TW201827353A - Reduction method for waste sludge of semiconductor adding a dosage of coagulant agent that is 20% less than of the theoretical value - Google Patents

Abstract

Disclosed is a reduction method for waste sludge of semiconductor, which is to inject wastewater containing anion hazardous substances into a chemical coagulation-precipitation tank, and to add a dosage of coagulant agent that is 20% less than of the theoretical value into the chemical coagulation-precipitation tank, then to adjust the pH value in the chemical coagulation-precipitation tank, so as to enable the anion hazardous substances in the wastewater to react with the coagulant agent and thereby producing a precipitation of waste sludge, in the meantime, the other anionic hazardous substances that cannot react with the coagulant agent are discharged along with the wastewater to an anion absorption device, therefore, the residues containing anion hazardous substances in the wastewater can be absorbed by the anion absorption device, so that the discharged wastewater meets effluent discharge standards, moreover, with decreased dosage of coagulant agent being added, the purpose of reducing the semiconductor sludge is achieved.

Description

Semiconductor sludge reduction method

The present invention relates to a semiconductor sludge reduction method, and more particularly to a method capable of reducing the amount of semiconductor sludge and reducing the cost of semiconductor sludge treatment.

Since the manufacturing process of the semiconductor manufacturing industry is determined according to the product design requirements, the types of pollutants produced are numerous and varied. In addition, due to the vigorous development of the optoelectronic industry, the development of new products is seeking new changes, and the types of waste generated and changed are also different. The main pollutants in the semiconductor manufacturing and optoelectronic industries are fluorine. Waste water and arsenic-based wastewater;

Most of the fluorine-based wastewater is chemically precipitated by chemical precipitation. The chemical formula is HF+CaCl ₂ →CaF ₂ +2HCl. Therefore, fluoride ions in wastewater usually add calcium chloride to hydrofluoric acid hydrofluoric acid (HF). (CaCl ₂ ) is subjected to a coagulation reaction to obtain a precipitation of a semiconductor sludge of calcium fluoride (CaF ₂ ), and the fluoride ion in the wastewater is less than 15 ppm in order to meet the wastewater discharge standard. However, in order to make the discharged wastewater less than 15ppm, the manufacturer must add a calcium chloride (CaCl ₂ ) coagulating dose greater than the theoretical value of the chemical equilibrium, so as to ensure that the discharged wastewater meets the standards, avoids punishment, and adds a large amount of chlorine. Calcium (CaCl ₂ ) will cause some calcium chloride (CaCl ₂ ) to fail to react with hydrofluoric acid hydrofluoric acid (HF), which cannot react with hydrofluoric acid hydrofluoric acid (CaCl _{2 )} It will react with water (H ₂ O) to form calcium dioxide (Ca(OH) ₂ ) sludge, which will cause an increase in semiconductor sludge.

The arsenic-based wastewater is due to the arsenic-containing wastewater formed in the semiconductor process. Currently, the wastewater is mainly treated by coagulation; the coagulant contains calcium chloride (CaCl ₂ ) or ferric chloride (FeCl ₃ ). The chemical formula is 2H ₃ AsO ₄ +3CaCl ₂ →Ca ₃ (AsO ₄ ) ₂ +6HCl or H ₃ AsO ₄ +FeCl ₃ →FeAsO ₄ +3HCl, therefore, the arsenic ions in the wastewater are usually in arsenic acid. (H ₃ AsO ₄₎ to add the calcium chloride (CaCl ₂₎ or ferric chloride (FeCl ₃₎ coagulating the reaction, to obtain calcium arsenate _{(Ca 3 (AsO 4) 2} ) or iron arsenate (FeAsO ₄₎ The precipitation of the semiconductor sludge allows the arsenic ions in the wastewater to be less than 0.5 ppm to meet the wastewater discharge standards. However, in order to make the discharged wastewater less than 0.5ppm, the manufacturer must add calcium chloride (CaCl ₂ ) or a coagulating amount larger than the theoretical value of the chemical equilibrium, so as to ensure that the discharged wastewater meets the standards and avoids punishment, and adds a large amount. Calcium chloride (CaCl ₂ ) or ferric chloride (FeCl _{3 )} will cause some calcium chloride (CaCl ₂ ) or ferric chloride (FeCl _{3) to} fail to react with arsenic ions, which cannot react with arsenic ions. Calcium Chloride (CaCl ₂ ) Ferric chloride (FeCl ₃₎ reacts with water (H ₂ O) to form calcium oxide (Ca(OH) ₂ ) or iron oxide (Fe(OH) ₃ ) sludge. At this time, it will cause an increase in semiconductor sludge.

