Flue gas desulfurization system and method for graphitization furnace

Abstract

According to the graphitization furnace flue gas desulfurization system and method, the mixer and the desulfurization slurry storage tank are arranged, desulfurization slurry in the desulfurization slurry storage tank is pumped into the mixer through the liquid transfer pump to be mixed with flue gas output by the graphitization furnace, sulfur dioxide in the flue gas is absorbed, and meanwhile the desulfurization slurry is discharged through the liquid transfer pump. Drying the desulfurized slurry by using the heat of the flue gas, and reducing the temperature of the flue gas; meanwhile, the dust remover is used for removing dust of the flue gas and then introducing the flue gas into the gas washing device for washing. The device disclosed by the invention is matched with the devices for use, so that the wastewater output in the gas washing process can be effectively reduced, and the treatment cost of an enterprise is reduced. In addition, the flue gas is desulfurized by the desulfurization slurry and desulfurized by the gas washing device through the mixer, so that the consumption of absorption liquid in the gas washing device is saved, and the desulfurization effect can be improved by combining the desulfurization slurry and the gas washing device.

Description

Technical Field

[0001] The present application relates to the technical field of flue gas desulfurization, and in particular to a graphitization furnace flue gas desulfurization system and method. Background Art

[0002] With the rapid development of new energy vehicles around the world, the market demand for negative electrode materials for lithium batteries has increased significantly. Graphitized materials are important negative electrode materials. Negative electrode materials for lithium-ion batteries are mainly graphitized in graphitization furnaces of Acheson, internal heat series and other furnace types. First, fill the graphitization furnace with materials, including negative electrode materials and resistor materials, and then power on the graphitization furnace to heat it to 2500~3000℃ to achieve graphitization. During the heating process, volatiles, sulfur and trace elements in the materials escape at different temperature ranges and enter the flue gas treatment system through the gas collection hood equipment on the furnace surface. The flue gas emissions must meet national standards, industry standards and local standards. Therefore, the flue gas treatment technology of the graphitization furnace is crucial to the sustainable development of the industry. The volatile matter in the material mainly evaporates below 1000°C, and the flue gas evaporated above 1000°C is mainly sulfur dioxide. In actual production, the flue gas will be collected and treated in sections. The sulfur-containing flue gas discharged from the graphitization furnace has the characteristics of high sulfur dioxide concentration and high temperature (150~300°C).

[0003] The traditional desulfurization method is to cool the flue gas and exchange heat before passing it into a scrubber. That is, an alkaline absorption liquid such as lime milk is used in the desulfurization tower for spraying and washing to remove sulfur dioxide from the flue gas. However, this desulfurization method will produce a large amount of wastewater, which is not only difficult to treat but also consumes water resources. Summary of the invention

[0004] The present application provides a graphitization furnace flue gas desulfurization system and method, which are used to solve the problem of large amount of wastewater and waste of water resources in the above-mentioned existing spray washing method for removing sulfur dioxide from flue gas.

[0005] In a first aspect, the present application provides a graphitization furnace flue gas desulfurization system, comprising a graphitization furnace, the graphitization furnace being sequentially connected to a mixer, an expansion tube, a first fan, a dust collector, a second fan and a scrubber; The mixer is also connected to the gas outlet of the dust collector and the liquid outlet of the liquid transfer pump respectively; The liquid transfer pump is connected to the desulfurization slurry storage tank; The dust collector is also connected to the dust collecting tank.

[0006] The system of the present application is provided with a mixer and a desulfurization slurry storage tank, and the desulfurization slurry in the desulfurization slurry storage tank is pumped into the mixer through a liquid transfer pump to be mixed with the flue gas output by the graphitization furnace. While absorbing sulfur dioxide in the flue gas, the heat of the flue gas is used to dry the desulfurization slurry and reduce the temperature of the flue gas; at the same time, the dust collector is provided to remove dust from the flue gas and then pass it into the scrubber for washing. The device of the present application can effectively reduce the amount of wastewater generated in the scrubbing process and reduce the processing cost of the enterprise by using the above-mentioned devices. And the product generated by the mixer when the desulfurization slurry is used to absorb sulfur dioxide in the flue gas is dry solid particles, which has the beneficial effect of being easy to handle, and the heat of the flue gas itself is used when the drying slurry is used, because it also has the characteristic of reducing energy waste. In addition, in the present application, the flue gas is desulfurized by the desulfurization slurry through the mixer and the scrubber is used for desulfurization together, which can save the amount of absorption liquid in the scrubber, and the combination of the two can also improve the desulfurization effect.

[0007] Optionally, an air mixing tank is further provided between the second fan and the air washing device, and the air mixing tank is further connected to the air filter via the third fan.

[0008] Optionally, the mixer comprises a mixing section, a converging section and a diverging section which are connected in sequence; The mixing section and the tapering section are connected via a connecting pipe; At least one spray gun is arranged in the mixing section; The air inlet end of the spray gun is connected to the gas output end of the dust collector, and the liquid inlet end of the spray gun is connected to the liquid output port of the liquid transfer pump.

