Patent Publication Number: US-2017370155-A1

Title: Device and method for crushing rock by means of pulsed electric energy

Description:
BACKGROUND 
     The present invention relates to a method for processing material at the bottom of a body of water, like the bottom of the sea, by application of electric energy, comprising providing electrodes in a process zone proximate the material for providing electric energy for crushing the material. 
     WO9924694 (A1) relates to a method for crushing rock by means of pulsed electric energy. Costs of a dredging project may rise high as a result of a small volume percentage of rock, because the device used is unsuitable for dredging this material. Additionally it is not always possible to use explosives. Therefore WO9924694 (A1) aims to crush rock in a simple manner into pieces of a small size and provides therefore a method for crushing rock comprising the generation of a shock wave with a preprogrammed form, strength and length of time for crushing rock. WO9924694 (A1) alleges that because the shock wave is given such a preprogrammed form, strength and length of time, the crushing of rock produces a desired size of pieces, and/or the crushing of rock takes place over a desired surface of the rock and/or the crushing of rock takes place up to a desired depth in the rock. 
     WO 2006/023998 A2 relates to pulsed electric rock drilling, fracturing and crushing methods on land. Herein a number of techniques are described to process material by application of electric energy through electrodes. 
     RU2008118585 relates to electro hydraulic breaking and crushing method for solid materials. Two electrodes are placed inside a cylindrical airtight housing. Shock waves are precisely directed through hollows and linings arranged on the housing. 
     In connection with processing material by application of electric energy, U.S. Pat. No. 5,845,854 A shows an example of a method, for use on land, of solid insulator destruction which destroys solid insulators by electric pulse discharges. The method of U.S. Pat. No. 5,845,854 A is not suitable for offshore use. 
     With the known methods, the effect in terms of crushed rock is poor, in particular when executing prior art methods in seawater. There is room for improvement in that respect. 
     SUMMARY OF THE INVENTION 
     The invention aims to provide a more effective method for processing material at the bottom of a body of water, like the bottom of the sea, by application of electric energy. More effective has to be understood as more crushed rock per applied electric energy. 
     Another object of the invention is to improve a known method for processing material at the bottom of a body of water by application of electric energy, in that a problem associated therewith is at least partly solved. 
     Yet another object of the invention is to provide an alternative method for processing material at the bottom of a body of water by application of electric energy. 
     According to a first aspect of the invention this is realized with a method for processing submerged material at the bottom of a body of water, like the bottom of the sea, by application of electric energy, comprising providing electrodes for application of the electric energy in a process zone proximate the material for crushing the material, and displacing of fluid of the body of water away from the process zone to outside the process zone before application of the electric energy. 
     The displacing of fluid of the body of water away from the process zone to outside the process zone before application of the electric energy enables to lower the electrical conductivity in the process zone and therefore more electric energy is applied to the material. As a consequence, more crushed material at the bottom of the sea is obtained. Usually, the submerged material comprises rock. 
     This type of method is in the art referred to with e.g. pulsed power technology, fracturing rock is the plasma-hydraulic (PH) or electrohydraulic rock fracturing, and spark discharge drill. While the method specifies the processing of the material at the bottom to crushing, the processing may also include fracturing, pulverizing, eroding etc. 
     The method according to the invention is particularly useful when laying pipelines on the bottom of the sea. In performing the method, obstacles, like boulders or men made concrete structures, can be removed so that the pipe laying can continue. 
     In an embodiment of the method, the displacing of fluid of the body of water away from the process zone comprises introducing an electrically insulating body in the process zone. 
     In an embodiment of the method, the displacing of fluid of the body of water away from the process zone comprises introducing an electrically insulating fluid under pressure in the process zone. It will be apparent that the insulating fluid may be a gas, a liquid or a mixture thereof. 
     The electrically insulating fluid has a low electrical conductivity, in particular below 500 mS/m, more particular below 50 mS/m. 
     According to an aspect of the invention the method comprises on site producing the electrically insulating fluid. 
     In an embodiment of the method, fluid of the body of water is partly displaced away from the process zone to outside the process zone such that a layer of fluid of the body of water remains on top of the submerged material before application of the electric energy. This way, it is possible to create a shockwave in the layer of fluid of the body of water on top of the submerged material. This shockwave then has its crushing effect on the submerged material. In this embodiment the electric energy is applied to the submerged material indirectly through the layer of fluid. 
     In an embodiment of the method, substantially all fluid of the body of water is displaced away from the process zone to outside the process zone such that the application of the electric energy causes providing an electric current through the material. In this embodiment the electric energy is applied directly to the submerged material. 
     According to a further aspect of the invention this is realized with a device for processing submerged material at the bottom of a body of water, like the bottom of the sea, by application of electric energy, wherein the device comprises electrodes configured to be arranged in a process zone proximate the material for providing an electric current through the material, and means for displacing fluid of the body of water away from the process zone to outside the process zone before application of the electric energy. 
     In an embodiment of the device, the means for displacing fluid of the body of water comprises an electrically insulating body arranged proximate the electrodes. 
     In an embodiment of the device, the means for displacing fluid of the body of water comprise a discharge opening arranged proximate the electrodes for introducing an electrically insulating fluid under pressure in the process zone. 
     In an embodiment, the device comprises a container filled with the electrically insulating fluid, which container is in fluid connection with the discharge opening. The electrically insulating fluid may be pressurized with any suitable means, like a pump. 
