DE19502588C1 - Reduction of chemical potential in built up matter in liquid flows - Google Patents

Abstract

To reduce the chemical potential of built-up matter in flowing liquids, AC pulse sequences are generated by electrodes (11) immersed directly in the liquid. In an initial phase, they are at a high frequency (12) of 1-100 kHz to inject charges into the matter. A second phase uses lower frequencies of 10-100 Hz (14) across the liquid flow (16) to accelerate the growth of previously weakly charged small build-ups (15) into larger clumps.

Description

State of the art

Under static conditions and the effect of gravity collect Aggregates with a density higher than that of the surrounding medium on which Bottom of the corresponding vessels. Aerosols and suspensions made by the same named charge and secondary dipole effect are stabilized, resist for quite some time of this aggregation, although smaller particles in ver have a higher reactivity than large drops and bodies and grow together isothermally. (Kortüm, Lachmann, introduction to chemical Thermodynamics, Verlag Chemie, Weinheim 1981, pp. 377-378).

Examples are droplets of moisture in the air (fog) and gold suspensions. A malfunction of the charging by creating a field leads to quick ver Enlargement of the particles (electrophoresis).

In liquids such as water, oil suspensions or solutions in life medium, pharmaceutical and chemical industries are one Large number of particles in the nanometer range. These submicroparticles are in size above the molecularly dissolved substances, but still below those with the wavelength of the light correlating diameters of visible particles.

They have a chemical potential that, depending on interfacial tension and Ratio volume to surface, is larger than that of a micrometer visible crystal. The consequence is therefore not only greater reactivity, but also a higher solubility. Nevertheless, these agglomerates, like the one above thinks, either by the dipole effect of the solvent or by the same named surface charge kept in the metastable state.

Especially drinking water, sewage and crude oil with very different amounts dissolved gases such as oxygen, nitrogen, carbon dioxide or salt quantities such as Cal cium carbonate, magnesium sulfate, sodium chloride, or oxides such as quartz, iron oxide, manganese oxide are good examples.

In a flowing medium containing these gas and solid agglomerates holds, the conditions are dependent on frictional forces, wall charges, tur bulent and laminar flow, much more complex.  

A first significant difference to statics in hydrodynamics is that larger particles with high structural instability (amorphicity) are sheared apart and smaller particles even without the same charge via the so-called hydro dynamic free path length can be stabilized.

This process results in being comparable to the macroscopic pebble Movement and gas bubble formation in flowing water, for further formation more reactive Submicroparticles. Furthermore, through temperature stratification, flow, Kavita tion, outgassing, permanently the parameters of the molecular solubility of a solid changed body. This also forms depending on the absolute disturbance and Dy namik agglomerates.

In addition, the particles, similar to the so-called ξ charge of Pipe walls with the same name under fluid dynamic conditions. This leads to the stabilization of this inherently unstable, reactive state. That leaves as in the static area, the reactivity and increased surface tension preserved long distances.

Such a reactive particle comes under the influence of the flow in one Pipe that is much longer than the so-called dynamic free path of the reactive particle, then the probability of a wall impact becomes high. The Agglomerate reacts with the wall by releasing the increased chemical energy. Depending on the material, this either leads to corrosive pitting) or to an uninhibited layer structure while reducing the pipe diameter.

To prevent this and improve quality e.g. B. of the process water achieve static and dynamic magnetic fields in the liquid (DE 34 33 417 or 38 43 514). These magnetic fields have only with them secondary effect generated and transferred into the flowing medium, a very low efficiency. The gradations are with the effectiveness 1 / r⁴, 1 / r⁶ 1 / r⁸ and the thermodynamic energy value (1 / kT) are described in detail (Hirsch fields, Curtiss and Bird, Molecular Theory of Gases and Liquids, John Wiley & Sons, New York 1964, p. 26-30). With these transferred energies that are far below the binding forces of the liquids, it is impossible, as in the calculation Example 1 described to generate a significant lateral acceleration.

Electrical fields that are directly connected to the electrodes are much better flowing liquid are introduced (DE 42 24 604, DE 41 07 708, DE 38 28 825) and thus both a setting via the conductivity and a direct one Allow transverse acceleration of charged particles.  

In G 90 17 493 an electronic limescale protection device is presented by a frequency in the range of 1 to 10 kHz and a current control for includes constant alternating currents. The procedure for leging shown there flow of the flowing medium and to control the system not the different sizes of the primary particles and agglomes rate. In addition, keeping the current constant while reducing the Guiding values for an increase and not for an adapted minimization of the brought energy.

The present invention, described in claims 1 to 8, is the The task is based on the initially defined method of reducing damage Lichen chemical potential in such a way that the necessary energy targeted in charge without loss to overcome the interface potentials injection and interface reduction, d. H. Particle growth can be introduced can.

This object is according to the invention, presented in the main claim and the subsequent claims, solved in that different over electrode pairs AC pulse sequences introduced and these sequences due to a Current measurement both in pulse height as well as pulse width and pause times be controlled.

