Method for efficient deamination and recycling of ammonia-containing calcium slag

Abstract

The present application belongs to the technical field of solid waste treatment, and particularly relates to a method for efficient ammonia removal and recycling of ammonia-containing calcium residue. The method comprises the following steps: S1, preheating and ammonia removal: using calcination flue gas to preheat the ammonia-containing calcium residue, so that free ammonia is converted from liquid state to gaseous state and removed, obtaining ammonia-removed calcium residue and ammonia-containing gas; S2, water cooling and absorption: cooling and condensing the ammonia-containing gas into ammonia water through a heat exchanger, and returning the ammonia water to preparation of a tungsten smelting desorbent; S3, calcination conversion: calcining and converting the ammonia-removed calcium residue into quicklime; S4, pH value adjustment: using the prepared quicklime to adjust the pH value of ammonia-containing wastewater, and returning the ammonia-containing calcium residue after pressure filtration to step S1 for recycling. The method realizes efficient removal and resource recycling of ammonia in the ammonia-containing calcium residue, and converts the calcium residue into quicklime, thereby constructing a closed recycling path, solving the common problem of difficult disposal and utilization of the ammonia-containing calcium residue, and having the advantages of energy saving and environmental protection, low cost, simple operation, etc.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment and relates to a method for efficient ammonia removal and recycling of ammonia-containing calcium slag. Background Technology

[0002] Tungsten smelting processes generate large quantities of complex ammonia nitrogen wastewater. Treating this type of wastewater is costly and difficult, severely hindering the industry's green and high-quality development. To address the disposal of this ammonia-containing wastewater, researchers have developed processes such as stripping, distillation, and chemical oxidation. Chemical oxidation typically uses calcium perchlorate, sodium hypochlorite, or chlorine as oxidants to remove ammonia nitrogen (removal principle: 2NH3 + 3NaClO → N2↑ + 3H2O + 3NaCl). However, this method consumes large amounts of oxidants and easily releases toxic gases (such as chlorine) on-site, making it difficult to meet production safety and environmental protection requirements. Both stripping and distillation require the addition of liquid alkali to adjust the pH, making the ammonia nitrogen wastewater alkaline (the purpose being to remove NH4+ from the wastewater). + The ammonia nitrogen is converted into easily removable free ammonia (NH3·H2O) and then removed by air stripping or steam heating. This type of process is highly efficient when treating high-concentration, single-component ammonia nitrogen wastewater, but when treating wastewater with complex components and variable ammonia nitrogen concentrations, the consumption of liquid alkali is extremely high, resulting in high costs and making continuous operation difficult.

[0003] To further reduce the treatment cost of ammonia nitrogen wastewater, researchers developed a process involving adjusting the pH value with quicklime (calcium oxide) (replacing liquid alkali for pH adjustment), followed by stripping or distillation to remove ammonia from complex ammonia nitrogen wastewater. (Removal principle: NH4) + +OH - The process of adjusting pH using calcium oxide (NH3·H2O→NH3↑+H2O) simultaneously produces high-quality ammonia water, significantly reducing disposal costs. However, this process generates a large amount of calcium hydroxide slag (200-800 kg of slag is produced for every ton of calcium oxide used to adjust pH, with fluctuations depending on the final pH setting). This slag contains residual ammonia. Stockpiling this slag not only occupies significant land resources but also poses a risk of leakage and migration of the residual ammonia, severely impacting the environment. Direct roasting of the ammonia-containing calcium slag is energy-intensive, and the mixing of ammonia with high-temperature furnace gas makes treatment extremely difficult, hindering the resource utilization of the ammonia. Therefore, achieving efficient ammonia removal and recycling of ammonia-containing calcium slag is a pressing issue that needs to be addressed. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for efficient deammoniation and recycling of ammonia-containing calcium slag.

[0005] To solve the above technical problems, the embodiment of the present application provides a kind of method for efficient deamination and recycling of ammonia-containing calcium residue, and the steps are as follows:

[0006] S1, preheating deamination: the ammonia-containing calcium residue is put into the drying box, and then the calcination flue gas is introduced into the heat exchange fin provided in the drying box to heat the heat exchange fin, thereby preheating the ammonia-containing calcium residue, so that the free ammonia remaining in the ammonia-containing calcium residue is quickly converted from liquid to gas during the preheating process, thereby realizing the removal of free ammonia. After preheating and deamination treatment is completed, ammonia-depleted calcium residue and ammonia-containing gas are obtained.

