CS252233B1 - The method of reducing the loss of silver in the thermal treatment of solid photochemical waste - Google Patents

Abstract

The solution consists in adding small amounts of barium carbonate, which reduces the volatilization of halides. Various wastes containing barium carbonate can also be used. The invention can be used in the photochemical and pigment industry in waste disposal and also in the metallurgical recovery of metallic silver from the ashes of photochemical wastes.

Description

The invention relates to a method for reducing silver losses in the thermal treatment of solid photochemical wastes.

Solid waste from the photochemical industry is mainly photo paper and film material. Furthermore, it may also be some combustible filter baffles (e.g. peat) used to trap silver containing particles from photochemical waste water. These solid wastes are often thermally treated - they are incinerated in either continuous or discontinuous furnaces. Most of the silver is most often in the form of silver halide (mainly silver bromide) and goes to ash. This is then processed metallurgically to obtain metallic silver. However, during these thermal processes (especially in the combustion of solid photochemical wastes), part of the silver halide is volatilizing (silver bromide noticeably at 700 ° C). The halide exits in fumes with flue gases and reduces the yield of the entire process, which in discontinuous combustion is then about 75% of silver and often less than 65% in continuous combustion.

Thus, silver losses represent one quarter to more than one third of its total content in photochemical waste; at an elevated combustion temperature, for example due to the disposal of waste with a higher proportion of film material, losses may be even greater. Moreover, after the condensation of the vaporized silver halide in the flue gas, the silver-containing microparticles formed are readily introduced into the space, which entails environmental problems due to their possible oligodynamic effects.

The method of reducing silver losses in the thermal treatment of solid photochemical wastes, according to the invention, is characterized in that the combustion of these wastes is carried out with the addition of barium carbonate in an amount of at least 0.001 wt. %, preferably from 0.025 to 0.05 wt. per 100 wt. parts of waste. The carbonate source may also be various waste media, for example, concentrated carbonate sludge obtained in the removal of barium ions from some wastewater, or paper or plastic packages used to transport carbonate, which are heavily contaminated with carbonate after use and have disposal problems.

Barium carbonate binds the silver halide during the combustion of photochemical wastes, preventing it from volatilizing or at least significantly reducing it, depending on the combustion temperature used. At the same time, decomposition or volatilization of the carbonate itself practically does not occur, which is advantageous because it is classified as so-called other poisons? moreover, it is used only in very small quantities. It is therefore possible, if the basic conditions of hygiene are respected in waste handling, to eliminate its possible adverse consequences. In addition, by preventing or reducing the volatility of silver compounds, or reducing it to the flue gases, the adverse environmental consequences associated with their oligodynamic effects are eliminated or reduced.

Advantages of the method according to the invention:

- reduction of silver losses during thermal treatment of solid photochemical wastes

- facilitating the recovery of metallic silver in the metallurgical treatment of ash

- low cost, use of existing facilities

- recovery and recovery of barium carbonate-containing wastes

- preventing or reducing the escape of silver-containing particles into the flue gases and the resulting ecological consequences.

Example 1

000 kg of solid photochemical waste (photo paper) was overlaid with waste paper packaging from the transport of barium carbonate containing 500 g of carbonate residues. After incineration in a discontinuous furnace, the recovered ash contained 88.8 i of silver from its original total in solid photochemical waste, which is 11.5% more than incineration without the addition of barium carbonate.

Example 2

To the continuous furnace, while burning solid photochemical wastes containing an increased proportion of film wastes, concentrated barium carbonate waste sludge was added in an amount of 0.025 wt. parts by weight of carbonate per 100 wt. parts of photochemical waste. The ash analysis showed 83.2% of the total silver content in the starting waste, which is 15.2% more than in the case of incineration without the addition of barium carbonate.

Claims (1)

SUBJECT OF THE INVENTION Method for reducing silver losses in thermal treatment of solid photochemical waste, characterized in that the waste incineration is carried out with the addition of barium carbonate in an amount of at least 0.001 wt. %, preferably 0.012 to 0.05 wt. per 100 wt. parts of waste.