Patent Application
20250012047
The present invention relates to a discharging system, particularly, to a discharging system for a hopper. The present invention further relates to a method of discharging dredged material from the hopper.
Trailing suction hopper dredgers (“TSHD”) are vessels that excavates sand and sediment from the bottom while sailing. It trails a drag head over the sea floor that breaks the coherence of the sand with water jets and teeth. A centrifugal pump suctions a mixture of sand and water and transports this to a hold, the so-called hopper. As soon as the hopper is filled with sufficient sediment, the pipe and drag head are pulled or lifted in and the ship sails to the discharge location. At this location the material is discharged by opening the bottom doors (dumping) or by pumping the material out through a pipeline.
The discharge of the load through the bottom doors or valves usually costs little time. After the pumps are started and the water comes out of the pipe the discharge of the load is started. Because the material in the hopper is in general pretty loose packed, the process is similar to the process of a stationary suction dredger. The sand breaches to the opening of the suction pipe. If the hopper is not equipped with an installation that improves the breaching by means of water-jets, then, as a rule of thumb, the discharge time is equal to the suction time. If the hopper is equipped with water-jets to fluidize or loosen the load, then the discharge time can be shortened.
According to the invention, there is provided a discharging system for a hopper, the discharging system comprising a plurality of sensors on at least one wall of the hopper for acquiring information over a dredged material stored within the hopper; an outlet on a lower part of the hopper for discharging the dredged material; and at least one water jet valve for fluidizing the dredged material while discharging; wherein a quantity of water flowing out of the at least one water jet valve is based on the acquired information from the plurality of sensors. By controlling the quantity of water flowing out of the water jet valve(s), the dredged material can be efficiently fluidized while discharging. Such arrangement is believed to be considerably more versatile in optimizing the time needed for emptying the hopper. In the present context, reference to dredged material is intended to refer to solid or semisolid material including silt, sand, sediment, soil, clay, mud, gravel and fractured rock as may generally be encountered during dredging operations. Furthermore, although reference may be made to a seabed, this is equally intended to cover and include beds of rivers, lakes, canals, estuaries and the like.
According to an embodiment of the invention, the discharging system comprises a water level measurement system for acquiring a water level information of a water level within the hopper. This is beneficial since the acquired information from the plurality of sensors, in particular pressure sensors, can be corrected for a hydrostatic pressure based on the water level information.
According to an embodiment of the invention, the plurality of sensors comprises at least one pressure sensor. The pressure sensor enables to measure a pore pressure, that is local pressure at the sensor upon dilatation of sand. The acquired pressure information enables to apply jet water at strategic locations counteracting the stiffening effect of negative pore pressures (underpressure) on the dynamic soil behaviour. By doing so the sediment stored in the hopper is loosened effectively. Importantly, jet water can be used more efficiently. In contrast it is normal practice to use a huge amount of jet water at a high pressure of normally 6 bar to ensure the emptying of the hopper since the process of breaching is under the surface and hardly visible. Now according to the invention, by measuring pore pressures, jet water is used only at these locations where jet water is needed. This decreases the use of water, decreases the time needed for emptying the hopper, lowers the fuel consumption and, in turn, leads to less CO2 emissions. As another important advantage, the inclination angle of the inclined hopper walls can be lowered, which increases the hopper volume. Furthermore, the centre of gravity of the vessel is lowered when fully loaded. The lowering of the centre of gravity has a positive effect on the stability of the vessel. The pressure can also detect added pressure due to the jets and increased pressure due to hydrostatic pressure when the sand is fluidized, this further enables to monitor and control the emptying of the hopper.
According to an embodiment of the invention, the plurality of sensors comprises at least one density sensor or concentration sensor. Measuring the pore pressures in combination with sediment density or concentrations sensors provides information that all the more enables to apply jet water at strategic locations. In addition, by measuring the pore pressure in combination with the concentration sensors, the homogeneity of the sand mixture (e.g. sand and water) is more controllable when discharging the sand mixture. This importantly leads to a higher quality of a base layer that is made of the sand mixture, i.e. increased stability of the soil embankment, used at the reclamation site. The working principle of a density sensor or concentration sensor can be based on electrical conductivity of the sand mixture. However, any suitable density sensor or concentration sensor is conceivable.
According to an embodiment of the invention, the plurality of sensors comprises at least four sensors. It will be clear that any suitable number of sensors is conceivable depending on the dimensions of the hopper. In terms of cost, one can favor less sensors however in case of a fine-meshed grid of sensors, the discharging system may provide a more optimal delivery of jet water to fluidize the sand in the hopper.
According to an embodiment of the invention, the hopper comprises a number of hopper sections, and at least one hopper section comprises a sensor of the a plurality of sensors as well as at least one water jet valve both associated with the hopper section, and wherein the quantity of water flowing out of the at least one water jet valve and into the hopper section is based on the acquired information from the sensor. Dividing the hopper into hopper sections enables to fluidize sand in hopper sections even if jet water is scarce.
