RU2579309C1 - Method of drying inner surfaces of the shell and cover heat exchanger and device therefor - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to drying chambers of various equipment including tube and inter-tube space. In the method, based on evacuation, followed by blowing, vacuum drying, gas drying with dried air, the last dried surface of the tube space prior to vacuum drying surfaces of annular space. During the vacuum drying is blown ion wind in non-uniform electric field. Simultaneously proceeds with blowing tube space with dried air to ensure heat feed, compensating phase transition in evaporation of liquid from the surface of the tubular space until the given value of residual moisture of pumped air. Device for implementation of this method comprises drying heat exchanger (1) with tube bundle (2). Tube bundle (2) is connected to filter (4), absorber (5), pump (6), heat exchanger (7) for heating of dried atmospheric air fed into tube space of the tube bundle (2). Evacuation system (10) is connected through filter (12) with annular space (13) of heat exchange unit (1). Air duct (14) is connected with lower loses annular space (13) of heat exchange unit (1). In air duct (14) there is a set of corona electrodes (15) connected to high-voltage source (16), air duct (14) is a fan of corona discharge and acts as precipitation electrode. Air flow rate is controlled by the number of corona electrodes (15).

EFFECT: higher efficiency of drying of inner surfaces of shell-and-tube heat exchangers, including complex spatial geometry of tube space, containing dead-end zone, of slot.

5 cl, 6 dwg, 1 tbl

Description

The invention relates to a technology for drying cavities of heat-exchange equipment containing pipe and annular spaces, and can be used in power engineering, chemical, oil, gas, oil and gas processing and other industries.

Any technological heat exchange equipment operating under pressure is subjected to hydraulic tests for strength and tightness on the cavities of the working medium. After water is displaced from the equipment cavity, a water film with a thickness of 0.1 ... 0.2 mm remains on its inner surface. Given that the surface of the equipment, including the heat exchange surface, can be very large, the residual amount of water in each cavity of the equipment reaches significant values. The interaction of residual water with air, hydrocarbons and other working fluids leads to various types of corrosion of the heat exchange equipment, a decrease in the throughput and purity of the final product, and, ultimately, to complete failure of the heat exchange equipment. Therefore, before the drying process of any cavity of the heat exchange equipment, a more complete removal of residual moisture is necessary while minimizing production costs. The known main types of cavity drying (thermal, chemical, gas and vacuum) are not used in their pure form, since any combination of them is much more effective, due to the fact that the disadvantages of one type of drying are compensated by the advantages of another. However, in this case, the set of equipment necessary for the implementation of the process and energy consumption are significantly increased.

A known method of drying hollow products by creating a vacuum in the cavity of the product with the simultaneous supply of dry air in them in a volume of at least 10-15% of the volume of the cavity, while the residual pressure in the cavity is maintained to values (4-7) · 10 ³ Pa [1 ].

However, if the residual pressure decreases less than 4 · 10 ³ Pa and the amount of dry air supplied to the drained cavity is less than 10%, the drying efficiency of cavities of complex spatial geometry, mainly dead-end stagnant zones or crevices, is reduced due to the deterioration of mixing of the supplied air with residual water vapor .

There is a known method of drying pipes, in which the outside air is pre-dried in a special dryer and then blown out by suction through the pipes while heating them to the boiling point of water when the discharge is created in the pipes. A pipe drying device that implements this method is also known, in which the pipe is dried by blowing through it under rarefaction of atmospheric air dried in the dryer by pumping air from the pipe cavity, connected via a tip to a vacuum device and throttling the air at the pipe inlet using a throttle placed on the input line and equipped with means for heating the pipe [2].

An advantage of the known drying method is that atmospheric air is used for purging, which excludes the use of compressor equipment. However, since in the known method the pipes are purged with atmospheric air, each portion of air must first be drained in a special dryer. The need for preliminary additional drying of a new portion of atmospheric air is due to the fact that atmospheric air has its own humidity. In the case of unsatisfactory preliminary drying of the air, additional moisture may enter the drained cavity, as a result of which the drying efficiency of the cavity is reduced. At the same time, additional time and energy consumption are expended in removing moisture from atmospheric air. In addition, this method can only dry one cavity. The drying of cavities of complex spatial geometry, in which there may be dead-end zones, crevices, or there is no direct contact with the gaseous medium, is difficult.

