Process for producing polyaluminum chloride by recycling aluminum ash

Abstract

The invention discloses a process for producing polyaluminum chloride by recycling aluminum ash. The process comprises a primary aluminum ash pretreatment process, a secondary aluminum ash deamination process, an ammonium chloride crystallization process, a liquid polyaluminum chloride process and a solid polyaluminum chloride process, the primary aluminum ash pretreatment procedure comprises a first cyclone separator, a ball mill, a screening machine and a bag-type dust collector, the input end of the first cyclone separator is connected with a primary aluminum ash bin through conveying equipment, the coarse ash end of the first cyclone separator is connected with a feeding port of the ball mill, and a discharging port of the ball mill is connected with a feeding port of the screening machine; fine powder screened by the screening machine and secondary aluminum ash fine powder discharged by the first cyclone separator are collected into a secondary aluminum ash bin, and dust outlets of the first cyclone separator, the ball mill and the screening machine are connected with a dust inlet of the bag-type dust collector through pipelines. By arranging a series of structures, the produced polyaluminum chloride is high in purity, the economic benefit of the process is improved, tail gas is washed, and the pollution is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum chloride production, in particular to a process for producing polyaluminum chloride by utilizing aluminum ash as a resource. Background Art

[0002] Polyaluminium chloride is a water-soluble inorganic high molecular polymer between AlCl3 and Al(OH)3, with the general chemical formula [Al2(OH)nCl6-n]m, where m represents the degree of polymerization, and n represents the neutrality of the PAC product. n=1~5 is a highly charged polymeric ring chain with a Keggin structure, which has a high degree of electrical neutralization and bridging effect on colloids and particulate matter in water, and can strongly remove toxic substances and heavy metal ions. It has stable properties and is often used as an emerging water purification material and coagulant, and is widely used in the purification of drinking water, industrial wastewater and urban sewage.

[0003] At present, the production process of polyaluminium chloride is single. Due to the influence of impurities and particle size of the raw materials for polyaluminium chloride production, the quality of the produced polyaluminium chloride products is poor. In addition, the waste and tail gas generated in the production process cause great material loss and environmental pollution. Summary of the invention

[0004] The purpose of the present invention is to provide a process for producing polyaluminium chloride from aluminium ash resources to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical scheme: a process for producing polyaluminium chloride from aluminium ash resources, comprising a primary aluminium ash pretreatment process, a secondary aluminium ash deammoniation process, an ammonium chloride crystallization process, a liquid polyaluminium chloride process and a solid polyaluminium chloride process; The primary aluminum ash pretreatment process includes a first cyclone separator, a ball mill, a screening machine and a bag dust collector, the input end of the first cyclone separator is connected to the primary aluminum ash bin through a conveying device, the coarse ash end of the first cyclone separator is connected to the feed port of the ball mill, the discharge port of the ball mill is connected to the feed port of the screening machine, the fine powder screened by the screening machine and the secondary aluminum ash fine powder discharged by the first cyclone separator are collected in the secondary aluminum ash bin, the dust outlets of the first cyclone separator, the ball mill and the screening machine are connected to the dust inlet of the bag dust collector through a pipeline, and the bag dust collector is connected to the input end of the induced draft fan through a pipeline; The secondary aluminum ash deamination process comprises a deamination reaction tank, a first plate-frame filter press, an ammonium chloride storage tank, a water-washing slag tank and a deamination section tail gas washing device. The secondary aluminum ash generated in the primary aluminum ash pretreatment process is connected to the deamination reaction tank through a conveying device. The output end of the deamination reaction tank is connected to the input end of the first plate-frame filter press through a filter press conveying pump. The liquid outlet of the first plate-frame filter press is connected to the input end of the ammonium chloride storage tank. The filter cake outlet of the first plate-frame filter press is connected to the water-washing slag tank. The tail gas of the deamination reaction tank and the first plate-frame filter press is connected to the deamination section tail gas washing device through a pipeline. The ammonium chloride crystallization process includes an MVR forced evaporator, an OSLO crystallizer, a centrifuge, a dryer and a concentrated crystallization drying tail gas washing device. The liquid outlet of the ammonium chloride storage tank is connected to the input end of the MVR forced evaporator through a pipeline, the output end of the MVR forced evaporator is connected to the input end of the OSLO crystallizer, the output end of the OSLO crystallizer is connected to the input end of the centrifuge through a pipeline, the output end of the centrifuge is connected to the input end of the dryer through a pipeline, and the tail gas of the MVR forced evaporator and the dryer is connected to the concentrated crystallization drying tail gas washing device through a pipeline; The liquid polyaluminium chloride process comprises a polymerization reaction tank, a second plate-frame filter press and a liquid PAC finished product tank, the deaminated and fluorinated aluminium hydroxide filter cake produced by the first plate-frame filter press is transported to the polymerization reaction tank, the polymerization reaction tank is connected to the input end of the second plate-frame filter press through a filter press feed pump, the liquid outlet end of the second plate-frame filter press is connected to the liquid PAC finished product tank through a pipeline, and the tail gas of the polymerization reaction tank is connected to the tail gas washing equipment of the polymerization reaction section through a pipeline; The solid polyaluminium chloride process comprises an airflow drying tower and a second cyclone separator, the outlet of the liquid PAC finished product tank is connected to the input end of the airflow drying tower through a delivery pump, the output end of the airflow drying tower is connected to the input end of the second cyclone separator, the bottom of the second cyclone separator is connected to the solid PAC powder silo, and the tail gas of the second cyclone separator is connected to the PAC concentrated drying tail gas washing equipment through a pipeline.

