RU2346760C2 - Method for ultrasonic cleaning of deposits in heat exchange devices - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: method for ultrasonic cleaning of deposits in heat exchange devices consists in application of modes of dynamic control of duration, amplitude, resonance frequency, number of control excitation pulses in packet and periodicity of their repetition via microprogrammed control according to individual program of heat exchange device operation, automatic detection of faults in electric circuits and disconnection from power electric circuit.

EFFECT: higher efficiency of deposit formation prevention on working surfaces of heat exchange equipment heating.

2 cl, 2 dwg

Description

The invention relates to ultrasonic technology and is intended for cleaning, preventing and reducing the formation of scale and iron oxide deposits on working surfaces of heating in heat-exchange equipment of technical preparation systems of the carrier.

The main carrier of the heat exchange equipment is water, the hardness (temporary, constant) of which is determined by the concentration of salts of the calcium and magnesium groups dissolved in it. When water is heated to the boiling point, salts of temporary hardness form insoluble compounds, known as scale, which, settling on the working surfaces of heat-exchange units, reduces their technical characteristics. Long contact of the coolant with the working surfaces of such equipment further develops the process of formation of iron oxide deposits. Among the chemical and physical methods of protecting heat-exchanging equipment from solid deposits, the ultrasonic method, which has wide capabilities and efficiency and is constantly being improved, is increasingly being used, making it possible to obtain simple, reliable and inexpensive auxiliary equipment. Today, a number of methods are known for eliminating and preventing the formation of solid deposits in industrial heat exchange units using ultrasonic vibrations.

A known method of creating acoustic oscillations according to A.S. No. 1022748 SU, B06B 1/00, BI No. 22, 1983, based on the shock excitation of ultrasonic pulses on the heating surface of a thermal unit created by a magnetostrictor by a pulse signal of an electric generator. In this case, the excitation signal in order to increase the amplitude of the mechanical vibration is formed in the form of unidirectional half-periods of cosine voltage with a duration of one to two half-periods of the acoustic wave and multiples of the frequency of these oscillations.

This method has insufficient efficiency in the formation of complex-shaped acoustic vibrations on the working surface of heat exchange units due to the incomplete use of the supplied and converted energy of the vibration source (magnetostrictor).

There is another method of ultrasonic cleaning of heat aggregates from deposits according to Patent RU No. 2141877, B06B 1/08, publ. 1999.11.27. The method is designed to excite ultrasonic vibrations on the working surfaces of a heat-exchange unit through n pairs of magnetostrictors, to which packets of electric vibrations from a half-wave rectifier and storage capacitance are supplied, the emergency state of pairs of switching elements of magnetostrictors is detected when they are simultaneously opened with respect to the derivative of the switching current and a signal is issued that prohibits the arrival of control pulses on the switching elements.

There is also a method of ultrasonic cleaning of heat generating units from deposits according to the Application RU No. 2004129037/12 A1, B08B 3/12, publ. 2006.03.10, selected as a prototype. The method is designed to excite ultrasonic vibrations of complex shape on the surface of heat exchangers by n magnetostrictors, to which a packet of control pulses is supplied, determine the emergency state of the simultaneous opening of a pair of switching elements and generate a signal to prohibit the supply of control signals to the switching elements. In the pauses between the supply of a packet of control pulses from a half-wave rectification direct current source, a magnetizing current is supplied to the magnetostrictor field winding.

Known methods [2, 3] have common disadvantages associated with the inability to obtain optimal control excitation signals due to technological variation and temporary changes in the parameters of acoustic vibration sources (a system of n magnetostrictors) and operating modes of heat exchange equipment. As a result, it is difficult to obtain a high intensity of ultrasonic irradiation of the working surfaces of the equipment without the additional cost of electric energy, and hence effective anti-scale treatment of the coolant. For example, according to method [3], the amplitude of a complex oscillation in the form of a burst of pulses can reach five times the value of a single amplitude of an ultrasonic pulse, which in some cases turns out to be insufficient with a complex configuration and poor wave conductivity of the working surface of the heat exchange unit.

The technical result of the invention is to increase the efficiency of preventing the formation of deposits on the working surfaces of the heating of heat exchange units.

To achieve a technical result in a method for ultrasonic cleaning of deposits in heat exchange units, which includes generating ultrasonic waves of complex shape on the waveguiding surface by means of n magnetostrictors, the double windings of which are supplied with packs of electric excitation pulses within a half-period of the supply voltage, and an emergency state is detected when the windings of any of the n magnetostrictors simultaneously supply electrical excitation pulses with According to the invention, by introducing microprogram control of the process of excitation of ultrasonic vibrations at the selective points of the heating waveguide surface, taking into account its configuration and controlling the amplitude of these oscillations, the amplitude, duration and number of electric pulses of excitation in the packet are synchronized with the phase of the supply voltage over a half-period of the supply voltage, and the formation frequency is selectively changed packs of electrical excitation pulses and carry out a frequency change following electrical excitation pulses in the pack according to a linear law within a given range of values and generate a signal to disconnect from the supply voltage when a malfunction occurs in the power circuit. In addition, at the microprogram level, an individual program is set up for generating ultrasonic vibrations of a complex shape of a heating waveguide surface, taking into account its configuration during the selected period and mode of operation of the equipment.