A known method of drying the internal surfaces of the hydraulic system, including blowing with hot compressed air with a constant maximum temperature for the hydraulic system and a pressure corresponding to its working pressure, until a constant value of the air temperature at the outlet of the hydraulic system is established. In this case, after damping the output of the hydraulic system, the closed hydraulic system is charged with air with the purge parameters until the working pressure is established in the entire hydraulic system, soaking is carried out at the working pressure until the moisture is saturated in the micropores and microcracks of the hydraulic system with gas, then the hydraulic system is evacuated. The processes of purging, filling and holding the hydraulic system at its working pressure with hot air, as well as evacuation, are cyclically repeated until the specified value of the moisture content of the hydraulic system is reached. The implementation of this method of drying this hydraulic system is provided if the device connected to the hydraulic system has a vacuum unit, an electric heater, means for measuring temperature and pressure, evacuation, valves [3].

A disadvantage of the known method of drying the surfaces of a hydraulic system is that the processes of purging, filling and holding the hydraulic system at its working pressure with hot air, as well as evacuation are cyclically repeated until the specified moisture content in the drained hydraulic system is reached, as a result of which additional time is spent on drying. In this case, energy consumption increases, and the efficiency of drying the hydraulic system cavities decreases. In addition, this method provides drying of only one cavity. The drying of cavities of complex spatial geometry, in which there may be dead-end zones, crevices, or there is no direct contact with the gaseous medium, is difficult.

A device for air purging is known that uses ionic wind energy in a system of corona electrodes and a grounded structure located inside the equipment cavity and allows the cooling air to move through the equipment cavity and also to draw an additional volume of cooling air into the cooling process. Since the corona electrode - grounded structure provides direct conversion of electrical energy to wind energy, no mechanical devices are needed to advance the cooling air, while the energy conversion loss is minimal. The system of the corona electrode - a grounded design allows you to form a wind flow of an arbitrarily large cross section and is determined by the area of the structure [4].

A device for blowing air containing corona and precipitation electrodes located parallel to the gas stream, connected to a high voltage source, and participating in the formation of the directional flow and air velocity [5].

Also known is an air purge system, which is a multi-stage design of the electrode system, which allows to obtain a directed air flow, the speed of which depends on the number of corona electrodes. The advantages of this device are simplicity of design, lack of mechanics, lack of vibration, low noise level, the ability to work in aggressive environments and at high temperature [6].

However, the known systems [4, 5, 6] have a limited scope and provide only the creation of directional movement of the air flow at a certain speed, depending on the number of corona electrodes to remove heat from heated equipment or purge and clean the air from dust and chemical pollution in the premises. Known systems [4, 5, 6] are not used for drying equipment cavities, including cavities of complex spatial geometry.

The closest in technical essence and the achieved effect is a method of drying a cavity of equipment, including vacuum, vacuum drying and gas drying with dried hot air, purging a vacuum cavity. Atmospheric air is throttled when introduced into a drained cavity under vacuum and drained directly in the cavity by expansion. Atmospheric air is introduced in an amount that provides a stationary regime of vacuum purging and for a period of time up to reaching a predetermined value of residual moisture in the drained cavity, while atmospheric air is additionally introduced directly into the stagnant zones of the drained cavity. A device for implementing this method includes a vacuum system and a purge channel connected to the drained cavity of the equipment and equipped with valves, filtering means, means for controlling pressure and residual humidity, an adjustable throttle installed at the entrance to the drained cavity [7].

To intensify the drying process, especially in its dead-end zones, the movement of moist air inside the drained cavity is organized. For this, pre-drained atmospheric air is used, supplied into the drained cavity and moving in it due to the pressure difference between the evacuated cavity and the environment (atmosphere). The need to purge a vacuum drained cavity with atmospheric air is a significant drawback. The disadvantages of the known methods include the impossibility of draining the shell-and-tube heat exchangers having two drained cavities: the tube and annular spaces. The disadvantages of the device for the implementation of drying by this method also include the need for additional purge channels and throttling devices designed to purge and dry each of the stagnant zones separately, which leads to an increase in the amount of necessary equipment and energy consumption.

The necessary conditions for blowing dry surfaces, including dead ends, can be achieved using an ionic wind for this purpose, in which the movement of gas (air) is generated using an inhomogeneous electric field that creates a stream of charged particles created by an electrostatic accelerator containing corona and precipitation electrodes.

