Pickling filter cake roasting dechlorination system and method

Abstract

The invention discloses a pickling filter cake roasting dechlorination system and method, and belongs to the technical field of solid waste recycling. The system comprises a vertical multi-hearth roasting furnace, a feeding unit, a material driving mechanism, a temperature control unit and a flue gas collecting and processing system, and the roasting furnace is provided with a drying dehydration section, a pre-roasting decomposition section, a roasting decomposition section and a cooling section from top to bottom to realize segmented processing. The dechlorination rate is not lower than 98.5% and the chlorine ion content of the treated material is less than or equal to 0.5% through layered precise temperature control, regulation and control of the retention time of the material by a scraper assembly and combination of flue gas waste heat recovery and acid liquor cyclic utilization. Compared with a traditional process, the system is compact and efficient, energy is saved by 4.1%-5.3%, the system is low-carbon and environment-friendly, and harmless treatment and resource recycling of the pickling filter cakes of iron and steel enterprises can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste resource utilization, in particular to a system and method for roasting and dechlorinating pickling filter cake. BACKGROUND

[0002] The pickling filter cake generated in the cold rolling acid regeneration process of a steel enterprise is a hazardous waste. After plate and frame filter dewatering, it contains about 40-60% water, about 40%-45% TFe in dry basis, about 7%-30% Cl ion content, and a pH value of 4-6. It is acid corrosive. Current treatment methods include lime neutralization and dechlorination, low-temperature roasting and dechlorination, direct return to sintering for utilization, and landfill. Dechlorination treatment and resource utilization are the direction of technological development.

[0003] The patent with application number 202410995860.7, "Pickling filter cake iron-chlorine separation device system and separation method thereof", discloses a pickling filter cake iron-chlorine separation device system, which includes a receiving hopper, a paddle-type low-temperature dryer connected through a screw conveyor, a rotary roasting furnace connected to the material outlet of the low-temperature dryer, a material bin connected to the material outlet of the rotary roasting furnace, a spray tower connected to the smoke outlets of the paddle-type low-temperature dryer and the rotary roasting furnace, a waste acid outlet of the spray tower connected to a waste acid tank, and a chimney connected to the smoke outlet of the spray tower through a fan. The invention provides the system composition of the pickling filter cake roasting and dechlorination device, including material input and output, smoke collection and treatment, and roasting operation process, etc. However, this scheme uses a paddle-type low-temperature dryer and a rotary roasting furnace to realize the drying and decomposition reaction of the pickling filter cake, which is relatively complex in design, and the temperature control accuracy of the rotary roasting furnace is relatively poor. The technical solution of the present application adopts a vertical multi-layer furnace chamber structure, the temperature control range of different furnace layers is different, which can simplify the system structure and realize the utilization of smoke heat.

[0004] The patent with application number 202411610431.X, "Steel plant pickling filter cake roasting device", discloses a steel plant pickling filter cake roasting device, which includes a furnace body, a feed valve pipe and a discharge valve pipe installed at the top and bottom of the furnace body for feeding and discharging materials, a furnace chamber for roasting materials installed inside the furnace body, a furnace bed installed in the furnace chamber for receiving materials for roasting operation; a driving mechanism and a material driving mechanism are installed inside the furnace body, a driving shaft is installed inside the furnace body, and the driving shaft controls the operation of the driving mechanism and the material driving mechanism. The invention only describes the function and structure of the treatment device, does not describe the operating parameters of the device, and does not provide a solution to the corrosion problem of the pickling filter cake. In addition, it does not provide a solution to the smoke treatment of the system.

[0005] Patent No. 200810024330.9 "Acid pickling iron red desilication filter cake treatment device and treatment method" discloses an acid pickling iron red desilication filter cake treatment device for harmless treatment of acid pickling iron red desilication filter cake. The device is provided with heating devices and recovery devices in process order and is connected to each other. The heating devices heat and decompose the acid pickling iron red desilication filter cake. The recovery devices recover the solid and gas materials generated by the heating and decomposing of the heating devices. The invention only describes the function and structure of the treatment device, and does not describe the operation parameters of the device and the solution to the corrosion problem of the acid pickling filter cake.

[0006] Patent No. 202111443636.X "Waste acid recycling online recovery treatment system and process" The invention describes a waste acid recycling online recovery treatment system and process. The waste acid recycling online recovery treatment system includes a waste acid regeneration system. The waste acid regeneration system is connected to the inlet of the drying system through the exhaust outlet. The outlet of the drying system is connected to the sorting and sintering system. The outlet of the drying system is connected to the inlet of the waste acid regeneration system. The invention mainly aims at waste acid recycling online recovery treatment. The connection between each functional template in the system is described. The treatment object, function design and technical difficulty of the invention are different.

