RU2709609C1 - Method of reducing liquid hydrocarbons electrization when handling - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to the field of electrical engineering, namely to the technologies of storage, transportation of inflammable and combustible liquids. Method involves adding antistatic additives containing multilayer carbon nanotubes (MWCNT) dispersed in base liquids and then stabilized by electrophysical action during filling, emptying of containers, pumping of liquid hydrocarbons from stationary and mobile tanks. Nano-fluids with MWCNT obtained under conditions of electrophysical effect are characterized by higher stability and reduced electric conductivity, wherein nanoparticles agglomeration process leading to increase in nanofluid specific resistance is slowed down under action of variable frequency-modulated potential (VFMP). Application of dispersed carbon nanoparticles as additives for reduction of electrification of hydrocarbon liquids in a combination with electrophysical action, by action of alternating electric field with the specified frequency, leads to change of double electric layer structure due to variable polarization of substance at interface boundary.

EFFECT: reduced liquid hydrocarbons electrification; disclosed method reduces fire hazard during storage and transportation of hydrocarbon liquids.

1 cl, 2 tbl, 5 dwg

Description

The invention relates to a method for preventing the formation of electrostatic charges and can be used to ensure fire safety of technological processes of storage and transportation of liquid hydrocarbons. The invention is reflected in the totality of the application of methods of incorporation (dispersion) of multilayer carbon nanotubes into oil products and the electrostatic stabilization of carbon nanostructures to ensure a technical result - to reduce the electrification of oil products during their transportation, homogenization and atomization.

A known method (patent RU 2488627 C1 "Method of preventing the accumulation of electrostatic charges in emulsions during oil production and transportation") reduce electrification using neutralizing devices by introducing antistatic surfactants and dispensing demulsifiers.

The disadvantage of this method is the significant consumption of the emulsifier, as well as the additional costs of its removal from the oil.

The reduction of static electrification in oil products is achieved due to the influence of external electric fields. A known method of reducing the rate of accumulation of electrostatic charges (RF patent No. 2479005 "Method and device for controlling physicochemical processes in a substance and at the phase boundary") by changing the electrical conductivity of a double electric layer (DEL) by exposure to an electric variable frequency-modulated signal ( PCMS) with two intervals of uniformity.

The disadvantage of this method is the difficulty of its application for substances with high electrical resistivity, so when exposed to electric fields of low frequency there is no significant change in electrical conductivity.

Electrification of liquid hydrocarbons depends on the value of electrical conductivity (or volumetric electrical resistivity (UES)), the average theoretical [1] and experimental [2] data show that when UES decreases, electrification decreases during homogenization, spraying and pumping of oil products.

Since the electrical conductivity of liquid hydrocarbons depends mainly on the presence of impurities in them, antistatic additives are used to reduce the electrification of liquid hydrocarbons. Surfactants, which include carbon nanomaterials, are widely used and developed. However, their use may be limited due to the rapid aggregation of carbon nanoparticles.

Known methods for reducing electrification (patent US 20150302948 A1 "Composite materials with magnetically aligned carbon nanoparticles having enhanced electrical properties and methods of preparation", patent US 20140302296 A9 "Transparent conductive films with carbon nanotubes, inks to form the films and corresponding processes") by introducing metallized and magnetosensitive nanoparticles as part of nanocomponent additives to control the electrical properties of nanofluids. To increase the electrical conductivity, in addition to carbon nanostructures, metallized magnetically sensitive nanoparticles and surfactants were used to achieve stable nanofluids. This composition allows to increase the electrical conductivity of nanofluids by more than four orders of magnitude.

The disadvantage of these methods is the rapid formation of particle aggregates, which can lead to their subsidence and erosion of the walls of metal containers and equipment, where the obtained hydrocarbon-based nanofluids are circulated, which leads to a sharp decrease in the usefulness of these additives. Also, this method is not effective due to the use of surfactants that cause a change in the chemical composition of the product, the difficulty of removing multilayer carbon nanotubes (MWCNTs) from the base fluid and the presence of surfactants in them.