[0009] Optionally, the scrubber comprises a first desulfurization tower, a second desulfurization tower and a third desulfurization tower connected in series in sequence; The absorption liquid output end of the first desulfurization tower is connected to the dehydration device; The absorption liquid input end of the third desulfurization tower is connected to the lime slurry storage tank; The dehydration device is also connected to the gypsum storage bin and the lime slurry storage tank respectively.

[0010] Optionally, a flue gas distributor and a spiral sprayer are coaxially arranged on the top of the first desulfurization tower; The spiral sprayer is connected to the first liquid storage area at the bottom of the tower through the first circulation pump; The smoke distributor is connected to the gas output end of the second fan; The absorption liquid input end of the first liquid storage area is connected to the liquid discharge end of the second desulfurization tower; the absorption liquid output end of the first liquid storage area is connected to the dehydration device.

[0011] Optionally, multiple first spray layers are arranged from top to bottom in the second desulfurization tower, and each first spray layer is connected to the second liquid storage area at the bottom of the tower through a second circulation pump; The flue gas input end at the lower part of the second desulfurization tower is connected to the flue gas output end at the lower part of the first desulfurization tower; The second liquid storage area is connected to the absorption liquid output end of the third desulfurization tower.

[0012] Optionally, a tray layer is provided in the third desulfurization tower, and multiple layers of second spray layers are provided between the tower top and the tray layer, and each second spray layer is connected to the third liquid storage area at the bottom of the tower through a third circulation pump; The absorption liquid input end of the third liquid storage area is connected to the lime slurry storage tank; The gas input end at the lower part of the third desulfurization tower is connected to the gas output end at the top of the second desulfurization tower.

[0013] In a second aspect, the present application provides a method for desulfurizing flue gas in a graphitization furnace, comprising the following steps: The solid adsorbent is crushed and passed through a 500-mesh sieve to obtain a powder, and an alkali solution is added to the powder to prepare a desulfurization slurry with a concentration of 45-55wt%; The desulfurized slurry is sprayed into the mixer through a spray gun and mixed with the flue gas discharged from the graphitization furnace to obtain mixed flue gas; Passing the mixed flue gas into a dust collector for dust removal to obtain dust-removed flue gas; The dust-removed flue gas is passed into a multi-stage desulfurization scrubber for scrubbing to obtain purified gas.

[0014] Optionally, the solid adsorbent includes one or more of slag, fly ash, activated carbon, and zeolite.

[0015] Optionally, the alkali solution is an aqueous solution of an inorganic alkali or an organic alkali with a concentration of 10-15wt%. The beneficial effects of the flue gas desulfurization method for a graphitization furnace provided in the present application are the same as the beneficial effects of the flue gas desulfurization system for a graphitization furnace provided in the first aspect above, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 A schematic diagram of a flue gas desulfurization system for a graphitization furnace provided in one embodiment of the present application; Figure 2 A schematic diagram of a flue gas desulfurization system for a graphitization furnace provided in another embodiment of the present application; Figure 3 A schematic diagram of the structure of a mixer provided in one embodiment of the present application; Figure 4A schematic diagram of a scrubbing device provided in one embodiment of the present application.

[0018] Description of reference numerals: 1. Graphitization furnace; 2. Mixer; 3. Expansion tube; 4. Dust collector; 5. Scrubber; 6. Desulfurization slurry storage tank; 7. Mixing tank; 10. First fan; 20. Second fan; 21. Mixing section; 22. Gradually contracting section; 23. Gradually expanding section; 24. Connecting pipe; 25. Spray gun; 30. Liquid transfer pump; 40. Third fan; 41. Dust collecting tank; 51. First desulfurization tower; 52. Second desulfurization tower; 53. Third desulfurization tower ; 54. Dehydration device; 55. Lime slurry storage tank; 61. Air filter; 510. First circulation pump; 511. Flue gas distributor; 512. Spiral sprayer; 513. First liquid storage area; 520. Second circulation pump; 521. First spray layer; 522. Second liquid storage area; 530. Third circulation pump; 531. Tray layer; 532. Second spray layer; 533. Third liquid storage area; 541. Gypsum storage bin. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work also fall within the scope of protection of the present application.

[0020] like Figure 1 As shown, in the first aspect, the present application provides a graphitization furnace flue gas desulfurization system, comprising a graphitization furnace 1, the graphitization furnace 1 is sequentially connected to a mixer 2, an expansion tube 3, a first fan 10, a dust collector 4, a second fan 20 and a scrubber 5; The mixer 2 is also connected to the gas outlet of the dust collector 4 and the liquid outlet of the liquid transfer pump 30 respectively; The liquid transfer pump 30 is connected to the desulfurization slurry storage tank 6; The dust collector 4 is also connected to a dust collecting tank 41 .

[0021] When the system of the present application is in use, the flue gas emitted by the graphitization furnace 1 is passed into the mixer 2, and at the same time, the liquid transfer pump 30 pumps the desulfurization slurry (a slurry configured with a 500-mesh solid adsorbent with a concentration of 45~55wt%) stored in the desulfurization slurry storage tank 6 into the mixer 2 (the structure of the mixer 2 is similar to a venturi tube) to mix with the flue gas output by the graphitization furnace 1.

