Biomass pyrolysis and gasification coupled steel mill metallurgical dust and sludge treatment system

Abstract

The invention discloses a biomass pyrolysis and gasification coupled steel mill metallurgical dust and sludge treatment system which comprises a dust and sludge treatment unit, a biomass treatment unit, a gasification unit and a reaction unit, the dust and sludge treatment unit comprises a dust and sludge storage bin and a material mixing bin, and the dust and sludge storage bin is connected with the material mixing bin; the biomass treatment unit comprises a biomass storage bin and a pyrolysis reactor, the biomass storage bin is connected with the pyrolysis reactor, and the pyrolysis reactor is connected with the mixing bin; the gasification unit comprises a steam boiler and a gasification reactor, the steam boiler is connected with the gasification reactor, and the pyrolysis reactor is further connected with the gasification reactor; the reaction unit comprises a rotary hearth furnace and an air preheater; and the mixing bin, the gasification reactor and the air preheater are respectively connected with the rotary hearth furnace. Compared with the prior art, the dust sludge treatment system has the advantages that biomass is used as fuel to perform pyrolysis gasification reaction, high-calorific-value fuel gas and coke required by a rotary hearth furnace treatment process are generated, and no extra carbon dioxide emission is generated.

Description

Technical Field

[0001] This invention relates to the field of metallurgical dust and sludge treatment technology in steel plants, specifically to a biomass pyrolysis and gasification coupled metallurgical dust and sludge treatment system for steel plants. Background Technology

[0002] Steel companies inevitably generate large amounts of iron-containing dust and sludge during production. This dust and sludge contains valuable elements such as iron and carbon, but also harmful elements such as zinc. For a long time, most of this iron-containing dust and sludge generated by steel plants has been directly returned to sintering for reuse, while some has been stored on-site or sold externally.

[0003] With increasingly stringent environmental protection requirements, iron-containing dust and sludge that could previously be transported off-site can no longer be processed in the same way. If the dust and sludge are directly returned to the ironmaking system, the high content of harmful impurities such as zinc will cause damage to the blast furnace lining, nodules inside the furnace, and corrosion of gas pipelines, seriously affecting the smooth operation and service life of the blast furnace.

[0004] Currently, the main treatment processes for iron- and zinc-containing dust and sludge in China include wet treatment, rotary kiln treatment, and rotary hearth furnace treatment. The rotary hearth furnace treatment process usually uses coke oven gas as gaseous fuel and mixes dry-quenched coke powder into the raw materials as a carbon source. During the production process, a large amount of carbon dioxide emissions are generated, which does not meet the current carbon reduction requirements. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and propose a biomass pyrolysis gasification coupled steel plant metallurgical dust and sludge treatment system, which solves the technical problem that the use of rotary hearth furnaces to treat dust and sludge in the prior art will generate a large amount of carbon dioxide emissions.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: This invention provides a biomass pyrolysis and gasification coupled steel plant metallurgical dust and sludge treatment system, comprising: a dust and sludge treatment unit, a biomass treatment unit, a gasification unit, and a reaction unit. The dust and sludge treatment unit includes a dust and sludge storage bin and a mixing bin, wherein the dust and sludge storage bin is connected to the mixing bin for supplying dust and sludge to the mixing bin; The biomass processing unit includes a biomass storage bin and a pyrolysis reactor. The biomass storage bin is connected to the pyrolysis reactor to supply biomass into the pyrolysis reactor. The pyrolysis reactor can pyrolyze the biomass into coke and syngas. The pyrolysis reactor is connected to a mixing bin to supply a portion of coke into the mixing bin. The mixing bin can mix dust and coke. The gasification unit includes a steam boiler and a gasification reactor. The steam boiler is connected to the gasification reactor to supply steam into the gasification reactor. The pyrolysis reactor is also connected to the gasification reactor to supply the remaining coke and syngas to the gasification reactor. The gasification reactor can convert coke and steam into syngas. The reaction unit includes a rotary hearth furnace and an air preheater. The mixing bin, gasification reactor and air preheater are respectively connected to the rotary hearth furnace and are used to supply the mixed dust and coke, syngas and air into the rotary hearth furnace.

