Multi-source solid waste co-processing method and system

Abstract

According to the multi-source solid waste co-processing method and system, metal solid waste and organic solid waste are distributed in a layered mode, oxygen-deficient hot air is adopted for drying preheating, hot charging reduction and smelting, on one hand, rapid absorption processing of the organic solid waste can be achieved; oxidation of metal and carbonaceous reducing agents in materials before reduction smelting is effectively avoided, and energy consumption of subsequent rotary kiln reduction and electric furnace smelting is reduced; and on the other hand, organic solid waste pyrolysis and chemical energy and physical heat generated by the rotary kiln and the electric furnace system are coupled and utilized, so that gradient utilization of energy and internal circulation of the system are achieved, the energy utilization efficiency is further improved, and meanwhile pollution to the environment is effectively reduced. According to the method, the traditional mindset of'quality-based treatment 'is broken through, and the recycling purposes of'treating waste with waste and turning waste into wealth' are achieved by deeply coupling and coordinating the solid wastes which are dispersed in the steel mill and have different properties on the aspects of material flow and energy flow.

Description

Technical Field

[0001] This invention relates to the co-processing of multi-source solid waste from steel plants, specifically to a method and system for the co-processing of multi-source solid waste, belonging to the technical field of co-processing of multi-source solid waste from steel plants. Background Technology

[0002] Stainless steel production is a complex process involving multiple steps such as steelmaking, hot rolling, and cold rolling, which generates a large amount of solid waste with varying compositions and forms. This mainly includes: 1) Metal dust and sludge: Dust collected from sintering, ironmaking, and steelmaking processes, rich in valuable metals such as iron, nickel, chromium, and manganese, but also containing volatile harmful impurities such as zinc and lead, as well as alkali metals. Improper disposal will cause serious resource waste and environmental pollution; 2) Rust scale: Iron oxide scale generated during hot and cold rolling, whose main component is iron oxide, is a valuable iron resource. However, due to its loose structure and low density, direct reuse can easily cause splashing during the smelting process and increase energy consumption; 3) Organic solid waste: Such as packaging tape, which is usually incinerated or landfilled as general industrial waste, not only wasting its chemical energy but also potentially producing toxic gases such as dioxins. Achieving resource recovery, harmless treatment, and volume reduction of these solid wastes is a key step for the stainless steel industry towards green, low-carbon, and sustainable development, and it is also the focus and challenge of current research on solid waste resource recovery technologies.

[0003] Existing treatment technologies often adopt the simple idea of ​​"separate treatment of different types of solid waste", that is, they use independent treatment processes for different types of solid waste, and fail to integrate the system from the perspective of the coordination of material flow and energy flow of the whole plant, resulting in problems such as lengthy process flow, low energy efficiency, high risk of secondary pollution and poor economic efficiency. (1) Treatment of metal dust and sludge: Existing technologies usually use cold solidification and pelletizing (such as briquetting) and then return it directly to smelting, or use separate metallization pellet production process (such as rotary hearth furnace, rotary kiln) for treatment; cold solidification pellets directly enter the electric furnace, which requires a lot of electricity to heat and melt the gangue components in the pellets and complete the reduction of metal oxides. The power consumption is extremely high, the efficiency is low and the recovery rate is poor; while direct entry into the furnace can easily lead to the cyclic enrichment of harmful elements such as zinc and lead in the dust, affecting the smooth operation of the furnace and the life of the equipment. In addition, if an independent rotary hearth furnace or rotary kiln production line is established, although the production of metallized pellets and dezincification can be achieved, an additional large heating and reduction system needs to be built, and the investment and operating costs are high; especially the rotary kiln process, the drying and preheating of materials in the kiln requires a large amount of fuel, the energy utilization efficiency is low, and the latent heat and chemical energy of solid waste itself are not fully utilized. (2) Treatment of rust scale: Existing technologies mostly use simple briquetting or pelletizing, and then add it to the electric furnace or AOD furnace in the form of cold material. The cold lumps will significantly increase the smelting power consumption and prolong the smelting cycle; in addition, the strength of cold-pressed lumps is usually not high, and powder is easily generated during transportation and feeding, which affects the reaction efficiency of the molten pool after entering the furnace and may increase dust emissions. (3) Treatment of organic solid waste (such as tape): Existing technologies usually mix it with other domestic waste and then send it to waste incineration plants for incineration or sanitary landfill, which is the most extensive treatment. Organic materials such as tape have high calorific value, and landfill treatment completely wastes their chemical energy, while off-site incineration fails to reuse this part of the energy in the stainless steel production process itself. Moreover, if the incineration is not properly controlled, it is very easy to generate persistent organic pollutants such as dioxins, which poses a risk of secondary pollution. In addition, enterprises also need to pay additional waste disposal fees, which increases operating costs. Summary of the Invention

[0004] To address the problems of low energy utilization and poor economic efficiency in the existing technology of separate and independent disposal of multi-source solid waste from steel plants, this invention separates and distributes the metal-containing solid waste molding material and organic solid waste fragments in layers before rotary kiln reduction. Using oxygen-deficient hot air as a heat source, these materials undergo sequential preheating and drying via exhaust and forced draft. This achieves pyrolysis of the organic solid waste while effectively preventing the oxidation of metals and carbonaceous reducing agents in the molding material before entering the kiln, maintaining a high metallization rate and reducing the difficulty of subsequent rotary kiln reduction and electric arc furnace smelting, thus lowering energy consumption and production costs. Furthermore, the pyrolysis gas generated from the organic solid waste pyrolysis is used as fuel for rotary kiln reduction, and the rotary kiln dust removal flue gas and electric arc furnace gas are subjected to oxygen-deficient hot air combustion. This achieves cascaded energy utilization and internal system circulation, further improving energy efficiency while reducing environmental pollution.

[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0006] According to a first embodiment of the present invention, a method for the co-processing of multi-source solid waste is provided:

[0007] A method for the co-processing of multi-source solid waste, the method comprising the following steps:

[0008] S1: Multi-source solid waste is classified into metallic solid waste and organic solid waste. The metallic solid waste is mixed with auxiliary materials and then molded to obtain molded material. The organic solid waste is crushed to obtain organic fragments.

[0009] S2: The molded material and organic scraps are used as the bottom layer and top layer respectively to form a mixed material.

[0010] S3: The mixture is fed into a drying and preheating device for sequential drying and preheating. The preheating heat source is oxygen-deficient hot air, and the drying heat source is the preheated exhaust gas. After the drying and preheating processes are completed, a hot mixture and dry exhaust gas are obtained.

[0011] S4: The hot mixture is screened to obtain clinker and residual carbon (i.e., pyrolytic carbon from the pyrolysis of organic solid waste). The clinker is fed into a rotary kiln for reduction treatment to obtain reducing feedstock and reduction flue gas. The reduction flue gas is treated with dust removal to obtain lead-zinc dust and dust removal flue gas.

[0012] S5: The raw materials are fed into the electric furnace and mixed with flux and reducing agent for reduction smelting to obtain metal mother liquor (after cooling, metal alloy ingots), electric furnace slag and electric furnace gas.

[0013] Preferably, the method further includes step S6: using the electric furnace gas obtained in step S5 as fuel and the dust removal flue gas obtained in step S4 as combustion air to perform oxygen-deficient combustion to obtain oxygen-deficient flue gas, and returning the oxygen-deficient flue gas to step S3 for use as oxygen-deficient hot air.

[0014] Preferably, in step S1, the multi-source solid waste includes, but is not limited to, metal-containing dust (e.g., dust containing iron, zinc, lead, nickel, bismuth, etc.), rust scale, and packaging tape.

[0015] Preferably, in step S1, the excipients include one or more of carbonaceous reducing agents, binders, and water.

[0016] Preferably, the carbonaceous reducing agent is one or more of coal powder (or coal particles), coke powder (or coke particles), and carbon powder (or carbon particles). The binder is one or more of cement, bentonite, and organic binders (e.g., starch, humic acid, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylamide, waste molasses, etc.).

