas), has a core design that involves introducing low-temperature flue gas into the coke bin to dry the coke, while simultaneously installing a desulfurization tower at the coke bin outlet for a single-stage desulfurization process. However, this technology also has significant shortcomings: firstly, purification is achieved through a single desulfurization process, resulting in limited desulfurization efficiency and difficulty in meeting current ultra-low emission requirements; secondly, the desulfurizing agent uses a fixed-ratio magnesium-based composite agent, leading to high procurement costs and poor versatility, making it unsuitable for various operating conditions; and thirdly, it lacks a flue gas temperature control mechanism and a pipeline anti-adhesion structure, causing desulfurization products and coke powder to easily deposit and adhere within the pipeline, resulting in high equipment maintenance costs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an integrated device and method for low-temperature flue gas desulfurization and waste heat utilization.

[0007] To solve the above technical problems, the technical solution of the present invention is as follows: An integrated device for low-temperature flue gas desulfurization and waste heat utilization includes a hot blast stove, a heat exchanger, a chimney, a mixing device, an induced draft fan, a desulfurizing agent silo, a blast furnace charge silo, a dust collector, a dust removal fan, an exhaust stack, and an ash silo. The outlet end of the hot blast stove is connected to the inlet end of the heat exchanger and the first inlet end of the air mixing device, respectively. The outlet end of the heat exchanger is connected to the inlet end of the chimney and the second inlet end of the air mixing device, respectively. The outlet end of the air mixing device is connected to the inlet end of the induced draft fan. The first outlet end of the induced draft fan is connected to the inlet end of the blast furnace silo. The outlet end of the blast furnace silo is connected to the inlet end of the dust collector. The gas outlet end of the dust collector is connected to the exhaust stack through the dust collector fan. The solid outlet end at the bottom of the dust collector is connected to the inlet end of the ash silo. The first injection port of the desulfurizing agent silo is connected to the flue gas duct between the outlet end of the blast furnace silo and the inlet end of the dust collector.

[0008] As a preferred embodiment of the integrated low-temperature flue gas desulfurization and waste heat utilization device of the present invention, the blast furnace silo includes several coke silos, the inlet end of the bottom of each coke silo is connected to the first outlet end of the induced draft fan, and the outlet end of the top of each coke silo is connected to the flue gas pipeline between the dust collector and the blast furnace silo via a pipeline.

[0009] As a preferred embodiment of the integrated low-temperature flue gas desulfurization and waste heat utilization device of the present invention, wherein: along the flow direction of the flue gas, the connection between the first injection port of the desulfurizing agent silo and the flue gas pipeline is located behind the connection between the coke silo and the flue gas pipeline; The desulfurizing agent silo is also provided with several second spray ports, and the number of the second spray ports is the same as the number of the coke silos. Each second spray port is connected to a pipe between the coke silo and the flue gas pipe.

[0010] As a preferred embodiment of the integrated low-temperature flue gas desulfurization and waste heat utilization device of the present invention, the induced draft fan is further provided with a second air outlet, the second air outlet is connected to the flue gas pipeline between the dust collector and the blast furnace silo, and a control valve is provided on the pipeline where the second air outlet is located. Along the flow direction of the flue gas, the connection point between the second outlet and the flue gas duct is located behind the connection point between the first injection port of the desulfurizing agent silo and the flue gas duct.

[0011] As a preferred embodiment of the integrated low-temperature flue gas desulfurization and waste heat utilization device of the present invention, a U-shaped pipe is also provided on the flue gas pipeline between the dust collector and the blast furnace silo. The U-shaped pipe is close to the inlet end of the dust collector, and an ash discharge port connected to the inlet end of the ash silo is provided at the bottom of the U-shaped pipe.

[0012] As a preferred embodiment of the integrated low-temperature flue gas desulfurization and waste heat utilization device of the present invention, a flue gas shut-off valve is provided on the pipe between the heat exchanger and the chimney.

[0013] As a preferred embodiment of the integrated low-temperature flue gas desulfurization and waste heat utilization device of the present invention, the outlet end of the U-shaped tube is connected to the inlet end of the dust collector, the slope of both sides of the U-shaped tube is 3°~5°, and the inner lining of the U-shaped tube is made of ceramic material.

