EP3218256B1

EP3218256B1 - Hold offloading system

Info

Publication number: EP3218256B1
Application number: EP15830882.5A
Authority: EP
Inventors: Tom WAMBEKE; Vincentius Jacobus Jozef VAN DIJK
Original assignee: IHC Holland lE BV
Current assignee: IHC Holland lE BV
Priority date: 2014-11-12
Filing date: 2015-11-11
Publication date: 2019-08-21
Anticipated expiration: 2035-11-11
Also published as: PL3218256T3; WO2016076717A1; NL2013784B1; HRP20191568T1; EP3218256A1

Description

BACKGROUND

The process of causing soil to flow is called breaching, and for saturated soils requires that the pore size be locally increased. To facilitate this increase, water needs to flow toward the point where pore space increase is needed. However, the water flow is hindered by the soil itself as soils can have a low permeability. Additionally the amount of water needed is dependent on the difference in porosity between the in-situ soil and the flowing soil.
In the dredging industry, a variety of dredging vessels are used. Many of the vessels have a hopper for holding the dredged material, which must be offloaded at some point.
Typical hoppers are offloaded by opening one or more discharge valves in each section of the hopper. When the offloading rate or production decreases, the section is closed and a following section is opened. However, soil is still present in the previously closed section, and the valve is opened again after more liquid is added to the section for breaching, and a subsequent attempt to remove at least part of the soil that still remains. Thus, the offloading takes several rounds due to the limiting fluidization capacity of the breaching process.
Examples of discharge valves for sections of the hopper can be seen in WO2012/026808 , EP0158385 A1 , US4030435 and DE98118 . Each of these has a central valve portion that can extend downwards to allow flow out. However, the valve constructions and components can interfere with the discharge as the moveable valve member and often the valve stem is still sitting directly in the flowpath and thus in the way of flow even when open. A further system for discharging materials from a hopper can be found in FR335670 . This system includes trap doors which swing open to allow flow out of the hopper. Each of these systems provide a single flowpath to the discharge valve or door for offloading, and can be subject to the same issues described above.

SUMMARY

According to a first aspect of the invention, a hold offloading system comprises a holding space for containing a soil and liquid; an outlet with a valve for offloading the soil and liquid from the holding space; and an obstacle positioned near the outlet, wherein the obstacle is positioned and shaped to create a plurality of flow paths leading to the outlet.
Such a hold offloading system can improve the flow to an outlet of the holding space by creating a plurality of flow paths and thereby more breaching surfaces. This can result in a holding space that can be offloaded more efficiently.
According to the invention, the obstacle is suspended from a top or is supported from a floor of the holding space.
According to an embodiment, the obstacle is pyramid shaped.
According to an embodiment, the obstacle is supported from above the obstacle.
According to an embodiment, the obstacle has a center hole.
According to an embodiment, the obstacle is positioned directly above the outlet.
According to an embodiment, the obstacle is one or more plates.
According to an embodiment, the obstacle has an outer surface oriented so that the slope of the outer surface approximates an internal friction angle of the soil. For example, the slope of the outer surface can be equal to or close to the internal friction angle of the soil. The angle depends on the type of soil, and can be, for example, within the range of about 15 to about 45 degrees.
According to an embodiment, the system further comprises a jetting system within the hopper. The jetting system can further improve the offloading process by providing liquid to the soil at specific areas to promote flow towards the outlet.
According to an embodiment, the jetting system is connected to the obstacle.
According to an embodiment, the jetting system comprises a plurality of jets directed at a flow path leading to the outlet.
According to an embodiment, the hold offloading system forms a part of a hopper. Optionally, the hopper is geometrically shaped to improve flow toward the outlet. Further optionally, an outer surface of the obstacle is parallel to an inner surface of the hopper.
According to a second aspect of the invention, a method of forming an offloading system for a holding space comprises obtaining an obstacle shaped to direct flow through a holding space to an outlet; and positioning the obstacle in the holding space near the outlet to form a plurality of flow paths to the outlet.
According to an embodiment, the method further comprises positioning a jetting system in the holding space to direct flow toward the outlet.
According to an embodiment, the step of positioning a jetting system comprises securing a plurality of jets to the obstacle.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross-sectional view of a hopper with a breaching offloading system.
Fig. 2 is a cross-sectional view of a hopper with a second embodiment of a breaching offloading system and a jetting system.

