SU812755A1 - Method of purifying acid iron-containing waste water - Google Patents

Description

This invention relates to methods for purifying iron-containing wastewater from sulphate and mixed etching by neutralization with lime milk and can be applied in ferrous metallurgy and other industries.

There is a known method of stabilizing the leaching waters of the pickling compartments for the purpose of using them in the circulating water supply, in which, for a more complete crystallization of calcium sulfate, gypsum seed Ij is fed to the neutralized washing water ..

The disadvantage of this method is that the preparation of gypsum seed requires a large amount of deficient sulfuric acid. Moreover, the preparation of seed itself requires special additional equipment and does not intensify the process of clarifying neutralized water.

The known method of purification of acidic iron-containing wastewater includes neutralization with lime milk, separation of the mixture into reused water and sludge, which is then subjected to crystallization by heating and aeration and returned to the neutralization stage 2 ... With this method, the volume of water that should be removed from the system to prevent the formation of deposits is 25% or more, depending on the initial composition, temperature ... and other conditions. A higher degree of water utilization in circulation leads to the formation of gypsum deposits due to the fact that the planting of gypsum from supersaturated solutions on recycled sediment occurs slowly.

The purpose of the invention is to intensify the process of purifying acidic iron-containing waste water by accelerating the separation of the mixture and the crystallization of sulphate-calcium in recycled water.

The goal is achieved by adding a magnetite / gypsum mixture in a 1: 2-3 ratio to 1/43/4 sediment (by volume) returned to neutralization and mixing.

Mainly stirring is carried out at 20-80 ° C for 10-120 minutes

The method is carried out as follows.

Acidic iron-containing wastewater is neutralized with lime milk to a pH of 8-10. The mixture is divided into recycled water containing calcium sulphate and sediment. The precipitate is removed from the settling tanks to aerators, where it is subjected to crystallization. To 1 / 4-3 / 4 (by volume) sludge is added a mixture of magnetite with gypsum in the ratio of 1: 2-3, then return to the stage of neutralization of wastewater and stirred for 10-120 minutes at.

The limits of the supplied magnetite and gypsum are due to the fact that when the mass of gypsum is reduced, the size of the active surface of the part is insufficient to accelerate the crystallization of calcium sulfate from water. Increasing the amount of gypsum to the added one, against this, does not affect the increase in the rate of the crystallization process, and will require additional costs for obtaining gypsum.

In tab. Figure 1 shows the data for the removal of calcium sulfate supersaturation by recycling sludge.

. Seal of Ogg from

9,2 zpzm. pr mzh: vnny waters

Compacted sludge from sludge industrial water + 1/2 of its volume a mixture of magnetite and gypsum in a ratio of 1: 2

Compacted sludge sediment in water

+ 1/2 of its volume is a mixture of magnetite and gypsum in a ratio of 1: 4

Compacted sediment from the sludge wash water + 1/2 of its volume a mixture of magnetite and gypsum in a 1: 1 ratio

As can be seen, the decrease in the amount of gypsum in the added mixture is lower than 1: 2 (up to 1: 1) dramatically reduces the degree of removal of supersaturation: calcium sulfate (34% versus 16%), while an increase in interp in the mixture to the ratio 1: 4 almost does not affect the final concentration of calcium sulfate in clarified water 2.50 g / l (13% supersaturation) versus 2.58 g / l (16% transfer) The amount of recycled (fed to neutralization) sediment is from 1 / 4 to 3/4 of the total, preferably 1/2 by volume. The volume of returned sludge is due to the fact that chuo at a lower dose of it, the effect of compaction of sediment in the settling tank is insignificant, and at a higher dose

Table

40.0

3.11

16,0

2.58

13.0

2.50

34.0

2.98

the load on the settling tank and the cost of recycling the sludge increases, while the effect of compaction does not significantly change. .

