WO2014118397A1 - Method for melting aluminium chips - Google Patents

Abstract

The invention relates to a method for melting aluminum chips. The aim of said method is to reduce the initial investment which involves the initial acquisition of the existing equipment for said purposes, at the same time being able to work with small quantities of chips, which renders the method according to the invention useful to the user who either only melts aluminum chips or performs other activities which involve working with aluminum and producing chips that are currently treated as waste. This method for melting aluminum chips is performed in a furnace, preferably a crucible-type furnace, and comprises a series of steps.

Description

 "ALUMINUM CHIEF FUSION PROCEDURE"

- Descriptive memory -

Object of the Invention

 More specifically, the invention relates to a new method of melting aluminum chips, in which crucible or similar furnaces are used, by means of which and with the corresponding heat input and without any prior drying operation of the chip, it is merged.

State of the art.

 The process of melting aluminum shavings by means of a rotary kiln is currently carried out by means of a chamber preferably cylindrical. Said rotary chambers are equipped with one or two doors with the function of loading / unloading, and are positioned at the ends of said chamber where at least one of them the chip is introduced.

The heat necessary for melting the chip is provided by means of a fuel or gas burner, within the same chamber where the chip is melted. To minimize direct contact between the flame and the chip, a significant amount of salts is applied to the surface of the chip. The flame heats both the chamber and the refractory that covers it internally, and in this way the chip is melted. Another of the known procedures and the use is the fusion of the chip by immersion of the same in a vortex generated by a pump, and recirculation of the Liquid metal. For the practice of the same, a previously treated chip is required to remove any remaining moisture that may contain, for example, water, oil taladrina and others.

 Said fusion process is carried out in an oven with a main chamber of liquid aluminum and an auxiliary chamber, which is where the vortex is separated. These two cameras are connected in such a way that the generated vortex ends up dragging the flow towards the main chamber. To create this vortex, a pump specially designed for this is used. At the same point of the vortex is where the previously treated chip is dosed, and is absorbed immediately.

 The disadvantages of the chip melting process by rotary kiln, disclosed to date are:

It requires an important investment for its purchase and installation.

 It needs to be economically viable for a significant volume of chips for the production of each laundry.

 Salts are required to protect aluminum.

It is mandatory to have a large capacity oven with liquid metal.

 The gases generated in the chip fusion are in contact with the aluminum.

 Danger when opening one of the doors that an aluminothermic process is generated.

On the other hand, if the chip fusion system is used with the pump vortex system, the following inconveniences have been detected: A high investment is required for its implementation.

 To be profitable it is necessary to use an important volume of chips, in each filling of the oven.

 Before its fusion the chip needs a previous treatment.

 It is obligatory to work with an oven with liquid metal in continuous.

 The combustion gases are in contact with aluminum.

 The process generates the immersion of aluminum oxides in the main chamber, reducing the purity of aluminum.

The disadvantages of the oxidation of aluminum have their origin in that it is a very electropositive chemical element, consequently, it has a high oxidation potential and is an energy reducing agent. However, it is very resistant to corrosion, both by water and by air. This is because, on its surface, a layer of A1203 aluminum oxide is formed that protects it.

Purpose of the Invention

Reduce the initial investment that presupposes the initial acquisition of the aforementioned equipment while it is possible to work with small amounts of chips which makes it possible for the process and equipment of the invention to be useful to the user who only dedicates himself to the fusion of aluminum chip or others activities, in which aluminum is worked and chips are produced that are currently treated as waste, assuming an additional cost to the manufacture of the product in question its disposal.

Description of the Invention

 The melting process of the aluminum chip is carried out in an oven, preferably of the crucible type.

 The procedure is started by preheating the oven until it reaches a starting temperature of the IT process, if it is not previously heated. Said process start temperature IT is preferably between 500 and 600 ° C.

 Once said temperature TI has been reached, the process of filling (or loading) said furnace through its upper part is carried out for a certain period of time ti.

 Said process can be carried out directly or preferably indirectly and gradually through a feeding element, such as a double hopper, and without using any pre-drying treatment.

 In the second case (indirect and gradual loading) the loading process operates in such a way that the chip level gradually decreases, and once the chip is heated due to the heat transmitted through the walls of the feeding device, the it is falling by gravity inside the oven, while the oven is still being loaded superiorly to its full capacity.

The period of time that lasts the process of top loading of chips in the oven is preferably between 1 and 3 hours. The mentioned period of time that lasts the process of top loading of chips in the oven is between 1 and 3 hours.