[0014] This invention also provides an integrated method for low-temperature flue gas desulfurization and waste heat utilization, which is based on the above-mentioned integrated device for low-temperature flue gas desulfurization and waste heat utilization, and includes: Close the flue gas shut-off valve on the pipe between the heat exchanger and the chimney; The high-temperature flue gas discharged from the hot air furnace outlet and the low-temperature flue gas discharged from the heat exchanger outlet enter the mixing device through the first inlet and the second inlet of the mixing device, respectively, and mix. The induced draft fan divides the mixed flue gas in the mixing device into two paths. One path serves as the main hot air pipe, which enters each coke silo through the bottom of the coke silo and forms convection with the coke falling in the coke silo, evaporating the moisture on the surface of the coke and raising the surface temperature of the coke to 40~70℃. At the same time, it completes the first catalytic oxidation desulfurization of the flue gas. The other path serves as the hot air branch pipe. When the flue gas temperature at the dust collector inlet is detected to be lower than the preset temperature, the control valve is opened to adjust the air volume until the flue gas temperature at the dust collector inlet is within the target temperature range. The determination of whether the desulfurizing agent injection volume needs to be adjusted separately is based on the coke moisture content in each coke bin. If not, the desulfurizing agent in the desulfurizing agent bin is controlled to be sprayed out from the first injection port and come into contact with the flue gas in the flue gas duct. If so, the desulfurizing agent in the desulfurizing agent bin is controlled to be sprayed out from the second injection port, and the desulfurizing agent injection volume of each second injection port is controlled according to the coke moisture content in each coke bin to complete the secondary precise desulfurization of the flue gas. After secondary precision desulfurization, the flue gas enters the U-shaped pipe, and the desulfurization products formed are discharged into the ash silo through the solid outlet end at the bottom of the U-shaped pipe, while the flue gas enters the dust collector. The flue gas is filtered by the dust collector to remove dust. At the same time, coke powder, unreacted desulfurizing agent and its desulfurization products are enriched on the surface of the filter bag to form a porous filter cake. Through the synergistic effect of physical adsorption and chemical adsorption, three-stage deep desulfurization is completed.

[0015] As a preferred embodiment of the integrated method for low-temperature flue gas desulfurization and waste heat utilization described in this invention, the desulfurizing agent in the desulfurizing agent silo is a mixed powder of Ca(OH)2 and CaO, and the mass ratio of Ca(OH)2 to CaO is 3:1 to 19:1.

[0016] As a preferred embodiment of the integrated low-temperature flue gas desulfurization and waste heat utilization method of the present invention, the step of determining whether separate desulfurizing agent injection volume adjustment is required based on the coke moisture content in each coke bin includes: When the moisture content of coke is less than or equal to 3%, the desulfurizing agent injection rate is 0.6 kg / h, and the proportion of CaO in the desulfurizing agent is 5%. When the moisture content of coke is greater than 3% and less than or equal to 7%, the desulfurizing agent injection rate is greater than 0.5 kg / h and less than or equal to 1.0 kg / h, and the proportion of CaO in the desulfurizing agent is greater than 5% and less than or equal to 15%. When the moisture content of coke is greater than 7% and less than or equal to 10%, the desulfurizing agent injection rate is greater than 1.0 kg / h and less than 1.5 kg / h, and the proportion of CaO in the desulfurizing agent is greater than 15% and less than 25%. When the moisture content of coke is greater than 10%, the desulfurizing agent injection rate is 1.5 kg / h, and the proportion of CaO in the desulfurizing agent is 25%.

[0017] The beneficial effects of this invention are: (1) The present invention adopts a gradient synergistic design of “one-stage catalytic oxidation desulfurization + two-stage precise neutralization desulfurization + three-stage filter cake deep desulfurization”. Compared with the single or two-stage desulfurization process of the prior art, the desulfurization and purification effect is significantly improved. The final sulfur dioxide concentration in the flue gas is ≤30mg / m³, which far exceeds the environmental protection ultra-low emission requirements. At the same time, after the acid gas is removed in multiple stages, the corrosion effect on the dust removal pipeline is greatly reduced, and the service life of the equipment is extended.

