CN111689560A - Silicon removal process for silicon-containing high-salinity wastewater - Google Patents
Silicon removal process for silicon-containing high-salinity wastewater Download PDFInfo
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Abstract
The invention relates to a silicon removal process for silicon-containing high-salinity wastewater. A silicon removal process of silicon-containing high-salt wastewater comprises the following steps: s10: adding lime into the silicon-containing high-salt wastewater, stirring for 0.1-5h, and filtering to obtain filtered silicon-containing high-salt wastewater; s20: adding a flocculating agent into the filtered high-salinity silicon-containing wastewater, stirring for 0.1-5h, and filtering to obtain recyclable high-salinity water. The silicon removal process of the silicon-containing high-salt wastewater can reduce the concentration of Si (IV) in the silicon-containing high-salt wastewater to be lower than 0.3mg/L, namely SiO2After the concentration is lower than 0.642mg/L, the sodium chloride is recycled and used in the chlor-alkali industry; the recycling of the silicon-containing high-salt wastewater realizes the purposes of energy conservation and emission reduction and saves the production cost.
Description
Technical Field
The invention belongs to the field of brine desiliconization, and particularly relates to a desiliconization process for high-salinity wastewater containing silicon.
Background
The chlor-alkali industry produces hydrogen by electrolysis of saturated brine (NaCl solution)Qi (H)2) Chlorine (Cl)2) And sodium hydroxide (a strong base, formula NaOH) solution. The main process flow is to inject water into the salt dissolving pool, and add crude salt (crude sodium chloride crystal, chemical formula NaCl, crude salt contains many other impurities), and generate saturated salt water (NaCl solution) in the salt dissolving pool, which is called primary salt water. Various refined reagents are added into the primary brine, and impurities are removed to obtain refined brine. The refined brine enters an electrolytic bath, and electrolytic reaction is carried out on an ionic membrane to generate gaseous hydrogen, chlorine and sodium hydroxide solution.
In the whole process flow, the core equipment is an ionic membrane on an electrolytic bath. Some impurity ions in the primary brine tend to affect the operation of the ionic membrane. In order to ensure high-performance operation of the ionic membrane, impurity ions affecting the operation of the ionic membrane in the primary brine must be removed, and thus the purification process of the primary brine must be strictly performed.
The primary brine contains various cationic impurities, wherein the impurities harmless to the ionic membrane are K+、Fe2+、Fe3+Ca is an impurity harmful to the ionic membrane2+、Mg2+、Ba2+、Sr2+、Ni2+、Al3+And a Si-containing compound. Among these impurities harmful to the ionic membrane, Ca2+、Mg2+、Ba2+、Sr2+、Ni2+All carbonates of (2) are insoluble in water, Al3+And
a double hydrolysis reaction takes place. Sodium carbonate (Na) can be used as the impurity ions2CO3) The ion reaction equation for removal is as follows:
in addition, Fe harmless to ionic membrane2+、Fe3+And also removed, the ion reaction equation is as follows:
the most difficult of all impurities to remove is the Si-containing compound, and the traditional silicon removal agent is magnesium hydroxide [ Mg (OH) ]2]Magnesium oxide (MgO), magnesium chloride (MgCl)2) And the like. However, magnesium (Mg) containing reagents have limited silicon removal efficiency. In recent years, many new silicon removal processes including reactive agent silicon removal, flocculant/coagulant silicon removal, adsorbent silicon removal, etc. have been developed at home and abroad.
The conventional chlor-alkali industry uses magnesium-containing reagents to remove silicon-containing compounds from brines. CN 108751523A provides a method for removing hard silicon from high-salinity wastewater, which can remove the concentration of silicon dioxide to below 15 mg/L. CN 105540939A provides a device and a method for removing calcium, magnesium, fluorine and silicon from wastewater, and the silicon removal rate reaches more than 96%. CN 108751531A provides a method for removing silicon and concentrating wastewater, which can remove silicon to about 8 mg/L.
The silicon removal methods or the added reagents have various types or large dosage; and enters a high current density natural circulation multi-stage membrane polar distance ionic membraneSilicon dioxide (SiO) in the indication of refined brine of the electrolytic cell2) The concentration is not higher than 2.3 mg/L. After the silicon-containing high-salt wastewater is treated by the silicon removal methods, the silicon concentration is still high and does not meet the index, so the silicon-containing high-salt wastewater cannot enter an electrolytic cell for recycling.
