RU2495729C2 - Method of scale removal - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to scale removal and can be used under household and industrial conditions, for example, for removal of scale from teakettles or from "wet" surfaces of automotive engine cylinder blocks, or the like. Acid-based detergent solutions are filled in the vessel to be cleaned and held therein for a definite time. Said vessel is prefilled with water to be boiled and cooled to ambient temperature. Then, vessel is cooled further to below minus four degrees Centigrade to generate vibration in scale area. Then, vessel with ice is heated and, again, scale is subjected to vibration to remove water along with scale particles. Cooling temperature is selected with due allowance for tank material strength. Frequency of vibration should, in the first case, equal the scale material intrinsic oscillation frequency and, in the second case, it must equal to tank material intrinsic frequency.

EFFECT: higher efficiency of scale removal.

Description

The invention relates to methods for removing solid deposits from surfaces of various metal products, both in industrial and domestic conditions, for example, for descaling from dummies or from the “wet” part of cylinder blocks of automotive engines or from other containers.

The known method [1, p. 82] cleaning surfaces using solutions of various multicomponent synthetic detergents. The advantage of which is that they do not cause corrosion of ferrous metals, do not have a harmful effect on the skin and clothing of workers. Parts washed (cleaned) with the help of them do not require subsequent rinsing with water. The disadvantage of these solutions is that they require heating to intensify the cleaning process, and this requires additional time and energy. To increase the intensity and quality of cleaning, pre-wetting of the surface is often used, for example, the solution is pre-poured into the container to be cleaned and kept for a long period for better wetting of contaminants, which also reduces the performance of the cleaning process. It has been established that solutions of synthetic detergents are effective only when cleaning easily removable contaminants, for example, with their help it is almost impossible to remove such type of contamination as carbon deposits, scale, etc.

The closest in technical essence to the alleged invention is a method of cleaning products using acid-based detergents [2, p. 94], for example, use solutions based on hydrochloric, sulfuric, phosphoric, chromic, lactic, acetic and citric acids. This method is more effective than the use of synthetic detergents, but also has its significant disadvantages. Firstly, any acid in itself is dangerous for workers, especially in production conditions, where it is quite difficult to comply with all safety requirements when working with various hazardous fluids. Secondly, acid-based washing solutions cause corrosion of ferrous and non-ferrous metals, therefore, after cleaning, it is necessary to rinse again, for example, with a solution of soda ash and trisodium phosphate, or use inhibitory compounds, which also increases the complexity and cost of the cleaning process.

Thus, the disadvantage of existing methods of cleaning the surfaces of any products is their low efficiency, considerable laboriousness, and danger to workers, especially when cleaning difficult to remove contaminants, such as scale. In addition, the tendency to the destruction of most products with the use of washing solutions, especially based on certain acids, reduces the resource of the cleaning object. These disadvantages relate directly to the cleaning process.

It is known that there are three types of scale: silicate, carbonate and mixed. Therefore, before starting descaling, using traditional methods, it is necessary to conduct an analysis to determine the type of scale and then select the appropriate solution, which is a serious procedure that requires appropriate preparations for analysis, methods and knowledge. Such an analysis in everyday conditions is almost impossible. Therefore, the use of various anti-scale descaling preparations, which are offered for descaling both in domestic and industrial conditions, is extremely inefficient.

The aim of the invention is to increase the efficiency of removal of solid contaminants from the surface of products, for example, in the form of scale.

The essence of the invention lies in the fact that the container, on the “wet” surface of which scale or other solid deposits formed, is pre-filled with water, then the water is brought to a boil, then the container together with the water is cooled to ambient temperature. Then it is cooled further to a temperature below minus four degrees Celsius, until all the water in the tank turns into ice. Then, to the mass of solid frozen [solid mass is ice, solid deposition (scale) and capacity] induce vibration with a frequency equal to the frequency of natural oscillations of scale.

Then, the ice container is reheated until the ice melts to a value so that it can be removed from the vessel along with the pieces of scale. Since the thermal conductivity of water, the scale and the material of the vessel are different, the coefficients of thermal expansion of ice, the scale and the material of the vessel are also different, then during the sequential heating and cooling at the boundaries of the contact of the scale with the surface of the tank, stresses arise that detach the scale particles from the tank . For a greater intensification of the process of separation of scale particles from the surface of the tank, and self-destruction of scale, after continuous ice has formed during the cooling process, a vibration is induced with a frequency equal to the frequency of the natural scale oscillations. After the ice has melted, re-induce vibration with a frequency equal to the natural frequency of the container material, which allows you to tear off the remaining scale particles from the surface of the container.

