Method for efficient deamination and cyclic utilization of ammonia-containing calcium slag

Abstract

The invention belongs to the technical field of solid waste treatment, and particularly relates to a method for efficient deamination and cyclic utilization of ammonia-containing calcium slag. The method comprises the following steps: S1, preheating for deamination: preheating ammonia-containing calcium slag by using roasting flue gas to convert free ammonia from a liquid state into a gaseous state for removal so as to obtain deaminated calcium slag and ammonia-containing gas; s2, water-cooling absorption: cooling and condensing the ammonia-containing gas into ammonia water through a heat exchanger, and recycling the ammonia water for preparing a tungsten smelting desorption agent; s3, roasting conversion: roasting and converting the deaminated calcium slag into quick lime; s4, adjusting the pH value: adjusting the pH value of the ammonia-containing wastewater by using the quicklime prepared by conversion, and returning ammonia-containing calcium slag after filter pressing to the step S1 for circular treatment. According to the method, efficient removal and resource recovery of ammonia in the ammonia-containing calcium slag are achieved, meanwhile, the calcium slag is converted into quick lime, a closed-loop cyclic utilization path is constructed, the common problem that the treatment and utilization difficulty of the ammonia-containing calcium slag is large is solved, and the method has the advantages of being energy-saving, environmentally friendly, low in cost, easy and convenient to operate and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solid waste treatment, and relates to a method for efficient ammonia removal and recycling of ammonia-containing calcium residue. BACKGROUND

[0002] A large amount of ammonia-nitrogen wastewater with complex components is generated in the tungsten smelting process. The treatment cost of this type of wastewater is high, and the deep treatment is difficult, which seriously limits the green and high-quality development of the industry. In order to solve the disposal problem of this type of ammonia-containing wastewater, researchers have developed processes such as stripping, distillation, and chemical reagent oxidation. The chemical reagent oxidation method usually uses calcium perchlorate, sodium hypochlorite, and chlorine gas as oxidants to achieve ammonia-nitrogen removal (removal principle: 2NH3+3NaClO→N2↑+3H2O+3NaCl), but the consumption of oxidants is large, and toxic gases (such as chlorine gas) are easily escaped on site, which is difficult to meet the requirements of production safety and environmental protection. The stripping method and the distillation method both require the addition of liquid alkali to adjust the pH value, so that the ammonia-nitrogen wastewater is alkaline (the purpose is to convert NH4 + +OH + →NH3·H2O→NH3↑+H2O) in the ammonia-nitrogen wastewater into free ammonia state NH3·H2O which is easy to remove), and then ammonia-nitrogen removal is achieved through air stripping or steam heating. This type of process is efficient in treating high-concentration, single-component ammonia-nitrogen wastewater, but in treating wastewater with complex components and variable ammonia-nitrogen concentration, the consumption of liquid alkali is extremely large, the cost is high, and it is difficult to operate continuously.

[0003] In order to further reduce the treatment cost of ammonia-nitrogen wastewater, researchers have developed a process of using lime (calcium oxide) to adjust the pH value (instead of using liquid alkali to adjust the pH value) and stripping or distillation removal, which has achieved efficient removal of ammonia in complex ammonia-nitrogen wastewater (removal principle: NH4 - +OH + →NH3·H2O→NH3↑+H2O), and has prepared high-quality ammonia water, greatly reducing the disposal cost. However, during the use of calcium oxide to adjust the pH value, a large amount of calcium hydroxide residue will be generated (200-800 kg of calcium hydroxide residue will be generated for every ton of calcium oxide used to adjust the pH value, with fluctuations according to the end point control of pH value adjustment), and there is still ammonia remaining in the residue. If the residue is stored, not only a large amount of land resources will be occupied, but also the remaining pollutants ammonia will have the risk of leakage and migration, seriously affecting the environment. If the ammonia-containing calcium residue is directly treated by calcination conversion, a large amount of energy will be consumed, and the ammonia in the calcium residue will mix with the high-temperature furnace gas, making the treatment extremely difficult, and the ammonia is also difficult to realize resource utilization. Therefore, how to achieve efficient ammonia removal and recycling of ammonia-containing calcium residue is a problem that needs to be solved. SUMMARY

[0004] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for efficient ammonia removal and recycling of ammonia-containing calcium residue.

[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: S1, preheating deamination: the ammonia-containing calcium residue is put into the drying box, then the calcination flue gas is introduced into the heat exchange fin 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, ammonia-depleted calcium residue and ammonia-containing gas are obtained.

[0006] 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, and the absorption of ammonia in the ammonia-containing gas is realized; 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 after being absorbed by dilute sulfuric acid once, it is directly discharged after reaching the standard.

[0007] S3, calcination conversion: the ammonia-depleted calcium residue in step S1 is put into a rotary furnace for calcination conversion treatment, and the obtained raw lime is collected after calcination.

