JPS62270416A - Method for continuously synthesizing aqueous solution of aluminum sulfate from aluminum hydroxide sludge and device thereof - Google Patents

Abstract

PURPOSE:To synthesize an aqueous solution aluminum sulfate continuously, by effectively using aluminum sludge, waste sulfuric acid and an aqueous solution of sulfuric acid containing aluminum sulfate which are produced in surface treatment process of aluminum and whose treatment is facing difficulty. CONSTITUTION:An aluminum sludge 1 which is produced in treatment process of anodized aluminum of aluminum product and comprises 8-12% Al(OH)3, 83-87% water and 3-6% impurity, waste sulfuric acid 5 which is produced in coating film removal process in aluminum surface treatment and comprises 75-90% free H2SO4 and 0.5-2% Al2(SO4)3 and an aqueous solution 4 of sulfuric acid containing aluminum sulfate which is produced in sulfuric acid recovery process of aluminum surface treatment process and comprises 3-6% H2SO4 and 7-9% Al2(SO4)3 are fed to plural reaction tanks R1-R5 and reacted at 80 deg.C - the boiling point of the reaction solution. In the operation, the aqueous solution 4 of sulfuric acid is partially fed to one of the second reaction tank R2 - the final reaction tank R5, the reaction solution in the final reaction tank R5 is adjusted to pH 1.6-2.5 and an aqueous solution of aluminum sulfate is continuously taken out.

Description

Detailed Description of the Invention 1. Detailed Description of the Invention Industrial Field of Application The present invention relates to the production of aluminum sulfate from aluminum sludge containing aluminum hydroxide as a main component, which is separated from wastewater from the alumite treatment process of aluminum-related companies. The present invention relates to a method for continuously synthesizing an aqueous solution and an apparatus therefor.

Conventional technology In the alumite treatment process, as a pretreatment, the aluminum is etched with caustic soda solution in order to remove scratches on the aluminum base surface and smooth the aluminum surface, and also to recycle defective aluminum products. During processing (recoloring), the oxide film on the aluminum material is removed using a caustic soda solution. Further, aluminum is subjected to anodic oxidation treatment and electrolytic coloring treatment in the sulfuric acid solution, and during these treatments, M ions are eluted into the solution and carried out into the adjacent washing tank. This washing water is sent to a wastewater treatment process and is neutralized to form a white precipitate of aluminum hydroxide.

These waste liquids (slurries) are usually added with a polymer flocculant such as acrylamide to form highly solid flocs, dehydrated to form aluminum sludge (hereinafter simply referred to as sludge), and then processed for the next process (disposal or recovery). ). This sludge usually has a moisture content of 83 to 87
The composition consists of 38-12% of AA(OH) and 6-3% of impurities (5 iOz, organic substances, etc.).

In addition, in the aluminum surface treatment process, an aqueous sulfuric acid solution is used in the process of peeling off the paint film on the aluminum surface and the paint film adhering to the surface of the jig. occurs. The composition of this waste sulfuric acid is usually Free H2SO475-9
0x, At2(SOa) 32-0.5%.

Sludge and waste sulfuric acid generated from the above-mentioned aluminum surface treatment process are generally used to synthesize an aqueous aluminum sulfate solution from the viewpoint of pollution prevention and resource conservation.

However, the reaction rate of aluminum sulfate synthesis is fast, making it difficult to control the reaction rate.
Since the pH of the final product, aluminum sulfate, is determined according to the intended use, the final pH of the synthesis solution must match this, and since this pH adjustment is difficult, aluminum sulfate aqueous solutions are manufactured using a continuous synthesis method. It was considered difficult to do so.

Therefore, the conventional synthesis of aluminum sulfate aqueous solution using sludge is carried out exclusively by the so-called batch method, in which a certain amount of waste sulfuric acid is generally charged into one synthesizer, and a certain amount of sludge is supplied to it while heating it. It was done by this.

Problems to be Solved by the Invention In the conventional method, 1-ha of high-concentration waste sulfuric acid is used at the beginning of synthesis.
Since 804 is the main component, a synthesizer made of a material with excellent corrosion resistance is required, and for example, a synthesizer with a glass lining is used. However, this material is expensive and difficult to maintain, including repairs and inspections, but it also breaks easily, and because it is a batch method, the synthesizer is large and requires a lot of driving power, and the equipment is large and requires a large installation area. Equipment costs are high, and capacity cannot be easily increased by adding more synthesizers. Furthermore, since it is a batch method, operation is complicated and workability is poor, and heating by a jacket method reduces thermal efficiency due to scaling and increases running costs.