 The oven temperature is then increased

5 until reaching a maximum temperature inside the oven T2 between 600 and 800 ° C, so that at this temperature the chip melts and passes into a liquid state, while in this melting phase all the non-metallic evaporation content,

0 for which the corresponding smoke outlet can be provided at the top.

 Optionally, in the case of having large furnaces, it is possible at this stage to homogenize the temperature of the molten chip that is

5 found inside the oven by applying an inert gas preferably applied to the bottom of the oven, which removes the chip and homogenizes the temperature gradient of the molten chip. For example, in the upper part of the interior of the oven

, 0 the chip can have a temperature of 650 ° C, while in the lower part of the interior of the oven the molten chip can have a temperature of 900 ° C. By applying an inert gas, it is possible to homogenize said temperature gradient reaching

, 5 an average temperature between the maximum and minimum values, thereby achieving a better quality and homogeneity of the molten chip.

 Said inert gas may be Nitrogen, Argon, Chlorine, or other similar gases.

0 The liquid aluminum deoxidation process is then started, for this purpose, according to a characteristic of the invention, a vigorous stirring in the laundry by means of a stirring element in order to achieve that a vortex with liquid aluminum is generated within it, at the same time as it is a second characteristic of the invention to make a contribution of flux or similar material, preferably between 500 and 2000 gr. of flux per ton of molten aluminum, with stirring and vortex being maintained for a certain time, for example between 1 to 3 minutes, in this way all the oxides accumulated on the surface of the broth, are easily removed, obtaining an optimum quality of liquid aluminum

 In the stirring stage the stirring element is preferably a propeller.

 In said stirring stage, the stirring of the laundry can optionally be carried out in one direction and then in the opposite direction for a short period of time, in order to improve said stirring process. In this case, the stirring element preferably rotates at a speed between 850 to 1,000 rpm in one direction, and between 440 to 640 rpm in the opposite direction; and preferably the rotation time of the stirring element is in a direction between 0.45 to 1.5 minutes, and in the opposite direction between 30 to 60 seconds.

 The fusion process ends with the elimination of the oxides, and it is cast.

In order to improve the filling of the furnace crucible, and as it is one of the preferred objects of the invention, it has been projected that for said filling a feeding device of the double-hopper type is preferably used, so that the process of load It is carried out gradually and the volume of the hopper is adequate to that of the crucible, with the walls of the hopper receiving the heat of the crucible so that the chips are heated by heat transfer through the walls of the hopper before fall into the oven crucible joining the filling.

 Other details and characteristics will be revealed in the course of the description given below, in which reference is made to the tables and graphs cited, by way of illustration but not limiting the different yields of the procedure.

Description of an embodiment of the invention.

 In a specific embodiment of the invention, the applicant has carried out field tests using specifically car tire machining chip, the chemical composition of said chip being AlSi7Mg (A356), with a non-metallic content of 2% between the moisture of the water and the cutting oil, the following results have been reached:

 The procedure is started with the preheating of the oven up to 550 ° C, the oven is loaded with the help of a double hopper, and as the chip level decreases, the oven continues to load until the end.

 The oven continues to be heated for one hour after loading with a maximum temperature of 755 ° C.

Then a stirring of the laundry is carried out for which a designed rotor is used especially for this, and 450 gr are added. of a special flux approximately 2kg per ton.

 Stirring and vortexing is maintained at 950 rpm for one minute, and at 540 rpm for 45 seconds in reverse.

 The oxides of the broth are removed, and it is strained.

The iron content of the alloy chips has been analyzed in order to quantify the iron contribution that is made in the chip melting process, and the result is 0.13% by weight, by emission spectrometry ICP-OES optics, and during the test it was possible to measure the moisture and chip oil content, with a result of 2.1%.

One of the granulometry tests performed to determine the size distribution of the chip in a specific case of the invention has revealed the following data:

 TABLE 1

However, the process object of the present invention can be applied for any type of chip, without being limited to the chip size shown in the table above. Also, a graph is reproduced below by bar chart of the percentage of material retained.

 9.34 mm 4.76 mm 2 mm 1, 18 mm BASE

 sieve lights

GRAPH 1

Finally, using a second bar chart graph, the results obtained with the weight of the ingot and the slags obtained and the total yield achieved are visualized:

Ingot I

Human waste

performance

 Wash

GRAPH 2 In one of the preferred embodiments of the present invention, the recommended fusion process comprises the following steps:

Preheating the oven until reaching process start temperature values between 500 and 600 ° C.