[0008] 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 into the ammonia-containing wastewater in tungsten smelting, and the mixture is stirred for 1h-2h, the pH value of the ammonia-containing wastewater is controlled at 11.5-13.5, the slurry with adjusted pH value is first filtered by a sealed plate and frame filter press, the filtrate is introduced into a distillation column for deamination, the ammonia-depleted wastewater after deamination is collected and discharged, and the filter residue is ammonia-containing calcium residue, which is returned to step S1 for treatment.

[0009] As some embodiments of the present application, in step S1, the temperature of the calcination flue gas for preheating and deamination is controlled at 80-220℃, and the preheating treatment time is 30-120min.

[0010] As some embodiments of the present application, in step S1, the standard for judging the preheating and deamination is that the ammonia-depleted 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 2h, the acid concentration at the end of the sulfuric acid leaching reaction is controlled at 0.5-1.0mol / L, the ammonia nitrogen in the leaching liquid is analyzed, and when the ammonia nitrogen concentration in the leaching liquid is ≤15ppm, the preheating and deamination is qualified.

[0011] 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℃.

[0012] 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%.

[0013] As some embodiments of the present application, in step S3, the judgment standard for completion of calcination is that, after taking the solid sample after calcination for detection, 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 the secondary calcination treatment is returned.

[0014] 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.

[0015] Compared with the prior art, the present application has the following beneficial effects: 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.

[0016] 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°C. 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°C, 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 procurement cost of fresh ammonia water through resource recycling, forming a virtuous cycle of "waste heat utilization-pollution control-resource value-added".

[0017] 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. The deaminated calcium slag is converted into lime with a calcium oxide content that meets the standard by roasting at 600-800°C, 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 that can be used to adjust the pH value of ammonia-containing wastewater in tungsten smelting, which fundamentally eliminates the risk of soil and water pollution caused by storage, realizes the reduction of industrial solid waste, the low-cost treatment of wastewater, and the efficient utilization of resources, and conforms to the sustainable development concept of green industry. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. 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.

[0019] Figure 1 The process flow diagram of the embodiment of the present application; Figure 2 The phase analysis result of the ammonia-containing calcium slag in tungsten smelting of the embodiment of the present application; Figure 3 The phase analysis result of the lime prepared in Example 1 of the present application; Figure 4The phase analysis result of the quicklime prepared for the embodiment 2 of the present application; Figure 5 The phase analysis result of the quicklime prepared for the embodiment 3 of the present application. DETAILED DESCRIPTION

[0020] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the technical solutions in the specific embodiments of the present application are described clearly and completely below to further illustrate the present application. Obviously, the described specific embodiments are only a part of the embodiments of the present application, not all.

[0021] In order to solve the problems of removing residual ammonia and recycling of the ammonia-containing calcium slag in tungsten smelting, the present application develops a method for efficient ammonia removal and recycling of the ammonia-containing calcium slag. This method not only solves the problems of ammonia removal and resource utilization of the ammonia-containing calcium slag, but also completes the conversion of the calcium slag into quicklime and realizes recycling, thereby providing a new path for solving the problem of soil and water pollution caused by calcium slag accumulation from the source.

[0022] The technical solutions in the embodiments of the present application are to solve the problems of removing residual ammonia and recycling of the ammonia-containing calcium slag in tungsten smelting, and the general idea is as follows: As shown in Figure 1 , first, the ammonia-containing calcium slag is preheated and ammonia is removed by using roasting flue gas (the calcium slag is alkaline, and the preheating and ammonia removal principle is: NH3·H2O→NH3↑+H2O). By controlling the appropriate temperature and time, the residual ammonia in the calcium slag 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 reconverted into liquid ammonia water (the principle of condensation and absorption for preparing liquid ammonia water is: NH3↑+H2O→NH3·H2O), realizing the removal and high-value utilization of ammonia. Finally, the ammonia-removed calcium slag is calcined and converted to prepare quicklime (the principle of heating and calcining conversion is: Ca(OH)2→CaO+H2O↑), which is returned for secondary utilization (reused for adjusting the pH value of the ammonia-containing wastewater in tungsten smelting, and the principle is: CaO+H2O→Ca(OH)2; Ca(OH)2→Ca 2+ +2OH - ;OH - +NH4 + →NH3·H2O), realizing efficient removal of ammonia from the calcium slag and recycling of the ammonia-containing calcium slag.

[0023] In order to better understand the above technical solutions, the above technical solutions are described in detail below with specific embodiments.

[0024] 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 ).

[0025] 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: S1, preheating and ammonia removal: Put the ammonia-containing calcium slag into a drying oven, and use the roasting flue gas to preheat and remove ammonia (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.). Introduce the roasting flue gas into the heat exchange fins installed in the drying oven. After heating the heat exchange fins, preheat the ammonia-containing calcium slag to convert the free ammonia remaining in the ammonia-containing calcium slag from liquid to gas 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 time is 120 minutes. After preheating and ammonia removal, the ammonia-removed calcium slag and ammonia-containing gas are obtained. Sample the ammonia-removed calcium slag, and then perform sulfuric acid leaching on the sampled calcium slag. The solid-liquid ratio of the leaching solution is 5:1 (L / g), the leaching time is 2 hours, and the final acidity of the sulfuric acid leaching reaction is controlled at 0.5 mol / L. Analyze the ammonia nitrogen in the leaching solution, and the ammonia nitrogen concentration in the leaching solution is 5.89 ppm, indicating that the preheating and ammonia removal are sufficient and meet the standards.