Nowadays, environmental protection is increasingly concerned by society, and the requirement of three wastes discharge of enterprises is more and more strict. Energy conservation and emission reduction gradually become inevitable and urgent problems to be solved for enterprises. In view of the above, the invention provides a novel silicon removal process for silicon-containing high-salt wastewater, which effectively solves the problem of discharge of the silicon-containing high-salt wastewater and is used in the chlor-alkali industry after silicon removal of the silicon-containing high-salt wastewater. Not only achieves the purposes of energy conservation and emission reduction, but also achieves the purpose of saving cost.
Disclosure of Invention
The invention aims to provide a silicon removal process for silicon-containing high-salt wastewater, which is used for removing Si (IV) in the silicon-containing high-salt wastewater to obtain recyclable high-salt water.
In order to realize the purpose, the adopted technical scheme is as follows:
a silicon removal process of silicon-containing high-salt wastewater comprises the following steps:
s10: adding lime into the silicon-containing high-salt wastewater, stirring for 0.1-5h at 10-100 ℃, and filtering to obtain filtered silicon-containing high-salt wastewater;
s20: adding a flocculating agent into the filtered high-salt wastewater containing silicon, stirring for 0.1-5h at 10-70 ℃, and filtering to obtain recyclable high-salt water.
Further, in the step S10, the stirring temperature is 20-70 ℃;
in the step S20, the stirring temperature is 20-50 ℃.
Further, in the step S10, the stirring temperature is 20-30 ℃;
in the step S20, the stirring temperature is 20-30 ℃.
Further, in the step S10, the stirring speed is 50-400 rpm.
Still further, in the step S10, the stirring speed is 100-300 rpm.
Further, in the step S10, the stirring time is 1-4 h.
Further, in the step S20, the rotation speed is 40-200 rpm.
Still further, in the step S20, the rotation speed of the stirring is 40-80 rpm.
Further, in the step S20, the stirring time is 1-4 h.
Further, in step S10, the lime may be one or more of quick lime, hydrated lime and soda lime.
Still further, the lime is hydrated lime.
Still further, the dosage of the hydrated lime is 0.5-1.8kg/m3Silicon-containing high-salt wastewater;
still further, the dosage of the hydrated lime is 0.7-1.2kg/m3Silicon-containing high-salt wastewater.
Further, the flocculating agent is one or more of an aluminum-based flocculating agent, an iron-based flocculating agent and an inorganic polymer flocculating agent.
Still further, the flocculating agent is an iron-based flocculating agent,
still further, the flocculant is ferric chloride hexahydrate.
Still further, the dosage of the ferric chloride hexahydrate is 0.5-1.4kg/m3Silicon-containing high-salt wastewater.
Still further, the dosage of the ferric chloride hexahydrate is 0.7-1.0kg/m3Silicon-containing high-salt wastewater.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention has high silicon removal efficiency which is higher than 99 percent, and the concentration of Si (IV) in the saline water is lower than 0.3mg/L, namely SiO2The concentration is lower than 0.642 mg/L.
2. The reagent used in the invention is easy to obtain, low in price and low in dosage.
3. The method has the advantages of short process flow, few equipment types and simple operation, and can react at normal temperature.
4. The precipitate generated by the silicon removal reaction is easy to treat and does not pollute the environment.
5. The silicon removal process of the silicon-containing high-salinity wastewater can realize industrial application.
Drawings
FIG. 1 is a process flow diagram of example 1.
Detailed Description
In order to further illustrate the silicon removal process of high-salinity wastewater containing silicon according to the present invention and achieve the desired objects, the following embodiments are combined with the preferred embodiments to further describe the detailed implementation, structure, features and effects of the silicon removal process of high-salinity wastewater containing silicon according to the present invention. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
The silicon removal process of the high-salinity wastewater containing silicon according to the present invention will be further described in detail with reference to the following specific examples:
the hydrogen-containing waste gas generated by each workshop of the factory area of the company contains a small amount of chlorosilane, such as silicon tetrachloride (SiCl)4) Trichlorosilane (SiHCl)3) Dichlorosilane (SiH)2Cl2) And the like. The hydrogen-containing waste gas must be washed by a two-stage washing tower, and the chlorosilane can be discharged after being dissolved. Wherein, the first-stage washing tower is an acid (hydrochloric acid, HCl solution) washing tower, and the second-stage washing tower is an alkali (NaOH solution) washing tower.