On the other hand, in addition to the above-mentioned sludge and waste sulfuric acid, a dilute aqueous sulfuric acid solution containing aluminum sulfate (hereinafter abbreviated as sulfuric acid bread) generated in the sulfuric acid recovery process of the electrolytic solution is also a problem as a waste product in the aluminum surface treatment process. In the past, such sulfuric acid aqueous solutions containing sulfuric acid breads could be adequately treated by wastewater treatment because they were not insects, but in recent years, with the development of electrolyte treatment methods such as ion exchange resin separation method and diffusion dialysis membrane separation method, Electrolyte treatment is actively carried out, and a large amount of sulfuric acid aqueous solution containing sulfuric acid is also generated. For example, in the ion-exchange resin separation method, a portion of the sulfuric acid-containing electrolyte in the electrolytic cell is subjected to ion-exchange treatment such as anodizing or alternating current coloring, and the recovered sulfuric acid is returned to the electrolytic cell. A treated water containing sulfuric acid and sulfuric acid is produced. Similarly, in the diffusion dialysis membrane separation method, a part of the electrolyte in the electrolytic cell is treated with a diffusion dialysis membrane and the recovered sulfuric acid is returned to the electrolytic cell, but the treated water contains some sulfuric acid and sulfuric acid. occurs. The dilute aqueous sulfuric acid solution containing these sulfuric acid breads usually contains 0.3 to 6% of 12S, At
g(80a)s has a composition of 7 to 9%, and is generated in large quantities due to the increasing installation of electrolyte treatment equipment in response to the recent improvement in the quality of aluminum surface treatment. The current situation is that we are in poverty. It is possible to use it in the above-mentioned batch-type aluminum sulfate aqueous solution synthesis method, and the present applicant has also used it in part, but since the sulfuric acid aqueous solution containing sulfuric acid bread is dilute, it is difficult to use it in large quantities due to the reaction rate. There are problems in that it is slow and is not suitable for industrialization because it is a batch method.

Therefore, the purpose of the present invention is to solve the above-mentioned problems, and to effectively utilize sludge, waste sulfuric acid, and sulfuric acid aqueous solution containing sulfuric acid bread, which are generated in the aluminum surface treatment process and are difficult to dispose of. The object of the present invention is to provide a method for continuously synthesizing an aluminum sulfate aqueous solution and an apparatus used therefor.

Another object of the present invention is to provide a method and apparatus for continuously synthesizing an aqueous aluminum sulfate solution with excellent productivity, workability, safety, etc., and with relatively low equipment costs and high yield. It is in.

Still another object of the present invention is to provide a method and apparatus for continuously synthesizing an aqueous aluminum sulfate solution with energy efficiency and low running costs.

Means for Solving the Problems According to the present invention, in order to achieve the above object, an aluminum sludge containing aluminum hydroxide as a main component produced in an aluminum surface treatment step and a paint film removal step in the surface treatment step are used. The generated waste sulfuric acid and the aqueous sulfuric acid solution containing aluminum sulfate produced in the sulfuric acid recovery step in the surface treatment step are supplied to a plurality of reaction tanks consisting of the first tank to the nth tank. The reaction is carried out at a temperature of 80° C. to the boiling point of the reaction solution while flowing sequentially to the tank (final tank), and a part of the sulfuric acid aqueous solution containing aluminum sulfate is poured into at least one of the tanks from the second tank to the final tank. The pH of the reaction solution in the final tank is 1.6-2.
．． Provided is a method for continuously producing an aqueous aluminum sulfate solution from a by-product produced in an aluminum surface treatment step, characterized in that the aluminum sulfate aqueous solution is adjusted to a pH of 5.

