Riser flow control

Abstract

A deep sea mining method includes: excavating matter at a bottom of a body of water; operating a riser system for transporting a slurry of matter and water; transporting the slurry from the bottom of a body of water upwards to a slurry processing base; and maintaining a controlled riser system pressure higher than the environmental pressure inside the riser system for avoiding forming of gas and expanding of gas contained in the slurry during transporting the slurry.

1 - 17 . (canceled) 
     
     
         18 . Deep sea mining method comprising;
 excavating matter ( 2 ) at a bottom ( 9 ) of a body of water ( 3 ),   operating a riser system ( 4 ) for transporting a slurry ( 13 ) of matter and water,   transporting the slurry from the bottom of a body of water upwards to a slurry processing base ( 6 ),   maintaining a controlled riser system pressure, higher than the environmental pressure, inside the riser system for avoiding forming or release of gas and expanding of gas contained in the slurry during transporting the slurry.   
     
     
         19 . Method according to  claim 18 , comprising the step measuring the pressure for providing a riser system pressure signal, and controlling the pressure in response to said pressure signal. 
     
     
         20 . Method according to  claim 19 , comprising controlling the riser system pressure to a predefined riser system pressure threshold. 
     
     
         21 . Method according to  claim 18 , wherein the maintaining a controlled riser system pressure comprises providing pressure control means ( 5   a,    5   b,    5   c,    5   d,    11 ). 
     
     
         22 . Method according to  claim 21 , wherein the pressure control means comprise active and/or passive means. 
     
     
         23 . Method according to  claim 21 , wherein the pressure control means are selected from restriction, systems of bends, turbines, pumps used as turbines, and pumps. 
     
     
         24 . Method according to  claim 21 , wherein a series of pressure control means is provided. 
     
     
         25 . Method according to  claim 24 , wherein the series of pressure control means is arranged along the length of the riser system for controlling pressure in the riser system. 
     
     
         26 . Method according to  claim 24 , wherein adjacent control means are arranged at a predefined mutual distance (d). 
     
     
         27 . Method according to  claim 21 , comprising recovering energy from the transported slurry through the pressure control means. 
     
     
         28 . Method according to  claim 18 , wherein the matter comprises gashydrates. 
     
     
         29 . Deep sea mining system ( 1 ) for use in a method according to  claim 18 , the system comprising;
 an excavating system ( 7 ) for excavating matter ( 2 ) at a bottom ( 9 ) of a body of water ( 3 ),   a riser system ( 4 ) for transporting a slurry ( 13 ) of matter and water from the bottom of a body of water upwards to a slurry processing base ( 6 ), the riser system comprising an adjustable pump means ( 11 ) proximate the bottom of a body of water,   pressure control means ( 5   a,    5   b,    5   c,    5   d ) for maintaining a controlled riser system pressure higher than the environmental pressure inside the riser system for avoiding forming or release of gas and expanding of gas contained in the slurry during transporting the slurry.   
     
     
         30 . Deep sea mining system according to  claim 29 , comprising a series of pressure control means arranged along the length of the riser pipe for controlling pressure in the riser pipe. 
     
     
         31 . Deep sea mining system according  claim 30 , wherein adjacent control means are arranged at a predefined mutual distance (d). 
     
     
         32 . Deep sea mining system according to  claim 29 , wherein the pressure control means comprise active and/or passive means. 
     
     
         33 . Deep sea mining system according to  claim 29 , wherein the pressure control means are selected from restrictor, systems of bends, turbines, pumps used as turbines, and pumps. 
     
     
         34 . Deep sea mining system according to  claim 29 , comprising;
 measuring means for measuring the riser system pressure in order to provide a riser system pressure signal,   a control unit operationally coupled with the measuring means and the pressure control means for controlling the riser system pressure in response to said pressure signal.   
     
     
         35 . Deep sea mining system ( 1 ) for use in a method according to  claim 19 , the system comprising;
 an excavating system ( 7 ) for excavating matter ( 2 ) at a bottom ( 9 ) of a body of water ( 3 ),   a riser system ( 4 ) for transporting a slurry ( 13 ) of matter and water from the bottom of a body of water upwards to a slurry processing base ( 6 ), the riser system comprising an adjustable pump means ( 11 ) proximate the bottom of a body of water,   pressure control means ( 5   a,    5   b,    5   c,    5   d ) for maintaining a controlled riser system pressure higher than the environmental pressure inside the riser system for avoiding forming or release of gas and expanding of gas contained in the slurry during transporting the slurry.   
     
     
         36 . Deep sea mining system ( 1 ) for use in a method according to  claim 20 , the system comprising;
 an excavating system ( 7 ) for excavating matter ( 2 ) at a bottom ( 9 ) of a body of water ( 3 ),   a riser system ( 4 ) for transporting a slurry ( 13 ) of matter and water from the bottom of a body of water upwards to a slurry processing base ( 6 ), the riser system comprising an adjustable pump means ( 11 ) proximate the bottom of a body of water,   pressure control means ( 5   a,    5   b,    5   c,    5   d ) for maintaining a controlled riser system pressure higher than the environmental pressure inside the riser system for avoiding forming or release of gas and expanding of gas contained in the slurry during transporting the slurry.   
     
     
         37 . Deep sea mining system ( 1 ) for use in a method according to  claim 21 , the system comprising;
 an excavating system ( 7 ) for excavating matter ( 2 ) at a bottom ( 9 ) of a body of water ( 3 ),   a riser system ( 4 ) for transporting a slurry ( 13 ) of matter and water from the bottom of a body of water upwards to a slurry processing base ( 6 ), the riser system comprising an adjustable pump means ( 11 ) proximate the bottom of a body of water,   pressure control means ( 5   a,    5   b,    5   c,    5   d ) for maintaining a controlled riser system pressure higher than the environmental pressure inside the riser system for avoiding forming or release of gas and expanding of gas contained in the slurry during transporting the slurry.