[0018] (2) The present invention establishes a quantitative corresponding adjustment mechanism for coke moisture content, desulfurizing agent dosage, and drying air volume. Compared with the fixed dosage desulfurization method used in the prior art, it can accurately adapt to the dynamic treatment requirements of different coke moisture conditions, and the desulfurization efficiency is stably maintained at over 95%, with more reliable treatment effect.

[0019] (3) The present invention uses a triple anti-adhesion design of "temperature control + U-shaped ceramic pipe + fixed discharge end". Compared with the existing technology that does not have a special anti-adhesion structure, the amount of adhesive material in the pipe is reduced by more than 80%, which greatly reduces the frequency of pipe cleaning, effectively reduces equipment maintenance costs and downtime losses, and improves the stability of continuous system operation.

[0020] (4) The present invention uses Ca(OH)2 and CaO mixed powder, which is readily available on the market, as a desulfurizing agent. It does not rely on special agents. Compared with magnesium-based composite agents, the procurement cost is reduced by more than 30%. It is highly universal and can be adapted to the working conditions of steel plants of different sizes. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A schematic diagram of the integrated low-temperature flue gas desulfurization and waste heat utilization device provided by the present invention; The components include: 1. Hot blast stove; 2. Heat exchanger; 3. Chimney; 4. Air mixing device; 5. Induced draft fan; 6. Desulfurizing agent bin; 7. Blast furnace charge bin; 8. Dust collector; 9. Dust removal fan; 10. Exhaust stack; 11. Ash bin; 12. U-shaped pipe. Detailed Implementation

[0023] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0024] Figure 1 The schematic diagram of the integrated low-temperature flue gas desulfurization and waste heat utilization device provided in the embodiments of this application includes a hot blast stove, heat exchanger, chimney, air mixing device, induced draft fan, desulfurizing agent silo, blast furnace charge silo, dust collector, dust removal fan, exhaust stack and ash silo.

[0025] Specifically, the outlet of the hot blast stove is connected to the inlet of the heat exchanger and the first inlet of the air mixing device. The outlet of the heat exchanger is connected to the inlet of the chimney and the second inlet of the air mixing device. The outlet of the air mixing device is connected to the inlet of the induced draft fan. The first outlet of the induced draft fan is connected to the inlet of the blast furnace silo. The outlet of the blast furnace silo is connected to the inlet of the dust collector. The gas outlet of the dust collector is connected to the exhaust stack via a dust collector fan. The solid outlet at the bottom of the dust collector is connected to the inlet of the ash silo. The first injection port of the desulfurizing agent silo is connected to the flue gas duct between the outlet of the blast furnace silo and the inlet of the dust collector. A flue gas shut-off valve is installed on the duct between the heat exchanger and the chimney.

[0026] High-temperature flue gas from the hot blast stove outlet and low-temperature flue gas from the heat exchanger outlet are both introduced into a mixing device. After mixing, the flue gas is brought to a suitable temperature range and then sent into the hot blast duct by an induced draft fan. It then enters the blast furnace silo from the bottom, where it forms convection currents with the falling coke. The mixed flue gas evaporates moisture from the coke surface, raising its temperature and simultaneously completing the first stage of catalytic oxidation desulfurization. After this first desulfurization, the flue gas enters the flue gas duct between the blast furnace silo outlet and the dust collector inlet, where it comes into contact with the desulfurizing agent sprayed from the desulfurizing agent chamber, completing a second stage of precise desulfurization. The flue gas then enters the dust collector for dust removal. Coke powder, unreacted desulfurizing agent, and their desulfurization products accumulate on the filter bag surface, forming a porous filter cake. Through the synergistic effect of physical and chemical adsorption, a third stage of deep desulfurization is completed.

[0027] The blast furnace charge silo comprises several coke charge silos, which can be used separately according to the type of coke. (See also...) Figure 1 In this embodiment, four coke silos are provided. The inlet end of the bottom of each coke silo is connected to the first outlet end of the induced draft fan, and the outlet end of the top of each coke silo is connected to the flue gas duct between the dust collector and the blast furnace silo via a pipeline. The coke particle size in the coke silos is 20~50mm.

