System and method for waste caustic liquid incineration tail gas upgrading reconstruction

Abstract

The application provides a system for upgrading and reforming waste lye incineration tail gas, which comprises a pretreatment unit, a purification unit and a discharge unit which are sequentially connected and arranged, and is used for sequentially performing pretreatment, purification and discharge on waste lye incineration tail gas; wherein the purification unit comprises a mist eliminator, a flue gas heat exchanger and an induced draft fan which are sequentially connected and arranged, and is used for performing purification and dust removal, heating and temperature rising and pressure dewatering on flue gas from the pretreatment unit; the discharge unit comprises a chimney, a blowdown tank and a blowdown pump; the chimney is connected to the induced draft fan and is used for discharging flue gas from the purification unit; the blowdown tank and the blowdown pump are connected and arranged, the blowdown tank is connected to a blowdown port of the mist eliminator, and the blowdown pump is connected to the pretreatment unit, so as to discharge sewage from the mist eliminator into the blowdown tank and then return the sewage to the pretreatment unit through the blowdown pump for recycling treatment. The system can remove particulate matters in flue gas, ensure that the flue gas particulate matters meet the new national standard emission requirements, and realize white smoke-free flue gas discharge.

Description

Technical Field

[0001] This invention belongs to the field of chemical waste gas treatment technology, specifically relating to a system and method for upgrading and retrofitting waste alkali incineration waste gas. Background Technology

[0002] In the existing coal chemical industry, the waste alkali incineration tail gas system is a fully positive pressure system. A blower drives the flue gas from the incinerator through a quench cooler, Venturi scrubber (12), flue gas condenser (14), and flue gas heat exchanger (22) to the chimney (31) before it is discharged into the atmosphere. The emitted flue gas does not meet the requirements of Clause 8.2.4 of the new national standard "Standard for Pollution Control of Hazardous Waste Incineration": the limit for particulate matter content in flue gas is 30 / 20 mg / Nm³. 3 (1-hour average / 24-hour average). In addition, the flue gas emitted from the waste alkali incineration tail gas is wet flue gas with a high relative humidity, close to 100%. The emitted flue gas mixes with the surrounding cold air, and the flue gas is cooled by the cold air, and the temperature drops. Under certain atmospheric temperature and humidity conditions, the water vapor in the flue gas condenses to form small droplets. There are a large number of droplets in the flue gas. During use, it will not only cause dew point corrosion to the equipment and pipelines such as fans, flues, and chimneys (31) of the flue gas system, but also reflect or refract sunlight at the chimney (31) outlet, forming white smoke. Specifically, the flue gas emitted by the traditional coal chemical waste alkali incineration tail gas device has the following disadvantages: (1) The content of particulate matter in the flue gas does not meet the requirements of the newly released national standards.

[0003] (2) Particulate matter in flue gas not only increases the consumption of process materials, but also causes great pollution to the environment.

[0004] (3) The existing equipment emits a large amount of white or gray smoke, causing visual pollution. It has failed to achieve effective smoke emission. The existing equipment's fans, flues, and chimneys (31) suffer from severe dew point corrosion.

[0005] (4) If the flue gas emissions do not meet the standards, the entire production unit needs to be shut down for renovation, which will affect the company's continuous production and cause serious economic losses.

[0006] To meet the environmental protection requirements of the new national standards, the existing waste alkali incineration tail gas emission process system needs to be upgraded to meet the production and environmental protection needs of the entire plant, ensure continuous production, and minimize economic losses to the industry.

[0007] Currently, there are no reports of upgrading and transformation solutions that can resolve the aforementioned technical issues. Summary of the Invention

[0008] The first objective of this invention is to provide a system for upgrading and retrofitting waste alkali incineration tail gas emissions, which can upgrade and retrofit existing waste alkali incineration tail gas emission processes and solve at least one of the aforementioned technical problems.

[0009] The second objective of this invention is to provide a method for upgrading the exhaust gas from waste alkali incineration using the aforementioned system.