The proposed technical solution is aimed at achieving a new technical result - the creation of a unified technology for drying the inner surfaces of a shell-and-tube heat exchanger having tube and annular spaces covered with a liquid film that fully preserves the advantages of gas and vacuum drying methods.

The objective of the invention is to increase the drying efficiency of the internal surfaces of a shell-and-tube heat exchanger apparatus, including the complex spatial geometry of the annular space containing dead ends, gaps in which there is no direct contact with the gas medium, using ion wind technology.

This object is achieved by the fact that in the claimed method of drying the inner surfaces of a shell-and-tube heat exchanger based on evacuation, subsequent purging, vacuum drying, gas drying, dried air, additionally, drained air drains the surfaces of the tube space before vacuum drying the surfaces of the annulus, while in the process vacuum drying carry out a purge by an ionic wind in an inhomogeneous electric field and at the same time continue to purge the pipe dried air space for heat-compensating the phase transition at the liquid film evaporates from the surfaces of the annulus to achieve the desired value of residual moisture is evacuated.

In this case, drained air with a temperature of 170-285 ° C, a pressure of 0.5-0.7 MPa and having an average speed in the pipes of at least 1.3 m / s can be used to dry the tube space.

In this case, the drying of the annular space can be carried out within 1000-2000 Pa.

At the same time, drained air with a temperature of 17.5-30 ° C, a pressure of 0.5-0.7 MPa and an average speed in the pipes of at least 1.3 m / s can be used to purge the tube space.

What is new is that gas drying of the tube space of the heat exchanger is first carried out by blowing it with hot, dry air. After drying of the tube space, the annular space of the heat exchanger is evacuated and its vacuum dried. At the same time, during the vacuum drying process, the pipe space is continued to be purged with hot dry air to supply heat, which compensates for the costs of the phase transition during the evaporation of moisture in the annulus.

Preliminary gas dehydration of the surface of the pipe space by purging with drained hot air before vacuum drying of the annulus contributes to the effective drying of the cavities of the complex spatial geometry of the annulus. Effective drying is achieved due to the possibility of direct heat supply, which compensates for the phase transition during evaporation of the liquid film from the annular surfaces, ensuring that the vacuum value is kept practically constant and the undesired cooling in this case of drained surfaces is eliminated.

Vacuum drying of the annulus surfaces, during which it is purged with an ionic wind and simultaneously blowing the tube space with drained hot air, increases the efficiency of drying the cavities of the complex spatial geometry of the annulus of the shell-and-tube heat exchanger, including dead ends, slots, because In the annular space of the heat exchange equipment, in addition to the tube bundle, additional structural elements (for example, spacing or supporting partitions, elements of the support system of the difficult beam) can be placed. Purging the annulus with the help of ionic wind provides a more complete removal of water vapor from the dead-end zones, cracks to achieve a predetermined residual moisture content of the evacuated air.

The combination of the gas drying method for the tube space and the vacuum drying method for the annulus with its blowing by the ion wind while drying the cavities of the heat exchange equipment gives the greatest effect on productivity. In this case, purged hot air is used to evaporate moisture in the pipe space, and the drying process is carried out at almost a constant initial temperature of the metal of the heat-exchange equipment design, since the heat supplied from the hot air is spent mainly on the evaporation of moisture. To evaporate the moisture in the annulus contained on the outer surfaces of the heat exchange tubes (most), in order to maintain constant values of the vacuum pressure, the temperature of the material of the pipe system and, accordingly, the performance of the vacuum system, heat is supplied to compensate for the phase transition. This compensating heat supply is realized by pumping dry air with the appropriate parameters (pressure, temperature and flow rate) through the already drained pipe space in order to obtain the required drying time.

The purging of the annular space under vacuum, the creation of an ionic wind arising in an inhomogeneous electric field, ensures the movement of moist air from the stagnant zones of the drained cavity into the vacuum system for its subsequent removal, which increases the efficiency of drying the annular cavities of complex spatial geometry. In the presence of stagnant zones in the drained surface of the annular space, an increase in the drying capacity (reduction of the necessary time) is also achieved due to the intensification of the evaporation of moisture from the drained surfaces by blowing with an ion wind, providing a dynamic effect of moist air. The use of an ionic wind arising in an inhomogeneous electric field of a corona discharge induced by a system of electrodes provides an effective purge of the annulus under vacuum. Molecules of water vapor differ from all other components of the air in their dipole moment, which means that they can be moved in the right direction by the gradient of the electric field, while this gradient will practically not affect all other components of the air.

