Analysis of Offline Regenerated Sand Casting Process

Offline regeneration process is a representative independent process technology that does not affect foundry production. Its technological process adopts the comprehensive treatment method of dry method + thermal method + dry method to convert a large amount of waste and old sand into high-quality recycled sand, which can be used as a commodity to replace the original and new sand and different types of foundry production sand. occasion. The off-line regeneration process is suitable for the production of independent and supporting small and medium-sized enterprises. It is an active, effective and reasonable resource reuse and an effective measure to reduce costs. At the same time, it also solves the worries for the waste sand treatment of foundry enterprises.

1. Main objects of offline regeneration processing
1.1 The sand agglomerates and agglomerates (stiff beans) of different shapes, sizes and qualities in the waste sand must be effectively crushed and screened.
1.2 The iron impurities mixed in the waste sand and the mixture (core) of different binders must be effectively screened, magnetically separated and necessary roasted.
1.3 Reasonable selection of core process equipment. Take advantage of its technological characteristics, give full play to the application advantages of off-line regeneration process equipment, and implement environmental protection measures (mainly related to the diffusion and emission of dust, flue gas and harmful gases).

2. Offline regeneration of waste sand.
A set of independent comprehensive regeneration technology scheme of dry method + thermal method + dry method is adopted, which is suitable for the process characteristics of conventional used sand regeneration, and considers the complexity of the source of used sand. By dry method + thermal method +
The comprehensive treatment of dry method makes the reclaimed sand meet the high-quality quality requirements, so that a large number of waste sand can be reborn through the regeneration process. At the same time, there is no large amount of waste discharge, which has little impact on environmental protection requirements.

3. Usually the selection types of sand regeneration are: dry method, wet method, thermal method and combined treatment method. It is generally believed that when the process conditions allow (considering the existing conditions of the factory), it is more economical and reasonable to choose dry regeneration first. For waste sand of organic fat casting type, it is more suitable to choose dry method + roasting combined regeneration. For more complex and unclear quality foundry waste sand, it is advisable to choose a combination of dry method + thermal method + wet method, which can achieve good sand regeneration effect. It is more economical and reasonable to choose the dry method to regenerate and reuse the waste sand of clay sand, and strengthen the treatment of strong grinding and dedusting. It is mainly aimed at the agglomeration (stiff beans) and dust in the clay sand, so that it can be regenerated after being crushed by strong grinding. The treatment of other iron impurities can be separated and purified by sieving and multi-channel magnetic separation. Sand temperature cooling is generally reasonable by means of air convection heat exchange (such as blast and vibration boiling cooling). There is also a dust removal system that can use the extrusion molding method of a wet screw mixer to avoid secondary pollution of the terminal.

4. Process design features
First of all, it must be emphasized that due to the complexity of waste sand, the process of off-line regeneration treatment is a targeted characteristic treatment process.
4.1 Process flow, the waste sand must be effectively decomposed and crushed (controlling particle size), secondary magnetic separation (cleaning iron impurities), roasting (removing film), cooling and screening (selecting particle size), grinding and crushing, and film removal. To ash, sand purification. Finally, the crushing, disintegration, loosening and cooling of complex waste sand agglomerates are realized. The organic lipid used sand can achieve the purpose of stripping, de-filming, de-ashing and rounding of inactive, brittle and collapsing inert films.

4.2 The comprehensive regeneration treatment method of dry method + thermal method + dry method mainly uses sand treatment equipment and core sand regeneration equipment to realize a high temperature resistance furnace heating method. These include: crushing and screening equipment, conveying equipment, roasting furnace, vibrating boiling cooling, powerful grinding and regeneration, secondary magnetic separation and air selection, etc., and finally quantitative packaging in the warehouse. The whole process is matched with a combined bag filter system.
It becomes an independent off-line regeneration process unit, and mechanized off-line production can be realized through the automatic control system.

4.3 Core sand regeneration equipment, including: trommel crushing and screening machine (loose decomposition), impact crusher (small block crushing), roaster (organic fat decomposition), vibration boiling cooler, powerful grinding and regeneration
machine, suspended strong magnetic separator, etc.

4.4 After the used sand is cooled, further particle purification of the regenerated sand is very important. Because one of the quality indicators of recycled sand is the requirement of sand particle purification. Under the premise of limited technical conditions and manufacturing costs, a reasonable process design scheme must be considered.

