JP2939222B1 - Pretreatment cleaning method for boiler - Google Patents

Abstract

Abstract: PROBLEM TO BE SOLVED: To perform a cleaning process before operating a boiler, does not require a detoxification process of a cleaning waste liquid, does not require a special anti-corrosion storage process after the cleaning, and pre-processes a boiler that is easy to process. Provide a cleaning method. SOLUTION: The pretreatment cleaning method of the boiler of the present invention comprises at least one selected from ascorbic acid, erythorbic acid or a salt thereof, aspartic acid or a salt thereof,
A treatment solution containing potassium hydroxide or sodium hydroxide is charged into a boiler and is characterized by being subjected to a heat treatment, and ascorbic acid, erythorbic acid or at least one selected from salts thereof, It is preferable to add aspartic acid or a salt thereof in a weight ratio of 0.1 to 100.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pretreatment cleaning method for a boiler, and more particularly to a pretreatment cleaning method for cleaning the inside of a boiler after newly installing or repairing a boiler.

[0002]

2. Description of the Related Art The interior of a newly installed boiler or a boiler whose smoke tube has been replaced for repair or the like is generally contaminated with oil or the like, and foreign substances are often attached thereto. Therefore, it is necessary to clean the inside of the boiler in order to remove contaminants before the operation starts. Normal,
Such boiler cleaning is often performed by a method of performing cleaning with water, cleaning with water, cleaning with an alkaline cleaning liquid, and further filling with an aqueous solution of caustic soda and heating, so-called boiled soda.

[0003] When boiler cleaning is performed by such a conventional method, there is no particular problem when the operation starts immediately after the cleaning, but when the operation is not started immediately, the corrosion of the iron material on the inner surface of the boiler proceeds. Since there is a danger, it is necessary to perform anticorrosion preservation treatment using a reducing agent such as hydrazine or sodium sulfite, and there is a problem that the operation is complicated. Further, since a strong alkaline waste liquid such as a cleaning liquid is generated, a treatment such as neutralization is required, and there is an inconvenience that a costly and complicated wastewater treatment must be performed each time.

[0004]

Accordingly, the present invention does not require the detoxification treatment of the washing waste liquid in performing the washing treatment before the operation of the boiler, and does not require any special anticorrosion storage treatment after the washing. It is an object of the present invention to provide a boiler pretreatment cleaning method that is easy to operate.

[0005]

The pretreatment cleaning method for a boiler of the present invention, which can achieve the above object, comprises at least one selected from ascorbic acid, erythorbic acid or a salt thereof, aspartic acid or A treatment liquid containing the salt and potassium hydroxide or sodium hydroxide is charged into a boiler, and the treatment liquid is kept at 140 to 210 ° C. to 1 to
It is characterized by being maintained for about three days and nights .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The treatment liquid used in the boiler pretreatment cleaning method of the present invention comprises at least one selected from ascorbic acid, erythorbic acid or a salt thereof, aspartic acid or a salt thereof, It is a chemical solution containing potassium or sodium hydroxide. The mixing ratio of aspartic acid or a salt thereof is 0. 1 part by weight of at least one selected from ascorbic acid, erythorbic acid or a salt thereof. It is preferably in the range of 1 to 100 parts by weight.

Further, such a processing solution used in the present invention contains other anticorrosives and scale inhibitors, such as polyacrylic acid or a salt thereof, polymethacrylic acid or a salt thereof, as long as the effects of the present invention are not impaired. Copolymer or salt thereof of acrylic acid and methacrylic acid, polymaleic acid or salt thereof, copolymer of styrenesulfonic acid and maleic acid or salt thereof, hydroxyethylidene diphosphonic acid or salt thereof, phosphonobutanetricarboxylic acid or salt thereof, acrylic Copolymer of acid and acrylamidomethylpropylsulfonic acid or salt thereof, sulfite, nitrite, zinc salt, tin salt, hydrazine, tannin, lignin, ligninsulfonic acid, molybdic acid or salt thereof, phosphinic acid, oxycarboxylic acid, phosphoric acid Alternatively, a salt, a saccharide or the like thereof can be added.

[0008] Further, such a chemical solution is charged into a boiler in the form of an aqueous solution dissolved in water, and a cleaning treatment can be performed by maintaining a state of being heated to, for example, 140 to 210 ° C for about 1 to 3 days and nights. it can. At this time, the concentration of the drug in the cleaning liquid is preferably in the range of 0.01 to 1.0% by weight.