After hydrogen-containing waste gas enters a first-stage washing tower, chlorosilane reacts as follows:
SiCl4+2H2O＝SiO2+4HCl
SiHCl3+2H2O＝SiO2+3HCl+H2
SiH2Cl2+2H2O＝SiO2+2HCl+2H2
undissolved chlorosilane in the first-stage washing tower reacts to generate HCl and H2Entering a secondary washing tower. With SiHCl3For example, chlorosilanes are washed in a secondary washThe following reactions take place in the column:
SiHCl3+2H2O＝SiO2+3HCl+H2
SiO2+2NaOH＝Na2SiO3+H2O
3HCl+3NaOH＝3NaCl+3H2O
the total reaction is as follows:
SiHCl3+5NaOH＝Na2SiO3+3NaCl+2H2O+H2
in addition, after the HCl gas generated in the first washing tower enters the second washing tower, a neutralization reaction also occurs:
HCl+NaOH＝NaCl+H2O
the pickling solution of the first-stage washing tower and the alkaline washing solution of the second-stage washing tower are filtered by a plate-and-frame filter press respectively, solid waste is filtered out and then mixed, and acid-base neutralization reaction is carried out again:
HCl+NaOH＝NaCl+H2O
after the pickling solution and the alkaline washing solution are mixed, wastewater with high salt (NaCl) concentration is generated, and the wastewater contains a certain amount of Si (IV) (compound containing tetravalent silicon) and a small amount of other metal ion impurities, which is hereinafter referred to as silicon-containing high-salt wastewater. If the silicon-containing high-salt wastewater is discharged to a sewage treatment plant, the treatment cost is extremely high, and a huge environmental protection problem is brought.
The electrolytic cell used in chlor-alkali industry of this company is a high current density natural circulation bipolar membrane polar distance ion membrane electrolytic cell, and the silicon dioxide (SiO) in the refined brine entering the electrolytic cell2) The concentration is not higher than 2.3 mg/L.
The impurities in the silicon-containing high-salt wastewater of the company comprise Si (IV) and Ca2+、Mg2+、Fe2+、Ba2+、Al3+、Ni2+、Sr2+The impurities can be divided into four types, ① IIA elements Mg, Ca, Ba and Sr, and is characterized by that all the carbonates are insoluble in water, and the solubility of hydroxide is successively increased according to atomic number, and the alkaline earth metal ions can be added with Na in the course of refining operation of brine2CO3Removal of ② group IIIAThe concentration of Al is lower than the lower limit of the measuring range of the instrument, namely less than 0.0001mg/L and can be ignored, ③ VIII family metal elements Fe and Ni are characterized in that hydroxide and carbonate are not dissolved in water, ④ IVA family element Si is mainly SiO2Is in the form of a mixture of
SiO2Is generated by the reaction of chlorosilane in a first-level washing tower,
is generated by the reaction of chlorosilane in a secondary washing tower.
Among the impurities, the influence of the non-metallic element Si on the normal operation of the ion membrane of the electrolytic cell is the largest, and the non-metallic element Si is the most difficult to remove, so that the non-metallic element Si is the largest obstacle to the recycling of the silicon-containing high-salt wastewater. As long as the Si concentration is reduced to the operation requirement of the ionic membrane, the remaining impurities can be easily removed, and then the silicon-containing high-salt wastewater can be recycled.
The technical scheme is as follows:
the invention aims to remove Si (IV) in silicon-containing high-salt wastewater to obtain recyclable high-salt water. Si (IV) is removed by a two-step process. The apparatus shown in fig. 1 was used. The silicon-containing high-salt wastewater enters a stirring tank D1, after lime is added, a stirring paddle is started, Si (IV) in the high-salt wastewater reacts with the lime at normal temperature or under heating and normal pressure, and precipitates are generated. The reacted silicon-containing high-salt wastewater is sent to a stirring tank D2 after the sediment of the silicon-containing high-salt wastewater is removed by a filter F1. And (3) after the flocculating agent is added into the stirring tank D2, starting a stirring paddle, reacting Si (IV) in the silicon-containing high-salt wastewater with the flocculating agent at normal temperature or under heating and normal pressure, and carrying out mesh-catching flocculation on the flocculating agent to generate coprecipitation. And (3) removing the precipitate from the silicon-containing high-salt wastewater after the reaction through a filter F2 to obtain recyclable high-salt water.