DETAILED DESCRIPTION

Fig. 1 is a cross-sectional view of hopper 10 with breaching offloading system 12, and includes hopper bottom 11, outlet 14, flow paths 16, settled mixture 18, liquid 20, flow arrows 22, pits 23, obstacle 24 and connection 26.
Hopper 10 has a sloped bottom 11 leading toward outlet 14, though in other embodiments hopper 10 could have a horizontal bottom. The sloped shaped of the bottom 11 of hopper 10 can help improve flow toward outlet 14. Outlet 14 can have a valve (not shown), which can be opened for offloading.
Breaching offloading system 12 includes obstacle 24, which forms a plurality of flow paths 16 to outlet 14 of hopper 10. In the embodiment shown, obstacle 24 is pyramid shaped and positioned directly above outlet 14. The outer surface of obstacle 24 is oriented so that the slope approximates an internal friction angle of the soil being offloaded, for example, about 30 degrees. Obstacle 24 is suspended by connection 26 from a top of hopper 10. In other embodiments, obstacle 24 can be positioned or suspended by other means. The positioning and/or suspension means can also be movable in some embodiments to change the position of obstacle 24 and therefore affect flow to outlet 14. The positioning can be based on, for example, flow characteristics, soil being offloaded or other system components, characteristics and/or requirements.
Hopper 10 can be part of a vessel, such as a trailing suction hopper dredger. In a trailing suction hopper dredger, the vessel can suction a mixture of water and solid particles, for example soil, through a suction tube. The mixture can then be transported to hopper 10, where the soil suspended in the mixture settles, with settled soil portion designated 18. Excess liquid 20 can be overflowed to allow for more settled soil 18 in hopper 10.
Offloading of the settled soil 18 in hopper 10 is done through outlet 14. Breaching offloading system 12 forms a plurality of flow paths 16 toward outlet 14. These plurality of flow paths 16 increase the breaching surfaces for offloading, thereby improving flow of soil out of hopper 10.
As mentioned above, to facilitate movement of saturated soil out of hopper 10, the pore space must be locally increased to bring the soil from the dense state to a flowing loose state. This is done by flowing water toward the point where pore space increases are required, but the dense soil itself can hinder the water flow, resulting in the need to perform several rounds of offloading with time for adding more liquid between. A single offloading point will give rise to a single pit formation above this offloading point, and breaching will take place to the sides of the offloading point.
By forming a plurality of flow paths 16 toward outlet 14 with obstacle 24, breaching offloading system 12 increases the number of offloading points and therefore the number of pits 23 and breaching surfaces. This results in improved flow of soil to outlet 14 of hopper without the need to stop offloading, add liquid and then re-start offloading after a period of time, as done in past systems. The use of breaching offloading system 12 can decrease the number of offloading rounds required to empty hopper 10, and in some cases reduce the offloading process to only needing one opening and closing of outlet 14 to completely empty hopper 10, making for a more efficient and effective offloading system.
Fig. 2 is a cross-sectional view of hopper 10 with a second embodiment of a breaching offloading system 12, which includes obstacles 30 and jetting system 32 with jets 34. Fig. 2 also includes outlet 14, flow 16, flow arrows 22, pits 23 and connections 26.
In the embodiment of Fig. 2, obstacles 30 include a plurality of plates supported from and parallel to sloped base 11 of hopper 10. Each obstacle 30 forms a pit 23 and flow path 16 towards outlet 14. In the center of obstacles 30 is a hole, forming a further flow path 16 and pit 23.
Connections 26 can be moveable, allowing obstacles to form different flow paths, depending on the characteristics of the soil in hopper 10. For example, connections 26 could be extendable, allowing for a different sized flow 16, and/or tiltable to change the slope of flow path 16. Each of these, and other characteristics can be modified to increase flow towards and through outlet 14 of hopper 10.
Jetting system 32 is formed by a plurality of jets 34, and in this case, connected to obstacles 30 and to hopper 10 sloping base 11. Jets 34 are positioned to direct a spray of liquid toward soil, flow 16, outlet 14 and/or toward another point which can assist in the offloading process. Jets 34 can add pressurized liquid at specific locations to improve flow through flow paths 16 and can assist in the start-up of the flow for offloading, thereby improving the flow toward outlet 14 and the efficiency of the offloading process. Additionally, jetting system 32 can help to ensure that obstacles 30 do not obstruct soil movement within hopper 10.
In summary, breaching offloading system 12 can improve the offloading process by adding one or more obstacles to form a plurality of flow paths 16 to outlet 14, thereby increasing the offloading points, pits 23 and breaching surfaces for offloading. This leads to improved flow of soil out of hopper 10 and a more efficient overall offloading process. Breaching offloading system 12 can include jetting system 32 and/or specific geometry of hopper 10 to further improve the offloading process. Jetting system 32 can assist in flowing soil to outlet 14 in hopper 10 by adding the necessary fluid required for soil flow, specifically at places where the soil needs to start and/or continue flowing during the offloading process and/or locations that have a tendency to need extra fluid to facilitate movement. Breaching offloading system 12 is adaptable to a number of different hoppers 10 or other holding devices, and can easily be incorporated into existing hoppers 10. In new holding devices, the design and overall geometry could be coordinated in combination with one or more obstacles to improve offloading efficiency.
While obstacle(s) forming a part of breaching offloading system 12 have been shown as an inverted pyramid shape (Fig. 1) and a plurality of plates (Fig. 2), obstacle(s) can be any shape to form a plurality of pits 23 and flow paths 16 toward outlet 14. Specifically, obstacles could include, an inverted cone, a triangle, a cylinder or any other shape or device which can form or assist in forming a flow path 16 through the obstacle and/or in combination with some part of hopper 10 and/or another surface or device.
In some embodiments of breaching offloading system 12, additional mechanical systems could be used to facilitate soil transportation to outlet 14, for example, a conveyor belt, Archimedes screw or plates pushing the soil toward outlet 14. Other systems could include one or more guides or guiding systems for the slurry transport.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

