A method for transferring material in solid form from a low pressure zone, at a pressure of 0.1 bar absolute to 10 bar absolute, to a high pressure zone, at a pressure of greater than 10 bar absolute to 250 bar absolute, comprising: (a) providing feed material in solid form to a first lock hopper; (b) closing a valve coupled to an inlet of said first lock hopper; (c) after step (b), providing fluid to said first lock hopper to pressurize the first lock hopper; (d) after the first lock hopper is pressurized, opening a valve coupled to an outlet of said first lock hopper, said outlet is in fluid communication with a circulation loop; (e) releasing pressurized content comprising fluid and feed material of the first lock hopper to the circulation loop via said outlet of the first lock hopper, said circulation loop is in fluid communication with an inlet of a first receiving unit; (f) providing feed material to a second lock hopper; (g) closing a valve coupled to an inlet of said second lock hopper; (h) after step (g), providing fluid to said second lock hopper to pressurize the second lock hopper; (i) opening a valve coupled to an outlet of said second lock hopper, said outlet is in fluid communication with the circulation loop; (j) releasing pressurized content comprising fluid and feed material of the second lock hopper to the circulation loop via said outlet of the second lock hopper; (k) providing at least a portion of pressurized content in the circulation loop to the first receiving unit via said inlet of the first receiving unit; (l) providing at least a portion of fluid from the first receiving unit to the circulation loop via an outlet of the first receiving unit, said outlet is in fluid communication with the circulation loop; wherein the pressurized content of the lock hoppers is carried by the flow of the circulation loop to the receiving units; (m) closing the valve coupled to the outlet of the first lock hopper; (n) releasing liquid from the first lock hopper to a containment unit to depressurize the first lock hopper; (o) closing the valve coupled to the outlet of the second lock hopper; and (p) releasing liquid from the second lock hopper to a containment unit to depressurize the second lock hopper. (a) providing feed material in solid form to a first lock hopper; (b) closing a valve coupled to an inlet of said first lock hopper; (c) after step (b), providing fluid to said first lock hopper to pressurize the first lock hopper; (d) after the first lock hopper is pressurized, opening a valve coupled to an outlet of said first lock hopper, said outlet is in fluid communication with a circulation loop; (e) releasing pressurized content comprising fluid and feed material of the first lock hopper to the circulation loop via said outlet of the first lock hopper, said circulation loop is in fluid communication with an inlet of a first receiving unit; (f) providing feed material to a second lock hopper; (g) closing a valve coupled to an inlet of said second lock hopper; (h) after step (g), providing fluid to said second lock hopper to pressurize the second lock hopper; (i) opening a valve coupled to an outlet of said second lock hopper, said outlet is in fluid communication with the circulation loop; (j) releasing pressurized content comprising fluid and feed material of the second lock hopper to the circulation loop via said outlet of the second lock hopper; (k) providing at least a portion of pressurized content in the circulation loop to the first receiving unit via said inlet of the first receiving unit; (l) providing at least a portion of fluid from the first receiving unit to the circulation loop via an outlet of the first receiving unit, said outlet is in fluid communication with the circulation loop; wherein the pressurized content of the lock hoppers is carried by the flow of the circulation loop to the receiving units; (m) closing the valve coupled to the outlet of the first lock hopper; (n) releasing liquid from the first lock hopper to a containment unit to depressurize the first lock hopper; (o) closing the valve coupled to the outlet of the second lock hopper; and (p) releasing liquid from the second lock hopper to a containment unit to depressurize the second lock hopper.