[0017] Preferably, in step S1, the molding process of mixing metal solid waste with auxiliary materials includes: mixing metal-containing dust with a carbonaceous reducing agent, a binder, and water for pelletizing to obtain green pellets. Alternatively, mixing rust scale with a binder and water for briquetting to obtain green briquettes. Preferably, the particle size of the molding material (green pellets and green briquettes are collectively referred to as molding material) is 8-12 mm. The particle size of the organic scrap is 20-50 mm.

[0018] Preferably, in the green pellets, the mass content of the carbonaceous reducing agent is 10-30%, the mass content of the binder is 0.5-10%, and the mass content of the water is 2-10%.

[0019] Preferably, in the raw agglomerate, the mass content of the binder is 2-10%, and the mass content of the water is 2-10%.

[0020] Preferably, in step S2, the thickness of the molding material is 100~500mm, more preferably 150~450mm.

[0021] Preferably, in step S2, the thickness of the organic crushed material is 10~50mm, more preferably 15~45mm.

[0022] Preferably, in step S3, the temperature of the oxygen-deficient hot air is 500~1000℃, more preferably 600~900℃.

[0023] Preferably, in step S3, the oxygen content index of the oxygen-deficient hot air is less than 1, preferably 0.1~0.7, and more preferably 0.3~0.5. The oxygen content index refers to the ratio (molar ratio, volume ratio, mass ratio, etc.) of the total amount of oxygen actually introduced during oxygen-deficient hot air preheating to the theoretical oxygen consumption required for the complete oxidation and combustion of organic debris. For example, when 100m³ of oxygen needs to be drawn in… 3Only oxygen-deficient hot air can meet the preheating requirements, and the theoretical oxygen demand for the complete oxidation and combustion of organic waste is currently 20 m³ / h. 3 At that time, the oxygen content index was taken as 0.4, meaning that the total amount of oxygen introduced during the preheating of the oxygen-deficient hot air was 0.4 × 20 m³. 3 =8m 3 That is, the current oxygen volume concentration in the oxygen-deficient hot air is approximately 8m³. 3 ÷100m 3 =8%. In other words, the oxygen concentration in the oxygen-deficient hot air is adaptively adjusted according to changes in actual working conditions.

[0024] Preferably, in step S3, the temperature of the hot mixture is 500~800℃, more preferably 550~700℃.

[0025] Preferably, in step S3, the temperature of the preheated exhaust gas is 150~300℃, more preferably 180~280℃.

[0026] Preferably, in step S4, the reduction treatment temperature is 1000~1200℃, more preferably 1050~1150℃. The reduction treatment duration is 0.5~5h, more preferably 1~3h.

[0027] Preferably, in step S5, the reduction smelting temperature is 1400~1600℃, more preferably 1450~1550℃. The reduction smelting time is 0.5~8h, more preferably 3~6h.

[0028] Preferably, in step S5, the flux is one or more of limestone, dolomite, marble, and silica. The reducing agent is a carbonaceous reducing agent. Preferably, the mass ratio of the reducing agent, flux, and reducing agent is 70~90:5~20:5~10.

[0029] According to a second embodiment of the present invention, the present invention also provides a system for the co-processing of multi-source solid waste:

[0030] A system for the co-processing of multi-source solid waste, or a system for the co-processing of multi-source solid waste using the method described in the first embodiment, includes a metal solid waste collection unit, an organic solid waste collection unit, a molding unit, a molding material distribution device, an organic solid waste distribution device, a drying and preheating device, a rotary kiln, and an electric furnace. The metal solid waste collection unit, molding unit, molding material distribution device, drying and preheating device, rotary kiln, and electric furnace are connected in series. The organic solid waste distribution device is arranged parallel to the molding material distribution device above the feed end of the drying and preheating device, and is located downstream of the molding material distribution device according to the material flow direction. The feed end of the organic solid waste distribution device is connected to the discharge end of the organic solid waste collection unit.

[0031] Preferably, the system also includes an oxygen-deficient combustion device. The drying and preheating device includes a drying section and a preheating section connected in series. The hot air outlet of the oxygen-deficient combustion device is connected to the top hot air inlet of the preheating section via an oxygen-deficient hot air conveying pipe. The bottom hot air outlet of the preheating section is connected to the bottom hot air inlet of the drying section via a preheating exhaust gas conveying pipe. The top hot air outlet of the drying section is connected to the air inlet of the rotary kiln via a drying exhaust gas conveying pipe. Preferably, a fan is also installed on the preheating exhaust gas conveying pipe.

[0032] Preferably, the metal solid waste collection unit includes several dust collection bins and several rust scale storage bins, or is composed of several dust collection bins and several rust scale storage bins.

[0033] Preferably, the organic solid waste collection unit includes or is composed of several organic waste bins.

[0034] Preferably, the molding unit includes a mixing device, a molding device, and an auxiliary material adding device. The inlet of the mixing device is connected to the outlet of the metal solid waste collection unit and the outlet of the auxiliary material adding device. The outlet of the mixing device is connected to the inlet of the molding device. The outlet of the molding device is connected to the inlet of the molding material distributing device.

[0035] Preferably, the forming device is a pelletizing machine (e.g., a disc pelletizing machine, a cylindrical pelletizing machine, or a high-pressure turbulence pelletizing machine) and / or a briquetting machine (e.g., a double-roller briquetting machine or a high-pressure briquetting machine). The auxiliary material adding device is internally equipped with a reducing agent storage chamber, a binder storage chamber, and a water chamber (or is composed of a reducing agent storage chamber, a binder storage chamber, and a water storage chamber arranged in parallel).

[0036] Preferably, the flue gas outlet of the rotary kiln is also connected to the combustion gas inlet of the oxygen-deficient combustion device via a reduction flue gas conveying pipeline. Similarly, the gas outlet at the top of the electric furnace is connected to the combustion gas inlet of the oxygen-deficient combustion device via a gas conveying pipeline.

[0037] As a preferred option, a dust collector is also installed on the flue gas conveying pipeline.

[0038] As a preferred option, an oxygen content detector is also installed in the oxygen-deficient hot air conveying pipeline.

[0039] Preferably, the molding material feeding device and the organic solid waste feeding device are each independently a shuttle feeder and / or a roller feeder.

[0040] Preferably, the drying and preheating device is one of a rotary drying and preheating furnace, a belt drying and preheating furnace, or a moving bed drying and preheating furnace (these drying and preheating furnaces all have permeable grates or moving beds, and are all existing mature commercial products).

[0041] In this invention, to improve the disposal efficiency of multi-source solid waste, it is necessary to pre-treat the solid waste separately, including forming treatment of metal solid waste and crushing treatment of organic solid waste (for example, cutting waste tape and other organic solid waste into strips of 20mm×50mm using a shearing machine). Among them, forming treatment includes pelletizing treatment and / or briquetting treatment: pelletizing treatment generally refers to: collecting dust and sludge containing iron, nickel, chromium, manganese, etc. generated from various processes in stainless steel plants, mixing it with carbonaceous reducing agents (such as coal powder, coke powder, etc.) in a certain proportion. The principle of proportioning is to ensure that the carbon content not only meets the needs of metal oxide reduction, but also needs to supplement the part that may be oxidized in the subsequent preheating process. Finally, the uniformly mixed material is fed into a pelletizing machine (such as a disc pelletizing machine or a double-roller briquetting machine), and an appropriate amount of water or binder (such as bentonite, starch, humic acid, etc.) is added to finally produce green pellets with a particle size range of 8~12mm. Briquetting generally refers to the process of collecting rust or iron oxide scale generated during hot rolling, cold rolling, and other processes, mixing it with an appropriate amount of binder (such as cement, bentonite, or organic binder), and then pressing it into high-strength briquettes using a high-pressure briquetting machine. Forming organic solid waste into large pellets or briquettes improves the permeability of the material bed during subsequent drying and preheating, enhances heat exchange efficiency, reduces kiln clogging during rotary kiln reduction, and improves the permeability of the electric furnace molten pool, thus improving smelting efficiency and safety.