[0010] To achieve the first objective of this invention, the following technical solution is adopted: A system for upgrading and retrofitting waste alkali incineration tail gas is characterized in that the system comprises a pretreatment unit, a purification unit, and an emission unit arranged sequentially, for sequentially pretreating, purifying, and discharging the waste alkali incineration tail gas; wherein... The purification unit includes a demister, a flue gas heat exchanger, and an induced draft fan arranged in sequence, which are used to purify and remove dust, heat up and pressurize the flue gas from the pretreatment unit, and dehydrate it. The emission unit includes a chimney, a sump, and a pump. The chimney is connected to the induced draft fan for discharging flue gas from the purification unit; The sewage discharge tank and the sewage pump are connected in a manner, with the sewage discharge tank connected to the sewage outlet of the demister and the sewage pump connected to the pretreatment unit. The sewage is used to discharge wastewater from the demister into the sewage discharge tank and then return it to the pretreatment unit for cyclic treatment via the sewage pump.

[0011] The present invention relates to a system for upgrading and retrofitting waste alkaline incineration tail gas, wherein preferably, the demister is an integrated precision demister.

[0012] The present invention relates to a system for upgrading and retrofitting waste alkaline incineration tail gas, preferably comprising a wire mesh demisting structure and a wet electrostatic demisting structure arranged sequentially from bottom to top within the system.

[0013] The present invention relates to a system for upgrading and retrofitting waste alkali incineration tail gas. Preferably, a booster pump is also provided on the water inlet pipeline of the demister to pressurize the water entering the demister.

[0014] The present invention relates to a system for upgrading and retrofitting waste alkali incineration tail gas. Preferably, the sewage discharge trough is also connected to the sewage discharge outlet of the chimney, for discharging sewage from the chimney into the sewage discharge trough.

[0015] This invention relates to a system for upgrading and retrofitting waste alkaline liquor incineration tail gas. Preferably, the pretreatment unit includes a quench tank, a Venturi dust collector, a Venturi circulating pump, and a flue gas condenser; wherein... The quench tank and the Venturi dust collector are connected in sequence to quench and remove dust from the waste alkaline liquid incineration tail gas in sequence. The inlet end of the Venturi circulating pump is connected to the drain port of the Venturi dust collector, and the outlet end is connected to the inlet port of the Venturi dust collector, for circulating the liquid inside the Venturi dust collector; The flue gas condenser inlet is connected to the venturi dust collector outlet, and the flue gas condenser outlet is connected to the demister, for cooling the flue gas from the venturi dust collector to condense and remove water before sending it to the demister for dust removal.

[0016] The present invention relates to a system for upgrading and retrofitting waste alkali incineration tail gas. Preferably, the sewage discharge tank is also connected to the liquid discharge port of the flue gas condenser for the flue gas condenser to discharge liquid into the sewage discharge tank.

[0017] The present invention relates to a system for upgrading and retrofitting waste alkali incineration tail gas. Preferably, the sewage pump is connected to the inlet of the Venturi dust collector to return the liquid from the sewage tank to the Venturi dust collector for circulation.

[0018] The present invention relates to a system for upgrading and retrofitting waste alkaline incineration tail gas. Preferably, in the purification unit, the heat exchange medium of the flue gas heat exchanger is steam; the drain tank is also connected to the drain port of the flue gas heat exchanger for discharging steam condensate from the flue gas heat exchanger to the drain tank.

[0019] The present invention relates to a system for upgrading and retrofitting waste alkali incineration tail gas. Preferably, the liquid inlet of the induced draft fan is connected to the water inlet pipe of the flue gas condenser, and the liquid outlet of the induced draft fan is connected to the water return pipe of the flue gas condenser.

[0020] The present invention relates to a system for upgrading and retrofitting waste alkali incineration tail gas. Preferably, the drain pipe of the flue gas condenser is provided with a downward slope along the material flow direction in the horizontal direction, and the slope is 1~2%.

[0021] The present invention relates to a system for upgrading and retrofitting waste alkali incineration tail gas. Preferably, the horizontally arranged portion of the chimney's sewage pipe is provided with a downward slope along the material flow direction, the slope being 1-2%.

[0022] To achieve the second objective of this invention, a method for upgrading the exhaust gas from waste alkali incineration using the aforementioned system is also provided.