The advantages achieved by the invention are in particular that The Ag optimal glomeration from particles with around 10 nm to particles with around 1000 nm and an average density of 0.9 to 3 g / cm³ independently and further segregation is avoided in the long term.  

Description of the pictures

A process that accomplishes this agglomeration and counteracts segregation must use energies that are higher than that of simple liquid binding energy. This is only possible through the targeted introduction of electrical alternating voltage pulse sequences ( 12 , 14 ) via electrodes ( 11 ). These alternating voltage pulse sequences act specifically on ions ( 13 ) or agglomerates ( 15 ) with different mobility ( FIG. 1).

The first phase consists of the formation of a reaction cylinder ( 20 ) ( FIG. 2) due to a high-frequency alternating field ( 12 ) and the preferred axis of the flow ( 16 ). Larger agglomerates ( 21 , 22 ) that do not follow the fast alternating field without a charge or with a very low space charge are hit by positive ( 13 ) or negative ( 17 ) ions. The result is an increasing charge (injection phase).

In the second phase ( Fig. 3), the frequency of the alternating field ( 14 ) must be adapted to the larger particles in order to impart a transverse acceleration to them in accordance with their larger mass. The Coulomb forces of oppositely charged particles ( 22 ) of different sizes then lead to a flow-stable species of ever larger particles ( FIG. 3, vectorial growth phase).

Fig. 4 shows the structure of stable particles ( 21 ) with rotational movement ( 41 ) from a zelions or less dimensionally stable structures with a shear plane ( 40 ).

In FIG. 5, the current response (50, 52) to the constant voltage pulses (12, 14) is shown. The maximum (varying) current value in correlation to the constant voltage peak gives the characteristic value for controlling the energy input in VAs.

Example 1: General definition of frequencies

Typical flow velocities of the liquids described in the following examples are approximately 0.1 to 1 m / s. With field strengths of 1000 to 2000 V / m, ion velocities (Na⁺, Cl-, Mg ²⁺ and Ca ²⁺ ) of around 20 * 10 ^-5 m / s can be achieved. This means that the ions travel around 10 to 20 nm below the frequency of 10 kHz. Larger units have a speed that is 10 to 100 times lower and require a frequency reduced by this order of magnitude for the same route. To determine the reaction cylinder ( 20 ), a correlation between the binding energy of the liquids and the Coulomb energy, which acts on the charged particles, is sufficient.

Without the influence of energy from the flowing medium, the charged particle would kept electric field. Studies show in the above field strength and ions a relation transverse speed / flow speed 100/1. A reaction cylinder (ellipsoid) therefore has a width of 0.1 m / s and 10 kHz 10-20 nm and a length of 100 nm per cycle.

In the case of larger particles, the width of the reaction cylinder should be retained; this requires a frequency of 100 Hz, based on an average speed in the field of 2 _* 10 ^-6 m / s. However, due to fluid dynamic influences, the above cross-speed / flow speed relationship is considerably reduced. A reaction cylinder then has a width of 10-20 nm and a length of 100,000 nm = 0.1 mm per cycle.

If due to this predominantly fluid dynamically fixed movement encounter differently charged agglomerates, this leads to a new one formation of larger units. This shows the paramount importance of the cargo injection tion, which only continue to work within the scope of the dynamic free path can, although the large particles are deflected from their flow direction.

Example 2: Treatment of surface water

Surface waters, which include the so-called flowing waters, have today already of considerable importance in the water supply of certain regions. These waters are characterized by the fact that they are washed out by air and Flow over sealed surfaces dusts, salts and organic substances sweep away, but also exhaust gases such as nitrogen oxides, sulfur oxides and various Absorb amounts of free carbon dioxide. This makes them particularly aggressive and germinating.

Due to extensive investigations, dust cores have been adhered to Agglomerates with pyrogenic activities increasingly found in these waters. At Pipeline walls also grow biofilm masses, but not so stick like the carbonate and oxide layers in drinking water pipes.

While the pyrogenic properties are only due to the entry of oxygen and chlorine, Electrolysis or UV radiation can be reduced, the layer formation influenced by alternating electrical fields. Here it has proven to be useful indicated, in advance by a sensor-controlled neutralization with calcium and Magnesium hydroxide to perform mineralization.  

The injection phase leads to the charging of the small agglomerates at high changes self-fields on a first pair of electrodes. The growth of the particles in the sem case mainly contain dusts and biomass, must at low Fre sequences (10-100 Hz) and small voltage amplitudes (5-10 volts) be performed. Filtering according to the growth phase depends on the application of the Water dependent.

3rd example: flocculation of solid agglomerates in waste water

In addition to the dissolved salts, wastewater contains that from the process water phase are a solid phase and suspended particles with average diameters with a diameter from 10 nm to the range from 1000 nm and larger. There are interactions for the construction of the intermediate phases between six substance classes:

(1) hydrophobic, (2) capillary nonionic, (3) capillary ionic, (4) capillary active ionically hydrated, (5) capillary active charge saturated hydrati siert and (6) uncharged hydrophilic.