The specific operation steps are as follows:
s10: adding lime into the silicon-containing high-salt wastewater, stirring for 0.1-5h at 10-100 ℃, and filtering to obtain filtered silicon-containing high-salt wastewater;
s20: adding a flocculating agent into the filtered high-salt wastewater containing silicon, stirring for 0.1-5h at 10-70 ℃, and filtering to obtain recyclable high-salt water.
Preferably, in the step S10, the stirring temperature is 20-70 ℃;
in the step S20, the stirring temperature is 20-50 ℃.
Further preferably, in the step S10, the stirring temperature is 20-30 ℃;
in the step S20, the stirring temperature is 20-30 ℃.
Preferably, in step S10, the stirring speed is 50-400 rpm.
Further preferably, in the step S10, the stirring speed is 100-300 rpm.
Preferably, in step S10, the stirring time is 1-4 h.
Preferably, in step S20, the rotation speed is 40-200 rpm.
Further preferably, in the step S20, the rotation speed of the stirring is 40-80 rpm.
Preferably, in step S20, the stirring time is 1-4 h.
Preferably, in step S10, the lime may be one or more of quick lime, hydrated lime and soda lime.
Further preferably, the lime is hydrated lime.
Further preferably, the amount of the hydrated lime is 0.5-1.8kg/m3Silicon-containing high-salt wastewater;
preferably, the amount of the hydrated lime is 0.7-1.2kg/m3Silicon-containing high-salt wastewater.
Preferably, the flocculating agent is one or more of an aluminum-based flocculating agent, an iron-based flocculating agent and an inorganic polymer flocculating agent.
Further preferably, the flocculant is an iron-based flocculant,
further preferably, the flocculant is ferric chloride hexahydrate.
The reaction principle is as follows:
taking hydrated lime as an example, the reaction principle of the first step silicon removal is as follows:
slaked lime [ Ca (OH)2]Dissociation reaction occurs in the silicon-containing high-salt wastewater:
Ca(OH)2＝Ca2++2OH-
si (IV) in the silicon-containing high-salt wastewater exists in the form of SiO generated in a primary washing tower2And generated in a secondary washing column
Wherein, SiO2Can generate weak acid H after being dissolved in water2SiO3The reaction equation is as follows:
SiO2+H2O＝H2SiO3
H2SiO3the following dissociation reactions occur:
formed by dissociation
Not all of which will diffuse into the solution, some of which will
Remains fixed on SiO2Surface, forming a negatively charged glue nucleus, and H+As counter-ion to form SiO with the colloidal nucleus2And (3) sol. The micelle structure is:
wherein the glue core structure is negatively charged
The colloidal particles are
The inverse particle outside the slidable surface is 2xH+The whole is electrically neutral. Because hydrated lime is added into the silicon-containing high-salt wastewater, Ca with positive electricity is dissociated2+Then can be applied to the colloidal particles
Surface and dissociated
The reaction takes place to form a precipitate, the chemical equation is as follows:
SiO2+H2O＝H2SiO3
H2SiO3+Ca(OH)2＝CaSiO3↓+2H2O
the overall reaction equation is:
SiO2+Ca(OH)2＝CaSiO3↓+H2O
generated in a secondary washing tower
The following ion reaction equation occurs:
in addition, Mg in silicon-containing high-salt wastewater2+、Fe2+、Ni2+A precipitate also forms, either totally or mostly removed, and the ion equation is as follows:
Mg2++2OH-＝Mg(OH)2↓
Fe2++2OH-＝Fe(OH)2↓
Ni2++2OH-＝Ni(OH)2↓
after the lime is added for reaction, most of Si (IV) and almost all Fe in the silicon-containing high-salt wastewater2+、Mg2+And Ni2+Is removedTo remove Ca2+The concentration increases. Filtering the precipitate to obtain Ca2+The concentration of Si (IV) of the clarified alkaline high-salt wastewater containing silicon with increased concentration does not meet the requirement of an ionic membrane, and the Si (IV) is further removed.
Taking ferric chloride as an example, the reaction principle of the second step of silicon removal is as follows:
FeCl3·6H2after O is dissolved in water, Fe (III) and
is present in solution.