[0023] The beneficial effects of this invention are as follows: This invention relates to a system for upgrading and retrofitting waste alkali incineration tail gas. By setting up a purification unit, the system utilizes a demister, flue gas heat exchanger, and induced draft fan to sequentially purify, remove dust, heat, pressurize, and dehydrate the flue gas from the pretreatment unit. This further removes particulate matter from the flue gas, ensuring negative pressure operation (i.e., below atmospheric pressure, such as -0.002 MPa(G)) in the flue gas pipeline. Low-pressure steam is used to heat the demisted, low-temperature flue gas to 100°C, achieving the effect of "whitening" emissions and ensuring that particulate matter emissions meet the new national emission standards, reducing corrosion of equipment and pipelines. The system is simple, reliable, easy to operate, and meets environmental protection requirements. Specifically, this includes: (1) reducing the concentration of particulate matter in flue gas; (2) eliminating white smoke or gray smoke to achieve the effect of "whitening" emissions; (3) ensuring the continuity of production, reducing the occurrence of production accidents, and reducing production costs; (4) enabling flue gas to meet emission standards, protecting the environment, and eliminating visual pollution; (5) avoiding dew point corrosion of fans, flues, chimneys, etc.; and (6) the process interlocking of demisters and flue gas heat exchangers ensures that operators have time to adjust and prepare corresponding contingency plans in case of changes in the content of emitted flue gas. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the system for upgrading and retrofitting waste alkali incineration tail gas in one embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the flue gas heat exchanger in one embodiment of the system for upgrading and retrofitting waste alkali incineration tail gas of the present invention. Detailed Implementation

[0026] The technical solution and its effects of the present invention will be further described below with reference to specific embodiments / examples. The following embodiments / examples are only for illustrating the content of the present invention, and the invention is not limited to the following embodiments or examples. Simple modifications made to the present invention based on the concept of the present invention are all within the scope of protection claimed by the present invention.

[0027] like Figures 1-2 As shown, this invention provides a system for upgrading and retrofitting waste alkali incineration tail gas, comprising a pretreatment unit, a purification unit, and an emission unit connected in sequence, for sequentially pretreating, purifying, and discharging the waste alkali incineration tail gas; wherein, The purification unit includes a demister 21, a flue gas heat exchanger 22 and an induced draft fan 23 connected in sequence, which are used to purify and remove dust, heat up and pressurize the flue gas from the pretreatment unit and dehydrate it. The emission unit includes a chimney 31, a sewage trough 32, and a sewage pump 33; The chimney 31 is connected to the induced draft fan 23 for discharging flue gas from the purification unit; The sewage discharge trough 32 and the sewage discharge pump 33 are connected and connected, with the sewage discharge trough 32 connected to the sewage discharge port of the demister 21 and the sewage discharge pump 33 connected to the pretreatment unit. The sewage from the demister 21 is discharged into the sewage discharge trough 32 and then returned to the pretreatment unit for cyclic treatment via the sewage discharge pump 33.

[0028] This invention relates to a system for upgrading the emissions of waste alkali incineration tail gas. By setting up a purification unit, the system utilizes a demister 21, a flue gas heat exchanger 22, and an induced draft fan 23 to sequentially purify, remove dust, heat, pressurize, and dehydrate the flue gas from the pretreatment unit. This further removes particulate matter from the flue gas, ensures negative pressure operation of the flue gas pipeline in the system, and uses low-pressure steam to heat the demisted, low-temperature flue gas to 100°C, achieving the effect of "whitening" emissions and ensuring that the particulate matter in the flue gas meets the new national emission standards, thus reducing the corrosion of equipment and pipelines by the flue gas.

[0029] In this invention, the flue gas treated by the demister 21 is close to saturated wet flue gas with a high relative humidity, nearly 100%. The flue gas is then heated and dehumidified by the flue gas heat exchanger 22 to reduce the H2O content in the flue gas, while simultaneously increasing the flue gas temperature and reducing the relative humidity, thus moving the flue gas away from the saturated state. After the flue gas is cooled, the amount of droplets decreases. Without droplets, no white smoke is produced, and the phenomenon of white smoke in the flue gas is significantly reduced.

[0030] This invention employs a flue gas heat exchanger 22, which uses low-pressure steam to heat the demisted, low-temperature flue gas to 100°C, reducing flue gas humidity. This not only prevents dew point corrosion of the fan, flue, and chimney, but also achieves the effect of eliminating white smoke emissions. Dehumidifying and heating the flue gas is key to white smoke control.

[0031] In some specific embodiments, the demister 21 is an integrated precision demister.

[0032] In some specific embodiments, the demister 21 includes a wire mesh demister structure and a wet electrostatic demister structure arranged sequentially from bottom to top therein, so that the flue gas passes through the wire mesh demister structure and the wet electrostatic demister structure sequentially from bottom to top to achieve the removal of particulate matter in the flue gas.

