CN109112546B

CN109112546B - Oxidation line system and process for recovering aluminum hydroxide and sodium sulfate from mold-stewing liquid

Info

Publication number: CN109112546B
Application number: CN201810843468.5A
Authority: CN
Inventors: 熊映明
Original assignee: Foshan Sanshui Xiongying Innovation Center For Aluminum Surface Technnologies Co ltd
Current assignee: Foshan Sanshui Xiongying Innovation Center For Aluminum Surface Technnologies Co ltd
Priority date: 2018-07-27
Filing date: 2018-07-27
Publication date: 2021-04-20
Anticipated expiration: 2038-07-27
Also published as: CN109112546A

Abstract

An oxidation line configuration and a process for recovering aluminum hydroxide and sodium sulfate from a mold-stewing liquid, wherein in the configuration, a secondary filtrate collecting tank, a number six pump, a mold-stewing groove, a wastewater diversion trench and a mold-stewing liquid collecting tank are adjacently connected; the pot die groove is used for a pot die of the aluminum material; the oil removing groove, the flowing water washing groove, the alkaline etching groove, the first alkaline etching liquid intercepting groove, the second alkaline etching liquid intercepting groove, the high-pressure atomization spraying groove and the neutralization groove are sequentially connected; the die-stewing liquid collecting tank, the seventh pump and the alkaline etching tank are sequentially connected; the second alkaline etching solution interception tank, the No. nine pump and the secondary filtrate collection tank are sequentially connected; the first alkaline etching liquid interception tank, the eighth pump and the alkaline etching liquid collection tank are sequentially connected; collecting the alkaline etching waste liquid by an alkaline etching liquid collecting tank, and transmitting the alkaline etching waste liquid to a reaction liquid treatment system; the reaction liquid treatment system, the filtrate collection system and the primary filtrate separation system are sequentially connected; the process comprises the steps of adding the alkaline etching waste liquid into a reaction liquid treatment system, adding the oxidation waste liquid into the reaction liquid treatment system for reaction, and separating aluminum hydroxide and sodium sulfate through a filtrate collection system and a primary filtrate separation system.

Description

Oxidation line system and process for recovering aluminum hydroxide and sodium sulfate from mold-stewing liquid

Technical Field

The invention relates to the technical field of aluminum processing, in particular to an oxidation line system and process for recovering aluminum hydroxide and sodium sulfate from mold-stewing liquid, and in fact relates to an oxidation line system and process for recovering aluminum hydroxide and sodium sulfate from mold-stewing liquid instead of alkaline etching liquid.

Background

The aluminum alloy has the advantages of excellent processing performance, good corrosion resistance, beautiful surface, high recovery rate and the like, and is widely applied to the industries of buildings, transportation, machinery, electric power and the like. In recent years, the trend of replacing copper, wood and steel with aluminum and expanding the application range of aluminum is more obvious. The aluminum processing industry is not only a traditional industry, but also a sunrise industry full of bobby vitality. According to statistics, people in developed countries in Europe and America consume more than 32kg of aluminum alloy every year, while people in China only have about 13kg and only one third of developed countries, and the consumption of the aluminum alloy in China has huge growth space. However, in the new economic normality, the common problems of high energy consumption, large total pollution discharge amount and low resource recycling rate in the aluminum processing industry are obviously bottlenecks and obstacles for restricting the development of the industry.

The production in the aluminum industry comprises the working procedures of electrolysis, casting, pressure processing, surface treatment and the like, and waste gas, waste water and waste residue with different degrees are generated in each working procedure during production. A large amount of aluminum ash is generated during electrolysis and casting, a die-cooking alkaline waste liquid is generated in the extrusion process, and various waste water and waste residues containing acid, alkali, treatment agents, chromium, nickel heavy metal ions and other complex components are generated in the surface treatment process.

Disclosure of Invention

The invention aims to provide an oxidation line system for recovering aluminum hydroxide and sodium sulfate from mold-stewing liquid, wherein secondary filtrate can be used as a recovery system in the structure;

the invention also provides a process of the oxidation line system for recovering the aluminum hydroxide and the sodium sulfate from the mold-stewing liquid, which can effectively separate the sodium hydroxide and the sodium sulfate.

In order to achieve the purpose, the invention adopts the following technical scheme:

an oxidation line system for recovering aluminum hydroxide and sodium sulfate from mold liquor comprises: a secondary filtrate collecting tank, a die-stewing waste liquid treatment system, a raw material waste liquid treatment system, a reaction liquid treatment system and a primary filtrate collecting system;

the mould liquid water disposal system of stewing includes: a sixth pump, a pot die groove, a wastewater diversion ditch and a pot die liquid collection tank;

the secondary filtrate collecting tank, the number six pump, the pot die groove, the wastewater diversion trench and the pot die liquid collecting tank are adjacently and sequentially communicated and connected; a high-pressure atomizing water gun is arranged in the wastewater diversion trench; the high-pressure atomizing water gun is communicated with the No. six pump; the pot die groove is used for a pot die of aluminum materials;

the raw material waste liquid treatment system includes: an alkaline etching waste liquid generating system and an alkaline etching waste liquid collecting system; the alkaline etching waste liquid generation system includes: the device comprises an alkaline etching tank, a first alkaline etching solution intercepting tank, a second alkaline etching solution intercepting tank, an alkaline etching solution collecting tank, a seventh pump, an eighth pump and a ninth pump; the caustic etching waste liquid collection system includes: the device comprises an oil removing tank, a flowing rinsing tank, a high-pressure atomization spraying tank, a neutralizing tank and a spraying liquid collecting tank;

the oil removing groove, the flowing water washing groove, the alkaline etching groove, the first alkaline etching liquid intercepting groove, the second alkaline etching liquid intercepting groove, the high-pressure atomizing spraying groove and the neutralizing groove are sequentially connected; the die-stewing liquid collecting tank, the seventh pump and the alkaline etching tank are sequentially connected; the second alkaline etching solution interception tank, the No. nine pump and the secondary filtrate collection tank are sequentially connected; the first alkaline etching solution intercepting tank, the eighth pump and the alkaline etching solution collecting tank are sequentially connected; the high-pressure atomization spraying tank and the flowing water washing tank are respectively connected with a water inlet; the high-pressure atomization spraying tank, the spraying liquid collecting tank, the No. nine pump and the second caustic etching liquid intercepting tank are sequentially communicated and connected, and the No. nine pump is also connected with the secondary filtrate collecting tank;

the mold stewing liquid in the wastewater diversion trench sequentially passes through a mold stewing liquid collecting tank and an alkaline etching tank through the No. seven pump; the oil removing tank and the flowing water washing tank are respectively used for treating the aluminum material; the alkaline etching tank is used for treating the die-cooking liquid of the die-cooking liquid collecting tank, and alkaline etching the oil removing tank and the aluminum material treated by the flowing water to generate alkaline etching waste liquid; the first alkaline etching solution intercepting tank and the second alkaline etching solution intercepting tank are used for cleaning the aluminum material treated by the alkaline etching tanks; the high-pressure atomization spraying groove is used for spraying the aluminum material treated by the alkaline etching groove; the neutralization tank is used for neutralizing the treated aluminum material; the alkaline etching liquid collecting tank is used for collecting the alkaline etching waste liquid of the first alkaline etching liquid intercepting tank and transmitting the alkaline etching waste liquid to the reaction liquid treatment system;

the reaction liquid treatment system, the filtrate collection system and the primary filtrate separation system are communicated and connected in sequence;

the reaction liquid treatment system receives the alkaline etching waste liquid of the alkaline etching liquid collection tank, adds an oxidation waste liquid, mixes and reacts with the alkaline etching waste liquid, separates out aluminum hydroxide and primary filtrate through the filtrate collection system, and separates out sodium sulfate from the primary filtrate through the primary filtrate separation system;

the second alkaline etching liquid holds back the groove, sprays liquid collecting tank and high-pressure atomizing and sprays the groove and connect gradually, spray the liquid collecting tank with be equipped with No. nine pumps on the connecting pipeline of second alkaline etching liquid holding back the groove, it connects gradually to spray liquid collecting tank, No. nine pumps and secondary filtrating collecting pit, secondary filtrating collecting pit still is used for collecting the second alkaline etching liquid holds back the alkali etching waste liquid that groove and high-pressure atomizing sprayed the groove.

Further, the mold-stewing liquid collecting tank is used for collecting the mold-stewing liquid after the sodium hydroxide reacts with the aluminum mold;

when the die-stewing liquid passes through the die-stewing liquid collecting tank, the ratio of the concentration of free alkali of the die-stewing waste liquid to the concentration of aluminum ions is 3.8-4.2;

when the die-stewing waste liquid passes through the alkaline etching groove, the ratio of the free alkali concentration of the die-stewing waste liquid to the aluminum ion concentration is 3.5-4.0.

