RU2807405C1 - Method for producing alloy from thermite mixture - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention is related to a method for producing an alloy from a thermite mixture. A thermite mixture containing iron oxide and aluminium chips is prepared, the thermite mixture is loaded into a crucible, and an exothermic reaction is carried out to form a liquid alloy and slag. The thermite mixture is loaded into the crucible layer by layer, in at least four layers of equal mass. A layer of thermite mixture of the largest fractional composition is placed at the bottom of the crucible, then each subsequent layer of the mixture with a finer fractional composition than the previous layer is placed.

EFFECT: invention makes it possible to ensure stable occurrence of an exothermic reaction.

1 cl, 1 dwg

Description

The invention relates to a method for producing an alloy from a thermite mixture and can be used in metallurgy.

There is a known method for producing the alloy, which includes preparing a thermite mixture consisting of iron oxide, aluminum chips and fillers, its continuous loading into the reaction chamber, igniting the mixture and carrying out an exothermic reaction with the formation of liquid metal and slag, described in patent RU No. 2366723. This method makes it possible to recover iron from scale, but the exothermic reaction is unstable, because the speed of passage of the combustion front increases all the time, which reduces the safety of the reaction.

The closest in technical essence and achieved result is the method for producing the alloy described in patent RU 2637735, adopted by the applicant as a prototype. This method of producing an alloy from a thermite mixture involves preparing a thermite mixture containing iron oxide and aluminum chips as a reducing agent, placing the thermite mixture in a crucible and conducting an exothermic reaction in the crucible.

However, the exothermic reaction in this method proceeds at an uncontrolled speed and is unstable, which leads to increased gas formation, causing intense release of reaction products from the crucible in the form of splashes, this in turn leads to an increase in the volume of irretrievable losses of the reduced alloy and a decrease in the safety of the process.

The objective of the proposed technical solution is to stabilize the course of the exothermic reaction in the crucible when producing an alloy from a thermite mixture, which leads to reduced losses of the resulting alloy and increased process safety.

The achieved technical result is to ensure stabilization of the exothermic reaction in the crucible when producing an alloy from a thermite mixture.

The problem is solved due to the fact that in the method of producing an alloy from a thermite mixture, including preparing a thermite mixture containing iron oxide and aluminum chips, loading the thermite mixture into a crucible, carrying out an exothermic reaction with the formation of a liquid alloy and slag, the following differences are provided: loading the thermite mixture into the crucible in layers, at least four layers of the same mass, a layer of the thermite mixture of the largest fractional composition is placed at the bottom of the crucible, then each subsequent layer of the mixture with a finer fractional composition than the previous layer is placed.

What is new in the claimed method is that when producing an alloy from a thermite mixture in a crucible, the thermite mixture is loaded into the crucible in layers, in at least four layers of equal mass, a layer of the thermite mixture of the largest fractional composition is placed at the bottom of the crucible, then each subsequent layer is placed mixtures with a finer fractional composition than the previous layer.

Due to the fact that the thermite mixture is loaded into the crucible layer by layer, so that at the bottom of the crucible a layer of the thermite mixture of the largest fractional composition is placed, then each subsequent layer of the mixture is placed with a finer fractional composition than the previous layer, it is possible to reduce the burning rate of the thermite mixture during passage an exothermic reaction that passes from the layer with the smallest fraction of the mixture to the layer with the largest fraction of the mixture. It has been experimentally established that the burning rate of the thermite mixture decreases with increasing fractions of the initial components. The combination of layers of the thermite mixture makes it possible to ensure the burning rate of the thermite mixture in the crucible in the range of 1.4-15 kg/s⋅m ² . Carrying out the reaction from a layer with a finer fraction to a layer with a larger fraction makes it possible to reduce the reaction rate. This makes it possible to stabilize the course of the exothermic reaction in the crucible when producing an alloy from a thermite mixture, to make the course of the reaction in the thermite mixture smooth and stable, which leads to a decrease in losses of the resulting alloy and an increase in the safety of the process.