[0007] In some embodiments, the dust and sludge treatment unit further includes a first drying device, the mixing bin being connected to the rotary hearth furnace via the first drying device, the first drying device being used to dry the blended coke and biomass.

[0008] In some embodiments, the biomass processing unit further includes a first crushing device and a second drying device, and the biomass storage bin is connected to the pyrolysis reactor in sequence via the first crushing device and the second drying device. The first crushing device is used to crush the biomass, and the second drying device is used to dry the biomass.

[0009] In some embodiments, the biomass processing unit further includes a second crushing device, the pyrolysis reactor is connected to the second crushing device, the second crushing device is connected to the gasification reactor and the mixing silo respectively, and the second crushing device is used to crush the coke produced by the pyrolysis reactor to obtain coke powder, and to transport the coke powder to the gasification reactor and the mixing silo.

[0010] In some embodiments, the reaction unit further includes a hot air furnace, the gasification reactor being connected to the hot air furnace to supply syngas to the hot air furnace, the hot air furnace being connected to the air preheater; the syngas is burned in the hot air furnace to generate flue gas, the flue gas being used to heat air in the air preheater; the air preheater is also connected to the first drying device, the flue gas heated in the air preheater being used to dry dust and sludge in the first drying device.

[0011] In some embodiments, the reaction unit further includes a cooling device and a finished product silo, with the rotary hearth furnace connected to the finished product silo via the cooling device; the pellets produced by the rotary hearth furnace are cooled by the cooling device and then stored in the finished product silo.

[0012] In some embodiments, a flue gas treatment unit is further included, the flue gas treatment unit including a first heat exchanger and a second heat exchanger, the first heat exchanger being connected to the rotary hearth furnace and the gasification reactor, a portion of the flue gas generated by the rotary hearth furnace being heated to the gasification reactor via the first heat exchanger, and the second heat exchanger being connected to the rotary hearth furnace and the pyrolysis reactor, another portion of the flue gas generated by the rotary hearth furnace being heated to the pyrolysis reactor via the second heat exchanger.

[0013] In some embodiments, the first heat exchanger and the second heat exchanger are also connected to the steam boiler, and the flue gas after heat exchange through the first heat exchanger and the second heat exchanger heats the steam boiler to generate steam.

[0014] In some embodiments, the flue gas treatment unit further includes a dust removal reactor and a zinc storage tank, wherein the steam boiler is connected to the dust removal reactor and the zinc storage tank is connected to the dust removal reactor; the dust removal reactor is used to intercept dust in the flue gas passing through the steam boiler and to transport the dust to the zinc storage tank for storage.

[0015] In some embodiments, the dust removal reactor is connected to the second drying device and the hot air furnace. Part of the flue gas after dust removal by the dust removal reactor is used to dry the biomass in the second drying device, and the other part is transported to the hot air furnace for recycling.

[0016] Compared with existing technologies, the biomass pyrolysis gasification coupled steel plant metallurgical dust and sludge treatment system provided by this invention utilizes biomass as fuel for pyrolysis gasification reaction to produce high-calorific-value fuel gas and coke required for rotary hearth furnace processing. Biomass is a zero-carbon energy source, and the use of biomass pyrolysis gasification coupled with steel plant iron and zinc dust and sludge treatment does not produce additional carbon dioxide emissions. At the same time, the coke produced by biomass pyrolysis serves as a reducing agent for the reaction of iron and zinc dust and sludge in the rotary hearth furnace. Furthermore, the high-temperature flue gas produced by the rotary hearth furnace also serves as a heat source for biomass fuel drying, pyrolysis, gasification and other processes, eliminating the need to introduce external heat sources. Attached Figure Description

[0017] Figure 1 This is a layout block diagram of the biomass pyrolysis gasification coupled steel plant metallurgical dust and sludge treatment system provided in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] To address the technical problem of excessive carbon emissions from existing rotary hearth furnace processes, this invention provides a biomass pyrolysis gasification coupled with a steel plant metallurgical dust and sludge treatment system that can prevent the generation of additional carbon dioxide emissions.