[0006] Preferably, hydrochloric acid, process water and liquid calcium chloride are added in proportion while adding secondary aluminum ash to the deamination reaction tank. The pH value of the mixed liquid in the deamination reaction tank is controlled at 3.0-3.5 in the early stage, the temperature is maintained at 0-30°C, and the proportion of calcium chloride is 2%-5%. After the secondary aluminum ash is added to the deamination reaction tank, under the action of steam, the aluminum nitride in the secondary aluminum ash reacts quickly with water to generate ammonia water, and then reacts with hydrochloric acid to generate liquid ammonium chloride. At this time, the temperature is maintained at 85-95°C. The reaction of secondary aluminum ash with water will provide the pH value of the mixed liquid. Hydrochloric acid is slowly added through a metering pump to lower the pH value, and the pH value is maintained at 3.0-3.5. The deamination and fluorine fixation reaction is continued for 8 hours, and the pH value is maintained at 3.0-3.5, which can reduce and slow down the volatilization of ammonia. The purpose of adding calcium chloride is to fix fluorine.

[0007] Preferably, an agitator is provided inside the water-washed slag tank, the liquid outlet of the water-washed slag tank is connected to the input end of the first plate-frame filter press through a filter press delivery pump, and the washing water clear liquid outlet of the first plate-frame filter press is connected to the deammoniation reaction tank through a pipeline.

[0008] Preferably, in the liquid polyaluminium chloride process, while adding deamination and solid fluoride aluminium hydroxide filter cakes in a certain proportion to the polymerization reaction tank, 30% hydrochloric acid and washing process water are added in proportion, and 1 ton of 30% hydrochloric acid, 0.5 ton of process water and 0.55 ton of deamination and solid fluoride aluminium hydroxide filter cake are added; steam is introduced into the polymerization reaction tank to increase the temperature to fully react and reach the designed temperature of 95°C. After maintaining the temperature for 5 hours, process water and washing water are added to the polymerization reaction tank to adjust the concentration to 18 degrees, and then calcium aluminate powder is added to adjust the basicity and concentration of the product to reach the target material concentration of 32 degrees, pH value of 3.2-3.5, basicity of 85%, and alumina content of 12%. After the stable index polymerization reaction is carried out for 1.5-2 hours, it is fed into the second plate and frame filter press through the filter press feed pump.

[0009] Preferably, the liquid PAC product in the liquid PAC product tank enters the airflow drying tower from the bottom of the drying tower together with the high-temperature hot air delivered by the hot air furnace through a delivery pump at a certain flow rate. In the airflow drying tower, the PAC liquid is atomized, fully contacted with the hot air, and quickly dried to become PAC powder, and enters the second cyclone separator with the hot air at a certain flow rate.

[0010] Preferably, the tail gas washing equipment of the deamination section includes one group of washing towers, two groups of washing towers, three groups of washing towers and a water circulation tank. The tail gas of the deamination reaction tank and the first plate and frame filter press is connected to the input end of the first group of washing towers through a pipeline, the output end of the first group of washing towers is connected to the input end of the second group of washing towers, the output end of the second group of washing towers is connected to the input end of the third group of washing towers, and the first group of washing towers, the second group of washing towers and the third group of washing towers are all connected to the water circulation tank through a delivery pump.