[0007] S2, water-cooled absorption: the ammonia-containing gas in step S1 is introduced into the heat exchanger, and the circulating tap water is used for heat exchange cooling. The ammonia in the ammonia-containing gas is condensed into liquid ammonia water, realizing the absorption of ammonia in the ammonia-containing gas. The prepared ammonia water is collected and returned to the tungsten smelting desorbent preparation link for secondary utilization. The gas after absorbing ammonia is introduced into the primary spray tower and is absorbed by dilute sulfuric acid after primary spraying. The standard gas is directly discharged.

[0008] S3, calcination conversion: the ammonia-depleted calcium residue in step S1 is put into a rotary furnace for calcination conversion treatment. After calcination is completed, the obtained raw lime is collected.

[0009] S4, pH value adjustment: the raw lime obtained in step S3 is used to adjust the pH value of the ammonia-containing wastewater in tungsten smelting. The raw lime is gradually added to the ammonia-containing wastewater in tungsten smelting, and stirred for 1h-2h for sufficient mixing. The end point control of the pH value of the ammonia-containing wastewater is 11.5-13.5. The slurry with adjusted pH value is first filtered by using a sealed plate and frame filter press. The obtained filtrate is introduced into a distillation column for deamination. The standard wastewater after deamination is collected and discharged. The filter residue is ammonia-containing calcium residue, which is returned to step S1 for treatment.

[0010] As some embodiments of the present application, in step S1, the temperature of the calcination flue gas for preheating deamination is controlled to be 80℃-220℃, and the preheating treatment time is 30min-120min.

[0011] As some embodiments of the present application, in step S1, the standard judgment for preheating deamination is that the ammonia-depleted calcium residue is sampled, sulfuric acid leaching is carried out, the leaching liquid solid ratio is 5:1 (L / g), the leaching time is 2h, the acid concentration of the sulfuric acid leaching reaction end point is controlled to be 0.5mol / L-1.0mol / L, and then the ammonia nitrogen in the leaching liquid is analyzed. When the ammonia nitrogen concentration in the leaching liquid is ≤15ppm, the preheating deamination is qualified.

[0012] As some embodiments of the present application, in step S2, the inlet water temperature of the heat exchange cooling water is 20℃-30℃, and the outlet water temperature after cooling is ≤35℃.

[0013] As some embodiments of the present application, in step S3, the calcination temperature is 600-800 DEG C, the calcination time is 2-6 hours, the rotary furnace rotation speed is 0.5-2.0 r / min, and the rotary furnace inclination angle is 0.5-1.0%.

[0014] As some embodiments of the present application, in step S3, the judgment standard for completion of calcination is that, after detection of the solid sample after calcination, if the CaO content in the solid after calcination is greater than or equal to 80%, it is a qualified product, greater than or equal to 85% is a good product, and greater than or equal to 90% is an excellent product; if the CaO content in the solid sample after calcination is less than 80%, it is determined that the calcination is not up to standard, and secondary calcination treatment is returned.

[0015] As some embodiments of the present application, the calcination flue gas in step S1 comes from the boiler tail gas and / or the calcium residue calcination tail gas after ammonia removal in step S3, and the main components of the calcination flue gas are CO2, N2, O2, etc.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] The method first uses the calcination flue gas to preheat and remove ammonia from the ammonia-containing calcium residue (the calcium residue is alkaline, and the preheating and ammonia removal principle is NH3·H2O→NH3↑+H2O), by controlling appropriate temperature and time, the residual ammonia in the calcium residue is converted from liquid state to gaseous state, realizing the separation of ammonia and slag, and the gaseous ammonia is cooled and absorbed by circulating water to be converted into liquid ammonia water (condensation and absorption principle for preparing liquid ammonia water: NH3↑+H2O→NH3·H2O), realizing the removal and high-value utilization of ammonia. Finally, the calcium residue after ammonia removal is calcined and converted to produce quicklime (heating and calcination conversion principle: Ca(OH)2→CaO+H2O↑), which is returned for secondary utilization (reused to adjust the pH value in ammonia-nitrogen wastewater principle: CaO+H2O→Ca(OH)2; Ca(OH)2→Ca 2+ +2OH - ;OH - +NH4 + →NH3·H2O), which realizes efficient removal of ammonia from calcium residue and recycling of calcium residue. The method not only solves the problems of ammonia removal and resource utilization of ammonia-containing calcium residue, but also realizes the conversion of calcium residue to quicklime and recycling, providing a new path for solving the problem of calcium residue accumulation polluting soil and water from the source.