[0028] It should be noted that, along the flow direction of the flue gas, the connection between the first injection port of the desulfurizing agent silo and the flue gas duct is located behind the connection between the coke silo and the flue gas duct.

[0029] Because different types of coke have varying moisture contents, the drying air volume and desulfurizing agent ratio need to be adjusted accordingly. Therefore, the desulfurizing agent silo is also equipped with several second spray nozzles, and the number of second spray nozzles is the same as the number of coke silos. In this embodiment, the desulfurizing agent silo has four second spray nozzles, each connected to the pipe between the corresponding coke silo and the flue gas duct. The four second spray nozzles can precisely adapt to the dynamic processing requirements of different coke moisture conditions.

[0030] In this embodiment, the desulfurizing agent in the desulfurizing agent silo is a mixed powder of Ca(OH)2 and CaO, and the mass ratio of Ca(OH)2 to CaO is 3:1 to 19:1.

[0031] Preferably, the induced draft fan also has a second outlet, which connects to the flue gas duct between the dust collector and the blast furnace silo. A control valve is installed on the duct where the second outlet is located. Along the flue gas flow direction, the connection between the second outlet and the flue gas duct is located behind the connection between the first injection port of the desulfurizing agent silo and the flue gas duct. The induced draft fan divides the mixed flue gas in the hot air duct into two paths: one is the main hot air pipe, which enters the coke silo from the bottom; the other is a hot air branch pipe, serving as a temperature control pipe. The flue gas temperature at the dust collector inlet is monitored in real time by a temperature sensor. When the flue gas temperature is below 55℃, the control valve opens the hot air branch pipe and adjusts the airflow to bring the flue gas temperature back to 55~65℃.

[0032] By supplementing heat through hot air branch pipes, the temperature of flue gas in the flue gas duct is always maintained at greater than or equal to 55℃ (dew point temperature threshold), which prevents H2O in the flue gas from condensing into liquid water and prevents desulfurization products (CaSO3, CaSO4) from dissolving and adhering to the inner wall of the duct.

[0033] See Figure 1 A U-shaped pipe is installed on the flue gas duct between the dust collector and the blast furnace silo, with the U-shaped pipe located near the inlet end of the dust collector. An ash discharge port, connecting to the ash silo inlet, is located at the bottom of the U-shaped pipe. The slope of the U-shaped pipe is 3°~5°, conforming to the law of gravity settling, facilitating ash deposition to the bottom ash discharge port. The inner lining of the U-shaped pipe is made of ceramic material. The low surface energy of the ceramic lining reduces ash adsorption, and combined with regular ash discharge operations, effectively avoids the risk of pipe adhesion.

[0034] Therefore, the risk of pipe adhesion is avoided from both the thermodynamic and structural dimensions by supplementing heat through hot air branch pipes at the temperature control level and by using U-shaped pipes to facilitate ash deposition at the structural design level.

[0035] This application also provides an integrated method for low-temperature flue gas desulfurization and waste heat utilization, based on the aforementioned integrated device for low-temperature flue gas desulfurization and waste heat utilization. The method includes the following steps: Step S101: Close the flue gas shut-off valve on the pipe between the heat exchanger and the chimney to prevent low-temperature flue gas from being directly discharged through the chimney, thereby achieving full recovery of the flue gas.

[0036] Step S102: The high-temperature flue gas discharged from the hot air furnace outlet and the low-temperature flue gas discharged from the heat exchanger outlet enter the mixing device through the first inlet and the second inlet of the mixing device respectively and mix.

[0037] Specifically, the high-temperature flue gas below 350°C discharged from the hot blast furnace outlet and the low-temperature flue gas below 200°C discharged from the heat exchanger outlet are both fed into the mixing device, where they are mixed to adjust the temperature of the mixed flue gas to 120~180°C.