[0011] Preferably, dilute sulfuric acid and process water are added into the tail gas washing equipment of the deamination section.

[0012] Preferably, the filtered dust outlet of the bag filter is connected to the secondary aluminum ash silo through a pipeline.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. The process for producing polyaluminium chloride from aluminium ash resources comprises a primary aluminium ash pretreatment process, a secondary aluminium ash deamination process, an ammonium chloride crystallization process, a liquid polyaluminium chloride process and a solid polyaluminium chloride process. The main mechanism of aluminium ash deamination is acid dissolution, i.e. hydrochloric acid is used to react with aluminium nitride in the aluminium ash and water to form ammonia water to produce ammonium chloride. The produced polyaluminium chloride has high purity. The solid ammonium chloride produced in the process can be sold externally. The filter residue can be used to make building material panels, thereby improving the economic benefits of the process.

[0014] 2. In the process of producing polyaluminium chloride from aluminium ash resources, the tail gas generated in the primary aluminium ash pretreatment process, the secondary aluminium ash deammoniation process, the ammonium chloride crystallization process, the liquid polyaluminium chloride process and the solid polyaluminium chloride process is treated with corresponding tail gas washing equipment to reduce pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a process flow chart of the ammonium chloride crystallization process in the present invention; Figure 3 It is a process flow chart of the tail gas washing equipment of the deamination section in the present invention.

[0016] In the figure: 1. first cyclone separator; 2. ball mill; 3. screening machine; 4. bag filter; 5. deamination reaction tank; 6. first plate and frame filter press; 7. ammonium chloride storage tank; 8. water washing slag tank; 9. deamination section tail gas washing equipment; 91. one group of washing towers; 92. two groups of washing towers; 93. three groups of washing towers; 94. water circulation tank; 10. MVR forced evaporator; 11. OSLO crystallizer; 12. centrifuge; 13. dryer; 14. concentrated crystallization and drying tail gas washing equipment; 15. polymerization reaction tank; 16. second plate and frame filter press; 17. liquid PAC finished product tank; 18. airflow drying tower; 19. second cyclone separator; 20. PAC concentrated drying tail gas washing equipment; 21. polymerization section tail gas washing equipment. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0019] like Figures 1 to 3 As shown, the process for producing polyaluminium chloride from aluminium ash resources in this embodiment includes a primary aluminium ash pretreatment process, a secondary aluminium ash deammoniation process, an ammonium chloride crystallization process, a liquid polyaluminium chloride process and a solid polyaluminium chloride process; The primary aluminum ash pretreatment process includes a first cyclone separator 1, a ball mill 2, a screening machine 3 and a bag dust collector 4. The input end of the first cyclone separator 1 is connected to the primary aluminum ash bin through a conveying device, the coarse ash end of the first cyclone separator 1 is connected to the feed port of the ball mill 2, the discharge port of the ball mill 2 is connected to the feed port of the screening machine 3, the fine powder screened by the screening machine 3 and the secondary aluminum ash fine powder discharged by the first cyclone separator 1 are collected into the secondary aluminum ash bin, the dust outlets of the first cyclone separator 1, the ball mill 2 and the screening machine 3 are connected to the dust inlet of the bag dust collector 4 through a pipeline, and the bag dust collector 4 is connected to the input end of the induced draft fan through a pipeline; The secondary aluminum ash deamination process includes a deamination reaction tank 5, a first plate-frame filter press 6, an ammonium chloride storage tank 7, a water-washing slag tank 8 and a deamination section tail gas washing equipment 9. The secondary aluminum ash generated in the primary aluminum ash pretreatment process is connected to the deamination reaction tank 5 through a conveying device, the output end of the deamination reaction tank 5 is connected to the input end of the first plate-frame filter press 6 through a filter press delivery pump, the liquid outlet of the first plate-frame filter press 6 is connected to the input end of the ammonium chloride storage tank 7, the filter cake outlet of the first plate-frame filter press 6 is connected to the water-washing slag tank 8, and the tail gas of the deamination reaction tank 5 and the first plate-frame filter press 6 is connected to the deamination section tail gas washing equipment 9 through a pipeline; The ammonium chloride crystallization process comprises an MVR forced evaporator 10, an OSLO crystallizer 11, a centrifuge 12, a dryer 13 and a concentrated crystallization drying tail gas washing device 14, the liquid outlet of the ammonium chloride storage tank 7 is connected to the input end of the MVR forced evaporator 10 through a pipeline, the output end of the MVR forced evaporator 10 is connected to the input end of the OSLO crystallizer 11, the output end of the OSLO crystallizer 11 is connected to the input end of the centrifuge 12 through a pipeline, the output end of the centrifuge 12 is connected to the input end of the dryer 13 through a pipeline, and the tail gas of the MVR forced evaporator 10 and the dryer 13 is connected to the concentrated crystallization drying tail gas washing device 14 through a pipeline; The liquid polyaluminium chloride process comprises a polymerization reaction tank 15, a second plate-frame filter press 16 and a liquid PAC finished product tank 17. The deaminated and fluorinated aluminium hydroxide filter cake produced by the first plate-frame filter press 6 is transported to the polymerization reaction tank 15. The polymerization reaction tank 15 is connected to the input end of the second plate-frame filter press 16 through a filter press feed pump. The liquid outlet end of the second plate-frame filter press 16 is connected to the liquid PAC finished product tank 17 through a pipeline. The tail gas of the polymerization reaction tank 15 is connected to the tail gas washing equipment 21 of the polymerization reaction section through a pipeline. The solid polyaluminium chloride process includes an airflow drying tower 18 and a second cyclone separator 19. The outlet of the liquid PAC finished product tank 17 is connected to the input end of the airflow drying tower 18 through a delivery pump, the output end of the airflow drying tower 18 is connected to the input end of the second cyclone separator 19, the bottom of the second cyclone separator 19 is connected to the solid PAC powder silo, and the tail gas of the second cyclone separator 19 is connected to the PAC concentrated drying tail gas washing equipment 20 through a pipeline.

