SU1433632A1 - Method of regenerating waste sand-betonite moulding and sand-resin mixtures - Google Patents

Abstract

The invention relates to foundry, specifically to thermo-hydraulic regeneration of sand from waste sand-bentonite molding and sand-resin core mixtures in shops of small and medium casting under conditions of large-scale and mass production. The purpose of the invention is to improve the quality of regenerated sand and reduce energy consumption. The method of regeneration of mixtures involves their magnetic separation, screening with the imparting of the oversize product, subjected to oxidative roasting, and the undersize product, mixing these products in a ratio of 1: (5-20), respectively, hydraulic polishing, washing, dehydration and drying. (L G: 00 00 9: with to

Description

The invention relates to foundry production, namely, to thermohydraulic regeneration of sands from spent rock-bentonite molding and sand-resin core mixtures in shops of small and medium casting under conditions of large-scale and mass production.

The purpose of the invention is to improve the quality of regenerated sand and reduce energy consumption.

The goal is achieved by agreeing to the method of regenerating sand-bentonig molding and sand-resin nong core mixtures, including magnetic separation, screening with separation of the superlattice product being crushed, and the undersize product, mixing these materials with oxidizing roasting, scrubbing, scrubbing, washing, dismantling, dismounting, washing, dismantling, dismantling, dismantling, dismantling, dismantling, dismantling, dismantling, dismantling, dismantling, disintegrating, dismantling, washing, dismantling, removing and drying, mixing the above-sieve and under the sieve products is carried out after calcining the above-sieve product at a ratio of 1: (5-20).

The method is carried out as follows.

The spent mixture is subjected to magnetic separation using an overhead separator and sieved on a vibrating screen with a hole size of 10-20 mm. The screen grater is ground on a rotary crusher and roasted at 700-800 ° C in a kiln, then the resulting material is cooled and mixed with the sub-screen rumble product in a ratio of 1: (5-20). The blended material is sent to a hopper, from where it enters a drum scrubber for mixing with water, in a spiral classifier. Then the material is directed to the hydraulic rubbing on the scouring mashes (with a pulp density of 50-73% solid), for washing in a spiral classifier and dewatering on a vacuum belt filter. The dehydrated regenerated sand is dried, cooled in a fluidized bed drying and cooling unit and fed by a pneumatic transport system to the warehouse.

The implementation of oxidative roasting of only the sheath of the product is necessary because most of it consists of pieces of defective rods and incompletely burned rods. Used baking roasting

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The burning of residues of resin binder, which has a positive effect on the quality of the regenerated material, since it eliminates the accumulation of harmful organic impurities. However, the oversize product also contains chunks of the molding sand-bentonite mixture. The active bentonite in this mixture during the oxidative roasting process is chamotised, which further reduces the efficiency of hydraulic regeneration and leads to a decrease in the quality of the regenerate obtained.

In practice, it was found that mixing the above-sieve and sublattice products in a ratio of 1: (5-20) is optimal because it allows oxidative roasting to be carried out in order to remove organic binders, and at the same time does not degrade the quality of the obtained regenerate, since the content of bamotonite is bentonite in the specified amount of subsurface product does not have a significant effect on it.

When mixing the oversize product with the undersize in a ratio of more than 1: 5, the quality of the regenerate deteriorates due to the increase in the proportion of fireclay bentonite.

During oxidative roasting, only the oversize product, the amount of which in the total mass of the mixture is 5–20%, reduces energy consumption by 80–95%. 5 Bentonite in the undersize product is eliminated and the removal of binder residues from the surface is facilitated. grains of sand in the process of hydro-regeneration.

Thus, the proposed regeneration method makes it possible to improve the quality of the regenerate, improve the physicomechanical properties of the rod mixture prepared on its basis, and at the same time significantly reduce the energy consumption during thermal and hydraulic regeneration.

Example. A representative sample of the spent mixture of the KamAZ foundry is crushed on a 10 mm sieve. The amount of oversize product is 10%. Under laboratory conditions, the oversize product is crushed on a rotary crusher and the oxidizer} is burned at 800 ° C in laborer3.

torn drum furnace. After cooling the sand to 20-3 () C, it is mixed with the undersize product in a ratio of 1:10.

The mixed product is subjected to hydraulic pereeepaip H on a laboratory bench, the technological chain of which simulates a hydraulic regeneration complex installed at the KamAZ foundry and includes operations of rubbing sand grains from binder residues, washing, dewatering and drying the material.

As the proportion of the oversize product in the composition of the spent mixture increases from 1:10 to 1:20, the quality of the regenerated sand decreases slightly. The tensile strength after 30 seconds of cure decreases from 0.30 to 0.27 MPa in the hot state and from 2.43 to 2.25 MPa in the cold state. This is due to the negative effect of the shyrotized bentonite formed during the repeated pouring of the molding sand.

By reducing the proportion of the oversize product to a ratio of 1:25, the quality of the regenerated sand is markedly reduced. The strength of the core mixture after 30 seconds of curing decreases to 0.18 MPa in the hot state and to 1.85 MPa in the cold state.

An increase in the proportion of the oversize product in the composition of the spent mixture over a ratio of 1: 5, for example 1: 1.5, indicates the presence in the composition of the oversize product a significant content of molding sand-bento nitrite mixture. The intake of this mixture into the oversize product indicates an increased moisture content of the sand-bentonite mixture, which makes screening the grain 10-20 mm in size difficult. The ingestion of a significant amount of the sand-bennet of the tonite mixture into the oversize product, which is subsequently calcined, leads to a decrease in the quality of the obtained regenerated sand.

Thus, the strength of the core mixture prepared on regenerated sand obtained from the spent mixture with an oversize to undersize product ratio of 1: 1.5 decreases to 0.2 MPa in the hot state and 1.64 MPa in the cold state.

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A core mixture is prepared from the recirculating sands obtained and produced sample 1C 1 to determine tensile strengths. The core mixture has the following composition,%: sand 100; iron oxide 0.5; a mixture of resins KF-90 and FPR-24 in a ratio of 2: 1-2; catalyst based on Cu (NOj) 2 0.5.

Q It has been established that samples from the regenerate obtained in a known manner have low strengths after. 10 s heating in a rod box. Samples from regenerate obtained

5 by the proposed method, have a large initial strength, and the strength of the samples obtained at high exposures in the core box is higher than the corresponding strengths of the samples,

20 manufactured in a known manner by 30-40%. At the same time, the fluidity and survivability of core mixtures are the same and satisfy industrial requirements.

25 Improving the quality and improving the physicomechanical properties of the regenerate obtained by the proposed method, in comparison with the quality and properties of the regenerate obtained by the well-known method, makes it possible to use it for partial replacement of fresh sand in the manufacture of rods in hot boxes. If the regenerate obtained by a known method was used only to refresh the molding sand-bentonite mixture, then the regenerate obtained by the proposed method can be used in the core mixture by 30-50%,

Q According to a known method, during oxidative roasting in a furnace of the design used, 68 m of natural gas is consumed per 1 ton of regenerate. In the proposed method, the amount of gas consumed per pound is reduced to 20 m per 1 ton of regenerate.

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Claims (1)

Invention Formula The method of regeneration of waste sand-bentonite molding and sand-resin core mixtures, including magnetic separation, screening with the release of oversize product, subjected to crushing, and undersize product, mixing these materials, oxidative annealing, hydraulic scrubbing And washing, dehydration and drying, different , that, with the aim of raising 514336326 The quality of the regenerated sand product is carried out after calcining and reducing energy consumption, mixing the superlattice product at their ratio of the superlattice and sublattice 1: (5-20).