RU2729673C2 - Method for cleaning reservoir from deposits - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: method of cleaning reservoir from deposits relates to purification processes, in particular to cleaning of inner surfaces of reservoirs, and can be used in industry, for example in oil industry. Method includes thermal treatment of washing medium, supply of liquid or steam flow under pressure by means of washing plant for mechanical cleaning. For washing out of deposits water flow is used under pressure from 5 to 300 MPa with temperature of 35–374 ºC or steam under pressure from 0.2 to 22 MPa with temperature from 100 ºC to 374 ºC, supplied through remotely controlled mobile washing plant. Plant is driven by hydraulic drive with hydraulic fluid fed at pressure from 5 to 300 MPa. Removal of bottom sediments is performed through suction pipe of vacuum intake device with rarefaction from -0.01 to -1.00 MPa. Control of reservoir cleaning is carried out remotely.

EFFECT: higher efficiency of sediment washing with preservation of waste characteristics, which allow their secondary use, reduction of losses of stored products at minimization of harmful effect on a person.

8 cl, 4 ex

Description

The method for cleaning a tank from deposits relates to cleaning processes, in particular to cleaning the inner surfaces of tanks, and can be used in industry, for example, in the oil industry.

There is a known method of cleaning a reservoir, which consists in pumping a washing liquid and gas into a reservoir, removing a washing liquid with impurities from the reservoir under the influence of a pressure difference, draining a washing fluid with impurities into a separator. In this case, the pumping of the washing liquid into the tank is carried out from the separator under pressure by a pressure pump through an ejector-type dispersing device, into which an ozone-containing gas mixture is additionally fed. (analogue RF Patent No. 2537593, IPC B08B 9/08, publ. 01/10/2015). There is a known cleaning method for washing cargo tanks of ships, in particular, oil tankers, and a device in which this method is implemented (analogue of US Patent 3420444, MKI B 05 B 3/14, publ, 07.01.69). The method includes supplying a washing liquid through a controlled barrel with a nozzle for washing out oil residues from the inner surfaces of the tank, and washing is carried out according to a predetermined program. The washed-out oil residue is then removed through a sweep pipe. The device in which this method is implemented is a barrel with a nozzle mounted for reciprocating movement and rotation about its axis, and a mechanism for controlling the barrel with a nozzle. In this case, the barrel with the nozzle moves according to a given program in mutually perpendicular planes, which makes it possible to wash the entire inner surface of the tank.

The known method of cleaning a reservoir from bottom sediments includes supplying erosion fluid through a controlled bore with a nozzle to the surface of bottom sediments, washing out bottom sediments with a jet of erosion liquid from a controlled bore with a nozzle and removing eroded suspended sediments simultaneously with the erosion process. Erosion is performed by dividing bottom sediments into separate sections with a jet of erosion liquid, and the barrel with a nozzle is controlled depending on the state of bottom sediments over the area of the bottom of the tank. During cleaning, the composition of the mixture of bottom sediments with erosion liquid is monitored and the erosion zone is expanded while the suspension of bottom sediments decreases. The device for cleaning the tank from bottom sediments includes a controlled shaft with a nozzle, a pressure pipeline and a stripping pipeline mounted on one of the side lower hatches. The stripping pipeline can be moved to another hatch. The control mechanism of the barrel with the nozzle is configured to fix the position of the barrel with the nozzle. (prototype - RF patent No. 2196062, IPC B60S 3/00, publ. 10.01.2003)

The known solutions have the following disadvantages.

The control of the borehole with the nozzle does not allow to provide the necessary force of the supplied liquid jet for washing away the removed and solid deposits, including with numerous hardened deposits over the area of the tank bottom and in the presence of areas remote from the location of the borehole. These disadvantages are exacerbated in the case of using the known method and device in the reservoirs of large oil storage facilities, where the deposits are for a long time and represent a dense mass, uneven in composition and consistency. Taking into account the significant distances from which the erosion of sediments is carried out (from several meters to several tens of meters), the erosion fluid must be supplied in the form of a significant flow (from several cubic meters per hour) and under low pressure (up to 20 bar / up to 2 MPa: otherwise In this case, the jet will not be able to reach the deposits with the proper supply of energy). Thus, washing under low pressure from long distances requires significant consumption of erosion fluid, which leads to increased costs for:

• the liquid itself, its storage, transportation and collection in the tank;

• heating the liquid;

• separation of the emulsion (liquid runoff and products washed off by it) for further use and / or disposal.