Further, the reaction liquid processing system includes: a reaction liquid addition system and a reaction liquid separation system;

the reaction liquid addition system includes: the device comprises an oxidizing liquid collecting tank, a reaction tank, a first pump and a second pump; the oxidation liquid collecting tank, the first pump and the reaction tank are respectively communicated and connected in sequence, so that the oxidation waste liquid in the oxidation liquid collecting tank is transferred to the reaction tank through the first pump; the reaction tank and the alkaline etching liquid collecting tank are connected with the second pump, so that the second pump transmits the alkaline etching waste liquid in the alkaline etching liquid collecting tank to the reaction tank;

the reaction liquid separation system includes: the device comprises a solid-liquid separation tank, a first centrifugal machine, a first filtrate recovery tank and a third pump; the solid-liquid separation tank, the first centrifuge, the first filtrate recovery tank and the third pump are adjacently communicated and connected in sequence;

the upper layer of the reaction tank, a second pump and a first filtrate recovery tank are sequentially communicated and connected, and the second pump is used for transferring primary filtrate of the first filtrate recovery tank to the reaction tank;

the upper end of the solid-liquid separation tank, the first filtrate recovery tank and the second pump are respectively communicated and connected with the reaction tank;

pipelines leading to the third pump are respectively arranged at the bottom and the middle part of the first filtrate recovery tank and are respectively controlled by a nineteen valve and an eighteen valve; the third pump is also connected with the reaction tank;

the first centrifuge is used for separating sodium oxide at the pH value of 7.00-7.50, and guiding liquid to the first filtrate recovery tank; and the third pump is connected with the primary filtrate separation system, so that sodium sulfate is separated from the primary filtrate separation system at the pH value of 7.00-7.50 after primary filtrate in the first filtrate recovery tank is transferred to the primary filtrate separation system.

More specifically, the number of the reaction tanks is 2; the reaction tanks are respectively communicated and connected with the middle part and the lower part of the side walls of the reaction tanks and the bottom of the reaction tank, and are jointly connected with the second pump;

the second pump is arranged in the upper layer connected with the reaction tanks, a connecting pipeline of the second pump is provided with a thirteen-number valve at the inlet of one of the reaction tanks, and a fourteen-number valve at the inlet of the other reaction tank;

a third valve is arranged at the outlet of the middle part of one of the reaction tanks, a fifth valve is arranged at the outlet of the lower part of the one of the reaction tanks, and a seventh valve is arranged at the bottom of the one of the reaction tanks; a fourth valve is arranged at the outlet of the middle part of the other reaction tank, a sixth valve is arranged at the outlet of the lower part of the other reaction tank, and an eighth valve is arranged at the bottom of the reaction tank; a ninth valve is arranged on a connecting pipeline of the reaction tanks which are connected with the second pump;

the first pump is respectively connected to the top of the reaction tank, and a first valve is respectively arranged on the connected pipelines.

Further illustratively, the filtrate collection system comprises: the system comprises a sodium sulfate crystallization tank, a fourth pump, a second centrifuge, a second filtrate recovery tank and a fifth pump; the third pump, the sodium sulfate crystallizing tank, the fourth pump, the second centrifuge, the second filtrate recovery tank and the fifth pump are adjacently connected in sequence; the third pump is connected into the sodium sulfate crystallizing tank; the fifth pump is communicated and connected with the secondary filtrate collecting tank;

an ice maker is arranged in the sodium sulfate crystallizing tank; the second centrifuge is used to separate the sodium sulfate.

Further, a plurality of pot mold containers are arranged in the pot mold groove; the inlet of the die stewing container is respectively connected with the number six pump, and a fourteen valve is arranged at the inlet of the die stewing container; the outlet of the die stewing container is connected with the wastewater diversion trench, and a thirty-two valve is arranged at the outlet of the die stewing container;

furthermore, the side of the reaction tank is provided with an anti-overflow port; the overflow preventing port is arranged between the top and the middle of the side wall of the reaction tank; the first filtrate recovery tank is respectively connected with the overflow preventing port through a pipeline;

and stirrers are arranged in the reaction tank, the solid-liquid separation tank, the filtrate recovery tank and the sodium sulfate crystallization tank.

Further, the process of the oxidation line system for recovering the aluminum hydroxide and the sodium sulfate from the mold-stewing liquid comprises the following steps: (1) recovering a die-stewing waste liquid, (2) generating an alkaline etching waste liquid, (3) collecting the alkaline etching waste liquid, (4) collecting an oxidation waste liquid, (5) adding the alkaline etching waste liquid, (6) separating reaction liquid, (7) collecting and recovering primary filtrate, (8) recovering sodium sulfate, and (9) collecting secondary filtrate;

the invention has the beneficial effects that:

1. the invention uses the secondary filtrate as a recovery system for the first time: grooving the die cavity of the pot, and recycling secondary filtrate; cleaning the die by using secondary filtrate with the aid of a high-pressure atomizing water gun, reducing cleaning water and ensuring the concentration of recovered die-cooking waste liquid; under the premise that a large amount of water for evaporation and sodium sulfate decahydrate consume a large amount of crystal water during mold cooking, a large system of a mold cooking workshop is lack of water, the spraying water of a high-pressure atomization spraying groove is used in the whole mold cooking workshop, and water is supplemented to a secondary filtrate collecting pool through a No. nine pump, so that the pollution of sodium ions to the center of wastewater in the mold cooking operation and the alkaline etching operation is thoroughly blocked, and the zero discharge of wastewater and waste residues is realized; pumping the waste water into a secondary filtrate collecting pool by a fifth pump for recycling, waiting for the next recycling, thoroughly isolating sodium ions in the center of the waste water, realizing zero discharge of waste water and waste residue in a die-stewing workshop, and removing the largest sodium ion barrier for recycling reclaimed water;

2. r is the ratio of the concentration of free alkali to the concentration of aluminum ions by using sodium hydroxide, and the decomposition rule of the mold-cooking liquid is fully researched for the first time, so that the condition that R is 3.00 is the decomposition point of sodium metaaluminate is obtained; under the condition that the seed crystal is not available and R is more than or equal to 3.50, the mold boiling liquid can be conveyed by a pipeline; the mold boiling liquid can be stored for a long time under the condition that the seed crystal is not available and R is more than or equal to 4.00; the method lays a solid foundation for on-line recovery by converting the mold boiling liquid into the alkaline etching liquid, storing and conveying the alkaline etching liquid to the alkaline etching tank.

3. The invention firstly utilizes the oxidation waste liquid as the reaction liquid, adds the recovered alkaline etching waste liquid, and recovers the byproducts of the aluminum hydroxide and the sodium sulfate when the pH value is between 7.00 and 7.50, thereby obtaining the recovery product with high purity.

Drawings

FIG. 1 is a block diagram of a raw material waste liquid treatment system;

FIG. 2 is a diagram of the connection structure of the secondary filtrate collection tank and the waste liquid treatment system;

FIG. 3 is a diagram showing the connection structure of a raw material waste liquid treatment system, a reaction liquid treatment system and a filtrate collection system;

FIG. 4 is a block diagram of a primary filtrate separation system;

wherein:

an oxidation liquid collecting tank 1, a reaction tank 2, an alkaline etching liquid collecting tank 3, a solid-liquid separation tank 4, a first centrifuge 51, a second centrifuge 52, a first filtrate recovering tank 61, a second filtrate recovering tank 62, a pot die groove 7, a wastewater diversion trench 8, a secondary filtrate collecting tank 9 and a sodium sulfate crystallizing tank 111; a high-pressure atomizing water gun 81; a mold pot liquid collection tank 99; a water inlet 88;

an oil removing groove 71, a flowing water washing groove 72, an alkaline etching groove 74, a first alkaline etching liquid retaining groove 75, a second alkaline etching liquid retaining groove 76, a high-pressure atomization spraying groove 77 and a neutralizing groove 78; spray liquid collection tank 771

The first pump 01, the second pump 02, the third pump 03, the fourth pump 04, the fifth pump 05, the sixth pump 06, the seventh pump 07, the eighth pump 08, the ninth pump 09 and the tenth pump 010;

valve 0001, valve 0003, valve 0004, valve 0005, valve 0006, valve 0007, valve 0008, valve 0009 and valve 0010; valve 0011, valve 0012, valve 0013, valve 0014, valve 0015, valve 0016, valve 0017, valve 0018, valve 0019 and valve 0020; a twenty-first valve 0021 and a twenty-second valve 0022; a twenty-five valve 0025, a twenty-six valve 0026, a twenty-seven valve 0027, a twenty-eight valve 0028, a twenty-nine valve 0029 and a thirty valve 0030; a thirty-one valve 0031 and a thirty-two valve 0032; a fourteen-gauge valve 0044; fifty-six number valve 0056, fifty-seven number valve 0057, fifty-eight number valve 0058, fifty-nine number valve 0059; a sixty-one valve 0061, a sixty-one valve 0060, a sixty-two valve 0062, and a sixty-three valve 0063;

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.