The inventive method of ultrasonic cleaning of deposits in heat exchange units is illustrated by drawings. Figure 1 and figure 2 shows the dependence of the form σ / σ _o = f (K) and h _nak = f (V _H , K, t), confirming the effectiveness of the method.

Technical treatment of the coolant in heat exchangers according to the claimed method is as follows.

The formation of solid deposits on the working surfaces of heat-exchanging units changes their technical characteristics (consumed energy - heat, electricity, flow rate, proportion of recirculation and the outlet temperature of the coolant) and reduces the time of trouble-free operation. At the same time, it is known that the growth rate of a film of deposits depends on the chemical composition of the coolant and increases asymptotically with increasing parameters such as the speed V _{H of the} motion and the frequency (fraction) of carrier recirculation through a heat exchange unit, directly related to the operating modes of the equipment and design features. Therefore, the process of formation of solid deposits is multifactorial and subject to changes over time. To reduce and prevent it, an adequate approach is necessary at the stage of technical processing of the carrier in industrial heat exchange units.

For this, at the selective points of the working heating and wave-conducting surface of the heat-exchange unit, acoustic vibrations of the required shape and power are created, taking into account its configuration and operating parameters. To obtain the necessary power (intensity) of acoustic vibrations, for example, by means of double-winding magnetostrictors, microprograms generate electrical control pulses of excitation of acoustic oscillation sources according to a given law and perform their amplitude control in a given zone of the wave-conducting heating surface of the heat-exchange unit.

The use of microprogram control of the formation of probing ultrasonic vibrations along the working surface of heat-exchange equipment makes it possible to fully take into account the multi-factor scale formation process and effectively resist it, ensuring the following operations are performed for the entire period of scheduled operation:

- change in the duration, amplitude and period of the control excitation pulses for individual parameters of sources of acoustic vibrations (magnetostrictors);

- the formation of packs of control excitation pulses by establishing the number of pulses in a packet, the frequency of their repetition in a packet, the frequency of repetition of the packets for a selected period of equipment operation;

- the introduction of an individual program for managing sources of acoustic vibrations (magnetostrictors) in time, taking into account the configuration of the heat exchange unit and changes in its technical characteristics and operating modes;

- identification of emergency conditions of the control mode and the generation of a signal to disconnect from the power circuit.

To obtain the maximum possible amplitude of acoustic vibrations in the working medium of an object (unit), firstly, it is necessary to generate an electric pulse of excitation of optimal duration τ _i.opt = L _eff / V _in , taking into account the size L _{eff of} the effective magnetomechanical transformation zone and the velocity V _{in the} longitudinal ultrasonic waves in a magnetostrictor medium, i.e. to fulfill the condition τ _and = τ _i.opt , where τ _and is the control excitation pulse. In this case, the parameter L _eff = f (L, a, τ _and , V _c ) is functionally related to the structural values of the source (magnetostrictor) - the longitudinal dimensions L of its inductive converter (winding) and its air gap a.

Secondly, the amplitude of the driving excitation pulses is selected from the condition of optimal consumption of electric energy and obtaining the required amplitude (power) of acoustic vibrations at a controlled point on the working heating and waveguiding surface of the heat exchange unit. For example, such control can be carried out using an acoustic vibration sensor with a measuring circuit.

Thirdly, the choice of the excitation frequency of the source of acoustic vibrations (magnetostrictor) is based on the geometric dimensions and shape of its packet and concentrator according to known dependencies [see, for example, Tebenikhin E.F. Non-reagent methods of water treatment in power plants - M .: Energoatomizdat, 1985. - P.113].

The use of microprogram control makes it possible to optimize the input acoustic vibrations of ultrasonic frequency in the environment of the object by software without replacing the means of additional electronic equipment for the individual parameters of the executive elements (magnetostrictors), which, in addition to the technological spread at the manufacturing stage, tend to temporarily drift parameters (aging, environmental influences) etc.). Therefore, the proposed approach of dynamically adjusting the shape and frequency of control excitation pulses during operation of the heat exchange equipment is relevant and new relative to the known approaches [1-3].

It is possible to increase the intensity (power) of acoustic vibrations of the ultrasonic frequency of the working surface of heat-exchanging units due to the formation of a series (pack) of m electric excitation pulses following at a given frequency, as suggested in [2, 3].

In the proposed method, in order to obtain the greatest efficiency of reducing and preventing the formation of solid deposits on the technological object, the number of K pulses in the packet is selected programmatically and selectively, for example, in the range from K = 1 to K = 50 for each half-period of the mains voltage, depending on the wave-conducting properties and configurations of the working heating surface. The optimal pulse repetition rate in the series is selected from the condition F = 1/2 · τ _i.opt . This allows you to generate acoustic vibrations of increased amplitude (figure 1)

,

,

where σ _i (t) = k _and σ _o (t) · exp (-β · L _o ) is the deformation stress of a single ultrasonic wave σ _o (t) at the point L _{o of} superposition addition with an interpolation coefficient k _{and the} resulting wave and damping decrement β, with the optimal power consumption mode of additional equipment.