Below is a theoretical substantiation of the proposed method for cleaning tanks using the example of cleaning Vertical Steel Tanks (hereinafter referred to as Tanks) from deposits of fuel oil or other dark oil products (with a saturated vapor pressure of no more than 26.6 kPa and a flash point above 61 ° C), which is the main difficulty for works of this kind.

Dark oil products, like crude oil, are highly viscous substances with a pour point of about 35 ° C. Their mechanical collection without giving them fluidity (that is, without heating) seems to be a very difficult and costly task, including taking into account the fire and explosion hazard of the product, while after imparting fluidity (for example, with hot water or steam), the extraction of such an emulsion becomes relatively an easily solvable task.

In 1959, Henkel Chemical Engineer Dr. Herbert Zinner formulated the basic principles of surface cleaning from contamination. His theory is that the most effective solution to any cleaning task depends on the correct combination of 4 factors:

• mechanical impact;

• temperature regime;

• detergent (chemistry);

• the time of exposure to each of the factors.

The listed items are easy to represent in the form of a pie chart - hence the name of the theory "Zinner's circle", which is divided into 4 sectors: "mechanical action", "temperature", "chemistry", "time". The relationship between the components of the circle is non-linear. An increase in any of the components is offset by a decrease in the rest.

Time limiters of exposure are:

- the need to save the tank downtime for the time of its cleaning, due to which the time of any type of exposure must be minimized to ensure the practical side - benefits;

- the need for the fastest possible extraction of the product: in the overwhelming majority of cases, the ambient temperature is insufficient to impart natural fluidity to dark oil products (that is, below + 35 ° C), and even the heated product quickly cools down, again becoming viscous. Maintaining fluidity by increasing the heating time (or temperature) is a waste of time;

- the need to minimize the participation of people in any work inside the tanks due to the increased danger of poisoning with vapors of oil products, as well as the explosion and fire hazard of these objects.

Due to these circumstances, it seems appropriate to use remotely or programmatically controlled manipulative or robotic devices as stripping modules.

Limiters in chemical exposure are:

- the high cost and complexity of the use of chemically active substances (for exposure to large product residues, significant amounts of chemicals are required; transportation, storage and use of large volumes of chemical products are always associated with increased costs);

- loss of properties of the residue of the recoverable product - for example, in the case of stripping from oil products with a chemical agent, for example, caustic soda (alkaline solution), which effectively destroys hydrocarbon chains, but the oil product becomes already an oil waste, which is extremely economically unprofitable for the owner. Based on Zinner's theory, to optimize the stripping technology, you need to make the most of the two remaining factors: Mechanical and Temperature effects.

The optimal mechanical action, which also provides fluidity to the removed product residue, can be the impact of a stream of maximum hot water at the maximum high pressure.

Limiters in the increase in water temperature are:

- boiling point (transition to steam with loss of effectiveness of impact on the bottom residue);

- cavitation (the process of formation of bubbles filled with steam), which leads to accelerated wear of mechanical components (high pressure pumps, valves, spray nozzles, etc.)

Thus, the optimal water temperature for this task at atmospheric pressure is in the region of 85-95 ° C.

Limiters in increasing water pressure are:

- the danger from the generation of sparks in the explosive zone caused by the high speed of movement of any objects - the maximum permissible pressure of the water flow is normatively limited to 50 MPa (500 bar) [in the countries of the European Union; this is not yet in Russia, but sooner or later it will also appear];

- reduction of the range of effective action of the jet with increasing pressure due to the increase in air resistance (a similar volumetric flow of water in the air disintegrates the faster, the higher the pressure of the jet).