[0020] Please see Figure 1 , Figure 1 This is a block diagram of the layout of a biomass pyrolysis gasification coupled steel plant metallurgical dust and sludge treatment system provided in an embodiment of the present invention. This biomass pyrolysis gasification coupled steel plant metallurgical dust and sludge treatment system includes a dust and sludge treatment unit 1, a biomass treatment unit 2, a gasification unit, and a reaction unit 4.

[0021] The dust and sludge treatment unit 1 includes a dust and sludge storage bin 11 and a mixing bin 12. The dust and sludge storage bin 11 is connected to the mixing bin 12 to supply metallurgical dust and sludge containing iron and zinc to the mixing bin 12.

[0022] The biomass processing unit 2 includes a biomass storage bin 21 and a pyrolysis reactor 22. The biomass storage bin 21 is connected to the pyrolysis reactor 22 to supply biomass into the pyrolysis reactor 22. The pyrolysis reactor 22 can pyrolyze the biomass into coke and syngas. The pyrolysis reactor 22 is connected to a mixing bin 12 to supply a portion of the coke into the mixing bin 12. The mixing bin 12 can mix dust and coke according to a preset ratio.

[0023] The gasification unit includes a steam boiler 31 and a gasification reactor 32. The steam boiler 31 is connected to the gasification reactor 32 to supply steam to the gasification reactor 32. The pyrolysis reactor 22 is also connected to the gasification reactor 32 to supply the remaining coke and syngas to the gasification reactor 32, which converts coke, oxygen, and steam into syngas. It is easy to understand that the gasification reactor 32 is also connected to equipment for supplying oxygen.

[0024] The reaction unit 4 includes a rotary hearth furnace 41 and an air preheater 42. The mixing bin 12, the gasification reactor 32, and the air preheater 42 are respectively connected to the rotary hearth furnace 41 and are used to supply the mixed dust and coke, syngas, and air into the rotary hearth furnace 41. The rotary hearth furnace 41 uses coke as a reducing agent and syngas as fuel to convert iron- and zinc-containing metallurgical dust and sludge into pellets.

[0025] In some embodiments, the dust and sludge treatment unit 1 further includes a first drying device 13, and the mixing bin 12 is connected to the rotary hearth furnace 41 via the first drying device 13. The first drying device 13 is used to dry the blended coke and biomass.

[0026] In some embodiments, the biomass processing unit 2 further includes a first crushing device 23 and a second drying device 24, and the biomass storage bin 21 is connected to the pyrolysis reactor 22 via the first crushing device 23 and the second drying device 24 in sequence. The first crushing device 23 is used to crush the biomass, and the second drying device 24 is used to dry the biomass. The crushed and dried biomass is then transported to the pyrolysis reactor 22 for pyrolysis reaction.

[0027] In some embodiments, the biomass processing unit 2 further includes a second crushing device 25, which is connected to the pyrolysis reactor 2 and to the gasification reactor 31 and the mixing bin 12, respectively. The second crushing device 25 is used to crush the coke produced in the pyrolysis reactor to obtain coke powder, and then conveys the coke powder to the gasification reactor 32 and the mixing bin 12. Smaller coke powder particles are more conducive to the production of syngas in the gasification reactor 32 and to uniform mixing with biomass in the mixing bin 12.

