Patent Application
20120171101
1. Field of the Invention
The present invention relates to a recycling and treatment method of waste liquid in cutting mono silicon and the device thereto.
2. Description of Related Art
With increasing energy shortage and pollution aggravation, various countries pay much attention to the clean energy, driving the booming research and development of solar battery in the world; and extensive utilization of solar battery has contributed to rapid growth of mono silicon as a main material of solar battery. Mono silicon wafer for solar battery is produced by cutting and processing mono silicon sticks. Numerous waste liquid is generated since cutting fluid with cooling effect must be used in the cutting process. At present, the cutting waste fluid commonly used is a mixture containing: polyethylene glycol, silicon carbide, triethavolamine, saponified fluid and kerosene, with its COD value obviously exceeding wastewater discharge standard. So, discharge of such waste fluid is strictly prohibited as per environmental protection requirements. Yet, there is not an appropriate method of waste liquid recycling and treatment; the domestic producers have to pile up a great deal of waste liquid, resulting in a serious problem for themselves. Therefore, there is an urgent demand to seek for a simple and effective method of recycling and treatment of mono silicon's cutting waste liquid, so as to recover polyethylene glycol, silicon carbide and silicon. The recycling and treatment of waste liquid not only solves environmental problems, but also has significant economic benefits.
The present invention provides a recycling and treatment method of waste liquid in cutting mono silicon, with the flow process shown in
1. Put mono silicon's cutting waste liquid without kerosene into a spray stirrer, and add diluted hydrochloric acid with a concentration of 0.0001.-0.4 mol by a ratio of 1 kg waste liquid to 100-500 ml hydrochloric acid solution; then stir circularly 10-30 min to obtain the preliminary mixture, discharge into a spray mixer, then mix circularly 10-30 min with temperature rise to 30-50° C., and finally obtain the secondary mixture and discharge it;
The producer has recovered the waste liquid stored in barrel by means of decantation, so the kerosene contained in waste liquid is basically removed.
Mono silicon's cutting waste liquid is a kind of highly viscous material containing solid particles, making it difficult for flow, transportation and processing. In this invention, the waste liquid is processed by diluted hydrochloric acid, and alkaline substances contained in the waste liquid, such as triethavolamine and saponified fluid, are removed by salt generated from neutralization, so as to obviously decrease viscosity of the waste liquid. Then, through circulatory spraying stirring and mixing in the spray stirrer and mixer, the waste liquid is turned into a kind of homogeneous mixture for easy flow, transportation and processing.
The spray stirrer enables stirring and reaction of acid and viscous liquid by circulatory spraying and stirring. The mixture is sprayed from the first spray channel in the spray stirrer, and mixed in a bigger cycle; then, as a negative pressure is formed in the nozzle chamber, the mixture is fed into the nozzle chamber through a liquid flow hole and then mixed in a smaller cycle, thus increasing greatly the stirring and reaction effect.
The spray mixer is structured in a way that a spray channel and deflector are set in the sprayer, and a turbulence channel set in the spray channel, with Reynolds number Re (ratio of inertia force to internal friction) of liquid flow over 3000. Due to the turbulent flow of liquids, molecular impact and friction of mixture in the turbulence channel could further mix the mixture and make the particles finer. With the setting of a deflector, the mixture flows in a smaller range, bringing about better mixing and reaction effect.
2. Secondary mixture discharged from spray mixer is fed into a solid-liquid separator, and heated by an electric heating plate of 50-80□, so as to evaporate the water vapor and Polyethylene glycol. Then, mixed solution of water and Polyethylene glycol is obtained by cooing in the first condenser. Next, the mixed solution is fed into the spray dehydrator, circularly sprayed and dehydrated for 15-40 min at 40-80□. Polyethylene glycol can be recovered by discharging water vapor from the spray dehydrator. Coarse solid mixture of silicon carbide and silicon is discharged from the bottom of solid-liquid separator;
Operating principle of spray dehydrator: the liquid flow of water and polyethylene glycol flows turbulently in the turbulence channel; molecular impact and friction in the turbulence channel makes the molecular particle of water and polyethylene glycol finer; while temperature rises gradually in the circulatory spraying and mixing process, water molecule of lower boiling point is vaporized to realize dehydration of polyethylene glycol.