[0022] The mixed flue gas is discharged from the mixer 2 to the expansion pipe 3 for further expansion. Since the flue gas has a relatively high temperature (150-300°C), the water in the slurry evaporates after the flue gas is mixed with the atomized slurry, and the slurry is dried. The dried slurry forms solid particles and water vapor. At the same time, since the slurry is prepared by 12-15wt% alkali solution, the slurry will react with sulfur dioxide in the flue gas. At this time, the solid particles formed by the dried slurry can be used as the attachment point for absorbing sulfur dioxide and the reaction product of alkali solution and sulfur dioxide, thereby absorbing and removing sulfur dioxide in the flue gas.

[0023] When the mixed flue gas is in the expansion pipe 3, the airflow velocity is further reduced due to the increase in the cross section (the diameter of the expansion pipe 3 is 2 to 3 times the inner diameter of the output end of the mixer 2), and the air pressure is reduced. Part of the solid particles in the mixed flue gas will settle in the expansion pipe 3. At the same time, due to the reduction in air pressure, it is conducive to the full vaporization of the water in the droplets of the slurry, and the solid-liquid separation in the slurry is realized. The mixed flue gas expanded, decelerated and separated by the expansion pipe 3 is compressed and pressurized by the first fan 10 and then input into the dust collector 4 (the dust collector 4 is a cyclone dust collector, a bag dust collector or an electrostatic precipitator) for dust removal, and the sulfur-containing dust after dust removal is stored in the dust collecting tank 41; a part of the dust-removed flue gas after dust removal is input into the mixer 2 for atomization desulfurization slurry, and the other part is compressed and pressurized again by the second fan 20 and input into the scrubber 5 to use the absorption liquid (lime milk in this application) for spray washing to obtain purified gas.

[0024] The system of the present application is provided with a mixer 2 and a desulfurization slurry storage tank 6, and the desulfurization slurry in the desulfurization slurry storage tank 6 is pumped into the mixer 2 through a liquid transfer pump 30 to be mixed with the flue gas output by the graphitization furnace 1. While absorbing sulfur dioxide in the flue gas, the desulfurization slurry is dried by using the heat of the flue gas and the temperature of the flue gas is reduced; at the same time, the dust collector 4 is provided to remove dust from the flue gas and then pass it into the scrubber 5 for washing. The device of the present application can effectively reduce the amount of wastewater generated in the scrubbing process and reduce the processing cost of the enterprise by using the above-mentioned devices. And the product generated by the mixer 2 when using the desulfurization slurry to absorb sulfur dioxide in the flue gas is dry solid particles, which has the beneficial effect of being easy to handle, and the heat of the flue gas itself is used when the drying slurry is used, because it also has the characteristic of reducing energy waste. In addition, in the present application, the flue gas is desulfurized by the desulfurization slurry through the mixer 2 and the scrubber 5 is used together for desulfurization, which saves the amount of absorption liquid in the scrubber 5, and the combination of the two can also improve the desulfurization effect.

[0025] like Figure 2 As shown, optionally, an air mixing tank 7 is further provided between the second fan 20 and the air washing device 5 , and the air mixing tank 7 is further connected to the air filter 61 through the third fan 40 .

[0026] In the present application, part of the dust-removed flue gas after dust removal is input into the mixer 2 for use as atomized desulfurization slurry, and the other part is compressed and pressurized again by the second fan 20 and then input into the mixing tank 7 to mix with the air sucked by the third fan 40 and filtered by the air filter 61. This method can further reduce the temperature of the flue gas entering the scrubber 5. The volume ratio of the air sucked by the third fan 40 to the dust-removed flue gas is 1:5~6; at the same time, it can also reduce the concentration of sulfur dioxide in the flue gas, which is beneficial to the scrubbing and removal of sulfur dioxide by the scrubber 5, and the introduced air can increase the oxygen content in the flue gas, which is beneficial to the oxidation of sulfite generated by the reaction of the flue gas and the absorption liquid into stable sulfuric acid, thereby facilitating the desulfurization of the flue gas.

[0027] like Figure 3 As shown, optionally, the mixer 2 includes a mixing section 21, a tapering section 22 and a gradually expanding section 23 which are connected in sequence; The mixing section 21 and the tapered section 22 are connected via a connecting pipe 24; At least one spray gun 25 is provided in the mixing section 21; The air inlet end of the spray gun 25 is connected to the gas output end of the dust collector 4 , and the liquid inlet end of the spray gun 25 is connected to the liquid output port of the liquid transfer pump 30 .

[0028] In the present application, when in use, the flue gas discharged from the graphitization furnace 1 is introduced into the mixer 2, and at the same time, the liquid transfer pump 30 pumps the desulfurization slurry (a slurry configured with a 500-mesh solid adsorbent with a concentration of 45-55wt%) stored in the desulfurization slurry storage tank 6 into the spray gun 25, and mixes it with the dust removal flue gas output by the dust collector 4 (the gas-liquid ratio is 10-15:1), and is sprayed into the mixer 2 in the form of mist, and mixed with the flue gas output by the graphitization furnace 1.

