DE2318079A1 - Heat-treating refuse in oscillating conveyor - with radiator arranged over it, esp. for foundry sand - Google Patents

Abstract

Refuse especially foundry sand is supplied at one end of a refractory oscillating trough and is moved downstream underneath a radiator (10-20 cm above) which is heated by gas lead in co- or counter-current to the refuse. The gas is burnt on the surface of the radiator without a flame. The impurities, e.g. resin, is used foundry sand are burnt away. The trough may be oscillated by a magnetic or unbalanced weight drive.

Description

Device for the thermal treatment of bulk materials It is in der Technik Ublicn, bulk goods for the purpose of drying, calcining, des To be treated thermally roasting or glowing. Temperatures of up to 900 ° C are required for this required, which are produced in special annealing furnaces.

A special area of application is the thermal regeneration of Foundry sand. Molding sand in foundries contains quartz sand as a basic component various additives, for example clays or synthetic resins as binders. By the nonen temperatures during pouring, the sand is heated very strongly. As a result, a certain proportion of the quartz grains will be smashed, so that if they are repeated several times Circulation can result in a high level of dust accumulation in the sand.

At the same time, some of the additives are annealed. These substances lose then their effect and are only contained as ballast in the surrounding sand.

So that the malleability of the sand remains old, it is necessary to to regularly excrete the constituents that have changed due to temperature effects and you can replace new fabrics.

Due to the special composition of molding sand, it is completely impossible only the splintered resin components and the annealed additives need to be eliminated. You therefore help yourself to a certain amount before reprocessing Remove used sand and replace it with fresh materials. In this way you have the guarantee that the surrounding molding sand has approximately the same shape properties retains.

The used sand removed is not for use in the foundry more suitable. It was therefore previously stored in heaps without hesitation. That has However, there are significant disadvantages, since the used sand still contains many harmful organic components that can have a negative impact on groundwater. The one practiced earlier Landfilling is therefore not sustainable in the long term. In addition, the retired contains Used sand always has a certain proportion of still usable quartz grains that pass through the storage on the stockpile is lost for further use.

The process is therefore also quite uneconomical.

Today we are starting to regenerate the used sand that has been separated out and only to store the harmless, no longer usable portion on the heap. The aggregates enveloping the quartz grain, for example synthetic resin binders, are completely burned in a thermal regeneration. The purified quartz components can then be used again as new sand after the shattered grains have been separated out be used. If the elimination is too costly, all of the used sand, which after thermal regeneration is free from harmful organic components is brought to the dump.

A static bed can only be influenced thermally very slowly, because the thermal conductivity of sands is very low. The same disadvantage exists when the sand is conveyed on conveyor belts. For thermal treatment So a certain loosening of the sand is necessary.

Besides the way the sand is exposed to thermal treatment it is also very important how the heat source is assigned to the sand to be treated is. Both factors work together to determine the efficiency of a system for the thermal treatment of bulk materials, especially foundry molding sand.

According to the invention a device is proposed which is characterized is through a vibratory conveyor trough that transports and loosens the sand and a heat radiator arranged above the vibrating conveyor chute. The radiant heater is preferably used as a beam wall for the flameless surface combustion of heating gas educated.

During the transport on a vibrating conveyor trough, a continuous one takes place Circulation and mixing of the material to be treated. The individual particles will be thus exposed to the heat to a far greater extent than is the case with bulk material at rest would be possible. The goods are moved according to the micro-throwing principle.

A similar effect is obtained when the transport is carried out in a fluidized bed achieved using a carrier gas. There is also a loosening up of the sand. However, the disadvantage here is an undesired sighting and whirling up of dust.

In addition, bulk goods with a greater spread can be transported with the vibrating conveyor the grain size are transported. It is even possible to use those existing in the old sand To transport lumps and iron constituents, what happens when they are transported in a fluidized bed leads to considerable difficulties.

The beam wall is preferably 10-20 cm above the surface of the bulk material arranged in a fixed or hinged hood. Through flameless combustion a gas-air mixture creates infrared radiation that directly hits the loosened Treatment good acts. A portion of the generated heat of combustion is by convection transferred to the estate.

The inventive combination of a vibrating conveyor trough with one The heat radiator arranged above the item to be treated has significant advantages affect the thermal treatment of bulk materials of all kinds. In particular can these advantages can be used in the thermal regeneration of foundry sand, since here a complete combustion of the organic components with as little as possible Effort is to be aimed for.

The main advantages are: As a result of the intensive heat emission thanks to the radiant heater, the heating-up time is short. The large-area heating source guarantees uniform heat output that is easy to regulate. Since no burners no burner noises occur.

An oxidizing, neutral or reducing atmosphere can be used on request can be set. The area of application is therefore quite diverse.

The vibration creates a homogeneous temperature distribution in the Bulk material layer achieved, whereby also deeper layers are covered. local overheating is avoided. Due to the relative movement between the conveyed goods and contact surfaces, the formation of a boundary layer is avoided, so that a high heat transfer is present.

The conveyor trough has no mutually moving or one on top of the other sliding parts. The transport is therefore very gentle.

The conveying speed can be adjusted by changing the amplitude and frequency and thus continuously adjust the dwell time of the goods in the area of the radiant heater.

Further details of the invention are from the accompanying drawing, which represents an embodiment can be found.

They show: FIG. 1: A device in side view and FIG. 2: A cross section through a device.

The vibrating conveyor 1 is mounted on springs 2 and is through a known unbalance or magnetic drive 5 in motion law. The support takes place by supports 4, which are anchored in the foundation. The item to be treated passes through the funnel 5 onto the transport trough 6 made of heat-resistant Material and is discharged at the end of 7.

The heat radiator 8 is mounted on the supports 9 in a vibration-free manner and consists of a porous jet wall 10 with an upstream mixing chamber 11. The heating gases can be in cocurrent or countercurrent with natural or artificial Train to be passed over the estate. In the case shown, they are fed through the funnel 12 discharged. The furnace chamber is sealed off from the atmosphere heat-resistant aprons.

As a result of the good mixing and the favorable allocation of the heat source the bulk material results in an optimal degree of efficiency.

Claims (2)

Claims 1. Device for the thermal treatment of bulk materials, in particular of foundry sand, g e k e n n n z e i c h n e t d u r c h one that transports the sand and loosening vibratory conveyor trough (1) and one arranged above the same Heat radiator (8). 2. Apparatus according to claim 1, d a d u r c h g e k e n nz e i c h n e t that the heat radiator (8) as a beam wall (10) for the flameless surface combustion is formed by heating gas.