[0033] Neither wire mesh demisters nor wet electrostatic precipitators alone can achieve the goal of separating solid particulate matter from flue gas. The droplets discharged from the pretreatment unit (including the flue gas condenser) contain mechanical droplets (droplets generated by mechanical action) and steam condensate droplets (droplets generated by steam condensation). The mechanical droplets have a diameter range of 5–900 μm, while the steam condensate droplets have a diameter range of 0.1–30 μm. Wire mesh demisters can separate droplets larger than 3–5 μm, thus removing large droplets from the flue gas. Wet electrostatic precipitators are suitable for precision demisting, achieving a removal efficiency of 98–99% for droplets with a diameter of 1–2 μm. The combined use of the wire mesh demister structure and the wet electrostatic demister structure in the demister 21 can cover the entire diameter range of solid particulate matter in the flue gas, thereby ensuring demisting efficiency.

[0034] In this invention, the pretreated flue gas is fed into a demister 21. Under the combined action of a wire mesh demister structure and a wet electrostatic demister structure arranged sequentially from bottom to top within the demister, particulate matter and mist droplets are separated from the flue gas, and the particulate matter emission concentration can reach 30 / 20 mg / Nm³. 3 (1-hour average / 24-hour average) below, effectively preventing excessive dust in flue gas.

[0035] In some specific embodiments, the demister 21 has a water inlet and a smoke outlet located separately at its top, a smoke inlet located on its lower side wall, and a drain outlet located at its bottom.

[0036] In some specific embodiments, a booster pump 24 is also provided on the water inlet pipeline of the demister 21 to boost the water entering the demister 21, for example, to 0.35~0.5 MPa, such as 0.35 MPa, 0.4 MPa, 0.45 MPa and 0.5 MPa, as well as any value and range within this range.

[0037] In some specific embodiments, the water inlet pipe of the demister 21 is connected to the water inlet at its top, for introducing water into the demister 21 from top to bottom, so as to atomize and remove dust from the flue gas introduced from bottom to top, thereby removing particulate matter and achieving purification and dust removal of the flue gas.

[0038] In some specific implementation methods, such as Figure 2 As shown, the flue gas heat exchanger 22 includes a steam inlet and a cooling material outlet disposed on its side wall, a flue gas inlet disposed on its top and a flue gas outlet disposed on its bottom, and a flue gas flow channel formed in the middle along its central axis.

[0039] In some specific embodiments, the flue gas heat exchanger 22 has at least two steam inlets, such as two to twenty, and these inlets are spaced apart from top to bottom on its side wall to uniformly introduce steam into it for heat exchange and temperature increase of the introduced flue gas.

[0040] This invention utilizes low-pressure steam to heat the demisted, low-temperature flue gas to 100°C, achieving the effect of "whitening" emissions and ensuring that particulate matter emissions meet the new national emission standards, while reducing the corrosion of equipment and pipelines by the flue gas.

[0041] In some specific embodiments, the flue gas heat exchanger 22 has at least two outlets for cooling materials, such as two to twenty, and these outlets are spaced apart from top to bottom on its side wall to output the steam condensate obtained after heat exchange and cooling with the flue gas.

[0042] In some specific embodiments, in the flue gas heat exchanger 22, the steam inlet and the cooling material outlet are respectively positioned opposite each other on their side walls and are staggered.

[0043] In some specific embodiments, in the flue gas heat exchanger 22, the potential of the steam inlet is higher than that of the cooling material outlet in the corresponding steam inlet and cooling material outlet.

[0044] In some specific embodiments, the sewage trough 32 is also connected to the sewage outlet of the chimney 31, for the chimney 31 to discharge sewage into the sewage trough 32.

[0045] In some specific embodiments, the pretreatment unit includes a quench tank 11, a Venturi dust collector 12, a Venturi circulating pump 13, and a flue gas condenser 14; wherein, The quench tank 11 and the Venturi dust collector 12 are connected in sequence to quench and remove dust from the waste alkaline liquid incineration tail gas in sequence. The inlet end of the Venturi circulating pump 13 is connected to the drain port of the Venturi dust collector 12, and the outlet end is connected to the inlet port of the Venturi dust collector 12, for circulating the liquid in the Venturi dust collector 12. The inlet of the flue gas condenser 14 is connected to the outlet of the Venturi dust collector 12, and the outlet of the flue gas condenser 14 is connected to the demister 21. The flue gas is cooled from the Venturi dust collector 12 to condense and remove water before being sent to the demister 21 for demisting and dust removal.

