Method and device for resource utilization of desulfurized fly ash and co-processing of high-pyrite ore powder

Abstract

The invention relates to the field of resource utilization of desulfurized fly ash, in particular to a method and a device for resource utilization of desulfurized fly ash and co-processing of high-pyrite powder. Reacting with SO2 in pre-desulfurized roasting flue gas of high-pyrite powder or sintering machine flue gas of the high-pyrite powder to generate gypsum; 2, fully aerating the desulfurized fly ash slurry after the dissolution reaction, wherein the main component calcium sulfite in the slurry is completely oxidized into dihydrate gypsum; 3, extracting effective calcium ions in the desulfurized fly ash; 4, roasting the high-pyrite powder in a three-blade closed rotary kiln by using blast furnace gas or carbon-containing fuel as a reducing agent; and 5, the effective calcium ions in the step 3 are used as a high-pyrite powder roasting kiln desulfurizing agent, and calcium sulfite in the effective calcium ions is oxidized into dihydrate gypsum again. And by controlling the ratio of effective calcium ions to sulfur in the iron powder, the resource utilization that the desulfurized fly ash is completely converted into high-purity dihydrate gypsum is achieved.

Description

Technical Field

[0001] The present invention relates to the field of resource utilization of desulfurization ash, and in particular to a method and device for resource utilization of desulfurization ash and coordinated disposal of high-sulfur iron ore powder. Background Art

[0002] 1. Desulfurization ash

[0003] Desulfurization ash is a solid waste generated during the flue gas desulfurization process. Most steel companies' sintering machines are equipped with semi-dry desulfurization equipment. The output of dry desulfurization ash has exceeded 15 million tons, and the number is still increasing. However, the comprehensive utilization of desulfurization ash is currently difficult. Only a small part of it is used for mine backfill or road paving, and the vast majority is still stockpiled, causing environmental pollution pressure on enterprises.

[0004] 1. Complex and unstable ingredients:

[0005] (1) Coexistence of multiple components: The main components of sulfur-containing minerals in dry desulfurization ash are calcium sulfite and calcium sulfate. The side reaction products include calcium carbonate and alkaline substances such as unreacted calcium hydroxide. In addition, it may contain some impurities such as heavy metals from steel production raw materials. This multi-component characteristic increases the complexity of treatment.

[0006] (2) Large fluctuations in composition: Affected by the quality of the desulfurizer, the operating conditions of the desulfurization system, the properties of the fuel and other raw materials used in steel production, the main elemental components of the desulfurization ash produced in different batches or even in different periods of the same batch vary greatly. This makes it difficult to formulate a unified and fixed treatment plan, and it is necessary to continuously adjust the treatment process and parameters according to the specific composition.

[0007] 2. Reactivity problem:

[0008] (1) Calcium sulfite oxidation problem: Calcium sulfite in desulfurization ash has the risk of oxidation under certain conditions, which may cause expansion and other problems during the treatment process, affecting subsequent utilization. If used in fields such as building materials, the volume change when calcium sulfite oxidizes to calcium sulfate may cause material structural instability.

[0009] (2) Impact of incomplete reaction products: Dry desulfurization itself has the problem of incomplete reaction. Some unreacted desulfurizer and unremoved sulfur dioxide will exist in the desulfurization ash. These substances may continue to react in subsequent treatments, interfere with the treatment process, and reduce the treatment effect and product quality.

[0010] 3. Problems caused by product characteristics:

[0011] (1) Fine particles are prone to dust: Dry desulfurization ash usually has fine particles, which easily generates dust during storage, transportation and processing. This will not only cause material loss, but also pollute the environment and endanger the health of operators. Special dust prevention and dust collection equipment is required, which increases the cost and difficulty of processing.

[0012] (2) Stickiness problem: Desulfurization ash may be sticky under certain humidity and other conditions, and easily adhere to the inner wall of equipment and pipelines, causing blockage and equipment failure, affecting the normal operation of the treatment system, and requiring frequent cleaning and maintenance.

[0013] 4. Limited comprehensive utilization technology:

[0014] (1) Few high value-added utilization approaches: Although desulfurization ash can be used in some fields, such as the production of building materials, in general, there are relatively few technologies and approaches to achieve high value-added utilization. A large amount of desulfurization ash can only be used at a low level or simply piled up, resulting in resource waste and environmental pressure.

[0015] (2) Conflict between technical maturity and economic efficiency: Although some desulfurization ash treatment and utilization technologies have achieved certain results in laboratory or small-scale tests, they are difficult to promote and apply due to problems such as insufficient technical maturity, high operating costs, and poor economic benefits when applied on a large scale in industry.

[0016] (3) The main ways to comprehensively utilize desulfurization ash resources are:

[0017] 1) Application in building materials production: Desulfurization ash is used in the production of building materials such as cement, bricks, and concrete. Calcium, silicon, and other components in desulfurization ash can serve as active materials in cement and concrete, replacing some cement clinker and sand and gravel aggregates. This not only reduces the cost of desulfurization ash disposal, but also lowers the production cost of building materials.

[0018] 2) Soil conditioner: Desulfurization ash, which contains certain nutrients and low heavy metal content, can be used as a soil conditioner in agricultural production or land reclamation after proper treatment. This not only solves the problem of desulfurization ash disposal, but also brings certain economic benefits.

[0019] 3) Valuable metal recovery: If the desulfurization ash contains a certain amount of valuable metals, such as zinc and iron, appropriate technologies can be used to recover them. For example, magnetic separation, flotation, chemical leaching, etc. can be used to recover the metals, thereby achieving resource reuse, increasing the added value of the desulfurization ash, and reducing processing costs.

[0020] 5. Strict environmental protection requirements:

[0021] (1) Control of heavy metals and other pollutants: If heavy metals and other pollutants in desulfurization ash are not handled properly, they may enter the soil and water bodies through rainwater and other channels, causing environmental pollution. Environmental protection requires strict control over the treatment and discharge of these pollutants, which increases the difficulty and cost of treatment.