[0029] When mixing in the mixer 2 (the structure of the mixer 2 is similar to that of a venturi tube), the mist slurry sprayed from the spray gun 25 is mixed with the flue gas in the mixing section 21, and then further mixed through the tapering section 22. At the same time, since the diameter of the tapering section 22 gradually decreases, the flow rate of the mixed flue gas of the slurry and the flue gas will increase, and since the diameter of the tapering section 22 gradually decreases, it is also beneficial to the mixing of the two. The mixed flue gas passing through the tapering section 22 enters the expanding section 23 through the connecting pipe 24. At this time, the flow rate of the mixed flue gas gradually decreases, and is discharged from the expanding section 23 to the expansion pipe 3 for further expansion.

[0030] like Figure 4 As shown, optionally, the scrubber 5 comprises a first desulfurization tower 51, a second desulfurization tower 52 and a third desulfurization tower 53 connected in series in sequence; The absorption liquid output end of the first desulfurization tower 51 is connected to the dehydration device 54; The absorption liquid input end of the third desulfurization tower 53 is connected to the lime slurry storage tank 55; The dehydration device 54 is also connected to the gypsum storage bin 541 and the lime slurry storage tank 55 respectively.

[0031] In the present application, when the absorption liquid in the first desulfurization tower 51 is saturated, the absorption liquid is discharged into the dehydration device 54 (the dehydration device is, for example, a centrifugal dehydrator, a filter press, etc.) for dehydration to obtain separated water and solid gypsum. The gypsum is stored in the gypsum storage bin 541, and the separated water is returned to the lime slurry storage tank 55 for the preparation of the absorption liquid.

[0032] like Figure 4 As shown, optionally, a flue gas distributor 511 and a spiral sprayer 512 are coaxially arranged on the top of the first desulfurization tower 51; The spiral sprayer 512 is connected to the first liquid storage area 513 at the bottom of the tower through the first circulation pump 510; The smoke distributor 511 is connected to the gas output end of the second fan 20; The absorption liquid input end of the first liquid storage area 513 is connected to the liquid discharge end of the second desulfurization tower 52 ; the absorption liquid output end of the first liquid storage area 513 is connected to the dehydration device 54 .

[0033] In the first desulfurization tower 51, the mixed flue gas enters the flue gas distributor 511 at the top of the first desulfurization tower 51, and at the same time, the first circulating pump 510 pumps the absorption liquid (lime milk) in the first liquid storage area 513 at the bottom of the tower to the spiral sprayer 512 at the top of the tower, and mixes and washes it in parallel with the flue gas sprayed from the flue gas distributor 511. The washed absorption liquid is temporarily stored in the first liquid storage area 513 and circulated and sprayed by the first circulating pump 510. The washed flue gas is discharged from the flue gas outlet at the lower side of the tower and enters the second desulfurization tower 52.

[0034] like Figure 4 As shown, optionally, multiple first spray layers 521 are arranged from top to bottom in the second desulfurization tower 52, and each first spray layer 521 is connected to the second liquid storage area 522 at the bottom of the tower through a second circulation pump 520; The flue gas input end at the lower part of the second desulfurization tower 52 is connected to the flue gas output end at the lower part of the first desulfurization tower 51; The second liquid storage area 522 is connected to the absorption liquid output end of the third desulfurization tower 53 .

[0035] When in use, the flue gas output from the first desulfurization tower 51 enters from the flue gas inlet at the bottom of the second desulfurization tower 52 and moves from bottom to top. At the same time, the second circulation pump 520 pumps the absorption liquid in the second liquid storage area 522 at the bottom of the tower into the multiple first spray layers 521 in the upper part of the tower. The absorption liquid is sprayed from the first spray layer 521 from top to bottom, countercurrently contacting the flue gas to wash the flue gas. The washed flue gas is discharged from the flue gas outlet at the top of the tower to the third desulfurization tower 53; the washed absorption liquid falls into the second liquid storage area 522 and is circulated and sprayed by the second circulation pump 520.

[0036] Taking into account the gas blocking and desulfurization effects, the number of layers of the first spray layer 521 is preferably 4 to 5.

[0037] like Figure 4 As shown, optionally, a tray layer 531 is provided in the third desulfurization tower 53, and multiple layers of second spray layers 532 are provided between the tower top and the tray layer 531, and each second spray layer 532 is connected to the third liquid storage area 533 at the bottom of the tower through a third circulation pump 530; The absorption liquid input end of the third liquid storage area 533 is connected to the lime slurry storage tank 55; The gas input end at the bottom of the third desulfurization tower 53 is connected to the gas output end at the top of the second desulfurization tower 52 .

[0038] When in use, the flue gas output from the second desulfurization tower 52 enters the third desulfurization tower 53 and moves from bottom to top, and continues to move upward after being distributed through the tray layer 531. At the same time, the third circulation pump 530 pumps the absorption liquid in the third liquid storage area 533 at the bottom of the tower into the multiple second spray layers 532 at the upper part of the tower. The absorption liquid sprays from the second spray layer 532 from top to bottom, and contacts with the flue gas in countercurrent to wash the flue gas. The cleaned gas after washing is discharged from the flue gas outlet at the top of the tower, and the absorption liquid falls into the third liquid storage area 533 and is circulated and sprayed by the third circulation pump 530.