In the study of changes in the electrification of nanofluids obtained under the conditions of electrophysical effects, carbon nanomaterials containing MWCNT (l = 10 ... 20 μm, d = 10 ... 30 nm) were used on the basis of liquid hydrocarbons. This type of MWCNT was obtained by the method of catalytic pyrolysis at the CVDomna installation with subsequent purification from impurities [3] and does not contain metallized and magnetically sensitive nanoparticles in concentrations detected by standard methods. However, there is a need for additional stabilization of nanostructures (prevention of aggregate formation) in order to increase the retention time of improved nanofluid properties.

Known methods for increasing the time of the process of formation of aggregates of nanoparticles in liquids (RF patent No. 2352618 "Cerium oxide nanoparticles as fuel additives", US patent 20160017253 A1 "Gelling nanofluids for dispersion stability", US patent 6432320 B1 "Refrigerant and heat transfer fluid additive") by functionalizing the nanomaterial and adding a surfactant as a stabilizer.

The disadvantage in the application of these methods is the addition of surfactants to the liquid, and therefore the removal of nanoparticles from the base liquid is impossible, as well as the functionalization of nanostructures. The acid treatment of nanomaterials leads to improved performance of the nanomaterial, however, this can lead to the difficulty of removing nanoparticles for the purification of base liquids. Processing nanomaterials under the influence of high temperatures can lead to a partial destruction of nanostructures, which reduces the efficiency of this type of nanoparticles.

The aim of the present invention is to reduce the electrification of liquid hydrocarbons by introducing MWCNT in combination with electrostatic stabilization of nanofluids in order to prolong the given parameters of nanostructures.

To achieve this goal, it is proposed to reduce the electrification of liquid hydrocarbons due to the introduction of MWCNT, dispersion and further stabilization of nanostructures by exposure to an alternating electric field, as a result of which a change in impurity and cataphoretic conductivity is achieved for a long time while maintaining one of the characteristic parameters of nanofluid (nanoparticle size and distance between them).

The process of stabilization of nanostructures consists in changing the electrokinetic potential (zeta potential) [4] of nanoparticles at the liquid-gas interface under electrophysical exposure with the parameters of the PMF device.

To implement the present invention, an electrophysical effect with the parameters of the PMF device is applied directly to liquid hydrocarbons (Fig. 1). The stabilization of nanostructures is achieved through the action of an alternating frequency-modulated potential on a liquid-nanoparticle dispersion medium in a grounded container with the following parameters:

U = U _max ⋅cos (wt)

where U _max = 56 V;

w - circular frequency, determined in accordance with the dependence:

,

,

, Гн;where L is the inductance of the oscillatory circuit

, Mr.;

On the _ground - the electric capacitance of the Earth (~ 740 μF);

C is the capacity of the double electric layer arising between the liquid layer and the nanoparticles.

Figure 1. The structural diagram of the stabilization of nanostructures in a hydrocarbon liquid by electrophysical exposure with the parameters of the PMP device. 1 - metal container, 2 - modified MWCNT hydrocarbon liquid, 3 - electrode, 4 - PCMP device U = 56 V, ƒ = 50 Hz.

Figure 2. The dependence of the specific resistance of a nanofluid based on ethanol on the stabilization time of MWCNT, under conditions of electrophysical exposure.

Figure 3. The dependence of the specific resistance of the acetone-based nanofluids on the stabilization time of MWCNT, under the conditions of electrophysical exposure.

Figure 4. The dependence of the resistivity of the nanofluid based on ortho-xylene on the stabilization time of MWCNT, under conditions of electrophysical exposure.

Figure 5. The topology of aggregation of nanostructures in nanofluids based on: a, b - ethanol; c, g - acetone; d, e - ortho-xylene, a, c, d - samples without exposure to an alternating electric field; b, d, e - samples exposed to an alternating electric field.