[0038] Step S103: The induced draft fan divides the mixed flue gas in the mixing device into two paths. One path serves as the main hot air pipe (air volume 8000~12000m³ / h), which enters each coke silo through the bottom of the coke silo and forms convection with the coke falling in the coke silo, evaporating the surface moisture of the coke (the moisture content of the dried coke is ≤3%), and raising the surface temperature of the coke to 40~70℃. At the same time, the primary catalytic oxidation desulfurization of the flue gas is completed. The other path serves as the hot air branch pipe. When the flue gas temperature at the dust collector inlet is detected to be lower than 55℃, the control valve is opened to adjust the air volume until the flue gas temperature at the dust collector inlet is within the temperature range of 55~65℃.

[0039] Step S104: Determine whether the desulfurizing agent injection volume needs to be adjusted separately based on the coke moisture content in each coke bin. If not, control the desulfurizing agent in the desulfurizing agent bin to be sprayed out from the first injection port and contact the flue gas in the flue gas duct. If necessary, control the desulfurizing agent in the desulfurizing agent bin to be sprayed out from the second injection port, and control the desulfurizing agent injection volume of each second injection port according to the coke moisture content in each coke bin to complete the secondary precise desulfurization of the flue gas.

[0040] It is understandable that different types of coke have different moisture contents, requiring adjustments to the drying air volume and desulfurizer ratio. The specific adjustment methods are as follows: When the moisture content of coke is less than or equal to 3%, the desulfurizing agent injection rate is 0.6 kg / h, and the proportion of CaO in the desulfurizing agent is 5%. When the moisture content of coke is greater than 3% and less than or equal to 7%, the desulfurizing agent injection rate is greater than 0.5 kg / h and less than or equal to 1.0 kg / h, and the proportion of CaO in the desulfurizing agent is greater than 5% and less than or equal to 15%. When the moisture content of coke is greater than 7% and less than or equal to 10%, the desulfurizing agent injection rate is greater than 1.0 kg / h and less than 1.5 kg / h, and the proportion of CaO in the desulfurizing agent is greater than 15% and less than 25%. When the moisture content of coke is greater than 10%, the desulfurizing agent injection rate is 1.5 kg / h, and the proportion of CaO in the desulfurizing agent is 25%.

[0041] Step S105: The flue gas after secondary precision desulfurization enters the U-shaped pipe, and the desulfurization products formed are discharged into the ash silo through the solid outlet end at the bottom of the U-shaped pipe, while the flue gas enters the dust collector.

[0042] Step S106: The flue gas is filtered by the dust collector to remove dust. Simultaneously, coke dust, unreacted desulfurizing agent, and their desulfurization products accumulate on the filter bag surface, forming a porous filter cake. Through the synergistic effect of physical and chemical adsorption, three stages of deep desulfurization are completed. The desulfurization products and coke dust are discharged into the ash silo through the solid outlet at the bottom of the dust collector. The purified flue gas (sulfur dioxide concentration ≤30mg / m³) is sent into the exhaust stack by the dust collector fan and discharged in compliance with standards.

[0043] The above desulfurization reaction mechanism is as follows: Primary desulfurization mechanism (catalytic oxidation reaction): When low-temperature flue gas (120~180℃) comes into contact with moist coke, the carbon element (C) on the surface of the coke plays a catalytic role, reducing the activation energy of the sulfur dioxide oxidation reaction and triggering the reaction: 2SO2 + O2 + 2H2O === C 2H2SO4; the generated sulfuric acid (H2SO4) rapidly neutralizes the naturally occurring alkaline oxides (such as CaO and MgO) in the coke: H2SO4 + CaO = CaSO4 + H2O, forming stable sulfates to achieve the initial removal of sulfur dioxide; at the same time, the evaporation process of coke moisture provides sufficient H2O for the reaction, forming a "drying-desulfurization" synergistic effect.

[0044] Secondary desulfurization mechanism (acid-base neutralization reaction): Ca(OH)2 in the desulfurizing agent is a strong base, which can directly neutralize the residual sulfur dioxide in the flue gas: Ca(OH)2 + SO2 = CaSO3↓ + H2O. The generated calcium sulfite (CaSO3) is easily oxidized to stable calcium sulfate (CaSO4): 2CaSO3 + O2 = 2CaSO4↓. CaO in the desulfurizing agent continuously replenishes the alkalinity in the reaction system through hydration reaction: CaO + H2O = Ca(OH)2. This is especially suitable for high-moisture coke conditions (sufficient moisture can promote CaO hydration), effectively solving the problem of poor compatibility of single desulfurizing agents.