3. Coarse solid mixture of silicon carbide and silicon is fed into the first spray cleaner, then circularly sprayed and cleaned for 10-30 min by adding water equivalent to 10-20% of coarse solid mixture; after the temperature rises to 40-80□, the cleaned mixture is put into the first shaking table to separate and remove “shell residues” of smaller specific weight, thus obtaining the preliminary solid mixture of silicon carbide and silicon. Then, the solid mixture is fed into the second spray cleaner for the same circulatory spraying and cleaning process, and next put into the second shaking table to separate and remove again the “shell residues”, thus obtaining the secondary solid mixture of silicon carbide and silicon;
Neutralized salt and other impurities contained in coarse solid mixture of silicon carbide and silicon are covered closely onto the powders of silicon carbide and silicon in “shell” form, making it difficult for removal. Through secondary water cleaning by the spray cleaner and repetitive circulatory stirring and cleaning, molecular impact and friction between materials and water occurs, so that the particle is refined and the “shell” is fractured and broken off. Then, the silicon carbide and silicon are separated with the “shell residues” by the shaking table due to different specific gravity, and next the separated shell residues are recovered as fertilizer.
4. Secondary solid mixture of silicon carbide and silicon is fed into a reactor to separate and recover silicon carbide and silicon via reactive generation of fluosilicic acid. The mixed acid solution of 5% HNO3 and 30% HF, with a volume ratio of HNO3:HF:=1:5, is added into solid mixture of silicon carbide and silicon by a ratio of 1-1.5 kg mixed acid solution to 1 kg solid mixture. Through 10-30 min circulatory spraying and stirring, the fluosilicic acid solution is vaporized when temperature rises to the counterflow temperature, and then cooled by the second condenser to recover the transparent fluosilicic acid solution. After being dried up by normal procedures, fluosilicic acid solution is processed into mono silicon for silicon recovery. Residual silicon carbide and acid solution in the reactor is filtered and flushed with 5-10 wt % alkali solution and water until pH reaches 7-7.5, and then dried up to recover silicon carbide. Said alkali solution can be prepared by NaOH, KOH or Na3C03.
The device of the present invention used for the recycling and treatment method of mono silicon's cutting waste liquid, comprising: a spray stirrer 49, with its structure shown in
A spray mixer 50, connected with the spray stirrer via the first discharge pipe 64 of the spray stirrer 49. Referring to
A solid-liquid separator 30, referring to
A spray dehydrator 51 (see
The spray dehydrator 51 structurally comprises: a mixing kettle 3′, feed tank 6′, sprayer 5′, diaphragm pump 1′, resistance thermometer sensor 2′, tee valve 7′, discharge pipe 4′ and drain pipe 21. The feed pipe 9′ at lower part of said feed tank 6′ is mounted onto the upper cover of the mixing kettle 3′, and also extended into the mixing kettle 3′. A drain pipe 21 is set on the upper cover of the mixing kettle 3′. Said sprayer 5′ consists of a spray channel 19′ and deflector 15′. The spray channel 19′ consists of interconnected nozzle inlet 10′, turbulence channel 11′, mixing chamber 12′ and nozzle exit 13′. The nozzle inlet 10′ is of a funnel shape, and the turbulence channel 11′ has a diameter of 1.2-3 mm; a liquid flow hole 14′ is set separately onto both sides of the wall of the mixing chamber 12′. The deflector 15′ is vertically arranged on the spray channel 19′, and located between the liquid flow hole 14′ and nozzle exit 13′; small holes 16′ of 1-3 mm are distributed onto the deflector 15′, with the aperture ratio of the deflector 15′ up to 60-80%. Said diaphragm pump 1 is arranged on the connecting pipe 8′ between the tee valve 7′ and discharge hole 18′ at bottom of the mixing kettle 3′, while the discharge pipe 4′ is connected with the tee valve 7′. And, said resistance thermometer sensor 2′ is located fixedly into the mixing kettle 3′, and connected with the temperature indicator 17′ by wiring the upper cover of the mixing kettle 3′.
