A regeneration process of spent sodium silicate sand for steel casting and a brand new sand and sodium silicate sand

Abstract

The application belongs to the field of casting, and particularly relates to a regeneration process of water glass old sand for steel casting and a water glass new sand. The regeneration process comprises the following steps: crushing the water glass old sand for steel casting to obtain crushed old sand; wet scrubbing the crushed old sand, and then sequentially dehydrating and drying the wet-scrubbed old sand to obtain dried old sand and sludge after dehydration; detecting the conductivity of the dried old sand; when the conductivity of the dried old sand is less than 500 us / cm, screening the dried old sand to obtain first regenerated sand; and when the conductivity of the dried old sand is greater than or equal to 500 us / cm, sequentially roasting and grinding the dried old sand to obtain ground powder and second regenerated sand. The regeneration process can effectively remove the residues on the surface of the water glass old sand, so that the performance of the water glass old sand is close to that of the new sand or the water glass new sand, the solid waste generated in the regeneration process can be recycled, the solid waste is treated, the cost of purchasing new sand is saved, and the strength of the water glass new sand is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of casting, and particularly relates to a regeneration process of water glass old sand for steel casting and brand new sand and water glass new sand. BACKGROUND

[0002] Casting steel products are widely used in the fields of nuclear energy, military industry, aerospace and the like, and the development of cast steel parts is extremely crucial. More than 60% of the cast steel process adopts sand casting, and since the water glass sand process has excellent characteristics of environmental protection and good high-temperature resistance, the performance of the water glass sand used for steel casting is particularly important. The main component of water glass is sodium silicate, and after pouring molten steel, the sodium silicate on the surface of the water glass sand is sintered, and the water glass old sand is obtained after the sand of the castings is cleaned. Every year, about one million tons of water glass old sand is buried and treated, and it is particularly important to develop a regeneration process of cast steel water glass old sand.

[0003] In the prior art, there are the following schemes:

[0004] 1. Patent CN111482554A discloses a method for preparing regenerated sand from water glass old sand, which comprises the following steps: primary crushing, water washing and impurity removal, secondary crushing, heavy separation and impurity removal, immersion in a surface modification liquid, aging, and drying. The surface modification liquid is used to immerse the water glass old sand after heavy separation and impurity removal in the surface modification liquid for a certain period of time to perform surface modification. After the surface modification is completed, the modified state is maintained for a certain period of time to allow the water glass sand to age and form a silicon gel film, and the water glass sand after aging is dried at a low temperature to obtain regenerated sand.

[0005] 2. Patent CN115889685A discloses a water glass sand wet regeneration system based on precious sand and a working method thereof. The old sand is sent to a buffer sand warehouse through a conveying device, transported and respectively passed through a sand-water pre-mixer, a vertical sand washer and a sand-water separator, and then enters a sand-water separation bin. The wet sand in the sand-water separation bin is subjected to pressure filtration until the water content in the old sand is lower than a threshold value. The old sand with a water content lower than the threshold value is output to a screw feeder through a vibrating feeder, conveyed into a drying machine for drying, and finally the dried sand is cooled in a sand cooler to obtain regenerated sand. Finally, the cooled regenerated sand is sent to a production workshop sand warehouse through a conveying device for storage or use.

[0006] 3. Patent CN114260418A discloses a casting water glass sand dry regeneration and utilization device and a using method thereof. The device comprises a crushing and sand milling device, a dust removal device and a sand collecting box. The device adopts a 3-axis tire, which increases the stability of the sand storage box on the 3-axis tire, and the old sand added to the sand storage box increases the milling pressure of the tire, so that the milled old sand can be self-milled and self-debinding. Since the tire and the sand are soft and abrasive, the debinding effect is improved, and the original sand shape is not damaged, so that the recovery rate reaches about 80%.

[0007] However, the above patent documents are all for single water glass old sand regeneration, and the application conditions of water glass sand are not considered, in fact, water glass sand is used in the process of casting aluminum, cast iron and cast steel, however, the temperature of casting aluminum is about 700 DEG C, the temperature of cast iron is about 1400 DEG C, and the temperature of cast steel is greater than 1500 DEG C, and different casting temperatures have a great influence on the performance of water glass old sand. The above prior art uses a single way to regenerate water glass sand, which is obviously unreasonable.