[0046] In this invention, the waste alkaline liquid incineration tail gas is quenched by the quench tank 11. The output flue gas contains non-condensable gases, a large amount of water vapor, and trace amounts of Na2CO3 particles that were not absorbed in the quench tank 11. This flue gas enters the Venturi dust collector 12 for washing and dust removal. The moisture in the flue gas is partially condensed in the Venturi dust collector 12. In some specific embodiments, a demister is provided at the flue gas outlet of the Venturi dust collector 11 to further separate the water entrained in the flue gas. The separated flue gas enters the flue gas condenser 14, where circulating water cools the flue gas, condensing the moisture entrained in the flue gas from the Venturi dust collector 12 and most of the saturated water vapor in the flue gas into liquid water, reducing the volume fraction of moisture in the flue gas to below 10%. The condensed liquid water is circulated back to the Venturi dust collector 12 by the Venturi circulation pump 13 for continued use. The flue gas drawn from the flue gas condenser 14 is sent to the purification unit for treatment.

[0047] In this invention, the flue gas output from the demister 21 is heated to 100°C by the flue gas heat exchanger 22, and then pressurized by the induced draft fan 23 before being sent to the chimney for high-altitude discharge. This avoids dew point corrosion of the fan, flue, and chimney. In some specific embodiments, the induced draft fan 23 adopts a variable frequency motor, which can automatically adjust the flue gas pressure at the outlet of the quench tank 11 within a safe range, without affecting the operating pressure of the waste alkali incinerator system, nor affecting the existing ignition control system and safety system.

[0048] In some specific embodiments, the drain trough 32 is also connected to the drain port of the flue gas condenser 14, for the flue gas condenser 14 to drain liquid into the drain trough 32.

[0049] In some specific embodiments, when the sewage pump 33 is connected to the pretreatment unit, it is connected to the liquid inlet of the Venturi dust collector 12 in the pretreatment unit, and is used to return the liquid from the sewage tank 32 to the Venturi dust collector 12 for circulation.

[0050] In some specific embodiments, in the purification unit, the heat exchange medium of the flue gas heat exchanger 22 is steam, such as low-pressure steam, for example, with a pressure of 0.9~1.1 MPa; the drain tank 32 is also connected to the drain port of the flue gas heat exchanger 22, for the flue gas heat exchanger 22 to discharge steam condensate to the drain tank 32.

[0051] In some specific embodiments, in the pretreatment unit, the condensing medium of the flue gas condenser 14 is water; the drain tank 32 is also connected to the drain port of the flue gas condenser 14 for partially draining liquid from the flue gas condenser 14 to the drain tank 32.

[0052] In some specific embodiments, the flue gas condenser 14 includes a water inlet line connected to a water inlet on its lower side for water intake to cool the flue gas from the Venturi dust collector 12.

[0053] In some specific embodiments, the flue gas condenser 14 includes a return water pipeline, one end of which is connected to the drain port at its bottom and the other end of which is connected to the return water port on its upper side wall, for recycling a portion of the liquid discharged from the flue gas condenser 14.

[0054] In some specific embodiments, the liquid inlet of the induced draft fan 23 is connected to the water inlet pipe of the flue gas condenser 14, and the liquid outlet of the induced draft fan 23 is connected to the water return pipe of the flue gas condenser 14, for introducing water into the induced draft fan 23 to adjust the humidity of the flue gas from the flue gas heat exchanger 22 and then returning the water to the flue gas condenser 14.

[0055] In some specific embodiments, the drain pipe of the flue gas condenser 14 is provided with a downward slope along the material flow direction in the horizontally arranged portion, the slope being 1 to 2%, such as 1%, 1.5% and 2%, and any value and range within this range.

[0056] In some specific embodiments, the sewage pipe of the chimney 31 is provided with a downward slope along the material flow direction in the horizontally arranged part, the slope being 1 to 2%, such as 1%, 1.5% and 2%, and any value and range within this range.

[0057] In this invention, slope is expressed as a percentage. For example, a slope of 2% means that the height of the slope is 2 units when the horizontal distance is 100 units. The percentage method is the most common way to express slope, that is, the percentage of the difference in elevation between two points to their horizontal distance.

[0058] In some specific embodiments, the drainage / liquid discharge from the demister 21 and the flue gas condenser 14 flows by gravity to the low-level sewage trough 32, and is then pressurized by the sewage pump 33 before being sent to the Venturi dust collector 12. The sewage pump 33 is interlocked to start and stop according to the liquid level in the sewage trough 32.