[0042] In this invention, the co-processing of metal solid waste and organic solid waste is mainly manifested in the following aspects: the molding material containing metal solid waste and the crushed organic fragments of organic solid waste are respectively used as the bottom material and the surface material for distribution. At the same time, high-temperature oxygen-deficient hot air is used as the heat source for drying and preheating, and the entire mixture is preheated by exhaust from top to bottom and dried by forced air from bottom to top. It should be noted that the high-temperature oxygen-deficient hot air can be hot exhaust gas generated from other processes in the steel plant, or it can be generated by the system itself through circulation. For example, it can use electric furnace gas generated from subsequent stainless steel electric furnace smelting as fuel and the tail gas after the reduction flue gas of the rotary kiln is separated into zinc oxide by dust removal as combustion air. It is then subjected to oxygen-deficient combustion through an oxygen-deficient combustion device set at the top of the drying and preheating device, thereby generating hot flue gas with high temperature (preferably 500~1000℃) but low oxygen content. Both electric arc furnace gas and reduction flue gas are inevitable byproducts of the system. Recycling these byproducts to further support rotary kiln reduction and electric arc furnace smelting optimizes the allocation of waste gas resources within the plant, further reducing dependence on external energy and operating costs. This embodies the green, low-carbon, and highly efficient waste management philosophy. It should also be noted that hot waste gas generated from other processes in the steel plant is generally used primarily during the initial system startup phase or when the system's oxygen-deficient hot air is insufficient.

[0043] In this invention, the preheating mechanism is a preheating system that protects the surface material from pyrolysis and the bottom material from a reducing atmosphere: the high-temperature hot air is drawn from the upper part of the material layer in the preheating section of the drying preheating furnace or penetrates the material layer downwards by pressure difference. The high-temperature, oxygen-deficient hot air first contacts the upper organic fragment material layer, causing it to pyrolyze (cracking) and generate high-temperature pyrolysis gas and pyrolysis carbon rich in H2, CO, CH4, and other components. The pyrolysis carbon remains on the surface (and is subsequently separated from the molding material by a hot screen; after crushing, the pyrolysis carbon can be recycled within the system as a carbonaceous reducing agent and fuel), while the generated high-temperature pyrolysis gas continues to flow downwards and preheats the lower layer of molding material containing metal solid waste. Crucially, the strong reducing atmosphere created by the pyrolysis gas effectively prevents the internal carbon and metal materials in the molding material from being oxidized during the preheating process, ensuring the reduction efficiency of the subsequent reduction process. In other words, this invention uses organic solid waste such as adhesive tape, which would normally require paid treatment, as "free fuel" within the system. The chemical energy and physical heat generated by its pyrolysis are directly used to preheat materials within the system, replacing some of the purchased fuel and achieving energy self-sufficiency and recycling. Furthermore, the low-temperature exhaust gas after drying and preheating is introduced into the rotary kiln as combustion air, further recovering low-grade waste heat and improving the overall thermal efficiency of the system.

[0044] In this invention, the drying process utilizes the waste heat of preheated waste gas in a stepped manner: after the high-temperature oxygen-deficient hot air and the pyrolysis gas generated in the preheating section penetrate the entire material layer of the preheating section, the gas temperature will decrease, meaning that the preheated waste gas still contains residual heat (generally between 150 and 300°C). At this point, this portion of preheated waste gas is blown in from the bottom of the drying section and passes through the material layer of the drying section from bottom to top to dry the material with forced air, removing residual moisture. The low-temperature dried waste gas after heat exchange still contains a large amount of reducing gases such as H2, CO, and CH4. Therefore, after dust removal and moisture removal, the dried waste gas can be recycled to the rotary kiln and enter the rotary kiln from the kiln head for combustion and heat release, which is used to heat up and reduce the material, thereby achieving internal absorption of the dried waste gas and helping to reduce the energy consumption of the rotary kiln reduction and improve the reduction efficiency.

[0045] In this invention, during rotary kiln reduction, the preheated and hot-state shaped material (i.e., clinker) is hot-charged into the rotary kiln. Since the clinker is already dried and preheated, fuel consumption for moisture evaporation and material heating within the rotary kiln is significantly reduced. Inside the rotary kiln, the clinker undergoes solid-state reduction of metal oxides at high temperatures (preferably 1000~1200℃). Volatile harmful elements such as zinc and lead are removed and enriched in the flue gas for recovery (i.e., during the rotary kiln reduction process, volatile harmful elements such as zinc and lead are effectively removed and enriched in the flue gas, which can be recovered as secondary zinc oxide products, completely cutting off the circulation and enrichment of these harmful elements in the smelting system and avoiding environmental pollution), ultimately producing reduced pellets with a high metallization rate. It should be noted that when the metal solid waste is iron rust scale, the molten clinker containing iron rust scale can be directly introduced into the subsequent electric furnace smelting process without undergoing the rotary kiln reduction process (that is, the discharge port of the drying and preheating device can be directly connected to the feed port of the rotary kiln through a chute or other feeding device, or it can be connected to the feed port of the electric furnace through a transfer device such as an insulated tank truck).

[0046] In this invention, during electric furnace smelting: hot reduced pellets and / or hot rust scale lumps (preheated) discharged from the rotary kiln are directly charged into the electric furnace (or AOD furnace) via a heat-insulated conveying device (e.g., a heat-insulated tank car). A certain amount of flux and reducing agent are added according to the material composition for reduction smelting. The large amount of sensible heat carried by the hot-charged materials significantly reduces the melting power consumption of the electric furnace. Inside the electric furnace, these materials are smelted, ultimately producing a high-value iron-nickel-chromium-manganese alloy (stainless steel mother liquor) and electric furnace slag.

[0047] In this invention, the traditional mindset of "separate treatment" is broken. Through ingenious process design, the dispersed and diverse solid wastes from multiple sources within the stainless steel plant are deeply coupled and coordinated in terms of material flow and energy flow, realizing a systematic innovation of "treating waste with waste and turning waste into treasure". This is mainly reflected in the following aspects: (1) Organic solid waste as an endogenous reducing protective gas generator: Organic solid waste such as tape is creatively no longer regarded as garbage that needs to be treated externally, but is used as "distributed energy" and "reducing gas raw material" within the system. By arranging it as a surface material and co-drying and preheating it with the molding material containing metal solid waste, the residual heat flue gas is used to pyrolyze it, generating high-temperature reducing pyrolysis gas and pyrolysis carbon rich in H2 and CO. (2) Preheating protection mechanism under reducing atmosphere: The pyrolysis gas generated by the pyrolysis of organic solid waste penetrates downwards into the preheating metal material layer, which not only provides the heat required for preheating, but its reducing atmosphere is also the core. It effectively prevents the metal and carbon in the metal solid waste pellets such as dust and ash from being oxidized during the preheating stage, and effectively ensures the stability of the metallization rate and carbon content of the material. This is the premise for the efficient reduction and energy saving of the rotary kiln in the subsequent process, and overcomes the problem of easy oxidation of materials in traditional preheating technology. (3) Energy cascade utilization and internal circulation of the system: Further utilize the physical sensible heat and chemical energy of the electric furnace gas combustion heat and the organic solid waste pyrolysis gas to complete the drying, preheating of metal materials and the treatment of organic solid waste itself. Maximize the utilization of low-quality waste heat and chemical energy of waste, replace external fuel, and form an energy closed loop inside the system. (4) Full process hot charging and energy-saving chain: The full process hot charging from the preheating process to the rotary kiln and then to the electric furnace is realized. Preheating the pellets and charging them into the rotary kiln saves energy within the kiln; the co-loading of hot-reduced pellets and hot-rust-scaled pellets into the electric furnace significantly reduces the furnace's power consumption, forming a complete energy-saving chain. In other words, this invention, through the above process, constructs a closed-loop system that deeply couples the material and energy flows of multi-source solid waste, achieving the green, low-carbon, and highly efficient resource utilization goal of "treating waste with waste and turning waste into treasure."