[0009]

EXAMPLES (First test example) Softened water having the water quality shown in Table 1 was prepared so that the concentration (g / L) shown in Table 2 was obtained.
Ascorbic acid (ASCA), sodium ascorbate (ASCN), erythorbic acid (ESB)
A), sodium erythorbate (ESBN), sodium aspartate (APGN), potassium hydroxide (K
OH) and sodium hydroxide (NaOH) were dissolved to prepare treatment solutions A to H containing the boiler pretreatment detergent of the present invention.

[0010]

[Table 1] Water quality of softened water pH: 7.5 Electrical conductivity (μS / cm): 390 M alkalinity (mgCaCO ₃ / L): 50 Total hardness (mg / L): <1 chloride ion (mgCl / L): 62 Silica (mgSiO ₂ / L): 5 Iron (mgFe / L): <0.05

For comparison, a treatment liquid X containing 2.0 g / L of sodium hydroxide (NaOH) is used as an example of conventional soda-boiled, and sodium hydroxide (NaOH) is used as an example of a conventional anticorrosive cleaning agent. 0g / L, hydrazine (HAZN)
Treatment solution Y containing 0.5 g / L, 2.0 g / L of sodium phosphate (NPHS), 0.9 g / L of glucose (GULC) as an example of a conventional anticorrosive for saccharide-based boilers, potassium hydroxide (KOH) 0.4 g / L, sodium phosphate (NPHS)
A processing solution Z containing 0.3 g / L was prepared.

[0012]

[Table 2]

On the other hand, a STPG steel pipe polished and cleaned is prepared to evaluate the corrosiveness of the processing liquid to metals, and 40 mm × 15 mm is used to evaluate the cleaning power of the processing liquid.
A test piece was prepared by uniformly and thinly applying machine oil (49 mg / dm ² ) to a polished mild steel sheet having a thickness of 2 mm.

An electric heater (surface area: 154 cm ² ) using the above-mentioned STPG steel tube as a sheath was attached to an autoclave (water volume: 1.5 L) so as to be immersed in water, and a test piece for evaluating the detergency was further prepared. Was also charged to the autoclave. After each of the treatment liquids was charged, the autoclave was sealed and operated at the temperature and time shown in Table 3, and the pH of the treatment liquid before and after the test, the STP
The corrosion area (cm ² ) of the G steel pipe, the occurrence of pitting, and the discoloration of the surface were examined.

Further, a test piece for evaluation of detergency is taken out from the autoclave, dried once, and then sufficiently washed with hexane at room temperature. (Mg / dm ² ). These test results are also shown in Table 3.

[0016]

[Table 3]

(Second Test Example) In the first test example, a STPG steel pipe subjected to a cleaning treatment test using the treatment solutions A, B, and D of the present invention and the treatment solutions X and Y of the comparative example was used as an electric heater. After being attached again as a sheath, and these electric heaters were attached to the autoclave in the same manner as in the first test example, corrosive artificial boiler water having a water quality as shown in Table 4 was charged into the autoclave, and the vapor pressure was set to 0.7 MPa.
a, After operating for 4 hours at a steam generation rate of 1.5 kg / hr and a blow rate of 10%, the operation was stopped, the water temperature was lowered to 60 ° C., and the valve was left open until the next day with the valve open. On the next day, the same operation was repeated again, and after the same operation was repeated for 4 days, the corrosion area of the surface of the heater sheath and the occurrence of pitting were measured. The results are shown in Table 5.

[0018]

[Table 4] Artificial boiler water quality M alkalinity (mgCaCO ₃ / L): 500 Chloride ion (mgCl / L): 2000 Sulfate ion (mgSO ₄ / L): 100 Silica (mgSiO ₂ / L): 100

[0019]

[Table 5]

[0020]

According to the boiler pretreatment cleaning method of the present invention, not only the cleaning effect is not inferior to the case of using the conventional boiler pretreatment agent, but also the anticorrosion of iron-based metals is excellent. After cleaning the inside of the boiler, the boiler can be kept on standby without performing a preservation process for corrosion prevention or the like, or can be put into operation immediately. In addition, the waste liquid after pre-treatment is almost neutral, so it can be subjected to general wastewater treatment without neutralization treatment, and the pre-treatment process can be greatly simplified. is there.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C23G 5/032 C23G 5/032

Claims (1)

(57) [Claims] 1. A treatment liquid containing at least one selected from ascorbic acid, erythorbic acid or a salt thereof, aspartic acid or a salt thereof, and potassium hydroxide or sodium hydroxide is charged into a boiler, and the treatment liquid is charged. From 140 to
A pretreatment cleaning method for a boiler, wherein the method is maintained at 210 ° C. for about 1 to 3 days and nights .