JPH05185066A - Method and apparatus for processing photographic waste liquid - Google Patents

Abstract

PURPOSE:To provide a method and equipment where the generation of gaseous SO2 and hydrogen sulfide is prevented even if photographic processing waste is heated and simultaneously the waste is safely and economically treated and handling is easy. CONSTITUTION:An evaporating vessel 4 housing silver salt photographic processing waste containing thiosulfate and a vessel 6 housing alkali of small solubility, such as slaked lime and calcium carbonate are provided. The vessels are connected by a circulating route 10 and by circulating the waste, pH of the waste in the evaporating vessel 4 is kept in the prescribed range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating a silver salt photographic processing waste liquid containing thiosulfate.

[0002]

2. Description of the Related Art Table 1 shows the components of typical photographic processing chemicals. Generally, the photographic processing waste liquid has a high degree of pollution, and BOD (biochemical oxygen demand) and COD (chemical oxygen demand). There are tens of thousands of PPM. As a general wastewater treatment method, there are known an activated sludge method, a method using activated carbon, a method using an oxidizing agent such as ozone, a method for treating with a separation membrane, a method for incinerating the waste solution, and a method for evaporating and concentrating the waste solution. Has been. Since the method of evaporating and concentrating the waste liquid requires a relatively simple device, it has been put to practical use in some cases.However, simple evaporation causes a considerable amount of pollutants to be contained in the evaporating water vapor, and the treated water that condenses it contains ammonia content. And COD are high and the treatment is insufficient. For this reason, the present inventor evaporates the waste liquid while maintaining the pH of the waste liquid during heating and evaporation within a range where sulfurous acid gas and hydrogen sulfide are not generated as a method for concentrating treatment to obtain sufficiently clean treated water, and mainly produces steam. Ammonia or organic substance gas to be mixed with a small amount of air is heated to 600 ° C or higher or heated to 200 ° C or higher to decompose a harmful component generated by contact with a catalyst, and is released to the atmosphere as a gas. Alternatively, a method of condensing and discharging gas (Japanese Patent Application No. 1-178072) is proposed.

[0003]

[Table 1]

According to this method, when simply evaporating and concentrating, the chemical liquid components in the photographic waste liquid are decomposed and ammonia and various other organic substance components are contained in the vaporized gas, and the condensed liquid contains a large amount of ammonium salt. COD of the condensate
Since the (chemical oxygen demand) is also high, it is necessary to reprocess the condensate in order to release it, but a much cleaner condensate is obtained, and it has the major feature that it can be released as it is. Further, in this method, various gases generated from the photographic waste liquid are treated only by thermal decomposition treatment, and therefore, generation of sulfurous acid gas or hydrogen sulfide, which cannot be treated in thermal decomposition and also becomes a catalyst poison when a catalyst is used, is eliminated. Therefore, it is necessary to keep the pH of the waste liquid during evaporation at about 4.6 or higher. The amount of alkali necessary for this purpose corresponds to the amount of ammonium thiosulfate salt in the waste liquid, and is generally converted to 100% caustic soda to remove the photographic processing waste liquid (developing waste liquid and fixing waste liquid, etc.). 1% to 3% was required.

The reason why sulfur dioxide and hydrogen sulfide are not generated from the waste liquid when the pH of the waste liquid is kept at about 4.6 or higher when the waste liquid is heated will be explained with reference to the following experimental examples. Table 2 shows the process of heating the bleach-fixing waste liquid to evaporate and concentrate it. From the phenomenon in the table, it can be inferred that the components undergo chemical changes. The malodorous component in the initial stage of heating is ammonia gas as measured by the detector tube, and the waste liquid changes to acidic. When the waste liquid is further evaporated by heating and concentrated, the pH further decreases, and when it becomes around 4.6, the waste liquid becomes turbid and at the same time sulfurous acid gas and hydrogen sulfide are generated.