An oxidation line system for recovering aluminum hydroxide and sodium sulfate from mold liquor comprises: a secondary filtrate collecting tank 9, a die-stewing waste liquid treatment system, a raw material waste liquid treatment system, a reaction liquid treatment system and a primary filtrate collecting system;

the mould liquid water disposal system of stewing includes: a sixth pump 06, a pot mould groove 7, a wastewater diversion ditch 8 and a pot mould liquid collecting tank 99;

the secondary filtrate collecting tank 9, a No. six pump 06, a pot mould groove 7, a wastewater diversion ditch 8 and a pot mould liquid collecting tank 99 are adjacently communicated and connected in sequence; a high-pressure atomizing water gun 81 is arranged in the wastewater diversion trench 8; the high-pressure atomizing water gun 81 is communicated with the No. six pump 06; the pot die groove 7 is used for a pot die of aluminum materials;

the raw material waste liquid treatment system includes: an alkaline etching waste liquid generating system and an alkaline etching waste liquid collecting system; the alkaline etching waste liquid generation system includes: an alkaline etching tank 74, a first alkaline etching solution retaining tank 75, a second alkaline etching solution retaining tank 76, an alkaline etching solution collecting tank 3, a seventh pump 07, an eighth pump 08 and a ninth pump 09; the caustic etching waste liquid collection system includes: an oil removing tank 71, a flowing water washing tank 72, a high-pressure atomization spraying tank 77, a neutralization tank 78 and a spraying liquid collecting tank 771;

the oil removing tank 71, the flowing water washing tank 72, the alkaline etching tank 74, the first alkaline etching liquid intercepting tank 75, the second alkaline etching liquid intercepting tank 76, the high-pressure atomization spraying tank 77 and the neutralization tank 78 are sequentially connected; the die-stewing liquid collecting tank 99, the No. seven pump 07 and the alkaline etching tank 74 are connected in sequence; the second caustic etching solution interception tank 76, the nine-pump 09 and the secondary filtrate collection tank 9 are connected in sequence; the first alkaline etching solution intercepting tank 75, the eighth pump 08 and the alkaline etching solution collecting tank 3 are connected in sequence; the high-pressure atomization spraying tank 77 and the flowing water washing tank 72 are respectively connected with a water inlet 88; the high-pressure atomization spraying tank 77, the spraying liquid collecting tank 771, the No. nine pump 09 and the second alkaline etching liquid intercepting tank 76 are sequentially communicated and connected, and the No. nine pump 09 is also connected with the secondary filtrate collecting tank 9;

the mold-stewing liquid in the wastewater diversion trench 8 sequentially passes through a mold-stewing liquid collection tank 99 and an alkaline etching tank 74 through the No. seven pump 07; the oil removing tank 71 and the flowing water washing tank 72 are respectively used for treating aluminum materials; the alkaline etching tank 74 is used for treating the mold-cooking liquid in the mold-cooking liquid collecting tank 99, and alkaline etching the oil removing tank 71 and the aluminum material treated by the flowing water to generate alkaline etching waste liquid; the first alkaline etching solution retaining tank 75 and the second alkaline etching solution retaining tank 76 are used for cleaning the aluminum material treated by the alkaline etching tank 74; the high-pressure atomization spraying groove 77 is used for spraying the aluminum material treated by the alkaline etching groove 74; the neutralizing tank 78 is used for neutralizing the treated aluminum material; the alkaline etching liquid collecting tank 3 is configured to collect the alkaline etching waste liquid of the first alkaline etching liquid retaining tank 75, and transfer the alkaline etching waste liquid to the reaction liquid treatment system;

the reaction liquid treatment system receives the alkaline etching waste liquid in the alkaline etching liquid collection tank 3, adds an oxidation waste liquid, mixes and reacts with the alkaline etching waste liquid, separates out aluminum hydroxide and primary filtrate through the filtrate collection system, and separates out sodium sulfate from the primary filtrate through the primary filtrate separation system;

second alkali etching liquid entrapment groove 76, spray liquid collection tank 771 and high-pressure atomization spray groove 77 and connect gradually, spray liquid collection tank 771 with be equipped with No. nine pumps 09 on the connecting pipeline of second alkali etching liquid entrapment groove 76, spray liquid collection tank 771, No. nine pumps 09 and secondary filtrating collecting pit 9 and connect gradually, secondary filtrating collecting pit 9 still is used for collecting the alkali etching waste liquid of second alkali etching liquid entrapment groove 76 and high-pressure atomization spray groove 77.

Further, the invention uses the secondary filtrate as a recovery system for the first time: grooving the die cavity 7 of the cooker, and recycling the secondary filtrate; cleaning the die by using secondary filtrate with the aid of a high-pressure atomizing water gun, reducing cleaning water and ensuring the concentration of recovered die-cooking waste liquid; under the premise that a large amount of water for evaporation and sodium sulfate decahydrate consume a large amount of crystal water during mold cooking, a large system of a mold cooking workshop is lack of water, the spraying water of a high-pressure atomizing spraying groove is used in the whole mold cooking workshop, and water is supplemented to a secondary filtrate collecting tank 9 through a No. nine pump 09, so that the pollution of sodium ions to the center of wastewater in the mold cooking operation and the alkaline etching operation is thoroughly blocked, and the zero discharge of wastewater and waste residues is realized; the filtrate is sent back to a secondary filtrate collecting pool 9 by a No. five pump 05 for recycling, the next recycling is waited, the sodium ions in the center of the wastewater are thoroughly isolated, the zero discharge of the wastewater and the waste residues in the die-filling workshop is realized, and the largest sodium ion barrier is removed for the reuse of reclaimed water;

in a further description, the mold-cooking waste liquid obtained after the reaction of the sodium hydroxide and the aluminum mold is passed through the mold-cooking liquid collecting tank 99;

when the die-stewing liquid passes through the die-stewing liquid collecting tank 99, the ratio of the concentration of free alkali of the die-stewing waste liquid to the concentration of aluminum ions is 3.8-4.2;

when the die-stewing waste liquid passes through the alkaline etching groove 74, the ratio of the free alkali concentration of the die-stewing waste liquid to the aluminum ion concentration is 3.5-4.0.

Further, the decomposition rule of the mold-stewing liquid is fully researched for the first time, and the result shows that R is 3.00 which is the decomposition point of sodium metaaluminate; under the condition that the seed crystal is not available and R is more than or equal to 3.50, the mold boiling liquid can be conveyed by a pipeline; the mold boiling liquid can be stored for a long time under the condition that the seed crystal is not available and R is more than or equal to 4.00;

the invention is provided with an alkaline etching waste liquid collecting system for the first time, which is responsible for sending the alkaline etching waste liquid intercepted by the first alkaline etching liquid intercepting groove 75 into the alkaline etching liquid collecting tank 3; sending the spray liquid collected by the spray liquid collection tank 771 to the second alkaline etching liquid interception tank 76, reversely flowing back to the first alkaline etching liquid interception tank 75, intercepting the alkaline etching waste liquid in a gradient way, and reversely collecting the alkaline etching waste liquid with high concentration before and low concentration after; pumping redundant spray liquid into a secondary filtrate collecting tank 9, replenishing water to a pot die workshop, and completely recycling sodium-containing wastewater in the whole pot die workshop and an oxidation workshop so as to thoroughly prevent sodium ions from polluting the center of the wastewater;

the reaction liquid addition system includes: the device comprises an oxidizing liquid collecting tank 1, a reaction tank 2, a first pump 01 and a second pump 02; the oxidation liquid collecting tank 1, the first pump 01 and the reaction tank 2 are communicated and connected in sequence respectively, so that the oxidation waste liquid in the oxidation liquid collecting tank 1 is transferred to the reaction tank 2 through the first pump 01; the reaction tank 2 and the alkaline etching liquid collecting tank 3 are connected with the second pump 02, so that the second pump 02 transfers the alkaline etching waste liquid of the alkaline etching liquid collecting tank 3 into the reaction tank 2;

the reaction liquid separation system includes: a solid-liquid separation tank 4, a first centrifuge 51, a first filtrate recovery tank 61 and a third pump 03; the solid-liquid separation tank 4, the first centrifuge 51, the first filtrate recovery tank 61 and the third pump 03 are adjacently and sequentially communicated and connected;

the upper layer of the reaction tank 2, the second pump 02 and the first filtrate recovery tank 61 are sequentially communicated and connected, and the second pump 02 is used for transferring the primary filtrate of the first filtrate recovery tank 61 to the reaction tank 2;

the upper end of the solid-liquid separation tank 4, the first filtrate recovery tank 61, the second pump 02 and the reaction tank 2 are respectively communicated and connected;

the bottom and the middle part of the first filtrate recovery tank 61 are respectively provided with a pipeline leading to the third pump 03 and are respectively controlled by a nineteen valve 0019 and an eighteen valve 0018; the third pump 03 is also connected with the reaction tank 2;

the first centrifuge 51 is configured to separate sodium oxide at a pH between 7.00 and 7.50 and to direct the liquid to the first filtrate recovery tank 61; the third pump 03 is connected with the primary filtrate separation system, so that the primary filtrate in the first filtrate recovery tank 61 is transferred to the primary filtrate separation system, and then sodium sulfate is separated by the primary filtrate separation system at a pH value of 7.00-7.50.

To be further explained, the number of the reaction tanks 2 is 2; the reaction tanks 2 are respectively communicated and connected with the middle part and the lower part of the side walls of the reaction tanks 2 and the bottom of the reaction tank 2, and are jointly connected with the second pump 02;

the second pump 02 is arranged in the upper layer connected with the reaction tanks 2, the connecting pipeline of the second pump is provided with a thirteen-numbered valve 0013 at the inlet of one of the reaction tanks 2, and a fourteen-numbered valve 0014 at the inlet of the other reaction tank 2;

a third valve 0003 is arranged at the outlet of the middle part of one of the reaction tanks 2, a fifth valve 0005 is arranged at the outlet of the lower part of the one of the reaction tanks 2, and a seventh valve 0007 is arranged at the bottom of the one of the reaction tanks 2; a fourth valve 0004 is arranged at the outlet of the middle part of the other reaction tank 2, a sixth valve 0006 is arranged at the outlet of the lower part of the other reaction tank 2, and an eighth valve 0008 is arranged at the bottom of the reaction tank 2; a nine-valve 0009 is arranged on a connecting pipeline of the reaction tanks 2 which are connected with the second pump 02;

the first pump 01 is respectively connected to the top of the reaction tank 2, and a first valve 0001 is respectively arranged on the connected pipelines.