[0007] The closest patent to the technical solution of the invention is Patent No. 202410995860.7 "Acid pickling filter cake iron-chlorine separation device system and separation method". The invention provides a system composition of the acid pickling filter cake roasting and dechlorination device, including material inlet and outlet, flue gas collection and treatment, and roasting operation process. However, the invention realizes the drying and decomposition reaction of the acid pickling filter cake through a paddle type low-temperature dryer and a rotary roasting furnace. The design is relatively complex, and the temperature control accuracy of the rotary roasting furnace is relatively poor. The technical solution of the invention adopts a vertical multi-layer furnace structure. The temperature control range of different furnace layers is different. The system structure can be simplified, the flue gas heat can be utilized, and a system solution for flue gas treatment is provided. SUMMARY

[0008] The invention aims at the resource utilization of cold-rolled acid pickling filter cake. The acid pickling filter cake dechlorination treatment system with a vertical multi-section furnace as the reactor is designed. The temperature and residence time of different levels in the multi-section roasting furnace are effectively controlled in layers. The dehydration and drying of the acid pickling filter cake and the decomposition and dechlorination reaction are realized in a reactor. At the same time, the flue gas generated in the roasting process can also be purified by a water washing acid removal tower and other supporting flue gas systems. The invention realizes the dechlorination treatment of the acid pickling filter cake and the resource utilization of the iron and halogen in the acid pickling filter cake.

[0009] To solve the above technical problems, the invention realizes the following technical solutions: In a first aspect, the present application provides a system for roasting and dechlorinating pickling filter cake, comprising: a vertical multi-layer hearth roaster, comprising, from top to bottom, a drying and dewatering hearth, a pre-roasting and decomposition hearth, a roasting and decomposition hearth, and a cooling hearth; a feeding unit for feeding pickling filter cake into the drying and dewatering hearth; a material driving mechanism, provided in each hearth, for driving the movement of the material in the hearth and the falling of the material into the next hearth; a temperature control unit, provided in each hearth, for independently measuring and regulating the heating temperature of each hearth; a flue gas collection and treatment system for collecting and treating the flue gas generated by the vertical multi-layer hearth roaster.

[0010] In a preferred technical solution of the present application, the material driving mechanism comprises a rotary motor, a central shaft, and a scraper assembly. The central shaft penetrates the vertical multi-layer hearth roaster from top to bottom. The rotary motor is drivingly connected to the end of the central shaft. The central shaft in each hearth is provided with the scraper assembly. The scraper assembly is driven by the rotary motor to move in a circular motion, for pushing the material to move in each hearth and controlling the residence time of the material in each hearth.

[0011] In a preferred technical solution of the present application, the flue gas collection and treatment system comprises a spray scrubber, a chimney, and a waste acid tank connected in sequence. The gas inlet of the spray scrubber is connected to the flue gas outlet of the vertical multi-layer hearth roaster through a pipeline. The liquid outlet of the spray scrubber is connected to the waste acid tank. The waste acid tank is used to return the collected acid liquid to an acid regeneration system. The gas outlet of the spray scrubber is connected to the chimney.

[0012] In a preferred technical solution of the present application, the temperature control unit comprises a temperature measuring component and a heating component provided in each hearth. The temperature measuring component is a thermocouple. The heating component is selected from a green electricity heating module or other environmentally friendly heat source module.

[0013] In a preferred technical solution of the present application, the feeding unit comprises a travelling crane, a hopper, and a two-stage feeding heavy hammer flap. The travelling crane is used to transport the hopper above the feeding port of the drying and dewatering hearth. The two-stage feeding heavy hammer flap is used to feed the material in the hopper into the feeding port of the drying and dewatering hearth.

[0014] In a preferred technical solution of the present application, each hearth is provided with a discharge port at the bottom and a maintenance port at the side.

[0015] In a second aspect, the present application provides a method for roasting and dechlorinating pickling filter cake using the system, comprising the following steps: S1, the pickling filter cake is sent into the drying and dewatering section of the vertical multi-layer hearth roasting furnace through the feeding unit, and drying and dewatering is carried out; S2, the dried material is pushed into the pre-roasting and decomposition section of the hearth by the material driving mechanism, and pre-roasting and decomposition are carried out; S3, the pre-roasted material is pushed into the roasting and decomposition section of the hearth by the material driving mechanism, and roasting and decomposition are carried out; S4, the roasted material is pushed into the cooling section of the hearth by the material driving mechanism, and is cooled to be discharged.

[0016] As a preferred technical solution of the present application, the temperature control range of the drying and dewatering section of the hearth is 65-110 DEG C, the temperature control range of the pre-roasting and decomposition section of the hearth is 110-350 DEG C, the temperature control range of the roasting and decomposition section of the hearth is 350-450 DEG C, and the discharge temperature of the cooling section of the hearth is lower than 150 DEG C.

[0017] As a preferred technical solution of the present application, the residence time of the material in each layer of the hearth is 5-30 minutes.

[0018] As a preferred technical solution of the present application, the content of chloride ions in the material treated in step S4 is not higher than 0.5%, and the removal rate of chloride ions is not lower than 98.5%.

