SU867883A1 - Method of waste water processing - Google Patents

Description

(54) METHOD FOR PROCESSING SEWAGE WATER

I

The invention relates to the recycling of wastewater, in particular, metallurgical production and can be used in the evaporation of wastewater containing sodium salts of the sulfide and sulfite series and alkaline earth metal hydroxide.

There is a known method for thermal processing of waste water from a metallurgical plant, which consists in evaporation of oil-containing solutions saturated with sodium salts, as well as industrial water from the pickling plant and chemical water treatment plant CHP containing calcium salts.

The process of evaporation is carried out in a multi-unit evaporator at a temperature of the boiling point 1 of the solution in the first housing. The distillate obtained from wastewater treatment is used to feed the boilers of the CHP plant and recycling water supply.

However, when processing wastewater containing sodium sulfide sulfide

And the sulphate series, known in terms, does not allow to obtain condensate suitable for feeding the CHP and recycling water without further purification.

The closest in technical essence and the achieved result to the proposed one is the way of wastewater containing sodium thiosulfates, sulfites and sulfides. AT

To this method, water purification from these salts is carried out by evaporation under vacuum at a temperature not exceeding 90 C. This method allows to obtain condensate suitable for circulating heating and boilers of the CHPG22.

The disadvantage of this method is its low cost due to the impossibility of using steam with a temperature above 90 s, especially

20 in the processing of large quantities of waste.

Claims (2)

It is impossible to increase the economics of the evaporation process by increasing the boiling point of the solution in the known process. This is due to the chemical instability of these solutions, with an increase in the boiling point of the solution above, the salts of the sulfide and sulfite series decompose. The optimal ratio of concentrations of alkali metal hydroxide and sodium salt is 1: 25-1: 20. When the ratio of alkaline earth metal hydroxide and sodium salt is higher than 1g25, the decomposition of sodium salts is observed at temperatures higher than. The process {decomposition of these salts is accompanied by the formation of gaseous products: hydrogen sulfide and sulfur dioxide. These gases, entering condensate, contaminate it, since they form sulfur and polycionic acids when interacting with each other. Distillate, content of these impurities, it is necessary to finish cleaning of the jSi heating surfaces of the pair of apparatuses periodically cleaned from sulfur. The purpose of the invention is to prevent the decomposition of sodium sulfides and sulfites during evaporation at 90-120 0. The goal is achieved by the fact that the evaporation of water containing sodium salts of sulfide and sulfite series and alkaline earth metal hydroxide is carried out at a ratio of concentrations of hydroxide alkaline earth metals and sodium salts of sulfide and sulfite series 1: 25-1: 20. The introduction of alkaline earth metal hydroxide into the solution to be evaporated increases the chemical stability of the solutions of sodium-containing sodium salts, which makes it possible to increase the solution charging temperature before and at the same time produce distillate not contaminated by the decomposition products of these salts. The ratio of components below 1:20 is impractical because it increases with alkali earth metal hydroxide consumption. The method is carried out as follows. Alkaline earth metal hydroxide is introduced into water to a ratio of alkaline earth metal hydroxide and sodium salts of sulfide and sulfite series 1: 20-1: 25 and subjected to evaporation with a continuous feed of water into the apparatus for evaporation to the centering of the effluent 10 times. p 1. Conduct processing Prim containing, mg / l: wastewater. NajSjOj N33504 Na, jS03 Ca (OH) 2 S is free Before evaporation, 84.9 mg / l of calcium hydroxide is added to water to a ratio of calcium hydroxide and sulfide and sulfite salts 1:20. The initial solution is poured into the apparatus for evaporation and o are heated to 90 ° C. The working pressure in the apparatus is 0.124 atm. Evaporation will be carried out with continuous supply of the solution until the effluent is concentrated in 10. time. A clear, odorless distillate is obtained, in which hydrogen sulfide, polythionic acids and elemental sulfur are not found. Example 2. The wastewater of the composition is treated as in example 1. Before evaporation, 62.7 ml / l of calcium hydroxide is additionally introduced into water (1:25 ratio), recharging is carried out at 90 s and an operating pressure of 0.124 atm. The odorless dihydrate is obtained, free of hydrogen sulfide, polythionic acids and elemental sulfur. Example 3. The wastewater is recycled under the conditions of Example 1, but evaporation is carried out at an operating pressure of 1.95 atm. A clear distillate is obtained that does not contain hydrogen sulfide, polycionic acids and free sulfur. Example 4. Water treatment is carried out under conditions of example 2, but evaporation is carried out at 120 ° C and a working pressure of 1.95 at. A clear distillate is obtained which does not contain hydrogen sulphide, polytyonic acids and free sulfur. Distillate obtained by evaporation of wastewater at a ratio of alkaline earth metal hydroxide and sodium salts 1: 20-1: 25 does not contain polythionic acid hydrogen sulfide, elemental sulfur. Carrying out the evaporation process in the temperature range of 90-120 ° C significantly increases the economics of the process, as it allows the use of steam with a higher temperature, unlike the known method. Claims A method for treating wastewater containing sodium salts of sulfide and sulfite series and alkaline earth metal hydroxide by evaporation, characterized in that, in order to prevent decomposition and sulfites at 90-120 ° C, evaporation is carried out at a ratio of sodium sulfide and sulfite p do: alkaline earth metal hydroxide 1: 25-1: 20. Sources of information attributed to the examination during the examination 1. Yurkin B.C. Installation for the utilization of saline wastewater from the metallurgical plant. Water and sanitation equipment, P 5, 1974, us. ten. 2. Azbel I.A. Nose forging soda gas purification from hydrogen sulfide. M., Goskhimizdat, 1956, p. 50.