RU2806305C1 - Jet mixing device for liquid contaminated dielectric media - Google Patents

Abstract

FIELD: oil refining industry.

SUBSTANCE: mixing liquid contaminated electrifying (dielectric) media with simultaneous ability to eliminate obstacles to the formation of deposits at the bottom of vertical and horizontal tanks and containers. The mixing device contains a pump connected to the pressure line and to a suction line located at the bottom of the tank, a jet device located in the lower part of the tank and having a narrowing element connected to the pressure line of the jet device, a confuser connected to the mixing chamber. According to the invention, the device additionally contains a filter located outside the tank and connected on one side to the pump using a return pipeline connected to the pressure line of the pump, and on the other side to the pressure line of the jet apparatus, additionally containing an induction neutralizer of static electricity connected on one side to the mixing chamber, and on the other hand, with the tank grounding circuit through a metallic potential equalization connection. With a horizontal tank, the pump is located inside the tank near its bottom and is a submersible or semi-submersible pump. With a vertical tank arrangement, the pump is located outside the tank and is a centrifugal cantilever or linear electric pump.

EFFECT: reduced risk of explosion and fire in tanks with contaminated electrifying media when cleaning the tank from solid particles without emptying the tank.

3 cl, 3 dwg

Description

The invention relates to the oil refining industry and can be used at production, storage and processing facilities of liquid hydrocarbons for mixing liquid contaminated electrifying (dielectric) media with the simultaneous ability to eliminate obstacles to the formation of deposits at the bottom of vertical and horizontal tanks and containers.

It is well known, in particular, that for mixing in various reservoirs and containers of various liquids, including those of different densities and compositions prone to stratification, jet pumps are widely used as jet mixers with nozzle ejectors, mechanical paddle mixing devices, as well as combined mixers consisting from the main and additional mixing devices.

It is known that in liquid media with high electrical resistivity, such as light and dark oil products, gas condensate, etc. when the latter move at high speeds and during mixing, static space charges are formed and accumulated; this process occurs especially intensively after the passage of pumps, filter elements and mixing devices. Of particular danger is the process of such a liquid transferring a charge into a container and accumulating a charge in the working environment that can discharge above the surface of the liquid in an explosive gas environment and ignite it.

A device is known for eroding bottom sediments of liquid hydrocarbons in a vertical steel tank (see RF patent for invention No. 2743557 according to class IPC B01F 15/02, published 02/19/2021), containing longitudinal and transverse pressure pipes with installed on their lateral sides parallel to the bottom of the tank with nozzles at equal distances from each other, a suction pipe, a pump, inlet and outlet flushing pipes, an intake flush pipe connected to a blind casing fixedly installed on the suction pipe, an intermediate flush pipe connected at one end to the suction pipe, and its other end connected to the blind casing.

However, the device is not intended for use in underground and horizontal tanks and cannot be used for electrified liquid media.

A device for filtering liquid petroleum products is known (see RF patent for invention No. 2618759 according to class IPC B01D 35/06, pub. 05/11/2017), containing a grounded housing with inlet and outlet pipes, filter elements having perforated conductive casings on the outer surfaces and fixed to form a cavity for the flow of petroleum product inside the housing on a horizontal partition in which flow channels for the purified petroleum product are made. Such a device allows you to obtain a purified working environment at the output and significantly reduce its electrification.

However, when this statically neutralized medium is introduced into the tank to perform the mixing function using a jet device (ejector), the flow will again acquire a charge at the orifice device (nozzle) due to high speed and turbulent mixing with the secondary (low-pressure) flow .

