Complex nickel-containing waste smelting flue gas cleaning and comprehensive utilization method

Abstract

The invention relates to the technical field of nickel-containing dangerous and solid waste recycling, and discloses a complex nickel-containing waste smelting flue gas cleaning and comprehensive utilization method which comprises the steps that smelting flue gas is fed into a dry-method deacidification tower after being subjected to waste heat recovery and shock cooling, coarse-particle calcium hydroxide is sprayed into the dry-method deacidification tower, defluorination is preferentially carried out in a first temperature interval of the dry-method deacidification tower, and defluorination is carried out in a second temperature interval of the dry-method deacidification tower; a defluorination product is collected, and fluorine-containing dust is separated and collected through electrostatic dust collection; the dedusted flue gas enters a semi-dry deacidification tower, and fine-particle calcium hydroxide is sprayed into the semi-dry deacidification tower for deep dechlorination in a lower second temperature interval of the semi-dry deacidification tower; and discharging the purified gas after denitration, washing and ionic liquid desulfurization. The defluorination product is washed and purified to prepare hydrofluoric acid, and the dechlorination slag is dissolved and subjected to a double decomposition reaction to prepare hydrochloric acid. According to the method, a temperature gradient and absorbent particle size gradient coupling process is utilized, so that directional separation and enrichment of gas-phase fluorine and chlorine pollutants are effectively realized, the problem that carnallite is difficult to utilize is solved, and full-process recycling and ultralow emission are realized.

Description

A method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste Technical Field

[0001] This invention relates to the field of nickel-containing hazardous and solid waste resource utilization technology, specifically a method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste. Background Technology

[0002] With the development of industrialization, the efficient and clean disposal of nickel-containing hazardous waste and solid waste, including resource recovery, harmlessness, and the recycling of valuable metals, has become a key focus of the industry. Such copper- and nickel-containing hazardous wastes are typically rich in valuable metals such as copper, nickel, zinc, and lead, comparable to high-grade ores, and possess high recycling value. Currently, the oxygen-enriched side-blown smelting and submerged combustion technology for treating nickel-containing hazardous waste and extracting valuable metals has become an important technical approach due to its strong adaptability and high processing efficiency. This technology not only reduces the environmental risks caused by improper disposal of copper-containing hazardous waste but also obtains economically valuable raw materials, realizing the transformation from resource advantage to value advantage.

[0003] However, due to the wide range of sources and complex composition of nickel-containing hazardous waste and solid waste, the raw materials often contain high levels of harmful elements such as fluorine and chlorine, posing a severe challenge to the treatment of smelting tail gas. Existing conventional flue gas treatment processes typically focus on the removal of particulate matter and sulfur dioxide, often lacking targeted separation methods for halogen elements such as fluorine and chlorine.

[0004] Traditional desulfurization processes often employ a single alkaline absorbent for mixed removal, leading to the simultaneous reaction of hydrogen fluoride and hydrogen chloride to form complex mixed fluorine-chlorine calcium salts. These mixed salts are difficult to separate effectively using conventional physical methods, making them unsuitable for direct industrial use. Ultimately, they must be disposed of as hazardous waste in landfills, wasting fluorine and chlorine resources and increasing environmental disposal costs for enterprises. Furthermore, high concentrations of fluorine and chlorine impurities in flue gas, if not effectively removed upstream, can pose corrosion and catalyst poisoning risks to subsequent acid production systems using high-sulfur flue gas, impacting the quality of sulfur dioxide recovery. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste. This method solves the technical problem that fluorine and chlorine pollutants in smelting flue gas from complex nickel-containing waste are difficult to separate effectively, resulting in the deacidification byproduct being a mixed salt that cannot be utilized as a resource.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste, comprising the following steps: recovering waste heat and rapidly cooling the flue gas generated from oxygen-enriched side-blown smelting of nickel-containing waste; sending the rapidly cooled flue gas into a dry desulfurization tower, injecting coarse-particle calcium hydroxide powder into the tower, and conducting a defluorination reaction in a first temperature range to generate defluorination products for resource recovery; the flue gas after the reaction undergoes solid-gas separation via an electrostatic precipitator to collect fluorine-containing dust; sending the flue gas after solid-gas separation into a semi-dry desulfurization tower, injecting fine-particle calcium hydroxide powder into the tower, and conducting a dechlorination reaction in a second temperature range; collecting the dechlorination slag discharged from the bottom of the tower for resource recovery; the second temperature range is lower than the first temperature range, and the mesh size of the fine-particle calcium hydroxide powder is higher than that of the coarse-particle calcium hydroxide powder; the flue gas treated by the semi-dry desulfurization tower is then discharged after sequentially undergoing denitrification, wet scrubbing, and ion-liquid desulfurization treatment.

[0007] By employing the above technical solution, a stepwise deacidification process coupling temperature gradient and absorbent particle size gradient was used to achieve the separation and directional enrichment of hydrogen fluoride and hydrogen chloride. The specific mechanism is as follows: First, preliminary separation is achieved by utilizing the difference in reaction thermodynamics and temperature control. Within the first temperature range set in the dry deacidification tower, the reactivity of calcium hydroxide with hydrogen fluoride is higher than that of hydrogen chloride. The higher temperature environment promotes the chemical reaction between calcium hydroxide and hydrogen fluoride to produce calcium fluoride and water; while the adsorption and reaction of hydrogen chloride are relatively inhibited at this temperature, causing most of the hydrogen chloride to penetrate the first-stage reaction zone in gaseous form.