Ionic wind, as described in the book of I.A. Krishtafovich, Yu.A. Krishtafovich. “Ionic wind and its application” (, date 10.10.2013), this is a physical phenomenon in which the movement of gas is created using an electric field created by an electrostatic accelerator. An electrostatic accelerator (ES) is a device that imparts movement to gases, in particular, to air without any moving parts. Instead of the mechanical energy of rotating blades, as in conventional fans, EI uses an electric field to give a torque to electrically charged air molecules. Electrostatic devices are fairly simple devices containing “sharp” and “blunt” electrodes with a high-voltage power source connected to them. A sharp electrode can be a needle, a blade, a thin wire. The acceleration of gas molecules is as follows. An electrostatic device generates a corona discharge in the immediate vicinity of a “sharp” electrode, called a corona electrode, and electrically charges air molecules, water vapor, turning them into ions. At the second stage, the formed ions are accelerated by a strong electric field towards the opposite electrode, called the precipitation electrode. In the process of motion, ions collide with neutral molecules and give them motion in the same direction. At the third stage, ions and other charged particles reach the surface of the precipitation electrode and give it the previously received electric charge.

In addition, an ionic wind can also be observed when using non-insulated high-voltage electrodes with a small radius of curvature, in cases where the field strength near the tip is high enough to ionize gas molecules (A.V. Selitrenikov, Yu.E. Zevatsky. Effect of an electric field on rate of evaporation of liquids ZAO, Novbytkhim, St. Petersburg, St. Petersburg State Technological Institute (Technical University), St. Petersburg, ed. 04/14/2010, / IzvetiyaTI / 2010/7 / Articles / 07 / files / assets / downloads / publication.pdf). Depending on the sign of the tip’s charge, gas molecules lose or acquire electrons, ion clusters are formed, which under the influence of Coulomb forces move in the direction of the electrode of the opposite sign, and transmit momentum to neutral molecules in collisions with them. When using a constant voltage of 20 kV, an ionic wind was observed only at the moments when the voltage source was turned on and off, regardless of the polarity of the electrodes. In the presence of a variable component of the voltage, the movement of air continued throughout the entire duration of the latter. When using an alternating voltage at the electrodes due to ionic wind, due to mixing of the liquid vapor, the transfer of matter from the phase interface to the blown volume is facilitated, i.e. the evaporation process is intensifying.

In the prototype, the organization of the movement of air in a vacuum cavity under vacuum is provided by outside atmospheric air, throttled when introduced into the cavity and drained directly in the cavity under vacuum, by abrupt expansion. In this case, air is introduced in an amount that provides a stationary regime of vacuum purging and for a period of time up to reaching a predetermined value of residual moisture in the drained cavity. The required amount of introduced air is determined by many factors: pressure, humidity and ambient temperature, the volume of the drained cavity, the residual pressure in it, the performance of the vacuum system and is provided by the cross-sectional area of the throttling channel through which the outside air is sucked when the drained cavity communicates with the surrounding space through opening the purge channel.

Preliminary drying of the pipe space by blowing with dried hot air with a temperature of 170-285 ° C, a pressure of 0.5-0.7 MPa and having an average speed of movement in the pipes of at least 1.3 m / s makes it possible to efficiently supply heat during the vacuum drying of the annular the space that compensates for the phase transition during the evaporation of a liquid film from the annular surfaces to eliminate undesirable, in this case, cooling of the drained surfaces, which increases the efficiency of drying the cavities of complex spatial The geometry of the annular space, preferably of blind zones, the slits.

The drying of the annulus within the vacuum pressure of 1000-2000 Pa helps to reduce the energy costs associated with the need to heat the surfaces to be dried to a higher saturation temperature corresponding to a higher vacuum pressure.

Purging the pipe space with hot air with a temperature of 17.5-30 ° C, a pressure of 0.5-0.7 MPa and having an average speed in the pipes of at least 1.3 m / s during the vacuum drying of the annulus provides a compensating phase transition at evaporation of the liquid film from the annular surfaces and eliminates the undesirable in this case cooling of the drained surfaces.