[0019] Compared with the prior art, the present application has the following advantages: 1. The vertical multi-layer hearth integrates the four core processes of drying and dewatering, pre-roasting and decomposition, deep roasting and decomposition, and material cooling in a single reactor, eliminates the independent drying machine and supporting conveying system in the traditional process, reduces the number of equipment and the occupied area, simplifies the process flow, and reduces the equipment investment and site occupation cost. The material driving mechanism of the through-type central shaft + scraper assembly drives the scraper to move in a circular motion through a rotating motor, which not only ensures the uniform distribution and smooth movement of the material in each layer of the hearth, but also avoids accumulation and blockage. The discharge port at the bottom of each layer of the hearth ensures that the material falls in an orderly manner to the next layer, realizes continuous production, and improves the overall operation efficiency. The maintenance opening is arranged on the side of each layer of the hearth, which is convenient for daily maintenance, fault diagnosis and component replacement, reduces downtime, and ensures stable and continuous operation of the system.

[0020] 2.Each layer of the furnace is equipped with a thermocouple temperature measuring component and an independent heating module, and the temperature control accuracy can reach ±5℃, which can accurately match the temperature requirements of each reaction stage (65-110℃ drying, 110-350℃ pre-roasting, 350-450℃ deep roasting, <150℃ cooling), avoiding the problem of large temperature fluctuations of traditional rotary roasting furnaces. The pre-roasting section realizes mild decomposition of easily decomposed chlorinated compounds, avoids "thermal shock" caused by direct jump of materials from low temperature to high temperature, and prevents material explosion, pulverization or surface sintering; the roasting section ensures stable decomposition of chlorinated compounds, and the "easy-to-difficult" staged strategy makes the dechlorination reaction more sufficient. Combined with a material residence time of 5-30 minutes, the final product has a chlorine ion content of ≤0.5%, a removal rate of ≥98.5% (up to 99.6%), which is much better than traditional processes, meets the strict requirements of subsequent ironmaking and other resource utilization, protects the physical structure of the material, reduces iron loss, and improves product quality.

[0021] 3.High-efficiency recovery of flue gas waste heat: When the 200-300℃ high-temperature flue gas generated in the lower roasting and decomposition section rises, it directly exchanges heat with the cold material descending from the upper layer, realizing pre-drying of the filter cake and "free" providing most of the heat energy required for drying, greatly reducing the demand for external heat energy; after heat exchange between the high-temperature material in the cooling section and the cooling medium, the heated air can be used as combustion air or supplemented to the drying section, realizing secondary recovery of heat and further reducing energy consumption. The heating component uses a green electricity heating module or other environmentally friendly heat sources to replace traditional high-pollution heat sources, reducing carbon emissions and meeting low-carbon environmental protection policies; compared with the traditional two-stage process (436.8kWh / ton of raw material), the comprehensive energy consumption of the present application is as low as 413.5-418.8kWh / ton of raw material, with an energy saving rate of 4.1%-5.3%, significantly reducing operating costs.

[0022] 4.Environmental treatment of flue gas and acid liquid: The flue gas collection and treatment system efficiently purifies the acid flue gas (removes HCl and other pollutants) through a spray washing tower, avoiding air pollution; the waste acid tank collects the washed acid liquid and returns it to the acid regeneration system, realizing acid resource recycling, reducing acid liquid waste and pollutant emissions, and forming an environmentally friendly closed loop. The acid-washed filter cake, as a hazardous waste of a steel enterprise, not only realizes harmlessness (high chlorine ion removal rate, no secondary pollution), but also recovers 40-45% of the iron therein, which is converted into low-chlorine iron-containing material that can be directly used for ironmaking, turning waste into treasure and improving the resource utilization rate of solid waste.

[0023] 5. Operation flexible adaptation: the rotation speed of the material driving mechanism can be adjusted, and the residence time (5-30 minutes) of the material in each layer of the hearth can be flexibly adjusted according to the water content and chlorine content of the pickling filter cake; the feeding unit adopts a crane + hopper + two-stage heavy hammer flap, has high automation degree, stable and controllable feeding, and is suitable for processing requirements of different batches and different characteristics of the material. In view of the acid corrosion of the pickling filter cake, the hearth bottom and the scraper assembly are made of 904L corrosion-resistant material, the hopper is made of glass fiber reinforced plastic, and the flue gas pipeline is made of 316L, so that the acid corrosion is effectively resisted, the service life of the equipment is prolonged, the risk of equipment scaling and damage is reduced, and the long-term maintenance cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 FIG. 1 is a structural schematic view of the pickling filter cake roasting and dechlorination system of the present application.

[0025] In the figure: 1, vertical multi-layer hearth roasting furnace; 101, drying and dewatering section hearth; 102, pre-roasting and decomposition section hearth; 103, roasting and decomposition section hearth; 104, cooling section hearth; 105, feeding port; 106, discharging port; 107, flue gas outlet; 108, maintenance opening; 2, feeding unit; 201, crane; 202, hopper; 3, material driving mechanism; 301, rotary motor; 302, central shaft; 303, scraper assembly; 4, temperature control unit; 401, temperature measuring part; 402, heating part; 5, flue gas collection and treatment system; 501, spray scrubbing tower; 502, chimney; 503, waste acid tank. DETAILED DESCRIPTION

[0026] In order to make the technical solutions, objects and advantages of the present application more clear, the pickling filter cake roasting and dechlorination system and method of the present application will be further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not constitute a limitation on the present application; the drawings are only used for exemplary description and cannot be understood as a limitation on the protection scope of the present patent, and some components may be omitted, enlarged or reduced in the drawings, and the proportion does not represent the actual product size; for those skilled in the art, the omission of some well-known structures and descriptions in the drawings is understandable, and the positional relationship described in the drawings is only used for exemplary description and does not constitute a limitation on the present patent.

