RU2232724C1 - Method of purification of the transportation-washing water at production of sugar - Google Patents

Abstract

FIELD: food-processing industry.

SUBSTANCE: the invention is dealt with the field of food-processing industry, in particular, with the methods of purification of industrial waters at the sugar mills. The transportation-washing water after removal of the rough solid impurities out of it divided into three streams, two of which are subjected to treatment with a direct electric current in a diaphragm electrochemical activator. At that and one of streams is treated in the cathode chamber till reaching рН equal to 13.5-14.0 and another - in the anodic chamber of the electroactivator till achieving рН equal to 1.5-2.0. Then both streams are mixed with the untreated water with production of two streams - one of which-with рН of no less than 10.0, and another - of no more than 5.5. Then the water is settled to remove impurities and mixed again till achieving рН of 7.0±0.5 units. The technical effect: the method allows to exclude application of an acid and alkali and at the same time to increase efficiency of water purification.

EFFECT: the method allows to exclude application of an acid and alkali and to increase efficiency of water purification.

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Description

The invention relates to the food industry, specifically to methods for purifying industrial waters of sugar factories.

A known method of purification of conveyor-washing water of a sugar factory from suspended particles using a reagent [1]. The cleaning process is carried out by sludge in two stages. At the first stage, water is sedimented from coarse suspensions without the use of reagents, where more than half of the mechanical impurities are separated. In the second stage, pre-settled water is treated with milk of lime to a pH of 10.5-11.5 and again defended, separating fine particles. After purification, water is sent for use in the production process. This method has several disadvantages, the main of which is an insufficient degree of purification, not reaching 90%, which complicates its further use. In addition, the cleaning process is two-stage with a high pH value of purified water and it uses scarce lime - Ca (OH) ₂ .

There is also known a method (prototype), which is, in fact, an improvement on the previous one. In it, the purified water is preliminarily divided into two unequal streams, the smaller stream is treated with lime to a pH of 10.0-11.0, and the larger stream is treated with hydrochloric acid to a pH of 4.0-6.0, and after settling, the streams are mixed to a pH of 6.5 -7.5, within which there is no foaming of purified water on the path of supply of beets to the plant [2].

The prototype method gives a slight increase in the degree of purification (by 5-8%) and is more productive. However, the achieved water treatment is also insufficient. Along with lime, the technology also uses a scarce and expensive reagent - hydrochloric acid, which, like alkali, requires special safety measures during transportation, storage and use.

The technical result of the invention is to increase the degree of purification of conveyor washing water, the exclusion from the technology of scarce, expensive and environmentally unsafe acids and alkalis.

This is achieved by the fact that the purified water is divided into 3 streams, two of which are subjected to direct electric current treatment in a diaphragm electrochemical activator, one of the streams being processed in the cathode chamber to achieve a pH of 13.5-14.0, and the other in the anode chamber electroactivator to a pH of 1.5-2.0.

After that, each stream of water treated in the electroactivator is mixed with untreated water from the third stream to obtain two streams, one of which has a pH of at least 10.0 and the other with a pH of not more than 5.5. Then, the water of each of the two streams is separated from impurities separately and, after settling, they are mixed to a pH of 7.0 ± 0.5 units.

The ratio of water flows during mixing in both cases - before and after sludge - is determined based on the pH values of each stream and the given pH values of the mixture as a weighted average, i.e. by the additivity rule, by the formula:

where pH cm, pH ₁ , pH ₂ - pH of the mixture, the 1st and 2nd flows, respectively;

g ₁ and g ₂ are the quantities of the 1st and 2nd flows, respectively,% (m ³ , part).

The ratio of the flow rate of water, treated water in the electroactivator and water not processed in it, which is mixed, can vary depending on production needs. In the limit, it is 100: 0%. And in this case, the obtained scheme for separating conveyor-washing water into 2 streams and their separate treatment in the electroactivator before settling.

The scheme of separation of purified water into 3 streams, two of which are treated in an electroactivator, and the third is used for mixing with treated water for sludge to obtain specified pH values, allows you to use the difference between the potential of the electroactivator to obtain maximum pH values (in the acidic and alkaline sides) and the preset pH of the water with sediment. Thus, it is possible to use devices with a 2 times lower productivity and thus increase the productivity of the system for preparing water for sludge by more than 50%.

The method is as follows.

Dirty water coming from the beet washing conveyor passes preliminary sludge from coarse organic and mineral suspensions (beet debris, tailings, earth particles, etc.) in a sump (radial or other type). From the sump, a part of the water containing the remaining fine particles is pumped through the cathode and anode chambers of the electroactivator in two streams by a pump. (At the entrance to the anode chamber, a solution of sodium chloride is pumped out based on the concentration of salt in the anolyte 0.5-1.0 wt.%).

Another part of the water (third stream) from the pre-sludge settler is pumped to the activator outlet for mixing with the flows of anode (anolyte) and cathode (catholyte) fractions of activated water. A mixture of anolyte and catholyte with untreated water in two parallel streams enters the flocculators, and then into the vertical metal sumps, where the water is clarified, 95–98% free of mechanical impurities. The water purified from suspension is pumped out of the settling tanks, mixed into one stream and sent to the water recycling system for use in the production process. In order to avoid strong foaming on the path of feeding and washing the beets, the pH of the purified water is maintained in the range of 6.5-7.5.

Examples. The table shows examples of the application of the proposed method of purification of conveyor-washing water of a sugar plant when used as reagents in the sedimentation of water of anolyte and catholyte. As a control experiment (for comparison), the results of water purification using acid (Hcl) and alkali [Ca (OH) ₂ ] are shown according to the prototype.

As can be seen from the table, the cleaning efficiency of conveyor washing water in the proposed method is significantly higher than in the prototype, and reaches 98.6%, which is practically the limit for the method of water purification by sludge, especially given the increased difficulty of removing impurities with increasing degree of purification. The range of the ratio of costs has been expanded compared with the prototype, which makes it easier to vary the performance of the electroactivator and water flows at all stages of water treatment.

Thus, the use of the proposed method of purification of conveyor washing water eliminates the use of scarce, expensive and environmentally unsafe acids and alkalis and at the same time increase the degree of water purification. The use of water activation to intensify the process of its sludge, among other things, allows the company not to be dependent on the supply of reagents.

Sources of information

1. Sapronov A.R. Technology of sugar production. M., Kolos, 1999, pp. 412-413.

2. USSR Copyright Certificate No. 1803389, class. C 02 F 1/58, 1993.

Claims (1)

The method of purification of conveyor washing water in the production of sugar, including the separation of the purified water into several streams, their separate treatment to different pH values, sludge, mixing the streams and return to the production process, characterized in that the purified water is divided into 3 streams, two of which subjected to direct current treatment in a diaphragm electrochemical activator, one of the streams being processed in a cathode chamber to achieve a pH of 13.5-14.0, and the other in an anode chamber of an electroactivator to pH 1, 5-2.0, mixed with untreated water to obtain two streams, one of them with a pH of at least 10.0, and the other no more than 5.5, after which the water is settled from impurities and then mixed to a pH of 7.0 ± 0.5 units.