RU2027682C1 - Method of reusable water supply in by-product coke industry - Google Patents

Abstract

FIELD: water supply. SUBSTANCE: water coolant system is filled up with sewage of by-product coke industry after biochemical treatment involving the sequence dephenolizing, derhodanizing and nitrification. Method is used for corrosion prevention and formation of carbonate crust on the surface of heat-exchange equipment. EFFECT: improved method of water supply.

Description

 The invention relates to recycling water supply of coke plants and can be used in coke production.

 Known reverse water cooling system, replenished with municipal wastewater (household) with a nitrite concentration below 200 mg / l, in which orthophosphate is added to inhibit corrosion of unalloyed steel [1].

 The disadvantage of this method is that it is necessary to disinfect household water in order to avoid the spread of pathogenic microorganisms that may be contained in these waters with air and drip moisture. This leads to an increase in capital and operating costs.

 Closest to the invention is a circulating water supply system of a coke production, replenished with fresh process water from a reservoir [2]. In this water recycling system, in order to reduce carbonate deposits on the heat transfer surface, industrial water is treated with ammonium sulfate.

 However, in this case, an increase in the concentration of sulfate ions occurs, which leads to an increase in the corrosion rate of steel in water. The treatment of water with ammonium sulfate does not solve the problem of corrosion inhibition. This method requires additional treatment of water with a corrosion inhibitor.

 The aim of the invention is to reduce corrosion of equipment and prevent deposits on its heat transfer surfaces.

 For this purpose, the water recycling system is replenished with wastewater from the coke-chemical industry, which has undergone biochemical treatment, including successively de-phenolization, de-anodization and nitrification.

Wastewater of coke production is a complex physicochemical system, so far poorly understood. It is possible to give the physicochemical properties of wastewater that has undergone biochemical defenolation, dehydrogenation and nitrification (based on the analysis of this water at one of the coke plants): Phenol content, mg / L 1 Rhodanide content, mg / L 5 Cyanide content, mg / L 10 Oil content, mg / l 15 Density, g / cm ³ ≈1 Temperature, ^о С 30-35 Freezing temperature, ^о С -5
In addition to these compounds, the following organic substances are contained in trace amounts in wastewater of coke production: sodium benzoate, organic compounds with a sulfo group, pyridine and its homologs, quinoline and its homologs, as well as a number of other substances.

 The invention is illustrated by examples.

 EXAMPLE 1. The total phenol-containing effluent of the coke industry after two-stage biochemical purification of phenols and rhodanides was subjected to biochemical nitrification, where they were purified from ammonium ions, which were oxidized to nitrite and nitrate ions. This treated wastewater was sent to replenish the circulating water cooling system of the closed heat-exchange equipment. The composition of the circulating water is as follows, mg / l: alkalinity 400; calcium 35; magnesium 25; ammonia 15; chlorides 635; sulfates 1230; dry residue 5500, pH 8.5.

The experiments were carried out on a laboratory-bench installation simulating a reverse water supply system. The corrosion rate was determined by the gravimetric method using standard samples of St3 steel with a size of 40x20x3 mm. The water temperature was maintained equal to 45 ^about C.

The corrosion rate after holding the samples in water for 1000 h was 0.04 g / m ² ˙ h. In addition, no deposits were found on the samples, incl. corrosion products. The appearance of the samples has not changed.

PRI me R 2. The experiments were carried out on the same laboratory bench stand as in example 1. In industrial water (industrial water is water taken from a natural source, for example from a lake or river, used without treatment or after purification only from suspended solids) was added ammonium sulfate in an amount of 250 mg / l (by a known method). The composition of process water is as follows: pH 7.8; hardness 3.3 mEq / l; alkalinity of 1.7 mEq / l; a calcium content of 1.5 mEq / l; ammonia content of 1.5 mg / l; chloride content 20 mg / l; sulfate content 48 mg / l; salt content 160 mg / l. The corrosion rate determined by the same method as in example 1 was equal to 1.7 g / m ² ˙ h. Carbonate deposits on the surface of the samples are practically absent, although it is covered with corrosion products.

In accordance with the proposed method, in the wastewater of a by-product coke plant that underwent biochemical treatment, which consistently de-phenols, de-anodizes and nitrifies, the corrosion rate is 0.04 g / m ² ˙ h, i.e. 42.5 times less than in industrial water with the addition of ammonium sulfate, and there are no deposits on the surface of the samples. Thus, the proposed method is much more efficient than the method of the prototype.

Claims (1)

 METHOD OF ROTARY WATER SUPPLY OF COXOCHEMICAL PRODUCTION, including replenishment of the reverse water cooling system of the closed heat-exchange equipment with water, characterized in that, in order to reduce corrosion of the equipment and prevent deposits on its heat-transferring surfaces, the water cooling system is replenished with wastewater of coke-chemical production, which is subjected to sequential biochemical treatment, including biochemical treatment de-phenolization, dehydrogenation and nitrification.