[0027] As Figure 1As shown, the acid pickling filter cake roasting dechlorination system provided by the embodiment of the present application comprises a vertical multi-layer hearth roasting furnace 1, a feeding unit 2, a material driving mechanism 3, a temperature control unit 4 and a flue gas collection and treatment system 5. The innovation of the system mainly lies in that the vertical multi-layer hearth structure roasting furnace is adopted, the temperature is accurately controlled, and the processes of dewatering and drying, roasting and decomposition and material cooling are realized in the same device in sections; the vertical multi-layer hearth structure, the high-temperature flue gas generated in the roasting and decomposition section in the lower layer can realize the drying of the acid pickling filter cake in the dewatering and drying section in the uplink process, and the energy saving effect is better.

[0028] In an embodiment of the present application, the vertical multi-layer hearth roasting furnace 1 comprises a drying and dewatering section hearth 101, a pre-roasting and decomposition section hearth 102, a roasting and decomposition section hearth 103 and a cooling section hearth 104 from top to bottom in sequence. The bottom of each layer of hearth is provided with a discharge port, and the side of each layer of hearth is provided with an inspection port 108. Each layer of hearth adopts a steel shell plus a corundum refractory lining, and the bottom of the hearth adopts 904L material.

[0029] In the above scheme, the drying and dewatering, pre-roasting and decomposition, roasting and decomposition and cooling functions are integrated in a single reactor by adopting the vertical multi-layer hearth integrated structure, the system structure is simplified, the equipment investment and land area are reduced, and the process is more compact and efficient. Each layer of hearth independently operates, the reaction conditions can be controlled accurately in sections, the problem of inaccurate temperature control of traditional equipment (such as a rotary roasting furnace) is solved, and the dechlorination reaction is ensured to be sufficient and thorough. When the high-temperature flue gas generated in the lower roasting and decomposition section goes up, it directly exchanges heat with the cold material going down in the upper layer, the flue gas waste heat is recovered, the external heat energy demand is greatly reduced, and the energy saving effect is improved. The flue gas collection and treatment system 5 is matched, flue gas purification and acid liquid recovery are realized, environmental protection and resource recycling are taken into account. The bottom of each layer of hearth is provided with a discharge port, which ensures that the material falls smoothly to the next layer, avoids the reaction being insufficient or the process being interrupted caused by material accumulation, and guarantees the continuity of material conveying. The side inspection port 108 facilitates daily maintenance, fault diagnosis and component replacement of the equipment, reduces downtime, and improves the stability and service life of the system.

[0030] In an embodiment of the present application, the feeding unit 2 is used to convey the acid pickling filter cake to the drying and dewatering section hearth 101. The feeding unit 2 comprises a travelling crane 201, a hopper 202 and two-stage feeding heavy hammer flaps, the travelling crane 201 is used to convey the hopper 202 to above the feeding port 105 of the drying and dewatering section hearth 101, and the two-stage feeding heavy hammer flaps are used to pour the material in the hopper 202 into the feeding port 105 of the drying and dewatering section hearth 101. The hopper 202 adopts glass steel material.

[0031] In the above scheme, the trolley 201 cooperates with the hopper 202 to realize efficient transfer of materials, and the two-stage feeding heavy hammer flap (the specific structure is the prior art) ensures stable and controllable feeding, avoids material leakage or blockage of the feeding port 105, and adapts to the structural requirements of the upper feeding of the vertical furnace. The hopper 202 is made of glass steel material (corrosion resistant), which is suitable for the acid corrosion characteristics of pickling filter cake, prolongs the service life of the equipment, and reduces the maintenance cost. The feeding process has high automation degree, reduces the labor intensity of manual operation, improves the feeding efficiency, and ensures the continuous operation of the system.

[0032] In an embodiment of the present application, the material driving mechanism 3 is correspondingly arranged in each layer of the furnace, for driving the material to move and fall in the furnace. The material driving mechanism 3 includes a rotary motor 301, a shaft 302 and a scraper assembly 303. The shaft 302 penetrates the vertical multi-layer furnace roasting furnace 1 from top to bottom, the rotary motor 301 is drivingly connected with the end of the shaft 302, and the shaft 302 in each layer of the furnace is provided with the scraper assembly 303. The scraper assembly 303 is driven by the rotary motor 301 to make circular motion, for pushing the material to move in each layer of the furnace and controlling the residence time of the material in each layer. The scraper assembly 303 is composed of a horizontal rod and a plurality of small scrapers, the horizontal rod is vertically arranged on the shaft 302, and the plurality of small scrapers are arranged below the horizontal rod, and the material is mainly pushed by the small scrapers. The shaft 302 is made of cast iron, and the scraper assembly 303 is made of 904L material.