[0008] In addition, unlike the general organic waste sand used for casting, the sodium silicate on the surface of the water glass old sand is inorganic and non-combustible, and the traditional thermal regeneration process cannot realize the recycling of the water glass old sand.

[0009] Therefore, based on this, the technical scheme of the present application is proposed. SUMMARY

[0010] In order to solve the problems existing in the prior art, the present application provides a regeneration process for water glass old sand for cast steel, which comprises the following steps:

[0011] (1) crushing the water glass old sand for cast steel to obtain crushed old sand;

[0012] (2) wet scrubbing the crushed old sand, and after completion, sequentially dehydrating and drying to obtain dried old sand and sludge after dehydration;

[0013] (3) detecting the conductivity of the dried old sand;

[0014] (3-1) when the conductivity of the dried old sand is < 500 us / cm, the dried old sand is sieved to complete the regeneration process;

[0015] (3-2) when the conductivity of the dried old sand is ≥ 500 us / cm, the dried old sand is sequentially calcined and ground to obtain ground powder and regenerated sand, and the regeneration process is completed.

[0016] In order to facilitate the understanding of the present application, the principle of the regeneration process of the present application is described:

[0017] Firstly, through wet scrubbing, the friction between the sand particles and the water solubility of the active water glass can remove 60% of the active water glass on the surface of the old sand, and the sand particles can be collected after dehydration. The sludge is mainly composed of active water glass.

[0018] Secondly, the water glass old sand after wet scrubbing is dried by batch dryer, and the electric conductivity of each batch is detected. The water glass on the surface of the old sand with electric conductivity < 500 us / cm is basically removed or only inactive water glass which is vitrified is left. Therefore, the performance of the first regenerated sand is basically close to that of the new sand, and the first regenerated sand can be used as new sand for sand casting. The content of active water glass on the surface of the old sand with electric conductivity ≥ 500 us / cm is high, and the second regenerated sand needs to be calcined and ground. The calcination process is to make the water glass on the surface of the old sand brittle, and the grinding process is to remove the surface residues by friction between the sand particles. However, the second regenerated sand has more active water glass on the surface which is difficult to remove completely, and has high alkalinity. If the second regenerated sand is used in cold box, coated sand and other sand casting processes, the risk is high, and the second regenerated sand can only be used to prepare new water glass sand.

[0019] Finally, the sludge collected in the wet scrubbing process and the grinding powder collected in the grinding process are used to prepare the enhancer. The main component of the sludge is active water glass, and the main component of the grinding powder is silicon dioxide. When the enhancer is added in the preparation of new water glass sand, the strength of the new water glass sand can be increased by 10% to 20%, and the waste is recycled, thereby reducing the cost.

[0020] Preferably, in step (1), the particle size of the crushed old sand is ≤ 16 mesh.

[0021] Preferably, in step (2), the stirring speed of the wet scrubbing is 120 to 720 r / min.

[0022] Preferably, in step (2), the dehydration is to 3% to 6% of water content, and the drying rate is 1 to 5 t / h.

[0023] Preferably, in step (3-2), the calcination temperature is 200 to 400°C, and the calcination time is 30 to 300 min.

[0024] Preferably, in step (3-2), the grinding speed is 1000 to 6000 r / min.

[0025] Based on the same technical concept, another purpose of the present application is to provide a new sand, which is the first regenerated sand according to claim 1.

[0026] Based on the same technical concept, another purpose of the present application is to provide a new water glass sand, which comprises the second regenerated sand, a binder and an enhancer.

[0027] Preferably, the weight ratio of the second regenerated sand, the binder and the enhancer is 100:1 to 5:0.1 to 0.3.

[0028] Preferably, the enhancing agent is prepared by mixing and stirring the dehydrated sludge with the ground powder.

[0029] Preferably, the weight ratio of the dehydrated sludge to the ground powder is 1:0.5 to 1, and the stirring time is 1 to 10 minutes.