[0028] In some embodiments, the reaction unit 4 further includes a hot blast furnace 43, to which the gasification reactor 32 is connected for supplying syngas. The hot blast furnace 43 is connected to an air preheater 42. The syngas is combusted in the hot blast furnace 43 to generate high-temperature flue gas, which heats the air in the air preheater 42. It is easy to understand that in the air preheater 42, the high-temperature flue gas and the air do not come into contact; only heat transfer occurs. The air preheater 42 is also connected to a first drying device 13, and the flue gas heated in the air preheater 42 is used to dry the dust and sludge in the first drying device 13. A multi-stage utilization treatment method is adopted for the high-temperature flue gas to fully utilize its waste heat.

[0029] In some embodiments, the reaction unit 4 further includes a cooling device 44 and a finished product silo 45, with the rotary hearth furnace 41 connected to the finished product silo 45 via the cooling device 44. The pellets produced by the rotary hearth furnace 41 are cooled by the cooling device 44 and then stored in the finished product silo 45.

[0030] In some embodiments, this biomass pyrolysis-gasification coupled steel plant metallurgical dust and sludge treatment system further includes a flue gas treatment unit. The flue gas treatment unit includes a first heat exchanger 51 and a second heat exchanger 52. The first heat exchanger 51 is connected to a rotary hearth furnace 41 and a gasification reactor 32. A portion of the flue gas generated by the rotary hearth furnace 32 is heated by the first heat exchanger 51 to the gasification reactor 32. The second heat exchanger 52 is connected to the rotary hearth furnace 41 and a pyrolysis reactor 22. Another portion of the flue gas generated by the rotary hearth furnace 41 is heated by the second heat exchanger 52 to the pyrolysis reactor 22. It is readily understood that the first heat exchanger 51 and the second heat exchanger 52 merely utilize high-temperature flue gas to heat the gasification reactor 32 and the pyrolysis reactor 22 respectively, without any mass exchange occurring.

[0031] In some embodiments, the first heat exchanger 51 and the second heat exchanger 52 are also connected to the steam boiler 31, and the flue gas after heat exchange through the first heat exchanger 51 and the second heat exchanger 52 is reused to heat the steam boiler 31 to generate steam.

[0032] In some embodiments, the flue gas treatment unit further includes a dust removal reactor 53 and a zinc storage tank 54. A steam boiler 31 is connected to the dust removal reactor 53, and the zinc storage tank 54 is connected to the dust removal reactor 53. The dust removal reactor 53 is used to trap dust in the flue gas passing through the steam boiler 31 and to transport the dust to the zinc storage tank 54 for storage. This dust contains a large amount of zinc oxide, which can be used for zinc recovery.

[0033] In some embodiments, the dust removal reactor 53 is connected to the second drying device 24 and the hot air furnace 43. Part of the flue gas after dust removal by the dust removal reactor 53 is used to dry the biomass in the second drying device 24, and the other part is sent to the hot air furnace 4 for recycling.

[0034] After passing through the second drying device 24 and the first drying device 13, the temperature of the flue gas has dropped low enough to lose its usability, and it is discharged to the outside through the chimney 55.

[0035] To better understand this invention, the following is combined with... Figure 1 The technical solution of the present invention will be described in detail below: Biomass feedstock is stored in biomass storage silo 21. After being crushed and dried sequentially by a first crushing device 23 and a second drying device 24, it enters the pyrolysis reactor 22, where it is pyrolyzed into coke and syngas. Syngas is transported to the gasification reactor 32, and the coke is transported to the second crushing device 25 to be crushed into coke powder. Part of the coke powder is transported to the gasification reactor 32, and the other part is transported to the mixing silo 12, where it is mixed with dust and sludge supplied by the dust and sludge storage silo 11 according to a preset ratio. The mixed coke powder and biomass are dried by the first drying device 13 and then transported to the rotary hearth furnace 41.