[0033] In the above scheme, the shaft 302 penetrates the multi-layer furnace, and the scraper assembly 303 makes circular motion, which can stably drive the material to move and fall, avoid the accumulation of the material in the furnace, and ensure the continuity of the process. By adjusting the rotating speed of the rotary motor 301, the residence time of the material in each layer of the furnace can be accurately controlled (adjustable range of 5-30 minutes), which adapts to the processing requirements of pickling filter cake with different characteristics and ensures sufficient reaction in each section. The scraper assembly 303 directly acts on the material, pushes the material to be uniformly distributed, improves the contact efficiency of the material and the heat source, strengthens the dehydration and dechlorination effect, and reduces the iron loss.

[0034] In an embodiment of the present application, the temperature control unit 4 is correspondingly arranged in each layer of the furnace, for independently measuring and regulating the heating temperature of each layer of the furnace.

[0035] In an embodiment of the present application, the temperature control unit 4 includes a temperature measuring component 401 and a heating component 402 arranged in each layer of the furnace. The temperature measuring component 401 is a thermocouple, and the heating component 402 is selected from a green electricity heating module or other environmentally friendly heat source module.

[0036] In the above scheme, the thermocouple is used to measure the temperature, and the independent heating component 402 is used to realize the temperature precision control of each layer of the hearth within ±5℃, so as to ensure that each reaction section is strictly in the best temperature interval (such as 350-450℃ in the calcination section), and the dechlorination efficiency is ensured. The green electricity heating module or the environment-friendly heat source is selected to replace the traditional high-pollution heat source, so as to reduce the carbon emission and meet the requirements of low-carbon environmental protection and green manufacturing. The temperature is independently controlled, the temperature requirements of different reaction stages (such as low temperature in the drying section and high temperature in the calcination section) are adapted, and the influence of temperature fluctuation on the reaction effect is avoided.

[0037] In an embodiment of the present application, a flue gas collection and treatment system 5 is used to collect and treat the flue gas generated by the vertical multi-layer hearth calcination furnace 1. The flue gas collection and treatment system 5 comprises a spray scrubber 501, a chimney 502 and a waste acid tank 503 connected in sequence, the gas inlet of the spray scrubber 501 is communicated with the flue gas outlet 107 of the vertical multi-layer hearth calcination furnace through a pipeline; the liquid outlet of the spray scrubber 501 is communicated with the waste acid tank 503, and the waste acid tank 503 is used to return the collected acid liquid to the acid regeneration system; and the gas outlet of the spray scrubber 501 is communicated with the chimney 502. The temperature of the flue gas at the flue gas outlet 107 is about 200-300℃, the pipeline between the flue gas outlet 107 and the spray scrubber 501 is made of 316L material, and the spray tower is made of glass steel material.

[0038] In the above scheme, the spray scrubber 501 efficiently purifies the HCl and other acidic pollutants in the flue gas, avoids the atmospheric pollution caused by the direct emission of acidic flue gas, and meets the environmental protection emission standard. The waste acid tank 503 collects the acid liquid after the spray scrubbing and returns it to the acid regeneration system, realizes the recycling of acid resources, reduces the waste of acid liquid, and reduces the operation cost. The system process is closed loop, the flue gas treatment and acid recovery are integrated, the environmental protection treatment process is simplified, and the overall resource utilization rate of the system is improved.

[0039] Based on the above structure design, the present application provides an acid pickling filter cake calcination dechlorination method using the system, which comprises the following steps: S1, the acid pickling filter cake is sent into the drying and dehydration section hearth 101 of the vertical multi-layer hearth calcination furnace 1 through the feeding unit 2, and drying and dehydration is performed; S2, the dried material is pushed into the pre-calcination and decomposition section hearth 102 by the material driving mechanism 3, and pre-calcination and decomposition is performed; S3, the pre-calcined material is pushed into the calcination and decomposition section hearth 103 by the material driving mechanism 3, and calcination and decomposition are performed; S4, the calcined material is pushed into the cooling section hearth 104 by the material driving mechanism 3, and then discharged through the discharge port 106.

[0040] In a preferred embodiment of the present application, the temperature control range of the drying and dewatering section furnace 101 is 65-110°C, the temperature control range of the pre-calcination and decomposition section furnace 102 is 110-350°C, the temperature control range of the calcination and decomposition section furnace 103 is 350-450°C, and the discharge temperature of the cooling section furnace 104 is lower than 150°C.