Simultaneous purging and drying of the annular space to achieve the required humidity of the pumped-out air and supplying heat to the pipe space to compensate for the heat of the phase transition during evaporation increases the efficiency of drying the cavities of the complex spatial geometry of the annular space, mainly dead ends, cracks.

A device for implementing the inventive method of drying, including a vacuum system connected to the drained space by means of a pipeline equipped with filtering means, means of drying, heating and purging atmospheric air, as well as controlling pressure, temperature and humidity, with valves, in addition, the device is equipped with an air duct connected to drained annular space of the heat exchanger, and installed in it a set of corona electrodes connected to the negative terminal a high voltage source, while a duct is used as a precipitation electrode connected to a heat exchanger connected to the grounded positive terminal of the high voltage source, and the means for drying and heating the atmospheric air are connected to the inlet of the pipe space through a pipe purge means.

Providing the device with an additional air duct and connecting it to the drained annular space of the heat exchanger provides purging of the annular space with the ion wind through a set of corona electrodes installed in the air duct connected to the negative terminal of the high voltage source, while an air duct connected to the heat exchanger connected to the precipitation electrodes is used to the grounded positive terminal of the high voltage source.

Ion wind purging provides an increase in the efficiency of drying cavities of complex spatial geometry of the annular space under vacuum, mainly of dead-ends, gaps due to mixing of liquid vapor and facilitating the transfer of matter from the interface to the blown volume, i.e. the evaporation process is intensifying.

When using ion wind technology for drying the annulus, there is no need to use any mechanical devices to purge the drained space, as well as atmospheric air and devices for its preliminary drying before entering the cavity to purge the drained space. In this case, the conversion of electrical energy into wind energy is provided, and the air flow rate is controlled by the number of corona electrodes installed in the duct.

Connecting the corona electrodes to the negative terminal of the high voltage source allows you to work at higher voltages and with a more stable negative corona. In addition, the breakdown voltage for the negative corona electrode is approximately twice that of the positive.

The connection of the means of drainage (adsorber) and heating of atmospheric air (heat exchanger) with the inlet of the pipe space through the purge means (pump) ensures its purging with pre-dried and heated atmospheric air, as well as heat supply, which compensates for the phase transition during evaporation of liquid from the annular surfaces, including the number of dead-end zones, gaps, as a result of which the efficiency of drying cavities of complex spatial geometry of the annulus increases.

The invention is illustrated by drawings, where,

- in FIG. 1 is a schematic diagram of a device for implementing the patented drying method;

- in FIG. 2 shows a diagram of the drying according to the claimed method on the example of the steam generator PGV-1000, the place for supplying the purge of the pipe space, the vacuum system and ducts with corona electrodes;

- in FIG. 3 is a view AA in FIG. 2 - shows the places for supplying the purge of the pipe space and the duct with corona electrodes to the PGV-1000 steam generator;

- in FIG. Figure 4 shows the estimated duration of drying the tube space of the PGV-1000 steam generator depending on the temperature and pressure of hot air at the inlet of the tube bundle at an average speed of its movement of at least 1.3 m / s;

- in FIG. Figure 5 shows the dependences of the performance of the vacuum system on temperature and pressure at an average speed of hot air at the entrance to the pipe space of at least 1.3 m / s;

- in FIG. Figure 6 shows the dependences of the drying time of the annulus on the productivity of the vacuum system.

The device for drying the internal surfaces of a shell-and-tube heat exchanger includes:

1 - heat exchanger (steam generator PGV-1000)

2 - tube bundle (heat transfer surface)

3 - valve

4 - filter

5 - adsorber (dehumidifier)

6 - pump (compressor)

7 - heat exchanger

8 - valve

9 - valve

10 - vacuum system

11 - valve

12 filter

13 - annular space of the heat exchanger

14 - duct (precipitation electrode)

15 - corona electrodes (anode)

16 - high voltage source

17- cathode

18 - purge inlet pipe (or pipes connected by a collector)

19 - purge outlet pipe (or pipes connected by a collector)

20 - pressure sensor

21 - temperature sensor

22 - valve

23 - humidity sensor in the vacuum system

24 - humidity sensor at the outlet of the adsorber

25 - humidity sensor at the exit of the tube bundle

A device for implementing the inventive drying method includes a heat exchanger 1, for example, a PGV-1000 steam generator, in the housing of which a tube bundle (heat exchange surface) 2 is installed, which forms a tube space connected to atmospheric air through valve 3, filter 4, an adsorber (dryer) 5 , pump (compressor) 6 and heat exchanger 7 and valve 8, which opens the entrance to the pipe space. The valve 9 connects the outlet of the tube space of the tube bundle 2 with the atmosphere (Fig. 1).