[0045] The three-stage desulfurization mechanism (filter cake adsorption reaction): The coke powder enriched on the filter bags of the bag filter has a porous structure, which can provide a large number of adsorption sites to capture residual sulfur dioxide in the flue gas through physical adsorption. At the same time, the unreacted Ca(OH)2 and CaO in the filter cake continue to undergo acid-base neutralization reactions with the adsorbed sulfur dioxide, and the active carbon sites on the surface of the coke powder can further catalyze the oxidation of sulfur dioxide, forming a deep purification mechanism of "physical adsorption + chemical adsorption" to ensure that the desulfurization efficiency meets the standards.

[0046] Therefore, the technical solution of this application, through a gradient synergistic design of "primary catalytic oxidation desulfurization + secondary precise neutralization desulfurization + tertiary filter cake deep desulfurization", significantly improves the desulfurization and purification effect compared with the single or two-stage desulfurization process of the existing technology. The final sulfur dioxide concentration in the flue gas is ≤30mg / m³, far exceeding the environmental protection ultra-low emission requirements. At the same time, after the acidic gas is removed in multiple stages, the corrosive effect on the dust removal pipeline is greatly reduced, extending the service life of the equipment.

[0047] In addition to the above embodiments, the present invention may have other implementation methods; all technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. An integrated device for low-temperature flue gas desulfurization and waste heat utilization, characterized in that: This includes hot blast stoves, heat exchangers, chimneys, air mixing devices, induced draft fans, desulfurizing agent bins, blast furnace charge bins, dust collectors, dust removal fans, exhaust stacks, and ash bins; The outlet end of the hot blast stove is connected to the inlet end of the heat exchanger and the first inlet end of the air mixing device, respectively. The outlet end of the heat exchanger is connected to the inlet end of the chimney and the second inlet end of the air mixing device, respectively. The outlet end of the air mixing device is connected to the inlet end of the induced draft fan. The first outlet end of the induced draft fan is connected to the inlet end of the blast furnace silo. The outlet end of the blast furnace silo is connected to the inlet end of the dust collector. The gas outlet end of the dust collector is connected to the exhaust stack through the dust collector fan. The solid outlet end at the bottom of the dust collector is connected to the inlet end of the ash silo. The first injection port of the desulfurizing agent silo is connected to the flue gas duct between the outlet end of the blast furnace silo and the inlet end of the dust collector.

2. The integrated low-temperature flue gas desulfurization and waste heat utilization device according to claim 1, characterized in that: The blast furnace silo includes several coke silos. The inlet end of the bottom of each coke silo is connected to the first outlet end of the induced draft fan, and the outlet end of the top of each coke silo is connected to the flue gas duct between the dust collector and the blast furnace silo via a pipeline.

3. The integrated low-temperature flue gas desulfurization and waste heat utilization device according to claim 2, characterized in that: Along the flow direction of the flue gas, the connection between the first injection port of the desulfurizing agent silo and the flue gas duct is located behind the connection between the coke silo and the flue gas duct; The desulfurizing agent silo is also provided with several second spray ports, and the number of the second spray ports is the same as the number of the coke silos. Each second spray port is connected to a pipe between the coke silo and the flue gas pipe.

4. The integrated low-temperature flue gas desulfurization and waste heat utilization device according to claim 3, characterized in that: The induced draft fan is also provided with a second air outlet, which is connected to the flue gas pipeline between the dust collector and the blast furnace silo. A control valve is provided on the pipeline where the second air outlet is located. Along the flow direction of the flue gas, the connection point between the second outlet and the flue gas duct is located behind the connection point between the first injection port of the desulfurizing agent silo and the flue gas duct.

5. The integrated low-temperature flue gas desulfurization and waste heat utilization device according to claim 4, characterized in that: A U-shaped pipe is also installed on the flue gas duct between the dust collector and the blast furnace silo. The U-shaped pipe is close to the inlet end of the dust collector, and an ash discharge port connected to the inlet end of the ash silo is provided at the bottom of the U-shaped pipe.