[0041] In the above scheme, for the first layer drying and dewatering section furnace: drying and dewatering section 65-110°C, the specific reaction process: the main purpose of this stage is physical dewatering. The filter cake with a water content of up to 52% enters the furnace and is indirectly or directly heated by the high-temperature flue gas from the lower layer. The free water and part of the bound water in the material are evaporated at a temperature of 65-110°C, and the material changes from a wet soft cake to a dry granular or powdery state. Effect: preparation for subsequent reactions: if the material with high water content directly enters the high-temperature zone, it will rapidly vaporize, causing the material to burst and pulverize, and a large amount of material will be lost with the flue gas, while the huge latent heat consumption will severely impact the temperature field of the high-temperature zone, causing a sharp increase in energy consumption. Preventing equipment scaling: wet material directly contacts high-temperature surfaces and is easily bonded to the equipment, forming scaling and affecting heat transfer and material transport. Benefits: energy recovery: using the upward waste gas from the lower layer (second and third layers) that has completed the calcination task but still has a relatively high temperature to dry the material, which is the key to energy saving of the entire system. It is equivalent to "free" obtaining most of the heat energy required for drying, greatly reducing the need for external heat sources. Compact process: integrating the drying function into the furnace saves the need for a separate dryer and the supporting conveying system, simplifying the process and reducing equipment investment and floor space.

[0042] For the second layer pre-calcination and decomposition section furnace: pre-calcination and decomposition section 110-350°C, the specific reaction process: the dried material enters this layer. At this temperature interval, part of the unstable chlorides in the filter cake (such as FeCl3·6H2O, etc.) begin to decompose and release HCl gas. This is a mild initial decomposition stage. Effect: mild decomposition: avoiding the "thermal shock" caused by the direct jump of the material from low temperature (such as 85°C) to the highest calcination temperature (such as 400°C). Thermal shock can cause physical structure damage to the material, produce excessive fine powder, and may cause the material surface to sinter, wrapping the internal chloride ions, thereby reducing the final dechlorination rate. Staged reaction to improve thoroughness: allowing easy-to-decompose chlorides to react first creates conditions for the third layer to handle more stable chlorides. This "easy first, hard later" staged reaction strategy ensures that the overall reaction is more complete and thorough. Benefits: protect the material and improve quality: mild preheating and pre-decomposition protect the physical structure of the material, resulting in better quality and lower iron loss. Optimize the final reaction: by removing part of the chlorine in advance, the load of the third layer main reaction section is reduced, allowing it to focus more on decomposing the most stubborn chlorides within the limited residence time in the third layer, thereby improving the overall dechlorination efficiency.

[0043] For the third layer roasting decomposition furnace: roasting decomposition section 350-450℃, the specific reaction process: this is the core stage of dechlorination reaction. At this high temperature, all stable chlorinated compounds in the filter cake (such as FeOCl, and residual various metal chlorides) undergo complete thermal decomposition reaction to generate metal oxides and HCl gas. The operating temperature of 400℃ in the example is to ensure that such reactions are quickly and completely carried out. Effect: achieve deep dechlorination: this is the "high-temperature holding section" necessary to achieve high dechlorination rate (such as 98.5% or more). Without high enough temperature and residence time, the dechlorination reaction will not be completed. Ensure the completeness of the reaction: a constant high-temperature zone is specially set up to provide an ideal environment for deep decomposition reaction. Benefits: sufficient reaction, excellent indicators: ensure that the chlorine content of the final product can be stably reached at a very low level (such as <0.5%), meeting the strict requirements of subsequent ironmaking or resource utilization. The dechlorination rate of 98.5%-99.6% in the example is due to this. Precise temperature control: as an independent furnace, its temperature can be very accurately controlled at the optimal reaction temperature (such as 400℃), avoiding the problem of large temperature fluctuations in traditional rotary kilns.

[0044] For the fourth layer cooling furnace: cooling section discharge temperature <150℃, the specific reaction process: this stage has no chemical reaction, it is a physical cooling process. The hot material of about 400℃ from the third layer exchanges heat with the introduced cold air or cooling medium, and the temperature is reduced to below 150℃. Effect: safety and subsequent processing: high-temperature material (400℃) cannot be directly transported by air, packaged or stored, which will damage downstream equipment and pose a safety hazard. Energy recovery: this is another key point of system energy saving. Benefits: secondary energy recovery: the heated cooling air (becomes hot air) can be introduced into the furnace as combustion air or supplemented to the drying section, recovering the sensible heat of the high-temperature material and further reducing the fuel consumption of the entire system. Ensure the safe and stable operation of the system: the discharge temperature meets the requirements of subsequent processing and storage, realizing continuous and safe production. In an embodiment of the present application, the residence time of the material in each furnace can be adjusted by adjusting the speed of the central shaft, and the residence time in each layer is adjustable between 5-30 minutes. The residence time can be flexibly adjusted by the speed of the central shaft to adapt to the processing needs of pickling filter cake with different water content and chlorine content, and to ensure that each reaction section (such as drying and roasting) has sufficient time to complete the reaction. For difficult-to-decompose chlorinated compounds, the residence time in the roasting section can be extended to further improve the dechlorination rate (up to 99.6%); for easy-to-process materials, the residence time can be shortened to improve the processing efficiency, balancing flexibility and practicality.

[0045] In an embodiment of the present application, each furnace is equipped with a temperature control unit for temperature measurement and control, with a precision of within ±5℃.

[0046] In an embodiment of the present application, the chloride ion content in the material treated in step S4 is not higher than 0.5%, and the chloride ion removal rate is not lower than 98.5%. The strict requirements of subsequent ironmaking or other resource utilization are met, the resource utilization value of the pickling filter cake is greatly improved, and the hazardous waste is turned into treasure. The product index is stable and reliable, the problem of insufficient dechlorination rate in the traditional process is solved, the corrosion risk of chloride ion to equipment in the subsequent use process is reduced, and the market applicability of the product is improved.