[0048] In this invention, during the drying and preheating process, under ideal conditions, the lower the oxygen content in the oxygen-deficient hot air, the better. That is, under the most ideal conditions, the oxygen content index in the oxygen-deficient hot air is 0. However, in actual conditions, since the oxygen-deficient hot air needs to have a relatively high temperature, it is mainly generated by the combustion of fuel (such as furnace top gas). The complete combustion of fuel requires sufficient oxygen. Therefore, the flue gas produced by a general combustion furnace is basically impossible to achieve oxygen-free conditions. Furthermore, further research revealed that in this invention, when the oxygen content index in the oxygen-deficient hot air is between 0.3 and 0.5, it is possible to ensure a high retention rate of the metallization rate (for iron-containing materials, this refers to the ratio of metallic iron to total iron mass content in the material) and carbon content of the preheated and dried pellets, while achieving complete fuel combustion. If the oxygen content index increases, it will cause significant fluctuations in the retention rate of the metallization rate and carbon content (retention rate decreases). While decreasing the oxygen content index will improve the retention rate of the metallization rate and carbon content, the improvement is limited. However, it may lead to incomplete fuel combustion during the previous combustion process, resulting in fuel waste and increasing the difficulty and cost of operating the combustion equipment.

[0049] This invention also provides a system for the co-processing of multi-source solid waste. Through the combined action of a metal solid waste collection unit, an organic solid waste collection unit, a molding unit, a molding material distribution device, an organic solid waste distribution device, a drying and preheating device, a rotary kiln, and an electric furnace, the system achieves the synchronous and co-processing of metal solid waste and organic solid waste. This provides the equipment foundation for realizing the green, low-carbon, and efficient resource utilization goal of "treating waste with waste and turning waste into treasure." Furthermore, all components or devices constituting the system of this invention are mature equipment in the industry (which can be directly purchased from the market or used independently in existing steel plant production lines). The system of this invention mainly optimizes and improves the positional and connection relationships of these existing components to match and achieve the purpose of co-processing metal solid waste and organic solid waste.

[0050] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0051] 1. The method and system of this invention can significantly save energy, reduce consumption, and improve energy efficiency: By efficiently preheating and hot-loading dust ash pellets and rust scale lumps, a large amount of energy is saved for the two subsequent high-temperature equipment (rotary kiln and electric furnace). Simultaneously, the chemical energy and physical heat generated from the synchronous pyrolysis of solid waste that would otherwise require paid treatment are directly used for material preheating in the system, replacing some of the purchased fuel and achieving energy self-sufficiency and recycling. Furthermore, the low-temperature waste gas after drying and preheating is introduced into the rotary kiln as combustion air, further recovering low-grade waste heat and improving the overall thermal efficiency of the system.

[0052] 2. The method and system of this invention have high efficiency in resource recovery and environmental protection: by converting all dust (containing metal dust), rust scale, etc., into high-value iron-nickel-chromium-manganese alloy raw materials and lead-zinc dust products, the maximum recovery of valuable metals is achieved, turning waste into treasure and making full use of valuable metals. In addition, the organic solid waste is pyrolyzed under a controlled reducing atmosphere, which avoids the conditions for the formation of highly toxic substances such as dioxins from the source. The residual carbon from the pyrolysis is also recovered as a reducing agent, realizing the harmlessness and resource utilization of the entire process.

[0053] 3. The method and system of this invention achieve process synergy and process intensification: Utilizing the reducing gases (H2, CO) generated from the pyrolysis of organic solid waste as a protective atmosphere for the preheating process effectively prevents the oxidation of internal carbon and metals in the pellets, ensuring the reduction efficiency of the subsequent rotary kiln and overcoming the industry problem of material oxidation caused by traditional preheating technologies. Furthermore, combining electric furnace gas and rotary kiln tail gas for oxygen-deficient combustion to obtain oxygen-deficient hot air for drying preheating achieves optimized allocation of waste gas resources within the plant, further reducing dependence on external energy and operating costs.

[0054] 4. The method and system of the present invention both realize the internal circulation closed loop of airflow: organic solid waste provides energy and generates protective gas → metal solid waste is preheated and protected → all solid waste is co-smelted into products → process waste gas is recycled; this closed loop design greatly improves the sustainability and economic competitiveness of the entire process. Attached Figure Description

[0055] Figure 1 This is a simplified process flow diagram of the method described in this invention.

[0056] Figure 2 This is a schematic diagram of the airflow direction during the drying and preheating process described in this invention.

[0057] Figure 3 This is a schematic diagram of the overall structure of the system described in this invention.

[0058] Reference numerals in the attached figures: 1: Metal solid waste collection unit; 101: Dust collection silo; 102: Rust scale storage silo; 2: Organic solid waste collection unit; 201: Organic scrap silo; 3: Molding unit; 301: Mixing device; 302: Molding device; 303: Auxiliary material adding device; 4: Molding material spreading device; 5: Organic solid waste spreading device; 6: Drying and preheating device; 601: Drying section; 602: Preheating section; 603: Preheating exhaust gas conveying pipeline; 604: Drying exhaust gas conveying pipeline; 605: Fan; 7: Rotary kiln; 701: Reduction flue gas conveying pipeline; 702: Dust collector; 8: Electric furnace; 801: Gas conveying pipeline; 9: Oxygen-deficient combustion device; 901: Oxygen-deficient hot air conveying pipeline; 902: Oxygen content detector. Detailed Implementation

[0059] The technical solution of the present invention will be illustrated below with examples. The scope of protection sought by the present invention includes, but is not limited to, the following embodiments.

[0060] like Figure 1-2 As shown, a method for the co-processing of multi-source solid waste includes the following steps:

[0061] S1: Multi-source solid waste is classified into metallic solid waste and organic solid waste. The metallic solid waste is mixed with auxiliary materials and then molded to obtain molded material. The organic solid waste is crushed to obtain organic fragments.

[0062] S2: The molded material and organic scraps are used as the bottom layer and top layer respectively to form a mixed material.

[0063] S3: The mixture is fed into a drying and preheating device for sequential drying and preheating. The preheating heat source is oxygen-deficient hot air, and the drying heat source is the preheated exhaust gas. After the drying and preheating processes are completed, a hot mixture and dry exhaust gas are obtained.

[0064] S4: The hot mixture is screened to obtain clinker and residual carbon. The clinker is fed into a rotary kiln for reduction treatment to obtain reducing feedstock and reduction flue gas. The reduction flue gas is treated with dust removal to obtain lead-zinc dust and dust removal flue gas.

[0065] S5: The raw materials are fed into the electric furnace and mixed with flux and reducing agent for reduction smelting to obtain metal mother liquor, electric furnace slag and electric furnace gas.

[0066] In a preferred embodiment of the present invention, the method further includes step S6: using the electric furnace gas obtained in step S5 as fuel and the dust removal flue gas obtained in step S4 as combustion air to perform oxygen-deficient combustion to obtain oxygen-deficient flue gas, and returning the oxygen-deficient flue gas to step S3 for use as oxygen-deficient hot air.

[0067] In a preferred embodiment of the present invention, except that in step S1, the multi-source solid waste includes, but is not limited to, metal-containing dust, rust, and packaging tape.

[0068] In a preferred embodiment of the present invention, except that in step S1, the excipients include one or more of carbonaceous reducing agents, binders, and water.

[0069] In a preferred embodiment of the present invention, the carbonaceous reducing agent is one or more of pulverized coal, coke powder, and carbon powder. The binder is one or more of cement, bentonite, starch, humic acid, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylamide, and waste molasses.

[0070] In a preferred embodiment of the present invention, step S1, which involves mixing metal solid waste with auxiliary materials for molding, includes: mixing metal-containing dust with a carbonaceous reducing agent, a binder, and water for pelletizing to obtain green pellets. Alternatively, mixing rust scale with a binder and water for briquetting to obtain green briquettes.

