BOE waste liquid treatment device

Abstract

The BOE waste liquid treatment device comprises a replacement reaction kettle, an evaporator, a neutralization reaction kettle, a triple-effect evaporator and a centrifugal machine which are connected in sequence, the fractionating tower is connected with the upper part of the evaporator and is used for fractionating the mixed steam to obtain concentrated hydrofluoric acid and wastewater; and the filter press is positioned at the rear part of the neutralization reaction kettle. By adopting the device to treat the BOE waste liquid, the bottleneck of market capacity of ammonium bifluoride is avoided, hydrofluoric acid products and ammonium sulfate products with huge market capacity are produced, the value orientation of turning waste into wealth, circular economy and environmental protection is really realized, and the device is suitable for industrial popularization and application.

Description

Technical Field

[0001] This utility model relates to the field of waste liquid recycling technology, and more specifically, to a BOE waste liquid treatment device. Background Technology

[0002] BOE (Buffered Oxide Etch) is a buffered oxide etchant, often abbreviated as "buffered etchant." It is composed of hydrofluoric acid (HF) and ammonium fluoride (NH4F) mixed in varying proportions. Used for etching semiconductor components (such as chips), HF primarily acts as the etching reaction agent, while NH4F serves as a buffer. HF reacts with silicon, and NH4F fixes the hydrogen... + The concentration is adjusted to maintain a certain etching rate. After a certain period of use, the BOE etching solution is discharged as waste liquid, becoming BOE waste liquid.

[0003] BOE wastewater mainly consists of ammonium fluoride (NH4F) and ammonium hydrogen fluoride (NH4HF2), with a small amount of ammonium fluorosilicate. It is classified as hazardous waste, and most semiconductor factories entrust qualified hazardous waste disposal companies to treat it harmlessly. This involves adding lime or slaked lime to react and produce calcium fluoride and ammonia. Some disposal companies recover the ammonia, while the calcium fluoride becomes sludge, which is then disposed of in landfills. This disposal method is costly, highly polluting, and involves expensive sludge treatment. Crucially, resources are not effectively utilized, making it a counterproductive approach.

[0004] Another treatment method involves adding hydrofluoric acid to produce ammonium bifluoride. Since ordinary industrial-grade ammonium bifluoride is produced using various fluorine-containing waste acids or byproduct fluorine-containing acids, and the market capacity for ammonium bifluoride is limited, it is necessary to broaden the recycling routes for BOE waste liquid and its products.

[0005] Hydrogen fluoride (HF) has a molecular weight of 20.01 and is readily soluble in water and ethanol. Anhydrous hydrogen fluoride (AHF) is a colorless, transparent liquid under low temperature or pressure, with a boiling point of 19.4℃, a melting point of -83.37℃, and a density of 1.008 g / cm³. 3 (Water = 1). It readily volatilizes into a white fumes at room temperature and ambient temperature. It is chemically extremely reactive, reacting with alkalis, metals, oxides, and silicates. Hydrogen fluoride is the foundation of modern fluorine chemical industry and the most basic raw material for producing elemental fluorine, various fluorinated refrigerants, fluorine-containing new materials, inorganic fluoride salts, and various organic fluorides. Hydrogen fluoride and water can be mixed in any mass ratio to form hydrofluoric acid (HF).

[0006] Ammonium sulfate is an inorganic compound with the chemical formula (NH4)2SO4. It is a colorless crystal or white granule with no odor. It decomposes above 280℃. Its solubility in water is 70.6g at 0℃ and 103.8g at 100℃. It is insoluble in ethanol and acetone. A 0.1mol / L aqueous solution has a pH of 5.5, a relative density of 1.77, and a refractive index of 1.521. Ammonium sulfate is mainly used as a fertilizer and is suitable for various soils and crops. Ammonium sulfate has a huge market potential.

[0007] Therefore, it is necessary to develop a BOE waste liquid treatment device to enable the comprehensive recycling and utilization of BOE waste liquid resources. Utility Model Content

[0008] In response to the problems in related technologies, this utility model proposes a BOE waste liquid treatment device.

[0009] To solve the above-mentioned technical problems, this utility model is achieved through the following technical solution:

[0010] A BOE waste liquid treatment device includes: a displacement reactor, an evaporator, a neutralization reactor, a triple-effect evaporator, and a centrifuge connected in sequence.

[0011] The displacement reactor includes an inlet and a outlet. BOE waste liquid and concentrated sulfuric acid are added sequentially through the inlet. After thorough stirring and reaction, the resulting reaction solution is discharged through the outlet.

[0012] The evaporator is connected to the drain port to evaporate the reaction liquid, obtaining mixed vapor and evaporation residue;

[0013] The neutralization reactor is connected to the lower part of the evaporator;

[0014] The triple-effect evaporator is connected to the neutralization reaction vessel to perform at least one evaporation and crystallization on the supernatant to obtain an ammonium sulfate crystal solution.

[0015] The centrifuge is located at the rear of the triple-effect evaporator and centrifuges the ammonium sulfate crystallization solution to obtain ammonium sulfate product and centrifugal mother liquor;

[0016] Also includes:

[0017] A fractionation tower is connected to the upper part of the evaporator to fractionate the mixed steam to obtain concentrated hydrofluoric acid and wastewater.