Therefore, for the wastewater treatment industry, the more the amount of wastewater sludge, the more cost must be spent to transport the wastewater sludge, and the more the amount of wastewater sludge will increase its weight, so the process of transporting wastewater sludge will The harder it is; therefore, if the added coagulant can be reduced, the amount of waste sludge generated can be reduced, and at the same time, an anionic harmful substance (arsenic ion or fluorine-based ion) in the fluorine-based wastewater or the arsenic-based wastewater can be ensured. Less, will be able to overcome the above problems, and this should be an optimal solution.

The present invention provides a semiconductor sludge reduction method capable of reducing a coagulant added below a desired value, thereby reducing the amount of waste sludge generated, and at the same time ensuring an anionic harmful substance in a fluorine-based wastewater or an arsenic-based wastewater. (Arsenic-based ions or fluorine-based ions) are reduced, and the cost and difficulty of wastewater treatment containing anionic hazardous substances can be reduced.

A semiconductor sludge reduction method is characterized in that: a waste water having an anionic harmful substance is injected into a mixed sedimentation tank, and a coagulant less than 20% of a theoretical value is placed in the chemical mixing sedimentation tank. And adjusting the pH value in the chemical mixing tank to react a part of the anionic harmful substance in the wastewater with the coagulant to form a sludge precipitate; and the anion which cannot react with the coagulant is harmful The substance is discharged to an anion adsorption device with the waste water to adsorb the remaining anionic harmful substances in the waste water, and after the adsorption, the waste water having only a trace amount of anionic harmful substances is discharged, so that the waste water reaches Emission standard; further cleaning the anion adsorption device through a syrup to form a regenerated wastewater, causing the anionic harmful substance adsorbed on the anion adsorption device to be separated from the anion adsorption device, and then regenerating the regenerated wastewater containing an anionic hazardous substance at a set time The inner fraction is refluxed into the mixed precipitation tank.

In a preferred embodiment, the anionic harmful substance is an arsenic ion, and the coagulant is CaCl ₂ or FeCl ₃ .

In a preferred embodiment, the anionic harmful substance is a fluorine-based ion, and the coagulant is CaCl ₂ .

In a preferred embodiment, wherein the pH value is adjusted by adding NaOH, the pH of the wastewater having an anionic hazardous substance is between 6 and 9.

In a preferred embodiment, the anion adsorption device has at least one special adsorbent material, and the special adsorbent material is activated carbon, activated aluminum, titanium oxide or amidoxime or iminodiacetic acid cationic chelate. Resin.

Other details, features, and advantages of the present invention will be apparent from the following description of the preferred embodiments.

Please refer to FIG. 1 , which is a schematic flow chart of a semiconductor sludge reduction method according to the present invention. As shown in FIG. 1 , the steps are as follows: (1) injecting a wastewater with an anionic hazardous substance into a mixed-precipitation tank, and then The coagulant 101 is placed in the chemical mixing tank with a lower than ideal value of 20%; (2) the pH value is adjusted in the chemical mixing tank to make a part of the anionic harmful substance in the wastewater and the The coagulant reacts to form a sludge precipitate 102; (3) an anionic hazardous substance that cannot react with the coagulant is discharged to the anion adsorption device with the waste water to adsorb the waste water by the anion adsorption device The remaining anionic harmful substances, and after the adsorption, waste water having only a trace amount of anionic harmful substances is discharged 103, and the discharged wastewater is in compliance with the discharge regulations.

Please refer to FIG. 2 , which is a schematic structural diagram of a semiconductor sludge reduction method according to the present invention. It can be seen from the figure that a wastewater having an anionic harmful substance (an anionic harmful substance is an arsenic ion or a fluorine ion) can be injected into the 202. In the chemical mixing tank 201, and at least one coagulant below 20% of the ideal value is added to the wastewater 203;

Then, sodium hydroxide (NaOH) is added to carry out the acid-base balance 204, so that the pH of the wastewater with an anionic harmful substance is between 6 and 9, so that some anionic harmful substances in the wastewater and the coagulant are The reaction is condensed into the sludge 205, and the precipitated sludge is discharged to the sludge dewatering machine 212 through the sludge discharge pipe 206 to perform mud-water separation. The separated water can be introduced into the wastewater tank or the chemical mixing sediment tank 201, and after dehydration The sludge is sent to the semiconductor sludge concentration zone 207;