[0071] In a preferred embodiment of the invention, the particle size of the molding material is 8-12 mm, and the particle size of the organic scrap is 20-50 mm.

[0072] In a preferred embodiment of the present invention, the carbonaceous reducing agent has a mass content of 10-30%, the binder has a mass content of 0.5-10%, and the water has a mass content of 2-10% in the green pellets.

[0073] In a preferred embodiment of the present invention, the binder has a mass content of 2-10% and the water has a mass content of 2-10% in the raw agglomerate.

[0074] In a preferred embodiment of the present invention, the thickness of the molding material in step S2 is 100-500 mm.

[0075] In a preferred embodiment of the present invention, the thickness of the molding material in step S2 is 150~450mm.

[0076] In a preferred embodiment of the present invention, the thickness of the organic crushed material in step S2 is 10-50 mm.

[0077] In a preferred embodiment of the present invention, the thickness of the organic crushed material in step S2 is 15-45 mm.

[0078] In a preferred embodiment of the present invention, the temperature of the oxygen-deficient hot air is 500~1000°C in step S3.

[0079] In a preferred embodiment of the present invention, the temperature of the oxygen-deficient hot air is 600~900°C in step S3.

[0080] In a preferred embodiment of the present invention, only in step S3, the oxygen content index in the oxygen-deficient hot air is 0.1 to 0.7.

[0081] In a preferred embodiment of the present invention, only in step S3, the oxygen content index in the oxygen-deficient hot air is 0.3 to 0.5.

[0082] In a preferred embodiment of the present invention, the temperature of the hot mixture is 500~800°C in step S3.

[0083] In a preferred embodiment of the present invention, the temperature of the hot mixture is 550~700°C in step S3.

[0084] In a preferred embodiment of the present invention, the temperature of the preheated exhaust gas is 150~300°C in step S3.

[0085] In a preferred embodiment of the present invention, the temperature of the preheated exhaust gas is 180~280°C in step S3.

[0086] In a preferred embodiment of the present invention, the reduction treatment temperature in step S4 is 1000~1200°C, and the reduction treatment duration is 0.5~5 hours.

[0087] In a preferred embodiment of the present invention, the reduction treatment temperature in step S4 is 1050~1150°C, and the reduction treatment duration is 1~3 hours.

[0088] In a preferred embodiment of the present invention, the reduction smelting temperature in step S5 is 1400~1600℃, and the reduction smelting time is 0.5~8h.

[0089] In a preferred embodiment of the present invention, the reduction smelting temperature in step S5 is 1450~1550°C, and the reduction smelting time is 3~6 hours.

[0090] In a preferred embodiment of the present invention, only in step S5, the flux is one or more of limestone, dolomite, marble, and silica. The reducing agent is a carbonaceous reducing agent.

[0091] In a preferred embodiment of the present invention, the mass ratio of raw materials, flux, and reducing agent is 70~90:5~20:5~10.

[0092] Example 1

[0093] like Figure 3 As shown, a system for the co-processing of multi-source solid waste includes a metal solid waste collection unit 1, an organic solid waste collection unit 2, a molding unit 3, a molding material distribution device 4, an organic solid waste distribution device 5, a drying and preheating device 6, a rotary kiln 7, and an electric furnace 8. The metal solid waste collection unit 1, molding unit 3, molding material distribution device 4, drying and preheating device 6, rotary kiln 7, and electric furnace 8 are connected in series. The organic solid waste distribution device 5 is arranged parallel to the molding material distribution device 4 above the feed end of the drying and preheating device 6, and is located downstream of the molding material distribution device 4 according to the material flow direction. The feed end of the organic solid waste distribution device 5 is connected to the discharge end of the organic solid waste collection unit 2.

[0094] Example 2

[0095] The system repeats Example 1, except that it also includes an oxygen-deficient combustion device 9. The drying and preheating device 6 includes a drying section 601 and a preheating section 602 connected in series. The hot air outlet of the oxygen-deficient combustion device 9 is connected to the top hot air inlet of the preheating section 602 via an oxygen-deficient hot air conveying pipe 901. The bottom hot air outlet of the preheating section 602 is connected to the bottom hot air inlet of the drying section 601 via a preheating exhaust gas conveying pipe 603. The top hot air outlet of the drying section 601 is connected to the air inlet of the rotary kiln 7 via a drying exhaust gas conveying pipe 604.

[0096] Example 3

[0097] The embodiment 2 is repeated, except that a fan 605 is also installed on the preheated waste gas conveying pipe 603.

[0098] Example 4

[0099] Example 3 is repeated, except that the metal solid waste collection unit 1 includes several dust collection bins 101 and several rust storage bins 102.

[0100] Example 5

[0101] Example 4 is repeated, except that the organic solid waste collection unit 2 includes several organic waste bins 201.

[0102] Example 6

[0103] The embodiment 5 is repeated, except that the molding unit 3 includes a mixing device 301, a molding device 302, and an auxiliary material adding device 303. The inlet of the mixing device 301 is connected to both the outlet of the metal solid waste collection unit 1 and the outlet of the auxiliary material adding device 303. The outlet of the mixing device 301 is connected to the inlet of the molding device 302. The outlet of the molding device 302 is connected to the inlet of the molding material spreading device 4.

[0104] Example 7

[0105] Example 6 is repeated, except that the forming device 302 is a disc pelletizer and a briquetting machine. The auxiliary material adding device 303 has an independently provided reducing agent storage chamber, a binder storage chamber, and a water chamber.

[0106] Example 8

[0107] Example 7 is repeated, except that the flue gas outlet of the rotary kiln 7 is also connected to the combustion gas inlet of the oxygen-deficient combustion device 9 via a reduction flue gas conveying pipe 701. The gas outlet at the top of the electric furnace 8 is also connected to the gas inlet of the oxygen-deficient combustion device 9 via a gas conveying pipe 801.

[0108] Example 9

[0109] The embodiment 8 is repeated, except that a dust collector 702 is also installed on the flue gas conveying pipe 701.

[0110] Example 10

[0111] Example 9 is repeated, except that an oxygen content detector 902 is also installed in the oxygen-deficient hot air conveying pipe 901.

[0112] Example 11

[0113] Example 10 is repeated, except that both the molding material feeding device 4 and the organic solid waste feeding device 5 are roller feeders.

[0114] Application Example 1

[0115] The system described in Example 11 is used to treat multi-source solid waste in a stainless steel plant:

[0116] Dust containing iron, nickel, chromium, and manganese generated from various processes in the stainless steel plant is collected and mixed to obtain metal-containing dust. Packaging tape from the stainless steel plant is collected and cut into strips of 20-500mm to obtain organic debris.

[0117] Metal dust, carbon powder, bentonite, and water were mixed in a mass ratio of 70:20:2:8 and pelletized using a disc pelletizer to obtain green pellets with a particle size range of 8-12 mm (metallization rate of approximately 47.0%).

[0118] First, a green pellet layer of about 400 mm is laid on the grate of the drying and preheating furnace. Then, an organic crushed material layer of about 30 mm is laid on the green pellet layer. The green pellet layer and the organic crushed material layer together constitute the mixture. The mixture is then fed into the drying section and the preheating section of the drying and preheating furnace for drying and preheating treatment. Specifically, hot flue gas with an oxygen content index of about 0.4 and a temperature of about 900°C, generated by the oxygen-deficient combustion of fuel in the oxygen-deficient combustion device, is fed into the preheating section of the drying and preheating furnace to preheat the mixture from top to bottom. At the same time, the preheated exhaust gas is fed into the drying section to dry the mixture from bottom to top. The dried exhaust gas is then fed into the subsequent rotary kiln for combustion and heating. The dried and preheated mixture is then subjected to hot screening to obtain hot clinker (with a metallization rate of about 45.3% and a carbon content of about 18.6%) and pyrolysis residual carbon (which is crushed and recycled as a carbonaceous reducing agent to be used for pelletizing with metal solid waste).

