Method for treating and recycling waste hydrochloric acid in quartz industry
The waste hydrochloric acid produced in the production process of high-purity quartz sand is treated by combining graphite heat exchanger and falling film absorption tower, which realizes the recycling and reuse of waste hydrochloric acid, solves the problem of high cost of waste hydrochloric acid treatment in the production of high-purity quartz sand, and reduces resource and energy consumption.
Patent Information
- Application Number
- CN202510198492.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-22
- Publication Date
- 2025-07-18
AI Technical Summary
In the prior art, waste hydrochloric acid produced in the production process of high purity quartz sand has high cost of treatment and is difficult to effectively recycle and utilize, resulting in large resource and energy consumption and high processing costs.
The hydrogen chloride waste gas and waste hydrochloric acid are treated by combining a graphite heat exchanger and a falling membrane absorption tower. The hydrochloric acid is recovered by evaporation and filtration, and the residue is neutralized with lime to achieve the reuse of waste acid.
It effectively reduces the waste liquid treatment volume, improves the recovery rate of hydrochloric acid, reduces the energy consumption and resource consumption of treatment, and reduces the treatment cost.
Smart Images
Figure CN120328488A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of waste hydrochloric acid treatment, and particularly to a method for treating and recycling waste hydrochloric acid in the quartz industry. Background Art
[0002] The production process of high-purity quartz sand is prepared by chemical vapor deposition of silicon tetrachloride in a hydrogen atmosphere. A large amount of hydrogen chloride gas and silicon dioxide dust are emitted in the tail gas of hydrogen combustion. The spray waste liquid generated by water absorption treatment of acidic waste gas is waste hydrochloric acid with a concentration of about 10%. The concentration of this waste hydrochloric acid is relatively high, and the main impurity component therein is silicon dioxide particles. The neutralization treatment cost is very high, and high-salt wastewater is generated after neutralization, which is difficult to treat. If it can be purified, it will have great economic and environmental benefits.
[0003] Another kind of high-purity natural quartz sand needs to use a mixed acid of hydrochloric acid and hydrofluoric acid during production to dissolve and remove impurities such as iron and aluminum (mainly iron oxide) in the quartz sand under heating conditions to improve its purity. Especially for high-purity quartz sand used in fields such as photovoltaics, electronics, and glass manufacturing, there are strict restrictions on the iron content, and chemical treatment is required to reduce the impurity content. The quartz sand is immersed in a hydrochloric acid or mixed acid solution with a certain concentration, and the impurities are dissolved through pickling reaction. After pickling, a large amount of pure water is needed to wash the quartz sand to remove the residual acid and by-products generated by the reaction.
[0004] Hydrochloric acid is corrosive, and the waste liquid generated after using hydrochloric acid must be neutralized, usually with lime or alkaline substances, to meet the discharge standards required by environmental protection. Most of the current treatment methods are to use liquid alkali for neutralization treatment and then discharge it into the sewage pipe network, and lime neutralization method for treatment and then press the sludge for discharge. The above two methods require a large amount of energy and treatment resources, greatly increasing the treatment cost. Summary of the Invention
[0005] The object of the present invention is to propose a method for treating and recycling waste hydrochloric acid in the quartz industry in view of the problems existing in the background art.
[0006] The technical solution of the present invention: A method for treating and recycling waste hydrochloric acid in the quartz industry includes the following steps: Step 1: The hydrogen chloride waste gas generated during the production of high-purity quartz sand by chemical vapor deposition method is heat-exchanged through a graphite heat exchanger, and the heat exchange coolant in the graphite heat exchanger uses the waste hydrochloric acid generated during the production of high-purity natural quartz sand. Step 2: The heat-exchanged hydrogen chloride waste gas enters a secondary falling film absorption tower for treatment, and then the absorbed concentrated liquid flows back to the primary falling film absorption tower for secondary absorption, and the concentration of the obtained hydrochloric acid concentrated liquid can reach 15%.
[0007] Step 3: The waste hydrochloric acid preheated by the graphite heat exchanger is injected into the graphite evaporation kettle for heating and evaporation. The generated steam is combined with the hydrogen chloride waste gas in Step 1 and enters the secondary falling film evaporator and the primary falling film absorption tower for treatment to recover the waste acid. Step 4: The waste liquid remaining after evaporation is neutralized with lime and then discharged up to the standard. Step 5: The waste acid obtained in Step 2 contains particulate impurities such as SiO2. After being filtered by a ceramic membrane, it is used for cleaning and regeneration of weak alkaline resin in the chemical synthesis of quartz sand process. When necessary, it can be reused in each link of the high-purity sand production process after removing metal impurities such as iron by resin adsorption.
[0008] Preferably, the waste gas finally discharged from the secondary falling film absorption tower and the primary falling film absorption tower is further treated by an alkali liquor absorption tower and then discharged at high altitude.
[0009] Preferably, the temperature during the treatment in the primary falling film absorption tower is controlled between 30°C and 40°C.
[0010] Preferably, when filtering the hydrochloric acid concentrate generated in Step 2, a natural sedimentation + PP cotton / ceramic ultrafiltration membrane filtration process can be used to treat the particulate impurities in the waste acid.
[0011] Compared with the prior art, the present invention has the following beneficial technical effects: By evaporating the hydrochloric acid waste liquid generated during the production of high-purity quartz sand, the present invention effectively reduces the amount of waste liquid to be treated. At the same time, the evaporated HC1 gas is absorbed, concentrated and filtered, which can improve the recovery rate of hydrochloric acid, effectively reduce the treatment energy consumption and resource consumption of hydrochloric acid waste liquid, and greatly reduce the treatment cost. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 It is a schematic flow chart of a method for treating and recycling waste hydrochloric acid in the quartz industry according to the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0013] The following further describes the technical solutions of the present invention in conjunction with specific embodiments.