In the above method, adjusting the pH of the reaction solution is an important factor, and according to the present invention, an apparatus for continuously producing an aqueous aluminum sulfate solution is provided, which is designed to appropriately adjust the pH. The equipment is capable of handling aluminum sludge mainly composed of aluminum hydroxide produced in the aluminum surface treatment process, waste sulfuric acid produced in the coating film removal process in the surface treatment process, and aluminum sulfate produced in the sulfuric acid recovery process in the surface treatment process. 1st tank to nth tank for continuously reacting sulfuric acid aqueous solutions containing
a reaction tank consisting of a tank, and a sulfuric acid aqueous solution containing the aluminum sulfate in the first reactor.
a first supply pipe for supplying to the tank; an n-th supply pipe (n = 2 or more) for supplying the sulfuric acid aqueous solution containing aluminum sulfate to at least one of the tanks after the second tank; a first pH indication adjustment recorder disposed in the first tank or the second tank; a first control valve that adjusts the flow rate in the first supply pipe in conjunction with the first pH indication adjustment recorder; and the second pH indication adjustment recorder. An n-th pH indicating adjustment recorder (n = 2 or more) disposed in at least one of the tanks after the tank, and adjusting the flow rate in the n-th supply pipe in conjunction with the n-th pH indicating adjusting recorder. An n-th control valve (n=2 or more).

Furthermore, temperature control of the reaction solution is also an important factor in the method, and therefore, according to the present invention, the reaction tank consisting of the first tank to the nth tank and the temperature control of the reaction solution obtained from the reaction tank are provided. a first heat exchanger for exchanging heat between the final aluminum sulfate aqueous solution close to the boiling point and the sulfuric acid aqueous solution containing the aluminum sulfate; a first steam pipe disposed in the first tank; and the first tank. a first temperature control valve that adjusts the flow rate of steam in the first steam pipe in conjunction with the first temperature control recorder; and a first temperature control valve disposed in the first steam pipe. When the number of n tanks is small (also known as the nth tank installed in the I tank)
Steam pipe (n = 2 or more) and nth temperature indicator recorder (n
= 2 or more); and an nth temperature control valve (n = 2 or more) that manually or automatically adjusts the steam flow rate in the nth steam pipe in conjunction with the nth temperature indicator recorder. Provided is a reaction temperature control device for continuously producing an aqueous aluminum sulfate solution from a byproduct produced in a characteristic aluminum surface treatment process.

Effect of the invention The aluminum sulfate synthesis solution obtained after the reaction is filtered,
It is concentrated to become the final product, aluminum sulfate, but the properties of the final product depend on the final pH of the aluminum sulfate synthesis solution, and are regulated within a certain range depending on its use. In the present invention, the dilute aqueous sulfuric acid solution containing sulfuric acid described above is used to adjust the pH of the reaction solution.

By the way, the synthetic reaction of aluminum sulfate is expressed by the following formula (1), and the calculated reaction formula is expressed by the following formula (2).

2At(OH) 3+ 3H2804→AL2(SOa
)3+6H20(1)AAsOs+3H2804→
, kLa (SOa) a + 3H20 (2) The influence of the reaction rate constant and pH on the above reaction was investigated using a dilute sulfuric acid aqueous solution containing sludge, waste sulfuric acid, and sulfuric bread having the composition shown in Table 1 below.

Table 1 Since the reaction of the three substances mentioned above can be regarded as a homogeneous second-order reaction by experiment, the rate constant was determined by a batch test. According to the experimental results, the rate constant at 90-100℃ is 0.12~
It was 0.671 t/Id-aos・mat・sec. As a result of trying various experiments by changing the mixing ratio of the above three components, it was found that the appropriate range of the rate constant is at least 0.01.
It was found that t/A of 1.203-mol-sec or more is sufficient. Furthermore, considering industrial manufacturing, l
, Ot/A7z03-mol-see.

Furthermore, if the pH value is high, that is, if the amount of Free HgSO4 is small, the reaction rate will be slow, making it unsuitable for industrial production. Therefore, considering that the final pH value of the synthetic solution is regulated, the p)1 value of the reaction solution in the first tank of the reaction tank should be lowered to increase the reaction rate, and the pH value of the reaction solution in each subsequent tank should be increased. In the case of continuous reactions, it is optimal to control the pH value to reach a predetermined final pH value of the synthesis solution while increasing the pH value sequentially.

