The disclosure concerns a reactor and a process for the hydrothermal treatment of an aqueous mixture, such as watery biomass. The reactor has an inlet for receiving the aqueous mixture, a tube-shaped reactor interior, which is inclined at an angle in the range of 1-45; a first zone in the reactor interior with means for heating the aqueous mixture; a second zone in the reactor interior for keeping the aqueous mixture at the predetermined temperature; a third zone in the reactor interior for cooling the aqueous mixture; an outlet for discharging a hydrothermally treated aqueous mixture, and an outlet for discharging gas. The inlet and outlet for discharging gas are positioned at the top part of the reactor and the outlet for discharging aqueous mixture is at the bottom part of the reactor. The inclined nature of the reactor ensures that all gases are efficiently removed from the liquid effluent, and the CO.sub.2 formed during the process is used to improved efficacy of the hydrothermal treatment.

The present invention includes: at least one feed hopper for retaining char separated from a generated gas that is generated in a gasifier; a char feed line for feeding char to the gasifier; a char flow rate adjustment device; a fuel feed line that feeds a carbon-containing solid fuel to the gasifier; a fuel flow rate adjustment device provided on the fuel feed line; an oxidant feed line for feeding an oxidant to the gasifier; an oxidant flow rate adjustment device provided on the oxidant feed line; and a control device. The control device is configured to control the char flow rate adjustment device so as to control the char flow rate depending on the load on a unit that uses a combustible gas, and to control at least one of the fuel flow rate adjustment device and the oxidant flow rate adjustment device depending on a total char level.

A feedstock delivery system transfers a carbonaceous material, such as municipal solid waste, into a product gas generation system. The feedstock delivery system includes a splitter for splitting bulk carbonaceous material into a plurality of carbonaceous material streams. Each stream is processed using a weighing system for gauging the quantity of carbonaceous material, a densification system for forming plugs of carbonaceous material, a de-densification system for breaking up the plugs of carbonaceous material, and a gas and carbonaceous material mixing system for forming a carbonaceous material and gas mixture. A pressure of the mixing gas is reduced prior to mixing with the carbonaceous material, and the carbonaceous material to gas weight ratio is monitored. A transport assembly conveys the carbonaceous material and gas mixture to a first reactor where at least the carbonaceous material within the mixture is subject to thermochemical reactions to form the product gas.