The dissociation equation occurs as follows:
of which 2 Fe (H)2O)5(OH)2+It can also be condensed into a dimer,
dimer [ Fe ]2(H2O)8(OH)2]4+Abbreviated as [ Fe ]2(OH)2]4+。
Dimers may be further condensed into multimers, multimeric forms such as [ Fe ]3(OH)4]5+，[Fe5(OH)9]6+，[Fe5(OH)8]7+，[Fe5(OH)7]8+，[Fe6(OH)12]6+，[Fe7(OH)12]9+，[Fe7(OH)11]10+，[Fe9(OH)20]7+，[Fe12(OH)34]2+And the like.
Fe (III) has different chemical form distribution modes in solution, and can be classified into three types according to form, namely Fea，Feb，Fec：①FeaRepresenting the free ion of iron and mononuclear hydroxyl complexes of each level ② Feb③ Fe is a series of polynuclear hydroxyl complexes with low polymerization degree, which are unstable in solution and tend to be further polymerized to form high polymerscIs a high polymer formed by further polymerizing the oligomer.
The molar ratio of OH-to Fe (III) in the solution is defined as the degree of basification B, i.e. B ═ OH-]/[Fe]. When B is about 0.1, Fe (III) in the solution is mainly Fea(ii) a When B is 0.4-1.0, FebAnd FecCoexisting, of the formula
If conversion of a hydroxyl group into an oxygen bridge is considered, this can be written as
When B is more than 1.5, Fe (III) is further polymerized into high polymer and even sol, and the polymerization degree can reach 104The order of magnitude, the stability is lower, and gelation and precipitation can occur.
Fe (III) in solution at a lower pH to begin the formation of Fe (OH)3Polymerizing to obtain Fe (OH) with a degree of polymerization of 2-903And (3) a polymer. When the alkalization degree is about 30%, the best impurity removal effect is achieved, and the impurity removal effect of Fe (III) is reduced along with the increase of B.
After the silicon-containing high-salt wastewater is added with lime for reaction and filtered, the obtained clear filtrate is alkaline, and the pH value is approximately equal to 12. Adding FeCl3·6H2After O, B is 0.2-0.7, Fe (III) exists in the silicon-containing high-salt wastewater in a form of positive electricity
SiO dissolved in high-salt wastewater2The colloidal core and colloidal particles of the sol are respectively negatively charged
And
and
with opposite charges. By the occurrence of an electrical neutralization effect,
as
The coagulated nuclei become targets for trapping when the flocculant is precipitated and dropped, and coprecipitation occurs. I.e. lime is not removed
By passing
Is removed by the action of the net-catching flocculation.
In addition, in small amounts
Can be combined with
The following double hydrolysis reaction takes place:
example 1.
At 0.2m3The method comprises the following steps of treating high-salt wastewater containing silicon, wherein the using amount of hydrated lime is 0.30kg, the using amount of ferric chloride hexahydrate is 0.25kg, performing two-stage reaction step by step, wherein the first-stage reaction temperature is 60 ℃, the stirring speed is 180rpm, the stirring time is 1h, the second-stage reaction temperature is 60 ℃, the stirring speed is 60rpm, and the stirring time is 1 h. Wherein, the Si concentration data of the brine before and after the reaction is obtained by measuring an Inductively Coupled Plasma Emission Spectrometer (ICPES). Converting the measured Si concentration data into SiO index of the ion film2And (4) concentration. This is true for the following examples and comparative examples. The reaction results are shown in Table 1.
Example 2.
At 0.2m3The method comprises the following steps of treating high-salt wastewater containing silicon, wherein the using amount of hydrated lime is 0.19kg, the using amount of ferric chloride hexahydrate is 0.23kg, and the two-stage reaction is carried out step by step, wherein the first-stage reaction temperature is 50 ℃, the stirring speed is 220rpm, the stirring time is 0.75h, the second-stage reaction temperature is 50 ℃, the stirring speed is 80rpm, and the stirring time is 0.5 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 1.
Example 3.
At 0.2m3The method comprises the following steps of treating the silicon-containing high-salt wastewater with the use amount of hydrated lime of 0.23kg and ferric chloride hexahydrate of 0.21kg, and carrying out two-stage reaction step by step, wherein the first-stage reaction is room temperature, the stirring speed is 220rpm, the stirring time is 1.5h, the second-stage reaction is room temperature, the stirring speed is 80rpm, and the stirring time is 1 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 1.