A first spray cleaner, connected with the solid outlet 37 of the solid-liquid separator 30. The first spray cleaner is structured in the same way with the spray mixer 50, namely, the first spray cleaner is connected with the first shaking table, the second spray cleaner and the second shaking table; of which the second spray cleaner is structured in the same way with the first spray cleaner, and also connected with a reactor 52.
A reactor 52 (see
The reactor 52 structurally comprises: a second mixing kettle 65′, second feed tank 63′, second spray channel 66′, second diaphragm pump 61′, second tee valve 62′, second discharge pipe 64′ and steamed liquid pipe 22. The second feed pipe 69′ at lower part of said second feed tank 63′ is mounted onto the upper cover of the second mixing kettle 65′, and also extended into the second mixing kettle 65′. A steamed liquid pipe 22 is also set on the upper cover of the second mixing kettle 65′. Said second spray channel 66′ consists of interconnected second nozzle 70′, second nozzle chamber 72′ and second nozzle exit 73′. A liquid flow orifice 71′ is set separately onto both sides of the wall of the nozzle chamber 72′, while the second nozzle has a diameter of 3-4 mm. Said second diaphragm pump 61′ is arranged on the second connecting pipe 68′ between the second tee valve 62′ and second discharge hole 67′ at bottom of the second mixing kettle 65′, while the second discharge pipe 64′ is connected with the second tee valve 62′.
Through actual implementation and operation, the present invention's recycling and treatment method of mono silicon's cutting waste liquid is characterized by that: simplicity, ease of operation, low cost and high recycling rate, with the overall yield of cutting waste liquid up to 26-46%, of which polyethylene glycol accounts for 20-30%, silicon carbide 5-15% and silicon 1-2%. Moreover, the quality of recycled products can reach or approach the standard indexes, so they can be directly used in solar battery production or other industrial applications. Thus, the promising method of the present invention presents remarkable economic benefits, and also contributes much to environmental protection.
Referring to
The preliminary mixture is fed into the mixing kettle 3 of the spray mixer 50 through the feed tank 6 and its feed pipe 9; the tee valve 7 and nozzle inlet 10 are opened, while the channel to the discharge pipe 4 is closed, then the diaphragm pump 1 is started; the mixture is discharged from the discharge hole 18 at bottom of the mixing kettle 3, then fed into the nozzle inlet 10 of the sprayer 5 and also into the turbulence channel 11 through the diaphragm pump 1, pipeline 8 and tee valve 7 (when the pump flow is 3 m3/h, the diameter of turbulence channel is 2.4 mm, when the mixture's dynamic viscosity is 33.2 Pa·S. Reynolds number=8326), with the mixture in a turbulence state. Due to the molecular impact and friction of mixture in the turbulence channel 11, the mixture is further mixed to make the particles finer, then tiny and uniform liquid is sprayed from the turbulence channel 11 to the mixing chamber 12, and ejected from the nozzle exit 13; some mixture passes reversely the small hole 16 on the deflector 15 until reaching out of the mixing chamber 12, such that a pressure difference is generated within and outside the wall of the mixing chamber 12; the mixture passes the liquid flow hole 14 to form a turbulent flow in a small range, creating better stirring and reaction effect. Thus, the mixture passes through the discharge hole 18 at bottom of the mixing kettle 3, the diaphragm pump 1 and sprayer 5 to form a circulation loop, enabling 25 min circulatory stirring and mixing with temperature rise to 35□ (the temperature is shown on the temperature indicator 17 after measurement by the resistance thermometer sensor 2). The channel to tee valve 7 and nozzle inlet 10 is closed, whilst the channel to the discharge pipe 4 is opened so as to discharge the secondary mixture from the discharge pipe 4; the viscosity of the sprayed secondary mixture will drop markedly, turning itself into easy-to-flow uniform mixture.
