CN111331071A - Method for preparing sodium silicate used sand through modification and regeneration - Google Patents
Method for preparing sodium silicate used sand through modification and regeneration Download PDFInfo
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- CN111331071A CN111331071A CN202010247280.1A CN202010247280A CN111331071A CN 111331071 A CN111331071 A CN 111331071A CN 202010247280 A CN202010247280 A CN 202010247280A CN 111331071 A CN111331071 A CN 111331071A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C5/00—Machines or devices specially designed for dressing or handling the mould material so far as specially adapted for that purpose
Abstract
The invention relates to the technical field of water glass, and discloses a method for preparing water glass used sand through modification and regeneration, which comprises the following steps: preparing a modified solution: (1) using NH4Aqueous Cl solution as base modification solution in NH4Adding a proper amount of metal salt mixture into the Cl aqueous solution to generate a repairing modified solution; (2) soaking modification: soaking the used sodium silicate sand in the modified solution; and (3) putting the used water glass sand into the thermal restoration modification solution for soaking and modifying for 10-120min, or soaking and modifying the used water glass sand by using the normal-temperature restoration modification solution for 30-200min, and stirring the used water glass sand at regular time in the modification process. The regenerated used sand can be recycled for multiple times, can completely replace natural sand, protects the resources of the natural sand, reduces industrial solid waste discharge, has the advantages of high sand mold strength, difficult sand sticking, difficult sand inclusion, good sand falling collapsibility and the like, and can reduce the problems of sand cleaning, repair and the like in the casting process.
Description
Technical Field
The invention relates to the technical field of water glass, in particular to a method for preparing used water glass sand through modification and regeneration.
Background
The characteristic of sodium silicate sand mold casting that it is more environmentally friendly than other casting methods is generally recognized as the most likely process for green casting. However, the properties of the reclaimed sand of the used water glass sand are obviously different from those of natural sand, so that the problems of low reclamation rate of the used water glass sand, poor collapsibility of the reclaimed sand, abnormal sand falling difficulty, easy sand sticking of castings and the like are caused, and the method becomes a key for hindering the development of the used water glass sand casting process.
The conventional regeneration method of used sodium silicate sand mainly comprises a dry method, a wet method, a chemical method, a biological method and the like, and a plurality of combined regeneration methods and technologies such as the dry method-wet method and the wet method-chemical method are formed on the basis.
The dry regeneration and the wet regeneration of the used sodium silicate sand are the most commonly adopted regeneration technology of the used sodium silicate sand at present. Whether the water glass used sand is regenerated by a dry method or a wet method, the basic principle is that the water glass membrane wrapped on the surface of the water glass used sand is removed by scrubbing the surface of the water glass used sand, including high-temperature scrubbing, mechanical scrubbing or soaking scrubbing. The two existing methods for regenerating used water glass sand are superior to dry regeneration in terms of use conditions, but both methods have mechanical action between sand grains or sand grains and other substances, so that the regeneration process can damage the surface structure and characteristics of the regenerated sand, the energy consumption of the regeneration process is high, secondary pollution of byproducts is serious and the like.
The existing chemical regeneration method of the used water glass sand mainly refers to the purpose of reducing the modulus of the water glass on the surface of the used water glass sand by using NaOH aqueous solution so as to remove the water glass film on the surface of the used water glass sand. In order to improve the effect of the method, the chemical regeneration method is combined with an ultrasonic technology, but the method is actually used at present, so that the method cannot remove the water glass film on the surface of the used water glass sand, the content of Na2O in the used water glass sand is increased, and the high-temperature resistance of the used water glass sand or core sand is deteriorated.