[0022] (2) Secondary pollution risk: During the desulfurization ash treatment process, improper stacking, transportation or treatment methods may generate secondary pollution such as dust and wastewater. A series of measures need to be taken to prevent and control them, which further increases the complexity and difficulty of treatment.

[0023] 2. High sulfur iron powder

[0024] High-sulfur iron powder generally refers to iron concentrate powder with a high sulfur content or iron powder containing a large amount of sulfur compounds such as iron sulfide. Its characteristics and processing difficulties are as follows:

[0025] 1. Characteristics of high sulfur iron powder:

[0026] (1)Chemical properties:

[0027] 1) High sulfur content: The sulfur content is usually significantly higher than that of ordinary iron powder, generally up to 15% to 50% or even higher, mainly in the form of sulfides, such as pyrite (FeS2), pyrrhotite (Fe 1-x S) etc.

[0028] 2) Oxidizability: Due to the presence of sulfur, high-sulfur iron powder is prone to oxidation reaction in the air, especially in a humid environment, the oxidation rate will be accelerated to produce iron oxides and sulfur-containing compounds, such as iron sulfate.

[0029] 3) Complex acid-base reactions: When reacting with acid, toxic and harmful gases such as hydrogen sulfide will be produced. The reaction with alkali is relatively weak, but under certain conditions, it may also react to produce substances such as thiosulfate.

[0030] (2) Physical properties:

[0031] 1) Color and gloss: The color is generally darker than ordinary iron powder, often appearing gray-black or dark brown, with a certain metallic luster. However, due to reasons such as easy surface oxidation, the glossiness may not be as good as pure iron powder or low-sulfur iron powder.

[0032] 2) Density: The density is slightly different from that of ordinary iron powder, generally between 4.5 and 5.2 g / cm 3 The specific density depends on the sulfur content and the content of other impurities.

[0033] 3) Magnetism: Some high-sulfur iron powders have certain magnetism, such as those containing pyrrhotite, but the magnetism is usually weaker than that of pure iron or iron oxide, and the magnetism will change with the sulfur content and mineral composition.

[0034] (3) Metallurgical properties:

[0035] 1) Impact on steel quality: Sulfur is a harmful element in the steel smelting process. The sulfur in high-sulfur iron powder can make steel hot brittle, reduce the strength, toughness, welding performance of steel, etc., and seriously affect the quality of steel products.

[0036] 2) Increased smelting difficulty: High-sulfur iron powder requires an additional desulfurization process during smelting to reduce the sulfur content to meet the quality requirements of steel products, which increases the complexity and cost of the smelting process.

[0037] 2. Difficulties in handling high-sulfur iron powder

[0038] (1) Desulfurization is difficult:

[0039] 1) High sulfide stability: Sulfides in high-sulfur iron powder, such as pyrite, have high chemical stability. Under conventional processing conditions, it is difficult to effectively remove the sulfur therein.

[0040] 2) Limitations of desulfurization methods: Commonly used physical mineral processing methods, such as flotation and magnetic separation, have limited effects on removing sulfides from high-sulfur iron powder and often require combination with chemical methods, such as oxidative roasting and sulfuric acid leaching. However, these methods have problems such as high cost, complex processes, and easy generation of secondary pollution.

[0041] (2) High risk of environmental pollution:

[0042] 1) Waste gas emissions: During the processing of high-sulfur iron powder, such as roasting and smelting, a large amount of waste gas containing harmful gases such as sulfur dioxide will be generated. If not handled properly, it will cause serious pollution to the atmospheric environment. It is necessary to equip efficient waste gas treatment equipment and technology for desulfurization, denitrification and other treatments.

[0043] 2) Wastewater treatment: When high-sulfur iron powder is treated by wet method, wastewater containing pollutants such as heavy metal ions and sulfides will be produced. If these wastewaters are discharged directly, they will pollute water bodies and soil. They are difficult to treat and require special wastewater treatment processes such as chemical precipitation and biological treatment to remove pollutants.

[0044] (3) Complex comprehensive utilization of resources:

[0045] 1) Complex composition: In addition to iron and sulfur, high-sulfur iron powder may also contain various valuable metals such as copper, lead, zinc, gold, and silver, as well as gangue minerals such as silicon, calcium, and magnesium. To achieve efficient and comprehensive utilization of resources, it is necessary to adopt multiple technologies and processes for different components, and the process is complicated.

[0046] 2) High technical requirements: The recovery and utilization of various resources in high-sulfur iron powder requires advanced technology and equipment. At present, some comprehensive resource utilization technologies are not mature enough or are not economically feasible, which limits the development of comprehensive utilization of high-sulfur iron powder resources.

[0047] 3. Common technical routes and methods for co-treatment of high-sulfur iron ore powder with dry desulfurization ash:

[0048] 1. Solid-state roasting magnetic separation route:

[0049] (1) Solid-state roasting magnetic separation process:

[0050] 1) Raw material preparation: Select suitable desulfurization ash with a CaSO4 content of ≥20%, and prepare anthracite, fat coal, lean coal, or coking coal as a reducing agent. Grind the desulfurization ash, coal, and high-sulfur iron ore powder separately to an average particle size of <90 μm.

[0051] 2) Mixing ingredients: Mix the ingredients according to the mass ratio of desulfurization ash and coal of 1.5-2.5:1, and the mass ratio of desulfurizer and high-sulfur iron ore of 1-1.5:1, while ensuring that (FeS) / (CaSO4)=0.25-1.25, where (FeS) is the molar content of FeS in high-sulfur iron ore, and (CaSO4) is the molar content of CaSO4 in desulfurization ash.