The secondary mixture from the spray mixer is fed into the solid-liquid separator 30 (shown in
The mixed solution of water and polyethylene glycol flows into the spray dehydrator 51. Referring to
The coarse solid mixture of silicon carbide and silicon discharged from the solid outlet 37 of the solid-liquid separator 30 is fed into the first spray cleaner, which has the same structure with the spray mixer 50; so the coarse solid mixture of silicon carbide and silicon is also fed into the mixing kettle 3 through the feed tank and its feed pipe, and water up to 15% of the coarse solid mixture is added. Next, the diaphragm pump is started for circulatory spraying cleaning in the same way as in the spray mixer 50, and the mixture is under turbulence state in the turbulence channel; when the circulating flow of the diaphragm pump is 2.1 m3/h, the diameter of the turbulence channel is 2.6 mm; when the dynamic viscosity of the mixture of solid mixture and water is 13.5 Pa·S, Reynolds number=3979. The circulatory spraying cleaning time is 30 min, and temperature rises to 70□, then the cleaned mixture is put into the first shaking table (model: HWY-211, supplied by Shanghai Huayan Instruments Co., Ltd), so as to separate and remove “shell residues” of smaller specific weight; water is discharged from the groove set on the shaking table to obtain the preliminary solid mixture of silicon carbide and silicon, and then fed into the second spray cleaner, which has the same structure with the first spray cleaner, enabling a circulatory spraying cleaning of solid mixture; when the circulating flow of the diaphragm pump is 3 m3/h, the diameter of the turbulence channel is 2.1 mm; when the dynamic viscosity of the mixture is 16.8 Pa·S, Reynolds number=8670. The cleaned mixture is put into the second shaking table (model: 350R, provided by Shanghai Huayan Instruments Co., Ltd), so as to separate and remove “shell residues” and water, and obtain the secondary solid mixture of silicon carbide and silicon. The separated “shell residues” are possibly recovered as fertilizer.
The secondary solid mixture of silicon carbide and silicon is fed into the reactor 52; referring to
50 kg mono silicon's cutting waste liquid without kerosene and 15 liter 0.001 mol diluted hydrochloric acid are fed into the first mixing kettle 65 of the spray stirrer 49 for 20 min circulatory spraying stirring and reaction. Then, the preliminary mixture is obtained and fed into the spray mixer 50 for 20 min circulatory spraying mixing and reaction, with the temperature rise to 50□; the mixture is under turbulence state in the turbulence channel 11; when the pump flow is 3 m3/h, the diameter of turbulence channel is 1.5 mm; when the dynamic viscosity of the mixture is 40.6 Pa·S, Reynolds number=9845. The secondary mixture from the spray mixer is fed into the solid-liquid separator 30, heated up by two electric heating plates at 60□, so water vapor and polyethylene glycol are evaporated, then condensed to obtain the mixed solution of water and polyethylene glycol. The coarse solid mixture of silicon carbide and silicon is discharged from the solid outlet 37 at bottom of the solid-liquid separator 30. The mixed solution of water and polyethylene glycol is fed into the spray dehydrator 51 for 15 min circulatory spraying dehydration, with temperature rise to 40□, and the liquid flow is under turbulence state in the turbulence channel 11′; when the circulating flow is 2.5 m3/h, the diameter of the turbulence channel is 2.5 mm; when the dynamic viscosity of the mixed solution of water and polyethylene glycol is 14 Pa·S, Reynolds number=5139. After dehydration, 11.9 kg transparent polyethylene glycol is obtained, with the recycling rate based on cutting waste liquid up to 23.8%. The coarse solid mixture of silicon carbide and silicon is fed into the first spray cleaner, then water equivalent to 10% of coarse solid mixture is added for circulatory spraying cleaning, and the liquid flow is under turbulence state in the turbulence channel; when the circulating flow is 2.1 m3/h, the diameter of the turbulence channel is 2.5 mm; when the dynamic viscosity of the mixture of solid mixture and water is 10.2 Pa·S, Reynolds number=5925. The circulatory mixing cleaning time is 10 min, and temperature rises to 80□. After the cleaned mixture is fed into the first shaking table for separation, the preliminary solid mixture