The biological regeneration of the used water glass sand mainly means that diatoms are cultured on the surface of the used water glass sand, and a water glass membrane on the surface of the used water glass sand is removed by utilizing the requirements of the diatoms on a slow-release silicon source and other nutrient substances, so that the aim of regenerating the used water glass sand is fulfilled, and diatom bloom in which a large amount of water glass is fixed in a body can also be regenerated into industrial raw materials through resource treatment. The method has the advantages that the method is very environment-friendly and almost achieves the complete utilization of resources, but the water glass film on the surface of the used water glass sand is almost insoluble in water, so that the absorption of diatom on the water glass is slow, the demoulding time of the used water glass sand is too long, in addition, the reproduction of diatom is greatly influenced by the environment, under the natural growth condition, the diatom is difficult to bloom, the aim of regenerating a large amount of used water glass sand cannot be achieved, and the aim cannot achieve the effect of industrial production.
At present, the combined regeneration technology of the used water glass sand mainly comprises a plurality of combined regeneration technologies such as a hot method-dry method, a dry method-wet method and a wet method-chemical method, but the core concept of the combined regeneration technologies still remains in the scope of scrubbing and demoulding the used water glass sand by scrubbing, and no substantial breakthrough is made.
In summary, the main current methods for regenerating used water glass sand are dry regeneration and wet regeneration, and the core ideas of the two regeneration methods are that the used water glass sand is scrubbed to remove the water glass film on the surface of the used water glass sand as much as possible, but the water glass film on the surface of the used water glass sand is too close to the sand grains in combination, and although the two regeneration methods have certain effects, the performances of the regenerated sand have large differences from the new sand, and an ideal demoulding effect cannot be achieved. The existing chemical regeneration method for the used water glass sand cannot remove the water glass film on the surface of the used water glass sand, and can increase the accumulation of Na2O content in the used water glass sand, but worsen the high-temperature performance of the used water glass sand or core sand. Although the biological method of the used sodium silicate sand is environment-friendly, the efficiency of the diatom digestion of the sodium silicate film on the surface of the used sodium silicate sand is extremely low, and the industrialization cannot be realized at present.
Disclosure of Invention
The invention aims to provide a preparation method for modifying and regenerating used sodium silicate sand by converting a sodium silicate film on the surface of the used sand into a modified film more thoroughly.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a method for preparing used sodium silicate sand through modification and regeneration comprises the following steps:
(1) preparing a modified solution: using NH4Aqueous Cl solution as base modification solution in NH4Adding a proper amount of metal salt mixture into the Cl aqueous solution to generate a repairing modified solution;
(2) soaking modification: soaking the used sodium silicate sand in the modified solution; soaking and modifying the used water glass sand in a thermal repair modification solution with a certain concentration for 10-120min, or soaking and modifying the used water glass sand in a normal-temperature repair modification solution for 30-200min, and stirring the used water glass sand at regular time in the modification process; the reaction equation is as follows:
Na2O·mSiO2·nH2O+2NH4Cl→mSiO2+2NaCl+2NH3↑+(n+1)H2O
Na2O·mSiO2·nH2O+CaCl2→mSiO2+2NaCl+Ca(OH)2+(n-1)H2O
Na2O·mSiO2·nH2O+MgCl2→mSiO2+2NaCl+Mg(OH)2+(n-1)H2O
3Na2O·mSiO2·nH2O+2AlCl3→mSiO2+6NaCl+2Al(OH)3+(n-3)H2O
preferably, the metal salt mixture is CaCl2、MgCl2And AlCl3Any one or a mixture of two or more of them.
Preferably, the mass percentage concentration of the metal salt mixture is 0.1-30%.
Preferably, the NH is4The mass percentage concentration of the Cl aqueous solution is 0.1-30%.
Preferably, the thermal repair modification solution is 50-100 ℃, and the normal-temperature repair modification solution is 25-30 ℃.
The preparation method of the invention adopts the sodium silicate used sand modification and regeneration, and has the following beneficial effects:
the invention only carries out surface modification on the used sodium silicate sand, does not carry out destructive scrubbing on the used sand and does not destroy the structure and the characteristics of the surface of the sand grains; the adopted modifier is common inorganic salt, has no toxicity and low cost, and can realize large-scale production; the regenerated used sand can be used as single facing sand or core sand, and can also be matched with natural sand according to any proportion for use; the regenerated used sand can be recycled for multiple times, can completely replace natural sand, protects the resources of the natural sand, reduces the emission of industrial solid waste, and is very environment-friendly; the sand mold made of the regenerated used sand has the advantages of high sand mold strength, difficult sand sticking, difficult sand inclusion, good shakeout collapsibility and the like, and can reduce the cost of the working procedures of sand cleaning, repair and the like in the casting process.
