JPH0293084A - Anticorrosive injector - Google Patents

Abstract

PURPOSE:To form a uniform and good-quality anticorrosive iron coating film on the inner surface of a copper contg. pipe by mixing an appropriate amt. of the carboxylic acid soln. controlled in conformity to the chlorine concn. and temp. of seawater with a ferrous sulfate soln. and injecting the mixture into the seawater to be passed through the pipe. CONSTITUTION:The carboxylic acid soln. and the ferrous sulfate soln. are supplied respectively from a carboxylic acid soln. tank 1a and a ferrous sulfate soln. tank 1b through fixed delivery pumps 3a and 3b, and mixed in a mixing tank 10. The mixture is injected into the seawater in a seawater inlet pipe 6 through an injection nozzle 5, and then passed through a copper alloy pipe 7. In the anticorrosive agent injector, a chlorine concn. detector 13 and a seawater temp. detector 14 are set in the seawater inlet pipe 6 on the upstream side of the insertion position for the nozzle 5. The detection signals therefrom are received by a controller 12, the pump 3a is controlled in conformity to the chlorine concn. and temp. of seawater, and the amt. of the carboxylic acid soln. to be injected is adjusted. By this method the optimum injection condition is maintained at all times, and a uniform and good-quality iron coating film can be formed on the inner wall surface of the pipe 7.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for injecting anticorrosive agent into copper or steel alloy pipes used in seawater utilization equipment, and relates to a device for injecting anticorrosive agent into copper or steel alloy pipes used in seawater utilization equipment, and is used for seawater utilization heat generation in ships, chemical plants, power generation plants, etc. The present invention relates to a device that can be advantageously applied when injecting an anticorrosive agent into the inner surface of copper alloy tubes such as exchangers and condensers, and especially into the inner surfaces of heat-dissipating steel alloy heat exchanger tubes of seawater desalination equipment.

[Conventional technology]

Currently, a method of injecting a small amount of iron ions into cooling seawater is widely used as a corrosion prevention measure for copper alloy pipes in seawater heat exchangers and condensers in various plants. This iron ion implantation method can be roughly divided into two types: those that use ferrous sulfate as an iron source, and those that electrolyze an iron material and use the resulting electrolyte.

The injection conditions are usually as follows.

(1) In the case of ferrous sulfate solution■ l 5~L Oppm (as 1Fe'') x 1~
2Hr 7 days @ [LO3~α1 ppm (as Fe”) continuous injection (2) For iron electrolysis ■ CL 05~CL 1 ppm (as Fe”)
Continuous injection These methods are mainly aimed at preventing corrosion of copper alloy pipes where the seawater supply to condensers etc. in power plants is a one-time system and the heat transfer pipe length is relatively short. The injections are carried out for several months.

On the other hand, in a seawater desalination device, the seawater supplied to the heat exchanger tubes in the heat release section is not discharged as is, but a portion of it is used in the heat recovery section. Furthermore, the heat dissipation section is composed of three stages. This causes the following problem.

(1) When seawater containing iron is used as evaporation water, scale deposits occur in the evaporation chamber. For this reason, iron ion implantation cannot be performed continuously for several months while the plant is operating, so it is necessary to form a good iron coating in a short period of time (for a short period, the seawater supply to the heat recovery section must be stopped). possible).

(2) The length of the heat transfer tube, that is, the length of the copper alloy tube is several times that of a condenser (18 m x 3 stages = 54 m).

Therefore, it is necessary to generate a uniform iron coating over a long distance.

As described above, the configurations and configurations of condensers in ships, originating plants, etc. and seawater desalination equipment are essentially different, and the conventional iron ion implantation method into condensers cannot be used as is.

As a pillar of iron coating by iron ion implantation, ■ The iron coating should have good adhesion (uniformity and adhesion).

■ Iron material yi=ifl is Fe, α2 my/υ2
That's all there is to it.

■ However, excessive adhesion reduces heat transfer efficiency] 1F
It is preferable that e is [150197 cm” or less.

is required.

Figure 4 shows the ferric acid molten NIL applied to the condenser.
This figure shows the distribution of iron deposits on the inner surface of a 60WI steel alloy pipe when the injection method is applied.

[Injection method] Preparation of ferrous sulfate solution Prepare water (city water) by adding P e S O4.7H,O, Fθ8 + ion concentration tfFe'' + 20,0
00 ppm. The pH of the solution was 52.