is fed into the second spray cleaner for the same circulatory spraying cleaning; when the circulating flow is 3 m3/h, the diameter of the turbulence channel is 1.8 mm; when the dynamic viscosity of the mixture is 20.6 Pa·S, Reynolds number=11229. The cleaned mixture is put into the second shaking table for separation, thus obtaining secondary solid mixture of silicon carbide and silicon. Next, the secondary solid mixture of silicon carbide and silicon is put into the reactor 52, and the mixed acid solution of HN03 and HF equivalent to 1.2 times of solid mixture is added for 10 min circulatory spraying stirring, thus recovering 0.8 kg silicon from fluosilicic acid solution, with the recycling rate based on cutting waste liquid up to 1.6%. The residue in the reactor is filtered, then flushed with 5 wt % KOH solution and water until pH is 7.2, so 5.1 kg grayish green silicon carbide powder is obtained, with the recycling rate based on 50 kg cutting waste liquid up to 10.2%; the other procedures in this preferred embodiment are the same with those in the preferred embodiment 1.
50 kg mono silicon's cutting waste liquid without kerosene and 25 liter 0.0001 mol diluted hydrochloric acid are fed into the first mixing kettle 65 of the spray stirrer 49 for 30 min circulatory spraying stirring and reaction. Then, the preliminary mixture is obtained and fed into the spray mixer 50 for 10 min circulatory spraying mixing and reaction, with the temperature rise to 40□; the mixture is under turbulence state in the turbulence channel 11; when the pump flow is 3 m3/h, the diameter of turbulence channel is 2.5 mm; when the dynamic viscosity of the mixture is 28.4 Pa·S, Reynolds number=3040. The secondary mixture from the spray mixer is fed into the solid-liquid separator 30, heated up by two electric heating plates at 80□, so water vapor and polyethylene glycol are evaporated, then condensed to obtain the mixed solution of water and polyethylene glycol. The coarse solid mixture of silicon carbide and silicon is discharged from the solid outlet 37 at bottom of the solid-liquid separator 30. The mixed solution of water and polyethylene glycol is fed into the spray dehydrator 51 for 40 min circulatory spraying dehydration, with temperature rise to 80□, and the liquid flow is under turbulence state in the turbulence channel 11′; when the circulating flow is 2.5 m3/h, the diameter of the turbulence channel is 1.8 mm; when the dynamic viscosity of the mixed solution of water and polyethylene glycol is 21.4 Pa·S, Reynolds number=9007. After dehydration, 10.2 kg transparent polyethylene glycol is obtained, with the recycling rate based on cutting waste liquid up to 20.4%. The coarse solid mixture of silicon carbide and silicon is fed into the first spray cleaner, then water equivalent to 15% of coarse solid mixture is added for circulatory spraying cleaning, and the liquid flow is under turbulence state in the turbulence channel; when the circulating flow is 2.1 m3/h, the diameter of the turbulence channel is 3.0 mm; when the dynamic viscosity of the mixture of solid mixture and water is 9.6 Pa·S, Reynolds number=3643. The circulatory mixing cleaning time is 30 min, and temperature rises to 70□. After the cleaned mixture is fed into the first shaking table for separation, the preliminary solid mixture is fed into the second spray cleaner for the same circulatory spraying cleaning; when the circulating flow is 3 m3/h, the diameter of the turbulence channel is 2.4 mm; when the dynamic viscosity of the mixture is 14.0 Pa·S, Reynolds number=6970. The cleaned mixture is put into the second shaking table for separation, thus obtaining secondary solid mixture of silicon carbide and silicon. Next, the secondary solid mixture of silicon carbide and silicon is put into the reactor 52, and the mixed acid solution of HN03 and HF equivalent to 1.5 times of solid mixture is added for 20 min circulatory spraying stirring, thus recovering 1 kg silicon from the fluosilicic acid solution, with the recycling rate based on cutting waste liquid up to 2%. The residue in the reactor 52 is filtered, then flushed with 10 wt % Na0H solution and water until pH is 7.3, so 2.9 kg grayish green silicon carbide powder is obtained, with the recycling rate based on 50 kg cutting waste liquid up to 5.8%; the other procedures in this preferred embodiment are the same with those in the preferred embodiment 1.
