JPS5934760B2 - Remover for deposits mainly composed of fuel ash - Google Patents

Description

[Detailed Description of the Invention] Heat transfer surfaces such as boiler tubes that are directly exposed to combustion gas in boiler furnaces that burn heavy oil, crude oil, and residual oil from petroleum plants have deposits mainly composed of these fuel ash. It is known to accumulate and cause the following problems.

That is, (1) a large amount adheres to the surface of the heat transfer surface in the boiler furnace, inhibiting heat transfer and reducing boiler efficiency.

(2) Since deposits generally have a low melting point, they can be found in areas where the combustion gas temperature is high (850-1100℃) or where the steam temperature is high (850-1100℃).
450-57 "C) In the environment, it often adheres in a molten state and is in close contact with the heat transfer surface, making it difficult to remove.

(3) Since the deposits are mainly composed of Na2S04 (sodium sulfate) and vanadium compounds (NaV03, Na2O-R2O4, R2O5, etc.), they are highly corrosive to metal materials and exist in the state shown in (2). If this occurs, the heat exchanger tubes will be corroded and worn out.

(4) When the amount of deposits increases, the combustion gas passage becomes narrower,
Heat transfer by the combustion gas and normal combustion themselves become a problem, making it difficult to control the operation of the boiler.

In order to deal with the above-mentioned problems, when the boiler is stopped for periodic inspections, fuel ash adhering to the heat transfer tube surface is removed by scraping, hammering, sandblasting, etc., but it requires a lot of manual labor. It requires a lot of work, and also causes a deterioration of the working environment, such as increased noise and dust, and it cannot be completely eliminated.

(Where the pipes overlap, the above method cannot be used.) Also, the used sand contains harmful substances such as heavy metals (vanadium, nickel, chromium, etc.) contained in the fuel ash. Therefore, problems remain when disposing of this as waste. Table 1 shows an example of the results of chemical analysis of fuel ash deposited inside a boiler furnace that burns heavy oil.

As is clear from this example, fuel ash contains a wide variety of elements (compounds).

In addition, there is a surprisingly large amount of water-soluble components, and even if they are fused to the heat exchanger tube, it is expected that if moisture is present, they will dissolve into the water and become loose, making it easy to mechanically remove them from the heat exchanger tube. The present invention relates to a remover for deposits mainly composed of fuel ash, which was created under these circumstances.
and 0.5y of an acid corrosion inhibitor and at least one gelling substance selected from the group consisting of carboxymethyl cellulose, starch, gum arabic, fleur-de-lis, agar, glue, and gelatin, to produce fuel ash. It is characterized by its high viscosity so that the thickness of the coating is 1 mm to 2 mm when applied to the surface of the surface, and it can be applied thickly even on vertical surfaces, making the application process easy and hygienic, and without corrosion problems. The object of the present invention is to provide a removing agent of this kind that can easily remove deposits.

As an example of the deposit remover of the present invention, one with the following composition was prepared and applied to a heat exchanger tube on which deposits having the chemical components shown in Table 1 were adhered, and after 24 hours, the deposits were removed with a scraper. Removed.

(1) and (3) are comparative examples for comparing cases in which no acid corrosion inhibitor is included, and (2) and (4) are examples in which an acid corrosion inhibitor is included. [Composition of remover] Each of the removers (1) and 4) has a gel-like form, so it can be applied to a thickness of 1 to 2 mm on the deposit.
Also, since it has a viscosity similar to that of mayonnaise, it will not fall to the bottom even if it is applied vertically.

Therefore, moisture can be supplied to the deposits on the application area for a long period of time, so that the hard deposits in the form of fusion gradually soften over time, making it easier to remove them from the surface of the heat exchanger tube. Moreover, when the softened deposits are scraped off the coated surface with a scraper or the like, the CMC-containing remover removes the deposits in a thin layer (similar to scraping wood with a planer), making it easy to handle. If the amount of deposits is extremely large and it is not possible to completely remove the deposits with just one application, it is possible to apply the remover in layers, and this method allows the supply of moisture to the deposits. It is possible to increase

The acid corrosion inhibitor added to the remover coexists in the same way when the water in the remover moves to the deposit and dissolves the water-soluble components, so the moisture passes through the deposit. It has been found that even if the acidic water-soluble components reach the surface of the heat exchanger tubes, the corrosion effect on the heat exchanger tubes caused by acidic water-soluble components is suppressed, thereby making it possible to prevent corrosion damage to the heat exchanger tubes that is likely to cause serious accidents. .

In other words, the results of removing deposits from the coated surface using a scraper after 24 hours are as shown in Table 2. If the gel-like deposit remover of the present invention is used, pipes can be very easily maintained in a strong state. The fuel ash adhering to the wall could be removed.

Additionally, Table 3 shows that when the remover of the present invention was applied at intervals of 10 hours and the fuel ash was removed after 50 hours and the condition of the pipe surface was observed, no corrosion was observed on the tubes coated with the remover of the present invention. On the other hand, pitting corrosion with a diameter of approximately 0.3 to 1 mm occurred in those to which no acid corrosion inhibitor was added.

This means that in the removing agent of the present invention, when the gel-like substance containing a large amount of water supplies the water of the fuel ash and dissolves the water-soluble components in the fuel ash, the water becomes acidic and the surface of the tube becomes This indicates that corrosion of the fuel was prevented by the action of the acid corrosion inhibitor, and although a gel-like material to which no acid corrosion inhibitor was added was effective in supplying moisture and removing fuel ash, This indicates that there is no effect on preventing corrosion of pipes.

In addition, in the examples, CMC and starch were used as gel-like substances, but in addition to these substances, gum arabic, french,
High viscosity imparting materials such as agar and glue (gelatin) can also be used.

Claims (1)

[Claims] 1 Per 1,000 ml of water, 2 g of surfactant, 0.5 g of acid corrosion inhibitor, and at least one gel selected from the group consisting of carboxymethyl cellulose, starch, gum arabic, fluff, agar, glue, and gelatin. The thickness of the coating film when applied to the surface of fuel ash is 1 mm.
A removal agent for deposits mainly composed of fuel ash, characterized by having a high viscosity of 2 mm to 2 mm.