(11) Injection Concentration and Injection Days Since it is necessary to form an iron film in a short period of time, Fe was set at i, Oppm, and the injection was carried out for 5 consecutive days.

(1■) Copper alloy pipe diameter and seawater flow rate inside the pipe Pipe diameter: 34φ
, seawater flow rate in the pipe; 2 m / 8θCIv) During the injection of ferrous sulfate solution, seawater was continuously passed through the alloy pipe, and υ was pumped using a metering pump.
Inject the ferrous sulfate solution into the seawater line. After continuous injection for 6 days, the metering pump and seawater flow were stopped, and the condition of the iron material on the inner surface of the steel alloy a was investigated.

In Figure 4, at a point 10 m from the injection point of the ferrous sulfate solution, the amount of Fe is 1.8 q/cm'', 55
At point m, the amount of iron deposition was less than CL 1.147cm'' as Fe, and there was excessive adhesion up to around 50m from the injection point, and after 40m, the amount of iron deposition was less than the amount required for corrosion protection, and there was no adhesion. It was wrinkled and not good.

As is clear from the results shown in Figure 4, the method applied to the condenser is not suitable for corrosion protection of long steel alloys in seawater desalination equipment, which require short-term treatment due to long pipes.

This submerged iron material jli it with a constant 4α circumference
As a result of extensive research into anticorrosive agents that can form iron coatings that are uniform and have good layer properties, we found that iron coatings are formed when iron ions are oxidized and change from oxide to colloidal state. To address the phenomenon of iron ions adhering to the inner surface of tubes, we realized that it would be a good idea to suppress iron ions from entering a colloidal state and prevent iron ions from existing alone, so we investigated and considered various substances for this purpose. As a result, it was confirmed that by adding a substance containing carboxylic acid ions -COO-, it was possible to suppress the colloidalization of iron ions and to control the amount of iron coating deposited. proposed a special food agent characterized by the coexistence of carboxylic acid ions with (Japanese Patent Application No. 61-291596).

When iron ions are made into a compound form, only the amount of iron ions that correspond to the equilibrium concentration of the compound will exist, so they will not be consumed at once, and once they are consumed, the compound will release S and supply iron ions. It becomes like this. As a result, it is possible to retain effective iron ions far from the injection point.

Representative examples of substances having a carboxylic acid ion -COO- include citric acid, acetic acid, formic acid, and tartaric acid.

However, it has been found that the implantation method of adding carboxylic acid ions also has the following problems.

(1) In actual plants, chlorine is injected into the water intake to prevent abnormal corrosion caused by blockage of pipes due to adhesion of marine organisms. In a seawater desalination plant, approximately 10 units are usually constructed and operations are started on a rolling basis; it is constructed together with a power generation plant; and the top and θ seawater intakes are shared. For this reason, it is necessary to control the salt concentration injected into the water intake when the constructed unit is stopped and the power plant is started or stopped.
The chlorine concentration in seawater often fluctuates due to poor management. Since chlorine is an oxidizing agent, it promotes colloidalization of iron ions. As a result, if the chlorine concentration is [lL2 p
Determine the amount of carboxylic 1″11 ion added as pm,
When iron ion implantation is started, if the chlorine concentration becomes as high as 1.0 ppm midway through, oxidation will be promoted and iron adhesion in long distance areas will deteriorate; conversely, if the chlorine concentration is almost Opp
When the distance reaches m, the colloidalization of iron ions is delayed and iron no longer adheres to the short distance area.

FIG. 2 shows the dependence of the amount of iron-coated 7aI on the chlorine concentration at a point 10 m and 60 rn from the injection point when iron ions were implanted using citric acid as the carboxylic acid. Moreover, FIG. 3 is a configuration diagram of a test apparatus for the above-mentioned iron ion implantation.

[Injection method] ■ Preparation of iron ion injection solution First, put city water into solution tank 01 and add citric acid t-1.
0001F was added and dissolved. Ferrous sulfate (Fe5
0. -71110) was added and dissolved at 30001F, and city water was further added to bring the total amount to 306.

■ Injection concentration and time...1.0 p as Fe
pmX 50 Hr ■ Flow velocity in copper alloy pipe...2m/aec■ Seawater temperature・
...18℃ ■ Copper alloy pipe diameter and length ...34-φX 60 m was poor. For these reasons, there is a need for an anticorrosive injection device that can respond to changes in chlorine concentration.