[0059] In some specific embodiments, there are at least two induced draft fans 23, which are connected in parallel.

[0060] In some specific embodiments, there are at least two sewage pumps 32, which are connected in parallel.

[0061] In some specific embodiments, there are at least two Venturi circulation pumps 13, which are connected in parallel.

[0062] In some specific embodiments, there are at least two booster pumps 24, which are connected in parallel.

[0063] In this invention, relevant valves and detection components are installed on the relevant pipelines, such as pressure detectors and temperature detectors, which are not shown in the figure and will not be further described in detail.

[0064] like Figures 1-2 As shown, the system for upgrading and retrofitting waste alkaline incineration tail gas of the present invention operates as follows: Waste alkaline incineration tail gas enters the pretreatment unit, and is sequentially cooled, dusted, and cooled to remove water by passing through the quench tank 11, the Venturi dust collector 12, and the flue gas condenser 14, thus completing the pretreatment and outputting low-temperature flue gas; during this period, the Venturi circulation pump 13 circulates the liquid in the Venturi dust collector 12. The pretreated flue gas enters the purification unit and is sequentially passed through the demister 21, the flue gas heat exchanger 22, and the induced draft fan 23 for purification, dust removal, heating, pressurization, and dehydration. Specifically, the pretreated flue gas enters the demister 21 to remove particulate matter and droplets, then enters the flue gas heat exchanger 22 to be heated to 100°C using low-pressure steam, and then passes through the induced draft fan 23 for pressurization and dehydration to complete the purification process. The purified flue gas enters the emission unit and is discharged into the atmosphere through the chimney 31. The flue gas condenser 14 partially discharges liquid into the sewage trough 32, the demister 21 discharges liquid into the sewage trough 32, the flue gas heat exchanger 22 discharges steam condensate into the sewage trough 32, and the chimney 31 discharges sewage into the sewage trough 32. The material in the sewage discharge tank 32 is returned to the Venturi dust collector 12 for circulation via the sewage discharge pump 33.

[0065] This invention relates to a system for upgrading and retrofitting waste alkali incineration tail gas. By setting up a purification unit, the system utilizes a demister 21, a flue gas heat exchanger 22, and an induced draft fan 23 to sequentially purify, remove dust, heat, pressurize, and dehydrate the flue gas from the pretreatment unit. This further removes particulate matter from the flue gas, ensuring negative pressure operation of the flue gas pipeline within the system. Low-pressure steam is used to heat the demisted, low-temperature flue gas to 100°C, achieving a "whitening" emission effect and ensuring that particulate matter emissions meet the new national emission standards, reducing corrosion of equipment and pipelines. The body includes: (1) reducing the concentration of particulate matter in flue gas; (2) eliminating white smoke or gray smoke, achieving the effect of "whitening" emission of flue gas; (3) ensuring the continuity of production, reducing the occurrence of production accidents, and reducing production costs; (4) enabling flue gas to meet emission standards, protecting the environment, and eliminating visual pollution; (5) avoiding dew point corrosion of fans, flues, chimneys, etc.; (6) the process interlocking of demister 21 and flue gas heat exchanger 22 ensures that operators have time to adjust and prepare corresponding treatment plans in case of changes in the content of emitted flue gas.

[0066] The present invention also provides a method for upgrading the exhaust gas from waste alkali incineration using the aforementioned system.

[0067] The present invention will be further illustrated by the following examples.