Further, the invention firstly arranges a No. ten valve 0010 in the reaction liquid adding system, utilizes the reaction liquid circulation formed by a No. eleven valve 0011, a No. thirteen valve 0013, a No. fourteen valve 0014, a reaction tank 2, a No. seven valve 0007, a No. eight valve 0008 and a No. two pump 02, and the No. ten valve 0010 is in the ingenious design of negative pressure, and sucks the alkaline etching waste liquid into the reaction tank 2; the alkaline etching waste liquid is fully mixed and reacted with the oxidizing liquid at the second pump 02 to generate aluminum hydroxide, and metal aluminum and sodium are recovered;

further illustratively, the filtrate collection system comprises: a sodium sulfate crystallization tank 111, a pump 04 with the fourth grade, a second centrifuge 52, a second filtrate recovery tank 62 and a pump 05 with the fifth grade; the third pump 03, the sodium sulfate crystallizing tank 111, the fourth pump 04, the second centrifuge 52, the second filtrate recovery tank 62 and the fifth pump 05 are adjacently and sequentially communicated and connected; the third pump 03 is connected into the sodium sulfate crystallizing tank 111; the fifth pump 05 is communicated and connected with the secondary filtrate collecting tank 9;

an ice maker is arranged in the sodium sulfate crystallizing tank 111; the second centrifuge 52 is used to separate the sodium sulfate.

More specifically, a plurality of pot mold containers are arranged in the pot mold groove 7; the inlet of the die stewing container is respectively connected with the number six pump 06, and the inlet of the die stewing container is provided with a fourteen valve 0044; the outlet of the die stewing container is connected with the wastewater diversion trench 8, and a thirty-two valve 0032 is arranged at the outlet of the die stewing container;

a twenty-ninth valve 0029 is arranged on a connecting pipeline of the secondary filtrate collecting tank 9 and the sixth pump 06; a thirty-grade valve 0030 is arranged on a connecting pipeline of the sixth pump 06 and the pot die cavity 7; a connecting pipeline of the high-pressure atomizing water gun 81 and the No. six pump 06 is provided with a No. thirty-one valve 0031;

a fifty-six valve 0056 is arranged on a connecting pipeline between the seven-pump 07 and the die-stewing liquid collecting tank 99; the first alkaline etching solution intercepting tank 75 is provided with a one-way fifty-seven valve 0057 to the alkaline etching tank 74; the second caustic etching solution intercepting tank 76 is provided with a one-way fifty-eight valve 0058 to the first caustic etching solution intercepting tank 75; a connecting pipeline of the first alkaline etching solution intercepting tank 75 and the eighth pump 08 is provided with a fifty-nine valve 0059; a sixty-two valve 0062 is arranged on a connecting pipeline of the second alkaline etching solution interception tank 76 and the nine-pump 09; a sixty-shaped valve 0060 is arranged on a connecting pipeline between the ten-shaped pump 010 and the water inlet 88; a sixty-one valve 0061 is arranged on a connecting pipeline of the high-pressure atomization spraying groove 77 and the high-pressure atomization spraying groove 77; a sixty-three valve 0063 is arranged on a connecting pipeline of the nine-pump 09 and the secondary filtrate collecting tank 9;

a connecting pipeline of the oxidizing liquid collecting tank 1 and the first pump 01 is provided with a twenty-two valve 0022; the alkaline etching liquid collecting tank 3 is connected to a connecting pipeline between the reaction tank 2 and the second pump 02, and a tenth valve 0010 is arranged between the connecting pipeline and the alkaline etching liquid collecting tank 3; the second pump 02 is also connected to the top of the reaction tank 2, and an eleventh valve 0011 is arranged on the connecting pipeline;

a sixteen-number valve 0016 is arranged on a connecting pipeline of the second pump 02 and the solid-liquid separation tank 4; a fifteen-valve 0015 is arranged at an inlet of the first filtrate recovery tank 61, and a twelve-valve 0012 is arranged at an outlet of the second pump 02 on a connecting pipeline between the first filtrate recovery tank 61 and the second pump 02; a seventeen valve 0017 is arranged at the outlet of the solid-liquid separation tank 4;

a twenty-number valve 0020 is arranged on a connecting pipeline of the third pump 03 and the sodium sulfate crystallizing tank 111; a connecting pipeline of the third pump 03 and the reaction tank 2 is provided with a twenty-first valve 0021; a twenty-five valve 0025 is arranged on a connecting pipeline between the fourth pump 04 and the sodium sulfate crystallizing tank 111; a connecting pipeline of the fourth pump 04 and the second centrifugal machine 52 is provided with a twenty-sixth valve 0026; a twenty-seventh valve 0027 is arranged on a connecting pipeline between the second filtrate recovery tank 62 and the fifth pump 05; and a connecting pipeline of the secondary filtrate collecting tank 9 and the fifth pump 05 is provided with a twenty-eight valve 0028.

Furthermore, the side of the reaction tank 2 is provided with an anti-overflow port; the overflow preventing port is arranged between the top and the middle of the side wall of the reaction tank 2; the first filtrate recovery tank 61 is respectively connected with the overflow preventing openings through pipelines;

and stirrers are arranged in the reaction tank 2, the solid-liquid separation tank 4, the filtrate recovery tank and the sodium sulfate crystallization tank 111.

Further, the production process of the oxidation line system for recovering the aluminum hydroxide and the sodium sulfate from the mold-stewing liquid comprises the following steps:

(1) recovering waste liquid of the pot mold: closing each valve and pump in the pot mold groove 7; opening a twenty-ninth valve 0029, a thirty-second valve 0030 and a thirty-ninth valve 0032, starting the sixth pump 06, and injecting water into the die cavity 7; grooving the mold cavity by using 150 and 250g/L sodium hydroxide; lifting the mould into the mould-cooking groove 7 for mould-cooking operation; after the die is cooked, the die is lifted out, the thirty-one valve 0031 is opened, the six-pump 06 is started, the high-pressure atomizing water gun 81 is used for cleaning the die, and the die is dried and recovered; guiding the water for cleaning the mould to the mould stewing liquid collecting tank 99 for recycling; when the aluminum ions of the mold stewing liquid reach more than 60g/L, guiding the mold stewing waste liquid to the mold stewing liquid collecting tank 99; adding 50% alkali liquor to adjust the ratio of free alkali concentration and aluminum ion concentration in the mold-cooking waste liquid to 3.8-4.2; opening the fifty-six valve 0056, starting the seven pump 07, and pumping the mold-cooking waste liquid into the caustic etching tank 74 as caustic etching liquid;

(2) generation of alkaline etching waste liquid: detecting the alkaline etching solution 74 of the alkaline etching tank, and adding sodium hydroxide to control the ratio of the concentration of free alkali to the concentration of aluminum ions to 3.5-4.0;

after the aluminum material is degreased in the oil removing groove 71 for 2-5 minutes, the aluminum material is cleaned in the flowing water washing groove 72 for 60-120s, trickles for 30s and then enters the alkaline etching groove 74; alkaline etching for 5-15 min at 50-60 deg.C; washing the slurry by the first alkaline etching solution retaining tank 75 and the second alkaline etching solution retaining tank 76 for 60s and dripping the slurry for 30 s; spraying for 60s through the high-pressure atomization spraying groove 77, and entering a neutralization groove 78 to finish generation of the alkaline etching waste liquid;

(3) collecting alkaline etching waste liquid: opening the tenth valve 0010, starting the eighth pump 08, and sending the alkaline etching waste liquid intercepted by the first alkaline etching liquid intercepting tank 75 to the alkaline etching liquid collecting tank 3; starting a No. nine pump 09, pumping the spray liquid collected by the spray liquid collecting tank 771 into the second alkaline etching liquid interception tank 76, passing through the No. sixty-two valve 0062 and the No. fifty-eight valve 0058, and reversely flowing back to the first alkaline etching liquid interception tank 75;

(4) and (3) collecting oxidation waste liquid: opening the first valve 0001 and the twenty-second valve 0022, starting the first pump 01, and pumping the oxidation waste liquid in the oxidation liquid collecting tank 1 into the reaction tank 2;

(5) adding alkaline etching waste liquid: according to the result of titrating the oxidized waste liquid by the alkaline etching waste liquid, estimating the volume of the alkaline etching waste liquid required to be added;

the third valve 0003, the fourth valve 0004, the fifth valve 0005, the sixth valve 0006, the eighth valve 0008, the twelfth valve 0012 and the fourteenth valve 0014 are closed, the seventh valve 0007, the ninth valve 0009, the eleventh valve 0011 and the thirteenth valve 0013 are opened, and the second pump 02 is started to circulate the oxidation waste liquid in one of the reaction tanks 2; or the third valve 0003, the fourth valve 0004, the fifth valve 0005, the sixth valve 0006, the seventh valve 0007, the twelfth valve 0012 and the thirteenth valve 0013 are closed, the eighth valve 0008, the ninth valve 0009, the eleventh valve 0011 and the fourteenth valve 0014 are opened, the second pump 02 is started, and the oxidation waste liquid in the other reaction tank 2 is circulated;

opening the tenth valve 0010, sucking the alkaline etching waste liquid in the alkaline etching liquid collecting tank 3 into the second pump 02 by using negative pressure, and sending the alkaline etching waste liquid into the reaction tank 2 to neutralize the oxidation waste liquid; adding the alkaline etching waste liquid until the pH value of the reaction liquid is 7.0-7.5, and reaching the reaction end point to generate aluminum hydroxide and sodium sulfate; closing the No. ten valve 0010, and stopping adding the alkaline etching waste liquid; continuously stirring for 30 minutes, and standing for 60 minutes;