[0119] Hot clinker was fed into a rotary kiln and reduced-roasted at 1100℃ for 2 hours, while the reduction flue gas was treated to obtain dust-removed flue gas and zinc-containing dust. After reduction roasting, a hot-reduced raw material was obtained (its metallization rate was detected to be approximately 95.5%). While still hot, the hot-reduced raw material was added to an electric furnace, with flux (silica) and reducing agent (coke particles) added in a mass ratio of hot-reduced raw material: flux: reducing agent = 85:10:5. The electric furnace was then started and heated to 1500℃ for smelting for 5 hours. After smelting, molten steel, electric furnace slag, and furnace top gas were obtained. The dust-removed flue gas and electric furnace gas were recycled and used as combustion air and fuel for an oxygen-deficient combustion device, respectively. The energy consumption of the rotary kiln was approximately 6,154,500 KJ / T, and the energy consumption of the electric furnace was approximately 948.4 KW·h / T-steel.

[0120] Application Example 2

[0121] The system described in Example 11 is used to treat multi-source solid waste in a stainless steel plant:

[0122] Iron oxide scale generated during the hot rolling and cold rolling processes of stainless steel plants is collected and mixed to obtain rust scale. Packaging tape from stainless steel plants is collected and cut into strips of 20-500mm to obtain organic scraps.

[0123] Iron rust, polyacrylamide, and water were mixed in a mass ratio of 90:4:6 and then briquetting was performed using a high-pressure briquetting machine to obtain raw briquettes with a particle size range of 8-12 mm (metallization rate of approximately 88.1%).

[0124] First, a layer of raw briquettes about 400 mm thick is laid on the grate of the drying and preheating furnace. Then, a layer of organic debris about 30 mm thick is laid on top of the raw briquettes. The raw briquettes and organic debris together form a mixture. The mixture is then fed into the drying section and the preheating section of the drying and preheating furnace for drying and preheating treatment. Specifically, hot flue gas with an oxygen content index of about 0.4 and a temperature of about 900°C, generated by the oxygen-deficient combustion of fuel in an oxygen-deficient combustion device, is fed into the preheating section of the drying and preheating furnace to preheat the mixture from top to bottom. At the same time, the preheated exhaust gas is fed into the drying section to dry the mixture from bottom to top. The dried exhaust gas is then fed into the subsequent rotary kiln for combustion and heating. The dried and preheated mixture is then subjected to hot screening to obtain hot clinker (with a metallization rate of about 86.1% and a carbon content of about 0.6%) and pyrolysis residual carbon (which is crushed and recycled as a carbonaceous reducing agent to be used for pelletizing with metal solid waste).

[0125] Hot clinker is added to the electric furnace while still hot, and flux (limestone) and reducing agent (coke granules) are added in a mass ratio of hot clinker: flux: reducing agent = 85:5:10. The electric furnace is then started and heated to 1500℃ for smelting for 5 hours. After smelting, molten steel, electric furnace slag, and furnace top gas are obtained. The dust removal flue gas and electric furnace gas are recycled and used as combustion air and fuel for the oxygen-deficient combustion device, respectively. The energy consumption of the electric furnace is approximately 787.88 kW·h / T-steel.

[0126] Application Example 3

[0127] The hot reducing material obtained from the rotary kiln reduction roasting in Application Example 1 was mixed with the hot feed obtained from the drying and preheating in Application Example 2 at a mass ratio of 65:35 to form the hot furnace charge. Then, flux (silica) and reducing agent (carbon powder / coke particles) were added at a mass ratio of hot furnace charge: flux: reducing agent = 88:5:7. The electric furnace was then started and heated to 1500℃ for smelting for 5 hours. After smelting, molten steel, electric furnace slag, and furnace top gas were obtained. The dust removal flue gas and electric furnace gas were recycled and used as combustion air and fuel for the oxygen-deficient combustion device, respectively. The energy consumption of the electric furnace was approximately 875.2 kW·h / T-steel.

[0128] Application Example 4

[0129] The application of Example 1 is repeated, except that the oxygen content index of the fuel produced by the oxygen-deficient combustion in the oxygen-deficient combustion device is about 0.5 and the temperature is about 900°C. The hot flue gas is sent to the preheating section of the drying and preheating furnace to preheat the mixture from top to bottom. At the same time, the preheated waste gas is sent to the drying section to dry the mixture from bottom to top. The dried waste gas is sent to the subsequent rotary kiln for combustion and heating. The dried and preheated mixture is subjected to hot screening to obtain hot clinker (the metallization rate was detected to be about 42.4% and the carbon content was about 18.1%) and pyrolysis residual carbon (which is crushed and recycled as a carbonaceous reducing agent to be used for pelletizing with metal solid waste).

[0130] Hot clinker was fed into a rotary kiln and reduced-roasted at 1100℃ for 2 hours, while the reduction flue gas was treated to obtain dust-removed flue gas and zinc-containing dust. After reduction roasting, a hot-reduced raw material was obtained (its metallization rate was detected to be approximately 94.6%). This hot-reduced raw material was then added to an electric furnace, with flux (silica) and reducing agent (coke particles) added in a mass ratio of hot-reduced raw material: flux: reducing agent = 85:10:5. The electric furnace was then started and heated to 1500℃ for smelting for 5 hours. After smelting, molten steel, electric furnace slag, and furnace top gas were obtained. The dust-removed flue gas and electric furnace gas were recycled and used as combustion air and fuel for an oxygen-deficient combustion device, respectively. The energy consumption of the rotary kiln was approximately 6213202 KJ / T, and the energy consumption of the electric furnace was approximately 967.32 KW·h / T-steel.

[0131] Application Example 5

[0132] The application of Example 1 is repeated, except that the oxygen content index of the fuel produced by the oxygen-deficient combustion in the oxygen-deficient combustion device is about 0.7 and the temperature is about 900°C. The hot flue gas is sent to the preheating section of the drying and preheating furnace to preheat the mixture from top to bottom. At the same time, the preheated waste gas is sent to the drying section to dry the mixture from bottom to top. The dried waste gas is sent to the subsequent rotary kiln for combustion and heating. The dried and preheated mixture is subjected to hot screening to obtain hot clinker (the metallization rate was detected to be about 38.3% and the carbon content was about 15.7%) and pyrolysis residual carbon (which is crushed and recycled as a carbonaceous reducing agent to be used for pelletizing with metal solid waste).

[0133] Hot clinker was fed into a rotary kiln and reduced-roasted at 1100℃ for 2 hours, while the reduction flue gas was treated to obtain dust-removed flue gas and zinc-containing dust. After reduction roasting, a hot-reduced raw material was obtained (its metallization rate was detected to be approximately 62.3%). While still hot, the hot-reduced raw material was added to an electric furnace, and flux (silica) and reducing agent (coke particles) were added at a mass ratio of hot-reduced raw material: flux: reducing agent = 78:9.2:12.8. The electric furnace was then started and heated to 1500℃ for smelting for 5 hours. After smelting, molten steel, electric furnace slag, and furnace top gas were obtained. The dust-removed flue gas and electric furnace gas were recycled and used as combustion air and fuel for an oxygen-deficient combustion device, respectively. The energy consumption of the rotary kiln was approximately 6271811 KJ / T, and the energy consumption of the electric furnace was approximately 1075.64 KW·h / T-steel.

[0134] Application Example 6

[0135] The application of Example 1 is repeated, except that the oxygen content index of the fuel produced by the oxygen-deficient combustion in the oxygen-deficient combustion device is about 0.3 and the temperature is about 900°C. The hot flue gas is sent to the preheating section of the drying and preheating furnace to preheat the mixture from top to bottom. At the same time, the preheated waste gas is sent to the drying section to dry the mixture from bottom to top. The dried waste gas is sent to the subsequent rotary kiln for combustion and heating. The dried and preheated mixture is subjected to hot screening to obtain hot clinker (the metallization rate was detected to be about 46.1% and the carbon content was about 19.2%) and pyrolysis residual carbon (which is crushed and recycled as a carbonaceous reducing agent to be used for pelletizing with metal solid waste).

