JP2002248465A - Evaporation-to-dryness method for wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaporation-to-dryness method for wastewater, which can smoothly discharge solidified waste to the outside of the system without sticking the solidified waste on the heater or near the outlet of the solidified waste and prevent reduction in a treatment capacity to enable stable operation, in the case that wastewater is treated in an evaporation-to-dryness apparatus to produce the solidified waste. SOLUTION: This evaporation-to-dryness method is a method for producing solidified waste by treating wastewater in an evaporating and drying apparatus 3. The waste water is treated in the apparatus 3 after adding waste water of a CMP-(chemical mechanical polishing) process thereto.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining solidified waste by, for example, treating wastewater discharged from a semiconductor device manufacturing process by an evaporative drying apparatus.

[0002]

2. Description of the Related Art As demineralized water for cleaning an object to be cleaned which is required to obtain an extremely clean surface such as a semiconductor wafer, fine particles, colloidal substances, organic substances, metals and ions are removed as much as possible. High-purity water called "ultra pure water" is used. Such ultrapure water is produced by a desalination apparatus and supplied to a place where the object to be cleaned is cleaned.
Wastewater discharged from the place of use is sent to a wastewater treatment device if it is extremely contaminated. In the wastewater treatment device, the wastewater is neutralized and subjected to concentration reduction treatment of organic substances, nitrogen, phosphorus and the like, and then discharged. In recent years, dewatering wastewater has been concentrated by an evaporator without a discharge facility due to stricter regulations related to environmental protection, and the concentrated liquid is processed by an evaporator and the solidified waste is sent to a waste disposal company. 2. Description of the Related Art There is known a closed system type wastewater treatment device to be delivered.

As the evaporative drying device used in the closed system type wastewater treatment device, a heat transfer heating type dryer or a pressurized air hot air dryer is known. Heat transfer heating dryers are used to dry the workpiece by indirect heating by heat conduction from a heat source.Drum dryers that use the outer peripheral surface of a cylindrical drum, and heat transfer on both sides of a hollow disk There is a CD (Compact Disc) type dryer used as a surface. In each of these, the solidified material adhering to the outer peripheral surface of the cylindrical drum and both side surfaces of the disk is scraped off with a scraper. Further, the pressurized air hot air dryer discharges the solidified matter dried in the drying zone from the solidified matter discharge port provided at the lower part to the outside of the system. In these evaporative drying apparatuses, it is particularly desired that the solidified material be continuously discharged to the outside of the system in terms of suppressing the production cost.

[0004]

However, in a heat transfer heating dryer, solids dried and solidified on the drum surface become sticky or too hard due to the concentration of salts and organic substances in wastewater, and solidification occurs. It is difficult to peel off objects from the drum. When the solidified material accumulates on the heat transfer surface, there is a problem that the heat transfer efficiency is remarkably reduced, and the processing amount is reduced to less than half of the state without accumulation. On the other hand, in the pressurized air hot air dryer, the solidified matter dried and solidified at the solidified substance discharge port or the wall near the solid substance absorbs and adheres to the solidified substance discharge port due to the influence of salts and organic substances in the wastewater, or the solidified substance discharge port There is a problem that the solidified matter accumulated on the upper wall of the above becomes a large lump and collapses downward, thereby blocking the solidified matter discharge port. In order to solve these problems, it is necessary to periodically clean and remove the adhered or accumulated solids,
It is difficult to secure cleaning workers who perform such heavy labor, and there is a problem of increasing production costs.

Therefore, an object of the present invention is to provide a method for obtaining solidified waste by treating wastewater with an evaporative drying treatment apparatus.
A method of evaporating and drying wastewater that can be discharged smoothly without solidified matter adhering to the heat transfer surface or near the solidified matter discharge port, and therefore can be operated stably without reducing its treatment capacity. Is to provide.

[0006]

Under these circumstances, the present inventors have conducted intensive studies and as a result, in a method of treating waste water with an evaporative drying treatment apparatus to obtain solidified waste, CMP wastewater was added to the waste water. After that, the solidified material can be continuously and smoothly discharged to the outside of the system without being adhered to the heat transfer surface and the vicinity of the solidified material discharge port by treating with the evaporative drying treatment apparatus. Was completed.