(6) reaction liquid separation operation: closing the fourth valve 0004, the sixth valve 0006, the seventh valve 0007, the eighth valve 0008, the tenth valve 0010, the eleventh valve 0011 and the sixteenth valve 0016; opening the valve No. three 0003 or the valve No. five 0005, opening the valve No. nine 0009, the valve No. twelve 0012 and the valve No. fifteen 0015, starting the pump No. two 02, and pumping the supernatant in the reaction tank 2 into the first filtrate recovery tank 61; closing the third valve 0003, the fifth valve 0005, the fifteenth valve 0015 and the seventeen valve 0017, opening the seventh valve 0007 and the sixteenth valve 0016, starting the second pump 02, pumping the solid-liquid mixture in the reaction tank 2 into a solid-liquid separation tank 4 in a stirring state, starting the first centrifuge 51, opening the seventeen valve 0017, and separating aluminum hydroxide and primary filtrate after solid-liquid separation and spraying; sending the primary filtrate to the first filtrate recovery tank 61;

or the third valve 0003, the fifth valve 0005, the seventh valve 0007, the eighth valve 0008, the tenth valve 0010, the eleventh valve 0011 and the sixteenth valve 0016 are closed; opening the valve 0004 or the valve 0006 of the fourth number, and the valve 0009, the valve 0012 of the twelfth number and the valve 0015 of the fifteenth number, starting the pump 02 of the second number, and pumping the supernatant in the reaction tank 2 into the first filtrate recovery tank 61; closing the fourth valve 0004, the sixth valve 0006, the fifteenth valve 0015 and the seventeen valve 0017, opening the eighth valve 0008 and the sixteenth valve 0016, starting the second pump 02, pumping the solid-liquid mixture in the reaction tank 2 into the solid-liquid separation tank 4 in a stirring state, starting the first centrifuge 51, opening the seventeen valve 0017, and separating aluminum hydroxide and primary filtrate after solid-liquid separation and spraying; sending the filtrate to the first filtrate recovery tank 61;

(7) primary filtrate collection and recovery: closing the fifteen-valve 0015, the eighteen-valve 0018, the nineteen-valve 0019, the twenty-valve 0020 and the twenty-first-valve 0021, and collecting primary filtrate in the first filtrate recovery tank 61 to finish primary filtrate collection; closing the nineteen-valve 0019 and the twenty-first valve 0021, opening the eighteen-valve 0018 and the twenty-valve 0020, starting the third pump 03, and pumping the supernatant in the filtrate recovery tank into the sodium sulfate crystallization tank 111; opening the nineteen-valve 0019 and the twenty-first valve 0021, closing the eighteen-valve 0018 and the twenty-valve 0020, starting the third pump 03, pumping the precipitate in the first filtrate recovery tank 61 in the stirring state into the reaction tank 2, and performing secondary recovery to finish primary filtrate recovery;

(8) recovering sodium sulfate: closing the twenty-five valve 0025, opening the ice machine, cooling the primary filtrate to below 5 ℃, and crystallizing and separating out sodium sulfate; starting electric stirring, opening the twenty-fifth valve 0025 and the twenty-sixth valve 0026, starting the second centrifugal machine 52, starting the fourth pump 04, and separating sodium sulfate from solid and liquid; the filtrate flows into a second filtrate recovery tank 62 to complete the operation process of the sodium sulfate recovery system;

(9) and (3) collecting secondary filtrate: closing the twenty-seventh valve 0027, and collecting secondary filtrate; and opening the twenty-seven valve 0027 and the twenty-eight valve 0028, starting the five-pump 05, and sending secondary filtrate into the secondary filtrate collecting tank 9.

Furthermore, the design utilizes the huge solubility difference of the sodium sulfate at different temperatures, and the sodium sulfate is separated and recovered by crystallization at the temperature of below 5 ℃, so that the recovery rate is improved;

in step (3), when the second caustic etching solution interception tank 76 cannot be refilled with the spray solution, a sixty-three valve 0063 is opened, the nine-pump 09 is started, and the excess spray solution is pumped into the secondary filtrate collection tank 9.

More specifically, the first pump 01 is connected to the upper end of the reaction tank 2, so that the first pump 01 in the step (4) injects the waste oxidation liquid in the oxidation liquid collection tank 1 from the upper end of the reaction tank 2;

the second pump 02 is connected to the upper end of the reaction tank 2, so that the second pump 02 injects the alkaline etching solution in the alkaline etching solution collecting tank 3 from the upper end of the reaction tank 2 in the step (5).

Further, the adding method realizes low-level addition of the alkaline etching waste liquid, avoids high-level addition above the reaction tank 2, avoids the risks that the alkaline etching waste liquid is added from the upper surface of the oxidation waste liquid and splashed out to hurt people in high-temperature reaction, and also utilizes the second pump 02 to stir at high speed and fully mix, thereby avoiding alkali liquid agglomeration, reducing electric stirring pressure and greatly shortening reaction time;

when the die is stewed (alkaline etching), the aluminum stub bar in the die undergoes the following chemical reaction in the alkaline etching solution:

Al₂O₃+2NaOH＝2NaAlO₂+H₂o (removing natural oxide film) (1)

2Al+2NaOH+2H₂O＝2NaAlO₂+3H₂↓ (dissolved aluminum) (2)

NaAlO₂+2H₂O＝Al(OH)₃↓ + NaOH (groove liquid decomposition, regeneration lye) (3)

2Al(OH)₃＝Al₂O₃.3H₂O (pipe blockage and scale wall) (4)

(2) Formula (3) under strong alkaline condition

2Al+6H₂O＝2Al(OH)₃↓+3H₂↑ (5)

(2) (3) whether or not Al (OH) is formed in the formulae (5)₃Precipitation, depending on the concentration of free base in the mold wash, when the R value (concentration of free base/concentration of aluminum ions) is greater than 3.5, the aluminum is NaAlO₂Form exists, when the content is less than 3.5, Al (OH) is decomposed and precipitated₃. Under the alkaline condition, the essence of the chemical reaction of the mold boiling liquid is the reaction of aluminum and water, the aluminum is dissolved, the water is decomposed, the hydrogen is released, hydroxyl is generated, the total alkali concentration of the mold boiling liquid is increased, the increase is one mole of aluminum, and three moles of total alkali are increased.

According to the formulas (1) and (2), the higher the alkali concentration is, the higher the aluminum dissolving speed is; according to the two formulas (3), (4) and (5), the mold boiling liquid is unstable, easy to decompose and form scales. According to the formulas (3), (4) and (5), in order to prevent the decomposition of sodium metaaluminate, the concentration of sodium hydroxide can be properly increased, the stability of sodium metaaluminate is kept, and the scale formation of recovery equipment, pumps and valves is prevented, so that the mold-stewing liquid can be recovered.

Gradually adding sulfuric acid (or oxidation waste liquid) into a mold cooking liquid containing sodium metaaluminate to perform the following chemical reaction:

reacting with a small amount of dilute sulfuric acid

2NaAlO2+H₂SO₄+2H₂O＝Na₂SO₄+2Al(OH)₃↓ (pH value above 7) (6)

Reaction with excess dilute sulfuric acid

2NaAlO₂+4H₂SO4＝＝Na₂SO4+Al₂(SO4)₃+4H₂O (pH value below 4.89) (7)

Shown in Table 1 (J is free base concentration g/L, L is aluminum ion concentration g/L, and R is free base concentration/Al³⁺Concentration).

TABLE 1 law of change of aluminum skimmings dissolved in alkali solution of different concentrations

Sample A

(1) The slotting index J is 98.88, L is 0, and with the increase of the addition amount of the aluminum scraps, according to the formula (1), the aluminum oxide on the surfaces of the aluminum scraps consumes free alkali, and the J value is gradually reduced; according to the formulas (2) and (5), the dissolution of aluminum releases hydrogen to generate total alkali, the total alkali is converted into sodium metaaluminate, free alkali is not consumed, the L value is continuously increased, the R value is continuously reduced, and the reduction of the J value is limited;

(2) when the aluminum scrap is increased to 50g, the L value is continuously increased, the indexes are that J is 94.76, L is 38.01 and R is 2.49, a sodium metaaluminate supersaturated solution is formed, the bath solution reaches the critical point of decomposition and precipitation of aluminum hydroxide, and R is the lowest point of 2.49;

(3) when the aluminum scrap is increased to 60g, the indexes of J-94.76, L-30.59 and R-3.10 are that the L value is reduced, the aluminum hydroxide is decomposed and precipitated, and the R value is increased back to 3.10;

(4) continuously adding aluminum scraps, enabling the bath solution to enter a Bayer process control interval according to the formula (3), continuously generating aluminum hydroxide by the dissolved aluminum, simultaneously dissolving and releasing hydrogen and generating hydroxyl radicals and generating and consuming hydroxyl radicals by the aluminum, separating out the aluminum hydroxide, and not consuming free alkali, so that the reduction of the J value is limited; because the bath solution contains a large amount of aluminum hydroxide seed crystals, the supersaturated state of the sodium metaaluminate can be basically eliminated, the R value continues to rise to a stable state, the R value is between 3.50 and 4.00 when the aluminum skimmings are added to the range of 80 to 160, and when the R value is more than or equal to 4.00 in consideration of the titration error, the sample A is absolutely stable and does not decompose and separate out the aluminum hydroxide.