The most preferable is the return of half the volume of the precipitate, since this is agreed upon by the ease of dosing. 5 An increase in the volume of recirculated sludge above 3/4 in volume leads to its most compacting and a decrease in humidity, but due to the increase in the total mass of the sludge, it does not lead to a decrease in its volume. When: TO / 1I reduction in recirculated sludge below 1/4, the overall effect (compaction and moisture reduction) is insignificant. The duration of mixing is related to the seed dose and temperature. At the usual

(25C) temperature requires not less than two hours stirring, ifpH increase in temperature from 25 to, it is reduced to 10 minutes with the same seed dose.

Compacted sediment from sludge wash water and 1/2 a mixture of magnetite with gypsum in a ratio of Example 1. Wash water composition, g / l: Fe (total.) 0,70; HjS04 0.30, the amount of chloride - and nitrate - ion 0.10; The sum of ions of manganese, zinc, copper 0.2 is prepared by dissolving technical salts and acids in water. The acidic water (in the amount of 2 l) is neutralized with lime milk to a pH of 8.6 in a porcelain cup and clarified in measuring cylinders with a capacity of 1 liter. New portions of salts and acid are added to the clarified water to produce water of the above composition. The precipitate from the cylinders is heated to 60 ° C and aerated with compressed air to be converted into crystalline ferrous oxide. A mixture of magnetite with gypsum in a ratio of 1: 2, respectively, in an amount of 50% by weight of the pulp is added to the obtained, compacted sediment. A neat portion (2 l) of acidic water is neutralized with lime milk to a pH of 8.9, and the resulting compacted precipitate with a mixture of magnetite and gypsum / neutralized water is added with neutralization and mixed at 120. The sulphate content calcium, the concentration of which is 2.42 g / l. Example 2. The acidic water of the composition indicated in example 1 is neutralized with lime milk to a pH of 9.1 at 50 ° C. At the time of neutralization, a compacted sludge is added to the beaker with the addition of a mixture of magnetite and gypsum. The amount of the additive amounts to 30% of the compacted weight. draft. Compacted sludge is obtained from sludge

; The data on the effect of temperature on the duration of the mixing time and the residual concentration of calcium sulfate in clarified water are given in Table. 2

Table 2 of the previously rationalized acidic water by heating to compressed air before the inlet. Neutrgized water is mixed with additives for 45 minutes. The concentration of calcium sulfate in clarified water is 2.48 g / l. Example 3. Wash water of the same composition as in the first two examples is neutralized with lime milk to a pH of 9.17 at 80 ° C. When neutralized, a precipitate is added to the water with the addition of a mixture of magnetite and gypsum. The amount of additive is 50% of the mass of sediment, the ratio of magnetite and gypsum in the added mixture was 1: 2, respectively. The neutralized water with additives is dragged for 10 minutes at. The concentration of calcium sulfate in clarified water is 2.43 g / l. Thus, in all three examples given, the degree of supersaturation of calcium sulfate in the clarified; water does not exceed 10-13% and, therefore, the amount of fresh water needed to blow the circulating water supply system can be reduced to 10-13%. The proposed method of purifying acidic iron-containing wastewater allows for the process of their clarification and crystallization of CLEANED sulphate. The technical and economic efficiency of the method is determined by an increase in the degree of use of water in the system: rotary water supply, while at the same time preventing it. education. gypsum deposits, which reduces

the cost of additional treatment of water before it is discharged into reservoirs, as well as reduce the cost of operating the working cycle.

Claims (2)

Invention Formula A method for purifying acidic iron containing wastewater, including neutralizing it with lime milk, separating the mixture into reusable water and sludge, which is then crystallized by heating and aeration and returned to the neutralization stage, characterized in that, in order to intensify the process by accelerating the separation of the mixture and crystallization of calcium sulfate in recycled water, to 1 / 4-3 / 4 of sediment (by volume) returned to neutralization, add a mixture of magnetite with gypsum in a 1: 2-3 ratio and stir ayut. 2. A method according to claim 1, characterized in that the stirring is carried out at 20-80 ° C for 10-120 minutes. Sources of information taken into account in the examination 1.Aksenov V.I. and others. Stabilizing the purified wash water of the pickling unit for use in the recycle cycle. - Water supply and sanitary equipment, 1973, 4, with. 4-5 .. 2. Authors certificate of the USSR 437720, cl. C 02 C 5/02, 1971.