[0008] Secondly, the separation effect is enhanced by utilizing differences in reaction kinetics and diffusion mechanisms. In the first-stage reaction, coarse-particle calcium hydroxide powder is used. Taking advantage of the small size and high electronegativity of hydrogen fluoride molecules, they preferentially undergo chemical adsorption on the surface of the coarse-particle calcium hydroxide, forming a dense calcium fluoride product layer. This dense product layer hinders the diffusion of hydrogen chloride molecules into the interior of the calcium hydroxide particles, limiting the conversion of hydrogen chloride. In contrast, in the second-stage reaction, fine-particle calcium hydroxide microparticles are used. This increases the specific surface area of ​​the gas-solid contact and reduces the internal diffusion resistance, allowing the hydrogen chloride not captured in the first stage to be fully absorbed by the calcium hydroxide microparticles in a lower second temperature range, reacting to form calcium chloride and water.

[0009] Finally, the electrostatic precipitator installed in the middle blocked the path of solid calcium fluoride into the subsequent process in the gas phase route, preventing the physical mixing of fluorine and chlorine byproducts, and ensuring that the defluorination product is mainly calcium fluoride and the dechlorination residue is mainly calcium chloride, thus providing the basic conditions for subsequent fractional resource utilization.

[0010] Preferably, the first temperature range in the dry deacidification tower is controlled at 180°C to 200°C, and the fineness of the coarse calcium hydroxide powder is 200 to 300 mesh; the second temperature range in the semi-dry deacidification tower is controlled at 160°C to 180°C, and the fineness of the fine calcium hydroxide powder is above 800 mesh.

[0011] By adopting the above technical solution, the process window for achieving fluoride-chlorine separation was defined. When the temperature is controlled above 180℃ and coarse particles of 200 to 300 mesh are used, a high hydrogen fluoride removal rate can be maintained, while inhibiting the co-reaction of hydrogen chloride. When the temperature is reduced to 160℃ to 180℃ and fine powder of 800 mesh or higher is used, the residual hydrogen chloride and calcium hydroxide can be fully contacted and reacted, reducing the concentration of acidic gases in the final emission gas.

[0012] Preferably, the defluorination product and resource recovery process includes: washing the collected defluorination product by pulping, removing soluble calcium salt impurities by utilizing solubility differences, obtaining refined calcium fluoride after solid-liquid separation; and reacting the refined calcium fluoride with concentrated sulfuric acid at high temperature to prepare hydrofluoric acid and calcium sulfate.

[0013] By employing the above technical solution, utilizing the physical property that calcium fluoride is poorly soluble in water while calcium chloride is readily soluble, a water washing process is used to remove calcium chloride and unreacted calcium hydroxide impurities entrained in the defluorination products, thereby improving the grade of calcium fluoride. The purified calcium fluoride meets the raw material requirements for reacting with concentrated sulfuric acid to prepare hydrofluoric acid, realizing the transformation from hazardous waste to chemical products.

[0014] Preferably, the dechlorination slag and resource utilization treatment step includes: dissolving the dechlorination slag in water and filtering to remove insoluble impurities to obtain a chlorine-containing clear liquid; adding dilute sulfuric acid to the chlorine-containing clear liquid to carry out a metathesis reaction, filtering to separate the precipitate, and then evaporating and concentrating the filtrate to prepare hydrochloric acid.

[0015] By adopting the above technical solution, the dechlorination slag generated by the semi-dry process is recycled. Inert dust impurities in the flue gas are removed by dissolution and filtration, and calcium chloride is converted into hydrochloric acid by metathesis reaction, reducing the accumulation of calcium chloride waste salt and realizing the recycling of chlorine.

[0016] Preferably, the concentration of the dilute sulfuric acid used to react with the chlorine-containing solution is 0.5 to 1.0 mol / L; the filtrate generated from the slurry washing of the defluorination product is recycled for the dissolution step of the dechlorination residue.

[0017] By adopting the above technical solution, the chlorine-containing filtrate generated during the washing process of defluorination products can be directly used in the dissolution process of dechlorination residue, which can recover the dissolved calcium chloride and reduce the consumption of fresh water and wastewater discharge.

[0018] Preferably, the specific method of the rapid cooling treatment is to rapidly cool the flue gas temperature from 550°C to below 220°C within 2 seconds by spraying water, thereby inhibiting the resynthesis of dioxins.

[0019] By adopting the above technical solutions, the flue gas can be quickly avoided from the temperature range of dioxin resynthesis, thus blocking the formation of dioxin-like organic pollutants under chlorine-containing conditions at the source and reducing the end-of-pipe treatment load.

[0020] Preferably, the ionic liquid desulfurization treatment includes: using desulfurization ionic liquid to circulate and spray to absorb sulfur dioxide in flue gas; the rich liquid after absorption saturation enters the desorption tower for heating and regeneration; the desorbed sulfur dioxide gas is used to prepare sulfuric acid and liquid sulfur dioxide; and the regenerated lean liquid is returned to the absorption step for recycling.