[0136] Hot clinker was fed into a rotary kiln and reduced-roasted at 1100℃ for 2 hours, while the reduction flue gas was treated to obtain dust-removed flue gas and zinc-containing dust. After reduction roasting, a hot-reduced raw material was obtained (its metallization rate was detected to be approximately 95.9%). This hot-reduced raw material was then added to an electric furnace, with flux (silica) and reducing agent (coke particles) added in a mass ratio of hot-reduced raw material: flux: reducing agent = 85:10:5. The electric furnace was then started and heated to 1500℃ for smelting for 5 hours. After smelting, molten steel, electric furnace slag, and furnace top gas were obtained. The dust-removed flue gas and electric furnace gas were recycled and used as combustion air and fuel for an oxygen-deficient combustion device, respectively. The energy consumption of the rotary kiln was approximately 6125209 KJ / T, and the energy consumption of the electric furnace was approximately 939.14 KW·h / T-steel.

[0137] Application Example 7

[0138] The application of Example 1 is repeated, except that the oxygen content index of the fuel produced by the oxygen-deficient combustion in the oxygen-deficient combustion device is about 0.1 and the temperature is about 900°C. The hot flue gas is sent to the preheating section of the drying and preheating furnace to preheat the mixture from top to bottom. At the same time, the preheated waste gas is sent to the drying section to dry the mixture from bottom to top. The dried waste gas is sent to the subsequent rotary kiln for combustion and heating. The dried and preheated mixture is subjected to hot screening to obtain hot clinker (the metallization rate was detected to be about 46.6% and the carbon content was about 19.5%) and pyrolysis residual carbon (which is crushed and recycled as a carbonaceous reducing agent to be used for pelletizing with metal solid waste).

[0139] Hot clinker was fed into a rotary kiln and reduced-roasted at 1100℃ for 2 hours, while the reduction flue gas was treated to obtain dust-removed flue gas and zinc-containing dust. After reduction roasting, a hot-reduced raw material was obtained (its metallization rate was detected to be approximately 96.2%). While still hot, the hot-reduced raw material was added to an electric furnace, with flux (silica) and reducing agent (coke particles) added in a mass ratio of hot-reduced raw material: flux: reducing agent = 85:10:5. The electric furnace was then started and heated to 1500℃ for smelting for 5 hours. After smelting, molten steel, electric furnace slag, and furnace top gas were obtained. The dust-removed flue gas and electric furnace gas were recycled and used as combustion air and fuel for an oxygen-deficient combustion device, respectively. The energy consumption of the rotary kiln was approximately 6,095,903 KJ / T, and the energy consumption of the electric furnace was approximately 930.11 KW·h / T-steel.

[0140] Comparative Example 1

[0141] The dust containing iron, nickel, chromium and manganese generated in various processes of the stainless steel plant is collected and mixed to obtain metal dust.

[0142] Metal dust, carbon powder, bentonite, and water were mixed in a mass ratio of 70:20:2:8 and pelletized using a disc pelletizer to obtain green pellets with a particle size range of 8-12 mm.

[0143] A green pellet layer of approximately 400 mm is laid on the grate of the drying and preheating furnace. The green pellet layer is then sequentially fed into the drying section and preheating section of the drying and preheating furnace for drying and preheating treatment. Specifically, hot flue gas with an oxygen content index of approximately 0.4 (based on application example 1) and a temperature of approximately 900°C, generated by the oxygen-deficient combustion of fuel in an oxygen-deficient combustion device, is fed into the preheating section of the drying and preheating furnace to preheat the green pellet layer from top to bottom. Simultaneously, the preheated exhaust gas is fed into the drying section to dry the unpreheated green pellet layer from bottom to top. The dried exhaust gas is then fed into the subsequent rotary kiln for combustion and heating. After drying and preheating, hot clinker is obtained (its metallization rate was detected to be approximately 21.4%, and its carbon content was approximately 10.3%).

[0144] Hot clinker was fed into a rotary kiln and reduced-roasted at 1100℃ for 2 hours, while the reduction flue gas was treated to obtain dust-removed flue gas and zinc-containing dust. After reduction roasting, a hot-reduced raw material was obtained (its metallization rate was detected to be approximately 53.1%). This hot-reduced raw material was then added to an electric furnace, with flux (silica) and reducing agent (coke particles) added in a mass ratio of hot-reduced raw material: flux: reducing agent = 75:9:16. The electric furnace was then started and heated to 1500℃ for smelting for 5 hours. After smelting, molten steel, electric furnace slag, and furnace top gas were obtained. The dust-removed flue gas and electric furnace gas were recycled and used as combustion air and fuel for an oxygen-deficient combustion device, respectively. The energy consumption of the rotary kiln was approximately 6,447,619 KJ / T, and the energy consumption of the electric furnace was approximately 1218.1 KW·h / T-steel.

[0145] Comparative Example 2

[0146] The dust containing iron, nickel, chromium and manganese generated in various processes of the stainless steel plant is collected and mixed to obtain metal dust.

[0147] Metal dust, carbon powder, bentonite, and water were mixed in a mass ratio of 70:20:2:8 and pelletized using a disc pelletizer to obtain green pellets with a particle size range of 8-12 mm.

[0148] A green pellet layer of approximately 400 mm is laid on the grate of the drying and preheating furnace. The green pellet layer is then sequentially fed into the drying section and preheating section of the drying and preheating furnace for drying and preheating treatment. Specifically, hot flue gas with an oxygen content index of approximately 1.2 (based on application example 1) and a temperature of approximately 900°C, generated by oxygen-enriched combustion of fuel in the combustion device, is fed into the preheating section of the drying and preheating furnace to preheat the green pellet layer from top to bottom. Simultaneously, the preheated exhaust gas is fed into the drying section to dry the unpreheated green pellet layer from bottom to top. The dried exhaust gas is then fed into the subsequent rotary kiln for combustion and heating. After drying and preheating, hot clinker is obtained (its metallization rate was detected to be approximately 1.2%, and its carbon content was approximately 5.5%).

[0149] Hot clinker was fed into a rotary kiln and reduced-roasted at 1100℃ for 2 hours, while the reduction flue gas was treated to obtain dust-removed flue gas and zinc-containing dust. After reduction roasting, a hot-reduced raw material was obtained (its metallization rate was detected to be approximately 10.3%). This hot-reduced raw material was then added to an electric furnace, and flux (silica) and reducing agent (coke particles) were added at a mass ratio of hot-reduced raw material: flux: reducing agent = 66.5:8.5:25. The electric furnace was then started and heated to 1500℃ for smelting for 5 hours. After smelting, molten steel, electric furnace slag, and furnace top gas were obtained. The dust-removed flue gas and electric furnace gas were recycled and used as combustion air and fuel for an oxygen-deficient combustion device, respectively. The energy consumption of the rotary kiln was approximately 7033824 KJ / T, and the energy consumption of the electric furnace was approximately 1585.2 KW·h / T-steel.

[0150] Comparative Example 3

[0151] Iron oxide scale generated during the hot rolling and cold rolling processes of stainless steel plants is collected and mixed to obtain rust scale.

[0152] Iron rust, polyacrylamide, and water were mixed in a mass ratio of 90:4:6 and then compressed into briquettes using a high-pressure briquetting machine to obtain raw briquettes with a particle size range of 8-12 mm.

[0153] A layer of raw clinker, approximately 400 mm thick, is laid on the grate of the drying and preheating furnace. This layer is then sequentially fed into the drying and preheating sections of the furnace for drying and preheating treatment. Specifically, hot flue gas with an oxygen content index of approximately 0.4 (based on application example 2) and a temperature of approximately 900°C, generated from the oxygen-deficient combustion of fuel in an oxygen-deficient combustion device, is fed into the preheating section of the furnace to preheat the mixture from top to bottom. Simultaneously, the preheated exhaust gas is fed into the drying section to dry the mixture from bottom to top. The dried exhaust gas is then fed into a subsequent rotary kiln for combustion and heating. The dried and preheated mixture is then subjected to hot screening to obtain hot clinker (with a metallization rate of approximately 42.3% and a carbon content of approximately 0.01%).