According to an embodiment of the invention, adjacent sensors among the plurality of sensors in a row are separated by a first distance. Optionally, the first distance is 55 mm or greater.
According to an embodiment of the invention, adjacent rows are spaced apart by a second distance. Optionally, the second distance is 110 mm or greater.
According to an embodiment of the invention, the plurality of sensors comprises at least a pair of sensors, each pair of sensors comprising a pressure sensor and a density sensor. Optionally, the pressure sensor and the density sensor in each pair of sensors are spaced apart by a third distance. Preferably, the third distance is 20 mm or greater.
According to an embodiment of the invention, a position of each sensor of the plurality of sensors is different than a position of each of the at least one water jet valve, and the position of each sensor is not in-line with a direction of water flowing out of the at least one water jet valve. This avoids unwanted direct influence of the water jet to the sensors which could disturb a proper monitoring of the discharging process.
According to an embodiment of the invention, a direction of water flowing out of the at least one water jet valve is adjusted based on the acquired information from the plurality of sensors.
According to an embodiment of the invention, a discharging system further comprising a control system for obtaining the acquired information over a dredged material from the plurality of sensors, and controlling the quantity of water flowing out of the at least one water jet valve based on the acquired information.
According to an embodiment of the invention, wherein the at least one bottom wall of the hopper has a slope. Preferably, the slope is 30 degrees or less which increases the volume of the hopper. In general a steeper bottom wall performs better when discharging a hopper, especially for cohesive soils.
According to an embodiment of the invention, the at least one bottom wall comprises a first bottom wall and a second bottom wall, such that the first bottom wall and the second bottom wall slope downwardly to the lower part of the hopper where the outlet is.
According to an embodiment of the invention, the discharging system comprises a discharging pump for controlling a quantity of dredged material discharged through the outlet on the lower part of the hopper.
According to an embodiment of the invention, the discharging system comprises a jet pump for controlling the quantity of water flowing out of the at least one water jet.
According to an embodiment of the invention, a dredging vessel comprising a hopper containing dredged material and a discharging system is provided.
According to an embodiment of the invention, there is provided a method of discharging dredged material from a hopper of a vessel within which the dredged material is stored, the method comprising, while the dredging material is being discharged through an outlet on a lower part of the hopper: acquiring, from at least one sensor, information of the dredged material; and fluidizing the dredged material by opening at least one water jet valve based on the acquired information of the dredged material such that the dredged material is discharged, wherein a quantity of water flowing out of the at least one water jet valve is based on the acquired information from the plurality of sensors.
According to an embodiment of the invention, there is provided a method comprising measuring a water level within the hopper; and correcting the acquired information from the plurality of sensors based on the measured water level.
According to an embodiment of the invention, there is provided a method, wherein the at least one sensor comprises at least one pressure sensor.
According to an embodiment of the invention, there is provided a method wherein the at least one sensor further comprises at least one density sensor.
The invention will be described in more detail below, with reference to preferred embodiments as shown in the drawings attached, in which:
The aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the disclosure are shown.
A plurality of sensors is placed on the bottom walls 14 of the hopper. The plurality of sensors are placed in a mirror symmetry arrangement on the two bottom walls 14, that is, the arrangement of sensors on one on the bottom walls 14 is identical to the arrangement of sensors on the other bottom wall 14 with respect to the discharging area 16. Alternatively, the plurality of sensors can be placed in an asymmetric arrangement on the two bottom walls 14.
As shown in
Optionally, the plurality of sensors can be grouped in pairs of sensors 25, i.e. a pressure sensor 22 and a density sensor 24. A pressure sensor 22 and a density sensor 24 in each pair 25 are spaced apart by a third distance (d3). The third distance depends on the arrangement and number of sensors in the hopper. The distance (d3) can be 20 mm or greater. Optionally, each pair of sensors 25 in the hopper can have a different distance between each sensor of the pair of sensors.
The discharging area 16 comprises two outlets 26 for discharging the dredged material. Alternatively, the discharging area 16 can comprise one outlet or a plurality of outlets. A discharging pump (not shown) can be connected to the outlets for pumping out the dredged material through the outlets. The discharging pump can be adjusted, for example by adjusting a flow rate or output pressure of the discharging pump, in order to control the quantity of dredged material discharged through the outlet.
The plurality of sensors comprises pressure sensors 22 and density sensors 24. Pressure sensors 22 are used for measuring the pore water pressure or pore pressure of a column of dredged material above the sensor and is usually measured with respect to the atmospheric pressure (e.g. atmospheric pressure at sea level), For example, when pressure sensors indicate a positive value (i.e. pressure is more than the atmospheric pressure), there is an overpressure; and when pressure sensors indicate a negative value (i.e. the pressure is less than the atmospheric pressure), there is an underpressure. The pore water pressure relates to the “stickiness” of the dredged material to the bottom wall of the hopper. The stickier, the slower the dredged material is discharged. When the measurement of the pressure sensor is below a pressure threshold (i.e. there is an underpressure), there is no discharging flow flowing. When the measurement of the pressure sensor is above the threshold, such that there is no underpressure but instead overpressure, the discharging flow is efficiently flowing. Hence, the pressure sensors 22 provide information over a first state of dredged material (i.e. how loosely or densely packed is the dredged material), and a state of flow (i.e. well flowing or not).