[0020] Specifically, when adding secondary aluminum ash to the deamination reaction tank 5, hydrochloric acid, process water and liquid calcium chloride are added in proportion. The pH value of the mixed liquid in the deamination reaction tank 5 is controlled at 3.0-3.5, the temperature is maintained at 0-30°C, and the proportion of calcium chloride is 2%-5%. After adding secondary aluminum ash to the deamination reaction tank 5, under the action of steam, the aluminum nitride in the secondary aluminum ash reacts quickly with water to generate ammonia water, and then reacts with hydrochloric acid to generate liquid ammonium chloride. At this time, the temperature is maintained at 85-95°C. The reaction of secondary aluminum ash with water will provide the pH value of the mixed liquid. Hydrochloric acid is slowly added through a metering pump to lower the pH value. The pH value is maintained at 3.0-3.5. The deamination and solid fluorine reaction is continued for 8 hours, and the pH value is maintained at 3.0-3.5, which can reduce and slow down the volatilization of ammonia. The purpose of adding calcium chloride is to fix fluorine.

[0021] Furthermore, a stirrer is provided inside the water-washing slag tank 8, and the liquid outlet end of the water-washing slag tank 8 is connected to the input end of the first plate-frame filter press 6 through a filter press delivery pump, and the washing water clear liquid outlet of the first plate-frame filter press 6 (the first one) is connected to the deamination reaction tank 5 through a pipeline. The filter cake separated by the first plate-frame filter press 6 still contains a small amount of ammonium chloride, and the filter cake is sent to the water-washing slag tank 8. At the same time, water is added to the water-washing slag tank 8 to wash the residual ammonium chloride. Through repeated stirring, the remaining ammonium chloride in the filter cake is fully cleaned, and then the suction liquid is sent to the first plate-frame filter press 6 (the second one) through the filter press delivery pump to separate the deammoniation and solid fluoride aluminum hydroxide filter cake, which is collected for standby use, and the washing water clear liquid separated by the first plate-frame filter press 6 is returned to the deamination reaction tank 5 for reuse.