[0036] In the gasification reactor 32, coke powder, steam, and oxygen react to produce syngas. Part of the syngas is fed into the rotary hearth furnace 41, and the other part into the hot blast stove 43. The syngas burns in the hot blast stove to produce high-temperature flue gas, which is then fed into the air preheater 42 to preheat the air. The preheated air is then fed into the rotary hearth furnace 41. Inside the rotary hearth furnace 41, coke powder, sludge, syngas, and air react to produce high-temperature flue gas and pellets. The pellets are cooled by the cooling device 44 and then stored in the finished product silo 45.

[0037] The high-temperature flue gas generated by the rotary hearth furnace 41 is respectively transported to the first heat exchanger 51 and the second heat exchanger 52, which supply heat to the gasification reactor 32 and the pyrolysis reactor 22. After heat exchange in the first heat exchanger 51 and the second heat exchanger 52, the flue gas temperature is still high, and it is transported to the steam boiler 31 to generate steam, which is then supplied to the gasification reactor for gasification. The flue gas after being used by the steam boiler 31 is transported to the dust removal reactor 53 to remove dust. The dust contains a large amount of zinc oxide, which is collected in the zinc storage tank 54. The flue gas after dust removal in the dust removal reactor 53 still has a certain temperature. A portion of it is transported to the second drying device 24 to dry the biomass raw materials, further utilizing the residual heat. The other portion is transported to the hot blast furnace 43 for recovery.

[0038] On the other hand, the high-temperature flue gas generated by the hot blast stove 43 preheats the air in the air preheater 42, and the cooled flue gas is then transported to the first drying device 13 to dry the blended biomass and coke powder, further making full use of the residual heat. After being used by the first drying device 13 and the second drying device 53, the flue gas is at a very low temperature and loses its utilization value, and is discharged to the outside through the chimney 55.

[0039] This biomass pyrolysis and gasification coupled steel plant metallurgical dust and sludge treatment system uses biomass to treat dust and sludge, and has the following advantages: 1. Biomass is a zero-carbon energy source. Utilizing biomass pyrolysis and gasification coupled with the treatment of iron- and zinc-containing dust and sludge from steel plants does not produce additional carbon dioxide emissions.

[0040] 2. The coke produced by biomass pyrolysis is used as a reducing agent for the reaction of iron- and zinc-containing dust and sludge in the rotary hearth furnace, without the use of any other reducing agents.

[0041] 3. Syngas produced by biomass gasification is used as a high-calorific-value fuel required for the reaction of the rotary hearth furnace and hot blast stove.

[0042] 4. The high-temperature flue gas generated by the rotary hearth furnace can be used as a heat source for the biomass fuel drying, pyrolysis, and gasification units, without the need to introduce an external heat source.

[0043] 5. Steam generated by the rotary hearth waste heat boiler is used as the gasification reactant in the biomass gasification unit.

[0044] Throughout the entire process, besides biomass, only water, air, and oxygen are needed, and the energy supply also mainly comes from biomass. Apart from biomass, the demand for external materials and energy is minimal, making it significant for steel plants to reduce emissions and energy consumption.

[0045] Furthermore, it should be noted that this technical solution focuses on protecting the connection relationships between the various devices in the system, rather than the individual devices themselves. The various devices used in this system, such as the crushing device, drying device, heat exchanger, and rotary hearth furnace, are all existing, mature equipment. Those skilled in the art are familiar with these devices and can use them normally, and can select appropriate models and assemble them according to the above connection scheme to ensure the system functions properly.