[0018] A filter press, located at the rear of the neutralization reactor, dewaters the lower layer of sludge and sends it to the dryer, where it is dried to obtain calcium fluoride product.

[0019] In some embodiments, the dehydrated waste liquid obtained by the filter press is transported to the triple-effect evaporator for evaporation and crystallization.

[0020] In some embodiments, the centrifuged mother liquor obtained by the centrifuge is returned to the triple-effect evaporator for recrystallization.

[0021] In some embodiments, an ammonium sulfate temporary storage tank is provided between the neutralization reactor and the triple-effect evaporator, and the dehydrated waste liquid obtained by the filter press is transported to the ammonium sulfate temporary storage tank.

[0022] This utility model has the following beneficial effects:

[0023] This device has a compact structure, simple connection, small footprint, and is suitable for industrial applications.

[0024] By using this device to treat BOE waste liquid, the bottleneck of the ammonium bifluoride market capacity is avoided, and hydrofluoric acid and ammonium sulfate products with huge market capacity are produced. This truly realizes the value orientation of turning waste into treasure, circular economy, and green environmental protection, and is suitable for industrial promotion and application. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the utility model embodiments, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the BOE waste liquid treatment device according to Embodiment 1 of this utility model;

[0027] in,

[0028] 1-Displacement reaction vessel, 2-Evaporator, 3-Neutralization reaction vessel, 4-Triple-effect evaporator, 5-Centrifuge, 6-Fracturing tower, 7-Filter press, 8-Dryer, 21-Reaction liquid storage tank, 22-Ammonium sulfate storage tank. Detailed Implementation

[0029] The technical solutions in the embodiments of this utility model will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0030] Example 1

[0031] Reference Figure 1As shown, a BOE waste liquid treatment device includes: a displacement reactor 1, an evaporator 2, a neutralization reactor 3, a triple-effect evaporator 4, a centrifuge 5, a fractionation tower 6, a filter press 7, and a dryer 8 connected in sequence.

[0032] The reaction vessel 1 includes an inlet and a outlet. BOE waste liquid and concentrated sulfuric acid are added sequentially through the inlet, and the resulting reaction solution is discharged through the outlet after thorough stirring. Evaporator 2 is connected to the outlet and evaporates the reaction solution to obtain mixed steam and residual liquid. Neutralization vessel 3 is connected to the lower part of evaporator 2, receives the residual liquid, and after sequential addition of ammonia and fluorogypsum emulsion, settles to obtain a supernatant and a lower sludge layer. Triple-effect evaporator 4 is connected to neutralization vessel 3 and performs at least one evaporation crystallization on the supernatant to obtain an ammonium sulfate crystal solution. Centrifuge 5 is located at the rear of triple-effect evaporator 4 and centrifuges the ammonium sulfate crystal solution to obtain ammonium sulfate product and centrifugal mother liquor.

[0033] In this invention, the fractionation tower 6 is connected to the upper part of the evaporator 2 to fractionate the mixed steam to obtain concentrated hydrofluoric acid and wastewater. The filter press 7 is located at the rear of the neutralization reactor 3, which dewaters the lower layer of sludge and sends it to the dryer 8 for drying to obtain calcium fluoride product (fluorite balls).

[0034] In order to store the reaction liquid obtained from the displacement reactor, a reaction liquid storage tank 21 is provided at the front of the evaporator 2. The reaction liquid storage tank 21 can better realize the continuous production of the subsequent process.

[0035] It is worth noting that the wastewater obtained from the fractionation tower 6 in this invention is discharged after treatment, and the wastewater contains only trace amounts of HF.

[0036] In this invention, the dehydrated waste liquid obtained from the filter press 7 is transported to the triple-effect evaporator 4 for evaporation and crystallization. This operation enables more effective recovery of the waste liquid, especially the ammonium sulfate product in the waste liquid. Similarly, the centrifugal mother liquor obtained from the centrifuge 5 is returned to the triple-effect evaporator 4 for re-evaporation and crystallization.

[0037] To achieve better continuous production, an ammonium sulfate temporary storage tank 341 is provided between the neutralization reactor 3 and the triple-effect evaporator 4, and the dehydrated waste liquid obtained from the filter press 7 is transported to the ammonium sulfate temporary storage tank 22.

[0038] Application Example 2-4

[0039] The BOE waste liquid used in the following examples is the waste liquid after chip cleaning, and its composition is shown in Table 1. All other chemical reagents used are commercially available products, and the equipment used is the equipment in Example 1.

[0040] Table 1 Composition of BOE Waste Liquid

[0041] .

[0042] A method for treating BOE waste liquid includes the following steps:

[0043] Step 1, sulfuric acid replacement

[0044] 500 kg of BOE waste liquid was pumped into the displacement reactor. Under stirring conditions, a certain amount of 98% concentrated sulfuric acid was added to the BOE waste liquid. After the addition was completed, stirring was continued for 20 minutes. The resulting reaction solution was then discharged from the drain port and transferred to a reaction solution storage tank. Relevant data are shown in Table 2.