[0052] 3) Calcination reaction: The mixed materials are placed in a calcination device and calcined at a temperature of 1100°C to 1200°C at a heating rate of 5°C / min to 10°C / min, so that the high-sulfur iron ore desulfurization and iron reduction processes proceed simultaneously to obtain an iron-containing mixture.

[0053] 4) Magnetic separation: The iron-containing mixture is first subjected to a first magnetic separation at a magnetic field strength of 0.8t to 1t to obtain a first magnetic separation product and a first metallic iron; the first magnetic separation product is then subjected to a second magnetic separation at a magnetic field strength of 0.1t to 0.15t to obtain a second metallic iron; finally, the first metallic iron and the second metallic iron are mixed, dried, and then pulverized to obtain metallic iron powder.

[0054] (2) Advantages of solid-state roasting magnetic separation method:

[0055] 1) High desulfurization efficiency: Through solid-state roasting, the sulfur in high-sulfur iron ore powder can fully react with desulfurization ash and other substances, fixing or converting the sulfur into sulfide and other forms, thereby effectively removing the sulfur element and achieving a higher desulfurization rate.

[0056] 2) Comprehensive utilization of resources: The use of desulfurization ash to coordinate the disposal of high-sulfur iron ore powder not only solves the disposal problem of desulfurization ash, but also realizes the desulfurization of high-sulfur iron ore powder and the recycling of iron resources, thereby improving the comprehensive utilization rate of resources and conforming to the concept of circular economy.

[0057] 3) Advantages of dry process: This process is a dry process. Compared with the wet process, it does not require a large amount of water, which can reduce the wastewater treatment process and costs. At the same time, it also avoids environmental pollution problems that may be caused by wastewater discharge, making it more environmentally friendly.

[0058] 4) Good magnetic separation effect: The roasted product can be magnetically separated to effectively separate iron minerals and other impurities based on the magnetic differences of the minerals, thereby obtaining higher-grade iron concentrate and improving the recovery quality of iron resources.

[0059] 5) Strong adaptability: It has certain adaptability to high-sulfur iron ore powder of different grades and sulfur contents. By adjusting parameters such as roasting conditions and desulfurization ash dosage, better desulfurization and separation effects can be achieved.

[0060] (3) Disadvantages of solid-state roasting magnetic separation method:

[0061] 1) High energy consumption: The solid-state roasting process needs to be carried out under high temperature conditions, which usually consumes a lot of energy to maintain the temperature required for the reaction, resulting in increased production costs. It also places high demands on energy supply and energy-saving technologies.

[0062] 2) Large equipment investment: It involves a variety of professional equipment such as solid-state roasting furnaces and magnetic separation equipment. In order to ensure the process effect and equipment stability, high requirements are placed on the equipment's material and manufacturing process, and the initial equipment investment cost is relatively high.

[0063] 3) Complex process control: During the solid-state roasting process, parameters such as temperature, atmosphere, and reaction time have a significant impact on the desulfurization effect and product quality, and require precise control and monitoring. Parameters such as the magnetic field strength and feed rate during the magnetic separation process also need to be precisely adjusted, which places high demands on the operator's technical level and operating experience.

[0064] 4) Secondary pollution may occur: If the roasting process is not properly controlled, harmful gases such as sulfur dioxide may escape, causing air pollution. At the same time, the desulfurization ash may contain some harmful substances such as heavy metals. If not handled properly, it may also cause pollution to the soil, water bodies, etc.

[0065] 5) High requirements for subsequent product processing: The iron concentrate obtained by magnetic separation may still contain some impurities and requires further processing and purification to meet the requirements of high-quality iron concentrate, which increases the difficulty and cost of subsequent processing.

[0066] 2. Pyrolysis-reduction route:

[0067] (1) Pyrolysis-reduction process:

[0068] 1) Pyrolysis of pyrite: Pyrite (main component FeS2) in high-sulfur iron ore is pyrolyzed using pyrolysis technology to obtain elemental sulfur and pyrolysis products such as FeS.

[0069] 2) Reduction reaction: Under certain conditions, CaO in the desulfurization ash and FeS produced by pyrolysis are reduced by hot carbon-quicklime to obtain elemental iron and form CaS.

[0070] 3) Desulfurization gypsum reduction: The generated CaS is used to react with the desulfurization gypsum in the desulfurization ash to obtain recyclable SO2 and recyclable CaO, thereby achieving high resource utilization of elements such as sulfur, iron, and calcium.

[0071] (2) Advantages of pyrolysis-reduction method:

[0072] 1) Good desulfurization effect: Under pyrolysis reduction conditions, certain components in the desulfurization ash can chemically react with the sulfur in the high-sulfur iron ore powder, causing the sulfur to escape in the form of gas such as hydrogen sulfide or be converted into sulfides and fixed, which can effectively reduce the sulfur content of the high-sulfur iron ore powder and improve the quality of iron concentrate.

[0073] 2) Efficient resource utilization: Desulfurization ash is used to treat waste with waste, reducing the storage and disposal pressure of desulfurization ash. High-sulfur iron ore powder is also effectively processed, and the iron resources therein are recovered, thereby improving the comprehensive utilization rate of resources and complying with the concepts of circular economy and sustainable development.

[0074] 3) Advantages of dry process: Compared with wet process, it does not require large amounts of water, thus avoiding wastewater generation and subsequent wastewater treatment problems, reducing the demand for water resources and the impact on the water environment, and also reducing the risk of environmental pollution caused by wastewater discharge.

[0075] 4) Strong adaptability: For high-sulfur iron ore powder of different types and sulfur contents and desulfurized ash of different compositions, by properly adjusting the process parameters such as temperature, time, and atmosphere of pyrolysis reduction, generally better synergistic treatment effects can be achieved, which has certain flexibility and adaptability.

[0076] 5) Reduce the risk of secondary pollution: Compared with some other desulfurization processes, under reasonable control, the thermal reduction method produces relatively few secondary pollutants and has a smaller overall impact on the environment.