[0007] That is, the present invention (1) is a method for obtaining solidified waste by treating wastewater with an evaporative drying treatment apparatus. After adding wastewater from a CMP step to the wastewater, the evaporative drying treatment apparatus is used. An object of the present invention is to provide a method of evaporating and drying wastewater to be treated. By adopting such a configuration, in the heat transfer heating dryer, even if there is concentration of salts and organic substances in the wastewater,
There is no adhesion of dried and solidified solids on the drum surface,
In the pressurized air hot air dryer, the solidified material can be continuously and smoothly discharged to the outside of the system without the solidified material adhering to the solidified material discharge port or a wall near the solidified material outlet or forming a large lump.

Further, the present invention (2) provides the evaporative drying treatment method according to the above (1), wherein the wastewater and the wastewater in the CMP step are both discharged from the same semiconductor device manufacturing factory. . By adopting such a configuration, CMP discharged from the same semiconductor device manufacturing factory
The process wastewater can be effectively used, and various operations and processes that occur when a separate solidification regulator is purchased can be omitted.

In the present invention (3), the CMP process wastewater is a CMP process wastewater concentrate obtained by reducing the volume of the CMP process wastewater by concentrating the wastewater with a separation membrane. )).
By adopting such a configuration, the subsequent evaporative drying process can be performed more efficiently.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The wastewater used in the evaporative drying treatment method of the present invention includes wastewater having an increased concentration of impurities such as salts discharged from a semiconductor device manufacturing factory or the like. Specifically, of the desalination equipment in a semiconductor device manufacturing factory, etc., concentrated water discharged from the concentration chamber of the electric deionized water production apparatus, concentrated water discharged from the concentration chamber of the reverse osmosis membrane apparatus, and ion exchange Regeneration waste liquid discharged when the apparatus is regenerated. These concentrated water and recycled wastewater are
Before being supplied to the evaporative drying apparatus, it is preferable to further concentrate by an evaporator to obtain a concentrated water having a higher salt concentration, since the efficiency in the evaporative drying processing is further enhanced. When wastewater contains high concentration of sodium sulfate (dehydrate of sodium sulfate), heat transfer surface such as cylindrical drum outer peripheral surface of heat transfer heating type dryer and both sides of hollow disk, pressure air hot air drying The solidified matter easily adheres to the vicinity of the solidified matter discharge port of the machine, and the effect of adding the wastewater from the CMP process described later is more remarkably exhibited.

In the present invention, before the wastewater is subjected to the evaporative drying treatment, wastewater from a chemical mechanical polishing (CMP) step is added to the wastewater. By the addition of the wastewater from the CMP step, the solidified substance does not adhere to the heat transfer surface of the evaporative drying apparatus, the solidified substance discharge port or a wall in the vicinity thereof, and the solidified waste is smoothly discharged out of the system. In the CMP process drainage, the CMP process refers to various polishing processes such as a flattening process of an interlayer insulating film and a precision process for forming an element isolation in the manufacture of a semiconductor device. Specifically, colloidal silica (SiO ₂ ), Al
Abrasive particles such as ₂ O ₃ , MnO ₂ , an electrolyte such as an ammonium salt or a potassium salt, an oxidizing agent such as hydrogen peroxide,
Inorganic acids such as nitric acid and hydrofluoric acid, organic acids such as carboxylic acid,
A step of polishing using a dispersion obtained by dispersing in water containing a chemical such as an inorganic or alkaline agent, an organic dispersant or a surfactant as a polishing liquid (CMP slurry),
Usually, polishing is performed on a polishing pad made of polyurethane or the like. Generally, the CMP slurry for polishing Al or W is acidic, and the CMP slurry for polishing Cu is weakly acidic or near neutral.

In the present invention, the CMP process wastewater generated by performing the CMP process using the above-mentioned CMP slurry is not only the above-mentioned CMP slurry component but also a barrier metal such as Ti, TiN and TaN, a metal film, an interlayer insulating film and the like. It contains refuse of polishing material, polishing pad debris, etc., and is diluted with rinsing water and discharged.

[0013] The CMP process wastewater may be added to the wastewater as a CMP process wastewater concentrate whose volume has been reduced by concentrating the CMP process wastewater with a separation membrane, so that the subsequent evaporative drying treatment is further performed. This is preferable in that it can be performed efficiently. The separation membrane (filtration membrane) is not particularly limited, and examples thereof include an organic or ceramic ultrafiltration membrane and a microfiltration membrane. The CMP process wastewater concentrate is usually disposed of as an industrial waste treatment, but by using it in the present invention, effective utilization can be achieved and it is extremely convenient. Separated water (filtrated water) obtained by condensing the wastewater from the CMP step with a separation membrane may be subjected to an activated carbon treatment or the like, and then returned to the raw water of the desalination apparatus. In addition, the CMP
If the process wastewater is discharged from the same factory as the semiconductor device manufacturing plant from which the wastewater is discharged, the problem of the present invention relating to the wastewater can be simply and at low cost and can be separately solidified. Various operations and steps that occur when purchasing the adjusting agent can be omitted. The same semiconductor device manufacturing plant is not limited to the same building, but includes the same site to the adjacent site as long as the addition of the wastewater from the CMP process to the wastewater is within the range that can be carried out by piping. It is.

