JPS60194088A - Corrosion preventive agent for colling water of heat exchanger - Google Patents

Abstract

PURPOSE:To provide a corrosion preventive agent for cooling water of a heat exchanger having the function to prevent corrosion which is effective with addition of an extremely small amt. by consisting said agent of the phytic acid expressed by the specific molecular formula or the K salt, Na salt and NH4 salt thereof. CONSTITUTION:The corrosion preventive agent of this invention is the phytic acid expressed by the molecular formula C6H18O24P6 or the K salt, Na salt and NH4 salt there of. Such acid or salt is used alone or the mixture composed thereof is used or additives are added thereto within the range where no problems arise. When an extremely small amt. of such corrosion preventive agent is added to the colling water of a heat exchanger, said agent prevents effectively corrosion of members such as heat transmitting tubes and other members consisting of copper and copper alloy of the heat exchanger. The trouble with corrosion of the heat transmitting tubes of the heat exchanger which is conventionally of problem is mostly eliminated. The corrosion preventing agent solves also water the problem of eutrophication by decreasing the concn. of phosphorus in waste and has the effect of preventing effectively the corrosion trouble of the heat exchanger at an economical and low cost and decreasing heat transmission loss.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling water corrosion inhibitor that prevents corrosion of Cu-based members of a heat exchanger caused by cooling water. It is possible to reduce the concentration.

Generally, heat exchangers that pass cooling water are of open circulation type, closed circulation type, or through-circulation type, and most of them use industrial water as the cooling water.

However, recent environmental pollution has caused a significant deterioration in water quality.
There are cases where corrosion occurs in Cu-based members such as heat exchanger tubes in heat exchangers that come in contact with cooling water, and we are struggling to find countermeasures.

One of the known countermeasures is to add corrosion inhibitors, so-called inhibitors, to the cooling water. Corrosion inhibitors include nitrites, borates, molybdates, chromates, phosphates, etc. It is used.

Among these corrosion inhibitors, chromate was the most effective, but it is no longer used due to pollution regulations.

Phosphorus MjJA has been confirmed to be highly effective and is currently in widespread use, but there is a risk of eutrophication if it is discharged into a closed water area, and to avoid this, low-phosphorus or non-phosphorus corrosion inhibitors are required. It is being considered. Also, other corrosion inhibitors have little effect (and are not used).

In order for phosphate-based corrosion inhibitors to exhibit sufficient corrosion protection effects, it is necessary to add them at a concentration of 20 ppmas-PO+ or more. There is an inconvenience. In addition, if the concentration exceeds 20ppIllas-P O÷, there is a risk of eutrophication in closed water areas as described above, and in open circulation systems or one-time cooling water, the wastewater discharged from areas with a high temperature of 21 degrees Environmentally undesirable. In addition, to prevent the growth of slime and algae, cooling water is also disinfected with chlorine, but if the chlorine concentration is mismanaged, holes may form in Cu-based components such as heat exchanger tubes. It had the disadvantage of causing eclipse.

In view of this, as a result of various studies, the present invention has created a corrosion inhibitor for heat exchanger cooling water that has an effective corrosion inhibitor function even when added in a very small amount. Cu
The molecular formula for preventing corrosion of system components is Cs H+ a Oz
It is characterized by consisting of phytic acid or its salts, Na salts, and NH+ salts represented by +Ps.

That is, the inhibitor of the present invention has a molecular formula of Cs hh a Oz+
Phytic acid or its salt represented by Ps, Na salt, NH
4 salts, and these salts may be used singly or as a mixture, or with additives added thereto to the extent that there is no practical problem. By adding a small amount of these to the cooling water of the heat exchanger, they can effectively prevent corrosion of heat exchanger tubes and other parts made of copper and copper alloys, and eliminate the problem of conventional heat exchangers. Most corrosion problems of heat exchanger tubes can be solved. This is because when the inhibitor of the present invention is added to cooling water in a very small amount, for example, 5 ppm+, a film is formed as a protective barrier on the surface of Qu-based members including the heat exchanger tubes in contact with the cooling water. This is to prevent attacks from seagull food vectors.

The inhibitor of the present invention also contains phosphorus, but unlike phosphate inhibitors, it has a sufficient effect with the addition of a very small amount.
The amount of phosphorus in wastewater is reduced, which is not only environmentally friendly, but also prevents eutrophication. That is, Cs H>s
Oz + Ps contains 33% phosphorus, but only 5 ppm
The addition of C contains only 1.4 DD of phosphorus. On the other hand, adding the phosphate inhibitor 201)l)Ilas-PO+ will result in a phosphorus content of 6.6 ppm, and by using the inhibitor of the present invention, the amount of phosphorus in wastewater will be lower than that of the conventional one. It can be suppressed to about 20%.

Furthermore, pitting corrosion caused by chlorine disinfection, which is the most inconvenient for Cu-based members, can also be effectively suppressed.

The present invention will be described in detail below with reference to Examples.

Example (1) In a centrifugal chiller that uses copper loaf-in tubes as heat transfer tubes and uses one-time cooling water, 50 ppm of polymerized phosphate was added to the cooling water, but due to eutrophication, , it became necessary to regulate phosphorus concentrations to low levels. Therefore, in place of the conventional polymerized phosphate, 5 p of phytic acid of the present invention was added.
pm was added. As a result, the problem of eutrophication of wastewater was resolved and two years passed, during which time corrosion failure of heat transfer tubes did not occur even once, and the cost was about 1/4 of that of polymerized phosphate.

Example (2) A department store is air-conditioned using open circulation cooling water. A plurality of heat exchangers are divided into two rows, and one row of heat exchangers uses untreated cooling water. 3 ppn+ for one series of
A comparative test was conducted using cooling water to which sodium phytate was added.

As a result, corrosion damage occurred twice in one year in a heat exchanger that used untreated cooling water, and the heat exchange rate was as low as 62%. On the other hand, in the heat exchanger using cooling water to which sodium phytate was added, 11X eating disorder did not occur and the heat exchange efficiency was as high as 90%.

In this way, the inhibitor of the present invention reduces the phosphorus concentration in wastewater, eliminates problems such as eutrophication, effectively prevents corrosion damage to heat exchangers at an economically low cost, and reduces heat transfer loss. It has remarkable effects such as preventing and preventing.

Claims (1)

[Claims] Cooling water for heat exchangers made of phytic acid whose molecular formula is Cs Hs Oz◆P6, or its salts, Na salts, and NH◆ salts, which is added to cooling water to prevent corrosion of Cu-based members of heat exchangers. corrosion inhibitor.