[0006]

[Table 2]

Table 3 shows the process of heating the mixed waste liquid of the developing waste liquid and the bleach-fixing waste liquid. Due to the high pH of the development waste liquid, ammonia gas is generated simply by mixing the two. Star
Although the pH of the solution is different from that in Table 2, the generation of sulfurous acid gas and hydrogen sulfide near pH 4.6 is the same as in Table 2.

[0008]

[Table 3]

Other malodorous gases when the photographic waste liquid is evaporated are ammonia, alcohols, amines, acetic acid and the like, all of which are decomposed and deodorized by heating at 600 ° C. or higher. Moreover, if a catalyst such as platinum is used, 2
The gas can be decomposed and deodorized by heating the gas to 00 ° C to 400 ° C and bringing it into contact with the catalyst. These temperatures may be lowered by several tens of degrees Celsius depending on the state of waste liquid, catalyst and the like.

From the above, in the photographic processing waste liquid containing thiosulfate, it is possible to evaporate and concentrate or evaporate to dryness without generating sulfurous acid gas or hydrogen sulfide by heating by keeping the pH at about 4.6 or more. I understand. Further, since sulfurous acid gas and hydrogen sulfide are generated almost at the same time, it is sufficient to pay attention to sulfurous acid gas as an index. Table 4 shows the process of evaporating the waste liquid used in Table 3 with caustic soda while keeping the pH at about 4.6 or higher. It can be seen that it can be highly concentrated without the generation of sulfurous acid gas or hydrogen sulfide. Evaporation chamber liquid volume 38
At the time of cc, the pH was lowered without adding caustic soda, and when the pH became approximately 4.6, the sulfur dioxide gas was measured with a detector tube, and it was found that the gas was generated. Evaporation was stopped when the amount of the can liquid was 15 cc, but when the liquid was brought to room temperature, solids were precipitated and became a very viscous slurry.

[0011]

[Table 4]

The above-mentioned processing apparatus is most economically effective if it is installed near the automatic developing machine of the photograph and the generated waste liquid is concentrated on the spot, but the necessary conditions for the apparatus therefor are: 1. 1. Compact device, 2. It should be as easy and trouble free as possible,
3. 3. Initial cost and operation cost are small.
Even an amateur can handle it safely.

The processing method and apparatus proposed by the present inventor sufficiently exert their effects as a large-sized apparatus, but when this is used together with an automatic processor (minilab) in an ordinary photo shop, etc. The following points need to be considered. One is the method of neutralization treatment. That is, the neutralization method by adding caustic soda, which is the most common neutralization method, is a well-established method as an apparatus, but when treating a waste liquid from a general automatic processor for one week, The amount of waste liquor treated is about 100 to 200 liters, the required amount for neutralization is from 2 to 4 kg, and caustic soda with a concentration of 10% or more is required due to the caustic soda supply conditions. .. Caustic soda is an expensive source of alkali and has problems in cost, but above all, if it is at such a high concentration, it will cause burns and rashes for an amateur without chemical knowledge to handle it. The danger to There is also known a method of using slaked lime as a neutralizing alkali. Slaked lime is inexpensive and has a low solubility in water, so it is safe for the human body, but slaked lime is a solid (powder). Therefore, it is difficult to add it to the waste liquid, and the method of adding powder as it is to the waste liquid using a feeder is 2. However, the method of adding slaked lime to the waste liquid in the state of slurry is too small, and the slurry liquid precipitates, or the slurry liquid solidifies and clogs the pump. Then, this is also the condition 2.
It was difficult to adapt to.

The second is the handling of the concentrated liquid.
That is, the concentrated liquid after sufficiently concentrating the photographic processing waste liquid including the fixing waste liquid is a fluid liquid while the temperature is high, but crystallizes into a solid when cooled to about 50 ° C. or lower. For this reason, if you do not take appropriate measures when the device is stopped, it will clog the pump, clog the piping,
It is a source of trouble. To meet this, condition 2.3. It was necessary to satisfy and solve at the same time.