Example 4.
At 0.2m3The silicon-containing high-salt wastewater has the dosage of hydrated lime of 0.20kg and the dosage of ferric chloride hexahydrate of 0.20kg, and the two-stage reaction is carried out step by step at the first-stage reaction temperatureThe stirring speed is 220rpm at 50 ℃, the stirring time is 1.25h, the secondary reaction temperature is 50 ℃, the stirring speed is 80rpm, and the stirring time is 0.75 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 1.
TABLE 1
According to the reaction result data of the above examples, the Si concentration is less than 0.3mg/L, i.e., SiO2The concentration is lower than 0.642 mg/L. The silicon removal efficiency is more than 99.6 percent.
Example 5.
At 0.2m3The method comprises the following steps of treating high-salt wastewater containing silicon, wherein the using amount of hydrated lime is 0.17kg, the using amount of ferric chloride hexahydrate is 0.15kg, performing two-stage reaction step by step, wherein the first-stage reaction temperature is 40 ℃, the stirring speed is 100rpm, the stirring time is 1h, the second-stage reaction temperature is 40 ℃, the stirring speed is 100rpm, and the stirring time is 1 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 2.
Comparative example 1.
At 0.2m3The method comprises the following steps of (1) simultaneously carrying out two-stage reaction on the silicon-containing high-salt wastewater, wherein the dosage of hydrated lime is 0.17kg, and the dosage of ferric chloride hexahydrate is 0.15kg, namely adding the hydrated lime and the ferric chloride hexahydrate into the silicon-containing high-salt wastewater simultaneously to carry out desilicification reaction, wherein the reaction temperature is 40 ℃, the stirring speed is 100rpm, and the stirring time is 2 hours. The reaction results are shown in table 2. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 2.
Comparative example 2.
At 0.2m3The method comprises the following steps of (1) simultaneously carrying out two-stage reaction on the silicon-containing high-salt wastewater, wherein the dosage of hydrated lime is 0.30kg, and the dosage of ferric chloride hexahydrate is 0.29kg, namely adding the hydrated lime and the ferric chloride hexahydrate into the silicon-containing high-salt wastewater simultaneously to carry out desilicification reaction, wherein the reaction temperature is 40 ℃, the stirring speed is 100rpm, and the stirring time is 2 hours. The reaction results are shown in table 2. Si concentration data of saline before and after reaction is measured by an inductively coupled plasma emission spectrometerAnd (4) obtaining the amount. The reaction results are shown in Table 2.
TABLE 2
As can be seen from the table, the two-stage reaction is preferably carried out stepwise in terms of silicon removal efficiency.
According to the invention, two-stage reaction is carried out step by step, so that the silicon removal efficiency is better while the dosage of the additive is reduced.
Example 6.
At 0.2m3The method comprises the following steps of treating the silicon-containing high-salt wastewater with the use amount of hydrated lime of 0.20kg and ferric chloride hexahydrate of 0.15kg, and performing two-stage reaction step by step, wherein the first-stage reaction is room temperature, the stirring speed is 100rpm, the stirring time is 0.5h, the second-stage reaction is room temperature, the stirring speed is 100rpm, and the stirring time is 0.5 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 3.
Comparative example 3.
At 0.2m3The silicon-containing high-salt wastewater with the hydrated lime amount of 0.33kg only undergoes the first-stage reaction, the reaction temperature is room temperature, the stirring speed is 100rpm, and the stirring time is 1 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 3.
Comparative example 4.
At 0.2m3The silicon-containing high-salt wastewater, the dosage of ferric chloride hexahydrate is 0.6kg, only secondary reaction is carried out, the reaction temperature is room temperature, the stirring speed is 100rpm, and the stirring time is 1 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 3.
TABLE 3
Increasing the dosage of a certain silicon removal reagent, and only carrying out primary silicon removal reaction or only using secondary silicon removal reaction to obtain SiO in the final brine2The concentrations are all greater than 2.3mg/L and are inconsistentMeets the requirement of recycling. The reagent dosage is reduced, two-stage silicon removal reaction is combined and is carried out step by step, and a good silicon removal effect is achieved.