6. The integrated low-temperature flue gas desulfurization and waste heat utilization device according to claim 5, characterized in that: A flue gas shut-off valve is installed on the pipe between the heat exchanger and the chimney.

7. The integrated low-temperature flue gas desulfurization and waste heat utilization device according to claim 5, characterized in that: The outlet end of the U-shaped tube is connected to the inlet end of the dust collector. The slope of the two sides of the U-shaped tube is 3°~5°, and the inner lining of the U-shaped tube is made of ceramic material.

8. A method for integrating low-temperature flue gas desulfurization and waste heat utilization, based on the integrated low-temperature flue gas desulfurization and waste heat utilization device according to claim 6, characterized in that: include: Close the flue gas shut-off valve on the pipe between the heat exchanger and the chimney; The high-temperature flue gas discharged from the hot air furnace outlet and the low-temperature flue gas discharged from the heat exchanger outlet enter the mixing device through the first inlet and the second inlet of the mixing device, respectively, and mix. The induced draft fan divides the mixed flue gas in the mixing device into two paths. One path serves as the main hot air pipe, which enters each coke silo through the bottom of the coke silo and forms convection with the coke falling in the coke silo, evaporating the moisture on the surface of the coke and raising the surface temperature of the coke to 40~70℃. At the same time, it completes the first catalytic oxidation desulfurization of the flue gas. The other path serves as the hot air branch pipe. When the flue gas temperature at the dust collector inlet is detected to be lower than the preset temperature, the control valve is opened to adjust the air volume until the flue gas temperature at the dust collector inlet is within the target temperature range. The determination of whether the desulfurizing agent injection volume needs to be adjusted separately is based on the coke moisture content in each coke bin. If not, the desulfurizing agent in the desulfurizing agent bin is controlled to be sprayed out from the first injection port and come into contact with the flue gas in the flue gas duct. If so, the desulfurizing agent in the desulfurizing agent bin is controlled to be sprayed out from the second injection port, and the desulfurizing agent injection volume of each second injection port is controlled according to the coke moisture content in each coke bin to complete the secondary precise desulfurization of the flue gas. After secondary precision desulfurization, the flue gas enters the U-shaped pipe, and the desulfurization products formed are discharged into the ash silo through the solid outlet end at the bottom of the U-shaped pipe, while the flue gas enters the dust collector. The flue gas is filtered by the dust collector to remove dust. At the same time, coke powder, unreacted desulfurizing agent and its desulfurization products are enriched on the surface of the filter bag to form a porous filter cake. Through the synergistic effect of physical adsorption and chemical adsorption, three-stage deep desulfurization is completed.

9. The integrated method for low-temperature flue gas desulfurization and waste heat utilization according to claim 8, characterized in that: The desulfurizing agent is a mixed powder of Ca(OH)2 and CaO, and the mass ratio of Ca(OH)2 to CaO is 3:1 to 19:

1.

10. The integrated method for low-temperature flue gas desulfurization and waste heat utilization according to claim 9, characterized in that: The method of determining whether individual desulfurizer injection volume adjustment is needed based on the coke moisture content in each coke silo includes: When the moisture content of coke is less than or equal to 3%, the desulfurizing agent injection rate is 0.6 kg / h, and the proportion of CaO in the desulfurizing agent is 5%. When the moisture content of coke is greater than 3% and less than or equal to 7%, the desulfurizing agent injection rate is greater than 0.5 kg / h and less than or equal to 1.0 kg / h, and the proportion of CaO in the desulfurizing agent is greater than 5% and less than or equal to 15%. When the moisture content of coke is greater than 7% and less than or equal to 10%, the desulfurizing agent injection rate is greater than 1.0 kg / h and less than 1.5 kg / h, and the proportion of CaO in the desulfurizing agent is greater than 15% and less than 25%. When the moisture content of coke is greater than 10%, the desulfurizing agent injection rate is 1.5 kg / h, and the proportion of CaO in the desulfurizing agent is 25%.

Images