KR20000067566A - Cooling water inhibitor and its feeding method in a stave cooler system - Google Patents

Abstract

PURPOSE: An antiscale agent for stave cooling and also a method for injecting the same into the stave cooling system are provided. The antiscale agent can prevent corrosion & scaling by both forming thin film on the inner surface of the stave cooler and bonding scale-inducing materials with high molecular compounds. CONSTITUTION: The antiscale agent comprises 20-30 wt.% of nitrite, 0.3-0.8 wt.% of a dispersing agent, 0.5-1.6 wt.% of polyol ester or an organic phosphate selected from the group consisting of triethanolamine phosphate, aminotrismethylene phosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4tricarboxylic acid and the rest of water. The method comprises the steps of (i) a first step of injecting the antiscale agent into cooling water for adjusting the concentration to 5000-6000ppm; a second step of measuring the concentration of NO2 ion in cooling water on realtime; and a third step of adding the supplementary agent thereto for maintaining NO2 ion to 600-1200ppm.

Description

Furnace stave coolant treatment agent and its feeding method {Cooling water inhibitor and its feeding method in a stave cooler system}

The present invention relates to a cooling water treatment agent for preventing corrosion and capstone of a stave cooler which is a cooling facility of an ironworks furnace body, and a method of introducing the treatment agent.

A furnace such as a pig iron-producing furnace or a corex melting furnace maintains a high temperature, and thus, a stave cooler is employed as a cooling device to protect the furnace shell. As shown in FIG. 1, the stave cooler 10 has a kite 12 embedded therein and has an elongated box shape in which a pipe in which cooling water flows is embedded. The cooling pipes 14 and 16 have a plurality of vertical cooling pipes 14 and a cooling pipe 16 that is repeatedly bent from side to side in a place where the furnace heat load is severe, and vertical cooling is performed in a place where the heat load is not severe. There is only a tube 12. Adjust the pipe spacing according to the heat load.

Since the stave cooler 10 is a large structure, it is not easy to repair or replace a defect caused by corrosion or wear. Therefore, it is necessary to maintain the cooling system well, which requires not only proper heat load management but also the management of the water quality of the cooling water to prevent corrosion and formation of capstone (scale). If the cooling equipment is corroded and the coolant flows into the blast furnace, it may cause a large explosion accident. If the capstone is attached to the inside of the cooling pipe, the thermal conductivity may deteriorate and the equipment accident may occur due to deformation or deterioration of the equipment.

Therefore, a treatment agent (chemical) containing a component capable of preventing corrosion and capstone is added to the cooling water to prevent equipment accidents.

Conventionally, the cooling water treatment agent contains chromate, NaOH, sulfate (Na ₂ SO ₃ ), hydrazine (N ₂ H ₄ ), or the like to prevent corrosion. Chromate is a carcinogen and is rarely used, and there is a risk of pitting if the amount of addition is insufficient. The NaOH promotes passivation of the surface by increasing the pH of the cooling water (Fe (OH) ₂ film formation) to suppress the Fe dissolution rate, or facilitate the precipitation of calcium carbonate to form a film of calcium carbonate in the cooling tube do. The sulfate (Na ₂ SO ₃ ) or hydrazine (N ₂ H ₄ ) to remove the dissolved oxygen dissolved in the water to inhibit the corrosion. If the cooling water system is completely enclosed, dissolved oxygen is consumed for corrosion and it does not exist in the water, so the corrosion is no longer developed. However, in the blast furnace cooling system, water is continuously dissolved because 10 ~ 30% of the cooling water is supplemented by leakage and evaporation. Corrosion by oxygen may occur.

In addition, in order to suppress the formation of capstone, the cooling water treatment agent is added with a capstone inhibitor such as phosphate to remove hardness (Ca, Mg) components. Such anticorrosives should be kept at a high pH at all times. Calcium hydroxide (Ca (OH) ₂ ), calcium carbonate (CaCO ₃ ), calcium phosphate (Ca ₃ (PO ₄ ) ₂ ), silicates Compounds such as Si (OH) ₄ ) constitute a major component that forms a capstone, which is a problem. Of course, it is possible to remove the compound by replacing the entire amount of cooling water within a suitable time after the chemical injection, but in the actual process, the effort to discharge the cooling water for each of the stave cooler unit is not enough to supplement the water or the cooling water flow path is very complicated There is a limit to the clean discharge of the product because it is necessary.