[0030] The beneficial effects of this invention are as follows:

[0031] The regeneration process described in this invention involves a series of steps including crushing, wet scrubbing, dehydration, drying, conductivity testing, calcination, and grinding. This process effectively removes residues from the surface of old water glass sand, making its properties close to those of virgin sand or new water glass sand. Simultaneously, it allows for the reuse of solid waste (dehydrated sludge and grinding powder) generated during the regeneration process. This not only treats the solid waste but also saves on the cost of purchasing new sand and improves the strength of the new water glass sand, achieving multiple benefits. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0033] Example 1

[0034] This embodiment provides a recycling process for water glass waste sand used in cast steel, which includes the following steps:

[0035] (1) The old water glass sand for casting steel is mechanically crushed to below 16 mesh to obtain crushed old sand and sent to the old sand silo;

[0036] (2) The crushed old sand is transported from the old sand silo to the wet scrubbing tank by a bucket elevator and stirred and scrubbed at 120 r / min. After completion, the sand and water are separated by a dewatering screen to obtain dewatered sludge and dewatered old sand with a moisture content of 3%.

[0037] (3) The dehydrated old sand is conveyed to the batch dryer by a screw feeder. Each batch is dried by 300 kg and the drying speed is 1 t / h to obtain dried old sand.

[0038] (4) The conductivity of the dried old sand was tested and the result was 79 μS / cm. Therefore, the dried old sand was screened and used directly as new sand, and the regeneration process was completed.

[0039] Example 2

[0040] The embodiment provides a regeneration process of water glass old sand for cast steel and a preparation method of water glass new sand, which comprises the following steps:

[0041] (1) The water glass old sand for cast steel is mechanically crushed to 14 meshes or less to obtain crushed old sand and is sent to an old sand bin;

[0042] (2) The crushed old sand is sent from the old sand bin to a wet scrubbing barrel through a bucket elevator, is stirred and scrubbed under the condition of 720 r / min, and after completion, is subjected to sand-water separation through a dewatering screen to obtain dewatered sludge and dewatered old sand with a water content of 6%;

[0043] (3) The dewatered old sand is sent to a batch dryer through a screw feeder, the drying weight of each batch is 500 kg, the drying speed is 5 t / h, and dewatered old sand is obtained;

[0044] (4) The dewatered old sand is subjected to conductivity detection, and the result is 510 us / cm;

[0045] (5) The dewatered old sand is put into a calcination furnace, is calcined under the condition that the calcination temperature is 300 DEG C for 60 min, is grinded in a grinder under the condition that the rotating speed of a grinding wheel is 1800 r / min, grinding powder generated in the grinding process is collected, and the second regenerated sand is obtained, and the regeneration process is completed.

[0046] In a subsequent stage, the second regenerated sand, the dewatered sludge and the grinding powder, and a binder can be combined to prepare the water glass new sand, and specifically,

[0047] (i) The dewatered sludge and the grinding powder are mixed according to the weight ratio of 1:1, are stirred for 10 min, and an enhancer is obtained;

[0048] (ii) The second regenerated sand, the binder and the enhancer are mixed according to the weight ratio of 100:2.5:0.2, and the water glass new sand is obtained.

[0049] Comparative Example 1

[0050] The comparative example provides a regeneration process of water glass old sand for cast steel and a preparation method of water glass new sand, which is different from the embodiment 2 in that the calcination process of the embodiment 2 is not adopted, and other implementation manners and conditions are the same as those of the embodiment 2.

[0051] Comparative Example 2

[0052] The comparative example provides a regeneration process of water glass old sand for cast steel and a preparation method of water glass new sand, which is different from the embodiment 2 in that the grinding process of the embodiment 2 is not adopted, and other implementation manners and conditions are the same as those of the embodiment 2.

[0053] Comparative Example 3

[0054] The present comparative example provides a regeneration process of water glass old sand for cast steel and a preparation method of water glass new sand, which is different from example 2 in that the reinforcing agent in example 2 is not used, and other embodiments and conditions are the same as those in example 2.

[0055] Test example

[0056] The new sand obtained in example 1, the water glass new sand obtained in example 2 and comparative examples 1 to 3 were tested, and the results are shown in table 1.