[0077] (3) Disadvantages of pyrolysis-reduction method:

[0078] 1) High energy consumption: The pyrolysis reduction process usually needs to be carried out under high temperature conditions, which generally consumes a lot of energy to maintain the temperature required for the reaction, resulting in increased production costs. It also puts forward higher requirements for energy supply and energy-saving technology.

[0079] 2) Large equipment investment: Specialized pyrolysis reduction equipment, gas purification equipment, etc. are required, which have high requirements on the equipment's material, high temperature resistance, and sealing performance. The equipment procurement, installation and maintenance costs are relatively high, and the initial investment is large.

[0080] 3) Difficulty in process control: Parameters such as temperature, atmosphere, and residence time during the pyrolysis reduction process significantly impact the desulfurization effect and product quality, requiring precise control and monitoring. Furthermore, factors such as the mixing ratio and particle size of the desulfurization ash and high-sulfur iron ore powder must be strictly controlled, requiring high operator skill and experience. Failure to do so may result in unstable desulfurization results or substandard product quality.

[0081] 4) High gas treatment requirements: Gases such as hydrogen sulfide produced during the pyrolysis reduction process are toxic and corrosive, and require a complete gas purification and treatment system to prevent harmful gases from leaking into the atmosphere and causing environmental pollution and safety hazards, which increases the complexity and cost of the process.

[0082] 5) There may be sulfur recovery problems: Although desulfurization can be achieved, the recovery and utilization of the generated sulfur-containing gas or sulfide may be difficult and costly. If it cannot be effectively recovered and utilized, it may cause waste of resources and certain environmental pressures.

[0083] 4. Current status of sintering flue gas desulfurization

[0084] 1. The mainstream process of sintering flue gas desulfurization has been formed.

[0085] Currently used desulfurization technologies primarily include dry, semi-dry, and wet methods. Dry and semi-dry processes primarily include the CFB circulating fluidized bed (CFB) method, dense phase desulfurization tower method, activated carbon adsorption method, NID flue circulation method, and SDA rotary semi-dry method. Wet processes primarily include the limestone-gypsum method, ammonia method, magnesium oxide method, and double alkali method. Of these, the circulating fluidized bed method is the primary dry desulfurization process, the SDA rotary method is the primary semi-dry desulfurization process, and the limestone-gypsum method is the primary wet desulfurization process. To date, my country has achieved significant results in sintering flue gas desulfurization. This is primarily due to significant improvements in the design, manufacturing, and operating experience of sintering flue gas desulfurization facilities. Furthermore, by 2023, SO2 emissions per ton of product from the sintering process will have dropped from 1.89 kg in 2010 to 0.24 kg, representing an 84.12% reduction in emission intensity compared to 2010 and a reduction of 1.7876 million tons of sulfur dioxide emissions. Sintering flue gas desulfurization coverage has reached 100%, and the majority of steel companies have achieved compliance with SO2 emission standards for sintering flue gas. However, this promising situation presents significant challenges. An investigation revealed that my country's sintering flue gas desulfurization market is relatively chaotic, characterized by widespread imitation, low-quality, low-price products, and unhealthy competition. Furthermore, efforts such as corrosion protection, external insulation, and by-product treatment are lacking. Furthermore, effective operational maintenance is lacking, resulting in high equipment failure rates and low commissioning rates. A 2022 inspection by relevant environmental protection departments revealed a national average comprehensive desulfurization failure rate of 38.6%. Currently, with the tightening of national environmental protection standards, existing sintering flue gas treatment facilities are increasingly unable to meet these requirements and require timely upgrades and renovations. This is particularly necessary for significant pre-removal of sulfur at the source of sintering, i.e., on the raw material side. As a high-tech enterprise in the environmental protection industry, our company is eager to contribute to this endeavor.

[0086] 2. The sintering flue gas desulfurization process has significant deficiencies:

[0087] (1) The existing desulfurization process is difficult to adapt to the environmental protection requirements that are increasing year by year. Since the desulfurization equipment in service was built two, three or even five years ago, the requirements for sintering flue gas desulfurization emission indicators were relatively broad at that time. Since then, the environmental protection situation has gradually tightened, and has been improved almost every year until today's ultra-low emissions and ultra-ultra-low emissions. In fact, the desulfurization capacity of any desulfurization technology has an upper limit. For example, the dry desulfurization process is only suitable for flue gas SO2 content of 1000mg / Nm 3 The following working conditions, semi-desulfurization process is only applicable to flue gas SO2 content of 2000mg / Nm 3 The wet desulfurization process is applicable to flue gas SO2 content of 3000mg / Nm 3Based on the above operating conditions, it can be seen that steel companies using dry or semi-dry desulfurization processes have only one way to achieve ultra-low SO2 emissions: significantly increase the amount of desulfurizer used, reaching a Ca / S ratio of 1.5-1.7. This desulfurizer consumption far exceeds the theoretical value, resulting in serious waste and increased desulfurization costs. However, even this is only a temporary solution, and the results are still unsatisfactory.

[0088] (2) Desulfurization by-products are difficult to utilize and can easily cause secondary pollution. Taking the by-products of dry and semi-dry desulfurization as an example, the by-products are mainly calcium sulfite, whose content can reach 40%, calcium sulfate content accounts for about 10%, calcium oxide and calcium carbonate account for 40%, and iron oxide and other impurities account for 10%. The excessively high calcium sulfite content limits its use as a cement concrete admixture; the high free calcium oxide content in desulfurization ash causes it to continuously generate calcium hydroxide during the long-term hydration process, causing the volume of products containing desulfurization ash materials to continue to expand and even crack. At present, this type of desulfurization ash is mostly handled in China by backfilling abandoned mines, selecting special storage yards for stacking, etc., which not only occupies land, but also may pollute soil and groundwater.