[0021] By adopting the above technical solution, the reversible absorption and desorption properties of ionic liquid for sulfur dioxide are utilized to replace the traditional limestone-gypsum method. This process can recover high-concentration sulfur dioxide gas for sulfuric acid production, realizing the utilization of sulfur resources and reducing the generation of desulfurization byproducts.

[0022] Preferably, in the wet scrubbing step, the flue gas temperature at the outlet of the scrubbing tower is controlled to be between 50°C and 90°C; the denitrification step includes SNCR high-temperature denitrification carried out in the waste heat recovery stage and SCR medium-temperature denitrification carried out before wet scrubbing.

[0023] By adopting the above technical solution, a multi-stage pollutant removal unit was constructed. Two-stage denitrification reduced the concentration of nitrogen oxide emissions; wet scrubbing, as a deep purification unit, can capture trace amounts of acidic gases, heavy metals, and dust, ensuring that flue gas emission indicators meet environmental protection requirements.

[0024] Preferably, the nickel-containing waste is pre-processed before smelting: nickel-containing waste dried to a moisture content of 15-20%, quartz sand and fuel coke powder are mixed in a mass ratio of 100:(10 to 20):(3 to 8) to obtain mixed furnace charge.

[0025] By adopting the above technical solutions, the moisture content and proportion of the materials fed into the furnace can be controlled, maintaining the thermal balance and slag stability of the oxygen-enriched side-blown smelting process, providing a relatively stable flue gas source for the subsequent flue gas treatment system, which is conducive to the continuous operation of the system.

[0026] This invention provides a method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste. It offers the following advantages: 1. This invention employs a stepwise deacidification process coupled with temperature gradients and absorbent particle size gradients, solving the technical problem of high impurity content in fluorinated and chlorinated byproducts and difficulty in utilization caused by traditional mixed deacidification methods. In the dry process stage, high temperature combined with coarse-particle calcium hydroxide preferentially solidifies hydrogen fluoride and limits the co-reaction of hydrogen chloride by utilizing reaction kinetic differences. Subsequently, in the semi-dry process stage, low temperature combined with micro-powder absorbent deeply removes hydrogen chloride. This staged control strategy achieves the directional separation and enrichment of fluorine and chlorine elements in the gas phase, increasing the main content of calcium fluoride in the primary byproduct and ensuring sufficient capture of hydrogen chloride in the secondary byproduct, laying a material foundation for subsequent high-value resource recovery.

[0027] 2. This invention establishes a comprehensive resource recovery pathway for fluorine and chlorine byproducts, realizing the transformation from hazardous waste to industrial chemicals. Utilizing the physical properties of calcium fluoride being poorly soluble and calcium chloride being readily soluble, the defluorination products are purified by water washing and prepared into hydrofluoric acid; the dechlorination residue is dissolved and subjected to metathesis reactions to prepare hydrochloric acid. This process route not only reduces the environmental risks and economic costs associated with hazardous waste landfill disposal but also produces marketable hydrofluoric acid and hydrochloric acid products, achieving resource recycling and economic value enhancement in the flue gas treatment process.

[0028] 3. This invention integrates rapid cooling and detoxification, multi-stage denitrification, and ionic liquid desulfurization technologies to ensure deep purification of smelting flue gas with complex components. The rapid cooling process effectively avoids the dioxin resynthesis temperature zone, reducing the risk of organic pollutant emissions at the source. The end-stage uses ionic liquid recycling absorption to replace the traditional limestone-gypsum method, ensuring ultra-low sulfur dioxide emissions while recovering high-concentration sulfur dioxide gas for acid production. This avoids the secondary storage problem of low-value desulfurization gypsum solid waste and meets increasingly stringent environmental emission standards. Attached Figure Description

[0029] Figure 1 shows the overall process flow of the method for cleaning and comprehensive utilization of smelting flue gas from complex nickel-containing waste according to the present invention. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, comparative examples, and test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Preparation Example 1: This preparation example provides a method for preparing a nickel-containing hazardous and solid waste mixed charge for oxygen-enriched side-blown smelting, comprising the following steps: feeding the nickel-containing hazardous and solid waste raw materials into a drying kiln for dehydration treatment, controlling the moisture content of the dried material to be 15%; precisely batching the dried nickel-containing hazardous and solid waste raw materials, auxiliary material quartz sand, and fuel coke powder at a mass ratio of 100:15:5 using a quantitative feeder; after the batched materials are evenly mixed by a mixing and conveying system, they are conveyed to the top charge silo of the oxygen-enriched side-blown smelting furnace for later use.

[0032] Examples 1-3: Examples

[0033] Referring to Figure 1, this embodiment provides a method for cleaning and comprehensive utilization of smelting flue gas from complex nickel-containing waste, including the following steps: the mixed furnace charge obtained in Preparation Example 1 is continuously added into an oxygen-enriched side-blown smelting furnace via a conveyor belt, while natural gas and oxygen-enriched air are injected into the furnace through multiple spray guns immersed in the molten pool, the oxygen concentration in the oxygen-enriched air is controlled at 75%, the temperature of the molten pool is controlled at 1300°C, the high-temperature smelting slag and low-grade nickel matte molten material generated during the smelting process are periodically discharged from the slag outlet and copper outlet, respectively, and the generated high-temperature dust-containing flue gas is sent to the flue gas treatment system.