And the solubility of the hydrated lime is 0.165g/100g of water and 0.2m at the temperature of 20 DEG C3The mass of slaked lime that is dissolved by the brine at the most is about 0.33kg, and the result of performing only one stage reaction is inferior to that of performing two stages. If the amount of the hydrated lime is increased continuously, the added hydrated lime cannot be dissolved to react. Not only wastes the lime consumption, but also can not achieve the silicon removal effect.
The secondary reaction was carried out only with ferric chloride hexahydrate flocculant, which gave poor results.
Example 7.
At 0.2m3The method comprises the following steps of treating high-salt wastewater containing silicon, wherein the using amount of hydrated lime is 0.22kg, the using amount of ferric chloride hexahydrate is 0.16kg, performing two-stage reaction step by step, wherein the first-stage reaction temperature is room temperature, the stirring speed is 300rpm, the stirring time is 1h, the second-stage reaction temperature is room temperature, the stirring speed is 150rpm, and the stirring time is 1 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 4.
Comparative example 5.
At 0.2m3The method comprises the following steps of treating high-salt wastewater containing silicon, wherein the using amount of hydrated lime is 0.22kg, the using amount of ferric chloride hexahydrate is 0.16kg, performing two-stage reaction step by step, wherein the first-stage reaction temperature is room temperature, the stirring speed is 550rpm, the stirring time is 1h, the second-stage reaction temperature is room temperature, the stirring speed is 150rpm, and the stirring time is 1 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 4.
Comparative example 6.
At 0.2m3The method comprises the following steps of treating high-salt wastewater containing silicon, wherein the using amount of hydrated lime is 0.22kg, the using amount of ferric chloride hexahydrate is 0.16kg, performing two-stage reaction step by step, wherein the first-stage reaction temperature is room temperature, the stirring speed is 20rpm, the stirring time is 1h, the second-stage reaction temperature is room temperature, the stirring speed is 150rpm, and the stirring time is 1 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 4.
Comparative example 7.
At 0.2m3The method comprises the following steps of treating high-salt wastewater containing silicon, wherein the using amount of hydrated lime is 0.22kg, the using amount of ferric chloride hexahydrate is 0.16kg, performing two-stage reaction step by step, wherein the first-stage reaction temperature is room temperature, the stirring speed is 300rpm, the stirring time is 1h, the second-stage reaction temperature is room temperature, the stirring speed is 300rpm, and the stirring time is 1 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 4.
Comparative example 8.
At 0.2m3The method comprises the following steps of treating high-salt wastewater containing silicon, wherein the using amount of hydrated lime is 0.22kg, the using amount of ferric chloride hexahydrate is 0.16kg, performing two-stage reaction step by step, wherein the first-stage reaction temperature is room temperature, the stirring speed is 300rpm, the stirring time is 1h, the second-stage reaction temperature is room temperature, the stirring speed is 30rpm, and the stirring time is 1 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 4.
TABLE 4
In both the first-stage reaction and the second-stage reaction, the silicon removal efficiency is affected by the excessively high or low stirring speed.
Example 8.
At 100m3The method comprises the following steps of treating high-salt wastewater containing silicon, wherein the using amount of hydrated lime is 160kg, the using amount of ferric chloride hexahydrate is 90kg, and two-stage reaction is carried out step by step, wherein the first-stage reaction temperature is room temperature, the stirring speed is 160rpm, the stirring time is 4 hours, the second-stage reaction temperature is room temperature, the stirring speed is 80rpm, and the stirring time is 2 hours. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 5.
TABLE 5
When the reaction is amplified, the silicon removing effect can be well achieved, and the silicon removing method can be directly applied to industrialization. Unlike some other additives, when the reaction is amplified, the expected silicon removal effect is not achieved, and the method cannot be directly applied to industrial production.
Example 9.
At 0.2m3The method comprises the following steps of treating silicon-containing high-salt wastewater with the use amount of 0.15kg of quicklime and 0.15kg of ferric chloride hexahydrate, and carrying out two-stage reaction step by step at the first-stage reaction temperature of 50 ℃, the stirring speed of 220rpm and the stirring time of 0.5h, at the second-stage reaction temperature of 50 ℃, the stirring speed of 80rpm and the stirring time of 0.5 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 6.
Example 10.