[0089] (3) The desulfurization capacity of the existing desulfurization equipment is insufficient, resulting in an increase in the cost of ironmaking raw materials. The main raw material for ironmaking is iron ore powder. The harmful sulfur element contained in it is mainly removed through the sintering process. The greater the capacity of the sintering machine flue gas desulfurization device, the higher the allowable sulfur content of the iron ore powder used. Currently, the purchase price difference between low-sulfur (≤0.2%) iron ore powder and high-sulfur (≥1.0%) iron ore powder on the market is 200 to 300 yuan. According to the design capacity of the existing desulfurization equipment, the dry and semi-dry processes can only meet the desulfurization needs of iron ore sinter with a sulfur content of 0.20 to 0.30%. As a result, steel companies are directly unable to use high-sulfur iron ore powder. Therefore, the overload of the existing desulfurization equipment has at least caused a significant increase in the ironmaking costs of steel companies. Summary of the Invention

[0090] In response to the problems in the prior art, the present invention provides a method and device for resource utilization of desulfurization ash and coordinated disposal of high-sulfur iron ore powder.

[0091] The technical solution adopted by the present invention to solve the technical problem is: a method and device for resource utilization of desulfurization ash and coordinated disposal of high-sulfur iron ore powder, which includes the following steps:

[0092] S1. Acid dissolution reaction. In a dissolution device such as a pipeline reactor or reactor, an acidic dissolution agent is used to dissolve the effective calcium content in the desulfurized ash. This acidic dissolution agent reacts with SO2 in the pre-desulfurized roasting flue gas of high-sulfur iron ore powder or the sintering machine flue gas of high-sulfur iron ore powder to form gypsum. The dissolution agent can be any of formic acid, acetic acid, adipic acid, etc. Taking acetic acid as an example, the dissolution chemical reaction equation is:

[0093] HAc+Ca(OH)2==Ca(Ac)2+H2O (1);

[0094] HAc+CaCO3==Ca(Ac)2+CO2+H2O (2);

[0095] Ca(Ac)2+SO2+1 / 2O2==CaSO4+HAc (3).

[0096] S2. Fully aerate the desulfurized ash slurry after the dissolution reaction. The main component of the slurry, calcium sulfite, is oxidized into dihydrate gypsum; the chemical reaction equation is:

[0097] CaSO3+1 / 2O2+H2O=CaSO4·2H2O (4).

[0098] S3. Separate the aerated product into solid and liquid form. Extract effective calcium ions such as calcium sulfate and calcium sulfite from the desulfurization ash;

[0099] S4, reduction roasting of high-sulfur iron powder. Use high-sulfur (≥1.0%) iron ore powder with a particle size of 100 mesh or more as raw material, use the effective calcium ions extracted from S3 as desulfurizer, use C or CO in blast furnace gas or carbon-containing fuel as reducing agent, and mix the ingredients according to the mass ratio of S3 desulfurization ash and coal (carbon-containing materials are calculated as C) of 1.5 to 2.5:1, and the mass ratio of S3 desulfurization ash and high-sulfur iron ore of 1 to 1.5:1. At a temperature of 1000℃ to 1100℃ or 1100℃ to 1200℃, the high-sulfur iron ore powder is reduction roasted in a three-leaf closed rotary kiln to desulfurize the high-sulfur iron ore and generate direct reduced iron. When using coal powder as a reducing agent, it should be ground into powder, and the proportion of particles less than 0.074mm should reach more than 80% to ensure that the reducing agent and iron ore can fully mix and react.

[0100] S5: Dihydrate gypsum is generated during the desulfurization reaction. The effective calcium ions extracted in S3 are used as a flue gas desulfurizer in the high-sulfur iron ore powder roasting kiln. In the flue gas desulfurization tower, all the calcium sulfite in the effective calcium ions is oxidized again to become dihydrate gypsum.

[0101] S6, magnetic separation. The direct reduced iron roasted in S4 is crushed and magnetically separated and pressed under a magnetic field strength of 0.8t to 1t to obtain metallic iron briquettes.

[0102] Preferably, the dissolving agent in S1 is any one of formic acid, acetic acid, adipic acid, etc.

[0103] Preferably, when blast furnace gas is used as fuel as described in S4, the powder is preheated, desulfurized, roasted, and cooled in the kiln to become the required low-sulfur product. The flue gas containing high concentration of SO2 is purified by wet desulfurization, denitrification, and wet electrostatic precipitator before meeting the emission standards. The SO2 in the flue gas eventually generates gypsum and is recovered together with the sulfide in the desulfurization ash. A small amount of NOx in the flue gas is reduced to generate N2 and discharged with the flue gas, and the dust in the flue gas is removed by the wet electrostatic precipitator.

[0104] Preferably, anthracite or coke powder is used as fuel as described in S4, and the powder is preheated, desulfurized, roasted, and cooled in the sintering machine to become the required low-sulfur product. The flue gas containing high concentration of SO2 is purified by wet desulfurization, denitrification, and wet electrostatic precipitator to meet the emission standards. The SO2 in the flue gas eventually turns into gypsum and is recovered together with the sulfide in the desulfurization ash. The small amount of NOx in the flue gas is reduced to generate N2 and is discharged with the flue gas, and the dust in the flue gas is removed by the wet electrostatic precipitator.

[0105] Preferably, the three-blade closed rotary kiln described in S4 is well ventilated and equipped with a material turning device. The material is roasted in the three-blade closed rotary kiln in a uniformly heated, self-gravity dispersed, semi-suspended state. By controlling the material filling rate to 15% to 30%, continuous and stable production is ensured.