In order to solve such a conventional problem, in the present invention, a dense and thin passivation film is formed on the surface of the stave steel pipe, and at the same time, the capstone forming components of the cooling water are combined with the polymer material to increase the solubility to provide a hard ore. It is an object of the present invention to provide a cooling water treatment agent which can prevent corrosion and capstone by preventing formation.

1 is a schematic diagram of a stave cooler of a blast furnace;

2 is an example of an experimental apparatus for checking the characteristics of the coolant treatment agent.

Figure 3 is an example of an experimental apparatus for determining the characteristics of the coolant treatment agent of the present invention for the actual cooling tube.

* Description of the symbols for the main parts of the drawings *

1 ....... Blast Furnace 10 ....... Stave Cooler

12 ..... lead and 14, 16 ..... coolant pipe

The cooling water treatment agent of the present invention for achieving the above object comprises nitrite: 20 to 30%, organophosphate or polyol ester: 0.5 to 1.6%, dispersant: 0.3 to 0.8% by weight of the remaining water.

In addition, the cooling water treatment agent input method of the present invention, the step of injecting the cooling water of the cooling tube embedded in the stave cooler so that the concentration of the cooling water treatment agent of claim 1 is 5000 ~ 6000ppm; Measuring the concentration of NO ₂ ions in the cooling water of the cooling tube in real time; And supplying the cooling water treatment agent to the supplemental water so that the measured concentration of the NO ₂ ion satisfies 600 to 1200 ppm.

Hereinafter, the present invention will be described by dividing the cooling water treatment agent and its input method.

[Coolant Treatment Agent]

The cooling water treatment agent of the present invention contains (a) nitrite, (b) organic phosphate, or polyol ester (c) dispersant as a main component, and (d) copper alloy corrosion inhibitor as necessary. .

(a) nitrite

Nitrite is to prevent corrosion by forming a surface of a thin dense γ-Fe coating ₂ O ₃ in the stacking eve steel pipe as an oxidizing agent, such nitrite include sodium nitrite (NaNO _2), potassium nitrite (KNO _2), nitrite, hydrogen (HNO ₂ ) and the like. Nitrite is preferably contained in an amount of 20-30% by weight (hereinafter simply referred to as%), which must be contained in an amount of 20% or more to effectively form a passivation film. If it is more than 30%, it is dissolved in water at room temperature. Because it becomes difficult.

(b) organic phosphates or polyesters

In the cooling water treatment agent of the present invention, organophosphate or polyester (POE) is used to prevent capstone. These ingredients not only prevent dialysis but also interact with nitrite to further lower the passivation film.

Examples of the organic phosphate include triethanolamine phosphate (TAEP), aminotrismethylene phosphonic acid (AMP), and 1-hydroxyethylidene-1,1-diphosphonic acid (1-hydroxyethylidene-1 , 1-diphosphonic acid (HEDP) and 2-phosphonobutane-1,2,4-tricarboxylic acid (2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC)). In the present invention, any one of them can be used to prevent capstone, but PBTC having high thermal stability is preferred when the stave cooling water is close to 100 ° C.

These organophosphates and polyol esters are chemisorbed on calcium carbonate or magnesium particles to change the shape of the crystals so that the scale crystal structure has a very weak cohesive force to prevent the formation of hard capstone. The amount of organophosphate used can prevent capstone formation even at a very small amount (0.5 to 5 ppm) relative to the calcium concentration. That is, the organic phosphate or polyol ester is contained in 0.5-1.0%, because it contains more than 0.5% for effective prevention of capstone, and even if it contains more than 1.0% does not have a large difference in the effect of increasing the amount added.

