Abstract:
A recycling and treatment method of mono silicon&#39;s cutting waste liquid, which includes the following steps: 1. treat the waste liquid with diluted hydrochloric acid, then stir into an easy-to-flow mixture; 2. heat up the mixture for solid-liquid separation, such that water and polyethylene glycol are evaporated, condensed and dehydrated to recover the polyethylene glycol, and obtain coarse solid mixture of silicon carbide and silicon; 3. obtain the secondary solid mixture of silicon carbide and silicon by secondary cleaning of the coarse solid mixture with water; 4. recycle silicon and silicon carbide by treatment with the mixed acid solution of HN0 3 +HF. This method features simplicity, ease of operation, low cost and high recycling rate, with the overall yield of cutting waste liquid up to 26-46%; moreover, the quality of recycled products can reach or approach the standard indexes, so they can be directly used in solar battery production.

Description:
BACKGROUND OF INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a recycling and treatment method of waste liquid in cutting mono silicon and the device thereto. 
         [0003]    2. Description of Related Art 
         [0004]    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&#39;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. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides a recycling and treatment method of waste liquid in cutting mono silicon, with the flow process shown in  FIG. 1 . This method includes the following steps: 
         [0006]    1. Put mono silicon&#39;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; 
         [0007]    The producer has recovered the waste liquid stored in barrel by means of decantation, so the kerosene contained in waste liquid is basically removed. 
         [0008]    Mono silicon&#39;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. 
         [0009]    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. 
         [0010]    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. 
         [0011]    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; 
         [0000]    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. 
         [0012]    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; 
         [0013]    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. 
         [0014]    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% HNO 3  and 30% HF, with a volume ratio of HNO 3 :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 Na 3 C0 3 . 
         [0015]    The device of the present invention used for the recycling and treatment method of mono silicon&#39;s cutting waste liquid, comprising: a spray stirrer  49 , with its structure shown in  FIGS. 2 and 3 , mainly consisting of: first mixing kettle  65 , first feed tank  63 , first spray channel  66 , first diaphragm pump  61 , first tee valve  62  and first discharge pipe  64 . A first feed pipe  69  at lower part of said first feed tank  63  is mounted onto the upper cover of the first mixing kettle  65 , and also extended into the first mixing kettle  65 . Said first spray channel  66  consists of interconnected nozzle  70 , nozzle chamber  72  and first nozzle exit  73 ; a liquid flow orifice  71  is set separately onto both sides of the wall of nozzle chamber  72 , with the diameter of nozzle about 3-4 mm. Said first diaphragm pump  61  is arranged on the first connecting pipe  68  between the first tee valve  62  and the first discharge hole  67  at bottom of the first mixing kettle  65 , while the first discharge pipe  64  is connected with the first tee valve  62 . 
         [0016]    A spray mixer  50 , connected with the spray stirrer via the first discharge pipe  64  of the spray stirrer  49 . Referring to  FIGS. 4-6 , the structure of the spray mixer  50  (an application of the utility model has claimed, with the application No.: 200620039272.3) mainly consists of: a mixing kettle  3 , feed tank  6 , sprayer  5 , diaphragm pump  1 , resistance thermometer sensor  2 , tee valve  7  and discharge pipe  4 . 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 . 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 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 . 
         [0017]    A solid-liquid separator  30 , referring to  FIGS. 7-8 , mainly consists of: a sprinkler head  31 , steam pipe  33 , tapered plate  42 , funneled plate  41  and solid outlet  37 . The discharge pipe  4  of the spray mixer is connected with the sprinkler head  31  set at the center of top cover of the solid-liquid separator  30 ; in the solid-liquid separator  30 , two electric heating plates are fastened symmetrically onto the outer wall  36 ; every electric heating plate is structured in a way that: a tapered plate  42  is located at the upper part, and a funneled plate  41  and hole  40  located at lower part; the diameter of the funneled plate  41  is bigger than that of the tapered plate  42 . The tapered plate  42  is fastened onto three locating pins  32  arranged in 120°, all of which are fixed onto the outer wall  36 . The funneled plate  41  is fastened onto the tray  35 , which is fixed onto the outer wall  36  via fix screw  34 . A steam pipe  33  is set on the top cover, and a solid outlet  37  at the bottom; a baffle plate  39  is set on the periphery of the solid outlet  37 , and a liquid outlet  38  also set at the bottom. 
         [0018]    A spray dehydrator  51  (see  FIG. 9 ; for the sprayer  5 ′ in  FIG. 9 , see also  FIGS. 5-6 ), which is structured almost the same way with the spray mixer  50 ; but a drain pipe  21  is set on its top cover; in this device, the solid-liquid separator  30  is connected with the spray dehydrator  51  via the first condenser. 
         [0019]    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 ′. 