[0106] Preferably, by controlling the reasonable rotation speed, the material is ensured to have sufficient residence time in the kiln to complete the reduction and co-treatment reaction. The general rotation speed is 0.5-1.2 r / min;

[0107] Preferably, by precisely controlling the temperature of different areas in the kiln, the ringing and blockage of the kiln body caused by the possible appearance of low-melting-point substances during the reaction process can be reduced; different areas in the kiln should have different temperature distributions, usually controlling the temperature of the kiln head at 900℃~1000℃, maintaining the temperature of the high-temperature zone in the kiln at 1000℃~1100℃ or 1100℃~1200℃, and the temperature at the kiln tail is usually 700℃~850℃, which is conducive to the selective reduction of iron-containing multi-component ore and the discharge of elements and oxides with low gasification temperature in gaseous state; the kiln needs to have a multi-zone temperature control function, and the temperature of each area can be accurately controlled by setting temperature monitoring points and heating devices at different positions.

[0108] Preferably, by controlling the atmosphere in the kiln and adjusting the air supply volume of each air duct, the oxygen content in the kiln is accurately controlled to provide a suitable reducing atmosphere for the reduction of high-sulfur iron powder and the disposal of desulfurization ash;

[0109] Preferably, the kiln body is sealed and a slight positive pressure of 20Pa to 30Pa is maintained at the discharge end to prevent air inhalation and avoid reoxidation of the product.

[0110] Preferably, the mass ratio of the effective calcium ion desulfurizer in S5 to the sulfur in the high-sulfur iron ore is controlled at 1 to 1.5:1, and (FeS) / (CaSO4)=0.25 to 1.25, where (FeS) is the molar content of FeS in the high-sulfur iron ore and (CaSO4) is the molar content of CaSO4 in the desulfurized ash.

[0111] Beneficial effects of the present invention:

[0112] 1) The utilization rate of desulfurization ash is nearly 100.0%, which greatly reduces the consumption of natural resource limestone;

[0113] 2) Desulfurization ash is turned into treasure, utilizing about 60.0% of the effective calcium and obtaining high-quality gypsum;

[0114] 3) High-sulfur iron ore powder can be used in whole or in part to produce qualified iron ore concentrate or sintered ore;

[0115] 4) It can save the purchase cost of iron ore concentrate by about RMB 150 / ton or more. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a schematic diagram of the main structure of the present invention. DETAILED DESCRIPTION

[0116] In order to enable those skilled in the art to better understand the present invention, the following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0117] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0118] The present invention is further described below.

[0119] Example

[0120] The present invention provides a method for resource utilization of desulfurized ash and coordinated disposal of high-sulfur iron ore powder, which comprises the following steps:

[0121] S1. Acid dissolution reaction. In the pipeline dissolution reactor, an acidic dissolution agent is used to dissolve the effective calcium component in the desulfurized ash, which reacts with SO2 in the sintering machine flue gas of high-sulfur iron ore powder to form gypsum. The dissolution agent is acetic acid, and the dissolution chemical reaction equation is:

[0122] HAc+Ca(OH)2==Ca(Ac)2+H2O (1);

[0123] HAc+CaCO3==Ca(Ac)2+CO2+H2O (2);

[0124] Ca(Ac)2+SO2+1 / 2O2==CaSO4+HAc (3).

[0125] S2. Fully aerate the desulfurized ash slurry after the dissolution reaction. The main component of the slurry, calcium sulfite, is oxidized into dihydrate gypsum; the chemical reaction equation is:

[0126] CaSO3+1 / 2O2+H2O=CaSO4·2H2O (4).

[0127] S3. Separate the aerated product into solid and liquid form. Extract effective calcium ions such as calcium sulfate and calcium sulfite from the desulfurization ash;

[0128] S4, reduction roasting of high-sulfur iron powder. Using high-sulfur (≥1.0%) iron ore powder with a particle size of 100 mesh or larger as raw material, the effective calcium ions extracted from S3 are used as a desulfurizer, and CO from blast furnace gas is used as a reducing agent. The ingredients are mixed in a mass ratio of S3 desulfurization ash to coal (carbon-containing materials are calculated as C) of 1.5-2.5:1, and a mass ratio of S3 desulfurization ash to high-sulfur iron ore of 1-1.5:1. During operation, the material filling rate is controlled at approximately 25%. The high-sulfur iron ore powder is reduction roasted in a three-blade sealed rotary kiln at a temperature of 1000°C to 1100°C or 1100°C to 1200°C to desulfurize the high-sulfur iron ore and produce direct reduced iron.

[0129] S5: Dihydrate gypsum is generated during the desulfurization reaction. The effective calcium ions extracted in S3 are used as a flue gas desulfurizer in the high-sulfur iron ore roasting kiln. In the dry flue gas desulfurization tower, all the calcium sulfite in the effective calcium ions is oxidized again to dihydrate gypsum.

[0130] The mass ratio of the effective calcium ion desulfurizer in S5 to the sulfur in the high-sulfur iron ore should be controlled at 1 to 1.5:1, and (FeS) / (CaSO4)=0.25 to 1.25, where (FeS) is the molar content of FeS in the high-sulfur iron ore and (CaSO4) is the molar content of CaSO4 in the desulfurized ash.

[0131] S6, magnetic separation. The direct reduced iron roasted in S4 is crushed and magnetically separated and pressed under a magnetic field strength of 0.8t to 1t to obtain metallic iron briquettes.

[0132] The working principle of the embodiment is as follows: According to laboratory analysis, the main component of dry and semi-dry desulfurization ash is calcium sulfite, which can reach 35%, calcium sulfate accounts for approximately 20%, calcium oxide accounts for 20%, and calcium carbonate and other impurities account for 25%. Excessively high calcium sulfite content limits its use as a cement concrete admixture. The high free calcium oxide content in desulfurization ash can easily cause it to continuously generate calcium hydroxide during long-term hydration, causing products containing desulfurization ash to continuously expand in volume and even crack. Therefore, currently, this type of desulfurization ash is mostly disposed of in China by backfilling abandoned mines or storing it in specialized storage yards, which not only occupies land but also may pollute soil and groundwater.