To generate complex-shaped acoustic vibrations simultaneously at n points on the working surface of the heat-exchange unit (using n magnetostrictors), using a packet of control excitation pulses, their repetition rate F is programmatically changed according to the law of linear frequency modulation (LFM) in the range ΔF = F ± ξ of the change in resonance properties ξ sources of acoustic vibrations (magnetostrictors) due to technological variation and changes in parameters. This ensures a smooth inclusion of additional equipment and efficient control of the system of sources of acoustic oscillations without preliminary sorting by resonance properties before use as part of additional equipment and distinguishes them from known approaches [2, 3].

Предлагаемый способ позволяет на микропрограммном уровне устанавливать периодичность формирования пачек управляющих импульсов возбуждения с учетом особенностей теплообменного оборудования и режима его работы с сохранением заданной интенсивности ультразвуковых колебаний. Это достигается выполнением программы по установлению в динамическом режиме количества К импульсов в пачке и частоты F_оп их повторения, чем и обеспечивается снижение излучаемого шума в окружающее пространство в 1,5-2 раза относительно известных подходов [1-3], создавая благоприятные условия работы обслуживающему персоналу. Например, использование перечисленных выше режимов позволяет снизить частоту повторения пачек импульсов возбуждения до значений F_оп≤1,0 Гц.Known methods for ultrasonic cleaning of solid deposits in heat exchange equipment [1-3] involve the formation of electrical control excitation pulses in the resonance frequency range ΔF = 18-44 kHz of acoustic oscillation sources with a repetition period of packs [2-3] of power network pulses

The proposed method allows you to set the frequency of the formation of packs of control excitation pulses at the microprogram level, taking into account the features of the heat exchange equipment and its operation mode while maintaining the specified intensity of ultrasonic vibrations. This is achieved by executing a program to establish in a dynamic mode the number K of pulses in a packet and the frequency F _{op of} their repetition, which ensures a reduction in the emitted noise into the environment by 1.5–2 times relative to known approaches [1-3], creating favorable working conditions attendants. For example, the use of the above modes allows to reduce the repetition rate of packs of excitation pulses to values of F _op ≤1.0 Hz.

An important factor of the proposed method is the ability to set an individual program for the formation of acoustic vibrations of complex shape of the working surface of heat-exchange units during the entire period of their operation. As a result, the efficiency of auxiliary equipment is increased (Fig. 2) due to the multifactorial nature of the deposition of solid compounds on the working surfaces of heat-exchange process equipment and a smooth transition between control modes. This distinguishes the proposed method from the known [1-3].

The trouble-free operation of the heat exchange and auxiliary equipment for a long period of time is possible when identifying emergency situations in the power switching circuits of the latter. The consequence is the automatic disconnection of auxiliary anti-scale equipment from the electric power circuit until the identified malfunction is eliminated by an emergency shutdown signal, thereby increasing the reliability and electrical safety of the equipment. Similar operations are absent in the known methods [2, 3].

Thus, the use of dynamic control modes for the duration, amplitude, resonance frequency, number of control excitation pulses in a packet and the frequency of their repetition through microprogram control using an individual program of operation of a heat exchange unit increases the efficiency of the ultrasonic method for cleaning solid deposits on working surfaces at optimal costs of electric energy, and also contributes to the expansion of functionality for use, which distinguishes the offer my method from known analogues and prototype, allowing to achieve a positive effect.

Sources of information taken into account when preparing the application

1. A.S. No. 1022748 SU, B06B 1/00, BI No. 22, 1983.

2. Patent RU No. 2141877, B06B 1/08. Publ. 1999.11.27.

3. Application RU No. 2004129037/12 A1, B08B 3/12. Publ. 2006.03.10. Prototype.

Claims (2)

1. The method of ultrasonic cleaning of deposits in heat-exchange units, which consists in the formation of acoustic waves of complex shape on the heating wave-conducting surface by n magnetostrictors, to the double windings of which they supply packs of electrical excitation pulses within a half-period of the supply voltage, to identify an emergency state when - out of n magnetostrictors simultaneously, electrical excitation pulses are supplied, characterized in that by introducing a micro Program control of the process of excitation of ultrasonic vibrations at the selective points of the heating waveguide surface, taking into account its configuration and controlling the amplitude of these oscillations, synchronizes with the phase of the supply voltage the amplitude, duration and number of electrical pulses of excitation in the packet for half a period of the supply voltage, selectively change the frequency of formation of the packet of electrical pulses excitation, carry out a change in the frequency of the electrical impulses in Excitations in the pack according to a linear law within a given range of values and generate a disconnect signal from the supply voltage when a malfunction occurs in the power circuit. 2. The method of ultrasonic cleaning of deposits in heat exchange units according to claim 1, characterized in that at the microprogram level, an individual program for generating ultrasonic vibrations of a complex shape of a heating waveguide surface is set up taking into account its configuration during the selected period and mode of operation of the equipment.

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