The vacuum system 10 is connected on one side through the valve 11 and the filter 12 with the annular space 13 of the heat exchanger 1, on the other hand, with the atmosphere. The duct 14 is connected to the drained annular space 13 of the heat exchanger 1. In the duct 14 there is a set of corona electrodes (anodes) 15 connected to the negative terminal of the high voltage source 16, the positive terminal of which is connected to the cathode 17. Cathode 17 is the positive terminal of the high voltage source 16 , grounded with the housing (mass) of the heat exchanger 1. The duct 14 with the corona electrodes 15 is a corona discharge fan in which the duct 14 acts as a precipitation electrode but. A corona discharge generated between the corona electrodes 15 and the precipitation electrode (duct 14) generates an ionic wind directed from the corona electrodes 15 through the duct 14 into the annular space 13 of the heat exchanger 1. The air flow rate is controlled by the number of corona electrodes 15. The duct 14 is connected to the annular the space 13 of the heat exchanger 1 by means of a purge inlet pipe (or nozzles connected by a collector) 18 and a purge outlet pipe (or nozzles combined x collector) 19 (FIG. 1-3). As a means of heating the dried atmospheric air, blown through the tube space of the tube bundle 2, a heat exchanger 7 is used, connected through a valve 8 on one side to the inlet of the tube bundle 2, and on the other hand, with a purge means. As a means of purging using a pump 6 (compressor). The pump 6 is connected to an adsorber (dehumidifier of atmospheric air) 5 entering the tube space of the tube bundle 2. The adsorber 5 is connected by a pipe through the filter 4 and valve 3 to the atmosphere. The pressure space and temperature control means are connected to the tube space of the tube bundle 2, using a pressure sensor 20 and a temperature sensor 21, respectively. The number of pairs of nozzles of the inlet 18 and outlet 19 for connecting the duct 14 to the annular space 13 is determined by the specific design of the heat exchanger 1 and the direction of the ionic wind. The valve 22 connects the heat exchanger 1 with the atmosphere and serves to maintain the necessary pressure in the annulus 13. A humidity sensor 23 is connected to the evacuation system 10 to determine the air humidity in the annulus 13. A humidity sensor 24 is connected to determine the humidity of the dried air at the outlet of the adsorber 5 The quality of the drying of the tube space of the tube bundle 2 is monitored by the humidity sensor 25. In FIG. Figure 4 shows the estimated duration of the drying of the tube space of the tube bundle 2 of the PGV-1000 steam generator, depending on the temperature of the hot air at the inlet of the tube bundle at an average speed of at least 1.3 m / s. In FIG. Figure 5 shows the calculated dependences of the productivity of the evacuation system 10 on temperature, pressure, and the average velocity of hot air at the entrance to the tube space of the tube bundle 2 of at least 1.3 m / s. In FIG. 6 shows the calculated dependences of the drying time of the annular space 13 on the performance of the evacuation system 10 (Fig. 6).

Drying according to the claimed method is carried out on the example of drying the steam generator PGV-1000, having the characteristics in accordance with table 1 and is carried out as follows:

