CS243639B1 - Method of cooling sludge from salt baths - Google Patents

Abstract

The method of cooling sludge from salt baths after it has been lifted out of the salt bath above the surface is solved in three phases. The lifted sludge is first cooled by air supplied from the surrounding area, then it is cooled by air with water vapor while simultaneously increasing the surface area of the sludge, up to a temperature of 40 to 60 °C. The last phase of cooling takes place in the aqueous solution of the salt bath, simultaneously with dilution at a solution temperature of up to 50 °C. Finally, after the sludge has been cooled, the salt bath solution is separated from the solid residue. The procedure is also suitable and safe for the cooling of alkaline melt sludge, where active components (hydride and sodium oxide) are present in concentrations of up to 0.5% by weight.

Description

The invention relates to a process for cooling sludge from an alkaline melt salt bath. Up to now, the cooling has been carried out in such a way that, after being pulled out of the salt baths, the sludge in the reservoir spontaneously cools for a long time before it can be washed away. The cooling time, depending on the amount of sludge, exceeds 2 days. In terms of occupational safety, flooding at higher temperatures cannot be performed because the sludge-water reaction is strongly exothermic and the presence of active substances (e.g. sodium oxide and hydride) further increases the exothermic reaction, which worsens occupational safety and hygiene conditions.

Said drawbacks are eliminated by the method of cooling the sludge from the salt baths of alkaline melts, where after the sludges are rolled out above the surface, they are gradually cooled from the temperature above the melting point of the bath according to the invention, which consists in cooling in three stages.

The process begins by cooling the sludge with air supplied from the outside to a temperature 50 to 100 ° C lower than the freezing point of the salt bath. This is followed by increasing the specific surface of the sludge by grinding it with a mixture of air and water vapor, while simultaneously hydrolyzing the active substances (hydride, sodium oxide) until the sludge temperature is reduced to 40 to 60 ° C and in the last step the grit is cooled. Dissolve in aqueous salt bath solution. The hydrolysis products of the active substances together with the alkaline bath pass into solution and thereby separate the soluble and insoluble sludge components.

The importance of the invention is that cooling of the sludge is ensured continuously and is particularly suitable for continuous operation equipment. The process can thus be mechanized to ensure better operational safety and hygiene conditions for the operator. Its utilization achieves a level of cooling of sludge and consequently enables even better disposal or treatment of waste. Significantly, the process allows safe disposal of sludge containing active substances (e.g. hydride and sodium oxide) up to 0.5% by weight.

Application example 1

The alkaline melt salt bath sludges were cooled successively in smaller portions (4-6 kg) from a temperature of 460 ° C, with a supply air flow, to 250 ° C, approximately 70 ° C below the melt temperature, after being rolled out of the bath. This was followed by further cooling of the sludge with a mixture of air and water vapor as the sludge surface grew to a temperature of 30 ° C. The final cooling phase was carried out in an aqueous salt bath solution at 35 ° C.

Application example 2

The salt bath sludges containing the active ingredients - hydride and sodium oxide - were rolled up gradually above the surface at 395 ° C and cooled by supply air to 240 ° C, approximately 80 ° C below the melting point of the melt. Cooling of the air / steam mixture reduced the temperature of the sludge, which increased the specific surface area by approximately 30x during cooling, to 50 ° C. This was followed by cooling in an aqueous salt bath solution at 40 [deg.] C. and, during cooling, the active substance content of 0.38 wt.

The method of cooling of sludge from salt baths can be used for sludge treatment or disposal, especially in metallurgical plants, where they are surface treated - descaled sheets, wires, pipes and strips of noble chrome, chromium-nickel and chrome-nickel-molybdenum materials.

Continuously drained descaling units can be used in the process according to the invention for continuous cooling under safe and hygienically safe conditions and the cooling can be followed by an improved sludge disposal or treatment process.

Claims (3)

OBJECT OF THE INVENTION of A method for cooling sludges from an alkaline melt salt bath, wherein after sludge is removed from the bath above the surface, the sludge is cooled successively from a temperature above the melting point of the bath, characterized in that the sludge is cooled in three successive phases. from the outside to a temperature of 50 to 100 ° C lower than the freezing point of the salt bath, followed by simultaneous enlargement of the specific surface of the sludge by crushing the air / water vapor mixture, and so the air / water vapor mixture passes through the sludge The pulp was cooled down in an aqueous salt bath solution. 2. Process according to claim 1, characterized in that, when cooling in an aqueous salt bath solution, sludges are simultaneously washed away, the separation of the solid and liquid phases being completed at a temperature of up to 50 ° C. 3. Process according to claim 1, characterized in that the hydride and sodium oxide residues are present in the sludge in concentrations of up to 0.5% by weight. % decompose and simultaneously decompose the products into the liquid phase.