Detailed Description
The following examples further illustrate embodiments of the present invention. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
(1) Preparing a modified solution: using NH4Aqueous Cl solution as base modification solution in NH4Adding a proper amount of metal salt mixture into the Cl aqueous solution to generate a repairing modified solution;
(2) soaking modification: soaking the used sodium silicate sand in the modified solution; the used water glass sand is put into a thermal restoration modification solution (50-100 ℃) with certain concentration for soaking and modification for 10-120min, or the used water glass sand is soaked and modified for 30-200min by a normal-temperature restoration modification solution (25-30 ℃), and the modification process of the used water glass sand is regularly stirred; the reaction equation is as follows:
Na2O·mSiO2·nH2O+2NH4Cl→mSiO2+2NaCl+2NH3↑+(n+1)H2O
Na2O·mSiO2·nH2O+CaCl2→mSiO2+2NaCl+Ca(OH)2+(n-1)H2O
Na2O·mSiO2·nH2O+MgCl2→mSiO2+2NaCl+Mg(OH)2+(n-1)H2O
3Na2O·mSiO2·nH2O+2AlCl3→mSiO2+6NaCl+2Al(OH)3+(n-3)H2O
using NH4Taking a Cl aqueous solution as a basic modification liquid, soaking the used sodium silicate sand, and carrying out NH treatment on different used sodium silicate sands4The concentration of the Cl aqueous solution varies from 0.1% to 30% due to NH4Cl is a true solution electrolyte, a solute is an ion, the radius is small, the solution viscosity is low, the diffusion and the permeation are easy, H + ions generated by the hydrolysis of NH4Cl replace Na + of water glass to promote the precipitation of silica gel, NH3 gas generated by a small amount of reaction escapes, so that the generated silica gel film is discontinuous, cracks exist, and the permeation of a modifier is facilitated, thereby completely replacing Na + in the water glass film of old sand from the surface to the inside of a reaction interface.
Adding CaCl into NH4Cl water solution2、MgCl2And AlCl3Any one, two or three of the three salts are combined to generate a repairing modified mixed solution, and CaCl in the mixed solution is added according to different sodium silicate used sands2、MgCl2And AlCl3The combined concentration of (A) varies from 0.1% to 30%. The three salts react with the water glass film of the used sand to form colloidal Ca (OH)2、Mg(OH)2Or Al (OH)3Most of the jelly will be combined with the modified silica gel to form a mixed film on the surface of the used sand reclaimed sand to wrap and protect the used sand reclaimed sand.
The preparation method for modifying and regenerating used sodium silicate sand disclosed by the invention has the following advantages:
1. the mixed membrane has a repairing effect on the surface of the reclaimed sand, and the strength and the stability of the mixed membrane are better than those of a single silica gel membrane due to the introduction of the colloidal metal hydroxide;
2. the mixed film can form a semi-molten glassy film at high temperature, and the semi-molten glassy film has poor fluidity compared with a liquid film formed by water glass at high temperature and certain cohesiveness, so that the strength of a sand mold at high temperature is improved;
3. the bonding strength of the mixed film, the water glass and the reclaimed sand is good, and in the experimental process, the data of the water glass sand mold made of the reclaimed sand with the mixed film, such as the adding amount of the water glass, the adding amount of the hardener, the 6-hour tensile strength, the 24-hour tensile strength, the hardening time and the like are basically equivalent to those of the natural sand;
4. in the experimental process, the collapsibility of the water glass reclaimed sand with the mixed film in the casting shakeout process is found to be better than that of natural sand, sand grains are basically kept intact, and the phenomenon of sintering together is hardly found.
Through a large number of experiments, the water glass film on the surface of the used water glass sand is embedded with the sand grains and is almost insoluble in water, and the water glass film is difficult to completely separate from the sand grains under the condition of not damaging the surface structure and the characteristics of the sand grains only by traditional regeneration methods such as scrubbing and the like.