Pre-drain the inner surface of the tube space of the tube bundle 2 of the steam generator. To do this, open the valve 3, the outside atmospheric air passes through the filter 4, where it is cleaned of impurities and enters the adsorber 5. In the adsorber 5, the air is drained to a relative humidity of not more than 1.6%. Next, the dried air by the pump 6 is fed into the heat exchanger 7, where it is heated to a temperature of 170-285 °. Then, pipes 6 of the tube bundle 2 are blown with hot pump air 6 under a pressure of 0.5-0.7 MPa (abs.) At an average speed of at least 1.3 m / s to dry the inner surface of the tube space for 19-27 hours Valves 8 and 9 regulate the necessary pressure and air flow in the drained pipe space. Pre-drying of the tube space by blowing with drained hot air provides a more efficient drying of the annulus 13 by providing direct heat input, compensates for the phase transition during evaporation of the liquid film from the annulus 13 surfaces and eliminates unwanted cooling of the annihilated surfaces of the annulus 13. Drying of the annulus beam 2 is considered complete when the readings of two humidity sensors 24 and 25 match formation, respectively, at the outlet of the adsorber 5 and tube bundle 2. In the example for drying the tubular space of the tube bundle of the steam generator 2 in adsorber 5 define the relative humidity of not more than 1.6%. In this case, the estimated duration of the drying of the tube space of the steam generator depending on the temperature of the hot air at the inlet to the tube bundle 2 is shown in FIG. 4. The calculation of dehydration was performed using the approximate theory of the boundary layer, according to which the diffusion transfers of mass, heat, and momentum in the longitudinal direction are negligible compared to transfers in the transverse direction. The approximate method based on the analogy of the processes of mass, energy and momentum transfer and the equation of material and energy balances for the interface is used in the calculation. The drying rate in this case will be determined by the intensity of the stefan mass flow [8].

Table 1 presents the characteristics of the PGV-1000 steam generator, in relation to which the annular space is dried according to the claimed method at an initial temperature of 15 ° C.

Then turn on the evacuation system 10, open the valve 11 and through the filter 12, evacuate the annulus 13 to a pressure of 1000-2000 Pa. At the same time, vacuum drying and purging of the annulus 13 is carried out until the required humidity of the pumped-out air is reached. To do this, turn on a high voltage source 16, to the negative terminal of which a set of corona electrodes (anodes) 15 are mounted inside the duct 14. A corona discharge is created in the duct 14, an inhomogeneous electric field is generated, and an ion wind is formed in the duct 14 and sent to the steam generator for purging annular space 13, including dead-end zones, cracks. Since the duct 14 is connected to the steam generator, the ion wind then returns from the steam generator through the inlet pipe 18 to the duct 14, from where it is again directed through the outlet pipe 19 to the annular space 13. Thus, the duct 14 with the corona electrodes 15 is a fan corona discharge. The air flow rate for purging the annulus 13 is controlled by the number of corona electrodes 15 installed in the duct 14. In this case, at least three corona electrodes 15 are required to purge the annulus of the PGV-1000 steam generator 15. The final number of corona electrodes 15 is determined based on the required degree of drying and allowable process time. It can be assumed that for drying the annulus 13, the relative air humidity at the outlet should be no more than the relative air humidity at the inlet of the tube space of the tube bundle 2 and be no more than 1.6%. Valve 22 maintain the necessary pressure (vacuum) in the annulus 13 of the steam generator.

At the same time, at the same stage, the tube tube 2 is blown through with dried hot air to provide heat supply that compensates for the phase transition during evaporation of the liquid film from the annular surfaces 13. The tube tube 2 is dried by the monitoring means: pressure sensor 20, sensor temperature 21, a humidity sensor 23 installed in the evacuation system 10. The drying process of the annular space 13 continues until The required parameters for humidity pumped out by the air evacuation system 10.

The calculated dependences of the required capacity of the vacuum system 10 on the temperature and pressure of hot air at an average velocity at the inlet of the pipe space of at least 1.3 m / s, excluding the use of ion wind, are shown in the graph of FIG. 5. As follows from the graph, the performance of the vacuum system 10 is a linear function of the temperature of the hot air at the entrance to the tube bundle. Moreover, an increase in heat supply leads to the need to increase the productivity of the vacuum system 10 due to the formation of a greater amount of water vapor during boiling of the water film. It is obvious that during the drying of the PGV-1000 steam generator, in order to maintain a constant vacuum in the annulus 13, the generated water vapor is removed using the necessary capacity of the vacuum system 10.

To estimate the drying time of the annulus 13 in FIG. Figure 6 shows the graphical dependences of the drying time on the performance of the vacuum system 10 at various pressures and the average speed of hot air at the entrance to the tube space of the tube bundle 2 of at least 1.3 m / s. These dependencies are nonlinear. From the dependences of the drying time of the annular space 13 on the productivity of the evacuation system 10 shown in FIG. 6, it follows that the pressure of hot air at the entrance to the tube space weakly affects the performance of the evacuation system, and its temperature is more affected. The drying time of the annular space 13 can be from 6.5 to 43 hours with a change in the performance of the vacuum system from 14300 to 2000 m ³ / h, respectively. The use of ionic wind increases the efficiency of drying the annulus.