[0046] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A system for processing biomass pyrolysis gasification coupled with steel plant metallurgical sludge, characterized in that, The application relates to a system for producing pellets from dust and biomass, comprising: a dust treatment unit, which comprises a dust storage bin and a mixing bin, the dust storage bin being connected to the mixing bin to supply dust to the mixing bin; a biomass treatment unit, which comprises a biomass storage bin and a pyrolysis reactor, the biomass storage bin being connected to the pyrolysis reactor to supply biomass to the pyrolysis reactor, the pyrolysis reactor being capable of pyrolyzing the biomass into coke and synthesis gas, the pyrolysis reactor being connected to the mixing bin to supply a part of the coke to the mixing bin; the mixing bin being capable of mixing the dust and the coke; a gasification unit, which comprises a steam boiler and a gasification reactor, the steam boiler being connected to the gasification reactor to supply steam to the gasification reactor, the pyrolysis reactor also being connected to the gasification reactor to supply the remaining coke and synthesis gas to the gasification reactor, the gasification reactor being capable of converting the coke and steam into synthesis gas; a reaction unit, which comprises a rotary hearth furnace and an air preheater, the mixing bin, the gasification reactor and the air preheater being connected to the rotary hearth furnace respectively to supply the mixed dust and coke, the synthesis gas and air to the rotary hearth furnace.

2. The system according to claim 1, wherein the system is characterized by: the dust treatment unit further comprises a first drying device, the mixing bin being connected to the rotary hearth furnace via the first drying device, the first drying device being used to dry the mixed coke and biomass.

3. The system according to claim 2, wherein the system is characterized by, the biomass treatment unit further comprises a first crushing device and a second drying device, the biomass storage bin being connected to the pyrolysis reactor via the first crushing device and the second drying device in sequence, the first crushing device being used to crush the biomass, and the second drying device being used to dry the biomass.

4. The system according to claim 1, wherein the system is characterized by: the biomass treatment unit further comprises a second crushing device, the pyrolysis reactor being connected to the second crushing device, the second crushing device being connected to the gasification reactor and the mixing bin respectively, the second crushing device being used to crush the coke produced by the pyrolysis reactor into coke powder and to deliver the coke powder to the gasification reactor and the mixing bin.

5. The system according to claim 3, wherein the system is characterized by: the reaction unit further comprises a hot blast stove, the gasification reactor being connected to the hot blast stove to supply the synthesis gas to the hot blast stove, the hot blast stove being connected to the air preheater; the synthesis gas is combusted in the hot blast stove to produce flue gas, the flue gas is used to heat air in the air preheater; the air preheater is also connected to the first drying device, the flue gas that has heated the air in the air preheater is used to dry the dust in the first drying device.

6. The system according to claim 1, wherein the system is characterized by: the reaction unit further comprises a cooling device and a finished product bin, the rotary hearth furnace being connected to the finished product bin via the cooling device; the pellets produced by the rotary hearth furnace are cooled by the cooling device and then enter the finished product bin for storage.

7. The system according to claim 5, wherein the system is characterized by: the application further comprises a flue gas treatment unit, which comprises a first heat exchanger and a second heat exchanger, the first heat exchanger being connected to the rotary hearth furnace and the gasification reactor, a part of the flue gas produced by the rotary hearth furnace being used to heat the gasification reactor via the first heat exchanger, the second heat exchanger being connected to the rotary hearth furnace and the pyrolysis reactor, another part of the flue gas produced by the rotary hearth furnace being used to heat the pyrolysis reactor via the second heat exchanger.

8. The system according to claim 7, wherein the system is characterized by, The first heat exchanger and the second heat exchanger are also connected to the steam boiler, and the flue gas after heat exchange through the first heat exchanger and the second heat exchanger heats the steam boiler to generate water vapor.

9. The system according to claim 8, wherein the system is characterized by, The flue gas treatment unit further comprises a dust removal reactor and a zinc storage, the steam boiler is connected to the dust removal reactor, and the zinc storage is connected to the dust removal reactor; the dust removal reactor is used for blocking dust in the flue gas passing through the steam boiler and conveying the dust to the zinc storage for storage.

10. The system according to claim 9, wherein the system is characterized by: The dust removal reactor is connected to the second drying device and the hot blast furnace, and the flue gas after dust removal through the dust removal reactor is partly used for drying the biomass in the second drying device and partly conveyed into the hot blast furnace for recovery.

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