[0154] Hot clinker is added to the electric furnace while still hot, and flux (limestone) and reducing agent (coke granules) are added in a mass ratio of hot clinker: flux: reducing agent = 75:4.5:20.5. The electric furnace is then started and heated to 1500℃ for smelting for 5 hours. After smelting, molten steel, electric furnace slag, and furnace top gas are obtained. The dust removal flue gas and electric furnace gas are recycled and used as combustion air and fuel for the oxygen-deficient combustion device, respectively. The energy consumption of the electric furnace is approximately 892.9 kW·h / T-steel.

Claims

1. A method for the co-processing of multi-source solid waste, characterized in that: The method includes the following steps: S1: Classify multi-source solid waste to obtain metallic solid waste and organic solid waste; mix metallic solid waste with auxiliary materials and perform molding treatment to obtain molded material; crush organic solid waste to obtain organic crushed material; S2: The molded material and organic scraps are used as the bottom layer and top layer respectively to obtain a mixed material; S3: The mixture is fed into the drying and preheating equipment for drying and preheating treatment in sequence; the preheating heat source is oxygen-deficient hot air, and the drying heat source is the preheated exhaust gas; after the drying and preheating treatment is completed, a hot mixture and dry exhaust gas are obtained. S4: The hot mixture is screened to obtain clinker and residual carbon; the clinker is fed into a rotary kiln for reduction treatment to obtain reducing material and reduction flue gas; the reduction flue gas is treated with dust removal to obtain lead-zinc dust and dust removal flue gas; S5: The raw materials are fed into the electric furnace and mixed with flux and reducing agent for reduction smelting to obtain metal mother liquor, electric furnace slag and electric furnace gas. Preferably, the method further includes step S6: using the electric furnace gas obtained in step S5 as fuel and the dust removal flue gas obtained in step S4 as combustion air to perform oxygen-deficient combustion to obtain oxygen-deficient flue gas, and returning the oxygen-deficient flue gas to step S3 for use as oxygen-deficient hot air.

2. The method according to claim 1, characterized in that: In step S1, the multi-source solid waste includes, but is not limited to, metal-containing dust, rust, and packaging tape; In step S1, the excipients include one or more of carbonaceous reducing agents, binders, and water; Preferably, the carbonaceous reducing agent is one or more of pulverized coal, coke powder, and carbon powder; the binder is one or more of cement, bentonite, starch, humic acid, carboxymethyl cellulose, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylamide, and waste molasses.

3. The method according to claim 2, characterized in that: In step S1, the metal solid waste and auxiliary materials are mixed and shaped, which includes: mixing metal-containing dust with carbonaceous reducing agent, binder and water to form pellets; or mixing rust scale with binder and water to press into briquettes; preferably, the particle size of the shaped material is 8-12 mm; the particle size of the organic fragments is 20-50 mm. Preferably, in the green pellets, the mass content of the carbonaceous reducing agent is 10-30%, the mass content of the binder is 0.5-10%, and the mass content of the water is 2-10%. Preferably, in the raw agglomerate, the mass content of the binder is 2-10%, and the mass content of the water is 2-10%.

4. The method according to any one of claims 1-3, characterized in that: In step S2, the thickness of the molding material is 100~500mm, preferably 150~450mm; and / or In step S2, the thickness of the organic crushed material is 10~50mm, preferably 15~45mm.

5. The method according to any one of claims 1-4, characterized in that: In step S3, the temperature of the oxygen-deficient hot air is 500~1000℃, preferably 600~900℃; and / or In step S3, the oxygen content index in the oxygen-deficient hot air is 0.1~0.7, preferably 0.3~0.5; and / or In step S3, the temperature of the hot mixture is 500~800℃, preferably 550~700℃; Preferably, in step S3, the temperature of the preheated exhaust gas is 150~300℃, more preferably 180~280℃.

6. The method according to any one of claims 1-5, characterized in that: In step S4, the reduction treatment temperature is 1000~1200℃, preferably 1050~1150℃; the reduction treatment duration is 0.5~5h, preferably 1~3h; and / or In step S5, the reduction smelting temperature is 1400~1600℃, preferably 1450~1550℃; the reduction smelting time is 0.5~8h, preferably 3~6h. Preferably, in step S5, the flux is one or more of limestone, dolomite, marble, and silica; the reducing agent is a carbonaceous reducing agent; preferably, the mass ratio of the reducing agent, flux, and reducing agent is 70~90:5~20:5~10.

7. A system for the co-processing of multi-source solid waste or a system for the co-processing of multi-source solid waste using the method described in any one of claims 1-6, characterized in that: The system includes a metal solid waste collection unit (1), an organic solid waste collection unit (2), a molding unit (3), a molding material distribution device (4), an organic solid waste distribution device (5), a drying and preheating device (6), a rotary kiln (7), and an electric furnace (8); the metal solid waste collection unit (1), molding unit (3), molding material distribution device (4), drying and preheating device (6), rotary kiln (7), and electric furnace (8) are connected in series; the organic solid waste distribution device (5) and the molding material distribution device (4) are arranged side by side above the feed end of the drying and preheating device (6), and the organic solid waste distribution device (5) is located downstream of the molding material distribution device (4) according to the direction of the material; the feed end of the organic solid waste distribution device (5) is connected to the discharge end of the organic solid waste collection unit (2); Preferably, the system also includes an oxygen-deficient combustion device (9); the drying and preheating device (6) includes a drying section (601) and a preheating section (602) connected in series; the hot air outlet of the oxygen-deficient combustion device (9) is connected to the top hot air inlet of the preheating section (602) through an oxygen-deficient hot air conveying pipe (901), the bottom hot air outlet of the preheating section (602) is connected to the bottom hot air inlet of the drying section (601) through a preheating waste gas conveying pipe (603), and the top hot air outlet of the drying section (601) is connected to the air inlet of the rotary kiln (7) through a drying waste gas conveying pipe (604); preferably, a fan (605) is also provided on the preheating waste gas conveying pipe (603).

8. The system according to claim 7, characterized in that: The metal solid waste collection unit (1) includes several dust collection bins (101) and several rust scale storage bins (102), or is composed of several dust collection bins (101) and several rust scale storage bins (102); and / or The organic solid waste collection unit (2) includes or is composed of several organic waste bins (201).

9. The system according to claim 7 or 8, characterized in that: The molding unit (3) includes a mixing device (301), a molding device (302), and an auxiliary material adding device (303); the inlet of the mixing device (301) is connected to the outlet of the metal solid waste collection unit (1) and the outlet of the auxiliary material adding device (303); the outlet of the mixing device (301) is connected to the inlet of the molding device (302); the outlet of the molding device (302) is connected to the inlet of the molding material spreading device (4); Preferably, the forming device (302) is a pelletizing machine and / or a briquetting machine; the auxiliary material adding device (303) is internally provided with a reducing agent storage chamber, a binder storage chamber and a water chamber.

10. The system according to any one of claims 7-9, characterized in that: The flue gas outlet of the rotary kiln (7) is also connected to the combustion gas inlet of the oxygen-deficient combustion device (9) through a reduction flue gas conveying pipe (701); the gas outlet at the top of the electric furnace (8) is also connected to the gas inlet of the oxygen-deficient combustion device (9) through a gas conveying pipe (801); preferably, a dust collector (702) is also provided on the reduction flue gas conveying pipe (701); preferably, an oxygen content detector (902) is also provided in the oxygen-deficient hot air conveying pipe (901). Preferably, the molding material feeding device (4) and the organic solid waste feeding device (5) are independently shuttle feeders and / or roller feeders.

Images