At 0.2m3Silicon-containing high-salt wastewater, 0.15kg of quicklime and polyaluminium chloride (PAC for short, chemical formula is Al (OH))2Cl6-n]The dosage is 0.15kg, the two-stage reaction is carried out step by step, the first-stage reaction temperature is 50 ℃, the stirring speed is 220rpm, the stirring time is 0.5h, the second-stage reaction temperature is 50 ℃, the stirring speed is 80rpm, and the stirring time is 0.5 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 6.
Example 11.
At 0.2m3The silicon-containing high-salt wastewater contains 0.15kg of quicklime and 0.47kg of polyaluminium chloride, and the two-stage reaction is carried out step by step, wherein the first-stage reaction temperature is 50 ℃, the stirring speed is 220rpm, the stirring time is 0.5h, the second-stage reaction temperature is 50 ℃, the stirring speed is 80rpm, and the stirring time is 0.5 h. The Si concentration data of the saline before and after the reaction is measured by an inductively coupled plasma emission spectrometer. The reaction results are shown in Table 6.
TABLE 6
Example 11 in the water samples after silicon removal, aluminum (Al) was detected3+) Has a concentration of 3.7423mgL。
In contrast to the above 3 examples, when polyaluminium chloride is used as a flocculant, the amount of polyaluminium chloride used to reach the ferric chloride hexahydrate is larger than that of ferric chloride hexahydrate, and aluminum is present in the final brine (aluminum in the brine is harmful, and the operating conditions of the aluminum-based flocculant are not easy to control).
The invention reduces the concentration of Si (IV) in the silicon-containing high-salt wastewater to be lower than 0.3mg/L, namely SiO2After the concentration is lower than 0.642mg/L, the sodium hypochlorite is recycled and used in the chlor-alkali industry. The recycling of the silicon-containing high-salt wastewater realizes the purposes of energy conservation and emission reduction and saves the production cost.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention are within the scope of the technical solution of the present invention.
Claims (18)
1. A silicon removal process for silicon-containing high-salt wastewater is characterized by comprising the following steps:
s10: adding lime into the silicon-containing high-salt wastewater, stirring for 0.1-5h at 10-100 ℃, and filtering to obtain filtered silicon-containing high-salt wastewater;
s20: adding a flocculating agent into the filtered high-salt wastewater containing silicon, stirring for 0.1-5h at 10-70 ℃, and filtering to obtain recyclable high-salt water.
2. The silicon removal process of claim 1,
in the step S10, the stirring temperature is 20-70 ℃;
in the step S20, the stirring temperature is 20-50 ℃.
3. The silicon removal process of claim 2,
in the step S10, the stirring temperature is 20-30 ℃;
in the step S20, the stirring temperature is 20-30 ℃.
4. The silicon removal process of claim 1,
in the step S10, the stirring speed is 50-400 rpm.
5. The silicon removal process of claim 4,
in the step S10, the stirring speed is 100-300 rpm.
6. The silicon removal process of claim 1,
in the step S10, the stirring time is 1-4 h.
7. The silicon removal process of claim 1,
in the step S20, the rotating speed is 40-200 rpm.
8. The silicon removal process of claim 7,
in the step S20, the stirring speed is 40-80 rpm.
9. The silicon removal process of claim 1,
in the step S20, the stirring time is 1-4 h.
10. The silicon removal process of claim 1,
in step S10, the lime may be one or more of quick lime, hydrated lime and soda lime.
11. The silicon removal process of claim 10,
the lime is hydrated lime.
12. The silicon removal process of claim 11,
the dosage of the hydrated lime is 0.5-1.8kg/m3Silicon-containing high-salt wastewater.
13. The silicon removal process of claim 1,
the dosage of the hydrated lime is 0.7-1.2kg/m3Silicon-containing high-salt wastewater.
14. The silicon removal process of claim 1,
the flocculating agent is one or more of an aluminum-based flocculating agent, an iron-based flocculating agent and an inorganic polymer flocculating agent.
15. The silicon removal process of claim 14,
the flocculant is an iron-based flocculant.
16. The silicon removal process of claim 15,
the flocculant is ferric chloride hexahydrate.
17. The silicon removal process of claim 16,
the dosage of the ferric chloride hexahydrate is 0.5-1.4kg/m3Silicon-containing high-salt wastewater.
18. The silicon removal process of claim 17,
the dosage of the ferric chloride hexahydrate is 0.7-1.0kg/m3Silicon-containing high-salt wastewater.
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