[0015]

DISCLOSURE OF THE INVENTION The present inventors have found that a waste liquid processing method and apparatus for heating and evaporating and concentrating a waste liquid for photographic processing while keeping the pH of the waste liquid for photographic processing within a range where sulfurous acid gas and hydrogen sulfide are not generated are safe for human body and trouble. (EN) A neutralizer and a waste liquid treatment method and device capable of easily handling a concentrated liquid.

[0016]

In a waste liquid treatment method and apparatus for heating and evaporating and concentrating a waste liquid while keeping the pH of the waste liquid for photographic processing within a range where sulfurous acid gas and hydrogen sulfide are not generated, a means for adjusting the pH of the waste liquid to a predetermined range As an alkali having a small solubility in water as a container is previously placed, and by circulating the waste liquid during the evaporation treatment between the evaporation container and the alkali container, the waste liquid and the alkali are brought into contact with each other and acidic components in the waste liquid The pH of the waste liquid is maintained within a predetermined range by reacting the alkali, dissolving the alkali in the waste liquid, and returning the waste liquid to the evaporation container. In addition, by storing the above-mentioned alkali in the concentrate receiving container in an amount necessary for treating a predetermined amount of the waste liquid in advance, and circulating the waste liquid during evaporation between the evaporation container and the concentrate receiving container. When the evaporating waste liquid and the alkali in the concentrate receiving container are brought into contact with each other to keep the pH of the waste liquid within a predetermined range and the evaporative concentration of a certain amount of the waste liquid is completed, the whole concentrate receiving container is replaced.

The inventor of the present invention has described the above-mentioned condition 2 "stability of the apparatus".
In consideration of “Safety to human body” of Condition 4 and the result of diligent research to manage safe handling of high-concentration caustic soda, it was absolutely safe and stable, and the drug cost We have found a way to make the equipment cheaper and less expensive. The present inventor first returned to the origin of the meaning of neutralization and studied. That is, the reason why the waste liquid must be neutralized is that when the waste liquid is heated, ammonium thiosulfate in the waste liquid is decomposed, and ammonia is diffused into the atmosphere, whereby the pH of the waste liquid is lowered and becomes about 4.6. This is because the thiosulfate starts to decompose and sulfurous acid gas and hydrogen sulfide are generated, which hinders the thermal decomposition treatment of the evaporative gas. That is, the pH of the waste liquid should be about 4.6, and it can be used as a neutralizing agent even if it is on the acidic side, if about 4.6 or more can be surely secured. The pH may theoretically be in the range of about 4.6 or higher as described above, but in practical use, it is preferably 6 to 10.

Table 5 shows the solubilities of various alkalis in water.
PH of saturated aqueous solution, pH of liquid in contact with boiling 3.5% ammonium thiosulfate solution, pH of liquid in contact with boiling photoprocessing waste liquid, ammonium thiosulfate 3.5% solution 1 liter Amount of alkali required for concentrating 1/10 of the amount, 1 liter of photographic processing waste liquid is 1/1
It is the amount of alkali required to be concentrated to 0. The pH of each alkali shown in the table is slightly lowered when it comes into contact with a liquid in a boiling state, but it is sufficiently possible to maintain the pH of the waste liquid at about 4.6 or more. The reason why the pH is slightly lowered seems to be that the rate at which ammonium thiosulfate in the liquid is decomposed by heat and the rate at which solid alkali reacts and dissolves are balanced. This can be inferred from the fact that when the temperature is lowered, the liquid in which the decomposition of ammonium thiosulfate is completed returns to the pH of a saturated aqueous solution by adding a sufficiently excess alkali. In addition, even if it does not dissolve well in neutral water,
It can be seen that when ammonium thiosulfate is decomposed into an acidic state, it is easily dissolved, and almost ammonium thiosulfate and an equivalent amount of alkali are dissolved.