[0047] The use effect of the system of the present application will be described below in combination with a specific application case.

[0048] A same batch of pickling filter cake material of an enterprise has a moisture content of 52%, a Cl content of 26.8%, and a TFe content of 40.6%. The treatment examples of using a paddle type low-temperature dryer drying and a rotary roaster decomposing and dechlorinating and using the technical solution of the present application are as follows: Comparative example: The ton bag packaged pickling filter cake is hoisted to the feeding port above the receiving hopper, each bag weighing about 600 kg, the pickling filter cake is conveyed to the low-temperature dryer by the screw conveyor, the drying temperature is 105℃, the material residence time is 10 min, the moisture content of the dried material is 0.2%, the Cl content is 19.4%, and the TFe content is 43.5%, the material is directly conveyed to the rotary roaster, the roaster roasting temperature is 400℃, and the material residence time is 5 min. After roasting, the material is conveyed to the silo by pneumatic conveying, the Cl content is 0.6%, and the chloride ion removal rate is 97.8%. It is calculated that the comprehensive energy consumption of the process is about 436.8 kWh / ton of raw material. The traditional process route is long, the equipment is much, the heat loss is large, and the high-temperature flue gas is not effectively recycled, resulting in high overall energy consumption.

[0049] Example 1: The system structure and material selection are designed and manufactured according to the claims, the system is started, 600 kg of pickling filter cake is loaded into the hopper and lifted to the top layer of the multi-stage roaster by the crane, and then enters the first layer of the multi-stage roaster through the two-stage feeding heavy hammer flap. After drying and dehydrating for 5 min, the temperature is 85℃, the material enters the second layer of the furnace for pre-roasting and decomposition, the temperature is 300℃, and after reacting for 5 min, the material enters the third layer of the furnace for further roasting and decomposition, the temperature is 400℃, and after reacting for 5 min, the material enters the fourth layer of the furnace for cooling for 8 min, the temperature of the material discharged from the discharge port is 110℃, the Cl content is 0.4%, and the chloride ion removal rate is 98.5%. It is calculated that the comprehensive energy consumption of the present example is about 418.8 kWh / ton of raw material, which is about 18.0 kWh lower than that of the traditional process of the comparative example, and the energy saving rate is 4.1%.

[0050] Example 2: The system structure and materials are designed and manufactured according to the claims. Start the system, load 600 kg of pickling filter cake into the hopper, lift it to the top layer of the multi-stage roasting furnace through the crane, and then enter the first layer of the multi-stage roasting furnace through the two-stage feeding heavy hammer flap. After drying and dehydrating for 10 min, the temperature is 85℃, and then enter the second layer of the furnace for pre-roasting decomposition, the temperature is 300℃, and after 5 min of reaction, the material enters the third layer of the furnace for further roasting decomposition, the temperature is 400℃, and after 10 min of reaction, the material enters the fourth layer of the furnace for cooling for 15 min, the discharge temperature at the discharge port is 85℃, the Cl content is 0.3%, and the chloride ion removal rate is 98.9%. Due to more complete heat exchange and lower discharge temperature, the comprehensive energy consumption of this embodiment is further reduced to about 415.9 kWh / ton of raw material, which is about 20.9 kWh / ton lower than the comparative example, and the energy saving rate is 4.8%.

[0051] Example 3: The system structure and materials are designed and manufactured according to the claims. Start the system, load 600 kg of pickling filter cake into the hopper, lift it to the top layer of the multi-stage roasting furnace through the crane, and then enter the first layer of the multi-stage roasting furnace through the two-stage feeding heavy hammer flap. After drying and dehydrating for 10 min, the temperature is 85℃, and then enter the second layer of the furnace for pre-roasting decomposition, the temperature is 300℃, and after 5 min of reaction, the material enters the third layer of the furnace for further roasting decomposition, the temperature is 400℃, and after 15 min of reaction, the material enters the fourth layer of the furnace for cooling for 20 min, the discharge temperature at the discharge port is 65℃, the Cl content is 0.1%, and the chloride ion removal rate is 99.6%. Since more sensible heat of the material is recovered in the cooling section, the net heat consumption of the system is effectively reduced, and the comprehensive energy consumption of this embodiment is optimal, about 413.5 kWh / ton of raw material, which is 23.3 kWh / ton lower than the comparative example, and the energy saving rate is as high as 5.3%.

[0052] In summary, the present application achieves step-by-step utilization and efficient recovery of energy through the innovative vertical multi-layer furnace structure, significantly improves the chloride ion removal rate, and achieves excellent energy saving effect. The example data shows that the comprehensive energy consumption of the technical scheme of the present application can be controlled within the range of 413.5~418.8 kWh / ton of raw material, which is 4.1%~5.3% lower than the traditional two-stage process (436.8 kWh / ton of raw material). This fully proves the great value of the present application in reducing operating costs and promoting green manufacturing.