[0018] 1. Energy-saving deamination and high-value recovery of ammonia resources by using waste heat of roasting flue gas. The ammonia-containing calcium slag is preheated and deaminated in the roasting flue gas at 80-220℃. By using the waste heat originally discharged in the industrial production process, the problem of additional energy consumption in the traditional deamination process is avoided, and the energy consumption cost of the deamination link is reduced. The ammonia-containing gas released in the deamination process is cooled and absorbed by circulating tap water at 20-30℃, and then can be prepared into liquid ammonia water and returned to the tungsten smelting process to prepare the desorbent, realizing the conversion of ammonia from waste slag to high-value chemical raw materials. This process not only avoids air pollution caused by direct ammonia discharge, but also reduces the purchase cost of fresh ammonia water through resource recycling, forming a virtuous cycle of "waste heat utilization-pollution control-resource value-added".

[0019] 2. Constructing a closed loop of calcium slag recycling to eliminate pollution hazards and reduce treatment cost. Specifically, through the preheating and deamination process of roasting flue gas, the ammonia-containing calcium slag which is difficult to utilize directly is separated into deaminated calcium slag and ammonia-containing gas. Among them, the deaminated calcium slag is converted into lime with a calcium oxide content that meets the standard by roasting at 600-800℃, and the lime can be directly used to adjust the pH value of ammonia-containing wastewater in tungsten smelting. The ammonia-containing calcium hydroxide slag generated in this process is returned to the preheating and deamination process of roasting flue gas, forming a cycle of "ammonia-containing calcium slag-deaminated calcium slag-lime-adjusting the pH value of ammonia-containing wastewater in tungsten smelting-ammonia-containing calcium slag". This cycle not only replaces the consumption of purchased lime in the traditional process, significantly reducing the reagent cost of wastewater treatment, but also realizes the efficient recycling of calcium elements from solid waste to reagents. Through the preheating and deamination process and the roasting conversion process, the ammonia-containing calcium slag is converted into calcium oxide which can be used to adjust the pH value of ammonia-containing wastewater in tungsten smelting, thereby fundamentally eliminating the risk of soil and water pollution caused by stacking, achieving industrial solid waste reduction, low-cost wastewater treatment, and efficient resource utilization, and meeting the sustainable development concept of green industry. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present application, and those skilled in the art can obtain other drawings according to these drawings without creating any inventive labor.

[0021] Figure 1 The process flow diagram of the embodiment of the present application;

[0022] Figure 2 The phase analysis result of the ammonia-containing calcium slag in tungsten smelting of the embodiment of the present application;

[0023] Figure 3 The phase analysis result of the lime prepared in Example 1 of the present application;

[0024] Figure 4 The phase analysis results are for quicklime prepared in Example 2 of this invention;

[0025] Figure 5 The results of phase analysis are for quicklime prepared in Example 3 of this invention. Detailed Implementation

[0026] To make the technical means, creative features, objectives and effects of this invention easier to understand, the technical solutions in the specific embodiments of this invention are described clearly and completely below to further illustrate this invention. Obviously, the specific embodiments described are only a part of the embodiments of this invention, and not all of them.

[0027] This application proposes a method for the efficient removal and recycling of residual ammonia from ammonia-containing calcium slag in tungsten smelting. This method not only solves the problems of ammonia removal and resource utilization from ammonia-containing calcium slag, but also converts the calcium slag into quicklime, achieving recycling. This provides a new approach to addressing the problem of soil and water pollution caused by calcium slag accumulation at its source.