[0019]

[Table 5]

FIG. 3 shows changes in the pH of the waste solution when the photographic processing waste solution containing ammonium thiosulfate is heated and concentrated. The curve (A) is the change when no alkali is added, and the curve (B) is excessive. Shows the change in the presence of calcium carbonate. If there is no alkali, waste liquid p
H decreases as the concentration progresses, 20% of the volume
When the pH of the waste liquid reaches approximately 4.6, hydrogen sulfide and sulfurous acid gas begin to be generated. On the other hand, if excess calcium carbonate is present, the pH of the waste liquid is
A value that is thought to be a point where the decrease and the solution speed are balanced (Omitted)
6.6) is almost constant. Considering that the purpose of this neutralization should be approximately 4.6 or more, this has the advantage of providing a self-control function and eliminating the need for a neutralization control device (pH meter, etc.), which is extremely convenient. Is.

As the alkali that can be used here, slaked lime, calcium carbonate, magnesium hydroxide, magnesium carbonate and alkalis having a sufficient solubility on the acidic side of pH 4.6 or more can be applied. As examples thereof, ferric hydroxide, zinc hydroxide, manganese hydroxide and the like having a solubility product of 10 ⁻⁴ to 10 ⁻¹⁸ metal hydroxide and the like can be applied.

[0022]

EXAMPLE In FIG. 1, a photographic processing waste liquid (2) stored in a waste liquid tank (1) is sent to an evaporation container (4) by a pump (3), and the waste liquid is pumped to an alkali storage container (4). 6) Sent. The alkali (7) corresponding to the total amount of the waste liquid to be treated is previously stored in the container (6). The waste liquid comes into contact with the solid state alkali (7) in the alkali storage container, dissolves the alkali content to be neutralized, and returns to the evaporation container through the reboiler (8).

As described above, the waste liquid is circulated between the evaporation container and the alkali container via the pump (5), so that as shown in FIG.
It becomes H and can be stably neutralized without a pH controller. Moreover, since slaked lime or the like is not handled in a high-concentration slurry state, stable operation can be performed without causing pipe troubles and pump troubles due to sedimentation. Of course, even if some undissolved solid alkali is circulated and circulated between the evaporation container and the alkali container, there is no problem as a neutralizing function,
When the concentrated solution is drawn into the concentrated solution receiving container, undissolved alkali is entrained and the alkali is wasted, and it causes clogging of pumps, pipes, valves, etc. It is preferable not to rush. In the illustrated one, the circulation path (10)
By providing a bypass (11) and valves (12) and (13) in the container, adjusting the flow rate of the waste liquid flowing into the alkali storage container (6), and providing a straightening plate (9) to make the flow of the waste liquid uniform, The neutralization state and the state of solid alkali infusion are adjusted.

A reboiler (8) is provided in the evaporation container (4).
Is attached, whereby the waste liquid kept at a predetermined pH as described above is heated to a temperature higher than the boiling point. The waste gas composed mainly of evaporated water vapor is mixed with a small amount of air sent from the air pump (14) in the mixer (15) and sent to the catalytic combustion device (16). The waste gas sent to the catalytic combustion device (16) is heated to about 200 ° C or higher by the electric heater (17) and comes into contact with the catalyst (18) to decompose the ammonia gas and the malodorous gas of organic matter in the waste gas. To be done. The decomposed waste gas is pressurized by the compressor (19) and sent to the heating tube (20) of the reboiler (8),
The waste liquid (2) is heated, the waste gas is condensed, and the gas-liquid separator (21)
It is separated and released into gas and condensate. On the other hand, the evaporated and concentrated waste liquid can be opened and closed by opening and closing the solenoid valve (22).
It is discharged to 3). (24) is an auxiliary electric heater for heating the waste liquid used at the start-up or when the boiling point of the waste liquid rises at the end of concentration.

In FIG. 2, the alkali in the alkali container is stored in the concentrated liquid receiving container (25) without providing a separate alkali container in FIG. 1, and the waste liquid during evaporation is evaporated in the evaporation container (4). ) And the concentrated liquid receiving container (25). The volume of the concentrate receiving container (25) should be set in advance so that the total amount of the waste liquid to be processed can be kept after the concentration, and further it is necessary when evaporating and concentrating the total amount of the waste liquid in the container. By storing the amount of alkali, at the end of processing the predetermined amount of waste liquid,
Since all the concentrated waste liquid is stored in the concentrate receiving container, the next waste liquid can be treated again by completely replacing the concentrate receiving container, which makes it extremely easy to handle. In addition, since the waste liquid is inevitably extracted once each time a predetermined amount is processed instead of the continuous operation, the probability that the concentrated liquid solidifies and causes a trouble becomes extremely low.