[0053] According to the description and drawings of the present application, a person skilled in the art can easily manufacture or use the pickling filter cake roasting and dechlorination system and method of the present application, and can produce the positive effects described in the present application.

[0054] Unless otherwise defined, all terms used in disclosing aspects of the application, such as professional terms and technical terms, have the meanings as commonly understood by one of ordinary skill in the art to which this application belongs. By way of non-limiting example, the following definitions are provided.

[0055] Unless otherwise defined, all terms used in disclosing aspects of the application, such as professional terms and technical terms, have the meanings as commonly understood by one of ordinary skill in the art to which this application belongs. By way of non-limiting example, the following definitions are provided.

[0056] The above description is only the preferred embodiment of the application, not any form of limitation on the application, any simple modification and equivalent change of the above embodiment according to the technical essence of the application shall fall within the protection scope of the application.

Claims

1. A system for roasting and dechlorinating pickled filter cake, characterized in that, include: The vertical multi-layer furnace roasting furnace (1) includes, from top to bottom, a drying and dehydration section furnace (101), a pre-roasting and decomposition section furnace (102), a roasting and decomposition section furnace (103), and a cooling section furnace (104). The feeding unit (2) is used to convey the pickled filter cake to the drying and dehydration section furnace (101). The material driving mechanism (3) is correspondingly installed in each layer of the furnace to drive the material to move in the furnace and fall to the next layer of the furnace. Temperature control unit (4) is installed in each layer of the furnace to independently measure and control the heating temperature of each layer of the furnace; The flue gas collection and treatment system (5) is used to collect and treat the flue gas generated by the vertical multi-layer furnace roasting furnace (1).

2. The acid-washed filter cake roasting and dechlorination system according to claim 1, characterized in that, The material driving mechanism (3) includes a rotary motor (301), a central shaft (302), and a scraper assembly (303). The central shaft (302) runs through the vertical multi-layer furnace roasting furnace (1) from top to bottom. The rotary motor (301) is driven to the end of the central shaft (302). The scraper assembly (303) is provided on the central shaft (302) in each layer of the furnace. The scraper assembly (303) is driven by the rotary motor (301) to make a circular motion, which is used to push the material to move in each layer of the furnace and control the residence time of the material in each layer.

3. The acid-washed filter cake roasting and dechlorination system according to claim 1, characterized in that, The flue gas collection and treatment system (5) includes a spray scrubbing tower (501), a chimney (502), and a waste acid tank (503) connected in sequence. The air inlet of the spray scrubbing tower (501) is connected to the flue gas outlet (107) of the vertical multi-stage roasting furnace through a pipe. The liquid outlet of the spray scrubbing tower (501) is connected to the waste acid tank (503), which is used to return the collected acid liquid to the acid regeneration system. The air outlet of the spray scrubbing tower (501) is connected to the chimney (502).

4. The acid-washed filter cake roasting and dechlorination system according to claim 1, characterized in that, The temperature control unit (4) includes a temperature measuring component (401) and a heating component (402) installed in each layer of the furnace. The temperature measuring component (401) is a thermocouple, and the heating component (402) is a green electric heating module or other environmentally friendly heat source module.

5. The acid-washed filter cake roasting and dechlorination system according to claim 1, characterized in that, The feeding unit (2) includes a crane (201), a hopper (202) and a two-stage feeding counterweight flap. The crane (201) is used to transport the hopper (202) to the feed inlet (105) of the furnace (101) of the drying and dehydration section. The two-stage feeding counterweight flap is used to feed the material in the hopper (202) into the feed inlet (105) of the furnace (101) of the drying and dehydration section.

6. The acid-washed filter cake roasting and dechlorination system according to claim 1, characterized in that, Each furnace layer has a feeding port at the bottom and an inspection port (108) on the side of each furnace layer.

7. A method for dechlorinating acid-washed filter cake by roasting using the system described in any one of claims 1-6, characterized in that, Includes the following steps: S1. The pickled filter cake is fed into the drying and dehydration section (101) of the vertical multi-layer furnace roasting furnace (1) through the feeding unit (2) for drying and dehydration. S2. The dried material is pushed into the pre-roasting decomposition section furnace (102) by the material driving mechanism (3) for pre-roasting decomposition. S3. The pre-roasted material is pushed into the roasting and decomposition section furnace (103) by the material driving mechanism (3) for roasting and decomposition. S4. The roasted material is pushed into the cooling section furnace (104) by the driving mechanism (3) and cooled before being discharged.

8. The method according to claim 7, characterized in that, The temperature control range of the drying and dehydration section furnace (101) is 65-110℃, the temperature control range of the pre-calcination and decomposition section furnace (102) is 110-350℃, the temperature control range of the calcination and decomposition section furnace (103) is 350-450℃, and the discharge temperature of the cooling section furnace (104) is below 150℃.

9. The method according to claim 7, characterized in that, The residence time of materials in each layer of the furnace is 5-30 minutes.

10. The method according to claim 7, characterized in that, The chloride ion content in the material after step S4 is no higher than 0.5%, and the chloride ion removal rate is no less than 98.5%.

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