[0022] Furthermore, in the liquid polyaluminium chloride process, deamination and solid fluoride aluminium hydroxide filter cakes are added to the polymerization reaction tank 15 in a certain proportion, and 30% hydrochloric acid and washing process water are added in proportion, such as 1 ton of 30% hydrochloric acid, 0.5 ton of process water and 0.55 ton of deamination and solid fluoride aluminium hydroxide filter cake; steam is introduced into the polymerization reaction tank 15 to increase the temperature so that the reaction is sufficient to reach the design temperature of 95°C. After the temperature is kept constant for 5 hours, process water and washing water are added to the polymerization reaction tank 15 to adjust the concentration to 18°C, and then calcium aluminate powder is added to adjust the basicity and concentration of the product to reach the target material concentration of 32°C, pH value of 3.2-3.5, basicity of 85%, and alumina content of 12%. After the stable polymerization reaction for 1.5-2 hours, the product is sent to the second plate and frame filter press 16 through the filter press feed pump, and the separated liquid PAC product is sent to the liquid PAC finished product tank 17 for standby use. The filter residue separated by the second plate and frame filter press 16 can be used to make building material plates.

[0023] Furthermore, the liquid PAC product in the liquid PAC product tank 17 enters the airflow drying tower 18 from the bottom of the drying tower together with the high-temperature hot air delivered by the hot air furnace through a delivery pump at a certain flow rate. In the airflow drying tower 18, the PAC liquid is atomized, fully contacted with the hot air, and quickly dried to become PAC powder. The liquid PAC enters the second cyclone separator 19 at a certain flow rate with the hot air, and solid PAC powder is obtained at the bottom of the second cyclone separator 19.

[0024] Furthermore, the tail gas washing equipment 9 of the deamination section includes a group of washing towers 91, two groups of washing towers 92, three groups of washing towers 93 and a water circulation tank 94. The tail gas of the deamination reaction tank 5 and the first plate and frame filter press 6 is connected to the input end of the group of washing towers 91 through a pipeline, the output end of the group of washing towers 91 is connected to the input end of the two groups of washing towers 92, the output end of the two groups of washing towers 92 is connected to the input end of the three groups of washing towers 93, the group of washing towers 91, the two groups of washing towers 92 and the three groups of washing towers 93 are all connected to the water circulation tank 94 through a delivery pump, and multiple groups of washing towers cooperate to achieve multiple washing of the tail gas.

[0025] Furthermore, dilute sulfuric acid and process water are added to the interior of the tail gas washing equipment 9 of the deammoniation section. By adding dilute sulfuric acid and process water, under the action of the circulating pump and utilizing the absorption characteristics of the packed tower, the toxic and harmful substances in the tail gas are cleaned, and the tail gas finally meets the emission standards.

[0026] Furthermore, the filter dust outlet of the bag filter 4 is connected to the secondary aluminum ash silo through a pipeline. The dust generated during the operation of the first cyclone separator 1, the ball mill 2, and the screening machine 3 is filtered and removed from the solid particles through the bag filter 4 under the action of the induced draft fan. The solid dust is collected under the backblowing of compressed air and enters the secondary aluminum ash silo as a raw material for polychlorinated production.