[0039] Taking into account the gas blocking and desulfurization effects, the number of layers of the second spray layer 532 is preferably 3 to 4.

[0040] In addition, the above-mentioned first liquid storage tank 513, second liquid storage tank 522 and third liquid storage tank 533 can be connected to oxygen supply fans, which can continuously blow air or oxygen into the tank to facilitate the oxidation of sulfite (calcium sulfite) generated in the tank into more stable sulfate (calcium sulfate), thereby fixing sulfur in the form of sulfate to achieve flue gas desulfurization.

[0041] The working process of a graphitization furnace flue gas desulfurization system is as follows: When in use, the flue gas discharged from the graphitization furnace 1 is introduced into the mixer 2, and at the same time, the liquid transfer pump 30 pumps the desulfurization slurry (a slurry configured with a 500-mesh solid adsorbent with a concentration of 45-55wt%) stored in the desulfurization slurry storage tank 6 into the spray gun 25, and mixes it with the dust-removed flue gas output by the dust-removing flue gas dust collector 4 (the gas-liquid ratio is 10-15:1), and is sprayed into the mixer 2 in the form of mist, and mixed with the flue gas output by the graphitization furnace 1.

[0042] When mixing in the mixer 2 (the structure of the mixer 2 is similar to that of a venturi tube), the mist slurry sprayed from the spray gun 25 is mixed with the flue gas in the mixing section 21, and then further mixed through the tapering section 22. At the same time, since the diameter of the tapering section 22 gradually decreases, the flow rate of the mixed flue gas of the slurry and the flue gas will increase, and since the diameter of the tapering section 22 gradually decreases, it is also beneficial to the mixing of the two. The mixed flue gas passing through the tapering section 22 enters the expanding section 23 through the connecting pipe 24. At this time, the flow rate of the mixed flue gas gradually decreases, and is discharged from the expanding section 23 to the expansion pipe 3 for further expansion. And because the flue gas has a relatively high temperature (150~300℃), the water in the slurry evaporates after the flue gas is mixed with the atomized slurry, and the slurry is dried. The dried slurry forms solid particles and water vapor. At the same time, because the slurry is prepared by 12~15wt% of alkali solution, the slurry will react with sulfur dioxide in the flue gas. At this time, the solid particles formed by the dry slurry can be used as an adsorbent for absorbing sulfur dioxide, as well as an attachment point for the alkali solution and sulfur dioxide reactants, thereby absorbing and removing sulfur dioxide from the flue gas.

[0043] When the mixed flue gas is in the expansion tube 3, the air flow velocity is further reduced due to the increase in the cross-section (the diameter of the expansion tube 3 is 2 to 3 times the inner diameter of the output end of the gradually expanding section 23), and the air pressure is reduced. Part of the solid particles in the mixed flue gas will settle in the expansion tube 3. At the same time, due to the reduction in air pressure, it is beneficial to fully vaporize the water in the droplets of the slurry, thereby realizing the solid-liquid separation in the slurry. The mixed flue gas expanded, decelerated and separated by the expansion tube 3 is compressed and pressurized by the first fan 10 and then input into the dust collector 4 (the dust collector 4 is a cyclone dust collector, a bag dust collector or an electrostatic precipitator) for dust removal, and the sulfur-containing dust after dust removal is stored in the dust collecting tank 41; a part of the dust-removed flue gas after dust removal is input into the spray gun 25 for use as atomized desulfurization slurry, and the other part is compressed and pressurized again by the second fan 20 and then input into the mixing tank 7 to be mixed with the air sucked by the third fan 40 and filtered by the air filter 61 (this method can further reduce the temperature of the flue gas entering the tower, and the volume ratio of the air sucked by the third fan 40 to the dust-removed flue gas is 1:5~6).

[0044] The mixed flue gas enters the flue gas distributor 511 at the top of the first desulfurization tower 51. At the same time, the first circulating pump 510 pumps the absorption liquid (lime milk) in the first liquid storage area 513 at the bottom of the tower to the spiral sprayer 512 at the top of the tower, and mixes and washes it in parallel with the flue gas sprayed from the flue gas distributor 511. The washed absorption liquid is temporarily stored in the first liquid storage area 513 and circulated and sprayed by the first circulating pump 510. The washed flue gas is discharged from the flue gas outlet at the lower part of the tower side and enters the flue gas outlet at the lower part of the second desulfurization tower 52. The gas inlet moves from bottom to top, and at the same time, the second circulation pump 520 pumps the absorption liquid in the second liquid storage area 522 at the bottom of the tower into multiple first spray layers 521 in the upper part of the tower. The absorption liquid is sprayed from the first spray layer 521 from top to bottom, countercurrently contacting the flue gas to wash the flue gas. The washed flue gas is discharged from the flue gas outlet at the top of the tower and enters from the flue gas inlet on the lower side of the third desulfurization tower 53; the washed absorption liquid falls into the second liquid storage area 522 and is circulated and sprayed by the second circulation pump 520.