4.5 Thermal regeneration is generally implemented by means of high temperature combustion in a roaster. The raw materials burned in the roaster include natural gas, coal gas, light oil and other media, as well as the form of burning coal char, but the pollution is relatively serious, and it is currently a process type that is eliminated. Natural gas combustion is a process method widely used in the foundry industry at present. However, the existing problems are that the application cost of natural gas is high. Generally, small and medium-sized foundry enterprises are limited in the output of used sand regeneration treatment (insufficient regeneration amount, small-scale state), and the benefit cost is high (the value of producing qualified recycled used sand is much lower than market value of natural gas consumed). The investment cost of disposable sand regeneration treatment equipment is also high. Therefore, many owners are often discouraged from technical transformation. Natural gas roasting is not unique to thermal regeneration applications Yes, in addition to gas, there is also electric heating as a thermal regeneration process.

5. Quality characteristics of reclaimed sand
5.1 Analysis of the complexity of waste sand
5.11 Sand for conventional modeling: composed of 0.05~1.0mm quartz particles (usually called silica sand), generally smaller than 0.05mm quartz particles are called quartz powder.
5.12 Commonly used refractory materials include refractory clay (pottery clay), chrome sand, magnesia, chrome magnesia and other materials, which are used to prepare molding sand for large and heavy castings and alloy steel castings, and the material burning loss is about 10%.
5.13 Among the molding materials, the amount of recycled sand generally accounts for about 30% to 50% of the amount of new sand (1 t of waste sand per ton of castings). The complex substances that may exist in the waste sand include iron impurities, sintered bentonite (stiff bean), over-burned organic grease (brittle film), ferrochromium slag, surfactant residues, coal powder flake graphite mixture and organic impurities in the operation process. Room for things.

5.2 Controlling the quality indicators of regenerated sand According to the technical requirements of foundry sand, the quality control of waste sand after comprehensive regeneration treatment by the production line usually selects several main technical indicators: loss on ignition (regeneration of old sand with organic grease), particle size Distribution, acid residue (pH value), particle size uniformity (surface morphology) dust content and sand temperature control, etc.
5.21 The old sand agglomerates and particles after comprehensive regeneration treatment should be completely disintegrated, the quality of the sand grains should be uniform and round, and the ash powder and inerts of the old sand should be purified, so that the quality of the old sand is close to the performance of the original sand, and it should meet the relevant comprehensive quality indicators. skills requirement. However, the regeneration of old sand is not infinite. With the increase of the number of regenerations, the tensile strength of the molding sand will decrease, so the application occasion should be selected reasonably.
5.22 Temperature control of regenerative roaster: the roasting temperature of waste sand should be controlled at 300~400C, which can effectively control the release rate of organic grease and used sand. The temperature should not be too high, which will affect the cost.
5.23 The burning loss of organic grease used sand should be controlled below 2.0% and kept relatively stable, otherwise it will directly affect the performance of molding sand (when the burning temperature of used sand is 400C, the burning loss value can be reduced to more than 3.0%
Down).
5.24 Attention should be paid to strictly distinguish the properties of used sand mixtures such as resin sand, water glass sand, and clay sand (because the properties of water content, pH, dust and iron impurities are variable), and timely inspection and testing, and timely adjustment of production. process measures.

6. Advantages of offline regeneration technology
6.1 Offline regeneration treatment process
The off-line regeneration treatment process is an environmentally friendly measure for the centralized treatment of waste sand. It uses the waste sand of various enterprises for centralized regeneration treatment, which not only solves the problem of enterprises''''discharge of waste and used sand, but also provides enterprises with the reuse (re-sale) of recycled sand in production, which reduces the production cost of enterprises.
6.2 Offline regeneration process scheme
The overall layout first considers the external environment and the layout of the comprehensive regeneration treatment production line (the site requirements are not large), as well as the dust emission and dust collector system, waste sand logistics transportation, workshop production process and terminal waste treatment.

Qingdao Sanzhuji Equipment Manufacturing Co., Ltd. specializes in the production of Green Sand Molding Line,Self-hardening sand molding line,foundry machines,Sand molding machine,Sand casting equipment,sand mixer,GS high efficiency rotary mixer,Resin sand mixer,no-bake resin sand mixer,Jolt squeeze molding machine/Jolt-squeezing moulding machines,Multi- Piston Moulding Machine/Hydraulic multi-piston moulding machine,sand casting molding machine,sand reclamation equipment，foundry molding machine,flaskless moulding machine,shot blasting machine,dust collector,according to the amount of old sand recovered Carry out plan customization, and provide sand reclamation equipment installation, commissioning, and training. Welcome guests to visit the factory.