A hold offloading system (12) comprising:
a holding space for containing a soil (18) and liquid (20);

an outlet (14) with a valve for offloading the soil (18) and liquid (20) from the holding space; characterised in that the hold offloading system further comprises

an obstacle (24; 30) positioned near the outlet (14), wherein the obstacle (24; 30) is positioned and shaped to create a plurality of flow paths (16) leading to the outlet (14), said plurality of flow paths (16) increasing the breaching surfaces for offloading, and

wherein the obstacle is suspended from a top or is supported from a floor of the holding space.
The hold offloading system (12) of any of the preceding claims, wherein the obstacle (24; 30) is pyramid shaped.
The hold offloading system (12) of any of the preceding claims, wherein the obstacle (24; 30) is supported from above the obstacle (24).
The hold offloading system (12) of any of the preceding claims, wherein the obstacle (24; 30) has a center hole.
The hold offloading system (12) of any of the preceding claims, wherein the obstacle (24; 30) is positioned directly above the outlet (14).
The hold offloading system (12) of any of the preceding claims, wherein the obstacle (24; 30) is one or more plates (30).
The hold offloading system (12) of any of the preceding claims, wherein the obstacle (24; 30) has an outer surface oriented so that the slope of the outer surface approximates an internal friction angle of the soil (18).
The hold offloading system (12) of any of the preceding claims, and further comprising a jetting system (32) within the hopper (10), wherein the jetting system (32) is connected to the obstacle (24; 30).
The hold offloading system (12) of claim 8 wherein the jetting system (32) comprises a plurality of jets (34) directed at a flow path (16) leading to the outlet (14).
A hopper (10) comprising the hold offloading system (12) of any of the preceding claims, wherein the hopper (10) is geometrically shaped to improve flow toward the outlet (14).
The hopper (10) of claim 10, wherein an outer surface of the obstacle (24; 30) is parallel to an inner surface (11) of the hopper (10).
A method of forming an offloading system (12) for a holding space according to one of the claims 1 to 11, the method comprising:
obtaining an obstacle (24; 30) shaped to direct flow through a holding space to an outlet (14); and

positioning the obstacle (24; 30) in the holding space near the outlet (14) to form a plurality of flow paths (16) to the outlet (14), wherein the obstacle (24; 30) is suspended from a top or is supported from a floor of the holding space.
The method of claim 12, and further comprising: positioning a jetting system (32) in the holding space to direct flow toward the outlet (14).
The method of claim 13, wherein the step of positioning a jetting system (32) comprises:
securing a plurality of jets (34) to the obstacle (24; 30).