The ratio of addition of the wastewater of the CMP process or the concentrate of the wastewater of the CMP process (hereinafter simply referred to as “the wastewater of the CMP process, etc.” to the wastewater) is not particularly limited, but may be, for example, an evaporator. When the CMP process wastewater concentrate is added to the wastewater concentrated in the step, the CMP process wastewater concentrate is 25 parts by weight to 100 parts by weight with respect to 100 parts by weight of the wastewater concentrated by the evaporator. On the basis of the concentration (%), the amount of the wastewater concentrate added in the CMP process should be 0.1 to 1.0 times the wastewater concentrated by the evaporator, so that the efficiency of the subsequent evaporative drying treatment can be increased. It is preferable because it can be performed. If the addition amount of the wastewater concentrate in the CMP process is too small relative to the wastewater concentrated by the evaporator, the solidified matter adheres on the heat transfer surface of the evaporative drying apparatus or in the vicinity of the solidified matter discharge port. On the other hand, even if the addition is excessive, the effect of reducing solid matter adhesion is saturated, and the amount of excess addition and the efficiency of the evaporative drying treatment of wastewater are reduced.

In the present invention, as the evaporative drying apparatus, a conventionally known apparatus can be used, and examples thereof include a heat transfer heating dryer and a pressurized air hot air dryer. The heat transfer heating dryer is a device that performs indirect heating and drying of the object to be processed by heat conduction from a heat source.For example, a drum dryer using the outer peripheral surface of a cylindrical drum and both sides of a hollow disc are used. CD used as heat transfer surface (Comp
act Disc) type dryer. A pressure air hot air dryer, for example, blows compressed air into wastewater that is passing through a nozzle and makes it easier to dry by atomization, moisture evaporates instantaneously, and powdered solidified matter is collected from a dust collector. It has a structure to discharge.

In the present invention, the method for evaporating and drying the mixture of wastewater and wastewater from the CMP step is not particularly limited, and a conventionally known method is applied. One example of the method is shown in FIG. explain. FIG. 1 is a flowchart for carrying out an evaporative drying method according to an embodiment of the present invention.
In the figure, a wastewater treatment apparatus 10 includes a treatment liquid supply unit A including a desalination system wastewater discharged from a semiconductor device manufacturing plant and a CMP process drainage system discharged from the semiconductor device manufacturing plant, and an evaporative drying treatment unit B. It is composed of The wastewater concentrate concentrated by the evaporator (not shown) is mixed with the wastewater concentrate in the CMP process supplied by the pipe 9 on the way, and the mixture (liquid to be treated) is supplied to the three-fluid nozzle 2 by the liquid supply pipe 7 to be treated. Supplied. The three-fluid nozzle 2 is further supplied with hot air at 300 to 600 ° C. from the pipe 11 and compressed air from the pipe 12, respectively. CMP process wastewater concentrate
The wastewater from the MP process is drained off by the filtration device 1 on the concentration side, and the filtration side is reused as filtered water through the pipe 14. The liquid to be treated sent to the three-fluid nozzle 2 is atomized by compressed air, the surface area per unit volume is enlarged, and this is jetted into the drying zone 3a by hot air within the above temperature range. At this time, the liquid to be treated is ejected in the form of fine water droplets by compressed air and hot air, and the fine water droplets evaporate instantaneously, and the evaporated water and powder are separated by the bag filter 4 to become powder. The solidified waste falls due to gravity near the solidified material discharge port such as a relatively low temperature hopper wall 6. In the present invention, for example, even in the case of wastewater containing a large amount of highly hygroscopic sodium sulfate, inorganic abrasive particles and inorganic polishing debris contained in the wastewater of the CMP process act effectively to suppress moisture absorption. In order to maintain the dry state or to contain the silicon compound in the solidified waste, the specific gravity of the solidified waste is increased, and the solidified waste is easily dropped off. Solid matter is smoothly discharged out of the system through the open / close valve 51 and the pipe 13 from the solidified matter discharge port 5 provided below the hopper. On the other hand, the evaporated water is exhausted out of the system through the pipe 41. The temperature of the drying zone 3a is usually around 125 ° C.