50 kg mono silicon's cutting waste liquid without kerosene and 7.5 liter 0.2 mol diluted hydrochloric acid are fed into the first mixing kettle 65 of the spray stirrer 49 for 15 min circulatory spraying stirring and reaction. Then, the preliminary mixture is obtained and fed into the spray mixer 50 for 20 min circulatory spraying mixing and reaction, with the temperature rise to 30□; the mixture is under turbulence state in the turbulence channel 11; when the pump flow is 3 m3/h, the diameter of turbulence channel is 2.0 mm; when the dynamic viscosity of the mixture is 35.6 Pa·S, Reynolds number=4736. The secondary mixture from the spray mixer is fed into the solid-liquid separator 30, heated up by two electric heating plates at 50□, so water vapor and polyethylene glycol are evaporated, then condensed to obtain the mixed solution of water and polyethylene glycol. The coarse solid mixture of silicon carbide and silicon is discharged from the solid outlet 37 at bottom of the solid-liquid separator 30. The mixed solution of water and polyethylene glycol is fed into the spray dehydrator 51 for 15 min circulatory spraying dehydration, with temperature rise to 50□, and the liquid flow is under turbulence state in the turbulence channel 11′; when the circulating flow is 2.5 m3/h, the diameter of the turbulence channel is 3.0 mm; when the dynamic viscosity of the mixed solution of water and polyethylene glycol is 11.5 Pa·S, Reynolds number=3620. After dehydration, 13.7 kg transparent polyethylene glycol is obtained, with the recycling rate based on cutting waste liquid up to 27.4%. The coarse solid mixture of silicon carbide and silicon is fed into the first spray cleaner, then water equivalent to 20% of coarse solid mixture is added for circulatory spraying cleaning, and the liquid flow is under turbulence state in the turbulence channel; when the circulating flow is 2.1 m3/h, the diameter of the turbulence channel is 2.7 mm; when the dynamic viscosity of the mixture of solid mixture and water is 11.2 Pa·S, Reynolds number=4283, The circulatory mixing cleaning time is 20 min, and temperature rises to 50□. After the cleaned mixture is fed into the first shaking table for separation, the preliminary solid mixture is fed into the second spray cleaner for the same circulatory spraying cleaning; when the circulating flow is 3 m3/h, the diameter of the turbulence channel is 3.0 mm; when the dynamic viscosity of the mixture is 16.8 Pa·S, Reynolds number=4626. The cleaned mixture is put into the second shaking table for separation, thus obtaining secondary solid mixture of silicon carbide and silicon. Next, the secondary solid mixture of silicon carbide and silicon is put into the reactor 52, and the mixed acid solution of HN03 and HF equivalent to 1.1 times of solid mixture is added for 30 min circulatory spraying stirring, thus recovering 0.5 kg silicon from the fluosilicic acid solution, with the recycling rate based on cutting waste liquid up to 1%. The residue in the reactor 52 is filtered, then flushed with 7 wt % KOH solution until pH is 7, so 6.3 kg grayish green silicon carbide powder is obtained, with the recycling rate based on 50 kg cutting waste liquid up to 12.6%; the other procedures in this preferred embodiment are the same with those in the preferred embodiment 1.