The closest to the claimed one is a jet mixing device for leveling the composition of motor fuels in tanks (see RF patent for invention No. 2314151 according to IPC class B01F 5/04, publ. 01/10/2008), which includes a pump with suction and pressure pipelines and nozzle ejector installed at the outlet of the pressure pipeline at the bottom of the tank. The ejector has a cylindrical mixing chamber, on the inner surface of which spiral ribs are located at an angle of 30-45 ^o to the axis to impart rotational motion to the liquid, the nozzle is made with a diameter that ensures a liquid flow rate of 40-50 m/s, and the ejector is installed in a horizontal plane on a separate line for supplying fuel to the tank at an angle of 60° from the perpendicular to the plane of the mounting hatch and in a vertical plane at an angle to the horizontal, ensuring the point of impact of the jet at 50% of the working height of the tank.

However, such a device has limited use, since it cannot work with electrifying dielectric explosive and fire hazardous media, such as gas condensate and methanol, since they do not allow high speeds of movement of the medium without neutralizing static electricity. Disadvantages are also that mixing occurs only when the tank is filled, there is no possibility of cleaning contaminated working media from solid particles, the scope of application is limited to vertical tanks of large volumes.

The technical problem of the claimed invention is the development of jet devices designed for mixing liquid contaminated electrifying (dielectric) media with the simultaneous ability to eliminate obstacles to the formation of solid particle deposits at the bottom of vertical and horizontal tanks and containers.

The technical result is to reduce the risk of explosion and fire in tanks with contaminated electrifying media when cleaning the tank from solid particles without emptying the tank.

To achieve the technical result, a jet mixing device containing a pump connected to a pressure line and to a suction line located at the bottom of the tank, a jet device located in the lower part of the tank and having a narrowing element connected to the pressure line of the jet device, a confuser connected to the chamber mixing, according to the invention, the device additionally contains a filter located outside the tank and connected on one side to the pump using a return pipeline connected to the pressure line of the pump, and on the other side to the pressure line of the jet apparatus, additionally containing an induction neutralizer of static electricity connected on the one hand with the mixing chamber, and on the other hand with the grounding circuit of the tank through a metallic potential equalization connection.

With a horizontal tank, the pump is located inside the tank near its bottom and is a submersible or semi-submersible pump.

With a vertical tank arrangement, the pump is located outside the tank and is a centrifugal cantilever or linear electric pump.

The invention is illustrated by drawings, which show:

- in fig. 1 option of using the device in a horizontally located tank (container);

- in fig. 2 option of using the device in a vertically located tank (container);

- in fig. 3 - jet apparatus.

Positions in the drawings indicate:

1 pump unit;

2 suction line of the pump unit;

3 pressure line of the pumping unit;

4 return pipeline;

5 liquid filter;

6 pressure line of the jet apparatus;

7 jet apparatus;

8 tank (capacity);

9 narrowing element;

10 confuser;

11 mixing chamber;

12 induction static electricity neutralizer;

13 metal bond potential equalization (grounding)

14 tank grounding circuit.

A jet mixing device for liquid contaminated dielectric (electrified) media contains (see Figs 1 and 2) a pump unit 1, the suction line 2 of which is located as close as possible to the bottom of the reservoir (container) 8, and the pressure line 3 of the pump unit is connected via a return pipeline 4 with a liquid filter 5 located outside the container 8 and connected by its outlet to at least one pressure line 6 of the jet apparatus 7. Pressure line 6 is connected to at least one restriction device 9 of the jet apparatus 7 (see Fig. 3), located at the bottom of the container 8 and including a confuser 10 connected to the mixing chamber 11, with a built-in induction neutralizer of static electricity 12 and connected through metal potential equalization connections 13 to the grounding circuit of the container 14.

In the case of using the device in a horizontal underground or above-ground tank (see Fig. 1), the pump unit 1 is located inside the tank 8 and is a submersible electric pump or semi-submersible electric pump on top of the tank 8 with a pumping part inside the tank 8.

In the case of using the device in a vertical container or reservoir (see Fig. 2), the pump unit 1 is located outside the container 8 and is, for example, a centrifugal cantilever electric pump, or a centrifugal linear electric pump.

The inventive device operates as follows.