[0034] High-temperature dusty flue gas enters a waste heat boiler to recover waste heat. In the middle of the waste heat boiler, ammonia water with a concentration of 25% is injected into the area with a temperature of 950℃ to carry out SNCR high-temperature denitrification. After the flue gas is recovered from waste heat, the outlet temperature drops to 550℃.

[0035] The flue gas then enters a quench tower, where the temperature is rapidly cooled to 220°C within 2 seconds by water atomization to inhibit the resynthesis of dioxins. The quenched flue gas then enters a dry desulfurization tower, where 200-300 mesh calcium hydroxide powder is sprayed into the tower. The reaction temperature inside the tower is controlled at 190°C. Taking advantage of the preferential reaction of calcium hydroxide with hydrogen fluoride under these temperature and humidity conditions, fluorine in the flue gas is removed, and defluorination products are generated and collected. The solid particles generated are discharged with the flue gas.

[0036] The flue gas enters an electrostatic precipitator for solid-gas separation, with the dust removal temperature controlled at 180℃. The collected defluorination products are used as raw materials for fluorine resource recovery. The flue gas after dust removal enters a semi-dry deacidification tower, where 800-mesh calcium hydroxide powder and water mist are injected into the tower, and the reaction temperature inside the tower is controlled at 170℃. Under these conditions, hydrogen chloride in the flue gas is primarily removed. The dechlorination residue collected at the bottom of the tower is used as raw material for chlorine resource recovery. The semi-dry deacidification tower is equipped with a venturi dust collector to further filter dust in the flue gas.

[0037] After being dechlorinated by the semi-dry method, the flue gas is heated by the RTO heat exchanger and then enters the SCR reactor for medium-temperature denitrification. Subsequently, it enters the high-efficiency scrubbing tower, where residual hydrogen bromide, trace amounts of hydrogen fluoride, hydrogen chloride, heavy metals, and dust are further removed by scrubbing liquid spraying. The flue gas temperature at the outlet of the scrubbing tower is controlled at 70℃ (±5-10℃).

[0038] Clean flue gas enters the desulfurization absorption tower, where sulfur dioxide is absorbed by circulating desulfurization ionic liquid. The sulfur dioxide concentration in the purified flue gas is below 35 mg / Nm3, and it is discharged through the chimney in compliance with standards. The rich liquid that has absorbed sulfur dioxide enters the desorption tower for heating and regeneration. The high-concentration sulfur dioxide gas desorbed is sent to the acid production workshop to produce sulfuric acid, and the regenerated lean liquid is returned to the absorption tower for recycling.

[0039] For data on the separation efficiency of fluorine and chlorine, final emission indicators, and resource recovery rate throughout the entire process of this embodiment, please refer to the relevant tables in the test examples. Example

[0040] This embodiment provides a method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste, including the following steps: Deep resource utilization of fluorine-containing and chlorine-containing byproducts collected separately during the process of Example 1. The defluorinated product collected by the dry deacidification tower in Example 1 is sent to a water washing tank, and clean water is added for slurry washing. Utilizing the characteristic that calcium chloride is easily soluble in water while calcium fluoride is poorly soluble in water, soluble impurities such as calcium chloride carried in the dust are dissolved and removed. The washed slurry is filtered, washed, and dried by a filter press to obtain purified calcium fluoride. The changes in composition before and after water washing and purification are shown in Test Example 1. The purified calcium fluoride is sent to a rotary reactor, and concentrated sulfuric acid with a mass fraction of 98% is added. The reaction is carried out at 250°C to generate hydrogen fluoride gas and calcium sulfate. The generated hydrogen fluoride gas is condensed and distilled to obtain hydrofluoric acid product.

[0041] The dechlorination residue discharged from the bottom of the semi-dry deacidification tower in Example 1 was sent to a dissolving tank, where water was added and stirred to fully dissolve the calcium chloride. After filtration to remove insoluble impurities, a clear calcium chloride solution was obtained. This solution was pumped into a reaction vessel, where 0.5 mol / L dilute sulfuric acid was added to initiate a metathesis reaction, producing calcium sulfate precipitate and dilute hydrochloric acid. The reaction slurry was filtered to separate the calcium sulfate byproduct, and the filtrate was concentrated using an evaporation and concentration system to obtain the hydrochloric acid product. Example

[0042] This embodiment provides a method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste, including the following steps: This embodiment adjusts some process parameters based on Embodiment 1, while the rest of the process remains the same as in Embodiment 1.

[0043] The mixed charge prepared in Example 1 was added to an oxygen-enriched side-blown smelting furnace, with the oxygen concentration in the oxygen-enriched air controlled at 80% and the smelting temperature controlled at 1350℃. After the smelting flue gas underwent waste heat recovery in a waste heat boiler and SNCR denitrification, it was cooled to 220℃ by water atomization in a quenching tower.

[0044] The flue gas then enters a dry desulfurization tower, where 200-mesh calcium hydroxide powder is injected. The reaction temperature inside the tower is controlled at 180°C, at which temperature hydrogen fluoride in the flue gas is preferentially removed. Dust is collected by an electrostatic precipitator at 180°C. The dust-removed flue gas then enters a semi-dry desulfurization tower, where 800-mesh calcium hydroxide powder is injected. The reaction temperature inside the tower is controlled at 160°C for further removal of hydrogen chloride.