[0027] The method of use of this embodiment is as follows: the primary aluminum ash from outside the boundary area enters the first cyclone separator 1 through the conveying equipment, and enters the first cyclone separator 1 by the tangential direction of the airflow to rotate and separate. Under the action of inertial centrifugal force, large particles of coarse ash are separated from the lower part and enter the cylinder of the ball mill through the feed port. The grinding balls in the cylinder continuously collide, rub and impact with the rotation of the cylinder, so that the coarse ash is continuously refined and at the same time, under the action of friction, the residual elemental aluminum in the aluminum ash will be precipitated in the form of large particles (hereinafter referred to as: aluminum beans). The material coming out of the ball mill passes through the screening machine 3 to separate large particles of aluminum beans, which can be sold as products; the fine powder screened out and the fine powder coming out of the first cyclone separator 1 (hereinafter referred to as: secondary aluminum ash), these secondary aluminum ashes are collected into the secondary aluminum ash silo to provide raw materials for polychloride production; the dust generated during the working process of the first cyclone separator 1, the ball mill and the screening machine 3, under the action of the induced draft fan, passes through the bag filter 4 to filter out the dust of solid particles, and is collected under the backblowing of compressed air to obtain solid dust, which is also accurately entered into the secondary aluminum ash silo as raw material for polychloride production; The secondary aluminum ash enters the deamination reaction tank 5 through the conveying equipment in a certain proportion, and hydrochloric acid, process water and liquid calcium chloride are added according to the designed proportion (the pH value of the mixed liquid in the deamination reaction tank 5 is controlled between 3.0-3.5 in the early stage, the temperature is maintained between 0-30 degrees, and the proportion of calcium chloride is between 2%-5%); after the secondary aluminum ash is added, under the action of steam, the aluminum nitride in the secondary aluminum ash reacts quickly with water to generate ammonia water, and then reacts with hydrochloric acid to generate liquid ammonium chloride (at this time, the temperature is maintained between 85-95 degrees, and the reaction of the secondary aluminum ash and water will provide the pH value of the mixed liquid. At this time, hydrochloric acid is slowly added through a metering pump to lower the pH value, and the pH value is maintained between 3.0-3.5 to continue the deamination and fluorine fixation reaction for 8 hours. The pH value is maintained between 3.0-3.5 to reduce and slow down the volatilization of ammonia. The purpose of adding calcium chloride is to fix fluorine); after the deamination and fluorine fixation is completed, the mixture that reaches the processing time enters the first plate and frame filter press 6 through the filter press conveying pump for solid-liquid separation. The ammonium chloride liquid is obtained by separation, and the liquid is sent to the ammonium chloride storage tank 7. The filter cake after separation by the first first plate and frame filter press 6 still contains a small amount of ammonium chloride. The filter cake is sent to the water washing slag tank 8, and water is added to the water washing slag tank 8 to wash the residual ammonium chloride. The remaining ammonium chloride in the filter cake is fully washed by repeated stirring, and then the suction slag liquid is sent to the second first plate and frame filter press 6 by the filter press delivery pump to separate the deammoniation and solid fluoride aluminum hydroxide filter cake, which is collected for standby use, and the second first The washing water clear liquid separated by the plate-frame filter press 6 is returned to the deamination reaction tank 5 for reuse; during the secondary aluminum ash deamination process, the tail gas containing ammonia, ammonium chloride, hydrogen chloride, dust, and water vapor generated during the reaction process of the deamination reaction tank 5 and the separation and unloading process of the first plate-frame filter press 6 enters the deamination section tail gas washing equipment 9, and by adding dilute sulfuric acid and process water, under the action of a circulating pump, the toxic and harmful substances in the tail gas are cleaned by utilizing the absorption characteristics of the packed tower, and the tail gas finally meets the emission standards; The ammonium chloride crystallization adopts MVR forced evaporator 10, evaporation increases the solubility of the ammonium chloride solution, and solid ammonium chloride is precipitated in OSLO crystallizer 11 by freezing and cooling, and then solid-liquid separation is performed by centrifuge 12 to obtain solid ammonium chloride. The separated liquid is returned to the evaporator for recycling, and the ammonium chloride solid enters the dryer 13 again to remove free water, and obtains dry solid ammonium chloride, which is sold as a product. The tail gas generated by the MVR forced evaporator 10 and the dryer 13 is washed and treated by the concentrated crystallization drying tail gas washing equipment 14; The aluminum hydroxide filter cake after deamination and fluorination is added to the polymerization reaction tank 15 by a crane in a certain proportion, and 30% hydrochloric acid and washing process water are added in proportion (1 ton of 30% hydrochloric acid, 0.5 ton of process water, and 0.55 ton of deamination and fluorination aluminum hydroxide filter cake are added); steam is introduced into the polymerization reaction tank 15 to increase the temperature to make the reaction fully reach the design temperature (95 degrees). After keeping the temperature constant for 5 hours, process water and washing water are added to the polymerization reaction tank 15, and the concentration is adjusted to 18 degrees. Then calcium aluminate powder is added to adjust the basicity and concentration of the product to meet the index. After the material (concentration 32 degrees, pH value 3.2-3.5, basicity 85%, alumina content 12%) stabilizes the polymerization reaction for 1.5-2 hours, it is sent to the plate-frame filter press through the filter press feed pump, and the separated liquid PAC product is sent to the liquid PAC finished product tank 17 for standby use. The filter residue separated by the second plate-frame filter press 16 can be used to make building material boards; during the reaction and filtration process, tail gas containing hydrogen chloride gas and solid dust is generated, which is sent to the polymerization reaction section tail gas washing equipment 21, and the tail gas is finally discharged in compliance with the standards through the circulating washing of the packed tower; The liquid PAC finished product enters the airflow drying tower 18 from the bottom of the airflow drying tower 18 through a delivery pump at a certain flow rate together with the high-temperature hot air sent out by the hot air furnace. In the tower, the PAC liquid is atomized, fully contacted with the hot air, and quickly dried to become PAC powder. It enters the second cyclone separator 19 with the hot air at a certain flow rate, and solid PAC powder is obtained at the bottom of the second cyclone separator 19. After separation, the hot air containing a small amount of small particles of dust enters the PAC concentrated drying tail gas washing equipment 20, and is discharged into the atmosphere after the solid content of the tail gas is reduced through filler circulation washing.