As a result of the inventor's experiments, a dilute sulfuric acid aqueous solution containing sludge, waste sulfuric acid, and sulfuric acid bread was mixed at a constant volume and temperature (80°C to the boiling point of the reaction liquid, preferably 90°C to the boiling point) according to the amount of treatment.
By continuously supplying at a constant weight ratio to a multi-stage (3 to 6 stages) reaction tank, the pH value (
1.6-2.5 preferably 1.8-2. It has been found that the aluminum sulfate synthesis solution o) can be obtained continuously.

A dilute aqueous sulfuric acid solution containing sulfuric acid is supplied to keep the pH of each reaction solution constant, but in order to increase the reaction rate and obtain an aqueous aluminum sulfate solution with a high yield, it is necessary to It is desirable to control the pH of the tank to 1 to 1.0.

EXAMPLES Hereinafter, the present invention will be described in detail while explaining examples shown in the accompanying drawings.

FIG. 1 is a flow sheet showing an example of an apparatus suitable for continuous synthesis of an aqueous aluminum sulfate solution by a multi-tank co-current reaction according to the present invention. A belt conveyor is used for conveyance, 2 is a mixing tank, 3 is a reaction (1q) tank consisting of the first tank to the nth tank, 4 is a dilute sulfuric acid tank containing sulfur bread, and 5 is a waste sulfuric acid tank.

The reaction tank shown in Fig. 1 shows the case where n = 5, and consists of 5 tanks, and between the 14th WRx and the 2nd tank R2 is an impaction partition 8a that protrudes upward so that the water surface overflows. The second tank 2 and the third tank 1t3, the third tank R3 and the fourth tank R4, and the fourth tank R4 and the fifth tank R5 have communication ports at the bottom. Bulkhead 8 suspended from the top
A stirrer 9 rotated by an electric motor M is installed in each type.

The sludge is supplied to the mixing tank 2 by a belt conveyor j, while the dilute sulfuric acid aqueous solution containing room-temperature sulfuric acid bread in the dilute sulfuric acid tank 4 is sent via the supply line II by the pump 10 to the first heat exchanger 6. Heat exchanged with the generated aluminum sulfate synthetic liquid at about 100℃ to about 65-70℃
It is then heated to a high temperature of about 95 to 100 degrees Celsius by exchanging heat with boiling point steam in the second heat exchanger 7, and then transferred to the mixing tank 2 through the first supply pipe 12, and a part of it is A second supply pipe 13 supplies the fourth tank before the final tank. The mixture of sludge and sulfuric acid aqueous solution containing sulfuric acid bread in the mixing tank 2 is in a high temperature state of about 70 to 80°C, and after being stirred and mixed by the stirrer 9, it is sent to the first reaction tank &. on the other hand,
The waste sulfuric acid in the waste sulfuric acid tank 5 is sent to the waste sulfuric acid receiving tank 15 by the pump 14, and after removing suspended solids by the screen 16 disposed in the receiving tank 15, the waste sulfuric acid is sent to the first reaction tank R1 by the pump 17. .

In the reaction tank 3, the reaction liquid consisting of a mixture of sludge, waste sulfuric acid, and sulfuric acid aqueous solution containing sulfuric acid in the first tank R1 is as follows:
While being stirred by the stirrer 9, the reaction is carried out according to the reaction formula (1) while flowing from the first tank R1 to the final fifth tank, and an aluminum sulfate synthetic solution at about 100°C is obtained from the fifth tank. is pumped from the product line 19 by the pump 18 to the first
It is sent to a filtration and purification facility (not shown) through a heat exchanger 6.

Next, control system 9 will be explained. First, to explain the control of the pH of the reaction liquid, the pH of the reaction liquid in the first tank R1 and the second tank R2 is set to about 0.8K.

If the supply amount of sludge fluctuates and is much lower than the theoretical supply amount, the amount of waste sulfuric acid supplied will be relatively large, and the p
Since H will shift from the set value, that is, pH 0.8, to an acidic side (for example, pH 0.2, etc.), pH adjustment is necessary. This pH adjustment is carried out using the first tube installed in the second tank I fan.
When the pH value of the first pH indicator and adjustment recorder is below pH 0.8 (strongly acidic side), the first supply of dilute sulfuric acid aqueous solution containing sulfuric acid The first control valve 21, which is connected to the recorder 20 disposed in the tube 12, is closed, and the pH is set to 0.8.
When the pH of the initial reaction solution reaches 0.8, the first control valve 21 is opened and the pH of the initial reaction solution is automatically adjusted to 0.8 depending on the amount of dilute sulfuric acid aqueous solution containing sulfuric acid bread.

