JPS5896996A - Surface treatment material of heat exchanger - Google Patents

Abstract

PURPOSE:To bestow the function to neutralize dew condensed water and to purify combustion gas by a method wherein the surface of a heat exchanger is coated with heat resisting paint, which consists of pigment of low-melting-point glass frit and silicon resin bonding agent, added with alkaline material. CONSTITUTION:At first, a copper base metal 7 is coated with aluminum or aluminum alloy 8 and further coated with silicon resin 10 employed low-melting- point glass frit as pigment. In this case, about 1-20wt% of carbonate or hydroxide 11 of alkaline earth metal or alkali metal is added to the paint, which consists of pigment of low-melting-point glass frit 9 and silicon resin bonding agent. As a result, the low-melting-point glass frit 9 reacts with strong acid dew condensed water so as to neutralize the dew condensed water to have its pH values of about 5.5-7.5 and the alkaline material reacts with NO2 and SO2 in the combustion gas in order to decompote them into harmless gases.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a surface treatment coating for an auxiliary heat exchanger provided in order to improve the thermal efficiency of bathtubs, instantaneous water heaters, etc. with a heat-resistant paint. The present invention relates to a heat exchanger surface treatment material that can neutralize dew condensation water and purify combustion exhaust gas at the same time.

BACKGROUND ART Conventionally, in order to improve the thermal efficiency of gas water heaters, systems have been developed in which an auxiliary heat exchanger is provided and water, which is a substance to be heated, is preheated using latent heat of combustion exhaust gas. The outline is shown in Fig. 1.

1 is the main heat exchanger, 2 is the auxiliary heat exchanger, 3 is the gas fire, 4
is a pipe, 5 is a drain, and 6 is condensed water. The principle of this type of gas water heater is that water, which is an object to be heated, passes through a pipe 4 and is preheated by the latent heat in the combustion exhaust gas in the auxiliary heat exchanger 2, and then is supplied in the direction of the arrow. It has been confirmed that the water heater using this method has a thermal efficiency of 10#1% higher than the conventional method using only a main heat exchanger without an auxiliary heat exchanger.

However, in water heaters equipped with auxiliary and auxiliary heat exchangers, the latent heat of the combustion exhaust gas is utilized, so the moisture contained in the combustion exhaust gas drops below the dew point in the auxiliary heat exchanger, causing severe condensation. occurs. Gases such as nitrogen monoxide, nitrogen dioxide, sulfur dioxide, and carbon dioxide in the combustion exhaust gas dissolve into this condensed water, and it becomes strongly acidic with a pH (hydrogen ion concentration) of around 3.0. There has been a problem in that the surface treatment material of the Pb-8n alloy used in the past and the copper material are corroded, causing a hole formation phenomenon, and eventually leading to a state where the heat exchanger function is no longer available.

For this reason, it is dangerous to directly drain condensed water into the sewer system when the condensed water is being discharged, and some kind of neutralization treatment is required. For this reason, conventionally, alkaline earth metals such as magnesium metals have been used for neutralization treatment by providing treatment tanks. Since such treatment is required, there is a drawback that a neutralization treatment tank must be provided.

As mentioned above, among the various compounds contained in combustion exhaust gas, -nitrogen oxide, nitrogen dioxide, and sulfur dioxide dissolve into condensed water and contribute to its strong acidity. The disadvantage is that not all of these gases are dissolved in the condensed water, and some of them are emitted into the air as harmful substances in the gas phase.

The present invention applies an alkaline earth metal or alkali metal hydroxide to a paint made of a low melting point glass frit pigment and a silicone resin binder on the surface of an auxiliary heat exchanger provided in order to improve the thermal efficiency of a water heater. Alternatively, a heat exchanger surface treatment material can be coated with a surface treatment material containing carbonate, and can simultaneously neutralize dew condensation water on the surface of the auxiliary heat exchanger and purify combustion exhaust gas. The goal is to provide the following.

FIG. 2 shows a structure coated with the surface treatment material of the present invention. The present invention will be explained in detail with reference to FIG.

The top of the copper base 7 is coated with Vc full copper or aluminum alloy 8, and then a low melting point glass frit 9 is coated with a silicone resin 10 containing a pigment.

In this case, 1 to 20% by weight of a carbonate or hydroxide of an alkaline earth metal or alkali metal 11 is added to a paint containing low melting point glass frit 9 as a pigment and silicone resin as a binder. 12 is a copper pipe.

If these paints are directly coated on the copper base 7, a copper oxide film will be formed when the paint dries, and the adhesion between the copper base 7 and the silicone resin 10 will be weak and will easily peel off. For this reason, as mentioned above, the copper base 7 is coated with aluminum or aluminum alloy 8 to improve the adhesion of the paint, but if the adhesion between the copper base and the paint is strong, There is no need to coat other metals, and it can be coated directly on copper substrates.

Furthermore, since many pinholes occur after coating with silicone resin alone, the 7 holes in the bottle are filled by using low melting point glass frit as a pigment.

The low melting point glass 7 liters 9 contained in the surface treatment material coated on the copper substrate 7 in this way reacts with the strongly acidic condensed water to neutralize it to a pH of 5.5 to 7.5.

In addition, N02 in the combustion exhaust gas passing near this surface treated material
(Nitrous acid) and SO□ (sulfurous acid) react with the alkaline substances Ca (0H)2 and Mg (OH)2 as shown in the following formula and are decomposed and discharged as harmless substances. ru0 4NO2+ 2Ca (0H)2 →Ca (No 2
) 2 + Ca (NO3)z+ H2O280□
+2Ca(OH)2−+ 2CaSO4・1/2 H2
0+H20 In other words, it has the effect of purifying combustion exhaust gas, the reaction is significantly faster than conventional ones, and it can be processed on an auxiliary heat exchanger, allowing for a compact design with an integrated heat exchanger. .

In order to purify these combustion exhaust gases, the reaction proceeds smoothly when Ca(OH)2 or Mg(OH)2, which is an alkaline substance, is preferably added in an amount of 1 to 20% by weight as a single substance or a compound. This is a surface treatment material for the auxiliary heat exchanger that neutralizes strongly acidic condensed water on the surface of the heat exchanger and also purifies the combustion exhaust gas. It is a chemical heat exchanger. This eliminates the need for a treatment tank, which was required in the conventional method, and has the effect of purifying the combustion exhaust gas.

[Brief explanation of drawings]

FIG. 1 shows a conventional water heater equipped with an auxiliary heat exchanger, and FIG. 2 shows a configuration of the surface treatment material of the present invention. 9...Low melting point glass frit, 10...
・・・・・・Silicone resin, 11・・・・・・・・・
・Alkali metal. Figure 1 Figure 2 “Tomoe Ichicho)! )゛′

Claims (3)

[Claims] (1) An auxiliary heat exchanger for preheating the substance to be heated is installed downstream of the combustion exhaust gas generated in the main heat exchanger, and the surface of the heat exchanger is made of a pigment made of low-melting glass frit and a binder of silicone resin. B. A heat exchanger surface treatment material, which is coated with a heat-resistant paint containing an alkaline substance, thereby imparting a neutralizing effect on dew condensation generated in the heat exchanger and a purifying effect on combustion exhaust gas. (2) The heat exchanger surface treatment material according to claim (1), characterized in that the alkaline substance is an alkaline earth metal and an alkali metal carbonate or hydroxide. (3) The heat exchanger surface treatment material according to claim (1), characterized in that Ca (OH) 2 or Mg (OH) 2 is added as a fluoric substance. A heat exchanger surface treatment material according to claim (1), characterized in that 1 to 20% by weight of the following is added singly or in combination.