Background of the Invention Different methods of vapour generation in boilers have been known.

The method of fluid evaporation in canal by its heating to the temperature more than the saturation temperature of the vapour generated is known (1).

In sufficient reliability and higher material consumption because of the necessity to increase fluid pressure are the disadvantages of the known method.

The method of fluid evaporation by reduction of its pressure less than the pressure of saturation due to decreasing the twist radius of the fluid stream in centrifuge is known (2). The limited application and higher power consumption may be considered to be the disadvantages of the method.

The prototype of the invention offered is assumed the method of fluid evaporation (3) at which the fluid in the canal is heated more than the saturation temperature of the generating vapour and the pressure of the evaporating fluid is reduced due to heating the fluid by using saturated vapour pressure kept at definite speed, here the temperature of the canal sides being maintained less than the extreme overheating temperature of the evaporating fluid.

The peculiar feature of the adopted as prototype method is that the necessary speed of fluid heating is achieved also by choosing the material of the sides of the vapour generating canals, with they being wetted by all means with evaporating fluid. During the work of the boiler, however, the canal inner sides are covered with scale. It changes the wetting effect of evaporating fluid, thus breaking the heating conditions foreseen by the prototype method.

Canal heat transfer decreases and vaporization intensity drops. In order to keep it to the former level it is necessary to increase heat flow with the danger to arise the crisis of heat exchange, namely, the transition of the nuclear

boiling into the film one. Such method of fluid evaporation gives no possibility to influence on the double electrical layer (4) forming on the surface of the bubbles at their origination. They appear on the surface of heating in the places where fluid wetting of solid body is small (5). Here, there is no influence on the electrostatic component of wetting surface forces, this component mainly determining the intensity of vaporization (6).

Due to the particular feature mentioned above the insufficient efficiency is the main disadvantage of the method taken as a prototype.

Disclosing of the Invention The aim of the invention offered is to increase the efficiency of the operation by decreasing the fuel consumption at fluid evaporation.

In the proposed method which supposes heating the evaporating fluid in the canal to the temperature more than the saturation temperature of the generating vapour, decreasing the pressure in it and keeping the temperature of the canal sides less than the temperature of the extreme overheating of the evaporating fluid, in order to increase the efficiency of the work, the heat transfer of the canal is increased by electrostatic weakening of its sides, thereby decreasing wetting of their surface with evaporating fluid that leads to increasing the number of centers of vaporization, decreasing tearing off diameter of the bubbles, increasing the frequency of their tearing off and to decreasing the temperature of the side.

According to the invention electrostatic weakening of the canal sides is carried out, in particular, by imposing neutralizing electrical potential to them which is set in the limits of V.

The canal is made of metal corresponding to the invention.

If neutralizing potential does not reach the value of 10,0 V, it will be impossible to get in full desired removal of electrical charges from the surface of canal sides, to decrease wetting and increase vaporization intensity. If the potential is more than 60,0 V, it will lead to coming out the zone of weak

electrical fields where the breaking of double electrical layer occurs due to tunnel effect.

Industrial Application The examples of the offered method realization.

Example 1.

To run the process realizing the method, it was used the steam boiler, double drummed of KV type, with permitted steam pressure of 2,0 MPa, vapour productivity of 50,0 t/h and vapour temperature of 325°C. Natural gas of 33,6 MJ/m3 at 20°C for three gas burners was used as a fuel. The boiler worked with stability of vapour productivity of 45 t/h, here the overheated vapour pressure being 1,28 MPa, vapour pressure in the drum being 1,37 MPa, the overheated vapour temperature of 230°C, the feeding water temperature was 110°C, the temperature of the issued gases was 360°C.

The temperature of canal sides was kept lower than the extreme in order to exclude fluid nuclear boiling transition into the film one. In such regime the specific fuel consumption was 41,8 kg of conventional fuel/GJ.

In order to get the process of the realizing method run, the electrostatic weakening of the boiler canal sides is carried out. The canal was made of metal. The time of electrostatic weakening was long equal to the time of the boiler operation. The value of neutralizing potential is set equal to 10,0 V.

The undertaken electrostatic weakening guarantees the removal of electrical charges from metallic sides of the canal. These charges have made the evaporating fluid wet the surface of canal sides. As a result, the wetting of the surface decreases and the density of the boiling centers increases.

The process had been running for four days. Dry remainder in the boiler water in the interval of blows increased during that time from 1300 mg/kg to 1500 mg/kg which proves decreasing the scale formation. Neutralizing electrical potential guarantees also the discharge of double electrical layer appearing as a result of electrolyzing in evaporating vapour gas bubbles

surface on the boundary of phase division. This eliminates the electrical resistance to structurization process, leads to decreasing the tearing off bubble diameter as well as to increasing the frequency of their tearing off from the canal sides. Thus, in the process of the method implementation heat transfer of the canal increased, the intensity of vaporization increased, the boiler vapour productivity increased as well. As the boiler efficiency is of nonlinear, with optimum dependence upon vapour productivity, hence, in order to eliminate this nonlinear influence, vapour productivity was kept to be 45 t/h during these four days at vapour pressure of 1,37 MPa in the drum due to the fuel consumption decrease. In four days the process stabilized and the following fortnight the average specific fuel consumption become 39,4 kg of conventional fuel/GJ and the same vapour productivity of 45 t/h and vapour pressure in the drum of 1,37 MPa.

Example 2.

Vapour generation was carried out in the same boiler corresponding to all the regimes and parameters given in example 1, but neutralizing electrical potential was set equal to 40,0 V. As the result of the test carried out it was determined that in stabilized long term regime the averaged specific fuel consumption was 37,5 kg of conventional fuel/GJ.

Example 3.

Vapour generation was carried out in the same boiler corresponding to all the regimes and parameters, given in example 1, but neutralizing electrical potential was set equal to 60,0 V. As the result of the test carried out it was determined that in stabilized long term regime the averaged specific fuel consumption was 38,9 kg of conventional fuel/GJ.

Positive results achieved by the realization of the offered method and proved by the examples given above are presented in the Table. They are shown in comparison with the data got from the same boiler before the method of the offered invention been tested.

The Table The examples of Productivity Vapour pressure Specific consumption of fuel method realization in drum kg of conventional fuel/GJ t/h MPa Example 1 45 1, 37 39, 4 Example 2 45 1, 37 37,5 Example 3 45 1, 37 38, 9 Prototype 45 1, 37 41, 8

The best variant of the invention realization In the given Table it is seen that the best results have been achieved in realizing the offered method corresponding to example 2. In operating the technological process in stabilized long term regime the average fuel consumption was 37,5 kg of conventional fuel/GJ.

Thus, the technical advantage of the method offered in comparison with the known solutions is the decreased fuel consumption in fluid evaporation.

INFORMATION SOURCES <BR> <BR> <BR> <BR> <BR> <BR> 1. Patent USA N9 3326640,1. cl. B 01 J 1/00,1967.<BR> <BR> <BR> <BR> <BR> <BR> <P>2. Author's Certificate USSR Ng 419687,1. cl. F 22 B 3/04,1974.<BR> <BR> <BR> <BR> <BR> <P>3. Author's Certificate USSR N9 954693,1. cl. F 22 B 1/00,1982.

4. Bondarenko N. F., Gack E. Z."Electromagnetic biophysics and nature phenomena", SPb, 1994, p. 151.

5. Frenkel Ya. I."Selected works"V. 3, M, Nauka, 1961, p. 390.

6. Deryagin B. V., Churaev N. V.,"Wetting films", M, Nauka, 1984.