[0045] The flue gas output from the second desulfurization tower 52 enters the third desulfurization tower 53 and moves from bottom to top. After being distributed through the tray layer 531, it continues to move upward. At the same time, the third circulation pump 530 pumps the absorption liquid in the third liquid storage area 533 at the bottom of the tower into the multiple second spray layers 532 in the upper part of the tower. The absorption liquid sprays from the second spray layer 532 from top to bottom, and contacts with the flue gas in countercurrent to wash the flue gas. The cleaned gas after washing is discharged from the flue gas outlet at the top of the tower, and the absorption liquid falls into the third liquid storage area 533 and is circulated and sprayed by the third circulation pump 530.

[0046] During operation, the lime slurry storage tank 55 is used to replenish the absorption liquid to the third desulfurization tower 53, the absorption liquid in the third liquid storage area 533 at the bottom of the third desulfurization tower 53 is used to replenish the absorption liquid to the second liquid storage area 522 of the second desulfurization tower 52, and the second liquid storage area 522 of the second desulfurization tower 52 is used to replenish the absorption liquid to the first liquid storage area 513 of the first desulfurization tower 51.

[0047] When the absorption liquid in the first desulfurization tower 51 is saturated, the absorption liquid is discharged into the dehydration device 54 (the dehydration device is, for example, a centrifugal dehydrator, a filter press, etc.) for dehydration to obtain separated water and solid gypsum. The gypsum is stored in the gypsum storage bin 541, and the separated water is returned to the lime slurry storage tank 55 for the preparation of the absorption liquid.

[0048] In a second aspect, the present application provides a method for desulfurizing flue gas in a graphitization furnace, comprising the following steps: The solid adsorbent is crushed and passed through a 500-mesh sieve to obtain a powder, and an alkali solution is added to the powder to prepare a desulfurization slurry with a concentration of 45-55wt%; The desulfurized slurry is sprayed into the mixer through a spray gun and mixed with the flue gas discharged from the graphitization furnace to obtain mixed flue gas; Passing the mixed flue gas into a dust collector for dust removal to obtain dust-removed flue gas; The dust-removed flue gas is passed into a multi-stage desulfurization scrubber for scrubbing to obtain purified gas.

[0049] In one achievable manner, the above-mentioned graphitization furnace flue gas desulfurization method includes the following specific operating steps: The solid adsorbent is crushed and passed through a 500-mesh sieve to obtain a powder, and an alkali solution with a concentration of 10-15wt% is added to the powder to prepare a desulfurization slurry with a concentration of 55wt%; The desulfurized slurry is sprayed into the mixer through a spray gun, and mixed with the flue gas discharged from the graphitization furnace to obtain mixed flue gas. The ratio of the total flow of the desulfurized slurry sprayed by the spray gun to the flue gas flow entering the mixer is (0.1-0.2):1, and the gas-liquid mixing ratio in the spray gun is (10-15):1; Passing the mixed flue gas into a dust collector for dust removal to obtain dust-removed flue gas; The dust-removed flue gas is sequentially passed into the first desulfurization tower, the second desulfurization tower and the third desulfurization tower for scrubbing to obtain purified gas. The speed of the atomizing turntable in the first desulfurization tower is 18000~22000rpm, and the total flow rate of the absorption liquid is 1~1.5% of the flue gas flow rate entering the tower; the total flow rate of the absorption liquid in the second desulfurization tower is 2~3% of the flue gas flow rate entering the tower; the total flow rate of the absorption liquid in the third desulfurization tower is 2~3% of the flue gas flow rate entering the tower.

[0050] The total flow rate of the desulfurization slurry sprayed by the above-mentioned spray gun is calculated based on the liquid volume of the desulfurization slurry, rather than the spray flow rate.

[0051] The beneficial effects of the graphitization furnace flue gas desulfurization method provided in the present application are the same as the beneficial effects of the graphitization furnace flue gas desulfurization system provided in the first aspect above, which will not be repeated here.

[0052] Optionally, the solid adsorbent includes one or more of slag, fly ash, activated carbon, and zeolite.

[0053] In the present application, the solid adsorbents of slag, fly ash, activated carbon and zeolite are selected because the above materials are not only cheap and easily available, but also contain pores that can play a further adsorption role.

[0054] Optionally, the alkali solution is an aqueous solution of an inorganic alkali or an organic alkali with a concentration of 10-15wt%.

[0055] In the present application, the inorganic base is, for example, sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. Since calcium hydroxide has a low solubility in water, it can be prepared into lime milk of corresponding concentration for use; the organic base is a water-soluble organic base such as quaternary ammonium hydroxide, guanidine, etc.

[0056] Example 1 A method for desulfurizing flue gas from a graphitization furnace is implemented by the following steps: S101, crushing the solid adsorbent (fly ash) and passing it through a 500-mesh sieve to obtain a powder, adding an alkali solution (sodium hydroxide) with a concentration of 10wt% to the powder to prepare a desulfurization slurry with a concentration of 55wt%; S102, spraying the desulfurized slurry into the mixer through a spray gun, and mixing it with the flue gas discharged from the graphitization furnace to obtain mixed flue gas, the ratio of the total flow of the desulfurized slurry sprayed by the spray gun to the flow of the flue gas entering the mixer is 0.1:1, and the gas-liquid mixing ratio in the spray gun is 15:1; S103, passing the mixed flue gas into a dust collector for dust removal to obtain dust-removed flue gas; S104. The dust-removed flue gas is sequentially passed into the first desulfurization tower, the second desulfurization tower and the third desulfurization tower for scrubbing to obtain purified gas. The speed of the atomizing turntable in the first desulfurization tower is 18000-22000rpm, and the total flow rate of the absorption liquid is 1% of the flue gas flow entering the tower; the total flow rate of the absorption liquid in the second desulfurization tower is 2% of the flue gas flow entering the tower; the total flow rate of the absorption liquid in the third desulfurization tower is 2% of the flue gas flow entering the tower.