This diversity of substance groups, combined with the flow influences, led in wastewater treatment for the construction of large sedimentation tanks and / or for addition of flocculants. Both of these measures can be reduced significantly, though the water is subject to alternating electrical fields. About so-called inert Electrodes, such as those used in corrosion protection technology, are used in the first Phase a high-frequency field with about 10 kHz and a voltage amplitude of 100 volts used. In this injection phase, not only particles in the Size charged from 10 to 100 nm, but also from larger amorphous structure tures smaller, more stable agglomerates with higher density.

The second phase requires due to the usually lower flow rate electrodes with a dwell time of 1 to 10 seconds in low frequency Field are adjusted. The growth phase then runs in a small partition basin out.  

4. Example: suspensions and salt hydrates in crude oils

Crude oils are not only characterized by a wide range of organic products sher substances, they have very different admixtures of gases, Water, salts and solids such as oxides and silicates. In this case too auxiliaries are added to separate the mostly very stable suspensions. The technical specifications for crude oil are usually very long Transport routes in pipes where low viscosities play a role. The subsequent distillative separation of the different fractions requires due the high evaporation enthalpy of water separates the hydrophilic Shares. For these reasons, both a fine distribution of the suspensions a separation of the hydrate phase is also necessary.

The injection phase therefore consists of an alternating electrical field with higher ones Frequencies from 10-100 kHz, variable voltage amplitude and a current border. The growth phase can then be separated from the injection phase being constructed. Because in contrast to the previous examples, the carriers liquid is highly hydrophobic, the growth phase at higher frequencies of the alternating fields.

5. Example: calcium carbonate in drinking water

Calcium carbonate CaCO₃ dissolves with about 14 mg per kg of water, the presence of carbon dioxide increases the solubility at 4 to 7 ° C to about 1300 mg per kg of water. With increasing temperatures, the solubility drops again, preferably smaller ion aggregates are formed with a high reactivity, for example in the diameter range from 10 to 100 nm. These particles with an average mass of 10 ^-21 to 10 ^-17 kg contain several thousand to several million calcium and carbonate ions. They react with the pipe wall of water pipes together with carbon dioxide under corrosion or lead to a reduction in the pipe diameter due to uncontrolled layer formation. Both effects destroy the water supply pipes within a few years.

The treatment with high and low frequency electrical fields affects here the injection phase with influencing the ions and small ion aggregates, the follow a frequency of 10³ to a maximum of 10⁵ Hz. So that vibrations generates an amplitude in the at an average ion mobility Order of magnitude of 100 to 1000 times the ion diameter results. A 10 cm long electrode with a flow rate of 0.1 m / s min at least 1000 vibratory movements of a small particle. The transferred  Energy is sufficient for slower particles of the 100 nm limit with excess ions loaded. In an alternating field with 10-100 applied to two further electrodes Hz then become the weakly charged particles with the same voltage ampli tude but much slower transverse acceleration.

This treatment leads to the formation of larger particles, which are still the Mineral properties of drinking water, but not only their dangerous Have lost reactivity with regard to the pipe walls, but also as Germs for a loose and easily removable limestone in additional coals Dioxide removal (water heating) serve. This is both an immediate we kung as well as an aftereffect over a long period of time.

Claims (8)

1. A method for reducing the chemical potential of agglomerates in flowing liquids, characterized in that via electrodes ( 11 ) which are directly immersed in the liquid, alternating voltage pulse sequences are given in such a way that in a first phase high frequencies ( 12 ) of 1 up to 100 kHz for the injection of charges into the agglomerates, a second phase at lower frequencies from 10 to 100 Hz ( 14 ) transverse to the direction of flow ( 16 ) the growth of the previously weakly charged smaller agglomerates ( 15 ) into flow-stable larger units ( 21 ) accelerated. 2. The method according to claim 1, characterized in that the simultaneously determined alternating current is used as a measure of the originally existing and reduced during the action chemical potential for self-control of the AC voltage pulse sequences mentioned in claim 1 that the initial current value of the high-frequency phase ( 50 ) Duration of the two alternating voltage pulse sequences, which determines the low-frequency phase ( 52 ) the pause times ( 51 ) between these alternating voltage pulse sequences. 3. The method according to claim 1, characterized in that the two AC pulse train at low flow velocity over one Electrode pair one after the other at high flow rates liquid media over two or more pairs of electrodes simultaneously or only slightly to be broadcast at different times. 4. The method according to claim 1 or 3, characterized in that the change voltage pulse sequences with simultaneous start and the same number of pulses 100 to 1000 cycles and thus the pulse train of the second electro runs longer because of the lower frequency. 5. The method according to the preceding claims, characterized in that Pulse times, determined by the lower frequencies, make up 10 to 100 s and the pause times are between 10 seconds and 10 minutes.   6. The method according to the preceding claims, characterized in that the voltage amplitudes are designed so that the alternating current during a Pulse sequence drops and there is no dangerous decomposition of the liquid. 7. The method according to claims 1 or 2, characterized in that a Characteristic value for self-control from the quotients of the specified voltage pulse heights and the initial measuring currents is calculated. 8. The method according to claims 1, 2 or 7, characterized in that the mentioned characteristic value for error messages in the event of a cable break or lack of water is pulled.