Sample B

(1) The slotting index J is 199.82, L is 0, and with the increase of the addition amount of the aluminum scraps, according to the formula (1), the aluminum oxide on the surfaces of the aluminum scraps consumes free alkali, and the J value is gradually reduced; according to the formulas (2) and (5), the dissolution of aluminum releases hydrogen to generate total alkali, the total alkali is converted into sodium metaaluminate, free alkali is not consumed, the L value is continuously increased, the R value is continuously reduced, and the reduction of the J value is limited;

(2) when the aluminum scrap is increased to 90g, the L value is continuously increased, the indexes are that J is 199.76, L is 68.13 and R is 2.93, a sodium metaaluminate supersaturated solution is formed, the bath solution reaches the critical point of decomposition and precipitation of aluminum hydroxide, and R is the lowest point of 2.93;

(3) when the amount of aluminum scraps is increased to 100g, the indexes of J-193.64, L-68.60 and R-2.82 are that the L value is unchanged, aluminum hydroxide is decomposed and precipitated, and the R value is 2.82;

(4) continuously adding aluminum scraps, enabling the aluminum oxide on the surface of the aluminum scraps to enter a Bayer process control interval according to the formula (3), continuously generating aluminum hydroxide by the dissolved aluminum, simultaneously dissolving and releasing hydrogen and generating hydroxyl radicals and generating and consuming hydroxyl radicals by the aluminum, separating out the aluminum hydroxide, and consuming no free alkali, so that the reduction of the J value is limited; because the bath solution contains a large amount of aluminum hydroxide seed crystals, the supersaturated state of sodium metaaluminate can be basically eliminated, the R value continues to rise to a stable state, the R value is between 4.00 and 4.15 when aluminum scraps are added to the range of 120-160, and when the R value is more than or equal to 4.20 in consideration of titration error, the sample B is absolutely stable and does not decompose and separate out aluminum hydroxide.

Sample C

(1) The slotting index J is 313.12, L is 0, and with the increase of the addition amount of the aluminum scraps, according to the formula (1), the aluminum oxide on the surfaces of the aluminum scraps consumes free alkali, and the J value is gradually reduced; according to the formulas (2) and (5), the dissolution of aluminum releases hydrogen to generate total alkali, the total alkali is converted into sodium metaaluminate, free alkali is not consumed, the L value is continuously increased, the R value is continuously reduced, and the reduction of the J value is limited;

(2) when the aluminum scrap is increased to 130g, the L value is continuously increased, the indexes are that J is 276.04, L is 92.79 and R is 2.98, a sodium metaaluminate supersaturated solution is formed, the bath solution reaches the critical point of decomposition and precipitation of aluminum hydroxide, and R is the lowest point of 2.98;

(3) when the aluminum scrap is increased to 140g, the indexes are J-273.98, L-93.261 and R-2.94, the change of L value is small, the aluminum hydroxide is decomposed and separated out, and the R value is 2.94;

(4) continuously adding aluminum scraps, enabling the bath solution to enter a Bayer process control interval according to the formula (3), continuously generating aluminum hydroxide by the dissolved aluminum, simultaneously dissolving and releasing hydrogen and generating hydroxyl radicals and generating and consuming hydroxyl radicals by the aluminum hydroxide, separating out the aluminum hydroxide, and not consuming free alkali, so that the reduction of the J value is limited; because the bath solution contains a large amount of aluminum hydroxide seed crystals, the supersaturated state of the sodium metaaluminate can be basically eliminated, the R value continues to rise to a steady state, and the R value is between 3.18 and 3.25 when the aluminum scraps are added to the range of 120-160; because the viscosity of the bath solution is too high, decomposed aluminum hydroxide is difficult to precipitate after stirring, the titration error is too large, the data of the addition amount of aluminum scraps more than 160g cannot be obtained, and the steady state R value of the sample C cannot be obtained.

Analysis of Experimental results

(1) And samples A to C all had a decomposition critical point. The decomposition critical point of A is 94.76, L38.01 and R2.49, the decomposition critical point of B is 199.76, L68.13 and R2.93, the decomposition critical point of C is 276.04, L92.79 and R2.98; above the decomposition critical point, J is slightly reduced, L is increased, R is reduced, the bath solution gradually enters a sodium metaaluminate supersaturation interval, and no aluminum hydroxide is separated out;

(2) and samples A to C, all had decomposition points. The decomposition points of A are J-94.76, L-30.59 and R-3.10, B are J-193.64, L-68.60 and R-2.82, C is J-273.98, L-93.261 and R-2.94, J is slightly reduced below the decomposition points, L is not greatly increased with the addition of aluminum scraps, R is not greatly reduced with the addition of aluminum scraps, the bath solution enters a Bayer sodium metaaluminate decomposition section, and a large amount of aluminum hydroxide is decomposed and precipitated. The sample A has obvious supersaturation, the critical point L is 38.01, the R is 2.49, the decomposition point L is 30.59, and the R is 3.10, after 10g of aluminum scraps are added, the L is not increased, but is greatly reduced, a large amount of aluminum hydroxide is separated out, and the R rebounds to 3.10; the supersaturation phenomenon of the sample B is not obvious, the critical point L is 68.13, R is 2.93, the decomposition point L is 68.60, R is 2.82, the added 10g of aluminum chips are directly decomposed into aluminum hydroxide, L, R is almost unchanged, and the bath solution directly enters the decomposition section of the Bayer process sodium metaaluminate; the supersaturation phenomenon of the sample C is not obvious, the critical point L (92.79), R (2.98) and the decomposition point L (93.261), R (2.94) are in smooth transition, 10g of added aluminum chips are directly decomposed into aluminum hydroxide, L, R is almost unchanged, and the bath solution directly enters the decomposition section of the Bayer process sodium metaaluminate;

(3) and after entering a Bayer sodium metaaluminate decomposition interval, continuously adding aluminum chips, wherein L is not increased any more, and R is continuously increased. The R value of the sample A gradually approaches to the interval of 3.50-4.00, and the R value of the sample B gradually approaches to the interval of 4.00-4.15; in addition to the direct decomposition of the added aluminum scraps into aluminum hydroxide, the existence of a large amount of aluminum hydroxide seed crystals further induces the decomposition of sodium metaaluminate, thoroughly eliminates the supersaturation phenomenon and realizes the dynamic balance of the chemical reaction of the formula (3);

(4) the indexes of pouring the mold-boiling liquid are that J is 250, L is 50 and R is 5.00, and the sample B, C is the closest to the working index of the mold-boiling liquid. The experimental result shows that the R value of the decomposition of the die-stewing liquid is about 3.00 under the condition without the seed crystal, the die-stewing liquid must be decomposed to recover the aluminum in the die-stewing liquid, acid with a certain concentration is added, free alkali is consumed, the R value is reduced to about 3.00, and the aluminum hydroxide can be decomposed; the R value is required to be more than 3.00 for pipeline transportation of the mold-stewing liquid, and the R value is preferably transported above 3.50 in consideration of the introduction of accidental seed crystals to induce the decomposition of sodium metaaluminate; the mold-stewing liquid should be stored for a long time without decomposition and precipitation, and the R value is preferably controlled to be above 4.00.

Law of change of solubility of anhydrous sodium sulfate with temperature

Taking 100ml of pure water, adding anhydrous sodium sulfate from 0 ℃, and recording the weight (g) of the dissolved anhydrous sodium sulfate at a saturation point; detecting once every 10 ℃ to obtain the change rule of the saturated concentration of the anhydrous sodium sulfate along with the temperature, as shown in Table 2:

TABLE 2 law of change of solubility of anhydrous sodium sulfate with temperature

Analysis of Experimental results

(1) The solubility of the anhydrous sodium sulfate varies greatly with the temperature, and is 4.9g/100ml at 0 ℃ and 48.8g/100ml at 40 ℃, and the difference is nearly 10 times;

(2) the solubility is increased sharply within the range of 0-40 ℃; the solubility is slightly reduced at 40-100 ℃;

(3) crystallizing and separating out sodium sulfate decahydrate by a cooling method, and obtaining a sodium sulfate decahydrate product through solid-liquid separation; the content of sodium sulfate in the filtrate is greatly reduced.

Experimental result of neutralizing and recycling aluminum hydroxide and sodium sulfate by oxidizing solution and mold-stewing solution (alkaline etching solution)

And (5) performing qualitative and quantitative analysis. According to the formulas (6) and (7), the mold-boiling liquid is added into sulfuric acid (or oxidation waste acid), so that aluminum hydroxide and sodium sulfate or aluminum sulfate and sodium sulfate can be recovered. The aluminum hydroxide is insoluble in water, and the separation of the aluminum hydroxide and the sodium sulfate is easy to realize; the aluminum sulfate and the sodium sulfate are dissolved in water to realize the recovery of the aluminum sulfate and the sodium sulfate, the online separation has certain difficulty, a large amount of cleaning water is consumed, the cleaning water is discharged to enter a wastewater center, and sodium ions pollute reclaimed water and hinder the reuse of the reclaimed water.