[0045] Table 2. Raw Material Dosage Quantity Table (Unit: Kg)

[0046] .

[0047] The second step is evaporation to remove fluoride.

[0048] The reaction solution was pumped into an evaporator and evaporated at atmospheric pressure at a temperature of 105-106°C. Most of the HF and water were evaporated, and the total content of ammonium sulfate and ammonium bisulfate in the evaporation residue was controlled to be 45%-55%. The evaporated mixed vapor and evaporation residue were transferred to subsequent processes. Relevant data are shown in Table 3.

[0049] Table 3. Quantity and Composition of Evaporation Residue

[0050] .

[0051] The third step is fractional distillation and concentration.

[0052] The mixed steam (evaporated HF and moisture) from step two is introduced into a fractionation tower for fractionation, with the reflux ratio controlled at ≥1.055. This yields acidic wastewater with an HF content ≤1% in the top condensate, while the bottom product is concentrated hydrofluoric acid with an HF content ≥20%. When the HF content is ≥20%, it meets the requirements for use in industries such as glass thinning. The acidic wastewater collected from the top of the tower is then sent to a wastewater treatment plant. Relevant data are shown in Table 4.

[0053] Table 4. Quantity and Composition of Concentrated Acid

[0054] .

[0055] Step 4: Neutralization and defluorination

[0056] The residual liquid from evaporation was pumped into a neutralization reactor. Under stirring, a certain amount of 20% ammonia water was added, and stirring continued for 20 minutes after the ammonia water addition was complete. Then, a certain amount of 20% fluorogypsum emulsion was slowly added, and stirring continued for 30 minutes after the emulsion addition was complete. Subsequently, polyaluminum sulfate (PAS) coagulant and PAM flocculant were added dropwise. The stirrer was stopped, and the mixture was allowed to settle naturally, yielding a supernatant and a lower sludge layer. The sludge was filtered to obtain sludge with a high calcium fluoride content, which, after pelletizing, can be used as an additive in steelmaking. Specific data are shown in Table 2.

[0057] Step 5: Evaporation and crystallization

[0058] The supernatant was pumped into a triple-effect evaporator for concentration, evaporation, and crystallization to obtain a crystallized slurry. This slurry was then separated by a centrifuge to obtain ammonium sulfate product and centrifugal mother liquor. The centrifugal mother liquor was returned to the triple-effect evaporator for further concentration, evaporation, and crystallization. The evaporated gas was condensed to obtain ammonia nitrogen wastewater, which was sent to a wastewater treatment plant. Specific data are shown in Tables 5 and 6.

[0059] Table 5. Quantity and Composition of Ammonium Sulfate Products

[0060] .

[0061] Table 6. Quantity and Composition of Ammonia Nitrogen Wastewater

[0062] .

[0063] Step 6: Drying to produce fluorite

[0064] The lower layer of sludge from step four is pumped into a filter press for filtration to obtain calcium fluoride sludge and mother liquor. The mother liquor is recovered and concentrated in a triple-effect evaporator in step five for evaporation and crystallization. The calcium fluoride sludge is then dried to obtain calcium fluoride product (fluorite balls). Specific data are shown in Table 7.

[0065] Table 7. Quantity and Composition of Spherical Calcium Fluoride

[0066] .

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. A BOE waste liquid treatment device, characterized in that, include: The displacement reactor, evaporator, neutralization reactor, triple-effect evaporator, and centrifuge are connected in sequence. The displacement reactor includes an inlet and a outlet. BOE waste liquid and concentrated sulfuric acid are added sequentially through the inlet. After thorough stirring and reaction, the resulting reaction solution is discharged through the outlet. The evaporator is connected to the drain port to evaporate the reaction liquid, obtaining mixed vapor and evaporation residue; The neutralization reactor is connected to the lower part of the evaporator; The triple-effect evaporator is connected to the neutralization reaction vessel to perform at least one evaporation and crystallization on the supernatant to obtain an ammonium sulfate crystal solution. The centrifuge is located at the rear of the triple-effect evaporator and centrifuges the ammonium sulfate crystallization solution to obtain ammonium sulfate product and centrifugal mother liquor; Also includes: A fractionation tower is connected to the upper part of the evaporator to fractionate the mixed steam to obtain concentrated hydrofluoric acid and wastewater. A filter press, located at the rear of the neutralization reactor, dewaters the lower layer of sludge and sends it to a dryer, where it is dried to obtain calcium fluoride.

2. The BOE waste liquid treatment device according to claim 1, characterized in that, The dehydrated waste liquid obtained from the filter press is transported to the triple-effect evaporator for evaporation and crystallization.

3. The BOE waste liquid treatment device according to claim 1, characterized in that, The centrifuged mother liquor obtained by the centrifuge is returned to the triple-effect evaporator for re-evaporation and crystallization.

4. The BOE waste liquid treatment device according to claim 1, characterized in that, An ammonium sulfate temporary storage tank is provided between the neutralization reactor and the triple-effect evaporator, and the dehydrated waste liquid obtained by the filter press is transported to the ammonium sulfate temporary storage tank.

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