The technical result of the proposed method is:

- improving the quality characteristics of liquid hydrocarbons through the use, as a stabilizer, of the electrophysical effect with parameters of a variable frequency-modulated potential U = 56 V, ƒ = 50 Hz;

- the invariability of the chemical composition of liquid-based nanofluids, due to the chemical neutrality of the MWCNT used;

- the ability to remove MWCNT after use, by filtration (up to 90%) of the nanofluid and / or purification by electrophoretic deposition (up to 100%);

- slowed down the process of formation of aggregations of MWCNT (up to 4 times);

- the ability to control the processes of electrification of liquid hydrocarbons by regulating the size of the aggregates of nanostructures and the distance between them.

The feasibility of the proposed method is confirmed experimentally on the basis of St. Petersburg University of the State Fire Service EMERCOM of Russia. Nanofluids were obtained by dispersing nanomaterials (with a concentration of 0.5 and 1.0 vol.%) With MWCNT in the base fluid (C ₂ H ₅ (OH), C ₃ H ₅ (OH), C ₈ H ₁₀ ) when exposed to a source ultrasound at a frequency of 100 kHz for 1 hour at a temperature of 40 ° C. Further, to ensure the stabilization conditions, the nanofluids were subjected to electrophysical effects with the parameters of the PMF U = 56 V, ƒ = 50 Hz for 1 hour.

The dependence of the conductivity of nanofluids on the stabilization conditions in it of MWCNT nanoparticles was studied in the measuring cell of the E6-13A teraohmmeter. A previously prepared nanofluid was placed in a measuring cell, where measurements were taken every equal time intervals until the initial parameters of the specific volume electric resistivity were established.

Research data show (Fig. 2, Fig. 3, Fig. 4) that with an increase in the concentration of MWCNT in a liquid, its specific resistance decreases by an average of 45%. Under the influence of PCMP, a slower increase in the values (68%) of the electrical resistivity of the liquid occurs, which is associated with a slower process of aggregation of nanoparticles during electrophysical exposure [5].

In the table. Figures 1 and 2 show the results of studies of the electric field strength during the pumping of modified liquid hydrocarbons and during the homogenization of nanofluids. The results obtained indicate a significant contribution of stabilized nanoparticles to the change in the kinetics of electrostatic charge accumulation during the pumping of modified liquids.

By changing such characteristics as concentration, particle size and the distance between them, it becomes possible to control the electrification of liquid hydrocarbons (Table 1, Table 2). A study of the conservation of the properties of nanofluids, namely, the size and distance between MWCNTs, was carried out using atomic force microscopy on an NT MDTIntegra setup. In the topology of aggregation of carbon nanostructures in nanofluids under the influence of an alternating electric field, the distance between the nanostructures and a decrease in their linear dimensions are observed (Fig. 5). Thus, the results of the study prove the possibility of regulating the parameters of nanostructures.

Literature

1. Bobrovsky S.A., Yakovlev E.I. "Protection against static electricity in the oil industry"; Moscow "NEDRA"; 1983.

2. Ivanov A.V., Skripnik I.L., Voronin S.V. “The study of electrification processes when handling modified nanofluids and paints and varnishes”; Problems of risk management in the technosphere; No. 3 (47); 2018; 110-119.

3. Bobrinetsky II. "Technology for the production of carbon nanotubes by the method of catalytic pyrolysis from the gas phase of ethanol"; Chemical Technology; 2007; No. 2; p. 58-62.

4. Yu W., Xie N. A review on nanofiuids: preparation, stability mechanisms, and applications // Journal of Nanomaterials. - 2012. - 17 p. DOI: 10.1155 / 2012/435873.

5. Ivanov A.B., Miftakhutdinova A.A., Nefediev S.A., Simonova M.A., Maslakov M.D. Stabilization conditions for nanostructures for the safe transport of flammable liquids. Fire and Explosion Safety. 2017; 26 (9): 35-43.

Claims (1)

A method for preventing the electrification of liquid hydrocarbons during their transportation, including adding a modifying additive before transportation, characterized in that carbon nanoparticles in an amount of 0.5-1.0 vol.% Are used as a modifying additive, after which the liquid hydrocarbons are treated with ultrasound at a frequency of 100 kHz for 1 hour at a temperature of 40 ° C and additionally stabilized with a frequency-modulated potential at U = 56 V, ƒ = 50 Hz, for 1 hour.

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