[0045] The purified flue gas is sequentially subjected to SCR denitrification, high-efficiency scrubbing tower washing, and ionic liquid circulation absorption desulfurization before being discharged in compliance with standards. In the subsequent resource utilization treatment of by-products, the calcium chloride clear liquid obtained by dissolving the dechlorination slag is subjected to a metathesis reaction with 1.0 mol / L dilute sulfuric acid to recover hydrochloric acid. For the overall treatment effect and various emission indicators, please refer to the test example.

[0046] Comparative Examples 1-2: Comparative Example 1: Compared with Example 1, the difference is that the separate treatment steps of dry defluorination and semi-dry dechlorination were eliminated, and instead, combined deacidification was performed. The specific operation is as follows: After the flue gas is cooled by water atomization in the quench tower, it directly enters the semi-dry deacidification tower. Commercially available 325-mesh calcium hydroxide powder is injected into the tower, and the reaction temperature is controlled at 160°C. At the same time, fluorine and chlorine in the flue gas are removed. The collected solid product is a mixed salt of calcium fluoride and calcium chloride. The remaining steps and parameters are the same as in Example 1.

[0047] Comparative Example 2: Compared with Example 1, the difference lies in the change of the particle size of calcium hydroxide used in the dry and semi-dry processes. Specifically, 800-mesh calcium hydroxide powder is sprayed into the dry deacidification tower, and 200-300-mesh calcium hydroxide powder is sprayed into the semi-dry deacidification tower. The remaining process steps and parameters are the same as in Example 1.

[0048] Test Examples 1-4: Test Example 1: This test example aims to verify the actual effect of the process of the present invention on the deep purification and resource utilization of dry defluorination by-products. The defluorination residue discharged from the bottom of the dry desulfurization tower during continuous operation in Example 1 was selected as raw material, and water washing, pressure filtration, and drying tests were conducted according to the resource utilization process of Example 2. To verify the adaptability of the process, defluorination residue samples (batch 1 and batch 2) from two different production periods were selected for testing.

[0049] The experimental steps are as follows: Two batches of solid powder samples were collected from the ash discharge port of the dry desulfurization tower and labeled as batch 1 defluorination residue and batch 2 defluorination residue, respectively. After mixing and reducing, 1000g of each sample was taken as the original sample to be tested.

[0050] The original sample to be tested was placed in a slurry tank equipped with a stirring device, and room temperature water was added for slurry washing. The liquid-solid mass ratio was controlled at 4:1, the stirring speed was set to 300 r / min, and stirring was continued for 45 minutes. The difference in solubility of calcium chloride, calcium hydroxide and calcium fluoride in water was used to transfer the easily soluble components in the material to the liquid phase.

[0051] The slurry is pumped into a plate and frame filter press for solid-liquid separation. The filtrate is discharged into a collection system. The filter cake is kept under pressure in the filter press and rinsed with clean water equivalent to twice the volume of the filter cake to replace the residual mother liquor in the pores of the filter cake.

[0052] The washed filter cake was removed and placed in a forced-air drying oven, where it was dried to constant weight at 105°C to obtain the purified solid product, which was labeled as CaF2 product of batch 1 and CaF2 product of batch 2, respectively.

[0053] Chemical titration combined with X-ray fluorescence spectroscopy was used to perform full elemental quantitative analysis on the samples before and after treatment, and the mass percentage of each major component was determined.

[0054] The specific component data obtained from the experiment are shown in the table below: Table 1. Component analysis of dry defluorination byproducts before and after water washing and purification

[0055] Conclusion: Based on the data analysis in Table 1, the high-temperature dry coarse desulfurization and water washing deep refining process adopted in this invention achieves efficient enrichment of fluorine resources and effective separation of chlorine impurities.

[0056] From the perspective of compositional changes, the washing process removes calcium chloride and unreacted calcium hydroxide from the material. In batch 1, the calcium chloride content decreased from 11.10% to 2.89%, and the calcium hydroxide content decreased from 13.00% to 2.57%, resulting in an increase in the main grade of calcium fluoride from 69.18% to 87.36%. In batch 2, where operating conditions fluctuated significantly and raw material quality was poor, although the initial defluorination residue contained as much as 21.30% calcium chloride and 21.82% calcium hydroxide, resulting in an initial calcium fluoride content of only 46.97%, after treatment with this process, the calcium chloride content was still reduced to 3.69%, and the calcium fluoride grade increased to 81.12%.

[0057] This result confirms that by utilizing the physicochemical properties of calcium fluoride being poorly soluble in water while calcium chloride and calcium hydroxide are readily soluble or slightly soluble, slurry washing can effectively solve the problem of insufficient purity of byproducts caused by the selectivity limitations of heterogeneous reactions during dry deacidification. It also eliminates the potential for equipment corrosion and product contamination due to the presence of chloride ions during the subsequent reaction of calcium fluoride with concentrated sulfuric acid to produce hydrofluoric acid. The purified product grade is consistently above 80%, meeting the raw material requirements for subsequent resource utilization, indicating that the process has strong raw material adaptability and engineering applicability.