Note that the first pH indicating adjustment recorder 20 may be disposed within the first tank R1 to detect the pH on the outflow side of the first tank R1. As the reaction progresses, the pH of the reaction solution increases to the weakly acidic side, but the pH of the aluminum sulfate synthesis solution in the fifth tank (final tank) R6 remains at a predetermined value (1.6 to 2.5, preferably 1. , 8 to 2.0) or less, the second pH indicator adjustment recorder (P
The detector of HICR, ) 22 detects this, and the second
The control valve 23 is closed, and if the value exceeds a predetermined value, the second control valve 23 is automatically opened. In addition, a supply pipe for a dilute sulfuric acid aqueous solution containing sulfuric acid bread is connected to the 6 tanks, a pH indicator adjustment recorder is installed in the 6 tanks, and the pH of the reaction solution in the 6 tanks is finely adjusted according to the same specifications as above. is also possible. In any case, the pH of the reaction solution is controlled by adjusting the amount of dilute sulfuric acid aqueous solution containing sulfuric acid, and the pH value of the reaction solution is 0.8 or more.
Since the reaction rate of the tank is about 90% and the pH value of the second tank will never be lower than the above value, the material of the first tank is SO831.
6JIL, the material of the reaction tanks after the second tank is SO8316L.
A grade of stainless steel is sufficient.

Next, to explain the temperature control of the reaction liquid, first, the temperature of the mixture of sludge and dilute aqueous sulfuric acid solution containing sulfuric acid in the mixing tank 2 is controlled to 70 to 80°C by supplying the dilute aqueous sulfuric acid solution containing sulfuric acid at about 95 to 100°C. However, the room temperature dilute sulfuric acid aqueous solution containing sulfuric acid in the dilute sulfuric acid tank 4 is heated to about 65 to 70°C in the first heat exchanger 6 as described above.
temperature indicator recorder (TR) 24), second heat exchanger 7
The temperature is raised to about 95-100°C.

This temperature is determined by a temperature indicating control recorder (TRC) installed after the second heat exchanger 7 in the supply line of the dilute sulfuric acid aqueous solution containing sulfuric acid.
) 25, and if the temperature is below the set temperature, the steam control valve 27 linked to the recorder 25 provided in the steam supply pipe 26 is opened, and if the temperature is above the set temperature, the steam control valve 27 is closed and the second heat exchanger is closed. By adjusting the amount of steam entering 7, the temperature is automatically controlled to the set temperature. A steam supply pipe is connected to each reaction tank, and the first tank R]
The first steam pipe 28 is immersed in any form such as a fill shape or a flat plate shape 24) in the reaction solution inside the reactor, and then led to a drainage groove 32 for heat exchange. A second steam pipe 29, a third steam pipe 30, and a fourth steam pipe 31 are respectively connected to the fourth tank so that steam can be introduced thereto. The temperature of the reaction solution in the first tank R1 is determined by the jth
The temperature of the reaction liquid in the first tank R1 is regulated by a temperature indication control recorder (TRC) 33 and a first temperature control valve 34 which is interlocked with the recorder 33 disposed in the first steam pipe 28, so that the temperature of the reaction liquid in the first tank R1 reaches the set value. In the above case, the first temperature control valve 34 is closed, and when the temperature is below the set value, it is opened and the temperature is automatically controlled to the set temperature. Third and fifth temperature recorders (TR) are installed in the third tank R3 and fifth tank R5, respectively.
35 and 36 are arranged, and the second to fourth temperature control valves 37 to 39 are manually adjusted by opening and closing according to the detected temperatures of these temperature indicator recorders 35 and 36, but the temperature of the reaction liquid Adjustment can also be done intransitively by installing temperature indicating adjustment recorders in the six tanks and interlocking the temperature control valves of each steam pipe. In addition, in the case of the method of raising the temperature by introducing steam into the 6th tank, the reaction liquid becomes diluted and extra energy is required in the subsequent purification process, so the temperature rise of the reaction liquid in the 1st tank will be as shown in the figure. It is preferable to use a heat exchange system between a steam pipe and a reaction liquid. In addition, the reference numeral 40 in FIG. L.C.
), which works in conjunction with the pump 14 to automatically operate the pump 14 when the liquid level of waste sulfuric acid in the waste sulfuric acid receiving tank 15 falls below a certain level, and stops operating when it rises above a certain level. let Reference numeral 41 indicates a liquid level indicator controller (LICA) with a reporting device for controlling the liquid level of the reaction tank 3, and when the liquid level of the reaction liquid falls below a set value, the control valve 42 is automatically throttled. Opens when the temperature rises above the set value.