[0017]

Next, the present invention will be described in more detail with reference to examples, but this is merely an example and does not limit the present invention. Example 1 Wastewater and CM concentrated by an evaporator using a wastewater treatment apparatus having the flow shown in FIG. 1 and according to the above-described treatment method
The mixture of the P step wastewater concentrate was treated in the evaporative drying treatment apparatus 3 continuously for 24 hours. Wastewater concentrated in the evaporator (E
Table 1 shows the properties of the VP concentrated water) and the CMP process wastewater concentrate (CMP concentrated water). Further, the state of accumulation of the solidified waste on the wall 6 of the hopper or the state of discharge from the pipe 13 was observed by the following evaluation method. Table 2 shows the results.

(Liquid to be treated) EVP concentrated water: CMP concentrated water = 4: 1 (weight ratio) (Evaporation drying treatment equipment) CC dryer L type (EBARA BUSINESS CO., LTD.) Wastewater treatment amount: 560 kg / hour (Evaluation Method)-During the treatment operation, the state of discharge of the solidified waste from the pipe 13 to the outside of the system is observed. On the other hand, after the end of the continuous operation, the accumulation state of the solidified waste in the vicinity of the wall 6 of the hopper is observed from the inspection port (not shown) in the drying zone. In addition, if there is a deposit, the deposit is scraped off with a pestle, and the adhesion state of the deposit is observed.

[0019]

[Table 1]

Examples 2 to 4 The ratio of 4: 1 (weight ratio) of EVP concentrated water to CMP concentrated water was
8: 3 (weight ratio) (Example 2), 2: 1 (weight ratio) (Example 3), 3: 2 (weight ratio) (Example 4) I went in. Table 2 shows the results.

Comparative Example 1 The same procedure as in Example 1 was carried out, except that the EVP concentrated water was supplied as it was to the evaporative drying apparatus without adding the CMP concentrated water. Table 2 shows the results.

[0022]

[Table 2]

As can be seen from Table 2, the wastewater EV
In Comparative Example 1 in which the P-concentrated water was evaporated and dried without adding the CMP-concentrated water, the hygroscopic mass was deposited on the wall of the hopper after an operation time of 2 hours. Cleaning work was required. On the other hand, E
In Examples 1 to 4 in which the CMP concentrated water was added to the VP concentrated water to evaporate and dry, the solidified waste was dry and smoothly discharged to the outside of the system, which hindered continuous operation for 24 hours. Could be done without.

[0024]

According to the present invention (1), in the heat transfer heating dryer, even when salts and organic substances in the wastewater are concentrated, the solidified solids do not adhere to the drum surface. In the pressurized air hot air dryer, the solidified material can be continuously and smoothly discharged to the outside of the system without the solidified material adhering to the solidified material discharge port or a wall near the solidified material outlet or forming a large lump.
Further, according to the present invention (2), the wastewater from the CMP process discharged from the same semiconductor device manufacturing factory can be effectively used, and various operations and processes that occur when purchasing a separate solidification regulator are omitted. can do. Further, according to the present invention (3), the subsequent evaporative drying can be performed more efficiently.

[Brief description of the drawings]

FIG. 1 is a flowchart for carrying out an evaporative drying method according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Filtration apparatus 2 3 Fluid nozzle 3 Evaporation drying processing apparatus 3a Drying zone 4 Bag filter 5 Solidified substance discharge port 6 Wall of hopper 7 Liquid supply pipe to be processed 9, 11, 12, 13, 14, 41 Pipe 10 Waste water treatment apparatus 51 On-off valve A Liquid supply part to be treated B Evaporation drying processing part

Claims (3)

[Claims] 1. A method for obtaining solidified waste by treating wastewater with an evaporative drying apparatus, comprising adding wastewater from a CMP process to the wastewater and treating the wastewater with the evaporative drying apparatus. Wastewater evaporation drying method. 2. The method according to claim 1, wherein the wastewater and the wastewater from the CMP step are both discharged from the same semiconductor device manufacturing factory. 3. The evaporative drying according to claim 1, wherein the CMP process wastewater is a CMP process wastewater concentrate obtained by reducing the volume of the CMP process wastewater by concentrating the wastewater with a separation membrane. Processing method.