[0026] S2, water cooling and absorption: Introduce the ammonia-containing gas obtained by preheating and ammonia removal of the ammonia-containing calcium slag in step S1 into a heat exchanger, and use circulating tap water for heat exchange and cooling. 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 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.

[0027] S3, roasting and conversion: Put the ammonia-removed calcium slag obtained in step S1 into a rotary furnace for roasting and conversion treatment. The roasting temperature is controlled at 800°C, the roasting time is 4 hours, 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 obtained raw lime is collected and the solid sample is detected and analyzed. The main phase of the raw lime obtained by conversion is calcium oxide (the main phase analysis results of the prepared raw lime are shown in Figure 3 ), and the content is 96.33%. The obtained raw lime is used in the next step.

[0028] 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 column. 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.

[0029] 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: 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 the boiler tail gas and the calcination tail gas of the calcium residue 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 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 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, the ammonia-removed calcium residue and ammonia-containing gas are obtained. The ammonia-removed calcium residue 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.

[0030] 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.

[0031] S3, calcination and conversion: The ammonia-removed calcium residue 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

[0032] ​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 tower. 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.

[0033] 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: 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 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 during 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 ammonia-containing gas and the 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 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.

[0034] 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.

[0035] 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 prepared 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

[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 1.5 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.

[0037] 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-described 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, 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.

[0038] In addition, it should be understood that although the present specification is described in terms of each embodiment, not every embodiment contains only one independent technical solution, and the description manner of the specification is only for the sake of clarity, 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 deammoniation and recycling of ammonia-containing calcium slag, characterized in that, The steps are as follows: S1. Preheating and deammoniation removal: The calcium slag containing ammonia is placed in a drying oven, and then the roasting flue gas is introduced into the heat exchange plate in the drying oven to heat the heat exchange plate, thereby preheating the calcium slag containing ammonia. During the preheating process, the free ammonia remaining in the calcium slag is rapidly changed from liquid to gas, thereby removing the free ammonia. After the preheating and deammoniation treatment is completed, the calcium slag after deammoniation and the ammonia-containing gas are obtained. S2, Water-cooled absorption: The ammonia-containing gas from step S1 is introduced into a heat exchanger and cooled by circulating tap water. The ammonia in the ammonia-containing gas condenses into liquid ammonia water, thus absorbing the ammonia in the ammonia-containing gas. The prepared ammonia water is collected and returned to the tungsten smelting desorbent preparation stage for secondary utilization. S3. Calcination and conversion: The calcium slag after deammoniation in step S1 is placed in a rotary kiln for calcination and conversion. After calcination is completed, quicklime is obtained. S4. Adjust pH value: Gradually add the quicklime obtained in step S3 to the ammonia-containing wastewater from tungsten smelting, stir for 1 to 2 hours to mix thoroughly, and adjust the pH value of the ammonia-containing wastewater to 11.5 to 13.

5. First, filter the slurry with adjusted pH value using a sealed plate and frame filter press. The filtrate is then fed into a distillation tower for ammonia removal. The qualified wastewater after ammonia removal is collected and discharged. The filter residue is ammonia-containing calcium slag, which is returned to step S1 for treatment.

2. The method for efficient deammoniation and recycling of ammonia-containing calcium slag according to claim 1, characterized in that, In step S1, the temperature of the roasting flue gas for preheating and deammoniation is controlled at 80℃~220℃, and the preheating time is 30min~120min.

3. The method for efficient deammoniation and recycling of ammonia-containing calcium slag according to claim 1, characterized in that, In step S1, the criteria for judging whether preheating deammoniation meets the standard are as follows: take a sample of the calcium slag after deammoniation, perform sulfuric acid leaching, the leaching liquid-to-solid ratio is 5:1 (L / g), the leaching time is 2h, the acid concentration at the end of the sulfuric acid leaching reaction is controlled at 0.5mol / L~1.0mol / L, and then analyze the ammonia nitrogen in the leaching liquid. When the ammonia nitrogen concentration in the leaching liquid is ≤15ppm, the preheating deammoniation meets the standard.

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

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

6. The method for efficient deammoniation 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 2h~6h, the rotary kiln speed is 0.5r / min~2.0r / min, and the rotary kiln tilt angle is 0.5%~1.0%.

7. The method for efficient deammoniation and recycling of ammonia-containing calcium slag according to claim 1, characterized in that, In step S3, the criteria for determining whether roasting is complete are as follows: take a roasted solid sample for testing. If the calcium oxide content in the roasted solid is ≥80%, it is a qualified product; ≥85% is a good product; and ≥90% is a superior product. If the calcium oxide content in the roasted solid sample is <80%, it is determined that the roasting is substandard and the sample is returned for a second roasting process.

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

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