A. Taking the aged mold-cooking liquid before discharging, wherein J is 253.33, L is 51.35, R is 4.93 liters, and the total alkali content J is 12.04 equivalents; 200g/L dilute sulfuric acid with an equivalent concentration of 4.08 is added, and the reaction is completely neutral, so that 2.951 liters of dilute sulfuric acid and 12.04 equivalents of sulfuric acid are consumed. The reaction product is: the total volume of the reaction liquid is 3.951 liters, and the aluminum content is 5.71 equivalent and the sulfate radical content is 12.04 equivalent; generating 12.04 equivalent of sodium sulfate decahydrate, and calculating 1938.44 g; 5.71 equivalent of aluminum hydroxide is generated, and 148.46g is calculated;

B. and (5) in the initial stage of reaction. Taking 2.951 liters of 200g/L dilute sulfuric acid, adding mold-boiling liquid with the indexes of J253.33, L51.35 and R4.93, and continuously increasing the pH value; according to the formula (7), in the pH range of 4.5-4.89, the reaction products are aluminum sulfate and sodium sulfate; the two chemical products can be separated by crystallization by utilizing the different solubility of the aluminum sulfate and the sodium sulfate at different temperatures. Considering that the online treatment, the large amount of waste liquid of die-boiling in aluminum material factories, the large output of the two chemical products, the water solubility, the large amount of cleaning water, the large difficulty of online separation, the water discharge, environmental protection and the online generation of aluminum sulfate and sodium sulfate are not suitable; one crystal can be separated out, solid-liquid separation is carried out, and aluminum sulfate and sodium sulfate are separated after later recrystallization;

C. and (5) at the end of the reaction. Continuously adding the mold-stewing liquid, when the pH value is more than 4.89, decomposing the bath solution and separating out aluminum hydroxide, adding the mold-stewing liquid till the reaction end point, wherein the pH value is between 7.00 and 7.50, and most of sodium metaaluminate is decomposed and separated out; filtering, rinsing and drying to obtain a high-purity aluminum hydroxide product meeting the national standard requirement; cooling the primary filtrate to below 5 ℃, crystallizing and separating out sodium sulfate by utilizing the physical characteristic that the solubility of the sodium sulfate is sharply reduced at low temperature, carrying out solid-liquid separation, rinsing and drying to obtain a sodium sulfate product; the secondary filtrate is sent back to the die cavity 7 for continuous die-cooking, so that the zero discharge of waste water and waste residue of the die-cooking is realized;

D. reacting with the oxidizing liquid. 2.951 liters of waste oxidation liquid (total acid 200g/L and aluminum ion 20/L) is taken, mold boiling liquid (J is 253.33, L is 51.35 and R is 4.93) is added until the end of the reaction, the pH value is between 7.00 and 7.50, and sodium metaaluminate is decomposed and separated out; filtering, rinsing and drying to obtain a high-purity aluminum hydroxide product meeting the national standard requirements, which is shown in Table 3; cooling the primary filtrate to below 5 ℃, crystallizing and separating out sodium sulfate by utilizing the physical characteristic that the solubility of the sodium sulfate is sharply reduced at low temperature, carrying out solid-liquid separation, rinsing and drying to obtain a high-quality sodium sulfate product, wherein the high-quality sodium sulfate product is shown in Table 4; the secondary filtrate is sent back to the die cavity 7 for continuous die-cooking, so that the zero discharge of waste water and waste residue of the die-cooking is realized; the method cools the primary filtrate to below 5 ℃, and sodium sulfate is separated out through crystallization to produce a sodium sulfate product; the secondary filtrate is sent back to the die cavity 7 for continuous die boiling, so that the sodium ions are completely isolated from the center of the wastewater, and the largest ion barrier is swept for recycling the reclaimed water.

TABLE 3 detection results of neutralization production of aluminum hydroxide by oxidation liquid and mold-stewing liquid

TABLE 4 detection results of sodium sulfate production by neutralization of oxidizing solution and mold-cooking solution

Thirdly, qualitative analysis of test results of neutralizing and recycling aluminum hydroxide and sodium sulfate by-products by oxidizing solution and mold-stewing solution (alkaline etching solution)

According to the tests 1-4 and the detection results, the following analysis can be made:

1. adding mold-cooking liquid or other alkali solution containing sodium metaaluminate and sodium hydroxide (such as oxidation line alkaline etching solution (without additive), alkali solution of aluminum ash, etc., R is not less than 3.5) into oxidized waste liquid (or dilute sulfuric acid), and recovering aluminum sulfate and sodium sulfate by-products when the pH is between 4.50-4.89; at pH between 7.00-7.50, aluminum hydroxide and sodium sulfate by-products can be recovered;

2. at the reaction end point pH7.0-7.5, the sodium metaaluminate is completely decomposed and separated out to generate aluminum hydroxide; solid-liquid separation, rinsing and drying are carried out, and high-quality aluminum hydroxide meeting the national standard requirements can be obtained;

3. cooling the primary filtrate to a temperature not higher than 5 ℃, and crystallizing a large amount of sodium sulfate; solid-liquid separation and drying are carried out, and high-quality sodium sulfate meeting the national standard requirements can be obtained;

4. the secondary filtrate containing a small amount of sodium sulfate can be sent back to the die cavity 7 for recycling, the sodium ions in the center of the wastewater are completely isolated after the next recycling, and the zero discharge of the wastewater and waste residues in the die cavity workshop is realized.

The technical principle of the present invention is described above in connection with specific embodiments. The description is made for the purpose of illustrating the principles of the invention and should not be construed in any way as limiting the scope of the invention. Based on the explanations herein, those skilled in the art will be able to conceive of other embodiments of the present invention without inventive effort, which would fall within the scope of the present invention.

Claims

1. A pot mould liquid retrieves oxidation line system of aluminium hydroxide and sodium sulfate, its characterized in that includes: a secondary filtrate collecting tank, a die-stewing waste liquid treatment system, a raw material waste liquid treatment system, a reaction liquid treatment system, a filtrate collecting system and a primary filtrate separating system;

the reaction liquid treatment system receives the alkaline etching waste liquid of the alkaline etching liquid collection tank, adds an oxidation waste liquid to mix and react with the alkaline etching waste liquid, separates out aluminum hydroxide and primary filtrate through the filtrate collection system, and separates out sodium sulfate from the primary filtrate through the primary filtrate separation system;

2. The oxidation line system for recovering aluminum hydroxide and sodium sulfate from the die-filling liquid as claimed in claim 1, wherein the die-filling liquid collection tank is filled with the die-filling waste liquid obtained by reacting sodium hydroxide with the aluminum die;

3. The oxidation line system for recovering aluminum hydroxide and sodium sulfate from a pot mold liquid as claimed in claim 2, wherein the reaction liquid treatment system comprises: a reaction liquid addition system and a reaction liquid separation system;

the first centrifuge is used for separating sodium oxide and primary filtrate at the pH of 7.00-7.50, and guiding the primary filtrate to the first filtrate recovery tank; and the third pump is connected with the primary filtrate separation system, so that sodium sulfate is separated from the primary filtrate separation system at the pH value of 7.00-7.50 after primary filtrate in the first filtrate recovery tank is transferred to the primary filtrate separation system.

4. The oxidation line system for recovering aluminum hydroxide and sodium sulfate from mold-stewing liquid as claimed in claim 3, wherein the number of the reaction tanks is 2; the reaction tanks are respectively communicated and connected with the middle part and the lower part of the side walls of the reaction tanks and the bottom of the reaction tank, and are jointly connected with the second pump;

5. The oxidation line system for recovering aluminum hydroxide and sodium sulfate from mold pot liquor as claimed in claim 4, wherein the filtrate collection system comprises: the system comprises a sodium sulfate crystallization tank, a fourth pump, a second centrifuge, a second filtrate recovery tank and a fifth pump; the third pump, the sodium sulfate crystallizing tank, the fourth pump, the second centrifuge, the second filtrate recovery tank and the fifth pump are adjacently connected in sequence; the third pump is connected into the sodium sulfate crystallizing tank; the fifth pump is communicated and connected with the secondary filtrate collecting tank;

