SU775165A1 - Method of preparing alkaline melt - Google Patents

Description

one

The invention relates to the field of chemical cleaning of metals, in particular, steel from scale and burn.

A method is known for producing a melt from a mixture of alkalis with free alkali metals, such as the treatment of a melt of oxygen and oxygen with gas, which sparks through the melt at a temperature of 200-500 ° C. 1.10 The method was tested on a mixture of alkalis containing mainly KOH, NaOH, KN and NaH with a concentration of hydrides of 4 wt.%. Such a mixture is obtained in the production of metallic potassium and | 5 is a side industrial pro-. by duct

In this method, the free alkali metals (in the form of hydrides) are oxidized with oxygen-20 containing gas while bubbling it through the melt. The known method for the oxidation of free alkali metals in a hydroxide melt has the following advantages: a relatively complex 25 instrumental implementation of the method (a barbo device, a compressor, pressure sensors and gas flow rates, etc., are required); process safety is ensured by small jo

Ash baths. In large volumes of the melt, there is no even access to oxygen. In connection with this, a significant amount of alkali metal hydride is oxidized with evolution of hydrogen. An explosive mixture of oxygen and hydrogen is formed above the bath.

The purpose of the invention is to simplify the process and ensure safe working conditions.

The goal is achieved by taking sodium nitrate as the oxidant with its molar ratio to the free alkali metal, equal to (0.42-0.5) :.

The essence of the proposed method consists in the following.

A mixture of alkalis, containing mainly caustic soda, caustic potassium, and free alkali metals (in the form of hydrides), is heated and melted. Sodium nitrate is added to the liquid phase.

The introduction of nitrate provides fast and safe oxidation of alkali metals.

For example, for sodium, by the reaction: lONaH + NaNO, 7Na, O + +) Oxidation of {chain metals by nitrate proceeds rapidly (3-5 minutes), and gaseous products — oat nitrogen, which is not flammable. Moreover, a pad with a high nitrogen content is formed above the melt, which ensures the safety of the process.

The lower limit of the operating temperature at which the melt preparation is carried out is 280 ° C. At lower temperatures, the rate of oxidation of alkali metals with nitrate is markedly reduced. On the other hand, at temperatures above that, due to the very vigorous progression of this reaction. And low alkali viscosity, melt is carried away by the vapor of nitrogen. Therefore, we recommend that our optimum melt preparation temperature is 280-450 ° C.

Alkali metal nitrate is introduced into the melt in a calculated amount one time. The addition of nitrate at a rate of less than mol per 1 mol of alkali metal does not ensure complete conversion according to reaction (1). If the nitrate is introduced in the amount of a bolt: o our than 5 mol per 1 mol of alkali metal, this leads to its incomplete consumption, i.e. the presence of nitrate in the melt as a component. Maximum efficiency is ensured if molar is observed; Ratio (0 ,, 5): 1. Moreover, the nitrate is completely consumed for the oxidation reaction (1) and also partly for the binding of the colloid distribution of the lONa-t-2NaNO + N. (2)

The use of NaNOj as an oxidizing agent instead of purging the melt with oxygen allows to obtain an alkaline melt enriched with sodium oxide. The last component in the hydroxide environment is an activator of the process of cleaning the surface of metals from scale and burn. Thus, a melt with high reactivity to remove oxides from the surface of metals is obtained from a cheap product — waste from the production of metallic potassium.

Example 1. In the reactor, sequential melting of two initial mixtures was carried out. In this case, the melting of one mixture was carried out without sodium nitrate in an atmosphere of air. Small amounts of the initial mixture (20-25 g) were placed in a sealed reactor connected to a system that allows measuring the amount of evolved gas. The reactor, equipped with a lid with a hydraulic shutter, was heated to 280-32 ° C. The composition of the evolved gas was established by chemical analysis.

The data at ved1gny in tab. 1. As follows from Table 1, when melting a mixture of alkalis with free alkali metals under air, the main gaseous oxidation product of an alkali metal (in the form of a hydride) is hydrogen - 94.3% by volume. If nitrate was added to the melt in the proposed ratio, the main gaseous products were nitrogen and partially water. The process was completed 3-5 minutes after the nitrate was added.

, Table 1

Example 2 The mixture of alkalis for loading was taken in an amount of 0.1-0.5 kg.

The process was carried out using corundum crucibles placed in a furnace with a given temperature (280450 ° C).

The data are given in table. 2

As follows from the table. 2, the exposure of the mixture of alkalis with free alkali metals in air already in the amount of 100-112 g is accompanied by gas burning or microexplosion. It is dangerous to melt large amounts of the initial mixture: possible. In those experiments where sodium nitrate, burning or explosions were introduced with the appearance of the liquid phase, was not observed. The process proceeded calmly.

table 2

100.5

4,06280

4,52360

112.0

108.3

4,36450

19,39280 480.0

Thus, the use of sodium nitrate significantly simplifies the process of preparing an alkaline melt and ensures the safety of the process & num ber of the formation of Ng above the melt.

Claims (1)

1. USSR author's certificate No. 482506, cl. From 22 to 26/10, 15.05.73.