[0133] The present invention separates and processes desulfurized ash. First, a dissolving agent is used to dissolve the effective calcium component, which reacts with SO2 to form gypsum. The dissolving agent can be any one of formic acid, acetic acid, adipic acid, etc. Taking acetic acid as an example, the dissolution chemical reaction equation is:

[0134] HAc+Ca(OH)2=Ca(Ac)2+H2O (1)

[0135] HAc+CaCO3=Ca(Ac)2+CO2+H2O (2)

[0136] Ca(Ac)2+SO2+1 / 2O2=CaSO4+HAc (3)

[0137] The source of SO2 can be taken from the pre-desulfurization roasting flue gas of high-sulfur iron ore powder or the sintering machine flue gas of high-sulfur iron ore powder.

[0138] After the effective calcium is dissolved, the desulfurized ash slurry is fully aerated, and the main component of the slurry, calcium sulfite, is completely oxidized to form dihydrate gypsum. The chemical reaction equation is:

[0139] CaSO3+1 / 2O2+H2O=CaSO4·2H2O (4)

[0140] The present invention extracts effective calcium ions from desulfurization ash for use in desulfurization of high-sulfur iron ore powder, and then oxidizes the calcium sulfite therein into dihydrate gypsum, thereby achieving the purpose of resource utilization of desulfurization ash and coordinated disposal of high-sulfur iron ore powder.

[0141] As the equipment to achieve the above purpose, the present invention selects:

[0142] 1. The pipeline dissolution reactor is used for the dissolution reaction of desulfurized ash, which has the advantages of continuous and stable operation. If the processing volume is not large, you can also choose to use a dissolution device with smaller investment, such as a reactor.

[0143] 2. Three-blade rotary high-temperature kiln + wet desulfurization and denitrification tower + wet electrostatic precipitator are used for pre-desulfurization of high-sulfur iron ore powder, and the products are low-sulfur iron ore concentrate and high-purity dihydrate gypsum.

[0144] 3. Sintering machine + wet desulfurization tower system + other flue gas purification equipment, used to produce sintered ore from high-sulfur iron ore powder, the products are qualified sintered ore and dihydrate gypsum.

[0145] (1) Example of processing 200.0 tons of dry desulfurization ash per day for desulfurization of high-sulfur iron ore powder using rotary kiln method:

[0146] Using iron ore powder with a grade of 62.0% and a sulfur content ≥1.50% as raw material and 200.0 tons of desulfurized ash as desulfurizer, the daily output is 2,400 tons of iron ore concentrate with a grade of 64.0% and low sulfur (sulfur content ≤0.20%) and 400.0 tons of high-quality dihydrate gypsum.

[0147] 1) Construct a Φ×L=3.6×38m three-leaf closed rotary kiln, a Φ×H=7.0×45m wet desulfurization and denitrification dust removal tower system, a 2000.0t / h calcium ion desulfurization liquid preparation system, and a 20t / h gypsum treatment system.

[0148] 2) The project covers an area of 18,000 m 2 , building area 6000.0m 2 .

[0149] 3) The power load of the project supporting construction is 2520.0kVA, and the blast furnace gas is 550,000m3 3 , water consumption: 125.0 tons / h.

[0150] 4) The simple process flow is as follows: using blast furnace gas as fuel, the powder undergoes preheating, desulfurization, roasting, and cooling in the kiln to produce the desired low-sulfur product. Flue gas containing high concentrations of SO2 is purified by a wet desulfurization and denitrification tower and a wet electrostatic precipitator, achieving emission standards. The SO2 in the flue gas is ultimately converted into gypsum, which is recovered along with the sulfides in the desulfurization ash. Small amounts of NOx in the flue gas are reduced to nitrogen, which is discharged with the flue gas. Dust in the flue gas is removed by the wet electrostatic precipitator.

[0151] (2) 500.0 tons of dry desulfurization ash is processed daily for 360m 2 Example of sintering machine producing sintered ore:

[0152] Using iron ore powder with a grade of 62.0% and a sulfur content of ≥1.50% as raw material, the company produces 12,000.0 tons of sintered ore with a grade of 64.0% and low sulfur (sulfur content ≤0.07%) and 1,000.0 tons of high-quality dihydrate gypsum per day.

[0153] 1) Build a wet desulfurization and pre-desulfurization system, including a Φ×H=12.0×45m desulfurization tower, a 4500.0 t / h calcium-based desulfurization ion liquid preparation device, and a 40.0 t / h high-quality gypsum treatment system.

[0154] 2) The project covers an area of 2000.0m 2 , building area 1000.0m 2 .

[0155] 3) The project's supporting power load is 4560.0kVA and water consumption is 160.0 tons / h.

[0156] 4) The simple process is: the high sulfur content flue gas from the head is first electrostatically precipitated and then introduced into the wet desulfurization tower. When the SO2 content in the flue gas is reduced to 200mg / m 3 After that, the dry and semi-dry desulfurization systems are introduced to mix with the hot flue gas coming from the tail of the engine, and further purify it before it is discharged to meet the standards.