The alkali contained in the concentrate receiving container is
In order to improve contact with the waste liquid, it is most preferable to store the alkali in a simple partition (26) as shown in the apparatus example of FIG. 4 so that the waste liquid passes through the alkali layer. As the residence time can be relatively long, it is possible to store the alkali in the bag of the mouth cloth and hang the bag in the concentrate receiving container, or simply put the alkali directly into the container as shown in FIG. In some cases it may be enough to leave it alone. Since the waste liquid is evaporating, a odorous gas such as ammonia gas is naturally generated, but from the gas suction pipe (28) attached to the cap (27) of the waste liquid receiving container, the air is used for the thermal decomposition of the evaporative gas to the outside air through the gap between the caps. Even if the container is not closed by suctioning with it, no odor will be leaked to the surroundings. By adjusting this and the flow rate of the circulation flow rate control valve (29) and the circulation pump (5), it is not necessary to seal the cap and the container, the container replacement work becomes easy, and the device special It can be used without the container.
This means that if you use a heat-resistant plastic container such as polyester for the concentrate receiver, you can directly put the concentrate into the silver recovery blast furnace of a non-ferrous metal mine without recovering the concentrate and recover the silver. Handling of collection is possible. In addition, heat-resistant plastic containers can be reused once used for other purposes, which is a resource reuse.

[0027]

As described above, the present invention circulates the photographic processing waste liquid between the evaporation container for containing the photographic processing liquid and the container for storing the alkali for keeping the pH of the waste liquid within a predetermined range, and the alkali is dissolved in the solubility of slaked lime or the like. Since it is small, it is safe and easy to handle, it is economical to obtain, and it is easy to use without clogging pipes and the like.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing another example.

FIG. 3 is the pH of the photographic processing waste liquid when it is heated and concentrated.
It is a graph which shows the change of.

FIG. 4 is a schematic view showing another example of the concentrated waste liquid receiving container.

[Explanation of symbols]

4: Evaporation container, 5: Circulation pump, 6: Alkali storage container, 7: Alkali, 10: Circulation path, 16: Catalytic combustion device, 1
8: Catalyst, 23, 25: Receptacle for concentrate

Claims (4)

[Claims] 1. An alkali is applied to the waste liquid in order to keep the pH of the waste liquid in a predetermined range so that sulfurous acid gas and hydrogen sulfide are not generated when the waste liquid for photographic processing contained in an evaporation container is heated. And then evaporating and concentrating, the alkali having a low solubility such as slaked lime or calcium carbonate is used, and the alkali is stored in another container, and the waste liquid is circulated between the alkali container and the evaporation container. A method for treating photographic waste liquid, characterized in that the pH of the waste liquid in the evaporation container is kept within a predetermined range. 2. A vaporization container for heating and evaporating and concentrating the photographic processing waste liquid and a container for containing an alkali having a low solubility such as slaked lime and calcium carbonate are provided, and sulfurous acid gas and hydrogen sulfide are generated even when the waste liquid is heated. An apparatus for processing photographic waste liquid, comprising means for circulating between the evaporation container and the container containing the alkali so as to keep the pH in a range not to be maintained. 3. An evaporation container for heating and evaporating and concentrating the photographic processing waste liquid, and a container for accommodating the alkali having a low solubility such as slaked lime and calcium carbonate and receiving the concentrated waste liquid in the evaporation container are provided. An apparatus for treating photographic waste liquid, comprising means for circulating the vapor between the evaporation container and the container for receiving the concentrated waste liquid so as to keep the pH in a range where sulfurous acid gas and hydrogen sulfide gas are not generated even when heated. 4. The processing apparatus for photographic waste liquid according to claim 3, wherein the container for receiving the concentrated waste liquid is formed so as to be replaceable with the container.