CS267563B1 - A method for disposing of waste tempering salts from thermal quenching processes and apparatus for carrying out the method - Google Patents

Abstract

The invention relates to a method and a device for the disposal of functionally exhausted mixtures of salt melts containing toxic ions, especially nitrites, barium, and possibly also cyanides, resulting from thermal hardening processes in the metal industry.

Description

The procedures used so far to remove the above-mentioned toxic wastes are a kind of way out of difficulties, which often cause storage of excessive amounts of useless and moreover water-soluble and highly toxic waste in metallurgical plants, but these procedures do not address waste disposal and disposal as required by needs. the environment. By incinerating the mentioned wastes, for example, the cyanide ion is disposed of into harmless components, but for example nitrite and nitrate ions - apart from the possibility of possible explosion in the incinerator - are often prevented quantitatively, such as intravenous exhalation into the air; barium salt ions, on the other hand, by combustion or High temperature or coal reduction preceding water-soluble barium hydroxide or hydrolysable barium sulphide and landfills of slag and fly ash risk leaching highly toxic barium ions into surface and groundwater. suitable only for the disposal of cyanide ions) and reduction procedures with wet urea (intended for nitrites) may not be as quantitative under operating conditions as ae assumes in the laboratory; in each case, these water processes also result in considerable amounts of very saline water fractions, and the handling and further disposal of which, for example by evaporation, results in unbearable additional costs, which make such liquidations difficult to realize. Even other processes, calculating, for example, the further oxidation of duitants to nitrates and their agricultural use, cannot be taken seriously in the conditions of metallurgical plants and cannot therefore be considered a suitable solution.

The above-mentioned drawbacks are eliminated by the method and apparatus for disposing of waste tempered salts from the thermal hardening processes according to the invention. The process according to the invention is generally carried out in such a way that the waste functionally depleted melt ae is gradually dissolved in an aqueous solution of sulfite or pyroulphite in the presence of ferrous iron ions, concentrated sulfuric acid being metered into the solution with vigorous stirring. The acid solution detoxified by the reduction of nitrites (and nitrates) to nitrogen and containing an insoluble barium sulphate precipitate is neutralized with solid hydrated lime, ev. the cyanides present are degraded on the alkaline side by chlorine or calcium hypochlorite to give potassium and sodium calcium chlorides and carbon dioxide and nitrogen, the detoxified mixture is mixed with powdered gypsum and left to solidify spontaneously; possibly ae shaped detoxified waste Still surface impregnated against ev. leaching of salts, for example by immersion in bitumen or gum asphalt aqueous emulsion. As a safeguard against salt leaching in the landfill.

An apparatus for carrying out the method according to the invention is illustrated by way of example in the attached figure. The device consists of a reaction vessel 6, provided with a plug-in submersible perforated waste tank 2, a reactor mixing high-speed turbine 3, a concentrated sulfuric acid tank 4 with a dosing device 5 and a safety emergency tank 6, and a fan-type advantage.

The above-mentioned exemplary embodiments and devices do not exclude or exhaust the possibilities of the invention, for example in the continuous version, nor do they exclude possible variations and changes in the concentrations of the excipients used and adaptations of the apparatus to the continuous version.

Example 1

In a 25 dm ³ vessel equipped with the accessories according to the attached figure, 5 kg of spent waste salt melt from the hardening bath, containing according to the analysis about 20.5 wt.%, Was gradually dissolved. % nitrite, 19 wt. % nitrates, 7.5 wt. % chlorides. 10.5 carbonates, 0.002 wt. % cyanides, 10.5 wt. % Na * and 13 wt. % K ⁺ ; of insoluble fractions was about 9 wt.%, of which 87 wt. % barium carbonate, the remainder being elemental iron and graphite. The following procedure was followed during processing:

5 kg of the above-mentioned waste was presented in the extended perforated container of the apparatus, which was 1/3 of the container immersed in a reaction vessel with 4 dm ^{3 of} service water with dissolved 0.5 kg of N82SO3 and 50 g of FeSO4. After starting the reactor with a high-speed stirrer, a total of 1.2 dm ^{3 of} concentrated HgSO 4 was metered in by means of a metering pump over a period of 60 minutes. The decomposition of the mixture took place at a reaction temperature of up to 55 ° C, practically without releasing any exhalations.

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The resulting aqueous suspension contained no nitrites, only a trace nitrate content was detected and all Ba ⁺⁺ ions were converted to the insoluble form of BaSO 4. Traces of cyanides were converted to insoluble calcium ferrocyanide in the following operation: a suspension of pH · 1 was neutralized with 700 g of powdered hydrated lime to pH · »7) 5. With the addition of 5 kg of powdered technical gypsum, the suspension is left in conical form after mixing for up to 2 days, spontaneously solidified, the fittings are impregnated with a bitumen emulsion and stored in a landfill without any liquid waste.

Example 2

A material very similar to that of Example 1, but containing 6 hn>. % CN 'was treated in a completely similar manner to the same using half the amount of sodium metabisulfite, i.e. 0.25 kg Na ₂ S ₂ ° 5 per 5 kg input waste; also the amount of concentrated acid required dropped to about half, i.e. to 700 cm 3. Neutralization with hydrated lime was performed up to pH 9.0 and in this phase the insoluble calcium ferrocyanide was subjected to degradation by chlorine gas to form calcium chloride, potassium, carbon dioxide and nitrogen. The resulting suspension did not show the presence of CN '. Further processing into gypsum blocks was quite similar to Example 1, including impregnation and penetration with a gum asphalt emulsion. ·

The waste was completely non-toxic, against ev. leaching of non-toxic salts and salinisation of groundwater were detoxified fittings Impregnated with surface protection with gum asphalt; the volume reduction of the waste was about 1/3 of the reduction at a slightly increased weight.

Claims (2)

1. Method for disposing of waste tempered salts from thermal hardening processes as well as blacking salts or degreasing salts containing significant proportions of toxic components, especially nitrites or barnet salts, or 1 cyanides, characterized in that solid solid waste ss gradually dissolves in aqueous solution of sulphite or pyrosulphite sodium from the addition of ferrous sulphate, the mixture is gradually acidified with concentrated sulfuric acid to pH - 1 during the dissolution of the waste, after which it is adjusted to pH 7.5 to 9.0 with solid hydrated lime, or any cyanides present are degraded by chlorine gas chlorine. smlsl with the same material content of gypsum powder as the mass of the original waste and is allowed to solidify in the specified forms, before the surface of the non-toxic fittings is preferably impregnated with, for example, a gum asphalt emulsion or a lumen for landfilling. 2. Apparatus for carrying out the process according to item 1, characterized in that it consists of a reaction vessel which is provided with a plug-in submersible perforated waste tank (2), a reactor mixing high-turbine turbine (3), a concentrated sulfuric acid tank (4) with a dosing device. (5) and a safety emergency scrubber (6), preferably of the fan type. The water-soluble toxic waste is gradually dissolved in an aqueous solution of elite or bisulphite, most often sodium, the solution being acidified with concentrated sulfuric acid. The acid detoxified solution is then neutralized with solid hydrated lime, any cyanide content is further degraded by chlorine gas or calcium chlorene, and the aqueous mixture is strengthened by the addition of gypsum, suitably shaped and optionally protected from damage and accidental leaching by impregnating the surface of deposition fittings. eg blumumen or gumfaltalt.