Density sensors 24 (or concentration sensors) are used for measuring the amount of water in the dredged material column above the sensor. When the measurement of the density sensor is smaller than a density threshold and this measurement decreases or remains constant while discharging, the discharging flow is efficiently flowing, and when the measurement of the density sensor is greater than the threshold but this measurement increases or remains constant while discharging, the discharging flow is not efficiently flowing due to due to the packing of the submerged dredged. The density threshold is physically defined to be a density defined by the soil porosity, which is somewhere between the maximum and minimum porosity of the soil. Hence, the density sensors 24 provide information over a second state of the dredged material (i.e. how packed the dredged material is or volume concentration of solids). In the present invention it is considered that the discharging flow is efficiently flowing when density sensors measure between 50% and 65% of solid material (or between 35% and 50% of water or liquid material).
Table 1 shows a state of the dredged material based on information of the sensors. While discharging the dredged material through outlets, a hole is formed around the outlets with almost vertical slopes. When time passes these vertical slopes move away radially from the outlets, while the dredged material flows over a certain slope to the outlets. This process is known as breaching. When sensors indicate an underpressure and high density (or concentration), the dredged material breaches slowly, that is the dredged material is slowly discharged through the outlets. When sensors indicate an overpressure and high density (or concentration), the dredged material is fluidized, thereby breaching is faster and the dredged material is fast discharged through the outlets. When sensors indicate low pressure and low density (or concentration), there is no (or almost nothing) dredged material present in the hopper, thereby the hopper is (almost) empty.
Referring back to
The water jet valves 30 can be connected through a pipeline (not shown) to a jet pump (not shown) for controlling the quantity of water flowing out of the water jet valves 30, in which the quantity of water flowing out of the water jet valves 30 is based on the acquired information from the plurality of sensors. Water flowing out of the water jet valves 30 fluidizes the dredged material, thereby improving its fast discharging through the outlets 26. Since the plurality of sensors provide information of the dredged material (or the state of the dredged material) continuously while the dredged material is being discharged, the jet pump can be adjusted, and thus the water jet valves 30, such that the quantity of water flowing out of the water jet valves 30 is continuously controlled, avoiding then that too much water or too low water is present in the dredged material. The jet pump can be easily adjusted (e.g. increasing/decreasing the revolutions per minute, r.p.m.) so a flow pressure of water flowing out of the water jet valves is adjusted, and as a result, the quantity of water (or volume flow rate) flowing out of the at least one water jet valve can be also easily controlled or adjusted. Therefore, the dredged material can be efficiently discharged, and as a consequence the time for emptying the hopper is reduced. If the hopper is emptied faster, more cycles of dredging material, transporting and discharging can be performed, reducing then the dredging costs, lowering the fuel consumption and, in turn, leading to less CO2 emissions. Furthermore, since quantity of water is controllable and water is only flowing out of selected water jet valves based on sensor measurements, then the quantity and pressure of water used for emptying the hopper is minimized, which align with a possible water scarcity or shortage in the vessel.
The water level 19 in the hopper as shown in
Water flowing out of each water jet valve 30 are provided at a close proximity or at a distance from the sensors, such that, on each bottom wall 14, the position of each sensor 22,24 is not in-line with a direction of the water flowing out of each water jet valve 30. Such arrangement of the sensors and water flowing out of the water jet valves, avoids any influence of the water flowing out over the measurement of the sensors. If sensors are in-line with the direction of the water jets, the water jets might influence the measurement of the sensors, or clear the dredged material so quickly that there is nothing to measure above the sensor, leading then to a wrong assessment that the hopper is empty. As shown in
Alternatively, the water jet valves 30 and plurality of sensors 22,24 can be arranged in sections. Each section can be controllable in a different way (e.g. quantity of water flowing out of water jet valves within a section can be different than a quantity of water in another section). Each section can comprise at least one water jet valve and at least one sensor or pair of sensors. Optionally, sections can be separated by walls. Optionally, sections can be emptied at different time.
As shown in
Optionally, the control system 80 can comprise a memory (not shown) for storing the information acquired from the sensors, a processor (not shown) and/or controller (not shown) for determining whether the quantity of water flowing out of the water jet valves 30 need to be adjusted and for outputting command for controlling the water jet valves 30 and/or jet pump, although reference may be made to a control system, this is equally intended to cover and include a unit, module, and the like.
These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and to fully convey the scope of all aspects of the disclosure to those skilled in the art. Like numbers refer to like elements throughout the description.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2029628 | Nov 2021 | NL | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/NL2022/050619 | 11/2/2022 | WO |