         [0020]    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 . 
         [0021]    A reactor  52  (see  FIG. 10 ; for the enlarged view of spray channel  66 ′ in  FIG. 10 , see  FIG. 3 ) is structured almost the same way with the spray stirrer  49 , but a steamed liquid pipe  22  is set on its top cover; in this device, the steamed liquid pipe  22  is connected with the second condenser. 
         [0022]    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 ′. 
         [0023]    Through actual implementation and operation, the present invention&#39;s recycling and treatment method of mono silicon&#39;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. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1 : a flow process chart of the recycling and treatment method of mono silicon&#39;s cutting waste liquid of the present invention, 
           [0025]      FIG. 2 : a structure diagram of spray stirrer of the present invention. 
           [0026]      FIG. 3 : an enlarged view of position A in  FIG. 2 . 
           [0027]      FIG. 4 : a structure diagram of spray mixer of the present invention. 
           [0028]      FIG. 5 : a longitudinal sectional view of sprayer in  FIG. 4 . 
           [0029]      FIG. 6 : a left-side view of deflector in  FIG. 5 . 
           [0030]      FIG. 7 : a structure diagram of solid-liquid separator of the present invention. 
           [0031]      FIG. 8 : a top view of A-A direction in  FIG. 7 . 
           [0032]      FIG. 9 : a structure diagram of spray dehydrator of the present invention. 
           [0033]      FIG. 10 : a structure diagram of reactor of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Preferred Embodiment 1 
       [0034]    Referring to  FIGS. 1˜6 , 50 kg mono silicon&#39;s cutting waste liquid without kerosene and 10 liter 0.01 mol diluted hydrochloric acid are fed into the first mixing kettle  65  of the spray stirrer  49  through the first feed tank  63  and its first feed pipe  69 . The first tee valve  62  and first nozzle channel  66  are opened, while the channel to the first discharge pipe  64  is closed, then the first diaphragm pump  61  (a QBY-40 pneumatic diaphragm pump, produced by Shanghai Changquan Pump Manufacture Co., Ltd) is started, with air pressure of 3 kg/cm 2 ; the mixture is discharged from the first discharge hole  67  through the first mixing kettle  65 , then fed into a 3 min nozzle  70  of the first spray channel  66  through the first diaphragm pump  61 , first pipe  68  and first tee valve  62 , and quickly sprayed from the first nozzle exit  73  of the nozzle chamber  72  for mixing in a bigger cycle. As a negative pressure is formed in the nozzle chamber  72  to generate a pressure difference within and outside the wall of the nozzle chamber  72 , the external mixture is fed into the nozzle chamber  72  through liquid flow orifice  71  and then mixed in a smaller cycle, thus creating better stirring and reaction effect. Thus, the mixture passes through the first discharge hole  67  at bottom of the first mixing kettle  65 , the first diaphragm pump  61  and first nozzle channel  66  to form a circulation loop, enabling 25 min circulatory stirring and mixing. Next, the first tee valve  62  and first nozzle channel  66  are closed, and the channel to the first discharge pipe  64  is opened, such that the preliminary mixture is discharged from the first discharge pipe  64  into the spray mixer  50  for mixing. In this way, the preliminary mixture is obtained by the spray stirrer, with its viscosity slightly lower than waste liquid; however, non-uniform liquid and solid powder still exist. 
         [0035]    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 m 3 /h, the diameter of turbulence channel is 2.4 mm, when the mixture&#39;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. 
         [0036]    The secondary mixture from the spray mixer is fed into the solid-liquid separator  30  (shown in  FIGS. 7 and 8 ), which mainly comprises: sprinkler head  31 , steam pipe  33 , tapered plate  42 , funneled plate  41  and solid outlet  37 . In the solid-liquid separator  30 , two electric heating plates are fastened symmetrically onto the outer wall  36 ; the mixture is sprayed into the solid-liquid separator  30  by the sprinkler head  31  set at the center of top cover, then onto the external layer of the overhead tapered plate  42  of the first electric heating plate, and subsequently onto the inner layer of the lower funneled plate  41  for heating up. Next, the mixture is then fed onto the second electric heating plate through a hole  40  at bottom of the funneled plate  41 , and heated up in the same way, when the electric heating plate is maintained at 70□. After the mixture is heated up, water vapor and polyethylene glycol are evaporated quickly from the steam pipe  33 , and then cooled by the first condenser to obtain the mixed solution of water and polyethylene glycol. A small amount of condensed drop on the inner wall of the solid-liquid separator  30  may flow down, and then is discharged from the liquid outlet  38 . The solid obtained from heating separation is discharged from the solid outlet  37  at bottom of the solid-liquid separator  30 , the effluent is a coarse solid mixture of silicon carbide and silicon, namely, a solid mixture of silicon carbide and silicon containing salt and other impurities. To prevent the coarse solid mixture of silicon carbide and silicon from splashing onto the wall or the liquid drop from inner wall into the solid outlet  37 , a baffle plate  39  is set around to make it flow down and discharge from the solid outlet  37 . 