Reference numeral 43 is a flow rate integration indicator (FIQ) that indicates the supply amount of the dilute sulfuric acid aqueous solution containing sulfur.

Using the apparatus shown in FIG. 1 described above, continuous synthesis of an aqueous aluminum sulfate solution was carried out under the following conditions.

Synthesis conditions sludge: Supply amount 1429 land mass composition A/=(OH) 3 9-5 impurities in wt
3.7〃 H2O86-8〃 Waste sulfuric acid: Supply amount 72・bt7 hours Composition Free
-H280490-Owt XAta (80a) 30.
6p Specific gravity +404 (25℃) Aqueous sulfuric acid solution containing sulfuric acid bread: Supply amount 31+2t/hour Composition
Free-H2SO, 5.3wt%At2(Sot)
3 F3, 9 ttH20 remainder specific gravity 1.134 (12°C) Reaction temperature: 99-100°C 1st MpH: about 0.8 5th tank pH: about 2.0 As a result, aluminum sulfate aqueous solution with a reaction rate of about 9% could be synthesized continuously. The resulting aluminum sulfate aqueous solution was synthesized using: Synthetic liquid volume: 300-1, Filtration temperature: 20°C, Filtration method: Vacuum method (no auxiliary agent), Filtration area: 95cr11 Filter paper: Toyo Roshi #2, Filtration pressure (degree of vacuum): 120To
A filtration test was conducted under the conditions of rr, but there were no problems with filtration.

FIG. 2 shows another embodiment of the apparatus for continuously synthesizing an aqueous aluminum sulfate solution of the present invention, showing only the modified parts of the apparatus shown in FIG. 1, and equipment not shown in FIG. (heat exchanger, etc.), instrumentation (for example, a pH indicator and adjustment recorder, etc.), and supply lines (for example, a sulfuric acid aqueous solution supply line containing sulfuric acid bread) are the same as those shown in FIG.

The device shown in Figure 1 is equipped with a mixing tank 2, but this was installed because it would not be possible to install a reaction tank under the belt conveyor if the existing equipment was used as is. It is not necessarily necessary to provide a tank;
As shown in Figure 2, the three raw materials are directly fed into the reaction tank 3.
1411R1. In FIG. 2, the sludge is pumped and supplied through the sludge supply pipe 44, but it goes without saying that it may be supplied by a belt conveyor as shown in FIG. In the reaction tank 3 shown in FIG. 2, each tank R1-5 is divided alternately by the impaction partition wall 8a and the partition wall 8bK suspended from the upper part, so as to prevent a short bath of the reaction liquid. There is.

In order to more effectively prevent this short bath of the reaction solution, a barrier plate 53 may be provided in the tank as shown in FIG.

Further, the temperature of the reaction liquid in the first tank R1 is controlled by a first temperature control valve 34 provided in the first steam pipe 2B using a first temperature indication adjustment recorder 33, similar to the device shown in FIG. This is done automatically, but the second to fourth
The temperature of the reaction liquid in tanks R4 to R4 is also controlled by the second to fourth temperature indicator control recorders (
TRC) 45-47 and 2nd-4th steam pipes 29-3
The second to fourth temperature control valves 48 to 5 provided in 1
0 automatically.

Furthermore, the temperature control of the tower tanks is controlled by controlling the reaction liquid in each tank and the coil-shaped or flat plate-shaped coils immersed therein.
This is done by heat exchange with a steam pipe.

