Patent Application
20240208632
The present invention relates to the field of vessels, platforms, rigs and production facilities, and more specifically, the present invention refers to a gas dispersion intensifier assembly to be applied to a floating production, storage and offloading (FPSO) unit with difficulties in dispersing gases from a pressure relief system (“vent post”).
In FPSO production units, due to the fact that the transported cargo (hydrocarbons) is highly volatile and flammable, it is necessary to have a protection system against possible overpressure events (pressure above the design pressure of the tanks) inside the cargo tanks. In general, hydrocarbon vapors loaded into an FPSO do not ignite in atmospheres with an oxygen concentration of less than approximately 11%. Thus, a tank is protected from the risk of explosion when its atmosphere is maintained with an oxygen concentration below this value.
In order to keep this oxygen concentration low in the environment, an inert gas (e.g., nitrogen or carbon dioxide) is pumped into the cargo tanks during the discharge of flammable fluids. It is worth noting that, in addition to being responsible for controlling the environment and preventing the formation of flammable substances, inert gas is produced on board the FPSO by burning diesel oil or fuel gas in an inert gas generator.
Therefore, the inert gas, when introduced into the tank, “inerts” the environment, preventing the formation of an explosive mixture. However, variations in temperature and pressure can affect the tank and cause damage and risks. When there is excess pressure in the tank, a valve is opened, releasing the gas phase from inside the tank to a pressure relief system that will conduct the gas along a pipeline until it is discharged through a gas vent/exhaust on the platform deck.
Unfavorable weather conditions, such as winds with low intensity (ocean wind profile in calm conditions), combined with the presence of gases with high percentage of heavy fractions (propane, butane and higher) bring some problems to the system responsible for the pressure relief of platform tanks and FPSO vessels. This pressure relief system is known as “vent post”.
More specifically, for an FPSO in shallow or deep waters, winds with low intensity and gases with a high percentage of heavy fractions running through the pipeline, from the vent post to the gas outlet region (vent), are elements that hinder the proper dispersion of the gas stream coming from the platform tanks, resulting in a risk of plume return (continuous outflow of flammable gases released from the vent) towards the rig process plant.
To mitigate the risk of plume return, operations of pressure relief via the vent post system are usually restricted during adverse weather conditions, possibly resulting in a need to limit production on the platforms.
Additionally, another type of solution currently proposed is to carry out the integration of equipment (such as additional safety valves, for example) in internal sections of the vent post system, which can generate a considerable change in the deck (topside) of the platform, or even the inadequate discharge of gases into the atmosphere.
Therefore, there is an evident need in the state of the art for the development of systems capable of promoting dispersion of gases from the vent post in a safe and efficient manner, maintaining operational continuity, and capable of reducing the occurrence of alarms and production stoppages in the units due to the presence of flammable gases.
Investigating the background of the specified invention resulted in the discovery of documents that disclose topics related to the technological field of the current invention.
Document WO 2015/197455 describes a device for releasing unused or excess gases into ships or floating bodies, or the like, having a ventilation mast that has an outlet and is designed to guide excess, unused or similar gases to the outlet, and a feed tube that has an outlet and is designed to suck in ambient air and conduct it to the outlet. In said document, the feed tube runs to the outlet of the ventilation mast and is arranged with its outlet adjacent to the ventilation mast outlet, so that excess or unused gases, or the like, are forcibly mixed with the ambient air coming out of the feed tube, so as to fall below the lower flammability limit of the gas concentration in a mixing zone formed at the ventilation mast outlet. This document proposes a solution for gas dispersion based on the use of an additional flow of compressed air supplied from the deck of the unit directly as the dilution agent of the vent gas stream, which may not be advantageous in installations with low compressed air flow availability, or even, it may require substantial modifications to the platform design for routing high airflow pipes to the vicinity of the disposal point.
Document GB 1 387 678 refers to a method and installation for reducing the concentration of fuel gases in tanks by evacuating gas through tubes extending from the bottom of the tank into the open air, while fresh air is supplied from above. The document relates to a ventilation mast for releasing gas, inside which, to accelerate the exhaust air, additionally, a compressed air pipe is arranged at least with its outlet side section, in which the outlet of the compressed air pipe is at a considerable distance from the mast outlet and is formed so that the compressed air coming out inside the mast carries the exhaust air with it. However, the document is intended for a conventional confined space exhaust application, without the commitment to disperse the gas stream released into the external atmosphere safely in an upper region of an FPSO.
Finally, document FR 3 109 896 describes a device and method for gas treatment of a gas exhaust mast. The document refers to a gas treatment system of a gas exhaust mast of a tank containing a cold liquid from a structure such that a ship comprising at least one inlet line of a fluid, has a temperature at least higher than that of the gases at its mast outlet, up to at least one spray. The spray is located at a distance not exceeding one meter from the mast head, and is capable of spraying said fluid at an angle between 0 degrees and 90 degrees with respect to the aforementioned z′z axis, so that the fluid and gases meet, and a control circuit capable of controlling spraying of fluid by the spray when gases are evacuated by the gas exhaust mast. However, the system disclosed by the cited document employs a liquid spray on the exhaust gas, that is, it presents a working principle based on the thermal exchange between the spray (made with water at a temperature higher than the gas), with applications focused on LNG (Liquified Natural Gas).
The present invention belongs to the field of technologies aimed at production units with difficulties in dispersing gases from pressure relief systems.