[0068] Example 1 (S1) like Figures 1-2 The system shown for upgrading the exhaust gas from waste alkali incineration includes a pretreatment unit, a purification unit, and an emission unit connected in sequence, used to pretreat, purify, and discharge the exhaust gas from waste alkali incineration in sequence; wherein... The pretreatment unit includes a quench tank 11, a Venturi dust collector 12, a Venturi circulating pump 13, and a flue gas condenser 14. The quench tank 11 and the Venturi dust collector 12 are connected in sequence to quench and remove dust from the waste alkaline liquid incineration tail gas in sequence. The inlet end of the Venturi circulating pump 13 is connected to the drain port of the Venturi dust collector 12, and the outlet end is connected to the inlet port of the Venturi dust collector 12, for circulating the liquid in the Venturi dust collector 12. The flue gas condenser 14 has its inlet connected to the outlet of the Venturi dust collector 12, and its outlet connected to the demister 21. The flue gas condenser 14 is used to cool down the flue gas from the Venturi dust collector 12 to condense and remove the water before sending it to the demister 21 for dust removal. The purification unit includes a demister 21, a flue gas heat exchanger 22 and an induced draft fan 23 connected in sequence, which are used to purify and remove dust, heat up and pressurize the flue gas from the pretreatment unit and dehydrate it. The demister 21 includes a wire mesh demister structure and a wet electrostatic demister structure arranged sequentially from bottom to top therein; A booster pump 24 is also installed on the water inlet pipe of the demister 21 to boost the water entering the demister 21. The emission unit includes a chimney 31, a sewage trough 32, and a sewage pump 33; The chimney 31 is connected to the induced draft fan 23 for discharging flue gas from the purification unit; The sewage discharge tank 32 and the sewage discharge pump 33 are connected and connected, with the sewage discharge tank 32 connected to the sewage discharge port of the demister 21 and the sewage discharge pump 33 connected to the pretreatment unit. The sewage is used to discharge the sewage from the demister 21 into the sewage discharge tank 32 and then return it to the pretreatment unit for recycling via the sewage discharge pump 33. The sewage trough 32 is also connected to the sewage outlet of the chimney 31, for discharging sewage from the chimney 31 into the sewage trough 32; The drain pipe of the flue gas condenser 14 has a downward slope along the material flow direction in the horizontal direction. The slope is 2%. The sewage pipe of the chimney 31 has a downward slope along the material flow direction in the horizontally arranged portion, and the slope is 2%. The drain trough 32 is also connected to the drain port of the flue gas condenser 14, for the flue gas condenser 14 to drain liquid into the drain trough 32; The sewage pump 33 is connected to the liquid inlet of the Venturi dust collector 12 and is used to return the liquid from the sewage tank 32 to the Venturi dust collector 12 for circulation. The heat exchange medium of the flue gas heat exchanger 22 is steam; the drain tank 32 is also connected to the drain port of the flue gas heat exchanger 22, for the flue gas heat exchanger 22 to discharge steam condensate into the drain tank 32. The liquid inlet of the induced draft fan 23 is connected to the water inlet pipe of the flue gas condenser 14, and the liquid outlet of the induced draft fan 23 is connected to the water return pipe of the flue gas condenser 14.

[0069] This system was used to upgrade the exhaust gas from the waste alkali incineration process according to the aforementioned operating procedure. Testing revealed that... The particulate matter content in the exhaust gas from the incineration of waste alkaline solution is 300~500 mg / Nm³. 3 ; The particulate matter content in the flue gas exiting chimney 31 was 20 / 10 mg / Nm³. 3 (1-hour average / 24-hour average).

[0070] Based on the test results and operation process, it can be seen that compared with the exhaust gas from the waste alkali incineration, the particulate matter content in the flue gas from the outlet of chimney 31 is greatly reduced, and the particulate matter emission concentration can reach 20 / 10 mg / Nm³. 3 (1-hour average / 24-hour average) below, avoiding excessive dust in the flue gas, ensuring that particulate matter in the flue gas meets the new national emission standards, and reducing the corrosion of equipment and pipelines by the flue gas; and during operation, after the flue gas temperature rises to 100℃, it is pressurized by the induced draft fan and then sent to the chimney for high-altitude emission, achieving the effect of "whitening" the flue gas emission and eliminating visual pollution; avoiding dew point corrosion of fans, flues, chimneys, etc.

[0071] Comparative Example 1 (D1) The waste alkali incineration tail gas is treated using an existing treatment system for waste alkali incineration tail gas; however, the existing treatment system for waste alkali incineration tail gas differs from the system in Example 1 in the following ways: The purification unit only includes a flue gas heater, but does not include a demister 21, a flue gas heat exchanger 22, or an induced draft fan 23. The emission unit includes only the chimney 31, but does not include the sewage trough 32 and the sewage pump 33.

[0072] This system is used to treat the exhaust gas from the incineration of waste alkaline solution. Testing revealed... The particulate matter content in the exhaust gas from the incineration of waste alkaline solution is 300~500 mg / Nm³. 3 ; The particulate matter content in the flue gas exiting chimney 31 is 50~60 mg / Nm³. 3 .

[0073] According to the test results and operation process, although the particulate matter content in the flue gas at the outlet of chimney 31 is reduced compared to the waste alkali incineration tail gas, the particulate matter content in the discharged flue gas is still as high as 50~60 mg / Nm³. 3 The particulate matter emission concentration cannot meet the new national emission standards, and the flue gas corrodes equipment and pipelines; when the flue gas is emitted high into the air through the chimney, it produces white smoke, which causes visual pollution.