There is a container 8 filled with a contaminated electrifying liquid medium to a level above the minimum required for pump 1 to operate. The jet apparatus 9 is completely immersed in the liquid medium.

When the pump unit 1 is turned on, the working medium with suspended solid particles of volume Q1 is drawn into the suction line 2 of the pump unit and acquires a given pressure sufficient to overcome the hydraulic resistance of the pressure line 3 of the pump unit, the return pipeline 4, the liquid filter 5, where capture and retention of solid particles of contaminants.

Through the pressure line 6 of the jet apparatus 7, the medium returns to the container through the orifice 9 with a speed V1 and pressure H1 such that the flow Q1, the so-called working one, has high kinetic energy at the exit of the orifice 9 and, entering the mixing chamber 11, transfers kinetic energy and impulse, the so-called injected flow Q2, which carries the flow through the confuser 10 into the mixing chamber 11.

In mixing chamber 11, flows Q1 and Q2 are mixed, their speeds and pressures are equalized. At the same time, the processes of increasing the pressure and speed of flow Q1 by the pump, its filtration, acceleration in the constriction device and mixing with flow Q2 lead to the formation of volumetric static charges in the mixed flow Q1 + Q2.

At the outlet of the mixing chamber 11, an induction neutralizer of static electricity 12 is installed of such a design that its hydraulic resistance is low to significantly increase the speed of the mixed flow, and the length is sufficient so that its discharge metal strings or plates connected to the metal body of the mixing chamber capture charges (ions ), distributed in a mixed flow, which, in turn, flow through metallic potential equalization bonds to the ground loop 14 of the tank.

The pump parameters, the geometry of the orifice, confuser and mixing chamber are selected in such a way that the mixed flow Q3, devoid of acquired charge, has sufficient kinetic energy to lift solid particles from the bottom of the tank, mix the working medium to eliminate the effect of sedimentation of a suspension of solid particles and speed V3, safe for the formation of new charges.

Thus, over a finite period of time, the working environment will be safely cleared of contaminants by the transfer and retention of solid particles in the liquid filter and can be turned off.

For a given working medium (dielectric fluid) and known parameters of contaminants (solid particles), the hydraulic particle size is estimated, i.e. the speed of its uniform fall in calm water, for example, according to formula (1)

(1),

where U is the hydraulic particle size (m/s); - particle density (kg/m3); - liquid density (kg/m3); d—particle diameter (m/s); g-gravitational acceleration (g = 9.80665 m/ ^s2 ).

Formula (1) is applicable for the turbulent deposition regime, in which the resistance exerted by the liquid does not depend on its viscosity, but is determined by the square of the falling velocity of the particle (quadratic region), which is typical for large particles . To estimate the hydraulic size of smaller particles, which are characterized by transitional and laminar sedimentation regimes, other formulas or tables of experimental data from the theory of sediment transport should be used (see, for example, Karaushev A.V. Theory and methods for calculating river sediment. L.: Gidrometeoizdat Yu 1977. - 271 p.).

To prevent the formation of solid particle deposits at the bottom of a known tank, it is necessary to ensure the movement of the working medium (hydraulic fluid flows) at a speed not lower than the found estimated hydraulic particle size throughout the entire volume of the working medium of the tank. Since it is not possible to evaluate the fulfillment of this condition for each given combination of conditions, such as: tank configuration, level of the working medium, location and orientation of the jet apparatus, its productivity and pressure, analytically, it is recommended to use software and calculation systems to determine the required productivity Q3 and pressure P3 of the jet apparatus. At the same time, for small volumetric concentrations of contaminants in a liquid, on the order of 1-2%, it is advisable, in order to reduce the calculation time, to simplify the calculations by not taking into account the solid phase in a two-phase working environment, i.e. solid particles themselves (see, for example, https://www.stadyo.ru/about/customers/customerslist/114/2840/ Work by Belostotsky A.M. “Numerical modeling of hydraulic flows for an accumulating settling tank using the ANSYS software package ").