Due to this factor, it is required to provide a very small distance from the nozzles to the removed residue, which implies the use of a mobile rather than a stationary device.

The last property of a mechanical flow is its magnitude.

Increasing the flow gives the following advantages (benefits):

- reducing the time of stripping;

- providing a sufficient amount of heat to impart and maintain the fluidity of the collected product, including when it is delivered to a new container (reservoir).

The flow increase is limited by:

- cost (economic feasibility in increasing costs for all factors);

- limitation of the through-passage section of the manhole-manhole of the tanks, which limits the dimensions of the mobile stripping device.

There is a need for a modular mobile module of optimal performance from separate components (each of which can separately go through the hatch) and / or the simultaneous use of several less efficient mobile modules.

Minimization of the flow gives the following advantages (benefits): - reduction of water consumption,

- Reducing the cost of all components of the solution (high-pressure pumps, heating modules, spray nozzles, vacuum module, treatment facilities, and others).

Limiters in minimizing the flow are:

- the time factor (the smaller the flow, the longer it takes to perform the same amount of work);

- low fluidity of the removed product: to impart and maintain fluidity, a certain amount of heat is required, delivered by hot water, which at its fixed temperature is determined exclusively by the flow rate.

Based on these factors, it is proposed to use as a working tool:

- water without the addition of chemicals under a pressure of 50 MPa with a temperature of about 90 ° C;

- the water flow is assigned taking into account the size of the product residue, its temperature, viscosity and the required cleaning performance.

Based on the optimal flow rate, a mobile device must have technical parameters that allow:

- be delivered to the inside of the tank through a typical manhole, including in parts;

- in a controlled manner, direct a stream of hot water under pressure in the immediate vicinity of the stripping point to liquefy the residue;

- have means for prompt collection and removal of the cooling effluent emulsion, for example, a screw and a vacuum intake device;

- have remote control without the need for the presence of people in the tank.

The technical result from the use of the claimed technical solution can be expressed in an increase in the efficiency of erosion of bottom sediments while maintaining the characteristics of waste, allowing their reuse, i.e. reducing the loss of stored products while minimizing harmful effects on humans.

The claimed technical result is achieved as follows.

A method for cleaning a tank from bottom sediments, including thermal preparation of a cleaning medium, supplying a flow of liquid or steam under pressure using a washing installation to provide mechanical cleaning. For erosion of sediments, a liquid flow under a pressure of 5 to 300 MPa with a temperature of more than 35 ºС or steam under a pressure of 0.2 to 22 MPa with a temperature of 100 ºС to 374 ºС is used, supplied through a remotely controlled mobile washing installation. The installation is driven by a hydraulic drive with a working hydraulic fluid supplied under a pressure of 5 to 300 MPa. Bottom sediments are removed through the suction pipe of a vacuum intake device with a vacuum from -0.01 to -1.00 MPa.

Mechanical stripping is performed using a rotary device with a screw.

A collapsible installation is used as a mobile device to enable the device to pass through the manhole of the tanks.

The process of assembling and disassembling the installation to enable the device to pass through the hatch-hole of the tanks is carried out automatically without operators entering the tanks.

The removal of bottom sediments through the suction pipe of the vacuum intake device is mainly carried out with a vacuum from -0.08 to -0.10 MPa

Choose a vacuum intake device with a capacity of 250 to 5000 m ³ / h.

Tank cleaning is controlled remotely.

The implementation of the method is illustrated by the following examples.

Example 1

To wash out bottom, wall and ceiling deposits of diesel fuel in a vertical steel tank (Vertical Steel Tank) with a volume of 5000 m3 with a remaining fuel in the volume of 5 +/- 1% with an oval hatch-manhole type LL-600x900, a water flow of 140 l / min under pressure is used 5 MPa with a temperature of 35 ° C. The flow is fed through a remotely controlled mobile washing unit, driven by a hydraulic drive with water under a pressure of 5 MPa as a working hydraulic fluid. Bottom sediments are removed through a suction pipe with a diameter of 150 mm of a vacuum intake device with a vacuum of –0.01 MPa.