(2) To determine the size of the Wttul ferrous solution tank and the capacity of the injection bonder [carboxylic acid + Fe SO
, 7B, 0] was conducted. The results are shown in Table 1. As the carboxylic acid, enoic acid was used because it was easily available.

Under the above conditions, the seawater pumped into the seawater tank 06a was supplied to the copper alloy f07 via the vinyl chloride pipe 06Cf by the seawater bonder 06b, and the ferrous sulfate m solution containing citric acid in the solution tank 01 was quantified. It was injected into the end of the vinyl chloride pipe 06a through the vinyl hose 04 using the pump 05.

As is clear from FIG. 2, it can be seen that the amount of iron 4 film deposited on the skin depends on the chlorine concentration. Also, the chlorine concentration t Op
In the case of pm, the state of layering was remarkable in the first table.

■ Pour 600C1 of city water into a 1t beaker. The water temperature at this time was 20°C.

■ Add citric acid and dissolve (citric acid will dissolve completely).

■ Add PeSO4・7H20 and dissolve it.

■ The total area is 1 ton with city water.

In Table 1, when the amount of PeSO4.7H,O dissolved was large (tests 1 to 3), a phenomenon in which ferrous sulfate settled to the bottom of the beaker was observed. Therefore, in some cases, ferrous sulfate may precipitate in the solution tank 01, making it impossible to pour the solution. If the amount of ferrous iron dissolved in Wc acid is lowered, it will be completely dissolved, but it will be necessary to increase the tank capacity and the capacity of the injection pump. Furthermore, it was found that although di-iron sulfate alone can dissolve 7 S OOO ppm as Fθ (dissolving up to 7000 ppm at 20° C.), the presence of citric acid makes it difficult to dissolve.

From these facts, it will be understood that in the iron ion implantation method in which citric acid is added, an anticorrosive injection device that does not cause precipitation of ferrous sulfate is required.

[Purpose of the invention]

In view of the above-mentioned conventional state of the art and the problems of the previously proposed method, it is possible to always maintain appropriate conditions for injection of anti-corrosion agent into copper or -alloy pipes using seawater, and to produce an even and high-quality anti-corrosion coating on iron. It is an object of the present invention to provide an anticorrosive injection device that can be formed on the inner surface of copper or copper alloy pipes.

[Means to achieve the purpose]

That is, the present invention provides a carboxylic acid dissolving tank and a ferrous sulfate dissolving tank, each independent of the other, a mixing tank for mixing the carboxylic acid solution and the ferrous sulfate solution, and the carboxylic acid dissolving tank and the ferrous sulfate dissolving tank. a pipe line connecting the mixing tank via a pump; a pipe line connecting the ferrous sulfate dissolving tank and the mixing tank via a pump; one end connected to the mixing tank;
An injection pipe whose other end connects to a nozzle inserted into the seawater introduction pipe, and a seawater chlorine concentration detector and a seawater temperature detector arranged in the seawater introduction pipe upstream from the insertion position of the nozzle. and a control device that receives a signal from the detector and controls the amount of the carboxylic acid bath liquid to be injected into the mixing tank.

A preferred embodiment is to provide a heating means in the mixing tank and a heat retaining means in the injection pipe in the above-mentioned configuration.

[Implementation row]

An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a configuration diagram of an anticorrosive injection device that is an embodiment of the present invention. In FIG. 1, reference numeral 1a denotes a carboxylic acid dissolving tank, which is connected to a mixing tank 10 via a carboxylic acid solution supply pipe 2a, a carboxylic acid solution supply constant pump 3a, and a carboxylic acid solution supply pipe 4a. On the other hand, in the 1bIIi ferrous sulfate dissolution tank, the ferrous sulfate solution supply pipe 2b.

It is connected to the mixing tank 10 via a sulfur r:a ferrous solution supply metering pump 5tl and a ferrous sulfate solution supply pipe line 4b. It is preferable that a heating device 15 is provided in the mixing tank 10 for mixing the carboxylic acid bath liquid and the ferrous sulfate solution. 11
is an injection pipe for introducing the mixed solution in the mixing tank 10 into seawater), and is connected to the injection nozzle 5 provided in the seawater introduction pipe 6. It is preferable to perform heat insulation treatment.