For the found productivity (volume flow) of the jet apparatus Q3, find the diameter of the outlet section of the mixing chamber F3 using formula (2), taking into account the maximum permissible outflow velocity for a flooded jet (the jet apparatus must be below the minimum operating level during operation) for a given electrifying liquid Vmax .

(2)

Liquids with a specific volumetric electrical resistance of less than 10 ⁵ Ohm*m are practically not electrified, and their transportation at speeds of up to 10 m/s is obviously safe.

Electrification, which can lead to spark discharges, is excluded for liquids with a specific volumetric electrical resistance of up to 10 ⁹ Ohm*m when transporting them through pipelines at speeds of up to 5 m/s.

For liquids having a specific volumetric electrical resistance of more than 10 ⁹ Ohm*m, the maximum safe transportation speeds through pipelines and permissible outflow speeds into devices and tanks of various shapes and sizes from various loading pipes can be determined using the Guiding Technical Material RTM 6-28- 007-78 (see, for example, https://files.stroyinf.ru/Data1/9/9191). At the same time, limiting the transportation speed to the maximum safe value eliminates the occurrence of dangerous discharges in any filled apparatus (reservoir) with any method of liquid supply that prevents splashing. Limiting the flow rate in the pipeline to the permissible flow rate eliminates dangerous discharges only with a given method of supplying liquid to a device (reservoir) of given shapes and sizes. (see, for example, RTM 6-28-007-78 Permissible speeds of movement of liquids through pipelines and outflow into containers (devices, tanks); Rules for protection against static electricity in the chemical, petrochemical and oil refining industries).

Based on certain values of Q3, P3, F3 and the desired type of jet apparatus (with a diffuser, without a diffuser, permissible length of the mixing chamber, permissible hydraulic losses, etc.), its geometric dimensions are calculated using known methods (see, for example, Sokolov E. Ya., Zinger N.M. “Jet devices” - 3rd ed., revised - M.: Energoatomizdat, 1989. - 352 pp.; Lyamaev B.F. “Hydraulic jet pumps and installations” - L. : Mechanical Engineering, Leningrad Branch, 1988. - 256 pp.). In this case, it is necessary to additionally take into account the hydraulic resistance of the induction neutralizer of static electricity, which removes the accumulated volumetric charge of the mixed flow. The design of the induction neutralizer of static electricity built into the jet apparatus can be different: string, plate, or needle. (see, for example, USSR copyright certificate No. 1736015, RF patent No. 2490835).

The maximum permissible value of charge density at the outlet of a jet apparatus is defined as the charge density in the volume of liquid at which the probability of a discharge with an energy equal to 0.25 of the minimum ignition energy of a mixture of vapors of this liquid with air does not exceed 10 ^-3 and is calculated according to RTM 6 -28-007-78.

Thus, the inventive device makes it possible to mix liquid contaminated electrifying (dielectric) media, while reducing explosion and fire safety, with the simultaneous ability to eliminate obstacles to the formation of deposits at the bottom of vertical and horizontal tanks and containers, providing cleaning from solid particles without special emptying.

Claims (3)

1. Jet mixing device containing a pump connected to a pressure line and to a suction line located at the bottom of the tank, a jet device located in the lower part of the tank and having a narrowing element connected to the pressure line of the jet device, a confuser connected to the mixing chamber, different in that the device additionally contains a filter located outside the tank and connected on one side to the pump using a return pipeline connected to the pressure line of the pump, and on the other side to the pressure line of the jet apparatus, additionally containing an induction neutralizer of static electricity connected to one side with the mixing chamber, and on the other side - with the grounding circuit of the tank through a metallic potential equalization connection. 2. Jet mixing device according to claim 1, characterized in that when the tank is horizontal, the pump is located inside the tank near its bottom and is a submersible or semi-submersible pump. 3. Jet mixing device according to claim 1, characterized in that when the tank is vertical, the pump is located outside the tank and is a centrifugal cantilever or linear electric pump.