[0028] The technical solution in this application embodiment is to solve the problem of removing residual ammonia and recycling the ammonia-containing calcium slag in tungsten smelting. The overall idea is as follows:

[0029] like Figure 1 As shown, the ammonia-containing calcium slag is first preheated and deamed using roasting flue gas (calcium slag is alkaline; the principle of preheating and deaming is: NH3·H2O→NH3↑+H2O). By controlling the appropriate temperature and time, the residual ammonia in the calcium slag is converted from liquid to gaseous state, achieving separation of ammonia from slag. The gaseous ammonia is then cooled and absorbed by circulating water, and converted back into liquid ammonia water (the principle of condensation absorption for preparing liquid ammonia water is: NH3↑+H2O→NH3·H2O), achieving ammonia removal and high-value utilization. Finally, the deamed calcium slag is roasted and converted into quicklime (the principle of heating and roasting conversion is: Ca(OH)2→CaO+H2O↑), which is then reused (reused to adjust the pH value of ammonia-containing wastewater from tungsten smelting, the principle being: CaO+H2O→Ca(OH)2; Ca(OH)2→CaO). 2+ +2OH - ;OH - +NH4 + →NH3·H2O), which not only achieves efficient ammonia removal from calcium slag, but also enables the recycling of ammonia-containing calcium slag.

[0030] To better understand the above technical solution, the following detailed description of the specific implementation method is provided.

[0031] The ammonia-containing calcium slag used in the following examples is from a tungsten smelting plant in Ganzhou, Jiangxi Province, and is generated in the pH adjustment process using calcium oxide. The ammonia content of the ammonia-containing calcium slag is 0.12%, the water content is 14.25%, and the main phase is calcium hydroxide (the phase analysis results are shown in Figure 2 ).

[0032] Example 1: In this example, a method for efficient ammonia removal and recycling of ammonia-containing calcium slag is used to treat the ammonia-containing calcium slag as described above. The steps are as follows:

[0033] S1, preheating and ammonia removal: The ammonia-containing calcium slag is placed in a drying oven, and preheating and ammonia removal are performed using roasting flue gas (the roasting flue gas comes from the boiler tail gas and the roasting tail gas of the calcium slag after ammonia removal in step S3, and the main components of the roasting flue gas are CO2, N2, O2, etc.). The roasting flue gas is introduced into the heat exchange fins provided in the drying oven, and the ammonia-containing calcium slag is preheated by heating the heat exchange fins, thereby rapidly converting the free ammonia remaining in the ammonia-containing calcium slag from a liquid state to a gaseous state during the preheating process, thereby achieving the removal of free ammonia. The temperature of the roasting flue gas is controlled at 150°C, and the preheating treatment time is 120 min. After preheating and ammonia removal treatment is completed, ammonia-containing gas and calcium slag after ammonia removal are obtained. The calcium slag after ammonia removal is sampled, and the sampled calcium slag is subjected to sulfuric acid leaching. The leaching liquid-solid ratio is 5:1 (L / g), the leaching time is 2 h, and the sulfuric acid leaching reaction endpoint acidity is controlled at 0.5 mol / L. The ammonia nitrogen in the leaching liquid is analyzed, and the ammonia nitrogen concentration in the leaching liquid is 5.89 ppm, indicating that the preheating and ammonia removal is sufficient and meets the standard.

[0034] S2, water cooling and absorption: The ammonia-containing gas obtained by preheating and ammonia removal treatment of the ammonia-containing calcium slag in step S1 is introduced into a heat exchanger, and the ammonia in the ammonia-containing gas is condensed into liquid ammonia water by circulating tap water for heat exchange and cooling. The ammonia in the ammonia-containing gas is absorbed, the inlet water temperature of the heat exchange cooling water is controlled at 25°C, and the outlet water temperature after cooling is 32°C. The prepared ammonia water is collected and returned to the tungsten smelting desorbent preparation link for secondary utilization.

[0035] S3, roasting and conversion: The calcium slag after ammonia removal obtained in step S1 is placed in a rotary furnace for roasting and conversion treatment. The roasting temperature is controlled at 800°C, the roasting time is 4 h, the rotary speed of the rotary furnace is 0.5 r / min, and the inclination angle of the rotary furnace is 0.5%. After roasting, the prepared quicklime is collected and the solid sample is detected and analyzed. The main phase of the quicklime obtained by conversion is calcium oxide (the main phase analysis results of the prepared quicklime are shown in Figure 3 ), and the content is 96.33%. The obtained quicklime is used in the next step.