 Top loading of the chip into the oven gradually depending on the capacity of the oven, with the help of a feeding device such as a double-hopper or similar or equivalent device.

 Increase in the oven temperature until reaching values between 730 and 780 ° C.

 Stirring of the laundry to create a vortex, using a propeller or similar element and adding flux in amounts between 1.5 to 2.5 kg. per ton of chip. As an example, the rotor is rotated at a speed between 900 to 1000 rpm for a period of time between 0.5 to 1.5 minutes, and between 30 to 60 seconds at a rotation speed between 500 to 600 rpm in reverse.

 The oxides of the broth are removed, and it is strained.

Described sufficiently the present invention in correspondence with the attached figures, it is easy to understand that any modifications of detail that are deemed convenient may be made therein, provided that the essence is not altered of the invention which is summarized in the following claims.

Claims

R E I V I N D I C A C I O N E S: I ^a - "ALUMINUM CHIEF FUSION PROCEDURE" of those who use heat input both on the oven walls and on the chip mass by adding during the melting process to suppress direct contact between the flame and the chip a significant amount of salts, characterized in that the process comprises the following steps: Preheating the oven to an IT temperature, in case the oven is not already preheated.  Once the TI temperature is reached, an upper loading process is carried out in the oven top loading process in the oven gradually over a period of time ti, so that the chip is fed into the upper part of the oven and once said chip is heated by gravity falls inside the oven, while the oven is still being loaded superiorly until it reaches full capacity.  The temperature of the furnace is increased until it reaches a temperature inside the furnace T2, so that at this temperature the chip melts and passes into a liquid state, at the same time that in this melting phase all the non-metallic content is released by evaporation Next, stirring of the laundry is carried out, for which a stirring element is used, adding an amount between 500 and 2000 gr. of flux for every ton of cast aluminum. The oxides of the broth are removed, and it is strained. 2 ^a - "VIRUTA FUSION PROCEDURE OF ALUMINUM "according ^to claim 1, characterized in that the temperature of the chip inside the oven can optionally be homogenized in step 3 of increasing the oven temperature by applying an inert gas preferably applied in the lower part , which removes the chip. ₃ a _ "ALUMINUM CHIEF FUSION PROCEDURE" according ^to claim 1, characterized in that the stirring element is a propeller. a _ "ALUMINUM CHIEF FUSION PROCEDURE" according ^to claim 1, characterized in that the stirring of the casting of step 4 is optionally carried out in one direction, and then in the opposite direction for a short period of time. 5 ^a - "ALUMINUM CHIEF FUSION PROCEDURE" according ^to claim 4, characterized in that in stage 4 the agitation of the stirring element is performed at a speed between 850 to 1,000 rpm in one direction, and between 440 to 640 rpm in the opposite direction. 6 ^a - "ALUMINUM CHIEF FUSION PROCEDURE" according ^to claim 4, characterized in that the rotation time of the stirring element in the Stage 4 in one direction is between 0.45 to 1.5 minutes, and in reverse direction between 30 to 60 seconds. ₇ a _ "ALUMINUM CHIEF FUSION PROCEDURE" according ^to claim 1, characterized in that the TI temperature of step 1 is between 500 and 600 ° C. ga _ ^« ALUMINUM CHIEF FUSION PROCEDURE" according ^to claim 1, characterized in that the period of time that lasts the process of top loading of chips in the oven is between 1 and 3 hours. 9 ^a - "PROCEDURE OF VIRUTA FUSION OF ALUMINUM "according ^to claim 1, characterized in that the process of top loading of chips in the oven is carried out by means of a feeding element placed in the upper part of the oven. 10 ^a - "ALUMINUM CHIEF FUSION PROCEDURE" according ^to claim 9, characterized in that the feeding element is a double hopper, provided with a wall heating system from the oven heat, which transfers the heat to the chip that is inside said double hopper. 11 ^a - "ALUMINUM CHIEF FUSION PROCEDURE" according ^to claim 1, characterized in that the temperature T2 of step 2 is between 600 and 800 ° C. 12 ^a - "ALUMINUM CHIEF FUSION PROCEDURE" according ^to claim 8, characterized in that the temperature T2 of step 3 is about 700 ° C. 13 ^a - "ALUMINUM CHIEF FUSION PROCEDURE" according ^to claim 1, characterized in that the inert gas can be Nitrogen, Slang or Chlorine. 14 ^a - "VIRUTA FUSION PROCEDURE OF ALUMINUM "according ^to claim 1, characterized in that the melting process is carried out in a crucible furnace.