     In an embodiment, the device comprises a shielding member arranged around the process zone for holding the electrically insulating fluid in the process zone. 
     In an embodiment, the device comprises measuring means arranged in the process zone for measuring electrical conductivity in the process zone. 
     In an embodiment of the device, the electrodes comprise a pair of concentric electrodes. This pair of concentric electrodes is in particular useful when a layer of fluid of the body of water remains on top of the submerged material before application of the electric energy. As described above, it is then possible to create a shockwave in the layer of fluid of the body of water on top of the submerged material. This shockwave then has its crushing effect on the submerged material. 
     The invention further relates to a device comprising one or more of the characterising features described in the description and/or shown in the attached drawings. 
     The invention further relates to a method comprising one or more of the characterising features described in the description and/or shown in the attached drawings. 
     The various aspects discussed in this patent can be combined in order to provide additional advantages. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention will be further elucidated referring to embodiments shown in the schematic drawings wherein shown in: 
         FIG. 1  in side view electrodes in a process zone while executing a prior art method; 
         FIG. 2  in side view electrodes in a process zone while executing a method according to the invention; 
         FIG. 3  in side view a device according to the invention for processing submerged material at the bottom of the sea by application of electric energy; and 
         FIG. 4  in side view a further embodiment of a device according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows in side view electrodes  1  in a process zone while executing a prior art method. The process zone is filled with sea water  4 . Because of the electrical conductivity of seawater, a discharge  12  between the electrodes  1  will take a path through the seawater and will therefore not have a desired effect of crushing the submerged material  6 . 
       FIG. 2  shows in side view electrodes  1  in a process zone  2  while executing a method according to the invention. The electrodes  1  are arranged proximate the material  6  at the bottom of the body of water  4 . Here, the electrodes  1  do not contact the material  6 . The submerged material  6  at the bottom of the sea, is processed by application of electric energy, shown as a spark  12 . Seawater  3  is displaced (see  FIGS. 3 and 4 ), that is removed, from the process zone  2  away from the process zone  2  to outside the process zone  2  before application of the electric energy. As a result, the electric energy is more effective in terms of crushed material at the bottom of the sea. Usually, the material  6  at the bottom of the sea comprises rock. 
       FIG. 3  shows in side view a device according to the invention for processing submerged material  6  at the bottom of the sea by application of electric energy. The fluid of the body of water  4  is displaced away from the process zone  2  through introducing an electrically insulating body  5  in the process zone  2 . The electrically insulating body is an example of a means for displacing fluid of the body of water  4  away from the process zone  2  to outside the process zone before application of the electric energy. The electrically insulating body  5  is arranged proximate the electrodes  1 . Here, the electrically insulating body  5  extends between the electrodes  1 . In this case, the electrically insulating body  5  contacts the material  6  at the bottom of the sea. 
     In dashed line, the electrically insulating body  5  is shown in a position wherein the fluid of the body of water is partly displaced away from the process zone to outside the process zone. In this position of the electrically insulating body  5 , a layer of fluid of the body of water remains on top of the submerged material before application of the electric energy. This way, it is possible to create a shockwave in the layer of fluid of the body of water on top of the submerged material. This shockwave then has its effect on the submerged material. In this embodiment the electric energy is applied to the submerged material indirectly through the layer of fluid. 
       FIG. 4  shows in side view a further embodiment of a device according to the invention. The device is provided with a nozzle  8  as a means for displacing fluid of the body of water  4  away from the process zone  2  to outside the process zone  2  before application of the electric energy. The nozzle  8  is arranged proximate the electrodes  1 . The nozzle introduces an electrically insulating fluid  7  under pressure in the process zone  2 . The electrically insulating fluid  7  displaces fluid of the body of water  4  away from the process zone  2  to outside the process zone  2 . The electrically insulating fluid under pressure has a low electrical conductivity, in particular below 500 mS/m, more particular below 50 mS/m. 
     In this case, the electrically insulating fluid is produced on site. To store the insulating fluid  7 , the device comprises a container  9  filled with the electrically insulating fluid  7 . The container  9  is in fluid connection with the nozzle  8 . The insulating fluid  7  is pressurized by any suitable means. 
     As an option, the device has a shielding member  10  for holding the electrically insulating fluid  7  in the process zone  2 . The shielding member  10  is arranged around the process zone  2  for holding the electrically insulating fluid  7  in the process zone  2 . 
     As a further option, the device comprises a measuring means  11  for measuring electrical conductivity in the process zone  2 . The measuring means  11  is arranged in the process zone  2 . 
     In dashed line, the possibility is shown that the fluid of the body of water is partly displaced away from the process zone to outside the process zone such that a layer of fluid of the body of water remains on top of the submerged material before application of the electric energy. This way, it is possible to create a shockwave in the layer of fluid of the body of water on top of the submerged material. This shockwave then has its effect on the submerged material  6 . In this embodiment the electric energy is applied to the submerged material  6  indirectly through the layer of fluid. 
     It will also be obvious after the above description and drawings are included to illustrate some embodiments of the invention, and not to limit the scope of protection. Starting from this disclosure, many more embodiments will be evident to a skilled person which are within the scope of protection and the essence of this invention and which are obvious combinations of prior art techniques and the disclosure of this patent.