At present, the water glass film on the surface of the used water glass sand is generally considered to be the main cause of the poor performances of the used water glass sand, and therefore, if the water glass film on the surface of the used water glass sand is modified into a substance which does not affect the performances of the reclaimed sand, the problem of the poor performances of the reclaimed sand of the used water glass sand is solved.
The most common method for modifying water glass is to convert the water glass into silica gel, and the most intuitive method is to reduce Na in reclaimed sand2The content of O. However, the water glass film on the surface of the used sand has two problems in the modification process:
firstly, the main component of the water glass film is high-modulus water glass which is hardly dissolved in water, and the reaction speed in the solution is very slow;
and secondly, once a compact silica gel film is generated on the surface of the water glass film of the used sand, the water glass film on the surface of the used sand is isolated from the modification solution, so that the further progress of the modification reaction is prevented.
Aiming at the first problem, the solution is heated to a certain temperature, the stirring is increased or the modification time is prolonged;
aiming at the second problem, the solution is to select a modifier with good diffusivity and permeability, prevent a compact diaphragm from being formed between the water glass membrane of the used sand and the modification solution, enable the modification solution to permeate into the water glass membrane of the used sand, continuously carry out the modification reaction and finally completely modify the water glass membrane into a silica gel membrane.
Although the water glass film on the surface of the used water glass sand can be modified into the silica gel film by adopting the two steps, Na in the reclaimed sand can be effectively reduced2The content of O, but in the process of practical experiments, the regenerated sand is still at a certain distance from the natural sand in the aspect of high temperature resistance even if the water glass film on the surface of the used water glass sand is completely modified into the silica gel film, and finally, the regenerated sand is concluded to be the reason of two aspects:
on the one hand, the strength of a silica gel film generated on the surface of used sand is insufficient, the used sand is easy to pulverize in the heating dehydration process, meanwhile, the used sand inevitably has the defects of cracks, shrinkage cavities and the like on the surface of the used sand after high-temperature casting, the mechanical strength of the used sand is also reduced, if certain repair is not carried out in the regeneration process of the used sand, the regenerated sand can be cracked or pulverized in the contact process with high-temperature molten iron, the strength and the refractoriness of a sand mold of the regenerated sand at high temperature are influenced, and the defects of sand inclusion and the like of a casting are easily caused.
On the other hand, the nature of the silica gel film is amorphous silica, the silica gel film is not a silica crystal, the activity of the silica gel film is very high, the reclaimed sand with the silica gel film is easy to react with added water glass in the casting process to generate high-modulus water glass, the high-modulus water glass can tightly wrap or even combine the reclaimed sand, and the problems of poor collapsibility, easy surface sintering of the sand mold, easy sand sticking of castings and the like in the sand falling process can be caused although the strength of the sand mold at normal temperature is improved.
Therefore, the simple silica gel film is not the optimal modified film of the used water glass sand, and the reasons that the molding sand after the regeneration of the used water glass sand has poor high-temperature strength and poor collapsibility and is easy to cause sand sticking of a casting are not simply the reasons that the refractoriness of the regenerated sand is insufficient, and the modified film has a great relationship with the problems that the regenerated sand has poor strength, is easy to pulverize and is easy to be combined with a water glass binder too tightly and even bonded into a whole.
The final modification requirements on the sodium silicate film on the surface of the used sand are as follows:
1. the water glass film on the surface of the used sand can be more thoroughly converted into a modified film by increasing the modification temperature or prolonging the modification time;
2. the water glass film on the surface of the used sand cannot be directly modified into the silicon gel film in the modification process, because the silicon gel film can prevent the modification reaction from being carried out;
3. the modified film must be tightly combined with the used sand and has a certain repairing effect on cracks on the surface of the used sand;
4. the modified film cannot influence the strength of the reclaimed sand mold of the water glass at normal temperature and high temperature, but cannot lead the reclaimed sand and the water glass binder to be combined too tightly, thus causing the problems of poor collapsibility of molding sand, easy surface sintering of the sand mold, easy sand sticking of the casting and the like during the sand falling of the casting.