A device for implementing the inventive method of drying, the schematic diagram of which is presented in figure 1, consists of standard, commercially available units, devices and fittings (vacuum system, heat exchanger, adsorber, pump, high voltage source (about 20 kV), valves, measuring instruments ) The main part is a system for purging the annular space by an ionic wind in an inhomogeneous electric field by means of corona electrodes installed in the duct.

Thus, the use of the proposed technical solution increases the efficiency of drying the inner surfaces of shell-and-tube heat exchangers, including the complex spatial geometry of the annular space containing dead ends, gaps in which there is no direct contact with the gas medium after hydrotesting. The drying efficiency is achieved by creating an ion-wind technology that fully preserves the advantages of gas and vacuum drying methods and is achieved by pre-drying the tube space with subsequent simultaneous vacuum drying and blowing the annular surfaces with an ion wind in an inhomogeneous electric field and blowing the tube space, providing a heat supply that compensates phase transition during the evaporation of water in the annulus.

Sources of information taken into account:

1. Patent RU No. 20155465 C1, IPC F26B 3/04, F26B 5/04, dated 09.11.1989, publ. 06/30/1994 - an analogue.

2. A.c. SU No. 909505 A, IPC F26B 21/06, dated 08.04.1976, publ. 02/28/1982 - an analogue.

3. Patent RU No. 2182691 C1, IPC F26B 7/00, F26B 5/04, dated October 30, 2000, publ. 05/20/2002 - an analogue.

4. Patent RU No. 2494328 C1, IPC F28C 1/16, dated March 15, 2012, publ. September 27, 2013 - an analogue.

5. Patent RU No. 2492394 C2, IPC F24F 3/00, dated November 21, 2011, publ. 09/10/2013 - an analogue.

6. N.M. Vereshchagin, A.E. Korolev, V.V. Vasiliev, K.V. Shemarin. “Study of a corona discharge fan.”, Vestnik RGTRU No. 4 (Issue 46), part 3, Ryazan, 2013) - analogue.

7. Patent RU No. 2198361 C2, IPC F26B 7/00, F26B 5/04, F26B 19/00, dated January 4, 2001, publ. 02/10/2003) - a prototype.

8. Tsvetkov F.F., Grigoryev B.A. Heat and mass transfer: Textbook for universities. - 2nd ed., Rev. and add. - M.: Publishing House MPEI, 2005, pp. 397-401.

Claims (5)

1. A method of drying the inner surfaces of a shell-and-tube heat exchanger based on evacuation, subsequent purging, vacuum drying, gas drying using dried air, characterized in that the pipe surfaces are dried with dried air before vacuum drying of the annular surfaces, while the process of vacuum drying is carried out ionic wind in an inhomogeneous electric field and at the same time continue to purge the tube space with dried air to ensure eplopodvoda compensating phase transition when liquid evaporates from the surfaces of the annulus to achieve the desired value of residual moisture is evacuated. 2. The method according to p. 1, characterized in that for drying the tube space can be used dried air with a temperature of 170-285 ° C, a pressure of 0.5-0.7 MPa with an average air velocity in the pipes of at least 1.3 m / s 3. The method according to p. 1, characterized in that the drying of the annular space can be carried out within 1000-2000 PA. 4. The method according to p. 1, characterized in that for purging the tube space can be used dried air with a temperature of 17.5-30 ° C, a pressure of 0.5-0.7 MPa with an average air velocity in the pipes of at least 1 , 3 m / s. 5. A device for drying the internal surfaces of a shell-and-tube heat exchanger, including a vacuum system connected to the drained space by means of a pipeline equipped with filtering means, means of drying and heating and blowing of atmospheric air, as well as controlling pressure, temperature and humidity, with valves, characterized in that the device is equipped with an air duct connected to a drained annular space of the heat exchanger and a set of corona electrodes installed in it s connected to the negative terminal of the high voltage source, while a duct connected to the heat exchanger connected to the grounded positive terminal of the high voltage source is used as a precipitation electrode, and the means for drying and heating the atmospheric air are connected to the inlet of the pipe space through the pipe space blower.

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