[0057] The sulfur dioxide concentration in the flue gas discharged from the graphitization furnace is 35000mg / Nm 3 The humidity of the purified gas discharged from the top exhaust port of the third desulfurization tower is 20L / Nm 3 , sulfur dioxide concentration is 20mg / Nm 3 .

[0058] Example 2 A method for desulfurizing flue gas from a graphitization furnace is implemented by the following steps: S201, crushing the solid adsorbent (fly ash) and passing it through a 500-mesh sieve to obtain a powder, adding an alkali solution (sodium hydroxide) with a concentration of 15wt% to the powder to prepare a desulfurization slurry with a concentration of 45wt%; S202, spraying the desulfurized slurry into the mixer through a spray gun, and mixing it with the flue gas discharged from the graphitization furnace to obtain mixed flue gas, the ratio of the total flow of the desulfurized slurry sprayed by the spray gun to the flow of the flue gas entering the mixer is 0.2:1, and the gas-liquid mixing ratio in the spray gun is 10:1; S203, passing the mixed flue gas into a dust collector for dust removal to obtain dust-removed flue gas; S204. The dust-removed flue gas is sequentially passed into the first desulfurization tower, the second desulfurization tower and the third desulfurization tower for scrubbing to obtain purified gas. The rotation speed of the atomizing turntable in the first desulfurization tower is 18000-22000rpm, and the total flow rate of the absorption liquid is 1.5% of the flue gas flow rate entering the tower; the total flow rate of the absorption liquid in the second desulfurization tower is 3% of the flue gas flow rate entering the tower; the total flow rate of the absorption liquid in the third desulfurization tower is 3% of the flue gas flow rate entering the tower.

[0059] The sulfur dioxide concentration in the flue gas discharged from the graphitization furnace is 35000mg / Nm 3 The humidity of the purified gas discharged from the top exhaust port of the third desulfurization tower is 18L / Nm 3 , sulfur dioxide concentration is 15mg / Nm 3 .

[0060] Example 3 A method for desulfurizing flue gas from a graphitization furnace is implemented by the following steps: S301, crushing the solid adsorbent (fly ash) and passing it through a 500-mesh sieve to obtain a powder, adding an alkali solution (sodium hydroxide) with a concentration of 12wt% to the powder to prepare a desulfurization slurry with a concentration of 50wt%; S302, spraying the desulfurized slurry into the mixer through a spray gun, and mixing it with the flue gas discharged from the graphitization furnace to obtain mixed flue gas, the ratio of the total flow of the desulfurized slurry sprayed by the spray gun to the flue gas flow entering the mixer is 0.15, and the gas-liquid mixing ratio in the spray gun is 12:1; S303, passing the mixed flue gas into a dust collector for dust removal to obtain dust-removed flue gas; S304. The dust-removed flue gas is sequentially passed into the first desulfurization tower, the second desulfurization tower and the third desulfurization tower for scrubbing to obtain purified gas. The speed of the atomizing turntable in the first desulfurization tower is 18000-22000rpm, and the total flow rate of the absorption liquid is 1.2% of the flue gas flow entering the tower; the total flow rate of the absorption liquid in the second desulfurization tower is 2.5% of the flue gas flow entering the tower; the total flow rate of the absorption liquid in the third desulfurization tower is 2.5% of the flue gas flow entering the tower.

[0061] The sulfur dioxide concentration in the flue gas discharged from the graphitization furnace is 35000mg / Nm 3 The humidity of the purified gas discharged from the top exhaust port of the third desulfurization tower is 20L / Nm 3 , sulfur dioxide concentration is 18mg / Nm 3 .

[0062] The above embodiments were tested using the same set of equipment. Five spray layers were set in the second desulfurization tower, and four spray layers were set in the third desulfurization tower.

[0063] Comparative Example 1 A method for desulfurizing flue gas from a graphitization furnace is implemented by the following steps: D101, passing the flue gas discharged from the graphitization furnace into a dust collector for dust removal to obtain dust-removed flue gas; D102. The dust-removed flue gas is cooled to the same pre-tower temperature as in Example 3, and then passed into a multi-stage desulfurization washing tower for washing to obtain purified gas. The speed of the atomizing turntable in the first desulfurization tower is 18000-22000 rpm, and the total flow rate of the absorption liquid is 1.2% of the flue gas flow rate entering the tower; the total flow rate of the absorption liquid in the second desulfurization tower is 2.5% of the flue gas flow rate entering the tower; and the total flow rate of the absorption liquid in the third desulfurization tower is 2.5% of the flue gas flow rate entering the tower.