After cleaning for 16 hours, it was found that residual deposits do not exceed 0.01% of the tank capacity.

Example 2

For erosion of bottom, wall and ceiling deposits of crude oil in a reservoir with a volume of 5000 m3 with an oil residue in the volume of 10 +/- 2% with an oval hatch-manhole type LL-600x900, saturated steam in a volume of 0.3 Gcal / h (450 kg / h) under a pressure of 8 atm with a temperature of 189 ° C. Steam is supplied through a remotely controlled mobile washing unit, driven by a hydraulic drive with oil under a pressure of 5 MPa as a working hydraulic fluid. Bottom sediments are removed through a suction pipe with a diameter of 100 mm of a vacuum intake device with a vacuum of 0.01 MPa.

After cleaning for 48 hours, it was found that residual deposits do not exceed 1.5% of the tank capacity.

Example 3

For washing out gasoline deposits (with a saturated vapor pressure of 26.6-93.3 kPa, as well as a flash point of not more than 61 ° C) in a tank with a volume of 10,000 m ³ with a gasoline residue in the volume of 1 +/- 0.1% with an oval manhole-manhole type LL-600x900 use a water flow of 120 l / min under a pressure of 25 MPa with a temperature of 75 ° C. The flow is fed through a remotely controlled mobile washing unit, driven by a hydraulic drive with water under a pressure of 25 MPa as a working hydraulic fluid. Bottom sediments are removed through a suction pipe with a diameter of 100 mm of a vacuum intake device with a vacuum of –0.08 MPa with a flow rate of 720 m ³ / h.

After cleaning for 38 hours, it was found that residual deposits do not exceed 0.02% of the tank capacity.

Example 4.

To wash away deposits of fuel oil or other dark oil products (with a saturated vapor pressure of no more than 26.6 kPa, as well as a flash point above 61 ° C) in a tank with a volume of 1,000 m ³ with a round manhole hatch of the LL-500 type, a water flow of 450 l / min under a pressure of 50 MPa with a temperature of 95 ° C. The flow is fed through a remotely controlled mobile washing unit, driven by a hydraulic drive with water at a pressure of 50 MPa as a working hydraulic fluid. The removal of bottom sediments is carried out through a suction pipe with a diameter of 200 mm of a vacuum intake device with a vacuum of -0.08 MPa with a feed of 720 m ³ / h.

After cleaning for 14 hours, it was found that residual deposits do not exceed 0.02% of the tank capacity.

Claims (8)

1. A method of cleaning a reservoir from deposits, including thermal preparation of a washing medium, supplying a flow of liquid or steam under pressure using a washing installation to provide mechanical cleaning, characterized in that for washing out deposits, a flow of water under a pressure of 5 to 300 MPa is used as a liquid flow with a temperature of 35 ° C to 374 ° C or steam under a pressure of 0.2 to 22 MPa with a temperature of 100 ° C to 374 ° C, supplied through a remotely controlled mobile washing unit, driven by a hydraulic drive with a working hydraulic fluid supplied under a pressure of 5 to 300 MPa, sediments are removed through the suction pipe of the vacuum intake device with a vacuum from -0.01 to -1.00 MPa. 2. A method according to claim 1, characterized in that mechanical cleaning is performed using a rotary device with a screw. 3. The method according to claim 1, characterized in that a collapsible installation is used as a mobile device to allow the device to pass into the manhole of the tanks. 4. The method according to claim. 3, characterized in that the process of assembly and disassembly of the installation for the possibility of passage of the device into the hatch of the tanks is carried out automatically without operators entering the tanks. 5. The method according to claim 1, characterized in that the removal of bottom sediments through the suction pipe of the vacuum intake device is performed with a vacuum from -0.08 to -0.10 MPa. 6. The method according to claim 1, characterized in that a vacuum intake device with a capacity of 250 to 10,000 m ³ / h is used. 7. A method according to claim 1, characterized in that the tank cleaning is controlled remotely. 8. A method according to claim 1, characterized in that an elongated barrel with a nozzle is used to clean the walls and ceiling of the tank.