In this process, some of the anionic harmful substances in the wastewater react with the coagulant to react some of the anionic harmful substances in the wastewater with the coagulant to condense into sludge and form a precipitate. After the sludge, the concentration of some anionic harmful substances in the wastewater can be reduced;

An anionic hazardous substance in the wastewater that is incapable of reacting with the coagulant is discharged through the waste water discharge pipe 208 to at least one anion adsorption device 209 having at least one special adsorbent material therein. Therefore, it is possible to adsorb the remaining anionic harmful substances in the wastewater; because different anion harmful substances are selected by different special adsorption materials, the special adsorption material can be activated carbon, activated aluminum, titanium oxide, or amidoxime. Or iminodiacetic acid cationic chelate resin;

By the anion adsorption device 209, the concentration of the anion harmful substance in the wastewater can be again reduced, and the concentration of the anion harmful substance in the wastewater can be again lowered again, so that the waste water discharge pipe 208 can Has a trace of anionic hazardous substances, and meets the prescribed wastewater discharge 210;

Since the anion adsorption material is adsorbed on the special adsorption material of the anion adsorption device 209, in order to enable the special adsorption material of the anion adsorption device 209 to be reused again, a regeneration liquid must be injected into the 211 (syrup injection) to clean the special adsorption. And washing the syrup of the special adsorbent material to carry a portion of the anion harmful substance adsorbed on the special adsorbent material of the anion adsorption device 209 to form a regenerated wastewater, and then regenerating the regenerated waste water containing an anionic hazardous substance In the set date, it is returned to the chemical mixing tank 201 in a divided manner. Since it is a fractional reflux method, the concentration of the anionic harmful substances in the chemical mixing tank is not greatly affected, and the semiconductor sludge reduction is performed again. deal with.

However, the reason why the framework of the present invention can achieve the purpose of reducing the amount of semiconductor sludge, the coagulant added for different anionic hazardous substances will be different, as follows: (1) When the anionic harmful substance is an arsenic ion, The coagulant comprises calcium chloride (CaCl ₂ ) or ferric chloride (FeCl ₃ ); the chemical formula is 2H ₃ AsO ₄ +3CaCl ₂ →Ca ₃ (AsO ₄ ) ₂ +6HCl or H ₃ AsO ₄ +FeCl ₃ →Fe AsO ₄ +3HCl, therefore, when adding less than ideal 20% of CaCl ₂ or FeCl ₃ , it will cause all added calcium chloride (CaCl ₂ ) or ferric chloride (FeCl ₃ ) to be combined with arsenic The ions react, so no residual calcium chloride (CaCl ₂ ) or ferric chloride (FeCl _{3 )} reacts with water (H ₂ O), so there is no calcium oxide (Ca(OH) ₂ ) or oxidation. The formation of iron (Fe(OH) ₃ ) sludge can achieve the purpose of reducing semiconductor sludge. In addition, although the sludge is reduced, the discharged wastewater is still higher than 0.5 ppm. Therefore, in the present invention, the wastewater which has not reached the standard in the mixing and sedimentation tank 201 is introduced into the anion adsorption device 209 for anion adsorption, and then discharged outside the plant. The discharged wastewater can reach an emission standard of less than 0.5 ppm. Therefore, with the arrangement of the present invention, the semiconductor sludge reduction can be achieved at the same time and the wastewater discharge standard can be achieved. (2) When the anion harmful substance is a fluorine-based ion, the added coagulant is CaCl ₂ or sodium aluminide, and if it is CaCl _{2 ,} the chemical formula is HF+CaCl ₂ →CaF ₂ +2HCl, therefore, in the wastewater In the fluoride ion, calcium chloride (CaCl ₂ ) is usually added to hydrofluoric acid (HF) for coagulation reaction to obtain calcium fluoride (CaF ₂ ) semiconductor sludge precipitation, so that the fluoride ion in the wastewater is lower than 15ppm to meet the wastewater discharge standards. In order to reduce the semiconductor sludge, the invention adds a calcium chloride (CaCl ₂ ) coagulant which is lower than the ideal value of 20%, so that all the added calcium chloride (CaCl ₂ ) can react with hydrofluoric acid (HF). There will be no residual calcium chloride (CaCl ₂ ) reacting with water (H ₂ O), therefore, calcium dioxide (Ca(OH) ₂ ) sludge will not be formed, which will result in the reduction of semiconductor sludge. However, although the sludge is reduced, the discharged wastewater is still higher than 15 ppm. Therefore, in the present invention, the wastewater which has not reached the standard in the mixing and sedimentation tank 201 is introduced into the anion adsorption device 209 for anion adsorption, and then discharged outside the plant. The discharged wastewater can reach the discharge standard of 15ppm or less. Therefore, with the arrangement of the present invention, the semiconductor sludge reduction can be achieved at the same time and the wastewater discharge standard can be achieved.

