The COHYGEN (Coal to Hydrogen Generation) pilot plant was developed in 2008 in order to study and optimize a syngas treatment process for combined production of hydrogen and electrical energy with CO2 capture. It is located in the Sotacarbo Research Centre in Carbonia (South-West Sardinia, Italy). The COHYGEN pilot plant is based on a 300 mm diameter fixed-bed up-draft gasifier, equipped with several sections for syngas treatment and both power generation and hydrogen production with CO2 capture. The plant is extremely flexible and suitable for several kinds of experimental tests. Summarizing, the plant includes the following gross sections:
In the gasification reactor, the fuel bed operates at about 0.11-0.14 MPa. The gasification agents (air, if necessary enriched with oxygen, and steam) can be pre-heated up to 250°C in order to avoid steam condensation before the injection into the gasifier. They are introduced into the reactor near the bottom, below the fuel grate. The syngas cleaning system is composed of a wet scrubber for a first gross removal of dust and tar, a first cold gas desulphurization stage and an electrostatic precipitator (ESP) for a fine dust and tar removal. Then syngas can be sent to a power generation line, which includes a packed column for a fine cold gas desulphurization (but frequently used also as a CO2 absorber) and a 24 kW internal combustion engine (ICE). Otherwise, syngas can be desulphurized in a hot gas desulphurization system which uses zinc oxides as the sorbent. An integrated CO-shift and CO2 removal unit includes a double stage water gas shift reactor (which can be filled with both conventional and advanced catalysts) with an intermediate and a secondary CO2 absorber (based on two identical bubbling reactors in which syngas reacts with amine-based solvents). The system operates at atmospheric pressure (but the system will be improved soon to operate at high pressure) and the configuration is very flexible. Finally, a hydrogen purification system (by pressure swing adsorption, PSA) allows separation of H2 from the remaining nitrogen. In order to support experimental tests, the pilot plant is equipped with a control and sampling system that allows monitoring of the main operating parameters (such as pressures, temperatures, volume flows etc) and evaluation of the process performance. Syngas composition is measured by three different systems:
The plant has been widely tested (about 2500 hours) and, together with ZECOMIX (Enea Research Centre in Casaccia), it is one of the most important infrastructures involved in the Italian CCS national programme, mainly for studying capture technologies (both pre- and post-combustion) in power plants fed with low rank coal.