[0028] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A process for producing polyaluminium chloride from aluminium ash resources, characterized in that: It includes a primary aluminum ash pretreatment process, a secondary aluminum ash deammoniation process, an ammonium chloride crystallization process, a liquid polyaluminum chloride process and a solid polyaluminum chloride process; The primary aluminum ash pretreatment process comprises a first cyclone separator (1), a ball mill (2), a screening machine (3) and a bag dust collector (4); the input end of the first cyclone separator (1) is connected to a primary aluminum ash bin via a conveying device; the coarse ash end of the first cyclone separator (1) is connected to a feed port of the ball mill (2); the discharge port of the ball mill (2) is connected to a feed port of the screening machine (3); the fine powder screened by the screening machine (3) and the secondary aluminum ash fine powder discharged by the first cyclone separator (1) are collected in a secondary aluminum ash bin; the dust outlets of the first cyclone separator (1), the ball mill (2) and the screening machine (3) are connected to a dust inlet of the bag dust collector (4) via a pipeline; and the bag dust collector (4) is connected to the input end of an induced draft fan via a pipeline; The secondary aluminum ash deamination process comprises a deamination reaction tank (5), a first plate-frame filter press (6), an ammonium chloride storage tank (7), a water-washing slag tank (8), and a deamination section tail gas washing device (9); the secondary aluminum ash generated in the primary aluminum ash pretreatment process is connected to the deamination reaction tank (5) via a conveying device; the output end of the deamination reaction tank (5) is connected to the input end of the first plate-frame filter press (6) via a filter press conveying pump; the liquid outlet end of the first plate-frame filter press (6) is connected to the input end of the ammonium chloride storage tank (7); the filter cake outlet of the first plate-frame filter press (6) is connected to the water-washing slag tank (8); and the tail gas from the deamination reaction tank (5) and the first plate-frame filter press (6) is connected to the deamination section tail gas washing device (9) via a pipeline; The ammonium chloride crystallization process comprises an MVR forced evaporator (10), an OSLO crystallizer (11), a centrifuge (12), a dryer (13) and a concentrated crystallization drying tail gas washing device (14); the liquid outlet of the ammonium chloride storage tank (7) is connected to the input end of the MVR forced evaporator (10) through a pipeline; the output end of the MVR forced evaporator (10) is connected to the input end of the OSLO crystallizer (11); the output end of the OSLO crystallizer (11) is connected to the input end of the centrifuge (12) through a pipeline; the output end of the centrifuge (12) is connected to the input end of the dryer (13) through a pipeline; and the tail gas of the MVR forced evaporator (10) and the dryer (13) is connected to the concentrated crystallization drying tail gas washing device (14) through a pipeline; The liquid polyaluminium chloride process comprises a polymerization reaction tank (15), a second plate-frame filter press (16) and a liquid PAC finished product tank (17); the deaminated and fluorinated aluminium hydroxide filter cake produced by the first plate-frame filter press (6) is transported to the polymerization reaction tank (15); the polymerization reaction tank (15) is connected to the input end of the second plate-frame filter press (16) via a filter press feed pump; the liquid outlet end of the second plate-frame filter press (16) is connected to the liquid PAC finished product tank (17) via a pipeline; and the tail gas of the polymerization reaction tank (15) is connected to the tail gas washing equipment (21) of the polymerization reaction section via a pipeline; The solid polyaluminium chloride process comprises an airflow drying tower (18) and a second cyclone separator (19); the outlet of the liquid PAC finished product tank (17) is connected to the input end of the airflow drying tower (18) via a delivery pump; the output end of the airflow drying tower (18) is connected to the input end of the second cyclone separator (19); the bottom of the second cyclone separator (19) is connected to a solid PAC powder silo; and the tail gas of the second cyclone separator (19) is connected to a PAC concentrated drying tail gas washing device (20) via a pipeline.