6. The oxidation line system for recovering aluminum hydroxide and sodium sulfate from a pot mold liquid as claimed in claim 5, wherein a plurality of pot mold containers are arranged in the pot mold cavity; the inlet of the die stewing container is respectively connected with the number six pump, and a fourteen valve is arranged at the inlet of the die stewing container; the outlet of the die stewing container is connected with the wastewater diversion trench, and a thirty-two valve is arranged at the outlet of the die stewing container;

a twenty-ninth valve is arranged on a connecting pipeline between the secondary filtrate collecting tank and the sixth pump; a thirty-grade valve is arranged on a connecting pipeline between the six-grade pump and the die cavity; a connecting pipeline of the high-pressure atomizing water gun and the No. six pump is provided with a No. thirty-one valve;

a fifty-six valve is arranged on a connecting pipeline of the seven-pump and the die-stewing liquid collecting tank; the first alkaline etching solution intercepting tank is provided with a one-way fifty-seven valve towards the alkaline etching tank; the second alkaline etching solution intercepting tank is provided with a one-way fifty-eight valve towards the first alkaline etching solution intercepting tank; a connecting pipeline of the first alkaline etching solution intercepting tank and the eighth pump is provided with a fifty-nine valve; a connecting pipeline of the second caustic etching solution intercepting tank and the ninth pump is provided with a sixty-two valve; a sixty valve is arranged on a connecting pipeline between the ten pump and the water inlet; a sixty-one valve is arranged on a connecting pipeline of the high-pressure atomization spraying groove and the high-pressure atomization spraying groove; a sixty-three valve is arranged on a connecting pipeline of the ninth pump and the secondary filtrate collecting tank;

a connecting pipeline of the oxidation liquid collecting tank and the first pump is provided with a twenty-two valve; the alkaline etching liquid collecting tank is connected with the reaction tank and the second pump connecting pipeline, and a No. ten valve is arranged between the connecting pipeline and the alkaline etching liquid collecting tank; the second pump is also connected with the top of the reaction tank, and an eleventh valve is arranged on the connecting pipeline;

a sixteen-number valve is arranged on a connecting pipeline of the second pump and the solid-liquid separation tank; a fifteen-valve is arranged at the inlet of the first filtrate recovery tank and a twelve-valve is arranged at the outlet of the second pump on a connecting pipeline between the first filtrate recovery tank and the second pump; a seventeen valve is arranged at the outlet of the solid-liquid separation tank;

a twenty-number valve is arranged on a connecting pipeline of the third pump and the sodium sulfate crystallizing tank; a twenty-first valve is arranged on a connecting pipeline between the third pump and the reaction tank; a twenty-five valve is arranged on a connecting pipeline between the fourth pump and the sodium sulfate crystallizing tank; a twenty-sixth valve is arranged on a connecting pipeline between the fourth pump and the second centrifugal machine; a twenty-seventh valve is arranged on a connecting pipeline between the second filtrate recovery tank and the fifth pump; and a twenty-eight valve is arranged on a connecting pipeline of the secondary filtrate collecting tank and the fifth pump.

7. The oxidation line system for recovering aluminum hydroxide and sodium sulfate from mold-stewing liquid as claimed in claim 6, wherein an anti-overflow port is arranged on the side of the reaction tank; the overflow preventing port is arranged between the top and the middle of the side wall of the reaction tank; the first filtrate recovery tank is respectively connected with the overflow preventing port through a pipeline;

8. An oxidation line process using the oxidation line system of claim 7, comprising the steps of:

(1) recovering waste liquid of the pot mold: closing each valve and pump in the die cavity; opening a twenty-ninth valve, a thirty-second valve and a thirty-ninth valve, starting a sixth pump and injecting water into the die cavity of the cooker; grooving in a mould cavity by using 150 and 250g/L sodium hydroxide; lifting the mould into a mould cooking groove for mould cooking operation; lifting the mould after the mould stewing operation is finished, opening a thirty-one valve, starting a six-pump, cleaning the mould by using a high-pressure atomizing water gun, and airing and recovering the mould; guiding the water for cleaning the die to a die-stewing liquid collecting tank for recycling; when aluminum ions of the mold stewing liquid reach more than 60g/L, guiding the mold stewing waste liquid to a mold stewing liquid collecting tank; adding 50% alkali liquor to adjust the ratio of free alkali concentration and aluminum ion concentration in the mold-cooking waste liquid to 3.8-4.2; opening a fifty-six valve, starting a seven pump, and pumping the die-stewing waste liquid serving as an alkaline etching liquid into an alkaline etching tank;

(2) generation of alkaline etching waste liquid: detecting the alkaline etching solution in the alkaline etching tank, and adding sodium hydroxide to control the ratio of the concentration of free alkali to the concentration of aluminum ions to 3.5-4.0;

after the aluminum material is degreased in a degreasing tank for 2-5 minutes, cleaning the aluminum material for 60-120s through a flowing water washing tank, dripping the aluminum material for 30s, and then entering an alkaline etching tank; alkaline etching for 5-15 min at 50-60 deg.C; cleaning the mixture for 60s by a first alkaline etching solution interception tank and a second alkaline etching solution interception tank, and dripping for 30 s; spraying for 60s through a high-pressure atomization spraying groove, and entering a neutralization groove to finish generation of the alkaline etching waste liquid;

(3) collecting alkaline etching waste liquid: opening a tenth valve, starting an eighth pump, and sending the alkaline etching waste liquid intercepted by the first alkaline etching liquid intercepting tank into an alkaline etching liquid collecting tank; starting a No. nine pump, pumping the spray liquid collected by the spray liquid collecting tank into a second alkaline etching liquid interception tank, and reversely flowing back to the first alkaline etching liquid interception tank through a sixty-two valve and a fifty-eight valve;

(4) and (3) collecting oxidation waste liquid: opening the first valve and the twenty-second valve, starting the first pump, and pumping the oxidation waste liquid in the oxidation liquid collection tank into the reaction tank;

(5) adding alkaline etching waste liquid: titrating the oxidized waste liquid according to the alkaline etching waste liquid, and estimating the volume of the alkaline etching waste liquid to be added;

closing the third valve, the fourth valve, the fifth valve, the sixth valve, the eighth valve, the twelfth valve and the fourteenth valve, opening the seventh valve, the ninth valve, the eleventh valve and the thirteenth valve, starting the second pump, and circulating the oxidation waste liquid in one of the reaction tanks; or the third valve, the fourth valve, the fifth valve, the sixth valve, the seventh valve, the twelfth valve and the thirteenth valve are closed, the eighth valve, the ninth valve, the eleventh valve and the fourteenth valve are opened, the second pump is started, and the oxidation waste liquid of the other reaction tank is circulated;

opening a tenth valve, sucking the alkaline etching waste liquid in the alkaline etching liquid collecting tank into a second pump by utilizing negative pressure, and sending the alkaline etching waste liquid into a reaction tank to neutralize the oxidation waste liquid; adding the alkaline etching waste liquid until the pH value of the reaction liquid is 7.0-7.5, and reaching the reaction end point to generate aluminum hydroxide and sodium sulfate; closing the No. ten valve, and stopping adding the alkaline etching waste liquid; continuously stirring for 30 minutes, and standing for 60 minutes;

(6) reaction liquid separation operation: closing the fourth valve, the sixth valve, the seventh valve, the eighth valve, the tenth valve, the eleventh valve and the sixteenth valve; opening a third valve or a fifth valve, opening a ninth valve, a twelfth valve and a fifteenth valve, starting a second pump, and pumping the supernatant in the reaction tank into a first filtrate recovery tank; closing the third valve, the fifth valve, the fifteenth valve and the seventeen valve, opening the seventh valve and the sixteenth valve, starting the second pump, pumping the solid-liquid mixture in the reaction tank into a solid-liquid separation tank in a stirring state, starting the first centrifuge, opening the seventeen valve, and separating aluminum hydroxide and primary filtrate after solid-liquid separation and spraying; sending the primary filtrate into a first filtrate recovery tank;

or the third valve, the fifth valve, the seventh valve, the eighth valve, the tenth valve, the eleventh valve and the sixteenth valve are closed; opening a fourth valve or a sixth valve, a ninth valve, a twelfth valve and a fifteenth valve, starting a second pump, and pumping the supernatant in the reaction tank into a first filtrate recovery tank; closing the fourth valve, the sixth valve, the fifteenth valve and the seventeen valve, opening the eighth valve and the sixteen valve, starting the second pump, pumping the solid-liquid mixture in the reaction tank into a solid-liquid separation tank in a stirring state, starting the first centrifuge, opening the seventeen valve, and separating aluminum hydroxide and primary filtrate after solid-liquid separation and spraying; sending the filtrate into a first filtrate recovery tank;

(7) primary filtrate collection and recovery: closing the valve No. fifteen, the valve No. eighteen, the valve No. nineteen, the valve No. twenty and the valve No. twenty-one, and collecting primary filtrate in a first filtrate recovery tank to finish primary filtrate collection; closing the nineteen valve and the twenty-first valve, opening the eighteen valve and the twenty-first valve, starting the third pump, and pumping the supernatant in the filtrate recovery tank into a sodium sulfate crystallization tank; opening a nineteen valve and a twenty-first valve, closing an eighteen valve and a twenty valve, starting a third pump, pumping the precipitate in the first filtrate recovery tank in a stirring state into a reaction tank, and performing secondary recovery to complete primary filtrate recovery;

(8) recovering sodium sulfate: closing the twenty-fifth valve, opening an ice maker, cooling the primary filtrate to below the temperature, and crystallizing and separating out sodium sulfate; starting electric stirring, opening a twenty-fifth valve and a twenty-sixth valve, starting a second centrifugal machine, starting a fourth pump, and separating sodium sulfate from solid and liquid; the filtrate flows into a second filtrate recovery tank to complete the operation process of the sodium sulfate recovery system;

(9) and (3) collecting secondary filtrate: closing the twenty-seventh valve, and collecting secondary filtrate; and opening a twenty-seventh valve and a twenty-eighth valve, starting a fifth pump, and sending the secondary filtrate into a secondary filtrate collecting tank.

9. The oxidation line process of claim 8, wherein in step (3), when the second caustic etching solution retaining tank cannot be refilled with the spray solution, the sixty-three valve is opened, the nine pump is started, and the excess spray solution is pumped into the secondary filtrate collecting tank.

10. The oxidation line process according to claim 8, wherein a first pump is connected to the upper end of the reaction tank, so that the first pump in the step (4) injects the oxidation waste liquid in the oxidation liquid collection tank from the upper end of the reaction tank;

and (4) connecting the second pump to the upper end of the reaction tank, so that the second pump injects the alkaline etching solution in the alkaline etching solution collecting tank from the upper end of the reaction tank in the step (5).