[0036] S4, pH value adjustment: The quicklime obtained in step S3 is used to adjust the pH value of the tungsten smelting ammonia-containing wastewater. The quicklime is gradually added into the tungsten smelting ammonia-containing wastewater, and stirring is performed for 1 h to complete the full mixing. The pH value of the ammonia-containing wastewater is controlled to be 12.5 at the end point. Then, the slurry with the adjusted pH value is first subjected to pressure filtration using a sealed plate and frame filter press. The obtained filtrate is subjected to ammonia removal in a distillation tower. After the ammonia removal treatment, the ammonia nitrogen concentration of the filtrate is 8.61 ppm, and the filtrate is collected and discharged. The obtained filter residue is ammonia-containing calcium residue, which is returned to step S1 for treatment.

[0037] Example 2: In this example, a method for efficient ammonia removal and recycling of ammonia-containing calcium residue is used to treat the ammonia-containing calcium residue as described above. The steps are as follows:

[0038] S1, preheating and ammonia removal: The ammonia-containing calcium residue is placed in a drying oven, and preheating and ammonia removal are performed using calcination flue gas (the calcination flue gas is obtained from the boiler tail gas and the calcium residue calcination tail gas after ammonia removal in step S3, and the main components of the calcination flue gas are CO2, N2, O2, etc.). The calcination flue gas is introduced into the heat exchange fins provided in the drying oven. After heating the heat exchange fins, the ammonia-containing calcium residue is preheated, so that the free ammonia remaining in the ammonia-containing calcium residue is quickly converted from a liquid state to a gaseous state during the preheating process, thereby achieving the removal of free ammonia. The temperature of the calcination flue gas is controlled to be 200°C, and the preheating treatment time is 120 min. After the preheating and ammonia removal treatment is completed, ammonia-containing gas and calcium residue after ammonia removal are obtained. The calcium residue after ammonia removal is sampled, and the sampled calcium residue is subjected to sulfuric acid leaching. The solid-liquid ratio of the leaching liquid is 5:1 (L / g), the leaching time is 2 h, and the final acidity of the sulfuric acid leaching reaction is controlled to be 1.0 mol / L. The ammonia nitrogen in the leaching liquid is analyzed, and the ammonia nitrogen concentration in the leaching liquid is 1.24 ppm. The preheating and ammonia removal are sufficient and meet the standards.

[0039] S2, water cooling and absorption: The ammonia-containing gas obtained by preheating and ammonia removal treatment of the ammonia-containing calcium residue in step S1 is introduced into a heat exchanger, and heat exchange cooling is performed using circulating tap water. The ammonia in the ammonia-containing gas is condensed into liquid ammonia water, achieving the absorption of ammonia in the ammonia-containing gas. The inlet water temperature of the heat exchange cooling water is controlled to be 25°C, and the outlet water temperature after cooling is 35°C. The prepared ammonia water is collected and returned to the tungsten smelting desorbent preparation link for secondary utilization.

[0040] S3, calcination and conversion: The calcium residue after ammonia removal obtained in step S1 is placed in a rotary furnace for calcination and conversion treatment. The calcination temperature is controlled to be 800°C, the calcination time is 6 h, the rotary speed of the rotary furnace is 0.5 r / min, and the inclination angle of the rotary furnace is 0.5%. After calcination, the obtained quicklime is collected and sampled for detection. Analysis shows that the main phase of the obtained quicklime is calcium oxide (see Table 1 for the analysis results of the main phase of the prepared quicklime), and the content of calcium oxide is 98.26%. The obtained quicklime is used in the next step. Figure 4

[0041] ​S4, pH value adjustment: The quicklime obtained in step S3 is used to adjust the pH value of the tungsten smelting ammonia-containing wastewater. The quicklime is gradually added into the tungsten smelting ammonia-containing wastewater, and stirring is performed for 2 h to complete the full mixing. The pH value of the ammonia-containing wastewater is controlled to be 13.5 at the end point. Then, the slurry with the adjusted pH value is first subjected to pressure filtration using a sealed plate-and-frame filter press. The obtained filtrate is subjected to ammonia removal in a distillation column. After the ammonia removal treatment, the ammonia nitrogen concentration of the filtrate is 6.72 ppm, and the filtrate is collected and discharged. The obtained filter residue is ammonia-containing calcium residue, which is returned to step S1 for treatment.