[0058] Test Example 2: This test example aims to verify the selective separation effect of the dry desulfurization system in Example 1 on hydrogen fluoride and hydrogen chloride, as well as the final recovery efficiency of fluorine and chlorine resources in the entire process. The experiment selected 72 hours of continuous and stable system operation as the monitoring period, and the chemical reaction selectivity of the multi-stage desulfurization process was examined through material balance.

[0059] The experimental steps are as follows: A flue gas sampling point is set up in the inlet pipe section of the dry desulfurization tower. A high-temperature corrosion-resistant flue gas flow meter is used to continuously monitor and calculate the total mass flow rate of hydrogen fluoride and hydrogen chloride gas entering the system, which serves as the input benchmark for material balance.

[0060] The solid byproduct (crude calcium fluoride) discharged from the bottom of the dry desulfurization tower was continuously sampled and weighed. The chloride ion content in the sample was determined by ion chromatography. The mass of chlorine element fixed by reaction in the dry defluorination step was calculated in combination with the total ash discharge, and then the chlorine removal rate (i.e. chlorine false capture rate) of this step was obtained.

[0061] The output data of the subsequent semi-dry dechlorination system and resource recovery unit are statistically analyzed, including the weight of the final refined calcium fluoride product and the total amount of recovered calcium chloride (or equivalent hydrochloric acid). Combined with the product purity analysis results, the fluorine resource recovery rate and chlorine resource recovery rate of the entire process are calculated.

[0062] By summarizing the monitoring data and comparing the gas phase input and solid / liquid phase recovery, the actual regulatory effect of temperature gradient and absorbent particle size difference on halogen separation was verified.

[0063] The experimental data are summarized in the table below: Table 2. Statistics on Fluorine-Chlorine Separation Efficiency and Resource Recovery Rate

[0064] Conclusion: Based on the data analysis in Table 2, the temperature and particle size dual-gradient stepwise deacidification process constructed in this invention achieves efficient separation and targeted recovery of fluorine and chlorine components in the gas phase.

[0065] Data shows that the chlorine removal rate in the defluorination step was only 5.56%, indicating that within the temperature range of 180℃-200℃, and with calcium hydroxide powder of 200-300 mesh size, the gas-solid reaction exhibited high kinetic selectivity. The vast majority of hydrogen chloride gas did not react within the dry defluorination tower, but successfully penetrated this stage into the subsequent semi-dry dechlorination system. This data confirms that by controlling the reaction temperature slightly above the hygroscopic reaction range of calcium chloride, and simultaneously using a coarse-particle absorbent to limit the diffusion rate, the competitive reaction between calcium hydroxide and hydrogen chloride can be effectively suppressed, thus ensuring that the dry stage primarily captures hydrogen fluoride.

[0066] Meanwhile, the fluorine recovery rate in the byproduct calcium fluoride reached 94.20%, and the chlorine recovery rate in the byproduct chlorine-containing products reached 98.50%. This indicates that despite the segmented treatment strategy, the system's overall halogen resource capture capacity was not compromised. Fluorine was concentrated and fixed in the dry ash, and subsequently purified into high-quality calcium fluoride; chlorine was efficiently intercepted and converted into calcium chloride or hydrochloric acid products mainly in the semi-dry process section. This process layout, while solving the corrosive problem of complex nickel-containing flue gas, transforms the originally difficult-to-separate mixed waste gas into two independent chemical raw materials, verifying the advantages of the technical solution in resource utilization.

[0067] Test Example 3: This test example aims to compare and verify the differences between the process method of Example 1 of the present invention and Comparative Example 1 (combined deacidification) and Comparative Example 2 (interchangeable absorbent particle size) in terms of pollutant removal efficiency and by-product resource utilization quality. The experiment was conducted on the same pilot-scale simulation platform, keeping the flue gas flow rate, initial temperature, and pollutant inlet concentration consistent for each group of experiments, and running continuously for 48 hours.

[0068] The experimental steps are as follows: The operating modes of the deacidification system were adjusted sequentially according to the process conditions set in Example 1, Comparative Example 1, and Comparative Example 2. Example 1 used a high-temperature coarse particle dry defluorination method combined with a medium-temperature micro-powder semi-dry dechlorination method; Comparative Example 1 used a medium-temperature conventional powder one-step deacidification method; and Comparative Example 2 used a high-temperature micro-powder dry method combined with a medium-temperature coarse particle semi-dry method.

[0069] The actual flue gas generated by the oxygen-enriched side-blown smelting furnace is introduced into the system, and the inlet flue gas volume is controlled at 45,000 Nm3 / h. The concentrations of the main pollutants at the inlet are maintained at: hydrogen fluoride 850 mg / Nm3, hydrogen chloride 6,500 mg / Nm3, and sulfur dioxide 68,000 mg / Nm3.

[0070] During the operation of each group of experiments, the pollutant concentration at the system terminal exhaust outlet was detected every 4 hours; at the same time, solid by-product samples were collected at the bottom of the dry deacidification tower (or the mixed deacidification tower of Comparative Example 1).

[0071] Chemical composition analysis was performed on the collected solid byproducts, focusing on determining the main content of calcium fluoride and the content of calcium chloride impurities, in order to assess the purity of the byproducts and the difficulty of subsequent resource utilization.