From these facts, it is possible to prevent the precipitation of ferrous sulfate as observed in the conventional dissolving tank 01 shown in FIG. In other words, since the amount of carboxylic acid and ferrous sulfate can be dissolved in the independent dissolution tank Ia, 11), the dissolvable concentration of each can be adjusted, and the carboxylic acid solution and ferrous sulfate solution can be The mixing tank 10 in which the mixed solution is mixed can be heated by a heating device 15 as necessary to a temperature that does not cause sedimentation, and the injection pipe 11 into which the mixed solution is injected can be heated as necessary to prevent sedimentation from occurring. It can be kept warm according to your needs.

Incidentally, the solubility of ferrous sulfur rR and carbo:yrIR in water is as shown in Table 2, and it can be seen that the amount dissolved increases as the liquid temperature increases.

Table 2 13#'i A galvanic electrode type chlorine concentration detector is used to detect the chlorine concentration in seawater, and this chlorine concentration detector 13
A still starvation device 12 for controlling the supply capacity of the metering pump 5a for supplying the carboxylic acid bath liquid is electrically linked. Reference numeral 14 denotes a seawater temperature detector (for example, a platinum resistance thermometer type) for detecting the water temperature, and the control device 12 is electrically linked to the seawater temperature detector 14.

The split φ1 device 12 is a fixed pump 3a for supplying carboxylic acid solution.
It is electrically connected to the chlorine 11k degree detector 13,
For example, it is a control device of a stroke number control type that can control the supply capacity of the quantitative bong 5B for supplying carboxylic acid solution based on the detection information from the seawater temperature detection a14,
The optimum amount of carboxylic acid bath liquid for the salt Xl# degrees and seawater temperature in the seawater can be supplied to the mixing tank 10, and the optimum ferrous sulfate injection solution can be injected into the seawater from the injection nozzle 5.

In other words, even after ferrous sulfate injection starts, it is possible to maintain optimal injection conditions at all times even if the seawater properties fluctuate, and to maintain a good corrosion-resistant rupture of the iron without hemulation on the inner surface of steel alloy pipes in group 7. It can be formed.

Note that the higher the seawater temperature is, the more oxidation and colloidalization of iron ions are promoted, so the control of the metering pump 3a for supplying the carboxylic acid solution by detecting the seawater temperature is incorporated.

In the present invention, the mixing tank 1oK/JO temperature device 15 and the injection pipe 11 are provided with heat insulation treatment, but this may be omitted if the ferrous sulfate solution concentration is low and there is no risk of sedimentation. It is possible to do this.

〔Effect of the invention〕

(1) The dissolution tank for carboxylic acid and the dissolution tank for ferrous sulfate are installed separately, making it possible to control the amount of carboxylic acid solution supplied according to the seawater properties, making it possible to maintain optimal injection conditions at all times and eliminate uneven injection. A high-quality iron anti-corrosion coating can be formed on the inner surface of the copper alloy bone.

(2) The carboxylic acid dissolution tank and the ferrous sulfate dissolution tank were installed separately, and the mixing tank and injection flow path, where there is a risk of sedimentation, were heated and kept warm, so there was no blockage of the flow path, etc. Allows for smooth injection.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an anticorrosive injection device according to an embodiment of the present invention, and Fig. 2 shows the relationship between the amount of iron coating and the chlorine concentration in seawater when using a conventional anticorrosion injection device. Graph showing,
FIG. 3 is a block diagram of a conventional anticorrosive injection device, and FIG. 4 is a graph showing the distribution of the amount of iron film deposited when a conventional anticorrosive is injected.

Claims (1)

[Claims] A carboxylic acid dissolving tank and a ferrous sulfate dissolving tank, each of which is independent, a mixing tank for mixing the carboxylic acid solution and the ferrous sulfate solution, and a pump for the carboxylic acid dissolving tank and the mixing tank. A pipe line that connects the ferrous sulfate dissolving tank and the mixing tank via a pump, one end of which is connected to the mixing tank, and the other end of which is connected to the mixing tank. An injection pipe line connected to the nozzle inserted into the pipe, a seawater chlorine concentration detector and a seawater temperature detector installed in the seawater introduction pipe upstream of the insertion position of the nozzle, and the detector. A control device for receiving a signal and controlling the amount of the carboxylic acid solution to be injected into the mixing tank.