[0042] Example 3: In this example, a method for efficient ammonia removal and recycling of ammonia-containing calcium residue is used to treat the ammonia-containing calcium residue as described above. The steps are as follows:

[0043] S1, preheating and ammonia removal: The ammonia-containing calcium residue is placed in a drying box, and preheating and ammonia removal are performed using calcination flue gas (the calcination flue gas is obtained from boiler tail gas and calcination flue gas after ammonia removal of the calcium residue, and the main components of the calcination flue gas are CO2, N2, O2, etc.). The calcination flue gas is introduced into the heat exchange fins provided in the drying box. After heating the heat exchange fins, the ammonia-containing calcium residue is preheated, so that the free ammonia remaining in the ammonia-containing calcium residue is quickly converted from a liquid state to a gaseous state in the preheating process, thereby achieving the removal of free ammonia. The temperature of the calcination flue gas is controlled to be 180°C, and the preheating treatment time is 90 min. After the preheating and ammonia removal treatment is completed, the calcium residue after ammonia removal and ammonia-containing gas are obtained. The calcium residue after ammonia removal is sampled, and the sampled calcium residue is subjected to sulfuric acid leaching. The solid-liquid ratio of the leaching liquid is 5:1 (L / g), the leaching time is 2 h, and the final acidity of the sulfuric acid leaching reaction is controlled to be 0.5 mol / L. The ammonia nitrogen in the leaching liquid is analyzed, and the ammonia nitrogen concentration in the leaching liquid is 9.28 ppm. The preheating and ammonia removal are sufficient and meet the standards.

[0044] S2, water cooling and absorption: The ammonia-containing gas obtained by preheating and ammonia removal treatment of the ammonia-containing calcium residue in step S1 is introduced into a heat exchanger, and heat exchange cooling is performed using circulating tap water. The ammonia in the ammonia-containing gas is condensed into liquid ammonia water, achieving the absorption of ammonia in the ammonia-containing gas. The inlet water temperature of the heat exchange cooling water is controlled to be 25°C, and the outlet water temperature after cooling is 34°C. The prepared ammonia water is collected and returned to the tungsten smelting desorbent preparation link, achieving secondary utilization.

[0045] S3, calcination and conversion: The calcium residue after ammonia removal obtained in step S1 is placed in a rotary furnace for calcination and conversion treatment. The calcination temperature is controlled to be 700°C, the calcination time is 5 h, the rotary speed of the rotary furnace is 0.5 r / min, and the inclination angle of the rotary furnace is 0.5%. After calcination, the obtained quicklime is collected and sampled for detection. Analysis shows that the main phase of the obtained quicklime is calcium oxide (see Table 1 for the analysis results of the main phase of the prepared quicklime), and the content is 97.13%. The obtained quicklime is used in the next step. Figure 5

[0046] ​S4, pH value adjustment: the quicklime obtained in step S3 is used to adjust the pH value of the tungsten smelting ammonia-containing wastewater, the quicklime is gradually added into the tungsten smelting ammonia-containing wastewater, and stirring is performed for 1.5 h to complete the full mixing, the pH value of the ammonia-containing wastewater is controlled to be 12 at the end point, and then the slurry with the adjusted pH value is first subjected to pressure filtration by using a sealed plate and frame filter press. The obtained filtrate is subjected to ammonia removal in a distillation tower, the ammonia nitrogen concentration of the filtrate after the ammonia removal treatment is 12.45 ppm, and the filtrate is collected and discharged. The obtained filter residue is ammonia-containing calcium residue, which is returned to step S1 for treatment.

[0047] The above describes the main technical features and basic principles of the present application and related advantages. It is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the concept or basic features of the present application. Therefore, the above-described embodiments should be regarded as exemplary and non-limiting, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application.