[0014] Embodiment A method for treating and recycling waste hydrochloric acid in the quartz industry proposed by the present invention includes the following steps: Step 1: The hydrogen chloride waste gas generated during the production of high-purity quartz sand is heat-exchanged by a graphite heat exchanger. The heat exchange coolant in the graphite heat exchanger uses the hydrochloric acid waste liquid generated during the pickling of high-purity natural quartz sand. On the one hand, it can cool down the hydrogen chloride waste gas to ensure the subsequent treatment effect. On the other hand, it can preheat the hydrochloric acid waste liquid, reduce the energy consumption of later heating, and improve the treatment efficiency. Step 2: The heat-exchanged hydrogen chloride waste gas enters the secondary falling film evaporator for treatment. Then, the concentrated liquid absorbed flows back to the primary falling film absorption tower for secondary treatment, and the concentration of the obtained hydrochloric acid concentrated liquid can reach 15%.
[0015] Step 3: The hydrochloric acid waste liquid preheated by the graphite heat exchanger is injected into the graphite evaporation kettle for heating and evaporation. The generated steam is combined with the hydrogen chloride waste gas in Step 1 and enters the secondary falling film evaporator and the primary falling film absorption tower for treatment together to recover the waste acid. When performing the above treatment, the temperature is controlled between 30°C and 40°C. The solubility of HCl is relatively high, the system equipment operates stably, it is not easy to have condensation and dew condensation problems, the mass transfer efficiency of the absorption process is relatively high, and it is easier to control the hydrochloric acid concentration range. Step 4: The waste liquid remaining after evaporation is neutralized with lime and then discharged. Step 5: The waste acid obtained in Step 2 contains particulate impurities such as SiO2. After being filtered by a ceramic membrane, it can be used. It is also possible to adopt the process of natural precipitation + PP cotton / ceramic ultrafiltration membrane to filter the particulate impurities in the waste acid. When necessary, it can be reused in the production of high-purity sand after removing metal impurities such as iron by resin adsorption to ensure the reuse effect of the recovery.
[0016] The waste gas finally discharged from the secondary falling film evaporator and the primary falling film absorption tower is further treated by an alkali liquid absorption tower and then discharged at a high altitude.
[0017] In this embodiment, the hydrogen chloride waste gas is cooled to below 50°C by the graphite heat exchanger, and the heat is carried away by the waste acid generated from high-purity sand. Then, it undergoes secondary falling film absorption to recover the effective components of the HCl waste gas. The concentration of the secondary falling film absorption liquid is about 5%, and it flows back to the primary falling film absorption tower, and the concentration can reach about 15%. The tail gas is treated by an alkali liquid absorption tower and discharged up to the standard at a high altitude. The waste acid preheated by the graphite heat exchanger is heated and evaporated by the graphite evaporation kettle, and the steam is treated together with the HCl waste gas to recover the waste acid. The residual waste liquid after evaporation is neutralized with lime and then discharged. The recovered waste acid contains particulate impurities such as SiO2. After being filtered by a ceramic membrane, if necessary, it is reused in the production of high-purity sand after removing metal impurities such as iron by resin adsorption.
[0018] The above specific embodiments are merely a preferred embodiment of the present invention. Based on the technical solution of the present invention and the relevant inspirations of the above embodiments, those skilled in the art can make various alternative improvements and combinations to the above specific embodiments.
Claims
1. A method for treating and recycling waste hydrochloric acid in the quartz industry, characterized in that, It includes the following steps: Step 1: The hydrogen chloride waste gas generated during the production of high-purity quartz sand is heat-exchanged through a graphite heat exchanger, and the heat exchange coolant in the graphite heat exchanger uses the hydrochloric acid waste liquid generated during the production of high-purity quartz sand; Step 2: The heat-exchanged hydrogen chloride waste gas enters a secondary falling-film evaporator for treatment, and then the absorbed concentrated liquid flows back to the primary falling-film absorption tower for secondary treatment, and the concentration of the obtained hydrochloric acid concentrated liquid can reach 31%; Step 3: The hydrochloric acid waste liquid preheated by the graphite heat exchanger is injected into a graphite evaporation kettle for heating and evaporation, and the generated steam is combined with the hydrogen chloride waste gas in Step 1 and enters the secondary falling-film evaporator and the primary falling-film absorption tower for treatment together to carry out waste acid recovery; Step 4: The waste liquid remaining after evaporation is neutralized with lime and then discharged; Step 5: The waste acid obtained in Step 2 contains particulate impurities such as SiO2, and after being filtered by a ceramic membrane, it is used. When necessary, it can be reused in the production of high-purity sand after removing metal impurities such as iron by resin adsorption; 2. A method for treating and recycling waste hydrochloric acid in the quartz industry according to claim 1, characterized in that: The waste gas finally discharged from the secondary falling-film evaporator and the primary falling-film absorption tower is treated by an alkali liquor absorption tower and then discharged into the air at a high altitude; 3. A method for treating and recycling waste hydrochloric acid in the quartz industry according to claim 1, characterized in that: The temperature during the treatment of the primary falling-film absorption tower is controlled between 30°C and 40°C; 4. A method for treating and recycling waste hydrochloric acid in the quartz industry according to claim 1, characterized in that: When filtering the hydrochloric acid concentrated liquid generated in Step 2, a natural sedimentation + PP cotton / ceramic ultrafiltration membrane filtration process can be used to treat the particulate impurities in the waste acid.