[0072] Record the hydrogen chloride concentration at the outlet of the semi-dry deacidification tower (or the mixed tower of Comparative Example 1) in each group of experiments to verify the emission compliance capacity under different process conditions.

[0073] The experimental data are summarized in the table below: Table 3. Comparison of purification effects and by-product quality under different process conditions

[0074] Conclusion: Based on the data analysis in Table 3, the specific process parameters used in Example 1 of this invention are superior to the comparative example in terms of resource utilization quality and emission control.

[0075] Comparing Example 1 with Comparative Example 1, it can be seen that although the one-step combined treatment method, which eliminates the stepwise deacidification, can barely maintain the standard emission of hydrogen chloride, the solid byproducts produced contain as much as 42.60% calcium chloride and only 35.40% calcium fluoride. This mixture of high-chlorine salts is difficult to separate from fluorine and chlorine, making it unsuitable as a raw material for producing hydrofluoric acid and thus losing its resource value. This verifies that stepwise treatment is a prerequisite for resource recovery.

[0076] Comparing Example 1 and Comparative Example 2, it can be seen that relying solely on the temperature gradient while ignoring absorbent particle size matching leads to a severe decline in system performance. When 800-mesh micro-powder is used in the high-temperature dry process section, the reaction kinetic barrier disappears due to the excessively large specific surface area, resulting in a large amount of hydrogen chloride reacting non-selectively with calcium hydroxide at this stage. This causes the calcium chloride impurity in the byproduct to surge to 18.50%, destroying the fluorine-chlorine separation effect. Simultaneously, using 200-mesh coarse particles in the semi-dry process section results in insufficient reactivity, failing to deeply remove the remaining hydrogen chloride, leading to a final emission concentration as high as 115.4 mg / Nm3, exceeding the emission standard of 50 mg / Nm3.

[0077] In summary, this invention, through an innovative setup of 180-200℃ high temperature combined with 200-300 mesh coarse particles, successfully constructs a selective window for fluorine-chlorine separation by utilizing the differences in gas-solid reaction kinetics and thermodynamics. This not only ensures the high-purity resource utilization of by-products but also guarantees high-standard emissions compliance of exhaust gases, demonstrating the scientific nature and irreplaceable nature of the process parameter combination.

[0078] Test Example 4: This test example aims to verify the comprehensive purification performance and resource conversion efficiency of the process system in Example 1 under long-term operation conditions for smelting flue gas containing complex nickel-containing hazardous and solid waste. The focus is on evaluating the system's resilience to drastic changes in inlet pollutant concentration caused by fluctuations in raw material composition, as well as the final resource recovery indicators.

[0079] The experimental steps are as follows: 168 hours of continuous and stable production of the oxygen-enriched side-blown smelting pool system was selected as the monitoring period. This period covered the time period of high sulfur and high chlorine raw material ratio in order to test the system's ultimate processing capacity.

[0080] A raw flue gas sampling point is set at the outlet of the waste heat boiler, and a clean flue gas sampling point is set at the outlet of the ion liquid desulfurization tower (before the emission chimney). A high-temperature corrosion-resistant flue gas flow meter and an online continuous flue gas monitoring system are installed.

[0081] For sulfur dioxide, non-dispersive infrared absorption spectrometry was used for continuous monitoring. For hydrogen fluoride, hydrogen chloride, and hydrogen bromide, isokinetic sampling tubes combined with condensation absorption spectrometry were used for collection, followed by quantitative analysis using ion chromatography. The sampling frequency was set to once every 4 hours, and the concentration fluctuation range and weighted average value were recorded within the monitoring period.

[0082] The quantities of crude calcium fluoride powder produced by the dry desulfurization system after water washing and purification, and the quantities of dechlorination slag produced by the semi-dry desulfurization system after resource recovery treatment are simultaneously measured within this cycle. Based on the flue gas flow integral data and raw material input, the removal rate of gaseous pollutants and the resource recovery rate of fluorine and chlorine are calculated according to the material balance principle.

[0083] The experimental data are summarized in the table below: Table 4. Statistical Table of System Comprehensive Purification Performance and Resource Recovery Indicators

[0084] Note: — indicates that this indicator is not applicable to solid products or there is no corresponding gas phase concentration limit.

[0085] Conclusion: Based on the data analysis in Table 4, the combined process of oxygen-enriched side-blown smelting, staged deacidification, and ionic liquid desulfurization of the present invention demonstrates excellent stability and resource utilization in treating complex nickel-containing hazardous waste flue gas.

[0086] Deep purification and resistance to fluctuations: Monitoring data shows that the inlet flue gas is highly corrosive and volatile, with SO2 concentrations fluctuating between 50,000 and 97,000 mg / Nm3, and HCl concentrations reaching a maximum of 12,000 mg / Nm3. After treatment by this system, the SO2 outlet concentration stabilized at 22.0 mg / Nm3, far below the ultra-low emission standard of 35 mg / Nm3; the outlet concentrations of HF and HCl were 8.4 mg / Nm3 and 28.6 mg / Nm3, respectively, both exceeding the national hazardous waste incineration pollution control standards. This confirms the multi-stage barrier effect of the process, including quenching, dry, semi-dry, and wet methods. Through the tiered configuration of absorbents with different temperature ranges and particle sizes, the impact of high-concentration acidic gases was effectively mitigated, ensuring long-term compliance with end-emission standards.