(c) dispersant

Dispersants are added to soften the surface of the capstone forming particles to make it difficult to attach to the cooling tube, and various polymers or copolymers (Co, ter-polymer) are commonly used. For example in the form of acrylic acid polymers or copolymers, alkali or ammonia salts thereof. This conventional dispersant is also used in this invention. The content of such a dispersant is preferably 0.3 to 0.8% in consideration of the interaction between the corrosion preventing component and the capstone preventing component.

(d) Copper anticorrosive

If the material of the pump or the like exposed to the stave cooling water is copper (Cu) alloy, the corrosion of the cooling water treatment agent is preferably included a copper alloy corrosion inhibitor. The copper alloy corrosion inhibitor used in the present invention uses mercaptobenzothiazole, benzotriazole or tolytriazole. These chemicals are adsorbed onto the copper alloy and the electrochemical reaction prevents the corrosion of the copper. Such a copper alloy may be contained 0.1 to 0.3% in the cooling water treatment agent of the present invention.

[How to add coolant treatment agent]

In general, the furnace body employs a stave cooler for cooling the furnace body, and the stave cooler includes a cooling tube through which cooling water flows as shown in FIG. 1. Cooling water in the cooling pipe is supplied through the supplemental water pipe by 10 ~ 30% of the cooling water every day to make up for the loss due to leakage and evaporation. In the conventional method of adding the coolant treatment agent, the required amount of the coolant treatment agent is added to the cooling tube.If the coolant is insufficient, the supplemental water is supplied. Appropriately put in. Therefore, there is a disadvantage that the concentration control of the coolant treatment agent in the coolant is not accurate. In the present invention, as a result of various examinations for the most effective addition of the coolant treatment agent of the present invention, in consideration of the characteristics of the coolant treatment agent of the present invention, the amount of the coolant treatment agent is set more effectively through the setting of the concentration and the concentration management method thereof. A method to prevent corrosion of the cooling tube and capstone was derived. The method is as follows.

First, the cooling water treatment agent of the present invention is added to the cooling water of the cooling tube built into the stave cooler according to the present invention so that its concentration is 5000 ppm or more, preferably 5000 to 6000 ppm. This is because when the coolant treatment agent is added to the cooling water of 5000ppm or more, it satisfies the corrosion protection standard of the critical equipment, but even if it is added more than 6000ppm, the effect is not so large that it is not economical.

Then, the concentration of NO ₂ ions in the cooling water of the cooling tube is measured in real time. As the operation progresses, replenishment of the shortage of cooling water is necessary. In this case, the amount of cooling water treatment agent that can satisfy the concentration of NO ₂ ions of 600 to 1200 ppm is set, and this amount is added to the replenishment water pipe. To the cooling tube together. This is because if the concentration of NO ₂ ions in the cooling water satisfies 600 to 1200 ppm, the cooling water treatment agent is managed to be 5000 to 6000 ppm in the cooling water. Therefore, in the past, more than 10 water quality items such as pH, hardness component, and dissolved oxygen concentration were separately managed. However, in the present invention, only the NO 2 concentration needs to be managed, so that the cooling water can be managed more easily.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

Conventional drug I (sodium hydroxide: 125ppm, sodium phosphate: 720ppm, sodium sulfite: 20ppm), conventional drug II (sodium phosphate: 158ppm, hydrazine: 80ppm, dispersant (polyacrylic acid): 60ppm)), and the present drug (sodium nitrite : 1250ppm, organophosphate (PBTC): 40ppm, dispersant (polyacrylic acid): 25ppm, tolytriazole: 10ppm)) were put into cooling water of the same water quality, and experiments on corrosion and capstone formation were performed. Experiment is to put the coolant, chemicals, the specimen 25 in the triangular flask 24 having the heating plate 20, the common grinding section cooler 21 and the rotating magnet bar 23 as shown in FIG. While stirring the cooling water for 10 days to maintain the cooling water temperature 40 ℃, 80 ℃. The cooling water used in the experiment was 200 ppm of hardness (Ca ⁺ ) component and 350 ppm of Cl ⁻ concentration.