One of the objectives of this invention is to allow flexibility for changes to a disposal device of the vent post system and to present an appropriate technical solution, depending on the device configurations and the parameters of the expelled gases, so as to avoid gas plume return at critical concentrations to the FPSO.
Therefore, the present invention provides a gas dispersion intensifier assembly that uses one or more “blower” devices for vent post systems that will act locally to increase the airflow near the gas outlet region in a vent configuration.
Particularly, one or more blowers are positioned in the vicinity of a gas outlet region of the pipeline, in order to direct and disperse the gas flow leaving there, preventing the highly flammable gas from spreading over the vessel deck, posing a risk to equipment and people.
The blowers can be positioned in different positions and angles in the vicinity of the gas outlet of the pressure relief system.
This invention eliminates the need for the use of electrical equipment in a classified area (a region that has the possibility of an explosive atmosphere), allowing the dispersion of gases at a safe level and maintaining operational continuity, reducing the occurrence of alarms and production stoppages in the units due to the presence of flammable gases.
Therefore, the advantages and objectives of the present invention are achieved by providing a gas dispersion intensifier assembly for a pressure relief system, which comprises: at least one blower; and a gas dispersion pipe with a gas outlet nozzle; wherein at least one blower is arranged externally and in the vicinity of the gas outlet nozzle, and projects an air flow toward the gas flow expelled by the gas outlet nozzle.
The previous brief description, as well as the breakdown of the preferred embodiments of the invention under discussion, presented below, will be better understood when read in conjunction with the attached drawings. For the purpose of illustrating the present invention, embodiments thereof are shown in the drawings. However, it must be understood that the invention under discussion is not limited only to the precise arrangements and instruments shown.
Thus, the present invention will be described below with reference to the typical embodiments thereof and also with reference to the attached drawings, wherein:
Reference is made in detail below to the preferred modalities of the present invention illustrated in the attached drawings. Whenever possible, the same or similar reference numbers will be used throughout the drawings to refer to the same or similar characteristics. It should be noted that the drawings are in simplified form and are not drawn at precise scale, so slight variations may occur.
Before describing in detail the characteristics of the gas dispersion intensifier assembly of this invention, it is necessary to elucidate the concept of lower flammability limit (LII). The LII refers to the range of minimum concentration, in the air, of vapors of a substance that can lead to a flammable condition.
The different configurations, techniques and methodologies that will be described below refer to a gas dispersion intensifier assembly for an FPSO pressure relief system, which provides one or more blowers installed in the vicinity of a gas dispersion nozzle of a vent post system, and the one or more blowers have specific mounting configurations, capable of varying in height and degree, to intensify the dispersion of the expelled gases by the gas dispersion nozzle in the pipeline discharge region, ensuring a mixture between the flow of the expelled gases and the air flow generated by one or more blowers.
To implement at least one air blower in the vicinity of the pipeline gas discharge region, the present invention also takes into account wind intensity and direction in the unit.
Thus, the present invention is ideal to be used in situations where the average speed of gases out of the gas outlet nozzle (vent post termination) is low, which also hinders the dispersion of gases in low wind conditions.
Reference is made to
In a first embodiment of the present invention, as shown in
In a second embodiment of the present invention, as shown in
In a third embodiment of the present invention, as shown in
In a fourth embodiment of the present invention, as shown in
In a fifth embodiment of the present invention, as shown in
In a sixth embodiment of the present invention, as shown in
In a seventh embodiment of the present invention, as shown in
It should be noted that, although the embodiments described above have one or two blowers 20, the present invention can be adapted to work with three or more blowers 20, depending on the design conditions and implementation, so that the objective of dispersing gases in a more efficient and safe manner is achieved.
In addition, the blowers 20 of the intensifier assembly of the present invention are connected to a compressed air supply source, and supplied by it with a compressed air flow rate between approximately 211 m3/h and approximately 844 m3/h, with the compressed air pressure ranging from approximately 300 kPa (3 bar) to approximately 550 kPa (5.5 bar). The blowers 20 being configured to operate with an air flow rate at the output of the blower 20 between about 4,055 m3/h and about 5,970 m3/h. It is important to highlight that the blower of the present invention provides high air flow at the outlet of the diffuser end, since the blower uses the compressed air supply flow as the driving fluid to generate Venturi effect locally and suck ambient air close to the airflow disposal point.
The air blower, according to an embodiment of the present invention, has a frustoconical shape, with the diameter of the base of the blower being smaller than the diameter of the diffuser end that expels the airflow.
Also, as shown as an example in
The present invention further provides that each blower 20 may be moved or tilted, in any direction, to direct the airflow in the direction of the gas flow coming from the gas outlet nozzle 11 in order to intensify the dispersion of the gases, depending on the intensity and direction of the winds and the flow rate of expelled gas.
Therefore, one person skilled in the art will understand that each blower 20 described above of the dispersion intensifier assembly of the present invention may be positioned at any location in the vicinity of the gas outlet nozzle 11 of the vent post system and tilted in any direction, without departing from the purpose of the present invention to intensify the dispersion of the expelled gases and maintain the safety and productivity of the operation in an FPSO.
The skilled in the art will value the knowledge presented herein and can reproduce the invention in the presented embodiments and their variants, which are covered in the scope of the claims below.
| Number | Date | Country | Kind |
|---|---|---|---|
| BR 1020220265879 | Dec 2022 | BR | national |