The cooling temperature should be lower than minus four degrees Celsius, but such that there is no rupture of the container material due to the strong increase in ice volume during the cooling process. That is, the cooling temperature must be selected depending on the material of the container so as to create maximum shear stresses at the point of contact of the scale with the surface of the container, at the same time so that there is no rupture of the container material from an excessive increase in ice volume. Thus, even a simple heating of the water filled into the tank to be cleaned, followed by cooling and heating, gives the effect of separation of solid deposits from the walls of the tank. Introducing vibration with a frequency equal to the natural frequency of oscillations of scale or other solid deposits, first in the scale material, and then in the material of the tank, dramatically increase the efficiency of self-destruction of the solid deposit and its separation from the surface of the tank. In the process of freezing water, the scale layer experiences pressure from the ice and from the side of the inner surface of the tank, that is, it experiences mechanical compression, which allows you to bring the resonant frequency to it.

The physical meaning of this method is as follows.

1. When the surface of a metal container is rapidly heated (without scum), due to differences in the coefficients of linear expansion of the product metal and scum, tangential stresses arise in the contact zone, causing a shift in the microvolumes of the product material relative to the scum layer, contributing to the destruction of adhesive bonds between the product and scum surfaces.

2. The imposition of vibration of the resonant frequency increases the amplitude of the oscillations of the tangential stress in the zone of contact of the surface of the product with scale.

3. The wetting of the scale with subsequent freezing helps to increase the temperature difference in the zone of contact of the surface of the product with scale with subsequent heating of the product, which in turn will increase the shear stress between the surfaces.

Laboratory tests have shown the effectiveness and feasibility of the proposed method.

Removal of solid deposits, for example, scale from the surface of products (containers) is carried out in the following sequence. The container is pre-filled with water, then the water is brought to a boil. Then the heat source is turned off, and the water tank is cooled to ambient temperature. Then, the container with water is cooled to a temperature below minus four degrees, but so that there is no destruction of the container material from an increase in ice volume, that is, the cooling temperature is selected taking into account the strength of the container material. They induce vibration with a frequency equal to the frequency of natural vibrations of the scale material to increase the efficiency of separation of scale particles from the inner surface of the tank.

Then, the ice container is quickly heated and vibrated again with a frequency equal to the natural frequency of the vessel material for the final detachment of scale particles from the inner surface of the vessel.

Vibration can be induced in different ways, for example, by installing a container on a vibrating table, or by hammering in places where the thickness of the scale is greatest with different strengths and different frequency of impacts. At the same time, the material of the hammer should have a lower hardness than the hardness of the material of the container in order to avoid deformation of the surface of the container from impacts, the impact force should also exclude deformation.

The technical effect is achieved due to physical phenomena that occur in the zone of contact of ice with the surface of the scale and in the area of contact of the surface of the scale with the inner "wet" surface of the tank, which removes scale during heating and cooling, and also due to vibration induced in the material of the container, first after cooling, then after heating, thereby increasing the efficiency and quality of removal of hard-to-remove hard deposits of the “scale” type from the surface of the products.

Information sources

1. Maintenance and repair of machines. / I.E. Ulman, G.S. Ignatiev, V.A. Borisenko et al .; Under the total. ed. I.E. Ullman. - M.: Agropromizdat, 1990 .-- 399 p .: ill. - (Textbooks and teaching aids for agricultural technical schools). ISBN 5 - 1- - 000814 - 8.

2. Savchenko V.I. Repair of equipment on collective and state farms. M., Rosselkhozizdat, 1975.216 p. silt.

Claims (1)

The method of descaling from the inner "wet" surface of various metal containers for liquids, for example water tanks, which consists in the fact that acid-based detergent solutions are poured into the container, they stand for a certain time, followed by heating, characterized in that the container is pre-filled with water , then bring the water to a boil, cool to ambient temperature, then cool further to a temperature below minus four degrees Celsius, vibrate the scale material, then heat container with ice and re-induce vibration in the container material and remove water along with scale pieces from the container, and the cooling temperature is selected taking into account the strength of the container material, the vibration frequency should in the first case be equal to the frequency of natural vibrations of the scale material, and in the second to the frequency of natural fluctuations in the material of the container.