[0157] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method and device for resource utilization of desulfurized ash and coordinated disposal of high-sulfur iron ore powder, characterized in that: It includes the following steps: S1, acid dissolution reaction, in a dissolution device such as a pipeline reactor or a reactor, an acidic dissolution agent is used to dissolve the effective calcium component in the desulfurized ash, and react with SO2 in the pre-desulfurized roasting flue gas of the high-sulfur iron ore powder or the sintering machine flue gas of the high-sulfur iron ore powder to form gypsum; the dissolution agent is any one of formic acid, acetic acid, adipic acid, etc. Taking acetic acid as an example, the dissolution chemical reaction equation is: HAc+Ca(OH)2==Ca(Ac)2+H2O (1); HAc+CaCO3==Ca(Ac)2+CO2+H2O (2); Ca(Ac)2+SO2+1 / 2O2==CaSO4+HAc (3); S2. The desulfurized ash slurry after the dissolution reaction is fully aerated, and the main component of the slurry, calcium sulfite, is oxidized into dihydrate gypsum; the chemical reaction equation is: CaSO3+1 / 2O2+H2O=CaSO4·2H2O (4); S3, perform solid-liquid separation on the aerated product to extract effective calcium ions such as calcium sulfate and calcium sulfite from the desulfurization ash; S4, reduction roasting of high-sulfur iron powder, using high-sulfur (≥1.0%) iron ore powder with a particle size of 100 mesh or more as raw material, the effective calcium ions extracted from S3 as a desulfurizer, and C or CO in blast furnace gas or carbon-containing fuel as a reducing agent. The materials are mixed according to the mass ratio of S3 desulfurization ash and coal (carbon-containing materials are calculated as C) of 1.5 to 2.5:1, and the mass ratio of S3 desulfurization ash and high-sulfur iron ore of 1 to 1.5:

1. The high-sulfur iron ore powder is reduction roasted in a three-leaf closed rotary kiln at a temperature of 1000° C. to 1100° C. or 1100° C. to 1200° C. to desulfurize the high-sulfur iron ore and generate direct reduced iron. When using coal powder as a reducing agent, it should be ground, and the proportion of particles less than 0.074 mm should reach more than 80% to ensure that the reducing agent and iron ore can fully mix and react; S5, dihydrate gypsum is generated during the desulfurization reaction, and the effective calcium ions extracted in S3 are used as a flue gas desulfurizer in the high-sulfur iron ore powder roasting kiln. All calcium sulfite in the effective calcium ions is oxidized again in the flue gas desulfurization tower to become dihydrate gypsum; S6, magnetic separation, the direct reduced iron roasted in S4 is crushed, magnetically separated and pressed under a magnetic field strength of 0.8t to 1t to obtain metallic iron briquettes.

2. The method and device for resource utilization of desulfurized ash and coordinated disposal of high-sulfur iron ore powder according to claim 1, characterized in that: The dissolving agent in S1 is any one of formic acid, acetic acid, adipic acid, etc.

3. The method and device for resource utilization of desulfurization ash and coordinated disposal of high-sulfur iron ore powder according to claim 1, characterized in that: When blast furnace gas is used as fuel as described in S4, the powder is preheated, desulfurized, roasted, and cooled in the kiln to become the required low-sulfur product. The flue gas containing high concentration of SO2 is purified by wet desulfurization, denitrification, and wet electrostatic precipitator before meeting the emission standards. The SO2 in the flue gas is eventually converted into gypsum and recovered together with the sulfide in the desulfurization ash. A small amount of NOx in the flue gas is reduced to generate N2 and discharged with the flue gas. The dust in the flue gas is removed by the wet electrostatic precipitator.

4. The method and device for resource utilization of desulfurization ash and coordinated disposal of high-sulfur iron ore powder according to claim 1, characterized in that: As described in S4, anthracite or coke powder is used as fuel. The powder is preheated, desulfurized, roasted, and cooled in the sintering machine to become the required low-sulfur product. The flue gas containing high concentration of SO2 is purified by wet desulfurization, denitrification, and wet electrostatic precipitator before it meets the emission standards. The SO2 in the flue gas is eventually converted into gypsum and recovered together with the sulfide in the desulfurization ash. A small amount of NOx in the flue gas is reduced to generate N2 and discharged with the flue gas. The dust in the flue gas is removed by the wet electrostatic precipitator.

5. The method and device for resource utilization of desulfurized ash and coordinated disposal of high-sulfur iron ore powder according to claim 1, characterized in that: The three-blade closed rotary kiln described in S4 is well ventilated and has a built-in material turning device. The material is roasted in the three-blade closed rotary kiln in a uniformly heated, self-gravity dispersed and semi-suspended state. By controlling the material filling rate at 15% to 30%, continuous and stable production is ensured. By controlling the reasonable rotation speed, ensure that the material has enough residence time in the kiln to complete the reduction and co-treatment reaction. The general rotation speed is 0.5-1.2r / min; By precisely controlling the temperature of different zones in the kiln, ringing and blockage of the kiln caused by the presence of low-melting-point substances during the reaction process can be reduced. Different zones in the kiln should have different temperature distributions. The kiln head temperature is usually controlled at 900°C to 1000°C, the high-temperature zone in the kiln is maintained at 1000°C to 1100°C or 1100°C to 1200°C, and the kiln tail temperature is usually between 700°C and 850°C. This is conducive to the selective reduction of iron-containing multi-component paragenetic ores and the gaseous discharge of elements and oxides with low gasification temperatures. The kiln must have a multi-zone temperature control function, and the temperature of each zone can be precisely controlled by setting temperature monitoring points and heating devices at different locations. By controlling the atmosphere in the kiln and adjusting the air supply volume of each air duct, the oxygen content in the kiln is accurately controlled to provide a suitable reducing atmosphere for the reduction of high-sulfur iron powder and the disposal of desulfurization ash; By sealing the kiln body and maintaining a slight positive pressure of 20Pa to 30Pa at the discharge end, air inhalation is prevented and product reoxidation is avoided.

6. The method and device for resource utilization of desulfurization ash and coordinated disposal of high-sulfur iron ore powder according to claim 1, characterized in that: The mass ratio of the effective calcium ion desulfurizer described in S5 to the sulfur in the high-sulfur iron ore should be controlled at 1-1.5:1, and ensure that FeS / CaSO4=0.25-1.25, where FeS is the molar content of FeS in the high-sulfur iron ore and CaSO4 is the molar content of CaSO4 in the desulfurization ash.

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