[0064] The sulfur dioxide concentration in the flue gas discharged from the graphitization furnace is 35000mg / Nm 3 The humidity of the purified gas discharged from the top exhaust port of the third desulfurization tower is 20L / Nm 3 , sulfur dioxide concentration is 56mg / Nm 3 .

[0065] Comparative Example 2 The dust removal flue gas in Example 3 was collected to detect the sulfur dioxide concentration in the flue gas, and the sulfur dioxide concentration was measured to be 10000 mg / Nm 3 .

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A graphitization furnace flue gas desulfurization system, comprising a graphitization furnace (1), characterized in that: The graphitization furnace (1) is connected in sequence to a mixer (2), an expansion tube (3), a first fan (10), a dust collector (4), a second fan (20) and a gas scrubber (5); The mixer (2) is also connected to the gas outlet of the dust collector (4) and the liquid outlet of the liquid transfer pump (30) respectively; The liquid transfer pump (30) is connected to the desulfurization slurry storage tank (6); The dust collector (4) is also connected to a dust collecting tank (41).

2. The graphitization furnace flue gas desulfurization system according to claim 1, characterized in that: An air mixing tank (7) is also provided between the second fan (20) and the air scrubber (5), and the air mixing tank (7) is also connected to an air filter (61) via a third fan (40).

3. The graphitization furnace flue gas desulfurization system according to claim 1, characterized in that: The mixer (2) comprises a mixing section (21), a gradually contracting section (22) and a gradually expanding section (23) which are connected in sequence; The mixing section (21) and the tapered section (22) are connected via a connecting pipe (24); At least one spray gun (25) is arranged in the mixing section (21); The air inlet end of the spray gun (25) is connected to the gas output end of the dust collector (4), and the liquid inlet end of the spray gun (25) is connected to the liquid output port of the liquid transfer pump (30).

4. The graphitization furnace flue gas desulfurization system according to claim 1, characterized in that: The gas scrubber (5) comprises a first desulfurization tower (51), a second desulfurization tower (52) and a third desulfurization tower (53) which are connected in series in sequence; The absorption liquid output end of the first desulfurization tower (51) is connected to a dehydration device (54); The absorption liquid input end of the third desulfurization tower (53) is connected to the lime slurry storage tank (55); The dehydration device (54) is also connected to the gypsum storage bin (541) and the lime slurry storage tank (55) respectively.

5. The graphitization furnace flue gas desulfurization system according to claim 4, characterized in that: A flue gas distributor (511) and a spiral sprayer (512) are coaxially arranged on the top of the first desulfurization tower (51); The spiral sprayer (512) is connected to the first liquid storage area (513) at the bottom of the tower via a first circulation pump (510); The smoke distributor (511) is connected to the gas output end of the second fan (20); The absorption liquid input end of the first liquid storage area (513) is connected to the liquid discharge end of the second desulfurization tower (52); and the absorption liquid output end of the first liquid storage area (513) is connected to the dehydration device (54).

6. The graphitization furnace flue gas desulfurization system according to claim 4, characterized in that: The second desulfurization tower (52) is provided with multiple first spray layers (521) from top to bottom, and each first spray layer (521) is connected to the second liquid storage area (522) at the bottom of the tower via a second circulation pump (520); A flue gas input end at the lower portion of the second desulfurization tower (52) is connected to a flue gas output end at the lower portion of the first desulfurization tower; The second liquid storage area (522) is connected to the absorption liquid output end of the third desulfurization tower (53).

7. The graphitization furnace flue gas desulfurization system according to claim 4, characterized in that: The third desulfurization tower (53) is provided with a tray layer (531), and a plurality of second spray layers (532) are provided between the tower top and the tray layer (531), and each of the second spray layers (532) is connected to the third liquid storage area (533) at the bottom of the tower via a third circulation pump (530); The absorption liquid input end of the third liquid storage area (533) and the lime slurry storage tank (55); The gas input end at the bottom of the third desulfurization tower (53) is connected to the gas output end at the top of the second desulfurization tower (52).

8. A method for desulfurizing flue gas from a graphitization furnace, applied to the desulfurizing flue gas from a graphitization furnace system according to any one of claims 1 to 7, characterized in that: The steps include: The solid adsorbent is crushed and passed through a 500-mesh sieve to obtain a powder, and an alkali solution is added to the powder to prepare a desulfurization slurry with a concentration of 45-55wt%; The desulfurized slurry is sprayed into the mixer through a spray gun and mixed with the flue gas discharged from the graphitization furnace to obtain mixed flue gas; Passing the mixed flue gas into a dust collector for dust removal to obtain dust-removed flue gas; The dust-removed flue gas is passed into a multi-stage desulfurization scrubber for scrubbing to obtain purified gas.

9. The method for desulfurizing flue gas from a graphitization furnace according to claim 8, characterized in that: The solid adsorbent includes one or more of slag, fly ash, activated carbon and zeolite.

10. The method for desulfurizing flue gas from a graphitization furnace according to claim 9, characterized in that: The alkali solution is an aqueous solution of an inorganic alkali or an organic alkali with a concentration of 10-15wt%.

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