         [0037]    The mixed solution of water and polyethylene glycol flows into the spray dehydrator  51 . Referring to  FIG. 9 , the spray dehydrator  51  is structured almost the same way with the spray mixer  50 ; but a drain pipe  21  is set on its top cover. The mixed solution of water and polyethylene glycol flows into the mixing kettle  3  of the spray dehydrator  51  through the feed tank  6 ′ and its feed pipe  9 ′, then the diaphragm pump  1  is started for circulatory spraying dehydration in the same way as in the spray mixer, and the liquid flow is under turbulence state in the turbulence channel  11 ′; when the circulating flow of the diaphragm pump  1 ′ is 2.5 m 3 /h, the diameter of turbulence channel is 2.0 mm; when the dynamic viscosity of the mixed solution of water and polyethylene glycol is 19.2 Pa·S, Reynolds number=−7319. The circulatory spraying dehydration time is 20 min, and temperature rises to 70□; after water is discharged from the drain pipe  21 , the channel to the tee valve  7 ′ and nozzle inlet  10 ′ is closed, while the channel to the discharge pipe  4 ′ is opened, so polyethylene glycol is discharged from the discharge pipe  4 ′ to recover 15 kg transparent polyethylene glycol, with the molecular weight measured as 205, pH=6.5, moisture content&lt;0.3 wt % (molecular weight of standard polyethylene glycol is 300, pH=4-7, moisture content&lt;=0.5 wt %), and the recycling rate of polyethylene glycol based on 50 kg cutting waste liquid up to 30%. 
         [0038]    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 m 3 /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 m 3 /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. 
         [0039]    The secondary solid mixture of silicon carbide and silicon is fed into the reactor  52 ; referring to  FIG. 10 , the reactor  52  is structured almost the same way with the spray stirrer  49 ; but a steamed liquid pipe  22  is set on its top cover. The secondary solid mixture of silicon carbide and silicon is fed into the second mixing kettle  65  of the reactor  52  through the second feed tank  63 ′ and its second feed pipe  69 , and the mixed acid solution (volume HN0 3 :HF=1:5) of 5% HN0 3  and 30% HF equivalent to solid mixture is added, then the second diaphragm pump  61 ′ is started for 10 min circulatory spraying stirring, with the diameter of second nozzle up to 3.5 mm; when the temperature reaches the return temperature, fluosilicic acid solution is evaporated from the steamed liquid pipe  22 , and cooled by the second condenser to recover a transparent fluosilicic acid solution of 30 wt %. The fluosilicic acid solution is normally dried up, then put into mono-silicon furnace crucible to be processed into mono silicon. The mono-silicon furnace crucible is vacuumized, and protective hydrogen is charged, then it is melted by electric heating, and the furnace temperature is maintained about 1420□ with isolated case&#39;s cooling water; once upon crystallization, a small mono-silicon block is pulled out as a primer to obtain mono silicon stick and 0.6 kg silicon, with a recycling rate based on 50 kg cutting waste liquid up to 1.2%. The recycled silicon is subject to Fermi energy measurement: C B =10 15  cm −3  on Fermi energy diagram means p=5.0 ohm·cm, of which the position of Fermi energy is 0.31 ev higher than the center of energy bandgap, 0.24 ev lower than the bottom of conduction band, and 0.86 ev higher than the top of valence band. According to the measurement, the aforementioned indexes are close to mono silicon. In the reactor  52 , the residual silicon carbide and acid solution are discharged and filtered out by the second discharge pipe  64 ′, and flushed with 5 wt % Na0H solution and water until pH=7.5, then dried up to recover 7.5 kg grayish green silicon carbide powder. It is learnt from analysis that, its purity is 94%, mohs&#39; hardness is 9.5, so the crystal measured by electronic microscope belongs to α-SiC hexagonal system (the purity of standard silicon carbide is 94-99%, mohs&#39; hardness is 9.2-9.6 in α-SiC hexagonal system), with the recycling rate based on 50 kg cutting waste liquid up to 15%. 
       Preferred Embodiment 2 
       [0040]    50 kg mono silicon&#39;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 m 3 /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 m 3 /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 m 3 /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 m 3 /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 HN0 3  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. 
       Preferred Embodiment 3 
       [0041]    50 kg mono silicon&#39;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 m 3 /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 m 3 /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 m 3 /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 m 3 /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 HN0 3  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. 
       Preferred Embodiment 4 
       [0042]    50 kg mono silicon&#39;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 m 3 /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 m 3 /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 m 3 /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 m 3 /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 HN0 3  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.