In the apparatus shown in Fig. 2, a pump 1 for discharging the synthetic liquid is used.
Synthetic liquid circulation line 52 returning from the discharge side of No. 8 to the first tank R1
is provided. As a result, the second pH indicator control recorder (PHICR) 22 (the first
(see figure) shows an abnormal value (outside the appropriate range), open the manual valve 51 and pour the aluminum sulfate aqueous solution into the first tank R1
It can be returned. Of course, this circulation line may also be provided in the apparatus shown in FIG.

Effects of the Invention As is clear from the above description, the present invention provides the following effects and advantages.

a) Since the aluminum sulfate aqueous solution is synthesized by a continuous reaction using a multi-stage parallel flow reaction, the production capacity is greatly improved compared to the conventional batch pressure system, and therefore the equipment is small, and the installation space is small and it can be used indoors. Installation is also possible.

b) In addition, since a dilute aqueous sulfuric acid solution containing sulfuric acid is used to adjust the pH of the reaction system, pH adjustment is easy, and the Free-H2SO4 concentration in the first tank is low, making it possible to adjust the pH of various reaction solutions.
By keeping the value between 0.8 and 2.5, stainless steel can be used as the material for the reaction tank. Therefore, welding repair and inspection of the reaction tank is possible, maintenance is easy, equipment costs are low, and continuous operation allows continuous control of the pH of the reaction solution without switching operations of valves, pumps, stirrers, etc. It is easy to automate and is effective in terms of workability and safety.

C) Furthermore, capacity can be increased by small-scale improvements based on experimental data on reaction rate constants.

d) Furthermore, according to the reaction temperature control system of the present invention, there is almost no decrease in thermal efficiency due to thermal scaling of Calorie due to the heat exchange system separate from the reaction tank, and the temperature can be controlled automatically. Therefore, together with the effect of continuous operation, the advantages of high energy efficiency, low driving power consumption, and low running cost (3·l) can be obtained.

Other advantages and effects of the present invention will be apparent from the foregoing description.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing one embodiment of an apparatus suitable for continuous synthesis of an aqueous aluminum sulfate solution according to the present invention, FIG. 2 is a partial flow sheet showing another embodiment, and FIG. It is a partial sectional view showing an example. 2... Mixing tank, 3... Reaction tank, 4... Dilute sulfuric acid tank containing sulfur bread, 5... Waste sulfuric acid tank, 6... First heat exchanger, 7... Second Heat exchanger, 8a, 8b...
Partition wall, I2...first supply pipe, 13...second supply pipe,
2゜...1st pH indication adjustment recorder, 21...1st
Control valve, 22...Second pH indicator adjustment recorder, 23...Second control valve, 26...
Steam supply pipe, 28...first steam pipe, 33...
- 1st temperature indication adjustment recorder, 34... 1st temperature control valve, 53... baffle board. Procedural amendment (voluntary) April 3, 1932

Claims (1)