[0087] Resource recovery indicator verification: The data highly matches the technical indicators in the disclosure document. The resource recovery rate of calcium fluoride in the system reaches 98.85%, and the resource recovery rate of calcium chloride reaches 98.50%. This indicates that the system not only achieves a gas-phase removal rate of over 99% for HF and HCl, but more importantly, through high-temperature selective defluorination in the dry section and subsequent water washing and refining process, the captured halogen elements are efficiently converted into high-purity by-products, rather than simply transferred to the waste residue. In particular, for sulfur resources, sulfuric acid or liquid SO2 is produced through ionic liquid desorption, coupled with a removal rate as high as 99.9%, achieving full-scale resource recovery of F, Cl, and S elements. This verifies that this solution not only solves the problem of treating nickel-containing hazardous waste smelting flue gas, but also possesses circular economy benefits.

Claims

1. A method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste, characterized in that, Includes the following steps: The flue gas generated from the oxygen-enriched side-blown smelting of nickel-containing waste undergoes waste heat recovery and rapid cooling. The rapidly cooled flue gas is then fed into a dry desulfurization tower, where coarse-particle calcium hydroxide powder is injected. A defluorination reaction occurs in the first temperature zone, generating defluorination products which are then recycled. The resulting flue gas undergoes solid-gas separation via an electrostatic precipitator to collect fluorine-containing dust. The electrostatic precipitator then sends the solid-gas separated flue gas into a semi-dry desulfurization tower, where fine-particle calcium hydroxide powder is injected. A dechlorination reaction occurs in the second temperature zone, and the dechlorination slag discharged from the bottom of the tower is collected and recycled. The second temperature zone is lower than the first temperature zone, and the fine-particle calcium hydroxide powder has a higher mesh size than the coarse-particle calcium hydroxide powder. The flue gas treated in the semi-dry desulfurization tower is then successively treated for denitrification, wet scrubbing, and ionic liquid desulfurization before being discharged.

2. The method for clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste as described in claim 1, characterized in that, The first temperature range in the dry deacidification tower is controlled at 180℃-200℃, and the fineness of the coarse-particle calcium hydroxide powder is 200-300 mesh; the semi-dry deacidification tower is equipped with a Venturi dust collector, and the second temperature range in the semi-dry deacidification tower is controlled at 160℃-180℃, and the fine-particle calcium hydroxide powder has a fineness of 800 mesh or more.

3. The method for clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste as described in claim 1, characterized in that, The defluorination product and resource utilization process includes: washing the collected defluorination product by pulping, removing soluble calcium salt impurities by utilizing solubility differences, and obtaining refined calcium fluoride after solid-liquid separation; reacting the refined calcium fluoride with concentrated sulfuric acid at high temperature to prepare hydrofluoric acid and calcium sulfate.

4. The method for clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste as described in claim 3, characterized in that, The dechlorination slag and resource utilization treatment steps include: dissolving the dechlorination slag in water and filtering to remove insoluble impurities to obtain a chlorine-containing clear liquid; adding dilute sulfuric acid to the chlorine-containing clear liquid to carry out a metathesis reaction, filtering to separate the precipitate, and then evaporating and concentrating the filtrate to prepare hydrochloric acid.

5. The method for clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste as described in claim 4, characterized in that, The concentration of dilute sulfuric acid used to react with the chlorine-containing solution is 0.5-1.0 mol / L; the filtrate generated from the pulping and washing of the defluorination product is recycled for the dissolution step of the dechlorination residue.

6. The method for clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste as described in claim 1, characterized in that, The specific method of the rapid cooling treatment is as follows: the flue gas temperature is rapidly cooled from 550°C to below 220°C within 2 seconds by water spraying, thereby inhibiting the resynthesis of dioxins.

7. A method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste as described in claim 1, characterized in that, The ionic liquid desulfurization treatment includes: using desulfurization ionic liquid to circulate and spray to absorb sulfur dioxide in flue gas; the rich liquid after absorption saturation enters the desorption tower for heating and regeneration; the desorbed sulfur dioxide gas is used to prepare sulfuric acid and liquid sulfur dioxide; and the regenerated lean liquid is returned to the absorption step for recycling.

8. The method for clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste as described in claim 1, characterized in that, In the wet scrubbing step, the flue gas temperature at the outlet of the scrubbing tower is controlled at 50℃-90℃; the denitrification step includes SNCR high-temperature denitrification carried out in the waste heat recovery stage and SCR medium-temperature denitrification carried out before wet scrubbing.

9. A method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste as described in claim 1, characterized in that, During the oxygen-enriched side-blown smelting process, the oxygen concentration in the oxygen-enriched air injected by the spray gun is controlled to be 75%-80%, and the temperature of the molten pool is controlled to be 1300℃-1350℃.

10. A method for the clean and comprehensive utilization of smelting flue gas from complex nickel-containing waste as described in claim 1, characterized in that, The nickel-containing waste is pre-processed before smelting: the nickel-containing waste dried to a moisture content of 15-20%, quartz sand and fuel coke powder are mixed in a mass ratio of 100:(10-20):(3-8) to obtain mixed furnace charge.

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