As the reaction progresses, the transition between layers is accompanied by a decrease in the reaction rate; this decrease occurs in jumps, and if there are fewer than four layers, then the magnitude of these rate jumps will be such that they will not contribute to the stabilization of the reaction. It was experimentally established that stabilization of the exothermic reaction is achieved by placing the thermite mixture in a crucible in at least four layers.

The arrangement of the thermite mixture in a crucible in less than four layers leads to a longer reaction in each layer, due to the characteristics of the layer, as well as a significant reduction in the burning rates of the mixture layers when moving from layer to layer, which does not guarantee stabilization of the alloy production process.

Layers of the same mass of different fractional compositions release the same amount of heat during the reaction, but the layer of the smaller fraction releases this amount of heat in a shorter period of time than the layer of the larger fraction.

When burning a thermite mixture that has not undergone fractional separation, the burning rate is determined by the average burning rate of the fractions that make up the mixture. The rate of reaction in dispersed mixtures laid in layers will also be determined by the average rate of passage of the combustion front in each layer. It has been experimentally established that fine-grained compositions of thermite mixtures have higher combustion rates compared to mixtures containing large fractions. To maintain average rates of the reduction reaction, it is necessary to form layers of thermite mixture of equal mass, but different fractional compositions. Thermite mixtures of different fractional compositions have the same calorific value, but due to different combustion rates, the intensity of heat release will be different. This property forms the basis of the claimed invention. Using thermite compositions with small particle sizes at the beginning of the method, an intense increase in heat is obtained in the reacting medium, which promotes the formation of liquid reaction products with a high temperature. Additionally, the use of a finer fraction at the initial stage eliminates the cooling of the reaction products and its uncontrolled inhibition or termination. When the combustion front moves together with the alloy of reaction products, covering the next layers containing particles of a larger fraction, the reaction rate decreases and the intensity of heat and gases decreases, which ensures the formation of new portions of reaction products and maintaining their temperature without melt emissions and excessive waste of the components of the thermite mixture

The method is carried out using a device shown schematically in the figure. The device contains a crucible 1, into which the thermite mixture is poured layer by layer, and an activator 2 for igniting the thermite mixture. A drain hole 3 is made in the bottom of the crucible 1. A mold 4 is coaxially installed under the crucible 1.

The method is carried out as follows. Prepare the thermite mixture. The thermite mixture is prepared based on obtaining the required mass of the alloy. For example, to obtain an alloy for pouring into a mold with a metal content of 2 kg, it is necessary to prepare 4 kg of thermite mixture, since the yield of the thermite alloy is on average 50% of the mass of the thermite mixture. When the thermite mixture is arranged in a crucible, for example, in four layers, the iron and aluminum oxide granules are sifted into four fractions, for example, 0.2-1.5 mm, 1.5-2.5 mm, 2.5-3, 2 mm and more than 3.2 mm. Next, a thermite mixture is created for each layer of the same mass, for our case - each layer is 1 kg, containing a certain fractional composition of components, i.e. iron oxide granules and aluminum chips by mixing them. We place the largest fraction at the bottom of crucible 1, forming a lower layer, on which layers of the thermite mixture with a smaller fraction are successively placed. In our case, four layers are obtained. Activator 2 starts the exothermic reaction. The top layer of the thermal mixture is ignited; reaction products are formed, which, together with the combustion front, move from layer to layer to the bottom of crucible 1. A liquid alloy is formed in crucible 1, on the surface of which there is slag. The liquid alloy is drained through the drain hole 3 into the mold 4.

Claims (1)

A method for producing an alloy from a thermite mixture, including preparing a thermite mixture containing iron oxide and aluminum chips, loading the thermite mixture into a crucible, conducting an exothermic reaction with the formation of a liquid alloy and slag, characterized in that the thermite mixture is loaded into the crucible layer by layer, at least in four layers of the same mass; at the bottom of the crucible a layer of the thermite mixture of the largest fractional composition is placed, then each subsequent layer of the mixture with a finer fractional composition than the previous layer is placed.