division Weight change of specimen Remarks Before experiment (g) After experiment (g) Weight change (g) One 11.2342 11.4540 +0.220 Conventional Chemicals I (40 ℃) 2 11.2983 11.4995 +0.2012 Conventional Chemicals I (80 ℃) 3 11.2996 11.0716 -0.2280 Conventional Chemicals II (40 ℃) 4 11.2924 11.0872 -0.2052 Conventional Chemicals II (80 ℃) 5 11.2716 11.2722 +0.0008 Invention drug (40 ℃) 6 11.2128 11.2190 +0.0062 Invention drug (80 ℃)

division pH Hardness component (ppm) Electrical Conductivity (mσ / cm) Ca ²⁺ (ppm) Cl ^- (ppm) One 7.31 107.8 2.41 43.0 412 2 6.43 72.9 1263.0 29.1 419 3 7.72 116.6 2.35 46.5 402 4 6.66 82.9 1247.0 33.1 402 5 7.97 270.4 2.35 108.1 406 6 8.08 254.2 2.32 101.6 412

In the case of using the conventional drug I from Tables 1 and 2, the hardness component reacted with the drug to form a capstone, attached to the test specimen, and the weight of the test specimen increased, and the cooling water showed a light milky color. In case of using the conventional drug II, the surface of the specimen was dark red, corroded, the weight was reduced, and the cooling water was dark red. According to the present invention, the drug maintains the original specimen surface color and there is little change in weight. Cooling water also remained clear. The electrical conductivity of the coolant to which the chemical of the present invention was added was high. The Ca or Mg component dissolved in the cooling water of the chemical to which the chemical was added or the capstone was not dissolved due to an increase in solubility by the chemical of the present invention. Because it melts.

Example 2

Drugs were evaluated by applying the tj used in Example 1 to the actual blast furnace. By cutting the cooling tube connecting the stave cooler and the cooler cycle of the actual blast furnace, install a test column (26) containing the specimen 25 as shown in Figure 3 to observe the corrosion of the specimen or adhesion of the capstone and the results Table 1 shows. In addition, the degree of corrosion was measured while varying the input amount in the cooling water of 40 ℃ for the chemical of the present invention and the results are shown in Table 3.

division Conventional Chemicals I Conventional Chemicals II Drug of the invention Corrosion degree (MDD) 0.5 to 3 16-37 0.3-1.7 Adhesion (MCM) 0.03 to 0.1 0.01 to 0.5 0.01 to 0.05

As shown in Table 3, the conventional drug II was shown that the corrosion control value far exceeds 5MDD, the chemicals according to the present invention was found to be superior to the conventional corrosion resistance, adhesion. In Table 3, the difference between corrosion and adhesion depends on the specimen condition and cooling water temperature.

Chemical dosage of the present invention (ppm) Corrosion degree (MDD) 500 4.4 1000 8.2 2000 5.4 3000 3.1 4000 1.2 5000 0.61 6000 0.58 7000 0.37 8000 0.26 9000 0.22 10000 0.17

As can be seen in Table 4, when the chemical of the present invention is added to maintain the concentration of more than 5000ppm in the cooling water, the corrosion degree was found to satisfy 1MDD or less.

As described above, the present invention can provide a cooling water treatment agent that can greatly reduce corrosion and capstone, and when such cooling water treatment agent is properly applied to an actual furnace, cooling water quality management can be easily performed.

Claims (3)

A nitrite: 20 to 30% by weight, organophosphate or polyol ester: 0.5 to 1.6%, dispersant: 0.3 to 0.8%, the furnace stave cooling water treatment agent which consists of remaining water. The method of claim 1, wherein the organophosphate is triethanolamine phosphate, aminotrismethylenephosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4-tri Furnace stave cooling water treatment agent, characterized in that one selected from the group of carboxylic acid. Injecting the cooling water of the cooling tube embedded in the stave cooler so that the concentration of the cooling water treatment agent of claim 1 is 5000 to 6000 ppm; Measuring the concentration of NO ₂ ions in the cooling water of the cooling tube in real time; And supplying the cooling water treatment agent to the supplemental water so that the measured concentration of NO ₂ ions satisfies 600 to 1200 ppm, and supplying the cooling water treatment agent to the cooling tube.