[0074] As can be seen from the comparison between Example 1 and Comparative Example 1, when the system of the present invention is used to treat the exhaust gas of waste alkaline liquid incineration, the dust removal effect is good, the particulate matter content in the emitted flue gas is low, the particulate matter emission concentration meets the new national emission standard requirements, and there is no white smoke emitted, thus avoiding visual pollution.

[0075] The above embodiments / examples are only used to illustrate the content of the present invention and are not limited thereto. Any simple changes made to the present invention based on the concept of the present invention are within the scope of protection claimed by the present invention.

Claims

1. A system for upgrading and retrofitting waste alkali incineration tail gas, characterized in that, The system includes a pretreatment unit, a purification unit, and a discharge unit arranged in sequence, used to pretreat, purify, and discharge the waste alkaline liquor incineration tail gas in sequence; wherein... The purification unit includes a demister (21), a flue gas heat exchanger (22), and an induced draft fan (23) connected in sequence, which are used to purify and remove dust, heat and pressurize the flue gas from the pretreatment unit and dehydrate it. The emission unit includes a chimney (31), a sewage trough (32), and a sewage pump (33). The chimney (31) is connected to the induced draft fan (23) for discharging flue gas from the purification unit; The sewage trough (32) and the sewage pump (33) are connected in a manner, and the sewage trough (32) is connected to the sewage outlet of the demister (21), and the sewage pump (33) is connected to the pretreatment unit. The sewage from the demister (21) is discharged into the sewage trough (32) and then returned to the pretreatment unit for cyclic treatment via the sewage pump (33).

2. The system according to claim 1, characterized in that, The demister (21) is an integrated precision demister; and / or, The demister (21) includes a wire mesh demister structure and a wet electrostatic demister structure arranged sequentially from bottom to top within it.

3. The system according to claim 1 or 2, characterized in that, A booster pump (24) is also installed on the water inlet pipeline of the demister (21) to pressurize the water entering the demister (21).

4. The system according to any one of claims 1-3, characterized in that, The sewage trough (32) is also connected to the sewage outlet of the chimney (31) for discharging sewage from the chimney (31) into the sewage trough (32).

5. The system according to any one of claims 1-4, characterized in that, The pretreatment unit includes a quench tank (11), a Venturi dust collector (12), a Venturi circulating pump (13), and a flue gas condenser (14); wherein, The quench tank (11) and the Venturi dust collector (12) are connected in sequence to quench and remove dust from the waste alkaline liquid incineration tail gas in sequence. The inlet end of the Venturi circulating pump (13) is connected to the drain port of the Venturi dust collector (12), and the outlet end is connected to the inlet port of the Venturi dust collector (12) for circulating the liquid in the Venturi dust collector (12). The inlet of the flue gas condenser (14) is connected to the outlet of the Venturi dust collector (12), and the outlet of the flue gas condenser (14) is connected to the demister (21) to cool down the flue gas from the Venturi dust collector (12) to condense and remove the water in it before sending it to the demister (21) for dust removal.

6. The system according to claim 5, characterized in that, The drain trough (32) is also connected to the drain port of the flue gas condenser (14) for draining liquid from the flue gas condenser (14) into the drain trough (32); and / or, The sewage pump (33) is connected to the inlet of the Venturi dust collector (12) to return the liquid from the sewage tank (32) to the Venturi dust collector (12) for circulation.

7. The system according to claim 5 or 6, characterized in that, In the purification unit, the heat exchange medium of the flue gas heat exchanger (22) is steam; the drain tank (32) is also connected to the drain port of the flue gas heat exchanger (22) for the flue gas heat exchanger (22) to discharge steam condensate into the drain tank (32).

8. The system according to any one of claims 5-7, characterized in that, The liquid inlet of the induced draft fan (23) is connected to the water inlet pipe of the flue gas condenser (14), and the liquid outlet of the induced draft fan (23) is connected to the water return pipe of the flue gas condenser (14).

9. The system according to any one of claims 6-8, characterized in that, The drain pipe of the flue gas condenser (14) has a downward slope along the material flow direction in the horizontally arranged portion, the slope being 1-2%; and / or, The sewage pipe of the chimney (31) has a downward slope along the material flow direction in the horizontally arranged part, and the slope is 1~2%.

10. A method for upgrading the tail gas emissions from waste alkali incineration using the system described in any one of claims 1-9.

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