[0057] Table 1

[0058]

[0059] Note: The test reference standard is GB / T 2684-2009, and the conductivity tester model is DDSJ-308A.

[0060] From table 1, it can be seen that:

[0061] 1. The new sand obtained in example 1 and the water glass new sand obtained in example 2 are very close in performance compared with commercially available new sand, proving that the regeneration process of the present application achieves good results.

[0062] 2. Comparing example 2 with comparative example 1, the removal of the roasting process increases the conductivity of the regenerated sand by more than 80%, the acid consumption value increases by about 3 mL, the clay content also increases by 450%, and the tensile strength decreases by nearly 60%. It is shown that: without the roasting process step, the removal rate of surface residues of the regenerated sand decreases significantly, the conductivity is high, the acid consumption value is high, the clay content is high, which directly affects the use strength of the regenerated sand.

[0063] 3. Comparing example 2 with comparative example 2, the removal of the grinding process increases the conductivity of the regenerated sand by nearly 80%, the acid consumption value increases by about 1.2 mL, the clay content also increases by 2550%, and the tensile strength decreases by nearly 30%. It is shown that: without the grinding process step, the removal rate of surface residues of the regenerated sand decreases significantly, the acid consumption value is high, the conductivity is high, and the clay content increases sharply, which directly affects the use strength of the regenerated sand, and the large increase in clay content also brings great risk to the sand sticking defects of castings.

[0064] 4. Comparing example 2 with comparative example 3, the tensile strength decreases by more than 50% after removing the reinforcing agent. It is shown that: the reuse strength of the regenerated sand without adding the reinforcing agent is low, and the effect of the reinforcing agent of the present application is significant.

[0065] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A process for the regeneration of spent sodium silicate sand for casting steel, characterized in that, The regeneration process comprises the following steps: (1) crushing the used water glass sand for casting steel to obtain crushed used sand; (2) wet scrubbing the crushed used sand, and then dehydrating and drying the wet-scrubbed sand to obtain dried used sand and sludge after dehydration; (3) detecting the conductivity of the dried used sand; (3-1) when the conductivity of the dried used sand is less than 500 us / cm, screening the dried used sand to obtain first regenerated sand, i.e. completing the regeneration process; (3-2) when the conductivity of the dried used sand is greater than or equal to 500 us / cm, roasting and grinding the dried used sand to obtain ground powder and second regenerated sand, i.e. completing the regeneration process; The regeneration process further comprises mixing the sludge after dehydration obtained in step (2) and the ground powder obtained in step (3-2) to prepare a reinforcing agent.

2. The process for regeneration of spent sodium silicate sand for casting steel according to claim 1, characterized in that, In step (1), the particle size of the crushed used sand is less than or equal to 16 mesh.

3. The process for regeneration of spent sodium silicate sand for casting steel according to claim 1, wherein, In step (2), the stirring speed of the wet scrubbing is 120-720 r / min.

4. The process for regeneration of spent sodium silicate sand for casting steel according to claim 1, wherein, In step (2), the dehydration is performed to a water content of 3-6%, and the drying rate is 1-5 t / h.

5. The process for regeneration of spent sodium silicate sand for casting steel according to claim 1, wherein, In step (3-2), the roasting temperature is 200-400 DEG C, and the roasting time is 30-300 min.

6. The process for regeneration of spent sodium silicate sand for casting steel according to claim 1, wherein, In step (3-2), the grinding speed is 1000-6000 r / min.

7. A virgin sand characterized in that, The brand new sand is the first regenerated sand of claim 1.

8. A water glass fresh sand, characterized by, The water glass new sand comprises the second regenerated sand, a binder and a reinforcing agent of claim 1.

9. The water glass new sand according to claim 8, characterized in that, The weight ratio of the second regenerated sand, the binder and the reinforcing agent is 100:1-5:0.1-0.

3.

10. The water glass new sand according to claim 8, characterized in that, The preparation method of the reinforcing agent comprises mixing and stirring the sludge after dehydration and the ground powder; the weight ratio of the sludge after dehydration and the ground powder is 1:0.5-1, and the stirring time is 1-10 min.

Images