The embodiments of the present invention have been described in detail with reference to the examples, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, and the scope of protection is still within the scope of the invention.
Claims (5)
1. A method for preparing used sodium silicate sand by modification and regeneration is characterized by comprising the following steps: the method comprises the following steps:
(1) preparing a modified solution: using NH4Aqueous Cl solution as base modification solution in NH4Adding a proper amount of metal salt mixture into the Cl aqueous solution to generate a repairing modified solution;
(2) soaking modification: soaking the used sodium silicate sand in the modified solution; soaking and modifying the used water glass sand in a thermal repair modification solution with a certain concentration for 10-120min, or soaking and modifying the used water glass sand in a normal-temperature repair modification solution for 30-200min, and stirring the used water glass sand at regular time in the modification process; the reaction equation is as follows:
Na2O·mSiO2·nH2O+2NH4Cl→mSiO2+2NaCl+2NH3↑+(n+1)H2O
Na2O·mSiO2·nH2O+CaCl2→mSiO2+2NaCl+Ca(OH)2+(n-1)H2O
Na2O·mSiO2·nH2O+MgCl2→mSiO2+2NaCl+Mg(OH)2+(n-1)H2O
3Na2O·mSiO2·nH2O+2AlCl3→mSiO2+6NaCl+2Al(OH)3+(n-3)H2O
2. the method for preparing the used sodium silicate sand by modification and regeneration as claimed in claim 1, which is characterized in that: the metal salt mixture is CaCl2、MgCl2And AlCl3One or a mixture of two or more of them.
3. The method for preparing used sodium silicate sand by modification and regeneration as claimed in claim 2, which is characterized in that: the mass percentage concentration of the metal salt mixture is 0.1-30%.
4. The method for preparing the used sodium silicate sand by modification and regeneration as claimed in claim 1, which is characterized in that: the NH4The mass percentage concentration of the Cl aqueous solution is 0.1-30%.
5. The method for preparing the used sodium silicate sand by modification and regeneration as claimed in claim 1, which is characterized in that: the thermal restoration modification solution is 50-100 ℃, and the normal-temperature restoration modification solution is 25-30 ℃.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114406187A (en) * | 2022-01-27 | 2022-04-29 | 福建弈尘环保科技有限公司 | Regeneration method of waste water glass casting sand, regenerated sand and casting mold |
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| CN1481950A (en) * | 2002-09-13 | 2004-03-17 | 李明星 | Renovation and reclamation process for silicate-bonded sand |
| CN105486801A (en) * | 2015-11-12 | 2016-04-13 | 武汉纺织大学 | Determination method for harmful compositions in used-sodium-silicate-sand surface adhesive film |
| CN110434280A (en) * | 2019-09-03 | 2019-11-12 | 南阳仁创砂业科技有限公司 | A kind of inorganic regenerating used method of waterglass |
| CN110523917A (en) * | 2019-09-09 | 2019-12-03 | 武汉纺织大学 | A kind of New Type Silicate old sand chemical regeneration method |
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2020
- 2020-03-31 CN CN202010247280.1A patent/CN111331071A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1481950A (en) * | 2002-09-13 | 2004-03-17 | 李明星 | Renovation and reclamation process for silicate-bonded sand |
| CN105486801A (en) * | 2015-11-12 | 2016-04-13 | 武汉纺织大学 | Determination method for harmful compositions in used-sodium-silicate-sand surface adhesive film |
| CN110434280A (en) * | 2019-09-03 | 2019-11-12 | 南阳仁创砂业科技有限公司 | A kind of inorganic regenerating used method of waterglass |
| CN110523917A (en) * | 2019-09-09 | 2019-12-03 | 武汉纺织大学 | A kind of New Type Silicate old sand chemical regeneration method |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114406187A (en) * | 2022-01-27 | 2022-04-29 | 福建弈尘环保科技有限公司 | Regeneration method of waste water glass casting sand, regenerated sand and casting mold |
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Application publication date: 20200626 |