A reactor comprising a thermal barrier surrounding a combustion zone. The reactor further comprises a cooling jacket inner wall and a binder disposed between the cooling jacket inner wall and the thermal barrier, and a cooling jacket outer wall, wherein the cooling jacket inner wall and the cooling jacket outer wall define a cooling channel. The reactor further comprises an outer reactor wall disposed over the cooling jacket outer wall, wherein the outer reactor wall is impermeable and is configured to contain high pressure gas within the reactor.

A reactor for the synthesis of urea comprising a vertical shell and perforated baffles or trays (3) arranged to define compartments of the reactor, wherein each baffle comprises an array of individual perforated tiles (10) wherein each tile (101) comprises side walls (101A-101D) and a top face (101F), the side walls having first perforations for the liquid and said top face having second perforations for the gas, wherein said second perforations are smaller than said first perforations, and the tiles are distributed over the baffle with a two-dimensional pattern where adjacent tiles are separated by gaps (17).

Fuel mixed in water is combusted in a reactor having an internal operating pressure and temperature greater than 3200 psi and greater than 374 C., where the combustion of the fuel is exothermic. Air and fuel are pressurized for introduction into the reactor to a pressure greater than the internal operating pressure using energy generated from the combustion of the fuel, and the pressurized air and the pressurized fuel are injected into the reactor. Pressurized water from the reactor is injected into a drive water column that is partially filled with water to increase a pressure of the drive water column, and water at a temperature less than 100 C. is injected into the reactor to replace water from the reactor that is injected into the drive water column. Pressurized water from the drive water column is used to drive a hydroelectric drive system to produce electrical power.