2. The process for producing polyaluminium chloride from aluminium ash resources according to claim 1, characterized in that: When the secondary aluminum ash is added to the deamination reaction tank (5), hydrochloric acid, process water and liquid calcium chloride are added in proportion. The pH value of the mixed liquid in the deamination reaction tank (5) is controlled at 3.0-3.5 in the early stage, the temperature is maintained at 0-30°C, and the proportion of calcium chloride is 2%-5%. After the secondary aluminum ash is added to the deamination reaction tank (5), under the action of steam, the aluminum nitride in the secondary aluminum ash reacts quickly with water to generate ammonia water, and then reacts with hydrochloric acid to generate liquid ammonium chloride. At this time, the temperature is maintained at 85-95°C. The reaction of the secondary aluminum ash with water will increase the pH value of the mixed liquid. Hydrochloric acid is slowly added through a metering pump to reduce the pH value. The pH value is maintained at 3.0-3.

5. The deamination and fluorine fixation reaction is continued for 8 hours, and the pH value is maintained at 3.0-3.

5.

3. The process for producing polyaluminium chloride from aluminium ash resources according to claim 1, characterized in that: A stirrer is provided inside the water-washing slag tank (8); the liquid outlet of the water-washing slag tank (8) is connected to the input end of the first plate-frame filter press (6) via a filter press delivery pump; and the washing water clear liquid outlet of the first plate-frame filter press (6) is connected to the deamination reaction tank (5) via a pipeline.

4. The process for producing polyaluminium chloride from aluminium ash resources according to claim 1, characterized in that: In the liquid polyaluminium chloride process, deaminated and fluorinated aluminium hydroxide filter cakes are added to the polymerization reaction tank (15) in a certain proportion, and 30% hydrochloric acid and washing process water are added in proportion, such as 1 ton of 30% hydrochloric acid, 0.5 ton of process water, and 0.55 ton of deaminated and fluorinated aluminium hydroxide filter cake. Steam is introduced into the polymerization reaction tank (15) to increase the temperature to a designed temperature of 95°C. After the temperature is kept constant for 5 hours, process water and washing water are added to the polymerization reaction tank (15) to adjust the concentration to 18°C. Calcium aluminate powder is then added to adjust the basicity and concentration of the product to a target material concentration of 32°C, a pH value of 3.2-3.5, a basicity of 85%, and an alumina content of 12%. After the target polymerization reaction is stabilized for 1.5-2 hours, the product is fed into the second plate and frame filter press (16) through the filter press feed pump.

5. The process for producing polyaluminium chloride from aluminium ash resources according to claim 1, characterized in that: The liquid PAC product in the liquid PAC product tank (17) is conveyed by a delivery pump at a certain flow rate together with the high-temperature hot air delivered by the hot air furnace, and enters the airflow drying tower (18) from the bottom of the drying tower. In the airflow drying tower (18), the PAC liquid is atomized, fully contacts with the hot air, and is quickly dried to become PAC powder, and enters the second cyclone separator (19) at a certain flow rate together with the hot air.

6. The process for producing polyaluminium chloride from aluminium ash resources according to claim 1, characterized in that: The deamination section tail gas washing equipment (9) comprises a first group of washing towers (91), a second group of washing towers (92), a third group of washing towers (93) and a water circulation tank (94); the tail gas from the deamination reaction tank (5) and the first plate-frame filter press (6) is connected to the input end of the first group of washing towers (91) through a pipeline; the output end of the first group of washing towers (91) is connected to the input end of the second group of washing towers (92); the output end of the second group of washing towers (92) is connected to the input end of the third group of washing towers (93); and the first group of washing towers (91), the second group of washing towers (92) and the third group of washing towers (93) are all connected to the water circulation tank (94) through a delivery pump.

7. The process for producing polyaluminium chloride from aluminium ash resources according to claim 1, characterized in that: Dilute sulfuric acid and process water are added to the interior of the deamination section tail gas washing equipment (9).

8. The process for producing polyaluminium chloride from aluminium ash resources according to claim 1, characterized in that: The dust filtering outlet of the bag filter (4) is connected to the secondary aluminum ash silo through a pipeline.

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