[0048] In addition, it should be understood that although the present specification is described in terms of each embodiment, each embodiment does not contain only one independent technical solution, and the description manner of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A method for efficient deamination and recycling of ammonia-containing calcium slag, characterized in that, The steps are as follows: S1, preheating and deamination: the ammonia-containing calcium residue is put into a drying box, and then the calcination flue gas is introduced into the heat exchange fins in the drying box to heat the heat exchange fins, thereby preheating the ammonia-containing calcium residue, making the free ammonia remaining in the ammonia-containing calcium residue quickly change from liquid state to gaseous state in the preheating process, thereby realizing the removal of free ammonia, after the preheating and deamination treatment is completed, the deaminated calcium residue and ammonia-containing gas are obtained; S2, water cooling and absorption: the ammonia-containing gas in step S1 is introduced into a heat exchanger, and is cooled by circulating tap water, the ammonia in the ammonia-containing gas is condensed into liquid ammonia water, realizing the absorption of ammonia in the ammonia-containing gas; the prepared ammonia water is collected and returned to the tungsten smelting desorbent preparation link for secondary utilization; S3, calcination conversion: the deaminated calcium residue in step S1 is put into a rotary furnace for calcination conversion treatment, and after calcination, raw lime is obtained; S4, adjusting pH value: the raw lime obtained in step S3 is gradually added into the ammonia-containing wastewater of tungsten smelting, stirred for 1-2 hours for fully mixing, and the pH value of the ammonia-containing wastewater is adjusted to 11.5-13.5, the slurry with adjusted pH value is first filtered by a sealed plate and frame filter press, the obtained filtrate is introduced into a distillation column for deamination, the deaminated wastewater meeting the standard is collected and discharged, and the filter residue is the ammonia-containing calcium residue which is returned to step S1 for treatment.

2. The method for efficient deamination and recycling of ammonia-containing calcium slag according to claim 1, characterized in that, In step S1, the temperature of the calcination flue gas for preheating and deamination is controlled to be 80-220℃, and the preheating treatment time is 30-120 minutes.

3. The method for efficient deamination and recycling of ammonia-containing calcium slag according to claim 1, characterized in that, In step S1, the standard for judging whether the preheating and deamination is qualified or not is that the deaminated calcium residue is sampled, sulfuric acid leaching is carried out, the solid-liquid ratio of the leaching liquid is 5:1 (L / g), the leaching time is 2 hours, the acid concentration at the end of the sulfuric acid leaching reaction is controlled to be 0.5-1.0 mol / L, then the ammonia nitrogen in the leaching liquid is analyzed, and when the ammonia nitrogen concentration in the leaching liquid is ≤15 ppm, it is considered that the preheating and deamination is qualified.

4. The method for efficient deamination and recycling of ammonia-containing calcium slag according to claim 1, characterized in that, In step S2, the inlet water temperature of the heat exchange cooling water is 20-30℃, and the outlet water temperature after cooling is ≤35℃.

5. The method for efficient deamination and recycling of ammonia-containing calcium slag according to claim 1, characterized in that, In step S2, the gas after absorbing ammonia is introduced into a primary spray tower, and after being absorbed by dilute sulfuric acid by one-time spraying, it is directly discharged after meeting the standard.

6. The method for efficient deamination and recycling of ammonia-containing calcium slag according to claim 1, characterized in that, In step S3, the calcination temperature is 600-800℃, the calcination time is 2-6 hours, the rotary speed of the rotary furnace is 0.5-2.0 r / min, and the inclination angle of the rotary furnace is 0.5-1.0%.

7. The method for efficient deamination and recycling of ammonia-containing calcium slag according to claim 1, characterized in that, In step S3, the judgment standard for judging whether the calcination is completed or not is that the calcined solid sample is detected, the content of calcium oxide in the calcined solid is ≥80% for qualified product, ≥85% for good grade product, and ≥90% for excellent grade product, if the content of calcium oxide in the calcined solid sample is <80%, it is considered that the calcination is unqualified, and the secondary calcination treatment is carried out.

8. The method for efficient deamination and recycling of ammonia-containing calcium slag according to claim 1, characterized in that, The calcination flue gas in step S1 comes from the boiler tail gas and / or the calcination tail gas of the deaminated calcium residue in step S3, and the main components of the calcination flue gas are CO2, N2 and O2.

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