Referring to FIG. 3, the difference from FIG. 2 is that the chemical mixing tank 201 directly discharges the sludge to the sludge dewatering machine 212 for slurry separation, and then transfers the separated sludge to the semiconductor sludge concentration area. 207, and the separated water is sent to the anion adsorption device 209 via the waste water discharge pipe 208 for anion adsorption, and then anion regeneration is periodically performed by the regeneration liquid injection 211, and the regenerated anions are returned to the mixture within a set date. The rest of the mixing and sedimentation tank 201 is the same as that described in FIG. 2 and will not be described herein.

The semiconductor sludge reduction method provided by the present invention has the following advantages when compared with other conventional techniques: 1. The present invention can reuse fluorine-based wastewater or arsenic-based wastewater by using an anion adsorption device having a special adsorption material. The amount of anionic hazardous substances (arsenic-based ions or fluorine-based ions) is small, and as long as a coagulant of less than 20% of the desired value is added, the purpose of reducing the semiconductor sludge can be achieved. 2. Since the present invention can reduce the added coagulant, the amount of waste sludge generated is reduced, which makes it possible to reduce the cost and difficulty of wastewater treatment with anionic hazardous substances.

The present invention has been disclosed above by the above-described embodiments, and is not intended to limit the present invention. Any of those skilled in the art can understand the foregoing technical features and embodiments of the present invention without departing from the present invention. In the spirit and scope of the invention, the scope of the invention is to be determined by the scope of the appended claims.

201‧‧‧Chemical mixing tank

202‧‧‧ Wastewater injection

203‧‧‧acid-base balance

204‧‧‧Coagulant addition

205‧‧‧ sludge

206‧‧‧Sludge discharge pipe

207‧‧‧Semiconductor sludge concentration

208‧‧‧Waste discharge pipe

209‧‧‧Anion adsorption device

210‧‧‧Compliant with specified wastewater discharge

211‧‧‧Regenerant injection

212‧‧‧Sludge dewatering machine

[Fig. 1] is a schematic flow chart of a semiconductor sludge reduction method of the present invention. [Fig. 2] is a schematic view showing the structure of the semiconductor sludge reduction method of the present invention. [Fig. 3] Fig. 3 is a schematic view showing another structure of the semiconductor sludge reduction method of the present invention.

Claims (6)

A semiconductor sludge reduction method is characterized in that: a waste water having an anionic harmful substance is injected into a mixed sedimentation tank, and a coagulant lower than a theoretical value is placed in the chemical mixing sedimentation tank; Adjusting the pH value of the mixed-precipitation tank so that some of the anionic harmful substances in the wastewater react with the coagulant to form a sludge precipitate; and an anionic harmful substance that cannot react with the coagulant The waste water is discharged to an anion adsorption device to adsorb the remaining anionic harmful substances in the waste water, and after the adsorption, the waste water having only a trace amount of anionic harmful substances is discharged, so that the waste water reaches the discharge standard; The anion adsorption device is cleaned by a syrup to form a regenerated wastewater, the anion harmful substances adsorbed on the anion adsorption device are separated from the anion adsorption device, and the regenerated wastewater containing an anionic hazardous substance is recirculated in a set time. Into the chemical mixing tank. The semiconductor sludge reduction method according to claim 1, wherein the anionic harmful substance is an arsenic-based ion, and the coagulant is CaCl ₂ or FeCl ₃ . The method for reducing semiconductor sludge according to claim 1, wherein the anionic harmful substance is a fluorine-based ion, and the coagulant is CaCl ₂ . The semiconductor sludge reduction method according to claim 1, wherein the pH value is adjusted by adding NaOH to make the pH of the wastewater having an anionic harmful substance between 6 and 9. The semiconductor sludge reduction method according to claim 1, wherein the anion adsorption device has at least one special adsorption material, and the special adsorption material is activated carbon, activated aluminum, titanium oxide, or an amidoxime or an imino group. Diacetate cationic chelate resin. The semiconductor sludge reduction method according to claim 1, wherein the addition of a coagulant of less than 20% of the ideal value enables the semiconductor sludge to be reduced.