[Claims] 1. Aluminum sludge mainly composed of aluminum hydroxide produced in the aluminum surface treatment step, waste sulfuric acid produced in the coating film removal step in the surface treatment step, and sulfuric acid recovery step in the surface treatment step A sulfuric acid aqueous solution containing aluminum sulfate produced in is supplied to a plurality of reaction tanks consisting of the first tank to the nth tank, and
The reaction is carried out at a temperature of 80° C. to the boiling point of the reaction solution while flowing sequentially to the tank (final tank), and a part of the sulfuric acid aqueous solution containing aluminum sulfate is poured into at least one of the tanks from the second tank to the final tank. p of the reaction solution in the final tank.
A method for continuously producing an aqueous aluminum sulfate solution from a by-product produced in an aluminum surface treatment step, the method comprising adjusting H to 1.6 to 2.5. 2. The method according to claim 1, characterized in that when the pH of the reaction solution in the final tank falls outside the appropriate range, a part of the aluminum sulfate aqueous solution discharged from the final tank is refluxed to the reaction tank. . 3. Claim 2, characterized in that a part of the aluminum sulfate aqueous solution discharged from the final tank is refluxed to the first tank.
The method described in section. 4. Adjust the pH of the reaction solution in the first tank or second tank to 0.1~
Claim 1 characterized in that the adjustment is made to 1.0.
The method according to any one of Items 3 to 3. 6. The method according to claim 4, wherein the pH of the reaction solution is adjusted by controlling the amount of the sulfuric acid aqueous solution containing aluminum sulfate supplied to the first tank. 6. The method according to any one of claims 1 to 5, wherein the temperature of the reaction liquid in the reaction tank is controlled by supplying water vapor to the reaction liquid. 7. Any one of claims 1 to 5, characterized in that the temperature of the reaction liquid in the reaction tank is controlled by heat exchange between the reaction liquid and a steam tube immersed in the reaction liquid. Method described. 8. The method according to any one of claims 1 to 7, characterized in that a high temperature aqueous sulfuric acid solution containing aluminum sulfate is supplied to the first tank. 9. Aluminum sludge mainly composed of aluminum hydroxide generated in the aluminum surface treatment process, waste sulfuric acid generated in the coating film removal process in the surface treatment process, and aluminum sulfate generated in the sulfuric acid recovery process in the surface treatment process. a reaction tank consisting of a first tank to an nth tank for continuously reacting the sulfuric acid aqueous solution containing the aluminum sulfate; a first supply pipe for supplying the sulfuric acid aqueous solution containing the aluminum sulfate to the first tank; an n-th supply pipe (n = 2 or more) for supplying the sulfuric acid aqueous solution containing aluminum to at least one of the tanks after the second tank; and a first pH indicator disposed in the first tank or the second tank. a control recorder; a first control valve that adjusts the flow rate in the first supply pipe in conjunction with the first pH indicator control recorder; It is characterized by comprising: an indicating adjustment recorder (n = 2 or more); and an nth control valve (n = 2 or more) that adjusts the flow rate in the nth supply pipe in conjunction with the nth pH indicating adjusting recorder. This equipment continuously produces an aqueous aluminum sulfate solution from the by-products generated in the aluminum surface treatment process. 10. The n-th supply pipe is a supply pipe for supplying the aluminum sulfate-containing sulfuric acid aqueous solution to a tank before the final tank, and the n-th pH indicating adjustment recorder is disposed in the final tank,
10. The apparatus according to claim 9, wherein an n-th control valve interlocked with the pH indicating adjustment recorder is disposed in the supply pipe. 11. The reaction tank is separated from the first tank to the nth tank by a partition wall suspended from the top so as to have a communication port at the bottom and/or a weir-like partition wall projecting upward so that the water surface overflows. 11. The apparatus according to claim 9 or 10, wherein the liquid is fractionated into each tank. 12. The apparatus according to claim 11, characterized in that a baffle plate is provided in at least one of the first to nth tanks to prevent a short bath of the reaction solution. 13. Aluminum sludge containing aluminum hydroxide as a main component produced in the aluminum surface treatment process, and waste sulfuric acid produced in the coating film removal process in the surface treatment process;
A reaction tank consisting of a first tank to an nth tank for continuously reacting the sulfuric acid aqueous solution containing aluminum sulfate produced in the sulfuric acid recovery step in the surface treatment step, and a reaction tank close to the boiling point of the reaction liquid obtained from the reaction tank. a first heat exchanger for exchanging heat between the final aluminum sulfate aqueous solution and the sulfuric acid aqueous solution containing aluminum sulfate; a first steam pipe disposed within the first tank; and a first steam pipe disposed within the first tank. a first temperature control valve that adjusts the flow rate of steam in the first steam pipe in conjunction with the first temperature control recorder; and at least one of the second to nth tanks. nth installed in one tank
Steam tube (n = 2 or more) and nth temperature indicator recorder (n
= 2 or more); and an nth temperature control valve (n = 2 or more) that manually or automatically adjusts the steam flow rate in the nth steam pipe in conjunction with the nth temperature indicator recorder. A reaction temperature control device for continuously producing an aqueous aluminum sulfate solution from a byproduct produced in the aluminum surface treatment process. 14. Claim 13, characterized in that a second heat exchanger for further heat exchange with steam is provided after the first heat exchanger in the supply line of the sulfuric acid aqueous solution containing aluminum sulfate. Device. 15. A steam control that provides a temperature indication adjustment recorder after the second heat exchanger in the supply line of the aluminum sulfate-containing sulfuric acid aqueous solution, and adjusts the amount of steam supplied to the second heat exchanger in conjunction with the recorder. 15. Device according to claim 14, characterized in that a valve is provided in the steam supply pipe to the second heat exchanger.